A Novel Dominant Allele from 93-11, ES(4), Represses Reactive Oxygen Species Scavenging and Leads to Early-Senescence in Rice

Senescence is the last developmental process in plant,which has an important impact on crop yield and quality.In this study,a stable hereditary early-senescence line BC64 was isolated from the high-generation recombinant inbred lines of 93-11 and Wuyunjing7(W7).Genetic analysis showed that the premature aging phenotype was controlled by a dominant gene derived from 93-11.By linkage analysis,the gene was primarily mapped in the region between marker B4 and B5 near the centromere of chromosome 4,described as ES(4).Through multiple backcrossing with W7,the near-isogenic line of ES(4)(NIL-ES(4))was obtained.Compared with wild-type W7,NIL-ES(4)plants showed more sever senescence phenotype in both nature and dark conditions.In NIL plants,leaves turned yellow at the fully tillering stage;photosynthetic rate,pollen fertility and seed setting rate were decreased.Moreover,the malondialdehyde,proline content and relative conductivity in NIL-ES(4)were significantly higher than those in W7;both transcript level and activities of reactive oxygen species scavenging enzymes were repressed;H2O2 and O^(2−)were significantly accumulated.This study provides a basis for further cloning and function identification of ES(4).

Effect of Antioxidants on Endothelial Cell Reactive Oxygen Species (ROD Generation and Adhesion of Leukocytes to Endothelial Cells

Objective To investigatewhether antioxidants inhibit adhesion of leukocytes to endothelium and furthermore, whether all antioxidants regulate NF-KB activation through a redox sensitive mechanism. Methods The effect of the antioxidative substances pyrrolidin dithiocarbamat (PDTC), dichloroisocumarin (DCI), chrysin and probucol on the endothelial leukocyte adhesion were examined under near physiological flow conditions. The antioxidative activity of antioxidants was measured in a DCF fluorescence assay with flow cytometry. The activation of NF-kB in endothelial cells was investigated in a gel shift assay. Results PDTC and probucol did not show an inhibitory effect to the formation of intracellular H2O2 in TNFa activated human vascular endothelial cells (HUVEC) . Chrysin showed a moderate effect. DCI showed a strong antioxidative effect. In contrast, PDTC and chrysin inhibited the adhesion of HL 60 cells to TNFa-stimulated HUVEC. DCI and probucol did not have influence on the adhesion within the area of the examined shear stresses. Only PDTC inhibited the TNFa-induced activation of NF-KB in endothelial cells. Conclusion The inhibition of the endothelial leukocyte adhesion by antioxidative substances is not to be explained by its antioxidative characteristics only. The inhibitory effect of PDTC on NF-KB activation was probably not related to its antioxidative properties. Endothelial cell Antioxidants NF-kappa-B

Evaluation of Reactive Oxygen Species (ROS) Generated on the Surface of Copper Using Chemiluminesence

The antibacterial activity of copper is well-known from an ancient civilization, however, its biocidal mechanism has not been necessarily elucidated. Notwithstanding up to now, mainly 4 processes have been proposed. Among them, it is cleared that 4 kinds of reactive oxygen species (ROS): hydroxyl radical ·OH, hydrogen per oxide H2O2, superoxide anion ·O-2 and singlet oxygen 1O2, play an important role for contact-killing of bacteria, viruses and fungi. In this paper, generation of ROS on the surfaces of copper plates heated from room temperature to 673 K for 4.2 × 102 s in air, was investigated using the chemiluminescence. ROS have been evaluated by selecting the most suitable scavengers, such as 2-propanol for ·OH, sodium pyruvate for H2O2, nitro blue tetrazolium for ·O-2, and sodium azide NaN3 for 1O2. At the same time the outermost surface of copper, on which thin film of cuprous oxide Cu2O was first formed and then cupric oxide CuO was laminated on Cu2O, was examined by thin-film XRD and TEM analysis to estimate the amounts and kinds of copper oxides. It was found that the most amounts of ROS were obtained for the 573 K-heated Cu plate and they were composed of ·OH, H2O2, and ·O-2..

