Raf inhibition protects cortical cells against beta-amyloid toxicity

Alzheimer's disease (AD) is the main cause of dementia in the elderly. The discovery of new targets of therapeutic intervention is fundamental to the development of new drugs against AD pathology. Upregulation of cRaf-1 has been found post-mortem in the brains of AD patients. cRaf-1 is a cytosolic protein kinase that regulates neuronal survival and senescence. In this study, we investigated cRaf-1 in the brains of aged APPswe mice presenting AD-like pathology and whether Raf inhibitors protected cultured cortical cells against amyloid beta toxicity (Abeta). We found a dysregulation of cRaf-1 in the cortex of APPswe mice, which showed a 147% increase in the active form phosphorylated at serine 338 and a 40% decrease in the levels of the inactive form of cRaf-1, phospho-cRaf-1[Ser259]. Furthermore, treatment of primary cortical neurons with the cRaf-1 inhibitors, GW5074 or ZM336372, and the nuclear factor kappa B (NFkappaB) inhibitor SN50, protected cortical neurons against Abeta toxicity. Since Raf stimulates NFkappaB, we studied the effect of Raf inhibition on its activation by studying changes in NFkappaB phosphorylation at serine 276. Our results suggest that Raf inhibition with GW5074 is neuroprotective against Abeta toxicity through a mechanism that involves NFkappaB inhibition.     

Radix clematidis extract protects against cytokine- and streptozotocin-induced beta-cell damage by suppressing the NF-kappaB pathway

Although Radix clematidis has commonly been used in Chinese medicine for the treatment of arthralgia, the anti-diabetic effects of Radix clematidis have not yet been reported. In the present study, we demonstrated that Radix clematidis extract (RCE) could prevent cytokine-induced beta-cell damage and streptozotocin (STZ)-induced diabetes in mice. Treatment of RINm5F insulinoma cells with interleukin-1beta and interferon-gamma reduced cell viability; however, RCE protected the cells from this cytokine-mediated viability reduction in a concentration-dependent manner. Additionally, incubation with RCE resulted in a significant suppression of cytokine-induced nitric oxide (NO) production, which was correlated with reduced levels of the inducible form of NO synthase (iNOS) mRNA and protein. The molecular mechanism by which RCE inhibited iNOS gene expression appeared to involve inhibition of NF-kappaB activation. Furthermore, RCE abolished the cytokine-induced increases in NF-kappaB binding activity and p65 subunit levels in the nucleus, as well as IkappaBalphadegradation in the cytosol when compared to unstimulated cells. The protective effect of RCE was further demonstrated by the observed suppression of NF-kappaB-dependent iNOS expression and normal insulin secreting responses to glucose in cytokines-treated islets. The anti-diabetic effect of RCE was even more striking in vivo, where nearly complete protection against STZ-induced diabetes was observed. Treatment of mice with STZ resulted in hyperglycemia and hypoinsulinemia, which was further evidenced by immunohistochemical staining; however, pretreatment of mice with RCE blocked the destruction of STZ-induced islets and the development of type 1 diabetes.     

Peroxynitrite is a mediator of cytokine-induced destruction of human pancreatic islet beta cells.

The proinflammatory cytokines, interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNFalpha), and interferon gamma (IFNgamma), are cytotoxic to pancreatic islet beta cells, possibly by inducing nitric oxide and/or oxygen radical production in the beta cells. Peroxynitrite, the reaction product of nitric oxide and the superoxide radical, is a strong oxidant and cytotoxic mediator; therefore, we hypothesized that peroxynitrite might be a mediator of cytokine-induced islet beta-cell destruction. To test this hypothesis we incubated islets isolated from human pancreata with the cytokine combination of IL-1beta, TNFalpha, and IFNgamma. We found that these cytokines induced significant increases in nitrotyrosine, a marker of peroxynitrite, in islet beta cells, and the increase in nitrotyrosine preceded islet-cell destruction. Peroxynitrite mimicked the effects of cytokines on nitrotyrosine formation and islet beta-cell destruction. L-N(G)-monomethyl arginine, an inhibitor of nitric oxide synthase, prevented cytokine-induced nitric oxide production but not hydrogen peroxide production, nitrotyrosine formation, or islet beta-cell destruction. In contrast, guanidinoethyldisulphide, an inhibitor of inducible nitric oxide synthase and scavenger of peroxynitrite, prevented cytokine-induced nitric oxide and hydrogen peroxide production, nitrotyrosine formation, and islet beta-cell destruction. These results suggest that cytokine-induced peroxynitrite formation is dependent upon increased generation of superoxide (measured as hydrogen peroxide) and that peroxynitrite is a mediator of cytokine-induced destruction of human pancreatic islet beta cells.     

