skin barrier function, skin conductivity
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Skin barrier function, skin conductivity. Michal Jurajda. Terminology. Keratos = horn in Greek Cornu = horn in Latin. Skin is the body organ. epidermis. skin adnexa. +. dermis. tela subcutanea. Skin functions. Barrier functions (phys., chem. and biol.) - PowerPoint PPT PresentationTRANSCRIPT
Skin barrier function,skin conductivity
Michal Jurajda
Terminology
• Keratos = horn in Greek
• Cornu = horn in Latin
Skin is the body organ
epidermis
dermis
tela subcutanea
skin adnexa+
Skin functions
• Barrier functions (phys., chem. and biol.)
• metabolic functions (vit.D activation, excretion)
• immune function, APC (Langerhansovy buňky)
• Senzoring of temperatute and pain
• Thermoregulation
Skin barrier - epidermis
• Epidermal layers
Stratum corneum
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum dysjunktumStratum compactum
Skin barrier
• System of two compartments– „ bricks and mortar “
• keratinocytes (corneocytes)
• intersticium
Skin barrier
• „Bricks“– Keratinized cells
• „Mortar“– Produced by keratinocytes (Odland bodies,
lamellar bodies)– Excretions of skin glands
• FFA, ceramids, cholesterol
Skin barrier – cellular component
– Mechanic function– Hydratation– UV protection– Inflammatory response (APC)
Keratin
• Epithelial cells almost always coexpress pairs of type I and type II keratins, and the pairs that are coexpressed are highly characteristic of a given epithelial tissue.
• In human epidermis, 3 different pairs of keratins are expressed: keratins 5 (type II) and 14 (type I), characteristic of basal or proliferative cells; keratins 1 (type II) and 10 (type I), characteristic of suprabasal terminally differentiating cells; and keratins 6 (type II) and 16 (type I) and keratin 17 (type I), characteristic of cells induced to hyperproliferate by disease or injury, and epithelial cells grown in cell culture.
Filaggrin
• Protein from corneocytes
• In the deeper layers of epidermis connected to keratin
• In the upper layers of epidermis is hydrolyzed. Free aminoacids are released.
• Acidic pH and osmotic activity
UCA urocanic acid
• Originates from filaggrin.
• Acidic pH of the epidemmis
• Natural sunscreen
• Cis-UCA immunosupression
1.Ultraviolet C (UVC, 100-290 nm) are the shortest and most energetic portion of the UV spectrum. These highly energetic wavelengths are the most dangerous in terms of the damage it can inflict on living material. The important wavelengths in the UVC are removed within the atmosphere, mainly by absorption in the ozone layer and not reach the earth's surface in any quantity.
2.Ultraviolet B (UVB, 290-320nm) is the most damaging part of UVR that we encounter. It is currently thought to generate most of the photodamage to skin, though not all. UVB are wavelengths mostly blocked by dense clouds, closely woven clothing and glass window panes. Significant amounts are transmitted from blue sky in the middle of the day in summer. It is less dangerous when the sun is low in the sky, at high latitude in winter, and in early mornings and late evenings in summer.
3.Ultraviolet A (UVA, 320-400nm) is about 1000 times less damaging to the skin than UVB as measured by sunburn (Erythema) or damage to cell DNA. On the other hand, 20 times more UVA than UVB reaches the earth in the middle of a summer's day. It is not greatly affected by absorption and scattering in the atmosphere when the sun is low in the sky, and is now known to contribute significantly to the total exposure at moderate levels throughout the whole day and year. UVA penetrates deeper into the skin and leads to deeper damage than UVB does. It penetrates cloud cover, light clothing and untinted glass relatively easily, and may induce a degree of continuing skin damage over long periods, even when UVR exposure is not obvious.
