UVA-induced immunosuppression

Immune Checkpoint Blockade in Advanced Cutaneous Squamous Cell Carcinoma: What Do We Currently Know in 2020?

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer that predominantly arises in chronically sun-damaged skin. Immunosuppression, genetic disorders such as xeroderma pigmentosum (XP), exposure to certain drugs and environmental noxae have been identified as major risk factors. Surgical removal of cSCC is the therapy of choice and mostly curative in early stages. However, a minority of patients develop locally advanced tumors or distant metastases that are still challenging to treat. Immune checkpoint blockade (ICB) targeting CTLA-4, PD-L1 and PD-1 has tremendously changed the field of oncological therapy and especially the treatment of skin cancers as tumors with a high mutational burden. In this review, we focus on the differences between cSCC and cutaneous melanoma (CM) and their implications on therapy, summarize the current evidence on ICB for the treatment of advanced cSCC and discuss the chances and pitfalls of this therapy option for this cancer entity. Furthermore, we focus on special subgroups of interest such as organ transplant recipients, patients with hematologic malignancies, XP and field cancerization.

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.

An Overview of Properties and Analytical Methods for Lycopene in Organic Nanocarriers

Lycopene (LYC), a natural compound responsible for the red color of some fruits like pink grapefruit, red guava, watermelon, papaya and, mainly, present in tomatoes (Solanum lycopersicum). LYC has been extensively studied because of its various pharmacological properties such as antioxidant, cardioprotective, hypocholesterolemic, antineophasic, photoprotection, antidiabetic and antimicrobial activity. However, LYC uses in therapy is limited due to its insolubility in aqueous solvents, resulting in low bioavailability and stability. In order to overcome these drawbacks, it is essential to use of organic nanocarriers for LYC controlled release. Up to now, the description of LYC-loaded organic nanocarriers are scarce, mainly related to organic nanosystems based on lipid nanostructures such as nanoemulsions (NE), liposomes (LP), niosomes (NI), nanostructured lipid carriers (NLC) and solid lipid nanoparticles (SLN). Taking into account the development of new formulations, is indispensable the use of sensitive and suitable analytical methods previously validated. Among the analytical methods described here, high-performance liquid chromatography (HPLC) stands out due to its good accuracy, precision and desirable detection limit. In this review, we highlights the main biological and physicochemical properties of LYC, as well as LYC-based organic nanocarriers for controlled drug delivery and the analytical methods described in literature to determine LYC in any kind of matrix.

In situ antioxidant activity of a dermo-cosmetic product: A randomized controlled clinical study

Ultraviolet light enhances the generation of reactive oxygen species that are responsible for skin photoageing. The aim of this randomized, vehicle- and active-controlled double-blind, intra-individual monocentric study was to evaluate in situ the antioxidant activity of a dermo-cosmetic product in photoaged skin. Twenty healthy volunteers had defined skin areas randomized to receive a topical product containing 3 antioxidants (pre-tocopheryl® , retinaldehyde and glycylglycine ole-amide), its vehicle and a positive antioxidant control cream. The products were applied daily for 30-day period. The skin areas were exposed to a controlled dose of UVA rays, and the skin oxidative status was evaluated 4 and 24 hours post-UVA exposure at D0 (basal value) and after 15 and 30 days of product application. Skin layers were collected by stripping, and antioxidant capacity was measured using the ferric reducing ability of a plasma assay. Lipid peroxidation (LPO) was assessed using the malonyldialdehyde test. The tested product significantly improved the skin antioxidant capacity after 15 and 30 days and significantly decreased the basal level of the skin LPO. The skin LPO level significantly decreased 4 and 24 hours after UVA exposure at 15 and 30 days. These findings were comparable to positive control treated sites and were significantly different from the vehicle and untreated sites. This minimally invasive methodology enabled a quantitative evaluation of potent antioxidant activity in situ in the stratum corneum reflecting real-life skin conditions and confirming the benefits of the topical application of a product containing 3 antioxidants in the prevention of UVA-induced oxidative damage.

Insight into immunocytes infiltrations in polymorphous light eruption

Polymorphous light eruption (PLE) which is one of the most common photodermatoses has been demonstrated to be immune-mediated disorder. Resistance to UV-induced immunosuppression resulting from differential immune cells infiltration and cytokines secretion has been highlighted in the pathogenesis of PLE. In this study, we reviewed differential patterns of immune cells infiltrations and cytokines secretion that may contribute to PLE occurrence and development.

Update on the biology and clinical management of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare but aggressive neuroendocrine cutaneous malignancy, with a predilection for sun-exposed sites in elderly patients. Despite an incidence 30 times less than that of melanoma, its disease-specific mortality is three times higher. Management of MCC remains challenging because of a limited understanding of its molecular biology, lack of prospective clinical trials, and limitations associated with retrospective reviews of therapeutic options. With the recent discovery of an associated human polyomavirus, significant progress has been made in the understanding of the pathogenesis of this malignancy. With this progress, there has been increasing optimism regarding new tools in the therapeutic armamentarium to fight this deadly disease. Here we present an overview on MCC with an emphasis on the most recent biologic discoveries and the rationale for novel targeted and immunotherapies.

