Modulation of basophil activity: a novel function of the neuropeptide α-melanocyte-stimulating hormone

The correlation between tic disorders and allergic conditions in children: A systematic review and meta-analysis of observational studies

Aim

To evaluate the correlation between tic disorders and allergies and to inform strategies for the treatment and prevention of tic disorders.

Methods

We conducted online searches of the MEDLINE, Embase, Cochrane, CNKI, CBM, WanFang, and VIP Information databases. Case-control studies and cohort studies related to tic disorders and allergic conditions were searched. Two researchers screened the literature, extracted data, and evaluated quality in strict accordance with the predetermined retrieval strategy and inclusion criteria. Finally, RevMan 5.4 software was used to conduct a meta-analysis. We used the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach to rating the certainty of evidence about each allergy outcome as high, moderate, low, or very low.

Results

We obtained seven eligible studies involving eight allergic conditions. The following allergic conditions were significantly associated with the presence of a tic disorder: asthma (OR = 1.90, 95% CI = 1.57-2.30, P < 0.001), allergic rhinitis (OR = 2.61, 95% CI = 1.90-3.57, P < 0.001), allergic conjunctivitis (OR = 3.65, 95% CI = 1.53-8,67, P = 0.003), eczema (OR = 3.87, 95% CI = 2.24-6.67, P < 0.001) and food allergy (OR = 2.79, 95% CI = 1.56-4.99, P < 0.001). There was no significant correlation between atopic dermatitis, urticaria, drug allergy, and tic disorder.

Conclusion

The occurrence of tic disorders may be associated with the presence of certain allergic disorders. However, whether allergy is one of the causes of tic disorders remains unclear.

Systematic review registration

The registration number for this systematic review is PROSPERO: CRD42021231658.

Skin as an endocrine organ: A narrative review

Skin being the largest organ of the body, is equipped with numerous functional properties. Over the past few years, intricate research into the biology of skin has led to a gamut of discoveries. Skin is now regarded as one of the most vital endocrine organs. The skin contains equivalents of the hypothalamo-pituitary-adrenal axis, hypothalamo-pituitary-thyroid axis and the appendages produce multiple hormones such as Vitamin D, sex steroids, retinoids and opioids. In this article, we will explore the role of skin as a target and source of some of the hormones of the human body, and briefly touch on the clinical applications.

Comparative Intracerebroventricular and Intrathecal Administration of a Nanomolar Macrocyclic Melanocortin Receptor Agonist MDE6-5-2c (c[Pro-His-DPhe-Arg-Trp-Dap-Ala-DPro]) Decreases Food Intake in Mice

There is a critical need to find safe therapeutics to treat an increasingly obese population and diseases associated with an imbalance in energy homeostasis. The melanocortin-3 receptor (MC3R) and melanocortin-4 receptor (MC4R) ligands have long been the focus to help scientists understand energy homeostasis and the regulation of feeding behavior. Herein, we use a nanomolar macrocyclic melanocortin receptor agonist ligand MDE6-5-2c (c[Pro-His-DPhe-Arg-Trp-Dap-Ala-DPro) to examine metabolic and energy hemostasis profiles upon intrathecal (IT) administration directly into the spinal cord as compared to intracerebroventricular (ICV) administration directly into the brain. Overall, central ICV administration of MDE6-5-2c resulted in decreased food intake, in a dose-dependent manner, and decreased respiratory exchange ratio (RER). Comparison of IT versus ICV routes of MDE6-5-2c administration resulted in MDE6-5-2c possessing a longer duration of action on both feeding behavior and RER via IT. The C-peptide, ghrelin, GIP, leptin, IL-6, and resistin plasma hormones and biomarkers were compared using IT versus ICV MDE6-5-2c routes of administration. Plasma resistin levels were decreased upon ICV treatment of MDE6-5-2c, as compared to ICV vehicle control treatment. Intrathecal treatment resulted in significantly decreased inflammatory cytokine interleukin-6 (IL-6) levels compared to ICV administration. Investigation of the nonselective MC3R and MC4R macrocyclic agonist MDE6-5-2c molecule revealed differences in food intake, RER, and plasma biomarker profiles based upon ICV or IT routes of administration and characterize this novel molecular chemotype as a molecular probe to study the melanocortin system in vivo.

