Hydrogen sulfide donor sodium hydrosulfide-improved heat tolerance in maize and involvement of proline

Hydrogen sulfide (H₂S) has long been considered as a phytotoxin, but nowadays as a cell signal molecule involved in growth, development, and the acquisition of stress tolerance in higher plants. In the present study, hydrogen sulfide donor, sodium hydrosulfide (NaHS), pretreatment markedly improved germination percentage of seeds and survival percentage of seedlings of maize under heat stress, and alleviated an increase in electrolyte leakage of roots, a decrease in tissue vitality and an accumulation of malondialdehyde (MDA) in coleoptiles of maize seedlings. In addition, pretreatment of NaHS could improve the activity of Δ¹-pyrroline-5-carboxylate synthetase (P5CS) and lower proline dehydrogenase (ProDH) activity, which in turn induced accumulation of endogenous proline in maize seedlings. Also, application of proline could enhance endogenous proline content, followed by mitigated accumulation of MDA and increased survival percentage of maize seedlings under heat stress. These results suggest that sodium hydrosulfide pretreatment could improve heat tolerance of maize and the acquisition of this heat tolerance may be involved in proline.     

Levels of 5-methyltetrahydrofolate and ascorbic acid in cerebrospinal fluid are correlated: Implications for the accelerated degradation of folate by reactive oxygen species

Deficiency of 5-methyltetrahydrofolate (5-MTHF) in cerebrospinal fluid (CSF) is associated with a number of neurometabolic conditions including mitochondrial electron transport chain defects. Whilst failure of the active transport of 5-methyltetrahydrofolate (5-MTHF) into the CSF compartment has been proposed as a potential mechanism responsible for the 5-MTHF deficiency seen in mitochondrial disorders, it is becoming increasingly clear that other mechanisms are involved. Here, we have considered the role of oxidative stress as a contributing mechanism. Concerning, ascorbic acid (AA), we have established a CSF reference range (103–303 μM) and demonstrated a significant positive correlation between 5-MTHF and AA. Furthermore, CSF itself was also shown to convey antioxidant properties towards 5-MTHF. However, this protection could be overcome by the introduction of a hydroxyl radical generating system. Using a neuronal model system, inhibition of mitochondrial complex I, by 58%, was associated with a 23% increase in superoxide generation and a significantly increased loss of 5-MTHF from the extracellular medium. Addition of AA (150 μM) was able to prevent this increased 5-MTHF catabolism. We conclude that increased generation of reactive oxygen species and/or loss of CSF antioxidants are also factors to consider with regard to the development of a central 5-MTHF deficiency. Co-supplementation of AA together with appropriate folate replacement may be of therapeutic benefit.     

Deferoxamine inhibits iron induced hippocampal tau phosphorylation in the Alzheimer transgenic mouse brain

Prior work has shown that iron interacts with hyperphosphorylated tau, which contributes to the formation of neurofibrillary tangles (NFTs) in Alzheimer’s disease (AD), whereas iron chelator desferrioxamine (DFO) slows down the clinical progression of the cognitive decline associated with this disease. However, the effects of DFO on tau phosphorylation in the presence or absence of iron have yet to be determined. Using amyloid precursor protein (APP) and presenilin 1 (PS1) double transgenic mouse brain as a model system, we investigated the effects and potential mechanisms of intranasal administration of DFO on iron induced abnormal tau phosphorylation. High-dose iron treatment markedly increased the levels of tau phosphorylation at the sites of Thr205, Thr231 and Ser396, whereas highly induced tau phosphorylation was abolished by intranasal administration of DFO in APP/PS1 transgenic mice. Moreover, DFO intranasal administration also decreases Fe-induced the activities of cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3β (GSK3β), which in turn suppressing tau phosphorylation. Cumulatively, our data show that intranasal DFO treatment exerts its suppressive effects on iron induced tau phosphorylation via CDK5 and GSK3β pathways. More importantly, elucidation of DFO mechanism in suppressing tau phosphorylation may provide insights for developing therapeutic strategies to combat AD.     

Chronic morphine exposure and its abstinence alters dendritic spine morphology and upregulates Shank1

Exposure to chronic drugs of abuse has been reported to produce significant changes in postsynaptic protein profile, dendritic spine morphology and synaptic transmission. In the present study we demonstrate alterations in dendritic spine morphology in the frontal cortex and nucleus accumbens of mice following chronic morphine treatment as well as during abstinence for two months. Such alterations were accompanied with significant upregulation of the postsynaptic protein Shank1 in synaptosomal enriched fractions. mRNA levels of Shank1 was also markedly increased during morphine treatment and during withdrawal. Studies of the different postsynaptic proteins at the protein and mRNA levels showed significant alterations in the morphine treated groups compared to that of saline treated controls. Taken together, these observations suggest that Shank1 may have an important role in the regulation of spine morphology induced by chronic morphine leading to addiction.     

