PARP inhibition in vivo blocks alcohol-induced brain neurodegeneration and neuroinflammatory cytosolic phospholipase A2 elevations

Chronic alcoholism promotes brain damage that impairs memory and cognition. High binge alcohol levels in adult rats also cause substantial neurodamage to memory-linked regions, notably, the hippocampus (HC) and entorhinal cortex (ECX). Concurrent with neurodegeneration, alcohol elevates poly (ADP-ribose) polymerase-1 (PARP-1) and cytosolic phospholipase A2 (cPLA2) levels. PARP-1 triggers necrosis when excessively activated, while cPLA2 liberates neuroinflammatory ω-6 arachidonic acid. Inhibitors of PARP exert in vitro neuroprotection while suppressing cPLA2 elevations in alcohol-treated HC-ECX slice cultures. Here, we examined in vivo neuroprotection and cPLA2 suppression by the PARP inhibitor, veliparib, in a recognized adult rat model of alcohol-binging. Adult male rats received Vanilla Ensure containing alcohol (ethanol, 7.1 ± 0.3 g/kg/day), or control (dextrose) ± veliparib (25 mg/kg/day), by gavage 3x daily for 4 days. Rats were sacrificed on the morning after the final binge. HC and ECX neurodegeneration was assessed in fixed sections by Fluoro-Jade B (FJB) staining. Dorsal HC, ventral HC, and ECX cPLA2 levels were quantified by immunoblotting. Like other studies using this model, alcohol binges elevated FJB staining in the HC (dentate gyrus) and ECX, indicating neurodegeneration. Veliparib co-treatment significantly reduced dentate gyrus and ECX neurodegeneration by 79% and 66%, respectively. Alcohol binges increased cPLA2 in the ventral HC by 34% and ECX by 72%, which veliparib co-treatment largely prevented. Dorsal HC cPLA2 levels remained unaffected by alcohol binges, consistent with negligible FJB staining in this brain region. These in vivo results support an emerging key role for PARP in binge alcohol-induced neurodegeneration and cPLA2-related neuroinflammation.

Ethanol causes and lithium prevents neuroapoptosis and suppression of pERK in the infant mouse brain

Transient exposure of immature animals during the brain growth spurt period to ethanol triggers neuroapoptosis in the developing brain. Here we report that lithium, when administered in a single, well-tolerated dose to infant mice, suppresses spontaneous neuroapoptosis that occurs naturally in the developing brain, and prevents ethanol from triggering neuroapoptosis. To explore lithium's mechanism of action, we focused on kinase signaling systems (ERK, Akt, JNK) that are believed to play a regulatory role in cell survival, and found that very rapidly after ethanol administration there is a suppression of ERK phosphorylation, and that lithium stimulates ERK phosphorylation and prevents ethanol from suppressing this phosphorylation process. Ethanol also suppressed pAKT, but lithium did not counteract this effect. We also found that ethanol activates the JNK system, but this cannot explain the neurotoxic action of ethanol, because JNK activation did not occur in the same neuronal populations that are killed by ethanol.

24-Hour rhythm in gene expression of nitric oxide synthase and heme-peroxidase in anterior pituitary of ethanol-fed rats

Chronic exposure of rats to ethanol results in significant changes in pituitary hormone secretion. However, identification of the site(s) and mechanism of action of ethanol to induce these effects remains elusive. Free radical damage at the adenohypophyseal level may play a role in the decline in serum gonadotropin levels in ethanol-fed rats. Since 24-h changes in redox state occurred, we analyzed the 24-h changes in pituitary gene expression of the prooxidant enzymes nitric oxide synthase (NOS) 1 and 2, and of heme oxygenase-1 (HO-1) enzyme, and in plasma NO(2)(-) and NO(3)(-) (NO(x)) levels, in ethanol and control rats. Male rats, 35-day-old, received a liquid diet for 4 weeks. The ethanol-fed group received a similar diet to controls except for that maltose was isocalorically replaced by ethanol. Animals were killed at six time intervals during a 24-h cycle. Anterior pituitary mRNA levels encoding NOS1, NOS2 and HO-1 were measured by real-time PCR analysis. Plasma NO(x) concentration was determined by the Griess reaction. Ethanol feeding of prepubertal rats changed significantly the 24-h pattern of expression of NOS1, NOS2 and HO-1 in the adenohypophysis and augmented NOS2 and HO-1 mRNA levels. Peak values for the three enzymes in ethanol-fed rats occurred at the beginning of the scotophase (i.e., at 21:00 h). Ethanol feeding augmented mean values plasma NO(x) levels with a maximum at 13:00 h while in controls a biphasic pattern was observed, with peaks at 09:00 h and 17:00-21:00 h. One of the mechanisms by which ethanol augments oxidative damage in the adenohypophysis may include overproduction of nitric oxide and carbon monoxide.

