Calcineurin inhibition normalizes beta-adrenergic responsiveness in the spontaneously hypertensive rat

Cardiac Effects of Phosphodiesterase-5 Inhibitors: Efficacy and Safety

The coexistence of cardiovascular disease and erectile dysfunction is widespread, possibly owing to underlying endothelial dysfunction in both diseases. Millions of patients with cardiovascular disease are prescribed phosphodiesterase-5 (PDE5) inhibitors for the management of erectile dysfunction. Although the role of PDE5 inhibitors in erectile dysfunction therapy is well established, their effects on the cardiovascular system are unclear. Preclinical studies investigating the effect of PDE5 inhibitors on ischemia-reperfusion injury, pressure overload-induced hypertrophy, and chemotoxicity suggested a possible clinical role for each of these medications; however, attempts to translate these findings to the bedside have resulted in mixed outcomes. In this review, we explore the biologic preclinical effects of PDE5 inhibitors in mediating cardioprotection. We then examine clinical trials investigating PDE5 inhibition in patients with heart failure, coronary artery disease, and ventricular arrhythmias and discuss why the studies likely have yet to show positive results and efficacy with PDE5 inhibition despite no safety concerns.

Beta 1 adrenoceptor blockade promotes angiogenesis in hypertrophied myocardium of transverse aortic constricted mice

Left ventricular hypertrophy (LVH) is an adaptive structural remodelling consequent to uncontrolled blood pressure. Impaired angiogenesis plays a vital role in transiting LVH into cardiac failure. Catecholamines modulate myocardial function through beta adrenoceptors, and their blockers (β-AR) reduce cardiovascular morbidity and mortality by decelerating the LVH progression. Nonetheless, the effect of β-AR blockers on myocardial vascular bed remains largely obscure. Hence, this study is focussed on analysing the possible outcomes of β-AR blockers on myocardial vascular remodelling using a surgically induced LVH mice model. Transverse aortic constricted mice and sham-operated mice were administered with metoprolol at a dose of 30 mg/kg/d for 60 days and myocardial vascular endothelial growth factor (VEGF) alpha levels, GSH/GSSG ratio, myocardial protein carbonyl content, hypertrophy index and global myocardial function, trans-aortic fluid dynamics and expression pattern of angiopoietin-1 and VEGF alpha were assessed. These findings were further confirmed by histochemical analysis for myocardial capillary density, perivascular fibrosis ratio and intimal thickening. Sub- chronic β-AR blockade reduced the oxidative stress, hypertrophic index, intimal thickening and perivascular fibrosis ratio. A marked increase in myocardial VEGF, angiopoietin 1, global myocardial function and myocardial capillary density was also observed. There was a reduction in the LVH and upregulation of myocardial angiogenesis concluding that β-AR blockers prevent adverse vascular remodelling which might underlie its concealed mechanism of action.

E4BP4 inhibits AngII-induced apoptosis in H9c2 cardiomyoblasts by activating the PI3K-Akt pathway and promoting calcium uptake

The bZIP transcription factor E4BP4 is a survival factor that is known to be elevated in diseased heart and promote cell survival. In this study the role of E4BP4 on angiotensin-II (AngII)-induced apoptosis has been examined in in vitro cell model. H9c2 cardiomyoblast cells that overexpressed E4BP4 were exposed to AngII to observe the cardio-protective effects of E4BP4 on hypertension related apoptosis. The results from TUNEL assays revealed that E4BP4 significantly attenuated AngII-induced apoptosis. Further analysis by Western blot and RT-PCR showed that E4BP4 inhibited AngII-induced IGF-II mRNA expression and cleavage of caspase-3 through the PI3K-Akt pathway. In addition, E4BP4 enhanced calcium reuptake into the sacroplasmic reticulum by down-regulating PP2A and by up-regulating the phosphorylation of PKA and PLB proteins. Our findings indicate that E4BP4 functions as a survival factor in cardiomyoblasts by inhibiting IGF-II transcription and by regulating calcium cycling.

