GYY4137, a novel hydrogen sulfide-releasing molecule, protects against endotoxic shock in the rat

GYY4137 (morpholin-4-ium-4-methoxyphenyl(morpholino) phosphinodithioate) is a slow-releasing hydrogen sulfide (H(2)S) donor. Administration of GYY4137 (50 mg/kg, iv) to anesthetized rats 10 min after lipopolysaccharide (LPS; 4 mg/kg, iv) decreased the slowly developing hypotension. GYY4137 inhibited LPS-induced TNF-alpha production in rat blood and reduced the LPS-evoked rise in NF-kappaB activation, inducible nitric oxide synthase/cyclooxygenase-2 expression, and generation of PGE(2) and nitrate/nitrite in RAW 264.7 macrophages. GYY4137 (50 mg/kg, ip) administered to conscious rats 1 or 2 h after (but not 1 h before) LPS decreased the subsequent (4 h) rise in plasma proinflammatory cytokines (TNF-alpha, IL-1beta, IL-6), nitrite/nitrate, C-reactive protein, and L-selectin. GYY4137 administration also decreased the LPS-evoked increase in lung myeloperoxidase activity, increased plasma concentration of the anti-inflammatory cytokine IL-10, and decreased tissue damage as determined histologically and by measurement of plasma creatinine and alanine aminotransferase activity. Time-expired GYY4137 (50 mg/kg, ip) did not affect the LPS-induced rise in plasma TNF-alpha or lung myeloperoxidase activity. GYY4137 also decreased the LPS-mediated upregulation of liver transcription factors (NF-kappaB and STAT-3). These results suggest an anti-inflammatory effect of GYY4137. The possibility that GYY4137 and other slow-releasing H(2)S donors exert anti-inflammatory activity in other models of inflammation and in humans warrants further study.

Blueberry-induced changes in spatial working memory correlate with changes in hippocampal CREB phosphorylation and brain-derived neurotrophic factor (BDNF) levels

Phytochemical-rich foods have been shown to be effective at reversing age-related deficits in memory in both animals and humans. We show that a supplementation with a blueberry diet (2% w/w) for 12 weeks improves the performance of aged animals in spatial working memory tasks. This improvement emerged within 3 weeks and persisted for the remainder of the testing period. Memory performance correlated well with the activation of cAMP-response element-binding protein (CREB) and increases in both pro- and mature levels of brain-derived neurotrophic factor (BDNF) in the hippocampus. Changes in CREB and BDNF in aged and blueberry-supplemented animals were accompanied by increases in the phosphorylation state of extracellular signal-related kinase (ERK1/2), rather than that of calcium calmodulin kinase (CaMKII and CaMKIV) or protein kinase A. Furthermore, age and blueberry supplementation were linked to changes in the activation state of Akt, mTOR, and the levels of Arc/Arg3.1 in the hippocampus, suggesting that pathways involved in de novo protein synthesis may be involved. Although causal relationships cannot be made among supplementation, behavior, and biochemical parameters, the measurement of anthocyanins and flavanols in the brain following blueberry supplementation may indicate that changes in spatial working memory in aged animals are linked to the effects of flavonoids on the ERK-CREB-BDNF pathway.

Characterization of a novel, water-soluble hydrogen sulfide-releasing molecule (GYY4137): new insights into the biology of hydrogen sulfide

BACKGROUND

The potential biological significance of hydrogen sulfide (H(2)S) has attracted growing interest in recent years. The aim of this study was to characterize a novel, water-soluble, slow-releasing H(2)S compound [morpholin-4-ium 4 methoxyphenyl(morpholino) phosphinodithioate (GYY4137)] and evaluate its use as a tool to investigate the cardiovascular biology of this gas.

