miRNA‐138‐5p suppresses cigarette smoke‐induced apoptosis in testicular cells by targeting Caspase‐3 through the Bcl‐2 signaling pathway

Abstract Long‐term cigarette smoking (CS) can cause testicular toxicity, which interferes with normal spermatogenesis and leads to male infertility. One possible mechanism for this is the activation of the apoptosis signaling pathway, which leads to the irreversible apoptosis of testicular cells. However, the exact mechanism for this is not completely understood. Cell viability, cell apoptosis, and lactate dehydrogenase release assays were performed to elucidate the function of micro RNA (miRNA) in the pathogenesis of male testicular cell injury induced by CS. The results suggested that testicular cell injury was associated with CS both in vitro and in vivo. CS extract (CSE)‐treated Leydig and Sertoli cells showed noticeable apoptosis. Based on the results of Agilent miRNA microarray and bioinformatics analyses, miRNA‐138‐5p was used in subsequent experiments. Quantitative polymerase chain reaction and Western blot assays showed a negative correlation between miR‐138‐5p and Caspase‐3 expression. Transfection of miR‐138‐5p mimic significantly inhibited apoptosis and downregulated the expression of Caspase‐3 in TM3 and TM4 cells. Furthermore, a dual‐luciferase reporter assay demonstrated that miR‐138‐5p directly targeted Caspase‐3 to regulate the apoptosis of testicular cells mediated by CSE. In addition, overexpression of miR‐138‐5p markedly downregulated the expression of p53 and Bak, which played critical roles in the Bcl‐2 pathway. These results demonstrate that miRNA‐138‐5p inhibits CS‐induced apoptosis in testicular cells by targeting Caspase‐3 through the Bcl‐2 signaling pathway.