Effects of marginal iron overload on iron homeostasis and immune function in alveolar macrophages isolated from pregnant and normal rats

The effects of changes in macrophage iron status, induced by single or multiple iron injections, iron depletion or pregnancy, on both immune function and mRNA expression of genes involved in iron influx and egress have been evaluated. Macrophages isolated from iron deficient rats, or pregnant rats at day 21 of gestation, either supplemented with a single dose of iron dextran, 10 mg, at the commencement of pregnancy, or not, showed significant increases of macrophage ferroportin mRNA expression, which was paralleled by significant decreases in hepatic Hamp mRNA expression. IRP activity in macrophages was not significantly altered by iron status or the inducement of pregnancy ± a single iron supplement. Macrophage immune function was significantly altered by iron supplementation and pregnancy. Iron supplementation, alone or combined with pregnancy, increased the activities of both NADPH oxidase and nuclear factor kappa B (NFκB). In contrast, the imposition of pregnancy reduced the ability of these parameters to respond to an inflammatory stimuli. Increasing iron status, if only marginally, will reduce the ability of macrophages to mount a sustained response to inflammation as well as altering iron homeostatic mechanisms.     

Structure and Assembly of Group B Streptococcus Pilus 2b Backbone Protein

Group B Streptococcus (GBS) is a major cause of invasive disease in infants. Like other Gram-positive bacteria, GBS uses a sortase C-catalyzed transpeptidation mechanism to generate cell surface pili from backbone and ancillary pilin precursor substrates. The three pilus types identified in GBS contain structural subunits that are highly immunogenic and are promising candidates for the development of a broadly-protective vaccine. Here we report the X-ray crystal structure of the backbone protein of pilus 2b (BP-2b) at 1.06Å resolution. The structure reveals a classical IgG-like fold typical of the pilin subunits of other Gram-positive bacteria. The crystallized portion of the protein (residues 185-468) encompasses domains D2 and D3 that together confer high stability to the protein due to the presence of an internal isopeptide bond within each domain. The D2+D3 region, lacking the N-terminal D1 domain, was as potent as the entire protein in conferring protection against GBS challenge in a well-established mouse model. By site-directed mutagenesis and complementation studies in GBS knock-out strains we identified the residues and motives essential for assembly of the BP-2b monomers into high-molecular weight complexes, thus providing new insights into pilus 2b polymerization.     

Tree Foliar Chemistry in an African Savanna and Its Relation to Life History Strategies and Environmental Filters

Understanding the relative importance of environment and life history strategies in determining leaf chemical traits remains a key objective of plant ecology. We assessed 20 foliar chemical properties among 12 African savanna woody plant species and their relation to environmental variables (hillslope position, precipitation, geology) and two functional traits (thorn type and seed dispersal mechanism). We found that combinations of six leaf chemical traits (lignin, hemi-cellulose, zinc, boron, magnesium, and manganese) predicted the species with 91% accuracy. Hillslope position, precipitation, and geology accounted for only 12% of the total variance in these six chemical traits. However, thorn type and seed dispersal mechanism accounted for 46% of variance in these chemical traits. The physically defended species had the highest concentrations of hemi-cellulose and boron. Species without physical defense had the highest lignin content if dispersed by vertebrates, but threefold lower lignin content if dispersed by wind. One of the most abundant woody species in southern Africa, Colophospermum mopane, was found to have the highest foliar concentrations of zinc, phosphorus, and δ¹³C, suggesting that zinc chelation may be used by this species to bind metallic toxins and increase uptake of soil phosphorus. Across all studied species, taxonomy and physical traits accounted for the majority of variability in leaf chemistry.     

