Discovery of selective CYP11B2 (aldosterone synthase) inhibitors for the therapy of congestive heart failure and myocardial fibrosis

An increased aldosterone concentration due to congestive heart failure leads to a further progression of the disease as well as to myocardial fibrosis. To interfere with these fatal processes selective inhibition of aldosterone synthase (CYP11B2) is required. CYP11B1, a key enzyme in glucocorticoid biosynthesis showing a high homology to the target enzyme (>93%), must not be inhibited. Screening of our P450 inhibitor library for inhibition of bovine aldosterone synthase resulted in a high number of compounds showing reasonable inhibition. In the next step substances were tested for oral absorption using two artificial membrane assays. The inhibition of human CYP11B2 was evaluated using assays in fission yeast and V79MZ cells stably expressing the active human target enzyme. For selectivity, inhibition of CYP11B1, CYP11A1, CYP17, CYP19 and CYP5 was determined. Rather potent and selective compounds obtained in this way were structurally further optimised, finally leading to inhibitors showing IC(50) values within the low nanomolar range.

Alterations in G protein and MAP kinase signaling pathways during cardiac remodeling in hypertension and heart failure

The present study was undertaken to elucidate the G-protein and mitogen-activated kinase (MAP kinase) coupled signaling profile in a genetic model of hypertension and congestive heart failure (CHF) that mimics similar disease in humans. At the receptor level, Ang II type 1 receptor (AT1R) increased in left ventricular hypertrophy (LVH) and reverted to normal in CHF, whereas there was a downregulation of the Ang II type 2 receptor (AT2R) in CHF. At the transducer level, Galphaq and Galpha12 protein levels were unchanged during LVH but decreased significantly in CHF. In contrast, Gbeta and Galpha13 protein content were markedly upregulated in CHF. Furthermore, using phospho-specific antibodies in Western blots and in vitro kinase assays, we found at the effector level an upregulation of the small G-protein Rac1 activity during LVH but a decrease during CHF. In parallel, small G-protein Rho activity was significantly increased during LVH but was unchanged in failure. We found at the downstream level that MAP kinase isoforms extracellular signal regulated-kinase (ERK1/2), big mitogen-activated kinase (BMK1/ERK5), C-jun N-terminal-activated kinase (JNKs/SAPKs), and stress-activated kinase (p38) bioactivities were increased during LVH. During CHF, ERK1/2 and JNK1/2 kinase activities were decreased, whereas BMK1/ERK5 kinase activity reverted to normal values. In conclusion, this study demonstrates, for the first time, multistep alterations of G-protein and MAP kinase signaling pathways in LVH and progression to failure in a genetic model of hypertension and failure.

PKA phosphorylation activates the calcium release channel (ryanodine receptor) in skeletal muscle: defective regulation in heart failure

The type 1 ryanodine receptor (RyR1) on the sarcoplasmic reticulum (SR) is the major calcium (Ca2+) release channel required for skeletal muscle excitation-contraction (EC) coupling. RyR1 function is modulated by proteins that bind to its large cytoplasmic scaffold domain, including the FK506 binding protein (FKBP12) and PKA. PKA is activated during sympathetic nervous system (SNS) stimulation. We show that PKA phosphorylation of RyR1 at Ser2843 activates the channel by releasing FKBP12. When FKB12 is bound to RyR1, it inhibits the channel by stabilizing its closed state. RyR1 in skeletal muscle from animals with heart failure (HF), a chronic hyperadrenergic state, were PKA hyperphosphorylated, depleted of FKBP12, and exhibited increased activity, suggesting that the channels are "leaky." RyR1 PKA hyperphosphorylation correlated with impaired SR Ca2+ release and early fatigue in HF skeletal muscle. These findings identify a novel mechanism that regulates RyR1 function via PKA phosphorylation in response to SNS stimulation. PKA hyperphosphorylation of RyR1 may contribute to impaired skeletal muscle function in HF, suggesting that a generalized EC coupling myopathy may play a role in HF.

