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.

Endothelial dysfunction due to eNOS uncoupling: molecular mechanisms as potential therapeutic targets

Nitric oxide (NO) is one of the most important molecules released by endothelial cells, and its antiatherogenic properties support cardiovascular homeostasis. Diminished NO bioavailability is a common hallmark of endothelial dysfunction underlying the pathogenesis of the cardiovascular disease. Vascular NO is synthesized by endothelial nitric oxide synthase (eNOS) from the substrate L-arginine (L-Arg), with tetrahydrobiopterin (BH₄) as an essential cofactor. Cardiovascular risk factors such as diabetes, dyslipidemia, hypertension, aging, or smoking increase vascular oxidative stress that strongly affects eNOS activity and leads to eNOS uncoupling. Uncoupled eNOS produces superoxide anion (O₂^-) instead of NO, thus becoming a source of harmful free radicals exacerbating the oxidative stress further. eNOS uncoupling is thought to be one of the major underlying causes of endothelial dysfunction observed in the pathogenesis of vascular diseases. Here, we discuss the main mechanisms of eNOS uncoupling, including oxidative depletion of the critical eNOS cofactor BH₄, deficiency of eNOS substrate L-Arg, or accumulation of its analog asymmetrical dimethylarginine (ADMA), and eNOS S-glutathionylation. Moreover, potential therapeutic approaches that prevent eNOS uncoupling by improving cofactor availability, restoration of L-Arg/ADMA ratio, or modulation of eNOS S-glutathionylation are briefly outlined.

NADPH oxidase family proteins: signaling dynamics to disease management

Reactive oxygen species (ROS) are pervasive signaling molecules in biological systems. In humans, a lack of ROS causes chronic and extreme bacterial infections, while uncontrolled release of these factors causes pathologies due to excessive inflammation. Professional phagocytes such as neutrophils (PMNs), eosinophils, monocytes, and macrophages use superoxide-generating NADPH oxidase (NOX) as part of their arsenal of antimicrobial mechanisms to produce high levels of ROS. NOX is a multisubunit enzyme complex composed of five essential subunits, two of which are localized in the membrane, while three are localized in the cytosol. In resting phagocytes, the oxidase complex is unassembled and inactive; however, it becomes activated after cytosolic components translocate to the membrane and are assembled into a functional oxidase. The NOX isoforms play a variety of roles in cellular differentiation, development, proliferation, apoptosis, cytoskeletal control, migration, and contraction. Recent studies have identified NOX as a major contributor to disease pathologies, resulting in a shift in focus on inhibiting the formation of potentially harmful free radicals. Therefore, a better understanding of the molecular mechanisms and the transduction pathways involved in NOX-mediated signaling is essential for the development of new therapeutic agents that minimize the hyperproduction of ROS. The current review provides a thorough overview of the various NOX enzymes and their roles in disease pathophysiology, highlights pharmacological strategies, and discusses the importance of computational modeling for future NOX-related studies.

The effect of long-term alcohol intoxication on the morphological structures and enzymatic activity of rat salivary glands

BACKGROUND

To study changes in the morphological structures and enzymatic activity of the submandibular salivary gland (SMG) and parotid salivary gland (PG) in rats after prolonged alcohol intoxication.

METHODS

Sexually mature male Wistar rats consumed 20% ethanol (6.9 g/kg/day) for 180 consecutive days. The PG and SMG were collected for morphometric and histochemical analyses (nonparametric Mann-Whitney U test, p < 0.05).

RESULTS

After exposure to ethanol for 180 days, the PG showed a change in the shape of the acini and the secretory cells that formed them, uneven expansion of the interlobular excretory ducts, and moderate fatty infiltration in the stroma. After exposure to ethanol for 180 days, the SMG showed fatty infiltration and stromal edema, and changes in acinar cells, intercalated ducts, and striated ducts. There was a significant decrease in the relative and absolute weight of the SMG. The number of mast cells in the PG and SMG and their degranulation index increased 2-fold after exposure to ethanol. All mast cells were highly active. After ethanol exposure, the activity of alkaline phosphatase increased significantly in the myoepithelial cells of the SMG and PG; the activity of NADPH oxidase increased only in the acini SMG, and the activity of succinate dehydrogenase remained at the control level in the acini of both glands. In the ducts of these glands, the activity of other enzymes did not change.

CONCLUSIONS

Changes in the morphological structures, morphometric parameters, and enzymatic activity of the rat salivary glands after 180 days of ethanol intoxication are shown for the first time. The most pronounced changes were found in the SMG.

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.

