title: Essential role of Rac1/NADPH oxidase in nerve growth factor induction of TRPV1 expression.
abstract: Nerve growth factor (NGF) regulates the nociceptive properties of a subset of small diameter sensory neurons by increasing the expression of the heat-sensing transient receptor potential (TRP) channel, TRPV1. This action involves activation of the tyrosine kinase receptor (Trk) A/p38 MAPK pathway. Recent studies indicate that activation of TrkA promotes superoxide generation via NADPH oxidase. In this study, we determined whether the NADPH oxidase pathway is involved in NGF-stimulated TRPV1 expression using a rat pheochromocytoma 12 line and rat dorsal root ganglion neurons. Treatment of these cells with NGF (100 ng/mL) increased TRPV1 protein expression (approx. twofold) but not mRNA. This increase was mimicked by H(2)O(2) and attenuated by catalase and inhibitors of NADPH oxidase. NGF stimulated NADPH oxidase activity, while 24 h exposure further increased expression of the Rac1 and gp91(phox) subunits of the holoenzyme. Inhibition of NADPH oxidase by transient transfection of a dominant negative Rac1 mutant (RacN17) plasmid blocked NGF-stimulated TRPV1 protein expression, while expression of a constitutively active Rac1 increased basal and NGF-stimulated TRPV1 levels. Inhibition of NADPH oxidase activity also attenuated NGF-dependent p38 MAPK activation. We conclude that the Rac1/NADPH oxidase pathway regulates p38 activation and TRPV1 expression which aids in the maintenance of peripheral neuron integrity and pain perception.
authors.affiliation: Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois 62794-9629, USA.
authors.forename: Preeti
authors.initials: P
authors.lastname: Puntambekar
authors.forename: Debashree
authors.initials: D
authors.lastname: Mukherjea
authors.forename: Sarvesh
authors.initials: S
authors.lastname: Jajoo
authors.forename: Vickram
authors.initials: V
authors.lastname: Ramkumar
mesh_terms: D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000502:physiology; D005452:Fluoresceins; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D007150:Immunohistochemistry; D019255:NADPH Oxidases / Q000502:physiology*; D009414:Nerve Growth Factors / Q000096:biosynthesis*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D016716:PC12 Cells; D012333:RNA, Messenger / Q000096:biosynthesis; D011869:Radioligand Assay; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050916:TRPV Cation Channels / Q000096:biosynthesis*; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000502:physiology*
chemical_list: D005452:Fluoresceins; D009414:Nerve Growth Factors; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; C029569:diacetyldichlorofluorescein; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D019255:NADPH Oxidases; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein