Role of melatonin, melatonin receptors and STAT3 in the cardioprotective effect of chronic and moderate consumption of red wine.

We have recently discovered that melatonin, given acutely and directly to the isolated heart at the concentration found in wine, confers cardioprotection against ischemia-reperfusion (I/R). However, whether the presence of melatonin in wine contributes to the cardioprotective effect of chronic and moderate consumption of wine and its signalling mechanisms of protection are unknown. We therefore used both in vivo and in vitro models of I/R to investigate whether the presence of melatonin in red wine may contribute to the cardioprotective effect of chronic and moderate consumption of red wine. Wistar rats and C57black6 mice (WT) received drinking water supplemented daily with a moderate amount of red wine or melatonin given at the concentration found in the red wine. Rats were also pretreated with luzindole, a specific inhibitor of melatonin receptors 1 and 2 (2.3 mg/kg/day, intraperitoneally) or prazosin, a specific inhibitor of melatonin receptor type 3 (2.5 mg/kg/day, intraperitoneally). After 14 days, hearts were subjected to I/R in vivo or ex vivo. Red wine reduced the infarct size in both rats and WT mice (p < 0.001). Luzindole did not affect wine-induced cardioprotection, while prazosin reduced the infarct sparing effect of red wine (p < 0.05). Furthermore, red wine or melatonin failed to protect tumor necrosis factor alpha (TNF) receptor 2 knockout or cardiomyocyte specific signal transducer and activator of transcription 3 (STAT3) deficient mice (n.s. vs. control). Our novel findings suggest that the presence of melatonin in red wine contributes to the cardioprotective effect of chronic and moderate consumption of red wine against lethal I/R injuries. This effect is most likely mediated, at least in part, via melatonin receptor 3 and the activation of TNF and STAT3, both key players of the prosurvival and well described SAFE pathway.

Impaired SIRT1 nucleocytoplasmic shuttling in the senescent heart during ischemic stress.

A "longevity " gene, sirtuin 1 (SIRT1), can attenuate age-dependent induction of left ventricular dysfunction. This study aimed to characterize the role of SIRT1 in the tolerance of aged heart to ischemic insults. Male C57BL/6 young (4-6 mo) and aged (24-26 mo) mice were used to determine the role of SIRT1 in myocardial ischemia/reperfusion (I/R) tolerance. SIRT1 localization was assessed by confocal microscopy. Immunoblotting was used to evaluate SIRT1 expression and translocation. The results demonstrated that SIRT1 is expressed predominantly as a sumoylated form in cardiomyocyte nuclei. Moreover, cardiac overexpression of desumoylase, sentrin-specific protease 2 (SENP2), significantly reduces nuclear sumoylated SIRT1 levels (P<0.05). Interestingly, I/R stress leads to desumoylation and translocation of nuclear SIRT1 into the cytoplasm in aged but not in young hearts. SIRT1 activity in ischemic young hearts was 3.2-fold higher than that seen in ischemic aged hearts, which suggests that aging causes impaired nucleocytoplasmic shuttling and activation of SIRT1 during ischemic stress. The infarct size in aged and Sirt1(+/-) knockout hearts was higher than that observed in young and Sirt1(+/+) WT littermate hearts, respectively (all P<0.05). SIRT1 agonist, SRT1720, reduced myocardial infarction in both aged and Sirt1(+/-) hearts. Therefore, impaired cardiac SIRT1 activity plays a critical role in the observed increase in susceptibility of the aged heart to I/R injury. SIRT1 agonist can restore this aging-related loss of cardioprotection.

Impaired macrophage migration inhibitory factor-AMP-activated protein kinase activation and ischemic recovery in the senescent heart.

BACKGROUND: Elderly patients are more sensitive than younger patients to myocardial ischemia, which results in higher mortality. We investigated how aging affects the cardioprotective AMP-activated protein kinase (AMPK) signaling pathway. METHODS AND RESULTS: Ischemic AMPK activation was impaired in aged compared with young murine hearts. The expression and secretion of the AMPK upstream regulator, macrophage migration inhibitory factor (MIF), were lower in aged compared with young adult hearts. Additionally, the levels of hypoxia-inducible factor 1alpha, a known transcriptional activator of MIF, were reduced in aged compared with young hearts. Ischemia-induced AMPK activation in MIF knockout mice was blunted, leading to greater contractile dysfunction in MIF-deficient than in wild-type hearts. Furthermore, intramyocardial injection of adenovirus encoding MIF in aged mice increased MIF expression and ischemic AMPK activation and reduced infarct size. CONCLUSIONS: An impaired MIF-AMPK activation response in senescence thus may be attributed to an aging-associated defect in hypoxia-inducible factor 1alpha, the transcription factor for MIF. In the clinical setting, impaired cardiac hypoxia-inducible factor 1alpha activation and consequent reduced MIF expression may play an important role in the increased susceptibility to myocardial ischemia observed in older cardiac patients.

Transgenic overexpression of aldehyde dehydrogenase-2 rescues chronic alcohol intake-induced myocardial hypertrophy and contractile dysfunction.

BACKGROUND: Chronic alcoholism leads to the onset and progression of alcoholic cardiomyopathy through toxic mechanisms of ethanol and its metabolite, acetaldehyde. This study examined the impact of altered acetaldehyde metabolism through systemic transgenic overexpression of aldehyde dehydrogenase-2 (ALDH2) on chronic alcohol ingestion-induced myocardial damage. METHODS AND RESULTS: ALDH2 transgenic mice were produced with the chicken beta-actin promoter. Wild-type FVB and ALDH2 mice were placed on a 4% alcohol diet or a control diet for 14 weeks. Myocardial and cardiomyocyte contraction, intracellular Ca(2+) handling, histology (hematoxylin and eosin, Masson trichrome), protein damage, and apoptosis were determined. Western blot was used to monitor the expression of NADPH oxidase, calcineurin, apoptosis-stimulated kinase (ASK-1), glycogen synthase kinase-3beta (GSK-3beta), GATA4, and cAMP-response element binding (CREB) protein. ALDH2 reduced the chronic alcohol ingestion-induced elevation in plasma and tissue acetaldehyde levels. Chronic alcohol consumption led to cardiac hypertrophy, reduced fractional shortening, cell shortening, and impaired intracellular Ca(2+) homeostasis, the effect of which was alleviated by ALDH2. In addition, the ALDH2 transgene significantly attenuated chronic alcohol intake-induced myocardial fibrosis, protein carbonyl formation, apoptosis, enhanced NADPH oxidase p47(phox) and calcineurin expression, as well as phosphorylation of ASK-1, GSK-3beta, GATA4, and CREB. CONCLUSIONS: The present results suggest that transgenic overexpression of ALDH2 effectively antagonizes chronic alcohol intake-elicited myocardial hypertrophy and contractile defect through a mechanism that is associated, at least in part, with phosphorylation of ASK-1, GSK-3beta, GATA4, and CREB. These data strongly support the notion that acetaldehyde may be an essential contributor to the chronic development of alcoholic cardiomyopathy.

Sex Differences in Cardiac AMP-Activated Protein Kinase Following Exhaustive Exercise.

Ischemic heart disease presents with significant differences between sexes. Endurance exercise protects the heart against ischemic disease and also distinctly impacts male and female patients through unidentified mechanisms, though some evidence implicates 5'-AMP-activated protein kinase (AMPK). The purpose of this investigation was to assess the impact of training and sex on cardiac AMPK activation following exhaustive exercise. AMPK activation was measured in trained and sedentary mice of both sexes. Trained mice ran on a treadmill at progressively increasing speeds and duration for 12 weeks. Trained and sedentary mice of both sexes were euthanized immediately following exhaustive exercise and compared to sedentary controls. Endurance training elicited adaptations indicative of aerobic adaptation including higher max running velocities and cardiac hypertrophy with no differences between males and females. AMPK activity was higher in male compared to females, and trained exhibited higher AMPK activity compared to sedentary mice. In response to training, male mice activated AMPK more robustly than female mice. Chronic exercise training increases the ability to activate cardiac AMPK in response to exhaustive exercise in a sex-specific manner. Understanding the interaction between exercise and sex is vital for use of exercise as medicine for heart disease in both men and women.

Caspase recruitment domain-containing protein 9 (CARD9) knockout reduces regional ischemia/reperfusion injury through an attenuated inflammatory response.

Ischemic heart disease remains a leading cause of morbidity and mortality in the United States. Interventional reperfusion induces further damage to the ischemic myocardium through neutrophil infiltration and acute inflammation. As caspase recruitment domain-containing protein 9 (CARD9) plays a critical role in innate immune response and inflammation, we hypothesized that CARD9 knockout would provide protection against ischemia and reperfusion (I/R) injury through attenuation of acute inflammatory responses. C57BL/6 wild-type (WT) and CARD9-/- mice were subjected to 45 min left anterior descending (LAD) coronary artery occlusion followed by 24-h reperfusion. Area at risk (AAR) and infarct size were measured by Evans blue and triphenyltetrazolium chloride (TTC) staining. Frozen heart sections were stained with anti-mouse GR-1 antibody to detect infiltrated neutrophils. Concentrations of cytokines/chemokines TNF-α, IL-6, CXCL-1 and MCP-1 were determined in heart tissue homogenate and serum by ELISA assay. Western immunoblotting analyses were performed to measure the phosphorylation of p38 MAPK. Our results indicate that following I/R, infarct size was significantly smaller in CARD9-/- mice compared to WT. The number of infiltrated neutrophils was significantly lower in CARD9-/- mice compared to WT. Levels of TNF-α, IL-6, CXCL-1 and MCP-1 were significantly reduced in heart tissue and serum from CARD9-/- mice compared to WT. CARD9-/- mice also exhibited significantly lower levels of phosphorylated p38 MAPK. Taken together, our results suggest that CARD9 knockout protects the heart from ischemia/reperfusion (I/R) injury, possibly through reduction of neutrophil infiltration and attenuation of CARD9-associated acute inflammatory signaling.

Aldosterone antagonism fails to attenuate age-associated left ventricular fibrosis.

Collagen accumulates disproportionately in cardiac remodeling induced by hypertension and associated with advancing age. Spironolactone (Spiro), an aldosterone antagonist, attenuates the accumulation of collagen induced by hypertension. It was hypothesized that Spiro would attenuate the age-associated increase in percent collagen in the heart. Female Fisher 344 rats at 3 months (Y), 12 months (M), and 21 months (O) of age were treated with Spiro (30 mg/kg/d) or vehicle (Veh) for 2 months, yielding six groups: Y-Veh, Y-Spiro, M-Veh, M-Spiro, O-Veh, and O-Spiro. Hearts were harvested for immunoblotting, RNA blotting, and biochemical analysis. Percent collagen in the left ventricle and septum was greatest in the oldest rats. Spiro did not significantly attenuate the age-associated increase in collagen fraction or the age-associated increases in expression of atrial natriuretic factor and beta-myosin heavy chain messenger RNA. Chronic aldosterone antagonism does not attenuate the age-associated increase in collagen fraction in the female Fisher 344 rat heart.

Curcumin inhibits platelet-derived growth factor-stimulated vascular smooth muscle cell function and injury-induced neointima formation.

OBJECTIVE: Vascular smooth muscle cell (VSMC) migration, proliferation, and collagen synthesis are key events involved in the pathogenesis of cardiovascular disease. Growth factors, such as platelet-derived growth factor (PDGF) and fibroblast growth factor, released during vascular injury plays a pivotal role in regulating these events. Curcumin (diferuloyl methane), a major component of the spice turmeric (Curcuma longa), has been shown recently to have beneficial effects in chronic conditions, such as inflammation, cancer, cystic fibrosis, and Alzheimer's disease. The objective of this study was to investigate the ability of curcumin to inhibit PDGF-stimulated migration, proliferation, and collagen synthesis in cultured VSMCs and neointima formation after carotid artery injury in rats. METHODS AND RESULTS: Curcumin (1 to 25 microM) produced a concentration-dependent inhibition of PDGF-elicited VSMC migration, proliferation, and collagen synthesis assessed by chemotaxis, [3H]thymidine incorporation, and [3H]-L-proline incorporation, respectively. Curcumin blocked PDGF-induced VSMC actin-cytoskeleton reorganization, attenuated PDGF signal transduction, and inhibited the binding of PDGF to its receptors. Carotid artery neointima formation was significantly attenuated by perivascular curcumin compared with vehicle controls 14 days after injury, characterized by reduced DNA synthesis, collagen synthesis, and PDGF receptor phosphorylation. CONCLUSIONS: These data suggest that curcumin is a potent inhibitor of key PDGF-stimulated VSMC functions and may play a critical role in regulating these events after vascular injury.