ATP-binding cassette transporters protect sea urchin gametes and embryonic cells against the harmful effects of ultraviolet light

Embryos of marine organisms whose development occurs externally are particularly sensitive to ultraviolet (UV) light (bands A and B, respectively, UVA and UVB). ATP-binding cassette (ABC) transporters are the first line of cellular defense against chemical or physical stress. The present work investigated the involvement of ABC transporters on UVA or UVB effects on eggs, spermatozoa, and embryonic cells of the sea urchin Echinometra lucunter. Gametes or embryos were exposed to UVA (3.6-14.4 kJ m(-2)) or UVB (0.112-14.4 kJ m(-2)), and embryonic development was monitored by optical microscopy at different developmental stages in the presence or absence of the ABC-transporter blockers reversin205 (ABCB1 blocker) or MK571 (ABCC1 blocker). E. lucunter eggs, spermatozoa and embryos were resistant to UVA exposure. Resistance to the harmful effects of UVB was strongly associated to ABC transporter activity (embryos > eggs > spermatozoa). ABCB1 or ABCC1 blockage promoted the injurious effects of UVA on spermatozoa. ABCC1 transporter blockage increased UVB-dependent damage in eggs while ABCB1 transporter inhibition increased harmful effects of UVB in embryonic cells. ABC-transporter activity was not, however, affected by UVB exposure. In conclusion, the present study is the first report on the protective role of ABC transporters against harmful effects of UVA and UVB on sea urchin eggs and embryonic cells.

The Merkel cell polyomavirus and its involvement in Merkel cell carcinoma

BACKGROUND

The discovery of the Merkel cell polyomavirus (MCV) in a large number of Merkel cell carcinomas (MCCs) has led to many investigations into its potential role as an oncovirus. Many studies have recently explored the differences between MCCs infected and not infected with MCV.

OBJECTIVE

To review the role of MCV in MCC and its potential to influence diagnosis, prognosis, and treatment.

METHODS AND MATERIALS

An extensive literature search was performed on MCV and its relationship with other polyomaviruses and MCC. The immune system's role in MCC was also investigated.

RESULTS

We included 60 articles regarding MCC and MCV and seven pertinent to general processes involved with MCC and MCV.

CONCLUSION

Merkel cell polyomavirus appears to affect many aspects of MCC. An understanding of this virus may aid in future therapy options and current pathology protocols in diagnosing MCC. The host's immune function appears to affect MCV's ability to cause cellular transformation leading to MCC.

Ultraviolet light and resistance to infectious diseases

Exposure to ultraviolet (UV) radiation, as in sunlight, can modulate immune responses in animals and humans. This immunomodulation can lead to positive health effects especially with respect to certain autoimmune diseases and allergies. However, UV-induced immunomodulation has also been shown to be deleterious. Experimental animal studies have revealed that UV exposure can impair the resistance to many infectious agents, such as bacteria, parasites, viruses, and fungi. Importantly, these effects are not restricted to skin-associated infections, but also concern systemic infections. UV radiation induces a multistep process, locally in the skin as well as systemically, that ultimately leads to immunosuppression. The first event is the absorption of "UV" photons by chromophores, or so-called photoreceptors, such as DNA and urocanic acid (UCA) in the upper cell layers of the skin. Upon absorption of UV radiation, trans-UCA isomerizes to the cis-isomer. Cis-UCA is likely the most important mediator of UV-induced immunosuppression, as this compound has been shown to modulate the induction of contact type hypersensitivity and delayed type hypersensitivity, allograft rejection, and the functions of monocytes and T-lymphocytes as well as natural killer cells. The real consequences of UV-induced immunomodulation on resistance to infectious diseases for humans are not fully known. Risk estimations have been performed through extrapolation of animal data, obtained from infection models, to the human situation. This estimation indicated that UV doses relevant to outdoor exposure can impair the human immune system sufficiently to have effects on resistance to infections, but also indicated that human data are necessary to further quantify and validate this risk estimation. Further information has been obtained from vaccination studies in human volunteers as ethical reasons prohibit studies with infectious agents. Studies in mice and human volunteers on the effects of prior UVB exposure on hepatitis B vaccination responses revealed suppressed cellular and humoral immune responses in mice but not in human volunteers. However, subgroups within the performed human volunteer study made by determination of cytokine polymorphisms or UVB-induced mediators, revealed that some individuals have suppressed hepatitis B vaccination responses after UVB exposure. Thus, it might be concluded that the human immune system can be affected by UVB exposure, and decreased resistance to infectious diseases can be expected after sun exposure.

Immunobiology of Merkel cell carcinoma: implications for immunotherapy of a polyomavirus-associated cancer

Merkel cell carcinoma (MCC) is an aggressive skin malignancy with a high mortality rate and an increasing incidence. The recent discovery of Merkel cell polyomavirus has revolutionized our understanding of MCC pathogenesis. Viral oncoproteins appear to play a critical role in tumor progression and are expressed in the majority of MCC tumors. Virus-specific humoral and cellular immune responses are detectable in MCC patients and are linked to the natural history of the disease. Despite persistent expression of immunogenic viral proteins, however, MCC tumors are able to evade the immune system. Understanding of the mechanisms of immune evasion employed by MCC tumors is rapidly increasing and offers opportunities for development of rational immune therapies to improve patient outcomes. Here we review recent discoveries in MCC with a special focus on the pathogenic role of Merkel cell polyomavirus and the immunobiology of this virus-associated disease.

