Estrogen modulation of the ethanol-evoked myocardial oxidative stress and dysfunction via DAPK3/Akt/ERK activation in male rats. Toxicol Appl Pharmacol. 2015; Jun 23. [Epub ahead of print]. [PMID: 26111663 DOI: 10.1016/j.taap.2015.06.015]

Estrogen-mediated mitigation of cardiac oxidative stress in ovariectomized rats is associated with upregulated cardiac circadian clock Per2 and heart-specific miRNAs

AIM

Estrogen (E2) confers cardioprotection in premenopausal women and in models of menopause and its effects, mostly studied in female reproductive organs, vary on a circadian rhythm basis in relation to the circadian clock genes. However, it remains unknown if a similar circadian pattern exists in the female heart in a manner that explains, at least partly, the cardioprotective effect of E2. The aim of the present investigation was to determine if upregulation of the circadian clock Per2 and its regulated heart-specific miRNAs, and redox enzymes contribute to the E2-mediated cardioprotection in ovariectomized rats.

MAIN METHODS

Rats were subjected to ovariectomy (OVX) 2-weeks prior to a 2-week E2 treatment. On the last treatment day, hearts were collected every 4 h. for ex-vivo biochemical measurements. In parallel studies, telemetric mean arterial pressure (MAP) was obtained at the tissue collection times.

KEY FINDINGS

OVX + E2 rats exhibited lower body weight during daytime and MAP during day and night times, and their hearts exhibited: (1) higher Per2 protein abundance, cardioprotective miRNAs (miRNA1, miRNA133a, miRNA208a, miRNA499), mALDH2, and catalase; (2) lower reactive oxygen species, cardio-detrimental miRNA652, carbonyl, MDA and HO-1 levels. The reciprocal Per2/HO-1 relationship was more evident during the daytime and correlated with the upregulated cardioprotective miRNAs in OVX + E2 rats. Finally, cardiac Per2, heart-specific miRNAs and reactive oxygen species levels and redox enzymes activities were similar in normal female and OVX + E2 rats.

SIGNIFICANCE

Enhancement of cardiac Per2, redox enzymes and heart-specific miRNAs likely contribute to E2-mediated mitigation of cardiac oxidative stress in OVX rats.

Coral Hydrate, a Novel Antioxidant, Improves Alcohol Intoxication in Mice

Alcohol-drinking culture may cause individuals to periodically experience unpleasant hangovers. In addition, ethanol catabolism stimulates the production of free radicals that may cause liver injury and further lead to the development of chronic alcoholic fatty liver disease. Although a number of studies have suggested that hydrogenated water may be consumed to act as free radical scavenger, its instability limits its application. In this study, we used coral hydrate (i.e., hydrogenated coral materials) as a more stable hydrogen source and evaluated its effects in a murine model of alcohol intoxication. In solution, coral hydrate exhibited much more stable redox potential than did hydrogenated water. Furthermore, administration of coral hydrate by oral gavage significantly prolonged the time to fall asleep and decreased the total sleep time in mice that received intraperitoneal injection of ethanol. The mice receiving coral hydrate also had lower plasma ethanol and acetaldehyde levels than controls. In line with this observation, hepatic expression of alcohol dehydrogenase, acetaldehyde dehydrogenase, catalase and glutathione peroxidase were all significantly increased by the treatment. Meanwhile, alcohol-induced upregulation of pro-inflammatory factors was attenuated by the administration of coral hydrate. Taken together, our data suggest that coral hydrate might be an effective novel treatment for alcohol intoxication.

