Yedy Israel

Long-term treatment of alcoholic liver disease with propylthiouracil

Propylthiouracil has been shown experimentally to protect against alcohol-induced hepatocellular necrosis in hypoxic conditions. An earlier, short-term study of patients with alcoholism and liver disease indicated clinical improvement with propylthiouracil, but the effect on mortality could not be assessed. In the present study, we investigated the effect of propylthiouracil on mortality in patients with alcoholic liver disease in a long-term, double-blind, randomized clinical trial involving 310 compliant patients who received propylthiouracil (n = 157) or placebo (n = 153) for a maximum of two years. There were no differences between the two groups in demographic and clinical characteristics and biopsy-confirmed diagnoses at randomization, or in daily urinary alcohol levels during the study. The cumulative dropout rate over two years was not significantly different (propylthiouracil group, 0.68; placebo group, 0.60). The group receiving propylthiouracil (300 mg per day) had a cumulative mortality rate half that in the group receiving placebo (0.13 vs. 0.25 [P less than 0.05] in the total sample, and 0.25 vs. 0.55 [P less than 0.03] in a subgroup of severely ill patients [propylthiouracil group, n = 56; placebo group, n = 41]). Proportional-hazards stepwise regression analyses indicated that only propylthiouracil treatment, prothrombin time, hemoglobin levels, and mean daily urinary alcohol levels significantly affected mortality. The hazards ratio for the complete group indicated that mortality in the propylthiouracil group was 0.38 (95 percent confidence interval, 0.20 to 0.83) that of the placebo group. Protection by propylthiouracil was not observed in patients with high morning urinary alcohol levels. No clinically important side effects of propylthiouracil were observed at the dose used. We conclude that the administration of propylthiouracil can reduce mortality due to alcoholic liver disease.

The UChA and UChB rat lines : metabolic and genetic differences influencing ethanol intake

Ethanol non‐drinker (UChA) and drinker (UChB) rat lines derived from an original Wistar colony have been selectively bred at the University of Chile for over 70 generations. Two main differences between these lines are clear. (1) Drinker rats display a markedly faster acute tolerance than non‐drinker rats. In F2 UChA × UChB rats (in which all genes are ‘shuffled’), a high acute tolerance of the offspring predicts higher drinking than a low acute tolerance. It is further shown that high‐drinker animals ‘learn’ to drink, starting from consumption levels that are one half of the maximum consumptions reached after 1 month of unrestricted access to 10% ethanol and water. It is likely that acquired tolerance is at the basis of the increases in ethanol consumption over time. (2) Non‐drinker rats carry a previously unreported allele of aldehyde dehydrogenase‐2 (Aldh2) that encodes an enzyme with a low affinity for Nicotinamide‐adenine‐dinuclectide (NAD+) (Aldh22), while drinker rats present two Aldh2 alleles (Aldh21 and Aldh23) with four‐ to fivefold higher affinities for NAD+. Further, the ALDH2 encoded by Aldh21 also shows a 33% higher Vmax than those encoded by Aldh22 and Aldh23. Maximal voluntary ethanol intakes are the following: UChA Aldh22/Aldh22 = 0.3–0.6 g/kg/day; UChB Aldh23/Aldh23 = 4.5–5.0 g/kg/day; UChB Aldh21/Aldh21 = 7.0–7.5 g/kg/day. In F2 offspring of UChA × UChB, the Aldh22/Aldh22 genotype predicts a 40–60% of the alcohol consumption. Studies also show that the low alcohol consumption phenotype of Aldh22/Aldh22 animals depends on the existence of a maternally derived low‐activity mitochondrial reduced form of nicotinamide‐adenine‐dinucleotide (NADH)‐ubiquinone complex I. The latter does not influence ethanol consumption of animals exhibiting an ALDH2 with a higher affinity for NAD+. An illuminating finding is the existence of an ‘acetaldehyde burst’ in animals with a low capacity to oxidize acetaldehyde, being fivefold higher in UChA than in UChB animals. We propose that such a burst results from a great generation of acetaldehyde by alcohol dehydrogenase in pre‐steady‐state conditions that is not met by the high rate of acetaldehyde oxidation in mitochondria. The acetaldehyde burst is seen despite the lack of differences between UChA and UChB rats in acetaldehyde levels or rates of alcohol metabolism in steady state. Inferences are drawn as to how these studies might explain the protection against alcoholism seen in humans that carry the high‐activity alcohol dehydrogenase but metabolize ethanol at about normal rates.

