PS-BPB02-2: POLYMORPHISM OF DNA REPAIR GENE IS ASSOCIATED WITH HYPERTENSION-INDUCED LEFT VENTRICULAR HYPERTROPHY - ROLE OF DNA DAMAGE AND CELL SENESCENCE

Abstract

Objective: Deficiency of X-ray repair cross-complementing protein 3 (XRCC3), a DNA-damage repair molecule, and 241Met variant of XRCC3 are prone to increase endoreduplication, resulting in pathological polyploidy. In this study we investigated the impact of XRCC3 polymorphism on the incidence of hypertension-induced left ventricular hypertrophy (LVH) and underlying mechanisms. Design and method: Patients under hemodialysis (n = 77) were genotyped for XRCC3 Thr241Met polymorphism. LVH was determined by echocardiography. To investigate the possible mechanisms for LVH, human XRCC3 cDNA of 241Thr or that of 241Met was introduced into cultured cells. The surface area of the cells was measured and spontaneous DNA double-strand breaks were detected by immunofluorescent study with anti-53BP1 antibody. The mRNA levels of basal and TNF-α-stimulated MCP-1 were quantified by real-time RT PCR. FACS analysis was performed to count the percentage of polyploidy. Results: In patients under hemodialysis, XRCC3 241Thr/Met genotype was more frequent in LVH (+) group than in LVH (-) group (42.3% vs. 13.7%, χ2 = 7.85, p = 0.0051). To investigate the possible mechanisms for LVH, following in vitro experiments were performed. The surface area of Chinese hamster ovary cells expressing XRCC3 241Met variant was larger than those expressing 241Thr. The accumulation of spontaneous DNA double-strand breaks (DSBs) was increased in NIH3T3 cells expressing 241Met (3T3–241Met) than those expressing 241Thr (3T3–241Thr). Ionizing radiation-induced cell senescence was significantly enhanced in 3T3–241Met than in 3T3–241Thr. The mRNA levels of basal and TNF-α-stimulated MCP-1 were higher in 3T3–241Met variant than 3T3–241Thr. Finally, FACS analysis revealed that the cell percentage in G2/M phase including polyploidy was significantly increased in 3T3–241Met compared with 3T3–241Thr. In addition, the basal mRNA level of MCP-1 was positively correlated with the cell percentage in G2/M phase and polyploidy. Conclusion: The current study suggests that XRCC3 241Met variant increases the risk of LVH via the accumulation of DNA damage, alteration of cell cycle progression, and induction of cell senescence and proinflammatory phenotype.