Overexpression of components of the Frizzled-Dishevelled cascade results in apoptotic cell death, mediated by beta-catenin

TENT5A Increases Glioma Malignancy and Promotes its Progression

BACKGROUND

Recent studies reported that terminal nucleotidyltransferase 5A (TENT5A) is highly expressed in glioblastoma and associated with poor prognosis. In this work, we aim to specify the expression level of TENT5A in different grades of glioma and explore its role in glioma progression.

METHODS

GEPIA online tools were used to perform the bioinformatic analysis. qRT-PCR, Western blot, and Immunohistochemistry were performed in glioma cells or tissues. Furthermore, CCK8, colony formation, transwell, flow cytometry and scratch assays were performed.

RESULTS

TENT5A was highly expressed in glioma and its level was associated with the pathological grade of glioma. Knockdown of TENT5A suppressed cell proliferation, colony formation ability, cell invasion and migration. Overexpression of TENT5A was lethal to the glioma cells.

CONCLUSION

Our data showed that the expression of TENT5A is associated with the pathological grade of glioma. Knockdown of TENT5A decreased the ability of proliferation, invasion and migration of glioma cells. High levels of TENT5A in glioma cells are lethal. Therefore, TENT5A could be a new target for glioma treatment.

Dishevelled-1 regulated apoptosis through NF-κB in cerebral ischemia/reperfusion injury in rats

Dishevelled-1(DVL-1) has been reported associated with the regulation of cell polarity and neuronal function. However, the effect of DVL-1 in cerebral ischemia-reperfusion injury of rats remains poorly understood. In this study, we give evidence that the level of DVL-1 is increased after a middle cerebral artery occlusion/reperfusion model (MCAO) in rats, with a peak at 12 h. On the side, knockdown of DVL-1 may relieve I/R damage and restrain apoptosis after MCAO model in rats. In the part of mechanism, DVL-1 could regulate apoptosis through NF-κB. These results suggest that DVL-1 may be a potential target in I/R injury in rats.

First in vitro evidence of modulated electro-hyperthermia treatment performance in combination with megavoltage radiation by clonogenic assay

Modulated electro-hyperthermia (mEHT) is a form of hyperthermia used in the treatment of cancer. It is a variation that relies on a particular form of enhanced selectivity to enable more effective cancerous cell death yet maintaining the integrity of healthy non-cancerous cells. It is yet to successfully make the major step into the wider medical community despite several encouraging trials. In this study, we investigate mEHT from an in vitro perspective. We demonstrate a supra-additive effect on 9 L gliosarcoma cells when exposed to mEHT in combination with MV X-ray radiation. The supra-additive effect is hypothesized to be induced by the mEHT mechanism that in turn causes apoptosis, membrane damage and an increase in rate of cell growth. This proves to be extremely advantageous in the case of the aggressive 9 L cell line as it is known to be radioresistant. However, the universal success of this multimodal treatment does not appear to be positive for all cell lines and requires further research. Due to the fundamental approach taken in this research, our results also provide a new prospect for mEHT to be a tool for sterilizing otherwise radioresistant cancers.

Planar cell polarity gene Fuz triggers apoptosis in neurodegenerative disease models

Planar cell polarity (PCP) describes a cell-cell communication process through which individual cells coordinate and align within the plane of a tissue. In this study, we show that overexpression of Fuz, a PCP gene, triggers neuronal apoptosis via the dishevelled/Rac1 GTPase/MEKK1/JNK/caspase signalling axis. Consistent with this finding, endogenous Fuz expression is upregulated in models of polyglutamine (polyQ) diseases and in fibroblasts from spinocerebellar ataxia type 3 (SCA3) patients. The disruption of this upregulation mitigates polyQ-induced neurodegeneration in Drosophila We show that the transcriptional regulator Yin Yang 1 (YY1) associates with the Fuz promoter. Overexpression of YY1 promotes the hypermethylation of Fuz promoter, causing transcriptional repression of Fuz Remarkably, YY1 protein is recruited to ATXN3-Q84 aggregates, which reduces the level of functional, soluble YY1, resulting in Fuz transcriptional derepression and induction of neuronal apoptosis. Furthermore, Fuz transcript level is elevated in amyloid beta-peptide, Tau and α-synuclein models, implicating its potential involvement in other neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Taken together, this study unveils a generic Fuz-mediated apoptotic cell death pathway in neurodegenerative disorders.

Secreted frizzled related protein 1 protects H9C2 cells from hypoxia/re-oxygenation injury by blocking the Wnt signaling pathway

Background

In animal models, secreted frizzled related protein 1 (Sfrp1) inhibition of the Wnt signaling pathway is beneficial because Sfrp1 reduces myocardial apoptosis and prevents heart failure. The mechanisms mediating the cellular survival effect of Sfrp1 has not been completely elucidated. The present study was designed to investigate the possible protective actions of Sfrp1 on cardiac muscle cells using an in vitro model of ischemia/reperfusion, and to evaluate the possible involvement of the Wnt signaling pathway.