Tetranucleotide GGGA Motif in Primary RNA Transcripts NOVEL TARGET SITE FOR ANTISENSE DESIGN

Selecting effective antisense target sites on a given mRNA molecule constitutes a major problem in antisense therapeutics. By trial-and-error, only 1 in 18 (6%) of antisense oligonucleotides designed to target the primary RNA transcript of tumor necrosis factor-α (TNF-α) strongly inhibited TNF-α synthesis. Subsequent studies showed that the area in RNA targeted by antisense oligonucleotides could be moved effectively 10–15 bases in either direction from the original area. We observed that only molecules that incorporated a tetranucleotide motif TCCC (complementary to GGGA on RNA) yielded potent antisense oligonucleotides against TNF-α. A comprehensive literature survey showed that this motif is unwittingly present in 48% of the most potent antisense oligonucleotides reported in the literature. This finding was prospectively used to predict the sequences of additional antisense oligonucleotides for the rat TNF-α primary RNA transcript. Over 50% of antisense constructs (13 of 22) containing the TCCC motif were found to effectively inhibit TNF-α synthesis. Marked reductions in mRNA were also observed. This motif was found to be most effective when targeting introns in the primary RNA transcript, suggesting a nuclear localization for the antisense action. Predicting target sites based on the presence of this motif in primary RNA transcripts should be of value in the development on new antisense pharmacotherapy.

Ethanol as a Prodrug: Brain Metabolism of Ethanol Mediates its Reinforcing effects

BACKGROUND  While the molecular entity responsible for the rewarding effects of virtually all drugs of abuse is known, that for ethanol remains uncertain. Some lines of evidence suggest that the rewarding effects of alcohol are mediated not by ethanol per se but by acetaldehyde generated by catalase in the brain. However, the lack of specific inhibitors of catalase has not allowed strong conclusions to be drawn about its role on the rewarding properties of ethanol. The present studies determined the effect on voluntary alcohol consumption of two gene vectors, one designed to inhibit catalase synthesis and one designed to synthesize alcohol dehydrogenase (ADH), to respectively inhibit or increase brain acetaldehyde synthesis. METHODS  The lentiviral vectors, which incorporate the genes they carry into the cell genome, were (i) one encoding a shRNA anticatalase synthesis and (ii) one encoding alcohol dehydrogenase (rADH1). These were stereotaxically microinjected into the brain ventral tegmental area (VTA) of Wistar-derived rats bred for generations for their high alcohol preference (UChB), which were allowed access to an ethanol solution and water. RESULTS  Microinjection into the VTA of the lentiviral vector encoding the anticatalase shRNA virtually abolished (-94% p < 0.001) the voluntary consumption of alcohol by the rats. Conversely, injection into the VTA of the lentiviral vector coding for ADH greatly stimulated (2 to 3 fold p < 0.001) their voluntary ethanol consumption. CONCLUSIONS The study strongly suggests that to generate reward and reinforcement, ethanol must be metabolized into acetaldehyde in the brain. Data suggest novel targets for interventions aimed at reducing chronic alcohol intake.

Mechanism of protection against alcoholism by an alcohol dehydrogenase polymorphism: development of an animal model.

Humans who carry a point mutation in the gene coding for alcohol dehydrogenase‐lB (ADH1B*2; Arg47His) are markedly protected against alcoholism. Although this mutation results in a 100‐fold increase in enzyme activity, it has not been reported to cause higher levels of acetaldehyde, a metabolite of ethanol known to deter alcohol intake. Hence, the mechanism by which this mutation confers protection against alcoholism is unknown. To study this protective effect, the wild‐type rat cDNA encoding rADH‐47Arg was mutated to encode rADH‐47His, mimicking the human mutation. The mutated cDNA was incorporated into an adenoviral vector and administered to genetically selected alcohol‐preferring rats. The Vmax of rADH‐47His was 6‐fold higher (P<0.001) than that of the wild‐type rADH‐47Arg. Animals transduced with rAdh‐47His showed a 90% (P<0.01) increase in liver ADH activity and a 50% reduction (P< 0.001) in voluntary ethanol intake. In animals transduced with rAdh‐47His, administration of ethanol (1g/kg) produced a short‐lived increase of arterial blood acetaldehyde concentration to levels that were 3.5‐ to 5‐fold greater than those in animals transduced with the wild‐type rAdh‐47Arg vector or with a noncoding vector. This brief increase (burst) in arterial acetaldehyde concentration after ethanol ingestion may constitute the mechanism by which humans carrying the ADH1B*2 allele are protected against alcoholism.—Rivera‐Meza, M., Quin‐tanilla, M. E., Tampier, L., Mura, C. V., Sapag, A., Israel, Y. Mechanism of protection against alcoholism by an alcohol dehydrogenase polymorphism: development of an animal model. FASEB J. 24, 266–274 (2010). www.fasebj.org