Protein kinases and transcription factors activation in response to UV-radiation of skin: implications for carcinogenesis

Solar ultraviolet (UV) radiation is an important environmental factor that leads to immune suppression, inflammation, photoaging, and skin carcinogenesis. Here, we reviewed the specific signal transduction pathways and transcription factors involved in the cellular response to UV-irradiation. Increasing experimental data supporting a role for p38, MAPK, JNK, ERK1/2, and ATM kinases in the response network to UV exposure is discussed. We also reviewed the participation of NF-κB, AP-1, and NRF2 transcription factors in the control of gene expression after UV-irradiation. In addition, we discussed the promising chemotherapeutic intervention of transcription factors signaling by natural compounds. Finally, we focused on the review of data emerging from the use of DNA microarray technology to determine changes in global gene expression in keratinocytes and melanocytes in response to UV treatment. Efforts to obtain a comprehensive portrait of the transcriptional events regulating photodamage of intact human epidermis after UV exposure reveals the existence of novel factors participating in UV-induced cell death. Progress in understanding the multitude of mechanisms induced by UV-irradiation could lead to the potential use of protein kinases and novel proteins as specific targets for the prevention and control of skin cancer.

In vivo UVA irradiation of mouse is more efficient in promoting pulmonary melanoma metastasis than in vitro

BACKGROUND

We have previously shown in vitro that UVA increases the adhesiveness of mouse B16-F1 melanoma cells to endothelium.We have also shown in vivo that UVA exposure of C57BL/6 mice, i.v. injected with B16-F1 cells, increases formation of pulmonary colonies of melanoma. The aim of the present animal study was to confirm the previously observed in vivo UVA effect and to determine whether in vitro UVA-exposure of melanoma cells, prior the i.v. injection, will have an enhancing effect on the pulmonary colonization capacity of melanoma cells. As a second aim, UVA-derived immunosuppression was determined.

METHODS

Mice were i.v. injected with B16-F1 cells into the tail vein and then immediately exposed to UVA. Alternatively, to study the effect of UVA-induced adhesiveness on the colonization capacity of B16-F1 melanoma, cells were in vitro exposed prior to i.v. injection. Fourteen days after injection, lungs were collected and the number of pulmonary nodules was determined under dissecting microscope. The UVA-derived immunosuppression was measured by standard contact hypersensitivity assay.

RESULTS AND DISCUSSION

Obtained results have confirmed that mice, i.v. injected with B16-F1 cells and thereafter exposed to UVA, developed 4-times more of melanoma colonies in lungs as compared with the UVA non-exposed group (p < 0.01). The in vitro exposure of melanoma cells prior to their injection into mice, led only to induction of 1.5-times more of pulmonary tumor nodules, being however a statistically non-significant change. The obtained results postulate that the UVA-induced changes in the adhesive properties of melanoma cells do not alone account for the 4-fold increase in the pulmonary tumor formation. Instead, it suggests that some systemic effect in a mouse might be responsible for the increased metastasis formation. Indeed, UVA was found to induce moderate systemic immunosuppression, which effect might contribute to the UVA-induced melanoma metastasis in mice lungs.

Modes of action of diclofenac 3%/hyaluronic acid 2.5% in the treatment of actinic keratosis

BACKGROUND

The efficacy of topically applied diclofenac 3 % in combination with hyaluronic acid 2.5 % in the treatment of actinic keratoses (AKs) has been demonstrated in several clinical studies, but the exact mode of action is still unclear. This study evaluates the potential molecular and cellular main modes of action of topically applied diclofenac in the treatment of AKs.

PATIENTS AND METHODS

In this prospective study 20 male patients with AKs were treated for 90 days with topically applied diclofenac 3 %/hyaluronic acid 2.5 %. Before and after treatment, skin biopsies were taken from the treatment area and were investigated histologically and immunohistochemically as well as compared to healthy skin. For this purpose, markers for inflammation (COX-2, CD3, CD8), apoptosis (p53), cell cycle arrest (p53, p21), proliferation (Ki67), and angiogenesis (CD31) were examined.

RESULTS

The immunohistochemical analysis demonstrated a significant decrease in expression of COX-2, CD3 and CD8. Furthermore, there was a clear reduction of CD31 expression as a marker for angiogenetic processes. Additionally, there was a tendency toward a reduction in markers for proliferation and apoptosis.

CONCLUSIONS

The efficacy of diclofenac 3 %/hyaluronic acid 2.5 % in the treatment of AKs is probably due to anti-inflammatory and anti-angiogenic effects, potentially associated with anti-proliferative and apoptosis-inducing underlying mechanisms.

The use of some nanoemulsions based on aqueous propolis and lycopene extract in the skin's protective mechanisms against UVA radiation

BACKGROUND

The use of natural products based on aqueous extract of propolis and lycopene in the skin's protective mechanisms against UVA radiation was evaluated by means of experimental acute inflammation on rat paw edema. The aim of the present study was to evaluate the harmlessness of propolis - lycopene system through evaluation of skin level changes and anti-inflammatory action. The regenerative and protective effect of the aqueous propolis and lycopene extract is based on its richness in biologically active substances such as: tocopherols, flavonoids, amino acids, polyunsaturated fatty acids, the chlorophyll pigment, all substances with strong antioxidant activity, that modify the oxidative stress, mainly by reducing the prooxidant processes and enhancing the antioxidant ones. These substances participate in the synthesis of prostaglandins and phospholipids components of cell membrane thus enhancing skin protection mechanisms.

RESULTS

The experimental systems offered a sustained release of the drug, in vitro, for aim eight hours. The prepared formulations aim did not reveal a deteriorating effect on tissues. They proved a better therapeutic efficiency Compared to standard suspension, they provided a better therapeutic efficiency coupled with extended time interval of tested parameters (24 hours). Preliminary examination of tissues showed that the experimental formulations did not irritate. Local application of propolis and lycopene aqueous extract nanoemulsion has a high potential both regarding its efficiency (the analgesic effect) and therapeutic safety.

