Enhanced Reactive Oxygen Species Scavenging Research Articles

Development of Oral pH-sensitive redox Nanotherapeutics for gastric ulcer therapy

Gastric ulcer is a common gastrointestinal disorder worldwide. Although its pathogenesis is unclear, the overproduction of reactive oxygen species (ROS), which results in an oxidative imbalance, has been reported as a central driving mechanism. Within the scope of this investigation, we developed two different self-assembling redox nanoparticles (RNPs) with ROS-scavenging features for the oral treatment of gastric ulcers. One of them, referred to as RNPN, disintegrates in response to acidic pH, whereas the other, denoted as RNPO, remains intact regardless of pH variations. Both types of RNPs showed different free radical scavenging activities in vitro. Protonation of the amino linkages in the side chains of RNPN caused the micelle structure to collapse and the nitroxide radicals encapsulated in the core were exposed to the outside, resulting in a significant increase in antioxidant capacity as the pH decreases. In contrast, RNPO maintained its spherical structure and consistent antioxidant reactivity irrespective of pH changes. The in vivo gastric retention of orally administered RNPN was significantly improved compared to that of RNPO which might be explained by the increased exposure of cationic protonating segments in RNPN on the negatively charged gastric mucosal surface. Owing to its improved gastric retention and enhanced ROS scavenging capacity under acidic pH conditions, RNPN exhibited superior protective effects against oxidative stress induced by aspirin in a gastric ulcer mouse model compared to RNPO. In addition, neither RNPN nor RNPO resulted in severe lethal effects or significant changes in the morphology of zebrafish embryos, indicating their biosafety. Our results suggest that the oral administration of RNPs has a high therapeutic potential for gastric ulcer treatment.

Inhaled tea polyphenol-loaded nanoparticles coated with platelet membranes largely attenuate asthmatic inflammation

BackgroundTea polyphenols (TPs), prominent constituents of green tea, possess remarkable antioxidant and anti-inflammatory properties. However, their therapeutic potential is limited due to low absorption and poor bioavailability. To address this limitation and enhance their efficacy, we developed a biomimetic nanoplatform by coating platelet membrane (PM) onto poly-lactic-co-glycolic acid (PLGA) nanoparticles (NPs) to create targeted delivery vehicles for TPs (PM@TP/NPs) to the inflamed tissues in asthma.MethodsAfter synthesizing and characterizing PM@TP/NPs, we assessed their biocompatibility and biosafety through cell viability assays, hemolysis tests, and inflammation analysis in vivo and in vitro. The therapeutic effect of PM@TP/NPs on asthma was then evaluated using a mouse model of HDM-induced asthma. Additionally, PM@TP/NPs-mediated reactive oxygen species (ROS) scavenging capacity, as well as the activation of signaling pathways, were analyzed in HBE cells and asthmatic mice via flow cytometry, RT-qPCR, and western blotting.ResultsCompared with free TPs, PM@TP/NPs demonstrated excellent biocompatibility and safety profiles in both in vitro and in vivo, as well as enhanced retention in inflamed lungs. In HDM-induced mouse asthma model, inhaled PM@TP/NPs largely attenuated lung inflammation and reduced the secretion of type 2 pro-inflammatory cytokines in the lungs compared to free TPs. The therapeutic effects of PM@TP/NPs on asthma might be associated with an enhanced ROS scavenging capacity, increased activation of the Nrf2/HO-1 pathway, and decreased activation of the CCL2/MAPK and TLR4/NF-κB pathway in the lungs.ConclusionsOur findings demonstrate that inhalation of PM@TP/NPs largely attenuated lung inflammation in HDM-induced asthmatic mice. These results suggest that PM@TP/NPs might be a novel therapeutic strategy for asthma.

The Stylo Cysteine-Rich Peptide SgSnakin1 Is Involved in Aluminum Tolerance through Enhancing Reactive Oxygen Species Scavenging.

