C-reactive protein induces interleukin-6 and thrombospondin-1 protein and mRNA expression through activation of nuclear factor-ĸB in HK-2 cells.
BACKGROUND
Although C-reactive protein (CRP) is significantly increased in patients with diabetic nephropathy, whether CRP exerts direct proinflammatory effects on human renal tubular epithelial cells (HK-2 cells) is still unclear.


METHODS
HK-2 cells were incubated with purified CRP at clinically relevant concentrations (0, 5, 10, 20 and 40 μg/ml). The protein and transcript levels of thrombospondin-1 (TSP-1) and interleukin-6 (IL-6) were determined by ELISA and RT-PCR. Phosphorylation of p38MAPK was investigated through Western blot analysis in HK-2 cells induced by CRP. The activation of nuclear factor-kappa B (NF-κB) was studied via EMSA. A specific p38MAPK inhibitor (SB203580) and an NF-κB inhibitor (PDTC; pyrrolidine dithiocarbamate) were used to analyze the signal transduction in CRP induction. To explore the direct or indirect role of CRP in HK-2 cells, IL-6 or TSP-1 antibodies were used. The expression of IL-6, TSP-1 and transforming growth factor-β(1 )(TGF-β(1)) were determined through Western blot analysis in HK-2 cells.


RESULTS
In HK-2 cells, purified CRP significantly induced protein release and mRNA expression of IL-6 and TSP-1 in a dose- and time-dependent manner. TGF-β(1) protein was overexpressed in HK-2 cells induced by CRP, which cannot be inhibited by IL-6 or TSP-1 antibodies. CRP triggered phosphorylation of p38MAPK and activation of NF-κB-mediated signal transduction. SB203580 (5 μM) and PDTC (50 μM) efficiently suppressed those effects of CRP in HK-2 cells.


CONCLUSIONS
CRP induces IL-6 and TSP-1 protein release and mRNA expression from HK-2 cells via activation of the p38MAPK and NF-κB signaling pathways and TGF-β(1) was highly expressed in HK-2 cells, suggesting that CRP plays an important role in the propagation and prolongation of inflammation in renal fibrosis.
Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, People's Republic of China. wanghai2192@sina.com
Hai-rong
HR
Wang
De-liang
DL
Chen
Mingming
M
Zhao
Shao-wu
SW
Shu
Shi-xi
SX
Xiong
Xue-dong
XD
Gan
Sheng-ping
SP
Chao
Jian-lei
JL
Cao
D002097:C-Reactive Protein / Q000494:pharmacology* / Q000502:physiology; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis*; D016328:NF-kappa B / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis*; D019700:Thrombospondin 1 / Q000096:biosynthesis*
C508600:IL6 protein, human; D015850:Interleukin-6; D016328:NF-kappa B; D012333:RNA, Messenger; D019700:Thrombospondin 1; D002097:C-Reactive Protein