The TNFSF12/TWEAK modulates colonic inflammatory fibroblast differentiation and promotes fibroblast-monocyte interactions
Fibroblasts acquire a pro-inflammatory phenotype in inflammatory bowel disease (IBD), but the factors driving this process and how fibroblasts contribute to the immune response is incompletely understood. The TNF superfamily factor 12 (TWEAK) has gained interest as a mediator of chronic inflammation. Here, we explore its role as a driver of inflammatory responses in fibroblasts and its contribution to fibroblast-monocyte interaction using human primary colonic fibroblasts, THP1 and peripheral blood mononuclear cells (PBMC). TWEAK induced the expression of cytokines, chemokines and immune receptors in fibroblasts. The TWEAK up-regulated transcriptome shared 29% homology with the previously published transcriptional profile of inflammatory fibroblasts from ulcerative colitis. TWEAK elevated surface expression of activated fibroblasts markers and adhesion molecules (PDPN, ICAM-1 and VCAM-1) and secretion of IL-6, CCL2 and CXCL10. In co-culture, fibroblasts induced monocyte adhesion and promoted a CD14high/ICAM-1 high phenotype in THP1 cells, both of which were enhanced when fibroblasts were pre-stimulated with TWEAK. Medium from TWEAK-treated fibroblast-THP1 co-cultures had elevated levels of CXCL1 and IL-8. PBMCs in co-culture with TWEAK-treated fibroblasts had altered surface expression of CCR2 and CD16, and increased CXCL1 and CXCL10. Our results indicate that TWEAK promotes and inflammatory fibroblast-monocyte crosstalk that may be amenable for therapeutic intervention. Overall design: To test the role of TWEAK in colonic fibroblast differentiation, human colonic fibroblasts were treated with TWEAK for 24 hours and the transcriptional profile compared to vehicle was assessed using bulk RNA sequencing.