TRPA1-PI3K/Akt-OPA1-ferroptosis axis in ozone-induced bronchial epithelial cell and lung injury

BACKGROUND

Transient receptor potential (TRP) ankyrin 1 (TRPA1) could mediate ozone-induced lung injury. Optic Atrophy 1 (OPA1) is one of the significant mitochondrial fusion proteins. Impaired mitochondrial fusion, resulting in mitochondrial dysfunction and ferroptosis, may drive the onset and progression of lung injury. In this study, we examined whether TRPA1 mediated ozone-induced bronchial epithelial cell and lung injury by activating PI3K/Akt with the involvement of OPA1, leading to ferroptosis.

METHODS

Wild-type, TRPA1-knockout (KO) mice (C57BL/6 J background) and ferrostatin-1 (Fer-1)-pretreated mice were exposed to 2.5 ppm ozone for 3 h. Human bronchial epithelial (BEAS-2B) cells were treated with 1 ppm ozone for 3 h in the presence of TRPA1 inhibitor A967079 or TRPA1-knockdown (KD) as well as pharmacological modulators of PI3K/Akt-OPA1-ferroptosis. Transcriptome was used to screen and decipher the differential gene expressions and pathways. Oxidative stress, inflammation and ferroptosis were measured together with mitochondrial morphology, function and dynamics.

RESULTS

Acute ozone exposure induced airway inflammation and airway hyperresponsiveness (AHR), reduced mitochondrial fusion, and enhanced ferroptosis in mice. Similarly, acute ozone exposure induced inflammatory responses, altered redox responses, abnormal mitochondrial structure and function, reduced mitochondrial fusion and enhanced ferroptosis in BEAS-2B cells. There were increased mitochondrial fusion, reduced inflammatory responses, decreased redox responses and ferroptosis in ozone-exposed TRPA1-KO mice and Fer-1-pretreated ozone-exposed mice. A967079 and TRPA1-KD enhanced OPA1 and prevented ferroptosis through the PI3K/Akt pathway in BEAS-2B cells. These in vitro results were further confirmed in pharmacological modulator experiments.

CONCLUSION

Exposure to ozone induces mitochondrial dysfunction in human bronchial epithelial cells and mouse lungs by activating TRPA1, which results in ferroptosis mediated via a PI3K/Akt/OPA1 axis. This supports a potential role of TRPA1 blockade in preventing the deleterious effects of ozone.

Growth, ultrastructural and physiological characteristics of Abelmoschus cytotypes under elevated ozone stress: a study on ploidy-specific responses

Tropospheric ozone (O3 ) is a significant abiotic stressor whose rising concentration negatively influences plant growth. Studies related to the differential response of Abelmoschus cytotypes to elevated O3 treatment are scarce and need further exploration to recognise the role of polyploidisation in stress tolerance. In this study, we analysed the changes in growth pattern, ultrastructure, physiology and foliar protein profile occurring under O3 stress in Abelmoschus moschatus (monoploid), Abelmoschus esculentus (diploid) and Abelmoschus caillei (triploid). Our findings showed that higher stomatal conductance in A. moschatus triggered higher O3 intake, causing damage to stomatal cells and photosynthetic pigments. Additionally, it caused a reduction in photosynthetic rates, leading to reduced plant growth, total biomass and economic yield. This O3 -induced toxicity was less in diploid and triploid cytotypes of Abelmoschus . Protein profiling by sodium dodecyl sulpate-polyacrylamide gel electrophoresis showed a significant decrease in the commonly found RuBisCO larger and smaller subunits. The decrease was more prominent in monoploid compared to diploid and triploid. This study provides crucial data for research that aim to enhance plant ability to withstand O3 induced oxidative stress. Our findings may help in developing a tolerant variety through plant breeding techniques, which will be economically more advantageous in reaching the objective of sustainable production at the high O3 levels projected under a climate change scenario.

Circadian rhythm disturbances involved in ozone-induced glucose metabolism disorder in mouse liver

Ozone (O3) is a key environmental factor for developing diabetes. Nevertheless, the underlying mechanisms remain unclear. This study aimed to investigate alterations of glycometabolism in mice after O3 exposure and the role of circadian rhythms in this process. C57BL/6 male mice were randomly assigned to O3 (0.5 ppm) or filtered air for four weeks (4 h/day). Then, hepatic tissues of mice were collected at 4 h intervals within 24 h after O3 exposure to test. The results showed that hepatic circadian rhythm genes oscillated abnormally, mainly at zeitgeber time (ZT)8 and ZT20 after O3 exposure. Furthermore, detection of glycometabolism (metabolites, enzymes, and genes) revealed that O3 caused change in the daily oscillations of glycometabolism. The serum glucose content decreased at ZT4 and ZT20, while hepatic glucose enhanced at ZT16 and ZT24(0). Both G6pc and Pck1, which are associated with hepatic gluconeogenesis, significantly increased at ZT20. O3 exposure disrupted glycometabolism by increasing gluconeogenesis and decreasing glycolysis in mice liver. Finally, correlation analysis showed that the association between Bmal1 and O3-induced disruption of glycometabolism was the strongest. The findings emphasized the interaction between adverse outcomes of circadian rhythms and glycometabolism following O3 exposure.

Ozone treatment modulates reactive oxygen species levels in kiwifruit through the antioxidant system: Insights from transcriptomic analysis

Owing to its easy decomposition and residue-free properties, ozone has been used as an effective and environmentally friendly physical preservation method for maintaining the post-harvest quality of fruits. This study aimed to investigate the effects of ozone treatment on the levels of oxidative stress markers and the status of the antioxidant defense system in refrigerated kiwifruit. Additionally, the study aimed to identify the differences in gene expression levels and potential regulatory effects from the transcriptional level. The results showed that ozone treatment reduced the respiration rate, maintained the fruit hardness and storage quality, and inhibited the ripening and senescence of kiwifruit. Ozone treatment activated antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and ascorbate-glutathione cycle to prevent the increase of reactive oxygen species levels (H2O2, O2-•) and malonaldehyde content, maintaining lower membrane lipid peroxidation and reactive oxygen species (ROS) accumulation than the control treatment. Further analysis showed that the regulatory ability of ROS in kiwifruit treated with ozone was not only related to the synergistic effect of enzyme activity and gene expression related to the antioxidant oxidase system and the ascorbate-glutathione (ASA-GSH) cycle but also related to downstream hormone signaling. This study provides a foundation for understanding the potential effects of ozone treatment on the antioxidant cycle of kiwifruit and provides valuable insights into the molecular basis and related key genes involved in regulating ROS to delay aging in kiwifruit.

Hydroxymethylbutenyl diphosphate accumulation reveals MEP pathway regulation for high CO2-induced suppression of isoprene emission

Isoprene is emitted by some plants and is the most abundant biogenic hydrocarbon entering the atmosphere. Multiple studies have elucidated protective roles of isoprene against several environmental stresses, including high temperature, excessive ozone, and herbivory attack. However, isoprene emission adversely affects atmospheric chemistry by contributing to ozone production and aerosol formation. Thus, understanding the regulation of isoprene emission in response to varying environmental conditions, for example, elevated CO2, is critical to comprehend how plants will respond to climate change. Isoprene emission decreases with increasing CO2 concentration; however, the underlying mechanism of this response is currently unknown. We demonstrated that high-CO2-mediated suppression of isoprene emission is independent of photosynthesis and light intensity, but it is reduced with increasing temperature. Furthermore, we measured methylerythritol 4-phosphate (MEP) pathway metabolites in poplar leaves harvested at ambient and high CO2 to identify why isoprene emission is reduced under high CO2. We found that hydroxymethylbutenyl diphosphate (HMBDP) was increased and dimethylallyl diphosphate (DMADP) decreased at high CO2. This implies that high CO2 impeded the conversion of HMBDP to DMADP, possibly through the inhibition of HMBDP reductase activity, resulting in reduced isoprene emission. We further demonstrated that although this phenomenon appears similar to abscisic acid (ABA)-dependent stomatal regulation, it is unrelated as ABA treatment did not alter the effect of elevated CO2 on the suppression of isoprene emission. Thus, this study provides a comprehensive understanding of the regulation of the MEP pathway and isoprene emission in the face of increasing CO2.

