Generation Of Reactive Nitrogen Species Research Articles

Inactivation of virus and bacteria using cold atmospheric pressure air plasmas and the role of reactive nitrogen species

Cold atmospheric pressure plasma has potential as a non-thermal processing technology to decontaminate food and food contact surfaces due to its ability to generate an abundance of reactive oxygen and nitrogen species with antimicrobial attributes at ambient conditions. In this study, we present a comparison on the effectiveness of surface decontamination against feline calicivirus (FCV) and Salmonella spp using four different plasma sources, a dielectric barrier discharge (DBD) in direct contact with the substrate and three remote plasma treatment sources: a 2D DBD, a volumetric DBD and a gliding arc discharge. The plasma sources were all operated in air at atmospheric pressure. The decontamination efficacy was enhanced by the presence of humidity on the sample surface and only direct contact between plasma and samples allowed the inactivation of pathogens on dry substrates. Across all sources, FCV was seen to be more susceptible to the plasma-generated species than Salmonella spp. The diminished effectiveness of the gliding arc discharge compared to the DBDs operating at the same power is most likely due to the low Henry’s law constant of NO, the dominant reactive species generated by the gliding arc. Control experiments illustrate that the co-existence of O3 and NO2, as in the afterglow of the remote DBDs enhances the inactivation compared to the inactivation by O3 or NO2 only. A chemical kinetics model of the plasma effluent and the plasma treatments show a strong correlation between the gas-phase concentration of N2O5 and inactivation of the virus. We experimentally show that the production of N2O5 coincides with the enhanced generation of reactive nitrogen species in the liquid phase.

Mitigation of Cu(II)-induced damage in human blood cells by carnosine: An in vitro study

Copper (Cu) is an essential micronutrient but human exposure to high level of this metal results in adverse health effects. Oxidative stress is assumed to play a major role in the mechanism of Cu-induced toxicity. The protective role of carnosine, an antioxidant and antiglycating agent, was examined against Cu-induced toxicity in isolated human blood cells. Red blood cells (RBC) were treated with 0.5 mM copper chloride (CuCl2), a Cu(II) compound, either alone or after treatment with carnosine. Incubation of RBC with CuCl2 increased protein oxidation, lipid peroxidation, methemoglobin formation and lowered glutathione content. The antioxidant defense system was impaired and production of reactive oxygen (ROS) and reactive nitrogen species (RNS) was enhanced. Pre-incubation of RBC with carnosine protected the cells against CuCl2-induced oxidative damage. It restored the activities of several antioxidant, membrane-bound and metabolic enzymes, decreased the generation of ROS and RNS, enhanced the antioxidant power of cells and prevented inactivation of plasma membrane redox system. Carnosine also protected human lymphocytes from CuCl2-induced DNA damage. The protective effects of carnosine were concentration-dependent while carnosine itself did not exhibit any adverse effect. Carnosine can, therefore, be used as a possible chemoprotectant against the harmful effects of this extremely redox active metal.

Nonthermal Atmospheric Plasma-Induced Cellular Envelope Damage of Staphylococcus aureus and Candida albicans Biofilms: Spectroscopic and Biochemical Investigations

Objective: Nonthermal plasma at atmospheric condition using dielectric barrier discharge (DBD) is reported to be useful in many applications. Here, we have developed a strategy to generate nonthermal atmospheric plasma (NTAP) at ambient conditions for potential biomedical applications. Methods: We have explored the active ingredients of the nonthermal plasma using atomic emission spectroscopy. The potential mechanism of the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) from the generated plasma for therapeutic use has been demonstrated. Major results: The antimicrobial efficacy of the nonthermal plasma application to model Staphylococcus aureus and Candida albicans biofilms has been investigated. Our detailed electron microscopic studies followed by biochemical investigation reveal the mechanism of bacterial/fungal deactivation process. The nuclear magnetic resonance (NMR) studies on the live cell of C . albicans before and after NTAP treatment clearly conclude the disruption of cellular envelope leading to necrosis as evidenced by fluorescence-assisted cell sorting (FACS) studies. Conclusions: The proposed NTAP setup may find relevance in novel strategies in bacterial and fungal biofilm destruction in the future development of nonfluid hand sanitization.

