Comparison of Notoginsenoside R1 and TPO on Thrombopoiesis in Irradiated Mice.

The use of combination of Chinese herbs as a treatment for thrombocytopenia has been reported to be effective and safe. We have reported that Angelica Polysaccharide (extracts of Angelica Sinensis) has promoting effect on blood stem cells and megakaryocytopoiesis (Yang et al, Blood, 2002, 100 (11); 53a). Sanqi, Radix Notoginseng, is the dried roots of Panax notoginseng (Burk.) F. H. Chen (Araliaceae). It has been used for treatment of trauma and bleeding due to internal and external injuries. Its main constituents are ginsenosides (a kind of saponins), as well as notoginsenosides (only rich in Notoginseng species). Although Sanqi is a well-known haemostatic drug, its effects and mechanisms on megakaryocyte/platelet production have not been studied. The objective of this study was to compare the effect of a purified notoginsenoside R1 (NR1) and thrombopoietin (TPO) on thrombopoiesis in irradiated mice. NR1 (2.5 mg) and TPO (0.25 ug) were dissolved in distilled water and given by intra-peritoneal injection daily for 14 days starting from the day after radiotherapy. Peripheral blood platelets, white blood cells (WBC), and red blood cells (RBC) were analyzed from NR1, TPO, and vehicle control groups on day 0, 7 and 14. On day 14, the mice were sacrificed and bone marrow cells were harvested for CFU-MK, CFU-GM, BFU-E and CFU-F (fibroblastoid) assays (n=5). Our results showed that NR1 enhanced the recovery of platelets, WBC, and RBC count. Moreover, NR1 also promoted the CFU-F (12 ± 0.7 vs 19 ± 0.38 colonies/2 x 10⁶ cells, p=0.0034), CFU-MK (22 ± 1.9 vs 26 ± 3.8 colonies/2 x 10⁵ cells, p=0.025), CFU-GM (26 ± 5.2 vs 37 ± 4.3 colonies/2 x 10⁵ cells, p=0.002), and BFU-E (13 ± 2.9 vs 18 ± 1.9 colonies/2 x 10⁵ cells, p=0.003) formation. Similar results were obtained in TPO-treated group. In in-vitro study, we further analyzed the effect of NR1 (0–50mM) on mouse CFU-MK formation using a plasma clot colony assay. The results showed that NR1 (20 mM) enhanced TPO (50 ng/ml)-induced CFU-MK formation (19 ± 2.2 vs 30 ± 6.8 colonies/2 x 10⁵ cells, p=0.02, n=5). Furthermore, the effect of NR1 (5–50 mM) on the growth of bone marrow stromal cells was also investigated using CFU-F assay. NR1 (50mM) had a promoting effect on CFU-F growth (18 ± 3.7 vs 24 ± 1.8 colonies/2 x 10⁶ cells, p=0.043, n=5). Our studies showed that NR1 enhances thrombopoiesis in vivo and the growth of bone marrow stromal cells as well as megakaryocytes in vitro. Therefore, we speculate that the thrombopoietic activity of NR1 may be mediated via promoting the progenitor of platelet, megakaryocytes, and bone marrow stromal cells. Although TPO has been used as an agent for the recovery of platelet production after the onset of thrombocytopenia, long-term clinical usage of TPO may induce potential side effects such as thrombosis. Here we reported that the effect of NR1 is comparable with TPO on the production of platelets in irradiated mice.