N-乙酰半胱氨酸拮抗6-羟基多巴胺对骨髓基质细胞的毒性作用

背景：内源性6-羟基多巴胺能参与氧化应激,N-乙酰半胱氨酸能有效抗氧化和清除自由基。 目的：探讨6-羟基多巴胺对骨髓基质细胞的毒性作用及N-乙酰半胱氨酸对其的拮抗作用。 方法：在体外培养SD大鼠骨髓基质细胞,取第3代骨髓基质细胞分别加入终浓度为0,0.05,0.1 g/L的6-羟基多巴胺和终浓度为0,0.075,0.3,1.2,4.8 g/L的N-乙酰半胱氨酸。 结果与结论：MTT检测发现0.05和0.1 g/L 6-羟基多巴胺可以明显降低骨髓基质细胞的细胞活性,而加入6-羟基多巴胺的同时加入0.3 g/L N-乙酰半胱氨酸可以显著抑制6-羟基多巴胺的毒性作用。提示抗氧化剂N-乙酰半胱氨酸可以影响6-羟基多巴胺的作用。     

Lovastatin protects human neurons against Abeta-induced toxicity and causes activation of beta-catenin-TCF/LEF signaling

Alzheimer's disease (AD) is characterized by cognitive decline due to excess amyloid beta peptide (Abeta), neurofibrillary tangles, and neuronal loss. Abeta promotes neuronal apoptosis in AD by activating glycogen synthase kinase-3beta (GSK-3beta), leading to degradation of beta-catenin and inactivation of Wnt signaling. beta-Catenin interacts with the T-cell factor (TCF)/Lymphoid enhancer factor (LEF)-nuclear complex to mediate Wnt signaling and cell survival. Statins are associated with decreased prevalence of AD. Lovastatin has been shown to decrease the production of Abeta and to promote neuronal survival. The mechanisms of how statins promote neuronal survival are unclear. We propose that the neuroprotective effect of lovastatin may be due to inactivation of GSK-3beta activity, resulting in induction of Wnt signaling. Here, we report that lovastatin prevented Abeta-induced apoptosis in human SK-NSH cells. This was accompanied by reduction in active GSK-3beta, and increased nuclear translocation of beta-catenin, TCF-3, and LEF-1. Lovastatin treatment induced an increase in TCF/LEF-chloramphenicol acetyl transferase (CAT) gene reporter activity. More importantly, beta-catenin and TCF were required for the neuroprotective function of lovastatin. Our results suggest that lovastatin protects neuronal cells from Abeta-induced apoptosis and causes reduction in GSK-3beta activity, resulting in activation of Wnt signaling.     

Mutant huntingtin alters MAPK signaling pathways in PC12 and striatal cells: ERK1/2 protects against mutant huntingtin-associated toxicity

Huntington's disease (HD) is a devastating neurodegenerative disorder caused by an expanded polyglutamine (polyQ) tract within the huntingtin protein (Htt). Identifying the pathways that are altered in response to the mutant protein is crucial for understanding the cellular processes impacted by the disease as well as for the rational development of effective pharmacological interventions. Here, expression profiling of a cellular HD model identifies genes that implicate altered mitogen-activated protein kinase (MAPK) signaling. Targeted biochemical studies and pharmacological modulation of these MAPK pathways suggest that mutant Htt affects signaling at upstream points such that both ERK and JNK are activated. Modulation of the ERK pathway suggests that this pathway is associated with cell survival, whereas inhibition of JNK was found to effectively suppress pathogenesis. These studies suggest that pharmacological intervention in MAPK pathways, particularly at the level of ERK activation, may be an appropriate approach to HD therapy.     

