Succinic acid inhibits the uptake of Brucella abortus 544 into RAW 264.7 cells and promotes survival of B. abortus in ICR mice

Abstract

This study aims to investigate the effects of exogenous succinic acid (SCA) on Brucella (B.) abortus infection in macrophage RAW 264.7 cells and ICR mice. Firstly, the in vitro experiment was conducted by MTT cytotoxicity and bacterial internalization assay to evaluate the uptake of B. abortus into macrophage cells. Two non-cytotoxic concentrations of SCA demonstrated attenuated invasion of Brucella into macrophages at 30 and 45 min post- infection (pi). Secondly, ICR mice were treated with SCA and infected with B. abortus. On day-14 pi, spleen and blood serum were collected to evaluate the bacterial burden and total spleen weight as well as the production of cytokine/chemokine, respectively. The results showed that SCA treatment promoted bacterial growth and reduced the total spleen weight in mice. Furthermore, SCA treatment increased the level of IL-10 cytokine in the sera, while dampening the production of MCP-1 chemokine compared to the control. The results of bacterial load in spleen and spleen weight together with cytokine/chemokine production profile in the sera indicated that SCA induced the host anti-inflammatory response which is beneficial for the survival of Brucella. Therefore, these findings suggest that SCA contributed to host immunity against Brucella infection and the emerging potential topic-immunometabolism should be invested for further investigations.