Identifying panaxynol, a natural activator of nuclear factor erythroid-2 related factor 2 (Nrf2) from American ginseng as a suppressor of inflamed macrophage-induced cardiomyocyte hypertrophy

doi:10.1016/j.jep.2015.04.004

Get rights and content

Abstract

Ethnopharmacological relevance

American ginseng is capable of ameliorating cardiac dysfunction and activating Nrf2, a master regulator of antioxidant defense, in the heart. This study was designed to isolate compounds from American ginseng and to determine those responsible for the Nrf2-mediated resolution of inflamed macrophage-induced cardiomyocyte hypertrophy.

Materials and methods

A standardized crude extract of American ginseng was supplied by the National Research Council of Canada, Institute for National Measurement Standards. A bioassay-based fractionization of American ginseng was performed to identify the putative substances which could activate Nrf2-mediated suppression of pro-inflammatory cytokine expression in macrophages and macrophage-mediated pro-hypertrophic growth in cardiomyocytes.

Results

A hexane fraction of an anti-inflammatory crude extract of American ginseng was found to be most effective in suppressing the inflammatory responses in macrophages. Preparative, reverse-phase HPLC and a comparative analysis by analytical scale LC–UV/MS revealed the hexane fraction contains predominantly C₁₇ polyacetylenes and linolenic acid. Panaxynol, one of the major polyacetylenes, was found to be a potent Nrf2 activator. Panaxynol posttranscriptionally activated Nrf2 by inhibiting Kelch-like ECH-associated protein (Keap) 1-mediated degradation without affecting the binding of Keap1 and Nrf2. Moreover, panaxynol suppressed a selected set of cytokine expression via the activation of Nrf2 while minimally regulating nuclear factor-kappa B (NF-κB)-mediated cytokine expression in macrophages. It also dramatically inhibited the inflamed macrophage-mediated cardiomyocyte death and hypertrophy by activating Nrf2 in macrophages.

Conclusions

These results demonstrate that American ginseng-derived panaxynol is a specific Nrf2 activator and panaxynol-activated Nrf2 signaling is at least partly responsible for American ginseng-induced health benefit in the heart.

Graphical abstract

Emerging evidence has suggested that regular use of ginseng is helpful for the treatment of cardiovascular diseases; however, the underlying mechanisms are not fully understood. Our results reveal for the first time that panaxynol isolated from American ginseng activates Nrf2-operated anti-inflammatory signaling in inflamed macrophages, thereby suppressing inflamed macrophage-mediated cardiomyocyte death and hypertrophy.

Abbreviations

Nrf2, nuclear factor erythroid-2 related factor 2;
Am. G, American ginseng;
iNOS, inducible nitric oxide synthase;
LPS, lipopolysaccharide;
MCP-1, monocyte chemotactic protein-1;
MIP-1β, macrophage inflammatory protein-1 beta;
IL-1β, interleukin-1 beta;
IL-6, interleukin-6;
TNFα, tumor necrosis factor alpha;
ARE, antioxidant response element;
Atg7, autophagy related gene 7;
CSF, colony-stimulating factor;
FACS, fluorescence activated cell sorting;
LDH, lactate dehydrogenase;
NQO-1, NAD(P)H dehydrogenase, quinone 1;
WT, wild type;
LC–UV DAD, Liquid chromatography with UV diode array detection;
LC–MS, Liquid chromatography mass spectrometry

Keywords

American ginseng;
Panaxynol;
Nrf2;
Inflammation;
Macrophages;
Cardiomyocytes

: Corresponding author.

: Corresponding author at: Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, SC 29208, USA.

Cheryl & ethnovet

twitter

Wednesday, 22 April 2015