title: 5-HT(2A) receptors stimulate mitogen-activated protein kinase via H(2)O(2) generation in rat renal mesangial cells.
abstract: Serotonin (5-HT) stimulates mitogenesis in rat renal mesangial cells through a G protein-coupled 5-HT(2A) receptor. We tested the hypothesis that oxidants might be involved in the signal transduction pathway linking the receptor to extracellular signal-regulated protein kinase (ERK). 5-HT rapidly increased the activity and phosphorylation of ERK. These effects were blocked by the 5-HT(2A) receptor antagonist ketanserin. The peak effect was noted at 5-10 min, and half-maximal stimulation was achieved at 10-30 nM 5-HT. Chemical inhibitor and activator studies supported the involvement of phospholipase C, protein kinase C (PKC), and reactive oxygen species (ROS, i.e., H(2)O(2) and superoxide) generated by an NAD(P)H oxidase-like enzyme in the ERK activation cascade. Mapping studies supported a location for the NAD(P)H oxidase enzyme and the ROS downstream from PKC. Our studies are most consistent with an ERK activation pathway as follows: 5-HT(2A) receptor --> G(q) protein --> phospholipase C --> diacylglycerol --> classical PKC --> NAD(P)H oxidase --> superoxide --> superoxide dismutase --> H(2)O(2) --> mitogen-activated extracellular signal-regulated kinase --> ERK. These studies demonstrate a role for the 5-HT(2A) receptor in rapid, potent, and efficacious activation of ERK in rat renal mesangial cells. They support a role for oxidants in conveying the stimulatory signal from 5-HT, because 1) chemical antioxidants attenuate the 5-HT signal, 2) oxidants and 5-HT selectively activate ERK to a similar degree, 3) 5-HT produces superoxide and H(2)O(2) in these cells, and 4) a specific enzyme [NAD(P)H oxidase] has been implicated as the source of the ROS, which react selectively downstream of classical PKC.
authors.affiliation: Nephrology Division, Department of Internal Medicine, Medical University of South Carolina, and Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425, USA. greeneel@musc.edu
authors.forename: E L
authors.initials: EL
authors.lastname: Greene
authors.forename: O
authors.initials: O
authors.lastname: Houghton
authors.forename: G
authors.initials: G
authors.lastname: Collinsworth
authors.forename: M N
authors.initials: MN
authors.lastname: Garnovskaya
authors.forename: T
authors.initials: T
authors.lastname: Nagai
authors.forename: T
authors.initials: T
authors.lastname: Sajjad
authors.forename: V
authors.initials: V
authors.lastname: Bheemanathini
authors.forename: J S
authors.initials: JS
authors.lastname: Grewal
authors.forename: R V
authors.initials: RV
authors.lastname: Paul
authors.forename: J R
authors.initials: JR
authors.lastname: Raymond
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000502:physiology; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000502:physiology; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D017382:Reactive Oxygen Species; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D010566:Virulence Factors, Bordetella; D012701:Serotonin; D006861:Hydrogen Peroxide; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins