Isolation and characterization of five fibrin(ogen)olytic enzymes from the venom of Philodryas olfersii (green snake)

The Venom Composition of the Snake Tribe Philodryadini: 'Omic' Techniques Reveal Intergeneric Variability among South American Racers

Snakes of the Philodryadini tribe are included in the Dipsadidae family, which is a diverse group of rear-fanged snakes widespread in different ecological conditions, including habitats and diet. However, little is known about the composition and effects of their venoms despite their relevance for understanding the evolution of these snakes or even their impact on the occasional cases of human envenoming. In this study, we integrated venom gland transcriptomics, venom proteomics and functional assays to characterize the venoms from eight species of the Philodryadini tribe, which includes the genus Philodryas, Chlorosoma and Xenoxybelis. The most abundant components identified in the venoms were snake venom metalloproteinases (SVMPs), cysteine-rich secretory proteins (CRISPs), C-type lectins (CTLs), snake endogenous matrix metalloproteinases type 9 (seMMP-9) and snake venom serinoproteinases (SVSPs). These protein families showed a variable expression profile in each genus. SVMPs were the most abundant components in Philodryas, while seMMP-9 and CRISPs were the most expressed in Chlorosoma and Xenoxybelis, respectively. Lineage-specific differences in venom composition were also observed among Philodryas species, whereas P. olfersii presented the highest amount of SVSPs and P. agassizii was the only species to express significant amounts of 3FTx. The variability observed in venom composition was confirmed by the venom functional assays. Philodryas species presented the highest SVMP activity, whereas Chlorosoma species showed higher levels of gelatin activity, which may correlate to the seMMP-9 enzymes. The variability observed in the composition of these venoms may be related to the tribe phylogeny and influenced by their diets. In the presented study, we expanded the set of venomics studies of the Philodryadini tribe, which paves new roads for further studies on the evolution and ecology of Dipsadidae snakes.

The Influence of Silver Nanoparticles Against Toxic Effects of Philodryas olfersii Venom

Purpose

A silver nanoparticle obtained by reducing salts with solid dispersion of curcumin (130 nm, 0.081 mg mL⁻¹) was used to counteract against the toxic – edematogenic, myotoxic, and neurotoxic – effects of Philodryas olfersii venom.

Methods

The edematogenic effect was evaluated by plasma extravasation in rat dorsal skin after injection of 50 µg per site of venom alone or preincubated with 1, 10, and 100 µL of AgNPs; the myotoxicity was evaluated by measuring the creatine kinase released into the organ-bath before the treatment and at the end of each experiment; and neurotoxicity was evaluated in chick biventer cervicis using the conventional myographic technique, face to the exogenous acetylcholine (ACh) and potassium chloride (KCl) added into the bath before the treatment and after each experiment. Preliminarily, a concentration-response curve of AgNPs was carried out to select the concentration to be used for neutralizing assays, which consists of neutralizing the venom-induced neuromuscular paralysis and edema by preincubating AgNPs with venom for 30 min.

Results

The P. olfersii venom-induced edema (n=6) and a complete neuromuscular blockade (n=4) that includes the total and unrecovered block of ACh and KCl contractures. AgNPs produced a concentration-dependent decrease the venom-induced edema (n=6) from 223.3% to 134.4% and to 100.5% after 10 and 100 µL AgNPs-preincubation, respectively. The preincubation of venom with AgNPs (1 µL; n=6) was able to maintain 46.5 ± 10.9% of neuromuscular response under indirect stimuli, 39.2 ± 9.7% of extrinsic nicotinic receptors functioning in absence of electrical stimulus and 28.3 ± 8.1% of responsiveness to potassium on the sarcolemmal membrane. The CK release was not affected by any experimental protocol which was like control.

Conclusion

AgNPs interact with constituents of P. olfersii venom responsible for the edema-forming activity and neuromuscular blockade, but not on the sarcolemma membrane-acting constituents. The protective effect of the studied AgNPs on avian preparation points out to molecular targets as intrinsic and extrinsic nicotinic receptors.

Bites by Philodryas olfersii (Lichtenstein, 1823) and Philodryas aestiva (Duméril, Bibron and Duméril, 1854) (serpentes, dipsadidae) in São Paulo, Brazil: A retrospective observational study of 155 cases

Despite the biological relevance and abundance of non-front-fanged colubroid snakes, little is known about the medical significance of the majority these species. Herein, we described bites by two green racer species of colubroid snakes, with respect to clinical, epidemiological, and biological features. We retrospectively analyzed proven cases of Philodryas olfersii and Philodryas aestiva bites. Only cases in which the causative animal was brought and identified by an expert were included. Analysis included variables related to the snake, patient demographics, clinical findings, whole blood clotting time (WBCT20), and treatments. Total 155 medical records were analyzed, of which 141 and 14 patients each were bitten by P. olfersii and P. aestiva, respectively. Most bites occurred in spring and summer seasons, predominantly during daytime. Most snakes were female and adult. Bites by P. olfersii adults were more frequent in summer (p < 0.001) and spring (p < 0.001). The hands were most frequently bitten by P. olfersii (59.6%), while the feet and legs (71.4%) were most bitten by P. aestiva. The most common local signs or symptoms observed were pain, edema, erythema, and transitory local bleeding. Severe pain, extensive edema, ecchymosis, and paresthesia were present only in patients bitten by P. olfersii. Significant association was observed between local bleeding and adult snakes (p = 0.019), as well as between the snout-vent-length and pain (p = 0.018), extensive edema (p = 0.024), and erythema (p = 0.047). WBCT20 was normal in the 35 cases in which it was available. Two patients were wrongly treated with anti-Bothrops antivenom. These results indicated that most accidents caused by P. olfersii and P. aestiva present mild local symptomatology. Some bites of P. olfersii bites may present local symptoms, resembling bites by Bothrops-like snakes. Physicians should be informed about these kinds of accidents, to avoid unnecessary distress to the patient and over prescription of antivenom.

