Phosphodiesterase inhibitors control A172 human glioblastoma cell death through cAMP-mediated activation of protein kinase A and Epac1/Rap1 pathways

Life Sci. 2012 Feb 27;90(9-10):373-80. doi: 10.1016/j.lfs.2011.12.010. Epub 2011 Dec 28.

Abstract

Aims: We investigated whether cAMP-mediated protein kinase A(PKA) and Epac1/Rap1 pathways differentially affect brain tumor cell death using 4-(3-cyclopentyloxy-4-methoxyphenyl)-2-pyrrolidone(rolipram), specific phosphodiesterase type IV(PDE IV) inhibitor.

Main methods: A172 and U87MG human glioblastoma cells were used. Percentage of cell survival was determined by MTT assay. PKA and Epac1/Rap1 activation was determined by western blotting and pull-down assay, respectively. Cell cycle and hypodiploid cell formation were assessed by flow cytometry analysis.

Key findings: Non-specific PDE inhibitors, isobutylmethylxanthine(IBMX) and theophylline reduce survival percentage of A172 and U87MG cells. The expression of PDE4A and PDE4B was detected in A172 and U87MG cells. Rolipram-treated A172 or U87MG cell survival was lower in the presence of forskolin, adenylate cyclase activator, than that in its absence. Co-treatment with rolipram and forskolin also enhanced CREB phosphorylation on serine 133 that was inhibited by H-89, PKA inhibitor and cAMP-responsive guanine nucleotide exchange factor 1(Epac1), a Rap GDP exchange factor-mediated Rap1 activity in A172 cells. When A172 cells were treated with cell-permeable dibutyryl-cAMP(dbcAMP), PKA activator or 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate(CPT), Epac1 activator, basal level of cell death was increased and cell cycle was arrested at the phase of G2/M. Rolipram-induced A172 cell death was also increased by the co-treatment with dbcAMP or CPT, but it was inhibited by the pre-treatment with H-89.

Significance: These findings demonstrate that PKA and Epac1/Rap1 pathways could cooperatively play a role in rolipram-induced brain tumor cell death. It suggests that rolipram might regulate glioblastoma cell density through dual pathways of PKA- and Epac1/Rap1-mediated cell death and cell cycle arrest.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-3-isobutylxanthine / pharmacology
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology*
  • Apoptosis / drug effects*
  • Brain Neoplasms / enzymology*
  • Cell Cycle Checkpoints / drug effects
  • Cell Line, Tumor
  • Colforsin / pharmacology
  • Cyclic AMP / metabolism
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Cyclic Nucleotide Phosphodiesterases, Type 4 / analysis
  • Cyclic Nucleotide Phosphodiesterases, Type 4 / metabolism
  • Dose-Response Relationship, Drug
  • Glioblastoma / enzymology*
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Humans
  • Isoquinolines / pharmacology
  • Phosphodiesterase Inhibitors / pharmacology*
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology
  • Rolipram / pharmacology*
  • Signal Transduction / drug effects
  • Sulfonamides / pharmacology
  • Telomere-Binding Proteins / metabolism*
  • Theophylline / pharmacology

Substances

  • Guanine Nucleotide Exchange Factors
  • Isoquinolines
  • Phosphodiesterase Inhibitors
  • Protein Kinase Inhibitors
  • RAPGEF3 protein, human
  • Sulfonamides
  • TERF2IP protein, human
  • Telomere-Binding Proteins
  • Colforsin
  • Theophylline
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • Cyclic Nucleotide Phosphodiesterases, Type 4
  • Rolipram
  • N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide
  • 1-Methyl-3-isobutylxanthine