Division of Endocrinology and Metabolism, Chang Gung Memorial Hospital, Chiayi, Taiwan.
Am J Med Sci. 2012 Nov;344(5):374-82. doi: 10.1097/MAJ.0b013e31824369c5.
Although diabetic nephropathy is attributable to transforming growth factor-β1 (TGF-β1) overproduction in glomer-ular mesangial cells, the biological role of Wnt/β-catenin signaling in controlling high glucose-induced TGF-β1 has not yet been elucidated.
This study found that sustained Wnt/β-catenin signaling was required to protect glomerular mesangial cells from high glucose induction of TGF-β1-mediated fibrosis using in vitro and in vivo diabetic models.
High glucose down-regulated the Wnt signaling associated with increased TGF-β1 and fibronectin messenger RNA expression in glomerular mesangial cells. Restoring Wnt4, Wnt5a and cytosolic β-catenin levels by transfecting Wnt4, Wnt5a and stable β-catenin alleviated the stimulatory effect of high glucose on c-Jun mediated TGF-β1 fibrosis. Transfection of kinase-active glycogen synthase kinase-3β (GSK-3β) also abrogated high glucose promotion of nuclear c-Jun levels, TGF-β1 and fibronectin messenger RNA expression in mesangial cells. Pharmacological modulation of GSK-3ββ and ββ-catenin signaling by recombinant Wnt5a or GSK-3β inhibitor (BIO or LiCl) suppressed high glucose promotion of TGF-β1-mediated fibrosis. Exogenous BIO and SB216763 alleviated TGF-β1-mediated fibrogenic expression in the kidneys of diabetic rats. Immunohistochemistry showed that GSK-3β inhibitor significantly reversed the diabetic attenuation of TGF-β1 and c-Jun coinciding with fibronectin immunoreactivity within glomeruli. Immunofluorescence demonstrated that cells within the glomeruli restored β-catenin expression after BIO and SB216763 treatment in cells within diabetic glomeruli colocalized with fragmented nuclei by 4',6-diamidino-2-phenylindole staining.
Sustained Wnt signaling reduced c-Jun-dependent TGF-β1-mediated fibronectin accumulation in mesangial cells. These findings suggest that modulation of Wnt signaling is a viable alternative strategy to rescue the TGF-β1-mediated fibrotic signaling pathway in diabetic renal injury.
尽管糖尿病肾病归因于肾小球系膜细胞中转化生长因子-β1（TGF-β1）的过度产生，但 Wnt/β-catenin 信号在控制高糖诱导的 TGF-β1 中的生物学作用尚未阐明。
本研究发现，在体外和体内糖尿病模型中，持续的 Wnt/β-catenin 信号对于保护肾小球系膜细胞免受高糖诱导的 TGF-β1 介导的纤维化是必需的。
高糖下调与肾小球系膜细胞中 TGF-β1 和纤维连接蛋白信使 RNA 表达增加相关的 Wnt 信号。通过转染 Wnt4、Wnt5a 和稳定的β-catenin 来恢复 Wnt4、Wnt5a 和胞质β-catenin 水平，减轻了高糖对 c-Jun 介导的 TGF-β1 纤维化的刺激作用。转染激酶活性糖原合酶激酶-3β（GSK-3β）也可消除高糖对核 c-Jun 水平、TGF-β1 和纤维连接蛋白信使 RNA 在系膜细胞中表达的促进作用。重组 Wnt5a 或 GSK-3β 抑制剂（BIO 或 LiCl）对 GSK-3ββ 和ββ-catenin 信号的药理学调节抑制了高糖对 TGF-β1 介导的纤维化的促进作用。外源性 BIO 和 SB216763 减轻了糖尿病大鼠肾脏中 TGF-β1 介导的纤维生成表达。免疫组织化学显示，GSK-3β 抑制剂显著逆转了糖尿病对 TGF-β1 和 c-Jun 的减弱作用，同时与肾小球内纤维连接蛋白免疫反应性相吻合。免疫荧光显示，在 BIO 和 SB216763 处理后，糖尿病肾小球内的细胞恢复了β-catenin 表达，4'，6-二脒基-2-苯基吲哚染色显示细胞内的核碎片。
持续的 Wnt 信号降低了 c-Jun 依赖性 TGF-β1 介导的纤维连接蛋白在系膜细胞中的积累。这些发现表明，调节 Wnt 信号是挽救糖尿病肾损伤中 TGF-β1 介导的纤维化信号通路的一种可行的替代策略。
