THE ROLE OF CYTOCHROME P450 ISOFORMS OF HEPATOCYTE ENDOPLASMIC RETICULUM IN ETHANOL METABOLISM

Background. Three metabolic pathways that can function simultaneously are known to be involved in ethanol oxidation in the liver: alcohol dehydrogenase pathway, microsomal ethanol-oxidizing system, and catalase pathway. Though the cytochrome P450-dependent microsomal ethanol-oxidizing system plays an insignificant role in metabolism of small amounts of ethanol, it is induced in case of ethanol excess and becomes essential when ethanol is abused. The main components of this system are cytochrome P450 (CYP) isoforms of smooth endoplasmic reticulum. Objective. To characterize the role of the key isoforms of cytochrome P450 in ethanol oxidation. Material and methods. We carried out an analysis of modern literature data on the role of the main isoforms of cytochrome P450 in liver metabolism of ethanol. Results. Data on the primary role of cytochrome CYP2E1 in ethanol metabolism, as well as on the contribution of isoforms CYP1A2, CYP2B1/2, CYP2C, CYP3A4, CYP4B1 to ethanol oxidation are presented. Conclusions. Ethanol is metabolized by many CYPs of endoplasmic reticulum of hepatocytes. The importance of CYP in biotransformation processes in the liver necessitates the study of the role of individual CYP isoforms in ethanol metabolism for predicting changes in the pharmacokinetics of drugs and metabolism of endogenous compounds under the influence of ethanol.

Modulation of the Drosophila Transcriptome by Developmental Exposure to Alcohol

Prenatal exposure to ethanol can cause fetal alcohol spectrum disorder (FASD), a prevalent, preventable pediatric disorder. Identifying genetic risk alleles for FASD is challenging since time, dose, and frequency of exposure are often unknown, and manifestations of FASD are diverse and evident long after exposure. Drosophila melanogaster is an excellent model to study the genetic basis of the effects of developmental alcohol exposure since many individuals of the same genotype can be reared under controlled environmental conditions. We used 96 sequenced, wild-derived inbred lines from the Drosophila melanogaster Genetic Reference Panel (DGRP) to profile genome-wide transcript abundances in young adult flies that developed on ethanol-supplemented medium or standard culture medium. We found substantial genetic variation in gene expression in response to ethanol with extensive sexual dimorphism. We constructed sex-specific genetic networks associated with alcohol-dependent modulation of gene expression that include protein-coding genes, Novel Transcribed Regions (NTRs, postulated to encode long non-coding RNAs) and female-specific coordinated regulation of snoRNAs that regulate pseudouridylation of ribosomal RNA. We reared DGRP lines which showed extreme upregulation or downregulation of snoRNA expression during developmental alcohol exposure on standard or ethanol supplemented medium and demonstrated that developmental exposure to ethanol has genotype-specific effects on adult locomotor activity and sleep. There is significant and sex-specific natural genetic variation in the transcriptional response to developmental exposure to ethanol in Drosophila that comprises networks of genes affecting nervous system development and ethanol metabolism as well as networks of regulatory non-coding RNAs.

Periodic ethanol supply as a path towards unlimited lifespan of C.elegans dauer larvae

The dauer larva is a specialized stage of development optimized for survival under harsh conditions that has been used as a model for stress resistance, metabolic adaptations, and longevity. Recent findings suggest that the dauer larva of C.elegans may utilize external ethanol as an energy source to extend their lifespan. It was shown that while ethanol may serve as an effectively infinite source of energy, some toxic compounds accumulating as byproducts of its metabolism may lead to the damage of mitochondria and thus limit the lifespan of larvae. A minimal mathematical model was proposed to explain the connection between the lifespan of dauer larva and its ethanol metabolism. To explore theoretically if it is possible to extend even further the lifespan of dauer larvae, we incorporated two natural mechanisms describing the recovery of damaged mitochondria and elimination of toxic compounds, which were previously omitted in the model. Numerical simulations of the revised model suggest that while the ethanol concentration is constant, the lifespan still stays limited. However, if ethanol is supplied periodically, with a suitable frequency and amplitude, the dauer could survive as long as we observe the system. Analytical methods further help to explain how the feeding frequency and amplitude affect the lifespan extension. Based on comparison of the model with experimental data for fixed ethanol concentration, we propose the range of feeding protocols that could lead to even longer dauer survival and can be tested experimentally.

