Study on the superoxide-producing enzyme of eosinophils and neutrophils--comparison of the NADPH oxidase components.

It has been known that eosinophils produce more superoxide anion (O2-) than neutrophils. To elucidate the mechanism involved in the difference in the superoxide-producing activities, we compared the NADPH oxidase components and the translocation of the cytosolic components between eosinophils and neutrophils. Membrane-bound cytochrome b558, cytosolic p47-phox, p67-phox, and p40-phox were present in both neutrophils and eosinophils, but the amounts of these components were 1.5- to 3.3-fold greater in eosinophils than neutrophils. Upon activation, p47-phox, p67-phox, and p40-phox were translocated to the membranes in both leukocytes, but larger amounts were translocated in eosinophils than in neutrophils. Furthermore, the cross-mixing experiments using membrane and cytosol of eosinophils and neutrophils revealed that more cytosolic components were translocated, and more superoxide-producing activities were obtained using eosinophil fractions. Interestingly, Km values of activated oxidase for NADPH were almost the same in any combination of membrane and cytosol from both leukocytes, indicating that oxidase components are likely similar in both eosinophils and neutrophils. These observations suggest that NADPH oxidase components are more abundant in eosinophils than neutrophils, and, upon activation, larger amounts of NADPH oxidase complex are formed in eosinophils than in neutrophils.