5-Aza-2'-deoxycytidine, a DNA methylation inhibitor, induces cytotoxicity, cell cycle dynamics and alters expression of DNA methyltransferase 1 and 3A in mouse hippocampus-derived neuronal HT22 cells

dCas9-guided demethylation of the AKT1 promoter improves milk protein synthesis in a bovine mastitis mammary gland epithelial model induced by using Staphylococcus aureus

Mastitis is among the main factors affecting milk quality and yield. Although DNA methylation is associated with mastitis, its role in mastitis remains unclear. In this study, a bovine mastitis mammary epithelial cells (BMMECs) model was established via Staphylococcus aureus infection of bovine mammary gland epithelial cells (BMECs). Bisulfite sequencing PCR was used to determine the methylation status of the AKT1 promoter in BMMECs. We found that the degree of the AKT1 promoter methylation in BMMECs was significantly greater than that in BMECs, and the expression levels of genes related to milk protein synthesis were significantly decreased. We used the pdCas9-C-Tet1-SgRNA 2.0 system to regulate the methylation status of the AKT1 promoter. High-efficiency sgRNAs were screened and dCas9-guided AKT1 promoter demethylation vectors were constructed. Following transfection with the vectors, the degree of methylation of the AKT1 promoter was significantly reduced in BMMECs, while AKT1 protein levels increased. When the methylation level of the AKT1 promoter decreased, the synthesis of milk proteins and the expression levels of genes related to milk protein synthesis increased significantly. The viability of the BMMECs was enhanced. Taken together, these results indicate that demethylation guided by the pdCas9-C-Tet1-SgRNA 2.0 system on the AKT1 promoter can reactivate the expression of AKT1 and AKT1/mTOR signaling pathway-related proteins by reducing the AKT1 promoter methylation level and promoting the recovery milk protein expression in BMMECs, thereby alleviating the symptoms of mastitis.

Insights into DNMT1 and programmed cell death in diseases

DNMT1 (DNA methyltransferase 1) is the predominant member of the DNMT family and the most abundant DNMT in various cell types. It functions as a maintenance DNMT and is involved in various diseases, including cancer and nervous system diseases. Programmed cell death (PCD) is a fundamental mechanism that regulates cell proliferation and maintains the development and homeostasis of multicellular organisms. DNMT1 plays a regulatory role in various types of PCD, including apoptosis, autophagy, necroptosis, ferroptosis, and others. DNMT1 is closely associated with the development of various diseases by regulating key genes and pathways involved in PCD, including caspase 3/7 activities in apoptosis, Beclin 1, LC3, and some autophagy-related proteins in autophagy, glutathione peroxidase 4 (GPX4) and nuclear receptor coactivator 4 (NCOA4) in ferroptosis, and receptor-interacting protein kinase 1-receptor-interacting protein kinase 3-mixed lineage kinase domain-like protein (RIPK1-RIPK3-MLKL) in necroptosis. Our study summarizes the regulatory relationship between DNMT1 and different types of PCD in various diseases and discusses the potential of DNMT1 as a common regulatory hub in multiple types of PCD, offering a perspective for therapeutic approaches in disease.

Epigenetic PPARγ preservation attenuates temporomandibular joint osteoarthritis

OBJECTIVE

Previous studies have demonstrated that PPARγ deficiency is associated with osteoarthritis in the knee joint. However, whether epigenetic PPARγ dysregulation has any effect on temporomandibular joint osteoarthritis (TMJOA) is unknown. This study aims to determine the role and mechanism of epigenetic PPARγ dysregulation in TMJOA.

METHODS

Partial TMJ discectomy was performed to induce TMJOA in rat. Primary condylar chondrocytes were isolated, and TNF-α-induced inflammatory condition was created in vitro. The expressions of PPARγ and DNA methyltransferase were investigated in vivo and in vitro. The association of PPARγ and DNA methylation was further studied by treating chondrocytes with DNA demethylation agent 5-Aza-2'-deoxycytidine (5Aza) and transfecting with siRNA of DNA methyltransferase (DNMT)1 and DNMT3a, and the methylation level of PPARγ promoter was evaluated by Bisulfite-sequencing PCR. The chondroprotective effects of 5Aza were explored in vitro and in vivo.

RESULTS

PPARγ suppression and upregulated DNMT1/DNMT3a expression exist in TMJOA cartilage in vivo and primary condylar chondrocytes under TNF-α-induced inflammatory conditions in vitro. DNMT1 and DNMT3a elevation contributes to PPARγ-promoter hypermethylation in TMJ chondrocytes under TNF-α-induced inflammation conditions. DNA demethylation intervention by 5Aza protects chondrocytes from inflammation response in vitro. Mechanistically, 5Aza reversed the hypermethylation of the PPARγ promoter and subsequently resulted in PPARγ restoration and decreased expression of cartilage-catabolic factors in chondrocytes. Rat TMJOA model revealed that 5Aza, by reversing PPARγ suppression, effectively attenuated cartilage degeneration and stabilized cartilage homeostasis by balancing anabolic factor and catabolic factor expression.

