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Marta N. Cordeiro - One of the best experts on this subject based on the ideXlab platform.

  • Immunodetection of toxins in historesin-embedded sections of Phoneutria nigriventer venom glands using laser confocal scanning microscopy.
    Toxicon, 2019
    Co-Authors: Luciana Maria Silva, Paulo Filemon Paolucci Pimenta, Rafael Nacif-pimenta, Marta N. Cordeiro, Carlos Chávez-olórtegui, Paula Ladeira Ortolani, Layla Mosqueira Moura, Consuelo Latorre Fortes-dias
    Abstract:

    In the last decades, main advances were achieved in the identification, structural and pharmacological characterization of Phoneutria nigriventer toxins. However, studies on the venom-producing apparatus are rare. Presently, we applied immunolabeling to historesin-embedded cross-sections of P. nigriventer venom glands. Toxins and toxin-secreting cells were successfully located in situ, using laser confocal scanning microscopy. The methodological strategy was successful and may be applied in future studies on venom glands and other secreting tissues, in general.

  • Phoneutria nigriventer spider toxin pntx2 1 δ ctenitoxin pn1a is a modulator of sodium channel gating
    Toxins, 2018
    Co-Authors: Steve Peigneur, Ana Luiza Bittencourt Paiva, Marta N. Cordeiro, Maria Elena De Lima, Marcia Helena Borges, Marcelo Ribeiro Vasconcelos Diniz, Jan Tytgat
    Abstract:

    : Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian NaV-channel isoforms, one insect NaV channel and one arachnid NaV channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on NaV1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac NaV channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current.

  • Phoneutria nigriventer Spider Toxin PnTx2-1 (δ-Ctenitoxin-Pn1a) Is a Modulator of Sodium Channel Gating
    MDPI AG, 2018
    Co-Authors: Steve Peigneur, Marta N. Cordeiro, Maria Elena De Lima, Marcia Helena Borges, Marcelo Ribeiro Vasconcelos Diniz, Ana Luiza B. Paiva, Jan Tytgat
    Abstract:

    Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian NaV-channel isoforms, one insect NaV channel and one arachnid NaV channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on NaV1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac NaV channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current

  • The Phoneutria nigriventer spider toxin, PnTx4-5-5, promotes neuronal survival by blocking NMDA receptors.
    Toxicon, 2016
    Co-Authors: Flavia Rodrigues Da Silva, Marta N. Cordeiro, Christopher Kushmerick, Marcus Vinicius Gomez, Luciene B Vieira, Edleusa M. L. Batista, Juliana F. Da Silva, Fabiola M. Ribeiro
    Abstract:

    Spider toxins are recognized as useful sources of bioactive substances, showing a wide range of pharmacological effects on neurotransmission. Several spider toxins have been identified biochemically and some of them are specific glutamate receptors antagonists. Previous data indicate that PnTx4-5-5, a toxin isolated from the spider Phoneutria nigriventer, inhibits the N-methyl-d-aspartate receptor (NMDAR), with little or no effect on AMPA, kainate or GABA receptors. In agreement with these results, our findings in this study show that PnTx4-5-5 reduces the amplitude of NMDAR-mediated EPSCs in hippocampal slices. It is well established that glutamate-mediated excitotoxic neuronal cell death occurs mainly via NMDAR activation. Thus, we decided to investigate whether PnTx4-5-5 would protect against various cell death insults. For that, we used primary-cultured corticostriatal neurons from wild type (WT) mice, as well as from a mouse model of Huntington's disease, BACHD. Our results showed that PnTx4-5-5 promotes neuroprotection of WT and BACHD neurons under the insult of high levels of glutamate. Moreover, the toxin is also able to protect WT neurons against amyloid β (Aβ) peptide toxicity. These results indicate that the toxin PnTx4-5-5 is a potential neuroprotective drug.

