Jianrong Xu

Astrocytes are the most abundant and functionally versatile glial cells in the central nervous system, where they maintain homeostasis, regulate metabolic function, and communicate extensively with neurons, microglia and other CNS cell types. To mediate these interactions, astrocytes use G-protein-coupled receptors (GPCRs) to receive diverse extracellular signals, such as neurotransmitters, secreted signals and inflammatory factors. GPCRs translate extracellular signals into intracellular signaling cascades in astrocytes and are essential for intercellular communication. Despite decades of investigation, however, astrocytic GPCR signaling remains difficult to explain within a unified framework, as receptor activation does not necessarily produce predictable outcomes based on receptor identity or G-protein signaling alone. To address this gap, we critically examine representative studies of canonical and noncanonical GPCR signaling and astrocyte-centered cellular crosstalk, considering astrocyte state and the cellular position of receptors within communication pathways. We compare receptor-specific manipulations, functional outcomes, and methodological limitations to distinguish experimentally supported causal relationships from unresolved interpretations. This evidence-oriented approach identifies testable questions and experimental priorities for investigating astrocytic GPCR signaling in physiology and disease.

Background: Transient receptor potential vanilloid 1 (TRPV1) is increasingly recognized as an important regulator of microglial response during neuroinflammation, a key pathological feature of various neurodegenerative diseases such as Alzheimer’s disease. Capsaicin, the primary pungent component in chili peppers, executes its anti-inflammatory properties as a TRPV1 agonist. Although the mechanism of TRPV1 channel activation and signal transduction by capsaicin has been extensively studied, the protein–protein interaction-based mechanisms by which TRPV1 modulates microglial inflammatory responses in the context of neurodegeneration remains unclear. Methods: We used a lipopolysaccharide-induced acute neuroinflammation model to examine the effects of TRPV1 activation and pharmacological blockade of TRPV1 channel gating on microglial inflammatory responses. Proximity labeling-based proteomics, bioluminescence resonance energy transfer, and NanoLuc Binary Technology were used to identify and characterize TRPV1-interacting proteins. Signal sequence receptor subunit 4 (SSR4) knockdown and forced interaction between TRPV1 and SSR4 were performed to assess the functional contribution of the TRPV1–SSR4 interaction. Structural modeling, BRET-based domain mapping, and colocalization analyses were further used to examine the molecular and subcellular features of SSR4 recruitment by TRPV1. Results: In the neuroinflammatory model, the TRPV1 agonist capsaicin attenuated pro-inflammatory cytokine production, neuronal apoptosis, microgliosis, and microglial soma enlargement in a TRPV1-dependent manner. Notably, pharmacological blockade of TRPV1 channel gating by capsazepine did not abolish the anti-inflammatory action of capsaicin, suggesting an alternative mechanism of action beyond the canonical ligand-gated Ca ² ⁺ influx. Screening of TRPV1 prey proteins and validation strategy identified SSR4 as a capsaicin-responsive, TRPV1-associated protein. SSR4 knockdown in microglia significantly diminished the suppression of inflammatory responses caused by TRPV1 activation. Conversely, forced interaction between TRPV1 and SSR4 partially mimicked the anti-inflammatory effects of TRPV1 activation. Further structural and cellular analyses suggested that the transmembrane region of TRPV1 supports SSR4 recruitment. Conclusions: Our findings suggest that capsaicin suppresses microglial inflammation mediated by the TRPV1–SSR4 interaction, providing new insights into the chemical biology basis of TRPV1 interoceptive signaling and potential applications of natural TRPV1 agonists for modifying therapy of neuroinflammation-associated neurodegeneration.

