Project description:Adolescent cannabis use increases the risk for cognitive impairments and psychiatric disorders. Cannabinoid receptor type 1 (Cnr1) is expressed not only in neurons and astrocytes, but also in microglia, which shape synaptic connections during adolescence. Nonetheless, until now, the role of microglia in mediating the adverse cognitive effects of delta-9-tetrahydrocannabinol (THC), the principal psychoactive constituent of cannabis, has been unexplored. Here, we report that adolescent THC exposure produces microglial apoptosis in the medial prefrontal cortex (mPFC), which was exacerbated in the mouse model of 16p11.2 duplication, a representative copy number variation (CNV) risk factor for psychiatric disorders. These effects are mediated by microglial Cnr1, leading to reduction in the excitability of mPFC pyramidal-tract neurons and deficits in social memory in adulthood. Our findings highlight the importance of microglial Cnr1 to produce the adverse effect of cannabis exposure in genetically vulnerable individuals.
Project description:Population-based studies show cannabis use doubles the risk of developing schizophrenia especially when use occurs in early adolescence (prior to age 15). However, the cause-and-effect mechanisms are largely unknown. To investigate the effect of cannabis on brain maturation and relation to the development of psychosis-like behaviours in adulthood, we treated young adolescent mice with vehicle or cannabis extract once a day for 2 weeks between postnatal days 14 and 28, and then collected hippocampal tissue for microarray analysis 12 weeks later. We identify a total of 78 differentially expressed genes (25 upregulated and 53 downregulated; p<0.05, fold change ± 1.2) and validate increases in dopamine D2 receptor (Drd2) and fatty acid amide hydrolase (Faah). Changes in Faah expression were limited to the hippocampus however Drd2 also increased in striatum but not prefrontal cortex or amygdala. When tested in adulthood with a behavioural panel relevant to schizophrenia, cannabis-treated mice displayed lower anxiety in the elevated zero-maze, decreased social preference, increased social novelty preference, mild cognitive impairments in a spatial version of the novel object recognition task and absence of latent inhibition when compared to vehicle controls. Adolescent treatment with cannabis extract thus lead to long-lasting changes in gene expression within the hippocampus which together result in behavioural deficits consistent with the negative and positive symptoms of schizophrenia.
Project description:Adolescence is a critical period in cognitive and emotional development, characterized by high levels of social interaction and increases in risk-taking behavior including binge drinking. Adolescent exposure to social stress and binge ethanol have individually been associated with the development of social, emotional, and cognitive deficits, as well as increased risk for alcohol use disorder. Disruption of cortical development by early life social stress and/or binge drinking may partly underlie these enduring emotional, cognitive, and behavioral effects. The study goal is to implement a novel neighbor housing environment to identify the effects of adolescent neighbor housing and/or binge ethanol drinking on (1) a battery of emotional and cognitive tasks (2) adult ethanol drinking behavior, and (3) the nucleus accumbens and prefrontal cortex transcriptome. Adolescent male and female C57BL/6J mice were single or neighbor housed with or without access to intermittent ethanol. One cohort underwent behavioral testing during adulthood to determine social preference, expression of anxiety-like behavior, cognitive performance, and patterns of ethanol intake. The second cohort was sacrificed in late adolescence and brain tissue was used for transcriptomics analysis. As adults, single housed mice displayed decreased social interaction, deficits in the novel object recognition task, and increased anxiety-like behavior, relative to neighbor-housed mice. There was no effect of housing condition on adolescent or adult ethanol consumption. Adolescent ethanol exposure did not alter adult ethanol intake. Transcriptomics analysis revealed that adolescent housing condition and ethanol exposure resulted in differential expression of genes related to synaptic plasticity in the nucleus accumbens and genes related to methylation, the extracellular matrix and inflammation in the prefrontal cortex. The behavioral results indicate that social interaction during adolescence via the neighbor housing model may protect against emotional, social, and cognitive deficits. In addition, the transcriptomics results suggest that these behavioral alterations may be mediated in part by dysregulation of transcription in the frontal cortex or the nucleus accumbens
Project description:Adolescent cannabis use has been associated with long-term cognitive dysfunction attributed to action of the main cannabis ingredient, delta-9-tetrahydrocannabinol (Δ9-THC), on the cannabinoid receptor 1 (CNR1). However, not all marijuana users develop cognitive impairment, suggesting a genetic vulnerability to adverse effects of cannabis. As both neurons and glial cells express CNR1, genetic vulnerability could influence Δ9-THC-induced signaling in a cell type-specific manner. Here we use an animal model of inducible expression of dominant-negative Disrupted-In-Schizophrenia-1 (DN-DISC1) selectively in astrocytes to evaluate the molecular mechanisms whereby an astrocyte genetic vulnerability could synergistically interact with adolescent Δ9-THC exposure to impair recognition memory in adulthood. We report that selective expression of DN-DISC1 in astrocytes and adolescent treatment with Δ9-THC synergistically affected recognition memory in adult mice. Similar deficits in recognition memory were observed following knockdown of endogenous Disc1 in hippocampal astrocytes in mice treated with Δ9-THC during adolescence. At the molecular level, DN-DISC1 and Δ9-THC synergistically activated the NF-kB-COX-2 (encoded by Ptgs2 gene) pathway in astrocytes and decreased immunoreactivity of parvalbumin-positive pre-synaptic inhibitory boutons around pyramidal neurons of the CA3 area of the hippocampus. The cognitive abnormalities were prevented in DN-DISC1 mice exposed to Δ9-THC by simultaneous adolescent treatment with the COX-2 inhibitor, NS389. Our data demonstrate that individual vulnerability to cannabis can be exclusively mediated by astrocytes. Results of this work suggest that genetic predisposition within astrocytes can exaggerate Δ9-THC-produced cognitive impairments via convergent inflammatory signaling, suggesting possible targets for preventing adverse effects of cannabis within susceptible individuals.