Ethanol: striking the cardiovascular system by harming the gut microbiota

Ethanol consumption represents a significant public health problem, and excessive ethanol intake is a risk factor for cardiovascular disease (CVD), one of the leading causes of death and disability worldwide. The mechanisms underlying the effects of ethanol on the cardiovascular system are complex and not fully comprehended. The gut microbiota and their metabolites are indispensable symbionts essential for health and homeostasis and therefore, have emerged as potential contributors to ethanol-induced cardiovascular system dysfunction. By mechanisms that are not completely understood, the gut microbiota modulates the immune system and activates several signaling pathways that stimulate inflammatory responses, which in turn, contribute to the development and progression of CVD. This review summarizes preclinical and clinical evidence on the effects of ethanol in the gut microbiota and discusses the mechanisms by which ethanol-induced gut dysbiosis leads to the activation of the immune system and cardiovascular dysfunction. The cross talk between ethanol consumption and the gut microbiota and its implications are detailed. In summary, an imbalance in the symbiotic relationship between the host and the commensal microbiota in a holobiont, as seen with ethanol consumption, may contribute to CVD. Therefore, manipulating the gut microbiota, by using antibiotics, probiotics, prebiotics, and fecal microbiota transplantation might prove a valuable opportunity to prevent/mitigate the deleterious effects of ethanol and improve cardiovascular health and risk prevention.

Inducible nitric oxide synthase (iNOS) mediates ethanol-induced redox imbalance and upregulation of inflammatory cytokines in the kidney

Overexpression of the inducible isoform of the enzyme nitric oxide synthase (iNOS) has been associated to pathological processes in the kidney. Ethanol consumption induces the renal expression of iNOS; however, the contribution of this enzyme to the deleterious effects of ethanol in the kidney remains elusive. We examined whether iNOS plays a role in the renal dysfunction and oxidative stress induced by ethanol consumption. With this purpose, male C57BL/6 wild-type (WT) or iNOS-deficient (iNOS^-/-) mice were treated with ethanol (20% v/v) for 10 weeks. Treatment with ethanol increased the expression of Nox4 as well as the concentration of thiobarbituric acid reactive substances and the levels of tumor necrosis factor α in the renal cortex of WT but not iNOS^-/- mice. Augmented serum levels of creatinine and increased systolic blood pressure were found in WT and iNOS^-/- mice treated with ethanol. WT mice treated with ethanol showed increased production of reactive oxygen species and myeloperoxidase activity, but these responses were attenuated in iNOS^-/- mice. We concluded that iNOS played a role in ethanol-induced oxidative stress and pro-inflammatory cytokine production in the kidney. These are mechanisms that may contribute to the renal toxicity induced by ethanol.

Ethanol consumption increases renal dysfunction and mortality in a mice model of sub-lethal sepsis

Chronic ethanol consumption and sepsis cause oxidative stress and renal dysfunction. This study aimed to examine whether chronic ethanol consumption sensitizes the mouse kidney to sub-lethal cecal ligation and puncture (SL-CLP) sepsis, leading to impairment of renal function by tissue oxidative and inflammatory damage. Male C57BL/6J mice were treated for 9 weeks with ethanol (20%, v/v) before SL-CLP was induced. Systolic blood pressure (SBP), survival rate, creatinine plasma, oxidative stress, and inflammatory parameters, inducible nitric oxide synthase (iNOS), cytokines, and metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) levels were evaluated. Chronic ethanol consumption increased SBP, plasma creatinine, O₂^.-, H₂O₂, lipid peroxidation, catalase activity, Nox4, IL-6, and TNF-α levels, and MMP-9/TIMP-1 ratio. SL-CLP decreased SBP, increased creatinine, lipid peroxidation, IL-6, TNF-α, nitrate/nitrite (NOx), and iNOS levels, and MMP-2/TIMP-2 ratio, and decreased catalase activity. SL-CLP mice previously treated with ethanol showed a similar decrease in SBP but higher mortality and creatinine levels than SL-CLP alone. These responses were mediated by increased O₂^-, lipid peroxidation, IL-6, TNF-α, NOx, iNOS, MMP-2, and MMP-9 levels, and MMP-9/TIMP-1 and MMP-2/TIMP-2 ratios. Our findings demonstrated that previous oxidative stress and inflammatory damage caused by ethanol consumption sensitizes the kidney to SL-CLP injury, resulting in impaired kidney function and sepsis prognosis.

