Neuropeptide control mechanisms in cutaneous biology: physiological and clinical significance

Antimicrobial Neuropeptides and Their Receptors: Immunoregulator and Therapeutic Targets for Immune Disorders

The interaction between the neuroendocrine system and the immune system plays a key role in the onset and progression of various diseases. Neuropeptides, recognized as common biochemical mediators of communication between these systems, are receiving increasing attention because of their potential therapeutic applications in immune-related disorders. Additionally, many neuropeptides share significant similarities with antimicrobial peptides (AMPs), and evidence shows that these antimicrobial neuropeptides are directly involved in innate immunity. This review examines 10 antimicrobial neuropeptides, including pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP), α-melanocyte stimulating hormone (α-MSH), ghrelin, adrenomedullin (AM), neuropeptide Y (NPY), urocortin II (UCN II), calcitonin gene-related peptide (CGRP), substance P (SP), and catestatin (CST). Their expression characteristics and the immunomodulatory mechanisms mediated by their specific receptors are summarized, along with potential drugs targeting these receptors. Future studies should focus on further investigating antimicrobial neuropeptides and advancing the development of related drugs in preclinical and/or clinical studies to improve the treatment of immune-related diseases.

Intradermal injection of botulinum toxin for erythema in rosacea: A scoping review and meta-analysis

Background Rosacea is a skin condition characterised by persistent facial erythema, flushing, papules, pustules, and telangiectasia. Botulinum toxin A (BoNT-A) has been used to treat a variety of conditions, but its effectiveness in improving facial erythema in rosacea patients is uncertain. Objectives The aim of the study is to evaluate the effectiveness and determine the optimal dose of BoNT-A treatment for rosacea. Methods An online database search (Pubmed, Cochrane Library and Embase) was conducted on 30th June 2023 to identify studies that used intradermal injection of BoNT-A to treat facial erythema in rosacea patients and excluded studies in which BoNT-A was used for facial erythema due to other known medical condition such as menopause, drug or pregnancy. The primary outcome measure for this study was the improvement in erythema score as objectively assessed. A random effect model was used in the meta-analysis. Results Seven studies involving a total of 167 rosacea patients were included in the meta-analysis. Meta-analysis of two randomised controlled trials showed improvement of erythema on the third month after treatment standardized mean difference (SMD): 1.676, 95% confidence interval (CI): 2.278-1.074, I2: 35.76%). A separate analysis of seven single-armed treatment studies found significant improvement in erythema with intradermal injection of BoNT-A at one, two and three months after treatment (first month: SMD: 2.712, 95% CI: 4.1182-1.243; second month: SMD:2.213, 95% CI: 3.702-0.725; third month: SMD: 1.912, 95% CI: 2.882-0.941). Adverse events, including mild facial paralysis and injectional purpura, were reported in some studies. Limitation The limitations of this study include heterogeneity in study design and a small sample size. Conclusion Intradermal injection of BoNT-A may be an effective treatment for facial erythema in rosacea. Unwanted facial muscle paralysis was seen in different BoNT-A concentration but not noted when the dose was less than 0.02ml per site. Future studies particularly randomised trials are required to identify the volume of injection required to reduce the erythema.

Sensory Symptoms as an Early Manifestation of Active Vitiligo: A Case-Control Clinical and Molecular Study

Vitiligo pathogenesis is complex. There is some evidence in support of the neurohormonal pathways involved. Although considered a nonpruritic condition, some patients may experience itching, which can occur ahead of the appearance of the patches. We aimed to assess sensory symptoms in active and stable vitiligo patients and to measure 3 neuropeptide expressions in their lesional skin (neuropeptide Y [NPY], calcitonin gene-related peptide [CGRP], and nerve growth factors [NGF]) to correlate neuropeptide levels and sensory symptoms, with vitiligo activity. This case-control study included 85 patients, aged 18 years and older, analyzed into active or stable vitiligo groups. Patients were screened for itching or other abnormal neurological sensations such as paresthesia and numbness. The Vitiligo Disease Activity Score, Vitiligo Signs of Activity Score, and dermoscopic score were performed to assess disease activity. Three neuropeptides were quantified by enzyme-linked immunosorbent assay in skin biopsies from the edge of vitiligo lesions. A normal control group was also included. Results showed that 24.7% of patients had sensory symptoms: itching (18.8%), paresthesia (2.4%), and numbness (3.5%). The NGF, CGRP, and NPY levels were significantly higher in skin of normal controls compared to stable and active vitiligo patients. They were lowest in active vitiligo skin (p = 0.001, 0.016, and 0.01, respectively). NGF was the most relevant neuropeptide to vitiligo activity and sensory manifestations. In conclusion, almost one-third of the patients with active vitiligo reported sensory symptoms, predominantly itching, thus sensory manifestations may suggest a prodroma of activity and could be included in the screening tools for vitiligo activity. Trial Registration: www.clinicaltrials.gov (NCT05390164).

Skin Innervation

All layers and appendages of the skin are densely innervated by afferent and efferent neurons providing sensory information and controlling skin perfusion and sweating. In mice, neuronal functions have been comprehensively linked to unique single-cell expression patterns and to characteristic arborization of nerve endings in skin and dorsal horn, whereas for humans, specific molecular markers for functional classes of afferent neurons are still lacking. Moreover, bidirectional communication between sensory neurons and local skin cells has become of particular interest, resulting in a broader physiological understanding of sensory function but also of trophic functions and immunomodulation in disease states.

Neuroanatomy of the Cutaneous Nervous System Regarding Wound Healing

Wound healing is an important topic in modern medicine across many disciplines. Healing of all cutaneous wounds, whether accidentally sustained or intentionally created, requires the common yet complex set of interactions between the immune, circulatory, nervous, endocrine, and integumentary systems. Deficits in any of these systems or the molecular factors that mediate their communications can contribute to impaired healing of cutaneous wounds. While the stages of wound repair, angiogenesis, growth factors, and cytokines involved have been extensively studied, the role of the cutaneous nervous system in wound healing has not been well outlined. We have provided a basic overview of cutaneous innervation and wound repair for the dermatologic surgeon by outlining the normal cutaneous nervous anatomy and function and discussing the most important neuropeptides that mediate the wound healing process.

Examination of Subbasal Nerve Plexus and Central Corneal Stromal Microstructure in Subjects With Congenital Aniridia, Using in Vivo Confocal Laser Scanning Microscopy

PURPOSE

During life up to 70% of aniridia subjects develop aniridia-associated keratopathy (AAK). AAK is characterized by limbal stem cell insufficiency, impaired corneal epithelial cell differentiation and abnormal cell adhesion, which leads to centripetal spreading vascularization, conjunctivalization, and thickening of the cornea. Our aim was to examine the subbasal nerve plexus and central corneal stromal microstructure in subjects with congenital aniridia, using in vivo confocal laser scanning microscopy CLSM.

METHODS

31 eyes of 18 patients (55.6% males, mean age: 25.22 ± 16.35 years) with congenital aniridia and 46 eyes of 29 healthy subjects (41.4% males, mean age 30 ± 14.82 years) were examined using the Rostock Cornea Module of Heidelberg Retina Tomograph-III. At the subbasal nerve plexus, corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), corneal total branch density (CTBD), and corneal nerve fiber width (CNFW) were analyzed using ACCMetrics software. Keratocyte density in the anterior, middle and posterior stroma was assessed manually.

