Mechanisms of UV-induced immunosuppression

Formulation of Ensulizole with Beta-Cyclodextrins for Improved Sunscreen Activity and Biocompatibility

In today's context, prolonged exposure to sunlight is widely recognized as a threat to human health, leading to a range of adverse consequences, including skin cancers, premature skin aging, and erythema. To mitigate these risks, preventive actions mainly focus on advocating the application of sunscreen lotions and minimizing direct exposure to sunlight. This research study specifically centered on ensulizole (ENS), a prominent ingredient in sunscreens. The objective was to create inclusion complexes (ICs) with Beta-cyclodextrin (B-CD) and its hydroxypropyl derivatives (H-CD). Using phase solubility measurements, we determined that both B-CD and H-CD form 1:1 stoichiometric ICs with ENS. Proton nuclear magnetic resonance spectral (1H NMR) analysis confirmed that the phenyl portion of ENS is encapsulated within the B-CD cavity. Significant changes in surface morphology were observed during the formation of these ICs compared to ENS and CDs alone. Quantum mechanical calculations were employed to further support the formation of ICs by providing energy data. Particularly, the photostability of the ENS:B-CD ICs remained intact for up to four hours of UV exposure, with no significant alterations in the structure of ENS. Furthermore, comprehensive biocompatibility assessments yielded encouraging results, suggesting the potential application of these inclusion complexes in cosmetics as a UVB sunscreen. In summary, our research underscores the successful creation of inclusion complexes characterized by enhanced photostability and safe biocompatibility.

The Climate Change Burden on Immune Health: Are Persons Living with HIV More at Risk?

Climate change poses one of the most significant modern threats to overall human health,especially for vulnerable populations including persons living with HIV (PLWH). In this perspective, we specifically explore the concept of immune resilience in human health and how climate change phenomena - including extreme weather events, food insecurity, pollution, and emerging diseases - may exacerbate immune dysfunction and comorbidities faced by PLWH and hinder access to HIV treatment and prevention services. Multidisciplinary, collaborative efforts are urgently needed to quantify these impacts, develop mitigation strategies, and strengthen policies and funding to bolster immune resilience for PLWH in the face of accelerating climate change.

Downregulation of SMAD4 protects HaCaT cells against UVB-induced damage and oxidative stress through the activation of EMT

As a member of the SMAD family, SMAD4 plays a crucial role in several cellular biological processes. However, its function in UVB radiation-induced keratinocyte damage is not yet clarified. Our study aims to provide mechanistic insight for the development of future UVB protective therapies and therapeutics involving SMAD4. HaCaT cells were treated with UVB, and the dose dependence and time dependence of UVB were measured. The cell function of UVB-treated HaCaT cells and the activity of epithelial-mesenchymal transition (EMT) after overexpression or silencing of SMAD4 was observed by flow cytometry, quantitative reverse transcription PCR (qRT-PCR) and Western Blots (WB). We found that a significant decrease in SMAD4 was observed in HaCaT cells induced by UVB. Our data confirm SMAD4 as a direct downstream target of miR-664. The down-regulation of SMAD4 preserved the viability of the UVB-treated HaCaT cells by inhibiting autophagy or apoptosis. Furthermore, the silencing of SMAD4 activated the EMT process in UVB-treated HaCaT cells. Down-regulation of SMAD4 plays a protective role in UVB-treated HaCaT cells via the activation of EMT.

Interferon alpha promotes caspase-8 dependent ultraviolet light-mediated keratinocyte apoptosis via interferon regulatory factor 1

Introduction

Ultraviolet (UV) light is a known trigger of both cutaneous and systemic disease manifestations in lupus patients. Lupus skin has elevated expression of type I interferons (IFNs) that promote increased keratinocyte (KC) death after UV exposure. The mechanisms by which KC cell death is increased by type I IFNs are unknown.

Methods

Here, we examine the specific cell death pathways that are activated in KCs by type I IFN priming and UVB exposure using a variety of pharmacological and genetic approaches. Mice that overexpress Ifnk in the epidermis were exposed to UVB light and cell death was measured. RNA-sequencing from IFN-treated KCs was analyzed to identify candidate genes for further analysis that could drive enhanced cell death responses after UVB exposure.

Results

We identify enhanced activation of caspase-8 dependent apoptosis, but not other cell death pathways, in type I IFN and UVB-exposed KCs. In vivo, overexpression of epidermal Ifnk resulted in increased apoptosis in murine skin after UVB treatment. This increase in KC apoptosis was not dependent on known death ligands but rather dependent on type I IFN-upregulation of interferon regulatory factor 1 (IRF1).

Discussion

These data suggest that enhanced sensitivity to UV light exhibited by lupus patients results from type I IFN priming of KCs that drives IRF1 expression resulting in caspase-8 activation and increased apoptosis after minimal exposures to UVB.

Modeling pulsed dye laser treatment of psoriatic plaques by combining numerical methods and image-derived lesion morphologies

OBJECTIVES

Knowledge of the physical effects of pulsed dye laser (PDL) treatment of psoriatic lesions is essential in unraveling the remedial mechanisms of this treatment and hence also in maximizing in its disease-modifying potential. Therefore, the main objective of this study was to provide estimates of these physical effects (for laser wavelengths of 585 and 595 nm), with the aim of identifying pathogenic processes that may be affected by these conditions.

METHODS

We modeled the laser light propagation and subsequent photothermal heating by numerically solving the transient diffusion and heat equations simultaneously. To this end, we used the finite element method in conjunction with an image-derived psoriatic lesion morphology (which was defined by segmenting blood vessels from a confocal microscopy image of a fluorescently labeled section of a 3 mm punch biopsy of a psoriatic lesion). The resulting predictions of the generated temperature field within the lesion were then used to assess the possibility of stalling or arresting some suspected pathogenic processes.

RESULTS

According to our results, it is conceivable that perivascular nerves are thermally denatured, as almost all locations that reach 60°C were found to be within 18 µm (at 585 nm) and 11 µm (at 595 nm) of a blood vessel wall. Furthermore, activation of TRPV1 and TRPV2 channels in perivascular neuronal and immune cells is highly likely, since a critical temperature of 43°C is generated at locations within up to 350 µm of a vessel wall (at both wavelengths) and sustained for up to 700 ms (at 585 nm) and 40 ms (at 595 nm), while a critical temperature of 52°C is reached by locations within 80 µm (at 585 nm) and 30 µm (at 595 nm) of a vessel wall and sustained for up to 100  ms (at 585 nm) and 30 ms (at 595 nm). Finally, we found that the blood vessel coagulation-inducing temperature of 70°C is sustained in the vascular epithelium for up to 19 and 5 ms at 585 and 595 nm, respectively, rendering partial or total loss of vascular functionality a distinct possibility.

CONCLUSIONS

The presented approach constitutes a useful tool to provide realistic estimates of the photothermal effects of PDL treatment of psoriatic plaques (as well as other selective photothermolysis-based treatments), yielding information that is essential in guiding future experimental studies toward unraveling the remedial mechanisms of these treatments.