Methods

We used a recombinant AAV9 vector to deliver the Sfrp1 gene into H9C2 rat cardiomyoblasts and adopted an in vitro model of ischemia/reperfusion. Cell vitality was measured by CKK-8 and the trypan blue exclusion assay. Western blot was used to evaluate the expression of Dvl-1, β-catenin, c-Myc, Bax, and Bcl-2. Flow cytometry analysis of cardiomyocyte apoptosis was performed.

Results

We confirmed that Sfrp1 significantly increased cell viability (assayed by trypan blue and CKK-8) and decreased apoptosis (assayed by flow cytometry analysis and the Bax/Bcl-2 ratio). These effects were partly attributable to the ability of Sfrp1 to down-regulate Wnt signaling pathway (assayed by Western blot to evaluate the expression of Dvl-1, β-catenin, and c-Myc). Indeed, reactivation of the Wnt signaling pathway activity with the specific activator, Licl, reduced Sfrp1-induced cardioprotection during hypoxia and reoxygenation.

Conclusions

The present study demonstrated that Sfrp1 directly protected H9C2 cells from hypoxia and reoxygenation-induced reperfusion injury and apoptosis through inhibition of the Wnt signaling pathway, and added new mechanistic insight regarding the cardioprotective role of Sfrp1 on ischemic damage.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0240-5) contains supplementary material, which is available to authorized users.

FrzA gene protects cardiomyocytes from H2O2-induced oxidative stress through restraining the Wnt/Frizzled pathway

Background

Lately, there is accumulating evidence that the Wnt/Frizzled pathway is reactivated after myocardial infarction, the inhibition of the pathway is beneficial since it reduce of myocardial apoptosis and prevents heart failure. FrzA/Sfrp-1, a secreted frizzled-related protein and antagonist for the wnt/frizzled pathway. We assessed the hypothesis that FrzA protects cardiomyocytes from H₂O₂-Induced Oxidative damage through the inhibition of Wnt/Frizzled pathway activity.

Methods

We used a recombinant AAV9 vector to deliver FrzA gene into neonatal rat ventricle myocytes and developed an oxidative stress model using H₂O₂. The cell vitality was measured by MTT colorimetric assay. Western blot and RT-PCR were used to evaluate the expressions of Dvl-1, β-catenin, c-Myc, Bax and Bcl-2. Flow cytometry analysis of cardiomyocytes apoptosis.

Results

We confirmed that Wnt/frizzled pathway is involved in H₂O₂-induced apoptosis in cardiomyocytes. Compared with controls, H₂O₂ induced the upregulation of Dvl-1, β-catenin, and c-Myc. FrzA suppressed the expression of Dvl-1, β-catenin, c-Myc and the activity of the Wnt/frizzled pathway. Furthermore, FrzA over-expression decreased the apoptotic rate, and the Bax/Bcl-2 ratio in cardiomyocytes treated with H₂O₂.

Conclusions

FrzA, through the inhibition of Wnt/Frizzled pathway activity reduced H₂O₂-induced cardiomyocytes apoptosis and could be a potential therapeutic target for prevention of cardiac oxidative damage.

Brain intraventricular injection of amyloid-β in zebrafish embryo impairs cognition and increases tau phosphorylation, effects reversed by lithium

Alzheimer's disease (AD) is a devastating neurodegenerative disorder with no effective treatment and commonly diagnosed only on late stages. Amyloid-β (Aβ) accumulation and exacerbated tau phosphorylation are molecular hallmarks of AD implicated in cognitive deficits and synaptic and neuronal loss. The Aβ and tau connection is beginning to be elucidated and attributed to interaction with different components of common signaling pathways. Recent evidences suggest that non-fibrillary Aβ forms bind to membrane receptors and modulate GSK-3β activity, which in turn phosphorylates the microtubule-associated tau protein leading to axonal disruption and toxic accumulation. Available AD animal models, ranging from rodent to invertebrates, significantly contributed to our current knowledge, but complementary platforms for mechanistic and candidate drug screenings remain critical for the identification of early stage biomarkers and potential disease-modifying therapies. Here we show that Aβ1-42 injection in the hindbrain ventricle of 24 hpf zebrafish embryos results in specific cognitive deficits and increased tau phosphorylation in GSK-3β target residues at 5dpf larvae. These effects are reversed by lithium incubation and not accompanied by apoptotic markers. We believe this may represent a straightforward platform useful to identification of cellular and molecular mechanisms of early stage AD-like symptoms and the effects of neuroactive molecules in pharmacological screenings.

Oncothermia: a new paradigm and promising method in cancer therapies

In "hypethermia", the procedure of raising the temperature of a part, or the whole body, up to 42 degrees C to kill cancer cells for a defined period of time is applied alone or as an adjunctive with various established cancer treatment modalities such as radiotherapy and chemotherapy. However, "hyperthermia" is not generally accepted as conventional therapy due to the complications of deep heating and lack of focusing of the heat effect only for malignant tissues. The idea of oncothermia solves the selective deep action on malignant tissue on nearly cellular level. Oncothermia is highly improved, safe and effective "hyperthermia" in clinical cancer therapy supported by in vivo, in vitro, and human research as shown in this article. Advantage of oncothermia: while the classical insufficiently, focused "hyperthermia" has to heat up in case of the multiple lesions overlapping all the volume, which contains both normal tissues and malignant tissues; while oncothermia automatically focuses on the malignant tissues in its multiple places, without treating the healthy tissue in between. The modulated radiofrequency current (RF) flows through the malignancies only. The radiofrequency modulated current with 13,56 MHz (fractal modulated) between 2 electrodes automatically focuses through malignant tissues with lower impedance and will flow mainly in the extracellular electrolyte because the normal cells are electronically isolated by their membrane by more than one-million V/m electrical field strength. Oncothermia today has the ability to be a candidate to a widely accepted modality of the standard cancer treatment.

