Alpha1beta1 integrin is crucial for accumulation of epidermal T cells and the development of psoriasis.

Psoriasis is a common T cell-mediated autoimmune inflammatory disease. We show that blocking the interaction of alpha1beta1 integrin (VLA-1) with collagen prevented accumulation of epidermal T cells and immunopathology of psoriasis. Alpha1beta1 integrin, a major collagen-binding surface receptor, was exclusively expressed by epidermal but not dermal T cells. Alpha1beta1-positive T cells showed characteristic surface markers of effector memory cells and contained high levels of interferon-gamma but not interleukin-4. Blockade of alpha1beta1 inhibited migration of T cells into the epidermis in a clinically relevant xenotransplantation model. This was paralleled by a complete inhibition of psoriasis development, comparable to that caused by tumor necrosis factor-alpha blockers. These results define a crucial role for alpha1beta1 in controlling the accumulation of epidermal type 1 polarized effector memory T cells in a common human immunopathology and provide the basis for new strategies in psoriasis treatment focusing on T cell-extracellular matrix interactions.

Sustained 24-hour blockade of the renin-angiotensin system: a high dose of a long-acting blocker is as effective as a lower dose combined with an angiotensin-converting enzyme inhibitor

Résumé en français Jusqu'alors, il n'avait jamais été formellement démontré qu'une forte dose d'un antagoniste de l'angiotensine II à longue durée d'action pouvait être aussi efficace sur le blocage du système rénine-angiotensine que l'association d'un inhibiteur de l'enzyme de conversion avec le même antagoniste de l'angiotensine II à des doses plus faibles. Dans cette étude randomisée en double aveugle, nous avons étudié le blocage du système rénine-angiotensine obtenu avec trois doses d'olmesartan medoxomil (20, 40 et 80 mg) chez 30 volontaires sains que nous avons comparé au blocage obtenu par du lisinopril (20 mg), seul ou associé à de l'olmesartan medoxomil (20 et 40 mg). L'étude s'est déroulée en deux phases selon un design par crossover. A deux reprises, chaque volontaire à reçu durant une semaine l'un des six traitements possibles. Un intervalle d'une semaine a été respecté entre les deux phases (période de washout). L'objectif principal était d'étudier, 24 heures après la dernière dose, le blocage de l'élévation de la pression systolique en réponse à l'administration d'angiotensine I. Ce blocage était de 58% ± 19% (moyenne ± déviation standard) avec 20 mg de lisinopril, de 58% ± 11% avec 20 mg d'olmesartan medoxomil, de 62% ± 16% avec 40 mg d'olmesartan medoxomil, et de 76% ± 12% avec la plus forte dose d'olmesartan medoxomil (80 mg) (P=.016 versus 20 mg de lisinopril et P=.0015 versus 20 mg d'olmesartan medoxomil). Le blocage était de 80% ± 22% avec 20 mg de lisinopril associé à 20 mg d'olmesartan medoxomil et de 83% ± 9% avec 20 mg de lisinopril associé à 40 mg d'olmesartan medoxomil (P= .3 versus 80 mg d'olmesartan medoxomil). Ces résultats montrent, que chez les volontaires sains, une dose suffisamment élevée d'olmesartan medoxomil peut induire un blocage à 24 heures quasi complet de l'élévation de la pression artérielle en réponse à l'administration d'angiotensine I. De même, en terme de blocage de l'effet vasculaire de l'angiotensine I, une dose suffisamment élevée d'un antagoniste de l'angiotensine II de longue durée d'action est tout aussi efficace que ce même antagoniste à des doses plus faibles associé avec à un inhibiteur de l'enzyme de conversion.

The effect of mutations in the DRY motif on the constitutive activity and structural instability of the histamine H(2) receptor.

In previous studies we showed that the wild-type histamine H(2) receptor stably expressed in Chinese hamster ovary cells is constitutively active. Because constitutive activity of the H(2) receptor is already found at low expression levels (300 fmol/mg protein) this receptor is a relatively unique member of the G-protein-coupled receptor (GPCR) family and a useful tool for studying GPCR activation. In this study the role of the highly conserved DRY motif in activation of the H(2) receptor was investigated. Mutation of the aspartate 115 residue in this motif resulted in H(2) receptors with high constitutive activity, increased agonist affinity, and increased signaling properties. In addition, the mutant receptors were shown to be highly structurally instable. Mutation of the arginine 116 residue in the DRY motif resulted also in a highly structurally instable receptor; expression of the receptor could only be detected after stabilization with either an agonist or inverse agonist. Moreover, the agonist affinity at the Arg-116 mutant receptors was increased, whereas the signal transduction properties of these receptors were decreased. We conclude that the Arg-116 mutant receptors can adopt an active conformation but have a decreased ability to couple to or activate the G(s)-protein. This study examines the pivotal role of the aspartate and arginine residues of the DRY motif in GPCR function. Disruption of receptor stabilizing constraints by mutation in the DRY motif leads to the formation of active GPCR conformations, but concomitantly to GPCR instability.

