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At least 667 records · Page 37Linked to original sources
PubMed2006

Therapeutic potential of chlorotoxin-like neurotoxin from the Chinese scorpion for human gliomas.

Chlorotoxin, one of the key toxins in scorpion Leiurus quinquestriatus venom, has been shown to bind specifically to glioma cell surface as a specific chloride channel blocker. In this study, a purified, recombinant chlorotoxin-like peptide from the scorpion Buthus martensii Karsch (named rBmK CTa) was characterized by in vivo and in vitro studies. The results from cell proliferation assay with human glioma (SHG-44) cells showed that rBmK CTa inhibits the growth of glioma cells in a dose-dependent manner, with an IC(50) value of approximately 0.28microM. Under the same conditions, the IC(50) value for normal astrocytes increased to 8microM. This clearly indicated that rBmK CTa had specific toxicity against glioma cells but not astrocytes. Results from whole-cell patch-clamp recording showed that chloride current in SHG-44 was inhibited by rBmK CTa in a voltage-dependent manner and percent inhibitions for the blocking action of rBmK CTa (0.07 and 0.14microM) on I(Cl) was 17.64+/-3.06% and 55.86+/-2.83%, respectively. Histological analysis of rBmK CTa treated mice showed that brain, leg muscle and cardiac muscle were the target organs of this toxin. These results suggest that rBmK CTa may have potential therapeutic application in clinical treatment of human glioma. It represents an approach for developing a novel therapeutic agent.

Astrocytes↗
PubMed2005

Molecular modeling and docking simulations of scorpion toxins and related analogs on human SKCa2 and SKCa3 channels.

The small-conductance Ca2+-activated K+ (SKCa) channels modulate cytosolic Ca2+ concentration in excitable and non-excitable tissues by regulating the membrane potential and are responsible of slow action potential after hyperpolarization that inhibits cell firing. Among these, human SKCa2 and SKCa3 channels differ in the pore region by only two residues: Ala331 and Asn367 (human small-conductance calcium-activated potassium channel, hSKCa2) instead of Val485 and His521 (hSKCa3). To design highly selective blockers of hSKCa channels, a number of known hSKCa2 and/or hSKCa3-active peptides (i.e. scorpion toxins and analogs thereof) were analyzed for their interactions and selectivities toward these channels. Molecular models of hSKCa2 and hSKCa3 channels (S5-H5-S6 portion) were generated, and scorpion toxins/peptides of unsolved three-dimensional (3D) structures were modeled. Models of toxin-channel complexes were generated by the bimolecular complex generation with global evaluation, and ranking (BiGGER) docking software and selected by using a screening method of the docking solutions. A high degree of correlation was found to exist between docking energies and experimental Kd values of peptides that blocked hSKCa2 and/or hSKCa3 channels, suggesting it could be appropriate to predict Kd values of other bioactive peptides. The best scoring complexes were also used to identify key residues of both interacting partners, indicating that such an approach should help the design of more active and/or selective peptide blockers of targeted ion channels.

Amino Acid Motifs↗
PubMed2004

The kinin system in the envenomation caused by the Tityus serrulatus scorpion sting.

Several lines of evidence in experimental animals indicate that the kinin system may participate in the pathogenesis of envenomation by the Tityus serrulatus (Ts) scorpion sting, but there are no studies in humans with regard to this system. In this study, we evaluated the plasma levels of high-molecular (HKg) and low-molecular (LKg) weight kininogens (detected by ELISA), the activities of plasma or tissue kallikreins and kininase II (enzymatic action upon selective substrates), and the Ts plasma venom levels (ELISA). A total of 27 patients (12 males) aged 12-72 were evaluated immediately at hospital admittance. According to the severity of envenomation, patients were classified as mild (n = 15), moderate (n = 8), and severe cases (n = 4). Controls were paired for age and sex. Plasma venom levels were associated with the severity of envenomation. Severe cases presented lower levels of LKg in relation to mild and controls. Inverse correlations were seen between LKg levels and the venom concentration. The results of this study suggested that the kinin system may participate in the pathogenesis of human Ts envenomation and knowledge about this system may be useful to develop new strategies to reduce the damage caused by scorpion envenomation.

Adolescent↗
PubMed2004

Bacterial expression, purification and functional characterization of a recombinant chimeric Fab derived from murine mAb BCF2 that neutralizes the venom of the scorpion Centruroides noxius hoffmann.

The murine monoclonal antibody BCF2 is able to neutralize the venom of the scorpion Centruroides noxius Hoffmann. A chimeric Fab of BCF2 (chFab-BCF2) comprising the variable regions of murine BCF2 and human constant regions was assembled. chFab-BCF2 was expressed as a soluble and functional protein in the periplasmic space of Escherichia coli. An expression yield of 1 mg/l was reached by combination of late-log-phase induction, rich culture medium, low expression temperature and addition of sucrose (0.3 M) to the culture medium. The addition of sucrose induced secretion of 60% of the protein into the medium. After expression for 23 h, a novel process was used to release the remaining periplasmic protein in situ consisting in the addition of lysozyme and sucrose up to 0.6 M (20%) directly to the culture medium. chFab-BCF2 was recovered by ammonium sulfate precipitation and purified in a single step by affinity chromatography using anti-human anti-F(ab')(2) IgG coupled to Sepharose-proteinG. Pure chFab-BCF2 maintained a similar nanomolar affinity as BCF2 to its cognate antigen, the Na(+)-channel-affecting toxin Cn2. Recombinant chFab-BCF2 was able to neutralize Cn2 in vivo even at a molar ratio of 1:1, as well as the whole venom of C. noxius. Thus, it is a promising candidate to be used as a specific and efficient recombinant antidote against scorpion stings.

Animals↗
PubMed2004

Engineering of a recombinant Fab from a neutralizing IgG directed against scorpion neurotoxin AahI, and functional evaluation versus other antibody fragments.

Antibody-based therapy is the only specific treatment for scorpion envenomation. However, there are still major drawbacks associated with its use; mainly because antivenoms are still prepared from immune equine serum raised against crude venoms, whereas only a limited number of neurotoxins are responsible for the lethality of the venom. Using a murine hybridoma that secretes a well-characterized neutralizing IgG directed to neurotoxins AahI and AahIII from the venom of the scorpion Androctonus australis, we constructed a recombinant Fab (rFab) fragment, which was produced and purified from transformed bacteria. It recognized toxin AahI with a high affinity (KD = 8.2 x 10(-11)) equivalent to the homologous pFab prepared by papain digestion of whole IgG. Although the AahI-neutralizing capacity of protein L-purified rFab was low compared to other recombinant antibody formats (scFv and diabody) investigated in parallel, the antibody engineering approach presented here provides an innovative way to synthesize novel toxin-neutralizing molecules. It may serve as a strategy for designing a new generation of antivenoms.

Amino Acid Sequence↗
PubMed2004

Ardiscretin a novel arthropod-selective toxin from Tityus discrepans scorpion venom.

A new arthropod selective toxin was purified from the venom of the Venezuelan scorpion Tityus discrepans, and its amino acid sequence, cDNA clone and biological activity are reported here. The amino acid sequence of this peptide, named ardiscretin (from arthropod toxin of T. discrepans) was completed by Edman degradation and mass spectrometry. It is a single polypeptide composed by 61 amino acids with an amidated cysteine residue at the C-terminal end, closely packed by four disulfide bridges. The atomic mass unit (a.m.u.) experimentally determined was 7103.8 a.m.u. This peptide was shown to be specific for invertebrates (crickets, triatomides, crabs and squids), but non-toxic to mice, at the dose assayed. Ardiscretin inhibits the Na(+)-currents of squid giant axons in an apparent irreversible manner, whose inhibitory effect is reached at 30 microM toxin concentration. Sequence comparison showed that it is phylogenetically closely related to insect-specific scorpion toxins. Ardiscretin produced a small depolarization and induced repetitive firing in squid axons resembling those of DDT [1,1'(p-chlorobenzyl)2-tricloretane] in its ability to slow down action potential, to induce repetitive firing, and in that the concentration required for any effect in squid axon is rather high.

Amino Acid Sequence↗
PubMed2004

Amino acid sequence and function of a new alpha-toxin from the Amazonian scorpion Tityus cambridgei.

A toxic peptide earlier denominated Tc48b [Toxicon 40 (2002) 557] was purified to homogeneity and its amino acid sequence determined. It has 64 amino acid residues stabilized by four disulfide bridges with a molecular weight of 7,385.2 atomic mass units (a.m.u.). It affects Na(+)-permeability in pituitary GH3 cells in culture, in a similar fashion as those reported for alpha-scorpion toxins, contrary to most of the New World scorpion toxins that are beta-toxins.

Amino Acid Sequence↗
PubMed2004

Quantitative variability in the biodistribution and in toxinokinetic studies of the three main alpha toxins from the Androctonus australis hector scorpion venom.

Scorpion stings represent a medical problem in numerous countries. The scorpion Androctonus australis hector produces three alpha toxins (Aah I to III), which are responsible for most of the lethality in mammals. These toxins act on sodium channel and do not cross-react immunologically. We used RIA and ELISA to measure the concentrations of these three toxins in plasma, urine and different organs after i.v. and s.c. injections of water extracts of venoms in rabbits or mice. In both animals, the toxins rapidly appeared in plasma after s.c. injection as it was previously described for the whole venom. However, the toxins disappeared from the blood more quickly than did other main components of the venom. Thus, serotherapy must be initiated immediately to prevent the toxin from reaching its target. We also detected the toxins in urine, kidneys, heart and lungs, but not in the brain. However, the concentration of Aah II was always lower than that of Aah I. Analysis of five samples of venom collected in different areas of southern Tunisia showed that a large polymorphism exists for the three toxins. This is yet another difficulty for serotherapy as there is no cross-antigenicity between them.

Animals↗
PubMed2005

Monoamine oxidase inhibitory activities of the scorpion Mesobuthus gibbosus (Buthidae) venom peptides.

In the present study, crude venom of Mesobuthus gibbosus (Buthidae), a scorpion distributed all over Anatolia was isolated and purified by the Sephadex G-50 gel filtration and high pressure liquid chromatographic (HPLC) separation. Two of the five fractions (fractions 4 and 5) obtained from the Sephadex G-50 filtration and detected as lethal on mice and Musca domestica larvae in in vivo toxicity tests, were independently subjected to the HPLC separation. Only one of seven fractions (fraction 5.5*) obtained from the HPLC separation of the fraction 5 was found to be extremely lethal. Sodium dodecylsulfate polyacrylamide gel electrophoretic (SDS-PAGE) analysis of the crude venom and its chromatographic fractions demonstrated that crude venom consisted of peptides with molecular weights of 6500-210,000 Da. The neurotoxic fraction 5.5* appeared as a single band of 28,000 Da and two bands of 6200 and 22,000 Da in SDS-PAGE under non-reducing and reducing conditions, respectively, suggesting that it might consist of two chains attached by a disulfide bridge. Fractions 5 and 5.5* inhibited monoamine oxidase A (MAO-A) of rat liver reversibly and non-competitively, in a concentration-dependent manner. Fraction 5.5* appeared as a potent and specific MAO-A inhibitor with a Ki value of 0.12 mg venom proteinml(-1). The inhibitory effect of venom peptide 5.5* on MAO-A was found to be dependent on the preincubation time suggesting that the peptide binds to some site other than the substrate-binding site. Results of the present study demonstrated that M. gibbosus venom contains a peptide with specific MAO-A inhibitory activity which may be responsible for the anxiogenic effects of the scorpion venoms on animals and humans.

Animals↗
PubMed2005

Pharmacokinetic studies of scorpion venom before and after antivenom immunotherapy.

The improvement of the immunotherapeutic treatment of envenomations requires a better knowledge of the pharmacological actions of the scorpion venom and of the mechanism of its in vivo neutralization by antivenom. In the present work, we determined the toxicokinetic parameters of the toxic fraction of Androctonus australis garzonii venom in the absence and after antivenom immunotherapy, in experimentally envenomed rabbits. After subcutaneous injection of the scorpion venom, toxins showed a fast and complete resorption from the site of injection associated with a simultaneous distribution in a large extracellular compartment and with an important body clearance. The precocious intravenous injection of an appropriate antivenom dose was shown to induce an immediate, complete and durable neutralization of toxins, as well as their rapid redistribution from the peripheric compartment to the vascular one. On the contrary, the intramuscular injection of the same antivenom dose produced a slower and partial redistribution of toxins, leading to a delayed neutralization of the venom. The intravenous injection of smaller antivenom doses induced transient decreases of circulating toxins, indicating that a minimal antivenom dose has to be administered to allow an efficient and durable neutralization of the venom. We concluded also that this minimal effective dose of antivenom has to be injected precociously, by intravenous route, to achieve an efficient immunotherapy.

Animals↗
PubMed2005

Molecular characterization of a neutralizing murine monoclonal antibody against Tityus serrulatus scorpion venom.

Monoclonal antibodies (mAbs) against Tityus serrulatus venom were obtained by the fusion of SP2/0 murine myeloma cells and spleen cells from BALB/c mice immunized with a toxic fraction (TstFG50) of the Tityus venom (this G50 chromatography fraction represents most of the toxicity of the crude venom) conjugated to bovine serum albumin (BSA) with glutaraldehyde. From the initial screening of over 200 hybridoma fusion wells, a panel of 9 anti-TstFG50 secreting hybridomas was established. The capacity of mAbs to neutralize the TstFG50 toxic fraction toxic was determined by in vitro neutralization assays and by inhibition of the binding of 125I-TsVII to its site on rat brain synaptosomes. Only mAbTs1 neutralized 50% of the toxic effects produced by scorpion venom and showed 35% inhibition of the binding of 125I-TsVII at 10(-7) M. To map the epitope recognized by the protective mAbTs1, we prepared a comprehensive series of overlapping 15-mer synthetic peptides covering the amino acid sequences of the four Tityus proteins. MAbTs1 reacted with peptide 26 of TsIV (KKSKDKKADSGYSYW), peptide 30 of TsVII (KKGSSGYSAWPASYS) and peptide 31 of TsNTxP (KKGSSGYSAWPASYS). MAbTs1 was not reactive with any peptide from TsII. The N-terminal lysine residue from the epitope was found to be critical for mAbTs1 binding. The epitope was positioned on the available three-dimensional structure of TsVII together with the recently identified residues from the pharmacophore of beta-scorpion toxins. The neutralizing properties of mAbTs1 might be explained by spatial vicinity of epitope residues with pharmacophore residues.

Amino Acid Sequence↗
PubMed2006

Epidemiological and clinical characteristics of scorpionism in Colima, Mexico (2000-2001).

We analyzed 13,223 clinical records of patients treated for scorpion sting in hospitals of the Mexican Institute of Public Health and the Ministry of Health in the state of Colima, Mexico, during the years 2000-2001. A database containing demographic, epidemiological and clinical information was constructed and analyzed retrospectively. Patients were classified in the categories as mild (49.2%), moderate (33.8%) and severe (17.0%) according to commonly accepted standards. Most common symptoms recorded were local pain (94.7%), local paresthesia (67.2%), pruritus/itching (54.3%), sensation of a lump or hair in the throat (47.3%), and sialorrhoea (27.7%). The median time from sting to admission to the emergency room (patient delay) was 33min (interquartile range: 12-60). We found that older and clinically severe patients were significantly associated with longer times of admission to the emergency room. Age was significantly associated with clinical severity: the age group 0-10 years included a higher proportion of severe cases than the group 11 years and older. In four cases, patients died. An educational campaign to inform the population about the importance of receiving prompt attention following a scorpion sting has potential value in reducing complications in the emergency room.

Adolescent↗
PubMed2006

Characterization of venom components from the scorpion Androctonus crassicauda of Turkey: peptides and genes.

The soluble venom from the scorpion Androctonus crassicauda was fractionated by high performance liquid chromatography. At least 44 different sub-fractions were resolved and collected for finger print mass analysis using an electrospray mass spectrometer. This analysis revealed the presence of 80 distinct molecular mass components, from which five were further characterized. A peptide, named Acra1 was fully sequenced. It contains 58 amino acid residues cross-bridged by six cysteines forming three disulfide pairs, with a molecular mass of 6497 Da. A second purified peptide named Acra2 was partially sequenced with a molecular mass of 7849 Da. Acra1 is toxic and Acra2 is lethal to mice, at the dose assayed. Additionally, a cDNA library of the venomous gland of one specimen was prepared and several clones were obtained among which is one that codes for Acra1. Three analog gene sequences were found with point mutations either in the section that corresponds to the mature peptide or to the signal peptide. The signal peptide is 22 amino acid residues long. Several other gene sequences obtained suggest the presence in this venom of three distinct groups of peptides, among which are peptides similar to known Na(+)-channel specific toxins of other scorpions. A new type of peptide was identified with odd number of cysteines (seven), allowing the formation of heterodimers with molecular masses in the range of 16,000 atomic mass units (a.m.u.).

Amino Acid Sequence↗
PubMed2006

Effect of acid secretion blockade on acute gastric mucosal lesions induced by Tityus serrulatus scorpion toxin in anaesthetized rats.

Scorpion venom (TX) promotes gastric acid and pepsin secretion leading to acute gastric mucosal lesions (AGML), when injected in animals. The goal of the present study was to observe the effects of acid gastric secretion blockers over the incidence of TX-induced AGML in vivo. To verify this model, we used male albino rats, fasted 18-20 h (n=122) and anaesthetized with urethane (1.4 g/kg, i.p.). Their trachea and left femoral vein were both cannulated; the first to avoid airway obstructions during scorpion intoxication and the second for administration of saline, TX and acid blockers. Following the surgical procedure, the animals were divided in 10 groups of at least 10 animals each. Control groups were injected with NaCl 0.9% 1 ml/kg (n=10) or TX 375 microg/kg (n=32). Test groups (n=10, each) received atropine 5 mg/kg, cimetidine 10mg/kg, ranitidine 2.5mg/kg, ranitidine 5mg/kg, omeprazol 1 mg/kg, omeprazol 4 mg/kg, octreotide 80 and octreotide 100 microg/kg 10 min before the TX was injected. After 1h of intoxication, the stomach was resected for macroscopic study and the gastric secretion was collected for volume, pH and acid output assessment. We observed that all blockers were able to completely or partially prevent the TX-induced acid secretion as well as the AGML (p<0.05). Our data suggest the TX-induced AGML can be prevented by different class of acid blockers injected before the intoxication.

Acute Disease↗
PubMed2006

Novel paradigms on scorpion toxins that affects the activating mechanism of sodium channels.

Scorpion toxins classified as beta-class are reviewed using a new paradigm. Four distinct sub types are recognized: "classical", "Tsgamma-like", "excitatory" and "depressant"beta-scorpion toxins. Recent experimental data have made possible to identify the interacting interfaces of the Na(+) channel-receptor site 4 with some of these toxins. The voltage-sensor trapping mechanism proposed for the action of these toxic peptides is analyzed in the context of what causes a modification of the activating mechanism of Na(+) channels. A cartoon model is presented with the purpose of summarizing the most current knowledge on the field. Finally, the recent advances on the knowledge of the specific interactions of beta-toxins and different sub types of Na(+) channels are also reviewed.

Animals↗
PubMed2002

Brownian dynamics simulations of the recognition of the scorpion toxin maurotoxin with the voltage-gated potassium ion channels.

The recognition of the scorpion toxin maurotoxin (MTX) by the voltage-gated potassium (Kv1) channels, Kv1.1, Kv1.2, and Kv1.3, has been studied by means of Brownian dynamics (BD) simulations. All of the 35 available structures of MTX in the Protein Data Bank (http://www.rcsb.org/pdb) determined by nuclear magnetic resonance were considered during the simulations, which indicated that the conformation of MTX significantly affected both the recognition and the binding between MTX and the Kv1 channels. Comparing the top five highest-frequency structures of MTX binding to the Kv1 channels, we found that the Kv1.2 channel, with the highest docking frequencies and the lowest electrostatic interaction energies, was the most favorable for MTX binding, whereas Kv1.1 was intermediate, and Kv1.3 was the least favorable one. Among the 35 structures of MTX, the 10th structure docked into the binding site of the Kv1.2 channel with the highest probability and the most favorable electrostatic interactions. From the MTX-Kv1.2 binding model, we identified the critical residues for the recognition of these two proteins through triplet contact analyses. MTX locates around the extracellular mouth of the Kv1 channels, making contacts with its beta-sheets. Lys23, a conserved amino acid in the scorpion toxins, protrudes into the pore of the Kv1.2 channel and forms two hydrogen bonds with the conserved residues Gly401(D) and Tyr400(C) and one hydrophobic contact with Gly401(C) of the Kv1.2 channel. The critical triplet contacts for recognition between MTX and the Kv1.2 channel are Lys23(MTX)-Asp402(C)(Kv1), Lys27(MTX)-Asp378(D)(Kv1), and Lys30(MTX)-Asp402(A)(Kv1). In addition, six hydrogen-bonding interactions are formed between residues Lys23, Lys27, Lys30, and Tyr32 of MTX and residues Gly401, Tyr400, Asp402, Asp378, and Thr406 of Kv1.2. Many of them are formed by side chains of residues of MTX and backbone atoms of the Kv1.2 channel. Five hydrophobic contacts exist between residues Pro20, Lys23, Lys30 and Tyr32 of MTX and residues Asp402, Val404, Gly401, and Arg377 of the Kv1.2 channel. The simulation results are in agreement with the previous molecular biology experiments and explain the binding phenomena between MTX and Kv1 channels at the molecular level. The consistency between the results of the BD simulations and the experimental data indicated that our three-dimensional model of the MTX-Kv1.2 channel complex is reasonable and can be used in additional biological studies, such as rational design of novel therapeutic agents blocking the voltage-gated channels and in mutagenesis studies in both the toxins and the Kv1 channels. In particular, both the BD simulations and the molecular mechanics refinements indicate that residue Asp378 of the Kv1.2 channel is critical for its recognition and binding functionality toward MTX. This phenomenon has not been appreciated in the previous mutagenesis experiments, indicating this might be a new clue for additional functional study of Kv1 channels.

