Isolation and pharmacological properties of phospholipases A2 from Vipera russelli (Russell's viper) snake venom

Proteomics, toxicity and antivenom neutralization of Sri Lankan and Indian Russell's viper (Daboia russelii) venoms

BACKGROUND

The western Russell's viper (Daboia russelii) is widely distributed in South Asia, and geographical venom variation is anticipated among distant populations. Antivenoms used for Russell's viper envenomation are, however, raised typically against snakes from Southern India. The present study investigated and compared the venom proteomes of D. russelii from Sri Lanka (DrSL) and India (DrI), the immunorecognition of Indian VINS Polyvalent Antivenom (VPAV) and its efficacy in neutralizing the venom toxicity.

METHODS

The venoms of DrSL and DrI were decomplexed with C18 high-performance liquid chromatography and SDS-polyacrylamide gel electrophoresis under reducing conditions. The proteins fractionated were identified through nano-ESI-liquid chromatography-tandem mass spectrometry (LCMS/MS). The immunological studies were conducted with enzyme-linked immunosorbent assay. The neutralization of the venom procoagulant effect was evaluated in citrated human plasma. The neutralization of the venom lethality was assessed in vivo in mice adopting the WHO protocol.

RESULTS

DrSL and DrI venom proteomes showed comparable major protein families, with phospholipases A2 (PLA2) being the most abundant (> 60% of total venom proteins) and diverse (six protein forms identified). Both venoms were highly procoagulant and lethal (intravenous median lethal dose in mice, LD50 = 0.24 and 0.32 µg/g, for DrSL and DrI, respectively), while lacking hemorrhagic and anticoagulant activities. VPAV was immunoreactive toward DrSL and DrI venoms, indicating conserved protein antigenicity in the venoms. The high molecular weight venom proteins were, however, more effectively immunorecognized than small ones. VPAV was able to neutralize the coagulopathic and lethal effects of the venoms moderately.

CONCLUSION

Considering that a large amount of venom can be injected by Russell's viper during envenomation, the potency of antivenom can be further improved for optimal neutralization and effective treatment. Region-specific venoms and key toxins may be incorporated into the immunization procedure during antivenom production.

Phospholipase A2 isolated from the venom of Crotalus durissus terrificus inactivates dengue virus and other enveloped viruses by disrupting the viral envelope

The Flaviviridae family includes several virus pathogens associated with human diseases worldwide. Within this family, Dengue virus is the most serious threat to public health, especially in tropical and sub-tropical regions of the world. Currently, there are no vaccines or specific antiviral drugs against Dengue virus or against most of the viruses of this family. Therefore, the development of vaccines and the discovery of therapeutic compounds against the medically most important flaviviruses remain a global public health priority. We previously showed that phospholipase A₂ isolated from the venom of Crotalus durissus terrificus was able to inhibit Dengue virus and Yellow fever virus infection in Vero cells. Here, we present evidence that phospholipase A₂ has a direct effect on Dengue virus particles, inducing a partial exposure of genomic RNA, which strongly suggests inhibition via the cleavage of glycerophospholipids at the virus lipid bilayer envelope. This cleavage might induce a disruption of the lipid bilayer that causes a destabilization of the E proteins on the virus surface, resulting in inactivation. We show by computational analysis that phospholipase A₂ might gain access to the Dengue virus lipid bilayer through the pores found on each of the twenty 3-fold vertices of the E protein shell on the virus surface. In addition, phospholipase A₂ is able to inactivate other enveloped viruses, highlighting its potential as a natural product lead for developing broad-spectrum antiviral drugs.

Anterior Segment Ischemia in Viper Bite

PURPOSE

To describe the clinical and histopathological features of post viper bite anterior segment ischemia.

METHODS

Seven patients with ocular complications following viper bite referred to uveitis clinic had slit-lamp examination, intraocular pressure (IOP) measurement, and fundus evaluation. Iris and fundus fluorescein angiography was performed on 2 patients. Histopathological examination was performed on iris tissues collected during cataract surgery.

RESULTS

Strikingly similar clinical findings were noted, including circumpupillary superficial iris atrophy, mid dilated fixed pupil, marked pigment dispersion, low IOP, and cataract. All clinical signs were noted only in the anterior segment; the posterior segment was normal. Histopathology of iris revealed atrophy of iris stroma, necrotic iris pigment epithelium, and infiltration of T lymphocytes and fibrous membrane. Poor visual outcome was noted in patients with low IOP.

CONCLUSION

Viper bite victims presented with clinical and histopathological signs of anterior segment ischemia and secondary inflammatory signs mimicking uveitis.

The effects of a chactoid scorpion venom and its purified toxins on rat blood pressure and mast cells histamine release

The effect of the venom of the Chactoid family of scorpions on blood pressure was scantly investigated and was addressed in the present study using the venom of the Israeli scorpion, Scorpio maurus palmatus. Blood pressure in rats was monitored via cannulated femoral artery, while venom and toxins were introduced into femoral vein. Venom injection elicited a biphasic effect, expressed first by a fast and transient hypotensive response, which lasted up to 10 min, followed by a hypertensive response, which lasted up to one hour. It was found that these effects resulted from different venom components. Phospholipase A₂ produced the hypotensive effect, while a non-enzymatic neurotoxic polypeptide fraction produced the hypertensive effect. Surprisingly, the main neurotoxic polypeptide to mice had no effect on blood pressure. In vitro experiments indicated that the hypertensive factors caused histamine release from the peritoneal mast cells, but this effect is assumed to be not relevant to their in vivo effect. In spite of the cytotoxic activity of phospholipase A₂, it did not release histamine. These findings suggest that the effects of venom and isolated fractions on blood pressure parameters are mediated by different mechanisms, which deserve further pharmacological investigation.