Cardio-protection afforded by ß-blockade is maintained during resistance exercise.

OBJECTIVES: Whether or not the cardio-protective effect of ß-adrenergic blockade is retained during resistance exercise has not been systematically evaluated. Therefore the purpose of this study was to measure selected cardiorespiratory responses to isometric exercise involving hand-gripping, single-leg extension, or double-leg dead-lift, under placebo (control), ß1-selective (atenolol), and non-selective (propranolol) adrenergic blockade conditions. DESIGN: Eleven young male adults were evaluated in a randomized, double-blinded, repeated measures study design and performed all three exercise modalities at 30% of maximal voluntary contraction under placebo, atenolol and propranolol conditions. METHODS: Heart rate, systolic and diastolic blood pressure, rate-pressure product, oxygen uptake, cardiac output, stroke volume and total peripheral resistance were directly measured or calculated at rest and during the third minute of each of the three exercise modes. RESULTS: Irrespective of drug condition, a graded pressor response was observed going from rest to exercise so that rest

Endurance exercise accelerates myocardial tissue oxygenation recovery and reduces ischemia reperfusion injury in mice.

Exercise training offers cardioprotection against ischemia and reperfusion (I/R) injury. However, few essential signals have been identified to underscore the protection from injury. In the present study, we hypothesized that exercise-induced acceleration of myocardial tissue oxygenation recovery contributes to this protection. C57BL/6 mice (4 weeks old) were trained on treadmills for 45 min/day at a treading rate of 15 m/min for 8 weeks. At the end of 8-week exercise training, mice underwent 30-min left anterior descending coronary artery occlusion followed by 60-min or 24-h reperfusion. Electron paramagnetic resonance oximetry was performed to measure myocardial tissue oxygenation. Western immunoblotting analyses, gene transfection, and myography were examined. The oximetry study demonstrated that exercise markedly shortened myocardial tissue oxygenation recovery time following reperfusion. Exercise training up-regulated Kir6.1 protein expression (a subunit of ATP-sensitive K(+)channel on vascular smooth muscle cells, VSMC sarc-K(ATP)) and protected the heart from I/R injury. In vivo gene transfer of dominant negative Kir6.1AAA prolonged the recovery time and enlarged infarct size. In addition, transfection of Kir6.1AAA increased the stiffness and reduced the relaxation capacity in the vasculature. Together, our study demonstrated that exercise training up-regulated Kir6.1, improved tissue oxygenation recovery, and protected the heart against I/R injury. This exercise-induced cardioprotective mechanism may provide a potential therapeutic intervention targeting VSMC sarc-K(ATP) channels and reperfusion recovery.

Exercise training post-MI favorably modifies heart extracellular matrix in the rat.

