A sustained increase in the intracellular Ca²⁺ concentration induces proteolytic cleavage of EAG2 channel

Voltage-gated EAG2 channel is abundant in the brain and enhances cancer cell growth by controlling cell volume. The channel contains a cyclic nucleotide-binding homology (CNBH) domain and multiple calmodulin-binding motifs. Here we show that a raised intracellular Ca(2+) concentration causes proteolytic digestion of heterologously expressed and native EAG2 channels. A treatment of EAG2-expressing cells with the Ca(2+) ionophore A23187 for 1h reduces the full-length protein by ∼80% with a concomitant appearance of 30-35-kDa peptides. Similarly, a treatment with the Ca(2+)-ATPase inhibitor thapsigargin for 3h removes 30-35-kDa peptides from ∼1/3 of the channel protein. Moreover, an incubation of the isolated rat brain membrane with CaCl2 leads to the generation of fragments with similar sizes. This Ca(2+)-induced digestion is not seen with EAG1. Mutations in a C-terminal calmodulin-binding motif alter the degrees and positions of the cleavage. Truncated channels that mimic the digested proteins exhibit a reduced current density and altered channel gating. In particular, these shorter channels lack a rapid activation typical in EAG channels with more than 20-mV positive shifts in voltage dependence of activation. The truncation also eliminates the ability of EAG2 channel to reduce cell volume. These results suggest that a sustained increase in the intracellular Ca(2+) concentration leads to proteolytic cleavage at the C-terminal cytosolic region following the CNBH domain by altering its interaction with calmodulin. The observed Ca(2+)-induced proteolytic cleavage of EAG2 channel may act as an adaptive response under physiological and/or pathological conditions.

Functional and morphological olfactory bulb modifications in mice after vanadium inhalation

Neurodegenerative disorders, such as Parkinson's and Alzheimer's diseases, have olfaction impairment. These pathologies have also been linked to environmental pollutants. Vanadium is a pollutant, and its toxic mechanisms are related to the production of oxidative stress. In this study, we evaluated the effects of inhaled vanadium on olfaction, the olfactory bulb antioxidant, through histological and ultrastructural changes in granule cells. Mice in control group were made to inhale saline; the experimental group inhaled 0.02-M vanadium pentoxide (V2O5) for 1 hr twice a week for 4 weeks. Animals were sacrificed at 1, 2, 3, and 4 weeks after inhalation. Olfactory function was evaluated by the odorant test. The activity of glutathione peroxidase (GPx) and glutathione reductase (GR) was assayed in olfactory bulbs and processed for rapid Golgi method and ultrastructural analysis. Results show that olfactory function decreased at 4-week vanadium exposure; granule cells showed a decrease in dendritic spine density and increased lipofuscin, Golgi apparatus vacuolation, apoptosis, and necrosis. The activity of GPx and GR in the olfactory bulb was increased compared to that of the controls. Our results demonstrate that vanadium inhalation disturbs olfaction, histology, and the ultrastructure of the granule cells that might be associated with oxidative stress, a risk factor in neurodegenerative diseases.

α-Hydroxy coordination of mononuclear vanadyl citrate, malate and S-citramalate with N-heterocycle ligand, implying a new protonation pathway of iron-vanadium cofactor in nitrogenase

Unlike the most of α-alkoxy coordination in α-hydroxycarboxylates to vanadium, novel α-hydroxy coordination to vanadium(IV) has been observed for a series of chiral and achiral monomeric α-hydroxycarboxylato vanadyl complexes [VO(H2cit)(bpy)]·2H2O (1), [VO(Hmal)(bpy)]·H2O (2), [VO(H2cit)(phen)]·1.5H2O (3), [VO(Hmal)(phen)]·H2O (4), and [(Δ)VO(S-Hcitmal)(bpy)]·2H2O (5), [VO(H2cit)(phen)]2·6.5H2O (6), which were isolated from the reactions of vanadyl sulfate with α-hydroxycarboxylates and N-heterocycle ligands in acidic solution. The complexes feature a tridentate citrate, malate or citramalate that chelates to vanadium atom through their α-hydroxy, α-carboxy and β-carboxy groups; while the other β-carboxylic acidic group of citrate is free to participate strong hydrogen bonds with lattice water molecule. The neutral α-hydroxy group also forms strong intermolecular hydrogen bonds with water molecule and the negatively-charged α-carboxy group in the environment. The inclusion of a hydrogen ion in α-alkoxy group results in the formation of a series of neutral complexes with one less positive charge. There are two different configurations of citrate with respect to the trans-position of axial oxo group, where the complex with trans-hydroxy configuration seems more stable with less hindrance. The average bond distances of V-Ohydroxy and V-Oα-carboxy are 2.196 and 2.003Å respectively, which are comparable to the VO distance (2.15Å) of homocitrate in FeV-cofactor of V-nitrogenase. A new structural model is suggested for R-homocitrato iron vanadium cofactor as VFe7S9C(R-Hhomocit) (H4homocit=homocitric acid) with one more proton in homocitrate ligand.

