Marine n3 polyunsaturated fatty acids enhance resistance to mitochondrial permeability transition in heart failure but do not improve survival.

Mitochondrial dysfunction in heart failure includes greater susceptibility to mitochondrial permeability transition (MPT), which may worsen cardiac function and decrease survival. Treatment with a mixture of the n3 polyunsaturated fatty acids (n3 PUFAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) is beneficial in heart failure patients and increases resistance to MPT in animal models. We assessed whether DHA and EPA have similar effects when given individually, and whether they prolong survival in heart failure. Male δ-sarcoglycan null cardiomyopathic hamsters were untreated or given either DHA, EPA, or a 1:1 mixture of DHA + EPA at 2.1% of energy intake. Treatment did not prolong survival: mean survival was 298 ± 15 days in untreated hamsters and 335 ± 17, 328 ± 14, and 311 ± 15 days with DHA, EPA, and DHA + EPA, respectively (n = 27-32/group). A subgroup of cardiomyopathic hamsters treated for 26 wk had impaired left ventricular function and increased cardiomyocyte apoptosis compared with normal hamsters, which was unaffected by n3 PUFA treatment. Evaluation of oxidative phosphorylation in isolated subsarcolemmal and interfibrillar mitochondria with substrates for complex I or II showed no effect of n3 PUFA treatment. On the other hand, interfibrillar mitochondria from cardiomyopathic hamsters were significantly more sensitive to Ca(2+)-induced MPT, which was completely normalized by treatment with DHA and partially corrected by EPA. In conclusion, treatment with DHA or EPA normalizes Ca(2+)-induced MPT in cardiomyopathic hamsters but does not prolong survival or improve cardiac function. This suggest that greater susceptibility to MPT is not a contributor to cardiac pathology and poor survival in heart failure.

Enhanced resistance to permeability transition in interfibrillar cardiac mitochondria in dogs: effects of aging and long-term aldosterone infusion.

Functional differences between subsarcolemmal and interfibrillar cardiac mitochondria (SSM and IFM) have been observed with aging and pathological conditions in rodents. Results are contradictory, and there is little information from large animal models. We assessed the respiratory function and resistance to mitochondrial permeability transition (MPT) in SSM and IFM from healthy young (1 yr) and old (8 yr) female beagles and in old beagles with hypertension and left ventricular (LV) wall thickening induced by 16 wk of aldosterone infusion. MPT was assessed in SSM and IFM by Ca(2+) retention and swelling. Healthy young and old beagles had similar mitochondrial structure, respiratory function, and Ca(2+)-induced MPT within SSM and IFM subpopulations. On the other hand, oxidative capacity and resistance to Ca(2+)-induced MPT were significantly greater in IFM compared with SSM in all groups. Old beagles treated with aldosterone had greater LV wall thickness and worse diastolic filling but normal LV chamber volume and systolic function. Treatment with aldosterone did not alter mitochondrial respiratory function but accelerated Ca(2+)-induced MPT in SSM, but not IFM, compared with healthy old and young beagles. In conclusion, in a large animal model, oxidative capacity and resistance to MPT were greater in IFM than in SSM. Furthermore, aldosterone infusion increased susceptibility to MPT in SSM, but not IFM. Together this suggests that SSM are less resilient to acute stress than IFM in the healthy heart and are more susceptible to the development of pathology with chronic stress.

Effects of acute intravenous infusion of apelin on left ventricular function in dogs with advanced heart failure.

BACKGROUND: Apelin-13 (APLN) through apelin receptor (APJ) exerts peripheral vasodilatory and potent positive inotropic effects. We examined the effects of exogenous intravenous infusion of APLN on left ventricular (LV) systolic function in dogs with heart failure (HF, LV ejection fraction, EF~30%). METHODS AND RESULTS: Studies were performed in 7 dogs with microembolization-induced HF. Each dog received an intravenous infusion of low dose and high dose APLN followed by washout period. LV end-diastolic volume (EDV), end-systolic volume (ESV) and LV EF were measured at specified time points. APLN protein level was determined in plasma at all time points. mRNA and protein levels of APLN and APJ in LV tissue were also measured in 7 normal (NL) and 7 heart failure (HF) dogs. APLN reduced EDV only at the high dose, significantly reduced ESV and increased EF with both doses. In plasma of HF dogs, APLN levels were reduced significantly compared to NL dogs. APLN treatment in HF dogs significantly increased the plasma APLN levels at both low and high doses. Expression of APLN, but not of APJ, was reduced in LV tissue of HF dogs compared to NL. CONCLUSIONS: Exogenous administration of APLN improved LV systolic function in dogs with advanced HF.

Acute intravenous infusion of an adenosine regulating agent improves left ventricular function in dogs with advanced heart failure.

PURPOSE: GP531 is a second generation adenosine regulating agent (ARA) that increases concentrations of endogenous adenosine, a natural cardioprotective agent, in ischemic/hypoxic tissue. This study examined the effects of acute intravenous infusions of GP531 on left ventricular (LV) systolic and diastolic function in dogs with advanced chronic heart failure (HF) (LV ejection fraction, EF <30 %). METHODS: Six dogs with intracoronary microembolization-induced HF received a constant intravenous infusion of GP531 (10 µg/kg/min) or vehicle (normal saline) for 6 h in random order 1 week apart. Hemodynamic measurements were made at baseline and at 1, 2, 3, 4, 5 and 6 h after initiating drug infusion. Myocardial oxygen consumption (MVO2) was measured at baseline and 4 and 6 h. LV pressure-volume relationship (PVR) was measured at baseline and 6 h. RESULTS: Vehicle infusions had no effect on indexes of LV systolic and diastolic function. GP531 infusion had no effect on heart rate or mean aortic pressure but significantly decreased LV end-diastolic pressure, end-diastolic volume, end-systolic volume and end-diastolic wall stress. GP531 significantly increased LV EF (27 ± 1 at baseline to 34 ± 1 after 6 h of drug infusion, p < 0.05), deceleration time of early mitral inflow velocity and the slope of end-systolic PVR without increasing MVO2. CONCLUSIONS: Results of the study indicate that approaches which increase the local release of adenosine in failing LV myocardium, such as ARAs, have a favorable impact on LV performance. These observations support the continued development of ARA's for the treatment of acute HF syndromes.

Pleiotropic effects of long-term monotherapy with rosuvastatin in dogs with moderate heart failure.

OBJECTIVE: The objective of this study was to investigate the potential pleiotropic effects of rosuvastatin (RSV) in the left ventricular (LV) myocardium of dogs with moderate heart failure (HF). METHODS: LV tissue was obtained from HF dogs randomized to 3 months therapy with low-dose RSV (n = 7), high-dose RSV (n = 7) or to no therapy (Control, n = 7) and from 7 normal dogs. mRNA and protein expression of prohypertrophic mediator NGFI-A binding protein 1 (Nab1), phosphatase and tensin homolog (PTEN), phosphoinositide-3 kinase (PI3K) and mammalian target of rapamycin (mTOR) were measured, as well as that of proinflammatory cytokine interleukin-6 (IL-6), bone marrow-derived stem cell markers cKit and Sca1, vascular endothelial and fibroblast growth factors (VEGF and FGF) and nitric oxide synthase (NOS) isoforms. RESULTS: Nab1, PTEN, PI3K, mTOR and IL-6 increased in the controls. High-dose RSV reduced expression of Nab1, PTEN, PI3K, mTOR and IL-6 to near-normal levels. cKit and Sca1 significantly increased, while VEGF and FGF decreased in the controls compared to the normal dogs. RSV therapy further increased expression of cKit, Sca1, VEGF and FGF. High-dose RSV normalized the expression of NOS isoforms. CONCLUSION: These pleiotropic effects of RSV may account, in part, for the observed beneficial effect of RSV on LV function and structural remodeling.

Myocardial transfection with naked DNA plasmid encoding hepatocyte growth factor prevents the progression of heart failure in dogs.

This study examined the effects of localized intramyocardial injections of hepatocyte growth factor (HGF) naked DNA plasmid on the progression of left ventricular (LV) dysfunction and remodeling in dogs with moderate heart failure (HF). Twenty-one dogs with intracoronary microembolization-induced HF [LV ejection fraction (EF) = 35-40%] were randomized into three treatment groups, namely, high-dose HGF plasmid (4.0 mg, n = 7), low-dose HGF plasmid (0.4 mg, n = 7), and sham-operated controls treated with normal saline (n = 7). A total of 10-15 injections of HGF plasmid or saline were made directly into the anterior wall of LV. LV EF and end-systolic volume (ESV) were measured before randomization (pretreatment) and at the end of 3 mo of follow-up (posttreatment). Treatment effect (Δ) was calculated as the change from pre- to posttreatment. Protein expression of sarcoplasmic reticulum (SR) Ca(2+)-cycling proteins was determined in LV tissue obtained from the sites of HGF injection and remote areas. Low-dose HGF attenuated the decline in EF (ΔEF: -3 ± 1 vs. -8 ± 1%, P < 0.05) and the increase in ESV (ΔESV: 6 ± 2 vs. 10 ± 1 ml, P < 0.05) seen in control sham-operated dogs, whereas high-dose HGF significantly increased EF (ΔEF: 4 ± 1 vs. -8 ± 1%, P < 0.05) and prevented the increase in ΔESV (ESV: -1 ± 1 vs. 10 ± 1 ml, P < 0.05) compared with control dogs. Treatment with high- and low-dose HGF improved the expression of the SR Ca(2+)-cycling proteins compared with controls. In conclusion, regional intramyocardial injections of HGF naked DNA plasmid improve regional and global LV function and prevent progressive LV remodeling.

Vagus nerve stimulation in experimental heart failure.

Chronic heart failure (HF) is associated with autonomic dysregulation characterized by a sustained increase in sympathetic drive and by withdrawal of parasympathetic activity. Sympathetic overdrive and increased heart rate are predictors of poor long-term outcome in patients with HF. Considerable evidence exists that supports the use of pharmacologic agents that partially inhibit sympathetic activity as effective long-term therapy for patients with HF; the classic example is the wide use of selective and non-selective beta-adrenergic receptor blockers. In contrast, modulation of parasympathetic activation as potential therapy for HF has received only limited attention over the years given its complex cardiovascular effects. In this article, we review the results of recent experimental animal studies that provide support for the possible use of electrical Vagus nerve stimulation (VNS) as a long-term therapy for the treatment of chronic HF. In addition to exploring the effects of chronic VNS on left ventricular (LV) function, the review will also address the effects of VNS on potential modifiers of the HF state that include cytokine production and nitric oxide elaboration. Finally, we will briefly review other nerve stimulation approaches which is also currently under investigation as potential therapeutic modalities for treating chronic HF.

Effects of adiponectin deficiency on structural and metabolic remodeling in mice subjected to pressure overload.

Recent data suggest adiponectin, an adipocyte-derived hormone, affects development of heart failure in response to hypertension. Severe short-term pressure overload [1-3 wk of transverse aortic constriction (TAC)] in adiponectin(-/-) mice causes greater left ventricle (LV) hypertrophy than in wild-type (WT) mice, but conflicting results are reported regarding LV remodeling, with either increased or decreased LV end diastolic volume compared with WT mice. Here we assessed the effects of prolonged TAC on LV hypertrophy and remodeling. WT and adiponectin(-/-) mice were subjected to TAC and maintained for 6 wk. Regardless of strain, TAC induced similar LV hypertrophy ( approximately 70%) and upregulation of mRNA for heart failure marker genes. However, LV chamber size was dramatically different, with classic LV dilation in WT TAC mice but concentric LV hypertrophy in adiponectin(-/-) mice. LV end diastolic and systolic volumes were lower and ejection fraction higher in adiponectin(-/-) TAC mice compared with WT, indicating that adiponectin deletion prevented LV remodeling and deterioration in systolic function. The activities of marker enzymes of mitochondrial oxidative capacity were reduced in WT TAC mice by approximately 35%, whereas enzyme activities were maintained at sham levels in adiponectin(-/-) TAC mice. In conclusion, in WT mice, long-term pressure overload caused dilated LV hypertrophy accompanied by decreased activity of mitochondrial oxidative enzymes. Although adiponectin deletion did not affect LV hypertrophy, it prevented LV chamber remodeling and preserved mitochondrial oxidative capacity, suggesting that adiponectin plays a permissive role in mediating changes in cardiac structure and metabolism in response to pressure overload.

