Solid-state sodium batteries, a relatively safe and potentially cost-effective energy-storage technology, have attracted increasing scientific attention recently for application in stationary ...grid-scale energy storage. Identifying solid electrolytes with high electrochemical stability and high Na
-ion conductivity at room temperature is critically important to enable high energy densities with enhanced rate capabilities. We evaluated sodium sulfide-silicon sulfide, xNa
S + (1- x)SiS
, glasses as potential glassy solid electrolytes (GSEs) using molecular dynamics (MD) simulations. We employed ab initio MD to determine ion conduction mechanisms, to calculate energy barriers for ion hops, and to correlate these to the local short-range structure of 0.50Na
S + 0.50SiS
glass. To simulate much larger systems for accurately calculating the ionic conductivity, we parameterized empirical Buckingham-type potential and performed classical MD simulations. After validating these calculations by comparing the structure obtained from MD to that from X-ray scattering data, we calculated the ionic conductivity of these glasses for the range of 0.33 ≤ x ≤ 0.67 compositions. The calculated ionic conductivities at room temperature were in the range of ∼10
S/cm for the x = 0.50 composition and increased significantly with sodium sulfide ( x) content. These calculations provide theoretical insights into the role of Na
S content on the ionic conductivity of GSEs aiding in the selection of specific compositions to enhance the ionic conductivity.
Ortholog protein complexes are responsible for equivalent functions in different organisms. However, during evolution, each organism adapts to meet its physiological needs and the environmental ...challenges imposed by its niche. This selection pressure leads to structural diversity in protein complexes, which are often difficult to specify, especially in the absence of high-resolution structures. Here, we describe a multilevel experimental approach based on native mass spectrometry (MS) tools for elucidating the structural preservation and variations among highly related protein complexes. The 20S proteasome, an essential protein degradation machinery, served as our model system, wherein we examined five complexes isolated from different organisms. We show that throughout evolution, from the Thermoplasma acidophilum archaeal prokaryotic complex to the eukaryotic 20S proteasomes in yeast (Saccharomyces cerevisiae) and mammals (rat - Rattus norvegicus, rabbit - Oryctolagus cuniculus and human - HEK293 cells), the proteasome increased both in size and stability. Native MS structural signatures of the rat and rabbit 20S proteasomes, which heretofore lacked high-resolution, three-dimensional structures, highly resembled that of the human complex. Using cryoelectron microscopy single-particle analysis, we were able to obtain a high-resolution structure of the rat 20S proteasome, allowing us to validate the MS-based results. Our study also revealed that the yeast complex, and not those in mammals, was the largest in size and displayed the greatest degree of kinetic stability. Moreover, we also identified a new proteoform of the PSMA7 subunit that resides within the rat and rabbit complexes, which to our knowledge have not been previously described. Altogether, our strategy enables elucidation of the unique structural properties of protein complexes that are highly similar to one another, a framework that is valid not only to ortholog protein complexes, but also for other highly related protein assemblies.
Reactive astrocytes frequently surround degenerating motor neurons in patients and transgenic animal models of amyotrophic lateral sclerosis (ALS). We report here that reactive astrocytes in the ...ventral spinal cord of transgenic ALS‐mutant G93A superoxide dismutase (SOD) mice expressed nerve growth factor (NGF) in regions where degenerating motor neurons expressed p75 neurotrophin receptor (p75NTR) and were immunoreactive for nitrotyrosine. Cultured spinal cord astrocytes incubated with lipopolysaccharide (LPS) or peroxynitrite became reactive and accumulated NGF in the culture medium. Reactive astrocytes caused apoptosis of embryonic rat motor neurons plated on the top of the monolayer. Such motor neuron apoptosis could be prevented when either NGF or p75NTR was inhibited with blocking antibodies. In addition, nitric oxide synthase inhibitors were also protective. Exogenous NGF stimulated motor neuron apoptosis only in the presence of a low steady state concentration of nitric oxide. NGF induced apoptosis in motor neurons from p75NTR +/+ mouse embryos but had no effect in p75NTR –/– knockout embryos. Culture media from reactive astrocytes as well as spinal cord lysates from symptomatic G93A SOD mice‐stimulated motor neuron apoptosis, but only when incubated with exogenous nitric oxide. This effect was prevented by either NGF or p75NTR blocking‐antibodies suggesting that it might be mediated by NGF and/or its precursor forms. Our findings show that NGF secreted by reactive astrocytes induce the death of p75‐expressing motor neurons by a mechanism involving nitric oxide and peroxynitrite formation. Thus, reactive astrocytes might contribute to the progressive motor neuron degeneration characterizing ALS.
Recently, crosstalk between sphingolipid signaling pathways and steroid hormones has been illuminated as a possible therapeutic target. Sphingosine kinase (SK), the key enzyme metabolizing ...pro-apoptotic ceramide to pro-survival sphingosine-1-phosphate (S1P), is a promising therapeutic target for solid tumor cancers. In this study, we examined the ability of pharmacological inhibition of S1P formation to block estrogen signaling as a targeted breast cancer therapy. We found that the Sphk1/2 selective inhibitor (SK inhibitor (SKI))-II, blocked breast cancer viability, clonogenic survival and proliferation. Furthermore, SKI-II dose-dependently decreased estrogen-stimulated estrogen response element transcriptional activity and diminished mRNA levels of the estrogen receptor (ER)-regulated genes progesterone receptor and steroid derived factor-1. This inhibitor binds the ER directly in the antagonist ligand-binding domain. Taken together, our results suggest that SKIs have the ability to act as novel ER signaling inhibitors in breast carcinoma.
