Smad and p38 MAP kinase-mediated signaling of proteoglycan synthesis in vascular smooth muscle

Atherosclerosis is the underlying pathological process of most cardiovascular disease. A critical component of the "response to retention" hypothesis of atherogenesis is proteoglycan/low density lipoprotein (LDL) binding. Transforming growth factor β (TGF-β) is present in atherosclerotic lesions, regulates vascular smooth muscle cell (VSMC) proteoglycan synthesis via an unknown signaling pathway, and increases proteoglycan/LDL binding. This pathway was investigated using the activin receptor-like kinase 5 (ALK5) inhibitor SB431542 and inhibitors of p38 MAP kinase as a possible downstream or alternative mediator. TGF-β stimulated and SB431542 inhibited the phosphorylation of Smad2/3. In human VSMC, TGF-β increased [ 35S]sulfate incorporation into proteoglycans associated with a 19% increase in glycosaminoglycan (GAG) chain size by size exclusion chromatography. SB431542 caused a concentration-dependent decrease in TGF-β-mediated [ 35S]sulfate incorporation with 92% inhibition at 3 μM. Two different p38 MAP kinase inhibitors, SB203580 and SB202190, but not the inactive analogue SB202474, concentration dependently blocked TGF-β-mediated [ 35S]sulfate incorporation. TGF-β increased [ 3H]glucosamine incorporation into glycosaminoglycans by 180% and [ 35S]Met/Cys incorporation into proteoglycan core proteins by 35% with both effects completely inhibited by SB431542. Blocking both Smad2/3 and p38 MAP kinase pathways prevented the effect of TGF-β to increase proteoglycan to LDL binding. TGF-β mediates its effects on proteoglycan synthesis in VSMCs via the ALK5/Smad2/3 phosphorylation pathway as well as via the p38 MAP kinase signaling cascade. Further studies of downstream pathways controlling proteoglycan synthesis may identify potential therapeutic targets for the prevention of atherosclerosis and cardiovascular disease

Thrombin-mediated proteoglycan synthesis utilizes both protein-tyrosine kinase and serine/threonine kinase receptor transactivation in vascular smooth muscle cells

Background: GPCR transactivation of PTKRs and TGF-αRs mediates proteoglycan synthesis in human VSMC. Results: Transactivation of TGF-αRs is integrin-dependent, and inhibition of both transactivation pathways blocks proteoglycan synthesis. Conclusion: GPCR utilize transactivation pathways and not classical signaling in proteoglycan synthesis. Significance: GPCR transactivation of receptor kinase pathways may be broader and more significant than previously recognized

Biosynthesis of Natural and Hyperelongated Chondroitin Sulfate Glycosaminoglycans: New Insights into an Elusive Process

Proteoglycans are important components of the extracellular matrix of all tissues. Proteoglycans are comprised of a core protein and one or more covalently attached glycosaminoglycan (GAG) chains. The major chondroitin sulfate (CS) and dermatan sulfate (DS) proteoglycans are aggrecan, versican, biglycan and decorin. Cells synthesize GAGs of natural or basal lengths and the GAG chains are subject to considerable growth factor, hormonal and metabolic regulation to yield longer GAG chains with altered structure and function. The mechanism by which the CS/DS GAG chains are polymerized is unknown. Recent work has identified several monosaccharide transferases which when co-expressed yield GAG polymers and the length of the polymers depends upon the pair of enzymes coexpressed. The further extension of these chains is regulated by signaling pathways. Inhibition of these latter pathways may be a therapeutic target to prevent the elongation which is associated with increased binding of atherogenic lipids and the disease process of atherosclerosis

Anti-proliferative activity of oral anti-hyperglycemic agents on human vascular smooth muscle cells: thiazolidinediones (glitazones) have enhanced activity under high glucose conditions

Background: Inhibition of vascular smooth muscle cell (vSMC) proliferation by oral anti-hyperglycemic agents may have a role to play in the amelioration of vascular disease in diabetes. Thiazolidinediones (TZDs) inhibit vSMC proliferation but it has been reported that they anomalously stimulate [3H]-thymidine incorporation. We investigated three TZDs, two biguanides and two sulfonylureas for their ability of inhibit vSMC proliferation. People with diabetes obviously have fluctuating blood glucose levels thus we determined the effect of media glucose concentration on the inhibitory activity of TZDs in a vSMC preparation that grew considerably more rapidly under high glucose conditions. We further explored the mechanisms by which TZDs increase [3H]-thymidine incorporation. Methods: VSMC proliferation was investigated by [3H]- thymidine incorporation into DNA and cell counting. Activation and inhibition of thymidine kinase utilized short term [3H]- thymidine uptake. Cell cycle events were analyzed by FACS

