Regional distribution of ethanol-inducible cytochrome P450 IIE1 in the rat central nervous system

Roles of Oxidative Stress and Autophagy in Alcohol-Mediated Brain Damage

Excessive alcohol consumption significantly impacts human health, particularly the brain, due to its susceptibility to oxidative stress, which contributes to neurodegenerative conditions. Alcohol metabolism in the brain occurs primarily via catalase, followed by CYP2E1 pathways. Excess alcohol metabolized by CYP2E1 generates reactive oxygen/nitrogen species (ROS/RNS), leading to cell injury via altering many different pathways. Elevated oxidative stress impairs autophagic processes, increasing post-translational modifications and further exacerbating mitochondrial dysfunction and ER stress, leading to cell death. The literature highlights that alcohol-induced oxidative stress disrupts autophagy and mitophagy, contributing to neuronal damage. Key mechanisms include mitochondrial dysfunction, ER stress, epigenetics, and the accumulation of oxidatively modified proteins, which lead to neuroinflammation and impaired cellular quality control. These processes are exacerbated by chronic alcohol exposure, resulting in the suppression of protective pathways like NRF2-mediated antioxidant responses and increased susceptibility to neurodegenerative changes in the brain. Alcohol-mediated neurotoxicity involves complex interactions between alcohol metabolism, oxidative stress, and autophagy regulation, which are influenced by various factors such as drinking patterns, nutritional status, and genetic/environmental factors, highlighting the need for further molecular studies to unravel these mechanisms and develop targeted interventions.

Exploring the action mechanism of Gegensan in the treatment of alcoholic liver disease based on network pharmacology and bioinformatics

Gegensan (GGS) has been reported for the treatment of alcoholic liver disease (ALD), but its therapeutic mechanism is still unclear. This paper aims to determine the therapeutic mechanism and targets of action of GGS on alcoholic liver disease utilizing network pharmacology and bioinformatics. The active ingredients in GGS were screened in the literature and databases, and common targets of ALD were then obtained from public databases to construct the network diagram of traditional Chinese medicine-active ingredient targets. Based on the common targets, Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed to find target enrichment pathways, and the core targets were screened out by combining differential analysis and protein-protein interaction network analysis. Molecular docking was performed to verify the binding effect between the core targets and the corresponding active ingredients. ALD and GGS have 84 common targets, corresponding to 91 active ingredients. After subsequent differential analysis and protein-protein interaction network analysis, 10 core targets were identified. Gene Ontology and KEGG enrichment analyses showed that the main BPs corresponding to the common targets included the response to lipopolysaccharide, inflammatory response, etc. The KEGG pathways involved in the regulation of the common targets included the lipid-atherosclerosis pathway and the alcoholic liver disease pathway, etc. Further molecular docking showed that the core targets CYP1A1, CYP1A2, CXCL8, ADH1C, MMP1, SERPINE1, COL1A1, APOB, MMP1, and their corresponding 4 active ingredients, Naringenin, Kaempferol, Quercetin, and Stigmasterol, have a greater docking potential. The above results suggest that GGS can regulate lipid metabolism and inflammatory response in the ALD process, and alleviate the lipid accumulation and oxidative stress caused by ethanol. This study analyzed the core targets and mechanisms of action of GGS on ALD, which provides certain theoretical support for the further development of GGS in the treatment of ALD, and provides a reference for the subsequent research on the treatment of ALD.

Daucosterol Alleviates Alcohol-Induced Hepatic Injury and Inflammation through P38/NF-κB/NLRP3 Inflammasome Pathway

Alcoholic liver disease (ALD) is caused by chronic excessive alcohol consumption, which leads to inflammation, oxidative stress, lipid accumulation, liver fibrosis/cirrhosis, and even liver cancer. However, there are currently no effective drugs for ALD. Herein, we report that a natural phytosterol Daucosterol (DAU) can effectively protect against liver injury caused by alcohol, which plays anti-inflammatory and antioxidative roles in many chronic inflammatory diseases. Our results demonstrate that DAU ameliorates liver inflammation induced by alcohol through p38/nuclear factor kappa B (NF-κB)/NOD-like receptor protein-3 (NLRP3) inflammasome pathway. Briefly, DAU decreases NF-κB nuclear translocation and inhibits NLRP3 activation by decreasing p38 phosphorylation. At the same time, DAU also protects against hepatic oxidative stress and lipid accumulation. In conclusion, our research provides a new clue about the protective effects of naturally active substances on ALD.

Interleukin-1β-induced inflammation and acetaminophen during infancy: Distinct and interactive effects on social-emotional and repetitive behavior in C57BL/6J mice

Acetaminophen (APAP) exposure early in life has been associated with increased risk of neurodevelopmental disorders in epidemiological studies. In rodent models, early-life APAP has similarly been shown to produce long-term changes in brain and behavior, including altered activity levels and social behavior. Most rodent studies to date have, nevertheless, attempted to model early-life APAP without considering that most APAP exposure occurs in a context of immune activation and/or fever. To mimic the repeated infections common during infancy, we employed the cytokine interleukin-1β (IL-1β) to induce immune activation three times during early postnatal development (i.e., day 5, 8, and 11). On these days, C57BL/6J pups were administered either IL-1β (0.2 μg/kg) or saline vehicle followed, after 45 min, by either APAP (103.9 mg/kg) or vehicle. Mice were subsequently administered a battery of tests of social-emotional and repetitive behavior. A number of distinct long-term effects of IL-1β and APAP treatments were found, including sex-specific shifts in repetitive behavior and emotional hyperthermia following early-life IL-1β and increased social caution in males following early-life APAP. We also observed significant interaction between IL-1β and APAP: as adults, 'two-hit' IL-1β + APAP females displayed greater anxiety-related thigmotaxis across a number of tests, including an open field. 'Two hit' males, in turn, showed elevated levels of avoidance of an unfamiliar social partner during a social interaction test. Our results highlight that IL-1β-induced inflammation and APAP have both distinct effects and significant interactions during early life, with enduring sex-specific effects on phenotypes relevant to neurodevelopmental disorders.

Potential Role of MANF, an ER Stress Responsive Neurotrophic Factor, in Protecting Against Alcohol Neurotoxicity

Alcohol exposure during pregnancy is harmful to the fetus and causes a wide range of long-lasting physiological and neurocognitive impairments, collectively referred to as fetal alcohol spectrum disorders (FASD). The neurobehavioral deficits observed in FASD result from structural and functional damages in the brain, with neurodegeneration being the most destructive consequence. Currently, there are no therapies for FASD. It is exigent to delineate the underlying mechanisms of alcohol neurotoxicity and develop an effective strategy of treatment. ER stress, caused by the accumulation of unfolded/misfolded proteins in the ER, is the hallmark of many neurodegenerative diseases, including alcohol-induced neurodegeneration. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a newly discovered endoplasmic reticulum (ER) stress responsive neurotrophic factor that regulates diverse neuronal functions. This review summarizes the recent findings revealing the effects of MANF on the CNS and its protective role against neurodegeneration. Particularly, we focus the role of MANF on alcohol-induced ER stress and neurodegeneration and discuss the therapeutic potential of MANF in treating alcohol neurotoxicity such as FASD.

