Polygenic Risk for Alcohol Use Disorder Affects Cellular Responses to Ethanol Exposure in a Human Microglial Cell Model II
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ABSTRACT: Polygenic risk scores (PRS) assess genetic susceptibility to Alcohol Use Disorder (AUD), yet their molecular implications remain underexplored. Neuroimmune interactions, particularly in microglia, are recognized as significant contributors to AUD pathophysiology. We investigated the interplay between AUD PRS and ethanol in human microglia derived from iPSCs from individuals with high-or low-PRS (HPRS or LPRS) of AUD. Ethanol exposure induced elevated CD68 expression and morphological changes in microglia, with differential responses between HPRS and LPRS microglial cells. Transcriptomic analysis revealed expression differences in MHCII complex and phagocytosis-related genes following ethanol exposure; HPRS microglial cells displayed enhanced phagocytosis and increased CLEC7Aexpression, unlike LPRS microglial cells. Synapse numbers in co-cultures of induced neurons with microglia after alcohol exposure were lower in HRPS co-cultures, suggesting possible excess synapse pruning. This study provides insights into the intricate relationship between AUD PRS, ethanol, and microglial function, potentially influencing neuronal functions in developing AUD.
Project description:Polygenic risk scores (PRS) assess genetic susceptibility to Alcohol Use Disorder (AUD), yet their molecular implications remain underexplored. Neuroimmune interactions, particularly in microglia, are recognized as significant contributors to AUD pathophysiology. We investigated the interplay between AUD PRS and ethanol in human microglia derived from iPSCs from individuals with high-or low-PRS (HPRS or LPRS) of AUD. Ethanol exposure induced elevated CD68 expression and morphological changes in microglia, with differential responses between HPRS and LPRS microglial cells. Transcriptomic analysis revealed expression differences in MHCII complex and phagocytosis-related genes following ethanol exposure; HPRS microglial cells displayed enhanced phagocytosis and increased CLEC7Aexpression, unlike LPRS microglial cells. Synapse numbers in co-cultures of induced neurons with microglia after alcohol exposure were lower in HRPS co-cultures, suggesting possible excess synapse pruning. This study provides insights into the intricate relationship between AUD PRS, ethanol, and microglial function, potentially influencing neuronal functions in developing AUD.
Project description:Alcohol use disorders (AUD) are one of the most common preventable mental health disorders and can result in pathology within the CNS, including the cerebellum. Cerebellar alcohol exposure during adulthood has been associated with disruptions in proper cerebellar function. However, the mechanisms regulating ethanol-induced cerebellar neuropathology are not well understood. High-throughput next generation sequencing was performed to compare control versus ethanol treated adult C57BL/6J mice in a chronic plus binge model of AUD. Mice were euthanized, cerebella were microdissected, RNA was isolated, and RNA-sequencing was performed. Down-stream transcriptomic analyses revealed significant changes in gene expression and global biological pathways in control versus ethanol treated mice that included pathogen-influenced signaling pathways and cellular immune response pathways. Microglial associated genes showed a decrease in homeostatic molecules and an increase in molecules associated with chronic neurodegenerative diseases, while astrocyte associated genes showed an increase in molecules associated with acute injury. Oligodendrocyte lineage cell genes showed a decrease in molecules associated with both early-stage progenitors as well as mature myelinating oligodendrocytes. These data provide new insight into the mechanisms by which ethanol induces cerebellar neuropathology and alterations to the immune response in AUD.
Project description:Alzheimer’s disease (AD) is a progressive neurodegenerative disorder marked by the buildup of amyloid-β and tau protein tangles. Alcohol use has been identified as a risk factor for AD; however, the molecular mechanisms underlying this potential causal link remain elusive. An emerging area of research focuses on the role of microglia, the brain's innate immune cells, in AD pathogenesis, with evidence suggesting that alcohol exposure may prime microglia to exhibit an exaggerated immune response when they are subsequently exposed to proinflammatory stimuli. We used a single 10-day chronic-plus-binge alcohol exposure model in male and female C57BL/J mice aged 8- to 10-weeks old. One month later, tauopathy was induced via adenoviral vector (AAV)-mediated overexpression of h-p301L tau. After 2.5 months, the mice underwent behavioral and cognitive testing. Two weeks later, microglia were collected using fluorescence-activated cell sorting (FACS) and processed for unbiased mass spectrometry and deep proteomic analysis to determine the molecular pathways related to microglial reactivity. Microglia from mice exposed to alcohol in young adulthood exhibited a blunted immune response when challenged with AAV-mediated delivery and accumulation of human tau later in life. This was characterized by decreased expression of MHC II- and interferon-associated proteins and bioinformatic prediction of inhibited inflammation-related pathways in the absence of gross histological, behavioral, or cognitive deficits. These results demonstrate unique, temporally specific microglial reactivity to tau that is modulated by early life alcohol exposure, implicating a microglial response that could negatively affect the mechanisms necessary for tau clearance and potentially exacerbate tau pathogenesis. This study provides novel insights into the long-term effects of early alcohol exposure on microglial function and the complexity of context-dependent microglial involvement in tau pathology. Consideration of early life environmental factors is critical for understanding and potentially mitigating the risk of neurodegenerative diseases, such as AD.