  • Mechanisms Involved in the Nociception Triggered by the Venom of the Armed Spider Phoneutria nigriventer
    PLOS Neglected Tropical Diseases, 2013
    Co-Authors: Camila De Campos Velho Gewehr, Marta N. Cordeiro, Sara Marchesan Oliveira, Mateus Fortes Rossato, Gabriela Trevisan, Gerusa Duarte Dalmolin, Juliano Ferreira, Flávia Karine Rigo, Célio José De Castro Junior, Marcus V. Gomez
    Abstract:

    BACKGROUND: The frequency of accidental spider bites in Brazil is growing, and poisoning due to bites from the spider genus Phoneutria nigriventer is the second most frequent source of such accidents. Intense local pain is the major symptom reported after bites of P. nigriventer, although the mechanisms involved are still poorly understood. Therefore, the aim of this study was to identify the mechanisms involved in nociception triggered by the venom of Phoneutria nigriventer (PNV). METHODOLOGYPRINCIPAL FINDINGS: Twenty microliters of PNV or PBS was injected into the mouse paw (intraplantar, i.pl.). The time spent licking the injected paw was considered indicative of the level of nociception. I.pl. injection of PNV produced spontaneous nociception, which was reduced by arachnid antivenin (ArAv), local anaesthetics, opioids, acetaminophen and dipyrone, but not indomethacin. Boiling or dialysing the venom reduced the nociception induced by the venom. PNV-induced nociception is not dependent on glutamate or histamine receptors or on mast cell degranulation, but it is mediated by the stimulation of sensory fibres that contain serotonin 4 (5-HT4) and vanilloid receptors (TRPV1). We detected a kallikrein-like kinin-generating enzyme activity in tissue treated with PNV, which also contributes to nociception. Inhibition of enzymatic activity or administration of a receptor antagonist for kinin B2 was able to inhibit the nociception induced by PNV. PNV nociception was also reduced by the blockade of tetrodotoxin-sensitive Na(+) channels, acid-sensitive ion channels (ASIC) and TRPV1 receptors. CONCLUSIONSIGNIFICANCE: Results suggest that both low- and high-molecular-weight toxins of PNV produce spontaneous nociception through direct or indirect action of kinin B2, TRPV1, 5-HT4 or ASIC receptors and voltage-dependent sodium channels present in sensory neurons but not in mast cells. Understanding the mechanisms involved in nociception caused by PNV are of interest not only for better treating poisoning by P. nigriventer but also appreciating the diversity of targets triggered by PNV toxins. Language: en

Edson Antunes - One of the best experts on this subject based on the ideXlab platform.

  • Systemic envenomation caused by the wandering spider Phoneutria nigriventer, with quantification of circulating venom
    Clinical Toxicology, 2008
    Co-Authors: Fabio Bucaretchi, Ronan Jose Vieira, Sueli Moreira Mello, Ronei Luciano Mamoni, Maria Heloisa Souza Lima Blotta, Edson Antunes
    Abstract:

    Introduction. Bites by Phoneutria spp. spiders are common in Brazil, although only 0.5–1% result in severe envenomation, with most of these occurring in children. Cases of systemic envenomation in adults are very unusual, and no serum venom levels have been previously quantified in these cases. Case report. A 52-year-old man was bitten on the neck by an adult female Phoneutria nigriventer. Immediately after the bite, there was intense local pain followed by blurred vision, profuse sweating, tremors, and an episode of vomiting; 1–2 h post bite the patient showed agitation and a blood pressure of 200/130 mmHg, and was given captopril and meperidine. Upon admission to our service 4 h post bite (time zero – T0), his blood pressure was 130/80 mmHg with a heart rate of 150 beats/min, mild tachypnea, agitation, cold extremities, profuse sweating, generalized tremors, and priapism. The patient was treated with antivenom, local anesthetic, and fluid replacement. Most of the systemic manifestations disappeared within 1 h after antivenom. Laboratory blood analyses at T0, T1, T6, T24, and T48 detected circulating venom by ELISA only at T0, before antivenom infusion (47.5 ng/mL; cut-off, 17.1 ng/mL); his serum blood sugar was 163 mg/dL at T0. The patient was discharged on the second day with a normal arterial blood pressure and a follow-up evaluation revealed no sequelae. Conclusion. This is the first report of confirmed moderate/severe envenoming in an adult caused by P. nigriventer with the quantification of circulating venom.

