Acetylcholinesterase from desert Cobra (Walterinnesia aegyptia) venom: Optimization and kinetics study

Acetylcholinesterase (AChE) was investigated inWalterinnesia aegyptia venom and characterized with respect to its kinetic properties. It was found that 4.0 ug of crude venom protein and an incubation time of 4.0 min were suitable conditions for linearity of AChE activity at 25°C. The optimum strength of the sodium phosphate buffer was 0.05 M, and the optimum pH was 7.75. The optimum temperature was 30°C. The activation energy and the heat of activation were observed to be 6510 and 5922 cal/mole. The AChE was specific for acetylthiocholine but it did not hydrolyse butyrylthiocholine. The optimum substrate concentration was 3.0 mM but at higher substrate concentrations, the AChE activity declined. The ASCh concentration ranges for different orders of the reactions were determined and kinetic parameters (K_m, V_max, k_cat, and k_sp) were established at each order of the reaction.Abbreviations AChE acetylcholinesterase - ASCh acetylthiocholine - K_m Michaelis-Menten constant - V_max the limiting maximal velocity - AChE_a acylated enzyme - k_cat turnover number - k_sp specificity constant     

Purification and characterization of phosphodiesterase i from Walterinnesia aegyptia venom

A phosphodiesterase I (EC 3.1.4.1; PDE-I) was purified from Walterinnesia aegyptia venom by preparative native polyacrylamide gel electrophoresis (PAGE). A single protein band was observed in analytical native PAGE and sodium dodecyl sulfate (SDS)-PAGE. PDE-I was a single-chain glycoprotein with an estimated molecular mass of 158 kD (SDS-PAGE). The enzyme was free of 5'-nucleotidase and alkaline phosphatase activities. The optimum pH and temperature were 9.0 and 60°C, respectively. The energy of activation (Ea) was 96.4, the V(max) and K(m) were 1.14 μM/min/mg and 1.9 × 10(-3) M, respectively, and the K(cat) and K(sp) were 7 s(-1) and 60 M(-1) min(-1) respectively. Cysteine was a noncompetitive inhibitor, with K(i) = 6.2 × 10(-3) M and an IC(50) of 2.6 mM, whereas adenosine diphosphate was a competitive inhibitor, with K(i) = 0.8 × 10(-3) M and an IC(50) of 8.3 mM. Glutathione, o-phenanthroline, zinc, and ethylenediamine tetraacetic acid (EDTA) inhibited PDE-I activity whereas Mg(2+) slightly potentiated the activity. PDE-I hydrolyzed thymidine-5'-monophosphate p-nitrophenyl ester most readily, whereas cyclic 3'-5'-AMP was least susceptible to hydrolysis. PDE-I was not lethal to mice at a dose of 4.0 mg/kg, ip, but had an anticoagulant effect on human plasma. These findings indicate that W. aegyptia PDE-I shares various characteristics with this enzyme from other snake venoms.     

The effect of the desert cobra (Walterinnesia aegyptia) crude venom and its protein fractions on the metabolic activity of cultured human fibroblasts

Fibroblast cultures were used to study the effect of crude venom and six venom protein fractions (F₂–F₇) fromWalterinnesia aegyptia) on their metabolic activity. This was done by incubation of six fibroblast cultures with 10 g of crude venom for 3 h at 37°C. The activities of phosphofructokinase, lactate dehydrogenase, and citrate synthase were significantly lowered upon incubation with all fractions except F₂. Glycogen phosphorylase activity was significantly increased, leading to a significant concurrent drop of glycogen content. This effect was only seen for fractions F₃ and F₅. Creatine kinase activity and cellular ATP levels rose significantly upon incubation with all venom proteins except fractions F₂ and F₇. Increases were seen for aspartate and alanine amino-transferases by all venom proteins except fractions F₂ and F₄. Incubation of cell sonicates with all the venom proteins did not significantly alter activities of any of the parameters. Thus, fibroblasts in culture under such conditions appear to mobilize glycogen, phosphocreatine, and protein for ATP production to compensate for decreased glucose.Abbreviations ALT alanine aminotransferase - AST aspartate aminotransferase - ATP adenosine 5-triphosphate - CS citrate synthhase - GP glycogen phosphorylase - LDH lactate dehydrogenase - PFK phosphofructokinase     

