Phototoxic assessment of a sunscreen formulation and its excipients: An in vivo and in vitro study.

BACKGROUND: Cosmetic preservatives are used to protect cosmetic formulations and improve its shelf-life. However, these substances may exert phototoxic effects when used under sunlight. OBJECTIVE: To assess safety, efficacy and putative phototoxic effects of a sunscreen formulation SPF 30 and its excipients. MATERIALS/METHODS: Irradiation was performed with solar simulated light (SSL) and the sunscreen from the School of Pharmacy/UFRJ/Brazil. We used albino hairless mice in different groups (control (G1), only irradiated (G2), sunscreen plus irradiation (G3) and vehicle plus irradiation (G4) for morphological assessment and immunefluorescence detection to OKL38. In vitro analyses were with a Saccharomyces cerevisiae (SC) strain plus SSL in the presence of methylparaben, propylparaben, imidazolidinyl urea, aminomethyl propanol and their association. RESULTS: G3 and G4 displayed photosensitization leading to thickening of the epidermis and increased dermal cellularity. G4 displayed strong OKL38 labeling when compared with other groups. Aminomethyl propanol, methylparaben and propylparaben are endowed with phototoxic activity against SC. Propylparaben displayed the highest phototoxic effect, followed by excipients association. CONCLUSIONS: The sunscreen's vehicle is endowed with phototoxic activity. Propylparaben was the most phototoxic agent, increasing the overall phototoxicity of excipient association, pointing to a critical concern regarding vehicle associations intended to cosmetic purposes.

Effects of a sunscreen formulation on albino hairless mice: a morphological approach.

The purpose of the study was to evaluate the effects of a sunscreen formulation on the skin of albino hairless mice subjected to simulated solar light (SSL) in terms of morphological changes. Young adult albino hairless mice HRS/J (n = 36) were used as an experimental model for determining skin photoaging changes. Mice were irradiated with SSL, and the sunscreen (estimated SPF 30, PF-UVA) was obtained from the Pharmacy College/UFRJ, Brazil. The animals were divided into four groups: non-treated (G1), radiation only (G2), sunscreen-treated (G3) and vehicle + radiation (G4). Animals from groups G2, G3 and G4 were irradiated weekly (5 weeks), with no immobilization. One week after the final exposure, the dorsal skin was observed using a dermatoscopic camera. Biopsies were analyzed in order to quantify neovascularization and to evaluate histological aspects of the skin. Neovascularization was also evaluated with immunohistochemical reactions for the Von Willebrand factor. Animals from G2 displayed classical morphological changes denoting skin photoaging: thickening of the epidermis, increased dermal cellularity, follicular keratosis, sebaceous gland hyperplasia, and angiogenesis. Animals from groups G3 and G1 displayed similar morphological profiles, without these changes. Animals from group G4 showed more morphological changes than group G2, emphasizing the relative importance of the putative photosensitizing components present in the vehicle formulation. The extent of the morphological skin changes suggested that the sunscreen formulation was effective against SSL, and showed the importance of assessing the phototoxicity of vehicle formulations.

A structural study of the retinal photoreceptor, plexiform and ganglion cell layers following exposure to UV-B and UV-C radiation in the albino rat.

Over the last two decades, ultraviolet radiation levels (UV), reaching the Earth's surface, have been increasing at a rate of 1.5% per each 1% loss of the ozone layer. Moreover, artificial UV-sources have also proliferated and contributed to the rising UV-stress that many organisms have to face. To assess how the vertebrate retina responds to an exposure of short wavelength UV, we focused our attention on the rat retina, observing photoreceptor (containing outer and inner segments of rods and cones), inner plexiform, and ganglion cell layers by light and transmission electron microscopy using conventional and cytochemical techniques. We analyzed how cells of the layers in question responded to a 30 min exposure to UV-C and UV-B radiation with doses of 7200 and 590 J/cm(2), respectively. The results show that there are significant changes in the nuclei and cytoplasmic organelles of the exposed retinae when compared with those of the unexposed controls. The changes include an increase in heterochromatin, distension of rough endoplasmic reticulum, mitochondrial disruptions, and increases in the number of myelin bodies. The recorded morphological changes, especially those of the ganglion cells, are suggestive of apoptotic processes and show that the exposure of vertebrate retina to wavelengths ranging from 254 to 312 nm can produce alterations that are likely to impact negatively on the retina's proper functioning.

Ultrastructural study of first and second order neurons in the visual system of the crab Ucides cordatus following exposure to ultraviolet radiation.

The visual system as an interface between the environment and the living organism can serve as a sensitive indicator especially in studies that deal with effects of radiation. The crab retina as the seat of the photoreceptors and the lamina ganglionaris as the place of second order neurons were the targets of our study. Conventional specimen preparation techniques for transmission electron microscopy (TEM) are adequate to preserve any modifications that may occur as a consequence of the experimental treatment. In this study we analyzed by TEM how retinal and lamina ganglionaris cells of the crab Ucides cordatus responded to a 30 min exposure to ultraviolet C (UV-C) and ultraviolet B (UV-B) radiation with doses of 7200 and 590J/cm(2), respectively. The results show that damaged cells occurred in both retina and lamina ganglionaris, but that the retinal cells were affected to a greater extent. Morphological alterations of the pigment granules and an increase in the quantity of lipid droplets of the retinal cells were also observed. Additional changes include an increase in heterochromatin, nuclear karyolyses and karyorrhexes, distention of rough endoplasmic reticulum and mitochondrial disruptions. The observed morphological changes are indicative of apoptotic processes and show that an exposure to light of wavelengths of 254 and 312 nm may be injurious to the visual system of invertebrates.