Amyloid protein-mediated differential DNA methylation status regulates gene expression in Alzheimer's disease model cell line.

The Swedish mutation of amyloid precursor protein (APP-sw) has been reported to dramatically increase beta amyloid production through aberrant cleavage at the beta secretase site, causing early-onset Alzheimer's disease (AD). DNA methylation has been reported to be associated with AD pathogenesis, but the underlying molecular mechanism of APP-sw-mediated epigenetic alterations in AD pathogenesis remains largely unknown. We analyzed genome-wide interplay between promoter CpG DNA methylation and gene expression in an APP-sw-expressing AD model cell line. To identify genes whose expression was regulated by DNA methylation status, we performed integrated analysis of CpG methylation and mRNA expression profiles, and identified three target genes of the APP-sw mutant; hypomethylated CTIF (CBP80/CBP20-dependent translation initiation factor) and NXT2 (nuclear exporting factor 2), and hypermethylated DDR2 (discoidin domain receptor 2). Treatment with the demethylating agent 5-aza-2'-deoxycytidine restored mRNA expression of these three genes, implying methylation-dependent transcriptional regulation. The profound alteration in the methylation status was detected at the -435, -295, and -271 CpG sites of CTIF, and at the -505 to -341 region in the promoter of DDR2. In the promoter region of NXT2, only one CpG site located at -432 was differentially unmethylated in APP-sw cells. Thus, we demonstrated the effect of the APP-sw mutation on alteration of DNA methylation and subsequent gene expression. This epigenetic regulatory mechanism may contribute to the pathogenesis of AD.

Protective role of ABCA1 in ischemic preconditioning is mediated by downregulation of miR-33-5p and miR-135-5p.

Ischemic preconditioning (IPC) significantly reduces ischemia-reperfusion injury in the brain by inducing ischemic tolerance. Although emerging evidence suggests that microRNAs (miRNAs) contribute to the pathogenesis of brain ischemia and IPC-induced neuroprotection, the role of miRNAs and their underlying mechanisms are still unclear. IPC was induced in male C57BL/6 mice by brief bilateral common carotid artery occlusion. After 24 h, mice underwent transient middle cerebral artery occlusion followed by 3 h of reperfusion. Expression levels of messenger RNAs (mRNAs) and proteins were examined in the ipsilateral cortex, and mimics and inhibitors of selective miRNAs were transfected into Neuro-2a cells before oxygen-glucose deprivation (OGD). Post-IPC miRNA expression profiling identified neuroprotection-associated changes in miRNA expression in the ipsilateral cortex after ischemic stroke. Among them, miR-33-5p and miR-135b-5p were significantly downregulated by IPC. Inhibition of miR-33-5p and miR-135b-5p expression protected Neuro-2a cells from OGD-induced apoptosis. Inhibition of these two miRNAs significantly increased mRNA and protein levels of ATP-binding cassette subfamily A member 1 (ABCA1), and a binding assay showed that these two miRNAs showed specificity for Abca1 mRNA. Overexpression of ABCA1 decreased the Bax/Bcl2 mRNA ratio and activation of caspase-9 and caspase-3, whereas knockdown of ABCA1 expression increased the Bax/Bcl2 mRNA ratio and the percentage of Neuro-2a cells with a loss of mitochondrial membrane potential after OGD-treatment. In conclusion, ABCA1 expression is regulated by miR-33-5p and miR-135b-5p. Increased ABCA1 expression following IPC exerts a protective influence against cerebral ischemia via suppression of a mitochondria-dependent apoptosis pathway.

Aberrant hypomethylation-mediated AGR2 overexpression induces an aggressive phenotype in ovarian cancer cells.

The metastatic properties of cancer cells result from genetic and epigenetic alterations that lead to the abnormal expression of key genes regulating tumor phenotypes. Recent discoveries suggest that aberrant DNA methylation provides cancer cells with advanced metastatic properties; however, the precise regulatory mechanisms controlling metastasis-associated genes and their roles in metastatic transformation are largely unknown. We injected SK-OV-3 human ovarian cancer cells into the perineum of nude mice to generate a mouse model that mimics human ovarian cancer metastasis. We analyzed the mRNA expression and DNA methylation profiles in metastasized tumor tissues in the mice. The pro-oncogenic anterior gradient 2 (AGR2) gene showed increased mRNA expression and hypomethylation at CpG sites in its promoter region in the metastatic tumor tissues compared with the cultured SK-OV-3 cells. We identified crucial cytosine residues at CpG sites in the AGR2 promoter region. Treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine reduced the level of CpG methylation in the AGR2 promoter and increased the level of AGR2 expression. Next, we explored the functional role of AGR2 in the metastatic transformation of SK-OV-3 cells. SK-OV-3 cells overexpressing AGR2 showed increased migratory and invasive activity. Our results indicate that DNA methylation within the AGR2 promoter modulates more aggressive cancer cell phenotypes.

