AGE-LDL activates Toll like receptor 4 pathway and promotes inflammatory cytokines production in renal tubular epithelial cells.
OBJECTIVE
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.


METHODS
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.


RESULTS
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-κB (NF-κB). Pharmacologic inhibitor of Akt suppressed AGE-LDL-induced activation of NF-κB, but the inhibitor of JNK, p38 or ERK1/2 had no effect. Blocking MyD88, p38, JNK, Akt or NF-κB attenuated AGE-LDL-triggered IL-6 production.


CONCLUSIONS
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.
Division of Nephrology, Nanfang Hospital, Southern Medical University, Research Institute of Nephrology Guangdong Province, Key Lab for Organ Failure Research, Ministry of Education, Guangzhou, P.R. China.
Ao
A
Cheng
Yuanyuan
Y
Dong
Fengxin
F
Zhu
Youhua
Y
Liu
Fan Fan
FF
Hou
Jing
J
Nie
D002460:Cell Line; D016207:Cytokines / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism*; D017127:Glycation End Products, Advanced / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D007684:Kidney Tubules / Q000166:cytology*; D008077:Lipoproteins, LDL; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
D016207:Cytokines; D017127:Glycation End Products, Advanced; D015850:Interleukin-6; D016209:Interleukin-8; D008077:Lipoproteins, LDL; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4
AGE-LDL; IL-6.; MyD88; NF-κB; Toll like receptor