A pharmacological examination of venoms from three species of death adder (Acanthophis antarcticus, Acanthophis praelongus and Acanthophis pyrrhus)

In Vitro Toxicity of Chinese Russell’s Viper (Daboia siamensis) Venom and Neutralisation by Antivenoms

Daboia siamensis (Russell’s viper) is a highly venomous and medically important snake in China, as well as much of Asia. There is minimal information on the pharmacological activity of the venom of the Chinese species, and currently no commercially available specific antivenom in China. This has led to the use of non-specific antivenoms to treat D. siamensis envenomation. In this study, the in vitro neurotoxicity and myotoxicity of D. siamensis venom was examined and the efficacy of four antivenoms was investigated, including the recently developed Chinese D. siamensis monovalent antivenom (C-DsMAV) and three commercially available antivenoms (Thai D. siamensis (Thai-DsMAV) monovalent antivenom, Deinagkistrodon acutus monovalent antivenom (DaAV), and Gloydius brevicaudus monovalent antivenom (GbAV). D. siamensis venom (10–30 µg/mL) caused the concentration-dependent inhibition of indirect twitches in the chick biventer cervicis nerve muscle preparation, without abolishing contractile responses to exogenous agonists ACh or CCh, indicating pre-synaptic neurotoxicity. Myotoxicity was also evident at these concentrations with inhibition of direct twitches, an increase in baseline tension, and the partial inhibition of ACh, CCh, and KCl responses. The prior addition of C-DsMAV or Thai-DsMAV prevented the neurotoxic and myotoxic activity of D. siamensis venom (10 µg/mL). The addition of non-specific antivenoms (GbAV and DaAV) partially prevented the neurotoxic activity of venom (10 µg/mL) but failed to neutralize the myotoxic effects. We have shown that D. siamensis venom exhibits in vitro weak presynaptic neurotoxicity and myotoxicity, which can be prevented by the pre-addition of the Chinese and Thai Russell’s viper antivenoms. Non-specific antivenoms were poorly efficacious. There should be further development of a monospecific antivenom against D. siamensis envenomation in China.

An Examination of the Neutralization of In Vitro Toxicity of Chinese Cobra (Naja atra) Venom by Different Antivenoms

The Chinese Cobra (Naja atra) is an elapid snake of major medical importance in southern China. We describe the in vitro neurotoxic, myotoxic, and cytotoxic effects of N. atra venom, as well as examining the efficacy of three Chinese monovalent antivenoms (N. atra antivenom, Gloydius brevicaudus antivenom and Deinagkistrodon acutus antivenom) and an Australian polyvalent snake antivenom. In the chick biventer cervicis nerve-muscle preparation, N. atra venom (1–10 µg/mL) abolished indirect twitches in a concentration-dependent manner, as well as abolishing contractile responses to exogenous acetylcholine chloride (ACh) and carbamylcholine chloride (CCh), indicative of post-synaptic neurotoxicity. Contractile responses to potassium chloride (KCl) were also significantly inhibited by venom indicating myotoxicity. The prior addition of Chinese N. atra antivenom (0.75 U/mL) or Australian polyvalent snake antivenom (3 U/mL), markedly attenuated the neurotoxic actions of venom (3 µg/mL) and prevented the inhibition of contractile responses to ACh, CCh, and KCl. The addition of Chinese antivenom (0.75 U/mL) or Australian polyvalent antivenom (3 U/mL) at the t₉₀ time point after the addition of venom (3 µg/mL), partially reversed the inhibition of twitches and significantly reversed the venom-induced inhibition of responses to ACh and CCh, but had no significant effect on the response to KCl. Venom (30 µg/mL) also abolished direct twitches in the chick biventer cervicis nerve-muscle preparation and caused a significant increase in baseline tension, further indicative of myotoxicity. N. atra antivenom (4 U/mL) prevented the myotoxic effects of venom (30 µg/mL). However, G. brevicaudus antivenom (24 U/mL), D. acutus antivenom (8 U/mL) and Australian polyvalent snake antivenom (33 U/mL) were unable to prevent venom (30 µg/mL) induced myotoxicity. In the L6 rat skeletal muscle myoblast cell line, N. atra venom caused concentration-dependent inhibition of cell viability, with a half maximal inhibitory concentration (IC₅₀) of 2.8 ± 0.48 μg/mL. N. atra antivenom significantly attenuated the cytotoxic effect of the venom, whereas Australian polyvalent snake antivenom was less effective but still attenuated the cytotoxic effects at lower venom concentrations. Neither G. brevicaudus antivenom or D. acutus antivenom were able to prevent the cytotoxicity. This study indicates that Chinese N. atra monovalent antivenom is efficacious against the neurotoxic, myotoxic and cytotoxic effects of N. atra venom but the clinical effectiveness of the antivenom is likely to be diminished, even if given early after envenoming. The use of Chinese viper antivenoms (i.e., G. brevicaudus and D. acutus antivenoms) in cases of envenoming by the Chinese cobra is not supported by the results of the current study.