Amyloid beta-mediated epigenetic alteration of insulin-like growth factor binding protein 3 controls cell survival in Alzheimer's disease.

Swedish double mutation (KM670/671NL) of amyloid precursor protein (APP) is reported to increase toxic amyloid ß (Aß) production via aberrant cleavage at the ß-secretase site and thereby cause early-onset Alzheimer's disease (AD). However, the underlying molecular mechanisms leading to AD pathogenesis remains largely unknown. Previously, our transcriptome sequence analyses revealed global expressional modifications of over 600 genes in APP-Swedish mutant-expressing H4 (H4-sw) cells compared to wild type H4 cells. Insulin-like growth factor binding protein 3 (IGFBP3) is one gene that showed significantly decreased mRNA expression in H4-sw cells. In this study, we investigated the functional role of IGFBP3 in AD pathogenesis and elucidated the mechanisms regulating its expression. We observed decreased IGFBP3 expression in the H4-sw cell line as well as the hippocampus of AD model transgenic mice. Treatment with exogenous IGFBP3 protein inhibited Aß1-42- induced cell death and caspase-3 activity, whereas siRNA-mediated suppression of IGFBP3 expression induced cell death and caspase-3 cleavage. In primary hippocampal neurons, administration of IGFBP3 protein blocked apoptotic cell death due to Aß1-42 toxicity. These data implicate a protective role for IGFBP3 against Aß1-42-mediated apoptosis. Next, we investigated the regulatory mechanisms of IGFBP3 expression in AD pathogenesis. We observed abnormal IGFBP3 hypermethylation within the promoter CpG island in H4-sw cells. Treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine restored IGFBP3 expression at both the mRNA and protein levels. Chronic exposure to Aß1-42 induced IGFBP3 hypermethylation at CpGs, particularly at loci -164 and -173, and subsequently suppressed IGFBP3 expression. Therefore, we demonstrate that expression of anti-apoptotic IGFBP3 is regulated by epigenetic DNA methylation, suggesting a mechanism that contributes to AD pathogenesis.

Aberrant DNA methylation in the IFITM1 promoter enhances the metastatic phenotype in an intraperitoneal xenograft model of human ovarian cancer.

A lack of reliable biomarkers for the early detection and risk of metastatic recurrences makes ovarian cancer the most lethal gynecological cancer. To understand the molecular mechanisms involved in ovarian cancer metastasis in vivo, we analyzed the transcriptional expression pattern in metastatic implants of human ovarian carcinoma xenografts in mice. The expression of 937 genes was significantly different, by at least 2-fold, in the xenografts compared with that in SK-OV-3 cells. We investigated the mechanisms that regulate the expression of one of the profoundly upregulated genes, interferon-induced transmembrane protein 1 (IFITM1), in the metastatic implants. Specific CpG sites within the IFITM1 promoter were hypomethylated in the metastatic implants relative to those in the wild-type SK-OV-3 cells. Treating wild-type SK-OV-3 cells with the demethylating agent 5-aza-2'-deoxycytidine enhanced IFITM1 expression in a dose-dependent manner, implying transcriptional regulation by promoter methylation. We also found that IFITM1 overexpression caused increased migration and invasiveness in SK-OV-3 cells. Our results demonstrate that IFITM1 could be a novel metastasis-promoting gene that enhances the metastatic phenotype in ovarian cancer via epigenetic transcriptional regulation. Our findings also suggest that the status of DNA methylation within the IFITM1 promoter region could be a biomarker indicating metastatic progression in ovarian cancer.

Possible role of transforming growth factor-ß1 and vascular endothelial growth factor in Fabry disease nephropathy.