Envenomation by opisthoglyphous snake Thamnodynastes hypoconia (Cope, 1860) (Dipsadinae: Tachymenini) in southern Brazil

We report here a case of human envenoming by Thamnodynastes hypoconia, a common and abundant non-front-fanged snake belonging to the subfamily Dipsadinae. The case was registered in the municipality of Tapes, Rio Grande do Sul state, Brazil, in a 27-year-old female. The snakebite was on the wrist of the left arm while handling the snake in a field outing. No pain sensation was noted during the bite, and after 20 minutes edema developed along the hand and forearm with a slight sensation of numbness and mild pain when moving the fingers. After 15 hours, the victim began to develop erythema, paraesthesia, and a sensation of warmth at the bite site. After 30 hours, ecchymosis occurred on the fingers and forearms, and the edema began to decrease. After 70 hours from the time of the bite, ecchymosis along with pruritus and mild pain were still evident. The patient was treated with prescribed medications, and after 7 days no further symptoms were observed. This is the first reported case of envenoming by T. hypoconia.

Cloning, purification and characterization of a recombinant protease with novel thrombolytic activity in human plasma and rat thrombosis models

BACKGROUND

There is a need to identify and develop novel thrombolytic agents that can directly digest fibrin clots from various biological resources.

OBJECTIVE

To clone, express, purify, and characterize a recombinant protease named rvFMP capable of cleaving fibrinogen, fibrin polymer, and cross-linked fibrin in human plasma milieu and rat thrombosis model systems.

RESULTS

We cloned a vFMP-encoding gene from the genomic DNA of V. furnissii KCCM41679 using polymerase chain reaction (PCR), expressed in Escherichia coli, and purified rvFMP (stands for recombinant vibrio furnissii metalloprotease). The proteolytic activity of purified rvFMP enzyme could be clearly inhibited by 1,10-phenanthroline and ethylene glycol tetraacetic acid, but not by diisopropyl fluorophosphate, suggesting that it can be a typical metalloprotease. rvFMP showed an effective proteolytic activity in cleaving cross-linked fibrins in human plasma milieu. Remarkably, rvFMP exhibited a clear thrombolytic activity in rat thrombosis models such as ferric chloride-exposed rat carotid artery and carrageenan-treated rat tail. However, rvFMP (1.5 mg/kg) evoked no internal bleeding and also showed no lethal effect in mice. The recombinant enzyme also showed no cytotoxicity and had an inability to induce tumour necrosis factor-α (TNF-α) in Raw264.7 cells.

CONCLUSION

rvFMP can be a candidate enzyme capable of being developed as a novel direct-acting thrombolytic agent.

Philodryas (Serpentes: Dipsadidae) Envenomation, a Neglected Issue in Chile

Snakebite envenomation is considered a neglected tropical disease, although it also occurs outside the tropics. In this work, we analyzed the literature on Philodryas species in Chile (Philodryaschamissonis, P.simonsii, and P.tachymenoides) from 1834 to 2019, searching for epidemiological, clinical, and molecular aspects of envenomation. Ninety-one percent of the studies found regarded taxonomy, ecology, and natural history, suggesting that snakebites and venom toxins are a neglected issue in Chile. All snakebite cases reported and toxicological studies concerned the species Philodryaschamissonis. Using 185 distributional records from the literature and museum collections for this species, we show for the first time that the reported snakebite cases correlate with human population density, occurring in the Valparaiso and Metropolitan regions in Central Chile. The reduced number of snakebite cases, which were previously considered as having a low incidence in Chile, may be a consequence of under-reported cases, probably due to the inadequate publication or scarce research on this issue. Absence of information about official pharmacological treatment, post-envenoming sequels, clinical management of particular patient groups (e.g., with non-communicable diseases, pregnant women, and the elderly) was also detected. In conclusion, despite having over 185 years of literature on Chilean snakes, knowledge on the envenomation of Philodryas genus remains scarce, seriously affecting adequate medical handling during an ophidic accident. This review highlights the need to develop deep research in this area and urgent improvements to the management of this disease in Chile.

Biochemical characterization of venom from Pseudoboa neuwiedii (Neuwied's false boa; Xenodontinae; Pseudoboini)

In this work, we examined the proteolytic and phospholipase A₂ (PLA₂) activities of venom from the opisthoglyphous colubrid Pseudoboa neuwiedii. Proteolytic activity (3 and 10 μg of venom) was comparable to that of Bothrops neuwiedii venom but less than Bothrops atrox. This activity was inhibited by EDTA and 1,10-phenanthroline but only slightly affected (≤30% inhibition) by PMSF and AEBSF, indicating it was mediated by snake venom metalloproteinases (SVMPs). The pH and temperature optima for proteolytic activity were 8.0 and 37 °C, respectively. The venom had no esterase activity, whereas PLA₂ activity was similar to B. atrox, greater than B. neuwiedii but less than B. jararacussu. SDS-PAGE revealed venom proteins >100 kDa, 45-70 kDa, 21-24 kDa and ~15 kDa, and mass spectrometry of protein bands revealed SVMPs, cysteine-rich secretory proteins (CRISPs) and PLA₂, but no serine proteinases. In gelatin zymography, the most active bands occurred at 65-68 kDa (seen with 0.05-0.25 μg of venom). Caseinolytic activity occurred at 50-66 kDa and was generally weaker than gelatinolytic activity. RP-HPLC of venom yielded 15 peaks, five of which showed gelatinolytic activity; peak 7 was the most active and apparently contained a P-III class SVMP. The venom showed α-fibrinogenase activity, without affecting the β and γ chains; this activity was inhibited by EDTA and 1,10-phenanthroline. The venom did not clot rat citrated plasma but reduced the rate and extent of coagulation after plasma recalcification. In conclusion, P. neuwiedii venom is highly proteolytic and could potentially affect coagulation in vivo by degrading fibrinogen via SVMPs.

What killed Karl Patterson Schmidt? Combined venom gland transcriptomic, venomic and antivenomic analysis of the South African green tree snake (the boomslang), Dispholidus typus

Background

Non-front-fanged colubroid snakes comprise about two-thirds of extant ophidian species. The medical significance of the majority of these snakes is unknown, but at least five species have caused life-threatening or fatal human envenomings. However, the venoms of only a small number of species have been explored.

Methods

A combined venomic and venom gland transcriptomic approach was employed to characterise of venom of Dispholidus typus (boomslang), the snake that caused the tragic death of Professor Karl Patterson Schmidt. The ability of CroFab™ antivenom to immunocapture boomslang venom proteins was investigated using antivenomics.

