Date of Award

1-1-2014

Document Type

Open Access Dissertation

Department

Biomedical Engineering

First Advisor

Taixing Cui

Abstract

Nuclear factor erythroid-2 related factor 2 (Nrf2), a major transcription factor of the endogenous antioxidant defense system, has been proposed as a potential therapeutic target for the treatment of various diseases. However, a small molecule-driven Nrf2 signaling therapeutic approach remains to be established. Herein, we report one such possibility discovered by the bioassay-based fractionation of American ginseng. Since crude extract of American ginseng was found to suppress the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-inflamed macrophages via activating Nrf2, we further fractioned the crude extract using solvents including hexane, dichloromethane, ethyl acetate, butanol, and water, and found that the hexane fraction was the most effective fraction in activating Nrf2-mediated suppression of iNOS expression in macrophages. By utilizing preparative, reverse-phase HPLC and a comparative analysis by analytical scale LC-UV, we found that hexane fraction contains predominantly polyacetylenes and linolenic acid, and we identified panaxynol as the major compound in polyacetylenes. We report a unique and Nrf2-dependent anti-inflammatory profile of panaxynol in inflamed macrophages. In lipopolysaccharide (LPS)-inflamed RAW264.7 macrophages, panaxynol dramatically suppressed the expression of pro-inflammatory cytokines including inducible nitric oxide synthase (iNOS) and monocyte chemotactic protein-1 (MCP-1), but it has no effects on regulate expression of interleulin-6 (IL-6), interleulin-1B (IL-1B), and tumor necrosis factor alpha (TNF-a), this results suggested activation of specific pathway; that is Panaxynol potently activated Nrf2 signaling; but, it did not affect NF-kB activity in LPS inflamed macrophages. Moreover, knockout of Nrf2 blocked the panaxynol induced anti-inflammatory responses in LPS-inflamed macrophages. These results demonstrated that panaxynol suppresses pro-inflammatory responses in macrophages via an activation of Nrf2 independently of NF-kB, suggesting a potential mechanism responsible for the American ginseng-mediated health benefits and a unique therapeutic potential of panaxynol for specific targeting Nrf2-mediated resolution of inflammation.

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