Elevated H2O2 Levels Research Articles

Markers of Oxidative Stress in the Saliva of Type 2 Diabetic Patients

Objective: Diabetes mellitus is associated with increased prevalence of oral diseases for which reactive oxygen species have been implicated. The saliva contains protective antioxidants which statutorily curtail these destructive oxygen molecules. A functional compromise of the antioxidants may precipitate oxidative stress leading to the increased oral disease susceptibility. However, salivary markers of oxidative stress have not been sufficiently studied in the diabetics. Methods: A total of 166 adults were recruited for this study. They comprised of 95 Type 2 diabetic patients and 71 healthy non-diabetic controls. About 3 ml of unstimulated saliva samples were collected from participants and processed, levels of salivary H2O2, NO and MDA were measured using spectrophotometry method and compared between the two groups. Data was analysed using t-test, logistic regression and receiver operating characteristics (ROC) with statistical significance set at p<0.05. Results: Salivary H2O2 (p=0.024) and NO (p=0.002) were significantly higher in the diabetic patients when compared to the healthy non-diabetic control group. Binary logistic regression showed that patients with Type 2 diabetic mellitus are more likely to have elevated salivary H2O2 (OR= 1.013; p=0.025) and NO (OR=1.016; p=0.003) levels. ROC analysis showed statistically significant performance of salivary NO levels in distinguishing between T2DM patients and healthy controls. Conclusions: Higher levels of oxidative stress markers including salivary H2O2 and NO in the diabetic groups could be a pointer to the characteristic high prevalence of oral diseases in diabetes mellitus, given that oxidative stress predisposes to disease vulnerability. This calls for increased attention to oral health in diabetes management to minimise co-morbidity.

Peroxiredoxin 6 Knockout Mice Demonstrate Anxiety Behavior and Attenuated Contextual Fear Memory after Receiving Acute Immobilization Stress.

Stress can elicit glucocorticoid release to promote coping mechanisms and influence learning and memory performance. Individual memory performance varies in response to stress, and the underlying mechanism is not clear yet. Peroxiredoxin 6 (PRDX6) is a multifunctional enzyme participating in both physiological and pathological conditions. Several studies have demonstrated the correlation between PRDX6 expression level and stress-related disorders. Our recent finding indicates that lack of the Prdx6 gene leads to enhanced fear memory. However, it is unknown whether PRDX6 is involved in changes in anxiety response and memory performance upon stress. The present study reveals that hippocampal PRDX6 level is downregulated 30 min after acute immobilization stress (AIS) and trace fear conditioning (TFC). In human retinal pigment epithelium (ARPE-19) cells, the PRDX6 expression level decreases after being treated with stress hormone corticosterone. Lack of PRDX6 caused elevated basal H2O2 levels in the hippocampus, basolateral amygdala, and medial prefrontal cortex, brain regions involved in anxiety response and fear memory formation. Additionally, this H2O2 level was still high in the medial prefrontal cortex of the knockout mice under AIS. Anxiety behavior of Prdx6−/− mice was enhanced after immobilization for 30 min. After exposure to AIS before a contextual test, Prdx6−/− mice displayed a contextual fear memory deficit. Our results showed that the memory performance of Prdx6−/− mice was impaired when responding to AIS, accompanied by dysregulated H2O2 levels. The present study helps better understand the function of PRDX6 in memory performance after acute stress.

Epigallocathechin-O-3-Gallate Inhibits Trypanothione Reductase of Leishmania infantum, Causing Alterations in Redox Balance and Leading to Parasite Death.