Growth and DNA Methylation Alteration in Rice (Oryza sativa L.) in Response to Ozone Stress

With the development of urban industrialization, the increasing ozone concentration (O3) at ground level stresses on the survival of plants. Plants have to adapt to ozone stress. DNA methylation is crucial for a rapid response to abiotic stress in plants. Little information is known regarding the epigenetic response of DNA methylation of plants to O3 stress. This study is designed to explore the epigenetic mechanism and identify a possible core modification of DNA methylation or genes in the plant, in response to O3 stress. We investigated the agronomic traits and genome-wide DNA methylation variations of the Japonica rice cultivar Nipponbare in response to O3 stress at three high concentrations (80, 160, and 200 nmol·mol-1), simulated using open-top chambers (OTC). The flag leaf length, panicle length, and hundred-grain weight of rice showed beneficial effects at 80 nmol·mol-1 O3 and an inhibitory effect at both 160 and 200 nmol·mol-1 O3. The methylation-sensitive amplified polymorphism results showed that the O3-induced genome-wide methylation alterations account for 14.72-15.18% at three different concentrations. Our results demonstrated that methylation and demethylation alteration sites were activated throughout the O3 stress, mainly at CNG sites. By recovering and sequencing bands with methylation alteration, ten stress-related differentially amplified sequences, widely present on different chromosomes, were obtained. Our findings show that DNA methylation may be an active and rapid epigenetic response to ozone stress. These results can provide us with a theoretical basis and a reference to look for more hereditary information about the molecular mechanism of plant resistance to O3 pollution.

Involvements of Nrf2 and oxidative stress in the ozone-elicited exacerbation in an allergic rhinitis model

OBJECTIVE AND DESIGN

An experimental rat allergic rhinitis(AR) model was made to explore the effect of different concentrations of ozone exposure and evaluate the roles of nuclear factor erythroid 2-related factor 2(Nrf2) and oxidative stress in ozone exposure.

METHOD

Sprague-Dawley rats were sensitized with ovalbumin (OVA). Three groups of AR rats were exposed respectively to different concentrations of ozone for 2 h on 6 weeks. Nasal symptoms and OVA- specific Ig E in the serum were evaluated. The pathological changes in the nasal mucosa were examined. Malondialdehyde (MDA) level and activity of superoxide dismutase(SOD) and glutathione peroxidase (GSH-Px,GPX) in the nasal mucosa tissue were measured through a spectrophotometry-based method. Nrf2、Kelch-1ike ECH- associated protein-l (Keap1) proteins was measured by western blotting. GPX1、GPX2 mRNA were detected by quantitative real time-PCR(qRT-PCR).

RESULTS

Our results showed that ozone exposure induced a significant increase of the number of sneezes, nasal rubs, amount of nasal secretion and OVA-sIgE in the serum of AR model. Ozone effected oxidative stress in different concentration. The content of MDA in AREH group was significantly higher than AR groups. The activities of SOD and GSH-Px in nasal mucosa showed different trends in different concentration groups. The activities of SOD and GSH-Px in AREL and AREM groups were higher than AR group, but decreased at AREH group. The nucleoprotein level of Nrf2 in AREL and AREM groups was higher than AR groups. However, in AREH group, it was significantly decreased, compared with AREL and AREM groups. GPX1 and GPX2 mRNA levels in nasal mucosa showed the same trend in different exposure groups.

CONCLUSIONS

Different concentrations of ozone inhalation causes changes of the expression of Nrf2 nuclear protein and its target genes in nasal mucosa of AR. High concentration ozone breaks the redox balance and aggravates oxidative damage in AR. This study suggests that inhibiting oxidative stress might be a solution for ozone-elicited detrimental effects on AR.

The bidirectional lung brain-axis of amyloid-β pathology: ozone dysregulates the peri-plaque microenvironment

The mechanisms underlying how urban air pollution affects Alzheimer's disease (AD) are largely unknown. Ozone (O3) is a reactive gas component of air pollution linked to increased AD risk, but is confined to the respiratory tract after inhalation, implicating the peripheral immune response to air pollution in AD neuropathology. Here, we demonstrate that O3 exposure impaired the ability of microglia, the brain's parenchymal immune cells, to associate with and form a protective barrier around Aβ plaques, leading to augmented dystrophic neurites and increased Aβ plaque load. Spatial proteomic profiling analysis of peri-plaque proteins revealed a microenvironment-specific signature of dysregulated disease-associated microglia protein expression and increased pathogenic molecule levels with O3 exposure. Unexpectedly, 5xFAD mice exhibited an augmented pulmonary cell and humoral immune response to O3, supporting that ongoing neuropathology may regulate the peripheral O3 response. Circulating HMGB1 was one factor upregulated in only 5xFAD mice, and peripheral HMGB1 was separately shown to regulate brain Trem2 mRNA expression. These findings demonstrate a bidirectional lung-brain axis regulating the central and peripheral AD immune response and highlight this interaction as a potential novel therapeutic target in AD.

Chronic ozone exposure impairs the mineral nutrition of date palm (Phoenix dactylifera) seedlings

Chronic ozone (O₃) exposure in the atmosphere preferentially disturbs metabolic processes in the roots rather than the shoot as a consequence of reduced photosynthesis and carbohydrate allocation from the leaves to the roots. The aim of the present study was to elucidate if mineral nutrition is also impaired by chronic O₃ exposure. For this purpose, date palm (Phoenix dactylifera) plants were fumigated with ambient, 1.5 × ambient and 2 × ambient O₃ in a free air controlled exposure (FACE) system for one growing season and concentrations of major nutrients were analyzed in leaves and roots. In addition, concentrations of C and N and their partitioning between different metabolic C and N pools were determined in both organs. The results showed that calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), sodium (Na) and potassium (K) acquisition by roots was diminished by O₃ exposure of the shoot. For Ca, Mg, Fe and Zn reduced uptake by the roots was combined with reduced allocation to the shoot, resulting in a decline of foliar concentrations; for Na and K, allocation to the shoot was maintained at the expense of the roots. Thus, elevated O₃ impaired both mineral uptake by the roots and partitioning of minerals between roots and shoots, but in an element specific way. Thereby, elevated O₃ affected roots and shoots differently already after one growing season. However, considerable changes in total C and N concentrations and their partitioning between different metabolic pools upon chronic O₃ exposure were not observed in either leaves or roots, except for reduced foliar lignin concentrations at 2 × ambient O₃. Significant differences in these parameters were shown between leaves and roots independent of O₃ application. The physiological consequences of the effects of chronic O₃ exposure on mineral acquisition and partitioning between leaves and roots are discussed.

The impact of subchronic ozone exposure on serum metabolome and the mechanisms of abnormal bile acid and arachidonic acid metabolisms in the liver

Ambient ozone (O₃) pollution can induce respiratory and cardiovascular toxicity. However, its impact on the metabolome and the underlying mechanisms remain unclear. This study first investigated the serum metabolite changes in rats exposed to 0.5 ppm O₃ for 3 months using untargeted metabolomic approach. Results showed chronic ozone exposure significantly altered the serum levels of 34 metabolites with potential increased risk of digestive, respiratory and cardiovascular disease. Moreover, bile acid synthesis and secretion, and arachidonic acid (AA) metabolism became the most prominent affected metabolic pathways after O₃ exposure. Further studies on the mechanisms found that the elevated serum toxic bile acid was not due to the increased biosynthesis in the liver, but the reduced reuptake from the portal vein to hepatocytes owing to repressed Ntcp and Oatp1a1, and the decreased bile acid efflux in hepatocytes as a results of inhibited Bsep, Ostalpha and Ostbeta. Meanwhile, decreased expressions of detoxification enzyme of SULT2A1 and the important regulators of FXR, PXR and HNF4α also contributed to the abnormal bile acids. In addition, O₃ promoted the conversion of AA into thromboxane A2 (TXA2) and 20-hydroxyarachidonic acid (20-HETE) in the liver by up-regulation of Fads2, Cyp4a and Tbxas1 which resulting in decreased AA and linoleic acid (LA), and increased thromboxane B2 (TXB2) and 20-HETE in the serum. Furthermore, apparent hepatic chronic inflammation, fibrosis and abnormal function were found in ozone-exposed rats. These results indicated chronic ozone exposure could alter serum metabolites by interfering their metabolism in the liver, and inducing liver injury to aggravate metabolic disorders.

Advances in understanding mechanisms underlying mitochondrial structure and function damage by ozone

Mitochondria are double-membraned organelles found in eukaryotic cells. The integrity of mitochondrial structure and function determines cell destiny. Mitochondria are also the "energy factories of cells." The production of energy is accompanied by reactive oxygen species (ROS) generation. Generally, the production and consumption of ROS maintains a balance in cells. Ozone is a highly oxidizing, harmful substance in ground-level atmosphere. Ozone inhalation causes oxidative injury owing to the generation of ROS, resulting in mitochondrial oxidative stress overload. Oxidative damage to the mitochondria induces a vicious cycle of ROS production which might destroy mitochondrial DNA and mitochondrial structure and function in cells. ROS can alter the phosphorylation of various signaling molecules, triggering a series of downstream signaling pathway reactions. These include inflammatory responses, pyroptosis, autophagy, and apoptosis. Changes involving these molecular mechanisms may be related to the occurrence of disease. According to numerous epidemiological investigations, ozone exposure induces respiratory, cardiovascular, and nervous system diseases in humans. In addition, these systems require large quantities of energy. Hence, the mitochondrial damage caused by ozone may act as a bridge between human diseases. However, the specific molecular mechanisms involved require further investigation. This review discusses our understanding of the structure and function of mitochondria the mechanisms underlying ozone-induced mitochondrial damage.

