AimTo purify the platelet aggregation inhibitor from Echis multisquamatis snake venom (PAIEM) and characterize its effect on platelet aggregation and HeLa cell proliferation.MethodsSodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) were used for PAIEM identification. Platelet aggregation in the presence of PAIEM was studied on aggregometer Solar-AP2110. The changes of shape and granularity of platelets in the presence of PAIEM were studied on flow cytometer COULTER EPICS XL, and degranulation of platelets was estimated using spectrofluorimetry. Indirect enzyme-linked immunosorbent assay was used for the determination of target of PAIEM on platelet surface. An assay based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used to evaluate the effect of PAIEM on the proliferation of HeLa cells in cell culture.ResultsThe molecular weight of the protein purified from Echis multisquamatis venom was 14.9 kDa. Half-maximal inhibitory concentration (IC50) of PAIEM needed to inhibit adenosine diphosphate (ADP)-induced platelet aggregation was 7 μM. PAIEM did not affect thrombin- or ADP-induced platelet activation, but it did prevent binding of the anti-IIb antibody to glycoprotein IIb/IIIa (GPIIbIIIa)-receptor of adhered platelets and inhibited the viability of HeLa cells by 54%.ConclusionAs a member of the disintegrin family, PAIEM inhibited platelet aggregation and cell proliferation possibly by blocking integrin-mediated interactions. However, it did not impair cellular signaling causing any changes in platelet shape and granularity and did not affect ADP-induced platelet degranulation. This disintegrin was shown to be a potent inhibitor of integrin-mediated cellular interactions including platelet aggregation or cancer cell proliferation.
Cell therapy with platelets is a widely accepted approach for wound healing and tissue regeneration in medicine. however, with most available methods poorly concentrated platelet suspensions (up to 0.3•10 6 1/ µl) or suspensions of mostly inactivated or lost platelets are obtained. In this study, we aimed to develop a simple and effective method for preparing a suspension of native and resting platelets with over 1•10 6 1/µl. Platelet-rich plasma (PRP) was obtained from fresh blood of healthy donors (n = 5) collected using different amounts of heparin as the anticoagulant. Samples of PrP were spun down and re-suspended in auto logous blood plasma. Count and vitality of platelets in each sample were determined by aggregation study on the Solar aP2110 aggregometer. Platelet shape and cytoplasmic granularity that indicate the nativity of platelets were monitored on the CoULter ePICS XL Flow Cytometer. this study of aggregation of platelets in PrP obtained using various amounts of heparin allowed us to reduce final concentrations to the amount that effectively prevented clotting and did not affect platelet reactivi ty (5 U/ml). PRP concentrated 5 times with a total concentration of cells of 1•10 6 1/µl was able to be activated by adenosine diphosphate (aDP) (aggregation rate 54 ± 7%). the amount of cells with altered shape and granularity in concentrated suspension was not higher than 20%. This finding means that the platelets would still be able to release a number of growth factors and other biologically active compounds after stimulation or injection into tissue during cell therapy. the decrease in heparin concentrations also minimizes haemorrhage in the injection site supporting biomedical use of the suspension. A simple and effective method for preparation of highly-concentrated PRP (1.2•10 6 1/ µl) for biomedical use was developed. Aggregometry and flow cytometry proved that obtained platelets were resting and able to be activated. Being autologous, the preparation can be widely used for cell therapy without additional precautions. k e y w o r d s: cell therapy, platelets, autologous, platelet rich plasma, preparation protocol.
Meizothrombin (MT) is one of prothrombin derivatives which appears in haemostasis activation area. However, its role in haemostasis regulation isn't clear. We studied the role of MT in fibrin formation, platelet activation and aggregation. A new effective method of obtaining MT from native human prothrombin was developed using immobilised prothrombin activator from Echis multisquamatis venom. The protein was stable and electrophoretically pure. Platelet-rich plasma for aggregation study and gel-sieved platelets for flow-cytometry were separated from blood of healthy donors. It was shown that MT transformed fibrinogen to fibrin and activated clotting factor XIII. MT didn't activate gel-sieved intact platelets, but in platelet-rich plasma, increased platelet aggregation induced by ADP, collagen and adrenalin.
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