E2/ER β inhibit ISO-induced cardiac cellular hypertrophy by suppressing Ca2+-calcineurin signaling

Cardiovascular incidences are markedly higher in men than in pre-menstrual women. However, this advantage in women declines with aging and therefore can be correlated with the sex hormone 17β-Estradiol (E2) which is reported to protect heart cells by acting though estrogen receptors (ERs). In this study we have determined the effect of E2/ERβ against ISO induced cellular hypertrophy in H9c2 cardiomyoblast cells. The results confirm that ISO induced cardiac-hypertrophy by elevating the levels of hypertrophy associated proteins, ANP and BNP and further by upregulating p-CaMKII, calcineurin, p-GATA4 and NFATc3 which was correlated with a significant enlargement of the H9c2 cardiomyoblast. However, overexpression of ERβ and/or administration of E2 inhibited ISO-induced hypertrophy in H9c2 cells. In addition, E2/ERβ also inhibited ISO-induced NFATc3 translocation, and reduced the protein level of downstream marker, BNP. Furthermore, by testing with the calcineurin inhibitor (CsA), it was confirmed that calcineurin acted as a key mediator for the anti-hypertrophic effect of E2/ERβ. In cells treated with calcium blocker (BATPA), the inhibitory effect of E2/ERβ on ISO-induced Ca²⁺ influx and hypertrophic effects were totally blocked suggesting that E2/ERβ inhibited calcineurin activity to activate I-1 protein and suppress PP1, then induce PLB protein phosphorylation and activation, resulting in Ca²⁺ reuptake into sarcoplasmic reticulum through SR Ca²⁺ cycling modification. In conclusion, E2/ERβ suppresses the Ca²⁺ influx and calcineurin activity induced by ISO to enhance the PLB protein activity and SR Ca²⁺ cycling.

Control of cytoplasmic and nuclear protein kinase A by phosphodiesterases and phosphatases in cardiac myocytes

AIMS

The cAMP-dependent protein kinase (PKA) mediates β-adrenoceptor (β-AR) regulation of cardiac contraction and gene expression. Whereas PKA activity is well characterized in various subcellular compartments of adult cardiomyocytes, its regulation in the nucleus remains largely unknown. The aim of the present study was to compare the modalities of PKA regulation in the cytoplasm and nucleus of cardiomyocytes.

METHODS AND RESULTS

Cytoplasmic and nuclear cAMP and PKA activity were measured with targeted fluorescence resonance energy transfer probes in adult rat ventricular myocytes. β-AR stimulation with isoprenaline (Iso) led to fast cAMP elevation in both compartments, whereas PKA activity was fast in the cytoplasm but markedly slower in the nucleus. Iso was also more potent and efficient in activating cytoplasmic than nuclear PKA. Similar slow kinetics of nuclear PKA activation was observed upon adenylyl cyclase activation with L-858051 or phosphodiesterase (PDE) inhibition with 3-isobutyl-1-methylxantine. Consistently, pulse stimulation with Iso (15 s) maximally induced PKA and myosin-binding protein C phosphorylation in the cytoplasm, but marginally activated PKA and cAMP response element-binding protein phosphorylation in the nucleus. Inhibition of PDE4 or ablation of the Pde4d gene in mice prolonged cytoplasmic PKA activation and enhanced nuclear PKA responses. In the cytoplasm, phosphatase 1 (PP1) and 2A (PP2A) contributed to the termination of PKA responses, whereas only PP1 played a role in the nucleus.

CONCLUSION

Our study reveals a differential integration of cytoplasmic and nuclear PKA responses to β-AR stimulation in cardiac myocytes. This may have important implications in the physiological and pathological hypertrophic response to β-AR stimulation.

The role of Ca2+/calmodulin-dependent protein kinase II and calcineurin in TNF-α-induced myocardial hypertrophy

We investigated whether Ca2+/calmodulin-dependent kinase II (CaMKII) and calcineurin (CaN) are involved in myocardial hypertrophy induced by tumor necrosis factor α (TNF-α). The cardiomyocytes of neonatal Wistar rats (1-2 days old) were cultured and stimulated by TNF-α (100 μg/L), and Ca2+ signal transduction was blocked by several antagonists, including BAPTA (4 µM), KN-93 (0.2 µM) and cyclosporin A (CsA, 0.2 µM). Protein content, protein synthesis, cardiomyocyte volumes, [Ca2+]i transients, CaMKIIδB and CaN were evaluated by the Lowry method, [³H]-leucine incorporation, a computerized image analysis system, a Till imaging system, and Western blot analysis, respectively. TNF-α induced a significant increase in protein content in a dose-dependent manner from 10 µg/L (53.56 µg protein/well) to 100 μg/L (72.18 µg protein/well), and in a time-dependent manner from 12 h (37.42 µg protein/well) to 72 h (42.81 µg protein/well). TNF-α (100 μg/L) significantly increased the amplitude of spontaneous [Ca2+]i transients, the total protein content, cell size, and [³H]-leucine incorporation in cultured cardiomyocytes, which was abolished by 4 µM BAPTA, an intracellular Ca2+ chelator. The increases in protein content, cell size and [³H]-leucine incorporation were abolished by 0.2 µM KN-93 or 0.2 µM CsA. TNF-α increased the expression of CaMKIIδB by 35.21% and that of CaN by 22.22% compared to control. These effects were abolished by 4 µM BAPTA, which itself had no effect. These results suggest that TNF-α induces increases in [Ca2+]i, CaMKIIδB and CaN and promotes cardiac hypertrophy. Therefore, we hypothesize that the Ca2+/CaMKII- and CaN-dependent signaling pathways are involved in myocardial hypertrophy induced by TNF-α.

Neuronal nitric oxide synthase is up-regulated by angiotensin II and attenuates NADPH oxidase activity and facilitates relaxation in murine left ventricular myocytes

Angiotensin II (Ang II) is critical in myocardial pathogenesis, mostly via stimulating NADPH oxidase. Neuronal nitric oxide synthase (nNOS) has recently been shown to play important roles in modulating myocardial oxidative stress and contractility. Here, we examine whether nNOS is regulated by Ang II and affects NADPH oxidase production of intracellular reactive oxygen species (ROS(i)) and contractile function in left ventricular (LV) myocytes. Our results showed that Ang II induced biphasic effects on ROS(i) and LV myocyte relaxation (TR(50)) without affecting the amplitude of sarcomere shortening and L-type Ca(2+) current density: TR(50) was prolonged at 30 min but was shortened after 3h (or after Ang II treatment in vivo). Correspondingly, ROS(i) was increased, followed by a reduction to control level. Quantitative RT-PCR and immunoblotting experiments showed that Ang II (3h) increased the mRNA and protein expression of nNOS and increased NO production (nitrite assay) in LV myocyte homogenates, suggesting that nNOS activity may be enhanced and involved in mediating the effects of Ang II. Indeed, n(omega)-nitro-l-arginine methyl ester (l-NAME) or a selective nNOS inhibitor, S-methyl-l-thiocitrulline (SMTC) increased NADPH oxidase production of superoxide/ROS(i) and abolished faster myocyte relaxation induced by Ang II. The positive lusitropic effect of Ang II was not mediated by PKA-, CaMKII-dependent signaling or peroxynitrite. Conversely, inhibition of cGMP/PKG pathway abolished the Ang II-induced faster relaxation by reducing phospholamban (PLN) Ser(16) phosphorylation. Taken together, these results clearly demonstrate that myocardial nNOS is up-regulated by Ang II and functions as an early adaptive mechanism to attenuate NADPH oxidase activity and facilitate myocardial relaxation.

Cardiac β-adrenergic responsiveness with exercise

Left ventricular performance is enhanced with chronic exercise training. Alterations in cardiomyocyte β-adrenergic responsiveness (BAR) may, in part, mediate this response. In this study, cardiac BAR and the expression of some key cardiac hypertrophic signaling molecules following 3 months of treadmill training were examined. Four-month old, female, Wistar Kyoto (WKY) rats were randomly assigned into either a sedentary (WKY-SED, n = 15) or an exercise-trained (WKY-TRD, n = 11) group. All rats were maintained on a 12-h light/dark cycle, and fed ad libitum. Exercise training consisted of motorized treadmill training at 25 m/min, 0% grade, 60 continuous minutes, 5 days/week for a period of 12 weeks. RT-PCR was used to establish basal cardiac calcineurin A, ANP, and AKT mRNA expression. In vitro cardiac BAR responsiveness was determined in Langendorff, isolated hearts. Following baseline, isoproterenol (ISO) was incrementally infused at concentrations ranging from 1 × 10(-10) to 1 × 10(-7) mol/L. There were no group differences for heart weight, heart to body weight ratio, calcineurin A, ANP, or AKT mRNA levels between WKY-SED and WKY-TRD. WKY-TRD showed enhanced cardiac BAR relative to WKY-SED (at ISO 1 × 10(-7) mol/L; P < 0.05). Moderate intensity treadmill exercise improved cardiac BAR responsiveness to a high concentration of isoproterenol. This adaptation was independent of training-induced alterations in cardiac hypertrophy or hypertrophic marker expression.

