CXCL12/CXCR4 signalling in neuronal cell migration

The chemokine CXCL12 (or SDF-1) and its receptor CXCR4 have originally been described as regulators of cell interactions in the immune system. However, over the past years it has become clear that this receptor/ligand pair is an important component of the machinery that controls cell migration in different regions of the developing nervous system. Here we will review some of these functions of the CXCL12/CXCR4 system, focusing on migration events in the cerebellum and the cortex. Furthermore, we will discuss these findings in light of the recently discovered second receptor for CXCL12, CXCR7, and the original functional properties of this molecule that have been described in zebrafish.     

Effect of bovine growth hormone on rat liver plasma membranes as studied by circular dichroism and fluorescence using the extrinsic probe 7,12-dimethylbenzanthracene

Conformational changes produced by in vitro bovine growth hormone addition to plasma membranes of hypophysectomized rat liver proteins and lipids have been studied by circular dichroism as well as intrinsic and extrinsic fluorescence. 7,12-Dimethylbenzanthracene has been used as a fluorescent probe of changes in membrane structure. The exposure of membranes to bovine growth hormone produced a change in membrane negative ellipticity. Dimethylbenzanthracene at concentrations similar to those employed in fluorescence studies had no effect on the membrane circular dichroism spectrum. Its presence did, however, prevent a response to growth hormone. There was a decrease in peak fluorescence intensity and a peak shift when bovine growth hormone (0.5 · 10^?12 M) was added to liver membranes. The addition of dimethylbenzanthracene (1.6 · 10^?6 M) to membranes resulted in a decrease in the intensity of the protein fluorescence peak at 335 nm and the appearance of two peaks at 430 and 407 nm, assignable to the probe. The addition of bovine growth hormone (0.5 · 10^?12 M) produced a decrease in fluorescence at 335 nm and also in the peaks at 407 and 430 nm. These data are consistent with the conclusion that bovine growth hormone produces a conformational change in rat liver plasma membrane proteins and lipids.     

Enhanced Sensitivity to Low Dose Irradiation of ApoE?/? Mice Mediated by Early Pro-Inflammatory Profile and Delayed Activation of the TGFβ1 Cascade Involved in Fibrogenesis

Aim

Investigating long-term cardiac effects of low doses of ionizing radiation is highly relevant in the context of interventional cardiology and radiotherapy. Epidemiological data report that low doses of irradiation to the heart can result in significant increase in the cardiovascular mortality by yet unknown mechanisms. In addition co-morbidity factor such as hypertension or/and atherosclerosis can enhance cardiac complications. Therefore, we explored the mechanisms that lead to long-term cardiac remodelling and investigated the interaction of radiation-induced damage to heart and cardiovascular systems with atherosclerosis, using wild-type and ApoE-deficient mice.

Methods and Results

ApoE−/− and wild-type mice were locally irradiated to the heart at 0, 0.2 and 2 Gy (RX). Twenty, 40 and 60 weeks post-irradiation, echocardiography were performed and hearts were collected for cardiomyocyte isolation, histopathological analysis, study of inflammatory infiltration and fibrosis deposition. Common and strain-specific pathogenic pathways were found. Significant alteration of left ventricular function (eccentric hypertrophy) occurred in both strains of mice. Low dose irradiation (0.2 Gy) induced premature death in ApoE−/− mice (47% died at 20 weeks). Acute inflammatory infiltrate was observed in scarring areas with accumulation of M1-macrophages and secretion of IL-6. Increased expression of the fibrogenic factors (TGF-β1 and PAI-1) was measured earlier in cardiomyocytes isolated from ApoE−/− than in wt animals.

Conclusion

The present study shows that cardiac exposure to low dose of ionizing radiation induce significant physiological, histopathological, cellular and molecular alterations in irradiated heart with mild functional impairment. Atherosclerotic predisposition precipitated cardiac damage induced by low doses with an early pro-inflammatory polarization of macrophages.     

