Synthesis of 2-deoxy-2-fluoro and 1,2-ene derivatives of the naturally occurring glycosidase inhibitor, salacinol, and their inhibitory activities against recombinant human maltase glucoamylase

2-Deoxy-2-fluorosalacinol and a 1,2-ene derivative of the naturally occurring glycosidase inhibitor salacinol were synthesized for structure activity studies with human maltase glucoamylase (MGA). 2-Deoxy-2-fluorosalacinol was synthesized through the coupling reaction of 2-deoxy-2-fluoro-3,5-di-O-p-methoxybenzyl-1,4-anhydro-4-thio-D-arabinitol with 2,4-O-benzylidene-l-erythritol-1,3-cyclic sulfate in hexafluoroisopropanol (HFIP) containing 0.3 equiv of K(2)CO(3). Excess of K(2)CO(3) resulted in the elimination of HF from the coupled product, and the formation of an alkene derivative of salacinol. Nucleophilic attack of the 1,4-anhydro-4-thio-D-arabinitol moiety on the cyclic sulfate did not proceed in the absence of K(2)CO(3). No reaction was observed in acetonitrile containing K(2)CO(3). The target compounds were obtained by deprotection with TFA. The 2-deoxy-1-ene derivative of salacinol and 2-deoxy-2-fluorosalacinol inhibited recombinant human maltase glucoamylase, one of the key intestinal enzymes involved in the breakdown of glucose, with an IC(50) value of 150 microM and a K(i) value of 6+/-1 microM, respectively.     

Memantine inhibits and reverses the Alzheimer type abnormal hyperphosphorylation of tau and associated neurodegeneration

Memantine, an N-methyl-D-aspartate (NMDA) receptor antagonist, reduces the clinical deterioration in moderate-to-severe Alzheimer disease (AD) for which other treatments are not available. The activity of protein phosphatase (PP)-2A is compromised in AD brain and is believed to be a cause of the abnormal hyperphosphorylation of tau and the consequent neurofibrillary degeneration. Here we show that memantine inhibits and reverses the PP-2A inhibition-induced abnormal hyperphosphorylation and accumulation of tau in organotypic culture of rat hippocampal slices. Such restorative effects of memantine were not detected either with 5,7-dichlorokynurenic acid or with D(-)-2-amino-5-phosphopentanoic acid, NMDA receptor antagonists active at the glycine binding site and at the glutamate binding site, respectively. These findings show (1) that memantine inhibits and reverses the PP-2A inhibition-induced abnormal hyperphosphorylation of tau/neurofibrillary degeneration and (2) that this drug might be useful for the treatment of AD and related tauopathies.     

Homer modulates NFAT-dependent signaling during muscle differentiation

While changes in intracellular calcium are well known to influence muscle contraction through excitation contraction coupling, little is understood of the calcium signaling events regulating gene expression through the calcineurin/NFAT pathway in muscle. Here, we demonstrate that Ca(+2) released via the inositol trisphosphate receptor (IP3R) increases nuclear entry of NFAT in undifferentiated skeletal myoblasts, but the IP3R Ca(+2) pool in differentiated myotubes promotes nuclear exit of NFAT despite a comparable quantitative change in [Ca(+2)]i. In contrast, Ca(+2) released via ryanodine receptors (RYR) increases NFAT nuclear entry in myotubes. The scaffolding protein Homer, known to interact with both IP3R and RYR, is expressed as part of the myogenic differentiation program and enhances NFAT-dependent signaling by increasing RYR Ca(+2) release. These results demonstrate that differentiated skeletal myotubes employ discrete pools of intracellular calcium to restrain (IP3R pool) or activate (RYR pool) NFAT-dependent signaling, in a manner distinct from undifferentiated myoblasts. The selective expression of Homer proteins contributes to these differentiation-dependent features of calcium signaling.     

Inhibition of LPS-induced apoptosis in differentiated-PC12 cells by new triazine derivatives through NF-κB-mediated suppression of COX-2

Anti-inflammatory therapy approaches have been in the focus of attention in the treatment of neurodegenerative diseases, such as Alzheimer's disease (AD). In this study, we examined the role of new 1,2,4-triazine derivatives against cytotoxicity exerted by lipopolysaccharide (LPS) in differentiated rat pheochromocytoma (PC12) cell line. Our results indicated that LPS-induced cell death can be inhibited in the presence of some of these compounds, as measured by MTT test, acridine orange/ethidium bromide staining and caspase-3 expression assay. We further showed that these compounds exert their protective effects through the inhibition of LPS-induced generation of nitric oxide and reactive oxygen species. Triazine derivatives inhibited LPS-induced nuclear translocation of nuclear factor- κB, a known regulator of a host of genes involved in specific stress and inflammatory responses. Pretreatment of PC12 cells with triazine derivatives also suppressed LPS-induced cyclooxygenase-2 expression while up-regulated heat shock protein-70 (Hsp-70). Moreover, the treatment of brain diseases is limited by the insufficiency in delivering therapeutic drugs into brain relating to highly limited transport of compounds through blood-brain barrier (BBB). Using a reliable model based on the artificial neural network, we indicated that these compounds are capable of penetrating BBB and may be useful agents for preventing neuroinflammatory diseases like AD.     

Induced pluripotent stem cells (iPSCs) as game-changing tools in the treatment of neurodegenerative disease: Mirage or reality?

Based on investigations, there exist tight correlations between neurodegenerative diseases' incidence and progression and aberrant protein aggregreferates in nervous tissue. However, the pathology of these diseases is not well known, leading to an inability to find an appropriate therapeutic approach to delay occurrence or slow many neurodegenerative diseases' development. The accessibility of induced pluripotent stem cells (iPSCs) in mimicking the phenotypes of various late-onset neurodegenerative diseases presents a novel strategy for in vitro disease modeling. The iPSCs provide a valuable and well-identified resource to clarify neurodegenerative disease mechanisms, as well as prepare a promising human stem cell platform for drug screening. Undoubtedly, neurodegenerative disease modeling using iPSCs has established innovative opportunities for both mechanistic types of research and recognition of novel disease treatments. Most important, the iPSCs have been considered as a novel autologous cell origin for cell-based therapy of neurodegenerative diseases following differentiation to varied types of neural lineage cells (e.g. GABAergic neurons, dopamine neurons, cortical neurons, and motor neurons). In this review, we summarize iPSC-based disease modeling in neurodegenerative diseases including Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and Huntington's disease. Moreover, we discuss the efficacy of cell-replacement therapies for neurodegenerative disease.     

EEG-Based Functional Brain Networks: Does the Network Size Matter?

Functional connectivity in human brain can be represented as a network using electroencephalography (EEG) signals. These networks--whose nodes can vary from tens to hundreds--are characterized by neurobiologically meaningful graph theory metrics. This study investigates the degree to which various graph metrics depend upon the network size. To this end, EEGs from 32 normal subjects were recorded and functional networks of three different sizes were extracted. A state-space based method was used to calculate cross-correlation matrices between different brain regions. These correlation matrices were used to construct binary adjacency connectomes, which were assessed with regards to a number of graph metrics such as clustering coefficient, modularity, efficiency, economic efficiency, and assortativity. We showed that the estimates of these metrics significantly differ depending on the network size. Larger networks had higher efficiency, higher assortativity and lower modularity compared to those with smaller size and the same density. These findings indicate that the network size should be considered in any comparison of networks across studies.     

Platelet-derived toll-like receptor 4 (tlr-4) is sufficient to promote microvascular thrombosis in endotoxemia