Reduced Ca2+-calmodulin-dependent protein kinase activity and expression in LV myocardium of dogs with heart failure

Studies on the status of multifunctional Ca(2+)-calmodulin (CaM)-dependent protein kinase-II (CaMKII) in failing hearts are limited and controversial. The study was performed in the left ventricular (LV) myocardium of six dogs with heart failure (HF) (LV ejection fraction, 23 +/- 2%) and six normal (NL) dogs. In the LV homogenate, CaMKII activity and its protein level were determined by using the CaMKII peptide and antibody, respectively. Furthermore, the protein level of CaM and phosphorylated phospholamban (PLB) at threonine-17 (PLB-Thr(17)) and serine-16 (PLB-Ser(16)) were also determined in the LV homogenate using a specific antibody. In addition, the level of zinc, which inhibits protein kinase A activity, was determined in the LV tissue by inductively coupled plasma mass spectrometry. CaMKII activity and phosphorylated PLB-Thr(17) and PLB-Ser(16) levels, but not CaM and Zn levels, were significantly reduced in the LV homogenate of dogs with HF compared with NL dogs. These results suggest that CaMKII activity is reduced in the failing LV myocardium, and this abnormality is associated with reduced protein expression level of the enzyme but not due to changes in CaM and zinc levels. In conclusion, reduced CaMKII activity and phosphorylated PLB level may be partly responsible for impaired sarcoplasmic reticulum function in HF.

Differential G protein receptor kinase 2 expression in compensated hypertrophy and heart failure after myocardial infarction in the rat

The onset of heart failure is associated with characteristic changes in myocardial expression of G protein receptor kinase 2 (GRK2). Although, GRK2 significantly contributes to the regulation of myocardial function in the failing heart, the GRK2 expression during cardiac hypertrophy without heart failure remains to be explored. We here report a differential expression of GRK2 in cardiac hypertrophy with or without heart failure in response to a myocardial infarction in the rat. Postmyocardial infarction animals were divided into two groups depending on the absence or presence of pulmonary edema, which is a manifestation of heart failure. Remarkably, cardiac GRK2 expression and activity were inhibited in animals with cardiac hypertrophy without heart failure, whereas animals with heart failure had elevated GRK2. Thus, three weeks after the infarction cardiac GRK2 expression in animals with hypertrophy alone was decreased to 0.34 of control, whereas in the group of animals with heart failure GRK2 expression was 1.89-fold higher than in sham-operated animals. GRK2 activity was affected in a similar way, three and nine weeks after the infarction cardiac GRK2 activity was reduced to 0.58 and 0.62 in animals with hypertrophy without heart failure when compared to sham operated animals. By contrast, GRK2 activity was increased by 1.32- and 1.21-fold three and nine weeks postinfarction in animals with heart failure when compared to sham animals. These data suggest that GRK2 expression is differentially regulated in hypertrophic, non-failing and hypertrophic, failing hearts.

Differential activation of matrix metalloproteinases in heart failure with and without ventricular dilatation

OBJECTIVE

Remodeling of extracellular matrix (ECM) is considered to contribute to progression of left ventricular (LV) remodeling and matrix metalloproteinases (MMPs) play crucial roles in regulation of ECM. Activation of MMPs is observed in systolic heart failure (SHF) and is suggested to be responsible for LV dilatation in SHF. Diastolic heart failure (DHF) that is not associated with LV dilatation is also accompanied with collagen accumulation; however, differences in ECM regulatory system, especially activation of MMPs, between SHF and DHF remain to be clarified. This study was conducted to clarify whether MMPs are activated even in DHF, and if so, to characterize the difference in activation of MMPs between SHF and DHF for identification of a target for the prevention of LV remodeling in SHF.

METHODS

To exclude effects of differences in underling cardiovascular diseases and genetic background on the comparison between DHF and SHF, we used Dahl salt-sensitive rats fed on high salt diet starting at 7 weeks of age as DHF model and at 8 weeks as SHF model, both of which our laboratory recently developed.

RESULTS

LV fibrosis progressed in the DHF and SHF model rats. MMP-2 was activated to the same degree in both rats. Activation of MMP-9 was enhanced in the DHF model rats, but the activity was more enhanced in the SHF rats. Film in situ zymography showed that enhanced gelatinolytic activity appeared only in the mid layer of the LV wall in the DHF rats and throughout the wall in the SHF rats. The distribution of gelatinolytic activity was consistent with that of expression of MMP-9 as assessed in immunohistochemical study.

