NR4A1 modulates inflammation-associated intestinal fibrosis and dampens fibrogenic signaling in myofibroblasts.

Abstract

BACKGROUND\nIntestinal fibrosis is a common complication of the inflammatory bowel diseases(IBD), contributing to tissue stiffening and luminal narrowing. NR4A1 was previously reported to regulate mesenchymal cell function and dampen fibrogenic signaling. NR4A1 gene variants are associated with IBD risk, and it has been shown to regulate intestinal inflammation. Here, we tested the hypothesis that NR4A1 acts as a negative regulator of intestinal fibrosis through regulating myofibroblast function.\n\n\nMETHODS\nUsing the SAMP1/YitFc mouse, we tested whether two pharmacological agents known to enhance NR4A1 signaling: cytosporone B(Csn-B) or 6-mercaptopurine(6-MP); could reduce fibrosis. We also employed the dextran sulphate sodium(DSS) model of colitis and assessed the magnitude of colonic fibrosis in Nr4a1-/- and their wild-type littermates(Nr4a1+/+). Lastly, intestinal myofibroblasts isolated from Nr4a1-/- and Nr4a1+/+ mice or primary human intestinal myofibroblasts were stimulated with transforming growth factor-beta-1(TGF-β1), in the presence or absence of Csn-B or 6-MP, and proliferation and ECM gene expression assessed.\n\n\nRESULTS\nCsn-B or 6-MP treatment significantly reduced ileal thickness, collagen and overall ECM content in SAMP1/YitFc mice. This was associated with a reduction in proliferative markers within the mesenchymal compartment. Nr4a1-/- mice exposed to DSS exhibited increased colonic thickening and ECM content. Nr4a1-/- myofibroblasts displayed enhanced TGF-β1-induced proliferation. Furthermore, Csn-B or 6-MP treatment was anti-proliferative in Nr4a1+/+, but not Nr4a1-/- cells. Lastly, activating NR4A1 in human myofibroblasts reduced TGF-β1-induced collagen deposition and fibrosis-related gene expression.\n\n\nCONCLUSIONS\nOur data suggest that NR4A1 can attenuate fibrotic processes in intestinal myofibroblasts and could provide a valuable clinical target to treat inflammation-associated intestinal fibrosis.