2-2--(hydroxynitrosohydrazono)bis-ethanamine and Hypertension

Nitric Oxide (NO), a potent vasodilator and vital signaling molecule, has been shown to contribute to the regulation of glomerular ultrafiltration. However, whether changes in NO occur in podocytes during the pathogenesis of salt-sensitive hypertension has not yet been thoroughly examined. We showed here that podocytes produce NO, and further hypothesized that hypertensive animals would exhibit reduced NO production in these cells in response to various paracrine factors, which might contribute to the damage of glomeruli filtration barrier and development of proteinuria. To test this, we isolated glomeruli from the kidneys of Dahl salt-sensitive (SS) rats fed a low salt (LS; 0.4% NaCl) or high salt (HS; 4% NaCl, 3 weeks) diets and loaded podocytes with either a combination of NO and Ca

Topics: Angiotensin II; Animals; Calcium Signaling; Glomerular Filtration Barrier; Hydrogen Peroxide; Hypertension; Kidney Glomerulus; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitroso Compounds; Podocytes; Rats, Inbred Dahl; Sodium Chloride, Dietary

There is a 1-4 mmol/L rise in plasma sodium concentrations in individuals with high salt intake and in patients with essential hypertension. In this study, we used 3 independent assays to determine whether such a small increase in sodium concentrations per se alters endothelial nitric oxide synthase (eNOS) function and contributes to hypertension. By directly measuring NOS activity in living bovine aortic endothelial cells, we demonstrated that a 5-mmol/L increase in salt concentration (from 137 to 142 mmol/L) caused a 25% decrease in NOS activity. Importantly, the decrease in NOS activity was in a salt concentration-dependent manner. The NOS activity was decreased by 25, 45, and 70%, with the increase of 5, 10, and 20 mmol/L of NaCl, respectively. Using Chinese hamster ovary cells stably expressing eNOS, we confirmed the inhibitory effects of salt on eNOS activity. The eNOS activity was unaffected in the presence of equal milliosmol of mannitol, which excludes an osmotic effect. Using an ex vivo aortic angiogenesis assay, we demonstrated that salt attenuated the nitric oxide (NO)-dependent proliferation of endothelial cells. By directly monitoring blood pressure changes in response to salt infusion, we found that in vivo infusion of salt induced an acute increase in blood pressure in a salt concentration-dependent manner. In conclusion, our findings demonstrated that eNOS is sensitive to changes in salt concentration. A 5-mmol/L rise in salt concentration, within the range observed in essential hypertension patients or in individuals with high salt intake, could significantly suppress eNOS activity. This salt-induced reduction in NO generation in endothelial cells may contribute to the development of hypertension.

Topics: Animals; Aorta; Cattle; CHO Cells; Cricetinae; Cricetulus; Dose-Response Relationship, Drug; Endothelial Cells; Hypertension; Male; Mice; Mice, Inbred C57BL; Neovascularization, Physiologic; Nitric Oxide Donors; Nitric Oxide Synthase Type III; Nitroso Compounds; Rats; Rats, Sprague-Dawley; Sodium Chloride

