CGRP, PACAP, and VIP Modulate Langerhans Cell Function by Inhibiting NF-κB Activation

Airway and cardiovascular remodeling in chronic obstructive pulmonary disease (COPD) as a target for transient receptor potential ankyrin 1 (TRPA1) channel modulators

Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation, which leads to airway remodeling (AR). AR refers to various structural changes occurring in the airway wall, resulting in thickening, and narrowing of the airways. Apart from airways, and lung tissue, pulmonary vasculature also undergoes remodeling. Thus, the pressure in vascular bed is increased, leading to pulmonary hypertension and further right and left ventricle hypertrophy, as well as myocardial fibrosis. Currently, there is lack of effective treatment directly targeting airway and cardiovascular remodeling in the course of COPD. Due to a lot of research showing involvement of transient receptor potential ankyrin 1 (TRPA1) in respiratory disorders, it seems reasonable to consider this ion channel as a molecular target in treatment of remodeling consequences of COPD. The aim of this review is to summarize current knowledge of its role in this case and to identify areas requiring further research. Moreover, we provide few patented structures intended to treat chronic respiratory diseases, which may be worth investigating in the context of airway remodeling.

Neuroimmune interplay during type 2 inflammation: Symptoms, mechanisms, and therapeutic targets in atopic diseases

Type 2 inflammation is characterized by overexpression and heightened activity of type 2 cytokines, mediators, and cells that drive neuroimmune activation and sensitization to previously subthreshold stimuli. The consequences of altered neuroimmune activity differ by tissue type and disease; they include skin inflammation, sensitization to pruritogens, and itch amplification in atopic dermatitis and prurigo nodularis; airway inflammation and/or hyperresponsiveness, loss of expiratory volume, airflow obstruction and increased mucus production in asthma; loss of sense of smell in chronic rhinosinusitis with nasal polyps; and dysphagia in eosinophilic esophagitis. We describe the neuroimmune interactions that underlie the various sensory and autonomic pathologies in type 2 inflammatory diseases and present recent advances in targeted treatment approaches to reduce type 2 inflammation and its associated symptoms in these diseases. Further research is needed to better understand the neuroimmune mechanisms that underlie chronic, sustained inflammation and its related sensory pathologies in diseases associated with type 2 inflammation.

Control of myeloid cell functions by nociceptors

The immune system has evolved to protect the host from infectious agents, parasites, and tumor growth, and to ensure the maintenance of homeostasis. Similarly, the primary function of the somatosensory branch of the peripheral nervous system is to collect and interpret sensory information about the environment, allowing the organism to react to or avoid situations that could otherwise have deleterious effects. Consequently, a teleological argument can be made that it is of advantage for the two systems to cooperate and form an “integrated defense system” that benefits from the unique strengths of both subsystems. Indeed, nociceptors, sensory neurons that detect noxious stimuli and elicit the sensation of pain or itch, exhibit potent immunomodulatory capabilities. Depending on the context and the cellular identity of their communication partners, nociceptors can play both pro- or anti-inflammatory roles, promote tissue repair or aggravate inflammatory damage, improve resistance to pathogens or impair their clearance. In light of such variability, it is not surprising that the full extent of interactions between nociceptors and the immune system remains to be established. Nonetheless, the field of peripheral neuroimmunology is advancing at a rapid pace, and general rules that appear to govern the outcomes of such neuroimmune interactions are beginning to emerge. Thus, in this review, we summarize our current understanding of the interaction between nociceptors and, specifically, the myeloid cells of the innate immune system, while pointing out some of the outstanding questions and unresolved controversies in the field. We focus on such interactions within the densely innervated barrier tissues, which can serve as points of entry for infectious agents and, where known, highlight the molecular mechanisms underlying these interactions.

Anatomical contacts between sensory neurons and epidermal cells: an unrecognized anatomical network for neuro-immuno-cutaneous crosstalk

Sensory neurons innervating the skin are conventionally thought to be the sole transducers of touch, temperature, pain and itch. However, recent studies have shown that keratinocytes - like Merkel cells - act as sensory transducers, whether for innocuous or noxious mechanical, thermal or chemical stimuli, and communicate with intraepidermal free nerve endings via chemical synaptic contacts. This paradigm shift leads to consideration of the whole epidermis as a sensory epithelium. Sensory neurons additionally function as an efferent system. Through the release of neuropeptides in intimate neuroepidermal contact areas, they contribute to epidermal homeostasis and to the pathogenesis of inflammatory skin diseases. To counteract the dogma regarding neurocutaneous interactions, seen exclusively from the perspective of soluble and spreading mediators, this review highlights the essential contribution of the unrecognized anatomical contacts between sensory neurons and epidermal cells (keratinocytes, melanocytes, Langerhans cells and Merkel cells), which take part in the reciprocal dialogue between the skin, nervous system and immune system.

Immunomodulatory Role of Neuropeptides in the Cornea

The transparency of the cornea along with its dense sensory innervation and resident leukocyte populations make it an ideal tissue to study interactions between the nervous and immune systems. The cornea is the most densely innervated tissue of the body and possesses both immune and vascular privilege, in part due to its unique repertoire of resident immune cells. Corneal nerves produce various neuropeptides that have a wide range of functions on immune cells. As research in this area expands, further insights are made into the role of neuropeptides and their immunomodulatory functions in the healthy and diseased cornea. Much remains to be known regarding the details of neuropeptide signaling and how it contributes to pathophysiology, which is likely due to complex interactions among neuropeptides, receptor isoform-specific signaling events, and the inflammatory microenvironment in disease. However, progress in this area has led to an increase in studies that have begun modulating neuropeptide activity for the treatment of corneal diseases with promising results, necessitating the need for a comprehensive review of the literature. This review focuses on the role of neuropeptides in maintaining the homeostasis of the ocular surface, alterations in disease settings, and the possible therapeutic potential of targeting these systems.

Regulation of Carcinogenesis by Sensory Neurons and Neuromediators

Interactions between the immune system and the nervous system are crucial in maintaining homeostasis, and disturbances of these neuro-immune interactions may participate in carcinogenesis and metastasis. Nerve endings have been identified within solid tumors in humans and experimental animals. Although the involvement of the efferent sympathetic and parasympathetic innervation in carcinogenesis has been extensively investigated, the role of the afferent sensory neurons and the neuropeptides in tumor development, growth, and progression is recently appreciated. Similarly, current findings point to the significant role of Schwann cells as part of neuro-immune interactions. Hence, in this review, we mainly focus on local and systemic effects of sensory nerve activity as well as Schwann cells in carcinogenesis and metastasis. Specific denervation of vagal sensory nerve fibers, or vagotomy, in animal models, has been reported to markedly increase lung metastases of breast carcinoma as well as pancreatic and gastric tumor growth, with the formation of liver metastases demonstrating the protective role of vagal sensory fibers against cancer. Clinical studies have revealed that patients with gastric ulcers who have undergone a vagotomy have a greater risk of stomach, colorectal, biliary tract, and lung cancers. Protective effects of vagal activity have also been documented by epidemiological studies demonstrating that high vagal activity predicts longer survival rates in patients with colon, non-small cell lung, prostate, and breast cancers. However, several studies have reported that inhibition of sensory neuronal activity reduces the development of solid tumors, including prostate, gastric, pancreatic, head and neck, cervical, ovarian, and skin cancers. These contradictory findings are likely to be due to the post-nerve injury-induced activation of systemic sensory fibers, the level of aggressiveness of the tumor model used, and the local heterogeneity of sensory fibers. As the aggressiveness of the tumor model and the level of the inflammatory response increase, the protective role of sensory nerve fibers is apparent and might be mostly due to systemic alterations in the neuro-immune response. Hence, more insights into inductive and permissive mechanisms, such as systemic, cellular neuro-immunological mechanisms of carcinogenesis and metastasis formation, are needed to understand the role of sensory neurons in tumor growth and spread.

