Endotoxemia-Mediated Induction of Cardiac Inducible Nitric-Oxide Synthase Expression Accounts for the Hypotensive Effect of Ethanol in Female Rats

Abstract

We have recently shown that intragastric (i.g.) ethanol lowers blood pressure (BP) in conscious female rats via a reduction in cardiac output (CO). However, the mechanisms implicated in these hemodynamic effects of ethanol are not known. Therefore, we tested the hypothesis that ethanol-evoked endotoxemia mediates the reduction in CO via enhanced myocardial inducible nitric-oxide synthase (iNOS) expression. Immunoblot (myocardial iNOS), biochemical (plasma endotoxin and nitrite/ nitrate), and integrative [BP, heart rate, CO, stroke volume (SV), and total peripheral resistance (TPR)] studies were conducted in conscious female rats that received i.g. ethanol (1 g/kg) in the absence or presence of 1400W (N-(3-[aminomethyl]benzyl) acetamidine) or ampicillin to selectively inhibit iNOS and to eliminate endogenous endotoxin, respectively. Ethanol-evoked hypotension coincided with reductions in CO and SV and increases in: 1) TPR, 2) plasma endotoxin and nitrite/nitrate, and 3) myocardial iNOS expression. These effects of ethanol were virtually abolished in rats pretreated with ampicillin (200 mg/kg/ day for 2 days by gavage) or with 1400W (5 mg/kg i.p.) except for the increase in plasma endotoxin, which persisted in 1400W-pretreated rats. These findings yield insight into the mechanistic role of endotoxin-myocardial iNOS signaling in the cardiodepressant action of ethanol, which accounts for its hypotensive effect in conscious female rats.Ethanol elicits hypotension in female, but not in age-matched male, rats (El-Mas and Abdel-Rahman, 1999a). Furthermore, the hypotensive effect of ethanol is estrogen-dependent (El-Mas and Abdel-Rahman, 1999b). It is imperative also to note that moderate ethanol consumption is associated with lower BP in young but not in old women (Klatsky, 1990), which highlights the clinical relevance of the reported experimental findings. The precise mechanism by which ethanol elicits hypotension in female rats is not known. It is noteworthy that there are similarities between the cardiovascular effects of ethanol and estrogen, which include inhibition of calcium influx (Turlapaty et al., 1979;Zhang et al., 1994), enhancement of NOS activity (Weiner et al., 1994;Wang and Abdel-Rahman, 2005;Zhang et al., 2005), and reduction of ␣-adrenergic receptor responsiveness (Abdel-Rahman et al., 1985;Sudhir et al., 1997). Indeed, the NOS-derived NO seems to be the major mediator of the estrogen-dependent hypotensive effect of ethanol because NO is directly or indirectly linked to vasodilation and reduces cardiac contractility (Yeh et al., 2005). It is possible, therefore, that ethanol may interact synergistically with estrogen to produce vascular and/or cardiac changes that might lead to hypotension.Built on the premise that ethanol enhances iNOS signaling (Durante et al., 1995), we demonstrated in a recent study the ability of ethanol to increase vascular (aortic) iNOS expression in female rats (El-Mas et al., 2006). Such a response could not be mechanistically linked to the hypotensive effect of ethan...

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

“…Heparinized blood was centrifuged at 5000 rpm for 10 minutes and ethanol content was determined by the enzymatic method (Kristoffersen et al, 2005, El-Mas et al, 2008) with modification. Briefly, 150 μl of buffer (sodium pyrophosphate 74.5mM, semicarbazide hydrochloride 74 mM glycine 22.4 mM), 25 μl of β-Nicotinamide adenine dinucleotide (25.1mM), 25 μl of perchloric acid (2%) and 5 μl of sample or ethanol standard, was added in 96-well plate, respectively.…”

Estrogen modulation of the ethanol-evoked myocardial oxidative stress and dysfunction via DAPK3/Akt/ERK activation in male rats

“…Protein bands were quantified by integrated intensities using Odyssey Infrared Imaging Software, which serve as good surrogates for the relative express levels of targeting proteins. Data were normalized to the corresponding total protein in the same sample and results were then expressed as percent of control (El-Mas et al, 2008, 2009b, El-Mas and Abdel-Rahman, 2014). …”

Inhibition of iNOS protects endothelial-dependent vasodilation in aged rats

“…Therefore, we used the highly selective iNOS inhibitor 1400W in our present study. It has been reported that 1400W inhibited iNOS activity by binding with iNOS [27] , but some studies found that 1400W could decrease iNOS expression [28,29] . In this study, we also found that iNOS expression was increased significantly in vascular tissue of aged rats.…”