Serine/threonine protein phosphatase 6 modulates the radiation sensitivity of glioblastoma

Increasing the sensitivity of glioblastoma cells to radiation is a promising approach to improve survival in patients with glioblastoma multiforme (GBM). This study aims to determine if serine/threonine phosphatase (protein phosphatase 6 (PP6)) is a molecular target for GBM radiosensitization treatment. The GBM orthotopic xenograft mice model was used in this study. Our data demonstrated that the protein level of PP6 catalytic subunit (PP6c) was upregulated in the GBM tissue from about 50% patients compared with the surrounding tissue or control tissue. Both the in vitro survival fraction of GBM cells and the patient survival time were highly correlated or inversely correlated with PP6c expression (R²=0.755 and −0.707, respectively). We also found that siRNA knockdown of PP6c reduced DNA-dependent protein kinase (DNA-PK) activity in three different GBM cell lines, increasing their sensitivity to radiation. In the orthotopic mice model, the overexpression of PP6c in GBM U87 cells attenuated the effect of radiation treatment, and reduced the survival time of mice compared with the control mice, while the PP6c knocking-down improved the effect of radiation treatment, and increased the survival time of mice. These findings demonstrate that PP6 regulates the sensitivity of GBM cells to radiation, and suggest small molecules disrupting or inhibiting PP6 association with DNA-PK is a potential radiosensitizer for GBM.

Polarity determination by electron energy-loss spectroscopy: application to ultra-small III-nitride semiconductor nanocolumns

Channeling-enhanced electron energy-loss spectroscopy is applied to determine the polarity of ultra-small nitride semiconductor nanocolumns in transmission electron microscopy. The technique demonstrates some practical advantages in the nanostructure analysis, especially for feature sizes of less than 50 nm. We have studied GaN and (Al, Ga)N nanocolumns grown in a self-assembled way by molecular beam epitaxy directly on bare Si(111) substrates and on AlN buffer layers, respectively. The GaN nanocolumns on Si show an N polarity, while the (Al, Ga)N nanocolumns on an AlN buffer exhibit a Ga polarity. The different polarities of nanocolumns grown in a similar procedure are interpreted in terms of the specific interface bonding configurations. Our investigation contributes to the understanding of polarity control in III-nitride nanocolumn growth.

AMPK potentiates hypertonicity-induced apoptosis by suppressing NFκB/COX-2 in medullary interstitial cells

Cells residing in the hypertonic, hypoxic renal medulla depend on dynamic adaptation mechanisms to respond to changes in energy supply and demand. The serine/threonine kinase 5'-AMP protein kinase (AMPK) is a sensor of cellular energy status, but whether it contributes to the survival of cells in the renal medulla is unknown. Here, hypertonic conditions induced a decrease in AMPK phosphorylation within 12 hours in renal medullary interstitial cells (RMIC), followed by a gradual return to baseline levels. Activation of AMPK markedly increased hypertonicity-induced apoptosis of RMICs and suppressed both hypertonicity-induced NFκB nuclear translocation and cyclooxygenase-2 (COX-2) activation; overexpression of COX-2 significantly attenuated these effects. AMPK activation also markedly reduced generation of reactive oxygen species and nuclear expression of tonicity-responsive enhancer-binding protein, which prevented upregulation of osmoprotective genes. In vivo, pharmacologic activation of AMPK led to massive apoptosis of RMICs and renal dysfunction in the setting of water deprivation in mice. Taken together, these results identify a critical role for AMPK in the maintenance of RMIC viability and suggest that AMPK modulates the NFκB-COX-2 survival pathway in the renal medulla. Furthermore, this study raises safety concerns for the development of AMPK activators as anti-diabetic drugs, especially for patients prone to dehydration.

PredCSF: an integrated feature-based approach for predicting conotoxin superfamily

Conotoxins are small disulfide-rich peptides that are invaluable channel-targeted peptides and target neuronal receptors. They show prospects for being potent pharmaceuticals in the treatment of Alzheimer's disease, Parkinson's disease, and epilepsy. Accurate and fast prediction of conotoxin superfamily is very helpful towards the understanding of its biological and pharmacological functions especially in the post-genomic era. In the present study, we have developed a novel approach called PredCSF for predicting the conotoxin superfamily from the amino acid sequence directly based on fusing different kinds of sequential features by using modified one-versus-rest SVMs. The input features to the PredCSF classifiers are composed of physicochemical properties, evolutionary information, predicted second structure and amino acid composition, where the most important features are further screened by random forest feature selection to improve the prediction performance. The prediction results show that PredCSF can obtain an overall accuracy of 90.65% based on a benchmark dataset constructed from the most recent database, which consists of 4 main conotoxin superfamilies and 1 class of non-conotoxin class. Systematic experiments also show that combing different features is helpful for enhancing the prediction power when dealing with complex biological problems. PredCSF is expected to be a powerful tool for in silico identification of novel conotonxins and is freely available for academic use at http://www.csbio.sjtu.edu.cn/bioinf/PredCSF.

Targeted disruption of the prostaglandin E2 E-prostanoid 2 receptor exacerbates vascular neointimal formation in mice

OBJECTIVE

Restenosis after angioplasty remains a major clinical problem. Prostaglandin E(2) (PGE(2)) plays an important role in vascular homeostasis. The PGE(2) receptor E-prostanoid 2 (EP2) is involved in the proliferation and migration of various cell types. We aimed to determine the role of EP2 in the pathogenesis of neointimal formation after vascular injury.

METHODS AND RESULTS

Wire-mediated vascular injury was induced in the femoral arteries of male wild-type (EP2+/+) and EP2 gene-deficient (EP2-/-) mice. In EP2+/+ mice, EP2 mRNA expression was increased in injured vessels for at least 4 weeks after vascular injury. Neointimal hyperplasia was markedly accelerated in EP2-/- mice, which was associated with increased proliferation and migration of vascular smooth muscle cells (VSMCs) and increased cyclin D1 expression in the neointima layer. Platelet-derived growth factor-BB (PDGF-BB) treatment resulted in more significant cell proliferation and migration in VSMCs of EP2-/- mice than in those of EP2+/+ mice. Activation and overexpression of EP2 attenuated PDGF-BB-elicited cell proliferation and migration, induced G(1)→S-phase arrest and reduced PDGF-BB-stimulated extracellular signal-regulated kinase phosphorylation in EP2+/+ VSMCs.

CONCLUSIONS

These findings reveal a novel role of the EP2 receptor in neointimal hyperplasia after arterial injury. The EP2 receptor may represent a potential therapeutic target for restenosis after angioplasty.

Sequencing of Lp-PLA2-encoding PLA2G7 gene in 2000 Europeans reveals several rare loss-of-function mutations

Elevated plasma levels of lipoprotein-associated phospholipase A₂ (Lp-PLA2) activity have been shown to be associated with increased risk of coronary heart disease and an inhibitor of this enzyme is under development for the treatment of that condition. A Val279Phe null allele in this gene, that may influence patient eligibility for treatment, is relatively common in East Asians but has not been observed in Europeans. We investigated the existence and functional effects of low frequency alleles in a Western European population by re-sequencing the exons of PLA2G7 in 2000 samples. In all, 19 non-synonymous single-nucleotide polymorphisms (nsSNPs) were found, 14 in fewer than four subjects (minor allele frequency <0.1%). Lp-PLA2 activity was significantly lower in rare nsSNP carriers compared with non-carriers (167.8±63.2 vs 204.6±41.8, P=0.01) and seven variants had enzyme activities consistent with a null allele. The cumulative frequency of these null alleles was 0.25%, so <1 in 10 000 Europeans would be expected to be homozygous, and thus not potentially benefit from treatment with an Lp-PLA2 inhibitor.

