bluuebunny/crossref_metadata_2025 huggingface dataset:
New markets and technological change for the traditional cereals in semiarid sub‐Saharan Africa: the Malian case
Authors: Vitale Jeffrey D. , Sanders John H.
Published: August 2010

During the last three decades in sub‐Saharan Africa, development and research resources have concentrated on the higher‐rainfall and irrigated regions, especially on export crops and the principal food crops grown there. There has been much less concern and investment in semiarid regions without irrigation. Another negative factor has been the lack of public policy concern with the profitability of the basic food crops. With good weather, prices collapse. With bad weather, governments and NGOs dispense food crops as food aid or at subsidized prices. This article documents the importance of the demand side to facilitate diffusion of new technologies for the basic food commodities of semiarid regions—the traditional cereals. With farm programming models aggregated into a sector model, the combination of technological change and demand shifts for sorghum are evaluated in one semiarid region where the traditional cereals are concentrated. It focuses on combining policies to increase the prices farmers receive after introduction of technologies that use higher input levels. It also compares benefits of a strategy that focuses on yield and demand increases for a traditional cereal of the semiarid region, sorghum, with two alternative strategies for the higher‐rainfall zone.
Risk preference and optimal enterprise combinations in Kahuro division of Murang'a district, Kenya
Authors: Nyikal Rose A. , Kosura Willis O.
Published: August 2010

Financing smallholder farming has been one of the major concerns of Kenya's agricultural development efforts. Many credit programs have evolved over the years but with dismal performance. In a study that sought to find the best way to finance smallholder agriculture, it became necessary to analyze and document, in the first place, the farmers' preferred enterprise patterns. Any financial innovations would hence address the preferred patterns. Of particular interest was the effect of risk preference on such patterns, which had been ignored in many previous farm management studies. Murang'a district was chosen as a typical smallholder district. Sample farmers, obtained through cluster sampling, were visited and structured questionnaires administered to cover farm events and physical resources of short rains 1995 to long rains 1996. This formed a basis for formulating the farm patterns. A quadratic programming model was used to analyze observed farm plans. The model incorporates farmers' risk preferences, revenue fluctuations, and resource and subsistence restrictions. The results showed that: (1) changes in risk preference do affect the optimal crop combinations; (2) the typical cropping pattern is rational as the farmer meets both food and cash under modest variability of income; (3) insisting on producing most subsistence food requirements by the farmers reduces efficiency and limits the feasible plans.
Yield and income risk‐efficiency analysis of alternative systems for rice production in the Guinea Savannah of Northern Ghana
Authors: Langyintuo Augustine S. , Yiridoe Emmanuel K. , Dogbe Wilson , Lowenberg‐Deboer James
Published: August 2010

Risk efficiency of rice grain yield and returns to farm operators' household resources generated from an improved short‐duration cover crop fallow system were compared with (traditional) natural bush fallow, and continuous rice‐cropping systems. The improved fallow system involved maintaining Calopogonium mucunoides, seeded into a natural bush fallow for 2 years before planting to rice. With no chemical fertilizer application, which reflects farmers' practice in the area, average grain yield for continuous rice (1,185 kg/ha) and the cropping sequence incorporating a natural bush fallow (1,175 kg/ha) did not differ, but were higher for the improved fallow system (1,304 kg/ha). This suggests that nutrient contribution from the leguminous cover crop made up for critical crop N requirements in the improved fallow. Stochastic dominance of grain yield distributions from the improved fallow system, relative to the other two cropping systems, was more dramatic with no N fertilizer application compared to treatments with 30 kg/ha N. Average returns were highest for the improved fallow system, followed by the natural bush fallow‐cropping system, and then continuous rice, under the no N fertilizer treatment regime. With 30 kg/ha N fertilizer, income risk efficiency was less clear (compared to treatments with no N fertilizer), especially between continuous rice and the improved fallow treatment, because of faster N mineralization effects on continuous rice. In contrast, the improved cover crop fallow system completely dominated the natural bush fallow treatment under both fertilizer regimes. Rice production systems that incorporated the leguminous cover crop fallow were superior to the natural bush fallow system, based on both grain yield and average farm income risk‐efficiency considerations.
Farmers' perceptions of benefits and factors affecting the adoption of improved dual‐purpose cowpea in the dry savannas of Nigeria
Authors: Kristjanson P. , Okike I. , Tarawali S. , Singh B. B. , Manyong V. M.
Published: August 2010

This study links participatory research methods, geographic information systems (GIS) techniques, village and household‐level surveys, and a tobit analysis to examine the adoption and impact issues related to a new technology, improved varieties of dual‐purpose cowpea (IDPC), developed by International Institute of Tropical Agriculture (IITA) and International Livestock Research Institute (ILRI) and recently released in Nigeria. The article analyzes factors affecting the adoption and impact of the technology across different socioeconomic domains as defined by degree of market access and population density. The results show multiple benefits from this flexible leguminous crop, many of which relate to the fodder and soil fertility‐enhancing aspects of IDPC rather than higher grain yields per se. The intensity of adoption was affected by different village‐ and household‐level factors in each socioeconomic domain, allowing more sharply defined recommendation domain‐targeting strategies. The multiple research approaches taken also provided useful lessons at different system levels regarding the benefits of, and perceived problems with, this technology for researchers, development practitioners, and policy makers. The collaborative research approaches taken in this study are helping to close the “feedback loop” from farmers back to researchers and others attempting to disseminate the technology, and by doing so, should contribute to faster and more widespread uptake of this technology.
Organization of the peripheral nervous system
Authors: Sternini C.
Published: August 2010

