miR-297 Protects Human Umbilical Vein Endothelial Cells against LPS-Induced Inflammatory Response and Apoptosis

Recently, microRNA-297 (miR-297) and signal transducer and activator of transcription 3 (STAT3) have been demonstrated to be involved in dysfunction of vascular endothelial cells and inflammatory conditions, such as sepsis. The present study aimed to investigate the role of miR-297 and STAT3 in lipopolysaccharide (LPS)-induced inflammatory human umbilical vein endothelial cells (HUVECs). HUVECs were stimulated by different concentrations of LPS. miR-297 mimics were transfected into HUVECs to overexpress miR-297. The qRT-PCR was used to measure the expression level of miR-297. Western blot was used to detect the expressions of STAT3, inflammatory cytokines, adhesion molecules and apoptosis-related proteins. Cell apoptosis was determined by flow cytometry. Compared with parental HUVECs, the expression of miR-297 was significantly down-regulated, while the expression of STAT3 was obviously up-regulated in LPS-induced HUVECs. The expressions of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin were also increased in LPS-induced HUVECs than those in parental HUVECs. In addition, LPS induced apoptosis of HUVECs through up-regulation of Bax and cleaved caspase 3 expressions. Conversely, miR-297 mimics inhibited LPS-activated expressions of STAT3, inflammatory cytokines, and adhesion molecules, and protected HUVECs against LPS-induced apoptosis through inhibition of Bax and cleaved caspase 3 expressions. Mechanistically, the 3'-untranslated region (3'-UTR) of STAT3 mRNA was validated as a direct target of miR-297. Over-expression of STAT3 partially abrogated protective effects of miR-297, whereas silencin g of STAT3 contributed to miR-297-mediated biological effects. miR-297 protects HUVECs against LPS-induced inflammatory response and apoptosis by targeting STAT3 pathway. Thus, miR-297 may be a promising therapeutic target for patients with sepsis.