Dandelion Root Extract Induces Intracellular Ca(2+) Increases in HEK293 Cells

Dandelion (Taraxacum officinale Weber ex F.H.Wigg.) has been used for centuries as an ethnomedical remedy. Nonetheless, the extensive use of different kinds of dandelion extracts and preparations is based on empirical findings. Some of the tissue-specific effects reported for diverse dandelion extracts may result from their action on intracellular signaling cascades. Therefore, the aim of this study was to evaluate the effects of an ethanolic dandelion root extract (DRE) on Ca(2+) signaling in human embryonic kidney (HEK) 293 cells. The cytotoxicity of increasing doses of crude DRE was determined by the Calcein viability assay. Fura-2 and the fluorescence resonance energy transfer (FRET)-based probe ERD1 were used to measure cytoplasmic and intraluminal endoplasmic reticulum (ER) Ca(2+) levels, respectively. Furthermore, a green fluorescent protein (GFP)-based probe was used to monitor phospholipase C (PLC) activation (pleckstrin homology [PH]–PLCδ–GFP). DRE (10–400 µg/mL) exposure, in the presence of external Ca(2+), dose-dependently increased intracellular Ca(2+) levels. The DRE-induced Ca(2+) increase was significantly reduced in the absence of extracellular Ca(2+). In addition, DRE caused a significant Ca(2+) release from the ER of intact cells and a concomitant translocation of PH–PLCδ–GFP. In conclusion, DRE directly activates both the release of Ca(2+) from internal stores and a significant Ca(2+) influx at the plasma membrane. The resulting high Ca(2+) levels within the cell seem to directly stimulate PLC activity.