The peripheral nervous system comprises the autonomic and sensory (afferent) nervous systems. Major advances in our understanding of the autonomic and sensory transmission and function include the recognition of the phenotypic expression of a variety of transmitters and modulators that often coexist in individual neurons, the concept of co‐transmission and chemical coding, the evidence for local effector functions of primary afferent nerves, and the discovery of plasticity of both the autonomic and the sensory nervous system during development, aging, diseases states, and inflammation. Co‐transmission or plurichemical transmission, which indicates the release of more than one chemical messenger from the same neuron, enables autonomic and sensory neurons to exert a fine and highly regulated control of various functions such as circulation and immune response. The concept of chemical coding, in which the combination of transmitters/modulators is established, allows the identification of functional classes of neurons with their projections and targets. In addition to transmitters and modulators, autonomic and sensory neurons express multiple receptors, including G‐protein‐coupled and ion‐gated receptors, further supporting the complexity of autonomic and sensory transmission and function. Autonomic neurons regulate the internal environment and maintain multiple homeostatic functions, and sensory neurons act as receptive structures that activate their targets in response to stimulation but also exert effector functions including the control of blood flow and vascular permeability, maintenance of mineralized tissue, and regulation of gene expression.
α‐MSH and cAMP signalling in normal human melanocytes
Authors: Buscà R.
Published: August 2010

Melanocytes are neural crest‐derived skin cells specialized in the synthesis of melanin pigments responsible, in human, for skin and hair colour. The pro‐opiomelanocortin peptide, α‐MSH is a strong melanogenic agent secreted by keratinocytes following UV radiation. α‐MSH through the binding to the MC1R and activation of the cyclic AMP pathway plays a pivotal role in melanocyte differentiation and in the regulation of skin pigmentation. During the last few years, we have elucidated the molecular events linking the cAMP pathway to melanogenesis upregulation. This cascade involves the activation of protein kinase A and CREB transcription factor, leading to the upregulation of the expression of microphthalmia‐associated transcription factor (MITF). MITF binds and activates the melanogenic gene promoters thereby increasing their expression, which results in an increased melanin synthesis. Beyond this simplified scheme, other intracellular signalling pathways are regulated by cAMP and participate to the regulation of melanocyte differentiation. Indeed, cAMP inhibits the phosphatidyl inositol 3‐kinase pathway, leading to the inhibition of AKT and to the activation of GSK3β. This kinase phosphorylates MITF and allows its binding to the target sequence. Such pathways are involved in the upregulation of melanogenesis. α‐MSH and cAMP signalling also regulate melanocyte dendricity, and melanosome transport through the inhibition of the Rho GTPase cascade that function downstream the PI3 kinase. It should be also mentioned that cAMP activates the ERK pathway through a melanocyte‐specific pathway involving Ras and B‐Raf. The activation of ERK and RSK1 leads to the phosphorylation of MITF and target MITF to the proteasome degradation pathway. Interestingly, several proteins involved in melanocyte differentiation by α‐MSH (MC1R, PI3K, B‐Raf and MITF) have also been implicated in the development of melanoma, suggesting that the cAMP pathway could influence melanocyte transformation.
Regulation of MC1R signalling by G‐protein‐coupled receptor kinases
Authors: García‐Borrón J. C.
Published: August 2010

The melanocortin 1 receptor (MC1R) is a key regulator of melanocyte proliferation and differentiation and a major determinant of human skin phototype and skin cancer risk. Although the regulation of MC1R gene expression is fairly well understood, little is known about regulatory mechanisms acting at the protein level. In particular, no information is available on homologous desensitization of MC1R signalling. We studied MC1R and Mc1r desensitization and found that: 1) MC1R and Mc1r in melanoma cells undergo homologous desensitization, demonstrated by decreases in cAMP contents upon continuous exposure to agonists, 2) desensitization is not dependent on PKA, PKC, calcium mobilization or MAPKs but is agonist dose dependent, suggesting a role of receptor occupancy, 3) melanoma cells express two members of the GRK family of serine/threonine kinases, GRK2 and GRK6, 4. These kinases are expressed in normal melanocytes, 5) in cotransfection experiments performed with HEK 293T cells, GRK2 strongly impairs agonist‐dependent signalling by MC1R or Mc1r, 6) expression of a dominant negative GRK2 mutant in melanoma cells increases their cAMP response to MC1R agonists, 7) cotransfection of HEK 293T cells with GRK6 and MC1R inhibits both basal and agonist‐dependent signalling, and 8) cAMP production in agonist‐stimulated melanoma cells is strongly impaired by enrichment with GRK6 following stable transfection. Therefore, GRK2 and GRK6 are key regulators of MC1R signalling and may be important determinants of normal and pathological skin pigmentation.
The role of accessory proteins in melanocortin receptor signaling
Authors: Barsh G. , Candille S. , He L. , Aradhya S. , Kerns J.
Published: August 2010

