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Alain KHAIAT, Ph.D. Vice President R&D Johnson & Johnson Asia Pacific

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Presentation on theme: "Alain KHAIAT, Ph.D. Vice President R&D Johnson & Johnson Asia Pacific"— Presentation transcript:

1 Alain KHAIAT, Ph.D. Vice President R&D Johnson & Johnson Asia Pacific
SKIN BIOLOGY Alain KHAIAT, Ph.D. Vice President R&D Johnson & Johnson Asia Pacific

2 CONTENTS Inflammation Pigmentation Skin Aging

3 CONTENTS Inflammation Pigmentation Skin Aging irritation sensitization
biochemistry Pigmentation Skin Aging

4 EPIDERMIS The cells contained in the epidermis are: corneocytes
keratinocytes Langerhans cells

5 DEJ It is the site of adhesion of epidermis to dermis, via:
hemidesmosomes anchoring filaments (Kalinin) adhesive protein (Laminin) fibronectin

6 DEJ Basal cell Lamina lucida Anchoring filaments Lamina densa
Hemidesmosome Lamina lucida Anchoring filaments Lamina densa Anchoring fibril

7 DERMIS The dermis contains: fibrobalsts mast cells Langerhans cells
lymphocytes and blood vessels

8 The skin is the interface between the organism and its environment
Because it contains: Langerhans cell lymphocytes blood vessels masts cells exogenous or endogenous stimuli will create inflammation processes

9 INFLAMMATION Inflammation is the body’s general distress response to biological, physical or chemical causes of: irritation sensitization photosensitization

10 INFLAMMATION Clinically, inflammation has been defined through 4 signs: erythema edema pain heat

11 IRRITATION Irritants are chemical, biological or physical agents which can produce inflammation Irritation can be either objective or subjective Objective irritation is characterized by the 4 signs mentioned. It is externally observable Subjective irritation is characterized by: stinging, burning or itching

12 IRRITATION The result of insulting the skin is the release of histamine by the mast cells in the irritated area. Histamine is a potent vasodilator, it produces the visible erythema and increased vascular permeability (leaking of fluid = edema), allowing cells (PMN= polymorphonucleocytes) to migrate to the area

13 SENSITIZATION Skin sensitization is the result of exposure to sensitizers or allergens Skin sensitization is a delayed type humoral immune response mediated by the T cell

14 SKIN SENSITIZATION The sentitizing substance (hapten), combines with a protein in the skin to form the allergen The Langerhans cells in the stratum germinativum interacts with the allergen and migrates to the lymphoid gland It then “teaches” the T cells about the allergen

15 SKIN SENSITIZATION Sensitized T cells migrate to the site and, on contacting the allergen, liberate cytokines these cytokines attract leukocytes to the site and appear to raise the temperature of the area

16 Langehans cell Allergen cytokine T cell Activated T cell

17 CYTOKINES Cytokines are essential transmitters of intercellular communication They have an inherent role in the regulation of responses of the immune system Each cytokine has multiple functions More than one cytokine may mediate the same, or very similar, function

18 CYTOKINES They form part of a complex cellular signaling language
They are proteins

19 T CELL RESPONSE TYPE 1: cell mediated response, essentially to viruses, bacteria, protozoa, chemicals. Th1 response leads to secretion of: IL2  IFN TNF IL12

20 T CELL RESPONSE TYPE 2: humoral response following parasitic infection. Th2 releases: IL4 IL5 IL6 IL10 IL13

21 T CELL RESPONSE The type of response is function of genes and the environment. Th2 Th1 Genes Environment

22 T CELL RESPONSE Allergic contact dermatitis is in its early stages Th1 (IL2, IFN) becoming later Th2 (IL4). This explains why the reaction decreases Atopic dermatitis is a Th2: IL4, IL5, IL6, IL10, then IgE, mast cells growth, eosinophil infiltration

23 UV B EFFECT UV B has been shown to suppress immune reaction (induction phase only) UV B stimulates synthesis and release of TNF- by keratinocytes which in turn modifies the behavior and morphology of Langerhans cells

24 TWO MECHANISMS Mast cells can respond directly to external trauma, to antigen-IgE complexes on their surface or to mediators generated from complement (anaphylatoxins) by degranulating and releasing vaso active mediators: histamins Langerhans cells interact specifically with T-lymphocytes and keratinocytes to initiate host response to antigens