CONCLUSION

Epigenetic PPARγ suppression may play a causal role in TMJOA pathogenesis, which can be alleviated by DNA demethylation with 5Aza treatment. This study provides new insights into the pathogenic mechanism and therapeutic strategy of TMJOA.

Identification of molecular subtypes of ischaemic stroke based on immune-related genes and weighted co-expression network analysis

Immune system has been reported to play a key role in the development of ischaemic stroke (IS). Nevertheless, its exact immune-related mechanism has not yet been fully revealed. Gene expression data of IS and healthy control samples was downloaded from Gene Expression Omnibus database and differentially expressed genes (DEGs) was obtained. Immune-related genes (IRGs) data was downloaded from the ImmPort database. The molecular subtypes of IS were identified based on IRGs and weighted co-expression network analysis (WGCNA). 827 DEGs and 1142 IRGs were obtained in IS. Based on 1142 IRGs, 128 IS samples were clustered into two molecular subtypes: clusterA and clusterB. Based on the WGCNA, the authors found that the blue module had the highest correlation with IS. In the blue module, 90 genes were screened as candidate genes. The top 55 genes were selected as the central nodes according to gene degree in protein-protein interactions network of all genes in blue module. Through taking overlap, nine real hub genes were obtained that might distinguish between clusterA subtype and clusterB subtype of IS. The real hub genes (IL7R, ITK, SOD1, CD3D, LEF1, FBL, MAF, DNMT1, and SLAMF1) may be associated with molecular subtypes and immune regulation of IS.

Effects of 5-Aza on neurogenesis contribute to learning and memory in the mouse hippocampus

BACKGROUND

5-Aza-2'-deoxycytidine (5-Aza-CdR) is a demethylating agent that has various biological effects related to DNA methylation. DNA methylation plays important roles in learning and memory. We have reported that 5-Aza-CdR improved the performance of mice in the water maze and step-down tests. Some behaviours have been well recognized to be mediated by neurogenesis in the hippocampus. The Notch signalling pathway plays a key role in adult hippocampal neurogenesis. In this study, we examined whether 5-Aza-CdR (DNA methyltransferase inhibitor) affects neurogenesis and Notch1 expression.

METHODS

The learning and memory behaviour of mice was evaluated by a conditioned avoidance learning 24 h after 5-Aza-CdR treatment. The mRNA and protein expression levels of Notch1 and HES1 were measured by real-time PCR and Western blotting. The 5-bromo-2'-deoxyuridine (BrdU)-positive cells and the expression of Notch1 in the hippocampal DG were observed through laser confocal microscopy. To further clarify whether 5-Aza-CdR affects behaviour through neurogenesis, the expression level of Notch1, cell viability and cell cycle were analysed using the HT22 cell line.

RESULTS

The behaviour in conditioned avoidance learning was improved, while neurogenesis and the Notch1 pathway were increased in the hippocampus of mice that were injected with 5-Aza-CdR. In vitro experiments showed that 5-Aza-CdR increased the expression of the Notch1 pathway and upregulated S-phase in the cell cycle and cell viability.

CONCLUSIONS

Our results suggest that the effect of 5-Aza-CdR on behaviour may be related to an increase in neurogenesis with upregulation of the Notch1 pathway in the hippocampus.

Possible Involvement of DNA Methylation in TSC1 Gene Expression in Neuroprotection Induced by Hypoxic Preconditioning

