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Orexin A inhibits propofol-induced neurite retraction by a PLD-dependent mechanism in neurons
Linköping University, Department of Medical and Health Sciences, Anesthesiology. Linköping University, Faculty of Health Sciences. (Anestesiologi)
Linköping University, Department of Medical and Health Sciences, Anesthesiology. Linköping University, Faculty of Health Sciences. (Anestesiologi)
Linköping University, Department of Clinical and Experimental Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences. (Anestesiologi)
Linköping University, Department of Medical and Health Sciences, Anesthesiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Sinnescentrum, Department of Intensive Care UHL. (Anestesiologi)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Background: Propofol retracts neurites and reverses the transport of vesicles in rat cortical neurons in a γ-aminobutyric acid type A (GABAA) receptor dependent manner. Orexin A (OA) is an endogenous peptide regulating wakefulness, and is known to interact with anaesthetics. We aim to investigate whether OA inhibits propofol-induced neurite retraction and elucidate the intracellular signalling involved.

Methods: In primary cortical cell cultures from newborn rat brains, live cell light microscopy was used to measure neurite retraction after propofol (2 μM) with or without OA (10 nM) application after preincubation with the Rhokinase inhibitor (HA-1077), phospholipase D (PLD) inhibitor [5-fluoro-2- indolyl des-chlorohalopemide (FIPI)], protein kinase C (PKC) inhibitor (staurosporine) or PKC activator phorbol 12-myristate 13-acetate (PMA).

Results: The neurite retraction induced by propofol is blocked by HA-1077 and PMA. OA blocks neurite retraction induced by propofol, and this inhibitory effect could be prevented by FIPI, as well as staurosporine.

Conclusions: Rho-kinase is essential for propofol-induced neurite retraction in cortical neuronal cells. Activation of PKC plays an inhibitive role during neurite retraction caused by propofol. OA blocks propofol-induced neurite retraction by a PLD/PKC-mediated pathway.

Keyword [en]
Orexin A, propofol, PLD
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-77168OAI: oai:DiVA.org:liu-77168DiVA: diva2:525272
Available from: 2012-05-07 Created: 2012-05-07 Last updated: 2012-06-04Bibliographically approved
In thesis
1. Propofol changes the cytoskeletal function in neurons: An experimental study in cortical cultures
Open this publication in new window or tab >>Propofol changes the cytoskeletal function in neurons: An experimental study in cortical cultures
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Every day, general anaesthetics are given to a large number of patients around the world but the cellular mechanisms of how anaesthetics act are still not clear. General anaesthetics cause the intended unconsciousness, amnesia and immobility in patients, but also side effects such as a decrease in mean arterial pressure and arrhythmia, both of which contribute to complications such as heart damage and stroke. With more knowledge of the mechanism of anaesthetic drugs, these complications could be reduced.

It has been shown that anaesthetics cause a disruption of the thalamocortical connectivity and brain network connectivity. How the network communication is disrupted however is not known. Propofol and thiopental are both intravenous anaesthetic drugs used widely in clinical anaesthesia. They bind to the GABAA receptor and enhance its function.

The cytoskeleton helps the cell to maintain its shape and participate in cellular movement and transport. Cellular transport to and from a neuron’s cell body and periphery is performed by motor proteins that move vesicles, organelles and proteins along cytoskeletal tracks. We have previously shown that propofol causes a reorganisation of the cytoskeleton protein actin in neurons, but we were further interested to study the effects of propofol and thiopental on the cytoskeletal function of cultured cortical rat neurons.

Our results show that propofol and thiopental cause neurite (axon and dendrite) retraction. Propofol’s effects were time- and dose-dependent, and can be reversed when propofol is removed. We were able to inhibit propofolinduced neurite retraction if we stabilised actin by blocking either the motor protein myosin II or the GABAA receptor. We have previously shown that a small GTP-binding protein, RhoA, inhibits propofol-caused actin reorganisation. Propofol-induced neurite retraction was mediated via a downstream effector of RhoA, ROK, which induces phosphorylation of the myosin light chain and increases contractility. Furthermore, we have shown that propofol causes a switch from anterograde to retrograde transport and increases the average velocity of the moving vesicles in neurites. The propofol induced retrograde vesicle transport was GABAA receptor-mediated.

Orexin A is a neuropeptide which regulates the sleep/awake cycle and has also been shown to reduce anaesthesia in animals when given intracerebroventricularly. We found that orexin A reverses propofol and thiopental-induced neurite retraction and actin reorganisation. Moreover, we have shown that the orexin A inhibition of propofol-induced neurite retraction is mediated via the PLD/PKC intracellular signalling pathway. Propofol and thiopental decreased the tyrosine phosphorilation of the intermediate cytoskeletal protein vimentin which is reversed by orexin A.

Taken together, these results suggest that propofol causes a time- and dose-dependent, reversible and GABAAreceptor-mediated neurite retraction in cultured cortical rat neurons. Propofol also causes a switch from anterograde to retrograde vesicle transport in neurites. Orexin A reverses propofol and thiopental-induced neurite retraction and cytoskeletal reorganisation. Orexin A inhibits propofol-induced neurite retraction via the PLD/PKC intracellular signalling pathway.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 64 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1305
Keyword
Propofol, cytoskeleton
National Category
Medical and Health Sciences Basic Medicine Neurosciences
Identifiers
urn:nbn:se:liu:diva-77219 (URN)978-91-7519-910-8 (ISBN)
Public defence
2012-06-08, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2012-06-04 Created: 2012-05-08 Last updated: 2012-06-04Bibliographically approved

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Turina, DeanKarin, Björnström KarlssonSundqvist, TommyEintrei, Christina

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