Library

Notes: Skin innervation is extremely dense and reaches the most superficial layers of the epidermis (but not into the stratum corneum). The relationship between skin and the nervous system was neglected for a long time. Nowadays, this represents one of the most widely investigated fields of skin biology.Associations between nerve fibres and skin are so close that these can be observed at the cellular level. They are anatomical and physiological. Neurotransmitters are naturally synthesized by nerve endings, but cells from the skin and the immune system are also able to produce them. They are mediators for transmission of information between skin and the nervous system. All cutaneous and immune cells express specific receptors for these neuromediators, and enzymes for degrading them. Binding of the neurotransmitter to its receptor induces modulation of cell properties and skin functions (immunity, cell differentiation and proliferation, pigmentation, etc.). Hence, keratinocytes, Langerhans cells, melanocytes, endothelial cells, fibroblasts and the other cells of the skin or the immune system are modulated and controlled by the nerves. Reciprocally, skin is able to modulate neuronal activity and growth. All these data suggest that skin, nervous and immune systems are integrated in a unique system that we could name the neuro-immuno-cutaneous system (NICS).Hence, we can understand how the nervous system, and further the psychism, are involved in the maintenance of cutaneous homeostasis. In dermatological diseases or in cosmetological disorders, this equilibrium is broken. New fields of research are open: neuro-dermatology and of course neuro-cosmetics. Neuro-cosmetic products are supposed to modulate NICS functioning at the epidermal level. The French expression ‘avoir les nerfs à fleur de peau’ means that nervosity is so tense that one feels his nerves closely under or within skin, ready to explode. In fact, nerves are always ‘à fleur de peau’. Skin is an organ whose dense innervation involves the outermost skin layers, stratum corneum excepted. Long time neglected, the relation between skin and the nervous system are, today, a growing field of research within cutaneous biology.

Notes: The expression of receptors for neuropeptides in the skin is modified in skin diseases.〈section xml:id="abs1-3"〉〈title type="main"〉ObjectiveWe studied the cutaneous expression of substance P (SP) and somatostatin (SOM) receptors (SPR and SSTR, respectively) in skin affected by cutaneous inflammatory or tumoral T-cell infiltrates because these two neuropeptides are the ones most involved in inflammation.〈section xml:id="abs1-4"〉〈title type="main"〉MethodsWe revealed expression of these receptors using a binding in situ technique that gave highly specific results. Skin biopsies were incubated with biotinylated neuropeptides (SP or SOM).〈section xml:id="abs1-5"〉〈title type="main"〉ResultsIn normal skin, SSTR were observed on blood vessels, smooth muscle fibres and sweat glands. SSTR expression was modified only when expressed by keratinocytes in Ofuji papuloerythroderma and by plasmocytes in plasmocytoma. SPR distribution was not modified in subjects with atopic dermatitis or lupus. The expression of SPR in the epidermis was diminished in Ofuji papuloerythroderma and parapsoriasis and absent in mycosis fungoides.〈section xml:id="abs1-6"〉〈title type="main"〉ConclusionsThese results suggest that malignant lymphocytic infiltrates can inhibit SPR expression on keratinocytes.

Notes: Abstract:  All three-dimensional in vitro mucosal models constructed, thus far, have only been reconstituted by epithelial cells. We have developed a reconstructed oral and vaginal epithelium that integrates Langerhans' cells (LC), the dendritic cells (DC) of malpighian epithelia. The epithelium was composed of gingival or vaginal keratinocytes seeded on a de-epidermized dermis (DED) and grown in submerged culture for 2 weeks. LC precursors, obtained after differentiation of cord blood-derived CD34+ hematopoietic progenitor cells (CD34+HPC) by granulocyte macrophage-colony stimulating factor (GM-CSF), tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β) and Flt3-ligand (Flt3-L), were introduced after 6–8 days of culture into the reconstituted epithelium. The in vitro reconstituted mucosal epithelium formed a multilayered, well-differentiated epithelial structure, confirmed by the immunohistochemical expression of cytokeratins 4, 6, 10, 13, 14, 16 and involucrin. LC were identified in the basal and suprabasal epithelial layers by CD1a antigen, S100 protein and Langerin/CD207 expression, and by transmission electron microscopy. Type IV collagen was expressed at the chorio–epithelial junction, and most ultrastructural features of this junction were visualized by electron microscopy. This in vitro reconstructed gingiva or vagina integrating LC represents interesting models very similar to native tissues. Because LC play an important role in the mucosal immune system, our models could be useful for conducting studies on interactions with pathogenic agents (viruses, bacteria etc.), as well as in pharmacological, toxicological and clinical research.

Notes: In order to provide a model for in vitro studies of the interactions between skin and the nervous system, we have performed a co-culture of epidermal cells and neurons. We used a tri-compartmented box with separated domains. In the central part of this box, we put an epidermal suspension (4 millions cells/ml) obtained from biopsies of human skin. Around this central domain, we disposed sensorial neurons from the dorsal root ganglia of rats. The periphery was occupied by neurons from the dorsal horn of spinal cord. Sensorial neurons grew in low density (500 cells), on a glial layer, in a medium conditioned by astrocytes. After 15 days of culture, cells were fixed and stained with monoclonal antibodies directed against PGP 9.5, keratins, or cytokeratin 20 (Merkel cells). We obtained a co-culture with three identifiable territories, equivalents of epidermis, root ganglia, and spinal cord. Nervous fibers specifically grew from the sensorial neurons to epidermal cells or to the spinal cord equivalent. We observed synapse-like contacts between nerve endings and Merkel cells or keratinocytes. This model allows us to reconstruct in vitro an equivalent of sensitive nerve fibers, connected for one part to a spinal cord equivalent and on the other part to an epidermis equivalent. Such a model could be used to understand the origin and the function of Merkel cells in the epidermis and to study synapses in the skin.