Sexual dimorphism in melanocyte stem cell behavior reveals combinational therapeutic strategies for cutaneous repigmentation

Vitiligo is an autoimmune skin disease caused by cutaneous melanocyte loss. Although phototherapy and T cell suppression therapy have been widely used to induce epidermal re-pigmentation, full pigmentation recovery is rarely achieved due to our poor understanding of the cellular and molecular mechanisms governing this process. Here, we identify unique melanocyte stem cell (McSC) epidermal migration rates between male and female mice, which is due to sexually dimorphic cutaneous inflammatory responses generated by ultra-violet B exposure. Using genetically engineered mouse models, and unbiased bulk and single-cell mRNA sequencing approaches, we determine that manipulating the inflammatory response through cyclooxygenase and its downstream prostaglandin product regulates McSC proliferation and epidermal migration in response to UVB exposure. Furthermore, we demonstrate that a combinational therapy that manipulates both macrophages and T cells (or innate and adaptive immunity) significantly promotes epidermal melanocyte re-population. With these findings, we propose a novel therapeutic strategy for repigmentation in patients with depigmentation conditions such as vitiligo.

Thermal compensation reduces DNA damage from UV radiation

Increases in ultraviolet radiation (UVR) correlate spatially and temporally with global amphibian population declines and interact with other stressors such as disease and temperature. Declines have largely occurred in high-altitude areas associated with greater UVR and cooler temperatures. UVR is a powerful mutagenic harming organisms largely by damaging DNA. When acutely exposed to UVR at cool temperatures, amphibian larvae have increased levels of DNA damage. Amphibians may compensate for the depressive effects of temperature on DNA damage through acclimatisation, but it is unknown whether they have this capacity. We reared striped marsh frog larvae (Limnodynastes peronii) in warm (25 °C) and cool (15 °C) temperatures under a low or moderate daily dose of UVR (10 and 40 μW cm-2 UV-B for 1 h at midday, respectively) for 18-20 days and then measured DNA damage resulting from an acute high UVR dose (80 μW cm-2 UV-B for 1.5 h) at a range of temperatures (10, 15, 20, 25, and 30 °C). Larvae acclimated to 15 °C and exposed to UVR at 15 °C completely compensated UVR-induced DNA damage compared with 25 °C acclimated larvae exposed to UVR at 25 °C. Additionally, warm-acclimated larvae had higher DNA damage than cold-acclimated larvae across test temperatures, which indicated a cost of living in warmer temperatures. Larvae reared under elevated UVR levels showed no evidence of UVR acclimation resulting in lower DNA damage following high UVR exposure. Our finding that thermal acclimation in L. peronii larvae compensated UVR-induced DNA damage at low temperatures suggested that aquatic ectotherms living in cool temperatures may be more resilient to high UVR than previously realised. We suggested individuals or species with less capacity for thermal acclimation of DNA repair mechanisms may be more at risk if exposed to changing thermal and UVR exposure regimes.

Supercritical Fluid Chromatography Coupled to High-Resolution Mass Spectrometry Reveals Persistent Mobile Organic Compounds with Unknown Toxicity in Wastewater Effluents

Broad screening approaches for monitoring wastewater are normally based on reversed-phase liquid chromatography (LC) coupled to high-resolution mass spectrometry (HRMS). This method is not sufficient for the very polar micropollutants, neglected in the past due to a lack of suitable analytical methods. In this study, we used supercritical fluid chromatography (SFC) to detect very polar and yet-undetected micropollutants in wastewater effluents. We tentatively identified 85 compounds, whereas 18 have only rarely been detected and 11 have not previously been detected in wastewater effluents such as 17α-hydroxypregnenolone, a likely transformation product (TP) of steroids, and 1H-indole-3-carboxamide, a likely TP from new synthetic cannabinoids. Suspect screening of 25 effluent wastewater samples from 8 wastewater treatment plants revealed several distinct potential pollution sources such as a pharmaceutical company and a golf court. The analysis of the same samples with LC-HRMS showed clearly how SFC increases the ionization efficiency for low-molecular-weight micropollutants (m/z < 300 Da) by a factor 2 to 87 times, which significantly improved the mass spectra for identifying very polar compounds. In order to assess which micropollutants might be of environmental concern, literature and toxicological databases were screened. There was a lack of available hazard and bio-activity data for regulatory-relevant in vitro and in vivo assays for >50% of the micropollutants. Especially, 70% of the data were lacking for the whole organism (in vivo) tests.

Sexual dimorphism in melanocyte stem cell behavior reveals combinational therapeutic strategies for cutaneous repigmentation

Vitiligo is an autoimmune skin disease caused by cutaneous melanocyte loss. Although phototherapy and T cell suppression therapy have been widely used to induce epidermal repigmentation, full pigmentation recovery is rarely achieved due to our poor understanding of the cellular and molecular mechanisms governing this process. Here, we identify unique melanocyte stem cell (McSC) epidermal migration rates between male and female mice, which is due to sexually dimorphic cutaneous inflammatory responses generated by ultra-violet B exposure. Using genetically engineered mouse models, and unbiased bulk and single-cell mRNA sequencing approaches, we determine that manipulating the inflammatory response through cyclooxygenase and its downstream prostaglandin product regulates McSC proliferation and epidermal migration in response to UVB exposure. Furthermore, we demonstrate that a combinational therapy that manipulates both macrophages and T cells (or innate and adaptive immunity) significantly promotes epidermal melanocyte re-population. With these findings, we propose a novel therapeutic strategy for repigmentation in patients with depigmentation conditions such as vitiligo.

UVB-Induced Microvesicle Particle Release and Its Effects on the Cutaneous Microenvironment

Ultraviolet B radiation (UVB) has profound effects on human skin that results in a broad spectrum of immunological local and systemic responses and is the major cause of skin carcinogenesis. One important area of study in photobiology is how UVB is translated into effector signals. As the skin is exposed to UVB light, subcellular microvesicle particles (MVP), a subtype of bioactive extracellular vesicles, are released causing a variety of local and systemic immunological effects. In this review, we highlight keratinocyte MVP release in keratinocytes in response to UVB. Specifically, Platelet-activating factor receptor agonists generated by UVB result in MVP released from keratinocytes. The downstream effects of MVP release include the ability of these subcellular particles to transport agents including the glycerophosphocholine-derived lipid mediator Platelet-activating factor (PAF). Moreover, even though UVB is only absorbed in the epidermis, it appears that PAF release from MVPs also mediates systemic immunosuppression and enhances tumor growth and metastasis. Tumor cells expressing PAF receptors can use this mechanism to evade chemotherapy responses, leading to treatment resistance for advanced cancers such as melanoma. Furthermore, novel pharmacological agents provide greater insight into the UVB-induced immune response pathway and a potential target for pharmacological intervention. This review outlines the need to more clearly elucidate the mechanism linking UVB-irradiation with the cutaneous immune response and its pathological manifestations. An improved understanding of this process can result in new insights and treatment strategies for UVB-related disorders from carcinogenesis to photosensitivity.

Consideration of underlying immunodeficiency in refractory or recalcitrant warts: A review of the literature

Although the exact mechanisms have yet to be elucidated, it is clear that cellular immunity plays a role in clearance of human papillomavirus (HPV) infections as it relates to the development of warts. Patients with extensive, recalcitrant, or treatment‐refractory warts may have an underlying immune system impairment at the root of HPV susceptibility. Early recognition of genetic disorders associated with immunologic defects that allow for recalcitrant HPV infection may expedite appropriate treatment for patients. Early recognition is often pivotal in preventing subsequent morbidity and/or mortality that may arise from inborn errors of immunity, such as WHIM (Warts, Hypogammaglobulinemia, Infections, Myelokathexis) syndrome. Among these, cervical cancer is one of the most common malignancies associated with HPV, can be fatal if not treated early, and is seen more frequently in patients with underlying immune deficiencies. A review of diseases with susceptibility to HPV provides clues to understanding the pathophysiology of warts. We also present diagnostic guidance to facilitate the recognition of inborn errors of immunity in patients with extensive and/or recalcitrant HPV infections.

High pressure Raman investigation on trans-urocanic acid

Trans-urocanic acid (t-UCA) is an important epidermal UV protector predominantly found in human skin. Exposure of UV radiation triggers photoisomerization of t-UCA into its other conformer, cis-urocanic acid (cis-UCA), which has been shown to be a mediator of UV-induced immune-suppression leading to skin cancer. In this report, we present the investigation of molecular changes of t-UCA under high pressures by in-situ high pressure Raman spectroscopy. The study indicates onset of ring opening polymerization of t-UCA at pressure above 1.4 GPa. At pressures beyond 5 GPa, a well discernible characteristic vibrational mode (CC stretch) accompanied by several other spectral features such as δ CO₂^- and δ NH modes of cis-UCA point towards the isomerization of residual t-UCA monomers into cis-UCA. The content of cis-UCA gradually increased with increase in pressure. On release to ambient conditions, the spectrum of the quenched sample showed Raman modes of polymer and cis-UCA indicating that the changes are irreversible.

Changes in the skin microbiome associated with squamous cell carcinoma in transplant recipients

Actinic keratoses (AK) arise in severely photo-damaged skin and can progress to squamous cell carcinomas (SCC). AK and SCC are common in Caucasian populations, and immunosuppressed individuals have a markedly higher risk of developing SCC. An overabundance of Staphylococcus aureus has been reported in AK and SCC lesions of immunocompetent individuals, however, the AK/SCC microbiome in immunosuppressed cohorts has not been investigated. Here, the microbial profile and bacterial load of AK, SCC and control skin swabs from 32 immunosuppressed organ transplant recipients were characterised via SSU rRNA gene sequencing and qPCR, and compared to a previously described immunocompetent cohort. Although the taxonomic composition of skin swab samples was mostly subject-specific, significant differences were observed between control skin, AK, and SCC in both cohorts. Surface bacterial load was increased and alpha diversity decreased in AK and SCC compared to control skin due to an increased abundance of Staphylococcus species and relative decrease of skin commensals. Staphylococcus epidermidis predominated on SCC from transplant recipients in contrast to SCC of immunocompetent subjects dominated by S. aureus. In conclusion, AK and SCC of immunosuppressed and immunocompetent subjects present with distinctive microbial dysbioses, which may be relevant to SCC pathogenesis and progression.

Recent Advances on the Role and Therapeutic Potential of Regulatory T Cells in Atherosclerosis

Atherosclerotic diseases, including ischemic heart disease and stroke, are a main cause of mortality worldwide. Chronic vascular inflammation via immune dysregulation is critically involved in the pathogenesis of atherosclerosis. Accumulating evidence suggests that regulatory T cells (Tregs), responsible for maintaining immunological tolerance and suppressing excessive immune responses, play an important role in preventing the development and progression of atherosclerosis through the regulation of pathogenic immunoinflammatory responses. Several strategies to prevent and treat atherosclerosis through the promotion of regulatory immune responses have been developed, and could be clinically applied for the treatment of atherosclerotic cardiovascular disease. In this review, we summarize recent advances in our understanding of the protective role of Tregs in atherosclerosis and discuss attractive approaches to treat atherosclerotic disease by augmenting regulatory immune responses.

Intravenous immunoglobulin-induced severe vesicular eczematous eruption successfully treated with narrow band-ultraviolet B therapy

Intravenous immunoglobulins (IVIg) are increasingly being used to treat a wide spectrum of dermatological and neurological autoimmune diseases. Although the administration of IVIg does not usually result in severe adverse reactions, side effects of IVIg reportedly occur in 6-13% of patients. Most reported cases were not severe, and IVIg is considered a relatively safe drug. Some reports described a vesicular eczematous eruption caused by IVIg that was cured by applying topical steroid ointments or systemic steroids. Herein, we present, to the best of our knowledge, the first case of severe vesicular eczematous eruption all over the body induced by IVIg that was unresponsive to topical steroid ointment and was subsequently treated with narrow band-ultraviolet B (NB-UVB) therapy successfully. NB-UVB was started at a dose of 400 mJ/cm² once a week, and swift improvement was observed. The skin rash disappeared in the first 2 months, and the pathogenesis of IVIg-induced eczematous eruption remains unelucidated. No change in eosinophils and complement levels were observed in our case. Given the increase in the widespread use of IVIg, we have shown that NB-UVB therapy is a candidate choice for the treatment of IVIg-induced severe vesicular eczematous eruption.

Possible Roles of Permafrost Melting, Atmospheric Transport, and Solar Irradiance in the Development of Major Coronavirus and Influenza Pandemics

Major pandemics involving respiratory viruses develop semi-regularly and require a large flux of novel viruses, yet their origination is equivocal. This paper explores how natural processes could give rise to this puzzling combination of characteristics. Our model is based on available data regarding the emergence of historic influenzas, early COVID-19 cases and spreading, the microbiome of permafrost, long-distance airborne transport of viruses reaching stratospheric levels, ultraviolet immunosuppression, sunlight variations, weather patterns, Arctic thawing, and global warming. Atmospheric conveyance is supported by hemispheric distribution disparities, ties of COVID-19 cases to air pollution particulate concentrations, and contemporaneous animal infections. The following sequence is proposed: (1) virus emergence after hot Arctic summers, predominantly near solar irradiance maxima or involving wildfires, indicates release of large amounts of ancient viruses during extensive permafrost melting, which are then incorporated in autumn polar air circulation, where cold storage and little sunlight permit survival. (2) Pandemics onset in winter to spring at rather few locations: from climate data on Wuhan, emergence occurs where the North Polar Jet stream hovers while intersecting warmer, moist air, producing rain which deposits particulates with the viral harvest on a vulnerable human population. (3) Spring and summer increases in COVID-19 cases link to high solar irradiance, implicating ultraviolet immune suppression as one means of amplification. (4) Viruses multiplied by infected humans at close range being incorporated in atmospheric circulation explains rapid global spread, periodic case surges (waves), and multi-year durations. Pollution and wind geography affect uptake and re-distribution. Our model can be tested, e.g., against permafrost stored in laboratories as well as Artic air samples, and suggests mitigating actions.

Overcoming Immune Evasion in Melanoma

Melanoma is the most aggressive and dangerous form of skin cancer that develops from transformed melanocytes. It is crucial to identify melanoma at its early stages, in situ, as it is "curable" at this stage. However, after metastasis, it is difficult to treat and the five-year survival is only 25%. In recent years, a better understanding of the etiology of melanoma and its progression has made it possible for the development of targeted therapeutics, such as vemurafenib and immunotherapies, to treat advanced melanomas. In this review, we focus on the molecular mechanisms that mediate melanoma development and progression, with a special focus on the immune evasion strategies utilized by melanomas, to evade host immune surveillances. The proposed mechanism of action and the roles of immunotherapeutic agents, ipilimumab, nivolumab, pembrolizumab, and atezolizumab, adoptive T- cell therapy plus T-VEC in the treatment of advanced melanoma are discussed. In this review, we implore that a better understanding of the steps that mediate melanoma onset and progression, immune evasion strategies exploited by these tumor cells, and the identification of biomarkers to predict treatment response are critical in the design of improved strategies to improve clinical outcomes for patients with this deadly disease.

