title: Mast cell chymase induces smooth muscle cell apoptosis by disrupting NF-kappaB-mediated survival signaling.
abstract: Chymase released from activated mast cells induces apoptosis of vascular smooth muscle cells (SMCs) in vitro by degrading the pericellular matrix component fibronectin, so causing disruption of focal adhesion complexes and Akt dephosphorylation, which are necessary for cell adhesion and survival. However, the molecular mechanisms of chymase-mediated apoptosis downstream of Akt have remained elusive. Here, we show by means of RT-PCR, Western blotting, EMSA, immunocytochemistry and confocal microscopy, that chymase induces SMC apoptosis by disrupting NF-kappaB-mediated survival signaling. Following chymase treatment, the translocation of active NF-kappaB/p65 to the nucleus was partly abolished and the amount of nuclear p65 was reduced. Pretreatment of SMCs with chymase also inhibited LPS- and IL-1beta-induced nuclear translocation of p65. The chymase-induced degradation of p65 was mediated by active caspases. Loss of NF-kappaB-mediated transactivation resulted in downregulation of bcl-2 mRNA and protein expression, leading to mitochondrial swelling and release of cytochrome c. The apoptotic process involved activation of both caspase 9 and caspase 8. The results reveal that, by disrupting the NF-kappaB-mediated survival-signaling pathway, activated chymase-secreting mast cells can mediate apoptosis of cultured arterial SMCs. Since activated mast cells colocalize with apoptotic SMCs in vulnerable areas of human atherosclerotic plaques, they may participate in the weakening and rupture of atherosclerotic plaques.
authors.affiliation: Wihuri Research Institute, Kalliolinnantie 4, FI-00140 Helsinki, Finland.
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Leskinen
authors.forename: Hanna M
authors.initials: HM
authors.lastname: Heikkilä
authors.forename: Mei Y
authors.initials: MY
authors.lastname: Speer
authors.forename: Jukka K
authors.initials: JK
authors.lastname: Hakala
authors.forename: Mika
authors.initials: M
authors.lastname: Laine
authors.forename: Petri T
authors.initials: PT
authors.lastname: Kovanen
authors.forename: Ken A
authors.initials: KA
authors.lastname: Lindstedt
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D050197:Atherosclerosis / Q000201:enzymology / Q000503:physiopathology; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D053818:Chymases; D045304:Cytochromes c / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D018836:Inflammation Mediators / Q000494:pharmacology; D008297:Male; D008407:Mast Cells / Q000201:enzymology* / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012697:Serine Endopeptidases / Q000378:metabolism* / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D051996:Transcription Factor RelA / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology
chemical_list: D018836:Inflammation Mediators; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051996:Transcription Factor RelA; D045304:Cytochromes c; D012697:Serine Endopeptidases; D053818:Chymases; D020169:Caspases