Therapeutic time windows of compounds against NMDA receptors signaling pathways for ischemic stroke.

Much evidence has proved that excitotoxicity induced by excessive release of glutamate contributes largely to damage caused by ischemia. In view of the key role played by NMDA receptors in mediating excitotoxicity, compounds against NMDA receptors signaling pathways have become the most promising type of anti-stroke candidate compounds. However, the limited therapeutic time window for neuroprotection is a key factor preventing NMDA receptor-related compounds from showing efficacy in all clinical trials for ischemic stroke. In this perspective, the determination of therapeutic time windows of these kinds of compounds is useful in ensuring a therapeutic effect and accelerating clinical application. This mini-review discussed the therapeutic time windows of compounds against NMDA receptors signaling pathways, described related influence factors and the status of clinical studies. The purpose of this review is to look for compounds with wide therapeutic time windows and better clinical application prospect.

Potential of esterase DmtH in transforming plastic additive dimethyl terephthalate to less toxic mono-methyl terephthalate.

Dimethyl terephthalate (DMT) is a primary ingredient widely used in the manufacture of polyesters and industrial plastics; its environmental fate is of concern due to its global use. Microorganisms play key roles in the dissipation of DMT from the environment; however, the enzymes responsible for the initial transformation of DMT and the possible altered toxicity due to this biotransformation have not been extensively studied. To reduce DMT toxicity, we identified the esterase gene dmtH involved in the initial transformation of DMT from the AOPP herbicide-transforming strain Sphingobium sp. C3. DmtH shows 24-41% identity with α/ß-hydrolases and belongs to subfamily V of bacterial esterases. The purified recombinant DmtH was capable of transforming DMT to mono-methyl terephthalate (MMT) and potentially transforming other p-phthalic acid esters, including diallyl terephthalate (DAT) and diethyl terephthalate (DET). Using C. elegans as an assay model, we observed the severe toxicity of DMT in inducing reactive oxygen species (ROS) production, decreasing locomotion behavior, reducing lifespan, altering molecular basis for oxidative stress, and inducing mitochondrial stress. In contrast, exposure to MMT did not cause obvious toxicity, induce oxidative stress, and activate mitochondrial stress in nematodes. Our study highlights the usefulness of Sphingobium sp. C3 and its esterase DmtH in transforming p-phthalic acid esters and reducing the toxicity of DMT to organisms.

Chitinophaga deserti sp. nov., isolated from desert soil.

An aerobic bacterial strain, designated XJ-2T, was isolated from a soil sample collected from Gurbantunggut Sandy Desert in PR China. Cells of strain XJ-2T were Gram-stain-negative, non-motile, rod-shaped and non-spore-forming. The new isolate grew well at 10-37 °C (optimum, 28-30 °C), pH 6.0-11.0 (pH 7.0) and 0-1 % (w/v) NaCl (0 %). The 16S rRNA gene sequence of strain XJ-2T showed the highest similarity to that of Chitinophaga rhizosphaerae T16R-86T (99.0 %), followed by Chitinophaga barathri YLT18T (97.0 %), Chitinophagahumicola Ktm-2T (96.7 %) and Chitinophaga niabensis JS13-10T (96.4 %). The major menaquinone of strain XJ-2T was menaquinone 7 and the predominant fatty acids (>5 %) were iso-C15 : 0, C16 : 1ω5c and iso-C17 : 0 3-OH. The polar lipids consisted of phosphatidylethanolamine, an unidentified glycolipid, three unidentified aminolipids and five unidentified lipids. The genome size was 6.33 Mb, comprising 5268 predicted genes with a G+C content of 41.5 mol%. The DNA G+C content was 50.5 mol% based on total genome calculations. The average nucleotide identity and the digital DNA-DNA hybridization values between strain XJ-2T and strain T16R-86T were 79.6 and 22.3 %, respectively. DNA-DNA relatedness between strain XJ-2T and strain YLT18T was 17.0 %. Based on the physiological, biochemical and chemotaxonomic characteristics, strain XJ-2T represents a novel species of the genus Chitinophaga, for which the name Chitinophagadeserti sp. nov. is proposed. The type strain is XJ-2T (KCTC 62443T=CCTCC AB 2018019T).

Steroidobacter soli sp. nov., isolated from farmland soil.

A Gram-stain-negative bacterial strain, designated JW-3T, was isolated from a soil sample collected from farmland in Yantai, Shandong Province, PR China. Cells of strain JW-3T are motile rods and strictly aerobic, showing catalase- and oxidase-positive reactions. Strain JW-3T could grow at 16-37 °C (optimum, 30 °C), at pH 6.0-9.0 (pH 7.0) and in the presence of 0-1 % (w/v) NaCl (0.5 %, in Luria-Bertani broth). The major fatty acids were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c; 35.5 %), iso-C16 : 0 (16.7 %) and C12 : 0 (10.8 %). The major respiratory quinone was ubiquinone-8 (Q8). The polar lipids of strain JW-3T consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, four unidentified phospholipids, two unidentified lipids, two unidentified glycolipids and a partial unidentified aminophospholipid. Strain JW-3T was most closely related to Steroidobacter agariperforans KA5-BT with 97.67 % 16S rRNA gene sequence similarity. Results of phylogenetic analyses, based on 16S rRNA gene sequencing, showed that strain JW-3T forms a distinct phylogenic lineage within the genus Steroidobacter of the family Sinobacteraceae. The DNA G+C content of strain JW-3T was 62.57 mol%, based on its draft genome sequence. Average nucleotide identity values and digital DNA-DNA hybridization values for draft genomes, between strain JW-3T and strain KA5-BT, were 84.54 and 30.80 %, respectively. Based on its phenotypic, chemotaxonomic and molecular features, and DNA-DNA hybridization results, strain JW-3T represents a novel species of the genus Steroidobacter, for which the name Steroidobactersoli sp. nov. is proposed. The type strain is JW-3T (=CCTCC AB 2018184T=KCTC 62820T).

The differences between GluN2A and GluN2B signaling in the brain.

The N-methyl-d-aspartate (NMDA) receptor, a typical ionotropic glutamate receptor, is a crucial protein for maintaining brain function. GluN2A and GluN2B are the main types of NMDA receptor subunit in the adult forebrain. Studies have demonstrated that they play different roles in a number of pathophysiological processes. Although the underlying mechanism for this has not been clarified, the most fundamental reason may be the differences between the signaling pathways associated with GluN2A and GluN2B. With the aim of elucidating the reasons behind the diverse roles of these two subunits, we described the signaling differences between GluN2A and GluN2B from the aspects of C-terminus-associated molecules, effects on typical downstream signaling proteins, and metabotropic signaling. Because there are several factors interfering with the determination of subunit-specific signaling, there is still a long way to go toward clarifying the signaling differences between these two subunits. Developing better pharmacology tools, such as highly selective antagonists for triheteromeric GluN2A- and GluN2B-containing NMDA receptors, and establishing new molecular biological methods, for example, engineering photoswitchable NMDA receptors, may be useful for clarifying the signaling differences between GluN2A and GluN2B.

The Regulation of GluN2A by Endogenous and Exogenous Regulators in the Central Nervous System.

The NMDA receptor is the most widely studied ionotropic glutamate receptor, and it is central to many physiological and pathophysiological processes in the central nervous system. GluN2A is one of the two main types of GluN2 NMDA receptor subunits in the forebrain. The proper activity of GluN2A is important to brain function, as the abnormal regulation of GluN2A may induce some neuropsychiatric disorders. This review will examine the regulation of GluN2A by endogenous and exogenous regulators in the central nervous system.

Treatment of Cerebral Ischemia Through NMDA Receptors: Metabotropic Signaling and Future Directions.

Excessive activation of N-methyl-d-aspartic acid (NMDA) receptors after cerebral ischemia is a key cause of ischemic injury. For a long time, it was generally accepted that calcium influx is a necessary condition for ischemic injury mediated by NMDA receptors. However, recent studies have shown that NMDA receptor signaling, independent of ion flow, plays an important role in the regulation of ischemic brain injury. The purpose of this review is to better understand the roles of metabotropic NMDA receptor signaling in cerebral ischemia and to discuss the research and development directions of NMDA receptor antagonists against cerebral ischemia. This mini review provides a discussion on how metabotropic transduction is mediated by the NMDA receptor, related signaling molecules, and roles of metabotropic NMDA receptor signaling in cerebral ischemia. In view of the important roles of metabotropic signaling in cerebral ischemia, NMDA receptor antagonists, such as GluN2B-selective antagonists, which can effectively block both pro-death metabotropic and pro-death ionotropic signaling, may have better application prospects.

Enantioselective Catabolism of Napropamide Chiral Enantiomers in Sphingobium sp. A1 and B2.

