Chronic Ethanol Inhibits Inositol Metabolism in Specific Brain Regions

Protein kinase C isoforms as a target for manic-like behaviors and oxidative stress in a dopaminergic animal model of mania

Bipolar disorder (BD) is a chronic condition characterized by severe mood swings alternating between episodes of mania and depression. Evidence indicates that protein kinase C (PKC) and oxidative stress are important therapeutic targets for BD. However, what PKC isoforms that are precisely involved in this effect are unknown. Therefore, we evaluated the effects of the intracerebroventricular (ICV) injection of PKC inhibitors (lithium (Li), tamoxifen (TMX), PKCα inhibitor (iPKCα), PKCγ inhibitor (iPKCγ), and PKCε inhibitor (iPKCε)) on the manic-like behaviors and oxidative stress parameters (4-hydroxy-2-nonenal (4-HNE), 8-isoprostane (8-ISO), carbonyl groups, 3-nitrotyrosine (3-NT), glutathione peroxidase (GPx) and glutathione reductase (GR)) in the brains of rats submitted to the model of mania induced by methamphetamine (m-AMPH). Animals received a single ICV infusion of artificial cerebrospinal fluid, Li, TMX, iPKCα, iPKCγ or iPKCε followed by an intraperitoneal injection of saline or m-AMPH before the behavioral analysis (open-field task). Oxidative stress was evaluated in the striatum, frontal cortex, and hippocampus. ICV injection of Li, TMX or iPKCε blocked the m-AMPH-induced increase in the manic-like behaviors - crossings, rearings, visits to the center, sniffing, and grooming. ICV infusion of iPKCα triggered a decrease in these behaviors induced by m-AMPH. Besides, the iPKCε administration significantly prevented the oxidative damage to lipids and proteins, as well as disturbances in the activity of antioxidant enzymes induced by m-AMPH. The findings of the present study suggest that PKCε isoform is strongly implied in the antimanic and antioxidant effects of Li, TMX, and the other PKC inhibitors in the model of mania.

Cerebellar Vermis Proteome of Chronic Alcoholic Individuals

BACKGROUND

Cerebellar changes are commonly associated with alcoholism and chronic alcohol consumption can produce profound impairments in motor functioning and various aspects of cognition. Although the mechanisms underlying alcohol-induced changes in the cerebellar vermis are poorly understood, observations in the alcoholic vermis are thought to be consequential to common alcohol-related factors, particularly thiamine deficiency.

METHODS

In the present study, we used a proteomics-based approach to compare protein expression profiles of the cerebellar vermis from human alcoholic individuals (both neurologically uncomplicated and alcoholic individuals complicated with liver cirrhosis) and healthy control brains. This article complements our recent studies performed on alcoholic prefrontal gray and white matter and splenium of the corpus callosum (CC).

RESULTS

Like the CC study, several liver cirrhosis-specific proteins were identified in the vermis, perhaps indicating the effects of liver dysfunction in this brain region. Among other protein expression changes observed are disturbances in the levels of thiamine-dependent enzymes. A derangement in energy metabolism perhaps related to thiamine deficiency seems to be important in both alcoholic groups, even where there are no clinical or pathological findings of Wernicke-Korsakoff syndrome.

CONCLUSIONS

These results suggest that clinically and pathologically uncomplicated alcoholic cases may not in fact be "uncomplicated," as at the proteome level we seem to be isolating the confounding effects of nutritional deficiencies and liver dysfunction and perhaps their role in alcohol-related vermis damage. Together, these results indicate that the alcohol-related pathology of the vermis is more multifactorial than other brain regions examined previously (prefrontal region and CC splenium).

The effects of chronic ethanol consumption during early pregnancy on conceptus health and uterine function in pigs

BACKGROUND

Maternal ethanol consumption impairs fetal health, but it is unclear if this occurs through direct actions on the conceptus or indirectly through effects on the uterus. The objective of this study was to determine if chronic ethanol consumption in swine would impair early embryonic and fetal health either through direct effects on the conceptus or indirect effects on the endometrium.

METHODS

Four experiments evaluated the effects of chronic ethanol consumption during early pregnancy. Female pigs were fed either 350 ml of 95% ethanol or an isocaloric amount of dextrose at 10 to 14-hr intervals beginning on day 10 after pubertal estrus and continuing until ovariohysterectomy 11 to 35 days after mating. At the second estrus, pigs were mated to a fertile boar that did not consume alcohol.