METHODS AND RESULTS

The acute vasorelaxant effect of drugs was assessed in rat aortic rings and perfused rat kidney in vitro and in the anesthetized rat in vivo. The chronic effect of GYY4137 on blood pressure in normotensive and spontaneously hypertensive rats was determined by tail-cuff plethysmography. GYY4137 released H(2)S slowly both in aqueous solution in vitro and after intravenous or intraperitoneal administration in anesthetized rats in vivo. GYY4137 caused a slow relaxation of rat aortic rings and dilated the perfused rat renal vasculature by opening vascular smooth muscle K(ATP) channels. GYY4137 did not affect rat heart rate or force of contraction in vitro. GYY4137 exhibited antihypertensive activity as evidenced by ability to reduce N(G)-nitro-L-arginine methyl ester-evoked hypertension in the anesthetized rat and after chronic (14-day) administration in spontaneously hypertensive rats.

CONCLUSIONS

These results identify GYY4137 as a slow-releasing H(2)S compound with vasodilator and antihypertensive activity. GYY4137 is likely to prove useful in the study of the many and varied biological effects of H(2)S. GYY4137 may also prove of therapeutic value in cardiovascular disease.

Is antioxidant potential of the mitochondrial targeted ubiquinone derivative MitoQ conserved in cells lacking mtDNA?

MitoQ has been developed as a mitochondrial targeted antioxidant for diseases associated with oxidative stress. Here we show that MitoQ blocks the generation of reactive oxygen species (ROS) and mitochondrial protein thiol oxidation, and preserves mitochondrial function and ultrastructure after glutathione (GSH) depletion. Furthermore, the antioxidant effect of MitoQ is conserved in cells lacking mitochondrial DNA, indicating that its antioxidant properties do not depend on a functional electron transport chain (ETC). Our results elucidate the antioxidant mechanism of MitoQ and suggest that it may be a useful therapeutic for disorders associated with a dysfunctional ETC and increased ROS production.

Do mitochondriotropic antioxidants prevent chlorinative stress-induced mitochondrial and cellular injury?

Reactive chlorine species such as hypochlorous acid (HOCl) are cytotoxic oxidants generated by activated neutrophils at the sites of chronic inflammation. Since mitochondria are key mediators of apoptosis and necrosis, we hypothesized that mitochondriotropic antioxidants could limit HOCl-mediated intracellular oxidative injury to human fetal liver cells, preserve mitochondrial function, and prevent cell death. In this current study, we show that recently developed mitochondria-targeted antioxidants (MitoQ and SS31) significantly protected against HOCl-induced mitochondrial damage and cell death at concentrations >or=25 nM. Our study highlights the potential application of mitochondria-specific targeted antioxidants for the prevention of cellular dysfunction and cell death under conditions of chlorinative stress, as occurs during chronic inflammation.

Cell guidance in tissue engineering: SDF-1 mediates site-directed homing of mesenchymal stem cells within three-dimensional polycaprolactone scaffolds

Cell guidance is a new tissue engineering concept aimed at total in vivo tissue engineering without the need for cell seeding. This technique aims to create a biomimetic environment through constant delivery of cytokines to different areas of an implanted scaffold, such that site-specific homing of cells can be achieved. In this study, expression of CXCR4 on mesenchymal stem cells (MSCs) was characterized by immunohistochemistry and flow cytometry, subsequent to which chemotaxis toward stromal cell-derived factor 1 (SDF-1) was demonstrated. In a subsequent three-dimensional in vitro study, MSCs were shown to migrate within a polycaprolactone scaffold in response to SDF-1, such that polarized tissue formation could be achieved. A customized cytokine microdelivery system comprising a reservoir housing system and microneedle apparatus was fabricated to ensure constant delivery of SDF-1 to the scaffold. Following on this experiment, we demonstrated in an in vivo rat bone tissue engineering model that a cytokine combination consisting of vascular endothelial growth factor, SDF-1, and bone morphogenetic protein-6 delivered at 10-day intervals through the microneedle apparatus could lead to tissue formation through migrating cell fronts, with evidence of angiogenesis and vascularization without the need for cell seeding on scaffolds prior to implantation. In summary, cell guidance offers an advancement in cellular methodology for tissue engineering, and promises a novel, minimally invasive option for tissue regeneration.

Modified-release hydrocortisone for circadian therapy: a proof-of-principle study in dexamethasone-suppressed normal volunteers

BACKGROUND

All existing long-term glucocorticoid replacement therapy is suboptimal as the normal nocturnal rise and waking morning peak of serum cortisol is not reproduced.