Combined exposure of heat stress and ozone enhanced cognitive impairment via neuroinflammation and blood brain barrier disruption in male rats

BACKGROUND

Heat stress (HS) exposure has been linked to cognitive dysfunction. In reality, high temperature does not occur alone in environment, and ozone (O₃) and heatwaves usually co-exist in atmospheric environment. However, whether O₃ exposure exacerbates HS-induced cognitive impairment and the potential underlying mechanisms have not been explored experimentally. The aim of this study was to determine the co-effects and mechanisms of HS and O₃ on the cognitive dysfunction.

METHODS

48 Sprague Dawley male rats were randomly divided into 4 groups: control, HS, O₃ and HS plus O₃ (HO₃) groups. Rats in HS and HO₃ group were exposed to 40 °C every morning from 9:00 to 12:00 for 15 consecutive days. While rats in O₃ and HO₃ groups were exposed to 0.7 ppm O₃ the same day from 14:00 to 17:00 for 15 days. Cognitive performance was examined with Morris water maze test. Neurodegeneration, glial activation, neuroinflammation, blood brain barrier (BBB) disruption and apoptosis were evaluated by Western blot, Elisa, immunohistochemistry and immunofluorescence staining.

RESULTS

HS induced cognitive decline and neuronal damage in rats. Further studies showed that exposure of rats to HS could also induce glial activation, neuroinflammation and neuronal apoptosis in hippocampus, and decrease in the expressions of ZO-1, claudin-5 and occluding, indicative of BBB disruption. Impressively, the neuronal effects induced by HS, as depicted above, could be worsened by co-exposure to O₃ in rats.

CONCLUSIONS

Co-exposure to O₃ promotes HS-induced cognitive impairment in rats possibly through glial-mediated neuroinflammation and BBB disruption.

Surfactant protein D inhibits lipid-laden foamy macrophages and lung inflammation in chronic obstructive pulmonary disease

Increased levels of surfactant protein D (SP-D) and lipid-laden foamy macrophages (FMs) are frequently found under oxidative stress conditions and/or in patients with chronic obstructive pulmonary disease (COPD) who are also chronically exposed to cigarette smoke (CS). However, the roles and molecular mechanisms of SP-D and FMs in COPD have not yet been determined. In this study, increased levels of SP-D were found in the bronchoalveolar lavage fluid (BALF) and sera of ozone- and CS-exposed mice. Furthermore, SP-D-knockout mice showed increased lipid-laden FMs and airway inflammation caused by ozone and CS exposure, similar to that exhibited by our study cohort of chronic smokers and COPD patients. We also showed that an exogenous recombinant fragment of human SP-D (rfhSP-D) prevented the formation of oxidized low-density lipoprotein (oxLDL)-induced FMs in vitro and reversed the airway inflammation and emphysematous changes caused by oxidative stress and CS exposure in vivo. SP-D upregulated bone marrow-derived macrophage (BMDM) expression of genes involved in countering the oxidative stress and lipid metabolism perturbations induced by CS and oxLDL. Our study demonstrates the crucial roles of SP-D in the lipid homeostasis of dysfunctional alveolar macrophages caused by ozone and CS exposure in experimental mouse emphysema, which may provide a novel opportunity for the clinical application of SP-D in patients with COPD.

Ozone effect on the inflammatory and proteomic profile of human macrophages and airway epithelial cells

Ozone (O₃) is one of the most harmful urban pollutants, but its biological mechanisms have not been fully elucidated yet. Human bronchial epithelial cells (HBEpC) and human macrophage cells (differentiated human monocytic cell line) were exposed to O₃ at the concentration of 240 μg/m³ (120 ppb), corresponding to the European Union alert threshold. Cell viability, reactive oxygen species (ROS) production, and pro-inflammatory cytokines release (IL-8 and TNF-α) were evaluated. Results indicated that O₃ exposure increases ROS production in both cell types and enhances cytokines release in macrophages. O₃ stimulated IL-8 and TNF-α in HBEpC when the cells were pretreated with Lipopolysaccharide, used to mimic a pre-existing inflammatory condition. Proteomics analysis revealed that, in HBEpC, O₃ caused the up-regulation of aldo-keto reductase family 1 member B10, a recognized critical protein in lung carcinogenesis. In conclusion, our results show that 120 ppb O₃ can lead to potential damage to human health suggesting the need for a revision of the actual alert levels.

One-time ozone treatment improves the postharvest quality and antioxidant activity of Actinidia arguta fruit

The major aim of this study was to check the effect of one-time ozonation on selected quality parameters and antioxidant status of Actinidia arguta fruit. For this purpose, A. arguta fruit was ozonated with gas at a concentration of 10 and 100 ppm, which was carried out successively for 5, 15 and 30 min. Next, the selected quality attributes, antioxidants level as well as NADPH and mitochondrial energy metabolism in mini-kiwi fruit after ozonation were analysed. Our research has shown that ozonation reduced the level of yeast and mould without affecting the content of soluble solids or acidity. In turn, ozonation clearly influenced the antioxidant activity and the redox status of the fruit. The ozonated fruit was characterised by a lower level of ROS due to the higher level of low molecular weight antioxidants, as well as the higher activity of superoxide dismutase and catalase. In addition, improved quality and antioxidant activity of the fruit were indirectly due to improved energy metabolism and NADPH level. The ozonated fruit showed a higher level of ATP, due to both higher activity of succinate dehydrogenase and higher availability of NADH. Moreover, the increased level of NAD⁺ and the activity of NAD⁺ kinase and glucose-6-phosphate dehydrogenase contributed to higher levels of NADPH in the fruit.

Using Computational Drug-Gene Analysis to Identify Novel Therapeutic Candidates for Retinal Neuroprotection

Retinal cell death is responsible for irreversible vision loss in many retinal disorders. No commercially approved treatments are currently available to attenuate retinal cell loss and preserve vision. We seek to identify chemicals/drugs with thoroughly-studied biological functions that possess neuroprotective effects in the retina using a computational bioinformatics approach. We queried the National Center for Biotechnology Information (NCBI) to identify genes associated with retinal neuroprotection. Enrichment analysis was performed using ToppGene to identify compounds related to the identified genes. This analysis constructs a Pharmacome from multiple drug-gene interaction databases to predict compounds with statistically significant associations to genes involved in retinal neuroprotection. Compounds with known deleterious effects (e.g., asbestos, ethanol) or with no clinical indications (e.g., paraquat, ozone) were manually filtered. We identified numerous drug/chemical classes associated to multiple genes implicated in retinal neuroprotection using a systematic computational approach. Anti-diabetics, lipid-lowering medicines, and antioxidants are among the treatments anticipated by this analysis, and many of these drugs could be readily repurposed for retinal neuroprotection. Our technique serves as an unbiased tool that can be utilized in the future to lead focused preclinical and clinical investigations for complex processes such as neuroprotection, as well as a wide range of other ocular pathologies.

Elevated ozone inhibits isoprene emission of a diploid and a triploid genotype of Populus tomentosa by different mechanisms

Ozone (O3) pollution affects plant growth and isoprene (ISO) emission. However, the response mechanism of isoprene emission rate (ISOrate) to elevated O3 (EO3) remains poorly understood. ISOrate was investigated in two genotypes (diploid and triploid) of Chinese white poplar (Populus tomentosa Carr.) exposed to EO3 in an open top chamber system. The triploid genotype had higher photosynthetic rate (A) and stomatal conductance (gs) than the diploid one. EO3 significantly decreased A, gs, and ISOrate of middle and lower leaves in both genotypes. In the diploid genotype, the reduction of ISOrate was caused by a systematic decrease related to ISO synthesis capacity, as indicated by decreased contents of the isoprene precursor dimethylallyl diphosphate and decreased isoprene synthase protein and activity. On the other hand, the negative effect of O3 on ISOrate of the triploid genotype did not result from inhibited ISO synthesis capacity, but from increased ISO oxidative loss within the leaf. Our findings will be useful for breeding poplar genotypes with high yield and lower ISOrate, depending on local atmospheric volatile organic compound/NOx ratio, to cope with both the rising O3 concentrations and increasing biomass demand. They can also inform the incorporation of O3 effects into process-based models of isoprene emission.

