Ultraviolet radiation and skin mast cells: Effects, mechanisms and relevance for skin diseases

Expression of mast cell tryptase and immunoglobulin E is increased in cutaneous photodamage: implications for carcinogenesis

Purpose: Mast cells, their serine proteinase tryptase, and immunoglobulin E (IgE) can be involved in cutaneous carcinogenesis.Materials and methods: To study the association of tryptase+ and IgE+ cells with photodamage and skin cancers 385 adult patients (201 males, 184 females, 75 with immunosuppression) at risk of any type of skin cancer were examined. Skin biopsies were taken from the sun-protected medial arm and from the photodamaged dorsal forearm skin followed by immunohistochemical staining for tryptase and IgE.Results: The results show that tryptase+ and IgE+ cells are significantly higher in number in the photodamaged than sun-protected skin, both in immunocompetent and -compromised subjects, and there is a strong correlation between tryptase+ and IgE+ cells. The numbers of forearm tryptase+ and especially IgE+ cells associated significantly with the forearm photodamage severity. In the logistic regression analysis, the forearm to upper arm ratio of IgE+ cells produced a univariate odds ratio of 1.521 (p = .010) and a multivariate one of 3.875 (p = .047) for the history of squamous cell carcinoma. The serum level of total IgE correlated significantly to the IgE to tryptase ratio in both skin sites.Conclusions: Therefore, IgE+ mast cells participate in photodamage and carcinogenesis, though it is unclear whether they are tumor-protective or -causative.

Update on Melasma Treatments

Melasma is a prevalent hyperpigmentation condition known for its challenging treatment due to its resemblance to photoaged skin disorders. Numerous studies have shed light on the intricate nature of melasma, which often bears similarity to photoaging disorders. Various therapeutic approaches, encompassing topical and systemic treatments, chemical peeling, and laser therapy, have exhibited efficacy in managing melasma in previous research. However, melasma often reoccurs despite successful treatment, primarily due to its inherent photoaged properties. Given that melasma shares features with photoaging disorders, including disruptions in the basement membrane, solar elastosis, angiogenesis, and mast cell infiltration in the dermal layer, a comprehensive treatment strategy is imperative. Such an approach might involve addressing epidermal hyperpigmentation while concurrently restoring dermal components. In this article, we provide a comprehensive review of conventional treatment methods frequently employed in clinical practice, as well as innovative treatments currently under development for melasma management. Additionally, we offer an extensive overview of the pathogenesis of melasma.

Protective Mechanisms of Polyphenol-Enriched Blueberry Preparation in Preventing Inflammation in the Skin against UVB-Induced Damage in an Animal Model

UVB significantly impacts the occurrence of cutaneous disorders, ranging from inflammatory to neoplastic diseases. Polyphenols derived from plants have been found to exhibit photoprotective effects against various factors that contribute to skin cancer. During the fermentation of the polyphenol-enriched blueberry preparation (PEBP), small oligomers of polyphenols were released, thus enhancing their photoprotective effects. This study aimed to investigate the protective effects of PEBP on UVB-induced skin inflammation. Topical preparations of polyphenols were applied to the skin of dorsally shaved mice. Mice were subsequently exposed to UVB and were sacrificed 90 min after UVB exposure. This study revealed that pretreatment with PEBP significantly inhibited UVB-induced recruitment of mast and neutrophil cells and prevented the loss of skin thickness. Furthermore, the findings show that PEBP treatment resulted in the downregulation of miR-210, 146a, and 155 and the upregulation of miR-200c and miR-205 compared to the UVB-irradiated mice. Additionally, PEBP was found to reduce the expression of IL-6, IL-1β, and TNFα, inhibiting COX-2 and increasing IL-10 after UVB exposure. Moreover, DNA methylation analysis indicated that PEBP might potentially reduce the activation of inflammation-related pathways such as MAPK, Wnt, Notch, and PI3K-AKT signaling. Our finding suggests that topical application of PEBP treatment may effectively prevent UVB-induced skin damage by inhibiting inflammation.

