title: p38 MAPK is an early determinant of promiscuous Smad2/3 signaling in the aortas of fibrillin-1 (Fbn1)-null mice.
abstract: Excessive transforming growth factor-beta (TGF-beta) signaling characterizes the progression of aortic aneurysm in mouse models of Marfan syndrome, a systemic disorder of the connective tissue that is caused by mutations in the gene encoding the extracellular matrix protein fibrillin-1. Fibrillin-1 mutations are believed to promote abnormal Smad2/3 signaling by impairing the sequestration of latent TGF-beta complexes into the extracellular matrix. Here we report that promiscuous Smad2/3 signaling is the cell-autonomous phenotype of primary cultures of vascular smooth muscle cells (VSMC) explanted from the thoracic aortas of Fbn1 mutant mice with either neonatal onset or progressively severe aortic aneurysm. This cellular phenotype was characterized in VSMC isolated from Fbn1-null (mgN/mgN) mice, which recapitulate the most severe form of Marfan syndrome. We found that loss of fibrillin-1 deposition promotes the production of intracellular reactive oxygen species and abnormal accumulation of phosphorylated TGF-beta-activated kinase 1 and p38 MAPK, in addition to increasing the levels of endogenous phospho-Smad2. We showed that improper Smad2/3 signaling in Fbn1-null VSMC is in part stimulated by phospho-p38 MAPK, which is in turn activated in response to signals other than those mediated by the kinase activity of the ALK5 receptor. Consistent with these cell culture data, in vivo analyses documented that phospho-p38 MAPK accumulates earlier than phospho-Smad2 in the aortic wall of mgN/mgN mice and that systemic inhibition of phospho-p38 MAPK activity lowers the levels of phospho-Smad2 in this tissue. Collectively, these findings indicate that improper activation of p38 MAPK is a precursor of constitutive Smad2/3 signaling in the aortic wall of a mouse model of neonatal lethal Marfan syndrome.
authors.affiliation: Department of Pharmacology and Systems Therapeutics and the Cardiovascular Institute, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Luca
authors.initials: L
authors.lastname: Carta
authors.forename: Silvia
authors.initials: S
authors.lastname: Smaldone
authors.forename: Lior
authors.initials: L
authors.lastname: Zilberberg
authors.forename: David
authors.initials: D
authors.lastname: Loch
authors.forename: Harry C
authors.initials: HC
authors.lastname: Dietz
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Rifkin
authors.forename: Francesco
authors.initials: F
authors.lastname: Ramirez
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D000071838:Fibrillin-1; D000071837:Fibrillins; D018507:Gene Expression Regulation, Developmental; D015151:Immunoblotting; D007124:Immunoenzyme Techniques; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015398:Signal Transduction; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000099151:MAP Kinase Kinase Kinase 7; D054392:Adipokines
chemical_list: D000071838:Fibrillin-1; D000071837:Fibrillins; D020930:MAP Kinase Kinase Kinases; D008840:Microfilament Proteins; D017346:Protein Serine-Threonine Kinases; D017382:Reactive Oxygen Species; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta; D051899:Smad2 Protein; D051900:Smad3 Protein; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7; C000605724:Fbn1 protein, mouse; D054392:Adipokines; C497783:Smad2 protein, mouse; C497791:Smad3 protein, mouse; C000625842:Tgfbr1 protein, mouse