Original Articles
Copyright ©2009 The WJG Press and Baishideng. All rights reserved.
World J Gastroenterol. May 7, 2009; 15(17): 2109-2115
Published online May 7, 2009. doi: 10.3748/wjg.15.2109
Involvement of 90-kuD ribosomal S6 kinase in collagen type I expression in rat hepatic fibrosis
Miao-Fang Yang, Jun Xie, Xiao-Yi Gu, Xiao-Hua Zhang, Andrew K Davey, Shuang-Jie Zhang, Ji-Ping Wang, Ren-Min Zhu
Miao-Fang Yang, Jun Xie, Xiao-Hua Zhang, Ren-Min Zhu, Department of Gastroenterology, Jinling Hospital, Second Military Medical University, Nanjing 210002, Jiangsu Province, China
Xiao-Yi Gu, Department of Oncology, Zhongda Hospital, Medical School of Southeast University, Nanjing 210009, Jiangsu Province, China
Andrew K Davey, Shuang-Jie Zhang, Ji-Ping Wang, Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA 5000, Australia
Author contributions: Yang MF and Xie J performed the majority of experiments, wrote the manuscript, and contributed equally to this work; Gu XY provided vital reagents; Zhang XH provided technical support for this work; Davey AK, Zhang SJ and Wang JP provided analytical tools and also involved in editing the manuscript; Zhu RM designed the study.
Correspondence to: Ren-Min Zhu, Professor, Department of Gastroenterology, Jinling Hospital, Second Military Medical University, Zhongshan East Road 305, Nanjing 210002, Jiangsu Province, China. renminzhu@hotmail.com
Telephone: +86-25-81615950
Fax: +86-25-84212954
Received: January 23, 2009
Revised: March 24, 2009
Accepted: March 31, 2009
Published online: May 7, 2009

AIM: 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 &mgr;g/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.

CONCLUSION: p90RSK is over-expressed in activated HSCs and involved in regulating the abnormal expression of collagen type I through initiating the proliferation of HSCs.

Keywords: 90-kuD ribosomal S6 kinase, Collagen type I, Hepatic fibrosis, Hepatic stellate cell, RNAi