Gender difference in hepatic AMPK pathway activated lipid metabolism induced by aged polystyrene microplastics exposure

Microplastics (MPs) pollution becomes an increasing concern and researchers keep exploring the health effects caused by MPs exposure. The ageing process in the environment significantly alters the physicochemical characteristics of MPs and subsequently affects their toxicities. The health effects of aged MPs exposure and the mechanism underlying are worthy of exploration. Polystyrene microplastics (PS-MPs) (with size less than 50 µm) were obtained by grinding and screening polystyrene materials. PS-MPs continued to be aged by ozone treatment (0.4 mg/min, 9 h). Both male and female C57BL/6 mice were orally exposed to 0 or 2 mg/kg/d aged PS-MPs for 28 days. Results showed that PS-MPs were found in liver, ovary and spleen of females and liver, testis and spleen of males in the aged PS-MPs group. Exposure to aged PS-MPs significantly decreased abdominal fat/body coefficient, the adipocyte size and the serum LDL-C level in females. Compared to the control, serum estradiol (E2) level, the mRNA expression levels of genes regulating E2 production (17β-hsd, 3β-hsd and Star) in ovary and the protein expression levels of E2 receptors (ERα, ERβ), AMPKα and p-AMPKα1 in liver increased significantly, and the mRNA expression levels of AMP-activated protein kinase (AMPK) downstream genes (Srebp-1c, Fas and Scd1) in liver decreased significantly in the female aged PS-MPs group. Liver metabolomic profiling showed that differential metabolites between female aged PS-MPs group and female control group were enriched in biotin metabolism and the level of biotin increased significantly in the female aged PS-MPs group. However, no significant changes were detected in males. These results indicated that aged PS-MPs exposure increased ovarian E2 production and activated the AMPK pathway in the liver which might inhibit liver lipid synthesis only in females. Our findings provide new insights into the potential sex-specific health effects of environmental MPs pollution.

The response of mesophyll conductance to ozone-induced oxidative stress is genotype-dependent in poplar

The CO2 diffusion conductance within the leaf mesophyll (gm) is considered a major limiting factor of photosynthesis. However, the effects of the major secondary air pollutant ozone (O3) on gm have been poorly investigated. Eight genotypes of the economically important tree species Populus × canadensis Moench were exposed to 120 ppb O3 for 21 d. gm showed a genotype-dependent response to O3-induced oxidative stress and was a major limiting factor of net assimilation rate (Anet), ahead of stomatal conductance to CO2 (gsc) and of the maximum carboxylation capacity of the Rubisco enzyme (Vcmax) in half of the tested genotypes. Increased leaf dry mass per area (LMA) and decreased chlorophyll content were linked to the observed gm decrease, but this relationship did not entirely explain the different genotypic gm responses. Moreover, the oxidative stress defence metabolites ascorbate and glutathione were not related to O3 tolerance of gm. However, malondialdehyde probably mitigated the observed gm decrease in some genotypes due to its oxidative stress signalling function. The large variation of gm suggests different regulation mechanisms amongst poplar genotypes under oxidative stress.

Hypoxia pretreatment enhances the therapeutic potential of mesenchymal stem cells (BMSCs) on ozone-induced lung injury in rats

Ozone (O₃) gas is a double-sided weapon. It provides a shield that protects life on earth from the harmful ultraviolet (UV) rays, but ground-level O₃ is considered an urban air pollutant. So, a rat model of chronic O₃ inhalation was established to assess the biochemical and morphological alterations in the lung tissue and to investigate the ameliorative effects of bone marrow-derived mesenchymal stem cells (BMSCs) with or without hypoxia pre-treatment. Forty-two adult male albino rats were divided into four groups: control, ozone-exposed, normoxic BMSC-treated, and hypoxic BMSC-treated groups. Lung tissue sections were processed for light and electron microscope examination, immunohistochemical staining for caspase 3, and iNOS. Quantitative real-time PCR for IL-1α, IL-17, TNF-α, and Nrf2 mRNA gene expression were also performed. Chronic O₃ exposure caused elevated inflammatory cytokines and decreased antioxidant Nrf2 mRNA expression. Marked morphological alterations with increased collagen deposition and elevated apoptotic markers and iNOS were evident. BMSC treatment showed immunomodulatory (decreased inflammatory cytokine gene expression), antioxidant (increased Nrf2 expression and decreased iNOS), and anti-apoptotic (decreased caspase3 expression) effects. Consequently, ameliorated lung morphology with diminished collagen deposition was observed. Hypoxia pretreatment enhanced BMSC survival by MTT assay. It also augmented the previously mentioned effects of BMSCs on the lung tissue as proved by statistical analysis. Lung morphology was similar to that of control group. In conclusion, hypoxia pretreatment represents a valuable intervention to enhance the effects of MSCs on chronic lung injury.

TGF-β1, NAG-1, and antioxidant enzymes expression alterations in Cisplatin-induced nephrotoxicity in a rat model: Comparative modulating role of Melatonin, Vit. E and Ozone

Cisplatin (CP) is an anticancer medication that is commonly used to treat solid tumors. Its use is, however, dose-restricted due to nephrotoxicity. We planned to compare the nephroprotective effects of three major compounds, including melatonin (MN), Ozone, or vitamin E, against the CP-induced renal damage in rats. CP was given once intraperitoneally (10 mg/kg,) eliciting acute kidney injury as assured by several adverse histological changes; glomerulopathy, tubulopathy, and vasculopathy, an inflammatory response including elevated TNF-α, IL-6, and IL-1β. Furthermore, biochemical alterations including, elevated plasma levels of urea, uric acid, creatinine, phosphorous, decreased plasma calcium levels, and gene expression abnormalities; upregulation of N-acetyl-β-d-glucosaminidase (NAG) and Transforming growth factor-β1 (TGF-β1), downregulation of CAT and SOD. Concurrent supplementation with either MN (10 mg/kg per os) or Ozone (1.1 mg/kg ip) and Vit E given by oral gavage (1 g/kg) for five consecutive days prior to CP injection and five days afterward displayed variable significant nephroprotective effects by mitigating the pro-inflammatory secretion, augmenting antioxidant competence, and modulating the gene expression in the renal tissue. The obtained biochemical, histological, and gene expression data suggested that MN had foremost rescue effects followed by Ozone then Vit E. MN's ameliorative effect was augmented in many indices including TNF-α, IL-6 , IL1-β, uric acid, creatinine, sNGAL and GGT, more than observed in Ozone, and Vit E therapy. A combination of these medications is expected to be more useful in relieving the damaging renal effects of CP given to cancer patients, pending further toxicological and pharmacological research.

Transcription factor McWRKY71 induced by ozone stress regulates anthocyanin and proanthocyanidin biosynthesis in Malus crabapple

In plants, anthocyanins and proanthocyanidins (PAs) play important roles in plant resistance to abiotic stress. In this study, ozone (O₃) treatments caused the up-regulation of Malus crabapple structural genes McANS, McCHI, McANR and McF3H, which promoted anthocyanin and PA accumulation. We identified the WRKY transcription factor (TF) McWRKY71 by screening differentially expressed genes (DEGs) that were highly expressed in response to O₃ stress from an RNA sequencing (RNA-seq) analysis. Overexpressing McWRKY71 increased the resistance of 'Orin' apple calli to O₃ stress and promoted the accumulation of anthocyanins and PAs, which facilitated reactive oxygen species scavenging to further enhance O₃ tolerance. Biochemical and molecular analyses showed that McWRKY71 interacted with McMYB12 and directly bound the McANR promoter to participate in the regulation of PA biosynthesis. These findings provide new insights into the WRKY TFs mechanisms that regulate the biosynthesis of secondary metabolites, which respond to O₃ stress, in Malus crabapple.

Laccase-Catalyzed Oxidation of Allylbenzene Derivatives: Towards a Green Equivalent of Ozonolysis

Laccase-based biocatalytic reactions have been tested with and without mediators and optimized in the oxidation of allylbenzene derivatives, such as methyl eugenol taken as a model substrate. The reaction primarily consisted in the hydroxylation of the propenyl side chain, either upon isomerization of the double bond or not. Two pathways were then observed; oxidation of both allylic alcohol intermediates could either lead to the corresponding α,β-unsaturated carbonyl compound, or the corresponding benzaldehyde derivative by oxidative cleavage. Such a process constitutes a green equivalent of ozonolysis or other dangerous or waste-generating oxidation reactions. The conversion rate was sensitive to the substitution patterns of the benzenic ring and subsequent electronic effects.

