Wnt3a mediated activation of Wnt/β-catenin signaling promotes tumor progression in glioblastoma

Presence of a distinct population of cells that drives tumor progression supports the hierarchical model of tumor development in Glioblastoma (GBM) and substantiates the cancer stem cell hypothesis. Amongst the various developmental signaling pathways that are aberrantly activated, we here show that activated Wnt/β-catenin signaling pathway plays a critical role in malignant transformation and tumor progression in gliomas. We demonstrate that Wnt ligands — Wnt1 and Wnt3a are expressed in a graded manner in these tumors as well as over-expressed in glioma stem cell-lines. A selective inhibition of Wnt signaling pathway by selective knock-down of its ligands Wnt1 and Wnt3a in glioma-derived stem-like cells led to decreased cell proliferation, cell migration and chemo-resistance. Furthermore, Wnt silencing in glioma cells reduced the capacity to form intra-cranial tumors in vivo. Taken together, our study indicates Wnt/β-catenin signaling pathway as an essential driver of glioma tumorigenesis, recognizing role of Wnt3a as an oncogene and thereby offering novel therapeutic strategies for management of these tumors.     

Neuroprotective effect of rapamycin on spinal cord injury via activation of the Wnt/β-catenin signaling pathway

The Wnt/β-catenin signaling pathway plays a crucial role in neural development, axonal guidance, neuropathic pain remission and neuronal survival. In this study, we initially examined the effect of rapamycin on the Wnt/β-catenin signaling pathway after spinal cord injury, by intraperitoneally injecting spinal cord injured rats with rapamycin over 2 days. Western blot analysis and immunofluorescence staining were used to detect the expression levels of β-catenin protein, caspase-3 protein and brain-derived neurotrophic factor protein, components of the Wnt/β-catenin signaling pathway. Rapamycin increased the levels of β-catenin and brain-derived neurotrophic factor in the injured spinal cord, improved the pathological morphology at the injury site, reduced the loss of motor neurons, and promoted motor functional recovery in rats after spinal cord injury. Our experimental findings suggest that the neuroprotective effect of rapamycin intervention is mediated through activation of the Wnt/β-catenin signaling pathway after spinal cord injury.     

Nicotine contributes to the neural stem cells fate against toxicity of microglial-derived factors induced by Aβ via the Wnt/β-catenin pathway

Recent studies have demonstrated that the molecules secreted from microglias play important roles in the cell fate determination of neural stem cells (NSCs), and nicotinic acetylcholine receptor agonist treatment could reduce neuroinflammation in some neurodegenerative disease models, such as Alzheimer's disease (AD). However, it is not clear how nicotine plays a neuroprotective role in inflammation-mediated central nervous diseases, and its possible mechanisms in the process remain largely elusive. The aim of this study is to improve the survival microenvironment of NSCs co-cultured with microglias in vitro by weakening inflammation that mediated by accumulation of β-amyloid peptide (Aβ). The viability, proliferation, differentiation, apoptosis of NSCs and underlying mechanisms associated with Wnt signaling pathway were investigated. The results showed that Aβ could directly damage NSCs. Furthermore, concomitant to elevated levels of TNF-α, IL-1β derived from microglias, the NSCs had been damaged more severely with the upregulation of Axin 2, p-β-catenin and the downregulation of β-catenin, p-GSK-3β, microtubule-associated protein-2, choline acetyltransferase. However, addition of 10 μmol/L nicotine before microglias treated with Aβ was beneficial to protect the NSCs against neurotoxicity of microglial-derived factors induced by Aβ, which partially rescued proliferation, differentiation and inhibited apoptosis of NSCs via activation of Wnt/β-catenin pathway. Taken together, these data imply that low concentration nicotine attenuates NSCs injury induced by microglial-derived factors via Wnt signaling pathway. Thus, treatment with nicotinic acetylcholine receptor agonist provides a promising research field for neural stem cell fate and therapeutic intervention in neuroinflammation diseases.     