Vitamin Supplements as a Nutritional Strategy against Chronic Alcohol Consumption? An Updated Review

Several studies have shown that blood vitamin levels are low in alcoholic patients. In effect, alcohol use abuse is considered a chronic disease that promotes the pathogenesis of many fatal diseases, such as cancer and liver cirrhosis. The alcohol effects in the liver can be prevented by antioxidant mechanisms, which induces enzymatic as well as other nonenzymatic pathways. The effectiveness of several antioxidants has been evaluated. However, these studies have been accompanied by uncertainty as mixed results were reported. Thus, the aim of the present review article was to examine the current knowledge on vitamin deficiency and its role in chronic liver disease. Our review found that deficiencies in nutritional vitamins could develop rapidly during chronic liver disease due to diminished hepatic storage and that inadequate vitamins intake and alcohol consumption may interact to deplete vitamin levels. Numerous studies have described that vitamin supplementation could reduce hepatotoxicity. However, further studies with reference to the changes in vitamin status and the nutritional management of chronic liver disease are in demand.

Advanced glycation end products (AGEs) and other adducts in aging-related diseases and alcohol-mediated tissue injury

Advanced glycation end products (AGEs) are potentially harmful and heterogeneous molecules derived from nonenzymatic glycation. The pathological implications of AGEs are ascribed to their ability to promote oxidative stress, inflammation, and apoptosis. Recent studies in basic and translational research have revealed the contributing roles of AGEs in the development and progression of various aging-related pathological conditions, such as diabetes, cardiovascular complications, gut microbiome-associated illnesses, liver or neurodegenerative diseases, and cancer. Excessive chronic and/or acute binge consumption of alcohol (ethanol), a widely consumed addictive substance, is known to cause more than 200 diseases, including alcohol use disorder (addiction), alcoholic liver disease, and brain damage. However, despite the considerable amount of research in this area, the underlying molecular mechanisms by which alcohol abuse causes cellular toxicity and organ damage remain to be further characterized. In this review, we first briefly describe the properties of AGEs: their formation, accumulation, and receptor interactions. We then focus on the causative functions of AGEs that impact various aging-related diseases. We also highlight the biological connection of AGE-alcohol-adduct formations to alcohol-mediated tissue injury. Finally, we describe the potential translational research opportunities for treatment of various AGE- and/or alcohol-related adduct-associated disorders according to the mechanistic insights presented.

Cytochrome P450 CYP2E1 Suppression Ameliorates Cerebral Ischemia Reperfusion Injury

Despite existing strong evidence on oxidative markers overproduction following ischemia/reperfusion (I/R), the mechanism by which oxidative enzyme Cytochrome P450-2E1 (CYP2E1) contributes to I/R outcomes is not clear. In this study, we sought to evaluate the functional significance of CYP2E1 in I/R. CYP2E1 KO mice and controls were subjected to middle cerebral artery occlusion (MCAo-90 min) followed by 24 h of reperfusion to induce focal I/R injury as an acute stage model. Then, histological and chemical analyses were conducted to investigate the role of CYP2E1 in lesion volume, oxidative stress, and inflammation exacerbation. Furthermore, the role of CYP2E1 on the blood-brain barrier (BBB) integrity was investigated by measuring 20-hydroxyecosatetraenoic acid (20-HETE) activity, as well as, in vivo BBB transfer rate. Following I/R, the CYP2E1 KO mice exhibited a significantly lower lesion volume, and neurological deficits compared to controls (p < 0.005). Moreover, reactive oxygen species (ROS) production, apoptosis, and neurodegeneration were significantly lower in the CYP2E1(−/−) I/R group (p < 0.001). The BBB damage was significantly lower in CYP2E1(−/−) mice compared to wild-type (WT) (p < 0.001), while 20-HETE production was increased by 41%. Besides, inflammatory cytokines expression and the number of activated microglia were significantly lower in CYP2E1(−/−) mice following I/R. CYP2E1 suppression ameliorates I/R injury and protects BBB integrity by reducing both oxidative stress and inflammation.

Cytochrome P450 expression and regulation in the brain

The regulation of brain cytochrome P450 enzymes (CYPs) is different compared with respective hepatic enzymes. This may result from anatomical bases and physiological functions of the two organs. The brain is composed of a variety of functional structures built of different interconnected cell types endowed with specific receptors that receive various neuronal signals from other brain regions. Those signals activate transcription factors or alter functioning of enzyme proteins. Moreover, the blood-brain barrier (BBB) does not allow free penetration of all substances from the periphery into the brain. Differences in neurotransmitter signaling, availability to endogenous and exogenous active substances, and levels of transcription factors between neuronal and hepatic cells lead to differentiated expression and susceptibility to the regulation of CYP genes in the brain and liver. Herein, we briefly describe the CYP enzymes of CYP1-3 families, their distribution in the brain, and discuss brain-specific regulation of CYP genes. In parallel, a comparison to liver CYP regulation is presented. CYP enzymes play an essential role in maintaining the levels of bioactive molecules within normal ranges. These enzymes modulate the metabolism of endogenous neurochemicals, such as neurosteroids, dopamine, serotonin, melatonin, anandamide, and exogenous substances, including psychotropics, drugs of abuse, neurotoxins, and carcinogens. The role of these enzymes is not restricted to xenobiotic-induced neurotoxicity, but they are also involved in brain physiology. Therefore, it is crucial to recognize the function and regulation of CYP enzymes in the brain to build a foundation for future medicine and neuroprotection and for personalized treatment of brain diseases.

Brain ethanol-metabolizing enzymes are differentially expressed in lead-exposed animals after voluntary ethanol consumption: Pharmacological approaches

Developmentally-lead (Pb)-exposed rats showed an enhanced vulnerability to the stimulating and motivational effects of ethanol (EtOH). This is accompanied by differential activity of the brain EtOH-metabolizing enzymes catalase (CAT) and mitochondrial aldehyde dehydrogenase (ALDH2). Based on the theory that brain acetaldehyde accumulation is associated with the reinforcing properties of EtOH, this study sought to determine brain CAT and ALDH2 expression in limbic areas of control and Pb-exposed animals after voluntary EtOH intake. Thirty-five-day-old rats perinatally exposed to 220 ppm Pb were offered with water or increasing EtOH solutions (2-10% v/v) during 28 days until postnatal day (PND) 63. Once intake was stable, the animals were administered: 1) saline (SAL; test days 21-24 or 21-28, as corresponds), or 2) a CAT inhibitor: 3-amine 1, 2, 4-triazole (AT; 250 mg/kg intraperitoneally [i.p.], 5 h before the last eight EtOH intake sessions -test days 21-24 and 25-28), or 3) a CAT booster: 3-nitropropionic acid (3NPA; 20 mg/kg subcutaneously [s.c.], 45 min before the last four EtOH intake sessions -test days 25-28). Two additional groups were centrally-administered cyanamide (CY, an ALDH2 inhibitor, 0.3 mg i.c.v. immediately before the last four EtOH sessions, test days 25-28) or its corresponding vehicle (VEH). Lead exposure increased EtOH intake, an effect potentiated in both groups by 3NPA or CY pretreatments and reduced by AT, albeit selectivity in the Pb group. Catalase abundance in limbic areas parallels these observations in the Pb group, showing higher CAT expression in all areas after EtOH consumption respect to the controls, an effect prevented by AT administration. In contrast, ALDH2 expression was reduced in the Pb animals after EtOH intake, with CY potentiating this effect in all brain areas under study. Based on these results and on previous evidences, we suggest that Pb exposure promotes acetaldehyde accumulation in limbic regions, providing some insights into the mechanism of action that underlies the vulnerability to the excessive EtOH consumption reported in these animals.