Leishmania infantum is a protozoan parasite that causes a vector borne infectious disease in humans known as visceral leishmaniasis (VL). This pathology, also caused by L. donovani, presently impacts the health of 500,000 people worldwide, and is treated with outdated anti-parasitic drugs that suffer from poor treatment regimens, severe side effects, high cost and/or emergence of resistant parasites. In previous works we have disclosed the anti-Leishmania activity of (-)-Epigallocatechin 3-O-gallate (EGCG), a flavonoid compound present in green tea leaves. To date, the mechanism of action of EGCG against Leishmania remains unknown. This work aims to shed new light into the leishmanicidal mode of action of EGCG. Towards this goal, we first confirmed that EGCG inhibits L. infantum promastigote proliferation in a concentration-dependent manner. Second, we established that the leishmanicidal effect of EGCG was associated with i) mitochondria depolarization and ii) decreased concentration of intracellular ATP, and iii) increased concentration of intracellular H2O2. Third, we found that the leishmanicidal effect and the elevated H2O2 levels induced by of EGCG can be abolished by PEG-catalase, strongly suggesting that this flavonoid kills L. infantum promastigotes by disturbing their intracellular redox balance. Finally, we gathered in silico and in vitro evidence that EGCG binds to trypanothione reductase (TR), a central enzyme of the redox homeostasis of Leishmania, acting as a competitive inhibitor of its trypanothione substrate.

SlERF52 regulates SlTIP1;1 expression to accelerate tomato pedicel abscission.

Abscission of plant organs is induced by developmental signals and diverse environmental stimuli and involves multiple regulatory networks, including biotic or abiotic stress-impaired auxin flux in the abscission zone (AZ). Depletion of auxin activates AZ ethylene (ETH) production and triggers acceleration of abscission, a process that requires hydrogen peroxide (H2O2). However, the interaction between these networks and the underlying mechanisms that control abscission are poorly understood. Here, we found that expression of tonoplast intrinsic proteins, which belong to the aquaporin (AQP) family in the AZ was important for tomato (Solanum lycopersicum) pedicel abscission. Liquid chromatography-tandem mass spectrometry and in situ hybridization revealed that SlTIP1;1 was most abundant and specifically present in the tomato pedicel AZ. SlTIP1;1 localized in the plasma membrane and tonoplast. Knockout of SlTIP1;1 resulted in delayed abscission, whereas overexpression of SlTIP1;1 accelerated abscission. Further analysis indicated that SlTIP1;1 mediated abscission via gating of cytoplasmic H2O2 concentrations and osmotic water permeability (Pf). Elevated cytoplasmic levels of H2O2 caused a suppressed auxin signal in the early abscission stage and enhanced ETH production during abscission. Furthermore, we found that increasing Pf was required to enhance the turgor pressure to supply the break force for AZ cell separation. Moreover, we observed that SlERF52 bound directly to the SlTIP1;1 promoter to regulate its expression, demonstrating a positive loop in which cytoplasmic H2O2 activates ETH production, which activates SlERF52. This, in turn, induces SlTIP1;1, which leads to elevated cytoplasmic H2O2 and water influx.

Reactive oxygen species during heart regeneration in zebrafish: Lessons for future clinical therapies.

In humans, myocardial infarction (MI) is associated with irreversible damage to heart tissue, resulting in increased morbidity and mortality in patients. By comparison, the zebrafish (Danio rerio) is capable of repairing damaged and injured hearts by activating a full regenerative response. By studying model organisms that can regenerate loss heart tissue following injury, such as the zebrafish, a greater insight will be gained into the molecular pathways that can induce and sustain a regenerative response following injury. There is hope that such information may lead to new treatments or therapies aimed at stimulating a better regenerative response in humans that have suffered heart attacks. Recent findings in zebrafish have highlighted an important role for sustained elevated levels of Reactive Oxygen Species (ROS), including hydrogen peroxide (H2O2) in the promotion of a regenerative response. Given that elevated levels of H2O2 can be harmful, simply elevating ROS levels directly may not be easy or practical to translate clinically. An alternative approach would be to identify the critical downstream targets of ROS in the promotion of heart regeneration, and then target these clinically using drugs. One such family of potential downstream targets of ROS during heart regeneration are the family of protein tyrosine phosphatases (PTPs), which are known to be exquisitely sensitive to redox regulation and whose inhibition have been linked to the promotion of heart regeneration in zebrafish. In this review, we present an overview of the zebrafish as a model organism for studying cardiac regeneration, including the molecular mechanisms by which cardiac regeneration occurs in response to injury. We then present recent findings linking elevated ROS levels to heart regeneration and their potential downstream targets, the PTPs, including protein tyrosine phosphatase 1B (PTP1B) and the dual specificity phosphatase 6 (DUSP6) in the promotion of heart regeneration.

