Mexoryl® SX:: A broad absorption UVA filter protects human skin from the effects of repeated suberythemal doses of UVA

There is now considerable evidence that chronic UVA exposure induces damage in animal and human skin; however, little is known about WA protection of human skin. The aim of this study is to evaluate the efficacy of Mexoryl(R) SX, a broad WA absorber (lambda(max) = 345 nm) against UVA-induced changes in human skin. The regimen of UVA exposure (13 weeks with increasing suberythemal doses) induces intense pigmentation with no erythema. Skin hydration and elasticity decrease, whereas total skin thickness, assessed by echography, remains unchanged. Irradiated epidermis reveals a significant thickening of the stratum corneum, an absence of hyperplasia and an increase in the expression of the protective iron-storage protein ferritin. No significant alterations are seen using antisera against type IV collagen or laminin, suggesting that the dermal-epidermal junction (DEJ) is mainly preserved. In dermis, enhanced expression of tenascin is seen just below the DET but type I procollagen, which is localized at the same site, is unaltered. Although we are unable to visualize any changes in elastic network organization using Luna staining or specific antiserum directed against human elastin, we notice an increased deposition of lysozyme or alpha-1 antitrypsin on elastin fibres. Mexoryl(R) SX (5%) efficiently prevents these alterations. Thus, these results suggest that WA photoprotection can prevent early putative alterations leading to photoageing. (C) 1998 Elsevier Science S.A. All rights reserved.