Influence of neutrophil cationic proteins on generation of superoxide by human polymorphonuclear cells during phagocytosis |
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Authors: | Mahboob Alam Narendranath S Ranadive Waldemar Pruzanski |
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Institution: | (1) Departments of Pathology and Medicine, University of Toronto Medical Sciences Buiding Toronto, M5S 1A8, Ontario, Canada |
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Abstract: | The cationic proteins from neutrophyl lysosomes have been shown to modulate phagocytic activity of granulocytes. The present study reports the effects of the cationic protein fractions on the generation of O
2
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by human PMNs during phagocytosis. Human PMNs were reacted win different phagocytic stimuli in the presence and absence of lysosomal cationic proteins and the amount of O
2
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generated was determined by superoxide dismutase inhibitable reduction of cytochromec. Total cationic protein extract from neutrophil lysosomes enhanced O
2
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generated by PMNs during the phagocytosis of IgG-coated latex beads and opsonized zymosan particles. The analysis of the fractions of cationic proteins obtained from a Sephadex G-75 column showed that the O
2
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generation-enhancing activity was associated with the proteins eluted in fractions III and IV. A protein fraction mainly eluted in void volume inhibited the cytochromec reduction by O
2
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formed during phagocytosis. This was due to the presence of superoxide dismutase-like activity since O
2
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generated by the xanthine-xanthine oxidase system was also inhibited by this fraction. The cationic protein fractions III and IV from the Sephadex G-75 column were further subfractionated. Although the O
2
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-enhancing activity was eluted in the same fractions as chymotrypsin activity, there was no quantitative correlation between the amount of O
2
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generation and chymotrypsin activity. Moreover, commercial chymotrypsin did not enhance O
2
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generation. Electrophoretic analysis of the isolated protein fractions suggests that O
2
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generation enhancing protein (SGEP) is different from lysozyme or chymotrypsin and probably represents previously undescribed protein. |
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