Nitric oxide promotes cell-matrix adhesion of endothelial progenitor cells under hypoxia condition via ITGA5 CpG promoter demethylation.

Hypoxia or low oxygen tension causes changes in the structure and functional phenotype of the endothelial progenitor cells (EPCs). EPCs are found to be involved in angiogenesis and vascular repair. However, EPC's role in cell-matrix adhesion under hypoxia conditions is not clearly established. Nitric oxide (NO) exerts a wide range of biological functions, especially in regulating the mobilization and vascular repair of EPCs. In contrast, the link between NO and its role in cell-matrix deadhesion under hypoxia is not studied yet. Here, we investigated the protective role of NO in hypoxia-induced cell-matrix deadhesion of EPCs through an epigenetic mechanism. The EPCs were exposed to 2% hypoxia in the presence or absence of 10 μM Spermine NONOate (NO donor). The result demonstrates that hypoxia exposure intensified mitochondrial oxidative damage and energy defects. Using miScript miRNA qPCR array-based screening, the study found miR-148 as a novel target of hypoxia-induced DNMT1 activation. Mechanistically, the study discovered that hypoxia suppressed miR-148 levels and stimulated EPCs cell-matrix deadhesion via increasing DNMT1 mediated Integrin alpha-5 (ITGA5) CpG promoter hypermethylation. Treatment with a mitochondria-targeted antioxidant, MitoTEMPO, or epigenetic DNMT inhibitor, 5'-azacitidine, or miR-148 overexpression in hypoxic EPCs culture, prevented the cell-matrix deadhesion compared to hypoxic EPCs. Further, treatment of spNO or transient expression of eNOS-GFP attenuated hypoxia-induced cell-matrix deadhesion via inhibition of ITGA5 CpG island promoter methylation. In conclusion, the study provides evidence that NO is essential for cell-matrix adhesion of EPCs by epigenetically mitigating ITGA5 CpG promoter hypermethylation under hypoxia conditions. This finding uncovers the previously undefined mechanism of NO-mediated diminution of hypoxia-induced cell-matrix deadhesion and dysfunction induced by low oxygen tension.