Aspirin pretreatment reduces ethanol withdrawal severity in a mouse model of binge drinking

Downregulation of Gabra4 expression during alcohol withdrawal is mediated by specific microRNAs in cultured mouse cortical neurons

BACKGROUND

Alcohol abuse and dependence are a serious public health problem. A large number of alcohol-regulated genes, (ARGs) are known to be influenced by alcohol use and withdrawal (AW), and recent evidence suggests that neuroadaptation to alcohol may be due in part to epigenetic changes in the expression of ARGs. Gabra4, which encodes the α4 subunit of GABAA receptors (GABAARs), is one of a number of ARGs that show remarkable plasticity in response to alcohol, being rapidly upregulated by acute alcohol exposure. This study addressed the effects of AW on changes in the expression of Gabra4 and related genes that encode other subunits of GABAARs, and the potential regulation of Gabra4 by microRNAs.

METHODS

We studied gene and microRNAs expression, using RT-PCR and microRNA microarray in cultured cortical neurons treated with alcohol, which was then removed in order to simulate AW in vitro. We also used microRNA mimics or inhibitors, and a promoter-reporter construct carrying the 3'UTR of Gabra4.

RESULTS

Eleven hours after removal of alcohol, Gabra4 was downregulated, with a modest increase in the expression of Gabrg2, but no change in the expression of Gabra1, Gabrd, or Gabrb2. microRNA profiling in neurons undergoing AW revealed upregulation in the expression of miR-155, miR-186, miR-24, and miR-375 after 8 h of AW. Transfection with molecular mimics of miR-186, miR-24, or miR-375 also downregulated Gabra4 expression, whereas transfection with the corresponding inhibitors of these microRNAs normalized Gabra4 expression in AW neurons to the level measured in control neurons. Promoter-reporter experiments supported the idea that miR-155, miR-186, miR-24, miR-27b, or miR-375 bind to the 3'UTR of Gabra4 and thereby inhibit protein production.

CONCLUSIONS

Our data suggest that AW decreases Gabra4 expression, and that this may be mediated in part by the induction of specific microRNAs in cortical neurons during AW.

Acute illness-induced behavioral alterations are similar to those observed during withdrawal from acute alcohol exposure

Exposure to an immunogen results in a constellation of behavioral changes collectively referred to as "sickness behaviors," with alterations in cytokine expression previously shown to contribute to this sickness response. Since behaviors observed during ethanol withdrawal are strikingly similar to sickness behaviors, we hypothesized that behavioral manifestations of ethanol withdrawal might be an expression of sickness behaviors induced by ethanol-related changes in peripheral and/or central cytokine expression. Accordingly, behaviors exhibited during a modified social investigation test were first characterized in male rats following an acute injection of lipopolysaccharide (LPS; 100μg/kg). Subsequently, behavioral changes after either a high (4-g/kg; Experiment 2) or low dose (0.5g/kg; Experiment 3) of ethanol were also examined in the same social investigation test, as well as in the forced-swim test (FST; Experiment 4). Results from these experiments demonstrated similar reductions in both exploration and social investigatory behavior during acute illness and ethanol withdrawal, while a seemingly paradoxical decrease in immobility was observed in the FST during acute ethanol withdrawal. In follow-up studies, neither indomethacin (Experiment 5) nor interleukin-1 receptor antagonist (Experiment 6) pre-exposure reversed the ethanol withdrawal-induced behavioral changes observed in this social investigation test. Taken together, these studies demonstrate that the behavioral sequelae of acute illness and ethanol withdrawal are similar in nature, while antagonist studies suggest that these behavioral alterations are not reversed by blockade of IL-1 receptors or inhibition of prostaglandin synthesis. Though a direct mechanistic link between cytokines and the expression of acute ethanol withdrawal-related behaviors has yet to be found, future studies examining the involvement of brain cytokines as potential mediators of ethanol effects are greatly needed.

Catecholamine depletion by reserpine blocks the anxiolytic actions of ethanol in the rat

Neurochemical investigations of the anti-anxiety action of ethanol demonstrate that increased dopaminergic, noradrenergic, and serotonergic activity mediates the anxiolytic actions of ethanol. Results of studies with animals and human beings also confirm an involvement of the sympathetic nervous system in the behavioral actions of ethanol. Because enhanced sympathetic activity increases the release of norepinephrine from sympathetic terminals, the interruption of normal sympathetic activity might disrupt the anxiolytic action of ethanol. The present study examined the effect of chemical sympathectomy by reserpine pretreatment on the subsequent anxiolytic action of ethanol. Seventy-one, female, Sprague-Dawley rats were administered reserpine (0 or 5 mg/kg), followed 17-19 h later by ethanol (0, 0.5, or 1.0 g/kg). Animals were then tested in the elevated plus maze. Compared with saline pretreatment, which did not attenuate the anxiolytic actions of a 1.0-g/kg dose of ethanol, reserpine pretreatment completely blocked the anxiolytic action of a 1.0-g/kg dose of ethanol. Reserpine, by itself, did not possess anxiolytic or anxiogenic actions. Because the anxiolytic action of ethanol involves increased catecholamine activity and the depletion of norepinephrine and dopamine from sympathetic nerve terminals by reserpine blocked the anxiolytic action of ethanol, it is concluded that the anxiolytic action of ethanol requires the presence of normal catecholamine activity. We suggest that prostaglandin activity normally evoked by enhanced sympathetic nervous system activity might be involved in the anxiolytic action of ethanol.

Aspirin attenuates the anxiolytic actions of ethanol

The present study examined the effect of aspirin on the anxiolytic action of ethanol. Previous research has shown that ethanol reliably produces an anxiolytic effect on rodent's plus-maze performance while aspirin has been demonstrated to attenuate several of ethanol's behavioral actions. Female Sprague-Dawley rats were given s.c. aspirin doses of 0 or 150 mg/kg, followed 30 min later by s.c. ethanol doses of 0, 1.0 or 1.6 g/kg. After 5 min, animals were tested in the elevated plus-maze. Although aspirin did not have a significant effect on anxiety-related behavior, it did attenuate the anxiolytic action of ethanol at the dose of 1.0 g/kg, but not at the 1.6 g/kg dose. Thus, aspirin by itself does not appear to possess anxiolytic actions, but does modify the anxiolytic actions of 1.0 g/kg, but not 1.6 g/kg ethanol.