Corticotropin-releasing hormone receptor-1 is increased in mast cells in psoriasis and actinic keratosis, but not markedly in keratinocyte skin carcinomas

Corticotropin-releasing hormone receptor-1 (CRH-R1) is expressed in human mast cells, but its role in skin diseases is unknown. By using a sequential double-staining technique, the mast cell expression of CRH-R1 was investigated in biopsies from lesional and non-lesional skin samples of patients with actinic keratosis (AK), basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and psoriasis. Dermal tryptase+ mast cells expressed CRH-R1 immunoreactivity in the non-lesional skin in all patient groups. The CRH-R1 expression was significantly increased in the lesional skin of AK (p = 0.03) and psoriasis (p = 0.02), non-significantly in BCC (p = 0.129), but not increased in SCC. To investigate the regulation of CRH-R1, the LAD2 mast cell line was irradiated with UVB or stimulated with CRH or 1,25-dihydroxyvitamin D3 [1,25-(OH)2 D3 ]. Consequently, UVB at 90 mJ/cm2 (p = 0.041) and 120 mJ/cm2 (p = 0.039) decreased CRH-R1 expression. Instead, CRH at 100 and 1000 nM increased CRH-R1 immunostaining, but did not affect the proliferative response. The treatment with 10 and 100 nM 1,25-(OH)2 D3 led to a noticeable increase in CRH-R1 staining. After irradiating with UVB, the concentration of CRH increased in the conditioned medium, but not in sonicated LAD2 mast cells. In conclusion, the lack of sufficient levels of CRH-R1 in mast cells may be related to diminished antitumoural response in SCC and possibly in BCC.

Mast Cells as a Target-A Comprehensive Review of Recent Therapeutic Approaches

Mast cells (MCs) are the immune cells distributed throughout nearly all tissues, mainly in the skin, near blood vessels and lymph vessels, nerves, lungs, and the intestines. Although MCs are essential to the healthy immune response, their overactivity and pathological states can lead to numerous health hazards. The side effect of mast cell activity is usually caused by degranulation. It can be triggered by immunological factors, such as immunoglobulins, lymphocytes, or antigen-antibody complexes, and non-immune factors, such as radiation and pathogens. An intensive reaction of mast cells can even lead to anaphylaxis, one of the most life-threatening allergic reactions. What is more, mast cells play a role in the tumor microenvironment by modulating various events of tumor biology, such as cell proliferation and survival, angiogenesis, invasiveness, and metastasis. The mechanisms of the mast cell actions are still poorly understood, making it difficult to develop therapies for their pathological condition. This review focuses on the possible therapies targeting mast cell degranulation, anaphylaxis, and MC-derived tumors.

Update on Melasma-Part I: Pathogenesis

Melasma is a multifactorial dyschromia that results from exposure to external factors (such as solar radiation) and hormonal factors (such as sex hormones and pregnancy), as well as skin inflammation (such as contact dermatitis and esthetic procedures), in genetically predisposed individuals. Beyond hyperfunctional melanocytes, skin with melasma exhibits a series of structural and functional alterations in the epidermis, basement membrane, and upper dermis that interact to elicit and sustain a focal hypermelanogenic phenotype. Evolution in the knowledge of the genetic basis of melasma and the cutaneous response to solar radiation, as well as the roles of endocrine factors, antioxidant system, endothelium proliferation, fibroblast senescence, mast cell degranulation, autophagy deficits of the melanocyte, and the paracrine regulation of melanogenesis, will lead to the development of new treatments and preventive strategies. This review presents current knowledge on these aspects of the pathogenesis of melasma and discusses the effects of specific treatments and future research on these issues.

UV Protection in the Cornea: Failure and Rescue

Simple Summary

The sun is a deadly laser, and its damaging rays harm exposed tissues such as our skin and eyes. The skin’s protection and repair mechanisms are well understood and utilized in therapeutic approaches while the eye lacks such complete understanding of its defenses and therefore often lacks therapeutic support in most cases. The aim here was to document the similarities and differences between the two tissues as well as understand where current research stands on ocular, particularly corneal, ultraviolet protection. The objective is to identify what mechanisms may be best suited for future investigation and valuable therapeutic approaches.

