Fecal microbiota transplantation attenuates neuropathic pain in rats via gut microbiota-mediated immunomodulation of ion channels and nociceptors.

Abstract

INTRODUCTION: Neuropathic pain, resulting from somatosensory nervous system damage, presents significant treatment challenges due to limited effectiveness and adverse side effects of current therapies. Emerging evidence highlights the gut microbiome's potential role in pain regulation, yet the specific microbial species and mechanisms underlying chronic neuropathic pain remain largely unexplored. OBJECTIVES: This study aimed to determine the relationship between gut microbiota and neuropathic pain using fecal microbiota transplantation (FMT) in rats with chronic constriction injury (CCI). Additionally, it sought to identify microbial species associated with pain modulation. METHODS: CCI was performed in wildtype and antibiotic-treated pseudo-germ-free (PGF) rats. FMT was performed using fecal matter slurry from healthy (hFMT) and CCI-dysbiotic (dFMT) donors, transplanted into nerve-injured and healthy rats, respectively. Pain-related behaviors were assessed and microbial composition was analyzed via 16sRNA sequencing. Western blot and RT-PCR assays were conducted on dorsal root ganglion (DRG) and spinal cord tissues. RESULTS: CCI induced gut microbial dysbiosis, characterized by increased Proteobacteria and Fusobacteriota and decreased Actinobacteria. hFMT from healthy rats alleviated mechanical, thermal, and cold hyperalgesia but did not reverse mechanical allodynia in CCI rats. Conversely, dFMT from CCI rats induced pain-like hypersensitivity in healthy rats, mimicking nerve injury effects. Correlation analysis identified microbial species linked to pain modulation: Bifidobacterium animalis, Corynebacterium urealyticum, and Desulfovibrio piger were associated with reduced pain behaviors, while Pasteurellaceae bacterium, Bacillus sp., and Staphylococcus arlettae were linked to nerve injury-induced dysbiosis. hFMT restored claudin-5 and anti-inflammatory markers TGF-β and IL-10 while downregulating pain-related proteins TRPM8, Nav 1.8, Nav 1.7, and TRPA1 in CCI rats. In contrast, dFMT promoted neuroinflammation by increasing IBA1, TNF-α, and IL-1β, leading to microglial activation in healthy rats. CONCLUSION: Our findings demonstrate that the composition of gut bacteria influences pain-like behaviors through nerve injury-induced microbial dysbiosis, operating in a bidirectional manner. Additionally, the study suggests that a cocktail of Bifidobacterium animalis, Corynebacterium urealyticum, and Desulfovibrio piger could serve as a promising alternative for managing neuropathic pain.