Inhibiting Succinate Release Worsens Cardiac Reperfusion Injury by Enhancing Mitochondrial Reactive Oxygen Species Generation.

Content Provider	Europe PMC
Author	Milliken, Alexander S. Nadtochiy, Sergiy M. Brookes, Paul S.
Abstract	BackgroundThe metabolite succinate accumulates during cardiac ischemia. Within 5 minutes of reperfusion, succinate returns to baseline levels via both its release from cells and oxidation by mitochondrial complex II. The latter drives reactive oxygen species (ROS) generation and subsequent opening of the mitochondrial permeability transition (PT) pore, leading to cell death. Targeting succinate dynamics (accumulation/oxidation/release) may be therapeutically beneficial in cardiac ischemia–reperfusion (IR) injury. It has been proposed that blocking MCT1 (monocarboxylate transporter 1) may be beneficial in IR injury, by preventing succinate release and subsequent engagement of downstream inflammatory signaling pathways. In contrast, herein we hypothesized that blocking MCT1 would retain succinate in cells, exacerbating ROS generation and IR injury.Methods and ResultsUsing the mitochondrial ROS probe mitoSOX and a custom‐built murine heart perfusion rig built into a spectrofluorometer, we measured ROS generation in situ during the first moments of reperfusion. We found that acute MCT1 inhibition enhanced mitochondrial ROS generation at reperfusion and worsened IR injury (recovery of function and infarct size). Both of these effects were abrogated by tandem inhibition of mitochondrial complex II, suggesting that succinate retention worsens IR because it drives more mitochondrial ROS generation. Furthermore, using the PT pore inhibitor cyclosporin A, along with monitoring of PT pore opening via the mitochondrial membrane potential indicator tetramethylrhodamine ethyl ester, we herein provide evidence that ROS generation during early reperfusion is upstream of the PT pore, not downstream as proposed by others. In addition, pore opening was exacerbated by MCT1 inhibition.ConclusionsTogether, these findings highlight the importance of succinate dynamics and mitochondrial ROS generation as key determinants of PT pore opening and IR injury outcomes.
Page Count	21
Journal	Journal of the American Heart Association
Volume Number	11
PubMed Central reference number	PMC9333399
Issue Number	13
PubMed reference number	35766275
e-ISSN	20479980
DOI	10.1161/jaha.122.026135
Language	English
Publisher	John Wiley and Sons Inc.
Publisher Date	2022-06-29
Publisher Place	Hoboken
Access Restriction	Open
Rights License	This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. © 2022 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.
Subject Keyword	complex II ischemia metabolism mitochondria reactive oxygen species succinate Ischemia Metabolism Oxidant Stress
Content Type	Text
Resource Type	Article
Subject	Cardiology and Cardiovascular Medicine