In this study, human intestinal cells (Caco-2 cells) were incubated without or with 100µl /ml Echinacea extracts for 5 hours, after which total RNA was extracted and assayed using reverse transcription-PCR. The results from reverse transcript-PCR suggest that Echinacea extracts are capable of up-regulating the level of ApoA-I gene expression. Caco-2 cells incubated with Echinacea extracts exhibited approximately a 17-fold increase in the level of gene expression as compared to Caco-2 cells without Echinacea extracts (Figure 1). The relative amount of apoA-I protein secreted by the cells into the culture media was also analysed using protein immuno-precipitation followed by SDS-PAGE. Based ...view middle of the document...
Hence, Echinacea extracts, which are capable of increase apoA-I expression, would also play a part in regulating HDL concentration in the human body.
Although it is clearly shown that Echinacea are capable of regulation apoA-I gene expression, the underlying mechanism has yet been fully elucidated. However, by comparing results with other studies, possible reaction pathways of Echinacea extracts in regulation of apoA-I gene expression can still be suggested. Lamon-Fava and Micherone (2004) conducted an experiment showing that estrogen and genistein increase apoA-I gene transcription in Hep G2, a human liver carcinoma cell line. Their experiment has shown that estrogen and genistein do not participate in the transcription of apoA-I gene directly. Instead, estrogen regulates gene expression via a signaling pathway which involves mitogen-activated protein (MAP) kinases (Lamon-Fava and Micherone, 2004)). Such signaling pathway usually requires a membrane-bound estrogen receptor that, when activated, can elicit a specific response via second messengers. Flavonoids and other active ingredients in the Echinacea extracts may involve in the cell signaling pathway, triggering the release of second messengers which will then lead to an increased rate of transcription. Thus, a higher level of apoA-I mRNA expression was observed in the experiment.
On the other hand, in a recent study done by Yashiro et al (2013), 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) increased low density lipoprotein receptor mRNA expression in hepatocytes. This was process was found to be related to mRNA stabilisation involving an extracellular signal-regulated kinase1/2 (ERK1/2), instead of AMP-activated protein kinase activation. This shows that regulation of mRNA expression might not necessarily occur at the transcriptional level. Active ingredients in Echinacea also have a high probability acting on the post-transcriptional level to stablise the mRNA of apoA-I. Thus, a greater amount of mRNA was obtained from cell samples incubated with Echinacea extarcts.
In a study done by Zhang et al (2003), it is proven that overexpression of apo-AI promotes cholesterol reverse transport from macrophages to feces in vivo, thus inhibiting atherosclerosis. It is possible to deduce that molecules which are capable of upregulating apoA-I expression may have considerable anti-atherogenic effect, which confers benefits to the cardiovascular system. Thus, Echinacea may also be used to aid treatment of atherosclerosis in the future.
Other than the ability to upregulate apoA-I expression, Echinacea is also found to contain many potential active ingredients, such as glycoproteins, alkamides, and flavonoids. Many of the active ingredients have antioxidative activity, thus preventing oxidative modification of LDL. This also shows that Echinacea can help to prevent atherosclerosis and aid the treatment of cardiovascular disease.
The Echinacea leaf extract used in this experiment contains...