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From the School of Biological Sciences (D.G., J.L., X.C., S.Y.C., S.Z., Y.-K.C., S.G.-J., A.R.J.P., G.J.S.C.), Faculty of Science, and the Maurice Wilkins Centre for Molecular Biodiscovery (S.Z., G.J.S.C.), University of Auckland, Auckland, New Zealand; and the Department of Medicine, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (G.D.G., G.J.S.C.)
Received July 9, 2006; accepted September 14, 2006
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Abstract |
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1, Smad4, extracellular matrix (ECM) proteins, extracellular superoxide dismutase (EC-SOD), and heparan sulfate (HS). Eight-weeks of TETA treatment significantly improved cardiac diastolic function but not [glucose]plasma in diabetic animals. LV and aortic mRNAs corresponding to TGF-1, Smad4, collagen types I, III, and IV, and fibronectin-1, and plasminogen activator inhibitor-1, were elevated in untreated diabetic animals and normalized after TETA treatment. EC-SOD mRNA and protein, and [HS]tissue were significantly decreased in diabetes and restored by drug treatment. Candidate molecular mechanisms by which TETA could ameliorate diabetic cardiac and arteriovascular disease include the suppression of an activated TGF-/Smad signaling pathway that mediates increased ECM gene expression and restoration of normal EC-SOD and HS regulation. These findings are relevant to the restoration toward normal by TETA treatment of cardiac and arterial structure and function in diabetes.
). We recently demonstrated that the amount of CuII that can be extracted from the heart via coronary artery perfusion with triethylenetetramine (TETA) is substantively increased in diabetic rats (Cooper et al., 2004). TETA treatment stimulated urinary CuII excretion in streptozotocin (STZ)-diabetic rats and patients with type-2 diabetes to a greater extent than in matched controls and restored cardiac structure and function toward normal in both groups (Cooper et al., 2004, 2005). Specific underpinning mechanisms relating to CuII chelation in diseased diabetic cardiac and arterial tissues, however, remain to be elucidated.
Free Cu2+ is strongly pro-oxidant in mammalian tissues (Fraústo da Silva and Williams, 2001) and may activate pathways that cause the excessive generation of reactive oxygen species (ROS) such as superoxide (
) in diabetic cardiovascular tissues. There is an increased production in the heart and arteries of both animals and humans with diabetes or heart failure. Extracellular superoxide dismutase (EC-SOD/SOD3) is a major antioxidant in mammalian tissues. It is highly expressed and active in blood vessels (Marklund, 1984a), and protection of nitric oxide (NO) is believed to be a major function of EC-SOD (Oury et al., 1996). EC-SOD activity is decreased in the arteries of patients with diabetes (Fattman et al., 2003), resulting in increased susceptibility of vascular cells to effects of with consequent endothelial dysfunction.
We recently showed that elevation of circulating EC-SOD in type-2 diabetic humans was strongly correlated with an interaction between hemoglobin A1c and [Cu]plasma (Cooper et al., 2005). Furthermore, Cu2+ at high concentrations suppressed EC-SOD secretion from cultured vascular smooth muscle cells (Stralin et al., 2003). The extracellular content of EC-SOD in blood vessels is associated with the level of heparan sulfate (HS), a major binding anchor for EC-SOD (Sandstrom et al., 1993). Diabetic status can decrease arterial HS levels (Edwards et al., 2004) and compromise its function by modifying its structure (Vogl-Willis and Edwards, 2004).
Excessive accumulation of extracellular matrix (ECM) proteins and associated myocardial fibrosis are implicated as pathogenic mechanisms in diabetic heart disease (Marklund, 1992). We reported previously that long-term TETA treatment can regenerate the ECM in diabetic rat hearts (Cooper et al., 2004). TGF-1 stimulates ECM protein accumulation in diabetic tissues by up-regulating the expression of corresponding genes or down-regulating those for ECM-degrading enzymes (Roberts et al., 1992). There is evidence for a link between redox stress, TGF-1, and ECM production (Williams, 1998).
