Background: Ras homolog gene family, member A (RhoA)/Rho-associated coiled-coil forming protein kinase signaling is a key pathway in multiple types of solid organ fibrosis, including intestinal fibrosis. However, the pleiotropic effects of RhoA/Rho-associated coiled-coil forming protein kinase signaling have frustrated targeted drug discovery efforts. Recent recognition of the role of Rho-regulated gene transcription by serum response factor (SRF) and its transcriptional cofactor myocardin-related transcription factor A (MRTF-A) suggest a novel locus for pharmacological intervention.
Methods: Because RhoA signaling is mediated by both physical and biochemical stimuli, we examined whether pharmacological inhibition of RhoA or the downstream transcription pathway of MRTF-A/SRF could block intestinal fibrogenesis in 2 in vitro models.
Results: In this study, we demonstrate that inhibition of RhoA signaling blocks both matrix-stiffness and transforming growth factor beta–induced fibrogenesis in human colonic myofibroblasts. Repression of alpha-smooth muscle actin and collagen expression was associated with the inhibition of MRTF-A nuclear localization. CCG-1423, a first-generation Rho/MRTF/SRF pathway inhibitor, repressed fibrogenesis in both models, yet has unacceptable cytotoxicity. Novel second-generation inhibitors (CCG-100602 and CCG-203971) repressed both matrix-stiffness and transforming growth factor beta–mediated fibrogenesis as determined by protein and gene expression in a dose-dependent manner.
Conclusions: Targeting the Rho/MRTF/SRF mechanism with second-generation Rho/MRTF/SRF inhibitors may represent a novel approach to antifibrotic therapeutics.
Article first published online 25 November 2013
*Department of Internal Medicine,
†Department of Pharmacology, and
‡Vahlteich Medicinal Chemistry Core, College of Pharmacy, University of Michigan, Ann Arbor, Michigan.
Reprints: Peter D. R. Higgins, MD, PhD, MSc, Assistant Professor in Gastroenterology, Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Michigan Medical Center, SPC 5682, Room 6510D, Medical Science Research Building One, 1150 West Medical Center Drive, Ann Arbor, MI 48109-0682 (e-mail: firstname.lastname@example.org).
Supported by an NIH Grant, K08DK080172 (Higgins). The ImageXpress Micro screening system is supported in part by a National Functional Genomics Center Grant (W81XWH-10-2-0013) from the Department of Defense to the University of Michigan Center for Chemical Genomics.
The authors have no conflicts of interest to disclose.
Received September 30, 2013
Accepted October 2, 2013