Therapeutic efficacy and molecular mechanisms of snake (Walterinnesia aegyptia) venom-loaded silica nanoparticles in the treatment of breast cancer- and prostate cancer-bearing experimental mouse models

The treatment of drug-resistant cancer is a clinical challenge, and thus screening for novel anticancer drugs is critically important. We recently demonstrated a strong enhancement of the antitumor activity of snake (Walterinnesia aegyptia) venom (WEV) in vitro in breast carcinoma, prostate cancer, and multiple myeloma cell lines but not in normal cells when the venom was combined with silica nanoparticles (WEV+NP). In the present study, we investigated the in vivo therapeutic efficacy of WEV+NP in breast cancer- and prostate cancer-bearing experimental mouse models. Xenograft breast and prostate tumor mice models were randomized into 4 groups for each cancer model (10 mice per group) and were treated with vehicle (control), NP, WEV, or WEV+NP daily for 28 days post tumor inoculation. The tumor volumes were monitored throughout the experiment. On Day 28 post tumor inoculation, breast and prostate tumor cells were collected and either directly cultured for flow cytometry analysis or lysed for Western blot and ELISA analysis. Treatment with WEV+NP or WEV alone significantly reduced both breast and prostate tumor volumes compared to treatment with NP or vehicle alone. Compared to treatment with WEV alone, treatment of breast and prostate cancer cells with WEV+NP induced marked elevations in the levels of reactive oxygen species (ROS), hydroperoxides, and nitric oxide; robust reductions in the levels of the chemokines CXCL9, CXCL10, CXCL12, CXCL13, and CXCL16 and decreased surface expression of their cognate chemokine receptors CXCR3, CXCR4, CXCR5, and CXCR6; and subsequent reductions in the chemokine-dependent migration of both breast and prostate cancer cells. Furthermore, we found that WEV+NP strongly inhibited insulin-like growth factor 1 (IGF-1)- and epidermal growth factor (EGF)-mediated proliferation of breast and prostate cancer cells, respectively, and enhanced the induction of apoptosis by increasing the activity of caspase-3,–8, and -9 in both breast and prostate cancer cells. In addition, treatment of breast and prostate cancer cells with WEV+NP or WEV alone revealed that the combination of WEV with NP robustly decreased the phosphorylation of AKT, ERK, and IκBα; decreased the expression of cyclin D1, surviving, and the antiapoptotic Bcl-2 family members Bcl-2, Bcl-_XL, and Mcl-1; markedly increased the expression of cyclin B1 and the proapoptotic Bcl-2 family members Bak, Bax, and Bim; altered the mitochondrial membrane potential; and subsequently sensitized tumor cells to growth arrest. Our data reveal the therapeutic potential of the nanoparticle-sustained delivery of snake venom against different cancer cell types.     

Mitogenic activity of snake venom lectins

Five lactose-inhibitable lectins have been isolated from snake venoms. These five share certain biochemical properties but are not identical (Gartner, Stocker & Williams, 1980; Gartner & Ogilvie, 1984). In this study the lectins were tested for their ability to stimulate lymphocytes to undergo DNA synthesis. We found that three of the lectins were comparable in mitogenic activity to the T cell lectin, concanavalin A (Con A). The mitogenic activity was blocked by lactose, a sugar which also blocks the haemagglutination activity of these lectins. Although mitogenic response appeared to be due to T cells, it depended on the presence of accessory cells in the culture. This requirement for macrophages could be replaced by the phorbol ester tumour promoter, 12-o-tetradecanoylphorbol-13-acetate (TPA).     

