atrial-natriuretic-factor and cariporide

The serum- and glucocorticoid-inducible kinase Sgk1 contributes to cardiac remodeling and development of heart failure, which is paralelled by Sgk1-dependent stimulation of the cardiac Na(+)/H(+) exchanger Nhe1. Glucocorticoids are powerful stimulators of Sgk1 expression and influence cardiac remodeling. The present study thus explored whether the glucocorticoid receptor agonist dexamethasone influenced cardiac Sgk1 expression, as well as activity, expression and phosphorylation at Ser(703) of the cardiac Na(+)/H(+) exchanger Nhe1.. Experiments were performed in HL-1 cardiomyocytes and gene targeted mice lacking functional Sgk1 (sgk1(-/-)) and respective wild type mice (sgk1(+/+)). Gene expression was determined by quantitative RT-PCR and Nhe1 phosphorylation was determined utilizing a specific antibody against a 14-3-3 binding motif at P-Ser(703), which represents a putative phosphorylation site recognition motif for Sgk1 and is involved in Nhe1 activation. Cytosolic pH (pHi) was determined utilizing 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) fluorescence and Nhe activity by the Na(+)-dependent realkalinization after an ammonium pulse.. Treatment of HL-1 cardiomyocytes with dexamethasone was followed by a significant increase in Sgk1 mRNA expression, parallelled by increased Na(+)/H(+) exchanger activity. Furthermore, dexamethasone significantly increased Nhe1 and Spp1 mRNA expression. The effects of dexamethasone were blunted by cotreatment of HL-1 cardiomyocytes with the Sgk1 inhibitor EMD638683. Cotreatment with Nhe1 inhibitor cariporide similarly prevented dexamethasone-stimulated Spp1 mRNA expression. In sgk1(+/+) mice, dexamethasone significantly increased cardiac Sgk1 mRNA levels. In sgk1(+/+) mice, but not in sgk1(-/-) mice, dexamethasone significantly increased cardiac Nhe1 mRNA expression and Nhe1 phosphorylation at Ser(703). Furthermore, cardiac Spp1, Ctgf, Nppa and Nppb mRNA levels were significantly increased in dexamethasone treated sgk1(+/+) mice, effects significantly blunted in sgk1(-/-) mice.. Sgk1 is critically involved in the phosphorylation and activation of the cardiac Na(+)/H(+) exchanger Nhe1.

Topics: Amino Acid Motifs; Animals; Atrial Natriuretic Factor; Benzamides; Binding Sites; Cation Transport Proteins; Cell Line; Connective Tissue Growth Factor; Dexamethasone; Gene Expression; Guanidines; Hydrazines; Hydrogen-Ion Concentration; Immediate-Early Proteins; Mice; Myocytes, Cardiac; Natriuretic Peptide, C-Type; Osteopontin; Phosphorylation; Protein Precursors; Protein Serine-Threonine Kinases; RNA, Messenger; Sodium-Hydrogen Exchanger 1; Sodium-Hydrogen Exchangers; Sulfones

Reactive oxygen species (ROS) play a role in cardiovascular diseases such as hypertension and heart failure. The objective of the present study was to investigate the role of endogenous ROS in atrial hemodynamics and ANP secretion in isolated perfused beating rat atria. Pyrogallol (a generator of superoxide anion, 0.1, 1mM) or hydrogen peroxide (0.1, 1, 10, 30mM) was perfused into atria paced at 1.2Hz. Pyrogallol and hydrogen peroxide stimulated ANP secretion and concentration in a dose-dependent manner and dramatically decreased atrial contractility and translocation of extracellular fluid. The stimulatory effect of pyrogallol and hydrogen peroxide on ANP secretion was attenuated by the pretreatment with ascorbic acid (an antioxidant; 1mM) and cariporide (an inhibitor of the Na(+)/H(+) exchanger; 1μM) but negative inotropic effect was not changed. U120 (a MAPK(erk) pathway inhibitor; 10μM) attenuated the stimulatory effect of hydrogen peroxide on ANP secretion. However, U120 augmented negative inotropic effect and stimulatory effect of ANP concentration induced by pyrogallol. Antioxidant such as N-acetyl cystein, gallate, propyl gallate, or ellagic acid did not cause any significant changes in atrial parameters. These results suggest that intracellular - formed ROS stimulates ANP secretion partly through activation of MAPK(erk) pathway and Na(+)/H(+) exchanger.

Topics: Acetylcysteine; Animals; Ascorbic Acid; Atrial Natriuretic Factor; Cardiovascular Diseases; Extracellular Fluid; Guanidines; Heart Atria; Hemodynamics; Hydrogen Peroxide; Male; Mitogen-Activated Protein Kinase Kinases; Myocardial Contraction; Organ Culture Techniques; Oxidative Stress; Propyl Gallate; Pyrogallol; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Sodium-Hydrogen Exchangers; Sulfones

Pulmonary hypertension results in compensatory right ventricular (RV) hypertrophy. We studied the role of the Na+-H+ exchange (NHE) in the latter process by determining the effect of the NHE-1 inhibitor cariporide after monocrotaline-induced pulmonary artery injury. Sprague-Dawley rats received a control or cariporide diet for 7 days, at which time they were administered either monocrotaline (60 mg/kg) or its vehicle. Twenty-one days later, monocrotaline control, but not cariporide-fed animals, demonstrated increased RV weights and cell size of 65 and 52%, respectively. Monocrotaline alone significantly increased RV systolic pressure and end diastolic pressure by 70 and 94%, respectively, whereas corresponding values with cariporide were significantly reduced to 33 and 42%. Central venous pressure increased by 414% in control animals, which was significantly reduced by cariporide. Monocrotaline treatment produced a decrease in cardiac output of 28 and 8% in the absence or presence of cariporide (P < 0.05 between groups), respectively. Although body weights were significantly lower in both monocrotaline-treated groups compared with vehicle treatment, with cariporide the net gain in body weight was twice that seen in the monocrotaline-treated animals without cariporide. Monocrotaline also increased RV NHE-1 and atrial natriuretic peptide mRNA expression, which was abrogated by cariporide. Monocrotaline-induced myocardial necrosis, fibrosis, and mononuclear infiltration was completely prevented by cariporide. Cariporide had no effect on monocrotaline-induced pulmonary intimal wall thickening. Our results demonstrate that cariporide directly attenuates myocardial dysfunction after monocrotaline administration independent of pulmonary vascular effects. NHE-1 inhibition may represent an effective adjunctive therapy that selectively targets myocardial hypertrophic responses in pulmonary vascular injury.

Topics: Animals; Anti-Arrhythmia Agents; Atrial Natriuretic Factor; Cell Size; Enzyme Inhibitors; Guanidines; Heart Failure; Hemodynamics; Hypertrophy, Right Ventricular; Lung; Lung Diseases; Male; Monocrotaline; Myocardium; Organ Size; Poisons; Pulmonary Artery; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; RNA, Messenger; Sodium-Hydrogen Exchangers; Sulfones