title: Pain inhibition by blocking leukocytic and neuronal opioid peptidases in peripheral inflamed tissue.
abstract: Inflammatory pain can be controlled by endogenous opioid peptides. Here we blocked the degradation of opioids in peripheral injured tissue to locally augment this physiological system. In rats with hindpaw inflammation, inhibitors of aminopeptidase N (APN; bestatin) or neutral endopeptidase (NEP; thiorphan), and a dual inhibitor, NH(2)-CH-Ph-P(O)(OH)CH(2)-CH-CH(2)Ph(p-Ph)-CONH-CH-CH(3)-COOH (P8B), were applied to injured paws. Combined bestatin (1.25-5 mg)/thiorphan (0.2-0.8 mg) or P8B (0.0625-1 mg) alone elevated mechanical nociceptive thresholds to 307 and 227% of vehicle-treated controls, respectively. This analgesia was abolished by antibodies to methionine-enkephalin, leucine-enkephalin, and dynorphin A 1-17, by peripherally restricted and by selective μ-, δ-, and κ-opioid receptor antagonists. Flow cytometry and photospectrometry revealed expression and metabolic activity of APN and NEP on macrophages, granulocytes, and sciatic nerves from inflamed tissue. Radioimmunoassays showed that inhibition of leukocytic APN and NEP by bestatin (5-500 μM)/thiorphan (1-100 μM) combinations or by P8B (1-100 μM) prevented the degradation of enkephalins. Blockade of neuronal peptidases by bestatin (0.5-10 mM)/thiorphan (0.1-5 mM) or by P8B (0.1-10 mM) additionally hindered dynorphin A 1-17 catabolism. Thus, leukocytes and peripheral nerves are important sources of APN and NEP in inflamed tissue, and their blockade promotes peripheral opioid analgesia.
authors.affiliation: Klinik für Anästhesiologie und operative Intensivmedizin, Freie Universität Berlin, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Schreiter
authors.forename: Carmen
authors.initials: C
authors.lastname: Gore
authors.forename: Dominika
authors.initials: D
authors.lastname: Labuz
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Fournie-Zaluski
authors.forename: Bernard P
authors.initials: BP
authors.lastname: Roques
authors.forename: Christoph
authors.initials: C
authors.lastname: Stein
authors.forename: Halina
authors.initials: H
authors.lastname: Machelska
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D018826:CD13 Antigens / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D004743:Enkephalin, Leucine / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005434:Flow Cytometry; D006614:Hindlimb / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology; D007249:Inflammation / Q000150:complications / Q000201:enzymology / Q000517:prevention & control*; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D007962:Leukocytes / Q000187:drug effects / Q000201:enzymology; D008297:Male; D009292:Narcotic Antagonists; D015260:Neprilysin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000201:enzymology; D018847:Opioid Peptides / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D010146:Pain / Q000150:complications / Q000201:enzymology / Q000517:prevention & control*; D017288:Pain Threshold / Q000187:drug effects; D010721:Phosphinic Acids / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011957:Receptors, Opioid / Q000378:metabolism; D015244:Thiorphan / Q000494:pharmacology
chemical_list: D000906:Antibodies; D004791:Enzyme Inhibitors; D009292:Narcotic Antagonists; D018847:Opioid Peptides; D010721:Phosphinic Acids; D011957:Receptors, Opioid; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D004399:Dynorphins; D015244:Thiorphan; D018826:CD13 Antigens; D015260:Neprilysin; D007930:Leucine; C012211:ubenimex; D000409:Alanine