Investigating the interplay between LIGHT and HIF in inflammatory fibroblast responses

Abstract

Introduction: Intestinal fibroblast differentiation into an inflammatory phenotype likely plays a key role in Inflammatory Bowel Disease (IBD). However, the mechanisms that control this process are poorly understood. The cytokine TNFSF14 (LIGHT) drives inflammatory fibroblast responses in other diseases such as Eosinophilic esophagitis. Additionally, hypoxia, defined as low cellular or tissue levels of oxygen, is a feature of IBD progression. The use of hydroxylase inhibiting drugs which exhibit hypoxia mimetic conditions have been shown in murine models to have protective effects in IBD. Here we hypothesize the role of LIGHT to be of central importance in intestinal fibroblast differentiation and test how this inflammatory phenotype may be affected by hypoxia mimetic drugs and conversely what effect LIGHT may have on the hypoxic condition. Methods: Primary human colonic fibroblasts (18CO), the hepatic stellate cell line (LX2) and the epithelial cell line (T84) were treated with LIGHT in time course studies. 18COs were also treated with hydroxylase inhibitors Dimethyloxalylglycine (DMOG), JNJ42041935 and Roxadustat. Responses were analysed using qPCR, flowcytometry and Immunoblot-analysis. Results: LIGHT-treated 18COs upregulated CCL2 (7-fold ± increase, p=<0.001, n=5), CXCL10 (14-fold ± increase, p=<0.0001, n=3) and IL34 (30-fold ± increase, p=<0.05 n=5) at transcript level, and surface protein expression of ICAM1 (15% ± increase at 24 hours compared to vehicle, n=4) and VCAM1 (18% ± increase at 24 hours compared to vehicle, n=4) displaying distinct kinetics. This response was absent or to a much less significant degree in LX2s and T84s. DMOG decreased CCL2 (4-fold ± decrease compared to LIGHT treated samples, p=<0.001, n=5) and CXCL10 (11-fold ± decrease compared to LIGHT treated samples, p=<0.0001, n=3) gene expression in 18COs when subsequently treated with LIGHT for 8 hours but did not affect other targets tested such as CSF1, CXCL5, VCAM1 and ICAM1. Immunoblot analysis of 18COs showed a decreased HIF-1α stabilization when treated with hydroxylase inhibitors in the presence of LIGHT compared to hydroxylase inhibitors alone (3 different hydroxylase inhibiting drugs n=3-4, n=11 total). Preliminary data of HIF downstream activated genes VEGFA (14-fold ± increase, p=<0.05 n=3) and GLUT1 (6-fold ± increase, p=<0.05 n=3) show increased gene expression in 18COs when treated with DMOG with noticeable decreases when treated with a LIGHT DMOG combination. Conclusions: Our current studies show that LIGHT is a potential mediator of colonic inflammatory fibroblast differentiation and a possible inhibitor of HIF-1α stabilization. The effects of LIGHT are either significantly weaker or not displayed in colonic epithelial cells or hepatic stellate cells, indicating LIGHT-specific effects on intestinal stroma. Hydroxylase inhibitors show selective effects on the LIGHT driven response. Collectively our data reveals a potential LIGHT-hypoxia network that may be amenable for therapeutic interventions. SFI/IRC Pathway Fellows Award to Dr. Manresa, 21/PATH-S/9621. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.