Ex Vivo Analysis of Cell Differentiation, Oxidative Stress, Inflammation, and DNA Damage on Cutaneous Field Cancerization

Cutaneous field cancerization (CFC) refers to a skin region containing mutated cells' clones, predominantly arising from chronic exposure to ultraviolet radiation (UVR), which exhibits an elevated risk of developing precancerous and neoplastic lesions. Despite extensive research, many molecular aspects of CFC still need to be better understood. In this study, we conducted ex vivo assessment of cell differentiation, oxidative stress, inflammation, and DNA damage in CFC samples. We collected perilesional skin from 41 patients with skin cancer and non-photoexposed skin from 25 healthy control individuals. These biopsies were either paraffin-embedded for indirect immunofluorescence and immunohistochemistry stain or processed for proteins and mRNA extraction from the epidermidis. Our findings indicate a downregulation of p53 expression and an upregulation of Ki67 and p16 in CFC tissues. Additionally, there were alterations in keratinocyte differentiation markers, disrupted cell differentiation, increased expression of iNOS and proinflammatory cytokines IL-6 and IL-8, along with evidence of oxidative DNA damage. Collectively, our results suggest that despite its outwardly normal appearance, CFC tissue shows early signs of DNA damage, an active inflammatory state, oxidative stress, abnormal cell proliferation and differentiation.

Inhibition of UVB radiation-induced tissue swelling and immune suppression by nicotinamide riboside and pterostilbene

BACKGROUND

Environmental ultraviolet radiation has deleterious effects on humans, including sunburn and immune perturbations. These immune changes are involved in skin carcinogenesis.

OBJECTIVES

To determine whether nicotinamide riboside and/or pterostilbene administered systemically inhibits inflammatory and immune effects of exposure to mid-range ultraviolet radiation.

METHODS

To examine UVB radiation-induced inflammatory effects, mice were fed standard chow/water, 0.04% pterostilbene in chow and 0.2% nicotinamide riboside in drinking water, diet with nicotinamide riboside alone, or diet with pterostilbene alone. After 4 weeks, mice were exposed to UVB radiation (3500 J/m2), and 24-/48-h ear swelling was assessed. We also asked if each agent or the combination inhibits UVB radiation suppression of contact hypersensitivity in two models. Mice were fed standard diet/water or chow containing 0.08% pterostilbene, water with 0.4% nicotinamide riboside, or both for 4 weeks. Low-dose: Half the mice in each group were exposed on the depilated dorsum to UVB radiation (1700 J/m2) daily for 4 days, whereas half were mock-irradiated. Mice were immunized on the exposed dorsum to dinitrofluorobenzene 4 h after the last irradiation, challenged 7 days later on the ears with dinitrofluorobenzene, and 24-h ear swelling assessed. High dose: Mice were treated similarly except that a single dose of 10,000 J/m2 of radiation was administered and immunization was performed on the unirradiated shaved abdomen 3 days later.

RESULTS

Nicotinamide riboside and pterostilbene together inhibited UVB-induced skin swelling more than either alone. Pterostilbene alone and both given together could inhibit UVB-induced immune suppression in both the low-dose and high-dose models while nicotinamide riboside alone was more effective in the low-dose model than the high-dose model.

CONCLUSION

Nicotinamide riboside and pterostilbene have protective effects against UVB radiation-induced tissue swelling and immune suppression.

Alcohol drinking, smoking, and cutaneous melanoma risk: Mendelian randomization analysis

OBJECTIVE

To investigate the causal relationship between poor lifestyle habits, such as smoking and drinking, and cutaneous malignant melanoma.

METHOD

In the present study, alcohol consumption and smoking were used as exposure factors, and single nucleotide polymorphisms closely associated with alcohol consumption and smoking were used as instrumental variables, while cutaneous melanoma was set as an outcome variable. Two-sample Mendelian randomization analyses were run between alcohol consumption and melanoma and smoking and melanoma to investigate their causal associations, respectively.

RESULTS

We found a positive and statistically significant causal effect of alcohol intake on the risk of cutaneous malignant melanoma (OR: 2.23; 95%CI: 1.11-4.47; p=0.02). The present study showed no significant causal relationship between cigarettes per day and cutaneous melanoma (OR: 0.85; 95%CI: 0.54-1.35; p=0.50) or smoking initiation and cutaneous melanoma (OR: 1.02; 95%CI: 0.74-1.39; p=0.88).

CONCLUSIONS

This study provides Mendelian randomization evidence supporting alcohol consumption as a risk factor for cutaneous malignant melanoma. And the causal relationship between smoking and cutaneous malignant melanoma still needs to be further investigated.

The skin of the naked mole-rat and its resilience against aging and cancer

The naked mole-rat (NMR) Heterocephalus glaber (from the Greek/latin words ἕτερος, heteros = divergent, κεφαλή, kephalē = head and glabra = hairless) was first described by Rüppell (Fig. 1) and belongs to the Hystricognath (from the Greek words ὕστριξ, hystrix = porcupine and γνάθος, gnathos = jaw) as a suborder of rodents. NMR are characterized by the highest longevity among rodents and reveal a profound cancer resistance. Details of its skin-specific protective and resistance mechanisms against aging and carcinogenesis have so far not been adequately characterized. Recently, our knowledge of NMR skin biology was complemented and expanded by published data using state-of-the art histological and molecular techniques. Here we review and integrate novel published data regarding skin morphology and histology of the aging NMR and the underlying mechanisms at the cellular and molecular level. We relate this data to the longevity of the NMR and its resistance to neoplastic transformation and discuss further open questions to understand its extraordinary longevity. In addition, we will address the exposome, defined as "the total of all non-genetic, endogenous and exogenous environmental influences" on the skin, respiratory tract, stomach, and intestine. Finally, we will discuss in perspective further intriguing possibilities arising from the interaction of skin with other organs.

Endogenous Photosensitizers in Human Skin

Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.

Non-Melanoma Skin Cancer and Vitamin D: The "Lost Sunlight" Paradox and the Oxidative Stress Explanation

UV radiation (UVR) is responsible for inducing both harmful and beneficial effects on skin health. Specifically, it has been reported to disrupt oxidant and antioxidant levels, leading to oxidative stress conditions in skin tissue. This phenomenon might trigger photo-carcinogenesis, resulting in melanoma, NMSC (non-melanoma skin cancer), such as BCC (basal cell carcinoma) and SCC (squamous cell carcinoma), and actinic keratosis. On the other hand, UVR is essential for the production of adequate vitamin D levels, a hormone with important antioxidant, anticancer and immunomodulatory properties. The exact mechanisms implicated in this two-fold action are not well understood, as there still no clear relation established between skin cancer and vitamin D status. Oxidative stress seems to be a neglected aspect of this complex relation, despite its role in both skin cancer development and vitamin D deficiency. Therefore, the aim of the present study is to examine the correlation between vitamin D and oxidative stress in skin cancer patients. A total of 100 subjects (25 with SCC, 26 with BCC, 23 with actinic keratosis, and 27 controls) were assessed in terms of 25-hydroxyvitamin D (25(OH) D) and redox markers such as thiobarbituric acid reactive substances (TBARS), protein carbonyls, total antioxidant capacity (TAC) in plasma, glutathione (GSH) levels and catalase activity in erythrocytes. The majority of our patients revealed low vitamin D levels; 37% of the subjects showed deficiency (<20 ng/mL) and 35% insufficiency (21-29 ng/mL). The mean 25(OH) D level of the NMSC patients (20.87 ng/mL) was also found to be significantly lower (p = 0.004) than that of the non-cancer patients (28.14 ng/mL). Furthermore, higher vitamin D levels were also correlated with lower oxidative stress (positive correlation with GSH, catalase activity TAC index and negative correlation with TBARS and CARBS indices). NMSC patients diagnosed with SCC showed lower catalase activity values compared to non-cancer patients (p < 0.001), with the lowest values occurring in patients with a chronic cancer diagnosis (p < 0.001) and vitamin D deficiency (p < 0.001). Higher GSH levels (p = 0.001) and lower TBARS levels (p = 0.016) were found in the control group compared to the NMSC group, and to patients with actinic keratosis. Higher levels of CARBS were observed in patients with SCC (p < 0.001). Non-cancer patients with vitamin D sufficiency showed higher TAC values compared to non-cancer patients with vitamin D deficiency (p = 0.023) and to NMSC patients (p = 0.036). The above-mentioned results indicate that NMSC patients reveal increased levels of oxidative damage markers compared to control levels, while vitamin D status plays a critical role in the determination of individuals' oxidative status.

