Changes In Reactive Oxygen Species Research Articles

Natural melanin-based nanoparticles with photothermal/photodynamic activities induce ovarian cancer cell death

To investigate the physicochemical characteristics of natural melanin-like nanoparticles (PDA NPs) and their synergistic anti-tumor efficacy with photothermal and photodynamic (PTT/PDT) therapy. The chemically synthesized PDA NPs were characterized using transmission electron microscope (TEM), dynamic light scattering (DLS) and Zeta potential analysis, and their photothermal and photodynamic properties were assessed with near-infrared excitation light (NIR). The antitumor efficacy of free PDA or PDA combined with NIR irradiation (0.7 and 1.0 W/cm2) was evaluated in ovarian cancer cells using flow cytometry, Cell Counting Kit-8 (CCK-8), and Transwell assay and in a mouse model bearing subcutaneous ovarian cancer xenograft. The synthesized PDA NPs showed a spherical morphology with diameters around 100 nm and a zeta potential of -20 mV. Upon NIR irradiation at 0.7 and 1.0 W/cm2, the particles underwent temperature changes (ΔT) of about 15 and 30 ℃, respectively, and produced a large amount of singlet oxygen, demonstrating their excellent PTT/PDT properties. In ovarian cancer cells, treatment with PDA NPs alone did not induce obvious changes in reactive oxygen species (ROS) production or mitochondrial membrane potential (MTP), but when combined with NIR irradiation, these particles caused a significant increase of ROS and a reduction of MTP (P < 0.001), and such changes were more prominent with high power NIR (P < 0.01). PDA NPs alone showed no obvious cytotoxicity, but the combination of PDA with NIR irradiation produced potent killing effect on ovarian cancer cells (P < 0.001), and the effect was much stronger with a high power irradiation (P < 0.001). While PDA alone showed no inhibitory effect on tumor cell metastasis, the combined treatment with PDA and NIR irradiation, especially at a high power, significantly suppressed invasion and migration of ovarian cancer cells (P < 0.001). In the tumor-bearing mouse model, the combined treatment, but not PDA alone, produced a significant inhibitory effect on tumor growth (P < 0.001). PDA NPs combined with NIR has a strong anti-tumor effect, suggesting a potential new therapeutic strategy for ovarian cancer.

Tempol Inhibits the Growth of Lung Cancer and Normal Cells through Apoptosis Accompanied by Increased O2•- Levels and Glutathione Depletion.

Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) is a stable, cell-permeable redox-cycling nitroxide water-soluble superoxide dismutase (SOD) mimetic agent. However, little is known about its cytotoxic effects on lung-related cells. Thus, the present study investigated the effects of Tempol on cell growth and death as well as changes in reactive oxygen species (ROS) and glutathione (GSH) levels in Calu-6 and A549 lung cancer cells, normal lung WI-38 VA-13 cells, and primary pulmonary fibroblast cells. Results showed that Tempol (0.5~4 mM) dose-dependently inhibited the growth of lung cancer and normal cells with an IC50 of approximately 1~2 mM at 48 h. Tempol induced apoptosis in lung cells with loss of mitochondrial membrane potential (MMP; ∆Ψm) and activation of caspase-3. There was no significant difference in susceptibility to Tempol between lung cancer and normal cells. Z-VAD, a pan-caspase inhibitor, significantly decreased the number of annexin V-positive cells in Tempol-treated Calu-6, A549, and WI-38 VA-13 cells. A 2 mM concentration of Tempol increased ROS levels, including O2•- in A549 and WI-38 VA-13 cells after 48 h, and specifically increased O2•- levels in Calu-6 cells. In addition, Tempol increased the number of GSH-depleted cells in Calu-6, A549, and WI-38 VA-13 cells at 48 h. Z-VAD partially downregulated O2•- levels and GSH depletion in Tempol-treated these cells. In conclusion, treatment with Tempol inhibited the growth of both lung cancer and normal cells via apoptosis and/or necrosis, which was correlated with increased O2•- levels and GSH depletion.

