Indomethacin restores loss of hippocampal neurogenesis and cholinergic innervation and reduces innate immune expression and reversal learning deficits in adult male and female rats following adolescent ethanol exposure

BACKGROUND

Adolescent intermittent ethanol (AIE) exposure causes long-term changes in the brain and behavior of adult male rodents, including persistent induction of innate immune pathways, reductions in hippocampal neurogenic and forebrain cholinergic neuronal markers, and reversal learning deficits. The current study tests the hypothesis that proinflammatory induction mediates AIE-induced (1) loss of adult neurogenesis (i.e., doublecortin (DCX) expressing immature neurons), (2) reductions in forebrain and hippocampal cholinergic markers, and (3) reversal learning deficits.

METHODS

Male and female rats underwent AIE (5.0 g/kg/day ethanol or water, i.g., 2 day-on/2 day-off from postnatal day (PND) 25-54), followed by a 2-week regimen of the anti-inflammatory compound indomethacin (4.0 g/kg/day, PND 56-69) or vehicle, after which one cohort was euthanized for immunohistochemical markers (PND 70) and the second underwent the Morris water maze to assess reversal learning.

RESULTS

AIE reduced adult (PND 70) DCX+ immunoreactivity (IR) and increased hippocampal expression of the innate immune signal's high-mobility group box protein 1 (HMGB1 + IR) and cyclooxygenase-2 (COX-2 + IR) in adult male and female rats. AIE also reduced choline acetyltransferase (ChAT+IR) in the basal forebrain and co-labeling of hippocampal vesicular acetylcholine transporter (VAChT+) cholinergic terminals on DCX + IR neurons. Indomethacin treatment after AIE restored molecular endpoints to control levels and rescued AIE-induced reversal learning deficits in the Morris water maze in both sexes. Of note, indomethacin produced several adverse effects selectively in control conditions, highlighting the uniquely beneficial effect of indomethacin in AIE rats.

CONCLUSIONS

These data suggest that in males and females, (1) AIE persistent neuroimmune induction mediates both the loss of adult hippocampal DCX and loss of basal forebrain cholinergic neurons and their innervation to hippocampal targets, and (2) anti-inflammatory indomethacin treatment following AIE that restores these persistent molecular pathologies also restores spatial reversal learning deficits.

Galantamine prevents and reverses neuroimmune induction and loss of adult hippocampal neurogenesis following adolescent alcohol exposure

BACKGROUND

Binge ethanol exposure during adolescence reduces hippocampal neurogenesis, a reduction which persists throughout adulthood despite abstinence. This loss of neurogenesis, indicated by reduced doublecortin+ immunoreactivity (DCX+IR), is paralleled by an increase in hippocampal proinflammatory signaling cascades. As galantamine, a cholinesterase inhibitor, has anti-inflammatory actions, we tested the hypothesis that galantamine would prevent (study 1) or restore (study 2) AIE induction of proinflammatory signals within the hippocampus as well as AIE-induced loss of hippocampal neurogenesis.

METHODS

Galantamine (4 mg/kg) or vehicle (saline) was administered to Wistar rats during adolescent intermittent ethanol (AIE; 5.0 g/kg ethanol, 2 days on/2 days off, postnatal day [P] 25-54) (study 1, prevention) or after AIE during abstinent maturation to adulthood (study 2, restoration).

RESULTS

Results indicate AIE reduced DCX+IR and induced cleaved caspase3 (Casp3) in DCX-expressing immature neurons. Excitingly, AIE induction of activated Casp3 in DCX-expressing neurons is both prevented and reversed by galantamine treatment, which also resulted in prevention and restoration of neurogenesis (DCX+IR). Similarly, galantamine prevented and/or reversed AIE induction of proinflammatory markers, including the chemokine (C-C motif) ligand 2 (CCL2), cyclooxygenase-2 (COX-2), and high mobility group box 1 (HMGB1) protein, suggesting that AIE induction of proinflammatory signaling mediates both cell death cascades and hippocampal neurogenesis. Interestingly, galantamine treatment increased Ki67+IR generally as well as increased pan-Trk expression specifically in AIE-treated rats but failed to reverse AIE induction of NADPH-oxidase (gp91phox).

CONCLUSIONS

Collectively, our studies suggest that (1) loss of neurogenesis after AIE is mediated by persistent induction of proinflammatory cascades which drive activation of cell death machinery in immature neurons, and (2) galantamine can prevent and restore AIE disruptions in the hippocampal environmental milieu to then prevent and restore AIE-mediated loss of neurogenesis.