Cold atmospheric plasma induces silver nanoparticle uptake, oxidative dissolution and enhanced cytotoxicity in glioblastoma multiforme cells

Silver nanoparticles (AgNP) emerged as a promising reagent for cancer therapy with oxidative stress implicated in the toxicity. Meanwhile, studies reported cold atmospheric plasma (CAP) generation of reactive oxygen and nitrogen species has selectivity towards cancer cells. Gold nanoparticles display synergistic cytotoxicity when combined with CAP against cancer cells but there is a paucity of information using AgNP, prompting to investigate the combined effects of CAP using dielectric barrier discharge system (voltage of 75 kV, current is 62.5 mA, duty cycle of 7.5kVA and input frequency of 50–60Hz) and 10 nm PVA-coated AgNP using U373MG Glioblastoma Multiforme cells. Cytotoxicity in U373MG cells was >100-fold greater when treated with both CAP and PVA-AgNP compared with either therapy alone (IC50 of 4.30 μg/mL with PVA-AgNP alone compared with 0.07 μg/mL after 25s CAP and 0.01 μg/mL 40s CAP). Combined cytotoxicity was ROS-dependent and was prevented using N-Acetyl Cysteine. A novel darkfield spectral imaging method investigated and quantified AgNP uptake in cells determining significantly enhanced uptake, aggregation and subcellular accumulation following CAP treatment, which was confirmed and quantified using atomic absorption spectroscopy. The results indicate that CAP decreases nanoparticle size, decreases surface charge distribution of AgNP and induces uptake, aggregation and enhanced cytotoxicity in vitro.

Degradation of antibiotic enrofloxacin in water by gas-liquid nsp-DBD plasma: Parametric analysis, effect of H2O2 and CaO2 additives and exploration of degradation mechanisms

Enrofloxacin (ENRO) is a highly toxic fluoroquinolone antibiotic widely used in a broad spectrum of human activities and therefore increased ENRO levels found in aquatic environments pose serious threats for human and livestock health. In this study, a gas–liquid nanosecond pulsed dielectric barrier discharge (nsp-DBD) plasma reactor was used for the degradation of ENRO in aqueous solutions. The increase of pulse peak voltage and the pulse repetition rate, up to a certain limit, were found to enhance ENRO degradation efficiency, degradation rate and energy yield. Under the optimum pulse voltage and pulse frequency, ENRO was completely degraded after 20 min with the corresponding energy yield being 1.1 g/kWh. Air and O2 as working gases displayed superior impact on degradation compared to N2. Additives such as CaO2 and H2O2 were found to enhance the degradation rate with CaO2 being superior promoter compared to H2O2. The UV–Vis emission spectra of the plasma discharge revealed the generation of various reactive nitrogen and oxygen species in the gas phase whereas the concentrations of the reactive gaseous NOx were also measured. In liquid phase, the importance of OH and 1O2 in the degradation process was confirmed by using appropriate scavengers, while H2O2 concentration was quantified by reflectance photometry. A degradation pathway was proposed following HPLC and UPLC/MS analysis of treated samples at various time points of the nsp-DBD treatment. Overall, the complete degradation of enrofloxacin in water was achieved with very high-energy yield suggesting that the current nsp-DBD system could be considered an appealing alternative as a cost-effective technology for the remediation of antibiotic-polluted water systems.

Redox Control of the Immune Response in the Hepatic Progenitor Cell Niche.

