RETRACTED: Effect of thioredoxin-interacting protein on Wnt/β-catenin signaling pathway and diabetic myocardial infarction.

To explore the regulatory role of thioredoxin-interacting protein (TXNIP) in Wnt/β-catenin signaling pathway and therefore to elucidate its function in diabetic myocardial infarction. Diabetic myocardial infarction models were generated in mice. The expression levels of TXNIP and β-catenin and level of reactive oxygen species (ROS) were determined and compared with those in control group. Human umbilical vein endothelial cells were treated with high-concentration glucose and/or silencing TXNIP and/or H2O2. After 24 h, expression levels of TXNIP, β-catenin and its downstream protein Cyclin D1, and C-myc gene were determined by real-time PCR, Western blot and immunofluorescence method. The cell proliferation and ROS production capability in different groups were determined by methyl thiazolyl tetrazolium assay. Compared with control group, hyperglycemia significantly up-regulated TXNIP expression and ROS level in the myocardium and endothelial cells of myocardial infarction area, whereas the β-catenin expression was down-regulated, and the difference was statistically significant (P < 0.05). In comparison with Human umbilical vein endothelial cells in the control group, high glucose level increased the levels of TXNIP expression and ROS level in cells, but reduced cell proliferation as well as migration capability and expression levels of β-catenin, Cyclin D1 and C-myc; the difference was statistically significant (P < 0.05). However, this trend can be partially reversed by silencing TXNIP. Diabetic myocardial ischemia could up-regulate levels of TXNIP expression and ROS production in endothelial cells of myocardial infarction area. The regulation effect of TXNIP on β-catenin was partially achieved by changing ROS levels.

Yu H ，Zhao XX ，Shan XH ，Li P ，Chen T ... -  《-》

Dysregulated Txnip-ROS-Wnt axis contributes to the impaired ischemic heart repair in diabetic mice.

Hyperglycemia-induced impairment of angiogenesis contributes to the unfavorable prognosis of myocardial ischemia in long-standing diabetes mellitus. The underlying mechanism remains largely unknown and therapeutic strategies thereby limited. In the present study, we investigated the possible involvement of thioredoxin-interacting protein (TXNIP) and Wnt/β-catenin signaling in the context, and their possible relation was also explored. STZ induced diabetic mice were subjected to myocardial infarction (MI). Adenovirus expressing shTXNIP, shCtnnb1 (β-catenin) driven by VE-Cadherin promoter was administered intramyocardially immediately after MI. Cardiac function, histology, and molecular analyses were performed at predetermined time points. Increased endothelial expression of TXNIP was found in diabetic hearts, which correlated well with reduced nuclear β-catenin expression, insufficient angiogenesis, aggravated cardiac remodeling, and poor survival. Endothelial-specific knockdown of TXNIP significantly rescued β-catenin activity, together with increased angiogenesis, preserved cardiac function, and improved survival rate. Moreover, additional knockdown of β-catenin essentially reversed the beneficial effects of TXNIP downregulation. In vitro, high glucose treatment of human umbilical vein endothelial cells (HUVECs) increased TXNIP levels and ROS concentration, while it reduced β-catenin activity. Silencing TXNIP or ROS scavenger restored the high glucose induced reduction of Wnt/β-catenin activity in HUVECs. In addition, either reduction of TXNIP expression or supplementation of exogenous Wnt3a improved the HUVECs quantity and migration under high glucose conditions. Diabetes-induced increase of TXNIP expression in the endothelium contributes to impaired angiogenesis after MI, especially via the elevation of ROS and the impaired Wnt/β-catenin signaling. Targeting TXNIP-ROS-Wnt is a promising strategy in improving the prognosis.

Shen M ，Bai D ，Liu B ，Lu X ，Hou R ，Zeng C ，Li N ，Fu Z ，Li C ，Tao L ，Wang H ，Yin T ... -  《-》

Wnt/β-catenin signaling pathway and thioredoxin-interacting protein (TXNIP) mediate the "glucose sensor" mechanism in metastatic breast cancer-derived cells MDA-MB-231.

In this study we investigated the effect of glucose on GSK3β and β-catenin expression and the involvement of the N-linked glycosylation and hexosamine pathways in the Wnt canonical pathway in response to in vitro conditions resembling normoglycemia (5  mmol) and hyperglycemia (20  mmol) in the metastatic breast cancer-derived cell line MDA-MB-231. We also investigated the relationship between this circuitry and the thioredoxin-interacting protein (TXNIP) regulation that seems to be related. MDA-MB-231 cells were grown either in 5 or 20  mM glucose chronically prior to plating. For glucose shift (5/20), cells were plated in 5  mM glucose and shifted to 20  mM at time 0. Both protein and mRNA levels for GSK3β but only the protein expression for β-catenin, were increased in response to high glucose. Furthermore, we assessed the response of GSK3β, β-catenin, and TXNIP to inhibition of the N-linked glycosylation, hexosamine, and Wnt pathways. Wnt signaling pathway activation was validated by specific reporter assay. We show that high levels of glucose regulate mRNA and protein expression of GSK3β, and consequently higher levels of activated β-catenin protein, which locates to the nucleus and is associated with increased levels of cyclin D1 expression. This event coincides with increased level of N-terminal Ser 9 phosphorylation of GSK3β protein. The inhibition of both the hexosamine pathway and N-linked glycosylation along with Wnt signaling pathway by sFRP1 and DKK1 is associated with significant decrease of the protein levels of GSK3β, β-catenin, and TXNIP RNA. Our work illuminates a novel and never described before function of this signaling pathway that relates glucose metabolism with redox regulation mechanism.

Vaira S ，Friday E ，Scott K ，Conrad S ，Turturro F ... -  《-》

Impaired cardiac anti-oxidant activity in diabetes: human and correlative experimental studies.

Connelly KA ，Advani A ，Advani SL ，Zhang Y ，Kim YM ，Shen V ，Thai K ，Kelly DJ ，Gilbert RE ... -  《-》

Knockdown of thioredoxin-interacting protein ameliorates high glucose-induced epithelial to mesenchymal transition in renal tubular epithelial cells.

Epithelial to mesenchymal transition (EMT) of tubular cells contributes to the renal accumulation of matrix protein that is associated with diabetic nephropathy. Both high glucose and transforming growth factor-β (TGF-β) are able to induce EMT in cell culture. In this study, we examined the role of the thioredoxin-interacting protein (TXNIP) on EMT induced by high glucose or TGF-β1 in HK-2 cells. EMT was assessed by the expression of α-smooth muscle actin (α-SMA) and E-cadherin and the induction of a myofibroblastic phenotype. High glucose (30mM) was shown to induce EMT at 72h. This was blocked by knockdown of TXNIP or antioxidant NAC. Meanwhile, we also found that knockdown of TXNIP or antioxidant NAC inhibited high glucose-induced generation of reactive oxygen species (ROS), phosphorylation of p38 MAPK and ERK1/2 and expression of TGF-β1. HK-2 cells that were exposed to TGF-β1 (4ng/ml) also underwent EMT. The expression of TXNIP gene and protein was increased in HK-2 cells treated with TGF-β1. Transfection with TXNIP shRNA was able to attenuate TGF-β1 induced-EMT. These results suggested that knockdown of TXNIP antagonized high glucose-induced EMT by inhibiting ROS production, activation of p38 MAPK and ERK1/2, and expression of TGF-β1, highlighting TXNIP as a potential therapy target for diabetic nephropathy.

Wei J ，Shi Y ，Hou Y ，Ren Y ，Du C ，Zhang L ，Li Y ，Duan H ... -  《-》