Sustained hemodynamic stress disrupts normal circadian rhythms in calcineurin-dependent signaling and protein phosphorylation in the heart

RATIONALE

Despite overwhelming evidence of the importance of circadian rhythms in cardiovascular health and disease, little is known regarding the circadian regulation of intracellular signaling pathways controlling cardiac function and remodeling.

OBJECTIVE

To assess circadian changes in processes dependent on the protein phosphatase calcineurin, relative to changes in phosphorylation of cardiac proteins, in normal, hypertrophic, and failing hearts.

METHODS AND RESULTS

We found evidence of large circadian oscillations in calcineurin-dependent activities in the left ventricle of healthy C57BL/6 mice. Calcineurin-dependent transcript levels and nuclear occupancy of the NFAT (nuclear factor of activated T cells) regularly fluctuated as much as 20-fold over the course of a day, peaking in the morning when mice enter a period of rest. Phosphorylation of the protein phosphatase 1 inhibitor 1 (I-1), a direct calcineurin substrate, and phospholamban, an indirect target, oscillated directly out of phase with calcineurin-dependent signaling. Using a surgical model of cardiac pressure overload, we found that although calcineurin-dependent activities were markedly elevated, the circadian pattern of activation was maintained, whereas, oscillations in phospholamban and I-1 phosphorylation were lost. Changes in the expression of fetal gene markers of heart failure did not mirror the rhythm in calcineurin/NFAT activation, suggesting that these may not be direct transcriptional target genes. Cardiac function in mice subjected to pressure overload was significantly lower in the morning than in the evening when assessed by echocardiography.

CONCLUSIONS

Normal, opposing circadian oscillations in calcineurin-dependent activities and phosphorylation of proteins that regulate contractility are disrupted in heart failure.

Protective effect of the endothelin antagonist CPU0213 against isoprenaline-induced heart failure by suppressing abnormal expression of leptin, calcineurin and SERCA2a in rats

Heart failure (HF) may be produced by sustained β-adrenoceptor stimulation by causing changes in the expression of endothelin-1 (ET-1), the leptin system, calcineurin and sarcoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) underlying cardiac dysfunction. The aim of this study was to verify whether isoprenaline (ISO)-induced HF is attributed to changes in the above molecular markers, and whether the dual ET-receptor antagonist CPU0213 could reverse the cardiac dysfunction caused by ISO treatment, focusing on these molecular markers. HF was induced in rats by administration of ISO (2 mgkg−1 s.c.) for 10 days. CPU0213 (30 mgkg−1 s.c.) and propranolol (4 mgkg−1 s.c.) were administered on days 7–10. HF developed after 10 days' ISO administration and was manifest as impaired cardiac performance, increased heart weight index, oxidative stress, elevated serum enzymes, and disordered expression of the endothelin system, leptin system, calcineurin and SERCA2a. All these abnormalities were significantly reversed by CPU0213, and the effectiveness of this ET-receptor antagonist was comparable to that of propranolol. Thus, antagonism of ET receptors by CPU0213 normalizes these changes in molecular markers, alleviating HF.

Left ventricular remodeling with exercise in hypertension

We investigated how exercise training superimposed on chronic hypertension impacted left ventricular remodeling. Cardiomyocyte hypertrophy, apoptosis, and proliferation in hearts from female spontaneously hypertensive rats (SHRs) were examined. Four-month-old SHR animals were placed into a sedentary group (SHR-SED; n = 18) or a treadmill running group (SHR-TRD, 20 m/min, 1 h/day, 5 days/wk, 12 wk; n = 18). Age-matched, sedentary Wistar Kyoto (WKY) rats were controls (n = 18). Heart weight was greater in SHR-TRD vs. both WKY (P < 0.01) and SHR-SED (P < 0.05). Morphometric-derived left ventricular anterior, posterior, and septal wall thickness were increased in SHR-SED relative to WKY and augmented in SHR-TRD. Cardiomyocyte surface area, length, and width were increased in SHR-SED relative to WKY and further increased in SHR-TRD. Calcineurin abundance was increased in SHR-SED vs. WKY (P < 0.001) and attenuated in SHR-TRD relative to SHR-SED (P < 0.05). Protein abundance and mRNA of Akt was not different among groups. The rate of apoptosis was increased in SHR-SED relative to WKY and mitigated in SHR-TRD. The abundance of Ki-67(+) cells across groups was not statistically different across groups. The abundance of cardiac progenitor cells (c-Kit(+) cells) was increased in SHR-TRD relative to WKY. These data suggest that exercise training superimposed on hypertension augmented cardiomyocyte hypertrophy, despite attenuating calcineurin abundance. Exercise training also mitigated apoptosis in hypertension and showed a tendency to enhance the abundance of cardiac progenitor cells, resulting in a more favorable cardiomyocyte number in the exercise-trained hypertensive heart.

Cardiac anti-remodelling effect of aerobic training is associated with a reduction in the calcineurin/NFAT signalling pathway in heart failure mice

Cardiomyocyte hypertrophy occurs in response to a variety of physiological and pathological stimuli. While pathological hypertrophy in heart failure is usually coupled with depressed contractile function, physiological hypertrophy associates with increased contractility. In the present study, we explored whether 8 weeks of moderate intensity exercise training would lead to a cardiac anti-remodelling effect in an experimental model of heart failure associated with a deactivation of a pathological (calcineurin/NFAT, CaMKII/HDAC) or activation of a physiological (Akt-mTOR) hypertrophy signalling pathway. The cardiac dysfunction, exercise intolerance, left ventricle dilatation, increased heart weight and cardiomyocyte hypertrophy from mice lacking alpha(2A) and alpha(2C) adrenoceptors (alpha(2A)/alpha(2C)ARKO mice) were associated with sympathetic hyperactivity induced heart failure. The relative contribution of Ca(2+)-calmodulin high-affinity (calcineurin/NFAT) and low-affinity (CaMKII/HDAC) targets to pathological hypertrophy of alpha(2A)/alpha(2C)ARKO mice was verified. While nuclear calcineurin B, NFATc3 and GATA-4 translocation were significantly increased in alpha(2A)/alpha(2C)ARKO mice, no changes were observed in CaMKII/HDAC activation. As expected, cyclosporine treatment decreased nuclear translocation of calcineurin/NFAT in alpha(2A)/alpha(2C)ARKO mice, which was associated with improved ventricular function and a pronounced anti-remodelling effect. The Akt/mTOR signalling pathway was not activated in alpha(2A)/alpha(2C)ARKO mice. Exercise training improved cardiac function and exercise capacity in alpha(2A)/alpha(2C)ARKO mice and decreased heart weight and cardiomyocyte width paralleled by diminished nuclear NFATc3 and GATA-4 translocation as well as GATA-4 expression levels. When combined, these findings support the notion that deactivation of calcineurin/NFAT pathway-induced pathological hypertrophy is a preferential mechanism by which exercise training leads to the cardiac anti-remodelling effect in heart failure.

Cardiac force-frequency relationship and frequency-dependent acceleration of relaxation are impaired in LPS-treated rats

Introduction

Frequency-dependent acceleration of relaxation (FDAR) ensures appropriate ventricular filling at high heart rates and results from accelerated sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) activity independent of calcium removal from the cell. Because lipopolysaccharide (LPS) challenge may induce aberrations in calcium trafficking and protein phosphorylation, we tested whether LPS would abolish FDAR in rats.

Methods

Following LPS injection, changes in force-frequency relationship and FDAR were studied in cardiomyocytes, isolated hearts and in vivo by echocardiography. Calcium uptake and phosphatase activities were studied in sarcoplasmic reticulum (SR) vesicle preparations. Western blots of phospholamban and calcium/calmodulin-dependent protein kinase II, and serine/threonine phosphatase activity were studied in heart preparations.

Results

In cardiomyocytes and isolated heart preparations, reductions in time constant of relaxation (τ) and time to 50% relaxation at increasing rate of pacing were blunted in LPS-treated rats compared with controls. Early diastolic velocity of the mitral annulus (Ea), a relaxation parameter which correlates in vivo with τ, was reduced in LPS rats compared with control rats. LPS impaired SR calcium uptake, reduced phospholamban phosphorylation and increased serine/threonine protein phosphatase activity. In vivo inhibition of phosphatase activity partially restored FDAR, reduced phosphatase activity and prevented phospholamban dephosphorylation in LPS rat hearts.

Conclusions

LPS impaired phospholamban phosphorylation, cardiac force-frequency relationship and FDAR. Disruption of frequency-dependent acceleration of LV relaxation, which normally participates in optimal heart cavity filling, may be detrimental in sepsis, which is typically associated with elevated heart rates and preload dependency.

Sildenafil stops progressive chamber, cellular, and molecular remodeling and improves calcium handling and function in hearts with pre-existing advanced hypertrophy caused by pressure overload

OBJECTIVE

This study sought to test the efficacy of phosphodiesterase type 5A (PDE5A) inhibition for treating advanced hypertrophy/remodeling caused by pressure overload, and to elucidate cellular and molecular mechanisms for this response.

BACKGROUND

Sildenafil (SIL) inhibits cyclic guanosine monophosphate-specific PDE5A and can blunt the evolution of cardiac hypertrophy and dysfunction in mice subjected to pressure overload. Whether and how it ameliorates more established advanced disease and dysfunction is unknown.

METHODS

Mice were subjected to transverse aortic constriction (TAC) for 3 weeks to establish hypertrophy/dilation, and subsequently treated with SIL (100 mg/kg/day) or placebo for 6 weeks of additional TAC.

RESULTS

The SIL arrested further progressive chamber dilation, dysfunction, fibrosis, and molecular remodeling, increasing myocardial protein kinase G activity. Isolated myocytes from TAC-SIL hearts showed greater sarcomere shortening and relaxation, and enhanced Ca(2+) transients and decay compared with nontreated TAC hearts. The SIL treatment restored gene and protein expression of sarcoplasmic reticulum Ca(2+) uptake adenosine triphosphatase (SERCA2a), phospholamban (PLB), and increased PLB phosphorylation (S16), consistent with improved calcium handling. The phosphatase calcineurin (Cn) and/or protein kinase C-alpha (PKCalpha) can both lower phosphorylated phospholamban and depress myocyte calcium cycling. The Cn expression and PKCalpha activation (outer membrane translocation) were enhanced by chronic TAC and reduced by SIL treatment. Expression of PKCdelta and PKCepsilon also increased with TAC but were unaltered by SIL treatment.

CONCLUSIONS

SIL treatment applied to well-established hypertrophic cardiac disease can prevent further cardiac and myocyte dysfunction and progressive remodeling. This is associated with improved calcium cycling, and reduction of Cn and PKCalpha activation may be important to this improvement.

Phosphodiesterase 5 inhibition blocks pressure overload-induced cardiac hypertrophy independent of the calcineurin pathway

AIMS

Cyclic GMP (cGMP)-specific phosphodiesterase 5 (PDE5) inhibition by sildenafil (SIL) activates myocardial cGMP-dependent protein kinase G (PKG) and blunts cardiac hypertrophy. To date, the only documented target of PKG in myocardium is the serine-threonine phosphatase calcineurin (Cn), which is central to pathological cardiac hypertrophy. We tested whether Cn suppression is necessary in order to observe anti-hypertrophic effects of SIL.

METHODS AND RESULTS

Mice lacking the Cn-Abeta subunit (CnAbeta(-/-)) and wild-type (WT) controls were subjected to transverse aorta constriction (TAC) with or without SIL (200 mg/kg/day, p.o.) for 3 weeks. TAC-induced elevation of Cn expression and activity in WT was absent in CnAbeta(-/-) hearts, and the latter accordingly developed less cardiac hypertrophy (50 vs. 100% increase in heart weight/tibia length, P < 0.03) and chamber dilation. SIL remained effective in CnAbeta(-/-) mice, increasing PKG activity similarly as in WT, suppressing hypertrophy and fetal gene expression, and enhancing heart function without altering afterload. TAC-stimulated calcium-calmodulin kinase II, Akt, and glycogen synthase kinase 3beta in both groups (the first rising more in CnAbeta(-/-) hearts), and SIL also suppressed these similarly. Activation of extracellular signal-regulated kinase observed in WT-TAC but not CnAbeta(-/-) hearts was also suppressed by SIL.

CONCLUSION

PDE5A inhibition and its accompanying PKG activation blunt hypertrophy and improve heart function even without Cn activation. This occurs by its modulation of several alternative pathways which may result from concomitant distal targeting, or activity against a common proximal node.