The liver commonly self-regenerates by a proliferation of mature cell types. Nevertheless, in case of severe or protracted damage, the organ renewal is mediated by the hepatic progenitor cells (HPCs), adult progenitors capable of differentiating toward the biliary and the hepatocyte lineages. This regeneration process is determined by the formation of a stereotypical niche surrounding the emerging progenitors. The organization of the HPC niche microenvironment is crucial to drive biliary or hepatocyte regeneration. Furthermore, this is the site of a complex immunological activity mediated by several immune and non-immune cells. Indeed, several cytokines produced by monocytes, macrophages and T-lymphocytes may promote the activation of HPCs in the niche. On the other side, HPCs may produce pro-inflammatory cytokines induced by liver inflammation. The inflamed liver is characterized by high generation of reactive oxygen and nitrogen species, which in turn lead to the oxidation of macromolecules and the alteration of signaling pathways. Reactive species and redox signaling are involved in both the immunological and the adult stem cell regeneration processes. It is then conceivable that redox balance may finely regulate the immune response in the HPC niche, modulating the regeneration process and the immune activity of HPCs. In this perspective article, we summarize the current knowledge on the role of reactive species in the regulation of hepatic immunity, suggesting future research directions for the study of redox signaling on the immunomodulatory properties of HPCs.

Photobiomodulation (PBM) regulates nitric oxide (NO) production by peripheral blood mononuclear cells (PBMC) isolated from Multiple Sclerosis (MS) patients

Abstract Multiple sclerosis (MS) is an autoimmune disease characterized by myelin destruction, neurodegeneration and mitochondrial dysfunction. High production of nitric oxide (NO) by iNOS contributes to the generation of reactive nitrogen species, leading to increased nitrosative stress and mitochondrial dysfunction linked to MS progression. Current therapies focus on the suppression of the immune system in early stages, but they are not effective in chronic stages where nitrosative stress takes control over pathogenic mechanisms. Thus, new therapies that reduce nitrosative stress and offer neuroprotection at any stage are needed. Photobiomodulation (PBM) has demonstrated efficacy to improve neurodegenerative disorders. Our lab showed that PBM at 670nm reduced clinical severity in the C57BL/6 mouse experimental autoimmune encephalomyelitis model of MS by down-regulation of nitrosative stress, apoptosis, and pro-inflammatory cytokines, and up-regulation of anti-inflammatory cytokines. Likewise, PBM modulated cytokine expression by peripheral blood mononuclear cells (PBMC) and CD4+ T cells isolated from MS patients. Here we show that PBM reduces NO production by PBMC from MS patients. PBMC were isolated by gradient centrifugation, activated with Phytohaemagglutinin (PHA) and received PBM treatment. As surrogate for NO, nitrite production in supernatants was measured by fluorometry. The most effective PBM doses at decreasing nitrite were 830nm (10J/cm2) and pulsed 640nm (3J/cm2). The expression of Interferon-γ correlated with nitrite expression at these same doses. PBM effect was dependent on the disease modifying drug that subjects were taking. The results show the potential of PBM on NO regulation in MS patients.

UV365 induced elimination of contaminants of emerging concern in the presence of residual nitrite: Roles of reactive nitrogen species

The presence of nitrite (NO2−) is inevitable with concentrations of several mg L−1 in some typical water bodies. In this study, UV at wavelength of 365 nm was investigated to degrade contaminants of emerging concern (CECs) in the presence of NO2− at environmentally relevant concentrations (0.1–5.0 mg L−1). Six selected CECs with different structures were efficiently removed because of the generation of reactive nitrogen species (RNS) and hydroxyl radical (HO•) from photolysis of NO2−. Contributions of UV365 photolysis, RNS, and HO• to CEC degradation in UV365/NO2− system were calculated, and RNS were found to be the predominant species that are responsible for CEC degradation. The second major contributor is HO• for the degradation of selected CECs except for the case of sulfadiazine. Impacts of water matrix components (including dissolved oxygen, solution pH, and natural organic matter) on CEC degradation in UV365/NO2− system were evaluated. Furthermore, evolution profiles of CECs and NO2− in UV365/NO2− system were tracked when actual water samples were used as background, and a simultaneous removal of CECs and NO2− was observed. Transformation products of bisphenol A and carbamazepine were proposed according to the results of HPLC/MS and quantum chemistry calculations. Nitration induced by RNS and hydroxylation induced by HO• are main reactions occurred during CEC degradation in UV365/NO2− system. Overall, UV365 is a potential technology to remove CECs and NO2− in aquatic environment when residual NO2− is present. Our present study also provides possibility for the application of sunlight to remediate water co-polluted by CECs and NO2−.

