Effect of hydrogen peroxide on calcium homeostasis in smooth muscle cells

Selective adhesion inhibition and hyaluronan envelope reduction of dermal tumor cells by cold plasma-activated medium

The sensitivity to cold plasma is specific to tumor cells while leaving normal tissue cells unaffected. This is the desired challenge in cancer therapy. Therefore, the focus of this work was a comparative study concerning the plasma sensitivity of dermal tumor cells (A-431) versus non-tumorigenic dermal cells (HaCaT) regarding their adhesion capacity. We found a selective inhibiting effect of plasma-activated medium on the adhesion of tumor cells while hardly affecting normal cells. We attributed this to a lower basal gene expression for the adhesion-relevant components CD44, hyaluronan synthase 2 (HAS2), HAS3, and the hyaluronidases in A431. Noteworthy, after plasma exposure, we revealed a significantly higher expression and synthesis of the hyaluronan envelope, the HAS3 gene, and the transmembrane adhesion receptors in non-tumorigenic HaCaTs.

Sesamin suppresses angiotensin-II-enhanced oxidative stress and hypertrophic markers in H9c2 cells

Myocardial hypertrophy plays a crucial role in cardiovascular disease (CVD) development. Myocardial hypertrophy is an adaptive response by myocardial cells to stress after cardiac injury to maintain cardiac output and function. Angiotensin II (Ang-II) regulates CVD through the renin-angiotensin-aldosterone system, and its signaling in cardiac myocytes leads to excessive reactive oxygen species (ROS) production, oxidative stress, and inflammation. Sesamin (SA), a natural compound in sesame seeds, has anti-inflammatory and anti-apoptotic effects. This study investigated whether SA could attenuate hypertrophic damage and oxidative injuries in H9c2 cells under Ang-II stimulation. We found that SA decreased the cell surface area. Furthermore, Ang-II treatment reduced Ang-II-increased ANP, BNP, and β-MHC expression. Ang-II enhanced NADPH oxidase activity, ROS formation, and decreased Superoxide Dismutase (SOD) activity. SA treatment reduces Ang-II-caused oxidative injuries. We also found that SA mitigates Ang-II-induced apoptosis and pro-inflammatory responses. In conclusion, SA could attenuate Ang-II-induced cardiac hypertrophic injuries by inhibiting oxidative stress, apoptosis, and inflammation in H9c2 cells. Therefore, SA might be a potential supplement for CVD management.

An Extracellular Redox Signal Triggers Calcium Release and Impacts the Asexual Development of Toxoplasma gondii

The ability of an organism to sense and respond to environmental redox fluctuations relies on a signaling network that is incompletely understood in apicomplexan parasites such as Toxoplasma gondii. The impact of changes in redox upon the development of this intracellular parasite is not known. Here, we provide a revised collection of 58 genes containing domains related to canonical antioxidant function, with their encoded proteins widely dispersed throughout different cellular compartments. We demonstrate that addition of exogenous H₂O₂ to human fibroblasts infected with T. gondii triggers a Ca²⁺ flux in the cytosol of intracellular parasites that can induce egress. In line with existing models, egress triggered by exogenous H₂O₂ is reliant upon both Calcium-Dependent Protein Kinase 3 and diacylglycerol kinases. Finally, we show that the overexpression a glutaredoxin-roGFP2 redox sensor fusion protein in the parasitophorous vacuole severely impacts parasite replication. These data highlight the rich redox network that exists in T. gondii, evidencing a link between extracellular redox and intracellular Ca²⁺ signaling that can culminate in parasite egress. Our findings also indicate that the redox potential of the intracellular environment contributes to normal parasite growth. Combined, our findings highlight the important role of redox as an unexplored regulator of parasite biology.

Morpho-metabotyping the oxidative stress response

Oxidative stress and reactive oxygen species (ROS) are central to many physiological and pathophysiological processes. However, due to multiple technical challenges, it is hard to capture a comprehensive readout of the cell, involving both biochemical and functional status. We addressed this problem by developing a fully parallelized workflow for metabolomics (providing absolute quantities for > 100 metabolites including TCA cycle, pentose phosphate pathway, purine metabolism, glutathione metabolism, cysteine and methionine metabolism, glycolysis and gluconeogenesis) and live cell imaging microscopy. The correlative imaging strategy was applied to study morphological and metabolic adaptation of cancer cells upon short-term hydrogen peroxide (H₂O₂) exposure in vitro. The combination provided rich metabolic information at the endpoint of exposure together with imaging of mitochondrial effects. As a response, superoxide concentrations were elevated with a strong mitochondrial localization, and multi-parametric image analysis revealed a shift towards fragmentation. In line with this, metabolism reflected both the impaired mitochondrial function and shifts to support the first-line cellular defense and compensate for energy loss. The presented workflow combining high-end technologies demonstrates the applicability for the study of short-term oxidative stress, but it can be suitable for the in-depth study of various short-term oxidative and other cellular stress-related phenomena.

Glucolipotoxicity: A Proposed Etiology for Wooden Breast and Related Myopathies in Commercial Broiler Chickens

Wooden breast is one of several myopathies of fast-growing commercial broilers that has emerged as a consequence of intensive selection practices in the poultry breeding industry. Despite the substantial economic burden presented to broiler producers worldwide by wooden breast and related muscle disorders such as white striping, the genetic and etiological underpinnings of these diseases are still poorly understood. Here we propose a new hypothesis on the primary causes of wooden breast that implicates dysregulation of lipid and glucose metabolism. Our hypothesis addresses recent findings that have suggested etiologic similarities between wooden breast and type 2 diabetes despite their phenotypic disparities. Unlike in mammals, dysregulation of lipid and glucose metabolism is not accompanied by an increase in plasma glucose levels but generates a unique skeletal muscle phenotype, i.e., wooden breast, in chickens. We hypothesize that these phenotypic disparities result from a major difference in skeletal muscle glucose transport between birds and mammals, and that the wooden breast phenotype most closely resembles complications of diabetes in smooth and cardiac muscle of mammals. Additional basic research on wooden breast and related muscle disorders in commercial broiler chickens is necessary and can be informative for poultry breeding and production as well as for human health and disease. To inform future studies, this paper reviews the current biological knowledge of wooden breast, outlines the major steps in its proposed pathogenesis, and examines how selection for production traits may have contributed to its prevalence.

Combustion Particle-Induced Changes in Calcium Homeostasis: A Contributing Factor to Vascular Disease?

Air pollution is the leading environmental risk factor for disease and premature death in the world. This is mainly due to exposure to urban air particle matter (PM), in particular, fine and ultrafine combustion-derived particles (CDP) from traffic-related air pollution. PM and CDP, including particles from diesel exhaust (DEP), and cigarette smoke have been linked to various cardiovascular diseases (CVDs) including atherosclerosis, but the underlying cellular mechanisms remain unclear. Moreover, CDP typically consist of carbon cores with a complex mixture of organic chemicals such as polycyclic aromatic hydrocarbons (PAHs) adhered. The relative contribution of the carbon core and adhered soluble components to cardiovascular effects of CDP is still a matter of discussion. In the present review, we summarize evidence showing that CDP affects intracellular calcium regulation, and argue that CDP-induced impairment of normal calcium control may be a critical cellular event through which CDP exposure contributes to development or exacerbation of cardiovascular disease. Furthermore, we highlight in vitro research suggesting that adhered organic chemicals such as PAHs may be key drivers of these responses. CDP, extractable organic material from CDP (CDP-EOM), and PAHs may increase intracellular calcium levels by interacting with calcium channels like transient receptor potential (TRP) channels, and receptors such as G protein-coupled receptors (GPCR; e.g., beta-adrenergic receptors [βAR] and protease-activated receptor 2 [PAR-2]) and the aryl hydrocarbon receptor (AhR). Clarifying a possible role of calcium signaling and mechanisms involved may increase our understanding of how air pollution contributes to CVD.

Polycystin 2 is increased in disease to protect against stress-induced cell death

Polycystin 2 (PC2 or TRPP1, formerly TRPP2) is a calcium-permeant Transient Receptor Potential (TRP) cation channel expressed primarily on the endoplasmic reticulum (ER) membrane and primary cilia of all cell and tissue types. Despite its ubiquitous expression throughout the body, studies of PC2 have focused primarily on its role in the kidney, as mutations in PC2 lead to the development of autosomal dominant polycystic kidney disease (ADPKD), a debilitating condition for which there is no cure. However, the endogenous role that PC2 plays in the regulation of general cellular homeostasis remains unclear. In this study, we measure how PC2 expression changes in different pathological states, determine that its abundance is increased under conditions of cellular stress in multiple tissues including human disease, and conclude that PC2-deficient cells have increased susceptibility to cell death induced by stress. Our results offer new insight into the normal function of PC2 as a ubiquitous stress-sensitive protein whose expression is up-regulated in response to cell stress to protect against pathological cell death in multiple diseases.