Stylo (Stylosanthes spp.) is an important pasture legume with strong aluminum (Al) resistance. However, the molecular mechanisms underlying its Al tolerance remain fragmentary. Due to the incomplete genome sequence information of stylo, we first conducted full-length transcriptome sequencing for stylo root tips treated with and without Al and identified three Snakin/GASA genes, namely, SgSnakin1, SgSnakin2, and SgSnakin3. Through quantitative RT-PCR, we found that only SgSnakin1 was significantly upregulated by Al treatments in stylo root tips. Histochemical localization assays further verified the Al-enhanced expression of SgSnakin1 in stylo root tips. Subcellular localization in both tobacco and onion epidermis cells showed that SgSnakin1 localized to the cell wall. Overexpression of SgSnakin1 conferred Al tolerance in transgenic Arabidopsis, as reflected by higher relative root growth and cell vitality, as well as lower Al concentration in the roots of transgenic plants. Additionally, overexpression of SgSnakin1 increased the activities of SOD and POD and decreased the levels of O2·- and H2O2 in transgenic Arabidopsis in response to Al stress. These findings indicate that SgSnakin1 may function in Al resistance by enhancing the scavenging of reactive oxygen species through the regulation of antioxidant enzyme activities.

NIR triggered polydopamine coated cerium dioxide nanozyme for ameliorating acute lung injury via enhanced ROS scavenging

Acute lung injury (ALI) is a life threatening disease in critically ill patients, and characterized by excessive reactive oxygen species (ROS) and inflammatory factors levels in the lung. Multiple evidences suggest that nanozyme with diversified catalytic capabilities plays a vital role in this fatal lung injury. At present, we developed a novel class of polydopamine (PDA) coated cerium dioxide (CeO2) nanozyme (Ce@P) that acts as the potent ROS scavenger for scavenging intracellular ROS and suppressing inflammatory responses against ALI. Herein, we aimed to identify that Ce@P combining with NIR irradiation could further strengthen its ROS scavenging capacity. Specifically, NIR triggered Ce@P exhibited the most potent antioxidant and anti-inflammatory behaviors in lipopolysaccharide (LPS) induced macrophages through decreasing the intracellular ROS levels, down-regulating the levels of TNF-α, IL-1β and IL-6, up-regulating the level of antioxidant cytokine (SOD-2), inducing M2 directional polarization (CD206 up-regulation), and increasing the expression level of HSP70. Besides, we performed intravenous (IV) injection of Ce@P in LPS induced ALI rat model, and found that it significantly accumulated in the lung tissue for 6 h after injection. It was also observed that Ce@P + NIR presented the superior behaviors of decreasing lung inflammation, alleviating diffuse alveolar damage, as well as promoting lung tissue repair. All in all, it has developed the strategy of using Ce@P combining with NIR irradiation for the synergistic enhanced treatment of ALI, which can serve as a promising therapeutic strategy for the clinical treatment of ROS derived diseases as well.

DNA methylation-mediated ROS production contributes to seed abortion in litchi

Although there is increasing evidence suggesting that DNA methylation regulates seed development, the underlying mechanisms remain poorly understood. Therefore, we aimed to shed light on this by conducting whole-genome bisulfite sequencing using seeds from the large-seeded cultivar 'HZ' and the abortive-seeded cultivar 'NMC'. Our analysis revealed that the 'HZ' seeds exhibited a hypermethylation level compared to the 'NMC' seeds. Furthermore, we found that the genes associated with differentially methylated regions (DMRs) and differentially expressed genes (DEGs) were mainly enriched in the reactive oxygen species (ROS) metabolic pathway. To investigate this further, we conducted nitroblue tetrazolium (NBT) and 2,7-Dichlorodihydrofluorescein (DCF) staining, which demonstrated a significantly higher amount of ROS in the 'NMC' seeds compared to the 'HZ' seeds. Moreover, we identified that the gene LcGPX6, involved in ROS scavenging, exhibited hypermethylation levels and parallelly lower expression levels in 'NMC' seeds compared to 'HZ' seeds. Interestingly, the ectopic expression of LcGPX6 in Arabidopsis enhanced ROS scavenging and resulted in lower seed production. Together, we suggest that DNA methylation-mediated ROS production plays a significant role in seed development in litchi, during which hypermethylation levels of LcGPX6 might repress its expression, resulting in the accumulation of excessive ROS and ultimately leading to seed abortion.

