In vitro antischistosomal activity of venom from the Egyptian snake Cerastes cerastes

Abstract INTRODUCTION: We studied the potential in vitro antischistosomal activity of Cerastes cerastes venom on adult Schistosoma mansoni worms. METHODS: Live specimens of the horned viper snake, C. cerastes were collected from the Aswan Governorate (Egypt). Venom was collected from snakes by manual milking. Worms of S. mansoni were obtained from infected hamsters by perfusion and isolated from blood using phosphate buffer. Mortality rates of worms were monitored after 3 days of exposure to snake venom at LC50 and various sublethal concentrations (10, 5, 2.5µg/ml). Scanning electron microscopy was used to investigate tegumental changes in treated worms after exposure to LC50 doses of venom. RESULTS: The LC50 of C. cerastes venom was 21.5µg/ml. The effect of C. cerastes venom on Schistosoma worms varied according to their sex. The mortality rate of male and female worms after 48-h exposure was 83.3% and 50%, respectively. LC50 of C. cerastes venom induced mild to severe tegumental damage in Schistosoma worms in the form of destruction of the oral sucker, shrinkage and erosion of the tegument, and loss of some tubercle spines. CONCLUSIONS: The present study demonstrated that C. cerastes venom exerts potential in vitro antischistosomal activity in a time and dose-dependent manner. These results may warrant further investigations to develop novel schistosomicidal agents from C. cerastes snake venom.

Modulation of rhodopsin gene expression and signaling mechanisms evoked by endothelins in goldfish and murine pigment cell lines

Endothelins (ETs) and sarafotoxins (SRTXs) belong to a family of vasoconstrictor peptides, which regulate pigment migration and/or production in vertebrate pigment cells. The teleost Carassius auratus erythrophoroma cell line, GEM-81, and Mus musculus B16 melanocytes express rhodopsin, as well as the ET receptors, ETB and ETA, respectively. Both cell lines are photoresponsive, and respond to light with a decreased proliferation rate. For B16, the doubling time of cells kept in 14-h light (14L):10-h darkness (10D) was higher compared to 10L:14D, or to DD. The doubling time of cells kept in 10L:14D was also higher compared to DD. Using real-time PCR, we demonstrated that SRTX S6c (12-h treatment, 100 pM and 1 nM; 24-h treatment, 1 nM) and ET-1 (12-h treatment, 10 and 100 pM; 24- and 48-h treatments, 100 pM) increased rhodopsin mRNA levels in GEM-81 and B16 cells, respectively. This modulation involves protein kinase C (PKC) and the mitogen-activated protein kinase cascade in GEM-81 cells, and phospholipase C, Ca2+, calmodulin, a Ca2+/calmodulin-dependent kinase, and PKC in B16 cells. Cells were kept under constant darkness throughout the gene expression experiments. These results show that rhodopsin mRNA levels can be modulated by SRTXs/ETs in vertebrate pigment cells. It is possible that SRTX S6c binding to the ETB receptors in GEM-81 cells, and ET-1 binding to ETA receptors in B16 melanocytes, although activating diverse intracellular signaling mechanisms, mobilize transcription factors such as c-Fos, c-Jun, c-Myc, and neural retina leucine zipper protein. These activated transcription factors may be involved in the positive regulation of rhodopsin mRNA levels in these cell lines.

Effects of Russell's viper venom on mediator production in cultured human umbilical vein endothelial cells.

Hemodynamic alterations in Russell's viper envenomation are the result of interactions of various vasoactive mediators and perhaps proinflammatory cytokines. Since vascular endothelium is likely to be exposed to high concentrations of the venom and the endothelial cell itself not only plays an important role in the physiologic control of the circulation, but also play a role in inflammation with the synthesis and secretion of proinflammatory cytokines. It was therefore, the objective of this study to determine the effects of Russell's viper venom (RVV) on proinflammatory cytokine production by cultured human umbilical vein endothelial cells (HUVEC) and the release of endothelium-derived substances. Endothelial cells were isolated from freshly obtained human umbilical cord vein and grown in tissue culture to confluence as a homogeneous population. Cells were then incubated at 37 degrees C under 5 per cent CO2 with RVV (0.2, 1.0, 5.0, and 25.0 microg/ml) or lipopolysaccharide (LPS, 10 microg/ml) for 3, 6, 12 and 24 hours. After an indicated time, the levels of endothelin-1 (ET-1); 6-keto-PGF1alpha (a stable metabolite of PGI2) tumor necrosis factor-alpha (TNF-alpha); interleukin-1beta (IL-1beta); and interleukin-6 (IL-6) in supernatants were measured by using ELISA or EIA. The effect of RVV or LPS on cell viability was also measured using MIT assay. The results showed copious amounts of ET-1 production irrespectively with the presence of RVV or LPS. Whereas, production of PGI2 (measured as 6-keto-PGF1alpha, a stable metabolite) was increased significantly higher in the RVV- and LPS-treated EC than in the control EC. However, TNF-alpha and IL-6 productions were not different among these groups. The levels of IL-1beta were very low, although IL-1beta was detectable in the group treated with RVV at a concentration of 25.0 microg/ml. In conclusion, RVV upto 25 microg/ml stimulated PGI2 production by cultured HUVEC. This effect was unlikely related to production of proinflammatory cytokines since LPS or RVV is not sufficient per se to elevate a substantial amount of EC-derived cytokines. The higher amount of IL-6 compared to TNF-alpha and IL-1beta may be produced through other pathways apart from production via a cascade of cytokines. This is the first report showing that RVV up to 25 microg/ml has no effect on prominent proinflammatory cytokine production by HUVEC. However, in blood circulation, the major source of cytokines production is monocyte-macrophage lineage cell. Thus, RVV in blood circulation may activate the production of proinflammatory cytokines mainly from those cells and subsequently induce toxicity.

