Failing Left Ventricles Have an Enhanced Post-Stimulation Potentiation Despite Their Impaired Force Frequency Relationship.

The left ventricular contractile force (LV dP/dtmax) of patients with left ventricular systolic dysfunction does not increase effectively with an increase in heart rate. In other words, their force-frequency relationship (FFR) is impaired. However, it is unknown whether a longer coupling interval subsequent to tachycardia causes a stronger contraction (poststimulation potentiation, PSP) in a rate-dependent manner.In 16 patients with idiopathic dilated cardiomyopathy (DCM) (48 ± 2 years old, LVEF 30 ± 10%) and 6 control patients (58 ± 4 years old, LVEF 70 ± 7%), FFR was assessed by right atrial pacing using a micro-manometer-tipped catheter. At each pacing rate, the increase of LV dP/dtmax over basal LV dP/dt (ΔFFR) and the increase of LV dP/dtmax of the first beat after pacing cessation over LV dP/dtmax during pacing (ΔPSP) were evaluated.Patients with DCM had smaller LV dP/dtmax at baseline (872 ± 251 versus 1370 ± 123 mmHg/second, P = 0.0002) and developed smaller ΔFFR (eg, at 120/minute, 77 ± 143 versus 331 ± 131 mmHg/second, P = 0.0011). In contrast, they showed a rate-dependent increase of LV dP/dtmax of PSP and had greater ΔPSP (eg, at 120/minute, 294 ± 173 versus -152 ± 131 mmHg/second, P < 0.0001).Failing left ventricles develop little contractile force during tachycardia despite their rate-dependent enhancement in post-stimulation potentiation, suggesting that refractoriness of contractile force underlies impaired FFR.

Mechanical alternans in human idiopathic dilated cardiomyopathy is caused with impaired force-frequency relationship and enhanced poststimulation potentiation.

Mechanical alternans (MA) is frequently observed in patients with heart failure, and is a predictor of cardiac events. However, there have been controversies regarding the conditions and mechanisms of MA. To clarify heart rate-dependent contractile properties related to MA, we performed incremental right atrial pacing in 17 idiopathic dilated cardiomyopathy (DCM) patients and in six control patients. The maximal increase in left ventricular dP/dt during pacing-induced tachycardia was assessed as the force gain in the force-frequency relationship (FG-FFR), and the maximal increase in left ventricular dP/dt of the first post-pacing beats was examined as the force gain in poststimulation potentiation (FG-PSP). As a result, MA was induced in 9 DCM patients (DCM MA(+)) but not in the other 8 DCM patients (DCM MA(-)), and not in any of the control patients. DCM MA(+) had significantly lower FG-FFR (34.7 ± 40.9 vs 159.4 ± 103.9 mmHg/s, P = 0.0091) and higher FG-PSP (500.0 ± 96.8 vs 321.9 ± 94.9 mmHg/s, P = 0.0017), and accordingly a wider gap between FG-PSP and FG-FFR (465.3 ± 119.4 vs 162.5 ± 123.6 mmHg/s, P = 0.0001) than DCM MA(-) patients. These characteristics of DCM MA(+) showed clear contrasts to those of the control patients. In conclusion, MA is caused with an impaired force-frequency relationship despite significant poststimulation potentiation, suggesting that MA reflects ineffective utilization of the potentiated intrinsic force during tachycardia.

Inhibition of cardiac oxidative and endoplasmic reticulum stress-mediated apoptosis by curcumin treatment contributes to protection against acute myocarditis.

Curcumin is used anecdotally as an herb in traditional Indian and Chinese medicine. In the present study, the effects and possible mechanism of curcumin in experimental autoimmune myocarditis (EAM) rats were further investigated. They were divided randomly into a treatment and vehicle group, and orally administrated curcumin (50 mg/kg/day) and 1% gum arabic, respectively, for 3 weeks after myosin injection. The results showed that curcumin significantly suppressed the myocardial protein expression of inducible nitric oxide synthase (iNOS) and the catalytic subunit of nicotinamide adenine dinucleotide phosphate reduced (NADPH) oxidase. In addition, curcumin significantly decreased myocardial endoplasmic reticulum (ER) stress signaling proteins and improved cardiac function. Furthermore, curcumin significantly decreased the key regulators or inducers of apoptosis. In summary, our results indicate that curcumin has the potential to protect EAM by modulating cardiac oxidative and ER stress-mediated apoptosis, and provides a novel therapeutic strategy for autoimmune myocarditis.

The antioxidant edaravone attenuates ER-stress-mediated cardiac apoptosis and dysfunction in rats with autoimmune myocarditis.

Experimental autoimmune myocarditis (EAM) is mediated by myocardial infiltration by myosin-specific T-cells secreting inflammatory cytokines. In this study, rat models of EAM were prepared by injection with porcine cardiac myosin. One week after immunization, edaravone was administered intraperitoneally at 3 or 10 mg/kg/day to rats for 2 weeks. Cardiac function was measured by haemodynamic and echocardiographic studies and TUNEL assay was performed. Left ventricular (LV) expression of NADPH oxidase sub-units (p47(phox) and p67(phox)), pro-inflammatory cytokines (TNF-alpha), endoplasmic reticulum (ER) stress signalling proteins (GRP78, caspase-12 and GADD153) and mitogen-activated protein kinase (MAPK) family proteins (phospho-p38 MAPK and phospho-JNK) were measured by western blotting. Edaravone improved LV function in a dose-dependent manner. Central venous pressure was significantly low and LV ejection fraction and fractional shortening was significantly high in edaravone groups compared with those in the vehicle group. In addition, edaravone treatment down-regulated LV expressions of p47(phox), TNF-alpha, GADD153, phospho-p38 MAPK and phospho-JNK. Furthermore, the LV expressions of p67(phox), GRP78, caspase-12 and TUNEL-positive cells of rats with EAM treated with edaravone were significantly low compared with those of the vehicle group. These findings suggest that edaravone ameliorated the progression of EAM by inhibiting oxidative and ER stress and, subsequently, cardiac apoptosis.

Selection of diverse and clinically relevant integrase inhibitor-resistant human immunodeficiency virus type 1 mutants.

Resistance passage studies were conducted with five INIs (integrase inhibitors) that have been tested in clinical trials to date: a new naphthyridinone-type INI S/GSK-364735, raltegravir, elvitegravir, L-870,810 and S-1360. In establishing the passage system and starting from concentrations several fold above the EC(50) value, resistance mutations against S-1360 and related diketoacid-type compounds could be isolated from infected MT-2 cell cultures from day 14 to 28. Q148R and F121Y were the two main pathways of resistance to S/GSK-364735. Q148R/K and N155H, which were found in patients failing raltegravir treatment in Phase IIb studies, were observed during passage with raltegravir with this method. The fold resistance of 40 mutant molecular clones versus wild type virus was compared with these five INIs. The overall resistance pattern of S/GSK-364735 was similar to that of raltegravir and other INIs. However, different fold resistances of particular mutations were noted among different INIs, reflecting a potential to develop INIs with distinctly different resistant profiles.

Comparative effects of pranidipine with amlodipine in rats with heart failure.

The aim of the present study was to compare the cardioprotective properties of long-acting calcium channel antagonist pranidipine with amlodipine in rat model of heart failure induced by autoimmune myocarditis. Twenty-eight days after immunization the surviving rats were randomized for the oral administration of low-dose amlodipine (1 mg/kg/day), high-dose amlodipine (5 mg/kg/day), pranidipine (0.3 mg/kg/day) or vehicle (0.5% methylcellulose). After oral administration for 1 month, the animals underwent echocardiography and hemodynamic analysis. Histopathology, immunohistochemistry, and Western immunoblotting were carried out in the heart samples. Both pranidipine and high-dose amlodipine increased survival rate. Although the heart rate did not differ among the four groups, left ventricular end-diastolic pressure was significantly decreased and +/-dP/dt was increased in the pranidipine- and high-dose amlodipine-treated rats, but not in low-dose amlodipine-treated rats. In comparison to amlodipine treatment, pranidipine treatment significantly reduced myocyte size and central venous pressure. Furthermore, both pranidipine and high-dose amlodipine treatment significantly reduced myocardial protein levels of atrial natriuretic peptide and inducible nitric oxide synthase, whereas pranidipine only significantly decreased tumor necrosis factor-alpha, and improved sarcoplasmic reticulum Ca2+ ATPase2 protein levels. We conclude that pranidipine ameliorates the progression of left ventricular dysfunction and cardiac remodeling in rats with heart failure after autoimmune myocarditis in a lower dose when compared to amlodipine and which may be a clinically potential therapeutic agent for the treatment of heart failure.

