Shigatoxin-induced endothelin-1 expression in cultured podocytes autocrinally mediates actin remodeling.
Shigatoxin (Stx) is the offending agent of post-diarrheal hemolytic uremic syndrome, characterized by glomerular ischemic changes preceding microvascular thrombosis. Because podocytes are highly sensitive to Stx cytotoxicity and represent a source of vasoactive molecules, we studied whether Stx-2 modulated the production of endothelin-1 (ET-1), taken as candidate mediator of podocyte dysfunction. Stx-2 enhanced ET-1 mRNA and protein expression via activation of nuclear factor kappaB (NF-kappaB) and activator protein-1 (Ap-1) to the extent that transfection with the dominant-negative mutant of IkappaB-kinase 2 or with Ap-1 decoy oligodeoxynucleotides reduced ET-1 mRNA levels. We propose a role for p38 and p42/44 mitogen-activated protein kinases (MAPKs) in mediating NF-kappaB-dependent gene transcription induced by Stx-2, based on data that Stx-2 phosphorylated p38 and p42/44 MAPKs and that MAPK inhibitors reduced transcription of NF-kappaB promoter/luciferase reporter gene construct induced by Stx-2. Stx-2 caused F-actin redistribution and intercellular gaps via production of ET-1 acting on ETA receptor, because cytoskeleton changes were prevented by ETA receptor blockade. Exogenous ET-1 induced cytoskeleton rearrangement and intercellular gaps via phosphatidylinositol-3 kinase and Rho-kinase pathway and increased protein permeability across the podocyte monolayer. These data suggest that the podocyte is a target of Stx, a novel stimulus for the synthesis of ET-1, which may control cytoskeleton remodeling and glomerular permeability in an autocrine fashion.
Morigi
Marina
M
Mario Negri Institute for Pharmacological Research, Unit of Nephrology and Dialysis, Azienda Ospedaliera, Ospedali Riuniti di Bergamo, Via Gavazzeni 11, 24125 Bergamo, Italy. morigi@marionegri.it
Buelli
Simona
S
Zanchi
Cristina
C
Longaretti
Lorena
L
Macconi
Daniela
D
Benigni
Ariela
A
Moioli
Daniela
D
Remuzzi
Giuseppe
G
Zoja
Carla
C
D000199:Actins / Q000378:metabolism*; D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000378:metabolism; D002454:Cell Differentiation; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D019332:Endothelin-1 / Q000096:biosynthesis / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000502:physiology; D050199:Podocytes / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism*; D022641:Shiga Toxin 2 / Q000494:pharmacology*; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000502:physiology; D014158:Transcription, Genetic; D015854:Up-Regulation
D000199:Actins; D015295:Antigens, Tumor-Associated, Carbohydrate; D019332:Endothelin-1; C472766:Gb3 antigen; D016328:NF-kappa B; D012333:RNA, Messenger; D022641:Shiga Toxin 2; D018808:Transcription Factor AP-1; D020928:Mitogen-Activated Protein Kinases