Pyrrolidine dithiocarbamate protects pancreatic β-cells from oxidative damage through regulation of FoxO1 activity in type 2 diabetes rats

Pyrrolidine dithiocarbamate （PDTC） can lower the bloot glucose level and improve the insulin sensitivity in diabeti, rats. However, the mechanisms underlying this effect o PDTC treatment in diabetic rats remained uncertain, h this study, we evaluated the mechanisms by which PDT（ conferred protection against oxidative damage to pancreat ic islet β-cells in rats with experimental type 2 diabete mellitus （DM）. DM in the rats was elicited by long-tern high-fat diet accompanied with a single intraperitonea （i.p.） injection of a low dose of streptozotocin. After a 7-da1 administration of PDTC （50 mg/kg/day i.p.）, blood glucos levels were measured and pancreatic tissues were collecte / for the determination of various biochemical and enzyma 1 ic activities using immunohistochemistry, immunofluoresI cence, and western blot techniques. The percentage o 1 apoptotic pancreatic islet β-cells was detected by flow cyto metry. The results showed that diabetic rats had elevate blood glucose levels and insulin resistance, accompanieq with an increase in malondialdehyde content, nitrotyrosin production, and inducible nitric oxide synthase expression A decrease in superoxide dismutase and glutathione pero idase activities was also observed in DM rats, culminatin with elevated β-cell apoptosis. PDTC treatment significantl reduced the oxidative damage and the β-cell apoptosi and also increased the insulin production through down-reg lating FoxO1 acetylation and up-regulating nuclear PDX- level. These data suggested that PDTC can protect islet βcells from oxidative damage and improve insulin productio through regulation of PDX-1 and FoxO1 in a DM rat model.     

Identification of EGF as an Important Regulator for Promoting CYP3A4 Expression in Human Embryonic Stem Cell-Derived Hepatocytes Using TALEN-Based Gene Targeting

Functional human hepatocytes are one of the most significant tools for studying drug absorption, distribution, metabolism and excretion/toxicity （ADME/Tox）, especially for applications in preclinical drug development （Sahi et al., 2010; Godoy et al., 2013）. They provide the closest in vitro model to the human liver and the only model that mimics the drug metabolic profiles found in vivo. However, these cells lose their metabolic function rapidly and dramatically during the in vitro culture process, which largely hinders their wider application in drug development （Sahi et al., 2010; Godoy et al., 2013）. To overcome this obstacle, it is important to regulate the activities of key genes which are responsible for the detoxification metabolic function of human hepatocytes.     

Efficient Gene Targeting in Zebrafish Mediated by a Zebrafish-Codon-Optimized Cas9 and Evaluation of Off-Targeting Effect

Targeted genome modifications with the Cas9/gRNA system derived from the clustered regularly interspaced short palin- dromic repeat/CRISPR-associated （CRISPR/Cas） system have been successfully used in cultured human cells as well as in most model organisms, including zebrafish （Danio rerio）, mouse, and fruit fly （Chang et al., 2013; Cong et al., 2013; Gratz et al., 2013; Hwang et al., 2013; Jao et al., 2013; Shen et al., 2013; Wei et al., 2013）. Its application in zebrafish is particu- larly attractive due to the ease of handling this organism and the simple application of this method by direct injection of Cas9/ gRNA. However, the information about its specificity in this organism is very limited and needs further evaluation. In addition, it is conceivable that a Cas9 mRNA optimized for zebrafish codon preference could enhance its activity.     

Chronic alcohol consumption potentiates the development of diabetes through pancreatic β-cell dysfunction

Chronic ethanol consumption is well established as a major risk factor for type-2 diabetes(T2D), which is evidenced by impaired glucose metabolism and insulin resistance. However, the relationships between alcoholconsumption and the development of T2 D remain controversial. In particular, the direct effects of ethanol consumption on proliferation of pancreatic β-cell and the exact mechanisms associated with ethanolmediated β-cell dysfunction and apoptosis remain elusive. Although alcoholism and alcohol consumption are prevalent and represent crucial public health problems worldwide, many people believe that low-tomoderate ethanol consumption may protect against T2 D and cardiovascular diseases. However, the J- or U-shaped curves obtained from cross-sectional and large prospective studies have not fully explained the relationship between alcohol consumption and T2 D. This review provides evidence for the harmful effects of chronic ethanol consumption on the progressive development of T2 D, particularly with respect to pancreatic β-cell mass and function in association with insulin synthesis and secretion. This review also discusses a conceptual framework for how ethanolproduced peroxynitrite contributes to pancreatic β-cell dysfunction and metabolic syndrome.     

