Superoxide induced by a high-glucose concentration attenuates production of angiogenic growth factors in hypoxic mouse mesenchymal stem cells

Abstract

Previous reports have shown that the paracrine system may be an important mediator in bone-marrow-derived mesenchymal stem cell (MSC) therapy for ischemic diseases. Hyperglycemia and hypoxia have been associated with increased levels of reactive oxygen species; oxidative stress may therefore influence the paracrine effects of MSCs under hypoxic conditions in diabetic patients, although the mechanism underlying this effect remains unknown. Hypoxia-inducible factor 1a (HIF-1a) regulates the transcription of hypoxia-inducible genes. We determined the effect of high-glucose concentrations on the production of angiogenic growth factors via HIF-1a induction in hypoxic MSCs. MSCs were cultured with different glucose concentration (5 . 6, 11, 20, or 30 mM) for 24 h. The cells were then incubated in a hypoxic chamber (5% O 2 ) or under normoxia (21% O 2 ) for 6 or 24 h. Protein levels of HIF-1a, vascular endothelial growth factor A 165 (VEGF-A 165 ), and platelet-derived growth factor B (PDGF-B) were attenuated by glucose in hypoxic MSCs in a dose-dependent manner. Treatment with MG132, a specific inhibitor of proteasome activity, significantly reversed the inhibitory effect of high-glucose concentrations in hypoxic MSCs. 4-Hydroxyl-tetramethylpiperidin-oxyl (a cell-permeable superoxide scavenger) or Apocynin (a NADPH oxidase inhibitor) significantly reversed glucose-induced attenuation of VEGF-A 165 , PDGF-B, and HIF-1a protein levels. Stimulation with a high-glucose concentration (30 mM) significantly increased intracellular superoxide levels in hypoxic MSCs. Our results suggest that in hypoxic MSCs the increase in intracellular superoxide levels induced by high-glucose concentrations may attenuate hypoxia-induced HIF-1a expression, which in turn attenuates hypoxiainduced VEGF-A 165 and PDGF-B transcription.

Recent Progress in Stem Cell Therapy for Diabetic Nephropathy

“…In diabetic patients, oxidative stress may also influence the paracrine effects of MSCs under hypoxic conditions. In hypoxic MSCs, high glucose attenuates the production of angiogenic growth factors, including hypoxia-induced factor-1α, VEGF-A, and PDGF-B, by significantly increased intracellular superoxide levels in MSCs [76,77] . In addition, the migratory capacity of MSCs is also impaired.…”

Pregestational Diabetes Induces Fetal Coronary Artery Malformation via Reactive Oxygen Species Signaling

“…Although low levels of ROS increase HIF-1a expression and promote cardiovascular differentiation, high levels of ROS may inhibit HIF-1a activity by inhibiting the binding of coactivator p300 to HIF-1a (36,37). Furthermore, diabetes increases ROS levels through hyperglycemia and decreases the expression and activity of HIF-1a (38,39). In the current study, ROS levels were significantly increased, whereas HIF-1a expression and the number of Wt1 + epicardial cells and EPDCs were decreased in the hearts of embryos of pregestational diabetic mice.…”

Altering Fate Determination of Human Bone Marrow-Derived Mesenchymal Stem Cells through Environmental and Transcriptional Cues

“…VEGF secretion in MSCs was enhanced by hypoxia in several studies, 372 and hypoxia has been shown both to induce expression of and increase the half-life of VEGF mRNA. 373 VEGF secretion has been shown to be attenuated in hypoxic cultures by the presence of high glucose concentrations, 345 which may explain why the observed effect here was not more pronounced.…”

“…MSCs have been previously reported to be more sensitive to oxygen deprivation in the face of concurrent nutrient deprivation. 344,345 We employed PCR arrays to screen for signaling pathways related to colony formation, which might be perturbed by hypoxia. We observed small but significant changes in several genes, some of which regulated glycolysis and IGF signaling, and many with interesting connections to regulation of Wnt /β-catenin signaling, which is critical for maintenance of stemness in adult and embryonic stem cell populations.…”

“…345 This has been shown to occur at glucose concentrations of 30 mM, compared to the 25 mM glucose present in commercially available high-glucose media…”