CONCLUSIONS

MMP-9 rather than MMP-2 may be involved in LV dilatation in SHF and be a specific target for the prevention of LV remodeling.

Sex, Digitalis, and the Sodium Pump

Foxglove and its constituents therapeutic agent digitalis have been used for centuries for the treatment of heart failure. All digitalis-like cardiotonic steroids enhance heart contraction through a mechanism involving the inhibition of the Na(+),K(+)- ATPase. Recently, Rathore and colleagues reported that sex-based differences may exist in the efficacy of digoxin for the treatment of heart failure. The authors of the study found that female patients exhibited increased risk of death associated with digoxin therapy, whereas male patients appeared to have no increased risk of death related to digoxin therapy. Blaustein and colleagues delve into the report and discuss possible explanations for these findings, suggest alternative ones, and advocate for enrolling greater numbers of women in clinical studies.

Selective matrix metalloproteinase inhibition with developing heart failure: effects on left ventricular function and structure

The matrix metalloproteinases (MMPs) are an endogenous family of proteolytic enzymes implicated to contribute to LV remodeling. However, broad-spectrum MMP inhibition (MMPi), particularly inhibition of interstitial collagenase (MMP-1), may not be clinically applicable. This study examined the effects of selective MMPi (sparing MMP-1) in a model of developing congestive heart failure. Pigs were randomly assigned to 3 groups: (1) rapid pacing for 3 weeks (240 bpm, n=10); (2) selective MMPi (20 mg/kg per day-PO;PGE7113313) and rapid pacing (n=12); and (3) controls (n=10). LV peak wall stress increased from controls with rapid pacing (140+/-6 versus 319+/-18 g/cm2; P<0.05) and was reduced with selective MMPi (208+/-9 g/cm2; P<0.05. Preload recruitable stroke work was reduced with rapid pacing (4.3+/-0.4 versus 1.2+/-0.2 dyne. cm/mm Hg; P<0.05) and was increased with selective MMPi (2.6+/-0.3 dyne. cm/mm Hg; P<0.05). Plasma norepinephrine increased by 6-fold in the rapid pacing group (P<0.05) and was reduced from untreated values with selective MMPi (P<0.05). At the myocardial level, myocyte cross-sectional area was increased with selective MMPi but fibrillar collagen volume fraction remained unchanged relative to control values. These results suggest that targeting a selective portfolio of myocardial MMP species for inhibition may provide a more rational therapeutic strategy in the setting of congestive heart failure.

Depressed phosphatidic acid-induced contractile activity of failing cardiomyocytes

The effects of phosphatidic acid (PA), a known inotropic agent, on Ca(2+) transients and contractile activity of cardiomyocytes in congestive heart failure (CHF) due to myocardial infarction were examined. In control cells, PA induced a significant increase (25%) in active cell shortening and Ca(2+) transients. The phospholipase C (PLC) inhibitor, 2-nitro-4-carboxyphenyl N,N-diphenylcarbonate, blocked the positive inotropic action induced by PA, indicating that PA induces an increase in contractile activity and Ca(2+) transients through stimulation of PLC. Conversely, in failing cardiomyocytes there was a loss of PA-induced increase in active cell shortening and Ca(2+) transients. PA did not alter resting cell length. Both diastolic and systolic [Ca(2+)] were significantly elevated in the failing cardiomyocytes. In vitro assessment of the cardiac sarcolemmal (SL) PLC activity revealed that the impaired failing cardiomyocyte response to PA was associated with a diminished stimulation of SL PLC activity by PA. Our results identify an important defect in the PA-PLC signaling pathway in failing cardiomyocytes, which may have significant implications for the depressed contractile function during CHF.

