Mitochondrial responses to long-term and cyclic hypoxia depend on the oxidized fuel in a hypoxia-tolerant marine bivalve Crassostrea gigas

These are the metadata for a publication "Mitochondrial responses to long-term and cyclic hypoxia depend on the oxidized fuel in a hypoxia-tolerant marine bivalve Crassostrea gigas" under consideration for publication in the Scientific reports. Sessile benthic organisms like oysters inhabits intertidal zone transitioning between aquatic and terrestrial condition during tidal movements exposing the organisms to alternating hypoxia and reoxygenation (H/R) episodes thereby altering the respiratory chain activities and metabolome compositions. Our study investigated the effects of constant long-term H/R stress (90 min at ~0% O_2, and 10 min reoxygenation) and constant cyclic H/R stress (5 cycles of 15 min at ~0% O_2, and 10 min reoxygenation) on isolated mitochondria from the gill and the digestive gland of C. gigas respiring on different substrates (pyruvate, palmitate, and succinate). Both gill and the digestive gland mitochondria exposed to constant long-term H/R suppressed OXPHOS respiration especially during Complex I oxidation with no change in ROS efflux but an increase FEL. In the gill mitochondria oxidizing Complex I substrates, exposure to constant cyclic H/R prompted a significant drop after the first H/R cycle. In contrast, succinate-driven respiration only showed significant decline after the fifth H/R cycle. ROS efflux and FEL however saw little to no change after constant cyclic H/R. This observation from our study further suggests succinate as a potential stress fuel under H/R stress and might assist in post-hypoxic recovery of oysters mitigating oxidative stress and supporting rapid ATP re-synthesis during oxygen fluctuations such as commonly observed in intertidal zones. Additionally, our study revealed that constant long-term hypoxia is more damaging than constant cyclic hypoxia.