Studies on histamine release induced by compound 48/80 and peptide 401

Conclusion The activity of the drugs under these conditions suggests that they, and possibly cyclic AMP, may have a wider role in regulating the intracellular concentration of calcium, whether derived from internal or external sources, or that they may have activities unrelated to calcium movements.     

Effect of cyclic AMP on histamine release induced by compound 48/80.

Bu2 cAMP(N6, O2'-dibutyryl adenosine-3',5'-cyclic monophosphate) inhibited the response of rat peritoneal mast cells to compound 48/80 in the presence of calcium ions. In the absence of calcium, the nucleotide partially prevented the desensitization induced by chelating agents. The response of cells, allowed to accumulate Bu2 cAMP in the presence of calcium (to avoid depletion of intracellular stores of the ion) and then challenged in the absence of extracellular calcium, was also inhibited. These results are discussed in terms of the postulated effects of Bu2 cAMP on the calcium-gatubg mechanism operative in histamine secretion.     

Ca-dependent and Ca-independent histamine release from mast cells induced by active components of compound 48/80

Compound 48/80 and 14C-labelled compound 48/80 were synthesized, and fractionated by thin-layer chromatography into 14 components with various histamine-releasing activities and different Ca++ requirements for their actions. The histamine release induced from rat mast cells in vitro by the most active component, fraction D (molecular weight = 2280, a tridecamer composed of 13 monomer units), was greatly elevated by extracellular Ca++, and was partially reduced by pretreatment of the cells with dinitrophenylated Ascaris antiserum, an IgE. In contrast, the histamine release induced by fraction H (molecular weight = 1580, a nonamer composed of 9 monomer units), was higher in Ca-free medium than in Ca-containing medium, and partially suppressed by pretreatment of mast cells with neurotensin or substance P, both Ca-independent releasers. The binding potencies of the 14C-labelled components estimated at 4 degrees C in the presence of Ca++, where no degranulation of the cells occurs, generally paralleled their histamine-releasing activities. However, Ca++ was inhibitory for the binding of 14C-fraction H. The binding of fraction D to [3H]arachidonic-acid-preloaded mast cells induced a rapid accumulation of the labelled arachidonic acid into phosphatidic acid, phosphatidylinositol and phosphatidylcholine, with concomitant decrease of the labelled arachidonic acid from phosphatidylethanolamine prior to the detectable histamine release.     

Effects of H1-antihistamine drug regimen on histamine release by nonlesional skin mast cells of patients with chronic urticaria.

Profiles of compound 48/80-induced histamine release (HR) from mast cells of uninvolved skin from patients with chronic urticaria (CU) and from a normal control (NC) group were compared, and the effects of anti-H1 medications were assessed versus placebo. Then, patients with CU (15) and NC subjects (10) were randomly assigned to take either hydroxyzine (100 mg/day), terfenadine (120 mg/day), or placebo for 28 days. The effects of such treatment on the clinical response and on the profile of compound 48/80-induced HR during a 4-hour period were analyzed. Treatment with hydroxyzine in patients with CU improved the clinical symptoms and modified the profile of HR; more histamine was recovered at 1 hour (p less than 0.05) and 2 hours (p less than 0.05), as compared with baseline. Terfenadine and placebo had no effect on the clinical response or on the profiles of HR. In the NC group, the amounts of histamine recovered at 1 hour after challenge with compound 48/80 were lower than amounts of the pretherapy values (p less than 0.01). It could be concluded that (1) the profile of HR in patients with CU is reproducible during a period of 28 days, (2) only hydroxyzine modifies both the clinical response and the profile of HR, and (3) anti-H1 compounds decrease the HR in the NC group.     

Oxygen consumption during histamine release by antigen and compound 48/80

The oxygen consumption of isolated rat mast cells has been determined using a micro capillary respirometer designed by Cunningham and Kirk and modified to permit stirring and addition of reactants. Uptake ranged from 0.5 pl. per cell per minute in 100 per cent O₂ to 0.1 pl. per cell per minute in 1 per cent O₂. It remained steady for at least 1 hour and was not affected by the presence of glucose.

