sildenafil-citrate and Cardiomegaly

Ventricular remodelling describes structural changes in the left ventricle in response to chronic alterations in loading conditions, with three major patterns: concentric remodelling, when a pressure load leads to growth in cardiomyocyte thickness; eccentric hypertrophy, when a volume load produces myocyte lengthening; and myocardial infarction, an amalgam of patterns in which stretched and dilated infarcted tissue increases left-ventricular volume with a combined volume and pressure load on non-infarcted areas. Whether left-ventricular hypertrophy is adaptive or maladaptive is controversial, as suggested by patterns of signalling pathways, transgenic models, and clinical findings in aortic stenosis. The transition from apparently compensated hypertrophy to the failing heart indicates a changing balance between metalloproteinases and their inhibitors, effects of reactive oxygen species, and death-promoting and profibrotic neurohumoral responses. These processes are evasive therapeutic targets. Here, we discuss potential novel therapies for these disorders, including: sildenafil, an unexpected option for anti-transition therapy; surgery for increased sphericity caused by chronic volume overload of mitral regurgitation; an antifibrotic peptide to inhibit the fibrogenic effects of transforming growth factor beta; mechanical intervention in advanced heart failure; and stem-cell therapy.

Topics: Animals; Attitude of Health Personnel; Cardiomegaly; Humans; Mitral Valve Insufficiency; Models, Cardiovascular; Oxidative Stress; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasodilator Agents; Ventricular Remodeling

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease (ESRD). Hypertension increases kidney stress, which deteriorates function, and leads to peripheral renal vascular resistance. Long-term hypoperfusion promotes interstitial fibrosis and glomerular sclerosis, resulting in nephrosclerosis. Although hypertension and DN are frequent ESRD complications, relevant animal models remain unavailable. We generated a deoxycorticosterone acetate (DOCA)-salt hypertensive uni-nephrectomized (UNx) KKA

Topics: Acetates; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cardiomegaly; Cyclic Nucleotide Phosphodiesterases, Type 4; Cyclic Nucleotide Phosphodiesterases, Type 5; Desoxycorticosterone; Female; Hyperglycemia; Hypertension; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mineralocorticoids; Phosphodiesterase 5 Inhibitors; Renal Insufficiency; Sildenafil Citrate; Sodium Chloride; Tyramine

Activation of the atrial natriuretic signaling pathway is intrinsic to the pathological responses associated with a range of cardiovascular diseases that stress the heart, especially those involved in sustained cardiac pressure overload which induces hypertrophy and the pathological remodeling that frequently leads to heart failure. We identify transient receptor potential cation channel, subfamily V, member 1, as a regulated molecular component, and therapeutic target of this signaling system. Data show that TRPV1 is a physical component of the natriuretic peptide A, cGMP, PKG signaling complex, interacting with the Natriuretic Peptide Receptor 1 (NPR1), and upon binding its ligand, Natriuretic Peptide A (NPPA, ANP) TRPV1 activation is subsequently suppressed through production of cGMP and PKG mediated phosphorylation of the TRPV1 channel. Further, inhibition of TRPV1, with orally delivered drugs, suppresses chamber and myocyte hypertrophy, and can longitudinally improve in vivo heart function in mice exposed to chronic pressure overload induced by transverse aortic constriction, reversing pre-established hypertrophy induced by pressure load while restoring chamber function. TRPV1 is a physical and regulated component of the natriuretic peptide signaling system, and TRPV1 inhibition may provide a new treatment strategy for treating, and reversing the loss of function associated with cardiac hypertrophy and heart failure.

Topics: Acrylamides; Administration, Oral; Animals; Bridged Bicyclo Compounds, Heterocyclic; Cardiomegaly; Heart Failure; HEK293 Cells; Humans; Male; Mice; Mice, Inbred C57BL; Molecular Structure; Signal Transduction; Sildenafil Citrate; TRPV Cation Channels