The current study investigated molecular mechanisms by which TETA reverses diabetic heart disease in an STZ model. We show here that oral TETA administration significantly improved diastolic function in diabetic rat hearts. We also show that treatment with TETA suppressed the diabetesevoked up-regulation of TGF-1/Smad4, collagens I, III, and IV, fibronectin-1, and plasminogen activator inhibitor (PAI)-1 in the LV and aorta of diabetic rats and that it elevated EC-SOD mRNA and protein expression in these tissues. TETA administration was further shown to restore diabetes-induced decreases of HS levels in both heart and aorta. These results support the idea that TETA reverses diabetic cardiac disease at least in part through enhanced disposal of extracellular and suppression of increases in ECM gene expression that may result from up-regulation of the TGF-/Smad signaling pathway.
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Materials and Methods |
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). Age-matched control rats were injected with equal volumes of saline (untreated nondiabetic control). Body weights and [glucose-]blood were monitored weekly for 16 weeks. After 8 weeks, diabetic rats were assigned to one of two groups: untreated diabetic; and TETA-treated diabetic. TETA (20 mg/day-rat) was administered in the drinking water (18 M
, Milli Q; Millipore Corporation, Billerica, MA) as triethylenetetramine dihydrochloride (trientine; Fluka, Buchs, Switzerland) or the equivalent molar dose of TETA disuccinate (Protemix, Auckland, New Zealand) for a further 8 weeks. In the HS study, the TETA was administered in the same manner to diabetic and control rats at a dose of 10 mg/day-rat. Rats were housed [12-h light/dark cycle; temperature, 22.5°C (range, 20-26°C); humidity, 60% (range, 50-70%)] in like pairs with ad libitum food (Teklad 2018; Harlan Teklad, Madison, WI) and water. Sixteen weeks after STZ injection, rats were anesthetized (halothane, 5%), appropriately heparinized (200 IU/kg i.v.), and organs were excised. Aortas and cardiac LV were either perfused or washed free of blood in ice-cold diethyl pyrocarbonate-treated phosphate-buffered saline. Tissues were stored in RNAlater (Ambion, Austin, TX) overnight at 4°C and then at -80°C for subsequent RNA isolation. Portions were also stored at -80°C for parallel protein analyses and from additional like-treated rats for HS analysis.
Measurement of Cardiac Function in Rats. Cardiac function was determined as previously detailed in isolated perfused working rat hearts (Cooper et al., 2004).
RNA Isolation and cDNA Synthesis. Total RNA was isolated from LV or aortic tissue using RNeasy Midi Kits (QIAGEN, Valencia, CA). One microgram of total RNA was treated with RQ1 RNase-free DNase (Promega, Madison, WI) at 37°C for 30 min and then reversetranscribed with random hexamers and SuperScript III Reverse Transcriptase (Invitrogen, Carlsbad, CA).
Real-Time Quantitative PCR Analysis. Messenger RNA levels were compared by real-time quantitative PCR with an ABI Prism 7900 HT Sequence Detection System (Applied Biosystems, Foster City, CA). Reactions were prepared in the presence of the fluorescent dye SYBR green I. The levels of gene expression of the target sequence were normalized to those of an active endogenous control, 18S ribosomal RNA (18S; Ambion) in the same cDNA sample. Table 1 displays a list of primers synthesized by Invitrogen for each gene analyzed. The primers and TaqMan probe used for type I collagen were proprietary to Applied Biosystems and so are not listed in Table 1. In PCR reactions, 1.5 and 0.25 ng of cDNA and 0.5 and 0.1 µM concentrations of primers were used for amplification of target genes and 18S rRNA, respectively. After PCR amplification, dissociation curves were constructed, and PCR products were subjected to agarose gel electrophoresis to confirm the formation of the specific PCR products. The threshold cycle at which the fluorescent signal reaches a particular value was used as a measure of gene expression. The linear range of dilution for target genes and 18S rRNA showed different slopes, indicating different amplification efficiency for control and target genes, and a standard curve method was therefore used. Analysis of mRNA expression was performed as described in User Bulletin #2 (Applied Biosystems) using standard curves prepared from serially diluted control cDNA samples.