Inhibition of transforming growth factor beta decreases pancreatic fibrosis and protects the pancreas against chronic injury in mice

Transforming growth factor-beta (TGF-beta) is an important cytokine in the fibrogenesis in many organs, including the pancreas. Using an adenoviral vector expressing the entire extracellular domain of type II human TGF-beta receptor (AdTbeta-ExR), we investigated whether inhibition of TGF-beta action is effective against persistent pancreatic fibrosis, and whether it exerts a beneficial effect on the pancreas in the process of chronic injury. To induce chronic pancreatic injury and pancreatic fibrosis, mice were subjected to three episodes of acute pancreatitis induced by six intraperitoneal injections of 50 microg/kg body weight cerulein at hourly intervals, per week for 3 consecutive weeks. Mice were infected once with AdTbeta-ExR, or with a control adenoviral vector expressing bacterial beta-galactosidase (AdLacZ). Pancreatic fibrosis was evaluated by histology and hydroxyproline content. Activation of pancreatic stellate cells (PSCs) was assessed by immunostaining for alpha-smooth muscle actin. Apoptosis and proliferation of acinar cells were assessed by immunostaining of ssDNA and Ki-67, respectively. Three-week cerulein injection induced pancreatic fibrosis and pancreatic atrophy with proliferation of activated PSCs. In AdTbeta-ExR-injected mice, but not AdLacZ-injected mice, pancreatic fibrosis was significantly attenuated. This finding was accompanied by a reduction of activated PSCs. AdTbeta-ExR, but not AdLacZ, significantly increased pancreas weight after chronic pancreatic injury. AdTbeta-ExR did not change the proportion of proliferating acinar cells, whereas it reduced the number of apoptotic acinar cells. Our results demonstrate that inhibition of TGF-beta action not only decreases pancreatic fibrosis but also protects the pancreas against chronic injury by preventing acinar cell apoptosis.     

Hypoxia protects human lung microvascular endothelial and epithelial-like cells against oxygen toxicity: role of phosphatidylinositol 3-kinase

Hypoxic preconditioning is protective against oxidant-related damage in various organs, such as the heart. We previously showed that rats exposed to hypoxia also exhibit resistance to lethal pulmonary oxygen toxicity. The underlying mechanism and whether similar preconditioning is applicable to cellular models is unknown. In the present study, it was found that hypoxic pre-exposure induces a significant protective effect against hyperoxia-induced cell death in human lung microvascular endothelial cells (HLMVECs) and epithelial type II-like A549 cells. This effect of hypoxia is mediated by the phosphatidylinositol 3-kinase (PI3-K) signaling pathway because the presence of the PI3-K inhibitors, LY294002 and wortmannin, during pre-exposure to hypoxia completely blocks subsequent protection. Further, the hypoxia-dependent protection from hyperoxia was found to be associated with a 2-fold increase in PI3-K activity in hypoxia. Transient overexpression of a catalytically active class IA PI3-K p110alpha isoform also enhanced survival of A549 cells 2-fold compared with the empty vector control. These results indicate that hypoxia-induced activation of PI3-K is an important event in the acquisition of resistance against subsequent hyperoxic toxicity.     

复方黄芪提取物抗急性肝损伤作用的研究

目的：研究复方黄芪提取物（ERAC）的抗急性肝损伤作用。方法： 分别采用D-氨基半乳糖（D-Galn）和四氯化碳（CCl4）造成急性肝损伤模型，检测血清中丙氨酸氨基转移酶（ALT）、天门冬氨酸氨基转移酶（AST）的活性及胆红素的含量，并进行病理学检查。结果： ERAC对肝损伤引起的ALT和AST活性增加以及胆红素增高均有明显的降低作用（P<0.05）。病理组织学检查：ERAC对肝损伤引起的肝细胞变性、坏死等病变有改善作用。结论： ERAC能减轻D-Galn和CCl4所引起的肝损伤，改善肝功能。     

Stereological study of the effects of orally administrated Otostegia persica extract on pancreatic beta cells in male diabetic rats

Otostegia persica extract was used as a traditional medicine for the management of diabetes mellitus in humans in some parts of Iran. This study investigated the effects of O. persica oral extract on pancreatic beta cells in streptozotocin-induced diabetic rats by stereological methods. Thirty-two matured normoglycemic male Sprague–Dawley rats, weighing 180–220 g, were selected and randomly divided into four groups: Control group consists of normal rats which did not receive the extract during the study. Diabetic group comprises diabetic rats but did not receive any extract. Treated control group rats were normal but received the extract at a dose of 500 mg/kg/day. Treated diabetic group (TD) was made up of diabetic rats and received the extract (500 mg/kg/day). Diabetes was induced by a single intraperitoneal injection of 50 mg/kg of streptozotocin. After 1 month, all the rats received deep anesthesia with ether, and then, the pancreas was dissected and processed. Isotropic uniform and random sections were obtained by orientator method. Volume of pancreatic beta cells and also volume density of pancreatic island were studied, using stereologic and ultrastereological methods. Blood glucose level (BGL) and blood insulin level (BIL) were measured in different phases during the investigation. Statistical analysis by one-way analysis of variance test showed the presence of hypertrophic changes in the volume of the remaining beta cells in diabetic group, not in the controls. But such changes reduced significantly (P?<?0.05) in the TD group which received the extract. Also, a significant reduction in pancreatic islet volume in diabetic and TD groups was seen, in comparison with the controls (P?<?0.01). BGL decreased significantly in TD group, compared to the diabetic group (P?<?0.001). BIL decreased in diabetic and TD groups in comparison to the controls (P?<?0.05). This study demonstrated that O. persica oral extract can play an effective role in the management of diabetes and probably by controlling the hyperglycemic condition and not stimulating the beta cell to increase insulin secretion can help prevent to a large extent the entering of the remaining beta cells to some pathologic changes, like hypertrophy.     

Skin deep: from dermal fibroblasts to pancreatic beta cells

Immunologic Research - Type I diabetes (T1D) is a chronic autoimmune disease caused by pancreatic β-cell destruction induced by autoantibodies and autoreactive T cells. After significant...     

Mangiferin protects against 1-methyl-4-phenylpyridinium toxicity mediated by oxidative stress in N2A cells

1-Methyl-4-phenyl-pyridine ion (MPP⁺), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces a Parkinsonian syndrome in humans and animals, a neurotoxic effect postulated to derive from oxidative stress. We report here the first investigation of MPP⁺-induced oxidative stress in the murine neuroblastoma cell line N2A. Significant cell death was observed following exposure to 0.25 mM MPP⁺. Markers of oxidative stress included decreased intracellular levels of GSH after 48 h of exposure (85% depletion) as well as an increase in GSSG. Expression of both superoxide dismutase 1 (sod1) and catalase (cat) mRNA was increased, as well the activity of catalase. These cellular effects were, at least partially, reversed by treatment with the natural polyphenol mangiferin. Administration of mangiferin protected N2A cells against MPP⁺-induced cytotoxicity, restored the GSH content (to 60% of control levels), and down-regulated both sod1 and cat mRNA expression. Together, these results suggest that the protective effect of mangiferin in N2A cells is mediated by the quenching of reactive oxygen intermediates. Therefore, mangiferin could be a useful compound in therapies for degenerative diseases, including Parkinson's disease, in which oxidative stress plays a crucial role.     

Inactivation of Merlin in malignant mesothelioma cells and the Hippo signaling cascade dysregulation

Malignant mesothelioma (MM) is an aggressive tumor arising primarily from pleural or peritoneal cavities, which is caused by asbestos exposure after long latency. One of the most frequently mutated genes detected in MM cells is the neurofibromatosis type 2 (NF2) tumor suppressor gene which is located at chromosome 22q12. The NF2 gene encodes Merlin, an ERM (Ezrin/Radixin/Moesin) protein. The underphosphorylated form of Merlin is active and acts as a tumor suppressor by regulating several distinct cellular signaling pathways. One of the downstream pathways regulated by Merlin is the Hippo signaling pathway, which is conserved from Drosophila to mammalian cells and plays important roles in organ size control and cancer development. Recent studies have identified alterations of the components in the Hippo signaling cascade in MM cells, including overexpression of Yes-associated protein (YAP) and inactivation of large tumor suppressor homolog 2 (LATS2). Dysregulation of the Merlin-Hippo signaling cascade is one of the frequent and key events of MM cell development and/or progression. Thus, a strategy to normalize this signaling cascade may be the rationale for developing a new target therapy against MM.     