Adolescent Alcohol Exposure Produces Protracted Cognitive-Behavioral Impairments in Adult Male and Female Rats

Binge drinking is common in adolescence. Rodent studies modeling adolescent binge drinking find persistent effects on the brain's physiology, including increased expression of neuroimmune genes, impaired neurogenesis, and changes in behavioral flexibility. This study used females and males to investigate the effects of adolescent intermittent ethanol (AIE) on a battery of behaviors assessing spatial navigation using a radial arm water maze, working memory using the Hebb-Williams maze, non-spatial long-term memory using novel object recognition, and dominance using a tube dominance test. Results indicate that AIE impairs adult acquisition in spatial navigational learning with deficits predominantly driven by females. Surprisingly, AIE slowed the transition from random to serial search strategies in both sexes, suggesting AIE impairs flexibility in problem-solving processing. In the Hebb-Williams maze working memory task, adult AIE rats exhibited deficits in problem solving, resulting in more errors across the 12 maze configurations, independent of sex. Conversely, AIE decreased dominance behaviors in female rats, and at 7 months post-alcohol, female AIE rats continued to exhibit deficits in novel object recognition. These results suggest that cognitive-behavioral alterations after adolescent binge drinking persist well into middle age, despite abstinence. Future studies should focus on intervening treatment strategies in both females and males.

The Cortical Neuroimmune Regulator TANK Affects Emotional Processing and Enhances Alcohol Drinking: A Translational Study

Alcohol abuse is a major public health problem worldwide. Understanding the molecular mechanisms that control regular drinking may help to reduce hazards of alcohol consumption. While immunological mechanisms have been related to alcohol drinking, most studies reported changes in immune function that are secondary to alcohol use. In this report, we analyse how the gene "TRAF family member-associated NF-κB activator" (TANK) affects alcohol drinking behavior. Based on our recent discovery in a large GWAS dataset that suggested an association of TANK, SNP rs197273, with alcohol drinking, we report that SNP rs197273 in TANK is associated both with gene expression (P = 1.16 × 10-19) and regional methylation (P = 5.90 × 10-25). A tank knock out mouse model suggests a role of TANK in alcohol drinking, anxiety-related behavior, as well as alcohol exposure induced activation of insular cortex NF-κB. Functional and structural neuroimaging studies among up to 1896 adolescents reveal that TANK is involved in the control of brain activity in areas of aversive interoceptive processing, including the insular cortex, but not in areas related to reinforcement, reward processing or impulsiveness. Our findings suggest that the cortical neuroimmune regulator TANK is associated with enhanced aversive emotional processing that better protects from the establishment of alcohol drinking behavior.

Automatic cortical thickness analysis on rodent brain

Localized difference in the cortex is one of the most useful morphometric traits in human and animal brain studies. There are many tools and methods already developed to automatically measure and analyze cortical thickness for the human brain. However, these tools cannot be directly applied to rodent brains due to the different scales; even adult rodent brains are 50 to 100 times smaller than humans. This paper describes an algorithm for automatically measuring the cortical thickness of mouse and rat brains. The algorithm consists of three steps: segmentation, thickness measurement, and statistical analysis among experimental groups. The segmentation step provides the neocortex separation from other brain structures and thus is a preprocessing step for the thickness measurement. In the thickness measurement step, the thickness is computed by solving a Laplacian PDE and a transport equation. The Laplacian PDE first creates streamlines as an analogy of cortical columns; the transport equation computes the length of the streamlines. The result is stored as a thickness map over the neocortex surface. For the statistical analysis, it is important to sample thickness at corresponding points. This is achieved by the particle correspondence algorithm which minimizes entropy between dynamically moving sample points called particles. Since the computational cost of the correspondence algorithm may limit the number of corresponding points, we use thin-plate spline based interpolation to increase the number of corresponding sample points. As a driving application, we measured the thickness difference to assess the effects of adolescent intermittent ethanol exposure that persist into adulthood and performed t-test between the control and exposed rat groups. We found significantly differing regions in both hemispheres.

