Activating ß-catenin/Pax6 axis negatively regulates osteoclastogenesis by selectively inhibiting phosphorylation of p38/MAPK.

Balance of osteoclast formation is regulated by the receptor activator of NF-κB ligand and extracellular negative regulators such as IFN-γ and IFN-ß. However, very little is known about the intrinsic negative regulatory factors of osteoclast differentiation. Recently, the paired-box homeodomain transcription factor Pax6 was shown to negatively regulate receptor activator of NF-κB ligand-mediated osteoclast differentiation. However, the mechanism underlying this regulation is still unclear. In this study, we show that a p38 inhibitor (VX-745) up-regulates the expression of Pax6 during osteoclast differentiation. Subsequently, we found that ß-catenin could bind to the proximal region of Pax6 promoter to induce its expression, and this action could be impaired by p38-induced ubiquitin-mediated degradation of ß-catenin. Our results suggest that Pax6 is regulated by a novel p38/ß-catenin pathway. Pax6 can further regulate the nuclear translocation of NF of activated T cells, cytoplasmic 1. Our study indicates that this novel p38/ß-catenin/Pax6 axis contributes to negative regulation of osteoclastogenesis. In addition, our study proposes a novel approach to treat osteoclast-related diseases through the use of VX-745 complemented with the ß-catenin activator SKL2001.-Jie, Z., Shen, S., Zhao, X., Xu, W., Zhang, X., Huang, B., Tang, P., Qin, A., Fan, S., Xie, Z. Activating ß-catenin/Pax6 axis negatively regulates osteoclastogenesis by selectively inhibiting phosphorylation of p38/MAPK.

A cellular model for Wilson's disease using patient-derived induced pluripotent stem cells revealed aberrant ß-catenin pathway during osteogenesis.

Wilson's disease (WD) is a rare autosomal recessive disorder of copper metabolism caused by an ATP7B gene mutation. Except for hepatic, neurological symptoms, lower bone mineral density is another most frequent clinical features of WD, but the underlying mechanisms have not been fully understood. This article aims to use induced pluripotent stem cells (iPSCs) to establish cellular osteoblasts model related to WD to identify abnormal osteogenesis and signaling pathways. In this study, we successfully produced functional osteoblasts from normal and WD iPSCs through embryoid bodies (EBs) formation method, and then we found WD osteoblasts may have a lower osteogenesis activity than normal controls by detection of osteogenic marker genes and mineralization ability. Further, through gene expression profiling, detection of ß-catenin in total protein and nuclear protein, and the nuclear localization of ß-catenin, we identified and validated that low osteogenic activity in WD may be due to abnormal ß-catenin pathway. Interestingly, we found SKL2001, a small molecule can reverse decreased osteogenesis of WD. In summery, our results suggested that the low bone density of WD may caused by abnormal ß-catenin signaling pathway, and these may provided a new target for the treatment of WD.

Role of Wnt/ß-catenin pathway agonist SKL2001 in Caerulein-induced acute pancreatitis.

The goal of this study was to clarify the protective role of the Wnt/ß-catenin pathway agonist SKL2001 in a rat model of Caerulein-induced acute pancreatitis. AR42J cells and rats were divided into 4 groups: control, Caerulein, SKL2001 + Caerulein, and SKL2001 + control. Cell apoptosis was examined using flow cytometry. Hematoxylin-eosin staining was performed to observe pathological changes in pancreatic and small intestinal tissues. Inflammatory cytokines were detected by enzyme-linked immunosorbent assay (ELISA), while genes related to the Wnt/ß-catenin pathway were quantified using quantitative real-time PCR. In vitro results showed that Caerulein promoted cell necrosis, inhibited the Wnt/ß-catenin pathway, and increased the level of inflammatory cytokines. However, SKL2001 reduced cell necrosis and inflammatory cytokines and activated the Wnt/ß-catenin pathway. Additionally, in vivo results demonstrated the accumulation of fluid (i.e., edema), hemorrhage, inflammation and necrosis of the pancreatic acini occurred 6 h after the final Caerulein induction, with the damage reaching a maximal level 12 h after the final Caerulein induction; meanwhile, the Wnt/ß-catenin pathway was evidently inhibited with an enhanced level of inflammatory cytokines. The aforementioned damage was further aggravated 12 h later. Nevertheless, the pancreatic and small intestinal tissue damages were alleviated in Caerulein-induced rats treated with SKL2001. In conclusion, activation of the Wnt/ß-catenin pathway could inhibit Caerulein-induced cell apoptosis and inflammatory cytokine release, thus improving pancreatic and intestinal damage in rats with acute pancreatitis.

SKL2001 suppresses colon cancer spheroid growth through regulation of the E-cadherin/ß-Catenin complex.

Aberrant activation of Wnt signaling plays a pivotal role in the development of human cancers including colon cancer. Small compounds that regulate Wnt signaling are attractive candidate for the colon cancer therapy. Here, we showed that SKL2001, which has been identified as an activator for Wnt signaling by disrupting the Axin/ß-Catenin complex, negatively regulates growth of colon cancer spheroids cultured in the 3D condition that simulates tumor microenvironment in vivo. SKL2001 inhibited proliferation of colon cancer cells cultured in 3D spheroid and induced them accumulation in the G0/G1 phase of the cell cycle with a reduced c-myc level. To examine the potential of arrested cells to recover, colon cancer spheroids that were treated with SKL2001 were then cultured in the SKL2001-free medium. We found that SKL2001-treated cells were resumed cell cycle progression and proliferated in the SKL2001-free medium. Notably, SKL2001 facilitated round-shape spheroid formation. This was associated with upregulated expressions of E-cadherin and ß-Catenin. These findings suggest that SKL2001 can suppress colon cancer spheroid growth through regulating cell cycle progression and cadherin/catenin mediated cell-cell contact.

Activation of ß-catenin causes defects in embryonic development during maternal-to-zygotic transition in mice.

The early stage of embryogenesis is an important and complex cell-remodeling event in reproductive biology. To develop into a normal zygote, maternal-to-zygotic transition (MZT) is especially important for both zygotic genome activation (ZGA) and degradation of maternal products during the early stage of embryonic development. ß-Catenin has been identified as an important regulator of embryonic development and adult stem cell division via the canonical Wnt/ß-catenin signalling pathway. However, the role of activated ß-catenin during MZT remains elusive. In the present study, we found that ß-catenin is mainly expressed during embryogenesis in the cell membrane from the zygote- to morula-stage embryos but not in MII oocytes. To analyze the function of activated ß-catenin during MZT, we conducted a ß-catenin activation assay during embryogenesis. Our results indicated that development beyond the two-cell stage was inhibited in zygotes with ß-catenin activation. Further analysis showed that activated form of ß-catenin protein was increased and the phosphorylated form of ß-catenin protein was decreased in culture embryos. Taken together, our study reveals that activation of ß-catenin may play a vital role in zygotic development, determining the developmental potential of mouse embryos.