Biology subjects

Bilbo, S. D.

Publications and source records attributed to Bilbo, S. D..

18 recordsLinked to original sources

bioRxiv2026

CGRP reception potentiates anxiety in an influenza A derived immune engram

An immune engram is a recently described phenomenon in which neuronal populations encode functional aspects of an immune challenge. Here we investigate an immune engram arising from respiratory infection with influenza A virus, demonstrating a molecular mechanism with differential influence over behavioral and immunological aspects of the engram. We first define a cellular response to acute non-neurotropic influenza A/Puerto Rico/8/1934 (PR8) infection by mapping cFos+ cells and microglia morphology across brain regions. In the posterior insula, this response has an early peak at 3 days post infection. Using a cre-dependent excitatory chemogenetic system in TRAP2 mice, we capture an engram at this same region and infection timepoint. Activation of this PR8 engram results in anxiety behavior and increased transcriptional expression of cytokines in lung tissue but not spleen tissue. We further explore how pulmonary signals contribute to this PR8 engram. Using tissue-specific, cre-dependent expression of diphtheria toxin fragment in Calcacre mice, we ablate Calca-expressing cells including pulmonary neuroendocrine cells in respiratory tissue. Loss of Calca-expressing cells prevents changes in synaptic engulfment by microglia in the insula during PR8 infection without altering the cellular response to infection in pulmonary tissue. Signaling of calcitonin gene related peptide (CGRP), a peptide encoded by Calca, can be blocked with the small molecule CGRP receptor antagonist rimegepant. Using rimegepant during acute PR8 infection we again demonstrate that loss of Calca signaling prevents the cellular response to PR8 infection in the insula. Finally, applying rimegepant alongside the chemogenetic system in TRAP2 mice we show that CGRP receptor antagonism during engram formation prevents anxiety behavior but not peripheral gene expression changes resulting from PR8 engram activation.

neuroscience↗

bioRxiv2025

Microglial MyD88-dependent signaling influences extracellular matrix development and interneuron maturation in the hippocampus

Parvalbumin interneurons (PVIs) are disrupted across diverse neurodevelopmental disorders, highlighting their vulnerability to developmental perturbations. Inflammation can perturb PVI development and function, and inflammatory mechanisms are often propagated within the brain by microglia. Yet the microglial mechanisms linking inflammatory signals to interneuron development are unclear. To test the role of microglial innate immune signaling in PVI development, we used mice lacking toll-like receptor adaptor MyD88 specifically in microglia. MyD88-deficient microglia showed reduced inflammatory responses but increased early-life phagocytosis of inhibitory synaptic material. In adulthood, males without microglial MyD88 exhibited increased hippocampal PVI density, increased extracellular matrix (ECM) deposition, increased inhibitory signaling, and impaired discrimination behaviors. We determined the cytokine interleukin (IL)-33, which normally drives adult microglial remodeling of the ECM, is developmentally regulated in the hippocampus. MyD88-deficient microglia fail to respond to IL-33, leading to reduced remodeling of the ECM component aggrecan. These results reveal microglial immune signaling via MyD88 regulates hippocampal inhibitory circuit development in a sex-specific manner.

neuroscience↗

bioRxiv2025

Preventing Microglial Reactivity Protects from Acute and Progressive Neuronal Dysfunction, Motor Impairments and Sedation following Alcohol Abuse

Alcohol abuse is the primary risk factor for alcohol use disorder (AUD), a leading cause of preventable morbidity and mortality, characterized by systemic inflammation, multi-organ damage, and neurological impairments. While direct effects of alcohol on brain function are well-established, the role of microglia in acute and chronic neurological dysfunction in AUD remains unclear. Using longitudinal in vivo imaging in mice during acute and repeated alcohol abuse, we found that microglia exhibit dynamic morphological responses that precede but parallel ethanol-induced sedation. Ethanol also induced microglia-dependent synapse elimination and reduced neuronal activity and density. Genetic disruption of microglial MyD88 reversed these ethanol-associated changes in microglial reactivity, neuronal structure, and function, while protecting against alcohol-induced intoxication and motor impairments. These findings identify microglia as cellular drivers of acute and chronic brain dysfunction following alcohol abuse, and highlight MyD88 as a critical therapeutic target for the detrimental neurological consequences of AUD.

