Endothelial Dysfunction Of Resistance Vessels Research Articles

Selective deficiency in endothelial PTP1B protects from diabetes and endoplasmic reticulum stress-associated endothelial dysfunction via preventing endothelial cell apoptosis

Diabetes notably increases the risk for endothelial dysfunction, a main precursor for microvascular complications. While endoplasmic reticulum stress (ERS) and protein tyrosine phosphatase 1B (PTP1B) have been associated with endothelial dysfunction in resistance vessels, whether these mechanisms also contribute to diabetes-mediated endothelial dysfunction in conduit arteries remains unknown. Herein, we tested the hypothesis that diabetes induces macrovascular endothelial dysfunction via endothelial ERS-induced, PTP1B-mediated apoptosis. We showed that diabetes concomitantly increased the expression of PTP1B and of markers of ERS, including GRP78, XBP1, splXBP1 and CHOP in human vessels. Exposure of aortic rings from wild-type mice to the ERS inducers tunicamycin and thapsigargin markedly reduced endothelium-dependent relaxation. Global and endothelial-specific deletion of PTP1B as well as pharmacological inhibition protected aortic rings from ERS-mediated endothelial dysfunction. Nitric oxide synthase inhibition with l-NAME abolished relaxation in the presence and absence of ERS, but neither reactive oxygen species scavenging with tempol or peg-catalase, nor cyclooxygenase inhibition with indomethacin prevented ERS-mediated endothelial dysfunction. However, both p38-MAPK and JNK inhibition protected aortic rings from ERS-mediated endothelial dysfunction. In HUVECs, PTP1B deletion prevented ERS-induced PARP cleavage and apoptosis. Lastly, acute ERS inhibition in aortic rings and selective deficiency of endothelial PTP1B in mice protected mice from diabetes-induced endothelial dysfunction. Altogether, these data support the contribution of the p38/JNK-apoptosis pathway in ERS-mediated endothelial dysfunction and present endothelial PTP1B as a major regulator of endothelial cell viability in conduit vessels and a potential target for the management of macrovascular diseases in diabetes.

Deficiency of T-type voltage-gated calcium channels results in attenuated weight gain and improved endothelium-dependent dilatation of resistance vessels induced by a high-fat diet in mice.

The deletion of T-type Cav3.1 channels may reduce high-fat diet (HFD)-induced weight gain, which correlates positively with obesity and endothelial dysfunction. Therefore, experiments were designed to study the involvement of T-type Cav3.1 channels in HFD-induced endothelial dysfunction in mice. Wildtype (WT) and Cav3.1-/- mice were fed either a normal diet (ND) or an HFD for 8weeks. Body composition was assessed, and thoracic aortae and mesenteric arteries were harvested for myography to assess endothelium-dependent responses. Changes in intracellular calcium were measured by fluorescence imaging, and behavior was assessed with the open-field test. Cav3.1-/- mice had attenuated HFD-induced weight gain and lower total fat mass compared with WT mice. Cav3.1-/- mice on an HFD had reduced plasma cholesterol levels compared with WT mice on the same diet. Increased feeding efficiency, independent of food intake, was observed in WT mice on an HFD compared with an ND, but no difference in feeding efficiency between diets was observed for Cav3.1-/- mice. Nitric oxide-dependent dilatation was increased in mesenteric arteries of Cav3.1-/- mice compared with WT mice on an HFD, with no difference observed in aortae. No differences in mouse locomotor activity were observed between the experimental groups. Mice on an HFD lacking T-type channels have reduced weight gain, lower total cholesterol levels, and increased dilatation of resistance vessels compared with WT mice on an HFD, suggesting that Cav3.1 deletion protects against endothelial dysfunction in resistance vessels but not in large conduit vessels.

Myocardial Production of Plasminogen Activator Inhibitor-1 is Associated with Coronary Endothelial and Ventricular Dysfunction after Acute Myocardial Infarction.