Protection from Ultraviolet Damage and Photocarcinogenesis by Vitamin D Compounds

Exposure of skin cells to UV radiation results in DNA damage, which if inadequately repaired, may cause mutations. UV-induced DNA damage and reactive oxygen and nitrogen species also cause local and systemic suppression of the adaptive immune system. Together, these changes underpin the development of skin tumours. The hormone derived from vitamin D, calcitriol (1,25-dihydroxyvitamin D₃) and other related compounds, working via the vitamin D receptor and at least in part through endoplasmic reticulum protein 57 (ERp57), reduce cyclobutane pyrimidine dimers and oxidative DNA damage in keratinocytes and other skin cell types after UV. Calcitriol and related compounds enhance DNA repair in keratinocytes, in part through decreased reactive oxygen species, increased p53 expression and/or activation, increased repair proteins and increased energy availability in the cell when calcitriol is present after UV exposure. There is mitochondrial damage in keratinocytes after UV. In the presence of calcitriol, but not vehicle, glycolysis is increased after UV, along with increased energy-conserving autophagy and changes consistent with enhanced mitophagy. Reduced DNA damage and reduced ROS/RNS should help reduce UV-induced immune suppression. Reduced UV immune suppression is observed after topical treatment with calcitriol and related compounds in hairless mice. These protective effects of calcitriol and related compounds presumably contribute to the observed reduction in skin tumour formation in mice after chronic exposure to UV followed by topical post-irradiation treatment with calcitriol and some, though not all, related compounds.

Bioactive Pigments from Isolated Bacteria and Its Antibacterial, Antioxidant and Sun Protective Application Useful for Cosmetic Products

Bacterial pigments are the unique and sustainable source of bioactive colour compounds used in cosmetics, food, textiles, printing and pharmaceutical products. Here, we report the pigment-producing isolates and their biological activities that could be benefited for different industries including cosmeceuticals. In this study, a total of 19 pigment-producing bacteria were isolated and purified from collected soil and water samples. The colour production ability of purified bacteria was observed up to 5 transfers. Of the 19 isolates, two isolates lost colour production ability in subsequent transfers. Crude pigments extracted from the remaining 17 isolates showed sunscreen activity in the range of 0.4-8.34. However, only 6 of them showed significant antibacterial and antioxidant activities. In the media optimization experiment, these 6 bacteria showed optimum growth in neutral to alkaline pH, while optimum temperatures for growth were different for different bacteria. One isolate produces the promising pigment, out of all six potential pigments. It is stable up to 5 transfers, having antioxidant and antibacterial activity with Sun protective activity; the strain was identified using 16srRNA gene sequencing and obtained accession number as MK770403 (probable strain is Staphylococcus xylosus) from National Center for Biotechnology Information (NCBI) database. The results of this study suggested that these bioactive pigments can further be developed and used as antibacterial, antioxidant and sun-protective ingredients in cosmeceuticals.

Polyethylene glycol functionalized cerium oxide nanoparticle confer protection against UV- induced oxidative damage in skin: evidences for a new class of UV filter

Acute exposure to high dose of ultraviolet (UV) radiations is known to cause significant harm to skin, primarily due to the generation of free radicals and damage to DNA, which often culminate in rapid aging of the skin, or cancers. Keratinocytes being the most abundant skin’s cells are affected most by UV. Although a degree of endogenous protection is present, the vulnerability of UV-induced damaged can be minimized using protective agents. A few UV filters (organic and inorganic) have been successfully commercialized, yet, due to prevailing disadvantages such as low solubility, photostability, and aesthetic sense, suitable and more efficient UV filters continue to be explored as potential ingredients of cosmaceutical agents. A recently studied antioxidant enzyme mimetic cerium oxide nanoparticles showed emerging piece of evidence on benefits under environmental stress. However, its protective abilities as potential UV filter and therefore applicability in cosmaceutical has not yet been completely explored. This study provides a piece of evidence in support of beneficial effects of this new class of UV filters, polyethyleneglycol functionalized nanoceria (PEG-CNP) against UV - induced damage in vitro and in vivo. The nanomolar concentration of PEG-CNPs in the cell culture showed significant protection from UV exposure, by direct ROS scavenging, the rescue of cells from cell cycle arrest and DNA damage. Further, a proof of the concept study in dehaired rat skin showed that the topical application of 50 μM PEG-CNPs prevented the initial signs of UV induced damage. Unlike conventional UV filters, PEG-CNPs confer protection by internalizing the cells, and scavenging the radicals.

Oxidative Stress and Photodynamic Therapy of Skin Cancers: Mechanisms, Challenges and Promising Developments

Ultraviolet radiation is one of the most pervasive environmental interactions with humans. Chronic ultraviolet irradiation increases the danger of skin carcinogenesis. Probably, oxidative stress is the most important mechanism by which ultraviolet radiation implements its damaging effects on normal cells. However, notwithstanding the data referring to the negative effects exerted by light radiation and oxidative stress on carcinogenesis, both factors are used in the treatment of skin cancer. Photodynamic therapy (PDT) consists of the administration of a photosensitiser, which undergoes excitation after suitable irradiation emitted from a light source and generates reactive oxygen species. Oxidative stress causes a condition in which cellular components, including DNA, proteins, and lipids, are oxidised and injured. Antitumor effects result from the combination of direct tumour cell photodamage, the destruction of tumour vasculature and the activation of an immune response. In this review, we report the data present in literature dealing with the main signalling molecular pathways modified by oxidative stress after photodynamic therapy to target skin cancer cells. Moreover, we describe the progress made in the design of anti-skin cancer photosensitisers, and the new possibilities of increasing the efficacy of PDT via the use of molecules capable of developing a synergistic antineoplastic action.

Deciphering UV-induced DNA Damage Responses to Prevent and Treat Skin Cancer

Ultraviolet (UV) radiation is among the most prevalent environmental factors that influence human health and disease. Even 1 h of UV irradiation extensively damages the genome. To cope with resulting deleterious DNA lesions, cells activate a multitude of DNA damage response pathways, including DNA repair. Strikingly, UV-induced DNA damage formation and repair are affected by chromatin state. When cells enter S phase with these lesions, a distinct mutation signature is created via error-prone translesion synthesis. Chronic UV exposure leads to high mutation burden in skin and consequently the development of skin cancer, the most common cancer in the United States. Intriguingly, UV-induced oxidative stress has opposing effects on carcinogenesis. Elucidating the molecular mechanisms of UV-induced DNA damage responses will be useful for preventing and treating skin cancer with greater precision. Excitingly, recent studies have uncovered substantial depth of novel findings regarding the molecular and cellular consequences of UV irradiation. In this review, we will discuss updated mechanisms of UV-induced DNA damage responses including the ATR pathway, which maintains genome integrity following UV irradiation. We will also present current strategies for preventing and treating nonmelanoma skin cancer, including ATR pathway inhibition for prevention and photodynamic therapy for treatment.