Spontaneously hypertensive rats (SHR) exhibit impaired endothelial vasodilation and enhanced vasoconstriction. The phosphodiesterase 5 (PDE5) inhibitor sildenafil (Sild) potentiates the nitric oxide (NO)-mediated effects exerting antioxidative and anti-inflammatory actions. In the present study, we hypothesized that Sild could improve endothelial function in SHR.. Male rats were treated daily for 60 days by oral gavage with Sild (45 mg/kg) before the onset of the hypertensive state (pre-hypertensive protocol). The aortic relaxation to acetylcholine (ACh), sodium nitroprusside (SNP) and the phenylephrine (Phe)-induced contraction was evaluated in SHR. Protein expression of eNOS, p-eNOS, caveolin, COX-1, COX-2, ERK and p-ERK was measured by Western blot.. Resting blood pressure was not modified by Sild administration. Treatment with Sild did not alter the relaxation response to SNP but improved the ACh-induced relaxation and reduced Phe-induced contraction in aortic rings from SHR. This protective effect of Sild could be attributed to reduced superoxide anions (O. Sild improves endothelial function in SHR aorta without affecting resting blood pressure values. These results indicate that PDE5 inhibition has a potential role in the improvement of vascular function and could be an adjuvant in the treatment of essential hypertension.

Topics: Animals; Cardiomegaly; Cells, Cultured; Cyclooxygenase 2; Endothelium, Vascular; Hypertension; Male; Nitric Oxide; Oxidative Stress; Rats; Rats, Inbred SHR; Sildenafil Citrate; Vasodilator Agents

Right ventricular (RV) dysfunction following left ventricular (LV) failure is associated with poor prognosis. RV remodeling is thought initiated by the increase in the afterload of RV due to secondary pulmonary hypertension (PH) to impaired LV function; however, RV molecular changes might occur in earlier stages of the disease. cGMP (cyclic guanosine monophosphate)-phosphodiesterase 5 (PDE5) inhibitors, widely used to treat PH through their pulmonary vasorelaxation properties, have shown direct cardiac benefits, but their impacts on the RV in LV diseases are not fully determined. Here we show that RV molecular alterations occur early in the absence of RV hemodynamic changes during LV pressure-overload and are ameliorated by PDE5 inhibition. Two-day moderate LV pressure-overload (transverse aortic constriction) neither altered RV pressure/ function nor RV weight in mice, while it induced only mild LV hypertrophy. Importantly, pathological molecular features were already induced in the RV free wall myocardium, including up-regulation of gene markers for hypertrophy and inflammation, and activation of extracellular signal-regulated kinase (ERK) and calcineurin. Concomitant PDE5 inhibition (sildenafil) prevented induction of such pathological genes and activation of ERK and calcineurin in the RV as well as in the LV. Importantly, dexamethasone also prevented these RV molecular changes, similarly to sildenafil treatment. These results suggest the contributory role of inflammation to the early pathological interventricular interaction between RV and LV. The current study provides the first evidence for the novel early molecular cross-talk between RV and LV, preceding RV hemodynamic changes in LV disease, and supports the therapeutic strategy of enhancing cGMP signaling pathway to treat heart diseases.

Topics: Animals; Calcineurin; Cardiomegaly; Cardiovascular Agents; Dexamethasone; Disease Models, Animal; Extracellular Signal-Regulated MAP Kinases; Heart Ventricles; Hemodynamics; Macrophages; Male; Mice, Inbred C57BL; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate; Ventricular Dysfunction; Ventricular Function, Left; Ventricular Function, Right; Ventricular Pressure

Phosphodiesterase 5A (PDE5A) specifically degrades the ubiquitous second messenger cGMP and experimental and clinical data highlight its important role in cardiac diseases. To address PDE5A role in cardiac physiology, three splice variants of the PDE5A were cloned for the first time from mouse cDNA library (mPde5a1, mPde5a2, and mPde5a3). The predicted amino acidic sequences of the three murine isoforms are different in the N-terminal regulatory domain. mPDE5A isoforms were transfected in HEK293T cells and they showed high affinity for cGMP and similar sensitivity to sildenafil inhibition. RT-PCR analysis showed that mPde5a1, mPde5a2, and mPde5a3 had differential tissue distribution. In the adult heart, mPde5a1 and mPde5a2 were expressed at different levels whereas mPde5a3 was undetectable. Overexpression of mPDE5As induced an increase of HL-1 number cells which progress into cell cycle. mPDE5A1 and mPDE5A3 overexpression increased the number of polyploid and binucleated cells, mPDE5A3 widened HL-1 areas, and modulated hypertrophic markers more efficiently respect to the other mPDE5A isoforms. Moreover, mPDE5A isoforms had differential subcellular localization: mPDE5A1 was mainly localized in the cytoplasm, mPDE5A2 and mPDE5A3 were also nuclear localized. These results demonstrate for the first time the existence of three PDE5A isoforms in mouse and highlight their potential role in the induction of hypertrophy.

