MiR-155 enhances phagocytosis of alveolar macrophages through the mTORC2/RhoA pathway.

Alveolar macrophage phagocytosis is significantly reduced in Chronic obstructive pulmonary disease, and cigarette smoke extract is one of the chief reasons for this decrease. Nevertheless, the specific underlying mechanism remains elusive. In this study, the role and possible mechanism of miR-155-5p/mTORC2/RhoA in the phagocytosis of mouse alveolar macrophages (MH-S) were explored. Our results revealed that cigarette smoke extract intervention reduced MH-S cell phagocytosis and miR-155-5p expression. Meanwhile, the dual-luciferase reporter assay validated that Rictor is a target of miR-155-5p. On the one hand, transfecting miR-155-5p mimic, mimic NC, miR-155-5p inhibitor, or inhibitor NC in MH-S cells overexpressing miR-155-5p increased the Alveolar macrophage phagocytotic rate, up-regulated the expression level of RhoA and p-RhoA, and down-regulated that of mTOR and Rictor mRNA and protein. On the other hand, inhibiting the expression of miR-155-5p lowered the phagocytotic rate, up-regulated the expression of mTOR, Rictor mRNA, and protein, and down-regulated the expression of RhoA and p-RhoA, which taken together, authenticated that miR-155-5p participates in macrophage phagocytosis via the mTORC2/RhoA pathway. Finally, confocal microscopy demonstrated that cells overexpressing miR-155-5p underwent cytoskeletal rearrangement during phagocytosis, and the phagocytic function of cells was enhanced, signaling that miR-155-5p participated in macrophage skeletal rearrangement and enhanced alveolar macrophage phagocytosis by targeting the expression of Rictor in the mTORC2/RhoA pathway.