Reactive Oxidant Species Formation Research Articles

Highly Efficient Copper Doping LaFeO3 Perovskite for Bisphenol A Removal by Activating Peroxymonosulfate

A series of copper doping LaFeO3 perovskite (LaCuxFe1−xO3, LCFO, x = 0.1, 0.4, 0.5, 0.6, 0.9) are successfully synthesized by the sol-gel method under mild conditions. In this study, it is applied for the activation of peroxymonosulfate (PMS) for bisphenol A (BPA) removal. More than 92.6% of BPA was degraded within 30 min at 0.7 g/L of LCFO and 10.0 mM of PMS over a wide pH range with limited leaching of copper and iron ions. The physical–chemical properties of the catalysts were demonstrated by using X-ray diffraction (XRD), N2 adsorption–desorption isotherms, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Furthermore, the effects of catalyst dosage, PMS concentration, initial pH value, and inorganic anions on the LCFO/PMS system were fully investigated. Quenching experiments were performed to verify the formation of reactive oxidant species, which showed that the radical reaction and mechanisms play a great role in the catalytic degradation of BPA. The perovskite LCFO is considered a stable, easy to synthesize, and efficient catalyst for the activation of PMS for wastewater treatment.

Syringic acid induces cancer cell death in the presence of Cu (II) ions via pro-oxidant activity

Objective: To investigate the effects of syringic acid on HEK 293 and HepG2 cells in the absence and presence of exogenous Cu (II) and Fe (II) ions. Methods: The antiproliferative effects of syringic acid on HEK 293 and HepG2 cells in the absence and presence of exogenous Cu (II) and Fe (II) ions were examined by MTT assay. Additionally, colony-forming, reactive oxidative species (ROS) generation, apoptosis induction, autophagy, mitochondrial membrane potential, and mitochondrial mass were investigated. Results: At 24 and 72 h, no significant differences were observed in the viability of HepG2 cells between the control and syringic acid + Fe (II) groups. However, exposure of HepG2 cells to syringic acid + Cu (II) for 72 h reduced the cell viability significantly. Furthermore, ROS formation, induction of apoptosis, and autophagic vacuoles were significantly increased in HepG2 cells without marked changes in mitochondrial membrane potential and mitochondrial mass. Moreover, syringic acid + Cu (II) reduced the plating efficiency and surviving fraction significantly. Conclusions: The combination of syringic acid with Cu (II) was toxic to cancer cells and showed pro-oxidant activity. In addition, this combination induced autophagy in cancer cells with less cytotoxic effects on normal cells, which is a potential candidate for the development of novel therapeutics towards cancer.

Heterogeneous Activation of Persulfate by LaMO3 (M=Co, Fe, Cu, Mn, Ni) Perovskite Catalysts for the Degradation of Organic Compounds

Sulfate radical-based advanced oxidation processes (SR-AOPs) are lately applied for the degradation of various pollutants through the formation of reactive oxidant species (ROS) from activation of oxidants, such as persulfate (PS) or peroxymonosulfate (PMS). In this study, LaMO3 (M=Co, Fe, Cu, Mn, Ni) perovskite catalysts were synthesized, characterized by several techniques, and tested for the activation of persulfate towards the degradation of phenolic pollutants. The effect of substitution of position B of La-based perovskites as well as calcination temperature was studied. Overall, the results showed that the decisive role in the catalytic activity was the presence of structures that enhance the transfer of electrons between perovskite and oxidant. LaNiO3 followed by LaCoO3 were found as the most active catalysts. Finally, the stability of the catalysts was studied, showing that B-metal leaching is significant for both catalysts, with LaCoO3 being the most stable one.

