Comparative Study of Biological Activities of Venom from Colubrid Snakes Rhabdophis tigrinus (Yamakagashi) and Rhabdophis lateralis

Clinical practice guidelines for management of disseminated intravascular coagulation in Japan 2024: part 4-trauma, burn, obstetrics, acute pancreatitis/liver failure, and others

Disseminated intravascular coagulation (DIC) is a complex condition with diverse etiologies. While its association with sepsis has been widely studied, less focus has been given to DIC arising from other critical conditions, such as trauma, burns, acute pancreatitis, and obstetric complications. The 2024 Clinical Practice Guidelines, developed by the Japanese Society on Thrombosis and Hemostasis (JSTH), aim to fill this gap and offer comprehensive recommendations for managing DIC across various conditions. This study, Part 4 of the guideline series, addresses DIC management in trauma, burns, obstetric complications, acute pancreatitis/liver failure, viral infections, and autoimmune diseases. For trauma-associated DIC, early administration of fresh-frozen plasma (FFP), coagulation factor concentrates such as fibrinogen and prothrombin complex concentrates, and tranexamic acid is recommended. The guidelines also highlight DIC in obstetrics, which is associated with massive bleeding, and recommend the administration of fibrinogen concentrate, antithrombin concentrate, and tranexamic acid. Through a systematic review of the current evidence, the guidelines provide stratified recommendations aimed at improving clinical outcomes in DIC management beyond sepsis, thereby serving as a valuable resource for healthcare providers globally.

Venom proteomics and Duvernoy's venom gland histology of Pseudoboa neuwiedii (Neuwied's false boa; Dipsadidae, Pseudoboini)

The venom of Colombian specimens of the rear-fanged snake Pseudoboa neuwiedii contains proteolytic and phospholipase A2 (PLA2) activities, but is devoid of esterases. Mass spectrometric analysis of electrophoretic bands indicated that this venom contains C-type lectins (CTL), cysteine-rich secretory proteins (CRiSP), PLA2, snake venom metalloproteinases (SVMP), and snake venom matrix metalloproteinases (svMMP). In this investigation, we extended our characterization of P. neuwiedii by undertaking a shotgun proteomic analysis of the venom and comparing the results with a transcriptomic database for Brazilian P. neuwiedii; proteomic data previously obtained by in-gel digestion of electrophoretic bands coupled with mass spectrometry were also reanalyzed by comparing them with the transcriptomic results. The histology of the Duvernoy's venom gland was also examined. Histological analysis revealed a structural organization similar to that of other colubrids that consisted of a serous venom gland and a mucous supralabial gland. When the shotgun proteomic data were run against a general UniProt database for serpents, only metalloproteinases were identified (99% SVMPs, 1% snake endogenous matrix metalloproteinases-9 or seMMP-9). In contrast, when run against a transcriptomic database derived from the venom gland of Brazilian P. neuwiedii that contains predominantly SVMP, CRiSP, type IIE PLA2 (PLA2-IIE), CTL and seMMP-9, the main components identified were seMMP-9 (49%), SVMP (47%), CRiSP (3%) and minor components that included CTL and PLA2-IIE. These findings confirmed the previously reported general composition of P. neuwiedii venom, with metalloproteinases (SVMP and seMMP-9) being the major components, and refined the identification of certain components, e.g., type IIA PLA2 now identified as PLA2-IIE and the detection of seMMP-9 rather than svMMP. The data also indicate compositional similarity between Brazilian and Colombian P. neuwiedii venoms, and stress the need for specific databases for non-front-fanged colubroid snakes to allow accurate and more comprehensive identification of the venom components of these snakes.

Age Is Just a Number: Ontogenetic Conservation in Activation of Blood Clotting Factors VII, X, and XII by Caucasus Blunt-Nosed Viper (Macrovipera lebetina obtusa) Venoms

This study examined the pathophysiological effects of venoms from neonate and adult specimens of the viperid snake Macrovipera lebetina obtusa, focusing on their ability to activate various blood clotting factors in human plasma. All venoms exhibited strong procoagulant properties. In concentration-response tests, the clotting potency of the neonate venoms fell within the range of their parents' maximum clotting velocities and areas under the curve. Intriguingly, females were more potent than males within each age group, but this requires a larger sample size to confirm. Antivenom neutralization efficacy was equipotent across age groups. The venoms potently activated Factor X (FX) robustly, consistent with previous knowledge of this genus. For the first time, the ability to activate Factors VII (FVII) and XII (FXII) was identified in this genus, with FXII exhibiting particularly strong activation. The study found no significant ontogenetic variation in procoagulant venom potency on human plasma, convergent with the Daboia genus, the other large-bodied lineage within the Palearctic viperid clade. However, the activation of FXII and FVII reveals previously undocumented pathways in the procoagulant activity of these venoms, contributing to the broader understanding of venom evolution and its clinical impacts. These findings have implications for venom biodiscovery and the development of antivenoms, highlighting the complexity of clotting factor activation beyond traditional investigations that have myopically focused upon FX and prothrombin pathways, thereby underscoring the importance of exploring additional clotting factors.

