(554.8) TNFα signaling impairs endothelial calcium signaling and elevates blood pressure in obesity

Poster Board Number: E56

Maniselvan Kuppusamy (University of Virginia), Matteo Ottolini (University of Virginia), Zdravka Daneva (University of Virginia), Yen-Lin Chen (University of Virginia), Swapnil Sonkusare (University of Virginia)

Endothelial dysfunction in small arteries is a hallmark of obesity-induced hypertension. Recent studies show that endothelial upregulation of inducible nitric oxide synthase (iNOS) and NADPH oxidase 1 (NOX1) plays a critical role in obesity-induced endothelial dysfunction. Endothelial upregulation of iNOS and NOX1 results in excessive formation of peroxynitrite, a reactive nitrogen species, which impairs endothelium-dependent vasodilation. It is well-known that inflammatory mediators elevate cellular iNOS, NOX1, and peroxynitrite levels. In this regard, tumor necrosis factor alpha (TNFa) signaling has been proposed as a key contributor to endothelial dysfunction in obesity. Notably, vascular smooth muscle cells (SMCs) were shown to generate TNFa in heart failure and diabetes. Therefore, we hypothesized that vascular wall-derived TNFa acts locally to impair endothelial function in obesity. Flow cytometry studies showed an increase in TNFa  levels in freshly isolated SMCs from small mesenteric arteries (MAs) of high-fat diet-fed (14 weeks) obese mice compared to normal chow-fed control mice. However, TNFa  levels in endothelial cells (ECs) from obese mice were not different from those in ECs from control mice. The levels of two other cytokines, IL-1b and IL-6, were not different between in SMCs and ECs from normal and obese mice. Additionally, qPCR studies in endothelium-denuded MAs provided further evidence that TNFa expression is increased in SMCs from obese mice compared to control mice. The pro-inflammatory effects of TNFa  are mediated mainly through TNFa  receptor I activation. Treating the obese mice with a selective inhibitor of TNFa  receptor I signaling (R7050, 10 mg/kg, i.p., once a day for 14 days) reduced the blood pressure to normal levels in obese mice, but had no effect on blood pressure in control mice. Treatment with R7050 also abolished obesity-induced increase in iNOS and NOX1 expression in endothelial cells. Further, R7050 administration restored acetylcholine-induced, endothelium-dependent vasodilation of MAs in pressure myography experiments. Previous studies showed that a decrease in Ca2+ influx through endothelial transient receptor potential vanilloid 4 (TRPV4) channels contributes to blood pressure elevation in obese mice. Notably, R7050 administration restored the Ca2+ influx signals through endothelial TRPV4 channels in MAs, as studied using high-speed confocal Ca2+ imaging. Collectively, our findings indicate that TNFa  signaling contributes to the impairment of endothelial calcium signaling and blood pressure elevation in obesity, and highlight the role of SMCs as a source of TNFa in obesity.

This work was supported by grants from the NIH to SKS (HL146914 and HL142808).