CRH functions as a growth factor/cytokine in the skin

Effects on peripheral and central nervous system of key inflammatory intercellular signalling peptides and proteins in psoriasis

Psoriasis is a chronic systemic inflammatory cutaneous disease. Where the immune system plays an important role in its pathogenesis, with key inflammatory intercellular signalling peptides and proteins including IL-17 and IL-23. The psychoneurological system also figures prominently in development of psoriasis. There is a high prevalence of comorbidity between psoriasis and mental health disorders such as depression, anxiety and mania. Patients with psoriasis often suffer from pathological pain in the lesions, and their neurological accidents could improve the lesions in innervated areas. The immune system and the psychoneurological system interact closely in the pathogenesis of psoriasis. Patients with psoriasis exhibit abnormal levels of neuropeptides both in circulating and localized lesion, acting as immunomodulators involved in the inflammatory response. Moreover, receptors for inflammatory factors are expressed in both peripheral and central nervous systems (CNSs), suggesting that nervous system can receive and be influenced by signals from immune system. Key inflammatory intercellular signalling peptides and proteins in psoriasis, such as IL-17 and IL-23, can be involved in sensory signalling and may affect synaptic plasticity and the blood-brain barrier of CNS through the circulation. This review provides an overview of the multiple effects on the peripheral and CNS under conditions of systemic inflammation in psoriasis, providing a framework and inspiration for in-depth studies of neuroimmunomodulation in psoriasis.

Natural tyrosinase enzyme inhibitors: A path from melanin to melanoma and its reported pharmacological activities

The skin containing melanin pigment acts as a protective barrier and counteracts the UVR and other environmental stressors to maintain or restore disrupted cutaneous homeostasis. The production of melanin pigment is dependent on tyrosine levels. L-tyrosine and L-dihydroxyphenylalanine (L-DOPA) can serve both as a substrates and intermediates of melanin synthetic pathway and as inducers and positive regulators of melanogenesis. The biosynthesis of melanin is stimulated upon exposure to UVR, which can also stimulate local production of hormonal factors, which can stimulate melanoma development by altering the chemical properties of eu- and pheomelanin. The process of melanogenesis can be altered by several pathways. One involves activation of POMC, with the production of POMC peptides including MSH and ACTH, which increase intracellular cAMP levels, which activates the MITF, and helps to stimulate tyrosinase (TYR) expression and activity. Defects in OCA1 to 4 affects melanogenic activity via posttranslational modifications resulting in proteasomal degradation and reducing pigmentation. Further, altering, the MITF factor, helps to regulate the expression of MRGE in melanoma, and helps to increase the TYR glycosylation in ER. CRH stimulates POMC peptides that regulate melanogenesis and also by itself can stimulate melanogenesis. The POMC, P53, ACTH, MSH, MC1R, MITF, and 6-BH4 are found to be important regulators for pigmentation. Melanogenesis can affect melanoma behaviour and inhibit immune responses. Therefore, we reviewed natural products that would alter melanin production. Our special focus was on targeting melanin synthesis and TYR enzyme activity to inhibit melanogenesis as an adjuvant therapy of melanotic melanoma. Furthermore, this review also outlines the current updated pharmacological studies targeting the TYR enzyme from natural sources and its consequential effects on melanin production.

Polymorphisms in corticotrophin-releasing hormone-proopiomalanocortin (CRH-POMC) system genes: Neuroimmune contributions to psoriasis disease

BACKGROUND

Skin is a target organ and source of the corticotropin-releasing hormone-proopiomelanocortin (CRH-POMC) system, operating as a coordinator and executor of responses to stress. Environmental stress exacerbates and triggers inflammatory skin diseases through modifying the cellular components of the immune system supporting the importance of CRH-POMC system in the pathogenesis of psoriasis. The aim of this study was to analyse the association of CRH-POMC polymorphisms with psoriasis and evaluate transcript expression of lesional psoriatic and normal skin in RNA-seq data.

METHODS

Samples of 104 patients with psoriasis and 174 healthy controls were genotyped for 42 single nucleotide polymorphisms (SNPs) of CRH-POMC using Applied Biosystems SNPlex™ method. The transcript quantification was performed using Salmon software v1.3.0.

RESULTS

This study demonstrated the associations between melanocortin 1 receptor (MC1R) polymorphisms rs2228479, rs3212369, dopachrome tautomerase (DCT) polymorphisms rs7987802, rs2031526, rs9524501 and psoriasis in the Tatar population. Very strong association was evident for the SNP rs7987802 in the DCT gene (pc  = 5.95е-006) in psoriasis patients. Additionally, the haplotype analysis provided AT DCT (rs7992630 and rs7987802) and AGA MC1R (rs3212358, 2228479 and 885479) haplotypes significantly associated (pc  ˂ 0.05) with psoriasis in the Tatar population, supporting the involvement of DCT and MC1R to the psoriasis susceptibility. Moreover, MC1R-203 and DCT-201 expression levels were decreased in psoriasis lesional skin compared with healthy control skin.

CONCLUSIONS

This study is the first to identify genetic variants of the MC1R and DCT genes significantly associated with psoriasis in Tatar population. Our results support potential roles of CRH-POMC system genes and DCT in the pathogenesis of psoriasis.

Mastocytosis and Skin Cancer: The Current State of Knowledge

Mastocytosis is a heterogeneous group of diseases associated with excessive proliferation and accumulation of mast cells in different organs. Recent studies have demonstrated that patients suffering from mastocytosis face an increased risk of melanoma and non-melanoma skin cancer. The cause of this has not yet been clearly identified. In the literature, the potential influence of several factors has been suggested, including genetic background, the role of cytokines produced by mast cells, iatrogenic and hormonal factors. The article summarizes the current state of knowledge regarding the epidemiology, pathogenesis, diagnosis, and management of skin neoplasia in mastocytosis patients.

Melanoma molecular subtyping and scoring model construction based on ligand-receptor pairs

Melanoma is a malignancy of melanocytes, responsible for a high percentage of skin cancer mortality. Ligand-Receptor pairs, a type of cellular communication, are essential for tumor genesis, growth, metastasis, and prognosis. Yet, the role of Ligand-Receptor pairs in melanoma has not been fully elucidated. Our research focused on the function of Ligand-Receptor pairs in melanoma prognosis. We screened 131 melanoma prognosis corresponded ligand-receptor pairs by analyzing the TCGA data of melanoma and the 2293 LR pairs retrieved from the connectomeDB2020 database. And further developed subtypes of melanoma according to the expression of these ligand-receptor pairs by Consensus Clustering. Then we using lasso cox regression and stepwise multivariate regression analysis established a ligand-receptor pairs-based scoring model for the evaluation of melanoma prognosis. Our study demonstrated that the ligand-receptor pairs are vital to the molecular heterogeneity of melanoma, and characterized three different melanoma ligand-receptor pairs subtypes. Among them, the C3 subtype showed a better prognosis, while the C1 subtype exhibited a low prognosis state. And our analysis then found out that this could be related to the differed activation and inhabitation of the cell cycle and immune-related pathways. Using lasso cox regression and stepwise multivariate regression analysis, we further identified 9 key ligand-receptor pairs and established a scoring model that effectively correlated with the prognosis, immune pathways, and therapy of melanoma, showing that the LR.score model was a trustworthy and independent biomarker for melanoma prognosis evaluation. In sum, we found that ligand-receptor pairs are significantly associated with the prognosis and therapy of melanoma. And our ligand-receptor-based scoring model showed potential for the evaluation of melanoma prognosis and immune therapy outcome prediction, which is crucial to the survival for the patients.

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.