细胞因子对骨骼肌细胞和胰岛β细胞的作用

BACKGROUND: A variety of cytokines such as cytokines, growth factors and inflammatory proteins play an important role in the development of skeletal muscle. OBJECTIVE:To investigate the biological characteristics of a variety of cytokines and their effects on skeletal muscle cells and pancreatic β cells. METHODS: Relevant articles published from 2002 to 2015 were retrieved in CNKI and PubMed databases using the English keywords “cytokines, adiponectin, leptin, visfatin, skeletal muscle cells, pancreatic β cells”. Initially 253 literatures were obtained, and finally 53 eligible literatures were included based on the exclusion criteria. RESULTS AND CONCLUSION: As a fat-specific protein newly found, adiponectin can improve the insulin sensitivity by promoting glucose uptake, storage and utilization in skeletal muscle cells. The activation of muscle satellite cells and skeletal myoblast proliferation are both dependent on leptin, so leptin plays a vital role in the skeletal muscle cell growth and development. Visfatin, a pleiotropic cytokine, widely presents in the skeletal muscle, liver and bone marrow, and participates in the regulation of inflammation and immune function. Furthermore, visfatin contributes to glucose uptake and metabolism in the skeletal muscle, and makes considerable effects on the stress and signal transduction of skeletal muscle cells. 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

小檗碱对胰岛β细胞的保护作用及其机制研究

 目的:探讨小檗碱对胰岛β细胞的保护作用及可能机制。方法: 采用四氧嘧啶(Axn)诱导INS-1胰岛β细胞损伤模型,并以不同浓度的硫酸小檗碱进行干预。将细胞分为对照组（Con组）、损伤组（Axn组）、低剂量小檗碱组（LBer组,小檗碱浓度为15 μmol/L）、中剂量小檗碱组（MBer组,小檗碱浓度为45 μmol/L）及高剂量小檗碱组（HBer组,小檗碱浓度为100 μmol/L）。流式细胞术观察各组细胞凋亡情况,Western blotting免疫印迹法分别观察各组PTEN/PI3K/Akt信号通路、HNF-1α/PDX-1信号通路活化情况以及激活型caspase-3的水平;酶联免疫吸附法（ELISA）观察各组基础胰岛素释放及葡萄糖刺激后胰岛素的释放水平。结果: 与Con组相比,Axn组凋亡率显著升高,但小檗碱干预后凋亡水平显著降低,且呈浓度依赖性。与Con组相比,Axn组PTEN表达水平明显升高,而PI3K/Akt活性被抑制,激活型caspase-3水平显著升高;而小檗碱处理则能逆转上述PTEN通路的促凋亡作用,且显示出浓度依赖性;与Con组相比,Axn组HNF-1α/PDX-1信号通路活性显著下降,但小檗碱处理则能提高该通路活性,表现出浓度依赖性。与Con组相比,Axn组基础及葡萄糖刺激下胰岛素释放水平均显著降低,而小檗碱处理则能显著恢复上述胰岛素释放水平,呈浓度依赖性。结论: 小檗碱对四氧嘧啶损伤的INS-1胰岛β细胞具有保护作用,表现为对其凋亡的抑制与胰岛素分泌功能的恢复,分别与影响细胞内PTEN/PI3K/Akt及HNF-1α/PDX-1信号通路有关。     

Nodal and lefty signaling regulates the growth of pancreatic cells.

Nodal and its antagonist, Lefty, are important mediators specifying the laterality of the organs during embryogenesis. Nodal signals through activin receptors in the presence of its co-receptor, Cripto. In the present study, we investigated the possible roles of Nodal and Lefty signaling during islet development and regeneration. We found that both Nodal and Lefty are expressed in the pancreas during embryogenesis and islet regeneration. In vitro studies demonstrated that Nodal inhibits, whereas Lefty enhances, the proliferation of a pancreatic cell line. In addition, we showed that Lefty-1 activates MAPK and Akt phosphorylation in these cells. In vivo blockade of endogenous Lefty using neutralizing Lefty-1 monoclonal antibody results in a significantly decreased proliferation of duct epithelial cells during islet regeneration. This is the first study to decipher the expression and function of Nodal and Lefty in pancreatic growth. Importantly, our results highlight a novel function of Nodal-Lefty signaling in the regulation of expansion of pancreatic cells.     