AIM

To test whether it is possible to reproduce the normal overnight rise and morning peak in serum cortisol using an oral delayed and sustained release preparation of hydrocortisone (Cortisol(ds)).

SUBJECTS AND METHODS

Six healthy normal male volunteers attended on two occasions, in a single-dose, open-label, nonrandomized study. Endogenous cortisol secretion was suppressed by administration of dexamethasone. Cortisol(ds) (formulation A or B) was administered at 2200 h on day 1. Blood samples for measurement of cortisol were taken from 2200 h every 30 min until 0700 h, then hourly until 2200 h on day 2. Fifteen body mass index (BMI)-matched control subjects had serum cortisol levels measured at 20-min intervals for 24 h. Serum cortisol profiles and pharmacokinetics after Cortisol(ds) were compared with those in controls.

RESULTS

Formulations A and B were associated with delayed drug release (by 2 h and 4 h, respectively), with median peak cortisol concentrations at 4.5 h (0245 h) and 10 h (0800 h), respectively, thereby reproducing the normal early morning rise in serum cortisol. Total cortisol exposure was not different from controls.

CONCLUSIONS

For the first time we have shown that it is possible to mimic the normal circadian rhythm of circulating cortisol with an oral modified-release formulation of hydrocortisone, providing the basis for development of physiological circadian replacement therapy in patients with adrenal insufficiency.

Detection and measurement of reactive oxygen intermediates in mitochondria and cells

Reactive oxygen intermediates (ROIs) play a key role in a number of human diseases either by inducing cell death, cellular proliferation, or by acting as mediators in cellular signaling. Therefore, their measurement in vivo and in cell culture is desirable but technically difficult and often troublesome. To address some of the key methodological issues in examining the formation of ROI in cells and mitochondria, this chapter discusses the following: (a) the cellular sources of ROI and their enzymatic removal, (b) common methods used to determine cellular and mitochondrial ROI such as chemiluminescence, electron paramagnetic resonance spectroscopy, fluorescence, and enzymatic techniques, and (c) some common problems associated with these assays and the interpretation of data. We also provide some simple protocols for the estimation of ROI production in cells and mitochondria, and when measuring ROI in cells and mitochondria, we emphasize the need for thorough understanding of results obtained and their interpretation.

The mitochondrial permeability transition regulates cytochrome c release for apoptosis during endoplasmic reticulum stress by remodeling the cristae junction

The role of the mitochondrial permeability transition (MPT) in apoptosis and necrosis is controversial. Here we show that the MPT regulates the release of cytochrome c for apoptosis during endoplasmic reticulum (ER) stress by remodeling the cristae junction (CJ). CEM cells, HCT116 colon cancer cells, and murine embryo fibroblast cells were treated with the ER stressor thapsigargin (THG), which led to cyclophilin D-dependent mitochondrial release of the profusion GTPase optic atrophy 1 (OPA1), which controls CJ integrity, and cytochrome c, leading to apoptosis. Interference RNA knockdown of Bax blocked OPA1 and cytochrome c release after THG treatment but did not prevent the MPT, showing that Bax was essential for the release of cytochrome c by MPT. In isolated mitochondria, MPT led to OPA1 and cytochrome c release independently of voltage-dependent anion channel and the outer membrane, indicating that the MPT is an inner membrane phenomenon. Last, the MPT was regulated by the electron transport chain but not mitochondrial reactive oxygen species, since THG-induced cell death was not blocked by antioxidants and did not occur in cells lacking mitochondrial DNA. Our results show that the MPT regulates CJ remodeling for cytochrome c-dependent apoptosis induced by ER stress and that mitochondrial electron transport is indispensable for this process.

