Circular RNA HIPK3 regulates human lens epithelial cell dysfunction by targeting the miR-221–3p/PI3K/AKT pathway in age-related cataract

Circular RNA Homeodomain Interacting Protein Kinase 3 (circHIPK3) was found to involve in the pathogenesis of age-related cataract (ARC). Here, we further disclosed the related target genes and molecular mechanism of circHIPK3 in the ARC progression. The expression of circHIPK3, microRNA (miR)-221–3p was detected using the quantitative real-time polymerase chain reaction. Human lens epithelial cell (HLEC) proliferation and apoptosis were measured by 3-(4, 5)-dimethylthiahiazo (-z-y1)-3, 5-di-phenytetrazoliumromide (MTT) assay and flow cytometry, respectively. Western blot was used to detect the levels of apoptosis-related proteins, and phosphoinositide 3-kinase (PI3K)/p-protein kinase B (AKT) pathway-related proteins. Levels of malondialdehyde (MDA) and glutathione peroxidase (GSH-PX) were measured by kits. The interaction between miR-221–3p and circHIPK3 was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assay. CircHIPK3 was down-regulated while miR-221–3p was up-regulated in human lens epithelium samples of ARC patients. CircHIPK3 up-regulation or miR-221–3p down-regulation mediated the promotion of proliferation, inhibition of apoptosis, decrease of MDA level as well as increase of GSH-PX level in HLECs. MiR-221–3p was a target of circHIPK3, and miR-221–3p overexpression reversed the protective action of circHIPK in HLEC functions. In addition, circHIPK3 activated PI3K/AKT pathway via regulating miR-221–3p, and silencing miR-221–3p protected HLECs from dysfunction by activating PI3K/AKT pathway. We demonstrated that circHIPK3 protected HLECs from dysfunction by regulating miR-221–3p/PI3K/AKT pathway, indicating a new insight into the pathogenesis of ARC and providing a potential therapeutic target for ARC.