Actividad neurotóxica del veneno de serpientes del género Micrurus y métodos para su análisis. Revisión de la literatura

Introducción. Las serpientes del género Micrurus son animales de hábitos fosoriales, de temperamento pasivo y escasa producción de un potente veneno con características neurotóxicas que bloquean la transmisión sináptica en la placa neuromuscular.Objetivo. Presentar un panorama general de la neurotoxicidad del veneno de las serpientes Micrurus y su caracterización funcional mediante métodos de análisis ex vivo.Materiales y métodos. Se realizó una revisión de la literatura en MedLine y ScienceDirect usando términos específicos y sus combinaciones. Estrategia de búsqueda: tipo de estudios: artículos sobre la neurotoxicidad del veneno de serpientes Micrurus y técnicas para determinar su actividad neurotóxica mediante modelos in vitro, in vivo y ex vivo; periodo de publicación: sin limite inicial a junio de 2018; idiomas: inglés y español.Resultados. De los 88 estudios identificados en la búsqueda inicial, se excluyeron 28 por no cumplir los criterios de inclusión (basándose en la lectura de títulos y resúmenes); además, se incluyeron 8 documentos adicionales (libros e informes), que, a criterio de los autores, complementaban la información reportada por las referencias seleccionadas. Los estudios incluidos en la revisión (n=68) correspondieron a las siguientes tipologías: investigaciones originales (n=44), artículos de revisión (n=16) y capítulos de libros, informes, guías y consultas en internet (n=8).Conclusiones. Los estudios que describen el uso de preparaciones ex vivo de músculo y nervio para evaluar el efecto de neurotoxinas ofrecen un buen modelo para la caracterización del efecto presináptico y postsináptico del veneno producido por las serpientes Micrurus.

Anti-Ophidian Properties of Herbal Medicinal Plants: Could it be a Remedy for Snake Bite Envenomation?

Snake bite envenoming causes high rates of morbidity and mortality and is one of the serious health-related concerns all over the globe. Around 3200 species of snakes have been discovered till date. Amid these species, about 1300 species of snakes are venomous. On account of its severity, World Health Organization (WHO) recently included snakebite envenoming in the list of neglected tropical diseases. Immunotherapy has partially solved the issues related to snakebite envenomation. However, it is associated with numerous adverse effects, due to which alternative treatment strategies are required for the treatment of snakebite. Traditionally, a large repository of herbal medicinal plants is known to possess activity against snake venom. An exploration of the therapeutic benefits of these medicinal plants used for the treatment of snakebites reveals the presence of various potential phytochemicals. The aim of the present review is to provide an outline regarding poisonous snakes all over the world, various compositions of snake venom, adverse effects related to anti-snake venom and numerous medicinal plants used for the anti-ophidian activity.

Dacin, one metalloproteinase from Deinagkistrodon acutus venom inhibiting contraction of mouse ileum muscle

Background

Mice were bitten by five-pace vipers (Deinagkistrodon acutus), and then envenomed. It was well-known that the snake venom mainly disturbed the blood homeostasis of the envenomed victims. Ocassionally, we found that the venom of D. acutus could inhibit the contraction tension of mouse ileum, so in this study we aimed to identify the active component inhibiting the contraction tension of mouse ileum in the snake venom.

Results

The active component inhibiting the contraction tension of mouse ileum, designated as Dacin, was isolated from D. acutus venom, purified to protein homogeneity and composed of a single peptide chain, about 23 kDa analyzed by SDS-PAGE, and 22, 947. 9 Da measured by MALDI-TOF-MS. Not only the results of its PMF blasted by Mascot indicated that Dacin may be one snake venom metalloproteinase (SVMP), but also the results of the biochemical and in-vivo assays as follow demonstrated that it was one SVMP: it cleaved Aα and Bβ chains, not Cγ of bovine fibrinogen within 1 h, and also hydrolyzed fibrin polymer; besides its fibrino(geno)lytic activities were strongly inhibited by β- mercaptoethanol, EDTA and EGTA; and it could induce a hemorrhagic reaction under the dorsal skin of mouse. In the isolated tissue assays, Dacin caused the concentration-dependent and time-dependent inhibitory actions on the spontaneous contraction tension of the ileum smooth muscle of mouse, and the inhibitory effects were irreversible.

Conclusions

Taken together, for the first time one active component (Dacin, a SVMP) that irreversibly inhibited the spontaneous contraction tension of mouse ileum has been isolated and identified from D. acutus venom. The findings may provide not only a new insight for toxicological researches on SVMPs and venoms of the vipers, but also a reference for clinicians to treat the snake-bitten victims. However, Dacin’s inhibitory molecular mechanism will be further studied in the future.

In vitro toxic effects of puff adder (Bitis arietans) venom, and their neutralization by antivenom

This study investigated the in vitro toxic effects of Bitis arietans venom and the ability of antivenom produced by the South African Institute of Medical Research (SAIMR) to neutralize these effects. The venom (50 µg/mL) reduced nerve-mediated twitches of the chick biventer muscle to 19% ± 2% of initial magnitude (n = 4) within 2 h. This inhibitory effect of the venom was significantly attenuated by prior incubation of tissues with SAIMR antivenom (0.864 µg/µL; 67% ± 4%; P < 0.05; n = 3–5, unpaired t-test). Addition of antivenom at t₅₀ failed to prevent further inhibition or reverse the inhibition of twitches and responses to agonists. The myotoxic action of the venom (50 µg/mL) was evidenced by a decrease in direct twitches (30% ± 6% of the initial twitch magnitude) and increase in baseline tension (by 0.7 ± 0.3 g within 3 h) of the chick biventer. Antivenom failed to block these effects. Antivenom however prevented the venom induced cytotoxic effects on L6 skeletal muscle cells. Venom induced a marginal but significant reduction in plasma clotting times at concentrations above 7.8 µg/100 µL of plasma, indicating poor procoagulant effects. In addition, the results of western immunoblotting indicate strong immunoreactivity with venom proteins, thus warranting further detailed studies on the neutralization of the effects of individual venom toxins by antivenom.

Neuromuscular activity of Micrurus laticollaris (Squamata: Elapidae) venom in vitro

In this work, we have examined the neuromuscular activity of Micrurus laticollaris (Mexican coral snake) venom (MLV) in vertebrate isolated nerve-muscle preparations. In chick biventer cervicis preparations, the MLV induced an irreversible concentration- and time-dependent (1–30 µg/mL) neuromuscular blockade, with 50% blockade occurring between 8 and 30 min. Muscle contractures evoked by exogenous acetylcholine were completely abolished by MLV, whereas those of KCl were also significantly altered (86% ± 11%, 53% ± 11%, 89% ± 5% and 89% ± 7% for one, three, 10 and 30 µg of venom/mL, respectively; n = 4; p < 0.05). In mouse phrenic nerve-diaphragm preparations, MLV (1–10 µg/mL) promoted a slight increase in the amplitude of twitch-tension (3 µg/mL), followed by neuromuscular blockade (n = 4); the highest concentration caused complete inhibition of the twitches (time for 50% blockade = 26 ± 3 min), without exhibiting a previous neuromuscular facilitation. The venom (3 µg/mL) induced a biphasic modulation in the frequency of miniature end-plate potentials (MEPPs)/min, causing a significant increase after 15 min, followed by a decrease after 60 min (from 17 ± 1.4 (basal) to 28 ± 2.5 (t₁₅) and 12 ± 2 (t₆₀)). The membrane resting potential of mouse diaphragm preparations pre-exposed or not to d-tubocurarine (5 µg/mL) was also significantly less negative with MLV (10 µg/mL). Together, these results indicate that M. laticollaris venom induces neuromuscular blockade by a combination of pre- and post-synaptic activities.

Vintage venoms: proteomic and pharmacological stability of snake venoms stored for up to eight decades

For over a century, venom samples from wild snakes have been collected and stored around the world. However, the quality of storage conditions for "vintage" venoms has rarely been assessed. The goal of this study was to determine whether such historical venom samples are still biochemically and pharmacologically viable for research purposes, or if new sample efforts are needed. In total, 52 samples spanning 5 genera and 13 species with regional variants of some species (e.g., 14 different populations of Notechis scutatus) were analysed by a combined proteomic and pharmacological approach to determine protein structural stability and bioactivity. When venoms were not exposed to air during storage, the proteomic results were virtually indistinguishable from that of fresh venom and bioactivity was equivalent or only slightly reduced. By contrast, a sample of Acanthophis antarcticus venom that was exposed to air (due to a loss of integrity of the rubber stopper) suffered significant degradation as evidenced by the proteomics profile. Interestingly, the neurotoxicity of this sample was nearly the same as fresh venom, indicating that degradation may have occurred in the free N- or C-terminus chains of the proteins, rather than at the tips of loops where the functional residues are located. These results suggest that these and other vintage venom collections may be of continuing value in toxin research. This is particularly important as many snake species worldwide are declining due to habitat destruction or modification. For some venoms (such as N. scutatus from Babel Island, Flinders Island, King Island and St. Francis Island) these were the first analyses ever conducted and these vintage samples may represent the only venom ever collected from these unique island forms of tiger snakes. Such vintage venoms may therefore represent the last remaining stocks of some local populations and thus are precious resources. These venoms also have significant historical value as the Oxyuranus venoms analysed include samples from the first coastal taipan (Oxyuranus scutellatus) collected for antivenom production (the snake that killed the collector Kevin Budden), as well as samples from the first Oxyuranus microlepidotus specimen collected after the species' rediscovery in 1976. These results demonstrate that with proper storage techniques, venom samples can retain structural and pharmacological stability. This article is part of a Special Issue entitled: Proteomics of non-model organisms.

BIOLOGICAL SIGNIFICANCE

Death adder envenoming causes neurotoxicity not reversed by antivenom--Australian Snakebite Project (ASP-16)

BACKGROUND

Death adders (Acanthophis spp) are found in Australia, Papua New Guinea and parts of eastern Indonesia. This study aimed to investigate the clinical syndrome of death adder envenoming and response to antivenom treatment.

METHODOLOGY/PRINCIPAL FINDINGS

Definite death adder bites were recruited from the Australian Snakebite Project (ASP) as defined by expert identification or detection of death adder venom in blood. Clinical effects and laboratory results were collected prospectively, including the time course of neurotoxicity and response to treatment. Enzyme immunoassay was used to measure venom concentrations. Twenty nine patients had definite death adder bites; median age 45 yr (5-74 yr); 25 were male. Envenoming occurred in 14 patients. Two further patients had allergic reactions without envenoming, both snake handlers with previous death adder bites. Of 14 envenomed patients, 12 developed neurotoxicity characterised by ptosis (12), diplopia (9), bulbar weakness (7), intercostal muscle weakness (2) and limb weakness (2). Intubation and mechanical ventilation were required for two patients for 17 and 83 hours. The median time to onset of neurotoxicity was 4 hours (0.5-15.5 hr). One patient bitten by a northern death adder developed myotoxicity and one patient only developed systemic symptoms without neurotoxicity. No patient developed venom induced consumption coagulopathy. Antivenom was administered to 13 patients, all receiving one vial initially. The median time for resolution of neurotoxicity post-antivenom was 21 hours (5-168). The median peak venom concentration in 13 envenomed patients with blood samples was 22 ng/mL (4.4-245 ng/mL). In eight patients where post-antivenom bloods were available, no venom was detected after one vial of antivenom.

