Selective inhibition of ion transport mechanisms regulating intracellular pH reduces proliferation and induces apoptosis in cholangiocarcinoma cells

BACKGROUND: Cells within the acidic extracellular environment of solid tumours maintain their intracellular pH through the activity of the Na(+)/H(+) exchanger and the Na(+) dependent Cl(-)/HCO(3)(-) exchanger. The inhibition of these mechanisms could therefore inhibit cancer cell growth. AIM: We evaluated the effect of two selective inhibitors of these transporters (cariporide and S3705) on proliferation and apoptosis of human cholangiocarcinoma cells (HUH-28 and Mz-ChA-1 cells) as a function of external pH (7.4 and 6.8). METHODS/RESULTS: HUH-28 cells incubated for 24h at external pH 7.4 or 6.8 without inhibitors maintained intracellular pH at physiological level, whereas incubation with cariporide and/or S3705 caused the intracellular pH of cells to drop. Incubation of HUH-28 cells with cariporide and/or S3705 was able to reduce proliferation, evaluated by a colorimetric ELISA method, and to induce apoptosis, evaluated by measuring caspase-3 activity and Annexin-V staining, and these effects were more evident at external pH 6.8. S3705 but not cariporide was able to inhibit serum-induced phosphorylation of ERK1/2, AKT and BAD, intracellular molecules involved in cancer cell proliferation and survival. Similar results were obtained in Mz-ChA-1 cells. CONCLUSIONS: (1) Inhibition of intracellular pH regulatory mechanisms by cariporide and S3705 reduces proliferation and induces apoptosis in cholangiocarcinoma cells; and (2) these drugs might have potential therapeutic value against cholangiocarcinoma.     

Castration reduces mRNA levels for calcium regulatory proteins in rat heart

Sex-related differences in the cardiac phenotype have been well established. This study was designed to determine whether androgens regulate myocardial gene expression and play a role in the sex-related differences in the myocardial phenotype. Gonadectomized male rats were treated with testosterone, and myocardial gene expression was examined in whole heart using quantitative real-time PCR. Gonadectomy produced a substantial decrease in mRNA levels for the androgen receptor, Na⁺/Ca²⁺ exchanger, L-type calcium channel, and β₁-adrenergic receptor (β₁AR). Supplementation of testosterone in castrates produced a fivefold increase in androgen receptor mRNA levels. Testosterone treatment of castrates produced almost a sixfold increase in Na⁺/Ca²⁺ exchanger mRNA, a tenfold increase in L-type calcium channel mRNA accumulation, and a fourfold increase in β₁AR mRNA levels. Increased calcium channel expression, β₁AR expression, and Na⁺/Ca²⁺ exchanger expression together may alter cytosolic calcium. These results provide the first evidence that testoster-one regulates expression of myocardial calcium regulating genes and thus may play a role in modulating the cardiac phenotype in males.     

Prevention of autoimmune gastritis in mice requires extra-thymic T-cell deletion and suppression by regulatory T cells

BACKGROUND AND AIMS: Autoimmune gastritis is one of the most common autoimmune diseases and is caused by a CD4(+) T-cell response to the gastric H(+)/K(+) ATPase encoded by Atp4a and Atp4b (H(+)/K(+) ATPase). Here, we have elucidated events that result in immunological tolerance to the H(+)/K(+) ATPase and thus the prevention of autoimmune gastritis. METHODS: T cells from H(+)/K(+) ATPase-deficient mice and H(+)/K(+) ATPase-specific T-cell receptor transgenic mice were purified and transferred to wild-type (WT) or H(+)/K(+) ATPase-deficient recipients to assess the impact of exposure to antigen on pathogenicity. RESULTS: The CD4(+) T-cell population from H(+)/K(+) ATPase-deficient mice was highly effective at inducing gastritis when compared with T cells from WT mice and, as a population, was comparatively resistant to the suppressive activity of regulatory T cells. Exposing T cells from H(+)/K(+) ATPase-deficient mice to H(+)/K(+) ATPase in WT mice decreased their ability to induce gastritis and resulted in a population that could be more easily suppressed by T(reg) cells. Transfer of clonotypic antigen-inexperienced H(+)/K(+) ATPase-specific T cells into WT mice resulted in extra-thymic clonal deletion. CONCLUSIONS: Prevention of autoimmune gastritis requires the extra-thymic purging of highly autoaggressive H(+)/K(+) ATPase-specific T cells to produce a T-cell repertoire that is more susceptible to the suppressive activity of regulatory T cells. Taken together with recent published data describing the role of T-cell receptor signalling in the maintenance of regulatory T-cell populations, we propose that exposure of T cells to antigen in the periphery is able to both delete autoaggressive specificities and maintain regulatory T-cell activity, establishing a balance between pathogenicity and regulation.     