Curcumin alleviates ketamine-induced oxidative stress and apoptosis via Nrf2 signaling pathway in rats' cerebral cortex and hippocampus.

To investigate curcumin's protective effect on nerve damage caused by ketamine anesthesia via the Nrf2 signaling pathway. Rats and PC12 cells were used in this experiment to investigate the mechanism of nerve injury caused by ketamine anesthesia. Furthermore, our findings suggest that curcumin may affect oxidative stress and apoptosis by targeting the Nrf2 pathway, thereby alleviating the nerve injury caused by ketamine. The rat cerebral cortex and hippocampus were stained with Nissl and immunohistochemistry to determine the number of neurons and the expression of Caspase-3, Bcl-2, and Bax. CCK-8 assay was used to determine the optimal concentration of ketamine, curcumin, and H2 O2 in PC12 cells. Flow cytometry was used to detect changes in reactive oxygen species and the rate of apoptosis in each group. To determine whether Nrf2 entered the nucleus, immunofluorescence was used. Both tissues and cells were subjected to RT-PCR and Western blotting detection at the same time. The levels of oxidative stress were determined using a malondialdehyde (MDA) and superoxide dismutase (SOD) assay kit. Ketamine reduced the number of neurons in the cortex and hippocampus of rats. The proteins Bax and Caspase-3 were upregulated, while Bcl-2 was down-regulated in the cortex and hippocampus. The viability of PC12 cells has decreased. MDA content increased while SOD activity decreased in cortex, hippocampus, and PC12 cells. Ketamine had an effect on the expression of some genes in the Nrf2 signaling pathway as well as apoptosis. Curcumin pretreatment may be able to prevent ketamine-induced damage. The oxidative stress and apoptosis caused by ketamine during growth of the cerebral cortex, hippocampus, and PC12 cells may be decreased by curcumin's activation of the Nrf2 signaling pathway. Our research provides a potential strategy for the secure administration of anesthetics in medical settings.

Modulation of Photosynthesis and ROS Scavenging Response by Beneficial Bacteria in Olea europaea Plantlets under Salt Stress Conditions.

Climate change consequences for agriculture involve an increase of saline soils which results in lower crop yields due to increased oxidative stress in plants. The present study reports the use of Plant Growth Promoting Bacteria (PGPB) as a tool to modulate plant innate mechanisms of adaptation to water stress (salinity and drought) in one year-old olive plantlets var. Arbosana and Arbequina. Integration of external changes in plants involve changes in Reactive Oxygen Species (ROS) that behave as signals to trigger plant adaptative mechanisms; however, they become toxic in high concentrations. For this reason, plants are endowed with antioxidant systems to keep ROS under control. So, the working hypothesis is that specific beneficial strains will induce a systemic response able to modulate oxidative stress and improve plant adaptation to water stress. Ten strains were assayed, evaluating changes in photosynthesis, pigments, ROS scavenging enzymes and antioxidant molecules, osmolytes and malondialdehyde, as oxidative stress marker. Photosynthesis and photosynthetic pigments were the most affected variables. Despite the specific response of each variety, the favorite targets of PGPBs to improve plant fitness were photosynthetic pigments and the antioxidant pools of glutathione and ascorbate. Our results show the potential of PGPBs to improve plant fitness modulating oxidative stress.

Mercury Induced Tissue Damage, Redox Metabolism, Ion Transport, Apoptosis, and Intestinal Microbiota Change in Red Swamp Crayfish (Procambarus clarkii): Application of Multi-Omics Analysis in Risk Assessment of Hg.