Behavioral and psychological symptoms of dementia (BPSD) affect the majority of patients with Alzheimer’s disease (AD), substantially increasing caregiver burden and the likelihood of institutionalization. The clinical management of BPSD remains challenging because of its poorly understood pathogenesis, the limited efficacy of conventional interventions, and significant safety concerns associated with current treatments. These limitations underscore the urgent need to identify novel therapeutic targets and develop glia-centered treatment strategies. As essential components of the central nervous system, glial cells maintain neural homeostasis, regulate neurotransmission, and mediate neuroinflammatory responses. Increasing evidence suggests that glial dysfunction contributes to the development of BPSD, thereby linking AD neuropathology and neuropsychiatric symptoms. Aberrant microglial activation, astrocytic dysfunction, and oligodendrocyte injury collectively compromise neural circuit integrity, disrupt neurotransmitter balance, and impair neuron–glia communication, ultimately promoting the progression of diverse BPSDs. Given the critical role of glial cells in regulating neurotransmitter systems, the dysregulation of which is closely associated with BPSD, this review summarizes the involvement of glial cells in BPSD, elucidates the underlying molecular mechanisms, and discusses recent advances in glia-based therapeutic strategies, thereby providing insights into the pathogenesis of BPSD in AD.

Microglia are a unique cell population in the central nervous system (CNS) and serve as its resident immune cells. They have long been recognized for their critical contributions to CNS development and the maintenance of neuronal network health, particularly in the context of neuroprotection against neurodegenerative diseases. However, the mechanisms by which microglia interact with and influence neurons have remained largely unclear. Recent advances in genetics, pharmacology, and imaging technologies have begun to unveil the mechanisms underlying microglia–neuron communication. Here, from the perspective of microglia, we review the diverse direct and indirect pathways and key molecules through which microglia interact with neurons under both physiological and pathological conditions. This rapidly expanding knowledge is reshaping our understanding of neuron–glia physiology and pathology in neurodegenerative diseases.

Microglia play a pivotal role in inflammatory regulation through multifarious signaling pathways within the central nervous system, and mitigating microglial inflammation is considered a promising strategy to delay the progression of neurodegeneration. However, the role of biased receptor signaling in modulating microglial inflammation remains largely unexplored. In this study, the anti‐inflammatory effects and the underlying mechanism of muscarinic receptor agonists pilocarpine and iperoxo were explored. Our results showed that pilocarpine, rather than iperoxo, inhibited the expression of TNF‐α and IL‐6, as well as restored ramified morphology and physiological phagocytosis of over‐activated microglia. RNA‐seq revealed that pilocarpine‐treated BV2 exhibited transcriptional profiles more similar to the control group, with upregulation of anti‐inflammatory genes. β‐arrestin2 knockdown attenuated the anti‐inflammatory effect of pilocarpine by reversing the expression of inflammatory factors and activation of NF‐κB. Furthermore, through chemogenetic DREADDs, activation of Gαq, Gαi, or β‐arrestin pathways demonstrated that β‐arrestin, but neither Gαq nor Gαi, inhibited the inflammatory response in microglia. Our findings proved that pilocarpine could abate the microglial inflammatory response via biased activation of the β‐arrestin2 pathway, which could be considered a promising therapeutic approach for anti‐neuroinflammation. image

Chiral spirocyclic scaffolds have garnered significant attention in drug discovery and chiral ligand development due to their rigid structures and potential bioactive properties, yet stereodivergent synthesis of such systems, particularly those bearing non-adjacent stereocenters, remains a formidable challenge. Herein, we report a dynamic radical recombination (DRR) strategy that enables cobalt-hydride-catalyzed ligand-controlled stereodivergent olefin hydroalkylation, delivering a series of spirocyclic compounds bearing 1,3-non-adjacent stereocenters with up to >99:1 er and >20:1 dr. Density functional theory (DFT) calculations reveal that different ligands induce distinct reaction mechanism, resulting in diastereoselectivity reversal through dynamic radical recombination pathway. Biological evaluations demonstrate that selected newly synthesized spirocyclic products markedly suppress lipopolysaccharide (LPS)-induced neuroinflammation in microglial cells, effectively reducing pro-inflammatory cytokine levels (TNF-α, IL-6, IL-1β) and restoring cells to pre-inflammatory states.