Ethanol and cyclophosphamide induce similar nephrotoxic effects: possible role for Nox4 and superoxide

We tested the hypothesis that ethanol consumption would aggravate the renal damage induced by cyclophosphamide (CYP). Male C57BL/6 J mice from control (n = 8) and CYP (n = 12) groups had free access to filtered water and standard rodent chow for 12 weeks. Then, 24 h before euthanasia mice received an intraperitoneal injection of saline or CYP (300 mg/kg). Mice from ethanol (n = 8) and CYP + ethanol (n = 12) groups had free access to increasing doses of ethanol for 12 weeks. Twenty-four hours before euthanasia, mice from ethanol and CYP + ethanol groups received an intraperitoneal injection of saline or CYP, respectively. Ethanol, CYP, or the association of both drugs augmented serum levels of creatinine and increased the levels of superoxide ([Formula: see text]) generation and thiobarbituric acid reactive substances in the renal cortex. Upregulation of Nox4 and increased activity of superoxide dismutase were detected in the renal cortex of mice treated with ethanol, CYP, or the combination of these drugs; however, these molecular alterations induced by CYP were not potentiated by ethanol consumption. Our findings revealed that chronic ethanol consumption had no potentiating effect on the nephrotoxic effects displayed by CYP. It is possible that the combination of these drugs showed no synergistic effect because they share the same molecular mechanisms of renal toxicity.

NADPH oxidase contributes to oxidative damage and mitochondrial impairment induced by acute ethanol treatment in rat hippocampal neurons

Acute ethanol treatment induces neurodegeneration in cultured neurons and can lead to brain damage in animal models. Neuronal cells exposed to ethanol showed an increase in reactive oxygen species (ROS), oxidative damage and mitochondrial impairment contributing to synaptic failure. However, the underlying mechanisms of these events are not well understood. Here, we studied the contribution of NADPH oxidase, as a relevant source of ROS production in the brain, to mitochondrial impairment and oxidative stress induced by ethanol. We used primary hippocampal neurons subjected to an acute treatment of ethanol at increasing concentrations (25, 50, and 75 mM, 24 h), and we evaluated ROS production, mitochondrial function, and synaptic vesicle activity. Our studies showed that after ethanol administration, hippocampal neurons presented an increase in ROS levels, mitochondrial dysfunction, calcium handling defects, and synaptic impairment. Interestingly, treatment with the NADPH inhibitor, apocynin, significantly prevented oxidative stress, mitochondrial dysfunction, and the impairment of synaptic vesicle activity induced by ethanol treatment. These results indicate that NADPH oxidase could be a key participant in the molecular mechanism by which alcohol affects the brain.

Ceftriaxone Attenuated Anxiety-Like Behavior and Enhanced Brain Glutamate Transport in Zebrafish Subjected to Alcohol Withdrawal

Chronic and/or excessive consumption of alcohol followed by reduced consumption or abstention can result in Alcohol Withdrawal Syndrome. A number of behavioral changes and neurological damage result from ethanol (EtOH) withdrawal. Ceftriaxone (Cef) modulates the activity of excitatory amino acid transporters by increasing their gene expression. Zebrafish are commonly used to study alcohol exposure. The aim of this study was to evaluate the influence of Cef (100 µM) on behavior patterns, glutamate transport activity, and oxidative stress in zebrafish brains subjected to EtOH (0.3% v/v) withdrawal. The exploratory tests using Novel tank showed that EtOH withdrawal promoted a decrease in the time spent and number of entries of in the bottom displaying an anxiety-like behavior. In contrast, treatment with Cef resulted in recovery of exploratory behavioral patterns. Ceftriaxone treatment resulted in increased glutamate uptake in zebrafish subjected to EtOH withdrawal. Furthermore, EtOH withdrawal increased reactive species, as determined using thiobarbituric acid and dichlorodihydrofluorescein assays. Treatment with Cef reversed these effects. Ceftriaxone promoted a significant reduction in brain sulfhydryl content in zebrafish subjected to EtOH withdrawal. Therefore, Cef treatment in conjunction with EtOH withdrawal induced anxiolytic-like effects due to possible neuromodulation of glutamatergic transporters, potentially through mitigation of oxidative stress.

Chronic ethanol consumption induces micturition dysfunction and alters the oxidative state of the urinary bladder

Oxidative stress is pointed out as a major mechanism by which ethanol induces functional and structural changes in distinctive tissues. We evaluated whether ethanol consumption would increase oxidative stress and cause micturition dysfunction. Male C57BL/6J mice were treated with 20% ethanol (v/v) for 10 weeks. Our findings showed that chronic ethanol consumption reduced micturition spots and urinary volume in conscious mice, whereas in anaesthetized animals cystometric analysis revealed reduced basal pressure and increased capacity, threshold pressure, and maximum voiding. Treatment with ethanol reduced the contraction induced by carbachol in isolated bladders. Chronic ethanol consumption increased the levels of oxidant molecules and thiobarbituric acid reactive species in the mouse bladder. Upregulation of Nox2 was detected in the bladder of ethanol-treated mice. Increased activity of both superoxide dismutase and catalase were detected in the mouse bladder after treatment with ethanol. Conversely, decreased levels of reduced glutathione were detected in the bladder of ethanol-treated mice. The present study first demonstrated that chronic ethanol consumption induced micturition dysfunction and that this response was accompanied by increased levels of oxidant molecules in the mousebladder. These findings suggest that ethanol consumption is a risk factor for vesical dysfunction.