CONCLUSIONS/SIGNIFICANCE

Death adder envenoming is characterised by neurotoxicity, which is mild in most cases. One vial of death adder antivenom was sufficient to bind all circulating venom. The persistent neurological effects despite antivenom, suggests that neurotoxicity is not reversed by antivenom.

Characterisation of the heterotrimeric presynaptic phospholipase A(2) neurotoxin complex from the venom of the common death adder (Acanthophis antarcticus)

While Australo-Papuan death adder neurotoxicity is generally considered to be due to the actions of reversible competitive postsynaptic alpha-neurotoxins, the neurotoxic effects are often poorly reversed by antivenom or anticholinesterases. This suggests that the venom may contain a snake presynaptic phospholipase A(2) (PLA(2)) neurotoxin (SPAN) that binds irreversibly to motor nerve terminals to inhibit neurotransmitter release. Using size-exclusion liquid chromatography under non-reducing conditions, we report the isolation and characterisation of a high molecular mass SPAN complex, P-elapitoxin-Aa1a (P-EPTX-Aa1a), from the venom of the common death adder Acanthophis antarcticus. Using the chick biventer-cervicis nerve-muscle preparation, P-EPTX-Aa1a (44,698Da) caused inhibition of nerve-evoked twitch contractions while responses to cholinergic agonists and KCl remained unaffected. P-EPTX-Aa1a also produced significant fade in tetanic contractions and a triphasic timecourse of neuromuscular blockade. These actions are consistent with other SPANs that inhibit acetylcholine release. P-EPTX-Aa1a was found to be a heterotrimeric complex composed of alpha, beta and gamma-subunits in a 1:1:1 stoichiometry with each subunit showing significant N-terminal sequence homology to the subunits of taipoxin, a SPAN from Oxyuranus s. scutellatus. Like taipoxin, only the alpha-chain produced any signs of neurotoxicity or displayed significant PLA(2) enzymatic activity. Preincubation with monovalent death adder antivenom or suramin, or inhibition of PLA(2) activity by incubation with 4-bromophenacyl bromide, either prevented or significantly delayed the onset of toxicity by P-EPTX-Aa1a. However, antivenom failed to reverse neurotoxicity. Early intervention with antivenom may therefore be important in severe cases of envenomation by A. antarcticus, given the presence of potent irreversible presynaptic neurotoxins.

Presence of presynaptic neurotoxin complexes in the venoms of Australo-Papuan death adders (Acanthophis spp.)

Australo-papuan death adders (Acanthophis spp.) are a cause of serious envenomations in Papua New Guinea and northern Australia often resulting in neurotoxic paralysis. Furthermore, victims occasionally present with delayed-onset neurotoxicity that sometimes responds poorly to antivenom or anticholinesterase treatment. This clinical outcome could be explained by the presence of potent snake presynaptic phospholipase A(2) neurotoxin (SPAN) complexes and monomers, in addition to long- and short-chain postsynaptic alpha-neurotoxins, that bind irreversibly, block neurotransmitter release and result in degeneration of the nerve terminal. The present study therefore aimed to determine within-genus variations in expression of high molecular mass SPAN complexes in the venoms of six major species of Acanthophis, four geographic variants of Acanthophis antarcticus. Venoms were separated by size-exclusion liquid chromatography under non-denaturing conditions and fractions corresponding to proteins in the range of 22 to >60 kDa were subjected to pharmacological characterization using the isolated chick biventer cervicis nerve-muscle (CBCNM) preparation. All venoms, except Acanthophis wellsi and Acanthophis pyrrhus, contained high mass fractions with phospholipase A(2) activity that inhibited twitch contractions of the CBCNM preparation. This inhibition was of slow onset, and responses to exogenous nicotinic agonists were not blocked, consistent with the presence of SPAN complexes. The results of the present study indicate that clinicians may need to be aware of possible prejunctional neurotoxicity following envenomations from A. antarcticus (all geographic variants except perhaps South Australia), Acanthophis praelongus, Acanthophis rugosus and Acanthophis. laevis species, and that early antivenom intervention is important in preventing further development of toxicity.

Cross-neutralisation of Australian brown snake, taipan and death adder venoms by monovalent antibodies

An understanding of the cross-neutralisation of snake venoms by antibodies is important for snake antivenom development. We investigated the cross-neutralisation of brown snake (Pseudonaja textilis) venom, taipan (Oxyuranus scutellatus) venom and death adder (Acanthophis antarcticus) with commercial antivenoms and monovalent anti-snake IgG, using enzyme immunoassays, in vitro clotting and neurotoxicity assays. Each commercial antivenom bound all three venoms, and neutralised clotting activity of brown snake and taipan venoms and neurotoxicity of death adder venom. The 'in-house' monovalent anti-snake venom IgG raised against procoagulant brown snake and taipan venoms, did not neutralise the neurotoxic effects of death adder venom. However, they did cross-neutralise the procoagulant effects of both procoagulant venoms. This supports the idea of developing antivenoms against groups of snake toxins rather than individual snake venoms.