Background. It has been reported that ischemia and ischemic preconditioning (IPC) have different effects on the expression of tuberous sclerosis complex 1 (TSC1), which may contribute to the tolerance to ischemia/hypoxia with the increase of autophagy. The mechanisms of TSC1 differential expression are still unclear under ischemia/IPC conditions in hippocampal Cornu Ammon 1 (CA1) and Cornu Ammon 3 (CA3) area neuronal cells. While we have shown that 5-Aza-CdR, a DNA methyltransferase inhibitor, can upregulate TSC1 and increase hypoxic tolerance by autophagy in vivo and in vitro, in this study, we examined whether DNA methylation was involved in the differential expression of TSC1 in the CA1 and CA3 regions induced by hypoxic preconditioning (HPC). Methods. Level of rapamycin (mTOR) autophagy, a downstream molecular pathway of TSC1/TSC2 complex, was detected in HPC mouse hippocampal CA1 and CA3 areas as well as in the HPC model of mouse hippocampal HT22 cells. DNA methylation level of TSC1 promoter (-720 bp~ -360 bp) was determined in CA1 and CA3 areas by bisulfite-modified DNA sequencing (BMDS). At the same time, autophagy was detected in HT22 cells transfected with GFP-LC3 plasmid. The role of TSC1 in neuroprotection was measured by cell viability and apoptosis, and the role of TSC1 in metabolism was checked by ATP assay and ROS assay in HT22 cells that overexpressed/knocked down TSC1. Results. HPC upregulated the expression of TSC1, downregulated the level of P-mTOR (Ser2448) and P-p70S6K (Thr389), and enhanced the activity of autophagy in both in vivo and in vitro. The increased expression of TSC1 in HPC may depend on its DNA hypomethylation in the promoter region in vivo. HPC also could reduce energy consumption in HT22 cells. Overexpression and knockdown of TSC1 can affect cell viability, cell apoptosis, and metabolism in HT22 cells exposed to hypoxia. Conclusion. TSC1 expression induced by HPC may relate to the downregulation of its DNA methylation level with the increase of autophagy and the decrease of energy demand.

The Role of DNA Methylation in Stroke Recovery

Epigenetic alterations affect the onset of ischemic stroke, brain injury after stroke, and mechanisms of poststroke recovery. In particular, DNA methylation can be dynamically altered by maintaining normal brain function or inducing abnormal brain damage. DNA methylation is regulated by DNA methyltransferase (DNMT), which promotes methylation, DNA demethylase, which removes methyl groups, and methyl-cytosine–phosphate–guanine-binding domain (MBD) protein, which binds methylated DNA and inhibits gene expression. Investigating the effects of modulating DNMT, TET, and MBD protein expression on neuronal cell death and neurorepair in ischemic stroke and elucidating the underlying mechanisms can facilitate the formulation of therapeutic strategies for neuroprotection and promotion of neuronal recovery after stroke. In this review, we summarize the role of DNA methylation in neuroprotection and neuronal recovery after stroke according to the current knowledge regarding the effects of DNA methylation on excitotoxicity, oxidative stress, apoptosis, neuroinflammation, and recovery after ischemic stroke. This review of the literature regarding the role of DNA methylation in neuroprotection and functional recovery after stroke may contribute to the development and application of novel therapeutic strategies for stroke.

Reciprocal SOX2 regulation by SMAD1-SMAD3 is critical for anoikis resistance and metastasis in cancer

Growth factors in tumor environments are regulators of cell survival and metastasis. Here, we reveal the dichotomy between TGF-β superfamily growth factors BMP and TGF-β/activin and their downstream SMAD effectors. Gene expression profiling uncovers SOX2 as a key contextual signaling node regulated in an opposing manner by BMP2, -4, and -9 and TGF-β and activin A to impact anchorage-independent cell survival. We find that SOX2 is repressed by BMPs, leading to a reduction in intraperitoneal tumor burden and improved survival of tumor-bearing mice. Repression of SOX2 is driven by SMAD1-dependent histone H3K27me3 recruitment and DNA methylation at SOX2's promoter. Conversely, TGF-β, which is elevated in patient ascites, and activin A can promote SOX2 expression and anchorage-independent survival by SMAD3-dependent histone H3K4me3 recruitment. Our findings identify SOX2 as a contextual and contrastingly regulated node downstream of TGF-β members controlling anchorage-independent survival and metastasis in ovarian cancers.

Icariin Promotes In Vitro Cardiomyocyte Proliferation and Differentiation in Human Bone Marrow-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are the excellent candidates in myocardial regeneration given their easy accessibility, low immunogenicity and high potential for cardiomyocyte differentiation. This work focused on investigating the role of icariin, a main active component of the Traditional Chinese herb epimedium, in human bone marrow-derived MSCs (BMSCs) proliferation and differentiation into cardiomyocytes In Vitro. Human BMSCs were cultivated In Vitro, and MTT assay was conducted to measure their proliferation. On this basis, we selected the optimal icariin dose for promoting the proliferation to induce cardiomyocyte differentiation of MSCs, which were pretreated with or without 5-azacytidine (5-Aza). Cardiac-specific cardiac troponin I (cTnI) and connexin 43 (Cx43)-positive cells were detected by immunofluorescent staining. The differentiation ratio of MSCs was examined by flow cytometry. This study measured early cardiac transcription factors (TFs) Nkx2.5 and GATA4 levels through RT-PCR and Western blotting (WB). As a result, icariin increased MSC proliferation dependent on its dose, and the optimal dose was determined to be 80 μg/l. Furthermore, MSCs showed minimal cardiomyogenic differentiation when induced by icariin alone as confirmed by the expression of cardiac-related markers. Moreover, a synergic interaction was observed when icariin and 5-Aza cooperated to induce cardiomyocyte differentiation of MSCs. In conclusion, Icariin stimulates proliferation and facilitates cardiomyocyte differentiation of MSCs In Vitro and may be potentially used as a new method for enhancing the MSCs efficacy in cardiovascular disease.

