The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin.

BACKGROUND: alpha-Hydroxy acids (alphaHAs) are reported to reduce signs of aging in the skin and are widely used cosmetic ingredients. Several studies suggest that alphaHA can increase the sensitivity of skin to ultraviolet radiation. More recently, beta-hydroxy acids (betaHAs), or combinations of alphaHA and betaHA have also been incorporated into antiaging skin care products. Concerns have also arisen about increased sensitivity to ultraviolet radiation following use of skin care products containing beta-HA. OBJECTIVE: To determine whether topical treatment with glycolic acid, a representative alphaHA, or with salicylic acid, a betaHA, modifies the short-term effects of solar simulated radiation (SSR) in human skin. METHODS: Fourteen subjects participated in this study. Three of the four test sites on the mid-back of each subject were treated daily Monday-Friday, for a total of 3.5 weeks, with glycolic acid (10%), salicylic acid (2%), or vehicle (control). The fourth site received no treatment. After the last treatment, each site was exposed to SSR, and shave biopsies from all four sites were obtained. The endpoints evaluated in this study were erythema (assessed visually and instrumentally), DNA damage and sunburn cell formation. RESULTS: Treatment with glycolic acid resulted in increased sensitivity of human skin to SSR, measured as an increase in erythema, DNA damage and sunburn cell formation. Salicylic acid did not produce significant changes in any of these biomarkers. CONCLUSIONS: Short-term topical application of glycolic acid in a cosmetic formulation increased the sensitivity of human skin to SSR, while a comparable treatment with salicylic acid did not.

The polyhydroxy acid gluconolactone protects against ultraviolet radiation in an in vitro model of cutaneous photoaging.

BACKGROUND: Ultraviolet (UV) radiation damages skin through a variety of mechanisms, including the generation of free radicals. Gluconolactone is a polyhydroxy acid (PHA) that is capable of chelating metals and may also function by scavenging free radicals, thereby protecting skin from some of the damaging effects of UV radiation. OBJECTIVE: This study measured the ability of gluconolactone to protect against UV radiation-induced damage. METHODS: The ability of gluconolactone to prevent UV radiation-induced elastin promoter activation was determined in vitro using a transgenic model of cutaneous photoaging. Gluconolactone was also evaluated to determine its ability to promote the formation of sunburn cells in human skin after exposure to UV radiation. RESULTS: Gluconolactone provided up to 50% protection against UV radiation, as measured in our in vitro system, and did not significantly increase sunburn cells in human skin. CONCLUSIONS: These results demonstrate the ability of the PHA gluconolactone to protect against UV radiation-induced elastin promoter activation. In addition, in vivo studies demonstrated that gluconolactone treatment does not result in a significant increase in sunburn cells. Further investigation of this and other PHAs is necessary to identify their potential role in preventing and repairing cutaneous photodamage.

Topical glycolic acid enhances photodamage by ultraviolet light.

BACKGROUND: Alpha-hydroxy acids (AHAs) are widely used as ingredients in cosmetics. Several studies suggest that AHAs can increase the sensitivity of skin to ultraviolet (UV) light. PURPOSE: This study was performed in order to determine whether short-term dermal treatment with glycolic acid, a representative AHA, can enhance the damaging effects of UV light. The duration of the effect of AHAs on the sensitivity of skin to UV light was also examined. METHODS: The backs of 29 Caucasian subjects were treated, once daily, 6 days per week with either 10% glycolic acid (pH 3.5) or placebo in a randomized double-blinded study. At the end of 4 weeks, sites within each treated area were exposed to 1.5 MED of UV light, determined on previously untreated skin. Specimens were obtained for enumeration of sunburn cells (SBCs) in the first group of subjects (n = 16), whereas cyclobutyl pyrimidine dimers (CPDs) in DNA were determined in the second group (n = 13). The minimal erythema dose (MED) in each site was also determined in the first group of subjects. Sunburn cells and MEDs were re-evaluated in the first group 1 week after discontinuing AHA applications. RESULTS: Glycolic acid caused enhanced sensitivity to UV light measured as increased SBC induction and lowered MEDs. Cyclobutyl pyrimidine dimers were elevated but not to a statistically significant level. No differences in SBCs or MEDs were evident after a week of discontinued treatments. CONCLUSION: Short-term application of 10% glycolic acid sensitizes the skin to the damaging effects of UV light. This photosensitivity is reversed within a week of terminating treatments.

Safety studies of topical imiquimod 5% cream on normal skin exposed to ultraviolet radiation.

BACKGROUND: Imiquimod 5% topical cream is an immune response modifier that induces interferon alpha and interleukin-12, and exhibits antiviral and tumor-inhibiting properties. It is currently available for treatment of genital and perianal warts. Three randomized, open-label or assessor-blinded, placebo-controlled studies were carried out to assess its safety on normal white skin exposed to ultraviolet radiation (UVR). METHODS: Healthy white volunteer adult subjects between the ages of 18 and 60 years with skin types I, II or III (Fitzpatrick Scale, US Federal Register 43:38260, 1978) were invited to participate. Imiquimod 5% cream (each dose approximately 0.1-0.2 ml) was compared with placebo cream. Two preliminary studies assessed the potential photosensitizing properties of the drug, and the third study added measurement of sunburn cell counts (SBC) and deoxyribonucleic acid (DNA) pyrimidine dimer (PD) formation. The three studies were: a 6-week standard photocontact allergenicity bioassay; a 4-day standard phototoxicity bioassay; and a 4-week photodamage study using biopsy sample analyses to determine SBC or PD frequency. RESULTS: Imiquimod had no detectable potential for inducing either photocontact allergy (n=115) or phototoxicity (n=20). The final study further assessing photodamage potential of imiquimod included 44 subjects. There were no significant differences between imiquimod vs. the control (no drug+UVB) for SBC counts (mean 0.88 vs. 0.93), or PD frequency (mean 60.86 vs. 70.03). CONCLUSIONS: Results from the two preliminary safety studies suggest that imiquimod 5% cream does not possess a detectable photosensitizing potential in humans. Furthermore, topical imiquimod did not enhance UVR-induced damage to epidermal cells or DNA.

Efeitos do lactato de amônio tópico sobre a atrofia cutânea causada por um corticosteróide tópico potente / Effects of topical ammonium lactate on cutaneous atrophy from a potent topical corticosteroid

Histórico: Os corticosteróides tópicos produzem alteraçöes atróficas na pele, inclusive diminuiçäo da espessura da epiderme e da substância essencial dérmica. Observamos que o lactato de amônio a 12 por cento produziu aumento da espessura da epiderme e aumento na qualidade de glicosaminoglicanos dérmicos. Objetivo: Determinar se o lactato de amônio a 12 por cento poderia minimizar a atrofia cutânea produzida por um corticosteróide tópico potente. Métodos: Ambos, o propionato de clobetasol e o lactato de amônio a 12 por cento, foram aplicados repetidas vezes sob patches oclusivos, bem como em patches abertos nos antebraços de voluntários durante 3 a 4 semanas. As amostras para biópsia foram avaliadas por análise de imagem quanto à espessura da epiderme e quanto à quantidade de glicosaminoglicanos dérmicos. Resultados: O lactato de amônio a 12 por cento atenuou significativamente a atrofia da epiderme e da derme sem nenhuma influência sobre a biodisponibilidade ou sobre as propriedades antiinflamatórias do corticosteróide. Conclusäo: O lactato de amônio a 12 por cento pode ser útil na atenuaçäo dos efeitos adversos do corticosteróide na pele