Role of endocannabinoids in alcohol consumption and intoxication: studies of mice lacking fatty acid amide hydrolase

Endocannabinoid signaling plays the important role in regulation of ethanol intake. Fatty acid amide hydrolase (FAAH) is a key membrane protein for metabolism of endocannabinoids, including anandamide, and blockade of FAAH increases the level of anandamide in the brain. To determine if FAAH regulates ethanol consumption, we studied mutant mice with deletion of the FAAH gene. Null mutant mice showed higher preference for alcohol and voluntarily consumed more alcohol than wild-type littermates. There was no significant difference in consumption of sweet or bitter solutions. To determine the specificity of FAAH for ethanol intake, we studied additional ethanol-related behaviors. There were no differences between null mutant and wild-type mice in severity of ethanol-induced acute withdrawal, conditioned taste aversion to alcohol, conditioned place preference, or sensitivity to hypnotic effect of ethanol. However, null mutant mice showed shorter duration of loss of righting reflex induced by low doses of ethanol (3.2 and 3.4 g/kg) and faster recovery from motor incoordination induced by ethanol. All three behavioral phenotypes (increased preference for ethanol, decreased sensitivity to ethanol-induced sedation, and faster recovery from ethanol-induced motor incoordination) seen in mutant mice were reproduced in wild-type mice by injection of a specific inhibitor of FAAH activity--URB597. These data suggest that increased endocannabinoid signaling increased ethanol consumption owing to decreased acute ethanol intoxication.

Antagonism of ethanol ataxia by intracerebellar nicotine: possible modulation by mouse cerebellar nitric oxide and cGMP

We have reported previously that intracerebellar nicotine attenuates ethanol ataxia via nicotinic-cholinergic receptors. We report now that attenuation of ethanol ataxia by intracerebellar nicotine is modulated by cerebellar nitric oxide-guanylyl cyclase (GC) messenger system. Intracerebellar microinfusion of SNP (sodium nitroprusside, a nitric oxide donor; 15, 30, and 60 pg) and SMT (S-methylisothiourea; 70, 140, and 280 fg; an inhibitor of inducible nitric oxide synthase), significantly enhanced and reduced, respectively, intracerebellar nicotine-induced attenuation of ethanol ataxia in a dose-related manner. Similarly, intracerebellar isoliquiritigenin (an activator of GC; 1, 2, and 4 pg) and ODQ (1H [1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one, an inhibitor of GC; 375, 750, and 1500 fg), significantly enhanced and reduced, respectively, intracerebellar nicotine-induced attenuation of ethanol ataxia in a dose-related fashion. These results suggest that the functional interaction between nicotine and ethanol may involve modulation by cerebellar nitric oxide and cGMP. Intracerebellar microinfusion of isoliquiritigenin (4, 8, and 16 pg) in the absence of nicotine significantly attenuated ethanol ataxia dose-dependently indicating a tonic involvement of cGMP in ethanol ataxia. Finally, intracerebellar nicotine (5 ng) significantly increased and ethanol 2 g/kg i.p. decreased levels of total cerebellar nitrite+nitrate (NOx) which were functionally correlated with ethanol ataxia and its attenuation by intracerebellar nicotine. The ethanol-induced decrease in NOx was significantly antagonized by intracerebellar nicotine. The NOx data further supported an involvement of nitric oxide in the behavioral interaction between nicotine and ethanol. Overall, the results of the present investigation demonstrate a functional correlation between cerebellar nitric oxide messenger system and the behavioral interaction between nicotine and ethanol.

