Epithelial MLCK deficiency alleviates alcohol-associated liver disease via dendritic-Th17 cell axis.

BACKGROUND & AIMS: Intestinal dendritic cells (DCs) have a key role in immune regulation, especially during injury. The role of intestinal epithelial paracellular permeability in DC antigen presentation and its regulation is unclear although it is known that myosin light chain kinase (MLCK) regulates barrier permeability. Thus, we examined the role of MLCK in DC function and immune responses in alcohol-associated liver disease (ALD).

METHODS

We used systemic and intestinal epithelial-specific Mylk-knockout models (n = 6 mice per group) to investigate the MLCK-mediated leak pathway in ALD. The effects of constitutively active MLCK in intestinal epithelial cells were also assessed (n = 6). Mechanistic investigations focused on LPA-LPAR2-Ca2+-dependent MLCK activation, while also evaluating tight junction integrity, DC antigen uptake and presentation by flow cytometry, and pathogenic Th17 cell responses (n = 3).

RESULTS

The MLCK-mediated leak pathway was upregulated in ALD (n = 6, p <0.05). Both systemic and intestinal epithelial-specific Mylk knockout attenuated ALD progression, as evidenced by reduced liver injury markers (ALT decreased by 50%, n = 6, p <0.05), whereas constitutively active MLCK accelerated disease (n = 6, p <0.05). LPA-LPAR2 signaling activated MLCK via Ca2+/CaM-dependent pathways, disrupted tight junctions, and enhanced DC antigen uptake and antigen-presenting capacity (by 1.4-fold, n = 3, p <0.05). This promoted pathogenic Th17 cell responses and GM-CSF production (by twofold, n = 6, p <0.05) associated with liver inflammation.

CONCLUSIONS

This study highlights the role of MLCK-regulated intestinal permeability in DC function and Th17 cell differentiation in ALD. Thus, targeting this pathway could provide new therapeutic strategies for ALD.

IMPACT AND IMPLICATIONS: This study reveals the crucial role of MLCK-regulated intestinal paracellular permeability in ALD, expanding our understanding of the gut-liver interaction. The findings provide new insights into immune regulation and barrier function, offering potential therapeutic implications for the treatment of ALD. By highlighting the role of MLCK-mediated barrier function in DC function and Th17 cell differentiation, this research opens new avenues for clinical application, particularly in developing targeted therapies for ALD. For researchers, these findings offer a fresh perspective on the interplay between the gut microbiota and immune responses, advancing the field of immunology and gastrointestinal diseases.