Aerobic oxidation of starch catalyzed by isopolyoxovanadate Na4Co(H2O)6V10O28

The partial oxidation of starch was achieved in the presence of oxygen with Na4Co(H2O)6V10O28·18H2O (abbreviated as CoV10) as catalyst. The oxidation degree of starch was determined by FT-IR, XRD and SEM measurements, which indicated that the aerobic oxidation of starch was promoted by oxidative catalyst CoV10. The application of CoV10 could give a high oxidation degree (DO) of 1.35 COOH/100 GU and 2.07 CO/100 GU with 86 wt.% yield of solid starch under mild reaction conditions (pH=6; reaction time, 8 h; temperature, 50 °C; catalyst amount, 8 mg, when 1.5 g starch was used as substrate; atmospheric pressure). Among some vanadium compounds, CoV10 exhibited 4-fold activity higher than orthovanadate due to its coordination effect of cobalt and V10O28. Meanwhile, CoV10 could be recycled for six times with only a slight decrease in activity. Thus, CoV10/O2 is one of the most efficient systems for partial oxidation of starch reported so far.

Emerging importance of oxidative stress in regulating striated muscle elasticity

The contractile function of striated muscle cells is altered by oxidative/nitrosative stress, which can be observed under physiological conditions but also in diseases like heart failure or muscular dystrophy. Oxidative stress causes oxidative modifications of myofilament proteins and can impair myocyte contractility. Recent evidence also suggests an important effect of oxidative stress on muscle elasticity and passive stiffness via modifications of the giant protein titin. In this review we provide a short overview of known oxidative modifications in thin and thick filament proteins and then discuss in more detail those oxidative stress-related modifications altering titin stiffness directly or indirectly. Direct modifications of titin include reversible disulfide bonding within the cardiac-specific N2-Bus domain, which increases titin stiffness, and reversible S-glutathionylation of cryptic cysteines in immunoglobulin-like domains, which only takes place after the domains have unfolded and which reduces titin stiffness in cardiac and skeletal muscle. Indirect effects of oxidative stress on titin can occur via reversible modifications of protein kinase signalling pathways (especially the NO-cGMP-PKG axis), which alter the phosphorylation level of certain disordered titin domains and thereby modulate titin stiffness. Oxidative stress also activates proteases such as matrix-metalloproteinase-2 and (indirectly via increasing the intracellular calcium level) calpain-1, both of which cleave titin to irreversibly reduce titin-based stiffness. Although some of these mechanisms require confirmation in the in vivo setting, there is evidence that oxidative stress-related modifications of titin are relevant in the context of biomarker design and represent potential targets for therapeutic intervention in some forms of muscle and heart disease.

Effects of vanadium (V) and magnesium (Mg) on rat bone tissue: mineral status and micromorphology. Consequences of V-Mg interactions

The extent to which the 12 week separate and combined administration of vanadium (as sodium metavanadate--SMV, 0.125 mg V per ml) and magnesium (as magnesium sulphate--MS, 0.06 mg Mg per ml) affects bone mineral status and micromorphology as well as the alkaline phosphatase (ALP) activity in femoral diaphysis (FD) was examined in male rats. The bone chemical composition of SMV-exposed rats was also investigated. SMV alone or in combination with MS (as SMV-MS) reduced the levels of MgFD (by 21% and 20%) and PFD (by 12% and 9%), lowered the CaFD content (by 7% and 10%), and caused a rise of the FeFD concentration (by 22.5% and 17%), compared with the control; SMV alone also reduced and enhanced the KFD and ZnFD concentrations (by 19% and 15%, respectively) but remained without significant effect on the femoral bone surface roughness (FBSR), whereas MS alone lowered the VFD, PFD, and CuFD levels (by 42%, 10%, and 20.6%), reduced FBSR, and created the regular femoral bone surface shape. The SMV-MS combination also induced a decline and rise in the levels of CuFD (by 30%) and NaFD (by 15%), respectively, compared with the control and the MS-supplemented rats; elevated ALPFD activity (by 24%, 35%, and 40%), compared with the control, SMV-exposed, and MS-supplemented animals; and increased FBSR. Relationships between the root mean square roughness (Sq) and skewness (Ssk): Sq [MS < SMV < Control < SMV-MS] ⇔ Ssk [SMV-MS > Control > SMV > MS], ALPFD and Sq: ALPFD⇔ Sq [SMV-MS > Control > SMV > MS], and between other variables were demonstrated. A partial limitation of the drop in the PFD and KFD levels and normalization of the ZnFD concentration were a consequence of the V-Mg antagonistic interaction whereas a consequence of the V-Mg synergistic interaction was the increase in the NaFD level, ALPFD activity, and FBSR. Ca10(PO4)5(SiO4)(OH) was part of the inorganic component of the bone of the SMV-exposed rats.

