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PnPP‐19, a spider toxin peptide, induces peripheral antinociception through opioid and cannabinoid receptors and inhibition of neutral endopeptidase
Author(s) -
Freitas A C N,
Pacheco D F,
Machado M F M,
Carmona A K,
Duarte I D G,
Lima M E
Publication year - 2016
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.13448
Subject(s) - chemistry , cannabinoid , receptor , enkephalin , pharmacology , cannabinoid receptor , opioid , am251 , naltrindole , opioid peptide , opioid receptor , agonist , biochemistry , medicine
Background and Purpose The synthetic peptide PnPP‐19 has been studied as a new drug candidate to treat erectile dysfunction. However, PnTx2–6, the spider toxin from which the peptide was designed, induces hyperalgesia. Therefore, we intended to investigate the role of PnPP‐19 in the nociceptive pathway. Experimental Approach Nociceptive thresholds were measured by paw pressure test. PnPP‐19 was administered intraplantarly alone or with selective cannabinoid or opioid receptor antagonists. The hydrolysis of PnPP‐19 by neutral endopeptidase (NEP) (EC 3.4.24.11), an enzyme that cleaves enkephalin, was monitored by HPLC and the cleavage sites were deduced by LC–MS. Inhibition by PnPP‐19 and Leu‐enkephalin of NEP enzyme activity was determined spectrofluorimetrically. Key Results PnPP‐19 (5, 10 and 20 μg per paw) induced peripheral antinociception in rats. Specific antagonists of μ opioid receptors (clocinnamox), δ opioid receptors (naltrindole) and CB 1 receptors (AM251) partly inhibited the antinociceptive effect of PnPP‐19. Inhibition of fatty acid amide hydrolase by MAFP or of anandamide uptake by VDM11 enhanced PnPP‐19‐induced antinociception. NEP cleaved PnPP‐19 only after a long incubation, and K i values of 35.6 ± 1.4 and 14.6 ± 0.44 μmol·L −1 were determined for PnPP‐19 and Leu‐enkephalin respectively as inhibitors of NEP activity. Conclusions and Implications Antinociception induced by PnPP‐19 appears to involve the inhibition of NEP and activation of CB 1 , μ and δ opioid receptors. Our data provide a greater understanding of the antinociceptive effects of PnPP‐19. This peptide could be useful as a new antinociceptive drug candidate.