Project description:We recently established ACSS2 as a potential candidate for therapeutic interventions in alcohol use disorders (AUD), in which memory of alcohol-associated environmental cues is a primary driver of craving and relapse. Prior research, however, has been limited to passive exposure to ethanol and the importance of this pathway in models of voluntary drinking that better approximate human alcohol consumption remains unknown. Therefore, we assessed the effect of genetic ACSS2 inhibition on voluntary alcohol intake and simultaneously assayed the epigenetic and transcriptional changes that accompany alcohol consumption.
Project description:Microglia, the resident immune cells of the brain, can exhibit a broad range of activation phenotypes, many of which have been implicated in several diseases and disorders of the central nervous system including alcohol use disorders and disorders. By utilizing a method optimized for sensitive and rapid quantitative proteomic analysis of microglia involving suspension trapping (S-Trap), we were able to produce efficient and reproducible protein extraction from low cell yielding primary mouse brains. Using a ~2 h gradient on a 75 cm UPLC column with a modified data dependent acquisition method on a hybrid quadrupole-Orbitrap mass spectrometer (QE Plus), 5,062 total proteins were identified where 4,928 of those proteins were quantifiable by label-free quantitation (with 5 biological replicates). This analysis resulted in the most comprehensive proteomic dataset for ethanol- and LPS-treated primary mouse microglia to date and even expanded upon the well-characterized macrophage/microglia response to LPS treatment. This study also highlights the subtle, yet significant changes ethanol exposure can induce when compared to control. Interestingly, these changes are not consistent with the robust classical activation induced by LPS treatment, but instead align with the emerging theory that ethanol-treated microglia yield an alternative activation response. The contrast to LPS-treated microglia leads us to conclude that ethanol does not elicit a strong inflammatory response but rather might have a general inhibitory effect on multiple pathways such as phagocytosis and cell migration.
Project description:Purpose: Alcohol dependence results in microglia proliferation in brain and changes in microglia morphology and function. However, it remains unknown if microglia initiate or simply amplify the neuroadaptations that lead to alcohol dependence. Here we determined microglia function in chronic intermittent ethanol exposure behaviors using a colony stimulating factor 1 receptor inhibitor (PLX5622) and 3’UTR biased-sequencing. Therefore, the purpose of this study was to provide insight into how microglia may regulate neuroadaptations due to alcohol dependence. Methods: We performed 3’UTR biased transcriptome sequencing (3’Tag-seq) on total homogenate isolated from the prefrontal cortex (PFC) and central nucleus of the amygdala (CeA) of C57BL6/J mice following microglia depletion and chronic intermittent ethanol exposure. Results: Differential expression analysis and WGCNA network analysis revealed that microglia depletion prevents both immune and synaptic gene expression changes that are linked with the formation of alcohol dependence. This suggested that microglia are key regulators of the transition from alcohol misuse to alcohol dependence. Conclusion: Taken together our behavioral and transcriptional data indicate that microglia are the primary effector cell responsible for regulation of alcohol dependence. In addition, our data represents a novel resource for groups interested in transcriptional effects of microglia depletion after alcohol dependence.
Project description:Purpose: The goal of this study to use ethanol-exposed human embryonic stem cell (hESC)-derived neural cells as models to investigate microRNA expression changes in the brains of subjects with alcohol use disorder (AUD). Methods: hESCs were differentiated into neural cells (mainly cortical interneurons), which were then cultured in media with or without ethanol (50-100 mM) for 7 days (by duplicate experiments). Total RNAs were extracted from hESC-derived neural cells (with or without ethanol exposure) for small RNA sequencing. The sequence reads were processed using the Comprehensive Analysis Pipeline for miRNA Sequencing Data (CAP-miRseq) workflow. Ethanol-induced miRNA transcriptomic changes were analyzed by the Limma-Voom method. Results: A 7-day ethanol exposure led to differential expression of six miRNAs (absolute FC>2.0 & P<0.05) in hESC-derived cortical interneurons. Three miRNAs were upregulated (>2-fold increase & P<0.05), while three other miRNAs were downregulated (> 2-fold decrease & P < 0.05) due to ethanol exposure. Conclusions: The hESC-derived neural cell model study can partially validate miRNA transcriptomic changes in postmortem brains of subjects with alcohol use disorder.