Enhanced ROS scavenging and tissue adhesive abilities in injectable hydrogels by protein modification with oligoethyleneimine.

Postsurgical treatment comprehensively benefits from the application of tissue-adhesive injectable hydrogels, which reduce postoperative complications by promoting wound closure and tissue regeneration. Although various hydrogels have been employed as clinical tissue adhesives, many exhibit deficiencies in adhesive strength under wet conditions or in immunomodulatory functions. Herein, we report the development of reactive oxygen species (ROS) scavenging and tissue-adhesive injectable hydrogels composed of polyamine-modified gelatin crosslinked with the 4-arm poly (ethylene glycol) crosslinker. Polyamine-modified gelatin was particularly potent in suppressing the secretion of proinflammatory cytokines from stimulated primary macrophages. This effect is attributed to its ability to scavenge ROS and inhibit the nuclear translocation of nuclear factor kappa-B. Polyamine-modified gelatin-based hydrogels exhibited ROS scavenging abilities and enhanced tissue adhesive strength on collagen casing. Notably, the hydrogel demonstrated exceptional tissue adhesive properties in a wet environment, as evidenced by its performance using porcine small intestine tissue. This approach holds significant promise for designing immunomodulatory hydrogels with superior tissue adhesion strength compared to conventional medical materials, thereby contributing to advancements in minimally invasive surgical techniques.

PEG-6000 Priming Improves Aged Soybean Seed Vigor via Carbon Metabolism, ROS Scavenging, Hormone Signaling, and Lignin Synthesis Regulation

Seed priming, a valuable seed pretreatment method widely employed in agricultural production, counteracts the decline in seed vigor attributed to aging and deterioration. However, PEG priming effectively enhances the vigor of aged soybean seeds. In this study, “TONGDOU13” soybean seeds were subjected to PEG-6000 priming at varying concentrations (10%, 20%, 30%, 40%) for three different durations (12 h, 24 h, 36 h). The results showed that a 24 h priming with 30% PEG-6000 significantly enhances the vigor of aged soybean seeds. To elucidate the mechanism underlying the heightened vigor resulting from PEG-6000 priming, we employed transcriptome sequencing and physiological–biochemical tests. Transcriptome sequencing analysis showed the significant down-regulation of carbon metabolism-related genes post PEG-6000 priming, which facilitated energetically efficient germination. Five peroxidase-encoding genes displayed significant up-regulation, promoting the conversion of coumaryl alcohol to hydroxy-phenyl lignin, a probable catalyst for augmented seed vigor. SOD and GST genes were significantly up-regulated, enhancing the scavenging ability of reactive oxygen species (ROS). The concurrent up-regulation of brassinolide (BR) and auxin (IAA) signals countered ABA signaling, thereby promoting aged seed germination. Further investigation included the measurements of antioxidant enzyme activity, hormone levels, and lignin content. Notably, primed aged seeds exhibited enhanced ROS scavenging ability, and increased lignin, BR, and IAA contents. Therefore, PEG priming may improve aged soybean seed vigor through the co-regulation of carbon metabolism, ROS scavenging, hormone signaling, and lignin synthesis. This study will be vital for preserving germplasm resources and reutilizing aged soybean seeds.

Transcriptome analysis reveals ZmERF055 contributes to waterlogging tolerance in sweetcorn