Under a variety of conditions neither histamine release by antigen added to sensitized cells nor by compound 48/80 added to normal cells resulted in any increase in the rate of oxygen uptake. Oxygen does not appear to be a rate limiting factor.

     

Broncho-Vaxom® inhibits histamine release from rat mast cells induced by compound 48/80 and ionophore A23187

Broncho-Vaxom (BV) inhibited in dose-dependent manner the release of histamine from and degranulation of isolated rat peritoneal mast cells stimulated with compound 48/80 and the ionophore A23187. Inhibition persisted after removal of BV from the incubation medium before stimulation, but did not occur when bovine serum albumin (BSA) was used instead of BV. Binding of BV to mast cells was observed by electron microscopy on cells that had been incubated with colloidal-gold labelled BV. There was no significant difference between the binding of BV gold and BSA gold to the mast cells. Washing before fixation removed most of the BV gold from the cells. This study establishes BV as anin vitro histamine release inhibitor.     

A histamine component in the vascular skin reactions induced by compound 48/80 in the guinea-pig

Conclusions Vascular skin reactions induced by compound 48/80 are ring shaped and are not homogenous. To some extent they are inhibited only by mepyramine and after low doses of compound 48/80 are resistant to burimamide.All the above features of vascular skin reactions induced by compound 48/80 may implicate the additional release of vasoactive substances other than histamine, evoking a vasoconstriction and microcirculatory stasis, especially in the central part of the skin reaction.     

Inhibition of IgE and compound 48/80-induced histamine release by lectins.

Lectins from Ricinus communis and Glycine max, as well as wheat germ agglutinin and concanavalin A, caused a dose-dependent release of histamine from mast cells present in the mixed peritoneal cells from the rat. In addition, histamine release in an IgE-mediated and a compound 48/80-mediated reaction was inhibited in cells which had been pretreated with these lectins. With concanavalin A and the R. communis lectin both effect were prevented by the addition of the appropriate monosaccharides to the incubations. However, the lectin-induced histamine release and the lectin-induced inhibition of subsequent IgE-mediated histamine release could be dissociated: thus L-rhamnose, a hexose not ordinarily found on mammalian cell membranes, a specifically inhibited histamine release which was caused by the lectin from R. communis without affecting the inhibition of IgE-mediated histamine release. Conversely, D-fucose, which also is not a constituent of cell membrane glycolipids or glycoproteins prevented the inhibition of IgE-mediated histamine release by this lectin without affecting the lectin-induced histamine release. Furthermore, the nominally galactose-specific lectins from Sophora japonica and Ulex europeus inhibited IgE-mediated histamine release while causing little if any histamine release themselves. High concentrations of the lectin from Lotus tetragonolobus failed to cause histamine release or to affect the IgE-mediated histamine release reaction. Based on the known structural specificity of these lectins and the amounts of the lectins which were required to demonstrate an effect, it was concluded that D-galactose, alpha-linked, intrachain D-glucose (or mannose), and N-acetylglucosamine residues but probably not N-acetyl-galactosamine or L-fucose residues in the glycolipids or glycoproteins of the mast cell membrane can play a role in the initiation of histamine release and in the desensitization of the cells to subsequent histamine release-inducing stimuli.     

Alterations in histamine levels in the rat induced by compound 48/80

Histamine release in the rat was inducedin vivo either by a single dose of compound 48/80 injected i.v. or by four repeated, daily doses of the same compound injected i.p. After i.v. injection the levels of blood histamine were determined and after i.p. injections the changes in both tele-methylhistamine and histamine levels in different tissues were investigated. I.v. injection of 48/80 induced a very rapid and marked increase of blood histamine by 7.4 to 11-fold over the control levels within the first two minutes. After repeated i.p. injections of compound 48/80 most tissues showed higher than normal tele-methylhistamine/histamine ratios. The results suggest that agents known to induce release of histamine from mast cells may exert significant changes in blood and tissue histamine levels and that liberated histamine is thereafter extensively catabolized.     

