Solar-Simulated Ultraviolet Radiation-Induced Upregulation of the Melanocortin-1 Receptor, Proopiomelanocortin, and α-Melanocyte-Stimulating Hormone in Human Epidermis In Vivo

Carotenoids in red fruit (Pandanus conoideus Lam.) have a potential role as an anti‑pigmentation agent (Review)

Melasma is a persistent condition characterized by excessive melanin production in the skin. The management of melasma necessitates a protracted treatment duration, which is associated with diminished levels of patient satisfaction. One effective strategy for mitigating occurrence of melasma is consumption of nutricosmetics with depigmentation properties. The present review aimed to investigate the potential of red fruit as a depigmentation agent. Carotenoids serve a crucial role in human nutrition as a precursor to vitamin A. Carotenoids serve as scavengers of reactive oxygen species generated by ultraviolet radiation. Carotenoids promote skin health. Red fruit, a fruit originating from Papua (Indonesia) has anti-pigmentation properties associated with its ability to block melanogenesis through various protein pathways such as PKA, ERK, and AKT signaling pathways. The consumption of food rich in carotenoids, such as red fruit, has advantageous properties to reduce hyperpigmentation and skin brightening.

The Keratinocyte in the Picture Cutaneous Melanoma Microenvironment

Melanoma progression is a multistep evolution from a common melanocytic nevus through a radial superficial growth phase, the invasive vertical growth phase finally leading to metastatic dissemination into distant organs. Melanoma aggressiveness largely depends on the propensity to metastasize, which means the capacity to escape from the physiological microenvironment since tissue damage due to primary melanoma lesions is generally modest. Physiologically, epidermal melanocytes are attached to the basement membrane, and their adhesion/migration is under the control of surrounding keratinocytes. Thus, the epidermal compartment represents the first microenvironment responsible for melanoma spread. This complex process involves cell-cell contact and a broad range of secreted bioactive molecules. Invasion, or at the beginning of the microinvasion, implies the breakdown of the dermo-epidermal basement membrane followed by the migration of neoplastic melanocytic cells in the superficial papillary dermis. Correspondingly, several experimental evidences documented the structural and functional rearrangement of the entire tissue surrounding neoplasm that in some way reflects the atypia of tumor cells. Lastly, the microenvironment must support the proliferation and survival of melanocytes outside the normal epidermal-melanin units. This task presumably is mostly delegated to fibroblasts and ultimately to the self-autonomous capacity of melanoma cells. This review will discuss remodeling that occurs in the epidermis during melanoma formation as well as skin changes that occur independently of melanocytic hyperproliferation having possible pro-tumoral features.

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.

Behind the Scene: Exploiting MC1R in Skin Cancer Risk and Prevention

Melanoma and non-melanoma skin cancers (NMSCs) are the most frequent cancers of the skin in white populations. An increased risk in the development of skin cancers has been associated with the combination of several environmental factors (i.e., ultraviolet exposure) and genetic background, including melanocortin-1 receptor (MC1R) status. In the last few years, advances in the diagnosis of skin cancers provided a great impact on clinical practice. Despite these advances, NMSCs are still the most common malignancy in humans and melanoma still shows a rising incidence and a poor prognosis when diagnosed at an advanced stage. Efforts are required to underlie the genetic and clinical heterogeneity of melanoma and NMSCs, leading to an optimization of the management of affected patients. The clinical implications of the impact of germline MC1R variants in melanoma and NMSCs' risk, together with the additional risk conferred by somatic mutations in other peculiar genes, as well as the role of MC1R screening in skin cancers' prevention will be addressed in the current review.

Neuropeptides and neurohormones in immune, inflammatory and cellular responses to ultraviolet radiation

Humans are exposed to varying amounts of ultraviolet radiation (UVR) through sunlight. UVR penetrates into human skin leading to release of neuropeptides, neurotransmitters and neuroendocrine hormones. These messengers released from local sensory nerves, keratinocytes, Langerhans cells (LCs), mast cells, melanocytes and endothelial cells (ECs) modulate local and systemic immune responses, mediate inflammation and promote differing cell biologic effects. In this review, we will focus on both animal and human studies that elucidate the roles of calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF), nitric oxide and proopiomelanocortin (POMC) derivatives in mediating immune and inflammatory effects of exposure to UVR as well as other cell biologic effects of UVR exposure.

Premature cell senescence in human skin: Dual face in chronic acquired pigmentary disorders

Although senescence was originally described as an in vitro acquired cellular characteristic, it was recently recognized that senescence is physiologically and pathologically involved in aging and age-related diseases in vivo. The definition of cellular senescence has expanded to include the growth arrest caused by various cellular stresses, including DNA damage, inadequate mitochondria function, activated oncogene or tumor suppressor genes and oxidative stress. While senescence in normal aging involves various tissues over time and contributes to a decline in tissue function even with healthy aging, disease-induced premature senescence may be restricted to one or a few organs triggering a prolonged and more intense rate of accumulation of senescent cells than in normal aging. Organ-specific high senescence rate could lead to chronic diseases, especially in post-mitotic rich tissue. Recently, two opposite acquired pathological conditions related to skin pigmentation were described to be associated with premature senescence: vitiligo and melasma. In both cases, it was demonstrated that pathological dysfunctions are not restricted to melanocytes, the cell type responsible for melanin production and transport to surrounding keratinocytes. Similar to physiological melanogenesis, dermal and epidermal cells contribute directly and indirectly to deregulate skin pigmentation as a result of complex intercellular communication. Thus, despite senescence usually being reported as a uniform phenotype sharing the expression of characteristic markers, skin senescence involving mainly the dermal compartment and its paracrine function could be associated with the disappearance of melanocytes in vitiligo lesions and with the exacerbated activity of melanocytes in the hyperpigmentation spots of melasma. This suggests that the difference may arise in melanocyte intrinsic differences and/or in highly defined microenvironment peculiarities poorly explored at the current state of the art. A similar dualistic phenotype has been attributed to intratumoral stromal cells as cancer-associated fibroblasts presenting a senescent-like phenotype which influence the behavior of neoplastic cells in either a tumor-promoting or tumor-inhibiting manner. Here, we present a framework dissecting senescent-related molecular alterations shared by vitiligo and melasma patients and we also discuss disease-specific differences representing new challenges for treatment.

