Leung Joseph C K, Chan Loretta Y Y, Li Felix F K, Tang Sydney C W, Chan Kwok Wa, Chan Tak Mao, Lam Man Fai, Wieslander Anders, Lai Kar Neng
Department of Medicine, University of Hong Kong, Room 409, Queen Mary Hospital, Pokfulam Road, Hong Kong.
Nephrol Dial Transplant. 2005 Jul;20(7):1336-49. doi: 10.1093/ndt/gfh814. Epub 2005 Apr 6.
Glucose degradation products (GDPs) are formed during heat sterilization of peritoneal dialysis fluid and, to a lesser extent, during their prolonged storage. In vitro studies have demonstrated that GDPs impair functions of peritoneal mesothelial cells, including proliferation, viability and cytokine release. In the present study, we studied the acute effect of GDPs on the expression of tight junction-associated protein, zonula occludens protein 1 (ZO-1), in human peritoneal mesothelial cells (HPMC). The role of the vascular endothelial growth factor (VEGF) induced by GDPs in the expression of ZO-1 was also examined.
HPMC were cultured with GDPs, including 2-furaldehyde (FurA), methylglyoxal (M-Glx) and 3,4-dideoxyglucosone-3-ene (3,4-DGE). The expression of ZO-1 and the synthesis of VEGF were examined. To define the role of VEGF on the regulation of ZO-1 expression, HPMC were cultured with GDPs in the presence or absence of neutralizing antibody to VEGF. The signal pathways involved in VEGF synthesis induced by GDPs were also characterized.
ZO-1 expression in HPMC was downregulated in a time- and dose-dependent manner following culture with subtoxic concentrations of GDPs (FurA, M-Glx and 3,4-DGE). All three GDPs increased VEGF synthesis in HPMC. Exogenous VEGF downregulated the expression of ZO-1 and neutralizing anti-VEGF antibody reversed the effect of GDPs on ZO-1 expression in HPMC, suggesting the action of GDPs on ZO-1 expression was mediated by VEGF. All three GDPs activated the p42/p44 mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) signal transduction pathways. The GDP-induced VEGF and transforming growth factor (TGF)-beta synthesis in HPMC was partially reduced by either the p42/p44 MAPK inhibitor (PD98059) or the PKC inhibitor (staurosporine). More importantly, the VEGF and TGF-beta synthesis induced by GDPs in HPMC was completely blocked by synergistic action of both inhibitors.
We have demonstrated that short-term exposure to GDPs downregulates ZO-1 expression in HPMC through the generation of VEGF. Our study provides evidence that GDPs can directly induce VEGF and TGF-beta production in HPMC through the activation of p42/44 MAPK and PKC signal transduction pathways.
葡萄糖降解产物（GDPs）在腹膜透析液热灭菌过程中形成，在其长期储存过程中形成量较少。体外研究表明，GDPs损害腹膜间皮细胞的功能，包括增殖、活力和细胞因子释放。在本研究中，我们研究了GDPs对人腹膜间皮细胞（HPMC）中紧密连接相关蛋白闭锁小带蛋白1（ZO-1）表达的急性影响。还研究了GDPs诱导的血管内皮生长因子（VEGF）在ZO-1表达中的作用。
用GDPs培养HPMC，包括2-糠醛（FurA）、甲基乙二醛（M-Glx）和3,4-二脱氧葡萄糖-3-烯（3,4-DGE）。检测ZO-1的表达和VEGF的合成。为了确定VEGF在ZO-1表达调节中的作用，在有或没有VEGF中和抗体的情况下，用GDPs培养HPMC。还对GDPs诱导的VEGF合成所涉及的信号通路进行了表征。
用亚毒性浓度的GDPs（FurA、M-Glx和3,4-DGE）培养后，HPMC中ZO-1的表达呈时间和剂量依赖性下调。所有三种GDPs均增加了HPMC中VEGF的合成。外源性VEGF下调了ZO-1的表达，中和性抗VEGF抗体逆转了GDPs对HPMC中ZO-1表达的影响，表明GDPs对ZO-1表达的作用是由VEGF介导的。所有三种GDPs均激活了p42/p44丝裂原活化蛋白激酶（MAPK）和蛋白激酶C（PKC）信号转导通路。p42/p44 MAPK抑制剂（PD98059）或PKC抑制剂（星形孢菌素）均可部分降低GDPs诱导的HPMC中VEGF和转化生长因子（TGF）-β的合成。更重要的是，两种抑制剂的协同作用完全阻断了GDPs诱导的HPMC中VEGF和TGF-β的合成。
我们已经证明，短期暴露于GDPs可通过产生VEGF下调HPMC中ZO-1的表达。我们的研究提供了证据，表明GDPs可通过激活p42/44 MAPK和PKC信号转导通路直接诱导HPMC中VEGF和TGF-β的产生。
