Background-Tumor necrosis factor-␣ (TNF-␣) and angiotensin II (Ang II) are implicated in the development and further progression of heart failure, which might be, at least in part, mediated by the production of reactive oxygen species (ROS). However, the cause and consequences of this agonist-mediated ROS production in cardiac myocytes have not been well defined. Recently, we demonstrated that increased ROS production was associated with mitochondrial DNA (mtDNA) damage and dysfunction in failing hearts. We thus investigated whether the direct exposure of cardiac myocytes to TNF-␣ and Ang II in vitro could induce mtDNA damage via production of ROS. Methods and Results-TNF-␣ increased ROS production within cultured neonatal rat ventricular myocytes after 1 hour, as assessed by 2Ј,7Ј-dichlorofluorescin diacetate fluorescence microscopy. TNF-␣ also decreased mtDNA copy number by Southern blot analysis in association with complex III activity, which was prevented in the presence of the antioxidant ␣-tocopherol. A direct exposure of myocytes to H 2 O 2 caused a similar decrease in mtDNA copy number. In contrast, Ang II did not affect mtDNA copy number, despite the similar increase in ROS production. TNF-␣-mediated ROS production and a decrease in mtDNA copy number were inhibited by the sphingomyelinase inhibitor D609. Furthermore, N-acetylsphingosine (C2-ceramide), a synthetic cell-permeable ceramide analogue, increased myocyte ROS production, suggesting that TNF-␣-mediated ROS production and subsequent mtDNA damage were mediated by the sphingomyelin-ceramide signaling pathway. Conclusions-The intimate link between TNF-␣, ROS, and mtDNA damage might play an important role in myocardial remodeling and failure.

. Targeted deletion of MMP-2 attenuates early LV rupture and late remodeling after experimental myocardial infarction. Am J Physiol Heart Circ Physiol 285: H1229-H1235, 2003. First published May 29, 2003 10.1152/ ajpheart.00207.2003.-Matrix metalloproteinase-2 (MMP-2) is prominently overexpressed both after myocardial infarction (MI) and in heart failure. However, its pathophysiological significance in these conditions is still unclear. We thus examined the effects of targeted deletion of MMP-2 on post-MI left ventricular (LV) remodeling and failure. Anterior MI was produced in 10-to 12-wk-old male MMP-2 knockout (KO) and sibling wild-type (WT) mice by ligating the left coronary artery. By day 28, MI resulted in a significant increase in mortality in association with LV cavity dilatation and dysfunction. The MMP-2 KO mice had a significantly better survival rate than WT mice (56% vs. 85%, P Ͻ 0.05), despite a comparable infarct size (50 Ϯ 3% vs. 51 Ϯ 3%, P ϭ not significant), heart rate, and arterial blood pressure. The KO mice had a significantly lower incidence of LV rupture (10% vs. 39%, P Ͻ 0.05), which occurred within 7 days of MI. The KO mice exerted less LV cavity dilatation and improved fractional shortening after MI by echocardiography. The LV zymographic MMP-2 level significantly increased in WT mice after coronary artery ligation; however, this was completely prevented in KO mice. In contrast, the increase in the LV zymographic MMP-9 level after MI was similar between KO and WT mice. MMP-2 activation is therefore considered to contribute to an early cardiac rupture as well as late LV remodeling after MI. The inhibition of MMP-2 activation may therefore be a potentially useful therapeutic strategy to manage post-MI hearts. matrix metalloproteinase; cardiac rupture; heart failure; myocyte; extracellular matrix; mouse MYOCARDIAL INFARCTION (MI) leads to complex structural alterations (remodeling) involving both the infarcted and noninfarcted left ventricular (LV) myocardium (21). Early remodeling as LV cavity dilatation occurs during the early phase of MI, which is likely due to wall thinning in the infarct region. This might lead to a cardiac rupture, thereby accounting for the 5-30% of in-hospital mortality after acute MI (1). During the first several days, LV enlargement follows, and, thereafter, a progressive dilatation of the noninfarcted LV occurs over weeks (21). These progressive changes in LV geometry contribute to the development of depressed cardiac function, clinical heart failure, and increased mortality. Accordingly, it is of critical importance to explore the mechanisms of LV remodeling and develop therapeutic strategies that will effectively inhibit this deleterious process.The dynamic synthesis and breakdown of extracellular matrix (ECM) proteins play an important role in post-MI LV remodeling. In particular, the increased expression and activation of matrix metalloproteinases (MMPs) have been implicated in this process (4,5). Several studies have demonstrated that MMPs are involved not...

Background-Mitochondrial DNA (mtDNA) copy number is decreased not only in mtDNA-mutation diseases but also in a wide variety of acquired degenerative and ischemic diseases. Mitochondrial transcription factor A (TFAM) is essential for mtDNA transcription and replication. Myocardial mtDNA copy number and TFAM expression both decreased in cardiac failure. However, the functional significance of TFAM has not been established in this disease state. Methods and Results-We have now addressed this question by creating transgenic (Tg) mice that overexpress human TFAM gene and examined whether TFAM could protect the heart from mtDNA deficiencies and attenuate left ventricular (LV) remodeling and failure after myocardial infarction (MI) created by ligating the left coronary artery. TFAM overexpression could ameliorate the decrease in mtDNA copy number and mitochondrial complex enzyme activities in post-MI hearts. Survival rate during 4 weeks of MI was significantly higher in Tg-MI than in wild-type (WT) littermates (WT-MI), although infarct size was comparable. LV cavity dilatation and dysfunction were significantly attenuated in Tg-MI. LV end-diastolic pressure was increased in WT-MI, and it was also reduced in Tg-MI. Improvement of LV function in Tg-MI was accompanied by a decrease in myocyte hypertrophy, apoptosis, and interstitial fibrosis as well as oxidative stress in the noninfarcted LV. Conclusions-Overexpression

The activation of TGF-beta is protective against ischemic myocardial damage during the early phase. However, the beneficial effects might be lost, when its expression is sustained, thereby leading to LV remodeling and failure after MI.