RESULTS

In experiment 1, ethanol consumption increased (p < 0.01) blood alcohol concentrations that peaked 2-3 hr after feeding. In experiment 2, ethanol was detectable in uterine flushings 2 hr after feeding on day 11 of pregnancy and was highly correlated (r = 0.989, p < 0.001) with blood alcohol concentration. In experiment 3, ethanol consumption did not affect endometrial phospholipase C activity on days 11 and 16 of pregnancy but decreased (p < 0.05) basal endometrial prostaglandin F(2alpha) production on day 16. However, ethanol consumption did not decrease the number of conceptuses on day 11 or conceptus DNA content on days 11 or 16. In experiment 4, ethanol consumption decreased (p < 0.05) fetal survival rate to 58% versus 85% in dextrose-fed controls on day 35 of pregnancy. For viable conceptuses, ethanol consumption reduced (p < 0.01) fetal weight, fetal crown-rump length, placental weight and volume of placental (chorio-allantoic + amniotic) fluid.

CONCLUSION

These results indicate that chronic ethanol consumption may impair conceptus health directly or indirectly through actions upon the endometrium. Thus, the pig may be a valuable experimental model for studies on the effects of maternal alcohol consumption on conceptus development.

Neuromodulatory role of the endocannabinoid signaling system in alcoholism: an overview

The current review evaluates the evidence that some of the pharmacological and behavioral effects of ethanol (EtOH), including EtOH-preferring behavior, may be mediated through the endocannabinoid signaling system. The recent advances in the understanding of the neurobiological basis of alcoholism suggest that the pharmacological and behavioral effects of EtOH are mediated through its action on neuronal signal transduction pathways and ligand-gated ion channels, receptor systems, and receptors that are coupled to G-proteins. The identification of a G-protein-coupled receptor, namely, the cannabinoid receptor (CB1 receptor) that was activated by Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the major psychoactive component of marijuana, led to the discovery of endogenous cannabinoid agonists. To date, two fatty acid derivatives identified to be arachidonylethanolamide (AEA) and 2-arachidonylglycerol (2-AG) have been isolated from both nervous and peripheral tissues. Both these compounds have been shown to mimic the pharmacological and behavioral effects of Delta(9)-THC. The involvement of the endocannabinoid signaling system in the development of tolerance to the drugs of abuse including EtOH has not been known until recently. Recent studies from our laboratory have demonstrated for the first time the down-regulation of CB1 receptor function and its signal transduction by chronic EtOH. The observed down-regulation of CB1 receptor binding and its signal transduction results from the persistent stimulation of the receptors by the endogenous CB1 receptor agonists, AEA and 2-AG, the synthesis of which has been found to be increased by chronic EtOH treatment. This enhanced formation of endocannabinoids may subsequently influence the release of neurotransmitters. It was found that the DBA/2 mice, known to avoid EtOH intake, have significantly reduced brain-CB1-receptor function consistent with other studies, where the CB1 receptor antagonist SR141716A has been shown to block voluntary EtOH intake in rodents. Similarly, activation of the CB1 receptor system promoted alcohol craving, suggesting a role for the CB1 receptor gene in excessive EtOH drinking behavior and development of alcoholism. Ongoing investigations may lead to the development of potential therapeutic strategies for the treatment of alcoholism.

Ethanol and lipid metabolic signaling

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Shivendra D. Shukla and Grace Y. Sun. The presentations were (1) Metabolic turnover of ethanol into cellular lipids and platelet activating factor, by Shivendra D. Shukla; (2) Ethanol action on the phospholipase A2 signaling pathways in astrocytes, by Grace Y. Sun; (3) Mechanisms of ethanol-induced perturbation of lipoprotein cholesterol transport, by W. Gibson Wood; (4) Transfer of an abnormal ethanol-induced phospholipid, phosphatidylethanol, between lipoproteins, by Markku J. Savolainen; (5) Phospholipase-d-mediated formation of phosphatidylethanol, by Christer Alling; and (6) Changes in phosphoinositide signaling after chronic ethanol treatment, by Jan B. Hoek.