DNA Methylation and Detoxification in the Earthworm Lumbricus terrestris Exposed to Cadmium and the DNA Demethylation Agent 5-aza-2'-deoxycytidine

Earthworms are well-established model organisms for testing the effects of heavy metal pollution. How DNA methylation affects cadmium (Cd) detoxification processes such as the expression of metallothionein 2 (MT2), however, is largely unknown. We therefore exposed Lumbricus terrestris to 200 mg concentrations of Cd and 5-aza-2'-deoxycytidine (Aza), a demethylating agent, and sampled tissue and coelomocytes, cells of the innate immune system, for 48 h. MT2 transcription significantly increased in the Cd- and Cd-Aza-treated groups. In tissue samples, a significant decrease in MT2 in the Aza-treated group was detected, showing that Aza treatment inhibits basal MT2 gene activity but has no effect on Cd-induced MT2 levels. Although Cd repressed the gene expression of DNA-(cytosine-5)-methyltransferase-1 (DNMT1), which is responsible for maintaining DNA methylation, DNMT activity was unchanged, meaning that methylation maintenance was not affected in coelomocytes. The treatment did not influence DNMT3, which mediates de novo methylation, TET gene expression, which orchestrates demethylation, and global levels of hydroxymethylcytosine (5hmC), a product of the demethylation process. Taken together, this study indicates that Aza inhibits basal gene activity, in contrast to Cd-induced MT2 gene expression, but does not affect global DNA methylation. We therefore conclude that Cd detoxification based on the induction of MT2 does not relate to DNA methylation changes.

Hypermethylation at the CXCR5 gene locus limits trafficking potential of CD8+ T cells into B-cell follicles during HIV-1 infection

CD8+ T-cells play an important role in HIV control. However, in human lymph nodes (LNs), only a small subset of CD8+ T-cells expresses CXCR5, the chemokine receptor required for cell migration into B cell follicles, which are major sanctuaries for HIV persistence in individuals on therapy. Here, we investigate the impact of HIV infection on follicular CD8+ T-cells (fCD8s) frequencies, trafficking pattern and CXCR5 regulation. We show that, although HIV infection results in a marginal increase of fCD8s in LN, the majority of HIV-specific CD8+ T-cells are CXCR5 negative (non-fCD8s) (p<0.003). Mechanistic investigations using ATAC-seq showed that non-fCD8s have closed chromatin at the CXCR5 transcriptional start site (TSS). DNA bisulfite sequencing identified DNA hypermethylation at the CXCR5 TSS as the most probable cause of closed chromatin. Transcriptional factor footprints analysis revealed enrichment of transforming growth factors (TGFs) at the TSS of fCD8s. In-vitro stimulation of non-fCD8s with recombinant TGF-β resulted in significant increase in CXCR5 expression (fCD8s). Thus, this study identifies TGF-β signaling as a viable strategy for increasing fCD8s frequencies in follicular areas of the LN where they are needed to eliminate HIV infected cells, with implications for HIV cure strategies.

The Differential Antitumor Activity of 5-Aza-2'-deoxycytidine in Prostate Cancer DU145, 22RV1, and LNCaP Cells

DNA methylation is a DNA methyltransferase-mediated epigenetic modification affecting gene expression. This process is involved in the initiation and development of malignant disease. 5-Aza-2'-deoxycytidine (5-Aza), a classic DNA methyltransferase inhibitor, possesses antitumor proliferation activity. However, whether 5-Aza induces cytotoxicity in solid tumors warrants further investigated. In this study, human prostate cancer (CaP) cells were treated with 5-Aza and subjected to cell viability and cytotoxicity analysis. Reverse transcription-polymerase chain reaction and methylation-specific polymerase chain reaction assay were utilized to test the gene expression and methylation status of the p53 and p21 gene promoters. The results showed that 5-Aza differentially inhibited spontaneous proliferation, arrested the cell cycle at S phase in DU145, at G1 phase in 22RV1 and LNCaP cells, and G2 phase in normal RWPE-1 cells, as well as induced the expression of phospho-H2A.X and tumor suppressive mammary serine protease inhibitor (maspin) in all three types of CaP cells. 5-Aza also increased p53 and p21 transcription through promoter demethylation, and decreased the expression of oncogene c-Myc in 22RV1 and LNCaP cells. Western blotting analysis showed that the poly (ADP-ribose) polymerase cleavage was detected in DU145 and 22RV1 cells. Moreover, there were no significant changes in p53, p21 and c-Myc expression in DU145 cells following treatment with 5-Aza. Thus, in responsible for its apoptotic induction and DNA damage, the mechanism of the antitumor activities of 5-Aza may involve in an increase of tumor suppressive maspin, upregulation of wild type p53-mediated p21 expression and a decrease of oncogene c-Myc level in 22RV1 and LNCaP cells, and enhancing the tumor suppressive maspin expression in DU145 cells. These results enriched our understanding of the multifaceted antitumor activity of 5-Aza, and provided the expression basis of biomarkers for its possible clinical application in prostate cancer.