Combined Acute Ozone and Water Stress Alters the Quantitative Relationships between O3 Uptake, Photosynthetic Characteristics and Volatile Emissions in Brassica nigra

Ozone (O₃) entry into plant leaves depends on atmospheric O₃ concentration, exposure time and openness of stomata. O₃ negatively impacts photosynthesis rate (A) and might induce the release of reactive volatile organic compounds (VOCs) that can quench O₃, and thereby partly ameliorate O₃ stress. Water stress reduces stomatal conductance (g_s) and O₃ uptake and can affect VOC release and O₃ quenching by VOC, but the interactive effects of O₃ exposure and water stress, as possibly mediated by VOC, are poorly understood. Well-watered (WW) and water-stressed (WS) Brassica nigra plants were exposed to 250 and 550 ppb O₃ for 1 h, and O₃ uptake rates, photosynthetic characteristics and VOC emissions were measured through 22 h recovery. The highest O₃ uptake was observed in WW plants exposed to 550 ppb O₃ with the greatest reduction and poorest recovery of g_s and A, and elicitation of lipoxygenase (LOX) pathway volatiles 10 min-1.5 h after exposure indicating cellular damage. Ozone uptake was similar in 250 ppb WW and 550 ppb WS plants and, in both treatments, O₃-dependent reduction in photosynthetic characteristics was moderate and fully reversible, and VOC emissions were little affected. Water stress alone did not affect the total amount and composition of VOC emissions. The results indicate that drought ameliorated O₃ stress by reducing O₃ uptake through stomatal closure and the two stresses operated in an antagonistic manner in B. nigra.

Impact of elevated ozone on yield and carbon-nitrogen content in soybean cultivar 'Jake'

Tropospheric ozone (O3) is a pollutant that leads to significant global yield loss in soybean [Glycine max (L.) Merr.]. To ensure soybean productivity in areas of rising O3, it is important to identify tolerant genotypes. This work describes the response of the high-yielding soybean cultivar 'Jake' to elevated O3 concentrations. 'Jake' was treated with either low O3 [charcoal-filtered (CF) air, 12 h mean: 20 ppb] or with O3-enriched air (12 h mean: 87 ppb) over the course of the entire growing season. In contrast to the absence of O3-induced leaf injury under low O3, elevated O3 caused severe leaf injury and decreased stomatal conductance and photosynthesis. Although elevated O3 reduced total leaf area, leaf number, and plant height at different developmental stages, above-ground and root biomass remained unchanged. Analyzing carbon and nitrogen content, we found that elevated O3 altered allocation of both elements, which ultimately led to a 15 % yield loss by decreasing seed size but not seed number. We concluded that cultivar 'Jake' possesses developmental strength to tolerate chronic O3 conditions, attributes that make it suitable breeding material for the generation of new O3 tolerant lines.

Metabolic response of soybean leaves induced by short-term exposure of ozone

The ever-increasing ozone (O3) concentration has led to reduced production and altered quality of soybean. Abundant reports have explored the damage mechanisms of O3 on soybean. However, how the elevated O3 affects metabolite profiling of soybean remains to be poorly understood. Here, we compare the metabolic profile of soybean leaves under charcoal filtered air (CF, <20 ppb) and short-term elevated O3 concentration (EO, 100 ppb). High level of O3 affects metabolites for the tricarbonic acid (TCA) cycle, reactive oxygen species, cell wall composition and amino acids. Significantly, jasmonic acid-related metabolite promoting stomata closure is highly induced with 125-fold change. Furthermore, O3 fumigation alters the expression of genes contributing to the biosynthesis of certain metabolites in TCA cycle. Together, these findings identify a wide range of changed metabolites in response to O3 pollution. Our results pave the way for the genetic improvement of soybean to adapt to O3 pollution to maintain stable yields.

Ozone tolerant maize hybrids maintain Rubisco content and activity during long-term exposure in the field

Ozone pollution is a damaging air pollutant that reduces maize yields equivalently to nutrient deficiency, heat, and aridity stress. Therefore, understanding the physiological and biochemical responses of maize to ozone pollution and identifying traits predictive of ozone tolerance is important. In this study, we examined the physiological, biochemical and yield responses of six maize hybrids to elevated ozone in the field using Free Air Ozone Enrichment. Elevated ozone stress reduced photosynthetic capacity, in vivo and in vitro, decreasing Rubisco content, but not activation state. Contrary to our hypotheses, variation in maize hybrid responses to ozone was not associated with stomatal limitation or antioxidant pools in maize. Rather, tolerance to ozone stress in the hybrid B73 × Mo17 was correlated with maintenance of leaf N content. Sensitive lines showed greater ozone-induced senescence and loss of photosynthetic capacity compared to the tolerant line.

Genetic dissection of bread wheat diversity and identification of adaptive loci in response to elevated tropospheric ozone

Rising tropospheric ozone affects the performance of important cereal crops thus threatening global food security. In this study, genetic variation of wheat regarding its physiological and yield responses to ozone was explored by exposing a diversity panel of 150 wheat genotypes to elevated ozone and control conditions throughout the growing season. Differential responses to ozone were observed for foliar symptom formation quantified as leaf bronzing score (LBS), vegetation indices and yield components. Vegetation indices representing the carotenoid to chlorophyll pigment ratio (such as Lic2) were particularly ozone-responsive and were thus considered suitable for the non-invasive diagnosing of ozone stress. Genetic variation in ozone-responsive traits was dissected by a genome-wide association study (GWAS). Significant marker-trait associations were identified for LBS on chromosome 5A and for vegetation indices (NDVI and Lic2) on chromosomes 6B and 6D. Analysis of linkage disequilibrium (LD) in these chromosomal regions revealed distinct LD blocks containing genes with a putative function in plant redox biology such as cytochrome P450 proteins and peroxidases. This study gives novel insight into the natural genetic variation in wheat ozone response, and lays the foundation for the molecular breeding of tolerant wheat varieties.

Ribulose 1,5-bisphosphate carboxylase/oxygenase activates O2 by electron transfer

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the cornerstone of atmospheric CO2 fixation by the biosphere. It catalyzes the addition of CO2 onto enolized ribulose 1,5-bisphosphate (RuBP), producing 3-phosphoglycerate which is then converted to sugars. The major problem of this reaction is competitive O2 addition, which forms a phosphorylated product (2-phosphoglycolate) that must be recycled by a series of biochemical reactions (photorespiratory metabolism). However, the way the enzyme activates O2 is still unknown. Here, we used isotope effects (with 2H, 25Mg, and 18O) to monitor O2 activation and assess the influence of outer sphere atoms, in two Rubisco forms of contrasted O2/CO2 selectivity. Neither the Rubisco form nor the use of solvent D2O and deuterated RuBP changed the 16O/18O isotope effect of O2 addition, in clear contrast with the 12C/13C isotope effect of CO2 addition. Furthermore, substitution of light magnesium (24Mg) by heavy, nuclear magnetic 25Mg had no effect on O2 addition. Therefore, outer sphere protons have no influence on the reaction and direct radical chemistry (intersystem crossing with triplet O2) does not seem to be involved in O2 activation. Computations indicate that the reduction potential of enolized RuBP (near 0.49 V) is compatible with superoxide (O2•-) production, must be insensitive to deuteration, and yields a predicted 16O/18O isotope effect and energy barrier close to observed values. Overall, O2 undergoes single electron transfer to form short-lived superoxide, which then recombines to form a peroxide intermediate.

The Effects of Ozone on Atlantic Salmon Post-Smolt in Brackish Water-Establishing Welfare Indicators and Thresholds

Ozone is a strong oxidant, and its use in aquaculture has been shown to improve water quality and fish health. At present, it is predominantly used in freshwater systems due to the high risk of toxic residual oxidant exposure in brackish water and seawater. Here, we report the effects of ozone on Atlantic salmon (Salmo salar) post-smolts (~100 g), in a brackish water (12 ppt) flow-through system. Salmon were exposed to oxidation reduction potential concentrations of 250 mV (control), 280 mV (low), 350 mV (medium), 425 mV (high) and 500 mV (very high). The physiological impacts of ozone were characterized by blood biochemical profiling, histopathologic examination and gene expression analysis in skin and gills. Fish exposed to 425 mV and higher showed ≥33% cumulative mortality in less than 10 days. No significant mortalities were recorded in the remaining groups. The skin surface quality and the thickness of the dermal and epidermal layers were not significantly affected by the treatments. On the other hand, gill histopathology showed the adverse effects of increasing ozone doses and the changes were more pronounced in the group exposed to 350 mV and higher. Cases of gill damages such as necrosis, lamellar fusion and hypertrophy were prevalent in the high and very high groups. Expression profiling of key biomarkers for mucosal health supported the histology results, showing that gills were significantly more affected by higher ozone doses compared to the skin. Increasing ozone doses triggered anti-oxidative stress and inflammatory responses in the gills, where transcript levels of glutathione reductase, copper/zinc superoxide dismutase, interleukin 1β and interleukin were significantly elevated. Heat shock protein 70 was significantly upregulated in the skin of fish exposed to 350 mV and higher. Bcl-2 associated x protein was the only gene marker that was significantly upregulated by increasing ozone doses in both mucosal tissues. In conclusion, the study revealed that short-term exposure to ozone at concentrations higher than 350 mV in salmon in brackish water resulted in significant health and welfare consequences, including mortality and gill damages. The results of the study will be valuable in developing water treatment protocols for salmon farming.