1,25-Dihydroxvitamin D3 attenuates the damage of human immortalized keratinocytes caused by Ultraviolet-B

Objective Ultraviolet-B (UVB) radiation is an important factor in causing skin damage. The study is to explore whether 1,25-Dihydroxvitamin D3(1,25(OH)₂D₃) will attenuate the damage of human immortalized keratinocytes (HaCaT) cells caused by UVB and relevant underlying mechanisms.

METHODS

CCK-8 was employed to determine the UVB irradiation intensity and 1,25(OH)₂D₃ concentration. Western blot was used to detect the expression of NF-κB, Caspase9, Caspase3, Bax, Bcl2, FADD, CytC, Beclin-1; Flowcytometry was applied to measure the production of ROS.

RESULTS

The concentration of 1,25(OH)₂D₃ used in the study was 100nM and the UVB irradiation intensity was 20 mJ/cm². Compared with the HaCaT cells irradiated with UVB, the HaCaT cells were pretreated with 1,25(OH)₂D₃ had lower production of ROS, lower expression of NF-κB, Caspase9, Caspase3, Bax, FADD, CytC and Beclin-1(P < 0.05).

CONCLUSION

1,25(OH)₂D₃ could inhibit the development of oxidative stress and apoptosis in HaCaTs triggered by UVB. This inhibition might be achieved through suppression of mitochondria-modulated apoptosis and autophagy. Vitamin D may be a potential UVB protective component.

The CaSR Modulator NPS-2143 Reduced UV-Induced DNA Damage in Skh:hr1 Hairless Mice but Minimally Inhibited Skin Tumours

The calcium-sensing receptor (CaSR) is an important regulator of epidermal function. We previously reported that knockdown of the CaSR or treatment with its negative allosteric modulator, NPS-2143, significantly reduced UV-induced DNA damage, a key factor in skin cancer development. We subsequently wanted to test whether topical NPS-2143 could also reduce UV-DNA damage, immune suppression, or skin tumour development in mice. In this study, topical application of NPS-2143 (228 or 2280 pmol/cm²) to Skh:hr1 female mice reduced UV-induced cyclobutane pyrimidine dimers (CPD) (p < 0.05) and oxidative DNA damage (8-OHdG) (p < 0.05) to a similar extent as the known photoprotective agent 1,25(OH)₂ vitamin D3 (calcitriol, 1,25D). Topical NPS-2143 failed to rescue UV-induced immunosuppression in a contact hypersensitivity study. In a chronic UV photocarcinogenesis protocol, topical NPS-2143 reduced squamous cell carcinomas for only up to 24 weeks (p < 0.02) but had no other effect on skin tumour development. In human keratinocytes, 1,25D, which protected mice from UV-induced skin tumours, significantly reduced UV-upregulated p-CREB expression (p < 0.01), a potential early anti-tumour marker, while NPS-2143 had no effect. This result, together with the failure to reduce UV-induced immunosuppression, may explain why the reduction in UV-DNA damage in mice with NPS-2143 was not sufficient to inhibit skin tumour formation.

Citrus Consumption and Risk of Melanoma: A Dose-Response Meta-Analysis of Prospective Cohort Studies

Background

Epidemiological studies of citrus consumption in relation to melanoma risk have yielded conflicting results. This meta-analysis was performed to investigate the dose-response association between citrus consumption and risk of melanoma.

Methods

Relevant prospective cohort studies were identified by searching PubMed, Embase, Scopus, and Web of Science databases up to February 28th, 2022. Results from individual studies were pooled using a random-effects model.

Results

Five prospective studies, with 8,836 melanoma cases and 977,558 participants, were included in the meta-analysis. A significantly increased risk of melanoma was associated with the highest categories of either total citrus products (RR: 1.20; 95% CI: 1.01–1.42) or citrus fruit consumption (1.15; 1.04–1.28), but consumption of citrus juice was not associated with melanoma risk (1.08; 0.97–1.21). The dose-response analyses revealed that for per 1 serving/day increase in total citrus or citrus fruit consumption, the risk of melanoma increased by 9 and 12%, respectively. An inverted U-shaped curvilinear relationship, but not linear association, was observed between citrus juice consumption and melanoma risk.

Conclusions

Citrus consumption was generally associated with a greater risk of malignant melanoma. Our findings may have important public health implications with respect to preventing melanoma.

Spleen tyrosine kinase regulates keratinocyte inflammasome activation and skin inflammation induced by UVB irradiation

UVB can induce inflammatory responses contributing to diverse skin damage. UVB-triggered inflammasome activation of human keratinocytes underlies UVB-induced skin sunburn reaction. Pleiotropic functions of spleen tyrosine kinase (Syk) have rendered it as a potential therapeutic target. In immunocytes, Syk modulates immunoreceptor signaling and NLRP3 inflammasome activation. In skin, Syk mediates EGFR signaling, regulates keratinocyte differentiation and is involved in inflammatory disorders. However, roles of Syk in UVB-induced inflammasome activation in keratinocytes remain elusive. We investigated roles of keratinocyte Syk in UVB-triggered photo-responses. Primary normal human epidermal keratinocytes (NHEKs) isolated from skin were used. Syk knockdown or Syk inhibitor R406 was applied to investigate functions of keratinocyte Syk in UVB photobiology. The possible in vivo role of Syk was evaluated by checking UVB-induced skin damage in R406-treated mice. UVB was able to induce Syk phosphorylation in NHEKs that could be regulated by reactive oxygen species (ROS) generation and EGFR. Syk knockdown or Syk inhibitor (R406) treatment reduced UVB-triggered apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) crosslinking, procaspase-1 cleavage, active IL-1β formation, and gasdermin D activation, indicating roles of Syk in UVB-triggered inflammasome activation in keratinocytes. UVB-induced production of IL-8, TNF-α, ROS, and phosphorylation of JNK and p38 were attenuated after Syk knockdown or inhibition. R406 ameliorated UVB-induced mouse skin damage, including erythema and transepidermal water loss (TEWL). Thus, Syk participated in UVB-induced inflammasome activation and inflammatory response in vitro and in vivo, suggesting potential photo-protective effects of Syk inhibition in UVB-induced skin inflammation.

