LncRNA-MEG3 Regulates the Inflammatory Responses and Apoptosis in Porcine Alveolar Macrophages Infected with Haemophilus parasuis Through Modulating the miR-210/TLR4 Axis

Haemophilus parasuis (H. parasuis, HPS) can elicit serious inflammatory responses and cause enormous economic loss to swine industry worldwide. However, the factors responsible for systemic infection and inflammatory responses of HPS have not yet been fully clarified. In this study, we found that lncRNA-MEG3 was significantly up-regulated in porcine alveolar macrophages (PAMs) infected with HPS. The gain- and loss-of-function analysis confirmed that lncRNA-MEG3 participated in the inflammatory responses and apoptosis in HPS-infected PAMs, which was assessed via several inflammatory cytokine genes (TNF-α, IL-1β, and IL-6) and apoptotic factors (Bcl-2, Bax, and C-caspase-3). Based on biotin-labeled RNA pull-down assay, we found that lncRNA-MEG3 bound with miR-210 in HPS-infected PAMs. Based on both overexpression and knockdown analysis of lncRNA-MEG3, our results indicated that lncRNA-MEG3 promoted the expression of TLR4 in HPS-infected PAMs. Using dual-luciferase reporter assays, we showed that lncRNA-MEG3 positively regulated the expression of TLR4 gene in HPS-infected PAMs through miR-210 pathway. Taken together, our results indicated that lncRNA-MEG3 participated in the inflammatory responses and apoptosis in HPS-infected PAMs through modulating the miR-210/TLR4 axis. The results from this investigation provided significant information for a novel target to control HPS infection in swine.