Ethanol-induced vasoconstriction is mediated via redox-sensitive cyclo-oxygenase-dependent mechanisms

Melatonin prevents overproduction of reactive oxygen species and vascular dysfunction induced by cyclophosphamide

AIMS

Overproduction of reactive oxygen species (ROS) is a pathologic hallmark of cyclophosphamide toxicity. For this reason, antioxidant compounds emerge as promising tools for preventing tissue damage induced by cyclophosphamide. We hypothesized that melatonin would display cytoprotective action in the vasculature by preventing cyclophosphamide-induced oxidative stress.

MATERIALS AND METHODS

Male C57BL/6 mice (22-25 g) were injected with a single dose of cyclophosphamide (300 mg/kg; i.p.). Mice were pretreated or not with melatonin (10 mg/kg/day, i.p.), given during 4 days before cyclophosphamide injection. Functional (vascular reactivity) and oxidative/inflammatory patterns were evaluated at 24 h in resistance arteries. The antioxidant action of melatonin was assessed in vitro in cultured vascular smooth muscle cells (VSMCs) of mesenteric arteries.

KEY FINDINGS

Cyclophosphamide induced ROS generation in both mesenteric arterial bed (MAB) and cultured VSMCs, and this was normalized by melatonin. Cyclophosphamide-induced ROS generation and lipoperoxidation in the bladder and kidney was also prevented by melatonin. Increased levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 were detected in the MAB of cyclophosphamide-treated mice, all of which were prevented by melatonin. Functional assays using second-order mesenteric arteries of cyclophosphamide-treated mice revealed a decrease in vascular contractility. Melatonin prevented vascular hypocontractility in the cyclophosphamide group. Melatonin partially prevented the decrease in myeloperoxidase (MPO) and N-acetyl-beta-D-glucosaminidase (NAG) activities in the MAB of the cyclophosphamide group.

SIGNIFICANCE

Melatonin may constitute a novel and promising therapeutic approach for management of the toxic effects induced by cyclophosphamide in the vasculature.

Vascular injury associated with ethanol intake is driven by AT1 receptor and mitochondrial dysfunction

BACKGROUND

Renin-angiotensin (Ang II)-aldosterone system (RAAS) is crucial for the cardiovascular risk associated with excessive ethanol consumption. Disturbs in mitochondria have been implicated in multiple cardiovascular diseases. However, if mitochondria dysfunction contributes to ethanol-induced vascular dysfunction is still unknown. We investigated whether ethanol leads to vascular dysfunction via RAAS activation, mitochondria dysfunction, and mitochondrial reactive oxygen species (mtROS).

METHODS

Male C57/BL6J or mt-keima mice (6-8-weeks old) were treated with ethanol (20% vol./vol.) for 12 weeks with or without Losartan (10 mg/kg/day).

RESULTS

Ethanol induced aortic hypercontractility in an endothelium-dependent manner. PGC1α (a marker of biogenesis), Mfn2, (an essential protein for mitochondria fusion), as well as Pink-1 and Parkin (markers of mitophagy), were reduced in aortas from ethanol-treated mice. Disturb in mitophagy flux was further confirmed in arteries from mt-keima mice. Additionally, ethanol increased mtROS and reduced SOD2 expression. Strikingly, losartan prevented vascular hypercontractility, mitochondrial dysfunction, mtROS, and restored SOD2 expression. Both MnTMPyP (SOD2 mimetic) and CCCP (a mitochondrial uncoupler) reverted ethanol-induced vascular dysfunction. Moreover, L-NAME (NOS inhibitor) and EUK 134 (superoxide dismutase/catalase mimetic) did not affect vascular response in ethanol group, suggesting that ethanol reduces aortic nitric oxide (NO) and H2O2 bioavailability. These responses were prevented by losartan.

CONCLUSION

AT1 receptor modulates ethanol-induced vascular hypercontractility by promoting mitochondrial dysfunction, mtROS, and reduction of NO and H2O2 bioavailability. Our findings shed a new light in our understanding of ethanol-induced vascular toxicity and open perspectives of new therapeutic approaches for patients with disorder associated with abusive ethanol drinking.

Dual-color miniscope imaging of microvessels and neuronal activity in the hippocampus CA1 region of freely moving mice following alcohol administration

Moderate-to-heavy episodic ("binge") drinking is the most common form of alcohol consumption in the United States. Alcohol at binge drinking concentrations reduces brain artery diameter in vivo and in vitro in many species including rats, mice, and humans. Despite the critical role played by brain vessels in maintaining neuronal function, there is a shortage of methodologies to simultaneously assess neuron and blood vessel function in deep brain regions. Here, we investigate cerebrovascular responses to ethanol by choosing a deep brain region that is implicated in alcohol disruption of brain function, the hippocampal CA1, and describe the process for obtaining simultaneous imaging of pyramidal neuron activity and diameter of nearby microvessels in freely moving mice via a dual-color miniscope. Recordings of neurovascular events were performed upon intraperitoneal injection of saline versus 3 g/kg ethanol in the same mouse. In male mice, ethanol mildly increased the amplitude of calcium signals while robustly decreasing their frequency. Simultaneously, ethanol decreased microvessel diameter. In females, ethanol did not change the amplitude or frequency of calcium signals from CA1 neurons but decreased microvessel diameter. A linear regression of ethanol-induced reduction in number of active neurons and microvessel constriction revealed a positive correlation (R = 0.981) in females. Together, these data demonstrate the feasibility of simultaneously evaluating neuronal and vascular components of alcohol actions in a deep brain area in freely moving mice, as well as the sexual dimorphism of hippocampal neurovascular responses to alcohol.