Ischemic cardiovascular involvement in psoriasis: a systematic review

Epidemiologic studies demonstrate that psoriasis is associated with shorter life expectancy, most frequently attributable to cardiovascular (CV) events. Although increased prevalence and incidence of CV risk factors for atherosclerosis have been reported in psoriatic patients, psoriasis likely plays an independent role in the increased cardiovascular risk, presumably linked to the chronic systemic inflammatory state. Consistently, preliminary investigations suggest that anti-inflammatory therapies may improve early subclinical vascular alterations and reduce cardiovascular morbidity and mortality. This review will focus on ischemic CV involvement in psoriatic patients, summarizing the prevalence and incidence of CV risk factors and CV events, as well as evidence on mechanisms of premature atherosclerosis and on effects of systemic anti-inflammatory therapies on CV risk profile. We performed a systematic review using Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) and evaluated the quality of studies comparing drug treatments using Detsky score. Our review documented that psoriatic patients are at increased CV risk, related to raised prevalence and incidence of CV risk factor and to inflammatory status. However, available literature lacks of studies that establish appropriate targets for CV risk factors and assess the clinical value of screening for subclinical organ damage and the impact of disease-modifying therapies on CV risk profile in psoriatic patients. Awareness of raised CV risk in psoriatic patients should foster further research aimed at elucidating these aspects.

Two novel compounds of vanadium and molybdenum with carnitine exhibiting potential pharmacological use

The reaction of sodium orthovanadate with carnitine hydrochloride molecule results in the precipitation of decavanadate compound of carnitine whereas the reaction of metallic molybdenum with hydrogen peroxide and carnitine results in the peroxo-molybdenum complex of carnitine. The decavanadate compound as well as the molybdenum complex of carnitine have been characterized by means of elemental analysis, IR, electronic spectra, (1)H NMR, 2D-COSY-NMR (=correlation spectroscopy) and thermo-gravimetric analysis (TGA). In addition decavanadate compound of carnitine was fully characterized by X-ray crystallography. The analytical data were in good agreement with the empirical formulae of both, decavanadate compound and molybdenum complex. The two compounds were also evaluated for cell toxicity and their anticancer activity by the MTT(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)-based assay method, using primary cells and tumor cell lines of both human and murine origins and the results show that compound 1 shows an increased biological activity in comparison with compound 2. Moreover using confocal microscopy and antibodies against cleaved caspase 3 we further analyzed the cell toxicity and we conclude that the apoptotic pathway is triggered efficiently with tumor specificity by compound 1 and not by compound 2.

A single mechanism can explain network-wide insulin resistance in adipocytes from obese patients with type 2 diabetes

The response to insulin is impaired in type 2 diabetes. Much information is available about insulin signaling, but understanding of the cellular mechanisms causing impaired signaling and insulin resistance is hampered by fragmented data, mainly obtained from different cell lines and animals. We have collected quantitative and systems-wide dynamic data on insulin signaling in primary adipocytes and compared cells isolated from healthy and diabetic individuals. Mathematical modeling and experimental verification identified mechanisms of insulin control of the MAPKs ERK1/2. We found that in human adipocytes, insulin stimulates phosphorylation of the ribosomal protein S6 and hence protein synthesis about equally via ERK1/2 and mTORC1. Using mathematical modeling, we examined the signaling network as a whole and show that a single mechanism can explain the insulin resistance of type 2 diabetes throughout the network, involving signaling both through IRS1, PKB, and mTOR and via ERK1/2 to the nuclear transcription factor Elk1. The most important part of the insulin resistance mechanism is an attenuated feedback from the protein kinase mTORC1 to IRS1, which spreads signal attenuation to all parts of the insulin signaling network. Experimental inhibition of mTORC1 using rapamycin in adipocytes from non-diabetic individuals induced and thus confirmed the predicted network-wide insulin resistance.

Circulating PGRN is significantly associated with systemic insulin sensitivity and autophagic activity in metabolic syndrome

Progranulin (PGRN) is a secreted protein that has recently emerged as an important regulatory adipokine of glucose metabolism and insulin sensitivity. We report here that serum PGRN concentrations were significantly higher in patients with metabolic syndrome (MS) than in subjects without MS and correlated positively with body mass index, waist circumference, fasting insulin, fasting plasma glucose, glycated hemoglobin A1c, triglyceride, and homeostasis model assessment of insulin resistance, and were inversely related to high-density lipoprotein cholesterol and homeostasis model assessment of β cell function. Subgroup analysis in 32 subjects showed that elevated expression levels of PGRN were positively correlated with increased autophagy markers LC3 and Atg7 proteins in omental adipose tissue of subjects with MS. Consistent with these findings, the enhanced PGRN levels were also observed in multiple insulin-resistant cellular models, whereas PGRN-deficient adipocytes were more susceptible to insulin action and refractory to tunicamycin-induced autophagic disorders. PGRN remarkably attenuated insulin sensitivity, increased autophagic activity, and triggered endoplasmic reticulum (ER) stress in cultured human adipocytes, whereas these effects were nullified by reduction of ER stress with phenylbutyric acid chemical chaperone treatment. In addition, PGRN-induced ER stress and impaired insulin sensitivity were improved in TNFR1(-/-) cells, indicating a causative role of TNF receptor in the action of PGRN. Collectively, our findings suggest that circulating PGRN is significantly associated with systemic insulin sensitivity and autophagic activity in adipose tissue and support the notion that PGRN functions as a potential link between chronic inflammation and insulin resistance.

FKBP5 expression in human adipose tissue increases following dexamethasone exposure and is associated with insulin resistance

OBJECTIVE

To study effects of dexamethasone on gene expression in human adipose tissue aiming to identify potential novel mechanisms for glucocorticoid-induced insulin resistance.