Revisiting the role of melatonin in human melanocyte physiology: A skin context perspective

The evolutionarily ancient methoxyindoleamine, melatonin, has long perplexed investigators by its versatility of functions and mechanisms of action, which include the regulation of vertebrate pigmentation. Although first discovered through its potent skin-lightening effects in amphibians, melatonin's role in human skin and hair follicle pigmentation and its impact on melanocyte physiology remain unclear. Synthesizing our limited current understanding of this role, we specifically examine its impact on melanogenesis, oxidative biology, mitochondrial function, melanocyte senescence, and pigmentation-related clock gene activity, with emphasis on human skin, yet without ignoring instructive pointers from nonhuman species. Given the strict dependence of melanocyte functions on the epithelial microenvironment, we underscore that melanocyte responses to melatonin are best interrogated in a physiological tissue context. Current evidence suggests that melatonin and some of its metabolites inhibit both, melanogenesis (via reducing tyrosinase activity) and melanocyte proliferation by stimulating melatonin membrane receptors (MT1, MT2). We discuss whether putative melanogenesis-inhibitory effects of melatonin may occur via activation of Nrf2-mediated PI3K/AKT signaling, estrogen receptor-mediated and/or melanocortin-1 receptor- and cAMP-dependent signaling, and/or via melatonin-regulated changes in peripheral clock genes that regulate human melanogenesis, namely Bmal1 and Per1. Melatonin and its metabolites also accumulate in melanocytes where they exert net cyto- and senescence-protective as well as antioxidative effects by operating as free radical scavengers, stimulating the synthesis and activity of ROS scavenging enzymes and other antioxidants, promoting DNA repair, and enhancing mitochondrial function. We argue that it is clinically and biologically important to definitively clarify whether melanocyte cell culture-based observations translate into melatonin-induced pigmentary changes in a physiological tissue context, that is, in human epidermis and hair follicles ex vivo, and are confirmed by clinical trial results. After defining major open questions in this field, we close by suggesting how to begin answering them in clinically relevant, currently available preclinical in situ research models.

The Brain-Skin Axis in Psoriasis-Psychological, Psychiatric, Hormonal, and Dermatological Aspects

Psoriasis is a chronic inflammatory skin disease with systemic manifestation, in which psychological factors play an important role. The etiology of psoriasis is complex and multifactorial, including genetic background and environmental factors such as emotional or physical stress. Psychological stress may also play a role in exacerbation of psoriasis, by dysregulation of the hypothalamic–pituitary–adrenal (HPA) axis, sympathetic–adrenal–medullary axis, peripheral nervous system, and immune system. Skin cells also express various neuropeptides and hormones in response to stress, including the fully functional analog of the HPA axis. The deterioration of psoriatic lesions is accompanied by increased production of inflammatory mediators, which could contribute to the imbalance of neurotransmitters and the development of symptoms of depression and anxiety. Therefore, deregulation of the crosstalk between endocrine, paracrine, and autocrine stress signaling pathways contributes to clinical manifestations of psoriasis, which requires multidisciplinary approaches.

Psychological Stress, Mast Cells, and Psoriasis-Is There Any Relationship?

Psoriasis vulgaris is a common inflammatory skin disease with still unknown pathogenesis. In recent years, genetic and environmental factors have been mentioned as the main causes. Among environmental factors, many researchers are trying to investigate the role of mental health and its importance in the development of many diseases. In the pathophysiology of psoriasis, the role of the interaction between the nervous, endocrine, and immune systems are often emphasized. So far, no one has clearly indicated where the pathological process begins. One of the hypotheses is that chronic stress influences the formation of hormonal changes (lowering the systemic cortisol level), which favors the processes of autoimmunity. In inflammatory skin conditions, mast cells (MCs) are localized close to blood vessels and peripheral nerves, where they probably play an important role in the response to environmental stimuli and emotional stress. They are usually connected with a fast immune response, not only in allergies but also a protective response to microbial antigens. Among many cells of the immune system, MCs have receptors for the hormones of the hypothalamic-pituitary-adrenal (HPA) axis on their surface. In this review, we will try to take a closer look at the role of MCs in the pathophysiology of psoriasis. This knowledge may give the opportunity to search for therapeutic solutions.

The significance of CYP11A1 expression in skin physiology and pathology

CYP11A1, a member of the cytochrome P450 family, plays several key roles in the human body. It catalyzes the first and rate-limiting step in steroidogenesis, converting cholesterol to pregnenolone. Aside from the classical steroidogenic tissues such as the adrenals, gonads and placenta, CYP11A1 has also been found in the brain, gastrointestinal tract, immune systems, and finally the skin. CYP11A1 activity in the skin is regulated predominately by StAR protein and hence cholesterol levels in the mitochondria. However, UVB, UVC, CRH, ACTH, cAMP, and cytokines IL-1, IL-6 and TNFα can also regulate its expression and activity. Indeed, CYP11A1 plays several critical roles in the skin through its initiation of local steroidogenesis and specific metabolism of vitamin D, lumisterol, and 7-dehydrocholesterol. Products of these pathways regulate the protective barrier and skin immune functions in a context-dependent fashion through interactions with a number of receptors. Disturbances in CYP11A1 activity can lead to skin pathology.

Stress and Nasal Allergy: Corticotropin-Releasing Hormone Stimulates Mast Cell Degranulation and Proliferation in Human Nasal Mucosa

Psychological stress exacerbates mast cell (MC)-dependent inflammation, including nasal allergy, but the underlying mechanisms are not thoroughly understood. Because the key stress-mediating neurohormone, corticotropin-releasing hormone (CRH), induces human skin MC degranulation, we hypothesized that CRH may be a key player in stress-aggravated nasal allergy. In the current study, we probed this hypothesis in human nasal mucosa MCs (hM-MCs) in situ using nasal polyp organ culture and tested whether CRH is required for murine M-MC activation by perceived stress in vivo. CRH stimulation significantly increased the number of hM-MCs, stimulated both their degranulation and proliferation ex vivo, and increased stem cell factor (SCF) expression in human nasal mucosa epithelium. CRH also sensitized hM-MCs to further CRH stimulation and promoted a pro-inflammatory hM-MC phenotype. The CRH-induced increase in hM-MCs was mitigated by co-administration of CRH receptor type 1 (CRH-R1)-specific antagonist antalarmin, CRH-R1 small interfering RNA (siRNA), or SCF-neutralizing antibody. In vivo, restraint stress significantly increased the number and degranulation of murine M-MCs compared with sham-stressed mice. This effect was mitigated by intranasal antalarmin. Our data suggest that CRH is a major activator of hM-MC in nasal mucosa, in part via promoting SCF production, and that CRH-R1 antagonists such as antalarmin are promising candidate therapeutics for nasal mucosa neuroinflammation induced by perceived stress.

Stress-induced Interaction of Skin Immune Cells, Hormones, and Neurotransmitters

PURPOSE

Although scientific articles mention the impact of psychological stress on skin diseases, few review the latest research on factors involved in this correlation. The skin actively responds to psychological stress, with involvement of skin immune cells, hormones, neurotransmitters. Skin immune cells actively regulate tissue inflammation with their proinflammatory and anti-inflammatory effects. Stress-induced skin reactions primarily include cytokine secretion (e.g. interleukin-6, interleukin-1, interferon-γ) and activation of skins peripheral corticotropin-releasing hormone (CRH)-proopiomelanocortin (POMC)-adrenocorticotropic hormone (ACTH)-corticosteroids axis, which leads to acute/chronic secretion of corticosteroids in the skin.

METHODS

This narrative review presents the current knowledge and latest findings regarding the impact of psychological stress on skin diseases, including information concerning psychoneuroimmune factors in stress-induced skin responses. Recent articles published in English available through the PubMed database and other prominent literature are discussed.