Electroacupuncture at Dazhui(GV14) and Mingmen(GV4) protects against spinal cord injury:the role of the Wnt/β-catenin signaling pathway

Electroacupuncture at Dazhui(GV14) and Mingmen(GV4) on the Governor Vessel has been shown to exhibit curative effects on spinal cord injury; however, the underlying mechanism remains poorly understood. In this study, we established rat models of spinal cord injury using a modified Allen's weight-drop method. Ninety-nine male Sprague-Dawley rats were randomly divided into three equal groups: sham(only laminectomy), SCI(induction of spinal cord injury at T10), and EA(induction of spinal cord injury at T10 and electroacupuncture intervention at GV14 and GV4 for 20 minutes once a day). Rats in the SCI and EA groups were further randomly divided into the following subgroups: 1-day(n = 11), 7-day(n = 11), and 14-day(n = 11). At 1, 7, and 14 days after electroacupuncture treatment, the Basso, Beattie and Bresnahan locomotor rating scale showed obvious improvement in rat hind limb locomotor function, hematoxylin-eosin staining showed that the histological change of injured spinal cord tissue was obviously alleviated, and immunohistochemistry and western blot analysis showed that Wnt1, Wnt3 a, β-catenin immunoreactivity and protein expression in the injured spinal cord tissue were greatly increased compared with the sham and SCI groups. These findings suggest that electroacupuncture at GV14 and GV4 upregulates Wnt1, Wnt3 a, and β-catenin expression in the Wnt/β-catenin signaling pathway, exhibiting neuroprotective effects against spinal cord injury.     

Leptin restores adult hippocampal neurogenesis in a chronic unpredictable stress model of depression and reverses glucocorticoid-induced inhibition of GSK-3β/β-catenin signaling

Stress and glucocorticoid stress hormones inhibit neurogenesis, whereas antidepressants increase neurogenesis and block stress-induced decrease in neurogenesis. Our previous studies have shown that leptin, an adipocyte-derived hormone with antidepressant-like properties, promotes baseline neurogenesis in the adult hippocampus. This study aimed to determine whether leptin is able to restore suppression of neurogenesis in a rat chronic unpredictable stress (CUS) model of depression. Chronic treatment with leptin reversed the CUS-induced reduction of hippocampal neurogenesis and depression-like behaviors. Leptin treatment elicited a delayed long-lasting antidepressant-like effect in the forced swim behavioral despair test, and this effect was blocked by ablation of neurogenesis with X-irradiation. The functional isoform of the leptin receptor, LepRb, and the glucocorticoid receptor (GR) were colocalized in hippocampal neural stem/progenitor cells in vivo and in vitro. Leptin treatment reversed the GR agonist dexamethasone (DEX)-induced reduction of proliferation of cultured neural stem/progenitor cells from adult hippocampus. Further mechanistic analysis revealed that leptin and DEX converged on glycogen synthase kinase-3β (GSK-3β) and β-catenin. While DEX decreased Ser9 phosphorylation and increased Tyr216 phosphorylation of GSK-3β, leptin increased Ser9 phosphorylation and attenuated the effects of DEX at both Ser9 and Tyr216 phosphorylation sites of GSK-3β. Moreover, leptin increased total level and nuclear translocation of β-catenin, a primary substrate of GSK-3β and a key regulator in controlling hippocampal neural progenitor cell proliferation, and reversed the inhibitory effects of DEX on β-catenin. Taken together, our results suggest that adult neurogenesis is involved in the delayed long-lasting antidepressant-like behavioral effects of leptin, and leptin treatment counteracts chronic stress and glucocorticoid-induced suppression of hippocampal neurogenesis via activating the GSK-3β/β-catenin signaling pathway.     

Low-dose radiation stimulates Wnt/β-catenin signaling, neural stem cell proliferation and neurogenesis of the mouse hippocampus in vitro and in vivo