PURPOSE: In order to assess the effect of daily exercise on extracellular matrix remodeling in the heart after myocardial infarction (MI), we measured collagen concentration (%COL) and nonreducible collagen cross-linking (hydroxylysylpyridinoline, HP) in the right ventricle (RV), and regionally within the infarcted (INF) and viable left ventricular free wall (LVF) and septum (LVS), using a rodent MI training model. METHODS: Infarcts (19%-24% of LV) were surgically induced in adult rats that were assigned to either trained (MI-TR) or sedentary (MI-SED) groups and compared to sham-surgery sedentary controls (SHAM). RESULTS: In LVF, 10 wk of treadmill running had no effect on the increase (P < 0.001) in %COL seen with MI (MI-SED = 7.14% ± 0.15%, MI-TR = 7.61% ± 0.19%, SHAM = 3.55% ± 0.19%). However, it normalized the increase (P < 0.05) in HP cross-linking (MI-SED = 0.43 ± 0.02, MI-TR = 0.27 ± 0.03, SHAM = 0.30 ± 0.04 mol HP·mol(-1) collagen). The INF scar in MI-SED rats showed a sevenfold increase in %COL (P < 0.001) compared to SHAM LVF myocardium, an increase that was attenuated by training (MI-SED = 26% ± 1% vs MI-TR = 21% ± 2%; P < 0.05). However, training had no effect on MI-induced increases in cross-linking in the INF scar (1.01 ± 0.22 vs 0.84 ± 0.14 mol HP·mol(-1) collagen). In LVS, although a small but significant increase in %COL was seen in both MI groups, HP cross-linking was unaltered compared to SHAM rats. Training also normalized the increase observed in cross-linking in RV after MI. CONCLUSIONS: Because increased HP cross-linking in the heart is associated with decreased chamber compliance, these findings may help to explain the improved heart function seen after daily exercise in cardiac rehabilitation patients.

Intra-myocardial delivery of mesenchymal stem cells ameliorates left ventricular and cardiomyocyte contractile dysfunction following myocardial infarction.

Although mesenchymal stem cells (MSCs) transplantation may improve the overall heart function, the heterogeneity of myocardial cells makes it difficult to determine the nature of cells benefited from transplantation. This study evaluated the effect of intra-myocardial MSC transplantation on myocardial function following MI. Enhanced green fluorescent protein (EGFP)-expressing donor MSCs from C57BL/6-Tg (UBC-GFP) 30Scha/J mice were transplanted into LV free wall in the region bordering an infarct in C57 recipient mice following ligation of left main coronary artery (MI+MSC group). Ten days after MI, LV function was assessed using echocardiography. Cardiomyocyte contractility and intracellular Ca(2+) transients were measured in cells from the area-at-risk surrounding the infarct scar. The EGFP donor cells were traced in the MSC recipient mice using fluorescence microscopy. TUNEL, H&E and Masson trichrome staining were used to assess apoptosis, angiogenesis and myocardial fibrosis, respectively. MI dilated LV as evidenced by increased end-diastolic and end-systolic diameters. MI significantly reduced fractional shortening, cardiomyocyte peak shortening, and maximal velocity of shortening and relengthening, all of which were attenuated or abrogated by MSC therapy. MI also reduced resting intracellular Ca(2+), intracellular Ca(2+) rise and decay rate, which were reconciled by MSC. MSC therapy attenuated MI-induced apoptosis and decreased angiogenesis but not myocardial fibrosis in the peri-infarct area. Taken together, our results demonstrated that MSC therapy significantly improved both LV and cardiomyocyte function possibly associated with its beneficial role in apoptosis and angiogenesis, indicating a key role for cardiomyocytes in stem cell tissue engineering.

Hypertrophic cardiomyopathy in high-fat diet-induced obesity: role of suppression of forkhead transcription factor and atrophy gene transcription.

