Platelet aggregation effects of Bauhinia inhibitors
Anjos, T.P.1; Sallai, R.C.1; Oliveira, C.1; Tobaruella, F.S.1; Cagliari, C.1;Lourenço, D.M.2; Chudzinsk-Tavassi, A.M.3; Sampaio, M.U.1; Oliva, M.L.V.1
1 Departamento de Bioquímica, Universidade Federal de São Paulo, Escola Paulista de Medicina, São Paulo, SP, Brazil. olivaml.bioq@epm.br
2 Disciplina de Hematologia e Hemoterapia, Universidade Federal de São Paulo, Escola Paulista de Medicina, São Paulo, SP, Brazil. 3 Laboratório de Bioquímica e Biofísica, Instituto Butantan, São Paulo, SP, Brazil.
20 Kda protease inhibitors showing 88% of similarity were characterized from different Bauhinia species, which differ on their specificity. BbCI, an inhibitor devoid of cysteine residues, inhibits two classes of enzymes, serine protease human neutrophil elastase (Kiapp 5.3 nM) and cathepsin G (Kiapp 160 nM) and the cysteine proteases cathepsin L (Kiapp 0.2 nM) and cruzipain (Kiapp 1.2 nM). BbKI and BpuTI are inhibitors of plasma kallikrein; however the affinity of BbKI for kallikrein is one order the magnitude higher than that of BpuTI (Kiapp 4.7 nM and 27 nM, respectively). BbKI contains only one cysteine residue whereas in BpuTI the N-terminal sequence shows similarity to inhibitors with four cysteine residues involved in two disulphide bridges.
Antithrombotic activity of these inhibitors was assessed on platelet aggregation "in vitro". The results obtained showed that BbCI and BbKI produced a dose-dependent inhibition of thrombin and collagen and ADP-induced aggregation. The calculated IC50 (half-maximal inhibition of thrombin, collagen and ADP-induced aggregation) was found to be identical with BbCI and BbKI. BpuTI did not affect platelet aggregation. BbCI did not alter human activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT), but BbKI prolonged APTT. The effect of those compounds could be related in part to their inhibitory activity. These results show potential properties of these inhibitors for treatment or prevention of platelet aggregation complications linked to vascular diseases. Experiments should be carried out to elucidate their mechanisms of action involved on the anti-aggregant effect.
Supported by FAPESP, CNPq and CAPES-GRICES-DAAD
|