Down-regulation of LFA-1-mediated T cell adhesion induced by the HIV envelope glycoprotein gp160 requires phosphatidylinositol-3-kinase activity

Human immunodeficiency virus binds to CD4⁺ T lymphocyte by the interaction, in part, between its gp120 envelope glycoprotein and the CD4 molecule. We and others have reported that the lipid kinase phosphatidylinositol-3-kinase (PI3-kinase) is associated with the CD4-p56^lck complex and can be activated by various CD4 ligands. In a previous report we showed that the gp160 envelope down-regulates lymphocyte function-associated antigen-1 (LFA-1)-dependent adhesion between CD4⁺ T cells and B cells. This down-regulation was shown to be p56^lck-dependent. Here we investigate the role of PI3-kinase in the inhibition of adhesion induced by gp160 binding to CD4. We found that gp160 activates the PI3-kinase of HUT78 CD4⁺ T cell lines in a way dependent on CD4-p56^lck association, since no activation was detected when the interaction between CD4 and p56^lck was disrupted. It was also shown, using different inhibitors of the PI3-kinase (wortmannin, Ly294002 and antisense oligonucleotides), that this lipid kinase was necessary for the down-regulation of LFA-1-mediated adhesion induced by gp160. These results strongly suggest that PI3-kinase activation induced by gp160 leads to down-regulation of LFA-1-mediated T cell adhesion to B cells. Inhibition by gp160 of cytoskeleton rearrangement-dependent, anti-CD3-mediated T cell adhesion to B cells was blocked by neutralization of PI3-kinase activity, while inhibition of cytoskeleton rearrangement-independent, Mg²⁺-induced T cell adhesion was not. These results emphasize the role of PI3-kinase in the regulation of cytoskeleton structure. It is proposed that gp160 activates both p56^lck and PI3-kinase which lead to a cytoskeleton organization unfavorable for LFA-1 function.     

Identification of prognostic markers in diffuse midline gliomas H3K27M‐mutant

Pediatric diffuse midline gliomas are devastating diseases. Among them, diffuse midline gliomas H3K27M‐mutant are associated with worse prognosis. However, recent studies have highlighted significant differences in clinical behavior and biological alterations within this specific subgroup. In this context, simple markers are needed to refine the prognosis of diffuse midline gliomas H3K27M‐mutant and guide the clinical management of patients. The aims of this study were (i) to describe the molecular, immunohistochemical and, especially, chromosomal features of a cohort of diffuse midline gliomas and (ii) to focus on H3K27M‐mutant tumors to identify new prognostic markers. Patients were retrospectively selected from 2001 to 2017. Tumor samples were analyzed by immunohistochemistry (including H3K27me3, EGFR, c‐MET and p53), next‐generation sequencing and comparative genomic hybridization array. Forty‐nine patients were included in the study. The median age at diagnosis was 9 years, and the median overall survival (OS) was 9.4 months. H3F3A or HIST1H3B mutations were identified in 80% of the samples. Within the H3K27M‐mutant tumors, PDGFRA amplification, loss of 17p and a complex chromosomal profile were significantly associated with worse survival. Three prognostic markers were identified in diffuse midline gliomas H3K27M‐mutant: PDGFRA amplification, loss of 17p and a complex chromosomal profile. These markers are easy to detect in daily practice and should be considered to refine the prognosis of this entity.     

Circulation of Chikungunya virus in Gabon, 2006-2007

This study reports the first isolation and partial genetic characterization of Chikungunya virus (CHIKV) from patients during a 2006-2007 dengue-like syndrome outbreak in Gabon. The isolated viruses were phylogenetically close to strains isolated in the Democratic Republic of the Congo 7 years ago and to strains isolated more recently in Cameroon. These results indicate a continuing circulation of a genetically stable CHIKV population during 7 years in Central Africa.     

