title: Immune cell-derived opioids protect against neuropathic pain in mice.
abstract: The analgesic effects of leukocyte-derived opioids have been exclusively demonstrated for somatic inflammatory pain, for example, the pain associated with surgery and arthritis. Neuropathic pain results from injury to nerves, is often resistant to current treatments, and can seriously impair a patient's quality of life. Although it has been recognized that neuronal damage can involve inflammation, it is generally assumed that immune cells act predominately as generators of neuropathic pain. However, in this study we have demonstrated that leukocytes containing opioids are essential regulators of pain in a mouse model of neuropathy. About 30%-40% of immune cells that accumulated at injured nerves expressed opioid peptides such as beta-endorphin, Met-enkephalin, and dynorphin A. Selective stimulation of these cells by local application of corticotropin-releasing factor led to opioid peptide-mediated activation of opioid receptors in damaged nerves. This ultimately abolished tactile allodynia, a highly debilitating heightened response to normally innocuous mechanical stimuli, which is symptomatic of neuropathy. Our findings suggest that selective targeting of opioid-containing immune cells promotes endogenous pain control and offers novel opportunities for management of painful neuropathies.
authors.affiliation: Klinik für Anaesthesiologie und operative Intensivmedizin, Freie Universität Berlin, Medizinische Fakultät Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Dominika
authors.initials: D
authors.lastname: Labuz
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Schmidt
authors.forename: Anja
authors.initials: A
authors.lastname: Schreiter
authors.forename: Heike L
authors.initials: HL
authors.lastname: Rittner
authors.forename: Shaaban A
authors.initials: SA
authors.lastname: Mousa
authors.forename: Halina
authors.initials: H
authors.lastname: Machelska
mesh_terms: D000818:Animals; D003346:Corticotropin-Releasing Hormone; D007962:Leukocytes / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018847:Opioid Peptides / Q000502:physiology*; D010146:Pain / Q000517:prevention & control*; D010523:Peripheral Nervous System Diseases / Q000517:prevention & control*; D011957:Receptors, Opioid / Q000502:physiology
chemical_list: D018847:Opioid Peptides; D011957:Receptors, Opioid; D003346:Corticotropin-Releasing Hormone