RESULTS

The CNFD (2.02 ± 4.08 vs 13.99 ± 6.34/mm2), CNFL (5.78 ± 2.68 vs 10.56 ± 2.82 mm/mm2) and CTBD (15.08 ± 15.62 vs 27.44 ± 15.05/mm2) were significantly lower in congenital aniridia subjects than in controls (p < 0.001 for all). CNFW was significantly higher in aniridia subjects than in controls (0.03 ± 0.004 vs 0.02 ± 0.003 mm/mm2) (p = 0.003). Keratocyte density was significantly lower in all stromal layers of aniridia subjects than in controls (p < 0.001 for all). Stromal alterations included confluent keratocytes, keratocytes with long extensions and hyperreflective dots between keratocytes in aniridia.

CONCLUSIONS

Decrease in CNFD, CNFL, and CTBD, as well as increase in CNFW well refer to the congenital aniridia-associated neuropathy. The decreased keratocyte density and the stromal alterations may be related to an increased cell death in congenital aniridia, nevertheless, stromal changes in different stages of AAK have to be further analyzed in detail.

Role of neurogenic inflammation in the pathogenesis of alopecia areata

Alopecia areata refers to an autoimmune illness indicated by persistent inflammation. The key requirement for alopecia areata occurrence is the disruption of immune-privileged regions within the hair follicles. Recent research has indicated that neuropeptides play a role in the damage to hair follicles by triggering neurogenic inflammation, stimulating mast cells ambient the follicles, and promoting apoptotic processes in keratinocytes. However, the exact pathogenesis of alopecia areata requires further investigation. Recently, there has been an increasing focus on understanding the mechanisms of immune diseases resulting from the interplay between the nervous and the immune system. Neurogenic inflammation due to neuroimmune disorders of the skin system may disrupt the inflammatory microenvironment of the hair follicle, which plays a crucial part in the progression of alopecia areata.

Contribution of cosmetic ingredients and skin care textures to emotions

OBJECTIVE

Emotions play an important role in consumers' perception of a sensory experience. The objective of this work was to investigate the ability of basic skin care formulas (i.e. without interference of odour, colour and packaging) and pillar ingredients (i.e. emollients and rheology modifiers) to elicit emotions. Another objective was to track, as claimed by neurocosmetics, the possible effect of formulas to trigger emotions from their direct biochemical effects on the skin.

METHODS

Standard methodologies were mobilized, combining subjective and behavioural parameters (i.e. verbatim, prosody and gesture). Sense and Story methodology based on a collection of metaphoric verbatim was conducted after an induction phase. In addition, an experimental electrophysiological real-time visualization method was tried as a first experience in cosmetics. Finally, the ability of formulations with emotional benefits to modulate the release of neuropeptides by sensory neurons was evaluated on a 3D human model (epidermis co-cultured with sensory neurons).

RESULTS

Skin care formulas were shown to play a role in emotional potential and the types of emotion generated, while changing one ingredient mostly acted on the intensity of the emotions. Verbatim provided contrasted answers depending on the protocol, highlighting the interest of non-verbal approaches to detect subtle effects. The in vitro model substantiated physiological effects of skin care formulas with emotional potential on human skin sensory neuron activity.

CONCLUSION

Emotions were impacted by the change in ingredients and were better captured through non-verbal methods.

Human Hair Graying Revisited: Principles, Misconceptions, and Key Research Frontiers

Hair graying holds psychosocial importance and serves as an excellent model for studying human pigmentation and aging in an accessible miniorgan. Current evidence suggests that graying results from an interindividually varying mixture of cumulative oxidative and DNA damage, excessive mTORC1 activity, melanocyte senescence, and inadequate production of pigmentation-promoting factors in the hair matrix. Various regulators modulate this process, including genetic factors (DNA repair defects and IRF4 sequence variation, peripheral clock genes, P-cadherin signaling, neuromediators, HGF, KIT ligand secretion, and autophagic flux. This leads to reduced MITF- and tyrosinase-controlled melanogenesis, defective melanosome transfer to precortical matrix keratinocytes, and eventual depletion of hair follicle (HF) pigmentary unit (HFPU) melanocytes and their local progenitors. Graying becomes irreversible only when bulge melanocyte stem cells are also depleted, occurring later in this process. Distinct pigmentary microenvironments are created as the HF cycles: early anagen is the most conducive phase for melanocytic reintegration and activation, and only during anagen can the phenotype of hair graying and repigmentation manifest, whereas the HFPU disassembles during catagen. The temporary reversibility of graying is highlighted by several drugs and hormones that induce repigmentation, indicating potential target pathways. We advise caution in directly applying mouse model concepts, define major open questions, and discuss future human antigraying strategies.

Alopecia areata: review of epidemiology, pathophysiology, current treatments and nanoparticulate delivery system

Alopecia areata (AA) is a kind of alopecia that affects hair follicles and nails. It typically comes with round patches and is a type of nonscarring hair loss. Various therapies are accessible for the management and treatment of AA, including topical, systemic and injectable modalities. It is a very complex type of autoimmune disease and is identified as round patches of hair loss and may occur at any age. This review paper highlights the epidemiology, clinical features, pathogenesis and new treatment options for AA, with a specific emphasis on nanoparticulate drug-delivery systems. By exploring these innovative treatment approaches, researchers aim to enhance the effectiveness and targeted delivery of therapeutic agents, ultimately improving outcomes for individuals living with AA.

A Novel Perspective on Neuronal Control of Anatomical Patterning, Remodeling, and Maintenance

While the nervous system may be best known as the sensory communication center of an organism, recent research has revealed a myriad of multifaceted roles for both the CNS and PNS from early development to adult regeneration and remodeling. These systems work to orchestrate tissue pattern formation during embryonic development and continue shaping pattering through transitional periods such as metamorphosis and growth. During periods of injury or wounding, the nervous system has also been shown to influence remodeling and wound healing. The neuronal mechanisms responsible for these events are largely conserved across species, suggesting this evidence may be important in understanding and resolving many human defects and diseases. By unraveling these diverse roles, this paper highlights the necessity of broadening our perspective on the nervous system beyond its conventional functions. A comprehensive understanding of the complex interactions and contributions of the nervous system throughout development and adulthood has the potential to revolutionize therapeutic strategies and open new avenues for regenerative medicine and tissue engineering. This review highlights an important role for the nervous system during the patterning and maintenance of complex tissues and provides a potential avenue for advancing biomedical applications.

Whole genome sequencing identifies genetic variants associated with neurogenic inflammation in rosacea

Rosacea is a chronic inflammatory skin disorder with high incidence rate. Although genetic predisposition to rosacea is suggested by existing evidence, the genetic basis remains largely unknown. Here we present the integrated results of whole genome sequencing (WGS) in 3 large rosacea families and whole exome sequencing (WES) in 49 additional validation families. We identify single rare deleterious variants of LRRC4, SH3PXD2A and SLC26A8 in large families, respectively. The relevance of SH3PXD2A, SLC26A8 and LRR family genes in rosacea predisposition is underscored by presence of additional variants in independent families. Gene ontology analysis suggests that these genes encode proteins taking part in neural synaptic processes and cell adhesion. In vitro functional analysis shows that mutations in LRRC4, SH3PXD2A and SLC26A8 induce the production of vasoactive neuropeptides in human neural cells. In a mouse model recapitulating a recurrent Lrrc4 mutation from human patients, we find rosacea-like skin inflammation, underpinned by excessive vasoactive intestinal peptide (VIP) release by peripheral neurons. These findings strongly support familial inheritance and neurogenic inflammation in rosacea development and provide mechanistic insight into the etiopathogenesis of the condition.

Effects of pulsed dye laser treatment in psoriasis: A nerve-wrecking process?

