8-oxo-7,8-dihydroguanosine triphosphate(8-oxoGTP) down-regulates respiratory burst of neutrophils by antagonizing GTP toward Rac, a small GTP binding protein.

8-oxo-7,8-dihydroguanosine triphosphate (8-oxoGTP) has been regarded simply as a oxidative mutagenic byproduct. The results obtained in this study imply that it may act as a down-regulator of respiratory burst of neutrophils. Human neutrophils treated with PMA produced superoxides and at the same time, the cytosol of these cells was intensely immunostained by 8-oxo-7,8-dihydroguanosine(8-oxoG) antibody, indicating that 8-oxoG-containing chemical species including 8-oxoGTP are produced. Human neutrophil lysates treated with PMA also produced superoxides, which was stimulated by GTPgammaS but inhibited by 8-oxoGTPgammaS. Moreover, 8-oxoGTPgammaS suppressed the stimulatory action of GTPgammaS. Likewise, GTPgammaS stimulated Rac activity in neutrophil lysates but 8-oxoGTPgammaS and GDP inhibited it. The inhibitory effect of GDP was one tenth that of 8-oxoGTPgammaS. Here again, 8-oxoGTPgammaS also suppressed the stimulatory action of GTPgammaS on Rac activity. These results imply the possibility that 8-oxoGTP is formed during respiratory burst of neutrophils and limits neutrophil production of superoxides by antagonizing GTP toward Rac.