AT1 receptors modulate ethanol-induced loss of anticontractile effect of perivascular adipose tissue

Ethanol consumption activates renin-angiotensin-aldosterone system (RAAS), which plays a major role in the pro-contractile and hypertensive effects linked to ethanol. We hypothesized that ethanol consumption induces loss of the anticontractile effect of perivascular adipose tissue (PVAT)through RAAS-mediated mechanisms. We examined the contribution of angiotensin II type 1 receptors (AT1R) to ethanol-induced PVAT dysfunction. With this purpose, male Wistar Hannover rats were treated with ethanol 20 % (in volume ratio) and/or losartan (antagonist of AT1R; 10 mg/kg/day, gavage) for 9 weeks. Losartan prevented the increase in blood pressure and the loss of the anticontractile effect of PVAT induced by ethanol consumption. PVAT dysfunction occurred after 3 and 9 weeks of treatment with ethanol in an endothelium-dependent manner. Blockade of AT1R prevented ethanol-induced reduction of adiponectin levels in PVAT from ethanol-treated rats. Functional assays revealed that ethanol impaired the anticontractile effect of PVAT-derived angiotensin (1-7) and endothelial nitric oxide (NO). In conclusion, AT1R are implicated in ethanol-induced loss of the anticontractile effect of PVAT. In PVAT, AT1R activation decreases the production of adiponectin, a PVAT-derived factor that promotes vasorelaxation in an endothelium-dependent manner. In the endothelium, AT1R favors the production of superoxide (O2•-) leading to a reduction in NO bioavailability. These responses impair the vasodilator action induced by PVAT-derived angiotensin (1-7), which occurs via Mas receptors located in endothelial cells. Ethanol-induced PVAT dysfunction favors vascular hypercontractility, a response that could contribute to the hypertensive state associated with ethanol consumption.

Reactive Oxygen Species Are Central Mediators of Vascular Dysfunction and Hypertension Induced by Ethanol Consumption

Consumption of high amounts of ethanol is a risk factor for development of cardiovascular diseases such as arterial hypertension. The hypertensive state induced by ethanol is a complex multi-factorial event, and oxidative stress is a pathophysiological hallmark of vascular dysfunction associated with ethanol consumption. Increasing levels of reactive oxygen species (ROS) in the vasculature trigger important processes underlying vascular injury, including accumulation of intracellular Ca2+ ions, reduced bioavailability of nitric oxide (NO), activation of mitogen-activated protein kinases (MAPKs), endothelial dysfunction, and loss of the anticontractile effect of perivascular adipose tissue (PVAT). The enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase plays a central role in vascular ROS generation in response to ethanol. Activation of the renin-angiotensin-aldosterone system (RAAS) is an upstream mechanism which contributes to NADPH oxidase stimulation, overproduction of ROS, and vascular dysfunction. This review discusses the mechanisms of vascular dysfunction induced by ethanol, detailing the contribution of ROS to these processes. Data examining the association between neuroendocrine changes and vascular oxidative stress induced by ethanol are also reviewed and discussed. These issues are of paramount interest to public health as ethanol contributes to blood pressure elevation in the general population, and it is linked to cardiovascular conditions and diseases.

Mineralocorticoid receptors contribute to ethanol-induced vascular hypercontractility through reactive oxygen species generation and up-regulation of cyclooxygenase 2

The effects on blood pressure produced byethanol consumption include both vasoconstriction and activation of the renin-angiotensin-aldosterone system (RAAS), although the detailed relationship between these processes is yet to be accomplished. Here, we sought to investigate the contribution of mineralocorticoid receptors (MR) to ethanol-induced hypertension and vascular hypercontractility. We analyzed blood pressure and vascular function of male Wistar Hannover rats treated with ethanol for five weeks. The contribution of the MR pathway to the cardiovascular effects of ethanol was evaluated with potassium canrenoate, a MR antagonist (MRA). Blockade of MR prevented ethanol-induced hypertension and hypercontractility of endothelium-intact and -denuded aortic rings. Ethanol up-regulated cyclooxygenase (COX)2 and augmented vascular levels of both reactive oxygen species (ROS) and thromboxane (TX)B₂, a stable metabolite of TXA₂. These responses were abrogated by MR blockade. Hyperreactivity to phenylephrine induced by ethanol consumption was reversed by tiron [a scavenger of superoxide (O₂∙^-)], SC236 (a selective COX2 inhibitor) or SQ29548 (an antagonist of TP receptors). Treatment with the antioxidant apocynin prevented the vascular hypercontractility, as well as the increases in COX2 expression and TXA₂ production induced by ethanol consumption. Our study has identified novel mechanisms through which ethanol consumption promotes its deleterious effects in the cardiovascular system. We provided evidence for a role of MR in the vascular hypercontractility and hypertension associated with ethanol consumption. The MR pathway triggers vascular hypercontractility through ROS generation, up-regulation of COX2 and overproduction of TXA₂, which will ultimately induce vascular contraction.

