Effects of sodium nitrite on natural killer cells isolated from human peripheral blood

The effect of different concentrations (0, 0.1, 0.2, 0.4, and 0.8 mg/ml) of sodium nitrite on the anti-tumor activity of natural killer (NK) cells isolated from human peripheral blood was examined. Sodium nitrite induced significant inhibition (25.3–66.6%) of NK cell activity against WEHI-164 cells. This reduction in NK cell cytotoxicity was found to be partially due to inhibition of NK cell production of interferon-γ (25.7–92.8%) and tumor necrosis factor-α (26.6–76.6%). In addition, exposure to sodium nitrite resulted in a significant decrease (17.5–81.1%) in proliferation of control and interleukin-2-stimulated NK cells. Furthermore, the release of granzyme A and N-acetyl-β-D-glucosaminidase by NK cells was also decreased by 21.7–72.2% and 33.5–81.2%, respectively. Therefore, sodium nitrite is of environmental concern in view of its inhibitory effects on NK cell activity that might contribute to tumor promotion in vivo.