cAMP inhibition of murine intestinal Na/H exchange requires CFTR-mediated cell shrinkage of villus epithelium

BACKGROUND AND AIMS: Unlike the intestine of normal subjects, small-intestinal epithelia of cystic fibrosis patients and cystic fibrosis transmembrane conductance regulator protein-null (CFTR(-)) mice do not respond to stimulation of intracellular cyclic adenosine monophosphate with inhibition of electroneutral NaCl absorption. Because CFTR-mediated anion secretion has been associated with changes in crypt cell volume, we hypothesized that CFTR-mediated cell volume reduction in villus epithelium is required for intracellular cyclic adenosine monophosphate inhibition of Na(+)/H(+) exchanger (primarily Na(+)/H(+) exchanger 3) activity in the proximal small intestine. METHODS: Transepithelial (22)Na flux across the jejuna of CFTR(+), CFTR(-), the basolateral membrane Na(+)/K(+)/2Cl(-) co-transporter protein NKCC1(+), and NKCC1(-) mice were correlated with changes in epithelial cell volume of the midvillus region. RESULTS: Stimulation of intracellular cyclic adenosine monophosphate resulted in cessation of Na(+)/H(+) exchanger-mediated Na(+) absorption (J(ms)(NHE)) in CFTR(+) jejunum but had no effect on J(ms)(NHE) across CFTR(-) jejunum. Cell volume indices indicated an approximately 30% volume reduction of villus epithelial cells in CFTR(+) jejunum but no changes in CFTR(-) epithelium after intracellular cyclic adenosine monophosphate stimulation. In contrast, cell shrinkage induced by hypertonic medium inhibited J(ms)(NHE) in both CFTR(+) and CFTR(-) mice. Bumetanide treatment to inhibit Cl(-) secretion by blockade of the Na(+)/K(+)/2Cl(-) co-transporter, NKCC1, of stimulated CFTR(+) jejunum prevented maximal volume reduction of villus epithelium and recovered approximately 40% of J(ms)(NHE). Likewise, J(ms)(NHE) and cell volume were unaffected by intracellular cyclic adenosine monophosphate stimulation in NKCC1(-) jejuna. CONCLUSIONS: These findings show a previously unrecognized role of functional CFTR expressed in villus epithelium: regulation of Na(+)/H(+) exchanger 3-mediated Na(+) absorption by alteration of epithelial cell volume.     

A New Hydrometallurgical Process for Metal Extraction from Electric Arc Furnace Dust Using Ionic Liquids

