Exogenous administration of a recombinant variant of TWEAK impairs healing after myocardial infarction by aggravation of inflammation.

BACKGROUND: Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor fibroblast growth factor-inducible 14 (Fn14) are upregulated after myocardial infarction (MI) in both humans and mice. They modulate inflammation and the extracellular matrix, and could therefore be important for healing and remodeling after MI. However, the function of TWEAK after MI remains poorly defined. METHODS AND RESULTS: Following ligation of the left coronary artery, mice were injected twice per week with a recombinant human serum albumin conjugated variant of TWEAK (HSA-Flag-TWEAK), mimicking the activity of soluble TWEAK. Treatment with HSA-Flag-TWEAK resulted in significantly increased mortality in comparison to the placebo group due to myocardial rupture. Infarct size, extracellular matrix remodeling, and apoptosis rates were not different after MI. However, HSA-Flag-TWEAK treatment increased infiltration of proinflammatory cells into the myocardium. Accordingly, depletion of neutrophils prevented cardiac ruptures without modulating all-cause mortality. CONCLUSION: Treatment of mice with HSA-Flag-TWEAK induces myocardial healing defects after experimental MI. This is mediated by an exaggerated neutrophil infiltration into the myocardium.

Medroxyprogesterone acetate aggravates oxidative stress and left ventricular dysfunction in rats with chronic myocardial infarction.

The role of estrogens during myocardial ischemia has been extensively studied. However, effects of a standard hormone replacement therapy including 17ß-estradiol (E2) combined with medroxyprogesterone acetate (MPA) have not been assessed, and this combination could have contributed to the negative outcomes of the clinical studies on hormone replacement. We hypothesized that adding MPA to an E2 treatment would aggravate chronic heart failure after experimental myocardial infarction (MI). To address this issue, we evaluated clinical signs of heart failure as well as left ventricular (LV) dysfunction and remodeling in ovariectomized rats subjected to chronic MI receiving E2 or E2 plus MPA. After eight weeks MI E2 showed no effects. Adding MPA to E2 aggravated LV remodeling and dysfunction as judged by increased heart weight, elevated myocyte cross-sectional areas, increased elevated left ventricle end diastolic pressure, and decreased LV fractional shortening. Impaired LV function in rats receiving MPA plus E2 was associated with increased cardiac reactive oxygen species generation and myocardial expression levels of NADPH oxidase subunits. These results support the interpretation that adding MPA to an E2 treatment complicates cardiovascular injury damage post-MI and therefore contributes to explain the adverse outcome of prospective clinical studies.

Both estrogen receptor subtypes, alpha and beta, attenuate cardiovascular remodeling in aldosterone salt-treated rats.

Experimental and population-based studies indicate that female gender and estrogens protect the cardiovascular system against aldosterone-induced injury. Understanding the function of estrogens in heart disease requires more precise information on the role of both estrogen receptor (ER) subtypes, ERalpha and ERbeta. Therefore, we determined whether selective activation of ERalpha or of ERbeta would confer redundant, specific, or opposing effects on cardiovascular remodeling in aldosterone salt-treated rats. The ERalpha agonist 16alpha-LE2, the ERbeta agonist 8beta-VE2, and the nonselective estrogen receptor agonist 17beta-estradiol lowered elevated blood pressure, cardiac mass, and cardiac myocyte cross-sectional areas, as well as increased perivascular collagen accumulation and vascular osteopontin expression in ovariectomized rats receiving chronic aldosterone infusion plus a high-salt diet for 8 weeks. Uterus atrophy was prevented by 16alpha-LE2 and 17beta-estradiol but not by 8beta-VE2. Cardiac proteome analyses by 2D gel electrophoresis, mass spectrometry, and peptide sequencing identified specific subsets of proteins involved in cardiac contractility, energy metabolism, cellular stress response and extracellular matrix formation that were regulated in opposite directions by aldosterone salt treatment and by different estrogen receptor agonists. We conclude that activation of either ERalpha or ERbeta protects the cardiovascular system against the detrimental effects of aldosterone salt treatment and confers redundant, as well as specific, effects on cardiac protein expression. Nonfeminizing ERbeta agonists such as 8beta-VE2 have a therapeutic potential in the treatment of hypertensive heart disease.

Tissue-specific effects of the nuclear factor kappaB subunit p50 on myocardial ischemia-reperfusion injury.

Nuclear factor kappaB (NF-kappaB) is a ubiquitous transcription factor activated by various stimuli implicated in ischemia-reperfusion injury. However, the role of NF-kappaB in cardiac ischemia-reperfusion injury has not yet been well defined. Therefore, we investigated reperfusion damage in mice with targeted deletion of the NF-kappaB subunit p50. Electrophoretic mobility shift assays validated NF-kappaB activation in wild-type (WT) but not p50 knockout (KO) mice. KO and WT animals underwent 30 minutes of coronary artery ligation and 24 hours of reperfusion in vivo. Ischemia-reperfusion damage was significantly reduced in the p50 KO when compared with matching WT mice. Although adhesion molecules such as intercellular adhesion molecule were up-regulated in left ventricles of p50 KO animals, fewer neutrophils infiltrated the infarct area, suggesting leukocytes as a potential mediator of the protection observed in the p50 KO. This was confirmed in adoptive transfer experiments: whereas transplantation of KO bone marrow in KO animals sustained the protective effect on ischemia-reperfusion injury, transplantation of WT bone marrow in KO animals abolished it. Thus, deletion of the NF-kappaB subunit p50 reduces ischemia-reperfusion injury in vivo, associated with less neutrophil infiltration. Bone marrow transplantation experiments indicate that impaired NF-kappaB activation in p50 KO leukocytes attenuates cardiac damage.

Role of 5-lipoxygenase in myocardial ischemia-reperfusion injury in mice.

Myocardial ischemia induces 5-lipoxygenase (LOX) translocation and leukotriene production in the heart. Leukotrienes increase inflammatory responses and could thereby aggravate ischemic injury. However, the role of lipoxygenase and leukotrienes in cardiac ischemia/reperfusion damage has not been well defined. Therefore, we tested the effect of ischemia reperfusion in mice with targeted deletion of 5-lipoxygenase, the enzyme converting arachidonic acid in leukotrienes. 5-LOX deficient (KO) and wild-type (WT) mice underwent 30 min of coronary artery ligation and 24 h of reperfusion in vivo. In mice with equivalent area at risk, infarct size was not significantly different between WT and KO mice (infarct/area at risk 61.7+/-3.9 vs. 55.8+/-6.6%, WT vs. KO, P=n.s.). However, neutrophil infiltration as well as tumor necrosis factor expression were increased in 5-lipoxygenase deficient mice. In summary, inhibition of 5-lipoxygenase does not affect cardiac ischemia-reperfusion injury but the post-ischemic inflammatory response.

High-dose 17beta-estradiol treatment prevents development of heart failure post-myocardial infarction in the rat.

OBJECTIVES: Prognosis of heart failure remains poor despite therapeutic advances, such as angiotensin converting enzyme inhibition or beta-receptor blockade. Thus, more effective forms of treatment are urgently needed. Since estrogens have been shown to modulate migration and proliferation of cardiac fibroblasts and to modulate the expression of estrogen receptors of cardiomyocytes we examined whether high-dose estrogen treatment can affect post-myocardial infarction left ventricular remodeling. METHODS: Female rats were treated with 17beta-estradiol (7.5 mg/90 d) or placebo for ten weeks, starting two weeks prior to experimental myocardial infarction. Eight weeks after infarction, in vivo echocardiographic and hemodynamic measurements as well as isolated heart perfusion were performed. RESULTS: In vivo, chronic estrogen treatment almost completely prevented the development of all signs of heart failure that occur in untreated infarcted hearts, such as increased left ventricular diameters (dilatation), reduced fractional shortening (systolic dysfunction) or increased left ventricular end-diastolic pressure (diastolic dysfunction). In vitro, the right- (indicating structural dilatation) and downward (indicating left ventricular dysfunction) shift of left ventricular pressure-volume curves occurring in untreated infarcted hearts was completely prevented by estrogen. CONCLUSIONS: High dose estradiol treatment prevented development of post-MI remodeling, as assessed by in vivo and in vitro parameters of LV dysfunction. Estrogen may hold the potential of becoming a new form of heart failure treatment.However, the mechanisms responsible for this striking and unexpected beneficial action of estrogen in heart failure remain to be elucidated.

Increased mortality and aggravation of heart failure in estrogen receptor-beta knockout mice after myocardial infarction.

BACKGROUND: Lower mortality rates among women with chronic heart failure than among men may depend in part on the action of female sex hormones, especially estrogens. The biological effects of estrogens are mediated by 2 distinct estrogen receptor (ER) subtypes (ERalpha and ERbeta). The present study was undertaken to determine the role of ERbeta in the development of chronic heart failure after experimental myocardial infarction (MI). METHODS AND RESULTS: Female ERbeta null mice (BERKO(Chapel Hill)) and wild-type littermates (WT) were ovariectomized, given 17beta-estradiol, and subjected to chronic anterior MI (MI; BERKO n=31, WT n=30) or sham operation (sham; BERKO n=14, WT n=14). At 8 weeks after MI, both genotypes revealed left ventricular remodeling and impaired contractile function at similar average infarct size (BERKO-MI 32.9+/-5% versus WT-MI 33.0+/-4%); however, BERKO mice showed increased mortality (BERKO-MI 42% versus WT-MI 23%), increased body weight and fluid retention (P<0.01), higher ventricular pro-ANP expression (BERKO-MI 27.9-fold versus sham, WT-MI 5.2-fold versus sham; BERKO-MI versus WT-MI P<0.001), higher atrial natriuretic peptide serum levels, and increased phospholamban expression (P<0.05) compared with WT mice. CONCLUSIONS: Systemic deletion of ERbeta in female mice increases mortality, aggravates clinical and biochemical markers of heart failure, and contributes to impaired expression of Ca(2+)-handling proteins in chronic heart failure after MI. Further studies are required to delineate the relative importance of cardiac and vascular effects of ERbeta and the role of ERalpha in the development of heart failure.

Repetitive postprandial hyperglycemia increases cardiac ischemia/reperfusion injury: prevention by the alpha-glucosidase inhibitor acarbose.

Protective effects of the alpha-glucosidase inhibitor acarbose have been reported for various diabetic complications. In the STOP-NIDDM study, even patients without overt diabetes, but with impaired glucose tolerance, had a reduction in cardiovascular events when treated with acarbose. Therefore, we investigated the effect of repetitive postprandial hyperglycemia on the cardiac ischemia/reperfusion injury in vivo. Mice were treated daily by single applications of placebo, sucrose (4 g/kg body weight), or sucrose + acarbose (10 mg/kg body weight) by gavage for 7 days. Acarbose treatment significantly reduced the sucrose-induced increase in plasma glucose concentration. Subsequently, animals underwent 30 min of ischemia by coronary artery ligation and 24 h of reperfusion in vivo. In the sucrose group, ischemia/reperfusion damage was significantly increased (infarct/area at risk, placebo vs. sucrose, 38.8+/-7.5% vs. 62.2+/-4.8%, P<0.05). This was prevented by acarbose treatment (infarct/area at risk 30.7+/-7.2%). While myocardial inflammation was similar in all groups, oxidative stress as indicated by a significant increase in lipid peroxides was enhanced in the sucrose, but not in the sucrose + acarbose group. In summary, repetitive postprandial hyperglycemia increases ischemia/reperfusion damage. This effect can be prevented by treatment with the alpha-glucosidase inhibitor acarbose.