Alcohol Use Disorders and Their Harmful Effects on the Contractility of Skeletal, Cardiac and Smooth Muscles

Alcohol misuse has deleterious effects on personal health, family, societal units, and global economies. Moreover, alcohol misuse usually leads to several diseases and conditions, including alcoholism, which is a chronic condition and a form of addiction. Alcohol misuse, whether as acute intoxication or alcoholism, adversely affects skeletal, cardiac and/or smooth muscle contraction. Ethanol (ethyl alcohol) is the main effector of alcohol-induced dysregulation of muscle contractility, regardless of alcoholic beverage type or the ethanol metabolite (with acetaldehyde being a notable exception). Ethanol, however, is a simple and "promiscuous" ligand that affects many targets to mediate a single biological effect. In this review, we firstly summarize the processes of excitation-contraction coupling and calcium homeostasis which are critical for the regulation of contractility in all muscle types. Secondly, we present the effects of acute and chronic alcohol exposure on the contractility of skeletal, cardiac, and vascular/ nonvascular smooth muscles. Distinctions are made between in vivo and in vitro experiments, intoxicating vs. sub-intoxicating ethanol levels, and human subjects vs. animal models. The differential effects of alcohol on biological sexes are also examined. Lastly, we show that alcohol-mediated disruption of muscle contractility, involves a wide variety of molecular players, including contractile proteins, their regulatory factors, membrane ion channels and pumps, and several signaling molecules. Clear identification of these molecular players constitutes a first step for a rationale design of pharmacotherapeutics to prevent, ameliorate and/or reverse the negative effects of alcohol on muscle contractility.

Melatonin reverses the loss of the anticontractile effect of perivascular adipose tissue in obese rats

Perivascular adipose tissue (PVAT) undergoes functional changes in obesity. Increased oxidative stress is a central mechanism whereby obesity induces loss of the anticontractile effect of PVAT. Melatonin is an antioxidant that displays vasoprotective action in cardiovascular disease. Here, we sought to investigate whether melatonin would restore the anticontractile effect of periaortic PVAT in obesity. Male Wistar Hannover rats were treated for 10 weeks with a high-calorie diet. Melatonin (5 mg/kg/d, p.o., gavage) was administered for 2 weeks. Functional findings showed that obesity-induced loss of the anticontractile effect of PVAT and treatment with melatonin reversed this response. Tiron [a scavenger of superoxide anion (O₂ ^- )] restored the anticontractile effect of PVAT in aortas from obese rats, suggesting a role for reactive oxygen species (ROS) in such response. Decreased superoxide dismutase (SOD) activity and augmented levels of ROS were detected in periaortic PVAT from obese rats. These responses were accompanied by decreased levels of nitric oxide (NO) in PVAT. Treatment with melatonin restored SOD activity, decreased ROS levels, and increased NO bioavailability in PVAT from obese rats. Here, we first reported the beneficial effects of melatonin in periaortic PVAT in obesity. Melatonin reversed the adverse effects of obesity in PVAT that included overproduction of ROS, reduced SOD activity, and decreased bioavailability of NO. Therefore, PVAT may constitute an important target for the treatment of obesity-induced vascular dysfunction and melatonin emerges as a potential tool in the management of the vascular complications induced by obesity.

Hydrogen peroxide and nitric oxide induce anticontractile effect of perivascular adipose tissue via renin angiotensin system activation

The perivascular adipose tissue (PVAT) is located around the adventitia, composed primarily by adipocytes, stromal cells, leukocytes, fibroblasts and capillaries. It is well described that PVAT is an important modulator of the vascular tone being considered a biologically active tissue, releasing both vasoconstrictor and vasodilators factors. The literature shows that the anti-contractile effect induced by PVAT may be due to activation of the renin-angiotensin system (RAS).

AIM

Investigate whether the renin-angiotensin system participates in the effect exerted by perivascular adipose tissue on the vascular tone.

METHODS AND RESULTS

For this study we used thoracic aorta from Balb/c mice and performed vascular reactivity, nitric oxide and hydrogen peroxide quantification using selective probes and fluorescence microscopy, immunofluorescence to locate receptors and enzymes involved in this response. Our results demonstrated that perivascular adipose tissue induces an anti-contractile effect in endothelium-independent manner and involves Mas and AT₂ receptors participation with subsequent PI3K/Akt pathway activation. This pathway culminated with nitric oxide and hydrogen peroxide production by neuronal nitric oxide synthase, being hydrogen peroxide most relevant for the anti-contractile effect of perivascular adipose tissue.

CONCLUSION

For the first time in the literature, our results show the presence of Mas and AT₂ receptors, as well as, nitric oxide synthase on perivascular adipose tissue. Furthermore, our results show the involvement of Mas and AT₂ receptors and consequently nitric oxide synthase activation in the anti-contractile effect exerted by perivascular adipose tissue.

Spontaneously hypertensive rats exhibit higher sensitivity to ethanol-induced hypotensive effects: Role of NMDA receptors and nitric oxide in rostral ventrolateral medulla