CONCLUSIONS

This study demonstrates that propolis and lycopene extract nanoemulsions, preparations contains active substances, can confer better therapeutic effects than those of the conventional formulations, based on local control-release of dozed form, for a longer period of time, which probably improve its efficiency and skin acceptance, meaning a better compliance. The information obtained in the present study suggests that administration of propolis and lycopene aqueous extract nanoemulsion is safe. The preparation can be useful for further preclinical studies lycopene embedded in aqueous propolis extract to be used in pharmaceuticals (targeted medical therapy).

Role of nicotinamide in DNA damage, mutagenesis, and DNA repair

Nicotinamide is a water-soluble amide form of niacin (nicotinic acid or vitamin B3). Both niacin and nicotinamide are widely available in plant and animal foods, and niacin can also be endogenously synthesized in the liver from dietary tryptophan. Nicotinamide is also commercially available in vitamin supplements and in a range of cosmetic, hair, and skin preparations. Nicotinamide is the primary precursor of nicotinamide adenine dinucleotide (NAD⁺), an essential coenzyme in ATP production and the sole substrate of the nuclear enzyme poly-ADP-ribose polymerase-1 (PARP-1). Numerous in vitro and in vivo studies have clearly shown that PARP-1 and NAD⁺ status influence cellular responses to genotoxicity which can lead to mutagenesis and cancer formation. This paper will examine the role of nicotinamide in the protection from carcinogenesis, DNA repair, and maintenance of genomic stability.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Macrophage inhibitory cytokine MIC-1 is upregulated by short-wavelength light in cultured normal human dermal fibroblasts

To better understand dermal response to visible light, we used DNA microarray analysis to search genes induced by blue or near-UV light in normal human dermal fibroblasts. Of about 12800 transcripts analyzed, near-UV light most prominently upregulated the transcript level of Mic-1, a gene encoding a TGF-beta superfamily protein. Quantitative RT-PCR and immunoblot analyses revealed that mRNA and protein levels of Mic-1 were upregulated by both short-wavelength light but not by green or red light. These results suggest that the human dermis is a site for macrophage inhibitory cytokine-1 (MIC-1) production and that visible light activates a dermal transcription cascade. Considering the role of MIC-1 in immune regulation and appetite control, photic MIC-1 regulation is of physiological importance.

Recent advances in urocanic acid photochemistry, photobiology and photoimmunology

Urocanic acid (UCA), produced in the upper layers of mammalian skin, is a major absorber of ultraviolet radiation (UVR). Originally thought to be a 'natural sunscreen', studies conducted a quarter of a century ago proposed that UCA may be a chromophore for the immunosuppression that follows exposure to UVR. With its intriguing photochemistry, its role in immunosuppression and skin cancer development, and skin barrier function, UCA continues to be the subject of intense research effort. This review summarises the photochemical, photobiological and photoimmunological findings regarding UCA, published since 1998.

Inactivation of glutathione peroxidase activity contributes to UV-induced squamous cell carcinoma formation

Cutaneous squamous cell carcinomas (CSCC) are a common malignancy of keratinocytes that arise in sites of the skin exposed to excessive UV radiation. In the present study, we show that human SCC cell lines, preneoplastic solar keratoses (SK), and CSCC are associated with perturbations in glutathione peroxidase (GPX) activity and peroxide levels. Specifically, we found that two of three SKs and four of five CSCCs, in vivo, were associated with decreased GPX activity and all SKs and CSCCs were associated with an elevated peroxide burden. Given the association of decreased GPX activity with CSCC, we examined the basis for the GPX deficiency in the CSCCs. Our data indicated that GPX was inactivated by a post-translational mechanism and that GPX could be inactivated by increases in intracellular peroxide levels. We next tested whether the decreased peroxidase activity coupled with an elevated peroxidative burden might contribute to CSCC formation in vivo. This was tested in Gpx1(-/-) and Gpx2(-/-) mice exposed to solar-simulated UV radiation. These studies showed that Gpx2 deficiency predisposed mice to UV-induced CSCC formation. These results suggest that inactivation of GPX2 in human skin may be an early event in UV-induced SCC formation.

Sun exposure and malignant lymphoma: A population-based case–control study in Germany

Although some causes for malignant lymphoma are known their etiology is not well understood so far. We analyze the relationship between sun exposure and malignant lymphoma in a multicenter, population-based case-control study. Patients with malignant lymphoma (n = 710, 18-80 years) were prospectively recruited in 6 study regions in Germany. For each case, a gender, region and age-matched control was drawn from population-registers. In personal interviews, lifetime holidays spent in sunny climate, outdoor leisure activities and sunbed or sunlamp use were recorded. On basis of job task-specific supplementary questionnaires, an occupational physician assessed the cumulative working time outside. Odds ratios (OR) and 95%-confidence-intervals (CI) were calculated using conditional logistic regression analysis, adjusted for smoking and alcohol consumption. To increase statistical power, patients with specific lymphoma subentities were additionally compared with the entire control group using unconditional logistic regression. We observed a reduced overall lymphoma risk among subjects having spent vacations at sunny climates or frequently used sunbeds or sunlamps. The analysis of lymphoma subentities revealed similar results with the exception of T-NHL and follicular lymphoma which were positively associated with outdoor leisure activities. While cumulative working time outside appeared unrelated to NHL overall and most subentities, it was negatively associated with follicular lymphoma and weakly positively to HL. This data suggest that exposure to natural and artificial ultraviolet radiation may reduce the OR for lymphoma in this study population.

