cRel expression regulates distinct transcriptional and functional profiles driving fibroblast matrix production in systemic sclerosis

Abstract

Objectives NF-κB regulates genes that control inflammation, cell proliferation, differentiation and survival. Dysregulated NF-κB signalling alters normal skin physiology and deletion of cRel limits bleomycin-induced skin fibrosis. This study investigates the role of cRel in modulating fibroblast phenotype in the context of SSc. Methods Fibrosis was assessed histologically in mice challenged with bleomycin to induce lung or skin fibrosis. RNA sequencing and pathway analysis was performed on wild type and Rel−/− murine lung and dermal fibroblasts. Functional assays examined fibroblast proliferation, migration and matrix production. cRel overexpression was investigated in human dermal fibroblasts. cRel immunostaining was performed on lung and skin tissue sections from SSc patients and non-fibrotic controls. Results cRel expression was elevated in murine lung and skin fibrosis models. Rel−/− mice were protected from developing pulmonary fibrosis. Soluble collagen production was significantly decreased in fibroblasts lacking cRel while proliferation and migration of these cells was significantly increased. cRel regulates genes involved in extracellular structure and matrix organization. Positive cRel staining was observed in fibroblasts in human SSc skin and lung tissue. Overexpression of constitutively active cRel in human dermal fibroblasts increased expression of matrix genes. An NF-κB gene signature was identified in diffuse SSc skin and nuclear cRel expression was elevated in SSc skin fibroblasts. Conclusion cRel regulates a pro-fibrogenic transcriptional programme in fibroblasts that may contribute to disease pathology. Targeting cRel signalling in fibroblasts of SSc patients could provide a novel therapeutic avenue to limit scar formation in this disease.

The Hexosamine Biosynthetic Pathway Links Innate Inflammation With Epithelial-Mesenchymal Plasticity in Airway Remodeling

“…Our evidence that RELA directly binds to the SNAI1 and ZEB1 promoters, enhancing their expression ( Tian et al, 2016 ) provides understanding how RELA functions as a master regulator of EMP in epithelial cells. These data are consistent with the role of cRel in driving fibroblast to myofibroblast transition in skin fibroblasts ( Worrell et al, 2020 ).…”

Bone Morphogenetic Protein Antagonist Gremlin-1 Increases Myofibroblast Transition in Dermal Fibroblasts: Implications for Systemic Sclerosis

“…Analysis of the Gremlin-1 promoter sequence demonstrates that it has STAT binding sequenced contained within. The relevance of inflammatory regulation of Gremlin-1 is demonstrated in our recent study in which RNA sequencing of skin fibroblasts from mice with a deletion in the nfkb subunit c-Rel revealed significantly reduced levels of Gremlin-1 in KO compared to wildtype mice (Worrell et al, 2020). Because IL-11 is an IL-6 family cytokine and we have recently described its pro-fibrotic role in SSc (Adami et al, 2021), we hypothesized that this would lead to increased Gremlin-1 expression similar to IL-6 stimulation.…”

Metabolic reprogramming of glycolysis and glutamine metabolism are key events in myofibroblast transition in systemic sclerosis pathogenesis

“…Of course, succinate is made in a variety of cell types and in SSc succinate could be released from macrophages to active the fibroblast to undergo fibrotic changes leading to enhanced ECM. Given that macrophages are key cell types in SSc, 48,49 this is a plausible explanation. How succinate may up-regulate collagen is unknown but appears to be independent of TGF-β1 as the Smad reporter assay did not increase after succinate incubation.…”