title: Linoleic acid epoxide promotes the maintenance of mitochondrial function and active Na+ transport following hypoxia.
abstract: Low concentrations of arachidonic acid monoepoxides protect against ischemia/reperfusion injury. This study examined whether low concentrations of the linoleic acid monoepoxide, cis-12,13-epoxy-9-octadecenoic acid (12,13-EOA), protect renal cells against decreases in mitochondrial and transport functions induced by hypoxia/reoxygenation. Primary cultures of rabbit renal proximal tubular cells (RPTC) were pretreated with diluent or 1, 5, or 10 microM 12,13-EOA for 1 h and exposed to 2 h hypoxia/0.5 h reoxygenation in the absence of 12,13-EOA. Basal respiration, oligomycin-sensitive oxygen consumption (QO2), and ATP content decreased 31, 35 and 65%, respectively, following hypoxia/reoxygenation. Hypoxia/reoxygenation also increased mitochondrial membrane potential (DeltaPsi(m)). Pretreatment with 12,13-EOA prevented decreases in basal and oligomycin-sensitive QO2s and increases in DeltaPsi(m). Despite the protection against decreases in mitochondrial function, 12,13-EOA pretreatment did not prevent the initial decrease in intracellular ATP content following hypoxia. However, pretreatment did accelerate the recovery of intracellular ATP levels during reoxygenation. Pretreatment with 12,13-EOA also prevented hypoxia-induced decreases in active Na+ transport. Ouabain-sensitive QO2 (a marker of active Na+ transport) decreased 38% following hypoxia/reoxygenation but was maintained in RPTC pretreated with 1, 5 or 10 microM 12,13-EOA prior to hypoxia. Pretreatment of RPTC with the hydrolyzed product of 12,13-EOA, 12,13-dihydroxyoctadecenoic acid, did not have any protective effects against mitochondrial dysfunction and decreases in active Na+ transport. Thus, this is the first report demonstrating that preconditioning of RPTC with low concentrations of 12,13-EOA, but not its hydrolyzed product, maintains mitochondrial respiration, accelerates restoration of ATP levels, and prevents decreases in active Na+ transport following hypoxia/reoxygenation.
authors.affiliation: Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA. gnowak@uams.edu
authors.forename: Grazyna
authors.initials: G
authors.lastname: Nowak
authors.forename: David F
authors.initials: DF
authors.lastname: Grant
authors.forename: Jeffery H
authors.initials: JH
authors.lastname: Moran
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D005456:Fluorescent Dyes; D000860:Hypoxia / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008041:Linoleic Acids / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009829:Oleic Acids / Q000138:chemical synthesis / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*
chemical_list: C119104:12,13-epoxy-9-octadecenoic acid; D005456:Fluorescent Dyes; D008041:Linoleic Acids; D009829:Oleic Acids; D000255:Adenosine Triphosphate; D012964:Sodium; D007770:L-Lactate Dehydrogenase; D006180:Proton-Translocating ATPases