Snake (Walterinnesia aegyptia) venom-loaded silica nanoparticles induce apoptosis and growth arrest in human prostate cancer cells

Prostate cancer (PCa) is the most commonly diagnosed cancer in men. The progression and invasion of PCa are normally mediated by the overexpression of chemokine receptors (CKRs) and the interaction between CKRs and their cognate ligands. We recently demonstrated that venom extracted from Walterinnesia aegyptia (WEV) either alone or in combination with silica nanoparticles (WEV+NP) mediated the growth arrest and apoptosis of breast cancer cells. In the present study, we evaluated the impact of WEV alone and WEV+NP on the migration, invasion, proliferation and apoptosis of prostate cancer cells. We found that WEV alone and WEV+NP decreased the viability of all cell types tested (PCa cells isolated from patient samples, PC3 cells and LNCaP cells) using an MTT assay. The IC₅₀ values were determined to be 10 and 5 μg/mL for WEV alone and WEV+NP, respectively. WEV+NP decreased the surface expression of the CKRs CXCR3, CXCR4, CXCR5 and CXCR6 to a greater extent than WEV alone and subsequently reduced migration and the invasion response of the cells to the cognate ligands of the CKRs (CXCL10, CXCL12, CXCL13 and CXCL16, respectively). Using a CFSE proliferation assay, we found that WEV+NP strongly inhibited epidermal growth factor-mediated PCa cell proliferation. Furthermore, analysis of the cell cycle indicated that WEV+NP strongly altered the cell cycle of PCa cells and enhanced the induction of apoptosis. Finally, we demonstrated that WEV+NP robustly decreased the expression of anti-apoptotic effectors, such as B cell Lymphoma-2 (Bcl-2), B cell Lymphoma-extra large (Bcl-_XL) and myeloid cell leukemia sequence-1 (Mcl-1), and increased the expression of pro-apoptotic effectors, such as Bcl-2 homologous antagonist/killer (Bak), Bcl-2-associated X protein (Bax) and Bcl-2-interacting mediator of cell death (Bim). WEV+NP also altered the membrane potential of mitochondria in the PCa cells. Our data reveal the potential of nanoparticle-sustained delivery of snake venom as effective treatments for prostate cancer.     

Effect of ethanol on respiratory activity of embryonal tissues

By estimating the respiratory activity of various chicken embryonal organs we have noted that it was the highest for the kidney tissues and lower and lower for liver, brain and heart tissues. After the addition of ethanol to the culture medium we may conclude that ethanol 2,5% does not substantially alter the cellular respiratory activity, whereas ethanol 5% remarkably appears to inhibit it. In fact for this last condition the heart and kidney fragments, when are transplanted after 48 hours in "pendent drop", result rarely surviving.     

Purification and some properties of low-molecular-weight proteins of Aspidelaps scutatus (shield or shield-nose snake) venom

1. Fourteen low-molecular-weight proteins from Aspidelaps scutatus venom were purified by gel filtration and ion exchange chromatography. 2. The proteins (toxins) have i.v. LD50 values ranging from 0.12 to 54 micrograms/g mouse. 3. The amino-terminal sequences of the proteins show that 12 of the 14 proteins were pure. 4. The proteins were preliminarily assigned as phospholipases A2, long neurotoxins and cytotoxin homologues.     

