Unveiling toxicological aspects of venom from the Aesculapian False Coral Snake Erythrolamprus aesculapii

Exploring the antibacterial potential of venoms from Argentinian animals

The resistance to antimicrobials developed by several bacterial species has become one of the main health problems in recent decades. It has been widely reported that natural products are important sources of antimicrobial compounds. Considering that animal venoms are under-explored in this line of research, in this study, we screened the antibacterial activity of venoms of eight snake and five lepidopteran species from northeastern Argentina. Twofold serial dilutions of venoms were tested by the agar well-diffusion method and the minimum inhibitory concentration (MIC) determination against seven bacterial strains. We studied the comparative protein profile of the venoms showing antibacterial activity. Only the viperid and elapid venoms showed remarkable dose-dependent antibacterial activity towards most of the strains tested. Bothrops diporus venom showed the lowest MIC values against all the strains, and S. aureus ATCC 25923 was the most sensitive strain for all the active venoms. Micrurus baliocoryphus venom was unable to inhibit the growth of Enterococcus faecalis. Neither colubrid snake nor lepidopteran venoms exhibited activity on any bacterial strain tested. The snake venoms exhibiting antibacterial activity showed distinctive protein profiles by SDS-PAGE, highlighting that we could reveal for the first time the main protein families which may be thought to contribute to the antibacterial activity of M. baliocoryphus venom. This study paves the way to search for new antibacterial agents from Argentinian snake venoms, which may be a further opportunity to give an added value to the local biodiversity.

Shedding Light on the Dentition and Venom Delivery System of the Rear-Fanged Snake, Galvarinus chilensis chilensis (Serpentes: Dipsadidae: Tachymenini) from Chile

Although the rear-fanged snake Galvarinus chilensis chilensis (formerly named Tachymenis ch. chilensis) causes ophidian accidents with clinical importance in Chile, the anatomical and histological characterizations of the venom delivery system (venom gland and fang) of this species still remain unknown. This study describes the dentition and characteristics of fangs and their ontogenetic variations in G. ch. chilensis. Moreover, histological and histochemistry analyses of the venom glands of this species are presented. Using micro-computed tomography and scanning electron microscopy, the dentitions of neonates, juveniles, and adults were analyzed, and no ontogenetic variations in teeth length and number present in the dentary and maxilla were observed. Moreover, we found three types of basic teeth, with distributional patterns conserved in all ontogenetic categories. The fangs exhibited a groove from the base to the middle. At the end of the groove, prominent ridges are formed. The fang and groove lengths were significantly distinct between ontogenetic categories. No differences between females and males were observed. Histologically, we found that the venom gland is close to the fangs and has a seromucous composition. Our results describe, for the first time, the distributional pattern and characteristics of the dentition and venom delivery system of the poorly studied snake G. ch. chilensis.

Venom production and secretion in reptiles

The venom glands of reptiles, particularly those of front-fanged advanced snakes, must satisfy conflicting biological demands: rapid synthesis of potentially labile and highly toxic proteins, storage in the gland lumen for long periods, stabilization of the stored secretions, immediate activation of toxins upon deployment and protection of the animal from the toxic effects of its own venom. This dynamic system could serve as a model for the study of a variety of different phenomena involving exocrine gland activation, protein synthesis, stabilization of protein products and secretory mechanisms. However, these studies have been hampered by a lack of a long-term model that can be propagated in the lab (as opposed to whole-animal studies). Numerous attempts have been made to extend the lifetime of venom gland secretory cells, but only recently has an organoid model been shown to have the requisite qualities of recapitulation of the native system, self-propagation and long-term viability (>1 year). A tractable model is now available for myriad cell- and molecular-level studies of venom glands, protein synthesis and secretion. However, venom glands of reptiles are not identical, and many differ very extensively in overall architecture, microanatomy and protein products produced. This Review summarizes the similarities among and differences between venom glands of helodermatid lizards and of rear-fanged and front-fanged snakes, highlighting those areas that are well understood and identifying areas where future studies can fill in significant gaps in knowledge of these ancient, yet fascinating systems.