Coeloglossum viride var. bracteatum extract attenuates staurosporine induced neurotoxicity by restoring the FGF2-PI3K/Akt signaling axis and Dnmt3

We previously demonstrated the antioxidant activity of Coeloglossum viride var. bracteatum extract (CE) in rat cortical neurons and in mice with chemically induced cognitive impairment. In this work, we established a staurosporine (STS)-induced toxicity model to decipher the neuroprotective mechanisms of CE. We found that CE protected cell viability and neurite integrity in STS-induced toxicity by restoring the levels of FGF2 and its associated PI3K/Akt signaling axis. LY294002, a pan-inhibitor of PI3K, antagonized the activity of CE, although its-mediated restoration of FGF2 was unaffected. In addition, CE restored levels of Bcl-2/Caspase-3, PKCα/CaM pathway, and Dnmt3a and Dnmt3b, two methyltransferases that contribute to de novo DNA methylation. The Dnmts inhibitor 5-azacytidine impaired CE-mediated restoration of Dnmt3 or CaM, as well as the transition of DNA methylation status on the Dnmt3 promoter. These results reveal potential mechanisms that could facilitate the study and application of CE as a neuroprotective agent.

Epigenetic effects of insecticides on early differentiation of mouse embryonic stem cells

Increasing evidence indicates that many insecticides produce significant epigenetic changes during embryogenesis, leading to developmental toxicities. However, the effects of insecticides on DNA methylation status during early development have not been well studied. We developed a novel nuclear phenotypic approach using mouse embryonic stem cells harboring enhanced green fluorescent protein fused with methyl CpG-binding protein to evaluate global DNA methylation changes via high-content imaging analysis. Exposure to imidacloprid, carbaryl, and o,p'-DDT increased the fluorescent intensity of granules in the nuclei, indicating global DNA methylating effects. However, DNA methylation profiling in cell-cycle-related genes, such as Cdkn2a, Dapk1, Cdh1, Mlh1, Timp3, and Rarb, decreased in imidacloprid treatments, suggesting the potential influence of DNA methylation patterns on cell differentiation. We developed a rapid method for evaluating global DNA methylation and used this approach to show that insecticides pose risks of developmental toxicity through DNA methylation.

Rapamycin ameliorates corneal injury after alkali burn through methylation modification in mouse TSC1 and mTOR genes

Alkali burn to the cornea is one of the most intractable injuries to the eye due to the opacity resulting from neovascularization (NV) and fibrosis. Numerous studies have focused on studying the effect of drugs on alkali-induced corneal injury in mouse, but fewer on the involvement of alkali-induced DNA methylation and the PI3K/AKT/mTOR signaling pathway in the mechanism of alkali-induced corneal injury. Thus, the aim of this study was to determine the involvement of DNA methyltransferase 3 B-madiated DNA methylation and PI3K/AKT/mTOR signaling modulation in the mechanism of alkali-induced corneal injury in a mouse model. To this end, we used bisulfite sequencing polymerase chain reaction and Western blot analysis, to study the effects of 5-aza-2'-deoxycytidine and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one, which inhibit methyltransferase and PI3K respectively, on DNA methylation and expression of downstream effectors of PI3K related to corneal NV, including TSC1 and mTOR genes. The results showed that, after an intraperitoneal injection of rapamycin (2 mg/kg/day) for seven days, the alkali-induced opacity and NV were remarkably decreased mainly by suppressing the infiltration of immune cells into injured corneas, angiogenesis, VEGF expression and myofibroblasts differentiation; as well as by promoting corneal cell proliferation and PI3K/AKT/mTOR signaling. More significantly, these findings showed that epigenetic regulatory mechanisms by DNA methylation played a key role in corneal NV, including in corneal alkali burn-induced methylation modification and rapamycin-induced DNA demethylation which involved the regulation of the PI3K/AKT/mTOR signaling pathway at the protein level. The precise findings of morphological improvement and regulatory mechanisms are helpful to guide the use of rapamycin in the treatment of corneal angiogenesis induced by alkaline-burn.