Alterations in Synaptic Plasticity and Oxidative Stress Following Long-Term Paracetamol Treatment in Rat Brain

Several studies have recently revealed that cognitive function can be affected by paracetamol (APAP) treatment. However, the exact impact of this drug treatment on learning and memory has not been clarified. This study aimed to investigate the effect of APAP treatment on the alteration of synapses and oxidative stress in the rat frontal cortex and hippocampus. APAP at a dose of 200 mg/kg bw was fed to adult male Wistar rats through either acute (n = 10), 15-day (n = 10), or 30-day (n = 10) treatment regimens. The synaptic ultrastructure and proteins, synaptophysin (SYP) and postsynaptic density-95 (PSD-95), were monitored. The amount of protein carbonyl oxidation (PCO) and glutathione (GSH) levels were examined. Our results demonstrated that acute treatment with APAP had no effect on synapses and oxidative stress. However, the synapses obtained from rats with 15-day APAP treatment showed a marked shortening of active zones and widening of the synaptic cleft. Decrement of SYP and PSD-95 proteins were demonstrated in these rats as well. With 30-day APAP treatment, the alteration of the synaptic ultrastructure and proteins was more evident. Moreover, the depletion of GSH and the elevation of PCO levels were demonstrated in the rats treated with APAP for 30 days. These results suggest that long-term APAP treatment can induce synaptic degeneration in the hippocampus and frontal cortex. The increase in oxidative stress in these brain areas may be due to the deleterious effect of this drug.

Alcoholic Liver Disease: Alcohol Metabolism, Cascade of Molecular Mechanisms, Cellular Targets, and Clinical Aspects

Alcoholic liver disease is the result of cascade events, which clinically first lead to alcoholic fatty liver, and then mostly via alcoholic steatohepatitis or alcoholic hepatitis potentially to cirrhosis and hepatocellular carcinoma. Pathogenetic events are linked to the metabolism of ethanol and acetaldehyde as its first oxidation product generated via hepatic alcohol dehydrogenase (ADH) and the microsomal ethanol-oxidizing system (MEOS), which depends on cytochrome P450 2E1 (CYP 2E1), and is inducible by chronic alcohol use. MEOS induction accelerates the metabolism of ethanol to acetaldehyde that facilitates organ injury including the liver, and it produces via CYP 2E1 many reactive oxygen species (ROS) such as ethoxy radical, hydroxyethyl radical, acetyl radical, singlet radical, superoxide radical, hydrogen peroxide, hydroxyl radical, alkoxyl radical, and peroxyl radical. These attack hepatocytes, Kupffer cells, stellate cells, and liver sinusoidal endothelial cells, and their signaling mediators such as interleukins, interferons, and growth factors, help to initiate liver injury including fibrosis and cirrhosis in susceptible individuals with specific risk factors. Through CYP 2E1-dependent ROS, more evidence is emerging that alcohol generates lipid peroxides and modifies the intestinal microbiome, thereby stimulating actions of endotoxins produced by intestinal bacteria; lipid peroxides and endotoxins are potential causes that are involved in alcoholic liver injury. Alcohol modifies SIRT1 (Sirtuin-1; derived from Silent mating type Information Regulation) and SIRT2, and most importantly, the innate and adapted immune systems, which may explain the individual differences of injury susceptibility. Metabolic pathways are also influenced by circadian rhythms, specific conditions known from living organisms including plants. Open for discussion is a 5-hit working hypothesis, attempting to define key elements involved in injury progression. In essence, although abundant biochemical mechanisms are proposed for the initiation and perpetuation of liver injury, patients with an alcohol problem benefit from permanent alcohol abstinence alone.

Investigating the CYP2E1 Potential Role in the Mechanisms Behind INH/LPS-Induced Hepatotoxicity

Tuberculosis (TB) is one of the oldest infectious diseases that affected humankind and remains one of the world's deadliest communicable diseases that could be considered as global emergency, but the discovery and development of isoniazid (INH) in the 1950s paved the way to an effective single and/or combined first-line anti-TB therapy. However, administration of INH induces severe hepatic toxicity in some patients. Previously, we establish a rat model of INH hepatotoxicity utilizing the inflammatory stress theory, in which bacterial lipopolysaccharide (LPS) potentially enhanced INH toxicity. These enhancing activities ranged between augmenting the inflammatory stress, oxidative stress, alteration of bile acid homeostasis, and CYP2E1 over-expression. Although pre-treatment with dexamethasone (DEX) helped overcome both inflammatory and oxidative stress which ended-up in alleviation of LPS augmenting effects, but still minor toxicities were being detected, alongside with CYP2E1 over expression. This finding positively indicated the corner-stone role played by CYP2E1 in the pathogenesis of INH/LPS-induced liver damage. Therefore, we examined whether INH/LPS co-treatment with CYP2E1 inhibitor diallyl sulfide (DAS) and DEX can protect against the INH/LPS-induced hepatotoxicity. Our results showed that pre-administration of both DAS and DEX caused significant reduction in serum TBA, TBil, and gamma-glutamyl transferase levels. Furthermore, the histopathological analysis showed that DAS and DEX could effectively reverse the liver lesions seen following INH/LPS treatment and protect against hepatic steatosis as indicated by absence of lipid accumulation. Pre-treatment with DAS alone could not completely block the CYP2E1 protein expression following INH/LPS treatment, as appeared in the immunoblotting and immunohistochemistry results. This is probably due to the fact that the combined enhancement activities of both INH and LPS on CYP2E1 protein expression levels might resist the blocking probabilities of DAS. In the meantime, addition of DEX to the DAS/INH/LPS combination caused a significant reduction in CYP2E1 protein expression as revealed by the immunoblotting and fading coloration in immunohistochemistry results. Thus, addition of DEX and DAS together caused strong protection against INH/LPS-induced hepatic damage. These findings reveal the potential therapeutic value of combining DAS and DEX with INH in TB management for reducing the potential risk and incidences of hepatotoxicity.

Relationship between the hippocampal expression of selected cytochrome P450 isoforms and the animal performance in the hippocampus-dependent learning task

Despite very extensive studies on the molecular mechanisms of memory formation, relatively little is known about the molecular correlates of individual variation in the learning skills within a random population of young normal subjects. The role of cytochrome P450 (CYP) enzymes in the brain also remains poorly understood. On the other hand, these enzymes are known to be related to the metabolism of substances important for neural functions including steroids, fatty acids, and retinoic acid. In the present study, we examined the potential correlation between the animals' performance in a place learning task and the levels of selected CYP isoforms (CYP2E1, CYP2D1 and CYP7A1) in the rat hippocampus. According to their performance, rats were classified as "good" learners (percent error/number of trials to criterion ≤ group mean - 3SEM) or "poor" learners (percent error/number of trials to criterion ≥ group mean + 3SEM). The CYP enzyme levels were determined by Western Blot at the early, intermediary and advanced stages of the task acquisition (day 4, day 8 and after reaching a performance criterion of 83% correct responses). In this study, as expected, CYP2E1 and CYP2D1 isoforms have been found in the rat hippocampus. However, a putative CYP7A1 isoform was also visualized. Hippocampal expression of these enzymes was shown to be dependent on the stage of learning and animals' cognitive status. In "good" learners compared to "poor" learners, significantly higher levels of CYP2E1 were found at the early stage of training, significantly higher levels of CYP2D1 were found at the intermediate stage of training, and significantly higher levels of CYP7A1-like protein were found after reaching the acquisition criterion. These findings suggest that the differential expression of some CYP isoforms in the hippocampus may have impact on individual learning skills and that different CYP isoforms may play different roles during the learning process.

