Peroxynitrite formed during a transient episode of brain ischemia increases endothelium-derived hyperpolarization-type dilations in thromboxane/prostaglandin receptor-stimulated rat cerebral arteries
Onetti Vilalta, Yara (Universitat Autònoma de Barcelona. Institut de Neurociències)
Dantas, A. P. (Institut d'Investigacions Biomèdiques August Pi i Sunyer)
Pérez, Belén (Universitat Autònoma de Barcelona. Institut de Neurociències)
McNeish, Alister J. (University of Reading. Reading School of Pharmacy)
Vila Calsina, Elisabet (Universitat Autònoma de Barcelona. Institut de Neurociències)
Jiménez Altayó, Francesc (Universitat Autònoma de Barcelona. Institut de Neurociències)

Data:	2016
Resum:	AIM: Increased thromboxane A2 and peroxynitrite are hallmarks of cerebral ischaemia/reperfusion (I/R). Stimulation of thromboxane/prostaglandin receptors (TP) attenuates endothelium-derived hyperpolarization (EDH). We investigated whether EDH-type middle cerebral artery (MCA) relaxations following TP stimulation are altered after I/R and the influence of peroxynitrite. METHODS: Vascular function was determined by wire myography after TP stimulation with the thromboxane A2 mimetic 9,11-dideoxy-9α, 11α -methano-epoxy prostaglandin F2α (U46619) in MCA of Sprague Dawley rats subjected to MCA occlusion (90 min)/reperfusion (24 h) or sham operation, and in non-operated (control) rats. Some rats were treated with saline or the peroxynitrite decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) (20 mg kg-1 ). Protein expression was evaluated in MCA and in human microvascular endothelial cells submitted to hypoxia (overnight)/reoxygenation (24 h) (H/R) using immunofluorescence and immunoblotting. RESULTS: In U46619-pre-constricted MCA, EDH-type relaxation by the proteinase-activated receptor 2 agonist serine-leucine-isoleucine-glycine-arginine-leucine-NH2 (SLIGRL) was greater in I/R than sham rats due to an increased contribution of small-conductance calcium-activated potassium channels (SKCa ), which was confirmed by the enlarged relaxation to the SKCa activator N-cyclohexyl-N-2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-4-pyrimidinamine. I/R and H/R induced endothelial protein tyrosine nitration and filamentous-actin disruption. In control MCA, either cytochalasin D or peroxynitrite disrupted endothelial filamentous-actin and augmented EDH-type relaxation. Furthermore, peroxynitrite decomposition during I/R prevented the increase in EDH-type responses. CONCLUSION: Following TP stimulation in MCA, EDH-type relaxation to SLIGRL is greater after I/R due to endothelial filamentous-actin disruption by peroxynitrite, which prevents TP-induced block of SKCa input to EDH. These results reveal a novel mechanism whereby peroxynitrite could promote post-ischaemic brain injury.
Ajuts:	Ministerio de Ciencia e Innovación SAF2010-19282 Ministerio de Ciencia e Innovación SAF2014-56111-R Agència de Gestió d'Ajuts Universitaris i de Recerca 2014/SGR-574 Instituto de Salud Carlos III FIS/PI13/0091 Instituto de Salud Carlos III RIC/RD12/0042/0006
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Matèria:	SKC a ; KCa2.3 ; Actin ; Calcium-activated potassium channels ; Ischaemia/reperfusion ; Stroke ; Thromboxane
Publicat a:	Acta Physiologica, Vol. 220, no. 1 (September 2016) , p. 150-166, ISSN 1748-1716

DOI: 10.1111/apha.12809

Post-print 39 p, 2.5 MB

Taules i Figures 8 p, 604.4 KB

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