Ethanol induces stronger dopamine release in nucleus accumbens (shell) of alcohol-preferring (bibulous) than in alcohol-avoiding (abstainer) rats

Several studies on the differences between ethanol-preferring versus non-preferring rat lines suggest an innate deficit in the mesolimbic dopaminergic system as an underlying factor for ethanol volition. Rats would try to overcome such deficit by engaging in a drug-seeking behaviour, when available, to drink an ethanol solution over water. Thus, in the present study we compared the effect of a single dose of ethanol (1 g/kg, i.p.) on the extracellular levels of monoamines measured by microdialysis in the shell of nucleus accumbens of University of Chile bibulous (UChB) and University of Chile Abstainer (UChA) rats, bred for 79 and 88 generations to prefer or reject ethanol, respectively. It is reported that under basal conditions extracellular dopamine levels are lower in the bibulous than in the abstainer rats, while ethanol induced a 2-fold greater increase of dopamine release in bibulous than in abstainer rats. The greater effect of ethanol in bibulous rats was not associated to differences in blood ethanol levels, since the concentration and elimination of ethanol were virtually identical in both rat lines, indicating that bibulous rats are more sensitive to the stimulation of dopamine release by ethanol than abstainer rats. No differences were observed in 5-hydroxytryptamine or metabolites measured simultaneously under basal or ethanol-stimulating conditions in bibulous and abstainer rats. Overall, the present results suggest that a low dopaminergic tone and a strong mesolimbic dopamine response to ethanol are concerted neurochemical features associated to an ethanol-seeking behaviour in rats.

Genetic and Environmental Influences on Ethanol Consumption: Perspectives From Preclinical Research

BACKGROUND Alcohol use disorders (abuse and dependence, AUD) are multifactorial phenomena, depending on the interplay of environmental and genetic variables. METHOD This review describes current developments in animal research that may help (a) develop gene therapies for the treatment of alcoholism, (b) understand the permissive role of stress on ethanol intake, and (c) elucidate why exposure to ethanol early in life is associated with a greater risk of AUD. RESULTS The polymorphisms found in liver alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) affect the elimination of ethanol and the susceptibility to ethanol intake. A highly active ADH protects against alcoholism, an effect related to a presteady state burst in arterial acetaldehyde. Social stressors, such as repeated early maternal separation or social defeat, exert a permissive effect on ethanol intake, perhaps by altering the normal development of the hypothalamic-pituitary-adrenal axis. Ethanol exposure during gestation, infancy, or adolescence increases the likelihood of AUD later in life. Early perception of ethanols positive and negative (anti-anxiety) reinforcing effects may play a role in this phenomenon. CONCLUSIONS The review underscores the advantages of using preclinical animal models of AUD and highlights points of intersection between the topics to help design a more integrated approach for the study of alcohol-related problems.

Reward and Relapse: Complete Gene-Induced Dissociation in an Animal Model of Alcohol Dependence

