A hepatocyte-specific transcriptional program driven by Rela and Stat3 exacerbates experimental colitis in mice by modulating bile synthesis

  1. Jyotsna
  2. Binayak Sarkar
  3. Mohit Yadav
  4. Alvina Deka
  5. Manasvini Markandey
  6. Priyadarshini Sanyal
  7. Perumal Nagarajan
  8. Nilesh Gaikward
  9. Vineet Ahuja
  10. Debasisa Mohanty
  11. Soumen Basak
  12. Rajesh S Gokhale

  • Curated by eLife

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    eLife assessment

    This important study reveals the RelA/Stat3-dependent gene program in the liver influences intestinal homeostasis. The evidence supporting the conclusions is compelling, although some additional experiments will strengthen the study. The work will be of interest to scientists in gastrointestinal research fields.

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Abstract

Hepatic factors secreted by the liver promote homeostasis and are pivotal for maintaining the liver-gut axis. Bile acid metabolism is one such example wherein, bile acid synthesis occurs in the liver and its biotransformation happens in the intestine. Dysfunctional interactions between the liver and the intestine stimulate varied pathological outcomes through its bidirectional portal communication. Indeed, aberrant bile acid metabolism has been reported in inflammatory bowel disease (IBD). However, the molecular mechanisms underlying these crosstalks that perpetuate intestinal permeability and inflammation remain obscure. Here, we identify a novel hepatic gene program regulated by Rela and Stat3 that accentuates the inflammation in an acute experimental colitis model. Hepatocyte-specific ablation of Rela and Stat3 reduces the levels of primary bile acids in both the liver and the gut and shows a restricted colitogenic phenotype. On supplementation of chenodeoxycholic acid (CDCA), knock-out mice exhibit enhanced colitis-induced alterations. This study provides persuasive evidence for the development of multi-organ strategies for treating IBD and identifies a hepatocyte-specific rela-stat3 network as a promising therapeutic target.

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  1. Version published to 10.1101/2023.09.21.558851v2 on bioRxiv
  2. eLife

    Author Response

    Reviewer #1 (Public Review):

    Summary:

    In this study, the authors showed that activation of RelA and Stat3 in hepatocytes of DSS-treated mice induced CYPs and thereby produced primary bile acids, particularly CDCA, which exacerbated intestinal inflammation.

    Strengths:

    This study reveals the RelA/Stat3-dependent gene program in the liver influences intestinal homeostasis.

    Weaknesses:

    Additional evidence will strengthen the conclusion.

    1. In Fig. 1C, photos show that phosphorylation of RelA and Stat3 was induced in only a few hepatocytes. The authors conclude that activation of both RelA and Stat3 induces inflammatory pathways. Therefore, the authors should show that phosphorylation of RelA and Stat3 is induced in the same hepatocytes during DSS treatment.

    Experiments in progress and data will be submitted in the revised manuscript- Co-staining of pRela and pStat3(727) on treated liver sections.

    1. In Fig. 5, the authors treated mice with CDCA intraperitoneally. In this experiment, the concentration of CDCA in the colon of CDCA-treated mice should be shown.

    Experiments in progress and data will be submitted in the revised manuscript - Supplementation of CDCA to knockout animals and estimation of CDCA in the colon of DSS treated and untreated animals.

    Reviewer #2 (Public Review):

    Singh and colleagues employ a methodic approach to reveal the function of the transcription factors Rela and Stat3 in the regulation of the inflammatory response in the intestine.

    Strengths of the manuscript include the focus on the function of these transcription factors in hepatocytes and the discovery of their role in the systemic response to experimental colitis. While the systemic response to induce colitis is appreciated, the cellular and molecular mechanisms that drive such systemic response, especially those involving other organs beyond the intestine are an active area of research. As such, this study contributes to this conceptual advance. Additional strengths are the complementary biochemical and metabolomics approaches to describe the activation of these transcription factors in the liver and their requirement - specifically in hepatocytes - for the production of bile acids in response to colitis.

    Some weaknesses are noted in the presentation of the data, including a lack of comprehensive representation of findings in all conditions and genotypes tested.

    These will be incorporated in the revised version.

    Reviewer #3 (Public Review):

    Summary:

    The authors try to elucidate the molecular mechanisms underlying the intra-organ crosstalks that perpetuate intestinal permeability and inflammation.

    Strengths:

    This study identifies a hepatocyte-specific rela/stat3 network as a potential therapeutic target for intestinal diseases via the gut-liver axis using both murine models and human samples.