No adaptation to UV-induced immunosuppression and DNA damage following exposure of mice to chronic UV-exposure

It is well known that ultraviolet (UV) radiation induces erythema, immunosuppression and carcinogenesis. We hypothesized that chronic exposure to solar UV radiation induces adaptation that eventually prevents the suppression of acquired immunity. We studied adaptation for UV-induced immunosuppression after chronic exposure of mice to a suberythemal dose of solar simulated radiation (SSR) with Cleo Natural lamps, and subsequent exposure to an immunosuppressive dose of solar or UVB radiation (TL12). After UV dosing, the mice were sensitized and challenged with either diphenylcyclopropenone (DPCP) or picryl chloride (PCl). To assess the adaptation induced by solar simulated radiation, we measured the proliferative response and cytokine production of skin-draining lymph node cells after immunization to DPCP, the contact hypersensitivity (CHS) response to PCl, and thymine-thymine (T-T) cyclobutane dimers in the skin of mice. After induction of immunosuppression by SSR or by TL12 lamps, the proliferative response of draining lymph node cells after challenge with DPCP, or the CHS after challenge with PCl, showed significant suppression of the immune response. Chronic irradiation from SSR preceding the immunosuppressive dose of UV failed to restore the suppressed immune response. Reduced lipopolysaccharide-triggered cytokine production (of IL-12p40, IFN-gamma, IL-6 and TNF-alpha) by draining lymph node cells of mice sensitized and challenged with DPCP indicated that no adaptation is induced. In addition, the mice were not protected from T-T dimer DNA damage after chronic solar irradiation. Our studies reveal no evidence that chronic exposure to low doses of SSR induces adaptation to UV-induced suppression of acquired immunity.

UVR, vitamin D and three autoimmune diseases--multiple sclerosis, type 1 diabetes, rheumatoid arthritis

We review the evidence indicating a possible beneficial role for UVR on three Th1-mediated autoimmune diseases: multiple sclerosis, type 1 diabetes and rheumatoid arthritis in relation to recent developments in photoimmunology. Recent work suggests that UVR exposure may be one factor that can attenuate the autoimmune activity leading to these three diseases through several pathways involving UVB and UVA irradiation, UVR-derived vitamin D synthesis and other routes such as alpha-melanocyte-stimulating hormone, calcitonin gene related peptide and melatonin. Ecological features, particularly a gradient of increasing prevalence of multiple sclerosis and type 1 diabetes with higher latitude, provide some support for a beneficial role of UVR. Analytical studies provide additional support, particularly as low vitamin D has been prospectively associated with disease onset for all three diseases, but are not definitive. Randomized controlled trial data are required. Further, we discuss how associated genetic studies may assist the accumulation of evidence with regard to the possible causal role of low UVR exposure and/or low vitamin D status in the development of these diseases.

Considering the potential benefits as well as adverse effects of sun exposure: can all the potential benefits be provided by oral vitamin D supplementation?

Exposure to ultraviolet radiation (UVR) is associated with both adverse and beneficial health effects. While many of the adverse effects of excessive exposure are well known, the adverse effects of insufficient UVR exposure are less clear-cut, but may include a heightened risk of several cancers and autoimmune disorders as well as of bone diseases such as rickets, osteomalacia and osteoporosis. Although some of the postulated beneficial effects of UVR exposure may occur through the maintenance of adequate levels of vitamin D, it is not clear that this can account for all of these effects. We briefly review the epidemiological literature with respect to vitamin D, UVR exposure and autoimmune diseases. We further outline alternative pathways, whereby UVR could alter the risk of development of some cancers and autoimmune disorders, independent of effects on vitamin D synthesis. Recognition of the beneficial effects of UVR exposure has led to a reconsideration of sun avoidance policies. It is important to recognize that all of the beneficial effects of UVR exposure may not occur only through UVR-induced vitamin D synthesis. Thus maintaining current sun avoidance policies while supplementing food with vitamin D may not be sufficient to avoid the risks of insufficient exposure to UVR.

Ultraviolet A exposure might increase metastasis of mouse melanoma: a pilot study

BACKGROUND

The major sources of long-wave ultraviolet A radiation (UVA; 320-400 nm) exposure are extensive sunbathing and tanning in solaria. While the carcinogenic effects of mid-wave ultraviolet B radiation (UVB; 280-320 nm) are well recognized, the potentially hazardous effects of UVA are less understood. Several studies have shown that a variety of physiological processes in the cell are modified by UVA exposure, some of which might be involved in the regulation of tumor metastasis. In this study we suggest that UVA radiation could lead to the increase of metastatic capability of melanoma cells in mice.

METHOD/RESULT

A pilot in vivo study was executed using C57BL/6 mice and syngeneic B16 melanoma cell lines. Mice were intravenously (i.v.) injected with either B16-F1 or B16-F10 melanoma cells into the tail vein and then immediately exposed to UVA. Fourteen days after melanoma injection, lungs were collected and the quantity and quality of metastases were determined under a dissecting microscope. As an outcome of the pilot study we observed that i.v. injected melanoma cells formed more lung metastases in the UVA-exposed mice in comparison with the control mice.

CONCLUSION

This result suggests that the UVA exposure of mice, with melanoma cells present in blood circulation, increases the formation of melanoma metastases in lungs. Further studies should determine whether a similar pro-metastatic effect, as observed in mice, could occur in humans and whether other than melanoma tumors might be susceptible.