On the Accuracy of In Vivo Ethanol and Acetaldehyde Monitoring, a Key Tile in the Puzzle of Acetaldehyde as a Neuroactive Agent

Over the last 20 years researchers have explored the postulated role of acetaldehyde (ACD) as a mediator of some of the actions of ethanol (EtOH) in the central nervous system (CNS). However, efforts have been hampered mainly by the difficulty of directly measuring in vivo EtOH and ACD levels in the CNS and thus, our knowledge is based on indirect evidences. Although technically challenging, the development of reliable methods for in vivo measurement of ACD and EtOH is of paramount importance to solve the “puzzle of acetaldehyde as a neuroactive agent.” In this short review we discuss the recent advances on brain EtOH pharmacokinetic and state-of-the-art available techniques that could be used for in vivo detect EtOH and ACD both non-invasively (magnetic resonance spectroscopy), and invasively (microdialysis and biosensors). Among the different in vivo sampling techniques described, particular emphasis is paid to the field of enzyme-based amperometric biosensors. Biosensors have gained much attention in recent years for their ability to online monitor biological signals in vivo, and several micro- and nano-structured devices have been successfully used for in vivo studies. Owing to their high temporal and spatial resolution, biosensors could provide the adequate technology for studying in vivo EtOH pharmacokinetic.

The Role of CYP2E1 in the Drug Metabolism or Bioactivation in the Brain

Organisms have metabolic pathways that are responsible for removing toxic agents. We always associate the liver as the major organ responsible for detoxification of the body; however this process occurs in many tissues. In the same way, as in the liver, the brain expresses metabolic pathways associated with the elimination of xenobiotics. Besides the detoxifying role of CYP2E1 for compounds such as electrophilic agents, reactive oxygen species, free radical products, and the bioactivation of xenobiotics, CYP2E1 is also related in several diseases and pathophysiological conditions. In this review, we describe the presence of phase I monooxygenase CYP2E1 in regions of the brain. We also explore the conditions where protein, mRNA, and the activity of CYP2E1 are induced. Finally, we describe the relation of CYP2E1 in brain disorders, including the behavioral relations for alcohol consumption via CYP2E1 metabolism.

Alteration in mitochondrial function and glutamate metabolism affected by 2-chloroethanol in primary cultured astrocytes

The aim of this study was to explore the mechanisms that contribute to 1,2-dichloroethane (1,2-DCE) induced brain edema by focusing on alteration of mitochondrial function and glutamate metabolism in primary cultured astrocytes induced by 2-chloroethanol (2-CE), a metabolite of 1,2-DCE in vivo. The cells were exposed to different levels of 2-CE in the media for 24h. Mitochondrial function was evaluated by its membrane potential and intracellular contents of ATP, lactic acid and reactive oxygen species (ROS). Glutamate metabolism was indicated by expression of glutamine synthase (GS), glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) at both protein and gene levels. Compared to the control group, exposure to 2-CE could cause a dose dependent damage in astrocytes, indicated by decreased cell viability and morphological changes, and supported by decreased levels of nonprotein sulfhydryl (NPSH) and inhibited activities of Na⁺/K⁺-ATPase and Ca²⁺-ATPase in the cells. The present study also revealed both mitochondrial function and glutamate metabolism in astrocytes were significantly disturbed by 2-CE. Of which, mitochondrial function was much vulnerable to the effects of 2-CE. In conclusion, our findings suggested that mitochondrial dysfunction and glutamate metabolism disorder could contribute to 2-CE-induced cytotoxicity in astrocytes, which might be related to 1,2-DCE-induced brain edema.

Metabolic methanol: molecular pathways and physiological roles

Methanol has been historically considered an exogenous product that leads only to pathological changes in the human body when consumed. However, in normal, healthy individuals, methanol and its short-lived oxidized product, formaldehyde, are naturally occurring compounds whose functions and origins have received limited attention. There are several sources of human physiological methanol. Fruits, vegetables, and alcoholic beverages are likely the main sources of exogenous methanol in the healthy human body. Metabolic methanol may occur as a result of fermentation by gut bacteria and metabolic processes involving S-adenosyl methionine. Regardless of its source, low levels of methanol in the body are maintained by physiological and metabolic clearance mechanisms. Although human blood contains small amounts of methanol and formaldehyde, the content of these molecules increases sharply after receiving even methanol-free ethanol, indicating an endogenous source of the metabolic methanol present at low levels in the blood regulated by a cluster of genes. Recent studies of the pathogenesis of neurological disorders indicate metabolic formaldehyde as a putative causative agent. The detection of increased formaldehyde content in the blood of both neurological patients and the elderly indicates the important role of genetic and biochemical mechanisms of maintaining low levels of methanol and formaldehyde.

Cell type-specific expression and localization of cytochrome P450 isoforms in tridimensional aggregating rat brain cell cultures

Within the Predict-IV FP7 project a strategy for measurement of in vitro biokinetics was developed, requiring the characterization of the cellular model used, especially regarding biotransformation, which frequently depends on cytochrome P450 (CYP) activity. The extrahepatic in situ CYP-mediated metabolism is especially relevant in target organ toxicity. In this study, the constitutive mRNA levels and protein localization of different CYP isoforms were investigated in 3D aggregating brain cell cultures. CYP1A1, CYP2B1/B2, CYP2D2/4, CYP2E1 and CYP3A were expressed; CYP1A1 and 2B1 represented almost 80% of the total mRNA content. Double-immunolabeling revealed their presence in astrocytes, in neurons, and to a minor extent in oligodendrocytes, confirming the cell-specific localization of CYPs in the brain. These results together with the recently reported formation of an amiodarone metabolite following repeated exposure suggest that this cell culture system possesses some metabolic potential, most likely contributing to its high performance in neurotoxicological studies and support the use of this model in studying brain neurotoxicity involving mechanisms of toxication/detoxication.