Results

Transcriptomic-assisted proteomic analysis identified venom proteins belonging to seven protein families: three-finger toxin (3FTx); phospholipase A₂ (PLA₂); cysteine-rich secretory proteins (CRISP); snake venom (SV) serine proteinase (SP); C-type lectin-like (CTL); SV metalloproteinases (SVMPs); and disintegrin-like/cysteine-rich (DC) proteolytic fragments. CroFab™ antivenom efficiently immunodepleted some boomslang SVMPs.

Conclusions

The present work is the first to address the overall proteomic profile of D. typus venom. This study allowed us to correlate the toxin composition with the toxic activities of the venom. The antivenomic analysis suggested that the antivenom available at the time of the unfortunate accident could have exhibited at least some immunoreactivity against the boomslang SVMPs responsible for the disseminated intravascular coagulation syndrome that caused K.P. Schmidt's fatal outcome.

General significance

This study may stimulate further research on other non-front-fanged colubroid snake venoms capable of causing life-threatening envenomings to humans, which in turn should contribute to prevent fatal human accidents, such as that unfortunately suffered by K.P. Schmidt.

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The venom proteome of Dispholidus typus (boomslang) is reported.

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Transcriptomic-assisted proteomic analysis identified venom proteins belonging to seven protein families.

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Boomslang venom proteome is dominated (75%) by snake venom PIII-metalloproteinases (PIII-SVMPs).

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CroFab™ antivenom efficiently immunodepleted some boomslang PIII-SVMPs.

Understanding Biological Roles of Venoms Among the Caenophidia: The Importance of Rear-Fanged Snakes

Snake venoms represent an adaptive trophic response to the challenges confronting a limbless predator for overcoming combative prey, and this chemical means of subduing prey shows several dominant phenotypes. Many front-fanged snakes, particularly vipers, feed on various vertebrate and invertebrate prey species, and some of their venom components (e.g., metalloproteinases, cobratoxin) appear to have been selected for "broad-brush" incapacitation of different prey taxa. Using proteomic and genomic techniques, the compositional diversity of front-fanged snakes is becoming well characterized; however, this is not the case for most rear-fanged colubroid snakes. Because these species consume a high diversity of prey, and because venoms are primarily a trophic adaptation, important clues for understanding specific selective pressures favoring venom component composition will be found among rear-fanged snake venoms. Rear-fanged snakes typically (but not always) produce venoms with lower complexity than front-fanged snakes, and there are even fewer dominant (and, arguably, biologically most relevant) venom protein families. We have demonstrated taxon-specific toxic effects, where lizards and birds show high susceptibility while mammals are largely unaffected, for both Old World and New World rear-fanged snakes, strongly indicating a causal link between toxin evolution and prey preference. New data are presented on myotoxin a, showing that the extremely rapid paralysis induced by this rattlesnake toxin is specific for rodents, and that myotoxin a is ineffectual against lizards. Relatively few rear-fanged snake venoms have been characterized, and basic natural history data are largely lacking, but directed sampling of specialized species indicates that novel compounds are likely among these specialists, particularly among those species feeding on invertebrate prey such as scorpions and centipedes. Because many of the more than 2200 species of colubroid snakes are rear-fanged, and many possess a Duvernoy's venom gland, understanding the nature of their venoms is foundational to understanding venom evolution in advanced snakes.

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.

Biochemical and biological analysis of Philodryas baroni (Baron’s Green Racer; Dipsadidae) venom

Philodryas baroni—an attractively colored snake—has become readily available through the exotic pet trade. Most people consider this species harmless; however, it has already caused human envenomation. As little is known about the venom from this South American opisthoglyphous “colubrid” snake, herein, we studied its protein composition by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), as well as its effects on the hemostatic system. Both reducing and nonreducing SDS-PAGE analysis demonstrated that the venom exhibits greatest complexity in the range of 50–80 kDa. The venom displayed proteolytic activity toward azocollagen, with a specific activity of 75.5 U mg−1, and rapidly hydrolyzed the Aα-chain of fibrinogen, exhibiting lower activity toward the Bβ- and γ-chains. The venom from P. baroni showed no platelet proaggregating activity per se, but it inhibited collagen- and thrombin-induced platelet aggregation. Prominent hemorrhage developed in mouse skin after intradermal injection of the crude venom, and its minimum hemorrhagic dose was 13.9 μg. When injected intramuscularly into the gastrocnemius of mice, the venom induced local effects such as hemorrhage, myonecrosis, edema, and leucocyte infiltration. Due to its venom toxicity shown herein, P. baroni should be considered dangerous to humans and any medically significant bite should be promptly reviewed by a qualified health professional.

Venom proteomes of South and North American opisthoglyphous (Colubridae and Dipsadidae) snake species: a preliminary approach to understanding their biological roles

Opisthoglyphous snake venoms remain under-explored despite being promising sources for ecological, evolutionary and biomedical/biotechnological research. Herein, we compared the protein composition and enzymatic properties of the venoms of Philodryas baroni (PbV), Philodryas olfersii olfersii (PooV) and Philodryas patagoniensis (PpV) from South America, and Hypsiglena torquata texana (HttV) and Trimorphodon biscutatus lambda (TblV) from North America. All venoms degraded azocasein, and this metalloproteinase activity was significantly inhibited by EDTA. PooV exhibited the highest level of catalytic activity towards synthetic substrates for serine proteinases. All venoms hydrolyzed acetylthiocholine at low levels, and only TblV showed phospholipase A(2) activity. 1D and 2D SDS-PAGE profile comparisons demonstrated species-specific components as well as several shared components. Size exclusion chromatograms from the three Philodryas venoms and HttV were similar, but TblV showed a notably different pattern. MALDI-TOF MS of crude venoms revealed as many as 49 distinct protein masses, assigned to six protein families. MALDI-TOF/TOF MS analysis of tryptic peptides confirmed the presence of cysteine-rich secretory proteins in all venoms, as well as a phospholipase A(2) and a three-finger toxin in TblV. Broad patterns of protein composition appear to follow phylogenetic lines, with finer scale variation likely influenced by ecological factors such as diet and habitat.

