Nicotine-induced upregulation of miR-132-5p enhances cell survival in PC12 cells by targeting the anti-apoptotic protein Bcl-2.

Objective : Activation of nicotinic acetylcholine receptors (nAChRs) results in neuroprotection via a poorly understood molecular mechanism. In this study, we aimed to investigate the effect of nAChR stimulation with nicotine on the regulation of microRNA (miRNA) expression and identify the molecular pathway involved in neuroprotection. Methods : We conducted miRNA expression profiling using a microarray to identify the miRNAs regulated by nicotine. miR-132-5p expression was validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. Cells were treated with nicotine, a miR-132-5p mimic or its inhibitor, and the cell viability was assessed. CREB, Bcl-2, Bax, cleaved caspase-3, and α-tubulin protein expression levels were determined by Western blotting analysis. Results : Using a rodent miRNA microarray, we identified 37 miRNAs regulated by nicotine. The microarray and RT-qPCR results showed 1.67-fold and 1.5-fold increases in miR-132-5p, respectively, upon nicotine treatment. Immunoblotting revealed a >2-fold increase in phosphorylation of CREB with nicotine, peaking at 4 h. Nicotine treatment of cells increased viability from 35% to 54%, and Bcl-2 immunoreactivity increased by 1.4-fold. Overexpression of miR-132-5p increased cell viability from 38% to 70% and increased Bcl-2 expression by 3.9-fold. Inhibition of miR-132-5p decreased cell viability to 25%, whereas no change was observed in Bcl-2. Bax expression remained unchanged following treatment with a miR-132-5p mimic or its inhibitor. Discussion : Our results suggest that nAChR activation facilitates cell survival by upregulating miR-132-5p, which upregulates the anti-apoptotic protein Bcl-2. These results present miR-132-5p as a potential novel therapeutic target to achieve neuroprotection via stimulation of nAChRs. Abbreviations : CCK-8: Cell counting kit-8; nAChR: Nicotinic acetylcholine receptor; NGF: Nerve growth factor; WST-8: [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt].