Differences in platelet enzyme activity between alcoholics and nonalcoholics

Ethanol intoxication in Drosophila: Genetic and pharmacological evidence for regulation by the cAMP signaling pathway

Upon exposure to ethanol, Drosophila display behaviors that are similar to ethanol intoxication in rodents and humans. Using an inebriometer to measure ethanol-induced loss of postural control, we identified cheapdate, a mutant with enhanced sensitivity to ethanol. Genetic and molecular analyses revealed that cheapdate is an allele of the memory mutant amnesiac. amnesiac has been postulated to encode a neuropeptide that activates the cAMP pathway. Consistent with this, we find that enhanced ethanol sensitivity of cheapdate can be reversed by treatment with agents that increase cAMP levels or PKA activity. Conversely, genetic or pharmacological reduction in PKA activity results in increased sensitivity to ethanol. Taken together, our results provide functional evidence for the involvement of the cAMP signal transduction pathway in the behavioral response to intoxicating levels of ethanol.

Platelet monoamine oxidase activity in subgroups of alcoholics and controls: results from the Collaborative Study on the Genetics of Alcoholism

OBJECTIVE

Platelet monoamine oxidase (MAO) B activity levels were evaluated to determine whether low platelet MAO activity is a marker for alcoholism, correlates of alcoholism (e.g., cigarette smoking), or a subtype of alcoholism.

METHODS

Adult women (n = 788) and men (n = 685) participating in the Collaborative Study on the Genetics of Alcoholism study were evaluated with a semistructured interview, and blood samples were obtained for determination of platelet MAO activity using tryptamine (0.1 mM) as substrate. DSM-III-R alcohol-dependent individuals were subgrouped using four currently available methods (e.g., two variations of the type 1/type 2 scheme, primary versus secondary typology, type A/type B dichotomy).

RESULTS

In the overall sample, subjects' gender, cigarette smoking status, and the Collaborative Study on the Genetics of Alcoholism site at which their platelets were prepared explained 22% of the variance in platelet MAO activity levels, and multivariate analysis showed that carrying a broad diagnosis of alcohol dependence did not uniquely explain any additional variance in platelet MAO activity levels. Furthermore, within each of the alcoholic subgrouping methods tested, there were no significant differences in platelet MAO activity for type 1 versus type 2, type A versus type B, or primary versus secondary alcoholics.

CONCLUSIONS

Cigarette smoking and male gender are associated with decreased platelet MAO activity levels. After considering these factors, a diagnosis of alcohol dependence does not predict any additional variance in MAO-B activity. Phenotypes of alcoholics (e.g., type 1 versus type 2, type A versus type B, primary versus secondary) do not differ in platelet MAO activity. The results suggest that decreased platelet MAO activity is not a trait marker of alcoholism or one of its subtypes; but, rather, is a state marker of cigarette smoking.

Reduced immunoreactivity of type I adenylyl cyclase in the postmortem brains of alcoholics

Reduced adenylyl cyclase activity after chronic ethanol exposure has been reported. In this study, we investigated by immunoblotting whether quantitative changes of adenylyl cyclase isoforms (type I, type II, and type V/VI adenylyl cyclases) exist in membrane preparations of the temporal cortex obtained from six alcoholics and six age-matched controls. The immunoreactivity of type I adenylyl cyclase decreased significantly in the temporal cortex of alcoholics when compared with controls (p < 0.05), whereas those of type II and type V/VI adenylyl cyclases showed no changes between the groups. These findings suggest that these isoform-specific afterations in the adenylyl cyclase system may be involved in the pathophysiology of alcoholism.

Platelet MAO activity in subtypes of alcoholics and controls in a homogenous population

The level of platelet monoamine oxidase (MAO) activity has been found to vary between alcoholics and healthy controls and between subtypes of alcoholics, in different populations. This study measured the MAO activity in a group of 46 abstinent alcohol dependent subjects and 22 healthy non-alcoholic controls, male and female, in an ethnically homogenous Irish population. The healthy control subjects had a mean MAO activity of 0.27 pmol/hr/10(5) platelets (+/- SEM 0.03), while the alcoholics overall had a mean activity of 0.34 pmol/hr/10(5) platelets (+/- 0.03) and this difference was not significant, P = 0.2. When the alcoholic group was divided into subtypes of alcoholism, (type 1 and type 2) there was no difference between subtypes of alcoholics nor between each subtype and the controls in their MAO activity. There was no correlation between MAO activity and the age of the subjects, the duration of abstinence from alcohol, the severity of alcoholism, smoking status or the gender of the subjects. These data are discussed in the context of the current literature on alcoholism and platelet MAO in different ethnic populations and the status of platelet MAO as a potential marker for alcoholism.

Adenylyl cyclase signal transduction and alcohol-induced sedation

This study examined adenylyl cyclase (AC) signal transduction in alcohol-sensitive brain regions of rats selectively bred for high (HAD) and low (LAD) alcohol drinking and correlated these findings with differences in sensitivity and tolerance to alcohol-induced sedation found within these lines. LAD rats were more sensitive to the sedative effects of alcohol than were HAD rats as evidenced by a shorter latency to lose the righting response (RR) after a single alcohol challenge. When time to recover the RR was compared after each of two alcohol challenges, HAD rats recovered the RR more rapidly following the second challenge compared to the first, indicating that the HAD rats rapidly developed tolerance to the sedative effects of alcohol. Tolerance did not develop in rats of the LAD line. Two months after completion of behavioral testing, adenylyl cyclase (AC) signal transduction was examined in alcohol-sensitive brain regions of rats from both lines. Immunoblot analyses indicated that LAD rats had greater Gs alpha expression in the frontal cortex (FC) and hippocampus (HIP) compared to HAD rats. Rats with the highest HIP and FC Gs alpha levels were more rapidly affected by the sedative properties of alcohol than were rats with lower Gs alpha levels. G protein expression and AC activity in the FC, HIP, cerebellum (CERE), and nucleus accumbens (ACB) were also correlated with sensitivity to the sedative properties of alcohol and with the rapid development of tolerance to this alcohol effect. The results suggest that sensitivity and tolerance to alcohol-induced sedation may be mediated in part through AC signal transduction.