The Timing and Effects of Low-Dose Ethanol Treatment on Acetaminophen-Induced Liver Injury

Acetaminophen (APAP) overdose is the major cause of drug-induced liver injury and acute liver failure. Approximately 10% of APAP is metabolized by cytochrome P450 (CYP2E1) into toxic N-acetyl-p-benzoquinone imine (NAPQI). CYP2E1 also contributes to ethanol metabolism, especially during conditions of high blood ethanol concentration. Acute and chronic ethanol consumption appears to have opposite effects on APAP-induced liver injury. We determined the effects of different doses, pre- and post-treatment, and various schedules of ethanol exposure in APAP-induced liver injury. Treatment with ethanol (0.5 g/kg) after 1 h of APAP (300 mg/kg) administration decreased serum ALT levels, histopathological features, and inflammatory cell infiltration. Moreover, ethanol treatment 1 h after APAP treatment reduced APAP-induced liver injury compared with later administration. Interestingly, ethanol pretreatment did not provide any protective effect. Furthermore, ethanol treatment was associated with a significant decrease in ERK and AKT phosphorylation during the acute injury phase. Ethanol exposure also increased CYP2E1 expression and decreased PCNA expression during the liver regeneration phase.

A single chromosome strain of S. cerevisiae exhibits diminished ethanol metabolism and tolerance

Background Eukaryotic organisms, like the model yeast S. cerevisiae, have linear chromosomes that facilitate organization and protection of nuclear DNA. A recent work described a stepwise break/repair method that enabled fusion of the 16 chromosomes of S. cerevisiae into a single large chromosome. Construction of this strain resulted in the removal of 30 of 32 telomeres, over 300 kb of subtelomeric DNA, and 107 subtelomeric ORFs. Despite these changes, characterization of the single chromosome strain uncovered modest phenotypes compared to a reference strain. Results This study further characterized the single chromosome strain and found that it exhibited a longer lag phase, increased doubling time, and lower final biomass concentration compared with a reference strain when grown on YPD. These phenotypes were amplified when ethanol was added to the medium or used as the sole carbon source. RNAseq analysis showed poor induction of genes involved in diauxic shift, ethanol metabolism, and fatty-acid ß-oxidation during growth on ethanol compared to the reference strain. Enzyme-constrained metabolic modeling identified decreased flux through the enzymes that are encoded by these poorly induced genes as a likely cause of diminished biomass accumulation. The diminished growth on ethanol for the single chromosome strain was rescued by nicotinamide, an inhibitor of sirtuin family deacetylases, which have been shown to silence gene expression in heterochromatic regions. Conclusions Our results indicate that sirtuin-mediated silencing in the single chromosome strain interferes with growth on non-fermentable carbon sources. We propose that the removal of subtelomeric DNA that would otherwise be bound by sirtuins leads to silencing at other loci in the single chromosome strain. Further, we hypothesize that the poorly induced genes in the single chromosome strain during ethanol growth could be silenced by sirtuins in wildtype S. cerevisiae during growth on glucose.

Integration of a physiologically-based pharmacokinetic model with a whole-body, organ-resolved genome-scale model for characterization of ethanol and acetaldehyde metabolism