Pathological effects of ionizing radiation: endothelial activation and dysfunction

The endothelium, a tissue that forms a single layer of cells lining various organs and cavities of the body, especially the heart and blood as well as lymphatic vessels, plays a complex role in vascular biology. It contributes to key aspects of vascular homeostasis and is also involved in pathophysiological processes, such as thrombosis, inflammation, and hypertension. Epidemiological data show that high doses of ionizing radiation lead to cardiovascular disease over time. The aim of this review is to summarize the current knowledge on endothelial cell activation and dysfunction after ionizing radiation exposure as a central feature preceding the development of cardiovascular diseases.

Hydrogen peroxide inhibits Ca2+ efflux through plasma membrane Ca2+-ATPase in mouse parotid acinar cells

Intracellular Ca²⁺ mobilization is closely linked with the initiation of salivary secretion in parotid acinar cells. Reactive oxygen species (ROS) are known to be related to a variety of oxidative stress-induced cellular disorders and believed to be involved in salivary impairments. In this study, we investigated the underlying mechanism of hydrogen peroxide (H₂O₂) on cytosolic Ca²⁺ accumulation in mouse parotid acinar cells. Intracellular Ca²⁺ levels were slowly elevated when 1 mM H₂O₂ was perfused in the presence of normal extracellular Ca²⁺. In a Ca²⁺-free medium, 1 mM H₂O₂ still enhanced the intracellular Ca²⁺ level. Ca²⁺ entry tested using manganese quenching technique was not affected by perfusion of 1 mM H₂O₂. On the other hand, 10 mM H₂O₂ induced more rapid Ca²⁺ accumulation and facilitated Ca²⁺ entry from extracellular fluid. Ca²⁺ refill into intracellular Ca²⁺ store and inositol 1,4,5-trisphosphate (1 µM)-induced Ca²⁺ release from Ca²⁺ store was not affected by 1 mM H₂O₂ in permeabilized cells. Ca²⁺ efflux through plasma membrane Ca²⁺-ATPase (PMCA) was markedly blocked by 1 mM H₂O₂ in thapsigargin-treated intact acinar cells. Antioxidants, either catalase or dithiothreitol, completely protected H₂O₂-induced Ca²⁺ accumulation through PMCA inactivation. From the above results, we suggest that excessive production of H₂O₂ under pathological conditions may lead to cytosolic Ca²⁺ accumulation and that the primary mechanism of H₂O₂-induced Ca²⁺ accumulation is likely to inhibit Ca²⁺ efflux through PMCA rather than mobilize Ca²⁺ ions from extracellular medium or intracellular stores in mouse parotid acinar cells.

Mitochondrial calcium uniporter in Drosophila transfers calcium between the endoplasmic reticulum and mitochondria in oxidative stress-induced cell death

Mitochondrial calcium plays critical roles in diverse cellular processes ranging from energy metabolism to cell death. Previous studies have demonstrated that mitochondrial calcium uptake is mainly mediated by the mitochondrial calcium uniporter (MCU) complex. However, the roles of the MCU complex in calcium transport, signaling, and dysregulation by oxidative stress still remain unclear. Here, we confirmed that Drosophila MCU contains evolutionarily conserved structures and requires essential MCU regulator (EMRE) for its calcium channel activities. We generated Drosophila MCU loss-of-function mutants, which lacked mitochondrial calcium uptake in response to caffeine stimulation. Basal metabolic activities were not significantly affected in these MCU mutants, as observed in examinations of body weight, food intake, body sugar level, and starvation-induced autophagy. However, oxidative stress-induced increases in mitochondrial calcium, mitochondrial membrane potential depolarization, and cell death were prevented in these mutants. We also found that inositol 1,4,5-trisphosphate receptor genetically interacts with Drosophila MCU and effectively modulates mitochondrial calcium uptake upon oxidative stress. Taken together, these results support the idea that Drosophila MCU is responsible for endoplasmic reticulum-to-mitochondrial calcium transfer and for cell death due to mitochondrial dysfunction under oxidative stress.

Flow of essential elements in subcellular fractions during oxidative stress

Essential trace elements are commonly found in altered concentrations in the brains of patients with neurodegenerative diseases. Many studies in trace metal determination and quantification are conducted in tissue, cell culture or whole brain. In the present investigation, we determined by ICP-MS Fe, Cu, Zn, Ca, Se, Co, Cr, Mg, and Mn in organelles (mitochondria, nuclei) and whole motor neuron cell cultured in vitro. We performed experiments using two ways to access oxidative stress: cell treatments with H₂O₂ or Aβ-42 peptide in its oligomeric form. Both treatments caused accumulation of markers of oxidative stress, such as oxidized proteins and lipids, and alteration in DNA. Regarding trace elements, cells treated with H₂O₂ showed higher levels of Zn and lower levels of Ca in nuclei when compared to control cells with no oxidative treatments. On the other hand, cells treated with Aβ-42 peptide in its oligomeric form showed higher levels of Mg, Ca, Fe and Zn in nuclei when compared to control cells. These differences showed that metal flux in cell organelles during an intrinsic external oxidative condition (H₂O₂ treatment) are different from an intrinsic external neurodegenerative treatment.

Calcium alterations signal either to senescence or to autophagy induction in stem cells upon oxidative stress

Intracellular calcium ([Ca2+]i) has been reported to play an important role in autophagy, apoptosis and necrosis, however, a little is known about its impact in senescence. Here we investigated [Ca2+]i contribution to oxidative stress-induced senescence of human endometrium-derived stem cells (hMESCs). In hMESCs sublethal H2O2-treatment resulted in a rapid calcium release from intracellular stores mediated by the activation of PLC/IP3/IP3R pathway. Notably, further senescence development was accompanied by persistently elevated [Ca2+]i levels. In H2O2-treated hMESCs, [Ca2+]i chelation by BAPTA-AM (BAPTA) was sufficient to prevent the expansion of the senescence phenotype, to decrease endogenous reactive oxygen species levels, to avoid G0/G1 cell cycle arrest, and finally to retain proliferation. Particularly, loading with BAPTA attenuated phosphorylation of the main DNA damage response members, including ATM, 53BP1 and H2A.X and reduced activation of the p53/p21/Rb pathway in H2O2-stimulated cells. Next, we revealed that BAPTA induced an early onset of AMPK-dependent autophagy in H2O2-treated cells as confirmed by both the phosphorylation status of AMPK/mTORC1 pathway and the dynamics of the LC3 lipidization. Summarizing the obtained data we can assume that calcium chelation is able to trigger short-term autophagy and to prevent the premature senescence of hMESCs under oxidative stress.

Specific combinations of ion channel inhibitors reduce excessive Ca2+ influx as a consequence of oxidative stress and increase neuronal and glial cell viability in vitro

Combinations of Ca²⁺ channel inhibitors have been proposed as an effective means to prevent excess Ca²⁺ flux and death of neurons and glia following neurotrauma in vivo. However, it is not yet known if beneficial outcomes such as improved viability have been due to direct effects on intracellular Ca²⁺ concentrations. Here, the effects of combinations of Lomerizine (Lom), 2,3-dioxo-7-(1H-imidazol-1-yl)6-nitro-1,2,3,4-tetrahydro-1-quinoxalinyl]acetic acid monohydrate (YM872), 3,5-dimethyl-1-adamantanamine (memantine (Mem)) and/or adenosine 5'-triphosphate periodate oxidized sodium salt (oxATP) to block voltage-gated Ca²⁺ channels, Ca²⁺ permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, NMDA receptors and purinergic P2X₇ receptors (P2X₇R) respectively, on Ca²⁺ concentration and viability of rat primary mixed cortical (MC) cultures exposed to hydrogen peroxide (H₂O₂) insult, were assessed. The contribution of ryanodine-sensitive intracellular stores to intracellular Ca²⁺ concentration was also assessed. Live cell calcium imaging revealed that a 30min H₂O₂ insult induced a slow increase in intracellular Ca²⁺, in part from intracellular sources, associated with loss of cell viability by 6h. Most combinations of inhibitors that included oxATP significantly decreased Ca²⁺ influx and increased cell viability when administered simultaneously with H₂O₂. However, reductions in intracellular Ca²⁺ concentration were not always linked to improved cell viability. Examination of the density of specific cell subpopulations demonstrated that most combinations of inhibitors that included oxATP preserved NG2+ non-oligodendroglial cells, but preservation of astrocytes and neurons required additional inhibitors. Olig2⁺ oligodendroglia and ED-1⁺ activated microglia/macrophages were not preserved by any of the inhibitor combinations. These data indicate that following H₂O₂ insult, limiting intracellular Ca²⁺ entry via P2X₇R is generally associated with increased cell viability. Protection of NG2+ non-oligodendroglial cells by Ca²⁺ channel inhibitor combinations may contribute to observed beneficial outcomes in vivo.