Hyperthermia versus Oncothermia: Cellular Effects in Cancer Therapy

Hyperthermia means overheating of the living object completely or partly. Hyperthermia, the procedure of raising the temperature of a part of or the whole body above the normal for a defined period of time, is applied alone or as an adjunctive with various established cancer treatment modalities such as radiotherapy and chemotherapy. The fact that is the hyperthermia is not generally accepted as conventional therapy. The problem is its controversial performance. The controversy is originated from the complications of the deep heating and the focusing of the heat effect. The idea of oncothermia solves the selective deep action on nearly cellular resolution. We would like to demonstrate the force and perspectives of oncothermia as a highly specialized hyperthermia in clinical oncology. Our aim is to prove the ability of oncothermia to be a candidate to become a widely accepted modality of the standard cancer care. We would like to show the proofs and the challenges of the hyperthermia and oncothermia applications to provide the presently available data and summarize the knowledge in the topic. Like many early-stage therapies, oncothermia lacks adequate treatment experience and long-range, comprehensive statistics that can help us optimize its use for all indications.

Hyperthermia versus Oncothermia: Cellular Effects in Complementary Cancer Therapy

Hyperthermia means overheating of the living object completely or partly. Hyperthermia, the procedure of raising the temperature of a part of or the whole body above normal for a defined period of time, is applied alone or as an adjunctive with various established cancer treatment modalities such as radiotherapy and chemotherapy. However, hyperthermia is not generally accepted as conventional therapy. The problem is its controversial performance. The controversy is originated from the complications of the deep heating and the focusing of the heat effect. The idea of oncothermia solves the selective deep action on nearly cellular resolution. We would like to demonstrate the force and perspectives of oncothermia, as a highly specialized hyperthermia in clinical oncology. Our aim is to prove the ability of oncothermia to be a candidate to become a widely accepted modality of the standard cancer care. We would like to show the proofs and the challenges of the hyperthermia and oncothermia applications to provide the presently available data and summarize the knowledge in the topic. Like many early stage therapies, oncothermia lacks adequate treatment experience and long-range, comprehensive statistics that can help us optimize its use for all indications.

WNT signaling in adult cardiac hypertrophy and remodeling: lessons learned from cardiac development

On pathological stress, the heart reactivates several signaling pathways that traditionally were thought to be operational only in the developing heart. One of these pathways is the WNT signaling pathway. WNT controls heart development but is also modulated during adult heart remodeling. This review summarizes the currently available data regarding WNT signaling during left ventricular (LV) remodeling. Upstream, soluble frizzled-related proteins (sFRPs) block WNT-dependent activation of the canonical WNT pathway. By inhibition of WNT activation, these factors also reduce β-catenin-dependent transcription by altering the ratio of cytoplasmic/nuclear β-catenin. In experimental settings, sFRPs injected into the heart attenuated LV remodeling. sFRPs are secreted from autologous bone marrow-derived mononuclear cells. Disheveled is a signaling intermediate of both the canonical and noncanonical WNT pathway. Similarly to the effect of sFRP, depletion of a disheveled isoform attenuated LV remodeling. In contrast, disheveled activation led to progressive dilated cardiomyopathy. Inhibition of nuclear β-catenin signaling downstream of the canonical WNT pathway significantly reduced postinfarct mortality and functional decline of LV function following chronic left anterior descending coronary artery ligation. WNT signaling also affects mobilization and homing of bone marrow-derived vasculogenic progenitor cells. Finally, heart-specific WNT/β-catenin interaction partners have been identified that will possibly allow targeting this pathway in a tissue-specific manner. In summary, the WNT pathway plays a pivotal role in adult cardiac remodeling and may be suitable for therapeutic interventions. Currently, several molecular and cellular mechanisms whereby WNT inhibition attenuates LV remodeling are proposed. Reactivation of the developmental program to restore functional LV myocardium from resident precursor cells may significantly contribute to this process.

Oncothermia treatment of cancer: from the laboratory to clinic

Oncothermia is a long-time applied method (since 1989) in oncology. Its clinical results excellently show its advantages, however the details of its mechanism are under investigation even today. The method is based on a self-selective process of energy concentration and targets the membrane of the malignant cell, using the temperature gradient and the beta-dispersion of the membrane proteins. To prove the theory we show the experimental evidences in vitro experiments where we showed the definite difference between the conventional heating and the oncothermia at the same temperature. In the next step, we studied some xenograft nude-mice models, verifying the temperature-dependent and non temperature dependent factors. In addition, the synergic effect with some chemotherapies were studied, having more efficacy of the oncothermia with drugs than the conventional heating. These experiments show the definite advantages of the oncothermia compared to its classical counterpart, acting on the same temperature. We have also proved the beneficial effect of oncothermia treatment in the veterinary practice Oncothermia is applied in numerous clinics and hospitals, and we would like to show some characteristic case-reports and also the clinical benefit on the survival time elongation of liver-, pancreas-, brain-, and lung-tumor-lesions.

