MicroRNA-124-3p attenuates severe community-acquired pneumonia progression in macrophages by targeting tumor necrosis factor receptor-associated factor 6

Abstract

Community-acquired pneumonia (CAP) is a severe type of pneumonia in adults, with a high mortality rate. Macrophages have been reported to mediate severe CAP (SCAP) in vitro following administration of LPS. Therefore, the present study established a SCAP model in Ana-1 macrophages by lipopolysaccharide (LPS) induction, and aimed to explore the function of microRNA (miR)-124-3p in the LPS-induced SCAP. The effect of LPS on Ana-1 cell viability was evaluated by an MTT assay. In addition, the protein and mRNA levels of interleukin (IL)-1β and tumor necrosis factor (TNF)-α were determined by enzyme-linked immunosorbent assay and reverse transcription-quantitative polymerase chain reaction, respectively. The nuclear factor (NF)-κB activity and phosphorylation of p38 mitogen-activated protein kinase (MAPK) were also evaluated by western blotting. The results demonstrated that exposure to 0.1 µg/ml LPS displayed no evident toxicity on macrophages. Compared with the control group, higher TNF receptor-associated factor 6 (TRAF6) mRNA and protein levels were observed subsequent to induction by LPS (0.1 µg/ml), suggesting the promoting role of TRAF6 in SCAP. Furthermore, miR-124-3p was proven to target the 3'-untranslated region (3'UTR) of TRAF6. The miR-124-3p mimic effectively inhibited the LPS-induced upregulation of IL-1β and TNF-α secretion, and mRNA expression levels in macrophages, which may be mediated by the p38 MAPK and NF-κB signaling pathway. Taken together, these results strongly indicated that miR-124-3p targeted the 3'UTR of TRAF6, while it attenuated SCAP by reducing LPS-induced inflammatory cytokine production and inhibiting the activation of p38 MAPK and NF-κB signaling pathways. These findings indicate the immunoregulatory role of miR-124-3p against macrophage-mediated SCAP.