Investigation of CUL4B in association with age-related cataract

Age-related cataract (ARC) is the most common reason for visual impairment and blindness in elderly people. Apoptosis of lens epithelial cells is a well-known cellular event in ARC. Cullin-4B (CUL4B) is a core component of the Cullin-RING E3 ligase complex, which plays an important role in various biological processes by mediating the ubiquitination and proteasomal degradation of target proteins. However, the role of CUL4B in ARC is unclear. Therefore, we analyzed CUL4B expression in patients with ARC and in the HLE-B3 cell line and its effects on apoptosis. We extracted total RNA from anterior lens capsules of patients with ARC and from HLE-B3 cells treated with different concentrations of H2O2 to mimic oxidative stress and untreated HLE-B3 cells. We detected CUL4B expression using quantitative real-time PCR (qRT–PCR). We determined cell viability using the WST-1 assay. We performed siRNA transfection to silence CUL4B expression in the cell line. We assessed the protein levels in H2O2-treated and untreated cells, knockdown of CUL4B, and the effect of CUL4B knockdown on protein levels of apoptotic markers Bcl-2, Caspase-3, Bax, and Bid through western blot analysis. CUL4B was downregulated in anterior lens capsules (p<0.0001) and H2O2-treated HLE-B3 cells (p<0.05). CUL4B levels were significantly lower in H2O2-treated HLE-B3 cells than in untreated cells (p<0.01). CUL4B was significantly knocked down at the mRNA (p<0.01) and protein levels (p<0.001) in HLE-B3 cells. Bcl-2 and Caspase-3 were significantly downregulated (p<0.01) in the knockdown group. Together, these findings show that silencing of CUL4B may promote apoptosis in lens epithelial cells. Our study may help understand the role of CUL4B in ARC pathogenesis and treatment.