Tunable electrochemistry and efficient antibacterial activity of plant-mediated copper oxide nanoparticles synthesized by Annona squamosa seed extract for agricultural utility.

The present report deals with the synthesis of plant-mediated copper oxide nanoparticles (pm-CuO NPs) from Annona squamosa aqueous seed extract for effective antibacterial activity and the further utilization of this as a platform for the electrocatalytic determination of hydrogen peroxide (H2O2) for applications in the agricultural domain. The structural, optical and morphological characteristics of the synthesized pm-CuO NPs were analyzed by UV-Vis, XRD, FT-IR, AFM, SEM, TEM, HR-TEM and EDX. After this, pm-CuO NPs were preliminarily investigated for antibacterial activity on Gram-positive and Gram-negative bacterial strains, and further, their activity was validated for assessing their antibacterial efficiency on the Xanthomonas oryzae, a plant pathogenic bacteria strain, and the obtained results showed that pm-CuO NPs have potency as an effective antibacterial agent for the treatment of the bacterial blight of rice caused by X. oryzae in the rice crop, which reduces the rice crop productivity. Further, pm-CuO NPs were electrophoretically deposited onto an indium–tin–oxide (ITO) glass substrate and assessed for the electro-oxidation of H2O2 by cyclic voltammetry (CV), and from this it was proved that pm-CuO NPs had a very high electrochemical sensitivity of 49 μA μM−1 cm−2 towards H2O2 and a low detection limit of 574 μM, with these responses obtained under optimized experimental conditions. Thus, pm-CuO NPs also provide a potential sensing platform for electrochemical studies to detect H2O2 produced during plant stress surroundings to properly manage crops susceptible to oxidative damage by elevated H2O2 levels during stress.

Nitric oxide donor, sodium nitroprusside, mitigates mercury toxicity in different cultivars of soybean

The present study reveals the effect of mercury (Hg) and sodium nitroprusside (SNP) on plant growth and metabolism in soybean cultivars (Pusa-24, Pusa-37and Pusa-40). Mercury stress decreased growth and biomass yield, and gas exchange attributes in all soybean cultivars. External supplementation of SNP mitigated Hg toxicity by improving growth and gas exchange parameters. Electrolyte leakage (EL) increased accompanied with elevated levels of malondialdehyde (MDA) and H2O2 under Hg stress, however, they were found to be reduced in all cultivars upon the exogenous application of SNP. The activities of anti-oxidative enzymes, superoxide dismutase and catalase (SOD and CAT) and those enzymes involved in the ascorbate-glutathione pathway were impaired by Hg stress, but they were regulated by the application of SNP. Accumulation of Hg and NO in the shoots and roots were also regulated by the application of NO. Although, all three cultivars were affected by Hg stress, Pusa-37 was relatively less affected. Mercury stress affected the growth and development of different soybean cultivars, but Pusa-37 being tolerant was less affected. Pusa-37 was found to be more responsive to SNP than Pusa-24, Pusa-40 under Hg toxicity. The external supplementation of SNP could be a sustainable approach to economically utilize Hg affected soils.

Evaluation of the Acute Hepatoprotective Potential of Hydroethanolic Extract of Duranta erecta L. Parts.

