Increased Cardiac Myocyte PDE5 Levels in Human and Murine Pressure Overload Hypertrophy Contribute to Adverse LV Remodeling

Background: The intracellular second messenger cGMP protects the heart under pathological conditions. We examined expression of phosphodiesterase 5 (PDE5), an enzyme that hydrolyzes cGMP, in human and mouse hearts subjected to sustained left ventricular (LV) pressure overload. We also determined the role of cardiac myocyte-specific PDE5 expression in adverse LV remodeling in mice after transverse aortic constriction (TAC). Methodology/Principal Findings: In patients with severe aortic stenosis (AS) undergoing valve replacement, we detected greater myocardial PDE5 expression than in control hearts. We observed robust expression in scattered cardiac myocytes of those AS patients with higher LV filling pressures and BNP serum levels. Following TAC, we detected similar, focal PDE5 expression in cardiac myocytes of C57BL/6NTac mice exhibiting the most pronounced LV remodeling. To examine the effect of cell-specific PDE5 expression, we subjected transgenic mice with cardiac myocyte-specific PDE5 overexpression (PDE5-TG) to TAC. LV hypertrophy and fibrosis were similar as in WT, but PDE5-TG had increased cardiac dimensions, and decreased dP/dtmax and dP/dtmin with prolonged tau (P<0.05 for all). Greater cardiac dysfunction in PDE5-TG was associated with reduced myocardial cGMP and SERCA2 levels, and higher passive force in cardiac myocytes in vitro. Conclusions/Significance: Myocardial PDE5 expression is increased in the hearts of humans and mice with chronic pressure overload. Increased cardiac myocyte-specific PDE5 expression is a molecular hallmark in hypertrophic hearts with contractile failure, and represents an important therapeutic target

Gender-Specific Modulation of the Response to Arterial Injury by Soluble Guanylate Cyclase α1

Objective: Soluble guanylate cyclase (sGC), a heterodimer composed of α and β subunits, synthesizes cGMP in response to nitric oxide (NO). NO modulates vascular tone and structure but the relative contributions of cGMP-dependent versus cGMP-independent mechanisms remain uncertain. We studied the response to vascular injury in male (M) and female (F) mice with targeted deletion of exon 6 of the sGCα1 subunit (sGCα1-/-), resulting in a non-functional heterodimer. Methods: We measured aortic cGMP levels and mRNA transcripts encoding sGC α1, α2, and β1 subunits in wild type (WT) and sGCa1-/- mice. To study the response to vascular injury, BrdU-incorporation and neointima formation (maximum intima to media (I/M) ratio) were determined 5 and 28 days after carotid artery ligation, respectively. Results: Aortic cGMP levels were 4-fold higher in F than in M mice in both genotypes, and, within each gender, 4-fold higher in WT than in sGCa1-/-. In contrast, sGCα1, sGCα2, and sGCβ1 mRNA expression did not differ between groups. 3H-thymidine incorporation in cultured sGCa1-/- smooth muscle cells (SMC) was 27%±12% lower than in WT SMC and BrdU-incorporation in carotid arteries 5 days after ligation was significantly less in sGCa1-/- M than in WT M. Neointima area and I/M 28 days after ligation were 65% and 62% lower in sGCa1-/- M than in WT M mice (p<0,05 for both) but were not different in F mice. Conclusion: Functional deletion of sGCa1 resulted in reduced cGMP levels in male sGCa1-/- mice and a gender-specific effect on the adaptive response to vascular injury

Improved Left Ventricular Regional Contractility Pattern after Ischemic Postconditioning

