No abstract

Abstract-Osteopontin (OPN), an extracellular matrix protein, is expressed in the myocardium with hypertrophy and failure. We tested the hypothesis that OPN plays a role in left ventricular (LV) remodeling after myocardial infarction (MI). Accordingly, OPN expression and LV structural and functional remodeling were determined in wild-type (WT) and OPN knockout (KO) mice 4 weeks after MI. Northern analysis showed increased OPN expression in the infarcted region, peaking 3 days after MI and gradually decreasing over the next 28 days. In the remote LV, OPN expression was biphasic, with peaks at 3 and 28 days. In situ hybridization and immunohistochemical analyses showed increased OPN mRNA and protein primarily in the interstitium. Infarct size, heart weight, and survival were similar in KO and WT mice after MI (PϭNS), whereas the lung wet weight/dry weight ratio was increased in the KO mice (PϽ0.005 versus sham-operated mice). Peak LV developed pressure was reduced to a similar degree after MI in the KO and WT mice. Key Words: extracellular matrix proteins Ⅲ osteopontin Ⅲ collagen Ⅲ myocyte slippage Ⅲ myocyte elongation T he dynamic synthesis and breakdown of extracellular matrix (ECM) proteins may play an important role in myocardial remodeling. 1,2 Recently, using spontaneously hypertensive and aortic-banded rats, we showed increased expression of osteopontin (OPN), an ECM protein, coincident with the development of heart failure. 3 Although first isolated from mineralized bone matrix, OPN has since been shown to be synthesized by several cell types, including cardiac myocytes, microvascular endothelial cells, and fibroblasts. 4 -6 OPN, an adhesive glycophosphoprotein with an arginineglycine-aspartic acid (RGD) sequence, has been shown to interact with integrins (␣ V ␤ 3 , ␣ V ␤ 1 , and ␣ V ␤ 5 ) and the CD44 receptor in an RGD-dependent manner. 4,7 OPN appears capable of mediating diverse biological functions, including cell adhesion, chemotaxis, and signaling. 4,8 OPN has also been shown to interact with fibronectin and collagen, suggesting its possible role in matrix organization and/or stability. 9 -11 Recently, using a mammary cell line, we observed that suppression of OPN synthesis leads to increased activity of matrix metalloproteinase (MMP)-2. 12 In fact, there is increased expression of OPN in several tissues in response to injury, suggesting a role in wound healing. Using a skin incision model, Liaw et al 13 observed disorganization of the matrix and alteration of collagen fibrillogenesis, leading to collagen fibrils with smaller diameters in OPN knockout (KO) mice. Similarly, OPN has been shown to play a critical role in the generation of interstitial fibrosis in the kidney after obstructive nephropathy. 14 Remodeling after myocardial infarction (MI) is associated with left ventricular (LV) dilation, decreased cardiac function, and increased mortality. 15 Early dilation of the LV is likely due to scar expansion in the infarcted region, 16 -18 followed later by progressive remodeling 19 in the noninf...

No abstract

We compared the activity and physiologic effects of cardiac angiotensin converting enzyme (ACE) using isovolumic hearts from male Wistar rats with left ventricular hypertrophy due to chronic experimental aortic stenosis and from control rats. In response to the infusion of 3.5 X 10-8 M angiotensin I in the isolated buffer perfused beating hearts, the intracardiac fractional conversion to angiotensin II was higher in the hypertrophied hearts compared with the controls (17.3±4.1% vs 6.8±1.3%, P < 0.01). ACE activity was also significantly increased in the free wall, septum, and apex of the hypertrophied left ventricle, whereas ACE activity from the nonhypertrophied right ventricle of the aortic stenosis rats was not different from that of the control rats. Northern blot analyses of poly(A)+ purified RNA demonstrated the expression of ACE mRNA, which was increased fourfold in left ventricular tissue obtained from the hearts with left ventricular hypertrophy compared with the controls. In both groups, the intracardiac conversion of angiotensin I to angiotensin II caused a comparable dose-dependent increase in coronary resistance. In the control hearts, angiotensin II activation had no significant effect on systolic or diastolic function; however, it was associated with a dose-dependent depression of left ventricular diastolic relaxation in the hypertrophied hearts. These novel observations suggest that cardiac ACE is induced in hearts with left ventricular hypertrophy, and that the resultant intracardiac activation of angiotensin II may have differential effects on myocardial relaxation in hypertrophied hearts relative to controls. (J. Clin.

