Genetic or pharmacological GHSR blockade has sexually dimorphic effects in rodents on a high-fat diet

The stomach-derived hormone ghrelin regulates essential physiological functions. The ghrelin receptor (GHSR) has ligand-independent actions, therefore, GHSR gene deletion may be a reasonable approach to investigate the role of this system in feeding behaviors and diet-induced obesity (DIO). Here we investigated the effects of a long-term (12 month) high-fat (HFD) versus regular diet on obesity-related measures in global GHSR-KO and wild type (WT) Wistar male and female rats. Our main findings were that the GHSR gene deletion protects against DIO and decreases food intake during HFD in male but not in female rats. GHSR gene deletion increased thermogenesis and brain glucose uptake in male rats and modified the effects of HFD on brain glucose metabolism in a sex-specific manner, as assessed with small animal positron emission tomography. RNA-sequencing was also used to show that GHSR-KO rats had upregulated expression of genes responsible for fat oxidation in brown adipose tissue. Central administration of a novel GHSR inverse agonist, PF-5190457, attenuated ghrelin-induced food intake, but only in male, not in female mice. HFD-induced binge-like eating was reduced by inverse agonism in both sexes. Our results support GHSR as a promising target for new pharmacotherapies for obesity.

A history of repeated alcohol intoxication promotes cognitive impairment and gene expression signatures of disease progression in the 3xTg mouse model of Alzheimer's disease

The impact of alcohol abuse on Alzheimer's disease (AD) is poorly understood. Here, we show that the onset of neurocognitive impairment in a mouse model of AD is hastened by repeated alcohol intoxication through exposure to alcohol vapor, and we provide a comprehensive gene expression dataset of the prefrontal cortex by the single-nucleus RNA sequencing of 113,242 cells. We observed a broad dysregulation of gene expression that involves neuronal excitability, neurodegeneration, and inflammation, including interferon genes. Several genes previously associated with AD in humans by genome-wide association studies were differentially regulated in specific neuronal populations. Gene expression patterns of AD mice with a history of alcohol intoxication were more similar to gene expression signatures of older AD mice with more advanced disease and cognitive impairment than those of younger AD mice with prodromic disease, suggesting that alcohol promotes transcriptional changes consistent with AD progression. Our gene expression dataset at the single-cell level provides a unique resource for investigations of the molecular bases of the detrimental role of excessive alcohol intake in AD.Significance statementAlzheimer's disease (AD) is the most common neurodegenerative disease worldwide. Many efforts have been geared toward the identification of environmental and genetic risk factors. However, alcohol has received limited attention as a potential risk factor for AD. We explored effects of the interaction of a history of alcohol intoxication with genetic AD susceptibility on cognitive performance and gene expression at the single-cell level. We found that a history of repeated alcohol intoxication promotes the emergence of spatial learning and memory impairments in pre-symptomatic triple transgenic AD (3xTg-AD) mice. We also show that a history of repeated alcohol intoxication induces prefrontal cortex transcriptional changes associated with AD progression.

Development of tolerance upon repeated administration with the GABAB receptor positive allosteric modulator, COR659, on alcohol drinking in rodents

Background: Recent work has demonstrated that acute administration of the novel positive allosteric modulator of the GABAB receptor, COR659, reduces several alcohol-related behaviors in rodents.Objective: To assess whether COR659 continues to lessen alcohol intake after repeated administration, a fundamental feature of drugs with therapeutic potential.Methods: Male C57BL/6J mice (n = 40) were exposed to daily 2-hour drinking sessions (20% (v/v) alcohol) under the 1-bottle "drinking in the dark" protocol and male Sardinian alcohol-preferring rats (n = 40) were exposed to daily 1-hour drinking sessions under the 2-bottle "alcohol (10%, v/v) vs water" choice regimen. COR659 (0, 10, 20, and 40 mg/kg in the mouse experiment; 0, 5, 10, and 20 mg/kg in the rat experiment) was administered intraperitoneally before 7 consecutive drinking sessions.Results: Alcohol intake in vehicle-treated mice and rats averaged 2.5-3.0 and 1.5-1.6 g/kg/session, respectively, indicative of high basal levels. In both experiments, treatment with COR659 resulted in an initial, dose-related suppression of alcohol intake (up to 70-80% compared to vehicle treatment; P < .0005 and P < .0001 in mouse and rat experiments, respectively). The magnitude of the reducing effect of COR659 on alcohol drinking diminished progressively, until vanishing over the subsequent 2-4 drinking sessions.Conclusion: COR659 effectively reduced alcohol intake in two different rodent models of excessive alcohol drinking. However, tolerance to the anti-alcohol effects of COR659 developed rapidly. If theoretically transposed to humans, these data would represent a possible limitation to the clinical use of COR659.

Escalated (Dependent) Oxycodone Self-Administration Is Associated with Cognitive Impairment and Transcriptional Evidence of Neurodegeneration in Human Immunodeficiency Virus (HIV) Transgenic Rats

Substance use disorder is associated with accelerated disease progression in people with human immunodeficiency virus (HIV; PWH). Problem opioid use, including high-dose opioid therapy, prescription drug misuse, and opioid abuse, is high and increasing in the PWH population. Oxycodone is a broadly prescribed opioid in both the general population and PWH. Here, we allowed HIV transgenic (Tg) rats and wildtype (WT) littermates to intravenously self-administer oxycodone under short-access (ShA) conditions, which led to moderate, stable, "recreational"-like levels of drug intake, or under long-access (LgA) conditions, which led to escalated (dependent) drug intake. HIV Tg rats with histories of oxycodone self-administration under LgA conditions exhibited significant impairment in memory performance in the novel object recognition (NOR) paradigm. RNA-sequencing expression profiling of the medial prefrontal cortex (mPFC) in HIV Tg rats that self-administered oxycodone under ShA conditions exhibited greater transcriptional evidence of inflammation than WT rats that self-administered oxycodone under the same conditions. HIV Tg rats that self-administered oxycodone under LgA conditions exhibited transcriptional evidence of an increase in neuronal injury and neurodegeneration compared with WT rats under the same conditions. Gene expression analysis indicated that glucocorticoid-dependent adaptations contributed to the gene expression effects of oxycodone self-administration. Overall, the present results indicate that a history of opioid intake promotes neuroinflammation and glucocorticoid dysregulation, and excessive opioid intake is associated with neurotoxicity and cognitive impairment in HIV Tg rats.

Probenecid Reduces Alcohol Drinking in Rodents. Is Pannexin1 a Novel Therapeutic Target for Alcohol Use Disorder?

AIMS

The development of novel and more effective medications for alcohol use disorder (AUD) is an important unmet medical need. Drug repositioning or repurposing is an appealing strategy to bring new therapies to the clinic because it greatly reduces the overall costs of drug development and expedites the availability of treatments to those who need them. Probenecid, p-(di-n-propylsulfamyl)-benzoic acid, is a drug used clinically to treat hyperuricemia and gout due to its activity as an inhibitor of the kidneys' organic anion transporter that reclaims uric acid from urine. Probenecid also inhibits pannexin1 channels that are involved in purinergic neurotransmission and inflammation, which have been implicated in alcohol's effects and motivation for alcohol. Therefore, we tested the effects of probenecid on alcohol intake in rodents.

METHODS

We tested the effects of probenecid on operant oral alcohol self-administration in alcohol-dependent rats during acute withdrawal as well as in nondependent rats and in the drinking-in-the-dark (DID) paradigm of binge-like drinking in mice.

RESULTS

Probenecid reduced alcohol intake in both dependent and nondependent rats and in the DID paradigm in mice without affecting water or saccharin intake, indicating that probenecid's effect was selective for alcohol and not the result of a general reduction in reward.

CONCLUSIONS

These results raise the possibility that pannexin1 is a novel therapeutic target for the treatment of AUD. The clinical use of probenecid has been found to be generally safe, suggesting that it can be a candidate for drug repositioning for the treatment of AUD.