Calcitonin gene-related peptide upregulates IL-17A and IL-22 in γδ-T cells through the paracrine effect of langerhans cells on LC/γδ-T co-culture model

Intense mental stimulation and stress often directly induce or exacerbate psoriasis. On the contrary, patients with nerve injury and nervous system dysfunction have psoriasis remission. The nervous system plays an important role in the inflammatory process of psoriasis, and neuropeptides are considered as local mediators of disease maintenance. To examine the molecular mechanism involved in this, first we analyzed calcitonin gene-related peptide (CGRP)-treated langerhans Cells and γδ-T cells separately. CGRP induced IL-23 mRNA and protein expression via PDK1-Rsk signaling pathway. However, CGRP had no effect on secretion of IL-17A and IL-22 in γδ-T cells. Then we treated LCs/γδ-T cells Co-culture Model with CGRP. CGRP upregulated IL-17A and IL-22 expression in co-culture model through the paracrine effect of LCs. IL-17A and IL-22 are key cytokines of psoriasis. These findings provide a potential mechanism by which nerve factors affect the development of psoriasis.

Roles of calcitonin gene-related peptide in the skin, and other physiological and pathophysiological functions

Skin immunity is regulated by many mediator molecules. One is the neuropeptide calcitonin gene-related peptide (CGRP). CGRP has roles in regulating the function of components of the immune system including T cells, B cells, dendritic cells (DCs), endothelial cells (ECs), and mast cells (MCs).

Herein we discuss actions of CGRP in mediating inflammatory and vascular effects in various cutaneous models and disorders.

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CGRP can help to recruit immune cells through endothelium-dependent vasodilation.

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CGRP plays an important role in the pathogenesis of neurogenic inflammation.

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Functions of many components in the immune system are influenced by CGRP.

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CGRP regulates various inflammatory processes in human skin by affecting different cell-types.

CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis

AIMS

Aberrant activation of cardiac fibroblasts leads to cardiac fibrosis, and evolving evidences suggest that endogenous bioactive substances derived from cardiac fibroblasts regulate cardiac fibroblasts activation in an autocrine/paracrine manner. Here we first presented evidence that cardiac fibroblasts can synthesize and secrete calcitonin gene-related peptide (CGRP), therefore, this study aimed to investigate the role of cardiac fibroblasts-derived CGRP in cardiac fibroblasts activation and its regulative mechanism.

METHODS AND RESULTS

The abundantly expression of CGRP in rat, mouse, and human myocardium allowed us to explore the cellular origin of CGRP, and found that the cardiac CGRP was mainly derived from cardiac fibroblasts. Activating TRPA1 with a specific agonist allyl isothiocyanate promoted the synthesis and secretion of CGRP, as well as intracellular Ca2+. These effects were reversed by TRPA1-specific antagonist HC030031 and Ca2+ chelator BAPTA-AM. TGF-β1 was applied to induce the activation of cardiac fibroblasts, and found that TGF-β1 can increase the mRNA expression and secretion levels of CGRP in cardiac fibroblasts. Either CGRP8-37 (CGRP receptor antagonist) or α-CGRP small interfering RNA (siRNA) aggravated TGF-β1-induced proliferation, differentiation, collagen production, and instigated inflammation in cardiac fibroblasts. Moreover, TGF-β1-induced NF-κB activation including IκBα phosphorylation and p65 nuclear translocation were also promoted by CGRP8-37 and α-CGRP siRNA. NF-κB inhibitor pyrrolidinedithiocarbamate ammonium (PDTC) reversed the effects of CGRP8-37 on NF-κB activation. The promotive effects of CGRP8-37 on TGF-β1-induced activation of cardiac fibroblasts were all reversed by PDTC. Monocrotaline (MCT) induces pulmonary arterial hypertension, progressively leading to right ventricular fibrosis. This model of cardiac fibrosis was developed here to test the potentially beneficial effects of TRPA1 activation in vivo. The non-toxic TRPA1 agonist Cinnamaldehyde (CA) inhibited MCT-induced elevation in right ventricle systolic pressure, RV/LV + S, and right ventricular collagen accumulation, as well as down-regulation of CGRP. CA increased the synthesis and secretion of CGRP, and inhibited TGF-β1-induced activation in cardiac fibroblasts.

CONCLUSION

Our data suggested an autocrine role for cardiac fibroblasts-derived CGRP in suppressing activation of cardiac fibroblasts through inhibiting NF-κB activation. Increasing autocrine CGRP by activating TRPA1 can ameliorate cardiac fibrosis. These findings support the notion that CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis.

Vasoactive intestinal peptide inhibits the activation of murine fibroblasts and expression of interleukin 17 receptor C

Acute respiratory distress syndrome (ARDS) is an acute, severe, and refractory pulmonary inflammation with high morbidity and mortality. Excessive activation of fibroblast during the fibroproliferative phase plays a pivotal role in the prognosis of ARDS. Our previous study demonstrated that the vasoactive intestinal peptide (VIP) is mediated by lentivirus attenuates lipopolysaccharide (LPS)-induced ARDS in a murine model, and VIP inhibits the release of interleukin-17A (IL-17A) from activation macrophages. However, the effects of VIP on the activation of murine fibroblast and expression of IL-17 receptor (IL-17R) in ARDS remain unclear. Here, a mouse model of ARDS was established by an intratracheal injection of LPS. We found that the gene expression of col3a1 and hydroxyproline contents in the lungs were significantly increased 24 h after LPS injection. IL-17RC rather than IL-17RA was increased in the lungs of mice with ARDS. In vitro, LPS activated NIH3T3 cells, which was suppressed by VIP in a dose-dependent manner. In detail, VIP reduced the hydroxyproline content and col3a1 messenger RNA induced by LPS in NIH3T3 cells, as well as the expression of α-smooth muscle actin. Furthermore, we found that VIP inhibited the expression of IL-17R in the lungs of mice with ARDS and NIH3T3 cells stimulated with LPS, which was partly inhibited by antagonists of protein kinase A and protein kinase C. Taken together, our results demonstrated that VIP inhibited the activation of fibroblast via downregulation of IL-17RC, which may contribute to the protective effects of VIP against ARDS in mice.