Pulsed dye laser (PDL) therapy can be effective in treating psoriasis, with a long duration of remission. Although PDL therapy, albeit on a modest scale, is being used for decades now, the underlying mechanisms responsible for the long-term remission of psoriasis remain poorly understood. The selective and rapid absorption of energy by the blood causes heating of the vascular wall and surrounding structures, like perivascular nerves. Several studies indicate the importance of nerves in psoriatic inflammation. Interestingly, denervation leads to a spontaneous remission of the psoriatic lesion. Among all dermal nerves, the perivascular nerves are the most likely to be affected during PDL treatment, possibly impairing the neuro-inflammatory processes that promote T-cell activation, expression of adhesion molecules, leukocyte infiltration and cytokine production. Repeated PDL therapy could cause a prolonged loss of innervation through nerve damage, or result in a 'reset' of neurogenic inflammation after temporary denervation. The current hypothesis provides strong arguments that PDL treatment affects nerve fibres in the skin and thereby abrogates the persistent and exaggerated inflammatory process underlying psoriasis, causing a long-term remission of psoriasis.

Neuroendocrine signaling in the skin with a special focus on the epidermal neuropeptides

The skin, which is comprised of the epidermis, dermis, and subcutaneous tissue, is the largest organ in the human body and it plays a crucial role in the regulation of the body's homeostasis. These functions are regulated by local neuroendocrine and immune systems with a plethora of signaling molecules produced by resident and immune cells. In addition, neurotransmitters, endocrine factors, neuropeptides, and cytokines released from nerve endings play a central role in the skin's responses to stress. These molecules act on the corresponding receptors in an intra-, juxta-, para-, or autocrine fashion. The epidermis as the outer most component of skin forms a barrier directly protecting against environmental stressors. This protection is assured by an intrinsic keratinocyte differentiation program, pigmentary system, and local nervous, immune, endocrine, and microbiome elements. These constituents communicate cross-functionally among themselves and with corresponding systems in the dermis and hypodermis to secure the basic epidermal functions to maintain local (skin) and global (systemic) homeostasis. The neurohormonal mediators and cytokines used in these communications regulate physiological skin functions separately or in concert. Disturbances in the functions in these systems lead to cutaneous pathology that includes inflammatory (i.e., psoriasis, allergic, or atopic dermatitis, etc.) and keratinocytic hyperproliferative disorders (i.e., seborrheic and solar keratoses), dysfunction of adnexal structure (i.e., hair follicles, eccrine, and sebaceous glands), hypersensitivity reactions, pigmentary disorders (vitiligo, melasma, and hypo- or hyperpigmentary responses), premature aging, and malignancies (melanoma and nonmelanoma skin cancers). These cellular, molecular, and neural components preserve skin integrity and protect against skin pathologies and can act as "messengers of the skin" to the central organs, all to preserve organismal survival.

The highest-elevation frog provides insights into mechanisms and evolution of defenses against high UV radiation

Defense against ultraviolet (UV) radiation exposure is essential for survival, especially in high-elevation species. Although some specific genes involved in UV response have been reported, the full view of UV defense mechanisms remains largely unexplored. Herein, we used integrated approaches to analyze UV responses in the highest-elevation frog, Nanorana parkeri. We show less damage and more efficient antioxidant activity in skin of this frog than those of its lower-elevation relatives after UV exposure. We also reveal genes related to UV defense and a corresponding temporal expression pattern in N. parkeri. Genomic and metabolomic analysis along with large-scale transcriptomic profiling revealed a time-dependent coordinated defense mechanism in N. parkeri. We also identified several microRNAs that play important regulatory roles, especially in decreasing the expression levels of cell cycle genes. Moreover, multiple defense genes (i.e., TYR for melanogenesis) exhibit positive selection with function-enhancing substitutions. Thus, both expression shifts and gene mutations contribute to UV adaptation in N. parkeri. Our work demonstrates a genetic framework for evolution of UV defense in a natural environment.

Interleukin 13 receptor alpha 2 (IL13Rα2): Expression, signaling pathways and therapeutic applications in cancer

Interleukin 13 receptor alpha 2 (IL13Rα2) is increasingly recognized as a relevant player in cancer invasion and metastasis. Despite being initially considered a decoy receptor for dampening the levels of interleukin 13 (IL-13) in diverse inflammatory conditions, accumulating evidences in the last decades indicate the capacity of IL13Rα2 for mediating IL-13 signaling in cancer cells. The biological reasons behind the expression of this receptor with such extremely high affinity for IL-13 in cancer cells remain unclear. Elevated expression of IL13Rα2 is commonly associated with invasion, late stage and cancer metastasis that results in poor prognosis for glioblastoma, colorectal or breast cancer, among others. The discovery of new mediators and effectors of IL13Rα2 signaling has been critical for deciphering its underlying molecular mechanisms in cancer progression. Still, many questions about the effects of inflammation, the cancer type and the tumor degree in the expression of IL13Rα2 remain largely uncharacterized. Here, we review and discuss the current status of the IL13Rα2 biology in cancer, with particular emphasis in the role of inflammation-driven expression and the regulation of different signaling pathways. As IL13Rα2 implications in cancer continue to grow exponentially, we highlight new targeted therapies recently developed for glioblastoma, colorectal cancer and other IL13Rα2-positive tumors.

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.

The Problem of Wound Healing in Diabetes—From Molecular Pathways to the Design of an Animal Model

Chronic wounds are becoming an increasingly common clinical problem due to an aging population and an increased incidence of diabetes, atherosclerosis, and venous insufficiency, which are the conditions that impair and delay the healing process. Patients with diabetes constitute a group of subjects in whom the healing process is particularly prolonged regardless of its initial etiology. Circulatory dysfunction, both at the microvascular and macrovascular levels, is a leading factor in delaying or precluding wound healing in diabetes. The prolonged period of wound healing increases the risk of complications such as the development of infection, including sepsis and even amputation. Currently, many substances applied topically or systemically are supposed to accelerate the process of wound regeneration and finally wound closure. The role of clinical trials and preclinical studies, including research based on animal models, is to create safe medicinal products and ensure the fastest possible healing. To achieve this goal and minimize the wide-ranging burdens associated with conducting clinical trials, a correct animal model is needed to replicate the wound conditions in patients with diabetes as closely as possible. The aim of the paper is to summarize the most important molecular pathways which are impaired in the hyperglycemic state in the context of designing an animal model of diabetic chronic wounds. The authors focus on research optimization, including economic aspects and model reproducibility, as well as the ethical dimension of minimizing the suffering of research subjects according to the 3 Rs principle (Replacement, Reduction, Refinement).

Skin codelivery of contact sensitizers and neurokinin-1 receptor antagonists integrated in microneedle arrays suppresses allergic contact dermatitis

BACKGROUND

Allergic contact dermatitis (CD) is a chronic inflammatory skin disease caused by type 1 biased adaptive immunity for which there is an unmet need for antigen (Ag)-specific immunotherapies. Exposure to skin sensitizers stimulates secretion of the proinflammatory neuropeptides substance P and hemokinin 1, which signal via the neurokinin-1 receptor (NK1R) to promote the innate and adaptive immune responses of CD. Accordingly, mice lacking the NK1R develop impaired CD. Nonetheless, the role and therapeutic opportunities of targeting the NK1R in CD remain to be elucidated.

OBJECTIVE

We sought to develop an Ag-specific immunosuppressive approach to treat CD by skin codelivery of hapten and NK1R antagonists integrated in dissolvable microneedle arrays (MNA).

METHODS

In vivo mouse models of contact hypersensitivity and ex vivo models of human skin were used to delineate the effects and mechanisms of NK1R signaling and the immunosuppressive effects of the contact sensitizer NK1R antagonist MNA in CD.