Switching from eumelanin to pheomelanin synthesis during hair growth is accomplished by transient synthesis of agouti protein, an inverse agonist for the melanocortin 1 receptor (Mc1r). The ability of agouti to signal via the Mc1r requires two additional genes, Attractin (Atrn) and Mahogunin (Mgrn1), which encode a type I transmembrane protein and an E3 ubiquitin ligase, respectively. Atrn and Mgrn1 are genetically upstream of the Mc1r, but transgenic and biochemical studies indicate that all three genes act in a melanocyte‐autonomous manner. To gain additional insight into pigment‐type switching, we have carried out biochemical and cell biologic studies which suggest that Mgrn and Atrn are part of a conserved biochemical and genetic pathway that acts to regulate Mc1r‐dependent signaling. We have also used an additional genetic model system based on coat color in dogs, in which we find that dominant inheritance of black coat color is caused neither by Mc1r nor by agouti, but instead maps to a region not previously implicated in pigmentation genetics.
Cutaneous neuroimmunology – lessons from the hair follicle
Authors: Paus R. , Ito N. , Ito T. , Peters E. , Bodo E. , Liotiri S. , Biro T. , Arck P.
Published: August 2010

The hair follicle offers an exquisite model for the experimental exploration of key issues of cutaneous neuroimmunology, for example, how local, intracutaneous and systemic stress–response systems are integrated with the skin immune system and with epithelial–mesenchymal interactions (as they occur during hair follicle growth and cycling). Previously, we had shown that skin mast cells, which operate as central switchboards of inflammation and tissue remodelling, also are important regulators of hair growth in mice and that endogenous, immunomodulatory mast cell secretagogues are potent hair growth modulators. This is true both for secretagogues that are generated by the hair follicle epithelium itself (e.g. ACTH) and for mast cell‐activating neuropeptides synthesized by the sensory hair follicle innervation (e.g. SP). Also, we had shown that the prototypic stress‐associated neuropeptide, SP, plays a crucial role in mediating the hair growth‐inhibitory, mast cell‐activating, inflammation‐ and catagen‐promoting properties of chronic psychoemotional stress on murine hair follicles. Now, we show that the immunomodulatory and mast cell‐activating neurotrophin, NGF, is also crucially involved in mediating the inhibitory effects of stress on murine hair growth. Furthermore, the central, stress‐related neurohormone CRH, a recognized mast cell secretagogue which is expressed by the hair follicle epithelium, also is a hair growth inhibitor and activates a fully functional peripheral equivalent of the hypothalamic‐pituitary‐adrenal axis within organ‐cultured human scalp hair follicles, including the synthesis and secretion of cortisol as well as the induction of classical feedback loops. We also demonstrate that one of the melanocortins whose intrafollicular synthesis is stimulated by CRH (α‐MSH) is a potent suppressor of MHC class I expression in situ and is thus capable of restoring the collapsed immune privilege of human anagen hair bulbs, while SP upregulates the ectopic expression of MHC class I, thus endangering the hair follicle immune privilege. Finally, we show that vanilloids long exploited as experimental tools for neuroimmunological research in the skin (capsaicin) can, in fact, directly modulate human hair growth via the stimulation of vanilloid receptors (VR1) expressed by the follicle epithelium, in addition to stimulating vanilloid expressed by skin mast cells. Therefore, the hair follicle offers an ideal, highly instructive and clinically most relevant research model for dissecting how nervous system, central and peripheral (neuro‐) endocrine signalling loops and the immune system interact in order to adapt skin functions to changing environmental conditions (e.g. in response to external stressors, by alterating, e.g. keratinocyte proliferation/apoptosis, skin immune status, as well as defined cutaneous metabolic and endocrine activities).
Neuroendocrine regulation of the sebaceous gland
Authors: Zouboulis Ch. C.
Published: August 2010

The sebaceous gland is the organ conferring upon the skin an endocrine function. It also seems to be involved in responses to stress expressing receptors for neuropeptides such as corticotropin‐releasing hormone (CRH), α‐melanocyte‐stimulating hormone (α‐MSH), β‐endorphin, vasoactive intestinal polypeptide, neuropeptide Y, and calcitonin gene‐related peptide. CRH is the most proximal element of the hypothalamic‐pituitary‐adrenal (HPA) axis, and it acts as central coordinator for neuroendocrine and behavioral responses to stress. The CRH/CRH‐binding protein/CRH receptor loop is expressed in human sebocytes in vivo and in vitro and is regulated and biologically active in cultured sebocytes. CRH may be an autocrine sebocyte factor that exerts homeostatic lipogenic activity by controlling the expression of Δ5‐3β‐hydroxysteroid dehydrogenase, whereas testosterone and growth hormone induce CRH negative feedback. α‐MSH and calcitonin gene‐related peptide are not produced by human sebocytes and downregulate the enhanced IL‐8 synthesis in IL‐1β‐challenged cells, therefore exhibiting an anti‐inflammatory effect. β‐endorphin is also a paracrine neuropeptide for human sebocytes which suppresses their proliferation induced by epidermal growth factor in Ca2+‐rich medium. Moreover, substance P‐immune reactive nerves are localized near the sebaceous glands and can stimulate undifferentiated sebocytes of the outmost sebaceous gland layer to express neutral endopeptidase, a substance P‐inactivatimg molecule. In addition, substance P stimulates lipid synthesis in human sebocytes. In conclusion, sebaceous glands may be involved in a hypothalamus‐pituitary‐skin pathway conceptually similar to that of the HPA axis. The current data implicate neuropeptides to possibly play a strategic role in the regulation of sebaceous gland activity in close coordination with other hormones making likely that they are involved in the development of various skin diseases.
Role of protease‐activated receptor‐2 during cutaneous inflam‐mation and the immune response
Authors: Steinhoff M.
Published: August 2010