Mindfulness-Based Cognitive Hypnotherapy and Skin Disorders

Mindfulness-based cognitive hypnotherapy integrates mindfulness, cognitive-behavioral therapy, and hypnotherapy to improve physical, emotional, mental, and/or spiritual aspects of skin disorders. Meditation, including mindfulness meditation, and hypnosis both utilize trance phenomena to help produce focalization and specific improvements in skin disorders through psycho-neuro-endocrine-immunologic mechanisms. Hypnosis, cognitive hypnotherapy, focused meditation, and mindfulness meditation are discussed with respect to improving various skin disorders including acne, acne excoriée, alopecia areata, atopic dermatitis, congenital ichthyosiform erythroderma, dyshidrotic dermatitis, erythema nodosum, erythromelalgia, furuncles, glossodynia, herpes simplex, hyperhidrosis, ichthyosis vulgaris, lichen planus, neurodermatitis, nummular dermatitis, postherpetic neuralgia, prurigo nodularis, pruritus, psoriasis, rosacea, trichotillomania, urticaria, verruca vulgaris, and vitiligo. Their integration into mindfulness-based cognitive hypnotherapy is then discussed and illustrated with improvement in a patient with systemic lupus erythematosus.

The Neuropeptides Vasoactive Intestinal Peptide and Pituitary Adenylate Cyclase-Activating Polypeptide Control HIV-1 Infection in Macrophages Through Activation of Protein Kinases A and C

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are highly similar neuropeptides present in several tissues, endowed with immunoregulatory functions and other systemic effects. We previously reported that both neuropeptides reduce viral production in HIV-1-infected primary macrophages, with the participation of β-chemokines and IL-10, and now we describe molecular mechanisms engaged in this activity. Macrophages exposed to VIP or PACAP before HIV-1 infection showed resistance to viral replication, comparable to that observed when the cells were treated after infection. Also, multiple treatments with a suboptimal dose of VIP or PACAP after macrophage infection resulted in a decline of virus production similar to the inhibition promoted by a single exposure to the optimal inhibitory concentration. Cellular signaling pathways involving cAMP production and activation of protein kinases A and C were critical components of the VIP and PACAP anti-HIV-1 effects. Analysis of the transcription factors and the transcriptional/cell cycle regulators showed that VIP and PACAP induced cAMP response element-binding protein activation, inhibited NF-kB, and reduced Cyclin D1 levels in HIV-1-infected cells. Remarkably, VIP and PACAP promoted G-to-A mutations in the HIV-1 provirus, matching those derived from the activity of the APOBEC family of viral restriction factors, and reduced viral infectivity. In conclusion, our findings strengthen the antiretroviral potential of VIP and PACAP and point to new therapeutic approaches to control the progression of HIV-1 infection.

Regulation of T helper cell responses during antigen presentation by norepinephrine-exposed endothelial cells

Dermal blood vessels and regional lymph nodes are innervated by sympathetic nerves and, under stress, sympathetic nerves release norepinephrine (NE). Exposure of primary murine dermal microvascular endothelial cells (pDMECs) to NE followed by co-culture with Langerhans cells (LCs), responsive CD4+ T-cells and antigen resulted in modulation of CD4+ T-cell responses. NE-treatment of pDMECs induced increased production of interleukin (IL)-6 and IL-17A while down-regulating interferon (IFN)-γ and IL-22 release. This effect did not require contact between pDMECs and LCs or T-cells and depended upon pDMEC production of IL-6. The presence of NE-treated pDMECs increased the proportion of CD4+ T-cells expressing intracellular IL-17A and increased IL-17A mRNA while decreasing the proportion of IFN-γ- or IL-22-expressing CD4+ T-cells and mRNA levels for those cytokines. Retinoic acid receptor-related orphan receptor gamma (ROR-γt) mRNA was significantly increased in CD4+ T-cells while T-box transcription factor (T-bet) mRNA was decreased. Intradermal administration of NE prior to hapten immunization at the injection site produced a similar bias in draining lymph node CD4+ T-cells towards IL-17A and away from IFN-γ and IL-22 production. Under stress, release of NE may have significant regulatory effects on the outcome of antigen presentation through actions on ECs with enhancement of inflammatory skin disorders involving IL-17/T helper type 17 (Th17) cells.

Role of vasoactive intestinal peptide in osteoarthritis

Vasoactive intestinal peptide (VIP) plays important roles in many biological functions, such as, stimulation of contractility in the heart, vasodilation, promoting neuroendocrine-immune communication, lowering arterial blood pressure, and anti-inflammatory and immune-modulatory activity. Osteoarthritis (OA) is a chronic and degenerative bone disease, which is one of the most common causes of disability and most common in both sexes as people become older. Interestingly VIP can prevent chronic cartilage damage and joint remodeling. This review article provides update information on the association of VIP and OA and its treatment. Evidences suggest that VIP is down-regulated in synovial fluid of OA, and VIP down-regulation leads to increase in the production of pro-inflammatory cytokines that might contribute to the pathogenesis of OA; however contradictory reports also exist suggesting that accumulation of VIP in joints can also contribute OA. A number of studies indicated that up-regulation of VIP can counteract the action of pro-inflammatory stimuli and alleviate the pain in OA. More clinical investigations are necessary to determine the biology of VIP and its therapeutic potential in OA that might represent the future standards of care for OA.

Neuronal TRPV1 activation regulates alveolar bone resorption by suppressing osteoclastogenesis via CGRP

The transient receptor potential vanilloid 1 (TRPV1) channel is abundantly expressed in peripheral sensory neurons where it acts as an important polymodal cellular sensor for heat, acidic pH, capsaicin, and other noxious stimuli. The oral cavity is densely innervated by afferent sensory neurons and is a highly specialized organ that protects against infections as well as physical, chemical, and thermal stresses in its capacity as the first part of the digestive system. While the function of TRPV1 in sensory neurons has been intensively studied in other organs, its physiological role in periodontal tissues is unclear. In this study we found that Trpv1^−/− mice developed severe bone loss in an experimental model of periodontitis. Chemical ablation of TRPV1-expressing sensory neurons recapitulated the phenotype of Trpv1^−/− mice, suggesting a functional link between neuronal TRPV1 signaling and periodontal bone loss. TRPV1 activation in gingival nerves induced production of the neuropeptide, calcitonin gene-related peptide (CGRP), and CGRP treatment inhibited osteoclastogenesis in vitro. Oral administration of the TRPV1 agonist, capsaicin, suppressed ligature-induced bone loss in mice with fewer tartrate-resistant acid phosphatase (TRAP)-positive cells in alveolar bone. These results suggest that neuronal TRPV1 signaling in periodontal tissue is crucial for the regulation of osteoclastogenesis via the neuropeptide CGRP.

Wedelolactone mitigates UVB induced oxidative stress, inflammation and early tumor promotion events in murine skin: plausible role of NFkB pathway

UVB (Ultra-violet B) radiation is one of the major etiological factors in various dermal pathology viz. dermatitis, actinic folliculitis, solar urticaria, psoriasis and cancer among many others. UVB causes toxic manifestation in tissues by inciting inflammatory and tumor promoting events. We have designed this study to assess the anti-inflammatory and anti-tumor promotion effect of Wedelolactone (WDL) a specific IKK inhibitor. Results indicate significant restoration of anti-oxidative enzymes due to WDL treatments. We also found that WDL was effective in mitigating inflammatory markers consisting of MPO (myeloperoxidase), Mast cells trafficking, Langerhans cells suppression and COX 2 expression up regulation due to UVB exposure. We also deduce that WDL presented a promising intervention in attenuating early tumor promotion events caused by UVB exposure as indicated by the results of ODC (Ornithine Decarboxylase), Thymidine assay, Vimentin and VEGF (Vascular-endothelial growth factor) expression. This study was able to provide substantial cues for the therapeutic ability of Wedelolactone against inflammatory and tumor promoting events in murine skin depicting plausible role of NFkB pathway.

