- 作者: Yi Chang, Steven Kuan-Hua Huang, Wan-Jung Lu, Chi-Li Chung, Wei-Lin Chen, Shun-Hua Lu, Kuan-Hung Lin and Joen-Rong Sheu
- 作者服務機構: Department of Anesthesiology, Shin Kong Wu Ho-Su Memorial Hospital, 95 Wen-Chang Rd, Taipei 11101, Taiwan, R.O.C
- 中文摘要: --
- 英文摘要:
Background: Brazilin, isolated from the heartwood of Caesalpinia sappan L., has been shown to possess
multiple pharmacological properties.
Methods:
In this study, platelet aggregation, flow cytometry, immunoblotting analysis, and electron
spin resonance (ESR) spectrometry were used to investigate the effects of brazilin on platelet
activation ex vivo. Moreover, fluorescein sodium-induced platelet thrombi of mesenteric
microvessels was also used in in vivo study.
Results: We demonstrated that relatively low concentrations of brazilin (1 to 10 μM) potentiated
platelet aggregation induced by collagen (0.1 μg/ml) in washed human platelets. Higher
concentrations of brazilin (20 to 50 μM) directly triggered platelet aggregation. Brazilinmediated
platelet aggregation was slightly inhibited by ATP (an antagonist of ADP). It was
not inhibited by yohimbine (an antagonist of epinephrine), by SCH79797 (an antagonist of
thrombin protease-activated receptor [PAR] 1), or by tcY-NH2 (an antagonist of PAR 4).
Brazilin did not significantly affect FITC-triflavin binding to the integrin αIIbβ3 in platelet
suspensions. Pretreatment of the platelets with caffeic acid phenethyl ester (an antagonist of
collagen receptors) or JAQ1 and Sam.Q4 monoclonal antibodies raised against collagen
receptor glycoprotein VI and integrin α2β1, respectively, abolished platelet aggregation
stimulated by collagen or brazilin. The immunoblotting analysis showed that brazilin
stimulated the phosphorylation of phospholipase C (PLC)γ2 and Lyn, which were
significantly attenuated in the presence of JAQ1 and Sam.Q4. In addition, brazilin did not
significantly trigger hydroxyl radical formation in ESR analysis. An in vivo mouse study
showed that brazilin treatment (2 and 4 mg/kg) significantly shortened the occlusion time for
platelet plug formation in mesenteric venules.
Conclusion: To the best of our knowledge, this study provides the first evidence that brazilin acts a novel
collagen receptor agonist. Brazilin is a plant-based natural product, may offer therapeutic
potential as intended anti-thrombotic agents for targeting of collagen receptors or to be used a
useful tool for the study of detailed mechanisms in collagen receptors-mediated platelet
activation. - 中文關鍵字: --
- 英文關鍵字: Brazilin, Collagen receptors, Lyn phosphorylation, Occlusion time, Platelet activation