Intake of ethanol (alcohol) affects cardiovascular function. Acute ethanol intake has been shown to lower blood pressure (BP) in hypertensive patients. The present study was undertaken to examine the effects and mechanisms of acute administration of ethanol on BP in hypertensive and normotensive rats. Ethanol was given by intraperitoneal (i.p.) injection in male spontaneously hypertensive rats (SHRs) and the normotensive Wistar-Kyoto rats (WKYs). BP responses were measured in free-moving conscious rats or in urethane-anesthetized rats. Inhibitors were applied by bilateral microinjection into the rostral ventrolateral medulla (RVLM). Nitric oxide (NO•) levels and glutamate levels were determined by nitrate and nitrite (NOx) analyzer and HPLC-ECD, respectively. Intraperitoneal (i.p.) injection of ethanol (1.6 g/kg) caused a significant decrease in BP in free-moving or in anesthetized SHRs but not in WKYs. A higher dose (3.2 g/kg) of ethanol decreased BP in both SHRs and WKYs, although the depressor responses in SHRs occurred significantly earlier than those in WKYs. The blood ethanol concentrations 60 min after injection were similar in SHRs and WKYs. Bilateral microinjection of nitric oxide synthase (NOS) inhibitors or glutamatergic NMDA receptor antagonists into the RVLM 5 min after administration of ethanol significantly inhibited the ethanol-induced depressor effects in SHRs. The levels of NOx and glutamate release in the RVLM following ethanol administration and the NOx content in the RVLM areas 30 min after administration were significantly increased in SHRs, but not in WKYs. Our results showed that SHRs were more sensitive to ethanol-induced hypotensive effects than WKYs because of augmentation of ethanol-induced expression of the glutamatergic NMDA receptor/NO• signal in the RVLM of SHRs.

Cholecalciferol in ethanol-preferring rats muscle fibers increases the number and area of type II fibers

The chronic use of ethanol causes neuropathy and atrophy of type II fibers and promotes vitamin D decrease. This study evaluated cholecalciferol effects on the deep fibular nerve and extensor digitorum longus (EDL) muscle using an UChB ethanol-preferring rats model. Blood analyses were carried out to measure levels of 25-hydroxycholecalciferol (25(OH)D), calcium (Ca²⁺), Phosphorus (P), and parathyroid hormone (PTH). It was used EDL muscle to evaluate oxidative stress. The deep fibular nerve and EDL muscle were used for morphologic and morphometric assessment. 25(OH)D plasma levels were higher in the supplemented group and no alterations were observed in other parameters including the oxidative stress evaluation. The G ratio remained constant which indicates nervous conduction normality. Cholecalciferol supplementation promoted an increase in the number and area of type II fibers and a decrease in the area of type I fibers. In the studied model, there was neither alcoholic myopathy nor neuropathy. The EDL muscle glycolytic patterns in the high-drinker UChB rats may be associated with the differential effects of cholecalciferol on metabolism and protein synthesis in skeletal muscle.

Perivascular adipose tissue protects against the vascular dysfunction induced by acute ethanol intake: Role of hydrogen peroxide

AIM

We investigated the consequences of acute ethanol intake on the anti-contractile effect of perivascular adipose tissue (PVAT).

METHODS

The effects of a single dose of ethanol (1 g/kg; p.o. gavage) on the vascular function were assessed within 30 min in male Wistar rats.

RESULTS

Ethanol decreased the relaxation induced by acetylcholine and increased the contraction induced by phenylephrine in endothelium-intact, but not in endothelium-denuded aortas without PVAT. The vascular dysfunction induced by ethanol was not observed in aortic rings with PVAT. N^ω-Nitro-l-arginine methyl ester (L-NAME), NG-nitro-l-arginine (L-NNA) and 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), but not tiron or tempol, increased the contraction induced by phenylephrine in endothelium-intact aortas with PVAT from control and ethanol-treated rats. Catalase increased phenylephrine-induced contraction in aortas with PVAT from ethanol-treated rats, but not from control rats. Conversely, inhibition of catalase with aminotriazole decreased phenylephrine-induced contraction in aortas from ethanol-treated rats. Treatment with ethanol increased hydrogen peroxide (H₂O₂) levels and decreased catalase activity in aortas with PVAT. Ethanol increased superoxide anion (O₂^-) generation in aortas with or without PVAT. Superoxide dismutase (SOD) activity was not affected by ethanol intake. In situ quantification of H₂O₂ using 2'7'dichlorodihydrofluorescein diacetate (DCFH-DA) revealed increased levels of H₂O₂ in periaortic PVAT from ethanol-treated rats. However, in situ evaluation of nitric oxide (NO) in both aorta and PVAT showed no differences between groups.

CONCLUSIONS

Our study provides novel evidence that the periaortic PVAT protects against the vascular dysfunction induced by acute ethanol intake through a mechanism that involves increased generation of H₂O₂.

Cardiovascular Consequences of Binge Drinking: An Integrative Review with Implications for Advocacy, Policy, and Research

Worldwide, binge drinking is a major public health problem. The popularized health risks associated with binge drinking include physical injury and motor vehicle crashes; less attention has been given to the negative effects on the cardiovascular (CV) system. The primary aims of this review were to provide a summary of the adverse effects of binge drinking on the risk and development of CV disease and to review potential pathophysiologic mechanisms. Using specific inclusion criteria, an integrative review was conducted that included data from human experimental, prospective cross-sectional, and cohort epidemiological studies that examined the association between binge drinking and CV conditions such as hypertension (HTN), myocardial infarction (MI), stroke, and arrhythmias. Studies were identified that examined the relationship between binge drinking and CV outcomes. Collectively, findings support that binge drinking is associated with a higher risk of pre-HTN, HTN, MI, and stroke in middle-aged and older adults. Binge drinking may also have adverse CV effects in young adults (aged 18 to 30). Mechanisms remain incompletely understood; however, available evidence suggests that binge drinking may induce oxidative stress and vascular injury and be proatherogenic. Public health messages regarding binge drinking need to include the effects of binge drinking on the CV system.