UVA Radiation Impairs Phenotypic and Functional Maturation of Human Dermal Dendritic Cells

There is now strong evidence that the ultraviolet A (UVA) part of the solar spectrum contributes to the development of skin cancers. Its effect on the skin immune system, however, has not been fully investigated. Here, we analyzed the effects of UVA radiation on dermal dendritic cells (DDC), which, in addition, provided further characterization of these cells. Dermal sheets were obtained from normal human skin and irradiated, or not, with UVA at 2 or 12 J per cm2. After a 2 d incubation, the phenotype of emigrant cells was analyzed by double immunostaining and flow cytometry. Results showed that migratory DDC were best characterized by CD1c expression and that only few cells co-expressed the Langerhans cell marker Langerin. Whereas the DC extracted from the dermis displayed an immature phenotype, emigrant DDC showed increased expression of HLA-DR and acquired co-stimulation and maturation markers. We showed here that UVA significantly decreased the number of viable emigrant DDC, a process related to increased apoptosis. Furthermore, UVA irradiation impaired the phenotypic and functional maturation of migrating DDC into potent antigen-presenting cells, in a concentration-dependent manner. The results provide further evidence that UVA are immunosuppressive and suggest an additional mechanism by which solar radiation impairs immune response.

Gene expression profiles of TNF-alpha, TACE, furin, IL-1beta and matrilysin in UVA- and UVB-irradiated HaCat cells

BACKGROUND/PURPOSE

It is known that solar ultraviolet (UV) irradiation exerts multiple effects on mammalian skin tissues, one of which is the induction of local and systemic immunosuppression as well as inflammation. Tumor necrosis factor-alpha (TNF-alpha) and other cytokines are suggested to play a role in these responses. Quantitative real-time polymerase chain reaction (TaqMan RTPCR) was used to elucidate the effect of UVA and UVB irradiation on the expression of genes coding for TNF-alpha, IL-1beta, IL-10, FasL, matrilysin, TACE and furin in HaCaT cells over a 48 h period (IL-1beta, interleukin-1beta; FasL, Fas ligand).

METHODS

Cultured HaCaT cells were either sham irradiated (control) or exposed to UVA (2000 and 8000 J/m2) or UVB (200 and 2000 J/m2) radiation. RNA was extracted from cells at 0, 4, 8, 12, 16, 24, 48 h post-irradiation and reverse transcribed to generate cDNA for subsequent real-time PCR amplification.

RESULTS

Significant increases in the mRNA levels for all genes tested were detected in both UVA- and UVB-irradiated HaCaT cells compared with control (sham-irradiated) cells. TNF-alpha mRNA levels were immediately up-regulated (0 h) after irradiation, with maximal induction at 8 h post 2000 J/m2 UVA and 200 J/m2 UVB irradiation, at 4 h post 8000 J UVA irradiation and at 48 h post 2000 J/m2 UVB irradiation. No correlation was observed between TNF-alpha, TACE and furin mRNA induction in the different irradiated cohorts.

CONCLUSION

Results suggest that time-distinct gene induction of TNF-alpha, furin, IL-1beta and matrilysin may be involved in UV-induced cellular responses, but not for TACE. In general, mRNA induction was dose dependent at some time points post-irradiation, but not throughout the whole time course tested. Our results show that quantitative real-time PCR is a useful tool in the analysis of quantitative changes of mRNA levels in cultured HaCaT cells after UV exposure.

Cutaneous photodamage, oxidative stress, and topical antioxidant protection

New methods to protect skin from photodamage from sun exposure are necessary if we are to conquer skin cancer and photoaging. Sunscreens are useful, but their protection is not ideal because of inadequate use, incomplete spectral protection, and toxicity. Skin naturally uses antioxidants (AOs) to protect itself from photodamage. This scientific review summarizes what is known about how photodamage occurs; why sunscreens--the current gold standard of photoprotection--are inadequate; and how topical AOs help protect against skin cancer and photoaging changes. This review is intended to be a reference source, including pertinent comprehensive reviews whenever available. Although not all AOs are included, an attempt has been made to select those AOs for which sufficient information is available to document their potential topical uses and benefits. Reviewed are the following physiologic and plant AOs: vitamin C, vitamin E, selenium, zinc, silymarin, soy isoflavones, and tea polyphenols. Their topical use may favorably supplement sunscreen protection and provide additional anticarcinogenic protection. (J Am Acad Dermatol 2003;48:1-19.)

LEARNING OBJECTIVE

At the completion of this learning activity, participants should have an understanding of current information about how the sun damages skin to produce skin cancer and photoaging changes, how the skin naturally protects itself from the sun, the shortcomings of sunscreens, and the added advantages of topical AOs for photoprotection.

Ultraviolet a irradiation of C57BL/6 mice suppresses systemic contact hypersensitivity or enhances secondary immunity depending on dose

Ultraviolet radiation is the most common environmental carcinogen humans are exposed to. It is now known that in order for skin cancers to develop, both genetic damage and immunosuppression is required. Ultraviolet-induced immunosuppression is therefore a key contributor to the development of skin cancer. Little is known about the relative contributions of the different ultraviolet spectra (A and B), however. Therefore detailed ultraviolet dose-response curves for systemic suppression of contact hypersensitivity in two mouse strains were determined to examine the relative contributions of each of these spectral components of sunlight to primary and secondary immunity. Whereas ultraviolet B caused a linear dose-related immunosuppression in both C57BL/6 and Balb/c mice, only C57BL/6 mice were immunosuppressed by medium doses of ultraviolet A. At higher ultraviolet A doses, C57BL/6 mice were protected from immunosuppression, suggesting a genetic predisposition to ultraviolet-A-induced immunomodulation. Surprisingly, we found that, in contrast to primary immunosuppression, low dose ultraviolet A enhanced the secondary immune response, whereas ultraviolet B caused antigen-specific tolerance. When ultraviolet A and ultraviolet B were combined to mimic sunlight (solar-simulated ultraviolet), immunosuppression and tolerance were only observed over a narrow dose range as the memory-enhancing effect of low dose ultraviolet A and the immunoprotective effect of higher dose ultraviolet A prevented the suppressive effects of ultraviolet B. These studies suggest that complex relationships between ultraviolet dose, immunomodulation, spectra, and genetic background are likely to be important for skin cancer induction. We also describe for the first time that low doses of ultraviolet A are able to enhance secondary immunity, which has important implications for vaccination strategies.

