Biochemical characterization and pharmacological properties of a phospholipase A2 myotoxin inhibitor from the plasma of the snake Bothrops asper

A protein that neutralizes the biological activities of basic phospholipase A2 (PLA2) myotoxin isoforms from the venom of the snake Bothrops asper was isolated from its blood by affinity chromatography with Sepharose-immobilized myotoxins. Biochemical characterization of this B. asper myotoxin inhibitor protein (BaMIP) indicated a subunit molecular mass of 23-25 kDa, an isoelectric point of 4, and glycosylation. Gel-filtration studies revealed a molecular mass of 120 kDa, suggesting that BaMIP possesses an oligomeric structure composed of five 23-25 kDa subunits. Functional studies indicated that BaMIP inhibits the PLA2 activity of B. asper basic myotoxins I and III, as well as the myotoxicity and edema-forming activity in vivo and cytolytic activity in vitro towards cultured endothelial cells, of all four myotoxin isoforms (I-IV) tested. Sequence analysis of the first 63 amino acid residues from the N-terminus of BaMIP indicated more than 65% sequence similarity to the PLA2 inhibitors isolated from the blood of the crotalid snakes Trimeresurus flavoviridis and Agkistrodon blomhoffii siniticus. These inhibitors also share sequences similar to the carbohydrate-recognition domains of human and rabbit cellular PLA2 receptors, suggesting a common domain evolution among snake plasma PLA2 inhibitors and mammalian PLA2 receptors. Despite this similarity, this is the first description of a natural anti-myotoxic factor from snake blood.

Inhibition of the hemorrhagic activity of Bothrops asper venom by a novel neutralizing mixture

This study screened 25 sera, 19 synthetic products and five antivenoms obtained after immunization for their ability to neutralize the hemorrhagic activity of venom from the snake Bothrops asper. Among the sera screened, the homologous serum of B. asper itself was found to possess the highest neutralizing capacity, abolishing the hemorrhagic effect of the venom at weight ratio of 3:1. It was more efficient than the antisera obtained by immunization. Among the synthetic compounds tested, only O-phenanthroline and EDTA salts inhibited the hemorrhagic activity at concentrations of 0.5-10 mM; however, only CaNa2EDTA was non-toxic at the concentrations studied. Intravenous injections and in situ administration of the non-toxic inhibitors revealed that a fraction of B. asper serum, the horse polyvalent antivenom and CaNa2EDTA were the most potent antihemorrhagic materials against B. asper venom, especially when administered in situ as a mixture. This work suggests that this neutralizing mixture could be highly useful in the neutralization of local and systemic hemorrhage developing after B. asper envenomation.

A comparison of in vitro methods for assessing the potency of therapeutic antisera against the venom of the coral snake Micrurus nigrocinctus

Therapeutic antisera against Micrurus nigrocinctus venom were tested for protection against lethality, as well as for inhibition of the nicotinic acetylcholine receptor (AchR)-binding and neutralization of phospholipase A2 (PLA2) activities of the homologous venom. Protection against venom lethality did not correlate with inhibition of AchR-binding activity, whereas there was a significant correlation between antisera potency and inhibition of PLA2 activity (r = 0.82, n = 10, P < 0.02). Inhibition of PLA2 activity could be useful in assessing the protective efficacy of M. nigrocinctus antisera during antivenom production. Micrurus nigrocinctus nigrocinctus venom proteins were fractionated by cation-exchange chromatography on Mono S FPLC and fractions assayed for lethality, AchR-binding and PLA2 activities. Antisera were titrated by enzyme-linked immunoassay (ELISA) against a crude M. n. nigrocinctus venom, two FPLC lethal fractions containing AchR-binding activity, and two toxins purified from M. n. nigrocinctus venom. No correlation was found between protective efficacy and the ELISA titer against any of these antigens. Compared to other elapid venoms that contain few toxins as major components, M. n. nigrocinctus venom appears to be more complex and its lethal effect is likely to be due to the combined effect of several neurotoxins.