neuroscience↗

bioRxiv2024

Neuron Derived Cytokine Interleukin-34 Controls Developmental Microglia Function

Neuron-microglia interactions dictate the development of neuronal circuits in the brain. However, the factors that regulate these processes across development are largely unknown. Here, we find that IL34, a neuron-derived cytokine, is upregulated in early development and maintains neuroprotective, mature microglia in the anterior cingulate cortex (ACC) of mice. We show that IL34 is upregulated in the second week of postnatal life and is expressed primarily in excitatory neurons. Excitatory-neuron specific knock-out of IL34 reduced microglia number and TMEM119 expression and increased aberrant microglial phagocytosis of excitatory thalamocortical synapses in the ACC. Acute, low dose blocking of IL34 at postnatal day 15 similarly decreased TMEM119 and inappropriately increased microglial phagocytosis of synapses. Viral overexpression of IL34 induced TMEM119 expression and prevented appropriate microglial phagocytosis of synapses. These findings establish IL34 as a key regulator of neuron-microglia crosstalk in postnatal brain development, controlling both microglial maturation and synapse engulfment.

neuroscience↗

bioRxiv2024

Microglial MyD88-dependent pathways are regulated in a sex specific manner in the context of HMGB1-induced anxiety

Chronic stress is a significant risk factor for the development and recurrence of anxiety disorders. Chronic stress impacts the immune system, causing microglial functional alterations in the medial prefrontal cortex (mPFC), a brain region involved in the pathogenesis of anxiety. High mobility group box 1 protein (HMGB1) is an established modulator of neuronal firing and a potent pro-inflammatory stimulus released from neuronal and non-neuronal cells following stress. HMGB1, in the context of stress, acts as a danger-associated molecular pattern (DAMP), instigating robust proinflammatory responses throughout the brain, so much so that localized drug delivery of HMGB1 alters behavior in the absence of any other forms of stress, i.e., social isolation, or behavioral stress models. Few studies have investigated the molecular mechanisms that underlie HMGB1-associated behavioral effects in a cell-specific manner. The aim of this study is to investigate cellular and molecular mechanisms underlying HMGB1-induced behavioral dysfunction with regard to cell-type specificity and potential sex differences. Here, we report that both male and female mice exhibited anxiety-like behavior following increased HMGB1 in the mPFC as well as changes in microglial morphology. Interestingly, our results demonstrate that HMGB1-induced anxiety may be mediated by distinct microglial MyD88-dependent mechanisms in females compared to males. This study supports the hypothesis that MyD88 signaling in microglia may be a crucial mediator of the stress response in adult female mice.

neuroscience↗

bioRxiv2023

Hofbauer cells and fetal brain microglia share transcriptional profiles and responses to maternal diet-induced obesity

Maternal immune activation is associated with adverse offspring neurodevelopmental outcomes, many mediated by in utero microglial programming. As microglia remain inaccessible throughout development, identification of noninvasive biomarkers reflecting fetal brain microglial programming could permit screening and intervention. We used lineage tracing to demonstrate the shared ontogeny between fetal brain macrophages (microglia) and fetal placental macrophages (Hofbauer cells) in a mouse model of maternal diet-induced obesity, and single-cell RNA-seq to demonstrate shared transcriptional programs. Comparison with human datasets demonstrated conservation of placental resident macrophage signatures between mice and humans. Single-cell RNA-seq identified common alterations in fetal microglial and Hofbauer cell gene expression induced by maternal obesity, as well as sex differences in these alterations. We propose that Hofbauer cells, which are easily accessible at birth, provide novel insights into fetal brain microglial programs, and may facilitate the early identification of offspring vulnerable to neurodevelopmental disorders in the setting of maternal exposures.

developmental biology↗

bioRxiv2023

Maternal diesel exposure and maternal choline supplementation interactions in fetal and placental immune factors

