Repeated administration of esketamine ameliorates mechanical allodynia in mice with chemotherapy-induced peripheral neuropathy: A role of gut microbiota and metabolites.

Chemotherapy-induced peripheral neuropathy (CIPN) severely diminishes the quality of life for cancer survivors, yet effective treatments remain scarce. Esketamine, a commonly used anesthetic, has demonstrated neuroprotective effects by restoring gut microbiome dysbiosis. In this study, we investigated the impact of esketamine on nociceptive sensitivity in a mouse model of CIPN and explored the potential involvement of the gut microbiome. In mice treated with oxaliplatin, repeated esketamine doses (in contrast to a single dose) significantly improved the paw withdrawal threshold (PWT). Western blot and qPCR analyses further revealed that repeated esketamine administration markedly reduced microglial activation and neuroinflammation in the dorsal root ganglion (DRG), underscoring its potent anti-inflammatory properties. Moreover, fecal 16S rRNA analysis indicated that esketamine partially restored the abnormal gut microbiota composition (β-diversity). Plasma metabolome analysis showed that repeated esketamine treatment significantly lowered the elevated levels of 6H-indolo[2,3-b]quinoline and restored the reduced levels of (3-exo)-3-[3-methyl-5-(1-methylethyl)-4H-1,2,4-triazol-4-yl]-8-azabicyclo[3.2.1]octane observed in oxaliplatin-treated mice. In addition, fecal microbiota transplantation from esketamine-treated CIPN mice notably improved both the diminished PWT and DRG neuroinflammation in oxaliplatin-treated mice. Collectively, these findings suggest that repeated esketamine administration may alleviate mechanical allodynia in CIPN mice by modulating neuroinflammation, gut microbiota, and associated metabolites.