TY  - JOUR
A1  - Mambretti, Egle M.
A1  - Kistner, Katrin
A1  - Mayer, Stefanie
A1  - Massotte, Dominique
A1  - Kieffer, Brigitte L.
A1  - Hoffmann, Carsten
A1  - Reeh, Peter W.
A1  - Brack, Alexander
A1  - Asan, Esther
A1  - Rittner, Heike L.
T1  - Functional and structural characterization of axonal opioid receptors as targets for analgesia
JF  - Molecular Pain
N2  - Background
Opioids are the gold standard for the treatment of acute pain despite serious side effects in the central and enteric nervous system. µ-opioid receptors (MOPs) are expressed and functional at the terminals of sensory axons, when activated by exogenous or endogenous ligands. However, the presence and function of MOP along nociceptive axons remains controversial particularly in naïve animals. Here, we characterized axonal MOPs by immunofluorescence, ultrastructural, and functional analyses. Furthermore, we evaluated hypertonic saline as a possible enhancer of opioid receptor function.

Results
Comparative immunolabeling showed that, among several tested antibodies, which all provided specific MOP detection in the rat central nervous system (CNS), only one monoclonal MOP-antibody yielded specificity and reproducibility for MOP detection in the rat peripheral nervous system including the sciatic nerve. Double immunolabeling documented that MOP immunoreactivity was confined to calcitonin gene-related peptide (CGRP) positive fibers and fiber bundles. Almost identical labeling and double labeling patterns were found using mcherry-immunolabeling on sciatic nerves of mice producing a MOP-mcherry fusion protein (MOP-mcherry knock-in mice). Preembedding immunogold electron microscopy on MOP-mcherry knock-in sciatic nerves indicated presence of MOP in cytoplasm and at membranes of unmyelinated axons. Application of [D-Ala\(^2\), N-MePhe\(^4\), Gly-ol]-enkephalin (DAMGO) or fentanyl dose-dependently inhibited depolarization-induced CGRP release from rat sciatic nerve axons ex vivo, which was blocked by naloxone. When the lipophilic opioid fentanyl was applied perisciatically in naïve Wistar rats, mechanical nociceptive thresholds increased. Subthreshold doses of fentanyl or the hydrophilic opioid DAMGO were only effective if injected together with hypertonic saline. In vitro, using β-arrestin-2/MOP double-transfected human embryonic kidney cells, DAMGO as well as fentanyl lead to a recruitment of β-arrestin-2 to the membrane followed by a β-arrestin-2 reappearance in the cytosol and MOP internalization. Pretreatment with hypertonic saline prevented MOP internalization.

Conclusion
MOPs are present and functional in the axonal membrane from naïve animals. Hypertonic saline acutely decreases ligand-induced internalization of MOP and thereby might improve MOP function. Further studies should explore potential clinical applications of opioids together with enhancers for regional analgesia.
KW  - µ-Opioid receptor
KW  - hypertonic solution
KW  - fentanyl
KW  - calcitonin gene-related peptide
KW  - DAMGO
KW  - internalization
KW  - peripheral nerve
KW  - ultrastructure
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-145917
IS  - 12
ER  - 
TY  - JOUR
A1  - Oehler, Beatrice
A1  - Kistner, Katrin
A1  - Martin, Corinna
A1  - Schiller, Jürgen
A1  - Mayer, Rafaela
A1  - Mohammadi, Milad
A1  - Sauer, Reine-Solange
A1  - Filipovic, Milos R.
A1  - Nieto, Francisco R.
A1  - Kloka, Jan
A1  - Pflücke, Diana
A1  - Hill, Kerstin
A1  - Schaefer, Michael
A1  - Malcangio, Marzia
A1  - Reeh, Peter W.
A1  - Brack, Alexander
A1  - Blum, Robert
A1  - Rittner, Heike L.
T1  - Inflammatory pain control by blocking oxidized phospholipid-mediated TRP channel activation
JF  - Scientific Reports
N2  - Phospholipids occurring in cell membranes and lipoproteins are converted into oxidized phospholipids (OxPL) by oxidative stress promoting atherosclerotic plaque formation. Here, OxPL were characterized as novel targets in acute and chronic inflammatory pain. Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) and its derivatives were identified in inflamed tissue by mass spectrometry and binding assays. They elicited calcium influx, hyperalgesia and induced pro-nociceptive peptide release. Genetic, pharmacological and mass spectrometric evidence in vivo as well as in vitro confirmed the role of transient receptor potential channels (TRPA1 and TRPV1) as OxPAPC targets. Treatment with the monoclonal antibody E06 or with apolipoprotein A-I mimetic peptide D-4F, capturing OxPAPC in atherosclerosis, prevented inflammatory hyperalgesia, and in vitro TRPA1 activation. Administration of D-4F or E06 to rats profoundly ameliorated mechanical hyperalgesia and inflammation in collagen-induced arthritis. These data reveal a clinically relevant role for OxPAPC in inflammation offering therapy for acute and chronic inflammatory pain treatment by scavenging OxPAPC.
KW  - chronic pain
KW  - ion channels in the nervous system
KW  - molecular medicine
KW  - pain
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-158536
VL  - 7
IS  - 5447
ER  -