α-Tocopherol Restriction Exacerbated Lipopolysaccharide-Induced Inflammatory Response in α-Tocopherol Transfer Protein-Null Mice

Abstract Objectives The α-tocopherol transfer protein-null (Ttpa−/−) mouse model is a valuable tool for studying the molecular and functional consequences of vitamin E (α-tocopherol, αT) deficiency. Our objective was to assess how dietary αT restriction, followed by lipopolysaccharide (LPS) exposure affected the inflammatory response in Ttpa−/− and wild-type (Ttpa+/+) mice. Methods After weaning (3 weeks of age), male Ttpa+/+ and Ttpa−/− littermates (n = 36/genotype) were fed an αT deficient diet ad libitum for 4 weeks. At 7 weeks of age, mice were injected with LPS (1 or 10 µg/mouse) or saline (control) intraperitoneally and sacrificed 4 hours post-injection. Brain and heart IL-6 levels, a marker of inflammatory response, and serum and tissue αT concentrations were measured via ELISA and HPLC-PDA, respectively. Hippocampal Il6, Tnf, and Gpx1 expression, markers of inflammatory and oxidative stress response, were measured via RT-qPCR, and blood immune cell profiles were measured via a hematology analyzer. Results αT concentrations in serum and most analyzed tissues were below the limit of detection in Ttpa−/− mice but not Ttpa+/+ mice. Circulating white blood cell levels, particularly lymphocytes, were lower in all LPS groups compared to controls (P < 0.01). The 10 µg LPS groups had elevated IL-6 in the cerebellum and heart compared to controls, confirming an acute inflammatory response (P < 0.01). Hippocampal Il6 and Tnf expression were significantly increased in Ttpa−/− mice that received 10 µg LPS compared to those that received saline (∼20- and ∼3-fold higher, respectively) (P < 0.01). Comparing expression patterns by genotype, the 10 µg LPS-Ttpa−/− mice had ∼2-fold lower Gpx1 and ∼2-fold higher Il6 expression than the 10 µg LPS-Ttpa+/+ mice. Hippocampal Il6 expression was increased by LPS in a dose-dependent manner (P < 0.05). Conclusions LPS, especially at the higher dose, altered inflammatory markers in the brain, heart, and serum. αT restriction further exacerbated the expression of select hippocampal genes. Funding Sources Abbott Nutrition via the Center for Nutrition, Learning and Memory, University of Illinois, Urbana-Champaign; Division of Nutritional Sciences Vision 20/20 and Margin of Excellence Research grants.