Females uniquely vulnerable to alcohol-induced neurotoxicity show altered glucocorticoid signaling

Abstract

Women are more sensitive to the harmful effects of alcohol (EtOH) abuse than men, yet the underlying mechanisms remain poorly understood. Previous gene expression analysis of the medial prefrontal cortex (mPFC) following a chronic intoxication paradigm using continuous 72 h vapor inhalation found that females, but not males, exhibit an inflammatory response at peak withdrawal that is associated with cell damage. Given that glucocorticoids can function as anti-inflammatories, are known to increase with EtOH exposure, and influence neurotoxicity, we hypothesized that males and females may exhibit an altered corticosterone (CORT) response following chronic intoxication. Analysis of serum CORT levels revealed the expected increase during withdrawal with no difference between males and females, while control males but not females exhibited higher CORT concentrations than naive animals. Glucocorticoid signaling characterized using focused qPCR arrays identified a sexually dimorphic response in the mPFC during withdrawal, particularly among astrocyte-enriched genes. These genes include aquaporin-1 (Aqp1), sphingosine kinase 1 (Sphk1) and connective tissue growth factor (Ctgf); genes associated with inflammatory signaling, and tissue damage and repair. Bioinformatic analysis also revealed activation of inflammatory signaling and cell death pathways in females. Confirmation studies showed that female mice exhibited significant neuronal degeneration within the anterior cingulate cortex (ACC). By contrast, EtOH exposure lead to a significant reduction in cell death in males. Thus, distinct glucocorticoid signaling pathways are associated with sexually dimorphic neurotoxicity, suggesting one mechanism by which EtOH-exposed females are particularly vulnerable to the damaging effects of alcohol in the CNS.

Astrocyte Dysfunction Induced by Alcohol in Females but Not Males

“…Nevertheless, increased vulnerability to EtOH-induced neurotoxicity in females remains controversial [reviewed in (51)] with additional studies needed to support or refute this hypothesis. This finding is buttressed by the observation that chronic ethanol exposure is associated with a strongly sexually dimorphic transcriptional response (44,118,119). In those studies, significantly regulated transcripts included several genes that are exclusively or predominantly expressed in astrocytes, suggesting that a component of the neuroadapative response in the brain after ethanol exposure reflects changes in astrocyte gene expression that are distinct between males and females.…”

“…WSR and WSP models were originally chosen for these studies based on their withdrawal phenotype differences, with the expectation that this phenotype would be an important factor underlying genetic responses to ethanol intoxication and/or withdrawal. This hypothesis was not supported during the immediate withdrawal period and instead sex, not withdrawal phenotype, was found to exert the greatest influence on responses to chronic ethanol intoxication and early withdrawal (44,118,119). Because sex was the most important influence, primary cultures were instead derived using B6D2F2 animals.…”

“…Females have higher rates or greater severity of cardiomyopathy, peripheral neuropathy, some types of cancer and liver cirrhosis (5,59). Increased vulnerability to ethanol-induced brain damage in the prefrontal cortex in females has been observed in some studies (44,118). Other studies have not confirmed female vulnerability, but have noted different "brain morphological deficits" between males and females supporting the notion that neurodamage occurs via different mechanisms depending on sex (94).…”

“…Importantly, astrocytes can produce potentially neurotoxic inflammatory mediators including tumor necrosis factor (TNF) (55). We have recently shown that following chronic intoxication in vivo, females exhibit a pro-inflammatory response in the medial prefrontal cortex that includes increased Tnf expression, while males show a pattern consistent with immune suppression (118,119). Associated with this pro-inflammatory tone, females also exhibit increased neurotoxicity (44,118).…”

“…We have recently shown that following chronic intoxication in vivo, females exhibit a pro-inflammatory response in the medial prefrontal cortex that includes increased Tnf expression, while males show a pattern consistent with immune suppression (118,119). Associated with this pro-inflammatory tone, females also exhibit increased neurotoxicity (44,118). Combined, our studies suggest the possibility that sexually dimorphic ethanol-induced neurotoxicity in the frontal cortex may be mediated in part by astrocytes both via induction and modulation of inflammatory signaling and through changes in astrocyte function including dysregulation of glutamate homeostasis.…”