Effect of maleimide derivatives, sulfhydryl reagents, on stimulation of neutrophil superoxide anion generation with concanavalin A

Isolation and properties of a soluble fraction of Paracentrotus lividus sea urchin eggs responsible for the calcium-induced oxidative burst

The system responsible for the oxidative burst (OB) activity in Paracentrotus lividus eggs is different from those described earlier for other sea urchin species. The OB in P. lividus is associated with a soluble fraction resulting from centrifugation at 150,000 g. A low-molecular-weight, -SH-containing molecule present in this supernatant is required for the OB activity. The sulfhydryl reagent N-ethylmaleimide completely inhibits the calcium stimulated OB activity of intact eggs in the presence of the calcium ionophore A23187, suggesting that this requirement of low-molecular-weight -SH-containing molecules for OB exists also in vivo.

NPGB-induced inhibition of superoxide anion production by normal Lewis rat macrophages

The treatment of Lewis rat peritoneal macrophages with p1-nitrophenyl p-guanidinobenzoate (NPGB) inhibited the superoxide anion production stimulated with phorbol myristate acetate (PMA). The addition of NPGB at the time of maximum superoxide generation was still able to block the superoxide release. It appears from these findings that NPGB may block either the activation process of the membrane bound NAD(P)H oxidase or directly on the active enzyme. Other protease inhibitors such as, epsilon-amino caproic acid (EACA), pepstatin, trans aminomethyl cyclohexane carboxylic acid (AMCA), aprotinin, and leupeptin did not inhibit the superoxide release. The superoxide anion release by the xanthine-xanthine oxidase system was not inhibited by NPGB. This finding indicates that NPGB does not itself react with superoxide. It has been also demonstrated that NPGB is a good reactant toward sulfhydryl group. The relevance of these finding to experimental allergic encephalomyelitis (EAE) is discussed.

Effect of vitamin K3 on macrophage functions and intracellular calcium

1. The effect of vitamin(vit) K3 on guinea-pig macrophage functions was studied. 2. Vit K3 inhibited macrophage locomotion, phagocytosis and lysosomal enzyme release. 3. Vit K3 inhibited the rise in the intracellular free calcium level induced by stimuli at the concentration at which vit K3 suppressed functions. 4. These results suggest that vit K3 inhibits macrophage functions through the interference with the mobilization of intracellular calcium.

The effect of apomorphine on exocytosis and metabolic burst of polymorphonuclear leukocytes

1 In rabbit polymorphonuclear leukocytes (PMNLs) apomorphine at 10-100 microM inhibits fMet-Leu-Phe and A23187-induced exocytosis, and the phorbol myristate acetate- and fMet-Leu-Phe-induced activation of the metabolic burst. The secretory response was not restored by washing the cells after pretreatment with apomorphine. 2 The inhibitory effect of apomorphine was not prevented by the dopamine receptor antagonists haloperidol and pimozide, nor did dopamine itself inhibit fMet-Leu-Phe-induced exocytosis. It therefore seems unlikely that effects are mediated via dopamine receptors. However, sulphydryl reagents reduced the inhibitory effect of apomorphine, suggesting that it may depend upon interaction with susceptible sulphydryl groups, the intactness of which is required for exocytosis and other functions of PMNLs.

Comparative study on the stimulation of superoxide production in guinea-pig eosinophils by the calcium ionophore A23187

The effect of calcium and/or magnesium on O2- production by guinea-pig eosinophils stimulated by the calcium ionophore A23187 was studied in comparison to neutrophils. In the absence of calcium, A23187 did not stimulate O2- production in resting eosinophils and neutrophils, regardless of the presence of extracellular magnesium. The A23187-induced O2- production by both cells increased linearly with extracellular Ca2+ concentrations. However, the concentration of Ca2+ required for maximum O2- production in eosinophils was about 10-times lower than that required of neutrophils. The addition of Mg2+ strongly inhibited O2- production, especially in eosinophils at low Ca2+ concentrations. The intracellular Ca2+ concentration was lower in eosinophils than in neutrophils in the resting state, and the enhancement of the intracellular Ca2+ concentration in response to A23187 was much lower in eosinophils than in neutrophils. The activation of the NADPH-dependent O2(-)-forming enzyme (NADPH oxidase) in eosinophils depended on extracellular calcium, as observed in O2- production. However, the NADPH oxidase activity in the particulate fraction from A23187-stimulated eosinophils was only slightly affected by the addition of divalent cations or EDTA. The compound W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride), a calmodulin antagonist, significantly inhibited O2- production by both cells. On the other hand, the compound H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride), a protein kinase C antagonist, was less effective on O2- production than was W-7. H-7 had little effect on O2- production of eosinophils. These findings suggest that NADPH oxidase might be activated by a smaller Ca2+ concentration through the calmodulin-dependent reaction. This was not observed with protein kinase C, at least in eosinophils.