Topics: Animals; Cardiomegaly; Cell Cycle; Cell Nucleus; Cell Proliferation; Cloning, Molecular; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Cytosol; Female; Flow Cytometry; Gene Expression Regulation, Enzymologic; HEK293 Cells; Humans; Male; Mice; Myocytes, Cardiac; NIH 3T3 Cells; Phosphodiesterase 5 Inhibitors; Polyploidy; Protein Isoforms; Signal Transduction; Sildenafil Citrate; Transfection

Sildenafil, a phosphodiesterase 5 (PDE5) inhibitor, has been shown to exert beneficial effects in heart failure. The purpose of this study was to test whether sildenafil suppressed transverse-tubule (T-tubule) remodeling in left ventricular (LV) failure and thereby providing the therapeutic benefits.. A pressure overload-induced murine heart failure model was established in mice by thoracic aortic banding (TAB). One day after TAB, the mice received sildenafil (100 mg·kg(-1)·d(-1), sc) or saline for 5 weeks. At the end of treatment, echocardiography was used to examine LV function. Then the intact hearts were dissected out and placed in Langendorff-perfusion chamber for in situ confocal imaging of T-tubule ultrastructure from epicardial myocytes.. TAB surgery resulted in heart failure accompanied by remarkable T-tubule remodeling. Sildenafil treatment significantly attenuated TAB-induced cardiac hypertrophy and congestive heart failure, improved LV contractile function, and preserved T-tubule integrity in LV cardiomyocytes. But sildenafil treatment did not significantly affect the chamber dilation. The integrity of LV T-tubule structure was correlated with cardiac hypertrophy (R(2)=0.74, P<0.01) and global LV function (R(2)=0.47, P<0.01).. Sildenafil effectively ameliorates LV T-tubule remodeling in TAB mice, revealing a novel mechanism underlying the therapeutic benefits of sildenafil in heart failure.

Topics: Animals; Cardiomegaly; Heart Failure; Male; Mice, Inbred C57BL; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate; Ventricular Function, Left; Ventricular Remodeling

We report a 14-month-old child with persistent truncus arteriosus and crossed pulmonary arteries. The potential advantage of crossed pulmonary artery arrangement in achieving surgical correction is discussed.

Topics: Abnormalities, Multiple; Anastomosis, Surgical; Cardiomegaly; Cardiopulmonary Bypass; Combined Modality Therapy; Dobutamine; Female; Humans; Hypertension, Pulmonary; Infant; Milrinone; Pulmonary Artery; Sildenafil Citrate; Truncus Arteriosus, Persistent; Vascular Surgical Procedures

Analyses of several mouse models imply that the phosphodiesterase 5 (PDE5) inhibitor sildenafil (SIL), via increasing cGMP, affords protection against angiotensin II (Ang II)-stimulated cardiac remodeling. However, it is unclear which cell types are involved in these beneficial effects, because Ang II may exert its adverse effects by modulating multiple renovascular and cardiac functions via Ang II type 1 receptors (AT1Rs). To test the hypothesis that SIL/cGMP inhibit cardiac stress provoked by amplified Ang II/AT1R directly in cardiomyocytes (CMs), we studied transgenic mice with CM-specific overexpression of the AT1R under the control of the α-myosin heavy chain promoter (αMHC-AT1R(tg/+)). The extent of cardiac growth was assessed in the absence or presence of SIL and defined by referring changes in heart weight to body weight or tibia length. Hypertrophic marker genes, extracellular matrix-regulating factors, and expression patterns of fibrosis markers were examined in αMHC-AT1R(tg/+) ventricles (with or without SIL) and corroborated by investigating different components of the natriuretic peptide/PDE5/cGMP pathway as well as cardiac functions. cGMP levels in heart lysates and intact CMs were measured by competitive immunoassays and Förster resonance energy transfer. We found higher cardiac and CM cGMP levels and upregulation of the cGMP-dependent protein kinase type I with AT1R overexpression. However, even a prolonged SIL treatment regimen did not limit the progressive CM growth, fibrosis, or decline in cardiac functions in the αMHC-AT1R(tg/+) model, suggesting that SIL does not interfere with the pathogenic actions of amplified AT1R signaling in CMs. Hence, the cardiac/noncardiac cells involved in the cross-talk between SIL-sensitive PDE activity and Ang II/AT1R still need to be identified.