Alsophinase, a new P-III metalloproteinase with α-fibrinogenolytic and hemorrhagic activity from the venom of the rear-fanged Puerto Rican Racer Alsophis portoricensis (Serpentes: Dipsadidae)

Metalloproteinases from snake venoms are often multi-domain enzymes involved in degradation of a variety of structural proteins. Hemorrhage and tissue necrosis are common manifestations of viperid envenomations in humans, largely due to the actions of prominent metalloproteinases, and envenomation by rear-fanged snakes may also cause hemorrhage. We purified the major metalloproteinase in Alsophis portoricensis (Puerto Rican Racer) venom through HPLC size exclusion and ion exchange chromatography. Named alsophinase, it is the first protein purified and characterized from the venom of Alsophis. Alsophinase is a single polypeptide chain protein, and based on mass, activity and complete inhibition by 1,10-phenanthroline, it is a class P-III snake venom member of the M12 ADAM family of metalloproteinases. Alsophinase has a molecular mass of 56.003kDa and an N-terminal sequence of QDTYLNAKKYIEFYLVVDNGMFxKYSxxFTV, with 67% sequence identity to a metalloproteinase isolated from venom of Philodryas olfersii (another rear-fanged species). Alsophinase rapidly catalyzed cleavage of only the Ala14-Leu15 bond of oxidized insulin B chain, had potent hemorrhagic activity in mice, and degraded only the α-subunit of human fibrinogen in vitro. Alsophinase is responsible for hemorrhagic and fibrinogenolytic activity of crude venom, and it may contribute to localized edema and ecchymosis associated with human envenomations by A. portoricensis. It may be more specific in peptide bond recognition than many well-characterized viperid P-III metalloproteinases, and it could have utility as a new protein fragmentation enzyme for mass spectrometry studies.

Biological and proteomic analysis of venom from the Puerto Rican Racer (Alsophis portoricensis: Dipsadidae)

The Puerto Rican Racer Alsophis portoricensis is known to use venom to subdue lizard prey, and extensive damage to specific lizard body tissues has been well documented. The toxicity and biochemistry of the venom, however, has not been explored extensively. We employed biological assays and proteomic techniques to characterize venom from A. portoricensis anegadae collected from Guana Island, British Virgin Islands. High metalloproteinase and gelatinase, as well as low acetylcholinesterase and phosphodiesterase activities were detected, and the venom hydrolyzed the alpha-subunit of human fibrinogen very rapidly. SDS-PAGE analysis of venoms revealed up to 22 protein bands, with masses of approximately 5-160 kDa; very little variation among individual snakes or within one snake between venom extractions was observed. Most bands were approximately 25-62 kD, but MALDI-TOF analysis of crude venom indicated considerable complexity in the 1.5-13 kD mass range, including low intensity peaks in the 6.2-8.8 kD mass range (potential three-finger toxins). MALDI-TOF/TOF MS analysis of tryptic peptides confirmed that a 25 kDa band was a venom cysteine-rich secretory protein (CRiSP) with sequence homology with tigrin, a CRiSP from the natricine colubrid Rhabdophis tigrinus. The venom was quite toxic to NSA mice (Mus musculus: LD(50)=2.1 microg/g), as well as to Anolis lizards (A. carolinensis: 3.8 microg/g). Histology of the venom gland showed distinctive differences from the supralabial salivary glands (serous vs. mucosecretory), and like the Brown Treesnake (Boiga irregularis), another rear-fanged snake, serous secretory cells are arranged in densely packed secretory tubules, with little venom present in tubule lumina. These results clearly demonstrate that venom from A. portoricensis shares components with venoms of front-fanged snakes as well as with other rear-fanged species. Venom from A. portoricensis, in particular the prominent metalloproteinase activity, likely serves an important trophic function by facilitating prey handling and predigestion of prey.

Neuromuscular action of venom from the South American colubrid snake Philodryas patagoniensis

Snakes of the opisthoglyphous genus Philodryas are widespread in South America and cause most bites by colubrids in this region. In this study, we examined the neurotoxic and myotoxic effects of venom from Philodryas patagoniensis in biventer cervicis and phrenic nerve-diaphragm preparations and we compared the biochemical activities of venoms from P. patagoniensis and Philodryas olfersii. Philodryas patagoniensis venom (40 microg/mL) had no effect on mouse phrenic nerve-diaphragm preparations but caused time-dependent neuromuscular blockade of chick biventer cervicis preparations. This blockade was not reversed by washing. The highest concentration of venom tested (40 microg/mL) significantly reduced (p<0.05) the contractures to exogenous acetylcholine (55 microM and 110 microM) and K(+) (13.4 mM) after 120 min; lower concentrations of venom had no consistent or significant effect on these responses. Venom caused a concentration- and time-dependent release of creatine kinase (CK) from biventer cervicis preparations. Histological analysis showed contracted muscle fibers at low venom concentrations and myonecrosis at high concentrations. Philodryas venoms had low esterase and phospholipase A(2) but high proteolytic activities compared to the pitviper Bothrops jararaca. SDS-PAGE showed that the Philodryas venoms had similar electrophoretic profiles, with most proteins having a molecular mass of 25-80 kDa. Both of the Philodryas venoms cross-reacted with bothropic antivenom in ELISA, indicating the presence of proteins immunologically related to Bothrops venoms. RP-HPLC of P. patagoniensis venom yielded four major peaks, each of which contained several proteins, as shown by SDS-PAGE. These results indicate that P. patagoniensis venom has neurotoxic and myotoxic components that may contribute to the effects of envenoming by this species.

Análise das atividades biológicas dos venenos de Philodryas olfersii (Lichtenstein) e P. patagoniensis (Girard) (Serpentes, Colubridae)

Philodryas olfersii (Lichtenstein, 1823) e P.patagonienis (Girard, 1857) são serpentes colubrídeas da série opistóglifa, restritas à América do Sul. Vários acidentes ocasionados por estas serpentes têm sido relatados, caracterizando-se por ação local importante: dor, edema e hemorragia. É um acidente muito semelhante àquele causado por serpentes do gênero Bothrops Wagler, 1824 e muitas vezes os pacientes são tratados com soro antibotrópico. Poucos estudos tratam da caracterização destes venenos, assim tivemos como objetivo de trabalho o estudo dos venenos de P.olfersii e P.patagonienis. Os venenos apresentaram teor de proteínas entre 75 e 90%. A atividade desfibrinante não foi detectada quando testada em camundongos. O quadro de dor causado pelo envenenamento experimental, em camundongos, mostrou que os venenos de P.olfersii e P.patagoniensis causaram intensa reatividade, sendo que o veneno de P.patagoniensis foi o mais ativo. Ambos os venenos apresentaram dose mínima edematogênica em torno de 1 µg/camundongo com ação máxima em 30 minutos.A ação hemorrágica se instalou rapidamente, com doses mínimas semelhantes. As atividades tóxicas foram semelhantes, com valores em torno de 60,0 µg/camundongo, comparáveis aos venenos botrópicos.