Oxidative Stress in the Pathogenesis of Antiphospholipid Syndrome: Implications for the Atherothrombotic Process

Atherothrombosis is a frequent complication of the clinical history of patients with antiphospholipid syndrome (APS). Both atherothrombosis and APS are characterized by increased oxidative stress. Oxidative modifications are implicated in the formation of antiphospholipid antibodies, which in turn may favour the oxidative imbalance by increasing the production of reactive oxidant species (ROS) or by a direct interaction with pro-oxidant/antioxidant enzymes. As a result of these processes, APS patients suffer from an oxidative imbalance that may contribute to the progression of the atherosclerotic process and to the onset of ischemic thrombotic complications. The aim of this review is to describe mechanisms implicated in the formation of ROS in APS patients and their involvement in the atherothrombotic process. We also provide an overview of potential therapeutic approaches to blunt oxidative stress and to prevent atherothrombotic complications in these patients.

The Overactivation of NADPH Oxidase during Clonorchis sinensis Infection and the Exposure to N-Nitroso Compounds Promote Periductal Fibrosis

Clonorchis sinensis, a high-risk pathogenic human liver fluke, provokes various hepatobiliary complications, including epithelial hyperplasia, inflammation, periductal fibrosis, and even cholangiocarcinogenesis via direct contact with worms and their excretory–secretory products (ESPs). These pathological changes are strongly associated with persistent increases in free radical accumulation, leading to oxidative stress-mediated lesions. The present study investigated C. sinensis infection- and/or carcinogen N-nitrosodimethylamine (NDMA)-associated fibrosis in cell culture and animal models. The treatment of human cholangiocytes (H69 cells) with ESPs or/and NDMA increased reactive oxidative species (ROS) generation via the activation of NADPH oxidase (NOX), resulting in augmented expression of fibrosis-related proteins. These increased expressions were markedly attenuated by preincubation with a NOX inhibitor (diphenyleneiodonium chloride) or an antioxidant (N-acetylcysteine), indicating the involvement of excessive NOX-dependent ROS formation in periductal fibrosis. The immunoreactive NOX subunits, p47phox and p67phox, were observed in the livers of mice infected with C. sinensis and both infection plus NDMA, concomitant with collagen deposition and immunoreactive fibronectin elevation. Staining intensities are proportional to lesion severity and infection duration or/and NDMA administration. Thus, excessive ROS formation via NOX overactivation is a detrimental factor for fibrogenesis during liver fluke infection and exposure to N-nitroso compounds.

Environmentally Friendly Fabrication of Ti/RuO2-IrO2-SnO2-Sb2O5 Anode with In Situ Incorporation of Reduced TiO2 Interlayer

The intensive use of chemical reagents in the pretreatment of Ti substrate and shorter electrode life constrict the wider application of the dimensionally stable anode (DSA). In this study, a simple method was developed to thermally pretreat the Ti substrate in the atmosphere of H2 and N2 (molar ratio 1:5) without chemicals consumption and wastewater discharge. It was found that the reduced TiO2 interlayer could be favorably created at temperature of 750 °C. This rendered Ti/reduced TiO2/RuO2-IrO2-SnO2-Sb2O5 anode with better stability and higher electrocatalytic activity. The accelerated lifetime for Ti/reduced TiO2/RuO2-IrO2-SnO2-Sb2O5 electrode was 65 h with the optimum catalyst loading amount (2.6 ± 0.05 mg cm−2), while it was only 50 h for traditional Ti/RuO2-IrO2-SnO2-Sb2O5 electrode. As compared with the counterparts, Ti/reduced TiO2/RuO2-IrO2-SnO2-Sb2O5 with higher oxygen evolution potential (1.42 V/SCE) and lower chlorine evolution potential (1.12 V/SCE), suggesting higher electro-catalytic activity toward reactive oxidative species formation. The deactivation test indicates that the anode deactivation mainly proceeded via the dissolution of the catalyst layer and then formation of insulated TiO2 on the substrate. Generally, an environmentally friendly Ti substrate pretreatment method was developed and demonstrated promising for upgrading DSA fabrication process in industrial application.