Human anti-snake venom IgG antibodies in a previously bitten snake-handler, but no protection against local envenoming

We report a 60 year old male bitten by snakes from the Acanthophis genus (Death adder) on two occasions who developed high titres of human IgG antibodies to Acanthophis venom detected at the time of the second bite. The patient was bitten by Acanthophis antarcticus (common death adder) on the first occasion, developed non-specific systemic effects and did not receive antivenom. Three months later he was bitten by Acanthophis praelongus (northern death adder) and he developed significant local myotoxicity associated with a moderate rise in the creatine kinase (maximum 4770 U/L). He was given antivenom 55 h after the bite and recovered over several days. Death adder venom was detected in serum at the time of the first bite, but not the second bite. Human IgG antibodies to death adder were detected on the second admission but not the first. However, despite the presence of antibodies to death adder venom and free venom not being detected, the patient still developed significant local myotoxicity.

Snake venoms and their toxins: An Australian perspective

Australia is home to a vast collection of highly venomous terrestrial and marine snakes. As such, Australia has proven to be an excellent source of investigative material for both local and international toxinologists. Research on snake venoms initially focussed on identifying the most lethal species, and the venom components responsible for the lethality, so that treatment strategies could be implemented. Since then, the focus of research has included the isolation and characterisation of toxins (primarily neurotoxins), examination of the efficacy of commercially available antivenoms and, more recently, the use of liquid chromatography/mass spectrometry (LCMS) to aid in the analysis of whole venoms. Given the vast quantity of research undertaken over the past 70 yr we have tried to provide a short insight into some of this excellent work and identify areas requiring further examination.

Treatment of snakebite in Australia: the current evidence base and questions requiring collaborative multicentre prospective studies

Despite the wealth of anecdotes and case reports there are fundamental questions of management of snakebite in Australia that remain unresolved or for which the current evidence is limited. The efficacy in the field, potential limitations and possibility of improvements in pressure immobilisation first aid need objective studies in humans. Optimal bandage sizes, stretch and pressure for different sized limbs need further evaluation, as does the use of pressure pads. Better definitions of specific clinical envenoming syndromes attributable to individual snake species are required, including elucidation of within-genus variations, similarities and differences. Venom studies suggest this is especially important for species within the brown snake (Pseudonaja) and death adder (Acanthophis) genera. Appropriate antivenom types, doses and dosing intervals for individual snake species should be more formally studied in patients. Especially important are confirmation of the need for higher doses of brown snake antivenom, while possibly limiting unnecessarily high doses, confirmation of the critical importance of early antivenom use to prevent pre-synaptic neurotoxicity in Taipan and tiger snake bites and ascertainment of whether larger doses of antivenom are unhelpful in Taipan bites after specified time delays. Confirmation of clinical efficacy and dosing recommendations for use of tiger snake (Notechis) antivenom in envenoming from Australian copperhead (Austrelaps spp.), broad headed (Hoplocephalus spp.) and rough-scaled snakes (Tropidechis carinatus) also require formal study in patients. Other examples of clinical relevance of cross-specificity of current and future monospecific antivenoms and whether there are geographical variations in antivenom responses within species will require elucidation. Prospective multicentre collaborative studies with predefined data collection and serial venom level assays are proposed as the way forward in Australia to help resolve therapeutic uncertainties and to establish a firmer evidence base for best-practice treatment guidelines for Australasian elapid snakebite.

Isolation and characterisation of acanmyotoxin-2 and acanmyotoxin-3, myotoxins from the venom of the death adder Acanthophis sp. Seram

Death adder (genus Acanthophis) venoms display neurotoxic activity but were thought to be devoid of myotoxic components. Studies from our laboratory have shown that some species (i.e. Acanthophis rugosus and Acanthophis sp. Seram) possess venom with myotoxic activity [Wickramaratna JC, Fry BG, Aguilar M, Kini RM, Hodgson WC. Isolation and pharmacological characterisation of a phospholipase A2 myotoxin from the venom of the Irian Jayan death adder (A. rugosus). Br J Pharmacol 2003;138:333-342; Wickramaratna JC, Fry BG, Hodgson WC. Species-dependent variations in the in vitro myotoxicity of death adder (Acanthophis) venoms. Toxicol Sci 2003;74:352-360]. The present study describes the isolation and characterisation of two myotoxins (acanmyotoxin-2 and acanmyotoxin-3) from A. sp. Seram venom. Venom was fractionated into approximately 12 major peaks using reverse phase high performance liquid chromatography. Two components caused concentration (0.1-1 microM) dependent inhibition of direct (2 ms, 0.1 Hz, supramaximal V) twitches and an increase in baseline tension in the chick biventer cervicis nerve-muscle. Histological examination of the muscle confirmed damage. PLA2 activity was detected in both acanmyotoxin-2 (390.2+/-19.7 micromol/(min mg); n=4) and acanmyotoxin-3 (14.2+/-7.7 micromol/(min mg); n=4). In comparison, A. sp. Seram whole venom had a specific activity of 461.3+/-90.4 micromol/(min mg) (n=3). Mass spectrometry analysis indicated acanmyotoxin-2 had a mass of 13,082 Da and acanmyotoxin-2 13,896 Da. Acanmyotoxin-2 and acanmyotoxin-3 accounted for approximately 7 and 4% of total venom composition, respectively. N-terminal sequencing of the first 30 amino acids of each toxin indicated they shared some sequence homology with known myotoxins. In conclusion, clinicians should be aware that symptoms of envenoming by some species of death adder may include signs of myotoxicity as well as neurotoxicity. Future studies will investigate the efficacy of the current antivenom treatment against the myotoxic components of A. sp. Seram venom.