Fabry disease is a lysosomal storage disorder (LSD) caused by deficiency of α-galactosidase A (α-gal A), resulting in deposition of globotriaosylceramide (Gb3; also known as ceramide trihexoside) in the vascular endothelium of many organs. A gradual accumulation of Gb3 leads to cardiovascular, cerebrovascular and renal dysfunction. Endothelial cell dysfunction leads to renal complications, one of the main symptoms of Fabry disease. However, the pathological mechanisms by which endothelial dysfunction occurs in Fabry disease are poorly characterized. The purpose of this study was to investigate whether the expression of transforming growth factor-ß1 (TGF-ß1) and vascular endothelial growth factor (VEGF) is associated with the renal pathogenesis of Fabry disease. We found that the protein expression levels of renal thrombospondin-1 (TSP-1), TGF-ß1 and VEGF were higher in the kidneys from Fabry mice compared to wild-type mice. The expression levels of VEGF receptor 2 (VEGFR2), fibroblast growth factor-2 (FGF-2) and phospho-p38 (P-p38) were also higher in the kidneys from Fabry mice compared with wild-type mice. Activities of cysteine aspartic acid protease (caspase)-6 and caspase-9 were higher in kidneys from Fabry than from the wild-type mice. These results suggest that overexpression of TGF-ß1 and VEGF in the Fabry mouse kidney might contribute to Fabry disease nephropathy by inducing apoptosis. To test whether Gb3 accumulation can induce apoptosis, we incubated bovine aortic endothelial cells with Gb3 and found increased expression of TGF-ß1, VEGFR2, VEGF, FGF-2 and P-p38. The combination of increased expression of TGF-ß1 and VEGF caused by Gb3 accumulation may allow upregulation of FGF-2, VEGFR2 and P-p38 expression, and these changes may be associated with Fabry disease nephropathy by inducing apoptosis.

Globotriaosylceramide leads to K(Ca)3.1 channel dysfunction: a new insight into endothelial dysfunction in Fabry disease.

AIMS: Excessive endothelial globotriaosylceramide (Gb3) accumulation is associated with endothelial dysfunction and impaired endothelium-dependent relaxation in Fabry disease. In endothelial cells, K(Ca)3.1 channels contribute to endothelium-dependent relaxation. However, the effect of Gb3 on K(Ca)3.1 channels and the underlying mechanisms of Gb3-induced dysfunction are unknown. Herein, we hypothesized that Gb3 accumulation induces K(Ca)3.1 channel dysfunction and aimed to clarify the underlying mechanisms. METHODS AND RESULTS: The animal model of Fabry disease, α-galactosidase A (Gla) knockout mice, displayed age-dependent K(Ca)3.1 channel dysfunction. K(Ca)3.1 current and the channel expression were significantly reduced in mouse aortic endothelial cells (MAECs) of aged Gla knockout mice, whereas they were not changed in MAECs of wild-type and young Gla knockout mice. In addition, K(Ca)3.1 current and the channel expression were concentration-dependently reduced in Gb3-treated MAECs. In both Gb3-treated and aged Gla knockout MAECs, extracellular signal-regulated kinase (ERK) and activator protein-1 (AP-1) were down-regulated and repressor element-1 silencing transcription factor (REST) was up-regulated. Gb3 inhibited class III phosphoinositide 3-kinase and decreased intracellular levels of phosphatidylinositol 3-phosphate [PI(3)P]. In addition, endothelium-dependent relaxation was significantly attenuated in Gb3-treated mouse aortic rings. CONCLUSION: Gb3 accumulation reduces K(Ca)3.1 channel expression by down-regulating ERK and AP-1 and up-regulating REST and the channel activity by decreasing intracellular levels of PI(3)P. Gb3 thereby evokes K(Ca)3.1 channel dysfunction, and the channel dysfunction in vascular endothelial cells may contribute to vasculopathy in Fabry disease.

Characterization of a novel mucopolysaccharidosis type II mouse model and recombinant AAV2/8 vector-mediated gene therapy.

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked inherited disorder caused by a deficiency of the enzyme iduronate-2-sulfatase (IDS), which results in the lysosomal accumulation of glycosaminoglycans (GAG) such as dermatan and heparan sulfate. Here, we report the generation of IDS knockout mice, a model of human MPS II, and an analysis of the resulting phenotype. We also evaluated the effect of gene therapy with a pseudotyped, recombinant adeno-associated virus 2/8 vector encoding the human IDS gene (rAAV-hIDS) in IDS-deficient mice. IDS activity and GAG levels were measured in serum and tissues after therapy. Gene therapy completely restored IDS activity in plasma and tissue of the knockout mice. The rescued enzymatic activity completely cleared the accumulated GAGs in all the tissues analyzed. This model can be used to explore the therapeutic potential of IDS replacement and other strategies for the treatment of MPS II. Additionally, AAV2/8 vectors have promising future clinical applications for the treatment of patients with MPS II.