Endotoxin (lipopolysaccharide, LPS) produced by gram-negative bacteria initiates a host of pro-inflammatory effects through Toll-like receptor 4 (TLR-4). We reported previously that LPS enhances microvascular thrombosis in cremaster venules of wild-type mice, but had no effect in mice deficient in TLR-4. Since TLR-4 is expressed on various cell types, the cellular origin of TLR-4 responsible for the LPS-enhanced thrombosis remains undetermined. Platelets are known to express functional TLR-4. Platelet-derived TLR-4 has been suggested to mediate various inflammatory responses in endotoxemia, including production of tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β), two cytokines reported to enhance microvascular thrombosis. We determined whether platelet-derived TLR-4 was sufficient to mediate the enhanced thrombosis induced by endotoxin and whether these responses were accompanied by systemic increases in TNF-α and IL-1β. We isolated platelets from wild-type mice and transfused them into either of two strains of TLR-4-deficient mice (C57BL/10ScN and B6.B10ScN-TLR-4(lps-del)/Jth). The mice were then injected with LPS or saline, and the kinetics of thrombosis were studied 4 hours later. Transfusion of wild-type platelets restored responsiveness to LPS in TLR-4-deficient mice with regards to microvascular thrombosis but not to plasma levels of TNF-α or IL-1β. The accelerated rates of microvascular thrombosis induced by platelet transfusions were specific to TLR-4, since isolation and transfusion of platelets derived from TLR-4-deficient donors did not restore responsiveness to LPS. These studies demonstrate that platelet-derived TLR-4 is sufficient to promote microvascular thrombosis in endotoxemia, independent of systemic increases in TNF-α or IL-1β.     

Serum vitamins A and E as modifiers of lipid trait genetics in the National Health and Nutrition Examination Surveys as part of the Population Architecture using Genomics and Epidemiology (PAGE) study

Both environmental and genetic factors impact lipid traits. Environmental modifiers of known genotype–phenotype associations may account for some of the “missing heritability” of these traits. To identify such modifiers, we genotyped 23 lipid-associated variants identified previously through genome-wide association studies (GWAS) in 2,435 non-Hispanic white, 1,407 non-Hispanic black, and 1,734 Mexican-American samples collected for the National Health and Nutrition Examination Surveys (NHANES). Along with lipid levels, NHANES collected environmental variables, including fat-soluble macronutrient serum levels of vitamin A and E levels. As part of the Population Architecture using Genomics and Epidemiology (PAGE) study, we modeled gene–environment interactions between vitamin A or vitamin E and 23 variants previously associated with high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) levels. We identified three SNP?×?vitamin A and six SNP?×?vitamin E interactions at a significance threshold of p?<?2.2?×?10^?3. The most significant interaction was APOB rs693?×?vitamin E (p?=?8.9?×?10^?7) for LDL-C levels among Mexican-Americans. The nine significant interaction models individually explained 0.35–1.61?% of the variation in any one of the lipid traits. Our results suggest that vitamins A and E may modify known genotype–phenotype associations; however, these interactions account for only a fraction of the overall variability observed for HDL-C, LDL-C, and TG levels in the general population.     

Arsenic trioxide prevents murine sclerodermatous graft-versus-host disease

Chronic graft-versus-host disease (GVHD) follows allogeneic hematopoietic stem cell transplantation. It results from alloreactive processes induced by minor MHC incompatibilities triggered by activated APCs, such as plasmacytoid dendritic cells (pDCs), and leading to the activation of CD4 T cells. Therefore, we tested whether CD4(+) and pDCs, activated cells that produce high levels of reactive oxygen species, could be killed by arsenic trioxide (As(2)O(3)), a chemotherapeutic drug used in the treatment of acute promyelocytic leukemia. Indeed, As(2)O(3) exerts its cytotoxic effects by inducing a powerful oxidative stress that exceeds the lethal threshold. Sclerodermatous GVHD was induced in BALB/c mice by body irradiation, followed by B10.D2 bone marrow and spleen cell transplantation. Mice were simultaneously treated with daily i.p. injections of As(2)O(3). Transplanted mice displayed severe clinical symptoms, including diarrhea, alopecia, vasculitis, and fibrosis of the skin and visceral organs. The symptoms were dramatically abrogated in mice treated with As(2)O(3). These beneficial effects were mediated through the depletion of glutathione and the overproduction of H(2)O(2) that killed activated CD4(+) T cells and pDCs. The dramatic improvement provided by As(2)O(3) in the model of sclerodermatous GVHD that associates fibrosis with immune activation provides a rationale for the evaluation of As(2)O(3) in the management of patients affected by chronic GVHD.