Abstract
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 Ca2+ 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) Ca2+ 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 Ca2+, dose-dependently increased intracellular Ca2+ levels. The DRE-induced Ca2+ increase was significantly reduced in the absence of extracellular Ca2+. In addition, DRE caused a significant Ca2+ release from the ER of intact cells and a concomitant translocation of PH–PLCδ–GFP. In conclusion, DRE directly activates both the release of Ca2+ from internal stores and a significant Ca2+ influx at the plasma membrane. The resulting high Ca2+ levels within the cell seem to directly stimulate PLC activity.
Highlights
To date, natural products from medicinal plants, microorganisms, marine organisms (e.g., Acmella oleracea [1], Sclerocarya birrea [2,3], Agelas clathrodes [4], and Tedania ignis [5]) are in the spotlight of many research and industrial laboratories for (i) biomedical applications, (ii) the recovery of bioactives, and (iii) the development of pharmacological drugs
We showed, for the first time, that acute exposure (2–5 min, 400 μg/mL) to an ethanolic dandelion root extract (DRE) induced a dose-dependent and reversible Ca2+ increase in HEK293 cells (Figure 2)
DRE-mediated increase in intracellular Ca2+ was characterized by using both classical experimental manoeuvres and direct comparison with drugs (e.g., ATP and ionomycin) that have a well-known action on Ca2+ homeostasis
Summary
Natural products from medicinal plants, microorganisms, marine organisms (e.g., Acmella oleracea [1], Sclerocarya birrea [2,3], Agelas clathrodes [4], and Tedania ignis [5]) are in the spotlight of many research and industrial laboratories for (i) biomedical applications, (ii) the recovery of bioactives, and (iii) the development of pharmacological drugs. A possible explanation of such a wide panel of physiological effects might be found in the chemical composition of the different dandelion preparations. The phytochemical composition of dandelion roots extracts (DRE) reported the presence of sesquiterpenes, various triterpenes, phytosterols, and phenolic compounds [6]. Hydroxycinnamic acid derivatives (chlorogenic, caffeic, 4-coumaric, 3-coumaric, ferulic acids) are the main represented class, whereas a small amount of flavonoids and hydroxybenzoic acid derivatives is generally reported [9,10,11]. Dandelion leaves and flowers are more enriched in flavonoids (luteolin and its glycoside derivatives, chrysoeriol) and coumarins (cichoriin and aesculin), and hydroxycinnamic acid derivatives (caffeic, chlorogenic, chicoric, and monocaffeoyltartaric acids) were reported to be present [10,12]
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