Search

Ischaemia-reperfusion (IR) injury, which occurs when blood supply to an organ is disrupted and then restored, underlies many disorders, notably heart attack and stroke. Thus while reperfusion of ischaemic tissue is essential for survival, it also initiates oxidative damage, cell death, and aberrant immune responses, driven in large part by generation of mitochondrial reactive oxygen species (ROS). Although mitochondrial ROS production in IR is established, it has generally been considered a non-specific response to reperfusion, consistent with the many apparently unconnected interventions that decrease IR damage. In contrast to this view, we have identified a critical post-translational modification on mitochondrial complex I that is sufficient to abolish mitochondrial ROS during IR. Using MitoSNO - a novel selective inhibitor of complex I - we establish that S-nitrosation of a single cysteine residue on the ND3 subunit sufficient to impair oxidoreductase activity on in the target protein.This inhibitory modification in turn diminished both ROS and tissue necrosis at reperfusion.These findings led us to pursue the intriguing hypothesis that mitochondrial ROS production during IR could be controlled by a distinct metabolic process that interacts with mitochondrial complex I. We developed a comparative in vivo metabolomic analysis and unexpectedly identified conserved metabolic pathways responsible for controlling mitochondrial ROS production during IR. In doing so, we establish a universal metabolic signature of ischaemic injury in a range of tissues that are predictive for mitochondrial ROS production through mitochondrial complex I during reperfusion of ischaemic tissue. Pharmacological inhibition of these pathways is sufficient to ameliorate in vivo IR injury in murine models of heart attack, stroke and kidney damage. Thus our work identifies a general metabolic response of tissues to ischaemia and reperfusion that provides a unifying explanation for many hitherto unconnected aspects of IR injury. [ABSTRACT FROM PUBLISHER]

Cardiac ischaemia-reperfusion (I/R) injury has been attributed to stress signals arising from an impaired mitochondrial electron transport chain (ETC), which include redox imbalance, metabolic stalling and excessive production of reactive oxygen species (ROS). The alternative oxidase (AOX) is a respiratory enzyme, absent in mammals, that accepts electrons from a reduced quinone pool to reduce oxygen to water, thereby restoring electron flux when impaired and, in the process, blunting ROS production. Hence, AOX represents a natural rescue mechanism from respiratory stress. This study aimed to determine how respiratory restoration through xenotopically expressed AOX affects the re-perfused post-ischaemic mouse heart. As expected, AOX supports ETC function and attenuates the ROS load in post-anoxic heart mitochondria. However, post-ischaemic cardiac remodelling over 3 and 9 weeks was not improved. AOX blunted transcript levels of factors known to be up-regulated upon I/R such as the atrial natriuretic peptide (Anp) whilst expression of pro-fibrotic and pro-apoptotic transcripts were increased. Ex vivo analysis revealed contractile failure at nine but not 3 weeks after ischaemia whilst label-free quantitative proteomics identified an increase in proteins promoting adverse extracellular matrix remodelling. Together, this indicates an essential role for ETC-derived signals during cardiac adaptive remodelling and identified ROS as a possible effector., (© 2020 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)