Interferon-gamma Impairs Human Coronary Artery Endothelial Glucose Metabolism via Tryptophan Catabolism and Activates Fatty Acid Oxidation, 2021, Lee

Abstract

Background: Endothelial cells depend on glycolysis for much of their energy production. Impaired endothelial glycolysis has been associated with various vascular pathobiologies, including impaired angiogenesis and atherogenesis. Interferon-gamma (IFN-γ)-producing CD4+ and CD8+ T-lymphocytes have been identified as the predominant pathologic cell subsets in human atherosclerotic plaques. While the immunological consequences of these cells have been extensively evaluated, their IFN-γ-mediated metabolic effects on endothelial cells remain unknown. The purpose of this study was to determine the metabolic consequences of the T-lymphocyte cytokine, IFN-γ, on human coronary artery endothelial cells (HCAEC).

Methods: The metabolic effects of IFN-γ on primary HCAEC were assessed by unbiased transcriptomic and metabolomic analyses combined with real-time extracellular flux analyses and molecular mechanistic studies. Cellular phenotypic correlations were made by measuring altered endothelial intracellular cyclic guanosine monophosphate (cGMP) content, wound healing capacity, and adhesion molecule expression.

Results: IFN-γ exposure inhibited basal glycolysis of quiescent primary HCAEC by 20% through the global transcriptional suppression of glycolytic enzymes resulting from decreased basal hypoxia inducible factor 1α (HIF1α) nuclear availability in normoxia. The decrease in HIF1α activity was a consequence of IFN-γ-induced tryptophan catabolism resulting in ARNT (aryl hydrocarbon receptor nuclear translocator)/HIF1β sequestration by the kynurenine-activated aryl hydrocarbon receptor (AHR). Additionally, IFN-γ resulted in a 23% depletion of intracellular NAD+ in HCAEC. This altered glucose metabolism was met with concomitant activation of fatty acid oxidation, which augmented its contribution to intracellular ATP balance by over 20%. These metabolic derangements were associated with adverse endothelial phenotypic changes, including decreased basal intracellular cGMP, impaired endothelial migration, and a switch to a pro-inflammatory state.

Conclusions: IFN-γ impairs endothelial glucose metabolism via altered tryptophan catabolism destabilizing HIF1, depletes NAD+, and results in a metabolic shift toward increased fatty acid oxidation. This work suggests a novel mechanistic basis for pathologic T-lymphocyte-endothelial interactions in atherosclerosis mediated by IFN-γ, linking endothelial glucose, tryptophan, and fatty acid metabolism with NAD(H) and ATP generation, and their adverse endothelial functional consequences.

Open access, https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.121.053960