Notes: Abstract: The hormone/neuropeptide somatostatin (SOM) exerts multiple functions in the central nervous system, the immune system, the hypothalamo-pituitary axis, the gastrointestinal tract, and the pancreas. Endogenous SOM occurs in 2 biologically active forms, with 14 or 28 amino acids. Five subtypes of SOM reporters have been cloned. SOM is present in human skin. We have investigated the expression of SOM receptors on human dermal normal fibroblasts. Biotinyl-SOM allowed the visualization of SOM receptors on human dermal fibroblasts. Radioligand binding with (3-[125I]iodotyrosy]11)-SOM-14 were performed on these cells and the effect of SOM-14 on the DNA synthesis by fibroblasts was evaluated by measuring [3H]-methyl thymidine incorporation. Saturation curve, and Scatchard plot showed a homogeneous class of receptors with a Bmax of 0.055±0.023 nM and KD of 2.0±0.4 nM (values: mean±SEM). Fibroblasts expressed 3,317±1,385 binding sites per cell. Commpetitive displacement experiments showed that SOM-14 IC50 was 69.3±4.5 nM (mean±SEM), for SOM-28 33.2±6.0 nM and for octreotide 36.5±3.3 nM. The KI values calculated from these IC50 were, respectively: 62.4±4.1 nM; 29.9±5.4 nm; 32.9±2.9 nM. We conclude that subtype 2 or 3 SOM receptros is present on human normal dermal fibroblasts. A weak effect of SOM-14 on DNA synthesis was observed with SOM concentrations of 10-7 and 10-6 M.

Notes: While the enormous clinical and psychosocial importance of pruritus in many areas of medicine and the detrimental effects of chronic ‘itch’ on the quality of life of an affected individual are widely appreciated, the complexity of this sensation is still often grossly underestimated. The current Controversies feature highlights this complexity by portraying pruritus as a truly interdisciplinary problem at the crossroads of neurophysiology, neuroimmunology, neuropharmacology, protease research, internal medicine, and dermatology, which is combated most successfully if one keeps the multilayered nature of ‘itch’ in mind and adopts a holistic treatment approach – beyond the customary, frequently frustrane monotherapy with histamine receptor antagonists. In view of the often unsatisfactory, unidimensional, and altogether rather crude standard instruments for pruritus management that we still tend to use in clinical practice today, an interdisciplinary team of pruritus experts here critically examines recent progress in pruritus research that future itch management must take into consideration. Focusing on new insights into the neuroimmunological, neuroendocrine, and neurophysiological bases of pruritus, and discussing available neuropharmacological tools, specific research avenues are highlighted, whose pursuit promises to lead to novel, and hopefully more effective, forms of pruritus management.

Notes: Connections between nerve fibres and cutaneous cells have been studied using confocal and electron microscopy. In the skin, nerve fibres may secrete neuromediators, i.e. substance P, vasoactive intestinal peptide, somatostatin, calcitonin-gene-related peptide, gastrin-releasing peptide, neuropeptide Y, peptide histidine-isoleucine, neurotensin, neurokinins A and B, bradykinin, acetylcholine, catecholamines, endorphins and enkephalins. Neurohormones such as prolactin, melanocyte-stimulating hormone and adrenocorticotrophic hormone are also expressed in the skin. Neuromediators and neurohormones may be secreted by cutaneous cells, which also express receptors. Functions of epidermal and dermal cells are modulated by these substances. Immune cells transiently present in the skin (e.g. macrophages and lymphocytes) are modulated by neuromediators through receptors. During the course of skin disorders, especially inflammatory reactions, the neuroimmunocutaneous system is destabilized. This is particularly true in psoriasis. This destabilization may be secondary, although evidence shows it can also be responsible for the induction and maintenance of the inflammatory process. The skin, the nervous system and immunity are not independent systems but are closely associated and use the same language of cytokines and neurotransmitters. A new concept is suggested: the neuroimmunocutaneous system.

Notes: Somatostatin (SOM) is a ubiquitous peptide which is responsible for the inhibition of numerous biological functions. SOM is described as an antiproliferative molecule and an inhibitor of exocrine or endocrine secretion from a variety of tissues, including pancreas, gastrointestinal tract, central and peripheral nervous system. Mediation of SOM effects can be indirect or direct, respectively, through other molecules or receptors on target cells. We have searched for the presence of SOM in the epidermis using immunofluorescence, confocal laser scanning microscopy, radioimmunoassay, and chromatography. Immunofluorescence and confocal laser scanning microscopy studies were performed using rabbit antiserum anti-SOM and mouse monoclonal antibody directed to CD1a Langerhans cell (LC) marker disclosed with fluorescein or tetramethylrhodamine isothiocyanate conjugates. SOM was extracted from whole skin or epidermal cell suspension or LC-enriched suspensions and analysed by radioimmunoassay. We used an antiserum which was reactive for the 6–11 portion of native SOM. Chromatographic columns were performed on extracts from whole skin. The epidermis was SOM immunoreactive. LC were immunoreactive for SOM and the staining was membranous. SOM was extracted from the whole skin at about 0·13±0·02 fmol/mg of tissue (mean±SEM). The SOM concentration in epidermal cell suspensions was 1·5±0·9 fmol/106 cells. Data obtained with LC-enriched suspensions showed large variations between donors. Extracts from skin showed one peak with an elution profile like that of 14 amino acid SOM. This study demonstrates that 14 amino acid SOM is expressed in normal human epidermis.