Although plasminogen activator inhibitor-1 (PAI-1) is abundantly expressed in infarcted myocardium, the pathogenic role of myocardial PAI-1 remains unknown. This study examined whether PAI-1 in the infarcted lesion contributes to coronary endothelial dysfunction and left ventricular (LV) dysfunction in patients with acute myocardial infarction (AMI). Plasma levels of PAI-1 activity and tissue-plasminogen activator (tPA) antigen were measured 2 weeks and 6 months after MI by ELISA in plasma obtained from the aortic root (AO) and anterior interventricular vein (AIV) in 28 patients with a first AMI due to occlusion of the left anterior descending coronary artery (LAD). Coronary blood flow responses in LAD to intracoronary infusion of acetylcholine (ACh) and left ventriculography were measured at the same time points: 2 weeks and 6 months after MI. The trans-myocardial gradient of PAI-1 from AO to AIV, reflecting production/release of PAI-1 in the infarcted lesion, was inversely correlated with the coronary blood flow response to ACh 6 months after MI (r=-0.43, p=0.02) and with the percentage change in LV regional motion in the LAD territory from 2 weeks to 6 months after MI (r=-0.38, p=0.04). The trans-myocardial gradient of tPA level showed no significant correlations. PAI-1 produced in the infarcted myocardium and released into the coronary circulation is associated with endothelial dysfunction in resistance vessels of the infarct-related coronary arteries and with progressive dysfunction of the infarcted region of the left ventricle in AMI survivors.

Abstract 12338: Production of Plasminogen Activator Inhibitor-1 in Infarcted Lesion was Associated With Coronary Endothelial Vasomotor Dysfunction and Progressive Dysfunction of Left Ventricle in Patients With Acute Myocardial Infarction

Experimental studies showed that plasminogen activator inhibitor-1 (PAI-1) is abundantly expressed in the infarcted myocardium and that the increased PAI-1 expression causes an impairment of fibrinolysis in the coronary vascular beds and left ventricular (LV) adverse remodeling after acute myocardial infarction (AMI). However, little is known in humans. Thus, this study examined whether PAI-1 produced in the infarcted lesion may contribute to coronary endothelial dysfunction and LV dysfunction in patients with AMI. Methods: Plasma levels of PAI-1 activity and tissue-plasminogen activator (tPA) protein were measured by ELISA in plasma obtained from aortic root (AO), anterior interventricular vein (AIV), and peripheral vein (PV) in 41 patients with a first AMI due to occlusion of a proximal segment of the LAD at 6 months (M) after MI. Coronary blood flow responses in the LAD to intracoronary infusion of acetylcholine (ACh, 50 μg/min) were measured by an intracoronary flow wire technique 6M after MI. Left ventriculography was repeated twice, 2 weeks (2W) and 6M after MI. Results: The trans-myocardial gradient of PAI-1 from AO to AIV (0.14 ± 0.15 ng/mL), reflecting a production/release of PAI-1 from the infarcted lesion, had an inverse correlation with coronary blood flow response to ACh (r = -0.43 , p = 0.02). The trans-myocardial gradient of PAI-1 had an inverse correlation with the % changes in LV regional motion in the LAD territory from 2W to 6M after MI (r = -0.37, p = 0.02). PAI-1 level in the PV and the trans-myocardial gradient of tPA had no significant correlation with the coronary blood flow response to ACh and the LV regional motion. The trans-myocardial gradient in PAI-1 level was lower in patients taking than not taking angiotensin II receptor blocker (ARB) (n = 22, -0.15 ± 0.19 ng/mL vs. n = 19, 0.48 ± 0.21 ng/mL, respectively, p = 0.03). Conclusions: PAI-1 produced in the infarcted myocardium and released into the coronary circulation was associated with endothelial dysfunction in resistance vessels of the infarct-related coronary arteries and progressive dysfunction of the infarcted region of LV in AMI survivors. ARB might inhibit PAI-1 production in the infarcted myocardium in the chronic phase of MI, which may represent an additional benefit of ARB therapy.

Vascular Arginase Contributes to Arteriolar Endothelial Dysfunction in a Rat Model of Hemorrhagic Shock