Automatic Skull-stripping of Rat MRI/DTI Scans and Atlas Building

3D Magnetic Resonance (MR) and Diffusion Tensor Imaging (DTI) have become important noninvasive tools for the study of animal models of brain development and neuropathologies. Fully automated analysis methods adapted to rodent scale for these images will allow high-throughput studies. A fundamental first step for most quantitative analysis algorithms is skull-stripping, which refers to the segmentation of the image into two tissue categories, brain and non-brain. In this manuscript, we present a fully automatic skull-stripping algorithm in an atlas-based manner. We also demonstrate how to either modify an external atlas or to build an atlas from the population itself to present a self-contained approach. We applied our method to three datasets of rat brain scans, at different ages (PND5, PND14 and adult), different study groups (control, ethanol exposed), as well as different image acquisition parameters. We validated our method by comparing the automated skull-strip results to manual delineations performed by our expert, which showed a discrepancy of less than a single voxel on average. We thus demonstrate that our algorithm can robustly and accurately perform the skull-stripping within one voxel of the manual delineation, and in a fraction of the time it takes a human expert.

Induction of innate immune gene expression cascades in brain slice cultures by ethanol: key role of NF-κB and proinflammatory cytokines

BACKGROUND

Postmortem human alcoholic brain has increased expression of proinflammatory cytokines (He and Crews, 2007). Nuclear factor kappaB (NF-kappaB) is a transcription factor known to induce proinflammatory cytokine expression. Ethanol exposure increases NF-kappaB-DNA binding in rat brain (Crews et al., 2006) and in brain slice cultures in vitro (Zou and Crews, 2006). Using hippocampal-entorhinal cortex (HEC) brain slice cultures, we explored the effect of ethanol on NF-kappaB-DNA binding, proinflammatory gene expression, and sensitivity to glutamate neurotoxicity.

METHODS

The HEC brain slice cultures are prepared from rats on P7 and used after 2 weeks in culture. NF-kappaB-DNA binding is determined by EMSA, NF-kappaB subunit-DNA binding by ELISA and mRNA by RT-PCR. Multiple antibody immunohistochemistry and confocal microscopy are used to characterize cell types expressing ethanol-induced genes.

RESULTS

Ethanol treatment results in a progressive increase in NF-kappaB-DNA binding that includes large increases in NF-kappaB subunit p50 protein-DNA binding. The expression of NF-kappaB proinflammatory target genes progressively increased with time of ethanol treatment. Ethanol induces proinflammatory cytokines TNFalpha, MCP-1, and IL-1beta, proinflammatory proteases TACE, and tissue plasminogen activator (tPA) as well as inducible nitric oxide synthase. Blockade of NF-kappaB by using NF-kappaB p65 siRNA and BHT reduces ethanol induction of proinflammatory genes. Neutralizing antibody to proinflammatory cytokine TNFalpha reduces ethanol induction of proinflammatory genes, suggesting cytokine propagation of proinflammatory gene induction. Furthermore, neutralizing antibodies to proinflammatory cytokines and protease tPA inhibitors blunt ethanol sensitization to glutamate neurotoxicity.

CONCLUSIONS

These findings indicate that ethanol treatment increases NF-kappaB-DNA binding and proinflammatory gene expression in brain slices. Ethanol-induced innate immune proinflammatory gene induction alters neurotransmission and likely contributes to alcoholic neurodegeneration.

Adolescent cortical development: a critical period of vulnerability for addiction

Cortical growth and remodeling continues from birth through youth and adolescence to stable adult levels changing slowly into senescence. There are critical periods of cortical development when specific experiences drive major synaptic rearrangements and learning that only occur during the critical period. For example, visual cortex is characterized by a critical period of plasticity involved in establishing visual acuity. Adolescence is defined by characteristic behaviors that include high levels of risk taking, exploration, novelty and sensation seeking, social interaction and play behaviors. In addition, adolescence is the final period of development of the adult during which talents, reasoning and complex adult behaviors mature. This maturation of behaviors corresponds with periods of marked changes in neurogenesis, cortical synaptic remodeling, neurotransmitter receptors and transporters, as well as major changes in hormones. Frontal cortical development is later in adolescence and likely contributes to refinement of reasoning, goal and priority setting, impulse control and evaluating long and short term rewards. Adolescent humans have high levels of binge drinking and experimentation with other drugs. This review presents findings supporting adolescence as a critical period of cortical development important for establishing life long adult characteristics that are disrupted by alcohol and drug use.

BHT blocks NF-kappaB activation and ethanol-induced brain damage

BACKGROUND

Binge ethanol administration causes corticolimbic brain damage that models alcoholic neurodegeneration. The mechanism of binge ethanol-induced degeneration is unknown, but is not simple glutamate-N-methyl-D-aspartate (NMDA) excitotoxicity. To test the hypothesis that oxidative stress and inflammation are mechanisms of binge ethanol-induced brain damage, we administered 4 antioxidants, e.g., butylated hydroxytoluene (BHT), ebselen (Eb), vitamin E (VE), and blueberry (BB) extract, during binge ethanol treatment and assessed various measures of neurodegeneration.

