Adipocyte-Mononuclear Cell Interaction, Toll-like Receptor 4 Activation, and High Glucose Synergistically Up-regulate Osteopontin Expression via an Interleukin 6-mediated Mechanism
Adipocyte-Mononuclear Cell Interaction, Toll-like Receptor 4 Activation, and High Glucose Synergistically Up-regulate Osteopontin Expression via an Interleukin 6-mediated Mechanism
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DOI：
10.1074/jbc.m109.033951
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发表时间：
2010-02-05
影响因子：
4.8
通讯作者：
Huang, Yan
中科院分区：
文献类型：
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作者：
Samuvel, Devadoss J.;Sundararaj, Kamala P.;Huang, Yan
尽管已有报道骨桥蛋白，一种基质糖蛋白和促炎细胞因子，介导肥胖诱导的脂肪组织巨噬细胞浸润和胰岛素抵抗，但仍不清楚骨桥蛋白如何在肥胖的人和动物的脂肪组织中上调。在这项研究中，我们培养U937单核细胞与脂肪细胞在transwell系统，研究细胞相互作用如何调节骨桥蛋白的表达。结果表明，与U937细胞的独立培养物相比，U937细胞与脂肪细胞的共培养导致骨桥蛋白的产生显着增加。此外，脂多糖或棕榈酸诱导的TLR 4活化和高糖进一步增强了共培养刺激的骨桥蛋白分泌。在人原代单核细胞和脂肪细胞的共培养物中进行了类似的观察。真实的时间PCR研究显示，U937细胞和脂肪细胞的共培养增加了U937细胞中的骨桥蛋白mRNA，但不增加脂肪细胞中的骨桥蛋白mRNA，这表明脂肪细胞衍生的可溶性因子可能刺激U937细胞的骨桥蛋白表达。在我们的研究中，我们发现针对白细胞介素（IL）-6或IL-6小干扰RNA转染脂肪细胞的中和抗体有效地抑制了共培养刺激的骨桥蛋白表达，这表明脂肪细胞释放的IL-6在共培养刺激的U937细胞骨桥蛋白表达中起着重要作用。总之，本研究表明，细胞相互作用，TLR 4激活，高糖上调骨桥蛋白的表达，脂肪细胞来源的IL-6在上调中发挥了重要作用。
Although it has been reported that osteopontin, a matrix glycoprotein and proinflammatory cytokine, mediates obesity-induced adipose tissue macrophage infiltration and insulin resistance, it remains unclear how osteopontin is up-regulated in adipose tissue in obese humans and animals. In this study, we incubated U937 mononuclear cells with adipocytes in a transwell system and studied how cell interaction regulated osteopontin expression. Results showed that coculture of U937 cells with adipocytes led to a marked increase in osteopontin production when compared with that released by independent cultures of U937 cells. Moreover, lipopolysaccharide or palmitic acid-induced TLR4 activation and high glucose further augmented the coculture-stimulated osteopontin secretion. Similar observations were made in the coculture of human primary monocytes and adipocytes. Real time PCR studies showed that coculture of U937 cells and adipocytes increased osteopontin mRNA in U937 cells, but not adipocytes, suggesting that adipocyte-derived soluble factor may stimulate osteopontin expression by U937 cells. In our studies to explore the underlying mechanism, we found that the neutralizing antibodies against interleukin (IL)-6 or IL-6 small interfering RNA transfection in adipocytes effectively inhibited coculture-stimulated osteopontin expression, suggesting that IL-6 released by adipocytes plays an essential role in the coculture-stimulated osteopontin expression by U937 cells. In conclusion, this study has demonstrated that cell interaction, TLR4 activation, and high glucose up-regulate osteopontin expression, and adipocyte-derived IL-6 played a major role in the up-regulation.