Liver disease is a major health problem and its treatment is costly in most developing countries with attendant adverse effects. This study aimed at determining the acute hepatoprotective efficacy of Duranta erecta hydroethanolic extracts of leaves, ripe and unripe fruits against CCl4-, and acetaminophen-induced hepatotoxicity in animals. Materials and Methods. CCl4 (1 mL/kg body weight in olive oil) and acetaminophen (500 mg/kg b.wt) were used to induce hepatotoxicity in the animals. Animals were treated with extracts at 250 mg/kg b.wt and standard drug, silymarin (100 mg/kg), for 7 days. Hepatoprotective efficacy was assessed by assaying serum biochemical markers such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (γGT), bilirubin (Bil), antioxidative biomarkers including reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione transferase (GST), superoxide dismutase (SOD), malondialdehyde (MDA), hydrogen peroxidase (H202), and nitric oxide (NO), as well as histological observations. Results. Exposure of the animals to CCl4 and acetaminophen resulted in liver injury as evidenced by elevated ALT, AST, ALP, γGT, Bil, MDA, H2O2, and NO levels with resultant derangement in liver microarchitecture. Pretreatment with hydroethanolic extracts, particularly ripe fruits of Duranta erecta, led to a reduction in these indicators and an increase in GSH, GPx, GST, and SOD levels. Biochemical data were supported by improvement in liver structure. Conclusion. The findings suggest that hydroethanolic Duranta erecta ripe fruits extract possesses hepatoprotective and antioxidative activities against CCl4- and acetaminophen-induced toxicity and could be developed as a potent agent for drug-induced liver diseases.

Physiological and structural responses of the seagrassCymodocea nodosato titanium dioxide nanoparticle exposure

AbstractThe extensive application of titanium dioxide nanoparticles (TiO2NPs) has raised concern about its environmental risks. The present study aims to elucidate TiO2NP ecotoxicity, by assessing effects on seagrasses at environmentally relevant concentrations. Changes in physiological and structural cell traits ofCymodocea nodosaleaves, treated with TiO2NPs at 0.0015–1.5 mg l−1for eight consecutive days, were investigated. Intracellular levels of hydrogen peroxide (H2O2) increased significantly, even early during the lowest exposure, despite an up-regulation of H2O2-scavenging enzyme activity. Actin filaments (AFs) and endoplasmic reticulum (ER) were affected in a concentration- and time-dependent pattern, while no changes in microtubule organization and cell ultrastructure were detected. The lowest effect concentrations for AF and ER impairment were 0.15 and 1.5 mg l−1, respectively; for cell death, these were 0.15–1.5 mg l−1, depending on leaf age, and for leaf elongation inhibition 0.15 mg l−1. Thus, elevated H2O2level can be considered as an early warning biomarker for TiO2NPs, while leaf elongation, AF and ER impairment are also reliable indicators. A risk quotient greater than 1 was estimated; thus, TiO2NPs might present a significant potential environmental risk. Our findings can be utilized for monitoring pollution levels in coastal environments.

Coping with stress: role of Arabidopsis phytoglobins in defence against Sclerotinia sclerotiorum

Phytoglobins (Pgbs) are multifaceted stress-responsive proteins implicated in regulating various physiological and stress-responsive pathways in plants. Previous work has demonstrated NO dioxygenase and peroxidase-like activity of Arabidopsis phytoglobin 3 (AHb3) and its potential role in defense against Sclerotinia sclerotiorum. The work reported here highlights the significance of the other two classes of Arabidopsis phytoglobins (AHb1 and AHb2) in response to S. sclerotiorum. Constitutive expression of AHb1 (OEAHb1) and AHb2 (OEAHb2) conferred marginal tolerance towards S. sclerotiorum whereas respective knockdown (RNAi) lines displayed enhanced susceptibility, with AHb1 RNAi (RNAi-1) lines being more susceptible in comparison to AHb2 RNAi (RNAi-2) lines. Interestingly, transgenic lines with a simultaneous reduction in the transcripts of AHb1 and AHb2 (RNAi-F) displayed greater disease spread in comparison to individual knockdown lines indicative of their additive effect. The enhanced susceptibility upon pathogen challenge correlated with the elevated NO and H2O2 levels in these lines. Furthermore, detailed structural analysis hints towards an alternate mechanism of NO dioxyegnation by AHbs. Taken together, the current investigation illustrates the NO dioxygenase and peroxidase-like activity of AHbs and highlights their role in defense against stem rot pathogen S. sclerotiorum.