Air pollution causes widespread inflammatory changes in the body and brain. When exposure to air pollution occurs early in development, children exhibit impaired working memory ability (Sunyer et al., 2015). In addition, prenatal exposure to diesel particulate matter (DEP) increases inflammatory cytokine expression in the whole brain of embryonic day 18 (E18) males and leads to adverse long-term negative outcomes (Bolton et al., 2012). In contrast, dietary choline supplementation is negatively correlated with inflammatory cytokine production in adult rats and cultured human cells (Zhang et al., 2018; Jiang et al., 2014). When administered as a supplement to pregnant rats, choline also improves working memory in adulthood (Meck et al., 2008; Meck & Williams, 1999; 1997). The current study sought to determine if prenatal dietary choline supplementation protects against the effects of air pollution in the developing brain and in the placenta and fetal liver. These data revealed region-specific microglial morphology alterations in fetal brain and in inflammatory gene expression in the placenta and fetal liver (specifically, Tnf, Tlr2, Tlr4, and Itgam) due to maternal choline supplementation and/or maternal air pollution exposure. We found that DEP led to changes in microglial morphology in the fetal dentate gyrus of E18 male, but not female, fetuses. In the placenta and fetal liver of males, inflammatory gene expression was affected by both DEP and maternal choline supplementation. However, maternal choline supplementation alone upregulated inflammatory gene expression in females, which may indicate an alteration in maturation rate. These data further contribute to the growing literature indicating region- and tissue-specificity in the developmental immune system in the context of maternal exposures.

neuroscience↗

bioRxiv2022

Gonadal Hormones Impart Male-Biased Behavioral Vulnerabilities to Immune Activation via Microglial Mitochondrial Function

There is a strong male bias in the prevalence of many neurodevelopmental disorders such as autism spectrum disorder. However, the mechanisms underlying this sex bias remain elusive. Infection during the perinatal period is associated with an increased risk of neurodevelopmental disorder development. Here, we used a mouse model of early-life immune activation that reliably induces deficits in social behaviors only in males. We demonstrate that male-biased alterations in social behavior are dependent upon microglial immune signaling and are coupled to alterations in mitochondrial morphology, gene expression, and function specifically within microglia, the innate immune cells of the brain. Additionally, we show that this behavioral and microglial mitochondrial vulnerability to early-life immune activation is programmed by the male-typical perinatal gonadal hormone surge. These findings demonstrate that social behavior in males over the lifespan are regulated by microglia-specific mechanisms that are shaped by events that occur in early development.

neuroscience↗

bioRxiv2022

Social deficits induced by pervasive environmental stressors are prevented by microbial or dopaminergic modulation

Environmental toxicant exposure, including air pollution, is increasing worldwide. However, toxicant exposures are not equitably distributed. Rather, low-income and minority communities bear the greatest burden, along with higher levels of psychosocial stress. Both air pollution and maternal stress during pregnancy have been linked to neurodevelopmental disorders such as autism, but biological mechanisms and targets for therapeutic intervention remain poorly understood. We demonstrate that combined prenatal exposure to air pollution (diesel exhaust particles, DEP) and maternal stress (MS) in mice induces social behavior deficits only in male offspring, in line with the male bias in autism. These behavioral deficits are accompanied by changes in microglia and dopaminergic circuits in the brain, along with changes in the structure of the gut epithelium and microbiome. Importantly, DEP/MS-induced social deficits in males are prevented by shifting the gut microbiome by cross-fostering at birth and reversed by chemogenetic activation of the dopamine system.

neuroscience↗

bioRxiv2021

Single cell profiling of Hofbauer cells and fetal brain microglia reveals shared programs and functions

