Structural and biological characterization of a crotapotin isoform isolated from Crotalus durissus cascavella venom

Cytotoxic effects of crotoxin from Crotalus durissus terrificus snake in canine mammary tumor cell lines

Background

Mammary gland tumors are the most prevalent neoplasm in intact female dogs, and they are good natural models to study comparative oncology. Most canine mammary malignancies, as in women, are commonly refractory to conventional therapies and demand continuous new therapeutic approaches. Crotalus durissus terrificus, also called rattlesnake, has more than 60 different proteins in its venom with multiple pharmaceutical uses, such as antitumor, antiviral, and antimicrobial action. Crotoxin, a potent β-neurotoxin formed by the junction of two subunits, a basic subunit (CB-PLA2) and an acidic subunit (crotapotin), has already been reported to have anticancer properties in different types of cancers.

Methods

In this work, we describe the cytotoxic potential of crotoxin and its subunits compared to doxorubicin (drug of choice) in two canine mammary carcinoma cell lines.

Results

Crotoxin, CB-PLA2, crotalic venom, and doxorubicin decreased cell viability and the ability to migrate in a dose-dependent manner, and crotapotin did not present an antitumoral effect. For all compounds, the predominant cell death mechanism was apoptosis. In addition, crotoxin did not show toxicity in normal canine mammary gland cells.

Conclusion

Therefore, this work showed that crotoxin and CB-PLA2 had cytotoxic activity, migration inhibition, and pro-apoptotic potential in canine mammary gland carcinoma cell lines, making their possible use in cancer research.

Crotalus durissus terrificus crotapotin naturally displays preferred positions for amino acid substitutions

Background

Classically, Crotalus durissus terrificus (Cdt) venom can be described, according to chromatographic criteria, as a simple venom, composed of four major toxins, namely: gyroxin, crotamine, crotoxin and convulxin. Crotoxin is a non-covalent heterodimeric neurotoxin constituted of two subunits: an active phospholipase A₂ and a chaperone protein, termed crotapotin. This molecule is composed of three peptide chains connected by seven disulfide bridges. Naturally occurring variants/isoforms of either crotoxin or crotapotin itself have already been reported.

Methods

The crude Cdt venom was separated by using RP-HPLC and the toxins were identified by mass spectrometry (MS). Crotapotin was purified, reduced and alkylated in order to separate the peptide chains that were further analyzed by mass spectrometry and de novo peptide sequencing.

Results

The RP-HPLC profile of the isolated crotapotin chains already indicated that the α chain would present isoforms, which was corroborated by the MS and tandem mass spectrometry analyses.

Conclusion

It was possible to observe that the Cdt crotapotin displays a preferred amino acid substitution pattern present in the α chain, at positions 31 and 40. Moreover, substitutions could also be observed in β and γ chains (one for each). The combinations of these four different peptides, with the already described chains, would produce ten different crotapotins, which is compatible to our previous observations for the Cdt venom.

Identification of two novel cytolysins from the hydrozoan Olindias sambaquiensis (Cnidaria)

BACKGROUND

Although the hydrozoan Olindias sambaquiensis is the most common jellyfish associated with human envenomation in southeastern and southern Brazil, information about the composition of its venom is rare. Thus, the present study aimed to analyze pharmacological aspects of O. sambaquiensis venom as well as clinical manifestations observed in affected patients. Crude protein extracts were prepared from the tentacles of animals; peptides and proteins were sequenced and submitted to circular dichroism spectroscopy. Creatine kinase, cytotoxicity and hemolytic activity were evaluated by specific methods.