Topics: Adaptor Proteins, Signal Transducing; Angiotensin II; Animals; Cardiomegaly; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Fibrosis; Mice; Mice, Inbred C57BL; Mice, Transgenic; Myocytes, Cardiac; Piperazines; Purines; Receptor, Angiotensin, Type 1; Signal Transduction; Sildenafil Citrate; Sulfonamides; Up-Regulation

Conflicting results have been reported for the roles of cGMP and cGMP-dependent protein kinase I (cGKI) in various pathological conditions leading to cardiac hypertrophy and fibrosis. A cardioprotective effect of cGMP/cGKI has been reported in whole animals and isolated cardiomyocytes, but recent evidence from a mouse model expressing cGKIβ only in smooth muscle (βRM) but not in cardiomyocytes, endothelial cells, or fibroblasts has forced a reevaluation of the requirement for cGKI activity in the cardiomyocyte antihypertrophic effects of cGMP. In particular, βRM mice developed the same hypertrophy as WT controls when subjected to thoracic aortic constriction or isoproterenol infusion. Here, we challenged βRM and WT (Ctr) littermate control mice with angiotensin II (AII) infusion (7 d; 2 mg ⋅ kg(-1) ⋅ d(-1)) to induce hypertrophy. Both genotypes developed cardiac hypertrophy, which was more pronounced in Ctr animals. Cardiomyocyte size and interstitial fibrosis were increased equally in both genotypes. Addition of sildenafil, a phosphodiesterase 5 (PDE5) inhibitor, in the drinking water had a small effect in reducing myocyte hypertrophy in WT mice and no effect in βRM mice. However, sildenafil substantially blocked the increase in collagen I, fibronectin 1, TGFβ, and CTGF mRNA in Ctr but not in βRM hearts. These data indicate that, for the initial phase of AII-induced cardiac hypertrophy, lack of cardiomyocyte cGKI activity does not worsen hypertrophic growth. However, expression of cGKI in one or more cell types other than smooth muscle is necessary to allow the antifibrotic effect of sildenafil.

Topics: Angiotensin II; Animals; Cardiomegaly; Cyclic GMP; Cyclic GMP-Dependent Protein Kinase Type I; Cyclic Nucleotide Phosphodiesterases, Type 5; Fibrosis; Genetic Markers; Hypertension; Mice; Muscle, Smooth; Myocardial Contraction; Myocytes, Cardiac; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasoconstrictor Agents

Transient receptor potential canonical (TRPCs) channels are up-regulated in the development of cardiac hypertrophy. Sildenafil inhibits TRPC6 activation and expression, leading to the prevention of cardiac hypertrophy. However, the effects of sildenafil on the expression of other TRPCs remain unknown. We hypothesized that in addition to its effects of TRPC6, sildenafil blocks the up-regulation of other TRPC channels to suppress cardiomyocyte hypertrophy.. In cultured neonatal rat cardiomyocytes, a 48 h treatment with 10nM endothelin (ET)-1 induced hypertrophic responses characterized by nuclear factor of activated T cells activation and enhancement of brain natriuretic peptide expression and cell surface area. Co-treatment with sildenafil (1 μM, 48 h) inhibited these ET-1-induced hypertrophic responses. Although ET-1 enhanced the gene expression of TRPCs, sildenafil inhibited the enhanced gene expression of TRPC1, C3 and C6. Moreover, co-treatment with sildenafil abolished the augmentation of SOCE in the hypertrophied cardiomyocytes.. These results suggest that sildenafil inhibits cardiomyocyte hypertrophy by suppressing the up-regulation of TRPC expression.

Topics: Animals; Calcium; Cardiomegaly; Cells, Cultured; Endothelin-1; Myocytes, Cardiac; NFATC Transcription Factors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Time Factors; Transcriptional Activation; TRPC Cation Channels; Up-Regulation