As one of the most toxic elements, mercury (Hg) is a widespread toxicant in aquatic environments. Crayfish are considered suitable for indicating the impact of heavy metals on aquatic crustaceans. Nevertheless, Hg toxicity on Procambarus clarkii is largely unknown. In this research, the acute Hg-induced alterations of biochemical responses, histopathology, hepatopancreatic transcriptome, and intestinal microbiome of Procambarus clarkii were studied. Firstly, Hg induced significant changes in reactive oxygen species (ROS) and malonaldehyde (MDA) content as well as antioxidant enzyme activity. Secondly, Hg exposure caused structural damage to the hepatopancreas (e.g., vacuolization of the epithelium and dilatation of the lumen) as well as to the intestines (e.g., dysregulation of lamina epithelialises and extension of lamina proprias). Thirdly, after treatment with three different concentrations of Hg, RNA-seq assays of the hepatopancreas revealed a large number of differentially expressed genes (DEGs) linked to a specific function. Among the DEGs, a lot of redox metabolism- (e.g., ACOX3, SMOX, GPX3, GLO1, and P4HA1), ion transport- (e.g., MICU3, MCTP, PYX, STEAP3, and SLC30A2), drug metabolism- (e.g., HSP70, HSP90A, CYP2L1, and CYP9E2), immune response- (e.g., SMAD4, HDAC1, and DUOX), and apoptosis-related genes (e.g., CTSL, CASP7, and BIRC2) were identified, which suggests that Hg exposure may perturb the redox equilibrium, disrupt the ion homeostasis, weaken immune response and ability, and cause apoptosis. Fourthly, bacterial 16S rRNA gene sequencing showed that Hg exposure decreased bacterial diversity and dysregulated intestinal microbiome composition. At the phylum level, there was a marked decrease in Proteobacteria and an increase in Firmicutes after exposure to high levels of Hg. With regards to genus, abundances of Bacteroides, Dysgonomonas, and Arcobacter were markedly dysregulated after Hg exposures. Our findings elucidate the mechanisms involved in Hg-mediated toxicity in aquatic crustaceans at the tissue, cellular, molecular as well as microbial levels.

Identification of Cladosporium fulvum infection responsive genes in tomato through cDNA-AFLP

Tomato (Solanum lycopersicum) is one of the highest-value vegetable crops worldwide, but tomato planting can be easily affected by leaf mold. Tomato leaf mold disease is caused by Cladosporium fulvum, and plants carrying the Cf genes have effective resistance to C. fulvum. To identify leaf mold resistant varieties and screen for specific cDNA amplified fragment length polymorphism (cDNA-AFLP) molecular markers, tomato plants harbouring genes Cf-5, Cf-11, Cf-19, and the moneymaker (MM) tomato line (without Cf gene) were used as plant materials. The changes in reactive oxygen species (ROS) levels and antioxidant activities of plant leaves after inoculation of C. fulvum were measured. Ethylene (ETH), abscisic acid (ABA) and salicylic acid (SA) contents were also determined. The results revealed that the ROS levels in Cf-19 tomato were the most sensitive to C. fulvum inoculation, while in MM they were the least. The antioxidant enzymes of Cf-carrying plants exhibited different activities as compared to those of MM. In the cDNA-AFLP analysis data, the expression of ERF109, sedoheptulose-1,7-bisphosphatase (SBPase), L-ascorbic acid oxidase (AAO) and Thioredoxin H2 (TRX2) were different between Cf-gene carriers and MM plants. In summary, in the process of leaf–mold interaction, the outbreak of ROS and development of systemic acquired resistance (SAR) are tightly combined with antioxidant enzymes, including thioredoxin. Tomato plants carrying the Cf-19 gene appear to have stronger C. fulvum resistance.

Toxicity mechanism of patulin on 293T cells and correlation analysis of Caspase family.

