title: Role of sarcoplasmic reticulum in mitochondrial permeability transition and cardiomyocyte death during reperfusion.
abstract: There is solid evidence that a sudden change in mitochondrial membrane permeability (mitochondrial permeability transition, MPT) plays a critical role in reperfusion-induced myocardial necrosis. We hypothesized that sarcoplasmic reticulum (SR) Ca(2+) cycling may induce partial MPT in microdomains of close anatomic proximity between mitochondria and SR, resulting in hypercontracture and cell death. MPT (mitochondrial calcein release), cell length, and sarcolemmal rupture (Trypan blue and lactate dehydrogenase release) were measured in adult rat cardiomyocytes submitted to simulated ischemia (NaCN/2-deoxyglucose, pH 6.4) and reperfusion. On simulated reperfusion, 83 +/- 2% of myocytes developed hypercontracture. In 22 +/- 6% of cases, hypercontracture was associated with sarcolemmal disruption [Trypan blue(+)]. During simulated reperfusion there was a 25% release of cyclosporin A-sensitive mitochondrial calcein (with respect to total mitochondrial calcein content). Simultaneous blockade of SR Ca(2+) uptake and release with thapsigargin and ryanodine, respectively, significantly reduced mitochondrial calcein release, hypercontracture, and cell death during simulated reperfusion. SR Ca(2+) blockers delayed mitochondrial Ca(2+) uptake in digitonin-permeabilized cardiomyocytes but did not have any effect on isolated mitochondria. Pretreatment with colchicine to disrupt microtubule network reduced the degree of fluorescent overlap between SR and mitochondria and abolished the protective effect of SR Ca(2+) blockers on MPT, hypercontracture, and cell death during reperfusion. We conclude that SR Ca(2+) cycling during reperfusion facilitates partial mitochondrial permeabilization due to the close anatomic proximity between both organelles, favoring hypercontracture and cell death.
authors.affiliation: Servicio de Cardiologia, Hospital Universitari Vall d'Hebron, 08035 Barcelona, Spain.
authors.forename: Marisol
authors.initials: M
authors.lastname: Ruiz-Meana
authors.forename: Arancha
authors.initials: A
authors.lastname: Abellán
authors.forename: Elisabet
authors.initials: E
authors.lastname: Miró-Casas
authors.forename: Esperanza
authors.initials: E
authors.lastname: Agulló
authors.forename: David
authors.initials: D
authors.lastname: Garcia-Dorado
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D016923:Cell Death; D002478:Cells, Cultured; D003078:Colchicine / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005452:Fluoresceins / Q000378:metabolism; D054061:Ischemic Contracture / Q000378:metabolism / Q000473:pathology; D008297:Male; D053078:Membrane Potential, Mitochondrial; D008870:Microtubules / Q000378:metabolism; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D033681:Mitochondrial Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012433:Ryanodine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D005452:Fluoresceins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D050257:Tubulin Modulators; D012433:Ryanodine; D019284:Thapsigargin; D016572:Cyclosporine; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D003078:Colchicine; C007740:fluorexon