Discovery of a Highly Selective MC1R Agonists Pentapeptide to Be Used as a Skin Pigmentation Enhancer and with Potential Anti-Aging Properties

One of the first lines of cutaneous defense against photoaging is (a) the synthesis of melanin and (b) the initiation of an oxidative stress response to protect skin against the harmful effects of solar radiation. Safe and selective means to stimulate epidermal pigmentation associated with oxidative stress defense are; however, scarce. Activation of the melanocortin-1 receptor (MC1R) on epidermal melanocytes represents a key step in cutaneous pigmentation initiation and, additionally, it regulates cellular defense mechanisms like oxidative stress and DNA-repair. Thus, making the activation of MC1R an attractive strategy for modulating skin pigmentation and oxidative stress. In this context, we designed and synthesized pentapeptides that act as MC1R agonists. These peptides bound, with high potency, to MC1R and activated cAMP synthesis in CHO cells expressing human MC1R. Using one lead pentapeptide, we could show that this activation of MC1R was specific as testing the activation of other G-protein coupled receptors, including the MC-receptor family, was negative. In vitro efficacy on mouse melanoma cells showed similar potency as for the synthetic MC1R agonist alpha-melanocyte stimulating hormone (NDP-alpha-MSH). Moreover, we could reproduce this activity in human skin tissue culture. The lead pentapeptide was able to induce ex-vivo protein expression of key melanogenesis markers melanocyte inducing transcription factor (MITF), tyrosinase (TYR), and tyrosinase-related protein 1 (TYRP-1). Concerning oxidative stress response, we found that the pentapeptide enhanced the activation of Nrf2 after UVA-irradiation. Our results make this pentapeptide an ideal candidate as a skin pigmentation enhancer that mimics alpha-MSH and may also have anti-photoaging effects on the skin.

Does the environment influence multiple sclerosis pathogenesis via UVB light and/or induction of vitamin D?

Multiple sclerosis (MS) is a disease of presumed auto-immune origin. Long-standing observations such as the correlation between MS incidence and geographical latitude or the levels of Vitamin D (Vit D) in the serum have implicated the environmental factors UVB radiation and diet in the etiology of the disease. Clinical trials have been conducted and are currently underway to elucidate whether a Vit D enriched diet or treatment with UVB can influence MS incidence, -severity, and -progression, as well as the ideal time point for treatment. This review summarizes the current scientific knowledge to the environmental factors UVB-light and Vit D concerning the clinical aspects of MS in epidemiological studies and clinical trials.

How UV Light Touches the Brain and Endocrine System Through Skin, and Why

The skin, a self-regulating protective barrier organ, is empowered with sensory and computing capabilities to counteract the environmental stressors to maintain and restore disrupted cutaneous homeostasis. These complex functions are coordinated by a cutaneous neuro-endocrine system that also communicates in a bidirectional fashion with the central nervous, endocrine, and immune systems, all acting in concert to control body homeostasis. Although UV energy has played an important role in the origin and evolution of life, UV absorption by the skin not only triggers mechanisms that defend skin integrity and regulate global homeostasis but also induces skin pathology (e.g., cancer, aging, autoimmune responses). These effects are secondary to the transduction of UV electromagnetic energy into chemical, hormonal, and neural signals, defined by the nature of the chromophores and tissue compartments receiving specific UV wavelength. UV radiation can upregulate local neuroendocrine axes, with UVB being markedly more efficient than UVA. The locally induced cytokines, corticotropin-releasing hormone, urocortins, proopiomelanocortin-peptides, enkephalins, or others can be released into circulation to exert systemic effects, including activation of the central hypothalamic-pituitary-adrenal axis, opioidogenic effects, and immunosuppression, independent of vitamin D synthesis. Similar effects are seen after exposure of the eyes and skin to UV, through which UVB activates hypothalamic paraventricular and arcuate nuclei and exerts very rapid stimulatory effects on the brain. Thus, UV touches the brain and central neuroendocrine system to reset body homeostasis. This invites multiple therapeutic applications of UV radiation, for example, in the management of autoimmune and mood disorders, addiction, and obesity.

Anti melanogenic effect of Croton roxburghii and Croton sublyratus leaves in α-MSH stimulated B16F10 cells

Croton roxburghii and Croton sublyratus have been used as skin treatments in traditional medicine. The objective of the present study was to investigate the antimelanogenic effect of ethanol extracts of Croton roxburghii (CRE) and Croton sublyratus (CSE) leaves on cellular melanin content and cellular tyrosinase activity as mediated by the action of microthalmia transcription factor (MITF) and melanogenic enzymes. Croton roxburghii and Croton sublyratus leaves were extracted by petroleum ether, dichloromethane and absolute ethanol, sequentially. The ethanolic crude extracts were examined for antimelanogenic activity by their ability to decrease melanin content and cellular tyrosinase activity in alpha-melanocyte-stimulating hormone-stimulated B16F10 melanoma cells. In addition, the extracts were evaluated to determine a plausible mechanism of melanogenesis suppression through determining the activation of MITF transcription factor and melanogenic proteins (tyrosinase, tyrosinase-related protein 1 or TRP-1 and tyrosinase-related protein 2 or TRP-2) at the transcriptional and translation levels in α-MSH-induced B16F10 cells. Upon treatment with CRE and CSE, the cells showed significant decreases in melanin content and cellular tyrosinase activity. CRE and CSE also suppressed MITF, tyrosinase, TRP-1 and TRP-2 at the transcription and translation levels in α-MSH-stimulated melanin biosynthesis in B16F10 cells. Our finding shows that CRE and CSE inhibit melanin content and cellular tyrosinase activity through suppressing MITF and melanogenic enzymes. CRE and CSE may be useful to combine with skin whitening agents for cosmetic uses.

Impact of UV-irradiation on electrical impedance spectroscopy of benign nevi: study protocol for a prospective, controlled, clinical study

INTRODUCTION

The clinical and histological changes of nevi after ultraviolet (UV) irradiation have been studied in detail. In contrast, the impact of UV irradiation on electrical impedance spectroscopy scores of nevi has not been investigated. However, for physicians, it is essential to know the extent to which changes in electrical impedance spectroscopy scores of nevi may be attributed to seasonal effects of UV irradiation.

METHODS

This is a prospective, controlled, clinical study evaluating the impact of UV irradiation on the electrical impedance spectroscopy scores of benign nevi in 50 patients undergoing phototherapy. To this end, benign nevi of patients with a medical indication for phototherapy will be measured by electrical impedance spectroscopy before, during and after UV irradiation. At the same time, non-irradiated nevi of the same patient will be measured to account for changes over time that are independent of direct UV irradiation.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the ethics committee of the medical faculty of the University of Heidelberg (ethics approval number S-279/2017). The design and the final results of the study will be published and made available to the public.

