title: Endogenous brain-derived neurotrophic factor and neurotrophin-3 antagonistically regulate survival of axotomized corticospinal neurons in vivo.
abstract: Neuronal growth factors regulate the survival of neurons by their survival and death-promoting activity on distinct populations of neurons. The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) promote neuronal survival via tyrosine kinase (Trk) receptors, whereas NGF and BDNF can also induce apoptosis in developing neurons through p75(NTR) receptors in the absence of their respective Trk receptors. Using mutant mice and inactivation of neurotrophins and their receptors with antibodies in rats, we show that endogenous NT-3 induces death of adult BDNF-dependent, axotomized corticospinal neurons (CSNs). When NT-3 is neutralized, the neurons survive even without BDNF, suggesting complete antagonism. Whereas virtually all unlesioned and axotomized CSNs express both trkB and trkC mRNA, p75 is barely detectable in unlesioned CSNs but strongly upregulated in axotomized CSNs by day 3 after lesion, the time point when cell death occurs. Blocking either cortical TrkC or p75(NTR) receptors alone prevents death, indicating that the opposing actions of NT-3 and BDNF require their respective Trk receptors, but induction of death depends on p75(NTR) cosignaling. The results show that neuronal survival can be regulated antagonistically by neurotrophins and that neurotrophins can induce neuronal death in the adult mammalian CNS. We further present evidence that signaling of tyrosine kinase receptors of the trk family can be crucially involved in the promotion of neuronal death in vivo.
authors.affiliation: University of Saarland, Department of Anatomy, 66421 Homburg/Saar, Germany. k.giehl@rz.uni-sb.de
authors.forename: K M
authors.initials: KM
authors.lastname: Giehl
authors.forename: S
authors.initials: S
authors.lastname: Röhrig
authors.forename: H
authors.initials: H
authors.lastname: Bonatz
authors.forename: M
authors.initials: M
authors.lastname: Gutjahr
authors.forename: B
authors.initials: B
authors.lastname: Leiner
authors.forename: I
authors.initials: I
authors.lastname: Bartke
authors.forename: Q
authors.initials: Q
authors.lastname: Yan
authors.forename: L F
authors.initials: LF
authors.lastname: Reichardt
authors.forename: C
authors.initials: C
authors.lastname: Backus
authors.forename: A A
authors.initials: AA
authors.lastname: Welcher
authors.forename: K
authors.initials: K
authors.lastname: Dethleffsen
authors.forename: P
authors.initials: P
authors.lastname: Mestres
authors.forename: M
authors.initials: M
authors.lastname: Meyer
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000008:administration & dosage; D019771:Axotomy; D019208:Brain-Derived Neurotrophic Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D016923:Cell Death / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004336:Drug Antagonism; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006579:Heterozygote; D007150:Immunohistochemistry; D007263:Infusions, Parenteral; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D020933:Neurotrophin 3 / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D011712:Pyramidal Tracts / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor; D020812:Receptor, trkC / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D017475:Receptors, Nerve Growth Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D019138:Antibodies, Blocking; D019208:Brain-Derived Neurotrophic Factor; D020933:Neurotrophin 3; D012333:RNA, Messenger; D020800:Receptor, Nerve Growth Factor; D017475:Receptors, Nerve Growth Factor; D020812:Receptor, trkC