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.

Tributyrin Supplementation Protects Immune Responses and Vasculature and Reduces Oxidative Stress in the Proximal Colon of Mice Exposed to Chronic-Binge Ethanol Feeding

Excessive ethanol consumption causes adverse effects and contributes to organ dysfunction. Ethanol metabolism triggers oxidative stress, altered immune function, and gut dysbiosis. The gut microbiome is known to contribute to the maintenance of intestinal homeostasis, and disturbances are associated with pathology. A consequence of gut dysbiosis is also alterations in its metabolic and fermentation byproducts. The gut microbiota ferments undigested dietary polysaccharides to yield short-chain fatty acids, predominantly acetate, propionate, and butyrate. Butyrate has many biological mechanisms of action including anti-inflammatory and immunoprotective effects, and its depletion is associated with intestinal injury. We previously showed that butyrate protects gut-liver injury during ethanol exposure. While the intestine is the largest immune organ in the body, little is known regarding the effects of ethanol on intestinal immune function. This work is aimed at investigating the effects of butyrate supplementation, in the form of the structured triglyceride tributyrin, on intestinal innate immune responses and oxidative stress following chronic-binge ethanol exposure in mice. Our work suggests that tributyrin supplementation preserved immune responses and reduced oxidative stress in the proximal colon during chronic-binge ethanol exposure. Our results also indicate a possible involvement of tributyrin in maintaining the integrity of intestinal villi vasculature disrupted by chronic-binge ethanol exposure.

Dysregulated mitogen-activated protein kinase and matrix metalloproteinase in ethanol-induced cavernosal dysfunction

We evaluated the effects of ethanol consumption on the mitogen-activated protein kinases (MAPK) and metalloproteinases (MMP) pathways in the rat cavernosal smooth muscle (CSM). Male Wistar rats were treated with ethanol (20% v/v) for 6 weeks. Quantitative real-time polymerase chain reaction experiments showed that ethanol consumption did not alter mRNA levels of p38MAPK, SAPK/JNK, ERK1/2, MMP-2, or MMP-9 in the rat CSM. Western immunoblotting experiments revealed decreased protein expression of p38MAPK and phosphorylation of SAPK/JNK in the CSM from ethanol-treated rats. Additionally, ethanol consumption decreased the expression of MMP-2. Functional assays showed that SP600125, an inhibitor of SAPK/JNK, prevented the increase in endothelin (ET)-1-induced contraction in the CSM from ethanol-treated rats. Treatment with ethanol decreased MMP-2 activity, but did not change net MMP activity in the rat CSM. Ethanol consumption increased the circulating levels of MMP-2, MMP-9, and TIMP-2 as well as the MMP-9/TIMP-1 ratio. The major finding of our study is that ethanol consumption down-regulates both MAPK and MMP pathways in the rat CSM, whereas it increases the circulating levels of MMP-9. Additionally, we found that SAPK/JNK plays a role in ethanol-induced increase on ET-1 contraction in the isolated rat CSM.

Data on the effects of losartan on protein expression, vascular reactivity and antioxidant capacity in the aorta of ethanol-treated rats

We describe the effects of losartan, a selective AT₁ receptor antagonist on the alterations induced by treatment with ethanol in the rat aorta. The data shown here are related to the article entitled “Angiotensin type 1 receptor mediates chronic ethanol consumption-induced hypertension and vascular oxidative stress” (P. Passaglia, C.S. Ceron, A.S. Mecawi, J. Antunes-Rodrigues, E.B. Coelho, C.R. Tirapelli, 2015) [1]. Here we include new data on the protective effect of losartan against ethanol-induced oxidative stress. Male Wistar rats treated for 2 weeks with ethanol (20%, vol./vol.) exhibited increased aortic production of reactive oxygen species (ROS) and losartan (10 mg/kg/day; p.o. gavage) prevented this response. Ethanol did not alter the expression of eNOS in the rat aorta. Losartan prevented ethanol-induced increase in the aortic expression of nNOS. Neither ethanol nor losartan affected superoxide dismutase (SOD) or catalase (CAT) activities in the rat aorta. Treatment with ethanol increased the contraction induced by phenylephrine in both endothelium-intact and endothelium-denuded aortas and these responses were prevented by losartan. Conversely, neither ethanol nor losartan affected the endothelium-dependent relaxation induced by acetylcholine.