Acute Ethanol Intake Induces NAD(P)H Oxidase Activation and Rhoa Translocation in Resistance Arteries

Background

The mechanism underlying the vascular dysfunction induced by ethanol is not totally understood. Identification of biochemical/molecular mechanisms that could explain such effects is warranted.

Objective

To investigate whether acute ethanol intake activates the vascular RhoA/Rho kinase pathway in resistance arteries and the role of NAD(P)H oxidase-derived reactive oxygen species (ROS) on such response. We also evaluated the requirement of p47phox translocation for ethanol-induced NAD(P)H oxidase activation.

Methods

Male Wistar rats were orally treated with ethanol (1g/kg, p.o. gavage) or water (control). Some rats were treated with vitamin C (250 mg/kg, p.o. gavage, 5 days) before administration of water or ethanol. The mesenteric arterial bed (MAB) was collected 30 min after ethanol administration.

Results

Vitamin C prevented ethanol-induced increase in superoxide anion (O₂^-) generation and lipoperoxidation in the MAB. Catalase and superoxide dismutase activities and the reduced glutathione, nitrate and hydrogen peroxide (H₂O₂) levels were not affected by ethanol. Vitamin C and 4-methylpyrazole prevented the increase on O₂^- generation induced by ethanol in cultured MAB vascular smooth muscle cells. Ethanol had no effect on phosphorylation levels of protein kinase B (Akt) and eNOS (Ser¹¹⁷⁷ or Thr⁴⁹⁵ residues) or MAB vascular reactivity. Vitamin C prevented ethanol-induced increase in the membrane: cytosol fraction ratio of p47phox and RhoA expression in the rat MAB.

Conclusion

Acute ethanol intake induces activation of the RhoA/Rho kinase pathway by a mechanism that involves ROS generation. In resistance arteries, ethanol activates NAD(P)H oxidase by inducing p47phox translocation by a redox-sensitive mechanism.

Chronic restraint stress increases angiotensin II potency in the rat carotid: role of cyclooxygenases and reactive oxygen species

OBJECTIVES

To investigate the mechanisms underlying the effects of chronic restraint stress on the vascular contractile response induced by angiotensin (Ang) II in rat carotid.

METHODS

Concentration-response curves for AngII were obtained in endothelium-intact or endothelium-denuded carotid rings, in the absence or presence of SC-560 (COX-1 inhibitor), SC-236 (COX-2 inhibitor), wortmannin (PI₃ K-Akt inhibitor), ML171 (NOX-1 inhibitor), VAS2870 (NOX-4 inhibitor), tiron (O2- scavenger) or PEG-catalase (H₂ O₂ scavenger). 6-ketoPGF_1α , TXB₂ , O2- or H₂ O₂ levels and superoxide dismutase and catalase activity or expression were also measured in rat carotid.

KEY FINDINGS

Stress increased AngII potency in rat carotid. Muscular COX-1 or COX-2-derived metabolites negatively modulated AngII-induced contraction in control rat carotid. Endothelial COX-1 or COX-2-derived metabolites positively modulated AngII-induced contraction in stressed rat carotid. PI₃ K-Akt, NOX-1, NOX-4, O2- and H₂ O₂ positively modulated AngII-induced contraction in stressed rat carotid. Stress increased 6-ketoPGF_1α or H₂ O₂ generation and reduced catalase activity in rat carotid. Protein expression of COX-1, NOX-4 or p-Akt was increased in stressed rat carotid.

CONCLUSIONS

Stress increases AngII potency in rat carotid by a mechanism that involves the increased generation of PGI₂ and H₂ O₂ and the activation of Akt pathway. Such mechanism could play a pathophysiological role in cardiovascular diseases correlated with stress.

Ethanol attenuates peripheral NMDAR-mediated vascular oxidative stress and pressor response

There are no studies on the acute effect of ethanol on peripheral N-methyl-d-aspartate receptor (NMDAR)-mediated increases in reactive oxygen species (ROS) and blood pressure (BP). We tested the hypothesis that ethanol antagonism of peripheral NMDAR dampens systemic NMDA-evoked increases in vascular ROS and BP. We investigated the effect of ethanol (1 g/kg) on BP and heart rate (HR) responses elicited by systemic bolus (125-1000 μg/kg, intra-venous [i.v.]) or infused (180 μg/kg/min) NMDA in conscious male Sprague-Dawley rats. We also hypothesized that peripheral NMDAR blockade with DL-2-Amino-5-phosphonopentanoic acid (AP-5; 5 mg/kg, i.v.) uncovers an ethanol- (1 or 1.5 g/kg) evoked hypotensive response. Ethanol attenuated the peripheral NMDAR-mediated pressor and bradycardic responses caused by NMDA infusion, and ex vivo studies revealed parallel ethanol attenuation of peripheral NMDAR-mediated increases in vascular ROS. While ethanol (1 or 1.5 g/kg) alone had no effect on BP, the higher dose caused a hypotensive response in the presence of NMDAR blockade (AP-5). Blood ethanol concentrations were not statistically different in the groups that received ethanol alone or along with NMDA or AP-5. These findings are the first to demonstrate ethanol attenuation of peripheral NMDAR-mediated pressor response, and the uncovering of ethanol-evoked hypotension in the presence of peripheral NMDAR blockade.