Phospholipase A2-dependent effects of the venom from the new guinean small-eyed snakeMicropechis ikaheka

The New Guinean small-eyed snake (Micropechis ikaheka) is a cause of life-threatening envenoming. Previous studies on M. ikaheka venom have indicated the presence of neurotoxins as well as myotoxins. This study examined the in vitro myotoxic effects of M. ikaheka venom and the efficacy of a polyvalent antivenom in neutralizing these effects. Venom (50 microg/ml) produced a slowly developing contracture and inhibition of direct twitches of the chick biventer cervicis nerve-muscle preparation in the presence of tubocurarine (10 microM). Myotoxicity was confirmed by subsequent histological examination of tissues. This myotoxicity was prevented by the prior addition of polyvalent snake antivenom (30 U/ml). However, the addition of antivenom (30 U/ml) 1 h after venom administration failed to reverse or prevent the further inhibition of direct twitches. In addition, venom (1-10 microg/ml) produced concentration-dependent contractions of the guinea-pig isolated ileum. These effects were dependent on phospholipase A2 (PLA2) activity of the venom as evidenced by the ability of the PLA2 inhibitor 4-bromophenacyl bromide (4-BPB; 1.8 mM) to prevent this activity. This study indicates that M. ikaheka venom causes significant myotoxicity and that polyvalent snake antivenom may be a potential treatment for the myotoxic effects in patients envenomed by this species.

The in vitro neuromuscular activity of Indo-Pacific sea-snake venoms: efficacy of two commercially available antivenoms

We examined the neurotoxicity of the following sea snake venoms: Enhydrina schistosa (geographical variants from Weipa and Malaysia), Lapemis curtus (Weipa and Malaysia), Laticauda colubrina, Aipysurus laevis, Aipysurus fuscus and Aipysurus foliosquamatus. Venom from a terrestrial snake, Notechis scutatus (tiger snake), was used as a reference. All venoms (1 and 3 microg/ml) abolished indirect twitches of the chick biventer cervicis muscle and significantly inhibited responses to ACh (1 mM) and CCh (20 microM), but not KCl (40 mM), indicating the presence of post-synaptic toxins. Prior administration (10 min) of CSL sea snake antivenom (1 unit/ml) attenuated the twitch blockade produced by N. scutatus venom and all sea snake venoms (1 microg/ml). Prior administration (10 min) of CSL tiger snake antivenom (1 unit/ml) attenuated the twitch blockade of all venoms except those produced by E. schistosa (Malaysia and Weipa) and A. foliosquamatus. Administration of CSL sea snake antivenom (1 unit/ml) at t90 (i.e. time at which 90% inhibition of initial twitch height occurred) reversed the inhibition of twitches (20-50%) produced by the sea snake venoms (1 microg/ml) but not by N. scutatus venom (1 microg/ml). CSL tiger snake antivenom (1 unit/ml) administered at t90 produced only minor reversal (i.e. 15-25%) of the twitch blockade caused by L. curtus (Weipa), A. foliosquamatus, L. colubrina and A. laevis venoms (1 microg/ml). Differences in the rate of reversal of the neurotoxicity produced by the two geographical variants of E. schistosa venom, after addition of CSL sea snake antivenom, indicate possible differences in venom components. This study shows that sea snake venoms contain potent post-synaptic activity that, despite the significant genetic distances between the lineages, can be neutralised with CSL sea snake antivenom. However, the effects of CSL tiger snake antivenom are more variable.

Cardiovascular, haematological and neurological effects of the venom of the Papua New Guinean small-eyed snake (Micropechis ikaheka) and their neutralisation with CSL polyvalent and black snake antivenoms

Cardiovascular and haematological effects of venom of the small-eyed Snake (Micropechis ikaheka) were examined in ventilated anaesthetised piglets. Neurotoxic effects were examined in chick biventer cervicis nerve-muscle preparations. Immunoreactivity of venom was tested against the monovalent antivenom components in a CSL Ltd Venom Detection Kit. Neutralisation was tested in vivo and in vitro with CSL Ltd polyvalent snake and Black Snake (Pseudechis australis) antivenoms. Venom in 0.1% bovine serum albumin in saline was infused into piglets in doses 1-2000 microg/kg. Pulmonary hypertension (P= 0.0007) and depression of cardiac output (P= 0.002) were observed up to 3 h after 150-160 microg/kg. The concentration of plasma free-haemoglobin increased more than 50-fold, indicating haemolysis. Neither coagulopathy nor thrombocytopenia occurred. Creatine phosphokinase and serum potassium levels did not increase suggesting absence of acute rhabdomyolysis. The venom caused post-synaptic neurotoxicty. Immunoreactivity of venom with Black Snake antivenom was observed at very high venom concentrations. Cardiovascular effects were absent and haemolysis was less after venom was pre-incubated at 37 degrees C for 30 min with polyvalent antivenom. Neutralisation by Black Snake antivenom was less effective. The neurotoxicity was neutralised by polyvalent or Black Snake antivenoms. Human envenomation may be treated with CSL Ltd polyvalent snake antivenom.