Chronic inhibition of Rho kinase blunts the process of left ventricular hypertrophy leading to cardiac contractile dysfunction in hypertension-induced heart failure

The Gq-RhoA-Rho kinase pathway, activated by neurohormonal factors such as angiotensin II (Ang II), has been proposed to be one of the important signaling pathways involved in the progression of left ventricular (LV) hypertrophy to heart failure. We tested the hypothesis that chronic inhibition of Rho kinase prevents this process. Heart failure was induced in Dahl salt-sensitive (DS) rats fed an 8% NaCl diet from 8 until 17 weeks of age. Y-27632 (5 mg/kg per day), a selective Rho kinase inhibitor, was applied orally to DS rats starting at 10 weeks of age for 7 weeks (DS/Y+). DS rats without Y-27632 (DS/Y-) and Dahl salt-resistant (DR) rats fed the 8% NaCl diet were regarded as non-therapeutic and normotensive controls, respectively. At 17 weeks of age, there was no significant difference in the blood pressure of DS/Y- and DS/Y+ rats. DS/Y- rats exhibited: (1) increases in LV mass, cross-sectional area (CSA) of cardiomyocytes, and interstitial fibrosis; (2) contractile dysfunction, i.e. decreases in LV ejection fraction and % fractional shortening, and prolongation of time to peak tension as well as to 50% relaxation in the twitch contraction of isolated papillary muscle; and (3) increases in the protein expression of Galphaq and Rho kinase in the myocardial membrane fraction. In DS/Y+ rats, the degree of myocardial hypertrophy was significantly inhibited in association with improved contractile function, without a decrease in the degree of interstitial fibrosis. Our results suggest the possibility that the Gq-Rho kinase pathway plays an important role in the process of hypertension-induced LV hypertrophy leading to contractile dysfunction.

Plasma matrix metalloproteinase and inhibitor profiles in patients with heart failure

BACKGROUND

Changes in myocardial matrix metalloproteinases (MMPs) and the inhibitors of MMPs (TIMPs) have been demonstrated in congestive heart failure (CHF). The first objective of this study was to measure plasma profiles of MMPs and TIMPs in CHF patients (n = 24; 62 +/- 3 years; left ventricular ejection fraction [LVEF] = 24 +/- 2%) and age-matched nonfailing patients (n = 48; 63 +/- 2 years; LVEF >/= 55%). Cytokines such as tumor necrosis factor (TNF)-alpha can induce MMP expression in vitro. The second objective of this study was to determine the relationship between soluble TNF-alpha receptors (TNFR1; TNFR2) and MMP plasma profiles.

METHODS AND RESULTS

Plasma levels of MMP-2, MMP-9, MMP-8, TIMP-1, TIMP-2, TNF-alpha, TNFR1, and TNFR2 were measured by enzyme-linked immunosorbent assay kits. Plasma MMP-9 levels were increased in CHF patients (25 +/- 6 versus 72 +/- 15 ng/mL, P <.05). Interestingly, plasma levels of MMP-8 were decreased in CHF patients (16 +/- 2 versus 9 +/- 2 ng/mL, P <.05). The MMP-9/TIMP-1 ratio was increased by 3-fold, whereas the MMP-9/TIMP-2 ratio was increased by 16-fold in CHF patients (both P <.05). With a 48-week follow-up in CHF patients, an absolute reduction in plasma TNFR1 from baseline was accompanied by reduced MMP-9 levels (-30 +/- 16 ng/mL; P =.058), whereas stable or increased plasma TNFR1 resulted in persistently elevated MMP-9 levels.

CONCLUSIONS

The unique findings of this study were 2-fold. First, a discordant change in plasma MMP and TIMP levels occurred in CHF patients. Second, changes in cytokine activity were related to changes in plasma MMP levels. These changes in MMP/TIMP levels likely reflect the progression and/or acceleration of the LV remodeling process in CHF. Thus serial measurements of plasma MMP/TIMP levels may hold diagnostic/prognostic significance in CHF patients.

Tissue transglutaminase antibodies in patients with end-stage heart failure

OBJECTIVE

For celiac disease (CD), screening a trend has recently emerged to measure tissue transglutaminase antibodies (tTGA) by immunoassays instead of the more laborious endomysial antibodies (EmA), as they recognize the same target, tissue transglutaminase (tTG). However, a high rate of false-positive results has been reported in some patient series with diseases known to be associated with CD. Moreover, tTG is a ubiquitous, multifunctional enzyme, overexpressed in experimental models of heart failure. Therefore, we assessed the specificity of tTGA assays in a large series of EmA-negative patients with end-stage heart failure.