Dihydroactinidiolide,a High Light-Induced 13-Carotene Derivative that Can Regulate Gene Expression and Photoacclimation in Arabidopsis

Dear Editor,
The physiological functions of carotenoids in plants go beyond their traditional roles as accessory light-har- vesting pigments, natural colorants, and quenchers of tri- plet chlorophyll and singlet oxygen （102）. Recent studies have indeed emphasized the functional role of molecules derived from carotenoids as phytohormones （Ruyter-Spira et al., 20β） or messengers in stress signaling pathways （Havaux, 2014）. In particular, chemical quenching of 102 by carotenoids within the photosystems involves oxidation of the carotenoid molecules, generating a variety of oxi- dized products （Ramel et al., 2012）. β-Cyclocitral, a volatile C7 derivative of β-carotene, is one such molecule produced during high light stress, which was found to induce changes in the expression of 102-responsive genes （Ramel et al., 2012）. Moreover, the β-cyclocitral-dependent gene repro- gramming was associated with an increased tolerance of the plants to photooxidative stress. These effects appeared to be specific to β-cyclocitral since they were not observed with β-ionone, a C9-oxidized derivative of ~-carotene, which was not able to induce or repress the expression of 1O2 gene markers. Based on those results, it was pro- posed that β-cyclocitral is a plastid messenger involved in the chloroplast-to-nucleus 1O2 signaling pathway lead- ing to acclimation to high light stress （Ramel et al., 2012）. However, in vitro 102 oxidation of β-carotene is known to produce other volatile compounds besides β-cyclocitral and IB-ionone, such as dihydroactinidiolide （dhA, Figure 1A） and a-ionene （Ramel et al., 2012）. The dhA molecule is a lac- tone （cyclic ester） resulting from the secondary oxidation of β-ionone through the intermediate 5,6-epoxy-β-ionone （Havaux, 2014）. Both dhA and o-ionene were detected in plant leaves and fruits （e.g. Del Mar Caja et al., 2009; Ramel et al., 2012）. Interestingly, dhA, but not o-ionene, was reported to accumulate in Arabidopsis leaves under hiclh liclht str     

Functional Analysis of a Rice Oxidosqualene Cyclase through Total Gene Synthesis

Dear Editor, Plants produce a large range of triterpenoids that serve as chemical defenses against pathogens. For example, β-amyrin synthase （AsbAS1） performs the initial enzymatic step in the biosynthesis of the potent antimicrobial avencins in oats （Haralampidis et al., 2001）. Additionally, other triterpenoids such as glycyrrhizin and QS21 are known to have beneficial or detrimental effects for human health （Osbourn et al., 2011）. For some time, heterologous expression of plant oxidos- qualene cyclases （OSCs） in yeast has been a powerful meth- odology for the functional characterization of this important family of triterpene biosynthetic enzymes.     

T-DNA-Induced Chromosomal Translocations in feronia and anxur2 Mutants Reveal Implications for the Mechanism of Collapsed Pollen Due to Chromosomal Rearrangements

Dear Editor, Approximately every fifth Arabidopsis T-DNA inser- tion line contains chromosomal translocations caused by the inserted T-DNA （Clark and Krysan, 2010）. Albeit broad use of T-DNA lines for mutant analysis, little is known about the consequences of these chromosomal rearrangements and only a few studies describe chromosomal aberrations in the mutant lines. While plant growth in general is not affected by such chromosomal translocations, defects in gametophyte development have been observed in lines that are heterozygous for the T-DNA insertion （Ray et al., 1997; Curtis et al., 2009）.     

To Grow or Not to Grow： FERONIA Has Her Say

Plant cells differ from their animal counterparts such that they are encased in a complex wall structure, crucial for cell growth through a dynamic equilibrium of rigidity and flexibility. Cell wall extensibility can be greatly influenced by apoplastic pH and reactive oxygen species （ROS） （Duan et al., 2014; Haruta et al., 2014）. Several recent works demonstrated that the receptor-like kinase （RLK） FERONIA （FER） is critical to fine-tune cell growth in a spatiotemporal and context-dependent manner by controlling apoplastic pH （Haruta et al., 2014） and ROS （Duan et al., 2010, 2014）, likely balancing wall rigidity for cell integrity and flexibility for cell expansion.     

