C-type lectin protein isoforms of Macrovipera lebetina: cDNA cloning and genetic diversity

Biphasic Hormetic-like Effect of Lebecetin, a C-type Lectin of Snake Venom, on Formalin-induced Inflammation in Mice

BACKGROUND

Integrins, important extracellular matrix (ECM) receptor proteins, are affected by inflammation and can participate in the maintenance of many painful conditions. Although they are ubiquitous and changeable across all cell types, the roles of these cell adhesion molecules in pathological pain have not been fully explored.

OBJECTIVE

We evaluated the effects of the subcutaneous injection of lebecetin, a C-type lectin isolated from Macrovipera lebetina snake venom, previously reported to inhibit α5β1 and αv integrin activity, on different components of inflammation induced by the formalin administration in the hind paw of mice.

METHODS

The formalin-induced nocifensive behavior, edema, and histopathological changes in the hind paw associated with cytokine, iNOS, and COX2 expression, nociceptive-specific neuron activity, and microglial activation analysis in the spinal cord were evaluated in mice receiving vehicle or lebecetin pretreatment.

RESULTS

Lebecetin inhibited the nocifensive responses in the formalin test, related edema, and cell infiltration in the injected paw in a biphasic, hormetic-like, and dose-dependent way. According to that hormetic trend, a reduction in pro-inflammatory cytokines IL-6, IL-8, and TNF-alpha and upregulation of the anti-inflammatory cytokine IL-10 in the spinal cord were found with the lowest doses of lebecetin. Moreover, COX2 and iNOS expression in serum and spinal cord followed the same biphasic pattern of cytokines. Finally, nociceptive neurons sensitization and activated microglia were normalized in the dorsal horn of the spinal cord by lebecetin.

CONCLUSION

These findings implicate specific roles of integrins in inflammation and tonic pain, as well as in the related central nervous system sequelae.

Exploring Toxin Genes of Myanmar Russell's Viper, Daboia siamensis, through De Novo Venom Gland Transcriptomics

The Russell's viper (Daboia siamensis) is a medically important venomous snake in Myanmar. Next-generation sequencing (NGS) shows potential to investigate the venom complexity, giving deeper insights into snakebite pathogenesis and possible drug discoveries. mRNA from venom gland tissue was extracted and sequenced on the Illumina HiSeq platform and de novo assembled by Trinity. The candidate toxin genes were identified via the Venomix pipeline. Protein sequences of identified toxin candidates were compared with the previously described venom proteins using Clustal Omega to assess the positional homology among candidates. Candidate venom transcripts were classified into 23 toxin gene families including 53 unique full-length transcripts. C-type lectins (CTLs) were the most highly expressed, followed by Kunitz-type serine protease inhibitors, disintegrins and Bradykinin potentiating peptide/C-type natriuretic peptide (BPP-CNP) precursors. Phospholipase A₂, snake venom serine proteases, metalloproteinases, vascular endothelial growth factors, L-amino acid oxidases and cysteine-rich secretory proteins were under-represented within the transcriptomes. Several isoforms of transcripts which had not been previously reported in this species were discovered and described. Myanmar Russell's viper venom glands displayed unique sex-specific transcriptome profiles which were correlated with clinical manifestation of envenoming. Our results show that NGS is a useful tool to comprehensively examine understudied venomous snakes.

Expression of the First Recombinant Anti-Tumoral Snake Venom Kunitz-Type Serine Protease Inhibitor

PIVL is a Kunitz-type serine protease inhibitor that was previously characterized from Tunisian snake venom, Macrovipera lebetina transmediterranea. It reduced glioblastoma cells’ development and significantly blocked angiogenesis in in-vitro and ex-vivo models. PIVL exerted these effects by interfering with αvβ3 integrin. In order to produce a biological active recombinant, the cDNA cloning and expression of PIVL was performed in Escherichia coli (BL21)-DE3 cells using pET-22b (+) vector. The recombinant PIVL protein (rPIVL) was purified by nickel affinity chromatography and has recognized monoclonal anti-His antibody. Functionally, rPIVL exhibited potent anti-tumor cell effects as well as anti-angiogenesis properties. Interestingly, we found that both native PIVL (nPIVL) and rPIVL modulated PI3/AKT and MAPK signaling pathways. In all, our results showed that we have successfully expressed the first active anti-oncogenic snake venom Kunitz-type protease inhibitor that can be a potential therapeutic drug against glioblastoma, in its native or recombinant form.