Protease‐activated receptors (PARs) constitute a new subfamily of G‐protein‐coupled receptors with seven transmembrane domains which are activated by various serine proteases such as thrombin, cathepsin G, trypsin or tryptase, and bacterial proteases or mite antigens, for example. PAR2 is a receptor for mast cell tryptase or house dust mite allergens, which is released during inflammation and allergic reactions. In the skin, PAR2 is diversely expressed by keratinocytes, endothelial cells, and occasionally sensory nerves of human skin in various disease states. Moreover, immunocompetent cells such as T cells and neutrophils express functional PAR2, thereby contributing to inflammation and host defense. Own data revealed that PAR2 contributes to neurogenic inflammation by releasing neuropeptides from sensory nerves resulting in oedema, plasma extravasation and infiltration of neutrophils. Thus, mast cells may communicate with sensory nerves in inflammatory tissues by activating PAR2 via tryptase. Moreover, PAR2 agonists upregulate the expression of certain cell‐adhesion molecules and cytokines such as interleukin‐6 and interleukin‐8 on dermal microvascular endothelial cells or regulate neutrophil migration, indicating that PAR2 plays an important role in leucocyte/endothelial interactions. These effects may be partly mediated by NF‐κB, an important transcription factor during inflammation and immune response. PAR2 stimulation results in the activation of NF‐κB on microvascular endothelial cells and keratinocytes, thereby regulating ICAM‐1 expression. We also demonstrate evidence for a diverse expression of PAR2 in various skin diseases and highlight the recent knowledge about the important role of PAR2 during inflammation and the immune response. Together, PAR2‐modulating agents may be new tools for the treatment of inflammatory and allergic diseases in the skin.
Functional role of somatostatin receptors in neuroendocrine and immune cells
Authors: Van Hagen P. M.
Published: August 2010

Somatostatin is a neuropeptide that is widely distributed throughout the body. It was first identified as a growth hormone release‐inhibiting factor synthesized in the hypothalamus. Outside the central nervous system (CNS), the peptide is present in endocrine as well as non‐endocrine tissues. Somatostatin functions as a peptide with a generally inhibitory action in the CNS and endocrine system. In the CNS, it can act as a neurotransmitter, while in peripheral tissues, it regulates endocrine and exocrine secretion and acts as a modulator of motor activity in the gastrointestinal tract. Besides these actions, somatostatin has also been shown to have antiproliferative effects in vitro. Somatostatin binds to five different subtype receptors (sst) which are differently expressed by various tissues. These receptors have been described also in the immune system of various species including humans. It is therefore a long known fact that human immune cells and their progenitors can express somatostatin receptors. As a consequence, ssts were described in primary and secondary human immune organs. Somatostatin produced by immune cells may act as an autocrine or paracrine regulator within the local immune microenvironment in mice. The synthesis, however, of somatostatin has not been demonstrated in human immune cells. In a recent study, the expression of another somatostatin‐like peptide; cortistatin‐17 (CST) was found in human lymphoid tissues, immune cells and lymphoid cell lines. On the basis of these observations, a role for CST as an endogenous ligand for sst in the human immune system, rather than SS itself was hypothesized. Somatostatin receptor expression can be detected in vivo somatostatin receptor scintigraphy after injection of 111In‐labelled octreotide, a somatostatin analogue. This technique is used extensively for the localization of neuroendocrine tumours and other malignancies that express high levels of sst. Among the non‐neuroendocrine tumours that can be visualized by octreotide scintigraphy are malignant lymphomas, both T and B non‐Hodgkin's lymphomas and Hodgkin's disease lymphomas. In a number of infectious diseases (e.g. tuberculosis), autoimmune diseases (e.g. Graves' ophthalmopathy) and other immune‐mediated diseases (e.g. sarcoidosis and rheumatoid arthritis), the sites of inflammation can also be visualized. Based on the receptor pattern in autoimmune diseases, controlled studies are warranted to investigate the efficacy of somatostatin analogues in the treatment of autoimmune diseases like rheumatoid arthritis. In rheumatoid arthritis, not only immune cells can be targeted by these analogues but also synoviocytes and synovial blood vessels. Moreover, receptor expression during treatment in such diseases can be monitored by octreotide scintigraphy.
Neuropeptides, a never‐ending story? Termination of cutaneous inflammation by proteolytic peptidases
Authors: Scholzen T. E. , Luger T. A.
Published: August 2010