Hydrogen sulphide reduces insulin secretion from HIT-T15 cells by a KATP channel-dependent pathway

Hydrogen sulphide (H(2)S), a naturally occurring gas exerts physiological effects by opening K(ATP) channels. Anti-diabetic drugs (e.g. glibenclamide) block K(ATP) channels and abrogate H(2)S-mediated physiological responses which suggest that H(2)S may also regulate insulin secretion by pancreatic beta-cells. To investigate this hypothesis, insulin-secreting (HIT-T15) cells were exposed to NaHS (100 microM) and the K(ATP) channel-driven pathway of insulin secretion was tracked with various fluorescent probes. The concentration of insulin released from HIT-T15 cells decreased significantly after NaHS exposure and this effect was reversed by the addition of glibenclamide (10 microM). Cell viability and intracellular ATP and glutathione (GSH) levels remained unchanged, suggesting that changes in insulin secretion were not ATP linked or redox dependent. Through fluorescence imaging studies, it was found that K(+) efflux occurs in cells exposed to NaHS. The hyperpolarised cell membrane, a result of K(+) leaving the cell, prevents the opening of voltage-gated Ca(2+) channels. This subsequently prevents Ca(2+) influx and the release of insulin from HIT-T15 cells. This data suggest that H(2)S reduces insulin secretion by a K(ATP) channel-dependent pathway in HIT-T15 cells. This study reports the molecular mechanism by which H(2)S reduces insulin secretion and provides further insight into a recent observation of increased pancreatic H(2)S production in streptozotocin-diabetic rats.

Hydrogen sulfide induced neuronal death occurs via glutamate receptor and is associated with calpain activation and lysosomal rupture in mouse primary cortical neurons

Hydrogen sulfide (H(2)S) is a cytotoxic gas recently proposed as a novel neuromodulator. Endogenous levels of H(2)S in the brain range between 50 and 160 microM and perturbed H(2)S synthesis has been reported in the brains from stroke, Alzheimer's disease and Down syndrome patients. Recently, in immature non-glutamate receptor expressing mouse cortical neurons H(2)S was shown to inhibit cell death exhibited by high concentrations of glutamate whereas H(2)S was not cytotoxic. Due to the reported role of H(2)S in facilitating LTP through NMDA receptors we examined the effects of H(2)S on glutamate receptor functioning using mature cortical neurons expressing functional glutamate receptor subtypes. Addition of 100 microM glutamate exhibited extensive cell death which was exacerbated by co-incubation with < or = 200 microM of the H(2)S donor sodium hydrosulfide (NaHS). At <200 microM NaHS induced apoptosis whereas >200 microM NaHS induced necrosis. Cell death was inhibited by pharmacological glutamate receptor antagonists MK801 and APV (NMDA receptor antagonists), and CNQX (kainate and AMPA receptor antagonist) but not kynurenate (broad spectrum glutamate receptor antagonist), GYKI52466 (more selective AMPA receptor antagonist) and CYZ (AMPA receptor potentiator). Although markers of apoptosis were observed, we did not detect caspase activation either by Western blotting or fluorescence assays and caspase inhibitors did not prevent cell death. Rather, H(2)S induced calpain activation and lysosomal membrane destabilization; processes inhibited by preferential antagonists of NMDA and kainate receptors. These data suggest that H(2)S induced neuronal death through ionotropic glutamate receptors, which recruits apoptosis to ensure cellular demise and employs calpains and lysosomal rupture. This study provides novel insights into cell death observed in neurodegenerative diseases involving glutamate receptor activation and perturbed H(2)S synthesis.

Reaction of the radical pair NO2* and CO3*- with 2-[6-(4'-amino)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (APF)

The fluorogenic indicator 2-[6-(4'-amino)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (APF) is used widely to detect and measure reactive nitrogen and oxygen species such as peroxynitrite, ONOO-, both in vivo and in vitro. We present in this work the results of a combined computational and experimental study to provide insights into the mechanism of the reaction of APF with the radical products of ONOO- reaction with CO2, namely NO2* and CO3*-. The experimental study on the inhibition of APF oxidation by HCO3- suggests that a direct reaction of APF with nitrosoperoxycarbonate, ONOOCO2-, is unlikely. The mechanism of APF action on NO2* and CO3*- was investigated using gas-phase and solvent modeled calculations at the MPW1K/6-311+G(d)//MPW1K/6-31G(d) level of theory. Our computational results suggest that two-electron oxidation of APF takes place in two rapid one-electron oxidation steps, the first being a proton-coupled electron transfer (PCET) between APF and NO2*, followed by addition of CO3*- and subsequent decomposition of the adduct to yield fluorescein.

