Inflammation & Allergy - Drug Targets, 2010, 9, 97-108 97

1871-5281/10 $55.00+.00 © 2010 Bentham Science Publishers Ltd.

Role of Redox Signaling, Protein Phosphatases and Histone Acetylation in the Inflammatory Cascade in Acute Pancreatitis: Therapeutic Implications

Javier Escobar1, Javier Pereda

1, Alessandro Arduini

1, Juan Sandoval

2, Luis Sabater

3, Luis Aparisi

4,

Máximo Vento5, Gerardo López-Rodas

2 and Juan Sastre

*,1

1Department of Physiology,

2Department of Biochemistry & Molecular Biology, University of Valencia, Spain

3Department of Surgery,

4Laboratory of Pancreatic Function, University Clinic Hospital, Spain

5Division of Neonatology, University Hospital “La Fe”, Valencia, Spain

Abstract: Acute pancreatitis starts as a local inflammation of the pancreatic tissue but often leads to the systemic

inflammatory response syndrome and death by multiple organ failure. Pro-inflammatory cytokines, particularly TNF-

and Il-1 , play a pivotal role together with oxidative stress and glutathione depletion in the inflammatory response in this

disease. Most inflammatory mediators act through mitogen activated protein kinases and nuclear factor B. Nevertheless,

elucidation of the precise mechanisms involved in activation and attenuation phases of the inflammatory cascade is still

underway. Redox signaling mediated by inactivation of protein phosphatases and histone acetylation triggered by histone

acetyltransferases, particularly CBP/p300, decisively contribute to the activation phase of the inflammatory cascade.

Reversible oxidation of thiols in serine threonine protein phosphatase PP2A and in protein tyrosin phosphatases SHP1,

SHP2 and CD45 leads to their inactivation generally by formation of intramolecular disulfides. Consequently, oxidative

stress promotes the activation of MAP kinases through the inactivation of protein phosphatases, which act as sensors of

the cellular redox state. On the other hand, histone deacetylases together with serine threonine protein phosphatases PP1

and PP2A and dual specificity phosphatases down-regulate the expression of pro-inflammatory genes in the attenuation

phase. Treatment with phosphodiesterase inhibitors, such as pentoxifylline, in the very early stage of the disease prevents

the loss of pancreatic PP2A activity abrogating the recruitment of histone acetyltransfereases to the promoters of pro-

inflammatory genes and their up-regulation. Inhibitors of histone deacetylases are also proposed as potential therapy in

acute pancreatitis, and their therapeutic window discussed.

Keywords: Acute pancreatitis, cytokines, serine/threonine protein phosphatases, PP2A, cAMP, CBP, phosphodiesterase inhibitors, pentoxifylline.

1. INFLAMMATORY MEDIATORS IN ACUTE PAN-

CREATITIS

Acute pancreatitis (AP) starts as a local inflammation of the pancreatic tissue but frequently affects extrapancreatic tissues leading to a systemic inflammatory response and complications. The mortality rate goes up to 20% in severe acute pancreatitis

[1, 2]. Mortality in AP is due to multiple

organ failure associated with the systemic inflammatory response syndrome. The incidence of AP is progressively rising in parallel with the corresponding increase in the frequency of its risk factors, i.e. alcohol abuse, gallstones and obesity [2]. Nevertheless, elucidation of the precise mechanisms involved in tissue injury and systemic effects is still underway.

The major local pathological features are inflammatory infiltrate –particularly of neutrophils-, edema and necrosis of the pancreatic tissue [1] (see Fig. 1). An early event in AP is the intrapancreatic activation of zymogen enzymes, such as trypsinogen

[3]. Intracellular factors involved in the

pathogenesis also include inhibition of secretion, inflammatory signals, calcium, heat shock proteins and cell

*Address correspondence to this author at the Department of Physiology,

School of Pharmacy, University of Valencia, Avda. Vicente Andrés Estellés

s/n, 46100 Burjasot (Valencia), Spain; Tel: 34-963543815; Fax: 34-

963543395; E-mail: juan.sastre@uv.es

death pathways [1]. Pancreatic cell survival is compromised and acinar cell apoptosis may occur together with necrosis. However, experimental and clinical evidences show that zymogen enzymes are not responsible for the conversion of a local inflammatory process into a systemic inflammatory response. Numerous inflammatory mediators, including pro-inflammatory cytokines, chemokines, free radicals, Ca

2+,

platelet activating factor, and adenosine, as well as neural and vascular responses have been involved in the pathogenesis of AP and its associated Systemic Inflammatory Response Syndrome (SRIS) [1, 4-6]. In this situation, visceral perfusion is compromised and other mechanisms related to inflam-mation may affect distant organs. Renal failure and lung injury are common systemic complications in AP (see Fig. 1). Severe SIRS may lead to multiorgan dysfunction syndrome (MODS) and eventually death. Around half of deaths in AP occur within the first two weeks and are attributed to multiple organ failure [1]. The remainder of deaths occurs weeks to months later and are ascribed to organ failures associated with infected necrosis or other complications [1]. Pancreatic necrosis is a key factor predictive of outcome and indeed, extensive pancreatic necrosis and infection determine severity and complications in AP [7, 8]. At present, there is general consensus to consider AP together with sepsis, trauma, burns and surgery, as a pathological condition that may lead to the systemic inflammatory response syndrome and multiple organ failure [9].

98 Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 Escobar et al.

The inflammatory response in AP should be ascribed not only to macrophages and neutrophils, but also to pancreatic acinar cells. Indeed, acinar cells behave as inflammatory cells because they respond, produce and release cytokines, chemokines and adhesion molecules

[4, 10, 11]. Therefore,

acinar cells together with leukocytes trigger the inflammatory cascade in response to the local damage of the pancreas.

Tumor necrosis factor alpha (TNF- ) and interleukin 1- (IL-1 ) play a pivotal role in AP since they initiate and propagate almost all the consequences of the systemic inflammatory response in AP

[5, 6, 12]. TNF- and IL-1

decisively contribute to the amplification of the inflammatory cascade by inducing the release of other cytokines and by a positive feed-back which up-regulate their own expression. Knock-out mice deficient in TNF- receptors exhibited restrained systemic response in necrotizing AP [13]. Similarly, blockade of IL-1 action by a specific receptor antagonist diminished the injury in distant organs in necrotizing AP [14, 15].

Other relevant pro-inflammatory cytokines in AP are IL 6 and IL-8. IL-6 is a mediator of the acute-phase response and a marker of severity of AP

[16]. IL-8 is involved in

neutrophil chemotaxis, activation and degranulation [17] and has also been considered a marker of severity [12].

Glutathione depletion and oxidative stress play a significant role in the development of AP [6, 18]. Pancreatic glutathione depletion is a hallmark of the initial phase of AP [19-21] and it contributes to the severity of AP [21, 22]. We found a rapid recovery of reduced glutathione (GSH) levels in mild edematous pancreatitis due to up-regulation of glutamate cysteine ligase, the enzyme that controls GSH synthesis [23]. However, the induction of this enzyme fails in severe necrotizing pancreatitis maintaining a long-lasting GSH depletion [23]. The major sources of reactive oxygen

species responsible for oxidative stress in AP are xanthine oxidase [24] and NADPH oxidase [25]. Oxidative stress contributes to the production of cytokines and chemokines, such as IL-6, monocyte chemoattractant protein-1 and cytokine-induced neutrophil chemoattractant, mainly through activation of NF- B and STAT3 [26, 27]. Oxidative stress activates NF- B mediated transcription through kappaB-alpha kinase or the recruitment of transcriptional co-activators [28].

Among the anti-inflammatory mediators in AP, IL-10 and pancreatitis associated protein-1 (PAP-1) should be highlighted [6]. IL-10 decreases pancreatic damage [29] and it exerts at least part of its anti-inflammatory actions through inhibition of IL-1 and TNF- [30]. PAP-1 inhibits the inflammatory response by blocking NF- B activation [31] and down-regulating cytokine production and adhesion molecule expression [31-33]. PAP-1 knock-out mice showed increased pancreatic inflammation but less necrosis in cerulein-induced pancreatitis [34]. Consequently, further studies are required to establish the precise protective role of PAP-1.

Pro-inflammatory cytokines together with oxidative stress activate intracellular signaling pathways mediated by protein kinases activated by mitogens (MAPK), which play a central role in the inflammatory process [6, 35]. MAPK signaling cascades are regulated by phosphorylation and dephosphorylation on serine and/or threonine residues, and respond to activation of receptors of cytokines and growth factors, receptor tyrosine kinases, other protein tyrosine kinases, and heterotrimeric G-protein-coupled receptors [36, 37]. The primary pro-inflammatory cytokines TNF- and IL-1 activate JNK, p38 and NF- B triggering up-regulation of cytokines, chemokines and other pro-inflammatory mediators [38, 39]. Extracellular signal regulated kinase (ERK), the other major MAPK, also contributes decisively to

Fig. (1). Mechanisms involved in the development of the systemic inflammatory response and multiple organ failure in severe acute

pancreatitis.

Inflammatory Cascade in Acute Pancreatitis Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 99

the amplification of the inflammatory cascade [40]. Elucidation of the role of protein phosphatases and redox signaling together with chromatin modifying complexes and chromatin remodeling in the inflammatory cascade, particularly in acute pancreatitis, is the focus of the present review.

2. REGULATION OF THE INFLAMMATORY RES-PONSE BY PROTEIN PHOSPHATASES AND REDOX

SIGNALING

Protein Phosphatases as Sensors of the Cellular Redox

State

Protein phosphatases regulate the inflammatory response by dephosphorylation of substrates –including kinases- generally decreasing their activation and turning them to a basal state. Among the 140 phosphatases identified so far [41], some of them play a very important role in down-regulation of gene expression in the immune response [42].