Purification and characterization of patagonfibrase, a metalloproteinase showing α-fibrinogenolytic and hemorrhagic activities, from Philodryas patagoniensis snake venom

Venoms of Colubridae snakes are a rich source of novel compounds, which may have applications in medicine and biochemistry. In the present study, we describe the purification and characterization of a metalloproteinase (patagonfibrase), the first protein to be isolated from Philodryas patagoniensis (Colubridae) snake venom. Patagonfibrase is a single-chain protein, showing a molecular mass of 53,224 Da and an acidic isoelectric point (5.8). It hydrolyzed selectively the Aalpha-chain of fibrinogen and when incubated with fibrinogen or plasma, the thrombin clotting time was prolonged. Prominent hemorrhage developed in mouse skin after intradermal injection of patagonfibrase. When administered into mouse gastrocnemius muscle, it induced local hemorrhage and necrosis, and systemic bleeding in lungs. Patagonfibrase showed proteolytic activity toward azocasein, which was enhanced by Ca(2+) and inhibited by Zn(2+), cysteine, dithiothreitol and Na(2)EDTA. Patagonfibrase impaired platelet aggregation induced by collagen and ADP. Thus, patagonfibrase may play a key role in the pathogenesis of disturbances that occur in P. patagoniensis envenomation, and may be used as a biological tool to explore many facets of hemostasis.

Systemic pathological alterations caused by Philodryas patagoniensis colubrid snake venom in rats

Very little is known about the systemic effects caused by Philodryas patagoniensis colubrid snake venom. In this work, this venom was tested for its ability to induce histopathological changes in rats after its intramuscular, subcutaneous or intravenous administration, by light microscopic examination of some organs (cerebellum, cerebrum, lung, liver, kidney and heart). Four rats were used for each dose of 0.23, 0.45 and 0.90 mg of venom in 0.3 ml of phosphate-buffered saline solution (pH 7.4). Aliquots of blood were withdrawn at different time intervals for enzymatic determination of alanine aminotransferase, aspartate aminotransferase and creatine kinase levels. After 2h the animals were killed by an overdose of anesthetic, and samples of kidney, heart, liver, lung, cerebrum and cerebellum were taken to microscopic examination (hematoxylin and eosin stain). Histologically, no abnormality was observed in heart tissue, in none of the administration routes of the venom used. However, histological observations showed multifocal hemorrhage in cerebellum, cerebrum and lung sections, severe peritubular capillary congestion in kidney sections and hydropic degeneration in liver sections, when venom was administrated intravenously. The subcutaneous route showed similar results to the previous one, with the exception of cerebellar hemorrhage. Intramuscularly, neither cerebral nor cerebellar hemorrhage was observed. Plasma alanine aminotransferase and aspartate aminotransferase increased levels were demonstrated, mainly when venom was administered intravenously or subcutaneously. Our results suggest that P. patagoniensis venom induces moderate histopathological changes in vital organs of rats. These changes are initiated at early stages of the envenomation and may be associated with a behavioral or functional abnormality of those organs during envenoming.

Some aspects of the venom proteome of the Colubridae snakePhilodryas olfersiirevealed from a Duvernoy's (venom) gland transcriptome

We investigated the putative toxins of Philodryas olfersii (Colubridae), a representative of a family of snakes neglected in venom studies despite their growing medical importance. Transcriptomic data of the venom gland complemented by proteomic analysis of the gland secretion revealed the presence of major toxin classes from the Viperidae family, including serine proteases, metalloproteases, C-type lectins, Crisps, and a C-type natriuretic peptide (CNP). Interestingly, the phylogenetic analysis of the CNP precursor showed it as a linker between two related precursors found in Viperidae and Elapidae snakes. We suggest that these precursors constitute a monophyletic group derived from the vertebrate CNPs.

Experimental ophitoxemia produced by the opisthoglyphous lora snake (Philodryas olfersii) venom

Several colubrid snakes produce venomous oral secretions. In this work, the venom collected from Venezuelan opisthoglyphous (rear-fanged) Philodryas olfersii snake was studied. Different proteins were present in its venom and they were characterized by 20% SDS-PAGE protein electrophoresis. The secretion exhibited proteolytic (gelatinase) activity, which was partially purified on a chromatography ionic exchange mono Q2 column. Additionally, the haemorrhagic activity of Philodryas olfersii venom on chicken embryos, mouse skin and peritoneum was demonstrated. Neurotoxic symptoms were demonstrated in mice inoculated with Philodryas olfersii venom. In conclusion, Philodryas olfersii venom showed proteolytic, haemorrhagic, and neurotoxic activities, thus increasing the interest in the high toxic action of Philodryas venom.

Duvernoy's gland secretion of Philodryas olfersii and Philodryas patagoniensis (Colubridae): Neutralization of local and systemic effects by commercial bothropic antivenom (Bothrops genus)

Colubrids involved in human envenomation in Brazil are mainly from the genera Helicops, Oxyrhopus, Thamnodynastes and Philodryas. There is a relatively large number of clinical descriptions involving the Xenodontinae snakes, Philodryas olfersii and Philodryas patagoniensis, in human accidents. The most common manifestations of envenomation are local pain, swelling, erythema and ecchymosis and regional lymphadenopathy with normal coagulation. The aims of this study were to characterize the biochemical and biological properties of P. olfersii and P. patagoniensis venoms, and to investigate their immunological cross-reactivities by using both specific antisera and anti-Bothrops sp serum used for human serum therapy in Brazil, in neutralizing the lethal and hemorrhagic effects of these venoms. We show here that P. olfersii e P. patagoniensis venoms present proteolytic and haemorrhagic activities but are devoid of phospholipase A2 activity. Haemorrhage and lethality induced by P. olfersii and P. patagoniensis are associated with metal-dependent proteinases, since EDTA could block these toxic activities. P. olfersii and P. patagoniensis venoms were immunogenic and the antisera produced were able to recognize several bands in P. olfersii, P. patagoniensis venoms in Bothrops jararaca venom.