Skin damage by UV rays
• direct- pyrimidin dimers formation – mostly thymin (UVB)- photoageing – induction/inhibition of gene expression
(↓colagen, ↑MMPs, ↑elastase)
• indirect- ROS formation (following excitation of „chromophores“ –
molecules containing conjugated double bonds and/or aromatic circles)
- retinoid depletion in skin- imunosupression (esp. UVA)- folate degradation – systemic effects
Melanin – protection against ultraviolet radiation
Interstitial compartment
– Permeability– Deskvamation– Antimicrobial effect– Absorption of drugs or poisons– Hydratation
Lamellar bodies (LB)
• Lipids + enzymes producing FFA cholesterol a ceramids - permeability
• Structural proteins (corneodesmin), serine proteases, proteases inhibitors – regulation of skin desquamation
• Antimicrobial peptides (β defensins, cathelicidiny – evolutionary old proteins)
Cosmetics and the skin barrier
• Cosmetics x pharmaceuticals
• Different sale regulations
• Different declaration of ingredients– Cosmetics: according to % in content– Pharmaceuticals: according to active
component
INCI
• International Nomenclature Cosmetics Ingredients – unified nomenclature for cosmetics
• Cosmetics, Toiletries & Fragrance Association (CTFA) – author of INCI
FD&C Yellow#5 Color
FD&C Red#40 Color
Ammonium Polyacrylate Dispersant
Isohexadecane Emollient
C13-14 Isoparaffin Emollient
Isopropyl Isostearate Emollient and skin conditioner
Sucrose Polycottonseedate Emollient and skin conditioner
Sorbitan starate Emulsifier
Laureth-7 Emulsifier
Sucrose Cocate Emulsifier
PEG 100 Stearate Emulsifier
Stearic Acid Emulsifier
Fragrance Fragrance
Examples
Diesodium EDTA Chelating agent
Titanium Dioxide Opacifying agent
Sodium Hydroxide pH adjuster
Benzyl Alcohol Preservative
Ethyl Paraben Preservative
Propyl Paraben Preservative
Methyl Paraben Preservative
Panthenol Pro Vitamin B5/Skin Conditioner
Dimethicone Skin Conditioner
Dimethiconol Skin Conditioner
Glycerin Skin conditioning agent/humectant
Water Solvent
Polyacrylamide Thickener
Cetyl Alcohol Thickener and skin conditioner
Stearyl Alcohol Thickener and skin conditioner
Niacinamide Vitamin B3, skin conditioner
Tocopherol Acetate Vitamin E, emollient and Skin Conditioner
Skin cleanser cosmetics
Water Solvent
Sodium laureth sulfate Mild cleansing and lathering
Sodium lauroamphoacetate Mild cleansing and lathering
PEG-6 caprylic/capric glycerides Moisturizer/emollient
Palm kernel acid Thickener/skin conditioner
Magnesium sulfate Thickener
Glycerin Moisturizer/humectant
Cocamide MEA Mild cleansing and lathering
Citric acid Adjusts pH
Maleated soybean oil Moisturizer/emollient/occlusive
Fragrance Fragrance
Polyquaternium-10 Skin conditioner and emollient
Disodium EDTA Chelator
Sodium benzoate Preservative
DMDM hydantoin Preservative
The importance of skin barrier function – why we are interested
in?
• Protection against environment– Professional exposure
• Skin diseases influence skin barrier– Atopic or contact dermatitis
• Drugs absorption
How to test skin barrier
• Resistence against given chemical compound
• Stripping tests
• Transparency test
• Transepidermal water loss
• Chemical analysis of skin eluates
Transparency test
Atopic dermatitis
• Sensibilization• Allergic reaction
Atopic dermatitis
Prick test
Contact dermatitis
• Haptens• nickel
Skin barrier tests
• Burckhardt test
• Locher test, nitrazolium yellow
• Skin conductivity
Measuring of skin conductivity by Dermotest
• AC 32Hz; 0-500 μS.
• standard load iontophoresis 1.5 mA, with NaCl (physiological saline).
The device measures 5 characteristic values (V1-V5):1min after the start (V1)30 a 60s after the start of electrophoresis (V2, V3)30 a 60s after switching off the electrophoresis(V4, V5)
Normal values
• V1 less than 30 μS
• V3 up to 200-300 μS
• V5 return to initial values
• Test might be repeated after 15 minutes with the same result
desquamation
occlusion
Course of atopic dermatitis therapy