18α-glycyrrhetinic acid down-regulates expression of type I and III collagen via TGF-Β1/Smad signaling pathway in human and rat hepatic stellate cells.
OBJECTIVE
To investigate the effects of 18α-glycyrrhetinic acid (18α-GA) on the expression of type I and III collagen in human and rat hepatic stellate cells (HSC) and to explore the role of TGF-β1/Smad signaling pathway involved.


METHODS
Following 18α-GA treatment, the cell viability and cell growth were detected to determine the optimal concentration of 18α-GA. The expressions of TGF-β1/Smad signaling-related genes including type I and III collagen in human and rat HSCs before and after 18α-GA treatment were measured by real time PCR. The expression of related proteins was verified by western blot assay. The phosphorylation level of Smad2 and Smad3 was detected by immunocytochemistry. The DNA binding activities of SP-1, AP-1 and NF-κB were measured by both EMSA and ArrayStar transcription factor activity assay.


RESULTS
18α-GA could decrease the mRNA and protein expression of Smad3, type I and III collagen, increase the Smad7 expression in human and rat HSCs (P<0.05), and reduce phosphorylation level of Smad3 at 24 h and 48 h after treatment. The DNA binding activities of transcription factors were suppressed by 18α-GA in human and rat HSCs at 24 h, and the activities reduced in a time dependent manner with the lowest activities at 48 h, especially for SP-1.


CONCLUSIONS
18α-GA could inhibit the mRNA and protein expression of type I and III collagen in human and rat HSCs, which may be attributed to down-regulation of Smad3, up-regulation of Smad7, and inhibition of DNA binding activities of SP-1, AP-1 and NF-κB.
Department of Gastroenterology, Shanghai First People's Hospital, Shanghai Jiaotong University School of Medicine, No.100 Haining Road, Shanghai, China.
Lei
L
Zong
Ying
Y
Qu
Ming-yi
MY
Xu
Yu-wei
YW
Dong
Lun-gen
LG
Lu
D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism*; D024061:Collagen Type III / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D024042:Collagen Type I; D024061:Collagen Type III; D006034:Glycyrrhetinic Acid; D053773:Transforming Growth Factor beta1; C541116:ACTA2 protein, human; C498862:Acta2 protein, rat; C119129:18alpha-glycyrrhetinic acid