Polydeoxyribonucleotides and nitric oxide release from guinea-pig hearts during ischaemia and reperfusion.

1. Two polydeoxyribonucleotides, produced by the controlled hydrolysis of DNA of mammalian lung (defibrotide and its lower molecular weight fraction, P.O. 085 DV), were studied for their ability to modify the release of nitrite and the coronary flow in perfusates collected from isolated, normally perfused hearts of guinea-pigs and from hearts subjected to regional ischaemia and reperfusion. 2. In guinea-pig normally perfused hearts, both defibrotide (DFT) and its fraction, P.O. 085 DV, increase the amount of nitrite appearing in perfusates in a concentration-dependent fashion. At the highest concentration studied (10(-6) M), P.O. 085 DV was more effective than DFT. A concomitant increase in the coronary flow was observed. 3. The increase in nitrite in perfusates and the increase in coronary flow induced by both DFT and P.O. 085 DV were significantly reduced by NG-monomethyl-L-arginine (L-NMMA, 10(-4) M), an inhibitor of nitric oxide synthase (NOS). 4. The endothelium-dependent vasodilator, acetylcholine (ACh), enhances the formation of nitrite and the coronary flow. Both the increase in coronary flow and in the formation of nitrite were significantly reduced by L-NMMA (10(-4) M). 5. In guinea-pig hearts subjected to ischaemia and reperfusion, the effect of both compounds in increasing the amount of nitrite in perfusates was more evident and more pronounced with P.O. 085 DV. 6. Reperfusion-induced arrhythmias were significantly reduced by both compounds to the extent of complete protection afforded by compound P.O. 085 DV. 7. The cardioprotective and antiarrhythmic effects of DFT and P.O. 085 DV are discussed.     

Thioperamide-elicited increase of histamine release from basolateral amygdala of freely moving rats and its therapeutic implications

Inflammation Research -     

Mast cell heterogeneity in response to cholinergic stimulation

Mast cell heterogeneity in response to acetylcholine has been evidentiated by the virtual lack of sensitivity or by the full reaction to nanomolar concentrations of acetylcholine, observed in samples of serosal mast cells isolated from the same animal species. The incubation with IgE of isolated rat mast cells renders the originally heterogeneous response homogeneous, the release of histamine evoked by acetylcholine being proportional to the IgE concentration. The histamine release induced by acetylcholine is due to the activation of muscarinic receptors, since it is blocked by atropine, not reproduced by acetylthiocholine and potentiated by exposure of the cells to the specific antigen.     

Modulation of anaphylactic histamine release by calcium channel agonists and antagonists

Calcium antagonists have been reported to exert protective effects in hypersensitivity reactions in man and animals. However, their effect on anaphylactic histamine release is highly variable and controversial. In the present paper we evaluate the effect of calcium entry blockers and BAY K 8644 on the response to specific antigen in isolated hearts taken from actively sensitized guinea-pigs and from isolated rat and guinea-pig mast cells, actively or passively sensitized. Verapamil, diltiazem, nifedipine and prenylamine dose-dependently decreased anaphylactic histamine release in isolated actively sensitized guinea-pig mast cells. BAY K 8644 was found to be ineffective. In isolated, passively sensitized rat mast cells, verapamil showed a highly signficant inhibitory effect, while prenylamine (10^–4 M) was able to evoke a histamine releasing effect. In cardiac anaphylaxis verapamil, diltiazem, prenylamine, but not nifedipine, were active in reducing the release of histamine without modifying the antigen-induced arrhythmias and positive chronotropic and inotropic effects.     

Nitric oxide modulates cardiac and mast cell anaphylaxis

Anaphylaxis in the isolated guinea-pig heart was associated with a sudden release of histamine with a long-lasting release of nitrite (NO ₂ ^– ), an oxidation product of NO.N ^G-monomethyl-l-arginine (MeArg, 300 M) increased the severity of cardiac anaphylaxis, as shown by the decrease in the coronary flow and by a prolonged duration of antigen-induced arrhythmias. Concomitantly, MeArg increased the release of histamine while decreasing the release of nitrite. Sodium nitroprusside (NaNP, 10^–5–10^–4 M) reduced the severity of cardiac anaphylaxis by increasing coronary flow and shortening the duration of antigen-induced arrhythmias. Concomitantly, NaNP decreased the release of histamine while increasing the release of nitrite. In mast cells isolated from actively sensitized guinea-pigs, the release of histamine elicited by specific antigen was increased by MeArg and decreased by NaNP.In conclusion, endogenous and exogenous NO antagonizes the effect of vasoconstrictor mediators released after antigen challenge and plays a protective role in anaphylactic reactions in vitro,     

Stimulation and resection of Vidian nerve in patients with chronic hypertrophic non-allergic rhinitis: effect on histamine content in nasal mucosa