New and classical methods to compare oxidative stress levels and parameters of vascular function in rat models of hypertension, diabetes and nitrate tolerance

BackgroundOxidative stress was identified as a hallmark of almost all cardiovascular and neurodegenerative diseases. The term oxidative stress describes a condition that is either characterized by increased generation of reactive oxygen and nitrogen species (RONS) and/or dysregulated cellular antioxidant defense mechanisms (e.g. decreased expression of central antioxidant enzymes). Since the transition between oxidative stress and redox signaling is a thin line, the exact knowledge of the identity of formed reactive species, the cellular and subcellular localization of their formation as well as their time duration and concentration are of high clinical and pharmacological importance.Methods and ResultsWith the present studies, we evaluated the specific probe for mitochondrial superoxide formation, mitochondria‐targeted, triphenylphosphonium‐linked hydroethidium (mitoSOX), for its usefulness in the detection of mitochondrial superoxide formation ex vivo/in vivo and compared this HPLC‐based assay with alternative/traditional methods. For this purpose, we used three different animal models with well‐established oxidative stress burden, namely diabetic, hypertensive and nitrate tolerant rats. With our previous work we have stressed that the traditional or old RONS assays are not necessarily inferior as compared to up‐to‐date or even cutting‐edge assays and at least have their specific features and application spectra. Vascular function was assessed by isometric tension methodology and was impaired in the rat models of oxidative stress. Vascular dysfunction correlated with increased mitoSOX oxidation but also classical RONS detection assays as well as typical markers of oxidative stress. Additionally, we successfully applied this method for the mitochondrial superoxide detection in hypertensive (AT‐II induced), aircraft noise exposure mouse model as well as in the combination of these two stressors. The application of this method was also effective in the wild type and Nox2 knockout mice exposed to e‐cigarette vapor over 3 days for 2 h/d.ConclusionIn conclusion, we report that mitoSOX/HPLC indeed represents a suitable method for quantification of mitochondrial superoxide formation in biological samples of animals with cardiometabolic disease, pharmacologically induced cardiovascular complications and cardiovascular diseases induced by novel (environmental/behavioral) stressors. The knowledge on the spatial distribution of RONS formation may be of specific interest for drug development and when it comes to therapy.Support or Funding InformationOur experimental studies were supported by vascular biology research grants from the Boehringer Ingelheim Foundation for the collaborative research group „Novel and neglected cardiovascular risk factors: molecular mechanisms and therapeutic implications”.

Modification of DNA structure by reactive nitrogen species as a result of 2-methoxyestradiol–induced neuronal nitric oxide synthase uncoupling in metastatic osteosarcoma cells

2-methoxyestradiol (2-ME) is a physiological anticancer compound, metabolite of 17β-estradiol. Previously, our group evidenced that from mechanistic point of view one of anticancer mechanisms of action of 2-ME is specific induction and nuclear hijacking of neuronal nitric oxide synthase (nNOS), resulting in local generation of nitro-oxidative stress and finally, cancer cell death.The current study aims to establish the substantial mechanism of generation of reactive nitrogen species by 2-ME. We further achieved to identify the specific reactive nitrogen species involved in DNA-damaging mechanism of 2-ME.The study was performed using metastatic osteosarcoma 143B cells. We detected the release of biologically active (free) nitric oxide (•NO) with concurrent measurements of peroxynitrite (ONOO−) in real time in a single cell of 143B cell line by using •NO/ONOO− sensitive microsensors after stimulation with calcium ionophore. Detection of nitrogen dioxide (•NO2) and determination of chemical rate constants were carried out by a stopped-flow technique. The affinity of reactive nitrogen species toward the guanine base of DNA was evaluated by density functional theory calculations. Expression and localization of nuclear factor NF-kB was determined using imaging cytometry, while cell viability assay was evaluated by MTT assay.Herein, we presented that 2-ME triggers pro-apoptotic signalling cascade by increasing cellular reactive nitrogen species overproduction – a result of enzymatic uncoupling of increased nNOS protein levels. In particular, we proved that ONOO− and •NO2 directly formed from peroxynitrous acid (ONOOH) and/or by auto-oxidation of •NO, are inducers of DNA damage in anticancer mechanism of 2-ME. Specifically, the affinity of reactive nitrogen species toward the guanine base of DNA, evaluated by density functional theory calculations, decreased in the order: ONOOH > ONOO− > •NO2 > •NO.Therefore, we propose to consider the specific inducers of nNOS as an effective tool in the field of chemotherapy.