TaNF-YB11,a gene of NF-Y transcription factor family in Triticum aestivum,confers drought tolerance on plants via modulating osmolyte accumulation and reactive oxygen species homeostasis

Transcription factors(TFs)regulate diverse stress defensive-associated physiological processes and plant stress responses.We characterized TaNF-YB11,a gene of the NF-YB TF family in Triticum aestivum,in mediating plant drought tolerance.TaNF-YB11 harbors the conserved domains specified by its NF-YB partners and targets the nucleus after the endoplasmic reticulum(ER)assortment.Yeast two-hybrid assay indicated the interactions of TaNF-YB11 with TaNF-YA2 and TaNF-YC3,two proteins encoded by genes in the NF-YA and NF-YC families,respectively.These results suggested that the heterotrimer established among them further regulated downstream genes at the transcriptional level.The transcripts of TaNF-YB11 were promoted in roots and leaves under a 27-h drought regime.Moreover,its upregulated expression levels under drought were gradually restored following a recovery treatment,suggesting its involvement in plant drought response.TaNF-YB11 conferred improved drought tolerance on plants;the lines overexpressing target gene displayed improved phenotype and biomass compared with wild type(WT)under drought treatments due to enhancement of stomata closing,osmolyte accumulation,and cellular reactive oxygen species(ROS)homeostasis.Knockdown expression of TaP5CS2,a P5CS family gene modulating proline biosynthesis that showed upregulated expression in drought-challenged TaNF-YB11 lines,alleviated proline accumulation of plants treated by drought.Likewise,TaSOD2 and TaCAT3,two genes encoding superoxide dismutase(SOD)and catalase(CAT)that were upregulated underlying TaNF-YB11 regulation,played critical roles in ROS homeostasis via regulating SOD and CAT activities.RNA-seq analysis revealed that numerous genes associated with processes of‘cellular processes',‘environmental information processing',‘genetic information processing',‘metabolism',and‘organismal systems'modified transcription under drought underlying control of TaNF-YB11.These results suggested that the TaNF-YB11-mediated drought response is possibly accomplished through the target gene in modifying gene transcription at the global level,which modulates complicated biological processes related to drought response.TaNF-YB11 is essential in plant drought adaptation and a valuable target for molecular breeding of drought-tolerant cultivars in T.aestivum.

DFT Study on Molecular Structures and ROS Scavenging Mechanisms of Novel Antioxidants from Lespedeza Virgata

The molecular structure and radical scavenging activity of three novel antioxidants from Lespedeza Virgata, lespedezavirgatol, lespedezavirgatal, and lespedezacoumestan, have been studied using density functional theory with the B3LYP and BhandHLYP methods. The optimized geometries of neutral, radical cation, radical and anion forms were obtained at the B3LYP/6-31G（d） level, in which it was found that all the most stable conformations contain intramolecular hydrogen bonds. The same results were obtained from the MP2 method. The homolytic O-H bond dissociation enthalpy and the adiabatic ionization potential of neutral and anion forms for the three new antioxidants and adiabatic electron affinity and H-atom affinity for hydroxyl radical, superoxide anion radical, and hydrogen peroxide radical were determined both in gas phase and in aqueous solution using IEF-PCM and CPCM model with UAHF or Bondi cavity. The antioxidant activities and reactive oxygen species scavenging mechanisms were then discussed, and the results obtained from different methods are consistent. Furthermore, the antioxidant activities are consistent with the experimental findings of the compounds under investigation.

Emerging Strategies in Enhancing Singlet Oxygen Generation of Nano-Photosensitizers Toward Advanced Phototherapy

The great promise of photodynamic therapy(PDT) has thrusted the rapid progress of developing highly effective photosensitizers(PS) in killing cancerous cells and bacteria. To mitigate the intrinsic limitations of the classical molecular photosensitizers, researchers have been looking into designing new generation of nanomaterial-based photosensitizers(nano-photosensitizers) with better photostability and higher singlet oxygen generation(SOG) efficiency, and ways of enhancing the performance of existing photosensitizers. In this paper, we review the recent development of nano-photosensitizers and nanoplasmonic strategies to enhance the SOG efficiency for better PDT performance. Firstly, we explain the mechanism of reactive oxygen species generation by classical photosensitizers, followed by a brief discussion on the commercially available photosensitizers and their limitations in PDT. We then introduce three types of new generation nanophotosensitizers that can effectively produce singlet oxygen molecules under visible light illumination, i.e., aggregation-induced emission nanodots, metal nanoclusters (< 2 nm), and carbon dots. Different design approaches to synthesize these nano-photosensitizers were also discussed. To further enhance the SOG rate of nano-photosensitizers, plasmonic strategies on using different types of metal nanoparticles in both colloidal and planar metal-PS systems are reviewed. The key parameters that determine the metal-enhanced SOG(ME-SOG) efficiency and their underlined enhancement mechanism are discussed. Lastly, we highlight the future prospects of these nanoengineering strategies, and discuss how the future development in nanobiotechnology and theoretical simulation could accelerate the design of new photosensitizers and ME-SOG systems for highly effective image-guided photodynamic therapy.

Glucose initially inhibits and later stimulates blood ROS generation

Background: Glucose is the main substrate for the generation of NADPH, the cofactor of the oxidative burst enzyme NADPH-oxidase of blood neutrophils. Changes in blood glucose are thus expected to modify the generation of reactive oxygen species (ROS). The new blood ROS generation assay (BRGA) quantifies ROS changes induced by blood glucose concentrations as they are found in diabetes mellitus. Material and Methods: Citrated or EDTA blood of 6 healthy donors were analyzed in the BRGA: 10 μl sample in black polystyrene F-microwells (Brand 781608) were incubated in triplicate with 125 μl Hanks’ balanced salt solution, 40 μl 0 - 200 mM glucose in 0.9% NaCl (final added conc.: 0 - 41 mM;final basal glucose conc.: about4 mM), 10 μl5 mMluminol, and 10 μl zymosan A (final conc.: 1.9 μg/ml) in 0.9% NaCl. The plates were measured within 0 - 250 min (37℃) in a photons-multiplyer microtiter plate luminometer (LUmo) with an integration time of 1 s. Results: Up to about 30 min reaction time the mean ROS generation was 50% inhibited by about1 mMadded glucose (= approx. IC50). At ≥80 min reaction time (possibly necessary for full phosphorylation of glucose to glucose-6-phosphate (G6P), the substrate metabolized by G6P-dehydrogenase to generate NADPH, the cofactor of the NADPH-oxidase) the mean ROS generation approximately doubled at about1 mMadded glucose (= approx. SC200) in citrated blood. Discussion: Elevated glucose concentrations not only increase systemic thrombin generation, they can also diminish cellular fibrinolysis and increase systemic inflammation, resulting in a chronic pro-thrombotic state. The fascinating importance of NADPH-oxidases not only in phagocytes but also in the beta cells of pancreas points towards a new pathogenesis explication of diabetes mellitus type 1: whatever stimulus (e.g. a pancreas-tropic virus) could activate the beta cell’s autodestructive NADPH-oxidase.

Scavenging of reactive oxygen and nitrogen species with nanomaterials

Reactive oxygen and nitrogen species （RONS） are essential for normal physiological processes and play important roles in cell signaling, immunity, and tissue homeostasis. However, excess radical species are implicated in the development and augmented pathogenesis of various diseases. Several antioxidants may restore the chemical balance, but their use is limited by disappointing results of clinical trials. Nanoparticles are an attractive therapeutic alternative because they can change the biodistribution profile of antioxidants, and possess intrinsic ability to scavenge RONS. Herein, we review the types of RONS, how they are implicated in several diseases, and the types of nanoparticles with inherent antioxidant capability, their mechanisms of action, and their biological applications.

Reactive Oxygen Species Scavenging Enzymes and Down-Adjustment of Metabolism Level in Mitochondria Associated with Desiccation-Tolerance Acquisition of Maize Embryo

It is a well-known fact that a mature seed can survive losing most of its water, yet how seeds acquire desiccation- tolerance is not well understood. Through sampling maize embryos of different developmental stages and comparatively studying the integrity, oxygen consumption rate and activities of antioxidant enzymes in the mitochondria, the main origin site of reactive oxygen species （ROS） production in seed cells, we found that before an embryo achieves desiccation-tolerance, its mitochondria shows a more active metabolism, and might produce more ROS and therefore need a more effective ROS scavenging system. However, embryo dehydration in this developmental stage declined the activities of most main antioxidant enzymes and accumulated thiobarbituric acid-reactive products in mitochondria, and then destroyed the structure and functional integrity of mitochondria. In physiologically-matured embryos （dehydration- tolerant）, mitochondria showed lower metabolism levels, and no decline in ROS scavenging enzyme activities and less accumulation of thiobarbituric acid-reactive products after embryo dehydration. These data indicate that seed desiccation- tolerance acquisition might be associated with down-adjustment of the metabolism level in the late development stage, resulting in less ROS production, and ROS scavenging enzymes becoming desiccation-tolerant and then ensuring the structure and functional integrity of mitochondria.

