The resilient phenotype elicited by ketamine against inflammatory stressors-induced depressive-like behavior is associated with NLRP3-driven signaling pathway.

A single injection of ketamine (5 mg/kg) given to mice one week before exposure to the inflammatory stressors lipopolysaccharide (LPS) or tumor necrosis factor-alpha (TNF-α) prevented depressive-like behaviors measured in the tail suspension test and splash test. A lower dose (1 mg/kg) did not have this effect. LPS increased markers of microglial activation and components of the NLRP3 inflammasome signaling pathway in the ventral hippocampus, while TNF-α only increased two of those components. Ketamine at 5 mg/kg, but not 1 mg/kg, blocked these increases. The findings suggest ketamine can promote resilience against inflammation-induced depressive-like behavior by suppressing NLRP3 inflammasome signaling.

Study at a glance

Abstract

Ketamine has emerged as a prophylactic agent against depressive-like behavior induced by stress. However, the possible pro-resilience effects of ketamine against inflammatory stressors-induced depressive-like behavior and the signaling pathways associated with this response remain to be determined. Therefore, this study investigated the ability of prophylactic ketamine administration to produce a pro-resilience effect against the depressive-like behavior induced by lipopolysaccharide (LPS - 0.83 mg/kg, i.p.) and tumor necrosis factor-alpha (TNF-α - 0.1 fg/site, i.c.v.) administration in mice. The possible contribution of the NLRP3 inflammasome-driven signaling pathway to this effect was evaluated in the ventral hippocampus. A single administration of ketamine (5 mg/kg, i.p.) given 1 week before the LPS or TNF-α administration prevented the depressive-like behavior induced by these inflammatory stressors in the tail suspension test (TST) and splash test (SPT). On the other hand, a lower dose of ketamine (1 mg/kg, i.p.) failed to produce a similar effect. The administration of LPS, but not TNF-α, increased the immunocontent of the microglial marker Iba-1 in the ventral hippocampus. LPS increased the immunocontent of all proteins related to NLRP3 signaling, namely ASC, NLRP3, TXNIP, cleaved caspase-1, and IL-1β in this brain region, while TNF-α only increased ASC and NLRP3 immunocontent. Ketamine administered at the dose of 5 mg/kg, but not at 1 mg/kg, prevented the increase on the immunocontent of NLRP3 inflammasome complex components and regulators induced by LPS or TNF-α administration. Collectively, these findings suggest that ketamine elicits a pro-resilient phenotype against inflammatory stressors-induced depressive-like behavior, an effect associated with the suppression of the NLRP3 inflammasome-driven signaling pathway.