Hemorrhagic shock causes hypoperfusion of peripheral tissues and promotes endothelial dysfunction, which may lead to further tissue injury. Trauma increases extrahepatic activity of arginase, an enzyme which competes for l-arginine with nitric oxide synthase, and plays a key role in the development of endothelial dysfunction during aging, hypertension, and diabetes. However, the role of arginase in hemorrhage-induced endothelial dysfunction has not been studied. This study tests the hypothesis that arginase inhibition improves endothelial function after hemorrhage. Male Sprague-Dawley rats were implanted with indwelling arterial catheters for blood pressure measurements and blood removal. Awake animals were subjected to a 45% fixed volume controlled hemorrhage and blood pressure was monitored. Unbled rats served as controls. Skeletal muscle arterioles were isolated 24 hours after hemorrhage and cannulated in a pressure myograph system. To study endothelial function, arterioles were exposed to constant midpoint, but altered endpoint pressures, to establish graded levels of luminal flow and internal diameter was measured. Hemorrhage lowered mean arterial pressure that spontaneously recovered to 78% and 88% of baseline in 2 hours and 20 hours, respectively. Vascular arginase II and blood glucose levels were elevated, whereas hemoglobin and insulin levels were decreased 24 hours after blood loss. In posthemorrhage arterioles, flow-induced dilation was abolished. Acute in vitro treatment with an inhibitor of arginase, N-hydroxy-nor-l-arginine, restored flow-induced dilation to unbled control levels. Similarly, the arginase and nitric oxide synthase substrate, l-arginine, but not the inactive isomer, d-arginine, restored flow-induced dilation. These results indicate that arginase contributes to endothelial dysfunction in resistance vessels after significant hemorrhage.

Endothelial dysfunction of resistance vessels in female apolipoprotein E-deficient mice

BackgroundThe effects of hypercholesterolemia on vasomotricity in apolipoprotein E-deficient (ApoE) mice, a murine model of spontaneous atherosclerosis, are still unclear. The studies were mostly performed in conductance vessels from male mice fed a high-fat diet. In the present study, we evaluated the endothelial function of resistance vessels from normal C57BL/6 (C57) and hypercholesterolemic (ApoE) female mice in both normal and ovariectomized conditions.MethodsTwenty week-old C57 and ApoE mice underwent ovariectomy or sham surgery and were studied 30 days later. The vascular reactivities to norepinephrine (NE, 10-9 to 2 × 10-3 mol/L), acetylcholine (ACh) and sodium nitroprusside (SNP) (10-10 to 10-3 mol/L) were evaluated in the isolated mesenteric arteriolar bed through dose-response curves.ResultsACh-induced relaxation was significantly reduced (P < 0.05) in ApoE compared with C57 animals, as indicated by both the maximal response (37 ± 4% vs. 72 ± 1%) and the LogEC50 (-5.67 ± 0.18 vs. -6.23 ± 0.09 mol/L). Ovariectomy caused a significant impairment in ACh-induced relaxation in the C57 group (maximal response: 61 ± 4%) but did not worsen the deficient state of relaxation in ApoE animals (maximal response: 39 ± 5%). SNP-induced vasorelaxation and NE-induced vasoconstriction were similar in ApoE and C57 female mice.ConclusionThese data show an impairment of endothelial function in the resistance vessels of spontaneously atherosclerotic (ApoE-deficient) female mice compared with normal (C57) female mice. The endothelial dysfunction in hypercholesterolemic animals was so marked that ovariectomy, which impaired endothelial function in C57 mice, did not cause additional vascular damage in ApoE-deficient mice.

Arginase contributes to arteriolar endothelial dysfunction following hemorrhage

Vascular tissues express arginase that metabolizes L-arginine (L-Arg) to L-ornithine and urea. Arginase competes for L-Arg with nitric oxide synthase (NOS) and contributes to endothelial dysfunction in hypertension and diabetes. Blood loss promotes endothelial dysfunction which contributes to compromised tissue perfusion. This study tests the hypothesis that increased arginase activity contributes to endothelial dysfunction following hemorrhage. Male Sprague-Dawley rats (300–350g) were subjected to a 45% blood loss over 5min. Blood pressure spontaneously returned to 90% of baseline within 1hr. Plasma arginase activity was increased 36hrs post-hemorrhage by 22%. Isolated first-order gracilis muscle arterioles were superfused with Krebs buffer and exposed to constant midpoint, but altered endpoint pressures to establish graded levels of luminal flow (0–50μl/min). In post-hemorrhage arterioles, flow-induced dilation was abolished (Δmax shock: 0±0 vs unbled: 18±1μm). Acute in vitro treatment with an inhibitor of arginase, 100μM Nω-hydroxy-nor-L-arginine (Δmax 22±2μm) or the NOS substrate, 1mM L-Arg restored flow-induced dilation to unbled control levels (Δmax 17±1μm). In unbled controls, flow-induced dilation was abolished by the NOS inhibitor, 1mM L-NAME. These results suggest that arginase activity is increased following massive hemorrhage and contributes to endothelial dysfunction in resistance vessels by inhibiting endothelial NOS. Supported by NIH grants HL64577 (RAJ) and HL074966 (WD).