Isolation and characterization of a myotoxic phospholipase A2 from the venom of the arboreal snake Bothriechis (Bothrops) schlegelii from Costa Rica

A new myotoxic phospholipase A2 was isolated from the venom of the arboreal snake Bothriechis schlegelii (formerly Bothrops schlegelii) from Costa Rica, by ion-exchange chromatography on CM-Sephadex. B. schlegelii myotoxin I is a basic protein (pI > 9.3) with a subunit molecular weight of 15 kDa, which migrates as a dimer in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions. This myotoxin is recognized by antibodies generated against Bothrops asper myotoxin II (a lysine-49 phospholipase A2), by both enzyme-immunoassay and gel immunodiffusion, in the latter case with a pattern of partial identity. The toxin induces rapid myonecrosis upon intramuscular injection in mice, as evidenced by the early increase in plasma creatine kinase activity and by direct intravital microscopic observation. B. schlegelii myotoxin I also induces edema in the mouse footpad assay and exerts lethal activity (LD50 approximately 2.5 microg/g) upon intravenous injection. The toxin has a low phospholipase A2 activity (4.2 microEq.mg-1.min-1) using egg yolk phospholipids as substrate. It also shows a weak anticoagulant effect in vitro. Its N-terminal sequence, SMYELGKMILLETGKNAATSYIAYG, shows 93% homology with both Bothrops asper myotoxin II and B. jararacussu bothropstoxin I, suggesting that B. schlegelii myotoxin I may be a new lysine-49 variant of this family of myotoxic phospholipases A2.

Chemical modification of histidine and lysine residues of myotoxic phospholipases A2 isolated from Bothrops asper and Bothrops godmani snake venoms: effects on enzymatic and pharmacological properties

Lysine and histidine residues of two myotoxic phospholipases A2, Bothrops asper myotoxin III and Bothrops godmani myotoxin I, were chemically modified in order to study the effects of these treatments on enzymatic and pharmacological properties. After lysine acetylation the overall basicity of these toxins was lost and their enzymatic activity was significantly reduced, although a residual effect remained, which corresponded to 25% of the activity of native toxins. This treatment abolished both myotoxic and anticoagulant effects, and partially reduced liposome-disrupting activity. Histidine alkylation with p-bromophenacyl bromide affected phospholipase A2, myotoxic and anticoagulant effects in a parallel way. After 24 hr of incubation with the alkylating reagent, these three activities were totally inhibited, in contrast to the liposome-disrupting effect which was only partially affected by this treatment. It is suggested that; (1) catalytic activity plays a role in the pharmacological effects of these myotoxins; (2) lysine residues are relevant for the toxic effects induced by these phospholipases A2; and (3) despite the apparent relevance of enzymatic activity to the pharmacological properties of these toxins, the dissociation observed in lysine acetylation experiments suggests that these myotoxins have a molecular region, different from the catalytic site, which might be also involved in the toxic effects observed.

Clinical and laboratory alterations in horses during immunization with snake venoms for the production of polyvalent (Crotalinae) antivenom

Six horses were immunized with the venoms of Bothrops asper, Crotalus durissus durissus and Lachesis muta stenophrys for the production of polyvalent (Crotalinae) antivenom. During the immunization, clinical and laboratory alterations were evaluated in these animals, and the development of humoral immune response was followed. Only moderate local tissue changes (edema, abscesses, fistules and fibrosis) were observed in these animals, whereas no systemic alterations occurred. Regarding laboratory tests, there was a drop in hemoglobin concentration and hematocrit, together with an increment in total serum protein. Horses developed a moderate leukocytosis, with increments in polymorphonuclear leukocytes and lymphocytes. No significant changes were observed in prothrombin time or platelet count. There were no alterations in serum lactic dehydrogenase and gamma glutamyl transferase activities, whereas minor increments in creatine kinase and alanine aminotransferase activities were observed, together with a decrease in aspartate aminotransferase. All these changes occurred after the injection of 9 mg venom, when sodium alginate was first used as adjuvant. Creatinine levels had a small increment, although no changes were observed in urea levels or in the urea/creatinine ratio. An important individual variability was observed in the humoral immune response, as judged not only by enzyme-linked immunosorbent assay, but also by assessing the neutralization of the indirect hemolytic activity of venoms.