Cardiac contractility modulation electrical signals normalize activity, expression, and phosphorylation of the Na+-Ca2+ exchanger in heart failure.

BACKGROUND: Expression 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. METHODS AND RESULTS: Studies 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). CONCLUSION: Chronic 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.

Activation of endothelial cells in conduit veins of dogs with heart failure and veins of normal dogs after vascular stretch by acute volume loading.

BACKGROUND: The venous endothelium is a key regulator of central blood volume, organ perfusion, and hemostasis in heart failure (HF). We previously reported activation of the inflammatory/oxidative program in venous endothelial cells collected from decompensated HF patients. The underlying causes are unknown. We tested the hypothesis that the pro-inflammatory state of HF and vascular strain associated with congestion can activate the endothelial inflammatory/oxidative and hemostatic programs. METHODS AND RESULTS: We studied 6 normal (NL) dogs (left ventricular ejection fraction [LVEF] >50%, central venous pressure [CVP] = 8 +/- 2 mm Hg) and 6 dogs with HF (LVEF approximately 30%, CVP 8 +/- 2 mm Hg) produced by intracoronary microembolizations. Normal dogs were studied at baseline and 1 hour after fluid load to a target CVP >or=20 mm Hg. Endothelial cells were scraped from jugular veins; mRNA expression was analyzed by reverse transcription polymerase chain reaction. The endothelial inflammatory/oxidative and hemostatic programs were significantly activated in HF dogs compared with NL. In NL dogs, fluid load significantly activated the endothelial inflammatory/oxidative and hemostatic programs, and, concurrently, caused a significant increase in plasma neurohumoral indices to levels that approached those of HF dogs. CONCLUSIONS: The pro-inflammatory state of HF and vascular strain associated with congestion can both activate venous endothelial cells in dogs in a manner consistent with that seen in HF patients.

Acute left ventricular unloading in dogs with chronic heart failure: continuous aortic flow augmentation versus intra-aortic balloon pumping.

BACKGROUND: Continuous aortic flow augmentation (CAFA) therapy with the Cancion System (Orqis Medical, Inc) was shown to effectively unload the left ventricle in dogs with chronic heart failure (HF). This study compared the extent of acute left ventricular (LV) unloading elicited by CAFA to that elicited by intra-aortic balloon counterpulsation (IABP) in normotensive dogs with coronary microembolization-induced HF. METHODS AND RESULTS: Seven HF dogs were studied with both CAFA and IABP in random order and 1 week apart. In both instances, active therapy was maintained for 4 hours. The Cancion system was positioned using a dual femoral approach configuration with a constant pump flow of 250 mL/min. In all dogs and with both devices, LV end-diastolic pressure (EDP), LV end-systolic volume (ESV), and LV ejection fraction (EF) were measured at baseline and at 2 and 4 hours after instituting CAFA or IABP. Plasma samples obtained at the end of 4 hours of therapy were used to measure a host of circulating biomarkers that included neurohormones, cytokines, and A-type and B-type natriuretic peptides. IABP had no significant effects on LVEDP, LVESV, and LVEF. In contrast, CAFA significantly decreased LVEDP and LVESV and increased LVEF. Compared with IABP, CAFA was accompanied by significant improvements in circulating levels of neurohormones, cytokines, and natriuretic peptides. CONCLUSIONS: The results indicate that CAFA is more effective than IABP in achieving acute global LV unloading in dogs with chronic HF not complicated by ongoing myocardial ischemia or cardiogenic shock.

Atenolol is inferior to metoprolol in improving left ventricular function and preventing ventricular remodeling in dogs with heart failure.