Protein phosphatases are classified into two major groups: serine/threonine phosphatases (PPPs) -PP1, PP2A, PP2B (calcineurin) and the metallo-dependent phosphatase (PPM) PP2C-, and protein tyrosine phosphatases (PTPs) which include a diverse group concerning domain structure and substrate preference [43, 44]. This latter group includes membrane protein phosphatases (RPTPs) such as CD45, cytosolic phosphatases such as SHP1 and SHP2, and dual specificity phosphatases (DSP), also called MAPK phosphatases (MKPs). MKPs dephosphorylate phospho-tyr and phospho-thr residues and control MAPK dephosphorylation [45, 46]. The gene expression of some MKPs is strongly induced by growth factors and cellular stress, providing a transcriptional mechanism for specific inactivation of MAP kinases.

Redox signaling in the inflammatory response relies on protein phosphatases because the activity of protein phosphatases is modulated by oxidative stress (see Fig. 2). Reversible oxidation of thiols in protein phosphatases leads to their inactivation generally by formation of intramolecular disulfides or sulfoamides [47]. Consequently, oxidative stress promotes the activation of MAP kinases through the inactivation of protein phosphatases (see Fig. 2), highlighting their key role as sensors of the cellular redox state.

Oxidative stress triggers intra- and inter-molecular disulfide bonds in PPPs decreasing their activity. Thus, PP2A activity is inhibited by GSSG and H2O2 and restored with DTT [48]. The catalytic subunit of PP2A (PP2Ac) has cysteines in the active site in which it can form intramolecular bonds with vicinal thiols or intermolecular disulfide bonds with regulatory subunits, thus reducing PP2A activity [49, 50]. Calcineurin (PP2B) also suffers inactivation by H2O2 [51-53] and its affinity towards Ca

2+ and its ability to activate target

enzymes, such as phosphodiesterases, can be decreased by formation of intramolecular disulfide bonds [54]. Additionally, methionine oxidation decreases calcineurin activity, affecting specially subunit A of the enzyme [55]. We have recently found that the activities of PPPs (PP2A, PP2B and PP2C) markedly diminish in pancreas in the early stage of acute pancreatitis [40], and what remains to be established is the role of oxidative stress in this decrease.

The PTP superfamily is characterized by a conserved cysteine in the catalytic site [56, 57]. Mild oxidative stress causes reversible oxidation of the catalytic cysteine to sulfenic acid, whereas a more intense oxidative stress may trigger the irreversible formation of sulfinic and sulfonic acids [58]. In addition, RPTP may be inactivated by disulfide bridges between two catalytic cysteines leading to dimerization [59]. Accordingly, oxidation of PTPs by H2O2 causes transient inactivation [59, 60]. Nevertheless, sensitivity to oxidative stress varies among the different PTPs. Thus, some PTPs exhibit high sensitivity to oxidation -such as PTEN or Sac1-, whereas others such as myotubularin lipid phosphatases seem to be resistant to oxidation [61].

Among tyrosin phosphatases, SHP1 and SHP2 and CD45 seem to play a key role in the regulation of the inflammatory response by acting on NF- B, MAPK and TNF- [62, 63]. SHP1 is a negative regulator of the inflammatory cascade through inhibition of NF- B. Although gene expression of tyrosin phosphatases SHP1 and SHP2 increases early in the course of pancreatitis [64], their activities diminish in the initial stage of the disease [65]. Since SHP1 and SHP2 may be inactivated by oxidative stress [66], the oxidative stress associated with AP may be responsible for the loss of activity. Furthermore, the loss of PTPs activity may have relevant consequences in the inflammatory response since inhibition of tyrosin phosphatases is involved in the formation of edema in pancreas during acute pancreatitis [65]. On the other hand, CD45 is a membrane tyrosin phosphatase present not only in leukocytes but also in pancreatic acinar cells and its expression regulates the up-regulation of TNF- [62]. Indeed, the decrease in CD45 expression that occurs in acute pancreatitis is associated with a parallel increase in the production of TNF- , and both effects are prevented by the antioxidant N-acetyl cysteine [62]. Consequently, the redox regulation of protein phosphatases appears to be a key event in the inflammatory response in acute pancreatitis [6].

Role of PP2A in the Inflammatory Response

PP2A includes a subfamily of heterotrimeric complexes that exhibit diverse biological activities depending on the individual regulatory subunits. PP2A may form complexes with IKK and down-regulate NF- B transcriptional activity

[67]. PR55 and PR55 regulatory subunits are inhibitors of JNK and c-SRC

[68]. The PP2A heterotrimeric complex

formed by the PR65 A subunit, the catalytic subunit (PP2Ac), and G5PR as regulatory subunit exhibits phosphatase activity on histone H1

[69].

PP2A seems to control ERK phosphorylation in the inflammatory response. Thus, dephosphorylation of the phosphothreonine residue of ERK by PP2A is considered a prerequisite for dephosphorylation of the phosphotyrosine residue by PTPs [70]. In this regard, we recently found that the loss of PP2A activity that occurs in the pancreas during taurocholate-induced pancreatitis was associated with ERK phosphorylation [40]. Furthermore, prevention of this loss of PP2A activity by the phosphodiesterase inhibitor pentoxifylline blockaded to a great extent the up-regulation of pro-inflammatory genes, such as TNF- , interleukin 6,

100 Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 Escobar et al.

Fig. (2). Redox regulation of protein phosphatases, MAPK signaling and cytokine expression.

Inflammatory Cascade in Acute Pancreatitis Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 101

intercellular adhesion molecule-1, and inducible nitric oxide synthase [40]. Pentoxifylline did not abrogate the loss of PP2B and PP2C activities in pancreas in pancreatitis. Consequently, the loss of PP2A activity in the pancreas –but not the decrease in PP2B and PP2C- contributes significantly to the activation phase of the inflammatory response in acute pancreatitis. Taurocholate also induced a transient loss of cAMP levels and PP2A activity in pancreatic acinar cells in vitro and this loss was abrogated by dibutyryl cAMP [40]. The decrease in cAMP levels seems to be ascribed to inhibition of adenylate cyclase induced by adenosine through A1 receptors. Therefore, the intense and rapid ATP catabolism characteristic of the initial phase of acute pancreatitis [71] causes accumulation of intracellular adenosine and its release to the extracellular space where it would trigger down-regulation of cAMP and PP2A and the subsequent ERK activation.

Role of Calcineurin (PP2B) and NFAT in the Inflam-matory Response

PP2B, also called calcineurin, is one of the best characterized Ca

2+-regulatory proteins. It is a Ca

2+ and

Ca2+

/calmodulin-dependent serine-threonine phosphatase that is considered one of the main transducers of calcium signaling in T cells [72].

The role of calcineurin seems to be complex in macrophages. Calcineurin negatively regulates NF- B activity and expression of inflammatory cytokines in macrophages in the absence of activation [73]. However, activation of macrophages by calcineurin inhibitors reduces responsiveness to lipopolysaccharide (LPS) inducing a form of LPS tolerance [74]. Furthermore, calcineurin inhibition provides protection against LPS-induced inflammatory response and toxicity in vivo [74].

A major substrate of calcineurin is the cytosolic nuclear factor of activated T cells (NFAT). The NFAT family of transcription factors is evolutionarily related to the NF- B family and at present it is well-known that it activates transcription of a large number of genes during the immune response, particularly in T cells [75]. NFAT is regulated by calcineurin and is activated by membrane receptors coupled to Ca

2+ entry via phospholipase C. Phosphorylated NFAT

proteins reside in the cytoplasm in resting conditions and upon Ca

2+ stimulation they are dephosphorylated by

calcineurin, translocating to the nucleus and triggering transcriptional activation of target genes, particularly in lymphocytes [75]. IL-6, a cytokine involved in the acute phase response, induces NFAT activation which promotes the differentiation of CD4+ T cells into effector Th2 cells [76].

NFAT not only mediates signal transduction in T cells, but also in neutrophils, macrophages, and endothelial cells. Indeed, treatment of human neutrophils with antigens, anti-Fc -receptor antibodies, or anti-immunoglobulin E increased Ca

2+ and calcineurin activity leading to NFAT2-mediated

up-regulation of cyclooxygenase 2 and release of prostaglandin PGE2 [77]. The calcineurin and NFAT signaling pathway also contributes to the transcriptional activation of TNF- and IL-13 [78]. NFAT activation triggered by the -glucan receptor also plays a key role in the induction of cyclooxygenase-2 (COX-2) in macrophages

[79]. In endothelial cells, NFAT contributes to the up-regulation of E-selectin and the subsequent leukocyte adhesion [80].

Regarding the pathophysiology of acute pancreatitis, it has been reported that pancreatic elastase activates not only NF- B but also NFAT in myeloid cells in vitro and both transcription factors are involved in the elastase-induced secretion of TNF- [81]. In addition, calcineurin seems to mediate pancreatic zymogen activation in acinar cells [82], and hence it would promote acinar cell injury and likely necrosis through this mechanism.

Role of Dual Specificity Protein Phosphatases in the Inflammatory Response

Dual specificity protein phosphatases (MKPs or DUSP), such as MAPK phosphatase-1 (MKP-1 or DUSP1) and MKPM-M, also play a relevant role in the attenuation of the inflammatory cascade mainly through inactivation of MAP kinases. Thus, MKP1 up-regulation is involved in the attenuating response to LPS

[83]. It is noteworthy that

MAPK not only trigger the activation phase but also the attenuation phase, as p38 is required for MKP1 induction

[83].

Concerning acute pancreatitis, up-regulation of MKP-1 (DUSP1), MKP-3, and MKP-5 is an early event during the disease [84]. The increase in MKPs gene expression should be considered an adaptive response contributing to attenuation of the inflammatory response. Actually, down-regulation of MAP kinase signaling by MKPs induction provides protective effects by protease-activated receptor 2 (PAR2) activation in caerulein-induced intrapancreatic damage [85].

3. CHROMATIN MODIFYING COMPLEXES AND CHROMATIN REMODELING

Eukaryotic cells have solved the problem of fitting their large DNA filaments (around 2 m long in humans) inside the nucleus (around 10 μm of diameter) by creating the compact structure of the chromatin, which is composed of DNA, histones and different non-histone proteins. Nucleosomes are the basic unit of eukaryotic chromatin and consist of a histone core with two copies of each core histones H2A, H2B, H3 and H4 together with 147 bp of DNA tightly wrapped around the histone octamers. Nucleosomes are structured along the DNA polymer as ‘beads on a string’, further compacted in presence of the linker histone H.

The closed chromatin state hinders the access of transcription factors to the compact DNA template. Opening of the chromatin as euchromatin requires binding of transcriptional activators that target chromatin enzymes to the promoters. These enzymes can be classified into two main classes: chromatin modifier complexes and ATP-dependent chromatin remodeling complexes.

The most studied chromatin modifier complexes are the histone acetyltransferases (HATs) and histone deacetylases (HDACs). HATs are enzymes that catalyze the transfer of an acetyl group from acetyl-coenzyme A to the -amino groups of conserved lysine residues. This process generally leads to transcriptional activation [86, 87].

102 Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 Escobar et al.

The p300/CBP family comprises the highly related p300 and CBP proteins that have a bromodomain and three cysteine/histidine rich domains (TAZ, PHD and ZZ) that serve as protein-protein interacting domains. Members of this family are co-activators for many transcription factors and seem to be specially associated with the inflammatory cascade.

HDACs are enzymes that remove acetyl groups from lysine residues of histones and non-histone proteins [88] and consequently reverse the action of HATs. The combined action of HATs and HDACs maintains a subtle balance in the steady-state levels of histone acetylation. Histone acetylation is generally considered as a positive mark associated with active transcription, whereas deacetylated histones lead to closed, inactive heterochromatin [89].

HDACs have been classified into four different subfamilies (I, II, III, and IV), based on their sequence homology to the yeast HDAC RPD3 (Reduced Potassium Dependency 3), HDA1 (Histone Deacetylase 1) and SIR2 (Silent Information Regulator-2) [90-92]. Class I and II HDACs contain zinc in the catalytic site and they are sensitive to the inhibitor trichostatin A [93], whereas class III HDACs (Sirtuins 1-7) are NAD

+-dependent and insensitive

to trichostatin treatment [94]. HDAC11 is so far the sole class IV member [92].

HDACs have to be localized in the nucleus to be active, but classes II and III can also be found in the cytosol [95]. Targeting of HDACs to the nucleus takes place by a nuclear localization signal (NLS) or by interacting with other proteins. The return to the cytosol is achieved through a nuclear export signal (NES) and by binding to export proteins [92, 96].

The second large group of complexes that affect chromatin, chromatin remodeling complexes, uses the energy of ATP hydrolysis to modify DNA-histone interactions and the accessibility of nucleosomal DNA to the enzymatic machinery that controls gene transcription, DNA replication, and DNA repair [97]. The most studied of these complexes are the SWI/SNF (Switching defective/Sucrose Nonfermenting) family and the CHD (Chromodomain-Helicase-DNA binding) family. The SWI/SNF family is considered as a master regulator of gene expression linked to a large number of transcription factors [98-101]. The complex contains one of two related catalytic subunits, either BGR1/SMARCA4 or BRM/SMARCA2. The CHD family exhibits functional diversity, with some CHD remodelers leading to transcriptional activation and others, such as the well studied NuRD (Nucleosome Remodeling and Deacetylase) complex, promoting transcription repression.

4. REGULATION OF THE INFLAMMATORY RES-PONSE BY CHROMATIN MODIFYING COMPLEXES

Toll-like receptors trigger two different patterns of gene expression, on the one hand primary response genes encoding pro-inflammatory mediators, and on the other hand secondary response genes encoding antimicrobial effectors –secondary genes-. Recently, Foster et al. have elucidated the mechanisms responsible for this gene-specific regulation that involve histone acetylation and methylation as well as nucleosome remodeling [102].

As mentioned previously, histone acetylation is a positive mark associated with active transcription. Thus, promoters of both primary and secondary genes were acetylated at histone H4 in macrophages stimulated with LPS [102].

Trimethylation of histone H3 at lysine 4 (H3K4me3) is also associated with active transcription [103]. H3K4me3 was induced in LPS-stimulated macrophages at promoters of both primary and secondary response genes [102]. Therefore, H3 methylation is involved in the up-regulation of pro-inflammatory and anti-microbial genes.

Role of CBP/p300 Histone Acetyl Transferases in the Activation Phase of the Inflammatory Response

Histone acetylation mediated by CBP/p300 is triggered by cAMP and different kinases. cAMP may activate gene expression via the cAMP-responsive element (CRE) and the transcription factor CRE-binding protein (CREB). CREB can be phosphorylated and activated by protein kinase A, kinases downstream of MAPK and CaMKIV

[104], and then

it recruits the histone acetyltransferases CREB-binding protein (CBP) and its homologue p300. Recruitment of CBP/p300 and the subsequent histone acetylation lead to transcription activation

[105].

Up-regulation of TNF- in LPS-stimulated macrophages requires recruitment of an enhancer complex involving ERK substrates Ets, together with the co-activators CBP and p300 to the TNF- promoter [106]. CBP and p300 are also co-activators of NF- B and hence NF- B-induced gene transcription is mediated by histone acetylation. Accordingly, NF- B is the major mediator of TNF- -induced IL-6 gene expression, which requires CBP/p300 histone acetyltransferase activity

[107]. CBP/p300 are also

required for transcriptional activation of other NF- B-driven promoters, such as those of IL-8, E-selectin and endothelial leukocyte adhesion molecule (ELAM) [107, 108]. The E-selectin and ELAM genes are rapidly expressed in endothelial cells upon inflammation promoting binding and extravasation of leukocytes. p300 is also needed for up-regulation of COX-2 by IL1 or LPS in macrophages

[109].

Consequently, CBP/p300-mediated gene expression plays a key role in the inflammatory cascade (see Fig. 3).

CBP/p300 trigger specific modifications in histone H3. Indeed, histone H3 acetylation (H3K9 and H3K14) and histone H3 methylation (H3R17) are regulated at the promoters of NF- B-target genes in a CBP/p300 dependent manner

[110]. Coactivator-associated arginine

methyltransferase-1 (CARM1) is recruited to NF- B-target promoters and participates in NF- B-mediated transcription through H3 methylation at arginine 17 (H3R17)

[110].

CBP/p300 play an important role in the acute phase response as STAT 3, the major signal transducer of IL-6, transactivates its target genes through recruitment of CBP/p300 co-activators

[111]. Thus, IL-6-induced

angiotensinogen expression is mediated by association of STAT3 with p300/CBP to trigger histone acetylation and chromatin remodeling

[112]. In addition, STAT3, DNA

methyltransferase 1 (DNMT1) and HDAC 1 form complexes that bind to the promoter of phosphatase SHP-1, a key negative regulator of cell signaling

[113]. Accordingly,

STAT3 may induce methylation of this promoter and epigenetic silencing of SHP-1 [113].

Inflammatory Cascade in Acute Pancreatitis Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 103

Role of Histone Deacetylases Together with Protein Phos-phatases in the Attenuation Phase of the Inflammatory

Response

Chromatin modifying complexes act coordinately to regulate transcription not only during the activation phase but also during the attenuation phase. Transcriptional repression is indeed a dynamic mechanism of down-regulation of genes essential for resolution of inflammation. cAMP-mediated transcription exhibits burst-attenuation kinetics in parallel with the PKA-dependent phosphorylation and subsequent PP1-mediated desphophorylation of CREB

[114]. Transcriptional attenuation of cAMP-induced gene expression requires CREB dephosphorylation by PP1, and hence PP1 blocks CRE-regulated gene expression [115]. PP1 is targeted to CREB by binding with class-I HDACs, such as HDAC1 and HDAC8, triggering CREB inactivation by dephosphorylation during pre-stimulus and attenuation phases of the cAMP response

[104, 114]. Consequently, PP1

and class-I HDACs regulate the duration of CREB-mediated gene transcription and the subsequent attenuation phase (see Fig. 3). Nevertheless, nuclear PP2A might also be involved in the dephosphorylation of CREB

[116].

HDAC3 is a member of class I HDACs that functions as part of complexes that repress transcription factors such as NF- B and AP-1 [117-119]. In addition, HDAC3 is a scaffold protein for PP2A to dephosphorylate STAT3 and promote inactivation of the STAT3-mediated signaling pathway

[120]. HDAC3 activity seems to be regulated by

serine/threonine protein phosphatase 4, since it forms a complex with this phosphatase and its activity is inversely proportional to the cellular PP4 levels

[119].

Class II HDACs are also transcriptional repressors whose activities are controlled via dephosphorylation-dependent nuclear shuttling

[121]. PP2A is responsible for

dephosphorylation of class II HDACs triggering nuclear localization and repression of target genes, whereas phosphorylation triggers cytoplasmatic localization leading to activation of target genes

[121, 122]. Nitric oxide (NO)

may induce the formation of a large complex between HDAC4, HDAC5, and PP2A that triggers HDAC4 and HDAC5 nuclear shuttling

[123]. Thus, NO enhances HDAC

activity inhibiting serum-induced histone acetylation in endothelial cells

[123].

In addition, repression of E-selectin expression is associated with recruitment of histone deacetylases

[108].

Down-regulation of cAMP-dependent transcription may also involve specific proteins, such as cAMP responsive element (CRE) modulator (CREM)- , which is a ubiquitously expressed transcription factor responsible for the termination of IL-2 expression in T cells

via recruitment of HDAC1 and

reduced acetylation of histones [124].