Increases in compulsivity, inflammation, and neural injury in HIV transgenic rats with escalated methamphetamine self-administration under extended-access conditions

The abuse of stimulants, such as methamphetamine (METH), is associated with treatment non-compliance, a greater risk of viral transmission, and the more rapid clinical progression of immunological and central nervous system human immunodeficiency virus (HIV) disease. The behavioral effects of METH in the setting of HIV remain largely uncharacterized. We used a state-of-the-art paradigm of the escalation of voluntary intravenous drug self-administration in HIV transgenic (Tg) and wildtype rats. The rats were first allowed to self-administer METH under short-access (ShA) conditions, which is characterized by a nondependent and more "recreational" pattern of METH use, and then allowed to self-administer METH under long-access (LgA) conditions, which leads to compulsive (dependent) METH intake. HIV Tg and wildtype rats self-administered equal amounts of METH under ShA conditions. HIV Tg rats self-administered METH under LgA conditions following a 4-week enforced abstinence period to model the intermittent pattern of stimulant abuse in humans. These HIV Tg rats developed greater motivation to self-administer METH and self-administered larger amounts of METH. Impairments in function of the medial prefrontal cortex (mPFC) contribute to compulsive drug and alcohol intake. Gene expression profiling of the mPFC in HIV Tg rats with a history of escalated METH self-administration under LgA conditions showed transcriptional evidence of increased inflammation, greater neural injury, and impaired aerobic glucose metabolism than wildtype rats that self-administered METH under LgA conditions. The detrimental effects of the interaction between neuroHIV and escalated METH intake on the mPFC are likely key factors in the greater vulnerability to excessive drug intake in the setting of HIV.

Charge Characteristics of Agouti-Related Protein Implicate Potent Involvement of Heparan Sulfate Proteoglycans in Metabolic Function

The endogenous melanocortin peptide agouti-related protein (AgRP) plays a well-known role in foraging, but its contribution to metabolic regulation is less understood. Mature AgRP_(83-132) has distinct residues for melanocortin receptor binding and heparan sulfate interactions. Here, we show that AgRP increases ad libitum feeding and operant responding for food in mice, decreases oxygen consumption, and lowers body temperature and activity, indicating lower energy expenditure. AgRP increased the respiratory exchange ratio, indicating a reduction of fat oxidation and a shift toward carbohydrates as the primary fuel source. The duration and intensity of AgRP's effects depended on the density of its positively charged amino acids, suggesting that its orexigenic and metabolic effects depend on its affinity for heparan sulfate. These findings may have major clinical implications by unveiling the critical involvement of interactions between AgRP and heparan sulfate to the central regulation of energy expenditure, fat utilization, and possibly their contribution to metabolic disease.

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AgRP increases both ad libitum and operant food intake and reduces energy expenditure

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AgRP reduces fat utilization as a fuel source, which promotes body fat accumulation

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These actions of AgRP depend on the positive charges, outside its ICK motif, that bind heparan sulfate

Reduced intrinsic excitability of CA1 pyramidal neurons in human immunodeficiency virus (HIV) transgenic rats

The hippocampus is involved in key neuronal circuits that underlie cognition, memory, and anxiety, and it is increasingly recognized as a vulnerable structure that contributes to the pathogenesis of HIV-associated neurocognitive disorder (HAND). However, the mechanisms responsible for hippocampal dysfunction in neuroHIV remain unknown. The present study used HIV transgenic (Tg) rats and patch-clamp electrophysiological techniques to study the effects of the chronic low-level expression of HIV proteins on hippocampal CA1 pyramidal neurons. The dorsal and ventral areas of the hippocampus are involved in different neurocircuits and thus were evaluated separately. We found a significant decrease in the intrinsic excitability of CA1 neurons in the dorsal hippocampus in HIV Tg rats by comparing neuronal spiking induced by current step injections and by dynamic clamp to simulate neuronal spiking activity. The decrease in excitability in the dorsal hippocampus was accompanied by a higher rate of excitatory postsynaptic currents (EPSCs), whereas CA1 pyramidal neurons in the ventral hippocampus in HIV Tg rats had higher EPSC amplitudes. We also observed a reduction of hyperpolarization-activated nonspecific cationic current (Ih) in both the dorsal and ventral hippocampus. Neurotoxic HIV proteins have been shown to increase neuronal excitation. The lower excitability of CA1 pyramidal neurons that was observed herein may represent maladaptive homeostatic plasticity that seeks to stabilize baseline neuronal firing activity but may disrupt neural network function and contribute to HIV-associated neuropsychological disorders, such as HAND and depression.

Epitranscriptomics: Correlation of N6-methyladenosine RNA methylation and pathway dysregulation in the hippocampus of HIV transgenic rats

Internal RNA modifications have been known for decades, however their roles in mRNA regulation have only recently started to be elucidated. Here we investigated the most abundant mRNA modification, N6-methyladenosine (m6A) in transcripts from the hippocampus of HIV transgenic (Tg) rats. The distribution of m6A peaks within HIV transcripts in HIV Tg rats largely corresponded to the ones observed for HIV transcripts in cell lines and T cells. Host transcripts were found to be differentially m6A methylated in HIV Tg rats. The functional roles of the differentially m6A methylated pathways in HIV Tg rats is consistent with a key role of RNA methylation in the regulation of the brain transcriptome in chronic HIV disease. In particular, host transcripts show significant differential m6A methylation of genes involved in several pathways related to neural function, suggestive of synaptodendritic injury and neurodegeneration, inflammation and immune response, as well as RNA processing and metabolism, such as splicing. Changes in m6A methylation were usually positively correlated with differential expression, while differential m6A methylation of pathways involved in RNA processing were more likely to be negatively correlated with gene expression changes. Thus, sets of differentially m6A methylated, functionally-related transcripts appear to be involved in coordinated transcriptional responses in the context of chronic HIV. Altogether, our results support that m6A methylation represents an additional layer of regulation of HIV and host gene expression in vivo that contributes significantly to the transcriptional effects of chronic HIV.

Opiate dependence induces cell type-specific plasticity of intrinsic membrane properties in the rat juxtacapsular bed nucleus of stria terminalis (jcBNST)

RATIONALE

Drugs of abuse can alter circuit dynamics by modifying synaptic efficacy and/or the intrinsic membrane properties of neurons. The juxtacapsular subdivision of the bed nucleus of stria terminalis (jcBNST) has unique connectivity that positions it to integrate cortical and amygdala inputs and provide feed-forward inhibition to the central nucleus of the amygdala (CeA), among other regions. In this study, we investigated changes in the synaptic and intrinsic properties of neurons in the rat jcBNST during protracted withdrawal from morphine dependence using a combination of conventional electrophysiological methods and the dynamic clamp technique.

RESULTS

A history of opiate dependence induced a form of cell type-specific plasticity characterized by reduced inward rectification associated with more depolarized resting membrane potentials and increased membrane resistance. This cell type also showed a lower rheobase when stimulated with direct current (DC) pulses as well as a decreased firing threshold under simulated synaptic bombardment with the dynamic clamp. Morphine dependence also decreased excitatory postsynaptic potential amplification, suggesting the downregulation of the persistent Na⁺ current (I _NaP).

CONCLUSION

These findings show that a history of morphine dependence leads to persistent cell type-specific plasticity of the passive membrane properties of a jcBNST neuronal population, leading to an overall increased excitability of such neurons. By altering the activity of extended amygdala circuits where they are embedded, changes in the integration properties of jcBNST neurons may contribute to emotional dysregulation associated with drug dependence and withdrawal.

Molecular analyses of neurogenic defects in a human pluripotent stem cell model of fragile X syndrome

New research suggests that common pathways are altered in many neurodevelopmental disorders including autism spectrum disorder; however, little is known about early molecular events that contribute to the pathology of these diseases. The study of monogenic, neurodevelopmental disorders with a high incidence of autistic behaviours, such as fragile X syndrome, has the potential to identify genes and pathways that are dysregulated in autism spectrum disorder as well as fragile X syndrome. In vitro generation of human disease-relevant cell types provides the ability to investigate aspects of disease that are impossible to study in patients or animal models. Differentiation of human pluripotent stem cells recapitulates development of the neocortex, an area affected in both fragile X syndrome and autism spectrum disorder. We have generated induced human pluripotent stem cells from several individuals clinically diagnosed with fragile X syndrome and autism spectrum disorder. When differentiated to dorsal forebrain cell fates, our fragile X syndrome human pluripotent stem cell lines exhibited reproducible aberrant neurogenic phenotypes. Using global gene expression and DNA methylation profiling, we have analysed the early stages of neurogenesis in fragile X syndrome human pluripotent stem cells. We discovered aberrant DNA methylation patterns at specific genomic regions in fragile X syndrome cells, and identified dysregulated gene- and network-level correlates of fragile X syndrome that are associated with developmental signalling, cell migration, and neuronal maturation. Integration of our gene expression and epigenetic analysis identified altered epigenetic-mediated transcriptional regulation of a distinct set of genes in fragile X syndrome. These fragile X syndrome-aberrant networks are significantly enriched for genes associated with autism spectrum disorder, giving support to the idea that underlying similarities exist among these neurodevelopmental diseases.