Neurogenesis in the hippocampus is actively involved in neural circuit plasticity and learning function of mammals, but it may decrease dramatically with aging and aging-related neurodegenerative disorder Alzheimer's disease. Accumulating studies have indicated that Wnt/β-catenin signaling is critical in control of proliferation and differentiation fate of neural stem cells or progenitors in the hippocampus. In this study, the biological effects of low-dose radiation in stimulating Wnt/β-catenin signaling, neural stem cell proliferation and neurogenesis of hippocampus were interestingly identified by in vitro cell culture and in vivo animal studies. First, low-dose radiation (0.3Gy) induced significant increasing of Wnt1, Wnt3a, Wnt5a, and β-catenin expression in both neural stem cells and in situ hippocampus by immunohistochemical and PCR detection. Secondly, low-dose radiation enhanced the neurogenesis of hippocampus indicated by increasing proliferation and neuronal differentiation of neural stem cells, going up of nestin-expressing cells and BrdU-incorporation in hippocampus. Thirdly, it promoted cell survival and reduced apoptotic death of neuronal stem cells by flowcytometry analysis. Finally, Morris water-maze test showed behavioral improvement of animal learning in low-dose radiation group. Accordingly, detrimental influence on Wnt/β-catenin signaling or neurogenesis was confirmed in high-dose radiation (3.0Gy) group. Taken together, this study has revealed certain beneficial effects of low-dose radiation to stimulate neural stem cell proliferation, the neurogenesis of hippocampus and animal learning most possibly by triggering Wnt/β-catenin signaling cascades, suggesting its translational application role in devising new therapy for aging-related neurodegenerative disorders particularly Alzheimer's disease.     

The effect of citalopram on chronic stress-induced depressive-like behavior in rats through GSK3β/β-catenin activation in the medial prefrontal cortex

Antidepressant treatments enhance synaptic connectivity in stress-sensitive brain regions such as the medial prefrontal cortex (mPFC). The mPFC plays a key role in controlling cognition and emotion. While several signaling pathways are involved in this enhancement process, the exact mechanisms are not fully established. In the present study, we evaluated the role of the glycogen synthase kinase 3β (GSK3β)/β-catenin signaling pathway in the antidepressant effect of citalopram in rats exposed to forced swim stress. The acute stress group received the classic, two-day variant of the forced swimming test (FST), whereas the chronic stress group received swim stress for 14 consecutive days. We found that rats exposed to acute swim stress showed depressive-like behaviors and expressed normal GSK3β and β-catenin levels in the mPFC. Chronic swim stress, also induced a significant behavior changes but was associated with decreased levels of phosphorylated GSK3β and β-catenin in the rat's mPFC. Chronic citalopram treatment alleviated these behavioral changes in chronically stressed rats and normalized the downregulation of GSK3β/β-catenin signaling. Our results suggest that GSK3β/β-catenin signaling plays an important role in chronic but not acute stress-related depression and contributes, at least in part, to the antidepressant effects of citalopram in distinct brain regions associated with mood regulation.     

Tibolone modulates neuronal plasticity through regulating Tau,GSK3β/Akt/PI3K pathway and CDK5 p35/p25 complexes in the hippocampus of aged male mice

Aging is a key risk factor for cognitive decline and age-related neurodegenerative disorders. Also, an age-related decrease in sex steroid hormones may have a negative impact on the formation of neurofibrillary tangles(NFTs); these hormones can regulate Tau phosphorylation and the principal kinase GSK3β involved in this process. Hormone replacement therapy decreases NFTs, but it increases the risk of some types of cancer. However, other synthetic hormones such as tibolone(TIB) have been used for hormone replacement therapy. The aim of this work was to evaluate the long-term effects of TIB(0.01 mg/kg and 1 mg/kg, intragastrically for 12 weeks) on the content of total and hyperphosphorylated Tau(PHF-1) proteins and the regulation of GSK3β/Akt/PI3 K pathway and CDK5/p35/p25 complexes in the hippocampus of aged male mice. We observed that the content of PHF-1 decreased with TIB administration. In contrast, no changes were observed in the active form of GSK3β or PI3 K. TIB decreased the expression of the total and phosphorylated form of Akt while increased that of p110 and p85. The content of CDK5 was differentially modified with TIB: it was increased at low doses and decreased at high doses. When we analyzed the content of CDK5 activators, an increase was found on p35; however, the content of p25 decreased with administration of low dose of TIB. Our results suggest a possible mechanism of action of TIB in the hippocampus of aged male mice. Through the regulation of Tau and GSK3β/Akt/PI3 K pathway, and CDK5/p35/p25 complexes, TIB may modulate neuronal plasticity and regulate learning and memory processes.     

