Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.2.2.7 (heparinase)
1,270 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Arterial wall lipid retention is believed to be due primarily to ionic interactions between lipoproteins and proteoglycans. Thus, oxidized low density lipoproteins (LDL), with decreased positive charge relative to native LDL, should have decreased interaction with negatively charged proteoglycans. However, oxidized LDL does accumulate within arterial lesions. Therefore, this study investigated the binding of native and oxidized LDL to a complex smooth muscle extracellular matrix and the role of ionic charge interactions in their binding. LDL was modified with 2,2-azo-bis(2-amidinopropane)-2HCl, hypochlorite, soybean lipoxygenase, and phospholipase or copper sulfate. The extracellular matrix had 15- to 45-fold greater binding capacity for the different forms of oxidized LDL than for native LDL. However, the affinity of binding for all forms of oxidized LDL was high (K(a) = approximately 10(-9) M) and was similar to that for native LDL. Preincubation of the lipoproteins with chondroitin sulfate decreased the binding of native LDL, but had no effect on the binding of oxidized LDL. Digestion of matrices with chondroitin ABC lyase and heparinase decreased the binding of native LDL, but increased the binding of oxidized LDL; matrix digestion with pronase or trypsin markedly reduced the binding of both native and oxidized LDL.Thus, the binding of native LDL involves matrix proteoglycans, whereas the binding of oxidized LDL involves a nonproteoglycan component(s) of the matrix. The markedly enhanced retention of oxidized LDL compared with native LDL may play an important role in the progression of atherosclerosis.
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PMID:Oxidized LDL bind to nonproteoglycan components of smooth muscle extracellular matrices. 1135 90

Cysteine-rich 61 (Cyr61, CCN1) and connective tissue growth factor (CTGF, CCN2) are growth factor-inducible immediate-early gene products found in blood vessel walls and healing cutaneous wounds. We previously reported that the adhesion of endothelial cells, platelets, and fibroblasts to these extracellular matrix-associated proteins is mediated through integrin receptors. In this study, we demonstrated that both Cyr61 and CTGF are expressed in advanced atherosclerotic lesions of apolipoprotein E-deficient mice. Because monocyte adhesion and transmigration are important for atherosclerosis, wound healing, and inflammation, we examined the interaction of THP-1 monocytic cells and isolated peripheral blood monocytes with Cyr61 and CTGF. THP-1 cells and monocytes adhered to Cyr61- or CTGF-coated wells in an activation-dependent manner and this process was mediated primarily through integrin alpha(M)beta(2). Additionally, expression of alpha(M)beta(2) on human embryonic kidney 293 cells resulted in enhanced cell adhesion to Cyr61. Consistent with these data, a GST-fusion protein containing the I domain of the integrin alpha(M) subunit bound specifically to immobilized Cyr61 or CTGF. We have also investigated the requirement of cell surface heparan sulfate proteoglycans (HSPGs) as coreceptors for monocyte adhesion to Cyr61. Pretreatment of monocytes with heparin or heparinase I resulted in partial inhibition of cell adhesion to Cyr61. However, monocytes, but not fibroblasts, were capable of adhering to a Cyr61 mutant deficient in heparin binding activity. Collectively, these results show that activated monocytes adhere to Cyr61 and CTGF through integrin alpha(M)beta(2) and cell surface HSPGs. However, unlike fibroblast adhesion to Cyr61, cell surface HSPGs are not absolutely required for this adhesion process.
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PMID:Identification of integrin alpha(M)beta(2) as an adhesion receptor on peripheral blood monocytes for Cyr61 (CCN1) and connective tissue growth factor (CCN2): immediate-early gene products expressed in atherosclerotic lesions. 1203 76

