A Novel Prolyl Hydroxylase Inhibitor Protects Against Cell Death After Hypoxia

Hypoxia-inducible factor 1 (HIF-1) is regulated by the oxygen-dependent hydroxylation of proline residues by prolyl hydroxylases (PHDs). We recently developed a novel PHD inhibitor, TM6008, that suppresses the activity of PHDs, inducing continuous HIF-1α activation. In this study, we investigated how TM6008 affects cell survival after hypoxic conditions capable of inducing HIF-1α expression and how TM6008 regulates PHDs and genes downstream of HIF-1α. After SHSY-5Y cells had been subjected to hypoxia, TM6008 was added to the cell culture medium under normoxic conditions. Apoptotic cell death was significantly augmented just after the hypoxic conditions, compared with cell death under normoxic conditions. Notably, when TM6008 was added to the media after the cells had been subjected to hypoxia, the expression level of HIF-1α increased and the number of cell deaths decreased, compared with the results for cells cultured in media without TM6008 after hypoxia, during the 7-day incubation period under normoxic conditions. Moreover, the protein expression levels of heme oxygenase 1, erythropoietin, and glucose transporter-3, which were genes downstream of HIF-1α, were elevated in media to which TM6008 had been added, compared with media without TM6008, during the 7-day incubation period under normoxic conditions. However, the protein expression levels of PHD2 and p53 which suppressed cell proliferation were suppressed in the media to which TM6008 had been added. Thus, TM6008, which suppresses the protein expressions of PHD2 and p53, might play an important role in cell survival after hypoxic conditions, with possible applications as a new compound for treatment after ischemic stroke.     

Photoprotective responses of an ice algal community in Saroma-Ko Lagoon, Hokkaido, Japan

In polar seas, ice algal communities can acclimate to extremely low light conditions. Reduced acclimation to shade in ice algal communities, as a result of shortened ice seasons at the lower latitude limits of sea ice distribution, has been suggested as advantageous for avoiding strong photoinhibition when cells are released into high light levels at the water’s surface. Thermal dissipation of excess energy by xanthophyll cycle pigments in the de-epoxidated state may occur in ice algal communities released from retreating sea ice. A light exposure experiment was conducted on ice algal communities obtained from sea ice at Saroma-Ko Lagoon in Hokkaido, Japan. Photoprotective responses to direct sunlight were examined through non-photochemical quenching (NPQ) of chlorophyll fluorescence and xanthophyll pigments. De-epoxidation of diadinoxanthin (DD) to diatoxanthin (DT) occurred rapidly, and NPQ showed a dynamic response to high light exposure. The linear relationship between the ratio of DT to chlorophyll a and NPQ followed a steeper slope than previously observed for mesophilic diatoms. The steeper slope could be explained by an apparent increase in DT for the mesophilic diatoms and induction of NPQ in response to low temperatures only in the ice algal communities. Enhanced production of DT in mesophilic diatoms could be the result of de-epoxidation of DD plus de novo synthesis, and the enhancement of NPQ might be caused by low temperature stress in the ice algae. Although the response of NPQ might be related to temperature, NPQ independent of DT synthesis should also be studied.     

Modulation of Lipid Kinase PI4KIIα Activity and Lipid Raft Association of Presenilin 1 Underlies γ-Secretase Inhibition by Ginsenoside (20S)-Rg3

Amyloid β-peptide (Aβ) pathology is an invariant feature of Alzheimer disease, preceding any detectable clinical symptoms by more than a decade. To this end, we seek to identify agents that can reduce Aβ levels in the brain via novel mechanisms. We found that (20S)-Rg3, a triterpene natural compound known as ginsenoside, reduced Aβ levels in cultured primary neurons and in the brains of a mouse model of Alzheimer disease. The (20S)-Rg3 treatment induced a decrease in the association of presenilin 1 (PS1) fragments with lipid rafts where catalytic components of the γ-secretase complex are enriched. The Aβ-lowering activity of (20S)-Rg3 directly correlated with increased activity of phosphatidylinositol 4-kinase IIα (PI4KIIα), a lipid kinase that mediates the rate-limiting step in phosphatidylinositol 4,5-bisphosphate synthesis. PI4KIIα overexpression recapitulated the effects of (20S)-Rg3, whereas reduced expression of PI4KIIα abolished the Aβ-reducing activity of (20S)-Rg3 in neurons. Our results substantiate an important role for PI4KIIα and phosphoinositide modulation in γ-secretase activity and Aβ biogenesis.     

A Structural View on the Functional Importance of the Sugar Moiety and Steroid Hydroxyls of Cardiotonic Steroids in Binding to Na,K-ATPase

The Na,K-ATPase is specifically inhibited by cardiotonic steroids (CTSs) like digoxin and is of significant therapeutic value in the treatment of congestive heart failure and arrhythmia. Recently, new interest has arisen in developing Na,K-ATPase inhibitors as anticancer agents. In the present study, we compare the potency and rate of inhibition as well as the reactivation of enzyme activity following inhibition by various cardiac glycosides and their aglycones at different pH values using shark Na,K-ATPase stabilized in the E2MgP_i or in the E2BeF_x conformations. The effects of the number and nature of various sugar residues as well as changes in the positions of hydroxyl groups on the β-side of the steroid core of cardiotonic steroids were investigated by comparing various cardiac glycoside compounds like ouabain, digoxin, digitoxin, and gitoxin with their aglycones. The results confirm our previous hypothesis that CTS binds primarily to the E2-P ground state through an extracellular access channel and that binding of extracellular Na⁺ ions to K⁺ binding sites relieved the CTS inhibition. This reactivation depended on the presence or absence of the sugar moiety on the CTS, and a single sugar is enough to impede reactivation. Finally, increasing the number of hydroxyl groups of the steroid was sterically unfavorable and was found to decrease the inhibitory potency and to confer high pH sensitivity, depending on their position on the steroid β-face. The results are discussed with reference to the recent crystal structures of Na,K-ATPase in the unbound and ouabain-bound states.     

