Combination of azithromycin and methylprednisolone alleviates Mycoplasma pneumoniae induced pneumonia by regulating miR-499a-5p/STAT3 axis

Mycoplasma pneumoniae (M. pneumoniae) is a contributing factor to community-acquired pneumonia in children. The present study sought to explain the underlying mechanism of azithromycin (AZM) combined with methylprednisolone (MP) in the treatment of M. pneumoniae infection. Peripheral blood samples were obtained from patients with M. pneumoniae and healthy volunteers for analysis. A549 cells were infected with M. pneumoniae to construct an in vitro cell model with M. pneumoniae, followed by treatment with AZM and MP. Cell Counting Kit-8 and TUNEL assays were conducted to detect cell viability and apoptosis. RT-qPCR was employed to measure the expression levels of microRNA (miR)-499a-5p and STAT3. Western blotting was performed to measure the expression of STAT3 and apoptosis-related proteins. Luciferase report assay was performed to verify the binding site between miR-499a-5p and STAT3. The production of inflammatory cytokines was determined using ELISA kits. The results exhibited the downregulated miR-499a-5p and dysregulated inflammatory cytokines in peripheral blood of patients and M. pneumoniae-infected A549 cells. AZM and MP treatment alone or combined significantly inhibited inflammatory response, cell viability loss and promoted apoptosis in A549 cells infected with M. pneumoniae, which was partly reversed by inhibition of miR-499a-5p. Furthermore, miR-499a-5p could negatively regulate its direct target STAT3. In addition, STAT3 is also regulated by AZM and MP. Collectively, the present results suggested that combination treatment of AZM and MP could inhibit M. pneumoniae infection-induced inflammation, cell viability loss and promoted apoptosis partly by regulating miR-499a-5p/STAT3 axis.