Abstract
Smoking is highly associated with cardiovascular diseases. However, the effect of nicotine, a key ingredient in smoking products, on cardiomyocyte apoptosis remains controversial. The present study aims to clarify the role of nicotine on cardiomyocyte cell apoptosis and to investigate the underlying mechanism. In the present study, H9C2 cells were exposed to nicotine at various concentrations (0, 10 and 100 µM) for 48 h. Cell Counting Kit‑8 and TUNEL assays were performed to assess cell viability and apoptosis, respectively, and reverse transcription‑quantitative polymerase chain reaction and western blot analysis were used to investigate the mRNA and protein expression. PYR‑41, a ubiquitin E1 inhibitor, was employed to investigate whether the ubiquitin‑proteasome system was involved in the downregulation of Akt. An Akt1 overexpression plasmid was used to demonstrate the role of Akt in H9C2 cells apoptosis. Tetratricopeptide repeat domain 3 (TTC3) small interfering RNA (siRNA) was used to investigate the effect of TTC3 on Akt protein degradation. The results demonstrated that nicotine induced apoptosis in H9C2 cells compared with control cells (P<0.05). The protein level of Akt was downregulated by nicotine in a concentration‑dependent manner (P<0.05). PYR‑41 treatment restored the protein level of Akt. The cell viability was significantly improved by Akt overexpression when cells were exposed to nicotine at 10 µM, compared with control cells. Nicotine also upregulated the level of TTC3 mRNA (P<0.05) and the protein level of Akt, and cell viability was recovered by TTC3 siRNA. In conclusion, the current study demonstrated that nicotine induced H9C2 cell apoptosis via Akt protein degradation, which may be mediated by TTC3.