Mesenteric Artery Endothelial Function Research Articles

Acute vasopressin neutralization improves cardiac function in rats with chronic heart failure

Vasopressin is one of the leading pathophysiological drivers of chronic heart failure (CHF) acting via V1a-, V1b- and V2 receptors. Selective V2 and dual V1a-V2 receptor antagonists increases plasma sodium levels, but failed to reduce mortality in clinical studies. Vasopressin neutralization is an original alternative to receptor blockers but its effect in CHF is unknown. For this purpose, we investigated the short-term cardiac and vascular effects of the vasopressin neutralizing aptamer NOX-F37. Left ventricular (LV) function (hemodynamic by LV catheterization) and LV tissue perfusion (MRI) as well as mesenteric artery endothelial function (flow-mediated dilation by arteriography) were determined 2 hours after NOX-F37 administration (80 nM/kg; IP) to rats with CHF induced by left coronary artery ligation. Two hours after administration, NOX-F37 improved LV systolic function, illustrated by the increase in LV end-systolic pressure volume relationship (CHF: 20.2 ± 0.0.7; CHF + NOX: 23.3 ± 1.0 mmHg/RVU; P < 0.05) and diastolic function, illustrated by the decrease in LV end-diastolic pressure volume relationship (CHF: 4.03 ± 0.48; CHF + NOX: 2.06 ± 0.21 mmHg/RVU; P < 0.01), together with an increase in LV tissue perfusion (CHF: 6.12 ± 0.24; CHF + NOX: 10.10 ± 0.26 ml/min/g LV tissue; P < 0.001). However, mesenteric artery flow-induced dilatation was not improved (% dilatation at 150 μL/min; CHF: 10 ± 7; CHF + NOX: 9 ± 8). These results illustrate the immediate beneficial effects of vasopressin neutralization on cardiac function in CHF, confirming the existence of a deleterious vasopressinergic tone in this pathophysiological context. Investigations still needed to evaluate the persistence of effects of vasopressin neutralization over time during chronic and could contribute to the resolution of acute heart failure.

SGLT2 inhibition attenuates arterial dysfunction and decreases vascular F-actin content and expression of proteins associated with oxidative stress in aged mice

Aging of the vasculature is characterized by endothelial dysfunction and arterial stiffening, two key events in the pathogenesis of cardiovascular disease (CVD). Treatment with sodium glucose transporter 2 (SGLT2) inhibitors is now known to decrease cardiovascular morbidity and mortality in type 2 diabetes. However, whether SGLT2 inhibition attenuates vascular aging is unknown. We first confirmed in a cohort of adult subjects that aging is associated with impaired endothelial function and increased arterial stiffness and that these two variables are inversely correlated. Next, we investigated whether SGLT2 inhibition with empagliflozin (Empa) ameliorates endothelial dysfunction and reduces arterial stiffness in aged mice with confirmed vascular dysfunction. Specifically, we assessed mesenteric artery endothelial function and stiffness (via flow-mediated dilation and pressure myography mechanical responses, respectively) and aortic stiffness (in vivo via pulse wave velocity and ex vivo via atomic force microscopy) in Empa-treated (14 mg/kg/day for 6 weeks) and control 80-week-old C57BL/6 J male mice. We report that Empa-treated mice exhibited improved mesenteric endothelial function compared with control, in parallel with reduced mesenteric artery and aortic stiffness. Additionally, Empa-treated mice had greater vascular endothelial nitric oxide synthase activation, lower phosphorylated cofilin, and filamentous actin content, with downregulation of pathways involved in production of reactive oxygen species. Our findings demonstrate that Empa improves endothelial function and reduces arterial stiffness in a preclinical model of aging, making SGLT2 inhibition a potential therapeutic alternative to reduce the progression of CVD in older individuals.Graphical abstract

Empagliflozin, a sodium-glucose cotransporter inhibitor, improved heart remodeling and mesenteric artery endothelial function in the metabolic syndrome with HFpEF ZSF1 rat: Role of cyclooxygenases

Empagliflozin (EMPA), a selective SGLT2 inhibitor, significantly reduced cardiovascular mortality and hospitalization for heart failure in patients with type 2 diabetes at high cardiovascular risk, but the protective mechanisms remain unclear. This study evaluates the effect of EMPA on the endothelial function, and the heart structure and function in an experimental model of metabolic syndrome with HFpEF, the ZSF1 rat, and its lean control (Ctrl). Rats received either the control diet or the diet containing EMPA (30mg/kg/day) for 6 weeks. Vascular reactivity was assessed in the mesenteric artery using organ chambers, and the heart function and structural changes by echocardiography. In the mesenteric artery, acetylcholine (ACh)-induced endothelium-dependent relaxations were slightly but significantly reduced and endothelium-dependent contractile responses (EDCFs) increased in ZSF1 compared to Ctrl rats. The cyclooxygenase inhibitor indomethacin improved relaxations and abolished EDCFs to ACh in ZSF1 rats. The 6-week EMPA treatment improved the relaxation and blunted EDCFs to ACh in the ZSF1. The weight of the heart and of each part, and the left ventricle area were increased in the ZSF1, and significantly reduced by the EMPA treatment, except for left auricle plus septum weight, which did not reach significance. Left ventricle ejection fraction and cardiac output were similar in all groups. The EMPA treatment reduced the increased body weight and that of lungs, spleen, liver and perirenal fat, and hyperglycemia, and increased blood ketone levels and urinary glucose excretion in ZSF1 rats. The EMPA treatment improved body weight, hyperglycemia, and both endothelial function and cardiac remodeling in the metabolic syndrome with HFpEF ZSF1 rat. The protective vascular effect involves improved endothelium-dependent relaxations and blunted EDCFs most likely by targeting the cyclooxygenase pathway.

