Zhao, Shunyi

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.

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.