Species-dependent variations in the in vitro myotoxicity of death adder (Acanthophis) venoms

Based on early studies on Acanthophis antarcticus (common death adder) venom, it has long been thought that death adder snake venoms are devoid of myotoxicity. However, a recent clinical study reported rhabdomyolysis in patients following death adder envenomations, in Papua New Guinea, by a species thought to be different to A. antarcticus. Subsequently, a myotoxic phospholipase A2 component was isolated from A. rugosus (Irian Jayan death adder) venom. The present study examined the venoms of A. praelongus (northern), A. pyrrhus (desert), A. hawkei (Barkly Tableland), A. wellsi (black head), A. rugosus, A. sp. Seram and the regional variants of A. antarcticus for in vitro myotoxicity. Venoms (10-50 microg/ml) were examined for myotoxicity using the chick directly (0.1 Hz, 2 ms, supramaximal V) stimulated biventer cervicis nerve-muscle preparation. A significant contracture of skeletal muscle and/or inhibition of direct twitches were considered signs of myotoxicity. This was confirmed by histological examination. All venoms displayed high phospholipase A2 activity. The venoms (10-50 microg/ml) of A. sp. Seram, A. praelongus, A. rugosus,and A. wellsi caused a significant inhibition of direct twitches and an increase in baseline tension compared to the vehicle (n=4-6; two-way ANOVA, p<0.05). Furthermore, these venoms caused dose-dependent morphological changes in skeletal muscle. In contrast, the venoms (10-50 microg/ml; n=3-6) of A. hawkei, A. pyrrhus, and regional variants of A. antarcticus were devoid of myotoxicity. Prior incubation (10 min) of CSL death adder antivenom (5 U/ml) prevented the myotoxicity caused by A. sp. Seram, A. praelongus, A. rugosus, and A. wellsi venoms (50 microg/ml; n=4-7). In conclusion, clinicians may need to be mindful of possible myotoxicity following envenomations by A. praelongus, A. rugosus, A. sp. Seram, and A. wellsi species.

Comparison of the in vitro neuromuscular activity of venom from three Australian snakes (Hoplocephalus stephensi, Austrelaps superbus and Notechis scutatus): efficacy of tiger snake antivenom

1. Tiger snake antivenom, raised against Notechis scutatus venom, is indicated not only for the treatment of envenomation by this snake, but also that of the copperhead (Austrelaps superbus) and Stephen's banded snake (Hoplocephalus stephensi). The present study compared the neuromuscular pharmacology of venom from these snakes and the in vitro efficacy of tiger snake antivenom. 2. In chick biventer cervicis muscle and mouse phrenic nerve diaphragm preparations, all venoms (3-10 microg/mL) produced inhibition of indirect twitches. In the biventer muscle, venoms (10 micro g/mL) inhibited responses to acetylcholine (1 mmol/L) and carbachol (20 micromol/L), but not KCl (40 mmol/L). The prior (10 min) administration of 1 unit/mL antivenom markedly attenuated the neurotoxic effects of A. superbus and N. scutatus venoms (10 microg/mL), but was less effective against H. stephensi venom (10 microg/mL); 5 units/mL antivenom attenuated the neurotoxic activity of all venoms. 3. Administration of 5 units/mL antivenom at t90 partially reversed, over a period of 3 h, the inhibition of twitches produced by N. scutatus (10 microg/mL; 41% recovery), A. superbus (10 microg/mL; 25% recovery) and H. stephensi (10 microg/mL; 50% recovery) venoms. All venoms (10-100 microg/mL) also displayed signs of in vitro myotoxicity. 4. The results of the present study indicate that all three venoms contain neurotoxic activity that is effectively attenuated by tiger snake antivenom.

Isolation and pharmacological characterization of a phospholipase A2 myotoxin from the venom of the Irian Jayan death adder (Acanthophis rugosus)

1. It has long been thought that death adder venoms are devoid of myotoxic activity based on studies done on Acanthophis antarcticus (Common death adder) venom. However, a recent clinical study reported rhabdomyolysis in patients following death adder envenomations, in Papua New Guinea, by a species thought to be different to A. antarcticus. Consequently, the present study examined A. rugosus (Irian Jayan death adder) venom for myotoxicity, and isolated the first myotoxin (acanmyotoxin-1) from a death adder venom. 2. A. rugosus (10-50 micro g ml(-1)) and acanmyotoxin-1 (MW 13811; 0.1-1 micro M) were screened for myotoxicity using the chick directly (0.1 Hz, 2 ms, supramaximal V) stimulated biventer cervicis nerve-muscle (CBCNM) preparation. A significant contracture of skeletal muscle and/or inhibition of direct twitches were considered signs of myotoxicity. This was confirmed by histological examination. 3. High phospholipase A(2) (PLA(2)) activity was detected in both A. rugosus venom (140.2+/-10.4 micro mol min(-1) mg(-1); n=6) and acanmyotoxin-1 (153.4+/-11 micro mol min(-1) mg(-1); n=6). Both A. rugosus venom (10-50 micro g ml(-1)) and acanmyotoxin-1 (0.1-1 micro M) caused dose-dependent inhibition of direct twitches and increase in baseline tension (n=4-6). In addition, dose-dependent morphological changes in skeletal muscle were observed. 4. Prior incubation (10 min) of CSL death adder antivenom (5 units ml(-1); n=4) or inactivation of PLA(2) activity with 4-bromophenacyl bromide (1.8 mM; n=4) prevented the myotoxicity caused by acanmyotoxin-1 (1 micro M). 5. Acanmyotoxin-1 (0.1 micro M; n=4) displayed no significant neurotoxicity when it was examined using the indirectly (0.1 Hz, 0.2 ms, supramaximal V) stimulated CBCNM preparation. 6. In conclusion, clinicians may need to be mindful of possible myotoxicity following death adder envenomation in Irian Jaya.

