Restoration of TNF-alpha-induced ceramide generation and apoptosis in resistant human leukemia KG1a cells by the P-glycoprotein blocker PSC833

FASEB J. 1998 Jan;12(1):101-9. doi: 10.1096/fasebj.12.1.101.

Abstract

Tumor necrosis factor (TNF-alpha) is a cytokine with antitumor activity against several cellular models. TNF-alpha-induced apoptosis seems to be mediated by a signaling pathway termed 'sphingomyelin-ceramide' pathway, which consists of the hydrolysis of sphingomyelin and the production of its breakdown product ceramide. Our study shows that KG1a cells, which are inherently resistant to TNF-alpha and do not produce ceramide upon cytokine stimulation, can be sensitized by the use of the P-glycoprotein inhibitor PSC833. Coincubation with 1 microM of this cyclosporin derivative restored the apoptotic potential of 10 ng/ml TNF-alpha. This effect was associated with the restoration of ceramide generation (315%) and activation of neutral, but not acid sphingomyelinase activity (143%). Furthermore, we demonstrate that treatment of KG1a cells with 1 microM PSC833 led to a threefold increase in inner plasma membrane sphingomyelin content and basal neutral sphingomyelinase activity. These results support the hypothesis whereby resistance to TNF-alpha-mediated apoptosis of certain leukemic cells is linked to the disposability of the sphingomyelin pool. These data also suggest a role for P-glycoprotein in sphingomyelin transverse plasma membrane asymmetry.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / antagonists & inhibitors*
  • Apoptosis / drug effects*
  • Cell Survival / drug effects
  • Cyclosporins / pharmacology*
  • Humans
  • Leukemia, Myeloid / enzymology
  • Leukemia, Myeloid / metabolism*
  • Leukemia, Myeloid / pathology
  • Sphingomyelin Phosphodiesterase / metabolism
  • Sphingomyelins / biosynthesis*
  • Tumor Cells, Cultured
  • Tumor Necrosis Factor-alpha / pharmacology*

Substances

  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Cyclosporins
  • Sphingomyelins
  • Tumor Necrosis Factor-alpha
  • Sphingomyelin Phosphodiesterase
  • valspodar