Translation of BDNF-gene transcripts with short 3' UTR in hippocampal CA1 neurons improves memory formation and enhances synaptic plasticity-relevant signaling pathways

While the brain-derived neurotrophic factor (BDNF) gene and its multiple transcripts have been recognized as a key factor for learning, but the specific involvement of BDNF translated from BDNF transcripts with short-3' untranslated region (short 3' UTR) in learning and memory requires further analysis. In this paper, we present data to show that the transduction of hippocampal CA1 neurons with AAV9-5' UTR-BDNF (short 3' UTR)-IRES-ZsGreen and the subsequent expression of BDNF enhanced the phosphorylation of synaptic plasticity relevant proteins and improved passive avoidance and object location, but not object recognition memory. In addition, BDNF improved the relearning of object location. At higher BDNF overexpression levels, the fear behavior was accompanied with a decline in the passive avoidance memory 24h post training, and with an enhanced fear conditioning performance. In addition, these animals developed spontaneous seizures. Thus, the expression of BDNF in the hippocampal CA1 region has the potential to improve fear and object location memory in wild type mouse strains when the region and expression levels of BDNF are well controlled.

Identifying candidate drivers of alcohol dependence-induced excessive drinking by assembly and interrogation of brain-specific regulatory networks

BACKGROUND

A systems biology approach based on the assembly and interrogation of gene regulatory networks, or interactomes, was used to study neuroadaptation processes associated with the transition to alcohol dependence at the molecular level.

RESULTS

Using a rat model of dependent and non-dependent alcohol self-administration, we reverse engineered a global transcriptional regulatory network during protracted abstinence, a period when relapse rates are highest. We then interrogated the network to identify master regulator genes that mechanistically regulate brain region-specific signatures associated with dependent and non-dependent alcohol self-administration. Among these, the gene coding for the glucocorticoid receptor was independently identified as a master regulator in multiple brain regions, including the medial prefrontal cortex, nucleus accumbens, central nucleus of the amygdala, and ventral tegmental area, consistent with the view that brain reward and stress systems are dysregulated during protracted abstinence. Administration of the glucocorticoid antagonist mifepristone in either the nucleus accumbens or ventral tegmental area selectively decreased dependent, excessive, alcohol self-administration in rats but had no effect on non-dependent, moderate, alcohol self-administration.

CONCLUSIONS

Our study suggests that assembly and analysis of regulatory networks is an effective strategy for the identification of key regulators of long-term neuroplastic changes within specific brain regions that play a functional role in alcohol dependence. More specifically, our results support a key role for regulatory networks downstream of the glucocorticoid receptor in excessive alcohol drinking during protracted alcohol abstinence.

MeCP2 regulates ethanol sensitivity and intake

We have investigated the expression of chromatin-regulating genes in the prefrontal cortex and in the shell subdivision of the nucleus accumbens during protracted withdrawal in mice with increased ethanol drinking after chronic intermittent ethanol (CIE) vapor exposure and in mice with a history of non-dependent drinking. We observed that the methyl-CpG binding protein 2 (MeCP2) was one of the few chromatin-regulating genes to be differentially regulated by a history of dependence. As MeCP2 has the potential of acting as a broad gene regulator, we investigated sensitivity to ethanol and ethanol drinking in MeCP2(308/) (Y) mice, which harbor a truncated MeCP2 allele but have a milder phenotype than MeCP2 null mice. We observed that MeCP2(308/) (Y) mice were more sensitive to ethanol's stimulatory and sedative effects than wild-type (WT) mice, drank less ethanol in a limited access 2 bottle choice paradigm and did not show increased drinking after induction of dependence with exposure to CIE vapors. Alcohol metabolism did not differ in MeCP2(308/) (Y) and WT mice. Additionally, MeCP2(308/) (Y) mice did not differ from WT mice in ethanol preference in a 24-hour paradigm nor in their intake of graded solutions of saccharin or quinine, suggesting that the MeCP2(308/) (Y) mutation did not alter taste function. Lastly, using the Gene Set Enrichment Analysis algorithm, we found a significant overlap in the genes regulated by alcohol and by MeCP2. Together, these results suggest that MeCP2 contributes to the regulation of ethanol sensitivity and drinking.

Gene expression changes consistent with neuroAIDS and impaired working memory in HIV-1 transgenic rats

BACKGROUND

A thorough investigation of the neurobiology of HIV-induced neuronal dysfunction and its evolving phenotype in the setting of viral suppression has been limited by the lack of validated small animal models to probe the effects of concomitant low level expression of multiple HIV-1 products in disease-relevant cells in the CNS.

RESULTS

We report the results of gene expression profiling of the hippocampus of HIV-1 Tg rats, a rodent model of HIV infection in which multiple HIV-1 proteins are expressed under the control of the viral LTR promoter in disease-relevant cells including microglia and astrocytes. The Gene Set Enrichment Analysis (GSEA) algorithm was used for pathway analysis. Gene expression changes observed are consistent with astrogliosis and microgliosis and include evidence of inflammation and cell proliferation. Among the genes with increased expression in HIV-1 Tg rats was the interferon stimulated gene 15 (ISG-15), which was previously shown to be increased in the cerebrospinal fluid (CSF) of HIV patients and to correlate with neuropsychological impairment and neuropathology, and prostaglandin D2 (PGD2) synthase (Ptgds), which has been associated with immune activation and the induction of astrogliosis and microgliosis. GSEA-based pathway analysis highlighted a broad dysregulation of genes involved in neuronal trophism and neurodegenerative disorders. Among the latter are genesets associated with Huntington's disease, Parkinson's disease, mitochondrial, peroxisome function, and synaptic trophism and plasticity, such as IGF, ErbB and netrin signaling and the PI3K signal transduction pathway, a mediator of neural plasticity and of a vast array of trophic signals. Additionally, gene expression analyses also show altered lipid metabolism and peroxisomes dysfunction. Supporting the functional significance of these gene expression alterations, HIV-1 Tg rats showed working memory impairments in spontaneous alternation behavior in the T-Maze, a paradigm sensitive to prefrontal cortex and hippocampal function.

CONCLUSIONS

Altogether, differentially regulated genes and pathway analysis identify specific pathways that can be targeted therapeutically to increase trophic support, e.g. IGF, ErbB and netrin signaling, and reduce neuroinflammation, e.g. PGD2 synthesis, which may be beneficial in the treatment of chronic forms of HIV-associated neurocognitive disorders in the setting of viral suppression.

Excitability of jcBNST neurons is reduced in alcohol-dependent animals during protracted alcohol withdrawal

Alcohol dependence and withdrawal has been shown to cause neuroadaptive changes at multiple levels of the nervous system. At the neuron level, adaptations of synaptic connections have been extensively studied in a number of brain areas and accumulating evidence also shows the importance of alcohol dependence-related changes in the intrinsic cellular properties of neurons. At the same time, it is still largely unknown how such neural adaptations impact the firing and integrative properties of neurons. To address these problems, here, we analyze physiological properties of neurons in the bed nucleus of stria terminalis (jcBNST) in animals with a history of alcohol dependence. As a comprehensive approach, first we measure passive and active membrane properties of neurons using conventional current clamp protocols and then analyze their firing responses under the action of simulated synaptic bombardment via dynamic clamp. We find that most physiological properties as measured by DC current injection are barely affected during protracted withdrawal. However, neuronal excitability as measured from firing responses under simulated synaptic inputs with the dynamic clamp is markedly reduced in all 3 types of jcBNST neurons. These results support the importance of studying the effects of alcohol and drugs of abuse on the firing properties of neurons with dynamic clamp protocols designed to bring the neurons into a high conductance state. Since the jcBNST integrates excitatory inputs from the basolateral amygdala (BLA) and cortical inputs from the infralimbic and the insular cortices and in turn is believed to contribute to the inhibitory input to the central nucleus of the amygdala (CeA) the reduced excitability of the jcBNST during protracted withdrawal in alcohol-dependent animals will likely affect ability of the jcBNST to shape the activity and output of the CeA.