Mutants of common bean alpha-amylase inhibitor-2 as an approach to investigate binding specificity to alpha-amylases

Despite the presence of a family of defense proteins, Phaseolus vulgaris can be attacked by bruchid insects resulting in serious damage to stored grains. The two distinct active forms of a-amylase inhibitors, a-AI1 and a-AI2, in P. vulgaris show different specificity toward a-amylases. Zabrotes subfasciatus a-amylase is inhibited by a-AI2 but not by a-AI1. In contrast, porcine a-amylase is inhibited by a-AI1 but not by a-AI2. The objective of this work was to understand the molecular basis of the specificity of two inhibitors in P. vulgaris (a-AI1 and a-AI2) in relation to a-amylases. Mutants of a-AI2 were made and expressed in tobacco plants. The results showed that all the a-AI2 mutant inhibitors lost their activity against the insect a-amylases but none exhibited activity toward the mammalian a-amylase. The replacement of His33 of a-AI2 with the a-AI1-like sequence Ser-Tyr-Asn abolished inhibition of Z. subfasciatus a-amylase. From structural modeling, the conclusion is that the size and complexity of the amylase-inhibitor interface explain why mutation of the N-terminal loop and resultant abolition of Z. subfasciatus a-amylase inhibition are not accompanied by gain of inhibitory activity against porcine a-amylase.

PPAR beta/delta Agonists Modulate Platelet Function via a Mechanism Involving PPAR Receptors and Specific Association/Repression of PKC alpha-Brief Report

Objectives-Peroxisome proliferator-activated receptor beta/delta (PPAR beta/delta) is a nuclear receptor found in platelets. PPAR beta/delta agonists acutely inhibit platelet function within a few minutes of addition. As platelets are anucleated, the effects of PPAR beta/delta agonists on platelets must be nongenomic. Currently, the particular role of PPAR beta/delta receptors and their intracellular signaling pathways in platelets are not known. Methods and Results-We have used mice lacking PPAR beta/delta (PPAR beta/delta(-/-)) to show the effects of the PPAR beta/delta agonist GW501516 on platelet adhesion and cAMP levels are mediated specifically by PPAR beta/delta, however GW501516 had no PPAR beta/delta-specific effect on platelet aggregation. Studies in human platelets showed that PKC alpha, which can mediate platelet activation, was bound and repressed by PPAR beta/delta after platelets were treated with GW501516. Conclusions-These data provide evidence of a novel mechanism by which PPAR receptors influence platelet activity and thereby thrombotic risk. (Arterioscler Thromb Vasc Biol. 2009; 29: 1871-1873.)

Chemical probes that differentially modulate peroxisome proliferator-activated receptor alpha and BLTR, nuclear and cell surface receptors for leukotriene B(4).

Peroxisome proliferator-activated receptor alpha (PPARalpha)is a nuclear receptor for various fatty acids, eicosanoids, and hypolipidemic drugs. In the presence of ligand, this transcription factor increases expression of target genes that are primarily associated with lipid homeostasis. We have previously reported PPARalpha as a nuclear receptor of the inflammatory mediator leukotriene B(4) (LTB(4)) and demonstrated an anti-inflammatory function for PPARalpha in vivo (Devchand, P. R., Keller, H., Peters, J. M., Vazquez, M., Gonzalez, F. J., and Wahli, W. (1996) Nature 384, 39-43). LTB(4) also has a cell surface receptor (BLTR) that mediates proinflammatory events, such as chemotaxis and chemokinesis (Yokomizo, T., Izumi, T., Chang, K., Takuwa, Y., and Shimizu, T. (1997) Nature 387, 620-624). In this study, we report on chemical probes that differentially modulate activity of these two LTB(4) receptors. The compounds selected were originally characterized as synthetic BLTR effectors, both agonists and antagonists. Here, we evaluate the compounds as effectors of the three PPAR isotypes (alpha, beta, and gamma) by transient transfection assays and also determine whether the compounds are ligands for these nuclear receptors by coactivator-dependent receptor ligand interaction assay, a semifunctional in vitro assay. Because the compounds are PPARalpha selective, we further analyze their potency in a biological assay for the PPARalpha-mediated activity of lipid accumulation. These chemical probes will prove invaluable in dissecting processes that involve nuclear and cell surface LTB(4) receptors and also aid in drug discovery programs.

