Attenuation of colonic inflammation by PPARgamma in intestinal epithelial cells: effect on Toll-like receptor pathway.
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.
Eun
Chang Soo
CS
Department of Internal Medicine, Hallym University College of Medicine, Seoul, Korea.
Han
Dong Soo
DS
Lee
Seung Hyun
SH
Paik
Chang Hee
CH
Chung
Yong Woo
YW
Lee
Jin
J
Hahm
Joon Soo
JS
D015153:Blotting, Western; D002478:Cells, Cultured; D003092:Colitis / Q000503:physiopathology; D051546:Cyclooxygenase 2 / Q000032:analysis / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects; D019073:HT29 Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D016209:Interleukin-8 / Q000032:analysis / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D047495:PPAR gamma / Q000187:drug effects / Q000378:metabolism*; D011336:Probability; D012313:RNA / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000187:drug effects; D051193:Toll-Like Receptors / Q000187:drug effects / Q000378:metabolism*
D016209:Interleukin-8; D008070:Lipopolysaccharides; D047495:PPAR gamma; D051193:Toll-Like Receptors; D012313:RNA; D051546:Cyclooxygenase 2