First insights into the biochemical and toxicological characterization of venom from the Banded Cat-eyed Snake Leptodeira annulata pulchriceps

With the aim to widen the current knowledge of toxinological implications of bites from rear-fanged snakes and biological roles of their venoms, this study focuses on the biochemical composition and toxic effects of the venom of Leptodeira annulata pulchriceps from Argentina. We analyzed the protein composition by electrophoresis and mass spectrometry, and enzymatic properties by quantitative assays on different substrates. Additionally, we evaluated local and systemic toxicity in mice, and tested its cross-reactivity with elapid and viperid antivenoms used in Argentina. This venom showed features reminiscent of venoms from snakes of Bothrops genus, containing components ranging from ~17 to 75 kDa, which are mainly tissue-damaging toxins such as proteinases. Although showing low lethality to mice (LD₅₀ = 20 μg/g body weight), prominent hemorrhage developed locally in mice intramuscularly and intradermally injected with the venom, and the minimum hemorrhagic dose was found to be 12.7 μg/mouse. This study is the first comprehensive investigation of the venom of L. a. pulchriceps, and sheds new light on differences between this and those of the other two subspecies of L. annulata. Additionally, the study provides new insights into the venom components of "colubrid" snakes, advocating for considering bites from this rich diversity of snakes as a public health problem that needs to be addressed worldwide.

Replacement and Parallel Simplification of Nonhomologous Proteinases Maintain Venom Phenotypes in Rear-Fanged Snakes

Novel phenotypes are commonly associated with gene duplications and neofunctionalization, less documented are the cases of phenotypic maintenance through the recruitment of novel genes. Proteolysis is the primary toxic character of many snake venoms, and ADAM metalloproteinases, named snake venom metalloproteinases (SVMPs), are largely recognized as the major effectors of this phenotype. However, by investigating original transcriptomes from 58 species of advanced snakes (Caenophidia) across their phylogeny, we discovered that a different enzyme, matrix metalloproteinase (MMP), is actually the dominant venom component in three tribes (Tachymenini, Xenodontini, and Conophiini) of rear-fanged snakes (Dipsadidae). Proteomic and functional analyses of these venoms further indicate that MMPs are likely playing an "SVMP-like" function in the proteolytic phenotype. A detailed look into the venom-specific sequences revealed a new highly expressed MMP subtype, named snake venom MMP (svMMP), which originated independently on at least three occasions from an endogenous MMP-9. We further show that by losing ancillary noncatalytic domains present in its ancestors, svMMPs followed an evolutionary path toward a simplified structure during their expansion in the genomes, thus paralleling what has been proposed for the evolution of their Viperidae counterparts, the SVMPs. Moreover, we inferred an inverse relationship between the expression of svMMPs and SVMPs along the evolutionary history of Xenodontinae, pointing out that one type of enzyme may be substituting for the other, whereas the general (metallo)proteolytic phenotype is maintained. These results provide rare evidence on how relevant phenotypic traits can be optimized via natural selection on nonhomologous genes, yielding alternate biochemical components.

Venoms of New World Vinesnakes (Oxybelis aeneus and O. fulgidus)

Species of Oxybelis are extremely elongate arboreal snakes that are broadly distributed in the Americas, from extreme southeastern Arizona (USA) to central South America. Primarily feeding on lizards and birds, Oxybelis venoms are poorly known in general, but a prominent taxon-specific three-finger toxin (fulgimotoxin) was isolated from and is a prominent component of O. fulgidus venom; a homolog is also present in O. aeneus venom. As part of ongoing characterization of venoms from rear-fanged snakes, we describe here the composition of two broadly distributed species, O. aeneus and O. fulgidus. Venom proteomes were of very low complexity, and four protein families (LAAO, PIII SVMP, CRiSP and 3FTx) account for more than 90% of total protein composition. Venoms from both species are moderately toxic to mice and to Hemidactylus geckos, but they are nearly an order of magnitude more toxic to Anolis lizards (a native prey species). These results reflect a trend in colubrid venom composition that is becoming increasingly more common: the presence of taxon-specific toxins, specifically three-finger toxins, preferentially targeting lizards and/or birds.