Maternal immune activation is associated with adverse offspring neurodevelopmental outcomes, many of which are mediated by in utero microglial programming. Microglia remain inaccessible at birth and throughout development, thus identification of noninvasive biomarkers that can reflect fetal brain microglial programming may permit screening and intervention during critical developmental windows. Here we used lineage tracing to demonstrate the shared ontogeny between fetal brain macrophages (microglia) and fetal placental macrophages (Hofbauer cells). Single-cell RNA sequencing of murine fetal brain and placental macrophages demonstrated shared transcriptional programs. Comparison with human datasets demonstrated that placental resident macrophage signatures are highly conserved between mice and humans. Single-cell RNA-seq identified sex differences in fetal microglial and Hofbauer cell programs, and robust differences between placenta-associated maternal macrophage/monocyte (PAMM) populations in the context of a male versus a female fetus. We propose that Hofbauer cells, which are easily accessible at birth, provide novel insights into fetal brain microglial programs, potentially facilitating the early identification of offspring most vulnerable to neurodevelopmental disorders.

developmental biology↗

bioRxiv2021

Prenatal opioid exposure inhibits microglial sculpting of the dopamine system during adolescence

The current opioid epidemic has dramatically increased the number of children who are prenatally exposed to opioids, including oxycodone. A number of social and cognitive abnormalities have been documented in these children as they reach young adulthood. However, little is known about the mechanisms underlying developmental effects of prenatal opioid exposure. Microglia, the resident immune cells of the brain, respond to acute opioid exposure in adulthood. Moreover, microglia are known to sculpt neural circuits during healthy development. Indeed, we recently found that microglial phagocytosis of dopamine D1 receptors (D1R) in the nucleus accumbens (NAc) is required for the natural developmental decline in NAc-D1R that occurs between adolescence and adulthood in rats. This microglial pruning occurs only in males, and is required for the normal developmental trajectory of social play behavior. However, virtually nothing is known as to whether this developmental program is altered by prenatal exposure to opioids. Here, we show in rats that maternal oxycodone self-administration during pregnancy leads to reduced adolescent microglial phagocytosis of D1R and subsequently higher D1R density within the NAc in adult male, but not female, offspring. Finally, we show that prenatal opioid exposure abolishes the extinction of oxycodone-conditioned place preference in these male offspring. This work demonstrates for the first time that microglia play a key role in translating prenatal opioid exposure to long-term changes in neural systems and behavior. HighlightsO_LIPrenatal opioid exposure decreases offspring viability and body weight in males and females C_LIO_LIPrenatal opioid exposure decreases microglial phagocytosis of D1R in the nucleus accumbens in males only C_LIO_LIPrenatal opioid exposure increases nucleus accumbens dopamine D1 receptor expression in males but not females C_LIO_LIAdult males fail to extinguish oxycodone-conditioned place preference following prenatal oxycodone exposure C_LI

neuroscience↗

bioRxiv2021

Maternal diet disrupts the placenta-brain axis in a sex-specific manner

High maternal weight is associated with a number of detrimental outcomes in offspring, including increased susceptibility to neurological disorders such as anxiety, depression, and communicative disorders (e.g. autism spectrum disorders)1-8. Despite widespread acknowledgement of sex-biases in the prevalence, incidence, and age of onset of these disorders, few studies have investigated potential sex-biased mechanisms underlying disorder susceptibility. Here, we use a mouse model to demonstrate how maternal high-fat diet, one contributor to overweight, causes endotoxin accumulation in fetal tissue, and subsequent perinatal inflammation influences sex-specific behavioral outcomes in offspring. In male high-fat diet offspring, increased macrophage toll like receptor 4 signaling results in excess phagocytosis of serotonin neurons in the developing dorsal raphe nucleus, decreasing serotonin bioavailability in the fetal and adult brain. Bulk sequencing from a large cohort of matched first trimester human fetal brain, placenta, and maternal decidua samples reveals sex-specific transcriptome-wide changes in placenta and brain tissue in response to maternal triglyceride accumulation (a proxy for dietary fat content). Further, we find that fetal brain serotonin levels decrease as maternal dietary fat intake increases in males only. These findings uncover a microglia-dependent mechanism through which maternal diet may impact offspring susceptibility for neuropsychiatric disorder development in a sex-specific manner.

neuroscience↗

bioRxiv2021

Morphine exposure bidirectionally alters c-Fos expression in a sex-, age-, and brain region-specific manner during adolescence