Acetaldehyde-induced oxidative modifications and morphological changes in isolated human erythrocytes: an in vitro study.

Acetaldehyde is a toxic, mutagenic and carcinogenic metabolite of alcohol which can bind to proteins, DNA and several other cellular macromolecules. Chronic alcohol consumption increases intracellular acetaldehyde levels which enhances the generation of reactive oxygen and nitrogen species (ROS and RNS). In this study, we have examined the effect of acetaldehyde on human erythrocytes under in vitro conditions. Treatment of human erythrocytes with different concentrations of acetaldehyde (0.05-2mM) for 24h at 37°C increased intracellular generation of ROS and RNS. It also increased oxidation of proteins and lipids but decreased glutathione, total sulphhydryl and free amino group content. Methemoglobin level was increased accompanied by a decrease in methemoglobin reductase activity. Acetaldehyde impaired the antioxidant defence system and lowered the total antioxidant capacity of the cell. It decreased the activity of metabolic and membrane-bound enzymes and altered erythrocyte morphology. Our results show that acetaldehyde enhances the generation of ROS and RNS that results in oxidative modification of cellular components. This will lower the oxygen transporting ability of blood and shorten erythrocyte lifespan (red cell senescence).

Protective effect of catechin on pentachlorophenol-induced cytotoxicity and genotoxicity in isolated human blood cells.

Pentachlorophenol (PCP) is an organochlorine compound that is used as pesticide, biocide, and wood preservative. PCP is highly toxic and carcinogenic. It has been detected in food and several consumable products. The toxicity of PCP is thought to be due to generation of oxidative stress in cells. We examined whether the dietary antioxidant catechin can attenuate or protect human erythrocytes and lymphocytes against PCP-induced cytotoxicity and genotoxicity, respectively. Human erythrocytes were treated with increasing concentrations of catechin (0.05-2.5mM) for 30min followed by addition of 0.75mM PCP and further incubation for 4h at 37°C. Hemolysates were prepared and assayed for various biochemical parameters. Treatment with PCP alone increased the generation of reactive oxygen and nitrogen species, lipid and protein oxidation, and damaged the plasma membrane, when compared to PCP untreated (control) cells. It significantly decreased glutathione level, total sulfhydryl content, and cellular antioxidant power. PCP treatment lowered the activity of antioxidant enzymes and inhibited enzymes of glucose metabolism. However, prior incubation with catechin attenuated the PCP-induced changes in all these parameters in a catechin concentration-dependent manner. Scanning electron microscopy of erythrocytes confirmed these biochemical results. PCP treatment converted the normal discoidal erythrocytes to irregularly contracted cells, acanthocytes, and echinocytes but the presence of catechin inhibited these morphological changes and erythrocytes retained their biconcave shape to a large extent. Genotoxicity was studied in human lymphocytes by single-cell gel electrophoresis (comet assay). It showed strand breaks and longer comet tail length in PCP alone treated cells. The comet tail length was reduced in the catechin +PCP-treated lymphocytes showing that catechin protected cells from PCP-induced DNA damage. These results show that catechin protects human blood cells against PCP-induced oxidative damage.

