In vivo SPECT reporter gene imaging of regulatory T cells

Regulatory T cells (Tregs) were identified several years ago and are key in controlling autoimmune diseases and limiting immune responses to foreign antigens, including alloantigens. In vivo imaging techniques including intravital microscopy as well as whole body imaging using bioluminescence probes have contributed to the understanding of in vivo Treg function, their mechanisms of action and target cells. Imaging of the human sodium/iodide symporter via Single Photon Emission Computed Tomography (SPECT) has been used to image various cell types in vivo. It has several advantages over the aforementioned imaging techniques including high sensitivity, it allows non-invasive whole body studies of viable cell migration and localisation of cells over time and lastly it may offer the possibility to be translated to the clinic. This study addresses whether SPECT/CT imaging can be used to visualise the migratory pattern of Tregs in vivo. Treg lines derived from CD4(+)CD25(+)FoxP3(+) cells were retrovirally transduced with a construct encoding for the human Sodium Iodide Symporter (NIS) and the fluorescent protein mCherry and stimulated with autologous DCs. NIS expressing self-specific Tregs were specifically radiolabelled in vitro with Technetium-99m pertechnetate ((99m)TcO(4)(-)) and exposure of these cells to radioactivity did not affect cell viability, phenotype or function. In addition adoptively transferred Treg-NIS cells were imaged in vivo in C57BL/6 (BL/6) mice by SPECT/CT using (99m)TcO(4)(-). After 24 hours NIS expressing Tregs were observed in the spleen and their localisation was further confirmed by organ biodistribution studies and flow cytometry analysis. The data presented here suggests that SPECT/CT imaging can be utilised in preclinical imaging studies of adoptively transferred Tregs without affecting Treg function and viability thereby allowing longitudinal studies within disease models.     

Differentiation of mesenchymal stem cells derived from pancreatic islets and bone marrow into islet-like cell phenotype

Background

Regarding regenerative medicine for diabetes, accessible sources of Mesenchymal Stem Cells (MSCs) for induction of insular beta cell differentiation may be as important as mastering the differentiation process itself.

Methodology/Principal Findings

In the present work, stem cells from pancreatic islets (human islet-mesenchymal stem cells, HI-MSCs) and from human bone marrow (bone marrow mesenchymal stem cells, BM-MSCs) were cultured in custom-made serum-free medium, using suitable conditions in order to induce differentiation into Islet-like Cells (ILCs). HI-MSCs and BM-MSCs were positive for the MSC markers CD105, CD73, CD90, CD29. Following this induction, HI-MSC and BM-MSC formed evident islet-like structures in the culture flasks. To investigate functional modifications after induction to ILCs, ultrastructural analysis and immunofluorescence were performed. PDX1 (pancreatic duodenal homeobox gene-1), insulin, C peptide and Glut-2 were detected in HI-ILCs whereas BM-ILCs only expressed Glut-2 and insulin. Insulin was also detected in the culture medium following glucose stimulation, confirming an initial differentiation that resulted in glucose-sensitive endocrine secretion. In order to identify proteins that were modified following differentiation from basal MSC (HI-MSCs and BM-MSCs) to their HI-ILCs and BM-ILCs counterparts, proteomic analysis was performed. Three new proteins (APOA1, ATL2 and SODM) were present in both ILC types, while other detected proteins were verified to be unique to the single individual differentiated cells lines. Hierarchical analysis underscored the limited similarities between HI-MSCs and BM-MSCs after induction of differentiation, and the persistence of relevant differences related to cells of different origin.

Conclusions/Significance

Proteomic analysis highlighted differences in the MSCs according to site of origin, reflecting spontaneous differentiation and commitment. A more detailed understanding of protein assets may provide insights required to master the differentiation process of HI-MSCs to functional beta cells based only upon culture conditioning. These findings may open new strategies for the clinical use of BM-MSCs in diabetes.     

The bile acid receptor GPBAR-1 (TGR5) modulates integrity of intestinal barrier and immune response to experimental colitis

Background

GP-BAR1, a member G protein coupled receptor superfamily, is a cell surface bile acid-activated receptor highly expressed in the ileum and colon. In monocytes, ligation of GP-BAR1 by secondary bile acids results in a cAMP-dependent attenuation of cytokine generation.