Hydrogen peroxide homeostasis provides beneficial micro-environment for SHR-mediated periclinal division in Arabidopsis root.

The precise regulation of asymmetric cell division (ACD) is essential for plant organogenesis. In Arabidopsis roots, SHORT-ROOT (SHR) functions to promote periclinal division in cortex/endodermis initials, which generate the ground tissue patterning. Although multiple downstream transcription factors and interplaying hormone pathways have been reported, the cellular mechanism that affects SHR-mediated periclinal division remains largely unclear. Here, we found that SHR can substantially elevate reactive oxygen species (ROS) levels in Arabidopsis roots by activating respiratory burst oxidase homologs (RBOHs). Among the ROS products, hydrogen peroxide (H2 O2 ) rather than superoxide (O2- ) was shown to play a critical role in SHR-mediated periclinal division. Scavenging H2 O2 could markedly impair the ability of SHR to induce periclinal division. We also show that salicylic acid (SA) can promote H2 O2 production by repressing CAT expression, which greatly increased periclinal division in root endodermis. As a result, middle cortex was more frequently formed in the endodermis of snc1, a mutant with accumulated endogenous SA and H2 O2 . In addition to RBOHs, SHR also activated the SA pathway, which might contribute to the elevated H2 O2 level induced by SHR. Thus, our data suggest a mechanism by which SHR creates the optimal micro-environment for periclinal division by maintaining ROS homeostasis in Arabidopsis roots.

StRac1 plays an important role in potato resistance against Phytophthora infestans via regulating H2O2 production

ROP GTPases (Rho-related GTPases from plant), a unique subgroup of the Rho family in plants, is a group of key regulators of different signaling pathways controlling plant growth and development, cell polarity and differentiation, and plant response against biotic and abiotic stresses. The present study determined the potential regulatory mechanism of potato ROP GTPase (StRac1) against Phytophthora infestans (P. infestans) infection. Protein secondary structure analysis indicated that StRAC1 is a Rho GTPase. The expression level of StRac1 was variable in different tissues of potato, with the highest expression in young leaves of both Shepody and Hutou potato varieties. After challenging with P. infestans, the expression level of StRac1was higher in resistance varieties Zihuabai and Longshu 7 than in susceptible varieties Shepody and Desiree. StRAC1 fusion with GFP subcellularly localized at the plasma membrane (PM) in tobacco epidermal cells. The potato with transient or stable over-expression of CA-StRac1 (constitutively active form of StRac1)exhibited a dramatic enhancement of its resistance against P. infestans infections. The increased resistance level in transgenic potato was accompanied with elevated H2O2 levels. Importantly, silencing StRac1 via virus-induced gene silencing (VIGS) in potato resulted in higher susceptibility to P. infestans infection than in control plants. In summary, our data reveal that StRac1 regulates potato resistance against P. infestans via positively modulating the accumulation of H2O2.

In vivo assessment of silver nanoparticle induced reactive oxygen species reveals tissue specific effects on cellular redox status in the nematode Caenorhabditis elegans