Proteomics analysis reveals diabetic kidney as a ketogenic organ in type 2 diabetes

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. To date, the molecular mechanisms of DN remain largely unclear. The present study aimed to identify and characterize novel proteins involved in the development of DN by a proteomic approach. Proteomic analysis revealed that 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase 2 (HMGCS2), the key enzyme in ketogenesis, was increased fourfold in the kidneys of type 2 diabetic db/db mice. Consistently, the activity of HMGCS2 in kidneys and 24-h urinary excretion of the ketone body β-hydroxybutyrate (β-HB) were significantly increased in db/db mice. Immunohistochemistry, immunofluorescence, and real-time PCR studies further demonstrated that HMGCS2 was highly expressed in renal glomeruli of db/db mice, with weak expression in the kidneys of control mice. Because filtered ketone bodies are mainly reabsorbed in the proximal tubules, we used RPTC cells, a rat proximal tubule cell line, to examine the effect of the increased level of ketone bodies. Treating cultured RPTC cells with 1 mM β-HB significantly induced transforming growth factor-β1 expression, with a marked increase in collagen I expression. β-HB treatment also resulted in a marked increase in vimentin protein expression and a significant reduction in E-cadherin protein levels, suggesting an enhanced epithelial-to-mesenchymal transition in RPTCs. Collectively, these findings demonstrate that diabetic kidneys exhibit excess ketogenic activity resulting from increased HMGCS2 expression. Enhanced ketone body production in the diabetic kidney may represent a novel mechanism involved in the pathogenesis of DN.

Telomerase inhibition strategies by siRNAs against either hTR or hTERT in oral squamous cell carcinoma

Human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT) are considered effective molecular targets for current anticancer therapy. In this study, we investigated the therapeutic effects of targeting hTR and hTERT individually or in combination by recombinant adenovirus-delivered small interfering RNA (siRNA) in oral squamous cell carcinoma (OSCC) Tca8113. Further, we screened the optimal strategy for RNA interference. Our results show that these different recombinant adenoviruses specifically reduced the levels of hTR mRNA, hTERT mRNA, hTERT protein and telomerase activity in Tca8113 cells. Moreover, they successfully inhibited xenograft tumor growth in nude mice. The potency of their antitumor activities was ranked as follows: anti-hTR >anti-hTR+anti-hTERT >anti-hTERT. Therefore, we demonstrated that the siRNA-expressing recombinant adenoviruses were an effective anticancer tool for treatment of OSCC. Furthermore, the anticancer effect of solely targeting hTR was more direct and efficient, compared with the effect of targeting hTR and hTERT in combination, or hTERT exclusively. The mechanism of this anticancer effect in OSCC was not only related to the inhibition of cell proliferation and the induction of cell apoptosis, but might also involve the inhibition of tumor angiogenesis.

Ginsenoside Rd attenuates mitochondrial dysfunction and sequential apoptosis after transient focal ischemia

We previously found that ginsenoside Rd (Rd), one of the major active ingredients in Panax ginseng, protects neuronal cells from hydrogen peroxide and oxygen-glucose deprivation, an in vitro model of cerebral ischemia. In this study, we examined the protective effects of Rd in an animal model of focal cerebral ischemia. Rats administered with Rd or vehicle were subjected to transient middle cerebral artery occlusion (MCAO). Rd (50 mg/kg) significantly reduced the infarct volume by 52.8%. This reduction of injury volume was associated with an improvement in neurological function and was sustained for at least 2 weeks after the induction of ischemia. To evaluate the underlying mechanisms of Rd against stroke, brain tissues were assayed for mitochondrial enzyme activities, mitochondrial membrane potential (MMP), production of reactive oxygen species (ROS), energy metabolites, and apoptosis. Rd markedly protected mitochondria as indicated by preserved respiratory chain complex activities and aconitase activity, lowered mitochondrial hydrogen peroxide production, and hyperpolarized MMP. Microdialysis results illustrated that Rd significantly decreased the accumulation of lactate, the end product of anaerobic glycolysis, and increased pyruvate, the end product of aerobic glycolysis, hence inducing a lower lactate/pyruvate ratio. Additionally, in vitro studies further exhibited that Rd protected isolated mitochondria from calcium-induced damage by attenuating mitochondrial swelling, preserving MMP and decreasing ROS production. Moreover, Rd treatment reduced mitochondrial release of cytochrome c (CytoC) and apoptosis-inducing factor (AIF), thereby minimizing mitochondria-mediated apoptosis following ischemia. In conclusion, these findings demonstrated that Rd exerts neuroprotective effects in transient focal ischemia, which may involve an integrated process of the mitochondrial protection, energy restoration and inhibition of apoptosis.