Objective – Cardiac postconditioning (IPostC) limits reperfusion injury, but its effect on cardiac postischemic remodeling is insufficiently investigated. We studied cardiac morphology and regional contractility after IPostC in mice using cine magnetic resonance imaging (cMRI) with myocardial tagging and Left Ventricular (LV) pressure conductance analysis. Methods – Mice (C57BL6/J; age 12 weeks) were anesthetized with pentobarbital (50mg/kg), xylazine (2mg/kg), ketamine (30mg/kg) and atropine (.03mg/kg). After 30min LAD occlusion in vivo, 12 mice underwent reperfusion with IPostC (3 cycles of 10 s reperfusion-reocclusion) and 12without IPostC (noIPostC). cMRI and cardiac tagging was performed in a 9.4T Bruker Biospec after 1 and 10 weeks. Volumes and ejection fraction (EF) were calculated using home-written software and tagging grid deformation analysis with Diagnosoft 2.72 software. Load independent preload-recruitable stroke work (PRSW) was determined using pressure conductance analysis. Finally, hearts were excised, weighed and collagen content determined on 6μm Sirius red-stained sections using planimetry. Results –cMRI showed larger end-systolic and -diastolic volumes and reduced ejection fraction (EF) at both 1 and 10 weeks in noIPostC vs. others (all p<.05, EF at 10 weeks 45±10% in noIPostC, 55±6% in IPostC and 61±8% in SHAM ). Myocardial mass was higher in the noIPostC group vs. IPostC and sham at 10 weeks (72±9mg vs. 60±13mg and 59±8mg respectively, p<.05). The tagging grid deformation was less in the anterolateral wall (segment 5 and 6) while the interventricular septum (segment 2) showed significantly more compensatory deformation after IPostC (fig 1), evidenced by the individual strain curves and the calculated area under the curve. PRSW was lower in the noIPostC group (43±13 mmHg vs. 74±10 mmHg in IPostC and 87 ±9 mmHg in sham, both p<.01). The collagen content in the LV wall was higher in noIPostC (.09±.02 vs. .04±.02 in IPostC and .02±.01 in sham, both p<.001). Conclusions – The cardioprotective effect of IPostC is sustained after 10 weeks and protects against adverse LV remodeling. Myocardial tagging reveals an improved contractility pattern at both postischemic and remote areas, resulting in an increased global contractility.status: accepte

Nitric oxide inhalation improves microvascular row and decreases infarction size after myocardial ischemia and reperfusion

Objectives The purpose of this study was to test if nitric oxide (NO) could improve microvascular perfusion and decrease tissue injury in a porcine model of myocardial ischemia and reperfusion (I/R).status: publishe

Nitric Oxide For Inhalation Reduces Left Ventricular Remodeling After Myocardial Infarction In Pigs

Liu X., Pokreisz P., Gheysens O., Ghysels S., Maes F., Caluwe E., Gillijns H., Pellens M., Verbeken E., Bogaert J., Van de Werf F., Bloch K.D., Janssens S., ''Nitric oxide for inhalation reduces left ventricular remodeling after myocardial infarction in pigs'', Circulation, vol. 118, no. 18, suppl. 2, pp. S547, October 2008 (American Heart Association scientific sessions 2008, November 8-12, 2008, New Orleans, LA, USA).status: publishe

Soluble guanylate cyclase-α1 deficiency selectively inhibits the pulmonary vasodilator response to nitric oxide and increases the pulmonary vascular remodeling response to chronic hypoxia

Background - Nitric oxide ( NO) activates soluble guanylate cyclase (sGC), a heterodimer composed of alpha- and beta-subunits, to produce cGMP. NO reduces pulmonary vascular remodeling, but the role of sGC in vascular responses to acute and chronic hypoxia remains incompletely elucidated. We therefore studied pulmonary vascular responses to acute and chronic hypoxia in wild-type (WT) mice and mice with a nonfunctional alpha 1-subunit (sGC alpha 1(-/-)). Methods and Results - sGC alpha 1(-/-) mice had significantly reduced lung sGC activity and vasodilator-stimulated phosphoprotein phosphorylation. Right ventricular systolic pressure did not differ between genotypes at baseline and increased similarly in WT (22 +/- 2 to 34 +/- 2 mm Hg) and sGC alpha 1(-/-) (23 +/- 2 to 34 +/- 1 mm Hg) mice in response to acute hypoxia. Inhaled NO ( 40 ppm) blunted the increase in right ventricular systolic pressure in WT mice (22 +/- 2 to 24 +/- 2 mm Hg, P < 0.01 versus hypoxia without NO) but not in sGC alpha 1(-/-) mice (22 +/- 1 to 33 +/- 1 mm Hg) and was accompanied by a significant rise in lung cGMP content only in WT mice. In contrast, the NO-donor sodium nitroprusside (1.5 mg/kg) decreased systemic blood pressure similarly in awake WT and sGC alpha 1(-/-) mice as measured by telemetry (-37 +/- 2 versus -42 +/- 4 mm Hg). After 3 weeks of hypoxia, the increases in right ventricular systolic pressure, right ventricular hypertrophy, and muscularization of intra-acinar pulmonary vessels were 43%, 135%, and 46% greater, respectively, in sGC alpha 1(-/-) than in WT mice (P < 0.01). Increased remodeling in sGC alpha 1(-/-) mice was associated with an increased frequency of 5'-bromo-deoxyuridine-positive vessels after 1 and 3 weeks (P < 0.01 versus WT). Conclusions - Deficiency of sGC alpha 1 does not alter hypoxic pulmonary vasoconstriction. sGC alpha 1 is essential for NO-mediated pulmonary vasodilation and limits chronic hypoxia-induced pulmonary vascular remodeling