Molecular characterization of an acidic phospholipase A(2) from Bothrops pirajai snake venom: synthetic C-terminal peptide identifies its antiplatelet region

This paper describes a biochemical and pharmacological characterization of BpirPLA(2)-I, the first acidic Asp49-PLA(2) isolated from Bothrops pirajai. BpirPLA(2)-I caused hypotension in vivo, presented phospholipolytic activity upon artificial substrates and inhibitory effects on platelet aggregation in vitro. Moreover, a synthetic peptide of BpirPLA(2)-I, comprising residues of the C-terminal region, reproduced the antiplatelet activity of the intact protein. A cDNA fragment of 366 bp encompassing the mature form of BpirPLA(2)-I was cloned by reverse transcriptase-PCR of B. pirajai venom gland total RNA. A Bayesian phylogenetic analysis indicated that BpirPLA(2)-I forms a clade with other acid Asp49-PLA(2) enzymes from the Bothrops genus, which are characterized by the high catalytic activity associated with anticoagulant or hypotensive activity or both. Comparison of the electrostatic potential (EP) on the molecular surfaces calculated from a BpirPLA(2)-I homology model and from the crystallographic models of a group of close homologues revealed that the greatest number of charge inversions occurred on the face opposite to the active site entrance, particularly in the Ca(2+) ion binding loop. This observation suggests a possible relationship between the basic or acid character of PLA(2) enzymes and the functionality of the Ca(2+) ion binding loop.

Management of poisonous snake bites in southern Taiwan

Snake bite envenomation is not uncommon in Taiwan. This study focuses on the pattern of poisonous snake bites and their management in southern Taiwan over a 5-year period. The case histories of 37 patients with poisonous snake bites admitted to the Kaohsiung Medical University Hospital between June 2001 and July 2005 were analyzed retrospectively. Three patients, bitten by unknown species of venomous snakes, were excluded from this study. The frequency of snakebites from each species of snake, the local and systemic manifestations of snake bite, treatment of complications and final outcomes were analyzed. Of the remaining 34 patients, 11 (32.4%) were bitten by bamboo vipers, 10 (29.4%) by Russell's pit vipers, 8 (23.5%) by Taiwan cobras and 5 (14.7%) by Taiwan Habu. The majority of snake bites (28) occurred between May and November. Those affected were mainly outdoor hikers (14) and workers (9). The antivenin requirements for treatment in the emergency room were in accordance with standard procedures. No mortality was noted among those envenomed by poisonous snakes. Although poisonous snake bite is not a common life-threatening emergency in the study area, we observed both an environmental risk and a seasonal incidence of snake bite. Keeping the varied clinical manifestations of snake bite in mind is important for effective management. Ready availability and appropriate use of antivenin, close monitoring of patients, institution of ventilatory support and early referral to a larger hospital when required, all help reduce mortality.

Venom phospholipases of Russell's vipers from Myanmar and eastern India--cloning, characterization and phylogeographic analysis

Venoms of Russell's vipers (genus Daboia) are known for their deadly coagulopathic and other effects. We herein studied various isoforms of venom phospholipases A(2) (PLAs) from two Daboia species at their geographic boundary. From Myanmar Daboia siamensis venom (designated as DsM), four PLAs (designated DsM-aI, aI', aII' and bI') were purified, and the cDNAs encoding two acidic (DsM-aI and aII) and two basic PLAs (DsM-bI and S1) were also cloned from its venom-glands. DsM-S1 is identical to the major venom PLA of southern India Daboia russelii, but the protein is absent from the venom. Additionally, four PLAs (designated DrK-aI, aII, bI and bII) were cloned from cDNA obtained from venom glands of a Kolkata D. russelii, and the PLAs were purified from the pooled venom (designated as DrK). The acidic DrK-aI is the most neurotoxic and lethal among these PLAs; DsM-aI which differs from DrK-aI by only the Phe2 substitution shows greatly reduced enzymatic activity and lethality. Both acidic PLAs do not form dimeric complex with basic PLAs in the same venoms. DsM-bI' is neurotoxic and lethal but its orthologous DrK-bI (97% identical to DsM-bI') is a much weaker toxin. Given the fact that most of the orthologous PLAs of DrK and DsM share 97-100% sequence identity, Daboia vipers of Myanmar and Kolkata must be closely related. Molecular phylogenetic analyses on 30 venom PLAs of Eurasian vipers' revealed co-evolution of five subtypes of venom PLAs in both Daboia and Vipera genera. Our results shed light on the intra- and inter-species variations and structure-function relationships of viperid venom PLAs.