Translational Neuroendocrinology of Human Skin: Concepts and Perspectives

Human skin responds to numerous neurohormones, neuropeptides, and neurotransmitters that reach it via the vasculature or skin nerves, and/or are generated intracutaneously, thus acting in a para- and autocrine manner. This review focuses on how neurohormones impact on human skin physiology and pathology. We highlight basic concepts, major open questions, and translational research perspectives in cutaneous neuroendocrinology and argue that greater emphasis on neuroendocrine human skin research will foster the development of novel dermatological therapies. Furthermore, human skin and its appendages can be used as highly accessible and clinically relevant model systems for probing nonclassical, ancestral neurohormone functions. This calls for close interdisciplinary collaboration between dermatologists, skin biologists, neuroendocrinologists, and neuropharmacologists.

Are melanocortin peptides future therapeutics for cutaneous wound healing?

Cutaneous wound healing is a complex process divided into different phases, that is an inflammatory, proliferative and remodelling phase. During these phases, a variety of resident skin cell types but also cells of the immune system orchestrate the healing process. In the last year, it has been shown that the majority of cutaneous cell types express the melanocortin 1 receptor (MC1R) that binds α-melanocyte-stimulating hormone (α-MSH) with high affinity and elicits pleiotropic biological effects, for example modulation of inflammation and immune responses, cytoprotection, antioxidative defense and collagen turnover. Truncated α-MSH peptides such as Lys-Pro-Val (KPV) as well as derivatives like Lys-d-Pro-Thr (KdPT), the latter containing the amino acid sequence 193-195 of interleukin-1β, have been found to possess anti-inflammatory effects but to lack the pigment-inducing activity of α-MSH. We propose here that such peptides are promising future candidates for the treatment of cutaneous wounds and skin ulcers. Experimental approaches in silico, in vitro, ex vivo and in animal models are outlined. This is followed by an unbiased discussion of the pro and contra arguments of such peptides as future candidates for the therapeutic management of cutaneous wounds and a review of the so-far available data on melanocortin peptides and derivatives in wound healing.

A Direct in Vivo Comparison of the Melanocortin Monovalent Agonist Ac-His-DPhe-Arg-Trp-NH2 versus the Bivalent Agonist Ac-His-DPhe-Arg-Trp-PEDG20-His-DPhe-Arg-Trp-NH2: A Bivalent Advantage

Bivalent ligands targeting putative melanocortin receptor dimers have been developed and characterized in vitro; however, studies of their functional in vivo effects have been limited. The current report compares the effects of homobivalent ligand CJL-1-87, Ac-His-DPhe-Arg-Trp-PEDG20-His-DPhe-Arg-Trp-NH₂, to monovalent ligand CJL-1-14, Ac-His-DPhe-Arg-Trp-NH₂, on energy homeostasis in mice after central intracerebroventricular (ICV) administration into the lateral ventricle of the brain. Bivalent ligand CJL-1-87 had noteworthy advantages as an antiobesity probe over CJL-1-14 in a fasting-refeeding in vivo paradigm. Treatment with CJL-1-87 significantly decreased food intake compared to CJL-1-14 or saline (50% less intake 2-8 h after treatment). Furthermore, CJL-1-87 treatment decreased the respiratory exchange ratio (RER) without changing the energy expenditure indicating that fats were being burned as the primary fuel source. Additionally, CJL-1-87 treatment significantly lowered body fat mass percentage 6 h after administration (p < 0.05) without changing the lean mass percentage. The bivalent ligand significantly decreased insulin, C-peptide, leptin, GIP, and resistin plasma levels compared to levels after CJL-1-14 or saline treatments. Alternatively, ghrelin plasma levels were significantly increased. Serum stability of CJL-1-87 and CJL-1-14 (T_1/2 = 6.0 and 16.8 h, respectively) was sufficient to permit physiological effects. The differences in binding affinity of CJL-1-14 compared to CJL-1-87 are speculated as a possible mechanism for the bivalent ligand's unique effects. We also provide in vitro evidence for the formation of a MC3R-MC4R heterodimer complex, for the first time to our knowledge, that may be an unexploited neuronal molecular target. Regardless of the exact mechanism, the advantageous ability of CJL-1-87 compared to CJL-1-14 to increase in vitro binding affinity, increase the duration of action in spite of decreased serum stability, decrease in vivo food intake, decrease mice's body fat percent, and differentially affect mouse hormone levels demonstrates the distinct characteristics achieved from the current melanocortin agonist bivalent design strategy.