Actividad hemolítica de venenos de serpientes de los géneros Bothrops, Lachesis, Crotalus y Micrurus (Serpentes: Viperidae y Elapidae) / Haemolytic activity of venoms from snakes of the genera Bothrop, Lachesis, Crotalus and Micrurus (Serpentes: Viperidae and Elapidae)

Hemolytic activity of eight Peruvian snake venoms from the families Viperidae and Elapidae (Bothrops atrox, B. pictus, B. hyoprorus, B. bilineatus, B. neuwedii, Lachesis m. muta, Crotalus d. terrificus, Microrus tschudi), and three Brazilian viperids (B. jararacussu, B. alternatus and C. d. collilineatus) is described. None of the venoms cause direct lysis on washed human erythrocytes. However, all of then caused indirect hemolysis provided that the incubation medium contains an exogenous source of lecithin. Venom of Micrurus tschudi was the most hemolytic (HD50 2.8 ug/ml) while that of B. bilineatus was the least (HD50 681.3 ug/ml). Only six of eleven venoms showed parallel curves of hemolytic activity, and the HD50 varied from 198 to 681 ug/ml and the following decreasing order of hemolytic activity was obtained: L. muta, C. d. terrificus, C. d. collilineatus, B. hyoprorus, B. bilineatus, B. alternatus

Neuropharmacological studies on the venom of Vipera russelli.

Neuropharmacological studies have been conducted on the venom of V. russelli on experimental animals. The venom was found to produce alteration in general behaviour pattern, reduction in spontaneous motility, hypothermia, potentiation of pentobarbitone hypnosis, analgesia, reduction in exploratory behaviour pattern, muscle relaxant action, and suppression of aggressive behaviour. The venom caused a significant increase in brain GABA content in mice. The observations are suggestive of a potent CNS-depressant action of V. russelli venom.

Biochemical studies of liver & liver microsomes in envenomated rats.

Some biochemical parameters of liver and liver microsomes were studied in albino rats following administration of cobra and viper venoms at dose of 2 mg/kg body weight. The total protein content in cobra venom treated (CVT) animals and DNA and RNA contents of liver and liver microsomes were almost unaltered in both the venom treated animals while total protein content was significantly reduced in viper venom treated (VVT) animals. Alkaline and acid phosphatases activities of whole liver showed significant increase in both the venom treated animals whereas the rise in cholinesterase activity in CVT animals was not significant. Lactic acid content was significantly higher in CVT animals compared to either VVT animals or controls. The glycolytic enzymes viz., aldolase, phosphohexose isomerase and lactate dehydrogenase measured in hepatic microsomal fraction were significantly reduced while alanine and aspartate aminotransferases and gamma-glutamyl transpeptidase activities of liver microsomes were significantly elevated in both the venom treated animals compared to controls.

Changes in lipid profiles of brain of albino rats following envenomation.

Effect of high doses of cobra venom (150 micrograms/120 +/- 20 g body weight) and viper venom (300 micrograms/120 +/- 20 g body weight) on total lipid, triglyceride, phospholipid, cholesterol, high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C) of brain of albino rats was studied. Total lipid (TL) triglyceride (TG) and phospholipid (PL) are decreased in both viper and cobra venom treated groups while cholesterol (C), and LDL-C are increased in both the groups in relation to controlled ones. HDL-C content was almost unaltered. Decrease in triglyceride and phospholipid may be due to effect of lipases and phospholipases whereas increased cholesterol and LDL-C may be attributed to lysis of cell membrane.

Effect of envenomation on enzymes of brain of albino rats.

Effects of high doses of cobra venom, (150 micrograms/120 +/- 20 g body wt) and viper venom (300 micrograms/120 +/- 20 g body wt) on aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), acetylcholinesterase (ACh) and alkaline phosphatase (ALP) of brain of albino rats were studied. While AST, LDH, ACh and ALP activities increased in both viper and cobra venom treated rats, ALT decreased in both groups compared to control.