Effects of Russell's viper venom fractions on systemic and renal hemodynamics

Changes in systemic and renal hemodynamics induced by Russell's viper venom are well established. The component of the venom responsible for hemodynamic alteration has not been identified. By Sephadex column chromatography five fractions of Russell's viper (Daboia russellii siamensis) venom were isolated. Each venom fraction consisted of phospholipase A2, proteolytic enzyme, phosphomonoesterase, phosphodiesterase, arginine ester hydrolase and hyaluronidase of varying activities. Hemodynamic effects of each venom fraction including mean arterial pressure, cardiac output, systemic and renal vascular resistance, renal blood flow and glomerular filtration rate were studied in five groups of dogs; each group had four dogs. Minimal hemodynamic changes were observed in dogs receiving venom fraction I. Increased renal vascular resistance with diminution of renal blood flow and glomerular filtration rate was observed in dogs receiving venom fractions II, III, IV and V. A markedly increased renal vascular resistance with maximal decrease in renal blood flow and glomerular filtration rate was caused by fraction III of the venom with highest PLA2 and proteolytic enzyme activities. However, renal hemodynamic changes appeared to correlate better with proteolytic enzyme activity than PLA2 activity. The findings suggested the proteolytic enzyme as an important determinant of hemodynamic alteration. Fractional excretion of Na was increased in dogs injected with venom fraction IV, and is presumed to be due to the inhibition of tubular reabsorption of Na by a natriuretic factor in this venom fraction.

Group IB phospholipase A2 from Pseudonaja textilis

Pseudonaja textilis, an Australian Elapid, is known to produce a highly toxic venom. Both protein profiling and N-terminal sequence analysis showed the presence of four new phospholipases A(2) in this venom. Besides being non-lethal, the phospholipase A(2) proteins were found to be moderately active enzymes and they showed procoagulant property. cDNA cloning and characterization indicated the presence of two isoforms of PLA(2) proteins in a single snake, each containing the "pancreatic loop," characteristic of group IB phospholipase A(2). The genomic cloning also confirmed the presence of two genes each containing four exons that are interrupted by three introns. Phylogenetic analysis showed that the venom group IB PLA(2) gene is primitive and could have evolved from the same ancestor as the mammalian and venom group IA PLA(2) genes. In the present study, we report that the Pt-PLA2 gene could be responsible for the production of PL1, 2, and 3 possibly via RNA editing process.

Russell's viper snakebite in Taiwan: differences from other Asian countries

Formosan Russell's viper (Daboia russelli siamensis) is the sixth most frequent cause of snakebite in Taiwan. Its venom has been thought to have both neurotoxic and hematoxic properties. This viper's snakebite is rare and thus scarcely subjected to systemic studies. In this paper, we retrospectively analyzed and described 18 cases of viper snakebite from 1987 to 1999. Like that of the Russell's viper snakebite in other South East Asian areas, varied degrees of acute renal failure, incoagulable blood with bleeding diathesis and hemolysis were the major symptoms found in the systemic envenoming patients. Systemic thrombosis seems to be the distinguishing feature in Formosan Russell's viper snakebite. Neither symptoms nor signs of neuromuscular junction blocking effects were observed, which is another difference from symptoms observed after bites of some other Russell's viper subspecies, suggesting a significant geographic variation. These findings confirmed the clinical importance of Russell's viper snakebite in Taiwan.

Purification and characterization of a potent hemolytic toxin with phospholipase A2 activity from the venom of Indian Russell's viper

A potent toxin with phospholipase A2 (PLA2) and hemolytic activity in vitro was purified from the Russell's viper venom of eastern India (RVV-EI). The purified protein (RVV-PFIIc') of 15.3 kDa molecular weight, and a lethal toxicity dose (LD50i.p.) of 0.1 mg/kg body weight, was the most toxic PLA2 so far reported from the Indian subcontinent. The material also possessed anticoagulant activity as it enhanced the prothrombin induced plasma clotting time in vitro. The PLA2 toxin (RVV-PFIIc') was shown to be different from other PLA2s of RVV in respect to one or more of these parameters e.g. molecular weight, isoelectric pH, in vivo toxicity, specific activity of the enzyme and certain other biological activities. The first 19 amino terminal sequence (NLFQFAEMIVKMTGKEAVH) of RVV-PFIIc' showed variable degree of homology (42.1-94.7%) with those of other RVV-PLA2s described in the literature. Antisera raised against RVV-EI or RVV-PFIIc', though completely neutralized the in vivo lethal toxicity of RVV-EI or RVV-PFIIc', failed to inhibit their PLA2 activity in vitro thereby suggesting that in vivo toxicity and in vitro activity of the enzyme may not be directly related. Apart from RVV-PFIIc', at least two other PLA2 isozymes were found to be present in RVV-EI that were distinct from RVV-PFIIc' in respect to their molecular, biological as well as serological properties. The significance of these and related data in antivenom therapy is discussed.

Characterisation of the biochemical and biological variations from the venom of the death adder species (Acanthophis antarcticus, A. praelongus and A. pyrrhus)

We report on species variation in the venoms of the three species of death adder; the Common death adder (Acanthophis antarcticus), the Northern death adder (Acanthophis praelongus) and the Desert death adder (Acanthophis pyrrhus). The venoms were found to vary in their biochemical (chromatography) and biological (PLA(2) activity, anticoagulant activity and reactivity with commercial death adder antivenom) properties. Each species produced significant differences in the profile and distribution of PLA(2) activity, when whole venom was applied to a cation-exchange Mono-S column. PLA(2) enzymes were purified from each venom and termed acanthoxin B (from A. praelongus), acanthoxin C (from A. pyrrhus) and the previously characterised acanthoxin A (from A. antarcticus). Acanthoxin B and C showed lower enzymatic activities than acanthoxin A (4.0, 13.7 and 23.9 micromol of phospholipid hydrolyzed/min/mg protein, respectively). N-terminal sequencing revealed acanthoxin B to share highest homology with the numerous PLA(2) isozymes (Pa-12C, Pa-1G, Pa-12A) from the King brown snake (Pseudechis australis) and Acanthin I from the Common death adder. Similar to acanthoxin A, acanthoxin C showed highest homology with Acanthin I/II, and pseudexin A-chain from the Red-bellied black snake (Pseudechis porphyriacus). Whole venom from A. antarcticus, A. praelongus and A. pyrrhus each showed weak anticoagulant activity (being able to prolong coagulation of the plasma for 107, 220 and 195 s, respectively). By immunodiffusion, each venom produced precipitation bands against commercial death adder antivenom.

