Format

Send to

Choose Destination
See comment in PubMed Commons below
Graefes Arch Clin Exp Ophthalmol. 2012 Jan;250(1):15-23. doi: 10.1007/s00417-011-1766-x. Epub 2011 Aug 20.

The PI3K/Akt pathway mediates the expression of type I collagen induced by TGF-β2 in human retinal pigment epithelial cells.

Author information

1
Department of Ophthalmology, Faculty of Medicine, Oita University, Hasama-machi, Yufu-shi, Oita 879-5593, Japan.

Abstract

PURPOSE:

Transforming growth factor (TGF)-β is a key mediator of proliferative vitreoretinopathy, but the cellular mechanisms by which TGF-β induces extracellular matrix protein (ECM) synthesis are not fully understood. This study examined whether the PI3K/Akt pathway is involved in TGF-β2-induced collagen expression in human retinal pigment epithelial cells.

METHODS:

Human retinal pigment epithelial cells ARPE-19 were cultured and stimulated with TGF-β2. The role of the PI3K/Akt pathway was evaluated using the biochemical inhibitor, wortmannin. The effect of wortmannin on the expression of type I collagen mRNA (COL1A1, COL1A2) induced by TGF-β2 was evaluated by real-time RT-PCR. The effect of wortmannin on the synthesis of type I collagen induced by TGF-β2 was assessed by an immunocytochemical analysis with anti-type I collagen antibody. Luciferase reporter assays were performed to examine the effect of wortmannin on the transcriptional activities of COL1A2. A luciferase assay using a mutation construct of the Smad binding site in COL1A2 promoter (Smad-mut/Luc) was also performed to examine the crosstalk between the Smad pathway and the PI3K/Akt pathway. The effects of wortmannin on the transcriptional activity of Smad3 were also examined using CAGA12-Luc. Moreover, the effect of wortmannin on TGF-β2-induced Smad7 mRNA expression was evaluated.

RESULTS:

The biochemical blockade of PI3K/Akt activation inhibited TGF-β2-induced type I collagen mRNA expression and type I collagen synthesis. The blockade of PI3K/Akt pathway inhibited the increase in COL1A2 promoter activities when induced by TGF-β2 and reduced TGF-β2 induction of Smad-mut/Luc promoter activity and CAGA12-Luc activity. Moreover, wortmannin increased the TGF-β2-induced Smad7 mRNA expression levels.

CONCLUSIONS:

The PI3K/Akt pathway plays a role in relaying the TGF-β2 signal to induce type I collagen synthesis in the retinal pigment epithelium through Smad-dependent and Smad-independent pathways.

PMID:
21858467
PMCID:
PMC3262137
DOI:
10.1007/s00417-011-1766-x
[Indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Springer Icon for PubMed Central
    Loading ...
    Support Center