Type 2 diabetes caused by reductive redox potential?

<正>Reactive oxygen species arise(ROS)in the mitochondria as byproducts of respiration and oxidase activity and have important roles in many physiological and pathophysiological conditions.The current literature indicate that excessive levels of ROS can cause oxidative stress and that lots of evidences link ROS and oxidative stress to the pathogenesis of type 2 diabetes mellitus(T2DM)and development of complications.Several studies have shown elevated extraand intracellular glucose concentrations result in oxidative stress both in animal models of diabetes and in diabetic patients[1].And ROS can contribute to the development and progression of diabetes and related complications by directly damaging DNA,proteins,and lipids or indirectly activating a number of cellular stress-sensitive pathways to induce damage to tissues such as isletβcells[2].     

Heterologous expression of Hp BHY and Cr BKT increases heat tolerance in Physcomitrella patens

Heat stress can restrict plant growth,development,and crop yield.As essential plant antioxidants,carotenoids play significant roles in plant stress resistance.b-carotene hydroxylase(BHY)and b-carotene ketolase(BKT),which catalyze the conversions of b-carotene to zeaxanthin and b-carotene to canthaxanthin,respectively,are key enzymes in the carotenoid biosynthetic pathway,but little is known about their potential functions in stress resistance.Here,we investigated the roles of b-carotene hydroxylase and b-carotene ketolase during heat stress in Physcomitrella patens through expressing a b-carotene ketolase gene from Chlamydomonas reinhardtii(Cr BKT)and a b-carotene hydroxylase gene from Haematococcus pluvialis(Hp BHY)in the moss P.patens.In transgenic moss expressing these genes,carotenoids content increased(especially lutein content),and heat stress tolerance increased,with reduced leafy tissue necrosis.To investigate the mechanism of this heat stress resistance,we measured various physiological indicators and found a lower malondialdehyde level,higher peroxidase and superoxide dismutase activities,and higher endogenous abscisic acid and salicylate content in the transgenic plants in response to high-temperature stress.These results demonstrate that Cr BKT and Hp BHY increase plant heat stress resistance through the antioxidant and damage repair metabolism,which is related to abscisic acid and salicylate signaling.     

Redox Changes during the Legume-Rhizobium Symbiosis

Reactive Oxygen Species （ROS） are continuously produced as a result of aerobic metabolism or in response to biotic and abiotic stresses. ROS are not only toxic by-products of aerobic metabolism, but are also signaling molecules involved in plant growth and environmental adaptation. Antioxidants can protect the cell from oxidative damage by scavenging the ROS. Thus, they play an important role in optimizing cell function by regulating cellular redox state and modifying gene expression. This article aims to review recent studies highlighting the role of redox signals in establishing and maintaining symbiosis between rhizobia and legumes.     

Improvement of plant abiotic stress tolerance through modulation of the polyamine pathway FA简

Polyamines （mainly putrescine （Put）, spermidine （Spd）, and spermine （Spin）） have been widely found in a range of physiological processes and in almost all diverse environ- mental stresses. In various plant species, abiotic stresses modulated the accumulation of polyamines and related gene expression. Studies using loss-of-function mutants and transgenic overexpression plants modulating polyamine metabolic pathways confirmed protective roles of polyamines during plant abiotic stress responses, and indicated the possibility to improve plant tolerance through genetic manipulation of the polyamine pathway. Additionally, puta- tive mechanisms of polyamines involved in plant abiotic stress tolerance were thoroughly discussed and crosstalks among polyamine, abscisic acid, and nitric oxide in plant responses to abiotic stress were emphasized. Special attention was paid to the interaction between polyamine and reactive oxygen species, ion channels, amino acid and carbon metabolism, and other adaptive responses. Further studies are needed to elucidate the polyamine signaling pathway, especially polyamine-regulated downstream tar- gets and the connections between polyamines and other stress responsive molecules.     