Messenger RNA sequencing and pathway analysis provide novel insights into the biological basis of chickens' feed efficiency

Background

Advanced selection technologies have been developed and continually optimized to improve traits of agricultural importance; however, these methods have been primarily applied without knowledge of underlying biological changes that may be induced by selection. This study aims to characterize the biological basis of differences between chickens with low and high feed efficiency (FE) with a long-term goal of improving the ability to select for FE.

Results

High-throughput RNA sequencing was performed on 23 breast muscle samples from commercial broiler chickens with extremely high (n = 10) and low (n = 13) FE. An average of 34 million paired-end reads (75 bp) were produced for each sample, 80% of which were properly mapped to the chicken reference genome (Ensembl Galgal4). Differential expression analysis identified 1,059 genes (FDR < 0.05) that significantly divergently expressed in breast muscle between the high- and low-FE chickens. Gene function analysis revealed that genes involved in muscle remodeling, inflammatory response and free radical scavenging were mostly up-regulated in the high-FE birds. Additionally, growth hormone and IGFs/PI3K/Akt signaling pathways were enriched in differentially expressed genes, which might contribute to the high breast muscle yield in high-FE birds and partly explain the FE advantage of high-FE chickens.

Conclusions

This study provides novel insights into transcriptional differences in breast muscle between high- and low-FE broiler chickens. Our results show that feed efficiency is associated with breast muscle growth in these birds; furthermore, some physiological changes, e.g., inflammatory response and oxidative stress, may occur in the breast muscle of the high-FE chickens, which may be of concern for continued selection for both of these traits together in modern broiler chickens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1364-0) contains supplementary material, which is available to authorized users.

The effect of chemically defined medium on spontaneous calcium signaling of in situ chondrocytes during long-term culture

Chemically defined serum-free medium has been shown to better maintain the mechanical integrity of articular cartilage explants than serum-supplemented medium during long-term in vitro culture, but little is known about its effect on cellular mechanisms. We hypothesized that the chemically defined culture medium could regulate the spontaneous calcium signaling of in situ chondrocytes, which may modulate the cellular metabolic activities. Bovine cartilage explants were cultured in chemically defined serum-free or serum-supplemented medium for four weeks. The spontaneous intracellular calcium ([Ca(2+)]i) signaling of in situ chondrocytes was longitudinally measured together along with the biomechanical properties of the explants. The spontaneous [Ca(2+)]i oscillations in chondrocytes were enhanced at the initial exposure of serum-supplemented medium, but were significantly dampened afterwards. In contrast, cartilage explants in chemically defined medium preserved the level of calcium signaling, and showed more responsive cells with higher and more frequent [Ca(2+)]i peaks throughout the four week culture in comparison to those in serum medium. Regardless of the culture medium that the explants were exposed, a positive correlation was detected between the [Ca(2+)]i responsive rate and the stiffness of cartilage (Spearman's rank correlation coefficient=0.762). A stable pattern of [Ca(2+)]i peaks was revealed for each chondrocyte, i.e., the spatiotemporal features of [Ca(2+)]i peaks from a cell were highly consistent during the observation period (15 min). This study showed that the beneficial effect of chemically defined culture of cartilage explants is associated with the spontaneous [Ca(2+)]i signaling of chondrocytes in cartilage.

2,4-dinitrophenol partially alleviates ferrocyanide-induced toxicity in Drosophila melanogaster

The toxicity of potassium ferrocyanide (PFC) and protective effects of 2,4-dinitrophenol (DNP) under PFC treatment were tested on the Drosophila melanogaster model system. Fly larvae were raised on food supplemented with PFC at concentrations of 1.0 mM and mixtures with DNP in concentrations of 0.50 and 1.25 mM, either alone or in combination with 1.0 mM PFC. Food supplementation with PFC decreased larvae viability or pupation height, whereas when larvae were fed by PFC and DNP combination the decrease was less pronounced. Larval exposure to PFC and mixtures of DNP and PFC lowered activities of aconitase. Larval treatment with PFC resulted in higher carbonyl protein, uric acid, and low molecular mass thiols content and higher activity of thioredoxin reductase in adult flies, while DNP in mixtures with PFC relieved these effects. Furthermore, treatment with PFC/DNP mixtures resulted in higher activities of superoxide dismutase and glutathione-S-transferase. It is proposed that PFC toxicity is mainly related to the cyanide and iron ions, released during its decomposition. The potential mechanisms of protective DNP effects against PFC toxicity are discussed.

The role of free radicals in the aging brain and Parkinson's Disease: convergence and parallelism

Free radical production and their targeted action on biomolecules have roles in aging and age-related disorders such as Parkinson's disease (PD). There is an age-associated increase in oxidative damage to the brain, and aging is considered a risk factor for PD. Dopaminergic neurons show linear fallout of 5-10% per decade with aging; however, the rate and intensity of neuronal loss in patients with PD is more marked than that of aging. Here, we enumerate the common link between aging and PD at the cellular level with special reference to oxidative damage caused by free radicals. Oxidative damage includes mitochondrial dysfunction, dopamine auto-oxidation, α-synuclein aggregation, glial cell activation, alterations in calcium signaling, and excess free iron. Moreover, neurons encounter more oxidative stress as a counteracting mechanism with advancing age does not function properly. Alterations in transcriptional activity of various pathways, including nuclear factor erythroid 2-related factor 2, glycogen synthase kinase 3β, mitogen activated protein kinase, nuclear factor kappa B, and reduced activity of superoxide dismutase, catalase and glutathione with aging might be correlated with the increased incidence of PD.

Angiotensin II inhibits interleukin-6 mRNA expression of LPS-stimulated macrophages through down-regulating calcium signaling

BACKGROUND

The renin-angiotensin system plays a key role in the regulation of blood pressure following hemorrhage and shock. Recent studies also suggest renin-angiotensin system regulates inflammatory mediator production although the amechanism is largely unknown. This purpose of the study was to examine the effect of angiotensin II on macrophage (MØ) IL-6 messenger RNA (mRNA) expression induced by lipopolysaccharide (LPS) and on the alterations in the calcium influx.

METHODS

J774A.1 cells, a mouse MØ cell line, were exposed to E. coli LPS (1 or 10 μg/ml) in the presence of angiotensin II (10 nM to 1 μM). IL-6 mRNA expression was determined by the reverse transcription polymerase chain reaction technique. IL-6 protein production was measured by ELISA. To examine the involvement of calcium signaling in IL-6 mRNA expression, MØ were exposed to various calcium agonists and antagonists in the presence of LPS stimulation. Changes of intracellular [Ca(2+)] by LPS stimulation and angiotensin II treatment were determined by a fura-2 fluorescence ratio method.

RESULTS

LPS stimulation increased MØ IL-6 mRNA expression, which was inhibited by Angiotensin II in a dose-dependent fashion. Both thapsigargin and A23187 augmented the IL-6 mRNA levels induced by LPS stimulation, but only thapsigargin was able to induce IL-6 mRNA directly. TMB-8 but not verapamil inhibited LPS-stimulated MØ IL-6 mRNA. Finally, angiotensin II significantly altered the changes in intracellular [Ca(2+)] levels induced by LPS stimulation by reducing both the peak and slope of calcium spikes.

CONCLUSIONS

Our data show that calcium signaling is closely related to IL-6 mRNA expression. Angiotensin II inhibits IL-6 mRNA expression of LPS-stimulated MØ. The inhibitory effects of angiotensin II appear, at least in part, to be mediated through down regulating calcium dependent pathways.