Serotonergic dysfunction in addiction: effects of alcohol, cigarette smoking and heroin on platelet 5-HT content

The impact of ethanol, cigarette smoking and heroin on serotonin function was evaluated, first in alcoholics during chronic ethanol intoxication and in opiate addicts after long-term heroin consumption, and secondly in both patient groups after detoxification treatment (i.e. a short-term abstinence of 8 days). Our results showed that the 5-hydroxytryptamine (5-HT) content in platelets was: (1) increased in the subgroup of anti-social alcoholics; (2) transiently and differently altered in alcoholics compared to opiate addicts; and (3) lowered in drinking alcoholics and normal in alcoholics who were drinking as well as smoking (that may occur via MAO-B inhibition by smoke). The findings indicate that alterations of the peripheral and possibly the central serotonin system may occur as predisposing factors for alcoholism in individuals with anti-social traits; they may also have some impact on the progression of alcoholism due to its lowered function during chronic ethanol intoxication that is substantially modified by smoking.

Fatty acid ethyl esters: short-term and long-term serum markers of ethanol intake

This review includes a description of short-term and long-term markers of ethanol intake and their clinical utility. The major portion of this report is a summary of studies on fatty acid ethyl ester, a new marker for monitoring both acute and chronic ethanol intake. With the markers described in the review, algorithms to assess recent ethanol intake, chronic ethanol intake, and end organ damage are included to provide a practical approach to the evaluation of the patient.

No allelic association of an exon 13 polymorphism of the Gsα gene to alcohol and/or drug dependence

The adenylyl cyclase signal transduction system, a ubiquitous second messenger system, has been identified as a potential marker for genetic risk of alcohol and drug dependence. Using the polymerase chain reaction (PCR) to amplify exon 13 of the Gsα gene, two alleles were distinguished by denaturing gradient gel electrophoresis. One allele, designed A, contained the previously published C in the codon for asparagine 371, while the second allele, designated A, contains a C-T transition that conserves the asparagine residue at codon 371. The neutral polymorphism eliminates a Fok I restriction enzyme cleavage site, allowing use of restriction fragment length polymorphisms of PCR products to determine allelic frequency in 235 subjects with alcohol and/or drug dependence and in 85 control subjects. Since allele frequencies differ significantly by race, comparisons between affected individuals and controls were conducted separately for white and black groups. Within race, there were no significant differences in the frequency of the A allele among alcoholics, subjects dependent on cocaine or opioids, subjects dependent on these drugs and alcohol, and controls. We conclude that there is no association between alcohol and/or drug dependence and alleles of an exon 13 polymorphism of the Gsα gene in either black or white individuals.

Increased expression of Gs(alpha) enhances activation of the adenylyl cyclase signal transduction cascade

Expression of the stimulatory G protein, G(S)alpha, can vary over a 3-fold range in human tissues and in rodent central nervous system. In fact, the offspring of alcoholics have higher levels of G(S)alpha expression in certain tissues compared with the offspring of nonalcoholics. The aim of this research was to test the hypothesis that a causal relationship exists between the level of expression of G(S)alpha and induction of the adenylyl cyclase (AC) cascade. The methodology employed transient transfection of HEK 293 cells with a cDNA for the 52-kDa form of G(S)alpha under regulation by inducible metallothionein promoters. Transfectants were exposed to varying concentrations (0-125 microM) of zinc sulfate that produced a 3-fold range of membrane G(S)alpha expression. The range of G(S)alpha expression produced was found to mimic a physiologically relevant spectrum of G(S)alpha expression in membranes derived from human tissues and rat brain. It was observed that induction of G(S)alpha expression increased constitutive as well as stimulated cAMP accumulation. Moreover, induction of G(S)alpha expression increased events distal to the accumulation of cAMP including the phosphorylation of the transcription factor, cAMP response element binding protein and transcriptional activation of cAMP-dependent reporter genes. In summary, these studies show that the amount of G(S)alpha expression has a marked impact on the level of activity of the AC cascade from the membrane through to the nucleus. It is hypothesized that individuals who differ in G(S)alpha expression may also differ in the expression of certain cAMP-dependent genes.

Alcohol-induced bone disease: impact of ethanol on osteoblast proliferation

The habitual consumption of even moderate quantities of alcohol (1 to 2 drinks/day) is clearly linked with reduced bone mass (osteopenia). Biochemical and histological evaluation of patients with alcoholic bone disease reveal a marked impairment in bone formation in the face of relatively normal bone resorption. Experiments using well-defined osteoblastic model systems indicate that the observed reductions in bone formation result from a direct, antiproliferative effect of ethanol on the osteoblast itself. As bone remodeling and mineralization are dependent on osteoblasts, it follows that the deleterious effect of alcohol on these cells would result in slowed bone formation, aberrant remodeling of skeletal tissue and, ultimately, osteopenia and fractures. The skeletal consequences of alcohol intake during adolescence, when the rapid skeletal growth ultimately responsible for achieving peak bone mass is occurring, may be especially harmful. The specific subcellular mechanisms whereby ethanol inhibits cell proliferation are, as yet, unknown. During the last few years, attention has shifted from nonspecific membrane perturbation effects to actions on certain signaling proteins. Specifically, there is increasing evidence that ethanol may exert significant effects on transmembrane signal transduction processes that constitute major branches of cellular control mechanisms. At present, abstinence is the only effective therapy for alcohol-induced bone disease. An improved understanding of the pathogenesis of alcohol-induced bone disease may eventually result in alternative therapeutic avenues for those who are unable to abstain.

Platelet monoamine oxidase (MAO) activity and alcoholism: is there a genuine association?