Transdermal Iontophoretic Delivery of Lysine-Proline-Valine (KPV) Peptide Across Microporated Human Skin

Lysine-proline-valine (KPV) is a C-terminal peptide fragment of α-melanocyte stimulating hormone with potent anti-inflammatory properties. Present study investigates various transdermal enhancement strategies such as iontophoresis (ITP), microneedles (MN), and their combination (ITP + MN) on KPV delivery across dermatomed human skin. KPV attains a positive charge at pH less than 7.0, thus anodal ITP was used. The influence of current strength, KPV concentration, and duration of current application on the KPV delivery was investigated. At defined ITP parameters, the influence of MN on KPV delivery (ITP + MN) across skin was also determined. KPV permeation was less than detectable levels (limit of detection, 0.01 μg/mL) by simple passive diffusion. However, KPV permeation was increased to 4.4 μg/cm²/h by MN treatment. Furthermore, ITP and ITP + MN increased the permeation rate by 8 and 35 fold, respectively, as compared to MN alone. The skin retention levels of KPV by MN, ITP, and ITP + MN were increased by 5, 10, and 10 fold, respectively, as compared to passive diffusion. Confocal studies indicate that fluorescein isothiocyanate-labeled KPV migrated through the stratum corneum, along the microchannels and into the lower epidermal tissue because the fluorescence was observed beyond the depth of 100 μm.

Human basophils are a source of - and are differentially activated by - IL-31

BACKGROUND

Basophils are important effector cells involved in the pathogenesis of inflammatory skin diseases including chronic urticaria which is associated by increased IL-31 serum levels. So far the effects of IL-31 on human basophils are unknown.

OBJECTIVE

To analyse the functional role of IL-31 in basophil biology.

METHODS

IL-31 expression was evaluated in skin samples derived from chronic spontaneous urticaria patients. Oncostatin M receptor (OSMR), IL-31 receptor A (RA) and IL-31 protein expressions were analysed on human basophils from healthy donors. Basophil responses to IL-31 were assessed for chemotaxis, externalization of CD63 and CD203c as well as the release of histamine, IL-4 and IL-13.

RESULTS

IL-31RA and OSMR were expressed on human basophils. IL-31 was strongly expressed in the skin of patients with chronic spontaneous urticaria and was released from isolated basophils following either anti-IgE, IL-3 or fMLP stimulation. IL-31 induced chemotaxis and the release of IL-4 and IL-13 which was specifically inhibited by anti-IL-31RA and anti-OSMR. Conversely, IL-31 had no effect on CD63 and CD203c externalization or histamine release.

CONCLUSIONS AND CLINICAL RELEVANCE

Human basophils are a source of -and are activated by - IL-31 with the release of pro-inflammatory cytokines and the induction of chemotaxis indicating an important novel function of IL-31 in basophil biology.

Human basophil chemotaxis and activation are regulated via the histamine H4 receptor

BACKGROUND

IgE-mediated cross-linking of FcεRI results in the release of mediators stored in basophil granules, such as histamine and proteases, and in the de novo synthesis of sulfidoleukotrienes.

OBJECTIVE

In this study, we investigated the role of the histamine receptors, in particular that of the histamine H4 receptor (H4R), in modulating human basophil function.

METHODS

The mRNA expression of the histamine receptors was measured by real-time PCR. Migration of basophils was assessed using the modified Boyden chamber technique. The expression levels of CD63 and CD203c on the cell surface and the sulfidoleukotriene release were determined by flow cytometry and ELISA, respectively.

RESULTS

We could show that highly purified basophils express the H1R, H2R, and H4R but not the H3R mRNA. Human basophils expressed higher H4R mRNA levels as compared to the expression levels of the H1R (P < 0.01). Histamine and the H4R agonist ST-1006 initiated active migration of basophils (P < 0.001). A significant reduction in FcεRI cross-linking-mediated surface expression of CD63 and CD203c was observed on basophils after pre-incubation with histamine or the specific H4R agonist ST-1006 (P < 0.01). The synthesis and release of sulfidoleukotrienes from basophils after activation with different stimuli, by FcεRI cross-linking or by stimulation with hymenoptera venom allergens, were significantly reduced by histamine or the H4R agonist ST-1006 (P < 0.05-0.001).

CONCLUSION

These data imply that the H4R regulates IgE-dependent processes in human basophils and provides a novel function of the H4R preventing an overwhelming immune reaction by engagement of a negative feedback loop.