Multi-functionalized nanofibers with reactive oxygen species scavenging capability and fibrocartilage inductivity for tendon-bone integration

The presence of excessive reactive oxygen species(ROS)after injuries to the enthesis could lead to cellular oxidative damage,high inflammatory response,chronic inflammation,and limited fibrochondral inductivity,making tissue repair and functional recovery difficult.Here,a multifunctional silk fibroin nanofiber modified with polydopamine and kartogenin was designed and fabricated to not only effectively reduce inflammation by scavenging ROS in the early stage of the enthesis healing but also enhance fibrocartilage formation with fibrochondrogenic induction in the later stages.The in vitro results confirmed the antioxidant capability and the fibrochondral inductivity of the functionalized nanofibers.In vivo studies showed that the multifunctional nanofiber can significantly improve the integration of tendon-bone and accelerate the regeneration of interface tissue,resulting in an excellent biomechanical property.Thus,the incorporation of antioxidant and bio-active molecules into extracellular matrix-like biomaterials in interface tissue engineering provides an integrative approach that facilitates damaged tissue regeneration and functional recovery,thereby improving the clinical outcome of the engineered tissue.

水杨酸调控活性氧稳态维持马铃薯愈伤早期的细胞膜完整性

本研究用2 mmol/L水杨酸(salicylic acid,SA)溶液浸泡处理人工损伤的马铃薯块茎10 min,测定愈伤早期(损伤后12 h内)块茎伤口处的活性氧(reactive oxygen species,ROS)产生量及酶促清除系统相关酶活性,分析体外抗氧化能力以及细胞膜的完整性。结果表明,SA提高了愈伤早期块茎伤口处NADPH氧化酶和超氧化物歧化酶活性,促进了伤口处O_(2)^(―)·和H_(2)O_(2)的积累。SA总体提高了块茎伤口处过氧化物酶活性,但总体降低了过氧化氢酶活性。SA还提高了抗坏血酸过氧化物酶、脱氢抗坏血酸还原酶、单脱氢抗坏血酸还原酶和谷胱甘肽还原酶活性,以及抗坏血酸和还原型谷胱甘肽的水平。此外,SA提高了块茎伤口处的1,1-二苯基-2-三硝基苯肼自由基、2,2’-联氮双(3-乙基苯并噻唑啉-6-磺酸)阳离子自由基清除能力以及铁离子还原能力,降低了细胞膜渗透率和丙二醛含量。综上,SA可以通过调控马铃薯块茎愈伤早期伤口处的ROS稳态,提高体外抗氧化能力从而维持细胞膜的完整性,保证愈伤早期正常代谢的顺利进行。

Bone microenvironment regulative hydrogels with ROS scavenging and prolonged oxygen-generating for enhancing bone repair

Large bone defects resulting from fractures and disease are a major clinical challenge,being often unable to heal spontaneously by the body’s repair mechanisms.Lines of evidence have shown that hypoxia-induced overproduction of ROS in bone defect region has a major impact on delaying bone regeneration.However,replenishing excess oxygen in a short time cause high oxygen tension that affect the activity of osteoblast precursor cells.Therefore,reasonably restoring the hypoxic condition of bone microenvironment is essential for facilitating bone repair.Herein,we designed ROS scavenging and responsive prolonged oxygen-generating hydrogels(CPP-L/GelMA)as a“bone microenvironment regulative hydrogel”to reverse the hypoxic microenvironment in bone defects region.CPP-L/GelMA hydrogels comprises an antioxidant enzyme catalase(CAT)and ROS-responsive oxygen-releasing nanoparticles(PFC@PLGA/PPS)co-loaded liposome(CCP-L)and GelMA hydrogels.Under hypoxic condition,CPP-L/GelMA can release CAT for degrading hydrogen peroxide to generate oxygen and be triggered by superfluous ROS to continuously release the oxygen for more than 2 weeks.The prolonged oxygen enriched microenvironment generated by CPP-L/GelMA hydrogel significantly enhanced angiogenesis and osteogenesis while inhibited osteoclastogenesis.Finally,CPP-L/GelMA showed excellent bone regeneration effect in a mice skull defect model through the Nrf2-BMAL1-autophagy pathway.Hence,CPP-L/GelMA,as a bone microenvironment regulative hydrogel for bone tissue respiration,can effectively scavenge ROS and provide prolonged oxygen supply according to the demand in bone defect region,possessing of great clinical therapeutic potential.

