Rhizoma Bletillae polysaccharide elicits hemostatic effects in platelet-rich plasma by activating adenosine diphosphate receptor signaling pathway.

Rhizoma Bletillae, the tubes of Bletilla striata, has been traditionally used in China as a hemostatic agent. In preliminary studies, the major active fraction responsible for its hemostatic effect have been confirmed to be Rhizoma Bletillae polysaccharide (RBp), but the hemostatic mechanism of action of RBp is still unknown.The main aim of this study was to clarify its mechanism of hemostatic effect. RBp was prepared by 80 % ethanol precipitation of the water extract of Rhizoma Bletillae followed by the Sevag method to remove proteins. The average molecular weight (Mw) of the crude RBp maintained at a range of 30.06-200 KDa. The hemostatic effects of RBp were evaluated by testing its effect on the platelet aggregation of rat platelet-rich plasma (PRP). PRP was dealt with different concentrations of RBp and platelet aggregation was measured by the turbidimetric method. The hemostatic mechanism of RBp was investigated by examining its effect on platelet shape, platelet secretion, and activation of related receptors (P2Y1, P2Y12 and TXA2) by electron microscopy and the turbidimetric method. RBp significantly enhanced the platelet aggregations at concentrations of 50-200 mg/L in a concentration-dependent manner. The inhibitory rate of platelet aggregation was significantly increased by apyrase and Ro31-8220 in a concentration-dependent manner, while RBp-induced platelet aggregation was completely inhibited by P2Y1, P2Y12 and the PKC receptor antagonists. However, the aggregation was not sensitive to TXA2. RBp, the active ingredients of Rhizoma Bletillae responsible for its hemostatic effect, could significantly accelerate the platelet aggregation and shape change. The hemostatic mechanism may involve activation of the P2Y1, P2Y12, and PKC receptors in the adenosine diphosphate (ADP) receptor signaling pathway.

[Thymidine phosphorylase expressed in monocyte-macrophages enhanced anticancer effect of 5'-deoxy-5-fluorouridine on colorectal carcinoma cells].

OBJECTIVE: To detect the thymidine phosphorylase (dThdPase) expression in colorectal carcinoma tissue, and clarify whether dThdPase expressed in macrophage-like cell lines, and monocytes from human peripheral blood can modulate the anticancer effect of 5'-deoxy-5-fluorouridine (5'-DFUR) on colorectal carcinoma cells. METHODS: Forty specimens resected from 40 patients with colorectal carcinoma were immunohistochemically stained by the monoclonal antibodies 654-1 (anti-dThdPase) and PG-M1 (anti-macrophage marker CD68). Then morphometrical analysis and positive cell counting were performed. In 27 of 40 specimens, dThdPase activity analysis was assayed by HPLC. The dThdPase level were also measured by ELISA in 4 colorectal cancer cell lines, LS174T, Clone A, Colo320, MIP101, and 2 macrophage-like cell lines, THP-1, U937. After estimated the drug sensitivities of each colorectal carcinoma cell both to 5'-DFUR and 5-Fu by MTT assay, THP-1, U937, or monocytes isolated from human blood were incubated in the medium containing 5-Fu or 5'-DFUR for 24 hours, respectively. Then the supernatant was collected and 2-fold serially diluted with the medium, in which the macrophage-like cells, or monocytes were also cultivated for 24 h without anticancer agents. Using the serially diluted medium, MTT assay were also carried out on 4 colorectal carcinoma cell lines. Each experiment was repeated six times and the means of IC50 value +/- standard errors (mean +/- S.E.M.) were calculated. Finally, THP-1 or U937 cells were cultured in medium containing 400 micro mol/L of 5'-DFUR for 24 hours, then the supernatants were collected and the amount of generated 5-Fu was measured by HPLC. RESULTS: dThdPase activities was significantly increased (139.7 micro g x 5-Fu x h(-1) x ml(-1) +/- 61.5 micro g x 5-Fu x h(-1) x ml(-1)) in colorectal carcinoma tissues compared with adjacent normal tissues (42.2 micro g x 5-Fu x h(-1) x ml(-1) +/- 21.4 micro g x 5-Fu x h(-1) x ml(-1)), P < 0.001. In immunohistochemical analysis, it was confirmed that most cells expressed dThdPase-positive cells were the stromal cells, especially macrophages, which surrounding cancer nests, or along the invasive margin of cancer. The distribution patterns of dThdPase-positive stromal cells are similar to that of the CD68-positive cells. The number of dThdPase positive cells was correlated with the number of macrophages in the cancerous tissues, r = 0.76. The dThdPase protein were detected at the levels of 18.2 unit/mg in THP-1, 19.3 unit/mg in U937, and 0.5 unit/mg in LS174T, however, not detected in other 3 colorectal carcinoma cells. The values of IC50 of 5'-DFUR on the 4 colorectal carcinoma cell lines were 11.5 approximately 84.8 times higher than those of 5-Fu (all P < 0.01). It was showed that no inhibiting effect for 5'-DFUR on the growth rates of THP-1, U937, and monocyte cells. After incubated with THP-1 or U937, 5'-DFUR expressed a significant enhanced antitumor effect (P < 0.0001), while almost no change is observed to 5-Fu (P > 0.05). Same conclusion was also demonstrated in using the monocytes instead of THP-1 or U937. 40.2 micro mol/L and 29.5 micro mol/L of 5-Fu were detected in the medium containing 400 micro mol/L of 5'-DFUR treated with THP-1 and U937 cells, respectively. CONCLUSION: 5'-DFUR cannot be converted into 5-Fu in colorectal carcinoma cells in vitro because no dThdPase is expressed in those cells. After being incubated with macrophage-like cell, THP-1, U937, or human monocytes, the anticancer effect of 5'-DFUR is significantly increased due to the activation by dThdPase expressed in above cells.