Endothelial Dysfunction In Small Arteries Research Articles

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

Endothelial dysfunction in small arteries plays a pivotal role in obesity-induced hypertension. Recent investigations have unveiled the detrimental impact of peroxynitrite, a reactive nitrogen species, on endothelium calcium signaling and vasodilation. Vascular inflammation has emerged as a crucial contributor to the pathogenesis of cardiovascular disorders. In this regard, the inflammatory cytokine, tumor necrosis factor (TNF), has been linked to peroxynitrite formation and endothelial dysfunction. Although TNF signaling in cardiovascular disorders is mainly attributed to immune cells, recent studies suggest that endothelial cells (ECs) and smooth muscle cells (SMCs) also produce TNF. We hypothesized that TNF derived from the vascular wall acts locally to inhibit endothelium-dependent vasodilation in obesity. Male C57BL6J mice fed a high-fat diet (HFD, 60% kcal fat) for 14 weeks showed higher blood pressures that normal chow diet (NCD)-fed mice. Flow cytometry and mRNA expression studies showed an increase in TNF levels in freshly isolated SMCs from small mesenteric arteries (MAs) in HFD mice compared to NCD mice. However, TNF levels in ECs were not different between HFD or NCD mice. Control and EC-specific TNF knockout (TNFECKO) mice showed a similar increase in blood pressure after HFD feeding. However, HFD feeding failed to elevate blood pressure in SMC-specific TNF knockout (TNFSMCKO) mice, suggesting a critical role for SMC TNF in blood pressure elevation in HFD mice. Both TNFSMCKO and TNFECKO showed a similar increase in body weight after HFD feeding when compared to control mice, suggesting that differences in weight gain did not contribute to lower blood pressure in obese TNFSMCKO mice. The pro-inflammatory effects of TNF are primarily attributed to TNF receptor-I (TNFRI) signaling. Therefore, we postulated that TNF released from SMCs acts locally on EC TNFRI to impair endothelium-dependent vasodilation. EC-specific TNFRI deletion (TNFRIECKO) reduced blood pressure, whereas SMC-specific TNFRI deletion (TNFRISMCKO) had no effect on blood pressure after HFD feeding. These findings collectively underline the critical role of SMC-derived TNF and endothelial TNFRI in driving blood pressure elevation in diet-induced obesity. Consistent with these data, endothelium-dependent vasodilation in response to acetylcholine markedly improved in obese TNFSMCKO and TNFRIECKO mice compared to obese control mice. Previous studies showed that decreased Ca2+ influx through endothelial TRPV4 (transient receptor potential vanilloid 4) channels contributes to endothelia dysfunction and blood pressure elevation in obese mice. The activity of TRPV4 channels was improved in ECs from HFD-fed TNFSMCKO and TNFRIECKO mice. Additionally, the levels of endothelial peroxynitrite were diminished in obese TNFSMCKO and TNFRIECKO mice, ameliorating the peroxynitrite-dependent impairment of endothelial function. Furthermore, treatment with a selective TNFRI signaling inhibitor (R7050, 10 mg/kg, intraperitoneally, once daily for 14 days) restored blood pressure to normal levels in HFD-fed obese mice but had no effect on the blood pressure in NCD-fed mice. R7050 treatment also restored endothelium-dependent dilation of MAs and the activity of TRPV4 channels in ECs. Collectively, our findings identify a critical role of local TNF-TNFRI signaling in the vascular wall in obesity-induced impairment of endothelial function and blood pressure elevation. The National Institutes of Health to SKS (HL146914, HL142808, and HL147555). This is the full abstract presented at the American Physiology Summit 2024 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.

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

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.

Abstract P134: Tnfα Impairs Endothelial Calcium Signaling And Elevates Blood Pressure In Obesity.

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 (TNFα) signaling has been proposed as a critical contributor to endothelial dysfunction in obesity. Notably, vascular SMCs TNFα levels were increased in heart failure and diabetes. Therefore, we hypothesized that vascular wall-derived TNFα acts locally to impair endothelial function in obesity. Flow cytometry studies showed 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 ECs from obese mice were not different from those in ECs from control mice. The pro-inflammatory effects of TNFα are mediated mainly through TNFα receptor I activation. Treating the obese mice with a selective inhibitor of TNFα receptor I signaling reduced the blood pressure to normal levels in obese mice but did not affect blood pressure in control mice. Treatment with R7050 also abolished the 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 a decrease in Ca 2+ influx through endothelial TRPV4 channels contributes to blood pressure elevation in obese mice. Notably, R7050 administration restored the Ca 2+ influx signals through endothelial TRPV4 channels in MAs, as studied using high-speed confocal Ca 2+ imaging. Our findings collectively indicate that TNFα signaling contributes to the impairment of endothelial calcium signaling and blood pressure elevation in obesity and highlights the role of SMCs as a source of TNFα in obesity

TNFα signaling impairs endothelial calcium signaling and elevates blood pressure in obesity

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.

Endothelial dysfunction in small arteries and early signs\xa0 of atherosclerosis in ApoE knockout rats

Endothelial dysfunction is recognized as a major contributor to atherosclerosis and has been suggested to be evident far before plaque formation. Endothelial dysfunction in small resistance arteries has been suggested to initiate long before changes in conduit arteries. In this study, we address early changes in endothelial function of atherosclerosis prone rats. Male ApoE knockout (KO) rats (11- to 13-weeks-old) were subjected to either a Western or standard diet. The diet intervention continued for a period of 20–24 weeks. Endothelial function of pulmonary and mesenteric arteries was examined in vitro using an isometric myograph. We found that Western diet decreased the contribution of cyclooxygenase (COX) to control the vascular tone of both pulmonary and mesenteric arteries. These changes were associated with early stage atherosclerosis and elevated level of plasma total cholesterol, LDL and triglyceride in ApoE KO rats. Chondroid-transformed smooth muscle cells, calcifications, macrophages accumulation and foam cells were also observed in the aortic arch from ApoE KO rats fed Western diet. The ApoE KO rats are a new model to study endothelial dysfunction during the earlier stages of atherosclerosis and could help us improve preclinical drug development.

Endothelial Nitric Oxide Suppresses Action-Potential-Like Transient Spikes and Vasospasm in Small Resistance Arteries.

Endothelial dysfunction in small arteries is a ubiquitous, early feature of cardiovascular disease, including hypertension. Dysfunction reflects reduced bioavailability of endothelium-derived nitric oxide (NO) and depressed endothelium-dependent hyperpolarization that enhances vasoreactivity. We measured smooth muscle membrane potential and tension, smooth muscle calcium, and used real-time quantitative polymerase chain reaction in small arteries and isolated tubes of endothelium to investigate how dysfunction enhances vasoreactivity. Rat nonmyogenic mesenteric resistance arteries developed vasomotion to micromolar phenylephrine (α1-adrenoceptor agonist); symmetrical vasoconstrictor oscillations mediated by L-type voltage-gated Ca2+ channels (VGCCs). Inhibiting NO synthesis abolished vasomotion so nanomolar phenylephrine now stimulated rapid, transient depolarizing spikes in the smooth muscle associated with chaotic vasomotion/vasospasm. Endothelium-dependent hyperpolarization block also enabled phenylephrine-vasospasm but without spikes or chaotic vasomotion. Depolarizing spikes were Ca2+-based and abolished by either T-type or L-type VGCCs blockers with depressed vasoconstriction. Removing NO also enabled transient spikes/vasoconstriction to Bay K-8644 (L-type VGCC activator). However, these were abolished by the L-type VGCC blocker nifedipine but not T-type VGCC block. Phenylephrine also initiated T-type VGCC-transient spikes and enhanced vasoconstriction after NO loss in nonmyogenic arteries from spontaneously hypertensive rats. In contrast to mesenteric arteries, myogenic coronary arteries displayed transient spikes and further vasoconstriction spontaneously on loss of NO. T-type VGCC block abolished these spikes and additional vasoconstriction but not myogenic tone. Therefore, in myogenic and nonmyogenic small arteries, reduced NO bioavailability engages T-type VGCCs, triggering transient depolarizing spikes in normally quiescent vascular smooth muscle to cause vasospasm. T-type block may offer a means to suppress vasospasm without inhibiting myogenic tone mediated by L-type VGCCs.

Effects of Angiotensin-(1-7) and Angiotensin II on Acetylcholine-Induced Vascular Relaxation in Spontaneously Hypertensive Rats.

Endothelial dysfunction of small arteries occurs in patients with hypertension and in various hypertensive models. Endothelial function is usually evaluated by the degree of acetylcholine- (ACh-) induced vascular relaxation. Our previous study has found that compared to Wistar-Kyoto rats (WKY), ACh-induced vasodilatation was attenuated significantly in the mesenteric artery (MA), coronary artery (CA), and pulmonary artery (PA) of spontaneously hypertensive rats (SHR). This study investigated the influence of angiotensin- (Ang-) (1-7) and Ang II on blood pressure and ACh-induced vascular relaxation, as well as their interactive roles and downstream signal pathways in SHR and WKY. Intravenous injection of Ang II significantly increased, while Ang-(1-7) decreased the mean arterial pressure (MAP) in SHR. Ang-(1-7) improved ACh-induced relaxation in the MA, CA, and PA of SHR, while Ang II further attenuated it, which were inhibited by pretreatment with Mas receptor antagonist A-779 or AT1 receptor antagonist losartan, respectively. Ang-(1-7) decreased the basal arterial tension, and Ang II induced great vasoconstriction in SHR. Pretreatment with Ang-(1-7) inhibited the Ang II-induced pressor response, vasoconstriction, and the effects on ACh-induced relaxation in SHR. AT1 receptor expression was higher, while nitric oxide (NO), cGMP, and protein kinase G (PKG) levels of arteries were lower in SHR than in WKY. Ang II decreased, while Ang-(1-7) increased, the levels of NO, cGMP, and PKG of arteries. In addition, pretreatment with Ang-(1-7) inhibited the Ang II-induced reduction of NO, cGMP, and PKG in SHR. These results indicate that the activation of the Mas receptor by Ang-(1-7) can improve endothelial function and decrease MAP in SHR and inhibit the deteriorative effect of Ang II on endothelial function through the NO-cGMP-PKG pathway.