Phospholipids are the major raw material and starting point for the arachidonic acid pathway. Irritants increase the biosynthesis of phospholipids Arachidonic acid is resident to the cell membrane where it is the source of several major biochemical pathways

26 Hydroperoxitetraenoic
Phospholipides Steroids NSAID Eugenol Phospholipase A2 Arachidonic Acid Acetylsalycilic acid Cyclooxygenase Thromboxane 12-Lipoxygenase Prostaglandin G2 5-Lipoxygenase Prostacyclin Hydroperoxitetraenoic Acid (HETE) Prostaglandin H2 Leucotrienes Prostaglandins (PGE2, PGF2, etc)

27 ARACHIDONIC PATHWAY If arachidonic acid is acted upon by cyclo-oxygenase, prostaglandin G2 is generated. It is itself converted into thromboxane or prostacyclin or PGH2, the later then generating the other members of the PG family. Thromboxane stimulates platelet aggregation and is a vasoconstrictor

Prostacyclin inhibits platelet aggregation and vasoconstriction Prostaglandins are non protein chemical mediators: they are fatty acids 12-lipoxygenase transforms AA into HETE 5-lipoxygenase catalyses the production of the leukotriens (eicosanoid family)

Cytokines secretion by PBL (human peripheral blood lymphocytes) in culture following addition of a stimulant IL 6 release by human fibroblasts Contact hypersensitivity in mouse (ear edema), after application of Phorbol ester Ear edema in mouse following AA inflammation

30 CONTENTS Inflammation Pigmentation anomalies melanogenesis Skin Aging

31 PIGMENTATION Skin color is the result of: nature of the melanin
where the melanin is concentrated, i.e. quantity, type and distribution of melanosomes (epidermis or dermis) skin vascularisation

1. Melanocytes proliferation is normal: Freckles: eumelanin zones on pheomelanin backgrounds (skin areas exposed to the sun) Chloasma: pregnancy mask: hypersecretion of melanin induced by hormonal factors and amplified by the sun

Diffuse brown melanosis: endocrine system disorders or nutritional anomalies Hypermelanosis can follow cutaneous inflammations: pigmentation of scars, caused by irritants combined with sun (photosensitizers like bergamot oil)

2. Melanocytes do not proliferate correctly Lentigines: can be hereditary, appear anywhere on the body Solar Lentigo: wider lesion than freckle, occurs after serious sunburn Senile Lentigo: generally on the back of the hand of older subjects, stimulated by solar exposure

Dubreuilh melanosis or malignant lentigo of the elderly: large pigmented multi colored stain, pre-cancerous Moles or Naevus: accumulation of melanocytes in epidermis and dermis Malignant melanomas: cancerous tumors. The first signs are degeneration of existing naevus or Dubreuilh melanosis

36 PIGMENTATION All methods to reduce pigmentation on the market today have the objective to reduce melanogenesis


Inhibition of the production of active tyrosinase in the ribosomes: placental extract Inhibition of the transfer of tyrosinase to pre-melanosomes by interrupting glycosylation (tunicamycine, glucosamine) Elimination of inflammatory reactions (flavonoids, tannins, etc)

Inhibition of tyrosinase: Kojic acid, ascorbic acid, etc. EDTA or Phytic acid (since tyrosinase requires Cu++) Inhibition of the formation of eumelanin: by adding glutathion and glutathion reductase transforming GSSG into GSH, promote the formation of glutathion DOPA leading to pheomelanin

40 PIGMENTATION Melanin is formed in the Melanocytes, where it is stored in the melanosomes Melanocytes extend arms to transfer melanosomes into the keratinocytes It is the keratinocytes charged with the melanosomes that constitute the dark spots on the skin

41 Inflammatory Response
Pigmentation Formation Mechanism 1 UV Variety of Causes Variety of Responses 2 Irritation Inflammatory Response KERATINOCYTE (Epidermis) 3 Hormone MELANOCYTE (Basal Layer) Tyrosine Melanin Melanosome FIBROBLAST Tyrosinase Dermis 1

42 Basic Structure of Skin
Stratum Corneum Keratinocyte Viable Epidermis Melanocyte Basal Layer Dermis

43 PIGMENTATION A novel approach has recently been published: blocking the transfer of melanosomes from the melanocyte to the keratinocytes Accumulation of charged melanosomes inhibits melanin synthesis

44 SUGGESTED MECHANISM Depigmentation Less Less eumelanin melanosome
transfer Less eumelanin produced, lighter color Melanosomes accumulate 1. Less TRP-1 is made tyrosinase not stable 2. More TRP-2 is made shift to brownish melanins Negative feed-back

45 NOVEL MECHANISM Protease Activated Receptor (PAR-2) is expressed in keratinocytes. PAR-2 is activated by trypsin By inhibiting PAR-2, one probably blocks the keratinocyte-melanocyte interaction TRP1 (tyrosinase-related protein) decreases leading to less Eumelanin

46 PIGMENTATION TESTING Tyrosinase activity in solution: mushroom, mouse or human tyrosinase are used with different results S91 melanoma cells in culture Keratinocytes-Melanocytes co culture Guinea pig ear: 15 days treatment Microswine spotted model: 6-8 weeks

47 PIGMENTATION TESTING Human volunteers tests: 3 months minimum,
Chromameter® : L measure Mexameter® : evaluation of melanin and redness Photography : visible, UV with data analysis 3 months minimum, changes, so far, are not very significant against placebo

48 CONTENTS Inflammation Pigmentation Skin Aging skin changes
biochemical changes

Epidermis : reduction in cell renewal rate thickening of stratum corneum decrease in barrier efficiency : increase in TEWL and hyperkeratosis ridges are flattened out and intercellular spaces enlarged pigmentation problems : actinic lentigines decrease in skin immune system

Sebaceous glands : reduction in sebum secretion (hormones influenced) Sweat glands : less active HLP film : thinning of film means less protective barrier

Dermis : destruction of collagen and elastin fibers network proteoglycans and glycoproteins are reduced increase in elastin synthesis : elastosis The dermo - epidermal junction flattens out and loses its waviness. Less mechanical support : lower elasticity, higher fatigability.

52 PHOTOAGING 3 types of reactions to UV exposure:
Free Radicals, essentially due to UVA Direct cell death, essentially due to UVB MMP Enzymes

53 FREE RADICALS Free radicals or ROS (reactive oxygen species) can lead to breakage of important molecules: DNA (mutations, renewal failure, cell death) collagen, elastin, GAG (skin firmness) lipids (membrane or structural)


55 DNA DAMAGE UVA acts through oxidative stress forming “reactive oxygen species” (ROS) that will damage the DNA and lead to cancer

56 DNA DAMAGE UVB impact on DNA in the cell creating damages which may lead to cancer: non-melanoma skin cancer (NMSC)


58 UVB DAMAGE Following structural changes in DNA, there is an altered expression of oncogenes and tumor suppression genes, such as p53 NMSC show a high incidence of mutation in p53 gene


60 p 53 GENE Plays an important role in:
blocking the cell cycle after exposure to DNA-damaging agents e.g. UV, in order to allow for repair before duplication or killing the cell to avoid multiplication of damaged cells (formation of sunburn cells)

61 p 53 GENE The induction of detectable levels of p53 in human epidermis after UV exposure is relevant to skin carcinogenesis

62 Collagen & Photodamage
Major structural component of ECM 70% of the dry weight of skin Collagen degradation is believed to play a role in formation of wrinkles

63 Collagen Degradation A balance between MMP:TIMP


65 MMP ENZYMES Collagenases (1 to 4) are specific to various collagen,
Gelatinases (A & B) are non specific Stromelysins (1-3) specific of fibronectin, laminin, collagen IV, etc. Elastase: elastin etc

66 MEMBRANE EFFECTS With age, reduction in membrane fluidity leading to less efficient exchanges: intrinsic: reduction in the methylation of PE into PC extrinsic: lipid peroxides Methyl donors will restore membrane fluidity

Replenish antiox system Inhibition of oxidative stress ACTIVE PHOTOPROTECTION Reduce matrix degradation Quench ROS

68 Irradiation of Epidermal Equivalents with Solar Spectrum UV
Solar Simulator MM & TIMP-1

69 UV Irradiation of Epidermal Equivalents
Markers of damage MMP-1 induction TIMP-1 induction, but to a lesser extent than MMP-1 MMP:TIMP imbalance Protection provided by Sunscreens Anti-oxidants

70 UV Irradiation of Epidermal Equivalents
Model for assessing Photoprotective potential Botanical ingredients Fully formulated product


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