2025 Theses Doctoral

Discovery of unique metabolic features of mammalian cells and tissues

Neelakantan, Taruna Vani

Metabolism is fundamental to the function and survival of living things. The identification of metabolic vulnerabilities in cell types or unique metabolic features may guide novel therapeutic strategies. In this thesis, I investigated metabolism in three contexts —regulatory T cells, liver, and heart.

In my study on regulatory T cells (Tregs), I focused on ferroptosis, an iron-dependent regulated cell death mechanism controlled by metabolism. Ferroptosis is most commonly investigated in the neoplastic lineage, but minimally studied in Tregs. In aggressive cancers, Tregs contribute to an immunosuppressive tumor microenvironment, attenuate the efficacy of immunotherapies, and promote tumor progression. I probed the ferroptosis pathway in Tregs, and discovered a specific metabolic vulnerability; Tregs rely on mitochondrial complex I in oxidative phosphorylation (OXPHOS) for protection against ferroptosis.

Moreover, I found that PC (22:6; 22:6), a complex I-targeting dietary lipid with two docosahexaenoyl tails, induces ferroptosis in Tregs, enabling a translational, dietary approach to disrupt Treg metabolism to drive Treg-specific ferroptosis. I probed the mechanism of PC (22:6; 22:6)-induced ferroptosis in Tregs, discovering that PC (22:6; 22:6) treatment hinders the suppressive capacity of Tregs, increases the labile iron pool, and downregulates canonical Treg gene signatures. I also found that PC (22:6; 22:6) is well tolerated in vivo. Tregs in the tumor microenvironment (TME) of aggressive cancers are known to specifically rely on OXPHOS for their immunosuppressive activities, suggesting that PC (22:6; 22:6) may be of therapeutic benefit. Collectively, these findings provide the foundation to investigate targeting OXPHOS in Tregs as a potential therapeutic strategy; future studies may explore PC (22:6: 22:6) in combination with immunotherapies to reduce tumor burden and increase the efficacy of immunotherapies in cancers with high Treg infiltration.

I also investigated metabolism in organ contexts, specifically in normal liver and heart. In these collaborative studies, I leveraged spatial technologies to identify unique lipid and metabolite signatures. In the liver, I contributed to conducting a multimodal approach, combining mass spectrometry imaging (MSI) modalities and additional imaging techniques to identify cell-type-specific and zonation-specific lipids and metabolites in both mouse and human liver.

Additionally, I utilized desorption electrospray ionization-MSI (DESI-MSI) to probe lipid and metabolite distribution in mouse and human heart. I identified unique discriminatory metabolic signatures within the heart tissue architecture. The findings in both the liver and the heart not only underscore the utility in levering spatial technologies to identify novel metabolic signatures, but also provide a reference atlas for future investigations to probe metabolic signatures in diseases contexts.