A Brassinosteroid-Signaling Kinase Interacts withMultiple Receptor-Like Kinases in Arabidopsis

Dear Editor, Higher plants have evolved hundreds of genes encodingreceptor-like kinases （RLKs）, which function as cell surfacereceptors perceiving developmental and environmental sig-nals （Shiu et al., 2004）. Many RLKs have been shown to playspecific roles in hormone responses, developmental regula-tion, defense against pathogen infection, and adaptationto abiotic stresses （Chae et al., 2009; Antolin-Llovera et al.,2012）. The mechanisms that ensure specific signal transduc-tion from each RLK to target cellular responses remain poorlyunderstood. Recent studies revealed that many RLKs trans-duce signals by phosphorylating receptor-like cytoplasmickinases （RLCKs）, which lack the transmembrane domainsbut are anchored at the plasma membrane through lipidmodification （Tang et al., 2008; Zhang et al., 2010; Shi et al.,2013）. There are over 400 RLKs and only about 150 RLCKs inArabidopsis （Shiu et al., 2004）. One outstanding question iswhether each RLCK mediates signaling downstream of a spe-cific RLK, participates in multiple RLK pathways, or mediatescrosstalk between RLK pathways.     

PhGRL2 Protein,Interacting with PhACO1, Is Involved in Flower Senescence in the Petunia

Dear Editor, The pathways of ethylene biosynthesis and signaling have been studied in detail （Ji and Guo, 2013）. Arabidopsis REVERSION-TO-ETHYLENE SENSITIVITY1 （RTE1）, interacting with ETR1, and its homologs tomato GREEN RIPE （SlGR） and SlGRL1, and rice OsRTH1 negatively regulate the ethylene signaling （Barry and Giovannoni, 2006, Resnick et al., 2006; Dong et al., 2010; Zhang et al., 2012）. A newly published study suggested that a cytochrome b5 and RTE1 are functional partners in promoting ETRl-mediated repression of ethylene signaling in Arabidopsis （Chang et al., 2014）. However, AtRTH, RTE1 homolog in Arabidopsis, and its closest homolog in the tomato, SlGRL2 （GR-like2）, do not play a role in ethylene signaling （Dong et al., 2010）, and the function of the homologs of these members is not well known.     

Intracellular NHX-Type Cation/H＋ Antiporters inPlants

Cells depend on the homeostatic maintenance of pHwithin specific cellular compartments to ensure optimalconditions for metabolic and enzymatic processes as wellas protein structure and function. In the animal secre-tory pathway, cells maintain distinct luminal pHs withinvarious compartments （Paroutis et al., 2004）. Among themany molecular players that contribute to pH and ionhomeostasis in plants, Na＋（K＋）/H＋ exchangers （also knownas NHX-type cation/H＋ antiporters） appear to be particu-larly important for the regulation of a wide variety ofphysiological processes, including cell expansion, cellvolume regulation, osmotic adjustment, pH regulation,membrane trafficking, protein processing, and cellularstress responses （Pardo et al., 2006; Rodriguez-Rosaleset al., 2009; Bassil et al., 2012）. In plants, NHX antiportersappeared early in evolution and are ubiquitously encodedmembers of the CPA1 cation/H＋ antiporters subgroupthat belongs to the large family of monovalent cation/H＋ transporters CPA （Brett et al., 2005）. NHX antiport-ers are found, thus far, in all sequenced plant genomes（Bassil et al., 2012; Chanroj et al., 2012）. In Arabidopsis,the NHX family consists of eight isoforms, six of whichare intracellular （AtNHXl-AtNHX6）, located either to thevacuole （AtNHXl to AtNHX4） or endosomes （AtNHX5 andAtNHX6） and an additional two more divergent members（AtNHX7/SOSl and AtNHX8） at the plasma membrane（Bassil et al., 2012）. Orthologous sequences in each of thethree classes （plasma membrane, vacuolar, or endosomal）appear in all sequenced genomes, suggesting that distinctfunctional NHX classes appeared early in evolution andmay have conserved roles that are compartment-specific（Bassil et al., 2012）. Emerging new evidence highlightsthe importance of particular intracellular NHX antiport-ers in the regulation of vesicular and vacuolar pH andK＋ homeostasis. Vacuolar NHXs are needed to maintainK＋ homeostasis between the vacuole and cytosol, with-out which cell expansion is compromised （Bassil et al.,2011b）. Other NHX isoforms （endosomal） are requiredfor membrane trafficking and raise interesting new ques-tions about the role of pH and ion homeostasis in proteinprocessing and trafficking in the endomembrane system（Bassil et al., 2011a）. In this update, we aim to highlightrecent new evidence on intracellular NHX antiportersand emphasize possible novel and important cellular pro-cesses regulated by this particularly interesting group oftransporters.     

