Ruta graveolens aqueous extract inhibits proliferation of undifferentiated neural cells and induces differentiated neurons reentry in cell cycle

Introduction: In CNS, aberrant proliferation causes cancer and im- paired survival of differentiated neurons induces neurodegenerative disorders. In order to find novel ther- apeutic targets able to inhibit aber- rant cell proliferation and/or enhance differentiated cells survival, we ana- lyzed properties of aqueous extract of Ruta graveolens on differentiated and proliferating neural cells. Ruta g. is currently used for its diuretic, sedative, and analgesic effects and recent studies described antiprolifer- ative effects on different cancer cells. Materials and methods: We used a mouse mesencephalic embryonic cell line, A1 mes-c-myc cells (A1) that are proliferating/undifferenti- ated in the presence of serum. They cease to proliferate and differentiate when serum is withdrawn and cAMP is added. Aqueous extracts (Ruta g. a.e.) were obtained from young leaves chopped, infused in boil- ing water and lyophilized. Extract concentrations of 10 mg/ml, 1 mg/ ml and 0.1 mg/ml were tested. Cell counting was performed by MTT assay and Trypan blue method. Cell cycle was analyzed by cytometry af- ter PI incorporation. Cell signalling was analyzed by western blotting. Results: Ruta g. a.e. inhibits A1 cells proliferation and induces increase in ERK phosphorylation. In presence of the ERK pathway inhibitor, PD, Ruta g. a.e. is unable to induce cell death indicating that ERK is involved in the Ruta g. effect on A1 proliferating cells. On the other hand, when Ruta g. a.e. is added, the number of dif- ferentiated A1 cells appears signifi- cantly higher as compared to control conditions and the analysis of the cell cycle showed an increased number of cells in G2/M phase in differentiated cells treated with Ruta g. a.e. Conclu- sions: Ruta g. a.e. could represent an interesting therapeutic tool since it is able at the same time to inhibit un- differentiated cell proliferation and to induce re-entry in the cell cycle of differentiated neurons.