Fig. 2.

TcdB induces ROS production. (A) HeLa cells treated with the indicated concentrations of TcdA, TcdB, or TcdB-D270N or with 1 mM H₂O₂ for 16 h were analyzed for ROS production in a plate-based assay. Relative ROS production is a measure of ROS compared with a mock- treated control. (B) HeLa cells (shown in A) were assessed for cytotoxicity of each treatment and normalized to a mock-treated control. (C) HeLa cells treated with 10 nM toxin were assayed for ROS production and LDH release starting at 1.5 h postintoxication. ROS production and LDH release are relative to mock-treated controls. Error bars represent SE. P values were calculated by the Student t test and are relative to mock-treated controls.