Photosensitized growth inhibition of cultured human skin cells: mechanism and suppression of oxidative stress from solar irradiation of glycated proteins

Chronic exposure to sunlight plays a role in skin aging and carcinogenesis. The molecular mechanisms of photodamage by ultraviolet A, the sunlight's major ultraviolet constituent, are poorly understood. Here we provide evidence that advanced glycation end products on proteins are sensitizers of photo-oxidative stress in skin cells. Glycation is a process of protein damage by reducing sugars and other reactive carbonyl species leading to the formation of advanced glycation end products, which accumulate on long-lived proteins such as dermal elastin and collagen during skin aging. Growth inhibition as a result of advanced glycation end product photosensitization of ultraviolet A and solar-simulated light was demonstrated in human keratinocytes and fibroblasts. Using advanced glycation end product bovine serum albumin and advanced glycation end product collagen as model photosensitizers, ultraviolet A-induced formation of H2O2 was identified as the key mediator of skin cell growth inhibition as evidenced by complete protection by catalase treatment and equivalent growth inhibition of unirradiated cells treated with pre-irradiated advanced glycation end product protein. D-penicillamine protected against advanced glycation end product-photosensitized growth inhibition even when added following irradiation, suggesting the feasibility of therapeutic approaches for protection against skin ultraviolet A damage. Photosensitized growth inhibition increased with the degree of advanced glycation end product modification paralleled by the amount of H2O2 formed upon solar-simulated light irradiation of the protein. Photosensitization was not observed using bovine serum albumin modified with the major advanced glycation end product, Nepsilon-carboxymethyl-L-lysine, ruling out effects of cellular advanced glycation end product receptor (RAGE) stimulation. In contrast to bovine serum albumin, unglycated collagen showed photosensitization in CF3 fibroblasts and generation of H2O2 upon solar-simulated light irradiation. This study supports the hypothesis that advanced glycation end product-modified proteins are endogenous sensitizers of photo-oxidative cell damage in human skin by ultraviolet A-induced generation of reactive oxygen species contributing to photoaging and photocarcinogenesis.

Change of ultraviolet absorbance of sunscreens by exposure to solar-simulated radiation

Regarding the outdoor behavior of the Caucasian population, modern sunscreens should provide high and broad-spectrum ultraviolet protection in the ultraviolet B as well as in the ultraviolet A range and should be photochemically stable for ultraviolet doses, which can be expected in solar radiation. At present an assessment of the photostability of suncare products is not a general requirement before marketing. In order to evaluate the photostability of suncare products we conducted an in vitro test and measured the spectral absorbance of 16 sunscreens before, and after exposure to increasing biologically weighted standard erythema doses (5, 12.5, 25, 50) of solar-simulated radiation. Seven of 16 suncare products showed a significant dose- and wavelength-dependent decrease of the ultraviolet A protective capacity, whereas the ability to absorb ultraviolet B was not affected. In the ultraviolet A range, the decrease of absorbance (photoinactivation), respectively, the increase of transmission was 12-48% for an ultraviolet exposure of 25 standard erythema dose. Photoinactivation started in the wavelength range between 320 and 335 nm with a maximum above 350 nm. Furthermore, our analysis showed that the behavior of suncare products was not predictable from its individual ingredients. Neither complex combinations of organic filters nor addition of inorganic filters could absolutely prevent photoinactivation. The inclusion of a single photounstable filter did not mean photoinstability of the complete suncare product. Photoinactivation of sunscreens appears to be an underestimated hazard to the skin, first, by formation of free radicals, second, by increased ultraviolet A transmission.

Contrasting effects of an ultraviolet B and an ultraviolet A tanning lamp on interleukin-6, tumour necrosis factor-alpha and intercellular adhesion molecule-1 expression

BACKGROUND

Recent studies have demonstrated that a tanning lamp emitting predominantly ultraviolet (UV) A induces significant yields of the type of potentially mutagenic DNA damage that are associated with the onset of skin cancer (i.e. cyclobutane pyrimidine dimers). UV-induced immunosuppression is also an important event leading to skin cancer.

OBJECTIVES

To the modulation of key immunological molecules following exposure to a broad-spectrum UVB lamp and a predominantly UVA-emitting tanning lamp using model in vitro systems.

METHODS

We compared secretion and mRNA expression of interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha in normal human epidermal keratinocytes, and interferon (IFN)-gamma-induced intracellular adhesion molecule (ICAM)-1 in normal human fibroblasts irradiated in vitro with a broad-spectrum UVB lamp or with a Philips 'Performance' tanning lamp.

RESULTS

With broad-spectrum UVB irradiation, upregulation of IL-6 and TNF-alpha mRNA was detected 6 h after irradiation, and a dose-dependent increase of cytokines in the supernatants of irradiated cells was found 24 h after irradiation. In contrast, there was no cytokine secretion and little evidence for mRNA upregulation following exposure to a tanning lamp. When cells were exposed first to broad-spectrum UVB, then the tanning lamp, UVB-induced cytokine secretion was inhibited, although mRNA levels were upregulated to a level close to that observed with UVB alone. By using a Schott WG 320 nm filter to attenuate the level of UVB relative to UVA emitted by the tanning lamp, the inhibition of cytokine secretion was shown to be associated with UVA exposure. Both UV sources inhibited IFN-gamma-induced ICAM-1 mRNA expression in a dose-dependent fashion. By using a Schott WG 335 nm filter, inhibition of ICAM-1 mRNA expression by the tanning lamp was shown to be associated with UVB exposure.

