G. Vanechtendeckert et al., TURNOVER OF ENDOGENOUS CERAMIDE IN CULTURED NORMAL AND FARBER-FIBROBLASTS, Journal of lipid research, 38(12), 1997, pp. 2569-2579
De novo synthesis and turnover of endogenous ceramide in cultured skin
fibroblasts from patients affected with Farber lipogranulomatosis wer
e studied by biosynthetical labeling of cellular sphingolipids with [C
-14]serine. The cellular uptake of [C-14]serine and incorporation into
de novo synthesized ceramide was similar in normal and Farber fibrobl
asts, with a half life of newly synthesized ceramide of 2.7 h in norma
l and diseased cells. Newly synthesized ceramide was found to be chann
eled directly into biosynthesis of complex sphingolipids rather than c
ontributing to the pool of accumulated ceramide in Farber fibroblasts.
The degradation of ceramide generated by the catabolism of complex sp
hingolipids in Farber cells was greatly delayed compared with control
fibroblasts, with differences in the amount of radiolabeled cellular c
eramide becoming evident after 6 h chase time. Individual Farber cell
lines differed from each other in the amount of accumulated ceramide;
however, no correlation was found between ceramide accumulation and re
sidual acid ceramidase activity as determined in vitro. In addition, t
he amount of radiolabeled sphingomyelin was significantly increased in
Farber fibroblasts suggesting a delayed degradation of this compound
in this ceramide storage disorder. We propose biosynthetical labeling
of endogenous ceramide with [C-14]serine, in addition to other establi
shed methods, as a highly sensitive and reliable method for the diagno
sis of Farber disease, allowing semiquantitative measurement of cerami
de accumulation in cultured skin fibroblasts of patients affected with
Farber lipogranulomatosis.