Alkylamides from Echinacea Modulate Induced Immune Responses in Macrophages

Abstract

The ability of Echinacea and its components to alter the immune response was examined 'in vitro' in a macrophage cell line under either basal or immunostimulated conditions. Potential immunostimulatory and inflammatory activity was determined using a nuclear transcription factor (NFкB) expression, tumour necrosis factor α (TNFα) and nitric oxide (NO) production as biomarkers. In the absence of alternate stimulation, the only significant effects seen were a decrease in NFкB expression by a 2-ene alkylamide ((2E)-N-isobutylundeca-2-ene-8,10-diynamide (1)) and a decrease in TNFα levels by cichoric acid and an Echinacea alkylamide fraction (EPL AA). When the cells were stimulated by lipopolysaccharide (LPS), inhibition of the increased NFкB expression levels was caused by cichoric acid, an Echinacea preparation (EPL), EPL AA and a 2,4-diene ((2E,4E,8Z,10Z)-N-isobutyldodeca-2,4,8,10-tetraenamide (2)). Increases in TNFα levels were inhibited by cichoric acid, EPL and EPL AA but enhanced by 1 in the presence of LPS, while only EPL AA was able to inhibit the stimulated increases in NO. When using phorbol myristate acetate to stimulate the cells, NFкB and NO levels were unaffected by Echinacea or its components while only cichoric acid and 2 inhibited TNFα levels. Although cichoric acid was found to have an effect, it is probably not an important contributor to the Echinacea modulation of the immune response in vivo, as it is not bioavailable. Echinacea appears to attenuate the response of macrophages to an immune stimulus and its combination of phytochemicals exhibits different pharmacological properties to one or more of the isolated major individual components.