Procoagulant and platelet-aggregating properties of cerastocytin from Cerastes cerastes venom

Synergistic Effect of Proteinase Activity by Purification and Identification of Toxic Protease From Nemopilema nomurai

Scyphozoan Nemopilema nomurai envenomation is an unresolved threat to human health in Asian waters. Nemopilema nomurai venom metalloproteinases show important toxicities in skin damage and inflammation, but there is still no purified protein for further studies. In this study, high proteinase activity fractions in tentacle autolysis were isolated by ammonium sulfate precipitation, DEAE Sepharose Fast Flow, and Superdex 75 chromatography successively. Purification was guided by azocasein hydrolysis activity and SDS-PAGE. The final products were analyzed by LC-MS/MS. Four elution peaks purified by Superdex 75 chromatography had multiple protein bands but did not show proteinase activity. These fractions would recover proteinase activity after mixing again. Regulation mechanisms were speculated as binding metalloproteinase regulator or disaggregating metalloproteinase inhibitor by LC-MS/MS analysis. For the first time, a synergistic effect in N. nomurai proteinase activity was found in the purification process.

Cerastes cerastes snakebite complicated by coagulopathy and cardiotoxicity with electrocardiographic changes

Snakebites occur worldwide with varying frequency. Outcomes associated with snakebite are varied and depend on the type of snake and the general health of the patient. We report a case of snakebite by Cerastes cerastes or desert horned viper. Consumptive coagulopathy and cardiotoxicity with electrocardiographic changes complicated the clinical course of the patient. To the best of our knowledge, this is the first reported case in the state of Qatar.

Isolated biomolecules of pharmacological interest in hemostasis from Cerastes cerastes venom

Biomolecules from Cerastes cerastes venom have been purified and characterized. Two phospholipases isolated from Cerastes cerastes venom share 51% of homology. CC2-PLA2 exhibits antiplatelet activity that blocks coagulation. CCSV-MPase, a non-hemorrhagic Zn²⁺-metalloproteinase, significantly reduced the plasmatic fibrinogen level and hydrolyzes only its Bβ chain. Serine proteinases such as RP34, afaâcytin and CC3-SPase hydrolyze the fibrinogen and are respectively α, αβ and αβ fibrinogenases. In deficient human plasma, afaâcytin replaces the missing factors VIII and IX, and activates purified human factor X into factor Xa. It releases serotonin from platelets and directly aggregates human (but not rabbit) blood platelets. RP34 proteinase also had no effect on both human and rabbit blood platelet aggregation. CC3-SPase revealed a pro-coagulant activity. However, the insolubility of the obtained clot indicates that CC3-SPase does not activate factor XIII. In addition, CC3-SPase clotting activity was carried out with human plasmas from volunteer patients deficient in clotting factors. Results showed that CC3-SPase shortens clotting time of plasma deficient in factors II and VII but with weaker clotting than normal plasma. The clotting time of plasma deficient in factor II is similar to that obtained with normal plasma; suggesting that CC3-SPase is able to replace both factors IIa and VII in the coagulation cascade and thus could be involved in the blood clotting process via an extrinsic pathway. These results imply that CC3-SPase and afaâcytin could repair hemostatic abnormalities and may replace some factors missing in pathological deficiency. Afaâcytin also exhibits α fibrinase property similar to a plasmin-like proteinase. Despite its thrombin-like characteristics, afaâcytin is not inhibited by plasmatic thrombin inhibitors. The procoagulant properties of afaâcytin might have potential clinical applications.

Severe envenomation by Cerastes cerastes viper: an unusual mechanism of acute ischemic stroke

Cerebral complications after snake bites--particularly ischemic complications--are rare. Very few cases of cerebral infarction resulting from a viper bite have been reported, and we call attention to this uncommon etiology. We discuss 3 authenticated reports of acute ischemic cerebrovascular accidents after 3 typical severe envenomations by Cerastes cerastes vipers. The 3 patients developed extensive local swelling and life-threatening systemic envenomation characterized by disseminated intravascular coagulopathy, increased fibrinolysis, thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure. This clinical picture involved atypical neurologic manifestations. These patients had either low Glasgow Coma Scale (GCS) or hemiparesis within hours to 4 days after being bitten, and they were found to have computed tomographic evidence of single or multiple ischemic (nonhemorrhagic) strokes of small- to large-vessel territories of the brain. One patient had good clinical recovery without neurologic deficits. Thrombotic complications occurred an average of 36 hours after being bitten, and their importance depends on the degree of envenomation. The possible mechanisms for cerebral infarction in these cases include generalized prothrombotic action of the venom (consumptive coagulopathy), toxin-induced vasculitis, and endothelial damage.

