Nuclear Factor of Activated T‐Cells is involved in the regulation of osteopontin expression in vascular smooth muscle

Hyperglycemia has been suggested to play a role in the development of vascular disease associated with diabetes. Among other changes, the enhanced expression of osteopontin (OPN) is characteristic in arteries from diabetic rats and patients. We have recently shown that high‐glucose activates Nuclear Factor of Activated T‐cells (NFAT) in vascular smooth muscle. This effect involves the release of extracellular nucleotides such as UTP, acting on P2Y receptors. Here we show that NFAT is involved in the regulation of OPN expression in vascular smooth muscle. Using immunofluorescence confocal microscopy and western blotting, we show a time‐dependent induction of OPN upon organ culture of intact mouse aorta. Stimulation with UTP significantly enhanced OPN expression. Inhibition of NFAT signaling prevented UTP‐induced OPN expression. Using electrophoretic mobility shift assay, we show that NFATc3 isoform, but not NFATc4 or NFATc1, binds to NFAT binding elements in the mouse OPN promoter region. Interestingly, UTP activates NFATc3 but not NFATc4. Also, NFATc3 levels increase upon organ culture, whereas NFATc4 and NFATc1 decrease, suggesting a role for NFATc3 in the regulation of OPN expression.