Glutamine Stimulates the Proliferation, Migration, and Survival of Vascular Smooth Muscle Cells

Abstract

Glutamine is an abundant and versatile amino acid that contributes to cellular integrity and function. Glutamine is predominantly metabolized to glutamate and ammonia by the mitochondrial enzyme glutaminase-1 (GLS1). Glutamate is subsequently converted by glutamate dehydrogenase and/or aminotransferases to α-ketoglutarate (α-KG) which feeds into the tricarboxylic acid (TCA) cycle for ATP production and amino acid and lipid synthesis, thereby fulfilling both the energetic and macromolecular requirement of cells. While glutamine is known to regulate the function of vascular smooth muscle cells (SMCs), the metabolic pathways underlying this response are not fully known. Accordingly, the present study investigated the effect of glutamine and its metabolites on vascular SMC function. Incubation of cultured rat or human aortic SMCs with glutamine resulted in a progressive increase in cell proliferation and migration that was accompanied by an increase in cellular glutamate and ammonia levels. Treatment of SMCs with the selective GLS1 inhibitors bis-2-(5-phenylacetoamido-1,3,4,-thiazol-2-yl)ethyl sulfide (BPTES) or CB-839 inhibited the stimulatory effects of glutamine. Flow cytometry experiments revealed that GLS1 inhibitors arrested SMCs in the G0/G1 phase of the cell cycle, and this was associated with a significant decline in DNA synthesis. Glutamine depletion or GLS1 inhibition also sensitized SMCs to the toxic effects of hydrogen peroxide. Interestingly, the administration of cell permeable dimethyl α-KG increased the proliferation and migration of glutamine-deprived SMCs, while the application of ammonia had no effect. In contrast, ammonia, but not dimethyl α-KG, mitigated hydrogen peroxide-mediated death of glutamine-starved SMCs. In conclusion, this study demonstrates that the metabolism of glutamine by GLS1 promotes SMC proliferation, migration, and survival. While the replenishment of the TCA cycle by α-KG contributes to glutamine-dependent growth and motility, the generation of ammonia by GLS1 promotes glutamine-conditional survival. These results identify GLS1 as a promising therapeutic target in treating diseases associated with aberrant vascular SMC phenotypes. This work was supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health under Award Number R01 HL149727. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.