The sigma-1 receptor protects against cellular oxidative stress and activates antioxidant response elements

Sigma-1 receptors are associated with Alzheimer's disease, major depressive disorders, and schizophrenia. These receptors show progrowth/antiapoptotic properties via their chaperoning functions to counteract ER (endoplasmic reticulum) stress, to block neurodegeneration, and to regulate neuritogenesis. The sigma-1 receptor knock out mouse offered an opportunity to assess possible mechanisms by which the sigma-1 receptor modulates cellular oxidative stress. Nuclear magnetic resonance (NMR) metabolomic screening of the WT (wild type) and sigma-1 KO (knockout) livers was performed to investigate major changes in metabolites that are linked to oxidative stress. Significant changes in protein levels were also identified by two-dimensional (2D) gel electrophoresis and mass spectrometry. Increased levels of the antioxidant protein peroxiredoxin 6 (Prdx6), and the ER chaperone BiP (GRP78) compared to WT littermates were detected. Oxidative stress was measured in WT and sigma-1 KO mouse liver homogenates, in primary hepatocytes and in lung homogenates. Furthermore, sigma-1 receptor mediated activation of the antioxidant response element (ARE) to upregulate NAD(P)H quinone oxidoreductase 1 (NQO1) and superoxide dismutase 1 (SOD1) mRNA expression in COS cells was shown by RT PCR. These novel functions of the sigma-1 receptor were sensitive to well-known sigma ligands via their antagonist/agonist properties.

Inositol trisphosphate receptors in smooth muscle cells

Inositol 1,4,5-trisphosphate receptors (IP(3)Rs) are a family of tetrameric intracellular calcium (Ca(2+)) release channels that are located on the sarcoplasmic reticulum (SR) membrane of virtually all mammalian cell types, including smooth muscle cells (SMC). Here, we have reviewed literature investigating IP(3)R expression, cellular localization, tissue distribution, activity regulation, communication with ion channels and organelles, generation of Ca(2+) signals, modulation of physiological functions, and alterations in pathologies in SMCs. Three IP(3)R isoforms have been identified, with relative expression and cellular localization of each contributing to signaling differences in diverse SMC types. Several endogenous ligands, kinases, proteins, and other modulators control SMC IP(3)R channel activity. SMC IP(3)Rs communicate with nearby ryanodine-sensitive Ca(2+) channels and mitochondria to influence SR Ca(2+) release and reactive oxygen species generation. IP(3)R-mediated Ca(2+) release can stimulate plasma membrane-localized channels, including transient receptor potential (TRP) channels and store-operated Ca(2+) channels. SMC IP(3)Rs also signal to other proteins via SR Ca(2+) release-independent mechanisms through physical coupling to TRP channels and local communication with large-conductance Ca(2+)-activated potassium channels. IP(3)R-mediated Ca(2+) release generates a wide variety of intracellular Ca(2+) signals, which vary with respect to frequency, amplitude, spatial, and temporal properties. IP(3)R signaling controls multiple SMC functions, including contraction, gene expression, migration, and proliferation. IP(3)R expression and cellular signaling are altered in several SMC diseases, notably asthma, atherosclerosis, diabetes, and hypertension. In summary, IP(3)R-mediated pathways control diverse SMC physiological functions, with pathological alterations in IP(3)R signaling contributing to disease.

Pathophysiologically relevant levels of hydrogen peroxide induce glutamate-independent neurodegeneration that involves activation of transient receptor potential melastatin 7 channels

Stroke/brain ischemia is a leading cause of death and long-term disabilities. Increased oxidative stress plays an important role in the pathology of brain ischemia. Hydrogen peroxide (H(2)O(2)) is a major oxidant known to cause neuronal injury; however, the detailed mechanism remains unclear. Previous studies have suggested that H(2)O(2)-induced injury is associated with increased intracellular Ca(2+), mediated by glutamate receptors or voltage-gated Ca(2+) channels. Here, we demonstrate that, at concentrations relevant to stroke, H(2)O(2) induces a Ca(2+)-dependent injury of mouse cortical neurons in the absence of activation of these receptors/channels. With the culture medium containing blockers of glutamate receptors and voltage-gated Ca(2+) channels, brief exposure of neurons to H(2)O(2) induced a dose-dependent injury. Reducing [Ca(2+)](e) inhibited whereas increasing [Ca(2+)](e) potentiated the H(2)O(2) injury. Fluorescent Ca(2+) imaging confirmed the increase of [Ca(2+)](i) by H(2)O(2) in the presence of the blockers of glutamate receptors and voltage-gated Ca(2+) channels. Addition of 2-aminoethoxydiphenyl borate, an inhibitor of transient receptor potential melastatin 7 (TRPM7) channels, or the use of TRPM7-small interference RNA, protected the neurons from H(2)O(2) injury. In contrast, overexpressing TRPM7 channels in human embryonic kidney 293 cells increased H(2)O(2) injury. Our findings indicate that H(2)O(2) can induce Ca(2+) toxicity independent of glutamate receptors and voltage-gated Ca(2+) channels. Activation of TRPM7 channels is involved in such toxicity.

Superoxide dismutase mimetic drug tempol aggravates anti-GBM antibody-induced glomerulonephritis in mice

Oxidative stress plays an important role in the pathogenesis of anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM-GN). Superoxide dismutase (SOD) is the first line of defense against oxidative stress by converting superoxide to hydrogen peroxide (H(2)O(2)). We investigated the effect of the SOD mimetic drug tempol on anti-GBM-GN in mice. 129/svJ mice were challenged with rabbit anti-mouse-GBM sera to induce GN and subsequently divided into tempol (200 mg.kg(-1).day(-1), orally) and vehicle-treated groups. Routine histology, SOD and catalase activities, malondialdehyde (MDA), H(2)O(2), and immunohistochemical staining for neutrophils, lymphocytes, macrophages, p65-NF-kappaB, and osteopontin were performed. Mice with anti-GBM-GN had significantly reduced renal SOD and catalase activities and increased H(2)O(2) and MDA levels. Unexpectedly, tempol administration exacerbated anti-GBM-GN as evidenced by intensification of proteinuria, the presence of severe crescentic GN with leukocyte influx, and accelerated mortality in the treated group. Tempol treatment raised SOD activity and H(2)O(2) level in urine, upregulated p65-NF-kappaB and osteopontin in the kidney, but had no effect on renal catalase activity. Thus tempol aggravates anti-GBM-GN by increasing production of H(2)O(2) which is a potent NF-kappaB activator and as such can intensify inflammation and renal injury. This supposition is supported by increases seen in p65-NF-kappaB, osteopontin, and leukocyte influx in the kidneys of the tempol-treated group.

Roles of oxidative stress in signaling and inflammation induced by particulate matter

This review reports the role of oxidative stress in impairing the function of lung exposed to particulate matter (PM). PM constitutes a heterogeneous mixture of various types of particles, many of which are likely to be involved in oxidative stress induction and respiratory diseases. Probably, the ability of PM to cause oxidative stress underlies the association between increased exposure to PM and exacerbations of lung disease. Mostly because of their large surface area, ultrafine particles have been shown to cause oxidative stress and proinflammatory effects in different in vivo and in vitro studies. Particle components and surface area may act synergistically inducing lung inflammation. In this vein, reactive oxygen species elicited upon PM exposure have been shown to activate a number of redox-responsive signaling pathways and Ca(2+) influx in lung target cells that are involved in the expression of genes that modulate relevant responses to lung inflammation and disease.

Redox control of vascular smooth muscle migration

Vascular smooth muscle cell migration is important during vascular development and contributes to lesion formation in the adult vasculature. The mechanisms regulating migration of this cell type are therefore of great interest. Recent work has shown that reactive oxygen species (ROS) derived from NADPH oxidases are important mediators of promigratory signaling pathways. ROS regulate the intracellular signals responsible for lamellipodia formation, actin cytoskeleton remodeling, focal adhesion turnover, and contraction of the cell body. In addition, they contribute to matrix remodeling, a critical step to initiate and support vascular smooth muscle cell motility. Despite these recent advances in our understanding of the redox mechanisms that contribute to migration, additional work is needed to evaluate fully the potential of ROS-sensitive molecular signals as therapeutic targets to prevent inappropriate smooth muscle cell migration.

Taurocholate-induced nitric oxide signaling and the ensuing production of reactive oxygen species lead to an increase in epithelial permeability in cultivated mouse gastric epithelium

We have here elucidated whether ulcerogenic agents affect the production of NO and reactive oxygen species (ROS). The ulcerogenic agents dose dependently induced NO and ROS production in mouse gastric epithelial cells. Taurocholate (TC, 5 mM) exposure did not affect cell viability, but it increased inducible nitric oxide synthase (iNOS) expression, NO production, ROS production, and epithelial permeability. Epithelial permeability was inhibited with NOS inhibitors or antioxidants. Oxidative stress induced by acetylsalicylic acid (ASA) and ethanol was not inhibited with NOS inhibitors. ASA induced ROS production even at low concentrations (1 mM), which did not affect cell viability. Ethanol-induced ROS production was linked to cell viability, suggesting direct oxidative stress caused by ethanol. Taurocholate-induced NO signaling and the ensuing production of ROS might contribute to initiation of defensive or adaptive cellular mechanisms. ASA-induced ROS signaling might have similar effects, whereas ethanol induced direct oxidative stress, having an influence on cell viability.

Update on uses and properties of citrus flavonoids: new findings in anticancer, cardiovascular, and anti-inflammatory activity

Significantly, much of the activity of Citrus flavonoids appears to impact blood and microvascular endothelial cells, and it is not surprising that the two main areas of research on the biological actions of Citrus flavonoids have been inflammation and cancer. Epidemiological and animal studies point to a possible protective effect of flavonoids against cardiovascular diseases and some types of cancer. Although flavonoids have been studied for about 50 years, the cellular mechanisms involved in their biological action are still not completely known. Many of the pharmacological properties of Citrus flavonoids can be linked to the abilities of these compounds to inhibit enzymes involved in cell activation. Attempts to control cancer involve a variety of means, including the use of suppressing, blocking, and transforming agents. Suppressing agents prevent the formation of new cancers from procarcinogens, and blocking agents prevent carcinogenic compounds from reaching critical initiation sites, while transformation agents act to facilitate the metabolism of carcinogenic components into less toxic materials or prevent their biological actions. Flavonoids can act as all three types of agent. Many epidemiological studies have shown that regular flavonoid intake is associated with a reduced risk of cardiovascular diseases. In coronary heart disease, the protective effects of flavonoids include mainly antithrombotic, anti-ischemic, anti-oxidant, and vasorelaxant. It is suggested that flavonoids decrease the risk of coronary heart disease by three major actions: improving coronary vasodilatation, decreasing the ability of platelets in the blood to clot, and preventing low-density lipoproteins (LDLs) from oxidizing. The anti-inflammatory properties of the Citrus flavonoids have also been studied. Several key studies have shown that the anti-inflammatory properties of Citrus flavonoids are due to its inhibition of the synthesis and biological activities of different pro-inflammatory mediators, mainly the arachidonic acid derivatives, prostaglandins E 2, F 2, and thromboxane A 2. The anti-oxidant and anti-inflammatory properties of Citrus flavonoids can play a key role in their activity against several degenerative diseases and particularly brain diseases. The most abundant Citrus flavonoids are flavanones, such as hesperidin, naringin, or neohesperidin. However, generally, the flavones, such as diosmin, apigenin, or luteolin, exhibit higher biological activity, even though they occur in much lower concentrations. Diosmin and rutin have a demonstrated activity as a venotonic agent and are present in several pharmaceutical products. Apigenin and their glucosides have been shown a good anti-inflammatory activity without the side effects of other anti-inflammatory products. In this paper, we discuss the relation between each structural factor of Citrus flavonoids and the anticancer, anti-inflammatory, and cardiovascular protection activity of Citrus flavonoids and their role in degenerative diseases.

Hydrogen peroxide-induced Ca2+ mobilization in pulmonary arterial smooth muscle cells

Reactive oxygen species (ROS) generated from NADPH oxidases and mitochondria have been implicated as key messengers for pulmonary vasoconstriction and vascular remodeling induced by agonists and hypoxia. Since Ca2+ mobilization is essential for vasoconstriction and cell proliferation, we sought to characterize the Ca2+ response and to delineate the Ca2+ pathways activated by hydrogen peroxide (H2O2) in rat intralobar pulmonary arterial smooth muscle cells (PASMCs). Exogenous application of 10 μM to 1 mM H2O2 elicited concentration-dependent increase in intracellular Ca2+ concentration in PASMCs, with an initial rise followed by a plateau or slow secondary increase. The initial phase was related to intracellular release. It was attenuated by the inositol trisphosphate (IP3) receptor antagonist 2-aminoethyl diphenylborate, ryanodine, or thapsigargin, but was unaffected by the removal of Ca2+ in external solution. The secondary phase was dependent on extracellular Ca2+ influx. It was unaffected by the voltage-gated Ca2+ channel blocker nifedipine or the nonselective cation channel blockers SKF-96365 and La3+, but inhibited concentration dependently by millimolar Ni2+, and potentiated by the Na+/Ca2+ exchange inhibitor KB-R 7943. H2O2 did not alter the rate of Mn2+ quenching of fura 2, suggesting store- and receptor-operated Ca2+ channels were not involved. By contrast, H2O2 elicited a sustained inward current carried by Na+ at −70 mV, and the current was inhibited by Ni2+. These results suggest that H2O2 mobilizes intracellular Ca2+ through multiple pathways, including the IP3- and ryanodine receptor-gated Ca2+ stores, and Ni2+-sensitive cation channels. Activation of these Ca2+ pathways may play important roles in ROS signaling in PASMCs.

Temporal relationship of peroxynitrite-induced oxidative damage, calpain-mediated cytoskeletal degradation and neurodegeneration after traumatic brain injury

We assessed the temporal and spatial characteristics of PN-induced oxidative damage and its relationship to calpain-mediated cytoskeletal degradation and neurodegeneration in a severe unilateral controlled cortical impact (CCI) traumatic brain injury (TBI) model. Quantitative temporal time course studies were performed to measure two oxidative damage markers: 3-nitrotyrosine (3NT) and 4-hydroxynonenal (4HNE) at 30 min, 1, 3, 6, 12, 24, 48, 72 h and 7 days after injury in ipsilateral cortex of young adult male CF-1 mice. Secondly, the time course of Ca(++)-activated, calpain-mediated proteolysis was also analyzed using quantitative western-blot measurement of breakdown products of the cytoskeletal protein alpha-spectrin. Finally, the time course of neurodegeneration was examined using de Olmos silver staining. Both oxidative damage markers increased in cortical tissue immediately after injury (30 min) and elevated for the first 3-6 h before returning to baseline. In the immunostaining study, the PN-selective marker, 3NT, and the lipid peroxidation marker, 4HNE, were intense and overlapping in the injured cortical tissue. alpha-Spectrin breakdown products, which were used as biomarker for calpain-mediated cytoskeletal degradation, were also increased after injury, but the time course lagged behind the peak of oxidative damage and did not reach its maximum until 24 h post-injury. In turn, cytoskeletal degradation preceded the peak of neurodegeneration which occurred at 48 h post-injury. These studies have led us to the hypothesis that PN-mediated oxidative damage is an early event that contributes to a compromise of Ca(++) homeostatic mechanisms which causes a massive Ca(++) overload and calpain activation which is a final common pathway that results in post-traumatic neurodegeneration.

Mechanism underlying H2O2-induced inhibition of acetylcholine-induced contraction in rabbit tracheal smooth muscle

The mechanism underlying the inhibition by H2O2 of acetylcholine-induced contraction was investigated in epithelium-denuded strips of rabbit trachea. Acetylcholine (10 microM) generated a phasic, followed by a tonic increase in both the intracellular Ca2+ concentration ([Ca2+]i) and force. Although the acetylcholine-induced tonic contraction was around 9 times the high K+ (80 mM)-induced one, the two stimulants induced similar [Ca2+]i increases (around 0.2 microM), indicating that acetylcholine generates tonic contraction via increases in both [Ca2+]i and myofilament Ca2+-sensitivity. H2O2 (30 microM) (a) enhanced the acetylcholine-induced tonic (not phasic) increase in [Ca2+]i but attenuated both phases of the acetylcholine-induced contraction and (b) enhanced the high K+-induced increase in [Ca2+]i but did not modify the high K+-induced contraction. In beta-escin-skinned strips, application of acetylcholine in the presence of GTP enhanced the contraction induced by 0.3 microM Ca2+ so that its amplitude became similar to that induced by 1 microM Ca2+. H2O2 (30 microM) attenuated the contraction induced by 0.3 microM Ca2+ (alone or in the presence of acetylcholine) but not those induced by higher concentrations of Ca2+ alone (0.5 microM and 1 microM). These results indicate that H2O2 acts directly on contractile proteins in rabbit tracheal smooth muscle to inhibit the contraction induced by low concentrations of Ca2+ (<0.5 microM). An action of H2O2 that increases [Ca2+]i (and thereby masks this reactive-oxygen-induced inhibition of myofilament Ca2+-sensitivity) is apparent in the presence of high K+ but not of acetylcholine. Thus, in rabbit tracheal smooth muscle H2O2 downregulates myofilament Ca2+-sensitivity more potently during acetylcholine-induced contraction than during high-K+-induced contraction, leading to an effective inhibition of the former contraction.

