[Aldosterone stimulates alpha1-(1) procollagen mRNA expression in HSC via activation of ERK1/2 and AP-1].
OBJECTIVE
It has been known that the intrahepatic renin-angiotensin-aldosterone system (RAAS) plays a key role in the fibrogenesis in livers. Aldosterone (Aldo), the principal effector molecule of the RAAS, exerts local effects on cell growth and fibrogenesis. However, the signal transduction mechanisms underlying the effects of Aldo on hepatic fibrogenesis remain to be fully elucidated. The present study aims to investigate the signal transduction mechanism underlying the effects of Aldo on the signal passageway of active protein-1 (AP-1).


METHODS
In vitro, HSCs-T6 cell line was treated with Aldo for 10 min, 30 min, 60 min, 120 min and 180 min, and protein expression of Phospho-P42/44 was detected by Western blot. In addition, HSCs-T6 cell line was preincubated for 60 min or not with U0126 (an inhibitor of the MAPK/ERK kinase), and also with antioxidant-N-acetylcysteine (NAC) prior to exposure to Aldo for the indicated times. Protein expression of Phospho-P42/44 was measured by Western blot. DNA biding activity of AP-1 was analyzed by electrophoretic gel mobility shift assay (EMSA). By means of RT-PCR, expression of alpha1(1) procollagen mRNA was detected.


RESULTS
Aldo stimulated HSC via extracellular signal-regulated kinase (ERK1/2) pathway. Time course experiments showed that Aldo induced Phospho-P42/44 expression, which was abrogated by U0126, reaching a maximum at 10 minutes, and then declined progressively. NAC inhibited the Phospho-P42/44 expression. EMSA showed that stimulation of HSC by Aldo markedly increased AP-1 DNA binding activity. U0126 markedly reduced AP-1 DNA binding activity induced by Aldo; NAC partly decreased AP-1 activity induced by Aldo. Aldo up-regulated expression of alpha1(1) procollagen mRNA, which was attenuated by U0126 and NAC.


CONCLUSIONS
Stimulation of HSC by Aldo results in activation of AP-1 via ERK1/2 pathway, leading to up-regulation of AP-1 target gene alpha1(1) procollagen mRNA expression.
Li
Xu
X
Emergency Department, Nanfang Hospital, Nanfang Medical University, Guangzhou 510515, China. mylx99@163.com
Meng
Ying
Y
Cai
Shao-xi
SX
Yang
Xi-shan
XS
Wu
Ping-sheng
PS
D000450:Aldosterone / Q000494:pharmacology*; D002460:Cell Line; D024042:Collagen Type I / Q000096:biosynthesis* / Q000235:genetics; D000090602:Collagen Type I, alpha 1 Chain; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D000450:Aldosterone; D048052:Mitogen-Activated Protein Kinase 3