Endothelial Dysfunction in Small Arteries of Essential Hypertensive Patients

Essential hypertensive patients show a reduced nitric oxide availability secondary to oxidative stress generation in peripheral microcirculation. Cyclooxygenase (COX) contributes to reduce nitric oxide availability. We assessed the possible vascular sources of oxidative stress, including COX-1, COX-2, and nicotinamide adenine dinucleotide phosphate oxidase, as determinants of endothelial dysfunction in small arteries isolated from essential hypertensive patients or normotensive controls. Small arteries were dissected after subcutaneous fat biopsies and evaluated on a pressurized micromyograph. Endothelium-dependent vasodilation was assessed by acetylcholine, repeated under NG-nitro- l -arginine methyl ester, SC-560 (COX-1 inhibitor), DuP-697 (COX-2 inhibitor), ascorbic acid, or the nicotinamide adenine dinucleotide phosphate oxidase inhibitors apocynin or diphenylene iodonium. Vascular oxidative stress generation (fluorescent dihydroethidium), COX-1 and COX-2 expression (Western blot), and localization (immunohistochemistry) were also assessed. In controls, response to acetylcholine was blunted by NG-nitro- l -arginine methyl ester ( P <0.001) and unmodified by SC-560, DuP-697, or ascorbic acid. In hypertensive patients, relaxation to acetylcholine was blunted, resistant to NG-nitro- l -arginine methyl ester or SC-560, and enhanced ( P <0.01) by DuP-697, apocynin, or diphenylene iodonium ( P <0.05). Furthermore, in hypertensive patients, response to acetylcholine was normalized by ascorbic acid or apocynin+DuP-697. Intravascular oxidative stress generation was enhanced in hypertensive patients, decreased ( P <0.01) by DuP-697, partly attenuated by apocynin or diphenylene iodonium, and prevented by ascorbic acid. Enhanced COX-2 expression and localization in the vascular media of hypertensive patients were also detected. In small resistance arteries of essential hypertensive patients, COX-2 is overexpressed and reduces nitric oxide availability. COX-2 represents a major source of oxidative stress generation, whereas nicotinamide adenine dinucleotide phosphate oxidase plays a minor, but significant, role in promoting superoxide generation.

D-4F decreases brain arteriole inflammation and improves cognitive performance in LDL receptor-null mice on a Western diet

LDL receptor-null mice on a Western diet (WD) have inflammation in large arteries and endothelial dysfunction in small arteries, which are improved with the apolipoprotein A-I mimetic D-4F. The role of hyperlipidemia in causing inflammation of very small vessels such as brain arterioles has not previously been studied. A WD caused a marked increase in the percent of brain arterioles with associated macrophages (microglia) (P < 0.01), which was reduced by oral D-4F but not by scrambled D-4F (ScD-4F; P < 0.01). D-4F (but not ScD-4F) reduced the percent of brain arterioles associated with CCL3/macrophage inflammatory protein-1alpha (P < 0.01) and CCL2/monocyte chemoattractant protein-1 (P < 0.001). A WD increased (P < 0.001) brain arteriole wall thickness and smooth muscle alpha-actin, which was reduced by D-4F but not by ScD-4F (P < 0.0001). There was no difference in plasma lipid levels, blood pressure, or arteriole lumen diameter with D-4F treatment. Cognitive performance in the T-maze continuous alternation task and in the Morris Water Maze was impaired by a WD and was significantly improved with D-4F but not ScD-4F (P < 0.05). We conclude that a WD induces brain arteriole inflammation and cognitive impairment that is ameliorated by oral D-4F without altering plasma lipids, blood pressure, or arteriole lumen size.

Cerebral involvement in hypertensive cardiovascular disease

Stroke and dementia in hypertension are the culmination of a complex and largely silent pathogenesis that involves atherosclerosis, vascular remodelling, white matter lesions (WMLs), lacunae and microaneurysms. WMLs in apparently asymptomatic hypertensive persons are associated with incipient cognitive impairment and cardiac hypertrophy. Longitudinal studies have established a link between WMLs and future stoke, and between cognitive decline and hypertension. A small, sustained lowering of systolic/diastolic blood pressure reduces the relative risk of stroke by about 35—40%. A favourable prognosis appears to be not simply a matter of blood pressure control. Angiotensin II receptor blockers are more effective than beta-blockers in reducing the risk for stroke, dementia and left ventricular hypertrophy in hypertensive persons, despite similar reductions in blood pressure. The mechanisms of cognitive decline in hypertension are unclear, but it is known that vascular remodelling and endothelial dysfunction in small arteries are better corrected by blockade of the renin—angiotensin—aldosterone system (RAAS) than by beta-blockade. The role of RAAS blockade in cerebrovascular disease and its prevention will be further investigated in The ONgoing Telmisartan Alone and in combination with Ramipril Global Endpoint Trial (ONTARGET) Trial Programme. © 2003 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved