Overexpression of extracellular superoxide dismutase has a protective role against hyperoxia-induced brain injury in neonatal mice

There is increasing evidence that hyperoxia, particularly at the time of birth, may result in neurological injury, in particular to the susceptible vasculature of these tissues. This study was aimed at determining whether overexpression of extracellular superoxide dismutase (EC-SOD) is protective against brain injury induced by hyperoxia. Transgenic (TG) mice (with an extra copy of the human extracellular superoxide dismutase gene) and wild-type (WT) neonate mice were exposed to hyperoxia (95% of F(i) o(2) ) for 7 days after birth versus the control group in room air. Brain positron emission tomography (PET) scanning with fludeoxyglucose (FDG) isotope uptake was performed after exposure. To assess apoptosis induced by hyperoxia exposure, caspase 3 ELISA and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining were performed. Quantitative western blot for the following inflammatory markers was performed: glial fibrillary acidic protein, ionized calcium-binding adaptor molecule 1, macrophage-inhibiting factor, and phospho-AMP-activated protein kinase. PET scanning with FDG isotope uptake showed significantly higher uptake in the WT hyperoxia neonate brain group (0.14 ± 0.03) than in both the TG group (0.09 ± 0.01) and the control group (0.08 ± 0.02) (P< 0.05). Histopathological investigation showed more apoptosis and dead neurons in hippocampus and cerebellum brain sections of WT neonate mice after exposure to hyperoxia than in TG mice; this finding was also confirmed by TUNEL staining. The caspase 3 assay confirmed the finding of more apoptosis in WT hyperoxia neonates (0.814 ± 0.112) than in the TG hyperoxic group (0.579 ± 0.144) (P < 0.05); this finding was also confirmed by TUNEL staining. Quantitative western blotting for the inflammatory and metabolic markers showed significantly higher expression in the WT group than in the TG and control groups. Thus, overexpression of EC-SOD in the neonate brain offers significant protection against hyperoxia-induced brain damage.     

The functional relationship between ectodermal and mesodermal segmentation in the crustacean, Parhyale hawaiensis

In arthropods, annelids and chordates, segmentation of the body axis encompasses both ectodermal and mesodermal derivatives. In vertebrates, trunk mesoderm segments autonomously and induces segmental arrangement of the ectoderm-derived nervous system. In contrast, in the arthropod Drosophila melanogaster, the ectoderm segments autonomously and mesoderm segmentation is at least partially dependent on the ectoderm. While segmentation has been proposed to be a feature of the common ancestor of vertebrates and arthropods, considering vertebrates and Drosophila alone, it is impossible to conclude whether the ancestral primary segmented tissue was the ectoderm or the mesoderm. Furthermore, much of Drosophila segmentation occurs before gastrulation and thus may not accurately represent the mechanisms of segmentation in all arthropods. To better understand the relationship between segmented germ layers in arthropods, we asked whether segmentation is an intrinsic property of the ectoderm and/or the mesoderm in the crustacean Parhyale hawaiensis by ablating either the ectoderm or the mesoderm and then assaying for segmentation in the remaining tissue layer. We found that the ectoderm segments autonomously. However, mesoderm segmentation requires at least a permissive signal from the ectoderm. Although mesodermal stem cells undergo normal rounds of division in the absence of ectoderm, they do not migrate properly in respect to migration direction and distance. In addition, their progeny neither divide nor express the mesoderm segmentation markers Ph-twist and Ph-Even-skipped. As segmentation is ectoderm-dependent in both Parhyale and holometabola insects, we hypothesize that segmentation is primarily a property of the ectoderm in pancrustacea.     

The tardigrade Hypsibius dujardini, a new model for studying the evolution of development

