Nitric oxide synthase and cyclic GMP signaling in cardiac myocytes: From contractility to remodeling

Background: We have shown that inhibition of cyclic GMP-phosphodiesterase 5A (PDE5A) by sildenafil (SIL) blunts cardiomyocyte β-adrenergic stimulation, but this effect depends on the activity of endothelial nitric oxide synthase (eNOS) to generate a specific pool of cyclic GMP. PDE5A normally localizes at Z-bands in myocytes, but localization is more diffuse in cells with eNOS chronically inhibited. Here, we tested whether the influence of eNOS on PDE5A localization and anti-adrenergic action depends upon cyclic GMP. Methods and Results: Mouse in vivo hemodynamics were assessed by pressure-volume analysis. Isoproterenol (ISO: 20 ng/kg/min, iv ) stimulated contractility was inhibited by SIL (100 μg/kg/min, iv ), however this did not occur in mice given N w -nitro-L-arginine methyl ester (L-NAME: 1 mg/mL in drinking water for 1 week) to inhibit NOS. Myocytes transfected with an adenoviral vector encoding a fusion protein (PDE5A-DSred) in vivo were subsequently isolated and examined for PDE5A/α-actinin localization. Normal cells showed strong co-localization, whereas L-NAME-treated cells had diffuse PDE5A distribution. If L-NAME was stopped for 1-wk washout, SIL regained anti-adrenergic activity, and PDE5A z-band localization was restored. If L-NAME was continued but combined with Bay 41– 8543 (BAY: 30 mg/kg/day, po ), a soluble guanylate cyclase (sGC) activator, both PDE5A localization and SIL anti-adrenergic action were also restored. Chronic L-NAME suppressed phosphorylation of vasodilator-stimulated protein (VASP), a marker of protein kinase G (PKG) activity, in hearts acutely exposed to ISO+SIL. After L-NAME washout or L-NAME+BAY, VASP phosphorylation with ISO+SIL was restored. Conclusion: NOS-dependent modulation of both PDE5A sarcomere localization and anti-adrenergic activity depends upon sGC-derived cyclic GMP, and is linked to PKG activation. This suggests sGC activators may have synergistic effects with PDE5A inhibitors.

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Endothelin-1 ameliorates contractile depression by lipopolysaccharide in cardiac myocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1997.273.3.h1403 ◽

1997 ◽

Vol 273 (3) ◽

pp. H1403-H1407 ◽

Cited By ~ 1

Author(s):

S. Yasuda ◽

W. Y. Lew

Keyword(s):

Nitric Oxide ◽

Nitric Oxide Synthase ◽

Cardiac Myocytes ◽

Contractile Function ◽

Adult Rabbit ◽

Nitric Oxide Synthase Inhibitor ◽

Endothelin 1 ◽

Cardiac Depression ◽

Synthase Inhibitor ◽

Oxide Synthase

Lipopolysaccharide (LPS) induces cardiac depression by activating nitric oxide pathways to increase guanosine 3',5'-cyclic monophosphate (cGMP), a second messenger of nitric oxide. Endothelin-1 (ET-1) may interact with nitric oxide pathways. We hypothesized that ET-1 modulates LPS-induced contractile depression in cardiac myocytes. Adult rabbit cardiac myocytes exposed to LPS (10 ng/ml) developed decreased cell shortening after 6 h, with an increase in cardiac cGMP levels [606 +/- 36 (SE) fmol/mg protein] compared with control myocytes (360 +/- 26 fmol/mg protein, P < 0.05). LPS effects were completely blocked by coincubation with the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (1 mM). Coincubation with ET-1 (10 nM) attenuated the contractile depression and increase in cGMP with LPS (482 +/- 28 fmol/mg protein, P < 0.05 vs. LPS alone). ET-1 alone did not alter cGMP levels (350 +/- 30 fmol/mg protein). ET-1 effects on contractile function were blocked by BQ-123 (10 microM), a selective ET-1 type A receptor antagonist. We conclude that ET-1 ameliorates LPS-induced contractile depression in cardiac myocytes by attenuating LPS effects on nitric oxide-cGMP pathways.

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