Tetrahydrobiopterin paradoxically mediates cardiac oxidative stress and mitigates ethanol-evoked cardiac dysfunction in conscious female rats

Oxidation of tetrahydrobiopterin (BH4), a cofactor of nitric oxide synthase (NOS), by reactive oxidative species (ROS), leads to NOS uncoupling and superoxide production instead of NO. Further, oxidative stress plays a major role in ethanol-evoked cardiac dysfunction in proestrus female rats, and acute ethanol administration reduces brain BH4 level. Therefore, we discerned the unknown role of BH4 in ethanol-evoked cardiac dysfunction by pharmacologically increasing BH4 levels or inhibiting its effect in proestrus female rats. Acute ethanol (1.5 g/kg, i.v, 30 min) caused myocardial dysfunction (lowered dP/dtmax and LVDP) and hypotension, along with increases in myocardial: (i) levels of NO, ROS and malondialdehyde (MDA), (ii) activities of catalase, ALDH2 and NADPH oxidase (Nox), and (iii) phosphorylation of eNOS, nNOS. Further, ethanol suppressed myocardial arginase and superoxide dismutase (SOD) activities and enhanced eNOS uncoupling. While ethanol had no effect on cardiac BH4 levels, BH4 (19 mg/kg, i.v) supplementation paradoxically caused cardiac oxidative stress, but mitigated the cardiac dysfunction/hypotension and most of the adverse molecular responses caused by ethanol. Equally important, the BH4 inhibitor DAHP (1 g/kg, i.p) exacerbated the adverse molecular and cardiovascular effects caused by ethanol. Our pharmacological studies support a protective role for the NOS co-factor BH4 against ethanol-evoked cardiac dysfunction and hypotension in female rats.

Estrogen-dependent hypersensitivity to diabetes-evoked cardiac autonomic dysregulation: Role of hypothalamic neuroinflammation

AIMS

To investigate if autonomic dysregulation is exacerbated in female rats, subjected to diabetes mellitus (DM), via a paradoxical estrogen (E2)-evoked provocation of neuroinflammation/injury of the hypothalamic paraventricular nucleus (PVN).

MAIN METHODS

We measured cardiac autonomic function and conducted subsequent PVN neurochemical studies, in DM rats, and their respective controls, divided as follows: male, sham operated (SO), ovariectomized (OVX), and OVX with E2 supplementation (OVX/E2).

KEY FINDINGS

Autonomic dysregulation, expressed as sympathetic dominance (higher low frequency, LF, band), only occurred in DM E2-replete (SO and OVX/E2) rats, and was associated with higher neuronal activity (c-Fos) and higher levels of TNFα and phosphorylated death associated protein kinase-3 (p-DAPK3) in the PVN. These proinflammatory molecules likely contributed to the heightened PVN oxidative stress, injury and apoptosis. The PVN of these E2-replete DM rats also exhibited upregulations of estrogen receptors, ERα and ERβ, and proinflammatory adenosine A1 and A2a receptors.

SIGNIFICANCE

The E2-dependent autonomic dysregulation likely predisposes DM female rats and women to hypersensitivity to cardiac dysfunction. Further, upregulations of proinflammatory mediators including adenosine A1 and A2 receptors, TNFα and DAPK3, conceivably explain the paradoxical hypersensitivity of DM females to PVN inflammation/injury and the subsequent autonomic dysregulation in the presence of E2.

Aldehyde Dehydrogenase Inhibition Ameliorates Cardiac Dysfunction and Exacerbates Hypotension Caused by Alcohol in Female Rats

BACKGROUND

Aldehyde dehydrogenase 2 (ALDH2) protects against alcohol-evoked cardiac dysfunction in male rodents, but its role in the estrogen (E2 )-dependent hypersensitivity of female rats to alcohol-evoked myocardial oxidative stress and dysfunction is not known.

METHODS

We addressed this question by studying the effect of cyanamide (ALDH2 inhibitor) on cardiac function, blood pressure, alcohol-metabolizing enzyme (alcohol dehydrogenase, cytochrome P450 2E1, catalase, and ALDH2) activities, and cardiac redox status (reactive oxygen species, ROS; malondialdehyde, MDA) in the absence or presence of ethanol (EtOH) in female sham-operated (SO) and ovariectomized (OVX) rats.

