Background and Aims

Calciprotein particles (CPPs) arise in the blood at its supersaturation with calcium and phosphate characteristic for chronic kidney disease and osteopenia/osteoporosis. Representing a major calcium/phosphate depot and thereby maintaining mineral homeostasis, CPPs nevertheless have been shown to induce lysosome-dependent death of endothelial cells (ECs), provoking the development of intimal hyperplasia even in normolipidemic conditions. However, the molecular mechanisms behind these detrimental effects remain unclear. Here we asked whether CPP promote adhesion of leukocytes to ECs.

Methods

Primary human coronary artery and internal thoracic artery ECs were cultured under flow utilising Ibidi Pump System for 16 h (15 dyn/cm²) to adjust their expression profile to the physiological conditions and then exposed to spherical/amorphous or needle-shaped/crystalline CPPs for 4 h. Fluorescent-labeled primary human peripheral blood mononuclear cells were added to the flow for the last hour with the following microscopy analysis.

Results

CPPs provoked adhesion of leukocytes to either type of the ECs regardless of their shape and crystallinity. The number of leukocytes adhered upon the exposure to CPPs was 6-fold higher in comparison with the control cultures and was similar to the cultures pre-treated with TNF-α (20 ng/mL). Expression analysis by means of RT-qPCR and immunofluorescence staining concordantly demonstrated an increase in VCAM1, ICAM1, and E-selectin expression at both gene and protein level providing a mechanism for leukocyte adhesion.

Conclusions

Calciprotein particles enhance leukocyte-endothelial cell interactions, thereby potentially promoting vascular inflammation.

This study was funded by the Russian Science Foundation, grant number 19-15-00032 “Molecular mechanisms of endothelial toxicity induced by calcium phosphate bions”.