Hydrogen Peroxide-Induced Secreted Frizzled-Related Protein 1 Gene Demethylation Contributes to Hydrogen Peroxide-Induced Apoptosis in Human U251 Glioma Cells

Targeting the cochlin/SFRP1/CaMKII axis in the ocular posterior pole prevents the progression of nonpathologic myopia

Myopia is a major public health issue. However, interventional modalities for nonpathologic myopia are limited due to its complicated pathogenesis and the lack of precise targets. Here, we show that in guinea pig form-deprived myopia (FDM) and lens-induced myopia (LIM) models, the early initiation, phenotypic correlation, and stable maintenance of cochlin protein upregulation at the interface between retinal photoreceptors and retinal pigment epithelium (RPE) is identified by a proteomic analysis of ocular posterior pole tissues. Then, a microarray analysis reveals that cochlin upregulates the expression of the secreted frizzled-related protein 1 (SFRP1) gene in human RPE cells. Moreover, SFRP-1 elevates the intracellular Ca2+ concentration and activates Ca2+/calmodulin-dependent protein kinase II (CaMKII) signaling in a simian choroidal vascular endothelial cell line, and elicits vascular endothelial cell dysfunction. Furthermore, genetic knockdown of the cochlin gene and pharmacological blockade of SFRP1 abrogates the reduced choroidal blood perfusion and prevents myopia progression in the FDM model. Collectively, this study identifies a novel signaling axis that may involve cochlin in the retina, SFRP1 in the RPE, and CaMKII in choroidal vascular endothelial cells and contribute to the pathogenesis of nonpathologic myopia, implicating the potential of cochlin and SFRP1 as myopia interventional targets.

Double crosslinked biomimetic composite hydrogels containing topographical cues and WAY-316606 induce neural tissue regeneration and functional recovery after spinal cord injury

Spinal cord injury (SCI) is an overwhelming and incurable disabling condition, for which increasing forms of multifunctional biomaterials are being tested, but with limited progression. The promising material should be able to fill SCI-induced cavities and direct the growth of new neurons, with effective drug loading to improve the local micro-organism environment and promote neural tissue regeneration. In this study, a double crosslinked biomimetic composite hydrogel comprised of acellularized spinal cord matrix (ASCM) and gelatin-acrylated-β-cyclodextrin-polyethene glycol diacrylate (designated G-CD-PEGDA) hydrogel, loaded with WAY-316606 to activate canonical Wnt/β-catenin signaling, and reinforced by a bundle of three-dimensionally printed aligned polycaprolactone (PCL) microfibers, was constructed. The G-CD-PEGDA component endowed the composite hydrogel with a dynamic structure with a self-healing capability which enabled cell migration, while the ASCM component promoted neural cell affinity and proliferation. The diffusion of WAY-316606 could recruit endogenous neural stem cells and improve neuronal differentiation. The aligned PCL microfibers guided neurite elongation in the longitudinal direction. Animal behavior studies further showed that the composite hydrogel could significantly recover the motor function of rats after SCI. This study provides a proficient approach to produce a multifunctional system with desirable physiological, chemical, and topographical cues for treating patients with SCI.

Unravelling the toxic effects mediated by the neurodegenerative disease-associated S375G mutation of TDP-43 and its S375E phosphomimetic variant

TAR DNA-binding protein 43 (TDP-43) is a nucleic acid–binding protein found in the nucleus that accumulates in the cytoplasm under pathological conditions, leading to proteinopathies, such as frontotemporal dementia and ALS. An emerging area of TDP-43 research is represented by the study of its post-translational modifications, the way they are connected to disease-associated mutations, and what this means for pathological processes. Recently, we described a novel mutation in TDP-43 in an early onset ALS case that was affecting a potential phosphorylation site in position 375 (S375G). A preliminary characterization showed that both the S375G mutation and its phosphomimetic variant, S375E, displayed altered nuclear–cytoplasmic distribution and cellular toxicity. To better investigate these effects, here we established cell lines expressing inducible WT, S375G, and S375E TDP-43 variants. Interestingly, we found that these mutants do not seem to affect well-studied aspects of TDP-43, such as RNA splicing or autoregulation, or protein conformation, dynamics, or aggregation, although they do display dysmorphic nuclear shape and cell cycle alterations. In addition, RNA-Seq analysis of these cell lines showed that although the disease-associated S375G mutation and its phosphomimetic S375E variant regulate distinct sets of genes, they have a common target in mitochondrial apoptotic genes. Taken together, our data strongly support the growing evidence that alterations in TDP-43 post-translational modifications can play a potentially important role in disease pathogenesis and provide a further link between TDP-43 pathology and mitochondrial health.

