Project description:Pulmonary hypertension (PH) and cancer pathophysiology share common signal transduction pathways leading to abnormal endothelial and smooth muscle cell interactions and angioproliferative vasculopathy. Sorafenib (Sor) a drug in clinical trials for cancer treatment, is an inhibitor of multiple kinases important in angiogenesis (Raf-1 kinase, VEGFR-2, VEGFR-3, PDGFR-ï¢)ï©. In this study, we assessed the efficacy of Sor as a potential therapy for PH, and hypothesized that Sor prevents the development of both a conventional and an augmented rodent model of PH. We performed studies in Dahl Salt-Sensitive rats (SS) exposed to hypoxia alone and in combination with the VEGFR-2 inhibitor, SU5416, known to induce a well-characterized augmented PH phenotype. Rats were, thus, divided into 5 groups: normoxia/vehicle (Norm), hypoxia/vehicle (H), hypoxia/ SU5416 (H-SU), hypoxia/Sorafenib (H-Sor) and hypoxia/ SU5416/ Sorafenib (H-SU-Sor). Except for the Norm group, all rats were maintained in a hypoxia chamber with a FiO2 of 10%. Rats received a single injection of SU5416 on Day 1 (20 mg/kg) and Sor solution was administered daily by gavage (2.5mg/kg). After 3.5 weeks, all rats were assessed by open chest catheterizations for pulmonary vascular and right ventricular pressures. Lung and heart tissue were harvested for histological and microarray analyses. Our results showed H-SU rats developed severe PH with changes in hemodynamic and histologic parameters when compared to Norm controls while rats exposed to H alone only displayed mildly elevated pressures compared with Norm. There was no significant change in pressures in the H-Sor or H-SU-Sor compared to Norm. Histopathology demonstrated a dramatic prevention of the PH phenotype in the H-SU-Sor rats with no significant remodeling compared with H-SU rats. Expression profiling data from H (n=4) and H-SU (n=3) rat lungs were compared to Norm (n=4) using normalization in R and SAM (Î´>.639,) (minimum fold change >1.4). With false discovery rates (FDR) of 6.5% in hypoxia and 1.6% in H-SU, 1019 and 465 genes, respectively, were differentially-regulated compared to Norm. In addition, 38 genes were differentially expressed between H-SU and H-SU-Sor (n=4, FDR 6.7%) revealing a molecular signature with potentially novel target genes of Sor. Five differentially expressed genes (Tgfï¢3, C1qg, Nexn, Frzb, and Plaur) were examined by real-time RT-PCR and three were further validated by immunohistochemistry confirming the regulation on protein level. Based on the known pathways of hypoxic-induced PH and Sor, we further utilized immunohistochemistry to show the up-regulation of mediators of the MAPK cascade in the H and H-SU models of PH with subsequent, down-regulation by Sor. We therefore present Sor as a novel treatment for the development of severe PH and theorize that the MAPK cascade is a canonical pathway involved both in the development of PH and in the attenuation by Sor. This SuperSeries is composed of the following subset Series:; GSE8078: A Multi- Kinase Inhibitor Modulates Pulmonary Hypertension in a Rodent Model 1; GSE8132: A Multi- Kinase Inhibitor Modulates Pulmonary Hypertension in a Rodent Model 2 Experiment Overall Design: Refer to individual Series

Project description:Oxidants induce cell cycle arrest to halt cell proliferation; however, little is known about the redox-regulated effector proteins that mediate these processes. Here, we report a novel kinase-inhibitory disulfide bond in cyclin D-CDK4 and investigate its role in cell proliferation and PH. Oxidative modifications of cyclin D-CDK4 were detected in human pulmonary arterial smooth muscle cells (HPASMCs) and human pulmonary arterial endothelial cells (HPAECs). Cysteine to alanine mutants were generated, and cell cycle experiments were employed to characterize the nature of this reversible intermolecular disulfide bond. The functional role of the disulfide was delineated using in vitro kinase activity assays, HPASMCs and knock-in cells. Finally, the cyclin D-CDK4 disulfide was assessed in vivo in the pulmonary arteries and isolated HPASMCs of PAH patients, and in three preclinical models of PH. Cyclin D-CDK4 forms an oxidant-induced heterodimeric disulfide dimer between C7/8 and C135, respectively. This reversible modification forms in cells in vitro and in pulmonary arteries in vivo to inhibit cyclin D-CDK4 kinase activity and decrease retinoblastoma protein (Rb) phosphorylation. Correspondingly, treatment of HPASMCs with H2O2 or auranofin induces cell cycle arrest. Notably, mutation of CDK4 C135 causes a kinase-impaired phenotype, which decreases the proliferation rate of cells, suggesting this cysteine is indispensable for cyclin D-CDK4 kinase activity. Pulmonary arteries and HPASMCs from patients with pulmonary arterial hypertension (PAH) display a decreased level of CDK4 disulfide, consistent with CDK4 being hyperactive in PAH. Furthermore, auranofin treatment, which induces the cyclin D-CDK4 disulfide, attenuates disease severity in experimental models of PH, by mitigating pulmonary vascular remodeling. A novel disulfide bond in cyclin D-CDK4 acts as a rapid switch to inhibit kinase activity and halt cell proliferation. This oxidative modification forms at a critical cysteine residue, which is unique to CDK4, offering the potential for design of a selective covalent inhibitor that may prove beneficial in pulmonary hypertension

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