title: The inhaled anesthetic, isoflurane, enhances Ca2+-dependent survival signaling in cortical neurons and modulates MAP kinases, apoptosis proteins and transcription factors during hypoxia.
abstract: We tested whether the protection of hypoxic neurons by the inhaled anesthetic isoflurane is related to the Ca2+-dependent phosphorylation of MAP kinases and anti-apoptotic co-factors. In cultures of mouse cortical neurons we measured changes in the phosphorylation of Ca2+-dependent and Ca2+-independent MAP kinases, transcription factors, and apoptosis regulators after hypoxia or hypoxia combined with isoflurane (1% in gas phase). In hypoxic neurons, isoflurane reduced cell death and TUNEL staining by >80%. Isoflurane released Ca2+ from intracellular stores, increasing [Ca2+]i in oxygenated neurons by approximately 20%. Neuroprotection was associated with a smaller increase in [Ca2+]i in hypoxic neurons and required IP3 receptors and phospholipase C. In hypoxic neurons, isoflurane increased the phosphorylation of the Ca2+-dependent MAP kinases Pyk2 and p42/44 (ERK). The Ca2+-independent MAP kinase p38 pathway showed increased phosphorylation with isoflurane but not with ionomycin, a Ca2+ ionophore. JNK was phosphorylated in hypoxic neurons in the presence of isoflurane, as was the transcription factor c-Jun; JNK inhibition with SP600125 prevented both phosphorylation of c-Jun and neuroprotection. Isoflurane decreased phosphorylation of the pro-apoptotic cofactors Bad and p90RSK and increased Akt phosphorylation. However, with the exception of c-Jun, transcription factors (Elk-1, GSK-3, Forkhead, p90RSK) decreased or remained unchanged. We conclude that isoflurane's protection of hypoxic cortical neurons involves signaling that includes changes in intracellular Ca2+ regulation, several MAP kinase pathways and modulation of apoptosis regulators.
authors.affiliation: Severinghaus-Radiometer Research Laboratories, Department of Anesthesia and Perioperative Care, University of California at San Francisco, San Francisco, California 94143-0542, USA. bicklerp@anesthesia.ucsf.edu
authors.forename: Philip E
authors.initials: PE
authors.lastname: Bickler
authors.forename: Christian S
authors.initials: CS
authors.lastname: Fahlman
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D015687:Cell Hypoxia; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D020287:In Situ Nick-End Labeling; D007530:Isoflurane / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism*; D010738:Type C Phospholipases / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology
chemical_list: D018685:Anesthetics, Inhalation; D018696:Neuroprotective Agents; D014157:Transcription Factors; D007530:Isoflurane; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D002118:Calcium