Prevention of the ultraviolet effects on clinical and histopathological changes, as well as the heat shock protein-70 expression in mouse skin by topical application of algal UV-absorbing compounds

BackgroundSunscreens have long been used to protect against the acute effects of UV radiation. They can also have protective effects on chronic UV-induced changes, such as photoaging and skin cancer. Recent studies have focused on marine organisms as a source of natural bioactive molecules and some UV-absorbing algal compounds are under investigation as candidates for new natural sunscreens.ObjectiveThe cutaneous photoprotective ability of the mycosporine-like aminoacids (MAAs) Porphyra-334 and shinorine (P-334 + SH), high UV-absorbing compounds isolated from the red alga Porphyra rosengurttii, was evaluated by in vivo procedures in mouse skin. The expression of the heat shock protein HSP70 as a potential biomarker for acute UV damage was also investigated.MethodsA galenic formulation containing the MAA combination of P-334 + SH was applied topically to the dorsal skin of SkhR-1 H hairless mice, which were irradiated with a single UV radiation dose of 3.87 J cm−2 and compared with a combination of UVB- and UVA-absorbing reference filters. Clinical signs of sunburn, such as erythema and edema, as well as other quantifiable histological and biochemical parameters, such as the expression of the heat shock protein 70 and antioxidant enzyme activities, were measured from skin biopsies at 6, 24, 48 and 72 h post-radiation.ResultsThe formulation containing MAA prevented sunburn cell formation, as well as corneum stratum, malphigian, dermal and hypodermal thickening and other structural and morphological alterations observed in biopsies of non-photoprotected skin. A significant increase in Hsp70 was observed in the epidermis of non-photoprotected mouse skin, besides a de novo expression in deeper layers. P-334 + SH protected against the significant decrease in superoxide dismutase and catalase activities observed in non-photoprotected mice.ConclusionThe topical application of P-334 + SH protected against UV-induced skin damage in mice and contributed to maintaining the antioxidant defence system of the skin as well as Hsp70 expression.