Xie Lin-Shen, Qin Wei, Fan Jun-Ming, Huang Jun, Xie Xi-Sheng, Li Zi
Department of Nephrology, West China Hospital of Sichuan University, Chengdu City, Sichuan Province, China.
Clin Invest Med. 2010 Feb 1;33(1):E5-13. doi: 10.25011/cim.v33i1.11832.
IgA1 aberrant O-glycosylation is one of the main pathogenetic features of IgA nephropathy (IgAN). This study attempted to determine the role of C1GALT1C1 in aberrant IgA1 O-glycosylation induced by lipopolysaccharide (LPS) and identify potential therapeutic targets in IgAN.
Lymphocytes isolated from 22 patients with IgAN and 17 normal controls were cultured for 3 to 7 days with or without LPS and 5-azacytidine (5-AZA). Expression levels of C1GALT1C1 mRNA and protein were measured by real-time PCR and Western blot analysis, respectively. Concentration of IgA1 and level of O-glycosylation were determined by ELISA and Vicia villosa (VV) lectin-binding assay. Correlation analysis was performed between the expression of C1GALT1C1 protein and IgA1 O-glycosylation.
Lymphocytes from patients with IgAN secreted more IgA1 than that from normal controls after LPS stimulation (P=0.26, 0.002 and 0.005 on the 3rd, 5th and 7th day, respectively) which could be inhibited by 5-AZA (P=0.001, 0.025 and 0.001 on the 3rd, 5th and 7th day, respectively). Moreover, LPS stimulation could obviously inhibit C1GALT1C1 expression in patients with IgAN (decreased by 71%, 82% and 92% on the 3rd, 5th and 7th day, respectively; P < 0.001), and cause a significant decrease of IgA1 O-glycosylation compared with normal controls (P=0.004, 0.003 and 0.03 on the 3rd, 5th and 7th day, respectively). When 5-AZA was added, the level of C1GALT1C1 expression increased dramatically (1.98, 5.53 and 8.97 times on the 3rd, 5th and 7th day, respectively; P < 0.001) along with an increase of IgA1 O-glycosylation (P=0.295, 0.09 and 0.003 on the 3rd, 5th and 7th day, respectively). However, normal controls showed no significant change in C1GALT1C1 expression and IgA1 O-glycosylation after LPS stimulation (P > 0.05).
LPS induced IgA1 aberrant O-glycosylation and suppressed C1GALT1C1 expression in patients with IgAN. Upregulation of C1GALT1C1 expression by 5-AZA could reverse the IgA1 aberrant O-glycosylation. These results suggest that C1GALT1C1 may play a key role in the regulation of IgA1 O-glycosylation.
IgA1异常O-糖基化是IgA肾病（IgAN）的主要发病机制特征之一。本研究旨在确定C1GALT1C1在脂多糖（LPS）诱导的IgA1异常O-糖基化中的作用，并确定IgAN潜在的治疗靶点。
从22例IgAN患者和17例正常对照者中分离淋巴细胞，在有或无LPS和5-氮杂胞苷（5-AZA）的情况下培养3至7天。分别通过实时PCR和蛋白质印迹分析测定C1GALT1C1 mRNA和蛋白质的表达水平。通过ELISA和野豌豆（VV）凝集素结合试验测定IgA1浓度和O-糖基化水平。对C1GALT1C1蛋白表达与IgA1 O-糖基化进行相关性分析。
LPS刺激后，IgAN患者的淋巴细胞分泌的IgA1比正常对照者更多（第3、5和7天分别为P = 0.26、0.002和0.005），5-AZA可抑制这种分泌（第3、5和7天分别为P = 0.001、0.025和0.001）。此外，LPS刺激可明显抑制IgAN患者C1GALT1C1的表达（第3、5和7天分别下降71%、82%和92%；P < 0.001），与正常对照相比，IgA1 O-糖基化显著降低（第3、5和7天分别为P = 0.004、0.003和0.03）。加入5-AZA后，C1GALT1C1表达水平显著升高（第3、5和7天分别为1.98、5.53和8.97倍；P < 0.001），同时IgA1 O-糖基化增加（第3、5和7天分别为P = 0.295、0.09和0.003）。然而，LPS刺激后正常对照者的C1GALT1C1表达和IgA1 O-糖基化无显著变化（P > 0.05）。
LPS诱导IgAN患者IgA1异常O-糖基化并抑制C1GALT1C1表达。5-AZA上调C1GALT1C1表达可逆转IgA1异常O-糖基化。这些结果表明C1GALT1C1可能在IgA1 O-糖基化调节中起关键作用。
