Tamoxifen Modulates Spinal Cord Injury Repair Via CCL2/CCR2 Axis and its Mechanisms

Abstract

Spinal cord injury (SCI) represents a profoundly serious neurological disorder characterized by limited self-repair capabilities and accompanied by secondary inflammatory damage, rendering its treatment a pressing challenge in the field of medical science research. During the acute phase of SCI, the expression levels of C-C motif chemokine ligand 2 (CCL2) and its receptor, chemokine receptor 2 (CCR2), are significantly upregulated. The CCL2/CCR2 axis plays a critical role in regulating microglial activation, inflammatory responses, and apoptotic cascades within the injured spinal cord microenvironment. Emerging evidence suggests that tamoxifen (TAM), a selective estrogen receptor modulator, may exert neuroprotective effects in SCI by pharmacologically inhibiting the activity of the CCL2/CCR2 axis. Targeting this axis through TAM administration represents a promising therapeutic strategy to mitigate post-injury pathological progression and improve outcomes in SCI models. This study aims to address the critical issue of secondary inflammatory damage hindering neural regeneration and repair following SCI. By investigating the regulatory effects of TAM on the CCL2/CCR2 axis and its downstream pathways, we seek to elucidate its molecular mechanisms and provide novel strategies for pharmacological intervention in secondary injuries associated with SCI. Utilizing bioinformatics techniques, we identified differentially expressed genes post-SCI and analyzed signaling pathways related to the CCL2/CCR2 axis. We assessed the expression levels of this axis following SCI and employed behavioral assays, RT-PCR, ELISA, and Western blotting to validate the effects of TAM administration on the CCL2/CCR2 axis, its downstream pathways, and molecular mechanisms in both LPS-induced microglial inflammation models and complete transection models of SCI. Furthermore, we utilized the CCR2 antagonist INCB3344 and the PPAR-γ antagonist GW9662 to further validate the relationships within these pathways. TAM significantly reduced the expression of the CCL2/CCR2 axis in both in vitro and in vivo models following injury. By modulating this axis, TAM decreased NF-κB pathway expression and inhibited the secretion of inflammatory factors, facilitating the transition of microglia from a pro-inflammatory to an anti-inflammatory phenotype while activating the PPAR-γ pathway. Additionally, the activation of PPAR-γ reciprocally inhibited the expression of the CCL2/CCR2 axis. TAM may significantly alleviate secondary inflammatory responses following SCI through its modulation of the CCL2/CCR2 signaling pathway, exhibiting anti-apoptotic and anti-inflammatory effects. The findings of this study provide a theoretical foundation and experimental basis for the clinical application of TAM in SCI treatment research.