RESULTS

We identified two novel cytolysins denominated oshem 1 and oshem 2 from the tentacles of this jellyfish. The cytolysins presented the amino acid sequences NEGKAKCGNTAGSKLTFKSADECTKTGQK (oshem 1) and NNSKAKCGDLAGWSKLTFKSADECTKTGQKS (oshem 2) with respective molecular masses of 3.013 kDa and 3.375 kDa. Circular dichroism revealed that oshem 1 has random coils and small α-helix conformation as main secondary structure whereas oshem 2 presents mainly random coils as its main secondary structure probably due to the presence of W (13) in oshem 2. The hemolysis levels induced by oshem 1 and oshem 2 using a peptide concentration of 0.2 mg/mL were, respectively, 51.7 ± 6.5% and 32.9 ± 8.7% (n = 12 and p ≤ 0.05). Oshem 1 and oshem 2 showed significant myonecrotic activity, evaluated by respective CK level measurements of 1890.4 ± 89 and 1212.5 ± 103 (n = 4 and p ≤ 0.05). In addition, myonecrosis was also evaluated by cell survival, which was measured at 72.4 ± 8.6% and 83.5 ± 6.7% (n = 12 and p ≤ 0.05), respectively. The structural analysis showed that both oshem 1 and oshem 2 should be classified as a small basic hemolytic peptide.

CONCLUSION

The amino acid sequences of two peptides were highly similar while the primary amino acid sequence analysis revealed W (22th) as the most important mutation. Finally oshem 1 and oshem 2 are the first cytolytic peptides isolated from the Olindias sambaquiensis and should probably represent a novel class of cytolytic peptides.

Modulation of the pharmacological activities of secretory phospholipase A2 from Crotalus durissus cascavella induced by naringin

In this work we have characterized the action of the naringin, a flavonoid found in grapefruit and known for its various pharmacological effects, which include antioxidant blood lipid lowering and anticancer activity, on the structure and biochemical activities of a secretory phospholipase A (sPLA2) from Crotalus durissus cascavella, an important protein involved in the releasinge of arachidonic acid in phospholipid membranes. sPLA2 was incubated with naringin (mol:mol) at 37 °C and a discrete reduction in the UV scanning signal and a modification of the circular dichroism spectra were observed after treatment with naringin, suggesting modifications of the secondary structure of the protein. This flavonoid was able to decrease enzymatic activity and some pharmacological effects, such as myonecrosis, platelet aggregation, and neurotoxic activity caused by sPLA2, however, the inflammatory effect was not affected by naringin. In addition, small angle X-ray scattering (SAXS) data were collected for sPLA2 and naringin-treated sPLA2 to evaluate possible modifications of the protein structure. These structural investigations have shown that sPLA2 is an elongated dimer in solution and after treatment with naringin a conformational change in the dimeric configuration was observed. Our results suggest that structural modification may be correlated with the loss of enzymatic activity and alterations in pharmacological properties.

Effects of the Crotalus durissus terrificus snake venom on hepatic metabolism and oxidative stress

Snake venoms present different action mechanisms because of their complex composition, represented mainly by toxins and enzymes. This work aimed to investigate the effects of the Crotalus durissus terrificus(Cdt) venom in the liver. Wistar rats were inoculated intraperitoneally with saline (control) or Cdt venom. After 3, 4, or 6 h, the following parameters were analyzed: (a) hepatic function, (b) oxidative stress parameters, and (c) the metabolism of alanine in the isolated perfused liver. Plasma activities of alanine aminotransferase and aspartate aminotransferase and hepatic glutathione S-transferase and catalase presented significant elevation in rats inoculated with 300 μg ⋅ kg(-1) Cdt venom. Liver lipoperoxidation was enormously increased by venom doses of 100, 200, and 300 μg ⋅kg(-1) , whereas glutathione S-transferase was not changed. Perfused livers from rats inoculated with 1500 μg ⋅kg(-1) venom showed increased production of lactate, pyruvate, and ammonia when alanine was the metabolic substrate. These results demonstrate that the Cdt venom can produce several changes in hepatocytes. The causes of the changes are possibly related to the disequilibrium in the redox homeostasis but also to specific needs of the poisoned organism, for example, an increased supply of lactate and pyruvate in response to an increased activity of the Cori cycle.

