P0122THE MECHANISM OF DNA INJURY INDUCED COLLAGEN TYPE VI EXCRETION IN GLOMERULAR ENDOTHERIAL CELLS

Abstract

Abstract Background and Aims Collagen deposition is observed in various part of kidney tissue and is serious pathological damage in kidney. Nodular glomerulosclerosis is one of a phenotype of collagen deposition in glomerular lesion, which affects the prognosis of renal function, but there is no effective treatment at present. Recently, we identified that glomerular endothelial cells with DNA double-strand breaks (DSB) are involved in the long-term accumulation of ECM molecules, especially collagen type VI(COL6). However, the mechanism of glomerular COL6 accumulation is still unclear. Method We examined the phospho-histone H2AX (γ-H2AX) of the DSB marker and COL6 accumulation in biopsied human kidneys to investigate their association. In addition, we investigated in vitro the relationship between DSB and COL6 excretion and the intracellular signal pathways in human glomerular endothelial cells (HRGEc) using mitomycin C (MMc)-induced DNA damage. In this study, we focused on the expression of DSB response signal pathways, i.e. ATM, ATR and DNA-PK using their specific kinase inhibitors (KU55933, VE-821, Nu7441). Results COL6 deposits and γ-H2AX expression in nuclei were detected in human glomerular capillary loop and glomerular nodular lesions. The multiple regression analysis showed that γ-H2AX positive area is the most independent factor for COL6 accumulation in glomeruli (β: 0.539, t=2.668, p=0.014). Furthermore, COL6 was the independent factor of nodular lesion in various pathologic diseases such as diabetic nephropathy, hypertensive glomerulosclerosis and the long-term transplanted allografts (β: 0.373, t=2.268, p=0.032). In vitro study, COL6 excretion detected by the decrease of COL6 positive cells was suppressed only in the ATR-inhibited group (control vs. kinase inhibitors; 2 h, 40.1 ± 23.5 vs. 59.0 ± 23.2%, p <0.01; 24 h, 18.8 ± 23.6 vs. 56.3 ± 16.5%, p <0.001). Conclusion This study suggested that nodular glomerulosclerosis is induced by DNA damage and COL6 deposition through ATR pathway in glomerular capillary endothelial cells. These findings will provide great insights into the development of new therapies that would suppress glomerularsclerosis in various kidney diseases.