Exp Mol Med.
1999 Sep;31(3):142-150.
Effect of ceramide on apoptosis and phospholipase D activity in FRTL-5 thyroid
cells
- Affiliations
-
- 1Department of General Surgery, College of Medicine, Sung Kyun Kwan University,
Seoul, Korea.
Abstract
-
Ceramide, a product of sphingomyelin hydrolysis, is now recognized as an
intracellular lipid messenger, which mediates the effects of extracellular
agents on cellular growth, differentiation and apoptosis. Recently, ceramide has
been implicated in the regulation of phospholipase D (PLD). In this study, we
examined the effects of ceramide on the activity and mRNA level of PLD during
apoptotic process in FRTL-5 thyroid cells. C2-ceramide (N-acetyl sphingosine)
induced apoptosis in FRTL-5 thyroid cells. Fluorescent staining showed that
ceramide induced the typical features of apoptosis including condensed or
fragmented nuclei. DNA fragmentation was also observed by agarose gel
electrophoresis. Flow cytometric cell cycle analysis showed more clearly that
ceramide induced apoptotic cell death in FRTL-5 thyroid cells. The treatment of
FRTL-5 thyroid cells with thyroid-stimulating hormone (TSH) resulted in an
increased PLD activity in a dose- and time-dependent manner. However, the
TSH-induced increase in PLD activity was down-regulated within 2 h after
ceramide treatment. Furthermore, the levels of PLD mRNA were found to be
decreased throughout apoptotic process as inferred by reverse
transcription-polymerase chain reaction. However, the decreases in PLD mRNA
levels were not correlated with those in PLD activities after ceramide
treatment. Taken together, these data suggest that ceramide inhibits the PLD
activity in an early apoptotic phase and down-regulation of the levels of PLD
mRNA may be implicated in apoptotic process in FRTL-5 thyroid cells.