Tumor Necrosis Factor-alpha (TNF-α) Enhances miR-155-Mediated Endothelial Senescence by Targeting Sirtuin1 (SIRT1)
Qianyun Guo, Haitong Zhang, Bin Zhang, Erli Zhang, Yongjian Wu
State Key Laboratory of Cardiovascular Disease, Department of Cardiology, Fuwai Hospital, National Center of Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (mainland)
Med Sci Monit 2019; 25:8820-8835
Available online: 2019-11-21
Sirtuin1 (SIRT1) participates in a wide variety of cellular processes, but the molecular mechanism remains largely unknown. miR-155 is an element of the inflammatory signaling pathway in atherosclerosis. Therefore, we tested the hypothesis that TNF-alpha stimulates miR-155 to target SIRT1 and thereby regulates endothelial senescence, and we also explored the function of miR-155 as a regulator of cardiovascular diseases.
MATERIAL AND METHODS: TNF-alpha was used to stimulate human umbilical vein endothelial cells (HUVECs), after which protein and gene expression were assessed via Western blotting and RT-qPCR. miR-155 targeting of SIRT1 was confirmed via luciferase reporter assays, while MTT and senescence-associated ß-galactosidase (SA-ß-gal) assays were used for quantifying cellular proliferation and senescence.
RESULTS: We found that miR-155 was upregulated in response to TNF-alpha treatment, in addition to inducing marked changes in SIRT1/FoxO-1/p21 pathway protein level. When we overexpressed miR-155 mimics, SIRT1 was markedly reduced, whereas miR-155 inhibition had the opposite effect in TNF-alpha-treated cells. We additionally confirmed that miR-155 was able to directly bind to SIRT1 3’-UTR, and that inhibition of miR-155 reduced the ability of TNF-alpha to induce senescence in HUVECs, thereby leading to their enhanced proliferation.
Simvastatin was associated with suppression of miR-155 expression in HUVECs following TNF-alpha treatment, and with a corresponding reduction in TNF-alpha-induced senescence, whereas miR-155 overexpression had the opposite effect.
CONCLUSIONS: Our findings suggest that TNF-alpha upregulates miR-155, which then targets SIRT1, suppressing its expression and driving HUVEC apoptosis. Simvastatin disrupted this senescence mechanism via the miR-155/SIRT1/FoxO-1/p21 pathway signaling. Hence, miR-155 is a possible therapeutic approach to endothelial senescence in the development of cardiovascular diseases.
Keywords: atherosclerosis, endothelial cells, sirtuin 1, Tumor Necrosis Factor-alpha