Rôle de LEKTI dans le contrôle de l'inflammation allergique du syndrome de Netherton

Le syndrome de Netherton (SN, OMIM 256500) est une génodermatose rare et sévère due à des mutations du gène SPINK5 codant l'inhibiteur de protéases LEKTI. LEKTI joue un rôle crucial dans la fonction de barrière cutanée via la régulation de protéases épidermiques dont les kallikréines (KLK) 5 et 7. En absence de LEKTI, l'hyperactivité des kallikréines entraine un détachement anormal de la couche cornée et une perte de la fonction de barrière cutanée. A l'aide de modèles murins et de kératinocytes de patients SN, nous avons démontré que l'épiderme dépourvu de LEKTI avait également la capacité intrinsèque de produire des cytokines pro-Th2, telle que TSLP, suite à l'activation de PAR2 par la KLK5. Les animaux dépourvus à la fois des gènes Spink5 et Par2 nous ont permis de confirmer l'importance de la cascade KLK5-PAR2 dans l'induction des messages pro-allergiques précoces indépendament des stimuli environnementaux et du système immunitaire adaptatif. Cependant, l'inactivation de cette voie ne rétablit pas la fonction de barrière et réverse partiellement le phénotype inflammatoire dans une peau adulte. Ces résultats ainsi que la présence constante de manifestations atopiques chez les patients SN sont en faveur d'un biais de la réponse immune vers une différenciation de type Th2. Ainsi une étude de la polarisation de la réponse lymphocytaire T a été initiée chez ces patients. L'ensemble de ces travaux souligne ainsi l'importance du contrôle des deux versants du SN : le défaut de barrière cutanée et l'induction de signaux pro-allergiques intrinsèque à l'épiderme. De plus, il identifie de nouvelles cibles thérapeutiques potentielles pour le traitement de cette maladie orpheline.Netherton syndrome (NS, OMIM 256500) is a rare and severe autosomal recessive genodermatosis caused by mutations in SPINK5 gene encoding the protease inhibitor LEKTI. LEKTI play a key role in skin barrier function through the regulation of epidermal proteases, kallikreins (KLK) 5 and 7. In the absence of LEKTI, hyperactive KLK5 and 7 degrade intercorneocyte adhesion molecules leading to abnormal stratum corneum detachment and severe barrier function impairment. Analysis of mouse models and primary keratinocytes from NS, allowed us to demonstrate that LEKTI-deficient epidermis has also the intrinsic capacity to overexpress Th2 polarizing cytokines, such as TSLP, secondary to PAR2 activation by KLK5. Using double knockout mice deficient for Spink5 and Par2, we confirmed the major role of the KLK5-PAR2 pathway in the induction of early pro-inflammatory signaling independently of environmental stimuli and adaptive immune system. However inactivation of this pathway did not improve the skin barrier function and partially reversed cutaneous inflammation in adult skin. These results together with constant atopic manifestations in NS patients suggest that immune response could be biased in favour of a Th2 differentiation. Thus we studied the polarization of peripheral T cells isolated from NS patients. All together, our data emphasize the importance in controlling both sides of the disease: the skin barrier defect and the pro-allergic signals intrinsic of the epidermis. Moreover, we identified new potential therapeutic targets for the treatment of this orphan disease

Par2 Inactivation Inhibits Early Production of TSLP, but Not Cutaneous Inflammation, in Netherton Syndrome Adult Mouse Model

Netherton syndrome (NS) is a severe genodermatosis characterized by abnormal scaling and constant atopic manifestations. NS is caused by mutations in SPINK5 (Serine Protease INhibitor Kazal-type 5), which encodes LEKTI (LymphoEpithelial Kazal Type-related Inhibitor). Lack of LEKTI causes stratum corneum detachment secondary to epidermal proteases hyperactivity. Whereas a skin barrier defect is generally regarded as a major cause for atopy, we previously identified a cell-autonomous signaling cascade that triggers pro-Th2 cytokine thymic stromal lymphopoietin (TSLP) production in LEKTI-deficient epidermis. This signaling is initiated by unrestricted kallikrein 5 (KLK5) activity, which directly activates proteinase-activated receptor 2 (PAR2)-mediated expression of TSLP and favors a cutaneous proallergic microenvironment independently of the environment and of the adaptive immune system. To further confirm these results in vivo, we generated Spink5/Par2 double knockout (DKO) mice. At embryonic day 19.5, these mice display a dramatic decrease in TSLP expression, although stratum corneum detachment persists, confirming the role of the KLK5–PAR2 cascade in TSLP-mediated early proallergic signaling. However, deletion of Par2 in adult DKO-grafted skin does not rescue the inflammatory phenotype probably resulting from stratum corneum detachment. We conclude that several mechanisms trigger and maintain the inflammatory phenotype in NS. These include skin barrier impairment, mechanical stress secondary to stratum corneum detachment, as well as protease-induced proinflammatory and proallergic pathways, including PAR2-mediated overexpression of TSLP