[Ischaemic stroke secondary to viper envenomation in Morocco in the absence of adequate antivenom]

An ischaemic stroke is a rare complication of viper envenomation that is due to multifactorial pathophysiological mechanisms. The authors describe the case of a 55-year-old patient bitten by the viper Cerastes cerastes. The patient was admitted to the intensive care unit with multiple organ failure, disseminated intravascular coagulopathy, rhabdomyolysis, anuria and elevated troponin level. The persistent disturbance of consciousness has motivated a brain scan which has revealed a bifocal ischemic stroke. The complex venom of the species C. cerastes may induce hypotension, tissue necrosis, acute renal failure, bleeding disorders or DIC. With the cessation of a non-indicated heparintherapy and haemodialysis, the patient recovered in a few weeks despite the initial infusion of an unsuitable antivenom due to the late identification of the reptile. The preventive treatment of the complications of this envenomation is based on the infusion of the polyvalent antivenom Favirept(®).

Anti-platelet effect of cumanastatin 1, a disintegrin isolated from venom of South American Crotalus rattlesnake

Disintegrins have been previously described in the venom of several snake families inhibiting signal transduction, cell-cell interactions, and cell-matrix interactions and may have therapeutic potential in heart attacks, thrombotic diseases, and cancers. This investigation describes the first disintegrin isolated from South American Crotalus venom (Venezuelan rattlesnake Crotalus durissus cumanensis), which inhibits platelet adhesion to matrix proteins. C. d. cumanensis crude venom was first separated on a Sephadex G-100 column into 4 fractions (SI to SIV). Crude venom and SIII fraction significantly diminished platelet adhesion to fibrinogen (Fg) and to fibronectin (Fn). Anti-adhesive SIII fraction was further separated by DEAE-Sephacel followed by C-18 reverse phase high performance liquid chromatography (HPLC). The platelet anti-adhesive fraction obtained was designated as cumanastatin-1. This disintegrin has a mass of 7.442 kDa as determined by mass spectrometry (MALDI-TOF/TOF) and pI of 8.5. Cumanastatin-1 also inhibited ADP-induced platelet aggregation with an IC(50) of 158 nM. However, it did not significantly inhibit collagen and thrombin-induced platelet aggregation. Cumanastatin-1 considerably inhibited anti-alpha(IIb)beta(3) integrin binding to platelets in a dose-dependent manner; however, it did not present any effect on the alpha(5)beta(1) integrin or on P-selectin.

Snake venoms and hemostasis

Snake venoms are complex mixtures of biologically active proteins and peptides. Many of them affect hemostasis by activating or inhibiting coagulant factors or platelets, or by disrupting endothelium. Based on sequence, these snake venom components have been classified into various families, such as serine proteases, metalloproteinases, C-type lectins, disintegrins and phospholipases. The various members of a particular family act selectively on different blood coagulation factors, blood cells or tissues. For almost every factor involved in coagulation or fibrinolysis there is a venom protein that can activate or inactivate it. Venom proteins affect platelet function by binding or degrading vWF or platelet receptors, activating protease-activated receptors or modulating ADP release and thromboxane A2 formation. Some venom enzymes cleave key basement membrane components and directly affect capillary blood vessels to cause hemorrhaging. L-Amino acid oxidases activate platelets via H2O2 production.

Life-threatening envenoming by the Saharan horned viper (Cerastes cerastes) causing micro-angiopathic haemolysis, coagulopathy and acute renal failure: clinical cases and review

BACKGROUND

The desert horned vipers (Cerastes cerastes and C. gasperettii) are the most familiar snakes of the great deserts of North Africa and the Middle East, including the plains of Iraq. They are responsible for many human snake bites. In Western countries, they are popular among exotic-snake keepers.

AIM

To investigate mechanisms of life-threatening envenoming and treatment.

DESIGN

Clinical investigation.

METHODS

Clinical and laboratory studies with measurement of serum venom antigen concentrations by enzyme immunoassay.