Aims

To investigate the role GP-BAR1 in regulating intestinal homeostasis and inflammation-driven immune dysfunction in rodent models of colitis.

Methods

Colitis was induced in wild type and GP-BAR1^−/− mice by DSS and TNBS administration. Potential GP-BAR1 agonists were identified by in silico screening and computational docking studies.

Results

GP-BAR1^−/− mice develop an abnormal morphology of colonic mucous cells and an altered molecular architecture of epithelial tight junctions with increased expression and abnormal subcellular distribution of zonulin 1 resulting in increased intestinal permeability and susceptibility to develop severe colitis in response to DSS at early stage of life. By in silico screening and docking studies we identified ciprofloxacin as a GP-BAR1 ligand. In monocytes, ciprofloxacin increases cAMP concentrations and attenuates TNFα release induced by TLR4 ligation in a GP-BAR1 dependent manner. Treating mice rendered colitic by TNBS with ciprofloxacin and oleanolic acid, a well characterized GP-BAR1 ligand, abrogates signs and symptoms of colitis. Colonic expression of GP-BAR1 mRNA increases in rodent models of colitis and tissues from Crohn''s disease patients. Flow cytometry analysis demonstrates that ≈90% of CD14+ cells isolated from the lamina propria of TNBS-treated mice stained positively for GP-BAR1.

Conclusions

GP-BAR1 regulates intestinal barrier structure. Its expression increases in rodent models of colitis and Crohn''s disease. Ciprofloxacin is a GP-BAR1 ligand.     

Regulation of the membrane-localized prostaglandin E synthases mPGES-1 and mPGES-2 in cardiac myocytes and fibroblasts

The proinflammatory mediator cyclooxygenase (COX)-2 and its product PGE(2) are induced in the ischemic heart, contributing to inflammatory cell infiltration, fibroblast proliferation, and cardiac hypertrophy. PGE(2) synthesis coupled to COX-2 involves two membrane-localized PGE synthases, mPGES-1 and mPGES-2; however, it is not clear how these synthases are regulated in cardiac myocytes and fibroblasts. To study this, we used primary cultures of neonatal ventricular myocytes (VM) and fibroblasts (VF) treated with IL-1beta for 24 h. To test for involvement of MAPKs in IL-1beta regulation of mPGES-1 and-2, cells were pretreated with the pharmacological inhibitors of p42/44 MAPK, p38 MAPK, and c-Jun kinase (JNK). mRNA was analyzed by RT-PCR. Protein was analyzed by densitometry of Western blots. mPGES-1 was undetectable in untreated VF but induced by IL-1beta; inhibition of either p42/44 MAPK or JNK, but not p38 MAPK, was almost completely inhibitory. In VM, inhibition of the three MAPKs reduced IL-1beta-stimulated mPGES-1 protein by 70-90%. mPGES-2 was constitutively synthesized in both VM and VF and was not regulated by IL-1beta or MAPKs. Confocal microscopy revealed colocalization of both mPGES-1 and mPGES-2 with COX-2 in the perinuclear area of both VF and VM. Finally, PGE(2) production was higher in VM than VF. Our data show that 1) mPGES-1 is induced in both VF and VM, 2) regulation of mPGES-1 by MAPK family members is different in the two cell types, 3) mPGES-2 is constitutively synthesized in both VM and VF and is not regulated, and 4) mPGES-1 and mPGES-2 are colocalized with COX-2 in both cells. Thus differences in activity of mPGES-1 and COX-2 or coupling of COX-2 with mPGES-1 may contribute to differences in PGE(2) production by myocytes and fibroblasts.     

