Exosomal miR-132-3p from mesenchymal stem cells alleviated LPS-induced acute lung injury by repressing TRAF6

Exosomes isolated from mesenchymal stem cells (MSC) had shown beneficial effect on acute lung injury (ALI). However, the effective components in MSC-derived exosomes need further investigation. ALI mice model was established by lipopolysaccharide (LPS) injection. In vitro inflammatory model was established by LPS stimulation of MLE-12 cells. The cell proliferation was evaluated by EdU assay. TUNEL and Annexin V/PI were applied to evaluate the apoptosis of tissue and cell respectively. HE staining was performed to evaluate the lung injury. Transmission electronic microscope was used to observe isolated exosomes. Level of cytokines, MDA, KGF were determined by ELISA kit. Direct interaction of miR-132-3p and TRAF6 were verified by dual luciferase assay. The level of mRNA or proteins were determined by qRT-PCR or western blots respectively. TRAF6 was upregulated while miR-132-3p was downregulated in LPS-stimulated ALI model. MiR-132-3p negatively regulated TRAF6 by direct binding. MiR-132-3p potentiated proliferation and suppressed apoptosis of LPS-induced MLE-12 cells at least partly dependent on targeting TRAF6. Treatment of exosome alleviated the LPS-induced ALI in mice and LPS-induced inflammatory response in MLE-12 cells. Moreover, overexpression of miR-132-3p promoted the protective effect of exosomes in LPS-induced MLE-12 cells injury and LPS-induced ALI. Mechanically, it was suggested that miR-132-3p inactivated PI3K/Akt signalling via targeting TRAF6. In the present study, our results indicated that miR-132-3p mediated protective effect of MSC-derived exosomes on LPS-induced ALI. Exosomal miR-132-3p ameliorated LPS-induced ALI via targeting TRAF6 and inactivating PI3K/Akt signalling.