Synergistic Adsorption and Oxidation of Ciprofloxacin by Biochar Derived from Metal-Enriched Phytoremediation Plants: Experimental and Computational Insights.

Biochar is a promising candidate for the adsorptive removal of organic/inorganic pollutants, yet its role in metal-free catalyzed advanced oxidation processes still remains ambiguous. In this work, five biochar samples (PPBKx, where x represents the pyrolysis temperature) were prepared by using metal-enriched phytoremediation plant residue as the feedstock. Notably, PPBK exhibited a high specific surface area (as high as 1090.7 m2 g-1) and outstanding adsorption capacity toward ciprofloxacin (CIP, as much as 1.51 ± 0.19 mmol g-1). By introducing peroxymonosulfate (PMS, 5 mM) as the chemical oxidant, over 2 mmol g-1 CIP was synergistically adsorbed and oxidized within 30 min although PMS itself could not oxidize CIP efficiently, suggesting the formation of reactive oxidative species. Theoretical calculations revealed that PMS anions preferentially adsorbed on the activated C atoms adjacent to the graphitic N dopant, where the carbon matrix served as the electron donor, instead of as an electron mediator. The adsorbed PMS possessed a smaller molecular orbital energy gap, indicating that it was much easier to be activated than free PMS anions. Surface-bound reactive species were elucidated to be the dominant contributor through chemical quenching experiments and electrochemical characterizations. The catalytic activity of PPBK700 could be greatly retained in repeated oxidations because of the stable N species, which serve as the active catalytic sites, while the CIP adsorption was greatly deteriorated because of the diminishing active adsorption sites (carbon matrix edge) caused by the partial oxidation of PMS. This work not only provides a facile and low-cost approach for the synthesis of functional biochar toward environmental remediation but also deepens the understanding of biochar-catalyzed PMS activation and nonradical oxidation.

A novel role of MMP2 in regulating platelet NOX2 activation

NOX2 has a key role for cellular production of reactive oxidant species (ROS) and although the mechanism of its activation is well known, little is known about its regulation. Metallo-proteinases (MMPs) regulate numerous protein activities both in physiological and pathological conditions but their interplay with NOX2 and ROS formation is still unclear. We performed experimental studies in human platelets and polymorphonuclear leukocytes (PMNs) to investigate the interplay of MMP2 with NOX2 activity.In collagen-stimulated platelets and in PMA-stimulated PMNs from healthy subjects, an immediate burst of ROS was detected at 10 min to then decline at 20 min. Coincidentally, sNOX2-dp, a split-off product of NOX2, increased and peaked at 10 min. ROS production was persistent whereas sNOX2dp is not released in cells treated with MMP2 inhibitor compared to other MMPs inhibitors. Western blot analysis showed the highest MMP2 expression on the cell membrane 10 min after stimulation. Moreover, the co-immunoprecipitation assay confirms the interaction between MMP2 and NOX2 that formed an active immuno-complex. Treating cells with NOX2ds-tat, an inhibitor of NADPH oxidase, significantly reduced ROS formation, sNOX2-dp, MMP2 expression and MMP2-NOX2-complex, which were all restored if cells were added with H2O2.The study provides the first evidence that MMP2 has a key role in blunting platelet NOX2 activity and eventually ROS formation.

Mechanism underlying visible-light photocatalytic activity of Ag/AgBr: Experimental and theoretical approaches