Diamond-Like Carbon Depositing on the Surface of Polylactide Membrane for Prevention of Adhesion Formation During Tendon Repair

Post-traumatic peritendinous adhesion presents a significant challenge in clinical medicine.This study proposes the use of diamond-like carbon(DLC)deposited on polylactic acid(PLA)membranes as a biophysical mechanism for anti-adhesion barrier to encase ruptured tendons in tendon-injured rats.The results indicate that PLA/DLC composite membrane exhibits more efficient anti-adhesion effect than PLA membrane,with histological score decreasing from 3.12±0.27 to 2.20±0.22 and anti-adhesion effectiveness increasing from 21.61%to 44.72%.Mechanistically,the abundant C=O bond functional groups on the surface of DLC can reduce reactive oxygen species level effectively;thus,the phosphorylation of NF-κB and M1 polarization of macrophages are inhibited.Consequently,excessive inflammatory response augmented by M1 macrophage-originated cytokines including interleukin-6(IL-6),interleukin-1β(IL-1β),and tumor necrosis factor-α(TNF-α)is largely reduced.For biocompatibility evaluation,PLA/DLC membrane is slowly absorbed within tissue and displays prolonged barrier effects compared to traditional PLA membranes.Further studies show the DLC depositing decelerates the release of degradation product lactic acid and its induction of macrophage M2 polarization by interfering esterase and PLA ester bonds,which further delays the fibrosis process.It was found that the PLA/DLC membrane possess an efficient biophysical mechanism for treatment of peritendinous adhesion.

Response to temperature stress of reactive oxygen species scavenging enzymes in the cross-tolerance of barley seed germination

A number of studies have shown the existence of cross-tolerance in plants, but the physiological mechanism is poorly understood. In this study, we used the germination of barley seeds as a system to investigate the cross-tolerance of low-temperature pretreatment to high-temperature stress and the possible involvement of reactive oxygen species （ROS） scavenging enzymes in the cross-tolerance. After pretreatment at 0 ℃ for different periods of time, barley seeds were germinated at 35 ℃, and the content of malondialdehyde （MDA） and the activities of ROS scavenging enzymes were measured by a spectrophotometer analysis. The results showed that barley seed germinated very poorly at 35 ℃, and this inhibitive effect could be overcome by pretreatment at 0 ℃. The MDA content varied, depending on the temperature at which seeds germinated, while barley seeds pretreated at 0 ℃ did not change the MDA content. Compared with seeds germinated directly at 35 ℃, the seeds pretreated first at 0 ℃ and then germinated at 35 ℃ had markedly increased activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX）, catalase （CAT）, and glutathione reductase （GR）. The SOD and APX activities of seeds germinated at 35 ℃ after 0 ℃-pretreatment were even substantially higher than those at 25 ℃, and GR activity was similar to that at 25 ℃, at which the highest germination performance of barley seeds was achieved. These results indicate that low-temperature pretreatment can markedly increase the tolerance of barley seed to high temperature during germination, this being related to the increase in ROS scavenging enzyme activity. This may provide a new method for increasing seed germination under stress environments, and may be an excellent model system for the study of cross-tolerance.