The current study provides an in vivo analysis of the production of reactive oxygen species (ROS) and oxidative stress in the nematode Caenorhabditis elegans following exposure to EU reference silver nanoparticles NM300K and AgNO3. Induction of antioxidant defenses was measured through the application of a SOD-1 reporter, and the HyPer and GRX biosensor strains to monitor changes in the cellular redox state. Both forms of Ag resulted in an increase in sod-1 expression, elevated H2O2 levels and an imbalance in the cellular GSSG/GSH redox status. Microscopy analysis of the strains revealed that AgNO3 induced ROS-related effects in multiple tissues, including the pharynx, intestinal cells and muscle tissues. In contrast, NM300K resulted in localized ROS production and oxidative stress, specifically in tissues surrounding the intestinal lumen. This indicates that Ag from AgNO3 exposure was readily transported across the whole body, while Ag or ROS from NM300K exposure was predominantly confined within the luminal tissues. Concentrations resulting in an increase in ROS production and changes in GSSG/GSH ratio were in line with the levels associated with observed physiological toxic effects. However, sod-1 was not induced at the lowest Ag concentrations, although reprotoxicity was seen at these levels. While both forms of Ag caused oxidative stress, impaired development, and reprotoxicity, the results suggest different involvement of ROS production to the toxic effects of AgNO3versus NM300K.

Photobiomodulation (450 nm) alters the infection of periodontitis bacteria via the ROS/MAPK/mTOR signaling pathway

We aimed to investigate the effects of photobiomodulation (PBM) on periodontitis. A periodontitis model was established via Porphyromonas gingivalis infection in beagles. Mandibular second and third premolars were removed, and implants were positioned immediately after tooth extraction. Left gingiva was irradiated with PBM (450 nm) as the LG group, and right side without irradiation was regarded as the CG (control) group. PBM treatment increased oxidative stress by increasing the levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS). The elevated levels of H2O2 (a biomarker of oxidative stress) and the free radicals (NO• and O2•–) reduced the concentration of dominant pathogens and regulated ROS/RNS/AMP-activated protein kinase (AMPK)/mTOR pathway by affecting p-AMPK, Runt-related transcription factor 2 (RUNX2), p-c-Jun N-terminal kinase (JNK)/mammalian target of rapamycin (mTOR), and acetyl-CoA carboxylase 1 (ACC1). PBM therapy increased salivary levels of interleukin-1 receptor antagonist (IL-1ra), interleukin (IL)-10, total antioxidant capacity (TAC) and catalase (CAT), and reduced the levels of tumor necrosis factor (TNF)α and interleukin (IL)-1β, malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) (p < 0.05). All the results contributed to preventing periodontitis infection. PBM therapy improved bone mineral density and implant osseointegration by controlling dominant pathogens invasion via the upregulation of salivary anti-inflammatory and antioxidant defense by affecting ROS/RNS/AMPK/mTOR signaling pathway.

H2O2 and NO are involved in trehalose-regulated oxidative stress tolerance in cold-stressed tomato plants

Cold adversely affects tomato (Solanum lycopersicum) growth and yield during winter and early spring in northern China. Trehalose (Tre) is a growth regulator that is widely used to enhance plant stress tolerance. However, there are few reports on the mechanistic role of Tre in regulating tomato cold tolerance or the interactions between hydrogen peroxide (H2O2) and nitric oxide (NO) in Tre-induced cold stress tolerance in plants. Here, we explored the role of Tre in tomato cold tolerance and evaluated whether H2O2 and NO were involved in this regulation. Tre pretreatment significantly upregulated superoxide dismutase (Cu/Zn SOD) and glutathione reductase (GR1) transcription and increased catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities under normal temperatures. Under cold stress, Tre pretreatment dramatically elevated Cu/Zn SOD and CAT1 transcription and increased SOD and CAT activities. Tre pretreatment reduced membrane lipid peroxidation and alleviated plant growth inhibition caused by cold stress conditions. Under normal temperatures, Tre pretreatment upregulated the expression of respiratory burst oxidase homolog1 (RBOH1), nitrate reductase (NR), and nitric oxide synthase (NOS) and elevated H2O2 and NO levels. Treating tomato leaves with H2O2 and NO scavengers [dimethylthiourea (DMTU) and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), respectively] significantly diminished Tre-mediated alleviation of membrane lipid peroxidation. The effect of H2O2 on reducing cold stress-induced damage in tomato was essentially abolished by cPTIO treatment. These results indicated that exogenous Tre enhanced cold stress tolerance in tomato by regulating the antioxidant defense system. Tre may act as an exogenous inducer of H2O2 and NO that regulate antioxidase gene expression and activities to promote plant responses to cold stress, enhance cold stress tolerance, and reduce membrane lipid peroxidation and cellular injury. NO may act downstream of H2O2 to mediate Tre-regulated tomato oxidative stress tolerance under cold stress.