FINDINGS

Stress mediators, including cortisol, ACTH, and CRH from hypothalamus-pituitary-adrenal axis activation, induce various skin immune responses. Skin cells themselves can secrete these hormones and participate in skin inflammation. Thus, the local skin CRH-POMC-ACTH-corticosteroids axis plays a prominent role in stress-induced responses. Also, keratinocytes and fibroblasts produce hypothalamic and pituitary signal peptides and express receptors for them (CRH with receptors and POMC degradation peptides with melanocortin receptors), which allows them to respond to CRH by activating the POMC gene, which is then followed by ACTH and subsequently corticosteroids excretion. In addition, keratinocytes can express receptors for neurotransmitters (e.g. adrenaline, noradrenaline, dopamine, histamine, acetylcholine), neurotrophins, and neuropeptides (e.g. substance P, nerve growth factor), which are important in linking psychoneuroimmunologic mechanisms.

IMPLICATIONS

Psychoneuroimmunology provides an understanding that the skin is target and source of stress mediators. This locally expressed complex stress-induced network has been confirmed as active in many skin diseases (e.g. vulgar psoriasis, atopic dermatitis, chronic urticaria, human papillomavirus infections/warts, hair loss, acne). Skin reactions to stress and its influence on skin diseases may have implications for disease severity and exacerbation frequency, given the effect of locally secreted corticosteroids and other mediators that affect skin integrity, inflammation, and healing potential. Studies have also shown that introducing psychiatric treatment (drugs or psychotherapeutic methods) can have positive effects on dermatologic diseases influenced by psychological stress exposure. We hope this review provides clinicians and scientists with more complete background for further research in this field of skin psychoneuroimmunology.

Extra-adrenal glucocorticoid biosynthesis: implications for autoimmune and inflammatory disorders

Glucocorticoid synthesis is a complex, multistep process that starts with cholesterol being delivered to the inner membrane of mitochondria by StAR and StAR-related proteins. Here its side chain is cleaved by CYP11A1 producing pregnenolone. Pregnenolone is converted to cortisol by the enzymes 3-βHSD, CYP17A1, CYP21A2 and CYP11B1. Glucocorticoids play a critical role in the regulation of the immune system and exert their action through the glucocorticoid receptor (GR). Although corticosteroids are primarily produced in the adrenal gland, they can also be produced in a number of extra-adrenal tissue including the immune system, skin, brain, and intestine. Glucocorticoid production is regulated by ACTH, CRH, and cytokines such as IL-1, IL-6 and TNFα. The bioavailability of cortisol is also dependent on its interconversion to cortisone which is inactive, by 11βHSD1/2. Local and systemic glucocorticoid biosynthesis can be stimulated by ultraviolet B, explaining its immunosuppressive activity. In this review, we want to emphasize that dysregulation of extra-adrenal glucocorticoid production can play a key role in a variety of autoimmune diseases including multiple sclerosis (MS), lupus erythematosus (LE), rheumatoid arthritis (RA), and skin inflammatory disorders such as psoriasis and atopic dermatitis (AD). Further research on local glucocorticoid production and its bioavailability may open doors into new therapies for autoimmune diseases.

Neuroendocrinology and neurobiology of sebaceous glands

The nervous system communicates with peripheral tissues through nerve fibres and the systemic release of hypothalamic and pituitary neurohormones. Communication between the nervous system and the largest human organ, skin, has traditionally received little attention. In particular, the neuro-regulation of sebaceous glands (SGs), a major skin appendage, is rarely considered. Yet, it is clear that the SG is under stringent pituitary control, and forms a fascinating, clinically relevant peripheral target organ in which to study the neuroendocrine and neural regulation of epithelia. Sebum, the major secretory product of the SG, is composed of a complex mixture of lipids resulting from the holocrine secretion of specialised epithelial cells (sebocytes). It is indicative of a role of the neuroendocrine system in SG function that excess circulating levels of growth hormone, thyroxine or prolactin result in increased sebum production (seborrhoea). Conversely, growth hormone deficiency, hypothyroidism, and adrenal insufficiency result in reduced sebum production and dry skin. Furthermore, the androgen sensitivity of SGs appears to be under neuroendocrine control, as hypophysectomy (removal of the pituitary) renders SGs largely insensitive to stimulation by testosterone, which is crucial for maintaining SG homeostasis. However, several neurohormones, such as adrenocorticotropic hormone and α-melanocyte-stimulating hormone, can stimulate sebum production independently of either the testes or the adrenal glands, further underscoring the importance of neuroendocrine control in SG biology. Moreover, sebocytes synthesise several neurohormones and express their receptors, suggestive of the presence of neuro-autocrine mechanisms of sebocyte modulation. Aside from the neuroendocrine system, it is conceivable that secretion of neuropeptides and neurotransmitters from cutaneous nerve endings may also act on sebocytes or their progenitors, given that the skin is richly innervated. However, to date, the neural controls of SG development and function remain poorly investigated and incompletely understood. Botulinum toxin-mediated or facial paresis-associated reduction of human sebum secretion suggests that cutaneous nerve-derived substances modulate lipid and inflammatory cytokine synthesis by sebocytes, possibly implicating the nervous system in acne pathogenesis. Additionally, evidence suggests that cutaneous denervation in mice alters the expression of key regulators of SG homeostasis. In this review, we examine the current evidence regarding neuroendocrine and neurobiological regulation of human SG function in physiology and pathology. We further call attention to this line of research as an instructive model for probing and therapeutically manipulating the mechanistic links between the nervous system and mammalian skin.

Is prolactin a negative neuroendocrine regulator of human skin re-epithelisation after wounding?

Chronic wounds remain a major unmet healthcare challenge, associated with substantial morbidity and economic costs. Therefore, novel treatment strategies and therapeutic approaches need to be urgently developed. Yet, despite the increasingly recognized importance of neurohormonal signaling in skin physiology, the neuroendocrine regulation of cutaneous wound healing has received surprisingly little attention. Human skin, and its appendages, locally express the pleiotropic neurohormone prolactin (PRL), which not only regulates lactation but also hair follicle cycling, angiogenesis, keratinocyte proliferation, and epithelial stem cell functions. Therefore, we examined the effects of PRL in experimentally wounded female human skin organ culture. Overall, this revealed that PRL slightly, but significantly, inhibited epidermal regeneration (reepithelialisation), cytokeratin 6 protein expression and intraepidermal mitochondrial activity (MTCO1 expression), while it promoted keratinocyte terminal differentiation (i.e. involucrin expression) ex vivo. If the current pilot data are confirmed by further studies, PRL may serve as one of the-rarely studied-negative regulators of cutaneous wound healing that control excessive reepithelialisation. This raises the intriguing and clinically relevant question of whether PRL receptor antagonists could actually promote epidermal repair after human skin wounding.

Intrinsic and extrinsic regulation of human skin melanogenesis and pigmentation

In human skin, melanogenesis is a tightly regulated process. Indeed, several extracellular signals are transduced via dedicated signalling pathways and mostly converge to MITF, a transcription factor integrating upstream signalling and regulating downstream genes involved in the various inherent mechanisms modulating melanogenesis. The synthesis of melanin pigments occurs in melanocytes inside melanosomes where melanogenic enzymes (tyrosinase and related proteins) are addressed with the help of specific protein complexes. The melanosomes loaded with melanin are then transferred to keratinocytes. A more elaborate level of melanogenesis regulation comes into play via the action of non-coding RNAs (microRNAs, lncRNAs). Besides this canonical regulation, melanogenesis can also be modulated by other non-specific intrinsic pathways (hormonal environment, inflammation) and by extrinsic factors (solar irradiation such as ultraviolet irradiation, environmental pollution). We developed a bioinformatic interaction network gathering the multiple aspects of melanogenesis and skin pigmentation as a resource to better understand and study skin pigmentation biology.

