Regulation of the MAPK signaling pathway by miR-421-5p in rats under light pollution

The present study aimed to explore the difference in the expression profiles of ovarian microRNA sequences in rats in a light pollution environment and rats in a normal light environment. Rats in the control group were exposed to 12-h light/dark cycles, while rats in the model group were continuously exposed to 24-h light. The ovaries were extracted from the two groups of rats, and Illumina HiSeq 2500 high-throughput sequencing technology was used to detect the differences in microRNA (miRNA) expression among the two groups. Fluorescence quantitative reverse transcription-polymerase chain reaction was used to verify the differential expression of miRNA. The present study was designed to experimentally validate the interaction between miR-421-5p and mitogen-activated protein kinase (MAPK) 7 by using the dual-luciferase reporter system, and to explore the expression of proteins in the MAPK signaling pathway with a lentiviral vector-mediated small hairpin RNA interference against microRNA-421-5p. The expression of 45 miRNAs was significantly different. In total, 13 miRNAs were upregulated, of which 5 miRNA sequences were known and 8 were predicted. Furthermore, 32 miRNAs were down-regulated, of which 11 miRNA sequences were known and 21 were predicted. The results of the luciferase reporter assay confirmed the targeting association between miR-421-5p and MAPK7. The expression levels of MAPK and genes in its downstream signaling pathways, including c-Fos, CREB and c-Myc, were downregulated when miR-421-5p was overexpressed and upregulated when miR-421-5p was silenced. The differential expression of miRNAs may serve an important role in the development of the ovary in a light pollution environment. miR-421-5p may regulate ovarian growth and development by targeting the MAPK signaling pathway in light polluted rat ovaries.