Yamashita Akiko, Soga Yoshihiko, Iwamoto Yoshihiro, Yoshizawa Sayuri, Iwata Hirotaka, Kokeguchi Susumu, Takashiba Shogo, Nishimura Fusanori
Department of Pathophysiology-Periodontal Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
Obesity (Silver Spring). 2007 Nov;15(11):2549-52. doi: 10.1038/oby.2007.305.
Recent studies suggested macrophages were integrated in adipose tissues, interacting with adipocytes, thereby exacerbating inflammatory responses. Persistent low-grade infection by gram-negative bacteria appears to promote atherogenesis. We hypothesized a ligand for toll-like receptor 4 (TLR4), bacterial lipopolysaccharide (LPS), would further exaggerate macrophage-adipocyte interaction.
RAW264.7 macrophage cell line and differentiated 3T3-L1 preadipocytes were co-cultured using transwell system. As a control, each cell was cultured independently. After incubation of the cells with or without Escherichia coli LPS, tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 production was evaluated.
Co-culture of macrophages and adipocytes with low concentration of Escherichia coli LPS (1 ng/mL) markedly up-regulated IL-6 production (nearly 100-fold higher than that of adipocyte culture alone, p < 0.01), whereas TNF-alpha production was not significantly influenced. This increase was partially inhibited by anti-TNF-alpha neutralizing antibody. Recombinant TNF-alpha and LPS synergistically up-regulated IL-6 production in adipocytes. However, this increase did not reach the level of production observed in co-cultures stimulated with LPS.
A ligand for TLR-4 stimulates macrophages to produce TNF-alpha. TNF-alpha, thus produced, cooperatively up-regulates IL-6 production with other soluble factors secreted either from adipocytes or macrophages in these cells. Markedly up-regulated IL-6 would greatly influence the pathophysiology of diabetes and its vascular complications.
近期研究表明巨噬细胞存在于脂肪组织中，与脂肪细胞相互作用，从而加剧炎症反应。革兰氏阴性菌持续的低度感染似乎会促进动脉粥样硬化的发生。我们推测Toll样受体4（TLR4）的配体——细菌脂多糖（LPS）会进一步加剧巨噬细胞与脂肪细胞的相互作用。
使用Transwell系统将RAW264.7巨噬细胞系与分化的3T3-L1前脂肪细胞共培养。作为对照，每种细胞单独培养。在用或不用大肠杆菌LPS孵育细胞后，评估肿瘤坏死因子（TNF）-α和白细胞介素（IL）-6的产生。
低浓度（1 ng/mL）的大肠杆菌LPS共培养巨噬细胞和脂肪细胞显著上调IL-6的产生（比单独的脂肪细胞培养高近100倍，p<0.01），而TNF-α的产生没有受到显著影响。这种增加被抗TNF-α中和抗体部分抑制。重组TNF-α和LPS协同上调脂肪细胞中IL-6的产生。然而，这种增加未达到LPS刺激的共培养物中观察到的产生水平。
TLR-4的配体刺激巨噬细胞产生TNF-α。由此产生的TNF-α与这些细胞中脂肪细胞或巨噬细胞分泌的其他可溶性因子协同上调IL-6的产生。显著上调的IL-6将极大地影响糖尿病及其血管并发症的病理生理学。