Cellular hypertrophy is regulated by coordinated pro- and antigrowth machineries. Foxo transcription factors initiate an atrophy-related gene program to counter hypertrophic growth. This study was designed to evaluate the role of Akt, the forkhead transcription factor Foxo3a, and atrophy genes muscle-specific RING finger (MuRF)-1 and atrogin-1 in cardiac hypertrophy and contractile dysfunction associated with high-fat diet-induced obesity. Mice were fed a low- or high-fat diet for 6 mo along with a food-restricted high-fat weight control group. Echocardiography revealed decreased fractional shortening and increased end-systolic diameter and cardiac hypertrophy in high-fat obese but not in weight control mice. Cardiomyocytes from high-fat obese but not from weight control mice displayed contractile and intracellular Ca2+ defects including depressed maximal velocity of shortening/relengthening, prolonged duration of shortening/relengthening, and reduced intracellular Ca2+ rise and clearance. Caspase activities were greater in high-fat obese but not in weight control mouse hearts. Western blot analysis revealed enhanced basal Akt and Foxo3a phosphorylation and reduced insulin-stimulated phosphorylation of Akt and Foxo3a without changes in total protein expression of Akt and Foxo3a in high-fat obese hearts. RT-PCR and immunoblotting results displayed reduced levels of the atrogens atrogin-1 and MuRF-1, the upregulated hypertrophic markers GATA4 and ciliary neurotrophic factor receptor-alpha, as well as the unchanged calcineurin and proteasome ubiquitin in high-fat obese mouse hearts. Transfection of H9C2 myoblast cells with dominant-negative Foxo3a adenovirus mimicked palmitic acid (0.8 mM for 24 h)-induced GATA4 upregulation without an additive effect. Dominant-negative Foxo3a-induced upregulation of pAkt and repression of phosphatase and tensin homologue were abrogated by palmitic acid. These results suggest a cardiac hypertrophic response in high-fat diet-associated obesity at least in part through inactivation of Foxo3a by the Akt pathway.

Susceptibility to systolic dysfunction in the myocardium from chronically infarcted spontaneously hypertensive rats.

We explored whether the hypertensive heart is susceptible to myocardial dysfunction in viable noninfarcted tissue post-myocardial infarction (MI), the potential mechanisms thereof, and the impact of these changes on pump function. Six to seven months after the ligation of the left anterior descending coronary artery, left ventricular (LV) myocardial systolic function, as assessed from the percent shortening of the noninfarcted lateral wall segmental length determined over a range of filling pressures (ultrasonic transducers placed in the lateral wall in anaesthetized, open-chest, ventilated rats) and the percent thickening of the posterior wall (echocardiography), was reduced in infarcted spontaneous hypertensive rats (SHR-MI) (P < 0.05) but not in normotensive Wistar-Kyoto (WKY-MI) animals compared with corresponding controls [SHR-sham operations (Sham) and WKY-Sham]. This change in the regional myocardial function in SHR-MI, but not in WKY-MI, occurred despite a similar degree of LV dilatation (increased LV end-diastolic dimensions and volume intercept of the LV end-diastolic pressure-volume relation) in SHR-MI and WKY-MI rats and a lack of difference in LV relative wall thinning, LV wall stress, apoptosis [terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling (TUNEL)], or necrosis (pathological score) between SHR-MI and WKY-MI rats. Although the change in regional myocardial function in the SHR-MI group was not associated with a greater reduction in baseline global LV chamber systolic function [end-systolic elastance (LV E(es)) and endocardial fractional shortening determined in the absence of an adrenergic stimulus], in the presence of an isoproterenol challenge, noninfarct-zone LV systolic myocardial dysfunction manifested in a significant reduction in LV E(es) in SHR-MI compared with WKY-MI and SHR and WKY-Sham rats (P < 0.04). In conclusion, these data suggest that with chronic MI, the hypertensive heart is susceptible to the development of myocardial dysfunction, a change that cannot be attributed to excessive chamber dilatation, apoptosis, or necrosis, but which in turn contributes toward a reduced cardiac adrenergic inotropic reserve.

IGF-I alleviates diabetes-induced RhoA activation, eNOS uncoupling, and myocardial dysfunction.