BACKGROUND In animal models of continuous alcohol self-administration, in which physical dependence does not constitute the major factor of ethanol intake, 2 factors likely contribute to the perpetuation of alcohol self-administration: (i) the rewarding effects of ethanol and (ii) the contextual conditioning cues that exist along with the process of self-administration. Present studies are aimed at understanding the relative contribution of these factors on the perpetuation of heavy alcohol self-administration, as an indication of relapse. METHODS Wistar-derived UChB high ethanol drinker rats were allowed access to 10% ethanol and water on a 24-hour basis. In initial studies, an anticatalase shRNA gene-coding lentiviral vector aimed at inhibiting acetaldehyde generation was administered into the ventral tegmental area (VTA) of the animals prior to ethanol access. In subsequent studies, the lentiviral vector was administered to animals, which had consumed ethanol on a 24-hour basis, or a 1-hour basis, after the animals had reached high levels of ethanol intake for 60 to 80 days. In final studies, quinine (0.01%) was added to the ethanol solution to alter the conditioning taste/smell cues of alcohol that animals had chronically ingested. RESULTS Data indicate that the administration of an anticatalase vector into the VTA of naïve animals blocked reward and alcohol self-administration, while it was, nevertheless, inactive in inhibiting alcohol self-administration in rats that had been conditioned to ingest ethanol for over 2 months. The lack of inhibitory effect of the anticatalase vector on ethanol intake in animals that had chronically self-administered ethanol was fully reversed when the contextual conditioning cues of the alcohol solution were changed. CONCLUSIONS Data highlight the importance of conditioning factors in relapse and suggest that only abolishing or blunting it, along with long-lasting pharmacological treatment to reduce ethanol reward, may have protracted effects in reducing alcohol self-administration.

Polymorphisms in the mitochondrial aldehyde dehydrogenase gene (Aldh2) determine peak blood acetaldehyde levels and voluntary ethanol consumption in rats

Dependence on alcohol, a most widely used drug, has a heritability of 50–60%. Wistar-derived rats selectively bred as low-alcohol consumers for many generations present an allele (Aldh22) of mitochondrial aldehyde dehydrogenase that does not exist in high-alcohol consumers, which mostly carry the Aldh21 allele. The enzyme coded by Aldh22 has a four- to five-fold lower affinity for NAD+ than that coded by Aldh21. The present study was designed to determine whether these polymorphisms account for differences in voluntary ethanol intake and to investigate the biological mechanisms involved. Low-drinker F0Aldh22/Aldh22 rats were crossed with high-drinker F0Aldh21/Aldh21 rats to obtain an F1 generation, which was intercrossed to obtain an F2 generation that segregates the Aldh2 alleles from other genes that may have been coselected in the breeding for each phenotype. Data show that, with a mixed genetic background, F2Aldh21/Aldh21 rats voluntarily consume 65% more alcohol (P<0.01) than F2Aldh22/Aldh22 rats. A major phenotypic difference was a five-fold higher (P<0.0025) peak blood acetaldehyde level following ethanol administration in the lower drinker F2Aldh22/Aldh22 compared to the higher drinker F2Aldh21/Aldh21 animals, despite the existence of identical steady-state levels of blood acetaldehyde in animals of both genotypes. Polymorphisms in Aldh2 play an important role in: (i) determining peak blood acetaldehyde levels and (ii) modulating voluntary ethanol consumption. We postulate that the markedly higher peak of blood acetaldehyde generated in Aldh22/Aldh22 animals is aversive, leading to a reduced alcohol intake in Aldh22/Aldh22 versus that in Aldh21/Aldh21 animals.

The sequenced rat brain transcriptome - its use in identifying networks predisposing alcohol consumption

A quantitative genetic approach, which involves correlation of transcriptional networks with the phenotype in a recombinant inbred (RI) population and in selectively bred lines of rats, and determination of coinciding quantitative trait loci for gene expression and the trait of interest, has been applied in the present study. In this analysis, a novel approach was used that combined DNA‐Seq data, data from brain exon array analysis of HXB/BXH RI rat strains and six pairs of rat lines selectively bred for high and low alcohol preference, and RNA‐Seq data (including rat brain transcriptome reconstruction) to quantify transcript expression levels, generate co‐expression modules and identify biological functions that contribute to the predisposition of consuming varying amounts of alcohol. A gene co‐expression module was identified in the RI rat strains that contained both annotated and unannotated transcripts expressed in the brain, and was associated with alcohol consumption in the RI panel. This module was found to be enriched with differentially expressed genes from the selected lines of rats. The candidate genes within the module and differentially expressed genes between high and low drinking selected lines were associated with glia (microglia and astrocytes) and could be categorized as being related to immune function, energy metabolism and calcium homeostasis, as well as glial–neuronal communication. The results of the present study show that there are multiple combinations of genetic factors that can produce the same phenotypic outcome. Although no single gene accounts for predisposition to a particular level of alcohol consumption in every animal model, coordinated differential expression of subsets of genes in the identified pathways produce similar phenotypic outcomes.