Effects of interleukin 18 on injury and activation of human proximal tubular epithelial cells.
OBJECTIVE
Injury and activation of tubular proximal epithelial cells (TEC) play central roles in renal tubulointerstitial fibrosis (TIF), but its mechanisms remain obscure. Interleukin 18 (IL-18) is overproduced during chronic kidney diseases (CKD), but how IL-18 affects the biological behaviour of TEC is not clear. The aim of the present study is to reveal the role of IL-18 in renal TIF.


METHODS
The expressions of IL-18 and IL-18 receptor in TEC were detected by immunohistochemical staining in vivo and by reverse transcriptase polymerase chain reaction (RT-PCR) in vitro. TEC line (HK-2 cells) were incubated without or with IL-18. Cell proliferation and cell cycle were evaluated by methyl thiazolyl tetrazolium assay and flow cytometric analysis, respectively. Cell apoptosis was assessed by Hoechst 33258 staining. Expression of alpha-smooth muscle actin was evaluated by RT-PCR, immunocytochemical staining and flow cytometric analysis, respectively. Type I collagen, fibronectin, MCP-1 and RANTES in cultured supernatants were measured by enzyme-linked immunosorbent assay.


RESULTS
IL-18 expression in TEC increased significantly in CKD state. IL-18 receptor was constitutively expressed in normal proximal TEC, and its expression increased strongly in CKD state. Proliferation and cell cycle of HK-2 cells were not affected by IL-18. Cell apoptosis, alpha-smooth muscle actin expression, type I collagen and fibronectin production as well as MCP-1 secretion were promoted by IL-18 in dosage- and/or time-dependent manners, but RANTES secretion was not affected.


CONCLUSIONS
IL-18 may play a crucial role in the process of TIF by promoting TEC injury and activation, and could be a target of the therapeutic approaches against TIF.
Liang
Dong
D
Institute of Nephrology, Guangdong Medical College, Zhanjiang, Guangdong, China.
Liu
Hua-Feng
HF
Yao
Cui-Wei
CW
Liu
Hai-Yan
HY
Huang-Fu
Chang-Mei
CM
Chen
Xiang-Wen
XW
Du
Shen-Hua
SH
Chen
Xiao-Wen
XW
D002453:Cell Cycle; D002460:Cell Line; D018932:Chemokine CCL2 / Q000032:analysis; D018946:Chemokine CCL5 / Q000032:analysis; D024042:Collagen Type I / Q000032:analysis; D003470:Culture Media / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005353:Fibronectins / Q000032:analysis; D006801:Humans; D007150:Immunohistochemistry; D020382:Interleukin-18 / Q000378:metabolism* / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D012333:RNA, Messenger / Q000032:analysis; D053724:Receptors, Interleukin-18 / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
C111835:CCL2 protein, human; D018932:Chemokine CCL2; D018946:Chemokine CCL5; D024042:Collagen Type I; D003470:Culture Media; D005353:Fibronectins; D020382:Interleukin-18; D012333:RNA, Messenger; D053724:Receptors, Interleukin-18