Splenic γδ T cells mediate antidepressant and prophylactic actions of arketamine in lipopolysaccharide-induced depression in mice.

Arketamine, the (R)-enantiomer of ketamine, exhibits both therapeutic and sustained prophylactic effects in an inflammation-driven model of depression, although the precise mechanisms remain elusive. Given the involvement of γδ T cells in inflammatory processes, this study explored their role in the effects of arketamine. To assess therapeutic outcomes, mice received lipopolysaccharide (LPS:1.0 mg/kg), followed by either arketamine (10 mg/kg) or saline. For prophylactic assessment, arketamine or saline was administered six days prior to LPS exposure. A single dose of LPS (1.0 mg/kg) reduced the proportion of γδ T cells in the spleen but did not affect their levels in the blood, prefrontal cortex, or small intestine. Arketamine mitigated LPS-induced splenomegaly, counteracted the elevation of plasma interleukin-6 levels and the reduction in the proportion of splenic γδ T cells, and alleviated depression-like behavior as assessed by the forced swimming test. Notably, negative correlations were observed between the proportion of splenic γδ T cells and indicators of inflammation and depression. Furthermore, pretreatment with a γδ TCR antibody significantly countered the therapeutic and prophylactic effects of arketamine on LPS-induced changes. These findings highlight a novel role for splenic γδ T cells in inflammation-associated depression and suggest the potential of arketamine as a treatment option. Consequently, γδ T cells may represent a novel therapeutic target for inflammation-related depression. Further studies on the role of γδ T cells in depressed patients with inflammation are warranted.
Competing Interests: Declaration of competing interest Dr. Hashimoto is one of the editorial board members of this journal. Dr. Hashimoto is the inventor of filed patent applications on “The use of R-ketamine in the treatment of psychiatric diseases”, “(S)-norketamine and salt thereof as pharmaceutical”, “R-ketamine and derivative thereof as prophylactic or therapeutic agent for neurodegeneration disease or recognition function disorder”, “Preventive or therapeutic agent and pharmaceutical composition for inflammatory diseases or bone diseases”, and “R-ketamine and its derivatives as a preventive or therapeutic agent for a neurodevelopmental disorder” by the Chiba University. Dr. Hashimoto has also received speakers' honoraria, consultant fee, or research support from Otsuka. Other authors declare no conflict of interest.
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