Ozonation as a Method of Abiotic Elicitation Improving the Health-Promoting Properties of Plant Products-A Review

In this review, the primary objective was to systematize knowledge about the possibility of improving the health-promoting properties of raw plant products, defined as an increase in the content of bioactive compounds, by using ozone. The greatest attention has been paid to the postharvest treatment of plant raw materials with ozone because of its widespread use. The effect of this treatment on the health-promoting properties depends on the following different factors: type and variety of the fruit or vegetable, form and method of ozone treatment, and dosage of ozone. It seems that ozone applied in the form of ozonated water works more gently than in gaseous form. Relatively high concentration and long contact time used simultaneously might result in increased oxidative stress which leads to the degradation of quality. The majority of the literature demonstrates the degradation of vitamin C and deterioration of color after treatment with ozone. Unfortunately, it is not clear if ozone can be used as an elicitor to improve the quality of the raw material. Most sources prove that the best results in increasing the content of bioactive components can be obtained by applying ozone at a relatively low concentration for a short time immediately after harvest.

Antioxidative action of polyamines in protection of phospholipid membranes exposed to ozone stress

In the present work, Langmuir monolayers were used to study the interaction of putrescine (a cationic antioxidant) with anionic charged membranes (1,2-dioleoyl-sn-glycerol-3-phosphate) under oxidative stress caused by the presence of ozone in the water phase. Calcium ions and acidic environment were used to compare the electrostatic and antioxidant effects of putrescine with those of an inorganic cation. It has been shown that the main role of putrescine in protecting systems against oxidation is its rapid reaction with ROS. The initial rate of ROS neutralization rose as the concentration of putrescine increased. No such reaction was observed for calcium ions. The consequence of putrescine's ozone removal was lesser lipid destruction that depended on the pH conditions.

Transcriptome profiles of Quercus rubra responding to increased O3 stress

BACKGROUND

Climate plays an essential role in forest health, and climate change may increase forest productivity losses due to abiotic and biotic stress. Increased temperature leads to the increased formation of ozone (O3). Ozone is formed by the interaction of sunlight, molecular oxygen and by the reactions of chemicals commonly found in industrial and automobile emissions such as nitrogen oxides and volatile organic compounds. Although it is well known that productivity of Northern red oak (Quercus rubra) (NRO), an ecologically and economically important species in the forests of eastern North America, is reduced by exposure to O3, limited information is available on its responses to exogenous stimuli at the level of gene expression.

RESULTS

RNA sequencing yielded more than 323 million high-quality raw sequence reads. De novo assembly generated 52,662 unigenes, of which more than 42,000 sequences could be annotated through homology-based searches. A total of 4140 differential expressed genes (DEGs) were detected in response to O3 stress, as compared to their respective controls. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of the O3-response DEGs revealed perturbation of several biological pathways including energy, lipid, amino acid, carbohydrate and terpenoid metabolism as well as plant-pathogen interaction.

CONCLUSION

This study provides the first reference transcriptome for NRO and initial insights into the genomic responses of NRO to O3. Gene expression profiling reveals altered primary and secondary metabolism of NRO seedlings, including known defense responses such as terpenoid biosynthesis.

Heterogeneous reaction of ozone with syringic acid: Uptake of O3 and changes in the composition and optical property of syringic acid

Syringic acid, which is a typical methoxyphenol emitted from wood combustion, can provide heterogeneous reaction sites for gaseous active components, influencing the concentrations of trace gases and the compositions of syringic acid. The heterogeneous uptake of O₃ on syringic acid was investigated using a flow tube reactor under ambient pressure. The initial uptake coefficient (γ_i) and the steady-state uptake coefficient (γ_ss) of O₃ linearly increased with syringic acid mass (0-0.16 μg cm^-2) and temperature (278-328 K), while they decreased with increasing the O₃ concentration and the O₂ content. The γ_i was independent of relative humidity (20%-70%), whereas γ_ss decreased with relative humidity (7%-70%). The compositional changes of syringic acid by the ozonization were analyzed by the Fourier transform infrared spectrometer (FT-IR) and the gas chromatography-mass spectrometry (GC-MS), confirming the generation of 2,6-dimethoxy-1,4-benzoquinone. In addition, compared to that of fresh syringic acid, the mass absorption efficiency of syringic acid aged by O₃ exhibited an increase in the range of 290-320 nm.

Does the alternative respiratory pathway offer protection against the adverse effects resulting from climate change?

Elevated greenhouse gases (GHGs) induce adverse conditions directly and indirectly, causing decreases in plant productivity. To deal with climate change effects, plants have developed various mechanisms including the fine-tuning of metabolism. Plant respiratory metabolism is highly flexible due to the presence of various alternative pathways. The mitochondrial alternative oxidase (AOX) respiratory pathway is responsive to these changes, and several lines of evidence suggest it plays a role in reducing excesses of reactive oxygen species (ROS) and reactive nitrogen species (RNS) while providing metabolic flexibility under stress. Here we discuss the importance of the AOX pathway in dealing with elevated carbon dioxide (CO2), nitrogen oxides (NOx), ozone (O3), and the main abiotic stresses induced by climate change.

The influence of rising tropospheric carbon dioxide and ozone on plant productivity

Human activities result in a wide array of pollutants being released to the atmosphere. A number of these pollutants have direct effects on plants, including carbon dioxide (CO2 ), which is the substrate for photosynthesis, and ozone (O3 ), a damaging oxidant. How plants respond to changes in these atmospheric air pollutants, both directly and indirectly, feeds back on atmospheric composition and climate, global net primary productivity and ecosystem service provisioning. Here we discuss the past, current and future trends in emissions of CO2 and O3 and synthesise the current atmospheric CO2 and O3 budgets, describing the important role of vegetation in determining the atmospheric burden of those pollutants. While increased atmospheric CO2 concentration over the past 150 years has been accompanied by greater CO2 assimilation and storage in terrestrial ecosystems, there is evidence that rising temperatures and increased drought stress may limit the ability of future terrestrial ecosystems to buffer against atmospheric emissions. Long-term Free Air CO2 or O3 Enrichment (FACE) experiments provide critical experimentation about the effects of future CO2 and O3 on ecosystems, and highlight the important interactive effects of temperature, nutrients and water supply in determining ecosystem responses to air pollution. Long-term experimentation in both natural and cropping systems is needed to provide critical empirical data for modelling the effects of air pollutants on plant productivity in the decades to come.

Involvement of 4-hydroxy-2-nonenal in pollution-induced skin damage

The effects of environmental insults on human health are a major global concern. Some of the most noxious pollutants that humans are exposed to include ozone (O₃ ), particulate matter (PM), and cigarette smoke (CS). Since the skin is the first line of defense against environmental insults, it is considered one of the main target organs for the harmful insults of air pollution. Thus, there is solid evidence that skin pathologies such as premature aging, atopic dermatitis (AD), and psoriasis are associated with pollutant exposure; all of these skin conditions are also associated with an altered redox status. Therefore, although the mechanisms of action and concentrations of O₃ , PM, and CS that we are exposed to differ, exposure to all of these pollutants is associated with the development of similar skin conditions due to the fact that all of these pollutants alter redox homeostasis, increasing reactive oxygen species production and oxidative stress. A main product of oxidative stress, induced by exposure to the aforementioned pollutants, is 4-hydroxy-2-nonenal (HNE), which derives from the oxidation of ω-6 polyunsaturated fatty acids. HNE is a highly reactive compound that can form adducts with cellular proteins and even DNA; it is also an efficient cell signaling molecule able to regulate mitogen-activated protein kinase pathways and the activity of redox-sensitive transcription factors such as Nrf2, AP1, and NFκB. Therefore, increased levels of HNE in the skin, in response to pollutants, likely accelerates skin aging and exacerbates existing skin inflammatory conditions; thus, targeting HNE formation could be an innovative cosmeceutical approach for topical applications.

Growing season extension affects ozone uptake by European forests

Climate change significantly modifies terrestrial ecosystems and vegetation activity, yet little is known about how climate change and ozone pollution interact to affect forest health. Here we compared the trends of two metrics widely used to protect forests against negative impacts of ozone pollution, the AOT40 (Accumulated Ozone over Threshold of 40 ppb) which only depends on surface air ozone concentrations, and the POD (Phytotoxic Ozone Dose) which relies on the amount of ozone uptaken by plants through stomata. Using a chemistry transport model, driven by anthropogenic emission inventories, we found that European-averaged ground-level ozone concentrations significantly declined (-1.6%) over the time period 2000-2014, following successful control strategies to reduce the ozone precursors emission; as a consequence, the AOT40 metric declined (-22%). In contrast, climate change increased both growing season length (~7 days/decade) and stomatal conductance and thus enhanced the stomatal ozone uptake by forests (5.9%), leading to an overall increase of potential ozone damage on plants, despite the reduction in ozone concentrations. Our results suggest that stomatal-flux based strategies of forest protection against ozone in a changing climate require a proper consideration of the duration of the growing season with a better estimation of start and end of the growing season.

The effects of elevated ozone on the accumulation and allocation of poplar biomass depend strongly on water and nitrogen availability

Ozone (O₃) pollution can alter carbon allocation and reduce tree growth - both above and below ground, but the extent of these effects depends on the variation in soil water and nutrient availability. Here we present the accumulation and allocation of biomass in poplar clone 546 (Populus deltoides cv. '55/56' × P. deltoides cv. 'Imperial') for one growing season at two O₃ concentrations (charcoal-filtered air [CF] and non-filtered air + 40 ppb of O₃ [E-O₃]), two watering regimes (well-watered [WW] and reduced watering at 40% of WW irrigation [RW]) and two soil nitrogen addition treatments (no addition [N0] and the addition of 50 kg N ha^-1 year^-1 [N50]). We found that the deleterious effects of E-O₃ depended on the supply of water and nitrogen. Specifically, when the supplies of water and/or N (WW and/or N50) were abundant, E-O₃ significantly reduced whole plant biomass by >15% but had no significant effect on biomass when these supplies were limited (RW and N0). A significant reduction of biomass by E-O₃ occurred earlier in fine roots than in other plant organs, indicating greater sensitivity of fine root to E-O₃. These results suggest that rising O₃ concentrations may not ubiquitously lead to a large reduction in plant biomass since plant growth is often jointly constrained by water and nutrients.

Contribution of Bacillus cereus ERBP in ozone detoxification by Zamioculcas zamiifolia plants: Effect of ascorbate peroxidase, catalase and total flavonoid contents for ozone detoxification

Eighteen plant species were screened for ozone (O₃) removal in a continuous system. Zamioculcas zamiifolia had the highest O₃ removal efficiency. To enhance O₃ removal by Z. zamiifolia, adding a compatible endophytic bacteria, Bacillus cereus ERBP into Z. zamiifolia was studied. After operating under an O₃ continuous system (150-250 ppb) at a flow rate of 0.3 L min^-1 for 80 h, inoculated plants (74%) exhibited higher O₃ removal efficiency than non-inoculated ones (53%). In addition, after O₃ exposure (80 h), the population of B. cereus ERBP in inoculated plants was significantly increased in both shoots approximately 35 folds and leaves 13 folds compared to inoculated plants without O₃ exposure. The results also showed that B. cereus ERBP had the ability to protect Z. zamiifolia against O₃ stress conditions. The increase in B. cereus ERBP populations was attributed to the significant increase in ascorbate peroxidase (APX) and catalase (CAT) activity. In addition, increasing B. cereus ERBP populations led to raise total flavonoid contents which is one of antioxidant compounds. Increasing APX, CAT activities, and total flavonoid contents can enhance O₃ detoxification in plant tissues. The mechanism of B. cereus ERBP for enhancing O₃ phytoremediation was proposed in this study. The results suggested that B. cereus ERBP was a potential tool for alleviating O₃ stress on Z. zamiifolia and enhancing O₃ phytoremediation efficiency.

Role of transient receptor potential cation channel subfamily V member 1 (TRPV1) on ozone-exacerbated allergic asthma in mice

Around the globe, worsening air pollution is spawning major public health and environmental concerns, especially in the poorest and most populous cities. As a major secondary air pollutant, ozone is a potential risk factor for exacerbated asthma, although the underlying mechanisms remain uncertain. In this study, we aim to investigate the role of ozone on asthma exacerbation using a classic asthmatic model with allergic airway inflammation by treating Balb/c mice with ovalbumin (OVA). Our study shows ozone exposure significantly exacerbated OVA-induced asthmatic phenotypes, including serum immunoglobulin, Th cytokines, inflammatory cell counts, mucus production, airway remodeling, and airway hyper-responsiveness (AHR). Interestingly, expression of transient receptor potential cation channel subfamily V member1 (TRPV1) was also significantly elevated in ozone-exacerbated asthmatic mice and that treatment with TRPV1 antagonist effectively suppressed AHR, airway inflammation and remodeling. The underlying mechanisms of these effects may be associated with suppression of neuropeptide calcitonin gene-related peptide (CGRP) and thymic stromal lymphopoietin (TSLP), an epithelial cell-derived cytokine. Base on the role of TRPV1 in allergic asthma, this study further revealed that inhibition of TRPV1 by TRPV1 antagonist has significant anti-inflammatory effects on ozone-induced asthma exacerbation in this study. Induction of TRPV1 expression may be an important mechanism underlying the increased risks for asthma after exposure to environmental pollutants.

Molecular characterization and kinetics of isoprene degrading bacteria

Isoprene, the highly reactive volatile organic compound, is used as monomer for the synthesis of several useful polymers. Its extensive production and usage leads to contamination of air. Once released, it alters the atmospheric chemistry by reacting with hydroxyl radicals (OH) and nitrogen oxides (NO_x) to generate tropospheric ozone. Its prolonged exposure causes deleterious effects in human and plants. Therefore, its removal from the contaminated environment through biodegradation, provides a promising remedial solution. In the present study, isoprene utilizing bacteria namely, Pseudomonas sp., Arthrobacter sp., Bacillus sp. Sphingobacterium sp., Sphingobium sp., and Pantoea sp. were isolated and characterized from leaf surface of Madhuca latifolia and Tectona grandis, and also from soils under these plants. Their isoprene degrading capability and kinetics were assessed in batch mode. The isoprene degradation study indicated Pseudomonas sp. to be the most efficient isoprene degrader.

Signalling molecules responsive to ozone-induced oxidative stress in Salvia officinalis

Tropospheric ozone (O₃) is the most important gaseous pollutant and induces a mass of negative impacts on vegetation at functional and genic levels. The aim of the present study was to investigate the role of reactive oxygen species and signalling molecules in sage plants exposed to O₃ (200 ppb, 5 h). Ozone exposure induced only a transient oxidative burst, as confirmed by the rapid peak of anion superoxide during the first hours of exposure (+16% compared to controls). The spontaneous reaction of O₃ with membrane fatty acids stimulates peroxidative processes, as demonstrated by the rise of thiobarbituric acid reactive substances concentration starting after 1 h of exposure (+25%). The formation of lipid-based signalling molecules (e.g. jasmonic acid) may be regarded as a sort of O₃-perception. The concomitant accumulation of salicylic acid suggests that sage responds early to O₃ by inducing cellular antioxidants mechanisms in order to minimize O₃-oxidative burst. The transient increase of abscisic acid (+25% at the end of the treatment) twinned with the maximal ethylene emission (about two-fold higher than controls) could be interpreted as a first attempt by plants to regulate the signalling responses induced by O₃. In order to investigate the involvement of transcription factors in managing oxidative protection, BLASTX analysis against the Salvia miltiorrhiza sequence genome was carried out using Arabidopsis thaliana WRKY sequences as queries. Six gene sequences were identified for sage WRKYs and their relative gene expression analyses were characterized. WRKY4, WRKY5, WRKY11 and WRKY46 were up-regulated by O₃ at 2 and 5 h of exposure and they showed similarity with AtWRKY48, AtWRKY22 and AtWRKY53 in A. thaliana. These results suggest that WRKYs could play a pivotal role in the signalling mechanisms during the responses of plants to O₃.

When "thirsty" means "less able to activate the signalling wave trigged by a pulse of ozone": A case of study in two Mediterranean deciduous oak species with different drought sensitivity

There is a lack of knowledge about the possibility that plants facing abiotic stressors, such as drought, have an altered perception of a pulse of O₃ and incur in alterations of their signalling network. This poses some concerns as to whether defensive strategy to cope episodic O₃ peaks in healthy plants may fail under stress. In this study, a set of saplings of two Mediterranean deciduous species, Quercus cerris and Q. pubescens, was subjected to water withholding (20% of daily evapotranspiration for 15 days) while another set was kept well-watered. Saplings were then subjected to a pulse of O₃ (200 nl l^-1 for 5 h) or maintained in filtered air. Q. pubescens had a more severe decline of photosynthesis and leaf PDΨ_w (about -65% and 5-fold lower than in well-watered ones) and events of cell death were observed under drought when compared to Q. cerris, which is supportive for a higher sensitivity to drought exhibited by this species. When O₃ was applied after drought, patterns of signalling compounds were altered in both species. Only in Q. pubescens, the typical O₃-induced accumulation of apoplastic reactive oxygen species, which is the first necessary step for the activation of signalling cascade, was completely lost. In Q. cerris the most frequent changes encompassed the weakening of peaks of key signalling molecules (ethylene and salicylic acid), whereas in Q. pubescens both delayed (salicylic and jasmonic acid) or weakened (ethylene and salicylic acid) peaks were observed. This is translated to a higher ability of Q. cerris to maintain a prompt activation of defensive reaction to counteract oxidative damage due to the pollutant. Our results reveal the complexity of the signalling network in plants facing multiple stresses and highlight the need to further investigate possible alteration of defensive mechanism of tree species to predict their behavior.