不同强度光强胁迫对海带(Saccharina japonica)幼苗光合生理的影响

海带(Saccharinajaponica)是我国藻类生产的主要品种之一,其栽培面积和产量均居世界首位。2021~2022年产季,山东荣成海带主产区先后暴发了大规模病烂灾害,给当地水产经济造成了巨大损失。引起病烂的原因可能来自多方面,其中藻体所受光照过强及水体营养盐水平较低可能起到了一定作用,为此,基于海带幼苗的最小饱和光强、烟台高新区牟平自然海区海水氮磷浓度及不同海水深度下的光照强度测定结果,研究了梯度强光在不同海水营养盐水平下对海带生理的影响,以期为“烂菜”现象的病因分析提供一定的线索。结果显示,海带幼苗在700~900μE/(m^(2) s)强光胁迫3 d后, Fv/Fm可恢复至对照水平,光合色素合成活跃,营养盐含量较高的海水更有助于PSII的修复,但1 300~1 500μE/(m^(2) s)的强光辐射导致PSII不能恢复,岩藻黄素、叶绿素a及β-胡萝卜素含量显著降低。整个胁迫实验中,藻体总抗氧化能力(T-AOC)及其他抗氧化酶比活力大体上在强光胁迫的起始至第3天上调,而在胁迫第5天时又出现下降趋势,且在营养盐含量较高的处理组中,各样本活性均高于天然海水处理组样本。抗氧化酶基因的表达也呈现类似的变化趋势。在低于900μE/(m^(2) s)的光照条件下,抗氧化酶活性可以得到较好的维持,而海水中相对较为丰富的营养盐则有利于藻体抗氧化能力的维持。研究结果为荣成海带病烂暴发的原因分析提供了一定的借鉴。

纸片型1-MCP处理对‘朝霞’水蜜桃果实活性氧清除系统的影响

目的研究纸片型1-甲基环丙烯(1-methylcyclopropene,1-MCP)处理对‘朝霞’水蜜桃果实活性氧(reactive oxygen species,ROS)清除系统的影响。方法用1.2μL/L纸片型1-MCP处理‘朝霞’水蜜桃12 h,以没有1-MCP处理的‘朝霞’水蜜桃为对照,果实在(25±1)℃下贮藏12d,每隔2d取样分析果实超氧阴离子自由基(O_(2)^(-)·)产生速率、丙二醛(malondialdehyde,MDA)含量、内源抗氧化物质含量和ROS清除酶活性的变化。结果与对照‘朝霞’水蜜桃比较,1-MCP处理的‘朝霞’水蜜桃显现出较低的O_(2)^(-)·产生速率和MDA含量,较高的还原型谷胱甘肽和抗坏血酸含量,以及较高的过氧化氢酶、超氧化物歧化酶和抗坏血酸过氧化物酶活性。结论纸片型1-MCP处理能增强‘朝霞’水蜜桃ROS清除能力,有效减少其果实ROS的产生与MDA的积累,减轻‘朝霞’水蜜桃膜脂过氧化,维持细胞膜结构的完整性,从而保持‘朝霞’水蜜桃果实采后品质、增强其耐贮性。

四氧化三锰纳米颗粒抗氧化损伤保护骨髓间充质干细胞的伸展功能

背景:由于干细胞移植微环境原位产生的大量自由基造成移植干细胞伸展功能受损,进而降低细胞的移植存活率。近10年来,大量抗氧化应激纳米酶研究的出现为保护干细胞伸展功能提供了新的方法。四氧化三锰(Mn_(3)O_(4))作为一种新型纳米酶,含有的锰作为人体微量元素之一,具有抗氧化应激性能以及生物可降解性,可作为一种保护干细胞伸展功能的新型纳米材料。目的:制备纳米酶四氧化三锰颗粒,检测其在氧化应激环境中对骨髓间充质干细胞抗氧化作用和伸展功能的影响。方法:水热法制备四氧化三锰纳米颗粒,用扫描电子显微镜、X射线衍射分别表征材料形貌和结构;动态光散射仪检测模拟人体环境下的颗粒粒径和Zeta电位;在中性环境下检测四氧化三锰的抗氧化能力,使用CCK-8和活-死染色法检测四氧化三锰对骨髓间充质干细胞的生物毒性;过氧化氢诱导骨髓间充质干细胞氧化应激,检测四氧化三锰对骨髓间充质干细胞在氧化应激状态下抗氧化能力及伸展能力的影响。结果与结论:①扫描电子显微镜和X射线衍射测试结果显示该材料为平均直径70-80 nm的四氧化三锰纳米颗粒;动态光散射仪检测显示,在模拟人体缓冲环境下的四氧化三锰的粒径约为100 nm,Zeta电位约为+20 mV,抗氧化性能实验显示四氧化三锰具有一定的抗氧化能力;②CCK-8、活-死染色、活性氧清除实验显示四氧化三锰在40 mg/L的质量浓度下对骨髓间充质干细胞无生物毒性且有一定的活性氧清除能力;③细胞伸展实验显示过氧化氢对骨髓间充质干细胞的伸展功能具有明显抑制作用,而四氧化三锰加入细胞培养微环境后,细胞伸展面积较对照组无明显统计学差异(P>0.05),且单独使用四氧化三锰不会抑制骨髓间充质干细胞的伸展功能(P>0.05);④结果表明,在细胞微环境中加入四氧化三锰纳米颗粒能够抵抗氧化应激,并且对骨髓间充质干细胞的伸展功能具有一定的保护作用。

