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HOW THE EPIDERMIS AND DERMIS
INTERACT WITH EACH OTHER
JULIAN M MENTER PhD
Department of Microbiology, Biochemistry and Immunology
Morehouse School of Medicine
Atlanta, GA.
LIGHT MICROSCOPY OF NORMAL
HUMAN SKIN
• The epidermis and dermis are
commonly considered to be two
separate entities…
• …However, there is actually a great
deal of interaction between the two
layers
(Some) Examples of
Epidermal/Dermal Interactions
in the Ground State
Blood Vessels in Dermis Enter the
Epidermis as Capillaries (1)
EXAMPLES OF EPIDERMAL/DERMAL
INTERACTIONS (2)
• Epidermal Vascular Endothelial Growth Factor Production
Is Required for Permeability Barrier Homeostasis, Dermal
Angiogenesis, and the Development of Epidermal
Hyperplasia
• Implications for the Pathogenesis of Psoriasis
• Peter M. Elias,* Jack Arbiser,† Barbara E. Brown,* et al
• Am J Pathol. 2008 Sep; 173(3): 689–699.
• doi: 10.2353/ajpath.2008.080088
• PMCID: PMC2527083
•
Interactions between Whisker Dermal
Papillae and Epidermis
RESPONSES OF ORAL EPITHELIUM TO THE INFLUENCE
OF WHISKER DERMAL PAPILLAE IN THE ADULT RAT
R. F. OLIVER* Arch oral Bid. Vol. 18p, p.4 134211, (1973)
The EXPERIMENTAL INDUCTION OF WHISKER GROWTH IN
THE HOODED RAT BY IMPLANTATION OF DERMAL PAPILLAE
R. F. OLIVER J Embryol Exp Morphol, 18 (1967), pp. 43–51
“Whisker dermal papillae developed various epidermal modulations,
including generalized hyperplasia and the development of spikes of
keratinized cells, hair follicles, sebaceous gland cells and stellate
reticulum-like configurations reminiscent of the tooth germ.”
Nitric Oxide in Skin (1)
• NO plays a key role in orchestrating the skin's
response to external stimuli such as heat,
ultraviolet (UV) light, response to infection,
and wound healing, as well as possibly
underlying certain pathological conditions
• MM Cals-Grierson, OD Ormerod Nitric Oxide 2004 (4) 179 - 193
Nitric Oxide in Skin
• Keratinocytes, constitutively express the neuronal isoform of
NO synthase (NOS1),
• Fibroblasts in the dermis and other cell types in the skin
express the endothelial isoform (NOS3).
• Under certain conditions, virtually all skin cells appear to be
capable of expressing the inducible NOS isoform (NOS2)
• MM Cals-Grierson, OD Ormerod Nitric Oxide 2004 (4) 179 - 193
Melanin Couples Reaction of NO with Oxygen
Menter JM, Nokkaew C, Eatman D, Sprewell A, Silvestrov N, Patta AM
et al., Open J Phys Chem 3:157–162 (2013).
(Some) Examples of
Epidermal/Dermal Interactions
in the Excited State
Solar Spectrum (Wehrli, 1985)
2.0
2
Irradiance (W/cm /nm)
2.5
1.5
1.0
0.5
Wavelength (nm) vs W/cm2/nm
0.0
200
300
400
500
600
Wavelength (nm)
700
800
1
2
Irradiance (W/cm /nm)
Solar Spectrum (Wehrli, 1985)
0.1
Wavelength (nm) vs W/cm2/nm
200
300
400
500
600
Wavelength (nm)
700
800
THE SOLAR SPECTRUM
Long Wave UVA Augments UV Sunburn
Damage
EFFECTS OF LONG ·ULTRAVIOLET RAYS ON HUMAN SKIN:
PHOTOPROTECTIVE OR PHOTOAUGMENTATIVE?*
ISAAC WILLIS, M.D., ALBERT KLIGMAN, M.D., Ph.D., AND JOHN EPSTEIN, M.D. T HE JOURNAL OF
INVESTIGATI VE DERMATOLOGY
Vol. 59, No. 6, 416 – 420 (1972)
ABSTRACT:
“The effects of long ultraviolet (LUV) rays on human skin are generally believed to be
either harmless or protective against sunburn damage. Responses to LUV alone, LUV plus
sunburn radiation, and sunburn radiation alone were evaluated both clinically and
microscopically by routine histologic and autoradiographic techniques. Observations revealed
that contrary to previous accepted hypotheses, LUV rays have a striking augmentative effect on
sunburn damage. In addition, although LUV radiation alone causes no discernable adverse
clinical or histologic changes in skin , an effect on DNA metabolism does occur…”
Long Wave UVA Augments UV
Photocarcinogenesis
The rapid induction of cancers in the hairless mouse utilizing the principle of
photoaugmentation.