Project description:Purpose: The goal of this study to use ethanol-exposed human embryonic stem cell (hESC)-derived neural cells as models to investigate mRNA expression changes in the brains of subjects with alcohol use disorder (AUD). Methods: hESCs were differentiated into neural cells (mainly cortical interneurons), which were then cultured in media with or without ethanol (50-100 mM) for 7 days (by duplicate experiments). Total RNAs were extracted from hESC-derived neural cells (with or without ethanol exposure) for mRNA sequencing. The sequence reads were processed using the RNA-seq processing pipeline Pipeliner [Front Genet. 2019; 10:614] workflow. Ethanol-induced mRNA transcriptomic changes were analyzed by the Limma-Voom method. Results: When the significance level was set at FC>2.0 & P<0.01, 19 coding genes showed differential expression, and all of them were downregulated after a 7-day ethanol exposure. Conclusions: The hESC-derived neural cell model study can partially validate mRNA transcriptomic changes in postmortem brains of subjects with alcohol use disorder.
Project description:Neuron-microglia interactions dictate the development of neuronal circuits in the brain. However, the factors that support and broadly regulate these processes across developmental stages are largely unknown. Here, we find that IL34, a neuron-derived cytokine, is upregulated in development and plays a critical role in supporting and maintaining neuroprotective, mature microglia in the anterior cingulate cortex (ACC) of mice. We show that IL34 mRNA and protein is upregulated in neurons in the second week of postnatal life and that this increase coincides with increases in microglia number and expression of mature, homeostatic markers, e.g., TMEM119. We also found that IL34 mRNA is higher in excitatory (compared to inhibitory) neurons. Global genetic KO of IL34 reduced microglia numbers and prevented the functional maturation of microglia, and excitatory-neuron specific KO of IL34 similarly impacted microglia and increased aberrant microglial phagocytosis of excitatory thalamocortical synapses in the ACC. Acute, low dose blocking of IL34 at postnatal day (P)15 in mice decreased microglial TMEM119 protein and also increased microglial phagocytosis of excitatory thalamocortical synapses during an inappropriate time in development. In contrast, viral overexpression of IL34 early in life (P1-P8) caused early maturation of microglia and prevented microglial phagocytosis of thalamocortical synapses during the appropriate neurodevelopmental refinement window. Taken together, these findings establish IL34 as a key regulator of neuron microglia crosstalk in postnatal brain development, controlling both microglial maturation and synapse engulfment.
Project description:Repeated excessive alcohol consumption is a risk factor for alcohol use disorder (AUD). Although AUD has been more common in men than women, women develop more severe behavioral and physical impairments. However, relatively few new therapeutics targeting development of AUD have been validated. Here, to gain a better understanding of molecular mechanisms underlying alcohol intake, we conducted a genome-wide RNA-sequencing analysis in female mice exposed to different modes (acute vs chronic) of ethanol drinking. We focused on transcriptional profiles in amygdala including the central and basolateral subnuclei, brain areas previously implicated in alcohol drinking and seeking. We found distinct gene expression patterns and canonical pathways induced by both acute and chronic intake. Surprisingly, both drinking modes triggered similar transcriptional changes, including up-regulation of ribosome-related/translational pathways and myelination pathways, and down-regulation of chromatin binding and histone modification. Notably, multiple genes that were significantly altered with alcohol drinking, including Atp2b1, Hspa4, Slc4a7, Sbno1, Ubxn2b, Nfkb1, Nts, and Hdac2, had previously been associated with human AUD via GWAS or other genomic studies. In addition, subsequent analyses of hub genes and upstream regulatory pathways predicted that voluntary ethanol consumption affects epigenetic changes via histone deacetylation pathways, oligodendrocyte and myelin function, and the oligodendrocyte-related transcription factor, Sox17. Overall, our results suggest that the expression of oligodendrocyte-related genes in the central and basolateral subnuclei of the amygdala is sensitive to voluntary alcohol drinking. These findings suggest potential molecular targets for future therapeutic approaches to prevent the development of AUD, particularly in women, due to repeated excessive alcohol consumption