Ucf-101 protects in vivo and in vitro models of PD against 6-hydroxydopamine toxicity by alleviating endoplasmic reticulum stress via the Wnt/β-catenin pathway

The accumulation of α-syn which induce endoplasmic reticulum stress (ERS) and mediate various signaling pathways involved in DA neuronal degeneration, and the apoptosis of dopamine (DA) neurons are pathological markers of Parkinson’s disease (PD). High-temperature requirement protein A2 (HtrA2) is synthesized in the endoplasmic reticulum, and the expression level of HtrA2 can be upregulated by drugs or by unfolded proteins. Ucf-101 is a specific inhibitor of HtrA2, and studies have shown that Ucf-101 reduced apoptosis in PC12 cells. Our study showed that PC12 cells treated with 60 μM 6-OHDA for 24 h had significantly decreased cell viability compared to that of controls. A low concentration (2.5 μM) of Ucf-101 decreased the apoptosis rate of the PD cell model, but a high concentration (≥10 μM) increased the apoptosis rate, compared to that of controls. 6-OHDA upregulated the expression of HtrA2, α-syn, CHOP, Grp78 and active caspase-3 and reduced the levels of TH and XIAP. Ucf-101 reduced the level of ERS and apoptosis both in vivo and in vitro. The ratio of p-GSK3β (Tyr216 to Ser9) increased in PD rats. However, Ucf-101 down-regulated the activation of GSK3β and activated the Wnt/β-catenin pathway that was caused by 6-OHDA. Ucf-101 activated the Wnt/β-catenin pathway and significantly attenuated 6-OHDA-induced neurotoxicity, which was related to the inhibition of ERS and the reduction of the apoptosis rate of PC12 cells and DA neurons in the midbrain of PD rats. Ucf-101 has certain neuroprotective effects.     

Activation of MAPKs in the anti-β(2)GPI/β(2)GPI-induced tissue factor expression through TLR4/IRAKs pathway in THP-1 cells

Our previous study has demonstrated that the Toll-like receptor 4 (TLR4) signaling pathways contribute to the induction of tissue factor (TF) expression by anti-β₂-glycoprotein I/β₂-glycoprotein I (anti-β₂GPI/β₂GPI) in human acute monocytic leukemia cell line THP-1. In this study, we focused on the identification of the downstream targets of the TLR4 pathways. When THP-1 cells were treated with anti-β₂GPI/β₂GPI complex, enhanced TF expression was observed, along with induced phosphorylation of p38, ERK1/2 and JNK1/2 MAPKs. When the activity of MAPKs was blocked by their corresponding inhibitors (SB203580: p38; U0126: ERK; SP600125: JNK), the expression of TF was reduced significantly. Furthermore, the anti-β₂GPI/β₂GPI-induced phosphorylation of p38, ERK1/2 and JNK1/2 was inhibited significantly by TAK-242, a blocker of the signaling transduction mediated by the intracellular domain of TLR4; sc-204013, a specific inhibitor of IRAKs, was also able to partially inhibit the phosphorylation of the MAPKs. Our results demonstrated that MAPKs (p38, ERK1/2 and JNK1/2) were the crucial downstream targets of the anti-β₂GPI/β₂GPI-triggered TLR4 signaling pathways in THP-1 cells. This essential role of MAPKs may also promote better understanding of the pathogenesis of antiphospholipid syndrome (APS).     

The effect of IL-1β on synaptophysin expression and electrophysiology of hippocampal neurons through the PI3K/Akt/mTOR signaling pathway in a rat model of mesial temporal lobe epilepsy

Background: The inflammation induced by interleukin-1β (IL-1β) is a critical factor in the pathogenesis of mesial temporal lobe epilepsy (MTLE). Synaptophysin (SYN) and other changes, including neuron electrophysiology, participate in the pathophysiological processes of MTLE. Phosphatidylinositol 3-kinase (PI3K)/Akt/ mammalian target of rapamycin (mTOR) signaling pathway may play a critical role in regulating SYN expression and electrophysiology of hippocampal neurons.

Methods: We used lithium-pilocarpine-treated rats as model of human MTLE, detecting epileptic seizures with digital video-EEG, and evaluating the proteins related to the PI3K/Akt/mTOR signaling pathway by western blot (WB). Then, we cultured primary neuron and established a neuronal epilepsy model using Mg2+-free media. Immunocytochemistry and WB were used to investigate SYN expression, and whole-cell current clamp recording techniques were used to detect the electrophysiological properties of cultured neurons.

Results: We have demonstrated that IL-1β can activate the PI3K/Akt/mTOR signaling pathway in primary hippocampal neurons, and we speculate that IL-1β may affect SYN expression and neuron electrophysiology through PI3K/Akt/mTOR signaling pathway.