The identification of antioxidants in dark soy sauce

Soy sauce is a traditional fermented seasoning in Asian countries, that has high antioxidant activity in vitro and some antioxidant activity in vivo. We attempted to identify the major antioxidants present, using the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay as a guide. 3-Hydroxy-2-methyl-4H-pyran-4-one (maltol) was one of several active compounds found in an ethyl acetate extract of dark soy sauce (DSS) and was present at millimolar concentrations in DSS. However, most of the antioxidant activity was present in colored fractions, two of which (CP1 and CP2) were obtained by gel filtration chromatography. Their structural characteristics based on nuclear magnetic resonance (NMR) and electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS) analysis suggest that carbohydrate-containing pigments such as melanoidins are the major contributors to the high antioxidant capacity of DSS.

Nitric oxide-releasing flurbiprofen reduces formation of proinflammatory hydrogen sulfide in lipopolysaccharide-treated rat

The biosynthesis of both nitric oxide (NO) and hydrogen sulfide (H2S) is increased in lipopolysaccharide (LPS)-injected mice and rats but their interaction in these models is not known. In this study we examined the effect of the NO donor, nitroflurbiprofen (and the parent molecule flurbiprofen) on NO and H2S metabolism in tissues from LPS-pretreated rats. Administration of LPS (10 mg kg(-1), i.p.; 6 h) resulted in an increase (P<0.05) in plasma TNF-alpha, IL-1beta and nitrate/nitrite (NO(x)) concentrations, liver H2S synthesis (from added cysteine), CSE mRNA, inducible nitric oxide synthase (iNOS), myeloperoxidase (MPO) activity (marker for neutrophil infiltration) and nuclear factor-kappa B (NF-kappaB) activation. Nitroflurbiprofen (3-30 mg kg(-1), i.p.) administration resulted in a dose-dependent inhibition of the LPS-mediated increase in plasma TNF-alpha, IL-1beta and NO(x) concentration, liver H2S synthesis (55.00+/-0.95 nmole mg protein(-1), c.f. 62.38+/-0.47 nmole mg protein(-1), n = 5, P<0.05), CSE mRNA, iNOS, MPO activity and NF-kappaB activation. Flurbiprofen (21 mg kg(-1), i.p.) was without effect. These results show for the first time that nitroflurbiprofen downregulates the biosynthesis of proinflammatory H2S and suggest that such an effect may contribute to the augmented anti-inflammatory activity of this compound. These data also highlight the existence of 'crosstalk' between NO and H2S in this model of endotoxic shock.

The reaction of flavonoid metabolites with peroxynitrite

There is much interest in the bioactivity of in vivo flavonoid metabolites. We report for the first time the hierarchy of reactivity of flavonoid metabolites with peroxynitrite and characterise novel reaction products. O-Methylation of the B-ring catechol containing flavonoids epicatechin and quercetin, and O-glucuronidation of all flavonoids reduced their reactivity with peroxynitrite. The reaction of the flavanones hesperetin and naringenin and their glucuronides resulted in the formation of multiple mono-nitrated and nitrosated products. In contrast, the catechol-containing flavonoids epicatechin and quercetin yielded oxidation products which when trapped with glutathione led to the production of glutathionyl-conjugates. However, the O-methylated metabolites of epicatechin yielded both mono- and di-nitrated products and nitrosated metabolites. The 3'-O-methyl metabolite of quercetin also yielded a nitrosated species, although its counterpart 4'-O-methyl quercetin yielded only oxidation products. Such products may represent novel metabolic products in vivo and may also express cellular activity.

