Erythropoietin Protects the Myocardium Against Reperfusion Injury in Akt Dependent Manner

S84 Journal of Cardiac Failure Vol. 13 No. 6 Suppl. 2007 033 The Role of MK2 in p38 MAPK Induced Cardiac COX-2 Regulation and Heart Failure John M. Streicher1, Shuxun Ren1, Jing Gao1, Haiying Pu1, Yibin Wang1; 1Dept. of Anesthesiology, University of California - Los Angeles, Los Angeles, CA One of the mechanisms implicated in heart failure is the induction of inflammation in heart. COX-2 is a critical regulator of inflammation and its induction was observed in stressed myocardium. However, the regulatory mechanism of COX-2 expression is unclear. Here we investigated the role of the stress-activated kinase p38 and its downstream kinase MK2 in COX-2 expression in cardiomyocytes, as well as in heart failure. We demonstrated that MK2 was necessary and sufficient for COX-2 protein upregulation in cultured neonatal myocytes, using mutated MK2 transfected via adenovirus. However, MK2 was not sufficient to induce COX-2 mRNA, suggesting a protein level regulation of COX-2 by MK2. This finding was confirmed in MEF cells isolated from MK2 WT and KO embryos, which had decreased COX-2 protein in the KO cells with identical mRNA levels. These findings suggest a novel role for MK2 in the protein level regulation of COX-2, and also suggest a role for MK2 in heart failure. In order to investigate this role, we designed a conditional transgenic mouse which has a heart specific promoter driving expression of a floxed GFP cassette, followed by a constitutively active MKK3, which specifically activates p38. Activation of p38 in this manner is known to induce restrictive cardiomyopathy and failure. These mice were then bred with a mouse expressing a conditional tamoxifen sensitive cre recombinase. These mice were also bred with MK2 KO mice to generate two classes of transgenic mice, those with and without MK2. Upon tamoxifen induction, the MK2 WT mice showed significant mortality after 4 days, as well as pathologically remodeled left ventricle and atria, with lung congestion and increased doppler E/A ratio suggesting a loss of ventricular compliance. MK2 KO greatly improved some aspects of this pathology, with reduced mortality and a loss of atrial remodeling, while markers of decreased compliance remained the same. This data indicates that MK2 may have a strong role in p38 induced heart failure. However, MK2 is also likely limited to some aspects of the heart failure response, as not all pathological markers were reversed. The above data shows that MK2 has an important role in the regulation of COX-2, a molecule highly relevant to heart failure, as well as an important role in the induction of specific aspects of heart failure by p38. This research illuminates more of the complex network of signaling involved in heart failure, as well as highlights MK2 as an important future area of research.

035 Attenuation of Left Ventricular Vortex Formation Ability in Heart Failure Li Ching Lee1, Yee-Leng Tan1, Boon Lock Chia1, Kian Keong POH1; 1Cardiac Department, National University Hospital, Singapore, Singapore

Erythropoietin Protects the Myocardium Against Reperfusion Injury in Akt Dependent Manner Dong-Ju Choi1, Tae-Jin Yeon1, Woo-young Chung1, Ceol-Ho Kim1, Eun-Ji Kim1; 1 Cardiovascular Center, Bundang, Seoul National University, Seongnam, Gyeonggi-do, Korea