MATERIALS/METHODS

Subcutaneous and omental adipose tissue, obtained from non-diabetic donors (10 M/15 F; age: 28-60 years; BMI: 20.7-30.6 kg/m²), was incubated with or without dexamethasone (0.003-3 μmol/L) for 24 h. Gene expression was assessed by microarray and real time-PCR and protein expression by immunoblotting.

RESULTS

FKBP5 (FK506-binding protein 5) and CNR1 (cannabinoid receptor 1) were the most responsive genes to dexamethasone in both subcutaneous and omental adipose tissue (~7-fold). Dexamethasone increased FKBP5 gene and protein expression in a dose-dependent manner in both depots. The gene product, FKBP51 protein, was 10-fold higher in the omental than in the subcutaneous depot, whereas the mRNA levels were similar. Higher FKBP5 gene expression in omental adipose tissue was associated with reduced insulin effects on glucose uptake in both depots. Furthermore, FKBP5 gene expression in subcutaneous adipose tissue was positively correlated with serum insulin, HOMA-IR and subcutaneous adipocyte diameter and negatively with plasma HDL-cholesterol. FKBP5 SNPs were found to be associated with type 2 diabetes and diabetes-related phenotypes in large population-based samples.

CONCLUSIONS

Dexamethasone exposure promotes expression of FKBP5 in adipose tissue, a gene that may be implicated in glucocorticoid-induced insulin resistance.

mTOR inhibitors and dyslipidemia in transplant recipients: a cause for concern?

Post-transplant dyslipidemia is exacerbated by mammalian target of rapamycin (mTOR) inhibitors. Early clinical trials of mTOR inhibitors used fixed dosing with no concomitant reduction in calcineurin inhibitor (CNI) exposure, leading to concerns when consistent and marked dyslipidemia was observed. With use of modern concentration-controlled mTOR inhibitor regimens within CNI-free or reduced-exposure CNI regimens, however, the dyslipidemic effect persists but is less pronounced. Typically, total cholesterol levels are at the upper end of normal, or indicate borderline risk, in kidney and liver transplant recipients, and are lower in heart transplant patients under near-universal statin therapy. Of note, it is possible that mTOR inhibitors may offer a cardioprotective effect. Experimental evidence for delayed progression of atherosclerosis is consistent with evidence from heart transplantation that coronary artery intimal thickening and the incidence of cardiac allograft vasculopathy are reduced with everolimus versus cyclosporine therapy. Preliminary data also indicate that mTOR inhibitors may improve arterial stiffness, a predictor of cardiovascular events, and may reduce ventricular remodeling and decrease left ventricular mass through an anti-fibrotic effect. Post-transplant dyslipidemia under mTOR inhibitor therapy should be monitored and managed closely, but unless unresponsive to therapy should not be regarded as a barrier to its use.

Comparison of three different cell viability assays for evaluation of vanadyl sulphate cytotoxicity in a Chinese hamster ovary K1 cell line

Previously, evaluation of sodium metavanadate (NaVO3) cytotoxicity after 24 h exposure of Chinese hamster ovary K1 (CHO-K1) cells revealed different sensitivity of the in vitro assays used starting from the neutral red (NR, 3-amino-7-dimethylamino-2-methylphenazine hydrochloride) test (detecting lysosomal and possibly the Golgi apparatus damage) as the most sensitive followed by the 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide inner salt (XTT) and resazurin (7-hydroxy-3H-phenoxazin-3-one-10-oxide) tests (mitochondrial disruption). The trypan blue (TB) staining (plasma membrane permeability) showed cytotoxicity of NaVO3 at a much higher NaVO3 concentration than the above-mentioned assays. In the current study, using the same experimental approach, we have assessed the toxicity of vanadyl sulphate (VOSO4) and compared the obtained results with NaVO3 action. Unlike metavanadate, VOSO4 treatment at 24 h resulted in similar sensitivity of the NR and resazurin tests. Nevertheless, following the 48-h incubation with VOSO4, the NR test showed markedly higher sensitivity than the resazurin test when comparing the half maximal inhibitory concentration values (61 and 110 µM for the NR and resazurin test, respectively, p < 0.05). The TB staining method was the least susceptible for detecting vanadyl cytotoxicity at each exposure time point. In summary, both the NR and resazurin tests can be advocated as similarly sensitive in detection of VOSO4-induced cytotoxicity in the CHO-K1 cell line at 24 h. However, the longer incubation time with VOSO4 showed that the NR test is more sensitive than the resazurin assay. The differences in the results between the cytotoxicity tests employed probably arise from dissimilar susceptibility of the endpoints (targets) measured with these tests to the damage by vanadium. Considering this, the current and the previous studies highlight the role of lysosomes (and possibly the Golgi apparatus) apart from mitochondria in the toxicity mechanism induced by inorganic vanadium in mammalian cells.

