Introduction: Crohn’s Disease (CD), one of the major forms of inflammatory bowel disease (IBD), involves genetic and environmental factors and currently has no cure. Fibrosis is strongly associated with CD, has no pharmacological treatment, and often requires surgical intervention. Given the clinical consequences of this complication, there is an urgent need for novel therapies. Bromodomain-containing protein 4 (BRD4), an important epigenetic reader, has been implicated in hepatic, pulmonary, and cardiac fibrosis. BRD4 inhibition has shown promise as a target for pulmonary and cardiac fibrosis. However, the role of BRD4 in CD-associated fibrosis remains poorly understood. We previously observed an increase in BRD4 activity in IBD and that inhibiting BRD4 reduces activation of profibrotic MAPKAPK2 signaling in CD tissue explants. Thus, we hypothesize that BRD4 has potential as a therapeutic target to attenuate fibrosis in CD.
Methods: Myo-/fibroblasts were isolated from non-involved areas of human intestinal CD tissue. We used CD patient-derived inflamed and fibrotic tissue as well as a CD-relevant animal model of IL-10 KO spontaneous colitis to evaluate the efficacy of novel BRD4 inhibitors developed by our team. These included ZL0454, delivered through intraperitoneal injection (i.p.), and ZL0590, delivered through oral gavage (p.o.).
Results: TGF-β production and its downstream signaling are critical drivers of CD-associated fibrosis, and we found upregulation of this pathway in chronic CD. We demonstrated that 24h treatment with BRD4i ZL0454 or ZL0590 (0.1 µM) significantly reduced expression of TGF-β-induced profibrotic responses, including ACTA2 and Col1α2 expression. Additionally, ex vivo treatment of CD tissue with BRD4i (1 µM, 18h) also abrogated expression of these profibrotic genes. Use of these inhibitors as a therapeutic modality (0.1 mg/dose, daily, 10 days) in a CD-relevant IL-10 KO model of colitis significantly reduced profibrotic changes in colonic tissue architecture, including decreased extracellular matrix deposition and collagen thickness. We also observed reduced expression of profibrotic genes, including Col1α2, in this model. Furthermore, oral administration of BRD4i ZL0590 (p.o.) demonstrated superior efficacy over that of ZL0454 (i.p.) in the reduction of both colitis features and profibrotic responses.
Conclusions: Our data demonstrates that the use of orally bioavailable BRD4 inhibitors have potential as a novel therapeutic approach to mitigate CD-associated fibrosis.

Zonghui Ma

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