Effect of status epilepticus and antiepileptic drugs on CYP2E1 brain expression

P450 metabolic enzymes are expressed in the human and rodent brain. Recent data support their involvement in the pathophysiology of epilepsy. However, the determinants of metabolic enzyme expression in the epileptic brain are unclear. We tested the hypothesis that status epilepticus (SE) or exposure to phenytoin or phenobarbital affects brain expression of the metabolic enzyme CYP2E1. SE was induced in C57BL/6J mice by systemic kainic acid. Brain CYP2E1 expression was evaluated 18-24h after severe SE by immunohistochemistry. Co-localization with neuronal nuclei (NEUN), glial fibrillary acidic protein (GFAP) and CD31 was determined by confocal microscopy. The effect of phenytoin, carbamazepine and phenobarbital on CYP2E1 expression was evaluated in vivo or by using organotypic hippocampal cultures in vitro. CYP2E1 expression was investigated in brain resections from a cohort of drug-resistant epileptic brain resections and human endothelial cultures (EPI-EC). Immunohistochemistry showed an increase of CYP2E1 expression limited to hippocampal CA2/3 and hilar neurons after severe SE in mice. CYP2E1 expression was also observed at the astrocyte-vascular interface. Analysis of human brain specimens revealed CYP2E1 expression in neurons and vascular endothelial cells (EC). CYP2E1 was expressed in cultured human EC and over-expressed by EPI-EC. When analyzing the effect of drug exposure on CYP2E1 expression we found that, in vivo or in vitro, ethanol increased CYP2E1 levels in the brain and liver. Treatment with phenytoin induced localized CYP2E1 expression in the brain whereas no significant effects were exerted by carbamazepine or phenobarbital. Our data indicate that the effect of acute SE on brain CYP2E1 expression is localized and cell specific. Exposure to selected anti-epileptic drugs could play a role in determining CYP2E1 brain expression. Additional investigation is required to fully reproduce the culprits of P450 enzyme expression as observed in the human epileptic brain.

Triggering of protection mechanism against Phoneutria nigriventer spider venom in the brain

Severe accidents caused by the "armed" spider Phoneutria nigriventer cause neurotoxic manifestations in victims. In experiments with rats, P. nigriventer venom (PNV) temporarily disrupts the properties of the BBB by affecting both the transcellular and the paracellular route. However, it is unclear how cells and/or proteins participate in the transient opening of the BBB. The present study demonstrates that PNV is a substrate for the multidrug resistance protein-1 (MRP1) in cultured astrocyte and endothelial cells (HUVEC) and increases mrp1 and cx43 and down-regulates glut1 mRNA transcripts in cultured astrocytes. The inhibition of nNOS by 7-nitroindazole suggests that NO derived from nNOS mediates some of these effects by either accentuating or opposing the effects of PNV. In vivo, MRP1, GLUT1 and Cx43 protein expression is increased differentially in the hippocampus and cerebellum, indicating region-related modulation of effects. PNV contains a plethora of Ca(2+), K(+) and Na(+) channel-acting neurotoxins that interfere with glutamate handling. It is suggested that the findings of the present study are the result of a complex interaction of signaling pathways, one of which is the NO, which regulates BBB-associated proteins in response to PNV interference on ions physiology. The present study provides additional insight into PNV-induced BBB dysfunction and shows that a protective mechanism is activated against the venom. The data shows that PNV has qualities for potential use in drug permeability studies across the BBB.

Oxidation of ethanol in the rat brain and effects associated with chronic ethanol exposure

It has been reported that chronic and acute alcohol exposure decreases cerebral glucose metabolism and increases acetate oxidation. However, it remains unknown how much ethanol the living brain can oxidize directly and whether such a process would be affected by alcohol exposure. The questions have implications for reward, oxidative damage, and long-term adaptation to drinking. One group of adult male Sprague-Dawley rats was treated with ethanol vapor and the other given room air. After 3 wk the rats received i.v. [2-(13)C]ethanol and [1, 2-(13)C2]acetate for 2 h, and then the brain was fixed, removed, and divided into neocortex and subcortical tissues for measurement of (13)C isotopic labeling of glutamate and glutamine by magnetic resonance spectroscopy. Ethanol oxidation was seen to occur both in the cortex and the subcortex. In ethanol-naïve rats, cortical oxidation of ethanol occurred at rates of 0.017 ± 0.002 µmol/min/g in astroglia and 0.014 ± 0.003 µmol/min/g in neurons, and chronic alcohol exposure increased the astroglial ethanol oxidation to 0.028 ± 0.002 µmol/min/g (P = 0.001) with an insignificant effect on neuronal ethanol oxidation. Compared with published rates of overall oxidative metabolism in astroglia and neurons, ethanol provided 12.3 ± 1.4% of cortical astroglial oxidation in ethanol-naïve rats and 20.2 ± 1.5% in ethanol-treated rats. For cortical astroglia and neurons combined, the ethanol oxidation for naïve and treated rats was 3.2 ± 0.3% and 3.8 ± 0.2% of total oxidation, respectively. (13)C labeling from subcortical oxidation of ethanol was similar to that seen in cortex but was not affected by chronic ethanol exposure.

Curcumin Protects against 1-Methyl-4-phenylpyridinium Ion- and Lipopolysaccharide-Induced Cytotoxicities in the Mouse Mesencephalic Astrocyte via Inhibiting the Cytochrome P450 2E1

Curcumin is extracted from the rhizomes of the ginger family plant Curcuma longa L., which has a good protection for liver, kidney, and immune system. However, there is little information about its contribution in protection of astrocytes recently. The present study was undertaken to elucidate the protective effect of curcumin, an herbal antioxidant, on 1-methyl-4-phenylpyridinium ion- (MPP⁺-) and lipopolysaccharide- (LPS-) induced cytotoxicities, as well as the underlying mechanisms by using primary mouse mesencephalic astrocytes. The results showed that curcumin protected the mesencephalic astrocytes from MPP⁺- and LPS-induced toxicities along with reducing reactive oxygen species (P < 0.05) and maleic dialdehyde (P < 0.05) sufficiently. Moreover, curcumin significantly inhibited the cytochrome P450 2E1 (CYP2E1) expression (P < 0.01 at mRNA level, P < 0.05 at protein level) and its activity (P < 0.05) sufficiently induced by MPP⁺ and LPS in the mouse mesencephalic astrocytes. And curcumin as well as diallyl sulphide, a CYP2E1 positive inhibitor, ameliorated MPP⁺- and LPS-induced mouse mesencephalic astrocytes damage. Accordingly, curcumin protects against MPP⁺- and LPS-induced cytotoxicities in the mouse mesencephalic astrocyte via inhibiting the CYP2E1 expression and activity.

Biotransformation of carbon tetrachloride in cultured neurons and astrocytes

The ability of brain neuronal cells to metabolize carbon tetrachloride (CCl(4)) has been studied in an attempt to explain earlier observed toxic effects of CCl(4) on these cells. The expression of cytochrome P-450, the glutathione (GSH) content and the activity of glutathione-S-transferase (GST) were measured in cultured neurons and astrocytes from chick embryo cerebral hemispheres. The metabolism of CCl(4) in the neuron and astrocyte cultures was also assessed by determining the formation of: CCl(2) in membrane preparations of these cells. In the membrane fractions of neurons and astrocytes, no measurable levels of cytochrome P-450 were observed. Nevertheless, neurons as well as astrocytes had a capacity for the metabolism of CCl(4). The metabolic capacity of the neurons was significantly greater than that of the astrocytes. The neuron cultures had a higher initial content of GSH and a higher control activity of GST than had the astrocytes. Neither the GSH level nor GST activity were significantly affected in the neuron cultures after exposure to CCl(4). In astrocyte cultures 2 mm CCl(4) slightly depleted the GSH level and significantly induced GST activity. At 3 mm CCl(4), GSH was depleted by 30% and by more than 50% at 4 mm CCl(4). It can be concluded that the metabolic activation of CCl(4) was higher in neurons than in astrocytes. This can explain the earlier observation of CCl(4)-induced lipid peroxidation in cultured neurons. Moreover, neuron GSH was not able to protect these cells against CCl(4)-induced peroxidative damage. In the astrocytes, on the other hand, GSH and GST appeared to have a role in detoxification of CCl(4).