  • Role of Ca2+ in vascular smooth muscle contractions induced by Phoneutria nigriventer spider venom.
    Toxicon : official journal of the International Society on Toxinology, 2004
    Co-Authors: Cleber E. Teixeira, Gilberto De Nucci, A.p. Corrado, Edson Antunes
    Abstract:

    Abstract Phoneutria nigriventer venom (PNV) contracts vascular tissues and increases arterial blood pressure. This study aimed to investigate the mechanisms involved on PNV-induced contractions of rabbit mesenteric and celiac arteries. Strips of mesenteric and celiac arteries were suspended in a cascade system and superfused with warmed and oxygenated Krebs solution. PNV was dialyzed in order to exclude the participation of biogenic amines in the contractions elicited by the venom. Noradrenaline (NA, 30–300 pmol), PNV (1–10 μg), Bay K-8644 (0.3–3 nmol) and KCl (10–100 μmol) dose-dependently contracted the preparations. Ca 2+ -free solution reduced by 38 and 83% the PNV-induced contractions of mesenteric and celiac arteries, respectively. Subsequent infusion of EGTA (0.2 mM) suppressed the residual contractions. Nifedipine (1 μM) and verapamil (10 μM) abolished PNV- and Bay K-8644-evoked contractions, whereas those induced by NA were reduced to a lesser extent. Lanthanum chloride (0.2 mM) inhibited by 75–90% the mesenteric and celiac contractions mediated by PNV. Caffeine (2 mM) fully blocked contractions induced by NA (95% mean inhibition), but only partly reduced those induced by PNV (35% mean inhibition). Ryanodine (10 μM) inhibited by 50% the contractions evoked by NA, but had no effect on the PNV-induced contractions in both tissues. Our findings indicate that PNV contracts vascular smooth muscle mainly due to increased influx of Ca 2+ from extracellular sources.

  • Phoneutria nigriventer spider venom activates 5-HT4 receptors in rat-isolated vagus nerve.
    British journal of pharmacology, 2003
    Co-Authors: Soraia K.p. Costa, Gilberto De Nucci, Edson Antunes, Susan D. Brain, R. J. Docherty
    Abstract:

    The venom of Phoneutria nigriventer spider (PNV) causes intense pain and inflammation following an attack. We have investigated the involvement of capsaicin-sensitive nerve fibres by utilizing an in vitro nerve preparation. Extracellular DC potential recordings were made from the rat-isolated vagus nerve, a preparation that is rich in capsaicin-sensitive, that is, nociceptive, C-fibres. PNV (1–10 μg ml−1), capsaicin (0.03–0.3 μM) or 5-hydroxytriptamine (5-HT) (0.3–3 μM) induced dose-dependent depolarizations of vagus nerve fibres. Depolarizing responses to capsaicin were blocked by ruthenium red (RR, 10 μM), but responses to PNV were not. Depolarizing responses to PNV or veratridine (50 μM) were inhibited by tetrodotoxin (TTX, 10 μM), but those to capsaicin were not. This suggests that capsaicin and PNV depolarize the nerve fibres by distinct mechanisms. Depolarization in response to 5-HT (3 μM) was reduced by the 5-HT3 receptor antagonists Y25130 (0.5 μM) and tropisetron (10 nM) or, to a lesser extent, by the 5-HT4 receptor antagonist RS39604 (1 or 10 μM). Depolarizing responses to PNV were not affected significantly by Y25130 or tropisetron, but were blocked by RS39604. These data show that 5-HT4 receptors play a significant role in the activation of nociceptive sensory nerve fibres by PNV and suggest that this is of importance in the development of the pain and inflammation associated with bites from the P. nigriventer spider. British Journal of Pharmacology (2003) 139, 59–64. doi:10.1038/sj.bjp.0705240

  • Role of kinins and sensory neurons in the rat pleural leukocyte migration induced by Phoneutria nigriventer spider venom.
    Neuroscience letters, 2002
    Co-Authors: Soraia K.p. Costa, Gilberto De Nucci, Susan D. Brain, Laura C.m. Esquisatto, Ronilson Agnaldo Moreno, Luiz Juliano, Edson Antunes
    Abstract:

    Abstract The leukocyte migration induced by Phoneutria nigriventer spider venom (PNV) has been investigated in rats using the pleurisy model. Intrapleural injection of PNV (10–100 μg/cavity) caused a dose- and time-dependent leukocyte accumulation. The bradykinin B 2 receptor antagonist Hoe 140 (0.5 mg/kg) substantially inhibited PNV-induced cell accumulation, whereas the angiotensin-converting enzyme inhibitor captopril (2 mg/kg) potentiated by 80% this effect. The non-specific kallikrein inhibitor aprotinin and the plasma kallikrein inhibitor soybean trypsin inhibitor greatly reduced PNV-induced leukocyte migration, whereas the selective tissue kallikrein inhibitor P ac -F-S-R-EDDnp failed to affect PNV-induced responses. Treatment of rats with capsaicin (50 mg/kg) at the neonatal stage resulted in 67% inhibition of the PNV-induced cell migration. The neurokinin NK 1 receptor antagonist SR140333, but not the NK 2 receptor antagonist SR48968, reduced by 55% venom-induced cell accumulation. We conclude that bradykinin generation is involved in the PNV-induced pleural leukocyte migration in rats, where it can directly activate sensory nerves contributing to a neurogenic inflammatory mechanism.

