Functional Mining of the Crotalus Spp. Venom Protease Repertoire Reveals Potential for Chronic Wound Therapeutics

From birth to bite: the evolutionary ecology of India's medically most important snake venoms

BACKGROUND

Snake venoms can exhibit remarkable inter- and intraspecific variation. While diverse ecological and environmental factors are theorised to explain this variation, only a handful of studies have attempted to unravel their precise roles. This knowledge gap not only impedes our understanding of venom evolution but may also have dire consequences on snakebite treatment. To address this shortcoming, we investigated the evolutionary ecology of venoms of Russell's viper (Daboia russelii) and spectacled cobra (Naja naja), India's two clinically most important snakes responsible for an alarming number of human deaths and disabilities.

METHODOLOGY

Several individuals (n = 226) of D. russelii and N. naja belonging to multiple clutches (n = 9) and their mothers were maintained in captivity to source ontogenetic stage-specific venoms. Using various in vitro and in vivo assays, we assessed the significance of prey, ontogeny and sex in driving venom composition, function, and potency.

RESULTS

Considerable ontogenetic shifts in venom profiles were observed in D. russelii, with the venoms of newborns being many times as potent as juveniles and adults against mammalian (2.3-2.5 ×) and reptilian (2-10 ×) prey. This is the first documentation of the ontogenetic shift in viperine snakes. In stark contrast, N. naja, which shares a biogeographic distribution similar to D. russelii, deployed identical biochemical cocktails across development. Furthermore, the binding kinetics of cobra venom toxins against synthetic target receptors from various prey and predators shed light on the evolutionary arms race.

CONCLUSIONS

Our findings, therefore, provide fascinating insights into the roles of ecology and life history traits in shaping snake venoms.

Monitoring Snake Venom-Induced Extracellular Matrix Degradation and Identifying Proteolytically Active Venom Toxins Using Fluorescently Labeled Substrates

Snakebite envenoming is an important public health issue with devastating consequences and annual mortality rates that range between 81,000 and 138,000. Snake venoms may cause a range of pathophysiological effects affecting the nervous system and the cardiovascular system. Moreover, snake venom may have tissue-damaging activities that result in lifelong morbidities such as amputations, muscle degeneration, and organ malfunctioning. The tissue-damaging components in snake venoms comprise multiple toxin classes with various molecular targets including cellular membranes and the extracellular matrix (ECM). In this study, we present multiple assay formats that enable investigation of snake venom-induced ECM degradation using a variety of (dye-quenched) fluorescently labeled ECM components. Using a combinatorial approach, we were able to characterise different proteolytic profiles for different medically relevant snake venoms, followed by identification of the responsible components within the snake venoms. This workflow could provide valuable insights into the key mechanisms by which proteolytic venom components exert their effects and could therefore prove useful for the development of effective snakebite treatments against this severe pathology.

A novel broad spectrum venom metalloproteinase autoinhibitor in the rattlesnake Crotalus atrox evolved via a shift in paralog function

The complexity of snake venom composition reflects adaptation to the diversity of prey and may be driven at times by a coevolutionary arms race between snakes and venom-resistant prey. However, many snakes are also resistant to their own venom due to serum-borne inhibitors of venom toxins, which raises the question of how snake autoinhibitors maintain their efficacy as venom proteins evolve. To investigate this potential three-way arms race among venom, prey, and autoinhibitors, we have identified and traced the evolutionary origin of serum inhibitors of snake venom metalloproteinases (SVMPs) in the Western Diamondback rattlesnake Crotalus atrox which possesses the largest known battery of SVMP genes among crotalids examined. We found that C. atrox expresses five members of a Fetuin A-related metalloproteinase inhibitor family but that one family member, FETUA-3, is the major SVMP inhibitor that binds to approximately 20 different C. atrox SVMPs and inhibits activities of all three SVMP classes. We show that the fetua-3 gene arose deep within crotalid evolution before the origin of New World species but, surprisingly, fetua-3 belongs to a different paralog group than previously identified SVMP inhibitors in Asian and South American crotalids. Conversely, the C. atrox FETUA-2 ortholog of previously characterized crotalid SVMP inhibitors shows limited activity against C. atrox SVMPs. These results reveal that there has been a functional evolutionary shift in the major SVMP inhibitor in the C. atrox lineage as the SVMP family expanded and diversified in the Crotalus lineage. This broad-spectrum inhibitor may be of potential therapeutic interest.

The Middle Eastern Cousin: Comparative Venomics of Daboia palaestinae and Daboia russelii

Among the medically most important snakes in the world, the species belonging to the genus Daboia have been attributed to the highest number of human envenomings, deaths and disabilities. Given their significant clinical relevance, the venoms of Russell's vipers (D. russelii and D. siamensis) have been the primary focus of research. In contrast, the composition, activity, ecology and evolution of venom of its congener, the Palestine viper (D. palaestinae), have remained largely understudied. Therefore, to unravel the factors responsible for the enhanced medical relevance of D. russelii in comparison to D. palaestinae, we comparatively evaluated their venom proteomes, biochemical activities, and mortality and morbidity inflicting potentials. Furthermore, the synthesis and regulation of venom in snakes have also remained underinvestigated, and the relative contribution of each venom gland remains unclear. We address this knowledge gap by sequencing the tissue transcriptomes of both venom glands of D. palaestinae, and comparatively evaluating their contribution to the secreted venom concoction. Our findings highlight the disparity in the venom composition, function and toxicities of the two Daboia species. We also show that toxin production is not partitioned between the two venom glands of D. palaestinae.