Inhibition of the cGMP-specific phosphodiesterase 5 (PDE5) exerts profound beneficial effects on failing hearts. However, the mechanisms underlying the therapeutic effects of PDE5 inhibition on heart failure are unclear. The purpose of this study was to investigate whether PDE5 inhibition decreases endoplasmic reticulum (ER) stress, a key event in heart failure.. Heart failure was induced by isoprenaline s.c. injection in Sprague-Dawley rats and transverse aortic constriction (TAC) in mice. PDE5 was inhibited with sildenafil. Heart function was detected by invasive pressure-volume analysis and echocardiography. ER stress markers were analysed by Western blotting. Apoptosis was measured by flow cytometric analysis.. PDE5 inhibition markedly attenuated isoprenaline-induced and TAC-induced cardiac hypertrophy and dysfunction, and reduced ER stress and apoptosis. Further, PDE5 inhibition with sildenafil largely prevented ER stress and reduced apoptosis in isoprenaline- or thapsigargin-treated cardiomyocytes. PKG inhibition markedly prevented the protective effects of sildenafil in vivo and in vitro. To further understand the mechanism of the effect of PDE5 inhibition on ER stress, we demonstrated that PDE5 inhibitor increased sarco-(endo)-plasmic reticulum Ca(2+) -ATPase activity via phosphorylation of phospholamban at Ser(16) . This may contribute to the attenuation of ER stress induced by PDE5 inhibition.. These results suggest that PDE5 inhibition can attenuate ER stress and improve cardiac function in vivo and in vitro. Suppression of ER stress by inhibiting PDE5 may contribute to the therapeutic effects on heart failure.

Topics: Animals; Aorta; Apoptosis; Calcium-Binding Proteins; Cardiomegaly; Constriction; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Endoplasmic Reticulum; Endoplasmic Reticulum Stress; Heart Failure; Humans; Isoproterenol; Male; Mice; Mice, Inbred C57BL; Myocardial Contraction; Myocytes, Cardiac; Phosphodiesterase 5 Inhibitors; Phosphorylation; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Signal Transduction; Sildenafil Citrate; Stroke Volume; Sulfones; Ventricular Function, Left

Phosphodiesterase 5 inhibitors (PDE-5Is) can suppress and (or) reverse pressure overload induced myocardial hypertrophy. This study investigated the suppressive effect of 2 PDE-5Is (sildenafil and ordonafil) on N-nitro-l-arginine methyl ester (L-NAME)-induced cardiac hypertrophy in rabbit heart, and examined their possible mechanism of action. L-NAME increased left ventricular thickness to 6.1± 0.18 mm from 4.6 ± 0.13 mm (p < 0.05), which regressed after treatment with either sildenafil or ordonafil to 5.1 ± 0.1 mm and 4.8 ± 0.2 mm, respectively (p < 0.05). Phenylephrine increased neonatal rat ventricular myocyte cell surface area to 131% ± 3% of the control value, which was associated with significant increment in ERK1/2 to 143% ± 5% of the control value (p < 0.05). Ordonafil and sildenafil decreased cell surface area to 95% ± 3% and 90% ± 1% of the control value, respectively. Both drugs decreased ERK1/2 to 88% ± 4% of the control value. Calcineurin activity was significantly decreased after 1 h of treatment with 0.1 mg·L(-1) ordonafil (1.15 ± 0.05, p < 0.05). For sildenafil (0.1 mg·L(-1)), calcineurin activity significantly decreased only after 24 h of incubation (22%). Also p38 activation was attenuated by ordonafil and sildenafil (0.1 mg·L(-1)). It is suggested that both drugs have the ability to reverse L-NAME-induced cardiac hypertrophy and suppress phenylphrine-induced myocyte hypertrophy, and that these effects may be mediated through the attenuation of calcineurin and its downstream signaling pathways (p38) in neonatal rat ventricular myocytes.

Topics: Animals; Calcineurin; Cardiomegaly; Cell Size; Female; Male; Myocytes, Cardiac; NG-Nitroarginine Methyl Ester; p38 Mitogen-Activated Protein Kinases; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rabbits; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones

Chronic inhibition of phosphodiesterase-5 with sildenafil immediately after permanent occlusion of the left anterior descending coronary artery was shown to limit ischemic heart failure (HF) in mice. To mimic a more clinical scenario, we postulated that treatment with sildenafil beginning at 3 days post-myocardial infarction (MI) would also reduce HF progression through the inhibition of the RhoA/Rho-kinase pathway. Adult male ICR mice with fractional shortening < 25% at day 3 following permanent left anterior descending coronary artery ligation were continuously treated with either saline (volume matched, ip, 2 times/day) or sildenafil (21 mg/kg, ip, 2 times/day) for 25 days. Echocardiography showed fractional shortening preservation and less left ventricular end-diastolic dilatation with sildenafil treatment compared with saline treatment at 7 and 28 days post-MI (P < 0.05). Both fibrosis and apoptosis, determined by Masson's trichrome and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL), respectively, were attenuated in the sildenafil-treated mice (P < 0.05 vs. saline). Western blot analysis showed enchanced Bcl-2-to-Bax ratio with sildenafil treatment (P < 0.05 vs. saline). Activity assay showed sildenafil-mediated PKG activation 1 day after treatment (P < 0.05 vs. sham and saline). PKG activation was associated with sildenafil-mediated inhibition of Rho kinase (P < 0.05) compared with saline treatment, whereas PKG inhibition with KT-5823 abolished this inhibitory effect of sildenafil. In conclusion, for the first time, our findings show that chronic sildenafil treatment, initiated at 3 days post-MI, attenuates left ventricular dysfunction independent of its infarct-sparing effect, and this cardioprotection involves the inhibition of the RhoA/Rho-kinase pathway. Sildenafil may be a promising therapeutic tool for advanced HF in patients.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Cardiomegaly; Cyclic GMP-Dependent Protein Kinases; Heart Failure; Hemodynamics; Male; Mice; Mice, Inbred ICR; Models, Animal; Phosphodiesterase 5 Inhibitors; Piperazines; Proto-Oncogene Proteins c-bcl-2; Purines; rho-Associated Kinases; rhoA GTP-Binding Protein; Signal Transduction; Sildenafil Citrate; Sulfones; Ventricular Dysfunction, Left