Role of peroxynitrite in secondary oxidative damage after spinal cord injury

Peroxynitrite (PON, ONOO(-)), formed by nitric oxide synthase-generated nitric oxide radical ( NO) and superoxide radical (O(2) (-)), is a crucial player in post-traumatic oxidative damage. In the present study, we determined the spatial and temporal characteristics of PON-derived oxidative damage after a moderate contusion injury in rats. Our results showed that 3-nitrotyrosine (3-NT), a specific marker for PON, rapidly accumulated at early time points (1 and 3 h) and a significant increase compared with sham rats was sustained to 1 week after injury. Additionally, there was a coincident and maintained increase in the levels of protein oxidation-related protein carbonyl and lipid peroxidation-derived 4-hydroxynonenal (4-HNE). The peak increases of 3-NT and 4-HNE were observed at 24 h post-injury. In our immunohistochemical results, the co-localization of 3-NT and 4-HNE results indicates that PON is involved in lipid peroxidative as well as protein nitrative damage. One of the consequences of oxidative damage is an exacerbation of intracellular calcium overload, which activates the cysteine protease calpain leading to the degradation of several cellular targets including cytoskeletal protein (alpha-spectrin). Western blot analysis of alpha-spectrin breakdown products showed that the 145-kDa fragments of alpha-spectrin, which are specifically generated by calpain, were significantly increased as soon as 1 h following injury although the peak increase did not occur until 72 h post-injury. The later activation of calpain is most likely linked to PON-mediated secondary oxidative impairment of calcium homeostasis. Scavengers of PON, or its derived free radical species, may provide an improved antioxidant neuroprotective approach for the treatment of post-traumatic oxidative damage in the injured spinal cord.

Intermittent hyperthermia enhances skeletal muscle regrowth and attenuates oxidative damage following reloading

Skeletal muscle reloading following disuse is characterized by profound oxidative damage. This study tested the hypothesis that intermittent hyperthermia during reloading attenuates oxidative damage and augments skeletal muscle regrowth following immobilization. Forty animals were randomly divided into four groups: control (Con), immobilized (Im), reloaded (RC), and reloaded and heated (RH). All groups but Con were immobilized for 7 days. Animals in the RC and RH groups were then reloaded for 7 days with (RH) or without (RC) hyperthermia (41-41.5 degrees C for 30 min on alternating days) during reloading. Heating resulted in approximately 25% elevation in heat shock protein expression (P < 0.05) and an approximately 30% greater soleus regrowth (P < 0.05) in RH compared with RC. Furthermore, oxidant damage was lower in the RH group compared with RC because nitrotyrosine and 4-hydroxy-2-nonenol were returned to near baseline when heating was combined with reloading. Reduced oxidant damage was independent of antioxidant enzymes (manganese superoxide dismutase, copper-zinc superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase). In summary, these data suggest that intermittent hyperthermia during reloading attenuates oxidative stress and improves the rate of skeletal muscle regrowth during reloading after immobilization.

Direct effects of hydrogen peroxide on airway smooth muscle tone: roles of Ca2+ influx and Rho-kinase

Reactive oxidant species are implicated in the chronic airway inflammation related to asthma and chronic obstructive pulmonary disease. This study was designed to determine mechanisms underlying contraction induced by hydrogen peroxide (H(2)O(2)), a clinical marker of oxidative stress, in airway smooth muscle. Isometric tension and fluorescent intensities of fura-2, an index of intracellular Ca(2+) concentrations ([Ca(2+)](i)), were measured in epithelium-denuded tracheal smooth muscle tissues isolated from guinea pigs. H(2)O(2) (0.01-1 mM) caused contraction with an augmentation of [Ca(2+)](i) in a concentration-dependent manner in the normal physiological solution containing 2.4 mM of extracellular Ca(2+) concentrations. The contractile force and [Ca(2+)](i) by H(2)O(2) (1 mM) were approximately half of those in response to 1 microM methacholine. However, contraction by H(2)O(2) was not generated under the condition that extracellular Ca(2+) concentrations were less than 0.15 mM. Verapamil (10 microM), an inhibitor of voltage-operated Ca(2+) channels, partially but significantly inhibited the H(2)O(2)-induced contraction. In contrast, SKF-96365 (1-{beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl}-1H-imidazole hydrochloride) (100 microM), a non-selective inhibitor of Ca(2+) channels, completely abolished both the contraction and the increase in [Ca(2+)](i) elicited by H(2)O(2). Moreover, Y-27632 ((R)-(+)-trans-N-(4-Pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide) (0.03-10 microM), an inhibitor of Rho-kinase, caused a concentration-dependent inhibition of the H(2)O(2)-induced contraction. In conclusion, both the Ca(2+) influx from the extracellular side and the Ca(2+) sensitization by Rho-kinase are involved in the regulation of airway smooth muscle tone induced by H(2)O(2). An inhibition of the Rho/Rho-kinase pathway may be beneficial for the treatment of airflow limitation mediated by oxidative stress.

Reactive oxygen species and vascular remodelling in hypertension: still alive

Reactive oxygen species (ROS) are reactive derivatives of O2 metabolism, including superoxide anion, hydrogen peroxide, hydroxyl radical and nitric oxide. All types of vascular cells produce ROS, primarily via cell membrane-associated NAD(P)H oxidase. Cardiovascular diseases, such as hypertension, are associated with increased ROS formation (oxidative stress). Oxidative excess in the vasculature reduces levels of the vasodilator nitric oxide, causes tissue injury, promotes protein oxidation and DNA damage, and induces proinflammatory responses. ROS are also important intracellular signalling molecules that regulate vascular function by modulating vascular cell contraction/dilation, migration, growth/apoptosis, and extracellular matrix protein turnover, which contribute to vascular remodelling. Interventions to decrease ROS bioavailability regress remodelling and reduce blood pressure in experimental hypertension. Such strategies may have therapeutic potential in cardiovascular diseases.

Oxidative stress at the vascular wall. Mechanistic and pharmacological aspects

During the process of energy production in aerobic respiration, vascular cells produce reactive oxygen species (ROS). A growing body of evidence indicates that oxidative stress refers to a condition in which cells are subjected to excessive levels of ROS. Overall vascular function is dependent upon a fine balance of oxidant and antioxidant mechanisms, which determine endothelial functions. Considerable experimental and clinical data indicate that intracellular oxidant milieu is also involved in several redox-sensitive cellular signaling pathways such as ion transport systems, protein phosphorylation, and gene expression and thus also plays important roles as modulator of vascular cell functions such as cell growth, apoptosis, migration, angiogenesis and cell adhesion. Overproduction of ROS under pathophysiologic conditions is integral in the development of cardiovascular diseases. This fact has raised an intensive search of new pharmacological approaches to improve vascular hemostasis and particularly those intended to decrease oxidative stress or augment the antioxidant defense mechanisms.

Cremophor EL, a non-ionic surfactant, promotes Ca2+-dependent process of cell death in rat thymocytes

Cremophor EL, a surfactant for pharmaceutical products, augments the cytotoxicity of hydrogen peroxide in rat thymocytes [Iwase, K., Oyama, Y., Tatsuishi, T., Yamaguchi1, J., Nishimura1, Y., Kanada, A., Kobayashi, M., Maemura, Y., Ishida, S., Okano, Y., 2004. Cremophor EL augments the cytotoxicity of hydrogen peroxide in lymphocytes dissociated from rat thymus glands. Toxicol. Lett. 154, 143-148]. The effect of cremophor EL on Ca(2+)-dependent process of cell death has been examined using a flow cytometer since hydrogen peroxide increases intracellular Ca2+ concentration. Cremophor EL at clinically-relevant concentrations greatly increased the population of dead cells in rat thymocytes simultaneously treated with A23187, a calcium ionophore increasing intracellular Ca2+ concentration. Removal of Ca2+ from external solution diminished the cremophor EL-induced increase in the dead cell population. Result suggests that Ca(2+)-dependent process is involved in the cremophor EL-induced decrease in the cell viability in the simultaneous presence of A23187. The population of cells with hypodiploidal DNA was not increased by the application of cremophor EL and A23187 although the cell viability was greatly decreased, indicating that the type of cell death is necrosis. It is suggested that cremophor EL at clinically-relevant concentrations augments the Ca(2+)-dependent process of necrosis.

