Sharad Rastogi

Reversal of Chronic Molecular and Cellular Abnormalities Due to Heart Failure by Passive Mechanical Ventricular Containment

Abstract— Passive mechanical containment of failing left ventricle (LV) with the Acorn Cardiac Support Device (CSD) was shown to prevent progressive LV dilation in dogs with heart failure (HF) and increase ejection fraction. To examine possible mechanisms for improved LV function with the CSD, we examined the effect of CSD therapy on the expression of cardiac stretch response proteins, myocyte hypertrophy, sarcoplasmic reticulum Ca2+-ATPase activity and uptake, and mRNA gene expression for myosin heavy chain (MHC) isoforms. HF was produced in 12 dogs by intracoronary microembolization. Six dogs were implanted with the CSD and 6 served as concurrent controls. LV tissue from 6 normal dogs was used for comparison. Compared with normal dogs, untreated HF dogs showed reduced cardiomyocyte contraction and relaxation, upregulation of stretch response proteins (p21ras, c-fos, and p38 &agr;/&bgr; mitogen-activated protein kinase), increased myocyte hypertrophy, reduced SERCA2a activity with unchanged affinity for calcium, reduced proportion of mRNA gene expression for &agr;-MHC, and increased proportion of &bgr;-MHC. Therapy with the CSD was associated with improved cardiomyocyte contraction and relaxation, downregulation of stretch response proteins, attenuation of cardiomyocyte hypertrophy, increased affinity of the pump for calcium, and restoration of &agr;- and &bgr;-MHC isoforms ratio. The results suggest that preventing LV dilation and stretch with the CSD promotes downregulation of stretch response proteins, attenuates myocyte hypertrophy and improves SR calcium cycling. These data offer possible mechanisms for improvement of LV function after CSD therapy.

Cardiac Contractility Modulation Electrical Signals Normalize Activity, Expression, and Phosphorylation of the Na+-Ca2+ Exchanger in Heart Failure

BACKGROUNDnExpression and phosphorylation of the cardiac Na(+)-Ca(2+) exchanger-1 (NCX-1) are up-regulated in heart failure (HF). We examined the effects of chronic cardiac contractility modulation (CCM) therapy on the expression and phosphorylation of NCX-1 and its regulators GATA-4 and FOG-2 in HF dogs.nnnMETHODS AND RESULTSnStudies were performed in LV tissue from 7 CCM-treated HF dogs, 7 untreated HF dogs, and 6 normal (NL) dogs. mRNA expression of NCX-1, GATA-4, and FOG-2 was measured using reverse transcriptase polymerase chain reaction, and protein level was determined by Western blotting. Phosphorylated NCX-1 (P-NCX) was determined using a phosphoprotein enrichment kit. Compared with NL dogs, NCX-1 mRNA and protein expression and GATA-4 mRNA and protein expression increased in untreated HF dogs, whereas FOG-2 expression decreased. Compared with NL dogs, the level of P-NCX-1 normalized to total NCX-1 increased in untreated HF dogs (0.80+/-0.10 vs 0.37+/-0.04; P < .05). CCM therapy normalized NCX-1 expression, GATA-4, and FOG-2 expression, and the ratio of P-NCX-1 to total NCX-1 (0.62+/-0.10).nnnCONCLUSIONnChronic monotherapy with CCM restores expression and phosphorylation of NCX-1. These findings are consistent with previous observations of improved LV function and normalized sarcoplasmic reticulum calcium cycling in the left ventricles of HF dogs treated with CCM therapy.

