Alcohol and alcoholism (Oxford, Oxfordshire). Supplement最新文献

Microcirculatory disturbance is one of the main pathogenetic features of alcoholic liver damage. We have demonstrated that ethanol increased portal pressure, leading to hepatic hypoxia and hepatocellular necrosis. In this ethanol-induced hepatic vasoconstriction, nitric oxide, an endothelial derived relaxing factor, dilated constrictive hepatic vasculature and reduced liver injury by improving the microcirculatory disturbance.

Monoamine oxidases (A and B) are of great interest in connection with alcoholism. Low MAO activity has been found in the brains and the platelets of alcoholics and their relatives supporting the hypothesis that low MAO activity is a biological marker for vulnerability to misuse. In order to determine the role of the MAO genes in alcoholism we have measured MAO-B activity and typed two simple sequence repeats (one in the MAO-A gene and one in the MAO-B gene) in a sample of 133 unrelated alcoholics, 300 subjects from 30 two- and three-generation pedigrees ascertained through an alcoholic proband, and 92 normal controls. The unrelated alcoholic group did not differ in MAO-B activity from normal controls nor were there significant differences between subtypes. We did, however, find significant differences between alcoholic males and females (t = 2.836, p = .005), a difference that was not present in controls. A two-way analysis of variance of MAO-B activity as a function of the allelic variation of each marker locus and diagnosis among male subjects was performed. There was no evidence for mean differences in activity levels for different alleles. The distribution of MAO-A and MAO-B "alleles" in the alcoholic sample differed from that of the control sample. Affected sib pair linkage analysis of MAO genes and alcoholism showed no evidence for an excess of concordant affected sib pairs suggesting that this region of the X-chromosome does not harbor a susceptibility locus.

GABA (gamma-aminobutyric acid) receptors in the brain have been classified into GABAA and GABAB types. The GABAA receptor is an ionotropic type that forms the GABA-gated Cl- channel. The structure of GABAA receptor has been intensively analyzed and found to consist of several subunits and the combination of these subunits is heterogeneous. Therefore, it is likely that multiple GABAA receptors are present and exert various inhibitory actions in the brain. On the other hand, the GABAB receptor, a metabotropic type, inhibits cAMP formation as well as inositol phosphates turnover. The inhibition of adenylyl cyclase activity is mediated by GTP-binding protein such as Gi and/or Go which is coupled with GABAB receptor. Studies of the purified GABAB receptor obtained by baclofen-affinity and immunoaffinity column chromatographic procedures have indicated that this receptor protein is approximately 80 kDa in molecular weight and heterogeneous as determined by SDS-polyacrylamide gel electrophoresis. Alcohol induces the activation of GABA-gated Cl- channel but this activation is found to be diminished following the establishment of alcohol dependence. Furthermore, alcohol dependence induces the increase of GABAB receptor binding, while suppressing the functional coupling between GABAB receptor and adenylyl cyclase, possibly altering the function of Gi/Go type of GTP-binding protein which is coupled to GABAB receptor in the brain. The pathophysiological significance of these changes in the establishment of alcohol dependence and/or alcohol withdrawal syndrome is also briefly discussed.

The involvement of serotonergic mechanisms in the neuropharmacology of alcohol was appreciated before it was recognized that there were multiple subtypes of serotonin (5-hydroxytryptamine; 5-HT) receptors. Thus, it was known that manipulations of the central serotonergic system could lead to a modification of the rate of tolerance development to alcohol (Frankel et al., 1975) or to a modulation of alcohol intake (Myers and Martin, 1973; Myers and Melchior, 1975) before Peroutka and Snyder (1979) first suggested that there were at least two subtypes of 5-HT receptors. Since these early reports were written, there has been a wealth of studies which have continued to support a role for 5-HT in the regulation of alcohol intake (See McBride et al., 1993b; Sellers et al., 1992, for reviews). Simultaneously, a tremendous expansion in the number of known 5-HT receptor subtypes has occurred (See Peroutka, 1988). However, there have not been, to our knowledge, any papers which have examined the possible role of specific 5-HT receptor subtypes in the regulation of alcohol's central effects. The present review addresses this deficiency in the literature. This review will focus on three major areas: the pharmacological regulation of alcohol intake; differences in 5-HT receptor subtypes among alcohol-preferring and -nonpreferring rat strains; and alterations in 5-HT receptor subtypes following chronic exposure to alcohol.

Cytochrome P450 2E1 (CYP2E1) is constitutively expressed in liver and many other tissues. CYP2E1 is effectively induced in the liver by a diverse set of chemicals having various structures. The enzyme constitutes the only P450 form that is strongly induced by ethanol. CYP2E1 metabolizes a wide array of chemicals with different structures, in particular small and hydrophobic compounds, including potential carcinogens. In addition, CYP2E1 has a unique capacity to reduce dioxygen to reactive oxy radicals that might initiate membranous lipid peroxidation, yielding products, mainly aldehydes, which activate immune cells for cytokine production and Ito cells for collagen formation. CYP2E1 mediated formation of reactive lipid peroxidation products and alpha-hydroxyethyl radicals gives rise to protein adduct formation, some of which can cause autoimmune reactions. The regulation of CYP2E1 is unusually complicated and is exerted at several different cellular levels. CYP2E1 has received much attention, mainly because of its putative importance in the activation of chemicals to cytotoxic or carcinogenic products and its potential role in ethanol-induced hepatotoxicity.