Antibacterial and antiparasitic effects of Bothrops marajoensis venom and its fractions: Phospholipase A2 and L-amino acid oxidase

Some proteins present in snake venom possess enzymatic activities, such as phospholipase A(2) and l-amino acid oxidase. In this study, we verify the action of the Bothrops marajoensis venom (BmarTV), PLA(2) (BmarPLA(2)) and LAAO (BmarLAAO) on strains of bacteria, yeast, and Leishmania sp. The BmarTV was isolated by Protein Pack 5PW, and several fractions were obtained. Reverse phase HPLC showed that BmarPLA(2) was isolated from the venom, and N-terminal amino acid sequencing of sPLA(2) showed high amino acid identity with other lysine K49 sPLA(2)s isolated from Bothrops snakes. The BmarLAAO was purified to high molecular homogeneity and its N-terminal amino acid sequence demonstrated a high degree of amino acid conservation with others LAAOs. BmarLAAO was able to inhibit the growth of P. aeruginosa, C. albicans and S. aureus in a dose-dependent manner. The inhibitory effect was more significant on S. aureus, with a MIC=50 microg/mL and MLC=200 microg/mL. However, the BmarTV and BmarPLA(2) did not demonstrate inhibitory capacity. BmarLAAO was able to inhibit the growth of promastigote forms of L. chagasi and L. amazonensis, with an IC(50)=2.55 microg/mL and 2.86 microg/mL for L. amazonensis and L. chagasi, respectively. BmarTV also provided significant inhibition of parasitic growth, with an IC(50) of 86.56 microg/mL for L. amazonensis and 79.02 microg/mL for L. chagasi. BmarPLA(2) did not promote any inhibition of the growth of these parasites. The BmarLAAO and BmarTV presented low toxicity at the concentrations studied. In conclusion, whole venom as well as the l-amino acid oxidase from Bothrops marajoensis was able to inhibit the growth of several microorganisms, including S. aureus, Candida albicans, Pseudomonas aeruginosa, and Leishmania sp.

Purification and characterization of the biological effects of phospholipase A(2) from sea anemone Bunodosoma caissarum

Sea anemones contain a variety of biologically active substances. Bunodosoma caissarum is a sea anemone from the Cnidaria phylum, found only in Brazilian coastal waters. The aim of the present work was to study the biological effects of PLA(2) isolated from the sea anemone B. caissarum on the isolated perfused kidney, the arteriolar mesenteric bed and on insulin secretion. Specimens of B. caissarum were collected from the São Vicente Channel on the southern coast of the State of São Paulo, Brazil. Reverse phase HPLC analysis of the crude extract of B. caissarum detected three PLA(2) proteins (named BcPLA(2)1, BcPLA(2)2 and BcPLA(2)3) found to be active in B. caissarum extracts. MALDI-TOF mass spectrometry of BcPLA(2)1 showed one main peak at 14.7 kDa. The N-terminal amino acid sequence of BcPLA(2)1 showed high amino acid sequence identity with PLA(2) group III protein isolated from the Mexican lizard (PA23 HELSU, HELSU, PA22 HELSU) and with the honey bee Apis mellifera (PLA(2) and 1POC_A). In addition, BcPLA(2)1 also showed significant overall homology to bee PLA(2). The enzymatic activity induced by native BcPLA(2)1 (20 microg/well) was reduced by chemical treatment with p-bromophenacyl bromide (p-BPB) and with morin. BcPLA(2)1 strongly induced insulin secretion in presence of high glucose concentration. In isolated kidney, the PLA(2) from B. caissarum increased the perfusion pressure, renal vascular resistance, urinary flow, glomerular filtration rate, and sodium, potassium and chloride levels of excretion. BcPLA(2)1, however, did not increase the perfusion pressure on the mesenteric vascular bed. In conclusion, PLA(2), a group III phospholipase isolated from the sea anemone B. caissarum, exerted effects on renal function and induced insulin secretion in conditions of high glucose concentration.