Cold Plasma-Treated Ringer’s Saline: A Weapon to Target Osteosarcoma

Osteosarcoma (OS) is the main primary bone cancer, presenting poor prognosis and difficult treatment. An innovative therapy may be found in cold plasmas, which show anti-cancer effects related to the generation of reactive oxygen and nitrogen species in liquids. In vitro models are based on the effects of plasma-treated culture media on cell cultures. However, effects of plasma-activated saline solutions with clinical application have not yet been explored in OS. The aim of this study is to obtain mechanistic insights on the action of plasma-activated Ringer’s saline (PAR) for OS therapy in cell and organotypic cultures. To that aim, cold atmospheric plasma jets were used to obtain PAR, which produced cytotoxic effects in human OS cells (SaOS-2, MG-63, and U2-OS), related to the increasing concentration of reactive oxygen and nitrogen species generated. Proof of selectivity was found in the sustained viability of hBM-MSCs with the same treatments. Organotypic cultures of murine OS confirmed the time-dependent cytotoxicity observed in 2D. Histological analysis showed a decrease in proliferating cells (lower Ki-67 expression). It is shown that the selectivity of PAR is highly dependent on the concentrations of reactive species, being the differential intracellular reactive oxygen species increase and DNA damage between OS cells and hBM-MSCs key mediators for cell apoptosis.

Mitochondrial Genetics and Epigenetics in Osteoarthritis

During recent years, the significant influence of mitochondria on osteoarthritis (OA), the most common joint disease, has been consistently demonstrated. Not only mitochondrial dysfunction but also mitochondrial genetic polymorphisms, specifically the mitochondrial DNA haplogroups, have been shown to have an important influence on different OA-related features, including the prevalence, severity, incidence, and progression of the disease. This influence could probably be mediated by the role of mitochondria in the regulation of different processes involved in the pathogenesis of OA, such as energy production, the generation of reactive oxygen and nitrogen species, apoptosis, and inflammation. The regulation of these processes is at least partially controlled by the bi-directional communication between the nucleus and mitochondria, which permits the regulation of adaptation to a wide range of stressors and the maintenance of cellular homeostasis. This bi-directional communication consists of an “anterograde regulation” by which the nucleus regulates mitochondrial biogenesis and activity and a “retrograde regulation” by which both mitochondria and mitochondrial genetic variation exert a regulatory signaling control over the nuclear epigenome, which leads to the modulation of nuclear genes. Throughout this mini review, we will describe the evidence that demonstrates the profound influence of the mitochondrial genetic background in the pathogenesis of OA, as well as its influence on the nuclear DNA methylome of the only cell type present in the articular cartilage, the chondrocyte. This evidence leads to serious consideration of the mitochondrion as an important therapeutic target in OA.

Indoleamine 2, 3-dioxygenase 1enhanceshepatocytes ferroptosis in acute immune hepatitis associated with excess nitrative stress

Ferroptosis is a recently recognized form of regulated cell death that is characterized by lipid peroxidation. However, the molecular mechanisms of ferroptosis in acute immune hepatitis (AIH) are largely unknown. In this study, we investigated the classical ferroptotic events in the livers of mice with concanavalin A (ConA) to induce AIH. The dramatically upregulated gene indoleamine 2, 3-dioxygenase 1 (IDO1) was identified with AIH, and its role in generation of ferroptosis and reactive nitrogen species (RNS) was assessed both in vitro and in vivo by genetic deletion or pharmacologic inhibition of IDO1. We observed that ferroptosis contributed to the ConA-induced hepatic damage, which was confirmed by the therapeutical effects of ferroptosis inhibitor (ferrostatin-1). Noteworthy, upregulation of hepatic IDO1 and nitrative stress in ConA-induced hepatic damage were also remarkably inhibited by the ferroptosis abolishment. Additionally, IDO1 deficiency contributed to ferroptosis resistance by activating solute carrier family 7 member 11 (SLC7A11; also known as xCT) expression, accompanied with the reductions of murine liver lesions and RNS. Meanwhile, IDO inhibitor 1-methyl tryptophan alleviated murine liver damage with the reduction of inducible nitric oxide synthase and 3-nitrotyrosine expression. Consistent with the results in vivo, hepatocytes-specific knockdown of IDO1 led to ferroptosis resistance upon exposure to ferroptosis-inducing compound (Erastin) in vitro, whereas IDO1 overexpression aggravated the classical ferroptotic events, and the RNS stress. Overall, these results revealed a novel molecular mechanism of ferroptosis with the key feature of nitrative stress in ConA-induced liver injury, and also identified IDO1-dependent ferroptosis as a potential target for the treatment of AIH.

