The α-tocopherol-derived long-chain metabolite α-13′-COOH mediates endotoxin tolerance and modulates the inflammatory response via MAPK and NFkB pathways

Scope: The long-chain metabolites of (LCM) vitamin E are proposed as the active regulatory metabolites of vitamin E providing, with their anti-inflammatory properties, an explanatory approach for the inconsistent effects of vitamin E on inflammatory-driven diseases. We examined the modulation of cytokine expression and release from macrophages, a fundamental process in many diseases, to gain insights into the anti-inflammatory mechanisms of the alpha-tocopherol-derived LCM alpha-13'-COOH. Methods and results: Suppressed gene expression of C-C motif chemokine ligand 2 (Ccl(2)), tumor necrosis factor (Tnf), and interleukin (Il) 6 in response to lipopolysaccharides by 24 h pre-treatment with alpha-13'-COOH in RAW264.7 macrophages was revealed using quantitative reverse transcription PCR. Further, reduced secretion of IL1 beta and CCL2 was found in this setup using flow cytometry. In contrast, 1 h pre-treatment suppressed only CCL2. Consequent gene expression analysis within 24 h of alpha-13 '-COOH treatment revealed the induction of mitogen-activated protein kinases (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NFxB) negative feedback regulators including the 'master regulators' dual-specificity phosphatase 1 (Dusp1/ Mkp1) and tumor necrosis factor induced protein 3 (Tnfaip3/A20). Approaches with immunoblots and chemical antagonists suggest a feedback induction via activation of extracellular-signal regulated kinase (ERK), p38 MAPK and NFxB pathways. Conclusions: CCL2 is suppressed in murine macrophages by alpha-13'-COOH and the indirect suppression of MAPK and NFxB pathways is likely a relevant process contributing to anti-inflammatory actions of alpha-13'-COOH. These results improve the understanding of the effects of alpha-13'-COOH and provide a basis for new research strategies in the context of inflammatory diseases.

Automated summary

The study demonstrated that alpha-13'-COOH can suppress the production of inflammatory factors in macrophages and exert its anti-inflammatory effects by inhibiting the MAPK and NFxB pathways.