Effects of NO and cGMP on TNF-α-induced ceramide generation. Cells were treated with TNF-α (50 ng/ml)/CHX (1 μg/ml) (control) with or without PDMP (10 μM), fumonisin B1 (Fum, 3 μM), D609 (25 μg/ml), SNAP (300 μM), 8 Br-cGMP (3 mM), and ODQ (1 μM) as indicated in the key. Cell aliquots were collected and lysed, and ceramide content was measured by TLC as described in Materials and Methods. Ceramide concentrations are expressed as a percentage of those measured in cell samples run in parallel but not treated with TNF-α/CHX (140.4 ± 8.2 pmol/mg proteins, with no significant change over time) (n = 5).