Photoadaptation to ultraviolet B TL01 in psoriatic patients

BACKGROUND

In the biologic era, narrow-band ultraviolet B (NB-UVB) phototherapy still remains a valuable, effective, inexpensive, safe anti-psoriatic treatment. Patients can lose response to NB-UVB over time due to photoadaptation. This phenomenon is the tendency of the skin to respond to ultraviolet (UV) exposure by undergoing changes that may result in a decreased future response to an equivalent dose of radiation, thus leading to the need for an increased exposure during phototherapy course.

AIM

To characterize and quantify the determinants of photoadaptation in NB-UVB treated psoriatic patients.

METHODS

We enrolled 57 adult patients with moderate plaque psoriasis. Patients underwent 24 sessions of NB-UVB phototherapy delivered thrice a week. Dosing was started with 70% of the minimal erythema dose (MED) with percentage-based dose increments every two treatments. MED as well as change in the erythema and melanin index (MI) were measured at baseline and at the end of phototherapy course. Moreover, an adaptation factor (AF) was calculated for each patient.

RESULTS

Adaptation factor was not influenced by both baseline MED and skin type. We found a weak correlation between higher cumulative dosages and the initial MED (Spearman's rho = 0.32, P = 0.0154) as well as with the mean initial MI (Spearman's rho = 0.25, P = 0.0624, statistically borderline). Clearance and mean number of treatments were correlated (Spearman's rho = 0.48, P < 0.001).

CONCLUSION

Photoadaptation is a physiological skin response that negatively influences NB-UVB responsiveness and is not predictable by the baseline MED and skin type. Thus, starting with more aggressive protocols and increasing rapidly dosage progression to prevent AF may increase NB-UVB response.

Vitiligo: Mechanisms of Pathogenesis and Treatment

Vitiligo is an autoimmune disease of the skin that targets pigment-producing melanocytes and results in patches of depigmentation that are visible as white spots. Recent research studies have yielded a strong mechanistic understanding of this disease. Autoreactive cytotoxic CD8+ T cells engage melanocytes and promote disease progression through the local production of IFN-γ, and IFN-γ-induced chemokines are then secreted from surrounding keratinocytes to further recruit T cells to the skin through a positive-feedback loop. Both topical and systemic treatments that block IFN-γ signaling can effectively reverse vitiligo in humans; however, disease relapse is common after stopping treatments. Autoreactive resident memory T cells are responsible for relapse, and new treatment strategies focus on eliminating these cells to promote long-lasting benefit. Here, we discuss basic, translational, and clinical research studies that provide insight into the pathogenesis of vitiligo, and how this insight has been utilized to create new targeted treatment strategies.

Metal nanomaterials: Immune effects and implications of physicochemical properties on sensitization, elicitation, and exacerbation of allergic disease

The recent surge in incorporation of metallic and metal oxide nanomaterials into consumer products and their corresponding use in occupational settings have raised concerns over the potential for metals to induce size-specific adverse toxicological effects. Although nano-metals have been shown to induce greater lung injury and inflammation than their larger metal counterparts, their size-related effects on the immune system and allergic disease remain largely unknown. This knowledge gap is particularly concerning since metals are historically recognized as common inducers of allergic contact dermatitis, occupational asthma, and allergic adjuvancy. The investigation into the potential for adverse immune effects following exposure to metal nanomaterials is becoming an area of scientific interest since these characteristically lightweight materials are easily aerosolized and inhaled, and their small size may allow for penetration of the skin, which may promote unique size-specific immune effects with implications for allergic disease. Additionally, alterations in physicochemical properties of metals in the nano-scale greatly influence their interactions with components of biological systems, potentially leading to implications for inducing or exacerbating allergic disease. Although some research has been directed toward addressing these concerns, many aspects of metal nanomaterial-induced immune effects remain unclear. Overall, more scientific knowledge exists in regards to the potential for metal nanomaterials to exacerbate allergic disease than to their potential to induce allergic disease. Furthermore, effects of metal nanomaterial exposure on respiratory allergy have been more thoroughly-characterized than their potential influence on dermal allergy. Current knowledge regarding metal nanomaterials and their potential to induce/exacerbate dermal and respiratory allergy are summarized in this review. In addition, an examination of several remaining knowledge gaps and considerations for future studies is provided.

Recommendations for photoprotection in pediatric rheumatology patients

PURPOSE OF REVIEW

Patients seen at pediatric rheumatology are at increased risk of immediate and long-term consequences from sun exposure. The objective of this review is to build awareness of the need of sun protection in pediatric rheumatology patients.

RECENT FINDINGS

Sun exposure can lead to disease exacerbations in many rheumatic diseases. There is well documented literature linking the chronic use of immunosuppressants with long-term risk of skin cancer. Although there is a lack of literature in pediatric rheumatology addressing the need of sun protection in this patient population, the young age of patients, the nature of their disease and the treatments they receive, make them a high-risk population for the effects of the sun.

SUMMARY

Sun protection recommendations are outlined in the following manuscript, backed up by the rationale and biology of why it is important for pediatric rheumatology patients to be protected from the sun. The information reviewed in this article should be part of the education that all pediatric rheumatology patients should receive as part of their care.

Defense potential of secondary metabolites in medicinal plants under UV-B stress

Ultraviolet-B (UV-B) radiation has, for many decades now, been widely studied with respect to its consequences on plant and animal health. Though according to NASA, the ozone hole is on its way to recovery, it will still be a considerable time before UV-B levels reach pre-industrial limits. Thus, for the present, excessive UV-B reaching the Earth is a cause for concern, and UV-B related human ailments are on the rise. Plants produce various secondary metabolites as one of the defense strategies under UV-B. They provide photoprotection via their UV-B screening effects and by quenching the reactive oxygen- and nitrogen species produced under UV-B influence. These properties of plant secondary metabolites (PSMs) are being increasingly recognized and made use of in sunscreens and cosmetics, and pharma- and nutraceuticals are gradually becoming a part of the regular diet. Secondary metabolites derived from medicinal plants (alkaloids, terpenoids, and phenolics) are a source of pharmaceuticals, nutraceuticals, as well as more rigorously tested and regulated drugs. These metabolites have been implicated in providing protection not only to plants under the influence of UV-B, but also to animals/animal cell lines, when the innate defenses in the latter are not adequate under UV-B-induced damage. The present review focuses on the defense potential of secondary metabolites derived from medicinal plants in both plants and animals. In plants, the concentrations of the alkaloids, terpenes/terpenoids, and phenolics have been discussed under UV-B irradiation as well as the fate of the genes and enzymes involved in their biosynthetic pathways. Their role in providing protection to animal models subjected to UV-B has been subsequently elucidated. Finally, we discuss the possible futuristic scenarios and implications for plant, animal, and human health pertaining to the defense potential of these secondary metabolites under UV-B radiation-mediated damages.

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.