A randomized double-blind clinical trial of two antivenoms in patients bitten by Bothrops atrox in Colombia. The Regional Group on Antivenom Therapy Research (REGATHER)

A randomized double-blind clinical trial in 39 patients envenomed by Bothrops atrox in Antioquia and Chocó, Colombia, was performed to compare the efficacy and safety of 2 equine-derived antivenoms prepared at Instituto Clodomiro Picado, University of Costa Rica. Twenty patients received a monovalent anti-B. atrox antivenom (group A) and 19 patients were treated with a polyvalent (Crotalinae) antivenom (group B). Both antivenoms were equally efficient in the neutralization of the most relevant signs of envenoming (haemorrhage and blood clotting time alteration). Fourteen patients (36%) presented early adverse reactions to antivenoms and no significant difference between the 2 groups was observed. Urticaria (18%) was the most frequent early adverse reaction and there was no life-threatening anaphylactic reaction. Based on clinical criteria and serum venom levels, estimated by an enzyme immunoassay, 15 patients were classified into 2 groups: mild and moderate/severe envenoming. With the antivenom doses used in this study (3, 6 and 9 vials for mild, moderate and severe envenoming, respectively), both antivenoms were equally efficient in clearing serum venom levels within the first hour of treatment, and the levels remained below the lower limit of venom detection for 24 h. Antivenom concentration in serum remained high for up to 24 h after antivenom infusion, suggesting that an excess of antibody in relation to circulating antigen had been administered.

Effect of adjuvants on the antibody response of mice to Bothrops asper (Terciopelo) snake venom

The adjuvant properties of several immunostimulant molecules on the murine antibody response to Bothrops asper snake venom were evaluated. Mice receiving venom together with either sodium alginate, calcium alginate, aluminum hydroxide, muramyl dipeptide, killed Brucella abortus or B. abortus smooth lipopolysaccharide developed a similar antibody response. Despite the fact that in some cases animals injected with venom and Salmonella montevideo lipopolysaccharide developed a significantly higher antibody titer when compared to other experimental groups, no statistically significant differences were observed in most of the comparisons.

[Muscular spasms associated with a reflex sympathetic dystrophy]

The appearance of involuntary movements in the clinical course of reflex sympathetic dystrophy (DSR) constitutes a rare clinical entity. In this context, the most frequent changes in movements are muscle spasms and focal dystonia, although postural tremor, muscle weakness and rhythmic myoclonus have also been described. The disorder is more frequent in young women and in the lower limbs. It may have a focal, segmental, multifocal, hemicorporal or symmetrical distribution. It is almost always secondary to local trauma. The pathogenesis and most effective treatment are unknown. We present the case of a 62 year old woman with muscle spasms of both legs and feet as a complication of spontaneously appearing DSR. The electromyogram showed continuous non-rhythmic discharges with morphologically normal motor unit potentials in both anterior tibial muscles. The clinical course and symptomatic improvement following treatment with benzodiazepine seems to suggest that the disorder is of central origin.

Biochemical and biological characterization of Ecuadorian pitviper venoms (genera Bothriechis, Bothriopsis, Bothrops and Lachesis)

The lethality and enzymatic activities of venoms from six Ecuadorian pitvipers (Bothriechis schlegelii, Bothriopsis punctata, Bothriopsis taeniata, Bothrops asper, Bothrops atrox and Lachesis muta) are similar to those of other South and Central American species, but with a few exceptions: Bothriopsis taeniata venom had no coagulant activity, and Bothriechis schlegelii venom had no haemorrhagic activity.

Characterization of alpha-neurotoxin and phospholipase A2 activities from Micrurus venoms. Determination of the amino acid sequence and receptor-binding ability of the major alpha-neurotoxin from Micrurus nigrocinctus nigrocinctus

