最近，國(guó)際學(xué)術(shù)期刊Diabetologia在線發(fā)表了中科院上海生命科學(xué)研究院營(yíng)養(yǎng)所樂(lè)穎影研究組的最新研究成果：TNF-α acutely upregulates amylin expression in murine pancreatic beta cells。這項(xiàng)工作主要由博士生蔡坤等在樂(lè)穎影研究員的指導(dǎo)下完成。

胰淀素(amylin)，又稱(chēng)胰島淀粉樣多肽(islet amyloid polypeptide)，最初是從2型糖尿病病人的胰島淀粉樣沉淀中分離發(fā)現(xiàn)的。胰淀素主要由胰島β細(xì)胞合成和分泌，具有控制食欲、抑制胃排空、抑制胰島素分泌等生理功能。離體和整體實(shí)驗(yàn)表明，胰淀素能誘導(dǎo)胰島素抵抗、促進(jìn)胰島b細(xì)胞凋亡，參與2型糖尿病的發(fā)生發(fā)展。近年來(lái)發(fā)現(xiàn)在急性胰腺炎、胰腺移植后發(fā)生排斥的病人、肥胖癥和胰島素抵抗癥患者，血漿胰淀素水平顯著升高，但其原因及機(jī)制尚不清楚。

炎性細(xì)胞因子（如TNF-α、MCP-1等）在上述疾病的胰腺組織或血循環(huán)中顯著升高，它們不僅在急性胰腺炎和移植排斥中發(fā)揮重要作用，還參與胰島素抵抗和糖尿病的發(fā)生發(fā)展。蔡坤等利用小鼠胰島b細(xì)胞株MIN6和原代培養(yǎng)小鼠胰島，研究了炎性細(xì)胞因子對(duì)胰淀素表達(dá)的影響。研究發(fā)現(xiàn)，TNF-α能夠顯著上調(diào)胰淀素基因的表達(dá)，這種調(diào)節(jié)作用呈時(shí)間和濃度依賴(lài)性。TNF-α還能促進(jìn)胰淀素蛋白的合成，主要以胰淀素前體蛋白及其酶切中間產(chǎn)物為主。通過(guò)生化和分子生物學(xué)的多種研究手段，他們進(jìn)一步探討了TNF-α發(fā)揮調(diào)節(jié)作用的機(jī)制，發(fā)現(xiàn)TNF-α通過(guò)PKCζ-ERK1/2/JNK-AP1和PI3K-NF-κB相關(guān)信號(hào)通路上調(diào)胰淀素基因的表達(dá)。

炎性細(xì)胞因子TNF-α對(duì)胰淀素表達(dá)的上調(diào)作用及分子機(jī)制

此外還發(fā)現(xiàn)，TNF-α能顯著增強(qiáng)人胰淀素基因啟動(dòng)子的活性，且這種調(diào)節(jié)作用由AP1和NF-κB介導(dǎo)，說(shuō)明人胰淀素基因的表達(dá)和小鼠胰淀素基因一樣受TNF-α調(diào)節(jié)。這些結(jié)果提示在胰腺急性炎癥相關(guān)疾病中，炎性細(xì)胞因子除直接發(fā)揮作用外，還可能通過(guò)誘導(dǎo)胰淀素表達(dá)而促進(jìn)疾病的發(fā)展，為進(jìn)一步探討胰淀素的病理作用提供了新的線索。

此項(xiàng)工作得到國(guó)家科技部和上海市科委經(jīng)費(fèi)資助。

推薦原文出處：

Diabetologia  DOI 10.1007/s00125-010-1972-9

TNF-α acutely upregulates amylin expression in murine pancreatic beta cells.

Cai K, Qi D, Wang O, Chen J, Liu X, Deng B, Qian L, Liu X, Le Y.

Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, and the Graduate School of the Chinese Academy of Sciences, Shanghai, People's Republic of China.

Abstract

AIMS/HYPOTHESIS: Amylin, a secretory protein mainly produced by pancreatic beta cells, is elevated in the circulation of patients with diseases related to acute and chronic inflammation, including acute pancreatitis, pancreas graft rejection, obesity and insulin resistance. TNF-α is involved in these disorders. We investigated the effect of TNF-α on amylin levels and the underlying mechanisms, using murine pancreatic beta cell line MIN6 and pancreatic islets.

METHODS: Amylin, proinsulin and prohormone convertase 1/3, 2 (Pc1/3, Pc2 [also known as Pcsk1/3 and Pcsk2, respectively]) mRNA levels, and amylin promoter and nuclear factor κB (NF-κB) activation were examined by real-time PCR and luciferase reporter assay, respectively. Amylin protein level and mitogen-activated protein kinase phosphorylation were detected by western blot. Activator protein 1 (AP1) activation was examined by electrophoretic mobility shift assay (EMSA).

RESULTS: TNF-α acutely induced amylin expression at the transcriptional level and increased proamylin and the intermediate form of amylin in MIN6 cells and islets. However, it had no effect on proinsulin, Pc1/3 and Pc2 expression. Studies with (1) MIN6 cells treated with inhibitors of MEK1/2, c-Jun-N-terminal kinase (JNK) or protein kinase Cζ [Formula: see text], (2) MIN6 cells expressing a c-Jun-dominant negative construct and (3) islets from Fos knockout mice demonstrated that TNF-α induced amylin expression through the [Formula: see text] signal-regulated kinase (ERK)/JNK pathways. EMSA showed that [Formula: see text], JNK and ERK1/2 were involved in TNF-α-induced AP1 activation, suggesting that TNF-α induces murine amylin expression through the [Formula: see text] and [Formula: see text] pathways. Further studies showed that TNF-α also induced murine amylin expression through the phosphatidylinositol 3 kinase-NF-κB signalling pathway and enhanced human amylin promoter activation through NF-κB and AP1.

CONCLUSIONS/INTERPRETATION: TNF-α acutely induces amylin gene expression in beta cells through multiple signalling pathways, possibly contributing to amylin elevation in acute inflammation-related pancreatic disorders.

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