Glutathione (GSH) is the most abundant non-protein thiol present at millimolar concentrations in mammalian tissues. As an important intracellular antioxidant, it acts as a regulator of cellular redox state protecting cells from damage caused by lipid peroxides, reactive oxygen and nitrogen species, and xenobiotics. Recent studies have highlighted the importance of GSH in key signal transduction reactions as a controller of cell differentiation, proliferation, apoptosis, ferroptosis and immune function. Molecular changes in the GSH antioxidant system and disturbances in GSH homeostasis have been implicated in tumor initiation, progression, and treatment response. Hence, GSH has both protective and pathogenic roles. Although in healthy cells it is crucial for the removal and detoxification of carcinogens, elevated GSH levels in tumor cells are associated with tumor progression and increased resistance to chemotherapeutic drugs. Recently, several novel therapies have been developed to target the GSH antioxidant system in tumors as a means for increased response and decreased drug resistance. In this comprehensive review we explore mechanisms of GSH functionalities and different therapeutic approaches that either target GSH directly, indirectly or use GSH-based prodrugs. Consideration is also given to the computational methods used to describe GSH related processes for in silico testing of treatment effects.

Background: Alterations of metabolism, including changes in mitochondrial and glutathione (GSH) metabolism, are a well appreciated hallmark of many cancers. Mitochondrial GSH (mGSH) transport is a poorly characterized aspect of GSH metabolism, which we investigate in the context of cancer. Existing functional annotation approaches from machine (ML) or deep learning (DL) models based only on protein sequences are unable to annotate functions in biological contexts, meaning new approaches must be developed for this task. Results: We develop a flexible ML framework for functional annotation from diverse feature data. This hybrid approach leverages cancer cell line multi-omics data and other biological knowledge data as features, to uncover potential genes involved in mGSH metabolism and membrane transport in cancers. This framework achieves an average AUROC across functional annotation tasks of 0.900 and can be effectively applied to annotate a range of biological functions. For our application, classification models predict the known mGSH transporter SLC25A39 but not SLC25A40 as being highly probably related to GSH metabolism in cancers. SLC25A24 and the orphan SLC25A43 are also predicted to be associated with mGSH metabolism by this approach and structural analysis of these proteins reveal similarities in potential substrate binding regions to the binding residues of SLC25A39. Conclusion: These findings have implications for a better understanding of cancer cell metabolism and novel therapeutic targets with respect to GSH metabolism through potential novel functional annotations of genes. The hybrid ML framework proposed here can be applied to other biological function classifications or multi-omics datasets to generate hypotheses in various biological contexts. Code and a tutorial for generating models and predictions in this framework are available at: https://github.com/lkenn012/mGSH_cancerClassifiers.

Non-shivering thermogenesis (NST) in brown adipose tissue (BAT) is rapidly activated in cold environments and is an important thermoregulatory process. Despite the consensus that BAT is inactive under warm ambient temperatures, few studies have sought to examine the metabolic remodelling that occurs when recovering from the cold and re-acclimating to thermoneutral environments (28-32°C). To elucidate mitochondrial functional and structural aspects involved in BAT metabolic remodelling during cold deacclimation, we acclimated C57BL/6J mice to the cold (4°C) for 7 days, and subsequently transferred them to thermoneutrality (30°C) for 3 h, 12 h, 24 h, or 48 h. Comprehensive metabolic phenotyping analyses demonstrated elevated metabolic rates and high food intake during the cold acclimation period, which immediately decreased by ∼40% upon returning to thermoneutrality. High-resolution respirometry of saponin-permeabilized BAT revealed decreases in mitochondrial leak uncoupling by 24 h of cold deacclimation, which corresponded with gradual declines in mitochondrial protein content and UCP1 gene expression. Decreases in BAT mitochondrial content paralleled declines in protein content, as indicated by decreases in the mtDNA/nDNA ratio and mitochondrial surface area by 48 h of cold deacclimation. Metabolomic analysis of BAT from cold-acclimated mice and from mice deacclimated for 48 h at thermoneutrality revealed major changes in pathways related to amino acid metabolism, the tricarboxylic acid cycle (TCA), glutathione, and purine metabolism. Marked decreases in the abundance of N-acetylated amino acids in cold deacclimated mice corresponded with increased aminoacylase 1 ( Acy1 ) expression. Together, these findings highlight the profound metabolic remodelling in BAT during thermogenesis and deactivation.