Neuropeptide‐specific peptidases such as neutral endopeptidase (NEP, CD10) and angiotensin‐converting enzyme (ACE, CD143) effectively control the bioavailability of neuropeptides released from sensory nerves, immune and skin cells during neurogenic inflammation. Drug inhibition or genomic deletion of NEP or ACE results in a substance P (SP‐) and bradykinin‐dependent augmentation of murine allergic contact dermatitis (ACD) by affecting ACD sensitization and elicitation. The functional absence of NEP enhanced ACD inflammation by promoting bone marrow‐derived dendritic cell (BmDC) maturation and function. In vitro haptenized BmDCs from NEP–/– mice neurokinin‐1 receptor‐dependently stimulated proliferation of antigen‐specific NEP–/– and NEP+/+ T cells with higher efficacy compared to NEP+/+‐mice BmDCs. Importantly, adoptive transfer of in vitro haptenized DC from NEP–/– into wild‐type mice significantly promoted ACD in comparison with transfer of NEP+/+DC. Likewise, hapten uptake into DC from regional lymph nodes during ACD sensitization is increased in NEP–/– mice compared to normal mice. Moreover, in CD10‐ and CD143‐expressing human dermal microvascular endothelial cells and keratinocytes, UV light and inflammatory mediators regulated mRNA and protein expression, as well as proteolytic activity of these peptidases, which may be important for cell survival and the outcome of an inflammatory response. Likewise, NEP and ACE are also involved in the proteolytic processing of neuroendocrine hormones such as adrenocorticotropin and α‐melanocyte‐stimulating hormone. Thus, present data indicate that ACE and NEP by proteolytic cleavage of peptide mediators have a significant role in controlling cutaneous inflammatory responses.
Neural regulation of endothelial cell‐mediated inflammation
Authors: Ansel J. C.
Published: August 2010

There is much evidence that neurocutaneous interactions may play an important role in modulating a wide variety of biological processes in the skin including inflammation. Perhaps, the key cell type for directing inflammatory processes in the skin is the dermal microvascular endothelial cell (DMEC). All leukocyte trafficking during cutaneous inflammation is mediated by DMEC. This presentation will review various ways in which the cutaneous neurosensory system can modulate DMEC activities, and how this may lead to novel approaches in our understanding and treatment of inflammatory skin disease.
The role of neuropeptides and neuropeptide‐degrading enzymes in wound healing
Authors: Olerud John E.
Published: August 2010

Thirty to 40% of diabetic patients develop sensory neuropathy. Neuropathy is a major causal factor in diabetic ulcers. Only 31% of neuropathic diabetic ulcers heal in 20 weeks. Patients with neuropathy have a 15.5‐fold excess risk of amputation. Diabetic patients with neuropathy particularly lose epidermal and papillary dermal sensory nerves which release neuropeptides such as substance P (SP). Neutral endopeptidase (NEP), the enzyme that degrades SP, is dramatically over expressed in patients with diabetic neuropathy. SP has positive effect on wound healing. Treatment strategies related to the nervous system for prevention and treatment of diabetic ulcers currently being studied include prevention of neuropathy with tight control of blood glucose, application of neuropeptides, nerve growth factors (NGF), and antagonists of NEP.
Relevance of leptin for cutaneous wound healing
Authors: Goren I. , Pfeilschifter J. , Frank S.
Published: August 2010

Recently, we demonstrated a direct role for leptin in skin repair. However, pair‐fed experiments with caloric restricted ob/ob mice clearly suggested that resolution of insulin resistance also represents a pivotal process that contributes to an accelerated healing. Immunohistochemistry revealed wound keratinocytes to be the insulin‐sensitive skin compartment, as the cells strongly expressed the insulin receptor (InsR). We now focused to analyze the expression and activation of insulin‐signaling components in wound keratinocytes of healthy, diabetic, and leptin‐treated mice. First, we observed a downregulation of the InsR expression in normal wounds, which is precisely co‐regulated by a downregulation and phosphorylation‐dependent inactivation of its negative regulator, the InsR‐associated protein tyrosine phosphatase‐1B (PTP‐1B). In line, a strong expression of InsR during late repair was associated with an increased presence of a dephosphorylated and thus active PTP‐1B and the InsR substrate (IRS)‐1‐ and ‐2‐signaling molecules, suggesting that the InsR, its negative regulator PTP‐1B, and both IRS were functionally connected during healing. Impaired healing conditions were characterized by a loss of InsR, IRS‐1, and ‐2 expression but paralleled by increased amounts of phosphorylation‐inactived PTP‐1B. This finding suggested a regulatory mechanism to compensate for the loss of insulin‐signaling components and to allow a more efficient signaling from the reduced amount of remaining InsR and IRS‐1/‐2 during impaired healing. Interestingly, systemic treatment of ob/ob mice with leptin resolved the dysregulated availability of the insulin‐signaling components: InsR/IRS expression was upregulated, and the amount of dephosphorylated and thus active PTP‐1B co‐increased in wounds of treated animals. Finally, our findings could be confirmed by analysis of in vivo activation of protein kinase B as one possible readout for insulin signaling.
Nerve growth factor and its role in epidermal homeostasis
Authors: Pincelli C.
Published: August 2010