Conclusion: We confirmed that IL-1β stimulated SYN expression and epileptiform discharges, and that blocking the PI3K/Akt/mTOR pathway alleviated these phenomena. Therefore, activation of the PI3K/Akt/mTOR signaling pathway by IL-1β contributes to the pathogenesis of MTLE, and modulating this pathway is a promising strategy of study for therapies to prevent or reverse the cellular and molecular mechanisms of epileptogenesis in MTLE.     

EPO relies upon novel signaling of Wnt1 that requires Akt1, FoxO3a, GSK-3β, and β-catenin to foster vascular integrity during experimental diabetes

Multiple complications can ensue in the cardiovascular, renal, and nervous systems during diabetes mellitus (DM). Given that endothelial cells (ECs) are susceptible targets to elevated serum D-glucose, identification of novel cellular mechanisms that can protect ECs may foster the development of unique strategies for the prevention and treatment of DM complications. Erythropoietin (EPO) represents one of these novel strategies but the dependence of EPO upon Wnt1 and its downstream signaling in a clinically relevant model of DM with elevated D-glucose has not been elucidated. Here we show that EPO can not only maintain the integrity of EC membranes, but also prevent apoptotic nuclear DNA degradation and the externalization of membrane phosphatidylserine (PS) residues during elevated D-glucose over a 48-hour period. EPO modulates the expression of Wnt1 and utilizes Wnt1 to confer EC protection during elevated D-glucose exposure, since application of a Wnt1 neutralizing antibody, treatment with the Wnt1 antagonist DKK-1, or gene silencing of Wnt1 with Wnt1 siRNA transfection abrogates the protective capability of EPO. EPO through a novel Wnt1 dependent mechanism controls the post-translational phosphorylation of the "pro-apoptotic" forkhead member FoxO3a and blocks the trafficking of FoxO3a to the cell nucleus to prevent apoptotic demise. EPO also employs the activation of protein kinase B (Akt1) to foster phosphorylation of GSK-3β that appears required for EPO vascular protection. Through this inhibition of GSK-3β, EPO maintains β-catenin activity, allows the translocation of β-catenin from the EC cytoplasm to the nucleus through a Wnt1 pathway, and requires β-catenin for protection against elevated D-glucose since gene silencing of β-catenin eliminates the ability of EPO as well as Wnt1 to increase EC survival. Subsequently, we show that EPO requires modulation of both Wnt1 and FoxO3a to oversee mitochondrial membrane depolarization, cytochrome c release, and caspase activation during elevated D-glucose. Our studies identify critical elements of the protective cascade for EPO that rely upon modulation of Wnt1, Akt1, FoxO3a, GSK-3β, β-catenin, and mitochondrial apoptotic pathways for the development of new strategies against DM vascular complications.     

Thrombospondin-2 promotes the proliferation and migration of glioma cells and contributes to the progression of glioma

Background: Gliomas, especially high-grade gliomas, are highly malignant with a poor prognosis. Although existing treatments have improved the survival rate of patients with glioma, the recurrence and mortality rates are still not ideal. The molecular mechanisms involved in the occurrence and development of glioma are still poorly understood. We previously reported that thrombospondin-2 (TSP2) expression was increased in tumor specimens from rat models, promoting excitatory synapse formation. Ho...     

Interaction of mi R-21 and TGF-β/SMADs signaling pathway affects the formation of fibrotic scars after spinal cord injury

<正>Scarring after spinal cord injury(SCI)consists of glial scar formation followed by fibrotic scar formation.A glial scar is formed by reactive astrocytes during the acute phase of SCI.Reactive astrocytes are formed by astrocyte activation,proliferation and hypertrophy;they highly express glial fibrillary acidic protein,can fill the injured region,limit inflammatory diffusion,secrete and     

Interferon beta(IFN-β) treatment exerts potential neuroprotective effects through neurotrophic factors and novel neurotensin/neurotensin high affinity receptor 1 pathway

<正>Multiple sclerosis(MS)is a chronic autoimmune disease of the central nervous system(CNS)characterized by coexisting processes of inflammation,demyelination,axonal neurodegeneration,and gliosis.It is the most common disabling neurological disease in young adulthood.Although autoimmune inflammation contributes to axonal pathology