OBJECTIVES: beta-Blockers are standard therapy for patients with heart failure (HF). This study compared the effects of chronic monotherapy with 2 different beta(1)-selective adrenoceptor blockers, namely atenolol and metoprolol succinate, on left ventricular (LV) function and remodeling in dogs with coronary microembolization-induced HF [LV ejection fraction (EF) 30-40%]. METHODS: Twenty HF dogs were randomized to 3 months of therapy with atenolol (50 mg once daily, n = 6), metoprolol succinate (100 mg, once daily, n = 7) or to no therapy (control, n = 7). LV EF and volumes were measured before initiating therapy and after 3 months of therapy. The change (Delta) in EF and volumes between measurements before and after therapy was calculated and compared among study groups. RESULTS: In controls, EF decreased and end-systolic volume increased. Atenolol prevented the decrease in EF and the increase in ESV. In contrast, metoprolol succinate significantly increased EF and decreased end-systolic volume. DeltaEF was significantly higher and Deltaend-systolic volume significantly lower in metoprolol succinate-treated dogs compared to atenolol-treated dogs (EF: 6.0 +/- 0.86% vs. 0.8 +/- 0.85%, p < 0.05; end-systolic volume: -4.3 +/- 0.81 ml vs. -1 +/- 0.52 ml, p <0.05). CONCLUSIONS: In HF dogs, chronic therapy with atenolol does not elicit the same LV function and remodeling benefits as those achieved with metoprolol succinate.

Effects of chronic therapy with cardiac contractility modulation electrical signals on cytoskeletal proteins and matrix metalloproteinases in dogs with heart failure.

OBJECTIVES: Therapy with cardiac contractility modulation (CCM) electrical signals delivered to left ventricular (LV) muscle during the absolute refractory period improves LV systolic and diastolic function in dogs with heart failure (HF). This study examined the effects of CCM therapy on mRNA and protein expression of cytoskeletal proteins, matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) in the LV myocardium of dogs with HF. METHODS: HF was produced in 14 dogs by coronary microembolizations. Dogs were randomized to 3 months of CCM therapy (n = 7) or to sham-operated controls (n = 7). LV tissue from 6 normal (NL) dogs was used for comparison. mRNA expression was measured using reverse-transcriptase polymerase chain reaction and protein expression using Western blots. RESULTS: Compared with NL dogs, controls showed upregulation of mRNA and protein expression of the cytoskeletal proteins tubulin and fibronectin and MMP-1, MMP-2 and MMP-9, and downregulation of the cytoskeletal protein titin. Normalized expression of all these genes and proteins was seen after CCM therapy. No differences in expression of TIMP-1 and TIMP-2 were observed among groups. CONCLUSIONS: CCM therapy normalizes expression of key cytoskeletal proteins and MMPs and may partly explain the improvement in LV function seen in HF following CCM therapy.

Reversal of chronic molecular and cellular abnormalities due to heart failure by passive mechanical ventricular containment.

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 alpha/beta mitogen-activated protein kinase), increased myocyte hypertrophy, reduced SERCA2a activity with unchanged affinity for calcium, reduced proportion of mRNA gene expression for alpha-MHC, and increased proportion of beta-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 alpha- and beta-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.

Elevated levels of protein phosphatase 1 and phosphatase 2A may contribute to cardiac dysfunction in diabetes.

Although protein phosphorylation and dephosphorylation are known to regulate the activities of different enzymes, sufficient information on the role of dephosphorylation in cardiac function is not available. Since protein phosphatases mediate dephosphorylation, it is possible that cardiac dysfunction induced by diabetes may be due to alterations in the activities of these enzymes. We therefore determined cardiac protein phosphatase activity as well as protein contents of phosphatase 1 and phosphatase 2A in diabetic animals. For this purpose, rats were made diabetic by administering a single intravenous injection of streptozotocin (65 mg/kg body weight) and hearts were examined after 1, 2, 3, 4 and 8 weeks. Some of the 4-week diabetic animals received subcutaneous injections of insulin (3 U/day) for a further period of 4 weeks. Cardiac dysfunction was evident after 2 weeks of inducing diabetes and deteriorated further with time. A significant increase in protein phosphatase activity appeared after 1 week and persisted until 8 weeks. Increased protein phosphatase activity in the diabetic heart was associated with a corresponding increase in the protein contents of both phosphatase 1 and phosphatase 2A. Insulin treatment partly prevented the changes observed in diabetic animals. The results suggest that increased protein phosphatase activities and subsequent enhanced protein dephosphorylation may play a role in diabetes-induced cardiac dysfunction.

Heart rate reduction with ivabradine improves left ventricular function and reverses multiple pathological maladaptations in dogs with chronic heart failure.