Activation of Ca(2+) signaling induced by receptor stimulation and mechanical stress plays a critical role in the development of cardiac hypertrophy. A canonical transient receptor potential protein subfamily member, TRPC6, which is activated by diacylglycerol and mechanical stretch, works as an upstream regulator of the Ca(2+) signaling pathway. Although activation of protein kinase G (PKG) inhibits TRPC6 channel activity and cardiac hypertrophy, respectively, it is unclear whether PKG suppresses cardiac hypertrophy through inhibition of TRPC6. Here, we show that inhibition of cGMP-selective PDE5 (phosphodiesterase 5) suppresses endothelin-1-, diacylglycerol analog-, and mechanical stretch-induced hypertrophy through inhibition of Ca(2+) influx in rat neonatal cardiomyocytes. Inhibition of PDE5 suppressed the increase in frequency of Ca(2+) spikes induced by agonists or mechanical stretch. However, PDE5 inhibition did not suppress the hypertrophic responses induced by high KCl or the activation of protein kinase C, suggesting that PDE5 inhibition suppresses Ca(2+) influx itself or molecule(s) upstream of Ca(2+) influx. PKG activated by PDE5 inhibition phosphorylated TRPC6 proteins at Thr(69) and prevented TRPC6-mediated Ca(2+) influx. Substitution of Ala for Thr(69) in TRPC6 abolished the anti-hypertrophic effects of PDE5 inhibition. In addition, chronic PDE5 inhibition by oral sildenafil treatment actually induced TRPC6 phosphorylation in mouse hearts. Knockdown of RGS2 (regulator of G protein signaling 2) and RGS4, both of which are activated by PKG to reduce G alpha(q)-mediated signaling, did not affect the suppression of receptor-activated Ca(2+) influx by PDE5 inhibition. These results suggest that phosphorylation and functional suppression of TRPC6 underlie prevention of pathological hypertrophy by PDE5 inhibition.

Topics: Amino Acid Substitution; Animals; Calcium; Calcium Signaling; Cardiomegaly; Cell Line; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Diglycerides; Enzyme Activation; Gene Knockdown Techniques; GTP-Binding Protein alpha Subunits, Gq-G11; Humans; Male; Mice; Mutation, Missense; Myocytes, Cardiac; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Potassium Chloride; Protein Kinase C; Purines; Rats; Sildenafil Citrate; Sulfones; TRPC Cation Channels; TRPC6 Cation Channel

Topics: Animals; Cardiomegaly; Cyclic GMP-Dependent Protein Kinase Type I; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Mice; Mice, Knockout; Models, Cardiovascular; Myocytes, Cardiac; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; Signal Transduction; Sildenafil Citrate; Sulfones

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.. 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.. 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.