Proteolytic, edematogenic and myotoxic activities of a hemorrhagic metalloproteinase isolated from Bothrops alternatus venom

A hemorrhagic metalloproteinase has been isolated from Bothrops alternatus venom from specimens that inhabit the north-east region of Argentina. The present study aimed at evaluating the proteolytic, hemorrhagic, edematogenic and myotoxic activities of the purified metalloproteinase, in order to consider its participation on the phatophysiology of the intoxication by Bothrops alternatus venom. The hemorrhagic metalloproteinase was isolated by a combination of DEAE-Cellulose chromatography and gel filtration on Sephadex G-75. The enzyme showed a molecular mass around 55k Da, it exhibited a hemorrhagic activity with a minimal hemorrhagic dose of 1.9 microg, almost two fold minor than the whole venom (3.6 microg). The enzyme showed a weak proteolytic activity on casein (18.72 U/mg enzyme), similar to the one exhibited by the whole venom (20 U/mg venom). Besides, the ability to degrade casein could be detected by SDS-PAGE; beta-casein was the fraction that showed the higher degradation, followed by alphas(1)-casein and kappa-casein degradation. The hemorrhagic metalloproteinase rapidly hydrolysed the A alpha-chain of fibrinogen, followed by B beta-chain degradation and leaving the gamma-chain unaffected. Proteolytic activities were inhibited by EDTA whereas they were not inhibited by benzamidine and PMSF. The metalloproteinase showed several polypeptides chains after autocatalytic processing, including a chain of 28k Da, it could be the processed disintegrin-like and cysteine-rich domains. The isolated enzyme exhibited myotoxic activity with high CK levels at 6h, due to local ischemia resulting of its hemorrhagic activity, and a significant edema-inducing effect (MED=1.3 microg), corroborated both results by the histological observations of samples of gastrocnemius muscle. These findings showed that this hemorrhagic metalloproteinase, possesses high edematogenic and myotoxic activities and, in despite of exhibiting a weak proteolytic activity, it is able to degrade fibrinogen. So, this enzyme would contribute markedly to the phatophysiology of the bothropic envenomation.

Duvernoy's gland secretion of Philodryas patagoniensis from the northeast of Argentina: its effects on blood coagulation

Duvernoy's gland secretion of Philodryas patagoniensis exhibits high hemorrhagic activity, containing enzymes that are able to degrade the vascular wall. In this work we aim to determine if the secretion can also affect the hemostatic system by causing changes in blood coagulation. Procoagulant and coagulant activities were evaluated on plasma and fibrinogen, respectively. The delay in the thrombin clotting time of fibrinogen previously incubated with the secretion was also determined. Specific hydrolysis of fibrinogen and fibrin incubated with the secretion at different time intervals was shown by electrophoresis on polyacrylamide gel. To determine the structural characteristics of the enzymes degrading fibrinogen and fibrin, secretion were incubated in the presence of 45 mM Na(2)EDTA, 40 mM Benzamidine, and/or 2 mM PMSF before the incubation with fibrinogen or fibrin, respectively. The effect in vivo was investigated in adult male rats injected with different dose of secretion, aliquots of blood were withdrawn at different time intervals, and the fibrinogen concentration was determined. Duvernoy's gland secretion of P. patagoniensis did not clot plasma or fibrinogen. It exhibited a potent fibrinogenolytic activity degrading the Aalpha-chain faster than the Bbeta-chain, whereas gamma-chain was resistant. This latter corresponded with a strong delay in the thrombin clotting time of fibrinogen (4 mg/ml) pre-incubated with the secretion, being 9.53 microg the amount of protein from Duvernoy's gland secretion that increased the thrombin clotting time from 20 to 60 s. In vivo, the loss of rat plasma fibrinogen was proportional to the amount of secretion injected. The secretion also hydrolyzed fibrin degrading the alpha-monomer. Inhibition studies with Na(2)EDTA, Benzamidine, and/or PMSF showed that metalloproteinases and serinoproteinases are the main enzymes responsible for the hydrolyzing activity on fibrinogen and fibrin. All these results demonstrate that Duvernoy's gland secretion of P. patagoniensis possesses enzymes able to hydrolyze plasma components playing a relevant role in the blood coagulation. These hydrolyzing activities and those acting on the wall of blood vessels let the secretion exhibit a high hemorrhagic activity, which may result in permanent sequelae or even cause the death of the victims bitten by this colubrid snake.

Muscle and skin necrotizing and edema-forming activities of Duvernoy's gland secretion of the xenodontine colubrid snake Philodryas patagoniensis from the north-east of Argentina

Philodryas patagoniensis is a colubrid snake spread by all South America, but very little is known about the composition and biological activities of its Duvernoy's gland secretion. In order to characterize it, we studied edematogenic, dermonecrotic and myonecrotic activities. For edematogenic activity, solutions containing different amounts of secretion were injected s.c. in the right foot pad of mice, both feet were subsequently cut off and weighed individually. For myonecrotic activity, mice were injected i.m. with solutions containing 40 microg of secretion, and at various time intervals mice were bled to determine serum creatine kinase activity and gastrocnemius muscles were removed for microscopic examination (Hematoxylin-Eosin stain). For dermonecrotic activity, solutions containing different amounts of secretion were injected into the shaved dorsal skin of mice; the necrotic lesion was measured on the inner surface of the skin and trimmed for microscopic examination (Hematoxylin-Eosin stain). Phospholipase A(2) activity was evaluated using a kinetic method. Results showed that P. patagoniensis Duvernoy's gland secretion exhibits a high edematogenic activity and moderate myonecrotic and dermonecrotic activities, while lacking phospholipase A(2) effect. Regarding edema, a 30% increase in the weight was produced by injecting 0.26 microg of Duvernoy's gland secretion. Microscopically, myonecrosis reached its highest intensity 12 h after injection, which was also demonstrated by serum creatine kinase levels. Dermonecrosis was proportional to the amount of secretion injected, with a minimum necrotizing dose of 15.7 microg. Myonecrotic, edematogenic and dermonecrotic activities were inhibited when the secretion was pre-incubated with 1 mM Na(2)EDTA. This suggests that the enzymes responsible for those activities are mostly metalloproeinases. All the studies carried out up to now demonstrate the potential toxicity of P. patagoniensis Duvernoy's gland secretion (which inhabits the north-east region of Argentina) and that the local lesions caused by this colubrid snake are very similar to those found in bothropic accidents. This latter suggests a more careful evaluation of the victims when considering the medical treatment to be adopted.