Gene profiling of laser-microdissected brain regions and individual cells in drug abuse and schizophrenia research

Application of transcriptomics approaches to accurately dissected anatomically defined brain regions and individual neuronal populations remains a central focus of current neurobiological investigations. A vast selection of methods and commercial products are currently available that allow one to implement routine gene quantitation and profiling from laser-microdissected brain regions, subregions, and neuronal populations. The present chapter reviews laser microdissection strategies for gene expression analyses, strategies for RNA extraction, reverse transcriptase-coupled PCR (RT-PCR), and target preparation for microarray analyses that are in use in our labs.

Protein degradation by the proteasome is required for synaptic tagging and the heterosynaptic stabilization of hippocampal late-phase long-term potentiation

Activity-dependent regulation of synaptic efficacy is believed to underlie learning and memory formation. Here we show that protein degradation by the proteasome is required for the induction of the protein synthesis-dependent late-phase of long-term potentiation (late-LTP) but not for its maintenance. Proteasome activity was also key to the polarity of heterosynaptic interactions between synapses expressing synaptic plasticity and newly activated synapses. In fact, proteasome activity was required for the consolidation of an otherwise transient potentiation (early-LTP) into late-LTP by strong tetanization of a separate afferent pathway both in the "weak-before-strong" and in the "strong-before-weak" two-pathway paradigms [Frey and Morris (1997) Nature 385:533-536; Frey and Morris (1998) Neuropharmacology 37:545-552], suggesting that proteasome activity plays a role in the synaptic tagging and capture of plasticity-related proteins at stimulated synapses. Additionally, proteasome inhibition abrogated immunity against heterosynaptic depotentiation of an established late-LTP when applied during weak tetanic stimulation in the "strong-before-weak" two-pathway paradigm. Such a heterosynaptic destabilizing effect of proteasome inhibition was abolished by concomitant inhibition of N-methyl-d-aspartate (NMDA) receptors, suggesting that it is an active process. Together, these results indicate that the proteasome plays important roles in the establishment of late-LTP and in the preservation of potentiated synapses when a subsequent synaptic plasticity is induced within the same neuronal population.

A potential role for adiponectin receptor 2 (AdipoR2) in the regulation of alcohol intake

The anterior cingulate cortex (ACC) has been implicated in alcohol and drug addiction. We recently identified the small G protein K-ras as an alcohol-regulated gene in the ACC by gene expression analysis. We show here that the adiponectin receptor 2 (AdipoR2) was differentially regulated by alcohol in the ACC in a K-ras-dependent manner. Additionally, withdrawal-associated increased drinking was attenuated in AdipoR2 null mice. Intracellular recordings revealed that adiponectin increased the excitability of ACC neurons and that this effect was more pronounced during alcohol withdrawal, suggesting that AdipoR2 signaling may contribute to increased ACC activity. Altogether, the data implicate K-ras-regulated pathways involving AdipoR2 in the cellular and behavioral actions of alcohol that may contribute to overactivity of the ACC during withdrawal and excessive alcohol drinking.

Intrinsic neuronal plasticity in the juxtacapsular nucleus of the bed nuclei of the stria terminalis (jcBNST)

The juxtacapsular nucleus of the anterior division of the BNST (jcBNST) receives robust glutamatergic projections from the basolateral nucleus of the amygdala (BLA), the postpiriform transition area, and the insular cortex as well as dopamine (DA) inputs from the midbrain. In turn the jcBNST sends GABAergic projections to the medial division of the central nucleus of the amygdala (CEAm) as well as other brain regions. We recently described a form of long-term potentiation of the intrinsic excitability (LTP-IE) of neurons of the juxtacapsular nucleus of BNST (jcBNST) in response to high-frequency stimulation (HFS) of the stria terminalis that was impaired during protracted withdrawal from alcohol, cocaine, and heroin and in rats chronically treated with corticotropin-releasing factor (CRF) intracerebroventricularly. Here we show that DAergic neurotransmission is required for the induction of LTP-IE of jcBNST neurons through dopamine (DA) D1 receptors. Thus, activation of the central CRF stress system and altered DAergic neurotransmission during protracted withdrawal from alcohol and drugs of abuse may contribute to the disruption of LTP-IE in the jcBNST. Impairment of this form of intrinsic neuronal plasticity in the jcBNST could result in inadequate neuronal integration and reduced inhibition of the CEA, contributing to the negative affective state that characterizes protracted abstinence in post-dependent individuals. These results provide a novel neurobiological target for vulnerability to alcohol and drug dependence.

A recombinant human monoclonal antibody to human metapneumovirus fusion protein that neutralizes virus in vitro and is effective therapeutically in vivo

Human metapneumovirus (hMPV) is a recently discovered paramyxovirus that is a major cause of lower-respiratory-tract disease. hMPV is associated with more severe disease in infants and persons with underlying medical conditions. Animal studies have shown that the hMPV fusion (F) protein alone is capable of inducing protective immunity. Here, we report the use of phage display technology to generate a fully human monoclonal antibody fragment (Fab) with biological activity against hMPV. Phage antibody libraries prepared from human donor tissues were selected against recombinant hMPV F protein with multiple rounds of panning. Recombinant Fabs then were expressed in bacteria, and supernatants were screened by enzyme-linked immunosorbent assay and immunofluorescent assays. A number of Fabs that bound to hMPV F were isolated, and several of these exhibited neutralizing activity in vitro. Fab DS7 neutralized the parent strain of hMPV with a 60% plaque reduction activity of 1.1 mug/ml and bound to hMPV F with an affinity of 9.8 x10(-10) M, as measured by surface plasmon resonance. To test the in vivo activity of Fab DS7, groups of cotton rats were infected with hMPV and given Fab intranasally 3 days after infection. Nasal turbinates and lungs were harvested on day 4 postinfection and virus titers determined. Animals treated with Fab DS7 exhibited a >1,500-fold reduction in viral titer in the lungs, with a modest 4-fold reduction in the nasal tissues. There was a dose-response relationship between the dose of DS7 and virus titer. Human Fab DS7 may have prophylactic or therapeutic potential against severe hMPV infection.

Viral vector-induced amygdala NPY overexpression reverses increased alcohol intake caused by repeated deprivations in Wistar rats

Acute administration of neuropeptide Y (NPY) modulates alcohol intake in genetic and chemical models of high intake, while leaving intake unaffected during 'normal' or baseline conditions. In non-selected, normal rat lines, alcohol consumption can be increased by prolonged exposure to alcohol, and it is unclear what effect a constitutive increase in NPY function will have on alcohol intake. The purpose of the present study was to examine the effects on alcohol intake of an inducible, constitutive overexpression of NPY, one of the most abundant neuropeptides in the central nervous system. A liquid diet was used in combination with repeated alcohol deprivation sessions to increase alcohol intake in normal Wistar rats. We then examined the effect of NPY overexpression in the amygdala on excessive alcohol intake produced by prolonged exposure to alcohol and alcohol deprivation. Repeated withdrawal increased alcohol consumption in a 24-h continuous access two-bottle choice model. Both the number of withdrawals as well as the length of the withdrawal periods affected alcohol consumption with an increased intake resulting from multiple withdrawals and the alcohol deprivation effect being enhanced by longer periods of abstinence. The increase in intake following repeated abstinence was blunted by intra-amygdala administration of a Sindbis viral vector containing NPY cDNA. Amygdala NPY overexpression also was demonstrated to be anxiolytic in the open field test. Repeated withdrawal in combination with a history of alcohol consumption significantly elevated alcohol intake, and the amygdala may mediate the transition to high-drinking states in this model.