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Western Blot Analysis. Frozen aorta was homogenized in icecold lysis buffer [50 mM Tris-HCl, pH 7.6, 150 mM NaCl, 10 mM MgCl2, 50 mM EDTA, 2 mM dithiothreitol and 10% (v/v) glycerol] in the presence of a proteinase inhibitor cocktail (Roche, Indianapolis, IN). Homogenate was centrifuged at 13,000g for 20 min at 4°C. The supernatant was isolated, and protein concentration was determined with BCA Protein Assay (Pierce, Rockford, IL). Twenty micrograms of protein was separated by gel electrophoresis and transferred to a nitrocellulose membrane. Five micrograms of rat brain tissue extract (Stressgen Bioreagents, Canada) was used as a positive control. Western blots were performed using a rabbit anti-EC-SOD (Phoenix Pharmaceuticals, Belmont, CA), specific signal was detected with a donkey anti-rabbit IgG-horseradish peroxidase conjugate (GE Healthcare, Little Chalfont, Buckinghamshire, UK) and ECL Plus Western Blotting Detection Reagents (GE Healthcare) according to the manufacturer's instructions. Epson Perfection 4990 Scanner and SilverFast software (Epson, Singapore) were used to scan and evaluate densitometrically the signal on X-ray film.
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). In brief, the assay procedures were performed as follows: frozen LV or aortic tissue was homogenized in ice-cold phosphate-buffered saline, homogenate was centrifuged at 13,000g for 20 min at 4°C, and supernatant was isolated and protein concentrations determined (BCA). Then, 10 µl of 20 mg/ml actinase E (Kaken Pharmaceuticals, Tokyo, Japan) was added to 100 µl of supernatant and incubated at 55°C for 20 h to digest tissue and release bound heparan sulfate from proteins. After incubation, samples were boiled for 5 min, cooled, and centrifuged at 3000g for 10 min. Then samples were assayed according to manufacturer's instruction using a 96-well plate. After assay reactions, the plate was read at 450 nm using a microplate reader (SpectraMax 340; Molecular Devices, Sunnyvale, CA). Statistical Analysis. Data are expressed as means ± S.E.M. We planned comparisons for each gene between control and diabetic groups to verify the impact of diabetes and between diabetic and TETA-treated diabetic groups to measure the effect of the drug. The paired Student's t test was hence used to determine the significance of between-group gene expression differences (Prism, version 4.02; GraphPad Software Inc., San Diego, CA). Mixed linear effect models were fitted by restricted maximum likelihood using SPlus v7.0.2 (Insightful) to analyze (-dPLV/dt)mean. One-way analysis of variance with post hoc Tukey's test was used to determine the significance of between-group HS concentration differences (Prism, version 4.02). P values of <0.05 have been considered significant, and n values indicate the number of replicates.
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Results |
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Diabetes causes cardiac dysfunction and failure in STZ-diabetic rats (Cooper et al., 2004) and humans (Struthers and Morris, 2002). Diabetic rats showed a significantly higher ratio of cardiac mass to body mass than that of nondiabetic rats (4.48 ± 0.012 x 10-3 versus 2.71 ± 0.015 x 10-3; P < 0.001), showing that they had developed cardiac hypertrophy. This ratio was significantly restored toward normal in diabetic rats that received 8-week oral TETA treatment (4.18 ± 0.078 x 10-3; P < 0.05). Sixteen-week diabetic rats also had lowered (-dPLV/dt)mean (P = 0.017), whereas 8-week TETA treatment improved (-dPLV/dt)mean toward normal (P = 0.022) (Fig. 1C). Thus, consistent with our previous report (Cooper et al., 2004), diabetes caused cardiac hypertrophy and diastolic dysfunction that were substantively ameliorated by TETA treatment. These findings indicate that biochemical changes reported herein reflect structural and functional cardiac changes induced by diabetes and TETA treatment similar to those we reported previously (Cooper et al., 2004).