Chronic excessive Zn intake increases the testicular sensitivity to high ambient temperature in Bama miniature pigs

Zinc (Zn) can accumulate in the body of wild animal and human through bio-magnification effects in the food chain to pose chronic toxicity. Male spermatogenesis was sensitive to excessive Zn and elevated temperature. This study aimed to examine whether or not excessive Zn intake caused testicular toxicity and estimate the interaction between Zn and high temperature (HT) in testes of Bama miniature pigs. Six-month-old pigs were pre-fed with or without additional Zn at 1500 mg/kg diet for 30 d and afterward subjected to HT at 40 °C for 5 h daily for 8 consecutive days. Blood samples were collected on d 31 and d 38 and testes were obtained on d 38 immediately after HT exposure. Our data showed both scrotal surface temperature (T) and body surface T increased after 5-h HT exposure (p < 0.05). Pigs fed with additional Zn showed germ cell loss, the decreased testes weight (p < 0.01) and the elevated testicular H2O2 level (p < 0.05) as exposed to HT. In additional Zn groups, the autophagosomes or autolysosomes were more frequently observed in the Leydig cells and abnormal acrosomes increased in spermatids. Additional Zn diet increased p62 protein level (p < 0.05), decreased testicular Zn concentration (p < 0.01) and down-regulated the relative mRNA expression of heme oxygenase 1 (p < 0.05). There were significant interactions between T and Zn on testes weight, the relative weight of testes, testosterone concentration on d 31, and the relative mRNA expression of Zn transporters 1 and 2. In conclusion, chronic excessive Zn diet impacted testicular Zn concentration and made the testes more vulnerable to heat, leading to testicular toxicity in Bama miniature pigs.

Polyamine homeostasis in tomato biotic/abiotic stress cross-tolerance

Adverse conditions and biotic strain can lead to significant losses and impose limitations on plant yield. Polyamines (PAs) serve as regulatory molecules for both abiotic/biotic stress responses and cell protection in unfavourable environments. In this work, the transcription pattern of 24 genes orchestrating PA metabolism was investigated in Cucumber Mosaic Virus or Potato Virus Y infected and cold stressed tomato plants. Expression analysis revealed a differential/pleiotropic pattern of gene regulation in PA homeostasis upon biotic, abiotic or combined stress stimuli, thus revealing a discrete response specific to diverse stimuli: (i) biotic stress-influenced genes, (ii) abiotic stress-influenced genes, and (iii) concurrent biotic/abiotic stress-regulated genes. The results support different roles for PAs against abiotic and biotic stress. The expression of several genes, significantly induced under cold stress conditions, is mitigated by a previous viral infection, indicating a possible priming-like mechanism in tomato plants pointing to crosstalk among stress signalling. Several genes and resulting enzymes of PA catabolism were stimulated upon viral infection. Hence, we suggest that PA catabolism resulting in elevated H2O2 levels could mediate defence against viral infection. However, after chilling, the activities of enzymes implicated in PA catabolism remained relatively stable or slightly reduced. This correlates to an increase in free PA content, designating a per se protective role of these compounds against abiotic stress.

