Citations

Abstract How glial cells sense and regulate neuronal hypoactivity remains poorly understood. Using in vivo imaging in anesthetized, sleeping, and behaving mice, we identified a glial purinergic signaling mechanism that converts neuronal hypoactivity into local circuit regulation. Cortical hypoactivity increased spatially confined ATP release through astrocytic pannexin-1 hemichannels, which were structurally enriched near perisomatic parvalbumin-positive boutons. Local ATP release directed microglial process movement and stabilized bulbous endings through microglial P2Y12 signaling, accompanied by localized Ca²⁺ activity in microglial processes. Disruption of astrocytic pannexin-1 or microglial P2Y12 impaired bulbous-ending stabilization and abolished rebound increases in neuronal activity during emergence from anesthesia. Similar ATP release and bulbous-ending formation were observed during chemogenetic neuronal silencing or natural sleep in freely behaving mice. These findings identify astrocyte-to-microglia purinergic signaling as a mechanism that converts neuronal hypoactivity into synapse-selective microglial regulation of circuit activity.

Abstract In many cancers, a major barrier to effective immunotherapy is the dominance of tumor-associated myeloid cells (TAMs), which establish a profoundly immunosuppressive tumor microenvironment (TME). This challenge is particularly pronounced in glioblastoma (GBM), where myeloid cells represent the predominant immune population and actively suppress antitumor immunity. Identifying targets that can reprogram TAMs from an immunosuppressive state toward a pro-inflammatory, antigen-presenting phenotype remains a critical unmet need. Here, we identify the voltage-gated proton channel Hv1 as an immune-restricted regulator of glioma-associated macrophage function. Hv1 is notable not only for its immune-specific expression but also for its established roles in central nervous system (CNS) pathologies, where Hv1 depletion alters microglial and macrophage polarization, reduces myeloid accumulation, dampens inflammatory cytokine production, and limits secondary tissue damage. However, Hv1’s role in shaping the GBM immune landscape—particularly in vivo—has remained poorly understood due to low Hvcn1 transcript abundance and the lack of reliable antibodies and genetic tools. Given the dominance of myeloid cells in GBM and their central role in tumor immune regulation, we sought to define Hv1 function within this highly immunosuppressive brain TME. Analysis of patient datasets revealed that elevated Hv1 expression correlates with poor clinical prognosis. Consistently, Hv1 loss significantly prolonged survival in multiple murine glioma models. Using in vivo two-photon imaging and spectral flow cytometry, we show that Hv1 depletion reprograms TAMs toward an anti-tumor phenotype characterized by enhanced tumor cell phagocytosis, improved antigen presentation, and increased T cell infiltration. By generating new Hv1 reporter and conditional mouse lines, we further demonstrate that tumor-associated microglia and infiltrating macrophages are the principal sources of Hv1 and markedly upregulate its expression in response to glioma. Notably, selective deletion of Hv1 in infiltrating macrophages phenocopied the survival benefit observed with global Hv1 loss. Mechanistically, using mass spectrometry and genetic models, we identify the Stimulator of Interferon Genes (STING) as a previously unrecognized binding partner of Hv1, placing Hv1 within the STING signaling pathway, a central regulator of innate and adaptive immune responses. Together, these findings fill a critical gap in understanding myeloid Hv1 function in GBM and identify Hv1 as a promising target for reprogramming the tumor immune microenvironment. Citation Format: Jiaying Zheng, Lingxiao Wang, Shunyi Zhao, Katayoun Ayasoufi, Meijie Wang, Praveen N. Pallegar, Peter R. Strege, Langni Liu, Yushan Wan, Wenjing Zhang, Emma N. Goddery, Manling Xie, Arthur Beyder, Aaron J. Johnson, Long-Jun Wu. Myeloid Hv1-STING axis tunes glioma immunity [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Brain Cancer; 2026 Mar 23-25; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(6_Suppl):Abstract nr A016.

Neutrophils and neutrophil extracellular traps (NETs) contribute to early neuromyelitis optica (NMO) histopathology initiated by IgG targeting astrocytic aquaporin-4 (AQP4) water channels. Yet, the mechanisms underlying neutrophil recruitment and their pathogenic roles in disease progression remain unclear. To investigate molecular-cellular events preceding classical complement cascade activation in a mouse NMO model, we continuously infused, via spinal subarachnoid route, a non-complement-activating mouse monoclonal AQP4-IgG. Parenchymal infiltration of netting neutrophils containing C5a ensued with microglial activation and motor impairment but no blood-brain barrier leakage. Motor impairment and neuronal dysfunction both reversed when AQP4-IgG infusion stopped. Two-photon microscopy and electron microscopy–based reconstructions revealed physical interaction of infiltrating neutrophils with microglia. Ablation of either peripheral neutrophils or microglia attenuated the motor deficit, highlighting their synergistic pathogenic roles. Of note, mice lacking complement receptor C5aR1 exhibited reduction in neutrophil infiltration, microglial lysosomal activation, neuronal lipid droplet burden, and motor impairment. Pharmacological inhibition of C5aR1 recapitulated this protection. Immunohistochemical analysis of an NMO patient’s spinal cord revealed disease-associated microglia surrounding motor neurons in nondestructive lesions. Our study identifies neutrophil-derived C5a signaling through microglial C5aR1 as a key early driver of reversible motor neuron dysfunction in the precytolytic phase of NMO.