Radiobiologic response of medulloblastoma cell lines: involvement of beta-catenin?

Medulloblastoma (MB) is the most common brain malignancy in children. Whole neural axis irradiation is the treatment of choice, but it often results in long-term neurocognitive and developmental impairment. Only insights into MB biology will lead to improved therapeutic outcome. Wingless (WNT) signalling deregulation occurs in up to 25% of sporadic tumors, but the specific role of nuclear beta-catenin and its involvement in the radioresponse remains unsettled. Therefore we studied the gamma-radiation response of two MB cell lines from cellular and molecular points of view. Our data show that the p53 wild-type cell line is more sensitive to ionizing radiations (IR) than the p53 mutated line, but apoptosis is also induced in p53-mutated cells, suggesting an alternative p53-independent mechanism. In addition, this study is the first to demonstrate that gamma-rays trigger the WNT system in our in vitro models. Further studies are required to test if this could explain the radiosensitivity of MB and the favorable prognostic value of nuclear beta-catenin in this tumor.

Plasticity of gene expression in injured human dorsal root ganglia revealed by GeneChip oligonucleotide microarrays

Root avulsion from the spinal cord occurs in brachial plexus lesions. It is the practice to repair such injuries by transferring an intact neighbouring nerve to the distal stump of the damaged nerve; avulsed dorsal root ganglia (DRG) are removed to enable nerve transfer. Such avulsed adult human cervical DRG ( [Formula: see text] ) obtained at surgery were compared to controls, for the first time, using GeneChip oligonucleotide arrays. We report 91 genes whose expression levels are clearly altered by the injury. This first study provides a global assessment of the molecular events or "gene switches" as a consequence of DRG injuries, as the tissues represent a wide range of surgical delay, from 1 to 100 days. A number of these genes are novel with respect to sensory ganglia, while others are known to be involved in neurotransmission, trophism, cytokine functions, signal transduction, myelination, transcription regulation, and apoptosis. Cluster analysis showed that genes involved in the same functional groups are largely positioned close to each other. This study represents an important step in identifying new genes and molecular mechanisms in human DRG, with potential therapeutic relevance for nerve repair and relief of chronic neuropathic pain.

A positive feedback loop between hepatocyte growth factor receptor and beta-catenin sustains colorectal cancer cell invasive growth

Overexpressed or activated hepatocyte growth factor receptor, encoded by the MET proto-oncogene, was found in the majority of colorectal carcinomas (CRCs), whose stepwise progression to malignancy requires transcriptional activation of beta-catenin. We here demonstrate that a functional crosstalk between Met and beta-catenin signaling sustains and increases CRC cell invasive properties. Hepatocyte growth factor (HGF) stimulation prompts beta-catenin tyrosine phosphorylation and dissociation from Met, and upregulates beta-catenin expression via the phosphatidylinositol 3-kinase pathway in conditions that mimic those found by the invading and metastasizing cells. Additionally, a transcriptionally active form of beta-catenin, known to be oncogenic, enhances Met expression. Furthermore, HGF treatment increases the activity of the beta-catenin-regulated T-cell factor transcription factor in cells expressing the wild-type or the oncogenic beta-catenin. In the mirror experiments, either Met or beta-catenin knocking down also reduces their protein level. In biological assays, beta-catenin knocking down abrogates the HGF-induced motile phenotype, whereas active beta-catenin fosters ligand-independent cell scattering. Met and beta-catenin also cooperate in promoting entry into the cell cycle and in protecting cells from apoptosis. In conclusion, Met and beta-catenin pathways are mutually activated in CRC cells. This might generate a self-amplifying positive feedback loop resulting in the upregulation of the invasive growth properties of CRC cells.

Cadherin:catenin complex: A novel regulator of vascular smooth muscle cell behaviour

Dysfunctional vascular smooth muscle cell (VSMC) behaviour contributes to the pathogenesis of atherosclerosis and restenosis. Increased rates of VSMC apoptosis are thought to lead to thinning of the fibrous atherosclerotic plaque and thereby instability, while migration of VSMCs to the intima, and inappropriate VSMC proliferation, contribute to intimal thickening that occurs in atherosclerosis and restenosis. Studies, mainly in cancer and neuronal cells, have demonstrated that cell-cell adhesion by the cadherin:catenin complex modulates apoptosis, migration and proliferation. In contrast, until recently the involvement of this complex in the regulation of VSMC behaviour was relatively unstudied. In this review, evidence for the regulation of VSMC apoptosis, migration and proliferation by the cadherin:catenin complex will be discussed.