  • Comparative effect of Phoneutria nigriventer spider venom and capsaicin on the rat paw oedema
    Life Sciences, 2001
    Co-Authors: Soraia K.p. Costa, Gilberto De Nucci, Susan D. Brain, Laura C.m. Esquisatto, Enilton A. Camargo, Alessandra Gambero, Edson Antunes
    Abstract:

    Abstract Capsaicin, the pungent component of hot peppers, and the venom of the spider Phoneutria nigriventer are able to activate sensory nerves resulting in cutaneous neurogenic plasma extravasation. This study was undertaken to compare the ability of these substances to evoke oedema in the rat hind-paw and mechanisms underlying this effect. Subplantar injection of either Phoneutria nigriventer venom (PNV; 1–100 μg/paw) or capsaicin (10–200 μg/paw) caused a significant paw oedema that was potentiated by CGRP (10 pmol/paw). In rats treated neonatally with capsaicin to deplete neuropeptides, the paw oedema induced by either PNV (100 μg/paw) or capsaicin (100 μg/paw) was partially reduced (P 1 receptor antagonist SR140333 (0.2 μmol/kg; i.v.) prevented the paw oedema induced by the tachykinin NK 1 receptor agonist GR73632 (30 pmol/paw) and partially reduced paw oedema induced by PNV or capsaicin. Treatment of rats with compound 48/80 (5 mg/kg; s.c. 3 days) or with both H 1 receptor antagonist (mepyramine; 1 nmol/paw) and 5-HT receptor antagonist (methysergide; 1 nmol/paw) significantly inhibited PNV- or capsaicin-induced paw oedema. The combined treatment with mepyramine and methysergide and SR140333 further reduced PNV- and capsaicin-induced paw oedema. The bradykinin B 2 receptor antagonist Hoe 140 affected neither PNV- nor capsaicin-induced responses. Our results suggest that PNV and capsaicin each induce paw oedema that is partially mediated by activation of sensory fibers culminating in the release of substance P as well as by activation of mast cells which in turn release amines such as histamine and 5-HT.

Evanguedes Kalapothakis - One of the best experts on this subject based on the ideXlab platform.

  • Neuropharmacological effects of Phoneutria nigriventer venom on astrocytes
    Neurochemistry International, 2016
    Co-Authors: Catarina Rapôso, Evanguedes Kalapothakis, Maria Alice Da Cruz Höfling, Ulrika Björklund, Björn Biber, Elisabeth Hansson
    Abstract:

    Bites from genus Phoneutria (Ctenidae, Araneomorpha) are the second most frequent source of spider accidents in Southeast Brazil. Severe envenoming from Phoneutria nigriventer produces vision disturbance, tremor and convulsion, suggesting that the CNS is involved; however, the mechanisms by which P. nigriventer venom (PNV) affects the CNS remain poorly understood. The present study aimed to investigate whether PNV directly impairs astrocytes. Cultured astrocytes were exposed to PNV, and intracellular Ca(2+) release and signaling were measured (Fura-2/AM), Na(+)/K(+)-ATPase and Toll-like receptor 4 (TLR4) involvement were investigated, actin filaments were stained (Alexa™ 488-conjugated phalloidin probe), the G-actin/F-actin ratio was determined, and the expression level of connexin 43 (Cx43) was assessed. Incubation in Ca(2+)-free buffer did not change the Ca(2+) responses. However, pre-incubation in thapsigargin/caffeine completely abolished these responses, suggesting that PNV-evoked Ca(2+) transients were from intracellular Ca(2+) stores. Pretreatment with a Na(+)/K(+)-ATPase antagonist (ouabain) or a TLR4 antagonist (LPS-RS) decreased or increased the Ca(2+)-evoked transients, respectively. Astrocytes showed altered actin filament structure after PNV exposure. PNV treatment increased the expression levels of Na(+)/K(+)-ATPase and Cx43 but decreased those of TLR4. The present results suggest that PNV directly affects astrocytes. Na(+)/K(+)-ATPase may thus represent a more specific drug target for controlling the neurotoxicity of PNV.