Mitochondrial hydrogen peroxide production alters oxygen consumption in an oxygen-concentration-dependent manner

Metabolic responses of mammalian cells toward declining oxygen concentration are generally thought to occur when oxygen limits mitochondrial ATP production. However, at oxygen concentrations markedly above those limiting to mitochondria, several mammalian cell types display reduced rates of oxygen consumption without energy stress or compensatory increases in glycolytic ATP production. We used mammalian Jurkat T cells as a model system to identify mechanisms responsible for these changes in metabolic rate. Oxygen consumption was 31% greater at high oxygen (150-200 microM) compared to low oxygen (5-10 microM). Hydrogen peroxide was implicated in the response as catalase prevented the increase in oxygen consumption normally associated with high oxygen. Cell-derived hydrogen peroxide, predominately from the mitochondria, was elevated with high oxygen. Oxygen consumption related to intracellular calcium turnover was shown, through EDTA chelation and dantrolene antagonism of the ryanodine receptor, to account for 70% of the response. Oligomycin inhibition of oxygen consumption indicated that mitochondrial proton leak was also sensitive to changes in oxygen concentration. Our results point toward a mechanism in which changes in oxygen concentration influence the rate of hydrogen peroxide production by mitochondria, which, in turn, alters cellular ATP use associated with intracellular calcium turnover and energy wastage through mitochondrial proton leak.

Crystal and microparticle effects on MDCK cell superoxide production: oxalate-specific mitochondrial membrane potential changes

We have previously shown that crystals of calcium oxalate (COM) elicit a superoxide (O2-) response from mitochondria. We have now investigated: (i) if other microparticles can elicit the same response, (ii) if processing of crystals is involved, and (iii) at what level of mitochondrial function oxalate acts. O2- was measured in digitonin-permeabilized MDCK cells by lucigenin (10 microM) chemiluminescence. [(14)C]-COM dissociation was examined with or without EDTA and employing alternative chelators. Whereas mitochondrial O2- in COM-treated cells was three- to fourfold enhanced compared to controls, other particulates (uric acid, zymosan, and latex beads) either did not increase O2- or were much less effective (hydroxyapatite +50%, p < 0.01), with all at 28 microg/cm(2). Free oxalate (750 microM), at the level released from COM with EDTA (1 mM), increased O2- (+50%, p < 0.01). Omitting EDTA abrogated this signal, which was restored completely by EGTA and partially by ascorbate, but not by desferrioxamine or citrate. Omission of phosphate abrogated O2-, implicating phosphate-dependent mitochondrial dicarboxylate transport. COM caused a time-related increase in the mitochondrial membrane potential (deltapsi(m)) measured using TMRM fluorescence and confocal microscopy. Application of COM to Fura 2-loaded cells induced rapid, large-amplitude cytosolic Ca(2+) transients, which were inhibited by thapsigargin, indicating that COM induces release of Ca(2+) from internal stores. Thus, COM-induced mitochondrial O2- requires the release of free oxalate and contributes to a synergistic response. Intracellular dissociation of COM and the mitochondrial dicarboxylate transporter are important in O2- production, which is probably regulated by deltapsi(m).

Mobilization of intracellular calcium by peroxynitrite in arteriolar smooth muscle cells from rats

The present study was designed to investigate the possible effects of peroxynitrite (ONOO(-)) on the intracellular calcium concentration ([Ca(2+)](i)) of mesenteric arteriolar smooth muscle cells (ASMCs), and to reveal the underlying mechanisms by using fluorescence imaging analysis. The results showed that ONOO(-) could exert a concentration- and time-dependent but also a dual effect on [Ca(2+)](i). Bolus administration with a low concentration of ONOO(-) (25 microM) decreased [Ca(2+)](i), whereas higher concentrations (50 or 100 microM) increased [Ca(2+)](i) persistently. Further experiments demonstrated that pretreatment of ASMCs with calcium-free medium completely abolished [Ca(2+)](i) increase by 100 microM ONOO(-). Additionally, nifedipine, an antagonist of selective L-type voltage-gated calcium channels (VGCCs), delayed the [Ca(2+)](i) response to ONOO(-), and ryanodine, an inhibitor of intracellular calcium release from the sarcoplasmic reticulum, effectively antagonized [Ca(2+)](i) increase during the late stage of ONOO(-) exposure. Furthermore, [Ca(2+)](i) alteration by ONOO(-) appeared to be intimately associated with the subsequent membrane potential changes. Although the mechanisms by which ONOO(-) alters [Ca(2+)](i) are complex, we conclude that a series of variables such as external calcium influx, activation of VGCCs, intracellular calcium release, and membrane potential changes are involved. The decrease of [Ca(2+)](i) in ASMCs by a low concentration of ONOO(-) may participate in the pathogenesis of low vasoreactivity in shock, and the increase of [Ca(2+)](i) by high concentrations of ONOO(-) may lead to calcium overload with cellular injury.

A cytosolic source of calcium unveiled by hydrogen peroxide with relevance for epithelial cell death

Oxidative stress releases intracellular calcium, which plays a pathogenic role in mammalian cell death. Here we report a search for the source of oxidative calcium in HeLa cells based on confocal epifluorescence microscopy. H(2)O(2) caused a rapid increase in cytosolic calcium, which was followed by mitochondrial Ca(2+) loading. Combined mitochondrial uncoupling with full depletion of thapsigargin-sensitive stores abrogated inositol 1,4,5-trisphosphate-mediated calcium release but failed to inhibit H(2)O(2)-induced calcium release, observation that was confirmed in MDCK cells. Prevention of peroxide-induced acidification with a pH clamp was also ineffective, discarding a role for endosomal/lysosomal Ca(2+)/H(+) exchange. Lysosomal integrity was not affected by H(2)O(2). Mature human erythrocytes also reacted to peroxide by releasing intracellular calcium, thus directly demonstrating the cytosolic source. Glutathione depletion markedly sensitized cells to H(2)O(2), an effect opposite to that achieved by DTT. Iron chelation was ineffective. In summary, our results show the existence of a previously unrecognized sulfhydryl-sensitive source of pathogenic calcium in the cytosol of mammalian cells.

Differential Calcium Regulation by Hydrogen Peroxide and Superoxide in Vascular Smooth Muscle Cells from Spontaneously Hypertensive Rats

We investigated the role of reactive oxygen species (ROS), particularly hydrogen peroxide (H2O2) and superoxide anion (*O2-) in the regulation of vascular smooth muscle cell (VSMC) Ca2+ concentration ([Ca2+]i) and vascular contraction and assessed whether redox-dependent Ca2+ signaling and contraction are altered in hypertension. VSMCs and mesenteric arteries from Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) were studied. Cells were stimulated with H2O2 (10(-4) mol/l) or LY83583 (*O2- generator, 10(-5) mol/l). [Ca2+]i and cytosolic *O2- were measured by fura-2AM and tempo-9-AC fluorescence respectively. L-type and T-type Ca2+ channels were assessed using verapamil/diltiazem and mibefradil respectively and mRNA and protein expression of these channels was assessed by real-time PCR and immunoblotting respectively. H2O2 time-dependently increased [Ca2+]i and contraction with significantly greater effects in SHR versus WKY (P < 0.001). LY83583 increased [Ca2+]i in both strains, but responses were blunted in SHR. Removal of extracellular Ca2+ abrogated [Ca2+]i responses to H2O2 and *O2-. Verapamil and diltiazem, but not mibefradil, significantly decreased H2O2 -induced [Ca2+]i responses with greater effects in SHR (P < 0.01). L-type and T-type Ca2+ channel inhibition reduced LY83583-mediated [Ca2+]i increase only in WKY cells. Both types of Ca2+ channels were expressed (mRNA and protein) in VSMCs from WKY and SHR, with greater abundance in SHR than WKY (2- to 3-fold). These results demonstrate that ROS increase vascular [Ca2+]i and contraction, primarily via extracellular Ca2+ influx. Whereas responses to H2O2 are enhanced, *O2- -mediated actions are blunted in SHR. These effects may relate to differential activation of Ca2+ channels by H2O2 and *O2-. Enhanced activation of L-type Ca2+ channels and increased Ca2+ influx by H2O2 may contribute to increased Ca2+ signaling in VSMCs from SHR.