RESULTS

Two men bitten while handling captive Saharan horned vipers (Cerastes cerastes) in Europe developed extensive local swelling and life-threatening systemic envenoming, characterized by coagulopathy, increased fibrinolysis, thrombocytopenia, micro-angiopathic haemolytic anaemia and acute renal failure. The clinical picture is explicable by the presence in C. cerastes venom of several thrombin-like, Factor-X-activating, platelet-aggregating, haemorrhagic and nephrotoxic components. In one case, prophylactic use of subcutaneous epinephrine may have contributed to intracranial haemorrhage. The roles in treatment of heparin (rejected) and specific antivenom (recommended) are discussed.

DISCUSSION

Cerastes cerastes is capable of life-threatening envenoming in humans. Optimal treatment of envenoming is by early administration of specific antivenom, and avoidance of ineffective and potentially-dangerous ancillary methods.

Simultaneous isolation of platelet factor 4 and glycoprotein IIb–IIIa complex from rabbit platelets, and characterization of specific chicken antibodies to assay them

Rabbits are frequently used as models for studying coagulation and platelet disorders. However, few reports on literature have dealt with the purification and characterization of rabbit platelet proteins. Herein a protocol for the simultaneous purification of rabbit platelet factor 4 (PF4) and platelet glycoprotein IIb-IIIa (GPIIb-IIIa, integrin alpha(IIb)beta(3)) is described. Specific antibodies were raised in laying chicken, which were used for assaying PF4 by ELISA, and GPIIb-IIIa by direct immunofluorescence and flow cytometry. Furthermore, the binding of monoclonal antibodies specific for GPIIb-IIIa complex (P2), ligand-induced binding site of GPIIIa (LIBS1) and rabbit P-selectin (12A7), as well as of polyclonal IgY specific for rabbit GPIIb-IIIa, was compared in quiescent and thrombin-activated platelets. Polyclonal anti-rabbit PF4 IgY was a specific and sensitive probe that could be used for assaying PF4 in plasma samples. GPIIb-IIIa expression was increased in thrombin-activated platelets, as evaluated by flow cytometric analysis using P2 and polyclonal antibodies raised in chickens. Rabbit GPIIb-IIIa also exhibited a conformational modification that caused the appearance of ligand-induced binding sites. Increased P-selectin expression, used as a positive control, was also noticeable in thrombin-activated platelets. These data evidence that antibodies raised in laying chickens specific to rabbit PF4 and GPIIb-IIIa, as well as certain monoclonal antibodies specific for human GPIIb-IIIa, may be used for investigating rabbit platelet physiology.

Cerastes cerastes envenomation in an 18 year old female: a case report

An 18 year old woman was bitten on the second finger of her right hand by a Cerastes cerastes. A literature search revealed very few clinical cases, and most of those were only laboratory and in 'vitro studies'. Local signs included a hemorrhagic wound at the site of the bite with marked swelling of the entire hand. Twelve hours later, the patient developed coagulopathy, which lasted 3 days and required repeated administration of blood products. Treatment was essentially supportive and the patient was discharged from the hospital after 5 days in good condition.

Purification, properties, and amino acid sequence of a hemoglobinuria-inducing phospholipase A(2), MiPLA-1, from Micropechis ikaheka venom

Dark-colored urine is one of the clinical symptoms of envenomation by Micropechis ikaheka (New Guinea small-eyed snake). We have purified a phospholipase A(2), MiPLA-1, which induces dark-colored urine in experimental mice, to homogeneity. The analysis of the dark-colored urine by electrophoresis and N-terminal sequence determination indicated that the color of mouse urine is due to hemoglobin in the urine but not myoglobin. MiPLA-1 is the first hemoglobinuria-inducing toxin. Insignificant hemolytic activity of MiPLA-1 indicates that hemoglobinuria is not due to lysis of erythrocytes by MiPLA-1. This suggests that hemoglobinuria induced by MiPLA-1 may be due to kidney leakage caused by unknown mechanisms. MiPLA-1 also showed other biological effects, including myotoxicity as well as anticoagulant and antiplatelet effects. Structural studies show that MiPLA-1 is a basic protein with a molecular mass of 14041.60 +/- 1.78 as determined by electrospray mass spectrometry. We have determined the complete amino acid sequence of MiPLA-1. It is a 124-amino-acid protein with a "pancreatic loop" and belongs to group IB phospholipase A(2) enzymes. Two short segments flanked by proline brackets are found in the sequence of MiPLA-1. These segments are on the surface of the molecule and hence may be involved in protein-protein recognition.

