Local Tissue Oamaging (Hemorrhage and Myonecrosis) Toxins from Rattlcsnake and Other Pit Viper Venoms

Biochemical characterization of two crotamine isoforms isolated by a single step RP-HPLC from Crotalus durissus terrificus (South American rattlesnake) venom and their action on insulin secretion by pancreatic islets

Crotamine, a neurotoxin present in the venom of the South American rattlesnake Crotalus durrisus terrificus exists as several polymorphic variants, as demonstrated by recombinant DNA technology (Smith and Schmidt, Toxicon 28 (1990) 575-585). We have isolated native crotamine by chromatography on Sephadex G75, and have purified two crotamine isoforms (F2 and F3) by a single step of RP-HPLC. Native crotamine and RP-HPLC fractions F2 and F3 produced skeletal muscle spasms and spastic paralysis in mice. At low glucose concentrations (2.8-5.6 mmol/l), none of the crotamines altered the insulin secretion by rat isolated islets. In the presence of 16.7 mmol glucose/l, F2 (5 microg/ml), but not F3, increased insulin secretion two-fold, whereas native crotamine (1.5, 5 and 16.5 microg/ml) potentiated the secretion dose-dependently. The increase in insulin secretion induced by F2 fraction (5 microg/ml) was similar to that obtained with 16.5 microg of native crotamine/ml. These results indicate that the mode of action of the F2 and F3 isoforms in beta-cells is different from that in muscle cells. This difference may be related to the binding affinity of each isoform for the Na(+) channels located in the beta-cell membrane. Crotamine isoforms may be valuable tools for studying the involvement of Na(+) channels in the mechanism of insulin secretion.

Isolation and characterization of synergistic hemorrhagins from the venom of the snake Bothrops asper

Three hemorrhagic factors (BaH1, BH2 and BH3) were isolated from the venom of Bothrops asper by gel filtration on Sephacryl S-200, DEAE-Sepharose chromatography, metal chelate affinity chromatography and hydrophobic interaction chromatography. They contain 55% of the total hemorrhagic activity of the whole venom when they are mixed, but lose almost half of the activity if they are separated, indicating a synergism between the three. The main hemorrhagin is BaH1 (Bothrops asper hemorrhagin 1); the other two are weak hemorrhagins but contribute to the synergism. They are acidic proteins with a pI of 4.5, 5.2 and 5; their mol. wt is 64,000, 26,000 and 55,000 respectively. The minimal hemorrhagic dose (MHD) of BaH1, BH2 and BH3 is 0.18, 2 and 1.6 micrograms, with a specific activity 55, 5 and 6.25 higher than that of the whole venom. The hemorrhagic activity of all three factors was inhibited by EDTA and ortho-phenathroline, indicating that the hemorrhagic activity is metal dependent. Phosphoramidon, soybean trypsin inhibitor, PMSF, pepstatin and aprotinin did not affect the hemorrhagic activity of the isolated factors.

Effects of snake venoms on hemostasis

Proteins found in venoms, especially of the Viperidae snake family, exert, often with a narrow specificity, activating, inactivating, or other converting effects on different components of the hemostatic and fibrinolytic systems, respectively. Some purified snake venom proteins have become valuable tools in basic research and in diagnostic procedures in hemostaseology. "Procoagulant" as well as "anticoagulant" venom components have been identified in in vitro test systems. "Procoagulant" snake venom components may cause in vivo, upon massive application as in the case of snake-bite of small prey animals, intravascular coagulation leading to circulatory arrest and rapid death. Smaller doses of procoagulant venom components applied to large organisms as in the case of snake-bite accidents in humans, may cause a consumption coagulopathy with localized or generalized bleeding. Highly purified, specific fibrinogen coagulant venom proteinases are used in human medicine to produce therapeutic defibrinogenation. These practically nontoxic venom enzymes may act synergistically with other components aggravating their toxic effects.

Cloning and nucleotide sequences of crotamine genes

A cDNA library containing snake toxin genes was constructed in bacteriophage lambda by using mRNA isolated from the glands of the South American rattlesnake, Crotalus durissus terrificus. The first high-density screening of 400,000 plaques for crotamine-containing genes yielded over 800 positives when a labeled cDNA probe with sequence homology to crotamine was used. Four of these clones with insert sizes from 270 to 400 base pairs were chosen and their inserts subcloned into pGEM-3Z and sequenced. Nucleotide sequence analysis of the cloned cDNAs predicted the existence of multiple variants of the crotamine toxin. The different forms, identified from the DNA sequences, displayed discrepancies in amino acid sequence for crotamine when compared with previously published reports. Direct amino acid sequencing of commercially purified crotamine and CNBr fragments thereof confirmed the structures predicted by the nucleic acid sequences.