Monoamine oxidase (MAO) is a particle-bound flavoenzyme principally located in the outer mitochondrial membrane, which catalyzes the oxidative deamination of a variety of the amine transmitters in the central nervous system. There have been many reports from different groups around the world over the last 20 years that indicated a lower platelet MAO activity was associated with alcoholism. As there are multiple influences upon measured MAO activity, this article attempts to address each of the issues in turn for potential confounding of the reported association. These issues include: the duration of abstinence from alcohol, the substrate used for analysis, gender issues, association with different subtypes of alcoholics, the influence of other psychopathology, personality traits of alcoholics, the question of smoking, and proposed modes of transmission of MAO activity. The initial promise about MAO activity being a possible marker for alcoholism or a least a genetically predisposed subgroup has receded as the number of negative typology-based studies increases. The failure to account for a major confounding variable, e.g. smoking and other minor but possibly vital confounds in almost all these studies leaves the whole hypothesis open to criticism. However, the possible association between personality traits that might predispose to some if not all substances of addiction to low MAO activity may make it possible to reframe the hypothesized association in the setting of a generalized predisposition to addictions in particular, and to psychopathology in general. Nonetheless the association remains of great interest and may yet yield vital genetic and clinical information.

Human adenylyl cyclase type 7 contains polymorphic repeats in the 3' untranslated region: investigations of association with alcoholism

Platelet adenylyl cyclase activity has been proposed as a trait marker for alcoholism [Tabakoff et al. (1988): N Engl J Med 318:134-13;9; Parsian et al. (1996): Alcohol Clin Exp Res 20:745-751]. Human adenylyl cyclase type 7 (ADCY7) is a member of the adenylyl cyclase gene family, and it may be the major form of adenylyl cyclase expressed in human platelets. The published cDNA sequence of ADCY7 indicated the presence of potentially polymorphic regions in the 3' untranslated region of ADCY7. PCR techniques combined with fluorescently labeled primers were used to amplify two separate tetranucleotide repeat regions [(AACA)n] in the 3' untranslated region of ADCY7 from the genomic DNA of 62 unrelated individuals. The upstream (AACA)4-repeat was not polymorphic. Five different genotypes were found in the downstream (AACA)5-7 tetranucleotide repeat region. We also tested the association of the tetranucleotide polymorphism to alcohol dependence. When 30 alcoholic and 17 control individuals were compared, no difference was found in the ADCY7 tetranucleotide polymorphism between alcohol-dependent and control groups. Nevertheless, to our knowledge these are the first polymorphisms reported in an adenylyl cyclase gene. Adenylyl cyclases are important receptor-G protein-coupled effectors and are involved in numerous neuronal functions in the central nervous system. Whether variations in ADCY7 and possible variations in other members of this gene family are underlying other psychiatric disorders remains to be studied.

Genetic markers of alcohol abuse

In this paper, we review the current status of genetic markers for the development of alcohol abuse. Family, twin, half-sibling and adoption studies of alcoholic subjects suggest that the heritability of liability to alcoholism is at least 50%. These findings have fuelled intensive investigation in the fields of neurology, biochemistry, genetics and molecular biology aimed at the identification of markers for the risk of alcoholism. The most promising of these are discussed in detail. Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) polymorphisms, specifically the ADH3*1, ADH2*2, and ALDH2*2 genotypes appear to confer a protective effect against alcoholism, most notably in Oriental subjects. Caucasian alcohol abusers and their first-degree relatives exhibit depressed platelet monoamine oxidase activity, the degree of which is greater in Type II than Type I alcoholics. Electrophysiological characteristics of alcoholics and those at risk for developing alcoholism have also been identified, including the reduced amplitude of the event-related brain potential and, after ethanol ingestion, characteristic EEG alpha-wave activity. Lower platelet adenylate cyclase activity is seen in alcoholics compared to controls, presumably as a result of over-expression of an inhibitory G-protein. Markers related to other signal transduction pathways of the central nervous system including the serotoninergic, muscarinic and dopaminergic systems are also discussed. In this group of markers, the putative association between the inheritance of the AI allele of the D2 dopamine receptor and the susceptibility to alcoholism provides the most dramatic illustration of the challenges presently existing in this field of scientific investigation. Current limitations in the definition, diagnosis and classification of alcoholism, the confounding influences of race and gender on association studies, as well as the statistical approach of linkage studies are discussed as they relate to the endeavor to uncover valid genetic markers for the risk of alcoholism.

Decreased inositol 1,4,5-trisphosphate-specific binding in platelets from alcoholic subjects

We measured the degree of inositol 1,4,5-triphosphate (IP3)-specific binding in platelets from alcoholic and nonalcoholic subjects. IP3-specific binding in alcoholic subjects was 45% less than that in nonalcoholic subjects. There was no significant difference in the number of IP3 receptors as detected immunologically in the platelet membrane fractions from alcoholic and nonalcoholic subjects. These results indicate that the decrease in IP3-specific binding in alcoholic subjects may have been due to a decreased affinity, but not number of IP3 binding sites. In contrast to the decrease in IP3 receptor binding, there were no significant changes in phospholipase-C activity or immunoreactivity of phospholipase C-beta 1 in platelet membranes from alcoholic subjects. The decreased IP3-specific binding in platelets may allow for the development of biological markers for alcoholism.

Ethanol causes translocation of cAMP-dependent protein kinase catalytic subunit to the nucleus

Short- and long-term ethanol exposures have been shown to alter cellular levels of cAMP, but little is known about the effects of ethanol on cAMP-dependent protein kinase (PKA). When cAMP levels increase, the catalytic subunit of PKA (C alpha) is released from the regulatory subunit, phosphorylates nearby proteins, and then translocates to the nucleus, where it regulates gene expression. Altered localization of C alpha would have profound effects on multiple cellular functions. Therefore, we investigated whether ethanol alters intracellular localization of C alpha. NG108-15 cells were incubated in the presence or absence of ethanol for as long as 48 h, and localization of PKA subunits was determined by immunocytochemistry. We found that ethanol exposure produced a significant translocation of C alpha from the Golgi area to the nucleus. C alpha remained in the nucleus as long as ethanol was present. There was no effect of ethanol on localization of the type I regulatory subunit of PKA. Ethanol also caused a 43% decrease in the amount of type I regulatory subunit but had no effect on the amount of C alpha as determined by Western blot. These data suggest that ethanol-induced translocation of C alpha to the nucleus may account, in part, for diverse changes in cellular function and gene expression produced by alcohol.