Waterlogging is a major disaster damaging crop production. However, most sweetcorn cultivars are not tolerant to waterlogging, which severely threatens their production. In order to understand the genetic mechanisms underlying waterlogging tolerance in sweetcorn, this study conducted a comprehensive investigation of sweetcorn waterlogging tolerance at the levels of physiology, biochemistry, and transcriptome in two sweetcorn CSSLs (chromosome segment substitution lines), D120 and D81. We found that D120 showed increased plant height, root length, root area, adventitious root numbers, antioxidant enzyme activities, and aerenchyma area ratio compared to D81. The transcriptome results showed that 2492 and 2351 differentially expressed genes (DEGs) were obtained at 4 h and 8 h of waterlogging treatment, respectively. Genes involved in reactive oxygen species (ROS) homeostasis, photosynthesis, and alcohol fermentation are sensitive in the waterlogging tolerant genotype D120, resulting in enhanced ROS scavenging ability, adventitious roots, and aerenchyma formation. Additionally, ethylene-, auxin-, and ABA-related genes exhibited different responses to waterlogging stress in sweetcorn. We integrated transcriptome and differential chromosomal fragments data and identified that ZmERF055 on chromosome 9 was directly involved in waterlogging stress. ZmERF055-overexpressing plants consistently exhibited significantly increased waterlogging tolerance and ROS homeostasis in Arabidopsis. These results offer a network of plant hormone signaling, ROS homeostasis, and energy metabolism co-modulating waterlogging tolerance in sweetcorn. Additionally, the findings support ZmERF055 as a potential ideal target gene in crop breeding to improve plant waterlogging tolerance.

Transferrin-Targeted Iridium Nanoagglomerates with Multi-Enzyme Activities for Cerebral Ischemia-Reperfusion Injury Therapy.

Cerebral ischemia-reperfusion injury (CIRI) is a complex pathological condition with high mortality. In particular, reperfusion can stimulate overproduction of reactive oxygen species (ROS) and activation of inflammation, causing severe secondary injuries to the brain. Despite tremendous efforts, it remains urgent to rationally design antioxidative agents with straightforward and efficient ROS scavenging capability. Herein, a potent antioxidative agent was explored based on iridium oxide nano-agglomerates (Tf-IrO2 NAs) via the facile transferrin (Tf)-templated biomineralization approach, and innovatively applied to treat CIRI. Containing some small-size IrO2 aggregates, these NAs possess intrinsic hydroxyl radicals (•OH)-scavenging ability and multifarious enzyme activities, such as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Moreover, they also showed improved blood-brain barrier (BBB) penetration and enhanced accumulation in the ischemic brain via Tf receptor-mediated transcytosis. Therefore, Tf-IrO2 NAs achieved robust in vitro anti-inflammatory and cytoprotection effects against oxidative stress. Importantly, mice were effectively protected against CIRI by enhanced ROS scavenging activity in vivo, and the therapeutic mechanism was systematically verified. These findings broaden the idea of expanding Ir-based NAs as potent antioxidative agents to treat CIRI and other ROS-mediated diseases. STATEMENT OF SIGNIFICANCE: : (1) The ROS-scavenging activities of IrO2 are demonstrated comprehensively, which enriched the family of nano-antioxidants. (2) The engineering Tf-IrO2 nano-agglomerates present unique multifarious enzyme activities and simultaneous transferrin targeting and BBB crossing ability for cerebral ischemia-reperfusion injury therapy. (3) This work may open an avenue to enable the use of IrO2 to alleviate ROS-mediated inflammatory and brain injury diseases.

NIR-responsive molybdenum (Mo)-based nanoclusters enhance ROS scavenging for osteoarthritis therapy

Osteoarthritis (OA) is one of the most prevalent musculoskeletal disorders globally, and treating OA remains a significant challenge. Currently, pharmacological treatments primarily aim to alleviate the OA symptoms associated with inflammation and pain, and no disease-modifying therapies are available to delay OA development and progression. Reactive oxygen species (ROS) play an essential role in OA development and progression, which are a promising target for curing OA. In this study, it was found that photothermal properties of near-infrared (NIR) irradiation enhanced the ROS scavenging activity of molybdenum-based polyoxometalate (POM) nanoclusters. Because of enhanced ROS scavenging, NIR-responsive POM nanoclusters were developed as novel excellent nano-antioxidants for OA protection. The results demonstrated that NIR-responsive POM exhibited outstanding antioxidant activity and superexcellent anti-inflammatory effects, which could effectively alleviate the clinical symptoms of OA mice, diminish inflammatory cytokines, reduce catabolic proteases, and mitigate the progression of OA. Meanwhile, the local treatment had no side effects on normal tissues. Thus, this study pioneered the application of POM for alleviating OA with expected safety and efficiency.