Silver/silver halides (Ag/AgX) are potential visible-light (VL) photocatalysts due to synergistic effects of surface plasmon resonance (SPR) and semiconductor photocatalysis. However, many contradictory opinions are found in published literature about the mechanism underlying photocatalytic oxidation (PCO) by Ag/AgX. In this study, Ag/AgBr particles were prepared by a simple one-pot synthesis method and used for degradation of Reactive Black 5 (RB5) as a model pollutant aiming to understand the effect of concentration of excess silver ions on SPR phenomenon, and to employ experimental and theoretical approaches to pinpoint the reactive oxidative species (ROS) responsible for RB5 degradation. 16.2% of initial 50 mg/L RB5 was degraded using 0.5 g/L AgBr (Ag+:AgBr = 0, i.e. no excess Ag+) under 60 min VL irradiation. Under identical experimental conditions, RB5 degradation increased to 86.5% using Ag/AgBr synthesized as Ag+:AgBr = 0.4, due to improved SPR effect. Experimental evidence supported by theoretical calculations revealed that superoxide radicals (•O2) played a prime role in PCO followed by photo-generated holes, whereas the contribution of •OH was negligible. The presence of Ag0 on AgBr greatly influenced band energies and regulated the formation of ROS. With an increase in ratio Ag+:AgBr, the conductance and valence bands increasingly became more electro-negative and electro-positive, respectively, as compared to that at Ag+:AgBr = 0. The presence of Cl ̅ and SO42− ions adversely affected RB5 degradation, whereas CO32− did not cause any adverse impact. Ag/AgBr could be successfully immobilized over bacterial cellulose which, under identical conditions, provided 79.1% RB5 degradation in 60 min. The Ag/AgBr-BC could be reused five times.

Abstract 5087: Carvedilol prevents skin cancer independently of its antioxidant property

Abstract Carvedilol is an FDA approved β-blocker traditionally prescribed for cardiovascular diseases. Our previous work demonstrated that carvedilol has preventive activity against ultraviolet radiation (UVR)-induced skin damage, inflammation, and carcinogenesis. However, the photoprotective mechanism for carvedilol remains unknown. Interestingly, not all β-blockers have cancer preventive activity, suggesting that targeting the β-adrenergic receptors may not be responsible for carvedilol’s anticancer activity. Since carvedilol has been shown as a potent antioxidant and such property is not shared by majority of other β-blockers (e.g., metoprolol), we hypothesized that the antioxidant property may be, in part, responsible for carvedilol’s protective activity against photocarcinogenesis. The nontumorous mouse epidermal JB6 P+ cells were subjected to various doses of UVR exposure and H2O2 treatment to identify the optimal doses to examine protective activity. UVR and H2O2dose-dependently reduced cell viability. 25mJ/cm2 UVR and 100 μM H2O2 reduced cell viability detected by Trypan blue exclusion assay to 58.1% and 60.6%, respectively. 25mJ/cm2 UVR and 300 μM H2O2 increased the formation of intracellular fluorescent 2',7'-dichlorofluorescein (DCF) fluorescence, a marker of reactive oxidative species (ROS) detected by flow cytometry, to 5- and 4-fold compared to non-treated control, respectively. The cells were treated before or after UVR and H2O2 exposure with metoprolol, carvedilol or 4-hydroxycarbazole (4-OHC). 4-OHC is an intermediate compound for carvedilol synthesis that possesses an identical UV absorption profile as carvedilol. Additionally, the carbazole moiety is likely responsible for the antioxidant activity of carvedilol. Carvedilol, but not metoprolol and 4-OHC, was able to inhibit EGF-induced JB6 transformation in soft agar. Carvedilol, but not metoprolol and 4-OHC, also attenuated UVR and H2O2 induced cell death. Carvedilol, but not 4-OHC, inhibited UVR-induced NF-κB and AP-1 promoter activity. In addition, unlike carvedilol, 4-OHC failed to prevent chronic UVR induced skin carcinogenesis in SKH-1 mice. However, 4-OHC and carvedilol similarly attenuated UVR- and H2O2-induced ROS formation in JB6 P+ cells, while metoprolol had no effect. These results indicate that the photoprotective effects of carvedilol are primarily due to an unknown mechanism that is independent of β-adrenergic receptors and reactive oxygen species scavenging. Citation Format: Mengbing Chen, Sherry Liang, Bradley Andresen, Ying Huang. Carvedilol prevents skin cancer independently of its antioxidant property [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5087.

