Silymarin suppresses cellular inflammation by inducing reparative stress signaling

Abstract

Silymarin, a characterized extract of the seeds of milk thistle (Silybum marianum), suppresses cellular inflammation. To define how this occurs, transcriptional profiling, metabolomics, and signaling studies were performed in human liver and T cell lines. Cellular stress and metabolic pathways were modulated within 4 h of silymarin treatment: activation of Activating Transcription Factor 4 (ATF-4) and adenosine monophosphate protein kinase (AMPK) and inhibition of mammalian target of rapamycin (mTOR) signaling, the latter being associated with induction of DNA-damage-inducible transcript 4 (DDIT4). Metabolomics analyses revealed silymarin suppression of glycolytic, tricarboxylic acid (TCA) cycle, and amino acid metabolism. Antiinflammatory effects arose with prolonged (i.e. 24 h) silymarin exposure, with suppression of multiple pro-inflammatory mRNAs and signaling pathways including nuclear factor kappa B (NF-* Corresponding Author: (S.J. Polyak). . polyak@uw.edu. Supporting Information. Primer-probe sets for RT-PCR validation of microarray data and antibodies used in Western blotting are in Tables S1 and S2, respectively. Figures S1-S9 provide microarray heat map, microarray RT-PCR validation, protein validation, supporting IPA pinwheels, metabolomics heat map, AMPK knockout validation, and IPA legend. This material is available free of charge via the Internet at http://pubs.acs.org. Author ContributionsThe manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript κB) and forkhead box O (FOXO). Studies with murine knock out cells revealed that silymarin inhibition of both mTOR and NF-κB was partially AMPK dependent, while silymarin inhibition of mTOR required DDIT4. Other natural products induced similar stress responses, which correlated with their ability to suppress inflammation. Thus, natural products activate stress and repair responses that culminate in an anti-inflammatory cellular phenotype. Natural products like silymarin may be useful as tools to define how metabolic, stress, and repair pathways regulate cellular inflammation.Natural products are used to prevent and treat a plethora of chronic, debilitating, and inflammatory diseases. Over one-third of adults in the US reported self-medicating with complementary and alternative medicines (CAM). 1 Defining precise mechanisms of action is a critical barrier to the optimal application of botanicals as CAMs and as pharmaceuticals. Natural products, like the compounds contained in silymarin (a.k.a. milk thistle extract; from the plant Silybum marianum [L.] Gaertn.[Asteraceae]), protect cells by various antioxidant, anti-inflammatory, antiviral, immunomodulatory, proliferative, and metabolic effects, 2,3 resulting in diverse protective phenotypes, both in vitro and in vivo. For example, silymarin and silymarin-derived flavonolignans inhibit in vitro hepatitis C virus (HCV) infection of hu...

Hepatitis C virus dynamics and cellular gene expression in uPA‐SCID chimeric mice with humanized livers during intravenous silibinin monotherapy

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Silymarin improved diet-induced liver damage and insulin resistance by decreasing inflammation in mice

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A validated UHPLC-tandem mass spectrometry method for quantitative analysis of flavonolignans in milk thistle (Silybum marianum) extracts

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