Release of reactive oxygen intermediates by dengue virus-induced macrophage cytotoxin.

Dengue type 2 virus (DV) induces a subpopulation of T lymphocytes of mice to produce a cytokine, cytotoxic factor (mCF), which induces H-2A positive macrophages to produce macrophage cytotoxin (CF2). The present study was undertaken to investigate the mechanism of cytotoxicity of CF2. It was observed that CF2 induced production of superoxide anion (O2-) and hydrogen peroxide (H2O2) by the spleen cells of mice in vitro and in vivo. The maximum production of O2- (260 +/- 10 nM/4 x 10(6) cells) was at 45 minutes while that of H2O2 was at 90 minutes after inoculation of CF2. Pretreatment of mice or spleen cells with anti-CF2-antisera inhibited O2- and H2O2 production in a dose-dependent manner. Superoxide dismutase (SOD) inhibited O2- production and cytotoxicity while H2O2 production was increased by increasing SOD concentration in the culture. This indicated that O2- production is necessary for the cytotoxic activity of CF2. Pretreatment of the cells with Ca2+ channel blocking drugs, nifedipine or verapamil, inhibited CF2-induced O2- and H2O2 production in a dose-dependent manner. We have shown earlier that the cytotoxic activity of CF2 is known to be Ca2+ dependent and CF2-induced production of nitrite and the cytotoxicity is inhibited by NG-monomethyl-L-arginine. Thus, it is suggested that O2- and nitrite are necessary for cell killing by CF2 in a Ca(2+)-dependent manner and the killing may possibly be by generation of peroxynitrite.