Gallotannin Improves the Photoaged-Related Proteins by Extracellular Signal-Regulated Kinases/c-Jun N-Terminal Kinases Signaling Pathway in Human Epidermal Keratinocyte Cells

Tannins are a type of polyphenols found in several fruits such as grapes and berries, and nuts such as aronias and acorns. Both hydrolyzable tannins and condensed tannins are referred to as tannins. Among the hydrolyzable tannins, gallotannin has a strong antioxidative property and is known to protect the skin by inhibiting the precursors of elastolytic enzymes. However, its mechanism of protection against ultraviolet B (UVB) damage in human fibroblasts and keratinocytes has not yet been elucidated. In this study, we investigate the antioxidant and antiaging effect of gallotannin on UVB-irradiated human cells by studying its effect on extracellular signal-regulated kinases/c-Jun N-terminal kinases (EKRs/JNKs) signaling related to cell growth and differentiation/stress apoptosis. The results showed that gallotannin improved collagen synthesis, reduced metalloproteinase-1 (MMP-1) expression in a dose-dependent manner, and downregulated MMP-1 levels through the ERK/JNK signaling pathway in UVB-irradiated human cells. Gallotannin also increased glutathione but did not increase transforming growth factor beta 1, which induces fibrosis. We propose that gallotannin is a novel agent for protection against UVB, and acts as an antiaging agent that can be used in food, pharmaceuticals, and cosmetics.

Association between Stress and the HPA Axis in the Atopic Dermatitis

The hypothalamic–pituitary–adrenal (HPA) axis is one of the body’s neuroendocrine networks that responds to psychological stress (PS). In the skin, there exists a peripheral HPA axis similar to the central axis. Glucocorticoids (GCs) are key effector molecules of the HPA axis and are essential for cutaneous homeostasis. Atopic dermatitis (AD) is a condition typically characterized by a chronic relapsing course that often results in PS. HPA dysfunction is present in AD patients by the decreased response of GCs elevation to stress as compared to those unaffected by AD. Nevertheless, in skin, acute PS activates several metabolic responses that are of immediate benefit to the host. During the acute phase of PS, increased endogenous GCs have been shown to provide benefit rather than by aggravating cutaneous inflammatory dermatoses. However, a chronic T helper cell type 2 (Th2) predominant cytokine profile acts as a negative feedback loop to blunt the HPA axis response in AD. In this article, we reviewed the role of CRF, pro-opiomelanocortin (POMC)-derived peptides, GCs of the HPA, and 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) in AD, with a discussion of the pathogenetic mechanisms of inflammation and skin barrier functions, including antimicrobial defense, and their association with PS.

Does the corticotropin-releasing hormone system play a role in the pathogenesis of lichen planus?

Introduction

Lichen planus (LP) is a chronic inflammatory disease, where the psychogenic factors seem to play an important role in the pathogenesis.

Aim

To determine the expression of corticotropin-releasing hormone (CRH) receptor type 1 (CRH-R1) in LP.

Material and methods

Thirty-two LP patients and 17 age/gender-matched controls were included in the study. Detailed information about the disease and body surface area (BSA) covered by the lesions was recorded. Immunohistochemically, the expression of CRH-R1 was stained in the lesional skin of patients with LP and in the control group.

Results

The comparison of CRH-R1 expression showed a statistically significant difference between LP patients and the controls (p < 0.05). Additionally, we did not observe any correlation between BSA and staining intensity in LP patients.

Conclusions

Our study showed an increase in CRH-R1 expression in LP lesions. These results support the participation of the cutaneous CRH/CRH-R1 system in the pathogenesis of LP skin lesions.

Neuroendocrine factors: The missing link in non‑melanoma skin cancer (Review)

Non‑melanoma skin cancer (NMSC) is the most common form of cancer worldwide, comprising 95% of all cutaneous malignancies and approximately 40% of all cancers. In spite of intensive efforts aimed towards awareness campaigns and sun‑protective measures, epidemiological data indicate an increase in the incidence of NMSC. This category of skin cancers has many common environmental triggers. Arising primarily on sun‑exposed skin, it has been shown that ultraviolet radiation is, in the majority of cases, the main trigger involved in the pathogenesis of NMSC. Aside from the well‑known etiopathogenic factors, studies have indicated that several neuroactive factors are involved in the carcinogenesis of two of the most common types of NMSC, namely basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), with the exception of penile SCC, for which a paucity of specific data on their pathogenic role exists. The complex interaction between the peripheral nervous system and target cells in the skin appears to be mediated by locally released neuroendocrine factors, such as catecholamines, substance P, calcitonin gene‑related peptide and somatostatin, as well as neurohormones, such as proopiomelanocortin and its derived peptides, α‑melanocyte‑stimulating hormone and adrenocorticotropin. All these factors have been, at least at some point, a subject of debate regarding their precise role in the pathogenesis of NMSC. There is also a significant body of evidence indicating that psychological stress is a crucial impact factor influencing the course of skin cancers, including SCC and BCC. Numerous studies have suggested that neuroendocrine factor dysregulation, as observed in stress reactions, may be involved in tumorigenesis, accelerating the development and progression, and suppressing the regression of NMSC. Further studies are required in order to elucidate the exact mechanisms through which neuroactive molecules promote or inhibit cutaneous carcinogenesis, as this could lead to the development of more sophisticated and tailored treatment protocols, as well as open new perspectives in skin cancer research.

Characterisation of the cancer-associated glucocorticoid system: key role of 11β-hydroxysteroid dehydrogenase type 2

Background:

Recent studies have shown that production of cortisol not only takes place in several non-adrenal peripheral tissues such as epithelial cells but, also, the local inter-conversion between cortisone and cortisol is regulated by the 11β-hydroxysteroid dehydrogenases (11β-HSDs). However, little is known about the activity of this non-adrenal glucocorticoid system in cancers.

Methods:

The presence of a functioning glucocorticoid system was assessed in human skin squamous cell carcinoma (SCC) and melanoma and further, in 16 epithelial cell lines from 8 different tissue types using ELISA, western blotting and immunofluorescence. 11β-HSD2 was inhibited both pharmacologically and by siRNA technology. Naïve CD8⁺ T cells were used to test the paracrine effects of cancer-derived cortisol on the immune system in vitro. Functional assays included cell–cell adhesion and cohesion in two- and three-dimensional models. Immunohistochemical data of 11β-HSD expression were generated using tissue microarrays of 40 cases of human SCCs as well as a database featuring 315 cancer cases from 15 different tissues.

Results:

We show that cortisol production is a common feature of malignant cells and has paracrine functions. Cortisol production correlated with the magnitude of glucocorticoid receptor (GR)-dependent inhibition of tumour-specific CD8⁺ T cells in vitro. 11β-HSDs were detectable in human skin SCCs and melanoma. Analyses of publicly available protein expression data of 11β-HSDs demonstrated that 11β-HSD1 and -HSD2 were dysregulated in the majority (73%) of malignancies. Pharmacological manipulation of 11β-HSD2 activity by 18β-glycyrrhetinic acid (GA) and silencing by specific siRNAs modulated the bioavailability of cortisol. Cortisol also acted in an autocrine manner and promoted cell invasion in vitro and cell–cell adhesion and cohesion in two- and three-dimensional models. Immunohistochemical analyses using tissue microarrays showed that expression of 11β-HSD2 was significantly reduced in human SCCs of the skin.

Conclusions:

The results demonstrate evidence of a cancer-associated glucocorticoid system and show for the first time, the functional significance of cancer-derived cortisol in tumour progression.

