The minimal melanogenesis dose/minimal erythema dose ratio declines with increasing skin pigmentation using solar simulator and narrowband ultraviolet B exposure

Narrow-band phototherapy in the treatment of atopic dermatitis: mechanisms of action, methodology of implementation

Phototherapy is widely used to treat various chronic skin diseases. One of the most effective methods of treatment is narrow-band medium-wave ultraviolet radiation with a wavelength of 311 nm (UVB-311). UVB-311 is used for such immune-mediated diseases as atopic dermatitis, psoriasis, vitiligo, mycosis fungoides and others. Despite the fact that the method was developed more than 30 years ago, the exact mechanism of its therapeutic action remains insufficiently studied. To date, most of the effects of UVB-311 are explained by its effect on the immune cells of the skin. This review examines data on the effects on the main molecular targets, including T-lymphocytes, keratinocytes, Langerhans cells, cytokine profile, epidermal barrier proteins. Data on the features of the pathogenetic effect of UVB-311 on the immune mechanisms of pathogenesis in atopic dermatitis were obtained. The issues of dosing by determining the minimum erythemic dose (MED) or skin phototype, methodology of procedures are discussed. Prospects for further study of photobiological aspects of UVB-311 action are determined.

Effects of topical application of different molecular weight marine fish skin collagen oligopeptides on UVB-induced photoaging rat skin

OBJECTIVE

The objective of this work was to develop a peptide production process of the exact molecular weight propitious to topical application for cosmetics and to investigate the effects of enzymolysis-derived peptide on UVB-induced photoaging rat skin.

METHODS

The chum salmon fish skins were hydrolyzed by alkaline protease and neutral protease and spray-dried at different conditions, and three kinds of molecular weight peptide (MFSOP) were obtained. A total of 66 ICR rats (female, 20 ± 1 g) were randomly divided into eleven groups, including the normal, model, and experimental groups. The three kinds of MFSOP were dissolved at different dosages (5‰, 2.5%, and 5%) and then applied on the ICR hairless back skins prior to exposing UVB irradiation of 3000mJ/cm² to them 4 h later. After 8 weeks, the rats were killed and the hair-shaved skins were tested for skin moisture, hyaluronic acid, hydroxyproline, antioxidant activity, and RNA expression.

RESULTS

Three kinds of MFSOP were obtained, with the average molecular weights of 495.16, 1194.00, and 2032.46 Dalton, respectively. The MFSOPs, especially the MFSOP of average molecular weight of 1194.00 Dalton, played an important role in the recovery of the UVB-injured skin tissue in lock in moisture, in antioxidant activity and in promotion in collagen and elastin protein to some extent.

CONCLUSION

MFSOPs, especially MFSOP of average molecular weight of 1194.00 Dalton, derived from enzymolysis are potential materials to apply in cosmetics for the UVB9-induced anti-photoaging activity (lock in moisture, antioxidant activity, and promotion in collagen and elastin protein).

The effect of pre-phototest sun exposure on minimal erythema dose and minimal melanogenic dose among skin phototypes III, IV and V

BACKGROUND

Ethnicity, skin phototype and colour influenced minimal erythema dose (MED). Sun exposure has been postulated to increase MED. We determined immediate pigment darkening dose to UVA (IPDDA), MED and minimal melanogenic dose (MMD) for UVB and UVA, and investigated factors affecting these doses.

METHODS

Skin phototype was determined using Fitzpatrick phototype quiz, DSMII ColorMeter measured skin colours, sun exposure quantified using an index (SEI) and phototest performed with MEDlight-Multitester.

RESULTS

A total of 167 healthy volunteers participated. There were 110 (66%) females and 56 (34%) males; 124 (74.7%) were Malay, 27 (16.3%) Chinese and 14 (8.4%) Indians. One hundred and nine (65.7%) skin phototype IV, 30 (18.1%) phototype III and 27 (16.3%) phototype V. IPDDA ranges from 6 ± 1.5-5.7 ± 1.4 J/cm² . MED-UVB were 96.9 ± 17.6, 124 ± 29.3 and 118.6 ± 27.4 mJ/cm² for phototype III, IV and V, respectively. All MED-UVA were outside the tested dose range of 3.6-11 J/cm² . MMD-UVB were 106 ± 18.2, 134 ± 25.6 and 136 ± 31.1 mJ/cm² while MMD-UVA were 4.1 ± 4.1, 4.9 ± 3.8 and 5.7 ± 3.7 J/cm² respectively for phototypes III, IV and V. MED-UVB, MMD-UVB and MMD-UVA did not depend on skin phototype. Facultative skin whiteness (L*), erythema (E) and melanin content (M) correlated significantly with MED-UVB while constitutive skin colours were significant for L*, yellowness (b*), E and M. Sun exposure did not significantly correlate with MED-UVB and MMDs, however, an inverse relationship with MED-UVB was demonstrated.

CONCLUSION

Minimal erythema doses in our cohort were slightly different from other regional countries. Constitutive and facultative skin whiteness, erythema and melanin content correlated with MED. There was no association between skin phototype and sun exposure with MED or MMD.

Relationship between skin parameters (darkness or thickness) and photoreaction of Chinese Han skin

BACKGROUND

Skin pigmentation and the stratum corneum are the two primary natural factors that protect against UV damage. Although several classification systems exist to quantify the ability of the skin to protect itself from damaging UV radiation, few reports have assessed skin parameters and photoreaction in persons of Han Chinese descent.

AIMS

To understand the relationship between skin darkness, skin thickness, and photoreaction in Chinese Han subjects.

METHODS

Thirty-one subjects were exposed to UVA and UVB. Minimal persistent pigment darkening dose (MPPD) and minimal erythema dose (MED) were obtained. Before the UV irradiation, the test sites were measured by the Mexameter MX 16, Chromameter CR400, and Skin B-ultrasonic to determine skin color and thickness>. Using the ratio of J(MPPD)/J(MED), we classified the subjects into four energy skin phototypes (ESPTs) and the skin parameters for each of these groups were analyzed.

RESULTS

Skin color and skin thickness were significantly different among the ESPTs. There was also a significant positive correlation between skin group and the skin color and thickness parameters (b*, melanin index [MI], thickness). As the ESPTs increased from ESPT A to ESPT D, the mean dose to achieve MED increased, while the MPPD decreased.

CONCLUSION

As the ESPTs increased from type A to type D, there was a proclivity to tan rather than burn. Similarly, the skin became darker and thicker as the phototype increased from A to D.