Role Of Ultraviolet Radiation Research Articles

Finding the optimal dose for psoriasis ultraviolet radiation therapy through multi-objective evolutionary optimization on a skin model

Ultraviolet radiation (UVR) is proven to be an effective treatment for psoriasis yet it needs to be carefully controlled since it is a widely known carcinogen. Due to the time-consuming, expensive and hazardous nature of clinical tests on actual patients, the range of possible values for the optimal regimen set has not yet been thoroughly explored. An agent-based model was constructed in order to study the complex role of UVR in psoriasis phototherapy, including possible contribution to the formation of skin cancers. The treatment progression of the simulated psoriasis undergoing UVR phototherapy was monitored weekly and compared with the corresponding clinical data. For model calibration, a single-objective optimization via genetic algorithm was employed that aimed to minimize the discrepancy between the model output and the expected clinical result. After fitting and validation, the model was then subjected to multi-objective evolutionary optimization using Non-dominated Sorting Genetic Algorithm-II (NSGA-II) in order to suggest sets of optimal UVR phototherapy regimen for psoriasis taking into account the safety, clearance time as well as aggressiveness of the therapy. Results show a good model fit against clinical data and gave some plausible sets of dosimetry for UVR phototherapy that maximize its therapeutic efficacy while minimizing the associated skin cancer risk.

Shockingly low water abundances inHerschel/PACS observations of low-mass protostars in Perseus

Protostars interact with their surroundings through jets and winds impacting on the envelope and creating shocks, but the nature of these shocks is still poorly understood. Our aim is to survey far-infrared molecular line emission from a uniform and significant sample of deeply-embedded low-mass young stellar objects in order to characterize shocks and the possible role of ultraviolet radiation in the immediate protostellar environment. Herschel/PACS spectral maps of 22 objects in the Perseus molecular cloud were obtained as part of the `William Herschel Line Legacy' survey. Line emission from H$_\mathrm{2}$O, CO, and OH is tested against shock models from the literature. Observed line ratios are remarkably similar and do not show variations with source physical parameters. Observations show good agreement with the shock models when line ratios of the same species are compared. Ratios of various H$_\mathrm{2}$O lines provide a particularly good diagnostic of pre-shock gas densities, $n_\mathrm{H}\sim10^{5}$ cm$^{-3}$, in agreement with typical densities obtained from observations of the post-shock gas. The corresponding shock velocities, obtained from comparison with CO line ratios, are above 20 km\,s$^{-1}$. However, the observations consistently show one-to-two orders of magnitude lower H$_\mathrm{2}$O-to-CO and H$_\mathrm{2}$O-to-OH line ratios than predicted by the existing shock models. The overestimated model H$_\mathrm{2}$O fluxes are most likely caused by an overabundance of H$_\mathrm{2}$O in the models since the excitation is well-reproduced. Illumination of the shocked material by ultraviolet photons produced either in the star-disk system or, more locally, in the shock, would decrease the H$_\mathrm{2}$O abundances and reconcile the models with observations. Detections of hot H$_\mathrm{2}$O and strong OH lines support this scenario.

The Role of Ultraviolet Radiation in the Ocular System of Mammals

With decreasing levels of ozone in the atmosphere, we are being exposed to higher levels of ultraviolet radiation (UVR) than ever before. UVR carries higher energy than visible light, and its effects on tissues include DNA damage, gene mutations, immunosuppression, oxidative stress and inflammatory responses. In the eye, UVR is strongly associated with the development of basal and squamous cell carcinoma of the eyelid, pterygium, photokeratitis, climatic droplet keratopathy, ocular surface squamous neoplasia, cataracts, and uveal melanoma, and is weakly associated with age-related macular degeneration. Despite overwhelming evidence regarding the deleterious effects on UVR, public health measures to encourage UV protection of the eyes is generally lacking. Options for photoprotection include sunglasses, wide brim hats, windshields, plastic films for side windows in cars, UV blocking contact lenses, and following the UV Index report daily. The American National Standards Institute currently has regulations regarding properties of UV blocking sunglasses; however, compliance in the US is not mandatory. On the other hand, UVR does have therapeutic applications in the eye, particularly, riboflavin activated by ultraviolet A light (UVA) radiation is used clinically to slow the progression of keratoconus, post-LASIK keratectasia, and bullous keratopathy by crosslinking corneal collagen fibers. Additionally, riboflavin activated by UVA has been shown to have antibacterial, antiviral, and antiparasitic effects. This is clinically relevant in the treatment of infectious keratitis. Finally, exposure to low levels of light in the UV spectrum has been found to regulate the growth of the eye and lack of adequate exposure may increase the risk of development and progression of myopia.