Assignment of the aromatic 1H-NMR resonances of myotoxin a isolated from the venom of Crotalus viridis viridis

The 400 MHz 1H-NMR spectrum of myotoxin a from the venom of Crotalus viridis viridis is described. The identification of spin systems in the aromatic region corresponding to the six aromatic residues of myotoxin a was completed using both one- and two-dimensional NMR spectroscopy and the pH dependence of chemical shifts. Assignments of these spin systems to specific residues was possible for the singly occurring amino acids Tyr-1 and Phe-12. Resonances from Tyr-1, His-5 and His-10 were shifted significantly from their random coil values in a pH-dependent manner. These shift perturbations were deemed evidence of a helical arrangement of the amino terminal region which placed these residues in close proximity to each other.

Cytotoxic activity of various snake venoms on melanoma, B16F10 and chondrosarcoma

Elapid, crotalid and viperid venoms were screened in vitro and in vivo for cytotoxicity towards B16F10 melanoma and chondrosarcoma cell lines. The cytotoxic activity of elapid venoms was considerably higher than that of viperid or crotalid venoms. Elapid venoms disrupted the cell membrane within the first hour, leading to cell death. The strongest activity was found in the venom of Naja nigricollis. The venoms of some Viperidae and of all Crotalidae examined caused the cells to become rounded, without loss in their original volume, and to form aggregates. These changes were reversible when cells were changed to fresh medium. In vivo experiments with the venom of Naja nigricollis were in total agreement with the results achieved in vitro with melanoma cells and the venom exhibited similar cytotoxic activity on chondrosarcoma, inhibiting its development in vivo.

Further studies of plasma protease inhibitors in the hedgehog, Erinaceus europaeus; collagenase, papain and plasmin inhibitors

Hedgehog plasma was separated by gel filtration on Sephacryl S-200, the fractions resolved by electrophoresis and the electrophoretograms characterized for collagenase, papain and plasmin inhibiting activities with the high mol. wt substrate casein. The three inhibitors previously identified as alpha 2-, alpha 2-beta- and beta-macroglobulins were found to inhibit all three proteases. These were the only collagenase inhibitors found in plasma. Hedgehog alpha 2-chymotrypsin inhibitor and beta-protease inhibitor were both found to also inhibit papain. Three new inhibitors specific for papain (gamma-, alpha 2- and alpha 1-cysteine protease inhibitors) and one for plasmin (alpha 2-antiplasmin) were also found, bringing the number of protease inhibitors in hedgehog plasma to 14. Immunological cross-reactivity as studied by immunoelectrophoresis showed homology between hedgehog alpha 2-macroglobulin and rat murinoglobulin I and between hedgehog alpha 2-antithrombin and rat antithrombin III.

Purification of a hemorrhagic factor (LHF-I) from the venom of the bushmaster snake, Lachesis muta muta

Hemorrhagic factor (LHF-I), was isolated from Lachesis muta muta venom by a five-step procedure. Homogeneity was demonstrated by the presence of a single band on polyacrylamide gel electrophoresis, immunoelectrophoresis and immunodiffusion. LHF-I is a glycoprotein with molecular weight of approximately 100,000 as determined by sodium dodecyl sulfate polyacrylamide-gel electrophoresis. Caseinolytic activity was associated with the hemorrhagic activity throughout the purification procedure.

Venom resistance in the hedgehog, Erinaceus europaeus: purification and identification of macroglobulin inhibitors as plasma antihemorrhagic factors

Hedgehog (Erinaceus europaeus) plasma contains factor(s) which neutralize the hemorrhagic activity of European viper (Vipera berus) venom. These antihemorrhagic factor(s) were purified by gel filtration on Sephacryl S-200 and chromatography on Cibacron Blue Sepharose. The macroglobulin fraction obtained was characterized for proteinase inhibiting activity, molecular weight and purity by polyacrylamide gel electrophoresis and immunological cross-reactivity and was found to contain the three macroglobulin proteinase inhibitors--alpha 2-macroglobulin, alpha 2-beta-macroglobulin and beta-macroglobulin. The purified macroglobulins were totally able to neutralize Vipera berus venom hemorrhagic activity, but no distinction between them in this respect was possible.

