Ischemia time impacts on respiratory chain functions and Ca2+-handling of cardiac subsarcolemmal mitochondria subjected to ischemia reperfusion injury

• Published in: Journal of cardiothoracic surgery Vol. 14; no. 1; p. 92
• Main Authors: Leistner, Marcus, Sommer, Stefanie, Kanofsky, Peer, Leyh, Rainer, Sommer, Sebastian-Patrick
• Format: Journal Article
• Language: English
• Published: London BioMed Central Ltd 14.05.2019; BioMed Central; BMC
• Subjects: Adenosine diphosphate; Blood pressure; Calcium; Calcium (Nutrient); Calcium homeostasis; Calcium influx; Calcium ions; Calcium permeability; Cardiology; Care and treatment; Complications and side effects; Cytochrome; Dehydrogenases; EDTA; Electron transport; Electron transport chain; Fluorescence; Health aspects; Heart; Heart diseases; Heart surgery; Homeostasis; Hyperpolarization; Injuries; Ischemia; Ischemia reperfusion injury; Ischemia time; Kinases; Laboratory animals; Membrane permeability; Membrane potential; Methods; Mitochondria; Mitochondrial permeability transition pore; Muscle contraction; Myocardial ischemia; Oxygen consumption; Permeability; Physiological aspects; Polarization; Polarography; Prolongation; Pyruvic acid; Reperfusion; Reperfusion injury; Respiration; Rodents; Subsarcolemmal mitochondria; Surgery; Swelling; Systolic pressure; Ventricle; Germany; United Kingdom > UK
• ISSN: 1749-8090; 1749-8090
• DOI: 10.1186/s13019-019-0911-1

Background Mitochondrial impairment can result from myocardial ischemia reperfusion injury (IR). Despite cardioplegic arrest, IR-associated cardiodepression is a major problem in heart surgery. We determined the effect of increasing ischemia time on the respiratory chain (RC) function, the inner membrane polarization and Ca.sup.2+ homeostasis of rat cardiac subsarcolemmal mitochondria (SSM). Methods Wistar rat hearts were divided into 4 groups of stop-flow induced warm global IR using a pressure-controlled Langendorff system: 0, 15, 30 and 40 min of ischemia with 30 min of reperfusion, respectively. Myocardial contractility was determined from left ventricular pressure records (dP/dt, dPmax) with an intraventricular balloon. Following reperfusion, SSM were isolated and analyzed regarding electron transport chain (ETC) coupling by polarography (Clark-Type electrode), membrane polarization (JC1 fluorescence) and Ca.sup.2+-handling in terms of Ca.sup.2+-induced swelling and Ca.sup.2+-uptake/release (Calcium Green-5 N[R] fluorescence). Results LV contractility and systolic pressure during reperfusion were impaired by increasing ischemic times. Ischemia reduced ETC oxygen consumption in IR40/30 compared to IR0/30 at complex I-V (8.1 [+ or -] 1.2 vs. 18.2 [+ or -] 2.0 nmol/min) and II-IV/V (16.4 [+ or -] 2.6/14.8 [+ or -] 2.3 vs. 2.3 [+ or -] 0.6 nmol/min) in state 3 respiration (p < 0.01). Relative membrane potential revealed a distinct hyperpolarization in IR30/30 and IR40/30 (171.5 [+ or -] 17.4% and 170.9 [+ or -] 13.5%) compared to IR0/30 (p < 0.01), wearing off swiftly after CCCP-induced uncoupling. Excess mitochondrial permeability transition pore (mPTP)-gated Ca.sup.2+-induced swelling was recorded in all groups and was most pronounced in IR40/30. Pyruvate addition for mPTP blocking strongly reduced SSM swelling in IR40/30 (relative AUC, [+ or -] pyruvate; IR0/30: 1.00 vs. 0.61, IR15/30: 1.68 vs. 1.00, IR30/30: 1.42 vs. 0.75, IR40/30: 1.97 vs. 0.85; p < 0.01). Ca.sup.2+-uptake remained unaffected by previous IR. Though Ca.sup.2+-release was delayed for [greater than or equai to]30 min of ischemia (p < 0.01), Ca.sup.2+ retention was highest in IR15/30 (RFU; IR0/30: 6.3 [+ or -] 3.6, IR 15/30 42.9 [+ or -] 5.0, IR30/30 15.9 [+ or -] 3.8, IR40/30 11.5 [+ or -] 6.6; p [less than or equai to] 0.01 for IR15/30 against all other groups). Conclusions Ischemia prolongation in IR injury gradually impaired SSM in terms of respiratory chain function and Ca.sup.2+-homeostasis. Membrane hyperpolarization appears to be responsible for impaired Ca.sup.2+-cycling and ETC function. Ischemia time should be considered an important factor influencing IR experimental data on subsarcolemmal mitochondria. Periods of warm global ischemia should be minimized during cardiac surgery to avoid excessive damage to SSMs. Keywords: Subsarcolemmal mitochondria, Ischemia reperfusion injury, Ischemia time