Calcitonin Gene-Related Peptide-Exposed Endothelial Cells Bias Antigen Presentation to CD4+ T Cells toward a Th17 Response

Calcitonin gene-related peptide (CGRP) is a neuropeptide with well-established immunomodulatory functions. CGRP-containing nerves innervate dermal blood vessels and lymph nodes. We examined whether CGRP regulates the outcome of Ag presentation by Langerhans cells (LCs) to T cells through actions on microvascular endothelial cells (ECs). Exposure of primary murine dermal microvascular ECs (pDMECs) to CGRP followed by coculture with LCs, responsive CD4(+) T cells and Ag resulted in increased production of IL-6 and IL-17A accompanied by inhibition of IFN-γ, IL-4, and IL-22 compared with wells containing pDMECs treated with medium alone. Physical contact between ECs and LCs or T cells was not required for this effect and, except for IL-4, we demonstrated that IL-6 production by CGRP-treated pDMECs was involved in these effects. CD4(+) cells expressing cytoplasmic IL-17A were increased, whereas cells expressing cytoplasmic IFN-γ or IL-4 were decreased by the presence of CGRP-treated pDMECs. In addition, the level of retinoic acid receptor-related orphan receptor γt mRNA was significantly increased, whereas T-bet and GATA3 expression was inhibited. Immunization at the site of intradermally administered CGRP led to a similar bias in CD4(+) T cells from draining lymph node cells toward IL-17A and away from IFN-γ. Actions of nerve-derived CGRP on ECs may have important regulatory effects on the outcome of Ag presentation with consequences for the expression of inflammatory skin disorders involving Th17 cells.

Pituitary Adenylate Cyclase-Activating Polypeptide Is Upregulated in Murine Skin Inflammation and Mediates Transient Receptor Potential Vanilloid-1-Induced Neurogenic Edema

Although pituitary adenylate cyclase-activating polypeptide (PACAP) was described as a key vasoregulator in human skin, little is known about its expression in mouse skin. As it is important to investigate PACAP signaling in translational mouse dermatitis models, we determined its presence, regulation, and role in neurogenic and non-neurogenic cutaneous inflammatory mechanisms. The mRNA of PACAP and its specific receptor PAC1 was detected with real-time PCR in several skin regions at comparable levels. PACAP-38-immunoreactivity measured with radioimmunoassay was similar in plantar and dorsal paw skin and the ear but significantly smaller in the back skin. PACAP and PAC1 mRNA, as well as PACAP-38 and PAC1 protein expression, significantly increased in the plantar skin after intraplantar administration of capsaicin (50 μl, 100 μg ml(-1)), an agonist of the transient receptor potential vanilloid 1 (TRPV1) receptor, evoking chiefly neurogenic inflammation without inflammatory cell accumulation. Intraplantar complete Freund's adjuvant (CFA; 50 μl, 1 mg ml(-1)) also increased PACAP/PAC1 mRNA but not the PACAP peptide. Capsaicin-induced neurogenic paw edema, but not CFA-evoked non-neurogenic swelling, was significantly smaller in PACAP-deficient mice throughout a 24-hour period. To our knowledge, we provide previously unreported evidence for PACAP and PAC1 expression upregulation during skin inflammation of different mechanisms and for its pro-inflammatory function in neurogenic edema formation.

Exogenous α-calcitonin gene-related peptide attenuates lipopolysaccharide-induced acute lung injury in rats

α-Calcitonin gene-related peptide (α-CGRP) is a 37 amino-acid neuropeptide that is primarily released from C-type sensory neurons. α-CGRP exerts multiple modulatory effects on immune responses and visceral organ function, but the role of exogenous α-CGRP in lipopolysaccharide (LPS)-induced acute lung injury (ALI) has remained to be elucidated. Forty-eight rats were randomized to receive continuous intraperitoneal infusion of α-CGRP (0.4 μg/kg/min) or normal saline for 30 min, followed by intratracheal injection of 0.5 mg/kg LPS or saline. There were four groups of animals: The saline-saline (S-S) group; the saline-α-CGRP (S-C) group; the LPS-saline (L-S) group and the LPS-α-CGRP (L-C) group. Mean arterial pressure and arterial blood gases were assessed prior to α-CGRP and LPS administration and every hour following LPS treatment. After 4 h, bronchoalveolar lavage was performed and used to assess total cell count and levels of tumor necrosis factor-α, interleukin-1β, intracellular cell adhesion molecule 1 and macrophage inflammatory protein 2. Lung tissue was also collected for assessing wet-to-dry (W/D) ratio, histology and Evans blue (EB) dye extravasation. Pulmonary α-CGRP concentration and α-CGRP receptor expression were also examined, and inducible cyclic adenosine monophosphate early repressor (ICER) and TNF-α mRNA expression levels were measured. Treatment with exogenous α-CGRP improved oxygenation during LPS-induced ALI. Correspondingly, histological injury, total cell count, inflammatory cytokine levels, W/D ratio and EB dye extravasation were also significantly reduced. α-CGRP receptor 1 expression was noted in pulmonary endothelial cells and alveolar macrophages and α-CGRP receptor expression levels were decreased during ALI, whereas pulmonary α-CGRP expression was continuously increased. Furthermore, exogenous α-CGRP induced upregulation of ICER during LPS-induced ALI. In conclusion, exogenous α-CGRP improved oxygenation and ameliorated lung damage in LPS-induced ALI, and these effects were associated with the upregulation of ICER.

Calcitonin gene-related peptide: key regulator of cutaneous immunity

Calcitonin gene-related peptide (CGRP) has been viewed as a neuropeptide and vasodilator. However, CGRP is more appropriately thought of as a pleiotropic signalling molecule. Indeed, CGRP has key regulatory functions on immune and inflammatory processes within the skin. CGRP-containing nerves are intimately associated with epidermal Langerhans cells (LCs), and CGRP has profound regulatory effects on Langerhans cell antigen-presenting capability. When LCs are exposed to CGRP in vitro, their ability to present antigen for in vivo priming of naïve mice or elicitation of delayed-type hypersensitivity is inhibited in at least some situations. Administration of CGRP intradermally inhibits acquisition of immunity to Th1-dominant haptens applied to the injected site while augmenting immunity to Th2-dominant haptens, although the cellular targets of activity in these experiments remain unclear. Although CGRP can be a pro-inflammatory agent, several studies have demonstrated that administration of CGRP can inhibit the elicitation of inflammation by inflammatory stimuli in vivo. In this regard, CGRP inhibits the release of certain chemokines by stimulated endothelial cells. This is likely to be physiologically relevant as cutaneous blood vessels are innervated by sensory nerves. Exciting new studies suggest a significant role for CGRP in the pathogenesis of psoriasis and, most strikingly, that CGRP inhibits the ability of LCs to transmit the human immunodeficiency virus 1 to T lymphocytes. A more complete understanding of the role of CGRP in the skin immune system may lead to new and novel approaches for the therapy of immune-mediated skin disorders.

Cutaneous immunopathology of long-standing complex regional pain syndrome

BACKGROUND

Both increased mast cells numbers and raised immune mediator concentrations indicate immune activation in the affected skin of patients with early complex regional pain syndrome (CRPS), but little is known about regional immune cell involvement in late-stage CRPS. The aim of the current study was to determine skin immune cell populations in long-standing CRPS.

