Protection against UVA damage and effects on neutrophil-derived reactive oxygen species by beta-carotene

Objective: Phagocyte-derived reactive oxygen species (ROS) are involved in microbicidal activities as well as in tissue damage at sites of inflammation. Carotnoids play an important function in protecting cells from oxidant damage. We investigated the in vitro and in vivo effect of 13-cis and 9-cis-beta-carotene on human neutrophils. Methods: Neutrophils from healthy donors in the presence of 0.25 mu mol/L - 1 mu mol/1 beta-carotene and from subjects under beta-carotene supplementation and UVA or UVA/B exposure were stimulated by opsonized zymosan and the generation of ROS was measured by electron spin resonance spectroscopy. Results: Our in vitro results show different effects of the two isomers on stimulated neutrophils. 9-cis-beta-carotene did not produce any change, whereas 13-cis-beta-carotene significantly and concentration-dependent inhibited the ROS generation by stimulated neutrophils. Further, in a controlled study, we were able to demonstrate an in vivo protective effect of beta-carotene on neutrophils against UVA damage by beta-carotene supplemented subjects. Conclusions: beta-carotene preserves the capacity of neutrophils to generate ROS under UVA radiation.