The role of glycolysis and mitochondrial respiration in the formation and functioning of endothelial tip cells during angiogenesis

Abstract

During sprouting angiogenesis, an individual endothelial tip cell grows out from a pre-existing vascular network and guides following and proliferating stalk cells to form a new vessel. Metabolic pathways such as glycolysis and mitochondrial respiration as the major sources of adenosine 5′-triphosphate (ATP) for energy production are differentially activated in these types of endothelial cells (ECs) during angiogenesis. Therefore, we studied energy metabolism during angiogenesis in more detail in tip cell and non-tip cell human umbilical vein ECs. Small interfering RNA was used to inhibit transcription of glycolytic enzymes PFKFB3 or LDHA and mitochondrial enzyme PDHA1 to test whether inhibition of these specific pathways affects tip cell differentiation and sprouting angiogenesis in vitro and in vivo . We show that glycolysis is essential for tip cell differentiation, whereas both glycolysis and mitochondrial respiration occur during proliferation of non-tip cells and in sprouting angiogenesis in vitro and in vivo . Finally, we demonstrate that inhibition of mitochondrial respiration causes adaptation of EC metabolism by increasing glycolysis and vice versa. In conclusion, our studies show a complex but flexible role of the different metabolic pathways to produce ATP in the regulation of tip cell and non-tip cell differentiation and functioning during sprouting angiogenesis.

The Multifaceted Pyruvate Metabolism: Role of the Mitochondrial Pyruvate Carrier

“…Once formed, pyruvate can be either reduced to lactate by LDH in the cytosol, regenerating NAD + to fuel glycolysis, or fully oxidized within mitochondria, through the TCA cycle. The choice between these two pathways has important consequences for the cell, since glycolysis yields two molecules of ATP/molecule of glucose, whereas oxidative phosphorylation yields >30 molecules of ATP/molecule of glucose [ 2 , 3 ].…”

Impact of β-glycerophosphate on the bioenergetic profile of vascular smooth muscle cells

“…ATP, the main energy-storage molecule [ 33 ], represents the fuel for a multitude of cellular processes and an intracellular signalling molecule that connects physiological responses with cellular metabolic state [ 19 , 34 ]. Mitochondrial oxidative phosphorylation and glycolysis are the two major ATP-producing pathways in cells [ 19 , 26 ]. Mitochondrial respiration has a higher efficiency and represents the preferred pathway for ATP generation in differentiated cells [ 19 , 26 , 35 , 36 ].…”

“…Mitochondrial oxidative phosphorylation and glycolysis are the two major ATP-producing pathways in cells [ 19 , 26 ]. Mitochondrial respiration has a higher efficiency and represents the preferred pathway for ATP generation in differentiated cells [ 19 , 26 , 35 , 36 ]. However, similar to the Warburg effect described in cancer cells [ 35 , 36 ], VSMCs show high aerobic glycolysis under normal conditions [ 37 , 38 ], a metabolic characteristic of proliferating cells [ 26 , 36 , 39 ].…”

“…These findings point towards higher energy demand during β-glycerophosphate-induced transdifferentiation that is, probably, required to fuel cellular activity during this VSMC phenotype switch [ 17 – 20 , 24 , 25 ]. VSMCs may, thus, respond to the new energy demand by increasing ATP generation via mitochondrial oxidative phosphorylation, due to its superior efficiency [ 26 , 36 ]. Of note, ATP is also used by the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) to generate the essential calcification inhibitor pyrophosphate [ 40 ], which may show a compensatory increase after phosphate exposure [ 41 ].…”

“…In addition to the bioenergetic function [ 19 , 26 , 39 ], mitochondria are also a source of reactive oxygen species (ROS) as a by-product of ATP production [ 39 ]. While low levels of ROS act as intracellular signalling molecules [ 45 – 47 ], high ROS levels induce oxidative stress and oxidative damage [ 46 ].…”