Project description:Background: Adolescent cannabis use leads to long-lasting behavioral changes involving cognitive and reward processes. However, the underlying molecular mechanisms are not well understood. To address this limitation, we performed gene network analyses using transcriptomic data from mice exposed during adolescence to Δ-9-tetrahydrocannabinol (THC), the major psychoactive component of cannabis. Methods: We injected vehicle or THC in female and male mice during the entire adolescence period. Two weeks following the last exposure, we measured recognition memory, social interaction and anxiety-related behaviors. We generated 120 RNA-seq datasets from 5 brain regions for each mouse. We performed differential gene expression analysis and constructed co-expression networks to identify THC-induced transcriptional alterations at the level of individual genes, gene networks, biological pathways, and cellular specificity. Further, we integrated THC-correlated gene networks with human traits from genome-wide association studies and performed key driver analysis to identify potential regulators of disorder-associated networks. Results: THC impaired cognitive behaviors of mice, with memory being more impacted in females, which coincided with larger transcriptional alterations in the female brain. Gene network analyses identified brain region-, cell type- and sex- specific co-expressed genes (“modules”) dysregulated by THC. THC-induced memory deficits in females were correlated with disruption of gene networks involved in endocannabinoid signaling and inflammation. Additional THC-correlated modules in both sexes involved converging pathways related to dopamine signaling and addiction processes. Moreover, the connectivity map of THC-correlated modules uncovered intra- and inter-region molecular circuitries influenced by THC. Further, modules altered by THC treatment were enriched in genes relevant for human cognition and schizophrenia. Conclusions: These findings provide novel insights concerning the genes, cell types, and pathways underlying persistent behavioral deficits induced by adolescent exposure to THC in a sex-specific manner, and highlight the connection between adolescent cannabis use and neuropsychiatric disorders in humans.
Project description:The mammalian gastrointestinal tract contains a diverse ecosystem of microbial species collectively making up the gut microbiome. Emerging evidence highlights a critical relationship between gut microbiota and neurocognitive development. Consumption of unhealthy yet palatable dietary factors associated with obesity and metabolic dysfunction (e.g., saturated fat, added sugar) produces microbiota dysbiosis and negatively impacts neurocognitive function, particularly when consumed during early life developmental periods. Here we explore whether excessive early life consumption of added sugars negatively impacts neurocognitive development via the gut microbiome. Using a rodent model of habitual sugar-sweetened beverage (SSB) consumption during the adolescent stage of development, we first show that excessive early life sugar intake impairs hippocampal-dependent memory function when tested during adulthood while preserving other neurocognitive domains. Gut microbiome genomic sequencing analyses reveal that early life SSB consumption alters the abundance of various bacterial populations, including elevations in operational taxonomic units within the genus Parabacteroides (P. distasonis and P. johnsonii) whose abundance negatively correlated with memory task performance. Additional results reveal that in vivo Parabacteroides enrichment of cultured P. distasonis and P. johnsonii bacterial species in adolescent rats severely impairs memory function during adulthood. Hippocampus transcriptome analyses identify gene expression alterations in neurotransmitter synaptic signaling, intracellular kinase signaling, metabolic function, neurodegenerative disease, and dopaminergic synaptic signaling-associated pathways as potential mechanisms linking microbiome outcomes with memory impairment. Collectively these results identify microbiota dysbiosis as a mechanism through which early life unhealthy dietary patterns negatively impact neurocognitive outcomes.
Project description:Adolescence is marked in part by the ongoing development of the prefrontal cortex (PFC). Binge ethanol use during this critical stage in neurodevelopment induces significant structural changes to the PFC, as well as cognitive and behavioral deficits that can last into adulthood. Previous studies showed that adolescent binge ethanol causes lasting deficits in working memory, decreases in the expression of chromatin remodeling genes responsible for the methylation of histone 3 lysine 36 (H3K36), and global decreases in H3K36 in the PFC. H3K36me3 is present within the coding region of actively-transcribed genes, and safeguards against aberrant, cryptic transcription by RNA Polymerase II. We hypothesize that altered methylation of H3K36 could play a role in adolescent binge ethanol-induced memory deficits. To investigate this at the molecular level, ethanol (4g/kg, i.g.) or water was administered intermittently to adolescent mice. RNA- and ChIP-sequencing were then performed within the same tissue to determine gene expression changes and identify genes and loci where H3K36me3 was disrupted by ethanol. We further assessed ethanol-induced changes at the transcription level with differential exon-use and cryptic transcription analysis – a hallmark of decreased H3K36me3. Here, we found ethanol-induced changes to the gene expression and H3K36me3-regulation of synaptic-related genes in all our analyses. Notably, H3K36me3 was differentially trimethylated between ethanol and control conditions at synaptic-related genes, and Snap25 and Cplx1 showed evidence of cryptic transcription in males and females treated with ethanol during adolescence. Our results provide preliminary evidence that ethanol-induced changes to H3K36me3 during adolescent neurodevelopment may be linked to synaptic dysregulation at the transcriptional level, which may explain the reported ethanol-induced changes to PFC synaptic function.