A case-control pilot study on n-3 polyunsaturated fatty acid as a negative risk factor for myocardial infarction.

The relation between n-3 polyunsaturated fatty acid (PUFA) and nonfatal myocardial infarction is still controversial. A multicenter case-control pilot study on n-3 PUFA as a negative risk factor for myocardial infarction was performed in Niigata prefecture. Seventy-three patients with acute myocardial infarction (AMI) and age and gender matched controls (n = 84) were recruited. Serum leptin levels were significantly higher in patients with AMI than the controls (8.1 +/- 6.7 ng/mL versus 5.8 +/- 3.7 ng/mL, P < 0.01), and serum high-density lipoprotein cholesterol (HDLc) levels were significantly lower in patients with AMI than the controls (46 +/- 10.5 mg/dL versus 60 +/- 15 mg/dL, P < 0.00001). Statistically significant differences were preserved in leptin and HDLc when the data were analyzed separately by gender. Serum levels (%weight) of linolenic acid (C18:3:n3), eicosapentaenoic acid (C20:5:n3), docosapentaenoic acid (C22:5:n3), and total n-3 PUFA were significantly lower in patients with AMI than the control group (P < 0.000001, < 0.05, < 0.05, < 0.05, respectively). The serum n-3 PUFA/saturated fatty acid (SF) ratio and n-3 PUFA/n-9 monounsaturated fatty acid (MUFA) ratio were significantly lower in patients with AMI than the controls (P < 0.05 and < 0.01, respectively). When the subjects were separated into two categories according to an n-3/n-6 PUFA ratio below 0.3 or above 0.3, patients with AMI were more frequently in the former while the controls were more frequently in the latter (P < 0.05). N-3 PUFA may be a negative risk factor for AMI. The results suggest leptin is a risk factor for AMI irrespective of ethnicity and gender.

Effects of eplerenone, a selective aldosterone blocker, on the progression of left ventricular dysfunction and remodeling in rats with dilated cardiomyopathy.

Aldosterone blockade reduces morbidity and mortality in patients with heart failure. We studied the effects of eplerenone, a novel aldosterone blocker, on the progression of left ventricular dysfunction and remodeling in rats with dilated cardiomyopathy after autoimmune myocarditis. Twenty-eight days after immunization, the surviving Lewis rats were randomized to 1 month's oral treatment with low-dose eplerenone (group L), high-dose eplerenone (group H) or vehicle (group V). Five of 15 (33%) rats in group V and 3 of 15 (20%) rats in group L died during the course of treatment. High-dose eplerenone significantly reduced cardiomyocyte hypertrophy, heart weight and heart weight to body weight ratio. Eplerenone improved left ventricular function in a dose-dependent manner. Central venous pressure and left ventricular end-diastolic pressure were lower, and +/-dP/dt and fractional shortening were higher in group H than group V. Eplerenone also attenuated myocardial fibrosis and reduced left ventricular mRNA expressions of TGF-beta(1) and collagen-III. Our results indicate that treatment with eplerenone improved left ventricular dysfunction and attenuated left ventricular remodeling in rats with heart failure.

Effects of pranidipine, a novel calcium channel antagonist, on the progression of left ventricular dysfunction and remodeling in rats with heart failure.

