title: Neurotrophins regulate proliferation and survival of two microglial cell lines in vitro.
abstract: Microglia are thought to play a key role in the development and regeneration of the central nervous system although the mechanisms regulating their presence and activity are not fully understood. Substantial evidence suggests that members of the neurotrophin family such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 and -4 (NT-3/4) have a dramatic effect on both neurons and perineuronal cells. This study employed two murine microglial lines, BV-2 and N9, to examine the action of these neurotrophins on the mitotic activity and survival of microglia in vitro. Neurotrophins were incorporated into the media at the time of plating and cell number and levels of mitochondrial dehydrogenase activity (MTT) were determined at various time points in vitro. NGF increased cell number and MTT levels of both cell lines in a dose-dependent manner. BV-2 was more sensitive to NGF than N9. Similar responses were elicited by BDNF, although the sensitivity of each cell line was different than that found for NGF. NT-3 and NT-4 had no effect on cell proliferation. However, NT-4 had an effect on the survival of BV-2 and N9 cells. The response of these cells to neurotrophins was blocked by K252a, a tyrosine kinase inhibitor, suggesting that actions of neurotrophins were mediated by high-affinity tyrosine kinase receptors (Trk). Immunolocalization studies revealed positive Trk (pan) reactivity in the above cell lines and in primary microglia, but an absence of the low-affinity p75 neurotrophin receptor. Western blot analysis supported the above observations. These studies suggest that in addition to their neurotrophic actions, NGF and BDNF may also regulate microglial dynamics, thereby influencing the surrounding milieu during neuronal regeneration.
authors.affiliation: Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Louisville, KY 40292, USA.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Zhang
authors.forename: Changiz
authors.initials: C
authors.lastname: Geula
authors.forename: Chengliang
authors.initials: C
authors.lastname: Lu
authors.forename: Henry
authors.initials: H
authors.lastname: Koziel
authors.forename: Linda M
authors.initials: LM
authors.lastname: Hatcher
authors.forename: Fred J
authors.initials: FJ
authors.lastname: Roisen
mesh_terms: D000818:Animals; D015703:Antigens, CD; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D030161:Avian Proteins; D051926:Basigin; D001798:Blood Proteins; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D051379:Mice; D017628:Microglia / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D020932:Nerve Growth Factor / Q000494:pharmacology; D009414:Nerve Growth Factors / Q000494:pharmacology*; D020933:Neurotrophin 3 / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D020800:Receptor, Nerve Growth Factor; D020917:Receptor, trkA / Q000096:biosynthesis; D020813:Receptor, trkB / Q000096:biosynthesis; D017475:Receptors, Nerve Growth Factor / Q000096:biosynthesis
chemical_list: D015703:Antigens, CD; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D030161:Avian Proteins; D001798:Blood Proteins; D019208:Brain-Derived Neurotrophic Factor; C102624:Bsg protein, Gallus gallus; C497887:Bsg protein, mouse; C079432:Bsg protein, rat; D008562:Membrane Glycoproteins; D009414:Nerve Growth Factors; D020933:Neurotrophin 3; D020800:Receptor, Nerve Growth Factor; D017475:Receptors, Nerve Growth Factor; D051926:Basigin; D020932:Nerve Growth Factor; D011505:Protein-Tyrosine Kinases; D020917:Receptor, trkA; D020813:Receptor, trkB; C073922:neurotrophin 4