Endothelial injury by circulating IgA1 complex through the activation of mesangial cells in IgA nephropathy

IgA nephropathy (IgAN) commonly entails arteriolar microangiopathic (MA) lesions of the kidneys. The most significant reason for MA lesions is endothelial injury, although the mechanism of injury to the vascular endothelium is not clear.

59 patients with IgAN and 19 healthy controls were included for measuring the blood von Willebrand factor (vWF), soluble vascular cell adhesion molecule-1 (sVCAM1), and heparin-binding EGF-like growth factor (HB-EGF) by ELISA. Circulating IgA1 (cIgA1) was isolated from 12 patients with primary IgAN and 10 healthy controls. Then, the supernatant of growth-arrested human mesangial cells (HMCs) in a medium with cIgA1 was used to prepare the cIgA1-human mesangial cell medium (cIgA1-HMCM). Human umbilical vein endothelial cells (HUVECs) were grown in this medium along with or without Panax notoginseng saponins (PNS). ELISA was employed for the quantification of IL-6, CXCL1 and HB-EGF levels in cIgA1-HMCM, vWF, sVCAM1, and HB-EGF in the HUVEC medium.

The concentration of vWF, sVCAM-1, and HB-EGF was higher in the patients than in the healthy participants. The expressions of IL-6 and CXCL1 in HMCM were significantly higher in cIgA1 from patients with IgAN (IgAN-cIgA1) than from healthy controls. Levels of vWF, sVCAM-1, and HB-EGF induced by conditioned HMCM treated with IgAN-cIgA1 (IgAN-HMCM) were conspicuously more than those induced in healthy controls-HMCM (HC-HMCM). After culturing HUVECs in IgAN-HMCM and PNS, the vWF, sVCAM-1 and HB-EGF were remarkably low in the supernatants of cells grown in IgAN-HMCM+PNS compared to those grown in IgAN-HMCM only.

Activation of mesangial cells in vitro may occur by cIgA1 and, thus, cause endothelial cell injury via inflammation factors.