Ethanol is one of the most widely used recreational substances in the world and due to its ubiquitous use, ethanol abuse has been the cause of over 3.3 million deaths each year. In addition to its effects, ethanol’s primary metabolite, acetaldehyde, is a carcinogen that can cause symptoms of facial flushing, headaches, and nausea. How strongly ethanol or acetaldehyde affects an individual depends highly on the genetic polymorphisms of certain genes. In particular, the genetic polymorphisms of mitochondrial aldehyde dehydrogenase, ALDH2, play a large role in the metabolism of acetaldehyde. Thus, it is important to characterize how genetic variations can lead to different exposures and responses to ethanol and acetaldehyde. While the pharmacokinetics of ethanol metabolism through alcohol dehydrogenase have been thoroughly explored in previous studies, in this paper, we combined a base physiologically-based pharmacokinetic (PBPK) model with a whole-body genome-scale model (WBM) to gain further insight into the effect of other less explored processes and genetic variations on ethanol metabolism. This combined model was fit to clinical data and used to show the effect of alcohol concentrations, organ damage, ALDH2 enzyme polymorphisms, and ALDH2-inhibiting drug disulfiram on ethanol and acetaldehyde exposure. Through estimating the reaction rates of auxiliary processes with dynamic Flux Balance Analysis, The PBPK-WBM was able to navigate around a lack of kinetic constants traditionally associated with PK modelling and demonstrate the compensatory effects of the body in response to decreased liver enzyme expression. Additionally, the model demonstrated that acetaldehyde exposure increased with higher dosages of disulfiram and decreased ALDH2 efficiency, and that moderate consumption rates of ethanol could lead to unexpected accumulations in acetaldehyde. This modelling framework combines the comprehensive steady-state analyses from genome-scale models with the dynamics of traditional PK models to create a highly personalized form of PBPK modelling that can push the boundaries of precision medicine.

GENETIC FACTORS OF ALCOHOLIC PSYCHOSIS DEVELOPMENT

Известно, что наследственную предрасположенность к алкоголизму на фенотипическом уровне можно изучать с помощью генетических маркеров, возможно отражающих их связь с заболеванием [2, 3]. Многие авторы говорят о существовании биологической предрасположенности к алкоголизму, закрепленной на генетическом уровне [1, 4, 5, 6], однако природа и механизмы наследования при алкогольных психозах до настоящего времени остаются неясными. Цель настоящей работы - поиск маркеров повышенного риска развития алкогольных психозов путем проведения молекулярно-генетического анализа ДНК-маркеров основных ферментов метаболизма этанола It is known that the hereditary predisposition to alcoholism at the phenotypic level can be studied with the help of genetic markers, possibly reflecting their connection with the disease [2, 3]. Many authors say that there is a biological predisposition to alcoholism, fixed at the genetic level [1, 4, 5, 6], However, the nature and mechanisms of inheritance in alcoholic psychoses are still unclear. The aim of this work is to search for markers of increased risk of alcohol psychosis by conducting molecular genetic analysis of DNA markers of the main enzymes of ethanol metabolism.

Glutathione-S-Transferase Pi and Malondialdehyde in Alcoholic Patients Attending Smhrc and Avbrh Hospital

Introduction: Alcohol abuse is a global health problem. The liver maintains high muscle damage by over drinking because it is a major source of ethanol metabolism. Among substance abusers, about 35 % develop advanced liver disease because the number of viral mutations increases, slows down, or inhibits the progression of liver disease. Glutathione-S-transferase is a family of Phase II enzyme-releasing toxins that cause the synthesis of glutathione in a variety of chronic and external electrophilic types. GSTs are divided into two very different family members: family members bound by microsomal membrane and cytosolic. Aim: To study the Glutathione S Transferase π and Malondialdehyde in Alcoholic Patients. Materials and Methods: Present study comprises 100 Subjects were included in the study and distributed in two groups. Patients from group one was alcoholic patients, enrolled from medicine ward and 50 non-alcoholic healthy individuals from group two were from non-alcoholic population as well as medicine ward. Results: Rise of GGT, AST and ALT in Alcoholic patients (54.54 ± 3.72, 19.21 ± 0.68 and 24.32 ± 1.27 respectively) as compare to healthy individuals (24.40 ± 3.16, 10.36±0.35 and 17.06±0.84 respectively). The level of GST-π was decreased in alcoholic patients (62.44±26.30) as compare to control group (83.26±32.71). Similarly, the level of MDA was raised in alcoholic patients (5.36 ± 0.51) as compare to healthy individuals (4.73 ± 0.21). Conclusion: Present study suggests that it would be vital to contain SGOT, SGPT, GGT, MDA and GST-π calculation in the prognostic assessment of alcoholic patients.