Abstract Microglia are essential for maintaining brain homeostasis, including the sleep-wake cycle, but the underlying mechanisms remain unclear. Here, using in vivo two-photon imaging in both head-fixed and freely moving mice with simultaneous electroencephalogram–electromyogram (EEG–EMG) recording, we investigated microglial process dynamics and their interactions with locus coeruleus (LC) noradrenergic (NE) axons in the frontal cortex across sleep-wake states. During sleep or chemogenetic suppression of LC neurons, microglia enhanced their surveillance and increased interactions with NE axons. Correlative electron microscopy at nanometer resolution identified structural contacts between microglial process endings and NE boutons. Mechanistically, microglia-bouton interaction is primed by NE–β2-adrenergic receptor (β2AR) signaling, leading to enhanced Ca²⁺ activity in NE axons. These findings suggest that microglial interactions with NE axons promote cortical norepinephrine transmission and maintain stable wakefulness.

Abstract Description In the tumor microenvironment of glioblastoma, myeloid cells act as a double-edged sword—they are a major cellular component suppressing the immune response while serving as a promising therapeutic target. Our study sheds light on the voltage-gated proton channel Hv1, predominantly expressed in myeloid cells, as a pivotal regulator of their physiological functions. Elevated Hv1 expression correlates strongly with poor prognosis in glioblastoma patients, underscoring its clinical significance. Using a glioma mouse model, we demonstrated that Hv1 depletion markedly extended survival. To overcome the limitations of existing tools, we engineered novel transgenic mouse lines optimized for Hv1 research. Our findings revealed tumor-induced Hv1 upregulation, with glioma-associated macrophages identified as the principal contributors. Crucially, we identified that Hv1 in infiltrating macrophages as the major driver of survival phenotype differences. Through a multi-faceted approach combining in vivo two-photon imaging, spectral flow cytometry, and spatial transcriptomic sequencing, we discovered that Hv1 depletion limits macrophage infiltration and enhances antigen presentation, ultimately fostering a stronger adaptive immune response. These findings establish the Hv1 channel as a crucial new immune regulator within the brain tumor milieu, offering a promising target for reprogramming macrophage function to combat glioblastoma. Funding Sources Supported by NIH R35NS132326 (LJW); Mayo Clinic Cancer Center and Mayo Clinic Center for Biomedical Discovery. Topic Categories Neuroimmunology (NEUR)

Microglia actively survey the brain and dynamically interact with neurons to maintain brain homeostasis. Microglial Gi protein–coupled receptors (Gi-GPCRs) play a critical role in microglia-neuron communications. However, the impact of temporally activating microglial Gi signaling on microglial dynamics and neuronal activity in the homeostatic brain remains largely unknown. In this study, we used Gi-based designer receptors exclusively activated by designer drugs (Gi-DREADD) to selectively and temporally modulate microglial Gi signaling pathway. By integrating this chemogenetic approach with in vivo two-photon imaging, we observed that exogenous activation of microglial Gi signaling transiently inhibited microglial process dynamics, reduced neuronal activity, and impaired neuronal synchronization. These altered neuronal functions were associated with a decrease in interactions between microglia and neuron somata. Together, this study demonstrates that acute, exogenous activation of microglial Gi signaling regulates neuronal circuit function, offering a potential pharmacological target for the neuromodulation through microglia.