Genetic polymorphisms in CYP2E1: association with schizophrenia susceptibility and risperidone response in the Chinese Han population

Background

CYP2E1 is a member of the cytochrome P450 superfamily, which is involved in the metabolism and activation of both endobiotics and xenobiotics. The genetic polymorphisms of CYP2E1 gene (Chromosome 10q26.3, Accession Number NC_000010.10) are reported to be related to the development of several mental diseases and to be involved in the clinical efficacy of some psychiatric medications. We investigated the possible association of CYP2E1 polymorphisms with susceptibility to schizophrenia in the Chinese Han Population as well as the relationship with response to risperidone in schizophrenia patients.

Methods

In a case-control study, we identified 11 polymorphisms in the 5' flanking region of CYP2E1 in 228 schizophrenia patients and 384 healthy controls of Chinese Han origin. From among the cases, we chose 130 patients who had undergone 8 weeks of risperidone monotherapy to examine the relationship between their response to risperidone and CYP2E1 polymorphisms. Clinical efficacy was assessed using the Brief Psychiatric Rating Scale (BPRS).

Results

Statistically significant differences in allele or genotype frequencies were found between cases and controls at rs8192766 (genotype p = 0.0048, permutation p = 0.0483) and rs2070673 (allele: p = 0.0018, permutation p = 0.0199, OR = 1.4528 95%CI = 1.1487–1.8374; genotype: p = 0.0020, permutation p = 0.0225). In addition, a GTCAC haplotype containing 5 SNPs (rs3813867, rs2031920, rs2031921, rs3813870 and rs2031922) was observed to be significantly associated with schizophrenia (p = 7.47E-12, permutation p<0.0001). However, no association was found between CYP2E1 polymorphisms/haplotypes and risperidone response.

Conclusions

Our results suggest that CYP2E1 may be a potential risk gene for schizophrenia in the Chinese Han population. However, polymorphisms of the CYP2E1 gene may not contribute significantly to individual differences in the therapeutic efficacy of risperidone. Further studies in larger groups are warranted to confirm our results.

Acetaldehyde oral self-administration: evidence from the operant-conflict paradigm

BACKGROUND

Acetaldehyde (ACD), ethanol's first metabolite, has been reported to interact with the dopaminergic reward system, and with the neural circuits involved in stress response. Rats self-administer ACD directly into cerebral ventricles, and multiple intracerebroventricular infusions of ACD produce conditioned place preference. Self-administration has been largely employed to assess the reinforcing and addictive properties of most drugs of abuse. In particular, operant conditioning is a valid model to investigate drug-seeking and drug-taking behavior in rats.

METHODS

This study was aimed at the evaluation of (i) the motivational properties of oral ACD in the induction and maintenance of an operant-drinking behavior; (ii) ACD effect in a conflict situation employing the punishment-based Geller-Seifter procedure; and (iii) the onset of a relapse drinking behavior, following ACD deprivation. The lever-pressing procedure in a sound-attenuated operant-conditioning chamber was scheduled into 3 different periods: (i) training-rewarded responses with a fixed ratio 1; (ii) conflict-rewarded responses periodically associated with a 0.2 mA foot-shock; and (iii) relapse-rewarded lever presses following 1-week ACD abstinence.

RESULTS

Our results show that oral self-administrated ACD induced: a higher rate of punished responses in Geller-Seifter procedures; and the establishment of a relapse behavior following ACD deprivation.

CONCLUSIONS

In conclusion, our results indicate that ACD is able to induce an operant-drinking behavior, which is also maintained besides the conflict procedure and enhanced by the deprivation effect, supporting the hypothesis that ACD itself possesses motivational properties, such as alcohol and other substances of abuse.

Redox balance in the pathogenesis of nonalcoholic fatty liver disease: mechanisms and therapeutic opportunities

Nonalcoholic fatty liver disease (NAFLD) is currently the most common liver disease in the world. It encompasses a histological spectrum, ranging from simple, nonprogressive steatosis to nonalcoholic steatohepatitis (NASH), which may progress to cirrhosis and hepatocellular carcinoma. While liver-related complications are confined to NASH, emerging evidence suggests both simple steatosis and NASH predispose to type 2 diabetes and cardiovascular disease. The pathogenesis of NAFLD is currently unknown, but accumulating data suggest that oxidative stress and altered redox balance play a crucial role in the pathogenesis of steatosis, steatohepatitis, and fibrosis. We will examine intracellular mechanisms, including mitochondrial dysfunction and impaired oxidative free fatty acid metabolism, leading to reactive oxygen species generation; additionally, the potential pathogenetic role of extracellular sources of reactive oxygen species in NAFLD, including increased myeloperoxidase activity and oxidized low density lipoprotein accumulation, will be reviewed. We will discuss how these mechanisms converge to determine the whole pathophysiological spectrum of NAFLD, including hepatocyte triglyceride accumulation, hepatocyte apoptosis, hepatic inflammation, hepatic stellate cell activation, and fibrogenesis. Finally, available animal and human data on treatment opportunities with older and newer antioxidant will be presented.

HIV-1 infection and alcohol abuse: neurocognitive impairment, mechanisms of neurodegeneration and therapeutic interventions

Clinical studies indicate that alcohol dependence has an additive effect on cognitive deficits associated with HIV-1 infection. Findings in humans and animal models suggest that alcohol, similar to HIV-1, induces inflammatory processes in the brain leading to neurodegeneration. The causes of HIV-1-associated neurotoxicity are comparable to those mediating alcohol-induced neuronal injury. This review aims to present the mechanisms of the combined effects of HIV-1 and alcohol abuse in the brain and to discuss neuroprotective therapies. Oxidative stress, overproduction of pro-inflammatory factors, impairment of blood-brain barrier and glutamate associated neurotoxicity appear to play important roles in alcohol driven neurodegeneration. Diminution of neuroinflammation constitutes a logical approach for prevention of HIV-1 and alcohol mediated neurodegeneration. Agonists of cannabinoid receptor 2 (CB₂) possess potent anti-inflammatory and neuroprotective properties. We address multifaceted beneficial effects of CB₂ activation in the setting of HIV-1 brain infection and alcohol abuse.

The role of oxidative stress in fetal alcohol spectrum disorders

The ingestion of alcohol/ethanol during pregnancy can result in abnormal fetal development in both humans and a variety of experimental animal models. Depending on the pattern of consumption, the dose, and the period of exposure to ethanol, a myriad of structural and functional deficits can be observed. These teratogenic effects are thought to result from the ethanol-induced dysregulation of a variety of intracellular pathways ultimately culminating in toxicity and cell death. For instance, ethanol exposure can lead to the generation of reactive oxygen species (ROS) and produce an imbalance in the intracellular redox state, leading to an overall increase in oxidative stress. In the present review we will provide an up-to-date summary on the effects of prenatal/neonatal ethanol exposure on the levels of oxidative stress in the central nervous system (CNS) of experimental models of fetal alcohol spectrum disorders (FASD). We will also review the evidence for the use of antioxidants as potential therapeutic strategies for the treatment of some of the neuropathological deficits characteristic of both rodent models of FASD and children afflicted with these disorders. We conclude that an imbalance in the intracellular redox state contributes to the deficits seen in FASD and suggest that antioxidants are potential candidates for the development of novel therapeutic strategies for the treatment of these developmental disorders.