Background-Oxidative stress plays an important role in the pathophysiology of heart failure. We determined whether the overexpression of glutathione peroxidase (GSHPx) could attenuate left ventricular (LV) remodeling and failure after myocardial infarction (MI). Methods and Results-We created MI in 12-to 16-week-old, male GSHPx transgenic mice (TGϩMI) and nontransgenic wild-type littermates (WTϩMI) by ligating the left coronary artery. GSHPx activity was increased in the hearts of TG mice, with no significant changes in other antioxidant enzymes. LV concentrations of thiobarbituric acid-reactive substances measured in TGϩMI at 4 weeks were significantly lower than those in WTϩMI. The survival rate during 4 weeks of MI was significantly higher in TGϩMI than in WTϩMI, although the infarct size was comparable. LV cavity dilatation and dysfunction were significantly attenuated in TGϩMI. LV end-diastolic pressure was increased in WTϩMI and reduced in TGϩMI. Improvement of LV function in TGϩMI was accompanied by a decrease in myocyte hypertrophy, apoptosis, and interstitial fibrosis in the noninfarcted LV. Myocardial matrix metalloproteinase-9 zymographic and protein levels were increased in WTϩMI after 3 days but were attenuated in TGϩMI. Conclusions-Overexpression of GSHPx inhibited LV remodeling and failure after MI. Therapies designed to interfere with oxidative stress might be beneficial to prevent cardiac failure.

Background-Increased expression of monocyte chemoattractant protein-1 (MCP-1) has recently been described in clinical and experimental failing heart. However, its pathophysiological significance in heart failure remains obscure. We thus determined whether MCP-1 is increased in post-myocardial infarction (MI) hearts and its blockade can attenuate the development of left ventricular (LV) remodeling and failure. Methods and Results-Anterior MI was produced in mice by ligating the left coronary artery. After 4 weeks, MI mice exerted LV dilatation and contractile dysfunction in association with myocyte hypertrophy and interstitial fibrosis of noninfarcted LV. MCP-1 mRNA levels were increased by 40-fold in noninfarcted LV 1 day after ligation, which persisted until 28 days. To block the MCP-1 signals, an N-terminal deletion mutant of the human MCP-1 gene was transfected into the limb skeletal muscle 3 days before and 14 days after ligation. This method improved the survival rate of mice with MI at 4 weeks (61% versus 87%, PϽ0.05) as well as attenuated LV cavity dilatation and contractile dysfunction, interstitial fibrosis, recruitment of macrophages, and myocardial gene expression of tumor necrosis factor-␣ and transforming growth factor-␤ compared with the nontreated MI mice despite the comparable infarct size calculated as percent LV circumference. Conclusions-The

Background-Peroxisome proliferator-activated receptor-␥ activators have recently been implicated as regulators of cellular proliferation and inflammatory response such as cytokine expression. Because proinflammatory cytokines play a critical role in left ventricular (LV) remodeling after myocardial infarction (MI), we examined the effects of pioglitazone treatment in an experimental model of chronic heart failure. Methods and Results-Mice with extensive anterior MI were treated with placebo or pioglitazone (3 mg · kg Ϫ1 · d

Background-Mitochondrial oxidative stress and damage play major roles in the development and progression of left ventricular (LV) remodeling and failure after myocardial infarction (MI). We hypothesized that overexpression of the mitochondrial antioxidant, peroxiredoxin-3 (Prx-3), could attenuate this deleterious process. Methods and Results-We created MI in 12-to 16-week-old, male Prx-3-transgenic mice (TGϩMI, nϭ37) and nontransgenic wild-type mice (WTϩMI, nϭ39) by ligating the left coronary artery. Prx-3 protein levels were 1.8 times higher in the hearts from TG than WT mice, with no significant changes in other antioxidant enzymes. At 4 weeks after MI, LV thiobarbituric acid-reactive substances in the mitochondria were significantly lower in TGϩMI than in WTϩMI mice (meanϮSEM, 1.5Ϯ0.2 vs 2.2Ϯ0.2 nmol/mg protein; nϭ8 each, PϽ0.05). LV cavity dilatation and dysfunction were attenuated in TGϩMI compared with WTϩMI mice, with no significant differences in infarct size (56Ϯ1% vs 55Ϯ1%; nϭ6 each, PϭNS) and aortic pressure between groups. Mean LV end-diastolic pressures and lung weights in TGϩMI mice were also larger than those in WTϩsham-operated mice but smaller than those in WTϩMI mice. Improvement in LV function in TGϩMI mice was accompanied by a decrease in myocyte hypertrophy, interstitial fibrosis, and apoptosis in the noninfarcted LV. Mitochondrial DNA copy number and complex enzyme activities were significantly decreased in WTϩMI mice, and this decrease was also ameliorated in TGϩMI mice. Conclusions-Overexpression of Prx-3 inhibited LV remodeling and failure after MI. Therapies designed to interfere with mitochondrial oxidative stress including the antioxidant Prx-3 might be beneficial in preventing cardiac failure.