<it>Echinacea</it>-induced cytosolic Ca²⁺elevation in HEK293

• Main Authors: Nikolau Basil J (Author), Rizshsky Ludmila (Author), Jeftinija Srdija (Author), Jeftinija Ksenija (Author), Rowe Eric W (Author), Wu Lankun (Author), McKay Jodi (Author), Kohut Marian (Author), Wurtele Eve (Author)
• Format: Book
• Published: BMC, 2010-11-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

<p>Abstract</p> <p>Background</p> <p>With a traditional medical use for treatment of various ailments, herbal preparations of <it>Echinacea </it>are now popularly used to improve immune responses. One likely mode of action is that alkamides from <it>Echinacea </it>bind to cannabinoid type 2 (CB2) receptors and induce a transient increase in intracellular Ca²⁺. Here, we show that unidentified compounds from <it>Echinacea purpurea </it>induce cytosolic Ca²⁺elevation in non-immune-related cells, which lack CB2 receptors and that the Ca²⁺elevation is not influenced by alkamides.</p> <p>Methods</p> <p>A non-immune human cell line, HEK293, was chosen to evaluate <it>E. purpurea </it>root extracts and constituents as potential regulators of intracellular Ca²⁺levels. Changes in cytosolic Ca²⁺levels were monitored and visualized by intracellular calcium imaging. U73122, a phospholipase C inhibitor, and 2-aminoethoxydiphenyl borate (2-APB), an antagonist of inositol-1,4,5-trisphosphate (IP₃) receptor, were tested to determine the mechanism of this Ca²⁺signaling pathway. <it>E. purpurea </it>root ethanol extracts were fractionated by preparative HPLC, screened for bioactivity on HEK293 cells and by GC-MS for potential constituent(s) responsible for this bioactivity.</p> <p>Results</p> <p>A rapid transient increase in cytosolic Ca²⁺levels occurs when <it>E. purpurea </it>extracts are applied to HEK293 cells. These stimulatory effects are phospholipase C and IP₃receptor dependent. <it>Echinacea</it>-evoked responses could not be blocked by SR 144528, a specific CB2 receptor antagonist, indicating that CB2 is not involved. Ca²⁺elevation is sustained after the <it>Echinacea</it>-induced Ca²⁺release from intracellular Ca²⁺stores; this longer-term effect is abolished by 2-APB, indicating a possible store operated calcium entry involvement. Of 28 HPLC fractions from <it>E. purpurea </it>root extracts, six induce cytosolic Ca²⁺increase. Interestingly, GC-MS analysis of these fractions, as well as treatment of HEK293 cells with known individual and combined chemicals, indicates the components thought to be responsible for the major immunomodulatory bioactivity of <it>Echinacea do not </it>explain the observed Ca²⁺response. Rather, lipophilic constituents of unknown structures are associated with this bioactivity.</p> <p>Conclusions</p> <p>Our data indicate that as yet unidentified constituents from <it>Echinacea </it>stimulate an IP₃receptor and phospholipase C mediation of cytosolic Ca²⁺levels in non-immune mammalian cells. This pathway is distinct from that induced in immune associated cells via the CB2 receptor.</p>

Item Description

10.1186/1472-6882-10-72
1472-6882