RESULTS

Cyanamide attenuated the EtOH-evoked myocardial dysfunction (reduced dP/dtmax and LVDP) in SO rats. EtOH, cyanamide, or their combination did not alter dP/dtmax or LVDP in OVX rats. Cyanamide induced cardiac oxidative stress and abrogated the subsequent alcohol-evoked increases in ROS and MDA levels in SO rats. Neither EtOH nor cyanamide influenced ROS or MDA levels in OVX rats. Importantly, cyanamide exaggerated EtOH-evoked hypotension in SO and uncovered this hypotensive response in OVX rats, which implicates ALDH2 in the vasodilating effect of EtOH.

CONCLUSIONS

Contrary to our hypothesis, cyanamide attenuated the E2 -dependent cardiac dysfunction caused by alcohol, likely by preconditioning the heart to oxidative stress, while exacerbating the vasodilating effect of alcohol. The latter might predispose to syncope when cyanamide and alcohol are combined in females.

Ethanol exposure in prenatal and early postnatal induced cardiac injury in rats: involvement of oxidative stress, Hsp70, ERK 1/2, JNK, and apoptosis in a 3-month follow-up study

Alcohol exposure during pregnancy induces a wide range of structural and functional abnormalities in the fetal heart. However, the underlying mechanism of this phenomenon is not well known. This study was undertaken to elucidate probable mechanisms of myocardial damage induced by prenatal and early postnatal ethanol treatment. Pregnant Wistar rats received ethanol 4.5 g/kg BW once per day from the seventh day of gestation (GD7) throughout lactation. The oxidative stress injury of the myocardium in pups was evaluated by measuring levels of oxidative stress biomarkers. Histopathological examinations and Western blot were performed to evaluate histological features, apoptosis, and molecular alterations in the myocardial tissue of male pups on the postnatal day 21 (PN-21) and postnatal day 90 (PN-90). The results showed that maternal ethanol consumption caused oxidative stress (impaired total antioxidant capacity and malondialdehyde), histological changes, and apoptosis of the myocardium in the pups on PN-21 and PN-90. At the molecular levels, Western blot analysis revealed that ethanol modulated the protein expression of p-ERK1/2, p-JNK, and Hsp70 in the myocardial tissue of the pups after 21 and 90 days of birth compared with the controls. These findings revealed that maternal ethanol intake induced cardiac toxicity in part, mediated by oxidative stress and apoptosis in the pups. A further mechanism study revealed that ethanol enhanced ERK1/2 and JNK phosphorylation and Hsp70 protein expression.

Mechanisms Underlying Muscle Protein Imbalance Induced by Alcohol

Both acute intoxication and longer-term cumulative ingestion of alcohol negatively impact the metabolic phenotype of both skeletal and cardiac muscle, independent of overt protein calorie malnutrition, resulting in loss of skeletal muscle strength and cardiac contractility. In large part, these alcohol-induced changes are mediated by a decrease in protein synthesis that in turn is governed by impaired activity of a protein kinase, the mechanistic target of rapamycin (mTOR). Herein, we summarize recent advances in understanding mTOR signal transduction, similarities and differences between the effects of alcohol on this central metabolic controller in skeletal muscle and in the heart, and the effects of acute versus chronic alcohol intake. While alcohol-induced alterations in global proteolysis via activation of the ubiquitin-proteasome pathway are equivocal, emerging data suggest alcohol increases autophagy in muscle. Further studies are necessary to define the relative contributions of these bidirectional changes in protein synthesis and autophagy in the etiology of alcoholic myopathy in skeletal muscle and the heart.

