The effects of the nitric oxide donors molsidomine and SIN-1 on human polymorphonuclear leucocyte functionin vitro andex vivo

Abstract

The nitrovasodilator and nitric oxide donor molsidomine and its metabolite SIN-I dilate vascular smooth muscle and inhibit platelet activation by increasing intracellular concentrations of cyclic GMP. We have therefore studied the effects of molsidomine and SIN-I on isolated human polymorphonuclear leucocytes (PMN) in vitro and ex vivo. In vitro molsidomine dose-dependently reduced beta-glucuronidase release and the generation of superoxide anions from non-activated and from FMLP- or PAF-stimulated human PMNs. SIN-I was equally effective in reducing beta-glucuronidase release and totally inhibited oxygen radical generation at a concentration of 580 mumol.l-1. In a double-blind, placebo-controlled, randomized trial we also studied beta-glucuronidase release and the generation of superoxide anions from isolated PMNs. Blood was drawn from 12 healthy volunteers before and 3 h after oral molsidomine (16 mg) or placebo. There was no statistically significant difference in beta-glucuronidase release and superoxide anion formation when the PMNs were isolated before or after molsidomine or placebo. This was the case for non-activated, as well as FMLP- or PAF-stimulated PMNs. Thus, the nitric oxide donors molsidomine and its metabolite SIN-I caused a dose-dependent inhibition of PMN functions in vitro, but no significant inhibition when the PMNs were isolated after oral molsidomine.

Regulation of Leukocyte Degranulation by cGMP-Dependent Protein Kinase and Phosphoinositide 3-Kinase: Potential Roles in Phosphorylation of Target Membrane SNARE Complex Proteins in Rat Mast Cells

“…Data presented are percentage of inhibition and are means Ϯ SEM from three independent experiments. inhibition of leukocyte functions including chemotaxis and superoxide generation, especially when these NO donors were used at higher concentrations (25)(26)(27). With respect to degranulation, published reports indicate a biphasic dose response in which NO and cGMP enhance exocytosis at low concentrations and inhibits exocytosis at higher concentrations (48,(57)(58)(59).…”

“…It was reported that upon stimulation with formyl-methionyl-leucyl-phenylalanine (fMLF), PKG was activated and redistributed to subcellular compartments with intermediate filaments (24). However, published reports also indicate that several NO donors could inhibit neutrophil functions (25)(26)(27), raising the question of whether PKG positively or negatively regulates leukocyte degranulation. To clarify this issue and identify the signaling pathways used by PKG for regulating degranulation, we examined the rat mast cell line rat basophilic leukemia (RBL)-2H3 and a formyl peptide receptor (FPR)-expressing RBL cell line, using pharmacological inhibitors that block PKG.…”

Overexpression of a Constitutively Active Protein Kinase G Mutant Reduces Neointima Formation and In-Stent Restenosis

“…The culture medium was then changed to DMEM containing 4% FBS with or without 8-Br-cGMP (1 mmol/L) in the presence or absence of the PKG-inhibitor KT5823 (0.25 mol/L). After 12 hours, 5ϫ10 4 cells were transferred to a Transwell migration chamber, and migrating cells were counted 6 hours later, as described. 15 Migratory activities of adenovirus-infected and uninfected cells were compared.…”

“…The mechanisms whereby NO modulates neointima formation remain unclear but may involve cyclic guanosine monophosphate (cGMP)-dependent or cGMP-independent effects in the vessel wall, as well as the interaction of circulating cells with the injured vascular wall. 4 The cGMP-dependent effects of NO are mediated via a variety of cGMP targets, including the serine/threonine kinase cGMP-dependent protein kinase (PKG). 5,6 PKG activation in vascular smooth muscle cells (VSMCs) can result in relaxation, apoptosis, and reduced proliferation and migration.…”

The nitric oxide donors, azide and hydroxylamine, inhibit the programmed cell death of cytokine‐deprived human eosinophils

“…However, NO synthesis by neutrophils and by human macrophages is questioned [6--8]. In human, NO has been shown to down-modulate T cell proliferation [9], to activate peripheral blood mononuclear cells [10], to inhibit neutrophil degranulation [11], but to increase the release of TNF-a by neutrophils [12]. Azide and hydroxylamine generate NO in a well-documented enzymatic reaction catalyzed by endogenous catalase [13,14].…”