Region-specific transcriptional changes following the three antidepressant treatments electro convulsive therapy, sleep deprivation and fluoxetine

The significant proportion of depressed patients that are resistant to monoaminergic drug therapy and the slow onset of therapeutic effects of the selective serotonin reuptake inhibitors (SSRIs)/serotonin/noradrenaline reuptake inhibitors (SNRIs) are two major reasons for the sustained search for new antidepressants. In an attempt to identify common underlying mechanisms for fast- and slow-acting antidepressant modalities, we have examined the transcriptional changes in seven different brain regions of the rat brain induced by three clinically effective antidepressant treatments: electro convulsive therapy (ECT), sleep deprivation (SD), and fluoxetine (FLX), the most commonly used slow-onset antidepressant. Each of these antidepressant treatments was applied with the same regimen known to have clinical efficacy: 2 days of ECT (four sessions per day), 24 h of SD, and 14 days of daily treatment of FLX, respectively. Transcriptional changes were evaluated on RNA extracted from seven different brain regions using the Affymetrix rat genome microarray 230 2.0. The gene chip data were validated using in situ hybridization or autoradiography for selected genes. The major findings of the study are: 1. The transcriptional changes induced by SD, ECT and SSRI display a regionally specific distribution distinct to each treatment. 2. The fast-onset, short-lived antidepressant treatments ECT and SD evoked transcriptional changes primarily in the catecholaminergic system, whereas the slow-onset antidepressant FLX treatment evoked transcriptional changes in the serotonergic system. 3. ECT and SD affect in a similar manner the same brain regions, primarily the locus coeruleus, whereas the effects of FLX were primarily in the dorsal raphe and hypothalamus, suggesting that both different regions and pathways account for fast onset but short lasting effects as compared to slow-onset but long-lasting effects. However, the similarity between effects of ECT and SD is somewhat confounded by the fact that the two treatments appear to regulate a number of transcripts in an opposite manner. 4. Multiple transcripts (e.g. brain-derived neurotrophic factor (BDNF), serum/glucocorticoid-regulated kinase (Sgk1)), whose level was reported to be affected by antidepressants or behavioral manipulations, were also found to be regulated by the treatments used in the present study. Several novel findings of transcriptional regulation upon one, two or all three treatments were made, for the latter we highlight homer, erg2, HSP27, the proto oncogene ret, sulfotransferase family 1A (Sult1a1), glycerol 3-phosphate dehydrogenase (GPD3), the orphan receptor G protein-coupled receptor 88 (GPR88) and a large number of expressed sequence tags (ESTs). 5. Transcripts encoding proteins involved in synaptic plasticity in the hippocampus were strongly affected by ECT and SD, but not by FLX. The novel transcripts, concomitantly regulated by several antidepressant treatments, may represent novel targets for fast onset, long-duration antidepressants.

Increased expression of protein kinase A inhibitor alpha (PKI-alpha) and decreased PKA-regulated genes in chronic intermittent alcohol exposure

Intermittent models of alcohol exposure that mimic human patterns of alcohol consumption produce profound physiological and biochemical changes and induce rapid increases in alcohol self-administration. We used high-density oligonucleotide microarrays to investigate gene expression changes during chronic intermittent alcohol exposure in three brain regions that receive mesocorticolimbic dopaminergic projections and that are believed to be involved in alcohol's reinforcing actions: the medial prefrontal cortex, the nucleus accumbens and the amygdala. An independent replication of the experiment was used for RT-PCR validation of the microarray results. The protein kinase A inhibitor alpha (PKI-alpha, Pkia), a member of the endogenous PKI family implicated in reducing nuclear PKA activity, was found to be increased in all three regions tested. Conversely, we observed a downregulation of the expression of several PKA-regulated transcripts in one or more of the brain regions studied, including the activity and neurotransmitter-regulated early gene (Ania) - 1, -3, -7, -8, the transcription factors Egr1 and NGFI-B (Nr4a1) and the neuropeptide NPY. Reduced expression of PKA-regulated genes in mesocorticolimbic projection areas may have motivational significance in the rapid increase in alcohol self-administration induced by intermittent alcohol exposure.

Involvement of multiple phosphatidylinositol 3-kinase-dependent pathways in the persistence of late-phase long term potentiation expression

The mechanisms responsible for the stabilization and persistence of synaptic plasticity remain largely unknown. In this study, we investigated the time course of the dependence of late-phase long term potentiation of field excitatory post-synaptic potential on phosphatidylinositol 3-kinase and its downstream effectors mTOR and AKT. In agreement with our previous results obtained on an early-phase long-term potentiation paradigm we observed that application of a nanomolar concentration of wortmannin (100 nM) 1 h after late-phase long term potentiation induction reversed potentiation completely. However, application of wortmannin 4 h after late-phase long term potentiation induction resulted in a more limited reduction of field excitatory post-synaptic potential suggesting that the dependence of late-phase long term potentiation expression on phosphatidylinositol 3-kinase decreases over time. Application of a nanomolar concentration of rapamycin (200 nM) during the tetanization paradigm prevented the induction of late-phase long term potentiation consistent with our earlier results. Application of rapamycin 1 h after late-phase long term potentiation induction resulted in a less pronounced though significant decline of field excitatory post-synaptic potential. Immunohistological analysis demonstrated that the concentration of rapamycin used was effective in inhibiting the phosphorylation of p70S6K at Thr389, the main determinant of its pro-translational activity, and that Thr389 phosphorylation recovered after washout. Lastly, a transient application of Akt inhibitor I (10 microM) one hour after late-phase long term potentiation induction also induced a partial although significant reduction of potentiated field excitatory post-synaptic potential that stabilized at a level of approximately 114% of baseline three hours after application, suggesting that AKT also contributes to the stabilization of late-phase long term potentiation expression. These results confirm and extend previous observations that the expression of long term potentiation in the CA1 of rat hippocampus involves several elements of the phosphatidylinositol 3-kinase signaling pathway.

Impairment of dopaminergic system function after chronic treatment with corticotropin-releasing factor

Mounting evidence suggests that chronic stress may have a detrimental effect on dopaminergic function and, in certain individuals, could contribute to the pathophysiology of central nervous system disorders like depression, schizophrenia, and Parkinson's disease. Therefore, the effects of chronic elevated brain levels of corticotropin-releasing factor (CRF), a crucial mediator of the behavioral stress response, on dopaminergic function were investigated. Rats treated intracerebroventricularly (i.c.v.) with 1 microg of CRF per day for 13 days displayed a decreased stereotyped response to D-amphetamine 1 day after chronic CRF and 1 month post-CRF. These rats also displayed an increased cataleptic response to eticlopride at 2 days post-CRF, consistent with decreased functional activity in the dopaminergic systems. CRF treatment induced a transient decrease of dopamine tissue levels in the prefrontal cortex at 1 day and 1 week post-CRF, an increase in the nucleus accumbens 1 week post-CRF and no change in the striatum. An increase of the dihydroxyphenylacetic acid/dopamine (DOPAC/DA) ratio, an indicator of dopamine turnover, also was seen in the prefrontal cortex and striatum in CRF-treated animals at 1 week post-CRF. The dopaminergic system is very sensitive to oxidative insults. Levels of malondialdehyde, a membrane lipid peroxidation marker, also were measured in the same brain areas. In the prefrontal cortex, we observed a decrease of malondialdehyde at 1 week after chronic CRF treatment. This result may indicate an activation of the antioxidant system in response to chronic stress. These results show that chronic hyperactivity of the CRF system leads to a transient dysfunction of the dopaminergic systems, possibly through oxidative mechanisms, and suggest that stress could be a cofactor in the pathogenesis and/or progression of disorders of the dopaminergic systems.

Gene expression evidence for remodeling of lateral hypothalamic circuitry in cocaine addiction

By using high-density oligonucleotide arrays, we profiled gene expression in reward-related brain regions of rats that developed escalated cocaine intake after extended access to cocaine (6 h per day). Rats allowed restricted daily access to cocaine (only 1 h) that displayed a stable level of cocaine intake and cocaine naive rats were used for controls. Four analysis methods were compared: Affymetrix microarray suite 4 and microarray suite 5, which use perfect-match-minus-mismatch models, and dchip and rma, which use perfect-match-only models to generate expression values. Results were validated by RT-PCR in individual animals from an independent replication of the experiment. A small number of genes was associated with escalated cocaine intake (ESC genes). Unexpectedly, of the brain regions examined [prefrontal cortex, nucleus accumbens, septum, lateral hypothalamus (LH), amygdala, and ventral tegmental area], the LH was the most transcriptionally responsive in escalation of cocaine intake. Most of the ESC genes identified are also expressed during synaptogenesis and synaptic plasticity and include genes that code for several presynaptic and postsynaptic proteins involved in neurotransmission. These results suggest that LH intrinsic circuitry undergoes a structural reorganization during escalation of cocaine use. This remodeling of LH circuitry could contribute to the chronic deficit in reward function that has been hypothesized to drive the transition to drug addiction. Results also support the value of using multiple analysis strategies to identify the most robust changes in gene expression and to compensate for the biases that affect each strategy.

