Targeting glutaminase C, a splice variant of glutaminase 1, suppresses smooth muscle cell phenotypic modulation and neointimal hyperplasia.

Smooth muscle cell (SMC) phenotypic modulation plays a pivotal role in vascular proliferative disorders. During proliferation, SMCs utilize glutamine to fulfill their energy, biosynthesis, and redox needs. Glutaminase C (GAC), a splice variant of glutaminase (GLS), catalyzes the hydrolysis of glutamine to glutamate, which is ultimately used in the TCA cycle. Although GAC is known to stimulate the proliferation of human cancer cells, endothelial cells, and fibroblasts, its role in SMC proliferation and neointimal hyperplasia remains elusive. This study explores the role of the therapeutic potential of targeting GAC during SMC proliferation and neointimal hyperplasia. To assess the role of GAC on the proliferation of SMCs, murine aortic SMCs were treated with CB-839 (selectively inhibits GAC activity; 10 μM) for 60 min. SMCs were stimulated with Platelet-Derived Growth Factor-BB (PDGF-BB; 20 ng/ml) for 24 h. Using Western blotting and immunofluorescence, we report that GAC expression was significantly higher in SMCs stimulated by PDGF-BB and in the neointima of wire-injured mice as compared to the control. Deprivation of glutamine in the media impeded the proliferation and migration of SMCs. Pretreatment of SMCs with GAC inhibitor reduces PDGF-BB-induced SMC migration, proliferation, and phenotypic switching. GAC inhibition was associated with decreased phosphorylation of ERK and mTOR. GAC translocated to mitochondria and induced oxidative stress. The perivascular application of a GAC inhibitor attenuated injury-induced neointimal hyperplasia. The present study demonstrates that targeting glutamine metabolism by inhibiting GAC reduces SMC proliferation and may be a potential target for reducing neointimal hyperplasia.