OBJECTIVES: To investigate the antioxidative mechanism of snake venom-derived protein C activator (PCA) in mitigating vascular endothelial cell injury. METHODS: Human umbilical vein endothelial cells (HUVECs) were cultured in DMEM containing 1.0 g/L D-glucose and exposed to hypoxia (1% O₂) for 6 h followed by reoxygenation for 2 h to establish a cell model of oxygen-glucose deprivation/reoxygenation (OGD/R). The cell model was treated with 2 μg/mL PCA alone or in combination with 2-ME2 (a HIF-1α inhibitor) or DMOG (a HIF-1α stabilizer), and intracellular production of reactive oxygen species (ROS) and protein expression levels of HIF-1α, BNIP3, and Beclin-1 were detected using DCFH-DA fluorescence probe, flow cytometry, and Western blotting. The OGD/R cell model was transfected with a BNIP3-specific siRNA or a scrambled control sequence prior to PCA treatment, and the changes in protein expressions of HIF-1α, BNIP3 and Beclin-1 and intracellular ROS production were examined. RESULTS: In the OGD/R cell model, PCA treatment significantly upregulated HIF-1α, BNIP3 and Beclin-1 expressions and reduced ROS production. The effects of PCA were obviously attenuated by co-treatment with 2-ME2 but augmented by treatment with DMOG (a HIF-1α stabilizer). In the cell model with BNIP3 knockdown, PCA treatment increased BNIP3 expression and decreased ROS production without causing significant changes in HIF-1α expression. Compared with HUVECs with PCA treatment only, the cells with BNIP3 knockdown prior to PCA treatment showed significantly lower Beclin-1 expression and higher ROS levels. CONCLUSIONS Snake venom PCA alleviates OGD/R-induced endothelial cell injury by upregulating HIF-1α/BNIP3 signaling to suppress ROS generation, suggesting its potential as a therapeutic agent against oxidative stress in vascular pathologies.
Humans ; Reactive Oxygen Species/metabolism* ; Hypoxia-Inducible Factor 1, alpha Subunit/metabolism* ; Human Umbilical Vein Endothelial Cells/drug effects* ; Membrane Proteins/metabolism* ; Proto-Oncogene Proteins/metabolism* ; Up-Regulation ; Cell Hypoxia ; Cells, Cultured ; Snake Venoms/chemistry* ; Beclin-1

This study was designed to investigate inhibitory effects and possible mechanisms of snake venom tripeptide (pENW) on platelet adhesion in order to promote the development of a novel anti-platelet therapy. To study the inhibitory effects of pENW on platelet adhesion, washed platelets pre-incubated with pENW (116.5-466.2 μmol x L(-1)) were used to test the ability of platelet adhesion to fibrinogen. Effect of pENW on fibrin clot retraction was also tested. Effect of pENW on platelets viability was tested by MTT assay. Effect of pENW on reactive-oxygen species (ROS) levels of platelet was studied by flow cytometry assay. Calcium mobilization in Fura-2/AM-loaded platelets was monitored with a spectrofluorimeter. Cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP), thromboxane A2 (determined as its metabolite thromboxane B2) were measured using enzyme immunoassay kits. Akt, ERK and p38 phosphorylation were tested by Western blot. The results showed that pENW inhibited platelet adhesion and fibrin clot retraction in a concentration-dependent manner without cytotoxicity. Intracellular cGMP and cAMP in both resting and thrombin-activated platelets were increased by pENW. In addition, pENW attenuated intracellular Ca2+ mobilization and TXA2 production in platelets stimulated by thrombin. As shown by Western blot assay, Akt, ERK and p38 phosphorylation in thrombin-induced platelet were attenuated by pENW. However, inhibitory effects of pENW had nothing to do with ROS. Thus, pENW exhibited a significant inhibition on platelet adhesion to fibrinogen, which means pENW could block the first step of thrombosis as while as retard the more stable clot formation. The mechanisms of pENW on inhibition platelet adhesion might be related to instant regulations, such as protein kinases.
Blood Platelets ; drug effects ; Blotting, Western ; Calcium ; metabolism ; Cyclic AMP ; metabolism ; Cyclic GMP ; metabolism ; Flow Cytometry ; Phosphorylation ; Platelet Aggregation ; drug effects ; Reactive Oxygen Species ; metabolism ; Snake Venoms ; chemistry ; Thromboxane A2 ; metabolism ; Thromboxane B2 ; metabolism

Hemorrhagic snake venom specially induces apoptosis of VEC (vascular endothelial cells). Five apoptosis-inducing proteins had been purified and characterized from crude snake venom. Two of these are L-amino acid oxidase (LAO), the others belong to metalloprotease/disintegrin family. LAO catalyzes H2O2 production by oxidizing some plasma membrane proteins of VEC, disintegrins interfere with binding of integrins with their ligands. The expression of p53 and bcl-2 increases during VEC apoptosis induced by snake venom, moreover, the mRNA of bcl-2 is spliced into two fragments. It has been proved that one of adhesion-dependent signal molecules, alphavbeta3, and one of phospholipid signal molecules, PC-PLC (phosphatidylcholine-specific phospholipase C), are involved in above apoptosis-inducing signal transudation pathway. These results throw light on finding out specific component from protein is snake venom. This component is able to induce tumor vascular endothelial cells apoptosis. This review summarized progress of research on hemorrhagic snake venoms.
Amino Acid Oxidoreductases ; pharmacology ; Animals ; Apoptosis ; drug effects ; Endothelial Cells ; cytology ; drug effects ; Gene Expression Regulation ; drug effects ; Humans ; L-Amino Acid Oxidase ; Reactive Oxygen Species ; Signal Transduction ; Snake Venoms ; chemistry ; pharmacology