Project description:Adolescence is marked in part by the ongoing development of the prefrontal cortex (PFC). Binge ethanol use during this critical stage in neurodevelopment induces significant structural changes to the PFC, as well as cognitive and behavioral deficits that can last into adulthood. Previous studies showed that adolescent binge ethanol causes lasting deficits in working memory, decreases in the expression of chromatin remodeling genes responsible for the methylation of histone 3 lysine 36 (H3K36), and global decreases in H3K36 in the PFC. H3K36me3 is present within the coding region of actively-transcribed genes, and safeguards against aberrant, cryptic transcription by RNA Polymerase II. We hypothesize that altered methylation of H3K36 could play a role in adolescent binge ethanol-induced memory deficits. To investigate this at the molecular level, ethanol (4g/kg, i.g.) or water was administered intermittently to adolescent mice. RNA- and ChIP-sequencing were then performed within the same tissue to determine gene expression changes and identify genes and loci where H3K36me3 was disrupted by ethanol. We further assessed ethanol-induced changes at the transcription level with differential exon-use and cryptic transcription analysis – a hallmark of decreased H3K36me3. Here, we found ethanol-induced changes to the gene expression and H3K36me3-regulation of synaptic-related genes in all our analyses. Notably, H3K36me3 was differentially trimethylated between ethanol and control conditions at synaptic-related genes, and Snap25 and Cplx1 showed evidence of cryptic transcription in males and females treated with ethanol during adolescence. Our results provide preliminary evidence that ethanol-induced changes to H3K36me3 during adolescent neurodevelopment may be linked to synaptic dysregulation at the transcriptional level, which may explain the reported ethanol-induced changes to PFC synaptic function.
Project description:Peripubertal endocrine disruption has immediate and lifelong consequences on health, cognition, and lifespan. Disruption comes from dietary, environmental, and pharmaceutical sources. The plasticizer Bisphenol A (BPA) is one such endocrine disrupting chemical (EDC). However, it’s unclear if peripubertal BPA exposure incites long-lasting physiological, neuro-cognitive, and/or longevity-related metabolic impairments. Catabolism of cysteine via transsulfuration enzymes produces hydrogen sulfide (H2S), a redox-modulating gasotransmitter causative to endocrine and metabolic homeostasis and improved cognitive function with age. As thyroid hormone (TH) regulates hepatic H2S production and BPA is a TH receptor antagonist, we hypothesized BPA exposure during peripubertal development impairs metabolic and neuro-cognitive/behavioral endpoints in aged mice, in part, due to altered peripheral H2S production. Results: To test this, male C57BL/6J mice at 5 weeks of age were orally exposed for 5 weeks to 250 ug BPA/kg defined as low dose group (LD BPA), or 250 mg BPA/kg defined as high dose group (HD BPA). Both LD and HD BPA exposure decreased lean mass and increased fat mass. These changes were accompanied by decreased serum total TH. Additionally, LD BPA had an anxiogenic effect while HD BPA caused cognitive deficits. Notably, HD BPA attenuated renal H2S production both acutely and during aging, which correlated with spatial memory deficits. Innovation and Conclusion: These findings provide a potential mechanism of action for the acute and long-term health impacts of BPA-induced peripubertal endocrine disruption and bolster the need for improved monitoring and limitation of adolescent BPA exposure.
Project description:Alcohol use disorder (AUD) is a life-threatening disease characterized by compulsive drinking, cognitive deficits, and social impairment that continue despite negative consequences, which are driven by dysfunction of cortical areas, such as the orbitofrontal cortex (OFC), that normally balances decisions related to reward and risk. In this study, proteomics and machine learning analysis of post-mortem OFC brain samples collected from individuals with AUD revealed dysregulation of presynaptic (e.g., AP2A1) and mitochondrial proteins that predicted the occurrence and severity of AUD. Alcohol-sensitive OFC proteins also mapped to abnormal social behaviors and interactions. Validation using reverse genetics, we found that prefrontal Ap2a1 regulates alcohol drinking in genetically diverse mouse strains. Furthermore, we demonstrated sexual dimorphism in human OFC proteins that regulate extracellular matrix structure and signaling. Together, these findings highlight the impact of excessive alcohol consumption on the human OFC proteome and identify important cross-species cortical mechanisms underlying AUD.