Topics: Animals; Calcineurin; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Cardiomegaly; Cyclic GMP-Dependent Protein Kinases; Extracellular Signal-Regulated MAP Kinases; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Hypertension; Male; Mice; Mice, Inbred C57BL; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

The heart initially compensates for hypertension-mediated pressure overload by enhancing its contractile force and developing hypertrophy without dilation. Gq protein-coupled receptor pathways become activated and can depress function, leading to cardiac failure. Initial adaptation mechanisms to reduce cardiac damage during such stimulation remain largely unknown. Here we have shown that this initial adaptation requires regulator of G protein signaling 2 (RGS2). Mice lacking RGS2 had a normal basal cardiac phenotype, yet responded rapidly to pressure overload, with increased myocardial Gq signaling, marked cardiac hypertrophy and failure, and early mortality. Swimming exercise, which is not accompanied by Gq activation, induced a normal cardiac response, while Rgs2 deletion in Galphaq-overexpressing hearts exacerbated hypertrophy and dilation. In vascular smooth muscle, RGS2 is activated by cGMP-dependent protein kinase (PKG), suppressing Gq-stimulated vascular contraction. In normal mice, but not Rgs2-/- mice, PKG activation by the chronic inhibition of cGMP-selective phosphodiesterase 5 (PDE5) suppressed maladaptive cardiac hypertrophy, inhibiting Gq-coupled stimuli. Importantly, PKG was similarly activated by PDE5 inhibition in myocardium from both genotypes, but PKG plasma membrane translocation was more transient in Rgs2-/- myocytes than in controls and was unaffected by PDE5 inhibition. Thus, RGS2 is required for early myocardial compensation to pressure overload and mediates the initial antihypertrophic and cardioprotective effects of PDE5 inhibitors.

Topics: Animals; Cardiomegaly; Cyclic GMP-Dependent Protein Kinase Type I; Cyclic GMP-Dependent Protein Kinases; GTP-Binding Protein alpha Subunits, Gq-G11; Hypertension; Male; Mice; Mice, Inbred C57BL; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; RGS Proteins; Sildenafil Citrate; Sulfones

We tested the hypothesis that chronic treatment with sildenafil attenuates myocardial infarction (MI)-induced heart failure. Sildenafil has potent protective effects against necrosis and apoptosis following ischemia-reperfusion in the intact heart and cardiomyocytes. ICR mice underwent MI by left anterior descending coronary artery ligation and were treated with sildenafil (0.71 mg/kg bid) or saline for 4 wk. Infarct size (IS) was measured 24 h postinfarction, and apoptosis was measured by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. Left ventricular end-diastolic diameter (LVEDD) and fractional shortening (FS) were measured by echocardiography. Sildenafil reduced IS (40.0 +/- 4.6%) compared with that in saline (69.6 +/- 4.1%, P < 0.05). NG-nitro-l-arginine methyl ester, a nitric oxide synthase (NOS) inhibitor (15 mg/kg bid), blocked the protective effect of sildenafil (IS, 60.2 +/- 1.6%, P < 0.05 vs. sildenafil). Western blot analysis revealed a significant increase in endothelial NOS/inducible NOS proteins 24 h post-MI after treatment with sildenafil versus saline. Apoptosis decreased from 2.4 +/- 0.3% with saline to 1.2 +/- 0.1% with sildenafil (P < 0.05) on day 7 and from 2.0 +/- 0.2% with saline to 1.2 +/- 0.1% with sildenafil on day 28 (P < 0.05), which was associated with an early increase in the Bcl-2-to-Bax ratio. LVEDD increased from baseline value of 3.6 +/- 0.1 to 5.2 +/- 0.2 and to 5.5 +/- 0.1 mm on days 7 and 28, respectively, with saline (P < 0.05) but was attenuated to 4.4 +/- 0.2 and 4.4 +/- 0.1 mm following sildenafil treatment on days 7 and 28, respectively (P > 0.05 vs. baseline). FS significantly improved post-MI with sildenafil. A marked decline in cardiac hypertrophy was observed with sildenafil, which paralleled a reduction in pulmonary edema. Survival rate was lower with saline (36%) compared with sildenafil (93%, P < 0.05). Sildenafil attenuates ischemic cardiomyopathy in mice by limiting necrosis and apoptosis and by preserving left ventricular function possibly through a nitric oxide-dependent pathway.

Topics: Animals; Apoptosis; Blotting, Western; Cardiomegaly; Cardiomyopathy, Restrictive; Coronary Vessels; Echocardiography, Doppler; Enzyme Inhibitors; In Situ Nick-End Labeling; Ligation; Male; Mice; Mice, Inbred ICR; Myocardial Infarction; Necrosis; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Piperazines; Pulmonary Edema; Purines; Sildenafil Citrate; Sulfones; Survival Analysis; Vasodilator Agents; Ventricular Function, Left; Ventricular Remodeling