Photocatalytic disinfection efficiency of 2D structure graphitic carbon nitride-based nanocomposites: a review

Nanostructured carbon-based photocatalysts have gained attention in photocatalytic disinfection of microbial species. With distinctive features of possessing appropriate electronic band gap structure and high chemical and thermal stability, metal-free polymeric 2D stacked structure graphitic carbon nitride (g-C3N4) is an important photocatalytic material for environmental and energy applications. Besides, it has the potential for inactivation of harmful pathogens. Disinfection of microbial species is mainly ascribed to the formation of reactive oxidative species. Further, surface modification of g-C3N4 can remarkably improves photocatalytic disinfection efficiency. In this review, we have discussed the recent advances in photocatalytic disinfection using g-C3N4-based nanocomposites. An overview of metal-free nanostructure g-C3N4, metal (anions) and nonmetal (cations)-doped g-C3N4 and g-C3N4 hybridized with low band gap semiconductor is also presented. Moreover, we have emphasized on the photocatalytic disinfection mechanism associated with g-C3N4-modified composites. Nitrogen-rich g-C3N4 polymeric material can serve as an alternative to metal oxide (TiO2 and ZnO) photocatalysts for photocatalytic disinfection technology. Other applications such as CO2 photoreduction, H2 generation, organic pollutant degradation, and sensing using g-C3N4-based nanocomposites are also summarized.

44 - Endothelial cells (EC) regulate ROS generation in vascular smooth muscle cells (VSMC) from hypertensive rats

ECs can regulate by reactive oxidant species (ROS), several functions of VSMC. This study aimed to verify the role of ECs on ROS generation and proliferation of VSMC from normotensive (2K), renal hypertensive rats (2K-1C) and SHR. We used transwell® technique in which ECs and VSMCs are co-cultured. We tested NO and ROS production by fluorimetric assay and VSMCs proliferation by the proliferating cell nuclear antigen (PCNA) expression in VSMC, extracted from 2K-1C, 2K rats and SHR in monoculture and co-culture with EC (HUVECs). NO production was lower in the VSMCs from 2K-1C (936.0 ± 11.0 FI, P˂0.05) than in 2K VSMCs (1,234.1 ± 20.0 FI) whereas ROS production was higher in 2K-1C VSMC (1,072.6 ± 17.0 FI, P˂0.05) than in 2K (958.02 ± 27.1 FI). In the same way, NO production was lower in the VSMCs from SHR (3,700.3 ± 12.0 FI, P˂0.05) than in VSMCs from normotensive (4,633.3± 22.0 FI). ROS production was higher in SHR VSMCs (4,460 ± 19.0 FI, P˂0.05) than in normotensive (3,317 ± 23.1 FI). ROS generation in co-culture of VSMCs and ECs for 72 h from 2K-1C aortas (938.0 ± 12.0 FI, P˂0.05) was lower than in monoculture of 2K-1C VSMCs (1,072.7 ± 17.3 FI) and SHR (1,312.0± 10.1,FI). NO levels were greater in VSMCs co-cultured with ECs (1,096.0 ± 29.0 FI, P˂0.05) than in monoculture (929.66 ± 13 FI). ROS production was higher in 2K-1C and SHR than in 2K VSMCs. ECs treated with NO-synthase L-NAME or ibuprofen (COX inhibitor), did not alter ROS formation in VSMC, but Angiotensin-II abolished ROS-induced effects of ECs. PCNA expression was similar in VSMCs in monoculture and in co-culture, whereas it was greater in VSMCs from 2K-1C and SHR in monoculture than in co-culture. Our data suggest that ECs protect VSMCs from hypertensive rats due to NADPH oxidase inhibition.

Oxidative stress and cardiovascular disease: new insights.

