title: Interplay between Ca2+ cycling and mitochondrial permeability transition pores promotes reperfusion-induced injury of cardiac myocytes.
abstract: Uncontrolled release of Ca(2+) from the sarcoplasmic reticulum (SR) contributes to the reperfusion-induced cardiomyocyte injury, e.g. hypercontracture and necrosis. To find out the underlying cellular mechanisms of this phenomenon, we investigated whether the opening of mitochondrial permeability transition pores (MPTP), resulting in ATP depletion and reactive oxygen species (ROS) formation, may be involved. For this purpose, isolated cardiac myocytes from adult rats were subjected to simulated ischemia and reperfusion. MPTP opening was detected by calcein release and by monitoring the ΔΨ(m). Fura-2 was used to monitor cytosolic [Ca(2+)](i) or mitochondrial calcium [Ca(2+)](m), after quenching the cytosolic compartment with MnCl(2). Mitochondrial ROS [ROS](m) production was detected with MitoSOX Red and mag-fura-2 was used to monitor Mg(2+) concentration, which reflects changes in cellular ATP. Necrosis was determined by propidium iodide staining. Reperfusion led to a calcein release from mitochondria, ΔΨ(m) collapse and disturbance of ATP recovery. Simultaneously, Ca(2+) oscillations occurred, [Ca(2+)](m) and [ROS](m) increased, cells developed hypercontracture and underwent necrosis. Inhibition of the SR-driven Ca(2+) cycling with thapsigargine or ryanodine prevented mitochondrial dysfunction, ROS formation and MPTP opening. Suppression of the mitochondrial Ca(2+) uptake (Ru360) or MPTP (cyclosporine A) significantly attenuated Ca(2+) cycling, hypercontracture and necrosis. ROS scavengers (2-mercaptopropionyl glycine or N-acetylcysteine) had no effect on these parameters, but reduced [ROS](m). In conclusion, MPTP opening occurs early during reperfusion and is due to the Ca(2+) oscillations originating primarily from the SR and supported by MPTP. The interplay between Ca(2+) cycling and MPTP promotes the reperfusion-induced cardiomyocyte hypercontracture and necrosis. Mitochondrial ROS formation is a result rather than a cause of MPTP opening.
authors.affiliation: Institute of Physiology, Justus Liebig University, Giessen, Germany.
authors.forename: Yaser
authors.initials: Y
authors.lastname: Abdallah
authors.forename: Sascha A
authors.initials: SA
authors.lastname: Kasseckert
authors.forename: Wisam
authors.initials: W
authors.lastname: Iraqi
authors.forename: Maher
authors.initials: M
authors.lastname: Said
authors.forename: Tayyab
authors.initials: T
authors.lastname: Shahzad
authors.forename: Ali
authors.initials: A
authors.lastname: Erdogan
authors.forename: Christiane
authors.initials: C
authors.lastname: Neuhof
authors.forename: Dürsün
authors.initials: D
authors.lastname: Gündüz
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Schlüter
authors.forename: Harald
authors.initials: H
authors.lastname: Tillmanns
authors.forename: H Michael
authors.initials: HM
authors.lastname: Piper
authors.forename: H Peter
authors.initials: HP
authors.lastname: Reusch
authors.forename: Yury
authors.initials: Y
authors.lastname: Ladilov
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D016572:Cyclosporine / Q000494:pharmacology; D005452:Fluoresceins / Q000032:analysis; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D015428:Myocardial Reperfusion Injury / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000502:physiology*; D009336:Necrosis; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism*; D017975:Ruthenium Compounds / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D008625:Tiopronin / Q000494:pharmacology
chemical_list: D005452:Fluoresceins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017382:Reactive Oxygen Species; C112020:Ru 360; D017975:Ruthenium Compounds; D012433:Ryanodine; D019284:Thapsigargin; D016572:Cyclosporine; D000255:Adenosine Triphosphate; D008625:Tiopronin; D002118:Calcium; C007740:fluorexon; D000111:Acetylcysteine