Shikonin inhibits Vascular Smooth Muscle Cell Phenotypic Modulation and attenuates Neointimal Hyperplasia

Purpose: Enhanced glycolytic activity drives vascular smooth muscle cell proliferation and migration. Pyruvate kinase M2, a key glycolytic enzyme, modulates cancer cell proliferation. Shikonin, an inhibitor of pyruvate kinase M2, exerts anti-proliferative effects on cancer cells; still, its involvement in vascular smooth muscle cell proliferation and neointimal hyperplasia is not established. We investigated the effects of shikonin on platelet-derived growth factor-BB-induced changes in vascular smooth muscle cell function and neointimal hyperplasia. Methods: Murine aortic vascular smooth muscle cells were pretreated with shikonin and stimulated with platelet-derived growth factor-BB. Wire injury of the carotid artery was performed in C57Bl/J6 mice to induce neointimal hyperplasia. Results: Our study observes a marked upregulation of pyruvate kinase M2 in platelet-derived growth factor-BB stimulated vascular smooth muscle cells. Shikonin inhibited pyruvate kinase M2 expression and effectively reduced platelet-derived growth factor-BB-induced vascular smooth muscle cell proliferation and migration and also favoured the contractile vascular smooth muscle cell phenotype. Expression of matrix metalloproteinase-2 and interleukin-6 messenger RNAs was significantly lower in shikonin-treated vascular smooth muscle cells as compared to platelet-derived growth factor-BB-treated control. Pyruvate kinase M2 translocated to the mitochondria and pyruvate kinase M2 inhibition via shikonin promoted mitochondrial reactive oxygen species levels, increased oxidative stress and induced vascular smooth muscle cell apoptosis. Perivascular application of shikonin suppressed neointimal hyperplasia. Conclusion: Our findings indicate that shikonin suppresses vascular smooth muscle cell proliferation and migration, thereby limiting neointimal hyperplasia and potentially serving as a novel therapeutic strategy for atherosclerosis and restenosis.