Histone acetylation may also contribute to the attenuation phase of inflammation. Thus, LPS causes acetylation of histones H3 and H4 at the promoter of the dual specificity phosphatase MKP-M gene and this effect seems to be

Fig. (3). Role of protein phosphatases and histone acetylation in the activation and attenuation phases of acute inflammation. Modulation by

phosphodiesterase inhibitors.

104 Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 Escobar et al.

mediated by the CREB/CBP pathway [125]. MKPM-M is

rapidly induced by LPS in macrophages and leads to JNK inactivation and decreased TNF- secretion.

Regulation of the Inflammation Response by Chromatin Remodeling

Chromatin remodeling seems to play a critical role in the control of inflammation and also in the protection against infection [102, 126]. To facilitate gene activation, repressive and compact heterochromatin evolves to open euchromatin not only by histone modifying complexes but also by ATP-dependent remodeling complexes, such as SWI/SNF and Mi-2/NuRD complexes.

SWI/SNF complexes contain either BRG1 or BRM as ATPase subunits [87, 127, 128]. In LPS-stimulated macrophages, recruitment of BRG1/BRM subunits is required for the activation of primary response genes with delayed kinetics and secondary response genes, but not for rapidly induced primary response genes [126162]. However, BRG1 was only recruited to promoters of secondary response genes but not to those of primary response genes in tolerant macrophages [102].

In contrast, although the NURD-chromatin remodeler Mi-2 complex was recruited along with the SWI/SNF complexes to promoters of delayed primary response genes and secondary response genes, the Mi-2b complex limited the induction of these genes [126]. Consequently, Mi-2b complexes exhibit marked anti-inflammatory functions.

5. PHOSPHODIESTERASE INHIBITORS AND HDAC INHIBITORS AS POTENTIAL THERAPY IN ACUTE

PANCREATITIS

Despite numerous clinical trials regarding acute pancreatitis, no specific effective treatment has been reported so far for this disease. Hence, novel therapeutic strategies coming from experimental models should be considered. It has been reported that phosphodiesterase inhibitors, such as pentoxifylline and rolipram, ameliorate acute pancreatitis in rats

[19, 129, 130]. Their beneficial effects seem to be

mediated by inhibition of leukocyte activation and migration, reducing the up-regulation of TNF- and IL-6

[129-131].

We have recently shown that pentoxifylline specifically prevented the loss of serine/threonine phosphatase PP2A activity in pancreas, but not the decrease in PP2B and PP2C, early in the course of acute pancreatitis

[40]. This effect was

associated with reduced recruitment of histone acetyltransferases and transcription factors to the promoters of pro-inflammatory genes (tnf- , icam-1, and inos), together with abrogation of up-regulation of these genes

[40].

Consequently, phosphodiesterase inhibitors seem to be beneficial early in the course of acute pancreatitis by reducing histone acetylation and the resulting up-regulation of inflammatory mediators. It is worth noting that these effects are mediated by preventing the loss of cAMP levels and PP2A activity without increasing the recruitment of CBP [40].

The anti-inflammatory effects of phosphodiesterase inhibitors may also be mediated, at least in part, by stimulation of dual specificity phosphatases. Dipyridamole is a non-selective phosphodiesterase inhibitor that causes

transient activation of MKP-1 (DUSP1) which dephosphorylates and inactivates MAPK and specially p38

[132]. Dypiridamole inhibits the NF- B signaling pathway blocking the up-regulation of il-6, inos, cox-2, and monocyte chemoattractant protein-1 in LPS-activated macrophages

[132].

Nevertheless, the therapeutic window for treatment with phosphodiesterase inhibitors may be narrow and limited to the very early stage of the disease, for instance preventing the risk of acute pancreatitis induced by endoscopic retrograde cholangiopancreatography. The expected transient decrease in cAMP levels during the early stage of pancreatitis should limit the therapeutic window for phosphodiesterase inhibitors. Phosphodiesterase 4 inhibitors are generally considered anti-inflammatory agents due to the corresponding generation of cAMP [133,134]. Exchange protein directly activated by cAMP (EPAC) proteins seem to be responsible for cAMP-dependent down-regulation of inflammatory cytokine production [135,136]. However, cAMP signaling is complex and physiological stimuli that induce cAMP production may generate pro- or anti-inflammatory signals [137]. Thus, increased cAMP levels might activate the PKA/CREB/CBP pathway involved in cytokine up-regulation, and hence the administration of phosphodiesterase inhibitors might not be beneficial when the inflammatory cascade is already ongoing.

On the other hand, several studies have reported that HDAC inhibitors exhibit anti-inflammatory properties in vitro and in vivo. Thus, treatment of mice with suberoylanilide hydroxamic acid (SAHA), a pan-inhibitor of HDACs, suppressed LPS-induced production of TNF- , IL-1 , and IL-6 [138]. In accordance with these findings, HDAC inhibition promotes acetylation of STAT3 [139] and NF- B [140, 141], leading to impairment of NF- B activation [142]. It has also been recently reported that histone deacetylase inhibitors reduce inflammation and mortality in mice treated with LPS by blockade of MAPK signaling due to MKP-1 (DUSP1) acetylation

[143].

Acetylation of MKP-1 (DUSP1) is mediated by p300 upon LPS stimulation and it increases its phosphatase activity inhibiting innate immune signaling

[143].

Since HATs are involved in the up-regulation of pro-inflammatory cytokines and HDACs mediates the attenuation phase of inflammation, it seems paradoxical that HDAC inhibitors may exhibit anti-inflammatory properties.

Wang and colleagues [92] have recently proposed that the resolution of this paradox might involve four different mechanisms: i) gene up-regulation may be mediated by rapid acetylation and subsequent deacetylation rather than by sustained acetylation; ii) HDAC inhibition may result in the recruitment of as many repressors as activators; iii) HDAC inhibition may act on non-histone proteins, such as the transcription factor FOXP3, which exhibit immunosuppressive functions; iv) HDAC inhibitors may exhibit actions beyond acetylation, for instance promoting proteasomal degradation.

In the case of acute pancreatitis the therapeutic window for HDAC inhibitors might be limited to a late stage of the disease to promote attenuation of the inflammatory response because they may enhance CREB activity during the burst

Inflammatory Cascade in Acute Pancreatitis Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 105

phase. In addition, the occurrence of side effects, such as electrocardiographic abonormalities [144] in some cases upon treatment with HDAC inhibitors should limit their use as anti-inflammatory agents in clinical trials before specific HDAC inhibitors without side effects are available.

ACKNOWLEDGEMENTS

The authors thank Ms. Landy Menzies for revising the manuscript. This work was supported by Grants SAF2006-06963, SAF2009-09500 and Consolider CSD-2007-00020 to J. S.; and BFU2007-63120 and CSD2006-49 to G. L.-R.

ABBREVIATIONS

AP = Acute pancreatitis

COX-2 = Cyclooxygenase-2

ERK = Extracellular signal regulated kinase

HATs = Histone acetyltransferases

HDACs = Histone deacetylases

icam-1 = Intercellular adhesion molecule 1

IL-1 = Interleukin 1-

IL-6 = Interleukin 6

inos = Inducible nitric oxide synthase

JNK = c-Jun N-terminal kinase

LPS = Lipopolysaccharide

MAPK = Mitogen activated protein kinases

MKP = Dual specificity (thr/tyr) phosphatases

MCP-1 = Monocyte chemoattractant protein-1

MODS = Multiorgan dysfunction syndrome

NFAT = Nuclear factor of activated T cells

NF- B = Nuclear factor kB

PTPs = Protein tyrosin phosphatases

SAHA = Suberoylanilide hydroxamic acid

SRIS = Systemic Inflammatory Response Syndrome

TNF- = Tumor necrosis factor .

REFERENCES

[1] Pandol, S.J.; Saluja, A.K.; Imrie C.W.; Banks, P.A. Acute

pancreatitis: bench to the bedside. Gastroenterology, 2007, 133, 1056.e1-e25.

[2] Jha, R.K.; Ma, Q.; Sha, H.; Palikhe, M. Acute pancreatitis: a literature review. Med. Sci. Monit., 2009, 15, RA147-56.

[3] Grady, T.; Saluja, A.; Kaiser, A.; Steer, M. Edema and intrapancreatic trypsinogen activation precede glutathione

depletion during caerulein pancreatitis. Am. J. Physiol., 1996, 271, G20-6.

[4] Grady, T.; Liang, P.; Ernst, S.A.; Logsdon, C.D. Chemokine gene expression in rat pancreatic acinar cells is an early event associated

with acute pancreatitis. Gastroenterology, 1997, 113, 1966-75. [5] Pereda, J.; Sabater, L.; Aparisi, L.; Escobar, J.; Sandoval, J.; Viña,

J.; López-Rodas, G.; Sastre, J. Interaction between cytokines and oxidative stress in acute pancreatitis. Curr. Med. Chem., 2006, 13,

2775-87. [6] Escobar, J.; Pereda, J.; Arduini, A.; Sandoval, J.; Sabater, L.;

Aparisi, L.; López-Rodas, G.; Sastre, J. Cross-talk between oxidative stress and pro-inflammatory cytokines in acute

pancreatitis: a key role for protein phosphatases. Curr. Pharm. Des., 2009, 15, 3027-42.

[7] Kaiser, A.M.; Saluja, A.K.; Sengupta, A.; Saluja, M.; Steer, M.L.

Relationship between severity, necrosis, and apoptosis in five models of experimental acute pancreatitis. Am. J. Physiol., 1995,

269, C1295-304. [8] Xue, P.; Deng, L.H.; Zhang, Z.D.; Yang, X.N.; Wan, M.H.; Song,

B.; Xia, Q. Infectious Complications in Patients with Severe Acute Pancreatitis. Dig. Dis. Sci., 2008, 23.

