Pharmacological and biochemical studies on the venom of a clinically important viper snake (Echis carinatus) of Pakistan

Anti-5'-Nucleotidases (5'-ND) and Acetylcholinesterase (AChE) Activities of Medicinal Plants to Combat Echis carinatus Venom-Induced Toxicities

Echis carinatus is one of the highly venomous snakes of Pakistan that is responsible for numerous cases of envenomation and deaths. In Pakistan, medicinal plants are commonly used traditionally for snakebite treatment because of their low cost and easy availability in comparison with antivenom. The current research is aimed at evaluating the inhibitory activity of Pakistani medicinal plants against acetylcholinesterase and 5′-nucleotidases present in Echis carinatus venom. Acetylcholinesterase and 5′-nucleotidase enzymatic assays were performed at different venom concentrations to check the activity of these enzymes. Methanolic extracts from different parts of plants were used for in vitro determination of their inhibitory activity against 5′-nucleotidases in snake venom. Active methanolic extracts were subsequently fractioned using different solvents, and these fractions were also assessed for their anti-5′-nucleotidase activity. Results of this study exhibited that Eugenia jambolana Willd. ex O. Berg, Rubia cordifolia L., Trichodesma indicum (L.) R. Br., Calotropis procera (Wild.) R. Br., Curcuma longa L., and Fagonia arabica L. were able to significantly (p > 0.5) neutralize the 5′-nucleotidase activity by 88%, 86%, 86%, 85%, 83.7%, and 83%, respectively, compared with a standard antidote (snake venom antiserum). Thus, this study indicates that these plants possess the potential to neutralize one of the toxic enzymatic components of Echis carinatus venom and hence can help to augment the future efforts of developing alternative therapy for the management of snakebites.

Functional venomics of the Big-4 snakes of Pakistan

In South Asia, the "Big-4" venomous snakes Naja naja, Bungarus caeruleus, Daboia russelii, and Echis carinatus are so-called because they are the most medically important snakes in the region. Antivenom is the only effective treatment option for snakebite envenoming but antivenom is not produced domestically in Pakistan making the country reliant on polyvalent products imported from India and Saudi Arabia. The present study investigated the toxin composition and activity of the venoms of Pakistani specimens by means of proteomic and physio/pharmacological experiments. To evaluate the composition of venoms, 1D/2D-PAGE of crude venoms and RP-HPLC followed by SDS-PAGE were performed. Enzymatic, hemolytic, coagulant and platelet aggregating activities of crude venoms were assayed and were concordant with expectations based on the abundance of protein species in each. Neutralization assays were performed using Bharat polyvalent antivenom (BPAV), a product raised against venoms from Big-4 specimens from southern India. BPAV exhibited cross-reactivity against the Pakistani venoms, however, neutralization of clinically relevant activities was variable and rarely complete. Cumulatively, the presented data not only highlight geographical variations present in the venoms of the Big-4 snakes of South Asia, but also demonstrate the neutralization potential of Indian polyvalent against the venom of Pakistani specimens. Given the partial neutralization observed, it is clear that whilst BPAV is a life-saving product in Pakistan, in future it is hoped that a region-specific product might be manufactured domestically, using venoms of local snakes in the immunising mixture.

Antivenom Neutralization of Coagulopathic Snake Venom Toxins Assessed by Bioactivity Profiling Using Nanofractionation Analytics

Venomous snakebite is one of the world's most lethal neglected tropical diseases. Animal-derived antivenoms are the only standardized specific therapies currently available for treating snakebite envenoming, but due to venom variation, often this treatment is not effective in counteracting all clinical symptoms caused by the multitude of injected toxins. In this study, the coagulopathic toxicities of venoms from the medically relevant snake species Bothropsasper, Calloselasmarhodostoma, Deinagkistrodonacutus, Daboiarusselii, Echiscarinatus and Echisocellatus were assessed. The venoms were separated by liquid chromatography (LC) followed by nanofractionation and parallel mass spectrometry (MS). A recently developed high-throughput coagulation assay was employed to assess both the pro- and anticoagulant activity of separated venom toxins. The neutralization capacity of antivenoms on separated venom components was assessed and the coagulopathic venom peptides and enzymes that were either neutralized or remained active in the presence of antivenom were identified by correlating bioassay results with the MS data and with off-line generated proteomics data. The results showed that most snake venoms analyzed contained both procoagulants and anticoagulants. Most anticoagulants were identified as phospholipases A2s (PLA2s) and most procoagulants correlated with snake venom metalloproteinases (SVMPs) and serine proteases (SVSPs). This information can be used to better understand antivenom neutralization and can aid in the development of next-generation antivenom treatments.

Differential procoagulant effects of saw-scaled viper (Serpentes: Viperidae: Echis) snake venoms on human plasma and the narrow taxonomic ranges of antivenom efficacies

Saw-scaled vipers (genus Echis) are one of the leading causes of snakebite morbidity and mortality in parts of Sub-Saharan Africa, the Middle East, and vast regions of Asia, constituting a public health burden exceeding that of almost any other snake genus globally. Venom-induced consumption coagulopathy, owing to the action of potent procoagulant toxins, is one of the most relevant clinical manifestations of envenomings by Echis spp. Clinical experience and prior studies examining a limited range of venoms and restricted antivenoms have demonstrated for some antivenoms an extreme lack of antivenom cross-reactivity between different species of this genus, sometimes resulting in catastrophic treatment failure. This study undertook the most comprehensive testing of Echis venom effects upon the coagulation of human plasma, and also the broadest examination of antivenom potency and cross-reactivity, to-date. 10 Echis species/populations and four antivenoms (two African, two Asian) were studied. The results indicate that the venoms are, in general, potently procoagulant but that the relative dependence on calcium or phospholipid cofactors is highly variable. Additionally, three out of the four antivenoms tested demonstrated only a very narrow taxonomic range of effectiveness in preventing coagulopathy, with only the SAIMR antivenom displaying significant levels of cross-reactivity. These results were in conflict with previous studies using prolonged preincubation of antivenom with venom to suggest effective cross-reactivity levels for the ICP Echi-Tab antivenom. These findings both inform upon potential clinical effects of envenomation in humans and highlight the extreme limitations of available treatment. It is hoped that this will spur efforts into the development of antivenoms with more comprehensive coverage for bites not only from wild snakes but also from specimens widely kept in zoological collections.

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.