METHODS

Using 6-mm skin punch biopsies from CRPS-affected and non-affected tissues, and a combination of chemical and immunofluorescence staining, we examined the density and function of key cell populations including mast cells, epidermal Langerhans cells (LCs) and tissue resident T-cells.

RESULTS

We found no significant differences in either overall immune cell infiltrates, or mast cell density between CRPS-affected and non-affected sub-epidermal tissue sections, contrasting recent findings in early CRPS by other groups. However, CD1a(+) LC densities in the epidermal layer were significantly decreased in affected compared to non-affected CRPS limbs (p < 0.01). T-cell clones isolated from CRPS-affected sub-epidermal tissues displayed a trend towards increased IL-13 production in ELISPOT assays when compared to T-cells isolated from non-affected areas, suggesting a Th2 bias.

CONCLUSIONS

Immune cell abnormalities are maintained in late-stage CRPS disease as manifest by changes in epidermal LC density and tissue resident T-cell phenotype.

Calcitonin gene-related peptide inhibits human immunodeficiency type 1 transmission by Langerhans cells via an autocrine/paracrine feedback mechanism

AIM

Peripheral neurones innervating mucosal epithelia are in direct contact with resident immune cells, including Langerhans cells (LCs). Such neurones secrete the neuropeptide calcitonin gene-related peptide (CGRP) that modulates LCs function. We recently found that CGRP strongly inhibits human immunodeficiency virus type 1 (HIV-1) transmission, by interfering with multiple steps of mucosal LC-mediated HIV-1 transfer, including increased expression of the LC-specific lectin langerin. Herein, we investigated the anti-HIV-1 mechanism of CGRP.

METHODS

In the presence of CGRP, HIV-1 transfer from LCs to CD4+ T cells was tested with viral clones using either the HIV-1 co-receptor CCR5 (R5) or CXCR4 (X4). Surface expression of CCR5, CXCR4 and langerin was evaluated by flow cytometry. CGRP secretion by LCs was measured with an enzyme immunoassay. Expression of the multimeric CGRP receptor was examined by quantitative real-time RT-PCR and immuno-fluorescent microscopy.

RESULTS

Calcitonin gene-related peptide decreased transfer of HIV-1 R5, but increased that of X4. These opposing effects correlated with decreased CCR5 vs. increased CXCR4 surface expression in LCs. Inhibition of HIV-1 R5 transfer by CGRP involved signal transducer and activator of transcription 4 (STAT4) activation. Both αCGRP and βCGRP were similarly efficient in decreasing HIV-1 R5 transfer and increasing langerin expression. LCs secreted low basal levels of endogenous CGRP, which increased markedly following CGRP treatment. CGRP also increased expression of its cognate receptor in LCs.

CONCLUSION

CGRP engages a positive feedback mechanism that would further enhance its anti-HIV-1 activity. This information might be relevant for the therapeutic use of CGRP as a prophylactic agent against HIV-1.

Langerhans cells regulate cutaneous innervation density and mechanical sensitivity in mouse footpad

Langerhans cells are epidermal dendritic cells responsible for antigen presentation during an immune response. Langerhans cells associate intimately with epidermal sensory axons. While there is evidence that Langerhans cells may produce neurotrophic factors, a role in regulating cutaneous innervation has not been established. We used genetically engineered mice in which the diphtheria toxin (DT) receptor is targeted to Langerhans cells (Lang-DTR mice) to assess sensory axon-dendritic cell interactions. Diphtheria toxin administration to wild type mice did not affect epidermal structure, Langerhans cell content, or innervation density. A DT administration regimen supramaximal for completely ablating epidermal Langerhans cells in Lang-DTR mice reduced PGP 9.5-immunoreactive total innervation and calcitonin gene related peptide-immunoreactive peptidergic nociceptor innervation. Quantitative real-time polymerase chain reaction showed that epidermal gene expression of brain derived neurotrophic factor was unchanged, but nerve growth factor and glial cell line-derived neurotrophic factor mRNAs were reduced. Behavioral testing showed that, while thermal sensitivity was unaffected, mice depleted of Langerhans cells displayed mechanical hypersensitivity. These findings provide evidence that Langerhans cells play an important role in determining cutaneous sensory innervation density and mechanical sensitivity. This may involve alterations in neurotrophin production by Langerhans or other epidermal cells, which in turn may affect mechanical sensitivity directly or as a result of neuropathic changes.

Nerve-derived transmitters including peptides influence cutaneous immunology

Clinical observations suggest that the nervous and immune systems are closely related. For example, inflammatory skin disorders; such as psoriasis, atopic dermatitis, rosacea and acne; are widely believed to be exacerbated by stress. A growing body of research now suggests that neuropeptides and neurotransmitters serve as a link between these two systems. Neuropeptides and neurotransmitters are released by nerves innervating the skin to influence important actors of the immune system, such as Langerhans cells and mast cells, which are located within close anatomic proximity. Catecholamines and other sympathetic transmitters that are released in response to activation of the sympathetic nervous system are also able to reach the skin and affect immune cells. Neuropeptides appear to direct the outcome of Langerhans cell antigen presentation with regard to the subtypes of Th cells generated and neuropeptides induce the degranulation of mast cells, among other effects. Additionally, endothelial cells, which release many inflammatory mediators and express cell surface molecules that allow leukocytes to exit the bloodstream, appear to be regulated by certain neuropeptides and transmitters. This review focuses on the evidence that products of nerves have important regulatory activities on antigen presentation, mast cell function and endothelial cell biology. These activities are highly likely to have clinical and therapeutic relevance.

Calcitonin gene-related peptide inhibits Langerhans cell-mediated HIV-1 transmission

Upon its mucosal entry, human immunodeficiency virus type 1 (HIV-1) is internalized by Langerhans cells (LCs) in stratified epithelia and transferred locally to T cells. In such epithelia, LCs are in direct contact with peripheral neurons secreting calcitonin gene-related peptide (CGRP). Although CGRP has immunomodulatory effects on LC functions, its potential influence on the interactions between LCs and HIV-1 is unknown. We show that CGRP acts via its receptor expressed by LCs and interferes with multiple steps of LC-mediated HIV-1 transmission. CGRP increases langerin expression, decreases selected integrins, and activates NF-κB, resulting in decreased HIV-1 intracellular content, limited formation of LC-T cell conjugates, and elevated secretion of the CCR5-binding chemokine CCL3/MIP-1α. These mechanisms cooperate to efficiently inhibit HIV-1 transfer from LCs to T cells and T cell infection. In vivo, HIV-1 infection decreases CGRP plasma levels in both vaginally SHIV-challenged macaques and HIV-1-infected individuals. CGRP plasma levels return to baseline after highly active antiretroviral therapy. Our results reveal a novel path by which a peripheral neuropeptide acts at the molecular and cellular levels to limit mucosal HIV-1 transmission and suggest that CGRP receptor agonists might be used therapeutically against HIV-1.