New World elapids are coral snakes that belong to the genus Micrurus, and for which the venom biochemistry is mostly unknown. Analysis has been difficult because the coral snakes produce small quantities of venom. Clinical observations following bites show mainly neurotoxic effects. Experimentally, cardiotoxic, haemolytic and myotoxic activities are also reported. An experimental approach, using reverse-phase high-performance liquid chromatography and specific assays for alpha-neurotoxin and phospholipase A2 activities, was conducted on milligram quantities of venoms from three Micrurus species from Costa Rica; M. nigrocinctus nigrocinctus, M. alleni yatesi and M. multifasciatus. Neurotoxicity was determined by competition binding experiments with the Torpedo marmorata acetylcholine receptor. Phospholipase A2 activity was measured by fluorimetry using a pyrene lipid substrate. In this way, we purified and characterized seven alpha-neurotoxins, five phospholipases A2 and four toxin homologs. The amino acid sequence of the major alpha-neurotoxin from M. nigrocinctus nigrocinctus venom was fully determined and compared to Old Word representatives. Distance matrix data were generated to set up phylogeny relationships among elapid short-chain alpha-neurotoxins, which proved to be in accordance with the taxonomic classification and geographical distribution of snake species.

Dietary intervention in a hypercholesterolemic school-aged population from Northern Spain

A "before and after" intervention study, over a five year period, was done in order to find the degree of compliance to dietary recommendations and their effects on serum lipids in a hypercholesterolemic school-aged population. 383 children between 6 and 13 years of age, were identified with hypercholesterolemia (total serum levels above 4.8 mmol/l), in a previous randomized mass screening of 1095 individuals. Some dietary guidelines aimed at decreasing fat consumption and increasing fiber and carbohydrate ingestion were given to the families, and 226 of the children participated in the follow-up. Changes of address and/or school-center was the main cause of non-participation. The follow-up examination consisted in the evaluation of serum lipids and actual diet. Cholesterol serum levels decreased from a mean value of 5.4 mmol/l to 4.8 mmol/l. 59.3% of the sample had reached serum cholesterol levels below the risk threshold. Fat ingestion diminished significantly (40.3% of calories to 36.7%, p < 0.001), saturated fatty acids decreased from 15.3% of calories to 13.5% (p < 0.001), monounsaturated fatty acids decreased from 17.1% to 15.4% (p < 0.001) and polyunsaturated fatty acids remained unchanged. Carbohydrate consumption increased from 45% of the calories to 47.38% (p < 0.001). Dietary changes were greater in individuals out of risk than those who still had high cholesterol levels. These data indicate a good family compliance to the recommendations and that changes in food habits seem to be effective in controlling hyperlipidemia. Dietary changes are better accepted by younger children.

Organochlorine residues in tissues of striped dolphins affected by the 1990 Mediterranean epizootic: relationships with the fatty acid composition

A simple and rapid method was developed for the simultaneous determination of fatty acids, organochlorine pesticides, and polychlorinated biphenyl (PCB) congeners in the same sample in order to explore possible connections between levels of contaminants and fatty acid composition. The method was applied to samples of melon, cerebrum, cerebellum, lung, liver, kidneys, and skeletal muscle obtained from 5 male and 5 female striped dolphins (Stenella coeruleoalba) found stranded in 1990 in the northeastern Spanish coasts during the morbillivirus epizootic that affected this cetacean in the Mediterranean Sea. The results indicate that PCBs were dominant in all tissues, with the highest geometric mean concentration being found in melon (903 micrograms g-1 wet wt); sigma DDTs were also found at high concentrations (111 micrograms g-1 wet wt, in melon). Statistical analysis indicate that organochlorine concentration was correlated with the fatty acid composition of tissues, although some of these variations can be interpreted as a consequence of a shift in the diet produced in the striped dolphin population. However, other changes such as the negative correlation with arachidonic acid may suggest that the eicosanoid production could have been affected by the extremely high concentrations of PCBs and sigma DDTs.