MG132 induced apoptosis is associated with p53-independent induction of pro-apoptotic Noxa and transcriptional activity of beta-catenin

Noxa is a pro-apoptotic BH3-only member of the Bcl-2 family of proteins that is up-regulated at a transcriptional level by the nuclear protein p53 in response to cellular stresses such as DNA damage or growth factor deprivation. Noxa is able to interact with anti-apoptotic members of the Bcl-2 family and causes release of cytochrome c into the cytosol, leading to the activation of caspases and induction of apoptosis. Here we demonstrate that MG132, a proteasomal inhibitor, rapidly induces Noxa mRNA and protein in two human cell lines, T/C28a and Saos2. The induction of Noxa is associated with a significant reduction in the number of metabolically active cells over the first 24 h of exposure to MG132 and progressive activation of caspase-3, a hallmark of caspase-dependent apoptosis. Partial rescue of the phenotype is observed when cells are transfected with Noxa siRNA prior to treatment with MG132, indicating functional significance of the induction of Noxa. p53 has previously been shown to be non-functional in the T/C28a cell line and is absent by Western blotting in Saos2 cells, suggesting that the induction of Noxa is through a p53 independent mechanism. Western blotting and confocal microscopy showed that total beta-catenin protein is increased in both cell lines at the time of Noxa induction, with the bulk of the beta-catenin present in the nucleus. Transfection with the Tcf reporter vector pTOPFLASH confirms that treatment with MG132 leads to early increased transcriptional activity of beta-catenin in both T/C28a and Saos2 cells. However, although over-expression of transcriptionally active beta-catenin in T/C28a cells also induced apoptosis through a p53-independent mechanism, the levels of Noxa protein were unchanged, suggesting that beta-catenin mediated signaling and Noxa may play independent roles in MG132 induced apoptosis. In summary, our results demonstrate that MG132 induces the pro-apoptotic protein Noxa via a p53-independent mechanism that leads to caspase-dependent apoptosis. This is the first report showing that treatment with MG132 induces Noxa. This study also provides further evidence for a link between beta-catenin mediated signaling and the induction of apoptosis.

Bone morphogenetic protein-2 modulates Wnt and frizzled expression and enhances the canonical pathway of Wnt signaling in normal keratinocytes

BACKGROUND

Bone morphogenetic protein-2 (BMP-2) and Wnt are involved in the normal development and tumorigenesis of several organs, and in the development of skin and skin appendages as a morphogen. However, the crosstalk between BMP-2 and the Wnt/beta-catenin signaling pathway is not clear.

OBJECTIVE

We examined BMP-2-dependent expression of Wnt and its receptor frizzled in normal human keratinocytes.

METHODS

The mRNA expression of the Wnt and frizzled families was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) or ribonuclease protection assay. beta-Catenin expression was measured using RT-PCR and Western blotting. T-cell factor/lymphoid enhancing factor activity was analyzed using the luciferase reporter assay.

RESULTS

We detected the expression of Wnt-2b/13, -4, -5a, -5b, -7a, -7b, and -10a, frizzled-1, -4, -5, -6, -8, -9, and -10, MFRP, and SFRP-1/SARP-2 in keratinocytes. BMP-2 increased Wnt-2b/13, -5b, and -7b, and frizzled-6, -8, and -10. Conversely, BMP-2 suppressed Wnt-10a and SFRP-1/SARP-2. Although Wnt-4 expression was not affected by BMP-2 in confluent conditioned keratinocytes, BMP-2 suppressed cell density-dependent Wnt-4 induction. The transcriptional activity of TCF/LEF, which is a target of the canonical Wnt pathway, was upregulated by BMP-2 in both time- and dose-dependent manners. However, BMP-2-dependent differentiation of keratinocytes suppressed TCF/LEF transcriptional activity.

CONCLUSION

These results suggest that BMP-2 modulates the expression of molecules involved in Wnt signaling, and activates the canonical Wnt pathway in normal human keratinocytes. Moreover, Wnt signaling may be influenced by the fate of keratinocytes, such as proliferation, migration, and differentiation.

Wnt-independent activation of β-catenin mediated by a Dkk1-Fz5 fusion protein

An XWnt8-Fz5 fusion protein synergizes with LRP6 to potently activate beta-catenin-dependent signaling. Here, we generated a fusion in which XWnt8 was fused to the N-terminus of LRP6 and show it synergizes with both Fz4 and Fz5 to potently transactivate beta-catenin-dependent Wnt signaling. Based on this, we hypothesized that the main function of Wnt is to nucleate the formation of a physical complex between LRP6 and a Frizzled. Dkk1, but not the related Dkk3, binds LRP6 and inhibits canonical Wnt signaling by blocking the interaction of Wnt and LRP6. Therefore, we reasoned that a covalent fusion of Dkk1 to Fz5 (Dkk1-Fz5) would mimic Wnt ligand by nucleating the formation of a complex containing Fz5 and LRP6, while Dkk3 (Dkk3-Fz5) would not. We found that Dkk1-Fz5, but not Dkk3-Fz5, potently synergized with LRP6 to activate signaling in a dishevelled-dependent manner.