TRIAL REGISTRATION NUMBER

DRKS00012456; Pre-results.

Paracrine regulation of melanocyte genomic stability: a focus on nucleotide excision repair

UV radiation is a major environmental risk factor for the development of melanoma by causing DNA damage and mutations. Resistance to UV damage is largely determined by the capacity of melanocytes to respond to UV injury by repairing mutagenic photolesions. The nucleotide excision repair (NER) pathway is the major mechanism by which cells correct UV photodamage. This multistep process involves the basic steps of damage recognition, isolation, localized strand unwinding, assembly of a repair complex, excision of the damage-containing strand 3' and 5' to the photolesion, synthesis of a sequence-appropriate replacement strand, and finally ligation to restore continuity of genomic DNA. In melanocytes, the efficiency of NER is regulated by several hormonal pathways including the melanocortin and endothelin signaling pathways. Elucidating molecular mechanisms by which melanocyte DNA repair is regulated offers the possibility of developing novel melanoma-preventive strategies to reduce UV mutagenesis, especially in UV-sensitive melanoma-prone individuals.

The Preventive Effect of Coffee Compounds on Dermatitis and Epidermal Pigmentation after Ultraviolet Irradiation in Mice

BACKGROUND

Ultraviolet (UV) irradiation is well known to promote inflammation and pigmentation of skin. UVB mainly affects dermatitis and pigmentation. Coffee contains a number of polyphenols, such as caffeic acid (CA) and chlorogenic acid (CGA) but their in vivo bioactivity for photobiology remains unclear.

METHODS

C57BL/6j male mice were irradiated with UVB (1.0 kJ/m2/day) for 3 days. Five days after the final session of UVB irradiation, the dorsal skin, ear epidermis, and blood samples were analyzed to investigate the inflammatory factors, melanogenesis factors and related hormones.

RESULTS

After the oral administration of CA (100 mg/day) or CGA (100 mg/day) for 8 days, only CA was found to inhibit dermatitis and pigmentation. The pathway by which CA inhibits dermatitis is related to the mitogen-activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK)1/2/cAMP response element binding protein (CREB) pathway. Otherwise, the pathway by which CA inhibits pigmentation is related to the activation of the β-endorphin-μ-opioid receptor and suppresses the cAMP-microphthalmia-associated transcription factor (MITF) pathway.

CONCLUSION

It is suggested that the oral administration of CA prevented dermatitis and pigmentation after UVB irradiation in mice.

Dermoscopic Changes of Melanocytic Nevi after Psoralen-Ultraviolet A and Narrow-Band Ultraviolet B Phototherapy

Background:

Phototherapy may alter the morphologic features of melanocytic nevi. Dermoscopy is a non-invasive method for evaluation of skin lesions, specifically melanocytic nevi.

Aims and Objectives:

This study was designed to evaluate the effects of narrowband ultraviolet B (NB-UVB) and psoralen-ultraviolet A (PUVA) therapy on the dermoscopic features of nevi.

Methods:

A total of 74 melanocytic nevi were randomly selected from 20 patients. Out of those, 54 nevi received NB-UVB, while 20 received PUVA. 50% of the nevi in each group were exposed to radiation, while the remaining nevi were covered with an opaque tape. All nevi were demoscopically evaluated before and after 30 or 60 sessions of phototherapy.

Results:

Overall demoscopic changes were observed in 34/37 (91.8%) of the uncovered nevi compared to 16/37 (43.2%) of the covered nevi (P value 0.0001). The most common changes were new dot/globule formation (62.1%), darkening (32.4%), nevus enlargement (27%), and patchy pigmentation (18.8%). Compared to NB-UVB, dermoscopic changes were more frequent in both covered and uncovered nevi of the PUVA group. (P values 0.041 and 0.0172, respectively). New dot/globule formation was observed more frequently in the covered and uncovered nevi of PUVA group.

Conclusion:

PUVA and NB-UVB induce dermoscopic changes in the majority of the irradiated nevi. However, PUVA is associated with higher frequency of dermoscopic changes in both covered and uncovered nevi.

UVB Activates Hypothalamic-Pituitary-Adrenal Axis in C57BL/6 Mice

To test the hypothesis that ultraviolet B (UVB) can activate the hypothalamic-pituitary-adrenal (HPA) axis, the shaved back skin of C57BL/6 mice was exposed to 400 mJ/cm² of UVB or was shame irradiated. After 12 and 24 h of exposure, plasma, skin, brain, and adrenals were collected and processed to measure corticotropin-releasing hormone (CRH), urocortin (Ucn), β-endorphin (β-END), ACTH and corticosterone (CORT) or brain was fixed for immunohistochemical detection of CRH. UVB stimulated plasma levels of CRH, Ucn, β-END, ACTH and CORT, and increased skin expression of Ucn, β-END and CORT at the gene and protein/peptide levels. UVB stimulated CRH gene and protein expression in the brain that was localized to the paraventricular nucleus of the hypothalamus. In adrenal glands it increased mRNAs of melanocortin receptor type 2, StAR and CYP11B1. Hypophysectomy abolished UVB stimulation of plasma but not of skin CORT levels, and had no effect on UVB stimulation of CRH and Ucn levels in the plasma, demonstrating the requirement of an intact pituitary for the systemic effect. In conclusion, we identify mechanism of the regulation of body homeostasis by UVB through activation of the HPA axis that originates in the skin and requires pituitary for the systemic effect.

In vivo skin fluorescence imaging in young Caucasian adults with early malignant melanomas

Background

Human cutaneous malignant melanoma (CMM) is an aggressive cancer showing a dramatic worldwide increase in incidence over the past few decades. The most prominent relative epidemiological increase has been disclosed in young women. The aim of the study was to assess the effects of chronic sun exposures in order to rate the extend of melanocytic stimulations in the vicinity of CMM.

Methods

The study was designed to evaluate the melanin distribution and density using ultraviolet light illumination. The present study was performed on surgical excision specimens of thin CMM lesion removed from the upper limbs of 55 Caucasian adults (37 women and 18 men). Two control groups comprised 23 men and 21 women of similar ages who had medium-size congenital melanocytic nevi, also present on the upper limbs. The peritumoral skin was scrutinized using a Visioscan^® VC98 device, revealing the faint mosaic melanoderma (FMM) pattern that grossly indicates early signs of chronic photodamage in epidermal melanin units.

