Cellular mechanisms associated with spontaneous and ciliary neurotrophic factor-cAMP-induced survival and axonal regeneration of adult retinal ganglion cells

J Neurosci. 2004 Dec 1;24(48):10806-15. doi: 10.1523/JNEUROSCI.3532-04.2004.

Abstract

We have shown previously that intraocular elevation of cAMP using the cAMP analog 8-(4-chlorophenylthio)-cAMP (CPT-cAMP) failed to promote axonal regeneration of axotomized adult retinal ganglion cells (RGCs) into peripheral nerve (PN) grafts but significantly potentiated ciliary neurotrophic factor (CNTF)-induced axonal regeneration. Using the PN graft model, we now examine the mechanisms underlying spontaneous and CNTF/CPT-cAMP-induced neuronal survival and axonal regrowth. We found that blockade of the cAMP pathway executor protein kinase A (PKA) using the cell-permeable inhibitor KT5720 did not affect spontaneous survival and axonal regeneration but essentially abolished the CNTF/CPT-cAMP-induced RGC survival and axonal regeneration. Blockade of CNTF signaling pathways such as phosphotidylinositol 3-kinase (PI3K)/akt by 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) by 2-(2-diamino-3-methoxyphenyl-4H-1-benzopyran-4-one (PD98059), or Janus kinase (JAK)/signal transducer and activators of transcription (STAT3) by tyrphostin AG490 also blocked the CNTF/CPT-cAMP-dependent survival and regeneration effects. PKA activity assay and Western blots showed that KT5720, LY294002, and PD98059 almost completely inhibited PKA, PI3K/akt, and MAPK/ERK signal transduction, respectively, whereas AG490 substantially decreased JAK/STAT3 signal transduction. Intraocular injection of CPT-cAMP resulted in a small PKA-dependent increase in CNTF receptor alpha mRNA expression in the retinas, an effect that may facilitate CNTF action on survival and axonal regeneration. Surprisingly, in the absence of CNTF/CPT-cAMP, LY294002, PD98059, and AG490, but not KT5720, significantly enhanced spontaneous RGC survival, suggesting differential roles of these pathways in RGC survival under different conditions. Our data suggest that CNTF/CPT-cAMP-induced RGC survival and axonal regeneration are a result of multiple pathway actions, with PKA as an essential component, but that these pathways can function in an antagonistic manner under different conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / drug effects
  • Axons / physiology
  • Carbazoles / pharmacology
  • Cell Survival / drug effects
  • Chromones / pharmacology
  • Ciliary Neurotrophic Factor / antagonists & inhibitors
  • Ciliary Neurotrophic Factor / pharmacology
  • Ciliary Neurotrophic Factor / physiology*
  • Cyclic AMP / analogs & derivatives*
  • Cyclic AMP / pharmacology
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / physiology*
  • DNA-Binding Proteins / antagonists & inhibitors
  • Flavonoids / pharmacology
  • Indoles / pharmacology
  • MAP Kinase Signaling System / drug effects
  • Morpholines / pharmacology
  • Nerve Regeneration* / drug effects
  • Optic Nerve Injuries / enzymology
  • Optic Nerve Injuries / physiopathology
  • Peroneal Nerve / transplantation
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • Proto-Oncogene Proteins / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt
  • Pyrroles / pharmacology
  • Rats
  • Rats, Inbred F344
  • Receptor, Ciliary Neurotrophic Factor / biosynthesis
  • Receptor, Ciliary Neurotrophic Factor / drug effects
  • Receptor, Ciliary Neurotrophic Factor / genetics
  • Retinal Ganglion Cells / drug effects
  • Retinal Ganglion Cells / physiology*
  • STAT3 Transcription Factor
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Thionucleotides / pharmacology
  • Trans-Activators / antagonists & inhibitors
  • Tyrphostins / pharmacology
  • Up-Regulation

Substances

  • Carbazoles
  • Chromones
  • Ciliary Neurotrophic Factor
  • DNA-Binding Proteins
  • Flavonoids
  • Indoles
  • Morpholines
  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins
  • Pyrroles
  • Receptor, Ciliary Neurotrophic Factor
  • STAT3 Transcription Factor
  • Stat3 protein, rat
  • Thionucleotides
  • Trans-Activators
  • Tyrphostins
  • alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • 8-((4-chlorophenyl)thio)cyclic-3',5'-AMP
  • KT 5720
  • Cyclic AMP
  • Protein-Tyrosine Kinases
  • Akt1 protein, rat
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Cyclic AMP-Dependent Protein Kinases
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one