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Hypoxia is common in marine environments and a major stressor for marine organisms inhabiting benthic and intertidal zones. Several studies have explored the responses of these organisms to hypoxic stress at the whole organism level with a focus on energy metabolism and mitochondrial response, but the instrinsic mitochondrial responses that support the organelle’s function under hypoxia and reoxygenation (H/R) stress are not well understood. We studied the effects of acute H/R stress (10 min anoxia followed by 15 min reoxygenation) on mitochondrial respiration, production of reactive oxygen species (ROS) and posttranslational modifications (PTM) of the proteome in a marine facultative anaerobe, the blue mussel Mytilus edulis. The mussels’ mitochondria showed increased OXPHOS respiration and suppressed proton leak resulting in a higher coupling efficiency after H/R stress. ROS production decreased in both the resting (LEAK) and phosphorylating (OXPHOS) state indicating that M. edulis was able to prevent oxidative stress and mitochondrial damage during reoxygenation. Hypoxia did not lead to rearrangement of the mitochondrial supercomplexes but impacted the mitochondrial phosphoproteome including the proteins involved in OXPHOS, amino acid- and fatty acid catabolism, and protein quality control. This study indicates that mussels’ mitochondria possess intrinsic mechanisms (including regulation via reversible protein phosphorylation) that ensure high respiratory flux and mitigate oxidative damage during H/R stress and contribute to the hypoxia-tolerant mitochondrial phenotype of this metabolically plastic species.
Myocardial infarction is a leading cause for morbidity and mortality worldwide. The only
viable treatment for the ischemic insult is timely reperfusion, which further exacerbates myocardial
injury. Maintaining mitochondrial function is crucial in preserving cardiomyocyte function in
ischemia reperfusion (IR) injury. Poloxamer (P) 188 has been shown to improve cardiac IR injury
by improving cellular and mitochondrial function. The aim of this study was to show if P188
postconditioning has direct protective effects on mitochondrial function in the heart. Langendorff
prepared rat hearts were subjected to IR injury ex-vivo and reperfused for 10 min with 1 mM P188
vs. vehicle. Cardiac mitochondria were isolated with 1 mM P188 vs. 1 mM polyethylene glycol
(PEG) vs. vehicle by differential centrifugation. Mitochondrial function was assessed by adenosine
triphosphate synthesis, oxygen consumption, and calcium retention capacity. Mitochondrial function
decreased significantly after ischemia and showed mild improvement with reperfusion. P188 did
not improve mitochondrial function in the ex-vivo heart, and neither further P188 nor PEG induced
direct mitochondrial protection after IR injury in this model.
Over the past 10 years, the crisis of sepsis has remained a great challenge. According to data from 2016, the sepsis-related mortality rate remains high. In addition, sepsis consumes extensive medical resources in intensive care units, and anti-inflammatory agents fail to improve sepsis-associated hyperinflammation and symptoms of immunosuppression. The specific immune mechanism of sepsis remains to be elucidated. Reactive oxygen species (ROS) are triggered by energy metabolism and respiratory dysfunction in sepsis, which not only cause oxidative damage to tissues and organelles, but also directly and indirectly promote NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome activation. NLRP3 inflammasomes enlarge the inflammatory response and trigger apoptosis of immune cells to exacerbate sepsis progression. Inhibiting the negative effects of ROS and NLRP3 inflammasomes therefore provides the possibility of reversing the excessive inflammation during sepsis. In this review, we describe the interaction of ROS and NLRP3 inflammasomes during sepsis, provide prevention strategies, and identify fields that need further study.