Abstract

Ultraviolet (UV) irradiation induces DNA lesions in all directly exposed tissues. In the human body, two tissues are chronically exposed to UV: the skin and the cornea. The most frequent UV-induced DNA lesions are cyclobutane pyrimidine dimers (CPDs) that can lead to apoptosis or induce tumorigenesis. Lacking the protective pigmentation of the skin, the transparent cornea is particularly dependent on nucleotide excision repair (NER) to remove UV-induced DNA lesions. The DNA damage response also triggers intracellular autophagy mechanisms to remove damaged material in the cornea; these mechanisms are poorly understood despite their noted involvement in UV-related diseases. Therapeutic solutions involving xenogenic DNA-repair enzymes such as T4 endonuclease V or photolyases exist and are widely distributed for dermatological use. The corneal field lacks a similar set of tools to address DNA-lesions in photovulnerable patients, such as those with genetic disorders or recently transplanted tissue.

The Protective Effect of Edible Bird's Nest against the Immune-senescence Process of UVB-irradiated Hairless Mice†

Edible bird's nest (EBN) is a nutritious food with many beneficial effects, including protecting cells against oxidation and infection due to wounds, bacteria or viruses. EBN has shown antiaging, anti-inflammatory and wound-healing properties in skin cells. Here, we investigated whether EBN has protective effects against photoaging, inflammation and immune-senescence in hairless mice treated with UVB irradiation. The skin thickness was lower in mice on an EBN diet than in mice treated with UVB alone. The level of hydration was significantly increased, while the index of transepidermal water loss decreased, in groups on the EBN diet. EBN also reduced erythema index in UVB-irradiated mice. At the molecular level, skin elasticity and antiaging are associated with high expression of elastin, collagen and filaggrin and low expression of the membrane metalloproteinases, MMP-1 and MMP-2. Inflammatory markers such as interleukins, IL-1β and IL-6, and TNF-α decreased significantly in the EBN groups. Caspase-3, an important factor in the apoptotic pathway and in congenital and adaptive immune responses, decreased in the EBN groups. Moreover, EBN diminished the overexpression of immunoglobulin E and elevated mast cell counts in UVB-irradiated mice. Overall, these findings suggest that EBN protects skin against aging and alleviates inflammation in UVB-irradiated hairless mice.

Pathogenesis of solar urticaria: Classic perspectives and emerging concepts

Solar urticaria is a rare, immunologically mediated photodermatosis in which activation of cutaneous mast cells is triggered by specific wavelengths of solar electromagnetic radiation. This manifests clinically as the rapid development of cutaneous itch, erythema and wheal formation after several minutes of sun exposure. Disease mechanisms in solar urticaria remain incompletely elucidated and there have been few recent investigations of its pathobiology. Historic passive transfer experiments performed during the twentieth century provide support for a 'photoallergy' model of disease pathogenesis, wherein molecular alteration of a putative chromophore by solar electromagnetic radiation produces mast cell activation via an IgE-dependent mechanism. However, this model does not account for several observations made during passive transfer experiments nor does it explain a range of subsequent clinical and photobiological observations made in solar urticaria patients. Furthermore, increased understanding of the molecular dynamics underpinning cutaneous mast cell responses highlights the need to reformulate our understanding of solar urticaria pathogenesis in the context of this contemporary scientific landscape. In this review, we discuss the current understanding of solar urticaria pathogenesis and, by incorporating recent scientific and clinical observations, develop new hypotheses to drive future investigation into this intriguing disorder.

Efficacy of NB-UVB as Add-on Therapy to Antihistamine in the Treatment of Chronic Urticaria: A Systematic Review and Meta-analysis

Introduction

Narrow-band ultraviolet B (NB-UVB) phototherapy has been used for the treatment of chronic urticaria (CU), but the clinical efficacy of this treatment modality requires further evidence. A systematic review and meta-analysis of randomized clinical trials were conducted to evaluate the efficacy and safety of NB-UVB as add-on therapy in the treatment of CU.

Methods

A literature search was conducted in the Cochrane, Embase, PubMed, Web of Science, CNKI, CBM, VIP and WanFang databases up to October 2020. A total of nine studies involving 713 participants met the inclusion criteria.

Results

Two trials showed a significant difference in the Urticaria Activity Score between therapy with NB-UVB + antihistamines and that with antihistamines alone (mean difference 8.23, 95% confidence interval [CI] 5.78–10.68, p < 0.00001). Six trials (563 participants) showed a significant benefit of NB-UVB as add-on therapy to antihistamines in the total effective rate (risk ratio [RR] 1.56, 95% CI 1.39–1.75, p < 0.00001). In terms of adverse events, no statistically significant differences were found for NB-UVB + antihistamines versus antihistamines alone (RR 1.10, 95% CI 0.67–1.79, p = 0.71). Combination therapy of NB-UVB + antihistamines yielded a significantly lower risk of recurrence (RR 0.25, 95% CI 0.14–0.44, p < 0.00001).