Patulin (PAT), a kind of mycotoxin, is a widely disseminated mycotoxin found in agricultural products. Although the existing research results show that PAT can cause nerve, immune, and skin toxicities, resulting in heart, liver, and kidney damages. However, evidence on the underlying mechanisms of PAT is still lacking. Present study aims to investigate the renal toxicity and related mechanisms of PAT on 293T cells. Cell Counting Kit-8 method was used to reveal the dose-effect relationship and the time-effect relationship of PAT toxicity. Trypan blue staining and Hoechst 33342 staining were used to analyze PAT, which induced apoptosis on 293T cells. Superoxide-dismutase (SOD), GSH, and malondialdehyde (MDA) were used to measure the changes of oxidative stress status of 293T cells induced by PAT. The changes of reactive oxygen species (ROS) and ATP in mitochondria indicate the role of mitochondria when PAT induced cell damage and apoptosis. Through Cyt-C release assay analysis, caspase activity change, and correlation analysis, the potential mechanism of mitochondrial apoptosis pathway was proved. Results demonstrated that PAT significantly induced cell injury, and with the increase of time and concentration, the cell survival rate decreased significantly. Hoechst 33342 staining and Trypan blue staining showed that apoptosis rate was elevated by PAT. As PAT concentration increased, intracellular SOD, glutathion peroxidase activities were decreased and the MDA content was increased. The decrease of intracellular ATP level and accumulation of ROS content indicated an increased permeability of the mitochondrial membrane. Overexpression of Cyt-C activated the cascade reaction of caspase enzyme, leading to apoptosis. The results of enzyme activity assay and correlation analysis indicated that caspase 3 was the most critical caspase in the cascade system and that it was most correlated with caspase 8 and caspase 9.

Ultraprecise Real-Time Monitoring of Single Cells in Tumors in Response to Metal Ion-Mediated RNA Delivery.

With the deepening of cancer clinical research, miRNAs provide new ideas for molecular diagnosis and treatment of tumors. Improving the molecular delivery efficiency of miRNA is the key to the success of miRNA therapy. We have established self-assembly diagnosis and treatment technologies that can be used to achieve accurate targeting and "cargo" delivery at the cellular level. This technology builds a miRNA (let-7a) delivery system based on metal precursor [Au(III) and Fe(II)]-mediated tumor microenvironmental response to realize the self-assembly of Au&Fe-miRNA complexes for precise real-time imaging of tumor cells and targeted therapy. To accurately measure the changes in reactive oxygen species during complex formation in real time at the single-cell level, we employed small-size nanoscale devices as analytical tools. This study proposes an electrochemical sensor based on carbon fiber electrodes for ultraprecise and multiple monitoring of metal-ion-mediated miRNA delivery systems, precisely realizing targeted tracking of tumors and effective intervention inhibition.

Downregulation of Inflammatory Response via Nrf2/Trx1/TXNIP Axis in Oxidative Stress-Induced ARPE-19 Cells and Mouse Model of AMD.

Aim Chronic inflammation is crucial for age-related macular degeneration (AMD) pathogenesis. However, the mechanism involved in activating inflammation remains unclear. This study is aimed at investigating whether nuclear factor erythrocyte-associated factor 2 (Nrf2) negatively regulated the Nod-like receptor protein 3 (NLRP3) inflammasomes through the thioredoxin 1 (Trx1)/thioredoxin interaction protein (TXNIP) complex. Methods We determined the optimal hydrogen peroxide (H2O2) concentration, time, and changes in reactive oxygen species (ROS) levels. We also constructed animal models using blue LED irradiation. Then, the expression of Nrf2, TXNIP, Trx1, NLRP3, and inflammation-related factors and proteins, along with the changes in retinal thickness and functional status, was analyzed. Results The oxidative stress model was established after 1 h intervention with 100 μM H2O2. Nrf2 reduced ROS production, protected the ultrastructure of mitochondria, increased the thickness of the ONL layer, and increased the amplitude of a- and b-wave amplitudes in ERG. Trx1 knockdown increased the production of ROS, damaged the ultrastructure of mitochondria, reduced the thickness of the other ONL layer, and reduced the amplitudes of a- and b-waves in the electroretinogram (ERG). Thus, TXNIP in the cytoplasm activated the inflammasomes. Conclusions Nrf2 showed antioxidant and anti-inflammatory activity in the H2O2-induced cell stress model and blue LED-induced retinal light damage model. TXNIP transferred from the nucleus to the cytoplasm, activated NLRP3, and aggravated the retinal injury in both the cell stress model and the animal blue LED model. In contrast, Trx1 knockout promoted this process. This study revealed the possible role of the thioredoxin system in developing AMD while also providing newer insights for the future treatment of AMD.

