title: Bioenergetic and volume regulatory effects of mitoKATP channel modulators protect against hypoxia-reoxygenation-induced mitochondrial dysfunction.
abstract: The mitochondrial ATP-sensitive K(+) (mitoKATP) channel plays a significant role in mitochondrial physiology and protects against ischemic reperfusion injury in mammals. Although fish frequently face oxygen fluctuations in their environment, the role of the mitoKATP channel in regulating the responses to oxygen stress is rarely investigated in this class of animals. To elucidate whether and how the mitoKATP channel protects against hypoxia-reoxygenation (H-R)-induced mitochondrial dysfunction in fish, we first determined the mitochondrial bioenergetic effects of two key modulators of the channel, diazoxide and 5-hydroxydecanoate (5-HD), using a wide range of doses. Subsequently, the effects of low and high doses of the modulators on mitochondrial bioenergetics and volume under normoxia and after H-R using buffers with and without magnesium and ATP (Mg-ATP) were tested. In the absence of Mg-ATP (mitoKATP channel open), both low and high doses of diazoxide improved mitochondrial coupling, but only the high dose of 5-HD reversed the post-H-R coupling-enhancing effect of diazoxide. In the presence of Mg-ATP (mitoKATP channel closed), diazoxide at the low dose improved coupling post-H-R, and this effect was abolished by 5-HD at the low dose. Interestingly, both low and high doses of diazoxide reversed H-R-induced swelling under mitoKATP channel open conditions, but this effect was not sensitive to 5-HD. Under mitoKATP channel closed conditions, diazoxide at the low dose protected the mitochondria from H-R-induced swelling and 5-HD at the low dose reversed this effect. In contrast, diazoxide at the high dose failed to reduce the swelling caused by H-R, and the addition of the high dose of 5-HD enhanced mitochondrial swelling. Overall, our study showed that in the presence of Mg-ATP, both opening of mitoKATP channels and bioenergetic effects of diazoxide were protective against H-R in fish mitochondria, while in the absence of Mg-ATP only the bioenergetic effect of diazoxide was protective.
authors.affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3.
authors.forename: John O
authors.initials: JO
authors.lastname: Onukwufor
authors.affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3.
authors.forename: Don
authors.initials: D
authors.lastname: Stevens
authors.affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3 ckamunde@upei.ca.
authors.forename: Collins
authors.identifier: 0000-0003-3565-0049
authors.initials: C
authors.lastname: Kamunde
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002021:Buffers; D019069:Cell Respiration / Q000187:drug effects; D003652:Decanoic Acids / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D004734:Energy Metabolism / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects; D006880:Hydroxy Acids / Q000494:pharmacology; D000860:Hypoxia / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010100:Oxygen / Q000494:pharmacology*; D015221:Potassium Channels / Q000378:metabolism*; D020011:Protective Agents / Q000378:metabolism*
chemical_list: D002021:Buffers; D003652:Decanoic Acids; D006880:Hydroxy Acids; D015221:Potassium Channels; D020011:Protective Agents; C117780:mitochondrial K(ATP) channel; C052853:5-hydroxydecanoic acid; D000255:Adenosine Triphosphate; D003981:Diazoxide; D010100:Oxygen
keywords: 5-Hydroxydecanoate; Diazoxide; Mitochondrial bioenergetics; Swelling; Volume regulation