Signalling pathways regulating galactosaminoglycan synthesis and structure in vascular smooth muscle: implications for lipoprotein binding and atherosclerosis

Atherosclerosis commences with the trapping of low density lipoproteins (LDLs) in blood vessels by modified proteoglycans (PGs) with hyperelongated glycosaminoglycan (GAG) chains. GAG chain synthesis and growth factor mediated hyperelongation regulates the composition and size of PGs in a manner that would cause low density lipoprotein (LDLs) retention in vessel wall. Galactosaminoglycans are a class of GAGs, commonly observed on PGs. Multiple enzymes are involved in galactosaminoglycan biosynthesis. Galactosaminoglycan synthesis is regulated by various signalling pathways which are amenable to pharmacological manipulation to treat atherosclerosis. Receptor mediated signalling pathways including protein tyrosine kinase receptors (PTKRs), serine/threonine kinase receptors (S/TKRs) and G-protein coupled receptors (GPCRs) pathways regulate galactosaminoglycan synthesizing enzyme expression. Increased expression of these enzymes modify galactosaminoglycan chain structure by making them hyperelongated. This review focuses on the signalling pathways regulating the expression of genes involved in galactosaminoglycan synthesis and modification. Furthemore, there are multiple other processes for inhibiting the interactions between LDL and galactosaminoglycans such as peptide mimetics of ApoB100 and anti-galactosaminoglycan antibodies and the therapeutic potential of these strategies is also addressed

Potgrondproef met 12-10-18 bij tomaat

<p><b>Copyright information:</b></p><p>Taken from "Anti-proliferative activity of oral anti-hyperglycemic agents on human vascular smooth muscle cells: thiazolidinediones (glitazones) have enhanced activity under high glucose conditions"</p><p>http://www.cardiab.com/content/6/1/33</p><p>Cardiovascular Diabetology 2007;6():33-33.</p><p>Published online 28 Oct 2007</p><p>PMCID:PMC2211460.</p><p></p>e mean ± SEM, *P < 0.05 PDGF. B. Human vSMCs were treated with metformin (10–300 μM) and phenformin (10–300 μM) in the presence of 5% serum for 3 days and then counted on a Coulter counter. Data represent the mean ± SEM from 2 experiments in triplicate **P < 0.01, ***P < 0.001 the 5% FBS

Endothelin-1 actions on vascular smooth muscle cell functions as a target for the prevention of atherosclerosis

The formation and progression of atherosclerotic plaques followed by rupture, thrombus formation and vessel blockage leads to ischemic tissue damage and the clinical condition underlying most cardiovascular disease. Therapeutic agents for the prevention of atherosclerosis have all targeted epidemiologically-identified and relatively easily measured risk factors (e.g. lipids and blood pressure). This strategy has proven somewhat effective but is of less than optimal efficacy as rates of cardiovascular disease remain high. Treatment targeting the mechanisms of atherosclerosis in the vessel wall is a conceptually attractive proposition to complement the risk factor directed strategy. Vascular smooth muscle cells (VSMC) are the major cellular component of the vascular media and migration and proliferation leads to the formation of the neointima the development of which renders the vessels particularly sensitive to atherosclerosis. Numerous hormones and growth factors act on VSMC to cause migration, proliferation and the secretion of extracellular matrix and modulation or dysfunction of these processes is the most likely cause of atherosclerosis. Endothelin-1 (ET-1) is a 21 amino acid peptide that acts on 7 transmembrane G protein coupled receptors to elicit a plethora of responses that can modulate the behaviour of VSMCs and thus impact on the development of atherosclerosis. ET-1 is elevated in atherosclerotic plaques. People with diabetes have accelerated atherosclerosis and also show elevated plasma levels of ET-1. This review addresses the actions of ET-1 on VSMC and the signalling pathways through which it mediates its effects as the latter represent potential therapeutic targets for the prevention of atherosclerosis