Ethanol withdrawal-associated allodynia and hyperalgesia: age-dependent regulation by protein kinase C epsilon and gamma isoenzymes

Ethanol (EtOH) withdrawal increases sensitivity to painful stimuli in adult rats. In this study, withdrawal from a single, acute administration of EtOH dose-dependently produced mechanical allodynia and thermal hyperalgesia in postnatal day 7 (P7) rats. In contrast, P21 rats exhibited earlier and more prolonged mechanical allodynia but not thermal hyperalgesia. For both P7 and P21 rats, blood and spinal cord EtOH levels peaked at 30 minutes after administration, with P7 rats achieving overall higher spinal cord concentrations. Protein kinase C (PKC) has been implicated in mediating pain responses. Inhibitory PKC- and gamma-specific peptides attenuated mechanical allodynia and thermal hyperalgesia in P7 rats, whereas only the PKCgamma inhibitor prevented mechanical allodynia in P21 rats. Immunoreactive PKC in dorsal root ganglion and PKCgamma in lumbar spinal cord increased at 6 hours after EtOH administration in P7 rats. In P21 rats, the density of PKC immunoreactivity remained unchanged, whereas the density of PKCgamma immunoreactivity increased and translocation occurred. These studies demonstrate developmental differences in neonatal nociceptive responses after withdrawal from acute EtOH and implicate a role for specific PKC isozymes in EtOH withdrawal-associated allodynia and hyperalgesia.

PERSPECTIVE

This study examines age-specific nociceptive responses after ethanol exposure by using 2 different ages of rats. The results suggest that ethanol age-dependently alters sensitivity to mechanical and thermal stimuli via specific protein kinase C isozymes. These results begin to ascertain the mechanisms that produce abnormal pain after alcohol exposure.

DBH*444G/A polymorphism of the dopamine-β-hydroxylase gene is associated with alcoholism but not with severe alcohol withdrawal symptoms

As the enzyme dopamine-beta-hydroxylase (DbetaH) converts dopamine to norepinephrine and both transmitters seem to be involved in the pathology of alcoholism and severe alcohol withdrawal symptoms, the gene encoding DbetaH (DBH) was applied to explore the genetic background of alcoholism and severe withdrawal symptoms. 102 healthy control subjects and 208 alcoholics, including 97 patients with a history of mild withdrawal symptoms, 57 with a history of alcohol withdrawal seizure (AWS) and 82 with a history of delirium tremens (DT) were genotyped for the DBH*444G/A polymorphism revealing a significantly elevated frequency of genotypes carrying the A-allele (p = 0.02; after Bonferroni adjustment for multiple tests) in alcoholics compared to healthy controls. Frequencies of alleles and genotypes of individuals with mild withdrawal symptoms did not differ significantly from those of patients with DT or AWS.

Role of caspase-3 in ethanol-induced developmental neurodegeneration

Acute, transient exposure to ethanol causes a widespread pattern of caspase-3 activation and neuroapoptosis in the developing rodent brain. To determine whether caspase-3 activation is an essential step in ethanol-induced developmental neuroapoptosis, we treated homozygous caspase-3 knockout mice or wild-type mice on postnatal day 7 with an apoptosis-inducing dose of ethanol and examined the brains at appropriate survival times for evidence of apoptotic neurodegeneration. In caspase-3 knockout mice, the cell death process evolved more slowly than in wild-type mice, and morphological changes observed were not those typically associated with apoptosis. However, neuronal cell counts performed 2 weeks post-treatment revealed that the extent of neuron loss was similar in wild-type and caspase-3-deficient mice. We conclude that absence of functional caspase-3 alters the time course and morphological characteristics of the neurodegenerative process but does not prevent ethanol-induced neuron death.

Acute administration of alcohol modulates pyroglutamyl amino peptidase II activity and mRNA levels in rat limbic regions

