Désensibilisation: vers de nouvelles perspectives [Allergen specific immunotherapy: review of new perspectives].

Allergic diseases constitute a health problem worldwide. More than just a treatment option, the classical desensitization (SIT--Specific immunotherapy) by subcutaneous injection has profiled over time as a unique approach, able to attenuate the immune response to allergic stimuli proved. For a long time conservative, desensitization has now progressed in the knowledge of allergens, in the understanding of the mechanisms involved in immune response and in production techniques. From recombinants to alternative routes of allergen delivery, this article gives an overview of new perspectives and assesses SIT in order to provide guidance to the general physician before choosing to initiate such treatment or not in patients with respiratory allergy.

Glucocorticoid-induced tumor necrosis factor receptor is a p21Cip1/WAF1 transcriptional target conferring resistance of keratinocytes to UV light-induced apoptosis.

Glucocorticoid-induced tumor necrosis factor receptor (GITR) is a member of the tumor necrosis factor receptor superfamily, is expressed in T lymphocytes, and exerts an anti-apoptotic function in these cells. We reported that GITR is also highly expressed in the skin, specifically in keratinocytes, and that it is under negative transcriptional control of p21(Cip1/WAF1), independently from the cell cycle. Although GITR expression is higher in p21-deficient keratinocytes and skin, it is down-modulated with differentiation and in response to UVB. The combined analysis of keratinocytes with increased GITR expression versus normal keratinocytes and skin of mice with a disruption of the GITR gene indicates that this protein protects keratinocytes from UVB-induced apoptosis both in vitro and in vivo.

Differential gene expression, induced by salicylic acid and Fusarium oxysporum f. sp. lycopersici infection, in tomato

The objective of this work was to determine the transcript profile of tomato plants (Lycopersicon esculentum Mill.), during Fusarium oxysporum f. sp. lycopersici infection and after foliar application of salicylic acid. The suppression subtractive hybridization (SSH) technique was used to generate a cDNA library enriched for transcripts differentially expressed. A total of 307 clones was identified in two subtractive libraries, which allowed the isolation of several defense-related genes that play roles in different mechanisms of plant resistance to phytopathogens. Genes with unknown roles were also isolated from the two libraries, which indicates the possibility of identifying new genes not yet reported in studies of stress/defense response. The SSH technique is effective for identification of resistance genes activated by salicylic acid and F. oxysporum f. sp. lycopersici infection. Not only the application of this technique enables a cost effective isolation of differentially expressed sequences, but also it allows the identification of novel sequences in tomato from a relative small number of sequences.

Parametrial adipose tissue and metabolic dysfunctions induced by fructose-rich diet in normal and neonatal-androgenized adult female rats.

Hyperandrogenemia predisposes an organism toward developing impaired insulin sensitivity. The aim of our study was to evaluate endocrine and metabolic effects during early allostasis induced by a fructose-rich diet (FRD) in normal (control; CT) and neonatal-androgenized (testosterone propionate; TP) female adult rats. CT and TP rats were fed either a normal diet (ND) or an FRD for 3 weeks immediately before the day of study, which was at age 100 days. Energy intake, body weight (BW), parametrial (PM) fat characteristics, and endocrine/metabolic biomarkers were then evaluated. Daily energy intake was similar in CT and TP rats regardless of the differences in diet. When compared with CT-ND rats, the TP-ND rats were heavier, had larger PM fat, and were characterized by basal hypoadiponectinemia and enhanced plasma levels of non-esterified fatty acid (NEFA), plasminogen activator inhibitor-1 (PAI-1), and leptin. FRD-fed CT rats, when compared with CT-ND rats, had high plasma levels of NEFA, triglyceride (TG), PAI-1, leptin, and adiponectin. The TP-FRD rats, when compared with TP-ND rats, displayed enhanced leptinemia and triglyceridemia, and were hyperinsulinemic, with glucose intolerance. The PM fat taken from TP rats displayed increase in the size of adipocytes, decrease in adiponectin (protein/gene), and a greater abundance of the leptin gene. PM adipocyte response to insulin was impaired in CT-FRD, TP-ND, and TP-FRD rats. A very short duration of isocaloric FRD intake in TP rats induced severe metabolic dysfunction at the reproductive age. Our study supports the hypothesis that the early-androgenized female rat phenotype is highly susceptible to developing endocrine/metabolic dysfunction. In turn, these abnormalities enhance the risk of metabolic syndrome, obesity, type 2 diabetes, and cardiovascular disease.

TLR3 and Rig-like receptor on myeloid dendritic cells and Rig-like receptor on human NK cells are both mandatory for production of IFN-gamma in response to double-stranded RNA.