ECM Protein Expression (LV and Aorta). To investigate the molecular mechanisms by which TETA improved cardiac structure and function in diabetic rats, we analyzed the expression of mRNAs corresponding to major ECM proteins. Expression of collagen I (Fig. 2A), III (Fig. 2B), and IV (Fig. 2C), fibronectin-1 (Fig. 2D), and PAI-1 (Fig. 2E) in LV were elevated in diabetes, and these increases were suppressed by TETA treatment. Expression of collagens III (Fig. 2F) and IV (Fig. 2G), and fibronectin-1 (Fig. 2H) in the aortas of diabetic rats were also elevated, and these increases were also suppressed to normal by TETA treatment.
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TGF-1 and Smad4 Expression (LV and Aorta). To further characterize the mechanism by which TETA inhibited the accumulation of ECM proteins in diabetic rats, we analyzed the mRNA expression of genes involved in the TGF-/Smad signaling pathway, which elicits stimulation of collagen production and plays a pivotal role in fibrogenesis (Sharma and Ziyadeh, 1995). Expression levels of mRNAs corresponding to TGF-1 (Fig. 3A) and Smad4 (Fig. 3B) were increased by 1.9- and 1.4-fold, respectively, in LV tissue of diabetic rats compared with nondiabetic controls. In aortic tissue, TGF-1 (Fig. 3C) and Smad4 (Fig. 3D) mRNA expression levels were similarly increased by 3.3- and 1.5-fold, respectively; TETA treatment significantly reversed the increased expression of these mRNAs in both LV and aorta of diabetic rats (Fig. 3, A-D).
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). Activation of the TGF-/Smad signaling pathway reportedly suppresses EC-SOD expression (Marklund, 1992). Moreover, diabetesinduced oxidative stress was reported to stimulate TGF--mediated matrix synthesis in renal glomeruli through activation of protein kinase C- and advanced glycation end product-mediated processes (Akahori et al., 2005). Here, we showed that EC-SOD mRNA levels in LV and aorta from diabetic rats at 16 weeks were significantly decreased by 2.2- and 2.1-fold, respectively, compared with matched control values (Fig. 4, A and B). However, 8 weeks of TETA treatment significantly restored EC-SOD mRNA levels in these diabetic tissues by 2.8- and 1.8-fold, respectively (Fig. 4, A and B). It is interesting that EC-SOD protein expression level in diabetic aorta was lower than that in nondiabetic aorta, which was significantly increased by TETA treatment (Fig. 4, C and D).
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). It can bind and localize EC-SOD in the extracellular matrix of blood vessels, where it eliminates ROS and sustains NO bioavailability (Marklund, 2002). HS concentrations in both LV (Fig. 5A) and aorta (Fig. 5B) were significantly lower in diabetic rats than in matched controls. TETA treatment significantly increased HS levels in both tissues (Fig. 5, A and B), although mean values were still lower than those in nondiabetic controls. TETA-mediated elevations were correspondingly greater in aortic than LV tissue (Fig. 5), consistent with the hypothesis that its renormalizing effects on cardiac HS content could mainly reflect increases in HS content of coronary arteries.
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Discussion |
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), TETA ameliorated diabetes-evoked LV hypertrophy and diastolic dysfunction without lowering blood glucose (Fig. 1). Here, we have shown for the first time that CuII chelation suppressed diabetes-evoked up-regulation of mRNAs corresponding to several ECM proteins and inhibited diabetes-induced activation of the TGF-1/Smad signaling pathway. TETA treatment also caused robust increases in mRNA and protein expression of EC-SOD. Furthermore, HS was partially restored by TETA treatment in the heart and aorta of diabetic rats.
