Isoflurane neurotoxicity involves activation of hypoxia inducible factor-1α via intracellular calcium in neonatal rodents

Brain Res. 2016 Dec 15;1653:39-50. doi: 10.1016/j.brainres.2016.10.014. Epub 2016 Oct 18.

Abstract

Objective: Previously, we found that the inhaled anesthetic isoflurane up-regulated the transcriptional factor hypoxia inducible factor (HIF)-1α protein levels during induction of neurodegeneration in the brain of neonatal rats. Here, we investigated the role of HIF-1α and the underlying signaling pathway in the neurodegenration induced by isoflurane in rodent developing brain.

Methods: Primary hippocampal neurons were exposed to isoflurane (0.4mM) for 12h. Neuron injury was analyzed by 3-(4,5-dimethyithiazol-2-yl)-2,5-diphenyl-tetra-zolium bromide (MTT) test and quantification of lactate dehydrogenaserelease. HIF-1α gene expression and transcriptional activity, cleaved caspase-3 and phosphoinositide phospholipase C (PLC)-γ gene expression were quantified. Cytosolic calcium concentration was measured by calcium imagining. The role of HIF-1α on juvenile learning and memory impairment induced by isoflurane was studied by fear conditioning and extinction test and Morris water maze test.

Results: Isoflurane induced HIF-1α gene expression and transcriptional activity in vitro. Furthermore, pharmacological inhibition of HIF-1α or knockdown of HIF-1α by shRNA counteracted the neurotoxicity of isoflurane. Ca2+ signaling pathways involving PLC-γ activation are required for isoflurane-evoked HIF-1α accumulation. Finally, partial deficiency of HIF-1α attenuated isoflurane-induced neurodegeneration in developing brain, and alleviated juvenile learning and memory impairment induced by isoflurane.

Conclusion: HIF-1α activation via cytosolic Ca2+ signaling pathway play a role in the mechanism of isoflurane-induced neurodegeneration in neonatal rodents, suggesting HIF-1α as a potential therapeutic target for the prevention of the deleterious effects of prolonged exposures to anesthetics.

Keywords: Calcium; Hypoxia inducible factor-1α; Isoflurane; Neurotoxicity.

MeSH terms

  • Anesthetics, Inhalation / toxicity
  • Animals
  • Animals, Newborn
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Calcium / metabolism*
  • Calcium Signaling / drug effects
  • Calcium Signaling / physiology
  • Cells, Cultured
  • Disease Models, Animal
  • Hippocampus / drug effects*
  • Hippocampus / growth & development*
  • Hippocampus / metabolism
  • Hypoxia-Inducible Factor 1, alpha Subunit / deficiency
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Isoflurane / toxicity*
  • Learning Disabilities / chemically induced
  • Learning Disabilities / metabolism
  • Memory Disorders / chemically induced
  • Memory Disorders / metabolism
  • Mice, 129 Strain
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Nerve Degeneration / chemically induced
  • Nerve Degeneration / metabolism
  • Neurons / drug effects
  • Neurons / metabolism
  • Neurotoxicity Syndromes / metabolism
  • Phospholipase C gamma / metabolism
  • Rats, Sprague-Dawley

Substances

  • Anesthetics, Inhalation
  • Hif1a protein, mouse
  • Hif1a protein, rat
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Isoflurane
  • Phospholipase C gamma
  • Calcium