G protein-coupled receptors (GPCRs), the largest family of membrane proteins, serve as primary targets for over 30% of FDA-approved drugs. While signaling bias among Gα subtypes is well characterized, emerging evidence highlights that Gβγ subtypes govern the coupling of the Gα heterotrimer to GPCRs. However, whether Gβγ subtype selectivity depends on the receptor or the Gα subunit and the underlying mechanism remain unresolved. Here, we focused on Gαq-coupled GPCRs and investigated Gβγ preferences using bioluminescence resonance energy transfer assays to assess Gβγ selectivity along with Gαq-GPCR coupling and calcium flux assays to measure downstream Ca²⁺ mobilization. By characterizing seven Gαq-coupled receptors, including the muscarinic acetylcholine receptor family (M1 mAChR, M3 mAChR, M5 mAChR) and four other Gαq-coupled GPCRs (AT1R, NTSR1, KISS1R, hM3Dq), the Gβ1/2γ2 combinations were identified as the preferred subtypes for Gαq coupling. Structural analysis and site-directed mutagenesis assays revealed that three key residues in Gβ2 (F111, V178, and G179), distinct from Gβ4, are crucial for enhancing Gαq coupling. Notably, Gβ4 exhibited preferential recruitment of the Gαq heterotrimer in response to pilocarpine relative to acetylcholine, suggesting that pilocarpine may function as a Gβ4-biased agonist. These findings advance our understanding of Gβγ-mediated subtype selectivity and open avenues for developing biased ligands in drug discovery.

Astrocytic neuroinflammation contributes as a key player in neurodegenerative diseases. Capsazepine is a frequently used transient receptor potential vanilloid 1 (TRPV1) inhibitor; however, its effects, as well as the target, on inflammation remain controversial. This study examines the anti‐inflammatory actions of capsazepine and explores mechanisms beyond TRPV1 inhibition. By assessing astrocytic inflammation in vitro and in vivo experiments, capsazepine was found to inhibit astrocyte activation and attenuate neuroinflammation, with reduced levels of interleukin‐6 and complement 3. When utilizing TRPV1 deficient models, no significant decrease was observed in the anti‐inflammatory effects of capsazepine, suggesting there could be alternative targets in addition to TRPV1. Further investigations used drug affinity responsive target stability analysis, siRNA knockdown, cellular thermal shift assay, and molecular docking to hunt for new targets. Syntaxin 7, a modulator in cytokine trafficking and phagosome maturation, was identified as a crucial target to interact with capsazepine in the inhibition of astrocytic inflammation. This study verifies the anti‐inflammatory effects of capsazepine and identifies Syntaxin 7 as a potential novel therapeutic target for treating neuroinflammation.

The ongoing emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has led to resistance against multiple coronavirus disease 2019 (COVID-19) vaccines and therapeutic medications, making the development of effective therapeutics against SARS-CoV-2 a high priority. Studies have shown that bioactive polyphenols, particularly those with triphenol groups, can effectively inhibit the activity of SARS-CoV-2 3-chymotrypsin-like protease (3CL^pro). However, the structural instability of polyphenols necessitates further research. To address this, we conducted a literature review to identify triphenol compounds that are either approved or currently undergoing clinical trials, assessing their potential to inhibit SARS-CoV-2 3CL^pro. Exifone and benserazide hydrochloride were identified as the inhibitors of SARS-CoV-2 3CL^pro among these compounds, using a fluorescence resonance energy transfer (FRET)-based assay. Benserazide hydrochloride was confirmed as a covalent binder to SARS-CoV-2 3CL^pro through time-dependent inhibition and kinetic analysis, with its binding mode elucidated by molecular docking. Notably, exifone not only inhibited the protease activity but also blocked the interaction between the host cell receptor angiotensin-converting enzyme 2 (ACE2) and the SARS-CoV-2 spike protein receptor binding domain (S-RBD), as identified by surface plasmon resonance (SPR) and flow cytometry. Additionally, exifone demonstrated antiviral activity against various SARS-CoV-2-S pseudovirus variants. In conclusion, the discovery of exifone and benserazide hydrochloride underscores the potential of polyphenols in developing conserved 3CL^pro inhibitors for coronaviruses, offering new strategies for the rapid development of effective drugs against both current and future coronavirus pandemics.