Improved photoprotection in the UVA/visible radiation boundary region is essential to prevent DNA damage, oxidative stress and gene expression changes in human skin

Abstract

Background

Studies have demonstrated the potential for damage caused by exposure to radiation at the UVR/visible border region (380–410 nm) and beyond. This includes potentially mutagenic delayed DNA damage, increased gene expression related to photoageing and inflammation, pigmentation and the production of reaction oxygen species. Photoprotection in this region is limited, with a focus on shorter, more energetic UVR regions.

Objectives

To assess the ability of two sunscreens for their ability to prevent photodamage in the UVA/visible region. Both sunscreens were labelled as SPF 15 and would meet requirements for labelling as UVA protective in the EU and USA. Their ingredients were identical apart from the addition of bis- (diethylaminohydroxybenzoyl benzoyl) piperazine (BDBP), a recently approved organic filter that absorbs between 350 and 425 nm.

Methods

Sunscreens were assessed in vitro in human cell lines and in vivo in healthy human volunteers (Fitzpatrick skin type I–II volunteers). Endpoints were assessed including oxidative stress, gene expression and DNA damage.

Results

The formulation including the new filter provided significantly more protection than the conventional sunscreen for almost all endpoints tested. The conventional formulation provided some protection compared to unprotected skin or placebo control.

Conclusions

This study demonstrates the requirement for improved photoprotection at the UVR-visible border region and the importance of assessing sunscreens across a broader range of wavelengths than currently approved protocols require.