Isolation and characterization of a hemorrhagic factor from the venom of the snake Atractaspis engaddensis (Atractaspididae)

The venom of Atractaspis is unique in its composition and contains both high and low molecular weight fractions. The first peak obtained by gel filtration on Sephadex G-50 (S1) induces hemorrhage in the skin of mice. The hemorrhagic activity is stable over a pH range of 6-9; at pH 5 or 9.5 the activity decreases to half of the original and it is destroyed when incubated at 56 degrees C for 15 min. The hemorrhagic fraction was further purified by ion exchange chromatography on DEAE-Sepharose followed by ammonium sulphate precipitation. The purified factor had a molecular weight of about 50,000 and, in acrylamide disc electrophoresis, showed an acidic band which strongly stained with Coomassie Brilliant Blue and Periodic Acid Schiff. The specific activity of the isolated hemorrhagin was about 12 times higher than that of the crude venom. It has no measurable protease activity on azocoll, casein or gelatin, but the hemorrhagic activity was inactivated by EDTA and was not restored by prolonged incubation with Ca2+ or Zn2+. This activity was also neutralized by sera of venomous and non-venomous snakes. Moreover, antibodies prepared against the venom of Vipera palaestinae neutralized the activity of Atractaspis hemorrhagin and formed one precipitation line in the immunodiffusion test. It is thus evident that Atractaspis, now considered to belong to a separate family, has a hemorrhagic factor which is similar to that of the venoms of the Viperidae.

Species specific sensitivity towards the hemorrhagin of Ophiophagus hannah (Elapidae)

The filtration pattern of Ophiophagus hannah venom on Sephadex G-75 shows several peaks. The first peak, S1, includes high molecular weight proteins and contains the hemorrhagic and proteolytic activities. The proteolytic fractions overlap the hemorrhagic fractions, but are not identical with them. The crude venom and the high molecular weight peak have caseinase, benzoyl-L-arginine ethyl ester hydrolase and kallikrein-like activities, but not collagenase, gelatinase, thrombin, plasmin or urokinase-like activities. The hemorrhagin of Ophiophagus hannah shows species specific differences in its hemorrhagic effects: it causes hemorrhages in rabbits and hares (Lagomorpha), but not in rats, mice or guinea-pigs (Rodentia).

Purification and characterization of alpha 2-, alpha 2-beta- and beta-macroglobulin inhibitors in the hedgehog, Erinaceus europaeus: beta-macroglobulin identified as the plasma antihemorrhagic factor

Three macroglobulin inhibitors were purified from hedgehog (Erinaceus europaeus) plasma by sequential chromatography on Cibacron Blue Sepharose, Sephacryl S-200 and preparative agarose gel electrophoresis. Each macroglobulin was characterized for proteinase inhibiting activity, molecular weight by polyacrylamide gel electrophoresis (PAGE), subunit size by sodium dodecyl sulfate (SDS)-PAGE, immunological cross-reactivity to other macroglobulins and antihemorrhagic activity against European viper (Vipera berus) venom. Hedgehog alpha 2-macroglobulin is a tetramer (Mr 800,000) composed of identical monomers (Mr 200,000) that inhibits all proteinases tested and is the homologue of human alpha 2-macroglobulin, rat alpha 2-acute phase globulin, dog alpha 1-macroglobulin and swine alpha 2-macroglobulin fast. Hedgehog alpha 2-beta-macroglobulin is a dimer (Mr 450-550,000) composed of identical monomers (Mr 200,000) that inhibits all proteinases tested and appears to be structurally similar to other animal 'half-molecule' macroglobulins. Hedgehog beta-macroglobulin (Mr 700,000) gave subunits of 34,000 and 39,000 after SDS-PAGE and showed cross-reactivity with swine alpha 2-macroglobulin slow. It inhibits all proteinases tested and is the only macroglobulin with antihemorrhagic activity against V. berus venom. This antihemorrhagic activity may be due to beta-macroglobulin's different structure as compared to other macroglobulins, which may make it less susceptible to inactivation by venom proteinases.