A recently-developed method of gene mapping is reviewed. Several responses to EtOH were studied with the purpose of identifying genes with modest effects (Quantitative Trait Loci, or QTLs). As an example, results from a study of acute ethanol withdrawal severity are discussed. Mice from inbred strains C57BL/6J and DBA/2J, and 19 of their Recombinant Inbred (BXD RI) strains, were given 4 g/kg EtOH and their acute withdrawal severity assessed with the handling-induced convulsion (HIC). HIC scores varied markedly among strains. Comparison of the pattern of strain means for withdrawal with a database comprising genotype of each BXD RI strain for almost 800 mapped polymorphic genetic markers revealed associations with several potential QTLs appearing on several mouse chromosomes. To verify the presence of a gene affecting withdrawal, we then withdrawal-tested individual F2 mice bred from the F1 cross of the parental C57 and DBA strains. These mice were then genotyped for several polymorphic markers close to a putative QTL on chromosome 2. Possession of the DBA allele in severely withdrawing F2 animals was significantly associated with one such marker, D2Mit9, confirming the presence of a gene nearby affecting withdrawal. As a further test, mice of the replicated Withdrawal Seizure-Prone (WSP) and -Resistant (WSR) lines, selected for severity of EtOH withdrawal HIC, were also genotyped. Alleles at the D2Mit9 locus assorted disproportionately (and consistently) between the two pairs of WSP and WSR lines, while alleles at other loci did not. Thus, three tests consistently suggest the influence of a gene, tentatively termed Aw1, 37 cM from the centromere on chromosome 2, that appears to control as much as 40% of the genetic variance in withdrawal. The provisional locus is located very near to two candidate genes. Gad1 codes for the synthesis of glutamic acid decarboxylase, the rate-limiting enzyme for synthesis of GABA. A cluster of genes (Scn1, Scn2, Scn3) code for voltage-sensitive sodium channel proteins. These genes are plausible candidates for affecting withdrawal HIC.

The role of central monoamines and the distribution of ethanol to the brain in the genetically determined influences on voluntary ethanol consumption were examined by studying the extracellular levels of ethanol and monoamines in the nucleus accumbens of the alcohol preferring AA (Alko Alcohol) and alcohol avoiding ANA (Alko Non-Alcohol) rats with in vivo microdialysis. The results show that there is a steep rise in brain ethanol concentration within minutes after the injection of ethanol (1 g/kg ip), but there does not seem to be a difference in the distribution of ethanol into the brain of the two lines of rats. There was, however, some indication that ANA rats may absorb ethanol after intragastric administration faster than AA rats. Ethanol (0.5, 1, or 2 g/kg ip) significantly increased the extracellular levels of dopamine, DOPAC, and HVA, but not that of 5-HIAA, suggesting stimulation of dopamine release by ethanol. No difference in the extent or time course of stimulation of dopamine release between the AA and ANA rats was found.

This study investigated alterations in the receptor adenylyl cyclase system in the brain and platelets of alcoholics through the study of GTP binding (G) protein, which has a key role in the system, in the membranes of the post-mortem brain and platelets. Quantitative examination of G protein by immunoblotting showed that GsH alpha in the temporal cortex of the post-mortem alcoholic brain was significantly decreased with controls. Moreover, the extent of ethanol enhancement of functional photoaffinity GTP(azidoanilido GTP) labeling to Gs alpha and Gi alpha was decreased in all cortical regions (frontal, temporal, parietal, occipital cortex) from alcoholics. In the platelet membrane, a quantitative reduction in GsH alpha and GsL alpha levels as assessed by immunoblotting was seen in family history positive (FHP) alcoholics. A reduction in ethanol enhancement of AAGTP labeling to Gs alpha and Gi alpha was also observed in the FHP group. These alterations of G protein were not found in the platelets from family history negative (FHN) alcoholics. The dysfunctions of Gs protein occurring in platelet membranes of the FHP group are likely to parallel those that occur in the alcoholic brain. These results suggest that disturbances of G protein-mediated signal transduction may be involved in the pathophysiology of alcoholics and that platelet G protein may be used as a trait marker of alcoholics.

Apoptosis is a type of cell death which is clearly distinguishable from necrosis in its morphological and biochemical features. To clarify the role of apoptosis in alcoholic liver injury, we investigated the expression of apoptosis-related Lewis(Le)(y) antigen by immunohistochemistry in liver samples from patients suffering from alcoholic liver disease. Liver biopsy samples were taken from 20 patients who drank more than 80 g of ethanol per day on average. Indirect immunohistochemical staining was carried out using anti-cytokeratin and anti-Le(y) antibodies. To examine the relationship between Mallory bodies and apoptosis, double staining was performed using both antibodies. In alcoholic hepatitis, many Mallory bodies were stained with anti-cytokeratin antibody in hepatocytes of the centrilobular area. Le(y) antigen was also detected in hepatocytes in the same area. Immunohistochemical double staining showed that some of the hepatocytes containing Mallory bodies were stained with anti-Le(y) antibody. Few hepatocytes expressing Le(y) antigens, however, were observed in other types of alcoholic liver disease, including steatosis, fibrosis and cirrhosis. From these results, it is suggested that apoptosis may also be involved in alcoholic hepatitis and that hepatocytes containing Mallory bodies can be eliminated by apoptosis.

The mammalian alcohol dehydrogenase genes are a closely related gene family, and show complex patterns of expression. The promoters contain multiple cis-acting elements that are binding sites for transcription factors. Both positive and negative cis-acting elements have been found. The binding of transcription factors to these sites differs among tissues. The complexity of the promoters allows different amounts of expression of the ADHs in many tissues.