Calcitonin gene-related peptide and cyclic adenosine 5'-monophosphate/protein kinase A pathway promote IL-9 production in Th9 differentiation process

Th9 cells are a novel Th cell subset that produces IL-9 and is involved in type I hypersensitivity such as airway inflammation. Although its critical roles in asthma have attracted interest, the physiological regulatory mechanisms of Th9 cell differentiation and function are largely unknown. Asthma is easily affected by psychological factors. Therefore, we investigated one of the physiological mediators derived from the nervous system, calcitonin gene-related peptide (CGRP), in asthma and Th9 cells because CGRP and activation of the cAMP/protein kinase A (PKA) pathway by CGRP are known to be important regulators in several immune responses and allergic diseases. In this study, we demonstrated that the CGRP/cAMP/PKA pathway promotes IL-9 production via NFATc2 activation by PKA-dependent glycogen synthase kinase-3β inactivation. Moreover, CGRP also induces the expression of PU.1, a critical transcriptional factor in Th9 cells, which depends on PKA, but not NFATc2. Additionally, we demonstrated the physiological importance of CGRP in IL-9 production and Th9 differentiation using an OVA-induced airway inflammation model and T cell-specific CGRP receptor-deficient mice. The present study revealed a novel regulatory mechanism comprising G protein-coupled receptor ligands and nervous system-derived substances in Th9 cell differentiation and type I hypersensitivity.

Pituitary adenylate cyclase-activating peptide and vasoactive intestinal polypeptide bias Langerhans cell Ag presentation toward Th17 cells

Epidermal Langerhans cells (LCs) are dendritic APCs that play an important role in cutaneous immune responses. LCs are associated with epidermal nerves and the neuropeptides vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) inhibit LC Ag presentation for Th1-type immune responses. Here, we examined whether PACAP or VIP modulates LC Ag presentation for induction of IL-17A-producing CD4(+) T cells. Treatment with VIP or PACAP prior to in vitro LC Ag presentation to CD4(+) T cells enhanced IL-17A, IL-6, and IL-4 production, decreased interferon (IFN)-γ and interleukin (IL)-22 release, and increased RORγt and Gata3 mRNA expression while decreasing T-bet expression. The CD4(+) T-cell population was increased in IL-17A- and IL-4-expressing cells and decreased in IFN-γ-expressing cells. Addition of anti-IL-6 mAb blocked the enhanced IL-17A production seen with LC preexposure to VIP or PACAP. Intradermal administration of VIP or PACAP prior to application of a contact sensitizer at the injection site, followed by harvesting of draining lymph node CD4(+) T cells and stimulation with anti-CD3/anti-CD28 mAbs, enhanced IL-17A and IL-4 production but reduced production of IL-22 and IFN-γ. PACAP and VIP are endogenous mediators that likely regulate immunity and immune-mediated diseases within the skin.

Modulation of immune responses by the neuropeptide CGRP

The peripheral nervous system is connected with lymphoid organs through sensory nerves that mediate pain reflexes and may influence immune responses through the release of neuropeptides such as calcitonin gene-related peptide (CGRP). Local and systemic levels of CGRP increase rapidly during inflammatory responses. CGRP inhibits effector functions of various immune cells and dampens inflammation by distinct pathways involving the amplification of IL-10 production and/or the induction of the transcriptional repressor inducible cAMP early repressor (ICER). Thus, available evidence suggests that, in neuro-immunological interactions, CGRP mediates a potent peptidergic anti-inflammatory pathway.

Inhibition of Toll-like receptor 4 with vasoactive intestinal peptide attenuates liver ischemia-reperfusion injury

BACKGROUND

Toll-like receptor 4 (TLR4) has attracted a great deal of attention in ischemia-reperfusion (IR) injury in recent years. Vasoactive intestinal peptide (VIP) plays an important role in anti-inflammatory and immunomodulatory activity in several animal models. There are no data available regarding the effect of VIP on TLR4 expression in IR injury in vivo. In the present study, we study the effect of VIP on TLR4 expression in mouse macrophage cell line RAW 264.7 and a mouse partial IR model.

METHODS

The potential inhibitory effect of VIP on TLR4 mRNA and protein in a mouse macrophage cell line and in a mouse model of partial warm hepatic IR injury was assessed. We also assessed the expression tumor necrosis factor (TNF)-α and interleukin (IL)-6 in this model.

RESULTS

Expression of TLR4 mRNA levels was significantly decreased at 6, 12, and 24 hours after treat with VIP in mouse macrophage cell line RAW 264.7. Expression of TLR4 mRNA, TLR4 protein, alanine aminotransferase, TNF-α, and IL-6 levels were significantly increased in the IR group but significantly decreased in groups pretreated with VIP at a concentration of 5 and 10 nmol. Hematoxylin and eosin staining show apparent edema and necrosis were observed in the IR group, but in the VIP pretreatment group, edema and necrosis in IR modes were reduced.

CONCLUSION

This study showed that VIP might inhibit TLR4 in vitro and in vivo, and pretreatment with VIP might inhibited TLR4 activation and reduced warm IR injury.

Cutaneous denervation of psoriasiform mouse skin improves acanthosis and inflammation in a sensory neuropeptide-dependent manner

Nervous system involvement in psoriasis pathogenesis is supported by increases in nerve fiber numbers and neuropeptides in psoriatic skin and by reports detailing spontaneous plaque remission following nerve injury. Using the KC-Tie2 psoriasiform mouse model, we investigated the mechanisms by which nerve injury leads to inflammatory skin disease remission. Cutaneous nerves innervating dorsal skin of KC-Tie2 animals were surgically axotomized and beginning 1 day after denervation, CD11c(+) cell numbers decreased by 40% followed by a 30% improvement in acanthosis at 7 days and a 30% decrease in CD4(+) T-cell numbers by 10 days. Restoration of substance P (SP) signaling in denervated KC-Tie2 skin prevented decreases in CD11c(+) and CD4(+) cells, but had no effect on acanthosis; restoration of calcitonin gene-related peptide (CGRP) signaling reversed the improvement in acanthosis and prevented denervated-mediated decreases in CD4(+) cells. Under innervated conditions, small-molecule inhibition of SP in KC-Tie2 animals resulted in similar decreases to those observed following surgical denervation for cutaneous CD11c(+) and CD4(+) cell numbers; whereas small-molecule inhibition of CGRP resulted in significant reductions in CD4(+) cell numbers and acanthosis. These data demonstrate that sensory nerve-derived peptides mediate psoriasiform dendritic cell and T-cell infiltration and acanthosis and introduce targeting nerve-immunocyte/KC interactions as potential psoriasis therapeutic treatment strategies.

Calcitonin gene-related peptide is an important regulator of cutaneous immunity: effect on dendritic cell and T cell functions

Some cutaneous inflammations are induced by percutaneous exposure to foreign Ags, and many chemical mediators regulate this inflammation process. One of these mediators, calcitonin gene-related peptide (CGRP), is a neuropeptide released from nerve endings in the skin. CGRP binds to its receptors composed of receptor activity-modifying protein 1 and calcitonin receptor-like receptor to modulate immune cell function. We show that CGRP regulates skin inflammation under physiological conditions, using contact hypersensitivity (CHS) models of receptor activity-modifying protein 1-deficient mice. CGRP has different functions in CHS responses mediated by Th1 or Th2 cells; it inhibits Th1-type CHS, such as 2,4,6-trinitrochlorobenzene-induced CHS, but promotes Th2-type CHS, such as FITC-induced CHS. CGRP inhibits the migration of Langerin(+) dermal dendritic cells to the lymph nodes in 2,4,6-trinitrochlorobenzene-induced CHS, and upregulates IL-4 production of T cells in the draining lymph nodes in FITC-CHS. These findings suggest that CGRP regulates several types of CHS reactions under physiological conditions and plays an important role in cutaneous immunity.