Inhibition of vascular endothelial growth factor (VEGF) signaling in cancer causes loss of endothelial fenestrations, regression of tumor vessels, and appearance of basement membrane ghosts

Angiogenesis inhibitors are receiving increased attention as cancer therapeutics, but little is known of the cellular effects of these inhibitors on tumor vessels. We sought to determine whether two agents, AG013736 and VEGF-Trap, that inhibit vascular endothelial growth factor (VEGF) signaling, merely stop angiogenesis or cause regression of existing tumor vessels. Here, we report that treatment with these inhibitors caused robust and early changes in endothelial cells, pericytes, and basement membrane of vessels in spontaneous islet-cell tumors of RIP-Tag2 transgenic mice and in subcutaneously implanted Lewis lung carcinomas. Strikingly, within 24 hours, endothelial fenestrations in RIP-Tag2 tumors disappeared, vascular sprouting was suppressed, and patency and blood flow ceased in some vessels. By 7 days, vascular density decreased more than 70%, and VEGFR-2 and VEGFR-3 expression was reduced in surviving endothelial cells. Vessels in Lewis lung tumors, which lacked endothelial fenestrations, showed less regression. In both tumors, pericytes did not degenerate to the same extent as endothelial cells, and those on surviving tumor vessels acquired a more normal phenotype. Vascular basement membrane persisted after endothelial cells degenerated, providing a ghost-like record of pretreatment vessel number and location and a potential scaffold for vessel regrowth. The potent anti-vascular action observed is evidence that VEGF signaling inhibitors do more than stop angiogenesis. Early loss of endothelial fenestrations in RIP-Tag2 tumors is a clue that vessel phenotype may be predictive of exceptional sensitivity to these inhibitors.     

Notch1 expression on T cells is not required for CD4+ T helper differentiation

Notch1 proteins are involved in binary cell fate decisions. To determine the role of Notch1 in the differentiation of CD4(+) Th1 versus Th2 cells, we have compared T helper polarization in vitro in naive CD4(+) T cells isolated from mice in which the N1 gene is specifically inactivated in all mature T cells. Following activation, Notch1-deficient CD4(+) T cells transcribed and secreted IFN-gamma under Th1 conditions and IL-4 under Th2 conditions at levels similar to that of control CD4(+) T cells. These results show that Notch1 is dispensable for the development of Th1 and Th2 phenotypes in vitro. The requirement for Notch1 in Th1 differentiation in vivo was analyzed following inoculation of Leishmania major in mice with a T cell-specific inactivation of the Notch1 gene. Following infection, these mice controlled parasite growth at the site of infection and healed their lesions. The mice developed a protective Th1 immune response characterized by high levels of IFN-gamma mRNA and protein and low levels of IL-4 mRNA with no IL-4 protein in their lymph node cells. Taken together, these results indicate that Notch1 is not critically involved in CD4(+) T helper 1 differentiation and in resolution of lesions following infection with L. major.     

Human immunodeficiency virus 1 favors the persistence of infection by activating macrophages through TNF

Macrophages play a major role in HIV-1 persistence. In the present paper, we demonstrate that the absence of apoptosis in HIV-1-infected primary human monocyte-differentiated macrophages (MDM) correlates with an increase in anti-apoptotic (Bcl-2 and Bcl-x(L)) and a decrease in pro-apoptotic (Bax and Bad) proteins. This is associated with macrophage activation as shown by tumor necrosis factor (TNF) production and NF-kappaB activation upon infection. TNF production was shown to be involved in the upregulation of Bcl-2 and Bcl-x(L) because this increase was abolished by an anti-TNF anti-serum or an inhibitor of TNF synthesis. In parallel, inhibition of TNF production induced an increase in the number of apoptotic cells. Furthermore, using an inhibitor of NF-kappaB activation, we demonstrated that TNF-induced upregulation of Bcl-x(L) and Bcl-2 occurs, respectively, through a NF-kappaB-dependent and an NF-kappaB-independent pathway.     

Histamine stimulates neurogenesis in the rodent subventricular zone

Neural stem/progenitor cells present in the subventricular zone (SVZ) are a potential source of repairing cells after injury. Therefore, the identification of novel players that modulate neural stem cells differentiation can have a huge impact in stem cell-based therapies. Herein, we describe a unique role of histamine in inducing functional neuronal differentiation from cultured mouse SVZ stem/progenitor cells. This proneurogenic effect depends on histamine 1 receptor activation and involves epigenetic modifications and increased expression of Mash1, Dlx2, and Ngn1 genes. Biocompatible poly (lactic-co-glycolic acid) microparticles, engineered to release histamine in a controlled and prolonged manner, also triggered robust neuronal differentiation in vitro. Preconditioning with histamine-loaded microparticles facilitated neuronal differentiation of SVZ-GFP cells grafted in hippocampal slices and in in vivo rodent brain. We propose that neuronal commitment triggered by histamine per se or released from biomaterial-derived vehicles may represent a new tool for brain repair strategies. STEM CELLS 2012; 30:773-784.     

Differential roles of endothelin-1 ETA and ETB receptors and vasoactive intestinal polypeptide in regulation of the airways and the pulmonary vasculature in isolated rat lung

The available treatment strategies against pulmonary hypertension include the administration of endothelin-1 (ET-1) receptor subtype blockers (ET(A) and ET(B) antagonists); vasoactive intestinal polypeptide (VIP) has recently been suggested as a potential new therapeutic agent. We set out to investigate the ability of these agents to protect against the vasoconstriction and impairment of lung function commonly observed in patients with pulmonary hypertension. An ET(A) blocker (BQ123), ET(B) blocker (BQ788), a combination of these selective blockers (ET(A) + ET(B) blockers) or VIP (V6130) was administered into the pulmonary circulation in four groups of perfused normal rat lungs. Pulmonary vascular resistance (PVR) and forced oscillatory lung input impedance (Z(L)) were measured in all groups under baseline conditions and at 1 min intervals following ET-1 administrations. The airway resistance, inertance, tissue damping and elastance were extracted from the Z(L) spectra. While VIP, ET(A) blocker and combined ET(A) and ET(B) blockers significantly prevented the pulmonary vasoconstriction induced by ET-1, ET(B) blockade enhanced the ET-1-induced increases in PVR. In contrast, the ET(A) and ET(B) blockers markedly elevated the ET-1-induced increases in airway resistance, while VIP blunted this constrictor response. Our results suggest that VIP potently acts against the airway and pulmonary vascular constriction mediated by endothelin-1, while the ET(A) and ET(B) blockers exert a differential effect between airway resistance and PVR.     

The impact of bacterial infection on mast cell degranulation

In developed countries, the prevalence of allergy is on the rise. Although the causes are unknown, it seems that (1) the disappearance of microbiota may play a role in the increase of allergies and (2) exposure to bacterial infections during childhood decreases the incidence of allergies. Although several cell types are involved in the development of allergy, mast cells play a major role in orchestrating inflammation. Upon activation, mast cell secretory granules fuse with the plasma membrane, resulting in the release of a number of inflammatory mediators. In addition to allergy, mast cells contribute to the innate immune response against a variety of bacteria. This is accomplished through the secretion of cytokines and other soluble mediators. Interestingly, there is growing evidence that mast cells exposed to bacteria down-regulate degranulation in response to IgE/Allergen stimulation. This inhibitory effect seems to require direct contact between bacteria and mast cells, but the intracellular mechanism by which bacterial contact suppresses allergic responses is unknown. Here, we review different aspects of mast cell physiology and discuss hypotheses as to how bacteria may influence mast cell degranulation.     

Mutation of the BAFF furin cleavage site impairs B-cell homeostasis and antibody responses

B-cell-activating factor of the TNF family (BAFF)/BLyS contributes to B-cell homeostasis and function in the periphery. BAFF is expressed as a membrane-bound protein or released by proteolytic cleavage, but the functional importance of this processing event is poorly understood. Mice expressing BAFF with a mutated furin consensus cleavage site, i.e. furin-mutant BAFF (fmBAFF), were not different from BAFF-deficient mice with regard to their B-cell populations and responses to immunization. It is however noteworthy that an alternative processing event releases some soluble BAFF in fmBAFF mice. Mild overexpression (～ 5-fold) of fmBAFF alone generated intermediate levels of B cells without improving humoral responses to immunization. Processed BAFF was however important for B-cell homeostasis, as peripheral B-cell populations and antibody responses were readily restored by administration of soluble BAFF trimers in BAFF-deficient mice. However, the rescue of CD23 expression in B cells of BAFF-deficient mice required both soluble BAFF trimers and fmBAFF, or a polymeric form of soluble BAFF (BAFF 60-mer). These results point to a predominant role of processed BAFF for B-cell homeostasis and function, and indicate possible accessory roles for membrane-bound BAFF.