Gene profiling of laser-microdissected brain regions and sub-regions

The application of transcriptomics and proteomics approaches to accurately dissected anatomically-defined brain regions and sub-regions remains a central focus of current neurobiological investigations as well as a necessary step towards single-neuron neurogenomics and neuroproteomics. A protocol is described for the simple, rapid, and reproducible laser microdissection of brain regions and sub-regions for microarray-based gene expression analyses from individual rats or mice using two rounds of in vitro transcription (IVT). The results presented also demonstrate that the current Affymetrix GeneChip arrays are well suited for this experimental design with high reproducibility and limited effects of the shortening of target RNA caused by the double IVT approach.

Uncoupling protein 2 protects dopaminergic neurons from acute 1,2,3,6-methyl-phenyl-tetrahydropyridine toxicity

Oxidative stress is implicated in the death of dopaminergic neurons in sporadic forms of Parkinson's disease. Because oxidative stress can be modulated endogenously by uncoupling proteins (UCPs), we hypothesized that specific neuronal expression of UCP2, one member of the UCP family that is rapidly induced in the CNS following insults, could confer neuroprotection in a mouse model of Parkinson's disease. We generated transgenic mice overexpressing UCP2 in catecholaminergic neurons under the control of the tyrosine hydroxylase promoter (TH-UCP2). In these mice, dopaminergic neurons of the substantia nigra showed a twofold elevation in UCP2 expression, elevated uncoupling of their mitochondria, and a marked reduction in indicators of oxidative stress, an effect also observed in the striatum. Upon acute exposure to 1,2,3,6-methyl-phenyl-tetrahydropyridine, TH-UCP2 mice showed neuroprotection and retention of locomotor functions. Our data suggest that UCP2 may represent a drug target for slowing the progression of Parkinson's disease.

The metabotropic glutamate receptor 5 is necessary for late-phase long-term potentiation in the hippocampal CA1 region

Selective antagonists of the metabotropic receptors 1 (mGluR1), +/-2-methyl-4-carboxyphenylglycine (LY367385), and mGluR5, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), were used to investigate the role of group I metabotropic receptors in late-phase long-term potentiation (L-LTP) at Schaffer collateral/commissural fiber-CA1 synapses in rat hippocampal slices. L-LTP was induced with three trains of tetanization of 1 s duration at 100 Hz separated by 10-min intervals. Neither LY367385 nor MPEP affected basal synaptic responses at the doses used (200 and 10 microM, respectively) and only the mGluR5 inhibitor MPEP blocked L-LTP. However, in agreement with previous mouse mutant studies, we found that both LY367385 and MPEP inhibited the induction of an LTP obtained with a single train of tetanization of 1 s duration at 100 Hz. MPEP's ability to disrupt L-LTP was not due to an effect on NMDA responses since it did not affect pharmacologically isolated N-methyl-D-aspartate (NMDA) excitatory postsynaptic potentials (EPSPs). However, MPEP prevented the increased phosphorylation in dendrites of p70 S6 kinase (p70(S6K)) at Thr3889, a major regulator of translation required for the induction of protein synthesis-dependent forms of LTP.

HIV secreted protein Tat prevents long-term potentiation in the hippocampal CA1 region

HIV-associated dementia (HAD) is a complication of advanced HIV disease. Both viral products and host cytokines are believed to be involved in the pathogenesis of HIV-associated neurological manifestations. Among the viral products released by HIV-infected cells is the soluble protein Tat. We investigated the effect of exposure of organotypic hippocampal slices to 100 nM recombinant Tat 1-86 on long-term potentiation (LTP) of field excitatory postsynaptic potential (fEPSP) at Schaffer collateral/commissural fiber-CA1 synapses. Exposure to Tat 1-86 prevented the induction of LTP without affecting post-tetanic potentiation. Tat 1-72delta31-61, which lacks the neurotoxic domain of Tat, had no significant effect on LTP. Tat's ability to disrupt synaptic plasticity may be relevant to the pathogenesis of the cognitive impairments seen in patients with HIV disease.

Neurobiological mechanisms in the transition from drug use to drug dependence

Drug addiction is a chronic relapsing disorder characterized by compulsive drug intake, loss of control over intake, and impairment in social and occupational function. Animal models have been developed for various stages of the addiction cycle with a focus in our work on the motivational effects of drug dependence. A conceptual framework focused on allostatic changes in reward function that lead to excessive drug intake provides a heuristic framework with which to identify the neurobiologic mechanisms involved in the development of drug addiction. Neuropharmacologic studies in animal models have provided evidence for the dysregulation of specific neurochemical mechanisms in specific brain reward and stress circuits that provide the negative motivational state that drives addiction. The allostatic model integrates molecular, cellular and circuitry neuroadaptations in brain motivational systems produced by chronic drug ingestion with genetic vulnerability, and provides a new opportunity to translate advances in animal studies to the human condition.

Time-restricted role for dendritic activation of the mTOR-p70S6K pathway in the induction of late-phase long-term potentiation in the CA1

Mammalian target of rapamycin (mTOR) is a key regulator of translational capacity. The mTOR inhibitor rapamycin can prevent forms of protein synthesis-dependent synaptic plasticity such as long-term facilitation in Aplysia and late-phase long-term potentiation (L-LTP) in the hippocampal CA1 region of rodents. In the latter model, two issues remain to be addressed: defining the L-LTP phase sensitive to rapamycin and identifying the site of rapamycin-sensitive protein synthesis. Here, we show that L-LTP is sensitive to application of rapamycin only during the induction paradigm, whereas rapamycin application after the establishment of L-LTP was ineffective. Second, we observed that Thr-389-phosphorylated p70 S6 kinase (p70S6K), the main active phosphoform of the mTOR effector p70S6K, was induced in an N-methyl-D-aspartate and phosphatidylinositol 3-kinase-dependent manner throughout the dendrites but not in the cell bodies of CA1 neurons in hippocampal slices after L-LTP induction. A similar dendrite-wide activation of p70S6K was induced in primary hippocampal neurons by depolarization with KCL or glutamate. In primary hippocampal neurons, the sites of dendritic activation of p70S6K appeared as discrete compartments along dendritic shafts like the hotspots for fast dendritic translation. Conversely, only a subset of dendritic spines also displayed activated p70S6K. Taken together, the present data suggest that the N-methyl-d-aspartate-, phosphatidylinositol 3-kinase-dependent dendritic activation of the mTOR-p70S6K pathway is necessary for the induction phase of protein synthesis-dependent synaptic plasticity. Newly synthesized proteins in dendritic shafts could be targeted selectively to activity-tagged synapses. Thus, coordinated activation of dendrite-wide translation and synaptic-specific activation is likely to be necessary for long-term synaptic plasticity.

The transient depression of hippocampal CA1 LTP induced by chronic intermittent ethanol exposure is associated with an inhibition of the MAP kinase pathway

Using electrophysiological and biochemical approaches, we investigated the effects of chronic, intermittent ethanol (CIE) treatment on activation of the mitogen activated protein kinase (MAPK), also known as extracellular signal regulated protein kinase 1 and 2. In hippocampal slices taken from control rats, brief high-frequency stimulation to Schaffer collateral fibers induced a large post-tetanic potentiation (PTP) in the CA1 region that decayed to stable long-term potentiation (LTP) of field extracellular postsynaptic potentials. Western blot analyses showed that phosphorylation of MAPK was increased during PTP and returned to baseline levels during LTP. In slices from the rats removed immediately from CIE treatment, PTP and MAPK activation during the PTP was significantly less than that observed in control slices and LTP was absent. In slices from rats subjected to 1 day withdrawal from CIE treatment, both the reduction in MAPK phosphorylation during PTP and the impairment of PTP and LTP were still evident. Recovery of PTP and partial recovery of LTP was observed in slices obtained from 5-day withdrawn rats. However, MAPK activation during PTP was still attenuated significantly. Interestingly, MAPK activation was enhanced significantly during LTP in 5-day withdrawn rats as well as the sensitivity to MAPK inhibitor PD 098059. In addition to these changes in HFS-induced MAPK activation, we also observed a significant reduction in the basal phosphorylation of MAPK in slices removed from rats immediately after CIE treatment. These results implicate the MAPK signal transduction pathway as a potential cellular target of ethanol. Alterations in MAPKs could play an important role in the alcohol-induced changes in synaptic plasticity associated with the effects of alcohol abuse on learning and memory processes.

Neural plasticity and addiction: PI3-kinase and cocaine behavioral sensitization

Drug addiction has been linked to protracted functional changes in neural circuits involved in motivation that can lead to drug dependence, craving and relapse. Here we investigated the role of the phosphatidylinositol 3 kinase (PI3K) signal transduction pathway in long-lasting behavioral sensitization to cocaine in rats, an animal model of the long-lasting functional changes induced by repeated drug use. Our results show that PI3K is required for the expression, but not the induction, of behavioral sensitization to cocaine.