Dvl2 silencing in postdevelopmental cells results in aberrant cell membrane activity and actin disorganization

The upstream events by which endothelial cells perceive the necessity for migration and how this signal results in coordinated movement is unknown. The synchrony underlying these events shares parallels to events occurring during the movement of tissues in embryogenesis. While Wnt signaling is an important pathway in development, components of the cascade exist in postdevelopment endothelial cells. The objective of this study was to determine whether Dishevelled, a key modulation protein in canonical and PCP-CE Wnt signaling was present in endothelium and its potential function. Western blots of cell lysates and immunolabeling studies confirmed that Dishevelled 2 (Dvl2) is an abundant phosphoprotein in endothelial cells. Dvl2 was localized within the cytoplasm of cells as either F-actin-free or F-actin-associated. The disappearance of F-actin-free Dvl2 in vesicle-like organelles and targeting of actin filaments correlated with a loss in cell motility. Gene silencing of Dishevelled by siRNA duplexes resulted in cells with aberrant membrane activity and an inability to extend lamellipodia. Underlying these abnormalities was a disorganization of the actin filament system, including loss of actin-rich densities, indistinct stress fibers and an accompanying increase in diffuse and aggregate cytoplasmic actin. This study represents the first documentation of Dvl2 in postdevelopmental endothelial cells and its possible role in cell migration via manipulation of actin filament bundles.

Early gene response in lithium chloride induced apoptosis

Depending on the cellular context, lithium chloride can lead to enhanced proliferation, cell cycle arrest or apoptosis in mammalian cells. Although substantial work has been made to elucidate the downstream events in the case of lithium chloride-induced cellular proliferation, the molecular response to lithium chloride treatment in the apoptotic scenario is largely undefined. We have used quadruplicate human cDNA arrays with 8000 targets to analyze the early gene response in cultures of human T/C28a cells that undergo apoptosis in response to 20 mM lithium chloride treatment. Incubation of cell cultures with 20 mM lithium chloride for five hours caused alterations in the steady-state mRNA levels of a large number of genes. RT-PCR and real-time RT-PCR confirmed the array results for ten of eleven selected targets. In addition to one protein primarily associated with apoptosis, genes identified as differentially expressed based on microarray data mainly encode proteins involved in basic cellular functions such as signaling, cell cycle control and growth, cell-cell interaction, solute transport and transcription control. We present a list of 50 genes that were differentially expressed in response to lithium chloride treatment and which may represent a reference for further studies to define the pathways governing the apoptotic response to lithium chloride.

Secreted Frizzled-related Protein 1 (SFRP1) Protects Fibroblasts from Ceramide-induced Apoptosis

Secreted frizzled-related proteins (SFRPs) are soluble proteins that have highly restricted tissue distribution. Although not fully understood, a role of SFRP1 in the regulation of apoptosis has been suggested. Our previous study disclosed a much greater level of SFRP1 expression in periodontal ligament fibroblasts (PDLFs), which have been suggested to maintain a reduced level of apoptosis compared with gingival fibroblasts. We have tested the role of SFRP1 in the regulation of fibroblast apoptosis both in vitro and in vivo. Our data showed that SFRP1 was significantly up-regulated in cultured human PDLFs during ceramide-induced apoptosis. In vivo study demonstrated an increased SFRP1 expression in mice periodontal ligament during force-induced apoptosis. While inhibition of endogenous SFRP1 increased the percentage of cell death in cultured human PDLFs, exogenous SFRP1 substantially reduced apoptosis in cultured human gingival fibroblasts, which do not maintain a high level of endogenous SFRP1 expression. The effect of SFRP1 on apoptosis was linked to the regulation of several apoptosis-related genes, including p53, caspase-3, caspase-9, and BCL-2-interacting killer (BIK). Furthermore our results indicated that the addition of exogenous SFRP1 could reduce the level of apoptosis in dermal fibroblasts in vivo, and this effect was also linked to the regulation of similar apoptosis-related genes as observed in in vitro studies. Collectively our results suggest that the constitutive up-regulation of SFRP1 could be an adaptive cell survival mechanism inherent to functionally specialized fibroblasts, and the addition of SFRP1 may contribute to the inhibition of apoptosis in fibroblast-related cells.

Reduction of infarct size and prevention of cardiac rupture in transgenic mice overexpressing FrzA

BACKGROUND

FrzA/sFRP-1, a secreted, frizzled-related protein and antagonist for the wnt/frizzled pathway, is expressed in the heart and vessels during mouse embryogenesis and adulthood. FrzA is involved in cell cycle control of vascular cells and angiogenesis. We assessed the hypothesis that FrzA could control the healing process after myocardial infarction (MI).

METHODS AND RESULTS

We demonstrated an upregulation of sFRP-1 and distinct wnt and fz member expression after MI. We established transgenic (Tg) mice that overexpress FrzA under a cytomegalovirus promoter and developed a model of MI by coronary artery ligation. FrzA reduced cardiac rupture after MI in Tg (6.5% versus 26.4% in controls; n=165, P<0.01). MI was smaller in Tg at each time point (18+/-10.8% of left ventricular circumference versus 30+/-14.2% in controls at day 30; P<0.001). Similar results were found in cryolesion-induced MI. Cardiac function was improved in Tg mice (3800+/-370 mm Hg/s dP/dtmax versus 2800+/-840 in controls; -2800+/-440 dP/dtmin versus -1800+/-211 in controls at day 15; P<0.001). Early leukocyte infiltration had decreased in Tg mice during the first week. Apoptotic index was decreased by 50% in Tg mice at day 7. Matrix metalloproteinase-2 and -9 activity was reduced in Tg mice at day 4, and collagen deposition in the scar was increased in Tg mice. Capillary density in the scar was higher in Tg mice (290+/-103 vessels/mm2 versus 104+/-43 in controls at day 15; P<0.001). Vessels were more muscularized, and mean lumen area was 3-fold higher in Tg animals.