Glucocorticoids Inhibit Wound Healing: Novel Mechanism of Action

Jozic et al. describe mechanisms of glucocorticoid (GC) downregulation of wound healing by interaction with the membrane bound GC receptor, followed by stimulation of β-catenin and c-myc pathways. Targeting the membrane bound GC receptor or the recently discovered interaction of GC with mineralocorticoid receptors may counteract negative effects of GC on the skin barrier and potentially could serve as a remedy for age-related skin atrophy.

Frontline Science: Corticotropin-releasing factor receptor subtype 1 is a critical modulator of mast cell degranulation and stress-induced pathophysiology

Life stress is a major risk factor in the onset and exacerbation of mast cell-associated diseases, including allergy/anaphylaxis, asthma, and irritable bowel syndrome. Although it is known that mast cells are highly activated upon stressful events, the mechanisms by which stress modulates mast cell function and disease pathophysiology remains poorly understood. Here, we investigated the role of corticotropin-releasing factor receptor subtype 1 (CRF₁) in mast cell degranulation and associated disease pathophysiology. In a mast cell-dependent model of IgE-mediated passive systemic anaphylaxis (PSA), prophylactic administration of the CRF₁-antagonist antalarmin attenuated mast cell degranulation and hypothermia. Mast cell-deficient Kit^W-sh/W-sh mice engrafted with CRF₁^-/- bone marrow-derived mast cells (BMMCs) exhibited attenuated PSA-induced serum histamine, hypothermia, and clinical scores compared with wild-type BMMC-engrafted Kit^W-sh/W-sh mice. Kit^W-sh/W-sh mice engrafted with CRF₁^-/- BMMCs also exhibited suppressed in vivo mast cell degranulation and intestinal permeability in response to acute restraint stress. Genetic and pharmacologic experiments with murine BMMCs, rat RBL-2H3, and human LAD2 mast cells demonstrated that although CRF₁ activation did not directly induce MC degranulation, CRF₁ signaling potentiated the degranulation responses triggered by diverse mast cell stimuli and was associated with enhanced release of Ca²⁺ from intracellular stores. Taken together, our results revealed a prominent role for CRF₁ signaling in mast cells as a positive modulator of stimuli-induced degranulation and in vivo pathophysiologic responses to immunologic and psychologic stress.

Biochemical and functional analysis of corticotropin releasing factor purified from an aqueous extract of human placenta used as wound healer

Human placental extract constitutes of innumerable therapeutically important components mostly used in wound healing arising from the skin and burn injuries. However, there is still some bioactive present in the placental extracts yet to be characterized to better under the complex process of wound healing mediated by the placental extract. In this study, the presence of corticotropin releasing factor (CRF) in an aqueous extract of human placenta was detected and quantified by dot blot and CRF-ELISA immunoassay kit respectively. Subsequently, it was purified by immuno-affinity chromatography and quantified as 0.45±0.05μg of CRF per ml of placental extract where its molecular weight found to be 4.78kDa by MALDI-TOF. To study functional analysis of CRF, an in vitro WI-38 lung fibroblast cell scratch wound model was used which indicated proliferation, motility of cells after treatment with purified CRF. Moreover, reduction in apoptosis rate of cells during closure of wound was observed from microscopy studies and FACS analysis. Also, Antalarmin, an antagonist of CRF type 1 receptor inhibited the wound closure potency of the purified component. Faster healing of wound with an elevation of IL-6 and TGF-β during early stages of repair by placental CRF was observed on excision rat model. The process of healing was accompanied by the decrease in the level of TNF-α and IFN-γ.

Vitamin D signaling and melanoma: role of vitamin D and its receptors in melanoma progression and management

Ultraviolet B (UVB), in addition to having carcinogenic activity, is required for the production of vitamin D3 (D3) in the skin which supplies >90% of the body's requirement. Vitamin D is activated through hydroxylation by 25-hydroxylases (CYP2R1 or CYP27A1) and 1α-hydroxylase (CYP27B1) to produce 1,25(OH)₂D3, or through the action of CYP11A1 to produce mono-di- and trihydroxy-D3 products that can be further modified by CYP27B1, CYP27A1, and CYP24A1. The active forms of D3, in addition to regulating calcium metabolism, exert pleiotropic activities, which include anticarcinogenic and anti-melanoma effects in experimental models, with photoprotection against UVB-induced damage. These diverse effects are mediated through an interaction with the vitamin D receptor (VDR) and/or as most recently demonstrated through action on retinoic acid orphan receptors (ROR)α and RORγ. With respect to melanoma, low levels of 25(OH)D are associated with thicker tumors and reduced patient survival. Furthermore, single-nucleotide polymorphisms of VDR and the vitamin D-binding protein (VDP) genes affect melanomagenesis or disease outcome. Clinicopathological analyses have shown positive correlation between low or undetectable expression of VDR and/or CYP27B1 in melanoma with tumor progression and shorter overall (OS) and disease-free survival (DFS) times. Paradoxically, this correlation was reversed for CYP24A1 (inactivating 24-hydroxylase), indicating that this enzyme, while inactivating 1,25(OH)₂D3, can activate other forms of D3 that are products of the non-canonical pathway initiated by CYP11A1. An inverse correlation has been found between the levels of RORα and RORγ expression and melanoma progression and disease outcome. Therefore, we propose that defects in vitamin D signaling including D3 activation/inactivation, and the expression and activity of the corresponding receptors, affect melanoma progression and the outcome of the disease. The existence of multiple bioactive forms of D3 and alternative receptors affecting the behavior of melanoma should be taken into consideration when applying vitamin D management for melanoma therapy.

Bioactive forms of vitamin D selectively stimulate the skin analog of the hypothalamus-pituitary-adrenal axis in human epidermal keratinocytes

Ultraviolet radiation B stimulates both the production of vitamin D3 in the skin and the activation of the skin analog of the hypothalamic-pituitary-adrenal axis (HPA) as well as the central HPA. Since the role of vitamin D3 in the regulation of the HPA is largely unknown, we investigated the impact of 1,25(OH)2D3 and its noncalcemic analogs, 20(OH)D3 and 21(OH)pD, on the expression of the local HPA in human epidermal keratinocytes. The noncalcemic analogs showed similar efficacy to 1,25(OH)2D3 in stimulating the expression of neuropeptides, CRF, urocortins and POMC, and their receptors, CRFR1, CRFR2, MC1R, MC2R, MC3R and MC4R. Interestingly, unlike other secosteroids, the activity of 21(OH)pD did not correlate with induction of differentiation, suggesting a separate but overlapping mechanism of action. Thus, biologically active forms of vitamin D can regulate different elements of the local equivalent of the HPA with implications for the systemic HPA.

Neuroendocrinology of the skin

The skin is considered the mirror of the soul and is affected by neurohormonal triggers, especially stress. Hair follicles, keratinocytes, mast cells, melanocytes, and sebocytes all express sex and stress hormones implicating them in a local "hypothalamic-pituitary-adrenal axis." In particular, the peptides corticotropin-releasing hormone (CRH) and neurotensin (NT) have synergistic action stimulating mast cells and are uniquely elevated in the serum of patients with skin diseases exacerbated by stress. Addressing the neurohormonal regulation of skin function could lead to new targets for effective treatment of inflammatory skin diseases.

Stress-related skin disorders

Emerging research has suggested that the skin is not only a target of organismal distress but also an active participant of the stress response through production of local "HPA axis" components, peripheral nerve endings, and resident skin cells, including keratinocytes, mast cells, and immune/immune accessory cells. There are also bidirectional communication pathways between the brain and the skin, which play significant roles in integrating these interactions. In this review, we summarize the intricate relations between stress and several skin conditions. We have tried to identify the underlying mechanisms that link stress to the common dermatoses according to the latest scientific findings.

