To Örebro University

Background and Aims: Cells within atherosclerotic lesions have a higher glutamine demand than cells in healthy vessel although glutaminase, the enzyme converting glutamine to glutamate, is significantly downregulated in human carotid lesions. This may suggest rewiring of glutamine metabolic pathways in atherosclerotic lesions, caused by infiltrating immune cells and or their cytokines. Here we aimed at exploring the enzymes and transporters involved in glutamine metabolism in human carotid atherosclerotic tissues and aortic smooth muscle cells (hAoSMCs) exposed to interferon gamma.

Methods: Protein and mRNA from interferon gamma-treated hAoSMCs were subjected to Western blot or qRT-PCR for quantification of enzymes and transporters involved in glutamine metabolism. H2DCFDA probe was utilized for detection of intracellular reactive oxygen species (ROS) using flow cytometry. The expression of these enzymes and transporters was also evaluated in human carotid lesions (GEO accession: GSE43292).

Results: Interferon-treated hAoSMCs display a significantly lower expression of glutaminase followed by an increase in the expression of glutamine transporters, glutamine synthetase and glutamine-fructose-6-phosphate transaminase-1 (GFPT1). The level of ROS and the expression of enzymes involved in de novo synthesis of glutathione are elevated in interferon-treated cells. A similar expression pattern for these genes, expect for GFPT1, is also evident in human carotid lesions where glutaminase mRNA shows a strong positive correlation with SMC markers and a strong negative correlation with macrophage markers.

Conclusions: Glutamine metabolism is disrupted in human carotid lesions and interferon gamma alters glutamine metabolism in hAoSMCs, which may favor the production of UDP-GlcNAc and reactive oxygen species.