High-accuracy mapping of protein binding stability on nucleosornal DNA using a single-molecule method

Dear Editor, The conformation of nucleosomal DNA is significantly different from that of B-form double stranded DNA （dsDNA） （Richmond and Davey, 2003）. In nucieosomal DNA, specific DNA sequences are less flexible and less accessible than in free dsDNA, which might be due to the tight association of histone cores. The allosteric effect via DNA has been documented recently （Kim et al., 2013）, suggesting that DNA is not merely a solid rod providing recognition sequences. Previous studies of nucleosomal DNA-protein interactions only demonstrated the key mechanism involved--histone shielding （Li and Wrange, 1993; Hinz et al., 2010; Sahu et al., 2010）.     

Arabidopsis NRTI.1 Is a Bidirectional Transporter Involved in Root-to-Shoot Nitrate Translocation

Dear Editor, In most plants, nitrogen （N） is acquired by roots in the form of nitrate （NO3-）. In many species, NO3- is not assimi- lated in the roots, but is secreted into the xylem sap for translocation to the shoot, where it enters the cells to be metabolized and/or stored in the vacuoles. Several plasma membrane transporters involved in NO3- influx into the cell have been identified in Arabidopsis （Wang et ai., 2012）, especially in the roots where members of the NPF （NRTI/PTR Family, L~ran et al., 2013） and NRT2 transporter families are predominantiy implicated. Concerning efflux to the xylem sap, only one transporter, NPF7.3/NRT1.5, has been shown to be involved. However, physiological characterization of npf7.31nrtl.5 knockout mutant plants demonstrated that other transporter（s） is （are） also contributing to xylem Ioad- inq of NO~- （Lin et al., 2008）.     

A Start Point for Extracellular Nucleotide Signaling

A START POINT FOR EXTRACELLULAR NUCLEOTIDE SIGNALING
The recent discovery of a plant receptor for extracellu- lar nucleotides, reported by Choi et al. （2014）, is a major breakthrough that had been anticipated for over a dec- ade. Plants release ATP into their extracellular matrix （ECM） during growth and when they are induced by vari- ous biotic and abiotic stimuli （Clark and Roux, 2011）. That these extracellular nucleotides would activate receptors in plants was predicted by two sets of discoveries： that low- and sub-micromolar ATP could induce increases in [Ca2＋]cyt, NO, and superoxide signaling intermediates that led to downstream growth, stomatal, and defense responses, and that these changes could be blocked by antagonists that blocked extracellular nucleotide receptors in animals （Demidchik et al., 2003; Song et al., 2006; Clark et al., 2011; Demidchik et al., 2009, 2011）. Although mammalian biolo- gists had discovered two classes of receptors for extracel- lular nucleotides （P2X and P2Y） decades ago （Burnstock, 2007）, there were no plant proteins obviously similar to these in any sequence data available. Clearly, if there were plant purinoceptors, they would be different from the mammalian receptors, and they could not be discovered by motif searches.     

SGSM2, a putative Rab2a GAP,regulates lysozyme sorting in Paneth cells

正Dear Editor,Dense core vesicles(DCVs)are a class of secretory organelle present in a range of different cell types,including neurons,endocrine cells,such as adrenal chromaffin cells and isletβ-cells,and other secretory cells,such as intestinal Paneth cells(Kim et al.,2006).Cargos are packed into immature DCVs as they emerge from the trans-Golgi network.Immature     

Is There a Metabolic Requirement for Photorespiratory Enzyme Activities in Heterotrophic Tissues？

Photorespiration is an essential metabolic process in leaves that facilitates recovery of carbon lost by the oxygenase reaction of Rubisco and avoids the accumulation of the toxic product, 2-phosphoglycolate （2PG） of this reaction （Bauwe et al., 2012）. However, there is also evidence to suggest that photorespiration has a more complex role during normal growth than the mere detoxification of 2PG and the recovery of 3-phosphoglycerate （3PGA） （Bauwe et al., 2012）.     

Neuronal insulin receptor mediates a positive feedback regulation of insulin biosynthesis in Drosophila

<正>Insulin signaling is vital for the development and growth of mammals,which also plays a prominent role in the regulation of metabolism,stress response,reproduction,and behaviors.Therefore,insulin signaling is under tight regulation at the levels of insulin biosynthesis,secretion,and post-secretion action(Melloul et al.,2002;Na€ssel et al.,2013).Drosophila insulin-like peptides(DILPs)