Acute lung injury (ALI) and the subsequent acute respiratory distress syndrome remain devastating diseases with high mortality rates and poor prognoses among patients in intensive care units. The present study is aimed at investigating the role and underlying mechanisms of microRNA-31-5p (miR-31-5p) on lipopolysaccharide- (LPS-) induced ALI. Mice were pretreated with miR-31-5p agomir, antagomir, and their negative controls at indicated doses for 3 consecutive days, and then they received a single intratracheal injection of LPS (5 mg/kg) for 12 h to induce ALI. MH-S murine alveolar macrophage cell lines were cultured to further verify the role of miR-31-5p in vitro. For AMP-activated protein kinase α (AMPKα) and calcium-binding protein 39 (Cab39) inhibition, compound C or lentiviral vectors were used in vivo and in vitro. We observed an upregulation of miR-31-5p in lung tissue upon LPS injection. miR-31-5p antagomir alleviated, while miR-31-5p agomir exacerbated LPS-induced inflammation, oxidative damage, and pulmonary dysfunction in vivo and in vitro. Mechanistically, miR-31-5p antagomir activated AMPKα to exert the protective effects that were abrogated by AMPKα inhibition. Further studies revealed that Cab39 was required for AMPKα activation and pulmonary protection by miR-31-5p antagomir. We provide the evidence that endogenous miR-31-5p is a key pathogenic factor for inflammation and oxidative damage during LPS-induced ALI, which is related to Cab39-dependent inhibition of AMPKα.
Transdifferentiation of lung fibroblasts to myofibroblasts is a crucial pathophysiological process in pulmonary fibrosis. MicroRNA-375 (
miR-375
) was initially identified as a tumor-suppressive factor, and its expression was negatively associated with the severity of lung cancer; however, its role and potential mechanism in myofibroblast transdifferentiation and pulmonary fibrosis remain unclear. In the present study, human lung fibroblasts were stimulated with transforming growth factor-β (TGF-β) to induce myofibroblast transdifferentiation. A mimic and inhibitor of
miR-375
, and their negative controls, were used to overexpress or suppress
miR-375
in lung fibroblasts, respectively. The mRNA expression levels of fibrotic markers, and protein expression of α-smooth muscle actin and periostin, were subsequently detected by reverse transcription-quantitative PCR and western blotting, to assess myofibroblast transdifferentiation.
miR-375
was markedly upregulated in human lung fibroblasts after TGF-β stimulation. The
miR-375
mimic alleviated, whereas the
miR-375
inhibitor aggravated TGF-β-dependent transdifferentiation of lung fibroblasts. Mechanistically,
miR-375
prevented myofibroblast transdifferentiation and collagen synthesis by blocking the
P38
mitogen-activated protein kinases (P38) pathway, and P38 suppression abrogated the deleterious effect of the
miR-375
inhibitor on myofibroblast transdifferentiation. Furthermore, the present study revealed that mitogen-activated protein kinase kinase 6 was involved in P38 inactivation by
miR-375
. In conclusion,
miR-375
was implicated in modulating TGF-β-dependent transdifferentiation of lung fibroblasts, and targeting
miR-375
expression may help to develop therapeutic approaches for treating pulmonary fibrosis.
acute lung injury (ali) is a severe lung syndrome with high morbidity and mortality, due to its complex mechanism and lack of effective therapy. The use of placenta-derived mesenchymal stem cells (pMScs) has provided novel insight into treatment options of ali. The effects of pMScs on lipopolysaccharide (LPS)-induced inflammation were studied using a co-culture protocol with lPS-stimulated raW264.7 cells. an lPS-induced ali Sprague-dawley rat model was developed by intravenously injecting 7.5 mg/kg lPS, and intratracheal instillation of 1x10 5 pMScs was performed after administration of lPS to investigate the therapeutic potential of these cells. pMScs ameliorated lPS-induced ali, as suggested by downregulated pro-inflammatory cytokine tumor necrosis factor-α and increased anti-inflammatory cytokine interleukin-10 in both cell and animal models. Moreover, the protein and leukocyte cells in bronchoalveolar lavage fluid decreased at a rapid rate after treatment with pMScs. Histopathology demonstrated that pMScs alleviated the infiltration of inflammatory cells, pulmonary hyperemia and hemorrhage, and interstitial edema. in addition, pMSc reduced the lPS-induced expression of c-X-c motif chemokine ligand 12 in raW264.7 macrophages and in lung tissue of ali rats. This demonstrated that pMScs are therapeutically effective in lPS-induced ali.
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