CONCLUSIONS

Overexpression of FrzA, through direct or indirect interaction with different phases of infarct healing, reduced infarct size and improved cardiac function.

Beta-catenin inhibits cell growth of a malignant mesothelioma cell line, NCI-H28, with a 3p21.3 homozygous deletion

We have found that a malignant mesothelioma cell line, NCI-H28, had a chromosome 3p21.3 homozygous deletion containing the beta-catenin gene (CTNNB1), which suggested that the deletion of beta-catenin might have a growth advantage in the development of this tumor. To determine whether beta-catenin has a growth-inhibitory activity, we transfected wild-type beta-catenin, Ser37Cys mutant beta-catenin as an activated type, and C-terminus deletion mutant beta-catenin that lacks the transcription activity, into the NCI-H28 cells. A non-small cell lung cancer cell line, NCI-H1299, which expressed endogenous beta-catenin, was also studied. We tested the localization of exogenous beta-catenin in the NCI-H28 cells with immunofluorescence, and found that the wild-type beta-catenin and the C-terminus deletion mutant were more strongly expressed in the plasma membrane and cytoplasm than in the nucleus, while the Ser37Cys mutant was more in the nucleus than in the cytoplasm. By using luciferase-reporter assay, the beta-catenin/T-cell factor 4-mediated transactivity of the Ser37Cys mutant was shown to be higher than that of the wild-type beta-catenin in both cell lines. However, the transactivity of the C-terminus deletion mutant was strongly reduced in both. Colony formation of the NCI-H28 cells was reduced by 50% after transfection with the wild-type beta-catenin, and 60% with the Ser37Cys mutant, but only 20% with the C-terminus deletion mutant compared to the vector control. Inhibition of colony formation in NCI-H28 cells was because of apoptosis, manifested by positive staining of Annexin V and TUNEL assays in transfected cells. In contrast, when transfected with the wild-type beta-catenin, no significant reduction in colony formation was seen in beta-catenin wild-type NCI-H1299 cells. In conclusion, our data indicate that inactivation of beta-catenin by a 3p21.3 homozygous deletion might be a crucial event in the development of the mesothelioma NCI-H28 cells. Thus, while beta-catenin is well known to be a positive growth-stimulating factor for many human cancers, it can also act as a potential growth suppressor in some types of human cancer cells.

Neuroprotective properties of valproate: potential benefit for AD and tauopathies

Neuropsychiatric disturbances are extremely common in Alzheimer's disease (AD), and represent integral features of the illness, as well as appropriate targets for therapy. We are interested in designing trials aimed at preventing or delaying the emergence of psychopathology in AD. For symptomatic treatment of agitation, mood stabilizers, particularly sodium valproate, have proved to be beneficial in some patients. Since these effects take several weeks to emerge, we considered that they might be dependent on potentially neuroprotective actions of valproate, such as inhibition of apoptosis and slowing of neurofibrillary tangle formation. In this article we present the rationale for testing the neuroprotective potential of valproate experimentally in mouse models of tauopathy and in a clinical trial of patients with AD who lack psychopathology at baseline. Together, these studies will provide important tests of the hypothesis that valproate, either through inhibition of tau phosphorylation or some other mechanism, is a useful therapeutic agent to modify disease progression in AD.

Proliferation, but not apoptosis, is associated with distinct beta-catenin expression patterns in non-small-cell lung carcinomas: relationship with adenomatous polyposis coli and G(1)-to S-phase cell-cycle regulators

beta-catenin (beta-cat) is a versatile component of homotypic cell adhesion and signaling. Its subcellular localization and cytoplasmic levels are tightly regulated by the adenomatous polyposis coli (APC) protein. Mutations in beta-cat (exon 3) or APC (MCR) result in beta-cat aberrant overexpression that is associated with its nuclear accumulation and improper gene activation. Data from experimental models have shown that beta-cat overexpression has a multitude of effects on cell-cycle behavior. In many of these aspects its function depends on major G(1) phase regulators. To the best of our knowledge, most of these issues have never been addressed concurrently in tumors. For this reason we investigated in a panel of 92 non-small-cell lung carcinomas, beta-cat and APC expression, and their relationship with cell-cycle kinetics (PI and AI) and ploidy status. Moreover, the above correlations were examined in relation to the main G(1)/S-phase checkpoint regulators. Four beta-cat immunohistochemical expression patterns [membranous (11.1%), membranous-cytoplasmic (54.3%), cytoplasmic (9.9%), cytoplasmic-nuclear (24.7%)] and three APC immunohistochemical expression patterns [cytoplasmic (37.7%), cytoplasmic-nuclear (58%), nuclear (4.3%)] were observed, which were further confirmed by Western blot analysis on subcellular fractions in representative samples. The frequent presence of beta-cat in the cytoplasm is an indication of aberrant expression, whereas membranous and nuclear localization were inversely related. Absence of mutations in beta-cat (exon 3) and APC (MCR) suggest that beta-cat destruction mechanisms may be functional. However, expression analysis revealed attenuated levels for APC, indicating a residual ability to degrade beta-cat. Decreased levels were associated with loss of heterozygosity at the APC region in 24% of the cases suggesting that additional silencing mechanisms may be involved. Interestingly, the 90-kd APC isoform associated with apoptosis, was found to be the predominant isoform in normal and cancerous lung tissues. The most important finding in our study, was the correlation of nuclear beta-cat immunohistochemical localization with increased proliferation, overexpression of E2F1 and MDM2, aberrant p53, and low expression of p27(KIP), providing for the first time in vivo evidence that beta-cat-associated proliferation correlates with release of E2F1 activity and loss of p53- and p27(KIP)-dependent cell-cycle checkpoints. Loss of these checkpoints is accompanied by low levels of APC, which possibly reflects a diminished ability to degrade beta-cat. Taken together our data indicate that cases with nuclear beta-cat immunohistochemical expression represent a subset of non-small-cell lung carcinomas that have gained an increased proliferation advantage in contrast to the other beta-cat immunohistochemical expression profiles.