DNMT1-mediated Foxp3 gene promoter hypermethylation involved in immune dysfunction caused by arsenic in human lymphocytes

Growing evidence indicates that arsenic can cause long-lasting and irreversible damage to the function of the human immune system. It is known that forkhead box protein 3(Foxp3), which is specifically expressed in regulatory T cells (Tregs), plays a decisive role in immunoregulation and is regulated by DNA methylation. While evidence suggests that epigenetic regulated Foxp3 is involved in the immune disorders caused by arsenic exposure, the specific mechanism remains unclear. In this study, after primary human lymphocytes were treated with different doses of NaAsO₂, our results showed that arsenic induced the high expression of DNMT1 and Foxp3 gene promoter methylation level, thereby inhibiting the expression levels of Foxp3, followed by decreasing Tregs and reducing related anti-inflammatory cytokines, such as interleukin 10 (IL-10) and interleukin 10 (IL-35), and increasing the ratio of CD4⁺/CD8⁺ T cells in lymphocytes. Treatment with DNA methyltransferase inhibitor 5-Aza-CdR can notably inhibit the expression of DNMT1, effectively restoring the hypermethylation of the Foxp3 promoter region in primary human lymphocytes and upregulating the expression levels of Foxp3, balancing the ratio of CD4⁺/CD8⁺ T cells in lymphocytes. It also activates the secretion of anti-inflammatory cytokines and restores the immune regulatory functions of Tregs. In conclusion, our study provides limited evidence that DNMT1-mediated Foxp3 gene promoter hypermethylation is involved in immune dysfunction caused by arsenic in primary human lymphocytes. The study can provide a scientific basis for further understanding the arsenic-induced immune dysfunction in primary human lymphocytes.

Neuroprotective mechanisms of DNA methyltransferase in a mouse hippocampal neuronal cell line after hypoxic preconditioning

Hypoxic preconditioning has been shown to improve hypoxic tolerance in mice, accompanied by the downregulation of DNA methyltransferases (DNMTs) in the brain. However, the roles played by DNMTs in the multiple neuroprotective mechanisms associated with hypoxic preconditioning remain poorly understood. This study aimed to establish an in vitro model of hypoxic preconditioning, using a cultured mouse hippocampal neuronal cell line (HT22 cells), to examine the effects of DNMTs on the endogenous neuroprotective mechanisms that occur during hypoxic preconditioning. HT22 cells were divided into a control group, which received no exposure to hypoxia, a hypoxia group, which was exposed to hypoxia once, and a hypoxic preconditioning group, which was exposed to four cycles of hypoxia. To test the ability of hypoxic preadaptation to induce hypoxic tolerance, cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium assay. Cell viability improved in the hypoxic preconditioning group compared with that in the hypoxia group. The effects of hypoxic preconditioning on the cell cycle and apoptosis in HT22 cells were examined by western blot assay and flow cytometry. Compared with the hypoxia group, the expression levels of caspase-3 and spectrin, which are markers of early apoptosis and S-phase arrest, respectively, noticeably reduced in the hypoxic preconditioning group. Finally, enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and western blot assay were used to investigate the changes in DNMT expression and activity during hypoxic preconditioning. The results showed that compared with the control group, hypoxic preconditioning downregulated the expression levels of DNMT3A and DNMT3B mRNA and protein in HT22 cells and decreased the activities of total DNMTs and DNMT3B. In conclusion, hypoxic preconditioning may exert anti-hypoxic neuroprotective effects, maintaining HT22 cell viability and inhibiting cell apoptosis. These neuroprotective mechanisms may be associated with the inhibition of DNMT3A and DNMT3B.

5-Aza-2'-deoxycytidine increases hypoxia tolerance-dependent autophagy in mouse neuronal cells by initiating the TSC1/mTOR pathway

BACKGROUND

Our previous study found that 5-Aza-2'-deoxycytidine (5-Aza-CdR) can repress the expression and activity of protein serine/threonine phosphatase-1γ (PP1γ) in mouse hippocampus. It is well known that PP1γ regulates cell metabolism, which is related to hypoxia/ischaemia tolerance. It has been reported that it can also induce autophagy in cancer cells. Autophagy is important for maintaining cellular homeostasis associated with metabolism. In this study, we examined whether 5-Aza-CdR increases hypoxia tolerance-dependent autophagy by initiating the TSC1/mTOR/autophagy signalling pathway in neuronal cells.

