Duong 2020 Mitochondrion
|Duong QV, Hoffman A, Zhong K, Dessinger MJ, Zhang Y, Bazil JN (2020) Calcium overload decreases net free radical emission in cardiac mitochondria. Mitochondrion 51:126-39.|
Abstract: Elevated calcium and reactive oxygen species (ROS) are responsible for the bulk of cell death occurring in a variety of clinical settings that include acute coronary events, cerebrovascular accidents, and acute kidney injury. It is commonly believed that calcium and ROS participate in a viscous cycle during these events. However, the precise feedback mechanisms are unknown. We quantitatively demonstrate in this study that, on the contrary, calcium does not stimulate free radical production but suppresses it. Isolated mitochondria from guinea pig hearts were energized with a variety of substrates and exposed to calcium concentrations designed to induce moderate calcium overload conditions associated with ischemia/reperfusion injury but do not elicit the well-known mitochondrial permeability transition phenomenon. Metabolic function and free radical emission were simultaneously quantified using high-resolution respirometry and fluorimetry. Membrane potential, high amplitude swelling, and calcium dynamics were also quantified in parallel. Our results reveal that calcium overload does not lead to excessive ROS emission but does decrease ADP stimulated respiration rates for NADH-dependent pathways. Moreover, we developed an empirical model of mitochondrial free radical homeostasis to identify the processes that are different for each substrate and calcium condition. In summary, we show that in healthy guinea pig mitochondria, calcium uptake and free radical generation do not contribute to a viscous cycle and that the relationship between net free radical production and oxygen concentration is hyperbolic. Altogether, these results lay out an important foundation necessary to quantitatively determine the role of calcium in IR injury and ROS production.
Copyright © 2020 Elsevier B.V. and Mitochondria Research Society. All rights reserved.
Labels: MiParea: Respiration
Stress:Ischemia-reperfusion, Oxidative stress;RONS Organism: Guinea pig Tissue;cell: Heart Preparation: Isolated mitochondria
Regulation: Calcium Coupling state: LEAK, OXPHOS, ET Pathway: F, N, S HRR: Oxygraph-2k, O2k-Fluorometer
Labels, 2020-02, AmR