[9] Nyström, P.O.; The systemic inflammatory response syndrome: definitions and aetiology. J. Antimicrob. Chemother., 1998, 41, 1-7.

[10] Gukovskaya, A.S.; Gukovsky, I.; Zaninovic, V.; Song, M.; Sandoval, D.; Gukovsky, S.; Pandol, S.J. Pancreatic acinar cells

produce, release, and respond to tumor necrosis factor-alpha. Role in regulating cell death and pancreatitis. J. Clin. Invest., 1997, 100,

1853-62. [11] De Dios, I.; Ramudo, L.; Alonso, J.R.; Recio, J.S.; Garcia-Montero,

A.C.; Manso, M.A. CD45 expression on rat acinar cells: involvement in pro-inflammatory cytokine production. FEBS Lett.,

2005, 579, 6355-60. [12] Norman, J. The role of cytokines in the pathogenesis of acute

pancreatitis. Am. J. Surg., 1998, 175, 76-83. [13] Denham, W.; Yang, J.; Fink, G.; Denham, D.; Carter, G.; Ward, K.;

Norman, J. Gene targeting demonstrates additive detrimental effects of interleukin 1 and tumor necrosis factor during

pancreatitis. Gastroenterology, 1997, 113, 1741-46. [14] Tanaka, N.; Murata, A.; Uda, K.; Toda H.; Kato, T.; Hayashida, H.;

Matsuura, N.; Mori, T. Interleukin-1 receptor antagonist modifies the changes in vital organs induced by acute necrotizing

pancreatitis in a rat experimental model. Crit. Care Med., 1995, 23, 901-8.

[15] Norman, J.G.; Franz, M.G.; Fink, G.S.; Messina, J.; Fabri, P.J.; Gower, W.R.; Carey L.C. Decreased mortality of severe acute

pancreatitis after proximal cytokine blockade. Ann. Surg., 1995, 221, 625-31.

[16] Leser, H.G.; Gross, V.; Scheibenbogen, C.; Heinisch, A.; Salm, R.; Lausen, M.; Rückauer, K.; Andreesen, R.; Farthmann, E.H.;

Schölmerich J. Elevation of serum interleukin-6 concentration precedes acute-phase response and reflects severity in acute

pancreatitis. Gastroenterology, 1991, 101, 782-5. [17] Kusske, A.M.; Rongione, A.J.; Reber, H.A. Cytokines and acute

pancreatitis. Gastroenterology, 1996, 110, 639-42. [18] Sweiry, J.H.; Mann, GE. Role of oxidative stress in the

pathogenesis of acute pancreatitis. Scand. J. Gastroenterol. Suppl., 1996, 219, 10-5.

[19] Gómez-Cambronero, L.; Camps, B.; de La Asunción, J.G.; Cerdá, M.; Pellín, A.; Pallardó, F.V.; Calvete, J.; Sweiry, J.H.; Mann,

G.E.; Viña, J.; Sastre, J. Pentoxifylline ameliorates cerulein-induced pancreatitis in rats: role of glutathione and nitric oxide. J.

Pharmacol. Exp. Ther., 2000, 293, 670-6. [20] Schoenberg, M.H.; Büchler, M.; Beger, H.G. The role of oxygen

radicals in experimental acute pancreatitis. Free Radic. Biol. Med., 1992, 12, 515-22.

[21] Neuschwander-Tetri, B.A.; Ferrell, L.D.; Sukhabote, R.J.; Grendell, J.H. Glutathione monoethyl ester ameliorates caerulein-

induced pancreatitis in the mouse. J. Clin. Invest., 1992, 89, 109-16.

[22] Alsfasser, G.; Gock, M.; Herzog, L.; Gebhard, M.M.; Herfarth, C.; Klar, E.; Schmidt, J. Glutathione depletion with L-buthionine-

(S,R)-sulfoximine demonstrates deleterious effects in acute pancreatitis of the rat. Dig. Dis. Sci., 2002, 47,1793-9.

[23] Pereda, J.; Escobar, J.; Sandoval, J.; Rodríguez, J.L.; Sabater, L.; Pallardó, F.V.; Torres, L.; Franco, L.; Viña, J.; López-Rodas, G.;

Sastre, J. Glutamate cysteine ligase up-regulation fails in necrotizing pancreatitis. Free Radic. Biol. Med., 2008, 44, 1599-

609. [24] Closa, D.; Bulbena, O.; Hotter, G.; Rosello-Catafau, J.; Fernandez-

Cruz, L.; Gelpi, E. Xanthine oxidase activation in cerulein- and taurocholate-induced acute pancreatitis in rats. Arch. Int. Physiol.

Biochim. Biophys., 1994, 102, 167-70. [25] Bokoch, G.M.; Knaus, U.G. NADPH oxidases: not just for

leukocytes anymore! Trends Biochem. Sci., 2003, 28, 502-8. [26] Yubero, S.; Ramudo, L.; Manso, M.A.; de Dios I. The role of redox

status on chemokine expression in acute pancreatitis. Biochim. Biophys. Acta., 2009, 1792, 148-54.

[27] Yu, J.H.; Lim, J.W.; Kim, K.H.; Morio, T.; Kim, H. NADPH oxidase and apoptosis in cerulein-stimulated pancreatic acinar

AR42J cells. Free Radic. Biol. Med., 2005, 39, 590-602.

106 Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 Escobar et al.

[28] Rahman, I.; Adcock, I.M. Oxidative stress and redox regulation of

lung inflammation in COPD. Eur. Respir. J., 2006, 28, 219-42. [29] Keceli, M.; Kucuk, C.; Sozuer, E.; Kerek, M.; Ince, O.; Arar, M.

The effect of interleukin-10 on acute pancreatitis induced by cerulein in a rat experimental model. J. Invest. Surg., 2005, 18, 7-

12. [30] Fiorentino, D.F.; Zlotnik, A.; Mosmann, T.R.; Howard, M.;

O'Garra, A. IL-10 inhibits cytokine production by activated macrophages. J. Immunol., 1991, 147, 3815-22.

[31] Folch-Puy, E.; Granell, S.; Dagorn, J.C.; Iovanna, J.L.; Closa D. Pancreatitis-associated protein I suppresses NF-kappa B activation

through a JAK/STAT-mediated mechanism in epithelial cells. J. Immunol., 2006, 176, 3774-9.

[32] Vasseur, S.; Folch-Puy, E.; Hlouschek, V.; Garcia, S.; Fiedler, F.; Lerch, M.M.; Dagorn, J.C.; Closa, D.; Iovanna, J.L. p8 improves

pancreatic response to acute pancreatitis by enhancing the expression of the anti-inflammatory protein pancreatitis-associated

protein I. J. Biol. Chem., 2004, 279, 7199-207. [33] Gironella, M.; Iovanna, J.L.; Sans, M.; Gil, F.; Peñalva, M.; Closa,

D.; Miquel, R.; Piqué, J.M.; Panés J. Anti-inflammatory effects of pancreatitis associated protein in inflammatory bowel disease. Gut,

2005, 54, 1244-53. [34] Gironella, M.; Folch-Puy, E.; LeGoffic, A.; Garcia, S.; Christa, L.;

Smith, A.; Tebar, L.; Hunt, S.P.; Bayne, R.; Smith, A.J.; Dagorn, J.C.; Closa, D.; Iovanna, J.L. Experimental acute pancreatitis in

PAP/HIP knock-out mice. Gut, 2007, 56, 1091-7. [35] Dong, C.; Davis, R.J.; Flavell, R.A. MAP kinases in the immune

response. Annu. Rev. Immunol., 2002, 20, 55-72. [36] Blenis, J. Signal transduction via the MAP kinases: proceed at your

own RSK. Proc. Natl. Acad. Sci. U. S. A., 1993, 90, 5889-92. [37] Whitmarsh, A.J. Regulation of gene transcription by mitogen-

activated protein kinase signaling pathways. Biochim. Biophys. Acta., 2007, 1773, 1285-98.

[38] Rahman, I.; MacNee, W. Regulation of redox glutathione levels and gene transcription in lung inflammation: therapeutic

approaches. Free Radic. Biol. Med., 2000, 28, 1405-20. [39] Phelps, D.T.; Ferro, T.J.; Higgins, P.J.; Shankar, R.; Parker, D.M.;

Johnson, A. TNF-alpha induces peroxynitrite-mediated depletion of lung endothelial glutathione via protein kinase C. Am. J. Physiol.,

1995, 269, 551-9. [40] Sandoval, J.; Escobar, J.; Pereda, J.; Sacilotto, N.; Rodriguez, J.L.;

Sabater, L.; Aparisi, L.; Franco, L.; López-Rodas, G.; Sastre, J. Pentoxifylline prevents loss of PP2A phosphatase activity and

recruitment of histone acetyltransferases to proinflammatory genes in acute pancreatitis. J. Pharmacol. Exp. Ther., 2009, 331, 609-17.

[41] Arena, S.; Benvenuti, S.; Bardelli, A. Genetic analysis of the kinome and phosphatome in cancer. Cell Mol. Life Sci., 2005, 62,

2092-9. [42] Hunter, T. Protein kinases and phosphatases: the yin and yang of

protein phosphorylation and signaling. Cell, 1995, 80, 225-36. [43] Edelson, J.D.; Vadas, P.; Villar, J.; Mullen, J.B.; Pruzanski, W.

Acute lung injury induced by phospholipase A2. Structural and functional changes. Am. Rev. Respir. Dis., 1991, 143, 1102-9.

[44] Whicher, J.T.; Barnes, M.P.; Brown, A.; Cooper, M.J.; Read, R.; Walters, G.; Williamson, R.C. Complement activation and

complement control proteins in acute pancreatitis. Gut, 1982, 23, 944-50.