The role of endothelial nitric oxide synthase (eNOS) in ischemic preconditioning (PC) and cardioprotection is poorly understood. We addressed this issue using a genetic, rather than pharmacological, approach.. In the nonpreconditioned state, eNOS-/- mice exhibited infarct sizes similar to those of wild-type mice. A sequence of six 4-minute coronary occlusion/4-minute reperfusion cycles (ischemic PC) induced late PC in wild-type mice; genetic deletion of eNOS abrogated the cardioprotection induced by late PC. In wild-type mice, ischemic PC induced membranous translocation of protein kinase C (PKC) epsilon and an increase in pSer-MEK-1/2 and pTyr-p44/42 mitogen-activated protein kinase, nuclear pSer-signal transducers and activators of transcription (STAT)1 and pSer-STAT3, and nuclear STAT1/3 DNA binding activity, followed by upregulation of cyclooxygenase-2 protein and activity 24 hours later. All of these changes were abrogated in eNOS-/- mice. The NO donor diethylenetriamine/NO recapitulated the effects of ischemic PC.. In contrast to previous reports, we found that basal eNOS activity does not modulate infarct size in the nonpreconditioned state. However, eNOS is obligatorily required for the development of the cardioprotective effects of late PC and acts as the trigger of this process by activating the PKC epsilon-MEK-1/2-p44/42 mitogen-activated protein kinase pathway, leading to Ser-727 phosphorylation of STAT1 and STAT3 and consequent upregulation of STAT-dependent genes such as cyclooxygenase-2. The effects of eNOS-derived NO are reproduced by exogenous NO (NO donors), implying that nitrates can upregulate cardiac cyclooxygenase-2.

Topics: Adaptation, Physiological; Animals; Cyclooxygenase 2; DNA; Enzyme Activation; Enzyme Induction; Hypertension; Ischemic Preconditioning, Myocardial; MAP Kinase Kinase Kinase 1; MAP Kinase Kinase Kinase 2; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Mutant Strains; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Myocardial Infarction; Myocardial Reperfusion Injury; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Phosphorylation; Protein Kinase C-epsilon; Protein Processing, Post-Translational; Signal Transduction; Specific Pathogen-Free Organisms; STAT1 Transcription Factor; STAT3 Transcription Factor; Stress, Physiological; Time Factors; Triazenes

(Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA/NO) is a recently synthesized member of NO-releasing, polyamine zwitterions, the so-called NONOates, that spontaneously liberate NO in aqueous solutions. The aim of this study was to determine the hemodynamic effects of DETA/ NO in normotensive and hypertensive mice. Male Swiss Outbred mice were implanted with TA11PA-C20 blood pressure devices (Data Sciences International, USA). After recovery (7-10 days), blood pressure was monitored for 10 days while mice were receiving saline (0.1 ml/20 g/day, s.c.). Mice were then treated every four hours for 1 day with either DETA/NO 60 mg/kg i.p. or the inactive metabolite, diethylenetriamine 38 mg/kg (molar equivalent) i.p. After a 2 week wash-out period, mice were treated with adrenocorticotrophic hormone (ACTH: 500 microg/kg/day, s.c.) for 10 days and re-challenged with DETA/NO or diethylenetriamine. Results were expressed as mean +/- SEM. After 10 days of saline treatment, baseline systolic and diastolic blood pressure (BP) were similar for animals subsequently receiving DETA/NO or the amine (123 +/- 1/95 +/- 3 and 124 +/- 1/92 +/- 0.2 mmHg) respectively. DETA/NO induced a profound fall in BP [Systolic: 74 +/- 4 mmHg (-40 +/- 3%); Diastolic: 46 +/- 4 mmHg (-52 +/- 4%)] and an increase in heart rate [729 +/- 33 bpm (32 +/- 2%)] within the first 80 minutes. Diethylenetriamine had no effect. ACTH treatment increased BP in both groups (137 +/- 16/108 +/- 12 and 161 +/- 1/142 +/- 1 mmHg) respectively. DETA/ NO induced a profound fall in blood pressure [Systolic: 92 +/- 11 mmHg (-32 +/- 7%); Diastolic: 68 +/- 10 mmHg (-35 +/- 10%)] and an increase in heart rate [613 +/- 36 bpm (18 +/- 6%)] within the first 80 minutes. Again diethylenetriamine had no significant effect. There was no significant effect on body weight with any treatment. Thus DETA/NO has potent blood pressure lowering effects in both normotensive and hypertensive mice.

Topics: Adrenocorticotropic Hormone; Animals; Animals, Outbred Strains; Blood Pressure; Hypertension; Male; Mice; Nitric Oxide Donors; Sodium Chloride; Triazenes