Aquaporin-4 knockout enhances astrocyte toxicity induced by 1-methyl-4-phenylpyridinium ion and lipopolysaccharide via increasing the expression of cytochrome P4502E1

The role of aquaporin-4 (AQP4) in the regulation of astrocytes function has been widely investigated. However, there is little information about its contribution to the drug metabolism enzymes such as Cytochrome P4502E1. In the present study, we investigated whether AQP4 is involved in the process of the cell damage caused by MPP(+) and LPS through regulating the expression of CYP2E1 in astrocytes. Compared to the wild-type, in primary astrocytes, AQP4 knockout increased the cell damage and the reactive oxygen species (ROS) production which were induced by MPP(+), LPS and ethanol. Notably, AQP4 knockout enhanced the up-regulation of the expression of CYP2E1 in astrocytes exposed to MPP(+), LPS and ethanol. Furthermore, Diallylsulphide (DAS), a CYP2E1 inhibitor, partially or almost abolished the cell injury and the ROS production of the astrocytes induced by MPP(+) and LPS. These findings indicate AQP4 protects astrocytes from the damage caused by MPP(+) and LPS through reducing the ROS production correlation to the diminished expression of CYP2E1.

Putative role of brain acetaldehyde in ethanol addiction

The putative contribution of brain acetaldehyde (AcH) to ethanol (EtOH) tolerance and dependence (addiction) is reviewed. Although the role of AcH in EtOH addiction has been controversial, there are data showing a relationship. AcH can be formed in the brain tissues through the peroxidatic activity of catalase and by oxidation via other oxidizing enzymes such as cytochrome P-4502E1. Significant formation of AcH occurs in vitro in brain tissue at concentrations of EtOH that can be achieved by voluntary consumption of EtOH by rodents. AcH itself possesses reinforcing properties, which suggests that some of the behavioral pharmacological effects attributed to EtOH may be a result of the formation of AcH, and supports the involvement of AcH in EtOH addiction. Modulation of aldehyde dehydrogenase (ALDH) and brain catalase activity can change EtOH-related addictive behaviors presumably by changing AcH levels. Moreover, some condensation reaction products of AcH may promote some actions of EtOH and its consumption. On the basis of the findings, it can be concluded that AcH may mediate some of the CNS actions of EtOH including tolerance and dependence, although further exploration the involvement of AcH in EtOH addiction is warranted.

Role of oxidative stress in alcohol-induced liver injury

Reactive oxygen species (ROS) are highly reactive molecules that are naturally generated in small amounts during the body's metabolic reactions and can react with and damage complex cellular molecules such as lipids, proteins, or DNA. Acute and chronic ethanol treatments increase the production of ROS, lower cellular antioxidant levels, and enhance oxidative stress in many tissues, especially the liver. Ethanol-induced oxidative stress plays a major role in the mechanisms by which ethanol produces liver injury. Many pathways play a key role in how ethanol induces oxidative stress. This review summarizes some of the leading pathways and discusses the evidence for their contribution to alcohol-induced liver injury. Special emphasis is placed on CYP2E1, which is induced by alcohol and is reactive in metabolizing and activating many hepatotoxins, including ethanol, to reactive products, and in generating ROS.

Cytochrome P450 2E1 gene polymorphisms/haplotypes and Parkinson's disease in a Swedish population

Cytochrome P450 2E1 (CYP2E1), which inter alia is located in dopamine containing neurons in the substantia nigra, has been hypothesized to be of importance for the pathophysiology of Parkinson's disease (PD), either by its production of reactive oxygen species (ROS) or by its capability to detoxify putative neurotoxins. Numerous polymorphisms in the coding and non-coding regions of the gene for this enzyme have been reported. Different variants may account for inter-individual differences in the activity of the enzyme or production of ROS. In this study, the CYP2E1 gene was examined in a control population (n = 272) and a population with PD (n = 347), using a tag-single nucleotide polymorphism (tSNP) approach founded on HapMap Data. Six tSNPs were used in the analysis and haplotype block data were obtained. In case of significance, the SNP was further examined regarding early/late age of disease onset and presence of relatives with PD. We found an association between allele and genotype frequencies of the C/G polymorphism at intron 7 (rs2070676) of this gene and PD (P value of 0.026 and 0.027, respectively). Furthermore, analysis of the rs2070676 polymorphism in subgroups of patients with age of disease onset higher than 50 years and those not having a relative with PD also demonstrated a significant difference with controls. This was seen in both genotype (corresponding to P value = 0.039 and 0.032) and allele (P = 0.027 and 0.017 respectively) frequency. As a representative of many polymorphisms or in possible linkage disequilibrium with other functional variants, it is possible that rs2070676 could influence the regulation of the enzyme. In conclusion, our results display an association between the rs2070676 polymorphism and PD. Additional investigations are needed to elucidate the importance of this polymorphism for the activity of CYP2E1 and PD susceptibility.

MPTP-induced model of Parkinson's disease in cytochrome P450 2E1 knockout mice

Evidence for involvement of cytochrome P450 2E1 in the MPTP-induced mouse model of PD has been reported [Vaglini, F., Pardini, C., Viaggi, C., Bartoli, C., Dinucci, D., Corsini, G.U., 2004. Involvement of cytochrome P450 2E1 in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse model of Parkinson's disease. J. Neurochem. 91, 285-298]. We studied the sensitivity of Cyp2e1(-/-) mice to the acute administration of MPTP in comparison with their wild-type counterparts. In Cyp2e1(-/-) mice, the reduction of striatal DA content was less pronounced 7 days after MPTP treatment compared to treated wild-type mice. Similarly, TH immunoreactivity analysis of the substantia nigra of Cyp2e1(-/-) mice did not show any neuronal lesions after MPTP treatment. In contrast to this, wild-type animals showed a minimal but significant lesioning by the toxin as evaluated also by means of non-stereologic computerized assisted analysis of this brain area. Striatal levels of DA metabolites after 7 days were variably affected by the toxin, but consistent differences between the two animal strains were not observed. We evaluated short-term changes in the levels of striatal DA and its metabolites, and we monitored striatal MPP(+) levels. Striatal MPP(+) was cleared more rapidly in Cyp2e1(-/-) mice than in wild-type animals and, consistently, striatal DA content decreased faster in Cyp2e1(-/-) mice than in wild-type animals, and 3-methoxytyramine and HVA levels showed an early and sharp rise. Our findings suggest that Cyp2e1(-/-) mice are weakly sensitive to MPTP-induced brain lesions, markedly in contrast with a protective role of the enzyme as suggested previously. The differences observed between the knockout mice and their wild-type counterparts are modest and may be due to an efficient compensatory mechanism or genetic drift in the colonies.