The Wnt signaling pathway in bipolar disorder

The Wnt signaling pathway is a highly conserved pathway critical for proper embryonic development. However, recent evidence suggests that this pathway and one of its key enzymes, glycogen synthase kinase 3beta, may play important roles in regulating synaptic plasticity, cell survival, and circadian rhythms in the mature CNS-all of which have been implicated in the pathophysiology and treatment of bipolar disorder. Furthermore, two structurally highly dissimilar medications used to treat bipolar disorder, lithium and valproic acid, exert effects on components of the Wnt signaling pathway. Together, these data suggest that the Wnt signaling pathway may play an important role in the treatment of bipolar disorder. Here, the authors review the modulation of the Wnt/GSK-3beta signaling pathway by mood-stabilizing agents, focusing on two therapeutically relevant aspects: neuroprotection and modulation of circadian rhythms. The future development of selective GSK-3beta inhibitors may have considerable utility not only for the treatment of bipolar disorder but also for a variety of classical neurodegenerative disorders.

A novel set of Wnt-Frizzled fusion proteins identifies receptor components that activate beta -catenin-dependent signaling

Wnt proteins initiate the canonical (beta-catenin-regulated) signaling cascade by binding to seven-transmembrane spanning receptors of the Frizzled (Fz) family together with the coreceptors LRP5 and -6, members of the low density lipoprotein receptor-related protein family (LRP). Several reports have shown physical and functional associations between various Wnt, LRP, and Frizzled molecules; however, the underlying mechanisms for selectivity remain poorly understood. We present data on a novel set of Wnt-Fz fusion constructs that are useful for elucidating mechanisms of Wnt signal transduction specificity in both Xenopus embryos and 293T cells. In 293T cells, coexpression of several Wnt-Fz fusion proteins with LRP6, but not LRP5, significantly activated a Wnt-responsive promoter, Optimized TOPFlash. Interestingly, Wnt proteins from both the Wnt1 and Wnt5A classes, when fused to the same Frizzled, can synergize with LRP6 to activate signaling and induce secondary axes in Xenopus embryos. However, when several Wnt-Fz constructs containing different Frizzled molecules were tested, it was found that all Frizzled molecules are not equivalent in their ability to activate the canonical Wnt pathway in this context. The data suggest that the distinction between the two Wnt classes lies not in intrinsic differences in the molecules but via the Frizzled molecules with which they interact.

A role for the beta-catenin/T-cell factor signaling cascade in vascular remodeling

Beta-catenin and T cell factor (Tcf) are distal components of the highly conserved Wnt pathway that govern cell fate and proliferation in lower organisms. Thus, we hypothesized that the regulation of beta-catenin and Tcf played a critical role in vascular remodeling. The first objective was to define beta-catenin expression in vascular smooth muscle cells (VSMCs) after balloon injury. Indeed, beta-catenin mRNA and protein were significantly elevated 7 days after balloon injury in the rat carotid artery. We hypothesized that beta-catenin accumulation in response to vascular injury inhibited VSMC apoptosis. In line with our hypothesis, transfection of a degradation-resistant beta-catenin transgene into rat VSMCs significantly inhibited apoptosis. Accumulation of beta-catenin also resulted in a 10-fold increase in the activation of Tcf. To test if Tcf was necessary to confer beta-catenin-induced survival, loss of function studies were carried out with a dominant negative Tcf-4 transgene lacking the beta-catenin binding domain, Tcf4(N31). Indeed, loss of Tcf-4 activity abolished beta-catenin-induced survival. We further postulated that beta-catenin and Tcf promoted cell cycle progression by activating cyclin D1, a target gene of Tcf-4. Beta-catenin activated cyclin D1, and this activation was partially blocked with loss of Tcf-4. In parallel, blockade of Tcf-4 resulted in inhibition of [3H]thymidine incorporation and partial blockade of the G1-S phase transition. In conclusion, beta-catenin and Tcf-4 play a dual role in vascular remodeling by inhibiting VSMC apoptosis and promoting proliferation.