TY - JOUR
T1 - Nitric oxide-induced vasorelaxation in response to pntx2-6 toxin from phoneutria nigriventer spider in rat cavernosal tissue
AU - Nunes, Kenia P.
AU - Cordeiro, Marta N.
AU - Richardson, Michael
AU - Borges, Marcia N.
AU - Diniz, Simone O.F.
AU - Cardoso, Valbert N.
AU - Tostes, Rita
AU - De Lima, Maria Elena
AU - Webb, Robert Clinton
AU - Leite, Romulo
N1 - Funding Information:
This work was supported by NIH, FAPEMIG (Brazil) and INCTTOX (France). We thank Dr Brandi Wynne and Dr Fernando Carneiro for the suggestions.
PY - 2010/12
Y1 - 2010/12
N2 - Introduction. Priapism is one of several symptoms observed in accidental bites by the spider Phoneutria nigriventer. The venom of this spider is comprised of many toxins, and the majority has been shown to affect excitable ion channels, mainly sodium (Na+) channels. It has been demonstrated that PnTx2-6, a peptide extracted from the venom of P. nigriventer, causes erection in anesthetized rats and mice.Aim. We investigated the mechanism by which PnTx2-6 evokes relaxation in rat corpus cavernosum.Main Outcome Measures. PnTx2-6 toxin potentiates nitric oxide (NO)-dependent cavernosal relaxation.Methods. Rat cavernosal strips were incubated with bretylium (3 × 10-5 M) and contracted with phenylephrine (PE; 10-5 M). Relaxation responses were evoked by electrical field stimulation (EFS) or sodium nitroprusside (SNP) before and after 4 minutes of incubation with PnTx2-6 (10-8 M). The effect of PnTx2-6 on relaxation induced by EFS was also tested in the presence of atropine (10-6 M), a muscarinic receptor antagonist, N-type Ca2+ channel blockers (ω-conotoxin GVIA, 10-6 M) and sildenafil (3 × 10-8 M). Technetium99m radiolabeled PnTx2-6 subcutaneous injection was administrated in the penis.Results. Whereas relaxation induced by SNP was not affected by PnTx2-6, EFS-induced relaxation was significantly potentiated by this toxin as well as PnTx2-6 plus SNP. This potentiating effect was further increased by sildenafil, not altered by atropine, however was completely blocked by the N-type Ca2+ channels. High concentrated levels of radiolabeled PnTx2-6 was specifically found in the cavernosum tissue, suggesting PnTx2-6 is an important toxin responsible for P. nigriventer spider accident-induced priapism.Conclusion. We show that PnTx2-6 slows Na+ channels inactivation in nitrergic neurons, allowing Ca2+ influx to facilitate NO/cGMP signalling, which promotes increased NO production. In addition, this relaxation effect is independent of phosphodiesterase enzyme type 5 inhibition. Our data displays PnTx2-6 as possible pharmacological tool to study alternative treatments for erectile dysfunction.
AB - Introduction. Priapism is one of several symptoms observed in accidental bites by the spider Phoneutria nigriventer. The venom of this spider is comprised of many toxins, and the majority has been shown to affect excitable ion channels, mainly sodium (Na+) channels. It has been demonstrated that PnTx2-6, a peptide extracted from the venom of P. nigriventer, causes erection in anesthetized rats and mice.Aim. We investigated the mechanism by which PnTx2-6 evokes relaxation in rat corpus cavernosum.Main Outcome Measures. PnTx2-6 toxin potentiates nitric oxide (NO)-dependent cavernosal relaxation.Methods. Rat cavernosal strips were incubated with bretylium (3 × 10-5 M) and contracted with phenylephrine (PE; 10-5 M). Relaxation responses were evoked by electrical field stimulation (EFS) or sodium nitroprusside (SNP) before and after 4 minutes of incubation with PnTx2-6 (10-8 M). The effect of PnTx2-6 on relaxation induced by EFS was also tested in the presence of atropine (10-6 M), a muscarinic receptor antagonist, N-type Ca2+ channel blockers (ω-conotoxin GVIA, 10-6 M) and sildenafil (3 × 10-8 M). Technetium99m radiolabeled PnTx2-6 subcutaneous injection was administrated in the penis.Results. Whereas relaxation induced by SNP was not affected by PnTx2-6, EFS-induced relaxation was significantly potentiated by this toxin as well as PnTx2-6 plus SNP. This potentiating effect was further increased by sildenafil, not altered by atropine, however was completely blocked by the N-type Ca2+ channels. High concentrated levels of radiolabeled PnTx2-6 was specifically found in the cavernosum tissue, suggesting PnTx2-6 is an important toxin responsible for P. nigriventer spider accident-induced priapism.Conclusion. We show that PnTx2-6 slows Na+ channels inactivation in nitrergic neurons, allowing Ca2+ influx to facilitate NO/cGMP signalling, which promotes increased NO production. In addition, this relaxation effect is independent of phosphodiesterase enzyme type 5 inhibition. Our data displays PnTx2-6 as possible pharmacological tool to study alternative treatments for erectile dysfunction.
KW - Corpus Cavernosum
KW - Erectile Physiology
KW - Nitric Oxide
KW - PnTx2-6 Toxin
KW - Relaxation
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U2 - 10.1111/j.1743-6109.2010.01978.x
DO - 10.1111/j.1743-6109.2010.01978.x
M3 - Article
C2 - 20722794
AN - SCOPUS:78649825140
SN - 1743-6095
VL - 7
SP - 3879
EP - 3888
JO - Journal of Sexual Medicine
JF - Journal of Sexual Medicine
IS - 12
ER -