Primary amyloidosis is a systemic disorder characterized by the clonal production and tissue deposition of immunoglobulin light chain (LC) proteins. Congestive heart failure remains the greatest cause of death in primary amyloidosis, due to the development of a rapidly progressive amyloid cardiomyopathy. Amyloid cardiomyopathy is largely unresponsive to current heart failure therapies, and is associated with a median survival of less than 6 months and a 5-year survival of less than 10%. The mechanisms underlying this disorder, however, remain unknown. In this report, we demonstrate that physiological levels of human amyloid LC proteins, isolated from patients with amyloid cardiomyopathy (cardiac-LC), specifically alter cellular redox state in isolated cardiomyocytes, marked by an increase in intracellular reactive oxygen species and upregulation of the redox-sensitive protein, heme oxygenase-1. In contrast, vehicle or control LC proteins isolated from patients without cardiac involvement did not alter cardiomyocyte redox status. Oxidant stress imposed by cardiac-LC proteins further resulted in direct impairment of cardiomyocyte contractility and relaxation, associated with alterations in intracellular calcium handling. Cardiomyocyte dysfunction induced by cardiac-LC proteins was independent of neurohormonal stimulants, vascular factors, or extracellular fibril deposition, and was prevented through treatment with a superoxide dismutase/catalase mimetic. This study suggests that cardiac dysfunction in amyloid cardiomyopathy is directly mediated by LC protein-induced cardiomyocyte oxidant stress and alterations in cellular redox status, independent of fibril deposition. Antioxidant therapies or treatment strategies aimed at eliminating circulating LC proteins may therefore be beneficial in the treatment of this fatal disease. P rimary (AL) amyloidosis is a plasma cell dyscrasia resulting in the clonal production of immunoglobulin light chain proteins (LC) and subsequent multi-organ dysfunction. 1 Congestive heart failure remains the greatest cause of death in AL amyloidosis, due to the development of a rapidly progressive amyloid cardiomyopathy. Patients with amyloid cardiomyopathy are largely unresponsive to current heart failure therapies 2,3 and have a median survival of less than 6 months and a 5-year survival of less than 10%. 3,4 The mechanisms underlying this disorder, however, have yet to be determined. Prior theories have suggested that interstitial fibril deposition of AL proteins are the main cause of contractile dysfunction and cardiomyopathy. 2 This, however, is inconsistent with clinical observations, which have detailed a lack of correlation between myocardial fibril deposition and cardiac dysfunction in AL patients. 5 In addition, recent work in noncardiac tissues have suggested that other amyloidogenic proteins, including A␤ and transthyretin, may directly impair cellular function, independent of fibril deposition, through redox sensitive mechanisms. 6,7 In this report, we demonstrate that physio...

Background-This study sought to determine whether tight glycemic control with a modified glucose-insulin-potassium (GIK) solution in diabetic coronary artery bypass graft (CABG) patients would improve perioperative outcomes. Methods and Results-One hundred forty-one diabetic patients undergoing CABG were prospectively randomized to tight glycemic control (serum glucose, 125 to 200 mg/dL) with GIK or standard therapy (serum glucose Ͻ250 mg/dL) using intermittent subcutaneous insulin beginning before anesthesia and continuing for 12 hours after surgery. GIK patients had lower serum glucose levels (138Ϯ4 versus 260Ϯ6 mg/dL; PϽ0.0001), a lower incidence of atrial fibrillation (16.6% versus 42%; Pϭ0.0017), and a shorter postoperative length of stay (6.5Ϯ0.1 versus 9.2Ϯ0.3 days; Pϭ0.003). GIK patients also showed a survival advantage over the initial 2 years after surgery (Pϭ0.04) and decreased episodes of recurrent ischemia (5% versus 19%; Pϭ0.01) and developed fewer recurrent wound infections (1% versus 10%, Pϭ0.03). Conclusions-Tight glycemic control with GIK in diabetic CABG patients improves perioperative outcomes, enhances survival, and decreases the incidence of ischemic events and wound complications.

