Sialorphin, a Natural Inhibitor of Rat Membrane-Bound Neutral Endopeptidase That Displays Analgesic Activity

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 100; no. 14; pp. 8549 - 8554
• Main Authors: Rougeot, Catherine, Messaoudi, Michaël, Hermitte, Véronique, Rigault, Anne Gaëlle, Blisnick, Thierry, Dugave, Christophe, Desor, Didier, Rougeon, François
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 08.07.2003; National Acad Sciences
• Subjects: Amino Acid Sequence; Analgesics; Analgesics - pharmacology; Analgesics - therapeutic use; Animals; Biological Sciences; Cell membranes; Enkephalin, Methionine; Enkephalin, Methionine - metabolism; Enzymes; Formaldehyde; Formaldehyde - toxicity; Glycopeptides; Glycopeptides - pharmacology; Hydrolysis; Kidney; Kidney - drug effects; Kidney - enzymology; Kidneys; Leucine; Leucine - analogs & derivatives; Leucine - pharmacology; Life Sciences; Male; Membrane Proteins; Membrane Proteins - antagonists & inhibitors; Membrane Proteins - physiology; Membranes; Molecular Sequence Data; Naltrexone; Naltrexone - analogs & derivatives; Naltrexone - pharmacology; Neprilysin; Neprilysin - antagonists & inhibitors; Pain; Pain - chemically induced; Pain - drug therapy; Pain Measurement; Pharmaceutical sciences; Prostate; Prostate - metabolism; Protease Inhibitors; Protease Inhibitors - pharmacology; Protease Inhibitors - therapeutic use; Protein Precursors; Protein Precursors - chemistry; Protein Precursors - pharmacology; Protein Precursors - physiology; Protein Precursors - therapeutic use; Rats; Rats, Wistar; Receptors; Receptors, Opioid, delta; Receptors, Opioid, delta - drug effects; Receptors, Opioid, delta - physiology; Receptors, Opioid, mu; Receptors, Opioid, mu - drug effects; Receptors, Opioid, mu - physiology; Rodents; Salivary Proteins and Peptides; Salivary Proteins and Peptides - chemistry; Salivary Proteins and Peptides - pharmacology; Salivary Proteins and Peptides - physiology; Salivary Proteins and Peptides - therapeutic use; sialorphin; Spinal Cord; Spinal Cord - drug effects; Spinal Cord - enzymology; Submandibular Gland; Submandibular Gland - metabolism; Substance P; Substance P - metabolism; Thiorphan; Thiorphan - pharmacology; Vcsa1 protein; Vehicles; Wounds and Injuries; Wounds and Injuries - physiopathology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1431850100

Sialorphin is an exocrine and endocrine signaling mediator, which has been identified by a genomic approach. It is synthesized predominantly in the submandibular gland and prostate of adult rats in response to androgen steroids and is released locally and systemically in response to stress. We now demonstrate that the cell surface molecule to which sialorphin binds in vivo in the rat kidney is the membrane-anchored neutral endopeptidase (neprilysin; NEP, EC 3.4.24.11). NEP plays an important role in nervous and peripheral tissues, as it turns off several peptide-signaling events at the cell surface. We show that sialorphin prevents spinal and renal NEP from breaking down its two physiologically relevant substrates, substance P and Met-enkephalin in vitro. Sialorphin inhibited the breakdown of substance P with an IC50of$0.4\!-\!1\>\mu M$and behaved as a competitive inhibitor. In vivo, i.v. sialorphin elicited potent antinociceptive responses in two behavioral rat models of injury-induced acute and tonic pain, the pin-pain test and formalin test. The analgesia induced by$100\!-\!200\>\mu g/kg$doses of sialorphin required the activation of μ- and δ-opioid receptors, consistent with the involvement of endogenous opioid receptors in enkephalinergic transmission. We conclude that sialorphin protects endogenous enkephalins released after nociceptive stimuli by inhibiting NEP in vivo. Sialorphin is a natural systemically active regulator of NEP activity. Furthermore, our study provides evidence that it is a physiological modulator of pain perception after injury and might be the progenitor of a new class of therapeutic molecules.