Germ lineage properties in the urochordate Botryllus schlosseri – From markers to temporal niches

The primordial germ cells (PGCs) in the colonial urochordate Botryllus schlosseri are sequestered in late embryonic stage. PGC-like populations, located at any blastogenic stage in specific niches, inside modules with curtailed lifespan, survive throughout the life of the colony by repeated weekly migration to newly formed buds. This cyclical migration and the lack of specific markers for PGC-like populations are obstacles to the study on PGCs. For that purpose, we isolated the Botryllus DDX1 (BS-DDX1) and characterized it by normal expression patterns and by specific siRNA knockdown experiments. Expression of BS-DDX1 concurrent with BS-Vasa, γ-H2AX, BS-cadherin and phospho-Smad1/5/8, demarcate PGC cells from soma cells and from more differentiated germ cells lineages, which enabled the detection of additional putative transient niches in zooids. Employing BS-cadherin siRNA knockdown, retinoic acid (RA) administration or β-estradiol administration affirmed the BS-Vasa⁺BS-DDX1⁺BS-cadherin⁺γ-H2AX⁺phospho-Smad1/5/8⁺ population as the B. schlosseri PGC-like cells. By striving to understand the PGC-like cells trafficking between transient niches along blastogenic cycles, CM-DiI-stained PGC-like enriched populations from late blastogenic stage D zooids were injected into genetically matched colonial ramets at blastogenic stages A or C and their fates were observed for 9 days. Based on the accumulated data, we conceived a novel network of several transient and short lived ‘germ line niches’ that preserve PGCs homeostasis, protecting these cells from the weekly astogenic senescence processes, thus enabling the survival of the PGCs throughout the organism's life.     

Cathepsin L silencing enhances arsenic trioxide mediated in vitro cytotoxicity and apoptosis in glioblastoma U87MG spheroids

Despite improved treatment options, glioblastoma multiforme (GBM) remains the most aggressive brain tumour with the shortest post-diagnostic survival. Arsenite (As₂O₃) is already being used in the treatment of acute promyelocytic leukaemia (APL), yet its effects on GBM have not been evaluated in detail. In U87MG cell monolayers, we have previously shown that arsenite cytotoxicity significantly increases upon transient inhibition of lysosomal protease Cathepsin L (CatL). As multicellular spheroids more closely represent in vivo tumours, we aimed to evaluate the impact of permanent CatL silencing on arsenite treatment in U87MG spheroids. CatL was stably silenced using shRNA expression plasmid packed lentiviruses. By using metabolic- and cell viability assays, we demonstrated that long-term CatL silencing significantly increased arsenite cytotoxicity in U87MG spheroids. Silenced CatL also increased arsenite-mediated apoptosis in spheroids via elevated p53 expression, Bax/Bcl2 ratio and caspase 3/7 activity, though with lower efficacy than in monolayers. Arsenite cytotoxicity was enhanced by lower CatL activity, since similar cytotoxicity increase was also observed using the novel CatL inhibitor AT094. The results have significant translational impact, since stable CatL silencing would enable the application of lower systemic doses of arsenite to achieve the desired cytotoxic effects on GBMs in vivo.     

Methylerythritol phosphate pathway to isoprenoids: Kinetic modeling and in silico enzyme inhibitions in Plasmodium falciparum

The methylerythritol phosphate (MEP) pathway of Plasmodium falciparum (P. falciparum) has become an attractive target for anti-malarial drug discovery. This study describes a kinetic model of this pathway, its use in validating 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) as drug target from the systemic perspective, and additional target identification, using metabolic control analysis and in silico inhibition studies. In addition to DXR, 1-deoxy-d-xylulose 5-phosphate synthase (DXS) can be targeted because it is the first enzyme of the pathway and has the highest flux control coefficient followed by that of DXR. In silico inhibition of both enzymes caused large decrement in the pathway flux. An added advantage of targeting DXS is its influence on vitamin B1 and B6 biosynthesis. Two more potential targets, 2-C-methyl-d-erythritol 2,4-cyclodiphosphate synthase and 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase, were also identified. Their inhibition caused large accumulation of their substrates causing instability of the system.     

Knockout of pgdS and ggt genes improves γ‐PGA yield in B. subtilis

One of the emerging biopolymers that are currently under active investigation is bacterial poly(γ‐glutamic acid) (γ‐PGA). However, before its full industrial exploitation, a substantial increase in microbial productivity is required. γ‐PGA obtained from the Bacillus subtilis laboratory strain 168 offers the advantage of a producer characterized by a well defined genetic framework and simple manipulation techniques. In this strain, the knockout of genes for the major γ‐PGA degrading enzymes, pgdS and ggt, leads to a considerable improvement in polymer yield, which attains levels analogous to the top wild γ‐PGA producer strains. This study highlights the convenience of using the laboratory strain of B. subtilis over wild isolates in designing strain improvement strategies aimed at increasing γ‐PGA productivity. Biotechnol. Bioeng. 2013; 110: 2006–2012. © 2013 Wiley Periodicals, Inc.