Results

The median extent of relative FMM was significantly higher in the CMM male group. By contrast, the CMM female group showed a reverse bimodal distribution in FMM size. Only 12/37 (32.5%) of the CMM female group had an increased FMM size, whereas 25/37 (67.5%) of females with CMM had a global FMM extent in the normal range, relative to the controls.

Conclusion

Thin CMM supervening in young women appear unrelated to repeat photoexposure. Other mechanisms are possibly involved.

Is MC1 dispensable for regulation of cutaneous inflammatory and immune responses?

The melanocortin-1 receptor (MC1 ) - being most abundantly expressed in the skin by melanocytes - has a physiological role for melanin pigmentation in many vertebrate species. MC1 has also been implicated in regulation of skin inflammation as this receptor is detectable in the majority of non-melanocytic cell types and its ligand α-melanocyte-stimulating hormone (α-MSH) exerts immunoregulatory and anti-inflammatory effects. However, in vivo studies on mice with targeted disruption of MC1 have been missing in the context of skin inflammation until recently. Wolnicka-Glubisz et al. now reported that the course of ultraviolet (UV)-induced inflammation, contact hypersensitivity, neonatal immune tolerance and UV-induced immunosuppression is similar in MC1 signal-deficient (C57BL/6-Mc1r(e/e)) and wild-type mice. These unexpected findings are supported by own observations in experimentally induced immune-complex-mediated vasculitis: Mc1r(e/e) mice exhibited a similar extent of the reverse passive cutaneous Arthus reaction compared with wild-type animals. Future studies are thus needed to clarify whether these findings are due to limitations in the chosen mouse model and/or point to additional MC subtypes that may regulate inflammatory and immune responses in the skin.

Investigation of safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple doses of a long-acting α-MSH analog in healthy overweight and obese subjects

MC4-NN2-0453 is a novel, long-acting, selective, melanocortin-4-receptor agonist developed for treatment of obesity. This first-human-dose, randomized, double-blind, placebo-controlled trial investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple doses of MC4-NN2-0453 in overweight to obese but otherwise healthy subjects. The trial included a single-dose part of ascending subcutaneous 0.03-1.50 mg/kg doses in overweight to obese but otherwise healthy men, and a multiple-dose part of ascending subcutaneous 0.75-3.0 mg/day doses in obese but otherwise healthy men/women. The single-dose part included 7 cohorts of 8 subjects, randomized 6:2 to active drug/placebo; the multiple-dose part included 4 cohorts of 20 subjects, randomized 16:4 to active drug/placebo. MC4-NN2-0453 was well tolerated and raised no safety concerns except for nonserious skin-related adverse events, this along with lack of weight loss effect led to premature termination of the trial. Headache, sexual-arousal disturbance, and penile erection were also reported. Single-dose pharmacokinetics showed dose-linearity and dose-proportionality. Maximum plasma concentration was observed after 50-100 hours, which then declined with a of approximately 250 hours. Plasma concentration reached steady state after 4 weeks for 0.75 and 1.5 mg/day multiple-dose cohorts, and the was similar to single dose. There were no significant pharmacodynamic effects, including effect on body weight.

Photoprotection in contemporary dermatology and cosmetology: traditional issues and new data

The paper contains information of UVB and UVA influence on the various structures of the skin. Main principles of modern photoprotection, sunscreens as well as photoprotective role of clothes are discussed.

UVB-induced epidermal pigmentation in mice eyes with no contact lens wear and non-UVB blocking and UVB blocking contact lens wear

PURPOSE

Irradiation by ultraviolet (UV) B is known to increase the number of Dopa-positive melanocytes in the skin. This study examines the effectiveness of a contact lens for the defense of UVB eye irradiation-induced pigmentation.

METHODS

A 2.5 kJ/m(2) dose of UVB radiation was delivered by a sunlamp to the eye of C57BL/6j male mice, and changes in the expression of Dopa-positive melanocytes in the epidermis and the plasma level of alpha-melanocyte-stimulating hormone (α-MSH) was analyzed.

RESULTS

The degree of change in the Dopa-positive melanocytes expression was reduced by UVB blocking contact lens using mice given UVB irradiation to the eye. The plasma level of α-MSH increased in the C57BL/6j mice after irradiation to the eye, but there was no increase in the UVB blocking contact lens mice given UVB irradiation to the eye. Both the increase of the expression of Dopa-positive melanocytes and the plasma level of α-MSH were strongly suppressed by an alignment fitting UVB blocking contact lens and only a slightly suspended UVB blocking contact lens. In addition, these changes were successfully inhibited by a UVB blocking contact lens but not by a non-UVB blocking contact lens with a similar absorbance.

CONCLUSION

These observations suggest that the UVB blocking contact lens inhibits the pigmentation of the epidermis in mice by suppressing of the α-MSH.

MC1R expression in HaCaT keratinocytes inhibits UVA-induced ROS production via NADPH oxidase- and cAMP-dependent mechanisms

Ultraviolet A (UVA) radiations are responsible for deleterious effects, mainly due to reactive oxygen species (ROS) production. Alpha-melanocyte stimulating hormone (α-MSH) binds to melanocortin-1 receptor (MC1R) in melanocytes to stimulate pigmentation and modulate cutaneous inflammatory responses. MC1R may be induced in keratinocytes after UV exposure. To investigate the effect of MC1R signaling on UVA-induced ROS (UVA-ROS) production, we generated HaCaT cells that stably express human MC1R (HaCaT-MC1R) or the Arg151Cys (R(151)C) non-functional variant (HaCaT-R(151)C). We then assessed ROS production immediately after UVA exposure and found that: (1) UVA-ROS production was strongly reduced in HaCaT-MC1R but not in HaCaT-R(151)C cells compared to parental HaCaT cells; (2) this inhibitory effect was further amplified by incubation of HaCaT-MC1R cells with α-MSH before UVA exposure; (3) protein kinase A (PKA)-dependent NoxA1 phosphorylation was increased in HaCaT-MC1R compared to HaCaT and HaCaT-R(151)C cells. Inhibition of PKA in HaCaT-MC1R cells resulted in a marked increase of ROS production after UVA irradiation; (4) the ability of HaCaT-MC1R cells to produce UVA-ROS was restored by inhibiting epidermal growth factor receptor (EGFR) or extracellular signal-regulated kinases (ERK) activity before UVA exposure. Our findings suggest that constitutive activity of MC1R in keratinocytes may reduce UVA-induced oxidative stress via EGFR and cAMP-dependent mechanisms.