Released TRH is inactivated by an ectopeptidase, pyroglutamyl aminopeptidase II (PPII). PPII expression and activity are stringently regulated in adenohypophysis, and in rat brain, during kindling stimulation that activates TRHergic neurons. To gain further insight into the possible regulation of PPII, we studied the effect of an acute intraperitoneal ethanol administration that affects TRH content and expression. PPII activity was determined by a fluorometric assay and PPII mRNA levels by semi-quantitative RT-PCR. Activity decreased in frontal cortex 1 h after ethanol injection and, after 6 h, in hippocampus, amygdala and n. accumbens. PPII mRNA levels decreased at 30 and 60 min in frontal cortex and n. accumbens while increased at longer times in these regions and, in hippocampus and hypothalamus. NMDA and GABA(A) receptors' agonists and antagonists were tested at 1 h (+/-ethanol) on PPII activity and mRNA levels, as well as on TRH content and its mRNA. In n. accumbens, PPII mRNA levels decreased by ethanol, MK-801, and muscimol while picrotoxin or NMDA reversed ethanol's inhibition. Ethanol decreased TRH content and increased TRH mRNA levels as MK-801 or muscimol did (NMDA or picrotoxin reverted the effect of ethanol). In frontal cortex, PPII activity was inhibited by ethanol, NMDA and MK-801 with ethanol; its mRNA levels were reduced by ethanol, MK-801 and muscimol (NMDA and picrotoxin reverted ethanol's inhibition). These results show that PPII expression and activity can be regulated in conditions where TRHergic neurons are modulated. Effects of ethanol on PPII mRNA levels as well as those of TRH and its mRNA may involve GABA or NMDA receptors in n. accumbens. Changes observed in frontal cortex suggest combined effects with stress. The response was region-specific in magnitude, tendency and kinetics. These results give further support for brain PPII regulation in conditions that modulate the activity of TRHergic neurons.

Ethanol-induced iNOS and COX-2 expression in cultured astrocytes via NF-κB

The CNS is particularly susceptible to the effects of alcohol and toxicity. Astrocytes are immunoactive cells, and the activation of these cells is associated with several neurodegenerative disorders. By using cultured cortical astrocytes, we show that a short ethanol treatment (100 mM) is able to up-regulate both cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS) expression, and that these effects are regulated via nuclear factor kappa B (NF-kappa B) as revealed by the inhibition of NF-kappa B activation with pyrrolidine dithiocarbamate (PDTC) or BAY 11-7082. These results suggest that ethanol is able to induce inflammatory mediators in astrocytes through the NF-kappa B activation.

Ethanol-induced alteration in N-methyl-D-aspartate receptor 2A C-terminus and protein kinase C activity in rat brain

Ethanol is a potent inhibitor of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor. In the present study, expression of NR2A and its phosphorylation status were investigated in adult rat cerebral cortex and cerebellum, using an experimental paradigm of in vivo chronic ethanol exposure. In addition, PKC activity was measured in both cytosol and membrane fraction of cerebral cortex and cerebellum using Histone III S as substrate. Western blot analysis using NR2A antibody showed an increased immunoreactivity in cerebral cortex and no immunoreactivity in cerebellum of alcohol-treated rats. Furthermore, PKC activity was increased in both membrane and cytosolic fraction of alcohol-treated rat cerebellum, whereas PKC activity in cerebral cortex was found to be decreased in membrane fraction with no appreciable change in cytosolic fraction. In vitro phosphorylation study showed hypophosphorylation in ethanol-treated cerebral cortex and cerebellum. Our current findings imply that the truncation of NR2A subunit upon alcohol administration in cerebellum probably contributes to altered NMDA receptor function and cerebellar atrophy and motor incoordination in alcoholic rats.

Acute ethanol affects phosphorylation state of the NMDA receptor complex: implication of tyrosine phosphatases and protein kinase A

Phosphorylation has been shown to regulate N-methyl-D-aspartic acid receptor (NMDAR) function. The inhibitory effect of ethanol on NMDAR function could be due, at least in part, to a change in NMDAR phosphorylation states. In order to investigate the effect of ethanol on phosphorylation of NR1 and NR2 subunits, NMDAR complexes were immunoprecipitated from cortical slices pre-exposed to ethanol. Acute ethanol, 100 and 200 mM, significantly decreased the tyrosine phosphorylation of NR2 subunits (Tyr-NR2). Treatment with a tyrosine phosphatase inhibitor reduced the inhibition of Tyr-NR2 phosphorylation caused by 100 mM ethanol. This suggests an involvement of tyrosine phosphatases in ethanol-induced inhibition of Tyr-NR2 phosphorylation. Slices pre-exposed to 100 and 200 mM ethanol exhibited a significant increase in the phosphorylation of NR1 by PKA at serine 897 (Ser897-NR1), which was blocked by a PKA inhibitor. Moreover, at 200 mM, ethanol produced a significant increase in PKA activity. Together, these results indicate that ethanol may increase Ser897-NR1 phosphorylation by activating PKA. However, ethanol did not affect phosphorylation of NR1 subunits by PKC at serine 896. We conclude that ethanol has the ability to modulate phosphorylation of both NR2 and NR1 subunits and these effects appear to implicate tyrosine phosphatases and PKA, respectively.

