C5a and toll-like receptor 4 crosstalk in retinal pigment epithelial cells.
OBJECTIVE
To investigate the effect of the complement activation product C5a on toll-like receptor (TLR) 4-induced responses in RPE cells.


METHODS
Conﬂuent cultures of human RPE cells (ARPE-19) were stimulated with C5a, lipopolysaccharide (LPS), or a combination of the two. The expression of TLR4 was determined by real-time PCR and flow cytometry. Cytokine proﬁles were determined by real-time PCR and enzyme-linked immunosorbent assay (ELISA). The phosphorylation of p38, ERK 1/2, and JNK was measured by flow cytometry.


RESULTS
C5a stimulation enhanced the expression of TLR4 in a dose- and time-dependent manner. C5a was able to stimulate the production of TLR4-induced IL-6 and IL-8 by ARPE-19 cells. Blocking experiments showed that the effect of C5a on cytokine production was mediated via C5aR. ERK1/2, but not JNK or p38, were involved in the production of IL-6 and IL-8.


CONCLUSIONS
The results indicate that C5a can induce the TLR4 expression and enhance the production of TLR4-induced IL-6 and IL-8 by ARPE-19. The effect of C5a on cytokine production was mediated by C5aR and the phosphorylation of ERK1/2.
The People's Hospital of Kai County, Chongqing, China.
Yi
Y
Zhu
The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Ophthalmology, Chongqing Eye Institute, Chongqing, China.
Bingling
B
Dai
Chongqing Medical University, Chongqing, China.
Yongguo
Y
Li
The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Ophthalmology, Chongqing Eye Institute, Chongqing, China.
Hui
H
Peng
D002460:Cell Line; D015936:Complement C5a / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000276:immunology; D016209:Interleukin-8 / Q000235:genetics / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000276:immunology; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000276:immunology; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000276:immunology; D010766:Phosphorylation; D044087:Receptor, Anaphylatoxin C5a / Q000235:genetics / Q000276:immunology; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000235:genetics* / Q000276:immunology; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000276:immunology
C488033:C5AR1 protein, human; D004338:Drug Combinations; C508600:IL6 protein, human; D015850:Interleukin-6; D016209:Interleukin-8; D008070:Lipopolysaccharides; D044087:Receptor, Anaphylatoxin C5a; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D015936:Complement C5a; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4