[45] Camps, M.; Nichols, A.; Arkinstall, S. Dual specificity phosphatases: a gene family for control of MAP kinase function.

FASEB J., 2000, 14, 6-16. [46] Pulido, R.; Hooft van Huijsduijnen, R. Protein tyrosine

phosphatases: dual-specificity phosphatases in health and disease. FEBS J., 2008, 275, 848-66.

[47] Chiarugi, P. PTPs versus PTKs: the redox side of the coin. Free Radic. Res., 2005, 39, 353-364.

[48] Foley, T.D.; Armstrong, J.J.; Kupchak, B.R. Identification and H2O2 sensitivity of the major constitutive MAPK phosphatase

from rat brain. Biochem. Biophys. Res. Commun., 2004, 315, 568-74.

[49] Foley, T.D.; Kintner, M.E. Brain PP2A is modified by thiol-disulfide exchange and intermolecular disulfide formation.

Biochem. Biophys. Res. Commun., 2005, 330, 1224-9. [50] Foley, T.D.; Petro, L.A.; Stredny, C.M.; Coppa, T.M. Oxidative

inhibition of protein phosphatase 2A activity: role of catalytic subunit disulfides. Neurochem. Res., 2007, 32, 1957-64.

[51] Reiter, T.A.; Abraham, R.T.; Choi, M.; Rusnak, F. Redox

regulation of calcineurin in T-lymphocytes. J. Biol. Inorg. Chem., 1999, 4, 632-44.

[52] Bogumil, R.; Namgaladze, D.; Schaarschmidt, D.; Schmachtel, T.; Hellstern, S.; Mutzel, R.; Ullrich V. Inactivation of calcineurin by

hydrogen peroxide and phenylarsine oxide. Evidence for a dithiol-disulfide equilibrium and implications for redox regulation. Eur. J.

Biochem., 2000, 267, 1407-15. [53] Sommer, D.; Coleman, S.; Swanson, S.A.; Stemmer, P.M.

Differential susceptibilities of serine/threonine phosphatases to oxidative and nitrosative stress. Arch. Biochem. Biophys., 2002,

404, 271-8. [54] Tan, R.Y.; Mabuchi, Y.; Grabarek, Z. Blocking the Ca2+-induced

conformational transitions in calmodulin with disulfide bonds. J. Biol. Chem., 1996, 271, 7479-83.

[55] Carruthers, N.J.; Stemmer, P.M. Methionine oxidation in the calmodulin-binding domain of calcineurin disrupts calmodulin

binding and calcineurin activation. Biochemistry, 2008, 47, 3085-95.

[56] Zhang, Z.Y.; Dixon, J.E. Active site labeling of the Yersinia protein tyrosine phosphatase: the determination of the pKa of the

active site cysteine and the function of the conserved histidine 402. Biochemistry, 1993, 32, 9340-5.

[57] Peters, G.H.; Frimurer T.M.; Olsen, O.H. Electrostatic evaluation of the signature motif (H/V)CX5R(S/T) in protein-tyrosine

phosphatases. Biochemistry, 1998, 37, 5383-93. [58] Jackson, M.D.; Denu, J.M. Molecular reactions of protein

phosphatases--insights from structure and chemistry. Chem. Rev., 2001, 101, 2313-40.

[59] den Hertog, J.; Groen, A.; van der Wijk, T. Redox regulation of protein-tyrosine phosphatases. Arch. Biochem. Biophys., 2005,

c434, 11-5. [60] Cho, S.H.; Lee, C.H.; Ahn, Y.; Kim, H.; Kim, H.; Ahn, C.Y.;

Yang, K.S.; Lee, S.R. Redox regulation of PTEN and protein tyrosine phosphatases in H(2)O(2) mediated cell signaling. FEBS

Lett., 2004, 560, 7-13. [61] Ross, S.H.; Lindsay, Y.; Safrany, S.T.; Lorenzo, O.; Villa, F.; Toth,

R.; Clague, M.J.; Downes, C.P.; Leslie, N.R. Differential redox regulation within the PTP superfamily. Cell Signal., 2007, 19,

1521-30. [62] de Dios, I.; Ramudo, L.; García-Montero, A.C.; Manso, M.A.

Redox-sensitive modulation of CD45 expression in pancreatic acinar cells during acute pancreatitis. J. Pathol., 2006, 210, 234-9.

[63] Chong, Z.Z.; Maiese, K. The Src homology 2 domain tyrosine phosphatases SHP-1 and SHP-2: diversified control of cell growth,

inflammation, and injury. Histol. Histopathol., 2007, 22, 1251-67. [64] Sarmiento, N.; Sánchez-Bernal, C.; Ayra, M.; Pérez, N.;

Hernández-Hernández, A.; Calvo, J.J.; Sánchez-Yagüe J. Changes in the expression and dynamics of SHP-1 and SHP-2 during

cerulein-induced acute pancreatitis in rats. Biochim. Biophys. Acta, 2008, 1782, 271-9.

[65] Schnekenburger, J.; Mayerle, J.; Krüger, B.; Buchwalow, I.; Weiss, F.U.; Albrecht, E.; Samoilova, V.E.; Domschke, W.; Lerch, M.M.

Protein tyrosine phosphatase kappa and SHP-1 are involved in the regulation of cell-cell contacts at adherens junctions in the exocrine

pancreas. Gut, 2005, 54, 1445-55. [66] Lee, S.R.; Kwon, K.S.; Kim, S.R.; Rhee, S.G. Reversible

inactivation of protein-tyrosine phosphatase 1B in A431 cells stimulated with epidermal growth factor. J. Biol. Chem., 1998, 273,

15366-72. [67] Li, S.; Wang, L.; Berman, M.A.; Zhang, Y.; Dorf, ME. RNAi

screen in mouse astrocytes identifies phosphatases that regulate NF-kappaB signaling. Mol. Cell, 2006, 24, 497-509.

[68] Eichhorn, P.J.; Creyghton, M.P.; Wilhelmsen, K.; van Dam, H.; Bernards, R. A RNA interference screen identifies the protein

phosphatase 2A subunit PR55gamma as a stress-sensitive inhibitor of c-SRC. PLoS Genet., 2007, 3, e218.

[69] Kono, Y.; Maeda, K.; Kuwahara, K.; Yamamoto, H.; Miyamoto, E.; Yonezawa, K.; Takagi, K.; Sakaguchi, N. MCM3-binding

GANP DNA-primase is associated with a novel phosphatase component G5PR. Genes Cells., 2002; 7: 821-34.

[70] Alessi, D.R.; Gomez, N.; Moorhead, G.; Lewis, T.; Keyse, S.M.; Cohen, P. Inactivation of p42 MAP kinase by protein phosphatase

2A and a protein tyrosine phosphatase, but not CL100, in various cell lines. Curr. Biol., 1995, 5, 283-95.

Inflammatory Cascade in Acute Pancreatitis Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 107

[71] Lüthen, R.; Niederau, C.; Niederau, M.; Ferrell, L.D.; Grendell,

J.H. Influence of ductal pressure and infusates on activity and subcellular distribution of lysosomal enzymes in the rat pancreas.

Gastroenterology, 1995, 109, 573-81. [72] Baine, I.; Abe, B.T.; Macian, F. Regulation of T-cell tolerance by

calcium/NFAT signaling. Immunol. Rev., 2009, 231, 225-40. [73] Conboy, I.M.; Manoli, D.; Mhaiskar, V.; Jones, PP. Calcineurin

and vacuolar-type H+-ATPase modulate macrophage effector functions. Proc. Natl. Acad. Sci. USA, 1999, 96, 6324-9.

[74] Jennings, C.; Kusler, B.; Jones, P.P. Calcineurin inactivation leads to decreased responsiveness to LPS in macrophages and dendritic

cells and protects against LPS-induced toxicity in vivo. Innate Immun. 2009, 15, 109-20.

[75] Hogan, P.G.; Chen, L.; Nardone, J.; Rao, A. Transcriptional regulation by calcium, calcineurin, and NFAT. Genes Dev., 2003,

17, 2205-32. [76] Diehl, S.; Chow, C.W.; Weiss, L.; Palmetshofer, A.; Twardzik, T.;

Rounds, L.; Serfling, E.; Davis, R.J.; Anguita, J.; Rincón, M. Induction of NFATc2 expression by interleukin 6 promotes T

helper type 2 differentiation. J. Exp. Med., 2002, 196, 39-49. [77] Vega, A.; Chacón, P.; Monteseirín, J.; El Bekay, R.; Alba, G.;

Martín-Nieto, J.; Sobrino, F. Expression of the transcription factor NFAT2 in human neutrophils: IgE-dependent, Ca2+- and

calcineurin-mediated NFAT2 activation. J. Cell Sci., 2007, 120, 2328-37.

[78] Yang, J.; Hu, G.; Wang, S.W.; Li, Y.; Martin, R.; Li, K.; Yao, Z. Calcineurin/nuclear factors of activated T cells (NFAT)-activating

and immunoreceptor tyrosine-based activation motif (ITAM)-containing protein (CNAIP), a novel ITAM-containing protein that

activates the calcineurin/NFAT-signaling pathway. J. Biol. Chem., 2003, 278, 16797-801.

[79] Goodridge, H.S.; Simmons, R.M.; Underhill, D.M. Dectin-1 stimulation by Candida albicans yeast or zymosan triggers NFAT

activation in macrophages and dendritic cells. J. Immunol., 2007, 178, 3107-15.

[80] Cockerill, G.W.; Bert, A.G.; Ryan, G.R.; Gamble, J.R.; Vadas, M.A.; Cockerill, P.N. Regulation of granulocyte-macrophage

colony-stimulating factor and E-selectin expression in endothelial cells by cyclosporin A and the T-cell transcription factor NFAT.