Abstract Background Myeloid cells comprise up to 50% of the total tumor mass in glioblastoma (GBM) and have been implicated in promoting tumor progression and immunosuppression. Modulating the response of myeloid cells to the tumor has emerged as a promising new approach for cancer treatment. In this regard, we focus on the Triggering Receptor Expressed on Myeloid Cells 2 (TREM2), which has recently emerged as a novel immune modulator in peripheral tumors. Methods We studied the TREM2 expression profile in various patient tumor samples and conducted single-cell transcriptomic analysis in both GBM patients and the GL261 mouse glioma model. We utilized multiple mouse glioma models and employed state-of-the-art techniques such as invivo 2-photon imaging, spectrum flow cytometry, and in vitro co-culture assays to study TREM2 function in myeloid cell-mediated phagocytosis of tumor cells, antigen presentation, and response of CD4+ T cells within the tumor hemispheres. Results Our research revealed significantly elevated levels of TREM2 expression in brain tumors compared to other types of tumors in patients. TREM2 was predominantly localized in tumor-associated myeloid cells and was highly expressed in nearly all microglia, as well as various subtypes of macrophages. Surprisingly, in preclinical glioma models, TREM2 deficiency did not confer a beneficial effect; instead, it accelerated glioma progression. Through detailed investigations, we determined that TREM2 deficiency impaired the ability of tumor-myeloid cells to phagocytose tumor cells and led to reduced expression of MHCII. This deficiency further significantly decreased the presence of CD4+ T cells within the tumor hemispheres. Conclusions Our study unveiled a previously unrecognized protective role of tumor-myeloid TREM2. Specifically, we found that TREM2 enhances the phagocytosis of tumor cells and promotes an immune response by facilitating MHCII-associated CD4+ T-cell responses against gliomas.

Abstract Myeloid cells comprising up to 50% of total tumor mass in glioblastoma (GBM) contribute to tumor progression and immunosuppression. Restraining glioma-induced myeloid cell infiltration increases functional T cells within the tumors, improves the efficacy of checkpoint blockade, and significantly extends mouse survival. Here, we focus on an ion channel, voltage-gated proton channel Hv1, which is mainly expressed in myeloid cells and shapes the physiological functions of myeloid cells. Our bioinformatics analysis demonstrated that elevated Hv1 expression in the tumor mass correlates with poor disease prognosis in patients. Using the leading immunocompetent model of GBM in mice, we showed that Hv1 knockout mice (Hv1−/−) exhibit slower glioma progression and prolonged survival. Using in vivo two-photon imaging, we found that myeloid cells infiltrate into tumor mass since early time points and have intimate interaction with tumor cells. Notably, by full-spectrum flow cytometry, we found that Hv1−/− mice have reduced monocyte/macrophage infiltration, and increased PD-1+ CD4+ T cells in the tumor-burdened hemisphere. As a result, we combined anti-PD-1 treatment with Hv1 knockout in the middle stage of glioma, and found that approximately 30% of Hv1−/− mice were cured. Together, our results demonstrated that Hv1 controls myeloid infiltration and could be a novel therapeutic target for the treatment of GBM. Supported by R01NS110825, R01NS088627

Abstract Myeloid cells comprising up to 50% of total tumor mass in glioblastoma (GBM) contribute to tumor progression and immunosuppression. Restraining glioma-induced myeloid cell infiltration increases functional T cells within the tumors, improves the efficacy of checkpoint blockade, and significantly extends mouse survival. Here, we focus on an ion channel, voltage-gated proton channel Hv1, which is mainly expressed in myeloid cells and shapes the physiological functions of myeloid cells. Our bioinformatics analysis demonstrated that elevated Hv1 expression in the tumor mass correlates with poor disease prognosis in patients. Using the leading immunocompetent model of GBM in mice, we showed that Hv1 knockout mice (Hv1-/-) exhibit slower glioma progression and prolonged survival. Notably, in vivo two-photon imaging, immunofluorescence, and full-spectrum flow cytometry revealed that Hv1-/- mice have reduced monocyte/macrophage infiltration, higher frequency of MHCII+ among all infiltrating myeloid cells, and increased PD-1+CD4+ T cells in the tumor-burdened hemisphere. As a result, we combined anti-PD-1 treatment with Hv1 knockout in the middle stage of glioma, and found that approximately 30% of Hv1-/- mice were cured. Together, our results demonstrated that Hv1 regulates myeloid infiltration and could be a novel therapeutic target for the treatment of GBM.

AbstractAmyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is an aggressive motor neuron degenerative disease characterized by selective loss of both upper and lower motor neurons. The mechanisms underlying disease initiation and progression are poorly understood. The involvement of nonmotor neuraxis emphasizes the contribution of glial cells in disease progress. Microglia comprise a unique subset of glial cells and are the principal immune cells in the central nervous system (CNS). Triggering receptor expressed on myeloid cell 2 (TREM2) is a surface receptor that, within the CNS, is exclusively expressed on microglia and plays crucial roles in microglial proliferation, migration, activation, metabolism, and phagocytosis. Genetic evidence has linked TREM2 to neurodegenerative diseases including ALS, but its function in ALS pathogenesis is largely unknown. In this review, we summarize how microglial activation, with a specific focus on TREM2 function, affects ALS progression clinically and experimentally. Understanding microglial TREM2 function will help pinpoint the molecular target for ALS treatment.