Infected wound repair with an ultrasound-enhanced nanozyme hydrogel scaffold.

Chronic diabetic wounds persistently face the threat of evolving into diabetic foot ulcers owing to severe hypoxia, high levels of reactive oxygen species (ROS), and a complex inflammatory microenvironment. To concurrently surmount these obstacles, we developed an all-round therapeutic strategy based on nanozymes that simultaneously scavenge ROS, generate O2 and regulate the immune system. First, we designed a dynamic covalent bond hybrid of a metal-organic coordination polymer as a synthesis template, obtaining high-density platinum nanoparticle assemblies (PNAs). This compact assembly of platinum nanoparticles not only effectively simulates antioxidant enzymes (CAT, POD) but also, under ultrasound (US), enhances electron polarization through the surface plasmon resonance effect, endowing it with the ability to induce GSH generation by effectively replicating the enzyme function of glutathione reductase (GR). PNAs, by mimicking the activity of CAT and POD, effectively catalyze hydrogen peroxide, alleviate hypoxia, and effectively generate GSH under ultrasound, further enhancing ROS scavenging. Notably, PNAs can regulate macrophage responses in the inflammatory microenvironment, circumventing the use of any additives. It was confirmed that PNAs can enhance cell proliferation and migration, promote neoangiogenesis IN VITRO, and accelerate the healing of infected diabetic wounds IN VIVO. We believe that an all-round therapeutic method based on PNA nanozymes could be a promising strategy for sustained diabetic wound healing.

Transcriptomic and physiological analysis reveals the possible mechanism of ultrasound inhibiting strawberry (Fragaria × ananassa Duch.) postharvest softening.

Ultrasound effectively inhibited strawberry softening but the mechanism was not clear. In this study, physical data including firmness, soluble pectin (SP) contents, pectin esterase (PE), polygalacturonase (PG) activity and transcriptome sequencing data were analyzed to explore the mechanism of strawberry response to ultrasonic treatment. After 24 days storage, the firmness reduction rate and soluble contents (SP) increased rate of the strawberry treated with ultrasound (25 kHz, 0.15 W/cm2) for 3 min decreased 41.70 and 63.12% compared with the control, respectively. While the PG and PE enzyme activities of ultrasound-treated strawberries were significantly lower than control after storage for 18 days. A total of 1,905 diferentially expressed genes (DEGs) were identified between ultrasound-treated and control, with 714 genes upregulated and 1,254 genes downregulated, including 56 genes in reactive oxygen species (ROS), auxin (AUX), ethylene (ETH) and jasmonic acid (JA) signaling pathways. At 0 h, 15 genes including LOX, JMT, ARP, SKP, SAUR, IAA, ARF, and LAX were significantly upregulated compared with the control group, which means reactive oxygen specie, auxin, ethylene and jasmonic acid-mediated signaling pathway respond to ultrasound immediately. ERF109, ERF110, and ACS1_2_6 downregulated before 2 days storage indicated ethylene signaling pathway was inhibited, while after 2 days, 9 genes including ERF027, ERF109, and ERF110 were significantly upregulated indicating that the response of the ethylene signaling pathway was lagging. Therefore, in strawberry ultrasound enhanced ROS scavenging and activated JA biosynthesis, which acts as a signal for delaying the activation of ET signaling pathway, thus suppressing the activity of pectin-degrading enzymes PE and PG, and ultimately inhibiting postharvest softening.

Arbuscular mycorrhizal fungi contribute to reactive oxygen species homeostasis of Bombax ceiba L. under drought stress.

