The possible mechanisms of simvastatin on apoptosis of lung adenocarcinoma cells

Abstract

Objective: To explore the possible mechanisms of simvastatin-induced apoptosis in lung adenocarcinoma cells. Methods: The experiment was divided into control group (vehicle treated A549 cells), different concentrations (10, 20, 40, 80 mg/L) simvastatin group (simvastatin treated with different concentrations of A549 cells), aspartate specific proteinase (caspase) inhibitor (Z-VAD-FMK) group (50 μmol/L Z-VAD-FMK treated A549 cells), 40 mg/L simvastatin combined with Z-VAD-FMK group (40 mg/L simvastatin combined with 50 μmol/L Z-VAD-FMK co-treated A549 cells), interleukin-6 (IL-6) group (IL-6 acts on A549 cells) and different concentrations (10, 20, 40 mg/L) simvastatin combined with IL-6 group (simvastatin combined with IL-6 act on A549 cells). Cell counting kit-8 (CCK8) method was used to detect the effect on survival rate of lung adenocarcinoma A549 cells; Flow cytometry was used to detect the effect of simvastatin on A549 cell cycle; Mitochondrial membrane potential-1 (JC-1) fluorescent probe was wsed to detect the effect of simvastatin on mitochondrial membrane potential (MMP); Flow-type phosphatidl serine protein antibody Annexin V/propidium iodide (Annexin V-FITC/PI) double staining method was used to detect the effect of simvastatin on A549 cell apoptosis; CCK8 method was used to detect the effect of Z-VAD-FMK on the survival rate of A549 cells; TdT-mediated 2'-deoxyuridine 5'-triphosphate (dUTP) nick end labeling (TUNEL) method was used to detect the effect of Z-VAD-FMK on simvastatin-induced apoptosis in A549 cells; Western blot method was used to detect the effect of simvastatin on the expression levels of Janus kinase 2 and activation of signal transducers and activators of transcription 3 (JAK2/STAT3) pathway-related proteins phosphorylated JAK2 (p-JAK2), JAK2, phosphorylated STAT3 (p-STAT3), and STAT3 before and after the activator IL-6 of JAK2/STAT3 pathway acted on A549 cells. Results: The survival rates of A549 cells in the 20-80 mg/L simvastatin-treated groups were significantly lower than that in the control group (all P<0.05), and gradually decreased with the increase of the concentration of the simvastatin and the extension of the action time. The cells in the G(0)/G(1) phase of the simvastatin group were significantly higher than those in the control group, and the cells in the G(2)/M phase were significantly lower than those in the control group (all P<0.01). The MMP of the treatment group with different concentrations of simvastatin was significantly lower than that of the control group (all P<0.05). The apoptosis rate of the 20 mg/L and 40 mg/L simvastatin-treated group was significantly higher than that of the control group (both P<0.01). The cell survival rate of the 40 mg/L simvastatin group and the 40 mg/L simvastatin combined with Z-VAD-FMK group were (52.2±2.7)% and (57.5±3.8)%, respectively, were lower than that of the control group (100.0±2.7)% (both P<0.01). But the difference between 40 mg/L simvastatin group and the simvastatin combined with Z-VAD-FMK group was not statistically significant (P>0.05). The cell numbers with positive fluorescent staining in the 40 mg/L simvastatin group were significantly more than those in the control group, but the cell numbers with positive fluorescent staining in the 40 mg/L simvastatin combined with Z-VAD-FMK group had no statistical significance compared with the simvastatin group (P>0.05). The specific value of p-JAK2/JAK2 and p-STAT3/STAT3 protein relative expressions in the simvastatin-treated group (20, 40 mg/L) were significantly lower than that in the control group, respectively (both P<0.05). The specific value of p-JAK2/JAK2 and p-STAT3/STAT3 protein relative expressions in IL-6 group were significantly higher than those in control group (both P<0.05), the specific value of p-JAK2/JAK2 and p-STAT3/STAT3 protein relative expressions in simvastatin (20, 40 mg/L) combined with IL-6 groups were lower than those in IL-6 group (all P<0.05), respectively. Conclusion: Simvastatin can induce the apoptosis of A549 cells through a non-caspase-dependent mitochondrial apoptosis pathway, which may be achieved by inhibiting the JAK2/STAT3 pathway.