Long-term Pharmacological Activation of PPARγDoes not Prevent Left Ventricular Remodeling in Dogs with Advanced Heart Failure

BackgroundPeroxisome proliferator-activated receptor γ (PPARγ) activators affect the myocardium through inhibition of inflammatory cytokines and metabolic modulation but their effect in the progression of heart failure is unclear. In the present study, we examined the effects of the PPARγ activator, GW347845 (GW), on the progression of heart failure.Methods and resultsHeart failure was produced in 21 dogs by intracoronary microembolizations to LV ejection fraction (EF) less than 30% and randomized to 3xa0months of therapy with high-dose GW (10xa0mg/Kg daily, nu2009=u20097), low-dose GW (3xa0mg/Kg daily, nu2009=u20097), or no therapy (control, nu2009=u20097). In control dogs, EF significantly decreased (28u2009±u20091 vs. 22u2009±u20091%, pu2009<u20090.001) and end-diastolic volume (EDV) and end-systolic volume (ESV) increased during the 3xa0months of the follow-up period (64u2009±u20094 vs. 76u2009±u20095; pu2009=u20090.003, 46u2009±u20093 vs. 59u2009±u20094xa0ml, pu2009=u20090.002, respectively). In dogs treated with low-dose GW, EDV increased significantly (69u2009±u20094 vs.81u2009±u20095xa0ml, pu2009=u20090.01), whereas ESV remained statistically unchanged (50u2009±u20093 vs. 54u2009±u20093xa0ml, pu2009=u20090.10) resulting in modestly increased ejection fraction (27u2009±u20091 vs. 32u2009±u20093%, pu2009=u20090.05). In dogs treated with high-dose GW, both EDV and ESV increased (72u2009±u20094 vs. 79u2009±u20095xa0ml, pu2009=u20090.04; 53u2009±u20093 vs. 62u2009±u20095xa0ml, pu2009=u20090.04) and EF decreased (26u2009±u20091 vs. 23u2009±u20091%, pu2009=u20090.04) as with control dogs. There was significantly increased myocardial hypertrophy as evidenced by increased LV weight to body weight ratio and myocyte cross-section area in the GW treated animals compared to controls. Compared to control, treatment with GW had no effect on mRNA expression of PPARγ, inflammatory cytokines, stretch response proteins, or transcription factors that may induce hypertrophyConclusionsLong-term PPARγ activation with GW did not prevent progressive LV remodeling in dogs with advanced heart failure.

CVT-4325 Inhibits Myocardial Fatty Acid Uptake and Improves Left Ventricular Systolic Function without Increasing Myocardial Oxygen Consumption in Dogs with Chronic Heart Failure

BackgroundInhibition of myocardial fatty acid oxidation has been suggested as a therapeutic approach for improving cardiac function in chronic heart failure (HF). The novel piperazine derivative CVT-4325 was shown to inhibit fatty acid oxidation in cardiac mitochondria and in isolated perfused rat hearts. In the present study, we tested the hemodynamic and metabolic effects of acute intravenous CVT-4325 in dogs with HF.Methods and resultsHF (LV ejection fraction ≤35%) was created in eight dogs by multiple sequential intracoronary microembolizations. Treatment with CVT-4325 administered intravenously as 0.5xa0mg/kg bolus followed by a continuous infusion of 0.8xa0mg/kg/h for 40xa0min reduced free fatty acid (FFA) uptake (4.51u2009±u20090.96 to 1.65u2009±u20090.32xa0μmols/min, pu2009<u20090.04), coronary blood flow (56u2009±u20093 to 46u2009±u20094xa0ml/min, pu2009<u20090.01), and myocardial oxygen consumption (MVO2) (240u2009±u200923 to 172u2009±u20097xa0μmols/min, pu2009<u20090.03), and increased LV ejection fraction (30u2009±u20092 to 37u2009±u20091%, pu2009<u20090.0001). In the same study, but on a different day, the same dogs were treated with an inactive analogue of CVT-4325 (CVT-2540), and no hemodynamic or metabolic effects were observed.ConclusionsIn dogs with HF, acute intravenous infusion of CVT-4325 reduces FFA uptake and improves LV systolic function without increasing MVO2. The improvement in LV systolic function in the absence of an increase in MVO2 and a lower FFA uptake is consistent with the concept that inhibition of myocardial fatty acid oxidation may be an effective treatment for HF.