Perioperative Medicine  |   May 2017
Hypoxia Induces Internalization of κ-Opioid Receptor
Author Notes
  • From the Department of Anesthesia, Beijing Tongren Hospital, Capital Medical University, Beijing, China (C.X., X.L.); Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania (C.X., X.L., C.C., H.B., R.L.); and Department of Anesthesia, Beijing Shijitan Hospital, Capital Medical University, Beijing, China (T.L.).
  • C.X. and X.L. contributed equally to this article.
    C.X. and X.L. contributed equally to this article.×
  • Submitted for publication May 23, 2016. Accepted for publication January 17, 2017.
    Submitted for publication May 23, 2016. Accepted for publication January 17, 2017.×
  • Address correspondence to Dr. Liu: Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, 336 John Morgan Building, 3620 Hamilton Walk, Philadelphia, Pennsylvania 19104. liur@uphs.upenn.edu. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Perioperative Medicine / Basic Science / Pain Medicine / Pharmacology
Perioperative Medicine   |   May 2017
Hypoxia Induces Internalization of κ-Opioid Receptor
Anesthesiology 5 2017, Vol.126, 842-854. doi:10.1097/ALN.0000000000001571
Anesthesiology 5 2017, Vol.126, 842-854. doi:10.1097/ALN.0000000000001571
Abstract

Background: It has been demonstrated that κ-opioid receptor agonists can reduce hypoxia–ischemia brain injury in animal models. However, it is unclear how the κ-opioid receptor responds to hypoxia–ischemia. In the current study, the authors used an in vitro model of oxygen–glucose deprivation and reoxygenation to explore how κ-opioid receptors respond to hypoxia and reoxygenation.

Methods: Mouse neuroblastoma Neuro2A cells were stably transfected with mouse κ-opioid receptor–tdTomato fusion protein or Flag-tagged mouse κ-opioid receptor, divided into several groups (n = 6 to 12), and used to investigate the κ-opioid receptor movement. Observations were performed under normal oxygen, at 30 min to 1 h after oxygen–glucose deprivation and at 1 h after reoxygenation using high-resolution imaging techniques including immunoelectronmicroscopy in the presence and absence of κ-opioid receptor antagonist, dynamin inhibitors, potassium channel blockers, and dopamine receptor inhibitor.

Results: Hypoxic conditions caused the κ-opioid receptor to be internalized into the cells. Inhibition of dynamin by Dyngo-4a prevented the receptor internalization. Interestingly, a specific κ-opioid receptor antagonist norbinaltorphimine blocked internalization, suggesting the involvement of activation of a specific κ-opioid receptor. κ-Opioid receptor internalization appears to be reversed by reoxygenation. Quantities of intracellular κ-opioid receptor-associated gold particles as demonstrated by immunoelectron microscopy were increased from 37 to 85% (P < 0.01) after oxygen–glucose deprivation. Potassium channel blockers and dopamine receptor inhibitor failed to block hypoxia-induced κ-opioid receptor internalization.

Conclusions: Hypoxia induces reversible κ-opioid receptor internalization, which was inhibited by selective κ-opioid receptor antagonists or dynamin inhibitor, and can be reversed by reoxygenation in neuroblastoma cells, indicating the modulating effects between κ-opioid receptor and hypoxia via κ-opioid receptor activation and the dynamin-dependent mechanism.