Toyoda Masao, Suzuki Daisuke, Honma Masashi, Uehara Goro, Sakai Takako, Umezono Tomoya, Sakai Hideto
Division of Nephrology and Metabolism, Department of Internal Medicine, Tokai University School of Medicine, Isehara, Kanagawa, Japan.
Kidney Int. 2004 Sep;66(3):1107-14. doi: 10.1111/j.1523-1755.2004.00798.x.
Activation of protein kinase C (PKC) is a major signaling pathway for transforming growth factor (TGF)-beta to induce extracellular matrix (ECM) production in diabetic nephropathy (DN). PKC also activates mitogen-activated protein kinase (MAPK), which is called the PKC-MAPK pathway. The PKC-MAPK pathway is probably responsible for PKC-related abnormalities in diabetic glomeruli. To confirm the involvement of this pathway, we determined the localization and expression of mRNAs in glomeruli by in situ hybridization method.
In the present study, we examined expression of PKCbeta1, MAPK/ERK kinase (MEK) 1, MEK2, extracellular signal-regulated protein kinase (ERK) 1, ERK2, and TGF-beta1 mRNAs using renal tissue samples from kidneys affected by DN (N= 21) and from normal human kidney (NHK; N= 6). We also performed an immunohistochemical study using anti-phosphorylated MEK1/2 (P-MEK) and ERK1/2 (P-ERK) antibodies. The glomerular severity of DN was classified into three groups according to mesangial expansion: D1 (N= 4), D2 (N= 13), and D3 (N= 4). We analyzed differences and correlations between variables.
In the glomeruli, the number of cells that stained for these mRNAs in DN was significantly higher than in NHK. The expression of PKC-MAPK pathway mRNAs tended to be inversely proportional to the degree of mesangial expansion. The P-MEK and P-ERK signal intensity were parallel to its mRNA expression pattern. Furthermore, there were significant correlations among the P-MEK, P-ERK signal intensity, PKCbeta1 mRNA expression.
Our results suggest that high expression of PKC-MAPK pathway mRNAs plays an important role in the development and/or progression of early tissue damage in DN.
蛋白激酶C（PKC）激活是转化生长因子（TGF）-β诱导糖尿病肾病（DN）细胞外基质（ECM）产生的主要信号通路。PKC还可激活丝裂原活化蛋白激酶（MAPK），此即PKC-MAPK通路。PKC-MAPK通路可能与糖尿病肾小球中PKC相关异常有关。为证实该通路的参与情况，我们采用原位杂交法测定了肾小球中mRNA的定位和表达。
在本研究中，我们使用来自DN患者肾脏（N = 21）和正常人类肾脏（NHK；N = 6）的肾组织样本，检测了PKCβ1、MAPK/ERK激酶（MEK）1、MEK2、细胞外信号调节蛋白激酶（ERK）1、ERK2和TGF-β1 mRNA的表达。我们还使用抗磷酸化MEK1/2（P-MEK）和ERK1/2（P-ERK）抗体进行了免疫组织化学研究。根据系膜扩张情况，将DN的肾小球严重程度分为三组：D1（N = 4）、D2（N = 13）和D3（N = 4）。我们分析了变量之间的差异和相关性。
在肾小球中，DN中这些mRNA染色的细胞数量显著高于NHK。PKC-MAPK通路mRNA的表达倾向于与系膜扩张程度成反比。P-MEK和P-ERK信号强度与其mRNA表达模式平行。此外，P-MEK、P-ERK信号强度、PKCβ1 mRNA表达之间存在显著相关性。
我们的结果表明，PKC-MAPK通路mRNA的高表达在DN早期组织损伤的发生和/或进展中起重要作用。
