Biology subjects

Bollinger, J. L.

Publications and source records attributed to Bollinger, J. L..

6 recordsLinked to original sources

bioRxiv2025

Microglial brain-derived neurotrophic factor (BDNF) supports the behavioral and synaptogenic effects of ketamine

Microglia have been implicated in the pathogenesis for several psychiatric disorders, yet comparatively little is known about their role in treatments for these conditions. Prior work showed that the rapid-acting antidepressant ketamine increases synaptic density in the prefrontal cortex (PFC), and that brain-derived neurotrophic factor (BDNF) signaling is required for its synaptic and behavioral effects. These studies assumed that neurons were the primary source of BDNF, but other studies have since demonstrated that microglia can produce BDNF in the brain. Still, it remains unclear if microglial BDNF is important for the antidepressant-like effects of ketamine. Our initial studies show that the behavioral and synaptic effects of ketamine are associated with increased Bdnf expression in sorted PFC microglia 24 hours after injection. We then demonstrate that conditional BDNF depletion in microglia (Cx3cr1Cre/+:Bdnffl/fl) reduces GluN2B levels in PFC synaptoneurosomes and attenuates antidepressant-like responses following ketamine treatment compared to genotype controls (Cx3cr1Cre/+:Bdnf+/+). Consistent with this, we found that Cx3cr1Cre/+:Bdnffl/fl mice show no change in dendritic spine density in the PFC following ketamine. These results indicate that microglial BDNF is important for the effects of ketamine on brain and behavior, expanding upon the role of microglia in pharmacological interventions for psychiatric disorders.

neuroscience↗

bioRxiv2025

Characterization of active kinase signaling pathways in astrocytes and microglia

Protein kinases are central to healthy brain function, regulating critical cellular processes through complex signaling networks. However, understanding differences in kinase signaling of brain cells remains a preeminent challenge of neuroscience. This study aimed to characterize kinase pathways enriched in astrocytes and microglia isolated from male and female murine prefrontal cortex. Using the PamGene PamStation(R)12 platform, we discovered cell-type-specific kinomic profiles and computationally reconstructed each cell types unique active signaling protein-protein interaction network. Notably, our analysis revealed minimal overlap between kinase activity and respective cell-subtype specific kinase transcriptional profiles identified in the Allen Mouse Whole Brain Transcriptomic Cell Type Atlas, highlighting an important limitation of relying solely on gene mRNA expression levels for functional inference in kinase focused studies. These findings also suggest that cell- and sex-specific protein kinase signaling may influence susceptibility to deleterious brain conditions and consequently underscore the importance of considering activity as a biological variable in systems research, offering a new framework for developing targeted therapeutic interventions in precision medicine.

bioinformatics↗

bioRxiv2024

Stress-induced dysfunction of neurovascular astrocytes contributes to sex-specific behavioral deficits

Astrocytes form an integral component of the neurovascular unit, ensheathing brain blood vessels with projections high in aquaporin-4 (AQP4) expression. These AQP4-rich projections facilitate interaction between the vascular endothelium, astrocytes, and neurons, and help stabilize vascular morphology. Studies using preclinical models of psychological stress and post-mortem tissue from patients with major depressive disorder (MDD) have reported reductions in AQP4, loss of astrocytic structures, and vascular impairment in the prefrontal cortex (PFC). Though compelling, the role of AQP4 in mediating stress-induced alterations in blood vessel function and behavior remains unclear. Here, we address this, alongside potential sex differences in chronic unpredictable stress (CUS) effects on astrocyte phenotype, blood-brain barrier integrity, and behavior. CUS led to pronounced shifts in stress-coping behavior and working memory deficits in male -but not female- mice. Following behavioral testing, astrocytes from the frontal cortex were isolated for gene expression analyses. We found that CUS increased various transcripts associated with blood vessel maintenance in astrocytes from males, but either had no effect on-or decreased-these genes in females. Furthermore, CUS caused a reduction in vascular-localized AQP4 and elevated extravasation of a small molecule fluorescent reporter (Dextran) in the PFC in males but not females. Studies showed that knockdown of AQP4 in the PFC in males is sufficient to disrupt astrocyte phenotype and increase behavioral susceptibility to a sub-chronic stressor. Collectively, these findings provide initial evidence that sex-specific alterations in astrocyte phenotype and neurovascular integrity in the PFC contribute to behavioral and cognitive consequences following chronic stress.