PURPOSE: We tested the hypothesis that heart rate (HR) reduction with ivabradine (IVA) leads to reversal of structural, biochemical, and molecular maladaptations characteristic of the heart failure (HF) state. HR reduction with IVA has been shown to improve left ventricular (LV) systolic function and clinical outcome in patients with HF. METHODS: Studies were performed in 16 HF dogs produced by intracoronary microembolizations [LV ejection fraction (EF) ~35%]. Dogs were randomized to 3-month oral therapy with IVA (30 mg Bid, n = 8) or to no therapy (Control, n = 8). LV tissue was obtained from all dogs at the end of therapy and used for molecular, biochemical, and histological studies. RESULTS: Average 24-h ambulatory Holter monitoring showed a significant decrease of HR in IVA-treated dogs compared with controls. Compared with pre-therapy, LV EF decreased at 3 months in controls (36 ± 1 vs. 32 ± 2%, P < 0.05) but increased significantly with IVA (40 ± 3 vs. 35 ± 3%, P < 0.05). Treatment with IVA was associated with (i) improved LV diastolic function; (ii) increased sarcoplasmic reticulum Ca2+ uptake and ATPase activity; (iii) decreased plasma levels of vasoactive neurohormones, natriuretic peptides, and pro-inflammatory cytokines; (iv) normalization of messenger RNA gene expression of multiple signalling pathways; and (v) reduced cardiomyocyte apoptosis and hypertrophy. CONCLUSION: In dogs with HF, HR reduction with IVA reversed many of the structural, biochemical, and molecular maladaptations characteristic of HF. The findings support the concept that HR reduction in HF can elicit benefits, albeit indirect, on a host of maladaptations implicated in the progressive worsening of the HF state.

Chronic therapy with a partial adenosine A1-receptor agonist improves left ventricular function and remodeling in dogs with advanced heart failure.

BACKGROUND: Adenosine elicits cardioprotection through A1-receptor activation. Therapy with adenosine A1-receptor agonists, however, is limited by undesirable actions of full agonism, such as bradycardia. This study examined the effects of capadenoson (CAP), a partial adenosine A1-receptor agonist, on left ventricular (LV) function and remodeling in dogs with heart failure. METHODS AND RESULTS: Twelve dogs with microembolization-induced heart failure were randomized to 12 weeks oral therapy with CAP (7.5 mg BID; n=6) or to no therapy (control; n=6). LV end-diastolic and end-systolic volumes, ejection fraction, plasma norepinephrine, and n-terminal pro-brain natriuretic peptide were measured before (pre) and 1 and 12 weeks after therapy (post). LV tissue obtained at post was used to assess volume fraction of interstitial fibrosis, sarcoplasmic reticulum calcium ATPase-2a activity, expression of mitochondria uncoupling proteins (UCP) and glucose transporters (GLUT). In controls, end-diastolic and end-systolic volumes increased and ejection fraction decreased significantly from pre to post (ejection fraction, 30±2 versus 27±1%; P<0.05). In CAP-treated dogs, end-diastolic volume was unchanged; ejection fraction increased significantly after 1 week (36±2 versus 27±2%; P<0.05) with a further increase at post (39±2%; P<0.05), whereas end-systolic volume decreased. CAP significantly decreased volume fraction of interstitial fibrosis, normalized sarcoplasmic reticulum calcium ATPase-2a activity and expression of UCP-2 and UCP-3, and GLUT-1 and GLUT-2 and significantly decreased plasma norepinephrine and n-terminal pro-brain natriuretic peptide. CONCLUSIONS: In heart failure dogs, CAP improves LV function and prevents progressive remodeling. Improvement of LV systolic function occurs early after initiating therapy. The results support development of partial adenosine A1-receptor agonists for the treatment of chronic heart failure.

Augmentation of left ventricular wall thickness with alginate hydrogel implants improves left ventricular function and prevents progressive remodeling in dogs with chronic heart failure.