Although the pathogenesis of diabetic cardiovascular disease is multifactorial, tissue fibrosis is one of its main pathological hallmarks, and excessive accumulation of ECM is a key consequence thereof. Diabetes causes overproduction of cardiac ECM, which contributes to diastolic dysfunction, and ECM overaccumulation has been reported in the diabetic rat heart (Martin et al., 2005). Studies have shown that collagen IV and fibronectin coalesce around smooth muscle cells in the aortic media (Sista et al., 2005). In this study, mRNAs corresponding to these major ECM components were increased in experimental diabetes (Fig. 2). TETA normalized levels of collagen IV and fibronectin-1 mRNAs in diabetic rats (Fig. 2). Consistent with this finding, we showed previously that collagen III protein is substantively elevated in LV of diabetic rats and is normalized by TETA treatment (Cooper et al., 2004).
TGF-1, a potent fibrogenic factor, stimulates collagen synthesis in cultured stellate cells, and overexpression of TGF-1 in transgenic mice caused hepatic fibrosis (Sanderson et al., 1995). TGF--induced collagen production in cultured cardiac fibroblasts was increased by elevated glucose, indicating that TGF- signaling pathway may play a major role in cardiac fibrosis and dysfunction (Martin et al., 2005). In the current study, we present in vivo evidence for an inhibitory effect of TETA on diabetes-induced over-expression of TGF-1 and Smad4 mRNA in LV and aorta (Fig. 3). It is interesting that inhibition of TGF- expression has been reported to be associated with the inhibitory effect of both lung and liver fibrosis by copper-lowering therapy with tetrathiomolybdate (Brewer et al., 2003, 2004; Askari et al., 2004). Tetrathiomolybdate was also found to suppress nuclear factor 
B, which in turn controls transcription of many angiogenic cytokines (Brewer, 2005), and to inhibit long-term inflammation (Omoto et al., 2005). We suggest that this inhibition of mRNA expression of TGF-1 and one of its major downstream signaling components, Smad4, may be an important mechanism by which TETA ameliorates diabetesinduced cardiac and arterial diseases.
PAI-1 is the primary inhibitor of plasminogen activator in vivo and is believed to promote tissue fibrosis (Schnaper et al., 1995). Previous studies have shown that PAI-1, whose promoter contains Smad-binding elements, is significantly induced by TGF- via Smad activity (Stroschein et al., 1999). PAI-1 mRNA expression was induced by various inflammatory agents, including TGF- (Venugopal et al., 2004). It is interesting that PAI-1 has been shown to directly control TGF- expression and thereby ultimately regulate ECM production in diabetes (Nicholas et al., 2005). Here, we have provided in vivo evidence for the elevated expression of PAI-1 mRNA in diabetic LV, which was ameliorated by TETA treatment (Fig. 2). All of the results suggest that two feed-forward cycles of reciprocal stimulation between TGF-1 and PAI-1 may perpetuate the fibrotic response in diabetic heart disease. Diabetes-evoked activation of both TGF-1 and PAI-1, which regulate each other's expression, may create a selfstimulatory cycle that enhances ECM accumulation and tissue fibrosis.
EC-SOD was said to act, at least in part, via down-regulation of the profibrotic TGF- pathway. EC-SOD-null mice consistently displayed increased susceptibility to inflammation and pulmonary fibrosis, suggesting that one mechanism by which EC-SOD protects against pulmonary fibrosis is by inhibiting inflammation (Fattman et al., 2003). Here, we found that TETA treatment increased EC-SOD mRNA and artery-associated protein, whereas it suppressed mRNAs corresponding to collagens I, III, and IV and fibronectin-1 in LV and aortic tissue from diabetic rats. TETA-evoked suppression of the activated TGF-/Smad pathway and suppression of elevated mRNAs corresponding to ECM proteins may be associated with restoration of EC-SOD mRNA and protein. There have been prior suggestions that tumor necrosis factor-
also affects EC-SOD (Marklund, 1992), but we did not observe changes in tumor necrosis factor- in heart and aorta of diabetic rats in this study (data not shown). Our results support the idea that EC-SOD, acting as a TGF-1 antagonist, may disrupt the vicious cycle of TGF-1 over-production in cardiovascular fibrosis. On the other hand, suppression of EC-SOD in diabetic LV and aorta could result from activation of the TGF-/Smad signaling pathway.
