title: Neuronal K(ATP) channels mediate hypoxic preconditioning and reduce subsequent neonatal hypoxic-ischemic brain injury.
abstract: Neonatal hypoxic-ischemic brain injury and its related illness hypoxic-ischemic encephalopathy (HIE) are major causes of nervous system damage and neurological morbidity in children. Hypoxic preconditioning (HPC) is known to be neuroprotective in cerebral ischemic brain injury. K(ATP) channels are involved in ischemic preconditioning in the heart; however the involvement of neuronal K(ATP) channels in HPC in the brain has not been fully investigated. In this study, we investigated the role of HPC in hypoxia-ischemia (HI)-induced brain injury in postnatal seven-day-old (P7) CD1 mouse pups. Specifically, TTC (2,3,5-triphenyltetrazolium chloride) staining was used to assess the infarct volume, TUNEL (Terminal deoxynucleotidyl transferase mediated dUTP nick end-labeling) to detect apoptotic cells, Western blots to evaluate protein level, and patch-clamp recordings to measure K(ATP) channel current activities. Behavioral tests were performed to assess the functional recovery after hypoxic-ischemic insults. We found that hypoxic preconditioning reduced infarct volume, decreased the number of TUNEL-positive cells, and improved neurobehavioral functional recovery in neonatal mice following hypoxic-ischemic insults. Pre-treatment with a K(ATP) channel blocker, tolbutamide, inhibited hypoxic preconditioning-induced neuroprotection and augmented neurodegeneration following hypoxic-ischemic injury. Pre-treatment with a K(ATP) channel opener, diazoxide, reduced infarct volume and mimicked hypoxic preconditioning-induced neuroprotection. Hypoxic preconditioning induced upregulation of the protein level of the Kir6.2 isoform and enhanced current activities of K(ATP) channels. Hypoxic preconditioning restored the HI-reduced PKC and pAkt levels, and reduced caspase-3 level, while tolbutamide inhibited the effects of hypoxic preconditioning. We conclude that K(ATP) channels are involved in hypoxic preconditioning-induced neuroprotection in neonatal hypoxic-ischemic brain injury. K(ATP) channel openers may therefore have therapeutic effects in neonatal hypoxic-ischemic brain injury.
authors.affiliation: Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Pharmacology & Toxicology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada. Electronic address: hss.sun@utoronto.ca.
authors.forename: Hong-Shuo
authors.initials: HS
authors.lastname: Sun
authors.affiliation: Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Baofeng
authors.initials: B
authors.lastname: Xu
authors.affiliation: Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Wenliang
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Aijiao
authors.initials: A
authors.lastname: Xiao
authors.affiliation: Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Turlova
authors.affiliation: Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Ammar
authors.initials: A
authors.lastname: Alibraham
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Barszczyk
authors.affiliation: Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Christine Y J
authors.initials: CY
authors.lastname: Bae
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Yi
authors.initials: Y
authors.lastname: Quan
authors.affiliation: Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Baosong
authors.initials: B
authors.lastname: Liu
authors.affiliation: Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Lin
authors.initials: L
authors.lastname: Pei
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Faculty of Applied Science & Engineering, University of Toronto, Toronto, Ontario M5S 1A4, Canada.
authors.forename: Christopher L F
authors.initials: CL
authors.lastname: Sun
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Marielle
authors.initials: M
authors.lastname: Deurloo
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada. Electronic address: zp.feng@utoronto.ca.
authors.forename: Zhong-Ping
authors.initials: ZP
authors.lastname: Feng
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D001930:Brain Injuries / Q000378:metabolism*; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism*; D020287:In Situ Nick-End Labeling; D019194:Ischemic Preconditioning; D054086:KATP Channels / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D018696:Neuroprotective Agents / Q000494:pharmacology; D018408:Patch-Clamp Techniques
chemical_list: D054086:KATP Channels; D018696:Neuroprotective Agents
keywords: Hypoxic preconditioning; K(ATP) channel; Neonatal hypoxic–ischemic brain injury; Neuroprotection; PKC