TNFa-TNFRI interaction impairs endothelial calcium signaling and elevates blood pressure in obesity

Abstract

Endothelial dysfunction in small arteries is a hallmark of obesity-induced hypertension. Recent studies show that the formation of peroxynitrite, a reactive nitrogen species, impairs endothelium-dependent vasodilation. It is well known that inflammatory cytokines promote the formation of cellular peroxynitrite. In this regard, tumor necrosis factor-alpha (TNFα) signaling has been proposed as a contributor to endothelial dysfunction in obesity. Notably, the vascular wall has been proposed as a source of TNFα generation in obesity, although the vascular TNFα signaling mechanisms in obesity are unclear. We hypothesized that vascular wall-derived TNFα acts locally to impair endothelial function in obesity. We previously reported that high-fat diet feeding (60% kcal fat) for 14 weeks elevates blood pressure in mice. Flow cytometry and mRNA expression studies indicated an increase in TNFα levels in freshly isolated SMCs from small mesenteric arteries (MAs) of high-fat diet-fed obese mice compared to normal chow-fed control mice. However, TNFα levels in endothelial cells (ECs) from obese mice were not different from those in ECs from control mice. Tamoxifen-inducible SMC-specific TNFα -/- (TNFα SMC -/- ) mice did not show an increase in blood pressure after high-fat diet feeding. However, tamoxifen-inducible EC-specific TNFα -/- (TNFα EC -/- ) mice showed a similar increase in blood pressure after high-fat diet feeding compared to the control mice. Both TNFα SMC -/- and TNFα EC -/- showed a similar increase in body weight after high-fat diet feeding when compared to control mice, suggesting that differences in weight gain did not contribute to lower blood pressure in obese TNFα SMC -/- mice. Together, these results indicated that SMC TNFα plays a critical role in blood pressure elevation in obesity. The pro-inflammatory effects of TNFα occur mainly through TNFα receptor-I (TNFRI) activation. Therefore, we postulated that TNFα released from SMCs acts locally on EC TNFRI. Endothelium-dependent vasodilation to acetylcholine was improved in obese TNFα SMC -/- mice compared to obese control mice. Previous studies showed that decreased Ca 2+ influx through endothelial TRPV4 (transient receptor potential vanilloid 4) channels contribute to blood pressure elevation in obese mice. The activity of TRPV4 channels is also improved in ECs from obese TNFα SMC -/- mice. Treatment with a selective TNFRI signaling inhibitor (R7050, 10 mg/kg, i.p., once a day for 14 days) reduced the blood pressure to normal levels in obese mice but did not affect blood pressure in control mice. R7050 treatment also restored endothelium-dependent dilation of MAs and the activity of TRPV4 channels in ECs. Collectively, our findings indicate that vascular TNFα impairs endothelial calcium signaling and elevates blood pressure in obesity, highlighting the role of SMCs as a source of TNFα in obesity This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.