Differentiation of Keratinocytes Modulates Skin HPA Analog

It is well established, that epidermal keratinocytes express functional equivalent of hypothalamus-pituitary-adrenal axis (HPA) in order to respond to changing environment and maintain internal homeostasis. We are presenting data indicating that differentiation of primary neonatal human keratinocytes (HPEKp), induced by prolonged incubation or calcium is accompanied by significant changes in the expression of the elements of skin analog of HPA (sHPA). Expression of CRF, UCN1-3, POMC, ACTH, CRFR1, CRFR2, MC1R, MC2R, and GR (coded by NR3C1 gene) were observed on gene/protein levels along differentiation of keratinocytes in culture with similar pattern seen by immunohistochemistry on full thickness skin biopsies. Expression of CRF was more pronounced in less differentiated keratinocytes, which corresponded to the detection of CRF immunoreactivity preferentially in the stratum basale. POMC expression was enhanced in more differentiated keratinocytes, which corresponded to detection of ACTH immunoreactivity, predominantly in the stratum spinosum and stratum granulosum. Expression of urocortins was also affected by induction of HPEKp differentiation. Immunohistochemical studies showed high prevalence of CRFR1 in well differentiated keratinocytes, while smaller keratinocytes showed predominantly CRFR2 immunoreactivity. MC2R mRNA levels were elevated from days 4 to 8 of in vitro incubation, while MC2R immunoreactivity was the highest in the upper layers of epidermis. Similar changes in mRNA/protein levels of sHPA elements were observed in HPEKp keratinocytes treated with calcium. Summarizing, preferential expression of CRF and POMC (ACTH) by populations of keratinocytes on different stage of differentiation resembles organization of central HPA axis suggesting their distinct role in physiology and pathology of the epidermis. J. Cell. Physiol. 232: 154-166, 2017. © 2016 Wiley Periodicals, Inc.

Inhibiting interleukin-18 production through the mitogen-activated protein kinase pathway, a potential role of corticotropin-releasing hormone in chronic plaque psoriasis

Corticotropin-releasing hormone (CRH) and CRH receptors (CRH-Rs) are expressed in the skin; CRH-R1 is the predominant receptor. Whether the CRH/CRH-R1 system plays a role in psoriasis has not yet been assessed. Immunohistochemistry, real-time RT-PCR, ELISA assay, and Western blot analysis were used to investigate the expression of CRH/CRH-R1 in patients with chronic plaque psoriasis and that of IL-18 in CRH-treated HaCaT cells. CRH and CRH-R1 were downregulated in patients with chronic plaque psoriasis. In vitro, CRH attenuated the expression of IL-18 by a mitogen-activated protein kinase signaling pathway through CRH-R1 in HaCaT cells. Thus, an aberrant cutaneous CRH/CRH-R1 system exists in lesions from chronic plaque psoriasis which might play a role in psoriasis and offers further evidence for the study of CRH in the skin.

Somato stimulation and acupuncture therapy

Acupuncture is an oldest somato stimulus medical technique. As the most representative peripheral nerve stimulation therapy, it has a complete system of theory and application and is applicable to a large population. This paper expounds the bionic origins of acupuncture and analyzes the physiological mechanism by which acupuncture works. For living creatures, functionally sound viscera and effective endurance of pain are essential for survival. This paper discusses the way in which acupuncture increases the pain threshold of living creatures and the underlying mechanism from the perspective of bionics. Acupuncture can also help to adjust visceral functions and works most effectively in facilitating the process of digestion and restraining visceral pain. This paper makes an in-depth overview of peripheral nerve stimulation therapy represented by acupuncture. We look forward to the revival of acupuncture, a long-standing somato stimulus medicine, in the modern medical systems.

On the role of skin in the regulation of local and systemic steroidogenic activities

The mammalian skin is a heterogeneous organ/tissue covering our body, showing regional variations and endowed with neuroendocrine activities. The latter is represented by its ability to produce and respond to neurotransmitters, neuropeptides, hormones and neurohormones, of which expression and phenotypic activities can be modified by ultraviolet radiation, chemical and physical factors, as well as by cytokines. The neuroendocrine contribution to the responses of skin to stress is served, in part, by local synthesis of all elements of the hypothalamo-pituitary-adrenal axis. Skin with subcutis can also be classified as a steroidogenic tissue because it expresses the enzyme, CYP11A1, which initiates steroid synthesis by converting cholesterol to pregnenolone, as in other steroidogenic tissues. Pregnenolone, or steroidal precursors from the circulation, are further transformed in the skin to corticosteroids or sex hormones. Furthermore, in the skin CYP11A1 acts on 7-dehydrocholesterol with production of 7-dehydropregnolone, which can be further metabolized to other Δ7steroids, which after exposure to UVB undergo photochemical transformation to vitamin D like compounds with a short side chain. Vitamin D and lumisterol, produced in the skin after exposure to UVB, are also metabolized by CYP11A1 to several hydroxyderivatives. Vitamin D hydroxyderivatives generated by action of CYP11A1 are biologically active and are subject to further hydroxylations by CYP27B1, CYP27A1 and CP24A. Establishment of which intermediates are produced in the epidermis in vivo and whether they circulate on the systemic level represent a future research challenge. In summary, skin is a neuroendocrine organ endowed with steroid/secosteroidogenic activities.

Synthesis and Evaluation of Biological Activity of Antimicrobial--Pro-Proliferative Peptide Conjugates

Skin represents the largest organ of the human body and plays a crucial role in its protection from the negative impact of the outside environment, maintains its homeostasis, enables sensory interaction and thermoregulation. The traumatized skin tissue undergoes several phenotype switches due to progressive reoxygenation and release of cytokine and growth factors, that activate mechanisms of reparative processes. However, in case of wounds colonized with pathogenic microflora natural regenerative mechanisms become substantially impaired, that could lead to chronic inflammatory states with non-healing skin lesions. Herein, we present the initial results of our studies aimed at the design of bifunctional peptide-based compounds. The chemical approach, that was utilized in this work, was based on the conjugation of antimicrobial peptides with the peptides, that have potential pro-proliferative and/or cytoprotective activity towards human keratinocytes and fibroblasts, in order to obtain antimicrobials with reduced cytotoxicity or compounds that maintain both activities, i.e. inhibit bacterial or fungi growth and activate cell proliferation/migration in in vitro tests. As a result, we obtained a group of peptide conjugates that effectively inhibited the growth of selected bacterial and fungi strains and were able to stimulate proliferation and migration of keratinocytes and fibroblasts under their effective microbicidal concentrations.

Synthesis, F-18 radiolabeling, and microPET evaluation of 3-(2,4-dichlorophenyl)-N-alkyl-N-fluoroalkyl-2,5-dimethylpyrazolo[1,5-a]pyrimidin-7-amines as ligands of the corticotropin-releasing factor type-1 (CRF1) receptor

A series of 3-(2,4-dichlorophenyl)-N-alkyl-N-fluoroalkyl-2,5-dimethylpyrazolo[1,5-a]pyrimidin-7-amines were synthesized and evaluated as potential positron emission tomography (PET) tracers for the corticotropin-releasing factor type-1 (CRF1) receptor. Compounds 27, 28, 29, and 30 all displayed high binding affinity (⩽1.2 nM) to the CRF1 receptor when assessed by in vitro competition binding assays at 23 °C, whereas a decrease in affinity (⩾10-fold) was observed with compound 26. The logP7.4 values of [(18)F]26-[(18)F]29 were in the range of ∼2.2-2.8 and microPET evaluation of [(18)F]26-[(18)F]29 in an anesthetized male cynomolgus monkey demonstrated brain penetrance, but specific binding was not sufficient enough to differentiate regions of high CRF1 receptor density from regions of low CRF1 receptor density. Radioactivity uptake in the skull, and sphenoid bone and/or sphenoid sinus during studies with [(18)F]28, [(18)F]28-d8, and [(18)F]29 was attributed to a combination of [(18)F]fluoride generated by metabolic defluorination of the radiotracer and binding of intact radiotracer to CRF1 receptors expressed on mast cells in the bone marrow. Uptake of [(18)F]26 and [(18)F]27 in the skull and sphenoid region was rapid but then steadily washed out which suggests that this behavior was the result of binding to CRF1 receptors expressed on mast cells in the bone marrow with no contribution from [(18)F]fluoride.