Methodological CASPT2 study of the valence excited states of an iron-porphyrin complex

The singlet valence excited states of an iron-porphyrin-pyrazine-carbonyl complex are investigated up to the Soret band (about 3 eV) using multi-state complete active space with perturbation at the second order (MS-CASPT2). This complex is a model for the active site of carboxy-hemoglobin/myoglobin. The spectrum of the excited states is rather dense, comprising states of different nature: d→π* transitions, d→d states, π→π* excitations of the porphyrin, and doubly excited states involving simultaneous intra-porphyrin π→π* and d→d transitions. Specific features of the MS-CASPT2 method are investigated. The effect of varying the number of roots in the state average calculation is quantified as well as the consequence of targeted modifications of the active space. The effect of inclusion of standard ionization potential-electron affinity (IPEA) shift in the perturbation treatment is also investigated.     

Efficient in vivo electroporation of the postnatal rodent forebrain

Functional gene analysis in vivo represents still a major challenge in biomedical research. Here we present a new method for the efficient introduction of nucleic acids into the postnatal mouse forebrain. We show that intraventricular injection of DNA followed by electroporation induces strong expression of transgenes in radial glia, neuronal precursors and neurons of the olfactory system. We present two proof-of-principle experiments to validate our approach. First, we show that expression of a human isoform of the neural cell adhesion molecule (hNCAM-140) in radial glia cells induces their differentiation into cells showing a neural precursor phenotype. Second, we demonstrate that p21 acts as a cell cycle inhibitor for postnatal neural stem cells. This approach will represent an important tool for future studies of postnatal neurogenesis and of neural development in general.     

A common autoimmunity predisposing signal peptide variant of the cytotoxic T-lymphocyte antigen 4 results in inefficient glycosylation of the susceptibility allele

A common T17A polymorphism in the signal peptide of the cytotoxic T-lymphocyte antigen 4 (CTLA-4), a T-cell receptor that negatively regulates immune responses, is associated with risk for autoimmune disease. Because the polymorphism is absent from the mature protein, we hypothesized that its biological effect must involve early stages of protein processing, prior to signal peptide cleavage. Constructs representing the two alleles were compared by in vitro translation, in the presence of endoplasmic reticulum membranes. We studied glycosylation by endoglycosidase H digestion and glycosylation mutant constructs, cleavage of peptide with inhibitors, and membrane integration by ultracentrifugation and proteinase K sensitivity. A major cleaved and glycosylated product was seen for both alleles of the protein but a band representing incomplete glycosylation was markedly more abundant in the predisposing Ala allele (32.7 +/- 1.0 versus 10.6% +/- 1.2 for Thr, p < 10(-9)). In addition, differential intracellular/surface partitioning was studied with co-transfection of the alleles fused to distinct fluorescent proteins in COS-1 cells. By quantitative confocal microscopy we found a higher ratio of cell surface/total CTLAThr(17) versus CTLAAla(17) (p = 0.01). Our findings corroborate observations, in other proteins, that the signal peptide can determine the efficiency of post-translational modifications other than cleavage and suggest inefficient processing of the autoimmunity predisposing Ala allele as the explanation for the genetic effect.     

Plasma Ceruloplasmin Ferroxidase Activity Correlates with the Nigral Sonographic Area in Parkinson’s Disease Patients: A Pilot Study

Increased area of the substantia nigra (SN) associated to iron deposition has been proposed as a specific marker for Parkinson’s disease (PD). Echogenicity, assessed by transcranial sonography (TCS), has been used to measure such an iron deposition. On the other hand, ferroxidase activity is known to play a role in brain iron metabolism and thus could be involved in increased SN echogenicity of PD patients. The present study was conducted to search for a possible correlation between both markers: TCS of SN and plasma ferroxidase activity. Twenty-one PD patients and 13 healthy volunteers (HV) were included. Mean SN sonographic areas were 0.31 cm² for PD patients and 0.12 cm² for HV (P < 0.001), while plasma ferroxidase activity was reduced in PD patients (P < 0.001). Interestingly, plasma ferroxidase activity was inversely correlated with the SN size by TCS (R² = 0.31), suggesting a relationship between the two markers.