Activation of K+ channels and Na+/K+ ATPase prevents aortic endothelial dysfunction in 7-day lead-treated rats

AbstractSeven day exposure to a low concentration of lead acetate increases nitric oxide bioavailability suggesting a putative role of K+ channels affecting vascular reactivity. This could be an adaptive mechanism at the initial stages of toxicity from lead exposure due to oxidative stress. We evaluated whether lead alters the participation of K+ channels and Na+/K+-ATPase (NKA) on vascular function. Wistar rats were treated with lead (1st dose 4μg/100g, subsequent doses 0.05μg/100g, im, 7days) or vehicle. Lead treatment reduced the contractile response of aortic rings to phenylephrine (PHE) without changing the vasodilator response to acetylcholine (ACh) or sodium nitroprusside (SNP). Furthermore, this treatment increased basal O2− production, and apocynin (0.3μM), superoxide dismutase (150U/mL) and catalase (1000U/mL) reduced the response to PHE only in the treated group. Lead also increased aortic functional NKA activity evaluated by K+-induced relaxation curves. Ouabain (100μM) plus L-NAME (100μM), aminoguanidine (50μM) or tetraethylammonium (TEA, 2mM) reduced the K+-induced relaxation only in lead-treated rats. When aortic rings were precontracted with KCl (60mM/L) or preincubated with TEA (2mM), 4-aminopyridine (4-AP, 5mM), iberiotoxin (IbTX, 30nM), apamin (0.5μM) or charybdotoxin (0.1μM), the ACh-induced relaxation was more reduced in the lead-treated rats. Additionally, 4-AP and IbTX reduced the relaxation elicited by SNP more in the lead-treated rats. Results suggest that lead treatment promoted NKA and K+ channels activation and these effects might contribute to the preservation of aortic endothelial function against oxidative stress

Soybean oil increases SERCA2a expression and left ventricular contractility in rats without change in arterial blood pressure

<p>Abstract</p> <p>Background</p> <p>Our aim was to evaluate the effects of soybean oil treatment for 15 days on arterial and ventricular pressure, myocardial mechanics and proteins involved in calcium handling.</p> <p>Methods</p> <p>Wistar rats were divided in two groups receiving 100 μL of soybean oil (SB) or saline (CT) i.m. for 15 days. Ventricular performance was analyzed in male 12-weeks old Wistar rats by measuring left ventricle diastolic and systolic pressure in isolated perfused hearts according to the Langendorff technique. Protein expression was measured by Western blot analysis.</p> <p>Results</p> <p>Systolic and diastolic arterial pressures did not differ between CT and SB rats. However, heart rate was reduced in the SB group. In the perfused hearts, left ventricular isovolumetric systolic pressure was higher in the SB hearts. The inotropic response to extracellular Ca²⁺and isoproterenol was higher in the soybean-treated animals than in the control group. Myosin ATPase and Na⁺-K⁺ATPase activities, the expression of sarcoplasmic reticulum calcium pump (SERCA2a) and sodium calcium exchanger (NCX) were increased in the SB group. Although the phosfolamban (PLB) expression did not change, its phosphorylation at Ser¹⁶was reduced while the SERCA2a/PLB ratio was increased.</p> <p>Conclusions</p> <p>In summary, soybean treatment for 15 days in rats increases the left ventricular performance without affecting arterial blood pressure. These changes might be associated with an increase in the myosin ATPase activity and SERCA2a expression.</p

Low mercury concentration produces vasoconstriction, decreases nitric oxide bioavailability and increases oxidative stress in rat conductance artery.

Mercury is an environmental pollutant that reduces nitric oxide (NO) bioavailability and increases oxidative stress, having a close link with cardiovascular diseases, as carotid atherosclerosis, myocardial infarction, coronary heart disease and hypertension. One of the main sites affected by oxidative stress, which develops atherosclerosis, is the aorta. Under acute exposure to low mercury concentrations reactive oxygen species (ROS) production were only reported for resistance vessels but if low concentrations of mercury also affect conductance arteries it is still unclear. We investigated the acute effects of 6 nM HgCl(2) on endothelial function of aortic rings measuring the reactivity to phenylephrine in rings incubated, or not, with HgCl(2) for 45 min, the protein expression for cyclooxygenase 2 (COX-2) and the AT1 receptor. HgCl(2) increased Rmax and pD2 to phenylephrine without changing the vasorelaxation induced by acetylcholine and sodium nitroprusside. Endothelial damage abolished the increased reactivity to phenylephrine. The increase of Rmax and pD2 produced by L-NAME was smaller in the presence of HgCl(2). Enalapril, losartan, indomethacin, furegrelate, the selective COX-2 inhibitor NS 398, superoxide dismutase and the NADPH oxidase inhibitor apocynin reverted HgCl(2) effects on the reactivity to phenylephrine, COX-2 protein expression was increased, and AT1 expression reduced. At low concentration, below the reference values, HgCl(2) increased vasoconstrictor activity by reducing NO bioavailability due to increased ROS production by NADPH oxidase activity. Results suggest that this is due to local release of angiotensin II and prostanoid vasoconstrictors. Results also suggest that acute low concentration mercury exposure, occurring time to time could induce vascular injury due to endothelial oxidative stress and contributing to increase peripheral resistance, being a high risk factor for public health

(A, B) The effect of indomethacin (Indo, 10 µM), on the concentration-response curves for phenylephrine in aortic rings in control (CT) conditions or HgCl2.