The pro-inflammatory oxidant hypochlorous acid induces Bax-dependent mitochondrial permeabilisation and cell death through AIF-/EndoG-dependent pathways

At sites of chronic inflammation, such as in the inflamed rheumatoid joint, activated neutrophils release hydrogen peroxide (H(2)O(2)) and the enzyme myeloperoxidase to catalyse the formation of hypochlorous acid (HOCl). 3-chlorotyrosine, a marker of HOCl in vivo, has been observed in synovial fluid proteins from rheumatoid arthritis patients. However the mechanisms of HOCl-induced cytotxicity are unknown. We determined the molecular mechanisms by which HOCl induced cell death in human mesenchymal progenitor cells (MPCs) differentiated into a chondrocytic phenotype as a model of human cartilage cells and show that HOCl induced rapid Bax conformational change, mitochondrial permeability and release of intra-mitochondrial pro-apoptotic proteins which resulted in nuclear translocation of AIF and EndoG. siRNA-mediated knockdown of Bax substantially prevented mitochondrial permeability, release of intra-mitochondrial pro-apoptotic proteins. Cell death was inhibited by siRNA-mediated knockdown of Bax, AIF or EndoG. Although we observed several biochemical markers of apoptosis, caspase activation was not detected either by western blotting, fluorescence activity assays or by using caspase inhibitors to inhibit cell death. This was further supported by findings that (1) in vitro exposure of recombinant human caspases to HOCl caused significant inhibition of caspase activity and (2) the addition of HOCl to staurosporine-treated MPCs inhibited the activity of cellular caspases. Our results show for the first time that HOCl induced Bax-dependent mitochondrial permeability which led to cell death without caspase activity by processes involving AIF/EndoG-dependent pathways. Our study provides a novel insight into the potential mechanisms of cell death in the inflamed human joint.

Flurbiprofen and its nitric oxide-releasing derivative protect against septic shock in rats

OBJECTIVE

Flurbiprofen and nitroflurbiprofen were evaluated in a caecal ligation puncture (CLP) model of septic shock in the rat.

METHODS AND RESULTS

CLP (12 h) reduced blood pressure (72.5 +/- 1.0 mm Hg c. f. 101.0 +/- 3.6 mm Hg, P < 0.05), and increased plasma NOx (153.0 +/- 11.5 muM c. f. 36.2 +/- 3.2 microM, P < 0.05), IL-1beta (534.0 +/- 93.1 pg/mL c. f.; 9.6 +/- 9.6 pg/mL, P < 0.05), TNF-alpha (88.0 +/- 13.6 pg/mL, P < 0.05), inflammatory damage in lung and liver, and mortality. Both flurbiprofen (21 mg/kg, p. o.) and nitroflurbiprofen (30 mg/kg, p. o.) prevented the fall in blood pressure (e. g. 80.4 +/- 2.1 mm Hg and 79.8 +/- 1.2 mm Hg respectively, 12 h, P < 0.05), reduced organ damage and prolonged survival. Nitroflurbiprofen (but not flurbiprofen) increased plasma NOx and reduced plasma TNF-alpha concentration at all time points (except 1 h). Neither drug affected plasma IL-1beta-levels.

CONCLUSIONS

These results suggest a protective effect of flurbiprofen and nitroflurbiprofen in septic shock.

Hypochlorous acid induces apoptosis of cultured cortical neurons through activation of calpains and rupture of lysosomes

3-Chlorotyrosine, a bio-marker of hypochlorous acid (HOCl) in vivo, was reported to be substantially elevated in the Alzheimer's disease (AD) brains. Thus, HOCl might be implicated in the development of AD. However, its effect and mechanism on neuronal cell death have not been investigated. Here, we report for the first time that HOCl treatment induces an apoptotic-necrotic continuum of concentration-dependent cell death in cultured cortical neurons. Neurotoxicity caused by an intermediate concentration of HOCl (250 microm) exhibited several biochemical markers of apoptosis in the absence of caspase activation. However, the involvement of calpains was demonstrated by data showing that calpain inhibitors protect cortical neurons from apoptosis and the formation of 145/150 kDa alpha-fodrin fragments. Moreover, an increase in cytosolic Ca2+ concentration was associated with HOCl neurotoxicity and Ca2+ channel antagonists, and Ca2+ chelators prevented cleavage of alpha-fodrin and the induction of apoptosis. Finally, we found that calpain activation ruptured lysosomes. Stabilization of lysosomes by calpain inhibitors or imidazoline drugs, as well as inhibition of cathepsin protease activities, rescued cells from HOCl-induced neurotoxicity. Our results showed for the first time that HOCl induces apoptosis in cortical neurons, and that the cell death process involves calpain activation and rupture of lysosomes.