neuroscience↗

bioRxiv2022

Molecular Neurobiology of Loss

Psychological loss is a common experience that erodes well-being and negatively impacts quality of life. The molecular underpinnings of loss are poorly understood. Here, we investigate the mechanisms of loss using an enrichment removal (ER) paradigm in rats. A comprehensive multi-omics investigation of the basolateral amygdala (BLA) revealed alterations in microglia and extracellular matrix (ECM). Follow-up studies indicated that ER decreased microglia size, complexity, and phagocytosis, suggesting reduced immune surveillance. Loss also substantially increased ECM coverage, specifically targeting perineuronal nets surrounding parvalbumin interneurons, suggesting decreased plasticity and increased inhibition in the BLA following loss. Behavioral analyses suggest that these molecular effects are linked to impaired BLA salience evaluation, reflecting emotional blunting observed in human loss. These loss-like behaviors could be rescued by depleting BLA ECM during removal, helping us understand the mechanisms underlying loss and revealing novel molecular targets to ameliorate its impact.

neuroscience↗

bioRxiv2022

Microglial P2Y12 mediates chronic stress-induced synapse loss in the prefrontal cortex and associated behavioral consequences in male mice

Recent studies demonstrate that chronic unpredictable stress (CUS) drives microglia-mediated neuronal remodeling, contributing to synapse loss in the prefrontal cortex (PFC) and cognitive-behavioral dysfunction. Nonetheless, it remains unclear what mechanisms guide microglia-neuron interactions in stress. Evidence indicates that neuronal activity-dependent purinergic signaling directs microglial processes and microglia-synapse interaction via P2Y12, a purinergic receptor exclusively expressed by microglia in the brain. Stress exposure alters excitatory neurotransmission in the PFC, thus we aimed to determine if P2Y12 signaling promotes functional changes in microglia in the context of chronic stress. Using an activating DREADD, our initial studies showed that PFC microglia adopt a CUS-associated phenotype after repeated pyramidal neuronal activation. To further investigate the role of purinergic signaling, we used genetic (P2ry12-/-) or pharmacological (clopidogrel, ticagrelor) approaches to block P2Y12 in the context of CUS. Various behavioral, physiological, and cytometric endpoints were analyzed. Both P2Y12-deletion and treatment with clopidogrel prevented increases in forced swim test immobility and attenuated deficits in temporal object recognition following CUS. Flow cytometry of PFC microglia revealed that both P2ry12-/- mice and those treated with clopidogrel have significantly different phenotypes (independent of CUS); with diminished P2Y12 expression and altered surface levels of CX3CR1, CSF1R, and CD11b. Immunohistology in Thy1-GFP(M) mice demonstrated that pharmacological blockade of P2Y12 prevented stress-induced increases in the proportion of microglia with GFP+ neuronal inclusions and limited dendritic spine loss in the PFC. Together, these findings indicate that microglial P2Y12 is a critical mediator of stress-induced neuronal remodeling in the PFC and subsequent behavioral deficits.

neuroscience↗

bioRxiv2021

Acyloxyacyl Hydrolase Regulates Microglia-Mediated Pelvic Pain Through Toll-Like Receptor-4

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a devastating condition of chronic pelvic pain and urinary dysfunction. We have shown that mice deficient for the lipase acyloxyacyl hydrolase (AOAH) develop pelvic allodynia and exhibit symptoms and comorbidities consistent with IC/BPS, as well as gut dysbiosis. Microglia are resident immune cells of the central nervous system (CNS) that respond to changes in the gut microbiome, and studies have linked microglial activation to neuropathic pain. Additionally, microglia express toll-like receptors (TLRs), including TLR4, which are activated by microbial components. We have previously shown that AOAH-deficient mice exhibit increased gut permeability, suggesting a possible mechanism of microglial TLR4 activation via translocation of microbial products across the intestinal barrier to the brain. Here, we assessed the role of AOAH and TLR4 in microglial activation and pelvic pain. AOAH immunoreactivity co-localized with the microglial marker P2YR12 but not astrocytes, suggesting a functional role for AOAH in microglia. Pharmacologic ablation of CNS microglia with PLX5622 resulted in decreased pelvic allodynia in AOAH-deficient mice and resurgence of pelvic pain upon drug washout. Aligned with microglial activation, we observed altered cytokine abundance in Aoah-/- cortex that was reduced in Aoah/Tlr4-/- cortex. Consistent with our hypothesis of TLR4 activation by gut microbes, we observed microbiome-dependent activation of cultured BV2 microglial cells. Skeletal analyses revealed that AOAH-deficient mice have an activated microglia morphology in brain regions associated with neuropathic pain, independent of TLR4. Compared to Aoah-/- mice, Aoah/Tlr4-/- mice exhibited decreased pelvic pain and microglial cytokine expression. Together, these findings demonstrate differential roles for AOAH and TLR4 in microglial activation and pelvic pain and thus identify novel therapeutic targets for IC/BPS.

neuroscience↗