Hemorrhagic activity of the Duvernoy's gland secretion of the xenodontine colubrid Philodryas patagoniensis from the north-east region of Argentina

Colubrid snakes belonging to Philodryas genus, widespread all over South America, bring about lesions (swelling, ecchymosis, transient bleeding from the bite site punctures), that are similar to those produced by Bothrops species (yarará). In the present work we began the characterization of Philodryas patagoniensis venom. We examined if this venom produces hemorrhagic lesions as those observed in victims bitten by Philodryas olfersii. Hemorrhagic, proteolytic and fibrinogenolytic activities were evaluated, and histological observations in samples of gastrocnemius muscle were carried out. Inhibition studies were carried out in metal chelator (ethylenediaminetetraacetic acid) presence. Our results show a small Minimum Hemorrhagic Dose (MHD=0.035 microg) and a high proteolytic activity (143 U/mg), and prove the capacity of this venom to degrade fibrinogen in vitro rendering it unclottable by thrombin, supporting the presence of proteases, principally metalloproteases, in P. patagoniensis venom that are able to alterate the vascular wall and degrade fibrinogen, being both activities responsible of a high hemorrhagic activity.

Purification and characterisation of a haemorrhagic fraction from the venom of the Uracoan rattlesnake Crotalus vegrandis

Uracoan rattlesnake (Crotalus vegrandis) venom was subjected to chromatographic, electrophoretic, biochemical and in vivo haemorrhagic analysis. A haemorrhagic toxin (Uracoina-1) active on skin at the site of inoculation in mice was purified by Mono Q2 anion-exchange chromatography and size exclusion (SE) high-performance liquid chromatography. The purified preparation was a protein of M(r) 58,000 as revealed by sodium dodecyl sulphate--polyacrylamide gel electrophoresis under denatured conditions and with silver staining. The use of EDTA, EGTA and 1,10-phenanthroline inhibited haemorrhagic and proteolytic activities. Inhibitors of serine proteinases such as PMSF and TCLK had no effect on the haemorrhagic fraction. Uracoina-1 hydrolyses casein, hide powder azure and fibrinogen have an optimal pH of 8.2. It rapidly digests the A alpha-chain of fibrinogen. Thermal denaturation of Uracoina-1 after exposure at 60 degrees C for 15 min led to inactivation of the haemorrhagic activity. In addition, Uracoina-1 is myotoxic, lacking haemolytic, defibrinating and lethal effects. The N-terminal amino acid sequence (20 residues) was determined.

Characterization of venom (Duvernoy's secretion) from twelve species of colubrid snakes and partial sequence of four venom proteins

R.E. Hill and S.P. Mackessy. Characterization of venom (Duvernoy's secretion) from twelve species of colubrid snakes and partial sequence of four venom proteins. Toxicon XX, xx-yy, 2000. - Venomous colubrids, which include more than 700 snake species worldwide, represent a vast potential source of novel biological compounds. The present study characterized venom (Duvernoy's gland secretion) collected from twelve species of opisthoglyphous (rear-fanged) colubrid snakes, an extremely diverse assemblage of non-venomous to highly venomous snakes. Most venoms displayed proteolytic activity (casein), though activity levels varied considerably. Low phosphodiesterase activity was detected in several venoms (Amphiesma stolata, Diadophis punctatus, Heterodon nasicus kennerlyi, H. n. nasicus and Thamnophis elegans vagrans), and acetylcholinesterase was found in Boiga irregularis saliva and venom, but no venoms displayed hyaluronidase, thrombin-like or kallikrein-like activities. High phospholipase A(2) (PLA(2)) activity was found in Trimorphodon biscutatus lambda venom, and moderate levels were detected in Boiga dendrophila and D. p. regalis venoms as well as B. dendrophila and H. n. nasicus salivas. Non-reducing SDS-PAGE revealed 7-20 protein bands (3.5 to over 200 kD, depending on species) for all venoms analyzed, and electrophoretic profiles of venoms were typically quite distinct from saliva profiles. Components from A. stolata, Hydrodynastes gigas, Tantilla nigriceps and T. e. vagrans venoms showed protease activity when run on gelatin zymogram gels. N-terminal protein sequences for three 26 kD venom components of three species (H. gigas, H. torquata, T. biscutatus) and one 3.5 kD component (T. nigriceps) were also obtained, and the 3.5 kD peptide showed apparent sequence homology with human vascular endothelial growth factor; these data represent the first sequences of colubrid venom components. Protease, phosphodiesterase and PLA(2) activities are also common to elapid and viperid snake venoms, but it is apparent that numerous other (as yet undescribed) components make up the majority of colubrid venom proteins. The complex nature of venoms produced by most species surveyed, and the high levels of protease or phospholipase A(2) activity of some venoms, suggest that many colubrids could become an important source of human health concern as encounters with these snakes increase.

Bites by the colubrid snake Philodryas olfersii: a clinical and epidemiological study of 43 cases

Less than 10 cases of bites by Philodryas olfersii (Colubridae) have been reported in the literature. In this study, 43 patients admitted to the Instituto Butantan, São Paulo, Brazil, with the diagnosis of P. olfersii bite from 1982 to 1990 were reviewed. The 32 male (74.4%) and 11 female (25.6%) patients presented mainly from November to February (65%). The most common clinical features were local pain (37.2%), swelling (34.9%), erythema (18.6%) and ecchymosis (9.3%). The 20 minute whole blood clotting test was performed in 11 patients and in all of them the blood was coagulable. Most of the accidents occurred during the hottest months and during daylight hours. The most common bite site was the hands. Severe envenoming is not frequent in these accidents.

A novel high molecular weight fibrinogenase from the venom of Bitis arietans

A fibrinogenase (Ba100) with an apparent molecular mass of 100 kDa under non-reducing conditions and a pI of 5.4 was purified from the venom of the African puff adder (Bitis arietans) by fibrinogen affinity chromatography. Under reducing conditions the protease dissociates into subunits of 21 kDa and 16 kDa. N-Terminal amino acid sequencing showed these two chains to have 66.7% homology and homology to C-type lectins. The fibrinogenase activity of Ba100 cleaves the Aalpha and Bbeta chain of fibrinogen rendering the molecule unable to polymerise into fibrin clots. Ba100 inhibited platelet aggregation in platelet rich plasma, and clot formation in whole blood, in a concentration dependent manner.