Pharmacological characterization of the relaxant effect induced by adrenomedullin in rat cavernosal smooth muscle

The aim of the present study was to determine the mechanisms underlying the relaxant effect of adrenomedullin (AM) in rat cavernosal smooth muscle (CSM) and the expression of AM system components in this tissue. Functional assays using standard muscle bath procedures were performed in CSM isolated from male Wistar rats. Protein and mRNA levels of pre-pro-AM, calcitonin receptor-like receptor (CRLR), and Subtypes 1, 2 and 3 of the receptor activity-modifying protein (RAMP) family were assessed by Western immunoblotting and quantitative real-time polymerase chain reaction, respectively. Nitrate and 6-keto-prostaglandin F_1α (6-keto-PGF_1α; a stable product of prostacyclin) levels were determined using commercially available kits. Protein and mRNA of AM, CRLR, and RAMP 1, -2, and -3 were detected in rat CSM. Immunohistochemical assays demonstrated that AM and CRLR were expressed in rat CSM. AM relaxed CSM strips in a concentration-dependent manner. AM_22-52, a selective antagonist for AM receptors, reduced the relaxation induced by AM. Conversely, CGRP_8-37, a selective antagonist for calcitonin gene-related peptide receptors, did not affect AM-induced relaxation. Preincubation of CSM strips with N^G-nitro-L-arginine-methyl-ester (L-NAME, nitric oxide synthase inhibitor), 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, quanylyl cyclase inhibitor), Rp-8-Br-PET-cGMPS (cGMP-dependent protein kinase inhibitor), SC560 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethyl pyrazole, selective cyclooxygenase-1 inhibitor], and 4-aminopyridine (voltage-dependent K⁺ channel blocker) reduced AM-induced relaxation. On the other hand, 7-nitroindazole (selective neuronal nitric oxide synthase inhibitor), wortmannin (phosphatidylinositol 3-kinase inhibitor), H89 (protein kinase A inhibitor), SQ22536 [9-(tetrahydro-2-furanyl)-9H-purin-6-amine, adenylate cyclase inhibitor], glibenclamide (selective blocker of ATP-sensitive K⁺ channels), and apamin (Ca²⁺-activated channel blocker) did not affect AM-induced relaxation. AM increased nitrate levels and 6-keto-PGF_1α in rat CSM. The major new contribution of this research is that it demonstrated expression of AM and its receptor in rat CSM. Moreover, we provided evidence that AM-induced relaxation in this tissue is mediated by AM receptors by a mechanism that involves the nitric oxide-cGMP pathway, a vasodilator prostanoid, and the opening of voltage-dependent K⁺ channels.

Hydrogen peroxide induces vasorelaxation by enhancing 4-aminopyridine-sensitive Kv currents through S-glutathionylation

Hydrogen peroxide (H₂O₂) is an endothelium-derived hyperpolarizing factor. Since opposing vasoactive effects have been reported for H₂O₂ depending on the vascular bed and experimental conditions, this study was performed to assess whether H₂O₂ acts as a vasodilator in the rat mesenteric artery and, if so, to determine the underlying mechanisms. H₂O₂ elicited concentration-dependent relaxation in mesenteric arteries precontracted with norepinephrine. The vasodilatory effect of H₂O₂ was reversed by treatment with dithiothreitol. H₂O₂-elicited vasodilation was significantly reduced by blocking 4-aminopyridine (4-AP)-sensitive Kv channels, but it was resistant to blockers of big-conductance Ca²⁺-activated K⁺ channels and inward rectifier K⁺ channels. A patch-clamp study in mesenteric arterial smooth muscle cells (MASMCs) showed that H₂O₂ increased Kv currents in a concentration-dependent manner. H₂O₂ speeded up Kv channel activation and shifted steady state activation to hyperpolarizing potentials. Similar channel activation was seen with oxidized glutathione (GSSG). The H₂O₂-mediated channel activation was prevented by glutathione reductase. Consistent with S-glutathionylation, streptavidin pull-down assays with biotinylated glutathione ethyl ester showed incorporation of glutathione (GSH) in the Kv channel proteins in the presence of H₂O₂. Interestingly, conditions of increased oxidative stress within MASMCs impaired the capacity of H₂O₂ to stimulate Kv channels. Not only was the H₂O₂ stimulatory effect much weaker, but the inhibitory effect of H₂O₂ was unmasked. These data suggest that H₂O₂ activates 4-AP-sensitive Kv channels, possibly through S-glutathionylation, which elicits smooth muscle relaxation in rat mesenteric arteries. Furthermore, our results support the idea that the basal redox status of MASMCs determines the response of Kv currents to H₂O₂.

Acute ethanol intake induces mitogen-activated protein kinase activation, platelet-derived growth factor receptor phosphorylation, and oxidative stress in resistance arteries