This research proposes a new hydrometallurgical method for Zn, In, and Ga extraction, along with Fe as a common impurity, from electric arc furnace dust (EAFD), using ionic liquids. EAFD is a metal-containing waste fraction generated in significant amounts during the process of steelmaking from scrap material in an electric arc furnace. With valuable metal recovery as the main goal, two ionic liquids, [Bmim⁺HSO₄⁻] and [Bmim⁺Cl⁻], were studied in conjunction with three oxidants: Fe₂(SO₄)₃, KMnO₄, and H₂O₂. The results indicated that the best combination was [Bmim⁺HSO₄⁻] with [Fe₂(SO₄)₃]. An experimental series subsequently demonstrated that the combination of 30% v/v [Bmim⁺HSO₄⁻], 1 g of [Fe₂(SO₄)₃], S/L ratio = 1/20, a 240 min leaching time, and a temperature of 85 °C was optimal, resulting in maximum extractions of 92.7% Zn, 97.4% In, and 17.03% Ga. In addition, 80.2% of the impurity metal Fe was dissolved. The dissolution kinetics of these four elements over a temperature range of 55–85 °C was found to be diffusion controlled. The remaining phases present in the leached residue were low amounts of ZnO, Fe₃O₄, ZnFe₂O₄, and traces of Ca(OH)₂ and MnO₂, and additional sharp peaks indicative of PbSO₄ and CaSO₄ appeared within the XRD pattern. The intensity of the peaks related to ZnO and Fe₃O₄ were observed to have decreased considerably during leaching, whereas some of the refractory ZnFe₂O₄ phase remained. SEM-EDS analysis revealed that the initial EAFD morphology was composed of spherical-shaped fine-grained particle agglomerates, whereas the leached residue was dominated by calcium sulphate (Ca(SO₄))-rich needle-shaped crystals. The results clearly demonstrate that [Bmim⁺HSO₄⁻] is able to extract the target metals due to its acidic properties.     

Ga2Te3-Based Composite Anodes for High-Performance Sodium-Ion Batteries

Recently, metal chalcogenides have received considerable attention as prospective anode materials for sodium-ion batteries (SIBs) because of their high theoretical capacities based on their alloying or conversion reactions. Herein, we demonstrate a gallium(III) telluride (Ga₂Te₃)-based ternary composite (Ga₂Te₃–TiO₂–C) synthesized via a simple high-energy ball mill as a great candidate SIB anode material for the first time. The electrochemical performance, as well as the phase transition mechanism of Ga₂Te₃ during sodiation/desodiation, is investigated. Furthermore, the effect of C content on the performance of Ga₂Te₃–TiO₂–C is studied using various electrochemical analyses. As a result, Ga₂Te₃–TiO₂–C with an optimum carbon content of 10% (Ga₂Te₃–TiO₂–C(10%)) exhibited a specific capacity of 437 mAh·g⁻¹ after 300 cycles at 100 mA·g⁻¹ and a high-rate capability (capacity retention of 96% at 10 A·g⁻¹ relative to 0.1 A·g⁻¹). The good electrochemical properties of Ga₂Te₃–TiO₂–C(10%) benefited from the presence of the TiO₂–C hybrid buffering matrix, which improved the mechanical integrity and electrical conductivity of the electrode. This research opens a new direction for the improvement of high-performance advanced SIB anodes with a simple synthesis process.     

An A- and B-Site Substitutional Study of SrFeO3−δ Perovskites for Solar Thermochemical Air Separation

An A‑ and B‑site substitutional study of SrFeO_3−δ perovskites (A’_xA_1−xB’_yB_1−yO_3−δ, where A = Sr and B = Fe) was performed for a two‑step solar thermochemical air separation cycle. The cycle steps encompass (1) the thermal reduction of A’_xSr_1−xB’_yFe_1−yO_3−δ driven by concentrated solar irradiation and (2) the oxidation of A’_xSr_1−xB’_yFe_1−yO_3−δ in air to remove O₂, leaving N₂. The oxidized A’_xSr_1−xB’_yFe_1−yO_3−δ is recycled back to the first step to complete the cycle, resulting in the separation of N₂ from air and concentrated solar irradiation. A-site substitution fractions between 0 ≤ x ≤ 0.2 were examined for A’ = Ba, Ca, and La. B-site substitution fractions between 0 ≤ y ≤ 0.2 were examined for B’ = Cr, Cu, Co, and Mn. Samples were prepared with a modified Pechini method and characterized with X-ray diffractometry. The mass changes and deviations from stoichiometry were evaluated with thermogravimetry in three screenings with temperature- and O₂ pressure-swings between 573 and 1473 K and 20% O₂/Ar and 100% Ar at 1 bar, respectively. A’ = Ba or La and B’ = Co resulted in the most improved redox capacities amongst temperature- and O₂ pressure-swing experiments.     