  • In vitro effect of the Phoneutria nigriventer spider venom on cell viability, paracellular barrier function and transcellular transport in cultured cell lines
    Toxicon : official journal of the International Society on Toxinology, 2005
    Co-Authors: Luciana De Paula Le Sueur, Evanguedes Kalapothakis, C. B. Collares-buzato, Maria Alice Da Cruz Höfling
    Abstract:

    Phoneutria nigriventer spider venom (PNV) induces, in rats, local edema as result of an increased vascular permeability, as well as causes blood–brain barrier (BBB) breakdown by altering transendothelial transport routes in hippocampal microvessels. In this work we investigated the in vitro effects of PNV on cell viability and cellular transport routes using three cell lines, the ECV304 endothelial-, the C6 glioma- and the MDCK epithelial cells. We showed that PNV (14.6 and 292 μg crude venom/ml culture medium) had no direct cytotoxic effect on both the ECV304 and the MDCK cell lines but slightly reduced the viability of C6 glioma cells (P

  • Molecular cloning and characterization of Phoneutria nigriventer toxins active on calcium channels.
    Toxicon, 2003
    Co-Authors: Fernanda C. Cardoso, Carlos Chávez-olórtegui, Marcus Vinicius Gomez, L.g Pacı́fico, D.c Carvalho, Júnia Maria Netto Victória, A.l.g Neves, Evanguedes Kalapothakis
    Abstract:

    The aim of the present study was the molecular cloning of toxins active on calcium channels expressed by the spider Phoneutria nigriventer. Clones encoding the toxins Pn3-3A, Pn3-4A, Tx3-5, Pn3-5A, Tx3-6, Pn3-6A and Pn3-6B were identified from a cDNA library derived from the venom gland of this spider, revealing toxins of 49, 76, 45, 39, 55 and 58 amino acids residues, respectively, with polypeptide precursors being composed of three major portions: a signal peptide, a propeptide and finally, the mature toxin. A high degree of homology with the amino acid sequence was found between Pn3-3A and the neurotoxin Tx3-3 (identity of 79%), and between Pn3-4A and the neurotoxin Tx3-4 (identity of 95%). The deduced amino acid sequence for the mature polypeptides Tx3-5 and Tx3-6 confirms the polypeptide sequence previously published for these neurotoxins. In addition, the toxin Pn3-5A showed 58% identity to the Tx3-5 amino acid sequence, and the toxins Pn3-6A and Pn3-6B showed 85 and 33% identity, respectively, to the Tx3-6 amino acid sequence.

  • Expression of a functional recombinant Phoneutria nigriventer toxin active on K+ channels.
    Toxicon, 2003
    Co-Authors: Ana Carneiro, Marcus V. Gomez, Evanguedes Kalapothakis, Marta N. Cordeiro, Christopher Kushmerick, Janaina Koenen, M.h.l. Arndt, Carlos Chávez-olórtegui, Marco A. M. Prado
    Abstract:

    PnTx3-1 is a peptide isolated from the venom of the spider Phoneutria nigriventer that specifically inhibits A-type K+ currents (IA) in GH3 cells. Here we used a bacterial expression system to produce an NH2-extended mutant of PnTx3-1 (ISEF-PnTx3-1) and tested whether the toxin is functional. The recombinant toxin was purified from bacterial extracts by a combination of affinity and ion-exchange chromatography. The recombinant toxin blocked A-type K+ currents in GH3 cells in a fashion similar to that observed with the wild-type toxin purified from the spider venom. These results suggest that recombinant cDNA methods provide a novel source for the production of functional Phoneutria toxins. The recombinant ISEF-PnTx3-1 should be useful for further understanding of the role of A-type K+ currents in biological processes.