We reported previously that plasma EC-SOD was significantly higher in patients with diabetes than that in matched control subjects and that TETA treatment suppressed this elevation and restored circulating EC-SOD to normal (Cooper et al., 2005). Here, we have shown that arterial HS content was lower in rats with insulin-deficient diabetes than in matched controls, which is perhaps the cause of lower artery-bound EC-SOD. One possible explanation for these observations may lie, at least in part, in responses of arterial HS. Because most EC-SOD is bound in blood vessel walls (Marklund, 1984a), a minor release of EC-SOD into the blood may cause a significant increase in circulating EC-SOD, thereby generating a negative association between serum EC-SOD and vascular HS. This observation is consistent with evidence that EC-SOD bound in arterial walls is decreased in patients with diabetes (Ciechanowski et al., 2003; Fattman et al., 2003). TETA's ability to restore HS levels in blood vessels may be a factor underlying our observation that TETA treatment suppresses the elevated serum EC-SOD in patients with diabetes (Cooper et al., 2005). Not only can HS localize EC-SOD to improve vascular ROS disposal, but it also has antiatherogenic properties (Sivaram et al., 1995) to down-regulate fibroblast growth factor (Nugent et al., 1993) and to inhibit arterial smooth muscle cell proliferation (Castellot et al., 1981). TETA may also exert its effects in diabetic heart failure, at least in part, through vascular HS modulation.
In summary, we propose that TETA treatment attenuates extracellular Cu2+-evoked cardiac and arterial disease, at least in part by suppressing the activation of the TGF-/Smad signaling pathway and PAI-1 that would otherwise evoke increased ECM protein production and associated cardiac and arterial fibrosis. In addition, TETA treatment robustly stimulates the expression of EC-SOD, the sole antioxidant enzyme known to scavenge extracellular , thereby enhancing the potential for its disposal (Fig. 4). TETA also beneficially modified vascular HS, which was compromised by diabetes. Whether TETA affects HS synthesis or consumption is also under investigation. We also expect that the results reported here may well be relevant to cardiovascular diseases associated with other underlying conditions, such as hypertensive heart disease, ischemic cardiomyopathy, and ageing, in which there are metabolic perturbations similar to those in diabetes.
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Acknowledgements |
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Footnotes |
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The authors have all declared their association with Protemix Corporation, Auckland, New Zealand, and San Diego, California.
ABBREVIATIONS: TETA, triethylenetetramine; ECM, extracellular matrix; EC-SOD, extracellular superoxide dismutase; HS, heparan sulfate; LV, left ventricle; NO, nitric oxide; , superoxide anion; PAI-1, plasminogen activator inhibitor-1; PCR, polymerase chain reaction; ROS, reactive oxygen species; STZ, streptozotocin; TGF-1, transforming growth factor-1.
Address correspondence to: Dr. Garth J. S. Cooper, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand., E-mail: g.cooper{at}auckland.ac.nz
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References |
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TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
Askari FK, Dick R, Mao M, and Brewer GJ (2004) Tetrathiomolybdate therapy protects against concanavalin and carbon tetrachloride hepatic damage in mice. Exp Biol Med 229: 857-863.
Brewer GJ (2005) Copper lowering therapy with tetrathiomolybdate as an antiangiogenic strategy in cancer. Curr Cancer Drug Targets 5: 195-202.[CrossRef][Medline]
Brewer GJ, Dick R, Ullenbruch MR, Jin H, and Phan SH (2004) Inhibition of key cytokines by tetrathiomolybdate in the bleomycin model of pulmonary fibrosis. J Inorg Biochem 98: 2160-2167.[CrossRef][Medline]
Brewer GJ, Ullenbruch MR, Dick R, Olivarez L, and Phan SH (2003) Tetrathiomolybdate therapy protects against bleomycin-induced pulmonary fibrosis in mice. J Lab Clin Med 141: 210-216.[CrossRef][Medline]
Castellot JJ, Addonizio ML, Rosenberg R, and Karnovsky MJ (1981) Cultured endothelial cells produce a heparinlike inhibitor of smooth muscle cell growth. J Cell Biol 90: 372-379.