Local tissue damage induced by BaP1, a metalloproteinase isolated from Bothrops asper (Terciopelo) snake venom

The pathogenesis of hemorrhage and other local effects induced by the metalloproteinase BaP1, isolated from Bothrops asper venom, was investigated using various in vivo and in vitro models. Upon intramuscular injection in mice BaP1 caused rapid hemorrhage in muscular and adipose tissues. Vital microscopy using mouse cremaster muscle evidenced the formation of multiple hemorrhagic foci of an explosive character, originating from capillaries and small venules. In contrast to crude B. asper venom, which besides hemorrhage also induced myonecrosis and thrombosis, vital microscopy detected only hemorrhage after application of BaP1, during the 40-min observation period. However, histological observation in mouse gastrocnemius muscle evidenced a few areas of limited myonecrosis was followed by an incomplete regenerative response, since regenerating muscle fibers were interspersed with fibrosis in some areas. Metalloproteinase BaP1 was not cytotoxic to human and murine endothelial cells in culture, causing only a mild detachment from the culture plate. BaP1 hydrolyzed types I and IV collagen, fibronectin, and laminin upon incubation with these extracellular matrix proteins in vitro. These results suggest that hemorrhage induced by BaP1 is due primarily to the proteolytic degradation to basement membrane components of microvessels and that endothelial cell disruption may be a secondary event. It is concluded that, in addition to hemorrhage, BaP1 contributes to the local tissue damage caused by the venom by inducing myonecrosis, inflammation, and extracellular matrix alterations.

Phospholipase A2 myotoxins from Bothrops snake venoms

Several myotoxins have been isolated from Bothrops snake venoms during the last 10 years. All of them are group II basic phospholipases A2, although some lack enzymatic activity (i.e. Lys-49 variants). These myotoxins appear as an antigenically related family of proteins occurring in many, but not all, Bothrops venoms, bearing a close structural and antigenic relationship to toxins found in other crotalid venoms of the genera Agkistrodon and Trimeresurus. Myotoxins are quantitatively important venom components in some Bothrops species. Intramuscular injection of Bothrops myotoxins leads to a rapid series of drastic degenerative events, probably initiated at the plasma membrane level, which culminate in a selective skeletal muscle necrosis. This in vivo specificity contrasts with the ability of myotoxins to lyse many types of cells in culture. Muscle damage, as well as cytolysis and liposome disruption, occur in conditions where phospholipase A2 activity is inhibited, although enzymatic activity might enhance myotoxin actions. A membrane receptor for Bothrops myotoxins has not been identified yet. A working hypothesis on the mechanism of action is proposed. Current evidence suggests that these toxins interact with biological membranes via a molecular region distinct from their known catalytic site. The active region is likely to be formed by a combination of basic and hydrophobic amino acid residues near the C-terminus of the protein, which allow electrostatic interaction and bilayer penetration. These events may lead to membrane destabilization and loss of selective permeability to ions such as calcium, both of which appear to be important mediators in the process of muscle necrosis.

In vitro activity of BaH1, the main hemorrhagic toxin of Bothrops asper snake venom on bovine endothelial cells

Incubation of BaH1, the main hemorrhagic toxin purified from the venom of Bothrops asper, with endothelial cells caused the appearance of spaces among the cells. This effect became more noticeable with increasing hemorrhagin concentration and longer incubation time. Later, the cells became rounded and detached from the substrate into the medium. Augmentation of Trypan blue did not stain the detached cells, indicating their viability. Moreover, after washing the floating cells from the toxin they could be recultivated: they again spread on the substrate and proliferated, demonstrating that BaHl is not directly cytotoxic to the endothelial cells.

(Evaluation of neutralizing ability of four commercially available antivenoms against the venom of Bothrops asper from Costa Rica)

We studied the ability of four commercially available antivenoms to neutralize several toxic and enzymatic activities of Bothrops asper (terciopelo) venom from Costa Rica. Experiments with preincubation of venom and antivenom were carried out to test the neutralization of lethal, hemorrhagic, coagulant and indirect hemolytic activities. In addition, antibody titers against crude venom and myotoxin II purified from this venom were determined by enzyme immunoassay (ELISA). Results indicate that polyvalent antivenom from Instituto Clodomiro Picado (Costa Rica) has the highest neutralizing ability against lethal, coagulant and indirect hemolytic activities, whereas MYN polyvalent antivenom (México) has the highest neutralization against hemorrhagic activity. Antivenom from Instituto Clodomiro Picado also has the highest antibody titers against crude B. asper venom and against myotoxin II. Antivenoms from Universidad Central de Venezuela (Venezuela), Vencofarma (Brazil) and MYN (México) failed to neutralize the lethal effect of this venom. These results stress the need for rigorous quality control systems to evaluate the neutralizing ability of antivenoms in Central America.