Novel Facet of an Old Dietary Molecule? Direct Influence of Caffeine on Glucose and Biogenic Amine Handling by Human Adipocytes

Caffeine is a plant alkaloid present in food and beverages consumed worldwide. It has high lipid solubility with recognized actions in the central nervous system and in peripheral tissues, notably the adipose depots. However, the literature is scant regarding caffeine’s influence on adipocyte functions other than lipolysis, such as glucose incorporation into lipids (lipogenesis) and amine oxidation. The objective of this study was to explore the direct effects of caffeine and of isobutylmethylxanthine (IBMX) on these adipocyte functions. Glucose transport into fat cells freshly isolated from mice, rats, or humans was monitored by determining [3H]-2-deoxyglucose (2-DG) uptake, while the incorporation of radiolabeled glucose into cell lipids was used as an index of lipogenic activity. Oxidation of benzylamine by primary amine oxidase (PrAO) was inhibited by increasing doses of caffeine in human adipose tissue preparations with an inhibition constant (Ki) in the millimolar range. Caffeine inhibited basal and insulin-stimulated glucose transport as well as lipogenesis in rodent adipose cells. The antilipogenic action of caffeine was also observed in adipocytes from mice genetically invalidated for PrAO activity, indicating that PrAO activity was not required for lipogenesis inhibition. These caffeine inhibitory properties were extended to human adipocytes: relative to basal 2-DG uptake, set at 1.0 ± 0.2 for 6 individuals, 0.1 mM caffeine tended to reduce uptake to 0.83 ± 0.08. Insulin increased uptake by 3.86 ± 1.11 fold when tested alone at 100 nM, and by 3.21 ± 0.80 when combined with caffeine. Our results reinforce the recommendation of caffeine’s potential in the treatment or prevention of obesity complications

Kallikrein 5 induces atopic dermatitis–like lesions through PAR2-mediated thymic stromal lymphopoietin expression in Netherton syndrome

Netherton syndrome (NS) is a severe genetic skin disease with constant atopic manifestations that is caused by mutations in the serine protease inhibitor Kazal-type 5 (SPINK5) gene, which encodes the protease inhibitor lymphoepithelial Kazal-type–related inhibitor (LEKTI). Lack of LEKTI causes stratum corneum detachment secondary to epidermal proteases hyperactivity. This skin barrier defect favors allergen absorption and is generally regarded as the underlying cause for atopy in NS. We show for the first time that the pro-Th2 cytokine thymic stromal lymphopoietin (TSLP), the thymus and activation-regulated chemokine, and the macrophage-derived chemokine are overexpressed in LEKTI-deficient epidermis. This is part of an original biological cascade in which unregulated kallikrein (KLK) 5 directly activates proteinase-activated receptor 2 and induces nuclear factor κB–mediated overexpression of TSLP, intercellular adhesion molecule 1, tumor necrosis factor α, and IL8. This proinflammatory and proallergic pathway is independent of the primary epithelial failure and is activated under basal conditions in NS keratinocytes. This cell-autonomous process is already established in the epidermis of Spink5−/− embryos, and the resulting proinflammatory microenvironment leads to eosinophilic and mast cell infiltration in a skin graft model in nude mice. Collectively, these data establish that uncontrolled KLK5 activity in NS epidermis can trigger atopic dermatitis (AD)–like lesions, independently of the environment and the adaptive immune system. They illustrate the crucial role of protease signaling in skin inflammation and point to new therapeutic targets for NS as well as candidate genes for AD and atopy

Rôle de LEKTI dans le contrôle de l'inflammation allergique du syndrome de Netherton

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Blockade of specific NOTCH ligands: a new promising approach in cancer therapy.

SummaryThe signaling specificity conveyed by distinct combination of NOTCH receptors/ligands has remained elusive. In this issue of Cancer Discovery, through the development of ligand-specific NOTCH inhibitors, Kangsamaksin and colleagues uncovered unique signaling outcomes downstream of DLL- and JAG-receptor activation and demonstrated their effects in the suppression of tumor angiogenesis

Notch, lipids, and endothelial cells.

Purpose of reviewNotch signaling is an evolutionary conserved pathway critical for cardiovascular development and angiogenesis. More recently, the contribution of Notch signaling to the homeostasis of the adult vasculature has emerged as an important novel paradigm, but much remains to be understood.Recent findingsRecent findings shed light on the impact of Notch in vascular and immune responses to microenvironmental signals as well as on the onset of atherosclerosis. In the past year, studies in human and mice explored the role of Notch in the maintenance of a nonactivated endothelium. Novel pieces of evidence suggest that this pathway is sensitive to environmental factors, including inflammatory mediators and diet-derived by-products.SummaryAn emerging theme is the ability of Notch to respond to changes in the microenvironment, including glucose and lipid metabolites. In turn, alterations in Notch enable an important link between metabolism and transcriptional changes, thus this receptor appears to function as a metabolic sensor with direct implications to gene expression