Drug and alcohol use during adolescence is common, and data in both humans and preclinical animal models clearly indicate drug exposure during adolescence increases the risk of substance use and other mental health disorders later in life. Adolescence is a period of social, emotional, and cognitive development, and is characterized by increased exploratory behavior, risk-taking, and peer-centered social interactions. These are thought to be behavioral manifestations of developmental plasticity in reward regions of the brain. Human data indicate that adolescence is not a unitary developmental period, but rather different neural and behavioral sequelae can be observed in early vs. late adolescence. However, most studies with rodent models examine a single adolescent age compared to a mature adult age, and often only in males. Herein, we sought to determine whether the acute response to the opioid morphine would also differ across adolescence, and by sex. By quantifying c-Fos positive cells, a proxy for neural activity, at different stages during adolescence (pre-, early, mid-, and late adolescence) and in multiple reward regions (prefrontal cortex, nucleus accumbens, caudate/putamen), we determined that acute morphine can either reduce or increase c-Fos expression dependent on adolescent age, sex, and brain region. These data suggest that heterogeneity in the consequences of adolescent opioid exposure may be due to the interaction between age- and sex-specific developmental profiles of reward processing in individual brain regions. In future studies, it will be important to add age within adolescence as an independent variable to fully capture the consequences of healthy or abnormal reward-related neural development.

neuroscience↗

bioRxiv2021

Sexually dimorphic placental responses to maternal SARS-CoV-2 infection

There is a persistent male bias in the prevalence and severity of COVID-19 disease. Underlying mechanisms accounting for this sex difference remain incompletely understood. Interferon responses have been implicated as a modulator of disease in adults, and play a key role in the placental anti-viral response. Moreover, the interferon response has been shown to alter Fc-receptor expression, and therefore may impact placental antibody transfer. Here we examined the intersection of viral-induced placental interferon responses, maternal-fetal antibody transfer, and fetal sex. Placental interferon stimulated genes (ISGs), Fc-receptor expression, and SARS-CoV-2 antibody transfer were interrogated in 68 pregnancies. Sexually dimorphic placental expression of ISGs, interleukin-10, and Fc receptors was observed following maternal SARS-CoV-2 infection, with upregulation in males. Reduced maternal SARS-CoV-2-specific antibody titers and impaired placental antibody transfer were noted in pregnancies with a male fetus. These results demonstrate fetal sex-specific maternal and placental adaptive and innate immune responses to SARS-CoV-2.

immunology↗

bioRxiv2021

Targeting tau mitigates mitochondrial fragmentation and oxidative stress in amyotrophic lateral sclerosis

Understanding the mechanisms underlying amyotrophic lateral sclerosis (ALS) is crucial for the development of new therapies. Recent evidence suggest that tau may be involved in ALS pathogenesis. Here, we demonstrated that hyperphosphorylated tau (pTau-S396) is mis-localized to synapses in human post-mortem motor cortex (mCTX) across ALS subtypes. Treatment with ALS synaptoneurosomes (SNs) derived from post-mortem mCTX, enriched in pTau-S396, increased oxidative stress, induced mitochondrial fragmentation, and altered mitochondrial connectivity in vitro. Furthermore, our findings revealed that pTau-S396 interacts with the pro-fission dynamin-related protein (DRP1), and similar to pTau-S396, DRP1 accumulated in ALS SNs across ALS subtypes. Lastly, reducing tau with a specific bifunctional degrader, QC-01-175, prevented ALS SNs-induced mitochondrial fragmentation and oxidative stress in vitro. Collectively, our findings suggest that increases in pTau-S396 may lead to mitochondrial fragmentation and oxidative stress in ALS and decreasing tau may provide a novel strategy to mitigate mitochondrial dysfunction in ALS. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=173 SRC="FIGDIR/small/436505v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1d805baorg.highwire.dtl.DTLVardef@1601f49org.highwire.dtl.DTLVardef@1a62abforg.highwire.dtl.DTLVardef@40699f_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIpTau-S396 mis-localizes to synapses in ALS. C_LIO_LIALS synaptoneurosomes (SNs), enriched in pTau-S396, increase oxidative stress and induce mitochondrial fragmentation in vitro. C_LIO_LIpTau-S396 interacts with the pro-fission GTPase DRP1 in ALS. C_LIO_LIReducing tau with a specific degrader, QC-01-175, mitigates ALS SNs-induced mitochondrial fragmentation and increases in oxidative stress in vitro. C_LI

neuroscience↗

bioRxiv2020

Prenatal Environmental Stressors Impair Postnatal Microglia Function and Adult Behavior in Males