Purification and biological effects of L-amino acid oxidase isolated from Bothrops insularis venom

Bothrops insularis is a snake from Ilha da Queimada Grande, an island located about 20 miles away from the Southeastern coast of Brazil. Compared with other Brazilian species of Bothrops, the toxinology of B. insularis is still poorly understood, and so far, no fraction from this venom with amino acid oxidase activity had been isolated or its biological activity tested. We investigated the biochemical and biological effects of one l-amino acid oxidase enzyme isolated from B. insularis snake venom (BiLAO), which was purified using HPLC and sequence grade. We also evaluated the renal effects induced by BiLAO. Chromatographic profile of B. insularis whole venom disclosed seven main fractions (I, II, III, IV, V, VI and VII) and the main LAO enzymatic activity was detected in fraction II. The group treated with BiLAO showed a decrease in perfusion pressure (C(120)=110.28+/-3.69; BiLAO(120)=82.2+/-5.6 mmHg*); renal vascular resistance (C(120)=5.48+/-0.53; BiLAO(120)=4.12+/-0.42 mmHg/mL/g/min*), urinary flow (C(120)=0.160+/-0.020; BiLAO(120)=0.064+/-0.012 mL/g/min*), glomerular filtration rate (C(120)=0.697+/-0.084; BiLAO(120)=0.176+/-0.017 mL/g/min*), sodium (C(120)=79.76+/-0.56; BiLAO(120)=65.39+/-6.19%*), potassium (C(120)=69.94+/-6.86; BiLAO(120)=60.26+/-2.24%*) and chloride tubular reabsortion (C(120)=78.53+/-2.33; BiLAO(120)=64.58+/-6.68%*). Acute tubular necrosis foci were observed in the group treated with the LAO fraction of the B. insularis snake venom. Some findings have the same morphological aspect of apoptosis, more evident cortically; otherwise, reversible degenerative phenomena represented by hydropic ballooning with extensive cytoplasmic vacuolization and discontinuity of the cell brush borders in the proximal tubular epithelium were observed; furthermore, necrotic detachment of these cells into the tubular lumina, and increased amount of protein deposits in the distal and proximal tubules were observed. In conclusion, the slowness of blood flow and of glomerular filtration resulted in more time for filtration and tubular reabsorption, with elevation of the total percentage of sodium and chlorine reabsorption. The maintenance of the decrease in glomerular filtration rate would determine the subsequent decreases, which were noticed in these parameters. The necrosis observed was the result of damage cell induced by l-amino acid oxidase isolated from B. insularis venom.

Isolation of a new l-amino acid oxidase from Crotalus durissus cascavella venom

A novel l-amino acid oxidase (LAO) (Casca LAO) from Crotalus durissus cascavella venom was purified to a high degree of molecular homogeneity using a combination of molecular exclusion and ion-exchange chromatography system. The purified monomer of LAO presented a molecular mass of 68 kDa and pI estimated in 5.43, which were determined by two-dimensional electrophoresis. The 71st N-terminal amino acid sequence of the LAO from Crotalus durissus cascavella presented a high amino acid sequence similarities with other LAOs from Colloselasma rhosostoma, Crotalus adamanteus, Agkistrodon h. blomhoffi, Agkistrodon h. halys and Trimeresurus stejnegeri. LAO displayed a Michaelis-Menten behavior with a kilometer of 46.7 microM and an optimum pH for enzymatic activity of 6.5. Casca LAO induced a dose-dependent platelet aggregation, which was abolished by catalase and inhibited by indomethacin and aspirin. These results suggest that the production of H2O2 is involved in subsequent activation of inflammatory enzymes, such as thromboxane. Casca LAO also inhibited the bacterial growth of Gram-negative (Xanthomonas axonopodis pv passiflorae) and Gram-positive (S. mutans) strains. Electron microscopy assessments of both bacterial strains suggest that the hydrogen peroxide produced by LAO induce bacterial membrane rupture and consequently loss of cytoplasmatic content. This LAO exhibited a high antileishmanic activity against the promastigote of Leishmania amazonensis in vitro, its activity was dependent on the production of hydrogen peroxide, and the 50% inhibitory concentration was estimated in 2.39 microg/ml.

