RESUMO
The venom of the spider Phoneutria nigriventer contains several toxins that have bioactivity in mammals and insects. Accidents involving humans are characterized by various symptoms including penile erection. Here we investigated the action of Tx2-6, a toxin purified from the P. nigriventer spider venom that causes priapism in rats and mice. Erectile function was evaluated through changes in intracavernosal pressure/mean arterial pressure ratio (ICP/MAP) during electrical stimulation of the major pelvic ganglion (MPG) of normotensive and deoxycorticosterone-acetate (DOCA)-salt hypertensive rats. Nitric oxide (NO) release was detected in cavernosum slices with fluorescent dye (DAF-FM) and confocal microscopy. The effect of Tx2-6 was also characterized after intracavernosal injection of a non-selective nitric oxide synthase (NOS) inhibitor, L-NAME. Subcutaneous or intravenous injection of Tx2-6 potentiated the elevation of ICP/MAP induced by ganglionic stimulation. L-NAME inhibited penile erection and treatment with Tx2-6 was unable to reverse this inhibition. Tx2-6 treatment induced a significant increase of NO release in cavernosum tissue. Attenuated erectile function of DOCA-salt hypertensive rats was fully restored after toxin injection. Tx2-6 enhanced erectile function in normotensive and DOCA-salt hypertensive rats, via the NO pathway. Our studies suggest that Tx2-6 could be important for development of new pharmacological agents for treatment of erectile dysfunction.
Assuntos
Neuropeptídeos/farmacologia , Neurotoxinas/farmacologia , Ereção Peniana/efeitos dos fármacos , Pênis/efeitos dos fármacos , Venenos de Aranha/farmacologia , Aranhas , Animais , Modelos Animais de Doenças , Sinergismo Farmacológico , Estimulação Elétrica , Disfunção Erétil/complicações , Disfunção Erétil/tratamento farmacológico , Disfunção Erétil/fisiopatologia , Hipertensão/induzido quimicamente , Hipertensão/complicações , Hipertensão/fisiopatologia , Masculino , NG-Nitroarginina Metil Éster/farmacologia , Neuropeptídeos/isolamento & purificação , Neurotoxinas/isolamento & purificação , Óxido Nítrico/metabolismo , Ereção Peniana/fisiologia , Pênis/inervação , Pênis/metabolismo , Ratos , Ratos WistarRESUMO
In the current study, the putative cDNA for PnTx2-6 toxin of the Phoneutria nigriventer spider venom was cloned and expressed as tioredoxin fusion protein in the cytoplasm of Escherichia coli. The fusion protein was purified from the bacterial extracts by combination of immobilized Ni-ion affinity and gel filtration chromatographies. Then, it was cleaved by enterokinase and the generated recombinant PnTx2-6 (rPnTx2-6) was further purified by reverse-phase HPLC. Likewise the native toxin purified from the spider venom, rPnTx2-6 potentiates the erectile function when injected in rats. This result indicates that the production of functional recombinant PnTx2-6 might be an alternative to provide this basic and valuable tool for study, as well as for further understanding such complex physiological system, including its correlation with the central nervous system and local tissue factors.