ERK regulation in chronic ethanol exposure and withdrawal

The extracellular signal regulated protein kinases (ERKs), also known as mitogen-activated protein kinases (MAPK) of 42 and 44 kd, play a crucial role in the induction of various forms of neural plasticity. Ethanol induces long-lasting functional changes that are more severe following repeated exposure and may involve intracellular signal transduction mechanisms. Therefore, we investigated the regulation of the ERK signal transduction pathway in models of continuous and intermittent ethanol exposure and withdrawal. Moderate blood alcohol levels (BALs) reduced ERK activation in most of the brain regions studied. Conversely, during withdrawal, activation of ERK was increased in most areas with some regional variations in the levels and kinetics of induction. The most dramatic effects were observed in the amygdala, the cerebellum, the striatum and the hippocampus. In the amygdala and the cerebellum, the activation of ERK observed during withdrawal was significantly higher after intermittent ethanol exposure than after continuous exposure, suggesting the establishment of a form of sensitization to the effects of withdrawal on ERK regulation. Thus the dysregulation of the ERK pathway could contribute to escalation of withdrawal symptoms induced by repeated withdrawal and possibly to the neuroadaptative changes believed to underlie progression towards addiction.

Inhibition of the ERK pathway prevents HIVgp120-induced REM sleep increase

Approximately 35% of HIV-infected subjects, both children and adults, exhibit alterations in the sleep-waking cycle. HIV surface glycoprotein gp120 has been postulated to contribute to this abnormality. For example, it has been reported that HIVgp120 modifies sleep in freely-moving rats and that it also activates the ERK pathway in brain slices. The goal of this work was to determine if sleep changes induced by HIVgp120 in normal rats are mediated by the MAPK pathway. Our results show that a single intraventricular administration of HIVgp120 selectively increases REMS and that such an increase can be prevented by U0126, an inhibitor of ERK activating enzyme, MEK. In contrast, SB202190, a MAPK-p38 inhibitor, had no effect on HIVgp120-induced increase in REMS. These results suggest that HIVgp120 increases REMS in the rat by specifically affecting the ERK signal transduction pathway.

Anti-DNA antibodies are a major component of the intrathecal B cell response in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of unknown cause that afflicts the central nervous system. MS is typified by a highly clonally restricted antigen-driven antibody response that is confined largely to the central nervous system. The major antigenic targets of this response and the role of antibody in disease pathogenesis remain unclear. To help resolve these issues, we cloned the IgG repertoire directly from active plaque and periplaque regions in MS brain and from B cells recovered from the cerebrospinal fluid of a patient with MS with subacute disease. We found that high-affinity anti-DNA antibodies are a major component of the intrathecal IgG response in the patients with MS that we studied. Furthermore, we show DNA-specific monoclonal antibodies rescued from two subjects with MS as well as a DNA-specific antibody rescued from an individual suffering from systemic lupus erythematosus bound efficiently to the surface of neuronal cells and oligodendrocytes. For two of these antibodies, cell-surface recognition was DNA dependent. Our findings indicate that anti-DNA antibodies may promote important neuropathologic mechanisms in chronic inflammatory disorders, such as MS and systemic lupus erythematosus.

Cocaine-predictive stimulus induces drug-seeking behavior and neural activation in limbic brain regions after multiple months of abstinence: reversal by D(1) antagonists

The conditioning of cocaine's subjective actions with environmental stimuli may be a critical factor in long-lasting relapse risk associated with cocaine addiction. To study the significance of learning factors in persistent addictive behavior as well as the neurobiological basis of this phenomenon, rats were trained to associate discriminative stimuli (S(D)) with the availability of i.v. cocaine vs. nonrewarding saline solution, and then placed on extinction conditions during which the i.v. solutions and S(D)s were withheld. The effects of reexposure to the S(D) on the recovery of responding at the previously cocaine-paired lever and on Fos protein expression then were determined in two groups. One group was tested immediately after extinction, whereas rats in the second group were confined to their home cages for an additional 4 months before testing. In both groups, the cocaine S(D), but not the non-reward S(D), elicited strong recovery of responding and increased Fos immunoreactivity in the basolateral amygdala and medial prefrontal cortex (areas Cg1/Cg3). The response reinstatement and Fos expression induced by the cocaine S(D) were both reversed by selective dopamine D(1) receptor antagonists. The undiminished efficacy of the cocaine S(D) to elicit drug-seeking behavior after 4 months of abstinence parallels the long-lasting nature of conditioned cue reactivity and cue-induced cocaine craving in humans, and confirms a significant role of learning factors in the long-lasting addictive potential of cocaine. Moreover, the results implicate D(1)-dependent neural mechanisms within the medial prefrontal cortex and basolateral amygdala as substrates for cocaine-seeking behavior elicited by cocaine-predictive environmental stimuli.

Nerve growth factor (NGF) influences differentiation and proliferation of myogenic cells in vitro via TrKA

Classic studies have established that muscle cells exert trophic actions on neurons of the developing peripheral nervous system through the production of neurotrophins. For this reason neurotrophins are also known as 'target-derived factors'. During differentiation, muscle cells also express some neurotrophin receptors, such as the low-affinity p75 neurotrophin receptor, which binds all neurotrophins, and the high affinity tyrosine kinase receptor TrKA, nerve growth factor (NGF) transducing receptor. The functional roles of these receptors in muscle cells are still unclear and only fragmentary and controversial data are available regarding the responsiveness of muscle cells to NGF. The aim of the present study is to investigate the effects of NGF on cells of myogenic lineage. The rat myogenic cell line L6, primary cultures of adult human myoblasts, and the human rhabdomyosarcoma cell line TE-671 were used in this study. As expected, all the three cell types expressed NGF, p75 and TrKA. NGF was expressed by L6 and primary myoblasts following differentiation, but it was constitutively expressed at high levels in the TE-671 rhabdomyosarcoma cells. In L6 myoblasts, p75 receptor was expressed in myoblasts but not in myotubes early after plating; while some primary human myoblasts expressed it at all the time-points tested. Some fusiform cells of the TE-671 rhabdomyosarcoma cell line also expressed p75. TrKA was constitutively immunodetected in all the three cell lines, suggesting that these cells may respond to NGF. Addition of exogenous NGF increased the fusion rate of both primary and L6 myoblasts, as well as the proliferation of the slowly dividing primary myoblasts. Consistently, blocking the action of endogenously produced NGF with a specific neutralizing antibody decreased the percentage of fusion in both primary and L6 myoblasts. On the contrary, blocking the binding of NGF to p75 did not affect the percentage of fusion. Furthermore, neither exogenous NGF nor NGF- or p75-neutralizing antibodies appeared to affect the rhabdomyosarcoma cells, which have a high proliferation rate and do not fuse. Pharmacological inhibition of TrKA signal transduction with K252a (in the nM range) and tyrphostin AG879 (in the low microM range) resulted in a dramatic dose-dependent decrease in proliferation of all of the myogenic cell lines tested. Interestingly, this was especially evident in the rapidly dividing rhabdomyosarcoma cell line. The TrKA inhibitors also blocked fusion of L6 and primary myoblasts and induced morphological changes characterized by the flattening of the cells and a 'spider-like' rearrangement of the intermediate filaments in all three cell lines with some minor differences. A transfection study showed that p75-overexpressing L6 cells do not fuse and present changes in their morphology similar to the TrKA-inhibitors treated L6 cells. These data support the notion that NGF expression in skeletal muscle is not only associated with a classical target-derived neurotrophic function for peripheral nervous system neurons, but also with an autocrine action which affects the proliferation, fusion into myotubes, and cell morphology of developing myoblasts. The present data also suggest that these effects of NGF are mediated by TrKA receptors and that a sustained presence of NGF is needed for increase fusion into myotubes. Lastly, the dramatic anti-proliferative effect of TrKA inhibitors on myogenic cells, and especially on the TE-671 rhabdomyosarcoma cell line, suggests that pharmacological interference with NGF signal transduction could be effective in the control of these malignancies.