Platelet adenylyl cyclase activity in alcoholics and subtypes of alcoholics. WHO/ISBRA Study Clinical Centers

Adenylyl cyclase (AC) activity was measured in membrane preparations of platelets from control and alcoholic subjects. The sample consisted of 51 alcoholics who were categorized as type I or type II using the criteria of Gilligan et al. (Genet. Epidemiol. 4:395-414, 1987) and 54 normal controls. Alcoholic males exhibited significantly lower values than controls in basal and fluoride-stimulated platelet AC activity. When male alcoholics were segregated into type I and type II categories, the platelet AC activity did not differ between subtypes, and both subtypes had AC activity that was below control values. Western blot analysis of the quantity of Gs alpha and Gi alpha proteins in a subset of male controls and alcoholic subjects demonstrated no significant relationship between quantity of G proteins and AC activity. The results confirm lower platelet AC activity in male alcoholics, compared with controls. Given the lack of quantitative relations between Gs alpha and Gi alpha proteins and AC activity, the results support the contention that individual differences in platelet AC activity in the alcoholic subjects may reflect quantitative or qualitative differences in the AC catalytic units.

Defective calcium increase and inositol phosphate production in anti-CD3-stimulated lymphocytes of alcoholics without progressive liver disease

Intracellular free calcium concentration, phosphoinositide turnover, and inositol phosphate production were analyzed in peripheral blood lymphocytes from seven well-nourished alcoholic patients without severe acute or chronic liver disease, before and after stimulation with anti-CD3 antibody. Seven comparable nondrinkers were studied as controls. A lower increase in intracellular free calcium concentration was detected in alcoholics, after anti-CD3 stimulation of lymphocytes, than in control subjects. Lymphocyte activation generated inositol phosphates in both controls and alcoholics, but inositol phosphate production was significantly lower in alcoholics. The agreement between these findings indicates that the reduction in inositol phosphates is one of the most important events in the early phases of lymphocyte activation in alcoholics.

Individual and combined effects of ethanol and cocaine on intracellular signals and gene expression

1. Ethanol and cocaine are drugs of abuse that can produce long-lived changes in behavior, including dependence. 2. A common set of neural pathways appears to mediate the addictive actions of ethanol and cocaine. 3. Many prominent aspects of drug dependence may be the result of alterations in intracellular signals as well as specific patterns of gene expression. 4. For instance, changes in G proteins and cAMP, phosphorylation of proteins and induction of c-fos and zif/268 in specific drug-sensitive brain regions may represent adaptive changes in response to a drug-dependent state. 5. The concurrent use of ethanol and cocaine is the most prevalent pattern of drug abuse in humans. However, the number of studies investigating the behavioral and molecular effects of this combination are few. 6. Emerging evidence indicates a possible antagonistic effect of ethanol and cocaine action on transcription factor function. In addition, cocaethylene (a psychoactive metabolite derived from combined ethanol and cocaine exposure) has significant effects on gene expression as well.

Role of protein synthesis on ethanol regulation of adenylyl cyclase activity in wild-type S49 murine lymphoma cells

Adenylyl cyclase activity was determined in membranes from wild-type S49 murine lymphoma cells that had been exposed to ethanol for 4 hr. Mn-, NaF-, and forskolin-stimulated adenylyl cyclase activities of cells-pretreated with cycloheximide, puromycin, or serum deprivation-were significantly decreased by treatment with 50 mM of ethanol. As demonstrated for Mn-stimulated activity, the decrease was dose-dependent on ethanol and was temporal; a normal activity recovered after 16-24 hr treatment, even in the presence of cycloheximide and ethanol. Studies with a cell-free membrane system of S49 cells revealed a similar activity decrease after treatment of the membranes with ethanol. In contrast, cells treated with 50 mM of ethanol in a regular culture condition showed no decrease in adenylyl cyclase activity over 24 hr. These results indicate that ethanol regulation of adenylyl cyclase activity in S49 cells depends on reduced or impaired protein synthesis.

Selective effects of ethanol on the generation of cAMP by particular members of the adenylyl cyclase family

A selective action of ethanol on major signal transduction proteins, such as adenylyl cyclase, has been considered to be important for certain actions of ethanol, and alcoholics have been demonstrated to differ from controls in measures of platelet adenylyl cyclase activity. Recent advances in identification and characterization of isoforms of adenylyl cyclase have demonstrated that there exists at least eight different forms of this enzyme. To examine whether the effect of ethanol on generation of cAMP is modified by the presence of particular isoforms of adenylyl cyclase within a cell, we transiently expressed each of six adenylyl cyclases in human embryonic kidney (HEK293) cells and measured cAMP accumulation in whole cells in the presence and absence of ethanol. The treatment of cells expressing the various adenylyl cyclases with ethanol alone did not enhance cAMP generation. In the presence of prostaglandin E1, cAMP generation by type I and type III adenylyl cyclases was insensitive to ethanol. cAMP accumulation generated by the other adenylyl cyclases was, however, increased by incubation of cells with ethanol in the presence of stimulatory agonists (e.g., prostaglandin E1). Stimulation by ethanol of cAMP generation by type VII adenylyl cyclase was 2- to 3-fold greater than that seen with the other tested adenylyl cyclases. The noted stimulation of cAMP generation by ethanol was dose-dependent and required concurrent activation of adenylyl cyclase through the stimulatory G protein. The effects of ethanol were reversible and mimicked by butanol but not by chloroform.