Immunological studies on BaH1 and BaP1, two hemorrhagic metalloproteinases from the venom of the snake Bothrops asper

No immunological cross-reactivity was observed between BaH1 and BaP1, two hemorrhagic metalloproteinases isolated from B. asper venom, by gel immunodiffusion, Western blotting and neutralization studies. Cross-reactivity was detected with antisera against these toxins in several crotaline and viperine snake venoms by ELISA, whereas no reactivity was observed with either antiserum against the venoms of Bothrops nummifer, Crotalus durissus terrificus, Vipera russelli and several elapid venoms. Antiserum against native BaH1 neutralized hemorrhagic activity of the venoms of B. asper, B. atrox, B. jararaca, Crotalus atrox, C. durissus durissus, Echis carinatus and Trimeresurus flavoviridis, being ineffective against the venoms of Agkistrodon bilineatus and Lachesis muta.

Ability of six Latin American antivenoms to neutralize the venom of mapaná equis (Bothrops atrox) from Antioquia and Chocó (Colombia)

This investigation compared the ability of six Latin American antivenoms (monovalent antibothropic INS, Santafé de Bogotá; polyvalent INS; polyvalent probiol, Santafé de Bogotá; antibothropic Instituto Butantan, IB, São Paulo, Brazil; polyvalent Instituto Clodomiro Picado, ICP, San José, Costa Rica; polyvalent MYN, Mexico) to neutralize various pharmacological and enzymatic effects of Bothrops atrox venom from Antioquia and Chocó, north-west of Colombia. Our results demonstrated conspicuous differences in the ability of the six antivenoms. In terms of neutralization of lethality, the highest efficacy was observed in the polyvalent INS and the lowest in the polyvalent MYN antivenom. All antivenoms were highly effective in the neutralization of hemorrhage, polyvalent INS and probiol being the highest. In the neutralization of edema-forming activity, the most effective antivenom was the polyvalent (ICP); monovalent (INS) and polyvalent (MYN) were the least effective. All antivenoms were effective in the neutralization of the myotoxic activity of B. atrox venom, the most effective being the polyvalent (INS) and antibothropic (IB). Defibrinating activity was neutralized by all antivenoms; polyvalent (MYN) showed the lowest efficiency. Polyvalent (ICP) antivenom had the highest neutralizing ability against the indirect hemolytic effect of B. atrox venom; polyvalent (MYN) did not neutralize this enzymatic activity. Overall, the polyvalent antivenom (INS) showed the highest neutralizing ability.

The ability of specific antivenom and low temperature to inhibit the myotoxicity and neuromuscular block induced by Micrurus nigrocinctus venom

In the isolated mouse diaphragm preparation, Micrurus nigrocinctus venom produced a dose-dependent contracture and blockade of the contractile response to direct and indirect electrical stimulation of the muscle. This effect could not be completely reversed by repeated washing of the preparation nor by the addition of neostigmine or 3, 4-diaminopyridine. The observation that the direct blockade had to be preceded by indirect blockade together with the capacity for venom to prevent the ACh- but not the KCl-induced contractures in biventer cervicis and chronically denervated preparations strongly suggests a curarimimetic action for the venom. The temperature at which the experiment was performed greatly influenced the neuromuscular blocking and myotoxic actions of the venom and suggests that the venom component responsible for these effects is thermolabile. Both the neuromuscular blocking action and the myotoxicity of the venom could be prevented by a specific M. nigrocinctus antivenom regardless of whether this was added together with or after the venom. The muscle morphological changes induced by the venom were accompanied by a corresponding increase in the release of creatine kinase (CK) into the incubation medium. This release was, however, submaximal (35%) when compared to that induced by the detergent Triton X-100. In contrast to what has been demonstrated for other Micrurus venoms (M. frontalis, M. corallinus, M. lemniscatus and M. spixii), our results show that the myotoxic effect induced by M. nigrocinctus venom is important for the development of blockade of the muscle contractile response.

