Disruption of microtubules leads to glucocorticoid receptor degradation in HeLa cell line

The role of microtubules (MTs) in steroid hormone-dependent human glucocorticoid receptor (hGR) activation/translocation is controversial. It was demonstrated recently that colchicine (COL) down-regulates hGR-driven genes in primary human hepatocytes by a mechanism involving inhibition of hGR translocation to the nucleus. To investigate whether inhibition of hGR translocation is the sole reason for its inactivation, we used human cervical carcinoma cells (HeLa) as a model. Herein we present evidence that perturbation of microtubules in HeLa cells leads to rapid time- and dose-dependent degradation of hGR protein. Degradation is proteasome mediated as revealed by its reversibility by proteasome inhibitor MG132. Moreover, degradation was observed for neither wt-hGR nor hGR mutants S226A and K419A in transiently transfected COS-1 cells. On the other hand, c-jun N-terminal kinase (JNK) seems not to be involved in the process because JNK inhibitor 1,9-Pyrazoloanthrone (SP600125) does not reverse hGR degradation. Similarly, another hGR functional antagonist, nuclear factor kappa beta (NFkappaB), did not play any role in the degradation process.     

Small GTP-binding proteins in Plasmodium falciparum

Summary— During its erythrocytic life cycle Plasmodium falciparum exchanges compounds with host cells through phagocytosis and exocytosis. In eucaryotic cells, small GTP-binding proteins of the Ras superfamily appear to be involved in different steps of membrane trafficking and in intracellular signals. In this paper, we investigate the Rab4, Rab6 and Ras-related proteins in P falciparum infected red cells. We report that P falciparum Rab and Ras-related proteins could be distinguished from their counterparts by iso-electrofocusing and immunoblotting. The localization of P falciparum Rab 4 and Rab 6 was studied by immunogold electron microscopy on ultrathin frozen sections of infected red blood cells. Rab4 parasite-relate protein was found associated with the membranes of early endosome-like structures near the parasite plasma membrane. Rab6-related protein was associated with the Golgi/trans Golgi network, as already suggested by immunofluorescence microscopy studies and Ras-related protein was cytoplasmic and plasma membrane-associated. These results are in accordance with their mammalian counterparts and support the implication of Rab-related proteins in vesicular trafficking in Plasmodium.     

Nestling diet variation in an insular Mediterranean population of blue tits Parus caeruleus: effects of years,territories and individuals

Mediterranean evergreen forests of Corsica are characterized by relatively high species diversity of arthropods with low population densities. Food is never superabundant for Corsican blue tits Parus caeruleus. This study focused on the composition of the food of blue tit nestlings and especially on two main components, caterpillars and spiders. The nestling diet was studied for two years using 8-mm cameras that automatically took photographs of adult birds with food. The diet was composed of c. 50% caterpillars and c. 30% spiders. There were between-year and between-individual differences in these proportions. In both years of the study the proportion of caterpillars declined during the course of the breeding season. Individual and time effects on prey sizes were also observed. Pairs and individuals were fairly constant in the proportions of prey over the feeding period. Different food items were not brought in runs. These findings suggest that strong food limitation exists on Corsica, which can considerably influence life-history traits of the blue tit.     

Cell adhesion and integrin expression are modulated by oxidative stress in EA.hy 926 cells

The effects of oxidative stress on integrin-mediated cell adhesion to the extracellular matrix (ECM) and related apoptosis were investigated using the EA.hy926 endothelial cells treated (or not) with two oxidants: the hypoxanthine/xanthine oxidase system (HX/XO) or the tert-butyl hydroperoxide (t-BHP) which both increased cell apoptosis. Cell adhesion onto vitronectin (Vn) and fibronectin (Fn) was increased at low concentrations of HX/XO (up to 5 mU/ml) or t-BHP (up to 125 microM) and prevented ROS-induced apoptosis. Flow cytometry analysis of integrin expression showed that the expression of integrin alphav and alpha5 subunits was, respectively, increased and decreased. Cell adhesion inhibition experiments using function-blocking monoclonal antibodies against integrin subunits indicated that alphavbeta1 and alphavbeta3 integrins were involved in adhesion of cells to Vn, and alphavbeta3 integrin played a major role in oxidant-treated cells. For adhesion to Fn, alpha5beta1 and alphavbeta1 integrins were required for oxidant-treated cells. Taken together, the results suggest that reactive oxygen species (ROS) produced either by HX/XO or t-BHP could affect expression and/or activation of specific integrins in the interaction of EA.hy926 cells with ECM.     

Sustained calcium signalling and caspase-3 activation involve NMDA receptors in thymocytes in contact with dendritic cells

L-glutamate, the major excitatory neurotransmitter, also has a role in non-neuronal tissues and modulates immune responses. Whether NMDA receptor (NMDAR) signalling is involved in T-cell development is unknown. In this study, we show that mouse thymocytes expressed an array of glutamate receptors, including NMDARs subunits. Sustained calcium (Ca²⁺) signals and caspase-3 activation in thymocytes were induced by interaction with antigen-pulsed dendritic cells (DCs) and were inhibited by NMDAR antagonists MK801 and memantine. NMDARs were transiently activated, triggered the sustained Ca²⁺ signal and were corecruited with the PDZ-domain adaptor postsynaptic density (PSD)-95 to thymocyte-DC contact zones. Although T-cell receptor (TCR) activation was sufficient for relocalization of NMDAR and PSD-95 at the contact zone, NMDAR could be activated only in a synaptic context. In these T-DC contacts, thymocyte activation occurred in the absence of exogenous glutamate, indicating that DCs could be a physiological source of glutamate. DCs expressed glutamate, glutamate-specific vesicular glutamate transporters and were capable of fast glutamate release through a Ca²⁺-dependent mechanism. We suggest that glutamate released by DCs could elicit focal responses through NMDAR-signalling in T cells undergoing apoptosis. Thus, synapses between T and DCs could provide a functional platform for coupling TCR activation and NMDAR signalling, which might reflect on T-cell development and modulation of the immune response.     

Antigen presentation by endothelial cells: what role in the pathophysiology of malaria?

Disruption of the endothelial cell (EC) barrier leads to pathology via edema and inflammation. During infections, pathogens are known to invade the EC barrier and modulate vascular permeability. However, ECs are semi-professional antigen-presenting cells, triggering T-cell costimulation and specific immune-cell activation. This in turn leads to the release of inflammatory mediators and the destruction of infected cells by effectors such as CD8(+) T-cells. During malaria, transfer of parasite antigens to the EC surface is now established. At the same time, CD8 activation seems to play a major role in cerebral malaria. We summarize here some of the pathways leading to antigen presentation by ECs and address the involvement of these mechanisms in the pathophysiology of cerebral malaria.     

Mate choice, operational sex ratio, and social promiscuity in a wild population of the long-snouted seahorse Hippocampus guttulatus

Mate competition and mate choice are not mutually exclusivebehaviors. Both behaviors may drive sexual selection in oneor both sexes of a population. One of several factors affectingwhich behavior is exhibited by which sex is the operationalsex ratio (OSR) in the study population. The present study combinesbehavioral observations in the field with controlled experimentsin aquaria to investigate social interactions and mate choicein both male and female long-snouted seahorses Hippocampus guttulatusin the context of the population OSR. Compared with the morereadily studied pipefishes, data on OSR and mate choice in seahorsesare scarce in the published literature. Our field data providenovel evidence of social promiscuity, size-assortative mating,and an OSR that varies from being unbiased early and midseasonto male biased at the end of the breeding season. Our mate choiceexperiments revealed intersexual differences in mate preferencewith males significantly preferring larger females to familiarones. Taken together, our field and experimental results suggestthat mate choice rather than intrasexual competition could drivesexual selection in seahorses.     

Citicoline (CDP-choline): What role in the treatment of complications of infectious diseases

A dysregulated host immune response, as opposed to the intrinsic virulence of a microbial pathogen induces a large part of the pathology seen in infectious diseases. However, current therapies are designed to target the pathogen rather than the underlying pathogenic mechanisms responsible for the manifestation of the pathology. Recent studies have highlighted the role of endothelial cell alteration in the pathology induced in sepsis and cerebral malaria. The endothelial onslaught described, is similar to that seen during ischemia reperfusion in stroke. Protecting endothelial cell membranes during sepsis and cerebral malaria, using citicoline in the same way as in stroke, has thus emerged as a new strategy that needs to be evaluated urgently. Citicoline is a natural compound that is registered for use in ischemic stroke, head trauma and neurological disorders. It enters the phosphatidylcholine synthesis pathway as a rate-limiting step and is involved in the modulation of a large number of metabolic pathways and neurotransmitter levels, and also in the biosynthesis of phospholipids in neuronal membranes. This short review highlights the potential role of citicoline as part of adjunct therapy in the treatment of infectious diseases.