Reactivity-activity relationships of oral anti-diabetic vanadium complexes in gastrointestinal media: an X-ray absorption spectroscopic study

The reactions of oral V(V/IV) anti-diabetic drugs within the gastrointestinal environment (particularly in the presence of food) are a crucial factor that affects their biological activities, but to date these have been poorly understood. In order to build up reactivity-activity relationships, the first detailed study of the reactivities of typical V-based anti-diabetics, Na3V(V)O4 (A), [V(IV)O(OH2)5](SO4) (B), [V(IV)O(ma)2] (C, ma = maltolato(-)) and (NH4)[V(V)(O)2(dipic)] (D, dipic = pyridine-2,5-dicarboxylato(2-)) with simulated gastrointestinal (GI) media in the presence or absence of food components has been performed by the use of XANES (X-ray absorption near edge structure) spectroscopy. Changes in speciation under conditions that simulate interactions in the GI tract have been discerned using correlations of XANES parameters that were based on a library of model V(V), V(IV), and V(III) complexes for preliminary assessment of the oxidation states and coordination numbers. More detailed speciation analyses were performed using multiple linear regression fits of XANES from the model complexes to XANES obtained from the reaction products from interactions with the GI media. Compounds B and D were relatively stable in the gastric environment (pH ∼ 2) in the absence of food, while C was mostly dissociated, and A was converted to [V10O28](6-). Sequential gastric and intestinal digestion in the absence of food converted A, B and D to poorly absorbed tetrahedral vanadates, while C formed five- or six-coordinate V(V) species where the maltolato ligands were likely to be partially retained. XANES obtained from gastric digestion of A-D in the presence of typical food components converged to that of a mixture of V(IV)-aqua, V(IV)-amino acid and V(III)-aqua complexes. Subsequent intestinal digestion led predominantly to V(IV) complexes that were assigned as citrato or complexes with 2-hydroxyacidato donor groups from other organic compounds, including certain carbohydrates. The absence of strong reductants (such as ascorbate) in the food increased the V(V) component in gastrointestinal digestion products. These results can be used to predict the oral bioavailability of various types of V(V/IV) anti-diabetics, and the effects of taking such drugs with food.

Effect of vanadium toxicity at its different oxidation states on selected bacterial and protozoan isolates in wastewater systems

This study assesses and compares vanadium toxicity in its different oxidation states towards bacterial isolates (Pseudomonas putida and Bacillus licheniformis) and protozoan isolates (Peranema sp. and Trachelophyllum sp.). The isolates were exposed to various concentrations of V in mixed liquors and their tolerance to V was assessed at 30 degrees C at a pH of 4. The results revealed that the increase in V oxidation state increased its toxicity to bacterial isolates, whereas its toxicity decreased for protozoan isolates. Among the bacterial isolates, P putida was found to be more tolerant to V3+(24h-median lethal concentration (LC50): 390mg/l), V4+(24h-LC50: 230-250mg/l) and V5+(24h-LC50: 180-200mg/l), whereas for the protozoan isolates, Peranema sp. appeared to be more tolerant to V3+(24 h-LC50: 110-120 mg/l), V4+(24 h-LC50: 160-170 mg/l) and V5+(24 h-LC50: 160-200 mg/l). A comparison of both groups of organisms revealed Trachelophyllum sp. as the most sensitive organism to V at its various oxidation states. The visual and spectrophotometric methods used to assess V reduction revealed that P. putida was the only isolate able to reduce V5+, V4+ and V3+ to V2+ in mixed liquor media. Vanadium (+2) in concentrations of approximately 46.46 mg/l, 29.57 m mg/l and 38.01 mg/l found in the media was treated with V3+, V4+ and V5+, respectively, and inoculated with P. putida. This study revealed that the ability of V reduction, adopted with P putida, can be an effective strategy to remove V from polluted environments. This study also showed that the toxicity of V, in terms of its oxidation states, differs from one species to another and in kingdoms.

Decavanadate in vitro and in vivo effects: facts and opinions

This review covers recent advances in the understanding of the in vitro and in vivo effects of decavanadate, (V10O28)(6-), particularly in mitochondria. In vivo toxicological studies involving vanadium rarely account for the fact that under physiological conditions some vanadium may be present in the form of the decavanadate ion, which may behave differently from ortho- and metavanadates. It has for example been demonstrated that vanadium levels in heart or liver mitochondria are increased upon decavanadate exposure. Additionally, in vitro studies have shown that mitochondrial depolarization (IC50, 40 nM) and oxygen consumption (IC50, 99 nM) are strongly affected by decavanadate, which causes reduction of cytochrome b (complex III). We review these recent findings which together suggest that the observed cellular targets, metabolic pathway and toxicological effects differ according to the species of vanadium present. Finally, the toxicological effects of decavanadate depend on several factors such as the mode of administration, exposure time and type of tissue.

Purified NADH-cytochrome b5 reductase is a novel superoxide anion source inhibited by apocynin: sensitivity to nitric oxide and peroxynitrite