Conclusion

Our meta-analysis suggests that combination therapy of NB-UVB + antihistamines is significantly more effective in treating CU than antihistamines alone.

Hyptis mociniana: phytochemical fingerprint and photochemoprotective effect against UV-B radiation-induced erythema and skin carcinogenesis

Skin cancer is a public health problem due to its high incidence. Ultraviolet radiation (UVR) is the main etiological agent of this disease. Photochemoprotection involves the use of substances to avoid damage caused by UV exposure. The aim of this work was to determine the phytochemical fingerprint and photochemoprotective effect against UVB radiation-induced skin damage such as erythema and carcinogenesis of H. mociniana methanolic extract (MEHm). The chemical composition of the MEHm was analysed by LC/ESI-MS/MS. Three quercetin derivatives, two pectinolides, and two caffeic acid derivatives were identified in the methanolic extract. MEHm has antioxidant effect and it is not cytotoxic in HaCaT cells. Phytochemicals from H. mociniana have a photochemopreventive effect because they absorb UV light and protect HaCaT cells from UVR-induced cell death. Also, in SKH-1 mice -acute exposure-, it decreased erythema formation, modulating the inflammatory response, reduced the skin damage according to histological analysis and diminished p53 expression. Finally, MEHm protects from photocarcinogenesis by reducing the incidence and multiplicity of skin carcinomas in SKH-1 mice exposed chronically to UVB radiation.

Molecular Background, Clinical Features and Management of Pediatric Mastocytosis: Status 2021

Pediatric mastocytosis is a heterogeneous disease characterized by accumulation of mast cells in the skin and less frequently in other organs. Somatic or germline mutations in the KIT proto-oncogene are detected in most patients. Cutaneous mastocytosis is the most common form of the disease in children. In the majority of cases, skin lesions regress spontaneously around puberty. However, in few patients, mastocytosis is not a self-limiting disease, but persists into adulthood and can show signs of systemic involvement, especially when skin lesions are small-sized and monomorphic. Children with mastocytosis often suffer from mast cell mediator-related symptoms. Severe hypersensitivity reactions can also occur, mostly in patients with extensive skin lesions and blistering. In a substantial number of these cases, the triggering factor of anaphylaxis remains unidentified. Management of pediatric mastocytosis is mainly based on strict avoidance of triggers, treatment with H1 and H2 histamine receptor blockers, and equipment of patients and their families with epinephrine auto-injectors for use in severe anaphylactic reactions. Advanced systemic mastocytosis occurs occasionally. All children with mastocytosis require follow-up examinations. A bone marrow investigation is performed when advanced systemic mastocytosis is suspected and has an impact on therapy or when cutaneous disease persists into adulthood.

Protective Effects of Dietary Grape on UVB-Mediated Cutaneous Damages and Skin Tumorigenesis in SKH-1 Mice

Non-melanoma skin cancers (NMSCs) are the most diagnosed cancers in the US and occur more frequently in males. We previously demonstrated chemoprotective effects of dietary grape powder (GP) against UVB-mediated skin tumorigenesis in female SKH-1 mice. To expand on this, here, we determined the effects of GP in a short-term UVB exposure protocol (0 or 5% GP, followed by UVB every other day for 2 weeks) in male and female SKH-1 mice, as well as explored any sex-related differences in UVB carcinogenesis via male SKH-1 mice (0, 3, or 5% GP; UVB twice weekly for 28 weeks). In the short-term study, we found that GP protects against early-stage epithelial hyperplasia and mast cell infiltration in both sexes. In the long term, GP markedly reduced tumor counts and malignant conversion, along with significant decreases in mast cell infiltration, serum IgE and Eotaxin. We also found inhibition of P38 phosphorylation and reduced PCNA, Ki67 and BCL2 levels, suggesting that the anti-inflammatory effects of GP inhibits P38, acting as an upstream regulator to inhibit proliferation and reduce tumor cell survival. Together, GP appears to protect against UVB-mediated skin damage and carcinogenesis in SKH-1 mice and should be explored further as a supplement for NMSC prevention.