Pretomanid for the treatment of pulmonary tuberculosis.

Discovering novel drugs active against Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is currently one of the most unmet medical needs. In this context, pretomanid (PA-824), a novel nitroimidazole prodrug that targets both replicating and nonreplicating cells, is being developed by TB Alliance under license from Novartis. In replicating Mtb, pretomanid inhibits mycolic acid biosynthesis, which is an important building block of Mtb cell wall. Under nonreplicating conditions, pretomanid is reduced by deazaflavin-dependent nitroreductase, leading to generation of reactive nitrogen species exhibiting potent antimycobacterial activity. The U.S. Food and Drug Administration (FDA) has approved pretomanid under the Limited Population Pathway for Antibacterial and Antifungal Drugs (LPAD pathway) for treatment of adult patients with treatment-intolerant or nonresponsive multidrug-resistant TB and extensively drug-resistant TB in combination with bedaquiline and linezolid as part of the oral.

MiADMSA minimizes arsenic induced bone degeneration in Sprague Dawley rats

Arsenic considered as one of the most hazardous chemical while arsenic poisoning is also one of the serious medical issues worldwide. Long term arsenic exposure is associated with bone degeneration. The exact mechanism involving arsenic induced bone degeneration remains unclear but, plentiful literature suggested that oxidative/nitrosative stress caused by generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) is one of the leading causes.Various treatment strategies are available for bone degeneration however, the suitable treatment for arsenic induced bone degeneration still lacks. In the current investigation, we evaluated the efficacy of chelation against arsenic induced bone degeneration in experimental rats. Male Sprague Dawley rats were exposed to sodium arsenite and dimethylarsinic acid (DMA) (50 ppm) for 18 weeks. After arsenic exposure, animals were treated with Monoisoamyl dimercaptosuccinic acid (MiADMSA) for three course of treatment (50 mg/kg, p.o., once daily for 5 days) with an interval of one week between two courses of treatment. MiADMSA minimizes the bone degeneration through reduction of oxidative stress (Reactive Oxygen Species, Reactive Nitrogen Species, and thiobarbituric reactive substances), alteration of antioxidant status (rGSH, Superoxide dismutase, Catalase) which led to the depletion in the levels of inflammatory markers like TNFα and IL-1β and alteration in the bone remodelling biomarkers like ALP, RANKL, and Runx2. It can be concluded from this study that MiADMSA could be an effective therapeutic strategy against arsenic induced bone degeneration and the possible mechanism could be the chelation of arsenic accompanied by the reduction in oxidative stress and inflammation.

Responses of tropical tree species to urban air pollutants: ROS/RNS formation and scavenging

Air pollution in an urban environment is the major stress factor for vegetation due to the direct generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). To quantify urban air pollution-induced ROS/RNS formation, damage and detoxification, nine different biochemical parameters related to free radical formation, scavenging and membrane damage were estimated in twelve tropical tree species. The experiment was performed in three different seasons at four distinct urban environments in Varanasi city located in the Indo-Gangetic plain of India. Redundancy analysis was performed to statistically assess the relationship between air pollutants (PM2.5, NO2, SO2 and O3) and temperature with ROS/RNS generation and their detoxification. Significant effects of air pollution exposure and temperature on ROS/RNS formation, scavenging and membrane damage were recorded with increasing pollution load in the city for all the tree species. The extent of variability (47–87%) in responses of different tree species was due to their intrinsic ability to scavenge free radicals which minimized the membrane damage. PM2.5, NO2 and O3 were identified as major pollutants that influenced trees to different extents in regulating ROS/RNS. However, the response was maximum against NO2 (34–72%) followed by PM2.5 (16–64%) and O3 (3–31%), indicating that under urban environment, trees are considerably sensitive to the combined effects of both particulate and gaseous pollutants. Reactive oxygen intermediate release, total free radical scavenging activity, NO scavenging activity and membrane stability index were identified as major parameters which showed distinct responses with increasing pollution load. Caesalpinia sappan, Ficus religiosa and Albizia lebbeck were identified as most tolerant tree species having higher ROS/RNS scavenging potential resulted in lower membrane damage. Thus responses of urban trees to air pollution are governed by their intrinsic defence mechanisms to scavenge ROS/RNS by maintaining the membrane integrity through integrated cross-talk between different antioxidative pathways.