Cardiomyocyte-specific overexpression of nitric oxide synthase 3 improves left ventricular performance and reduces compensatory hypertrophy after myocardial infarction

Nitric oxide ( NO) is an important modulator of cardiac performance and left ventricular (LV) remodeling after myocardial infarction (MI). We tested the effect of cardiomyocyte-restricted overexpression of one NO synthase isoform, NOS3, on LV remodeling after MI in mice. LV structure and function before and after permanent LAD coronary artery ligation were compared in transgenic mice with cardiomyocyte-restricted NOS3 overexpression (NOS3-TG) and their wild-type littermates (WT). Before MI, systemic hemodynamic measurements, echocardiographic assessment of LV fractional shortening (FS), heart weight, and myocyte width (as assessed histologically) did not differ in NOS3-TG and WT mice. The inotropic response to graded doses of isoproterenol was significantly reduced in NOS3-TG mice. One week after LAD ligation, the infarcted fraction of the LV did not differ in WT and NOS3-TG mice (34 +/- 4% versus 36 +/- 12%, respectively). Four weeks after MI, however, end-systolic LVID was greater, and fractional shortening and maximum and minimum rates of LV pressure development were less in WT than in NOS3-TG mice. LV weight/body weight ratio was greater in WT than in NOS3-TG mice (5.3 +/- 0.2 versus 4.6 +/- 0.5 mg/g; P < 0.01). Myocyte width in noninfarcted myocardium was greater in WT than in NOS3-TG mice (18.8 +/- 2.0 versus 16.6 +/- 1.6 mu m; P < 0.05), whereas fibrosis in noninfarcted myocardium was similar in both genotypes. Cardiomyocyte-restricted overexpression of NOS3 limits LV dysfunction and remodeling after MI, in part by decreasing myocyte hypertrophy in noninfarcted myocardium.status: publishe

Placental growth factor increases regional myocardial blood flow and function in a new porcine model of chronic myocardial ischemia

Liu X., Caluwe E., Reyns G., Verhamme P., Pokreisz P., Vandenwijngaert S., Dubois C., Zalewski J., Ghysels S., Maes F., Gillijns H., Pellens M., Vanden Driessche N., Patel A., Van de Werf F., Verbeken E., Bogaert J., Janssens S., ''Placental growth factor increases regional myocardial blood flow and function in a new porcine model of chronic myocardial ischemia'', Circulation, vol. 120, no. 18, suppl., pp. S837, November 2009 (American Heart Association scientific sessions 2009, November 14-18, 2009, Orlando, Florida, USA).status: publishe

Increased Cardiac Myocyte PDE5 Levels in Human and Murine Pressure Overload Hypertrophy Contribute to Adverse LV Remodeling

BACKGROUND: The intracellular second messenger cGMP protects the heart under pathological conditions. We examined expression of phosphodiesterase 5 (PDE5), an enzyme that hydrolyzes cGMP, in human and mouse hearts subjected to sustained left ventricular (LV) pressure overload. We also determined the role of cardiac myocyte-specific PDE5 expression in adverse LV remodeling in mice after transverse aortic constriction (TAC). METHODOLOGYPRINCIPAL FINDINGS: In patients with severe aortic stenosis (AS) undergoing valve replacement, we detected greater myocardial PDE5 expression than in control hearts. We observed robust expression in scattered cardiac myocytes of those AS patients with higher LV filling pressures and BNP serum levels. Following TAC, we detected similar, focal PDE5 expression in cardiac myocytes of C57BL/6NTac mice exhibiting the most pronounced LV remodeling. To examine the effect of cell-specific PDE5 expression, we subjected transgenic mice with cardiac myocyte-specific PDE5 overexpression (PDE5-TG) to TAC. LV hypertrophy and fibrosis were similar as in WT, but PDE5-TG had increased cardiac dimensions, and decreased dP/dtmax and dP/dtmin with prolonged tau (P<0.05 for all). Greater cardiac dysfunction in PDE5-TG was associated with reduced myocardial cGMP and SERCA2 levels, and higher passive force in cardiac myocytes in vitro. CONCLUSIONSSIGNIFICANCE: Myocardial PDE5 expression is increased in the hearts of humans and mice with chronic pressure overload. Increased cardiac myocyte-specific PDE5 expression is a molecular hallmark in hypertrophic hearts with contractile failure, and represents an important therapeutic target.status: publishe