Monoamine oxidases and alcoholism. II. Studies in alcoholic families

Thirty-five alcoholic families have been studied to investigate the relationship between DNA markers at the monoamine oxidase (MAO) loci and 1) platelet activity levels and 2) alcoholism. A quantitative linkage analysis failed to reveal any evidence that the variation in activity levels cosegregates with the DNA markers. A sib-pair analysis did not reveal a significant excess of MAO haplotype sharing among alcoholic sibs, although the deviation from random sharing was in the direction consistent with an X-linked component. A reanalysis of platelet MAO activity levels in a subset of these families revealed that the lower levels previously found in alcoholics is more likely due to the differences between males and females. Only among males and only when a "broad" definition of alcoholism is used (and MAO activity levels are transformed to normality) does it appear that alcoholics have depressed activities compared to nonalcoholics. Finally, when the confounding due to gender difference is removed, no differences between type I and type II alcoholics are found in these families.

Monoamine oxidases and alcoholism. I. Studies in unrelated alcoholics and normal controls

Low platelet MAO activity has been associated with alcoholism. In order to evaluate the role of MAO genes in susceptibility to alcoholism, we have taken a biochemical and molecular genetic approach. The sample consisted of 133 alcoholic probands who were classified by subtypes of alcoholism and 92 normal controls. For those subjects typed for platelet MAO activity, alcoholics (N = 74) were found not to differ from the non-alcoholics controls (N = 34). Neither was there a significant difference between type I and type II alcoholics or between either subtype and normal controls. However, we do find significant differences between male and female alcoholics, but not between male and female controls. The allele frequency distribution for the MAO-A and MAO-B dinucleotide repeats is different between the alcoholic sample (N = 133) and the normal control sample (N = 92). In a two-way analysis of variance of MAO-B activity as a function of the allelic variation of each marker locus and diagnosis, there is no evidence for mean differences in activity levels for the different alleles. Our findings do not rule out a role for the MAO-B gene in controlling the enzyme activity because the dinucleotide repeats are located in introns.

Platelet monoamine oxidase activity levels in subgroups of alcoholics: diagnostic, temporal, and clinical correlates

Platelet monoamine oxidase (MAO) activity levels were measured in 47 male inpatient alcoholics to determine whether this biological marker might be useful in differentiating subtypes of alcoholics. Of the subgrouping methods tested, only type 2 alcoholics defined by the criteria of Gilligan et al had significantly lower platelet MAO activity than type 1 alcoholics at intake, but this finding was not stable over time in a subset of subjects. Neither separating male veteran alcoholics into either of two other variations of the type 1/type 2 subtypes, nor classifying the sample into primary alcoholics versus primary ASPD with secondary alcoholism categories, yielded significant differences between subgroups. Generally, enzyme activity levels (Vmax) were higher about 10 days after stopping drinking compared to platelet MAO values determined in thrombocytes obtained after approximately 4 weeks abstinence; these levels remained relatively stable 3 months later in a cohort of subjects. Tobacco smoking was significantly negatively correlated to platelet MAO activity levels.

Mechanisms of neurotoxicity: applications to human biomonitoring

Interactions of chemicals with cerebral neurotransmitters, receptors, and second messenger systems are often accompanied by similar changes involving components in non-neural tissues. On this basis, indirect strategies have been developed to investigate neural cell function parameters by methods using accessible cells such as platelets or peripheral blood lymphocytes. The validity of certain surrogate markers of biochemical events occurring in the nervous system has been documented by recent studies in both laboratory animals and humans. Although experience with neurotoxicants is still limited, advantages and limitations of methods using peripheral blood cells as indicators of chemically-induced nervous system changes have been documented by a number of studies in psychopharmacology and biological psychiatry. Applicability of this approach in conventional population studies of environmental chemicals remains to be demonstrated. However, recent data regarding the action of low doses of mercury and organophosphates on receptors and signal transduction pathways in peripheral lymphocytes suggest useful applications of certain surrogate markers in mechanistic studies of neurotoxicity in vivo and, possibly, in assessing early biochemical effects of neurotoxicants in humans.

Alcoholism among four aboriginal groups in Taiwan: high prevalences and their implications

An epidemiological study of alcohol use disorders was conducted on population samples from four aboriginal groups in Taiwan (a total of 993 subjects). The survey involved ethnographic observation and a semistructured psychiatric interview. The interview covered a detailed symptom profile that allowed diagnoses to be made according to different diagnostic criteria. The lifetime prevalences of alcoholism according to the ICD-10 (research criteria) and the DSM-III-R criteria were found to be 42.2-54.7% and 44.2-55.5%, respectively, much higher than the rates found in an earlier study (0.11-0.16%) conducted 40 years ago. Men in all groups were found to have higher prevalences, a lower mean age at onset, and a longer mean duration (except in one group) of alcoholism than women. Differences in the distribution of sociodemographic correlates (age, sex, marital status, education, and ethnicity) of ICD-10 harmful use of alcohol and alcohol dependence were examined by case-control analysis with logistic regression. The lifetime prevalences of alcohol use disorders were higher than in recent epidemiological surveys conducted elsewhere. Possible biological and sociocultural explanations for the high prevalence of alcoholism among the study populations are discussed.

Longitudinal observations of monoamine oxidase B in alcoholics: differentiation of marker characteristics

The marker characteristics of monoamine oxidase B (MAO B) in human platelets were investigated in a clinical study of 59 alcoholics (diagnosed according to the criteria of ICD-10) observed over a period of 6 months. Demographic and family history were obtained by a structured interview, including the substance abuse section of CIDI (Composite International Diagnostic Interview). The patient's personality was assessed by Cloninger's Tridimensional Personality Questionnaire (TPQ). Blood samples were first drawn during chronic intoxication (day of admission to the hospital for detoxication), after short-term abstinence (8 days later), medium-term (3 months later), and long-term abstinence (6 months later). A group of 22 matched healthy nonalcoholics served as controls studied under sober conditions and during acute intoxication (4 hr after ingestion of 1 g ethanol/kg body weight). All platelet samples were investigated with 6 kynuramine concentrations as substrate (fluorometric assay) in the absence and presence of 200 mM ethanol (ETOH) in vitro. MAO B activity was significantly reduced in alcoholics during chronic intoxication (Vmax: 2.70 +/- 0.15 nmol/mg protein) compared with sober (Vmax: 3.25 +/- 0.23 nmol/min/mg protein) and acutely intoxicated controls that turned to normal during abstinence. However, MAO B activity obtained during medium- and long-term abstinence was significantly lowered in patients with high novelty-seeking and impulsiveness scores in the TPQ, a history of suicide attempts, or an alcoholic mother. The affinity of MAO B (Km values) was unchanged in alcoholics at any time investigated. Addition of ETOH in vitro reduced the affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylate cyclase, a biochemical marker of alcoholism?

