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

Abstract

Background We documented the dependence of ethanol-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 ethanol in conscious ovariectomized (OVX) rats. Method OVX rats received a selective ERα (PPT), ERβ (DPN) or GPER (G1) agonist (10 μg/kg; i.v.) or vehicle 30 min before ethanol (1.0 g/kg; infused i.v. over 30 min) or saline, and the hemodynamic recording continued for additional 60 min. Thereafter, left ventricular tissue was collected for conducting ex vivo molecular/biochemical studies. Results Ethanol had no hemodynamic effects in OVX rats, but reduced the left ventricular contractility index, dP/dtmax, 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 ROS and MDA levels in the myocardium. GPER activation (G1) only unraveled a modest ethanol-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 ADH or CYP2E1 activities in the myocardium. Blood ethanol 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 ethanol-treated OVX rats. Conclusions ERα and ERβ play major roles in the E2-dependent myocardial dysfunction caused by ethanol by promoting combined accumulation of cardiotoxic (ROS and MDA) and cardio-depressant (NOS-derived NO) molecules in female myocardium.

Estrogen receptor α activation enhances its cell surface localization and improves myocardial redox status in ovariectomized rats

“…We have shown that the reduction in myocardial catalase activity in OVX rats is restored to proestrus rat levels within minutes after E 2 administration [31] or selective ERα activation [32]. Further, we showed that acute ERα blockade by its selective antagonist MPP significantly reduced myocardial catalase activity in proestrus rats [40].…”

“…All surgeries were performed under aseptic conditions following anesthesia with intraperitoneal ketamine (90 mg/kg) and xylazine (10 mg/kg) injection as detailed in our recent study [32]. Each rat received subcutaneous injections of the analgesic buprenorphine hydrochloride (Buprenex, 30 μg/kg) and penicillin G benzathine and penicillin G procaine (Dura-Pen, 100,000 U/kg).…”

“…The hearts used in the present study were collected from rats used in our previous studies [31, 32]. Two weeks after ovariectomy, 5 groups of conscious OVX rats (n = 4–6) received a single injection of E 2 (1 μg/kg, i.v), a selective ERα (PPT), ERβ (DPN) or GPER (G1) agonist (10 μg/kg, i.v, each) or vehicle (saline).…”

Influence of sex on cardiovascular drug responses: role of estrogen

“…This favorable redox effect is mediated, at least partly, by estrogen enhancement of the catalytic activity of two cardiac antioxidant enzymes, catalase and mitochondrial aldehyde dehydrogenase (6, 26). Interestingly, our recent studies showed that the effect of estrogen on these two cardiac enzymes is ER subtype-dependent because a highly selective ERα agonist replicated the effect of estrogen while ERβ or GPER activation caused a reduction in ALDH2 activity (27). The latter finding and the GPER-mediated relaxation of the coronary artery (24) support the tissue specificity of estrogen actions and underscores the complexity of estrogen regulation of cardiovascular function.…”

“…This concept gains credence from our findings, which established a causal link between oxidative stress and estrogen-dependent deleterious cardiac effects in vivo because: (i) the alcohol-evoked myocardial oxidative stress is tolerated in the absence of estrogen in ovariectomized and male rats, and (ii) such resilience is lost, and is transformed into myocardial dysfunction, when estrogen is co-administered with ethanol in both sexes (6, 29**, 30). Current evidence implicates the ERα and ERβ subtypes in mediating these estrogen-dependent adverse cardiac effects of ethanol (27, 29**), at least partly, via the PI3K-Akt-NOS pathway (29**, 31, 32). More mechanistic studies are warranted in this area of research given the widespread use of alcohol by young women (33, 34).…”