tc14012 and Ischemia

Endothelial progenitor cells (EPCs) play a critical role in repairing damaged vessels and triggering ischemic angiogenesis, but their number is reduced and function is impaired under diabetic conditions. Improving EPC function has been considered a promising strategy to ameliorate diabetic vascular complications. In the present study, we aim to investigate whether and how CXCR7 agonist TC14012 promotes the angiogenic function of diabetic EPCs.. High glucose (HG) treatment was used to mimic the hyperglycemia in diabetes. Tube formation, cell scratch recovery and transwell assay, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and cleaved-caspase3 expression were used to evaluate the angiogenic capability, cell migration, and apoptosis of EPCs, respectively. Hind limb ischemia (HLI) model was used to appraise the ability of TC14012 in promoting diabetic ischemic angiogenesis in vivo.. HG treatment impaired EPC tube formation and migration, and induced EPC apoptosis and oxidative damage, while TC14012 rescued tube formation and migration, and prevented HG-induced apoptosis and oxidative damage of EPCs. Furthermore, these beneficial effects of TC14012 on EPCs were attenuated by specific siRNAs against CXCR7, validating that CXCR7 is a functional target of TC14012 in EPCs. Mechanistic studies demonstrated that HG treatment reduced CXCR7 expression in EPCs, and impaired Akt and endothelial nitric oxide synthase (eNOS) phosphorylation and nitric oxide (NO) production; similarly, these signal impairments in HG-exposed EPCs could be rescued by TC14012. However, the protective effects of TC14012 on tube formation and migration, Akt and eNOS phosphorylation, and NO production in HG-treated EPCs were almost completely abolished by siRNAs against CXCR7 or Akt specific inhibitor wortmannin. More importantly, in vivo study showed that TC14012 administration enhanced blood perfusion recovery and angiogenesis in the ischemic hind limb and increased the EPC number in peripheral circulation of db/db mice, demonstrating the capability of TC14012 in promoting EPC mobilization and ischemia angiogenic function.. TC14012 can prevent EPCs from HG-induced dysfunction and apoptosis, improve eNOS activity and NO production via CXCR7/Akt signal pathway, and promote EPC mobilization and diabetic ischemia angiogenesis.

Topics: Animals; Cell Movement; Diabetes Mellitus; Endothelial Progenitor Cells; Ischemia; Mice; Neovascularization, Physiologic; Nitric Oxide Synthase Type III; Proto-Oncogene Proteins c-akt; Signal Transduction

Hypoxia causes increased expression of several proteins that have the potential to promote neovascularization. Vascular endothelial growth factor (VEGF) is up-regulated by hypoxia in the retina and plays a central role in the development of several types of ocular neovascularization, but the effects of other hypoxia-regulated proteins are less clear. Stromal-derived factor-1 (SDF-1) and its receptor, CXCR4, have hypoxia response elements in the promoter regions of their genes and are increased in hypoxic liver and heart. In this study, we found that SDF-1 and CXCR4 are increased in hypoxic retina, with SDF-1 localized in glial cells primarily near the surface of the retina and CXCR4 localized in bone marrow-derived cells. Glial cells also expressed CXCR4, which suggested the possibility of autocrine stimulation, but influx of bone marrow-derived cells is the major source of increased levels of CXCR4. High levels of VEGF in the retina in the absence of hypoxia also increased levels of Cxcr4 and Sdf1 mRNA. CXCR4 antagonists reduced influx of bone marrow-derived cells into ischemic retina and strongly suppressed retinal neovascularization, VEGF-induced subretinal neovascularization, and choroidal neovascularization. These data suggest that SDF-1 and CXCR4 contribute to the involvement of bone marrow-derived cells and collaborate with VEGF in the development of several types of ocular neovascularization. They provide new targets for therapeutic intervention that may help to bolster and supplement effects obtained with VEGF antagonists.

Topics: Animals; Antigens, Differentiation; Bone Marrow Cells; Chemokine CXCL12; Corneal Neovascularization; Humans; Hypoxia; Ischemia; Leukocyte Common Antigens; Mice; Mice, Inbred C57BL; Mice, Transgenic; Oligopeptides; Platelet Endothelial Cell Adhesion Molecule-1; Pyridines; Receptors, CXCR4; Retina; Retinal Neovascularization; Vascular Endothelial Growth Factor A