  • Breakdown of the blood-brain barrier and neuropathological changes induced by Phoneutria nigriventer spider venom
    Acta Neuropathologica, 2003
    Co-Authors: Luciana De Paula Le Sueur, Evanguedes Kalapothakis, Maria Alice Da Cruz Höfling
    Abstract:

    The blood-brain barrier (BBB) is responsible for selective flux of substances between blood and brain. The selective permeability of the BBB is crucial for the maintenance of the brain microenvironment homeostasis, and alterations in the barrier may be involved in many pathophysiological processes. Phoneutria nigriventer armed spider venom produces excitatory signals and symptoms in humans, and its recognized neurotoxic action suggests a potential ability to alter BBB permeability. The aim of the present study was to investigate the capacity of P. nigriventer venom (PNV) in promoting BBB breakdown in adult rats. After intravenous injection of 850 µg/kg of the whole venom, BBB lesions were evaluated after 18 h to 9 days by ultrastructural methods using the extracellular tracer lanthanum nitrate. Clinical signs and symptoms of rats showed acute neurotoxicity, with some of the animals presenting convulsions, but which were clinically resolved by 12 h post-envenoming. The results showed that PNV is able to increase BBB permeability, particularly in the hippocampus. Changes were first detected in arterioles and post-capillary venules 18 h to 5 days after venom inoculation. The increased permeation of the extracellular tracer peaked on day 1, representing about 42% of the examined vessels ( P

Maria Elena De Lima - One of the best experts on this subject based on the ideXlab platform.

  • Phoneutria nigriventer spider toxin pntx2 1 δ ctenitoxin pn1a is a modulator of sodium channel gating
    Toxins, 2018
    Co-Authors: Steve Peigneur, Ana Luiza Bittencourt Paiva, Marta N. Cordeiro, Maria Elena De Lima, Marcia Helena Borges, Marcelo Ribeiro Vasconcelos Diniz, Jan Tytgat
    Abstract:

    : Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian NaV-channel isoforms, one insect NaV channel and one arachnid NaV channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on NaV1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac NaV channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current.

  • Phoneutria nigriventer venom: A pharmacological treasure.
    Toxicon, 2018
    Co-Authors: Steve Peigneur, Maria Elena De Lima, Jan Tytgat
    Abstract:

    In millions of years, spiders have optimized their venoms in order to assure successful prey capture and defence against predators. Spider venoms have become unique cocktails of biological active components enabling potentially interesting application for drug discovery or for agricultural purposes. The venom of Phoneutria nigriventer has been studied for over 60 years. This spider is responsible for a high number of envenomations with severe clinical manifestations in humans, which necessitates a comprehensive knowledge of its venom composition. With over 40 different neurotoxic peptides characterized so far and still many more awaiting identification, this venom is undoubtedly a pharmacological treasure. This review provides an overview of the Phoneutria nigriventer toxins known today and describes their mechanism of action at a molecular level. We critically discuss the potential of the Phoneutria nigriventer venom peptides as pharmaceutical tools or lead compounds for drug development.

  • Phoneutria nigriventer Spider Toxin PnTx2-1 (δ-Ctenitoxin-Pn1a) Is a Modulator of Sodium Channel Gating
    MDPI AG, 2018
    Co-Authors: Steve Peigneur, Marta N. Cordeiro, Maria Elena De Lima, Marcia Helena Borges, Marcelo Ribeiro Vasconcelos Diniz, Ana Luiza B. Paiva, Jan Tytgat
    Abstract:

    Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian NaV-channel isoforms, one insect NaV channel and one arachnid NaV channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on NaV1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac NaV channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current

  • Phoneutria nigriventer Venom and Toxins: A Review
    Spider Venoms, 2015
    Co-Authors: Maria Elena De Lima, Suely G. Figueiredo, Alessandra Matavel, Kenia Pedrosa Nunes, Carolina Nunes Da Silva, Flávia De Marco Almeida, Marta Nascimento Do Cordeiro, Maria Stankiewicz, Paulo S.l. Beirão
    Abstract:

    The venom of Phoneutria nigriventer spider has been extensively studied. It is highly neurotoxic, with clinical manifestations occurring a few minutes after the bite, mainly in children. Among the intoxication signs that may lead to neurogenic shock are agitation, somnolence, sweating, nausea, profuse vomiting, lacrimation, excessive salivation, hypertension, tachycardia, tachypnea, tremors, muscle spasms, and priapism. Many toxins from this venom have been purified and characterized for their structure and/or function. The most studied Phoneutria nigriventer toxins are PnTx1, PnTx2-5, and PnTx2-6, which show complex effects on sodium channel kinetics. PnTx2-5 and PnTx2-6 are both described as responsible for priapism; PnTx4(6-1) and PnTx4(5-5) show insecticidal activities and act on insect sodium channels; PnTkPs are muscle-active peptides; and nigriventrine is a piperidine derivative that has neuroactive properties and causes convulsive spells. PnTx3-3 and PnTx3-4 toxins were demonstrated to be effective on preventing cell death after ischemia injury. On the other hand, PnTx3-6 was shown to be efficient in the treatment of persistent pathological pain. The present chapter compiles biochemical, physiological, and pharmacological studies of fractions and purified toxins from Phoneutria nigriventer venom, showing their great potential as new tools for pharmacological studies and drug development.

  • Erectile function is improved in aged rats by PnTx2-6, a toxin from Phoneutria nigriventer spider venom.
    The Journal of Sexual Medicine, 2012
    Co-Authors: Kenia Pedrosa Nunes, Michael K. Richardson, Marcia Helena Borges, Haroldo A. Toque, R. Clinton Webb, Maria Elena De Lima
    Abstract:

    ABSTRACT Introduction Age‐associated erectile dysfunction (ED) involves a decrease in nitric oxide (NO) availability and impaired relaxation. PnTx2‐6, a toxin from the Phoneutria nigriventer spider, has been demonstrated to improve erectile function via NO/cyclic guanosine monophosphate (cGMP) pathway. This spider's venom is characterized by several symptoms, including erection. PnTx2‐6 has been implicated in this phenomenon. Animal venoms have been postulated as potential drugs to treat ED. Aim PnTx2‐6 toxin improves erectile function in aged rats via NO/cGMP. We investigated the effect of PnTx2‐6 in the erectile function of aged rats. Main Outcome Measures ED was evaluated through changes in intracavernosal pressure/mean arterial pressure ratio during electrical field stimulation (EFS) of the pelvic ganglion of aged and adult rats (70 vs. 14 weeks). In functional studies, EFS‐induced relaxation of corpus cavernosum (CC) strips were performed with or without PnTx2‐6 (10‐8M). Results The decrease in erectile function associated with age was partially restored 15–20 minutes after injection of PnTx2‐6 and further improved by sildenafil. PnTx2‐6 enhanced EFS‐induced relaxation, as well as cGMP levels in CC, from young and aged rats. Relaxation due to PnTx2‐6 was further increased after 30 minutes incubation with Y‐27632, a Rho‐kinase inhibitor (10‐6 M), in aging CC. Nitric oxide synthase (NOS) activity in aged and young cavernosal tissue was increased by incubation with PnTx2‐6 (10 minutes). However, this toxin did not modify NOS expression. Conclusion PnTx2‐6 improves penile relaxation in aged rats, via increased NOS activity and NO release, resulting in enhanced cGMP levels. Nunes KP, Toque HA, Borges MH, Richardson M, Webb RC, and de Lima ME. Erectile function is improved in aged rats by PnTx2‐6, a toxin from Phoneutria nigriventer spider venom. J Sex Med **;**:**–**.

Marco A. M. Prado - One of the best experts on this subject based on the ideXlab platform.

  • Antiarrhythmogenic effects of a neurotoxin from the spider Phoneutria nigriventer
    Toxicon : official journal of the International Society on Toxinology, 2010
    Co-Authors: Alvair P. Almeida, Christopher Kushmerick, Alexandre Barbosa Andrade, Anderson J. Ferreira, Andrea C.g. Pires, Denis D. Damasceno, Márcia N.m. Alves, Enéas R.m. Gomes, Ricardo F. Lima, Marco A. M. Prado
    Abstract:

    In this study, we evaluated the effects of PhKv, a 4584 Da peptide isolated from the spider Phoneutria nigriventer venom, in the isolated rat heart and in isolated ventricular myocytes. Ventricular arrhythmias were induced by occlusion of the left anterior descending coronary artery for 15 min followed by 30 min of reperfusion. Administration of native PhKv (240 nM) 1 min before or after reperfusion markedly reduced the duration of arrhythmias. This effect was blocked by atropine, thereby indicating the participation of muscarinic receptors in the antiarrhythmogenic effect of PhKv. Notably, recombinant PhKv (240 nM) was also efficient to attenuate the arrhythmias (3.8 ± 0.9 vs. 8.0 ± 1.2 arbitrary units in control group). Furthermore, PhKv induced a significant reduction in heart rate. This bradycardia was partially blunted by atropine and potentiated by pyridostigmine. To further evaluate the participation of acetylcholine on the PhKv effects, we examined the release of this neurotransmitter from neuromuscular junctions. It was found that Phkv (200 nM) significantly increased the release of acetylcholine in this preparation. Moreover, PhKv (250 nM) did not cause any significant change in action potential or Ca(2+) transient parameters in isolated cardiomyocytes. Altogether, these findings show an important acetylcholine-mediated antiarrhythmogenic effect of the spider PhKv toxin in isolated hearts.