γδ T Cells Mediate Angiotensin II-Induced Hypertension and Vascular Injury.

Innate antigen-presenting cells and adaptive immune T cells have been implicated in the development of hypertension. However, the T-lymphocyte subsets involved in the pathophysiology of hypertension remain unclear. A small subset of innate-like T cells expressing the γδ T cell receptor (TCR) rather than the αβ TCR could play a role in the initiation of the immune response in hypertension. We aimed to determine whether angiotensin (Ang) II caused kinetic changes in γδ T cells; deficiency in γδ T cells blunted Ang II-induced hypertension, vascular injury, and T-cell activation; and γδ T cells are associated with human hypertension. Male C57BL/6 wild-type and Tcrδ-/- mice, which are devoid of γδ T cells, or wild-type mice injected IP with control isotype IgG or γδ T cell-depleting antibodies, were infused or not with Ang II for 3, 7, or 14 days. T-cell profiling was determined by flow cytometry, systolic blood pressure (SBP) by telemetry, and mesentery artery endothelial function by pressurized myography. TCR γ constant region gene expression levels and clinical data of a whole blood gene expression microarray study, including normotensive and hypertensive subjects, were used to demonstrate an association between γδ T cells and SBP. Seven- and 14-day Ang II infusion increased γδ T-cell numbers and activation in the spleen of wild-type mice (P<0.05). Fourteen days of Ang II infusion increased SBP (P<0.01) and decreased mesenteric artery endothelial function (P<0.01) in wild-type mice, both of which were abrogated in Tcrδ-/- mice (P<0.01). Anti-TCRγδ antibody-induced γδ T-cell depletion blunted Ang II-induced SBP rise and endothelial dysfunction (P<0.05), compared with isotype antibody-treated Ang II-infused mice. Ang II-induced T-cell activation in the spleen and perivascular adipose tissue was blunted in Tcrδ-/- mice (P<0.01). In humans, the association between SBP and γδ T cells was demonstrated by a multiple linear regression model integrating whole blood TCR γ constant region gene expression levels and age and sex (R2=0.12, P<1×10-6). γδ T cells mediate Ang II-induced SBP elevation, vascular injury, and T-cell activation in mice. γδ T cells might contribute to the development of hypertension in humans.

Abstract P617: Angiotensin II-induced Hypertension And Vascular Injury Is Mediated By Gamma/delta T Cells

Objective: Both innate antigen presenting cells and the adaptive immune system have been shown to play a role in the development of hypertension. Nevertheless, the T cell subset involved in the pathophysiology of hypertension remains unclear. There is a small subset of “innate-like” T cells expressing gamma/delta T cell receptor (TCR) rather than the alpha/beta TCR that could play a role in bridging between the innate and adaptive immune systems. However, it is unknown whether gamma/delta T cells contribute to development of hypertension. Method/Results: Thirteen to 15 week-old male C57BL/6 wild-type and Tcrd-/- mice, which are devoid of gamma/delta T cells, were infused or not with angiotensin (Ang) II (490 ng/kg/min, SC) for 7 or 14 days (n=4-9). Telemetric blood pressure, mesenteric artery endothelial function and vascular remodeling by pressurized myography and spleen T cell profile by flow cytometry were evaluated. Fourteen days of Ang II increased systolic blood pressure (167±4 vs 125±2 mmHg, P≤0.01) in wild-type compared to control mice. The frequency of gamma/delta T cells (6±1% vs 3±1%, P≤0.05) and activated (CD69+) gamma/delta T cells (11±1% vs 7±1%) was increased after 7 days of Ang II, and 7 days later were respectively unchanged or further increased (24±2% vs 10±1%) in wild-type compared to control mice. Ang II decreased mesenteric artery relaxation responses to acetylcholine (51±5% vs 88±3%, P≤0.01) and increased media/lumen (5±1 vs 3±0%, P≤0.01) in wild-type mice compare to controls. No gamma/delta T cells were detected in Tcrd-/- treated or not with Ang II. All the above Ang II effects were abrogated in Tcrd-/- mice. Conclusion: These data suggest that gamma/delta T cells mediate Ang II-induced blood pressure rise and vascular injury. Gamma/delta T cells could be key immune cells bridging innate and adaptive immune responses during the development of hypertension.