Mutual interaction between oxidative stress and endoplasmic reticulum stress in the pathogenesis of diseases specifically focusing on non-alcoholic fatty liver disease

Reactive oxygen species(ROS) are produced during normal physiologic processes with the consumption of oxygen. While ROS play signaling roles, when they are produced in excess beyond normal antioxidative capacity this can cause pathogenic damage to cells. The majority of such oxidation occurs in polyunsaturated fatty acids and sulfhydryl group in proteins, resulting in lipid peroxidation and protein misfolding, respectively. The accumulation of misfolded proteins in the endoplasmic reticulum(ER) is enhanced under conditions of oxidative stress and results in ER stress, which, together, leads to the malfunction of cellular homeostasis. Multiple types of defensive machinery are activated in unfolded protein response under ER stress to resolve this unfavorable situation. ER stress triggers the malfunction of protein secretion and is associated with a variety of pathogenic conditions including defective insulin secretion from pancreatic β-cells and accelerated lipid droplet formation in hepatocytes. Herein we use nonalcoholic fatty liver disease(NAFLD) as an illustration of such pathological liver conditions that result from ER stress in association with oxidative stress. Protecting the ER by eliminating excessive ROS viathe administration of antioxidants or by enhancing lipidmetabolizing capacity via the activation of peroxisome proliferator-activated receptors represent promising therapeutics for NAFLD.     

Activity of Stress-related Antioxidative Enzymes in the Invasive Plant Crofton Weed （Eupatorium adenophorum）

Crofton weed is an invasive weed in southwestern China. The activities of several antioxidative enzymes involved in plant protection against oxidative stress were assayed to determine physiological aspects of the crofton weed that might render the plant vulnerable to environmental stress. Stresses imposed on crofton weed were heat （progressively increasing temperatures： 25 ℃, 30 ℃, 35 ℃, 38℃ and 42 ℃ at 24 h intervals）, cold （progressively decreasing temperatures： 25 ℃, 20 ℃, 15℃, 10 ℃ and 5℃ at 24h intervals）, and drought （without watering up to 4days）. The three stresses induced oxidative damage as evidenced by an increase in lipid peroxidation. The effect varied with the stress imposed and the length of exposure. The activity of superoxide dismutase （SOD） increased in response to all stresses but was not significantly different from the controls （P 〈 0.05） when exposed to cold stress. Catalase （CAT） activity decreased in response to heat and drought stress but increased when exposed to cold conditions. Guaiacol peroxidase （POD） and glutathione reductase （GR） activities increased in response to cold and drought but decreased in response to heat stress. The activity of ascorbata peroxidase （APX） responded differently to all three stresses. Monodehydroascorbate reductase （MDHAR） activity decreased in response to heat and drought, and slightly increased in response to the cold stress but was not significantly different from the controls （P 〈 0.05）. The activity of dehydroascorbata reductase （DHAR） increased in response to all three stresses. Taken together, the co-ordinate increase of the oxygen-detoxifying enzymes might be more effective to protect crofton weed from the accumulation of oxygen radicals at low temperatures rather than at high temperatures.     

Transport,signaling, and homeostasis of potassium and sodium in plants

Potassium （K＋） is an essential macronutrient in plants and a lack of K＋ significantly reduces the potential for plant growth and development. By contrast, sodium （Na＋）, while beneficial to some extent, at high concentrations it disturbs and inhibits various physiological processes and plant growth. Due to their chemical similarities, some functions of K＋ can be undertaken by Na＋ but K＋ homeostasis is severely affected by salt stress, on the other hand. Recent advances have highlighted the fascinating regulatory mechanisms of K＋ and Na＋ transport and signaling in plants. This review summarizes three major topics： （i） the transport mechanisms of K＋ and Na＋ from the soil to the shoot and to the cellular - compartments; （ii） the mechanisms through which plants sense and respond to K＋ and Na＋ availability; and （iii） the components involved in maintenance of K＋/Na＋ homeostasis in plants under salt stress.     

H_2O_2-NOX系统：一种植物体内重要的发育调控与胁迫响应机制

以H2O2为中心的活性氧（reactive oxygen species,ROS）的产生是动植物发育与响应外界生物与非生物胁迫的普遍特征,其在生理和分子2个水平上调控植物的发育和对外界胁迫的响应,并与一系列信号转导过程相关联。作为关键的ROS产生酶,质膜NADPH氧化酶（plasma membrane NADPH oxidase,PM-NOX）在植物应对各种生物和非生物胁迫中具有重要作用,被广泛认为是胁迫条件下植物细胞ROS产生并积累的主要来源。该文简要综述了近年来人们在植物细胞ROS产生、清除、生理功能以及PM-NOX酶的结构特征与功能等方面的研究进展,并认为H2O2-NOX系统是一种植物体内普遍存在的重要发育调控与胁迫响应机制。     

Oxidative stress in plant cell culture: a role in production of beta-thujaplicin by Cupresssus lusitanica suspension culture