Drought stress is one of the major abiotic factors limiting plant growth and causing ecological degradation. The regulation of reactive oxygen species (ROS) generation and ROS scavenging is essential to plant growth under drought stress. To investigate the role of arbuscular mycorrhizal fungi (AMF) on ROS generation and ROS scavenging ability under drought stress in Bombax ceiba, the ROS content, the expression levels of respiratory burst oxidase homologue (Rbohs), and the antioxidant response were evaluated in AMF and NMF (non-inoculated AMF) plants under drought stress. 14 BcRboh genes were identified in the B. ceiba genome and divided into five subgroups based on phylogenetic analysis. The effect of AMF on the expression profiles of BcRbohs were different under our conditions. AMF mainly downregulated the expression of Rbohs (BcRbohA, BcRbohD, BcRbohDX2, BcRbohE, BcRbohFX1, and BcRbohI) in drought-stressed seedlings. For well-water (WW) treatment, AMF slightly upregulated Rbohs in seedlings. AMF inoculation decreased the malondialdehyde (MDA) content by 19.11 and 20.85%, decreased the O2⋅– production rate by 39.69 and 65.20% and decreased H2O2 content by 20.06 and 43.21% compared with non-mycorrhizal (NMF) plants under drought stress in root and shoot, respectively. In addition, AMF inoculation increased the non-enzymatic antioxidants glutathione (GSH) and ascorbic acid (AsA) content in roots by 153.52 and 28.18% under drought stress, respectively. The activities of antioxidant enzymes (SOD, PX, CAT, APX, GPX, GR, MDAR, and DHAR) all increased ranging from 19.47 - 131.54% due to AMF inoculation under drought stress. In conclusion, these results reveal that AMF inoculation can maintain ROS homeostasis by mitigating drought-induced ROS burst, via decreasing ROS generation and enhancing ROS scavenging ability of B. ceiba seedlings.

N7 -SSPP fusion gene improves salt stress tolerance in transgenic Arabidopsis and soybean through ROS scavenging.

Considerable signal crosstalk exists in the regulatory network of senescence and stress response. Numerous senescence-associated genes are also involved in plant stress tolerance. However, the underlying mechanisms and application potential of these genes in stress-tolerant crop breeding remain poorly explored. We found that overexpression of SENESCENCE-SUPPRESSED PROTEIN PHOSPHATASE (SSPP), a negative regulator of leaf senescence, significantly improved plant salt tolerance by increasing reactive oxygen species (ROS) scavenging in both Arabidopsis and soybean. However, overexpression of SSPP severely suppressed normal plant growth, limiting its direct use in agriculture. We previously revealed that the N-terminal 1-14 residues of ACS7 (termed 'N7 ') negatively regulated its protein stability through the ubiquitin/proteasome pathway, and the N7 -mediated protein degradation was suppressed by environmental and senescence signals. To avoid the adverse effects of SSPP, the N7 element was fused to the N-terminus of SSPP. We demonstrated that N7 -SSPP fusion gene effectively rescued SSPP-induced growth suppression but maintained enhanced salt tolerance in Arabidopsis and soybean. Particularly, N7 -SSPP enhanced tolerance to long-term salt stress and increased seed yield in soybean. These results suggest that N7 -SSPP overcomes the disadvantages of SSPP on plant growth inhibition and effectively improves salt tolerance through enhanced ROS scavenging, providing an effective strategy of using posttranslational regulatory element for salt-tolerant crop breeding.

Carboxymethyl cellulose-based water barrier coating regulated postharvest quality and ROS metabolism of pakchoi (Brassica chinensis L.)

The postharvest preservation of Brassica vegetables has received much attention for improving their nutritional and commercial value. In this study, carboxymethyl cellulose (CMC)-based cross-linking coating embedded with liquid paraffin was prepared to preserve fresh pakchoi (Brassica chinensis L.) and its effects on postharvest water loss, quality and reactive oxygen species (ROS) metabolism were evaluated. Results showed that ionic cross-linking and liquid paraffin reinforced the structure compactness and water barrier property of CMC coating by uniformly distributing liquid paraffin in cross-linking network. The novel CMC-based coating effectively reduced water loss and improved appearance and nutrition of fresh pakchoi stored at 25 °C and 60 % relative humidity for 48 h. Furthermore, the coating treatment enhanced ROS scavenging capacity and reduced lipid peroxidation, which was attributed to the improvement of antioxidant enzyme activities, ascorbate-glutathione cycle and phenylpropanoid metabolism. This work demonstrates that the novel CMC-based water barrier coating is promising to control the water loss of pakchoi and further maintain the whole quality by regulating ROS metabolism.

