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Acid enhancement of ROS generation by complex-I reverse electron transport is balanced by acid inhibition of complex-II: Relevance for tissue reperfusion injury.

ABSTRACT: Generation of mitochondrial reactive oxygen species (ROS) is an important process in triggering cellular necrosis and tissue infarction during ischemia-reperfusion (IR) injury. Ischemia results in accumulation of the metabolite succinate. Rapid oxidation of this succinate by mitochondrial complex II (Cx-II) during reperfusion reduces the co-enzyme Q (Co-Q) pool, thereby driving electrons backward into complex-I (Cx-I), a process known as reverse electron transport (RET), which is thought to be a major source of ROS. During ischemia, enhanced glycolysis results in an acidic cellular pH at the onset of reperfusion. While the process of RsET within Cx-I is known to be enhanced by a high mitochondrial trans-membrane ?pH, the impact of pH itself on the integrated process of Cx-II to Cx-I RET has not been fully studied. Using isolated mouse heart and liver mitochondria under conditions which mimic the onset of reperfusion (i.e., high [ADP]), we show that mitochondrial respiration (state 2 and state 3) as well as isolated Cx-II activity are impaired at acidic pH, whereas the overall generation of ROS by Cx-II to Cx-I RET was insensitive to pH. Together these data indicate that the acceleration of Cx-I RET ROS by ?pH appears to be cancelled out by the impact of pH on the source of electrons, i.e. Cx-II. Implications for the role of Cx-II to Cx-I RET derived ROS in IR injury are discussed.

SUBMITTER: Milliken AS

PROVIDER: S-EPMC7527751 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Acid enhancement of ROS generation by complex-I reverse electron transport is balanced by acid inhibition of complex-II: Relevance for tissue reperfusion injury.

Milliken Alexander S AS Kulkarni Chaitanya A CA Brookes Paul S PS

Redox biology 20200919

Generation of mitochondrial reactive oxygen species (ROS) is an important process in triggering cellular necrosis and tissue infarction during ischemia-reperfusion (IR) injury. Ischemia results in accumulation of the metabolite succinate. Rapid oxidation of this succinate by mitochondrial complex II (Cx-II) during reperfusion reduces the co-enzyme Q (Co-Q) pool, thereby driving electrons backward into complex-I (Cx-I), a process known as reverse electron transport (RET), which is thought to be a ...[more]

PMID: 33007502

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Project description:The management of cardiac ischemic injury has been challenged by ischemia and reperfusion (I/R) injury. Reactive oxygen species (ROS) generated from mitochondrial reverse electron transport (RET) during the early phase of reperfusion is considered to be the initiating cause for ischemia and reperfusion injury. Ginsenosides and their prescriptions are widely used in the clinic for treatment of myocardial ischemia, however, the action to combat ROS remains to be elucidated. In this work, we used TMT-based proteomic approach to detect differential proteins from mitochondrial fractions of mice hearts with ischemia-reperfusion. Results indicated that the mass error of identified peptides was within 10 ppm, and most of the identified peptides were composed of 7-23 amino acids. Using these qualified data, 17,262 peptides, with a confidence level ≥ 95%, were mapped to 3,054 protein groups. PCA analysis showed that the model group was clearly separated from the blank group, while the protein pattern was partly reversed with Rb1 treatment. With a criteria of p-value < 0.05, 591 significantly changed proteins including 186 increased and 405 decreased ones in the model group were identified compared with the blank group. These proteins were divided into 4 clusters. Proteins in Cluster I highly increased in the model group, but clearly decreased in the Rb1 group. Proteins in Cluster IV clearly decreased in the model group, but markedly increased in the Rb1 group. Proteins in Cluster III and in Cluster IV were not significantly or slightly regulated by the Rb1 treatment. GO analysis of Cluster I and II indicated that the molecular function of these proteins were closely related to oxidoreductase activity and NADH dehydrogenase activity. Our result showed that Rb1 administration before ischemia markedly decreased infarct size (48 h post-I/R), and preserved cardiac function (2 weeks post-I/R), and subsequently limited tissue fibrosis (28 days post-I/R). These results indicated that targeted inhibition of mitochondrial complex I in the early stage of reperfusion by Rb1 is a potential therapeutic strategy for alleviating IR injury. This work not only indicates a potent molecular target for the precision therapy of myocardial ischemia by Rb1, but also provides novel knowledge for the management of cardiac ischemic injury by traditional Chinese medicine.

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Acid enhancement of ROS generation by complex-I reverse electron transport is balanced by acid inhibition of complex-II: Relevance for tissue reperfusion injury.

Publications

Acid enhancement of ROS generation by complex-I reverse electron transport is balanced by acid inhibition of complex-II: Relevance for tissue reperfusion injury.

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