ABSTRACT
Objective To investigate the effects of saponins from Allium Macrostemon Bunge Bulbs (SMBB) on platelet aggregation and platelet-neutrophil-interactions. Methods The effects of SMBB on platelet aggregation in SD rats were observed in vivo and in vitro. The adhesion of platelets to neutrophils was measured by rosette test. The effect of SMBB on activated platelet calcium levels was detected. Results Platelet aggregation induced by platelet activating factor (PAF), adenosine diphosphate (ADP) and arachidonic acid (AA) was significantly inhibited by SMBB in vitro concentration-dependent. Platelet aggregation induced by PAF, AA and ADP was significantly inhibited by 5 mg/kg of SMBB. SMBB could reduce the intracellular calcium concentration in the wash platelets. SMBB significantly reduced the adhesion between neutrophils and thrombin-activated platelets and inhibited neutrophil supernatant-induced platelet aggregation, with IC50of 2.7 μmol/L and 9.6 μmol/L, respectively. Conclusion SMBB can inhibit platelet aggregation in vitro and ex vivo, and inhibit the interactions between platelets and neutrophils.
ABSTRACT
BACKGROUND: Platelets and P-selectin (CD62P) play an unequivocal role in the pathology of hepatic ischemia/reperfusion (I/R) injury. Inhibition or knock-out of P-selectin or immunodepletion of platelets results in amelioration of post-ischemic inflammation, reduced hepatocellular damage, and improved survival. However, P-selectin expression on platelets and endothelial cells, which concurs with platelet activation, has never been clearly demonstrated in I/R-subjected livers. AIMS: To determine whether platelets become activated and degranulate in the acute phase of liver I/R and whether the platelets interact with neutrophils. METHODS: Hepatic I/R was induced in male C57BL/6J mice (N = 12) using 37.5-min ischemia time. Platelets, endothelial cells, and neutrophils were fluorescently labeled by systemic administration of non-blocking antibodies. Cell kinetics were monitored by intravital spinning disk confocal microscopy during 90 min of reperfusion. Image analysis and quantification was performed with dedicated software. RESULTS: Platelets adhered to sinusoids more extensively in post-ischemic livers compared to livers not subjected to I/R and formed aggregates, which occurred directly after ischemia. Platelets and endothelial cells did not express P-selectin in post-ischemic livers. There was no interaction between platelets and neutrophils. CONCLUSIONS: Platelets aggregate but do not become activated and do not degranulate in post-ischemic livers. There is no platelet-neutrophil interplay during the early reperfusion phase in a moderate model of hepatic I/R injury. The mechanisms underlying the biological effects of platelets and P-selectin in this setting warrant further investigation. RELEVANCE FOR PATIENTS: I/R in surgical liver patients may compromise outcome due to post-ischemic oxidative stress and sterile inflammation. Both processes are mediated in part by platelets. Understanding platelet function during I/R is key to developing effective interventions for I/R injury and improving clinical outcomes.
ABSTRACT
Objective To investigate the effects of geraniin on platelet aggregation and platelet-neutrophil interactions.Methods Platelet aggregation,in vitro and ex vivo,was determined by use of Born's method,and the binding of thrombin-stimulated platelets to neutrophils was observed based on the rosette assay.Intracellular calcium concentration of platelets was measured by using Fura-2-AM.Results Geraniin in vitro significantly inhibited arachidonic acid (AA)-,adenosine diphosphate (ADP)-,or platelet activating factor (PAF)-induced platelet aggregation,in a concentration-dependent manner.The medium inhibitory concentrations (IC50) were 2.4,0.4 and 1.1 μmol/L,respectively.Intragastric geraniin at 5 mg/kg markedly suppressed platelet aggregation induced by AA,ADP,or PAF.Geraniin decreased the total rise of [Ca2+]i,Ca2+ release,and Ca2+ influx,in a concentration-dependant manner.The IC50 values were 71.9,84.9,and 62.9 μmol/L,respectively.Geraniin decreased the binding of thrombin-stimulated platelets to neutrophils,and significantly inhibited washed platelet aggregation stimulated by fMLP-activated neutrophils.The IC50 values were 3.2 and 10.2 μmol/L,respectively.Conclusion It is suggested that geraniin inhibited platelet aggregation in vitro and ex vivo,decreased the calcium mobilization of platelets,and suppressed the interactions between platelets and neutrophils.