Some biochemical properties of Russell's viper (Daboia russelli) venom from Eastern India: correlation with clinico-pathological manifestation in Russell's viper bite

In the present study, some biochemical properties and pathological effects of Daboia russelli venom from Burdwan district of West Bengal, eastern India are presented. The clinical features of Russell's viper envenomation observed in patients admitted to Burdwan Medical College & Hospital are also reported. In vitro, whole venom exerts strong trypsin inhibitory, phospholipase A2 and procoagulant activities in addition to moderate adenosine monophosphatase and adenosine triphosphatase activities. Lethality (LD50) of this venom sample is 0.7 mg kg (i.v.) of mice. Significant local tissue damaging effects including edema, hemorrhage and necrosis are observed in experimental animal models. An increase in the level of serum enzymes, such as aspartate transaminase, alkaline phosphatase, creatine phosphokinase, lactate dehydrogenase after D. russelli venom injection in albino rats is indicative of cell or tissue damage. High incidence of intravascular hemolysis in addition to hemostasis, haemoptysis and haematuria are observed as the most prominent features of RVV envenomation from this part of India. The present study reinforces the hypothesis that variation in the venom composition of RVV from eastern India with respect to venom samples of Russell's vipers from other parts of India is responsible for the differences in the clinical manifestation in patients from eastern India.

Acanthoxin, a toxic phospholipase A2 from the venom of the common death adder (Acanthophis antarcticus)

This is the first report of a phospholipase A2 (PLA2) from the venom of the common death adder, Acanthophis antarcticus. Acanthoxin is a basic, monomeric PLA2 of mol. wt 13,000, consistent with the weight of neurotoxic PLA2s from other Australian elapids. However, preliminary ultracentrifugation experimentation has shown that it is able to undergo concentration-dependent aggregation to form dimers. It has a relatively high degree of enzymatic activity (23.93 +/- 1.18 mumoles of phospholipid hydrolysed/min/mg protein), but a low level of toxicity (3.2 mg/kg, s.c.). Acanthoxin is known to exist as two isoforms (A1 and A2), both of which show a high degree of homology with numerous elapid PLA2 neurotoxins, in particular pseudexin A from the red-bellied black snake (Pseudechis porphyriacus).

A platelet aggregation inhibitor phospholipase A2 from Russell's viper (Vipera russelli) venom: isolation and characterization

Vipera russelli venom is reported to contain multiple forms of phospholipase A2 (PLA2). Three PLA2s (VRV-PL-V, VRV-PL-VI and VRV-PL-VIIIa) have been purified and characterized in this laboratory. A PLA2(VRV-PL-IIIb) inhibiting platelet aggregation was purified from the same venom in two steps involving CM-Sephadex C-25 column chromatography followed by gel filtration on Sephadex G-50. VRV-PL-IIIb is a basic (pI 7.3-7.7) isoenzyme, with a mol. wt between 14,000 and 15,000. It induced neurotoxic symptoms in experimental mice with an i.p. LD50 of 5.2 mg/kg body weight. VRV-PL-IIIb inhibits ADP-induced platelet aggregation in a dose-dependent manner. It induced oedema in the foot pads of mice and is devoid of anticoagulant, myotoxic and direct haemolytic activities. Antibodies to VRV-PL-IIIb showed a single precipitin line against the antigen as well as whole venom.

Synaptosomal binding of 125I-labelled daboiatoxin, a new PLA2 neurotoxin from the venom of Daboia russelli siamensis

