cx-5461 and Disease-Models--Animal

Clinical treatment of psoriasis remains challenging because of possible long-term drug toxicities and loss of therapeutic effects over time. CX-5461 is a novel selective inhibitor of RNA polymerase I. Our previous studies have shown that CX-5461 has potent anti-inflammatory effects. Here we investigated whether CX-5461 could inhibit the development of imiquimod-induced experimental psoriasis in mice. Adult male C57BL/6 mice were used, and psoriasis-like lesions were induced by topical imiquimod treatment. In vivo, we demonstrated that topical application of CX-5461 prevented the development of imiquimod-induced psoriasis, with decreases in keratinocyte proliferation, T-cell infiltration and pathological angiogenesis. CX-5461 also reversed existing skin inflammation induced imiquimod and retarded the development of 12-O-tetradecanoylphorbol-13-acetate-induced epidermal hyperplasia and inflammation. In vitro, CX-5461 induced cell cycle arrest in keratinocytes, inhibited expressions of interleukin-17, interleukin-23 receptor and retinoic acid receptor-related orphan receptor-γt in activated T cells, and reduced angiogenic functions of endothelial cells. In conclusion, CX-5461 exhibits therapeutic effects on experimental psoriasis in mice, likely via multiple mechanisms including anti-proliferative, anti-inflammatory and anti-angiogenic activities.

Topics: Animals; Anti-Inflammatory Agents; Antiviral Agents; Disease Models, Animal; Endothelial Cells; Imiquimod; Inflammation; Keratinocytes; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Psoriasis; RNA Polymerase I; Skin

CX-5461 is a novel selective RNA polymerase I (Pol I) inhibitor. Previously, we found that CX-5461 could inhibit pathological arterial remodelling caused by angioplasty and transplantation. In the present study, we explored the pharmacological effects of CX-5461 on experimental pulmonary arterial hypertension (PAH) and PAH-associated vascular remodelling.. PAH was induced in Sprague-Dawley rats by monocrotaline or Sugen/hypoxia.. We demonstrated that CX-5461 was well tolerated for in vivo treatments. CX-5461 prevented the development of pulmonary arterial remodelling, perivascular inflammation, pulmonary hypertension, and improved survival. More importantly, CX-5461 partly reversed established pulmonary hypertension. In vitro, CX-5461 induced cell cycle arrest in human pulmonary arterial smooth muscle cells. The beneficial effects of CX-5461 in vivo and in vitro were associated with increased activation (phosphorylation) of p53.. Our results suggest that pharmacological inhibition of Pol I may be a novel therapeutic strategy to treat otherwise drug-resistant PAH.

Topics: Animals; Benzothiazoles; Cell Proliferation; Disease Models, Animal; Monocrotaline; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Naphthyridines; Pulmonary Arterial Hypertension; Pulmonary Artery; Rats; Rats, Sprague-Dawley; RNA Polymerase I; Vascular Remodeling

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

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

Dysregulation of MYC is frequently implicated in both early and late myeloma progression events, yet its therapeutic targeting has remained a challenge. Among key MYC downstream targets is ribosomal biogenesis, enabling increases in protein translational capacity necessary to support the growth and self-renewal programmes of malignant cells. We therefore explored the selective targeting of ribosomal biogenesis with the small molecule RNA polymerase (pol) I inhibitor CX-5461 in myeloma. CX-5461 induced significant growth inhibition in wild-type (WT) and mutant TP53 myeloma cell lines and primary samples, in association with increases in downstream markers of apoptosis. Moreover, Pol I inhibition overcame adhesion-mediated drug resistance and resistance to conventional and novel agents. To probe the TP53-independent mechanisms of CX-5461, gene expression profiling was performed on isogenic TP53 WT and knockout cell lines and revealed reduction of MYC downstream targets. Mechanistic studies confirmed that CX-5461 rapidly suppressed both MYC protein and MYC mRNA levels. The latter was associated with an increased binding of the RNA-induced silencing complex (RISC) subunits TARBP2 and AGO2, the ribosomal protein RPL5, and MYC mRNA, resulting in increased MYC transcript degradation. Collectively, these studies provide a rationale for the clinical translation of CX-5461 as a novel therapeutic approach to target MYC in myeloma.

Topics: Animals; Antineoplastic Agents; Benzothiazoles; Cell Line, Tumor; Disease Models, Animal; Drug Resistance, Neoplasm; Gene Expression; Gene Expression Profiling; Humans; Mice; Molecular Targeted Therapy; Multiple Myeloma; Mutation; Naphthyridines; Proto-Oncogene Proteins c-myc; RNA Polymerase I; Tumor Burden; Tumor Suppressor Protein p53; Xenograft Model Antitumor Assays

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

Small cell lung cancer (SCLC) is a devastating neuroendocrine carcinoma. MYCL (L-Myc) is frequently amplified in human SCLC, but its roles in SCLC progression are poorly understood. We isolated preneoplastic neuroendocrine cells from a mouse model of SCLC and found that ectopic expression of L-Myc, c-Myc, or N-Myc conferred tumor-forming capacity. We focused on L-Myc, which promoted pre-rRNA synthesis and transcriptional programs associated with ribosomal biogenesis. Deletion of Mycl in two genetically engineered models of SCLC resulted in strong suppression of SCLC. The high degree of suppression suggested that L-Myc may constitute a therapeutic target for a broad subset of SCLC. We then used an RNA polymerase I inhibitor to target rRNA synthesis in an autochthonous Rb/p53-deleted mouse SCLC model and found significant tumor inhibition. These data reveal that activation of RNA polymerase I by L-Myc and other MYC family proteins provides an axis of vulnerability for this recalcitrant cancer.

Topics: Animals; Animals, Genetically Modified; Benzothiazoles; Disease Models, Animal; Enzyme Activation; Enzyme Inhibitors; Gene Silencing; Lung Neoplasms; Mice; Naphthyridines; Proto-Oncogene Proteins c-myc; Ribosomes; RNA Polymerase I; Small Cell Lung Carcinoma; Tumor Burden; Tumor Cells, Cultured