Chronic exposure to alcohol alters network activity and morphology of cultured hippocampal neurons

Nerve Growth Factor in Alcohol Use Disorders

The nerve growth factor (NGF) belongs to the family of neurotrophic factors. Initially discovered as a signaling molecule involved in the survival, protection, differentiation, and proliferation of sympathetic and peripheral sensory neurons, it also participates in the regulation of the immune system and endocrine system. NGF biological activity is due to the binding of two classes of receptors: the tropomyosin-related kinase A (TrkA) and the low-affinity NGF pan-neurotrophin receptor p75. Alcohol Use Disorders (AUD) are one of the most frequent mental disorders in developed countries, characterized by heavy drinking, despite the negative effects of alcohol on brain development and cognitive functions that cause individual’s work, medical, legal, educational, and social life problems. In addition, alcohol consumption during pregnancy disrupts the development of the fetal brain causing a wide range of neurobehavioral outcomes collectively known as fetal alcohol spectrum disorders (FASD). The rationale of this review is to describe crucial findings on the role of NGF in humans and animals, when exposed to prenatal, chronic alcohol consumption, and on binge drinking.

Proteomic Analysis of Brain Regions Reveals Brain Regional Differences and the Involvement of Multiple Keratins in Chronic Alcohol Neurotoxicity

AIMS

Alcohol abuse has attracted public attention and chronic alcohol exposure can result in irreversible structural changes in the brain. The molecular mechanisms underlying alcohol neurotoxicity are complex, mandating comprehensive mining of spatial protein expression profile.

METHODS

In this study, mice models of chronic alcohol intoxication were established after 95% alcohol vapor administration for 30 consecutive days. On Day 30, striatum (the dorsal and ventral striatum) and hippocampus, the two major brain regions responsible for learning and memorizing while being sensitive to alcohol toxicity, were collected. After that, isobaric tags for relative and absolute quantitation -based quantitative proteomic analysis were carried out for further exploration of the novel mechanisms underlying alcohol neurotoxicity.

RESULTS

Proteomic results showed that in the striatum, 29 proteins were significantly up-regulated and 17 proteins were significantly down-regulated. In the hippocampus, 72 proteins were significantly up-regulated, while 2 proteins were significantly down-regulated. Analysis of the overlay proteins revealed that a total of 102 proteins were consistently altered (P < 0.05) in both hippocampus and striatum regions, including multiple keratins such as Krt6a, Krt17 and Krt5. Ingenuity pathway analysis revealed that previously reported diseases/biofunctions such as dermatological diseases and developmental disorders were enriched in those proteins. Interestingly, the glucocorticoid receptor (GR) signaling was among the top enriched pathways in both brain regions, while multiple keratins from the GR signaling such as Krt1 and Krt17 exhibited significantly opposite expression patterns in the two brain nuclei. Moreover, there are several other involved pathways significantly differed between the hippocampus and striatum.

CONCLUSIONS

Our data revealed brain regional differences upon alcohol consumption and indicated the critical involvement of keratins from GR signaling in alcohol neurotoxicity. The differences in proteomic results between the striatum and hippocampus suggested a necessity of taking into consideration brain regional differences and intertwined signaling pathways rather than merely focusing on single nuclei or molecule during the study of drug-induced neurotoxicity in the future.

Cannabinoid 1 Receptor Antagonists Play a Neuroprotective Role in Chronic Alcoholic Hippocampal Injury Related to Pyroptosis Pathway

BACKGROUND

Alcohol use disorders affect millions of people worldwide, and there is growing evidence that excessive alcohol intake causes severe damage to the brain of both humans and animals. Numerous studies on chronic alcohol exposure in animal models have identified that many functional impairments are associated with the hippocampus, which is a structure exhibiting substantial vulnerability to alcohol exposure. However, the precise mechanisms that lead to structural and functional impairments of the hippocampus are poorly understood. Herein, we report a novel cell death type, namely pyroptosis, which accounts for alcohol neurotoxicity in mice.

METHODS

For this study, we used an in vivo model to induce alcohol-related neurotoxicity in the hippocampus. Adult male C57BL/6 mice were treated with 95% alcohol vapor either alone or in combination with selective cannabinoid receptor antagonists or agonists, and VX765 (Belnacasan), which is a selective caspase-1 inhibitor.

RESULTS

Alcohol-induced in vivo pyroptosis occurs because of an increase in the levels of pyroptotic proteins such as nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3), caspase-1, gasdermin D (GSDMD), and amplified inflammatory response. Our results indicated that VX765 suppressed the expression of caspase-1 and inhibited the maturation of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18. Additionally, chronic alcohol intake created an imbalance in the endocannabinoid system and regulated 2 cannabinoid receptors (CB1R and CB2R) in the hippocampus. Specific antagonists of CB1R (AM251 and AM281) significantly ameliorated alcohol-induced pyroptosis signaling and inactivated the inflammatory response.