Deciphering the main determinants of O3 tolerance in Euramerican poplar genotypes

Tropospheric ozone (O₃) is the main secondary pollutant and considered to be the most damaging for growth and productivity. O₃ is well known to induce oxidative stress and Reactive Oxygen Species accumulation in leaf tissues. Several mechanisms have been suggested to enable trees to cope with such stress; however, their relative contribution to O₃ tolerance is still unclear. Here, ten Euramerican poplar genotypes (Populus deltoides × nigra) were investigated regarding their response to 120 ppb of O₃ for 3 weeks in order to determine main mechanisms and identify the key traits and strategies linked to a better tolerance to O₃-induced oxidative stress. Results showed that ascorbate peroxidase and ascorbate regeneration through monodehydroascorbate reductase are the main determinants of O₃ tolerance in Euramerican poplar, in protecting photosynthesis capacity from oxidative stress and therefore, maintaining growth and productivity. Besides, stomatal closure was harmful in sensitive genotypes, suggesting that avoiding strategy can be further deleterious under chronic ozone. Finally, O₃-induced early senescence appeared essential when up scaling leaf-level mechanistic response to whole-plant productivity, in fine-tuning resource reallocation and photosynthesis area.

The influence of maternal and perinatal high-fat diet on ozone-induced pulmonary responses in offspring

There is growing interest in understanding how maternal diet might affect the sensitivity of offspring to environmental exposures. Previous studies demonstrated that adult rat offspring (approximately 6-months-old) from dams given a high-fat diet (HFD) prior to, during, and after pregnancy displayed elevated pulmonary responses to an acute ozone (O3) exposure. The aim of this study was to examine the influence of maternal and perinatal HFD on pulmonary and metabolic responses to O3 in male and female young-adult offspring (approximately 3-month old). One-month-old F0 female Long-Evans rats commenced HFD (60% kcal from fat) or control diet (CD; 10.5% kcal from fat) and were bred on PND 72. Offspring were maintained on respective HFD or CD until PND 29 when all groups were switched to CD. The 3-months-old female and male offspring (n = 10/group) were exposed to air or 0.8 ppm O3 for 5hr/day for 2 consecutive days. Maternal and perinatal HFD significantly increased body weight and body fat % in offspring regardless of gender. Ozone exposure, but not maternal and perinatal diet, induced hyperglycemia and glucose intolerance in the offspring. Ozone-induced alterations in pulmonary function were exacerbated by maternal and perinatal HFD in both offspring genders. Pulmonary injury/inflammation markers in response to O3 exposure such as bronchoalveolar lavage fluid total protein, lactate dehydrogenase, total cells, and neutrophils were further augmented in offspring (males>females) from dams fed the HFD. Data suggest that maternal and perinatal HFD may enhance the susceptibility of offspring to O3-induced pulmonary injury and that these effects may be sex-specific.

Ozone-induced inhibition of kiwifruit ripening is amplified by 1-methylcyclopropene and reversed by exogenous ethylene

BACKGROUND

Understanding the mechanisms involved in climacteric fruit ripening is key to improve fruit harvest quality and postharvest performance. Kiwifruit (Actinidia deliciosa cv. 'Hayward') ripening involves a series of metabolic changes regulated by ethylene. Although 1-methylcyclopropene (1-MCP, inhibitor of ethylene action) or ozone (O₃) exposure suppresses ethylene-related kiwifruit ripening, how these molecules interact during ripening is unknown.

RESULTS

Harvested 'Hayward' kiwifruits were treated with 1-MCP and exposed to ethylene-free cold storage (0 °C, RH 95%) with ambient atmosphere (control) or atmosphere enriched with O₃ (0.3 μL L^- 1) for up to 6 months. Their subsequent ripening performance at 20 °C (90% RH) was characterized. Treatment with either 1-MCP or O₃ inhibited endogenous ethylene biosynthesis and delayed fruit ripening at 20 °C. 1-MCP and O₃ in combination severely inhibited kiwifruit ripening, significantly extending fruit storage potential. To characterize ethylene sensitivity of kiwifruit following 1-MCP and O₃ treatments, fruit were exposed to exogenous ethylene (100 μL L^- 1, 24 h) upon transfer to 20 °C following 4 and 6 months of cold storage. Exogenous ethylene treatment restored ethylene biosynthesis in fruit previously exposed in an O₃-enriched atmosphere. Comparative proteomics analysis showed separate kiwifruit ripening responses, unraveled common 1-MCP- and O₃-dependent metabolic pathways and identified specific proteins associated with these different ripening behaviors. Protein components that were differentially expressed following exogenous ethylene exposure after 1-MCP or O₃ treatment were identified and their protein-protein interaction networks were determined. The expression of several kiwifruit ripening related genes, such as 1-aminocyclopropane-1-carboxylic acid oxidase (ACO1), ethylene receptor (ETR1), lipoxygenase (LOX1), geranylgeranyl diphosphate synthase (GGP1), and expansin (EXP2), was strongly affected by O₃, 1-MCP, their combination, and exogenously applied ethylene.

CONCLUSIONS

Our findings suggest that the combination of 1-MCP and O₃ functions as a robust repressive modulator of kiwifruit ripening and provide new insight into the metabolic events underlying ethylene-induced and ethylene-independent ripening outcomes.

Ethylenediurea (EDU) mitigates the negative effects of ozone in rice: Insights into its mode of action

Monitoring of ozone damage to crops plays an increasingly important role for the food security of many developing countries. Ethylenediurea (EDU) could be a tool to assess ozone damage to vegetation on field scale, but its physiological mode of action remains unclear. This study investigated mechanisms underlying the ozone-protection effect of EDU in controlled chamber experiments. Ozone sensitive and tolerant rice genotypes were exposed to ozone (108 ppb, 7 hr day^-1 ) and control conditions. EDU alleviated ozone effects on plant morphology, foliar symptoms, lipid peroxidation, and photosynthetic parameters in sensitive genotypes. Transcriptome profiling by RNA sequencing revealed that thousands of genes responded to ozone in a sensitive variety, but almost none responded to EDU. Significant interactions between ozone and EDU application occurred mostly in ozone responsive genes, in which up-regulation was mitigated by EDU application. Further experiments documented ozone degrading properties of EDU, as well as EDU deposits on leaf surfaces possibly related to surface protection. EDU application did not mitigate the reaction of plants to other abiotic stresses, including iron toxicity, zinc deficiency, and salinity. This study provided evidence that EDU is a surface protectant that specifically mitigates ozone stress without interfering directly with the plants' stress response systems.

Should we see urban trees as effective solutions to reduce increasing ozone levels in cities?

Outdoor air pollution is considered as the most serious environmental problem for human health, associated with some million deaths worldwide per year. Cities have to cope with the challenges due to poor air quality impacting human health and citizen well-being. According to an analysis in the framework of this study, the annual mean concentrations of tropospheric ozone (O₃) have been increasing by on average 0.16 ppb year^-1 in cities across the globe over the time period 1995-2014. Green urban infrastructure can improve air quality by removing O₃. To efficiently reduce O₃ in cities, it is important to define suitable urban forest management, including proper species selection, with focus on the removal ability of O₃ and other air pollutants, biogenic emission rates, allergenic effects and maintenance requirements. This study reanalyzes the literature to i) quantify O₃ removal by urban vegetation categorized into trees/shrubs and green roofs; ii) rank 95 urban plant species based on the ability to maximize air quality and minimize disservices, and iii) provide novel insights on the management of urban green spaces to maximize urban air quality. Trees showed higher O₃ removal capacity (3.4 g m^-2 year^-1 on average) than green roofs (2.9 g m^-2 year^-1 as average removal rate), with lower installation and maintenance costs (around 10 times). To overcome present gaps and uncertainties, a novel Species-specific Air Quality Index (S-AQI) of suitability to air quality improvement is proposed for tree/shrub species. We recommend city planners to select species with an S-AQI>8, i.e. with high O₃ removal capacity, O₃-tolerant, resistant to pests and diseases, tolerant to drought and non-allergenic (e.g. Acer sp., Carpinus sp., Larix decidua, Prunus sp.). Green roofs can be used to supplement urban trees in improving air quality in cities. Urban vegetation, as a cost-effective and nature-based approach, aids in meeting clean air standards and should be taken into account by policy-makers.