Autocatalytic acylation of phospholipase-like myotoxins

Several snake venoms contain a phospholipase A2 in which position 49 in the active site is occupied by a lysine or a serine instead of the aspartate residue normally found. Although these proteins do not bind Ca2+ and are devoid of catalytic activity, they are still highly specific myotoxins and have recently been shown to induce membrane leakage by a new type of cytolytic mechanism. Three of these toxins, myotoxin II from Bothrops asper, ammodytin L from Vipera ammodytes, and the K49 protein from Agkistrodon piscivorus piscivorus, were examined for their interaction with fatty acids and were found to bind long-chain fatty acids covalently by a rapid, spontaneous, autocatalytic process. The fatty acids could be released by treatment with 1 M NH2OH or NaOH, but not with 1 M NaCl or by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electron spin resonance studies using spin-labeled fatty acids showed that only the carboxyl headgroup of the fatty acid was linked to protein amino acid, the carbon chain had free mobility and did not bind tightly to the protein surface. Stearic acid methyl esters and short-chain fatty acids did not bind to the toxins. Acylated myotoxins bound to the surface of liposomes and isolated muscle membranes, with the fatty acid moiety inserted into the lipid bilayer and possibly acting as an anchor. The phospholipase-like myotoxins represent the first group of proteins able to undergo acylation by spontaneous reaction with free fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Skeletal muscle necrosis and regeneration after injection of BaH1, a hemorrhagic metalloproteinase isolated from the venom of the snake Bothrops asper (Terciopelo)

The effects of BaH1, a hemorrhagic metalloproteinase isolated from Bothrops asper venom, on mouse gastrocnemius muscle was investigated. The toxin induced severe hemorrhage within minutes after injection. Groups of necrotic muscle fibers were observed after the sixth hour, with evident disorganization of myofibrillar material. At the ultrastructural level myofibrils in these cells lost their regular arrangement, Z lines were absent, and sarcomeres were disoriented, although there was no evidence of myofilament clumping or hypercontraction. Plasma membrane was interrupted in many portions. Mitochondrial alterations included swelling and the formation of flocculent densities and dense intracristal plates. At 12, 24, and 48 hr necrotic cells had amorphous masses of myofilaments and abundant phagocytic cells were observed both within necrotic fibers and in the interstitial space. Fraction D-1, which contains the three hemorrhagic metalloproteinases BaH1, BH2, and BH3, did not cause direct muscle damage when incubated with gastrocnemius muscle in vitro. Upon intramuscular injection in mice this fraction induced a small but significant increment in muscle lactic acid levels. Observations carried out 7 and 14 days after BaH1 injection revealed some regenerating muscle fibers with centrally located nuclei. However, other areas had few regenerating fibers of reduced diameter, surrounded by abundant fibroblasts, fibrosis, calcification, and remnants of necrotic muscle cells. When BaH1 was injected together with B. asper myotoxin III, a myotoxic phospholipase A2 that induces myonecrosis but does not affect blood vessels, a poor muscle regeneration was observed. In contrast, if B. asper myotoxin III was injected alone, regeneration proceeded normally and successfully.

Isolation and characterization of a metalloproteinase with weak hemorrhagic activity from the venom of the snake Bothrops asper (terciopelo)

A metalloproteinase, named BaP1, was purified to homogeneity from the venom of Bothrops asper (Pacific region) of Costa Rica by ion-exchange chromatography on CM-Sephadex and gel filtration on Sephacryl S-200. The enzyme has a mol. wt of 24,000 and contains few Cys and high numbers of Asp, Leu, Ser and Glu. BaP1 hydrolyzes casein, hide powder azure and fibrinogen, having an optimal pH of 8.0. It rapidly digests the A alpha-chain of fibrinogen and, later on, the B beta-chain, leaving the gamma-chain unaffected. Chelating agents (EDTA and 1,10-phenanthroline) inhibited proteolytic activity, whereas 2-mercaptoethanol and soybean trypsin inhibitor did not affect this activity. BaP1 has a weak hemorrhagic activity, with a minimum hemorrhagic dose of 20 micrograms; this activity was inhibited by EDTA and was abolished after incubation at 60 degrees C. In addition, BaP1 induces edema and a mild myotoxic effect, lacking coagulant, defibrinating and lethal effects.