Daboiatoxin (DbTx), the PLA2 neurotoxin from Daboia russelli siamensis venom, was shown to bind specifically and saturably to rat cerebrocortical synaptosomes and synaptic membrane fragments. Two families of binding sites were detected by equilibrium binding analysis in the presence and absence of Ca2+. Scatchard analysis of biphasic plateaus revealed Kdl 5 nM and Bmax1, 6 pmoles/mg protein, and Kd2 80 nM and Bmax2 20 pmoles/mg protein, respectively, for the high- and low-affinity binding sites. The binding of 125I-DbTx to synaptosomes did not show marked dependence on Ca2+, Mg2+, Co2+ and Sr2+. Native DbTx was the only strong competitor to 125I-DbTx synaptosomal binding (IC50 12.5 nM, KI 5.5 nM). Two other crotalid PLA2 neurotoxins, crotoxin CB and mojave toxin basic subunit, and nontoxic C. Atrox PLA2 enzyme, were relatively weaker inhibitors, while two viperid PLA2 neurotoxins, ammodytoxin A and VRV PL V, were very weak inhibitors. Crotoxin CA was a poor inhibitor even at microM concentrations, whereas no inhibitory effect at all was observed with crotoxin CACB, ammodytoxin C, VRV PL VIIIa, taipoxin, beta-bungarotoxin, or with PLA2 enzymes from N. naja venom, E. schistosa venom, bee venom and porcine pancreas. All other pharmacologically active ligands examined (epinephrine, norepinephrine, histamine, choline, dopamine, serotonin, GABA, naloxone, WB-4101, atropine, hexamethonium and alpha-bun-garotoxin) also failed to interfere with 125I-DbTx binding. As those competitors that showed partial inhibition were effective only at microM concentration range compared to the Kd (5 nM) of 125I-DbTx synaptosomal binding, DbTx could well recognize a different neuronal binding site. Rabbit anti-DbTx polyclonal antisera completely blocked the specific binding. When a range of Ca2+ and K+ channels modulators were examined, Ca2+ channel blockers (omega-conotoxins GVIA and MVIIC, taicatoxin, calciseptine and nitrendiprene) did not affect the binding even at high concentrations, while charybdotoxin was the only K+ channel effector that could partially displace 125I-DbTx synaptosomal binding amongst the K+ channel blockers tested (apamin, dendrotoxin-I, iberiotoxin, MCD-peptide, 4-aminopyridine and tetraethylammonium), suggesting that neither K+ nor Ca2+ channels are associated with DbTx binding sites.

Two types of Russell's viper revealed by variation in phospholipases A2 from venom of the subspecies

This study compared the phospholipases A2 (PLA2S) present in four commercially available venoms of Russell's viper subspecies by HPLC fractionation and partial sequence analysis. A potent heterodimeric PLA2 neurotoxin (designated a Russtoxin) was found in the venoms of all Russell's vipers except Daboia russelli (Sri Lanka and South India). The venom PLA2S of D. r. russelli (southern India) used in a previous study appear to be the same as those of D. r. pulchella (Sri Lanka), while the venom PLA2S of D. r. russelli (Pakistan) and D. r. siamensis (Burma and Thailand) resemble those of D. r. formosensis (Taiwan). This study provides evidence for the presence of two types of Russell's viper. Daboia russelli formosensis (Taiwan). D. r. siamensis (Thailand and Burma) and D. r. russelli (Pakistan) represent one type whose venom contains PLA2S having an Asn residue at the N-terminus, while D. r. pulchella (South India and Sri Lanka) represents the other type, whose venom contains PLA2S with a N-terminal residue Ser.

Molecular cloning and characterization of a neurotoxic phospholipase A2 from the venom of Taiwan habu (Trimeresurus mucrosquamatus)

Using gel-filtration chromatography and reverse-phase (RP) HPLC we have purified a presynaptic neurotoxin (designated as trimucrotoxin) from the crude venom of Taiwan habu (Trimeresurus mucrosquamatus). Its complete primary structure was solved by an automated N-terminal sequencing and cDNA sequencing method. The enzyme inhibited the twitch of the chick biventer cervicis muscle at 0.1-1 micrograms/ml and showed lethality in mice (LD50 = 1.2 micrograms/g, when given intravenously). Trimucrotoxin exists mainly as a homodimer of 14 kDa subunits as shown by a gel-filtration experiment, and dissociates into monomers during SDS/PAGE in the absence of Ca2+. However, most of trimucrotoxin migrated as slowly as a trimer during nondenaturing SDS/PAGE in the presence of Ca2+ or Sr2+. Its amino acid sequence identity to crotoxin B and agkistrodotoxin is about 75%, and its cDNA sequence is 82% identical to that of crotoxin B. Rabbit antiserum against trimucrotoxin also cross-reacted with the other crotalid neurotoxic phospholipases A2. Furthermore, the purified acidic subunit of crotoxin potentiated the neurotoxicity of trimucrotoxin. A comparison of the sequences of these crotalid neurotoxins revealed some common features of the possible neurotoxic sites, including residues 6, 11, 76-81 and 119-125.

A major lethal factor of the venom of Burmese Russell's viper (Daboia russelli siamensis): isolation, N-terminal sequencing and biological activities of daboiatoxin

A major lethal factor, daboiatoxin (DbTx), showing strong PLA2 activity (specific activity 91.7 nmoles/min/mg), was purified to homogeneity from the venom of Burmese Russell's viper (Daboia r. siamensis) by a combination of gel filtration on Sephadex G-75 and ion-exchange chromatography on CM-Sephadex C-25, followed by purification on high-performance gel filtration Shim-pack Diol-150 column. DbTx is a single-chain PLA2 toxin with approximate mol. wt 15,000 as determined by HPLC gel filtration and SDS-PAGE. It constitutes 12% of total venom protein and is the main lethal component of Burmese Russell's viper venom with an LD50 i.p. (0.05 mg/kg) 12-fold greater than that of the whole venom (LD50 i.p. 0.6 mg/kg). DbTx produces neurotoxic symptoms in mice and exhibits potent oedema-inducing activity (minimum oedema dose 0.05 microgram), indirect haemolytic activity and a strong myonecrotic activity, but no haemorrhagic activity. DbTx is cytotoxic to HeLa cells causing cytolysis of the cells 24 hr post-exposure to toxin (50 micrograms/ml). The first 20 N-terminal amino acid sequence (NFFQF AEMIV KMTGK EAVHS) shows a significant resemblance to those of the PLA2s from the venoms of Bulgarian viper (V. a. ammodytes) and Taiwan Russell's viper (V. r. formosensis).

