Rivaroxaban significantly inhibits the stimulatory effects of bone-modulating hormones: In vitro study of primary female osteoblasts.

BACKGROUND: Anticoagulant therapy is a mainstay of treatment subsequent to major orthopedic surgeries. Evidence linking anticoagulant therapy, osteoporosis, and delayed fracture healing is not conclusive. We have previously reported that rivaroxaban significantly inhibited cell growth and energy metabolism in a human osteoblastic cell line. This study analyzed the response of primary female osteoblast cells to rivaroxaban in combination with various bone-modulating hormones. METHODS: Bone samples were taken from both premenopausal (pre-Ob) and postmenopausal (post-Ob) women. Cells were isolated from each sample and cultured to sub-confluence. Each sample was then treated with Rivaroxaban (10 µg/ml) in combination with the following hormones or with the hormones alone for 24 hours: 30nM estradiol-17ß (E2), 390nM estrogen receptor α (ERα) agonist PPT, 420nM estrogen receptor ß (ERß) agonist DPN, 50nM parathyroid hormone (PTH), and 1nM of vitamin D analog JKF. RESULTS: No effects were observed after exposure to rivaroxaban alone. When pre-Ob and post-Ob cells were exposed to the bone-modulating hormones as a control experiment, DNA synthesis and creatine kinase (CK)-specific activity was significantly stimulated with a greater response in the pre-Ob cells. When the cells were exposed to rivaroxaban in combination with bone-modulating hormones, the increased DNA synthesis and CK-specific activity previously observed were completely attenuated. CONCLUSIONS: Rivaroxaban significantly inhibited the stimulatory effects of bone-modulating hormones in both pre-Ob and post-Ob primary human cell lines. This finding may have clinical relevance for patients at high risk of osteoporosis managed with rivaroxaban or other factor Xa inhibitors.

Antagonism of saikosaponin-induced prostaglandin E2 release by baicalein in C6 rat glioma cells.

There are several Kampo medicines (Chinese herbal medicines) containing both Bupleuri Radix and Scutellariae Radix, which are used for the treatment of inflammation. Saikosaponins are derived from Bupleuri Radix, and baicalein is from Scutellariae Radix. The present study was undertaken to investigate the pharmacological interaction of saikosaponin b1 and baicalein in prostaglandin E2 (PGE2) release from C6 rat glioma cells in vitro. Saikosaponin a, b1 and d potently stimulated PGE2 release, while saikosaponin b2 and c moderately stimulated PGE2 release. Saikosaponin b1 caused an irreversible elevation of intracellular Ca2+ concentration, which was eliminated by removing extracellular Ca2+. On the other hand, baicalein inhibited saikosaponin b1-induced PGE2 release in a concentration-dependent manner. These results suggest that saikosaponins are activators of PGE2 release, and baicalein is one of the functional inhibitors of PGE2 release by saikosaponins.