(2R,6R)-HNK improved LPS-induced depression-like behavior by inhibiting Vcam1/Caspase-1/IL-1β pathway.

The ketamine metabolite (2R,6R)-hydroxynorketamine (HNK) reduces depression-like behavior in mice by suppressing neuroinflammation and neuronal pyroptosis. In experiments with male C57BL/6J mice and PC12 cells, HNK lowered expression of NLRP3, caspase-1, GSDMD, and interleukin-1β at both protein and mRNA levels, lessened neuronal injury, and reduced lactate dehydrogenase release. Transcriptomic analysis identified Vcam1 as a key differentially expressed gene. Overexpressing Vcam1 increased pyroptosis markers, while HNK reduced Vcam1 expression; knocking down Vcam1 had opposite effects. HNK thus attenuates LPS-induced pyroptosis and neuroinflammation partly by downregulating the Vcam1/caspase-1/IL-1β pathway, offering insights for depression treatment.

Study at a glance

Abstract

Depression-like behavior is closely associated with neuroinflammation. Lipopolysaccharide (LPS) can activate N-methyl-d-aspartate receptors and induce cellular pyroptosis and neuroinflammation, thereby triggering depression-like behavior in animals. The ketamine metabolite (2R,6R)-hydroxynorketamine (HNK) exerts significant antidepressant-like effects without the adverse effects associated with ketamine, such as addiction and abuse liability. However, its underlying mechanisms remain largely unclear. In this study, C57BL/6 J male mice and PC12 cells were used to establish an in vivo depression-like model and an in vitro neuroinflammatory model, respectively. The mechanism by which (2R,6R)-HNK ameliorated depression-like behavior in mice was investigated using histological staining, immunofluorescence, flow cytometry, gene transfection, western blots, RT-PCR, and other analyses. The results demonstrated that (2R,6R)-HNK significantly suppressed the protein and mRNA expression levels of NLRP3, caspase-1, GSDMD, and interleukin (IL)-1β both in vivo and in vitro. Meanwhile, neuronal injury was markedly alleviated, and lactate dehydrogenase release was reduced. Transcriptomic sequencing revealed that Vcam1 was significantly differentially expressed in different groups. Therefore, Vcam1 overexpression and si-Vcam1 vectors were subsequently transfected into PC12 cells. The results showed that Vcam1 overexpression upregulated the mRNA expression of pyroptosis-related markers, including caspase-1, caspase-11, GSDMD, and IL-1β, whereas (2R,6R)-HNK inhibited Vcam1 expression. In contrast, Vcam1 knockdown exerted opposite effects. In conclusion, (2R,6R)-HNK attenuates LPS-induced neuronal pyroptosis and neuroinflammation, and subsequently ameliorates depression-like behaviors in mice, partially by downregulating Vcam1/caspase-1/IL-1β pathway expression. The findings provide novel insights into the treatment of depression and the development of therapeutic agents for neuroinflammation-related disorders.