TCF3 Induces DNMT1 Expression to Regulate Wnt Signaling Pathway in Glioma

The epigenetic alteration is widely understood as the key to cancer initiation. Herein, we intended to clarify the role of transcription factor 3 (TCF3) in the development of glioma and the behind epigenetic mechanism. Through bioinformatics analysis, we identified a TCF3-DNA methyltransferase 1 (DNMT1)-secreted frizzled related protein 1 (SFRP1) axis which was differentially expressed and interacted in gliomas. More specifically, TCF3 activated DNMT1 transcription, and DNMT1 repressed SFRP1 expression. TCF3 and DNMT1 were overexpressed, while SFRP1 was downregulated in glioma. Functionally, TCF3 silencing inhibited cell proliferation and migration, and promoted apoptosis, which were reversed by DNMT1. SFRP1 inhibited the tumor supporting effects of DNMT1 on glioma cells. Moreover, TCF3 downregulation or SFRP1 overexpression inhibited tumorigenesis and enhanced apoptosis of glioma cells, while DNMT1 enhanced tumorigenesis and repressed apoptosis in tumor tissues in vivo. The Wnt pathway was a downstream effector of the TCF3-DNMT1-SFRP1 axis. Collectively, this study determined a novel therapeutic target TCF3 for glioma from the perspective of epigenetic alteration via regulation of SFRP1 expression in a DNMT1-dependent manner.

Epigenetic insights into multiple sclerosis disease progression

Multiple sclerosis (MS), a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system, is today a leading cause of unpredictable lifelong disability in young adults. The treatment of patients in progressive stages remains highly challenging, alluding to our limited understanding of the underlying pathological processes. In this review, we provide insights into the mechanisms underpinning MS progression from a perspective of epigenetics, that refers to stable and mitotically heritable, yet reversible, changes in the genome activity and gene expression. We first recapitulate findings from epigenetic studies examining the brain tissue of progressive MS patients, which support a contribution of DNA and histone modifications in impaired oligodendrocyte differentiation, defective myelination/remyelination and sustained neuro-axonal vulnerability. We next explore possibilities for identifying factors affecting progression using easily accessible tissues such as blood by comparing epigenetic signatures in peripheral immune cells and brain tissue. Despite minor overlap at individual methylation sites, nearly 30% of altered genes reported in peripheral immune cells of progressive MS patients were found in brain tissue, jointly converging on alterations of neuronal functions. We further speculate about the mechanisms underlying shared epigenetic patterns between blood and brain, which likely imply the influence of internal (genetic control) and/or external (e.g. smoking and ageing) factors imprinting a common signature in both compartments. Overall, we propose that epigenetics might shed light on clinically relevant mechanisms involved in disease progression and open new avenues for the treatment of progressive MS patients in the future.

Enhancing α-secretase Processing for Alzheimer's Disease-A View on SFRP1

Amyloid β (Aβ) peptides generated via sequential β- and γ-secretase processing of the amyloid precursor protein (APP) are major etiopathological agents of Alzheimer's disease (AD). However, an initial APP cleavage by an α-secretase, such as the a disintegrin and metalloproteinase domain-containing protein ADAM10, precludes β-secretase cleavage and leads to APP processing that does not produce Aβ. The latter appears to underlie the disease symptom-attenuating effects of a multitude of experimental therapeutics in AD animal models. Recent work has indicated that an endogenous inhibitor of ADAM10, secreted-frizzled-related protein 1 (SFRP1), is elevated in human AD brains and associated with amyloid plaques in mouse AD models. Importantly, genetic or functional attenuation of SFRP1 lowered Aβ accumulation and improved AD-related histopathological and neurological traits. Given SFRP1's well-known activity in attenuating Wnt signaling, which is also commonly impaired in AD, SFRP1 appears to be a promising therapeutic target for AD. This idea, however, needs to be addressed with care because of cancer enhancement potentials resulting from a systemic loss of SFRP1 activity, as well as an upregulation of ADAM10 activity. In this focused review, I shall discuss α-secretase-effected APP processing in AD with a focus on SFRP1, and explore the contrasting perspectives arising from the recent findings.

Epigenetics of SFRP1: The Dual Roles in Human Cancers

Secreted frizzled-related protein 1 (SFRP1) is a gene that belongs to the secreted glycoprotein SFRP family. SFRP1 has been classified as a tumor suppressor gene due to the loss of expression in various human cancers, which is mainly attributed by epigenetic inactivation via DNA methylation or transcriptional silencing by microRNAs. Epigenetic silencing of SFRP1 may cause dysregulation of cell proliferation, migration, and invasion, which lead to cancer cells formation, disease progression, poor prognosis, and treatment resistance. Hence, restoration of SFRP1 expression via demethylating drugs or over-expression experiments opens the possibility for new cancer therapy approach. While the role of SFRP1 as a tumor suppressor gene is well-established, some studies also reported the possible oncogenic properties of SFRP1 in cancers. In this review, we discussed in great detail the dual roles of SFRP1 in cancers-as tumor suppressor and tumor promoter. The epigenetic regulation of SFRP1 expression will also be underscored with additional emphasis on the potentials of SFRP1 in modulating responses toward chemotherapeutic and epigenetic-modifying drugs, which may encourage the development of novel drugs for cancer treatment. We also present findings from clinical trials and patents involving SFRP1 to illustrate its clinical utility, extensiveness of each research area, and progression toward commercialization. Lastly, this review provides directions for future research to advance SFRP1 as a promising cancer biomarker.