The role of oxidative stress in the onset and progression of atherosclerosis and its impact on the development of cardiovascular events has been widely described. Thus, increased oxidative stress has been described in several atherosclerotic risk factors, such as hypertension, dyslipidaemia, peripheral artery disease, metabolic syndrome, diabetes, and obesity. Among others, specific oxidative pathways involving both pro-oxidant and antioxidant enzymes seem to play a major role in the production of reactive oxidant species (ROS), such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, myeloperoxidase, superoxide dismutase, and glutathione peroxidase. In this review, we will discuss: 1) the most relevant enzyme systems involved in the formation and detoxification of ROS, 2) the relationship between oxidative stress and cardiovascular risk, and 3) therapeutic implications to modulate oxidative stress.

Inhibition of in vivo oxidation of native low‐density lipoprotein by N‐acetylcysteine is associated with decreased atherosclerosis

BackgroundLow‐density lipoprotein (LDL) is not atherogenic itself. Oxidized LDL (ox‐LDL) is a potent oxidative agent, produces reactive oxidative species (ROS), and critical to the development of atherosclerosis. N‐acetylcysteine (NAC) has anti‐atherosclerotic effect. The mechanisms for its anti‐atherosclerotic actions remain largely unknown.ObjectiveThe present study aimed to determine if NAC could attenuate in vivo oxidation of LDL and inhibit atherosclerosis.Methods and resultsA single dose of human native LDL (50 μg) was injected intravenously into male C57BL/6 mice with and without NAC treatment. Human ox‐LDL levels in the blood were measured at different time after LDL injection using ELISA kit. Measurable serum level of human ox‐LDL was detected 30 min after the injection, reached the peak in 3 hours, started to decline afterwards, and became undetectable in 12 hours. NAC treatment significantly reduced serum ox‐LDL level with no detectable ox‐LDL in blood 6 hours after injection. No difference in ox‐LDL clearance was observed in NAC‐treated animals. Intracellular and extracellular ROS production was significantly increased in the animals treated with ox‐LDL and in hyperlipidemic LDL receptor knockout (LDLR−/−) mice that was completely prevented with NAC treatment. NAC also significantly reduced atherosclerotic plaque formation in hyperlipidemic LDLR−/− mice.ConclusionNative LDL was converted to ox‐LDL in vivo. NAC attenuated in vivo oxidation of LDL and ROS formation from ox‐LDL that might contribute to decreased atherosclerotic plaque formation in hyperlipidemia.Support or Funding InformationNIH

Osteomeles schwerinae extracts inhibits the binding to receptors of advanced glycation end products and TGF-β1 expression in mesangial cells under diabetic conditions

BackgroundOsteomeles schwerinae C. K. Schneid. (Rosaceae, OSSC) is a medicinal plant traditionally used to treat various diseases in Asia. The chemical constituents of OSSC have an inhibitory effect on aldose reductase activity, which has been implicated in the pathogenesis of diabetic complications. However, the protective effects of the pharmacological activity and potential mechanisms in diabetic nephropathy are still not known. ObjectiveIn the present study, OSSC extracts and major compounds were examined for their effects on binding to the receptors of advanced glycation end products (RAGE) and on transforming growth factor-beta1 (TGF-β1) expression-related signal mechanisms in mouse glomerular mesangial cells (GMCs). Materials and methodsA simple, rapid and efficient method was developed for the simultaneous determination of the marker compounds in the ethanol extract of the leaves and twigs of OSSC using HPLC-diode array detector (DAD). In this study, we determined the effects of OSSC extract and hyperoside on AGE and RAGE binding, and studied the mechanism of OSSC extract effects on AGE-bovine serum albumin (BSA)-treated GMCs. GMCs overexpressing human RAGE were cultured in AGE-BSA labeled with Alexa 488, and OSSC extract. AGE/RAGE binding were measured using fluorescence (excitation 485nm/emission 528nm). TGF-β1 protein expression levels were determined by western blot analyses. ResultsOSSC extracts of leaves and twigs inhibited on AGE/RAGE binding and TGF-β1 protein expression in a dose-dependent manner in GMCs. Furthermore, OSSC extracts reduced the effects on AGE-BSA-induced reactive oxidative species (ROS) formation and nuclear translocalization of transcription factor NF-κB. OSSC extracts inhibited phosphorylation of extracellular signal-regulated protein kinases1/2 (ERK1/2), p38 mitogen-activated protein kinases (p38MAPK), and IκB. Hyperoside also inhibited AGE/RAGE binding and ROS formation, and reduced TGF-β1 expression and IkB phosphorylation. ConclusionsOSSC extracts and hyperoside may attenuate AGE/RAGE binding and expression of TGF-β1 by downregulating of pERK1/2, p38MAPK and IκB phosphorylations in GMCs under diabetic condition and retard the development of diabetic complications such as diabetic nephropathy.