Endothelium-derived reactive oxygen species: their relationship to endothelium-dependent hyperpolarization and vascular tone

Opinions on the role of reactive oxygen species (ROS) in the vasculature have shifted in recent years, such that they are no longer merely regarded as indicators of cellular damage or byproducts of metabolism--they may also be putative mediators of physiological functions. Hydrogen peroxide (H2O2), in particular, can initiate vascular myocyte proliferation (and, incongruously, apoptosis), hyperplasia, cell adhesion, migration, and the regulation of smooth muscle tone. Endothelial cells express enzymes that produce ROS in response to various stimuli, and H2O2 is a potent relaxant of vascular smooth muscle. H2O2 itself can mediate endothelium-dependent relaxations in some vascular beds. Although nitric oxide (NO) is well recognized as an endothelium-derived dilator, it is also well established, particularly in the microvasculature, that another factor, endothelium-derived hyperpolarizing factor (EDHF), is a significant determinant of vasodilatory tone. This review primarily focuses on the hypothesis that H2O2 is an EDHF in resistance arteries. Putative endothelial sources of H2O2 and the effects of H2O2 on potassium channels, calcium homeostasis, and vascular smooth muscle tone are discussed. Furthermore, given the perception that ROS can more likely elicit cytotoxic effects than perform signalling functions, the arguments for and against H2O2 being an endogenous vasodilator are assessed.

Both calcium and ROS as common signals mediate Na(2)SeO(3)-induced apoptosis in SW480 human colonic carcinoma cells

Recent studies have shown that reactive oxygen species (ROS) play a crucial role in Se-induced cell apoptosis. A number of studies have demonstrated that perturbed cellular calcium homeostasis has been implicated in apoptosis. The main objective of this study was to evaluate the role of Ca(2+) in Na(2)SeO(3)-induced apoptosis and the relationship between Ca(2+) and ROS in human colonic carcinoma cells SW480. When SW480 cells were exposed to 25-100 microM Na(2)SeO(3), both cell apoptosis and growth inhibition were observed by flow cytometric analysis and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Na(2)SeO(3) was able to induce increase of [Ca(2+)](i) and ROS production and disrupt mitochondrial membrane potential (Delta Psi m) in SW480 cells monitored by using a confocal laser scanning microscope. Ca(2+) channel inhibitor CoCl(2) and an intracellular Ca(2+) chelator o-phtalaldehyde, 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetra-acetic acid acetoxymethyl ester (BAPTA) completely inhibited [Ca(2+)](i) increase, but catalase had no effect on Na(2)SeO(3)-induced increase of [Ca(2+)](i). BAPTA-AM, CoCl(2), and mitochondrial Ca(2+) uptake inhibitor ruthenium red blocked Delta Psi m dissipation. The increase of ROS was also suppressed by CoCl(2), BAPTA, ruthenium red, N-acetylcysteine and catalase, respectively. The mitochondrial uncoupler carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) completely inhibited Na(2)SeO(3)-induced ROS increase. This showed that ROS increase is due to mitochondrial Ca(2+) overload. The Na(2)SeO(3)-induced apoptosis of SW480 cells was also inhibited by CoCl(2), BAPTA, ruthenium red, N-acetylcysteine, and catalase, respectively. The results mentioned above imply that both calcium and Ca(2+)-dependent ROS as a signal molecule mediate apoptosis induced by Na(2)SeO(3) in SW480 cells.

Effect of hydrogen peroxide on Ca2+ mobilisation in human platelets through sulphydryl oxidation dependent and independent mechanisms

Using Fura-2-loaded human platelets we studied the nature of the mechanisms involved in Ca2+ signalling mediated by H2O2. In a Ca2+-free medium, H2O2 (10 microM-100 mM) induced a concentration-dependent increase in [Ca2+]i. Depletion of either agonist-sensitive or mitochondrial Ca2+ pools reduced this effect while depletion of both stores abolished it. Xestospongin C, an inositol 1,3,5-trisphosphate (IP3) receptor inhibitor, reduced Ca2+ release evoked by 1 mM H2O2 by 45%, indicating that H2O2-induced Ca2+ release involves interaction with IP3 receptors. Blockade of the IP3 turnover by lithium or treatment with U-73122 did not modify H2O2-induced Ca2+ release from the agonist-sensitive pool, suggesting the involvement of a mechanism independent of IP3 generation. H2O2 inhibited Ca2+ reuptake into the agonist-sensitive stores mediated by the sarcoendoplasmic reticulum Ca2+ ATPase (SERCA). Thimerosal (5 microM), a sulphydryl reagent, induced Ca2+ release from the agonist-sensitive stores. This event was impaired by treatment with 2 mM DTT, which also inhibited H2O2-induced Ca2+ release from the agonist-sensitive pool but not from mitochondria. H2O2 reduced the ability of the plasma membrane Ca2+ ATPase (PMCA) to extrude Ca2+ by 75%, an effect that was unaffected by DTT. Consistent with this, thimerosal did not modify the PMCA activity. Finally, exposure to H2O2 triggered platelet aggregation, which was slower than that observed after agonist stimulation. We conclude that H2O2 induced Ca2+ release from agonist-sensitive stores by oxidation of sulphydryl groups in SERCA and the IP3 receptors independently of IP3 generation. In addition, H2O2 induced Ca2+ release from mitochondria and inhibited the PMCA activity by different mechanisms in human platelets.

Distinct roles of Ca2+, calmodulin, and protein kinase C in H2O2-induced activation of ERK1/2, p38 MAPK, and protein kinase B signaling in vascular smooth muscle cells

We have shown earlier that extracellular signal-regulated kinases 1 and 2 (ERK1/2) and protein kinase B (PKB), two key mediators of growth-promoting and proliferative responses, are activated by hydrogen peroxide (H(2)O(2)) in A10 vascular smooth muscle cells (VSMC). In the present studies, using a series of pharmacological inhibitors, we explored the upstream mechanisms responsible for their activation in response to H(2)O(2). H(2)O(2) treatment of VSMC stimulated ERK1/2, p38 mitogen-activated protein kinase (MAPK), and PKB phosphorylation in a dose- and time-dependent fashion. BAPTA-AM and EGTA, chelators of intracellular and extracellular Ca(2+), respectively, inhibited H(2)O(2)-stimulated ERK1/2, p38 MAPK, and PKB phosphorylation. Fluphenazine, an antagonist of the Ca(2+)-binding protein calmodulin, also suppressed the enhanced phosphorylation of ERK1/2, p38 MAPK, and PKB. In contrast, the protein kinase C (PKC) inhibitors Gö 6983 and Rö 31-8220 attenuated H(2)O(2)-induced ERK1/2 phosphorylation, but had no effect on p38 MAPK and PKB phosphorylation. Taken together, these data demonstrate that the activation of Ca(2+)/calmodulin-dependent pathways represents a key component mediating the stimulatory action of H(2)O(2) on ERK1/2, p38 MAPK, and PKB phosphorylation. On the other hand, PKC appears to be an upstream modulator of the increased ERK1/2 phosphorylation, but not of p38 MAPK and PKB in response to H(2)O(2) in VSMC.

Effects of hydrogen peroxide on sodium current in acutely isolated rat hippocampal CA1 neurons

The effects of hydrogen peroxide (H2O2) on sodium currents (Na+ currents) in freshly dissociated rat hippocampal neurons were studied using the whole-cell patch-clamp techniques. H2O2 caused a reversible increase of the voltage-activated Na+ currents in a concentration- and voltage-dependent manner. The half-increasing concentration (EC50) of H2O2 on Na+ currents was 10.79 microM. In addition, 10 microM H2O2 shifted the steady-state inactivation curve of Na+ currents toward positive potential (control Vh = -64.58 +/- 1.22 mV, H2O2 Vh = -53.55 +/- 0.94 mV, n = 10, P < 0.01 without changing the slope factor). However, the steady-state activation curve was not affected. These results indicated that H2O2 could increase the amplitudes of Na+ currents and change the inactivation properties of Na+ channels even in very low concentration.