Orexin A inhibits propofol-induced neurite retraction by a phospholipase D/protein kinase Cε-dependent mechanism in neurons.
BACKGROUND
The intravenous anaesthetic propofol retracts neurites and reverses the transport of vesicles in rat cortical neurons. Orexin A (OA) is an endogenous neuropeptide regulating wakefulness and may counterbalance anaesthesia. We aim to investigate if OA interacts with anaesthetics by inhibition of the propofol-induced neurite retraction.


METHODS
In primary cortical cell cultures from newborn rats' brains, live cell light microscopy was used to measure neurite retraction after propofol (2 µM) treatment with or without OA (10 nM) application. The intracellular signalling involved was tested using a protein kinase C (PKC) activator [phorbol 12-myristate 13-acetate (PMA)] and inhibitors of Rho-kinase (HA-1077), phospholipase D (PLD) [5-fluoro-2-indolyl des-chlorohalopemide (FIPI)], PKC (staurosporine), and a PKCε translocation inhibitor peptide. Changes in PKCε Ser729 phosphorylation were detected with Western blot.


RESULTS
The neurite retraction induced by propofol is blocked by Rho-kinase and PMA. OA blocks neurite retraction induced by propofol, and this inhibitory effect could be prevented by FIPI, staurosporine and PKCε translocation inhibitor peptide. OA increases via PLD and propofol decreases PKCε Ser729 phosphorylation, a crucial step in the activation of PKCε.


CONCLUSIONS
Rho-kinase is essential for propofol-induced neurite retraction in cortical neuronal cells. Activation of PKC inhibits neurite retraction caused by propofol. OA blocks propofol-induced neurite retraction by a PLD/PKCε-mediated pathway, and PKCε maybe the key enzyme where the wakefulness and anaesthesia signal pathways converge.
Department of Medical and Health Sciences, division of Anaesthesiology, Faculty of Health Sciences, Linköping University, Linköping, Sweden; Clinic of Anaesthesiology, Östergötland County Council UHL, Linköping, Sweden.
Karin
K
Björnström
Department of Medical and Health Sciences, division of Anaesthesiology, Faculty of Health Sciences, Linköping University, Linköping, Sweden; Clinic of Anaesthesiology, Östergötland County Council UHL, Linköping, Sweden.
Dean
D
Turina
Department of Medical and Health Sciences, division of Anaesthesiology, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
Tobias
T
Strid
Department of Clinical and Experimental Medicine, division of Medical Microbiology, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
Tommy
T
Sundqvist
Department of Medical and Health Sciences, division of Anaesthesiology, Faculty of Health Sciences, Linköping University, Linköping, Sweden; Clinic of Anaesthesiology, Östergötland County Council UHL, Linköping, Sweden.
Christina
C
Eintrei
D000818:Animals; D002478:Cells, Cultured; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects* / Q000378:metabolism; D009479:Neuropeptides / Q000494:pharmacology*; D000068797:Orexins; D010739:Phospholipase D / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D015742:Propofol / Q000494:pharmacology*; D051744:Protein Kinase C-epsilon / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D054460:rho-Associated Kinases / Q000378:metabolism
D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D054460:rho-Associated Kinases; D051744:Protein Kinase C-epsilon; D010739:Phospholipase D; D015742:Propofol