Willis I, Menter JM, Whyte HJ. J Invest Dermatol. 1981 May;76(5):404-8
•
•
Abstract
Exposure to highly erythemogenic, but otherwise clinically noninjurious, dose of
broad spectrum (290-400 nm) ultraviolet light is increased by 20% every 6th day.
Clinical and histological observations reveal the presence of squamous cell cancer
after as little as 18 days of irradiation. The rate of cancer induction is enhanced by
the 320-400 nm component and this enhancement is shown to be a
photoaugmentative effect. The results support the idea that stratum corneum
and/or malpighian layer thickening produced in early stages of tumor induction
tends to protect against the detrimental effects of UV radiation. Strict monitoring
of both the spectral distribution and output of the radiation source is imperative
for reproducible rates of tumor induction.
UVA and UVB Radiation Have
Different, Separate, Molecular
Targets.
UVA – (mainly) dermal targets
UVB – (mainly) epidermal targets
Important Epidermal Target
Chromophores
• DNA (Major Significance)
• (a) Pyridine 2 + 2 Photodimers
• (b) 6 - 4 Photoproducts
• KERATIN AND OTHER PROTEINS:
• Photoproducts essentially unknown
• Melanin:
• These absorb strongly at wavelengths
• < 300 nm
Important Difference Between UVB
and UVA – Mediated Reactions:
• UVB Reactions generally do not require
molecular O2, and are mostly “direct” reactions
• UVA Reactions generally do require molecular
O2 and are “sensitized” reactions
Important Difference Between UVB
and UVA – Mediated Reactions:
• UVB Reactions are generally in the epidermis,
• UVA reactions are mainly in the dermis
Action Spectra for CPD Dimers, Skin Cancer, and 8-Oxoguanine Production
Rünger TM1, Kappes UP..Mechanisms of mutation formation with long-wave ultraviolet light (UVA)
.Photodermatol Photoimmunol. Photomed.2008 Feb;24 Feb;24(1):2-10. doi: 10.1111/j.1600-0781.2008.00319.x
SOME IMPORTANT DERMAL TARGETS
• COLLAGEN:
• (a) Aromatic amino acids on teloptide region and their
postranslational products
• (b) Peptide linkage (UVC)
• ELASTIN
• (a) Desmosine
• (b) Amino acids (see above)
• PROTEINS, DRUGS, ENDOGENOUS, CHROMOPHORES ,(e.g.
Riboflavin, porphyrins, flavins and melanin)
Some UVA Sensitizers in the Dermis
Peter Karran, Reto Brem Protein oxidation, UVA and human DNA repair
DNA Repair 2016 Aug 44 178 - 185
“The Situation is Complicated”
•
•
•
Summary
“Long-wave ultraviolet (UV) A light is able to damage DNA, to cause mutations, and to induce skin cancer,
but the exact mechanisms of UVA-induced mutation formation remain a matter of debate. While
pyrimidine dimers are well established to mediate mutation formation with shortwave UVB, other types of
DNA damage, such as oxidative base damage, have long been thought to be the premutagenic lesions for
UVA mutagenesis. However, pyrimidine dimers can also be generated by UVA, and there are several lines
of evidence that these are the most important premutagenic lesions not only for UVB- but also for UVAinduced mutation formation. C→T transition mutations, which are generated by pyrimidine dimers, are
called UV-signature mutations. They cannot be interpreted to be solely UVB-induced, as they are
induced by UVA as well. Furthermore, there is no consistent evidence for a separate UVA-signature
mutation that is only generated with UVA*. We hypothesize that a weaker anti-mutagenic cellular
response, but not a different type of DNA damage, may be responsible for a higher mutation rate per DNA
photoproduct with UVA, as compared with UVB.”
•
Rünger TM1, Kappes UP..Mechanisms of mutation formation with long-wave ultraviolet light
(UVA).Photodermatol, Photoimmunol. Photomed.2008 Feb;24(1):2-10. doi: 10.1111/j.16000781.2008.00319.x.
