Cycloserine and threo-dihydrosphingosine inhibit TNF-α-induced cytotoxicity: evidence for the importance of de novo ceramide synthesis in TNF-α signaling

AbstractMeasuring the cell death induced by tumor necrosis factor (TNF-α) in L929 cells, we discovered for the first time that l-cycloserine, an established inhibitor of serine palmitoyltransferase, as well as dl-threo-dihydrosphingosine (threo-DHS, threo-sphinganine) significantly protected against TNF-α-induced cytotoxicity. Under the same conditions sphingosine and dl-erythro-dihydrosphingosine (erythro-DHS) did not change TNF-α-induced cytotoxicity, thus underlining the specificity of threo-DHS. In serine-labeled cells, newly (de novo) synthetized labeled ceramide was significantly diminished by threo-DHS alone or together with TNF-α, which makes the (dihydro) ceramide synthase the likely target of threo-DHS. These results suggest the decisive role of ceramide de novo synthesis in TNF signaling