The cardioprotective properties of pranidipine were studied in a rat model of heart failure after autoimmune myocarditis. Twenty-eight days after immunization the surviving rats were divided into three groups and received oral treatment of 0.03 mg/kg/day (group 0.03) or 0.3 mg/kg/day (group 0.3) of pranidipine or vehicle (group V) for 1 month. High-dose pranidipine (group 0.3) improved the survival rate, and significantly reduced heart weight, heart weight to body weight ratio, myocardial fibrosis, central venous pressure and left ventricular end-diastolic pressure than low-dose pranidipine (group 0.03) and group V. Pranidipine at high dose also decreased the left ventricular systolic and diastolic dimensions, and increased fractional shortening compared with group V. The increase in level of TGF-beta1 and collagen-III mRNA were suppressed by pranidipine in a dose-dependent manner. Our results indicated that pranidipine has cardioprotective effects on heart failure, and that the beneficial effect can be partly explained by attenuation of fibrotic response through suppression of TGF-beta1 and collagen-III mRNA expression, and regression of myocyte hypertrophy.

Maintenance of cold-preserved porcine hepatocyte function with UW solution and ascorbic acid-2 glucoside.

Normal human hepatocytes are an ideal source of liver-targeted cell therapies, such as hepatocyte transplantation and bioartificial livers, but availability of human donor livers for liver cell isolation is severely limited. To effectively utilize scarce donor organs for cell therapies, it is of extreme importance to establish an efficient isolation technique and an effective cold preservation solution for transportation of isolated cells. A lateral segment of the liver was surgically resected from pigs weighing 10 kg and a four-step collagenase and dispase digestion was conducted. Isolated hepatocytes were subjected to 8-h cold storage on ice. The following preservation solutions were tested: 1) University of Wisconsin (UW) solution, 2) UW with 100 microg/ml of ascorbic acid-2 glucoside (AA2G), 3) 100% fetal bovine serum (FBS), and 4) Dulbecco's modified Eagle's medium (DMEM) supplemented with 100% FBS. The mean viability of porcine hepatocytes was 95.5 +/- 2.5% when isolated in three independent experiments. Viability, plating efficiency, membrane stability, and ammonia metabolic capacity of cold-preserved hepatocytes were significantly better maintained by the use of UW solution. When AA2G (100 microg/ml) was combined with UW solution, such parameters were further improved. It was explained by inhibition of caspase-3 activation and retention of ATP at high levels of hepatocytes preserved with UW solution containing AA2G. The present work demonstrates that a combination of UW solution with AA2G (100 microg/ml) would be a useful cold preservation means for the development of cell therapies.

Contribution of sympathetic nervous system activity during administration of carvedilol in rats with dilated cardiomyopathy.

We investigated the contribution of the sympathetic nervous system (SNS) in maintaining blood pressure during administration of carvedilol in rats with dilated cardiomyopathy, and examined whether SNS hyperactivity induced by high-dose carvedilol is related to severity of heart failure. The hypotensive effect of carvedilol in rats with heart failure (Group F) was not significantly different to that in rats without (Group N). However, enhancement of the plasma norepinephrine concentration during carvedilol administration in Group F was higher than in Group N. The constitutive plasma NE concentration in Group F (562 +/- 146 pg/ml) was significantly higher than in Group N (203 +/- 55 pg/ml) and there was a significant positive correlation between the heart weight to body weight ratio and the plasma norepinephrine concentration. Values for the maximal effect of the norepinephrine hypertensive effect during norepinephrine intravenous infusion (Emax) decreased, and plasma norepinephrine concentrations at half-maximal effect of the norepinephrine hypertensive effect (EC50) increased in Group F compared with Group N (20.8 +/- 6.1 and 28.6 +/- 2.2 mmHg, and 4.5 +/- 1.9 and 1.5 +/- 0.2 ng/ml, respectively). These results suggested that the number of receptors (Emax) and sensitivity (EC50) to the norepinephrine hypertensive effect decreased in Group F. Changes in these parameters in Group F corresponded with the results of a beta-adrenergic receptor binding assay using I-125 iodocyanopindolol (Bmax = 32 +/- 4 in Group F and 53 +/- 2 fmol/mg protein in Group N). These results showed that the SNS (presynaptic) activity increased and the SNS receptor sensitivity in the blood pressure regulation system decreased in heart failure. Therefore, high-dose carvedilol treatment should be used with caution to avoid worsening heart failure.