Redundant effects of ketamine on the pathogenesis and severity of Brucella abortus infection

Brucella abortus is an intracellular bacterium and leading to a serious debilitating disease known as brucellosis. Ketamine is an anesthetic and a sedative that affects the immunomodulatory activities of various immune cells. The current study was to elucidate the role of ketamine in B. abortus infection, focusing on the phagocytic activity and immune response of macrophages. Following incubation of murine macrophages with ketamine, the phagocytosis of B. abortus was markedly reduced compared with the unincubated control. Interestingly, ketamine-incubated cells displayed a decreased intensity of F-actin fluorescence compared with the B. abortus-induced amplification of intensity. Conversely, the intracellular replication of B. abortus within macrophages was notably enhanced by ketamine. Furthermore, the in vivo assessment using a mouse model revealed that continual injections with ketamine led to augmented bacterial burdens in the spleen, which was accompanied by decreased levels of mRNA expression of cytokines in the spleen. The elevations of serum cytokines such as IFN-γ, IL-12 and IL-6, as well as the chemokine MCP-1, were also reduced by ketamine. These findings verify that ketamine suppresses the phagocytic activity and immune response during B. abortus infection. Therefore, the current study might provide novel insights into the potential influences of ketamine on infectious diseases caused by B. abortus, considering the host-pathogen interaction.