Hair(y) Matters in Melanoma Biology

Melanocyte stem cells (MeSCs), one candidate for the cellular origin of melanoma, reside in the bulge region of the hair follicle (HF), an immune-privileged tissue niche with impaired tumor immunosurveillance. Surprisingly, however, primary melanoma is only very rarely associated with HFs. Here, we explore the hypothesis that this profoundly immunoinhibitory signaling environment deprives both MeSCs and melanocytes of the anagen hair matrix of proinflammatory signals required for full oncogenic transformation. Understanding the cellular and molecular mechanisms for generating a putative antimelanoma tissue habitat, namely in the bulge, could help to recreate a similar melanoma-suppressive signaling environment in melanoma high-risk individuals. We further discuss how mimicking the bulge immune privilege may be an effective melanoma prevention strategy.

Transepidermal UV radiation of scalp skin ex vivo induces hair follicle damage that is alleviated by the topical treatment with caffeine

Objectives

Although the effect of ultraviolet radiation (UVR) on human skin has been extensively studied, very little is known on how UVR impacts on hair follicle (HF) homeostasis. Here, we investigated how solar spectrum UVR that hits the human skin surface impacts on HF biology, and whether any detrimental effects can be mitigated by a widely used cosmetic and nutraceutical ingredient, caffeine.

Methods

Human scalp skin with terminal HFs was irradiated transepidermally ex vivo using either 10 J/cm²UVA (340–440 nm) + 20 mJ/cm²UVB (290–320 nm) (low dose) or 50 J/cm²UVA + 50 mJ/cm²UVB (high dose) and organ‐cultured under serum‐free conditions for 1 or 3 days. 0.1% caffeine (5.15 mmol/L) was topically applied for 3 days prior to UV exposure with 40 J/cm²UVA + 40 mJ/cm²UVB and for 3 days after UVR. The effects on various toxicity and vitality read‐out parameters were measured in defined skin and HF compartments.

Results

Consistent with previous results, transepidermal UVR exerted skin cytotoxicity and epidermal damage. Treatment with high and/or low UVA+UVB doses also induced oxidative DNA damage and cytotoxicity in human HFs. In addition, it decreased proliferation and promoted apoptosis of HF outer root sheath (ORS) and hair matrix (HM) keratinocytes, stimulated catagen development, differentially regulated the expression of HF growth factors, and induced perifollicular mast cell degranulation. UVR‐mediated HF damage was more severe after irradiation with high UVR dose and reached also proximal HF compartments. The topical application of 0.1% caffeine did not induce skin or HF cytotoxicity and stimulated the expression of IGF‐1 in the proximal HF ORS. However, it promoted keratinocyte apoptosis in selected HF compartments. Moreover, caffeine provided protection towards UVR‐mediated HF cytotoxicity and dystrophy, keratinocyte apoptosis, and tendential up‐regulation of the catagen‐promoting growth factor.

Conclusion

Our study highlights the clinical relevance of our scalp UV irradiation ex vivo assay and provides the first evidence that transepidermal UV radiation negatively affects important human HF functions. This suggests that it is a sensible prophylactic strategy to integrate agents such as caffeine that can act as HF photoprotectants into sun‐protective cosmeceutical and nutraceutical formulations.

Ionizing radiation, but not ultraviolet radiation, induces mitotic catastrophe in mouse epidermal keratinocytes with aberrant cell cycle checkpoints

Ultraviolet radiation (UVR) and ionizing radiation (IR) are common genotoxic stresses that damage human skin, although the specific damages to the genomic DNA are different. Here, we show that in the mouse glabrous skin, both UVR and IR induce DNA damage, cell cycle arrest, and condensed cell nuclei. However, only IR induces mitotic catastrophe (MC) in the epidermis. This is because UVR induces a complete blockage of pRB phosphorylation and cell cycle arrest in the G1 phase, whereas pRB phosphorylation remains positive in a significant portion of the epidermal keratinocytes following IR exposure. Furthermore, Cyclin B1 expression is significantly downregulated only by IR but not UVR. Finally, there are more MC cells in the epidermis of p53-/- mice after IR exposure as compared to wild-type mice. Our results suggest that although both IR and UVR are genotoxic, they show distinct impacts on the cell cycle machinery and thus damage the epidermal keratinocytes via different mechanisms.

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.