Effects of prenatal exposure to ethanol on the cyclin-dependent kinase system in the developing rat cerebellum

Prenatal exposure to ethanol inhibits neurogenesis in the developing cerebellum. Cyclin-dependent kinases (CDKs) are a family of protein kinases that play multiple roles in the regulation of cell proliferation, differentiation and survival. The activity of CDKs is positively regulated by CDK activators, cyclins, and negatively regulated by CDK inhibitors (CDKIs). We hypothesize that impaired cerebellar development induced by gestational ethanol exposure is mediated by disruption of the CDK system. Pregnant rats were fed ad libitum with an ethanol-containing liquid diet (Et) or pair-fed an isocaloric control diet (Ct). Cerebella were collected from pups (postnatal day (P) 0 through P21) and examined for CDK, cyclin, or CDKI expression using a quantitative immunoblotting procedure. In Ct-treated rats, the expression of CDK2 and its activator, cyclin A, paralleled the pattern of granule cell proliferation. Prenatal ethanol exposure produced a significant down-regulation of CDK2/cyclin A expression. Although the amounts of CDK4/CDK6 and their activator, cyclin D2, did not oscillate during postnatal development, their expression in Et-treated pups was significantly (P<0.05) higher than in controls. The expression of a CDK inhibitor, p27(Kip), was inversely correlated to proliferation of cerebellar granule progenitors. Prenatal ethanol exposure caused the down-regulation of p27(Kip) between P0 and P21. Thus, prenatal exposure to ethanol disturbed the expression of cell cycle machineries in the postnatal cerebellum. This may account for the teratogenic effects of ethanol on the developing cerebellum.

Changes in Ca2+-dependent protein kinase C isoforms induced by chronic ethanol treatment in mice

Protein kinase C (PKC) has been shown to regulate ethanol sensitivity. The goal of the present study was to ascertain whether chronic in vivo ethanol treatment could affect PKC isoforms in the mouse brain. We measured the protein level of membrane-bound PKC isoforms following chronic ethanol treatment using Western blotting. The protein level of membrane-bound PKCalpha and PKCgamma isoforms, which are defined as Ca2+-dependent PKC isoforms (cPKC), in the limbic forebrain during chronic ethanol treatment was significantly increased, whereas the levels of both were significantly decreased in the frontal cortex. By contrast, there was no change in PKCepsilon, a Ca2+-independent PKC isoform, in both areas. These findings suggest that the change in membrane-bound cPKC in the limbic forebrain and frontal cortex may play substantial roles for the development of ethanol dependence.

Arylsulfatase A levels in patients with chronic alcoholism

BACKGROUND

The goal of this study was to find the association between low arylsulfatase A (ASA) activity and psychiatric disorders in chronic alcoholic patients.

METHODS

The study was carried out in 30 chronic alcoholic patients (27 male, 3 female); age range was 25-65 years. There were 20 normal controls (18 males, 2 females), and age range was 24-67 years. ASA and routine aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity laboratory tests were measured in blood serum from all patients and control subjects.

RESULTS

Alcoholic patients with psychiatric disorders have ASA average values of 68.25 nmol/mL/4 h. This is less than averages found in the alcoholics without psychiatric disorders group (82.48 nmol/mL/4 h) and the control group (90.8 nmol/mL/4 h). There were no statistically significant differences among the three groups studied. Alcoholic subjects with elevated activity of AST and ALT (n = 10) have ASA activity average values of 134.82 nmol/mL/4 h), which is 48.8% higher than the control group (90.6 nmol/mL/4 h). These means show statistically significant differences (p <0.05).

CONCLUSIONS

Results indicate an association between low serum ASA activity and alcoholism. The appearance of psychiatric manifestations could be related to the low activity of this enzyme in chronic alcoholic patients. Alcoholic patients with elevated enzyme activity of AST and ALT in sera also have elevated sera arylsulfatase A (ASA) activity. We consider that these findings may be useful for evaluating the psychiatric state as a prognosis in chronic alcoholic patients, and should be a routine laboratory test in alcoholic patients.