AGE-LDL Activates Toll Like Receptor 4 Pathway and Promotes Inflammatory Cytokines Production in Renal Tubular Epithelial Cells

• Main Author: Ao Cheng, Yuanyuan Dong, Fengxin Zhu, Youhua Liu, Fan Fan Hou, Jing Nie
• Format: Article
• Language: English
• Published: Ivyspring International Publisher 2013-01-01
• Series: International Journal of Biological Sciences
• Online Access: http://www.biolsci.org/v09p0094.htm

<p><b><i>Background/Aims:</i> </b>Accumulation of advanced glycation end-products, the well-recognized pro-inflammatory molecules, has been detected in renal tissues including tubules. The aim of the present study was to investigate the role of advanced glycation end-products modified low density lipoprotein (AGE-LDL) in inflammatory cytokines production in human proximal tubular epithelial cells and the underlying mechanism. <b><i>Methods: </i></b>The Interleukin-6 (IL-6) and Interleukin-8 (IL-8) production was examined by real-time PCR and ELISA. The expression of Toll-like receptor 2 and 4 (TLR2/4) was detected by flow cytometry and western blot. The interaction of TLR2/4 with AGE-LDL was examined by co-immunoprecipitation assay. The involvement of MyD88 and the downstream molecules in inflammatory cytokines production was examined by siRNA and pharmacologic inhibitors, respectively. <b><i>Results: </i></b>AGE-LDL interacted with TLR2 and TLR4. TLR4 siRNA showed stronger inhibition on AGE-LDL-induced IL-6 and IL-8 production than that of TLR2 siRNA. Silencing MyD88, but not TRIF, inhibited AGE-LDL-induced IL-6 and IL-8 production. AGE-LDL stimulation led to phosphorylation of JNK, p38, Akt and the p65 subunit of nuclear factor-&#954;B (NF-&#954;B). Pharmacologic inhibitor of Akt suppressed AGE-LDL-induced activation of NF-&#954;B, but the inhibitor of JNK, p38 or ERK1/2 had no effect. Blocking MyD88, p38, JNK, Akt or NF-&#954;B attenuated AGE-LDL-triggered IL-6 production. <b><i>Conclusion:</i></b> AGE-LDL induced IL-6 and IL-8 production via TLR2/4-MyD88-dependent pathway in tubular epithelial cells. These data suggest that activation of TLRs signaling in tubular epithelial cells by AGE-LDL might be a novel mechanism for the tubulointerstitial inflammation.</p>