Nerve growth factor (NGF) belongs to the neurotrophin (NT) family which also includes brain‐derived neurotrophic factor (BDNF), neurotrophin‐3 (NT‐3) and NT‐4/5. Human keratinocytes synthesize and release all NT and express both the low‐ (p75NTR) and the high‐affinity receptor (trk). Keratinocyte stem cells (KSCs) express higher levels of NGF as compared with young transit amplifying (TA) cells, while NGF levels are almost undetectable in TA cells. While trk is expressed in all basal keratinocytes in a homogeneous pattern, p75 is expressed only in a subpopulation of basal keratinocytes. p75 is strongly expressed in young TA cells, whereas it is scarcely visible in TA cells and absent in KSCs. Moreover, Ca++ strongly enhances p75 expression in subconfluent cells. NGF stimulates keratinocyte proliferation and protects keratinocytes from spontaneous and UVB‐induced apoptosis. These activities are performed through trk receptor, while the role of p75 is more controversial. p75 belongs to the TNF receptor superfamily, and it shares with other members of this family a death domain which signals apoptosis upon binding to the ligands. BDNF or NT‐4 induces keratinocyte apoptosis through p75, while the trk inhibitor K252 augments cell death in p75‐overexpressing keratinocytes. BDNF also activates c‐JUN kinase (JNK) in p75‐transfected keratinocytes. Taken together, these data point to a dual role of NT in epidermal homeostasis.
α‐MSH as a modulator of apoptosis in cutaneous biology
Authors: Böhm M. , Luger T. A. , Scholzen T. , Schwarz T. , Schwarz A.
Published: August 2010

The molecular pathways regulating ultraviolet (UV) radiation‐induced apoptosis of melanocytes, a cell population crucially involved in the protection of epidermal keratinocytes against the harmful effects of UV light, are poorly characterized. We show that the α‐melanocyte‐stimulating hormone (α‐MSH) blocks UVB‐induced apoptosis of normal human melanocytes in vitro. The effect of α‐MSH is not restricted to melanocytes but is also operative in cells that do not produce melanin, for example in human epidermal keratinocytes and in dermal fibroblasts. α‐MSH not only delays but also protects melanocytes from UVB‐induced cell death. The anti‐apoptotic activity of α‐MSH is not mediated by a filtering effect or induction of melanin synthesis. α‐MSH also does not induce changes in the cell cycle distribution or expression of Bcl2, Bclx, CD95 (Fas/APO‐1) and FasL. In contrast, α‐MSH markedly reduces the formation of cyclobutane pyrimidine dimers induced by UVB radiation. Human dermal fibroblasts carrying a defective XPA gene are not protected from UVB‐induced apoptosis by α‐MSH. These results highlight a novel biological activity of α‐MSH as well as novel regulatory pathways within the UV response of skin cells targeted by this neuropeptide.
Antioxidant and anti‐inflammatory activities of melanocortin peptides
Authors: Haycock J. W. , Hill R. P. , Elliott R. J. , Wagner M. J. , MacNeil S.
Published: August 2010

α‐Melanocyte‐stimulating hormone (α‐MSH) has previously been identified as a potent anti‐inflammatory agent in various tissues including the skin. It operates by binding to the melanocortin‐1 receptor (MC‐1R) which results in the elevation of cyclic AMP. α‐MSH opposes the action of several proinflammatory cytokines including tumour necrosis factor‐α (TNF‐α). We have shown that α‐MSH can inhibit TNF‐α‐stimulated activation of nuclear factor‐κB (NF‐κB) in human cultured melanocytes, melanoma cells, keratinocytes, fibroblasts, Schwann cells and olfactory ensheathing cells. It also inhibits TNF‐α‐stimulated upregulation of intercellular adhesion molecule‐1 (ICAM‐1) in many of these cells and can inhibit peroxide‐stimulated activation of glutathione peroxidase, suggesting an antioxidant role. α‐MSH is also able to stimulate intracellular calcium release in keratinocytes and fibroblasts (which do not readily show detectible cyclic AMP elevation) but only in the presence of PIA (an adenosine agonist). The carboxyl terminal tripeptides KPV/KP‐D‐V are reported to be the minimal sequences necessary to convey anti‐inflammatory potential, but evidence on how they act is not fully known. Stable transfection of Chinese hamster ovary cells with MC‐1R suggests that the KPV peptides operate by this receptor, at least by elevating intracellular calcium. Elevation of cyclic AMP by these tripeptides has not been detected in any cell type studied; however, calcium elevation can inhibit TNF‐α‐stimulated NF‐κB activity (as for cyclic AMP). In conclusion, the MSH peptides convey anti‐inflammatory and antioxidant activity in many cell types in skin and nerve, by counteracting proinflammatory cytokine signalling. The KPV peptides appear to act functionally via the MC‐1R and can also elevate intracellular calcium.
Melatonin as an antioxidant – a role in human aging?
Authors: Reiter R. J.
Published: August 2010