Ultraviolet Irradiation of Skin Alters the Faecal Microbiome Independently of Vitamin D in Mice

Reduced sunlight exposure has been associated with an increased incidence of Crohn’s disease and ulcerative colitis. The effect of ultraviolet radiation (UVR) on the faecal microbiome and susceptibility to colitis has not been explored. C57Bl/6 female mice were fed three different vitamin D-containing diets for 24 days before half of the mice in each group were UV-irradiated (1 kJ/m²) for each of four days, followed by twice-weekly irradiation of shaved dorsal skin for 35 days. Faecal DNA was extracted and high-throughput sequencing of the 16S RNA gene performed. UV irradiation of skin was associated with a significant change in the beta-diversity of faeces compared to nonirradiated mice, independently of vitamin D. Specifically, members of phylum Firmicutes, including Coprococcus, were enriched, whereas members of phylum Bacteroidetes, such as Bacteroidales, were depleted. Expression of colonic CYP27B1 increased by four-fold and IL1β decreased by five-fold, suggesting a UVR-induced anti-inflammatory effect. UV-irradiated mice, however, were not protected against colitis induced by dextran sodium sulfate (DSS), although distinct faecal microbiome differences were documented post-DSS between UV-irradiated and nonirradiated mice. Thus, skin exposure to UVR alters the faecal microbiome, and further investigations to explore the implications of this in health and disease are warranted.

Toward Understanding the Repeated Occurrence of Associations between Melanin-Based Coloration and Multiple Phenotypes

Melanin is the most widespread pigment in organisms. Melanin-based coloration has been repeatedly observed to be associated with the same traits and in the same direction in different vertebrate and insect species. However, whether any factors that are common to different taxa account for the repeated evolution of melanin-phenotype associations remains unclear. We propose to approach this question from the perspective of convergent and parallel evolution to clarify to what extent different species have evolved the same associations owing to a shared genetic basis and being subjected to similar selective pressures. Our current understanding of the genetic basis of melanin-phenotype associations allows for both convergent and parallel evolution, but this understanding is still limited. Further research is needed to clarify the generality and interdependencies of the different proposed mechanisms (supergenes, pleiotropy based on hormones, or neural crest cells). The general ecological scenarios whereby melanin-based coloration is under selection-protection from ultraviolet radiation, thermoregulation in cold environments, or as a signal of social status-offer a good opportunity to study how melanin-phenotype associations evolve. Reviewing these scenarios shows that some traits associated with melanin-based coloration might be selected together with coloration by also favoring adaptation but that other associated traits might impede adaptation, which may be indicative of genetic constraints. We therefore encourage further research on the relative roles that selection and genetic constraints play in shaping multiple melanin-phenotype associations. Placed into a phylogenetic context, this will help clarify to what extent these associations result from convergent or parallel evolutionary processes and why melanin-phenotype associations are so common across the tree of life.

The role of UVR and vitamin D on T cells and inflammatory bowel disease

Vitamin D deficiency is associated with the development of inflammatory bowel disease (IBD). In experimental IBD the targets of vitamin D that result in protection from IBD include gut epithelial cells, innate immune cells, T cells, and the microbiota. Ultraviolet radiation (UVR) induces production of vitamin D in the skin and suppresses T cell responses in the host. There is limited data demonstrating an effect of UVR on experimental IBD but the mechanisms of UVR suppression in IBD have not been defined. There are several shared effects of vitamin D and UVR on T cells including inhibition of proliferation and suppression of IFN-γ and IL-17 producing T cells. Conversely UVR decreases and vitamin D increases IL-4 production from T cells. Together the data suggest that UVR suppression of T cells and potentially IBD are both vitamin D dependent and independent.

Effect of narrow-band ultraviolet B on the serum of 25-hydroxyvitamin D in vitiligo patients

BACKGROUND

Narrow-band ultraviolet B (NB-UVB) is the gold standard in the treatment of vitiligo. 25-hydroxyvitamin D (25-OH- vitamin D) might play a physiological role in photo-induced melanogenesis in human skin so the association between vitamin D levels and vitiligo still needs to be investigated more thoroughly.

OBJECTIVE

we aim to investigate the influence of cumulative doses of NB-UVB phototherapy on vitamin D in patients with vitiligo and their correlation with NB-UVB-induced pigmentation.

METHODS

Eighty patients of vitiligo and twenty number of age and sex matched controls were recruited in a case-control study. Patients with vitiligo were treated with NB-UVB twice weekly for 24 weeks. 25-hydroxy vitamin D levels were measured at 0, 12, and 24 weeks in the cases and at 0 only in control by enzyme-linked immunosorbent assay (ELISA) and Vitiligo Area Severity Index (VASI) were calculated at 0 (baseline) and 24 weeks.

RESULTS

The mean baseline level of 25-hydroxyvitamin D (at 0 week) was significantly lower in patients than the control group. Levels of 25(OH) vitamin D at 12 and 24 weeks showed significant improvement and Patients show significant reduction in VASI score after 24 weeks of therapy.

CONCLUSIONS

Cumulative doses of NB-UVB therapy improve low vitamin D levels in patients with vitiligo, which might have a significant role in NB-UVB-induced repigmentation and may contribute to its therapeutic efficacy but further studies with larger sample size are needed to prove the complete mechanisms of NB-UVB-induced pigmentations and vitamin D in vitiligo.

Evaluation of galectin-1 and galectin-3 as prospective biomarkers in keratoconus

Aims

To evaluate the expression of β-galactoside-binding proteins galectin (Gal)-1 and Gal-3 in patients with keratoconus (KC) and postcorneal collagen cross-linking (CXL) treatment in vitro.

Methods

Tear fluid, cornea samples and conjunctival impression cytology specimens from control and KC patients were used to evaluate Gal-1 and Gal-3 expressions. Primary keratocytes were isolated by collagenase digestion from surgically removed corneas of five normal or KC human corneal buttons and cultured in Dulbecco’s modified eagle medium/Ham’s F12 medium supplemented with 2% fetal bovine serum. These cells were evaluated under two experimental conditions: control and submitted to the application of ultraviolet A light and riboflavin 0.1% (CXL) for 30 min.

Results

Patients with KC displayed increased levels of Gal-1 and Gal-3 in conjunctival epithelial cells compared with control. Furthermore, KC corneas were associated with intense expression of Gal-1 in the stroma, released by keratocytes. Ultrastructural analysis of keratocytes showed a marked increase of endogenous Gal-3 levels, but not Gal-1, in KC. In vitro, CXL induced significant release of Gal-1 in keratocyte supernatants (116±18 ng/mL, P<0.05) and decreased inflammatory biomarkers as interleukin (IL)-6, IL-8, matrix metalloproteinase (MMP)-2 and MMP-9. Gal-3 levels were not detected in the keratocyte supernatants.

Conclusion

Gal-1 and Gal-3 represent new interesting KC biomarkers as revealed by their different expression patterns in KC and control corneal samples. CXL has an immunosuppressive effect on keratocytes by reducing the release of cytokines and MMPs and increased expression of anti-inflammatory protein Gal-1.

Ultraviolet B Exposure Inhibits Angiotensin II-Induced Abdominal Aortic Aneurysm Formation in Mice by Expanding CD4+Foxp3+ Regulatory T Cells

Background

Pathogenic immune responses are known to play an important role in abdominal aortic aneurysm (AAA) development. Ultraviolet B (UVB) irradiation has been demonstrated to have therapeutic potential not only for cutaneous diseases but also for systemic inflammatory diseases in mice by suppressing immunoinflammatory responses. We investigated the effect of UVB irradiation on experimental AAA.