Lipoprotein lipase (LPL) is central to triacylglycerol (TG) metabolism, having both hydrolytic and bridging functions. The common LPL gene variant D9N is associated with raised TG, reduced HDL-cholesterol concentrations and increased risk of coronary artery disease (CAD). To investigate the functional basis for the phenotype in N9 carriers, CHO K1 cells were stably transfected with wild type (D9) or mutant (N9) LPL cDNA. LPL RNA expression levels, monomer-to-dimer ratios, and dimer specific activities were similar in D9 and N9 cells. Significantly enhanced binding (4.6-fold) and internalisation (2.6-fold) of 125I-LDL by N9 compared with D9 cells was eradicated by pre-treatment with either heparin or heparinase, confirming involvement of LPL and cell surface proteoglycans. N9 cells bound and internalised 3.8- and 4.4-fold more oxidised 125I-LDL, respectively, than D9 cells (both P<0.0001). Binding of monocytes was 7-fold greater to plates coated with purified LPL-N9 dimer compared with LPL-D9 (P<=0.005). Thus once on the cell surface, LPL-N9 enhances bridging, as assessed both by LDL binding and internalisation, and monocyte adhesion. This augmented LPL-N9 bridging provides a mechanism for the reported increased CAD risk in N9 carriers.
Atherosclerosis 2003 Feb
PMID:Enhanced bridging function and augmented monocyte adhesion by lipoprotein lipase N9: insights into increased risk of coronary artery disease in N9 carriers. 1253 36

Smooth muscle cells (SMC) of the rat carotid arterial media proliferate and migrate in response to injury during the formation of a neointima. The interaction of fibroblast growth factor (FGF-2), which is released at the site of injury, with heparan sulfate proteoglycans (HSPGs) is necessary to induce signaling, which elicits an FGF-dependent mitogenic response by arterial smooth muscle cells, and also serves as a mechanism for storage of the growth factor within the extracellular matrix. However, whether these interactions are critical during neointimal formation has not been directly tested. In this study, a model of FGF-2-dependent medial SMC mitogenic response in balloon-injured rat carotid artery was used to test the effect of degradation of vessel wall heparan sulfate on subsequent SMC proliferation. Treatment of balloon-catheterized rat carotid arteries with chondroitin ABC lyase and/or heparin lyases eliminated heparan sulfates in the vessel wall, as determined by immunoperoxidase staining. In contrast, the distribution in the carotid vessel wall of the large core protein of perlecan, a major vessel wall HSPG that binds FGF-2, is not decreased. The effect of glycosaminoglycan digestion in situ on medial SMC proliferation in response to a bolus injection of FGF-2 after injury was determined by measuring the percentage of SMC nuclei that incorporated 5-bromo-2'-deoxyuridine (BrdU) 48 h after injury. Enzymatic removal of heparan sulfate reduced BrdU incorporation into medial SMC by 60-70% (P < 0.001) at 48 h after injury. Moreover, pre-incubation of FGF-2 with heparin prior to injection restored SMC replication to the levels present in injured vessels treated with buffer alone (P < 0.01). These experiments indicate that endogenous HSPGs are essential to promote FGF-2-driven medial SMC proliferation following injury, and that heparinase treatment can abrogate FGF-2-dependent responses in vivo.
Atherosclerosis 2004 Jul
PMID:Removal of heparan sulfate by heparinase treatment inhibits FGF-2-dependent smooth muscle cell proliferation in injured rat carotid arteries. 1518 46