Purification, characterization and biological activities of phospholipase A from Russell's viper (Vipera russelli) venom

1. The major phospholipase A has been purified to electrophoretic homogeneity from the venom of Vipera russelli (Russell's viper). 2. The molecular weight of the purified enzyme was estimated to be 31,000 by Sephadex G-75 gel filtration chromatography and 29,000 by SDS-polyacrylamide gel electrophoresis. The enzyme exhibited an apparent Km value of 2.3 x 10(-2) M. 3. The phospholipase A showed edema forming, indirect hemolytic and myonecrotic activities but not hemorrhagic activity.

Characterization and molecular cloning of neurotoxic phospholipases A2 from Taiwan viper (Vipera russelli formosensis)

Two phospholipases A2 (PLA2s), designated as RV-4 and RV-7 were purified from venom of the Taiwan Russell's viper (Vipera russelli formosensis) by gel-filtration and reverse-phase HPLC. Their primary structures were solved by both protein sequencing and cDNA cloning and sequencing. The cDNA synthesized was amplified by the polymerase-chain reaction using a pair of synthetic oligonucleotide primers corresponding to the N- and the C-terminal flanking regions of the enzymes. The deduced amino acid sequences of RV-4 and RV-7 were 92% identical to those of the vipoxin and vipoxin inhibitor, respectively, from the Bulgarian Vipera a. ammodytes. RV-4 itself was neurotoxic, whereas RV-7 had much lower enzymatic activity and was not toxic. The low enzymatic activity of RV-7 may be attributed to five acidic residues at positions 7, 17, 59, 114 and 119, which presumably impair its binding to aggregated lipid substrates. Based on the sequence comparison among all the known group II PLA2s, residues 6, 12, 76-81, and 119-125 were identified as important for the neurotoxicity. RV-4 and RV-7 exist in the crude venom as heterodimers, which were again formed by mixing together the HPLC-purified RV-4 and RV-7. Moreover, RV-7 inhibited the enzymatic activity of RV-4 in vitro but potentiated its lethal potency and neurotoxicity. It is suggested that RV-7 may facilitate the specific binding of RV-4 to its presynaptic binding sites, probably by preventing its non-specific adsorption.

Phospholipase A2 inhibition by alkylbenzoylacrylic acids

3-(4-Alkylbenzoyl)acrylic acids (ABAAs) were synthesized by acylation of alkylbenzenes with maleic anhydride and then screened in vitro for inhibition of phospholipase A2 (PLA2) from snake venom and from porcine pancreas. The inhibitory potency of ABAAs increased with the length of the alkyl residues resulting in IC50 values of between 10(-7) and 10(-4) mol/L. The most potent inhibitors of the snake venom PLA2 were the 4-(n)-hexadecyl and octadecyl (OBAA) derivatives. Kinetic experiments referred to a time-dependent inhibitory reaction. Irreversibility was examined by dilution and dialysis. A molar ratio of inactivation of OBAA of nearly 20 was estimated. Double reciprocal replots of the apparent inactivation constants to the concentration of OBAA gave a (pseudo) first order rate constant of inactivation of 2.3 min-1. For the dissociation constant of the enzyme-inhibitor intermediate, a value of 6 x 10(-6) mol/L was obtained. On the other hand, the PLA2 from porcine pancreas seemed hardly to be inhibited by ABAAs. The present data are discussed in relation to the proposed model for PLA2 inactivation by manoalide. In human PMNs leukotriene B4 and 5-HETE production was essentially reduced. In human platelets the thrombin-induced TxA2 production was reduced. Since these effects disappeared after addition of arachidonic acid, these findings refer to a PLA2 inhibition. The immunologically induced bronchospasm in guinea pigs was significantly and dose-dependently inhibited by OBAA. This indicates that ABAAs might be useful in treating allergic diseases, such as asthma, eczema, allergic shock and others.

Purification and properties of a kininogenin from the venom of Lachesis muta (bushmaster)

An acidic kininogenin from Lachesis muta snake venom was purified to apparent homogeneity by a combination of gel filtration, isoelectric focusing and preparative gel electrophoresis. It was shown to be a highly stable serine protease (mol. wt 27,900; pI 5.4) capable of releasing bradykinin from low mol. wt bovine kininogen and of cleaving some synthetic chromogenic peptides with the following catalytic efficiencies (Kcat/Km, M-1.sec-1): N-benzoyl-Phe-Val-Arg-p-nitroanilide (1.92 x 10(4)); H-D-Val-Leu-Arg-p-nitroanilide (1.55 x 10(4)); N-acetyl-Phe-Arg-p-nitroanilide (3.98 x 10(2)); no hydrolysis was observed with N-benzoyl-Arg-p-nitroanilide. A marked and sustained hypotensive effect was recorded following i.v. injection of purified kininogenin into rats. Tachyphylaxis was observed after repeated i.v. injection of the enzyme, a phenomenon accompanied by a decrease of only 15% in the total circulating rat kininogen. Both the in vivo action and the enzymatic properties of the L. muta kininogenin indicate that this enzyme might be helpful for understanding the kinin-kininogen system.