A possible biochemical vulnerability (trait) marker is examined in a cross-sectional study to determine the biochemical factors associated with the development of alcoholism in a population of non-adult children of alcoholics. The activity of adenylate cyclase, an enzyme that plays a role in the signal transduction pathway of several hormones and neurotransmitters, is assessed in blood platelets. This activity was reported to be lower in blood cells of alcoholics and abstinent alcoholics compared with that in controls. In addition, dysregulation of adenylate cyclase in the CNS of animals seems to be involved in drug-seeking behaviour. The relation between these biochemical findings and psychopathology is currently being investigated in a project by the Amsterdam Institute for Addiction Research.

Platelet monoamine oxidase activity in alcoholics, alcoholics with drug dependence, and cocaine addicts

The main objective of this investigation was to study the influence of drug dependence on platelet monoamine oxidase (MAO) activity in the presence and absence of alcoholism. One hundred and thirteen admissions to alcohol and drug treatment facilities participated in the study. Twenty-six met the criteria for alcoholism (group I), seventy-eight subjects were alcohol-/cocaine- and cannabis-dependent (group II), and the remaining nine were patients with DSM-III-R diagnosis of cocaine addiction (group III). MAO activity was assayed radiochemically with [14C]tyramine as a substrate (221 microM). The results of this study showed that platelet MAO activity [nmol of product formed x (mg protein)-1 x hr-1] (mean +/- SE) was significantly (p < 0.01) lower in all of these subjects (group I, 5.50 +/- 0.80; group II, 3.90 +/- 0.50; group III, 4.3 +/- 1.60) as compared with controls (14.85 +/- 1.13). Measurements of platelet MAO activity may provide us with a reliable biochemical marker for alcoholism and perhaps addiction to other substances of abuse (i.e., cocaine).

Differential expression of guanosine triphosphate binding proteins in men at high and low risk for the future development of alcoholism

We evaluated G-proteins that are components of adenylyl cyclase (AC) signal transduction in erythrocyte and lymphocyte membranes from 26 family history positive (FHP) non-alcoholic and 26 family history negative (FHN) nonalcoholic subjects. Subjects were classified as FHP if their father met criteria for alcohol dependence; as FHN, if there was no history of alcoholism in any first or second degree relatives. Immunoblot analysis indicated that levels of erythrocyte membrane Gs alpha from FHP subjects were greater than levels in FHN subjects (171 +/- 11 vs 100 +/- 6, P < 0.001). To confirm the results of the immunoblot analysis, Gs alpha was quantitated by cholera toxin-dependent [32P]ADP-ribosylation. Levels of erythrocyte [32P]ADP-ribose-Gs alpha from FHP subjects were greater than levels in FHN subjects (236 +/- 28 vs 100 +/- 14, P < 0.001). Gs alpha levels did not correlate with age or alcohol consumption. By contrast to differences in Gs alpha, immunoblot analysis showed similar levels of Gi(2)alpha and Gi(3)alpha in erythrocyte membranes of FHP and FHN subjects. Pertussis toxin-catalyzed [32P]ADP-ribosylation of Gi-like G-proteins confirmed the immunoblot observations. Lastly, compared to FHN subjects, FHP subjects had enhanced Gs alpha expression in lymphocyte membranes as well (138 +/- 11 vs 100 +/- 5.5; P < 0.02). In summary, compared to FHN nonalcoholic men, FHP nonalcoholic men had greater levels of the stimulatory G-protein, Gs alpha, in erythrocyte and lymphocyte membranes. Enhanced expression of Gs alpha may be a marker of increased risk for the future development of alcoholism.

Genetic aspects and risk factors in alcoholism and alcoholic liver disease

There is a great deal of evidence for genetic predisposition to alcoholism; considerably less is known regarding predisposition to alcoholic liver disease. The specific genes involved in either disorder are not well understood, although the enzymes of alcohol metabolism appear to play some role. It will be interesting to determine whether genetic factors that alter the expression of these enzymes, in addition to altering the kinetics of the enzymes, could modify responses to drinking. Work in the next few years will include determination of which responses to alcohol are indeed genetically influenced in twin studies, testing additional candidate genes for alcohol-related traits in populations and families, as well as the application of genomic mapping methodologies to alcoholic pedigrees. The latter strategy will be integrated into the larger number of studies that will grow from the Human Genome Project. Animal studies with selectively bred lines of rodents that differ in voluntary alcohol consumption will lead the way to define the neuronal and behavioral substrates responsible for differences in alcohol-drinking behavior. The use of the quantitative trait locus (QTL) mapping approach in F2 intercross between two inbred strains of rodents with opposite alcohol-response characteristics and in recombinant inbred strains derived from F2 intercross already has and will continue to help identify chromosomal locations of genes relevant to voluntary alcohol consumption. Perhaps in the future selective breeding of rodents and QTL mapping strategies can also be used to determine the biology and genetics of alcohol-induced liver injury.