Cytochrome b5 reductase (Cb5R) is a pleiotropic flavoprotein that catalyzes multiple one-electron reduction reactions with various redox partners in cells. In earlier work from our laboratory, we have shown its implication in the generation of reactive oxygen species (ROS), primarily a superoxide anion overshoot peak, which plays a major role as a triggering event for the acceleration of apoptosis in cerebellar granule neurons in culture. However, the results obtained in that work did not allow us to exclude the possibility that this superoxide anion production could be derived from Cb5R acting in concert with other cellular components. In this work, we have purified Cb5R from pig liver and we have experimentally shown that this enzyme catalyzed NADH-dependent production of superoxide anion, assayed with cytochrome c and nitroblue tetrazolium as detection reagents for this particular ROS. The basic kinetic parameters for this novel NADH-dependent activity of Cb5R at 37°C are Vmax = 3.0 ± 0.5 μmol/min/mg of purified Cb5R and KM(NADH) = 2.8 ± 0.3 μM NADH. In addition, we report that apocynin, a widely used inhibitor of nonmitochondrial ROS production in mammalian cell cultures and tissues, is a potent inhibitor of purified Cb5R activity at the concentrations used in the experiments done with cell cultures. In the presence of apocynin the KM(NADH) value of Cb5R increases, and docking simulations indicate that apocynin can bind to a site near to or partially overlapping the NADH binding site of Cb5R. Other ROS, such as nitric oxide and peroxynitrite, have inhibitory effects on purified Cb5R, providing the basis for a feedback cellular protection mechanism through modulation of excessive extramitochondrial superoxide anion production by Cb5R. Both kinetic assays and docking simulations suggest that nitric oxide-induced nitrosylation (including covalent adduction of nitroso functional groups) of Cb5R cysteines and peroxynitrite-induced tyrosine nitration and cysteine oxidation modified the conformation of the NADH binding domain leading to a decreased affinity of Cb5R for NADH.

PAS kinase drives lipogenesis through SREBP-1 maturation

Elevated hepatic synthesis of fatty acids and triglycerides, driven by hyperactivation of the SREBP-1c transcription factor, has been implicated as a causal feature of metabolic syndrome. SREBP-1c activation requires the proteolytic maturation of the endoplasmic-reticulum-bound precursor to the active, nuclear transcription factor, which is stimulated by feeding and insulin signaling. Here, we show that feeding and insulin stimulate the hepatic expression of PASK. We also demonstrate, using genetic and pharmacological approaches, that PASK is required for the proteolytic maturation of SREBP-1c in cultured cells and in the mouse and rat liver. Inhibition of PASK improves lipid and glucose metabolism in dietary animal models of obesity and dyslipidemia. Administration of a PASK inhibitor decreases hepatic expression of lipogenic SREBP-1c target genes, decreases serum triglycerides, and partially reverses insulin resistance. While the signaling network that controls SREBP-1c activation is complex, we propose that PASK is an important component with therapeutic potential.

Caveolin-rich lipid rafts of the plasma membrane of mature cerebellar granule neurons are microcompartments for calcium/reactive oxygen and nitrogen species cross-talk signaling

In previous works, we have shown that L-type voltage-operated calcium channels, N-methyl-d-aspartate receptors (NMDAr), neuronal nitric oxide synthase (nNOS) and cytochrome b5 reductase (Cb5R) co-localize within the same lipid rafts-associated nanodomains in mature cerebellar granule neurons (CGN). In this work, we show that the calcium transport systems of the plasma membrane extruding calcium from the cytosol, plasma membrane calcium pumps (PMCA) and sodium-calcium exchangers (NCX), are also associated with these nanodomains. All these proteins were found to co-immunoprecipitate with caveolin-1 after treatment with 25mM methyl-β-cyclodextrin, a lipid rafts solubilizing agent. However, the treatment of CGN with methyl-β-cyclodextrin largely attenuated the rise of cytosolic calcium induced by l-glutamate through NMDAr. Fluorescence energy transfer imaging revealed that all of them are present in sub-microdomains of a size smaller than 200nm, with a peripheral distribution of the calcium extrusion systems PMCA and NCX. Fluorescence microscopy images analysis revealed high calcium dynamic sub-microcompartments near the plasma membrane in fura-2-loaded CGN at short times after addition of l-glutamate. In addition, the close proximity between sources of nitric oxide (nNOS) and superoxide anion (Cb5R) suggests that these nanodomains are involved in the fast and efficient cross-talk between calcium and redox signaling in neurons.

Small molecule delivery through nanofibrous scaffolds for musculoskeletal regenerative engineering

Musculoskeletal regenerative engineering approach using small bioactive molecules in conjunction with advanced materials has emerged as a highly promising strategy for musculoskeletal repair and regeneration. Advanced biomaterials technologies have revealed nanofiber-based scaffolds for musculoskeletal tissue engineering as vehicles for the controlled delivery of small molecule drugs. This review article highlights recent advances in nanofiber-based delivery of small molecules for musculoskeletal regenerative engineering. The article concludes with perspectives on the challenges and future directions.

FROM THE CLINICAL EDITOR

In this review, advances in nanofiber-based delivery of small molecules are discussed from the standpoint of their potential role in musculoskeletal regenerative engineering, highlighting both future directions and current challenges.

Visible light photooxidative performance of a high-nuclearity molecular bismuth vanadium oxide cluster

The visible light photooxidative performance of a new high-nuclearity molecular bismuth vanadium oxide cluster, H3[{Bi(dmso)3}4V13O40], is reported. Photocatalytic activity studies show faster reaction kinetics under anaerobic conditions, suggesting an oxygen-dependent quenching of the photoexcited cluster species. Further mechanistic analysis shows that the reaction proceeds via the intermediate formation of hydroxyl radicals which act as oxidant. Trapping experiments using ethanol as a hydroxyl radical scavenger show significantly decreased photocatalytic substrate oxidation in the presence of EtOH. Photocatalytic performance analyses using monochromatic visible light irradiation show that the quantum efficiency Φ for indigo photooxidation is strongly dependent on the irradiation wavelength, with higher quantum efficiencies being observed at shorter wavelengths (Φ395nm ca. 15%). Recycling tests show that the compound can be employed as homogeneous photooxidation catalyst multiple times without loss of catalytic activity. High turnover numbers (TON ca. 1200) and turnover frequencies up to TOF ca. 3.44 min(-1) are observed, illustrating the practical applicability of the cluster species.

Significance of adiponectin and its receptors in pathogenesis of gestational diabetes mellitus

AIM: To analyze the significance of adiponectin (APN) and its receptors in in the pathogenesis of gestational diabetes mellitus (GDM) and the relevant factors involved.

METHODS: Fifty pregnant women with GDM treated between June 2011 and June 2013 at our hospital and 50 normal pregnant women were included into an observation group and a control group, respectively. Fasting blood glucose, insulin and other laboratory indicators were retrospectively analyzed, and their relationship with serum APN was explored.

RESULTS: In the observation group, body mass index (BMI), fasting plasma glucose (FPG), total cholesterol (TC), triacylglycerol (TG), fasting insulin (FINS), homestasis model assessment for insulin resistance (HONA-IR) and APN were 24.97 kg/m² ± 4.32 kg/m², 7.02 mmol/L ± 0.63 mmol/L, 5.39 mmol/L ± 1.29 mmol/L, 2.27 mmol/L ± 1.18 mmol/L, 19.37 mU/L ± 6.37 mU/L, 9.27 mmol/L ± 1.56 mmol/L, 2.17 mg/L ± 0.69 mg/L and 1.31 mg/L ± 0.22 mg/L, respectively; the corresponding values in the control group were 23.77 kg/m² ± 2.39 kg/m², 3.91 mmol/L ± 0.59 mmol/L, 4.21 mmol/L ± 0.68 mmol/L, 1.12 mmol/L ± 0.28 mmol/L, 13.24 mU/L ± 5.61 mU/L, 3.26 mmol/L ± 0.51 mmol/L, 3.62 mg/L ± 1.02 mg/L and 0.11 mg/L ± 0.03 mg/L. The above indexes differed significantly between the two groups (P < 0.05 for all). Serum APN levels showed a negative correlation with pre-pregnancy BMI, TG, HOMA-IR and FINS (r = -0.371, -0.459, -0.281, -0.321, P < 0.01 for all).

CONCLUSION: In GDM patients, APN and its receptors are closely related to insulin resistance, and clinical determination of APN may be helpful for the diagnosis and treatment of GDM.

Cytotoxic, hematologic and histologic effects of niobium pentoxide in Swiss mice

The use of metal devices in medical application is increasing but it remains incompletely understood the physiological effects of component degradation. Niobium (Nb) alloys have already been investigated in the 1980's and recent studies demonstrated the potential of Nb as an implant material. The purpose of this study was to determine cytotoxic, hematologic and histologic effects of niobium in Swiss mice. Animals were treated with a single dose of 3 % niobium oxide (Nb2O5) diluted in PBS, i.p. Cytotoxic assay, hematologic and histologic evaluation were done 3, 7 and 12 days after niobium treatment. Data have shown increased number of cells after niobium treatment, but there was no difference in cell viability. Furthermore, it was not observed hematological modification 3, 7 or 12 days after niobium treatment. Despite the fact that animals treated with niobium for 3 and 7 days showed mild degeneration in hepatocytes, mice kept alive for 12 days showed liver cells regeneration. Our results suggested that niobium cytotoxicity was not progressive because 12 days after treatment there was an evident liver regeneration. Data obtained indicated that niobium may be promising alternatives to biomedical applications.

HMG CoA reductase inhibitor treatment induces dysglycemia in renal allograft recipients

BACKGROUND

Dysglycemia and dyslipidemia are important metabolic complications of organ transplantation. Statins are widely used to control dyslipidemia; however, long-term use of statins is related to diabetes mellitus (DM) and impaired fasting glucose (IFG). The aim of this study was to evaluate the influence of statins on the development of dysglycemia (IFG and/or DM) in renal allograft recipients.

METHODS

A total of 394 patients without previously known DM or IFG who underwent kidney transplantation were enrolled. Patients were grouped into the two groups according to the use of statin (control, n=149; statin, n=245). The major statins used were fluvastatin (80 mg/d, n=134) and atorvastatin (20 mg/d, n=111). We compared the incidence of IFG or DM during the follow-up period.

RESULTS

The incidence of IFG was higher in the statin group than that in the control group (28.6% vs. 8.7%, P<0.001). The incidence of dysglycemia was significantly higher in the statin group (40.0% vs. 15.4%, P=0.001). Time to development of dysglycemia after transplantation was shorter in the statin group than in the control group (38.8±29.7 vs. 47.2±23.3 months, P=0.002). Statin use was associated with an increased risk for dysglycemia after adjustment for age, sex, body mass index, hypertension, cholesterol levels, hepatitis C infection, and type of immunosuppressant (hazard ratio=3.08, 95% confidence interval=1.91-4.98). The dysglycemic effect was more profound in the patients who used atorvastatin than in those who used fluvastatin (hazard ratio=2.21, 95% confidence interval=1.02-4.76).