METHODS

We studied 288 patients with end-stage heart failure and 60 blood donors. No subject had clinical evidence of CD or IgA deficiency, and all were EmA negative. Serum IgA and IgG tTGA were measured by means of commercial kits using as substrate, either guinea pig or recombinant human tTG. Blocking studies and Western blots were also performed using recombinant human tTG.

RESULTS

All blood donor sera were IgA tTGA negative. IgA tTGA positivity was observed in 47.6% and 49.1% of patients with heart failure using, respectively, guinea pig tTG and recombinant human tTG as substrates. Preincubation of positive sera with recombinant human tTG resulted in 81% blocking of IgA tTGA in immunoassay. Western blot analysis confirmed the presence of antibodies against recombinant human tTG. IgA tTGA-positive sera were also IgG tTGA positive.

CONCLUSIONS

IgA and IgG tTGA occur in a large number of EmA-negative patients with end-stage heart failure, and their presence is unlikely to be caused by concomitant CD.

Involvement of extracellular signal-regulated kinases 1/2 in cardiac hypertrophy and cell death

In response to pathophysiological stress, the adult heart undergoes hypertrophic enlargement characterized by an increase in the cross-sectional area of individual myofibers. Although cardiac hypertrophy is initially a compensatory response, sustained hypertrophy is a leading predictor for the development of heart failure. At the molecular level, disease-related stimuli invoke endocrine, paracrine, and autocrine regulatory circuits, which directly influence cardiomyocyte hypertrophy, in part, through membrane bound G protein-coupled receptors and receptor tyrosine kinases. These membrane receptors activate intermediate signal transduction pathways within the cytoplasm such as mitogen-activated protein kinases (MAPKs), protein kinase C (PKC), and calcineurin, which directly modify transcriptional regulatory factors promoting alterations in cardiac gene expression. This review will weigh an increasing body of literature implicating the intermediate signaling pathway consisting of MEK1 and extracellular signal-regulated kinases (ERK1/2) as important regulators of cardiac hypertrophy and myocyte survival. The MEK1-ERK1/2 pathway likely occupies a central regulatory position in the signaling hierarchy of a cardiac myocyte given its unique ability to respond to virtually every characterized hypertrophic agonist and stress stimuli examined to date and based on its ability to promote myocyte growth in vitro and in vivo.

Increased expression of renal neutral endopeptidase in severe heart failure

The enzyme neutral endopeptidase (NEP; EC 3.4.24.11) cleaves several vasoactive peptides such as the atrial natriuretic peptide (ANP). ANP is a hormone of cardiac origin with diuretic and natriuretic actions. Despite elevated circulating levels of ANP, congestive heart failure (CHF) is characterized by progressive sodium and water retention. In order to elucidate the loss of natriuretic and diuretic properties of ANP in CHF we analyzed activity, protein concentrations, mRNA and immunostaining of NEP in kidneys of different models of severe CHF in the rat.CHF was induced by either aortocaval shunt, aortic banding or myocardial infarction in the rat. All models were defined by increased left ventricular end-diastolic pressure and decreased contractility. The diminished effectiveness of ANP was reflected by reduced cGMP/ANP ratio in animals with shunt or infarction. Renal NEP activity was increased in rats with aortocaval shunt (203 +/- 7%, p < 0.001), aortic banding (184 +/- 11%, p < 0.001) and infarction (149 +/- 10%, p < 0.005). Western blot analysis revealed a significant increase in renal NEP protein content in two models of CHF (shunt: 214 +/- 57%, p < 0.05; infarction: 310 +/- 53 %, p < 0.01). The elevated protein expression was paralleled by a threefold increase in renal NEP-mRNA level in the infarction model. The increased renal NEP protein expression and activity may lead to enhanced degradation of ANP and may contribute to the decreased renal response to ANP in heart failure. Thus, the capacity to counteract sodium and water retention, would be diminished. The increased renal NEP activity may therefore be a hitherto unknown factor in the progression of CHF.

