Paraquat treatment induces up-regulation of a caspase-dependent TDP-43 fragment. SH-SY5Y cells were treated overnight with 1 mM paraquat, 1 mM arginine, 100 μM SIN-1 (A), or 1 mM paraquat, 2 mM MPP+, 0.075 mM rotenone (B) and TDP-43 expression was determined by immunoblot. C: Cells were treated overnight with 1 mM paraquat with and without 50 μM Z-VAD-fmk (caspase inhibitor) and TDP-43 expression was determined by immunoblot. Middle panels represent a longer exposure to visualize the 35 kDa band. D-I: Cells were treated overnight with paraquat in the absence (F-G) and presence (H-I) of Z-VAD-fmk and examined for TDP-43-positive SGs. Green = TDP-43, Blue = DAPI. Arrows indicate TDP-43-positive SGs ≤ μm. Arrowheads indicate TDP-43-positive SGs ≥ 1 μm. Bar = 10 μm. Representative images from two-three separate experiments.