    Weaknesses:

    1. The mechanism by which DSS administration induces the activation of the Rela and Stat3 pathways and subsequent modification of the bile acid pathway remains clear. As the authors state, intestinal bacteria are one candidate, and this needs to be clarified. I recommend the authors investigate whether gut sterilization by administration of antibiotics or germ-free condition affects 1. the activation of the Rela and Stat3 pathway in the liver by DSS-treated WT mice and 2. the reduction of colitis in DSS-treated relaΔhepstat3Δhep mice.

    Experiments in progress and data will be submitted in the revised manuscript - Antibiotic treatment for 2/4 weeks, subsequently mice will be treated with DSS and the Rela and Stat3 phosphorylation will be tested using western blotting.

    1. It has not been shown whether DSS administration causes an increase in primary bile acids, represented by CDCA, in the colon of WT mice following activation of the Rela and Stat3 pathways, as demonstrated in Figure 6.

    We have demonstrated a enhanced level of CDCA in the colon following DSS treatment in the wild type animals in figure 4B.

    1. The implications of these results for IBD treatment, especially in what ways they may lead to therapeutic intervention, need to be discussed.

    These will be incorporated in the revised version.

  3. Version published to 10.7554/elife.93273.1 on eLife
  4. Version published to 10.7554/elife.93273 on eLife
  5. eLife

    eLife assessment

    This important study reveals the RelA/Stat3-dependent gene program in the liver influences intestinal homeostasis. The evidence supporting the conclusions is compelling, although some additional experiments will strengthen the study. The work will be of interest to scientists in gastrointestinal research fields.

  6. eLife

    Reviewer #1 (Public Review):

    Summary:

    In this study, the authors showed that activation of RelA and Stat3 in hepatocytes of DSS-treated mice induced CYPs and thereby produced primary bile acids, particularly CDCA, which exacerbated intestinal inflammation.

    Strengths:

    This study reveals the RelA/Stat3-dependent gene program in the liver influences intestinal homeostasis.

    Weaknesses:

    Additional evidence will strengthen the conclusion.

    1. In Fig. 1C, photos show that phosphorylation of RelA and Stat3 was induced in only a few hepatocytes. The authors conclude that activation of both RelA and Stat3 induces inflammatory pathways. Therefore, the authors should show that phosphorylation of RelA and Stat3 is induced in the same hepatocytes during DSS treatment.

    2. In Fig. 5, the authors treated mice with CDCA intraperitoneally. In this experiment, the concentration of CDCA in the colon of CDCA-treated mice should be shown.

  7. eLife

    Reviewer #2 (Public Review):

    Singh and colleagues employ a methodic approach to reveal the function of the transcription factors Rela and Stat3 in the regulation of the inflammatory response in the intestine.

    Strengths of the manuscript include the focus on the function of these transcription factors in hepatocytes and the discovery of their role in the systemic response to experimental colitis. While the systemic response to induce colitis is appreciated, the cellular and molecular mechanisms that drive such systemic response, especially those involving other organs beyond the intestine are an active area of research. As such, this study contributes to this conceptual advance. Additional strengths are the complementary biochemical and metabolomics approaches to describe the activation of these transcription factors in the liver and their requirement - specifically in hepatocytes - for the production of bile acids in response to colitis.

    Some weaknesses are noted in the presentation of the data, including a comprehensive representation of findings in all conditions and genotypes tested.

  8. eLife

    Reviewer #3 (Public Review):

    Summary:

    The authors try to elucidate the molecular mechanisms underlying the intra-organ crosstalks that perpetuate intestinal permeability and inflammation.

    Strengths:

    This study identifies a hepatocyte-specific rela/stat3 network as a potential therapeutic target for intestinal diseases via the gut-liver axis using both murine models and human samples.

    Weaknesses:

    1. The mechanism by which DSS administration induces the activation of the Rela and Stat3 pathways and subsequent modification of the bile acid pathway remains clear. As the authors state, intestinal bacteria are one candidate, and this needs to be clarified. I recommend the authors investigate whether gut sterilization by administration of antibiotics or germ-free condition affects 1. the activation of the Rela and Stat3 pathway in the liver by DSS-treated WT mice and 2. the reduction of colitis in DSS-treated relaΔhepstat3Δhep mice.

    2. It has not been shown whether DSS administration causes an increase in primary bile acids, represented by CDCA, in the colon of WT mice following activation of the Rela and Stat3 pathways, as demonstrated in Figure 6.

    3. The implications of these results for IBD treatment, especially in what ways they may lead to therapeutic intervention, need to be discussed.

  9. Version published to 10.1101/2023.09.21.558851v1 on bioRxiv