Metalloproteinase in myocardial adaptation and maladaptation

Ventricular remodeling is a compensatory response that comprises the processes of apoptosis, muscle cell hypertrophy, and rearrangement of the extracellular matrix fibers connecting the muscles. These processes are associated with transformation of endothelium and/or fibroblasts to myofibroblasts. Neutral matrix metalloproteinases, membrane type matrix metalloproteinases, and disintegrin metalloproteinase play a significant role in these processes. The cell-extracellular matrix connections are important in maintaining and synchronizing muscle function. However, a complete extracellular matrix-cell disconnect leads to a decrease in muscle cell strength, apoptosis, and hypertrophy.

Tissue angiotensin II during progression or ventricular hypertrophy to heart failure in hypertensive rats; differential effects on PKC epsilon and PKC beta

The protein kinase C (PKC) family has been implicated as second messengers in mechanosensitive modulation of cardiac hypertrophy. However, little information is available on the role of expression and activation of specific cardiac PKC isozymes during development of left ventricular hypertrophy (LVH) and failure (LVF). Dahl salt-sensitive rats fed an 8% salt diet developed systemic hypertension and concentric LVH at 11 weeks of age that is followed by left ventricle (LV) dilatation and global hypokinesis at 17 weeks. Among several PKC isozymes expressed in the LV myocardium, only PKC epsilon showed a 94% increase at the LVH stage. At the LVF stage, however, PKC epsilon returned to the control level, whereas PKC beta I and beta II increased by 158% and 155%, respectively. Hearts were studied at each stage using the Langendorff set-up, and a LV balloon was inflated to achieve an equivalent diastolic wall stress. Following mechanical stretch, PKC epsilon was significantly activated in LVH myocardium in which tissue angiotensin II levels were increased by 59%. Pre-treatment with valsartan, an AT(1)-receptor blocker, abolished the stretch-mediated PKC epsilon activation. Mechanical stretch no longer induced PKC epsilon activation in LVF. Chronic administration of valsartan blunted the progression of LVF and inhibited the increase in PKC beta. Mechanosensitive PKC epsilon activation is augmented and therefore may contribute to the development of compensatory hypertrophy. This effect was dependent on activation of tissue angiotensin II. However, this compensatory mechanism becomes inactive in LVF, where PKC beta may participate in the progression to cardiac dysfunction and LV remodeling.

Activation of NADPH oxidase during progression of cardiac hypertrophy to failure

Increased reactive oxygen species (ROS) production is implicated in the pathophysiology of left ventricular (LV) hypertrophy and heart failure. However, the enzymatic sources of myocardial ROS production are unclear. We examined the expression and activity of phagocyte-type NADPH oxidase in LV myocardium in an experimental guinea pig model of progressive pressure-overload LV hypertrophy. Concomitant with the development of LV hypertrophy, NADPH-dependent O2- production in LV homogenates, measured by lucigenin (5 micro mol/L) chemiluminescence or cytochrome c reduction assays, significantly and progressively increased (by approximately 40% at the stage of LV decompensation; P<0.05). O2- production was fully inhibited by diphenyleneiodonium (100 micromol/L). Immunoblotting revealed a progressive increase in expression of the NADPH oxidase subunits p22(phox), gp91(phox), p67(phox), and p47(phox) in the LV hypertrophy group, whereas immunolabeling studies indicated the presence of oxidase subunits in cardiomyocytes and endothelial cells. In parallel with the increase in O2- production, there was a significant increase in activation of extracellular signal-regulated kinase 1/2, extracellular signal-regulated kinase 5, c-Jun NH2-terminal kinase 1/2, and p38 mitogen-activated protein kinase. These data indicate that an NADPH oxidase expressed in cardiomyocytes is a major source of ROS generation in pressure overload LV hypertrophy and may contribute to pathophysiological changes such as the activation of redox-sensitive kinases and progression to heart failure.

The role of NOS in heart failure: lessons from murine genetic models

Nitric Oxide Synthases (NOSs) are a group of related proteins that produce nitric oxide (NO). In mammals, there are three known members of this gene family: nNOS (NOS1), iNOS (NOS2) and eNOS (NOS3). Each has been disrupted by targeted gene ablation in mice and the corresponding phenotypes examined. These mice have allowed an examination of the contribution of each NOS in a variety of experimental models and continue to provided insights into the patho-physiological role of NOS and NO. With increasing sophistication, murine transgenic approaches continue to offer a wealth of information, and invaluable tools to further study the NOS system. The focus of this review will be an examination of the tools available, and the insights gained from studies done on murine NOS genetic models in the context of heart failure.