Role of neuropeptides in skin inflammation and its involvement in diabetic wound healing

IMPORTANCE OF THE FIELD

In 2010, the world prevalence of diabetes is 6.4%, affecting 285 million adults. Diabetic patients are at risk of developing neuropathy and delayed wound healing that can culminate in incurable diabetic foot ulcerations (DFUs) or even foot amputation.

AREAS COVERED IN THIS REVIEW

The contrast between cellular and molecular events of wound healing and diabetic wound healing processes is characterized. Neuropeptides released from the autonomous nervous system and skin cells reveal a major role in the immunity of wound healing. Therefore, the signaling pathways that induce pro/anti-inflammatory cytokines expression and its involvement in diabetic wound healing are discussed. The involvement of neuropeptides in the activation, growth, migration and maturation of skin cells, like keratinocytes, Langerhans cells, macrophages and mast cells, are described.

WHAT THE READER WILL GAIN

This review attempts to address the role of neuropeptides in skin inflammation, focusing on signal transduction, inflammatory mediators and pro/anti-inflammatory function, occurring in each cell type, as well as, its connection with diabetic wound healing.

TAKE HOME MESSAGE

Understanding the role of neuropeptides in the skin, their application on skin wounds could be a potential therapy for skin pathologies, like the problematic and prevalent DFUs.

Catestatin, a neuroendocrine antimicrobial peptide, induces human mast cell migration, degranulation and production of cytokines and chemokines

Catestatin, a neuroendocrine peptide with effects on human autonomic function, has recently been found to be a cutaneous antimicrobial peptide. Human catestatin exhibits three single nucleotide polymorphisms: Gly364Ser, Pro370Leu and Arg374Gln. Given reports indicating that antimicrobial peptides and neuropeptides induce mast cell activation, we postulated that catestatin might stimulate numerous functions of human mast cells, thereby participating in the regulation of skin inflammatory responses. Catestatin and its naturally occurring variants caused the human mast cell line LAD2 and peripheral blood-derived mast cells to migrate, degranulate and release leukotriene C(4) and prostaglandins D(2) and E(2). Moreover, catestatins increased intracellular Ca(2+) mobilization in mast cells, and induced the production of pro-inflammatory cytokines/chemokines such as granulocyte-macrophage colony-stimulating factor, monocyte chemotactic protein-1/CCL2, macrophage inflammatory protein-1α/CCL3 and macrophage inflammatory protein-1β/CCL4. Our evaluation of possible cellular mechanisms suggested that G-proteins, phospholipase C and the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) are involved in catestatin-induced mast cell activation as evidenced by the inhibitory effects of pertussis toxin (G-protein inhibitor), U-73122 (phospholipase C inhibitor) and U0126 (ERK inhibitor), respectively. We also found that human mast cells express the α7 subunit of the nicotinic acetylcholine receptor at both the mRNA and protein levels. Given that silencing the α7 receptor mRNA and an α7-specific inhibitor did not affect catestatin-mediated activation of mast cells, however, we concluded that this receptor is not likely to be functional in human mast cell stimulation by catestatins. Our finding that the neuroendocrine antimicrobial peptide catestatin activates human mast cells suggests that this peptide might have immunomodulatory functions, and provides a new link between neuroendocrine and cutaneous immune systems.

A nonredundant role for canonical NF-κB in human myeloid dendritic cell development and function

The plastic role of dendritic cells (DCs) in the regulation of immune responses has made them interesting targets for immunotherapy, but also for pathogens or tumors to evade immunity. Functional alterations of DCs are often ascribed to manipulation of canonical NF-κB activity. However, though this pathway has been linked to murine myeloid DC biology, a detailed analysis of its importance in human myeloid DC differentiation, survival, maturation, and function is lacking. The myeloid DC subsets include interstitial DCs and Langerhans cells. In this study, we investigated the role of canonical NF-κB in human myeloid DCs generated from monocytes (monocyte-derived DCs [mo-DCs]) or CD34(+) progenitors (CD34-derived myeloid DCs [CD34-mDCs]). Inhibition of NF-κB activation during and after mo-DC, CD34-interstitial DC, or CD34-Langerhans cell differentiation resulted in apoptosis induction associated with caspase 3 activation and loss of mitochondrial transmembrane potential. Besides regulating survival, canonical NF-κB activity was required for the acquisition of a DC phenotype. Despite phenotypic differences, however, Ag uptake, costimulatory molecule and CCR7 expression, as well as T cell stimulatory capacity of cells generated under NF-κB inhibition were comparable to control DCs, indicating that canonical NF-κB activity during differentiation is redundant for the development of functional APCs. However, both mo-DC and CD34-mDC functionality were reduced by NF-κB inhibition during activation. In conclusion, canonical NF-κB activity is essential for the development and function of mo-DCs as well as CD34-mDCs. Insight into the role of this pathway may help in understanding how pathogens and tumors escape immunity and aid in developing novel treatment strategies aiming to interfere with human immune responses.

Thymic stromal lymphopoietin induces tight junction protein claudin-7 via NF-kappaB in dendritic cells

Epithelial-derived thymic stromal lymphopoietin (TSLP) is an IL-7-like cytokine that triggers dendritic cell (DC)-mediated Th2-type inflammatory responses. The activated DCs can penetrate the epithelium to directly take up antigen without compromising the barrier function. Although it is reported that DCs express tight junction molecules and can establish tight junction-like structures with adjacent epithelial cells to preserve the epithelial barrier, the regulation of expression of tight junction molecules in DCs remains unknown. In the present study, to investigate the mechanical regulation of expression of tight junction molecules in DCs, XS52 DCs that was a long-term DC line established from the epidermis of a newborn BALB/c mouse, were treated with TSLP or toll-like receptor (TLR) ligands. In XS52 cells, tight junction molecules claudin-1, -3, -4, -6, -7, -8, and occludin were detected. mRNA expression of TSLP receptor and all these tight junction molecules was significantly increased in activated XS52 cells after treatment with TSLP. In addition, expression of claudin-7 protein was increased in dose- and time-dependent manner. In XS52 cells, which express TLR2, TLR3, TLR4, and TLR7, but not TLR9, expression of claudin-7 protein was also increased after treatment with ligands of TLR2, TLR4 or TLR7/8, Pam3Cys-Ser-(Lys)4, LPS, or CL097. The NF-kappaB inhibitor IMD-0354 prevented upregulation of claudin-7 after treatment with TSLP or TLR ligands. These findings indicate that TSLP induces expression of tight junction protein claudin-7 in DCs via NF-kappaB as well as via TLRs and may control tight junctions of DCs to preserve the epithelial barrier during allergic inflammation.

