Serotonin 5-HT2A receptor induces TGF-beta1 expression in mesangial cells via ERK: proliferative and fibrotic signals.
We examined the links between fibrotic and proliferative pathways for the 5-HT2A receptor in rat mesangial cells. Serotonin (5-hydroxytryptamine, 5-HT) induced transforming growth factor-beta1 (TGF-beta1) mRNA in a concentration-dependent (peak at 30 nM 5-HT) and time-dependent fashion. For 10 nM 5-HT, the effect was noticeable at 1 h and maximal by 6 h. Inhibition of 1) protein kinase C (PKC), 2) mitogen- and extracellular signal-regulated kinase kinase (MEK1) with 2'-amino-3'-methoxyflavone (PD-90859), and 3) extracellular signal-regulated kinase (ERK) with apigenin attenuated this effect. The effect was blocked by antioxidants, N-acetyl-L-cysteine (NAC) and alpha-lipoic acid, and mimicked by direct application of H2O2. TGF-beta1 mRNA induction was also blocked by diphenyleneiodonium and 4-(2-aminoethyl)-benzenesulfonyl fluoride, which inhibit NAD(P)H oxidase, a source of oxidants. 5-HT increased the amount of TGF-beta1 protein, validating the mRNA studies and demonstrating that 5-HT potently activates ERK and induces TGF-beta1 mRNA and protein in mesangial cells. Mapping studies strongly supported relative positions of the components of the signaling cascade as follow: 5-HT2A receptor --> PKC --> NAD(P)H oxidase/reactive oxygen species --> MEK --> ERK --> TGF-beta1 mRNA. These studies demonstrate that mitogenic signaling components (PKC, MEK, and oxidants) are directly linked to the regulation of TGF-beta1, a key mediator of fibrosis. Thus a single stimulus can direct both proliferative and fibrotic signals in renal mesangial cells.
Grewal
J S
JS
Department of Medicine, Nephrology Division, Medical University of South Carolina and the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425, USA.
Mukhin
Y V
YV
Garnovskaya
M N
MN
Raymond
J R
JR
Greene
E L
EL
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D005355:Fibrosis; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000502:physiology; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D048369:MAP Kinase Kinase 1; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases; D019255:NADPH Oxidases / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000502:physiology; D011985:Receptors, Serotonin / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D011985:Receptors, Serotonin; D016212:Transforming Growth Factor beta; D010566:Virulence Factors, Bordetella; D019255:NADPH Oxidases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D019204:GTP-Binding Proteins