In vitro neuromuscular activity of snake venoms

1. Snake venoms consist of a multitude of pharmacologically active components used for the capture of prey. Neurotoxins are particularly important in this regard, producing paralysis of skeletal muscles. These neurotoxins can be classified according to their site of action (i.e. pre- or post-synaptic). 2. Presynaptic neurotoxins, which display varying phospholipase A2 activities, have been identified in the venoms of the four major families of venomous snakes (i.e. Crotalidae, Elapidae, Hydrophiidae and Viperidae). The blockade of transmission produced by these toxins is usually characterized by a triphasic effect on acetylcholine release. Considerable work has been directed at identifying the binding site(s) on the presynaptic nerve terminal for these toxins, although their mechanism of action remains unclear. 3. Post-synaptic neurotoxins are antagonists of the nicotinic receptor on the skeletal muscle. Depending on their sequence, post-synaptic toxins are subdivided into short- and long-chain toxins. These toxins display different binding kinetics and different affinity for subtypes of nicotinic receptors. Post-synaptic neurotoxins have only been identified in venoms from the families Elapidae and Hydrophiidae. 4. Due to the high cost of developing new antivenoms and the reluctance of many companies to engage in this area of research, new methodologies are required to test the efficacy of existing antivenoms to ensure their optimal use. While chicken eggs have proven useful for the examination of haemorrhagic venoms, this procedure is not suited to venoms that primarily display neurotoxic activity. The chick biventer cervicis muscle has proven useful for this procedure, enabling the rapid screening of antivenoms against a range of venoms. 5. Historically, the lethality of snake venoms has been based on murine LD50 studies. Due to ethical reasons, these studies are being superseded by in vitro studies. Instead, the time taken to produce 90% inhibition of nerve-mediated twitches (i.e. t90) in skeletal muscle preparations can be determined. However, these two procedures result in different rank orders because they are measuring two different parameters. While murine LD50 determinations are based on "quantity", t90 values are based on how "quick" a venom acts. Therefore, knowledge of both parameters is still desirable. 6. In vitro neuromuscular preparations have proven to be invaluable tools in the examination of snake venoms and isolated neurotoxins. They will continue to play a role in further elucidating the mechanism of action of these highly potent toxins. Further study of these toxins may provide more highly specific research tools or lead compounds for pharmaceutical agents.

Electrospray liquid chromatography/mass spectrometry fingerprinting of Acanthophis (death adder) venoms: taxonomic and toxinological implications

Death adders (genus Acanthophis) are unique among elapid snakes in both morphology and venom composition. Despite this genus being among the most divergent of all elapids, the venom has been historically regarded as relatively quite simple. In this study, liquid chromatography/mass spectrometry (LC/MS) analysis has revealed a much greater diversity in venom composition, including the presence of molecules of novel molecular weights that may represent a new class of venom component. Furthermore, significant variation exists between species and populations, which allow for the LC/MS fingerprinting of each species. Mass profiling of Acanthophis venoms clearly demonstrates the effectiveness of this technique which underpins fundamental studies ranging from chemotaxonomy to drug design.

Species and regional variations in the effectiveness of antivenom against the in vitro neurotoxicity of death adder (Acanthophis) venoms

Although viperlike in appearance and habit, death adders belong to the Elapidae family of snakes. Systemic envenomation represents a serious medical problem with antivenom, which is raised against Acanthophis antarcticus venom, representing the primary treatment. This study focused on the major Acanthophis variants from Australia and islands in the Indo-Pacific region. Venoms were profiled using liquid chromatography-mass spectrometry, and analyzed for in vitro neurotoxicity (0.3-10 microg/ml), as well as the effectiveness of antivenom (1-5 units/ml; 10 min prior to the addition of 10 microg/ml venom). The following death adder venoms were examined: A. antarcticus (from separate populations in New South Wales, Queensland, South Australia, and Western Australia), A. hawkei, A. praelongus, A. pyrrhus, A. rugosus, A. wellsi, and venom from an unnamed species from the Indonesian island of Seram. All venoms abolished indirect twitches of the chick isolated biventer cervicis nerve-muscle preparation in a dose-dependent manner. In addition, all venoms blocked responses to exogenous acetylcholine (1 mM) and carbachol (20 microM), but not KCl (40 mM), suggesting postsynaptic neurotoxicity. Death adder antivenom (1 unit/ml) prevented the neurotoxic effects of A. pyrrhus, A. praelongus, and A. hawkei venoms, although it was markedly less effective against venoms from A. antarcticus (NSW, SA, WA), A. rugosus, A. wellsi, and A. sp. Seram. However, at 5 units/ml, antivenom was effective against all venoms tested. Death adder venoms, including those from A. antarcticus geographic variants, differed not only in their venom composition but also in their neurotoxic activity and susceptibility to antivenom. For the first time toxicological aspects of A. hawkei, A. wellsi, A. rugosus, and A. sp. Seram venoms were studied.