Naveen Kumar

Conference 2024 Live Talk

Talk Title

Non-canonical NF-κB signaling promotes intestinal inflammation by restraining the tolerogenic β-catenin-Raldh2 axis in dendritic cells

Authors and Affiliations

Alvina Deka1,*, Naveen Kumar1,*, Meenakshi Chawla1, Namrata Bhattacharya2,3, Sk Asif Ali1, Swapnava Basu1, Bhawna1, Upasna Madan4, Shakti Kumar4, Bhabatosh Das4, Debarka Sengupta2, Amit Awasthi4, Soumen Basak1
1Systems Immunology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg,
New Delhi-110067, India
2Indraprastha Institute of Information Technology, Delhi, India
3Australian Prostate Cancer Research Centre—Queensland, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Queensland, Australia
4Translational Health Science and Technology Institute, Faridabad, India
* These authors have contributed equally to the work

Abstract

Background

Dendritic cells (DCs) orchestrate the balance between protective immune responses against pathogens and tolerance towards commensal microbes at the mucosal interface. Not surprisingly, distorted DC functions have been implicated in aberrant intestinal inflammation. However, the molecular mechanism that compromises DC-mediated immune controls in intestinal pathologies remains unclear. The non-canonical NF-kB pathway activates the RelB:p52 heterodimer, which is known to play a role in immune differentiation and development. Because genes encoding non-canonical NF-kB factors have been linked to the susceptibility loci for inflammatory bowel disease (IBD), we asked if non-canonical RelB:p52 NF-kB signaling perturbed DC functions in the inflamed gut.

Methods

We analyzed publicly available mouse experimental colitis and human IBD single cell RNASeq data to establish the involvement of heightened noncanonical NF-kB signaling in DCs. For mouse genetic studies, we employed DC-specific genetic knockout mice deficient in the noncanonical NF-kB signaling transducers- Relb/Nfkb2. We used flow cytometry to chart the DC- and T-cell profile of these knockout mice in the dextran sodium sulphate (DSS)-induced experimental colitis model. To genetically dissect the molecular circuitry in play, we used bone marrow derived dendritic cells (BMDCs) and sorted-intestinal DCs for gene expression, biochemistry and flow cytometry analysis. Microbiome studies were performed through 16s rRNA sequencing of the V3-V4 hypervariable region and qPCR using fecal DNA.

Results

Our results confirmed that genetic inactivation of this pathway in DCs alleviated inflammation in colitogenic mice. Unexpectedly, RelB:p52 deficiency diminished the transcription of Axin1, a critical component of the β-catenin destruction complex. This reinforced β-catenin-driven expression of Raldh2, which imparts tolerogenic DC attributes by promoting retinoic acid (RA) synthesis. Indeed, DC-specific non-canonical NF-kB impairment improved the colonic frequency of Tregs and IgA+ B cells, which fostered luminal IgA and eubiosis. Introducing β-catenin haploinsufficiency in non-canonical NF-kB-deficient DCs moderated Raldh2 activity, reinstating colitogenic sensitivity in mice. Finally, IBD patients displayed a deleterious non-canonical NF-kB signature in intestinal DCs.

Conclusions

In sum, we establish a DC network that integrates non-canonical NF-kB signaling to subvert RA metabolic pathway in fueling intestinal inflammation.