Activation of the mTORC1 pathway by inflammation contributes to vascular calcification in patients with end-stage renal disease.

BACKGROUND

Chronic inflammation plays an important role in the progression of vascular calcification (VC). This study was designed to explore the effects and underlying mechanisms of inflammation on VC in the radial arteries of patients with end-stage renal disease (ESRD) with arteriovenostomy.

METHODS

Forty-eight ESRD patients were divided into control (n = 25) and inflammation groups (n = 23) according to plasma C-reactive protein (CRP) level. Surgically removed tissues from the radial arteries of patients receiving arteriovenostomy were used in this study. Alizarin Red S staining was used to examine calcium deposition. The expression of inflammation markers, bone structure-associated proteins and mammalian target of rapamycin complex1 (mTORC1) pathway-related proteins was assessed by immunohistochemical staining.

RESULTS

The expression of tumor necrosis factor-α (TNF-α) and monocyte chemotactic protein-1 (MCP-1) was increased in the radial arteries of the inflammation group. Additionally, Alizarin Red S staining revealed a marked increase in calcium deposition in the inflammation group compared to controls. Further analysis by immunohistochemical staining demonstrated that the deposition was correlated with the increased expression of bone-associated proteins such as bone morphogenetic proteins-2 (BMP-2) and osteocalcin and collagen I, which suggested that inflammation induces osteogenic differentiation in vascular tissues and that osteogenic cells are the main cellular components involved in VC. Interestingly, there was a parallel increase in the expression of phosphorylated mTOR (p-mTOR) and pribosomal protein S6 kinase 1 (p-S6K1) in the inflammation group. Furthermore, mTORC1 pathway-related proteins were significantly associated with the enhanced expression of bone formation biomarkers.

CONCLUSIONS

Inflammation contributed to VC in the radial arteries of ESRD patients via the induction of osteogenic differentiation in vessel walls, which could be regulated by the activation of the mTORC1 pathway.