Role of Alcohol Oxidative Metabolism in Its Cardiovascular and Autonomic Effects

Several review articles have been published on the neurobehavioral actions of acetaldehyde and other ethanol metabolites as well as in major alcohol-related disorders such as cancer and liver and lung disease. However, very few reviews dealt with the role of alcohol metabolism in the adverse cardiac and autonomic effects of alcohol and their potential underlying mechanisms, particularly in vulnerable populations. In this chapter, following a brief overview of the dose-related favorable and adverse cardiovascular effects of alcohol, we discuss the role of ethanol metabolism in its adverse effects in the brainstem and heart. Notably, current knowledge dismisses a major role for acetaldehyde in the adverse autonomic and cardiac effects of alcohol because of its low tissue level in vivo. Contrary to these findings in men and male rodents, women and hypertensive individuals are more sensitive to the adverse cardiac effects of similar amounts of alcohol. To understand this discrepancy, we discuss the autonomic and cardiac effects of alcohol and its metabolite acetaldehyde in a model of hypertension, the spontaneously hypertensive rat (SHR) and female rats. We present evidence that enhanced catalase activity, which contributes to cardioprotection in hypertension (compensatory) and in the presence of estrogen (inherent), becomes detrimental due to catalase catalysis of alcohol metabolism to acetaldehyde. Noteworthy, studies in SHRs and in estrogen deprived or replete normotensive rats implicate acetaldehyde in triggering oxidative stress in autonomic nuclei and the heart via (i) the Akt/extracellular signal-regulated kinases (ERK)/nitric oxide synthase (NOS) cascade and (ii) estrogen receptor-alpha (ERα) mediation of the higher catalase activity, which generates higher ethanol-derived acetaldehyde in female heart. The latter is supported by the ability of ERα blockade or catalase inhibition to attenuate alcohol-evoked myocardial oxidative stress and dysfunction. More mechanistic studies are needed to further understand the mechanisms of this public health problem.

Combined Catalase and ADH Inhibition Ameliorates Ethanol-Induced Myocardial Dysfunction Despite Causing Oxidative Stress in Conscious Female Rats

BACKGROUND

Ethanol (EtOH)-evoked oxidative stress, which contributes to myocardial dysfunction in proestrus rats, is mediated by increases in NADPH oxidase (Nox) activity, malondialdehyde (MDA), and ERK1/2 phosphorylation. Whether these biochemical responses, which are triggered by alcohol-derived acetaldehyde in noncardiac tissues, occur in proestrus rats' hearts remains unknown. Therefore, we elucidated the roles of alcohol dehydrogenase (ADH), cytochrome P4502E1 (CYP2E1), and catalase, which catalyze alcohol oxidation to acetaldehyde, in these alcohol-evoked biochemical and hemodynamic responses in proestrus rats.

METHODS

Conscious proestrus rats prepared for measurements of left ventricular (LV) function and blood pressure (BP) received EtOH (1.5 g/kg, intravenous [i.v.] infusion over 30 minutes) or saline 30 minutes after an ADH and CYP2E1 inhibitor, 4-methylpyrazole (4-MP) (82 mg/kg, intraperitoneal), a catalase inhibitor, 3-AT (0.5 g/kg, i.v.), their combination, or vehicle. LV function and BP were monitored for additional 60 minutes after EtOH or saline infusion before collecting the hearts for ex vivo measurements of LV reactive oxygen species (ROS), Nox activity, MDA, and ERK1/2 phosphorylation.

RESULTS

EtOH reduced LV function (dP/dt_max and LV developed pressure) and BP, and increased cardiac Nox activity, ROS and MDA levels, and ERK1/2 phosphorylation. Either inhibitor partially, and their combination significantly, attenuated these responses despite the substantially higher blood EtOH level, and the increased cardiac oxidative stress and reduced BP caused by 3-AT alone or with 4-MP. The inhibitors reduced cardiac MDA level and reversed EtOH effect on cardiac and plasma MDA.

CONCLUSIONS

EtOH oxidative metabolism plays a pivotal role in the EtOH-evoked LV oxidative stress and dysfunction in proestrus rats. Notably, catalase inhibition (3-AT) caused cardiac oxidative stress and hypotension.