Ciechanowski K, Kedzierska K, Herdzik E, Bober J, Domanski L, Borowiak K, Rozanski J, and Myslak M (2003) Long-term hyperglycaemia decreases vascular fraction of extracellular superoxide dismutase. Diabetologia 46: 1026-1027.[CrossRef][Medline]
Cooper GJ, Chan YK, Dissanayake AM, Leahy FE, Keogh GF, Frampton CM, Gamble GD, Brunton DH, Baker JR, and Poppitt SD (2005) Demonstration of a hyperglycemia-driven pathogenic abnormality of copper homeostasis in diabetes and its reversibility by selective chelation: quantitative comparisons between the biology of copper and eight other nutritionally essential elements in normal and diabetic individuals. Diabetes 54: 1468-1476.
Cooper GJ, Phillips AR, Choong SY, Leonard BL, Crossman DJ, Brunton DH, Saafi EL, Dissanayake AM, Cowan BR, Young AA, et al. (2004) Regeneration of the heart in diabetes by selective copper chelation. Diabetes 53: 2501-2508.
Edwards IJ, Wagner JD, Vogl-Willis CA, Litwak KN, and Cefalu WT (2004) Arterial heparan sulfate is negatively associated with hyperglycemia and atherosclerosis in diabetic monkeys. Cardiovasc Diabetol 3: 6.[CrossRef][Medline]
Fattman CL, Schaefer LM, and Oury TD (2003) Extracellular superoxide dismutase in biology and medicine. Free Radic Biol Med 35: 236-256.[CrossRef][Medline]
Fraústo da Silva JJ and Williams RJ (2001) The Biological Chemistry of the Elements: The Inorganic Chemistry of Life. Clarendon Press, Oxford, UK.
Marklund SL (1984a) Extracellular superoxide dismutase and other superoxide dismutase isoenzymes in tissues from nine mammalian species. Biochem J 222: 649-655.[Medline]
Marklund SL (1984b) Extracellular superoxide dismutase in human tissues and human cell lines. J Clin Investig 74: 1398-1403.[Medline]
Marklund SL (1992) Regulation by cytokines of extracellular superoxide dismutase and other superoxide dismutase isoenzymes in fibroblasts. J Biol Chem 267: 6696-6701.
Marklund SL (2002) Extracellular superoxide dismutase. Methods Enzymol 349: 74-80.[Medline]
Martin J, Kelly DJ, Mifsud SA, Zhang Y, Cox AJ, See F, Krum H, Wilkinson-Berka J, and Gilbert RE (2005) Tranilast attenuates cardiac matrix deposition in experimental diabetes: role of transforming growth factor-. Cardiovasc Res 65: 694-701.
Nicholas SB, Aguiniga E, Ren Y, Kim J, Wong J, Govindarajan N, Noda M, Wang W, Kawano Y, Collins A, et al. (2005) Plasminogen activator inhibitor-1 deficiency retards diabetic nephropathy. Kidney Int 67: 1297-1307.[CrossRef][Medline]
Nugent MA, Karnovsky MJ, and Edelman ER (1993) Vascular cell-derived heparan sulfate shows coupled inhibition of basic fibroblast growth factor binding and mitogenesis in vascular smooth muscle cells. Circ Res 73: 1051-1060.