CONCLUSIONS

These results suggest that UV sources emitting different levels of UVA and UVB have differential effects on the modulation of different immunoregulatory molecules, and indicate that there are potential interactions between these wavelengths.

UVA exposure affects UVB and cis-urocanic acid-induced systemic suppression of immune responses in Listeria monocytogenes-infected Balb/c mice

Ultraviolet radiation can inhibit immune responses locally as well as systemically. Such effects have been measured in animals and humans exposed to ultraviolet B (wavelength 280-315 nm) (UVB) and ultraviolet A (315-400 nm) (UVA). The precise wavelength dependence is important for the identification of possible molecular targets and for assessments of risk of different artificial UV sources and solar UV. In such analyses, it is commonly assumed that radiation energy from each wavelength contributes to the effect independent of the other wavelengths. Here we show that this assumption does not hold good. In the present study, it was investigated whether exposure to broadband UVA or longwave ultraviolet A 1 (340-400 nm) (UVA 1) prior to the standard immunosuppressive UVB protocol might modulate the immunosuppressive effects induced by UVB. Preexposure to broadband UVA or longwave UVA 1, 1 day prior to the standard immunosuppressive UVB protocol, inhibited the UVB-induced suppression of delayed type hypersensitivity (DTH) to Listeria monocytogenes significantly. This effect was not associated with restoring the number of interleukin (IL-12)-positive cells in the spleen. Since isomerization of trans-urocanic acid (UCA) into the immunosuppressive cis-UCA isomer plays a crucial role in UVB-induced immunomodulation, in a second set of experiments it was investigated whether immunosuppression induced by cis-UCA might also be downregulated by preexposure to UVA. Animals were exposed to broad-band UVA or longwave UVA 1 prior to application of an immunosuppressive dose of cis- or trans-UCA as a control. Both UVA and UVA 1 appear to inhibit the cis-UCA-induced systemic immunosuppression (DTH and IL-12) to L. monocytogenes. These studies clearly show that UVA radiation modulates both UVB and cis-UCA-induced immunomodulation. In general, our studies indicate that both broadband UVA and longwave UVA 1 could induce modulation of UVB and cis-UCA-induced immunomodulation. As sunlight contains both UVA and UVB radiation the balance between these two radiations apparently determines the net immunomodulatory effect.

Comparative effects of UVA and UVB irradiation on the immune system of fish

Aquatic organisms can be harmed by the current levels of solar ultraviolet radiation. We have recently shown that exposure of fish to UVB irradiation alters the functioning of the fish immune system, but the effects of UVA radiation are unknown. The present study continues this work by characterizing UVA irradiation-induced immunological changes in fish. Roach, a cyprinid fish, were exposed to a single dose of either UVA (3.6 J/cm2) or UVB (0.5 J/cm2) irradiation. Both irradiations suppressed transiently mitogen-stimulated proliferation of blood lymphocytes. UVA, but not UVB, decreased hematocrit, plasma protein, and plasma immunoglobulin levels and increased the proportions of blood cells classified as unidentified leukocytes, possibly consisting of UVA-damaged lymphocytes. UVB, but not UVA, altered the functioning of head kidney and blood phagocytes, induced granulocytosis and lymphocytopenia in the blood and increased plasma cortisol concentration. These results imply that both UVA and UVB are potent modulators of the immune defence of fish.

Can Langerhans cell UV injury and dendritic cell infection by immunosuppressive viruses induce immunologic tolerance? First part

Though it has not been described by the HIV1-AIDS consensual thinkers, we propose the thesis according to which some immunocyte populations or their interactions can achieve tolerance or split immunologic tolerance in patients suffering from this disease. The proposed concept is based on data registered: 1) after Langerhans cell local injury by UV irradiation in their physiologic localisations, the skin and mucosae: and 2) after systemic infections of dendritic cells by immunosuppressive viruses, including some animal retroviruses, measles, lymphocytic choriomeningitis viruses, and HIV1. We can describe both types or manifestations concerning local UV injury and systemic viral infection combined in an AIDS patient, who received a PUVA irradiation before and at the beginning of his virostatic treatment, which he has now successfully received for eight years. The conditions of this patient differ from those of non-UV victim patients of the cohort to which he belongs, for two reasons: 1) the numbers of both his CD4+ and his suppressor T cells have been reduced to near 0 after UV irradiation; and b) his viral load, which has been exponentially reduced, has not reached, after eight years, the asymptotic part of the VL curve, characterized by PCR non-assessable viral load, which the non-UV victims of the cohort have reached. We wonder if, in this patient, there do not coexist two sorts of immunologic phenomena: 1) one bound to CTL, the numbers of which are increased, whose cytotoxicity is added to the virostatic action; and 2) one bound to the virus attack restriction by an immunologic tolerance. Contrary to the cohort controls, in whom an allogenic skin graft was only accepted for 20 days, the graft of the same donor has been tolerated in the UV victim patient for 70 days. This patient will be discussed in the second part of this editorial: the first part is devoted to the description of several conditions in which Langerhans cell injury by UV, or dendritic cell infections by measles, lymphocytic choriomeningitis viruses or animal retroviruses are followed, not only by immunodepression manifestations, but by immunologic tolerance.