Comparative study on effect of N-ethylmaleimide on the superoxide-generating system of guinea-pig eosinophils stimulated by soluble stimuli

1. The effect of N-ethylmaleimide (MalNEt) modification on O2- production by guinea-pig eosinophils mediated by different soluble stimuli was studied. 2. MalNEt pretreatment inhibited the O2- production stimulated by concanavalin A (Con A), cytochalasin E or digitonin, but not A23187 or sodium fluoride. 3. Particulate fractions from MalNEt-pretreated eosinophils before exposure to the stimulus showed the inhibition of the enhancement of NADPH-dependent O2- production induced by Con A, cytochalasin E or digitonin, but not A23187. 4. Treatment of eosinophils with MalNEt after stimulation had no effect on the NADPH oxidase activity. 5. These findings suggest that at least two pathways exist for the activation of the O2(-)-generating enzyme system, probably the NADPH oxidase system, in guinea-pig eosinophils.

An opsonised microelectrode. Observation of the respiratory burst of a single human neutrophil

A 10 micron diameter gold microvoltammetric electrode, opsonised with human IgG, was used to study the respiratory burst of a single human neutrophil. The electrode oxidised superoxide produced near its surface by the neutrophil back to dioxygen. It is suggested that the current so detected is proportional to the rate of superoxide production by the NADPH oxidase of a single cell. In all cases the response consisted of a relatively rapid rise in current after cell addition, followed by a 2-phase decay. It is further suggested that this complex decay results from the production of superoxide being rate-limited initially by the NADPH concentration and later by the coupled metabolism of the hexose monophosphate shunt.

Response of superoxide anion production by guinea pig eosinophils to various soluble stimuli: comparison to neutrophils

The effect of various soluble stimuli on the superoxide production by guinea pig eosinophils was studied in comparison to neutrophils. Phorbol myristate acetate, A23187, digitonin, NaF, concanavalin A (Con A), and cytochalasin E stimulated eosinophils and neutrophils to release O2-. The O2- production by these active agents, excluding Con A and cytochalasin E, was much greater in eosinophils than in neutrophils. Formyl-Met-Leu-Phe stimulated the O2- production in neutrophils but not in eosinophils. Neither histamine nor Val/Ala-Gly-Ser-Glu stimulated the O2- production in both types of leukocytes. A23187- or Con A-stimulated O2- production was greatly enhanced by cytochalasin B pretreatment in neutrophils but not in eosinophils. Lineweaver-Burk analysis of NADPH oxidase in particulate fractions showed that eosinophils possessed the same Km values as neutrophils and greater Vmax values than neutrophils, suggesting that eosinophils have a similar, but more active, O2- -generating enzyme system than neutrophils.

Effect of maleimide derivatives on superoxide-generating system of guinea-pig neutrophils stimulated by different soluble stimuli

The effect of modification of maleimide derivatives on superoxide production by guinea-pig neutrophils induced by a variety of different soluble stimuli was studied. Pretreatment of neutrophils by showdomycin, a very slowly penetrating-SH reagent, did not affect superoxide production by all of the stimuli used, suggesting no exposure of sulfhydryl groups involved in superoxide-generating system on the cell surface. Pretreatment with N-ethylmaleimide (MalNEt), a considerably penetrating-SH reagent, markedly inhibited superoxide production stimulated by formyl-methionyl-leucyl-phenylalanine (HCO-Met-Leu-Phe), cytochalasin E or digitonin, but not superoxide production stimulated by the ionophore A23187 or sodium fluoride. The oxygen consumption stimulated by HCO-Met-Leu-Phe or cytochalasin E was inhibited by MalNEt pretreatment, whereas the oxygen consumption stimulated by A23187 was not inhibited by MalNEt. The inhibition by MalNEt of superoxide production did not appear to be due to the interference with binding of the affected stimuli, since MalNEt pretreatment did not inhibit the release of lysozyme, granule enzyme, induced by HCO-Met-Leu-Phe, cytochalasin E or digitonin. Particulate fractions from MalNEt-pretreated neutrophils before exposure to the stimulus exhibited the inhibition of the enhancement of NADPH-dependent superoxide production induced by HCO-Met-Leu-Phe, cytochalasin E or digitonin, but not A23187, whereas treatment of neutrophils with MalNEt after activation by these stimuli had no effect on the NADPH oxidase activity in particulate fractions. Direct exposure of particulate fractions from A23187-stimulated neutrophils to MalNEt showed no actual susceptibility of NADPH oxidase to MalNEt inhibition. These findings suggest that the inhibitory effect of MalNEt is caused by the modification of the process of the activation by the affected stimuli of the superoxide system, probably NADPH oxidase and that at least two mechanisms exist for activation of superoxide-generating system in guinea-pig neutrophils on the basis of the susceptibility to MalNEt inhibition.

An opsonised electrode. The direct electrochemical detection of superoxide generated by human neutrophils

A pyrolytic graphite electrode was surface modified with human IgG and used as a stimulus to elicit a respiratory burst from human neutrophils. The oxidation current observed was shown to be due to re-oxidation of superoxide produced by the neutrophils. Both superoxide dismutase and N-ethylmaleimide were effective inhibitors of the oxidation current.