Saponin derived from the leaves of an indigenous plant Philippine ornamental plant (Schefflera odorata) was investigated for its potential signal transducing property. Leaf extract from S. odorata was used an as extracellular signal to initiate different intracellular reactions that lead to diverse cell responses.
Phosphotyrosine kinases are extracellular enzymes involved in the development of asthma. The effect of S. odorata on these enzymes in airway smooth muscle (ASM) cells was determined by SDS-PAGE and Western Blotting. Fetal calf serum (FCS) was used to stimulate the activation of these enzymes. Immunoblot of the ASM cell lysates treated with FCS and S. odorata showed concentration dependent inhibition of band formation at 205,112 and 42 kDa.
Mitogen activated protein kinase (MAPK) is one of the several enzymes that is activated by the activation of phosphotyrosine kinases. The effect of S. odorata on MAPK activation was determine by performing two assays, MAPK SDS-PAGE Mobility shiftand MAPK Peptide Assay. In SDS-PAGE Mobility shift assay, the activation of MAPK is indicated by its retarded mobility upon SDS-PAGE, as observed in ASM cells treated with FCS. However, this mobility shift was not observed when the cells were tretaed with FCS and 100 ug/ml of S. odorata. No band was formed at all when the concentration of S. odorata was increased to 200 ug/ml. The result in MAPK Mobility Shift assay was confirmed by the other assay, the MAPK Peptide Assay.
Thymidine Incorporation assay was done to determine the effect of S. odorata on DNA synthesis. FCS stimulated DNA synthesis was inhibited by 50% when treated with 100 ug/ml S. odorata. Almost 100% inhibition of DNA synthesis was observed when the ASM cells were treated with 200 ug/ml.
Previous study have shown that S. odorata is not directly cytotoxic to a number of cancer cell lines. However, lower concentration of S. odorata (50 ug/ml) can induce the differentiation of A549 (lung cancer) cells as shown by the expression of cytokeratin 4, a marker for epithelial differentiation while at high concentration of S. odorata (100 ug/ml), it can induce apoptosis, as monitored through DNA fragmentation.
The leaf extract was also investigated for its immunomodulating property. Monocytes incubated with the leaf extract gave a dose-dependent release of II-I that is comparable to LPS. However, the monocytes did not release a significant amount of TNF-a (alpha sign). Electron spin resonance study showed it could quench hydroxyl free radicals suggesting its antioxidant property.
General Objective: To evaluate the ability of aqueous saponin extracts from the roots and leaves of Schefflera odorata to induce differentiation and/or apoptosis in cultured human cells.Specific Objectives: 1. To monitor the effect of saponin extracts from the leaves and roots of Schefflera odorata on the growth pattern and changes in cell morphology of normal human lymphocytes and A549 cell line;2. To demonstrate the induction of differentiation in A549 cell line;3. To determine programmed cell death (apoptosis) in A549 cell line.