<p>Results (mean±SEM) are expressed as a percentage of the response to 75 mmol/l KCl. *<i>P</i><0.05 by ANOVA. Number of animals used in parentheses. (C) Differences in the area under the concentration-response curve (dAUC) in aortic rings cultured in the presence of indomethacin (10 µM) under control (CT) conditions and after acute incubation with mercury HgCl₂. *<i>P</i><0.05 by Student’s <i>t</i>-test.</p

Parameters of maximal response (Emax, mmHg) and sensitivity (pD2) of dose-response curves to phenyleprine in the aorta, before (E+) and after (E-) endothelial damage and after NG-nitro-L-arginine methyl ester (L-NAME, 100 µM) incubation, in the presence (HgCl2 E+) and absence of mercury chloride (E- HgCl2).

<p>Results are expressed as means ± SEM of the no. of animals shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049005#pone-0049005-g001" target="_blank">Figs. 1</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049005#pone-0049005-g002" target="_blank"></a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049005#pone-0049005-g003" target="_blank">3</a>. P<0.05 vs. CT (E+) (*).</p

The effect of apocynin (0.3 mM) on the concentration-response curves for phenylephrine in aortic rings in control (CT) conditions or HgCl2 (A,B).

<p>Results (mean±SEM) are expressed as a percentage of the response to 75 mmol/l KCl. *<i>P</i><0.05 by ANOVA. Number of animals used in parentheses. (C) Differences in the area under the concentration-response curve (dAUC) in aortic rings cultured the presence and absence apocynin (0.3 mM), under control (CT) conditions or HgCl₂. *<i>P</i><0.05 by Student’s <i>t</i>-test.</p

The effect of L-NAME (100 µM) on the concentration-response curves for phenylephrine in aortic rings in control (CT) conditions or HgCl2 (A,B).

<p>Results (mean±SEM) are expressed as a percentage of the response to 75 mmol/l KCl. *<i>P</i><0.05 by ANOVA. Number of animals used in parentheses. (C) Differences in the area under the concentration-response curve (dAUC) for aortic rings incubated in the presence and absence of L-NAME in controls (CT) or HgCl₂. *<i>P</i><0.05 by Student’s <i>t</i>-test.</p

The effect of endothelium removal (E-) on the concentration-response curves for phenylephrine in aortic rings in control (CT) conditions or HgCl2 (A,B).

<p>Results (mean±SEM) are expressed as a percentage of the response to 75 mmol/l KCl. *<i>P</i><0.05 by ANOVA. Number of animals used in parentheses. (C) Differences in area under the concentration-response curve (dAUC) in the presence and absence of the endothelium of aortic rings in control (CT) conditions or HgCl₂. *<i>P</i><0.05 by Student’s <i>t</i>-test.</p

(A,B) The effects of enalapril (10 µM) and (C,D) losartan (10 µM) on the concentration-response curves for phenylephrine and (E) densitometric analysis of the western blot for AT₁ in aortic rings in control (CT) conditions or HgCl2.

<p>Results (mean±SEM) are expressed as a percentage of the response to 75 mmol/l KCl. *<i>P</i><0.05 by ANOVA. (E) Densitometric analysis of the western blot for angiotensin receptor 1 (AT1) protein expression in aortic rings cultured in the absence (CT) of HgCl₂ and after acute incubation with HgCl₂. *<i>P</i><0.05 by Student’s <i>t</i>-test. Number of animals used in parentheses. Representative blots are also shown.</p

Modulating Vascular Hemodynamics With an Alpha Globin Mimetic Peptide (HbαX)

The ability of hemoglobin to scavenge the potent vasodilator nitric oxide (NO) in the blood has been well established as a mechanism of vascular tone homeostasis. In endothelial cells, the alpha chain of hemoglobin (hereafter, alpha globin) and endothelial NO synthase form a macromolecular complex, providing a sink for NO directly adjacent to the production source. We have developed an alpha globin mimetic peptide (named HbαX) that displaces endogenous alpha globin and increases bioavailable NO for vasodilation. Here we show that, in vivo, HbαX administration increases capillary oxygenation and blood flow in arterioles acutely and produces a sustained decrease in systolic blood pressure in normal and angiotensin II-induced hypertensive states. HbαX acts with high specificity and affinity to endothelial NO synthase, without toxicity to liver and kidney and no effect on p50 of O binding in red blood cells. In human vasculature, HbαX blunts vasoconstrictive response to cumulative doses of phenylephrine, a potent constricting agent. By binding to endothelial NO synthase and displacing endogenous alpha globin, HbαX modulates important metrics of vascular function, increasing vasodilation and flow in the resistance vasculature