Parathyroid hormone promotes osteoblastic differentiation of endothelial cells via the extracellular signal-regulated protein kinase 1/2 and nuclear factor-kappa B signaling pathways

Vascular calcification (VC) occurs in patients with chronic kidney disease (CKD) and contributes to cardiovascular dysfunction and mortality. Parathyroid hormone (PTH) is a crucial regulator of VC. High PTH serum levels constitute as a major risk factor for patients with CKD. However, the effect and mechanism of PTH on osteoblastic differentiation in endothelial cells have not been fully elucidated. In the present study, the role of PTH in VC was investigated using an in vitro calcification model. Endothelial cells were stimulated with PTH in the femto- to picomolar range. As determined by western blot analysis and ELISA, osteoblastic differentiation, as indicated by the BMP2 marker, occurred with maximum effect at 1x10(-10) mmol/l PTH. The results indicate that PTH promotes osteoblastic differentiation of endothelial cells, as demonstrated by the increased expression of bone morphogenetic protein (BMP) 2 and BMP4. In addition, western blot analysis revealed that PTH activated the extracellular signal-regulated protein kinase (Erk)1/2 and nuclear factor (NF)-kappa B signaling pathways. However, reverse transcription-quantitative polymerase chain reaction demonstrated that inhibitors specific to Erk1/2 and NF-kappa B eradicated the effect of PTH treatment on BMP2, BMP4, ALP and RUNX2 expression. These results demonstrate that PTH promotes the osteoblastic differentiation of endothelial cells via the Erk1/2 and NF-kappa B signaling pathways, which suggests a potential role of PTH in the promotion of VC. These findings provide an insight into the association between PTH and cardiovascular disease.