IGF-I rescues diabetic heart defects and oxidative stress, although the underlying mechanism of action remains poorly understood. This study was designed to delineate the beneficial effects of IGF-I with a focus on RhoA, Akt, and eNOS coupling. Echocardiography was performed in normal or diabetic Friend Virus-B type (FVB) and IGF-I transgenic mice. Cardiomyocyte contractile properties were evaluated using peak shortening (PS), time-to-90% relengthening (TR90), and intracellular Ca2+ rise and decay. Diabetes reduced fraction shortening, PS, and intracellular Ca2+; it increased chamber size, prolonged TR90, and intracellular Ca2+ decay. Levels of RhoA mRNA, active RhoA, and O2(-) were elevated, whereas nitric oxide (NO) levels were reduced in diabetes. Diabetes-induced O2(-) accumulation was ablated by the NO synthase (NOS) inhibitor nitro-L-arginine methyl ester (L-NAME), indicating endothelial NOS (eNOS) uncoupling, all of which except heart size were negated by IGF-I. The IGF-I-elicited beneficial effects were mimicked by the Rho kinase inhibitor Y27632 and BH4. Diabetes depressed expression of Kv1.2 and dihydrofolate reductase (DHFR), increased beta-myosin heavy-chain expression, stimulated p38 MAPK, and reduced levels of total Akt and phosphorylated Akt/eNOS, all of which with the exception of myosin heavy chain were attenuated by IGF-I. In addition, Y27632 and the eNOS coupler folate abrogated glucose toxicity-induced PS decline, TR90 prolongation, while it increased O2(-) and decreased NO and Kv1.2 levels. The DHFR inhibitor methotrexate impaired myocyte function, NO/O2(-) balance, and rescued Y27632-induced cardiac protection. These results revealed that IGF-I benefits diabetic hearts via Rho inhibition and antagonism of diabetes-induced decrease in pAkt, eNOS uncoupling, and K+ channel expression.

Earliest changes in the left ventricular transcriptome postmyocardial infarction.

We report a genome-wide survey of early responses of the mouse heart transcriptome to acute myocardial infarction (AMI). For three regions of the left ventricle (LV), namely, ischemic/infarcted tissue (IF), the surviving LV free wall (FW), and the interventricular septum (IVS), 36,899 transcripts were assayed at six time points from 15 min to 48 h post-AMI in both AMI and sham surgery mice. For each transcript, temporal expression patterns were systematically compared between AMI and sham groups, which identified 515 AMI-responsive genes in IF tissue, 35 in the FW, 7 in the IVS, with three genes induced in all three regions. Using the literature, we assigned functional annotations to all 519 nonredundant AMI-induced genes and present two testable models for central signaling pathways induced early post-AMI. First, the early induction of 15 genes involved in assembly and activation of the activator protein-1 (AP-1) family of transcription factors implicates AP-1 as a dominant regulator of earliest post-ischemic molecular events. Second, dramatic increases in transcripts for arginase 1 (ARG1), the enzymes of polyamine biosynthesis, and protein inhibitor of nitric oxide synthase (NOS) activity indicate that NO production may be regulated, in part, by inhibition of NOS and coordinate depletion of the NOS substrate, L: -arginine. ARG1: was the single-most highly induced transcript in the database (121-fold in IF region) and its induction in heart has not been previously reported.

Unloading-induced remodeling in the normal and hypertrophic left ventricle.

To date, no study has assessed the degree of similarity between left ventricular (LV) reverse remodeling and atrophic remodeling. Stable LV hypertrophy was induced by creation of an arteriovenous fistula (AVF) in Lewis rats (32 days). LV unloading was induced by heterotopic transplantation of normal (NL-HT) and/or hypertrophic (AVF-HT) hearts (7 days). We compared indexes of remodeling in AVF, NL-HT, and AVF-HT groups with those of normal controls. LV unloading induced decreases in cardiomyocyte size in NL-HT and AVF-HT hearts. NL-HT and AVF-HT LV were both characterized by relative increases in collagen concentration that were largely a reflection of decreases in myocyte volume. NL-HT and AVF-HT LV were associated with similar increases in matrix metalloproteinase (MMP-2 and -9) zymographic activity, without change in the abundance of the tissue inhibitors of the MMPs. In contrast, AVF-HT, but not NL-HT, was associated with a dramatic increase in collagen cross-linking. Our findings suggest an overall similarity in the response of the normal and hypertrophic LV to surgical unloading. However, the dramatic increase in collagen cross-linking after just 1 wk of unloading suggests a potential difference in the dynamics of collagen metabolism between the two models. Further studies will be required to determine the precise molecular mechanisms responsible for these differences in extracellular matrix regulation. However, with respect to these and related issues, heterotopic transplantation of hypertrophied hearts will be a useful small animal model for defining mechanisms of myocyte-matrix interactions during decreased loading conditions.