XAV939-Mediated ARTD Activity Inhibition in Human MB Cell Lines

Diphtheria toxin-like ADP-ribosyltransferases 1 and 5 (ARTD-1, ARTD-5) are poly ADP-ribose enzymes (PARP) involved in non-homologous end-joining (NHEJ), which is the major pathway of double-strand break (DSB) repair. In addition, ARTD-5, or Tankyrase (TNKS), is a positive regulator of the WNT signaling implicated in the development and biological behavior of many neoplasms, such as Medulloblastoma (MB), in which radiotherapy is an essential part of the treatment. The use of radiosensitizing agents may improve the therapeutic index in MB patients by increasing the efficacy of radiotherapy, while reducing toxicity to the neuroaxis. ARTD-5 seems to be a good molecular target for improving the current treatment of MB. In this study, we used the small molecule XAV939, a potent ARTD-5 inhibitor with a slight affinity for ARTD-1, in different human MB cell lines. XAV939 inhibited the WNT pathway and DNA-PKcs in our MB cells, with many biological consequences. The co-administration of XAV939 and ionizing radiations (IR) inhibited MB cells proliferation and clonogenic capacity, decreased their efficacy in repairing DNA damage, and increased IR-induced cell mortality. In conclusion, our in vitro data show that XAV939 could be a very promising small molecule in MB treatment, and these results lay the basis for further in vivo studies with the aim of improving the current therapy available for MB patients.     

Human Cystathionine-β-Synthase Phosphorylation on Serine227 Modulates Hydrogen Sulfide Production in Human Urothelium

Urothelium, the epithelial lining the inner surface of human bladder, plays a key role in bladder physiology and pathology. It responds to chemical, mechanical and thermal stimuli by releasing several factors and mediators. Recently it has been shown that hydrogen sulfide contributes to human bladder homeostasis. Hydrogen sulfide is mainly produced in human bladder by the action of cystathionine-β-synthase. Here, we demonstrate that human cystathionine-β-synthase activity is regulated in a cGMP/PKG-dependent manner through phosphorylation at serine 227. Incubation of human urothelium or T24 cell line with 8-Bromo-cyclic-guanosine monophosphate (8-Br-cGMP) but not dibutyryl-cyclic-adenosine monophosphate (d-cAMP) causes an increase in hydrogen sulfide production. This result is congruous with the finding that PKG is robustly expressed but PKA only weakly present in human urothelium as well as in T24 cells. The cGMP/PKG-dependent phosphorylation elicited by 8-Br-cGMP is selectively reverted by KT5823, a specific PKG inhibitor. Moreover, the silencing of cystathionine-β-synthase in T24 cells leads to a marked decrease in hydrogen sulfide production either in basal condition or following 8-Br-cGMP challenge. In order to identify the phosphorylation site, recombinant mutant proteins of cystathionine-β-synthase in which Ser32, Ser227 or Ser525 was mutated in Ala were generated. The Ser227Ala mutant cystathionine-β-synthase shows a notable reduction in basal biosynthesis of hydrogen sulfide becoming unresponsive to the 8-Br-cGMP challenge. A specific antibody that recognizes the phosphorylated form of cystathionine-β-synthase has been produced and validated by using T24 cells and human urothelium. In conclusion, human cystathionine-β-synthase can be phosphorylated in a PKG-dependent manner at Ser227 leading to an increased catalytic activity.     

Combination of an Antigen-Specific Therapy and an Immunomodulatory Treatment to Simultaneous Block Recurrent Autoimmunity and Alloreactivity in Non-Obese Diabetic Mice

Restoration of endogenous insulin production by islet transplantation is considered a curative option for patients with type 1 diabetes. However, recurrent autoimmunity and alloreactivity cause graft rejection hindering successful transplantation. Here we tested whether transplant tolerance to allogeneic islets could be achieved in non-obese diabetic (NOD) mice by simultaneously tackling autoimmunity via antigen-specific immunization, and alloreactivity via granulocyte colony stimulating factor (G-CSF) and rapamycin (RAPA) treatment. Immunization with insB_9-23 peptide alone or in combination with two islet peptides (IGRP_206-214 and GAD_524-543) in incomplete Freund’s adjuvant (IFA) were tested for promoting syngeneic pancreatic islet engraftment in spontaneously diabetic NOD mice. Treatment with G-CSF/RAPA alone or in combination with insB_9-23/IFA was examined for promoting allogeneic islet engraftment in the same mouse model. InsB_9-23/IFA immunization significantly prolonged syngeneic pancreatic islet survival in NOD mice by a mechanism that necessitated the presence of CD4⁺CD25⁺ T regulatory (Treg) cells, while combination of three islet epitopes was less efficacious in controlling recurrent autoimmunity. G-CSF/RAPA treatment was unable to reverse T1D or control recurrent autoimmunity but significantly prolonged islet allograft survival in NOD mice. Blockade of interleukin-10 (IL-10) during G-CSF/RAPA treatment resulted in allograft rejection suggesting that IL-10-producing cells were fundamental to achieve transplant tolerance. G-CSF/RAPA treatment combined with insB_9-23/IFA did not further increase the survival of allogeneic islets. Thus, insB_9-23/IFA immunization controls recurrent autoimmunity and G-CSF/RAPA treatment limits alloreactivity, however their combination does not further promote allogeneic pancreatic islet engraftment in NOD mice.     

