Isoflurane induces endoplasmic reticulum stress and caspase activation through ryanodine receptors.
BACKGROUND
Isoflurane has been reported to induce caspase-3 activation, which may induce neurotoxicity and contribute to the pathogenesis of Alzheimer's disease. However, the underlying mechanism is largely unknown, especially whether or not isoflurane can induce ryanodine receptors (RyRs)-associated endoplasmic reticulum (ER) stress, leading to caspase-3 activation. We therefore assessed the effects of isoflurane on RyRs-associated ER stress.


METHODS
We treated primary neurones from wild-type (C57BL/6J) mice with 1% and 2% isoflurane for 1, 3, or 6 h. We then measured levels of C/EBP homologous protein (CHOP) and caspase-12, two ER stress markers, using immunocytochemistry staining and western blotting analysis. Dantrolene (5 μM), the antagonist of RyRs, was used to investigate the role of RyRs in the isoflurane-induced ER stress and caspase-3 activation.


RESULTS
Isoflurane 2% for 6 h treatment increased the levels of CHOP (876% vs 100%, P=0.00009) and caspase-12 (276% vs 100%, P=0.006), and induced caspase-3 activation in the neurones. The administration of 2% isoflurane for 3 h (shorter duration), however, only increased the levels of CHOP (309% vs 100%, P=0.003) and caspase-12 (266% vs 100%, P=0.001), without causing caspase-3 activation. The isoflurane-induced ER stress (CHOP: F=16.64, P=0.0022; caspase-12: F=6.13, P=0.0383) and caspase-3 activation (F=32.06, P=0.0005) were attenuated by the dantrolene treatment.


CONCLUSIONS
These data imply that isoflurane might induce caspase-3 activation by causing ER stress through RyRs, and dantrolene could attenuate the isoflurane-induced ER stress and caspase-3 activation. Further investigations of the potential neurotoxicity of isoflurane are needed.
Geriatric Anaesthesia Research Unit, Department of Anaesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 149 13th St., Room 4310, Charlestown, MA 02129-2060, USA Department of Anaesthesiology, Tianjin Medical University General Hospital, Tianjin Research Institute of Anaesthesiology, Tianjin 300052, PR China.
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Wang
Geriatric Anaesthesia Research Unit, Department of Anaesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 149 13th St., Room 4310, Charlestown, MA 02129-2060, USA.
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Dong
Geriatric Anaesthesia Research Unit, Department of Anaesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 149 13th St., Room 4310, Charlestown, MA 02129-2060, USA Department of Anaesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China.
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Zhang
Geriatric Anaesthesia Research Unit, Department of Anaesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 149 13th St., Room 4310, Charlestown, MA 02129-2060, USA.
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Xu
Department of Anaesthesiology, Tianjin Medical University General Hospital, Tianjin Research Institute of Anaesthesiology, Tianjin 300052, PR China.
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Wang
Geriatric Anaesthesia Research Unit, Department of Anaesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 149 13th St., Room 4310, Charlestown, MA 02129-2060, USA.
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Swain
Geriatric Anaesthesia Research Unit, Department of Anaesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 149 13th St., Room 4310, Charlestown, MA 02129-2060, USA.
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Zhang
Geriatric Anaesthesia Research Unit, Department of Anaesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 149 13th St., Room 4310, Charlestown, MA 02129-2060, USA zxie@partners.org.
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Xie
D000199:Actins / Q000378:metabolism; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D053454:Caspase 12 / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D003620:Dantrolene / Q000494:pharmacology; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D007150:Immunohistochemistry; D007530:Isoflurane / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects*; D051742:Transcription Factor CHOP / Q000378:metabolism
D000199:Actins; D018685:Anesthetics, Inhalation; C497250:Ddit3 protein, mouse; D009125:Muscle Relaxants, Central; D019837:Ryanodine Receptor Calcium Release Channel; D051742:Transcription Factor CHOP; D007530:Isoflurane; D053454:Caspase 12; D053148:Caspase 3; D020169:Caspases; D003620:Dantrolene
endoplasmic reticulum; inhalation anaesthetics, isoflurane; receptors, ryanodine