METHODS

Adult Sprague-Dawley rats were treated with intragastric ethanol 3 times per day (8-12 g/kg/d) alone or in combination with antioxidants or isocaloric diet for 4 days. Animals were killed, and brains were perfused and extracted for histochemical silver stain determination of brain damage, markers of neurogenesis, or other immunohistochemistry. Some animals were used for determination of nuclear factor kappa B (NF-kappaB)-DNA binding by electrophoretic mobility shift assay (EMSA) or for reverse transcription-polymerase chain reaction (RT-PCR) of cyclooxygenase 2 (COX2).

RESULTS

Binge ethanol induced corticolimbic brain damage and reduced neurogenesis. Treatment with BHT reversed binge induced brain damage and blocked ethanol inhibition of neurogenesis in all regions studied. Interestingly, the other antioxidants studied, e.g., Eb, VE, and BB, did not protect against binge-induced brain damage. Binge ethanol treatment also caused microglia activation, increased NF-kappaB-DNA binding and COX2 expression. Butylated hydroxytoluene reduced binge-induced NF-kappaB-DNA binding and COX2 expression.

CONCLUSIONS

Binge-induced brain damage and activation of NF-kappaB-DNA binding are blocked by BHT. These studies support a neuroinflammatory mechanism of binge ethanol-induced brain damage.

CREB and NF-kappaB transcription factors regulate sensitivity to excitotoxic and oxidative stress induced neuronal cell death

1. Glutamate-NMDA receptor excitotoxicity and oxidative stress are two common mechanisms associated with most neurodegenerative diseases. We hypothesize that the vital state of neurons is regulated in part by two key transcription factors, CREB and NF-kappaB. To test this hypothesis we used hippocampal-entorhinal cortex slice cultures. 2. Glutamate neurotoxicity and oxidative stress neurotoxicity, using hydrogen peroxide (H(2)O(2)) are both associated with a decrease in CREB DNA binding and an increase in NF-kappaB DNA binding. 3. Agents that modulate CREB and NF-kappaB DNA-binding activity alter neurotoxicity. Rolipram, a phosphodiesterase IV inhibitor, increased CREB DNA binding activity and decreased toxicity, whereas TNFalpha, increased NF-kappaB DNA-binding activity and increased neurotoxicity to both glutamate and H(2)O(2). Ethanol decreased CREB and increased NF-kappaB DNA-binding activity and increased neurotoxicity to both glutamate and H(2)O(2). 4. Brain-derived neurotrophic factor (BDNF) is a transcriptionally regulated trophic factor whose expression follows sensitivity to toxicity suggesting it is one of the transcriptionally regulated factors that contributes to neuronal vitality secondary to the balance of CREB-NF-kappaB-activated transcription. Together these studies suggest that neurotoxicity through glutamate-NMDA receptors or oxidative stress is dependent upon CREB and NF-kappaB DNA transcription that regulates vitality of neurons.

Alcohol withdrawal increases neuropeptide Y immunoreactivity in rat brain

BACKGROUND

Neuropeptide Y (NPY) is widely expressed in the brain and is known to affect consummatory behaviors including drinking alcohol as well as to play a role in seizures. We investigated the effects of a 4 day binge ethanol treatment model that is known to induce physical dependence and withdrawal seizures to determine the effects of ethanol dependence and withdrawal on NPY expression.

METHODS

Male Sprague Dawley rats were treated with ethanol or control nutritionally complete diets by intragastric treatment three times per day for 2 or 4 days with an average daily dose of approximately 8 g/kg ethanol per day. Ethanol-fed rats treated for 4 days and then withdrawn for 24, 72, and 168 hr also were studied. Brains were perfused and sectioned for immunohistochemistry for NPY, phospho-cyclic adenosine monophosphate responsive element binding (pCREB), and other proteins.

