Shanmugam N, Todorov I T, Nair I, Omori K, Reddy M A, Natarajan R
Gonda Diabetes Centre, Beckman Research Institute of City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA.
Diabetologia. 2006 Jan;49(1):100-7. doi: 10.1007/s00125-005-0065-7. Epub 2005 Dec 10.
AIMS/HYPOTHESIS: The cyclooxygenase-2 (PTGS2, previously known as COX2) enzyme and its products, such as prostaglandin E(2) (PGE(2)), have been implicated in the pathogenesis of several inflammatory diseases including islet dysfunction under diabetic conditions. In this study we evaluated whether diabetic conditions in vitro, such as high-glucose (HG) culture or AGE, or in vivo in animal models of diabetes can induce PTGS2 expression and activity in pancreatic islets.
Isolated human pancreatic islets were treated for 24 h with HG (25 mmol/l) or with S100b (5 mg/l), a specific ligand for the AGE-specific receptor. PTGS2 and cyclooxygenase-1 (PTGS1, previously known as COX1) mRNA, protein expression and product PGE(2) were analysed by RT-PCR, Western blots and specific enzyme immunoassay respectively. Islet PTGS2 production in animal models was assessed by immunofluorescence.
Treatment of human pancreatic islets with HG and S100b led to a three-five-fold induction of PTGS2 mRNA (p<0.001). PTGS2 protein and its product PGE(2) (351.4+/-13.05 fg/ml vs control 39.4+/-0.11 fg/ml) were also increased (p<0.001). Pretreatment with specific inhibitors demonstrated the involvement of protein kinase C and oxidant stress in S100b- and HG-induced PTGS2 expression. However, insulin secretion was not significantly altered by S100b. Double immunofluorescent staining showed increased PTGS2 production in pancreatic islets from diabetic mice relative to corresponding controls.
CONCLUSION/INTERPRETATION: These results show for the first time that diabetes as well as diabetic conditions such as AGE and HG in vitro can directly upregulate the expression of the inflammatory PTGS2 gene in pancreatic islets. This might contribute to the pathogenesis of islet dysfunction in diabetes.
目的/假设：环氧化酶-2（PTGS2，以前称为COX2）酶及其产物，如前列腺素E2（PGE2），已被认为与包括糖尿病条件下胰岛功能障碍在内的几种炎症性疾病的发病机制有关。在本研究中，我们评估了体外糖尿病条件，如高糖（HG）培养或晚期糖基化终产物（AGE），或糖尿病动物模型体内是否能诱导胰岛中PTGS2的表达和活性。
分离的人胰岛用HG（25 mmol/l）或S100b（5 mg/l，AGE特异性受体的特异性配体）处理24小时。分别通过逆转录聚合酶链反应（RT-PCR）、蛋白质免疫印迹法和特异性酶免疫测定法分析PTGS2和环氧化酶-1（PTGS1，以前称为COX1）的信使核糖核酸（mRNA）、蛋白质表达及产物PGE2。通过免疫荧光评估动物模型中胰岛PTGS2的产生。
用HG和S100b处理人胰岛导致PTGS2 mRNA诱导三到五倍（p<0.001）。PTGS2蛋白及其产物PGE2（351.4±13.05飞克/毫升对对照组39.4±0.11飞克/毫升）也增加（p<0.001）。用特异性抑制剂预处理证明蛋白激酶C和氧化应激参与S100b和HG诱导的PTGS2表达。然而，S100b并未显著改变胰岛素分泌。双重免疫荧光染色显示，与相应对照组相比，糖尿病小鼠胰岛中PTGS2的产生增加。
结论/解读：这些结果首次表明，糖尿病以及体外的AGE和HG等糖尿病条件可直接上调胰岛中炎症性PTGS2基因的表达。这可能有助于糖尿病中胰岛功能障碍的发病机制。