Implanted skeletal myoblasts form viable grafts in infarcted myocardium, resulting in enhanced post-MI exercise capacity and contractile function and attenuated ventricular dilation. These data illustrate that syngeneic myoblast implantation after MI improves both in vivo and ex vivo indexes of global ventricular dysfunction and deleterious remodeling and suggests that cellular implantation may be beneficial after MI.

Abstract-Reactive oxygen species (ROS)-mediated cell injury contributes to the pathophysiology of cardiovascular disease and myocardial dysfunction. Protection against ROS requires maintenance of endogenous thiol pools, most importantly, reduced glutathione (GSH), by NADPH. In cardiomyocytes, GSH resides in two separate cellular compartments: the mitochondria and cytosol. Although mitochondrial GSH is maintained largely by transhydrogenase and isocitrate dehydrogenase, the mechanisms responsible for sustaining cytosolic GSH remain unclear. Glucose-6-phosphate dehydrogenase (G6PD) functions as the first and rate-limiting enzyme in the pentose phosphate pathway, responsible for the generation of NADPH in a reaction coupled to the de novo production of cellular ribose. We hypothesized that G6PD is required to maintain cytosolic GSH levels and protect against ROS injury in cardiomyocytes. We found that in adult cardiomyocytes, G6PD activity is rapidly increased in response to cellular oxidative stress, with translocation of G6PD to the cell membrane. Furthermore, inhibition of G6PD depletes cytosolic GSH levels and subsequently results in cardiomyocyte contractile dysfunction through dysregulation of calcium homeostasis. Cardiomyocyte dysfunction was reversed through treatment with either a thiol-repleting agent (L-2-oxothiazolidine-4-carboxylic acid) or antioxidant treatment (Eukarion-134), but not with exogenous ribose. Finally, in a murine model of G6PD deficiency, we demonstrate the development of in vivo adverse structural remodeling and impaired contractile function over time. We, therefore, conclude that G6PD is a critical cytosolic antioxidant enzyme, essential for maintenance of cytosolic redox status in adult cardiomyocytes. Deficiency of G6PD may contribute to cardiac dysfunction through increased susceptibility to free radical injury and impairment of intracellular calcium transport. The full text of this article is available online at http://www.circresaha.org. (Circ Res. 2003;93:e9-e16.)Key Words: glucose-6-phosphate dehydrogenase Ⅲ cardiomyocytes Ⅲ oxidant injury Ⅲ contractile dysfunction Ⅲ intracellular calcium R eactive oxygen species (ROS)-mediated cell injury contributes to the pathophysiology of cardiovascular disease and myocardial dysfunction. 1-3 These ROS originate from multiple sources, including cellular oxidase complexes and as mitochondrial byproducts of aerobic metabolism. 3,4 To protect against ROS, cardiomyocytes contain a highly active cellular antioxidant defense. Central to the neutralization of ROS is the endogenous thiol, reduced glutathione (GSH), and glutathione cycling. 5,6 GSH provides the reducing equivalents necessary for the conversion of hydrogen peroxide and lipid peroxides to water and lipid alcohols, respectively, thereby preventing degradation to highly toxic free radicals, including hydroxyl and peroxyl radicals. 7 GSH also plays an important role in protecting against oxidation of protein sulfhydryl groups. 8 In the presence of ROS, the cellular redox state is altere...