Ethanol and lipid metabolic signaling

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Shivendra D. Shukla and Grace Y. Sun. The presentations were (1) Metabolic turnover of ethanol into cellular lipids and platelet activating factor, by Shivendra D. Shukla; (2) Ethanol action on the phospholipase A2 signaling pathways in astrocytes, by Grace Y. Sun; (3) Mechanisms of ethanol-induced perturbation of lipoprotein cholesterol transport, by W. Gibson Wood; (4) Transfer of an abnormal ethanol-induced phospholipid, phosphatidylethanol, between lipoproteins, by Markku J. Savolainen; (5) Phospholipase-d-mediated formation of phosphatidylethanol, by Christer Alling; and (6) Changes in phosphoinositide signaling after chronic ethanol treatment, by Jan B. Hoek.

The involvement of phospholipase A(2) in ethanol-induced gastric muscle contraction

To understand the underlying mechanism of ethanol in tonic contraction, the effect of ethanol on phospholipase A(2) and phospholipase C activities and the effects of phospholipase inhibitors on ethanol-induced contraction of cat gastric smooth muscle were tested. Circular muscle strips (2.0 x 0.2 cm) obtained from the fundus of cat stomach were used to measure isometric contraction. Ethanol elicited tonic contraction and activated phospholipase A(2) activity in a dose-dependent manner. Phospholipase A(2) inhibitors, manoalide (0.1--10 microM) and oleyloxyethyl phosphorylcholine (1--10 microM), significantly inhibited ethanol-induced contraction. Furthermore, 342 mM ethanol-induced contraction was significantly inhibited by cyclooxygenase inhibitors, ibuprofen (10--100 microM) and indomethacin (10--100 microM), but not by lipoxygenase inhibitors. On the other hand, phospholipase C inhibitors had no effect on ethanol-induced contraction, indicating that phospholipase C is not involved in ethanol-induced contraction. It is suggested from the above results that ethanol-induced contraction in cat gastric smooth muscle is, in part, mediated by phospholipase A(2) and cyclooxygenase pathways.

Neuronal signaling systems and ethanol dependence

In recent years there have been remarkable developments toward the understanding of the molecular and/or cellular changes in the neuronal second-messenger pathways during ethanol dependence. In general, it is believed that the cyclic adenosine 3',5'-monophosphate (cAMP) and the phosphoinositide (PI) signal-transduction pathways may be the intracellular targets that mediate the action of ethanol and ultimately contribute to the molecular events involved in the development of ethanol tolerance and dependence. Several laboratories have demonstrated that acute ethanol exposure increases, whereas protracted ethanol exposure decreases, agonist-stimulated adenylate cyclase activity in a variety of cell systems, including the rodent brain. Recent studies indicate that various postreceptor events of the cAMP signal transduction cascade (i.e., Gs protein, protein kinase A [PKA], and cAMP-responsive element binding protein [CREB]) in the rodent brain are also modulated by chronic ethanol exposure. The PI signal-transduction cascade represents another important second-messenger system that is modulated by both acute and chronic ethanol exposure in a variety of cell systems. It has been shown that protracted ethanol exposure significantly decreases phospholipase C (PLC) activity in the cerebral cortex of mice and rats. The decreased PLC activity during chronic ethanol exposure may be caused by a decrease in the protein levels of the PLC-beta 1 isozyme but not of PLC-delta 1 or PLC-gamma 1 isozymes in the rat cerebral cortex. Protein kinase C (PKC), which is a key step in the PI-signaling cascade, has been shown to be altered in a variety of cell systems by acute or chronic ethanol exposure. It appears from the literature that PKC plays an important role in the modulation of the function of various neurotransmitter receptors (e.g., gamma-aminobutyrate type A [GABAA], N-methyl-D-aspartate [NMDA], serotonin2A [5-HT2A], and 5-HT2C, and muscarinic [m1] receptors) resulting from ethanol exposure. The findings described in this review article indicate that neuronal-signaling proteins represent a molecular locus for the action of ethanol and are possibly involved in the neuro-adaptational mechanisms to protracted ethanol exposure. These findings support the notion that alterations in the cAMP and the PI-signaling cascades during chronic ethanol exposure could be the critical molecular events associated with the development of ethanol dependence.