cx-5461 and Neointima

Transplant vasculopathy is a major cause of chronic rejection of transplanted organs. In the present study, we examined the effects of CX-5461, a novel selective inhibitor of RNA polymerase I, on development of transplant vasculopathy using a modified model of rat aortic transplantation.. The thoracic aortas from Fischer rats were transplanted into the abdominal cavity of Lewis rats. CX-5461 was mixed in pluronic gel and administered via perivascular release.. Treatment with CX-5461 mitigated the development of neointimal hyperplasia and vascular inflammation. This effect was likely to be attributable in part to inhibition of macrophage-dependent innate immunity reactions. Specifically, CX-5461 exhibited potent inhibitory effects on macrophage migration and lipopolysaccharide-induced activation. Treatment with CX-5461 also prevented macrophage differentiation and maturation from primary bone marrow cells. In macrophages, CX-5461 did not alter the total amount of p53 protein, but significantly increased p53 phosphorylation, which was involved in regulating cytokine-stimulated macrophage proliferation.. In conclusion, our results suggest that pharmacological inhibition of RNA polymerase I may be a novel strategy to treat transplantation-induced arterial remodeling.

Topics: Allografts; Animals; Aorta; Aortic Diseases; Arteriosclerosis; Benzothiazoles; Cell Movement; Disease Models, Animal; Enzyme Inhibitors; Heart Transplantation; Humans; Macrophages; Male; Mice; Mice, Inbred C57BL; Naphthyridines; Neointima; Primary Cell Culture; Rats; Rats, Inbred F344; RAW 264.7 Cells; RNA Polymerase I; Treatment Outcome; Vascular Remodeling

RNA polymerase I (Pol I)-dependent rRNA synthesis is a determinant factor in ribosome biogenesis and thus cell proliferation. The importance of dysregulated Pol I activity in cardiovascular disease, however, has not been recognized. Here, we tested the hypothesis that specific inhibition of Pol I might prevent arterial injury-induced neointimal hyperplasia.. CX-5461 is a novel selective Pol I inhibitor. Using this tool, we demonstrated that local inhibition of Pol I blocked balloon injury-induced neointima formation in rat carotid arteries in vivo. Neointimal development was associated with augmented rDNA transcriptional activity as evidenced by the increased phosphorylation of upstream binding factor-1. The beneficial effect of CX-5461 was mainly mediated by inducing G2/M cell cycle arrest of proliferating smooth muscle cells without obvious apoptosis. CX-5461 did not induce p53 stabilization but increased p53 phosphorylation and acetylation and activated the ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related (ATR) pathway. Inhibition of ATR, but not of ataxia telangiectasia mutated, abolished the cytostatic effect of CX-5461 and p53 phosphorylation. In addition, inhibition of p53 or knockdown of the p53 target GADD45 mimicked the effect of ATR inhibition. In vivo experiments showed that the levels of phospho-p53 and acetyl-p53, and activity of the ataxia telangiectasia mutated/ATR pathway were all augmented in CX-5461-treated vessels.. Pol I can be therapeutically targeted to inhibit the growth of neointima, supporting that Pol I is a novel biological target for preventing arterial restenosis. Mechanistically, Pol I inhibition elicited G2/M cell cycle arrest in smooth muscle cells via activation of the ATR-p53 axis.

Topics: Acetylation; Animals; Ataxia Telangiectasia Mutated Proteins; Benzothiazoles; Carotid Artery Injuries; Carotid Artery, Common; Cell Line; Cell Proliferation; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; G2 Phase Cell Cycle Checkpoints; Hyperplasia; Male; Mice; Muscle, Smooth, Vascular; Naphthyridines; Neointima; Phosphorylation; Rats, Wistar; RNA Polymerase I; Signal Transduction; Time Factors; Transcription, Genetic; Tumor Suppressor Protein p53