Cutaneous hypothalamic-pituitary-adrenal axis homolog: regulation by ultraviolet radiation

The hypothalamic-pituitary-adrenal (HPA) axis maintains basal and stress-related homeostasis in vertebrates. Skin expresses all elements of the HPA axis including corticotropin-releasing hormone (CRH), proopiomelanocortin (POMC), ACTH, β-endorphin (β-END) with corresponding receptors, the glucocorticoidogenic pathway, and the glucocorticoid receptor (GR). To test the hypothesis that cutaneous responses to environmental stressors follow the organizational structure of the central response to stress, the activity of the "cutaneous HPA" axis homolog was investigated after exposure to ultraviolet radiation (UVR) wavelengths of UVA (320-400 nm), UVB (280-320 nm), and UVC (100-280 nm) in human skin organ culture and in co-cultured keratinocytes/melanocytes. The level of stimulation of CRH, POMC, MC1R, MC2R, CYP11A1, and CYP11B1 genes was dependent on UV wavelengths and doses, with the highest effects observed for highly energetic UVC and UVB. ELISA and Western assays showed significant production of CRH, POMC, ACTH, and CYP11A1 proteins and of cortisol, with a decrease in GR expression only after UVB and UVC. However, β-END expression was also stimulated by UVA. Immunocytochemistry localized the deposition of the aforesaid antigens predominantly to the epidermis with additional accumulation of CRH, β-END, and ACTH in the dermis. UVR-stimulated CYP11A1 expression was seen in the basal layer of the epidermis and cells of adjacent dermis. Thus, the capacity to activate or change the spatial distribution of the cutaneous HPA axis elements is dependent on highly energetic wavelengths (UVC and UVB), implying a dependence of a local stress response on their noxious activity with overlapping or alternative mechanisms activated by UVA.

Histamine effect on melanocyte proliferation and vitiliginous keratinocyte survival

Repigmention of vitiligo requires melanocyte proliferation and migration. Keratinocytes have been shown to play a role in this process. Data from this laboratory showed that bee venom (BV) stimulated melanocyte proliferation and migration as well as melanogenesis. As histamine release is associated with BV, its effect on melanocyte proliferation and migration was examined. Cultured normal human melanocytes treated with histamine were studied with and without receptor-specific antagonists or agonists. The effect of histamine on vitiliginous keratinocytes, in cultured cells treated with a PI3K inhibitor in the presence of TNF-α, was also examined. Histamine exerted a more significant effect on melanocyte proliferation than on melanogenesis. This occurred through the H2 receptor with complex signalling to ERK, CREB, and Akt activation, which stimulated melanocyte migration. Histamine and the H2 receptor agonist also increased survival of vitiliginous, but not normal, keratinocytes, with NF-κB activation. Because expression levels of the H2 receptor was significantly decreased in depigmented compared to normally pigmented epidermis, in patients with vitiligo, histamine may increase the survival of vitiliginous keratinocytes. Overall, histamine stimulated the proliferation and migration of melanocytes and the vitiliginous keratinocyte survival, providing the basis for novel therapeutic approaches to vitiligo repigmentation.

Prevention of scattered light-induced asthenopia and fatigue by a polarized filter

BACKGROUND

It has been well documented that a long-time irradiation of the eye by a strong light elicits eyestrain and fatigue. To elucidate the mechanism for the induction of light-induced fatigue and asthenopia, changes in the mouse were analyzed after white light-irradiation to the eye.

METHODS

C57BL/6j male mice were irradiated with white light in a specially designed room equipped with four mirrors covering all areas of its four walls to elicit diffused reflected light, and changes in their plasma levels of cortisol, INF-gamma, interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) were analyzed.

RESULTS

Irradiation of mice with scattered white light significantly decreased the motional activity of animals, suggesting the occurrence of fatigue. Biochemical analysis and enzyme-immunoassay revealed that the irradiation of mice significantly elevated the plasma levels of cortisol, IFN-gamma, IL-10 and TGF-beta. All these changes were not observed with mice irradiated with the light in a similar room not equipped with mirrors. These changes were successfully inhibited by a polarized glass filter but not by a non-polarized filter with a similar absorbance.

CONCLUSIONS

These observations suggest that irradiation of the eye by scattered reflected light stimulated a stress response via hypothalamo-pituitary-adrenal axis to enhance the secretion of cortisol from the adrenal grand and increase the plasma levels of cytokines.

Age-related changes in pro-opiomelanocortin (POMC) and related receptors in human epidermis

SYNOPSIS

Much effort has been placed in cosmetic research for better understanding of the effects of ageing on skin's appearance, structure, mechanical properties and function. It is now of common knowledge that UV radiations induce pre-mature skin ageing notably in the epidermis where UV radiations induce keratinocyte differentiation. As UV radiations have also been shown to regulate the pro-opiomelanocortin (POMC) peptide family in the skin and because no study has been conducted so far to investigate the age-related changes in POMC and related receptors, we analysed POMC, MC-1R, MC-2R and MOR-1 at mRNA level and MC-1R, MC-2R and MOR-1 at protein level too in primary cultures of normal human keratinocytes obtained from female donors aged from 17 to 75 years old. Regarding the gene expressions, we observed that MC-1R, MC-2R and MOR-1 suffered a dramatic decrease after 50 years of age, whereas POMC increased five-fold. Western blot analysis confirmed these results except for MOR-1 whose expression appeared to decrease at older age, around 70 years old. Immunostainings specific to MC-1R, MC-2R and MOR-1 performed on full-thickness skin biopsies also revealed an intense staining in the basal and spinous layers of a 30-year-old donor, whereas no reactivity could be observed in a 60-year-old one. We conclude that POMC and POMC-related receptors suffer a dramatically disturbed balance with ageing and that this may be implicated in the general process of skin ageing.

Immunosuppression and melanocyte proliferation

Melanocytes are pigmented cells derived from the neural crest; their proliferation is restrained by immune system. The eruption of nevi after an immunosuppressive condition is a peculiar phenomenon indicating that the immune system may play a major role in limiting proliferation of melanocytes. In this review, we analyze the role of immunosuppressive regimens on melanocyte proliferation. In particular, we discuss the eruptive nevi phenomenon, which is determined by the inability of the immune system to inhibit melanocyte proliferation. These clinical observations indicate that the immune system has a pivotal role in restraining melanocyte proliferation. However, although the role of the immune system in the development of nonmelanoma skin cancer has been shown clearly in several studies involving organ transplant patients, the role of immunosuppression in melanoma genesis has not yet been established. Further investigations are required to establish the real immunogenicity of melanoma, particularly in the light of the dichotomy between the eruptive nevi phenomenon in immunosuppressed patients and the low incidence of melanoma in transplanted patients.