Isolation of a proteinase with plasminogen-activating activity from Lachesis muta muta (bushmaster) snake venom

A plasminogen activator enzyme (LV-PA) from Lachesis muta muta venom was purified to homogeneity using gel filtration and anion exchange chromatography. SDS-PAGE under reducing conditions showed a single protein band with an Mr of 33,000 Da. It is an acidic glycoprotein which activates plasminogen to plasmin indirectly, functioning via prior formation of a molecular complex, known as plasminogen activator. The purified preparation catalyzes the hydrolysis of several p-nitroanilide peptide substrates containing Lys at the scissile bond. In contrast, no hydrolysis was detected on the synthetic substrates TAME and BAPNA, which contain arginine. By the use of the plasmin-specific chromogenic substrate Tos-Gly-Pro-Lys-pNA, the preparation had a plasmin-like activity of 0.68 U/mg, which was 35.8-fold higher than that of the crude venom from which it was prepared. In vitro, fibrin hydrolysis using LV-PA as plasminogen activator displayed more similarity with the effect produced by streptokinase (SK). SDS-PAGE (10%) analysis showed a 115-kDa complex formation after incubation of plasminogen with either LV-PA or SK. At a molar ratio of 50:1 (fibrinogen:enzyme), the preparation exhibited weakly fibrinogenolytic activity. However, LV-PA is distinguished from thrombin in that it does not clot fibrinogen. After incubation of LV-PA with platelet-rich plasma, the enzyme (2 microM) showed no effect on platelet aggregation induced by ADP, epinephrine, or collagen. Comparison of the N-terminal sequence of LV-PA with other snake venom plasminogen activators revealed that LV-PA exhibits a high degree of sequence identity with the TsVPA from Trimeresurus stejnegeri (90%) and with the Haly-PA from Agkistrodon halys (85%). LV-PA also has homology with other snake venom serine proteinases such as the thrombin-like/gyroxin analogue (38%) from bushmaster venom and with other coagulation serine proteases. The proteinase was readily inhibited by treatment with p-nitrophenyl p-guanidinebenzoate, p-aminobenzamidine, and phenylmethanesulfonyl fluoride but was not affected by metal chelators.     

The effect of post-translational modifications on the hemorrhagic activity of snake venom metalloproteinases

Metalloproteinases (MPs) are Zn(+)-dependent endoproteolytic enzymes, abundant in crotalid and viperid snake venoms. Most snake venom metalloproteinases (svMPs) are active on extracellular matrix components and this effect is thought to result in bleeding as a consequence of the basement membrane disruption in capillaries. Jararhagin and ACLH are hemorrhagic svMPs from Bothrops jararaca and Agkistrodon contortrix laticinctus venom, respectively. Both enzymes demonstrate proteolytic activity on fibrinogen and fibronectin and jararhagin inhibits collagen-induced platelet aggregation in vitro. This work describes the expression, purification and successful refolding of the recombinant ACLH zymogen (rPRO-ACLH) as well as the catalytic domain of jararhagin (rCDJARA). The heterologous proteins were produced in E. coli, an in vivo expression system that does not make post-translational modifications. The recombinant refolded proteins did not show any hemorrhagic activity in mice skin, as well as the native deglycosylated jararhagin and ACLH. However, they preserved their proteolytic activity on fibrinogen and fibronectin. It seems that the hemorrhagic properties of these hemorrhagins are dependent on post-translational modifications, whereas their proteolytic activity is not dependent on such modifications.     

Effect of methylation of histidine-48 on some enzymatic and pharmacological activities of snake venom phospholipases A2

The effects on some pharmacological and enzymatic properties were determined following methylation of histidine at the enzymatic active site of the basic relatively toxic $\text{Naja}$$\text{nigricollis}$ and the acidic relatively non-toxic $\text{Naja}$$\text{naja}$$\text{atra}$ phospholipases A₂. Following methylation a very low residual enzymatic activity (0.4 -- 1% of control) was accompanied by a parallel loss in intraventricular lethality, anticoagulant potency, direct hemolytic action and ability to block directly and indirectly evoked contractions of the mouse phrenic nerve-diaphragm preparation. Since methylation does not impair the enzyme's ability to bind monomeric of micellar substrates or Ca²⁺, the results suggest that the pharmacologicallly active region of the molecule is different from the micellular substrate binding site but strongly influenced by the invariant histidine-48 located at the enzymatic active site.     