Severe hypertension following accidental clonidine overdose during the refilling of an implanted intrathecal drug delivery system.

BACKGROUND:   Complications associated with intrathecal pumps may be linked to the surgical procedure, the implanted device, or the medication itself.¦CASE REPORTS:   Three patients treated chronically with intrathecal clonidine presented with clonidine overdose due to inadvertent extravasation during the refilling procedure. All patients experienced loss of consciousness and severe systemic hypertension that required aggressive parenteral treatment.¦DISCUSSION:   Clonidine is an alpha-2 agonist with a nearly 100% bioavailability after oral or rectal administration. With high plasma concentration secondary to massive systemic overdose, the specificity for the alpha-2 receptor is lost and an alpha-1 agonist activity predominates and causes marked hypertension. Management of clonidine overdose consists of supportive therapy guided by signs and symptoms.¦CONCLUSION:   Inadvertent injection into the subcutaneous pocket rather than the reservoir is rare but very dangerous as the drug cannot be retrieved and massive doses are involved. Signs and symptoms of systemic overdose with drugs commonly used in implanted drugs delivery system should be well known to ensure early diagnosis and treatment.

Linking supply to demand: the neuronal monocarboxylate transporter MCT2 and the alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid receptor GluR2/3 subunit are associated in a common trafficking process.

MCT2 is the major neuronal monocarboxylate transporter (MCT) that allows the supply of alternative energy substrates such as lactate to neurons. Recent evidence obtained by electron microscopy has demonstrated that MCT2, like alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) receptors, is localized in dendritic spines of glutamatergic synapses. Using immunofluorescence, we show in this study that MCT2 colocalizes extensively with GluR2/3 subunits of AMPA receptors in neurons from various mouse brain regions as well as in cultured neurons. It also colocalizes with GluR2/3-interacting proteins, such as C-kinase-interacting protein 1, glutamate receptor-interacting protein 1 and clathrin adaptor protein. Coimmunoprecipitation of MCT2 with GluR2/3 and C-kinase-interacting protein 1 suggests their close interaction within spines. Parallel changes in the localization of both MCT2 and GluR2/3 subunits at and beneath the plasma membrane upon various stimulation paradigms were unraveled using an original immunocytochemical and transfection approach combined with three-dimensional image reconstruction. Cell culture incubation with AMPA or insulin triggered a marked intracellular accumulation of both MCT2 and GluR2/3, whereas both tumor necrosis factor alpha and glycine (with glutamate) increased their cell surface immunolabeling. Similar results were obtained using Western blots performed on membrane or cytoplasm-enriched cell fractions. Finally, an enhanced lactate flux into neurons was demonstrated after MCT2 translocation on the cell surface. These observations provide unequivocal evidence that MCT2 is linked to AMPA receptor GluR2/3 subunits and undergoes a similar translocation process in neurons upon activation. MCT2 emerges as a novel component of the synaptic machinery putatively linking neuroenergetics to synaptic transmission.

T cell receptor delta gene rearrangement and T early alpha (TEA) expression in immature alpha beta lineage thymocytes: implications for alpha beta/gamma delta lineage commitment.

Mature T cells comprise two mutually exclusive lineages expressing heterodimeric alpha beta or gamma delta antigen receptors. During development, beta, gamma, and delta genes rearrange before alpha, and mature gamma delta cells arise in the thymus prior to alpha beta cells. The mechanism underlying commitment of immature T cells to the alpha beta or gamma delta lineage is controversial. Since the delta locus is located within the alpha locus, rearrangement of alpha genes leads to deletion of delta. We have examined the rearrangement status of the delta locus immediately prior to alpha rearrangement. We find that many thymic precursors of alpha beta cells undergo VDJ delta rearrangements. Furthermore, the same cells frequently coexpress sterile T early alpha (TEA) transcripts originating 3' of C delta and 5' of the most upstream J alpha, thus implying that individual alpha beta lineage cells undergo sequential VDJ delta and VJ alpha rearrangements. Finally, VDJ delta rearrangements in immature alpha beta cells appear to be random, supporting models in which alpha beta lineage commitment is determined independently of the rearrangement status at the TCR delta locus.

Rhumatologie. Anti-TNF alpha: quels risques infectieux? Recommandations pratiques [Rheumatology. TNF alpha-inhibitors: infection risks? Practical recommendations].

Anti-TNF alpha are immunomodulatory treatments prescribed for some rheumatologic inflammatory diseases (ex: spondylarthropathy, rheumatoid polyarthritis). The randomised studies suggested that anti-TNF alpha therapy is associated with an overall risk of infectious diseases. The results of the observational studies are more reassuring. In this article, we will describe some results of theses studies and propose some practical recommendations in use of the anti-TNF alpha therapy.

Calcineurin blockade prevents cardiac mitogen-activated protein kinase activation and hypertrophy in renovascular hypertension.

Chronic stimulation of the renin-angiotensin system induces an elevation of blood pressure and the development of cardiac hypertrophy via the actions of its effector, angiotensin II. In cardiomyocytes, mitogen-activated protein kinases as well as protein kinase C isoforms have been shown to be important in the transduction of trophic signals. The Ca(2+)/calmodulin-dependent phosphatase calcineurin has also been suggested to play a role in cardiac growth. In the present report, we investigate possible cross-talks between calcineurin, protein kinase C, and mitogen-activated protein kinase pathways in controlling angiotensin II-induced hypertrophy. Angiotensin II-stimulated cardiomyocytes and mice with angiotensin II-dependent renovascular hypertension were treated with the calcineurin inhibitor cyclosporin A. Calcineurin, protein kinase C, and mitogen-activated protein kinase activations were determined. We show that cyclosporin A blocks angiotensin II-induced mitogen-activated protein kinase activation in cultured primary cardiomyocytes and in the heart of hypertensive mice. Cyclosporin A also inhibits specific protein kinase C isoforms. In vivo, cyclosporin A prevents the development of cardiac hypertrophy, and this effect appears to be independent of hemodynamic changes. These data suggest cross-talks between the calcineurin pathway, the protein kinase C, and the mitogen-activated protein kinase signaling cascades in transducing angiotensin II-mediated stimuli in cardiomyocytes and could provide the basis for an integrated model of cardiac hypertrophy.

Blockade of the Renin-Angiotensin system in hypertensive patients with atherosclerotic renal artery stenosis.

Renin angiotensin system (RAS) blockers are generally considered as contraindicated when an atheromatous renal artery stenosis (ARAS) is diagnosed. The main reason is the fear of inducing renal ischemia and, hence, accelerating renal fibrosis and the progression towards end stage renal disease, albeit RAS blocker have been shown to be highly effective in controlling blood pressure. Part of the solution came by the development of the revascularization. There is now growing evidence showing no superiority of angioplasty over medical treatment on cardiovascular events and mortality, renal function and blood pressure control. Hence, RAS blockers resurfaced based on their proven beneficial effects on blood pressure control and cardiovascular prevention in high risk atherosclerotic patients. Thus, RAS blockers belong today to the standard treatment of hypertensive patients with ARAS. However they were not systematically prescribed in trials focusing on ARAS. The ongoing CORAL trial will give us further information on the place of this class of antihypertensive drugs in patients with ARAS.

Inflammation-induced changes in expression and glycosylation of genetic variants of alpha 1-acid glycoprotein. Studies with human sera, primary cultures of human hepatocytes and transgenic mice.

The relative occurrence of genetic variants of human alpha 1-acid glycoprotein (AGP) in relation to changes in glycosylation was studied in sera of patients with burn injury, media of cytokine-treated primary cultures of human hepatocytes and Hep 3B cells, and sera of transgenic mice expressing the human AGP-A gene. It is concluded (i) that the glycosylation of AGP was not dependent on its genetic expression and (ii) that both the variants determined by the AGP-A gene as well as by the AGP-B/B' genes are increased after inflammation or treatment with interleukins 1 and 6.

Increased alpha activity and modulations of fronto-parietal balance during motor transitions in the elderly

A hallmark of aging is the sensorimotor deficit, characterized by an increased reaction time and a reduction of motor abilities. Some mechanisms such as motor inhibition deteriorate with aging because of neuronal density alterations and modifications of connections between brain regions. These deficits may be compensated throughout a recruitment of additional areas. Studies have shown that old adults have increased difficulty in performing bimanual coordination tasks compared with young adults. In contrast, motor switching is poorly documented and is expected to engage increasing resources in the elderly. The present study examines performances and electro-cortical correlates of motor switching in young and elderly adults.