Amino Acid Motifs↗
PubMed1982

Simultaneous modifications of sodium channel gating by two scorpion toxins.

The effects of purified scorpion toxins from two different species on the kinetics of sodium currents were evaluated in amphibian myelinated nerves under voltage clamp. A toxin from Leiurus quinquestriatus slowed and prevented sodium channel inactivation, exclusively, and a toxin from Centruroides sculpturatus Ewing reduced transient sodium currents during a maintained depolarization, and induced a novel inward current that appeared following repolarization, as previously reported by Cahalan (1975, J. Physiol. [Lond.]. 244:511-534) for the crude scorpion venom. Both of these effects were observed in fibers treated with both of these toxins, and the kinetics of the induced current were modified in a way that showed that the same sodium channels were modified simultaneously by both toxins. Although the toxins can act on different sites, the time course of the action of C. sculpturatus toxin was accelerated in the presence of the L. quinquestriatus toxin, indicating some form of interaction between the two toxin binding sites.

Animals↗
PubMed1999

Pharmacological evidence that neuropeptides mediate part of the actions of scorpion venom on the guinea pig ileum.

Severe human scorpion envenoming is characterised by instability of several physiological systems and death. These manifestations are explained by the ability of the venom toxins to activate sodium channels in nerve terminals with the subsequent release of neurotransmitters, specially acetylcholine and noradrenaline. However, there is evidence to suggest that other neurotransmitters are also released. We now have sought evidence for a role of the substance P receptor, the tachykinin NK1 receptor, in mediating part of the contractile actions of Tityus serrulatus venom on the isolated guinea pig ileum. Scorpion venom induced a significant elevation of baseline tension with frequent and periodic superimposed contractions on the elevated baseline. Pretreatment with atropine partially blocked the elevation in baseline and in the number of superimposed contractions. These responses were also partially inhibited by the tachykinin NK1 receptor antagonist, CP96,345 (the dihydrochloride salt of (2S,3S)-cis-2-(diphenylmethyl)-N-((2-methoxyphenyl)methyl)-1-az abicycol[2.2.2]octan-3-amine), but not by its inactive enantiomer, CP96,344 (the 2R-3R enantiomer of CP96,345). Pretreatment with the combination of atropine and CP96,345 completely inhibited the effects of the venom. Moreover, pretreatment with the combined drugs abolished the effects of toxin gamma, a toxin purified from the venom. Finally, another tachykinin NK1 receptor antagonist, RP67,580 ((3aR, 7ar)-7,7-diphenyl-2-[1-imino-2-(2-methoxy-phenyl)ethyl]perhydro isoindol-4-one), significantly inhibited the venom-induced contractions. These results demonstrate an important role for NK1 receptors in mediating part of the contractile effects of the venom on guinea pig ileum. The release of neuropeptides may play an important role in the systemic manifestations of severe envenoming.

Animals↗