N‐Acetyl‐5‐methoxytryptamine, commonly known as melatonin, was isolated and structurally identified by a dermatologist, Aaron B. Lerner, in 1958. His interest stemmed from the fact that melatonin has potent skin‐lightening effects in amphibians and some other non‐mammalian species. In humans, however, melatonin is not capable of lightening skin or in reducing pigmentation. While melatonin synthesis is the best known to occur in the pineal gland, it is also produced in several other organs including the skin. Melatonin is a powerful, multifaceted direct free radical scavenger and indirect antioxidant. Numerous studies have shown that melatonin production wanes with increasing age and its loss has been speculated to be consequential in free radical‐mediated cellular and organ deterioration that occurs in the elderly. Additionally, a number of free radical‐related diseases, e.g. Alzheimer's disease, Parkinsonism, cataract formation, etc., may in part be a consequence of the loss of endogenous melatonin production. The administration of melatonin in animal models of these diseases typically defers their progression and limits their severity. Likewise, due to its antioxidant properties and via other mechanisms, melatonin may reduce skin aging. Melatonin, when applied topically to the skin of humans, has obvious protective effects against ultraviolet (UV) light‐induced erythema. Also, lipid peroxidation in human skin fibroblasts due to their exposure to UV‐B is reduced when melatonin is present.
Acetylcholine receptors in cutaneous biology – receptorology and therapeutic implications
Authors: Grando S.
Published: August 2010

Free cytotransmitter acetylcholine (ACh) is present in physiologically relevant concentrations in human skin, and ACh and cholinergic drugs alter vital functions of keratinocytes (KCs). KCs respond to ACh via classical ACh receptor types that use Ca2+ as a second messenger. The repertoire of cholinergic receptors changes with cell maturation, so that at each stage of their development, KCs respond to ACh via different combinations of nicotinic (nAChR) and muscarinic (mAChR) receptors. Basal KCs respond to ACh predominantly via α3β2(β4) ± α5 nAChRs and the M3 mAChR; prickle KCs have more α5‐containing α3 nAChRs and also express α9 nAChR as well as M4 and M5 mAChRs; granular KCs posses mainly α7 nAChR and M1 mAChR. We used three independent approaches to elucidate role of each receptor in KC biology: 1) Subtype selective drugs, 2) Gene silencing with small interfering RNA or antisense oligonucleotides, and 3) Gene knockout in transgenic mice. Obtained results indicate that KC nAChRs and mAChR exhibit synergistic control of cell adhesion and crawling locomotion. KC cell‐cell adhesion is regulated through α3 and α9 nAChRs as well as M3 mAChR. KC chemokinesis is controlled by α3 and α7 nAChRs and M3 and M4 mAChRs. KC chemotaxis toward nicotinic agonists is mediated by α7 nAChR. These findings offer novel insights into the mechanisms of ACh‐mediated modulation of epidermalization and may aid the development of novel methods to promote wound healing and inhibit tumor metastasis.
Co‐culture of neurones with Merkel cells and keratinocytes
Authors: Château Y. , Dorange G. , Clément J. F. , Rougier N. , Misery L.
Published: August 2010

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.
NMDA receptors influence the intracellular calcium concen‐tration and the expression of differentiation markers in HaCaT cells
Authors: Fischer M. , Glanz D. , Klapperstueck T. , Wohlrab J. , Fiedler E. , Marsch W. C.
Published: August 2010

Ionotropic glutamate receptors (ligand‐gated, ion‐channel proteins) of the N‐methyl‐d‐aspartate (NMDA) receptor type could enable a transmembranous calcium influx from the extracellular space. Though ionotropic glutamate receptors are predominantly neuronal receptors, they are also expressed in non‐neuronal tissues like keratinocytes. Therefore, investigations were performed to study the function of NMDA receptors in HaCaT cells. The intracellular calcium concentration of HaCaT cells was studied under the influence of the selective receptor agonist NMDA and the selective NMDA antagonist MK‐801. The proliferation of HaCaT cells was investigated using the crystal‐violet method. Furthermore, the expression of Cytokeratin 10 and Filaggrin was examined in HaCaT cells after blocking NMDA receptors with MK‐801. Using NMDA, there was a significant increase in the number of HaCaT cells showing elevated intracellular calcium concentration, at a dose between 25 µm and 1 mm (up to 84.6% of cells). The NMDA‐associated calcium influx could be significantly suppressed by prior application of MK‐801. There was no influence of NMDA on the proliferation of HaCaT cells. There was also no cytotoxic effect of NMDA (up to 1 mm). The expression of Cytokeratin 10 and Filaggrin could be suppressed by blocking NMDA receptors with MK‐801. The investigations show that glutamate receptors of the NMDA‐type play a role in the differentiation of HaCaT cells by regulating their intracellular calcium concentration.
Synergistic regulation of neuropeptide levels by internal and external stimuli
Authors: Hosoi J. , Inoue K. , Ashida Y. , Tsuchiya T.
Published: August 2010

The skin is the most peripheral organ confronting the external environment. We found that the level of substance P is regulated by both internal and external stimuli. Mock interview induced the acute stress in human assessed by the measurement of serum cortisol. The serum level of substance P increased within 1 h after the mock interview. Interestingly, the increase was suppressed by inhalation of 1,3‐dimethoxy‐5‐methylbenzene. Similar regulation was observed in mice. Furthermore, restraint or the intravenous administration of substance P induced the activation of cutaneous mast cells. Housing under the condition of lower humidity (about 30%) for 24 h caused the increase in the substance P level both in peripheral blood and in the skin. Restraint for 2 h during the housing under the condition of lower humidity increased the substance P level further. The activation of cutaneous mast cells under the dry condition was reported. These data suggest that cutaneous neuropeptide level is regulated by both psychological and environmental mechanisms. The regulation may cause the downregulation of the threshold of the induction of itch and inflammation.
RAB4a‐ and RAB11a‐dependent recycling and resensitization of the neurokinin 1 receptor
Authors: Roosterman D. , Schmidlin F. , Steinhoff M. , Bunnett N. W.
Published: August 2010