Nicotinamide Attenuates UV-Induced Stress Damage in Human Primary Keratinocytes from Cancerization Fields

UVB radiation directly damages DNA, increases ROS and nitric oxide (NO) release, and promotes inflammation leading to genomic instability and cell death. Nicotinamide (NAM) is the precursor of NAM adenine dinucleotide, essential for cell energy production and DNA damage repair. NAM protects HaCat cells from UV-induced impairment; however, little is known about its effects on human primary keratinocytes and those isolated from field cancerization (i.e., field cancerization human primary keratinocytes [FC-HPKs]). We examined the role of NAM against UV-induced oxidative stress damages in FC-HPKs, isolated from precancerous lesions and skin cancers, and in normal human epidermal keratinocytes. Cells were treated for 18, 24, and 48 hours with NAM (5, 25, and 50 μM, respectively) before UVB irradiation. FC-HPK showed four-fold higher basal ROS levels than normal human epidermal keratinocytes; NAM downregulated ROS production only in irradiated FC-HPKs, which showed a greater sensibility to UV rays. UV exposure increased OGG1, inducible nitric oxide synthase, and IL-1β expression, an effect counteracted by NAM pretreatment. Intracellular nitric oxide production and DNA damages were inhibited by NAM exposure before irradiation. Collectively, our findings indicate that pretreatment with 25 μM NAM 24 hours before UVB irradiation effectively prevents oxidative stress formation, DNA damage, and inflammation in both normal human epidermal keratinocytes and FC-HPKs.

Xeroderma Pigmentosum C: A Valuable Tool to Decipher the Signaling Pathways in Skin Cancers

Xeroderma pigmentosum (XP) is a rare autosomal genodermatosis that manifests clinically with pronounced sensitivity to ultraviolet (UV) radiation and the high probability of the occurrence of different skin cancer types in XP patients. XP is mainly caused by mutations in XP-genes that are involved in the nucleotide excision repair (NER) pathway that functions in the removal of bulky DNA adducts. Besides, the aggregation of DNA lesions is a life-threatening event that might be a key for developing various mutations facilitating cancer appearance. One of the key players of NER is XPC that senses helical distortions found in damaged DNA. The majority of XPC gene mutations are nonsense, and some are missense leading either to the loss of XPC protein or to the expression of a truncated nonfunctional version. Given that no cure is yet available, XPC patients should be completely protected and isolated from all types of UV radiations (UVR). Although it is still poorly understood, the characterization of the proteomic signature of an XPC mutant is essential to identify mediators that could be targeted to prevent cancer development in XPC patients. Unraveling this proteomic signature is fundamental to decipher the signaling pathways affected by the loss of XPC expression following exposure to UVB radiation. In this review, we will focus on the signaling pathways disrupted in skin cancer, pathways modulating NER's function, including XPC, to disclose signaling pathways associated with XPC loss and skin cancer occurrence.

hSSB2 (NABP1) is required for the recruitment of RPA during the cellular response to DNA UV damage

Maintenance of genomic stability is critical to prevent diseases such as cancer. As such, eukaryotic cells have multiple pathways to efficiently detect, signal and repair DNA damage. One common form of exogenous DNA damage comes from ultraviolet B (UVB) radiation. UVB generates cyclobutane pyrimidine dimers (CPD) that must be rapidly detected and repaired to maintain the genetic code. The nucleotide excision repair (NER) pathway is the main repair system for this type of DNA damage. Here, we determined the role of the human Single-Stranded DNA Binding protein 2, hSSB2, in the response to UVB exposure. We demonstrate that hSSB2 levels increase in vitro and in vivo after UVB irradiation and that hSSB2 rapidly binds to chromatin. Depletion of hSSB2 results in significantly decreased Replication Protein A (RPA32) phosphorylation and impaired RPA32 localisation to the site of UV-induced DNA damage. Delayed recruitment of NER protein Xeroderma Pigmentosum group C (XPC) was also observed, leading to increased cellular sensitivity to UVB. Finally, hSSB2 was shown to have affinity for single-strand DNA containing a single CPD and for duplex DNA with a two-base mismatch mimicking a CPD moiety. Altogether our data demonstrate that hSSB2 is involved in the cellular response to UV exposure.

Keratinocytes Counteract UVB-Induced Immunosuppression in Mice Via HIF-1a Signaling

The transcription factor Hypoxia-Inducible Factor-1alpha (HIF-1a) regulates cellular metabolism under hypoxia but also immune responses and UVB-induced skin reactions. In keratinocytes, HIF-1a is an environmental sensor orchestrating the adaptation to environmental changes. Here, we investigated the role of HIF-1a in keratinocytes for skin reactions to acute and chronic UVB exposure in mice. The function of HIF-1a in keratinocytes under UVB exposure was analyzed in conditional keratinocyte-specific HIF-1a-KO (in short "cKO") mice. cKO mice were hypersensitive to acute high-dose UVB irradiation compared to wildtype (WT), displaying increased cell death and delayed barrier repair. After chronic low-dose UVB treatment, cKO mice also had stronger epidermal damage but reduced infiltration of dermal macrophages and T helper cells compared to WT mice. Irradiated cKO mice revealed accumulation of regulatory lymphocytes in dorsal skin-draining lymph nodes compared to WT and unirradiated mice. This was reflected by augmented IL-10 release of lymph node cells and a weaker contact hypersensitivity reaction to DNFB in UVB-exposed cKO mice compared to WT and unirradiated controls. In summary, we found that keratinocyte-specific HIF-1a expression is crucial for adaptation to UVB exposure and inhibits the development of UVB-induced immunosuppression in mice. Therefore, HIF-1a signaling in keratinocytes could ameliorate photoaging-related skin disorders.

UVB damage response of dermal stem cells as melanocyte precursors compared to keratinocytes, melanocytes, and fibroblasts from human foreskin

Ultraviolet B (UVB) radiation induces mutagenic DNA photolesions in skin cells especially in form of cyclobutane pyrimidine dimers (CPDs). Protection mechanisms as DNA repair and apoptosis are of great importance in order to prevent skin carcinogenesis. In human skin, neural crest-derived precursors of melanocytes, the dermal stem cells (DSCs), are discussed to be at the origin of melanoma. Although they are constantly exposed to solar UV radiation, it is still not investigated how DSCs cope with UV-induced DNA damage. Here, we report a comparative study of the DNA damage response after irradiation with a physiological relevant UVB dose in DSCs in comparison to fibroblasts, melanocytes and keratinocytes isolated from human foreskin. Within our experimental settings, DSCs were able to repair DNA photolesions as efficient as the other skin cell types with solely keratinocytes repairing significantly faster. Interestingly, only fibroblasts showed significant alterations in cell cycle distribution in terms of a transient S phase arrest following irradiation. Moreover, with the applied UVB dose none of the examined cell types was prone to UVB-induced apoptosis. This may cause persistent genomic alterations and in case of DSCs it may have severe consequences for their daughter cells, the differentiated melanocytes. Altogether, this is the first study demonstrating a similar UV response in dermal stem cells compared to differentiated skin cells.

Luteolin as a modulator of skin aging and inflammation

Luteolin belongs to the group of flavonoids and can be found in flowers, herbs, vegetables and spices. It plays an important role in defending plants, for example against UV radiation by partially absorbing UVA and UVB radiation. Thus, luteolin can also decrease adverse photobiological effects in the skin by acting as a first line of defense. Furthermore, anti-oxidative and anti-inflammatory activities of luteolin were described on keratinocytes and fibroblasts as well as on several immune cells (e.g., macrophages, mast cell, neutrophils, dendritic cells and T cells). Luteolin can suppress proinflammatory mediators (e.g., IL-1β, IL-6, IL-8, IL-17, IL-22, TNF-α and COX-2) and regulate various signaling pathway (e.g., the NF-κB, JAK-STAT as well as TLR signaling pathway). In this way, luteolin modulates many inflammatory processes of the skin. The present review summarizes the recent in vitro and in vivo research on luteolin in the field of skin aging and skin cancer, wound healing as well as inflammatory skin diseases, including psoriasis, contact dermatitis and atopic dermatitis. In conclusion, luteolin might be a promising molecule for the development of topic formulations and systemic agents against inflammatory skin diseases.

