Alteration of sphingolipid metabolism during 4‐HPR induced cell death in the ARPE‐19 human retinal pigment epithelial cell line

Abstract

A close association between the production of ceramide and the onset of programmed cell death has been well established. Ceramide generation can occur by de novo synthesis, sphingomyelin hydrolysis, or via acylation of sphingosine (salvage pathway). Ceramide acts as a second messenger in activating the apoptotic cascade. N‐(4‐hydroxyphenyl)‐retinamide (4‐HPR), a retinoic acid derivative, is known to induce cell death in many cell types including the human retinal pigment epithelial cell line ARPE‐19. Although the end result, cell death, is well established, the cellular and molecular mechanism(s) by which 4‐HPR causes cell death in ARPE‐19 are not well defined. Therefore, we investigated whether 4‐HPR can induce the production of ceramide in ARPE‐19 cells, which in turn can lead to apoptosis. Our results show, that 4‐HPR treatment of ARPE‐19 cells for 24‐h lead to the accumulation of dihydroceramide, as well as bioactive sphinganine (10‐ and 20‐fold increase, respectively). However, ceramide levels in 4‐HPR treated ARPE‐19 cells were similar to controls. It is possible that this alteration in sphingolipid metabolism, that is accumulation of sphinganine and dihydroceramide, caused by 4‐HPR contributes to cell death in ARPE‐19 cells. Support: Intramural Research Program of the National Eye Institute, National Institutes of Health.