Methods and Results

We used an angiotensin II–induced AAA model in apolipoprotein E–deficient mice fed a high‐cholesterol diet. Mice aged 10 weeks were irradiated with 5 kJ/m²UVB once weekly for 6 weeks (UVB‐irradiated, n=38; nonirradiated, n=42) and were euthanized for evaluation of AAA formation at 16 weeks. Overall, 93% of angiotensin II–infused mice developed AAA, with 60% mortality possibly because of aneurysm rupture. UVB irradiation significantly decreased the incidence (66%) and mortality (29%) of AAA (P=0.004 and P=0.006, respectively). UVB‐irradiated mice had significantly smaller diameter AAA (P=0.008) and fewer inflammatory cells in the aortic aneurysm tissue than nonirradiated mice, along with systemic expansion of CD4⁺Foxp3⁺ regulatory T cells and decreased effector CD4⁺CD44^highCD62L^low T cells in para‐aortic lymph nodes. Genetic depletion of regulatory T cells abrogated these beneficial effects of UVB treatment, demonstrating a critical role of regulatory T cells.

Conclusions

Our data suggest that UVB‐dependent expansion of regulatory T cells has beneficial effects on experimental AAA and may provide a novel strategy for the treatment of AAA.

In vivo quantification of quantum dot systemic transport in C57BL/6 hairless mice following skin application post-ultraviolet radiation

BACKGROUND

Previous work has demonstrated size, surface charge and skin barrier dependent penetration of nanoparticles into the viable layers of mouse skin. The goal of this work was to characterize the tissue distribution and mechanism of transport of nanoparticles beyond skin, with and without Ultraviolet Radiation (UVR) induced skin barrier disruption. Atomic absorption spectroscopy (AAS), flow cytometry and confocal microscopy were used to examine the effect of UVR dose (180 and 360 mJ/cm² UVB) on the skin penetration and systemic distribution of quantum dot (QD) nanoparticles topically applied at different time-points post UVR using a hairless C57BL/6 mouse model.

RESULTS

Results indicate that QDs can penetrate mouse skin, regardless of UVR exposure, as evidenced by the increased cadmium in the local lymph nodes of all QD treated mice. The average % recovery for all treatment groups was 69.68% with ~66.84% of the applied dose recovered from the skin (both epicutaneous and intracutaneous). An average of 0.024% of the applied dose was recovered from the lymph nodes across various treatment groups. When QDs are applied 4 days post UV irradiation, at the peak of the skin barrier defect and LC migration to the local lymph node, there is an increased cellular presence of QD in the lymph node; however, AAS analysis of local lymph nodes display no difference in cadmium levels due to UVR treatment.

CONCLUSIONS

Our data suggests that Langerhans cells (LCs) can engulf QDs in skin, but transport to the lymph node may occur by both cellular (dendritic and macrophage) and non-cellular mechanisms. It is interesting that these specific nanoparticles were retained in skin similarly regardless of UVR barrier disruption, but the observed skin immune cell interaction with nanoparticles suggest a potential for immunomodulation, which we are currently examining in a murine model of skin allergy.

Dietary proanthocyanidins prevent ultraviolet radiation-induced non-melanoma skin cancer through enhanced repair of damaged DNA-dependent activation of immune sensitivity

Numerous plant products have been used to prevent and manage a wide variety of diseases for centuries. These products are now considered as promising options for the development of more effective and less toxic alternatives to the systems of medicine developed primarily in developed countries in the modern era. Grape seed proanthocyanidins (GSPs) are of great interest due to their anti-carcinogenic effects that have been demonstrated using various tumor models including ultraviolet (UV) radiation-induced non-melanoma skin cancer. In a pre-clinical mouse model supplementation of a control diet (AIN76A) with GSPs at concentrations of 0.2% and 0.5% (w/w) significantly inhibits the growth and multiplicity of UVB radiation-induced skin tumors. In this review, we summarize the evidence that this inhibition of UVB-induced skin tumor development by dietary GSPs is mediated by a multiplicity of coordinated effects including: (i) Promotion of the repair of damaged DNA by nuclear excision repair mechanisms, and (ii) DNA repair-dependent stimulation of the immune system following the functional activation of dendritic cells and effector T cells. Dietary GSPs hold promise for the development of an effective alternative strategy for the prevention of excessive solar UVB radiation exposure-induced skin diseases including the risk of non-melanoma skin cancer in humans.

Influence of a pre-stimulation with chronic low-dose UVB on stress response mechanisms in human skin fibroblasts

Exposure to solar ultraviolet type B (UVB), through the induction of cyclobutane pyrimidine dimer (CPD), is the major risk factor for cutaneous cancer. Cells respond to UV-induced CPD by triggering the DNA damage response (DDR) responsible for signaling DNA repair, programmed cell death and cell cycle arrest. Underlying mechanisms implicated in the DDR have been extensively studied using single acute UVB irradiation. However, little is known concerning the consequences of chronic low-dose of UVB (CLUV) on the DDR. Thus, we have investigated the effect of a CLUV pre-stimulation on the different stress response pathways. We found that CLUV pre-stimulation enhances CPD repair capacity and leads to a cell cycle delay but leave residual unrepaired CPD. We further analyzed the consequence of the CLUV regimen on general gene and protein expression. We found that CLUV treatment influences biological processes related to the response to stress at the transcriptomic and proteomic levels. This overview study represents the first demonstration that human cells respond to chronic UV irradiation by modulating their genotoxic stress response mechanisms.

Crosstalk Among UV-Induced Inflammatory Mediators, DNA Damage and Epigenetic Regulators Facilitates Suppression of the Immune System

The suppression of the immune system by overexposure to ultraviolet (UV) radiation has been implicated in the initiation and progression of photocarcinogenesis. Numerous changes occur in the skin on UVB exposure, including the generation of inflammatory mediators, DNA damage, epigenetic modifications, and migration and functional alterations in the antigen-presenting dendritic cells. Although each of these alterations can elicit a cascade of events that have the potential to modulate immune sensitivity alone, there is emerging evidence that there is considerable crosstalk between these cascades. The development of an understanding of UV-induced changes in the skin that culminate in UV-induced immunosuppression, which has been implicated in the risk of nonmelanoma skin cancer, as a network of events has implications for the development of more effective chemopreventive strategies. In the current review article, we discuss the evidence of interactions between the various molecular targets and signaling mechanisms associated with UV-induced immunosuppression.

UVB Exposure Prevents Atherosclerosis by Regulating Immunoinflammatory Responses

OBJECTIVE

UVB irradiation is an established treatment for immunoinflammatory cutaneous disorders and has been shown to suppress cutaneous and systemic inflammatory diseases through modulation of the adaptive immune response. However, it remains unknown whether UVB irradiation prevents an immunoinflammatory disease of arteries such as atherosclerosis.

APPROACH AND RESULTS

Here, we show that UVB exposure inhibits the development and progression of atherosclerosis in atherosclerosis-prone mice by expanding and enhancing the functional capacity of CD4⁺ forkhead box P3⁺ regulatory T cells and regulating proatherogenic T-cell responses. Experimental studies in Langerhans cell-depleted mice revealed that epidermal Langerhans cells play a critical role in UVB-dependent induction of CD4⁺ forkhead box P3⁺ regulatory T cells, suppression of proatherogenic T-cell responses, and prevention of atherosclerotic plaque development.

CONCLUSIONS

Our findings suggest the skin immune system as a novel therapeutic target for atherosclerosis and provide a novel strategy for the treatment and prevention of atherosclerosis.