Revisiting the potential of South American rattlesnake Crotalus durissus terrificus toxins as therapeutic, theranostic and/or biotechnological agents

The potential biotechnological and biomedical applications of the animal venom components are widely recognized. Indeed, many components have been used either as drugs or as templates/prototypes for the development of innovative pharmaceutical drugs, among which many are still used for the treatment of human diseases. A specific South American rattlesnake, named Crotalus durissus terrificus, shows a venom composition relatively simpler compared to any viper or other snake species belonging to the Crotalus genus, although presenting a set of toxins with high potential for the treatment of several still unmet human therapeutic needs, as reviewed in this work. In addition to the main toxin named crotoxin, which is under clinical trials studies for antitumoral therapy and which has also anti-inflammatory and immunosuppressive activities, other toxins from the C. d. terrificus venom are also being studied, aiming for a wide variety of therapeutic applications, including as antinociceptive, anti-inflammatory, antimicrobial, antifungal, antitumoral or antiparasitic agent, or as modulator of animal metabolism, fibrin sealant (fibrin glue), gene carrier or theranostic agent. Among these rattlesnake toxins, the most relevant, considering the potential clinical applications, are crotamine, crotalphine and gyroxin. In this narrative revision, we propose to organize and present briefly the updates in the accumulated knowledge on potential therapeutic applications of toxins collectively found exclusively in the venom of this specific South American rattlesnake, with the objective of contributing to increase the chances of success in the discovery of drugs based on toxins.

LIMITED PROTEOLYSIS OF FIBRINOGEN BY PROTEASE OF Gloydius halys halys SNAKE VENOM

Aim. One of the approaches for studying structure and functions of proteins is their limited proteolysis. Proteolytic fragments of macromolecules can preserve the biological activity and can be used for the study of their structural and functional peculiarities. Thus, the characterization of new proteolytic enzymes and determination of the specificity of their action can be of interest for exploration. In the present work, we focused on the action of protease from the venom of Gloydius halys halys on fibrinogen, the crucial protein of blood coagulation system. Methods. Products of fibrinogen hydrolysis by protease from the venom of G. halys halys were studied by SDS-PAGE electrophoresis and western-blot analysis using monoclonal antibodies ІІ-5 Сand 1-5A targeted to 20‒78 and 549‒610 fragments of fibrinogen Aα-chain. Molecular weights of hydrolytic products were determined using MALDI-TOF analysis on Voyager DE PRO (USA). Sequence of hydrolytic products were predicted by «Peptide Mass Calculator» soft ware. Results. SDS-PAGE showed that protease from the venom of Gloydius halys halys initially cleaved Аα-chain of fibrinogen molecule. Western-blot analysis confirmed that this protease specifically cleaves off fragment of C-terminal parts of Аα-chain with apparent molecular weight of 22 kDa. Cleaved fragment was identified by MALDI-TOF analysis as the 21.1 kDa polypeptide. «Peptide Mass Calculator» predicted that such a fragment corresponded to Аα414-610 residue of fibrinogen molecule. Thus, we showed that studied protease cleaved peptide bond AαK413-L414 with the formation of stable partly hydrolyzed fibrinogen desAα414-610. Conclusions. The use of protease from the venom of Gloydius halys halys would allow obtaining the unique partly hydrolyzed fibrinogen des Aα 414‒610 that is suitable for the study of structure and functions of fibrinogen αС-regions.

Royal jelly from different floral sources possesses distinct wound-healing mechanisms and ingredient profiles

In recent years, population aging together with the increased prevalence of diabetes and obesity has fuelled a surge in the instances of cutaneous non-healing wounds. Royal jelly (RJ) is a traditional remedy for wound repair; however, the subjacent mechanisms and ingredient profiles are still largely unknown. Our previous study found that Castanea mollissima Bl. RJ (CmRJ-Zj) possessed superior wound healing-promoting effects on both the in vivo and in vitro models than Brassica napus L. RJ (BnRJ-Zj). This study conducted an in-depth investigation on the wound-repairing mechanisms of CmRJ-Zj and BnRJ-Zj to explain the previously observed phenomenon and also comprehensively characterized their constituents. It was found that chestnut RJ could enhance cutaneous wound healing by boosting the growth and mobility of keratinocytes, modulating the expression of aquaporin 3 (AQP3), regulating MAPK and calcium pathways, and mediating inflammatory responses. By employing LC-MS/MS-based proteomic and metabolomic techniques, the comprehensive molecules present in CmRJ-Zj and BnRJ-Zj were elucidated, resulting in a clear discrimination from each other. A total of 15 and 631 differential proteins and compounds were identified, and 217 proteins were newly found in RJ proteome. With bioinformatic functional analysis, we speculated that some differential components were responsible for the wound-healing properties of CmRJ-Zj. Therefore, this study provides an insight into the wound-healing mechanisms of RJ and is the first to explore the compositions of RJ from different nectar plants. It will facilitate the development of therapeutic agents from RJ to treat difficult-to-heal wounds and the distinction of different RJ categories.

Crotalus Durissus Ruruima: Current Knowledge on Natural History, Medical Importance, and Clinical Toxinology

Crotalus durissus ruruima is a rattlesnake subspecies mainly found in Roraima, the northernmost state of Brazil. Envenomings caused by this subspecies lead to severe clinical manifestations (e.g. respiratory muscle paralysis, rhabdomyolysis, and acute renal failure) that can lead to the victim’s death. In this review, we comprehensively describe C. d. ruruima biology and the challenges this subspecies poses for human health, including morphology, distribution, epidemiology, venom cocktail, clinical envenoming, and the current and future specific treatment of envenomings by this snake. Moreover, this review presents maps of the distribution of the snake subspecies and evidence that this species is responsible for some of the most severe envenomings in the country and causes the highest lethality rates. Finally, we also discuss the efficacy of the Brazilian horse-derived antivenoms to treat C. d. ruruima envenomings in Roraima state.