Sequential delivery for hepatic fibrosis treatment based on carvedilol loaded star-like nanozyme

Hepatic fibrosis, characterized by excessive reactive oxygen species (ROS) generation, hepatic stellate cells (HSCs) activation, and enormous extracellular matrix (ECM) production, can further cause liver cirrhosis, liver failure and liver cancer. However, the combination of limited solubility, low targeting, uncontrolled release and the sophisticated physiological barriers are tremendous challenges for therapeutic effect. In this study, we engineered a sequential delivery strategy based on autophagy inhibitor carvedilol (CAR) loaded and hyaluronic acid (HA) modified star-like Au nanozyme (Au NS@CAR-HA) for targeted HSCs suppression. In hepatic fibrosis acidic environment, CAR-HA can be firstly detached from Au NS@CAR-HA. Then, CAR would be released from CAR-HA conjugation by chemical bond breakage which triggered by intracellular acid potential, thus could suppressing autolysosome generation by up-regulation of autosome and lysosome pH value to inhibit HSCs activation. Meanwhile, Au NS exhibited enhanced ROS scavenging efficiency of hydrogen peroxides and superoxide, which was helpful to restrain the activity of peroxisome proliferators-activated receptors β (PPARβ) and c-Jun N-terminal kinase (JNK), thereby reducing HSCs proliferation to enhance HSCs inactivation efficacy. In conclusion, Au NS@CAR-HA can attenuate hepatic fibrosis via regulating the proliferation and activation of hepatic stellate cells, which provides a new strategy for hepatic fibrosis treatment.

Ethylene signaling in salt-stressed Arabidopsis thaliana ein2-1 and ctr1-1 mutants – A dissection of molecular mechanisms involved in acclimation

To pinpoint ethylene-mediated molecular mechanisms involved in the adaptive response to salt stress we conducted a comparative study of Arabidopsis thaliana wild type (Col-0), ethylene insensitive (ein2-1), and constitutive signaling (ctr1-1) mutant plants. Reduced germination and survival rates were observed in ein2-1 plants at increasing NaCl concentrations. By contrast, ctr1-1 mutation conferred salt stress tolerance during early vegetative development, corroborating earlier studies. Аll genotypes experienced strong stress as evidenced by the accumulation of reactive oxygen species (ROS) and increased membrane lipid peroxidation. However, the isoenzyme profiles of ROS scavenging enzymes demonstrated a higher peroxidase (POX) activity in ctr1-1 individuals under control and salt stress conditions. A markedly elevated free L-Proline (L-Pro) content was detected in the ethylene constitutive mutant. This coincided with the increased levels of Delta-1-Pyrroline-5-Carboxylate Synthase (P5CS) which is the rate-limiting enzyme from the proline biosynthetic pathway. A stabilized upregulation of a stress-induced P5CS1 splice variant was observed in the ctr1-1 background, which was not documented in the ethylene insensitive mutant ein2-1. Transcript profiling of the major SALT OVERLY SENSITIVE (SOS) pathway players (SOS1, SOS2, and SOS3) revealed altered gene expression in the organs of the ethylene signaling mutants. Overall suppressed SOS expression was observed in the ein2-1 mutants while only the SOS transcript profiles in the ctr1-1 roots were similar to the wild type. Altogether, we provide experimental evidence for ethylene-mediated molecular mechanisms implicated in the acclimation response to salt stress in Arabidopsis, which operate mainly through the regulation of free proline accumulation and enhanced ROS scavenging.