Genetics of alcoholism: role of the endogenous opioid system

At the present time alcoholism is recognized as a metabolic disease exhibiting the clinical features of craving for alcohol, loss of control over drinking, tolerance and physical dependence on alcohol, while both epidemiological and experimental studies have demonstrated that genetic factors may be important in determining whether an individual has a high or low vulnerability to develop alcoholism. Evidence also indicates that alcoholism is not characterized by a single gene single allele inheritance. Instead it seems that multiple genes and environmental factors interact to increase or decrease an individual's vulnerability to become an alcoholic. Current research is aimed at investigating whether certain behavioral, physiological and biochemical markers are highly associated with the incidence of alcoholism. Among the biochemical markers currently under investigation is the endogenous opioid system and its implication in mediating the reinforcing effects of ethanol. It is the objective of this manuscript to review current research on: (a) the interactions of ethanol with the endogenous opioid system at the molecular level; (b) the existence of genetically determined differences in the response of the endogenous opioid system to ethanol between subjects at high and low risk for excessive ethanol consumption, as well as between lines of animals showing preference or aversion for ethanol solutions; (c) the decrease of alcohol consumption following pretreatment with opioid antagonists; and (d) the possible use of specific opioid receptor antagonists together with behavioral therapy to modify drinking behavior, to control craving and to prevent relapse.

Primary early onset dysthymia, biochemical correlates of the therapeutic response to fluoxetine: I. Platelet monoamine oxidase and the dexamethasone suppression test

A subgroup of primary dysthymic patients have been reported to respond to traditional antidepressants and, more recently, to the newer serotonergic agents. Two putative biological markers of affective illness, platelet monoamine oxidase (MAO) activity and plasma cortisol levels following dexamethasone administration, were explored for their diagnostic and predictive potential in dysthymia. Compared to controls, patients had significantly lower platelet MAO activity. Among patients, those that responded to treatment with the serotonergic agent, fluoxetine, had lower pretreatment MAO activity than nonresponders. Higher pretreatment plasma cortisol levels following dexamethasone were also associated with a positive treatment response to this medication. These findings support the view that there is a biological substrate for some subgroups of dysthymics. This biological component may involve the hypothalamic pituitary adrenal axis and serotonergic system(s).

Enzymes and circulating proteins as markers of alcohol abuse

The identification of alcohol abuse is an important social and clinical objective for which various biochemical procedures have been utilized, serum enzymes and circulating proteins being predominant. Tests are required to detect alcohol abuse as screening procedures in the general population as well as for the specific diagnosis of those presenting as hospital inpatients or outpatients, especially when liver disease is present or suspected. The amino-transferases are of limited value, although the mitochondrial isoenzyme of aspartate amino-transferase has been strongly advocated and is quite useful in detecting alcoholics among patients with liver disease. Gammaglutamyl transferase, by contrast, is raised in all forms of liver disease but can identify 30-50% of those consuming excessive amounts of alcohol before organic damage becomes manifest. Serum carbohydrate-deficient transferrin (CDT) is raised in many alcohol abusers without and most with liver damage, but is rarely elevated in other forms of liver disease. Haemoglobin-associated acetaldehyde, the newest biochemical index to be evaluated in alcoholics, is one of several adducts formed by the reaction of acetaldehyde with various proteins, and antibodies to these adducts may contribute, at least in part, to immunological tissue damage provoked by chronic excessive consumption of alcohol. Its assay is technically complex and it appears to be present in higher concentrations in heavy drinkers than in those who fulfill the criteria of addictive alcohol abuse. Many other markers have been introduced in the last decade but the search for a reliable index continues. CDT comes closest at the present time to matching the desired specificity, although it is of limited value in screening unselected non-hospitalized subjects.

Hereditary variations in monoamine oxidase as a risk factor for Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder caused by loss of dopaminergic neurons in the brainstem. Recent studies suggest that several genes may have a role in determining individual susceptibility to this disease, and the degradative enzyme monoamine oxidase (MAO) has been implicated in the disease process. Wide differences in activity levels for both forms of this enzyme (MAO-A and MAO-B) exist in the human population, and levels of both are genetically determined. Here we have compared the frequency of haplotypes at the MAOA and MAOB loci on the X chromosome in 91 male patients with PD and 129 male controls. Alleles were marked using two restriction fragment length polymorphisms (RFLPs), a (GT)n repeat in the MAOA locus, and a (GT)n repeat in the MAOB locus. One particular haplotype marked by the RFLP's at MAOA was three times more frequent in patients with PD as compared with controls, and the overall distribution of these alleles was significantly different (p = 0.03) between these two groups. Another MAOA haplotype was about threefold more common in controls than in patients with PD (p = 0.005). No associations were observed between individual MAOB alleles and the disease state, but the frequency distribution for all alleles was significantly different in the two populations (p = 0.046). These findings support the idea that the MAO genes may be among the hereditary factors that influence susceptibility of individuals to PD.

Signal-transducing G proteins: basic and clinical implications

The pivotal role that G proteins play in transmembrane signal transduction is highlighted by the rapidly expanding list of receptors and effector molecules that are coupled through G proteins. G proteins are poised to allow discrimination and diversification of cellular signals into the cytosolic milieu. The utilization of an evolutionarily conserved "GTPase clock" by G proteins, offers insight into the fundamental role these proteins play in biology. Knowledge of the implication of altered expression or function of G proteins in human disease is now emerging. It is not surprising that deficiency or expression of altered forms of these important proteins can lead to global or restricted metabolic disturbances, depending upon the distribution and role of the G protein. Human disorders, including heart failure, alcoholism, endocrine abnormalities, and neoplasia, are now recognized as due in part to altered expression or function of G proteins.

Monoamine oxidase (MAO; E.C. 1.4.3.4) characteristics of platelets influenced by in vitro and in vivo ethanol on alcoholics and on control subjects

Ethanol (ETOH) in vitro displays a competitive inhibition of human platelet MAO-B with a Ki of 270 +/- 30 mM. Lineweaver-Burk analyses with 6 substrate concentrations (5-160 microM kynuramine) in the presence or absence of 200 mM ETOH were performed with platelets of alcoholics before withdrawal (Alc day 1), one week (Alc day 8) and 3 months (Alc mon 3) after withdrawal as well as in control subjects without and after ETOH intake. In all groups the Km increases highly significantly (p < 0.001) but the Vmax is unchanged by the presence of ETOH in vitro supporting the view of a competitive inhibition in each group. The Vmax of Alc day 1 is significantly 25% decreased, of Alc day 8 unchanged and of Alc mon 3 nonsignificantly 19% decreased in comparison with the controls. The increase of the Km in the presence of 200 mM ETOH is significantly 15% reduced in Alc day 1 and 9% in Alc day 8 but unchanged in Alc mon 3 compared with the controls.

