naphthoquinones and Atherosclerosis

Pyruvate kinase M2 is a critical enzyme that regulates cell metabolism and growth under different physiological conditions. In its metabolic role, pyruvate kinase M2 catalyzes the last glycolytic step which converts phosphoenolpyruvate to pyruvate with the generation of ATP. Beyond this metabolic role in glycolysis, PKM2 regulates gene expression in the nucleus, phosphorylates several essential proteins that regulate major cell signaling pathways, and contribute to the redox homeostasis of cancer cells. The expression of PKM2 has been demonstrated to be significantly elevated in several types of cancer, and the overall inflammatory response. The unusual pattern of PKM2 expression inspired scientists to investigate the unrevealed functions of PKM2 and the therapeutic potential of targeting PKM2 in cancer and other disorders. Therefore, the purpose of this review is to discuss the mechanistic and therapeutic potential of targeting PKM2 with the focus on cancer metabolism, redox homeostasis, inflammation, and metabolic disorders. This review highlights and provides insight into the metabolic and non-metabolic functions of PKM2 and its relevant association with health and disease.

Topics: Adenosine Triphosphate; Atherosclerosis; Carrier Proteins; Cell Proliferation; Enzyme Inhibitors; Gene Expression Regulation, Enzymologic; Glycolysis; Homeostasis; Humans; Inflammation; Inflammatory Bowel Diseases; Insulin; Kidney Diseases; Liver; Membrane Proteins; Metabolic Diseases; Naphthoquinones; Neoplasm Metastasis; Neoplasms; Neuralgia; Oxidants; Oxidation-Reduction; Protein Isoforms; Sepsis; Signal Transduction; Thyroid Hormone-Binding Proteins; Thyroid Hormones; Tissue Distribution

Increased glycolysis is involved in the proliferation and migration of vascular smooth muscle cells (VSMCs). Pyruvate kinase isoform M2 (PKM2), a key rate-limiting enzyme in glycolysis, accelerates the proliferation and migration of tumor cells. Although the intracellular mechanisms associated with oxidized low-density lipoprotein (oxLDL)-stimulated VSMC proliferation and migration have been extensively explored, it is still unclear whether oxLDL promotes the proliferation and migration of VSMCs by enhancing PKM2-dependent glycolysis. In the present study, we detected PKM2 expression and pyruvate kinase activity in oxLDL-treated VSMCs and explored the regulation of PKM2 in oxLDL-treated VSMCs and apoE-/- mice. The results showed that PKM2 expression in VSMCs was higher in the intima than in the media in plaques from atherosclerotic rabbits. Moreover, PKM2 level in VSMCs was increased during atherosclerosis progression in apoE-/- mice. Both PKM2 expression and pyruvate kinase activity were found to be upregulated by oxLDL stimulation in VSMCs. Shikonin (SKN), a specific inhibitor of PKM2, was found to inhibit the oxLDL-induced proliferation and migration in VSMCs, in addition to delaying the atherosclerosis progression in apoE-/- mice. More importantly, oxLDL increased glucose uptake, ATP and lactate production, and the extracellular acidification rate in VSMCs, which could be reversed by SKN. Meanwhile, oxygen consumption rate was unchanged after oxLDL stimulation, suggesting that glycolysis is the main contributor to the energy supply in oxLDL-treated VSMCs. Our results suggest that oxLDL induces VSMC proliferation and migration by upregulating PKM2-dependent glycolysis, thereby contributing to the atherosclerosis progression. Thus, targeting PKM2-dependent glycolysis might provide a novel therapeutic approach for the treatment of atherosclerosis.

Topics: Animals; Atherosclerosis; Carrier Proteins; Cell Movement; Cell Proliferation; Cells, Cultured; Gene Knockdown Techniques; Glycolysis; Humans; Lipoproteins, LDL; Male; Membrane Proteins; Mice; Mice, Knockout, ApoE; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Naphthoquinones; Pyruvate Kinase; Rabbits; Rats; Rats, Sprague-Dawley; Thyroid Hormone-Binding Proteins; Thyroid Hormones

Atherosclerosis, a disease of the large arteries, is the primary cause of heart disease and stroke. The abnormal proliferation of vascular smooth muscle cells (VSMCs) in arterial walls is an important pathogenetic factor of vascular disorders like atherosclerosis and restenosis after angioplasty. In the present study, the possible anti-proliferative effect of a synthetic 1,4-naphthoquinone derivative, 2-chloro-3-(4-hexylphenyl)-amino-1,4-naphthoquinone (NQ304) was investigated on rat aortic VSMCs. NQ304 was shown to potently inhibit 5% fetal bovine serum (FBS)-induced the growth of VSMCs. Pre-treatment of VSMCs with NQ304 (1-10 microM) for 24 h resulted in significant cell number decreases, i.e., inhibition percentages were 44.75+/-10.77, 73.85+/-6.38 and 89.77+/-6.52% at NQ304 concentrations of 1, 5 and 10 microM, respectively. NQ304 was also found to significantly inhibit 5% FBS-induced DNA synthesis in a concentration-dependent manner. Furthermore, NQ304 elevated p21(cip1) and p27(kip1) mRNA levels and caused G0/G1 phase arrest in cell cycle progression. However, no evidence of NQ304-induced apoptotic or necrotic cell death was obtained, as determined by flow cytometry analysis and DNA fragmentation assays. To investigate the mechanism underlying the anti-proliferative effect of NQ304, we examined the effects of NQ304 on c-fos mRNA expression, activator protein-1 (AP-1) binding activity and extracellular signal-regulated kinase1/2 (ERK1/2) and Akt activation. Pre-treatment of VSMCs with NQ304 (1-10 microM) was found to significantly inhibit the 5% FBS-induced phosphorylations of ERK1/2 and Akt, the activation of AP-1 and the expression of c-fos. These data suggest that the anti-proliferative and cell cycle arresting effects of NQ304 on serum-induced VSMCs may be mediated by AP-1 activation downregulation via the suppression of phosphatidylinositol 3-kinase (PI3K)/Akt and ERK1/2 signaling pathways, and it may contribute to the prevention of atherosclerosis through inhibition of VSMC proliferation.

Topics: Animals; Antimitotic Agents; Aorta; Atherosclerosis; Cell Cycle; Cell Proliferation; Cells, Cultured; DNA; Dose-Response Relationship, Drug; Extracellular Signal-Regulated MAP Kinases; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Naphthoquinones; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-fos; Rats; RNA, Messenger; Serum; Signal Transduction; Transcription Factor AP-1