BvrR of Brucella initiates microglial inflammation through the activation of the IRE1 pathway

Brucella-induced microglial inflammation plays a pivotal role in the neuropathology of neurobrucellosis. The virulence factor BvrR, critical for Brucella replication and survival within the host cell's endoplasmic reticulum (ER), has an undefined role in this inflammatory process. To elucidate this, HMC3 cells were transfected with pcDNA3.1-BvrR-His to investigate the impact of Brucella abortus BvrR on the ER and the activation of ATF2 and NF-κB p65 proteins. To support the hypothesis that BvrR mediates activation of the ATF2/IL-6 and NF-κB p65/TNF-α pathways via p-IRE1, the effects of the IRE1 activator IXA4 and inhibitor GSK2850163 on these pathways were evaluated. HMC3 cells expressing BvrR were treated with IXA4 and GSK2850163. Protein and mRNA expression levels were determined by Western blot and RT-qPCR, while IL-6 and TNF-α concentrations in the supernatant were quantified by ELISA. Results indicated that BvrR activated IRE1, which subsequently triggered the ATF2/IL-6 and NF-κB p65/TNF-α pathways. For in vivo analysis, HBAAV2/9-IBA1-BvrR-6*HIS-ZsGreen was stereotactically injected into the right hippocampus of mice. Hippocampal neuronal damage and cognitive function were evaluated using Nissl staining and the Morris water maze test. Additionally, IRE1, ATF2/IL-6, and NF-κB p65/TNF-α signaling were analyzed in hippocampal microglia by immunofluorescence and Western blot. These findings demonstrated that Brucella abortus BvrR activates microglial inflammatory pathways via p-IRE1, leading to neuronal damage.

Brucella abortus BvrR; IRE1/ATF2/IL-6; IRE1/NF-κB p65/TNF-α; microglia; neurobrucellosis; neuroinflammation.