Introduction

Intestinal mucosa harbours a unique microbial community of central importance for the mutualistic relationship between the host and its microbiota. Additional research is warranted to characterise this “hidden” ecosystem and uncover mechanisms by which it can promote health in intestinal and systemic pathological states. We decipher how TNK1 kinase impacts the composition of mucosa-associated microbiota and its interplay with host mucosa via microbial extracellular vesicles (mEVs) and metabolites.
TNK1 is an essential player in development and functioning of the gastrointestinal tract. Whereas TNK1 expression is tightly regulated in the adult gut, and only cellular stress can reverse the otherwise strong repression of the TNK1 promoter. Indeed, TNK is highly expressed in the gut in gastrointestinal and systemic pathological conditions, e.g. IBD, sepsis, hemorrhagic shock and critical conditions. We showed that TNK1 is an essential mediator of intestinal barrier breach and subsequent organ failure. Intestinal overexpression of TNK1 elicits a sepsis-like condition by inducing stem cell apoptosis, followed by epithelial disruption and microbial translocation. Conversely, intestine-specific knockout of Tnk1 (Tnk1-KO) alleviates local and systemic signs of inflammation in a murine model of colitis.

Aims & Methods

We aim to establish the link between TNK1, microbial EVs and metabolites, and host intestinal regeneration. Mucosal microbial samples from Tnk1-KO and wild-type littermates were subjected to microbiome profiling by 16S rRNA sequencing. The therapeutic potential of Tnk1-KO microbiota was probed by microbiota transfer to germ-free wild-type recipient mice, subsequently challenged with dextran sodium sulfate colitis. Murine stool samples were obtained to characterise faecal microbial EVs and metabolites. Murine colon organoids were exploited as an ex-vivo platform to analyse TNK1 downstream signalling and cross-talk between microbial extracellular vesicles and colon epithelium.

Results

The current study shows that the TNK1 expression pattern impacts the composition of mucosa-associated microbiota in response to colitis. Namely, we show that targeting TNK1 in the intestine preserves microbial diversity and facilitates an increase in the abundance of beneficial butyrate-producing bacterial phyla. Moreover, we demonstrated in the colitis model that microbiota transplantation from Tnk1-KO mice has beneficial therapeutic potential. Further data suggest TNK1 directs changes in microbiota composition via regulation of the expression of antimicrobial peptides in the intestinal epithelium. However, how TNK1 and changed microbiota impact intestinal integrity needs to be clarified. Microbial extracellular vesicles (mEVs) and metabolites are critical components of bacterial communication with the host. Thus, we also characterised the number and size of mEVS and showed an increase in their number in stool from Tnk1-KO mice. We hypothesise that TNK1's protective effect on intestinal mucosa in colitis is mediated via microbial products-metabolites and EVs.

Conclusion

Transplantation of microbiota modified by targeting TNK1 results in the preservation of the intestinal barrier, which may be related to the modulation of bsEV secretion. Additional cargo analysis of mEV is necessary to identify potential host targets.

References

Armacki, M., A. K. Trugenberger, A. K. Ellwanger, T. Eiseler, C. Schwerdt, L. Bettac, D. Langgartner, N. Azoitei, R. Halbgebauer, R. Gross, T. Barth, A. Lechel, B. M. Walter, J. M. Kraus, C. Wiegreffe, J. Grimm, A. Scheffold, M. R. Schneider, K. Peuker, S. Zeissig, S. Britsch, S. Rose-John, S. Vettorazzi, E. Wolf, A. Tannapfel, K. Steinestel, S. O. Reber, P. Walther, H. A. Kestler, P. Radermacher, T. F. Barth, M. Huber-Lang, A. Kleger and T. Seufferlein (2018). "Thirty-eight-negative kinase 1 mediates trauma-induced intestinal injury and multi-organ failure." J Clin Invest128(11): 5056-5072.

Disclosure

Authors declare no conflict of interest