Survival of glioblastoma cells in response to endogenous and exogenous oxidative challenges: possible implication of NMDA receptor-mediated regulation of redox homeostasis

Cancer cells are highly metabolically active and produce high levels of reactive oxygen species (ROS). Drug resistance in cancer cells is closely related to their redox status. The role of ROS and its impact on cancer cell survival seems far from elucidation. The mechanisms through which glioblastoma cells overcome aberrant ROS and oxidative stress in a milieu of hypermetabolic state is still elusive. We hypothesize that the formidable growth potential of glioma cells is through manipulation of tumor microenvironment for its survival and growth, which can be attributed to an astute redox regulation through a nexus between activation of N-methyl-d-aspartate receptor (NMDAR) and glutathione (GSH)-based antioxidant prowess. Hence, we examined the NMDAR activation on intracellular ROS level, and cell viability on exposure to hydrogen peroxide (H₂ O₂ ), and antioxidants in glutamate-rich microenvironment of glioblastoma. The activation of NMDAR attenuated the intracellular ROS production in LN18 and U251MG glioma cells. MK-801 significantly reversed this effect. On evaluation of GSH redox cycle in these cells, the level of reduced GSH and glutathione reductase (GR) activity were significantly increased. NMDAR significantly enhanced the cell viability in LN18 and U251MG glioblastoma cells, by attenuating exogenous H₂ O₂ -induced oxidative stress, and significantly increased catalase activity, the key antioxidant that detoxifies H₂ O₂ . We hereby report an unexplored role of NMDAR activation induced protection of the rapidly multiplying glioblastoma cells against both endogenous ROS as well as exogenous oxidative challenges. We propose potentiation of reduced GSH, GR, and catalase in glioblastoma cells through NMDAR as a novel rationale of chemoresistance in glioblastoma.

TRPM2 mediates mitochondria-dependent apoptosis of melanocytes under oxidative stress

Abnormal mitochondrial calcium accumulation plays a critical role in oxidative stress-induced apoptosis of melanocytes. Transient receptor potential cation channel subfamily M member 2 (TRPM2) is a calcium channel sensitive to oxidative stress. However, whether TRPM2 participates in melanocyte apoptosis under oxidative stress was unknown before. In the present study, we initially found that hydrogen peroxide (H₂O₂) induced the demethylation of the promoter region in TRPM2 gene and increased the expression of TRPM2 in normal human melanocytes (NHMs). Meanwhile, TRPM2 was overexpressed in lesional melanocytes of vitiligo that is a skin disease caused by melanocyte loss under oxidative stress. Furthermore, either TRPM2 inhibitors or TRPM2 shRNA could ameliorate H₂O₂-induced apoptosis, mitochondrial reactive oxygen species (ROS) accumulation and mitochondrial membrane potential (MMP) loss in NHMs, which was similar to the effects of an anti-oxidant. More importantly, TRPM2 mediated the calcium influx into the cytoplasm and the mitochondria of NHMs exposed to H₂O₂, and a specific mitochondrial Ca²⁺ uptake inhibitor Ruthenium 360 (Ru360) could also protect NHMs from apoptosis and mitochondrial damages caused by H₂O₂. Taken together, our findings demonstrate that oxidative stress promotes the expression of TRPM2 and thus facilitates mitochondria-dependent apoptosis of melanocytes by increasing calcium influx. Our study indicates that TRPM2 is a potential target for protecting melanocytes against oxidative damages in vitiligo.

Identification of Driver Genes and Key Pathways of Pediatric Brain Tumors and Comparison of Molecular Pathogenesis Based on Pathologic Types

OBJECTIVE

This study is to identify pediatric brain tumors (PBT) driver genes and key pathways to detect the expression of the driver genes and also to clarify the relationship between patients' prognosis and expression of driver genes.

METHODS

The gene expression profile of GSE50161 was analyzed to identify the differentially expressed genes (DEGs) between tumor tissue and the normal tissue. Gene ontology, Kyoto Encyclopedia of Genes and Genomes analysis, and protein-protein interaction network analysis were conducted to identify the enrichment functions, pathways, and hub genes. After hub genes were identified, quantitative reverse transcription polymerase chain reaction was used to confirm the differential expression of these hub genes. Survival data of 325 patients' were analyzed to clarify the relationship between prognosis and expression levels of the mutual hub genes.

RESULTS

Gene ontology and Kyoto Encyclopedia of Genes and Genomes analysis showed that there were 13 common functions and 3 common pathways which were upregulated or downregulated among the 4 groups. Mutual hub genes were somatostatin (SST), glutamate decarboxylase 2 (GAD2), and single copy human parvalbumin gene (PVALB). The expression of SST, GAD2, and PVALB in glioma cells significantly decreased compared with normal glial cells (P < 0.05). In addition, survival analysis showed a favorable progression-free and overall survival in patients with glioma with SST, GAD2, and PVALB high expression (P < 0.05).

CONCLUSIONS

SST, GAD2, and PVALB significantly decrease in glioma cells compared with normal glial cells. Survival analysis suggests that patients with high-expressed SST, GAD2, and PVALB have a longer overall and progression-free survival. The differential expressed genes identified in this study provide novel targets for diagnosis and treatment.