Early-life dietary spray-dried plasma influences immunological and intestinal injury responses to later-life Salmonella typhimurium challenge

Increasing evidence supports the concept that early-life environmental influences, including nutrition and stress, have an impact on long-term health outcomes and disease susceptibility. The objective of the present study was to determine whether dietary spray-dried plasma (SDP), fed during the first 2 weeks post-weaning (PW), influences subsequent immunological and intestinal injury responses to Salmonella typhimurium challenge. A total of thirty-two piglets (age 16-17 d) were weaned onto nursery diets containing 0, 2·5 % SDP (fed for 7 d PW) or 5 % SDP (fed for 14 d PW), and were then fed control diets (without SDP), for the remainder of the experiment. At 34 d PW (age 50 d), pigs were challenged with 3 × 10⁹ colony-forming units of S. typhimurium. A control group (non-challenged) that was fed 0 % SDP in the nursery was included. At 2 d post-challenge, the distal ileum was harvested for the measurement of inflammatory, histological and intestinal physiological parameters. S. typhimurium challenge induced elevated ileal histological scores, myeloperoxidase (MPO), IL-8 and TNF, and increased intestinal permeability (indicated by reduced transepithelial voltage (potential difference) and elevated 4 kDa fluorescein isothiocyanate dextran (FD4) flux rates). Compared with S. typhimurium-challenged controls (0 % SDP), pigs fed the 5 % SDP-14 d diet exhibited reduced ileal histological scores, MPO levels, IL-8 levels and FD4 flux rates. Pigs fed the 5 % SDP-14 d nursery diet exhibited increased levels of plasma and ileal TNF-α in response to the challenge, compared with the other treatments. These results indicate that inclusion of SDP in PW diets can have an influence on subsequent immunological and intestinal injury responses induced by later-life S. typhimurium challenge.

Brain-skin connection: stress, inflammation and skin aging

The intricate relationship between stress and skin conditions has been documented since ancient times. Recent clinical observations also link psychological stress to the onset or aggravation of multiple skin diseases. However, the exact underlying mechanisms have only been studied and partially revealed in the past 20 years or so. In this review, the authors will discuss the recent discoveries in the field of “Brain-Skin Connection”, summarizing findings from the overlapping fields of psychology, endocrinology, skin neurobiology, skin inflammation, immunology, and pharmacology.

Ultraviolet B radiation-stimulated urocortin 1 is involved in tyrosinase-related protein 1 production in human melanoma HMV-II cells

Ultraviolet B (UVB) radiation stimulates cutaneous melanin pigmentation. The melanosomal enzyme tyrosinase-related protein 1 (TRP1) is involved in the modulation of pigment production in response to this stressor. Recent molecular and biochemical analyses have revealed the presence of corticotropin-releasing factor (CRF) and urocortin 1 (Ucn1), together with their corresponding receptors, in mammalian skin. Although CRF and Ucn1 are thought to have potent effects on the skin system, their possible roles and regulations have yet to be determined fully. Our previous findings in human melanoma HMV-II cells suggest that both CRF and Ucn1 regulate TRP1 gene expression via Nurr-1/Nur77, transcription factors that constitute the nuclear receptor 4a subgroup of orphan nuclear receptors. HMV-II cells were found to express mainly Ucn1 mRNA. This study aimed to explore the effects of UVB on Ucn1 mRNA and TRP1 protein levels in HMV-II cells. UVB (30 mJ/cm(2)) increased Nurr-1, Nur77, and Ucn1 mRNA levels. UVB also increased TRP1 protein levels. Ucn1 knockdown inhibited the UVB-induced increases in TRP1 protein levels. These data suggest that UVB-stimulated Ucn1 contributes to TRP1 production via the transcription of both Nurr-1 and Nur77. Ucn1, produced in melanoma cells, acts on melanoma cells themselves in an autocrine manner.

Putative role of HIF transcriptional activity in melanocytes and melanoma biology

Hypoxia-inducible factor-1α (HIF-1α) is a highly oxygen sensitive bHLH protein that is part of the heterodimeric HIF-1 transcription factor. Under hypoxic stress, HIF-1 activity is induced to control expression of multiple downstream target genes, including vascular endothelial growth factor (VEGF). The normal epidermis exists in a constant mild hypoxic microenvironment and constitutively expresses HIF-1α and HIF-2α. Expression of HIF-1α and/or HIF-2α has been suggested to correlate with the increased malignant potential of melanocytes, therefore, failures of melanoma therapies may be partially linked to high HIF activity. Notably, melanomas that have the V600E BRAF mutation exhibit increased HIF-1α expression. We have utilized a bioinformatics approach to identify putative hypoxia response elements (HREs) in a set of genes known to participate in the process of melanogenesis (includingTRPM1, SLC45A2, HRAS, C-KIT, PMEL and CRH). While some of the mechanistic links between these genes and the HIF pathway have been previously explored, others await further investigation. Although agents targeting HIF activity have been proposed as novel treatment modalities for melanoma, there are currently no clinical trials in progress to test their efficacy in melanoma.

Cutaneous glucocorticosteroidogenesis: securing local homeostasis and the skin integrity

Human skin has the ability to synthesize glucocorticoids de novo from cholesterol or from steroid intermediates of systemic origin. By interacting with glucocorticoid receptors, they regulate skin immune functions as well as functions and phenotype of the epidermal, dermal and adnexal compartments. Most of the biochemical (enzyme and transporter activities) and regulatory (neuropeptides mediated activation of cAMP and protein kinase A dependent pathways) principles of steroidogenesis in the skin are similar to those operating in classical steroidogenic organs. However, there are also significant differences determined by the close proximity of synthesis and action (even within the same cells) allowing para-, auto- or intracrine modes of regulation. We also propose that ultraviolet light B (UVB) can regulate the availability of 7-dehydrocholesterol for transformation to cholesterol with its further metabolism to steroids, oxysterols or ∆7 steroids, because of its transformation to vitamin D3. In addition, UVB can rearrange locally produced ∆7 steroids to the corresponding secosteroids with a short- or no-side chain. Thus, different mechanisms of regulation occur in the skin that can be either stochastic or structuralized. We propose that local glucocorticosteroidogenic systems and their regulators, in concert with cognate receptors operate to stabilize skin homeostasis and prevent or attenuate skin pathology.

Immunomodulatory effects of sex hormones: requirements for pregnancy and relevance in melanoma

Similarities between the pathologic progression of cancer and the physiologic process of placentation (eg, proliferation, invasion, and local/systemic tolerance) have been recognized for many years. Sex hormones such as human chorionic gonadotropin, estrogens, progesterone, and others contribute to induction of immunologic tolerance at the beginning of gestation. Sex hormones have been shown to play contributory roles in the growth of cancers such as breast cancer, prostrate cancer, endometrial cancer, and ovarian cancer, but their involvement as putative mediators of the immunologic escape of cancer is still being elucidated. Herein, we compare the emerging mechanism by which sex hormones modulate systemic immunity in pregnancy and their potentially similar role in cancer. To do this, we conducted a PubMed search using combinations of the following keywords: "immune regulation," "sex hormones," "pregnancy," "melanoma," and "cancer." We did not limit our search to specific publication dates. Mimicking the maternal immune response to pregnancy, especially in late gestation, might aid in design of better therapies to reconstitute endogenous antitumor immunity and improve survival.