Gestational exposure to environmental toxins and socioeconomic stressors are epidemiologically linked to neurodevelopmental disorders with strong male-bias, such as autism. We modeled these prenatal risk factors in mice, by co-exposing pregnant dams to an environmental pollutant and limited-resource stress, which robustly activated the maternal immune system. Only male offspring displayed long-lasting behavioral abnormalities and alterations in the activity of brain networks encoding social interactions. Cellularly, prenatal stressors diminished microglial function within the anterior cingulate cortex, a central node of the social coding network, in males during early postnatal development. Genetic ablation of microglia during the same critical period mimicked the impact of prenatal stressors on a male-specific behavior, indicating that environmental stressors alter neural circuit formation in males via impairing microglia function during development.

neuroscience↗

bioRxiv2020

Neonatal immune challenge induces female-specific changes in social behavior and somatostatin cell number, independent of microglial inflammatory signaling

Decreases in social behavior are a hallmark aspect of acute "sickness behavior" in response to infection. However, immune insults that occur during the perinatal period may have long-lasting consequences for adult social behavior by impacting the developmental organization of underlying neural circuits. Microglia, the resident immune cells of the central nervous system, are sensitive to immune stimulation and play a critical role in the developmental sculpting of neural circuits, making them likely mediators of this process. Here, we investigated the impact of a postnatal day (PND) 4 lipopolysaccharide (LPS) challenge on social behavior in adult mice. Somewhat surprisingly, neonatal LPS treatment decreased sociability in adult female, but not male mice. LPS-treated females also displayed reduced social interaction and social memory in a social discrimination task as compared to saline-treated females. Somatostatin (SST) interneurons within the anterior cingulate cortex (ACC) have recently been suggested to modulate a variety of social behaviors. Interestingly, the female-specific changes in social behavior observed here were accompanied by an increase in SST interneuron number in the ACC. Finally, these changes in social behavior and SST cell number do not appear to depend on microglial inflammatory signaling, because microglia-specific genetic knock-down of myeloid differentiation response protein 88 (MyD88; the removal of which prevents LPS from increasing proinflammatory cytokines such as TNF and IL-1{beta}) did not prevent these LPS-induced changes. This study provides novel evidence for enduring effects of neonatal immune activation on social behavior and SST interneurons in females, independent of microglial inflammatory signaling.

neuroscience↗

bioRxiv2017

Microglial elimination of dopamine D1 receptors defines sex-specific changes in nucleus accumbens development and social play behavior during adolescence

Adolescence is a developmental period in which the mesolimbic dopaminergic reward circuitry of the brain, including the nucleus accumbens (NAc), undergoes significant developmental plasticity and neural circuit maturation. Dopamine D1 receptors (D1rs) in the NAc have recently been demonstrated to be critical modulators of social behavior, but how these receptors are regulated in adolescence to mediate social behavior is not well understood. In this report, we used multi-plexed immunohistochemistry with volumetric reconstructions, co-immunoprecipitation, ex vivo, and in vivo stereotaxic, microglial manipulation, and social behavior assessment to demonstrate that microglia and complement-mediated phagocytic activity shapes sex-specific NAc development. Moreover, we report for the first time that microglia-mediated phagocytosis is required for natural developmental changes in behavior, specifically, adolescent male social play behavior. These data have broad implications for understanding how experience interacts with the developing reward circuity, sex-specific responses to stimuli in adolescence, and how neuropsychiatric disorders may arise in a sexually dimorphic manner.

neuroscience↗