AUTHOR=Zhou Linyan , Xie Ying , Li Yan 

TITLE=Bifidobacterium infantis Promotes Foxp3 Expression in Colon Cells via PD-L1-Mediated Inhibition of the PI3K-Akt-mTOR Signaling Pathway

JOURNAL=Frontiers in Immunology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.871705

DOI=10.3389/fimmu.2022.871705

ISSN=1664-3224

ABSTRACT=<sec><title>Aim</title><p>Our objective was to investigate whether Bifidobacterium infantis inhibits PI3K-Akt-mTOR signaling and upregulates Foxp3 expression through PD-L1 and to explore the possible mechanism of action of B. infantis in cellular immunosuppression. </p></sec><sec><title>Method</title><p>The effects of B. infantis supernatant on PD-L1, PD-1, Foxp3, and the PI3K-Akt-mTOR signaling pathway were observed by culturing HCT-116 cells. Simultaneously, the effects of blocking PD-L1 on PD-1, on Foxp3 protein and mRNA, and on the PI3K-Akt-mTOR signaling pathway protein were observed.</p></sec><sec><title>Results</title><p>B. infantis supernatant was able to upregulate the protein and mRNA expression of PD-L1 and Foxp3 and downregulate the phosphorylated protein expression of PI3K, Akt, and mTOR (P &lt; 0.05); however, for PI3K, Akt, and mTOR, there was no change in the total protein expression. After the blocking of PD-L1, the stimulatory effect of B. infantis supernatant on Foxp3 and the inhibitory effect on the phosphorylated protein expression of PI3K, Akt, and mTOR were weakened.</p></sec><sec><title>Conclusion</title><p>B. infantis may inhibit the PI3K-Akt-mTOR signaling pathway and promote the expression of Foxp3 through PD-L1, which may be a target <italic>via</italic> which B. infantis exerts its immunosuppressive effect.</p></sec>