Morphological Evolution of TiB2 and TiAl3 in Al–Ti–B Master Alloy Using Different Ti Adding Routes

Three different Ti addition routes were used to prepare an Al–5Ti–B Master Alloy: the halide salt route, the Ti-sponge route, and the partial Ti-sponge route. In the halide salt route, the raw materials were Al + KBF₄ + K₂TiF₆; K₂TiF₆ was completely replaced by pure titanium for the Ti-sponge route versus the halide salt route; in the partial Ti-sponge route, K₂TiF₆ was partially replaced by pure titanium. Here, 30% Ti-sponge or 60% Ti-sponge route means that 30% or 60% K₂TiF₆ was replaced by pure titanium, respectively. The above Ti addition routes have a significant influence on the growth pattern and morphological evolution of TiAl₃ and TiB₂, which greatly affect the refining performance of Al–Ti–B Master Alloy. When using the halide salt route, a streamlined “rich Ti, B area” exists in the aluminum melt, which is a complex compound of (Ti_x, Al_1−x) B_y. The “rich Ti, B area” is essential for the nucleation and growth of TiAl₃ and TiB₂. Blocky TiAl₃ was obtained and its average size was 4.7 μm based on the halide salt route. In the Ti-sponge route, the nucleation of TiAl₃ mainly depends on the mutual diffusion of Al and Ti, and TiAl_x forms around pure Ti particles, i.e., the so-called Ti–TiAl_x mechanism. The average size of the blocky TiAl₃ was 9.8 μm based on the Ti–TiAl_x mechanism. For the partial Ti-sponge route, the “rich Ti, B area” gradually decreases with the increase in Ti powder’s contents, and large TiAl₃ coexists with the small TiAl₃. Compared with the Ti-sponge route, the halide salt route can form smaller TiAl₃. In the Ti-sponge route, there is a small amount of “rich Ti, B area” due to the influence of the Ti–TiAl_x mechanism, which does not meet the requirements of TiB₂ growth. In the halide salt route, there is sufficient “rich Ti, B area”, which is conducive to the formation of TiB₂. Both the crystal defects and the crowded growth environment caused by the “rich Ti, B area” are fundamental reasons for the fragility and the irregular shape of the TiB₂. The refining effect of the Al–Ti–B Master Alloy prepared by the halide salt route is better than the Ti-sponge route. The refining effect of 30% Ti-sponge route is better than that of Ti-sponge route and worse than that of halide salt route.     

RabGDIα is a negative regulator of interferon-γ–inducible GTPase-dependent cell-autonomous immunity to Toxoplasma gondii