Napropamide [ N, N-diethyl-2-(1-naphthalenyloxy)propenamide, NAP] is a highly efficient and broad-spectrum amide herbicide. Little is known about the bacterial catabolism of its different enantiomers. Here, we report the isolation of two NAP-degrading strains of Sphingobium sp., A1 and B2, and the different catabolic pathways of different enantiomers in these two strains. Strain A1 dioxygenated NAP at different positions of the naphthalene ring of different enantiomers, leading to the complete degradation of R-NAP while producing a dead-end product from S-NAP. Strain B2 cleaved the amido bonds of both enantiomers, but only the product from S-NAP could be further transformed to form α-naphthol and mineralize in strain B2. The degradation rates of R-NAP and S-NAP in the combination degradation by strains A1 and B2 were 24.8 and 7.5 times that in the single-strain degradation by strain B2 or A1, respectively, showing enhanced synergistic catabolism between strains A1 and B2. This study provides new insights into the enantioselective catabolic network of the chiral herbicide NAP in microorganisms.

The Role of GluN2A in Cerebral Ischemia: Promoting Neuron Death and Survival in the Early Stage and Thereafter.

Over-activation of NMDA receptors is a crucial step required for brain damage following a stroke. Although clinical trials for NMDA receptor blockers have failed, the role of GluN2A subunit in cerebral ischemia has been extensively evaluated in recent years. However, the effect of GluN2A on neuron damage induced by cerebral ischemia remains a matter of controversy. The underlying reason may be that GluN2A mediates both pro-death and pro-survival effects. These two effects result from two mutually excluding pathways, Ca2+ overload-dependent pro-death signaling and C-terminal-dependent pro-survival signaling, respectively. During the early stage of cerebral ischemia, over-activation of GluN2A plays an important role in Ca2+ overload. Under this condition, pro-death signaling might overcome pro-survival signaling. When GluN2A activity is restored almost to the normal level over time, pro-survival signaling of GluN2A will be dominant. The hypothesis that GluN2A promotes neuron death and survival in the early stage of cerebral ischemia and thereafter will be introduced in detail in this review.

The Functional and Molecular Properties, Physiological Functions, and Pathophysiological Roles of GluN2A in the Central Nervous System.

The NMDA receptor, which is heavily involved in several human brain diseases, is a heteromeric ligand-gated ion channel that interacts with multiple intracellular proteins through the C-termini of different subunits. GluN2A and GluN2B are the two primary types of GluN2 subunits in the forebrain. During the developmental period, there is a switch from GluN2B- to GluN2A-containing NMDA receptors in synapses. In the adult brain, GluN2A exists at synaptic sites more abundantly than GluN2B. GluN2A plays important roles not only in synaptic plasticity but also in mediating physiological functions, such as learning and memory. GluN2A has also been involved in many common human diseases, such as cerebral ischemia, seizure disorder, Alzheimer's disease, and systemic lupus erythematosus. The following review investigates the functional and molecular properties, physiological functions, and pathophysiological roles of the GluN2A subunit.

[Determination of a major constituent in deoxyspergualin drug by reversed-phase ion-pair chromatography].

A method was established for the determination of deoxyspergualin using reversed-phase ion-pair chromatography (RP-IPC). Several parameters, such as the chromatographic column, the types and concentration of ion-pair reagents, the concentration of the buffer and the pH value of the mobile phase were evaluated. The optimal separation conditions were as follows: C18 column (250 mm x 4.6 mm, 5 microm); mobile phase, 5 mmol/L di-potassium hydrogen phosphate (containing 5 mmol/L 1-pentanesulfonic acid sodium, pH 3.6 +/- 0.3)-acetonitrile (90: 10, v/v); flow rate, 1.0 mL/min; detection wavelength, 210 nm; column temperature, 30 degrees C; injection volume, 20 microL. Under the optimaized experimental conditions, good linear relationships was obtained and the limit of detection for deoxyspergualin was 0.5 mg/L.

[Chiral separation of pitavastatin calcium enantiomers by capillary zone electrophoresis].

A method of capillary zone electrophoresis (CZE) has been established for the chiral separation of pitavastatin calcium enantiomers. Several parameters, such as the running voltage, the composition and the pH value of the running buffer, the types of additive and so on, were evaluated. The optimal separation conditions were as follows: capillary, 53 cm (45 cm effective length, 50 microm); running buffer, 80 mmol/L Tris-HCl, pH 3.20, which contained 50 mmol/L HP-beta-CD (hydroxypropyl-beta-cyclodextrin) and 5 mmol/L SDS (sodium dodecylsulphate); applied voltage, 18 kV (54 microA); column temperature, 23 degrees C; injection, 2 s at the height of 17 cm. Under these conditions, pitavatatin calcium enantiomers were separated well with the resolution of 2.17. The results indicate that this method is rapid, simple, accurate and suitable for the chiral separation of pitvatin calcium enantiomers.