From Venom to Vein: Factor VII Activation as a Major Pathophysiological Target for Procoagulant Australian Elapid Snake Venoms

Australian elapid snake venoms are uniquely procoagulant, utilizing blood clotting enzyme Factor Xa (FXa) as a toxin, which evolved as a basal trait in this clade. The subsequent recruitment of Factor Va (FVa) as a toxin occurred in the last common ancestor of taipans (Oxyuranus species) and brown snakes (Pseudonaja species). Factor II (prothrombin) activation has been stated as the primary mechanism for the lethal coagulopathy, but this hypothesis has never been tested. The additional activation of Factor VII (FVII) by Oxyuranus/Pseudonaja venoms has historically been considered as a minor, unimportant novelty. This study aimed to investigate the significance of toxic FVII activation relative to prothrombin activation by testing a wide taxonomical range of Australian elapid species with procoagulant venoms. The activation of FVII or prothrombin, with and without the Factor Va as a cofactor, was assessed, along with the structural changes involved in these processes. All procoagulant species could activate FVII, establishing this as a basal trait. In contrast, only some lineages could activate prothrombin, indicating that this is a derived trait. For species able to activate both zymogens, Factor VII was consistently more strongly activated than prothrombin. FVa was revealed as an essential cofactor for FVII activation, a mechanism previously undocumented. Species lacking FVa in their venom utilized endogenous plasma FVa to exert this activity. The ability of the human FXa:FVa complex to activate FVII was also revealed as a new feedback loop in the endogenous clotting cascade. Toxin sequence analyses identified structural changes essential for the derived trait of prothrombin activation. This study presents a paradigm shift in understanding how elapid venoms activate coagulation factors, highlighting the critical role of FVII activation in the pathophysiological effects upon the coagulation cascade produced by Australian elapid snake venoms. It also documented the novel use of Factor Va as a cofactor for FVII activation for both venom and endogenous forms of FXa. These findings are crucial for developing better antivenoms and treatments for snakebite victims and have broader implications for drug design and the treatment of coagulation disorders. The research also advances the evolutionary biology knowledge of snake venoms.

Rhabdophis tigrinus (Yamakagashi) Bites in Japan Over the Last 50 Years: A Retrospective Survey

Introduction:Rhabdophis snakes, which include 27 species, are rear-fanged venomous snakes that are widely distributed from India to East Asia and Russia. Severe envenomation by R. tigrinus (Yamakagashi snake) in Japan and R. subminiatus in Southeast Asia has been reported. The epidemiology of R. tigrinus bites, such as geographical features, the incidence, and changes in the number of bites over time have not been comprehensively examined. Hence, we intended to clarify the epidemiological features of R. tigrinus bites through a careful review of scientific data over the last 50 years in Japan.

Methods: Patient records of R. tigrinus bites between 1971 and 2020 at the Japan Snake Institute were examined retrospectively. The following were ascertained: patient characteristics, clinical symptoms, laboratory data, treatment-related factors, and hospital mortality. These variables were compared in the antivenom and the without-antivenom groups.

Results: Over the 50-year study period, 43 R. tigrinus bites, including five fatal cases, were encountered. Severe cases of R. tigrinus bites have been treated with antivenom since 1985; however, fatalities occurred in 2006 and 2020. R. tigrinus bite cases have been well-distributed in the western part of Japan since 2000. The mortality rate in the antivenom group was significantly lower in the patient group that was not administered the antivenom (0 vs. 23.8%, p = 0.048).

Conclusion: This study clarified the epidemiology of R. tigrinus bites in Japan over a 50-year period. Almost all severe cases of R. tigrinus bites have been treated with the antivenom in the current situation, and fatalities occurred in cases not treated with the antivenom. It is important to diagnose R. tigrinus bites in the early phase of the clinical course. The antivenom, the definitive treatment for R. tigrinus bites, is an unapproved drug. Hence, approval needs to be obtained for the drug.