We report a simple method for the synthesis of peroxynitrite from nitrite and hydrogen peroxide that can generate hundreds of milliliters of 180 mM peroxynitrite within 1 h from start to finish. It ...can be scaled down to make small quantities of isotope-labeled peroxynitrite. The method requires only a syringe pump and tubing connectors and is feasible for any biochemical laboratory. Unreacted hydrogen peroxide is eliminated with manganese dioxide, using an improved preparation compared to commercially available manganese dioxide. A number of contaminants were detected by mass spectrometry in peroxynitrite solutions cleaned with commercially purchased manganese dioxide. Nitrite contamination of the peroxynitrite solution is less than 2% as determined using the Griess method. The residual contaminants are principally 0.28 M sodium chloride and 0.1 M sodium hydroxide, which pose few problems when peroxynitrite is diluted for use in biological experiments.
Adult human mesenchymal stem cells (hMSC) have been shown to home to sites of carcinoma and affect biological processes, including tumour growth and metastasis. Previous findings have been ...conflicting and a clear understanding of the effects of hMSCs on cancer remains to be established. Therefore, we set out to investigate the impact of hMSCs on the oestrogen receptor positive, hormone-dependent breast carcinoma cell line MCF-7.
In this study, we show the effects of hMSCs on cancer cells are mediated through a secreted factor(s) which are enhanced by cancer cell-hMSC contact/communication. In addition to enhanced proliferation when in co-culture with hMSCs, MCF-7 cells were found to have increased migration potential in vitro. Inhibition of ER signalling by the pure anti-oestrogen ICI 182,780 decreased the effect of hMSCs on MCF-7 cell proliferation and migration supporting a role for ER signalling in the hMSC/MCF-7 cell interaction. Additionally, hMSCs have been shown to secrete a wide variety of growth factors and chemokines including stromal cell-derived factor-1 (SDF-1). This coupled with the knowledge that SDF-1 is an ER-mediated gene linked with hormone-independence and metastasis led to the investigation of the SDF-1/CXCR4 signalling axis in hMSC-MCF-7 cell interaction. Experiments revealed an increase in SDF-1 gene expression both in vivo and in vitro when MCF-7 cells were cultured with hMSCs. SDF-1 treatment of MCF-7 cells alone increased proliferation to just below that seen with hMSC co-culture. Additionally, blocking SDF-1 signalling using a CXCR4-specific inhibitor decreased hMSC induced proliferation and migration of MCF-7. However, the combined treatment of ICI and AMD3100 reduced MCF-7 cell proliferation and migration below control levels, indicating targeting both the ER and CXCR4 pathways is effective in decreasing the hMSCs induction of MCF-7 cell proliferation and migration.
The sum of these data reveals the relationship between tumour microenvironment and tumour growth and progression. Better understanding of the mechanisms involved in this tumour stroma cell interaction may provide novel targets for the development of treatment strategies for oestrogen receptor positive, hormone-independent, and endocrine-resistant breast carcinoma.
The production of reactive oxygen and nitrogen species has been implicated in atherosclerosis principally as means of damaging low-density lipoprotein that in turn initiates the accumulation of ...cholesterol in macrophages. The diversity of novel oxidative modifications to lipids and proteins recently identified in atherosclerotic lesions has revealed surprising complexity in the mechanisms of oxidative damage and their potential role in atherosclerosis. Oxidative or nitrosative stress does not completely consume intracellular antioxidants leading to cell death as previously thought. Rather, oxidative and nitrosative stress have a more subtle impact on the atherogenic process by modulating intracellular signaling pathways in vascular tissues to affect inflammatory cell adhesion, migration, proliferation, and differentiation. Furthermore, cellular responses can affect the production of nitric oxide, which in turn can strongly influence the nature of oxidative modifications occurring in atherosclerosis. The dynamic interactions between endogenous low concentrations of oxidants or reactive nitrogen species with intracellular signaling pathways may have a general role in processes affecting wound healing to apoptosis, which can provide novel insights into the pathogenesis of atherosclerosis.
A model for hardness in multiphase materials is derived that assumes crack propagation is impeded by phase boundaries. The phase boundary surface area density is determined statistically and the ...crack impedance scales linearly with this quantity. For the (1−x)AlMgB14−xTiB2 material system experimentally determined hardness values and micrographs at x=0.6 are used to accurately calculate the hardness of the microstructure for (0<x<1). The model predicts that refining the microstructure of this system such that the particle size is less than 0.25μm will increase the hardness, making it superhard.
Endocrine resistance and metastatic progression are primary causes of treatment failure in breast cancer. While mitogen activated protein kinases (MAPKs) are known to promote ligand-independent cell ...growth, the role of the MEK5-ERK5 pathway in the progression of clinical breast carcinoma remains poorly understood. Here, we demonstrated increased ERK5 activation in 30 of 39 (76.9%) clinical tumor samples, as well as across breast cancer cell systems. Overexpression of MEK5 in MCF-7 cells promoted both hormone-dependent and hormone-independent tumorigenesis in vitro and in vivo and conferred endocrine therapy resistance to previously sensitive breast cancer cells. Expression of MEK5 suppressed estrogen receptor (ER)α, but not ER-β protein levels, and abrogated downstream estrogen response element (ERE) transcriptional activity and ER-mediated gene transcription. Global gene expression changes associated with upregulation of MEK5 included increased activation of ER-α independent growth signaling pathways and promotion of epithelial-to-mesenchymal transition (EMT) markers. Taken together, our findings show that the MEK5-ERK5 pathway mediates progression to an ER(-), mesenchymal and endocrine therapy resistant phenotype. Given the need for new clinical therapeutic targets, our results demonstrate the therapeutic potential of targeting the MEK5-ERK5 pathway in breast cancer.
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