Oral nicotinamide: The role in skin cancer chemoprevention

The incidence of skin cancer has gradually increased in the last years and exposition to ultraviolet radiation remains the main risk factor. We performed a comprehensive review on the role of nicotinamide (NAM) in the chemoprevention of skin cancers. NAM, a water-soluble form of vitamin B3, interferes with skin carcinogenesis as it regulates immunosuppressor genes such as p53 and sirtuins and restores intracellular level of NAD+, a co-enzyme essential for energy production. Efficacy and safety of NAM was evaluated in a Phase III double-blinded control-placebo study (ONTRAC), thus demonstrating that the incidence of actinic keratoses and non-melanoma skin cancers was lower in the nicotinamide group than in placebo group. Further studies showed the efficacy of NAM also in transplanted patients and among inhabitants living in arsenic contamination areas. Despite the quick response to NAM supplementation, its intake need to be carried on chronically as the efficacy seems to vanish rapidly.

Apoptosis, the only cell death pathway that can be measured in human diploid dermal fibroblasts following lethal UVB irradiation

Ultraviolet radiation (UVR) is a major environmental genotoxic agent. In skin, it can lead to the formation of mutagenic DNA damage. Several mechanisms are in place to prevent the conversion of these DNA damage into skin cancer-driver mutations. An important mutation prevention mechanism is the programmed cell death, which can safely dispose of the damaged cells. Apoptosis is the most studied and best characterised programmed cell death, but an increasing amount of new cell death pathways are emerging. Using different pharmacological cell death inhibitors and antioxidants, we have evaluated the implication of apoptosis, necroptosis, ferroptosis and parthanatos in UVB-induced cell death in human diploid dermal fibroblasts. Our results show that apoptosis is the only known cell death mechanism induced by UVB irradiation in fibroblasts. We also showed that lethal UVB irradiation induces a PARP-dependent drastic loss of cellular metabolic activity caused by an overused of NAD+.

The use of tissue-engineered skin to demonstrate the negative effect of CXCL5 on epidermal ultraviolet radiation-induced cyclobutane pyrimidine dimer repair efficiency

BACKGROUND

Ultraviolet radiation (UVR) is responsible for keratinocyte cancers through the induction of mutagenic cyclobutane pyrimidine dimers (CPDs). Many factors influence CPD repair in epidermal keratinocytes, and a better understanding of those factors might lead to prevention strategies against skin cancer.

OBJECTIVES

To evaluate the impact of dermal components on epidermal CPD repair efficiency and to investigate potential factors responsible for the dermal-epidermal crosstalk modulating UVR-induced DNA damage repair in keratinocytes.

METHODS

A model of self-assembled tissue-engineered skin containing human primary keratinocytes and fibroblasts was used in this study.

RESULTS

We showed that CPD repair in keratinocytes is positively influenced by the presence of a dermis. We investigated the secretome and found that the cytokine CXCL5 is virtually absent from the culture medium of reconstructed skin, compared with media from fibroblasts and keratinocytes alone. By modulating CXCL5 levels in culture media of keratinocytes, we have shown that CXCL5 is an inhibitor of CPD repair.

CONCLUSIONS

This work outlines the impact of the secreted dermal components on epidermal UVR-induced DNA damage repair and sheds light on a novel role of CXCL5 in CPD repair.

Long-term Effects of 222-nm ultraviolet radiation C Sterilizing Lamps on Mice Susceptible to Ultraviolet Radiation

Germicidal lamps that emit primarily 254 nm ultraviolet radiation (UV) are routinely utilized for surface sterilization but cannot be used for human skin because they cause genotoxicity. As an alternative, 222‐nm UVC has been reported to exert sterilizing ability comparable to that of 254‐nm UVC without producing cyclobutane pyrimidine dimers (CPDs), the major DNA lesions caused by UV. However, there has been no clear evidence for safety in chronic exposure to skin, particularly with respect to carcinogenesis. We therefore investigated the long‐term effects of 222‐nm UVC on skin using a highly photocarcinogenic phenotype mice that lack xeroderma pigmentosum complementation group A (Xpa‐) gene, which is involved in repairing of CPDs. CPDs formation was recognized only uppermost layer of epidermis even with high dose of 222‐nm UVC exposure. No tumors were observed in Xpa‐knockout mice and wild‐type mice by repetitive irradiation with 222‐nm UVC, using a protocol which had shown to produce tumor in Xpa‐knockout mice irradiated with broad‐band UVB. Furthermore, erythema and ear swelling were not observed in both genotype mice following 222‐nm UVC exposure. Our data suggest that 222‐nm UVC lamps can be safely used for sterilizing human skin as far as the perspective of skin cancer development.

Chronic Venous Insufficiency as a Predisposing Factor for Basal Cell Carcinoma on Legs

BACKGROUND

The main risk factor associated with basal cell carcinomas (BCCs) is believed to be exposure to ultraviolet radiation (UVR). In the case of lower limb BCC, the frequency is higher in women, possibly because of greater exposure of the leg to UVR. Chronic venous insufficiency (CVI), also more common in women, may have some association with leg BCCs.

METHODS

We retrospectively evaluated the histopathological features of leg BCCs removed between 1993 and 2017 in a tertiary referral center. The patients' clinical data were obtained from medical records, considering, in particular, CVI.

RESULTS

We selected 149 patients with leg BCCs, predominately occurring in elderly Caucasian women. Of those, 71 had a clinical diagnosis of CVI in whom the clinical tumor size and frequency of recurrences were significantly higher than patients without CVI. There was an association between clinical diagnosis of CVI and histological findings of (1) follicular induction in epidermis and (2) distal sweat duct hyperplasia.

CONCLUSIONS

CVI, besides the already known UVR exposure, is probably associated with leg BCCs and may determine a worse BCC course.

Galectin-3 regulates UVB-induced inflammation in skin

BACKGROUND

Galectin-3 is widely expressed in many immunocytes and epithelial cells including skin keratinocytes. Galectin-3 can regulate immunological or inflammatory processes and plays a proinflammatory role in some disease models. Galectin-3 has a role in disorders related to ultraviolet (UV) photodamage such as apoptosis, skin squamous cell carcinoma and basal cell carcinoma. However, the evidence of galectin-3 in UVB-induced skin inflammation is still limited and the underlying molecular mechanism remains elusive.

OBJECTIVE

We aimed to investigate the effects of galectin-3 in human epidermal keratinocytes and in mice after UVB irradiation.

METHODS

Primary human epidermal keratinocytes with galectin-3 knockdown were used as the in vitro model. ELISA, QPCR, and western blotting were applied to evaluate the released cytokine, mRNA and protein expression. Histologic analysis, measurement of erythema and transepidermal water loss (TEWL) were applied to evaluate UVB-induced skin damage in galectin-3 knockout mice.

RESULTS

In UVB-irradiated human keratinocytes, galectin-3 knockdown downregulated the UVB-induced ASC crosslinking, cleavage of caspase-1, and formation of active IL-1β. Galectin-3 knockdown also decreased UVB-induced production of reactive oxygen species, p38 phosphorylation, and COX2 expression in human keratinocytes. After four days of UVB irradiation, galectin-3 knockout mice showed reduced gross erythema, histologic features of tissue inflammation, quantified levels of erythema and TEWL compared to wild type mice. The skin tissue lysate also showed less expression of active IL-1β and COX2 in galectin-3 knockout mice.

