The impact of αlpha-tocopherol on lipopolysaccharide-induced inflammatory response

Hashida, Megumi

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https://hdl.handle.net/2142/122139 Copy

Description

Title

The impact of αlpha-tocopherol on lipopolysaccharide-induced inflammatory response

Author(s)

Hashida, Megumi

Issue Date

2023-11-29

Director of Research (if dissertation) or Advisor (if thesis)

Erdman, Jr., John W.

Doctoral Committee Chair(s)

Steelman, Andrew J.

Committee Member(s)

• Johnson, Rodney W.
• Amengual Teressa, Jaume

Department of Study

Nutritional Sciences

Discipline

Nutritional Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Vitamin E deficiency Natural alpha-tocopherol Grip strength Inflammation Lipopolysaccharide Ttpa-null mouse model

Abstract

α-Tocopherol (αT) scavenges peroxyl radicals to prevent excessive oxidative stress. Due to this antioxidant function in the nervous and immune systems, several endpoints in these body systems have been studied in the last century since vitamin E was discovered. Indeed, αT deficiency results in neurological disorders and an exacerbated immune activation due to elevated oxidative stress. This thesis primarily focuses on αT as the most biologically active form of vitamin E and having a higher affinity for hepatic α-tocopherol transfer protein (α-TTP) in comparison to other vitamin E metabolites. α-TTP contributes to maintaining vitamin E homeostasis as it regulates the turnover and delivery of αT to tissues. Importantly, α-TTP is mostly present in the liver, but it is also expressed in the brain. Modeling vitamin E deficiency in wild type (WT) mice is challenging because of the long half-life of αT. Therefore, we used α-TTP knockout (Ttpa-/-) mice as a model of vitamin E deficiency. Ttpa-/- mice, as it occurs in vitamin E-deficient subjects, develop neurological abnormalities, making this mouse model an adequate tool to study vitamin E-mediated neurological disorders. However, little is known about the mechanism(s) by which αT status impacts neurobehavioral outcomes in Ttpa-/- mice at different life stages, especially during adolescence/young adulthood. Therefore, we sought to optimize the mouse model evaluating the impact of length of αT depletion and use of lipopolysaccharide (LPS) exposure to evaluate the effect of αT deficiency on LPS-induced inflammatory and oxidative stress. In our first study, WT and Ttpa-/- weaning mice were fed a vitamin E deficient diet (Modified-AIN-93G with hydrogenated coconut oil) for 4 weeks (7-week-old mice at termination) (Chapter 2). Following vitamin E depletion, mice received a single intraperitoneal injection of either LPS (1 or 10 µg/mouse) or saline as a control group. Results showed lower tissue αT levels in Ttpa-/- mice compared to WT mice, while WT mice accumulated αT in the selected tissues and serum. LPS administration caused an acute inflammatory response in LPS-treated mice. Surprisingly, we did not observe differences between genotypes in selected inflammatory and oxidative stress markers, nor in circulating immune cells measured 4 hours after LPS treatment. Next, we evaluated 12-week-old mice after 9-week-feeding of αT deficient diet (Modified-AIN-93G with soybean oil), with intraperitoneal injection of LPS (10 µg/mouse) or saline as control. (Chapter 3). We added a functional endpoint (grip strength) as well as inflammatory/oxidative stress markers. LPS-induced reduction of grip strength was further decreased in Ttpa-/- compared to WT mice. However, despite their different tissue αT levels, markers related to inflammatory and oxidative stress responses were not altered by genotype. Next, we extended our feeding period of an αT deficient diet in mice over a period of 12 weeks in the next study (Chapter 4). The aim was to investigate whether LPS-induced sickness behaviors and inflammatory and oxidative stress responses. Upon LPS injection, mice displayed behaviors typically associated with sickness accompanied with the exacerbation of inflammatory response, particularly when testing at 4 hours following injection. After 24 hours of LPS treatment, improved grip strength and reduction of inflammatory response were observed in both Ttpa-/- and WT mice, while a slightly elevated oxidative stress level and altered circuiting immune cell profiles were found. Despite the differing αT tissue levels between Ttpa-/- and WT mice, we did not observe differences between genotypes in any LPS-induced behavior changes or markers of inflammatory and oxidative stress responses. Finally, we conducted a cell culture study in primary peritoneal macrophages isolated from weaned 3-week-old Ttpa-/- and WT mice fed an αT diet for 12 weeks (15-week-old mice at termination). We examined whether αT deficiency in cultured macrophages exposed to LPS influenced inflammatory and oxidative stress responses in vitro (Chapter 5). We observed that αT was depleted in peritoneal macrophages isolated from Ttpa-/- mice in comparison to WT mice. Despite the disparity in αT concentrations between groups, we did not observe differences on gene expression in selected inflammatory and oxidative stress markers in response to LPS or between the genotypes. In summary, our research reveals that αT deficiency leads to reduction of grip strength and altered immune response in mice fed αT deficient diets for 4 – 12 weeks. We hypothesized that there would be significant genotype effects whereby Ttpa-/- mice would have exacerbated responses compared to WT mice. However, despite differences in αT accumulation between WT and Ttpa-/- mice, we only saw genotype differences in grip strength following the 9-week depletion (Chapter 3). Additional markers or indicators to assess the impact of αT deficiency on LPS-induced inflammatory and oxidative stress responses did not differ between genotypes. The absence of genotype-specific effects in our thesis projects may be due to various factors, including the selected stressor (LPS), the timing of sacrifice, the selected LPS dosage, the duration of αT depletion, and the age of the mice. Collectively, this work furthers our understanding of the impact of vitamin E depletion in mice on biochemical and functional endpoint measures of αT deficiency. Additional studies will be necessary to further refine and optimize the model for αT depletion in LPS-mediated inflammatory and oxidative stress response.

Graduation Semester

2023-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Megumi Hashida

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