RESULTS

NPY immunoreactivity (NPY-IR) was found in several brain regions, with the hippocampus and cerebral cortex showing the most pronounced changes. NPY-IR was reduced by ethanol treatment in hippocampus and cortex, although at 72 hr of withdrawal there was a dramatic increase in NPY-IR in the hilus of the dentate gyrus and in CA3 and CA2 fields of hippocampus. Ethanol withdrawal seizures occurred around 12 to 24 hr of withdrawal, preceding the changes in NPY-IR at 72 hr. pCREB immunoreactivity (pCREB-IR) tended to decrease during ethanol treatment but showed a dramatic increase in dentate gyrus at 72 hr of withdrawal. Parvalbumin immunoreactivity indicated that some of the pCREB-IR and NPY-IR were within inhibitory interneuron basket cells of the hippocampal hilus. NPY-IR returned to control levels by 168 hr of withdrawal.

CONCLUSIONS

These studies suggest that hippocampal NPY is reduced during the development of ethanol dependence. Ethanol withdrawal seizures precede a dramatic increase in hippocampal NPY-IR. Previous studies have suggested that NPY in the hippocampus reduces seizure activity and that NPY is induced by seizure activity. Thus, the increase in NPY-IR at 72 hr of withdrawal after binge ethanol treatment may be protective against prolonged withdrawal seizure activity.

Chronic ethanol exposure potentiates NMDA excitotoxicity in cerebral cortical neurons

The effect of acute and chronic ethanol exposure on excitotoxicity in cultured rat cerebral cortical neurons was examined. Neuronal death was quantitated by measuring the accumulation of lactate dehydrogenase (LDH) in the culture media 20 h after exposure to NMDA. Addition of NMDA (25-100 microM) to the culture dishes for 25 min in Mg(2+)-free buffer resulted in a dose-dependent increase in LDH accumulation. Phase-contrast microscopy revealed obvious signs of cellular injury as evidenced by granulation and disintegration of cell bodies and neuritic processes. Chronic exposure of neuronal cultures to ethanol (100 mM) for 96 h followed by its removal before NMDA exposure, significantly increased NMDA-stimulated LDH release by 36 and 22% in response to 25 microM and 50 microM NMDA, respectively. Neither basal LDH release nor that in response to maximal NMDA (100 microM) stimulation was altered by chronic alcohol exposure. In contrast to the effects of chronic ethanol on NMDA neurotoxicity, inclusion of ethanol (100 mM) only during the NMDA exposure period significantly reduced LDH release by approximately 50% in both control and chronically treated dishes. This reduction by acute ethanol was also observed under phase-contrast microscopy as a lack of development of granulation and a sparing of disintegration of neuritic processes. These results indicate that chronic exposure of ethanol to cerebral cortical neurons in culture can sensitize neurons to excitotoxic NMDA receptor activation.

Effects of verapamil on platelet aggregation, ATP release and thromboxane generation

We examined the effects of verapamil on platelet function. Verapamil (0.5 micrograms/ml) in this study inhibited platelet aggregation induced by threshold amounts of ADP, AA, and epinephrine. With higher concentrations of aggregating stimuli, verapamil caused a dose-dependent inhibition of aggregation. Verapamil reduced the extent of epinephrine-induced primary wave, but not that by ADP. Ristocetin-induced aggregation was not affected at any concentration of verapamil. Platelet ATP release induced by AA and ADP was also inhibited. In vitro platelet TXA2 generation was inhibited by verapamil in concentrations lower than those required for inhibition of aggregation.

Comparison of umbilical vein models for measurement of relative prostacyclin and thromboxane production

There is growing evidence that blood vessels generate TXA2 in addition to PGI2. We examined effluents from continuously perfused human umbilical vein and supernatants from umbilical vein rings for TXB2 and 6-keto-PGF1 alpha measurements (stable metabolites of TXA2 and PGI2, respectively). TXB2 and 6-keto-PGF1 alpha were identified in all samples. 6-keto-PGF1 alpha to TXB2 ratio was higher in intact vein effluents than in the venous ring supernatants (112:1 and 28:1, respectively, P less than 0.01). Arachidonate stimulation increased 6-keto-PGF1 alpha and TXB2 levels similarly in the intact vein effluent. In contrast, stimulation of the venous rings resulted in a relatively larger increase in TXB2 than in 6-keto-PGF1 alpha. This caused 6-keto-PGF1 alpha to TXB2 ratio to decline (p less than 0.01). The identity of TXB2 was confirmed in several different ways. These data suggest that 1) human umbilical veins produce TXA2 in addition to PGI2, 2) TXA2 release is more by venous rings than by the intact vein probably reflecting contribution from non-endothelial layers, and 3) arachidonate stimulation causes relatively greater release of TXA2 than of PGI2 from the venous rings, whereas release of PGI2 and TXA2 is similar from the intact vein.