Background: Congestive heart failure relates to systolic and diastolic abnormalities of the ventricle, resulting in inefficient propagation of blood volume. This may be associated with reduced vortex formation (VF) ability of the left ventricle (LV) during early diastole. We hypothesize that echocardiographic (echo) derived VF index (VFI) correlates with early diastolic tissue Doppler (TD) indices of myocardial function and global myocardial performance index (Tei Index) and that VFI is reduced in heart failure. Method: Echo was performed in 100 normal controls and 140 patients admitted with heart failure (100, systolic and 40, isolated diastolic failure). Patients with significant valvular heart disease were excluded. In addition to biplane LV ejection fraction (EF) and conventional parameters, the Tei Index and TD indices were measured. VFI was obtained from the formula 4 X (1-b)/p X a3 X LVEF where b is the fraction of total transmitral diastolic stroke volume contributed by atrial contraction (assessed by time velocity integral of the mitral E and A waves) and a is the biplane end diastolic volume (EDV) 1/3 divided by mitral annular diameter during early diastole. Results: Mean VFI was 2.75 6 0.7 in control subjects; reduced in heart failure, diastolic, 2.20 6 0.9; systolic, 1.22 6 0.5 (P ! 0.001, Fig 1). It correlated positively with TD early diastolic myocardial velocities (E0 , septal, r 5 0.60; lateral, r 5 0.59, both P ! 0.001); inversely with LV filling pressure (E/E0 septal, r 5 0.44; lateral, r 5 0.44, both P ! 0.001) and the Tei index (r 5 0.57, P ! 0.001, curvilinear relation, Fig 2); and poorly with late diastolic TD velocities (A’, septal, r 5 0.17, P 5 0.007; lateral, r 5 0.16, P 5 0.012). In comparison with age, sex and LVEF-matched controls, VFI remained significantly attenuated in diastolic heart failure patients (2.01 6 0.7 vs 2.74 6 0.8, P 5 0.005). Conclusions: This novel dimensionless index, incorporating LV geometry, systolic and diastolic contributions to fluid dynamics, may provide new mechanistic insights into pathophysiology of heart failure. It correlates well with E0 , index of global myocardial performance and may be a useful adjunct in heart failure diagnosis and management.

Background: Erythropoietin (EPO), known to stimulate the production of red blood and be used to treat anemia in cancer and renal failure, has recently been shown to have a tissue protective effect on diabetic neuropathy, autoimmune encephalomyelitis, and stroke in experimental models. The goal of this study was to determine whether EPO could protect myocardium from ischemia/reperfusion injury. Methods: In anesthetized open-chest male Sprague-Dawley rats, receiving 5,000U/kg of erythropoietin (EPO) intravenously or saline 30 min prior to ischemia, area of necrosis (AN by TTC), the area at risk (AAR by Evans blue), % of infarct (AN/AAR and AN/LV), and Left ventricular hemodynamics by were measured after 30 min of coronary occlusion and 24 hours of reperfusion. LV hemodynamics was accessed by measuring the first derivative of left ventricular pressure (dP/dtMAX and dP/dtmin) and the end-systolic elastance, (Ees) by pressure-volume relationships with IV dobutamine infusion by using high fidelity microcatheter (Millar Mikro-TipÒ). To examine the mechanistic pathways involved in EPO-mediated protection, Akt phosphorylation was estimated 6 and 12 hours after EPO 1njection. Results: EPO administration reduced infarct size by 31% and 37%, respectively (%AAR/LV; control, 69.6 6 6.5% vs. EPO, 65.7 6 5.1%% and (%AN/LV 6 8.8% vs. EPO, 25.2 6 4.3%: p ! 0.01), whereas AAR was not changed in tow group (%AN/AAR; control, 57.5 6 10% vs. EPO, 38.5 6 6.9). EPO also improved ischemia/reperfusion-induced myocardial contractile dysfunction and responsiveness to dobutamine. Basal state LV function and) were increased in EPO (dP/dtMAX; 8418.6 6 1521 vs. 6390 6 978 mmHg/sec and dP/dtmin; -6586.7 6 1128 vs. -5375.6 6 797mmHg/sec, p ! 0.05) and myocardial responsiveness was also enhanced in EPO (Ees; 0.750 6 0.197 vs. 0.454 6 0.138, p ! 0.01). EPO induced phosphorylation of Akt. Conclusions: EPO, administered at the point of reperfusion, reduced infarct size in whole animal model with an Akt dependent manner. These results suggest that EPO may be able to directly protect the myocardium against ischemic-reperfusion injury and suggest the clinical implications in the situations as acute coronary syndrome.

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