Effect of nociceptin/orphanin FQ on the rewarding properties of morphine

The present study investigated the effect of nociceptin/orphanin FQ, the endogenous ligand of the opioid receptor-like 1 (ORL1) receptor, on the rewarding properties of morphine in the place conditioning paradigm. Intracerebroventricular (i.c.v.) injections of nociceptin/orphanin FQ, 500 or 1000 (but not 250) ng/rat, abolished conditioned place preference induced by subcutaneous (s.c.) injections of morphine (3 mg/kg). These doses of nociceptin/orphanin FQ induced neither place aversion nor preference per se. The same doses did not modify the rat performance in the Morris water test, suggesting that they do not disrupt spatial learning and memory. Moreover, these doses of nociceptin/orphanin FQ did not modify the development of morphine-induced locomotor sensitization, suggesting that they do not interfere with sensitization processes to morphine. The present results confirm and extend previous reports that nociceptin/orphanin FQ is able to abolish morphine-induced conditioned place preference, and raise interest for the possible role of nociceptin/orphanin FQ and ORL1 receptors in the control of opiate abuse.

A role for Src kinase in spontaneous epileptiform activity in the CA3 region of the hippocampus

Members of the Src family of nonreceptor protein tyrosine kinases (PTKs) have been implicated in the regulation of cellular excitability and synaptic plasticity. We have investigated the role of these PTKs in in vitro models of epileptiform activity. Spontaneous epileptiform discharges were induced in vitro in the CA3 region of rat hippocampal slices by superfusion with the potassium channel blocker 4-aminopyridine in Mg(2+)-free medium. In hippocampal slices treated in this fashion, Src kinase activity was increased and the frequency of epileptiform discharges could be greatly reduced by inhibitor of the Src family of PTKs, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), but not by the inactive structural analog 4-amino-7-phenylpyrazol[3,4-d]pyrimidine (PP3). 4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine also reduced epileptiform activity induced by either 4-aminopyridine or Mg(2+)-free medium alone. These observations demonstrate a role for Src family PTKs in the pathophysiology of epilepsy and suggest potential therapeutic targets for antiepileptic therapy.

Synergistic interactions of antibodies in rate of virus neutralization

Antibodies and antibody combinations are often evaluated only by their potency in inactivating a known quantity of virus in dose-effect assays. However, a crucial additional parameter is the rate at which neutralization takes place, or kinetics. Synergism of certain antibody combinations in dose-effect assays has been previously demonstrated. In the present report, using a battery of murine monoclonal antibodies to herpes simplex virus (HSV), we investigated whether antiviral antibodies can also synergize in neutralization kinetics. To determine whether synergism in dose-effect assays can predict synergism in neutralization rate, the ability of neutralizing antibodies to synergize in neutralization rate (kinetics) was compared to their ability to synergize in dose-effect assays (potency) in cell-free assays. Although certain antibody combinations synergized in both neutralization rate and potency, combinations that did not clearly synergize in potency could still significantly synergize in neutralization rate. Weak neutralizing antibodies could also greatly increase the neutralization rate of more potent antibodies. These results suggest that evaluating antibody combinations in dose-effect assays but not in neutralization kinetics provides a partial picture of neutralizing antibody dynamic interactions and may prevent the identification of certain favorable antibody combinations. These findings also support the importance of establishing defined antibody cocktails for prophylactic and therapeutic purposes. A simple strategy to evaluate antibody interactions in neutralization kinetics is proposed in which a quantitative prediction of additivity is made on the basis of the neutralization rate constants of the individual antibodies in the combination.

Localization of a passively transferred human recombinant monoclonal antibody to herpes simplex virus glycoprotein D to infected nerve fibers and sensory neurons in vivo

A human recombinant monoclonal antibody to herpes simplex virus (HSV) glycoprotein D labeled with the fluorescent dye Cy5 was administered to mice infected in the cornea with HSV type 1 (HSV-1). The distribution of such antibody in the corneas and trigeminal ganglia of the mice was then investigated by confocal microscopy. The antibody was detected on HSV-infected nerve fibers in the cornea--identified by colocalization with HSV antigens and the neuritic markers neurofilament, GAP-43, synapsin-1, and CNPase--and on the perikarya of sensory neurons in the HSV-1-infected neurons in ipsilateral trigeminal ganglia. Antibodies have been shown to be effective against many neurotropic viruses, often in the absence of obvious cell damage. Observations from experimental HSV infections suggest that antibodies could act in part by interfering with virus expression in the ganglia and/or with axonal spread. The present results provide morphological evidence of the localization of antiviral antibodies at anatomical sites relevant to such putative antibody-mediated protective actions and suggest that viral glycoproteins are accessible to antibodies on infected nerve fibers and sensory neurons.

Neutralizing antibodies inhibit axonal spread of herpes simplex virus type 1 to epidermal cells in vitro

The ability of antibodies to interfere with anterograde transmission of herpes simplex virus (HSV) from neuronal axons to the epidermis was investigated in an in vitro model consisting of human fetal dorsal root ganglia innervating autologous skin explants in a dual-chamber tissue culture system. The number and size of viral cytopathic plaques in epidermal cells after axonal transmission from HSV type 1 (HSV-1)-infected dorsal root ganglionic neurons were significantly reduced by addition to the outer chamber of neutralizing polyclonal human sera to HSV-1, of a human recombinant monoclonal group Ib antibody to glycoprotein D (gD), and of rabbit sera to HSV-1 gB and gD but not by rabbit anti-gE or anti-gG. A similar pattern of inhibition of direct infection of epidermal cells by these antibodies was observed. High concentrations of the monoclonal anti-gD reduced transmission by 90%. Rabbit anti-gB was not taken up into neurons, and human anti-gD did not influence spread of HSV in the dorsal root ganglia or axonal transport of HSV antigens when applied to individual dissociated neurons. These results suggest that anti-gD and -gB antibodies interfere with axonal spread of HSV-1, possibly by neutralizing HSV during transmission across an intercellular gap between axonal termini and epidermal cells, and thus contribute to control of HSV spread and shedding. Therefore, selected human monoclonal antibodies to protective epitopes might even be effective in preventing epidermis-to-neuron transmission during primary HSV infection, especially neonatal infection.

Modulation of serotonin 5-HT3 receptor expression in injured adult rat spinal cord motoneurons

The effects of sciatic nerve lesions on the expression of serotonin 5-HT3 receptor (5-HT3R) alpha subunit in motoneurons of the spinal cord was investigated by semi-quantitative immunohistochemistry. Following sciatic nerve crush, a significant reduction in density of staining in motoneurons was observed in longitudinal sections of the ventral horn at 3 and 15 days on the lesioned side when compared to the contralateral side (p<0.01). At 30 days after crush, after completion of sciatic nerve regeneration and reinnervation of peripheral targets, intensity of staining had returned to normal. Conversely, after sciatic nerve cut, a lesion that does not allow for target reinnervation, highly significant reductions were observed at 3, 15, 30 and 45 days. These results suggest a role for functional contacts with muscular targets in the maintenance of 5-HT3R expression in spinal motoneurons.

pFab-CMV, a single vector system for the rapid conversion of recombinant Fabs into whole IgG1 antibodies

We have constructed a single vector system for the rapid conversion of recombinant Fabs into whole IgG1 antibodies and their expression in eukaryotic cells. This vector, named pFab-CMV, utilizes the same unique cloning sites present on the pComb3 phagemid thus allowing for the direct subcloning of light chains and heavy chain Fd regions. pFab-CMV also allows for the expression of recombinant Fabs in eukaryotic cells by removal of a cassette containing part of the hinge, CH2 and CH3 sequences. Stable cell lines are rapidly obtained with pFab-CMV by NEO selection without the need for co-transfection of heavy and light chain expressing vectors.

Characterization of a type-common human recombinant monoclonal antibody to herpes simplex virus with high therapeutic potential

We report the characterization of a type-common human recombinant monoclonal antibody previously isolated by antigen selection from a phage-displayed combinatorial antibody library established from a herpes simplex virus (HSV)-seropositive individual. Competition with well-characterized murine monoclonal antibodies and immunodetection of gD truncations revealed that this antibody recognizes the group Ib antigenic site of glycoprotein D, a highly conserved and protective type-common determinant. To our knowledge, this is the first human group Ib monoclonal antibody ever described. The antibody also displayed first-order neutralization kinetics and a high neutralization rate constant, was capable of completely inhibiting syncytium formation by a fusogenic strain of HSV type 1, and efficiently neutralized low-passage clinical isolates of both HSV serotypes. Taken together with our earlier observations of the in vivo antiviral activities of this human recombinant antibody in animal models of HSV infection, the present results support the high therapeutic potential of this antibody.