Anti-Inflammatory Effects of Aspalathus linearis and Cyclopia spp. Extracts in a UVB/Keratinocyte (HaCaT) Model Utilising Interleukin-1α Accumulation as Biomarker

Ultraviolet B (UVB) radiation is one of the major predisposing risk factors of skin cancer. The anticancer and photoprotective effects of unoxidized rooibos (Aspalathus linearis) and honeybush (Cyclopia) herbal teas, containing high levels of dihydrochalones and xanthones, respectively, have been demonstrated in skin cancer models in vivo. In the current study, the anti-inflammatory effects of methanol and aqueous extracts of these herbal teas were investigated in a UVB/HaCaT keratinocyte model with intracellular interleukin-1α (icIL-1α) accumulation as a biomarker. Extracts of green tea (Camellia sinensis) served as benchmark. Both extracts of green tea and rooibos, as well as the aqueous extract of C. intermedia, enhanced UVB-induced inhibition of cell viability, proliferation and induction of apoptosis, facilitating the removal of icIL-1α. The underlying mechanisms may involve mitochondrial dysfunction exhibiting pro-oxidant responses via polyphenol-iron interactions. The methanol extracts of honeybush, however, protected against UVB-induced reduction of cell growth parameters, presumably via antioxidant mechanisms that prevented the removal of highly inflamed icIL-1α-containing keratinocytes via apoptosis. The dual antioxidant and/or pro-oxidant role of the polyphenolic herbal tea constituents should be considered in developing preventive strategies against UVB-induced skin carcinogenesis. The indirect removal of UVB damaged keratinocytes by herbal tea extracts via apoptosis may find application in the prevention of photo-induced inflammation.

Prevention of ultraviolet radiation‑induced immunosuppression by sunscreen in Candida albicans‑induced delayed‑type hypersensitivity

Ultraviolet (UV) radiation-induced immunosuppression leading to skin cancer has received increased attention in previous years. The present study aimed to investigate the immunoprotection offered by Anthelios sunscreen in a mouse model of Candida albicans-induced delayed-type hypersensitivity. Anthelios sunscreen was applied to the skin on the dorsal skin of BALB/c mice treated with a sub-erythema dose of solar-simulated radiation. Delayed-type hypersensitivity was induced by immunization with Candida albicans. Changes in the skin thickness of the foot pads were measured, and immunosuppression rates were also evaluated. The expression levels of CD207, CD80 and CD86 in the Langerhans cells were semi-quantitatively detected using Western blotting and immunohistochemical assays. The delayed-type hypersensitivity mouse model was successfully established. The minimal erythema doses of UVA and UVB exposure to the mice were 2,000 and 145 mJ/cm², respectively. The immunosuppression rates in the sunscreen group and non-sunscreen group were 24.39 and 65.85%, respectively (P<0.01). The results of the Western blotting and immunohistochemistry showed that the expression levels of CD207 (P<0.01), CD80 (P<0.05) and CD86 (P<0.01) were higher in the sunscreen group, compared with those in the non-sunscreen group. UV exposure reduced Candida albicans antigen-induced delayed-type hypersensitivity. Anthelios sunscreen was found to protect the skin from immunosuppression through the activation of epidermal Langerhans cells.

Exposure to Carbon Ions Triggers Proinflammatory Signals and Changes in Homeostasis and Epidermal Tissue Organization to a Similar Extent as Photons

The increasing application of charged particles in radiotherapy requires a deeper understanding of early and late side effects occurring in skin, which is exposed in all radiation treatments. We measured cellular and molecular changes related to the early inflammatory response of human skin irradiated with carbon ions, in particular cell death induction and changes in differentiation and proliferation of epidermal cells during the first days after exposure. Model systems for human skin from healthy donors of different complexity, i.e., keratinocytes, coculture of skin cells, 3D skin equivalents, and skin explants, were used to investigate the alterations induced by carbon ions (spread-out Bragg peak, dose-averaged LET 100 keV/μm) in comparison to X-ray and UV-B exposure. After exposure to ionizing radiation, in none of the model systems, apoptosis/necrosis was observed. Carbon ions triggered inflammatory signaling and accelerated differentiation of keratinocytes to a similar extent as X-rays at the same doses. High doses of carbon ions were more effective than X-rays in reducing proliferation and inducing abnormal differentiation. In contrast, changes identified following low-dose exposure (≤0.5 Gy) were induced more effectively after X-ray exposure, i.e., enhanced proliferation and change in the polarity of basal cells.

γ-H2AX responds to DNA damage induced by long-term exposure to combined low-dose-rate neutron and γ-ray radiation

Risk estimates for low-dose radiation (LDR) remain controversial. The possible involvement of DNA repair-related genes in long-term low-dose-rate neutron-gamma radiation exposure is poorly understood. In this study, 60 rats were divided into control groups and irradiated groups, which were exposed to low-dose-rate n-γ combined radiation (LDCR) for 15, 30, or 60 days. The effects of different cumulative radiation doses on peripheral blood cell (PBC), subsets of T cells of peripheral blood lymphocytes (PBL) and DNA damage repair were investigated. Real-time PCR and immunoblot analyses were used to detect expression of DNA DSB-repair-related genes involved in the NHEJ pathway, such as Ku70 and Ku80, in PBL. The mRNA level of H2AX and the expression level of γ-H2AX were detected by real-time PCR, immunoblot, and flow cytometry. White blood cells (WBC) and platelets (PLT) of all ionizing radiation (IR) groups decreased significantly, while no difference was seen between the 30 day and 60 day exposure groups. The numbers of CD3(+), CD4(+) T cells and CD4(+)/CD8(+) in the PBL of IR groups were lower than in the control group. In the 30 day and 60 day exposure groups, CD8(+) T cells decreased significantly. Real-time PCR and immunoblot results showed no significant difference in the mRNA and protein expression of Ku70 and Ku80 between the control groups and IR groups. However, the mRNA of H2AX increased significantly, and there was a positive correlation with dose. There was no difference in the protein expression of γ-H2AX between 30 day and 60 day groups, which may help to explain the damage to PBL. In conclusion, PBL damage increased with cumulative dose, suggesting that γ-H2AX, but neither Ku70 nor Ku80, plays an important role in PBL impairment induced by LDCR.

Ultraviolet Radiation on the Skin: A Painful Experience?

Excessive exposure of skin to ultraviolet radiation (UVR) has dramatic clinical effects in humans, and it is a significant public health concern. Discomfort and sensory changes caused by skin sunburn are the main common features experienced by many of us, a phenomena triggered by the combination of long and short wavelengths radiation (UVA and UVB, respectively). Although the biological processes underlying UVR exposure are not fully understood, in the last few years many studies have made significant progress in characterizing sunburn at the cellular and molecular levels, making use of both humans and laboratory animal models. Here we review and reason that UVR can be used as an excellent model of sensitization and inflammation for pain research. UVR, particularly UVB, produces a controllable and sterile inflammation that causes a robust dose‐dependent hypersensitivity with minimal confounding effects. Importantly, we show that UVR animal models precisely recapitulate the sensory, cellular, and molecular changes observed in human skin, giving it great confidence as a translational model. Furthermore, in this article, we give an overview of the pharmacology underlying UVB inflammation, the latest advances in the field, and potential new targets for inflammatory pain.