TNFSF14/LIGHT responses in intestinal and oesophageal fibroblasts are differentially modulated by hydroxylase inhibitors.

Fibroblasts have emerged as inflammatory entities in ulcerative colitis (UC) and eosinophilic oesophagitis, positioning these cells as attractive therapeutic targets. Previous studies have shown that hydroxylase inhibitors elicit anti-inflammatory responses, but their effects on fibroblasts during inflammation remain unknown. Here we test the effects of hydroxylase inhibitors on TNFSF14/LIGHT-driven inflammation in intestinal and oesophageal fibroblasts. Human endoscopic biopsies were obtained from paired inflamed or non-inflamed areas of active UC patients. Primary human colonic and oesophageal fibroblasts from healthy donors were pre-treated with hydroxylase inhibitors and/or treated with LIGHT. Flow cytometry, qRT-PCR, enzyme-linked immunosorbent assays, immunoblotting, immunofluorescence and RNAseq were used. LIGHT induced inflammatory responses in intestinal fibroblasts predominantly via lymphotoxin β receptor (LTβR), which was more highly expressed than herpes virus entry mediator in UC biopsies and colonic fibroblasts. A comparative analysis of the response to LIGHT between colonic and oesophageal fibroblasts revealed unique transcriptional profiles and a shared inflammatory gene programme. Pretreatment with hydroxylase inhibitors had a selective inhibitory effect on the expression of several LIGHT-mediated inflammatory factors in colonic and oesophageal fibroblasts. Mechanistic studies revealed differential molecular targets as LIGHT-driven non-canonical nuclear factor-κB activity was targeted by hydroxylase inhibitors in oesophageal but unaffected in colonic fibroblasts. While dimethyloxalylglycine (DMOG) abrogated LIGHT-induced p38 phosphorylation in colonic fibroblasts, p38 inhibitors did not phenocopy the anti-inflammatory effects of DMOG. In summary, we established a previously unrecognised LIGHT/LTβR-driven inflammatory response in intestinal fibroblasts and characterised differential effects and pathways for LIGHT signalling in intestinal and oesophageal fibroblasts. We identified therapeutic effects of hydroxylase inhibitors via targeting of distinct pathways in these cells. KEY POINTS: LIGHT induces partially conserved inflammatory responses in colonic and oesophageal fibroblasts. Hydroxylase inhibitors selectively diminish LIGHT-mediated inflammation in both types of fibroblasts. Dimethyloxalylglycine reduces accumulation of the non-canonical nuclear factor-κB member p52 in oesophageal fibroblasts. The mechanism whereby hydroxylase inhibitors reduce LIGHT-mediated inflammation in colonic fibroblasts remains to be elucidated.