Sub-cytotoxic concentrations of ionic silver promote the proliferation of human keratinocytes by inducing the production of reactive oxygen species

Silver-containing preparations are widely used in the management of skin wounds, but the effects of silver ions on skin wound healing remain poorly understood. This study investigated the effects of silver ions （Ag^＋） on the proliferation of human skin keratinocytes （HaCaT） and the production of intracellular reactive oxygen species （ROS）. After treating HaCaT cells with Ag^＋ and/or the active oxygen scavenger N-acetyl cysteine （NAC）, cell proliferation and intracellular ROS generation were assessed using CCK-8 reagent and DCFH-DA fluorescent probe, respectively. In addition, 5-bromo-2-deoxyUridine （BrdU） incorporation assays, cell cycle flow cytometry, and proliferating cell nuclear antigen （PCNA） immunocytochemistry were conducted to further evaluate the effects of sub-cytotoxic Ag^＋ concentrations on HaCaT cells. The proliferation of HaCaT cells was promoted in the presence of 10^-6 and 10^-5s mol/L Ag^＋at 24, 48, and 72 h. Intracellular ROS generation also significantly increased for 5 60 min after exposure to Ag^＋ The number of BrdU-positive cells and the presence of PCNA in HaCaT cells increased 48 h after the addition of 10^-6 and 10^-5 mol/L Ag^＋, with 10^-5 mol/L Ag^＋ markedly increasing the cell proliferation index. These effects of sub-cytotoxic Ag^＋ concentrations were repressed by 5 mmol/L NAC. Our results suggest that sub-cytotoxic Ag^＋ concentrations promote the proliferation of human keratinocytes and might be associated with a moderate increase in intracellular ROS levels. This study provides important experimental evidence for developing novel silver-based wound agents or dressings with few or no cytotoxicity.

活性氧清除系统对干旱胁迫的响应机制

干旱胁迫是影响植物生长发育的主要因子,干旱引起活性氧自由基增加,使植物细胞遭受氧化胁迫.植物体通过酶促和非酶促两大保护系统清除活性氧,活性氧自由基的变化也会引起抗氧化防御系统的不同变化,同时干旱胁迫下活性氧的产生也与ABA的积累、脯氨酸的积累以及叶绿素荧光猝灭密切相关,因此了解活性氧清除系统对干旱胁迫的响应机制以及活性氧在植物生理生化过程中的作用是非常必要的.

小麦幼苗叶片活性氧清除能力对干旱胁迫的响应

研究了不同干旱胁迫方式,即间断干旱胁迫和持续干旱胁迫对小麦幼苗叶片活性氧清除能力的影响,测定了3种活性氧[羟自由基(.OH),过氧化氢(H2O2)和超氧阴离子自由基(O2.-)]清除能力的变化。结果表明,正常生长小麦的叶片具有一定的清除活性氧(.OH,H2O2,O2.-)的能力;2种干旱方式均导致小麦.OH和O2.-清除能力上升,复水后仍维持在较高水平,2种干旱方式均导致小麦H2O2清除能力下降,复水后仍低于正常水平;根和叶对相同处理表现出不同的反应;与间断干旱比较,持续干旱处理使小麦表现出更强的活性氧清除能力,对小麦活性氧清除能力的影响较大且延续时间长,具有胁迫后效应。