Neurokinin 1 receptor (NK1R) is an important mediator of depression, pain, and inflammation. Understanding the molecular mechanisms regulating NK1R trafficking is of importance because of the essential role of receptor transport in regulating cell function and probably disease. We examined NK1R trafficking and resensitization with regard to the concentration dependency of the ligand, substance P. NK1R trafficking was characterized using GFP‐coupled β‐arrestin, rab5, rab4, and rab11. NK1R resensitization was calculated by calcium mobilization assays. NK1R stimulated with 10 nm substance P (SP) rapidly internalized. NK1R and β‐arrestin were sequestrated in the perinuclear location, as demonstrated by confocal microscopy. NK1R did not reappear at the cell surface 30 min after agonist stimulation. Expression of a dominant negative rab5a mutant impaired translocation from superficial to perinuclear locations at the stage of the early endosome. Similarly, β‐arrestin and rab5a induced rapid internalization of NK1R stimulated with 1 nm SP. In contrast, 1 nm SP mediated transport of receptor and β‐arrestin from the plasma membrane to only superficial vesicles. NK1R rapidly recycled after rab4 and rab11 activation. Stimulation with 1 nm SP did not induce sequestration of NK1R and associated proteins but resulted in receptor resensitization in less than 5 min. Overexpression of rab5a‐induced NK1R transport to perinuclear compartments. Thus, while β‐arrestin appears to be important for receptor endocytosis, the transport of NK1R seems to be regulated by rab5a. This study identifies a concentration‐dependent trafficking and resensitization mechanism of NK1R, indicating a new function of rab5 as a control protein for directing NK1R into different intracellular compartments and suggesting a role of rab11 in GPCR recycling via early sorting endosomes.
Mouse reconstructed skin from hair buds developed innervated hair follicles after grafting on athymic mice
Authors: Larouche D. , Gagnon V. , Berthod F. , Deschambeault A. , Germain L.
Published: August 2010

Recovery of sensation in grafted skin is a major concern in reconstructive surgery. Because the pilosebaceaous unit represents an important tactile organ within the skin, we developed a tissue‐engineered reconstructed skin allowing the formation of complete pilosebaceous units after grafting, and we evaluated nerve regeneration. This model is based on our self‐assembly approach of tissue engineering. Sheets obtained after culturing mouse fibroblasts for 35 days with ascorbic acid, which allows collagen synthesis, are superposed. Thereafter, hair buds taken from dermis of newborn mice after collagenase digestion or freshly isolated newborn mice keratinocytes were seeded on the reconstructed dermis, cultured 10 days and grafted on athymic mice. One month after grafting, complete pilosebaceous units where obtained in reconstructed skin containing initially hair buds and were maintained up to 6 months. NF150 (neurofilaments) immunostaining revealed systematical localization of nerves around the pilosebaceous units 1 month after grafting. In contrast, nerves colonization was almost always absent when hair buds were not included in the grafted reconstructed skin. However, after 6 months, the nerves were present in both skin grafted (with or without hairs). These results suggest that the presence of hairs inside the reconstructed skin promotes nerves regeneration after grafting. Furthermore, the connection of pilosebaceous units with nerves suggests that they may be functional for the detection of the tactile stimuli.
Detection of ACTH, MC‐1R and MC‐4R immunoreactivity in human terminal and vellus hair follicles
Authors: Stieler K. , Vogt A. , Li Z. , Böhm M. , Blume‐Peytavi U.
Published: August 2010

Pro‐opiomelanocortin (POMC) peptides such as ACTH and α‐MSH play an important role in the pigmentation of human skin and hair. Both peptides bind to a family of transmembrane receptors known as the melanocortin receptors (MC‐Rs). To investigate the in situ expression of α‐MSH, ACTH and MC‐Rs, we performed immunohistochemical studies on human terminal and vellus hair follicles. Immunoreactivity for ACTH, MC‐1R and MC‐4R was detected in both human terminal and vellus hair follicles, with a pronounced increase of staining intensity in the suprabulbar and bulbar region of anagen hair follicles. The MC‐1R immunoreactivity in situ was in accordance with in vitro studies showing expression of MC‐1R at the RNA level in human hair follicle keratinocytes. There was no detectable difference in the staining pattern of strong, pigmented terminal hair follicles as compared with fine, silky and non‐pigmented vellus hair follicles. These results indicate that POMC‐derived peptides may play a regulatory role in the human hair follicle independent of the pigmentation process. The expression pattern of ACTH and its receptors MC‐1R and MC‐4R in the human hair follicle correlates with the immune privilege of the human hair follicle which is characterized by the absence of immune cells in the bulbar region of anagen hair follicles. Thus, ACTH may possibly be involved in the maintenance of the peribulbar immune privilege in both, terminal and vellus hair follicles.