Parasympathetic innervation of nasal mucosa plays an important role in the pathogenesis of chronic hypertrophic non-allergic rhinitis (C.H.N.A.R.). The present study investigated the effect of Vidian nerve stimulation and resection on the histamine contents and on the morphological pattern in mucosal samples of patients with C.H.N.A.R. Vidian nerve stimulation determines a significant decrease in histamine content in the samples examined; microscopical observations showed significant variations in the glandular, stromal and vascular components.The changes indicate an enhanced secretory activity, intensive vasodilatation and active degranulation of mast cells, which were significantly decreased in number in the samples obtained after 90 sec of stimulation.The neurectomy of the Vidian nerve resolves quite completely the clinical symptomatology and in parallel decreases the mucosal histamine contents, which are increased in patients with C.H.N.A.R. before the operation in comparison with the normal controls.     

Modulation of the immunological response of guinea pig mast cells by carbon monoxide.

Challenge of guinea pig mast cells with antigen under aerobic conditions induced the expected release of histamine and led to a significant increase in intracellular calcium ([Ca2+]i) and cyclic adenosine monophosphate (cAMP) levels. Prior exposure to CO decreased the immunological histamine release. This effect was accompanied by a decrease in the levels of [Ca2+]i and by an increase in the cyclic guanosine monophosphate (cGMP) levels. The exposure of mast cells to nitrogen (N2) did not modify the release of histamine. The CO-mediated inhibition of the immunological release of histamine was reversed by the soluble guanylate cyclase inhibitor (1 H-[1.2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ) and by oxyhaemoglobin (HbO2). Incubation of mast cells for 4 h with hemin, a heme oxygenase (HO) inducer, resulted in an increase in HO activity, measured as bilirubin production. Hemin abated the immunological release of histamine, in similar fashion to exogenous CO, and increased the cGMP levels. These effects were reversed by ODQ and HbO2. It is proposed that CO from an exogenous or endogenous source stimulates guanylyl cyclase and causes cGMP formation which then induces calcium to be sequestrated so that the [Ca2+]i concentration falls and histamine release is inhibited.     

Presence of functionally active β-adrenoceptors in rat mast cells

Summary The correlation between the binding of a -adrenoceptor antagonist, (–)[³H]-dihydroalprenolol (DHAP), and the adrenergic inhibition of histamine release by acetylcholine and by compound 48/80 was studied with isolated purified rat mast cells and in rat mast cell crude membrane fractions.Acetylcholine-evoked histamine release was inhibited by catecholamines, in the order isoprenaline > adrenaline > noradrenaline. Pretreatment of cells with (–)alprenolol antagonized the inhibitory effect of isoprenaline on acetylcholine-induced histamine release.40/80-evoked histamine release was bocked by isoprenaline at significantly higher concentrations than those required to inhibit cholinergic histamine release. The inhibitory effect of isoprenaline was equally antagonized by preincubating mast cells with (–)alprenolol.Specific binding sites for DHAP have been demonstrated in rat mast cell membranes. The specific binding of DHAP was inhibited by adrenoceptor agonists and antagonists according to the stereospecificity of these compounds.A close correlation between the binding-inhibitory potency of various adrenergic compounds and the data obtained in the pharmacological experiments was found, thus indicating the presence of -adrenoceptors in rat mast cells.     

The contribution of protease-activated receptor 1 to neuronal damage caused by transient focal cerebral ischemia

The serine proteases tissue plasminogen activator, plasmin, and thrombin and their receptors have previously been suggested to contribute to neuronal damage in certain pathological situations. Here we demonstrate that mice lacking protease-activated receptor 1 (PAR1) have a 3.1-fold reduction in infarct volume after transient focal cerebral ischemia. Intracerebroventricular injection of PAR1 antagonist BMS-200261 reduced infarct volume 2.7-fold. There are no detectable differences between PAR1-/- and WT mice in cerebrovascular anatomy, capillary density, or capillary diameter, demonstrating that the neuroprotective phenotype is not likely related to congenital abnormalities in vascular development. We also show that the exogenously applied serine proteases thrombin, plasmin, and tissue plasminogen activator can activate PAR1 signaling in brain tissue. These data together suggest that if blood-derived serine proteases that enter brain tissue in ischemic situations can activate PAR1, this sequence of events may contribute to the harmful effects observed. Furthermore, PAR1 immunoreactivity is present in human brain, suggesting that inhibition of PAR1 may provide a novel potential therapeutic strategy for decreasing neuronal damage associated with ischemia and blood-brain barrier breakdown.     

Platelet aggregation and platelet histamine release by immunological stimulation in atopic patients: Modulation by nitric oxide

Inflammation Research -