Poster Session - Abstract # 29

Antioxidation System Metabolically Reprograms Survival and Expansion of Activated CD4 T-Lymphocytes 

Aprajita Tripathi, Anil Pant, and Kalyani Pyaram 

 Division of Biology, College of Arts and Sciences, Kansas State University, KS, USA

CD4 T-lymphocytes (T-cells) are a subset of adaptive immune cells that orchestrate immune responses and play an important role in host immunity.  Apart from being critical mediators of defense against infections and cancers they can also lead to autoimmune diseases like multiple sclerosis, colitis, arthritis, etc.  More recent studies show that cellular metabolism of CD4 T-cells governs their effector functions like activation, expansion, and differentiation.  Further, reactive oxygen species (ROS), the metabolic byproducts of cellular metabolism serve as second messengers of immune responses.  ROS levels are regulated by the antioxidation pathway, which is composed of Keap1 and Nrf2 proteins.  Nrf2 regulates oxidative stress and is known to modulate the immune functions yet its role in maintaining CD4 T-cell repertoire and activation-driven expansion is unclear.  In the current study, we aim to determine the role of antioxidation system in activation-driven expansion of CD4 T-cells and the underlying metabolic mechanisms.  Based on our published data on innate T-cells and our recent preliminary data, we hypothesize that Nrf2 acts as a metabolic checkpoint for CD4 T-cell activation and expansion by modulating glucose and glutamine metabolism.

Methods: To test our hypothesis, we used mice with T-cell specific deletion of Keap1 (Keap1-KO) or Nrf2 (Nrf2-KO) mice. CD4-T cells from these mice were isolated using magnetic separation method, activated in vitro and their responses were compared with wild type (WT) cells. Nutrient dependency of the WT, Keap1-KO and Nrf2-KO CD4 T-cells was tested by performing the in vitro activation in media lacking glucose or glutamine and then measuring their activation and expansion by flow cytometry. The cell trace violet (CTV) dye was used to measure expansion. Mtorc1 activity (pS6 levels) was measured by flow cytometry as well.

Results: We observed that Keap1-KO (Nrf2) in activated CD4 T-cells shows higher expansion as compared to WT and Nrf2-KO. Our nutrient dependency data suggests that Nrf2 relies on glutamine for activation-driven expansion in CD4 T-cells. We further show that increase in mTORC1 signaling in high Nrf2 condition supports glutamine metabolism in activated CD4 T-cells. Our findings identify a mechanism by which Nrf2 metabolically reprograms CD4 T-cells and modulates their metabolic dependencies to support cell expansion. A better understanding of this immunometabolic antioxidation crosstalk may pave way for new strategies or improve current Nrf2- modulating therapeutics.