[Polymorphism of the ACE gene, structural-functional state of the left ventricle in patients with post-infarction cardiac failure and effects of the ACE-inhibitor Perindopril]

AIM

To evaluate relationships between structural-functional state of the left ventricle (LV) and genotype of angiotensin converting enzyme (ACE) gene in patients with postinfarction chronic cardiac failure (CCF) and effects of ACE inhibitor perindopril on hemodynamics depending on ACE gene polymorphism.

MATERIAL AND METHODS

In 52 patients with CCF (functional class III-IV by NYHA criteria) who had survived macrofocal myocardial infarction we studied ACE gene using thermostable DNA-polymerase Taq. Isolation of genome DNA from human venous blood was made by phenolchloroform extraction with the use of chelate polymer Chelex-100. Polymerase chain reaction was conducted on amplificator PHC-2 or PolyChain II. LV contractile function was studied on echocardiograph "Toshiba SSH-160A (Japan). Echocardiography was performed before intake of perindopril, in the end of titration phase, on therapy month 6 and 12.

RESULTS

Genotype II of ACE gene was detected in 11(21.1%) patients, ID genotype--in 20(38.5%), DD genotype--in 21(40.4%). Patients with ACE gene genotype II and ID have no differences by parameters of central hemodynamics. They were divided into two groups: group 1--patients with genotypes II and ID of ACE gene, group 2--patients with genotype DD. End diastolic volume (EDV), end systolic volume (ESV), index of LV myocardial mass were significantly less in group 1 than in group 2 (by 45.7, 81.6 and 31.2%, respectively). In group 1 ejection fraction (EF) and %delta S were higher by 35.3 and 35.7%, respectively. The hemodynamic effect of perindopril was higher in group 2. A month therapy resulted in a 8.7 and 14.8% reduction in group 2 EDV and ESV, respectively (p < 0.05). This entailed an increase in EF and %delta S by 18.3% (p < 0.05) and 19.8% (p < 0.05). Later, perindopril retained influence on central hemodynamics. Diastolic function to the end of therapy in both groups differed insignificantly.

CONCLUSION

In CCF patients functional class III-IV with the history of myocardial infarction, structural-functional LV parameters depend on genotype of ACE gene. Perindopril is most effective in DD-genotype of ACE gene.

Alterations of sarcolemmal phospholipase D and phosphatidate phosphohydrolase in congestive heart failure

Phospholipase D 2 (PLD2) is the major PLD isozyme associated with the cardiac sarcolemmal (SL) membrane. Hydrolysis of SL phosphatidylcholine (PC) by PLD2 produces phosphatidic acid (PA), which is then converted to 1,2 diacylglycerol (DAG) by the action of phosphatidate phosphohydrolase type 2 (PAP2). In view of the role of both PA and DAG in the regulation of Ca(2+) movements and the association of abnormal Ca(2+) homeostasis with congestive heart failure (CHF), we examined the status of both PLD2 and PAP2 in SL membranes in the infarcted heart upon occluding the left coronary artery in rats for 1, 2, 4, 8 and 16 weeks. A time-dependent increase in both SL PLD2 and PAP2 activities was observed in the non-infarcted left ventricular tissue following myocardial infarction (MI); however, the increase in PAP2 activity was greater than that in PLD2 activity. Furthermore, the contents of both PA and PC were reduced, whereas that of DAG was increased in the failing heart SL membrane. Treatment of the CHF animals with imidapril, an angiotensin-converting enzyme (ACE) inhibitor, attenuated the observed changes in heart function, SL PLD2 and PAP2 activities, as well as SL PA, PC and DAG contents. The results suggest that heart failure is associated with increased activities of both PLD2 and PAP2 in the SL membrane and the beneficial effect of imidapril on heart function may be due to its ability to prevent these changes in the phospholipid signaling molecules in the cardiac SL membrane.

