Causal roles of stress kinase JNK2 in DNA methylation and binge alcohol withdrawal-evoked behavioral deficits

Excessive binge alcohol intake is a common drinking pattern in humans, especially during holidays. Cessation of the binge drinking often leads to aberrant withdrawal behaviors, as well as serious heart rhythm abnormalities (clinically diagnosed as Holiday Heart Syndrome (HHS)). In our HHS mouse model with well-characterized binge alcohol withdrawal (BAW)-induced heart phenotypes, BAW leads to anxiety-like behaviors and cognitive impairment. We have previously reported that stress-activated c-Jun NH(2)-terminal kinase (JNK) plays a causal role in BAW-induced heart phenotypes. In the HHS brain, we found that activation of JNK2 (but not JNK1 and JNK3) in the prefrontal cortex (PFC), but not hippocampus and amygdala, led to anxiety-like behaviors and impaired cognition. DNA methylation mediated by a crucial DNA methylation enzyme, DNA methyltransferase1 (DNMT1), is known to be critical in alcohol-associated behavioral deficits. In HHS mice, JNK2 in the PFC (but not hippocampus and amygdala) causally enhanced total genomic DNA methylation via increased DNMT1 expression, which was regulated by enhanced binding of JNK downstream transcriptional factor c-JUN to the DNMT1 promoter. JNK2-specific inhibition either by an inhibitor JNK2I or JNK2 knockout completely offset c-JUN-regulated DNMT1 upregulation and restored the level of DNA methylation in HHS PFC to the baseline levels seen in sham controls. Strikingly, either JNK2-specific inhibition or genetic JNK2 depletion or DNMT1 inhibition (by an inhibitor 5-Azacytidine) completely abolished BAW-evoked behavioral deficits. In conclusion, our studies revealed a novel mechanism by which JNK2 drives BAW-evoked behavioral deficits through a DNMT1-regulated DNA hypermethylation. JNK2 could be a novel therapeutic target for alcohol withdrawal treatment and/or prevention.

Association of High-Intensity Binge Drinking With Lipid and Liver Function Enzyme Levels

Importance

The prevalence of high-intensity binge drinking (HIBD), defined as consuming 2 or more times the binge threshold defined by the National Institute on Alcohol Abuse and Alcoholism (NIAAA), is rapidly increasing in the United States. While the relationship between alcohol consumption and lipid and liver function enzyme (LFT) biomarkers has been previously examined, the associations of HIBD with those biomarkers remain unknown.

Objective

To examine associations of HIBD with lipid and LFT levels in a cross-sectional sample enriched with participants who engage in HIBD.

Design, Setting, and Participants

Cross-sectional study using data from the NIAAA clinical sample collected from March 3, 2005, to August 21, 2017, with participants recruited for either the NIAAA screening protocols or inpatient alcohol treatment program. For this study, participants were stratified by self-reported alcohol consumption into 4 sex-specific binge levels: nonbinge and 1, 2, and 3 or more times the binge threshold (levels I, II, and III). Multivariable analyses examined the odds of clinically high levels of lipids and LFTs across binge levels. Analyses were performed from December 3, 2018, to January 30, 2019.

Main Outcomes and Measures

Serum levels of high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, total cholesterol, triglycerides, alanine aminotransferase, aspartate aminotransferase, and γ-glutamyltransferase.

Results

A total of 2065 participants underwent protocol screening; 1519 with data available on alcohol consumption, body mass index, lipid levels, and LFT levels were included in the final analyses. Mean (SD) age was 39.7 (12.1) years; mean (SD) body mass index was 26.6 (5.1); 978 (64.4%) were male; 718 (47.3%) were white; and 578 (31.1%) consumed alcohol at the nonbinge level, 321 (21.2%) at level I, 239 (15.7%) at level II, and 318 (25.1%) at level III. High-intensity binge drinking was associated with 2- to 8-fold increased odds for clinically high levels of HDL-C, total cholesterol, triglycerides, and all LFTs (eg, for HDL-C: level III odds ratio [OR], 8.65; 95% CI, 4.75-15.77 and for γ-glutamyltransferase: level III OR, 8.21; 95% CI, 5.90-11.43). Increased HIBD frequency (days consuming at levels II and III) was associated with increased odds for clinically high levels of HDL-C, total cholesterol, and all LFTs (per unit increase in days consuming at the respective binge level) (eg, for HDL-C: level II OR, 1.025; 95% CI, 1.014-1.036 and level III OR, 1.033; 95% CI, 1.019-1.047 and for γ-glutamyltransferase: level II OR, 1.028; 95% CI, 1.019-1.037 and level III OR, 1.033; 95% CI, 1.019-1.047).

Conclusions and Relevance

High-impact binge drinking was significantly associated with increased odds for clinically high levels of lipids and LFTs. Given that HIBD is increasingly common among US adults, targeted interventions aimed at reducing HIBD may have important health benefits.

Alcohol alters the activation of ERK1/2, a functional regulator of binge alcohol drinking in adult C57BL/6J mice

BACKGROUND

Binge alcohol drinking is a particularly risky pattern of alcohol consumption that often precedes alcohol dependence and addiction. The transition from binge alcohol drinking to alcohol addiction likely involves mechanisms of synaptic plasticity and learning in the brain. The mitogen-activated protein kinase (MAPK) signaling cascades have been shown to be involved in learning and memory, as well as the response to drugs of abuse, but their role in binge alcohol drinking remains unclear. The present experiments were designed to determine the effects of acute alcohol on extracellular signaling-related kinases (ERK1/2) expression and activity and to determine whether ERK1/2 activity functionally regulates binge-like alcohol drinking.

