Penta-acetyl geniposide induce apoptosis in C6 glioma cells by modulating the activation of neutral sphingomyelinase-induced p75 nerve growth factor receptor and protein kinase Cdelta pathway

Mol Pharmacol. 2006 Sep;70(3):997-1004. doi: 10.1124/mol.106.022178. Epub 2006 Jun 8.

Abstract

In our previous studies, we demonstrated the apoptotic cascades protein kinase C (PKC) delta/c-Jun NH2-terminal kinase (JNK)/Fas/caspases induced by penta-acetyl geniposide [(Ac)5GP]. However, the upstream signals mediating PKCdelta activation have not yet been clarified. Ceramide, mainly generated from the degradation of sphingomyelin, was hypothesized upstream above PKCdelta in (Ac)5GP-transduced apoptosis. Furthermore, nerve growth factor (NGF)/p75 is supposed to be involved because(Ac)5GP-induced apoptosis was demonstrated previously in glioma cells. In the present study, (Ac)5GP was shown to activate neutral sphingomyelinase (N-SMase) immediately, with its maximum at 15 min. The NGF and p75 enhanced by (Ac)5GP was inhibited when added with GW4869, the N-SMase inhibitor, indicating NGF/p75 as the downstream signals of N-SMase/ceramide. To investigate whether N-SMase is involved in (Ac)5GP-transduced apoptotic pathway, cells were treated with (Ac)5GP added with or without GW4869. It showed that N-SMase inhibition blocked FasL expression and caspase 3 activation. Likewise, p75 antagonist peptide attenuated the FasL/caspase 3 expression. The PKCdelta translocation induced by (Ac)5GP was also eliminated by GW4869 and p75 antagonist peptide. To further confirm whether N-SMase activation plays an important role in (Ac)5GP-induced apoptosis, cells were analyzed the apoptotic rate by 4', 6-diamidino-2-phenylindole (DAPI) staining. (Ac)5GP-induced apoptosis was reduced 40 and 80% by 10 and 20 microM GW4869, respectively. It indicated that N-SMase activation is pivotal in (Ac)5GP-mediated apoptosis. In conclusion, SMase and NGF/p75 are suggested to mediate upstream above PKCdelta, thus transducing FasL/caspase cascades in (Ac)5GP-induced apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Caspase 3
  • Caspases / metabolism
  • Enzyme Activation / drug effects
  • Fas Ligand Protein
  • Glioma / pathology*
  • Iridoids / chemistry
  • Iridoids / pharmacology*
  • Membrane Glycoproteins / metabolism
  • Models, Biological
  • Nerve Growth Factor / pharmacology
  • Protein Kinase C-delta / metabolism*
  • Protein Transport / drug effects
  • Pyrans / chemistry
  • Pyrans / pharmacology*
  • Rats
  • Receptor, Nerve Growth Factor / metabolism*
  • Signal Transduction / drug effects
  • Sphingomyelin Phosphodiesterase / metabolism*
  • Tumor Cells, Cultured
  • Tumor Necrosis Factors / metabolism

Substances

  • Fas Ligand Protein
  • Faslg protein, rat
  • Iridoids
  • Membrane Glycoproteins
  • Pyrans
  • Receptor, Nerve Growth Factor
  • Tumor Necrosis Factors
  • geniposide
  • Nerve Growth Factor
  • Protein Kinase C-delta
  • Sphingomyelin Phosphodiesterase
  • Casp3 protein, rat
  • Caspase 3
  • Caspases