No abstract

Background-Clinical studies have demonstrated that 50% of individuals with chronic renal disease (CRD) die of cardiovascular causes, including advanced calcific arterial and valvular disease; however, the mechanisms of accelerated calcification in CRD remain obscure, and no therapies can prevent disease progression. We recently demonstrated in vivo that inflammation triggers cardiovascular calcification. In vitro evidence also indicates that elastin degradation products may promote osteogenesis. Here, we used genetically modified mice and molecular imaging to test the hypothesis in vivo that cathepsin S (catS), a potent elastolytic proteinase, accelerates calcification in atherosclerotic mice with CRD induced by 5/6 nephrectomy. Methods and Results-Apolipoprotein-deficient (apoE Ϫ/Ϫ )/catS ϩ/ϩ (nϭ24) and apoE Ϫ/Ϫ /catS Ϫ/Ϫ (nϭ24) mice were assigned to CRD and control groups. CRD mice had significantly higher serum phosphate, creatinine, and cystatin C levels than those without CRD. To visualize catS activity and osteogenesis in vivo, we coadministered catS-activatable and calcification-targeted molecular imaging agents 10 weeks after nephrectomy. Imaging coregistered increased catS and osteogenic activities in the CRD apoE Ϫ/Ϫ /catS ϩ/ϩ cohort, whereas CRD apoE Ϫ/Ϫ /catS Ϫ/Ϫ mice exhibited less calcification. Quantitative histology demonstrated greater catS-associated elastin fragmentation and calcification in CRD apoE Ϫ/Ϫ /catS ϩ/ϩ than CRD apoE Ϫ/Ϫ /catS Ϫ/Ϫ aortas and aortic valves. Notably, catS deletion did not cause compensatory increases in RNA levels of other elastolytic cathepsins or matrix metalloproteinases. Elastin peptide and recombinant catS significantly increased calcification in smooth muscle cells in vitro, a process further amplified in phosphate-enriched culture medium. Key Words: calcification Ⅲ aortic valve Ⅲ atherosclerosis Ⅲ kidney failure, chronic Ⅲ elastin W esternized societies face a growing burden of cardiovascular calcification, a disease of disordered mineral metabolism. [1][2][3][4] The interaction of prevalent epidemiological factors such as age, hypercholesterolemia, and renal insufficiency accelerates arterial and aortic valve calcification. 5 Clinical studies have demonstrated that approximately 50% of individuals with chronic renal disease (CRD) die of a cardiovascular cause. 6 -8 In addition to the classic risk factors such as age and dyslipidemia, patients with CRD have hyperphosphatemia, which is considered an independent risk factor for cardiovascular death. 9,10 CRD accelerates the development of atherosclerosis and excessive calcification in both the intima and media of atheromatous lesions. 11,12 Although they have different causes, intimal and medial calcification both involve the activation of proinflammatory mechanisms and smooth muscle cell (SMC) proliferation, which likely share common calcification pathways. Conclusions-The Clinical Perspective p 1794Recent studies suggest that arterial and valvular calcification occurs through highly regulated molecular proce...

We find that calcium influx through voltage-dependent calcium channels causes extensive neurite outgrowth in PC12 cells. The calcium signal transduction pathway promoting neurite outgrowth causes the rapid activation of protein tyrosine kinases, which include Src. Protein tyrosine phosphorylation results in the formation of an Shc/Grb2 complex, leading to Ras activation, MAP kinase activation, and the subsequent induction of the immediate early gene NGFI-A. Protein tyrosine phosphorylation, gene induction, and neurite outgrowth are inhibited by the expression of dominant negative forms of both Src and Ras, indicating a requirement for both proto-oncoproteins in calcium signaling. Our results suggest that a signaling cassette which includes Src and Ras is likely to underlie a broad range of calcium of actions in the nervous system.