RESULTS

We demonstrated in mice that CD requires NK1R signaling by substance P and hemokinin 1. Specific deletion of the NK1R in keratinocytes and dendritic cells, but not in mast cells, prevented CD. Skin codelivery of hapten or Ag MNA inhibited neuropeptide-mediated skin inflammation in mouse and human skin, promoted deletion of Ag-specific effector T cells, and increased regulatory T cells, which prevented CD onset and relapses locally and systemically in an Ag-specific manner.

CONCLUSIONS

Immunoregulation by engineering localized skin neuroimmune networks can be used to treat cutaneous diseases that like CD are caused by type 1 immunity.

G Protein-Coupled Receptors as Potential Intercellular Communication Mediators in Trypanosomatidae

Detection and transduction of environmental signals, constitute a prerequisite for successful parasite invasion; i.e., Leishmania transmission, survival, pathogenesis and disease manifestation and dissemination, with diverse molecules functioning as inter-cellular signaling ligands. Receptors [i.e., G protein-coupled receptors (GPCRs)] and their associated transduction mechanisms, well conserved through evolution, specialize in this function. However, canonical GPCR-related signal transduction systems have not been described in Leishmania, although orthologs, with reduced domains and function, have been identified in Trypanosomatidae. These inter-cellular communication means seem to be essential for multicellular and unicellular organism’s survival. GPCRs are flexible in their molecular architecture and may interact with the so-called receptor activity-modifying proteins (RAMPs), which modulate their function, changing GPCRs pharmacology, acting as chaperones and regulating signaling and/or trafficking in a receptor-dependent manner. In the skin, vasoactive- and neuro- peptides released in response to the noxious stimuli represented by the insect bite may trigger parasite physiological responses, for example, chemotaxis. For instance, in Leishmania (V.) braziliensis, sensory [Substance P, SP, chemoattractant] and autonomic [Vasoactive Intestinal Peptide, VIP, and Neuropeptide Y, NPY, chemorepellent] neuropeptides at physiological levels stimulate in vitro effects on parasite taxis. VIP and NPY chemotactic effects are impaired by their corresponding receptor antagonists, suggesting that the stimulated responses might be mediated by putative GPCRs (with essential conserved receptor domains); the effect of SP is blocked by [(D-Pro 2, D-Trp7,9]-Substance P (10^-6 M)] suggesting that it might be mediated by neurokinin-1 transmembrane receptors. Additionally, vasoactive molecules like Calcitonin Gene-Related Peptide [CGRP] and Adrenomedullin [AM], exert a chemorepellent effect and increase the expression of a 24 kDa band recognized in western blot analysis by (human-)-RAMP-2 antibodies. In-silico search oriented towards GPCRs-like receptors and signaling cascades detected a RAMP-2-aligned sequence corresponding to Leishmania folylpolyglutamate synthase and a RAMP-3 aligned protein, a hypothetical Leishmania protein with yet unknown function, suggesting that in Leishmania, CGRP and AM activities may be modulated by RAMP- (-2) and (-3) homologs. The possible presence of proteins and molecules potentially involved in GPCRs cascades, i.e., RAMPs, signpost conservation of ancient signaling systems associated with responses, fundamental for cell survival, (i.e., taxis and migration) and may constitute an open field for description of pharmacophores against Leishmania parasites.

Too much or too little information: how unknown uncertainty fuels time inconsistency

Under uncertainty, there is considerable heterogeneity in expectations of results, and the outcome of each choice is a reflection of those expectations. This study aims to understand the role of subjective probabilistic inference in updating information for decision-making procedures under uncertainty. We show that adding uncertainty of trade-offs in decision-making criteria induces more inconsistent present preferences. We find that subjective probabilistic inference results in different levels of information acquisition, which plays a central role in many everyday cases of forecasting. The result of forecasting exerts substantive constraints on cognitive processes and shapes a type of restriction or stimulus in decision-making procedures. As uncertainty increases, generated fear of losses turns into an obstacle to the information acquisition process, and especially participants with low probabilistic inference tend to overestimate or underestimate future unknown rewards. In addition, our experiment shows that risk preference does not play a key role in decision-making procedures under unknown uncertainty. This finding is an experimental manifestation of Knight's argument (Risk, uncertainty, and profit, Houghton Mifflin, Boston, 1921), which explains unknown uncertainty, and shows the relationship between cognitive ability and time inconsistency.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43546-021-00189-9.

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.

The Importance of Cutaneous Innervation in Wound Healing: From Animal Studies to Clinical Applications

The skin is a neuroimmunoendocrine organ that regularly undergoes injury and repair. The complex process of wound healing relies heavily on the cutaneous nervous system. Despite the observation that wound healing deficiencies cause significant morbidity and mortality for patients with nervous dysfunction across many disciplinaries, the role of cutaneous innervation in wound repair has not been well elucidated. In a previous article, we learned the basics of cutaneous neuroanatomy and the important neuropeptides involved in the wound healing process. Currently, we aim to synthesize the basics with observations from animal models and human studies for a more comprehensive understanding of nervous system involvement in cutaneous wound healing. We have demonstrated in this review, the importance of the cutaneous nervous system in each phase of wound healing through basic science research, animal experiments, and human studies.

Pituitary adenylate cyclase-activating polypeptide promotes cutaneous dendritic cell functions in contact hypersensitivity

BACKGROUND

Sensory nerves regulate cutaneous local inflammation indirectly through induction of pruritus and directly by acting on local immune cells. The underlying mechanisms for how sensory nerves influence cutaneous acquired immune responses remain to be clarified.

OBJECTIVE

This study aimed to explore the effect of peripheral nerves on cutaneous immune cells in cutaneous acquired immune responses.

METHODS

We analyzed contact hypersensitivity (CHS) responses as a murine model of delayed-type hypersensitivity in absence or presence of resiniferatoxin-induced sensory nerve denervation. We conducted ear thickness measurements, flow cytometric analyses, and mRNA expression analyses in CHS.

RESULTS

CHS responses were attenuated in mice that were denervated during the sensitization phase of CHS. By screening neuropeptides, we found that pituitary adenylate cyclase-activating polypeptide (PACAP) mRNA expression was decreased in the dorsal root ganglia after denervation. Administration of PACAP restored attenuated CHS response in resiniferatoxin-treated mice, and pharmacological inhibition of PACAP suppressed CHS. Flow cytometric analysis of skin-draining lymph nodes showed that cutaneous dendritic cell migration and maturation were reduced in both denervated mice and PACAP antagonist-treated mice. The expression of chemokine receptors CCR7 and CXCR4 of dendritic cell s was enhanced by addition of PACAP in vitro.

CONCLUSION

These findings indicate that a neuropeptide PACAP promotes the development of CHS responses by inducing cutaneous dendritic cell functions during the sensitization phase.

Corneal Immune Cells Are Increased in Patients With Multiple Sclerosis

Purpose

Corneal confocal microscopy (CCM) is an ophthalmic imaging technique that has been used to identify increased corneal immune cells in patients with immune-mediated peripheral neuropathy. Given that multiple sclerosis has an immune-mediated etiology, we have compared corneal immune cell (IC) density and near-nerve distance in different subtypes of patients with multiple sclerosis (MS) to controls.

Methods

This is a blinded, cross-sectional study conducted at a tertiary hospital. Patients with clinically isolated syndrome (CIS) (n = 9), relapsing-remitting multiple sclerosis (RRMS) (n = 43), secondary progressive multiple sclerosis (SPMS) (n = 22), and control subjects (n = 20) underwent CCM. The total, mature, and immature corneal IC density and their nearest nerve distance were quantified.