Blood, 1995, 86, 2689-98. [81] Hietaranta, A.; Mustonen, H.; Puolakkainen, P.; Haapiainen, R.;

Kemppainen, E. Proinflammatory effects of pancreatic elastase are mediated through TLR4 and NF-kappaB. Biochem. Biophys. Res.

Commun., 2004, 323, 192-6. [82] Husain S.Z.; Grant, W.M.; Gorelick, F.S.; Nathanson, M.H.; Shah,

A.U. Caerulein-induced intracellular pancreatic zymogen activation is dependent on calcineurin. Am. J. Physiol. Gastrointest. Liver

Physiol., 2007, 292, 1594-9. [83] Hu, J.H.; Chen, T.; Zhuang, Z.H.; Kong, L.; Yu, M.C.; Liu, Y.;

Zang, J.W.; Ge, B.X. Feedback control of MKP-1 expression by p38. Cell Signal, 2007, 19, 393-400. Erratum in: Cell Signal, 2007,

19, 2414. [84] Höfken, T.; Keller, N.; Fleischer, F.; Göke, B.; Wagner, A.C. Map

kinase phosphatases (MKP's) are early responsive genes during induction of cerulein hyperstimulation pancreatitis. Biochem.

Biophys. Res. Commun., 2000, 276, 680-5. [85] Namkung, W.; Yoon, J.S.; Kim, K.H.; Lee, M.G. PAR2 exerts

local protection against acute pancreatitis via modulation of MAP kinase and MAP kinase phosphatase signaling. Am. J. Physiol.

Gastrointest. Liver Physiol., 2008, 295, 886-94. [86] Kouzarides, T. Chromatin modifications and their function. Cell,

2007, 128:693-705. [87] Roth, S.Y.; Denu, J.M.; Allis, C.D. Histone Acetyltransferases.

Annu. Rev. Biochem., 2001, 70, 81-120. [88] Hubbert, C.; Guardiola, A.; Shao, R.; Kawaguchi, Y.; Ito, A.;

Nixon, A.; Yoshida, M.; Wang, X.F.; Yao, T.P. HDAC6 is a microtubule-associated deacetylase. Nature, 2002, 417, 455-8.

[89] Kurdistani, S.K.; Grunstein, M. Histone acetylation and deacetylation in yeast. Nat. Rev. Mol. Cell Biol., 2003, 4, 276-84.

[90] Schwer, B.; North, B.J.; Frye, R.A.; Ott, M.; Verdin, E. The human silent information regulator (Sir)2 homologue hSIRT3 is a

mitochondrial nicotinamide adenine dinucleotide-dependent deacetylase. J. Cell Biol., 2002, 158, 647-57.

[91] Bjerling, P.; Silverstein, R.A.; Thon, G.; Caudy, A.; Grewal, S.; Ekwall, K. Functional divergence between histone deacetylases in

fission yeast by distinct cellular localization and in vivo specificity.

Mol. Cell. Biol., 2002, 22, 2170-2181. [92] Wang, L.; de Zoeten, E.F.; Greene, M.I.; Hancock, W.W.

Immunomodulatory effects of deacetylase inhibitors: therapeutic targeting of FOXP3+ regulatory T cells. Nat. Rev. Drug. Discov.,

2009, 8, 969-81. [93] Tsai, S.C.; Seto, E. Regulation of histone deacetylase 2 by protein

kinase CK2. J. Biol. Chem., 2002, 277, 31826-33. [94] Sengupta, N.; Seto, E. Regulation of histone deacetylase activities.

J. Cell. Biochem., 2004, 93, 57-67. [95] Rietveld, L.E.; Caldenhoven, E.; Stunnenberf, H.G. In vivo

repression of an erythroid-specific gene by distinct corepressor complexes. EMBO J., 2002, 6, 1389-97.

[96] de Ruijter, A.J.; van Gennip, A.H.; Caron, H.N.; Kemp, S.; van Kuilenburg, A.B. Histone deacetylases (HDACs): characterization

of the classical HDAC family. Biochem. J., 2003, 370, 737-49. [97] Clapier, C.R.; Cairns, B.R. The biology of chromatin remodeling

complexes. Annu. Rev. Biochem., 2009, 78, 273-304. [98] Jeong, K.W.; Lee, Y.H.; Stallcup, M.R. Recruitment of the

SWI/SNF chromatin remodeling complex to steroid hormone-regulated promoters by nuclear receptor coactivator flightless-I. J.

Biol. Chem., 2009, 284, 29298-309. [99] Letimier, F.A.; Passini, N.; Gasparian, S.; Bianchi, E.; Rogge, L.

Chromatin remodeling by the SWI/SNF-like BAF complex and STAT4 activation synergistically induce IL-12R 2 expression

during human Th1 cell differentiation. EMBO J., 2007, 26, 1292-302.

[100] Villagra, A.; Cruzat, F.; Carvallo, L.; Paredes, R.; Olate, J.; van Wijnen, A.J.; Stein, G.S.; Lian, J.B.; Stein, J.L.; Imbalzano, A.N.;

Montecino, M. Chromatin remodeling and transcriptional activity of the bone-specific osteocalcin gene require CCAAT/enhancer-

binding protein beta-dependent recruitment of SWI/SNF activity. J. Biol. Chem., 2006, 281, 22695-706.

[101] Pedersen, T.A.; Kowenz-Leutz, E.; Leutz, A.; Nerlov, C. Cooperation between C/EBPalpha TBP/TFIIB and SWI/SNF

recruiting domains is required for adipocyte differentiation. Genes Dev., 2001, 15, 3208-16.

[102] Foster, S.L.; Hargreaves, D.C.; Medzhitov, R. Gene-specific control of inflammation by TLR-induced chromatin modifications.

Nature, 2007, 447, 972-8. Erratum in: Nature. 2008, 451, 102. [103] 103Schneider, R.; Bannister, A.J.; Myers, F.A.; Thorne, A.W.;

Crane-Robinson, C.; Kouzarides, T. Histone H3 lysine 4 methylation patterns in higher eukaryotic genes. Nat. Cell Biol.,

2004, 6, 73-7. Erratum in: Nat. Cell Biol., 2004, 6, 465. [104] Gao, J.; Siddoway, B.; Huang, Q.; Xia, H. Inactivation of CREB

mediated gene transcription by HDAC8 bound protein phosphatase. Biochem. Biophys. Res. Commun., 2009, 379, 1-5.

[105] Yuan, L.W.; Gambee, J.E. Histone acetylation by p300 is involved in CREB-mediated transcription on chromatin. Biochim. Biophys.

Acta, 2001, 1541, 161-9. [106] Tsai, E.Y.; Falvo, J.V.; Tsytsykova, A.V.; Barczak, A.K.; Reimold,

A.M.; Glimcher, L.H.; Fenton, M.J.; Gordon, D.C.; Dunn, I.F.; Goldfeld, A.E. A lipopolysaccharide-specific enhancer complex

involving Ets, Elk-1, Sp1, and CREB binding protein and p300 is recruited to the tumor necrosis factor alpha promoter in vivo. Mol.

Cell. Biol., 2000, 20, 6084-94. [107] Vanden Berghe, W.; De Bosscher, K.; Boone, E.; Plaisance, S.;

Haegeman, G. The nuclear factor-kappaB engages CBP/p300 and histone acetyltransferase activity for transcriptional activation of

the interleukin-6 gene promoter. J. Biol. Chem., 1999, 274, 32091-8

[108] Edelstein, L.C.; Pan, A.; Collins, T. Chromatin modification and the endothelial-specific activation of the E-selectin gene. J. Biol.

Chem., 2005, 280, 11192-202. [109] Deng, W.G.; Zhu, Y.; Wu, K.K. Role of p300 and PCAF in

regulating cyclooxygenase-2 promoter activation by inflammatory mediators. Blood, 2004, 103, 2135-42.

[110] Miao, F.; Li, S.; Chavez, V.; Lanting, L.; Natarajan, R. Coactivator-associated arginine methyltransferase-1 enhances

nuclear factor-kappaB-mediated gene transcription through methylation of histone H3 at arginine 17. Mol. Endocrinol., 2006,

20, 1562-73. [111] Cvijic, H.; Bauer, K.; Löffler, D.; Pfeifer, G.; Blumert, C.;

Kretzschmar, A.K.; Henze, C.; Brocke-Heidrich, K.; Horn, F. Co-activator SRC-1 is dispensable for transcriptional control by

STAT3. Biochem. J., 2009, 420, 123-32.

108 Inflammation & Allergy - Drug Targets, 2010, Vol. 9, No. 2 Escobar et al.

[112] Ray, S.; Sherman, C.T.; Lu, M.; Brasier, A.R. Angiotensinogen

gene expression is dependent on signal transducer and activator of transcription 3-mediated p300/cAMP response element binding

protein-binding protein coactivator recruitment and histone acetyltransferase activity. Mol. Endocrinol., 2002, 16, 824-36.

[113] Zhang, Q.; Wang, H.Y.; Marzec, M.; Raghunath, P.N.; Nagasawa, T.; Wasik, M.A. STAT3- and DNA methyltransferase 1-mediated

epigenetic silencing of SHP-1 tyrosine phosphatase tumor suppressor gene in malignant T lymphocytes. Proc. Natl. Acad. Sci.

USA, 2005, 102, 6948-53. [114] Canettieri, G.; Morantte, I.; Guzmán, E.; Asahara, H.; Herzig, S.;

Anderson, S.D.; Yates, J.R. 3rd, Montminy, M. Attenuation of a phosphorylation-dependent activator by an HDAC-PP1 complex.