CONCLUSION

Galectin-3 may play a positive regulatory role in UVB-induced skin inflammation.

Photosensitised biphotonic chemistry of pyrimidine derivatives

Photosensitised biphotonic irradiation of DNA has been rarely addressed, probably due to the difficulties in the experimental design. This is associated with the selection of nucleobases and sensitisers with appropriate absorption spectra and photochemical reactivity, in combination with a laser source emitting intense UVA light of the adequate wavelength. The present paper presents a new strategy involving absorption of a first UVA photon by an adequate sensitiser followed by triplet energy transfer to a pyrimidine (Pyr) derivative and absorption of a second UVA photon by the resulting Pyr triplet excited state. The feasibility of the proposed strategy has been demonstrated using two model reactions: (i) the Norrish-Yang photocyclisation of a tert-butyluracil and (ii) the photohydration of its uracil analogue, lacking the tert-butyl substituent.

Skin Irritation Testing beyond Tissue Viability: Fucoxanthin Effects on Inflammation, Homeostasis, and Metabolism

UV light catalyzes the ozone formation from air pollutants, like nitrogen oxides. Since ozone reacts with cutaneous sebum lipids to peroxides and, thus, promotes inflammation, tumorigenesis, and aging, even broad-spectrum sunscreens cannot properly protect skin. Meanwhile, xanthophylls, like fucoxanthin, proved their antioxidant and cytoprotective functions, but the safety of their topical application in human cell-based models remains unknown. Aiming for a more detailed insight into the cutaneous fucoxanthin toxicity, we assessed the tissue viability according to OECD test guideline no. 439 as well as changes in inflammation (IL-1α, IL-6, IL-8), homeostasis (EGFR, HSPB1) and metabolism (NAT1). First, we proved the suitability of our 24-well-based reconstructed human skin for irritation testing. Next, we dissolved 0.5% fucoxanthin either in alkyl benzoate or in ethanol and applied both solutions onto the tissue surface. None of the solutions decreased RHS viability below 50%. In contrast, fucoxanthin ameliorated the detrimental effects of ethanol and reduced the gene expression of pro-inflammatory interleukins 6 and 8, while increasing NAT1 gene expression. In conclusion, we developed an organ-on-a-chip compatible RHS, being suitable for skin irritation testing beyond tissue viability assessment. Fucoxanthin proved to be non-irritant in RHS and already showed first skin protective effects following topical application.

Protein Oxidative Damage in UV-Related Skin Cancer and Dysplastic Lesions Contributes to Neoplastic Promotion and Progression

The ultraviolet (UV) component of solar radiation is the major driving force of skin carcinogenesis. Most of studies on UV carcinogenesis actually focus on DNA damage while their proteome-damaging ability and its contribution to skin carcinogenesis have remained largely underexplored. A redox proteomic analysis of oxidized proteins in solar-induced neoplastic skin lesion and perilesional areas has been conducted showing that the protein oxidative burden mostly concerns a selected number of proteins participating to a defined set of functions, namely: chaperoning and stress response; protein folding/refolding and protein quality control; proteasomal function; DNA damage repair; protein- and vesicle-trafficking; cell architecture, adhesion/extra-cellular matrix (ECM) interaction; proliferation/oncosuppression; apoptosis/survival, all of them ultimately concurring either to structural damage repair or to damage detoxication and stress response. In peri-neoplastic areas the oxidative alterations are conducive to the persistence of genetic alterations, dysfunctional apoptosis surveillance, and a disrupted extracellular environment, thus creating the condition for transformant clones to establish, expand and progress. A comparatively lower burden of oxidative damage is observed in neoplastic areas. Such a finding can reflect an adaptive selection of best fitting clones to the sharply pro-oxidant neoplastic environment. In this context the DNA damage response appears severely perturbed, thus sustaining an increased genomic instability and an accelerated rate of neoplastic evolution. In conclusion UV radiation, in addition to being a cancer-initiating agent, can act, through protein oxidation, as a cancer-promoting agent and as an inducer of genomic instability concurring with the neoplastic progression of established lesions.

Effects of solvent and micellar encapsulation on the photostability of avobenzone

Avobenzone, the only UVA-absorbing molecule approved for use in sunscreens by the FDA, degrades to its diketone structure under UV light. We found that this photoisomerization is effectively prevented when avobenzone is sequestered in micelles.

The Glucosamine-derivative NAPA Suppresses MAPK Activation and Restores Collagen Deposition in Human Diploid Fibroblasts Challenged with Environmental Levels of UVB

The ultraviolet (UV) component of solar radiation is the driving force of life on earth, but it can cause photoaging and skin cancer. In this study, we investigated the effects of the glucosamine-derivative 2-(N-Acetyl)-L-phenylalanylamido-2-deoxy-β-D-glucose (NAPA) on human primary fibroblasts (FBs) stimulated in vitro with environmental levels of UVB radiation. FBs were irradiated with 0.04 J cm^-2 UVB dose, which resulted a mild dosage as shown by the cell viability and ROS production measurement. This environmental UVB dose induced activation of MAP kinase ERK 1/2, the stimulation of c-fos and at lower extent of c-jun, and in turn AP-1-dependent up-regulation of pro-inflammatory factors IL-6 and IL-8 and suppression of collagen type I expression. On the contrary, 0.04 J cm^-2 UVB dose was not able to stimulate metalloprotease production. NAPA treatment was able to suppress the up-regulation of IL-6 and IL-8 via the inhibition of MAP kinase ERK phosphorylation and the following AP-1 activation, and was able to attenuate the collagen type I down-regulation induced by the UVBs. Taken together, our results show that NAPA, considering its dual action on suppression of inflammation and stimulation of collagen type I production, represents an interesting candidate as a new photoprotective and photorepairing agents.

Distinguishing Myth from Fact: Photocarcinogenesis and Phototherapy

Ultraviolet (UV) radiation contributes to the development of skin cancer through direct and indirect DNA damage, production of reactive oxygen species, and local immunomodulation. The association between UV radiation and skin cancer has raised concern for the risk of carcinogenesis following phototherapy. The photocarcinogenic impact of psoralen and UVA radiation (PUVA) has been extensively studied, whereas limited safety studies exist for other phototherapy modalities, such as broadband and narrowband UVB and UVA1. Because of the as of yet unclear risk, patients who have undergone any type of phototherapy should be followed for age-appropriate skin cancer screening.

Cigarette Smoking and the Risk of Cutaneous Melanoma: A Case-Control Study

OBJECTIVE

Previous studies regarding cigarette smoking causing a lower risk of melanoma are inconclusive. Here, we re-examined melanoma risk in relation to cigarette smoking in a large, case-control study.

METHODS

In total 1,157 patients with melanoma diagnosed between 2003 and 2011 in the Netherlands and 5,595 controls from the Nijmegen Biomedical Study were included. Information concerning smoking habits and known risk factors for melanoma were obtained through self-administered questionnaires. Logistic regression analyses stratified by gender were performed to study the risk of cigarette smoking on melanoma risk, adjusted for age, marital status, highest level of education, skin type, sun vacation, use of solarium, time spent outdoors, and sun protective measures.

RESULTS

Among men, current and former smokers did not have a higher risk of melanoma compared to never smokers: adjusted odds ratio (OR) = 0.56 (95% confidence interval [CI]: 0.40-0.79) and adjusted OR = 0.50 (95% CI: 0.39-0.64), respectively. With an increasing number of years smoked the risk of melanoma decreased: <20 years: OR = 0.61 (95% CI: 0.46-0.80); 21-40 years: OR = 0.50 (95% CI: 0.37-0.68); >40 years: OR = 0.26 (95% CI: 0.15-0.44). No clear trend was found for the number of cigarettes smoked. Results for females were less clear and not statistically significant (current smoker: adjusted OR = 0.96, 95% CI: 0.74-1.26, former smoker: adjusted OR = 0.89, 95% CI: 0.73-1.08).

