Characterisation of Ki11502 as a potent inhibitor of PDGF β receptor-mediated proteoglycan synthesis in vascular smooth muscle cells
Diabetes and Cell Biology of Diabetes Laboratory, BakerIDI Heart and Diabetes Institute, Commercial Road, Melbourne, Victoria 3141, Australia.European journal of pharmacology (Impact Factor: 2.53). 10/2009; 626(2-3):186-92. DOI: 10.1016/j.ejphar.2009.09.066
Platelet-derived growth factor (PDGF) receptor signalling is implicated in cardiovascular diseases such as atherosclerosis and restenosis. PDGF expression levels are elevated in atherosclerotic lesions and play a key role in migration and proliferation of vascular smooth muscle cells in the neointima. PDGF stimulates glycosaminoglycan elongation on vascular proteoglycans biglycan and decorin, a process implicated in the aetiology of atherosclerosis. We investigated the ability of the specific kinase inhibitor Ki11502 to inhibit PDGF beta receptor phosphorylation and proteoglycan synthesis in human vascular smooth muscle cells. Ki11502 inhibited PDGF-mediated tyrosine phosphorylation of the PDGF beta receptor autophosphorylation site and at least six other receptor-associated proteins. Ki11502 also caused a concentration-dependent inhibition of PDGF-stimulated [(3)H]-thymidine incorporation. Total proteoglycan synthesis was assessed as incorporation of [(35)S]-sulfate. PDGF-induced a two-fold increase in [(35)S]-sulfate incorporation into proteoglycans secreted over 24h and was inhibited in a concentration-dependent manner by Ki11502. PDGF treatment resulted in a statistically significant (P<0.01) increase in total proteoglycan core protein secretion. Treatment of cells with Ki11502 (300 nM) had no effect on basal core protein secretion and completely abolished the PDGF-stimulated component. Analysis of isolated cleaved glycosaminoglycan chains by size-exclusion chromatography demonstrated that PDGF stimulated the synthesis and secretion of proteoglycans with elongated glycosaminoglycan chains and this effect was inhibited by Ki11502. Inhibition was also seen in the length of xyloside-glycosaminoglycan chains. The results demonstrate that Ki11502 is a potent and selective inhibitor of PDGF beta receptor phosphorylation, proliferation and proteoglycan synthesis in human vascular smooth muscle cells.
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ABSTRACT: The initiation of atherosclerosis involves the subendothelial retention of lipoproteins by proteoglycans (PGs). Structural characteristics of glycosaminoglycan (GAG) chains on PGs influence lipoprotein binding and are altered adversely by platelet-derived growth factor (PDGF). The signaling pathway for PDGF-mediated GAG elongation via the PDGF receptor (PDGFR) was investigated. In human vascular smooth muscle cells, PDGF significantly increased (35)S-sulfate incorporation into PGs and GAG chain size. PGs from PDGF-stimulated cells showed increased binding low-density lipoprotein (P < 0.001) in gel mobility shift assays. Knockdown of PDGFRbeta using small interfering RNA demonstrated that PDGF mediated changes in PGs via PDGFRbeta. GAG synthesis and hyperelongation was blocked by inhibition of receptor tyrosine kinase autophosphorylation site Tyr857 activity using Ki11502 or imatinib. Downstream signaling to GAG hyperelongation was mediated through ERK MAPK and not phosphatidylinositol-3 kinase or phospholipase Cgamma. In high-fat-fed apolipoprotein E(-/-) mice, inhibition of PDGFRbeta activity by imatinib reduced aortic total lipid staining area by 35% (P < 0.05). Inhibition of PDGFRbeta tyrosine kinase activity leads to inhibition of GAG synthesis on vascular PGs and aortic lipid area in vivo. PDGFRbeta and its signaling pathways are potential targets for novel therapeutic agents to prevent the earliest stages atherosclerosis.
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ABSTRACT: The modern concept of the development of atherosclerosis implies that the underlying pathogenesis of this disease is vascular remodeling as a response of the vessel wall to hypertension associated with hyperlipidemia and subsequent inflammation. However, even though this disease has been investigated for decades, both from a basic and clinical research aspect, there are still many doubts as to what the initial phase of the disease is. In contemporary literature there are an increasing number of papers that stress the importance of the extracellular matrix (ECM) of the blood vessels connective tissue, particularly proteoglycans, in the formation of early atherosclerotic lesions of human coronary arteries.
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ABSTRACT: The main goal of this review is to provide more specific and effective targets for prevention and treatment of insulin resistance and associated atherosclerosis. Modern technologies and medicine have vastly improved human health and prolonged the average life span of humans primarily by eliminating various premature deaths and infectious diseases. The modern technologies have also provided us abundant food and convenient transportation tools such as cars. As a result, more people are becoming overfed and sedentary. People are generally ingesting more calories than their bodies' need, leading to the so-called "positive energy imbalance", which is inseparable from the development of insulin resistance and its associated atherosclerosis. A direct consequence of insulin resistance is hyperinsulinemia. The current general view is that insulin is not functional properly in the presence of insulin resistance. Thus, the role of insulin itself in the development of insulin resistance and associated atherosclerosis has not been recognized. We have recently observed that the basal level of insulin signaling is increased in the presence of insulin resistance and hyperinsulinemia. In this review, we will explain how the increased basal insulin signaling contributes to the development of insulin resistance and associated atherosclerosis. We will first explain how insulin causes insulin resistance through two arbitrary stages (before and after the presence of obvious insulin resistance), and, then, explain how the excess exposure to insulin and the relative insulin insufficiency contributes to the atherosclerotic diseases. We propose that blockade of the excess insulin signaling is a viable approach to prevent and/or reverse insulin resistance and its associated atherosclerosis.
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