Fructus Benincasae Recens extract prevents cytokine-induced nitric oxide formation and cytotoxicity of RINm5F cells

Cytokines produced by immune cells infiltrating pancreatic islets are important mediators of β-cell destruction in insulin-dependent diabetes mellitus. In this study, the effects of Fructus Benincasae Recens (FBR) extract on cytokine-induced β-cell dysfunction were examined. Fructus Benincasae Recens extract completely protected interleukin-1β (IL-1β) and interferon-γ (IFN-γ)-mediated cytotoxicity in rat insulinoma cell line (RINm5F). Incubation with FBR extract resulted in a significant reduction of IL-1β and IFN-γ-induced nitric oxide (NO) production, a finding that correlated well with reduced levels of the inducible form of NO synthase (iNOS) mRNA and protein. The molecular mechanism by which FBR extract inhibited iNOS gene expression appeared to involve the inhibition of NF-κB activation. Our results revealed the possible therapeutic value of FBR extract for the prevention of diabetes mellitus progression.     

Annulate lamellae in hepatic and pancreatic beta cells of the chick embryo

This study is concerned with the finding of cytoplasmic annulate lamellae in normally developing avian somatic tissues. Annulate lamellae were observed in hepatic parenchymal and pancreatic beta cells of the chick embryo on days five and eleven, respectively, of egg incubation. The presence of this cytoplasmic membrane system in normal embryonic tissues supports the view that annulate lamellae may represent normally occurring, transitory organelles common to virtually all cells during early embryonic differentiation.     

Expression of nerve growth factor in human pancreatic beta cells

Nerve growth factor (NGF) is an important modulator of rat pancreatic beta-cell physiology in vitro. In this study, we analysed the expression of NGF, TrkA and insulin in human pancreatic islets from normal, ductal adenocarcinoma and insulinoma-afflicted samples, using double immunofluorescent labelling and confocal microscopy. We found that in normal human pancreas, insulin and NGF are co-expressed in beta cells. Moreover, similar to previous observations in rat, the high affinity NGF receptor TrkA is also expressed in beta cells. Pancreatic beta cells in normal islets from adenocarcinoma and mucinous cystadenocarcinoma patients also expressed NGF. In 2 out of 15 exocrine tumour samples, NGF was detected also in the tissue surrounding the islets, while 2 out of 13 adenocarcinoma tumours expressed this growth factor. In five insulinoma samples, we observed weaker immunofluorescent labelling of insulin and NGF in the neoplastic tissue, compared to the islets not afflicted by the tumour, which may be a consequence of increased hormone secretion rate. We demonstrate that human beta cells express TrkA and NGF. These findings are consistent with the hypothesis that NGF modulates insulin secretion through a paracrine/autocrine loop, similar to the one observed in cultured rat beta cells.     

Vaccination with autoantigen protects against aggregated beta-amyloid and glutamate toxicity by controlling microglia: effect of CD4+CD25+ T cells

Neurodegenerative diseases differ in etiology but are propagated similarly. We show that neuronal loss caused by intraocular injection of aggregated beta-amyloid was significantly greater in immunodeficient mice than in normal mice. The neurodegeneration was attenuated or augmented by elimination or addition, respectively, of naturally occurring CD4(+)CD25(+) regulatory T cells (Treg). Vaccination with retina-derived antigens or with the synthetic copolymer glatiramer acetate (Copolymer-1, Cop-1), but not with beta-amyloid, reduced the ocular neuronal loss. In mouse hippocampal slices, microglia encountering activated T cells overcame the cytotoxicity of aggregated beta-amyloid. These findings support the concept of "protective autoimmunity", show that a given T cell-based vaccination is protective at a particular site irrespective of toxicity type, and suggest that locally activated T cells induce a microglial phenotype that helps neurons withstand the insult. Alzheimer's and other neurodegenerative diseases might be arrested or retarded by vaccination with Cop-1 or related compounds or by treatment with compounds that weaken Treg suppression.