Nutritional and therapeutic approaches to modulate NADPH oxidase-derived ROS signaling in platelets.

Experimental and clinical studies provided evidence that formation of intra-platelet reactive oxidant species (ROS) is implicated in the process of thrombosis. Animal models demonstrated that enhanced ROS formation was associated with serious thrombotic complications and death. In recent years, nutritional and therapeutic approaches were tested to modulate ROS mediated thrombus formation. The use of a nutritional approach stems from the observation that foods rich in antioxidant elements, such as polyphenols, were able to modulate ROS formation. Similarly, some drugs used for different diseases (i.e. statins) showed the ability to modulate oxidative stress. Aim of this review is to summarize current evidences supporting the role of nutrients rich in polyphenols, such as olive oil and cocoa, and of some drugs, such as statins as antiplatelet agents interfering with the Nicotinamide Adenine Dinucleotide Phosphate (NADPH) Oxidase signaling. Indeed, for nutrients and statins, the antiplatelet activity seems to be dependent, at least in part, upon the inhibition of platelet NADPH oxidase-derived ROS formation, resulting in down-regulation of isoprostanes, which are pro-aggregating molecules, and up-regulation of nitric oxide, which is a platelet inhibitor.

N-acetylcysteine inhibits in vivo oxidation of native low-density lipoprotein.

Low-density lipoprotein (LDL) is non-atherogenic, while oxidized LDL (ox-LDL) is critical to atherosclerosis. N-acetylcysteine (NAC) has anti-atherosclerotic effect with largely unknown mechanisms. The present study aimed to determine if NAC could attenuate in vivo LDL oxidation and inhibit atherosclerosis. A single dose of human native LDL was injected intravenously into male C57BL/6 mice with and without NAC treatment. Serum human ox-LDL was detected 30 min after injection, reached the peak in 3 hours, and became undetectable in 12 hours. NAC treatment significantly reduced serum ox-LDL level without detectable serum ox-LDL 6 hours after LDL injection. No difference in ox-LDL clearance was observed in NAC-treated animals. NAC treatment also significantly decreased serum ox-LDL level in patients with coronary artery diseases and hyperlipidemia without effect on LDL level. Intracellular and extracellular reactive oxidative species (ROS) production was significantly increased in the animals treated with native LDL, or ox-LDL and in hyperlipidemic LDL receptor knockout (LDLR−/−) mice that was effectively prevented with NAC treatment. NAC also significantly reduced atherosclerotic plaque formation in hyperlipidemic LDLR−/− mice. NAC attenuated in vivo oxidation of native LDL and ROS formation from ox-LDL associated with decreased atherosclerotic plaque formation in hyperlipidemia.

MWCNTs Induce ROS Generation, ERK Phosphorylation, and SOD-2 Expression in Human Mesothelial Cells.