Acetaldehyde sequestering prevents ethanol-induced stimulation of mesolimbic dopamine transmission

Acetaldehyde (ACD) has been postulated to mediate some of the neurobehavioral effects of ethanol (EtOH). In this study we sought to evaluate whether the stimulatory effects of EtOH on mesolimbic dopamine (DA) transmission are affected by the administration of ACD-sequestering agent D-penicillamine (Dp). To this end we studied the effect of EtOH and ACD in the rat mesoaccumbens pathway by in vivo microdialysis in the nucleus accumbens shell (NAccs), and by single cell extracellular recordings from antidromically identified mesoaccumbens DA neurons in the ventral tegmental area (VTA). Both EtOH (1g/kg) and ACD (20mg/kg) administration increased DA levels in the NAccs and increased the activity of mesoaccumbens DA neurons. Pretreatment with Dp (50mg/kg i.p. 1h before drug challenge) prevented both EtOH- and ACD-induced stimulation of the DA mesolimbic system without affecting morphine stimulatory actions. These observations add further support to the notion that EtOH-derived ACD stimulates the mesolimbic DA system and is essential in EtOH-induced stimulation of the DA mesoaccumbens system. We conclude that modulation of ACD bioavailability may influence the addictive profile of EtOH by decreasing its psychotropic effects and possibly leading the way to new pharmacological treatments of alcoholism.

Induction of brain CYP2E1 changes the effects of ethanol on dopamine release in nucleus accumbens shell

CYP2E1 is an important enzyme involved in the brain metabolism of ethanol that can be induced by chronic consumption of alcohol. Recent works have highlighted the importance of this system in the context of the behavioural effects of ethanol. Unfortunately, the underlying neurochemical events for these behavioural changes, has not been yet explored. In this work, we have started this exploration by analyzing the possible changes in the neurochemical response of the mesolimbic system to ethanol after pharmacological induction of brain CYP2E1. We have used the dopamine extracellular levels in nucleus accumbens (NAc) core and shell, measured by means of microdialysis in vivo, as an index of the effects of ethanol. Acetone 1% in the tap water was used to induce brain CYP2E1. Efficacy of the induction protocol was assessed by immunoblotting. Intravenous administration of 1.5 g/kg of ethanol in control rats provoked a significant increase of the dopamine levels in both the core (up to 127% of baseline) and the shell (up to 122% of baseline) of the NAc. However, the same dose of ethanol in acetone-treated rats only increased the dopamine extracellular levels in the core (up to 142% of baseline) whereas dopamine levels in the shell subregion remain unaltered relative to baseline. The results of this study indicate that induction of CYP2E1 changes the response of the mesolimbic system to ethanol in a region-dependent manner. Two hypotheses are postulated to explain the observed effects.

Reduction in the anxiolytic effects of ethanol by centrally formed acetaldehyde: the role of catalase inhibitors and acetaldehyde-sequestering agents

RATIONALE

Considerable evidence indicates that brain ethanol metabolism mediated by catalase is involved in modulating some of the behavioral and physiological effects of this drug, which suggests that the first metabolite of ethanol, acetaldehyde, may have central actions. Previous results have shown that acetaldehyde administered into the lateral ventricles produced anxiolysis in a novel open arena in rats.

OBJECTIVES

The present studies investigate the effects of centrally formed acetaldehyde on ethanol-induced anxiolysis.

MATERIALS AND METHODS

The effects of the catalase inhibitor sodium azide (SA; 0 or 10 mg/kg, IP) on ethanol-induced anxiolysis (0.0, 0.5, or 1.0 g/kg, IP) were evaluated in CD1 mice in two anxiety paradigms, the elevated plus maze and the dark/light box. Additional studies assessed the effect of the noncompetitive catalase inhibitor 3-amino-1,2,4-triazole (AT; 0.5 g/kg, IP) and the acetaldehyde inactivation agent D: -penicillamine (50 mg/kg, IP) on the plus maze.

RESULTS

SA reduced the anxiolytic effects of ethanol on several parameters evaluated in the elevated plus maze and in the dark/light box. In the plus maze, AT completely blocked and D-penicillamine significantly reduced the anxiolytic properties of ethanol.

CONCLUSIONS

Thus, when cerebral metabolism of ethanol into acetaldehyde is blocked by catalase inhibitors, or acetaldehyde is inactivated, there is a suppressive effect on the anxiolytic actions of ethanol. These data provide further support for the idea that centrally formed or administered acetaldehyde can contribute to some of the psychopharmacological actions of ethanol, including its anxiolytic properties.

Distribution and differential induction of CYP2E1 by ethanol and acetone in the mesocorticolimbic system of rat

AIMS

The expression of cytochrome P4502E1 (CYP2E1) in the brain has been demonstrated in several regions, nevertheless there is a lack of specific studies on the constitutive expression and induction at the mesocorticolimbic system, the most relevant brain pathway in the context of drug addiction and alcoholism. Hence, we have performed a detailed study of the CYP2E1 expression and induction in three key areas of the mesocorticolimbic system of the rat brain: prefrontal cortex (PFC), nucleus accumbens (NAc), and ventral tegmental area (VTA).

METHODS

Expression levels of CYP2E1 were analyzed by Western blot. The induction of the enzyme in the selected brain areas by chronic acetone (1% v/v acetone in drinking water for 11 days) and ethanol (3 g/kg by gavage for 7 days) was also assessed.

RESULTS

(i) CYP2E1 was expressed in PFC, Nac, and VTA, with the order of magnitude of the levels being VTA approximately PFC > Nac, and approximately 3-13% of it was encountered in liver; (ii) acetone treatment significantly increased CYP2E1 expression in Nac, up to 212% of the control levels, whereas not significant changes were observed in VTA and PFC; (iii) chronic ethanol treatment only resulted in a significant induction of enzyme levels in VTA (124%). A similar enhancement, though not significant, was found to occur in NAc.

CONCLUSIONS

CYP2E1 was present in the mesocorticolimbic system at different levels of expression. Chronic acetone and ethanol treatments are able to increase enzyme levels in specific areas of this system with the pattern of induction of the two agents being different.

CYP2E1 and oxidative liver injury by alcohol

Ethanol-induced oxidative stress seems to play a major role in mechanisms by which ethanol causes liver injury. Many pathways have been suggested to contribute to the ability of ethanol to induce a state of oxidative stress. One central pathway seems to be the induction of cytochrome P450 2E1 (CYP2E1) by ethanol. CYP2E1 metabolizes and activates many toxicological substrates, including ethanol, to more reactive, toxic products. Levels of CYP2E1 are elevated under a variety of physiological and pathophysiological conditions and after acute and chronic alcohol treatment. CYP2E1 is also an effective generator of reactive oxygen species such as the superoxide anion radical and hydrogen peroxide and, in the presence of iron catalysts, produces powerful oxidants such as the hydroxyl radical. This review article summarizes some of the biochemical and toxicological properties of CYP2E1 and briefly describes the use of cell lines developed to constitutively express CYP2E1 and CYP2E1 knockout mice in assessing the actions of CYP2E1. Possible therapeutic implications for treatment of alcoholic liver injury by inhibition of CYP2E1 or CYP2E1-dependent oxidative stress will be discussed, followed by some future directions which may help us to understand the actions of CYP2E1 and its role in alcoholic liver injury.