Dynamic genetic differentiation drives the widespread structural and functional convergent evolution of snake venom proteinaceous toxins

BACKGROUND

The explosive radiation and diversification of the advanced snakes (superfamily Colubroidea) was associated with changes in all aspects of the shared venom system. Morphological changes included the partitioning of the mixed ancestral glands into two discrete glands devoted for production of venom or mucous respectively, as well as changes in the location, size and structural elements of the venom-delivering teeth. Evidence also exists for homology among venom gland toxins expressed across the advanced snakes. However, despite the evolutionary novelty of snake venoms, in-depth toxin molecular evolutionary history reconstructions have been mostly limited to those types present in only two front-fanged snake families, Elapidae and Viperidae. To have a broader understanding of toxins shared among extant snakes, here we first sequenced the transcriptomes of eight taxonomically diverse rear-fanged species and four key viperid species and analysed major toxin types shared across the advanced snakes.

RESULTS

Transcriptomes were constructed for the following families and species: Colubridae - Helicops leopardinus, Heterodon nasicus, Rhabdophis subminiatus; Homalopsidae - Homalopsis buccata; Lamprophiidae - Malpolon monspessulanus, Psammophis schokari, Psammophis subtaeniatus, Rhamphiophis oxyrhynchus; and Viperidae - Bitis atropos, Pseudocerastes urarachnoides, Tropidolaeumus subannulatus, Vipera transcaucasiana. These sequences were combined with those from available databases of other species in order to facilitate a robust reconstruction of the molecular evolutionary history of the key toxin classes present in the venom of the last common ancestor of the advanced snakes, and thus present across the full diversity of colubroid snake venoms. In addition to differential rates of evolution in toxin classes between the snake lineages, these analyses revealed multiple instances of previously unknown instances of structural and functional convergences. Structural convergences included: the evolution of new cysteines to form heteromeric complexes, such as within kunitz peptides (the beta-bungarotoxin trait evolving on at least two occasions) and within SVMP enzymes (the P-IIId trait evolving on at least three occasions); and the C-terminal tail evolving on two separate occasions within the C-type natriuretic peptides, to create structural and functional analogues of the ANP/BNP tailed condition. Also shown was that the de novo evolution of new post-translationally liberated toxin families within the natriuretic peptide gene propeptide region occurred on at least five occasions, with novel functions ranging from induction of hypotension to post-synaptic neurotoxicity. Functional convergences included the following: multiple occasions of SVMP neofunctionalised in procoagulant venoms into activators of the clotting factors prothrombin and Factor X; multiple instances in procoagulant venoms where kunitz peptides were neofunctionalised into inhibitors of the clot destroying enzyme plasmin, thereby prolonging the half-life of the clots formed by the clotting activating enzymatic toxins; and multiple occasions of kunitz peptides neofunctionalised into neurotoxins acting on presynaptic targets, including twice just within Bungarus venoms.

CONCLUSIONS

We found novel convergences in both structural and functional evolution of snake toxins. These results provide a detailed roadmap for future work to elucidate predator-prey evolutionary arms races, ascertain differential clinical pathologies, as well as documenting rich biodiscovery resources for lead compounds in the drug design and discovery pipeline.

Attempt to Develop Rat Disseminated Intravascular Coagulation Model Using Yamakagashi (Rhabdophis tigrinus) Venom Injection

Disseminated intravascular coagulation, a severe clinical condition caused by an underlying disease, involves a markedly continuous and widespread activation of coagulation in the circulating blood and the formation of numerous microvascular thrombi. A snakebite, including that of the Yamakagashi (Rhabdophis tigrinus), demonstrates this clinical condition. Thus, an animal model using Yamakagashi venom was constructed. Yamakagashi venom was administered to rats, and its lethality and the changes in blood coagulation factors were detected after venom injection. When 300 μg venom was intramuscularly administered to 12-week-old rats, (1) they exhibited hematuria with plasma hemolysis and died within 48 h; (2) Thrombocytopenia in the blood was observed in the rats; (3) irreversible prolongation of prothrombin time in the plasma to the measurement limit occurred; (4) fibrinogen concentration in the plasma irreversibly decreased below the measurement limit; and (5) A transient increase in the plasma concentration of D-dimer was observed. In this model, a fixed amount of Rhabdophis tigrinus venom injection resulted in the clinical symptom similar to the human pathology with snakebite. The use of the rat model is very effective in validating the therapeutic effect of human disseminated intravascular coagulation condition due to snakebite.