Analyzing Efficacy and Safety of Anti-Fungal Blue Light Therapy via Kernel-Based Modeling the Reactive Oxygen Species Induced by Light.

The goal of this study is to investigate the efficacy, safety, and mechanism of ABL for inactivating Candida albicans (C. albicans), and to determine the best wavelength for treating candida infected disease, by experimental measurements and dynamic modeling. The changes in reactive oxygen species (ROS) in C. albicans and human host cells under the irradiation of 385, 405, and 415 nm wavelengths light with irradiance of 50 mW/cm2 were measured. Moreover, a kernel-based nonlinear dynamic model, i.e., nonlinear autoregressive with exogenous inputs (NARX), was developed and applied to predict the concentration of light-induced ROS, whose kernels were selected by a newly developed algorithm based on particle swarm optimization (PSO). The ROS concentration was increased respectively about 10-12 times in C. albicans and about 3-6 times in human epithelial cells by the ABL treatment with the same fluence of 90 J/cm2. The NARX models were respectively fitted to the data from the experiments on both types of cells. Besides, four different kernel functions, including Gaussian, Laplace, linear and polynomial kernels, were compared in their fitting accuracies. The errors with the Laplace kernel turned out to be only 0.2704 and 0.0593, as respectively fitted to the experimental data of the C. albicans and human host cells. The results demonstrated the effectiveness of the NARX modeling approach, and revealed that the 415 nm light was more effective as an anti-fungal treatment with less damage to the host cells than the 405 or 385 nm light. The kernel-based NARX model identification algorithm offers opportunities for determining the effective and safe light dosages in treating various fungal infection diseases.

The Anti-Apoptotic Effects of Caspase Inhibitors in Propyl Gallate-Treated Lung Cancer Cells Are Related to Changes in Reactive Oxygen Species and Glutathione Levels.

Propyl gallate [3,4,5-trihydroxybenzoic acid propyl ester; PG] exhibits an anti-growth effect in various cells. In this study, the anti-apoptotic effects of various caspase inhibitors were evaluated in PG-treated Calu-6 and A549 lung cancer cells in relation to reactive oxygen species (ROS) and glutathione (GSH) levels. Treatment with 800 μM PG inhibited the proliferation and induced the cell death of both Calu-6 and A549 cells at 24 h. Each inhibitor of pan-caspase, caspase-3, caspase-8, and caspase-9 reduced the number of dead and sub-G1 cells in both PG-treated cells at 24 h. PG increased ROS levels, including O2∙−, in both lung cancer cell lines at 24 h. Generally, caspase inhibitors appeared to decrease ROS levels in PG-treated lung cancer cells at 24 h and somewhat reduced O2∙− levels. PG augmented the number of GSH-depleted Calu-6 and A549 cells at 24 h. Caspase inhibitors did not affect the level of GSH depletion in PG-treated A549 cells but differently and partially altered the depletion level in PG-treated Calu-6 cells. In conclusion, PG exhibits an anti-proliferative effect in Calu-6 and A549 lung cancer cells and induced their cell death. PG-induced lung cancer death was accompanied by increases in ROS levels and GSH depletion. Therefore, the anti-apoptotic effects of caspase inhibitors were, at least in part, related to changes in ROS and GSH levels.

Dynamic Changes in Membrane Lipid Metabolism and Antioxidant Defense During Soybean (Glycine max L. Merr.) Seed Aging.

Seed viability depends upon the maintenance of functional lipids; however, how membrane lipid components dynamically change during the seed aging process remains obscure. Seed storage is accompanied by the oxidation of membrane lipids and loss of seed viability. Understanding membrane lipid changes and their effect on the cell membrane during seed aging can contribute to revealing the mechanism of seed longevity. In this study, the potential relationship between oxidative stress and membrane lipid metabolism was evaluated by using a non-targeted lipidomics approach during artificial aging of Glycine max L. Merr. Zhongdou No. 27 seeds. We determined changes in reactive oxygen species, malondialdehyde content, and membrane permeability and assessed antioxidant system activity. We found that decreased non-enzymatic antioxidant contents and catalase activity might lead to reactive oxygen species accumulation, resulting in higher electrolyte leakage and lipid peroxidation. The significantly decreased phospholipids and increased glycerolipids and lysophospholipids suggested that hydrolysis of phospholipids to form glycerolipids and lysophospholipids could be the primary pathway of membrane metabolism during seed aging. Moreover, the ratio of phosphatidylcholine to phosphatidylethanolamine, double bond index, and acyl chain length of phospholipids were found to jointly regulate membrane function. In addition, the observed changes in lipid metabolism suggest novel potential hallmarks of soybean seed aging, such as diacylglycerol 36:4; phosphatidylcholine 34:2, 36:2, and 36:4; and phosphatidylethanolamine 34:2. This knowledge can be of great significance for elucidating the molecular mechanism underlying seed aging and germplasm conservation.

Microgravity-induced stress mechanisms in human stem cell-derived cardiomyocytes

SummaryExposure to outer space microgravity poses a risk for the development of various pathologies including cardiovascular disease. To study this, we derived cardiomyocytes (CMs) from human-induced pluripotent stem cells and exposed them to simulated microgravity (SMG). We combined different “omics” and chromosome conformation capture technologies with live-cell imaging of various transgenic lines to discover that SMG impacts on the contractile velocity and function of CMs via the induction of senescence processes. This is linked to SMG-induced changes of reactive oxygen species (ROS) generation and energy metabolism by mitochondria. Taken together, we uncover a microgravity-controlled axis causing contractile dysfunctions to CMs. Our findings can contribute to the design of preventive and therapeutic strategies against senescence-associated disease.

Oxidative Stress and Antioxidative Therapy in Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is clinically characterized by a progressive increase in pulmonary artery pressure, followed by right ventricular hypertrophy and subsequently right heart failure. The underlying mechanism of PAH includes endothelial dysfunction and intimal smooth muscle proliferation. Numerous studies have shown that oxidative stress is critical in the pathophysiology of PAH and involves changes in reactive oxygen species (ROS), reactive nitrogen (RNS), and nitric oxide (NO) signaling pathways. Disrupted ROS and NO signaling pathways cause the proliferation of pulmonary arterial endothelial cells (PAECs) and pulmonary vascular smooth muscle cells (PASMCs), resulting in DNA damage, metabolic abnormalities, and vascular remodeling. Antioxidant treatment has become a main area of research for the treatment of PAH. This review mainly introduces oxidative stress in the pathogenesis of PAH and antioxidative therapies and explains why targeting oxidative stress is a valid strategy for PAH treatment.

Comparing the toxicity of iodinated X-ray contrast media on eukaryote- and prokaryote-based quantified microarray assays

This study compared the toxicity mechanisms of four X-ray-based iodinated contrast media (ICM) on Escherichia coli (E. coli) and yeast microarray assays, aiming to determine the diverse toxicity mechanisms among different exposed organisms and the relationship between toxicity and their physical and chemical characteristics. The conventional phenotypic endpoint cytotoxicity and the change in reactive oxygen species (ROS) level were employed in conjunction with toxicogenomics to quantify changes in the gene/protein biomarker level in the regulation of different damage/repair pathways. The results showed that molecular toxicity endpoints, named transcriptional effect level index (TELI) and protein effect level index (PELI) for E. coli and yeast, respectively, correlated well with the phenotypic endpoints. Temporal altered gene/protein expression profiles revealed dynamic and complex damage/toxic mechanisms. In particular, compared with E. coli cells, yeast cells exposed to ICM exhibited significantly higher stress intensity and diverse stress types, resulting in stress or damage to the organism. The toxic mechanisms of ICM are concentration/property-dependent and relevant to the cellular structure and defense systems in prokaryotes and eukaryotes. In particular, the toxicity of ionic ICM is higher than that of non-ionic ICM, and eukaryotes are more susceptible than prokaryotes to ICM exposure.