Characterization of a myotoxin from the Duvernoy's gland secretion of the xenodontine colubrid Philodryas olfersii (green snake): effects on striated muscle and the neuromuscular junction

A myotoxin has been isolated from the Duvernoy's gland (DG) secretion of the xenodontine colubrid Philodrvas olfersii (green snake) by gel filtration on Sephadex G-100 SF. Under non-reducing and reducing conditions in SDS-PAGE, the myotoxin migrates as a single band with a mol. wt. of 20000. The toxin has 182 amino acid residues (approximately 20% acidic), a pI of 4.8 and a blocked N-terminal. In the chick biventer cervicis preparation, P. olfersii myotoxin partially blocks potassium-evoked contractures without affecting either the twitch-tension resulting from indirect stimulation or the contractures evoked by acetylcholine. Both the DG secretion and the myotoxin increase the serum creatine kinase (CK) levels of mice and stimulate the release of CK from the biventer cervicis preparation in a dose- and time-dependent manner. The varying degrees of muscle cell lysis and extensive widening of the intercellular spaces caused by the DG secretion are reproduced by the myotoxin, with the exception that in the latter the partial or total loss of transverse muscle striations is restricted to the muscle periphery. This myotoxin is the first such protein to be characterized from a DG secretion.

Characterization of three fibrinogenolytic enzymes from Chinese green tree viper (Trimeresurus stejnegeri) venom

From the venom of Chinese green tree viper (Trimeresurus stejnegeri), three distinct fibrinogenolytic enzymes: stejnefibrase-1, stejnefibrase-2 and stejnefibrase-3, were purified by gel filtration, ion-exchange chromatography and reverse-phase high-performance chromatography (HPLC). SDS-PAGE analysis of those three enzymes showed that they consisted of a single polypeptide chain with mol. wt of 50000, 31000 and 32000, respectively. Like TSV-PA (a specific plasminogen activator) and stejnobin (a fibrinogen-clotting enzyme) purified from the same venom, stejnefibrase-1, -2 and -3 were able to hydrolyze several chromogenic substrate. On the other hand, different from TSV-PA and stejnobin, stejnefibrase-1, -2 and -3 did not activate plasminogen and did not possess fibrinogen-clotting activity. The three purified enzymes directly degraded fibrinogen to small fragments and rendered it unclottable by thrombin. Stejnefibrase-2 degraded preferentially Bbeta-chain while stejnefibrase-1 and -3 cleaved concomitantly Aalpha and Bbeta-chains of fibrinogen. None of these proteases degraded the gamma-chain of fibrinogen. When correlated with the loss of clottability of fibrinogen, the most active enzyme was stejnefibrase-1. The activities of the three enzymes were inhibited by phenylmethylsulfonyl fluoride (PMSF) and p-nitrophenyl-p-guanidinobenzoate (NPGB), indicating that like TSV-PA and stejnobin, they are venom serine proteases.

The effects of Duvernoy's gland secretion from the xenodontine colubrid Philodryas olfersii on striated muscle and the neuromuscular junction: partial characterization of a neuromuscular fraction

The effect of Philodryas olfersii Duvernoy's secretion was studied in vivo in mice and chicks as well as in the mouse phrenic nerve-diaphragm and the chick biventer cervicis preparations. The whole secretion (20-40 micrograms/ml) increased the creatine kinase (CK) levels in mice but had no effect on the mouse phrenic nerve-diaphragm preparation. In the chick, the secretion caused head drop and paresia as well as irreversible blockade of the twitch-tension evoked by indirect stimulation in the chick biventer cervicis preparation (50% paralysis in 34.5 +/- 2.7 min, n = 4). The secretion also caused muscle contracture (30% of the maximal twitch-tension generated) after a latency of nearly 9 min. Following fractionation on a Superose 12 FPLC column, the neuromuscular activity was recovered in the high mol. wt fraction (Peak I). At a concentration of 10 micrograms/ml in the chick biventer cervicis preparation, Peak I caused 50% paralysis within 18.5 +/- 3.0 min (n = 4), and evoked a strong contracture (70% of the maximal twitch-tension generated). The contractile responses of the chick preparation to ACh and KCL were partially blocked (90%) by the whole secretion and totally blocked by Peak I. CK release was increased by the whole secretion but not by Peak I. The whole secretion also produced various degrees of muscle cell lysis and extensive widening of the intercellular spaces. The latter showed a loosely arranged membranous network. In general, Peak I caused only minor morphological alterations compared with the whole secretion, although these were still significantly different from those observed in the control preparations. The changes principally involved hypercontraction of the muscle fibers. Based on the above results, we conclude that Peak I contains the factor(s) responsible for the in vitro effects on neuromuscular transmission, whereas the direct myotoxic effect is apparently caused by at least one other component of the Duvernoy's secretion.

Isolation and characterisation of two haemorrhagic proteins (HTa and HTb) from the venom of Bitis gabonica (Gaboon viper)

Two distinct haemorrhagic proteinases, HTa and HTb, were isolated from the venom of Bitis gabonica by gel filtration and ion-exchange chromatography with native mol. wts of 180,000 and 111,000, respectively. After reduction with dithiothreitol, smaller mol. wts of 77,600 and 69,200 were recorded for HTa and HTb, suggesting that under native conditions the haemorrhagins exist as dimeric molecules. Both toxins possessed caseinolytic and collagenase activity although HTa was 15-36 times more potent than HTb with respect to collagenase activity. No zinc could be detected in the toxins; however, dialysis against ethylenediamine tetracetic acid (EDTA) reduced caseinolytic activity, suggesting the dependence of the latter on other metal ions. HTa and HTb had a marked effect on the intrinsic cascade coagulation mechanism (factors IX, XI and XII) but no effect on the final common coagulation pathway (factor X and prothrombin). Light and electron microscopical studies demonstrated that both HTa and HTb caused organ-specific lesions, with the lungs, diaphragm and body wall muscle being most affected. HTa caused widespread haemorrhage whilst HTb caused discrete focal lesions near the site of injection and elsewhere. However, both toxins appeared to cause capillary rupture by the separation of cells from one another and both caused cell detachment and cell death of bovine endothelial cells cultured in vitro, consonant with the massive disruption of capillaries seen in vivo.