Results

The total IC density was higher in patients with MS (P = 0.02), RRMS (P = 0.01), and SPMS (P = 0.04) but not CIS (P = 0.99) compared to controls. Immature IC density was higher in patients with MS (P = 0.03) and RRMS (P = 0.02) but not SPMS (P = 0.10) or CIS (P = 0.99) compared to controls. Mature IC density (P = 0.15) did not differ between patients with MS and controls. The immature IC near-nerve distance was significantly greater in patients with MS (P = 0.001), RRMS (P = 0.007), and SPMS (P = 0.002) compared to controls. Immature IC density correlated with the Symbol Digit Modalities Test (r = –0.281, P = 0.02) and near-nerve distance correlated with the Expanded Disability Status Scale (r = 0.289, P = 0.005).

Conclusions

In vivo CCM demonstrates an increase in immature IC density and the near-nerve distance in patients with MS. These observations merit further studies to assess the utility of CCM in assessing neuroimmune alterations in MS.

Translational Relevance

Multiple sclerosis is an immune-mediated neurodegenerative disease. Dendritic cells mediate communication between the innate and adaptive immune systems. We have used in vivo CCM to show increased corneal ICs and suggest it may act as an imaging biomarker for disease status in patients with MS.

Current views on neuropeptides in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease involving skin barrier dysfunction and immune imbalance. However, the mechanism of AD is not clear completely and may be related to heredity and environment. Neuropeptides are a class of peptides secreted by nerve endings, they may play roles in promoting vasodilation, plasma extravasation, chemotaxis of inflammatory cells and mediating pruritus. Since itching and immune cell infiltration are the main manifestations of atopic dermatitis, to further investigate the impact of neuropeptides on AD, our review summarized the mechanisms of several common neuropeptides in AD and hypothesized that neuropeptides may be the novel potential targets in AD treatment.

Small Nerve Fiber Damage and Langerhans Cells in Type 1 and Type 2 Diabetes and LADA Measured by Corneal Confocal Microscopy

Purpose

Increased corneal and epidermal Langerhans cells (LCs) have been reported in patients with diabetic neuropathy. The aim of this study was to quantify the density of LCs in relation to corneal nerve morphology and the presence of diabetic neuropathy and to determine if this differed in patients with type 1 diabetes mellitus (T1DM), type 2 diabetes mellitus (T2DM), and latent autoimmune diabetes of adults (LADA).

Methods

Patients with T1DM (n = 25), T2DM (n = 36), or LADA (n = 23) and control subjects (n = 23) underwent detailed assessment of peripheral neuropathy and corneal confocal microscopy. Corneal nerve fiber density (CNFD), branch density (CNBD), length (CNFL) and total, immature and mature LC densities were quantified.

Results

Lower CNFD (P < 0.001), CNBD (P < 0.0001), and CNFL (P < 0.0001) and higher LC density (P = 0.03) were detected in patients with T1DM, T2DM, and LADA compared to controls. CNBD was inversely correlated with mature (r = -0.5; P = 0.008), immature (r = -0.4; P = 0.02) and total (r = -0.5; P = 0.01) LC density, and CNFL was inversely correlated with immature LC density (r = -0.4; P = 0.03) in patients with T1DM but not in patients with T2DM and LADA.

Conclusions

This study shows significant corneal nerve loss and an increase in LC density in patients with T1DM, T2DM, and LADA. Furthermore, increased LC density correlated with corneal nerve loss in patients with T1DM.

Radiofrequency Irradiation Modulates TRPV1-Related Burning Sensation in Rosacea

Rosacea is a skin inflammatory condition that is accompanied by not only redness and flushing but also unseen symptoms, such as burning, stinging, and itching. TRPV1 expression in UVB-exposed skin can lead to a painful burning sensation. Upregulated TRPV1 expression helps release neuropeptides, including calcitonin gene-related peptide, pituitary adenylate cyclase-activating polypeptide, and vasoactive intestinal peptide, which can activate macrophage and inflammatory molecules. In this study, we found that radiofrequency (RF) irradiation reduced TRPV1 activation and neuropeptide expression in a UVB-exposed in vivo model and UVB- or heat-treated in an in vitro model. RF irradiation attenuated neuropeptide-induced macrophage activation and inflammatory molecule expression. Interestingly, the burning sensation in the skin of UVB-exposed mice and patients with rosacea was significantly decreased by RF irradiation. These results can provide experimental and molecular evidence on the effective use of RF irradiation for the burning sensation in patients with rosacea.

Keratinocytes-Derived Reactive Oxygen Species Play an Active Role to Induce Type 2 Inflammation of the Skin: A Pathogenic Role of Reactive Oxygen Species at the Early Phase of Atopic Dermatitis

Background

Atopic dermatitis (AD) is characterized by chronic, relapsing skin inflammation (eczema) with itchy sensation. Keratinocytes, which are located at the outermost part of our body, are supposed to play important roles at the early phase of type 2 inflammation including AD pathogenesis.

Objective

The purpose of this study was to evaluate whether keratinocytes-derived reactive oxygen species (ROS) could be produced by the allergens or non-allergens, and the keratinocytes-derived ROS could modulate a set of biomarkers for type 2 inflammation of the skin.

Methods

Normal human epidermal keratinocytes (NHEKs) were treated with an allergen of house dust mites (HDM) or a non-allergen of compound 48/80 (C48/80). Then, biomarkers for type 2 inflammation of the skin including those for neurogenic inflammation were checked by reverse transcriptase-polymerase chain reaction and western immunoblot experiments.

Results

HDM or C48/80 was found to upregulate expression levels of our tested biomarkers, including type 2 T helper-driving pathway (KLK5, PAR2, and NFκB), epithelial-cell-derived cytokines (thymic stromal lymphopoietin, interleukin [IL]-25, IL-33), and neurogenic inflammation (NGF, CGRP). The HDM- or C-48/80-induced expression levels of the biomarkers could be blocked by an antioxidant treatment with 5 mM N-acetyl-cysteine. In contrast, pro-oxidant treatment with 1 mM H₂O₂ could upregulate expression levels of the tested biomarkers in NHEKs.

Conclusion

Our results reveal that keratinocytes-derived ROS, irrespective to their origins from allergens or non-allergens, have a potential to induce type 2 inflammation of AD skin.

Functional Impairment of Skin Appendages Due to Peripheral Nerve Involvement by Mycobacterium leprae

In the earliest stage of Mycobacterium leprae infection, bacteria parasitize fine fiber twigs of autonomic peripheral nerves supplying efferent impulses to appendages of the skin. This obligate intracellular pathogen invades Schwann cells, the glial cells of peripheral nerves. Intracellular events inhibit Schwann cell physiology in complex ways, which include demyelination and dedifferentiation. Ultimately, axons embraced by their surrounding dysfunctional glia are damaged by poorly understood mechanisms. Loss of nerve conduction impairs the functions of skin appendages including hair growth, sebaceous gland secretion, sweating, and skin pigmentation. At the clinical level, these changes may be subtle and may precede the more obvious anesthetic skin lesions associated with Hansen’s disease. Recognizing the early signs of skin appendage malfunction may aid in diagnosis leading to initiation of antimycobacterial treatment. Effective therapy administered early during infection may prevent irreversible peripheral nerve destruction, the presage for morbid complications of leprosy.