Molecular evolution and structure-function relationships of crotoxin-like and asparagine-6-containing phospholipases A2 in pit viper venoms

Some myotoxic or neurotoxic PLA2s (phospholipases A2) from pit viper venoms contain characteristic N6 substitutions. Our survey of the venoms of more than ten pit viper genera revealed that N6-PLA2s exist only in limited Asian pit vipers of two genera, Protobothrops and Gloydius, and exist as either monomers or the basic subunits of heterodimers in some New World pit vipers. For the newly identified N6-PLA2s, the neuromuscular blocking activities were assayed with the chick biventer cervicis neuromuscular tissue, whereas the increased serum creatine kinase level assessed their myotoxicities. The purified N6-PLA2s from Protobothrops mangshanensis and Gloydius intermedius saxatilis were found to be presynaptic neurotoxins. In contrast, all N6-PLA2s from the venoms of Sistrurus miliarius strackeri, S. m. barbouri, Crotalus viridis viridis, C. lepidus lepidus, Cerrophidion godmani and Bothreichis schlegelii were myotoxins without neurotoxicity even in the presence of crotoxin A. Crotoxin-like complexes were for the first time purified from the venoms of Sitrurus catenatus tergeminus, C. mitchelli mitchelli, C. horridus atricaudatus, C. basiliscus and C. durissus cumanensis. The cDNAs encoding six novel N6-PLA2s and subunits of the crotoxin-like complex from S. c. tergeminus were cloned and fully sequenced. Phylogeny analysis showed that two structural subtypes of N6-PLA2s with either F24 or S24 substitution have been evolved in parallel, possibly descended respectively from species related to present-day Protobothrops and Gloydius. Calmodulin binds all the N6-PLA2s but crotoxin A may inhibit its binding to crotoxin B and to other neurotoxic N6-PLA2s. Structure-activity relationships at various regions of the PLA2 molecules were extensively discussed.

Anti-sera raised in rabbits against crotoxin and phospholipase A2 from Crotalus durissus cascavella venom neutralize the neurotoxicity of the venom and crotoxin

Crotoxin, the principal neurotoxin in venom of the South American rattlesnakes Crotalus durissus terrificus and Crotalus durissus cascavella, contains a basic phospholipase A2 (PLA2) and an acidic protein, crotapotin. In this work, we examined the ability of rabbit anti-sera against crotoxin and its PLA2 subunit to neutralize the neurotoxicity of venom and crotoxin from C. d. cascavella in mouse phrenic nerve-diaphragm and chick biventer cervicis preparations. Immunoblotting showed that the anti-sera recognized C. d. cascavella crotoxin and PLA2. This was confirmed by ELISA, with both anti-sera having end-point dilutions of 3 x 10(-6). Anti-crotoxin serum neutralized the neuromuscular blockade in phrenic nerve-diaphragm muscle preparations at venom or crotoxin:anti-serum ratios of 1:2 and 1:3, respectively. Anti-PLA2 serum also neutralized this neuromuscular activity at a venom or crotoxin:anti-serum ratio of 1:1. In biventer cervicis preparations, the corresponding ratio for anti-crotoxin serum was 1:3 for venom and crotoxin, and 1:1 and 1:2 for anti-PLA2 serum. The neutralizing capacity of the sera in mouse preparations was comparable to that of commercial anti-serum raised against C. d. terrificus venom. These results show that anti-sera against crotoxin and PLA2 from C. d. cascavella venom neutralized the neuromuscular blockade induced by venom and crotoxin in both nerve-muscle preparations, with the anti-serum against crotoxin being slightly less potent than that against crotoxin.