Elevated intestinal epithelial tight junction permeability leads to systemic graft-versus-host disease propagation

On 1 February 2019, Sam C. Nalle from the Department of Pathology, The University of Chicago, Chicago, Illinois, USA, and colleagues published their analysis in The Journal of Clinical Investigation, on the impact of dysregulated intestinal permeability on the subsequent graft-versus-host disease (GvHD) propagation phase. Myosin light chain kinase (MLCK210), a serine/threonine-specific protein kinase that phosphorylates a specific myosin light chain, namely the regulatory light chain of myosin II, is also known as a key regulator of tight junction permeability. The study group hypothesized that MLCK210-dependent alterations in barrier function may drive GvHD propagation.

Methods

• Duodenal biopsies from patients with GvHD collected > 2 weeks post-transplant
• Donor female 129S6 and BALB/c mice
• Immunohistochemistry and immunofluorescence were performed
• Allogeneic bone marrow transplantation (allo-BMT)
• Cytokine measurements: ELISA – Ready-SET-Go! Kits
• MLCK210 transcript quantification
• Intestinal and vascular permeability assays
• Flow cytometry

Key findings

• MLCK210 activity and expression were elevated in human GvHD
• Intestinal epithelial MLCK210 upregulation and activity were increased after allo-BMT in mice
• Genetic MLCK210 inhibition in GvHD mouse model limited paracellular permeability and MLC phosphorylation in intestinal epithelia, but did not prevent increased microvascular permeability
• MLCK210-dependent processes contribute to systemic GvHD progression but has no effect on the initiation phase
• Cumulative GvHD severity and disease propagation are driven by MLCK210-dependent regulation of intestinal epithelial permeability
• MLCK210 deletion controls propagation of major antigen mismatch GvHD
• Intestinal epithelial MLCK210 is a key regulator of GvHD pathogenesis
• MLCK210 expression in the intestinal epithelium ameliorates the cytolytic function of CD8+ effector T cells within regional lymph nodes and this could be the major mechanism behind increased intestinal epithelial tight junction permeability and GvHD propagation

In conclusion, these findings demonstrate that MLCK210-mediated intestinal epithelial barrier dysfunction is a key driver to systemic GvHD propagation. These data also show that non-hematopoietic functions can be targeted, epithelial barrier integrity for instance, which may offer an alternative target for the treatment of GvHD.