Snake venoms and the hemostatic system

Snake venoms are complex mixtures containing many different biologically active proteins and peptides. A number of these proteins interact with components of the human hemostatic system. This review is focused on those venom constituents which affect the blood coagulation pathway, endothelial cells, and platelets. Only highly purified and well characterized snake venom proteins will be discussed in this review. Hemostatically active components are distributed widely in the venom of many different snake species, particularly from pit viper, viper and elapid venoms. The venom components can be grouped into a number of different categories depending on their hemostatic action. The following groups are discussed in this review: (i) enzymes that clot fibrinogen; (ii) enzymes that degrade fibrin(ogen); (iii) plasminogen activators; (iv) prothrombin activators; (v) factor V activators; (vi) factor X activators; (vii) anticoagulant activities including inhibitors of prothrombinase complex formation, inhibitors of thrombin, phospholipases, and protein C activators; (viii) enzymes with hemorrhagic activity; (ix) enzymes that degrade plasma serine proteinase inhibitors; (x) platelet aggregation inducers including direct acting enzymes, direct acting non-enzymatic components, and agents that require a cofactor; (xi) platelet aggregation inhibitors including: alpha-fibrinogenases, 5'-nucleotidases, phospholipases, and disintegrins. Although many snake venoms contain a number of hemostatically active components, it is safe to say that no single venom contains all the hemostatically active components described here. Several venom enzymes have been used clinically as anticoagulants and other venom components are being used in pre-clinical research to examine their possible therapeutic potential. The disintegrins are an interesting group of peptides that contain a cell adhesion recognition motif, Arg-Gly-Asp (RGD), in the carboxy-terminal half of their amino acid sequence. These agents act as fibrinogen receptor (integrin GPIIb/IIIa) antagonists. Since this integrin is believed to serve as the final common pathway leading to the formation of platelet-platelet bridges and platelet aggregation, blockage of this integrin leads to inhibition of platelet aggregation regardless of the stimulating agent. Clinical trials suggest that platelet GPIIb/IIIa blockade is an effective therapy for the thrombotic events and restenosis frequently accompanying cardiovascular and cerebrovascular disease. Therefore, because of their clinical poten tial, a large number of disintegrins have been isolated and characterized.

Cerastotin, a serine protease from Cerastes cerastes venom, with platelet-aggregating and agglutinating properties

Cerastotin, a thrombin-like enzyme from the venom of the desert viper Cerastes cerastes, has been purified by gel filtration on Sephadex G-75 and two ion-exchange chromatographies on Mono S columns. It is a neutral glycoprotein (pI = 6.6), present as a single polypeptide chain of 40 kDa. Its N-terminal sequence shows strong similarity with those of other thrombin-like enzymes from snake venoms. Cerastotin possesses esterase and amidolytic activities measured with N(alpha)-tosyl-L-arginine methyl ester and the thrombin chromogenic substrate D-phenylalanyl-L-pipecolyl-L-arginine p-nitroanilide, respectively. The amidolytic activity is inhibited by phenylmethylsulfonyl fluoride, N(alpha)-tosyl-L-lysine chloromethane, N(alpha)-tosyl-L-phenylalanyl chloromethane, D-phenylalanyl-L-prolyl-L-arginyl chloromethane and benzamidine, suggesting that cerastotin is a serine protease. Cerastotin efficiently clots human plasma and cleaves preferentially the alpha chain of fibrinogen. Cerastotin did not induce aggregation of washed normal platelets, but did aggregate platelets in the presence of exogenous fibrinogen. A monoclonal antibody directed against glycoprotein (GPIb), which specifically inhibits induced agglutination by ristocetin also completely blocks platelet aggregation induced by cerastotin. However, another anti-GPIb monoclonal antibody, which specifically inhibits alpha-thrombin binding to GPIb, did not prevent this aggregation. Furthermore, platelets which were desensitised by alpha-thrombin still aggregate in the presence of cerastotin, but not alpha-thrombin. Similarly a monoclonal antibody, anti-GPIIb-IIIa, which blocks fibrinogen binding, did not inhibit cerastotin-induced platelet aggregation. This activity is abolished in the presence of 1 mM phenylmethylsulfonyl fluoride and/or 10 mM EDTA. Cerastotin also agglutinates formalin-fixed and washed platelets, only in the simultaneous presence of fibrinogen and of Von Willebrand factor.