Biological oxidative responses are involved in the toxicity of multiwall carbon nanotubes (MWCNTs), which may cause asbestos-like pathogenicity. Superoxide dismutase 2 (SOD-2) has been proposed as a biomarker of early responses to mesothelioma-inducing fibers. This study was conducted to investigate the alteration of SOD-2 expression in the human mesothelial cell lines Met-5A after exposure to nontoxic doses of MWCNTs and the potential signaling pathway. The parameters measured included the viability, morphological change, superoxide formation, extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, and messenger RNA (mRNA)/protein levels of SOD-2. Our results showed that MWCNTs upregulated SOD-2 expression at both mRNA and protein level. Coincidently, both superoxide formation and ERK1/2 phosphorylation were observed in Met-5A cells exposed to MWCNTs and were diminished by pretreatment with the reactive oxidative species (ROS) scavenger, N-acetyl-l-(+)-cysteine (NAC). To further investigate the role of ROS/ERK1/2 in MWCNTs-induced SOD-2 overexpression, prior to MWCNTs exposure, cells were pretreated with the Mitogen-activated protein kinase kinase 1/2 (MEK 1/2) inhibitor (U0126) or with NAC. Both pretreatments decreased the MWCNTs-induced overexpression of SOD-2. These results suggest that upregulation of SOD-2 in Met-5A cells exposed to MWCNTs is mediated by ROS formation and ERK1/2 activation.

N‐acetylcysteine prevents in vivo oxidation of native low‐density lipoprotein

ObjectiveLow‐density lipoprotein (LDL) is not atherogenic. Oxidized LDL (ox‐LDL) produces reactive oxidative species (ROS) and is critical to atherosclerosis. N‐acetylcysteine (NAC) has anti‐atherosclerotic effect with largely unknown mechanisms. The present study aimed to determine if NAC could attenuate LDL oxidation in vivo.Approach and ResultsMeasurable serum level of human ox‐LDL was detected 30 min after a single dose intravenous injection of human native LDL into male C57BL/6 mice, reached the peak in 3 hours, then started to decline, and became undetectable in 12 hours. NAC treatment significantly reduced serum ox‐LDL level with no detectable serum ox‐LDL 6 hours after injection. No difference in ox‐LDL clearance was observed in NAC‐treated animals. NAC treatment also significantly decreased serum ox‐LDL level in patients with coronary artery disease and hyperlipidemia with no effect on LDL level. Intracellular and extracellular ROS production was significantly increased in the mice treated with native LDL, or ox‐LDL that was completely prevented with NAC treatment.ConclusionNAC attenuated native LDL in vivo oxidation and ROS formation from ox‐LDL.Sources of fundingNIH R01 HL094650

Interaction between endoplasmic/sarcoplasmic reticulum stress (ER/SR stress), mitochondrial signaling and Ca(2+) regulation in airway smooth muscle (ASM).

Airway inflammation is a key aspect of diseases such as asthma. Several inflammatory cytokines (e.g., TNFα and IL-13) increase cytosolic Ca(2+) ([Ca(2+)]cyt) responses to agonist stimulation and Ca(2+) sensitivity of force generation, thereby enhancing airway smooth muscle (ASM) contractility (hyper-reactive state). Inflammation also induces ASM proliferation and remodeling (synthetic state). In normal ASM, the transient elevation of [Ca(2+)]cyt induced by agonists leads to a transient increase in mitochondrial Ca(2+) ([Ca(2+)]mito) that may be important in matching ATP production with ATP consumption. In human ASM (hASM) exposed to TNFα and IL-13, the transient increase in [Ca(2+)]mito is blunted despite enhanced [Ca(2+)]cyt responses. We also found that TNFα and IL-13 induce reactive oxidant species (ROS) formation and endoplasmic/sarcoplasmic reticulum (ER/SR) stress (unfolded protein response) in hASM. ER/SR stress in hASM is associated with disruption of mitochondrial coupling with the ER/SR membrane, which relates to reduced mitofusin 2 (Mfn2) expression. Thus, in hASM it appears that TNFα and IL-13 result in ROS formation leading to ER/SR stress, reduced Mfn2 expression, disruption of mitochondrion-ER/SR coupling, decreased mitochondrial Ca(2+) buffering, mitochondrial fragmentation, and increased cell proliferation.