METHODS

5-Aza-CdR was either administered to mice via intracerebroventricular injection (i.c.v) or added to cultured hippocampal-derived neuronal cell line (HT22 cell) in the medium for cell culture. The hypoxia tolerance of mice was measured by hypoxia tolerance time and Perl's iron stain. The mRNA and protein expression levels of tuberous sclerosis complex 1 (TSC1), mammalian target of rapamycin (mTOR) and autophagy marker light chain 3 (LC3) were measured by real-time PCR and western blot. The p-mTOR and p-p70S6k proteins were used as markers for mTOR activity. In addition, the role of autophagy was determined by correlating its intensity with hypoxia tolerance in a time-dependent manner. At the same time, the involvement of the TSC1/mTOR pathway in autophagy was also examined through transfection with TSC1 (hamartin) plasmid.

RESULTS

5-Aza-CdR was revealed to increase hypoxia tolerance and induce autophagy, accompanied by an increase in mRNA and protein expression levels of TSC1, reduction in p-mTOR (Ser2448) and p-p70S6k (Thr389) protein levels, and an increase in the ratio of LC3-II/LC3-I in both mouse hippocampus and hippocampal-derived neuronal cell line (HT22). The fluorescence intensity of hamartin was enhanced in the hippocampus of mice exposed to 5-Aza-CdR. Moreover, HT22 cells that over-expressed TSC1 showed more autophagy.

CONCLUSIONS

5-Aza-CdR can increase hypoxia tolerance by inducing autophagy by initiating the TSC1/mTOR pathway.

Potassium bisperoxo (1,10-phenanthroline) oxovanadate suppresses proliferation of hippocampal neuronal cell lines by increasing DNA methyltransferases

Bisperoxo (1,10-phenanthroline) oxovanadate (BpV) can reportedly block the cell cycle. The present study examined whether BpV alters gene expression by affecting DNA methyltransferases (DNMTs), which would impact the cell cycle. Immortalized mouse hippocampal neuronal precursor cells (HT22) were treated with 0.3 or 3 μM BpV. Proliferation, morphology, and viability of HT22 cells were detected with an IncuCyte real-time video imaging system or inverted microscope and 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium, respectively. mRNA and protein expression of DNMTs and p21 in HT22 cells was detected by real-time polymerase chain reaction and immunoblotting, respectively. In addition, DNMT activity was measured with an enzyme-linked immunosorbent assay. Effects of BpV on the cell cycle were analyzed using flow cytometry. Results demonstrated that treatment with 0.3 μM BpV did not affect cell proliferation, morphology, or viability; however, treatment with 3 μM BpV decreased cell viability, increased expression of both DNMT3B mRNA and protein, and inhibited the proliferation of HT22 cells; and 3 μM BpV also blocked the cell cycle and increased expression of the regulatory factor p21 by increasing DNMT expression in mouse hippocampal neurons.

Limitations of current in vitro models for testing the clinical potential of epigenetic inhibitors for treatment of pediatric ependymoma

Background

Epigenetic modifications have been shown to play an important role in the classification and pathogenesis of the pediatric brain tumor ependymoma, suggesting they are a potential therapeutic target.

Results

Agents targeting epigenetic modifications inhibited the growth and induced the death of ependymoma cells with variable efficiency. However, this was often not at clinically achievable doses. Additionally, DNA methylation profiling revealed a lack of similarity to primary ependymomas suggesting alterations were induced during culture. Toxicity to fetal neural stem cells was also seen at similar drug concentrations

Conclusions

Agents targeting epigenetic modifications were able to inhibit the growth and induced the death of ependymoma cells grown in vitro. However, many agents were only active at high doses, outside clinical ranges, and also resulted in toxicity to normal brain cells. The lack of similarity in DNA methylation profiles between cultured cells and primary ependymomas questions the validity of using in vitro cultured cells for pre-clinical analysis of agents targeting epigenetic mechanisms and suggests further investigation using models that are more appropriate should be undertaken before agents are taken forward for clinical testing.

Materials and Methods

The effects of agents targeting epigenetic modifications on the growth and death of a panel of ependymoma cell lines was investigated, as well as toxicity to normal fetal neural stem cells. The ependymoma cell lines were characterized using DNA methylation profiling.

Involvement of nerve growth factor in mouse hippocampal neuronal cell line (HT22) differentiation and underlying role of DNA methyltransferases

DNA methylation is an epigenetic event involved in regulation of gene transcription during cell differentiation. DNA methyltransferases (DNMT) play a role in differentiation of neural stem cells into neurons. The aim of this study was to determine whether nerve growth factor (NGF) was involved in differentiation of mouse hippocampal neuronal cell line (HT22) as assessed by IncuCyte. Quantitative PCR and western blot were used to measure gene and protein expression of DNMT as well as the activity of DNMTs. Treatment with NGF was found to upregulate both gene and protein expressions as well as total activity of DNMTs in differentiating HT22 cells. Compared to undifferentiating cells, the percentage of differentiating cells at S phase increased significantly when incubated with NGF. In undifferentiated cells, NGF failed to induce gene and protein expressions and activity of DNMTs. Data demonstrate that differentiation of HT22 cells by exposure to NGF involve the activation of DNMTs pathway.

