Eun Chang Soo, Han Dong Soo, Lee Seung Hyun, Paik Chang Hee, Chung Yong Woo, Lee Jin, Hahm Joon Soo
Department of Internal Medicine, Hallym University College of Medicine, Seoul, Korea.
Dig Dis Sci. 2006 Apr;51(4):693-7. doi: 10.1007/s10620-006-3193-0.
The peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor highly expressed in the colon and playing an anti-inflammatory role through inhibition of the NF-kappaB pathway. Toll-like receptor 4 (TLR4) has been known to mediate LPS-induced cellular signaling through activation of NF-kappaB pathway in intestinal epithelial cells. The aims of this study were to evaluate attenuation of inflammation by PPARgamma in intestinal epithelial cells and to study the possible relation between PPARgamma and TLR4. HT-29 human epithelial cells were stimulated with LPS (20 microg/ml) and PPARgamma ligand, 15d-PGJ2 (10 microM), or with LPS (20 microg/ml) alone for 24 hr. COX-2, IL-8, TLR4, and PPARgamma mRNA expression was assessed by RT-PCR. IL-8 protein levels and TLR4 protein expression were analyzed by ELISA and Western blot, respectively. To evaluate the action mechanisms of PPARgamma ligand, Western blot analysis for IkappaBalpha degradation was performed. Costimulation with LPS and PPARgamma ligand in comparison to LPS stimulation alone (1) decreased COX-2, IL-8 mRNA expression and IL-8 protein secretion, (2) decreased TLR4 mRNA and protein expression, and (3) decreased PPARgamma mRNA expression. PPARgamma ligand delayed LPS-induced IkappaBalpha degradation. These findings suggest that PPAR-gamma ligands suppress inflammation in intestinal epithelial cells. PPARgamma and TLR, these two antagonistic signaling pathways in intestinal epithelial cells may be partially cross-linked.
过氧化物酶体增殖物激活受体γ（PPARγ）是一种在结肠中高度表达的核受体，通过抑制核因子κB（NF-κB）途径发挥抗炎作用。已知Toll样受体4（TLR4）通过激活肠上皮细胞中的NF-κB途径介导脂多糖（LPS）诱导的细胞信号传导。本研究的目的是评估PPARγ在肠上皮细胞中对炎症的减轻作用，并研究PPARγ与TLR4之间可能的关系。用LPS（20微克/毫升）和PPARγ配体15d-前列腺素J2（10微摩尔）或单独用LPS（20微克/毫升）刺激HT-29人上皮细胞24小时。通过逆转录聚合酶链反应（RT-PCR）评估环氧化酶-2（COX-2）、白细胞介素-8（IL-8）、TLR4和PPARγ的信使核糖核酸（mRNA）表达。分别通过酶联免疫吸附测定（ELISA）和蛋白质印迹法分析IL-8蛋白水平和TLR4蛋白表达。为了评估PPARγ配体的作用机制，进行了IkappaBα降解的蛋白质印迹分析。与单独的LPS刺激相比，LPS和PPARγ配体共同刺激（1）降低了COX-2、IL-8 mRNA表达和IL-8蛋白分泌，（2）降低了TLR4 mRNA和蛋白表达，（3）降低了PPARγ mRNA表达。PPARγ配体延迟了LPS诱导的IkappaBα降解。这些发现表明PPAR-γ配体抑制肠上皮细胞中的炎症。PPARγ和TLR这两条在肠上皮细胞中相互拮抗的信号通路可能部分交联。