A comparative study of the biological properties of venoms from snakes of the genus Vipera (true adders)

1. The hemorrhagic, procoagulant, anticoagulant, phosphodiesterase, hyaluronidase, alkaline phosphomonoesterase, 5'-nucleotidase, arginine ester hydrolase, phospholipase A, L-amino acid oxidase and protease activities of 26 samples of venoms of 13 taxa of Vipera were determined and the Sephadex G-75 gel filtration patterns for some of the venoms were also examined. 2. The results indicate the presence of certain common characteristics among the venoms, particularly if V. russelli is excluded from the comparison. The results also support the recently proposed reassignment of V. russelli to a separate genus. 3. The data show that information on venom biological properties can be used for differentiation of venoms of many species of Vipera. Particularly useful for this purpose are the protease, phosphodiesterase, phospholipase A and the procoagulant activities and the Sephadex G-75 gel filtration patterns of the venoms.

Purification and physiological study of a hypotensive factor from the venom of Vipera aspis aspis (aspic viper)

A hypotensive factor was isolated from the venom of Vipera aspis aspis by Sephadex G-75, S-Sepharose column chromatography, and reverse phase HPLC using a Develosil 300 ODS-7 column. The purified factor was a basic protein with a mol. wt of 25,000 and an isoelectric point of 7.95. Intravenous injection of hypotensive factor induced an immediate fall in blood pressure of rats, whose duration depended on the dose employed. The hypotensive response was not affected by dithiothreitol, beta-mercaptoethanol, EDTA, p-tosyl-L-phenylalanine chloromethylketone, p-chloromercuribenzoic acid, or diisopropyl fluorophosphate, and was resistant to heat-treatment at 100 degrees C for 30 min, however, it disappeared after incubation with antivenom prepared against the hypotensive factor. The factor is devoid of proteinase, esterase, phospholipase A2 and kallikrein-like activities, and lethal, hemorrhagic and capillary permeability increasing activities are also absent. Compared to the hypotension induced by the hypotensive factor in normotensive rats, a more potent response was observed when it was administered to 11-week-old spontaneously hypertensive rats.

Isolation and characterization of hemorrhagic, myonecrotic and edema-inducing toxins from Bothrops insularis (jararaca ilhoa) snake venom

Bothrops insularis snake venom was fractionated by gel filtration on Sephadex G-150 followed by ion-exchange chromatography on SP-Sephadex C-25. Two active fractions were purified to homogeneity: (1) SIII-SpI, approximate mol. wt 32,000 and N-terminal amino acid residue Val. This fraction showed esterase activity on TAME, edema-inducing activity on the rat hind paw and contractile activity on the isolated guinea pig ileum. The latter two activities were antagonized by benadryl plus methysergide; (2) SIII-SpVI, a myonecrotic and edema-inducing phospholipase, approximate mol. wt 29,000, N-terminal amino acid residue pyro-Glu, consisting of two chains of approximately 15,000 mol. wt each linked by disulphide bridge(s). The induction of edema by this fraction was not antagonized by benadryl plus methysergide, indomethacin, BW755C or BN52021, but it was antagonized by dexamethasone. Three highly purified hemorrhagic heterodimeric fractions, SIII-SpIII-3, SIII-SpIII-4 and SIII-SpIII-5, of approximate mol. wts 26,000, 29,000 and 26,000, and having N-terminal residues of Asx, Asx and Gly, respectively, were further isolated by preparative polyacrylamide slab gel electrophoresis. SIII-SpIII-4 and SIII-SpIII-5 increased the recalcification time of citrated rat plasma. None of the five isolated fractions showed any proteolytic (on casein) or kininogenase activity.

Purification and characterization of a major phospholipase A2 from Russell's viper (Vipera russelli) venom

A major phospholipase A2 (VRV PL-VIIIa) which constitutes 24% of the whole Vipera russelli venom was purified to homogeneity by CM-Sephadex C-25 column chromatography followed by gel filtration on Sephadex G-50. VRV PL-VIIIa is a basic protein with a molecular weight of 11,800 by SDS-PAGE. This enzyme contributes 45% of the total PLA2 activity of the venom, but it is least toxic compared to other purified basic PLA2 enzymes prepared from V. russelli venom. The LD50 value (i.p.) of VRV PL-VIIIa is 5.3 mg/kg body wt. It shows neurotoxic symptoms and damages vital organs such as lung, liver and kidney at LD50 doses. It induces myonecrosis when injected i.m. into the thigh muscle of mice and edema when injected into the foot pads.

Dissociation of catalytic activity and neurotoxicity of a basic phospholipase A2 from Russell's viper (Vipera russelli) venom

A neurotoxic phospholipase A2, VRV PL-V was purified from Vipera russelli venom in a single step by CM-Sephadex C-25 column chromatography. VRV PL-V is a basic PLA2 with a mol. wt of approximately 10,000. The lethal potency of VRV PL-V was greater than that of the crude V. russelli venom. VRV PL-V showed anticoagulant activity and induced edema in the foot pad of the mouse. VRV PL-V undergoes aggregation at pH 4.8. The size of the aggregate increased as the temperature at which the enzyme was incubated was raised. A highly aggregated form with a mol. wt of 53,100 was formed at 96 degrees C. This aggregate showed a two-fold increase in its catalytic activity, while its neurotoxic activity disappeared. The aggregate also showed a significant increase in its anticoagulant activity when compared to the monomeric form. Edema-inducing activity decreased upon association to higher molecular form.