Thiram-induced cytotoxicity and oxidative stress in human erythrocytes: an in vitro study

Tetramethylthiuram disulfide, commonly known as thiram, is an organosulfur compound which is used as a bactericide, fungicide and ectoparasiticide to prevent disease in seeds and crops. Being a fungicide there is a high probability of human occupational exposure to thiram and also via consumption of contaminated food. In this work, the cytotoxicity of thiram was studied under in vitro conditions using human erythrocytes as the cellular model. Erythrocytes were incubated with different concentrations of thiram (25–500 μM) for 4 h at 37 °C. Control cells (thiram untreated) were similarly incubated at 37 °C. Whole cells and hemolysates were analyzed for various biochemical parameters. Treatment of erythrocytes with thiram increased protein and lipid oxidation and hydrogen peroxide level in hemolysates but decreased glutathione and total sulfhydryl group content. This was accompanied by hemoglobin oxidation, heme degradation and release of free iron. Activities of all major antioxidant enzymes were inhibited. The antioxidant power of thiram treated erythrocytes was lowered resulting in decreased metal reducing and free radical quenching ability. These results suggest that thiram enhances the generation of reactive species that cause oxidative modification of cell components. This was confirmed by experiments that showed enhanced generation of reactive oxygen and nitrogen species in thiram treated erythrocytes. Activities of marker enzymes of glucose metabolism and erythrocyte membrane were also inhibited. All effects were seen in a thiram concentration-dependent manner. Electron microscopy further supported the damaging effect of thiram on erythrocytes. Thus thiram induces oxidative stress condition in human erythrocytes and causes oxidative modification of cell components.

Taurine attenuates Cr(VI)-induced cellular and DNA damage: an in vitro study using human erythrocytes and lymphocytes.

Hexavalent chromium [(Cr(VI)] is widely used in several industries, but human exposure results in multiple organ toxicity. Enhanced generation of free radicals and reactive species is thought to play a key role in Cr(VI)-induced toxicity. We have examined the effect of taurine, a simple sulphur-containing amino acid and an antioxidant, on potassium dichromate [K2Cr2O7, a Cr(VI) compound]-induced cytotoxicity and genotoxicity in human blood cells. Erythrocytes were treated with K2Cr2O7, either alone or after incubation with different concentrations of taurine. Treatment of erythrocytes with K2Cr2O7 alone led to marked increase in generation of reactive oxygen and nitrogen species, lipid and protein oxidation. This was accompanied by decrease in total sulfhydryl and glutathione content and lowered antioxidant power of the cells. This suggests that Cr(VI) induces oxidative stress in the cells. Incubation of erythrocytes with taurine prior to addition of K2Cr2O7, resulted in a concentration-dependent decrease in the generation of reactive oxygen and nitrogen species, mitigation of oxidative stress and amelioration of antioxidant power of these cells. It also restored the activities of several metabolic, antioxidant and membrane-bound enzymes. Cr(VI)-induced damage to erythrocyte membrane and lymphocyte DNA was also significantly attenuated by prior administration of taurine. These results suggest that taurine can function as a chemoprotectant against Cr(VI)-induced oxidative injury and can be potentially used to mitigate the toxic effects of this transition metal ion.