Lipoprotein lipase (LPL) is a key enzyme in the hydrolysis of triglyceride-rich lipoproteins. In vascular diseases, such as atherosclerosis, inflammation plays an important role in the pathogenesis of the disease. We examined the role of LPL in modulating tumor necrosis factor-alpha (TNF-alpha)- and interferon-gamma (IFN-gamma)-mediated inflammatory cytokine signal transduction pathways in human aortic endothelial cells (HAECs). LPL significantly suppressed TNF-alpha-induced gene expression, and this suppression was reversed by tetrahydrolipstatin and heparinase. In contrast, LPL synergistically enhanced IFN-gamma-induced gene expression in HAECs. To elucidate the molecular mechanisms of LPL action, we investigated the role of transcription factors nuclear factor kappa B (NF-kappaB) and signal transducer and activator of transcription factor 1 (Stat1). The anti-inflammatory response of LPL in suppressing TNF-alpha-induced gene expression was a result of its inhibition of NF-kappaB activity by the abrogation of IkappaB-alpha degradation and phosphorylation of the p65 subunit. Although LPL alone had no effect on Stat1 activation, LPL enhanced IFN-gamma-induced phosphorylation of Stat1 on tyrosine 701 and serine 727, as well as Stat1-mediated transactivation. The synergistic effect of LPL on IFN-gamma-induced Stat1 activation was mediated by enhanced activation of the tyrosine kinase JAK2 and was abrogated by LY294002, a specific inhibitor of the phosphatidylinositol 3'-kinase pathway. Our studies indicate that LPL has differential effects on several inflammatory pathways known to be important in atherosclerosis.
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PMID:Differential effects of lipoprotein lipase on tumor necrosis factor-alpha and interferon-gamma-mediated gene expression in human endothelial cells. 1599 21

Flow-induced mechanotransduction in vascular endothelial cells has been studied over the years with a major focus on putative connections between disturbed flow and atherosclerosis. Recent studies have brought in a new perspective that the glycocalyx, a structure decorating the luminal surface of vascular endothelium, may play an important role in the mechanotransduction. This study reports that modifying the amount of the glycocalyx affects both short-term and long-term shear responses significantly. It is well established that after 24 h of laminar flow, endothelial cells align in the direction of flow and their proliferation is suppressed. We report here that by removing the glycocalyx by using the specific enzyme heparinase III, endothelial cells no longer align under flow after 24 h and they proliferate as if there were no flow present. In addition, confluent endothelial cells respond rapidly to flow by decreasing their migration speed by 40% and increasing the amount of vascular endothelial cadherin in the cell-cell junctions. These responses are not observed in the cells treated with heparinase III. Heparan sulfate proteoglycans (a major component of the glycocalyx) redistribute after 24 h of flow application from a uniform surface profile to a distinct peripheral pattern with most molecules detected above cell-cell junctions. We conclude that the presence of the glycocalyx is necessary for the endothelial cells to respond to fluid shear, and the glycocalyx itself is modulated by the flow. The redistribution of the glycocalyx also appears to serve as a cell-adaptive mechanism by reducing the shear gradients that the cell surface experiences.
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PMID:Glycocalyx modulates the motility and proliferative response of vascular endothelium to fluid shear stress. 1746 37

The extracellular pH is locally decreased in advanced atherosclerotic lesions, particularly in lipid-rich areas of the lesions. Since accumulation of LDL-derived cholesterol and formation of foam cells are key processes in atherogenesis, we tested here the effects of acidic pH on the uptake of native LDL. First, human monocytes were differentiated into macrophages in the presence of granulocyte-monocyte-colony stimulating factor (GM-CSF) after which native LDL was applied to the monocyte-derived macrophages at pH 5.5, 6.5, or 7.5 and the binding and uptake of LDL by macrophages were determined. The lower the pH was, the higher was the binding and uptake of LDL by macrophages. Also, acidic pH was found to increase the production of cell surface proteoglycans by macrophages and binding of LDL to the glycosaminoglycan chains of the proteoglycans. The acidity-induced increase in the uptake of LDL by macrophages could be inhibited by pretreating the cells with heparinase and chondroitinase as well as by inhibiting the production of proteoglycans with NaClO(3). Thus, the observed increase in the uptake of native LDL to macrophages appears to depend on the increased ability of LDL to bind to cell surface proteoglycans at acidic pH. Taken together, our present results indicate that acidity increases the effective concentration of LDL on macrophage surfaces by increasing the amount of cell surface proteoglycans and by enhancing the binding of LDL to them and so promotes LDL uptake with ensuing foam cell formation.
Atherosclerosis 2011 Aug
PMID:Acidity increases the uptake of native LDL by human monocyte-derived macrophages. 2157 Dec 77


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