CONCLUSION

Statin treatment is associated with an elevation in fasting plasma glucose and in the development of dysglycemia in renal allograft recipients.

Structural and redox requirements for the action of anti-diabetic vanadium compounds

This study presents the first systematic investigation of the anti-diabetic properties of non-oxido V(IV) complexes. In particular, the insulin-mimetic activity of [V(IV)(taci)2](4+), [V(IV)(inoH-3)2](2-), [V(IV)(dhab)2], [V(IV)(hyph(Ph))2], [V(IV)(cat)3](2-) and [V(IV)(pdbh)2]--where taci is 1,3,5-triamino-1,3,5-trideoxy-cis-inositol, ino is cis-inositol, H2dhab is 2,2'-dihydroxyazobenzene, H2hyph(Ph) is 3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazole, H2cat is catechol and H2pdbh is pentan-2,4-dione benzoylhydrazone--was evaluated in terms of free fatty acid (FFA) release. Among the six compounds examined, only [V(IV)(pdbh)2], [V(IV)(cat)3](2-) and [V(IV)(hyph(Ph))2], which at the physiological pH convert to the corresponding V(IV)O complexes, were found to exhibit a significant insulin-mimetic activity compared to VOSO4. In contrast, [V(taci)2](4+), [V(inoH-3)2](2-) and [V(dhab)2], which at pH 7.4 keep their 'bare' non-oxido structure, did not cause any inhibition of FFA. The results, therefore, suggest that a V(IV)O functionality is necessary for vanadium complexes to exhibit anti-diabetic effects. This agrees with the notion that the biotransformations of V compounds in the organism are more important than the nature of the species.

Borophosphates and silicophosphates as plausible contributors to the emergence of life

Scientific explanations for the origin of life are incomplete and may differ on some issues. Here, we argue that some prebiological steps have occurred in environments with borophosphates and/or silicophosphates in the form of hydrogels, on the basis of their chemical groups and structural properties. These could have decreased the diffusion rate of some prebiotic molecules, stabilized molecules with vicinal cis-diol groups, reduced the hydrolytic activity of water and inserted catalytic metal ions into their networks. Additionally, these hydrogels could have acted as reaction media, supplied a phosphate source for phosphorylations and produced crystals that may have permitted enantiomeric enrichment of prebiotic molecules, thus providing conditions for the emergence of protocells.

Tacrolimus and sirolimus have distinct effects on insulin signaling in male and female rats

Although the contribution of the immunosuppressants tacrolimus (TAC) and sirolimus (SIR) to the development of posttransplant diabetes mellitus (PTDM) are being increasingly recognized, the mechanisms of immunosuppressant-induced hyperglycemia are unclear. SIR induces insulin resistance predominantly, but is associated with β-cell dysfunction in rodents. TAC affects islet function but is associated with worsening insulin sensitivity in a few, and improvement in some, clinical studies. We sought to clarify the contributions of TAC and SIR to insulin resistance and islet function. Four groups of male and female Sprague-Dawley rats received TAC, SIR, TAC and SIR, or control for 2 weeks. All rats were administered an oral glucose challenge at the end of treatment. Half the groups were sacrificed 10 minutes after administration of regular insulin whereas the other half did not receive insulin before sacrifice. Liver, pancreas, fat, and muscle were harvested subsequently. Quantification of Western blots revealed that SIR and TAC plus SIR suppressed the phospho-Akt (pAkt)-to-Akt ratios in liver, muscle, and fat compared with control, regardless of sex. TAC alone did not impair the pAkt-to-Akt ratios in any of the tissues in male and female rats. β-Cell mass was reduced significantly after TAC treatment in male rats. SIR did not affect β-cell mass, regardless of sex. Our study demonstrated very clearly that SIR impairs insulin signaling, without any effect on β-cell mass, and TAC does not impair insulin signaling but reduces β-cell mass. Our efforts are key to understanding the mechanisms of immunosuppressant-induced hyperglycemia and to tailoring treatments for PTDM.

The decrease of NAD(P)H:quinone oxidoreductase 1 activity and increase of ROS production by NADPH oxidases are early biomarkers in doxorubicin cardiotoxicity

CONTEXT

Doxorubicin cardiotoxicity displays a complex and multifactorial progression.

OBJECTIVE

Identify early biochemical mechanisms leading to a sustained imbalance of cellular bioenergetics.

METHODS

Measurements of the temporal evolution of selected biochemical markers after treatment of rats with doxorubicin (20 mg/kg body weight).

RESULTS

Doxorubicin treatment increased lipid oxidation, catalase activity and production of H₂O₂ by Nox-NADPH oxidases, and down-regulated

NAD(P)H

quinone oxidoreductase-1 prior eliciting changes in reduced glutathione, protein carbonyls and protein nitrotyrosines. Alterations of mitochondrial and myofibrillar bioenergetics biomarkers were detected only after this oxidative imbalance was established.

CONCLUSIONS

NAD(P)H

quinone oxidoreductase-1 activity and increase of hydrogen peroxide production by NADPH oxidases are early biomarkers in doxorubicin cardiotoxicity.