Purification and partial biochemical characterization of an edema inducing phospholipase A2 from Vipera russelli (Russell's viper) snake venom

A phospholipase A2 (VRV PL-VI) from Vipera russelli venom was purified to homogeneity in a single step on CM-Sephadex C-25 column. VRV PL-VI is a basic protein with a mol. wt of about 12,000 and showed a basic pH optimum and a high temperature maximum. It hydrolysed purified phospholipids in the order of phosphatidylethanolamine greater than phosphatidylcholine much greater than phosphatidylserine greater than phosphatidylinositol = 0. It is toxic with an LD50 value (i.p.) of 3.5 micrograms/g body weight in mice and it induced persistent edema in the mouse foot pad.

Relaxant effect of phospholipase A2 from Vipera russelli snake venom on rat aorta

The effect of the acidic phospholipase A2 (PLA2) from Vipera russelli venom on the rat aortic ring was studied and compared with that of acetylcholine (ACh). PLA2 induced relaxation of the aortic ring precontracted with noradrenaline (NA) in a dose-dependent manner. Removal of the endothelium did not reduce the relaxant effect of PLA2. Replacement of Ca2+ by Sr2+ in the medium to inhibit the PLA2 enzyme activity reduced the relaxant effect. Atropine, a muscarinic receptor antagonist, did not affect the relaxant response. The cyclooxygenase inhibitor indomethacin, when equilibrated for 50 min, potentiated the relaxation. The lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) partially reduced the relaxation. This relaxation was also partially reduced by the guanylate cyclase inhibitor methylene blue. In contrast, the relaxation elicited by ACh was abolished by de-endothelialization, atropine, NDGA or methylene blue. 6-keto-PGF1 alpha (degradation product of prostacyclin) and PGE2 produced by aortic rings were measured by radioimmunoassay. PLA2 (3 X 10(-6) g/ml) increased the output of 6-keto-PGF1 alpha about 10-fold. The production of PGE2 was also increased but to a lesser extent. ACh also increased the output of 6-keto-PGF1 alpha and PGE2. However, prostacyclin released by PLA2 and ACh appears not to contribute to the relaxant effect, since prostacyclin does not relax the rat aorta. It is concluded that the relaxation elicited by PLA2 in the rat aorta is endothelium-independent and partially mediated by lipoxygenase product(s) and cyclic GMP whereas the relaxation induced by ACh was endothelium-dependent, mediated by lipoxygenase product(s) and cyclic GMP, and blocked by atropine.

Release of slow reacting substance from the guinea-pig lung by phospholipases A2 of Vipera russelli snake venom

Phospholipases A2 (PLA2) of Vipera russelli venom were isolated by column chromatography. The ability of PLA2 fractions to release slow reacting substance (SRS) was studied in the guinea-pig lung perfused with Krebs' solution. The relationship between the perfusion pressure change produced by PLA2 and SRS release was also studied. Two PLA2 fractions (II-5 and III-3; 3-100 micrograms), injected into the lung increased the perfusion pressure and released SRS. Pretreatment of the lung with indomethacin (10 micrograms) reduced the pressure response induced by the PLA2 fractions. The SRS released in the lung effluent by PLA2 was identified by bioassay as a mixture of thromboxane A2 (TXA2), prostacyclin (PGI2) and leukotrienes. TXA2 and PGI2 release was also quantitated by radioimmunoassay of the degradation products TXB2 and 6-keto-PGF1 alpha, respectively. There was a positive linear correlation between the pressure increases and the ratios of TXB2 to 6-keto-PGF1 alpha (r = 0.87). It appears that the relative amounts of TXA2 and PGI2 released determine the effects of PLA2 fractions on the guinea-pig lung. The release of arachidonic acid metabolites, prostaglandins and leukotrienes may account for part of the hypotensive action of PLA2.

Effects of phospholipases A2 from Vipera russelli snake venom on blood pressure, plasma prostacyclin level and renin activity in rats

Vipera russelli venom contains several isoenzymes of phospholipase A2 (PLA2) which were isolated by column chromatography. The effects of PLA2 fractions on blood pressure, plasma prostacyclin level and renin activity were studied in normotensive and renal hypertensive rats. PLA2 fractions II-5, II-7, III-3 and III-6 (0.1 mg/kg) injected i.v. into rats decreased the arterial blood pressure. The hypotensive action of PLA2 fractions was not affected by heat treatment (70-80 degrees C, 30 min, pH 6.8). After indomethacin (30 mg/kg, i.v.), the hypotensive response to PLA2 was markedly reduced. Plasma prostacyclin (PGI2) and thromboxane A2 (TXA2) levels were measured by radioimmunoassays of their degradation products, 6-keto-PGF1 alpha and TXB2, respectively. PLA2 fractions (0.1 mg/kg) induced an increase in plasma PGI2 and TXA2 levels. There was a positive linear correlation between the PLA2-induced hypotensive effect and the ratio of increased 6-keto-PGF1 alpha to TXB2 (r = 0.83) in normotensive rats. In renal hypertensive rats, the increase in PGI2 level was larger than in normotensive rats. Plasma renin activity was also measured by the radioimmunoassay. Plasma renin activity was reduced by PLA2 fractions in renal hypertensive rats, but not in normotensive rats. These results suggest that the hypotensive effect of PLA2 fractions in normotensive rats may be partly due to the increase in plasma prostacyclin and thromboxane A2 levels. In addition to the larger increase in plasma PGI2 level, the reduction in plasma renin activity may also contribute to the greater hypotensive effect of PLA2 fractions in renal hypertensive rats.