Omoto A, Kawahito Y, Prudovsky I, Tubouchi Y, Kimura M, Ishino H, Wada M, Yoshida M, Kohno M, Yoshimura R, et al. (2005) Copper chelation with tetrathiomolybdate suppresses adjuvant-induced arthritis and inflammation-associated cachexia in rats. Arthritis Res Ther 7: R1174-R1182.[CrossRef][Medline]
Oury TD, Day BJ, and Crapo JD (1996) Extracellular superoxide dismutase: a regulator of nitric oxide bioavailability. Lab Investig 75: 617-636.[Medline]
Roberts AB, McCune BK, and Dunn SR (1992) TGF-: regulation of extracellular matrix. Kidney Int 41: 557-559.[Medline]
Sanderson N, Factor V, Nagy P, Kopp J, Kondaiah P, Wakefield L, Roberts AB, Sporn MB, and Thorgeirsson SS (1995) Hepatic expression of mature transforming growth factor beta 1 in transgenic mice results in multiple tissue lesions. Proc Natl Acad Sci USA 92: 2572-2576.
Sandstrom J, Karlsson K, Edlund T, and Marklund SL (1993) Heparin-affinity patterns and composition of extracellular superoxide dismutase in human plasma and tissues. Biochem J 294: 853-857.[Medline]
Schnaper HW, Barnathan ES, Mazar A, Maheshwari S, Ellis S, Cortez SL, Baricos WH, and Kleinman HK (1995) Plasminogen activators augment endothelial cell organization in vitro by two distinct pathways. J Cell Physiol 165: 107-118.[CrossRef][Medline]
Sharma K and Ziyadeh FN (1995) Hyperglycemia and diabetic kidney disease: the case for transforming growth factor- as a key mediator. Diabetes 44: 1139-1146.[Abstract]
Sicree R, Shaw J, Zimmet P, and Tapp R (2003) The global burden of diabetes, in Diabetes Atlas 2003 (Gan D ed), International Diabetes Federation, Brussels, Belgium.
Sista AK, O'Connell MK, Hinohara T, Oommen SS, Fenster BE, Glassford AJ, Schwartz EA, Taylor CA, Reaven GM, and Tsao PS (2005) Increased aortic stiffness in the insulin-resistant Zucker fa/fa rat. Am J Physiol 288: H133-H141.
Sivaram P, Obunike JC, and Goldberg IJ (1995) Lysolecithin-induced alteration of subendothelial heparan sulfate proteoglycans increases monocyte binding to matrix. J Biol Chem 270: 29760-29765.
Stralin P, Jacobsson H, and Marklund SL (2003) Oxidative stress, NO and smooth muscle cell extracellular superoxide dismutase expression. Biochim Biophys Acta 1619: 1-8.[Medline]
Stroschein SL, Wang W, and Luo K (1999) Cooperative binding of Smad proteins to two adjacent DNA elements in the plasminogen activator inhibitor-1 promoter mediates transforming growth factor -induced Smad-dependent transcriptional activation. J Biol Chem 274: 9431-9441.
Struthers AD and Morris AD (2002) Screening for and treating left-ventricular abnormalities in diabetes mellitus: a new way of reducing cardiac deaths. Lancet 359: 1430-1432.[CrossRef][Medline]
Venugopal J, Hanashiro K, Yang ZZ, and Nagamine Y (2004) Identification and modulation of a caveolae-dependent signal pathway that regulates plasminogen activator inhibitor-1 in insulin-resistant adipocytes. Proc Natl Acad Sci USA 101: 17120-17125.
Vogl-Willis CA and Edwards IJ (2004) High-glucose-induced structural changes in the heparan sulfate proteoglycan, perlecan, of cultured human aortic endothelial cells. Biochim Biophys Acta 1672: 36-45.[Medline]
Williams B (1998) Mechanical influences on vascular smooth muscle cell function. J Hypertens 16: 1921-1929.[CrossRef][Medline]
Yokoyama H, Sato K, Okudaira M, Morita C, Takahashi C, Suzuki D, Sakai H, and Iwamoto Y (1999) Serum and urinary concentrations of heparan sulfate in patients with diabetic nephropathy. Kidney Int 56: 650-658.[CrossRef][Medline]
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