RESUMO
Idiopathic pulmonary fibrosis (IPF) is a heterogeneous lung disease associated with high mortality. Disabled-2 (DAB2), an adapter protein, regulates cell-fibrinogen adhesion and fibrinogen uptake. DAB2 is differentially expressed in mouse fibrotic lungs induced by bleomycin according to a genome microarray analysis based on Gene Expression Omnibus database. However, the role of DAB2 in IPF has not been revealed. A bleomycin-induced mouse model of pulmonary fibrosis was constructed in the present study. It found that the expression of DAB2 was upregulated in bleomycin-induced fibrotic lung tissue with collagen fiber deposition and pulmonary interstitium thickening. Colocalization of DAB2 with α-smooth muscle actin (SMA) was observed in lung tissue sections. In vitro, human lung fibroblast MRC-5 cells were treated with TGF-ß1 and the expression of DAB2 was increased. Knockdown of DAB2 suppressed cell proliferation and the expression of α-SMA, collagen I, collagen IV and fibronectin in TGF-ß1-treated MRC-5 cells. The phosphorylation levels of PI3K and AKT were suppressed in DAB2-knockdown cells. IGF-1/IGF-1R has been reported to promote pulmonary fibrosis and activate the PI3K/Akt signaling. In the present study, the activation of IGF-1/IGF-1R signaling pathways in bleomycin-induced fibrotic lung tissues were positively associated with DAB2 expression. The phosphorylation level of IGF-1R was increased in MRC-5 cells with TGF-ß1 treatment, and DAB2 expression was decreased by silencing of IGF-1R. This suggested that DAB2 might be a downstream target of the IGF-1R pathway and thus induced PI3K/AKT signaling activation and fibrogenesis. The current study demonstrated the importance of DAB2 in pulmonary fibrosis and suggested the potential of IGF-1R/DAB2/PI3K in the pathogenesis of IPF.
RESUMO
Hyperglycemia is a major factor in vascular endothelial injury that finally leads to a cardiovascular event. Steroid receptor coactivators (SRCs) are a group of non-DNA binding proteins that induce structural changes in steroid receptors (nuclear receptors) critical for transcriptional activation. SRCs, namely, SRC-1, SRC-2, and SRC-3, are implicated in the regulation of vascular homeostasis. In this study we investigate the role of SRCs in hyperglycemia-induced endothelial injury. Aortic endothelial cells were prepared from normal and diabetic rats, respectively. Diabetic rats were prepared by injection of streptozotocin (50 mg/kg, i.p.). The expression levels of SRC-1 and SRC-3 were significantly decreased in endothelial cells from the diabetic rats. Similar phenomenon was also observed in aortic endothelial cells from the normal rats treated with a high glucose (25 mM) for 4 h or 8 h. The expression levels of SRC-2 were little affected by hyperglycemia. Overexpression of SRC-1 and SRC-3 in high glucose-treated endothelial cells significantly increased the cell viability, suspended cell senescence, and inhibited cell apoptosis compared with the control cells. We further showed that overexpression of SRC-1 and SRC-3 markedly suppressed endothelial injury through restoring nitric oxide production, upregulating the expression of antioxidant enzymes (SOD, GPX, and CAT), and activating the PI3K/Akt pathway. The beneficial effects of SRC-1 and SRC-3 overexpression were blocked by treatment with the PI3K inhibitor LY294002 (10 mM) or with the Akt inhibitor MK-2206 (100 nM). In conclusion, hyperglycemia decreased SRC-1 and SRC-3 expression levels in rat aortic endothelial cells. SRC-1 and SRC-3 overexpression might protect against endothelial injury via inhibition of oxidative stress and activation of PI3K/Akt pathway.