Enhanced activities and gene expression of phosphodiesterase types 3 and 4 in pressure-induced congestive heart failure

Phosphodiesterase (PDE) was shown to be downregulated in the failing hearts of transplant recipients, while it was upregulated in hypertrophied hearts induced by isoproterenol and calsequesterin overexpression. We examined the time course of gene expression and the activity of PDE3 and PDE4 in an animal model of salt-induced hypertension, left ventricular hypertrophy, and congestive heart failure (CHF). Dahl salt-sensitive (DS, n = 25) and salt-resistant rats (DR, n = 25) were fed with an 8% NaCl diet after the age of 6 weeks. At 11 weeks (hypertension and hypertrophy stage in DS), PDE4 activity in the heart was higher in DS than in DR. At 18 weeks (hypertension and CHF stage in DS), both PDE3 and PDE4 activity in both the heart and aorta was approximately twofold higher in DS than in DR. The ratios of PDE3 and PDE4 mRNA to GAPDH mRNA in the heart were both approximately twofold higher in DS than in DR at 11 and 18 weeks. The cardiac cyclic adenosine monophosphate content and plasma nitric oxide concentration were higher in DS than in DR at 11 weeks but both of them were lower in DS than in DR at 18 weeks of age. In this animal model, gene expressions of PDE3 and PDE4 were augmented from the hypertrophic stage. PDE3 and PDE4 activities were subsequently enhanced in the CHF stage and seemed to contribute to the development and exacerbation of CHF.

Critical role of Rho-kinase pathway for cardiac performance and remodeling in failing rat hearts

OBJECTIVES

Rho and Rho-kinase play a critical role in the regulation of cellular functions such as proliferation and migration. To elucidate the molecular mechanisms that regulate cardiac function and cardiovascular remodeling, we determined whether the signaling pathway through Rho is involved in Dahl salt-sensitive hypertensive rats with congestive heart failure (CHF) using a specific Rho-kinase inhibitor, Y-27632.

METHODS

Y-27632 was administered from the left ventricular hypertrophy stage (11 weeks) to the CHF stage (18 weeks) for 7 weeks. The left ventricular end-systolic pressure-volume relationship (contractility: E(es)) was evaluated using a conductance catheter.

RESULTS

Downregulated E(es) in the CHF stage was significantly ameliorated by Y-27632 treatment. Increased RhoA protein, Rho-kinase gene expression and myosin light chain phosphorylations in CHF rats were suppressed by Y-27632. Upregulated proto-oncogene c-fos gene expression in CHF rats was decreased by inhibiting Rho-kinase. In contrast, Y-27632 showed no effect on upregulated extracellular signal-regulated kinases (ERK) and p70S6 kinase phosphorylations, which were reported to be involved in protein synthesis. In the CHF stage, Y-27632 effectively inhibited vascular lesion formation such as medial thickness and perivascular fibrosis.

CONCLUSIONS

These results suggest that differential activation of the Rho-Rho-kinase and the ERK-p70S6 kinase pathways may play a critical role in CHF, and the Rho-Rho-kinase pathway is involved in the pathogenesis of cardiac dysfunction and cardiovascular remodeling. Thus, inhibition of the Rho-kinase pathway may be at least a potential therapeutic strategy for CHF.

Myocardial Na,K-ATPase: the molecular basis for the hemodynamic effect of digoxin therapy in congestive heart failure

Congestive heart failure may be deemed the epidemic of cardiology in the 21st century in the industrialized part of the world. Although new therapies improving morbidity and mortality from chronic heart failure have emerged it is likely that there is a growing role for digoxin. Thus, digoxin treatment is known to control symptoms of congestive heart failure when added to standard therapy. In this setting, we review the prevailing knowledge of the Na,K-ATPase, the cellular receptor for the inotropic action of digitalis glycosides, in relation to the hemodynamic effect of digoxin. It is concluded that if improvement of hemodynamics is needed in congestive heart failure, this knowledge should be taken into account and in many cases digoxin should be added to standard therapy. Digoxin is still the only safe inotropic drug for oral use that improves hemodynamics. Digoxin should be used to heart failure patients in sinus rhythm when they after institution of mortality reducing treatment still have heart failure symptoms, and to patients intolerant to heart failure mortality reducing drugs. Digoxin should probably in heart failure patients with sinus rhythm be given in the lowest possible dose that relieves symptoms sufficiently.