J David Symons, University of Utah
Life Sciences
Cardiovascular complications (e.g., arterial dysfunction) are more prevalent in patients with type 2 diabetes (T2DM). Patients with T2DM have elevated levels of circulating free fatty acids (FFAs). We have shown that when bovine aortic endothelial cells (BAECs) are treated with the physiologically relevant FFA palmitate, protein phosphatase 2A (PP2A) activity increases, phosphorylated endothelial nitric oxide (NO) synthase (eNOS) to total eNOS (p-eNOS:eNOS) decreases, and metabolites of NO production decrease. NO is an important endothelial-derived relaxing factor that is vasculoprotective. As such, FFA-induced, PP2A-mediated reductions in p-eNOS:eNOS and NO production might explain why vascular complications are more common in pathologies associated with lipotoxicity e.g., T2DM and diet-induced obesity. Recently we showed in BAECs that if PP2A is inhibited using okadaic acid (OA), palmitate-induced increases in PP2A activity, and reductions in p-eNOS:eNOS and indices of NO production are negated. We sought to translate these finding from BAECs to the intact organism. However, OA cannot be used in vivo. Lixte Biotechnology 1 (LB1) is a PP2A inhibitor that has been used in vivo in the context of cancer research. The purpose of this study was to determine the efficacy of LB1 under our experimental conditions, with the long-range goal of using LB1 in mice. Further, we used this opportunity to optimize the measurement of NO directly using electron paramagnetic resonance spectroscopy (EPR). BAECs were treated for 3 h with vehicle (V), 500 µM palmitate (P), 4 µM LB1, or P + LB1 (n=10 per treatment). P increased (p<0.05) PP2A activity (50±12%), and decreased (p<0.05) p-tyr307:PP2A (29±9%; redundant indicator of increased PP2A activity), p-eNOS:eNOS (30±3%), and NO production (27±9%). All P-induced effects were prevented by concurrent treatment with LB1. Future experiments will determine whether chronic treatment of mice with LB1 is capable of suppressing PP2A activity in intact arteries.