Nat. Struct. Biol., 2003, 10, 175-81. [115] Hagiwara, M.; Alberts, A.; Brindle, P.; Meinkoth, J.; Feramisco, J.;

Deng, T.; Karin, M.; Shenolikar, S.; Montminy, M. Transcriptional attenuation following cAMP induction requires PP-1-mediated

dephosphorylation of CREB. Cell, 1992, 70, 105-13. [116] Wadzinski, B.E.; Wheat, W.H.; Jaspers, S.; Peruski, L.F. Jr.;

Lickteig, R.L.; Johnson, G.L.; Klemm, D.J. Nuclear protein phosphatase 2A dephosphorylates protein kinase A-phosphorylated

CREB and regulates CREB transcriptional stimulation. Mol. Cell. Biol., 1993, 13, 2822-34.

[117] Fischle, W.; Dequiedt, F.; Hendzel, M.J.; Guenther, M.G.; Lazar, M.A.; Voelter, W.; Verdin, E. Enzymatic activity associated with

class II HDACs is dependent on a multiprotein complex containing HDAC3 and SMRT/N-CoR. Mol. Cell., 2002, 9, 45-57.

[118] Lahm, A.; Paolini, C.; Pallaoro, M.; Nardi, M.C.; Jones, P.; Neddermann, P.; Sambucini, S.; Bottomley, M.J.; Lo Surdo, P.;

Carfí, A.; Koch, U.; De Francesco, R.; Steinkühler, C.; Gallinari, P. Unraveling the hidden catalytic activity of vertebrate class IIa

histone deacetylases. Proc. Natl. Acad. Sci. USA., 2007, 104,17335-40.

[119] Zhang, X.; Ozawa, Y.; Lee, H.; Wen, Y.D.; Tan, T.H.; Wadzinski, B.E.; Seto, E. Histone deacetylase 3 (HDAC3) activity is regulated

by interaction with protein serine/threonine phosphatase 4. Genes Dev., 2005, 19, 827-39.

[120] Togi, S.; Kamitani, S.; Kawakami, S.; Ikeda, O.; Muromoto, R.; Nanbo, A.; Matsuda, T. HDAC3 influences phosphorylation of

STAT3 at serine 727 by interacting with PP2A. Biochem. Biophys. Res. Commun., 2009, 379, 616-20.

[121] Martin, M.; Potente, M.; Janssens, V.; Vertommen, D.; Twizere, J.C.; Rider, M.H.; Goris, J.; Dimmeler, S.; Kettmann, R.; Dequiedt,

F. Protein phosphatase 2A controls the activity of histone deacetylase 7 during T cell apoptosis and angiogenesis. Proc. Natl.

Acad. Sci. USA., 2008, 105, 4727-32. [122] Paroni, G.; Cernotta, N.; Dello Russo, C.; Gallinari, P.; Pallaoro,

M.; Foti, C.; Talamo, F.; Orsatti, L.; Steinkühler, C.; Brancolini, C. PP2A regulates HDAC4 nuclear import. Mol. Biol. Cell., 2008, 19,

655-67. [123] Illi, B.; Dello Russo, C.; Colussi, C.; Rosati, J.; Pallaoro, M.;

Spallotta, F.; Rotili, D.; Valente, S.; Ragone, G.; Martelli, F.; Biglioli, P.; Steinkuhler, C.; Gallinari, P.; Mai, A.; Capogrossi,

M.C.; Gaetano, C. Nitric oxide modulates chromatin folding in human endothelial cells via protein phosphatase 2A activation and

class II histone deacetylases nuclear shuttling. Circ. Res., 2008, 102, 51-8.

[124] Tenbrock, K.; Juang, Y.T.; Leukert, N.; Roth, J.; Tsokos, G.C. The transcriptional repressor cAMP response element modulator alpha

interacts with histone deacetylase 1 to repress promoter activity. J. Immunol., 2006, 177, 6159-64.

[125] Musikacharoen, T.; Yoshikai, Y.; Matsuguchi, T. Histone acetylation and activation of cAMP-response element-binding

protein regulate transcriptional activation of MKP-M in lipopolysaccharide-stimulated macrophages. J. Biol. Chem., 2003,

278, 9167-75. [126] Ramirez-Carrozzi, V.R.; Nazarian, A.A.; Li, C.C.; Gore, S.L.;

Sridharan, R.; Imbalzano, A.N.; Smale, S.T. Selective and antagonistic functions of SWI/SNF and Mi-2beta nucleosome

remodeling complexes during an inflammatory response. Genes Dev., 2006, 20, 282-96.

[127] Becker, P.B.; Hörz, W. ATP-dependent nucleosome remodeling.

Annu. Rev. Biochem., 2002, 71, 247-73. [128] Cairns B.R. Chromatin remodeling complexes: strength in

diversity, precision through specialization. Curr. Opin. Genet. Dev., 2005, 15, 185-90.

[129] Pereda, J.; Sabater, L.; Cassinello, N.; Gómez-Cambronero, L.; Closa, D.; Folch-Puy, E.; Aparisi, L.; Calvete, J.; Cerdá, M.; Lledó,

S.; Viña, J.; Sastre, J. Effect of simultaneous inhibition of TNF-alpha production and xanthine oxidase in experimental acute

pancreatitis: the role of mitogen activated protein kinases. Ann. Surg., 2004, 240, 108-16.

[130] Sato, T.; Otaka, M.; Odashima, M.; Kato, S.; Jin, M.; Konishi, N.; Matsuhashi, T.; Watanabe, S. Specific type IV phosphodiesterase

inhibitor ameliorates cerulein-induced pancreatitis in rats. Biochem. Biophys. Res. Commun., 2006, 346, 339-44.

[131] Haddad, J.J.; Land, S.C.; Tarnow-Mordi, W.O.; Zembala, M.; Kowalczyk, D.; Lauterbach, R. Immunopharmacological potential

of selective phosphodiesterase inhibition. I. Differential regulation of lipopolysaccharide-mediated proinflammatory cytokine

(interleukin-6 and tumor necrosis factor-alpha) biosynthesis in alveolar epithelial cells. J. Pharmacol. Exp. Ther., 2002, 300, 559-

66. [132] Chen, T.H.; Kao, Y.C.; Chen, B.C.; Chen, C.H.; Chan, P.; Lee,

H.M. Dipyridamole activation of mitogen-activated protein kinase phosphatase-1 mediates inhibition of lipopolysaccharide-induced

cyclooxygenase-2 expression in RAW 264.7 cells. Eur. J. Pharmacol., 2006, 541, 138-46.

[133] Huang, Z.; Mancini, J.A; Phosphodiesterase 4 inhibitors for the treatment of asthma and COPD. Curr. Med. Chem., 2006; 13,

3253-62. [134] Peters-Golden, M.; Putting on the brakes: cyclic AMP as a

multipronged controller of macrophage function. Sci. Signal., 2009; 2, pe37.

[135] Borland, G.; Smith, B.O.; Yarwood, S.J; EPAC proteins transduce diverse cellular actions of cAMP. Br. J. Pharmacol., 2009; 158, 70-

86. [136] Grandoch, M.; Roscioni, S.S.; Schmidt, M.; The role of Epac

proteins, novel cAMP mediators, in the regulation of immune, lung and neuronal function. Br. J. Pharmacol., 2010; 159, 265-84.

[137] Lorenowicz, M.J.; Fernandez-Borja, M.; Hordijk, P.L.; cAMP signaling in leukocyte transendothelial migration. Arterioscler.

Thromb. Vasc. Biol., 2007; 27, 1014-22. [138] Leoni, F.; Zaliani, A.; Bertolini, G.; Porro, G.; Pagani, P.; Pozzi, P.;

Donà, G.; Fossati, G.; Sozzani, S.; Azam, T.; Bufler, P.; Fantuzzi, G.; Goncharov, I.; Kim, S.H.; Pomerantz, B.J.; Reznikov, L.L.;

Siegmund, B.; Dinarello, C.A.; Mascagni, P. The antitumor histone deacetylase inhibitor suberoylanilide hydroxamic acid exhibits anti-

inflammatory properties via suppression of cytokines. Proc. Natl. Acad. Sci. USA., 2002, 99, 2995-3000.

[139] Sun, Y.; Chin, Y.E.; Weisiger, E.; Malter, C.; Tawara, I.; Toubai, T.; Gatza, E.; Mascagni, P.; Dinarello, C.A.; Reddy, P. Cutting

edge: Negative regulation of dendritic cells through acetylation of the nonhistone protein STAT-3. J. Immunol., 2009, 182, 5899-903.

[140] Matsuoka, H.; Fujimura, T.; Hayashi, M.; Matsuda, K.; Ishii, Y.; Aramori, I.; Mutoh, S. Disruption of HDAC4/N-CoR complex by

histone deacetylase inhibitors leads to inhibition of IL-2 gene expression. Biochem. Pharmacol., 2007, 74, 465-76.

[141] Matsuoka, H.; Fujimura, T.; Mori, H.; Aramori, I.; Mutoh, S. Mechanism of HDAC inhibitor FR235222-mediated IL-2

transcriptional repression in Jurkat cells. Int. Immunopharmacol., 2007, 7, 1422-32.

[142] Blanchard, F.; Chipoy, C. Histone deacetylase inhibitors: new drugs for the treatment of inflammatory diseases? Drug. Discov.

Today, 2005, 10, 197-204. [143] Cao, W.; Bao, C.; Padalko, E.; Lowenstein, C.J. Acetylation of

mitogen-activated protein kinase phosphatase-1 inhibits Toll-like receptor signaling. J. Exp. Med., 2008, 205, 1491-503.

[144] Strevel, E.L.; Ing, D.J.; Siu, L.L.; Molecularly targeted oncology therapeutics and prolongation of the QT interval. J. Clin. Oncol.,

2007, 25, 3362-71.

Received: January 11, 2010 Revised: March 2, 2010 Accepted: March 6, 2010