Differences in platelet enzyme activity between alcoholics and nonalcoholics

Improvement of inpatient treatment of the alcoholic as a function of neurotransmitter restoration: a pilot study

We report results of a double-blind evaluation of the nutritional supplement SAAVE for facilitating improvement in a 30-day inpatient alcohol and drug rehabilitation center. SAAVE is uniquely designed to elevate levels of enkephalin(s), serotonin, catecholamines, and GABA, which are believed to be functionally deficient in alcoholics. Twenty-two patients were studied. The SAAVE patients, as compared to the control group (a) had a lower BUD (building up to drink) score, 1 vs 2; (b) required no PRN benzodiazepines, 0% vs 94%; (c) ceased tremoring at 72 h, as compared to 96 h; and (d) had no severe depression on the MMPI, in contrast to 24% of control group. These preliminary data suggest that SAAVE is a valuable adjunct to therapy by aiding the patient's physical adjustment to a detoxified state while facilitating a more positive response to behavioral therapy.

Cultured lymphocytes from alcoholic subjects have altered cAMP signal transduction

Previous work has shown that freshly isolated lymphocytes from alcoholic subjects show significantly reduced basal and adenosine receptor-stimulated cAMP levels. This decrease could be due to ethanol-induced cellular adaptation or to a genetic difference in the regulation of cAMP signal transduction. Therefore, we cultured human lymphocytes in defined medium without ethanol for 7-8 days and then examined differences in receptor-dependent cAMP accumulation between lymphocytes from alcoholic and nonalcoholic subjects. After four to six generations in culture without ethanol, lymphocytes from alcoholic subjects have significantly higher cAMP levels than do cells from nonalcoholic subjects. Thus, a difference in cAMP signal transduction is demonstrable in cells from alcoholic subjects grown without ethanol. We also found that cultured lymphocytes from both alcoholic and nonalcoholic subjects show a decrease in receptor-stimulated cAMP levels after exposure to 200 mM ethanol for 48 hr. To determine whether alcoholic subjects have increased sensitivity to ethanol, lymphocytes were exposed to only 100 mM ethanol for 24 hr. Under these conditions, receptor-dependent cAMP levels did not change in cells from nonalcoholic subjects. However, lymphocytes from alcoholic subjects showed a 39% decrease (P less than 0.003) in adenosine receptor-stimulated cAMP levels. Taken together, the results show that (i) chronic ethanol treatment in culture reproduces the suppression of cAMP levels found in circulating lymphocytes from alcoholic subjects and (ii) despite four to six cell divisions in culture without ethanol, lymphocytes from alcoholic subjects exhibit significantly increased adenosine receptor-dependent cAMP levels and increased sensitivity to chronic exposure to ethanol. These findings suggest that the suppression of cAMP levels observed in freshly isolated lymphocytes from alcoholic subjects results from both a direct effect of chronic exposure to ethanol and a genetic difference leading to altered cAMP signal transduction.

Ethanol differentially regulates G proteins in neural cells

Long-term incubation of clonal neural cell lines with ethanol differentially reduces the stimulation of cAMP accumulation by hormones and cholera toxin. In the NG108-15 neuroblastoma chi glioma hybrid cell line, this heterologous desensitization was associated with a 42% reduction in the expression of Gs alpha and no significant change in Gi alpha. By contrast, ethanol treatment of the parental neuroblastoma cell line N18TG2 caused little loss of response to hormones or cholera toxin and no significant change in Gs alpha or Gi alpha. Ethanol induced heterologous desensitization in N1E-115 neuroblastoma cells; however, this cell line showed a dose-dependent increase in Gi alpha and a later decrease in Gs alpha. Thus, ethanol causes heterologous desensitization of hormone-stimulated cAMP accumulation by different mechanisms in related neural cell lines.

Chronic ethanol causes heterologous desensitization of receptors by reducing alpha s messenger RNA

One of the biochemical results of ethanol exposure is a change in the amount of the intracellular second messenger cyclic AMP (cAMP) produced in response to receptor stimulation. In general, acute ethanol exposure increases the amount of cAMP produced on stimulation of receptors coupled to the enzyme adenylyl cyclase via the GTP-binding protein Gs, whereas chronic ethanol exposure has the opposite effect (results for receptors coupled via Gi have been more variable). We previously reported that adaptation to continuous ethanol exposure reduces receptor-stimulated cAMP production by 25-35% in a neuroblastoma cell line (NG108-15), and an even greater reduction of 75% was observed in lymphocytes taken from actively-drinking alcoholics. This reduction in receptor-stimulated cAMP levels was recently confirmed in platelets from alcoholics. None of these studies, however, determined whether more than one receptor coupled to adenylyl cyclase activity was affected in the same cell. Here we report that chronic ethanol exposure causes desensitization of heterologous receptors coupled to Gs as cAMP production mediated by prostaglandin E1 as well as by adenosine is reduced by approximately 30% in NG108-15 cells. We show that, after chronic ethanol exposure, the activity of the alpha subunit of Gs is decreased by 29%, the amount of alpha s protein is decreased by 38.5%, and alpha s messenger RNA is decreased by 30%. Thus, cellular adaptation to ethanol involves a reduction in alpha s mRNA and, as a consequence, reduced cAMP production by heterologous receptors coupled to Gs. Such changes in cAMP production may account for the tolerance and physical dependence on ethanol in alcoholism.

The relevance to clinical care of recent research in neurobiology

Progress continues to be made in clarifying neurobiological factors in alcoholism and other chemical dependencies. Research in animal behavioral genetics and human genetics has revealed substantial genetic predispositions for some cases of alcoholism. Studies of neurotransmitters suggest that some alcoholics may have antecedent deficiencies in one or more important neurochemical systems. Cocaine dependence is considered to be related to biphasic change in dopaminergic neurons and receptor systems. Condensation products such as salsolinol, tetrahydropapaveroline, and beta carbolines can alter alcoholic preference and motivate heavy ethanol consumption in animals. However, hypothesized theoretical mechanisms underlying such increased drinking with infusions of condensation products are unclear and may require revision. New pharmacological treatments stemming from advances in neurobiological research have been applied successfully to treatment of withdrawal states, but none have been demonstrated to be appropriate for long-term maintenance of abstinence.