Inverse regulation of melanoma growth and migration by Orai1/STIM2-dependent calcium entry

Spontaneous melanoma phenotype switching is controlled by unknown environmental factors and may determine melanoma outcome and responsiveness to anticancer therapy. We show that Orai1 and STIM2 are highly expressed and control store-operated Ca(2+) entry in human melanoma. Lower extracellular Ca(2+) or silencing of Orai1/STIM2 caused a decrease in intracellular Ca(2+) , which correlated with enhanced proliferation and increased expression of microphthalmia-associated transcription factor, a marker for proliferative melanoma phenotype. In contrast, the invasive and migratory potential of melanoma cells was reduced upon silencing of Orai1 and/or STIM2. Accordingly, markers for a non-proliferative, tumor-maintaining phenotype such as JARID1B and Brn2 decreased. Immunohistochemical staining of primary melanomas and lymph node metastases revealed a heterogeneous distribution of Orai1 and STIM2 with elevated expression in the invasive rim of the tumor. In summary, our results support a dynamic model in which Orai1 and STIM2 inversely control melanoma growth and invasion. Pharmacological tuning of Orai1 and particularly STIM2 might thus prevent metastatic spread and render melanomas more susceptible to conventional therapy.

Current concepts of metastasis in melanoma

The main cause of death in melanoma patients is widespread metastases. Staging of melanoma is based on the primary tumor thickness, ulceration, lymph node and distant metastases. Metastases develop in regional lymph nodes, as satellite or in-transit lesions, or in distant organs. Lymph flow and chemotaxis is responsible for the homing of melanoma cells to different sites. Standard pathologic evaluation of sentinel lymph nodes fails to find occult melanoma in a significant proportion of cases. Detection of small numbers of malignant melanoma cells in these and other sites, such as adjacent to the primary site, bone marrow or the systemic circulation, may be enhanced by immunohistochemistry, reverse transcription PCR, evaluation of lymphatic vessel invasion and proteomics. In the organs to which melanoma cells metastasize, extravasation of melanoma cells is regulated by adhesion molecules, matrix metalloproteases, chemokines and growth factors. Melanoma cells may travel along external vessel lattices. After settling in the metastatic sites, melanoma cells develop mechanisms that protect them against the attack of the immune system. It is thought that one of the reasons why melanoma cells are especially resistant to killing is the fact that melanocytes (cells from which melanoma cells derive) are resistant to such noxious factors as ultraviolet light and reactive oxygen species. Targeted melanoma therapies are, so far, largely unsuccessful, and new ones, such as adjuvant inhibition of melanogenesis, are under development.

2,3,5,6-Tetramethylpyrazine of Ephedra sinica regulates melanogenesis and inflammation in a UVA-induced melanoma/keratinocytes co-culture system

BACKGROUND

2,3,5,6-Tetramethylpyrazine (TMP) is known as a composition of Ephedra sinica and it has been used in the treatment of several disorders such as asthma, heart failure, rhinitis, and urinary incontinence. It has been reported that TMP inhibits melanoma metastasis and suppression angiogenesis by VEGF.

OBJECTIVE

The inhibitory activity of melanogenic proteins by TMP was confirmed in UVA-induced melanoma/keratinocyte co-culture system in this paper.

METHODS

The melanin content, cell viability and cytokines release such as TNFα, IL-1β, IL-8 and GM-CSF were measured by ELISA assay. In addition, TRP1, MITF and MAPK signaling protein expression were also evaluated by Western blotting analysis.

RESULTS

Decreasing melanogenic factors (TRP1, MITF, and MAPK) and factors (TNFα, IL-1β, IL-8, and GM-CSF) improving skin cancer and inflammation were identified.

CONCLUSION

It suggests that TMP can serve as a potent candidate for regulation of melanogenesis.

Key role of CRF in the skin stress response system

The discovery of corticotropin-releasing factor (CRF) or CRH defining the upper regulatory arm of the hypothalamic-pituitary-adrenal (HPA) axis, along with the identification of the corresponding receptors (CRFRs 1 and 2), represents a milestone in our understanding of central mechanisms regulating body and local homeostasis. We focused on the CRF-led signaling systems in the skin and offer a model for regulation of peripheral homeostasis based on the interaction of CRF and the structurally related urocortins with corresponding receptors and the resulting direct or indirect phenotypic effects that include regulation of epidermal barrier function, skin immune, pigmentary, adnexal, and dermal functions necessary to maintain local and systemic homeostasis. The regulatory modes of action include the classical CRF-led cutaneous equivalent of the central HPA axis, the expression and function of CRF and related peptides, and the stimulation of pro-opiomelanocortin peptides or cytokines. The key regulatory role is assigned to the CRFR-1α receptor, with other isoforms having modulatory effects. CRF can be released from sensory nerves and immune cells in response to emotional and environmental stressors. The expression sequence of peptides includes urocortin/CRF→pro-opiomelanocortin→ACTH, MSH, and β-endorphin. Expression of these peptides and of CRFR-1α is environmentally regulated, and their dysfunction can lead to skin and systemic diseases. Environmentally stressed skin can activate both the central and local HPA axis through either sensory nerves or humoral factors to turn on homeostatic responses counteracting cutaneous and systemic environmental damage. CRF and CRFR-1 may constitute novel targets through the use of specific agonists or antagonists, especially for therapy of skin diseases that worsen with stress, such as atopic dermatitis and psoriasis.

Involvement of Nurr-1/Nur77 in corticotropin-releasing factor/urocortin1-induced tyrosinase-related protein 1 gene transcription in human melanoma HMV-II cells

Recent molecular and biochemical analyses have revealed the presence of corticotropin-releasing factor (CRF) and urocortin (Ucn), together with their corresponding receptors in mammalian skin. The melanosomal enzyme tyrosinase-related protein 1 (TRP1) is involved in modulation of pigment production in response to stressors. Although CRF and Ucn are thought to have potent effects on the skin system, their possible roles and regulation have yet to be fully determined. This study aimed to explore the effects of CRF and Ucn on TRP1 gene expression using human melanoma HMV-II cells. The mRNA of CRF, Ucn1, Ucn2, and CRF receptor type 1 (CRF1 receptor) was detected in HMV-II cells. CRF and Ucn1 stimulated TRP1 gene transcription via the CRF1 receptor, and increased both Nurr-1 and Nur77 mRNA expression levels. Both CRF- and Ucn1-induced Nurr-1/Nur77 acted via a NGFI-B response element on the TRP1 promoter. The combination of Nurr-1/Nur77 and microphthalmia-associated transcription factor, a melanocyte-specific transcription factor gene induced by α-melanocyte-stimulating hormone, had additive effects on activation of TRP1 gene transcription. The findings suggest that in human melanoma HMV-II cells both CRF and Ucn1 regulate TRP1 gene expression via Nurr-1/Nur77 production, independent of pro-opiomelanocortin or α-melanocyte-stimulating hormone stimulation.

The A, B, Cs of G-protein-coupled receptor pharmacology in assay development for HTS

G-protein-coupled receptors represent one of the most important areas of research in the pharmaceutical industry, being one of the largest druggable gene families. Recognising this fact, manufacturers have developed a huge variety of homogeneous assay technologies that facilitate the quantification of receptor ligand binding events and their downstream signalling cascades. However, while early emphasis was placed on the most sensitive, high-throughput and cost-effective screening technologies to enable identification of the most lead matter for further development, in recent years emphasis has shifted to a focus on maximising the identification of compounds that are new and developing assays that are more biologically/pharmacologically relevant. Therefore, this review provides an overview of the binding and functional techniques available for high-throughput screening, with particular attention on how assay application and configuration can be maximised to ensure their successful identification of relevant chemical matter and thereby optimising project success.