Immunomodulatory activity of Ulmus davidiana Planch (Ulmaceae) water and ethanolic extracts on bone cells: Stimulation of proliferation, alkaline phosphatase activity and type I collagen synthesis

Ulmus davidiana Planch (Ulmaceae) (UD) frequently appears as the main ingredient in prescriptions for bone injuries, however, the action mechanism is unclear. In the present study, (i) the effect of the aqueous extract of UD on bone cells was investigated in vitro and (ii) the immunomodulatory activity of UD was investigated with regard to cellular and humoral immunity. The osteoprecursor cells (OPC) were incubated in the medium with different concentrations of the UD and the cell proliferation was studied. When the concentration of UD was <100 μg/ml, the proliferation of OPC was enhanced. However, the proliferation of OPC was inhibited by UD with the concentrations >180 μg/ml. Under most treatments, the cells presented low expression for cyclooxygenase-2 (Cox-2) protein. On the other hand, oral administration of the ethanolic and water extracts of UD, at the doses of 20, 50, 100 and 200 mg/kg in mice, dose-dependently potentiated the delayed-type hypersensitivity reaction induced both by sheep red blood cells (SRBC) and oxazolone. It significantly enhanced the production of circulating antibody titers in mice in response to SRBC. UD had no any effect on macrophage phagocytosis. Chronic administration of UD significantly ameliorated the total white blood cell counts and also restored the myelosuppressive effects induced by cyclophosphamide. From the results, it was concluded that UD directly stimulates the proliferation, alkaline phosphatase activity, protein secretion and particularly type I collagen synthesis of OPC in a dose-dependent manner, and that UD possesses immunomodulatory activity.