The Role of Neuropeptide Endopeptidases in Cutaneous Immunity

Proteolytic processing and degradation plays an important role in modulating the generation and bioactivity of neuroendocrine peptide mediators, a class of key molecules in cutaneous biology.

Accordingly, the cellular localization and expression, and the molecular biology and structural properties of selected intracellular prohormone convertases and ectopically expressed zinc-binding metalloendoproteases are discussed.

A special reference will be made to the physiologic and pathophysiologic significance of these endopeptidases in cutaneous immunobiology.

Because of the number of pathologically relevant changes in inflammation and tumor progression that can be directly attributed to neprilysin and angiotensin-converting enzyme, a particular focus will be on the role of these enzymes in modulating innate and adaptive immune responses in the skin.

Dermal microdialysis of inflammatory markers induced by aliphatic hydrocarbons in rats

In the present study we made an attempt to understand the skin irritation cascade of selected aliphatic hydrocarbons using microdialysis technique. Microdialysis probes were inserted into dermis in the dorsal skin of hairless rats. After 2h of probes insertion, occlusive dermal exposure (2h) was carried out with 230 microl of nonane, dodecane and tetradecane, using Hill top chambers((R)). Inflammatory biomarkers such as substance P (SP), alpha-melanocyte stimulating hormone (alpha-MSH) Interleukin 6 (IL-6) and prostaglandin E2 (PGE(2)) were analyzed in the dialysis samples by enzyme immunoassay (EIA). SP, alpha-MSH and IL6 were released in significant amounts following the dermal exposure of nonane and dodecane, whereas tetradecane did not induce any of these markers in significant amounts compared to control. Nonane increased the PGE(2) levels in significant amounts within 2h of chemical exposure compared to dodecane and tetradecane. IL-6 response was found to be slow and 2-3-fold increase in IL-6 levels was observed after 5h following nonane and dodecane application. The magnitude of skin irritation exerted by all three chemicals was in the order of nonane>or=dodecane>or=tetradecane. The results demonstrate that microdialysis can be used to measure the inflammatory biomarkers in the skin irritation studies and irritation response of chemicals was quantifiable by this method. In conclusion, microdialysis was found to be an excellent tool to measure several inflammatory biomarkers as a function of time after dermal exposures with irritant chemicals.

Skin peptides: biological activity and therapeutic opportunities

The skin provides an effective barrier to the loss of body fluids and environmental assault. In addition to the physical barrier provided by the stratum corneum, the skin also contains a chemical barrier consisting of antimicrobial peptides (AMPs), which control microbial growth on the surface. These AMPs also have multiple roles as mediators of inflammation with effects on epithelial and inflammatory cells, influencing cell proliferation, wound healing, cytokine/chemokine production and chemotaxis. This review describes the range of peptides found in the skin, both constitutive and those induced in response to injury. The role these peptides play in normal skin function and in various skin conditions is described. A better understanding of their role in normal and skin disease may offer new strategies in skin disease, dermatology and as cosmeceuticals.

The melanocyte and the epidermal melanin unit: an expanded concept

There are many mechanisms by which melanocytes, keratinocytes, and Langerhans cells interact within the epidermis. Inflammatory mediators affect melanocyte function and melanogenic agents such as alpha-MSH alter the functions of keratinocytes and Langerhans cells. The epidermal melanin unit is better labeled the KLM unit.

Changes in the dermoscopic appearance of melanocytic naevi after photochemotherapy or narrow-band ultraviolet B phototherapy

BACKGROUND

Although phototherapeutic modalities are commonly used for the treatment of skin diseases, the effects of therapeutic ultraviolet (UV) irradiation on the dermoscopic appearance of melanocytic naevi are unknown.

OBJECTIVES

We aimed to analyse the effects of photochemotherapy (psoralen plus ultraviolet A, PUVA) and narrow-band ultraviolet B phototherapy (NB-UVB) on the dermoscopic appearance of naevi.

PATIENTS AND METHODS

We monitored 187 melanocytic naevi of 38 patients receiving NB-UVB or PUVA treatment for miscellaneous skin diseases. Dermoscopic images of naevi were taken before, shortly after, and after a median of 31 weeks after the UV therapy. A random selection of naevi was covered during UV treatment, the others remained uncovered. Baseline and follow-up images of naevi were viewed side by side on a computer screen to compare size, pigmentation, and dermoscopic structure of naevi.

RESULTS

Twenty-one patients received NB-UVB treatment, and 17 patients received PUVA treatment. Of 187 naevi, 70 (37%) were covered and 117 (63%) were uncovered during UV treatment. When NB-UVB- and PUVA-treated patients were analysed together, an increase in size of uncovered lesions was seen in both treatment groups. Pigmentation appeared darker at the end of UV treatment in 67.5% (n=79) of uncovered naevi compared with 41.4% (n=29) of covered naevi (P<0.001). In patients receiving NB-UVB therapy, a significant increase in the number of dots or globules in 20.3% (n=14) of uncovered naevi compared with only 5.0% (n=2) of covered naevi (P=0.03) was found. This effect was not observed after PUVA therapy. With the exception of four naevi with continuous enlargement and seven naevi with a persisting increase in dots and globules, the observed changes were reversible. All naevi with persistent changes belonged to the NB-UVB group.

CONCLUSION

In general, PUVA and NB-UVB therapy cause reversible dermoscopic changes in melanocytic naevi. Increase in dots and globules is more frequent with NB-UVB.