In the present study, we investigated the role of angiotensin type I (AT1) receptor in reactive oxygen species (ROS) generation and mitogen-activated protein kinases (MAPK) activation induced by acute ethanol intake in resistance arteries. We also evaluated the effect of ethanol on platelet-derived growth factor receptors (PDGF-R) phosphorylation and the role of this receptor on ROS generation by ethanol. Ethanol (1 g/kg; p.o. gavage) effects were assessed within 30 min in male Wistar rats. Acute ethanol intake did not alter angiotensin I or angiotensin II levels in the rat mesenteric arterial bed (MAB). Ethanol induced vascular oxidative stress, and this response was not prevented by losartan (10 mg/kg; p.o. gavage), a selective AT1 receptor antagonist. MAB from ethanol-treated rats displayed increased SAPK/JNK and PDGF-R phosphorylation, responses that were not prevented by losartan. The phosphorylation levels of protein kinase B (Akt) and eNOS were not affected by acute ethanol intake. MAB nitrate levels and the reactivity of this tissue to acetylcholine, phenylephrine, and sodium nitroprusside were not affected by ethanol intake. Ethanol did not alter plasma antioxidant capacity, the levels of reduced glutathione, or the activities of superoxide dismutase and catalase in the rat MAB. Short-term effects of ethanol (50 mmol/l) were evaluated in vascular smooth muscle cells (VSMC) isolated from rat MAB. Ethanol increased ROS generation, and this response was not affected by AG1296, a PDGF-R inhibitor, or losartan. Finally, ethanol did not alter MAPK or PDGF-R phosphorylation in cultured VSMC. Our study provides novel evidence that acute ethanol intake induces ROS generation, PDGF-R phosphorylation, and MAPK activation through AT(1)-independent mechanisms in resistance arteries in vivo. MAPK and PDGF-R play a role in vascular signaling and cardiovascular diseases and may contribute to the vascular pathobiology of ethanol.

Binge drinking impairs vascular function in young adults

OBJECTIVES

The aim of this study was to assess whether young binge drinkers (BD) have impaired macrovascular and microvascular function and cardiovascular disease risk factors compared with age-matched alcohol abstainers (A).

BACKGROUND

Binge drinking rates are highest on college campuses and among those age 18 to 25 years; however, macrovascular and microvascular endothelial function in young adults with histories of repeated binge drinking (≥ 5 standard drinks in 2 h in men, ≥ 4 standard drinks in 2 h in women) has not been investigated.

METHODS

Cardiovascular profiles, brachial artery endothelial-dependent flow-mediated dilation (FMD), and flow-independent nitroglycerin (NTG)-mediated dilation and vasoreactivity of resistance arteries (isolated from gluteal fat biopsies) were evaluated in A and BD.

RESULTS

Men and women (18 to 25 years of age; A, n = 17; BD, n = 19) were enrolled. In the BD group, past-month mean number of binge episodes was 6 ± 1, and the mean duration of binge drinking behavior was 4 ± 0.6 years. FMD and NTG-mediated dilation were significantly lower in the BD group (FMD: 8.4 ± 0.7%, p = 0.022; NTG-mediated dilation: 19.6 ± 2%, p = 0.009) than in the A group (FMD: 11 ± 0.7%; NTG-mediated dilation: 28.6 ± 2%). Acetylcholine-induced and sodium nitroprusside-induced dilation in resistance arteries was not significantly different between the A and BD groups. However, endothelin-1-induced constriction was significantly enhanced in the BD group compared with the A group (p = 0.032). No differences between groups were found in blood pressure, lipoproteins, and C-reactive protein.

CONCLUSIONS

Alterations in the macrocirculation and microcirculation may represent early clinical manifestations of cardiovascular risk in otherwise healthy young BD. This study has important clinical implications for screening young adults for a repeated history of binge drinking.

Alcohol and cardiovascular disease--modulation of vascular cell function

Alcohol is a commonly used drug worldwide. Epidemiological studies have identified alcohol consumption as a factor that may either positively or negatively influence many diseases including cardiovascular disease, certain cancers and dementia. Often there seems to be a differential effect of various drinking patterns, with frequent moderate consumption of alcohol being salutary and binge drinking or chronic abuse being deleterious to one’s health. A better understanding of the cellular and molecular mechanisms mediating the many effects of alcohol consumption is beginning to emerge, as well as a clearer picture as to whether these effects are due to the direct actions of alcohol itself, or caused in part by its metabolites, e.g., acetaldehyde, or by incidental components present in the alcoholic beverage (e.g., polyphenols in red wine). This review will discuss evidence to date as to how alcohol (ethanol) might affect atherosclerosis that underlies cardiovascular and cerebrovascular disease, and the putative mechanisms involved, focusing on vascular endothelial and smooth muscle cell effects.

Oxidative stress-dependent cyclooxygenase-2-derived prostaglandin f(2α) impairs endothelial function in renovascular hypertensive rats

Abstract Aims: The role of endothelium-derived contracting factors (EDCFs) in regulating renovascular function is yet to be elucidated in renovascular hypertension (RH). The current study investigated whether oxidative stress-dependent cyclooxygenase (COX)-2-derived prostaglandin F(2α) (PGF(2α)) impairs endothelial function in renal arteries of renovascular hypertensive rats (RHR).

RESULTS

Renal hypertension was induced in rats by renal artery stenosis of both kidneys using the 2-kidney 2-clip model. Acute treatment with reactive oxygen species (ROS) scavengers, COX-2 inhibitors, and thromboxane-prostanoid receptor antagonists, but not COX-1 inhibitors, improved endothelium-dependent relaxations and eliminated endothelium-dependent contractions in RHR renal arteries. Five weeks of treatment with celecoxib or tempol reduced blood pressure, increased renal blood flow, and restored endothelial function in RHRs. Increased ROS production in RHR arteries was inhibited by ROS scavengers, but unaffected by COX-2 inhibitors; whereas increased PGF(2α) release was reduced by both ROS scavengers and COX-2 inhibitors. ROS also induced COX-2-dependent contraction in RHR renal arteries, which was accompanied by the release of COX-2-derived PGF(2α). Further, chronic tempol treatment reduced COX-2 and BMP4 upregulation, p38MAPK phosphorylation, and the nitrotyrosine level in RHR renal arteries.