Coevolution of diet and prey-specific venom activity supports the role of selection in snake venom evolution

The processes that drive the evolution of snake venom variability, particularly the role of diet, have been a topic of intense recent research interest. Here, we test whether extensive variation in venom composition in the medically important viper genus Echis is associated with shifts in diet. Examination of stomach and hindgut contents revealed extreme variation between the major clades of Echis in the proportion of arthropod prey consumed. The toxicity (median lethal dose, LD₅₀) of representative Echis venoms to a natural scorpion prey species was found to be strongly associated with the degree of arthropod feeding. Mapping the results onto a novel Echis phylogeny generated from nuclear and mitochondrial sequence data revealed two independent instances of coevolution of venom toxicity and diet. Unlike venom LD₅₀, the speed with which venoms incapacitated and killed scorpions was not associated with the degree of arthropod feeding. The prey-specific venom toxicity of arthropod-feeding Echis may thus be adaptive primarily by reducing venom expenditure. Overall, our results provide strong evidence that variation in snake venom composition results from adaptive evolution driven by natural selection for different diets, and underscores the need for a multi-faceted, integrative approach to the study of the causes of venom evolution.     

Effect of black widow spider venom on the cockroach heart

The effect of black widow spider venom [crude gland extract (CGE), gland lumen venom (GLV), or from direct bite] on the cardiac activity of Periplaneta americana was assayed both in vivo and in vitro. It was shown that these different forms of venom in all cases blocked the cockroach heart-beat. Both CGE and GLV showed a selective activity on the heart function compared with their effect on the CNS. It is suggested that cardiac block is due to impairment of either the cardiac nerve ganglia function or the myocardial neuromuscular junctions, or of both of them. The mode of action of the toxic effects on the heart is discussed. Experiments with antiserum from CGE indicate that the antigenic fractions of CGE and GLV affecting the heart function, as well as those affecting the insect motor functions, are common to both toxic materials.     

日本蝮蛇蛇毒磷脂酶A2(Gln49-PLA2)的细胞毒性

从日本蝮蛇(Agkistrodonblomhoffiiussurens)蛇毒中分离得到PLA2同源物Gln49PLA2,该蛋白具有抗凝血活性、肌肉毒性,缺乏磷脂酶A2活性。分析了该蛋白质对不同培养细胞生长的影响,探讨其细胞毒性。结果表明:贴壁细胞的Gln49PLA2半致死量(LD50)明显低于悬浮细胞,肝素可以明显抑制Gln49PLA2的细胞毒性。将其作用于K562细胞,随着Gln49PLA2用量的增加乳酸脱氢酶(LDH)释放量增加,细胞凋亡率增大,线粒体膜电位下降,但Bcl2蛋白的表达量无明显变化。     

Potent histamine-releasing activity of atrahagin, a novel snake venom metalloproteinase

Poisonous snakebite wound is a popular disease worldwide. However, the pathogenesis remains unclear. In the present study, a novel metalloproteinase atrahagin in Chinese cobra (Naja atra) snake venom was purified, using heparin-sepharose followed by Superdex 75 gel filtration chromatography. Apart from its alpha-fibrinogenase activity, atrahagin potently activated human colon, lung and tonsil mast cells with the net histamine release being 25.9+/-4.4, 17.0+/-1.9, 13.2+/-3.6%, respectively. Time course studies revealed that the peak histamine release induced by atrahagin occurred at 12, 12 and 8 min following incubation of the enzyme with colon, lung and tonsil mast cells, respectively. The response of mast cells to atrahagin was abolished by preincubation of the cells with metabolic inhibitors or pertussis toxin, and by removal of Ca2+ and Mg2+ from the challenge buffer. In conclusion, activation of human mast cells by atrahagin indicated that the enzyme might contribute to the pathogenesis of snakebite wound.