Cell surface expression of melanocortin-1 receptor on HaCaT keratinocytes and alpha-melanocortin stimulation do not affect the formation and repair of UVB-induced DNA photoproducts

Ultraviolet (UV) exposure induces an up-regulation of melanocortin-1 receptor (MC1R) expression in human skin and the alpha-melanocyte-stimulating hormone (alpha-MSH) may reduce UVB-induced DNA damage in normal human melanocytes. Using high-performance liquid chromatography coupled to tandem mass spectrometry, we investigated the formation and repair of DNA lesions in UVB-irradiated HaCaT cells stably transfected with the wild type MC1R gene (HaCaT-MC1R). Similar levels of 8 bipyrimidine photoproducts including cyclobutane pyrimidine dimers (CPDs) (T<>T, T<>C, C<>T), (6-4) photoproducts ((6-4)PPs) (TT-(6-4)PPs, TC-(6-4)PPs) and their Dewar valence isomers together with 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) were found to be generated in both non-transfected and HaCaT-MC1R cells after UVB exposure. Time-course studies of DNA photoproduct yields indicated that the DNA repair ability depended upon radiation doses. It was shown that (6-4)PPs were removed from the DNA of UVB-irradiated cells much more efficiently than CPDs. The repair efficiency of 8-oxodGuo, CPDs and (6-4)PPs was relatively similar in both cell lines and was not modified by stimulation with alpha-MSH before UVB-exposure. In conclusion, cell surface-enforced expression of MC1Rs on HaCaT keratinocytes and alpha-MSH stimulation do not affect the formation of UVB-induced DNA photoproducts and their subsequent repair.

Differential expression of HPA axis homolog in the skin

Human skin expresses elements of the hypothalamo-pituitary-adrenal (HPA) axis including pro-opiomelanocortin (POMC), corticotropin releasing hormone (CRH), the CRH receptor-1 (CRH-R1), key enzymes of corticosteroid synthesis and synthesizes glucocorticoids. Expression of these elements is organized in functional, cell type-specific regulatory loops, which imitate the signaling hierarchy of the HPA axis. In melanocytes and fibroblasts CRH-induced CRH-R1 stimulation upregulates POMC expression and production of ACTH through activation of cAMP dependent pathway(s). Melanocytes respond with enhanced production of cortisol and corticosterone, which is dependent on POMC activity. Fibroblasts respond to CRH and ACTH with enhanced production of corticosterone, but not cortisol, which is produced constitutively. Organ-cultured human scalp hair follicles also show a fully functional HPA axis equivalent, including cortisol synthesis and secretion and negative feedback regulation by cortisol on CRH expression. Thus, differential, CRH-driven responses of defined cutaneous cell populations reproduce key features of the central HPA axis at the tissue/single cell levels.

Endogenous phospholipid metabolite containing topical product inhibits ultraviolet light-induced inflammation and DNA damage in human skin

BACKGROUND

N-palmitoylethanolamine (PEA) and organic osmolytes are endogenous components of the human epidermis and are generated from phospholipids in the stratum granulosum. PEA has been shown to exert potent antioxidant and anti-inflammatory activities. The endogenous organic osmolytes such as betaine and sarcosine control skin humidity, but have also been shown to inhibit ultraviolet (UV) light-induced oxidative stress in keratinocytes.

OBJECTIVES

To investigate the effect of a PEA- and organic osmolyte-containing topical product (Physiogel AI) on the development of UV light-induced erythema, thymine dimer formation and p53 tumor suppressor gene activation, as well as intercellular adhesion molecule 1 (ICAM-1) and Ki67 expression in normal human skin.

METHODS

The UV-induced erythema was measured by a spectrofluorometric method. Thymine dimers, p53, ICAM-1 and Ki67 were detected in skin biopsies using immunohistochemistry.

RESULTS

Physiogel AI cream significantly inhibited the development of UV light-induced erythema and thymine dimer formation in normal human skin, but did not alter the number of Ki67+ proliferating keratinocytes and the expression of p53 and ICAM-1.

CONCLUSIONS

Our results suggest that PEA and organic osmolytes might represent a new generation of compounds which suppress UV-induced photodamage.

Melanocortin 3 receptors control crystal‐induced inflammation

In this study we have characterized the anti-inflammatory profile of a selective melanocortin type 3 receptor (MC3-R) ligand [D-Trp8]-gamma-MSH, validating in vitro results with analyses in mice deficient for this receptor subtype. In wild-type (WT) macrophages, [D-Trp8]-gamma-MSH activated MC3-R (as tested by accumulation of cyclic AMP) and inhibited (approximately 50%) the release of interleukin (IL)-1 and the chemokine KC (CXCL1), but was ineffective in cells taken from MC3-R null mice. In vivo, administration of 3-30 microg [D-Trp8]-gamma-MSH significantly inhibited leukocyte influx and cytokine production in a model of crystal-induced peritonitis, and these effects were absent in MC3-R null mice or blocked by coadministration of an MC3-R antagonist. Finally, in a model of gouty arthritis, direct injection of urate crystals into the rat joint provoked a marked inflammatory reaction that was significantly inhibited (approximately 70%) by systemic or local administration of [D-Trp8]-gamma-MSH. In conclusion, using an integrated transgenic and pharmacological approach, we provide strong proof of concept for the development of selective MC3-R agonists as novel anti-inflammatory therapeutics.

Melanocortin Receptor Ligands: New Horizons for Skin Biology and Clinical Dermatology

The melanocortin (MC) system is probably the best characterized neuropeptide network of the skin. Most cutaneous cell types express MC receptors (MC-Rs) and synthesize MCs, such as alpha-melanocyte-stimulating hormone (alpha-MSH), that act in autocrine and paracrine fashion. In human skin cells, activation of adenylate cyclase by MCs occurs at 10(-6)-10(-9) M doses of the ligand, but effects are induced in some cell types at subnanomolar concentrations. In addition to the pigmentary action of MCs on epidermal melanocytes, the hair follicle is a source and target for MCs. MCs regulate lipogenesis in sebocytes expressing both MC-1R and MC-5R. In adipocytes, lipid metabolism is modulated by agouti signalling protein, a natural MC-1R/MC-4R antagonist. The anti-inflammatory activity of alpha-MSH includes immunomodulatory effects on several resident skin cells and antifibrogenic effects mediated via MC-1R expressed by dermal fibroblasts. In human mast cells, alpha-MSH appears to be proinflammatory due to histamine release. alpha-MSH exhibits cytoprotective activity against UVB-induced apoptosis and DNA damage, a finding that helps explain the increased risk of cutaneous melanoma in individuals with loss of function MC-1R mutations. These findings should improve our understanding of skin physiology and pathophysiology and may offer novel strategies with MCs as future therapeutics for skin diseases.

