Blockade of interleukin-6 receptor attenuates apoptosis and modulates the inflammatory response in Mycoplasma pneumoniae infected A549 cells.

OBJECTIVE: To investigate the effect of silencing the interleukin (IL)-6 gene on the induction of inflammation, oxidative stress and apoptosis in Mycoplasma pneumoniae (MP) infected A549 cells and its mechanism of action. METHODS: IL-6 small interfering RNA (siRNA) was synthesized and transfected into A549 cells, which were divided into a blank control group, a negative control group, and an IL-6 siRNA group. The mRNA and protein expression of IL-6 and the protein expression of CyclinD1, Cleaved caspase-3, Bax, B-cell lymphoma 2 (Bcl-2), signal transducer and activator of transcription 3 (STAT3), phosphorylated STAT3 (p-STAT3), matrix metalloproteinase (MMP)-2 and MMP-9 were measured. Besides, cell viability and apoptosis were determined. Additionally, the levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), IL-1ß, IL-8 and tumor necrosis factor (TNF)-α were measured. RESULTS: The mRNA and protein levels of IL-6 in the IL-6 siRNA group were lower than those in the blank and negative control groups (P < 0.05). The IL-6 siRNA group had higher viability but lower apoptosis rate of A549 cells at 24 h, 48 h and 72 h than the blank and negative control groups (P < 0.05). The IL-6 siRNA group had lower protein expression levels of Cleaved caspase-3 and Bax, but higher protein expression levels of CyclinD1 and Bcl-2 than the blank and negative control groups (P < 0.05). The IL-6 siRNA group had lower levels of IL-6, IL-8, TNF-α and MDA, but higher levels of SOD and GSH-PX than the blank and negative control groups (P < 0.05). CONCLUSION: Silencing the IL-6 gene can reduce the MP-induced inflammatory response and oxidative stress of A549 cells, enhance cell viability and inhibit apoptosis. Meanwhile, it was also found that STAT3 expression was inhibited after silencing IL-6 gene expression. Therefore, it is speculated that IL-6 may play a role by regulating STAT3, but its exact molecular biological mechanism still needs to be further explored.