Effects of 5-Aza on p-Y1472 NR2B related to learning and memory in the mouse hippocampus

BACKGROUND

We have previously reported that 5-Aza-2-deoxycytidine (5-Aza-cdR) can repress protein serine/threonine phosphatase-1γ (PP1γ) expression and activity in the mouse hippocampus and affect the behaviour of mice in a water maze. It is well known that the phosphorylation of N-methyl-d-aspartate receptor 2B subunit (NR2B) plays a role in behaviour. In this study, we examined whether 5-Aza-cdR affects NR2B phosphorylation at tyrosine 1472 (p-Y1472 NR2B) and whether it affected the responses of the mice in a passive avoidance test.

METHODS

5-Aza-cdR (10 μM) was administered to mice via intracerebroventricular injection (i.c.v). The learning and memory behaviour of the mice were evaluated by measuring their response in a step-down type passive avoidance test 24 h after the injection. The mRNA level of NR2B was measured by real-time PCR. NR2B and p-Y1472 NR2B protein expression in the mouse hippocampus was detected by western blot and immunofluorescence. CDK5 activity was detected by the ADP-Glo™ + CDK5/p35 Kinase Enzyme System. To further clarify whether the 5-Aza-cdR effects on behaviour were dependent on cellular proliferation or not, the effect of 5-Aza-cdR on the expression level of NR2B, the phosphorylation level of p-Y1472 NR2B, cell viability and the cell cycle were analysed using the immortalized mouse hippocampal neuronal cells neural cell line HT22 treated with 10 μM 5-Aza-cdR compared with an untreated control group.

RESULTS

After injection with 5-Aza-cdR, the behaviour of the mice in the step-down test was improved, while their phosphorylation level of p-Y1472 NR2B was increased and their CDK5 activity was decreased in the hippocampus. In vitro experiments showed 10 μM 5-Aza-cdR increased the p-Y1472 NR2B phosphorylation level with inhibition of cell viability and cell cycle arrest.

CONCLUSIONS

Our results suggested that the effect of 5-Aza-cdR on behaviour may be related to the increase in phosphorylation of p-Y1472 NR2B in the hippocampus.

The emerging spectrum of early life exposure-related inflammation and epigenetic therapy

Early life exposure to a variety of insults during sensitive windows of development can reprogram normal physiological responses and alter disease susceptibility later in life. During this process, Inflammation triggered by a variety of adverse exposures plays an important role in the initiation and development of many types of diseases including tumorigenesis. This review article summaries the current knowledge about the role and mechanism of inflammation in development of diseases. In addition, epigenome alteration related to inflammation and treatment options using epigenetic modifiers are highlighted and discussed.

Cytochrome P450 1B1 promotes cancer cell survival via specificity protein 1 (Sp1)-mediated suppression of death receptor 4

Cytochrome P450 1B1 (CYP1B1), a well-known oncogene, has garnered wide attention because of its tumor-specific expression pattern and actions as a carcinogenic factor. Although CYP1B1 might play a crucial role in carcinogenesis, the detailed molecular mechanisms underlying oncogenic involvement in cancer development remain unclear. The present study investigated the manner in which CYP1B1 promotes survival of various cancer cells. Treatment with 2,2',4,6'-tetramethoxystilbene (TMS), a specific CYP1B1 inhibitor, significantly inhibited cell viability in human breast cancer and leukemia cell lines, including MCF-7, MDA-MB-231, HL-60, and U937 cells. In order to characterize the cellular functions of CYP1B1 associated with cancer cell survival, the relationship between this oncogene and death receptor 4 (DR4) was determined. Following induction or inhibition of CYP1B1, mRNA and protein expression levels of DR4 were measured, and this oncogene was found to significantly repress DR4 mRNA and protein expression. Further, the suppression of DR4 by CYP1B1 was restored with 5-aza-2'-deoxycytidine (5-aza-dC), a DNA methyltransferase inhibitor, indicating that DNA methylation may be involved in CYP1B1-mediated DR4 inhibition. Methylation-specific polymerase chain reaction (PCR) in CYP1B1-overexpressed HL-60 cells revealed that this oncogene induced hypermethylation on DR4 promoter. Interestingly, data showed that DR4 suppression of CYP1B1 is mediated by the DNA-binding ability of specificity protein 1 (Sp1). These findings suggest that CYP1B1 promotes cancer cell survival through involvement of DNA methylation-mediated DR4 inhibition and that Sp1 may act as key mediator required for oncogenic action.