OBJECTIVES: The study tested the hypothesis that augmentation of the left ventricular (LV) wall thickness with direct intramyocardial injections of alginate hydrogel implants (AHI) reduces LV cavity size, restores LV shape, and improves LV function in dogs with heart failure (HF). BACKGROUND: Progressive LV dysfunction, enlargement, and chamber sphericity are features of HF associated with increased mortality and morbidity. METHODS: Studies were performed in 14 dogs with HF produced by intracoronary microembolizations (LV ejection fraction [EF] <30%). Dogs were randomized to AHI treatment (n = 8) or to sham-operated control (n = 6). During an open-chest procedure, dogs received either intramyocardial injections of 0.25 to 0.35 ml of alginate hydrogel (Algisyl-LVR, LoneStar Heart, Inc., Laguna Hills, California) or saline. Seven injections were made ∼ 1.0 to 1.5 cm apart (total volume 1.8 to 2.1 ml) along the circumference of the LV free wall halfway between the apex and base starting from the anteroseptal groove and ending at the posteroseptal groove. Hemodynamic and ventriculographic measurements were made before treatment (PRE) and repeated post-surgery for up to 17 weeks (POST). RESULTS: Compared to control, AHI significantly reduced LV end-diastolic and end-systolic volumes and improved LV sphericity. AHI treatment significantly increased EF (26 ± 0.4% at PRE to 31 ± 0.4% at POST; p < 0.05) compared to the decreased EF seen in control dogs (27 ± 0.3% at PRE to 24 ± 1.3% at POST; p < 0.05). AHI treatment was well tolerated and was not associated with increased LV diastolic stiffness. CONCLUSIONS: In HF dogs, circumferential augmentation of LV wall thickness with AHI improves LV structure and function. The results support continued development of AHI for the treatment of patients with advanced HF.

Association of genetic variation with gene expression and protein abundance within the natriuretic peptide pathway.

The natriuretic peptide (NP) system is a critical physiologic pathway in heart failure with wide individual variability in functioning. We investigated the genetic component by testing the association of single nucleotide polymorphisms (SNP) with RNA and protein expression. Samples of DNA, RNA, and tissue from human kidney (n = 103) underwent genotyping, RT-PCR, and protein quantitation (in lysates), for four candidate genes [NP receptor 1 (NPR1), NPR2, and NPR3 and membrane metalloendopeptidase]. The association of genetic variation with expression was tested using linear regression for individual SNPs, and a principal components (PC) method for overall gene variation. Eleven SNPs in NPR2 were significantly associated with protein expression (false discovery rate ≤0.05), but not RNA quantity. RNA and protein quantity correlated poorly with each other. The PC analysis showed only NPR2 as significant. Assessment of the clinical impact of NPR2 genetic variation is needed.

Vagus nerve stimulation improves left ventricular function in a canine model of chronic heart failure.

AIMS: Autonomic dysfunction is a feature of chronic heart failure (HF). This study tested the hypothesis that chronic open-loop electrical vagus nerve stimulation (VNS) improves LV structure and function in canines with chronic HF. METHODS AND RESULTS: Twenty-six canines with HF (EF ∼35%) produced by intracoronary microembolizations were implanted with a bipolar cuff electrode around the right cervical vagus nerve and connected to an implantable pulse generator. The canines were enrolled in Control (n = 7) vs. VNS therapy (n = 7) or a crossover study, with crossovers occurring at 3 months (C × VNS, n = 6; VNS × C, n = 6). After 6 months of VNS, LVEF and LV end-systolic volume (ESV) were significantly improved compared with Control (ΔEF Control -4.6 ± 0.9% vs. VNS 6.0 ± 1.6%, P < 0.001) and (ΔESV Control 8.3 ± 1.8 mL vs. VNS -3.0 ± 2.3 mL, P = 0.002. Plasma and tissue biomarkers were also improved. In the crossover study, VNS also resulted in a significant improvement in EF and ESV compared with Control (ΔEF Control -2.3 ± 0.65% vs. VNS 6.7 ± 1.1 mL, P < 0.001 and ΔESV Control 3.2 ± 1.2 mL vs. VNS -4.0 ± 0.9 mL, P < 0.001). Initiation of therapy in the Control group at 3 months resulted in a significant improvement in EF (Control -4.7 ± 1.4% vs. VNS 3.7 ± 0.74%, P < 0.001) and ESV (Control 1.5 ± 1.2 mL vs. NS -5.5 ± 1.6 mL, P = 0.003) by 6 months. CONCLUSIONS: In canines with HF, long-term, open-looped low levels of VNS therapy improves LV systolic function, prevents progressive LV enlargement, and improves biomarkers of HF when compared with control animals that did not receive therapy.