Etiology of alcoholic cardiomyopathy: Mitochondria, oxidative stress and apoptosis

Putative mechanisms leading to the development of alcoholic cardiomyopathy (ACM) include the interrelated cellular processes of mitochondria metabolism, oxidative stress and apoptosis. As mitochondria fuel the constant energy demands of this continually contracting tissue, it is not surprising that alcohol-induced molecular changes in this organelle contribute to cardiac dysfunction and ACM. As the causal relationship of these processes with ACM has already been established, the primary objective of this review is to provide an update of the experimental findings to more completely understand the aforementioned mechanisms. Accordingly, recent data indicate that alcohol impairs mitochondria function assessed by membrane potential and respiratory chain activity. Indictors of oxidative stress including superoxide dismutase, glutathione metabolites and malondialdehyde are also adversely affected by alcohol oftentimes in a sex-dependent manner. Additionally, myocardial apoptosis is increased based on assessment of TUNEL staining and caspase activity. Recent work has also emerged linking alcohol-induced oxidative stress with apoptosis providing new insight on the codependence of these interrelated mechanisms in ACM. Attention is also given to methodological differences including the dose of alcohol, experimental model system and the use of males versus females to highlight inconsistencies and areas that would benefit from establishment of a consistent model.

17β-Estradiol via SIRT1/Acetyl-p53/NF-kB Signaling Pathway Rescued Postnatal Rat Brain Against Acute Ethanol Intoxication

Growing evidences reveal that 17β-estradiol has a wide variety of neuroprotective potential. Recently, it has been shown that 17β-estradiol can limit ethanol-induced neurotoxicity in neonatal rats. Whether it can stimulate SIRT1 signaling against ethanol intoxicity in developing brain remain elusive. Here, we report for the first time that 17β-estradiol activated SIRT1 to deacetylate p53 proteins against acute ethanol-induced oxidative stress, neuroinflammation, and neurodegeneration. A single subcutaneous injection of ethanol-induced oxidative stress triggered phospho c-jun N terminal kinase (p-JNK) and phospho mammalian target of rapamycin (p-mTOR) accompanied by neuroinflammation and widespread neurodegeneration. In contrast, 17β-estradiol cotreatment positively regulated SIRT1, inhibited p53 acetylation, reactive oxygen species (ROS) production, p-JNK, and p-mTOR activation and reduced neuroinflammation and neuronal cell death in the postnatal rat brain. Interestingly, SIRT1 inhibition with its inhibitor, i.e., EX527 further enhanced ethanol intoxication and also abolished the beneficial effects of 17β-estradiol against ethanol in the young rat's brain. Indeed, 17β-estradiol treatment increased the cell viability (HT22 cells), inhibited ROS production via the SIRT1/Acetyl-p53 pathway, and reduced the nuclear translocation of phospho-nuclear factor kappa B (p-NF-kB) in the BV2 microglia cells. Taken together, these results show that 17β-estradiol can be used as a potential neuroprotective agent against acute ethanol intoxication.

Influence of sex on cardiovascular drug responses: role of estrogen

In this review we discuss the sex/estrogen-specific modulation of cardiovascular function and responses to current therapeutics. We discuss how anatomical differences such as a smaller kidney size, and lower glomerular filtration rate in females, reduce the clearance and increase the toxicity of some drugs in females. Other important sex differences include the dampening effect of estrogen on central sympathetic and renin angiotensin systems. Further, we discuss how a shift in myocardial redox status leads to paradoxical transformation of estrogen into a pro-inflammatory hormone. Finally, the review, along with cited recent publications, identify some areas that need further investigation to advance our understanding of the sex differences in cardiovascular disease outcomes to help develop female specific interventions for these anomalies.

Estrogen Receptors α and β Play Major Roles in Ethanol-Evoked Myocardial Oxidative Stress and Dysfunction in Conscious Ovariectomized Rats

BACKGROUND

We documented the dependence of ethanol (EtOH)-evoked myocardial dysfunction on estrogen (E₂ ), and our recent estrogen receptor (ER) blockade study, in proestrus rats, implicated ERα signaling in this phenomenon. However, a limitation of selective pharmacological loss-of-function approach is the potential contribution of the other 2 ERs to the observed effects because crosstalk exists between the 3 ERs. Here, we adopted a "regain"-of-function approach (using selective ER subtype agonists) to identify the ER subtype(s) required for unraveling the E₂ -dependent myocardial oxidative stress/dysfunction caused by EtOH in conscious ovariectomized (OVX) rats.

