Background The mechanism for ultraviolet A (UVA) involvement in age-related macular degeneration (AMD) is unclear. We examined the levels of autophagy-related proteins and ubiquitination of cell proteins after acute UVA exposure and determined whether UVA causes AMD by affecting autophagy in retinal pigment epithelium (RPE) cells.
Methods Western blotting was used to determine the level of Beclin-1, LC3, and p62 in ARPE-19 cells exposed to UVA. Co-immunoprecipitation was used to detect the ubiquitination of proteins in cells. Cell viability was determined with a CGD1 assay.
Results UVA irradiation increased the level of LC3 and the conversion of LC3-I to LC3-II in ARPE-19 cells within 24 h, inhibition of autophagy by NH4CL reversed the effect of UVA, and suppression of proteasomes by Epoxomicin (EPO) did not enhance the effect of UVA. UVA irradiation did not affect the level of Beclin-1. UVA up-regulated the expression of p62 and the ubiquitination of proteins in cells, especially k63-linked ubiquitination. ARPE-19 cells were lost in a short- time under exposure to UVA.
Conclusion UVA induces autophagy in ARPE-19 cells in a short period, and promotes protein degradation through the autophagy pathway. However, acute UVA irradiation leads to cell death. Therefore, while acute UVA irradiation cannot cause protein degeneration by impairing autophagy in RPE cells, it is still a risk factor for AMD occurrence due to its effect on reducing cells.