GPR34 Senses Demyelination to Promote Neuroinflammation and Pathologies

Neurology Rheumatology and Immunology Medicine Cell Biology Biophysics Life Sciences Immunology
neuroinflammation GPCRs microglia myelin debris immune response demyelination-associated diseases

Background Introduction

Sterile neuroinflammation is an important factor driving various neurological diseases. Myelin debris, released during the demyelination process in various neurological diseases (such as stroke, spinal cord injury (SCI), multiple sclerosis (MS), traumatic brain injury (TBI), and neurodegenerative diseases), can act as an inflammatory stimulus to activate innate immune cells, thereby promoting inflammatory responses during disease progression. However, the mechanism by which myelin debris triggers innate immunity and neuroinflammation remains unclear.

The authors of this paper explore the key role of the Lysophosphatidylserine (Lysops)-gpr34 axis in myelin debris-induced neuroinflammation. Previous studies have confirmed that myelin debris-induced microglial activation and pro-inflammatory cytokine expression depend on its lipid component Lysops. This paper aims to elucidate the specific mechanism by which myelin debris activates microglia through the Lysops-gpr34 axis and its practical application value in animal models.

Research Source

This paper was jointly written by Bolong Lin, Yubo Zhou, Zonghui Huang, Ming Ma, and others. The authors are affiliated with research units such as the Key Laboratory of Innate Immunity and Immunotherapy at the University of Science and Technology of China, the Institute of Immunology at Zhejiang University School of Medicine, and the Department of Geriatrics at the First Affiliated Hospital of Anhui Medical University. The paper was accepted for publication in the journal “Cellular & Molecular Immunology” on July 1, 2024.

Research Process

This paper describes an original study involving multiple steps, with the specific process as follows:

Detailed Description of Research Process

  1. Myelin Debris Extraction and Processing Myelin debris was extracted from mouse brains using standard methods, followed by ultracentrifugation and layered collection of myelin debris. The debris was then labeled with CFSE fluorescent dye for subsequent experiments.

  2. Microglial Culture and Stimulation Microglia extracted from newborn mouse brains were cultured in 24-well plates. In the experiment, cells were divided into control and treatment groups, stimulated with myelin debris and lipids (Lysops) respectively.

  3. Lipid Component Analysis Liquid chromatography-mass spectrometry (LC-MS) was used to analyze the lipid components extracted from myelin, revealing that Lysops has strong immunostimulatory activity.

  4. Gene Expression Analysis The gene expression profile of Lysops-stimulated microglia was analyzed through quantitative PCR (qPCR) and RNA sequencing (RNA-Seq), identifying multiple upregulated pro-inflammatory cytokine and chemokine genes.

  5. Identification and Knockout Experiments of Lysops Synthase The ABHD16A enzyme was knocked out using gene knockout technology to reduce Lysops production. Results showed that myelin debris from these knockout mice had significantly reduced ability to induce microglial activation and pro-inflammatory factor expression.

  6. Study of Gpr34-Mediated Signaling Pathway High expression of Gpr34 in microglia was verified. Experiments using Gpr34-deficient mice and Gpr34-specific antagonists confirmed the key role of Gpr34 in microglial activation through PI3K-Akt and Ras-ERK signaling pathways.

  7. Functional Studies in Animal Models ABHD16A-deficient mice and Gpr34-deficient mice were used in experimental autoimmune encephalomyelitis (EAE) and stroke models to study the role of the Lysops-Gpr34 axis in neuroinflammation and neuropathology.

Detailed Description of Research Results

  1. Activation Effects of Myelin Debris and Lysops on Microglia Both myelin debris and crude extracted lipids significantly increased the mRNA expression of newly produced pro-inflammatory cytokines in microglia. Further research found that Lysops was the most immunostimulatory component.

  2. Key Role of Gpr34 in Microglia Myelin debris and Lysops induce the production of various pro-inflammatory cytokines in microglia by activating the Gpr34 receptor through downstream PI3K-Akt and Ras-ERK signaling pathways. Experiments with Gpr34-deficient mice and its antagonists verified the key role of this signaling pathway.

  3. Role of Lysops in Demyelination-Related Diseases In EAE and stroke models, reducing Lysops content in myelin debris or inhibiting Gpr34 can reduce the progression of neuroinflammation and neuropathology. The experimental results from these two animal models support the importance of the Lysops-Gpr34 axis in these diseases.

Research Conclusions and Significance

Through this study, Gpr34 was identified as a key receptor in the microglial-mediated recognition of myelin debris. This not only reveals a new mechanism of neuroinflammation but also suggests Gpr34 as a potential therapeutic target. These findings provide new directions and methods for treating multiple sclerosis, stroke, and other neurodegenerative diseases.

Research Highlights

  1. Identification of the Lysops-Gpr34 Axis This study confirms for the first time the key role of the Lysops-Gpr34 axis in microglial activation and neuroinflammation.

  2. Combination Application of Multiple Experimental Methods The signaling mechanism of the Lysops-Gpr34 axis was systematically elucidated through the comprehensive application of gene knockout, pharmacological experiments, and various molecular biology techniques.

  3. Cross-Species Validation A series of experiments in mouse models validated the mechanism of myelin debris-induced neuroinflammation, with highly reproducible results.

Application Value and Significance of the Research

The discovery of the Lysops-Gpr34 axis provides a new perspective for understanding the mechanism of neuroinflammation and provides a theoretical basis as a new therapeutic strategy. Considering the important position of GPR-class receptors in drug development, this research provides potential clinical application prospects for the treatment of related diseases.

Other Important Content

This research also involves the application of various high-tech technologies and methods, such as mass spectrometry-based lipid analysis technology, the application of gene knockout mouse models, and the combination of various cellular and animal experimental methods. The mature application of these technologies has laid a solid foundation for in-depth exploration of the research, while also demonstrating the important role of multidisciplinary integration in modern life science research.