Natural Light Exposure,Sleep and Depression among Day Workers and Shiftworkers at Arctic and Equatorial Latitudes

Objectives

This study aimed to investigate the relationship between individual natural light exposure, sleep need, and depression at two latitudes, one extreme with a few hours of light per day during winter, and the other with equal hours of light and darkness throughout the year.

Methods

This cross-sectional study included a sample of Brazilian workers (Equatorial, n = 488 workers) and a Swedish sample (Arctic, n = 1,273).

Results

The reported mean total natural light exposure per 4-week cycle differed significantly between the Equatorial and Arctic regions. However, shiftworkers from both sites reported similar hours of natural light exposure. Short light exposure was a predictor for insufficient sleep.

Conclusion

Reduced exposure to natural light appears to increase the perception of obtaining insufficient sleep. Arctic workers were more prone to develop depression than Equatorial workers.     

Regional-Scale Drivers of Forest Structure and Function in Northwestern Amazonia

Field studies in Amazonia have found a relationship at continental scales between soil fertility and broad trends in forest structure and function. Little is known at regional scales, however, about how discrete patterns in forest structure or functional attributes map onto underlying edaphic or geological patterns. We collected airborne LiDAR (Light Detection and Ranging) data and VSWIR (Visible to Shortwave Infrared) imaging spectroscopy measurements over 600 km² of northwestern Amazonian lowland forests. We also established 83 inventories of plant species composition and soil properties, distributed between two widespread geological formations. Using these data, we mapped forest structure and canopy reflectance, and compared them to patterns in plant species composition, soils, and underlying geology. We found that variations in soils and species composition explained up to 70% of variation in canopy height, and corresponded to profound changes in forest vertical profiles. We further found that soils and plant species composition explained more than 90% of the variation in canopy reflectance as measured by imaging spectroscopy, indicating edaphic and compositional control of canopy chemical properties. We last found that soils explained between 30% and 70% of the variation in gap frequency in these forests, depending on the height threshold used to define gaps. Our findings indicate that a relatively small number of edaphic and compositional variables, corresponding to underlying geology, may be responsible for variations in canopy structure and chemistry over large expanses of Amazonian forest.     

Correlation between Central Memory T Cell Expression and Proinflammatory Cytokine Production with Clinical Presentation of Multibacillary Leprosy Relapse

BackgroundDespite the efficacy of multidrug therapy, surviving Mycobacterium leprae causes relapse in some leprosy patients, and these patients present signs and symptoms of disease after healing. This study focused on the cellular immune response in relapsed multibacillary patients but also included non-relapsed multibacillary cured individuals, newly diagnosed and untreated multibacillary patients, paucibacillary patients just before the beginning of treatment, and voluntary healthy individuals for comparative analysis.Conclusions/SignificanceInhibition of CD86 expression may function to reduce effector T cell responses against the M. leprae antigen. Furthermore, the predominance of central memory T cells in association with the high TNF/IL-10 ratio and no observed IFN-γ production may be related to the pathogenesis of relapse in multibacillary leprosy. Therefore, our findings may be a direct result of the clinical presentation, including a number of skin lesions and bacterial load, of relapsed patients. To our knowledge, this is the first study correlating immune response parameters with the clinical presentation of relapsed multibacillary patients.