CONCLUSIONS

Alcohol induces hippocampal pyroptosis, which leads to neurotoxicity, thereby indicating that pyroptosis may be an essential pathway involved in chronic alcohol-induced hippocampal neurotoxicity. Furthermore, cannabinoid receptors are regulated during this process, which suggests promising therapeutic strategies against alcohol-induced neurotoxicity through pharmacologic inhibition of CB1R.

Danshen formula granule and salvianic acid A alleviate ethanol-induced neurotoxicity

As a direct neurotoxin, ethanol exposure is associated with nerve damage and dysfunction of central nervous system (CNS) and induced obvious neurotoxicity by increasing the reactive oxygen species (ROS) production, activation of endogenous apoptotic as well as necrotic signals, and other molecular mechanisms. The previous studies had demonstrated that natural herbal medicine offers protective effectiveness on ethanol-induced nerve cell damage. Danshen and its extracts have been known to have an antioxidant property and neuroprotective effects. However, the protective effects of Danshen formula granule and salvianic acid A on ethanol-induced neurotoxicity remain unknown. In this study, we found that the Danshen formula granule and salvianic acid A significantly inhibited the ethanol-induced cell death, blocked LDH release, and reduced dendritic spine loss. Furthermore, the intracellular ROS, MDA production, and ethanol-induced apoptosis were significantly ameliorated with Danshen formula granule and salvianic acid A pretreatment by increasing the antioxidant enzymatic activity of CAT, SOD and GSH-Px, and inhibiting apoptotic pathways. In addition, Danshen formula granule and salvianic acid A pretreatment obviously inhibit the apoptotic pathways by regulating the protein expression of Bcl-2, Bax, and Caspase-3. In conclusion, our data demonstrated that the Danshen formula granule and salvianic acid A provide a significantly protective effectiveness against ethanol-induced neurotoxicity, which might be a potential therapeutic drug for ethanol-induced neurological disorders.

The flavonoid acetylpectolinarin counteracts the effects of low ethanol on spontaneous network activity in hippocampal cultures

ETHNOPHARMACOLOGICAL RELEVANCE

A major concern in modern society involves the lasting detrimental behavioral effects of exposure to alcoholic beverages. Consequently, hundreds of folk remedies for hangover have been suggested, most of them without a scientific basis, for lack of proper test systems. Over centuries, yellow toadflax (Linaria vulgaris Mill., Lv) tincture has been used in Russian traditional medicine to treat the spectrum of hangover symptoms such as vertigo, headache, drunken behaviors, and as a sedative.

MATERIALS AND METHODS

Here we use in-vitro cultured hippocampal neurons to examine the effect of the Lv extract as well as the flavonoid acetylpectolinarin (ACP) exclusively found in Lv extract, on spontaneous network activity of the cultured neurons exposed to low, physiological concentrations of ethanol.

RESULTS

As in previous studies, low (0.25-0.5%) ethanol causes an increase in network activity, which was converted to suppression, with high concentrations of ethanol. Lv extract and ACP, at low concentrations, had no appreciable effect on spontaneous activity, but they blocked the facilitating action of low ethanol. This action of ACP was also seen when the culture was exposed to 1-EBIO, a SK potassium channel opener, and was blocked by apamin, an SK channel antagonist. In contrast, ACP or Lv extracts did not reverse the suppressive effects of higher ethanol.

CONCLUSIONS

Our results suggest that ACP acts by interacting with the SK channel, to block the facilitatory effect of low concentration of ethanol, on network activity in hippocampal cultures.

New Implications for the Melanocortin System in Alcohol Drinking Behavior in Adolescents: The Glial Dysfunction Hypothesis

Alcohol dependence causes physical, social, and moral harms and currently represents an important public health concern. According to the World Health Organization (WHO), alcoholism is the third leading cause of death worldwide, after tobacco consumption and hypertension. Recent epidemiologic studies have shown a growing trend in alcohol abuse among adolescents, characterized by the consumption of large doses of alcohol over a short time period. Since brain development is an ongoing process during adolescence, short- and long-term brain damage associated with drinking behavior could lead to serious consequences for health and wellbeing. Accumulating evidence indicates that alcohol impairs the function of different components of the melanocortin system, a major player involved in the consolidation of addictive behaviors during adolescence and adulthood. Here, we hypothesize the possible implications of melanocortins and glial cells in the onset and progression of alcohol addiction. In particular, we propose that alcohol-induced decrease in α-MSH levels may trigger a cascade of glial inflammatory pathways that culminate in altered gliotransmission in the ventral tegmental area and nucleus accumbens (NAc). The latter might potentiate dopaminergic drive in the NAc, contributing to increase the vulnerability to alcohol dependence and addiction in the adolescence and adulthood.