Skin barrier function, skin conductivity

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Skin barrier function,skin conductivity

• Michal Jurajda

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Terminology

• Keratos horn in Greek
• Cornu horn in Latin

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Skin is the body organ
epidermis
skin adnexa

dermis
tela subcutanea
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Skin functions

• Barrier functions (phys., chem. and biol.)
• metabolic functions (vit.D activation, excretion)
• immune function, APC (Langerhansovy bunky)
• Senzoring of temperatute and pain
• Thermoregulation

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Skin barrier - epidermis

• Epidermal layers

Stratum dysjunktum Stratum compactum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
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Skin barrier

• System of two compartments
• bricks and mortar
• keratinocytes (corneocytes)
• intersticium

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Skin barrier

• Bricks
• Keratinized cells
• Mortar
• Produced by keratinocytes (Odland bodies,
  lamellar bodies)
• Excretions of skin glands
• FFA, ceramids, cholesterol

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Skin barrier cellular component

• Mechanic function
• Hydratation
• UV protection
• Inflammatory response (APC)

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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.

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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

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UCA urocanic acid

• Originates from filaggrin.
• Acidic pH of the epidemmis
• Natural sunscreen
• Cis-UCA immunosupression

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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. 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. 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.
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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

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Melanin protection against ultraviolet radiation
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Interstitial compartment

• Permeability
• Deskvamation
• Antimicrobial effect
• Absorption of drugs or poisons
• Hydratation

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Lamellar bodies (LB)

• Lipids enzymes producing FFA cholesterol a
  ceramids - permeability
• Structural proteins (corneodesmin), serine
  proteases, proteases inhibitors regulation of
  skin desquamation
• Antimicrobial peptides (ß defensins,
  cathelicidiny evolutionary old proteins)

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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

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INCI

• International Nomenclature Cosmetics Ingredients
  unified nomenclature for cosmetics
• Cosmetics, Toiletries Fragrance Association
  (CTFA) author of INCI

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Examples
FDC Yellow5 Color
FDC Red40 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
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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
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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
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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

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How to test skin barrier

• Resistence against given chemical compound
• Stripping tests
• Transparency test
• Transepidermal water loss
• Chemical analysis of skin eluates

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Transparency test
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Atopic dermatitis

• Sensibilization
• Allergic reaction

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Atopic dermatitis
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Prick test
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Contact dermatitis

• Haptens
• nickel

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Skin barrier tests

• Burckhardt test
• Locher test, nitrazolium yellow
• Skin conductivity

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Measuring of skin conductivity by Dermotest

• AC 32Hz 0-500 µS.
• standard load iontophoresis 1.5 mA, with NaCl
  (physiological saline).

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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)
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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

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desquamation
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occlusion
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Course of atopic dermatitis therapy