AUTHOR=Zhao Tianyi , Zhang Zedan , Li Yitao , Sun Zhihua , Liu Liangbo , Deng Xingmei , Guo Jia , Zhu Dexin , Cao Shuzhu , Chai Yingjin , Nikolaevna Usevich Vera , Maratbek Suleimenov , Wang Zhen , Zhang Hui 

TITLE=Brucella abortus modulates macrophage polarization and inflammatory response by targeting glutaminases through the NF-κB signaling pathway

JOURNAL=Frontiers in Immunology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1180837

DOI=10.3389/fimmu.2023.1180837

ISSN=1664-3224

ABSTRACT=<sec><title>Objectives</title><p>The mechanism of Brucella infection regulating macrophage phenotype has not been completely elucidated until now. This study aimed to determine the mechanism of <italic>Brucella abortus</italic> in the modulation of macrophage phenotype using RAW264.7 cells as a model.</p></sec><sec><title>Materials and methods</title><p>RT-qPCR, ELISA and flow cytometry were used to detect the inflammatory factor production and phenotype conversion associated with M1/M2 polarization of macrophages by <italic>Brucella abortus</italic> infection. Western blot and immunofluorescence were used to analyze the role of nuclear factor kappa B (NF-κB) signaling pathway in regulation of <italic>Brucella abortus</italic>-induced macrophage polarization. Chromatin immunoprecipitation sequencing (Chip‐seq), bioinformatics analysis and luciferase reporter assay were used to screen and validate NF-κB target genes associated with macrophage polarization and further verify its function.</p></sec><sec><title>Results</title><p>The results demonstrate that <italic>B. abortus</italic> induces a macrophage phenotypic switch and inflammatory response in a time-dependent manner. <italic>With the increase of infection time</italic>, <italic>B. abortus</italic> infection-induced M1-type increased first, peaked at 12 h, and then decreased, whereas the M2-type decreased first, trough at 12 h, and then increased. The trend of intracellular survival of <italic>B. abortus</italic> was consistent with that of M2 type. When NF-κB was inhibited, M1-type polarization was inhibited and M2-type was promoted, and the intracellular survival of <italic>B. abortus</italic> increased significantly. Chip‐seq and luciferase reporter assay results showed that NF-κB binds to the glutaminase gene (<italic>Gls</italic>). <italic>Gls</italic> expression was down-regulated when NF-κB was inhibited. Furthermore, when <italic>Gls</italic> was inhibited, M1-type polarization was inhibited and M2-type was promoted, the intracellular survival of <italic>B. abortus</italic> increased significantly. Our data further suggest that NF-κB and its key target gene <italic>Gls</italic> play an important role in controlling macrophage phenotypic transformation. </p></sec><sec><title>Conclusions</title><p>Taken together, our study demonstrates that <italic>B. abortus</italic> infection can induce dynamic transformation of M1/M2 phenotype in macrophages. Highlighting NF-κB as a central pathway that regulates M1/M2 phenotypic transition. This is the first to elucidate the molecular mechanism of <italic>B. abortus</italic> regulation of macrophage phenotype switch and inflammatory response by regulating the key gene <italic>Gls</italic>, which is regulated by the transcription factor NF-κB.</p></sec>