We evaluated the long-term effect of NO-donor, pentaerythrityl tetranitrate (Petn), and sildenafil citrate (sildenafil) on the cardiovascular system of the spontaneously hypertensive rat (SHR). Petn (100 mg/kg/day) and sildenafil (10 mg/kg/day) were administered to SHR individually or together from week 4 (pre-hypertensive period) to week 9 of age. Blood pressure (BP) was measured using a plethysmographic method. The animals were perfused with a glutaraldehyde fixative (120 mmHg). Carotid (AC) and coronary artery (RS) were processed according to electron microscopy procedure. Geometry of the arteries was measured on semi-thin sections using light microscopy. Administration of Petn and sildenafil to SHR individually or together did not prevent an increase of BP, but evoked a decrease of cardiac hypertrophy. Petn and sildenafil affected the geometry of RS and AC differently. In the RS, an increase of inner diameter (ID) without an increase of wall thickness (WT) resulted in increased WT/ID and circumferential stress. In the AC, changes in ID were accompanied by changes in WT and, thereby, WT/ID and circumferential stress remained unchanged. The arterial wall mass of both arteries was increased. The data suggest that administration of the NO donor, Petn, and/or sildenafil does not result in a beneficial effect on the myocardium or on the geometry of the carotid and coronary arteries.

Topics: Animals; Antihypertensive Agents; Blood Pressure; Cardiomegaly; Cardiovascular System; Carotid Arteries; Coronary Vessels; Disease Models, Animal; Disease Progression; Drug Administration Schedule; Drug Therapy, Combination; Hypertension; Nitric Oxide Donors; Pentaerythritol Tetranitrate; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Inbred SHR; Rats, Wistar; Sildenafil Citrate; Sulfones; Time Factors; Vasodilator Agents

Human Immunodeficiency Virus (HIV)-related pulmonary hypertension is a relatively rare disease that can affect HIV sufferers. This is almost always associated with a poor outcome and death. An 18 month-old girl, probably the youngest on record, was diagnosed to have pulmonary hypertension (PHT) and retrospectively found to have HIV infection. Sildenafil was used to control her PHT and she remains alive even after 2 years.

Topics: Cardiomegaly; Enzyme-Linked Immunosorbent Assay; Female; HIV Infections; Humans; Hypertension, Pulmonary; Infant; Piperazines; Purines; Sildenafil Citrate; Sulfones; Treatment Outcome; Vasodilator Agents

Sustained cardiac pressure overload induces hypertrophy and pathological remodeling, frequently leading to heart failure. Genetically engineered hyperstimulation of guanosine 3',5'-cyclic monophosphate (cGMP) synthesis counters this response. Here, we show that blocking the intrinsic catabolism of cGMP with an oral phosphodiesterase-5A (PDE5A) inhibitor (sildenafil) suppresses chamber and myocyte hypertrophy, and improves in vivo heart function in mice exposed to chronic pressure overload induced by transverse aortic constriction. Sildenafil also reverses pre-established hypertrophy induced by pressure load while restoring chamber function to normal. cGMP catabolism by PDE5A increases in pressure-loaded hearts, leading to activation of cGMP-dependent protein kinase with inhibition of PDE5A. PDE5A inhibition deactivates multiple hypertrophy signaling pathways triggered by pressure load (the calcineurin/NFAT, phosphoinositide-3 kinase (PI3K)/Akt, and ERK1/2 signaling pathways). But it does not suppress hypertrophy induced by overexpression of calcineurin in vitro or Akt in vivo, suggesting upstream targeting of these pathways. PDE5A inhibition may provide a new treatment strategy for cardiac hypertrophy and remodeling.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Animals, Newborn; Blood Pressure; Calcineurin; Cardiomegaly; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; DNA-Binding Proteins; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; Heart; Hemodynamics; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Myocardium; NFATC Transcription Factors; Nuclear Proteins; Phosphatidylinositol 3-Kinases; Phosphodiesterase Inhibitors; Piperazines; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Transcription Factors

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Antibiotics, Antineoplastic; Cardiomegaly; Cyclic Nucleotide Phosphodiesterases, Type 5; Doxorubicin; Mice; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Sildenafil Citrate; Sulfones

Topics: Administration, Inhalation; Blood Pressure; Bronchodilator Agents; Cardiomegaly; Child; Drug Administration Schedule; Electrocardiography; Heart Septal Defects, Ventricular; Humans; Hypertension, Pulmonary; Intubation, Intratracheal; Male; Nitric Oxide; Piperazines; Postoperative Care; Purines; Severity of Illness Index; Sildenafil Citrate; Sulfones; Time Factors; Vasodilator Agents