•
*This lack of “completely separate” UVA and UVB signature mutations seems to illustrate yet another
aspect of dermal/epidermal interactions. JMM
Optical Properties of Skin
PENETRATION OF LIGHT INTO SKIN
Type I Collagen is a Prognosticator of
Skin Damage
• Fluorescence Spectral and (Photo)chemical
Changes are Functions of:
•
•
•
•
Time
Temperature
Age of sample
Previous history
Telopeptides are Non – Helical Portions and the N- and
C- Terminal Ends of the Collagen Molecule
• (a) Telopeptides have an antiparallel β – pleated sheet*
• (b) Telopeptides are high in tyrosine and phenylalanine
residues, low in arginine and (hydroxy)lysine residues**
• (c) Tyrosine residues in favorable position to form dimers,
“excimers” and higher oxidation products**
• (d) Telopeptides (Mainly N- telopeptides) are necessary for
fibrillogenesis
•
•
* D. Helseth et al, Biopolymers 18 3005 – 3014 (1979)
* *A.L. Rubin et al, Science 139 37 – 38 (1963)
Tyrosine Can be Degraded by Thermal
Oxidation or UV radiation. Degraded
Collagen Has Different Fluorescence
Properties than Normal
Spectral Differences in Calf Skin Collagen
Depend on Previous History
Lot# 159 “New” (obtained Feb
2012 and used July 2012)
80
Wavelength (nm) vs Icorr#121
Wavelength (nm) vs Icorr#159
60
40
20
0
300
320
340
360
380
Wavelength (nm)
400
420
440
Corrected Fluorescence Intensity (a.u.)
Corrected Fluorescence Intensity (a.u.)
Lot# 121 (5 years old; kept in
refrigerator in dark at 4o C)
80
60
Wavelength (nm) vs Icorr#159
Wavelength (nm) vs Icorr#121
40
20
0
300
320
340
360
380
Wavelength (nm)
400
420
440
Temperature Dependence of Collagen
Photochemical Fluorescence Fading
• (1) Fluorescent State (radiative) not the same
as the photochemical state (radiationless)
• (2) In general, fluorescence intensity
decreases with temperature with concomitant
increase of photochemical or other
radiationless transistions (e.g. vibration) back
to the ground state.
Effect of Temperature on Fading and
Fluorescence Emission
• Higher Temperatures Favor Photochemical
Reaction (“Fading”) and Disfavor Fluorescence
Emission
• Lower Temperatures Favor Fluorescence
Emission and Disfavor Photochemical Fading
Tyrosine Dimerization to Dityrosine
Decreased in Autoxidized Collagen
• Fresh Collagen was
irradiated with UVC (254
nm) as a function of time.
• Black Dots - “aged”
collagen sample
• White Dots - fresh collagen
sample
•
See O Shimizu Photochem Photobiol 18(3)
123 – 133, 1973
Photodestruction of DOPA Oxidation Product is
Increased in Autoxidized Collagen
• Oxidized Sample “aged”
in dark at 4 C for ~ 5
years was irradiated with
UVC (254 nm) as a
function of time
• Black Dots – “aged”
collagen sample
• White Dots - new
collagen sample
Collagen as a Prognosticator of Skin
Damage
• Fluorescence spectral and photochemical
behavior indicate relative stability. The more the
spectra differ from a “tyrosine – like” spectrum,
the less stable they tend to be.
• Abnormal amounts of certain fluorescent species
(e.g. dityrosine, AGE’s, DOPA oxidation products
can reflect pathological conditions (e.g. diabetes,
skin cancer, collagen vascular diseases)
HOW ARE THE VARIOUS COMPONENTS
ORGANIZED?

The ECM has an organization where ECM structural protein
and polysaccharide components are linked to different cells.


Cells can then sense changes to the ECM.
The main organized components are the adhesive
glycoprotein:
1. Fibronectin
2. Laminin
PROTEOGLYCAN & GAGS
Preliminary Data
• Excess Hyaluronate Does Not Seem to Affect
Collagen Fading Rate.
Possible Reasons:
• Tyrosine is buried in hydrophobic region of telopeptide
• Photochemical reaction involves free radical mechanism
• Collagen/HA molecules are not packed close enough to each
other as they are in skin.
Acknowledgements
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Isaac Willis M.D.
Abrienne M Patta
Natalya Silvestrov
Latoya Freeman
Otega Edukuye
Gina Chu
Many Other Colleagues
• Supported in part by
• DOD Grant # W911NF-10-1-0445 from the US
Army Research Office
• RCMI Grant # 8G12 MD007602 to Morehouse
School of Medicine