title: Effects of intermittent hypoxia on oxidative stress and protein degradation in molluscan mitochondria.
abstract: Oxygen fluctuations represent a common stressor in estuarine and intertidal environments and can compromise the mitochondrial integrity and function in marine organisms. We assessed the role of mitochondrial protection mechanisms (ATP-dependent and -independent mitochondrial proteases, and antioxidants) in tolerance to intermittent hypoxia or anoxia in three species of marine bivalves: hypoxia-tolerant hard clams (Mercenaria mercenaria) and oysters (Crassostrea virginica), and a hypoxia-sensitive subtidal scallop (Argopecten irradians). In clams and oysters, mitochondrial tolerance to hypoxia (18 h at 5% O2), anoxia (18 h at 0.1% O2) and subsequent reoxygenation was associated with the ability to maintain the steady-state activity of ATP-dependent and -independent mitochondrial proteases and an anticipatory upregulation of the total antioxidant capacity under the low oxygen conditions. No accumulation of end-products of lipid or protein peroxidation was found during intermittent hypoxia or anoxia in clams and oysters (except for an increase in protein carbonyl concentration after hypoxia-reoxygenation in oysters). In contrast, hypoxia/anoxia and reoxygenation strongly suppressed activity of the ATP-dependent mitochondrial proteases in hypoxia-sensitive scallops. This suppression was associated with accumulation of oxidatively damaged mitochondrial proteins (including carbonylated proteins and proteins conjugated with a lipid peroxidation product malondialdehyde) despite high total antioxidant capacity levels in scallop mitochondria. These findings highlight a key role of mitochondrial proteases in protection against hypoxia-reoxygenation stress and adaptations to frequent oxygen fluctuations in intertidal mollusks.
authors.affiliation: Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28269, USA.
authors.forename: Anna V
authors.initials: AV
authors.lastname: Ivanina
authors.affiliation: Marine Biology, Institute for Biological Sciences, University of Rostock, 18055 Rostock, Germany inna.sokolova@uni-rostock.de.
authors.forename: Inna M
authors.identifier: 0000-0002-2068-4302
authors.initials: IM
authors.lastname: Sokolova
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology*; D049896:Crassostrea / Q000378:metabolism*; D049891:Mercenaria / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D049897:Pectinidae / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D059748:Proteolysis
chemical_list: D000975:Antioxidants; D024101:Mitochondrial Proteins; D010447:Peptide Hydrolases; D010100:Oxygen
keywords: ATP-dependent proteases; Antioxidants; Bivalves; Hypoxia–reoxygenation; Mitoproteases; Oxidative lesions