Chemotactic activities of vasoactive intestinal peptide, neuropeptide Y and substance P in Leishmania braziliensis

Cell-cell interaction and active migration (and invasion) of parasites into skin host-cell(s) are key steps for successful infection by Leishmania. Chemotaxis constitutes a primordial chapter of Leishmania-host cell interaction, potentially modulated by neuropeptides released into the skin due, for example, to the noxious stimuli represented by the insect bite. Herein we have evaluated in vitro the effect of sensory (Substance P, SP) and autonomic (Vasoactive Intestinal Peptide, VIP, and Neuropeptide Y, NPY) neuropeptides on parasite taxis, and investigated the potential modulatory effect of SP on Leishmania (Viannia) braziliensis-macrophage interaction. We demonstrated that VIP (10^-10 M) and NPY (10^-9 M) are chemorepellent to the parasites, while SP (10^-8 M) produces a chemoattractant response. SP did not affect macrophage viability but seems to impair parasite-macrophage interaction as it decreased promastigote adherence to macrophages. As this effect is blocked by ([D-Pro 2, D-Trp7,9]-Substance P (10^-6 M), the observed action may be mediated by neurokinin-1 (NK₁) transmembrane receptors. VIP and NPY repellent chemotactic effect is impaired by their corresponding receptor antagonists. Additionally, they suggest that SP may be a key molecule to guide promastigote migration towards, and interaction, with dendritic cells and macrophage host cells.

Translational research into the effects of cigarette smoke on inflammatory mediators and epithelial TRPV1 in Crohn's disease

Crohn's disease is a pathological condition of the gastro-intestinal tract, causing severe transmural inflammation in the ileum and/or colon. Cigarette smoking is one of the best known environmental risk factors for the development of Crohn's disease. Nevertheless, very little is known about the effect of prolonged cigarette smoke exposure on inflammatory modulators in the gut. We examined the effect of cigarette smoke on cytokine profiles in the healthy and inflamed gut of human subjects and in the trinitrobenzene sulphonic acid mouse model, which mimics distal Crohn-like colitis. In addition, the effect of cigarette smoke on epithelial expression of transient receptor potential channels and their concurrent increase with cigarette smoke-augmented cytokine production was investigated. Active smoking was associated with increased IL-8 transcription in ileum of controls (p < 0,001; n = 18-20/group). In the ileum, TRPV1 mRNA levels were decreased in never smoking Crohn's disease patients compared to healthy subjects (p <0,001; n = 20/group). In the colon, TRPV1 mRNA levels were decreased (p = 0,046) in smoking healthy controls (n = 20/group). Likewise, healthy mice chronically exposed to cigarette smoke (n = 10/group) showed elevated ileal Cxcl2 (p = 0,0075) and colonic Kc mRNA levels (p = 0,0186), whereas TRPV1 mRNA and protein levels were elevated in the ileum (p = 0,0315). Although cigarette smoke exposure prior to trinitrobenzene sulphonic acid administration did not alter disease activity, increased pro-inflammatory cytokine production was observed in the distal colon (Kc: p = 0,0273; Cxcl2: p = 0,104; Il1-β: p = 0,0796), in parallel with the increase of Trpv1 mRNA (p < 0,001). We infer that CS affects pro-inflammatory cytokine expression in healthy and inflamed gut, and that the simultaneous modulation of TRPV1 may point to a potential involvement of TRPV1 in cigarette smoke-induced production of inflammatory mediators.

Psychological Stress and Chronic Urticaria: A Neuro-immuno-cutaneous Crosstalk. A Systematic Review of the Existing Evidence

PURPOSE

It has been observed that certain patients with chronic spontaneous or idiopathic urticaria (CSU/CIU) have a personal history of a significant stressor before urticaria onset, while the prevalence of any psychopathology among these patients is significantly higher than in healthy individuals. Research has confirmed that skin is both an immediate stress perceiver and a target of stress responses. These complex interactions between stress, skin, and the nervous system may contribute to the onset of chronic urticaria. This systematic review investigated the association between CSU/CIU and neuroimmune inflammation with or without evidence of co-existing psychological stress from in vivo and ex vivo studies in human beings.

METHODS

PubMed and Scopus were searched to September 2019 for reports in human beings describing neuroimmune inflammation, stress, and CSU/CIU. A comprehensive search strategy was used that included all the relevant synonyms for the central concept.

FINDINGS

A total of 674 potentially relevant articles were identified. Only 13 satisfied the predefined inclusion criteria and were included in the systematic review. Five of these 13 studies evaluated the correlation between CSU/CIU, stress, and neuro-immune-cutaneous factors, while the remaining 8 focused on the association between CSU/CIU and these factors without examining any evidence of stress.

IMPLICATIONS

The complex neuro-immune-cutaneous model that involves numerous neuropeptides and neurokinins, inflammatory mediators and cells, hypothalamic-pituitary-adrenal axis hormones, and the skin may better explain the underlying pathophysiological mechanisms involved in the onset of urticaria. In addition, the elevated psychological stress level that has been closely related to CSU/CIU could be attributed to the imbalance or irregularity of this neuro-immune-cutaneous circuit. It is still unclear and must be further investigated whether any psychological stress results in or triggers CSU/CIU onset on top of a preexisting neuroimmune dysregulation. Nevertheless, new psycho-phenotypic or neuro-endotypic CSU/CIU subsets should be considered as the era of personalized treatment strategies emerges. A better understanding of CSU/CIU pathophysiology and consideration of the patient as a whole is vital for identifying targets for new potential treatment options.

Neurotransmitters, neuropeptides and their receptors interact with immune response in healthy and psoriatic skin

Psoriasis is a chronic inflammatory disease with a multifactorial origin that affects the skin. It is characterized by keratinocyte hyperproliferation, which results in erythemato-squamous plaques. Just as the immune system plays a fundamental role in psoriasis physiopathology, the nervous system maintains the inflammatory process through the neuropeptides and neurotransmitters synthesis, as histamine, serotonin, calcitonin gene-related peptide, nerve growth factor, vasoactive intestinal peptide, substance P, adenosine, glucagon-like peptide, somatostatin and pituitary adenylate cyclase polypeptide. In patients with psoriasis, the systemic or in situ expression of these chemical mediators and their receptors are altered, which affects the clinical activity of patients due to its link to the immune system, provoking neurogenic inflammation. It is important to establish the role of the nervous system since it could represent a therapeutic alternative for psoriasis patients. The aim of this review is to offer a detailed review of the current literature about the neuropeptides and neurotransmitters involved in the physiopathology of psoriasis.

Effects of endodontic treatment on salivary levels of CGRP and substance P: a pilot study

Objectives

The aim of this study was to evaluate the effects of endodontic treatment on levels of substance P (SP) and calcitonin gene-related peptide (CGRP) in the saliva of patients with symptomatic apical periodontitis.

Materials and Methods

Twelve patients with mandibular molars with symptomatic apical periodontitis were enrolled in this study. An initial saliva sample was collected just before administration of anesthesia for root canal treatment, which was performed at the first visit. A second saliva sample was collected at a control visit 1 week after treatment. Salivary SP and CGRP levels were evaluated quantitatively using biochemical assays. The data were analyzed using Pearson correlation analysis, the paired samples t-test, and the Mann-Whitney U test (p = 0.05).

Results

The postoperative salivary level of SP was significantly lower than the preoperative level (p = 0.005). However, the postoperative salivary level of CGRP was similar to the preoperative level (p = 0.932). Visual analog scale (VAS) scores of patients' subjective pain were found to be positively correlated with salivary levels of SP (r = 0.421; p = 0.040). No statistically significant correlations were observed between salivary levels of CGRP and VAS scores for patients' subjective percussion tenderness (p = 0.533) or VAS scores for patients' subjective pain (p = 0.459).

