DAB2 promotes pulmonary fibrosis and may act as an intermediate between IGF­1R and PI3K/AKT signaling pathways.

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.

Overexpression of steroid receptor coactivators alleviates hyperglycemia-induced endothelial cell injury in rats through activating the PI3K/Akt pathway.

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.

[Significance and effect of Glucosidorum Tripterygii tororum on expressions of Foxp3 in regulatory T cells in type 1 diabetic rat model].

AIM: To investigate the significance and effect of Glucosidorum Tripterygii tororum (GTT) on the expressions of Foxp3 in CD4(+)CD25(+) regulatory T cells (Tr) in type 1 diabetic rat model. METHODS: 48 rats were divided evenly into 3 groups by random. Diabetic model was developed by multiple low dose intraperitoneal injection of streptozotocin in group II, III, and group I was treated as normal control. After the establishment of the model, administration of GTT was conducted in group III, which was performed once a day, lasting three monthes. Lymphocyte proliferation was detected by lymphocyte transformation test (MTT assay). The expression of Foxp3 mRNA was measured in peripheral blood and spleen by using real-time PCR. The expression of Foxp3 protein in lymphoid node and spleen was detected by immunohistochemistry. RESULTS: The blood glucose level in group II, III was obviously higher than that of control group (P<0.01), followed with lymphocyte infiltrating in pancreatic islets. The infiltrating degree in group III was decreased than that of group II. The proliferation of splenic lymphocyte in group II, III was evidently increased comparing with the control group (P<0.01). After administration of GTT, the proliferation in group III was lower than that in group II. In group II, III, the expressions of Foxp3 mRNA and protein increased markedly compared with control group (P<0.05). Moreover, the level in group III was especially enhanced, but compared with group II, there was no significantly difference (P>0.05). CONCLUSION: Foxp3(+) Tr may involve in the pathogenesy of type 1 diabetes indused by STZ. GTT did have therapeutical effect on type 1 diabetes, possibly through upregulating the expressions of Foxp3 in Tr.