Oxidative stress is a common physiological stress that often challenges plants. Reactive oxygen species (ROS) are major factors in oxidative stress that significantly affect plant cell growth and secondary metabolism. Here we used beta-thujaplicin production by Cupressus lusitanica cell culture as an example to demonstrate the common occurrence of oxidative stress in cultivated plant cells and its effect on multiple aspects of cell culture process. C. lusitanica cells cultivated under Fe(2+) stress generate a significant level of ROS, and oxidative stress also occurs at late stages of C. lusitanica cell cultures under normal conditions. ROS production inhibited cell growth, induced lipid peroxidation and cell death, and enhanced ethylene and beta-thujaplicin production. It is demonstrated that Fe(2+) stress enhances ROS production via the Fenton reaction and promotes beta-thujaplicin production via ROS-induced lipid peroxidation that may activate cyclic oxylipin and ethylene pathways. Results further indicate that H(2)O(2) is a positive signal for beta-thujaplicin production, whereas superoxide anion radical (O(2) (- )) negatively affects beta-thujaplicin induction and strongly induces cell death. The study suggests that evaluating the oxidative stress and plant responses in a cell culture process is very necessary and important for understanding biochemical processes and for gaining the maximal productivity of target secondary metabolites.     

An Appraisal of Ancient Molecule GABA in Abiotic Stress Tolerance in Plants,and Its Crosstalk with Other Signaling Molecules

Gamma-aminobutyric acid (GABA), a non-proteinaceous amino acid, is reported in prokaryotes and eukaryotes, since ancient times. However, it has gained attention in the present time because of its rapid accumulation during stressed conditions in plants as well as in the cyanobacteria. In plants, it regulates the number of physiological processes such as pollen tube growth, root growth, TCA cycle, N₂-metabolism, and osmoregulation. Several biotic and abiotic stresses prevail in the environment, which lead to enhanced accumulation of reactive oxygen species (ROS) thus causing oxidative damage. However, a rapid increase in the accumulation of GABA during stress in various plant forms like bacteria, cyanobacteria, fungi, and plants indicates its putative role in stress regulation and acclimation. This review summarizes the biosynthesis of GABA, its role in abiotic stress tolerance, and its crosstalk with ROS, nitric oxide, Ca⁺² ions, phytohormones, and polyamines in stress acclimation.

     

Drought acclimation reduces O2*- accumulation and lipid peroxidation in wheat seedlings

Abiotic stresses cause ROS accumulation, which is detrimental to plant growth. It is well known that acclimation of plants under mild or sub-lethal stress condition leads to development of resistance in plants to severe or lethal stress condition. The generation of ROS and subsequent oxidative damage during drought stress is well documented in the crop plants. However, the effect of drought acclimation treatment on ROS accumulation and lipid peroxidation has not been examined so far. In this study, the effect of water stress acclimation treatment on superoxide radical (O(2)(-z.rad;)) accumulation and membrane lipid peroxidation was studied in leaves and roots of wheat (Triticum aestivum) cv. C306. EPR quantification of superoxide radicals revealed that drought acclimation treatment led to 2-fold increase in superoxide radical accumulation in leaf and roots with no apparent membrane damage. However under subsequent severe water stress condition, the leaf and roots of non-acclimated plants accumulated significantly higher amount of superoxide radicals and showed higher membrane damage than that of acclimated plants. Thus, acclimation-induced restriction of superoxide radical accumulation is one of the cellular processes that confers enhanced water stress tolerance to the acclimated wheat seedlings.     

H2O2-NOX系统: 一种植物体内重要的发育调控与胁迫响应机制

以H₂O₂为中心的活性氧(reactive oxygen species, ROS)的产生是动植物发育与响应外界生物与非生物胁迫的普遍 特征, 其在生理和分子2个水平上调控植物的发育和对外界胁迫的响应, 并与一系列信号转导过程相关联。作为关键的ROS产生酶, 质膜NADPH氧化酶(plasma membrane NADPH oxidase, PM-NOX)在植物应对各种生物和非生物胁迫中具有重要作用, 被广泛认为是胁迫条件下植物细胞ROS产生并积累的主要来源。该文简要综述了近年来人们在植物细胞ROS产生、清除、生理功能以及PM-NOX酶的结构特征与功能等方面的研究进展, 并认为H₂O₂-NOX系统是一种植物体内普遍存在的重要发育调控与胁迫响应机制。