CONCLUSION

This study shows a strong inverse association between cigarette smoking and melanoma risk in men. Fundamental laboratory research is necessary to investigate the biological relation between smoking cigarettes and melanoma.

Looking beyond the skin: Cutaneous and systemic oxidative stress in UVB-induced squamous cell carcinoma in hairless mice

Cumulative ultraviolet (UV) exposure is associated with squamous skin cell carcinoma. UV radiation induces oxidative modifications in biomolecules of the skin leading to photocarcinogenesis. Indeed, the cyclobutene pyrimidine dimers and other dimers formed by photoaddition between carbon-carbon bonds also have an important role in the initiation process. However, information on the systemic redox status during these processes is scarce. Thus, we investigated the systemic redox profile in UVB-induced squamous cell carcinoma in mice. Female hairless mice were exposed to UVB radiation (cumulative dose = 17.1 J/cm²). The dorsal skin of these mice developed actinic keratosis (AK) and squamous cell carcinoma (SCC) and presented increased levels of oxidative and nitrosative stress biomarkers (4-hydroxy-2-nonenal and 3-nitrotyrosine), and decreased antioxidant defenses. Systemically, we observed the consumption of plasmatic antioxidant defenses and increased levels of advanced oxidized protein products (AOPP), an oxidative stress product derived from systemic inflammatory response. Taken together, our results indicate that UVB chronic irradiation leads not only to adjacent and tumoral oxidative stress in the skin, but it systemically is reflected through the blood. These new findings clarify some aspects of the pathogenesis of SCC and should assist in formulating better chemoprevention strategies, while avoiding additional primary SCC development and metastasis.

Different photodynamic effects of blue light with and without riboflavin on methicillin-resistant Staphylococcus aureus (MRSA) and human keratinocytes in vitro

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of infections in humans. Photodynamic therapy using blue light (450 nm) could possibly be used to reduce MRSA on different human tissue surfaces without killing the human cells. It could be less harmful than 300-400 nm light or common disinfectants. We applied blue light ± riboflavin (RF) to MRSA and keratinocytes, in an in vitro liquid layer model, and compared the effect to elimination using common disinfection fluids. MRSA dilutions (8 × 10⁵/mL) in wells were exposed to blue light (450 nm) ± RF at four separate doses (15, 30, 56, and 84 J/cm²). Treated samples were cultivated on blood agar plates and the colony forming units (CFU) determined. Adherent human cells were cultivated (1 × 10⁴/mL) and treated in the same way. The cell activity was then measured by Cell Titer Blue assay after 24- and 48-h growth. The tested disinfectants were chlorhexidine and hydrogen peroxide. Blue light alone (84 J/cm²) eliminated 70% of MRSA. This dose and riboflavin eradicated 99-100% of MRSA. Keratinocytes were not affected by blue light alone at any dose. A dose of 30 J/cm² in riboflavin solution inactivated keratinocytes completely. Disinfectants inactivated all cells. Blue light alone at 450 nm can eliminate MRSA without inactivation of human keratinocytes. Hence, a high dose of blue light could perhaps be used to treat bacterial infections without loss of human skin cells. Photodynamic therapy using riboflavin and blue light should be explored further as it may perhaps be possible to exploit in treatment of skin diseases associated with keratinocyte hyperproliferation.

Validation of a predictive method for sunscreen formula evaluation using gene expression analysis in a Chinese reconstructed full-thickness skin model

OBJECTIVE

This study aimed to establish a predictive in vitro method for assessing the photoprotective properties of sunscreens using a reconstructed full-thickness skin model.

MATERIALS AND METHODS

A full-thickness skin model reconstructed with human fibroblasts and keratinocytes isolated from Chinese skin was exposed to daily UV radiation (DUVR). We examined the transcriptomic response, identifying genes for which expression was modulated by DUVR in a dose-dependent manner. We then validated the methodology for efficacy evaluation of different sunscreens formulas.

RESULTS

The reconstructed skin model was histologically consistent with human skin, and upon DUVR exposure, the constituent fibroblasts and keratinocytes exhibited transcriptomic alterations in pathways associated with oxidative stress, inflammation and extracellular matrix remodelling. When used to evaluate sunscreen protection on the model, the observed level of protection from UV-induced gene expression was consistent with the corresponding protection factors determined clinically and allowed for statistical ranking of sunscreen efficacy.

CONCLUSIONS

Within this study we show that quantification of gene modulation within the reconstructed skin model is a biologically relevant approach with sensitivity and predictability to evaluate photoprotection products.

Immune response and evasion mechanisms in lip carcinogenesis: An immunohistochemical study

OBJECTIVES

Programmed death ligand-1 (PD-L1) and human leukocyte antigen-G (HLA-G) are considered immune checkpoint molecules that inhibit T-cell effectiveness, contributing to tumor immune escape. This study investigated PD-L1, HLA-G, CD8, and granzyme B (GrB) expression at different stages of lip carcinogenesis.

DESIGN AND RESULTS

Forty cases of lip squamous cell carcinoma (LSCC), 55 actinic cheilitis (AC), and 10 healthy lip mucosa (HLM) were submitted to immunohistochemistry. Semiquantitative (PD-L1, HLA-G), and quantitative (CD8, GrB) analysis were performed. PD-L1 and HLA-G expression in neoplastic cells/keratinocytes and stroma/connective tissue was significantly higher in LSCC and AC, compared to HLM (p<0.05). PD-L1 was not associated with clinicopathological features of the lesions. HLA-G expression by malignant cells was significantly higher in LSCCs with distant metastasis (p = 0.041).CD8⁺ and GrB⁺ cell numbers progressively increased from HLMs to LSCC, with AC exhibiting intermediate numbers (p<0.01). Most LSCCs showed coexistence of PD-L1⁺ and CD8⁺ cells (72.5%). PD-L1 was directly correlated to CD8⁺ and GrB⁺ lymphocytic infiltration in LSCCs (p<0.05). Low cytotoxic immune response was associated with lymph node metastasis in LSCC (p<0.05).

CONCLUSIONS

PD-L1 and HLA-G-mediated immune evasion mechanisms are likely to occur from early pre-malignant to advanced malignant stages of lip carcinogenesis, which might provide a rationale for therapeutic blockade of these pathways. PD-L1 expression in LSCCs was correlated with the cytotoxic markers, suggesting that PD-L1 may appear as an escape mechanism in response to an active antitumor response.

Apigenin Inhibits UVB-Induced Skin Carcinogenesis: The Role of Thrombospondin-1 as an Anti-Inflammatory Factor

We have previously demonstrated that apigenin promotes the expression of antiangiogenic protein thrombospondin-1 (TSP1) via a mechanism driven by mRNA-binding protein HuR. Here, we generated a novel mouse model with whole-body THBS-1 gene knockout on SKH-1 genetic background, which allows studies of UVB-induced acute skin damage and carcinogenesis and tests TSP1 involvement in apigenin's anticancer effects. Apigenin significantly inhibited UVB-induced carcinogenesis in the wild-type (WT) animals but not in TSP1 KO (TKO) mice, suggesting that TSP1 is a critical component of apigenin's chemopreventive function in UVB-induced skin cancer. Importantly, TKO mice presented with the elevated cutaneous inflammation at baseline, which was manifested by increased inflammatory infiltrates (neutrophils and macrophages) and elevated levels of the two key inflammatory cytokines, IL-6 and IL-12. In agreement, maintaining normal TSP1 expression in the UVB-irradiated skin of WT mice using topical apigenin application caused a marked decrease of circulating inflammatory cytokines. Finally, TKO mice showed an altered population dynamics of the bone marrow myeloid progenitor cells (CD11b+), with dramatic expansion of the population of neutrophil progenitors (Ly6ClowLy6Ghigh) compared to the WT control. Our results indicate that the cutaneous tumor suppressor TSP1 is a critical mediator of the in vivo anticancer effect of apigenin in skin, specifically of its anti-inflammatory action.

