DDC-induced ROS formation is associated with a depletion of energy metabolism and antioxidant enzymes and is regulated by GAPDH. (A) Hepatocytes from C3H and C57BL mice were left untreated (−) or treated with either 0.1% DMSO vehicle (0) or the indicated concentrations of DDC for 48 h. Equal protein amounts (NP-40 lysates) were analyzed for expression of the indicated proteins. Samples from each strain were analyzed on separate gels. PDIA4 levels were unaltered (loading control). (B) C57BL hepatocytes were transfected with Control or GAPDH siRNA for 24 h and were then cultured for an additional 24 h in the presence of 0.025% DMSO vehicle (0) or 100 µM DDC or were left untreated (−). The NP-40 cell lysates were analyzed for the expression of the various proteins indicated. (C) Overexpression of Flag-tagged mouse GAPDH in isolated hepatocytes. NP-40 lysates were analyzed for expression of Flag-tagged GAPDH and total GAPDH. The Coomassie stain is included as a loading control. (D) Flag-GAPDH expression in C57BL hepatocytes, as determined by immunostaining with a mouse anti-Flag antibody (representing overexpressed GAPDH; green) and a rabbit anti-GAPDH antibody (representing total GAPDH; red). (E) C57BL hepatocytes were mock transfected (Control) or transfected with GAPDH siRNA or Flag-GAPDH mouse cDNA for 24 h and were then treated with 100 µM DDC for an additional 24 h. Representative images of ROS signal (green) with DAPI nuclear counterstain (blue) are shown. ROS levels (quantified as described in Materials and methods) exhibited a 2.2-fold increase after GAPDH knockdown and a 10-fold decrease after GAPDH overexpression relative to control. Bars, 20 µm.