Technical note: Quantification of neurocranial shape variation using the shortest paths connecting pairs of anatomical landmarks

Three‐dimensional geometric morphometric techniques have been widely used in quantitative comparisons of craniofacial morphology in humans and nonhuman primates. However, few anatomical landmarks can actually be defined on the neurocranium. In this study, an alternative method is proposed for defining semi‐landmarks on neurocranial surfaces for use in detailed analysis of cranial shape. Specifically, midsagittal, nuchal, and temporal lines were approximated using Bezier curves and equally spaced points along each of the curves were defined as semi‐landmarks. The shortest paths connecting pairs of anatomical landmarks as well as semi‐landmarks were then calculated in order to represent the surface morphology between landmarks using equally spaced points along the paths. To evaluate the efficacy of this method, the previously outlined technique was used in morphological analysis of sexual dimorphism in modern Japanese crania. The study sample comprised 22 specimens that were used to generate 110 anatomical semi‐landmarks, which were used in geometric morphometric analysis. Although variations due to sexual dimorphism in human crania are very small, differences could be identified using the proposed landmark placement, which demonstrated the efficacy of the proposed method. Am J Phys Anthropol 151:658–666, 2013. © 2013 Wiley Periodicals, Inc.     

Effects of arbuscular mycorrhizal fungi on the abundance of foliar-feeding insects and their natural enemy

We investigated the effects of symbiotic association between a plant and an arbuscular mycorrhizal fungus (AMF) on the abundance of aboveground foliar-feeding insects that differed in feeding mode and their predator. We examined effects on insect abundance as the result of AMF-related changes in the quality and quantity of plants in the field. The numbers of three insects with different foliar-feeding mode (phloem feeder, chewer, and cell-content feeder) and their generalist predator Orius sauteri Poppius on soybean Glycine max (L.) Merrill with and without the AMF Gigaspora margarita Becker & Hall were compared over time. Symbiotic association between the AMF and the soybean increased shoot biomass, the concentration of phosphorus in the soybean, and the abundance of the phloem feeder Aulacorthum solani Kaltenbach, but did not affect the abundance of generalist chewers. In addition, the effects of the symbiotic association on the abundance of cell-content feeding Thrips spp. and the generalist predator O. sauteri differed between sample dates. These results indicated that the effects of the symbiotic association on the number of foliar-feeding insects depended on feeding mode and the number of predators.     

Aeromonas molluscorum Av27 is a potential tributyltin (TBT) bioremediator: phenotypic and genotypic characterization indicates its safe application

Aeromonas molluscorum Av27 is an estuarine bacterium highly resistant to tributyltin (TBT). Also, the strain is able to degrade TBT into the less toxic compounds dibutyltin and monobutyltin. Therefore, this bacterium has potential to be employed in bioremediation processes. In this context, defining its biological safety is crucial. With that purpose a number of intrinsic characteristics, usually present/associated with virulent strains, were investigated. Few virulence factors were detected in strain Av27. For instance, a DNase gene is present, but it is not apparently expressed in vitro. Motility, adherence factor and phospholipase activity were also detected. Additionally, cytotoxicity to Vero cells was negative. Resistance to penicillin (10 μg ml^?1), amoxicillin/clavulanic acid (30 μg ml^?1) and cephalothin (30 μg ml^?1) and also to the vibriostatic agent O/129 was observed. Five plasmids (4, 7, 10, 100 kb and one greater than 100 kb) were identified. No Class I and II integrons were detected. Study of the optimal growth conditions showed that Av27 easily adapts to different environmental conditions. Overall, the results suggest that A. molluscorum Av27 can be considered safe to use to bioremediate TBT in contaminated environments.     

Discovery and structure–activity relationship of thienopyridine derivatives as bone anabolic agents

A cell-based assay was performed for the discovery of novel bone anabolic agents. Alkaline phosphatase (ALPase) activity of ST2 cells was utilized as an indicator of osteoblastic differentiation, and thienopyridine derivative 1 was identified as a hit compound. 3-Aminothieno[2,3-b]pyridine-2-carboxamide was confirmed to be a necessary core structure for the enhancement of ALPase activity, and then optimization of the C4-substituent on the thienopyridine ring was carried out. Introduction of cyclic amino groups to the C4-position of the thienopyridine ring improved the activity. Especially, N-phenyl-homopiperazine derivatives were found to be strong enhancers of ALPase among this new series. Furthermore, 3-amino-4-(4-phenyl-1,4-diazepan-1-yl)thieno[2,3-b]pyridine-2-carboxamide (15k) was orally administered to ovariectomized (OVX) rats over 6 weeks for evaluating the effects on areal bone mineral density (aBMD), and statistically significant improvements in aBMD were observed from the dosage of 10 mg/kg/day.     

Studies on Transfer of Antiseptics to Microbes and their Toxic Effect

The adsorption of phenols and esters of acid antiseptics by the bacterial cell (Escherichia coli and Staphylococcus aureus) was investigated in relatoin to their toxic effect, and it has been observed that the definite quantity of antiseptics must be adsorbed on the solid phase of the bacterial cell in order to give the definite toxic effect, and the toxic effect is independent of the quantity dissolved in the inner cell fluid or in the lipid phase of the cell. The result shows that the toxic effect of these antiseptics on either bacteria and yeast, is exclusively limited by the adsorbed quantity.

The adsorbed quantity required for the definite toxic effect was nearly the same as that previously observed in the case of the yeast, and the mechanism of the toxic action of these antiseptics was assumed to be same with each other in any case of microbes.