miR-9 targeting RUNX1 improves LPS-induced alveolar hypercoagulation and fibrinolysis inhibition through NF-KB inactivation in ARDS

Background: Acute respiratory distress syndrome (ARDS) is a clinical and pathophysiological complex syndrome with high mortality. Alveolar hypercoagulation and fibrinolytic inhibition constitute the core part of the path-ophysiology of ARDS. miR-9 (microRNA-9a-5p) plays an important role in the pathogenesis of ARDS, but whether it regulates alveolar pro-coagulation and fibrinolysis inhibition in ARDS remains to be elucidated. We aimed to determine the contributing role of miR-9 on alveolar hypercoagulation and fibrinolysis inhibition in ARDS.Methods: In the ARDS animal model, we first observed the miR-9 and runt-related transcription factor 1 (RUNX1) expression in lung tissue, the effects of miR-9 on alveolar hypercoagulation and fibrinolytic inhibition in ARDS rats, and the efficacy of miR-9 on acute lung injury. In the cell, alveolar epithelial cells type II (AECII) were treated with LPS, and the levels of miR-9 and RUNX1 were detected. Then we observed the effects of miR-9 on procoagulant and fibrinolysis inhibitor factors in cells. Finally, we explored whether the efficacies of miR-9 were associated with RUNX1; we also preliminarily examined the miR-9 and RUNX1 levels in plasma in patients with ARDS.Results: In ARDS rats, miR-9 expression decreased, but RUNX1 expression increased in the pulmonary tissue of ARDS rats. miR-9 displayed to attenuate lung injury and pulmonary wet/dry ratio. Study results in vivo demonstrated that miR-9 ameliorated alveolar hypercoagulation and fibrinolysis inhibition and attenuated the collagen III expressions in tissue. miR-9 also inhibited NF-kappa B signaling pathway activation in ARDS. In LPS-induced AECII, the expression changes of both miR-9 and RUNX1 were similar to those in pulmonary tissue in the animal ARDS model. miR-9 effectively inhabited tissue factor (TF), plasma activator inhibitor (PAI-1) ex-pressions, and NF-kappa B activation in LPS-treated ACEII cells. Besides, miR-9 directly targeted RUNX1, inhibiting TF and PAI-1 expression and attenuating NF-kappa B activation in LPS-treated AECII cells. Clinically, we preliminarily found that the expression of miR-9 was significantly reduced in ARDS patients compared to non-ARDS patients. Conclusion: Our experimental data indicate that by directly targeting RUNX1, miR-9 improves alveolar hyper -coagulation and fibrinolysis inhibition via suppressing NF-kappa B pathway activation in LPS-induced rat ARDS, implying that miR-9/RUNX1 is expected to be a new therapeutic target for ARDS treatment.