Quantitative analysis of MC1R gene expression in human skin cell cultures

To address the issue of melanocortin-1 receptor (MC1R) expression in non-melanocytic cells, we have quantitatively evaluated the relative expression levels of both MC1R mRNA and protein in a subset of different cell types. Using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) at high cycle numbers, we detected MC1R mRNA in all cell types examined, including human embryonic kidney-293 (HEK 293) cells, a cell type widely used as a negative control in melanocortin expression studies. Quantitative real-time PCR revealed the highest levels of MC1R transcripts were in melanocytic cells, whereas the keratinocyte and fibroblast cell cultures examined had only a low level of expression, similar to that of HEK 293 cells. Antibody mediated detection of MC1R protein in membrane extracts demonstrated exogenous receptor in MC1R transfected cell lines, as well as endogenous MC1R in melanoma cells. However, radioligand binding procedures were required to detect MC1R protein of normal human melanocytes and no surface expression of MC1R was detected in any of the non-melanocytic cells examined. This was consistent with their low level of mRNA, and suggests that, if present, the levels of surface receptor are significantly lower than that in melanocytes. The capacity of such limited levels of MC1R protein to influence non-melanocytic skin cell biology would likely be severely compromised. Indeed, the MC1R agonist [NIe(4), D-Phe(7)] alpha-melanocyte stimulating hormone (NDP-MSH) was unable to elevate intracellular cyclic adenosine monophosphate (cAMP) levels in the keratinocyte and fibroblast cells examined, whereas a robust increase was elicited in melanocytes. Although there are a variety of cell types with detectable MC1R mRNA, the expression of physiologically significant levels of the receptor may be more restricted than the current literature indicates, and within epidermal tissue may be limited to the melanocyte.

Melanocortin-1 receptor structure and functional regulation

The melanogenic actions of the melanocortins are mediated by the melanocortin-1 receptor (MC1R). MC1R is a member of the G-protein-coupled receptors (GPCR) superfamily expressed in cutaneous and hair follicle melanocytes. Activation of MC1R by adrenocorticotrophin or alpha-melanocyte stimulating hormone is positively coupled to the cAMP signaling pathway and leads to a stimulation of melanogenesis and a switch from the synthesis of pheomelanins to the production of eumelanic pigments. The functional behavior of the MC1R agrees with emerging concepts in GPCR signaling including dimerization, coupling to more than one signaling pathway and a high agonist-independent constitutive activity accounting for inverse agonism phenomena. In addition, MC1R displays unique properties such as an unusually high number of natural variants often associated with clearly visible phenotypes and the occurrence of endogenous peptide antagonists. Therefore MC1R is an ideal model to study GPCR function. Here we review our current knowledge of MC1R structure and function, with emphasis on information gathered from the analysis of natural variants. We also discuss recent data on the regulation of MC1R function by paracrine and endocrine factors and by external stimuli such as ultraviolet light.

Reduced expression of the melanocortin-1 receptor in human liver during brain death

OBJECTIVE

There is evidence that brain death has detrimental effects on peripheral organs. Clinical and experimental studies on organ donors showed marked inflammation in tissue samples of livers and kidneys collected during brain death. The inflammatory reaction is characterized by release of cytokines and inflammatory cell infiltration. Because melanocortins and their receptors are significant modulators of inflammation, we hypothesized that downregulation of melanocortin receptors during brain death could contribute to enhance inflammation.

METHODS

Using real-time polymerase chain reaction (PCR) analysis, we determined expression of melanocortin receptors in liver biopsies obtained from brain-dead organ donors before cold ischemia and in normal liver tissue during resection of benign focal lesions of the liver. Tissue biopsies were also analyzed for expression of intercellular adhesion molecule-1 (ICAM-1), which has a central function in inflammatory cell migration.

RESULTS

Expression of melanocortin-1 receptor (MC1R) mRNA was markedly reduced in liver samples obtained from brain-dead organ donors compared to hepatic tissue collected during resection of benign focal lesions of the liver. Conversely, expression of the adhesion molecule ICAM-1 was significantly increased in livers of brain-dead organ donors.

CONCLUSIONS

Disruption of the endogenous anti-inflammatory circuit based on MC1R could contribute to tissue damage during brain death.

Novel Emerging Sunscreen Technologies

Because of increases in the number of skin cancers diagnosed annually, adverse effects of ultraviolet (UV) rays are being recognized, and major public education programs have been undertaken concerning photoprotection, including the use of sunscreen. In daily life, UV exposure is unavoidable; therefore sunscreen should be used regularly. Development in sunscreen manufacturing has grown tremendously in the last decade. Sunscreen active ingredients now are incorporated into cosmetics products to minimize photoaging changes. With the advances in technologies, many new UV filters have been developed recently. These have improved efficacy and safety. This article reviews these new filters, along with regulatory issues in the United States.

Alpha-melanocyte-stimulating hormone suppresses antigen-induced lymphocyte proliferation in humans independently of melanocortin 1 receptor gene status

Studies in mice indicate that alpha-melanocyte-stimulating hormone (alphaMSH) is immunosuppressive, but it is not known whether alphaMSH suppresses human immune responses to exogenous Ags. Human PBMCs, including monocytes, express the melanocortin 1 receptor (MC1R), and it is thought that the ability of alphaMSH to alter monocyte-costimulatory molecule expression and IL-10 release is mediated by this receptor. However, the MC1R gene is polymorphic, and certain MC1R variants compromise receptor signaling via cAMP, resulting in red hair and fair skin. Here, we have investigated whether alphaMSH can suppress Ag-induced lymphocyte proliferation in humans and whether these effects are dependent on MC1R genotype. alphaMSH suppressed streptokinase-streptodornase-induced lymphocyte proliferation, with maximal inhibition at 10(-13)-10(-11) M alphaMSH. Anti-IL-10 Abs failed to prevent suppression by alphaMSH, indicating that it was not due to MC1R-mediated IL-10 release by monocytes. Despite variability in the degree of suppression between subjects, similar degrees of alphaMSH-induced immunosuppression were seen in individuals with wild-type, heterozygous variant, and homozygous/compound heterozygous variant MC1R alleles. RT-PCR of streptokinase-streptodornase-stimulated PBMCs for all five melanocortin receptors demonstrated MC1R expression by monocytes/macrophages, MC1R and MC3R expression by B lymphocytes, but no melanocortin receptor expression by T lymphocytes. In addition, alphaMSH did not significantly inhibit anti-CD3 Ab-induced lymphocyte proliferation, whereas alphaMSH and related analogs (SHU9119 and MTII) inhibited Ag-induced lymphocyte proliferation in monocyte-depleted and B lymphocyte-depleted assays. These findings demonstrate that alphaMSH, acting probably via MC1R on monocytes and B lymphocytes, and possibly also via MC3R on B lymphocytes, has immunosuppressive effects in humans but that suppression of Ag-induced lymphocyte proliferation by alphaMSH is independent of MC1R gene status.