High throughput screening and identification of coagulopathic snake venom proteins and peptides using nanofractionation and proteomics approaches

Snakebite is a neglected tropical disease that results in a variety of systemic and local pathologies in envenomed victims and is responsible for around 138,000 deaths every year. Many snake venoms cause severe coagulopathy that makes victims vulnerable to suffering life-threating haemorrhage. The mechanisms of action of coagulopathic snake venom toxins are diverse and can result in both anticoagulant and procoagulant effects. However, because snake venoms consist of a mixture of numerous protein and peptide components, high throughput characterizations of specific target bioactives is challenging. In this study, we applied a combination of analytical and pharmacological methods to identify snake venom toxins from a wide diversity of snake species that perturb coagulation. To do so, we used a high-throughput screening approach consisting of a miniaturised plasma coagulation assay in combination with a venom nanofractionation approach. Twenty snake venoms were first separated using reversed-phase liquid chromatography, and a post-column split allowed a small fraction to be analyzed with mass spectrometry, while the larger fraction was collected and dispensed onto 384-well plates. After fraction collection, any solvent present in the wells was removed by means of freeze-drying, after which it was possible to perform a plasma coagulation assay in order to detect coagulopathic activity. Our results demonstrate that many snake venoms simultaneously contain both procoagulant and anticoagulant bioactives that contribute to coagulopathy. In-depth identification analysis from seven medically-important venoms, via mass spectrometry and nanoLC-MS/MS, revealed that phospholipase A2 toxins are frequently identified in anticoagulant venom fractions, while serine protease and metalloproteinase toxins are often associated with procoagulant bioactivities. The nanofractionation and proteomics approach applied herein seems likely to be a valuable tool for the rational development of next-generation snakebite treatments by facilitating the rapid identification and fractionation of coagulopathic toxins, thereby enabling specific targeting of these toxins by new therapeutics such as monoclonal antibodies and small molecule inhibitors.

Identification and molecular characterization of five putative toxins from the venom gland of the snake Philodryas chamissonis (Serpentes: Dipsadidae)

Philodryas chamissonis is a rear-fanged snake endemic to Chile. Its bite produces mild to moderate symptoms with proteolytic and anti-coagulant effects. Presently, the composition of the venom, as well as, the biochemical and structural characteristics of its toxins, remains unknown. In this study, we cloned and reported the first full-length sequences of five toxin-encoding genes from the venom gland of this species: Type III snake venom metalloprotease (SVMP), snake venom serine protease (SVSP), Cysteine-rich secretory protein (CRISP), α and β subunits of C-type lectin-like protein (CLP) and C-type natriuretic peptide (NP). These genes are highly expressed in the venom gland and their sequences exhibited a putative signal peptide, suggesting that these are components of the venom. These putative toxins had different evolutionary relationships with those reported for some front-fanged snakes, being SVMP, SVSP and CRISP of P. chamissonis closely related to the toxins present in Elapidae species, while NP was more related to those of Viperidae species. In addition, analyses suggest that the α and β subunits of CLP of P. chamissonis might have a α-subunit scaffold in common with Viperidae species, whose highly variable C-terminal region might have allowed the diversification in α and β subunits. Our results provide the first molecular description of the toxins possibly implicated in the envenomation of prey and humans by the bite of P. chamissonis.

Phosphodiesterase from Vipera lebetina venom - structure and characterization

Nucleases and phosphatases are ubiquitous but mostly marginal components of snake venoms. These proteins have been studied quite extensively but up to now no data regarding their amino acid sequences confirmed at protein level have been published. The present study deals with purification, characterization, and structural properties of a phosphodiesterase from Vipera lebetina venom (VLPDE). The VLPDE with molecular mass of about 120 kDa hydrolyses ADP but not ATP and 5'-AMP. The aggregation of platelets induced by ADP or collagen is dose-dependently inhibited by VLPDE. The cloning and sequencing of the VLPDE-encoding cDNA resulted in 2772-nt sequence with ORF of 2556 nt. The translated sequence comprises 851 amino acids including the 23-amino acid signal peptide. VLPDE is synthesized as a 828-amino acid single-chain protein but subsequently cleaved to form a two-chain protein held together with disulfide bonds. In reducing conditions the enzyme behaves like a heterodimeric protein but, differently from the real heterodimers, it is synthesized as a single-chain protein. VLPDE is the first snake venom phosphodiesterase with established and confirmed primary structure.