Altered brain gene expression profiles associated with the pathogenesis of phenylketonuria in a mouse model.

BACKGROUND: Phenylketonuria (PKU) is an autosomal recessive disorder caused by a deficiency of phenylalanine hydroxylase (PAH), which catalyzes the conversion of phenylalanine to tyrosine. The resultant hyperphenylalaninemia causes mental retardation, seizure, and abnormalities in behavior and movement. METHODS: We analyzed gene expression profiles in brain tissues of Pah(enu2) mice to elucidate the mechanisms involved in phenylalanine-induced neurological damage. The altered gene expression was confirmed by real-time PCR and Western blotting. To identify markers associated with neurological damage, we examined TTR expression in serum by Western blotting. RESULTS: Gene expression profiling of brain tissue from a mouse model of PKU revealed overexpression of transthyretin (Ttr), sclerostin domain containing 1 (Sostdc1), alpha-Klotho (Kl), prolactin receptor (Prlr), and early growth response 2 (Egr2). In contrast to its overexpression in the brain, TTR expression was low in the sera of PKU mice offered unrestricted access to a diet containing phenylalanine. Expression of TTR decreased in a time-dependent manner in phenylalanine-treated HepG2 cells. CONCLUSIONS: These findings indicate that Ttr, Sostdc1, Kl, Prlr, and Egr2 can be involved in the pathogenesis of PKU and that phenylalanine might have a direct effect on the level of TTR in serum.

Interferon-gamma inhibits in vitro mobilization of eosinophils by interleukin-5.

BACKGROUND: Th2 cytokines play pivotal roles in allergic inflammation, including eosinophilia, and their actions are antagonized by Th1 cytokines, conferring them therapeutic potential. METHODS: In this study, we examined the ability of a number of cytokines to suppress the activation of eosinophils that function as effector cells for allergic airway diseases. RESULTS: Interleukin (IL)-5, IL-6, and tumor necrosis factor (TNF) induced an eosinophil shape change, whereas interferon (IFN)-gamma significantly inhibited the shape change. Other cytokines, including IL-1beta, IL-4, IL-10 and IL-13, had little or only slightly enhancing or reducing effects on the shape change. We further analyzed the IFN-gamma effect, showing that pretreatment with IFN-gamma strongly suppressed IL-5-induced eosinophil shape change, and cycloheximide (CHX) abrogated the suppression by IFN-gamma, suggesting that new protein synthesis is required for the inhibitory effect by this cytokine. In agreement with these results, IFN-gamma blocked the eosinophil migration and ERK phophorylation induced by IL-5, and the addition of CHX restored eosinophil chemotaxis. CONCLUSIONS: Collectively, IFN-gamma may attenuate eosinophilic inflammation by directly negating eosinophil mobilization.

A parallel signal-transduction pathway for eotaxin- and interleukin-5-induced eosinophil shape change.

Interleukin-5 (IL-5) and eotaxin are the most important cytokines/chemokines responsible for regulating eosinophil locomotion and are known to play a co-operative role in the selective recruitment of eosinophils to inflamed tissues. Following exposure to chemoattractants, eosinophils undergo a series of events, including reorganization of actin filaments and subsequent rapid shape changes, culminating in chemotaxis. In this study we examined the signalling pathways for eosinophil shape change regulated by eotaxin and IL-5, primarily using a gated autofluorescence/forward-scatter assay. Eotaxin and IL-5 were able to elicit shape change with peaks at 10 and 60 min, respectively, and IL-5 triggered the shape change more efficiently than eotaxin. The pharmacological inhibitors of mitogen-activated protein kinase (MAP kinase) and p38 blocked both eotaxin- and IL-5-induced eosinophil shape change in a dose-dependent manner. In addition, depletion of intracellular Ca2+ and inhibition of protein kinase A (PKA) strongly reduced eosinophil shape change. In contrast, even when used at high concentrations, protein tyrosine kinase (PTK) inhibitors caused only a slight reduction in the ability to change shape. However, treatment with protein kinase C (PKC) inhibitors, such as GF109203X and staurosporine, resulted in a striking inhibition of eosinophil shape change by IL-5, but not eotaxin. Data from the inhibition of activation and chemotaxis of the extracellular signal-regulated kinases (ERK1/2) by the PKC inhibitors were also consistent with findings from the experiments on shape change. Collectively, two eosinophil-selective cytokines/chemokines probably regulate eosinophil shape change via a largely overlapping signalling pathway, with involvement of PKC restricted to the IL-5 signal alone.