Erythropoietin-induced hypertension and vascular injury in mice overexpressing human endothelin-1

Erythropoietin used to correct anaemia in chronic kidney disease (CKD) has been shown to increase blood pressure (BP) in CKD patients and experimental animals. Endothelin (ET)-1 expression is increased in CKD animals and patients, and enhanced by erythropoietin. Erythropoietin-induced BP rise was blunted by ETA receptor blockers. This study was designed to determine whether preexisting endothelin (ET)-1 overexpression is required for erythropoietin to cause adverse vascular effects and whether this could be prevented by exercise training. Eight to 10-week old male wild-type mice and mice with endothelial-specific ET-1 overexpression (eET-1) were treated or not with EPO (100 IU/kg, SC, 3 times/week). eET-1 was subjected or not to swimming exercise training (1 h/day, 6 days/week) for 8 weeks. SBP, mesenteric artery endothelial function and remodelling, NADPH oxidase activity, reactive oxygen species (ROS) generation, vascular cell adhesion protein (VCAM)-1, monocyte/macrophage infiltration, T regulatory cells (Tregs) and tissue ET-1 and plasma endothelin were determined. Erythropoietin increased SBP by 24 mmHg (P < 0.05) and decreased by 25% vasodilatory responses to acetylcholine (P < 0.01) in eET-1 mice. Erythropoietin enhanced ET-1 induced increase in resistance artery media/lumen ratio (31%, P < 0.05), aortic NADPH oxidase activity (50%, P < 0.05), ROS generation (93%, P < 0.001), VCAM-1 (80%, P < 0.01) and monocyte/macrophage infiltration (159%, P < 0.001), and raised plasma and aortic ET-1 levels (≥130%, P < 0.05). EPO had no effect in wild-type mice. Exercise training prevented all of the above (P < 0.05). Erythropoietin-induced adverse vascular effects are dependent on preexisting elevated ET-1 expression. Exercise training prevented erythropoietin-induced adverse vascular effects in part by inhibiting ET-1 overexpression-induced oxidative stress, inflammation and immune activation.

Reduced EDHF responses and connexin activity in mesenteric arteries from the insulin-resistant obese Zucker rat

The objective of this study was to examine the effect of insulin resistance on endothelium-derived hyperpolarising factor (EDHF) and small mesenteric artery endothelial function using 25-week-old insulin-resistant obese Zucker rats (OZRs) and lean littermate control rats (LZRs). The involvement of gap junctions and their connexin subunits in the EDHF relaxation response was also assessed. Mesenteric arteries were evaluated using the following assays: (1) endothelial function by pressure myography, with internal diameter recorded using video microscopy; (2) connexin protein levels by western blotting; and (3) Cx mRNA expression by real-time PCR. Relaxations in response to acetylcholine were significantly smaller in mesenteric arteries from the OZRs than the LZRs, whereas there was no difference in relaxations in response to levcromakalim. Responses to acetylcholine were not altered by nitric oxide inhibitors, but were abolished by charybdotoxin in combination with apamin, which blocked the EDHF component of the response. 40Gap27 significantly attenuated the response to acetylcholine in the LZRs, but had no effect in the OZRs. Connexin 40 protein and Cx40 mRNA levels in mesenteric vascular homogenates were significantly smaller in the OZRs than in the LZRs, with no difference in connexin 43 or Cx43 mRNA levels. These findings demonstrate that endothelial dysfunction in mesenteric arteries from the insulin-resistant OZRs can be attributed to a defect in EDHF. The results also suggest that the defective EDHF is at least partly related to an impairment of connexin 40-associated gap junctions, through a decrease in connexin 40 protein and Cx40 mRNA expression in the OZRs.

Beneficial actions of S-nitroso-N-acetylpenicillamine, a nitric oxide donor, in murine traumatic shock.

We studied the effects of the nitric oxide donor, S-nitroso-N-acetylpenicillamine (SNAP), in rat traumatic shock characterized by hypotension, increases in plasma free amino-nitrogen (5.3 +/- 0.5 U/ml vs. 2.5 +/- 0.3 U/ml controls) and intestinal myeloperoxidase activities (2.7 +/- 1.0 U/100 mg vs. 0.2 +/- 0.1 U/100 mg controls), and a survival time of 143 +/- 20 min. Moreover, superior mesenteric artery rings isolated from rats in traumatic shock relaxed to the endothelium-dependent vasodilator acetylcholine only 21 +/- 6% of U-46619 induced contraction. Administration of 100 micrograms/kg SNAP 10 min post-trauma followed by 10 micrograms/kg/h infusion prolonged survival time to 273 +/- 18 min (p < .05), attenuated the increases in plasma free amino-nitrogen (3.1 +/- 0.4 U/ml, p < .05) and tissue myeloperoxidase activities (0.6 +/- 0.3 U/100 mg, p < .05). Moreover, SNAP significantly preserved superior mesenteric artery endothelial function; the vasorelaxation to acetylcholine was 54 +/- 4% (p < .01). Protective effects were not seen in traumatic shock rats treated with the non-NO-donating parent compound N-acetylpenicillamine. These results indicate that SNAP affords significant protection in murine traumatic shock which may be achieved through maintenance of systemic blood pressure, preservation of vascular endothelial integrity, and inhibition of neutrophil-endothelial interaction and the resultant reduced microvascular leakiness.