α-MSH modulates cell adhesion and inflammatory responses of synovial fibroblasts from osteoarthritis patients

INTRODUCTION

The synovium is a target for neuropeptides. Melanocortins have attained particular attention as they elicit antiinflammatory effects. Although synovial fluid from patients with rheumatic diseases contains α-melanocyte-stimulating hormone (α-MSH) it is unknown whether synovial fibroblasts generate α-MSH and respond to melanocortins.

METHODS

Synovial tissue was obtained from osteoarthritis (OA) patients. Cells were isolated and prepared either as primary mixed synoviocytes or propagated as synovial fibroblasts (OASFs). Melanocortin receptor (MC) and proopiomelanocortin (POMC) expression were investigated by endpoint RT-PCR, immunofluorescence and Western immunoblotting. Functional coupling of MC1 was assessed by cAMP and Ca(2+) assays. Cell adhesion was monitored by the xCELLigence system. Secretion of α-MSH, tumour necrosis factor (TNF), interleukin (IL)-6 and IL-8 was determined by ELISA.

RESULTS

OASFs in vitro expressed MC1. MC1 transcripts were present in synovial tissue and appropriate immunoreactivity was detected in synovial fibroblasts in situ. OASFs contained truncated POMC transcripts but neither full-length POMC mRNA, POMC protein nor α-MSH were detectable. In accordance with this only truncated POMC transcripts were present in synovial tissue. α-MSH increased cAMP dose-dependently but did not alter calcium in OASFs. α-MSH also enhanced adhesion of OASFs to fibronectin and reduced TNF, IL-6 and IL-8 secretion in primary mixed synoviocyte cultures. In OASFs, α-MSH modulated basal and TNF/IL-1β-mediated secretion of IL-6 and IL-8.

CONCLUSION

Synovial fibroblasts express MC1in vitro and in situ. α-MSH elicits biological effects in these cells suggesting an endogenous immunomodulatory role of melanocortins within the synovium. Our results encourage in vivo studies with melanocortins in OA models.

Regulation of melanocortin 1 receptor in allergic rhinitis in vitro and in vivo

BACKGROUND

α-melanocyte-stimulating hormone (α-MSH) was shown to inhibit allergic airway inflammation and exert suppressive effects on human basophils.

OBJECTIVE

This study aims to extend our current knowledge on the melanocortin 1 receptor (MC1R) expression in nasal tissue of patients with allergic rhinitis (AR) and functional effects of α-MSH in human basophils especially from patients with allergic rhinitis.

METHODS

MC1R expression before and after nasal allergen provocation was studied in nasal mucosal tissue of AR patients and in a mouse model of allergic airway inflammation using immunofluorescence. In vitro regulation of the MC1R and CD203c surface expression on whole-blood basophils of patients with AR and controls was assessed with flow cytometry. Functional effects of α-MSH on isolated basophils were analysed regarding apoptosis with flow cytometry and chemotaxis using a Boyden chamber assay.

RESULTS

We detected an accumulation of MC1R-positive basophils in nasal mucosa tissue of patients with AR 24 h after nasal allergen provocation. Such accumulation was not present in mucosa sections from healthy controls. In mice with allergic airway inflammation, we found a clear accumulation of MC1R-positive basophils in the nasal tissue compared to control mice. MC1R expression was inducible in AR patients and controls by stimulation with anti-IgE. α-MSH inhibited anti-IgE and grass pollen induced upregulation of CD203c, but had no effect on chemotaxis or apoptosis of basophils in vitro.

CONCLUSIONS AND CLINICAL RELEVANCE

MC1R-positive basophils accumulate in the nasal mucosa of patients with AR after nasal allergen provocation. Since α-MSH suppresses proinflammatory effector functions in human basophils via the MC1R, it constitutes an interesting novel target for modulating the allergic inflammatory response.