The effects of ethanol on rat brain monoamine oxidase activities

In contrast to the reported behaviour of human platelet MAO-B, chronic ethanol feeding does not significantly affect the sensitivities of either MAO-A or -B from rat brain to inhibition by ethanol in vitro. The thermal stabilities of rat brain MAO-A and -B are not significantly affected by chronic ethanol feeding.

Association of monoamine oxidase (MAO) activity with alcoholism and alcoholic subtypes

A familial/genetic study of platelet monoamine oxidase (MAO) activity in alcoholics was carried out. MAO activities were determined using phenylethylamine (PEA) as substrate at Km concentration (1.2 microM) and at saturating concentration (12.0 microM). Complex segregation analysis of familial data indicated a single major gene mode of transmission of activity at both substrate concentrations. In addition, the present sample size (13 families, 108 members) proved sufficient to allow correlation analysis of enzyme activity with affection status and clinical subtypes of affecteds. MAO activity was significantly correlated with alcoholism at both Km and saturating substrate concentrations and a significant correlation between low MAO activity and Cloninger Type II alcoholism was seen at Km substrate concentration. These results confirm a hierarchical cosegregation of platelet MAO activity and alcoholism suggesting that MAO activity warrants continued status as a marker in alcoholism.

Phosducin-like protein: an ethanol-responsive potential modulator of guanine nucleotide-binding protein function

Acute and chronic exposure to ethanol produces specific changes in several signal transduction cascades. Such alterations in signaling are thought to be a crucial aspect of the central nervous system's adaptive response, which occurs with chronic exposure to ethanol. We have recently identified and isolated several genes whose expression is specifically induced by ethanol in neural cell cultures. The product of one of these genes has extensive sequence homology to phosducin, a phosphoprotein expressed in retina and pineal gland that modulates trimeric guanine nucleotide-binding protein (G protein) function by binding to G-protein beta gamma subunits. We identified from a rat brain cDNA library an isolate encoding the phosducin-like protein (PhLP), which has 41% identity and 65% amino acid homology to phosducin. PhLP cDNA is expressed in all tissues screened by RNA blot-hybridization analysis and shows marked evolutionary conservation on Southern hybridization. We have identified four forms of PhLP cDNA varying only in their 5' ends, probably due to alternative splicing. This 5'-end variation generates two predicted forms of PhLP protein that differ by 79 aa at the NH2 terminus. Treatment of NG108-15 cells for 24 hr with concentrations of ethanol seen in actively drinking alcoholics (25-100 mM) causes up to a 3-fold increase in PhLP mRNA levels. Induction of PhLP by ethanol could account for at least some of the widespread alterations in signal transduction and G-protein function that are known to occur with chronic exposure to ethanol.

Norepinephrine metabolite in CSF correlates with ethanol consumption and heredity in humans

Previous studies showed that in cerebrospinal fluid (CSF) the concentration of 3-methoxy-4-hydroxy-phenylglycol (MHPG), the main metabolite of norepinephrine (NE), was positively correlated with blood ethanol concentrations in both healthy volunteers and in alcoholics. In this preliminary study we have extended those results by correlating MHPG concentrations in CSF with reported ethanol consumption and other indices of alcohol problems before and after consumption of 60-120 g of ethanol. MHPG in CSF correlates negatively with reported ethanol consumption, presence of first-degree relatives with alcohol problems, and presence of memory lapses, and correlates positively with age and the amount of ethanol consumed in the experiment. These results suggest that MHPG may indicate not only a high alcohol consumption but also a familial or genetic predisposition for alcoholism.

Neuroscience research: how has it contributed to our understanding of alcohol abuse and alcoholism? A review

Alcohol abuse and alcoholism are the greatest substance abuse problems in the United States today and contribute to numerous medical and social problems. To deal with many of these problems, an understanding of how alcohol acts on the brain is extremely important. Advances in neuroscience research have provided significant clues about where and how alcohol works on the brain. Alcohol clearly acts on membrane function, altering such processes as ion movements and neurotransmitter interactions with their receptors. Although these alcohol-induced alterations are presumed to relate to changes in behavior, this has not been clearly established. However, alcohol research is on the threshold of making a giant leap forward in our understanding the etiology of alcoholism.

Chronic ethanol exposure potentiates muscarinic receptor and alpha 2-adrenoceptor-mediated inhibition of cAMP accumulation in PC 12 cells

The effects of ethanol on receptor-mediated inhibition of cAMP production were investigated in PC 12 cells. The in vitro addition of ethanol enhanced N-ethylcarboxyadenosine (NECA)-stimulated cAMP production without altering the inhibitory action of carbachol or epinephrine. A 4 day exposure of PC 12 cells to ethanol decreased the stimulation of cAMP production by NECA, but increased the inhibition of NECA-stimulated cAMP production by carbachol and epinephrine.

Alterations of guanine nucleotide-binding proteins in post-mortem human brain in alcoholics

Qualitative and quantitative alterations of G proteins in membrane preparations from parietal and temporal cortex regions in post-mortem brains obtained from alcoholics and controls matched with respect to age and post-mortem delay were investigated by Western-blotting with polyclonal antibodies against specific G protein subunits and functional photoaffinity GTP binding. Quantitative immunoblotting showed that only Gs alpha (52 kDa species) in temporal cortex was significantly decreased (30%, P < 0.05) in alcoholics compared with controls. Moreover, ethanol-stimulated photoaffinity GTP labeling of Gs alpha and Gi/o alpha was decreased in alcoholics in both cortex regions. These results suggest that disturbances of G protein-mediated signal transduction may be involved in the pathophysiology of alcoholics.