Conclusions

According to the results of the present study, salivary SP levels may be used as an objective indicator in the diagnosis and assessment of the degree of pain in endodontic diseases.

Trial Registration

Thai Clinical Trials Registry Identifier: TCTR20161228001

Early corneal nerve fibre damage and increased Langerhans cell density in children with type 1 diabetes mellitus

Corneal confocal microscopy (CCM) has been used to identify corneal nerve damage and increased Langerhans cell (LC) density in adults with Type 1 diabetes mellitus (T1DM). The purpose of this study was to evaluate whether corneal confocal microscopy can identify early corneal nerve damage and change in LC density in children and adolescents with T1DM. 64 participants with T1DM (age-14.6 ± 2.5 years, duration of diabetes-9.1 ± 2.7 years, HbA1c-75.66 ± 2.53 mmol/mol [9.1 ± 1.8%]) and 48 age-matched healthy control subjects underwent CCM. Sub-basal corneal nerve morphology and the density of mature and immature LCs was quantified. Corneal nerve fibre length and branch density were lower, whilst fibre density and tortuosity did not differ and both immature and mature LC density was significantly higher in T1DM compared to control subjects. There was no association between HbA1c and duration of diabetes with nerve fibre parameters or LC's density. Children and adolescents with T1DM demonstrate early immune activation and nerve degeneration.

Recent Progress in TRPM8 Modulation: An Update

The transient receptor potential melastatin subtype 8 (TRPM8) is a nonselective, multimodal ion channel, activated by low temperatures (<28 °C), pressure, and cooling compounds (menthol, icilin). Experimental evidences indicated a role of TRPM8 in cold thermal transduction, different life-threatening tumors, and other pathologies, including migraine, urinary tract dysfunction, dry eye disease, and obesity. Hence, the modulation of the TRPM8 channel could be essential in order to understand its implications in these pathologies and for therapeutic intervention. This short review will cover recent progress on the TRPM8 agonists and antagonists, describing newly reported chemotypes, and their application in the pharmacological characterization of TRPM8 in health and disease. The recently described structures of the TRPM8 channel alone or complexed with known agonists and PIP₂ are also discussed.

3D-Organotypic Cultures to Unravel Molecular and Cellular Abnormalities in Atopic Dermatitis and Ichthyosis Vulgaris

Atopic dermatitis (AD) is characterized by dry and itchy skin evolving into disseminated skin lesions. AD is believed to result from a primary acquired or a genetically-induced epidermal barrier defect leading to immune hyper-responsiveness. Filaggrin (FLG) is a protein found in the cornified envelope of fully differentiated keratinocytes, referred to as corneocytes. Although FLG null mutations are strongly associated with AD, they are not sufficient to induce the disease. Moreover, most patients with ichthyosis vulgaris (IV), a monogenetic skin disease characterized by FLG homozygous, heterozygous, or compound heterozygous null mutations, display non-inflamed dry and scaly skin. Thus, all causes of epidermal barrier impairment in AD have not yet been identified, including those leading to the Th2-predominant inflammation observed in AD. Three dimensional organotypic cultures have emerged as valuable tools in skin research, replacing animal experimentation in many cases and precluding the need for repeated patient biopsies. Here, we review the results on IV and AD obtained with epidermal or skin equivalents and consider these findings in the context of human in vivo data. Further research utilizing complex models including immune cells and cutaneous innervation will enable finer dissection of the pathogenesis of AD and deepen our knowledge of epidermal biology.

Tabernaemontana catharinensis leaves exhibit topical anti-inflammatory activity without causing toxicity

BACKGROUND

Tabernaemontana catharinensis, popularly known as snake skin, has been empirically used as an anti-inflammatory to treat cutaneous skin disorders. However, no study proves its effectiveness as a topical anti-inflammatory.

STUDY DESIGN

We investigated the topical anti-inflammatory effect of T.catharinensis leaves crude extract (TcE) in irritant contact dermatitis models in mice and its preliminary toxicity profile.

METHODS

The topical anti-inflammatory effect was evaluated by ear thickness measurement, inflammatory cell infiltration (MPO activity measurement and histological procedure) and cytokines levels. TcE qualitative phytochemical analysis was performed by UHPLC-ESI-HRMS and the TcE effect (therapeutic dose; 10 µg/ear) on preliminary toxicological parameters was also evaluated (on the 14° day of experiment).

RESULTS

TcE (10 μg/ear) prevented the development of ear edema induced by cinnamaldehyde, capsaicin, arachidonic acid, phenol, and croton oil with maximum inhibition of 100% to cinnamaldehyde, arachidonic acid, phenol, and croton oil and 75 ± 6% to capsaicin. Besides, the TcE (10 μg/ear) also prevented the increase of MPO activity by 96 ± 2%, 48 ± 7%, 100%, 87 ± 8%, and 93 ± 4%, respectively, to the same irritant agents. The positive controls also prevented both ear edema and the increased of MPO activity by 100% and 42 ± 8% (HC-030031), 54 ± 6% and 80 ± 4% (SB-366791), 100% and 54 ± 5% (indomethacin), 100% and 80 ± 4% (dexamethasone in skin inflammation model induced by phenol) and 100% and 97 ± 3% (dexamethasone in inflammation model induced by croton oil), respectively. TcE also prevented the inflammatory cells infiltration and the increase of MIP-2, IL-1β and TNF-α levels irritant agents-induced. TcE topical anti-inflammatory effect may be attributed to the combined effect of indole alkaloids, terpenes, and phenolic compounds found in the extract and identified by dereplication method. The TcE' therapeutic dose proved to be safe in preliminary toxicological tests.

CONCLUSION

Our results suggest that TcE could be an interesting strategy for the treatment of inflammatory diseases.

Neuropeptides Profile and Increased Innervation in Becker's Nevus

Background

Melanocytes are derived from neural crest, and various pigmentary disorders may accompany abnormalities in nerve system or develop following dermatome, suggesting that melanocyte and pigmentation may be closely related to neural factors. There are reports of Becker's nevus (BN) showing linear and segmental configuration, suggesting the association of BN with nerve system. However, there are no studies regarding the expression of neuropeptides in BN.

Objective

We investigated the expression of neuropeptides and innervation in BN.

Methods

Polymerase chain reaction (PCR) array of 84 genes related to neuronal process was done. Among the genes with 10-fold or more increase in lesional, real-time PCR was performed for neuropeptide Y (NPY), galanin, neurotensin (NTS) and their receptors skin compared to normal skin. IHC stain was done to look for the expression of NPY, galanin, NTS and their receptors and the distribution of protein gene products (PGP) 9.5 immunoreactive nerve fibers.

Results

PCR array revealed that 16 out of 84 genes related to neuronal process were increased by 10-fold or more in lesional skin. In real-time PCR of NPY, galanin, NTS and their receptors, statistically significant increase of NPY1R (p<0.05) and marginally significant increase of NPY2R, GAL2R, and NTS2R (p<0.1) was verified in lesional skin. In immunohistochemistry, NPY, NPY1R NPY2R, and NTS2R were highly expressed in lesional skin and increased PGP 9.5 immunoreactive linear nerve fibers were found in the epidermis of BN.

Conclusion

NPY, galanin, NTS and their receptors and increased innervation may play a role in the pathogenesis of BN.

