Circular RNA erythrocyte membrane protein band 4.1 assuages ultraviolet irradiation-induced apoptosis of lens epithelial cells by stimulating 5’-bisphosphate nucleotidase 1 in a miR-24-3p-dependent manner

Apoptosis of lens epithelial cells contributed to the formation of age-related cataract (ARC), and previous data revealed that circular RNA (circRNA) was responsible for the underneath mechanism. The study was organized to explore the role of circular RNA erythrocyte membrane protein band 4.1 (circ_EPB41) in ultraviolet (UV) irradiation-induced apoptosis of lens epithelial cells. SRA01/04 cells were irradiated with UV to mimic the ARC cell model. The RNA levels of circ_EPB41, microRNA-24-3p (miR-24-3p), and 3ʹ(2ʹ), 5ʹ-bisphosphate nucleotidase 1 (BPNT1) were detected by quantitative real-time polymerase chain reaction. Protein expression was checked by western blot. 5-Ethynyl-29-deoxyuridine, 3-(4,5-Dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide and DNA content quantitation assays were performed to investigate cell proliferation. Flow cytometry was conducted to analyze cell apoptosis. Dual-luciferase reporter assay was implemented to confirm the interaction among circ_EPB41, miR-24-3p, and BPNT1. Our data showed that circ_EPB41 and BPNT1 expression were downregulated in ARC tissues and UV-irradiated SRA01/04 cells as compared with normal anterior lens capsules and untreated SRA01/04 cells. Circ_EPB41 overexpression ameliorated the effects of UV irradiation on the proliferation and apoptosis of SRA01/04 cells. Besides, miR-24-3p, a target miRNA of circ_EPB41, attenuated circ_EPB41 introduction-mediated proliferation, and apoptosis of UV-irradiated SRA01/04 cells. MiR-24-3p regulated UV irradiation-induced effects by targeting BPNT1. Importantly, it was found that circ_EPB41 stimulated BPNT1 production by miR-24-3p. Taken together, the enforced expression of circ_EPB41 ameliorated UV irradiation-induced apoptosis of lens epithelial cells by miR-24-3p/BPNT1 pathway, providing us with a potential target for the therapy of UV-caused ARC.晶状体上皮细胞凋亡参与年龄相关性白内障（age-related cataract, ARC）的发生发展，既往研究表明环状RNA（circular RNA, circRNA）在其潜在病理机制中发挥关键调控作用。本研究旨在探讨环状红细胞膜蛋白带4.1（circ_EPB41）在紫外线（ultraviolet, UV）照射诱导的晶状体上皮细胞凋亡中的作用。本研究采用UV照射SRA01/04细胞以构建年龄相关性白内障细胞模型，通过实时荧光定量聚合酶链反应检测circ_EPB41、微小RNA-24-3p（miR-24-3p）及3'(2'),5'-二磷酸核苷酸酶1（BPNT1）的RNA水平；采用蛋白质印迹法检测相关蛋白的表达水平。分别通过5-乙炔基-2'-脱氧尿苷实验、3-(4,5-二甲基噻唑-2-基)-2,5-二苯基溴化四氮唑蓝实验及DNA含量定量检测分析细胞增殖能力，采用流式细胞术检测细胞凋亡情况。通过双荧光素酶报告基因实验验证circ_EPB41、miR-24-3p与BPNT1三者间的相互作用。研究结果显示，相较于正常晶状体前囊膜及未接受UV照射的SRA01/04细胞，ARC组织与UV照射后的SRA01/04细胞中circ_EPB41与BPNT1的表达均显著下调。过表达circ_EPB41可缓解UV照射对SRA01/04细胞增殖与凋亡造成的异常影响。此外，作为circ_EPB41的靶微小RNA，miR-24-3p可削弱circ_EPB41过表达介导的对UV照射后SRA01/04细胞增殖及凋亡的调控作用。miR-24-3p可通过靶向BPNT1调节UV照射诱导的细胞效应。进一步研究发现，circ_EPB41可通过miR-24-3p促进BPNT1的表达。综上，过表达circ_EPB41可通过miR-24-3p/BPNT1通路缓解UV照射诱导的晶状体上皮细胞凋亡，为UV诱导的年龄相关性白内障的临床治疗提供了潜在靶点。