METHODS

Adult male C57BL/6J mice were injected with ethanol (EtOH) (3.0 mg/kg, intraperitoneally) 10, 30, or 90 minutes prior to brain tissue collection. Next, mice that were brought to freely consume unsweetened EtOH in a binge-like access procedure were pretreated with the MEK1/2 inhibitor SL327 or the p38 MAPK inhibitor SB239063.

RESULTS

Acute EtOH increased pERK1/2 immunoreactivity relative to vehicle in brain regions known to be involved in drug reward and addiction, including the central amygdala and prefrontal cortex. However, EtOH decreased pERK1/2 immunoreactivity relative to vehicle in the nucleus accumbens core. SB239063 pretreatment significantly decreased EtOH consumption only at doses that also produced nonspecific locomotor effects. SL327 pretreatment significantly increased EtOH, but not sucrose, consumption without inducing generalized locomotor effects.

CONCLUSIONS

These findings indicate that ERK1/2 MAPK signaling regulates binge-like alcohol drinking. As alcohol increased pERK1/2 immunoreactivity relative to vehicle in brain regions known to regulate drug self-administration, SL327 may have blocked this direct pharmacological effect of alcohol and thereby inhibited the termination of binge-like drinking.

Binge alcohol promotes hypoxic liver injury through a CYP2E1-HIF-1α-dependent apoptosis pathway in mice and humans

Binge drinking, a common pattern of alcohol ingestion, is known to potentiate liver injury caused by chronic alcohol abuse. This study was aimed at investigating the effects of acute binge alcohol on hypoxia-inducible factor-1α (HIF-1α)-mediated liver injury and the roles of alcohol-metabolizing enzymes in alcohol-induced hypoxia and hepatotoxicity. Mice and human specimens assigned to binge or nonbinge groups were analyzed for blood alcohol concentration (BAC), alcohol-metabolizing enzymes, HIF-1α-related protein nitration, and apoptosis. Binge alcohol promoted acute liver injury in mice with elevated levels of ethanol-inducible cytochrome P450 2E1 (CYP2E1) and hypoxia, both of which were colocalized in the centrilobular areas. We observed positive correlations among elevated BAC, CYP2E1, and HIF-1α in mice and humans exposed to binge alcohol. The CYP2E1 protein levels (r = 0.629, p = 0.001) and activity (r = 0.641, p = 0.001) showed a significantly positive correlation with BAC in human livers. HIF-1α levels were also positively correlated with BAC (r = 0.745, p < 0.001) or CYP2E1 activity (r = 0.792, p < 0.001) in humans. Binge alcohol promoted protein nitration and apoptosis with significant correlations observed between inducible nitric oxide synthase and BAC, CYP2E1, or HIF-1α in human specimens. Binge-alcohol-induced HIF-1α activation and subsequent protein nitration or apoptosis seen in wild type were significantly alleviated in the corresponding Cyp2e1-null mice, whereas pretreatment with an HIF-1α inhibitor, PX-478, prevented HIF-1α elevation with a trend of decreased levels of 3-nitrotyrosine and apoptosis, supporting the roles of CYP2E1 and HIF-1α in binge-alcohol-mediated protein nitration and hepatotoxicity. Thus binge alcohol promotes acute liver injury in mice and humans at least partly through a CYP2E1-HIF-1α-dependent apoptosis pathway.

Alcohol steatosis and cytotoxicity: the role of cytochrome P4502E1 and autophagy

The goal of the current study was to evaluate whether CYP2E1 plays a role in binge-ethanol induced steatosis and if autophagy impacts CYP2E1-mediated hepatotoxicity, oxidative stress and fatty liver formation produced by ethanol. Wild type (WT), CYP2E1 knockin (KI) and CYP2E1 knockout (KO) mice were gavaged with 3g/kg body wt ethanol twice a day for four days. This treatment caused fatty liver, elevation of CYP2E1 and oxidative stress in WT and KI mice but not KO mice. Autophagy was impaired in ethanol-treated KI mice compared to KO mice as reflected by a decline in the LC3-II/LC3-I ratio and lower total LC-3 and Beclin-1 levels coupled to increases in P62, pAKT/AKT and mTOR. Inhibition of macroautophagy by administration of 3-methyladenine enhanced the binge ethanol hepatotoxicity, steatosis and oxidant stress in CYP2E1 KI, but not CYP2E1 KO mice. Stimulation of autophagy by rapamycin blunted the elevated steatosis produced by binge ethanol. Treatment of HepG2 E47 cells which express CYP2E1 with 100mM ethanol for 8 days increased fat accumulation and oxidant stress but decreased autophagy. Ethanol had no effect on these reactions in HepG2 C34 cells which do not express CYP2E1. Inhibition of autophagy elevated ethanol toxicity, lipid accumulation and oxidant stress in the E47, but not C34 cells. The antioxidant N-acetylcysteine, and CYP2E1 inhibitor chlormethiazole blunted these effects of ethanol. These results indicate that CYP2E1 plays an important role in binge ethanol-induced fatty liver. We propose that CYP2E1-derived reactive oxygen species inhibit autophagy, which subsequently causes accumulation of lipid droplets. Inhibition of autophagy promotes binge ethanol induced hepatotoxicity, steatosis and oxidant stress via CYP2E1.