nitric oxide and lipid peroxidation - sfrbm:...

•NO & LPO Society For Free Radical Biology and Medicine O’Donnell et al. 1

Nitric Oxide and Lipid Peroxidation

Valerie B. O’Donnella, Neil Hoggb

and Victor M. Darley Usmarc

aDept of Med. Biochem.University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK. Ph: 0044-2920-748447Fax: 0044-2920-744905Email: [email protected]

bBiophysics Research Institute, Medical College of Wisconsin, Milwaukee, WI USA. cDepartment of Pathology, University of Alabama at Birmingham, AL USA


Nitric Oxide is a Free Radical

•N=O


Nitric oxide is not particularly oxidizing.Nitric oxide is (infinitely) stable*.

Nitric oxide does not rapidly react with organic molecules.

*In the absence of dioxygen.


The Nitric Oxide ‘Radical’ and some of its stable end-products

-O-N=O…nitrite

RO-N=O…alkyl nitrite

RS-N=O…nitrosothiol

•N=O…nitric oxide


Reactions of •NO with Other Free Radicals

Oxidation of •NO to nitrite:

4 •NO+ •O=O• +2H2O → 4HNO2

Nitric oxide reaction with organic peroxyl radicals: •NO+ ROO• → ROONO → ??


Lipid Peroxidation

LOO• + LH + O2 → LOO• + LOOH

LOO• is the central and rate-limiting species of lipid peroxidation


Non-enzymatic lipid oxidation

Initiation Propagation

L•

Propagation

LOOH

LOO•

LOOH

Metal orenzyme

LH

AOO•

O2

LOO•

LH

O2

LOO•L•LH

O2

LOOH

LOH

GPx

LOH

GPx


lipid hydroxides, hydroperoxides, aldehydes,epoxides, ketones, ceroid, isoprostanes

Necrotic core

Fibrous cap

Lipid peroxidation products in an atherosclerotic lesion are both enzymatically and non-

enzymatically produced.

Foam cell15-LOX ↑


Monocyte:PGHS-1,25, 15-LOX

Platelet:PGHS-112-LOX

Neutrophil:PGHS-1,25,12-LOX

Location of lipid oxidation enzymes in the vasculature

EndotheliumPGHS-1

Smooth muscle:12-LOX

LOX: lipoxygenasePGHS: prostaglandin H synthase


Lipid oxidation enzymes are upregulated during vascular disease.

* Inhibition of 12-LOX restores blood pressure in Angiotensin-II dependent hypertensive rats.

* Increased products of PGHS in hypertensive rats, and PGHS inhibition restores blood pressure in humans and rats.

* Smooth muscle 12-LOX ↑ in hypertension

* Platelet 12-LOX ↑ in hypertension

* Foam cell/macrophage 15-LOX ↑ in atherosclerosis.


Nitric oxide reaction with lipid peroxyl radicals

•NOLOONOLOO•

H2O [LO• •NO2]

LOOH + NO2

-

LO• •NO2

•NO [L(O)• •NO2]•NO

LONO NO2-

L(O)NO2


Reactions between •NO-derived reactive nitrogen species and unsaturated lipid

LH

•NO2

•NO

O2 O2•-

ONOO-

L• LOO•O2

LOONO

•NO2, ONOO-LNO2

LOOH

HONO

L(O)NO2

•NO

e-, H+


Nitric oxide inhibition of lipid oxidation coincideswith fast rates of •NO uptake during ABAP-dependent

linoleate oxidation.O

xyge

n (µ

M)

ABAP

(A) (B)

[ •NO] = 0.9 µM added at vertical lines to 7.3 mM linoleate in 0.5% cholate, 11 mM ABAP

0.6200

0.2

NO

(µM

)

100

-0.2

0 -0.60 400 1200800

Time/s


Mechanism of Inhibition of LDL Oxidation by •NO

LOO• + •NO → LOONO

LOOH

LO• + •NO2 → LONO2

OLOO• + •NO

OLOONO → OLONO2

Two •NO consumed for each LOO•

4 •NO + 2LOO• + H2O 2HNO2 + LONO2 + LONO


Apolipoprotein B

Phospholipid

α-Tocopherol

Cholesterol

L•

LOO• LNO2

LOOHL(O)NO2

Oxidant

•NO2O2

LH

L•

•NO2

•NO

LH•NO2

•NO

Cholesteryl Ester Triglyceride

O2


0 4 8 12SNN (µM)

0

100

200

300

400

500

leng

th o

f lag

tim

e (m

in)

SNN

SNN + HpODE

B

0 2 4 6 8 10BHT (µM)

0

50

100

150

200

BHT

BHT + HpODE

A

•NO and LDL

Oxidation: The effect of HPODE

Lag time of LDL (125 µg/ml) oxidation by Cu(II) (20 µM) with and without HPODE (5 µM)


Comparison of nitric oxide and tocopherol inhibition of linoleate oxidation.

0

100

200

300

0 200 400 600 800 1000 1200

Time/s

[Oxy

gen]

/µM

Tinh

ABAPα -tocopherol (1 µM)

•NO (1 µM)

Tinh

Oxidation of linoleate (7.3 mM) by ABAP (11 mM)


0

1

2

0 500 1000 1500

Time (secs)

NO

(µM

)

LOX LOXLOX

(i) (ii) (iii)

Nitric oxide is consumed by rabbit 15-lipoxygenaseduring oxidation of linoleate.

Add figure caption


Site of lipoxygenase inhibition by •NO

LOOH

E-Fe3+ LOO

E-Fe3+

E-Fe2+

NO

E-Fe2+ LOO

LE-Fe2+

O2


Activation of LOX inhibits activation of sGC by •NO

0

50

100

cGM

P(%

con

trol

)

control AA, 5 µM LOX AA, 5 µM, LOX

**

•NO Lox

sGC cGMP


Further Reading:

Darley-Usmar, VM et al., (1992) Free Radic. Res. Commun. 17, 9-20Graham, A et al., (1993) FEBS Lett. 330, 181-185Rubbo, H et al., (1994) J. Biol. Chem. 265, 26066-26075Hogg, N et al., (1995) J. Lipid Res. 36, 1756-1762Struck, N et al., (1995) FEBS Lett 361, 291-294O’Donnell, VB et al., (1997) Biochemistry 36, 15216-15223O’Donnell, VB et al., (1999) Chem. Res. Toxicol. 12, 83-92O’Donnell, VB et al., (1999) J. Biol. Chem. 274, 20083-20091Hogg, N & Kalyanaraman, B (1999) Biochim. Biophys. Acta. 1411, 378-384Rubbo, H et al., (2000) J. Biol. Chem. 275, 10812-10818O’Donnell, VB & Freeman, BA (2001) Circ. Res. 88, 16-25

nitric oxide and lipid peroxidation - sfrbm:...

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