  • Neuroprotective effect on brain injury by neurotoxins from the spider Phoneutria nigriventer.
    Neurochemistry international, 2006
    Co-Authors: Ana Cristina Do Nascimento Pinheiro, Marco A. M. Prado, Marta N. Cordeiro, Michael K. Richardson, Rodrigo S. Gomez, André R. Massensini, Marco Aurélio Romano-silva, Luiz De Marco, Marcus Vinicius Gomez
    Abstract:

    The role of calcium channels blockers in ischemic condition has been well documented. The PhTx3 neurotoxic fraction of the spider Phoneutria nigriventer venom is a broad-spectrum calcium channel blocker that inhibits glutamate release, calcium uptake and also glutamate uptake in synaptosomes. In the present study we describe the effect of PhTx3 (1.0 μg/mL), ω-conotoxin GVIA (1.0 μmol/L) and ω-conotoxin MVIIC (100 nmol/L) on neuroprotection of hippocampal slices and SN56 cells subjected to ischemia by oxygen deprivation and low glucose insult (ODLG). After the insult, cell viability in the slices and SN56 cells was assessed by confocal microscopy and epifluorescence, using live/dead kit containing calcein-AM and ethidium homodimer. Confocal images of CA1 region of the rat hippocampal slices subjected to ischemia insult and treated with ω-conotoxin GVIA, ω-conotoxin MVIIC and PhTx3 showed a percentage of dead cells of 68%, 54% and 18%, respectively. The SN56 cells subjected to ischemia were almost completely protected from damage by PhTx3 while with ω-conotoxin GVIA or ω-conotoxin MVIIC the cell protection was only partial. Thus, PhTx3 provided robust ischemic neuroprotection showing potential as a novel class of agents that targets multiple components and exerts neuroprotection in in vitro model of brain ischemia.

  • Expression of a functional recombinant Phoneutria nigriventer toxin active on K+ channels.
    Toxicon, 2003
    Co-Authors: Ana Carneiro, Marcus V. Gomez, Evanguedes Kalapothakis, Marta N. Cordeiro, Christopher Kushmerick, Janaina Koenen, M.h.l. Arndt, Carlos Chávez-olórtegui, Marco A. M. Prado
    Abstract:

    PnTx3-1 is a peptide isolated from the venom of the spider Phoneutria nigriventer that specifically inhibits A-type K+ currents (IA) in GH3 cells. Here we used a bacterial expression system to produce an NH2-extended mutant of PnTx3-1 (ISEF-PnTx3-1) and tested whether the toxin is functional. The recombinant toxin was purified from bacterial extracts by a combination of affinity and ion-exchange chromatography. The recombinant toxin blocked A-type K+ currents in GH3 cells in a fashion similar to that observed with the wild-type toxin purified from the spider venom. These results suggest that recombinant cDNA methods provide a novel source for the production of functional Phoneutria toxins. The recombinant ISEF-PnTx3-1 should be useful for further understanding of the role of A-type K+ currents in biological processes.

  • Phoneutria nigriventer Venom: A Cocktail of Toxins That Affect Ion Channels
    Cellular and Molecular Neurobiology, 2002
    Co-Authors: Marcus V. Gomez, Evanguedes Kalapothakis, Cristina Guatimosim, Marco A. M. Prado
    Abstract:

    1. We review the pharmacological actions of toxins present in the venom of the aggressive spider Phoneutria nigriventer . 2. This venom is rich in toxins that affect ion channels and neurotransmitter release. Voltage-gated sodium, calcium, and potassium channels have been described as the main targets of these toxins. 3. In addition to these classical actions Phoneutria toxins have also been shown to affect glutamate transporter. 4. It is expected that molecular genetics in addition to biochemical, biophysical and pharmacological approaches will help to further define Phoneutria toxins and their mechanisms of action in the near future.

  • Phoneutria nigriventer Venom: A Cocktail of Toxins That Affect Ion Channels
    Cellular and Molecular Neurobiology, 2002
    Co-Authors: Marcus V. Gomez, Evanguedes Kalapothakis, Cristina Guatimosim, Marco A. M. Prado
    Abstract:

    1. We review the pharmacological actions of toxins present in the venom of the aggressive spider Phoneutria nigriventer.