Cross-talk between NK cells and dendritic cells (DCs) is critical for the potent therapeutic response to dsRNA, but the receptors involved remained controversial. We show in this paper that two dsRNAs, polyadenylic-polyuridylic acid and polyinosinic-polycytidylic acid [poly(I:C)], similarly engaged human TLR3, whereas only poly(I:C) triggered human RIG-I and MDA5. Both dsRNA enhanced NK cell activation within PBMCs but only poly(I:C) induced IFN-gamma. Although myeloid DCs (mDCs) were required for NK cell activation, induction of cytolytic potential and IFN-gamma production did not require contact with mDCs but was dependent on type I IFN and IL-12, respectively. Poly(I:C) but not polyadenylic-polyuridylic acid synergized with mDC-derived IL-12 for IFN-gamma production by acting directly on NK cells. Finally, the requirement of both TLR3 and Rig-like receptor (RLR) on mDCs and RLRs but not TLR3 on NK cells for IFN-gamma production was demonstrated using TLR3- and Cardif-deficient mice and human RIG-I-specific activator. Thus, we report the requirement of cotriggering TLR3 and RLR on mDCs and RLRs on NK cells for a pathogen product to induce potent innate cell activation.

Vitamin D Receptor and Jak-STAT Signaling Crosstalk Results in Calcitriol-Mediated Increase of Hepatocellular Response to IFN-α.

Recent clinical research suggests a role for vitamin D in the response to IFN-α-based therapy of chronic hepatitis C. Therefore, we aimed to explore the underlying mechanisms in vitro. Huh-7.5 cells harboring subgenomic hepatitis C virus (HCV) replicons or infected with cell culture-derived HCV were exposed to bioactive 1,25-dihydroxyvitamin D3 (calcitriol) with or without IFN-α. In these experiments, calcitriol alone had no effect on the HCV life cycle. However, calcitriol enhanced the inhibitory effect of IFN-α on HCV replication. This effect was based on a calcitriol-mediated increase of IFN-α-induced gene expression. Further mechanistic studies revealed a constitutive inhibitory interaction between the inactive vitamin D receptor (VDR) and Stat1, which was released upon stimulation with calcitriol and IFN-α. As a consequence, IFN-α-induced binding of phosphorylated Stat1 to its DNA target sequences was enhanced by calcitriol. Importantly, and in line with these observations, silencing of the VDR resulted in an enhanced hepatocellular response to IFN-α. Our findings identify the VDR as a novel suppressor of IFN-α-induced signaling through the Jak-STAT pathway.

UVB-Induced Skin Inflammation and Cutaneous Tissue Injury Is Dependent on the MHC Class I-Like Protein, CD1d.

CD1d is a major histocompatibility complex class 1-like molecule that regulates the function and development of natural killer T (NKT) cells. Previously, we identified a critical role for the CD1d-NKT cell arm of innate immunity in promoting the development of UVB-induced p53 mutations, immune suppression, and skin tumors. Sunburn, an acute inflammatory response to UVB-induced cutaneous tissue injury, represents a clinical marker for non-melanoma skin cancer (NMSC) risk. However, the innate immune mechanisms controlling sunburn development are not considered relevant in NMSC etiology, and remain poorly investigated. Here we found that CD1d knockout (CD1d(-/-)) mice resist UVB-induced cutaneous tissue injury and inflammation compared with wild-type (WT) mice. This resistance was coupled with a faster epithelial tissue healing response. In contrast, the skins of UVB-irradiated invariant NKT cell-knockout (Jα18(-/-)) and NKT cell-deficient (TCRα(-/-)) mice, which express CD1d but are deficient in CD1d-dependent NKT cells, exhibited as much cutaneous tissue injury and inflammation as WT mice. In the absence of NKT cells, CD1d-deficient keratinocytes, dendritic cells, and macrophages exhibited diminished basal and stress-induced levels of pro-inflammatory mediators. Thus, our findings identify an essential role for CD1d in promoting UVB-induced cutaneous tissue injury and inflammation. They also suggest sunburn and NMSC etiologies are immunologically linked.

Mineralocorticoid receptor is essential for corticosteroid-induced up-regulation of L-type calcium currents in cultured neonatal cardiomyocytes.

Despite the fact that mineralocorticoid receptor (MR) antagonist drugs such as spironolactone and eplerenone reduce the mortality in heart failure patients, there is, thus far, no unambiguous demonstration of a functional role of MR in cardiac cells. The aim of this work was to investigate the activation pathway(s) mediating corticosteroid-induced up-regulation of cardiac calcium current (ICa). In this study, using neonatal cardiomyocytes from MR or glucocorticoid receptor (GR) knockout (KO) mice, we show that MR is essential for corticosteroid-induced up-regulation of ICa. This study provides the first direct and unequivocal evidence for MR function in the heart.

Insect oral secretions suppress wound-induced responses in Arabidopsis.

The induction of plant defences and their subsequent suppression by insects is thought to be an important factor in the evolutionary arms race between plants and herbivores. Although insect oral secretions (OS) contain elicitors that trigger plant immunity, little is known about the suppressors of plant defences. The Arabidopsis thaliana transcriptome was analysed in response to wounding and OS treatment. The expression of several wound-inducible genes was suppressed after the application of OS from two lepidopteran herbivores, Pieris brassicae and Spodoptera littoralis. This inhibition was correlated with enhanced S. littoralis larval growth, pointing to an effective role of insect OS in suppressing plant defences. Two genes, an ERF/AP2 transcription factor and a proteinase inhibitor, were then studied in more detail. OS-induced suppression lasted for at least 48 h, was independent of the jasmonate or salicylate pathways, and was not due to known elicitors. Interestingly, insect OS attenuated leaf water loss, suggesting that insects have evolved mechanisms to interfere with the induction of water-stress-related defences.

An essential role for transmembrane TNF in the resolution of the inflammatory lesion induced by Leishmania major infection.

TNF is an essential player in infections with Leishmania major, contributing to the control of the inflammatory lesion and, to a lesser degree, to parasite killing. However, the relative contribution of the soluble and transmembrane forms of TNF in these processes is unknown. To investigate the role of transmembrane TNF (mTNF) in the control of L. major infections, mTNF-knock-in (mTNF(Delta/Delta)) mice, which express functional mTNF but do not release soluble TNF, were infected with L. major, and the development of the inflammatory lesion and the immune response was compared to that occurring in L. major-infected TNF(-/-) and wild-type mice. mTNF(Delta/Delta) mice controlled the infection and resolved their inflammatory lesion as well as wild-type mice, a process associated with the early clearance of neutrophils at the site of parasite infection. In contrast, L. major-infected TNF(-/-) mice developed non-healing lesions, characterized by an elevated presence of neutrophils at the site of infection and partial control of parasite number within the lesions. Altogether, the results presented here demonstrate that mTNF, in absence of soluble TNF, is sufficient to control infection due to L. major, enabling the regulation of inflammation, and the optimal killing of Leishmania parasites at the site of infection.

Tenascin-C is a novel RBPJkappa-induced target gene for Notch signaling in gliomas.

Tenascin-C (TNC) expression is known to correlate with malignancy in glioblastoma (GBM), a highly invasive and aggressive brain tumor that shows limited response to conventional therapies. In these malignant gliomas as well as in GBM cell lines, we found Notch2 protein to be strongly expressed. In a GBM tumor tissue microarray, RBPJk protein, a Notch2 cofactor for transcription, was found to be significantly coexpressed with TNC. We show that the TNC gene is transactivated by Notch2 in an RBPJk-dependent manner mediated by an RBPJk binding element in the TNC promoter. The transactivation is abrogated by a Notch2 mutation, which we detected in the glioma cell line Hs683 that does not express TNC. This L1711M mutation resides in the RAM domain, the site of interaction between Notch2 and RBPJk. In addition, transfection of constructs encoding activated Notch2 or Notch1 increased endogenous TNC expression identifying TNC as a novel Notch target gene. Overexpression of a dominant negative form of the transcriptional coactivator MAML1 or knocking down RBPJk in LN319 cells led to a dramatic decrease in TNC protein levels accompanied by a significant reduction of cell migration. Because addition of purified TNC stimulated glioma cell migration, this represents a mechanism for the invasive properties of glioma cells controlled by Notch signaling and defines a novel oncogenic pathway in gliomagenesis that may be targeted for therapeutic intervention in GBM patients.

Loss of insulin synthesis and beta cell survival induced by oxidized LDL require activation of reticulum endoplasmic stress: a mechanism countered by HDL

Elevated circulating concentrations in modified LDL-cholesterol particles (e.g. oxidised LDL) and low levels in HDL increase not only the risk for diabetic patients to develop cardiovascular diseases but also may contribute to development and progression of diabetes by directly having adverse effects on β-cells. Chronic exposure of β-cells to 2 mM human oxidised LDL-cholesterol (oxLDL) increases the rate of apoptosis, reduce insulin biosynthesis and the secretory capacity of the cells in response to nutrients. In line with the protective role, HDL efficiently antagonised the harmful effects of ox- LDL, suggesting that low levels of HDL would be inefficient to protect β-cells against oxLDL attack in patients. Activation of endoplasmic reticulum (ER) stress is pointed out to contribute to β-cell dysfunction elicited by environmental stressors. In this study we investigated whether activation of ER stress is required for oxLDL to mediate detrimental effects on β-cells and we tested the potential antagonist properties of HDL: The mouse MIN6 insulin-secreting cells were cultured with 2 mM of LDL-cholesterol preparation (native or in vitro oxidized) in the presence or absence of 1 mM of HDL-cholesterol or the ER stress inhibitor 4-phenylbutyrate (4-PBA): Prolonged exposure of MIN6 cells to 2 mM oxLDL-cholesterol for 48 hours led to an increase in expression of ER stress markers such as ATF4, CHOP and p58 and stimulated the splicing of XBP-1 whereas, induction of these markers was not observable in the cells cultured with native LDL. Treatment of the cells with the 4-PBA chemical chaperone molecule efficiently blocked activation of the ER stress markers induced by oxLDL. The latter mediates β-cell dysfunction and apoptosis by diminishing the expression of islet brain 1 (IB1) and Bcl2. The levels of these two proteins were preserved in the cells that were co-treated with oxLDL and the 4-PBA. Consistent with this result we found that blockade of ER stress activation alleviated the loss of insulin synthesis and abolished apoptosis evoked by oxLDL. However incubation of the cells with 4-PBA did not prevent impairment of insulin secretion elicited by oxLDL, indicating that ER stress is not responsible for the oxLDL-mediated defect of insulin secretion. Co-incubation of the cells with HDL mimicked the effects of 4-PBA on the expression of IB1 and Blc2 and thereby counteracted oxLDL attacks on insulin synthesis and cell survivals. We found that HDL efficiently inhibited activation of the ER stress mediated by oxLDL: These data highlight the contribution of the ER stress in the defects of insulin synthesis and cell survivals induced by oxLDL and emphasize the potent role of HDL to counter activation of the oxLDL-mediated ER-stress activation:

Oviposition-induced changes in Arabidopsis genome expression: anticipating your enemy?

Plants have evolved exquisite ways to detect their enemies and are able to induce defenses responses tailored to their specific aggressors. Insect eggs deposited on a leaf represent a future threat as larvae hatching from the egg will ultimately feed on the plant. Although direct and indirect defenses towards oviposition have been documented, our knowledge of the molecular changes triggered by egg deposition is limited. Using a whole-genome microarray, we recently analyzed the expression profile of Arabidopsis thaliana leaves after oviposition by two pierid butterflies. Eggs laid by the large white Pieris brassicae modified the expression of hundreds of genes. The transcript signature included defense and stress-related genes that were also induced in plants experiencing localized cell death. Further analyses revealed that cellular changes associated with a hypersensitive response occur at the site of egg deposition and that they are triggered by egg-derived elicitors. Our study brings molecular evidence for previous observations of oviposition-induced necrosis in other plant species and might illustrate a direct defense of the plant against the egg. In this addendum, we discuss the relevance of the oviposition-induced gene expression changes and the possibility that plants use eggs as cues to anticipate their enemies.

Blood pressure-independent cardiac hypertrophy induced by locally activated renin-angiotensin system.

Cardiac hypertrophy is frequent in chronic hypertension. The renin-angiotensin system, via its effector angiotensin II (Ang II), regulates blood pressure and participates in sustaining hypertension. In addition, a growing body of evidence indicates that Ang II acts also as a growth factor. However, it is still a matter of debate whether the trophic effect of Ang II can trigger cardiac hypertrophy in the absence of elevated blood pressure. To address this question, transgenic mice overexpressing the rat angiotensinogen gene, specifically in the heart, were generated to increase the local activity of the renin-angiotensin system and therefore Ang II production. These mice develop myocardial hypertrophy without signs of fibrosis independently from the presence of hypertension, demonstrating that local Ang II production is important in mediating the hypertrophic response in vivo.

Results of a consensus meeting on the use of argatroban in patients with heparin-induced thrombocytopenia requiring antithrombotic therapy - a European Perspective.

Argatroban has been introduced as an alternative parenteral anticoagulant for HIT-patients in several European countries in 2005. In 2009 a panel of experts discussed their clinical experience with argatroban balancing risks and benefits of argatroban treatment in managing the highly procoagulant status of HIT-patients. This article summarizes the main conclusions of this round table discussion. An ongoing issue is the appropriate dosing of argatroban in special patient groups. Therefore, dosing recommendations for different HIT-patient groups (ICU patients; non-ICU patients, paediatric patients, and for patients undergoing renal replacement therapies) are summarized in this consensus statement. Because of the strong correlation between argatroban dosing requirements and scores used to characterize the severity of illness (APACHE; SAPS, SOFA) suitable dosing nomograms are given. This consensus statement contributes to clinically relevant information on the appropriate use and monitoring of argatroban based on the current literature, and provides additional information from clinical experience. As the two other approved drugs for HIT, danaparoid and lepirudin are either currently not available due to manufacturing problems (danaparoid) or will be withdrawn from the market in 2012 (lepirudin), this report should guide physicians who have limited experience with argatroban how to use this drug safely in patients with HIT.