Did Clinical Trials in Which Erythropoietin Failed to Reduce Acute Myocardial Infarct Size Miss a Narrow Therapeutic Window?

Background: To test a hypothesis that in negative clinical trials of erythropoietin in patients with acute myocardial infarction (MI) the erythropoietin (rhEPO) could be administered outside narrow therapeutic window. Despite overwhelming evidence of cardioprotective properties of rhEPO in animal studies, the outcomes of recently concluded phase II clinical trials have failed to demonstrate the efficacy of rhEPO in patients with acute MI. However, the time between symptoms onset and rhEPO administration in negative clinical trials was much longer that in successful animal experiments. Methodology/Principal Findings: MI was induced in rats either by a permanent ligation of a descending coronary artery or by a 2-hr occlusion followed by a reperfusion. rhEPO, 3000 IU/kg, was administered intraperitoneally at the time of reperfusion, 4 hrs after beginning of reperfusion, or 6 hrs after permanent occlusion. MI size was measured histologically 24 hrs after coronary occlusion. The area of myocardium at risk was similar among groups. The MI size in untreated rats averaged,42 % of area at risk, or,24 % of left ventricle, and was reduced by more than 50 % (p,0.001) in rats treated with rhEPO at the time of reperfusion. The MI size was not affected by treatment administered 4 hrs after reperfusion or 6 hrs after permanent coronary occlusion. Therefore, our study in a rat experimental model of MI demonstrates that rhEPO administered within 2 hrs of a coronary occlusion effectively reduces MI size, but when rhEPO was administered following a delay similar to that encountered in clinical trials, it had no effect on MI size

SRT1720 improves survival and healthspan of obese mice

Sirt1 is an NAD+-dependent deacetylase that extends lifespan in lower organisms and improves metabolism and delays the onset of age-related diseases in mammals. Here we show that SRT1720, a synthetic compound that was identified for its ability to activate Sirt1 in vitro, extends both mean and maximum lifespan of adult mice fed a high-fat diet. This lifespan extension is accompanied by health benefits including reduced liver steatosis, increased insulin sensitivity, enhanced locomotor activity and normalization of gene expression profiles and markers of inflammation and apoptosis, all in the absence of any observable toxicity. Using a conditional SIRT1 knockout mouse and specific gene knockdowns we show SRT1720 affects mitochondrial respiration in a Sirt1- and PGC-1α-dependent manner. These findings indicate that SRT1720 has long-term benefits and demonstrate for the first time the feasibility of designing novel molecules that are safe and effective in promoting longevity and preventing multiple age-related diseases in mammals

Fumarate is cardioprotective via activation of the Nrf2 antioxidant pathway

The citric acid cycle (CAC) metabolite fumarate has been proposed to be cardioprotective; however, its mechanisms of action remain to be determined. To augment cardiac fumarate levels and to assess fumarate's cardioprotective properties, we generated fumarate hydratase (Fh1) cardiac knockout (KO) mice. These fumarate-replete hearts were robustly protected from ischemia-reperfusion injury (I/R). To compensate for the loss of Fh1 activity, KO hearts maintain ATP levels in part by channeling amino acids into the CAC. In addition, by stabilizing the transcriptional regulator Nrf2, Fh1 KO hearts upregulate protective antioxidant response element genes. Supporting the importance of the latter mechanism, clinically relevant doses of dimethylfumarate upregulated Nrf2 and its target genes, hence protecting control hearts, but failed to similarly protect Nrf2-KO hearts in an in vivo model of myocardial infarction. We propose that clinically established fumarate derivatives activate the Nrf2 pathway and are readily testable cytoprotective agents. © 2012 Elsevier Inc

SRT1720 improves survival and healthspan of obese mice

Sirt1 is an NAD1-dependent deacetylase that extends lifespan in lower organisms and improves metabolism and delays the onset of age-related diseases in mammals. Here we show that SRT1720, a synthetic compound that was identified for its ability to activate Sirt1 in vitro, extends both mean and maximum lifespan of adult mice fed a high-fat diet. This lifespan extension is accompanied by health benefits including reduced liver steatosis, increased insulin sensitivity, enhanced locomotor activity and normalization of gene expression profiles and markers of inflammation and apoptosis, all in the absence of any observable toxicity. Using a conditional SIRT1 knockout mouse and specific gene knockdowns we show SRT1720 affects mitochondrial respiration in a Sirt1- and PGC-1a-dependent manner. These findings indicate that SRT1720 has long-term benefits and demonstrate for the first time the feasibility of designing novel molecules that are safe and effective in promoting longevity and preventing multiple age-related diseases in mammals

Acute hemodynamic effects of erythropoietin do not mediate its cardioprotective properties

Summary Activation of nitric oxide (NO) signaling is considered, at list partially, a mechanistic basis for EPO-induced cardioprotection. Surprisingly, hemodynamic response subsequent to NO activation after EPO administration has never been reported. The objectives of this study were to evaluate the acute hemodynamic and cardiovascular responses to EPO administration, to confirm their NO genesis, and to test the hypothesis that EPO-induced cardioprotection is mediated through cardiovascular changes related to NO activation. In Experiment 1, after 3000 U/kg of rhEPO was administered intravenously to Wistar rats, arterial blood pressure, monitored via indwelling catheter, progressively declined almost immediately until it leveled off 90 minutes after injection at 20% below control level. In Experiment 2 the 25% reduction of mean blood pressure, compared to control group, was observed 2 hours after intravenous injection of either 3000 or 150 U/kg of rhEPO. Detailed pressure–volume loop analyses of cardiac performance (Experiment 3) 2 hours after intravenous injection of human or rat recombinant EPO (3000 U/kg) revealed a significant reduction of systolic function (PRSW was 33% less than control). Reduction of arterial blood pressure and systolic cardiac function in response to rhEPO were blocked in rats pretreated with a non-selective inhibitor of nitric oxide synthase (L-NAME). In Experiment 4, 24 hours after a permanent ligation of a coronary artery, myocardial infarction (MI) measured 26±3.5% of left ventricle in untreated rats. MI in rats treated with 3000 U/kg of rhEPO immediately after coronary ligation was 56% smaller. Pretreatment with L-NAME did not attenuate the beneficial effect of rhEPO on MI size, while MI size in rats treated with L-NAME alone did not differ from control. Therefore, a single injection of rhEPO resulted in a significant, NO-mediated reduction of systemic blood pressure and corresponding reduction of cardiac systolic function. However, EPO-induced protection of myocardium from ischemic damage is not associated with NO activation or NO-mediated hemodynamic responses

Therapeutic Efficacy of a Combination of a ␤1-Adrenoreceptor (AR) Blocker and ␤2-AR Agonist in a Rat Model of Postmyocardial Infarction Dilated Heart Failure Exceeds That of a ␤1-AR Blocker plus Angiotensin-Converting Enzyme Inhibitor □ S

ABSTRACT We had proposed previously a novel combination of ␤2-adrenoreceptor (AR) agonist and ␤1-AR blocker that in the rat model of postmyocardial infarction (MI) dilated cardiomyopathy exceeds the therapeutic effectiveness of either monotherapy. In the present study, we compared that treatment with a combination of ␤1-AR blocker and angiotensin-converting enzyme inhibitor (ACEi), a current standard chronic heart failure (CHF) therapy. Two weeks after coronary artery ligation, rats were divided into groups of similar average MI size, measured by echocardiography, and the following 12-month treatments were initiated: fenoterol (250 g/kg/day), a ␤2-AR agonist, plus metoprolol (100 mg/kg/day), a ␤1-AR blocker (␤1-␤2ϩ); metoprolol plus enalapril (20 mg/kg/day), an ACEi (␤1-ACEi); and a combination of all three drugs (␤1-␤2ϩACEi). These treatment groups were compared with each other and with nontreated (nT) and sham groups. The 12-month mortality was significantly reduced in all treatment groups (44% in ␤1-␤2ϩ, 56% in ␤1-␤2ϩACEi, 59% in ␤1-ACEi versus 81% in nT). Bimonthly echocardiography revealed significant attenuation of the left ventricular (LV) chamber remodeling, LV functional deterioration, and MI expansion in all three treatment groups, but effects were significantly more pronounced when treatment included a ␤2-AR agonist. The results indicated that a combination of ␤1-AR blocker and ␤2-AR agonist is equipotent to a combination of ␤1-AR blocker and ACEi in the treatment of CHF in rats, with the respect to mortality, and exceeds the latter with respect to cardiac remodeling and MI expansion. Thus, this novel therapeutic regimen for CHF warrants detailed clinical investigation

Therapeutic Efficacy of a Combination of a β1-Adrenoreceptor (AR) Blocker and β2-AR Agonist in a Rat Model of Postmyocardial Infarction Dilated Heart Failure Exceeds That of a β1-AR Blocker plus Angiotensin-Converting Enzyme InhibitorS⃞

We had proposed previously a novel combination of β2-adrenoreceptor (AR) agonist and β1-AR blocker that in the rat model of postmyocardial infarction (MI) dilated cardiomyopathy exceeds the therapeutic effectiveness of either monotherapy. In the present study, we compared that treatment with a combination of β1-AR blocker and angiotensin-converting enzyme inhibitor (ACEi), a current standard chronic heart failure (CHF) therapy. Two weeks after coronary artery ligation, rats were divided into groups of similar average MI size, measured by echocardiography, and the following 12-month treatments were initiated: fenoterol (250 μg/kg/day), a β2-AR agonist, plus metoprolol (100 mg/kg/day), a β1-AR blocker (β1-β2+); metoprolol plus enalapril (20 mg/kg/day), an ACEi (β1-ACEi); and a combination of all three drugs (β1-β2+ACEi). These treatment groups were compared with each other and with nontreated (nT) and sham groups. The 12-month mortality was significantly reduced in all treatment groups (44% in β1-β2+, 56% in β1-β2+ACEi, 59% in β1-ACEi versus 81% in nT). Bimonthly echocardiography revealed significant attenuation of the left ventricular (LV) chamber remodeling, LV functional deterioration, and MI expansion in all three treatment groups, but effects were significantly more pronounced when treatment included a β2-AR agonist. The results indicated that a combination of β1-AR blocker and β2-AR agonist is equipotent to a combination of β1-AR blocker and ACEi in the treatment of CHF in rats, with the respect to mortality, and exceeds the latter with respect to cardiac remodeling and MI expansion. Thus, this novel therapeutic regimen for CHF warrants detailed clinical investigation

Clinical trials. Erythropoietin in treatment of acute MI.

<p>Clinical trials. Erythropoietin in treatment of acute MI.</p

Size of myocardial infarction.

<p>Area of myocardium at risk (AAR) and size of myocardial infarction (MI) 24 hrs after permanent occlusion of the left descending coronary artery or after 2 hrs of occlusion followed by 22 hrs of reperfusion. rhEPO is administered at the time of reperfusion (IR-EPO-0 h) or 4 hrs after beginning of reperfusion (IR-EPO-4 h) or 6 hrs after permanent coronary occlusion (MI-EPO-6 h). Data presented as means ± SEM. AAR is presented as % of left ventricle (LV). MI is presented as % of AAR or % of LV. *- p<0.05 vs all other group (Bonferroni post hoc comparison).</p