HucMSC-cm protects lipopolysaccharide-induced acute lung injury by activating AMP-activated protein kinase / 中华急诊医学杂志

ABSTRACT

Objective:To investigate the protective effect of human umbilical cord mesenchymal stem cell conditioned medium (HucMSC-cm) against lipopolysaccharide (LPS)-induced acute lung injury (ALI) and relevant mechanism of action.Methods:Forty 6-week-old male C57BL/6 mice were selected and randomized (random number) into the sham group, LPS group, LPS + HucMSC-cm (LPS+cm) group, and LPS+HucMSC-cm+Compound C (LPS+cm+cc) group, with 10 mice in each group. Mice were intratracheally injected with LPS (5 mg/kg) to establish ALI model, and intratracheally injected with hucMSC-CM (50 μL) 4 h after LPS treatment. Mice in the LPS+cm+cc group were intraperitoneally treated with Compound C (15 mg/kg) prior to LPS treatment. Neutrophils in peripheral blood were counted with the automated hematology analyzer 72 h after LPS administration. After that, mice were sacrificed, and the lung tissue pathology was observed using hematoxylin eosin (HE) staining. Besides, the expressions of IL-6, ICAM-1, VCAM-1 and P-AMP-activated protein kinase (P-AMPK) in the lung tissues were analyzed by Western blot and immunohistochemical assay. In vitro, human lung microvascular endothelial cells (HuLEC-5a) were cultured and divided into three groups control group, LPS group (10 μg/ mL), and LPS + HucMSC-cm group. After 24 h of treatment, the expressions of p-AMPK and AMPK were detected by Western blot, and the expressions of IL-6 and IL-8 were detected by real-time fluorescence quantitative PCR. Oneway analysis of variance was used to compare the mean values of normally distributed measurement data between groups. Comparisons between two groups were performed using the Tukey’s multiple comparison test. Results:Compared with the sham group, the LPS group showed lungs with congestion and swelling, thickened pulmonary septum, and inflammatory cell infiltration. Moreover, in the LPS group, the protein expressions of IL-6 ( P=0.003), ICAM-1 ( P<0.001) and VCAM-1 ( P=0.001) were increased significantly, while the expression of p-AMPK was decreased ( P=0.013), accompanied by an increase in the proportion of neutrophils in peripheral blood ( P<0.001). Compared with the LPS group, the LPS+HucMSC-cm group demonstrated eased congestion, edema and pathological injury of lung tissue, reversed protein expressions of IL-6 ( P=0.003), ICAM-1 ( P=0.002), VCAM-1 ( P=0.006) and P-AMPK ( P=0.002), as well as decreased proportion of neutrophils in peripheral blood ( P<0.005). Compared with the LPS+HucMSC-cm group, the LPS+cm+cc group exhibited more severe lung histopathological injury, significantly increased protein expressions of IL-6, ICAM-1 and VCAM-1 in lung tissues, as well as decreased expression of P-AMPK protein. The results of immunohistochemistry were consistent with those of protein. In vitro experiment, after LPS treatment, the mRNA expressions of IL-6 ( P<0.001) and IL-8 ( P=0.027) were increased and p-AMPK protein expression ( P=0.005) was decreased as compared with the control group. In comparison with the LPS group, the LPS+HucMSC-cm group showed decreased mRNA expression levels of IL-6 ( P=0.003) and IL-8 ( P=0.002), but increased protein level of p-AMPK ( P=0.003). Conclusions:HucMSC-cm has a protective effect against LPS-induced acute lung injury, which is mainly attributed to the inhibited expression of adhesion molecules and inflammatory factors under the activation of AMPK.