Echinacea purpurea (L.) Moench modulates human T-cell cytokine response

Abstract

The study objective was to evaluate the composition of a neutral and weakly acidic water-soluble extract from Echinacea purpurea (L.) Moench (EchNWA) previously shown to modify murine influenza infection, and to assess immunomodulatory effects on human T-cells. EchNWA extract from fresh aerial parts was extracted with water, ethanolic precipitation, and size-exclusion chromatography. The chemical profile of EchNWA was characterized by chromatography (size-exclusion, HPLC, GC-MS), and small molecule fingerprint analysis performed by HPLC-PDA. Jurkat T-cells at high and low cell density were pretreated or not with doses of EchNWA, followed by activation with phorbol 12-myristate 13-acetate plus ionomycin (PMA+I). Interleukin-2 (IL-2) and interferon gamma (IFNg) cytokine secretions were measured by multi-cytokine luminex technology. Results showed that EchNWA contains 80% polysaccharides, predominantly a 10kDa entity; phenolic compounds, cynarin, cichoric and caftaric acids, but no detectable alkylamides. Cytokine production required stimulation and was lower after PMA+I activation in high-density compared to low-density conditions. EchNWA mediated a strong dose-dependent enhancement of high-density T-cell production of IL-2 and IFNg response to PMA+I. EchNWA alone did not stimulate T-cells. EchNWA enhanced mean fluorescence intensity of IL-2 in Jurkat T-cells activated by PMA+1 or ionomycin alone. Conversely EchNWA mediated modest but significant suppression of IFNg response and reduced the percentage of CD25+ T-cells under low-density conditions. Conclusions are that EchNWA polysaccharides, but not phenolic compounds have dose-related adjuvant effects on human T-cell cytokine responses characterized by enhancing and suppressive effects that are regulated by T-cell density.

Keywords: Cytokine response; Echinacea; Human T-cell density; Immune modulation; Neutral and weakly acidic water-soluble extract; Polysaccharides and phenolic compounds; Small molecule fingerprint-analysis.

Copyright © 2014 Elsevier B.V. All rights reserved.

Figures

Fig. 1

Panel A: 2-ene alkamide reference substance and the UV–vis peak spectrum. Panel B: Echinacea NWA extract and UV–vis spectra. The chromatogram for all resolved peaks.

Fig. 2

Effect of EchNWA pretreatment on IL-2 response: Jurkat T-cells were cultured at low (0.5 × 106 cells/mL) or high (5 × 106 cells/mL) cell density, pretreated with or without EchNWA, and then stimulated with PMA + I. At high density, IL-2 response to PMA + I was less without EchNWA compared to low-density conditions (2-way ANOVA, p

Fig. 3

Effect of EchNWA pretreatment on T-cell response to ionomycin alone: Jurkat T-cells cultured at high density (5 × 106 cells/mL) were pretreated or not with EchNWA and stimulated with ionomycin (I) or phorbol ester + I (PMA + I) and evaluated for IL-2 production by multi-cytokine assay. The increase inmean fluorescence intensity (MFI) of the IL-2 response (MFI) at 100 μg/mL and 250 μg/mL of EchNWA was significant compared to ionomycin alone (p

Fig. 4

Effect of EchNWA pretreatment on IFN-γ response: Jurkat T-cells were cultured at low (0.5 × 106 cells/mL) or high (5 × 106 cells/mL) cell densities and pretreated with PMA + I. At high density, IFN-γ response to PMA + I was less without EchNWA pretreatment compared to low-density condition (2-way ANOVA, p < 0.0001 Bonferroni post-test). At 100 μg/mL and 250 μg/mL doses of EchNWA enhanced response in high-density T-cells (p < 0.0001, 1-way ANOVA, Tukey’s post test) compared to no pretreatment. Low-density T-cells showed mild dose dependent suppression that was significant at 100 μg/mL dose of EchNWA compared to PMI + I alone (p < 0.02, 1-way ANOVA, p < 0.05, Tukey’s posttest).

Fig. 5

Effect of EchNWA on CD25 Expression in High and Low Cell Density Jurkat T-cells: EchNWA reduced the percentage of T-cells expressing CD25 in response to PMA + Ionomycin in low-density conditions (p