Study of the influence of substrate and spectrophotometer characteristics on the in vitro measurement of sunscreens efficiency

All the methods used for the in vitro measurement of the SPF, the universal indicator of sunscreens efficiency, rely on a spectrophotometric analysis. What can vary about the experimental protocol used is mainly the substrate and the type of spectrophotometer chosen. We decided to work with polymethylmetacrylate plates that we analyzed using two spectrophotometers equipped with integrating spheres, the UV1000S and the UV2000 apparatus. Two marketed products were such tested, after spreading 2 mg/cm² on the plates, using one apparatus after another. We applied a non-parametric Wilcoxon test for paired data to the measures realized on 10 plates (as we systematically used the 2 apparatus), in order to compare the series of measures obtained with the two machines. This way, we were able to show a significant difference between the SPF values respectively obtained with the UV1000S and the UV2000 spectrophotometers. This difference could be explained by the decrease of the stray light in the case of the UV2000 apparatus.

Potential cutaneous carcinogenic risk of exposure to UV nail lamp: A review

The increased use of ultraviolet (UV) nail lamps in recent years has generated safety concerns of this device. A UV nail lamp is a source of artificial UVA radiation, often used to dry, harden, and cure the nails at home and in the salon. UVA radiation is known to be mutagenic and can cause damage to the DNA, resulting in cutaneous malignancy. Currently, there are only a few studies that have evaluated UV nail lamp irradiation and its potential carcinogenic risk. We review the literature on UV nail lamps, its safety, effect on nails and hands, and the potential role in increasing the risk of cutaneous malignancy. Based on available data, the carcinogenic risk is low; nonetheless, the use of a broad spectrum sunscreen with SPF >30 before UV nail lamp exposure is recommended.

Dual Effects of Alpha-Hydroxy Acids on the Skin

AHAs are organic acids with one hydroxyl group attached to the alpha position of the acid. AHAs including glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid are often used extensively in cosmetic formulations. AHAs have been used as superficial peeling agents as well as to ameliorate the appearance of keratoses and acne in dermatology. However, caution should be exercised in relation to certain adverse reactions among patients using products with AHAs, including swelling, burning, and pruritus. Whether AHAs enhance or decrease photo damage of the skin remains unclear, compelling us to ask the question, is AHA a friend or a foe of the skin? The aim of this manuscript is to review the various biological effects and mechanisms of AHAs on human keratinocytes and in an animal model. We conclude that whether AHA is a friend or foe of human skin depends on its concentration. These mechanisms of AHAs are currently well understood, aiding the development of novel approaches for the prevention of UV-induced skin damage.

UVB radiation represses CYLD expression in melanocytes

CYLD lysine 63 deubiquitinase (CYLD) was originally identified as a tumor suppressor that is mutated in familial cylindromatosis. Unlike in cylindromatosis, downregulation of the deubiquitinase CYLD in melanoma, a highly aggressive tumor, is not caused by mutations in the CYLD gene, but rather by a constitutive and high expression of the snail family transcriptional repressor 1 (SNAIL1). A reduced CYLD level leads to B-cell lymphoma-3/p50/p52-dependent nuclear factor-κB activation, which in turn triggers the expression of genes such as cyclin D1 and N-cadherin. Elevated levels of cyclin D1 and N-cadherin promote melanoma proliferation and invasion. By analyzing the regulation of CYLD expression in melanocytes, the present study identified a signaling pathway that is regulated in response to ultraviolet B (UVB) radiation in melanocytes. UVB light leads to an extracellular signal-regulated kinase-mediated induction of SNAIL1 and subsequent downregulation of CYLD expression in normal human epithelial melanocytes. The UVB-mediated suppression of CYLD in melanocytes may have a key role in the reaction to UV stimuli, and may also potentially be involved in the early malignant transformation processes.

Ultraviolet B eye irradiation aggravates atopic dermatitis via adrenocorticotropic hormone and NLRP3 inflammasome in NC/Nga mice

BACKGROUND

Ultraviolet (UV) B irradiation has been shown to improve atopic dermatitis (AD). However, the relationship between UVB eye irradiation and AD is not known. This issue was addressed using a mouse model of AD.

METHODS

The eyes of NC/Nga mice were irradiated with UVB at a dose of 1.0 kJ/m² using a 20SE sunlamp for the duration of the experimental period.

RESULTS

AD symptoms deteriorated upon UVB eye irradiation. The levels of adrenocorticotropic hormone (ACTH) in the plasma and nucleotide-binding domain and leucine-rich-containing family, pyrin domain-containing (NLRP)3 and neutrophil markers in the skin were increased in UVB-irradiated mice. Treatment with inhibitors of ACTH, caspase-1, interleukin-18, and thymic stromal lymphopoietin (TSLP) partly reversed the effects of irradiation, with the greatest improvement observed upon ACTH inhibition. The NLRP3 inflammasome was implicated in the effects of UVB irradiation.

CONCLUSIONS

UVB eye irradiation causes AD symptom deterioration, which is likely mediated by ACTH and the activity of the inflammasome.

Basal cell carcinoma pathogenesis and therapy involving hedgehog signaling and beyond

Basal cell carcinoma (BCC) of the skin is driven by aberrant hedgehog signaling. Thus blocking this signaling pathway by small molecules such as vismodegib inhibits tumor growth. Primary cilium in the epidermal cells plays an integral role in the processing of hedgehog signaling-related proteins. Recent genomic studies point to the involvement of additional genetic mutations that might be associated with the development of BCCs, suggesting significance of other signaling pathways, such as WNT, NOTCH, mTOR, and Hippo, aside from hedgehog in the pathogenesis of this human neoplasm. Some of these pathways could be regulated by noncoding microRNA. Altered microRNA expression profile is recognized with the progression of these lesions. Stopping treatment with Smoothened (SMO) inhibitors often leads to tumor reoccurrence in the patients with basal cell nevus syndrome, who develop 10-100 of BCCs. In addition, the initial effectiveness of these SMO inhibitors is impaired due to the onset of mutations in the drug-binding domain of SMO. These data point to a need to develop strategies to overcome tumor recurrence and resistance and to enhance efficacy by developing novel single agent-based or multiple agents-based combinatorial approaches. Immunotherapy and photodynamic therapy could be additional successful approaches particularly if developed in combination with chemotherapy for inoperable and metastatic BCCs.