Melatonin treatment delays postharvest senescence and maintains the organoleptic quality of ‘Newhall’ navel orange (Citrus sinensis (L.) Osbeck) by inhibiting respiration and enhancing antioxidant capacity

Melatonin can improve postharvest quality and strengthen resistance to oxidative stress-induced senescence of many horticultural products, however, the effects of melatonin on storage quality and physiological senescence of citrus fruit are still unclear. The objective of this study was to determine the effect of 200 μmol•L−1 melatonin on the organoleptic quality and antioxidant system of ‘Newhall’ navel orange stored under ambient conditions for 84 days post-harvest. Melatonin caused a significant decrease in respiration rate and weight loss rate, and increased in fruit firmness, total soluble solids, soluble sugar content, titratable acidity and Citrus Color Index (CCI) indicating inhibition of fruit quality deterioration. Melatonin treatment impeded the accumulation of hydrogen peroxide and malondialdehyde, suggesting an inhibition of reactive oxygen species (ROS) burst and oxidative damage. In addition, the application of melatonin enhanced ROS scavenging capacity by increasing the activity and expressions of catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase and by promoting the accumulation of ascorbate, reduced glutathione and total phenol. Moreover, the PCA (principal component analysis) demonstrated melatonin delayed postharvest senescence of orange fruit is associated with inhibition of postharvest respiration and stimulation of oxidant-defense system.

Reactive oxygen species scavenging mechanisms associated with polyethylene glycol mediated osmotic stress tolerance in Chinese potato

Influence of polyethylene glycol (PEG) mediated osmotic stress on reactive oxygen species (ROS) scavenging machinery of Chinese potato (Solenostemon rotundifolius (Poir.) J. K. Morton) was investigated. Five genotypes of Chinese potato were raised in Murashige and Skoog (MS) basal medium containing 6–benzylaminopurine (BAP, 1 mg L–1) along with various concentrations of PEG–6000 mediated stress conditions (0, –0.2 and –0.5 MPa) and evaluated for osmotic stress tolerance in vitro. The medium containing PEG–6000 had a detrimental effect on plantlet growth and development while compared with the control. Accumulation of H2O2 was lower in Sreedhara and Subala and higher in Nidhi under PEG stress, which was evident by in situ detection in leaves. Lipid peroxidation product such as malondialdehyde (MDA) content was increased due to PEG stress which was more in susceptible genotype than that in tolerant ones. An enhanced ROS–scavenging antioxidant enzyme was observed under stress with respect to the control. The enzymes of ascorbate–glutathione cycle showed an important role in scavenging ROS. The imposition of PEG stress also increased the non–enzymatic antioxidants viz., the ascorbate and reduced glutathione content which was prominent in tolerant genotypes in comparison to susceptible. The present study indicated that, Sreedhara and Subala showed more tolerance to osmotic stress with better ROS scavenging machineries which would be the lines of interest for augmenting future breeding strategies in this climate resilient minor tuber crop.

The transcription factor VaNAC17 from grapevine (Vitis amurensis) enhances drought tolerance by modulating jasmonic acid biosynthesis in transgenic Arabidopsis.

Expression of VaNAC17 improved drought tolerance in transgenic Arabidopsis by upregulating stress-responsive genes, modulating JA biosynthesis, and enhancing ROS scavenging. Water deficit severely affects the growth and development of plants such as grapevine (Vitis spp.). Members of the NAC (NAM, ATAF1/2, and CUC2) transcription factor (TF) family participate in drought-stress-induced signal transduction in plants, but little is known about the roles of NAC genes in drought tolerance in grapevine. Here, we explored the role of VaNAC17 in Vitis amurensis, a cold-hardy, drought-tolerant species of grapevine. VaNAC17 was strongly induced in grapevine by drought, exogenous abscisic acid (ABA), and methyl jasmonate (MeJA). A transient expression assay in yeast indicated that VaNAC17 functions as a transcriptional activator. Notably, heterologous expression of VaNAC17 in Arabidopsis thaliana enhanced drought tolerance. VaNAC17-expressing Arabidopsis plants showed decreased reactive oxygen species (ROS) accumulation compared to wild-type plants under drought conditions. RNA-seq analysis indicated that VaNAC17 expression increased the transcription of downstream stress-responsive genes after 5days of drought treatment, especially genes involved in jasmonic acid (JA) biosynthesis (such as LOX3, AOC1 and OPR3) and signaling (such as MYC2, JAZ1, VSP1 and CORI3) pathways. Endogenous JA levels increased in VaNAC17-OE plants under drought stress. Taken together, these results indicate that VaNAC17 plays a positive role in drought tolerance by modulating endogenous JA biosynthesis and ROS scavenging.