METHODS

OVX rats received a selective ERα (PPT), ERβ (DPN), or GPER (G1) agonist (10 μg/kg; i.v.) or vehicle 30 minutes before EtOH (1.0 g/kg; infused i.v. over 30 minutes) or saline, and the hemodynamic recording continued for additional 60 minutes. Thereafter, left ventricular tissue was collected for conducting ex vivo molecular/biochemical studies.

RESULTS

EtOH had no hemodynamic effects in OVX rats, but reduced the left ventricular contractility index, dP/dt_max , and MAP after acute ERα (PPT) or ERβ (DPN) activation. These responses were associated with increases in the phosphorylation of ERK1/2 and eNOS, and in reactive oxygen species (ROS) and malondialdehyde (MDA) levels in the myocardium. GPER activation (G1) only unraveled a modest EtOH-evoked hypotension and elevation in myocardial ROS. PPT enhanced catalase, DPN reduced ALDH2, while G1 had no effect on the activity of either enzyme, and none of the agonists influenced alcohol dehydrogenase or CYP2E1 activities in the myocardium. Blood EtOH concentration (96.0 mg/dl) was significantly reduced following ERα (59.8 mg/dl) or ERβ (62.9 mg/dl), but not GPER (100.3 mg/dl), activation in EtOH-treated OVX rats.

CONCLUSIONS

ERα and ERβ play major roles in the E₂ -dependent myocardial dysfunction caused by EtOH by promoting combined accumulation of cardiotoxic (ROS and MDA) and cardiodepressant (NOS-derived NO) molecules in female myocardium.

Estrogen receptor ERα plays a major role in ethanol-evoked myocardial oxidative stress and dysfunction in conscious female rats

Our previous studies showed that ethanol elicited estrogen (E2)-dependent myocardial oxidative stress and dysfunction. In the present study we tested the hypothesis that E2 signaling via the estrogen receptor (ER), ERα, mediates this myocardial detrimental effect of alcohol. To achieve this goal, conscious female rats in proestrus phase (highest endogenous E2 level) received a selective ER antagonist (200 μg/kg; intra-venous [i.v.]) for ERα (MPP), ERβ (PHTPP) or GPER (G15) or saline 30 min before ethanol (1 g/kg; i.v.) or saline infusion. ERα blockade virtually abrogated ethanol-evoked myocardial dysfunction and hypotension, while ERβ blockade had little effect on the hypotensive response, but caused delayed attenuation of the ethanol-evoked reductions in left ventricular developed pressure and the rate of left ventricle pressure rise. GPER blockade caused delayed attenuation of all cardiovascular effects of ethanol. All three antagonists attenuated the ethanol-evoked increases in myocardial catalase and ALDH2 activities, Akt, ERK1/2, p38, eNOS, and nNOS phosphorylation, except for a lack of effect of PHTPP on p38. Finally, all three ER antagonists attenuated ethanol-evoked elevation in myocardial ROS, but this effect was most notable with ERα blockade. In conclusion, ERα plays a greater role in, and might serve as a molecular target for ameliorating, the E2-dependent myocardial oxidative stress and dysfunction caused by ethanol.

Role of estrogen in diabetic gastroparesis

Gastroparesis is a highly prevalent chronic disorder of the stomach, which is characterized by delayed gastric emptying and accompanied by a series of upper gastrointestinal symptoms. Diabetic gastroparesis (DGP) is one of the severe complications of diabetes, seriously affecting the patient's quality of life. At present, the pathogenesis of DGP is still unclear. The majority of DGP patients are women, and women's symptoms change with the fluctuation of the level of estrogen. Therefore, we speculate that estrogen may play an vital role in the stomach motility. Gastric emptying is an objective index for the diagnosis of gastroparesis. This article reviews the role of estrogen in DGP and the possible mechanisms.