Figure 4. Role of TNF-α in the regulation of the recycling pathway.

(A) The role of TNF-α, which is known to regulate intracellular GSH levels, was examined using palmitate labelling experiments in cells treated with 1 nM TNF-α and D-e-C₆-cer in combination for 2 h in the absence (lanes 5) or presence (lane 6) of NAC, or presence of GSH (lane 7). Lanes 2–4 contain samples treated with ceramide, GSH or NAC alone respectively. Lane 1 contains untreated controls. (B) The effects of TNF-α in the presence of exogenous ceramide on the generation of ROS were measured using DCFH-DA. Results are means±S.D. * and #, P<0.05 compared with untreated or ceramide (alone)-treated controls respectively.