Binding of compound 48/80 by isolated rat mast cells in connection with histamine release

The binding of compound 48/80 in connection with histamine release from isolated rat mast cells was investigated by a two-step incubation procedure. After incubation of mast cells with known concentrations of compound 48/80, the supernatants were collected and subsequently exposed to fresh mast cells. The response in the second incubation step provided a measure of the amount of compound 48/80 remaining in the supernatants. At noncytotoxic concentrations of the releasing agent, binding capacities for compound 48/80 of up to 4 micrograms/10(5) mast cells (4% w/v) were observed. The binding of compound 48/80 was of high affinity, giving mast cell concentrations of the compound exceeding that in the incubation medium by four orders of magnitude. The binding occurred rapidly with a substantial proportion bound within the first minute. These findings indicate that quantitation of exocytotic events by means of basic dyes may be compromised by competition for granular binding sites by basic releasing agents.     

Comparison of histamine and serotonin release from rat peritoneal mast cells induced by nerve growth factor and compound 48/80

Inflammation Research -     

Cutaneous responses to histamine, compound 48/80, and codeine in patients with chronic renal failure

Pruritus is a common symptom associated with chronic renal failure (CRF). But increased plasma histamine levels and skin mast cell proliferation previously reported in these patients did not correlate with the intensity of the pruritus. Since increased mast cell releasability was described in chronic idiopathic urticaria, we attempted to examine whether this mechanism could explain pruritus in patients with CRF. Twenty-five patients with end stage renal failure were skin tested with histamine, codeine, and compound 48/80. There were nine patients on continuous ambulatory peritoneal dialysis, eight patients on hemodialysis, (tested both before and after dialysis) and eight patients with advanced CRF. Wheal area after intradermal injection of three concentrations of the above substances was measured. In general, the wheal areas in all patients with CRF were either similar to or smaller than those of the control group who were without renal impairment. In conclusion, patients with CRF with or without dialysis therapy demonstrated unchanged or decreased skin test responses to histamine, codeine, and compound 48/80. Increased mast cell releasability cannot explain the pruritus in patients with CRF.     

Dermal blood flow after local challenges with allergen, histamine, bradykinin and compound 48/80

Blood flow was determined in weal and flare reactions and in late dermal reactions after skin-prick tests with allergen, histamine, bradykinin and compound 48/80 in pollen-allergic subjects. Local blood flow was measured with laser Doppler flowmetry intermittently for up to 48 hr at three distances from the prick centre (2 mm; weal, 15 mm; flare and 30 mm). Continuous recordings were also made in the weal area after challenge with bradykinn and compound 48/80. The size of the induced weal and flare area of all the substances and the late phase after allergen was determined using digitized planimetry. Furthermore, simultaneous determinations of local dermal temperature and blood flow in the weal and flare site were performed intermittently for 6 hr after allergen and histamine challenges. There was a dose-dependent and distance-related increase in blood flow for all the substances tested. The blood flow in the 2-mm registrations had normalized 20 min after bradykinin, 1.5-2 hr after histamine and 3 hr after compound 48/80, while allergen induced a continuous increase in blood flow for more than 24 hr. The area of the weal and flare reaction was dose related for all substances, and a similar dose-dependent increase was noted for the observed dermal late-phase reactions present after allergen. The local temperature after challenge with allergen and histamine was also increased in a distance-dependent manner. These studies suggest that laser Doppler flowmetry is a sensitive and reproducible method to quantify blood flow changes occurring after skin-prick tests. Different putative mediators or mast cell stimulating substances produce various response profiles, all of which differ from those observed after allergen. Temperature measurements after skin-prick tests seem to follow the observed changes in blood flow as measured with laser Doppler flowmetry, which may be why both techniques might reflect changes in capillary blood flow.     

Inhibition of compound 48/80 induced histamine release from mast cells by chloride channel blockers is affected by methods of drug preincubation

Inflammation Research -