Development of an innervated tissue-engineered skin with human sensory neurons and Schwann cells differentiated from iPS cells

Cutaneous innervation is increasingly recognized as a major element of skin physiopathology through the neurogenic inflammation driven by neuropeptides that are sensed by endothelial cells and the immune system. To investigate this process in vitro, models of innervated tissue-engineered skin (TES) were developed, yet exclusively with murine sensory neurons extracted from dorsal root ganglions. In order to build a fully human model of innervated TES, we used induced pluripotent stem cells (iPSC) generated from human skin fibroblasts. Nearly 100% of the iPSC differentiated into sensory neurons were shown to express the neuronal markers BRN3A and β3-tubulin after 19 days of maturation. In addition, these cells were also positive to TRPV1 and neurofilament M, and some of them expressed Substance P, TrkA and TRPA1. When stimulated with molecules inducing neuropeptide release, iPSC-derived neurons released Substance P and CGRP, both in conventional monolayer culture and after seeding in a 3D fibroblast-populated collagen sponge model. Schwann cells, the essential partners of neurons for function and axonal migration, were also successfully differentiated from human iPSC as shown by their expression of the markers S100, GFAP, p75 and SOX10. When cultured for one additional month in the TES model, iPSC-derived neurons seeded at the bottom of the sponge formed a network of neurites spanning the whole TES up to the epidermis, but only when combined with mouse or iPSC-derived Schwann cells. This unique model of human innervated TES should be highly useful for the study of cutaneous neuroinflammation. STATEMENT OF SIGNIFICANCE: The purpose of this work was to develop in vitro an innovative fully human tissue-engineered skin enabling the investigation of the influence of cutaneous innervation on skin pathophysiology. To reach that aim, neurons were differentiated from human induced pluripotent stem cells (iPSCs) generated from normal human skin fibroblasts. This innervated tissue-engineered skin model will be the first one to show iPSC-derived neurons can be successfully used to build a 3D nerve network in vitro. Since innervation has been recently recognized to play a central role in many human skin diseases, such as psoriasis and atopic dermatitis, this construct promises to be at the forefront to model these diseases while using patient-derived cells.

Skin neurogenic inflammation

The epidermis closely interacts with nerve endings, and both epidermis and nerves produce substances for mutual sustenance. Neuropeptides, like substance P (SP) and calcitonin gene-related protein (CGRP), are produced by sensory nerves in the dermis; they induce mast cells to release vasoactive amines that facilitate infiltration of neutrophils and T cells. Some receptors are more important than others in the generation of itch. The Mas-related G protein-coupled receptors (Mrgpr) family as well as transient receptor potential ankyrin 1 (TRPA1) and protease activated receptor 2(Par2) have important roles in itch and inflammation. The activation of MrgprX1 degranulates mast cells to communicate with sensory nerve and cutaneous cells for developing neurogenic inflammation. Mrgprs and transient receptor potential vanilloid 4 (TRPV4) are crucial for the generation of skin diseases like rosacea, while SP, CGRP, somatostatin, β-endorphin, vasoactive intestinal peptide (VIP), and pituitary adenylate cyclase-activating polypeptide (PACAP) can modulate the immune system during psoriasis development. The increased level of SP, in atopic dermatitis, induces the release of interferon (IFN)-γ, interleukin (IL)-4, tumor necrosis factor (TNF)-α, and IL-10 from the peripheral blood mononuclear leukocytes. We are finally starting to understand the intricate connections between the skin neurons and resident skin cells and how their interaction can be key to controlling inflammation and from there the pathogenesis of diseases like atopic dermatitis, psoriasis, and rosacea.

Inflammatory Compounds: Neuropeptide Substance Pand Cytokines

Inflammatory diseases represent one of the major causes of morbidity and mortality throughout the world and they affect the functions of several tissues. The pathophysiology of these diseases involves release of many pro-inflammatory mediators such as cytokines/chemokines, histamine, C3a, C5a (complement components), bradykinin, leukotrienes (LTC4, LTD4, LTE4), PAF, and substance P, in addition to anti-inflammatory molecules. Recently, it has been demonstrated that neuroimmune interactions are important in the initiation and progress of inflammatory processes. Substance P is an 11-amino acid neuropeptide that is released from nerve endings in many tissues. It acts via membrane-bound NK1 receptors (NK1R). Inflammatory and neuropeptides such as substance P stimulate the release of chemokines, in particular IL-8, a potent neutrophil chemoattractant. Expression of IL-8 is regulated mainly by the transcription factors NF-kappaB, activating protein-1. Substance P plays an important role in immunological and inflammatory states, and it is a mediator of tissue injury, asthma, arthritis, allergy and autoimmune diseases. In this article, our studies revisited the interrelationship between these two powerful inflammatory compounds: substance P and cytokines. These observations suggest that these inflammatory molecules may represent a potential therapeutic target to treat several inflammatory states.

Rosacea: Epidemiology, pathogenesis, and treatment

Rosacea is a chronic relapsing inflammatory skin disease with a high prevalence among adults of Northern European heritage with fair skin. Symptoms present in various combinations and severity, often fluctuating between periods of exacerbation and remission. Based on morphological characteristics, rosacea is generally classified into four major subtypes: erythematotelangiectatic, papulopustular, phymatous, and ocular. Diverse environmental and endogenous factors have been shown to stimulate an augmented innate immune response and neurovascular dysregulation; however, rosacea's exact pathogenesis is still unclear. An evidence-based approach is essential in delineating differences between the many available treatments. Because of the diverse presentations of rosacea, approaches to treatment must be individualized based on the disease severity, quality-of-life implications, comorbidities, trigger factors, and the patient's commitment to therapy.

Innervation of the Male Breast: Psychological and Physiological Consequences

Breasts, including the nipple and areola, have two functions: lactation and as an erogenous area. Male breasts are much less studied that those of women. In men, breasts have only an erotic function. Because there is dense and very well organized innervation of the nipple-areola complex in men, nipple erection occurs frequently and via different mechanisms from penile erection. Although it seems to be less important for men than for women and it is poorly studied, the erotic value of breast stimulation is notable. Consequently, there is a need to include this aspect in sexological and andrological studies and to preserve breasts and their innervation or to reconstruct them in cases of surgical intervention.

The male beard hair and facial skin - challenges for shaving

The challenge of shaving is to cut the beard hair as closely as possible to the skin without unwanted effects on the skin. To achieve this requires the understanding of beard hair and male facial skin biology as both, the beard hair and the male facial skin, contribute to the difficulties in obtaining an effective shave without shaving-induced skin irritation. Little information is available on the biology of beard hairs and beard hair follicles. We know that, in beard hairs, the density, thickness, stiffness, as well as the rates of elliptical shape and low emerging angle, are high and highly heterogeneous. All of this makes it challenging to cut it, and shaving techniques commonly employed to overcome these challenges include shaving with increased pressure and multiple stroke shaving, which increase the probability and extent of shaving-induced skin irritation. Several features of male facial skin pose problems to a perfect shave. The male facial skin is heterogeneous in morphology and roughness, and male skin has a tendency to heal slower and to develop hyperinflammatory pigmentation. In addition, many males exhibit sensitive skin, with the face most often affected. Finally, the hair follicle is a sensory organ, and the perifollicular skin is highly responsive to external signals including mechanical and thermal stimulation. Perifollicular skin is rich in vasculature, innervation and cells of the innate and adaptive immune system. This makes perifollicular skin a highly responsive and inflammatory system, especially in individuals with sensitive skin. Activation of this system, by shaving, can result in shaving-induced skin irritation. Techniques commonly employed to avoid shaving-induced skin irritation include shaving with less pressure, pre- and post-shave skin treatment and to stop shaving altogether. Recent advances in shaving technology have addressed some but not all of these issues. A better understanding of beard hairs, beard hair follicles and male facial skin is needed to develop novel and better approaches to overcome the challenge of shaving. This article covers what is known about the physical properties of beard hairs and skin and why those present a challenge for blade and electric shaving, respectively.