A new in vitro assay to test UVR protection of dermal extracellular matrix components by a flat spectrum sunscreen

The efficacy of topical sunscreens is currently assessed by crude, costly and time consuming in vivo assays. We have previously demonstrated that components of the dermal extracellular matrix (ECM), rich in UV-absorbing amino acids, are susceptible to damage by solar simulated radiation (SSR) in vitro. Here we developed an in vitro method to test the ability of sunscreens to protect fibrillin-rich microfibrils (FRM) and fibronectin, key components of the dermal ECM from UV-induced damage. Solutions of FRM or fibronectin were irradiated without protection, in the presence of a vehicle or a commercially-available flat-spectrum sunscreen. The effect of SSR on molecular structure was determined by atomic force microscopy (FRM) and SDS-PAGE (fibronectin). Following irradiation, FRM periodicity became bi-modally distributed (peaks: 40nm & 59nm) compared to the unimodal distribution in unexposed controls (peak: 50nm). Irradiation in the presence of flat-spectrum sunscreen protected against this change, maintaining the unimodal distribution. SSR induced significant aggregation of fibronectin (p=0.005), which was abrogated by sunscreen. These results demonstrate that this in vitro assay system is sufficiently sensitive to act as an initial/additional screen of sunscreen efficacy. We conclude that sunscreen can reduce UV-mediated damage of key dermal ECM in vitro and thereby prevent remodelling associated with photoageing.

A Topical Zinc Ionophore Blocks Tumorigenic Progression in UV-exposed SKH-1 High-risk Mouse Skin

Nonmelanoma skin cancer (NMSC) is the most common malignancy in the United States representing a considerable public health burden. Pharmacological suppression of skin photocarcinogenesis has shown promise in preclinical and clinical studies, but more efficacious photochemopreventive agents are needed. Here, we tested feasibility of harnessing pharmacological disruption of intracellular zinc homeostasis for photochemoprevention in vitro and in vivo. Employing the zinc ionophore and FDA-approved microbicidal agent zinc pyrithione (ZnPT), used worldwide in over-the-counter (OTC) topical consumer products, we first demonstrated feasibility of achieving ZnPT-based intracellular Zn²⁺ overload in cultured malignant keratinocytes (HaCaT-ras II-4; SCC-25) employing membrane-permeable fluorescent probes. Zinc overload was accompanied by induction of intracellular oxidative stress, associated with mitochondrial superoxide release as substantiated by MitoSOX Red™ fluorescence microscopy. ZnPT-induced cell death observable in malignant keratinocytes was preceded by induction of metal (MT2A), proteotoxic (HSPA6, HSPA1A, DDIT3, HMOX1) and genotoxic stress response (GADD45A, XRCC2) gene expression at the mRNA and protein levels. Comet analysis revealed introduction of formamidopyrimidine-DNA glycosylase (Fpg)-sensitive oxidative DNA lesions. In a photocarcinogenesis model (UV-exposed SKH-1 high-risk mouse skin), topical ZnPT administration post-UV caused epidermal zinc overload and stress response gene expression with pronounced blockade of tumorigenesis. Taken together, these data suggest feasibility of repurposing a topical OTC drug for zinc-directed photochemoprevention of solar UV-induced NMSC.

Molecular signaling cascades involved in nonmelanoma skin carcinogenesis

Nonmelanoma skin cancer (NMSC) is the most common cancer worldwide and the incidence continues to rise, in part due to increasing numbers in high-risk groups such as organ transplant recipients and those taking photosensitizing medications. The most significant risk factor for NMSC is ultraviolet radiation (UVR) from sunlight, specifically UVB, which is the leading cause of DNA damage, photoaging, and malignant transformation in the skin. Activation of apoptosis following UVR exposure allows the elimination of irreversibly damaged cells that may harbor oncogenic mutations. However, UVR also activates signaling cascades that promote the survival of these potentially cancerous cells, resulting in tumor initiation. Thus, the UVR-induced stress response in the skin is multifaceted and requires coordinated activation of numerous pathways controlling DNA damage repair, inflammation, and kinase-mediated signal transduction that lead to either cell survival or cell death. This review focuses on the central signaling mechanisms that respond to UVR and the subsequent cellular changes. Given the prevalence of NMSC and the resulting health care burden, many of these pathways provide promising targets for continued study aimed at both chemoprevention and chemotherapy.

Linalool prevents oxidative stress activated protein kinases in single UVB-exposed human skin cells

Ultraviolet-B radiation (285–320 nm) elicits a number of cellular signaling elements. We investigated the preventive effect of linalool, a natural monoterpene, against UVB-induced oxidative imbalance, activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling in HDFa cells. We observed that linalool treatment (30 μM) prevented acute UVB-irradiation (20 mJ/cm²) mediated loss of activities of antioxidant enzymes in HDFa cells. The comet assay results illustrate that linalool significantly prevents UVB-mediated 8-deoxy guanosine formation (oxidative DNA damage) rather than UVB-induced cyclobutane pyrimidine (CPD) formation. This might be due to its ability to prevent UVB-induced ROS formation and to restore the oxidative imbalance of cells. This has been reflected in UVB-induced overexpression of MAPK and NF-κB signaling. We observed that linalool inhibited UVB-induced phosphorylation of ERK1, JNK and p38 proteins of MAPK family. Linalool inhibited UVB-induced activation of NF-κB/p65 by activating IκBa. We further observed that UVB-induced expression of TNF-α, IL6, IL-10, MMP-2 and MMP-9 was modulated by linalool treatment in HDFa cells. Thus, linalool protects the human skin cells from the oxidative damages of UVB radiation and modulates MAPK and NF-κB signaling in HDFa cells. The present findings substantiate that linalool may act as a photoprotective agent against UVB-induced skin damages.

Intercellular crosstalk in human malignant melanoma

Incidence of malignant melanoma is increasing globally. While the initial stages of tumors can be easily treated by a simple surgery, the therapy of advanced stages is rather limited. Melanoma cells spread rapidly through the body of a patient to form multiple metastases. Consequently, the survival rate is poor. Therefore, emphasis in melanoma research is given on early diagnosis and development of novel and more potent therapeutic options. The malignant melanoma is arising from melanocytes, cells protecting mitotically active keratinocytes against damage caused by UV light irradiation. The melanocytes originate in the neural crest and consequently migrate to the epidermis. The relationship between the melanoma cells, the melanocytes, and neural crest stem cells manifests when the melanoma cells are implanted to an early embryo: they use similar migratory routes as the normal neural crest cells. Moreover, malignant potential of these melanoma cells is overdriven in this experimental model, probably due to microenvironmental reprogramming. This observation demonstrates the crucial role of the microenvironment in melanoma biology. Indeed, malignant tumors in general represent complex ecosystems, where multiple cell types influence the growth of genetically mutated cancer cells. This concept is directly applicable to the malignant melanoma. Our review article focuses on possible strategies to modify the intercellular crosstalk in melanoma that can be employed for therapeutic purposes.

Melanoma Chemoprevention: Current Status and Future Prospects

The incidence of skin cancers, both nonmelanoma and melanoma, is increasing in the United States. The ultraviolet radiation, mainly from sun, is considered the major cause for these neoplasms. While nonmelanoma skin cancers are far more numerous, melanoma remains the most challenging. This is because melanoma can become extremely aggressive and its incidence is increasing worldwide due to lack of effective early detection, as well as disease recurrence, following both surgery and chemotherapy. Therefore, in addition to better treatment options, newer means are required to prevent melanomas from developing. Chemoprevention is a reasonable cost-effective approach to prevent carcinogenesis by inhibiting the processes of tumor initiation, promotion and progression. Melanoma is a progressive disease, which makes it very suitable for chemopreventive interventions, by targeting the processes and molecular pathways involved in the progression of melanoma. This review discusses the roles of various chemopreventive agents such as NSAIDs, statins, vitamins and dietary agents in melanoma and highlights current advancements and our perspective on future of melanoma chemoprevention. Although considerable preclinical data suggest that melanoma may be prevented or delayed by a numerous chemopreventive agents, we realize there are insufficient clinical studies evaluating their efficacy and long-term safety for human use.