Low-temperature stress affects reactive oxygen species, osmotic adjustment substances, and antioxidants in rice (Oryza sativa L.) at the reproductive stage

The sensitivity of rice to low-temperature stress (LTS), especially at the reproductive stage, is a primary factor of rice yield fluctuation in cold cultivate region. Here, the changes of reactive oxygen species (ROS), osmotic adjustment substances, and antioxidants in different tissues were analyzed during rice growing under low temperatures (LT) at the reproductive stage. Results showed that LTS increases the levels of proline (Pro), soluble protein (SP), glutathione (GSH), superoxidase (SOD), and ascorbate peroxidase (APX) in LJ25 (LTS-resistant) and LJ11 (LTS-sensitive). The activities of catalase (CAT) and peroxidase (POD) were significantly increased in LJ25 but decreased in LJ11 under LTS, while an opposite trend in ROS and malondialdehyde (MDA) was observed in both varieties. Moreover, most physicochemical properties were higher in flag leaves and panicles compared with those in leaf sheaths. The expression patterns of OsCOIN, OsCATC, OsMAP1, OsPOX1, and OsAPX were the same with phenotypic changes in Pro and the enzymes encoded by them, confirming the accuracy of the physicochemical analysis. Therefore, only CAT and POD increased more in LJ25, suggesting they could be the key factors used for LT-tolerant breeding of rice in cold regions.

Lack of evidence for the oxidative stress theory of bleaching in the sea anemone, Exaiptasia diaphana, under elevated temperature

To survive in nutrient-poor waters corals rely on a symbiotic association with intracellular microalgae. However, increased sea temperatures cause algal loss—known as coral bleaching—often followed by coral death. Some of the most compelling evidence in support of the ‘oxidative stress theory of coral bleaching’ comes from studies that exposed corals, cultures of their algal endosymbionts, or the coral model Exaiptasia diaphana to exogenous antioxidants during thermal stress. Here, we replicate these experiments using E.diaphana with the addition of the antioxidants ascorbate + catalase, catechin, or mannitol under ambient and elevated temperatures along with an antioxidant-free control. In the absence of exogenous antioxidants, E.diaphana exposed to elevated temperatures bleached with no change in reactive oxygen species (ROS) levels associated with their microalgal cells. Ascorbate + catalase and mannitol treatments rescued the anemones from bleaching, although microalgal ROS levels increased in these antioxidant treatments under elevated temperature conditions. While bleaching was not associated with changes in net ROS for the intracellular algal symbionts, it is evident from our findings that excess ROS is connected to the bleaching phenotype as exogenous antioxidants were successful in mitigating the effects of thermal stress in cnidarians. This understanding may assist applied research that aims to reduce the impact of climate change on coral reefs.

Pulmonary toxicology assessment of polyethylene terephthalate nanoplastic particles in vitro.

Nanoplastics are more likely to be suspended in air and pose a risk of respiratory exposure. However, the early health effects of low-dose nanoplastics on the respiratory system, which are expected to reflect the risk of atmospheric nanoplastics, need to be further evaluated. In this study, nanoparticles of polyethylene terephthalate, a representative plastic polymer in air, were prepared by a precipitation method. The toxicity impacts of nano-PET at environmental concentrations on the human lung carcinoma cell A549 cells were evaluated. Although the nano-PET was identified to enter the cells by confocal microscope observation and alkali-assisted thermal depolymerization coupled with LC-MS/MS analysis, the nano-PET exhibited low toxicity on mitochondrial membrane potential levels and cell apoptosis. At low concentrations of 0.10 and 0.98μg/mL, the nano-PET had a slight promotion effect on cell viability, while an inhibitory effect on cell viability presented at higher nano-PET concentrations of 98.40 and 196.79μg/mL. The cell survival rate at 98.4 and 196.79μg/mL of nano-PET are lower than that of the control, and significant oxidative stress in cells caused by the nano-PET exposure at 49.2μg/mL was observed. A decrease tendency of mitochondrial membrane potential with the increasing nano-PET exposure presents, which is consistent with the change of reactive oxygen species. Furthermore, nano-PET at ≦ 98.4μg/mL could not increase the sum of apoptotic in the cells, but the late apoptotic cells increased with the increase of the exposure dose. The major mechanism of the toxic effect of nano-PET on cells may be the increase of reactive oxygen species caused by oxidative stress, which in turn induces a decrease in the mitochondrial membrane potential. This study provides information on the toxicity of nano-PET at environmental concentrations in human lung cells, which helps to enrich the risk cognition of nanoplastics in the respiratory system.