IFN-γ orchestrates cell-autonomous host defense against various intracellular vacuolar pathogens. IFN-γ–inducible GTPases, such as p47 immunity-related GTPases (IRGs) and p65 guanylate-binding proteins (GBPs), are recruited to pathogen-containing vacuoles, which is important for disruption of the vacuoles, culminating in the cell-autonomous clearance. Although the positive regulation for the proper recruitment of IRGs and GBPs to the vacuoles has been elucidated, the suppressive mechanism is unclear. Here, we show that Rab GDP dissociation inhibitor α (RabGDIα), originally identified as a Rab small GTPase inhibitor, is a negative regulator of IFN-γ–inducible GTPases in cell-autonomous immunity to the intracellular pathogen Toxoplasma gondii. Overexpression of RabGDIα, but not of RabGDIβ, impaired IFN-γ–dependent reduction of T. gondii numbers. Conversely, RabGDIα deletion in macrophages and fibroblasts enhanced the IFN-γ–induced clearance of T. gondii. Furthermore, upon a high dose of infection by T. gondii, RabGDIα-deficient mice exhibited a decreased parasite burden in the brain and increased resistance in the chronic phase than did control mice. Among members of IRGs and GBPs important for the parasite clearance, Irga6 and Gbp2 alone were more frequently recruited to T. gondii-forming parasitophorous vacuoles in RabGDIα-deficient cells. Notably, Gbp2 positively controlled Irga6 recruitment that was inhibited by direct and specific interactions of RabGDIα with Gbp2 through the lipid-binding pocket. Taken together, our results suggest that RabGDIα inhibits host defense against T. gondii by negatively regulating the Gbp2–Irga6 axis of IFN-γ–dependent cell-autonomous immunity.IFN-γ is an important T-helper 1 (Th1) cytokine that inhibits the survival and growth of a wide range of intracellular pathogens, such as viruses, bacteria, and parasites (1). Stimulation of innate immune cells, such as macrophages, by IFN-γ up-regulates almost 2,000 effector genes encoding various IFN-γ–inducible proteins, including immunity-related GTPases such as the MX proteins, p47 immunity-related GTPases (IRGs), and p65 guanylate-binding proteins (GBPs) (2). MX proteins and GBPs have been shown to restrict replication of viruses (3). Moreover, IRGs and GBPs play roles in host defense against vacuole-forming bacteria, including Salmonella, Chlamydia, Mycobacteria, and Listeria, by induction of antibacterial responses involving autophagic effectors, inflammasomes, and phagocytic oxidases (4–6).Not only viruses and bacteria but also the vacuolar parasite Toxoplasma gondii is targeted by IFN-γ–inducible GTPases. T. gondii is an obligatory protozoan parasite that causes a life-threatening toxoplasmosis in humans and animals (7). After the active invasion of host cells, T. gondii forms a nonfusogenic cytoplasmic membranous structure called the parasitophorous vacuole (PV), in which the parasite efficiently proliferates (8, 9). In terms of cellular host defense against T. gondii, interleukin-12 (IL-12) is mainly produced from macrophages and dendritic cells, in which Toll-like receptors and the chemokine receptor CCR5 recognize T. gondii-derived ligands. Also, IL-12 promotes development of IFN-γ–producing Th1 cells (10–15). IFN-γ is critically required for suppression of T. gondii replication inside PVs and cell-autonomous clearance. Nitric oxide that is produced by inducible nitric oxide synthase (iNOS) in the infected cells mainly inhibits the replication (16, 17). On the other hand, T. gondii survival within infected cells is suppressed by cooperative action between IRGs and GBPs (18). Indeed, various types of cells (such as macrophages, fibroblasts, and astrocytes) derived from mice lacking IRGs [such as Irgm1 (also known as LRG-47), Irgm3 (IGTP), and Irga6 (IIGP1)] or GBPs [such as Gbp1, Gbp2, and a cluster of GBPs on murine chromosome 3 (GBP^chr3; Gbp1, Gbp2, Gbp3, Gbp5, and Gbp7)] were defective for IFN-γ–mediated intracellular killing of T. gondii (19–25). After the formation of PVs, GBPs and a subfamily of IRG members called GKS-IRGs [such as Irga6, Irgb6 (TGTP), and Irgb10] are shown to accumulate on PV membrane (PVM) and oligomerize dependently on GTP binding to destroy PV membrane integrity and structure (26, 27), resulting in cell-autonomous clearance by intracellular digestive pathways (20, 21, 28). The IFN-γ–mediated clearance by these GTPases is T. gondii strain-specific. Most T. gondii in North America and Europe belong to type I, type II, and type III (29). Virulent type I strain inactivates IFN-γ–inducible GTPases by effectors, such as ROP18 and ROP5, during the parasite infection (30). On the other hand, avirulent type II and type III strains are susceptible to IFN-γ–dependent clearance due to polymorphisms or reduced expression of the effectors (31–34).The regulatory mechanism of how IFN-γ–induced GTPases are recruited to PVs has gradually been elucidated. In the absence of essential autophagy-related proteins Atg3, Atg5, Atg7, and Atg16L1 and of another subfamily of IRGs called GMS-IRGs, such as Irgm1 and Irgm3, the recruitment of IFN-γ–inducible GTPases and the killing of T. gondii are severely impaired (35–39). Thus, Atg3/Atg5/Atg7/Atg16L1 and Irgm1/Irgm3 are required for proper targeting of GKS-IRGs and GBPs to T. gondii PVM and play positive roles in the cell-autonomous resistance to the pathogen. On the other hand, the inhibitory mechanism for the IFN-γ–inducible GTPase-dependent immunity remains unclear.To explore the molecular mechanism to control the action of IFN-γ–inducible GTPases, we have attempted to identify binding partners of Gbp2 because a single deletion of Gbp2 in mice has been shown to result in impaired in vitro and in vivo resistance to type II T. gondii (22). In the present study, we identify Rab GDP dissociation inhibitor α (RabGDIα) as a Gbp2-interacting protein. We have an interest in this protein for two reasons: One is because RabGDIα has been shown to participate in the regulation of Rab proteins, which, like GBPs, belong to another family of GTPases (40, 41), and the other is because we demonstrate that overexpression of RabGDIα in cells impairs IFN-γ–induced reduction of T. gondii numbers. We have tested whether RabGDIα acts as a regulator of IFN-γ–inducible GTPases under physiological conditions. Macrophages and fibroblasts from RabGDIα-deficient mice exhibit enhanced IFN-γ–dependent clearance of T. gondii. Moreover, the enhanced clearance by RabGDIα deficiency is accompanied by increased recruitment of Irga6 and Gbp2 to the parasite. Notably, Gbp2 is required for Irga6 recruitment, which is suppressed by direct and specific interactions of RabGDIα with Gbp2 through a lipid-binding pocket. Furthermore, a high dose of type II T. gondii infection in RabGDIα-deficient mice results in increased resistance, which is characterized by a decreased parasite burden in the brain. Taken together, our data indicate that RabGDIα plays a negative role in the Gbp2–Irga6 axis of IFN-γ–inducible GTPase-dependent cell-autonomous resistance to T. gondii.     

Two-Dimensional Cs3Sb2I9−xClx Film with (201) Preferred Orientation for Efficient Perovskite Solar Cells

All-inorganic Sb-perovskite has become a promising material for solar cell applications owing to its air stability and nontoxic lead-free constitution. However, the poor morphology and unexpected (001) orientation of Sb-based perovskite films strongly hinder the improvement of efficiency. In this work, two-dimensional Cs₃Sb₂Cl_xI_9−x with (201) preferred orientation has been successfully fabricated by introducing thiourea (TU) to the precursor solution. The presence of the C=S functional group in TU regulates the crystallization dynamics of Cs₃Sb₂I_9−xCl_x films and generates the (201) preferred orientation of Cs₃Sb₂Cl_xI_9−x films, which could effectively improve the carrier transport and film morphology. As a result, the Cs₃Sb₂I_9−xCl_x perovskite solar cells (PSCs) delivered a power conversion efficiency (PCE) of 2.22%. Moreover, after being stored in nitrogen at room temperature for 60 days, the devices retained above 87.69% of their original efficiency. This work demonstrates a potential pathway to achieve high-efficiency Sb-based PSCs.     

The Dielectric Constant of Ba6−3x(Sm1−yNdy)8+2xTi18O54 (x = 2/3) Ceramics for Microwave Communication by Linear Regression Analysis

The electronics related to the fifth generation mobile communication technology (5G) are projected to possess significant market potential. High dielectric constant microwave ceramics used as filters and resonators in 5G have thus attracted great attention. The Ba_6−3x(Sm_1−yNd_y)_8+2xTi₁₈O₅₄ (x = 2/3) ceramic system has aroused people’s interest due to its underlying excellent microwave dielectric properties. In this paper, the relationships between the dielectric constant, Nd-doped content, sintering temperature and the density of Ba_6−3x(Sm_1−yNd_y)_8+2xTi₁₈O₅₄ (x = 2/3) ceramics were studied. The linear regression equation was established by statistical product and service solution (SPSS) data analysis software, and the factors affecting the dielectric constant have been analyzed by using the enter and stepwise methods, respectively. It is found that the model established by the stepwise method is practically significant with Y = −71.168 + 6.946x₁ + 25.799x₃, where Y, x₁ and x₃ represent the dielectric constant, Nd content and the density, respectively. According to this model, the influence of density on the dielectric constant is greater than that of Nd doping concentration. We bring the linear regression analysis method into the research field of microwave dielectric ceramics, hoping to provide an instructive for the optimization of ceramic technology.     

