Saurus Pauliina, Kuusela Sara, Dumont Vincent, Lehtonen Eero, Fogarty Christopher L, Lassenius Mariann I, Forsblom Carol, Lehto Markku, Saleem Moin A, Groop Per-Henrik, Lehtonen Sanna
Department of Pathology, University of Helsinki, 00290 Helsinki, Finland.
Laboratory Animal Centre, University of Helsinki, 00290 Helsinki Finland.
Sci Rep. 2016 Feb 15;6:21664. doi: 10.1038/srep21664.
Loss of podocytes is an early feature of diabetic nephropathy (DN) and predicts its progression. We found that treatment of podocytes with sera from normoalbuminuric type 1 diabetes patients with high lipopolysaccharide (LPS) activity, known to predict progression of DN, downregulated CDK2 (cyclin-dependent kinase 2). LPS-treatment of mice also reduced CDK2 expression. LPS-induced downregulation of CDK2 was prevented in vitro and in vivo by inhibiting the Toll-like receptor (TLR) pathway using immunomodulatory agent GIT27. We also observed that CDK2 is downregulated in the glomeruli of obese Zucker rats before the onset of proteinuria. Knockdown of CDK2, or inhibiting its activity with roscovitine in podocytes increased apoptosis. CDK2 knockdown also reduced expression of PDK1, an activator of the cell survival kinase Akt, and reduced Akt phosphorylation. This suggests that CDK2 regulates the activity of the cell survival pathway via PDK1. Furthermore, PDK1 knockdown reduced the expression of CDK2 suggesting a regulatory loop between CDK2 and PDK1. Collectively, our data show that CDK2 protects podocytes from apoptosis and that reduced expression of CDK2 associates with the development of DN. Preventing downregulation of CDK2 by blocking the TLR pathway with GIT27 may provide a means to prevent podocyte apoptosis and progression of DN.
足细胞丢失是糖尿病肾病(DN)的早期特征,并可预测其进展。我们发现,用已知可预测DN进展的高脂多糖(LPS)活性的正常白蛋白尿1型糖尿病患者血清处理足细胞,会下调细胞周期蛋白依赖性激酶2(CDK2)。LPS处理小鼠也会降低CDK2表达。使用免疫调节剂GIT27抑制Toll样受体(TLR)途径可在体外和体内阻止LPS诱导的CDK2下调。我们还观察到,在肥胖Zucker大鼠出现蛋白尿之前,其肾小球中的CDK2就已下调。在足细胞中敲低CDK2或用roscovitine抑制其活性会增加细胞凋亡。敲低CDK2还会降低细胞存活激酶Akt的激活剂PDK1的表达,并降低Akt磷酸化。这表明CDK2通过PDK1调节细胞存活途径的活性。此外,敲低PDK1会降低CDK2的表达,提示CDK2与PDK1之间存在调节环。总体而言,我们的数据表明CDK2可保护足细胞免于凋亡,且CDK2表达降低与DN的发展相关。用GIT27阻断TLR途径以防止CDK2下调可能提供一种预防足细胞凋亡和DN进展的方法。
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