Abstract 15285: Shear Stress-induced Krúppel-like Factor 2 Reduces Endothelial Metabolic Activity: Interaction Between Endothelial Metabolism and Cellular Quiescence
The flow responsive transcription factor Krüppel-like Factor 2 (KLF2) is a pivotal mediator of the quiescent state of endothelial cells. However, the precise mechanism by which KLF2 drives endothelial cells towards quiescence is unclear. Recent studies suggest a link between the metabolism and cellular signaling and functions. Therefore, we hypothesize that KLF2 regulates endothelial quiescence by controlling endothelial metabolism. To study the role of KLF2 in metabolism of endothelial cells, we overexpressed human KLF2 in HUVECs by stable lentiviral integration, to levels similar to that of prolonged pulsatile flow exposure. Bioenergetic measurements on Seahorse XF analyzer revealed that cells overexpressing KLF2 have lower oxygen consumption rate (-1.49 fold ± 0.01, p<0.05) compared to mock transduced control cells, indicative of low mitochondrial respiration. Moreover, real time PCR data confirmed that KLF2 decreases endothelial mitochondrial content (-1.61 fold ± 0.07, p<0.05), without any significant change in cell proliferation between the two groups. Our data also showed that KLF2 reduced mitochondrial activity (-1.47 fold ± 0.07, p<0.01), but slightly increased mitochondrial membrane potential (1.2 fold ± 0.05, p<0.05), indicating that mitochondrial integrity is not perturbed. Interestingly, KLF2 did not induce glycolytic lactate production, indicating that lower oxygen consumption is not compensated by increased glycolysis. In addition, we also observed that KLF2 reduced glucose uptake (-1.23 fold ± 0.05, p<0.05). Analysis of mRNA profiling data of KLF2 overexpressing HUVECs showed a number of metabolism related pathways to be regulated, including TCA cycle and pentose phosphate pathway. To study endothelial metabolism under inflammatory conditions, we stimulated mock and KLF2 overexpressing HUVECs with TNF-α. Our data showed an increase in glucose uptake (1.49 fold, p<0.001) and mitochondrial content (1.48 fold, p<0.05) in mock controls, which was abrogated by KLF2 overexpression. In summary, metabolic and mitochondrial function analyses showed that KLF2 overexpression in endothelial cells reduces metabolic activity, and may thus contribute to maintaining an atheroprotective and quiescent state of the endothelium.
- © 2012 by American Heart Association, Inc.