title: The synthetic peptide PnPP-19 induces peripheral antinociception via activation of NO/cGMP/KATPpathway: Role of eNOS and nNOS.
abstract: BACKGROUND
  and purpose: The peptide PnPP-19, derived from the spider toxin PnTx2-6 (renamed as δ-CNTX-Pn1c), potentiates erectile function by activating the nitrergic system. Since NO has been studied as an antinociceptive molecule and PnPP-19 is known to induce peripheral antinociception, we intended to evaluate whether PnPP-19 could induce peripheral antinociception through activation of this pathway.
  
  
  METHODS
  Nociceptive thresholds were measured by paw pressure test. PGE2(2 μg/paw) was administered intraplantarly together with PnPP-19 and inhibitors/blockers of NOS, guanylyl cyclase and KATPchannels. The nitrite concentration was accessed by Griess test. The expression and phosphorylation of eNOS and nNOS were determined by western blot.
  
  
  RESULTS
  PnPP-19 (5, 10 and 20 μg/paw) induced peripheral antinociception in rats. Administration of NOS inhibitor (L-NOarg), selective nNOS inhibitor (L-NPA), guanylyl cyclase inhibitor (ODQ) and the blocker of KATP(glibenclamide) partially inhibited the antinociceptive effect of PnPP-19 (10 μg/paw). Tissue nitrite concentration increased after PnPP-19 (10 μg/paw) administration. Expression of eNOS and nNOS remained the same in all tested groups, however the phosphorylation of nNOS Ser852 (inactivation site) increased and phosphorylation of eNOS Ser1177 (activation site) decreased after PGE2injection. Administration of PnPP-19 reverted this PGE2-induced effect.
  
  
  CONCLUSIONS
  The peripheral antinociceptive effect induced by PnPP-19 is resulting from activation of NO-cGMP-KATPpathway. Activation of eNOS and nNOS might be required for such effect. Our results suggest PnPP-19 as a new drug candidate to treat pain and reinforce the importance of nNOS and eNOS activation, as well as endogenous NO release, for induction of peripheral antinociception.
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil.
authors.forename: A C N
authors.initials: AC
authors.lastname: Freitas
authors.affiliation: Departamento Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil.
authors.forename: G C
authors.initials: GC
authors.lastname: Silva
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil; Departamento Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil.
authors.forename: D F
authors.initials: DF
authors.lastname: Pacheco
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil.
authors.forename: A M C
authors.initials: AM
authors.lastname: Pimenta
authors.affiliation: Departamento Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil.
authors.forename: V S
authors.initials: VS
authors.lastname: Lemos
authors.affiliation: Departamento Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil.
authors.forename: I D G
authors.initials: ID
authors.lastname: Duarte
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil. Electronic address: melenalima@icb.ufmg.br.
authors.forename: M E
authors.initials: ME
authors.lastname: de Lima
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D006152:Cyclic GMP / Q000378:metabolism*; D005528:Foot / Q000503:physiopathology; D054086:KATP Channels / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000032:analysis / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000032:analysis / Q000378:metabolism*; D059408:Pain Management; D010455:Peptides / Q000494:pharmacology*; D017933:Peripheral Nervous System / Q000187:drug effects; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D013111:Spider Venoms
chemical_list: D000700:Analgesics; D054086:KATP Channels; D010455:Peptides; D013111:Spider Venoms; C540367:Tx2-6 protein, Phoneutria nigriventer; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496316:Nos3 protein, rat; D006152:Cyclic GMP
keywords: ATP-Sensitive potassium channels; Antinociception; Cyclic guanosine monophosphate; Endothelial nitric oxide synthase; K(ATP); NO; Neuronal nitric oxide synthase; Nitric oxide; PGE(2); Pain; PnPP-19; Prostaglandin E(2); Spider toxin; cGMP; eNOS; nNOS; nitric oxide