Dual effect of ultraviolet B on cholesterol efflux and regulated by ultraviolet radiation resistance-associated gene-mediated autophagy.

ABSTRACT

OBJECTIVE: In addition to diet and metabolism, the occurrence of foam cells and atherosclerosis are also related to environmental factors. Individual studies have shown that ultraviolet B (UVB) can regulate the progression of atherosclerosis, but with different results. Whether or not UVB has a dual effect on atherosclerosis and what mechanism is involved has not been reported. METHODS: After THP-1-derived foam cells were treated with UVB in different ways, the effects of UVB on foam cells were investigated by western blotting, cholesterol efflux experiment, oil red O staining and other methods. RESULTS: UVB plays a dual role on foam cell formation, and this effect is related to cholesterol efflux. UVB of 50 mJ/cm2 can promote cholesterol efflux in foam cells, while UVB of 200 mJ/cm2 can inhibit cholesterol efflux. UVB induces cholesterol efflux from foam cells in an autophagy-dependent manner, as the beneficial effect of UVB at 50 mJ/cm2 can be reversed by the autophagy inhibitor 3-Methyladenine (3-MA). In addition, silencing the expression of ultraviolet radiation resistance-associated gene (UVRAG) can inhibit autophagy and reduce cholesterol efflux, and overexpressing UVRAG yields the opposite result. CONCLUSION: In conclusion, our research proves that UVB exhibits a dual role in foam cell formation by regulating cholesterol efflux. Further more, we also reveal that UVRAG-mediated autophagy is the underlying mechanism of UVB-induced cholesterol efflux.