title: TNF-α induces phenotypic modulation in cerebral vascular smooth muscle cells: implications for cerebral aneurysm pathology.
abstract: Little is known about vascular smooth muscle cell (SMC) phenotypic modulation in the cerebral circulation or pathogenesis of intracranial aneurysms. Tumor necrosis factor-alpha (TNF-α) has been associated with aneurysms, but potential mechanisms are unclear. Cultured rat cerebral SMCs overexpressing myocardin induced expression of key SMC contractile genes (SM-α-actin, SM-22α, smooth muscle myosin heavy chain), while dominant-negative cells suppressed expression. Tumor necrosis factor-alpha treatment inhibited this contractile phenotype and induced pro-inflammatory/matrix-remodeling genes (monocyte chemoattractant protein-1, matrix metalloproteinase-3, matrix metalloproteinase-9, vascular cell adhesion molecule-1, interleukin-1 beta). Tumor necrosis factor-alpha increased expression of KLF4, a known regulator of SMC differentiation. Kruppel-like transcription factor 4 (KLF4) small interfering RNA abrogated TNF-α activation of inflammatory genes and suppression of contractile genes. These mechanisms were confirmed in vivo after exposure of rat carotid arteries to TNF-α and early on in a model of cerebral aneurysm formation. Treatment with the synthesized TNF-α inhibitor 3,6-dithiothalidomide reversed pathologic vessel wall alterations after induced hypertension and hemodynamic stress. Chromatin immunoprecipitation assays in vivo and in vitro demonstrated that TNF-α promotes epigenetic changes through KLF4-dependent alterations in promoter regions of myocardin, SMCs, and inflammatory genes. In conclusion, TNF-α induces phenotypic modulation of cerebral SMCs through myocardin and KLF4-regulated pathways. These results demonstrate a novel role for TNF-α in promoting a pro-inflammatory/matrix-remodeling phenotype, which has important implications for the mechanisms behind intracranial aneurysm formation.
authors.affiliation: Joseph and Marie Field Cerebrovascular Research Laboratory, Division of Neurovascular & Endovascular Surgery, Department of Neurological Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors.forename: Muhammad S
authors.initials: MS
authors.lastname: Ali
authors.forename: Robert M
authors.initials: RM
authors.lastname: Starke
authors.forename: Pascal M
authors.initials: PM
authors.lastname: Jabbour
authors.forename: Stavropoula I
authors.initials: SI
authors.lastname: Tjoumakaris
authors.forename: L Fernando
authors.initials: LF
authors.lastname: Gonzalez
authors.forename: Robert H
authors.initials: RH
authors.lastname: Rosenwasser
authors.forename: Gary K
authors.initials: GK
authors.lastname: Owens
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Koch
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Greig
authors.forename: Aaron S
authors.initials: AS
authors.lastname: Dumont
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002339:Carotid Arteries / Q000187:drug effects / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D002941:Circle of Willis / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D044127:Epigenesis, Genetic; D005819:Genetic Markers / Q000187:drug effects; D002532:Intracranial Aneurysm / Q000235:genetics / Q000276:immunology / Q000473:pathology*; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D009687:Nuclear Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D051381:Rats; D013792:Thalidomide / Q000031:analogs & derivatives / Q000494:pharmacology; D015534:Trans-Activators / Q000235:genetics; D059467:Transcriptome; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000494:pharmacology* / Q000502:physiology; D000099251:Myocardin
chemical_list: D005819:Genetic Markers; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D009687:Nuclear Proteins; D013792:Thalidomide; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; D000099251:Myocardin; C562075:3,6'-dithiothalidomide; C000715469:Klf4 protein, rat