LXR-β regulates microglial efferocytosis and neuroinflammation in CPSP via STAT6 activation

Abstract

Background: Central post-stroke pain (CPSP) is a chronic neuropathic pain syndrome that develops following cerebrovascular injury and currently lacks effective treatment options. Previous research from our group has found a significant number of apoptotic cells in the thalamus of CPSP rats, and in the nervous system, the failure to promptly clear apoptotic cell debris can activate microglia, triggering a persistent neuroinflammatory response that contributes to the onset and progression of CPSP. Microglia clear apoptotic cells in the central nervous system through efferocytosis, a process that reduces neuroinflammation and promotes the reprogramming of microglia toward the M2 phenotype, which is crucial for immune defense and repair mechanisms in the central nervous system. Recent studies have shown that Liver X Receptor β (LXR-β) can regulate microglial efferocytic function, reduce neuroinflammation after intracerebral hemorrhage, and promote recovery of neurological function. In this study, we explore the potential mechanism by which LXR-β regulates microglial efferocytosis to alleviate CPSP.

Methods: Based on the single-cell sequencing dataset of human brain hemorrhage patients and thalamic tissue samples from rats with central post-stroke pain, a systematic analysis of the dynamic changes in efferocytosis and the associated neuroinflammation was conducted. To verify whether LXR-β regulates CPSP through efferocytosis and its potential mechanism, rats were treated with GW3965 (LXR-β agonist), GSK2033 (LXR-β inhibitor), and AS1517499 (STAT6 inhibitor), either separately or in combination. Assessments included nociceptive behavior, efferocytosis, and the expression of efferocytosis-related molecules, inflammatory factors and microglial polarization markers. In vitro experiments using BV2 cells were also performed to further elucidate the underlying mechanisms.

Results: Human brain hemorrhage sequencing and the CPSP rat thalamic hemorrhage model results indicated that insufficient clearance of apoptotic cells and abnormal activation of microglia were key factors contributing to abnormal neuroinflammation following a stroke. The down-regulation of LXR-β is associated with mechanical allodynia after CPSP. Activation of LXR-β increased enhanced efferocytosis, and upregulated efferocytosis-related molecules (MerTK, Axl, and CD36). These effects contributed to reduced neuroinflammation, promoted microglial polarization toward the M2 phenotype, and alleviated CPSP. Biological analyses and experimental results indicated that LXR-β regulated these effects through the activation of p-STAT6. In vitro studies also confirmed that the LXR-β/p-STAT6 signaling pathway is closely associated with efferocytosis and inflammation regulation in BV2 cells.

Conclusions: LXR-β promotes microglial efferocytosis and the expression of efferocytosis-related molecules (Mertk, Axl, and CD36) by activating p-STAT6, thereby reducing neuroinflammation, reprogramming microglia toward the M2 phenotype, and alleviating CPSP. Targeting LXR-β or its downstream signaling pathways may offer a promising therapeutic strategy for central neuropathic pain.

Keywords: Central post-stroke pain; Efferocytosis; Microglial reprogramming; Neuroinflammation.