Studying development in diverse taxa can address a central issue in evolutionary biology: how morphological diversity arises through the evolution of developmental mechanisms. Two of the best-studied developmental model organisms, the arthropod Drosophila and the nematode Caenorhabditis elegans, have been found to belong to a single protostome superclade, the Ecdysozoa. This finding suggests that a closely related ecdysozoan phylum could serve as a valuable model for studying how developmental mechanisms evolve in ways that can produce diverse body plans. Tardigrades, also called water bears, make up a phylum of microscopic ecdysozoan animals. Tardigrades share many characteristics with C. elegans and Drosophila that could make them useful laboratory models, but long-term culturing of tardigrades historically has been a challenge, and there have been few studies of tardigrade development. Here, we show that the tardigrade Hypsibius dujardini can be cultured continuously for decades and can be cryopreserved. We report that H. dujardini has a compact genome, a little smaller than that of C. elegans or Drosophila, and that sequence evolution has occurred at a typical rate. H. dujardini has a short generation time, 13–14 days at room temperature. We have found that the embryos of H. dujardini have a stereotyped cleavage pattern with asymmetric cell divisions, nuclear migrations, and cell migrations occurring in reproducible patterns. We present a cell lineage of the early embryo and an embryonic staging series. We expect that these data can serve as a platform for using H. dujardini as a model for studying the evolution of developmental mechanisms.     

Regulation of 5-hydroxyeicosanoid dehydrogenase activity in monocytic cells

The requirement of DAG (diacylglycerol) to recruit PKD (protein kinase D) to the TGN (trans-Golgi network) for the targeting of transport carriers to the cell surface, has led us to a search for new components involved in this regulatory pathway. Previous findings reveal that the heterotrimeric Gbetagamma (GTP-binding protein betagamma subunits) act as PKD activators, leading to fission of transport vesicles at the TGN. We have recently shown that PKCeta (protein kinase Ceta) functions as an intermediate member in the vesicle generating pathway. DAG is capable of activating this kinase at the TGN, and at the same time is able to recruit PKD to this organelle in order to interact with PKCeta, allowing phosphorylation of PKD's activation loop. The most qualified candidates for the production of DAG at the TGN are PI-PLCs (phosphatidylinositol-specific phospholipases C), since some members of this family can be directly activated by Gbetagamma, utilizing PtdIns(4,5)P2 as a substrate, to produce the second messengers DAG and InsP3. In the present study we show that betagamma-dependent Golgi fragmentation, PKD1 activation and TGN to plasma membrane transport were affected by a specific PI-PLC inhibitor, U73122 [1-(6-{[17-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-1H-pyrrole-2,5-dione]. In addition, a recently described PI-PLC activator, m-3M3FBS [2,4,6-trimethyl-N-(m-3-trifluoromethylphenyl)benzenesulfonamide], induced vesiculation of the Golgi apparatus as well as PKD1 phosphorylation at its activation loop. Finally, using siRNA (small interfering RNA) to block several PI-PLCs, we were able to identify PLCbeta3 as the sole member of this family involved in the regulation of the formation of transport carriers at the TGN. In conclusion, we demonstrate that fission of transport carriers at the TGN is dependent on PI-PLCs, specifically PLCbeta3, which is necessary to activate PKCeta and PKD in that Golgi compartment, via DAG production.     

Mutational study of the bacterial hemoglobin distal heme pocket

Ligand binding experiments on three mutants in the distal heme pocket of Vitreoscilla hemoglobin (GlnE7His, ProE8Ala, and GlnE7His,ProE8Ala) were used to probe the role of GlnE7 and ProE8 in the pocket's unusual structure. The oxygen dissociation constants for the wild type, E8Ala mutant, and E7His mutant proteins were 4.5, 4.7, and 1.7microM, respectively; the K(d) for the double mutant was not determinable by our technique. Visible-Soret spectra of the carbonyl and cyanyl forms and FT-IR of the carbonyl form of the E8 mutant were similar to those of the wild type; the opposite was true for the GlnE7His and GlnE7His,ProE8Ala mutants, which also differed from wild type in the visible-Soret spectra of their oxidized forms. Models of the effects of the mutations on distal pocket structure were consistent with the experimental findings, particularly the larger effects of the GlnE7His change.     

EGFR and EphA2 are host factors for hepatitis C virus entry and possible targets for antiviral therapy

Hepatitis C virus (HCV) is a major cause of liver disease, but therapeutic options are limited and there are no prevention strategies. Viral entry is the first step of infection and requires the cooperative interaction of several host cell factors. Using a functional RNAi kinase screen, we identified epidermal growth factor receptor and ephrin receptor A2 as host cofactors for HCV entry. Blocking receptor kinase activity by approved inhibitors broadly impaired infection by all major HCV genotypes and viral escape variants in cell culture and in a human liver chimeric mouse model in vivo. The identified receptor tyrosine kinases (RTKs) mediate HCV entry by regulating CD81-claudin-1 co-receptor associations and viral glycoprotein-dependent membrane fusion. These results identify RTKs as previously unknown HCV entry cofactors and show that tyrosine kinase inhibitors have substantial antiviral activity. Inhibition of RTK function may constitute a new approach for prevention and treatment of HCV infection.     

