Prophylactic treatment with Bacteroides uniformis and Bifidobacterium bifidum counteracts hepatic NK cell immune tolerance in nonalcoholic steatohepatitis induced by high fat diet

ABSTRACT

Hepatic immunity is one of the driving forces for the development of nonalcoholic steatohepatitis (NASH), and targeting gut microbiota is believed to affect the hepatic immune constitution. Here, we aimed to investigate the hepatic immunological state in NASH, with a specific emphasis on natural killer (NK) cells. In addition, we aimed to identify the contributing species that target hepatic immunity to provide new directions and support the feasibility of immunotherapy for NASH. A possible NASH population was determined by combination of long-term severe fatty liver, metabolic disorders and increased serum CK18 to detect serum immune factors and gut microbiota. NASH was induced in mice fed a high-fat diet to verify the prophylactic effect of the functional species on the immunopathology and development of NASH. Hepatic immunologic state was examined, and the effector functions of NK cells were detected. Hepatic transcriptome, proteomic, and fecal metagenome were performed. We observed a statistical increase in serum IL-10 (p < 0.001) and non-statistical decrease in interferon-γ and IL-6 in NASH population, hinting at the possibility of immune tolerance. Fecal Bacteroides uniformis and Bifidobacterium bifidum were abundant in healthy population but depleted in NASH patients. In NASH mice, hepatic CD8+T cells, macrophages, and dendritic cells were increased (p < 0.01), and NK cells were inhibited, which were identified with decreased granzyme B (p < 0.05). Bacteroides uniformis and Bifidobacterium bifidum improved hepatic pathological and metabolic cues, increased hepatic NK cells and reduced macrophages (p < 0.05). Bacteroides uniformis also restored hepatic NK cell function, which was identified as increased CD107a (p < 0.05). Transcriptional and translational profiling revealed that the functional species might restore the function of hepatic NK cells through multiple pathways, such as reduction of inhibitory molecules in NK cells. Bacteroides uniformis and Bifidobacterium bifidum are novel prophylactics for NASH that restore the impaired function of hepatic NK cells.

KEYWORDS:

• Bacteroides uniformis
• Bifidobacterium bifidum
• natural killer cell
• immune tolerance
• nonalcoholic steatohepatitis

Acknowledgments

The authors would like thank the participants in Jinxi Town for their participation in this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Authors’ contributions

Jingyuan Xu, Yatao Wang, and Xiaolan Lu conceived and designed this study. Jingyuan Xu, Ting Wu, Yong Shao, Qiaoyun Xia, Yatao Wang, Nuyun Jin, Peiying Tian, Longyun Wu and Xiaolan Lu conducted the experiments. Jingyuan Xu and Qiaoyun Xia analyzed the data. Jingyuan Xu and Qiaoyun Xia wrote this manuscript. Xiaolan Lu revised the manuscript accordingly. All authors have reviewed the results and approved the final version of the manuscript.

Data availability statement

• This study did not report the original code.

• The authors confirm that the data supporting the findings of this study are available within the article and its supplementary material.

• Any additional information required to reanalyze the data reported in this paper is available from the lead contact upon request.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/19490976.2024.2302065

Additional information

Funding

This work was funded by the Natural Science Foundation of Shanghai [20ZR1450100], the National Natural Science Foundation of China [82070587], and the Pudong New Area Clinical Characteristic Discipline Project [PWYts2021-11].