CONCLUSION

These findings demonstrate the functional importance of oxidative stress, which serves as an initiator of increased COX-2 activity, and that COX-2-derived PGF(2α) plays an important role in mediating endothelial dysfunction in RH.

INNOVATION

The current study, thus, suggests that drugs targeting oxidative stress-dependent COX-2-derived PGF(2α) may be useful in the prevention and management of RH. Antioxid. Redox Signal. 16, 363-373.

The CAM-LDPI method: a novel platform for the assessment of drug absorption

OBJECTIVES

This study aimed to explore the use of the chicken chorioallantoic membrane (CAM) with laser doppler perfusion imaging (LDPI) as a platform to assess absorption of vasoactive drugs.

METHODS

The optimal age of the CAM to be employed in the test and the indicator of vasoactivity were first established. Test substances that included common solvents and vasoactive drugs were tested on the CAM surface to determine their irritancy and blood perfusion effects.

KEY FINDINGS

Insignificant changes in blood perfusion were observed with deionized water, 0.9% w/v soldium chloride and 5% w/v glucose monohydrate, as well as theophylline and glucagon. Complex changes in blood perfusion were detected with ethanol, N-methyl-2-pyrrolidone, glycerin and propranolol. Both caffeine and glyceryl trinitrate resulted in a drop in blood perfusion.

CONCLUSIONS

It was concluded that the LDPI offers a rapid and non-invasive method to measure blood perfusion in the CAM. The latter provides a potentially useful platform in formulation studies to evaluate the effects of additives on drug absorption using caffeine or glyceryl trinitrate as model drugs.

Ethanol induces vascular relaxation via redox-sensitive and nitric oxide-dependent pathways

We investigated the role of reactive oxygen species (ROS) and nitric oxide (NO) in ethanol-induced relaxation. Vascular reactivity experiments showed that ethanol (0.03-200 mmol/L) induced relaxation in endothelium-intact and denuded rat aortic rings isolated from male Wistar rats. Pre-incubation of intact or denuded rings with l-NAME (non selective NOS inhibitor, 100 μmol/L), 7-nitroindazole (selective nNOS inhibitor, 100 μmol/L), ODQ (selective inhibitor of guanylyl cyclase enzyme, 1 μmol/L), glibenclamide (selective blocker of ATP-sensitive K(+) channels, 3 μmol/L) and 4-aminopyridine (selective blocker of voltage-dependent K(+) channels, 4-AP, 1 mmol/L) reduced ethanol-induced relaxation. Similarly, tiron (superoxide anion (O(2)(-)) scavenger, 1 mmol/L) and catalase (hydrogen peroxide (H(2)O(2)) scavenger, 300 U/mL) reduced ethanol-induced relaxation to a similar extent in both endothelium-intact and denuded rings. Finally, prodifen (non-selective cytochrome P450 enzymes inhibitor, 10 μmol/L) and 4-methylpyrazole (selective alcohol dehydrogenase inhibitor, 10 μmol/L) reduced ethanol-induced relaxation. In cultured aortic vascular smooth muscle cells (VSMCs), ethanol stimulated generation of NO, which was significantly inhibited by l-NAME. In endothelial cells, flow cytometry studies showed that ethanol increased cytosolic Ca(2+) concentration ([Ca(2+)]c), O(2)(-) and cytosolic NO concentration ([NO]c). Tiron inhibited ethanol-induced increase in [Ca(2+)]c and [NO]c. The major new finding of this work is that ethanol induces relaxation via redox-sensitive and NO-cGMP-dependent pathways through direct effects on ROS production and NO signaling. These findings identify putative molecular mechanisms whereby ethanol, at pharmacological concentrations, influences vascular reactivity.

Long-term methylglyoxal treatment impairs smooth muscle contractility in organ-cultured rat mesenteric artery

Methylglyoxal (MGO), a metabolite of glucose accumulates in vascular tissues of hypertensive rats. We recently showed that short-term (30min) treatment with MGO inhibits noradrenaline (NA)-induced smooth muscle contraction in rat aorta and mesenteric artery. In the present study, long-term effect of MGO was examined using organ culture method. The contractility, morphology, and protein expression of rat mesenteric artery after organ culture with MGO for 3 days were examined. MGO (4 and 42μM) inhibited NA (0.1nM to 3μM) or KCl (72.7mM)-induced contraction. The inhibitory effect was higher in endothelium-denuded than endothelium-intact artery. An anti-oxidant drug, N-acetyl-l-cysteine (NAC; 1mM) or an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX), gp91ds-tat (0.1μM) prevented the inhibitory effect of MGO. MGO increased superoxide production as detected by lucigenin assay. In the medial layer of the arteries cultured with MGO, apoptotic morphological change was observed, and NAC or gp91ds-tat prevented it. MGO significantly increased expression of a homolog of gp91(phox), NOX1 but not gp91(phox) as determined by Western blotting. An NF-κB inhibitor, pyrrolidine dithiocarbamate prevented the MGO-induced NOX1 expression. MGO had no effect on protein expression of p22(phox), p67(phox), p47(phox), as well as superoxide dismutase (SOD)-1, SOD-2 and SOD-3. Present results indicate that long-term MGO treatment has an inhibitory effect on contractility of isolated blood vessel, which is likely mediated via increased NOX1-derived superoxide production and subsequent apoptosis.