DNA damage in human glomerular endothelial cells induces nodular glomerulosclerosis via an ATR and ANXA2 pathway

Collagen type VI (COL6) deposition occurs in various glomerular diseases, causing serious pathological damage like nodular lesions. However, the mechanisms underlying the deposition of COL6 remain unclear. In renal biopsy samples, immunohistochemical analyses revealed that COL6 and phosphorylated histone H2AX (γ-H2AX), a DNA damage marker, were detected mainly in diabetic nodular glomerulosclerosis, in which the γ-H2AX-positive area was identified as the independent factor significantly associated with the COL6-positive area (β: 0.539, t = 2.668). In in vitro studies, COL6 secretion from human renal glomerular endothelial cells (HRGECs) was assessed by measuring the decrease in the cytoplasmic COL6-positive cells and an increase in the amount of COL6 in the culture medium. Mitomycin C (MMc) treatment of HRGECs increased the number of γ-H2AX-positive cells and COL6 secretion, which were suppressed by a specific inhibitor of ataxia telangiectasia and Rad3-related (ATR). MMc-induced COL6 secretion was also suppressed by Annexin A2 (ANXA2) siRNA transfection. Moreover, the inhibition of ATR activity did not induce any extra suppression in the MMc-induced COL6 secretion by ANXA2 siRNA transfected cells. These results confirm that nodular glomerulosclerosis partially results from DNA damage in the glomerulus and that DNA damage-induced COL6 secretion from HRGECs occurs through an ATR and ANXA2-mediated pathway.