Effect of antigen sensitization and challenge on oscillatory mechanics of the lung and pulmonary inflammation in obese carboxypeptidase E-deficient mice

Atopic, obese asthmatics exhibit airway obstruction with variable degrees of eosinophilic airway inflammation. We previously reported that mice obese as a result of a genetic deficiency in either leptin (ob/ob mice) or the long isoform of the leptin receptor (db/db mice) exhibit enhanced airway obstruction in the presence of decreased numbers of bronchoalveolar lavage fluid (BALF) eosinophils compared with lean, wild-type mice following antigen (ovalbumin; OVA) sensitization and challenge. To determine whether the genetic modality of obesity induction influences the development of OVA-induced airway obstruction and OVA-induced pulmonary inflammation, we examined indices of these sequelae in mice obese as a result of a genetic deficiency in carboxypeptidase E, an enzyme that processes prohormones and proneuropeptides involved in satiety and energy expenditure (Cpe(fat) mice). Accordingly, Cpe(fat) and lean, wild-type (C57BL/6) mice were sensitized to OVA and then challenged with either aerosolized PBS or OVA. Compared with genotype-matched, OVA-sensitized and PBS-challenged mice, OVA sensitization and challenge elicited airway obstruction and increased BALF eosinophils, macrophages, neutrophils, IL-4, IL-13, IL-18, and chemerin. However, OVA challenge enhanced airway obstruction and pulmonary inflammation in Cpe(fat) compared with wild-type mice. These results demonstrate that OVA sensitization and challenge enhance airway obstruction in obese mice regardless of the genetic basis of obesity, whereas the degree of OVA-induced pulmonary inflammation is dependent on the genetic modality of obesity induction. These results have important implications for animal models of asthma, as modeling the pulmonary phenotypes for subpopulations of atopic, obese asthmatics critically depends on selecting the appropriate mouse model.

Advances in mechanisms of allergy and clinical immunology in 2012

Manuscripts published in the "Mechanisms of allergy and clinical immunology" section of the Journal of Allergy and Clinical Immunology during 2012 enhanced our knowledge of the involvement of cytokines and other mediators in allergic disorders and described novel approaches for understanding mechanisms of allergic and immunologic diseases. Also published were articles focused on mechanisms of allergen-specific immunotherapy and the development of novel antiallergic treatments, as well as strategies to achieve tolerance to allergens. The highlights of these studies and their potential clinical implications are summarized in this review.

KU812 basophils express urocortin, CRH-R, MC1R and steroidogenic enzymes and secrete progesterone

Little is known about neuroendocrine regulation of human basophils by components of the hypothalamic-pituitary-adrenal (HPA) axis. Using the basophil cell line KU812 as an in vitro model, we show that these cells express urocortin 1-3, specific isoforms of the corticotropin-releasing hormone (CRH) receptor (CRH-R)1 and CRH-R2 but not CRH itself. The precursor for melanocortins and β-endorphin, proopiomelanocortin, was not detectable, while the melanocortin-1 receptor was present at RNA and protein level in KU812 cells. KU812 basophils furthermore expressed key enzymes involved in steroidogenesis, that is, CYP11A1, CYP17 and CYP21A2. The relevance of steroidogenic enzyme expression in KU812 cells was confirmed by showing the presence of progesterone and 17OH-progesterone in conditioned media of these cells. Our data demonstrate the expression of some but not all components of the HPA axis in human basophils. These cells are not only target cells for multiple hormones of the HPA axis but may also generate neuroendocrine mediators autonomously.

Role of proopiomelanocortin-derived peptides and their receptors in the osteoarticular system: from basic to translational research

Proopiomelanocortin (POMC)-derived peptides such as melanocortins and β-endorphin (β-ED) exert their pleiotropic effects via binding to melanocortin receptors (MCR) and opioid receptors (OR). There is now compelling evidence for the existence of a functional POMC system within the osteoarticular system. Accordingly, distinct cell types of the synovial tissue and bone have been identified to generate POMC-derived peptides like β-ED, ACTH, or α-MSH. MCR subtypes, especially MC1R, MC2R (the ACTH receptor), MC3R, and MC4R, but also the μ-OR and δ-OR, have been detected in various cells of the synovium, cartilage, and bone. The respective ligands of these POMC-derived peptide receptors mediate an increasing number of newly recognized biological effects in the osteoarticular system. These include bone mineralization and longitudinal growth, cell proliferation and differentiation, extracellular matrix synthesis, osteoprotection, and immunomodulation. Importantly, bone formation is also regulated by the central melanocortin system via a complex hormonal interplay with other organs and tissues involved in energy metabolism. Among the POMC-derived peptides examined in cell culture systems from osteoarticular tissue and in animal models of experimentally induced arthritis, α-MSH, ACTH, and MC3R-specific agonists appear to have the most promising antiinflammatory actions. The effects of these melanocortin peptides may be exploited in future for the treatment of patients with inflammatory and degenerative joint diseases.