High-Temperature Chemical Stability of Cr(III) Oxide Refractories in the Presence of Calcium Aluminate Cement

Al₂O₃-CaO-Cr₂O₃ castables are used in various furnaces due to excellent corrosion resistance and sufficient early strength, but toxic Cr(VI) generation during service remains a concern. Here, we investigated the relative reactivity of analogous Cr(III) phases such as Cr₂O₃, (Al_1−xCr_x)₂O₃ and in situ Cr(III) solid solution with the calcium aluminate cement under an oxidizing atmosphere at various temperatures. The aim is to comprehend the relative Cr(VI) generation in the low-cement castables (Al₂O₃-CaO-Cr₂O₃-O₂ system) and achieve an environment-friendly application. The solid-state reactions and Cr(VI) formation were investigated using powder XRD, SEM, and leaching tests. Compared to Cr₂O₃, the stability of (Al_1−xCr_x)₂O₃ against CAC was much higher, which improved gradually with the concentration of Al₂O₃ in (Al_1−xCr_x)₂O₃. The substitution of Cr₂O₃ with (Al_1−xCr_x)₂O₃ in the Al₂O₃-CaO-Cr₂O₃ castables could completely inhibit the formation of Cr(VI) compound CaCrO₄ at 500–1100 °C and could drastically suppress Ca₄Al₆CrO₁₆ generation at 900 to 1300 °C. The Cr(VI) reduction amounting up to 98.1% could be achieved by replacing Cr₂O₃ with (Al_1−xCr_x)₂O₃ solid solution. However, in situ stabilized Cr(III) phases as a mixture of (Al_1−xCr_x)₂O₃ and Ca(Al_12−xCr_x)O₁₉ solid solution hardly reveal any reoxidation. Moreover, the CA₆ was much more stable than CA and CA₂, and it did not participate in any chemical reaction with (Al_1−xCr_x)₂O₃ solid solution.     

Estrogen exerts concentration-dependent pro-and anti-hypertrophic effects on adult cultured ventricular myocytes. Role of NHE-1 in estrogen-induced hypertrophy

Estrogen has been shown to protect the heart and attenuate myocardial hypertrophy and left ventricular remodelling through as yet to be defined mechanisms. In the present study we examined concentration-dependent effects of estrogen on hypertrophy of adult rat cardiomyocytes, potential underlying mechanisms related to intracellular pH (pH_i) and possible sex-dependent responses. Cardiomyocytes were isolated from adult male and female Sprague-Dawley rats and used immediately for pH_i determinations or cultured and subsequently treated for 24 h with 17β-estradiol to assess hypertrophic responses. Fluorometric measurements with the pH_i-sensitive dye BCECF demonstrated that at 1 pM 17β-estradiol increased pH_i (+ 0.05 pH units in females and + 0.12 pH units in males, P < 0.05) by a rapid non-genomic mechanism that was blocked by the sodium-hydrogen exchange isoform 1 (NHE-1) specific inhibitor AVE-4890 (AVE, 5 μM). Treatment with 1 pM 17β-estradiol for 24 h increased cell size (females: 20%, P < 0.05; males: 29%, P < 0.05) and ANP expression (females: 414%, P < 0.05; males: 497%, P < 0.05) in a NHE-1-, and ERK1/2 MAPK-dependent manner. At 1 nM, 17β-estradiol decreased pH_i (females: − 0.24 pH units, P < 0.05; males: − 0.07 pH units, P < 0.05) which was also prevented by AVE, although at this concentration the hormone had no direct hypertrophic effect but instead prevented hypertrophy induced by phenylephrine. Our results show that low levels of estrogen produce cardiomyocyte hypertrophy through ERK/NHE-1 activation and intracellular alkalinization whereas an antihypertrophic effect is seen at high concentrations. These effects may further our understanding of the role of estrogen in heart disease particularly associated with hypertrophy.