Visfatin is regulated by rosiglitazone in type 2 diabetes mellitus and influenced by NFκB and JNK in human abdominal subcutaneous adipocytes

Visfatin has been proposed as an insulin-mimicking adipocytokine, predominantly secreted from adipose tissue and correlated with obesity. However, recent studies suggest visfatin may act as a proinflammatory cytokine. Our studies sought to determine the significance of this adipocytokine and its potential role in the pathogenesis of T2DM. Firstly, we examined the effects of diabetic status on circulating visfatin levels, and several other adipocytokines, demonstrating that diabetic status increased visfatin*, TNF-α*** and IL-6*** compared with non-diabetic subjects (*p<0.05, **p<0.01, ***p<0.001, respectively). We then assessed the effects of an insulin sensitizer, rosiglitazone (RSG), in treatment naïve T2DM subjects, on circulating visfatin levels. Our findings showed that visfatin was reduced post-RSG treatment [vs. pre-treatment (*p<0.05)] accompanied by a reduction in HOMA-IR**, thus implicating a role for insulin in visfatin regulation. Further studies addressed the intracellular mechanisms by which visfatin may be regulated, and may exert pro-inflammatory effects, in human abdominal subcutaneous (Abd Sc) adipocytes. Following insulin (Ins) and RSG treatment, our in vitro findings highlighted that insulin (100 nM), alone, upregulated visfatin protein expression whereas, in combination with RSG (10 nM), it reduced visfatin*, IKKβ** and p-JNK1/2*. Furthermore, inhibition of JNK protein exacted a significant reduction in visfatin expression (**p<0.01), whilst NF-κB blockade increased visfatin (*p<0.05), thus identifying JNK as the more influential factor in visfatin regulation. Additional in vitro analysis on adipokines regulating visfatin showed that only Abd Sc adipocytes treated with recombinant human (rh)IL-6 increased visfatin protein (*p<0.05), whilst rh visfatin treatment, itself, had no influence on TNF-α, IL-6 or resistin secretion from Sc adipocytes. These data highlight visfatin''s regulation by insulin and RSG, potentially acting through NF-κB and JNK mechanisms, with only rh IL-6 modestly affecting visfatin regulation. Taken together, these findings suggest that visfatin may represent a pro-inflammatory cytokine that is influenced by insulin/insulin sensitivity via the NF-κB and JNK pathways.     

Identification of blottin: a novel gastric trefoil factor family-2 binding protein

The trefoil factor family (TFF) peptides are important in gastro-intestinal mucosal protection and repair. Their mechanism of action remains unclear and receptors are sought. We aimed to identify and characterise proteins binding to TFF2. A fusion protein of mouse TFF2 with alkaline phosphatase was generated and used to probe 2-D protein blots of mouse stomach. The resulting spots were analysed by MS. The protein identified was characterised by bioinformatics, rapid amplification of cDNA ends, in situ hybridisation (ISH) and immunohistochemistry (IHC). Functional assays were performed in gastrointestinal cell lines. A single major murine protein was identified and named blottin. It was previously unknown as a translated product. Blottin is also present in rat and human; the latter gene is also known as GDDR. The predicted full-length proteins are 184 amino acids long (20 kDa), reducing to 164 amino acids (18 kDa) after signal peptide cleavage. ISH of gastrointestinal tissues shows abundant blottin mRNA in gastric surface and foveolar epithelium. IHC shows cytoplasmic staining for blottin protein, and by immunoelectron microscopy in mucus granules and Golgi stacks. Previous work showed that blottin is down-regulated in gastric cancers. Blottin contains a BRICHOS domain, and has 56% similarity with gastrokine-1. Cultured HT-29 cells express blottin and show increased DNA synthesis with antiblottin antibody; however, this effect is reversed by the immunising peptide. We have identified and characterised a TFF2-binding protein produced by gastric epithelium. Blottin may play a role in gastrointestinal mucosal protection and modulate gut epithelial cell proliferation.