Activation of the NADPH oxidase in a cell-free system from human neutrophils stimulated by phorbol myristate acetate

Anti-inflammatory action of gentamycin through inhibitory effect on neutrophil NADPH oxidase activity

The effects of gentamycin on the NADPH oxidase (EC 1.6.99.6) from human neutrophils in both whole-cell and fully soluble (cell-free) systems were investigated. Gentamycin was found to inhibit, concentration-dependently, the superoxide generation of neutrophils exposed to phorbol myristate acetate in a whole-cell system and the activation of superoxide-generating NADPH oxidase by sodium dodecyl sulfate in a cell-free system. The concentrations of the drug required for 50% inhibition of the oxidase (IC50) were 150 microM in the whole-cell system and 10 microM in the cell-free system. In addition, in the cell-free system, the drug did not change the Km value for NADPH of the oxidase. However, gentamycin did not the superoxide generation of NADPH oxidase after its activation in the cell-free system, suggesting that the drug do not have superoxide-scavenger action. These results suggest that gentamycin, an aminoglycoside antibiotic, may exhibit an anti-inflammatory action due to inhibition of neutrophil NADPH oxidase activation.

Prostaglandin E and analogs of prostacyclin influencing superoxide production by the human neutrophil NADPH oxidase system

The effects of prostaglandin (PG) E1 and I2 analogs (OP-41483 and OP-2507) on the superoxide generation of human neutrophil NADPH oxidase (EC 1.6.99.6) in both whole-cell and cell-free systems were investigated. In a whole-cell system, OP-2507 inhibited the superoxide generation by neutrophils exposed to phorbol myristate acetate concentration-dependently through its superoxide-scavenging action. The concentration of the drug required for 50% inhibition of the oxidase (IC50) was 21 microM. In a cell-free system, however, the drug in concentrations of < 100 microM did not inhibit the activation of NADPH oxidase by sodium dodecyl sulfate because of its inactivation by the detergent. Although PGE1 and OP-41483 did not inhibit the superoxide production by stimulated neutrophils in a whole-cell system, they both inhibited the activation of NADPH oxidase in a cell-free system concentration-dependently, with IC50 values of 44 and 170 microM, respectively. In addition, in the cell-free system, the Km value for NADPH of the oxidase was unchanged by PGE1. The results suggest that the PGI2 analog, OP-2507, is a possible superoxide-scavenger and that PGE1 inhibits the NADPH oxidase activation by sodium dodecyl sulfate in a cell-free system concentration-dependently.

Mechanisms for the activation/electron transfer of neutrophil NADPH-oxidase complex and molecular pathology of chronic granulomatous disease

Professional phagocytes, neutrophils, possess a unique membrane-associated NADPH-oxidase system, dormant in resting cells, which becomes activated upon exposure to the appropriate stimuli and catalyzes the one-electron reduction of molecular oxygen to superoxide, O2-. Oxidase activation involves the assembly, in the plasma membrane, of membrane-bound and cytosolic constituents of the oxidase system, which are disassembled in the resting state. The oxidase system consists of two plasma membrane-bound components; low-potential cytochrome b558, which is composed of two subunits of 22-kDa, and 91-kDa, and a possible flavoprotein related to the electron transport between NADPH and cytochrome b558. Recent reports have indicated that FAD-binding sites of the oxidase are contained in cytochrome b558. At least two cytosolic components, 67-kDa protein and a phosphorylated 47-kDa protein, are known to translocate to the plasma membrane, ensuring assembly of an active O2(-)-generating NADPH-oxidase system. It is the purpose of this review to focus on recent data concerning electron transfer mechanisms of the activated neutrophil NADPH-oxidase complex and molecular pathology of chronic granulomatous disease.

Activation factors of neutrophil NADPH oxidase complex

Professional phagocytes, neutrophils, possess a unique membrane-associated NADPH oxidase system, dormant in resting cells, which becomes activated upon exposure to the appropriate stimuli and catalyzes the one-electron reduction of molecular oxygen to superoxide, O2-. Oxidase activation involves the assembly, in the plasma membrane, of membrane-bound and cytosolic constituents of the oxidase system, which are disassembled in the resting state. The oxidase system consists of two plasma membrane-bound components; low-potential cytochrome b558, which is composed of two subunits of 22 kDa and 91 kDa, and a flavoprotein related to the electron transport between NADPH and heme-binding domains of the oxidase. Recent reports have indicated that FAD-binding sites of the oxidase are contained in cytochrome b558 (flavocytochrome b558). At least two cytosolic components, 67 kDa protein and a phosphorylated 47 kDa protein, are known to translocate to the plasma membrane, ensuring assembly of an active O2(-)-generating NADPH oxidase system. More recently, the membrane (Raps) and cytosolic (Racs) GTP-binding proteins have been established as essential to oxidase assembly. It is the purpose of this review to focus on recent data concerning the regulatory mechanisms which lead to organization and activation of the neutrophil NADPH oxidase system.

Anti-inflammatory action of erythromycin. Its inhibitory effect on neutrophil NADPH oxidase activity

The effects of erythromycin on the NADPH oxidase activity in the neutrophils of normal subjects and patients with bronchiolitis were investigated. In the patients receiving erythromycin, NADPH oxidase activity was significantly lower in a whole-cell system than that before therapy. Erythromycin was also found to inhibit the superoxide generation of neutrophils exposed to phorbol myristate acetate in a whole-cell system and the activation of superoxide-generating NADPH oxidase by sodium lauryl sulfate (sodium dodecyl sulfate) in a cell-free system. The concentration of the drug required for 50 percent inhibition of the oxidase was 0.7 mM in the whole-cell system and 0.2 mM in the cell-free system. These results suggest that erythromycin, an antibiotic which penetrates well into human neutrophils, may exhibit an anti-inflammatory action due to inhibiting of neutrophil NADPH oxidase activation.

Effects of anti-allergic drugs on human neutrophil superoxide-generating NADPH oxidase

The effects of anti-allergic drugs with or without H1-receptor antagonism on the NADPH oxidase (EC 1.6.99.6) from human neutrophils in both whole-cell and fully soluble (cell-free) systems were investigated. Three anti-allergic drugs with H1-receptor antagonism, azelastine, ketotifen and oxatomide, were found to inhibit the superoxide generation of human neutrophils exposed to phorbol myristate acetate in a whole-cell system and the activation of superoxide-generating NADPH oxidase by sodium dodecyl sulfate in a cell-free system. The concentrations of these drugs required for 50% inhibition of the oxidase (IC50) were: azelastine--0.7 microM in the whole-cell system and 0.5 microM in the cell-free system; ketotifen--60 microM in the whole-cell system and 6.8 microM in the cell-free system; and oxatomide--25 microM in the whole-cell system and 9.7 microM in the cell-free system. In addition, in the cell-free system, these drugs did not change the Km values for the NADPH of the oxidase. However, these drugs did not inhibit the superoxide generation of NADPH oxidase after its activation in whole-cell and cell-free systems, suggesting that these drugs do not have superoxide-scavenger actions. Concentrations of less than 200 microM of anti-allergic drugs without H1-receptor antagonism, tranilast, repirinast and ibudilast, did not inhibit neutrophil NADPH oxidase in whole-cell and cell-free systems. The IC50 of hydrocortisone in the cell-free system was 60 microM. These results suggest that anti-allergic drugs with H1-receptor antagonism inhibit activation of the solubilized membrane-bound enzyme by sodium dodecyl sulfate in cell-free systems and that they have much stronger anti-inflammatory action than hydrocortisone.