Lebecin, a new C-type lectin like protein from Macrovipera lebetina venom with anti-tumor activity against the breast cancer cell line MDA-MB231

C-type lectins like proteins display various biological activities and are known to affect especially platelet aggregation. Few of them have been reported to have anti-tumor effects. In this study, we have identified and characterized a new C-type lectin like protein, named lebecin. Lebecin is a heterodimeric protein of 30 kDa. The N-terminal amino acid sequences of both subunits were determined by Edman degradation and the entire amino acid sequences were deduced from cDNAs. The precursors of both lebecin subunits contain a 23-amino acid residue signal peptide and the mature α and β subunits are composed of 129 and 131 amino acids, respectively. Lebecin is shown to be a potent inhibitor of MDA-MB231 human breast cancer cells proliferation. Furthermore, lebecin dose-dependently inhibited the integrin-mediated attachment of these cells to different adhesion substrata. This novel C-type lectin also completely blocked MDA-MB231 cells migration towards fibronectin and fibrinogen in haptotaxis assays.

Antitumoral potential of Tunisian snake venoms secreted phospholipases A2

Phospholipases type A₂ (PLA₂s) are the most abundant proteins found in Viperidae snake venom. They are quite fascinating from both a biological and structural point of view. Despite similarity in their structures and common catalytic properties, they exhibit a wide spectrum of pharmacological activities. Besides being hydrolases, secreted phospholipases A₂ (sPLA₂) are an important group of toxins, whose action at the molecular level is still a matter of debate. These proteins can display toxic effects by different mechanisms. In addition to neurotoxicity, myotoxicity, hemolytic activity, antibacterial, anticoagulant, and antiplatelet effects, some venom PLA₂s show antitumor and antiangiogenic activities by mechanisms independent of their enzymatic activity. This paper aims to discuss original finding against anti-tumor and anti-angiogenic activities of sPLA₂ isolated from Tunisian vipers: Cerastes cerastes and Macrovipera lebetina, representing new tools to target specific integrins, mainly, α5β1 and αv integrins.

Guillain-Barre syndrome: first description of a snake envenomation aetiology

BACKGROUND

Guillain-Barre syndrome (GBS) is considered as an acute, immune-mediated polyradiculoneuropathy with different clinical phenotypes arising after viral or bacterial infections, vaccination or surgery. However, in 40% of GBS patients the aetiology remains unknown. In this manuscript, we report the occurrence of GBS in a patient bitten by a snake (Vipera aspis) for which a cross-reaction was shown between GM2 ganglioside and glycosidic epitopes of venom proteins.

METHODS

The venom of the snake implied in the patient's envenomation was collected. Its composition was characterised by ELISA and SELDI-TOF MS. Cross-reactivities between venom proteins and GM2 gangliosides were identified by Western blot after immunoabsorption of patient's serum with increasing amounts of purified GM2. Enzymatic deglycosylation of the venom was performed to determine the specificity of the patient's serum cross-reaction.

FINDINGS

We proved the absence of neurotoxicity of the viper venom. The patient's serum presented specific cross-reactions with several glycosylated venom proteins. After deglycolysation of these proteins, the patient's serum cross-reactivity was abolished. Furthermore, we compared the immune response to venom proteins of sera from two groups of patients. The first group showed IgM reactivity against GM2 ganglioside associated with GBS, and cross-reacted with venom proteins. The second group presented an IgM reactivity against CMV, without neurological disorders, and reacted with neither venom proteins nor gangliosides.

INTERPRETATION

Our study proved the auto-immunological aetiology of GBS in our patient based on molecular mimicry mechanisms between venom proteins and GM2 ganglioside.