Arabidopsis has two redundant Cullin3 proteins that are essential for embryo development and that interact with RBX1 and BTB proteins to form multisubunit E3 ubiquitin ligase complexes in vivo

Cullin-based E3 ubiquitin ligases play important roles in the regulation of diverse developmental processes and environmental responses in eukaryotic organisms. Recently, it was shown in Schizosaccharomyces pombe, Caenorhabditis elegans, and mammals that Cullin3 (CUL3) directly associates with RBX1 and BTB domain proteins in vivo to form a new family of E3 ligases, with the BTB protein subunit functioning in substrate recognition. Here, we demonstrate that Arabidopsis thaliana has two redundant CUL3 (AtCUL3) genes that are essential for embryo development. Besides supporting anticipated specific AtCUL3 interactions with the RING protein AtRBX1 and representative Arabidopsis proteins containing a BTB domain in vitro, we show that AtCUL3 cofractionates and specifically associates with AtRBX1 and a representative BTB protein in vivo. Similar to the AtCUL1 subunit of the SKP1-CUL1-F-box protein-type E3 ligases, the AtCUL3 subunit of the BTB-containing E3 ligase complexes is subjected to modification and possible regulation by the ubiquitin-like protein Related to Ubiquitin in vivo. Together with the presence of large numbers of BTB proteins with diverse structural features and expression patterns, our data suggest that Arabidopsis has conserved AtCUL3-RBX1-BTB protein E3 ubiquitin ligases to target diverse protein substrates for degradation by the ubiquitin/proteasome pathway.     

Evaluation of chromogenic medium (ORSAB) for routine identification of methicillin resistant Staphylococcus aureus (MRSA)

Performance of chromogenic medium (ORSAB) for routine detection of methicillin resistant S. aureus (MRSA) was evaluated on 510 specimens collected from patients suspected of MRSA infection or colonization. Addition of ORSAB plates to the routine protocol allowed MRSA identification in 24 hours from samples plating. In 18 samples MRSA colonies were identified only on ORSAB plates, those cases would have been missed by routine protocol alone.     

Aneuploidy, centrosome alteration and securin overexpression as features of pituitary somatotroph and lactotroph adenomas

OBJECTIVE: To verify the presence of numerical chromosomal aberrations (NCAs) in different types of pituitary adenomas (PAs) and to investigate 2 of the mechanisms that are possibly related to aneuploidies in PAs: securin overexpression and centrosome alterations. STUDY DESIGN: Twenty-one PAs of different types were analyzed with interphase fluorescence in situ hybridization (FISH) on paraffin sections with centromeric probes for chromosomes 2, 3, 8, 11 and 12. In all cases, the immunohistochemical expression of securin was evaluated and the number of cells with abnormal nuclear shape recorded. The ultrastructural study of centrosomes was performed in a subset of 12 tumors. RESULTS: At interphase FISH analysis, growth hormone (GH)-cell and prolactin (PRL)-cell PAs showed multiple chromosome gains and a low frequency of chromosome losses, suggesting a hyperdiploid chromosome assessment. In contrast, in the other types of PAs a lower frequency of NCAs was observed. In addition, when compared to other types of PAs, GH-cell and PRL-cell adenomas showed overexpression of securin and a higher number of both cells with abnormal nuclear shape and cells with centrosomes. CONCLUSION: Somatotroph and lactotroph adenomas are characterized by aneuploidy, abnormal nuclear shape and centrosome amplification, which are possibly related to securin overexpression.     

Aster self-organization at meiosis: a conserved mechanism in insect parthenogenesis?

Unfertilized eggs usually lack maternal centrosomes and cannot develop without sperm contribution. However, several insect species lay eggs that develop to adulthood as unfertilized in the absence of a preexisting centrosome. We report that the oocyte of the parthenogenetic viviparous pea aphid Acyrthosiphon pisum is able to self-organize microtubule-based asters, which in turn interact with the female chromatin to form the first mitotic spindle. This mode of reproduction provides a good system to investigate how the oocyte can assemble new centrosomes and how their number can be exactly monitored. We propose that the cooperative interaction of motor proteins and randomly nucleated surface microtubules could lead to the formation of aster-like structures in the absence of pre-existing centrosomes. Recruitment of material along the microtubules might contribute to the accumulation of pericentriolar material and centriole precursors at the focus of the asters, thus leading to the formation of true centrosomes. The appearance of microtubule asters at the surface of activated oocytes could represent a possible common mechanism for centrosome formation during insect parthenogenesis.