Involvement of 90-kuD ribosomal S6 kinase in collagen type I expression in rat hepatic fibrosis.
OBJECTIVE
To investigate the relationship between 90-kuD ribosomal S6 kinase (p90RSK) and collagen type I expression during the development of hepatic fibrosis in vivo and in vitro.


METHODS
Rat hepatic fibrosis was induced by intraperitoneal injection of dimethylnitrosamine. The protein expression and cell location of p90RSK and their relationship with collagen type I were determined by co-immunofluoresence and confocal microscopy. Subsequently, RNAi strategy was employed to silence p90RSK mRNA expression in HSC-T6, an activated hepatic stellate cell (HSC) line. The expression of collagen type I in HSC-T6 cells was assessed by Western blotting and real-time polymerase chain reaction. Furthermore, HSCs were transfected with expression vectors or RNAi constructs of p90RSK to increase or decrease the p90RSK expression, then collagen type I promoter activity in the transfected HSCs was examined by reporter assay. Lastly HSC-T6 cells transfected with p90RSK siRNA was treated with or without platelet-derived growth factor (PDGF)-BB at a final concentration of 20 microg/L and the cell growth was determined by MTS conversion.


RESULTS
In fibrotic liver tissues, p90RSK was over-expressed in activated HSCs and had a significant positive correlation with collagen type I levels. In HSC-T6 cells transfected with RNAi targeted to p90RSK, the expression of collagen type I was down-regulated (61.8% in mRNA, P < 0.01, 89.1% in protein, P < 0.01). However, collagen type I promoter activity was not increased with over-expression of p90RSK and not decreased with low expression either, compared with controls in the same cell line (P = 0.076). Furthermore, p90RSK siRNA exerted the inhibition of HSC proliferation, and also abolished the effect of PDGF on the HSC proliferation.


CONCLUSIONS
p90RSK is over-expressed in activated HSCs and involved in regulating the abnormal expression of collagen type I through initiating the proliferation of HSCs.
Yang
Miao-Fang
MF
Department of Gastroenterology, Jinling Hospital, Second Military Medical University, Zhongshan East Road 305, Nanjing 210002, Jiangsu Province, China.
Xie
Jun
J
Gu
Xiao-Yi
XY
Zhang
Xiao-Hua
XH
Davey
Andrew-K
AK
Zhang
Shuang-Jie
SJ
Wang
Ji-Ping
JP
Zhu
Ren-Min
RM
D000818:Animals; D049109:Cell Proliferation; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism*; D004128:Dimethylnitrosamine / Q000008:administration & dosage / Q000633:toxicity; D055166:Hepatic Stellate Cells / Q000166:cytology / Q000502:physiology; D008103:Liver Cirrhosis / Q000378:metabolism*; D008297:Male; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000235:genetics / Q000378:metabolism*
D024042:Collagen Type I; D034741:RNA, Small Interfering; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D004128:Dimethylnitrosamine