Endothelium-restricted overexpression of human endothelin-1 causes vascular remodeling and endothelial dysfunction.

Endothelin (ET)-1 is a potent vasoconstrictor that contributes to vascular remodeling in hypertension and other cardiovascular diseases. Endogenous ET-1 is produced predominantly by vascular endothelial cells. To directly test the role of endothelium-derived ET-1 in cardiovascular pathophysiology, we specifically targeted expression of the human preproET-1 gene to the endothelium by using the Tie-2 promoter in C57BL/6 mice. Ten-week-old male C57BL/6 transgenic (TG) and nontransgenic (wild type; WT) littermates were studied. TG mice exhibited 3-fold higher vascular tissue ET-1 mRNA and 7-fold higher ET-1 plasma levels than did WT mice but no significant elevation in blood pressure. Despite the absence of significant blood pressure elevation, TG mice exhibited marked hypertrophic remodeling and oxidant excess-dependent endothelial dysfunction of resistance vessels, altered ET-1 and ET-3 vascular responses, and significant increases in ET(B) expression compared with WT littermates. Moreover, TG mice generated significantly higher oxidative stress, possibly through increased activity and expression of vascular NAD(P)H oxidase than did their WT counterparts. In this new murine model of endothelium-restricted human preproET-1 overexpression, ET-1 caused structural remodeling and endothelial dysfunction of resistance vessels, consistent with a direct nonhemodynamic effect of ET-1 on the vasculature, at least in part through the activation of vascular NAD(P)H oxidase.

Preserved Endothelial Function in Patients With Severe Hypertriglyceridemia and Low Functional Lipoprotein Lipase Activity

Objectives. We sought to determine whether hypertriglyceridemia in patients with lipoprotein lipase (LPL) dysfunction is associated with endothelial dysfunction in resistance vessels of the forearm vasculature.Background. Vasodilator responses to acetylcholine, acting through stimulation of nitric oxide (NO) release from the endothelium, are impaired in hypercholesterolemia and normalized by l-arginine, suggesting dysfunction of the l-arginine/NO pathway. Similar abnormalities have been reported in conditions associated with hypertriglyceridemia, such as non–insulin-dependent diabetes. The relation between endothelial function and plasma triglyceride concentrations has, however, not previously been studied in vivo.Methods. We examined forearm blood flow responses to brachial artery infusions of acetylcholine (alone and with l-arginine) and nitroprusside (an NO donor) in 17 patients with severe hypertriglyceridemia (mean [±SD] plasma triglyceride concentration 1,914 ± 1,288 mg/dl) but normal low density lipoprotein cholesterol (89 ± 31 mg/dl) and in 34 normolipidemic control subjects. Severe LPL dysfunction was demonstrated in 10 of 17 patients.Results. Acetylcholine (7.5 and 15 μg/min) produced similar forearm blood flow responses in hypertriglyceridemic patients (mean [±SEM] 7.7 ± 0.9 and 10.5 ± 1.2 ml/min per 100 ml) and in control subjects (7.5 ± 0.6 and 11.0 ± 0.8 ml/min per 100 ml, p = 0.78 by analysis of variance). Responses to acetylcholine co-infused with l-arginine (10 mg/min) and nitroprusside (3 and 10 μg/min) were also similar in hypertriglyceridemic patients and control subjects (p = 0.93 and p = 0.27 for acetylcholine with l-arginine and nitroprusside, respectively). The ratio response to acetylcholine/response to nitroprusside differed between hypertriglyceridemic patients and control subjects by only 1%. The study had >90% power (alpha = 0.05) to detect a difference >30% in this ratio.Conclusions. Severe hypertriglyceridemia associated with LPL dysfunction is not associated with the degree of endothelial dysfunction seen in moderate hypercholesterolemia when responses to acetylcholine are impaired by >40%.(J Am Coll Cardiol 1997;29:964–8)© 1997 by the American College of Cardiology