Brucella-induced activation of AIM2 inflammasome and Caspase-1 enhances Interleukin-18 secretion in THP-1 cells

Abstract

Introduction/Objective The purpose was to investigate the role of the inflammasome absent in melanoma 2 (AIM2) in Brucella-induced inflammatory responses in macrophages.

Methods A cell model of Brucella infection was established using a human macrophage cell line. Real-time quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) kits were employed to measure the expression of the inflammasome AIM2 and the inflammatory cytokine Interleukin-18 (IL-18) at different time points post-infection, as well as to analyze the correlation between AIM2 and IL-18. Experiments involving the activation and inhibition of AIM2 were conducted to verify its effect on the production of the cytokine IL-18. Western blotting was conducted to determine the expression of AIM2 and IL-18.

Results It is found that IL-18 mRNA and concentration levels increased post-infection, peaking at 48 hours before decreasing by using RT-qPCR and ELISA (p < 0.05). Western blot analysis confirmed a similar temporal pattern for IL-18 protein expression (p < 0.05). Additionally, AIM2 and Caspase mRNA and protein expression were evaluated, showing a peak at 48 hours (p < 0.05), indicating inflammasome activation. The critical role of the AIM2 inflammasome and caspase-1 in IL-18 secretion was further demonstrated with AIM2 activators, which increased IL-18 mRNA and protein levels, and AIM2 inhibitors or Caspase-1 knockout, which reduced them (p < 0.05).

Conclusion Brucella infection induces the activation of the AIM2 inflammasome and caspase-1, leading to the secretion of the pro-inflammatory cytokine IL-18 in THP-1 cells.

Keywords: brucellosis; macrophage; AIM2; caspase-1; IL-18