Sagittaria sagittifolia polysaccharides regulates Nrf2/HO-1 to relieve liver injury caused by multiple heavy metals in vivo and in vitro

This study explored whether Sagittaria sagittifolia polysaccharides(SSP) activates the nuclear factor erythroid-2-related factor2(Nrf2)/heme oxygenase-1(HO-1) signaling pathway to protect against liver damage jointly induced by multiple heavy metals. First, based on the proportion of dietary intake of six heavy metals in rice available in Beijing market, a heavy metal mixture was prepared for inducing mouse liver injury and HepG2 cell injury. Forty male Kunming mice were divided into five groups: control group, model group, glutathione positive control group, and low-and high-dose SSP groups, with eight mice in each group. After 30 days of intragastric administration, the liver injury in mice was observed by HE staining. In the in vitro experiment, MTT assay was conducted to detect the effects of SSP at 0.25, 0.5, 1, and 2 mg·mL~(-1) on HepG2 cell survival at different time points. The content of alanine transaminase(ALT) and aspartate aminotransferase(AST) in the 48-h cell culture fluid was measured using micro-plate cultivation method, followed by the detection of the change in reactive oxygen species(ROS) content by flow cytometry. The mRNA expression levels of Nrf2 and HO-1 in cells were determined by RT-PCR, and their protein expression by Western blot. HE staining results showed that compared with the model group, the SSP administration groups exhibited significantly alleviated inflammatory cell infiltration and fatty infiltration in the liver, with better outcomes observed in the high-dose SSP group. In the in vitro MTT assay, compared with the model group, SSP at four concentrations all significantly increased the cell survival rate, decreased the ALT, AST, and ROS content(P&lt;0.05), and down-regulated Nrf2 and HO-1 mRNA and protein expression(P&lt;0.05). SSP significantly improves inflammatory infiltration in the liver tissue of mice exposed to a variety of heavy metals and corrects the liver fat degeneration, which may be related to its regulation of the Nrf2/HO-1 signaling pathway, reduction of ROS, and alleviation of oxidative damage.

Dynamic Changes in Reactive Oxygen Species in the Shoot Apex Contribute to Stem Cell Death in Arabidopsis thaliana.

In monocarpic plants, stem cells are fated to die. However, the potential mechanism of stem cell death has remained elusive. Here, we reveal that the levels of two forms of reactive oxygen species (ROS), superoxide anion free radical () and hydrogen peroxide (H2O2), show dynamic changes in the shoot apex during the plant life cycle of Arabidopsis thaliana. We found that the level of decreased and disappeared at four weeks after bolting (WAB), while H2O2 appeared at 3 WAB and showed a burst at 5 WAB. The timing of dynamic changes in and H2O2 was delayed for approximately three weeks in clv3-2, which has a longer lifespan. Moreover, exogenous application of H2O2 inhibited the expression of the stem cell determinant WUSCHEL (WUS) and promoted the expression of the developmentally programmed cell death (dPCD) marker gene ORESARA 1 (ORE1). These results indicate that H2O2 triggers an important signal inducing dPCD in stem cells. Given that plays roles in maintaining WUS expression and stem cell activity, we speculate that the dynamic shift from to H2O2 in the shoot apex results in stem cell death. Our findings provide novel insights for understanding ROS-mediated regulation during plant stem cell death.