Diesel Exhaust Particle Exposure Compromises Alveolar Macrophage Mitochondrial Bioenergetics

Diesel exhaust particles (DEPs) are known pathogenic pollutants that constitute a significant quantity of air pollution. Given the ubiquitous presence of macrophages throughout the body, including the lungs, as well as their critical role in tissue and organismal metabolic function, we sought to determine the effect of DEP exposure on macrophage mitochondrial function. Following daily DEP exposure in mice, pulmonary macrophages were isolated for mitochondrial analyses, revealing reduced respiration rates and dramatically elevated H2O2 levels. Serum ceramides and inflammatory cytokines were increased. To determine the degree to which the changes in mitochondrial function in macrophages were not dependent on any cross-cell communication, primary pulmonary murine macrophages were used to replicate the DEP exposure in a cell culture model. We observed similar changes as seen in pulmonary macrophages, namely diminished mitochondrial respiration, but increased H2O2 production. Interestingly, when treated with myriocin to inhibit ceramide biosynthesis, these DEP-induced mitochondrial changes were mitigated. Altogether, these data suggest that DEP exposure may compromise macrophage mitochondrial and whole-body function via pathologic alterations in macrophage ceramide metabolism.

A conserved motif liganding the [4Fe–4S] cluster in [4Fe–4S] fumarases prevents irreversible inactivation of the enzyme during hydrogen peroxide stress

Organisms have evolved two different classes of the ubiquitous enzyme fumarase: the [4Fe–4S] cluster-containing class I enzymes are oxidant-sensitive, whereas the class II enzymes are iron-free and therefore oxidant-resistant. When hydrogen peroxide (H2O2) attacks the most-studied [4Fe–4S] fumarases, only the cluster is damaged, and thus the cell can rapidly repair the enzyme. However, this study shows that when elevated levels of H2O2 oxidized the class I fumarase of the obligate anaerobe Bacteroides thetaiotaomicron (Bt-Fum), a hydroxyl-like radical species was produced that caused irreversible covalent damage to the polypeptide. Unlike the fumarase of oxygen-tolerant bacteria, Bt-Fum lacks a key cysteine residue in the typical “CXnCX2C″ motif that ligands [4Fe–4S] clusters. Consequently H2O2 can access and oxidize an iron atom other than the catalytic one in its cluster. Phylogenetic analysis showed that certain clades of bacteria may have evolved the full “CXnCX2C″ motif to shield the [4Fe–4S] cluster of fumarase. This effect was reproduced by the construction of a chimeric enzyme. These data demonstrate the irreversible oxidation of Fe–S cluster enzymes and may recapitulate evolutionary steps that occurred when microorganisms originally confronted oxidizing environments. It is also suggested that, if H2O2 is generated within the colon as a consequence of inflammation or the action of lactic acid bacteria, the inactivation of fumarase could potentially impair the central fermentation pathway of Bacteroides species and contribute to gut dysbiosis.

Supplementation of Salicylic Acid and Citric Acid for Alleviation of Cadmium Toxicity to Brassica juncea

The reported study investigated the interaction between salicylic acid (SA) and citric acid (CA) in cadmium (Cd)-stressed Brassica juncea plants. Seedling received Cd (0.6 mM) stress through soil at 5-day stage of growth. SA (0.01 mM) and CA (0.6 mM) treatments were applied at 25 days after sowing. Growth, photosynthesis, oxidative burst, and antioxidant systems were examined at 30-day stage of growth. Growth and photosynthetic parameters reduced significantly in the presence of Cd, and elevated levels of H2O2 were indicative of oxidative burst which resulted in decline of cell viability. Foliar spray of SA and CA alone or in combination mitigated the toxic effects generated by Cd and enhanced plant growth parameters. The inhibitory effects of Cd toxicity on width of stomatal pore resulted in reduced internal CO2 concentration and carbonic anhydrase activity which consequently limited the photosynthetic rate. SA and CA alleviated the inhibitory effect of Cd on photosynthesis by stimulating the stomatal activity and pore size. The Cd-generated oxidative burst was reduced via enhanced antioxidant activity (catalase, peroxidase, and superoxide dismutase) upon follow-up treatment with SA and CA alone or in combination. A combined dose of SA and CA countered Cd-induced damage by reducing levels of reactive oxygen species and strengthening plant antioxidant defense systems, which resulted in membrane stabilization and recovery from stress. Combined dose of SA and CA proved more effective than their individual application towards Cd stress which suggests an effective synergism between the two acids.