The evolving function of Langerhans cells in adaptive skin immunity

Langerhans cells (LC) are dendritic cell that resides in the epidermis of skin. Paul Langerhans originally observed and named this epinonymous cell more than 140 years ago. Their network-like distribution and dendritic processes that extended up into the stratum corneum convinced him that they represented peripheral nerve cells. It was not determined until almost 100 years later that LC are, in fact, bone marrow-derived and function as skin-resident antigen presenting cells. Many studies have shown that LC are highly immunostimulatory. Recently, data have begun to accumulate suggesting LC have immunoregulatory properties. This review will focus on the participation of LC in the development and regulation of adaptive immune responses.

Revisiting the tolerogenicity of epidermal Langerhans cells

Langerhans cells (LC) are unique members of the dendritic cell (DC) family residing in the epidermis of skin and mucosa. Specific autocrine and environmental factors shape the biology of LC, such as TGF-beta1, IL-10, vitamin D(3), UV light or neuropeptides, which are required for LC development but also influence their capacity to induce immunity or tolerance. Both, immunogenic and tolerogenic functions require antigen transport from the skin to the draining lymph nodes, but the LC maturation grade directs the differential outcome. In this review, we recapitulate early indications for LC tolerogenicity and oppose them to more recent findings with gene-targeted mice, which dramatically challenged some of the early results. The newly discovered Langerin(+) dermal DC subset (DDC) seems to be responsible also for many tolerogenic effects that were initially attributed to steady state migratory LC. Transfer of antigens from LC to other DC subsets as well as transport of HIV are discussed as part of the complex interactions between LC and other cells or as mechanisms of immune evasion. Finally, the first clinical trials on allergy therapies targeting skin DC in the steady state are mentioned as they may open the door to curative tolerogenic therapies.

Activation of host antiviral RNA-sensing factors necessary for herpes simplex virus type 1-activated transcription of host cell fucosyltransferase genes FUT3, FUT5, and FUT6 and subsequent expression of sLe(x) in virus-infected cells

Herpes simplex virus type 1 (HSV-1) induces expression of a selectin receptor, the carbohydrate epitope sialyl Lewis X (sLe(x)), at the surface of infected cells. The molecular background to this phenomenon is that a viral immediate early RNA interacts with as yet unidentified host factors, eventually resulting in transcription of three dormant host fucosyltransferase genes (FUT3, FUT5, and FUT6), whose gene products are rate-limiting for synthesis of sLe(x). The aim of the present study was to define the immediate targets for the viral RNA in this process. We found that the Protein Kinase R (PKR) inhibitors 2-aminopurine (2-AP) and C16 inhibited FUT3, FUT5, and FUT6 expression as well as HSV-1-induced expression of sLe(x), indicating a primary role of PKR as a viral RNA target. The PKR-dependent activation of the FUT genes seemed neither to involve PKR effects on translation nor to involve NF-kappaB- or JNK-dependent activation. IMD-0354, known as an inhibitor of the NF-kappaB-activating factor IKK-2, induced FUT transcription via a novel IKK-2-independent mechanism, irrespective of whether the cells were virus-infected or not. Altogether, the results suggested that PKR is the primary target for HSV-1 early RNA during induction of FUT3, FUT5, and FUT6, and that the subsequent steps in the transcriptional activation of these host genes involve a hitherto unknown IMD-0354, yet IKK-2-independent, pathway.

The neuroendocrine peptide catestatin is a cutaneous antimicrobial and induced in the skin after injury

Epithelia establish a microbial barrier against infection through the production of antimicrobial peptides (AMPs). In this study, we investigated whether catestatin (Cst), a peptide derived from the neuroendocrine protein chromogranin A (CHGA), is a functional AMP and is present in the epidermis. We show that Cst is antimicrobial against relevant skin microbes, including gram-positive and gram-negative bacteria, yeast, and fungi. The antimicrobial mechanism of Cst was found to be similar to other AMPs, as it was dependent on bacterial charge and growth conditions, and induced membrane disruption. The potential relevance of Cst against skin pathogens was supported by the observation that CHGA was expressed in keratinocytes. In human skin, CHGA was found to be proteolytically processed into the antimicrobial fragment Cst, thus enabling its AMP function. Furthermore, Cst expression in murine skin increased in response to injury and infection, providing potential for increased protection against infection. These data demonstrate that a neuroendocrine peptide has antimicrobial function against a wide assortment of skin pathogens and is upregulated upon injury, thus demonstrating a direct link between the neuroendocrine and cutaneous immune systems. JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article please go to http://network.nature.com/group/jidclub.

VIP reverses the expression profiling of TLR4-stimulated signaling pathway in rheumatoid arthritis synovial fibroblasts

Since recent evidences point out the potential involvement of Toll-like receptors (TLRs) in the therapeutic effect of vasoactive intestinal peptide (VIP), the purpose of this study is to elucidate the role of VIP as a negative regulator of TLR-signaling. To this aim, we analyzed in fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA) or osteoarthritis (OA), the expression profile of TLR-pathway related molecules, as well as the alterations induced by LPS stimulation in RA-FLS and the effect of VIP treatment. Cultured FLS were obtained from patients with RA or OA. RA-FLS were next stimulated with lipopolysaccharide (LPS) in presence or absence of VIP. The gene expression profiling of molecules involved in LPS-mediated TLR4-signaling was studied by cRNA microarray analysis. Twenty three molecules involved in TLR signaling resulted over-expressed at mRNA level in basal RA-FLS compared to OA-FLS. Moreover, in RA-FLS, 23 of the analyzed genes were found to be up-regulated by LPS stimulation whereas 30 were not affected. VIP down-regulated the LPS-induced RNA expression of molecules involved in TLR signaling pathway. Up-regulation of RNA expression of CD14, MD2, TRAM, TRIF, IRAK4, TAB2, TRAF6 and TBK1 was corroborated by RT-PCR as well as the VIP regulatory effect. Increased protein levels of TRAF6, TBK1 and pIRAK1 after exposure to LPS, and the inhibitory effect of VIP, were described by Western blotting. As functional consequences, it was observed the VIP-induced impaired production of IL-6 and RANTES/CCL5 after LPS stimulation. In conclusion, VIP acts as a negative modulator of the TLR4-signaling by overturning the production of several checkpoints molecules of the cascade and thus, widening its potential therapeutic effects.

Norepinephrine modulates human dendritic cell activation by altering cytokine release

Norepinephrine (NE) can modulate dendritic cell (DC) activation in animal models, but the response of human DC to NE and other response modifiers is as yet not completely understood. Here we report the effect of NE on the cytokine response of a mixed population of human DC cells to extracellular stimuli. These cells were obtained by differentiating human cord blood CD34+ precursor cells. NE inhibited the lipopolysaccharide (LPS)-stimulated production of interleukin (IL)-23, IL-12 p40, tumor necrosis factor (TNF)-alpha and IL-6 whereas the expression of IL-10 was not significantly affected. Thus, human cord blood-derived DC respond to NE in a manner similar to mouse Langerhans cells (LC). Furthermore, forskolin also inhibited the LPS-induced levels of TNF-alpha, IL-12 p40, IL-23 p19 and IL-6, supporting the hypothesis that the effects of NE are mediated by cAMP. Data from experiments using inhibitors of adrenergic receptors suggest that NE acts through beta-adrenergic receptors. As IL-23 promotes the differentiation of CD4+ T cells required for T(H)1-mediated immunity, we suggest that NE decreases the differentiation of CD4+ T cells needed for T(H)1-mediated contact hypersensitivity and that NE is a candidate regulator of human DC functions in the skin.