A211 ANTIFIBROTIC ACTIVITY OF NOVEL TYROSINE KINASE INHIBITORS IN VITRO

Abstract

Abstract Background Chronic inflammation in inflammatory bowel disease (IBD) causes structural alterations of the intestine. In Crohn’s disease, this can lead to stricture formation, arising from unclear interactions among local inflammatory cells, cytokines, and mesenchymal intestinal cells. Specifically, proliferation of smooth muscle and increased deposition of collagen-rich extracellular matrix leads to fibrosis and obstructive wall thickening. Since there are minimal treatment options, we explored the effects of two multimodal tyrosine kinase inhibitors, nintedanib and pirfenidone, which were recently approved for idiopathic pulmonary fibrosis (IPF), a chronic lung condition resembling Crohn’s disease. Aims To understand the basic pharmacology of two novel anti-fibrotic tyrosine kinase inhibitors and their effects on cell proliferation and collagen deposition. Methods In vitro model systems of adult rat colonic circular smooth muscle cells (CSMS), rat IEC-18 intestinal epithelial cells or mouse 3T3 were assessed for response to serum or the mesenchymal growth factor PDGF-BB, evaluating growth responses by proliferation assay, and type I collagen expression by immunocytochemistry and western blotting. Programmed cell death was detected by ICC and western blotting for caspase-dependent apoptotic markers. Results Both 3T3 fibroblasts and rat ISMC showed concentration-dependent proliferation in response to serum or PDGF application. Nintedanib reduced this response to baseline at EC100 of 2.3 ± 0.7 (n=5) µM, and EC50 of 0.3 ± 0.1 (n=6) µM without cytotoxicity, while pirfenidone was ineffective at levels ≤ 5mM. Nintedanib (10 µM) was ineffective against serum-induced growth of rat IEC-18 cells while blocking growth of rat CSMC or mouse 3T3 fibroblasts in parallel assays, suggesting a selective effect on mesenchymal cell types. In nintedanib-treated cultures, nuclear staining showed concentration-dependent reduction of mitotic figures with proportional appearance of nuclear fragmentation, typical of apoptosis. Western blotting for collagen I identified at 125kD band for both CSMC and 3T3 cells and suggested down-regulation with both nintedanib and pirfenidone. Conclusions Novel anti-fibrotic therapies for chronic idiopathic pulmonary disease display distinctive effects on ISMC proliferation and extracellular matrix production. These address molecular mechanisms of fibrosis that are in common with IBD, and so the translation of therapeutic approaches may be a promising treatment option. Detecting specific mechanisms of action of nintedanib, such as apoptosis, leads to better targets for therapeutic options. Funding Agencies NSERC