Antenna development for high field plasma imaging

Electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) are two microwave nonperturbing plasma visualization techniques that employ millimeter-wave imaging arrays with lens-coupled planar antennas, yielding time-resolved images of temperature (via ECEI) and electron density (via MIR) fluctuations within high temperature magnetic fusion plasmas. A series of new planar antennas have been developed that extend this technology to frequencies as high as 220 GHz for use on high field plasma devices with toroidal fields in excess of 3 T. Antenna designs are presented together with theoretical calculations, simulations, and experimental measurements.

Innovations in optical coupling of the KSTAR electron cyclotron emission imaging diagnostic

The installation of a new electron cyclotron emission imaging diagnostic for the Korea Superconducting Tokamak Advanced Research (KSTAR) is underway, making use of a unique optical port cassette design, which allows placement of refractive elements inside the cryostat region without adverse effects. The result is unprecedented window access for the implementation of a state of the art imaging diagnostic. A dual-array optical design has been developed, capable of simultaneously imaging the high and low field sides of the plasma with independent features of focal plane translation, vertical zoom, and radial channel spacing. The number of translating optics has been minimized by making use of a zoom lens triplet and parabolic plasma facing lens for maximum channel uniformity over a continuous vertical zoom range of 3:1. The simulated performance of this design is presented along with preliminary laboratory characterization data.

Development of KSTAR ECE imaging system for measurement of temperature fluctuations and edge density fluctuations

The ECE imaging (ECEI) diagnostic tested on the TEXTOR tokamak revealed the sawtooth reconnection physics in unprecedented detail, including the first observation of high-field-side crash and collective heat transport [H. K. Park, N. C. Luhmann, Jr., A. J. H. Donné et al., Phys. Rev. Lett. 96, 195003 (2006)]. An improved ECEI system capable of visualizing both high- and low-field sides simultaneously with considerably better spatial coverage has been developed for the KSTAR tokamak in order to capture the full picture of core MHD dynamics. Direct 2D imaging of other MHD phenomena such as tearing modes, edge localized modes, and even Alfvén eigenmodes is expected to be feasible. Use of ECE images of the optically thin edge region to recover 2D electron density changes during L/H mode transitions is also envisioned, providing powerful information about the underlying physics. The influence of density fluctuations on optically thin ECE is discussed.

Commissioning of electron cyclotron emission imaging instrument on the DIII-D tokamak and first data

A new electron cyclotron emission imaging diagnostic has been commissioned on the DIII-D tokamak. Dual detector arrays provide simultaneous two-dimensional images of T(e) fluctuations over radially distinct and reconfigurable regions, each with both vertical and radial zoom capability. A total of 320 (20 vertical×16 radial) channels are available. First data from this diagnostic demonstrate the acquisition of coherent electron temperature fluctuations as low as 0.1% with excellent clarity and spatial resolution. Details of the diagnostic features and capabilities are presented.

Advancements in electron cyclotron emission imaging demonstrated by the TEXTOR ECEI diagnostic upgrade

A new TEXTOR electron cyclotron emission imaging system has been developed and employed, providing a diagnostic with new features and enhanced capabilities when compared to the legacy system it replaces. Optical coupling to the plasma has been completely redesigned, making use of new minilens arrays for reduced optical aberration and providing the new feature of vertical zoom, whereby the vertical coverage is now remotely adjustable on a shot-by-shot basis from 20-35 cm. Other innovations, such as the implementation of stacked quasioptical planar notch filters, allow for the diagnostic to be operated without interruption or degradation in performance during electron cyclotron resonance heating. Successful commissioning of the new diagnostic and a demonstration of the improved capabilities are presented in this paper, along with a discussion of the new technologies employed.