Do suncreens protect us?

Sunlight stimulates a multitude of important biological effects on skin, causing, amongst other pathological changes, photocarcinogenesis. Sunscreens are designed to provide protection against these harmful properties of ultraviolet radiation, and public health campaigns have been employed to encourage their use. Despite this, there has been a continued rise in the incidence and mortality of the most harmful skin cancer, malignant melanoma. This review article therefore looks at the role of ultraviolet radiation in causing skin cancer; summarizes the available evidence on both the beneficial and harmful effects of sunscreen use; and concludes with practical advice on how we might advise our patients to best protect themselves from photocarcinogenesis.

Synergism between mTORpathway and ultraviolet radiation in the pathogenesis of squamous cell carcinoma and its implication for solid‐organ transplant recipients

Nonmelanoma skin cancers (NMSCs) are the most common malignancies in the United States in immunocompetent patients. Among the solid-organ transplant recipients, NMSCs represent a significant disease burden, and they tend to be multiple and more aggressive. While the precise mechanisms responsible for the higher risk of developing cutaneous squamous cell carcinomas (SCCs) have not been completely elucidated, ultraviolet (UV) light has been established to be critical in initiation and promotion of tumor development. More recently, significant emphasis has been placed on the role of the mammalian target of rapamycin (mTOR) pathway in SCC pathogenesis. Furthermore, some studies have demonstrated the ability of mTOR inhibitors to decrease the incidence of new SCCs in the immunosuppressed transplanted patient population. In this review, we will highlight and examine the most recent available data on the role of UV radiation and its interaction with mTOR pathway signaling in SCC pathogenesis.

Skin cancer: role of ultraviolet radiation in carcinogenesis.

UV radiation is a carcinogen known to play a role in the development of non-melanoma and melanoma skin cancers. Acute and chronic exposure to UV radiation causes clinical and biological effects that promote the unregulated proliferation of skin cells. In recent decades, changes in climate and increased air pollution have led to environmental changes that increase UV light transmission. In this chapter, we discuss sources of UV radiation that are relevant to human health, as well as the acute and chronic effects that result from UV radiation exposure.

The invasion window for warmwater fish in clearwater lakes: the role of ultraviolet radiation and temperature

AbstractAimIn clear, cold‐water lakes, ultraviolet radiation (UV) and temperature are two important stressors that may prevent the establishment of aquatic invasive species by inhibiting the survival of sensitive early life history stages. In this study, we develop a UV–temperature response model to predict the establishment potential of a warmwater fish, largemouth bass (Micropterus salmoides), in a large subalpine lake based on the ability of bass larvae to tolerate UV and temperature stress along a UV–temperature stress gradient.LocationLake Tahoe (California/Nevada, USA).MethodsWe compared the UV tolerance of largemouth bass larvae to that of the native redside minnow (Richardsonius egregius) in outdoor UV exposure–response experiments. A UV–temperature response model for larval bass was developed that combined the experimentally derived UV exposure response from our outdoor experiments with a temperature response curve derived from the literature. We used the UV–temperature response model to predict reproductive success (i.e. larval survival) over the range of UV exposure and temperature conditions in nearshore Lake Tahoe. The model predictions were validated with in situ incubation experiments at nearshore locations.ResultsNon‐native bass were significantly less UV tolerant than native redside minnows. The UV–temperature response model predicted that larval bass survival varies seasonally, spatially and over depth gradients in nearshore Lake Tahoe and is constrained by UV and temperature conditions. In situ incubation experiments confirmed model predictions.Main conclusionsOur findings provide important insights into the potential for species invasion in clear, cold‐water lakes that are experiencing significant changes in both temperature and transparency. The conceptual model and approach that we employ is a potentially powerful tool for exploring unanswered questions in invasion biology, including the role of alternate stable states in facilitating invasion and the potential for invasive species to promote ‘invasional meltdown’ through their impacts on water clarity and temperature.

Targeting Activated KIT Signaling for Melanoma Therapy

Melanomas are composed of several biologically distinct categories of neoplasms that differ in their clinical and histologic presentations, cell of origin, age of onset, ethnic variation, pathogenetic role of ultraviolet radiation, predisposing germline alterations, type of genomic instability, pattern of metastasis, and patterns of somatic mutation. The latter contain a set of recurrent gain-of-function mutations in the genes NRAS, BRAF, KIT, GNAQ, and GNA11 that tend to occur in a mutually exclusive pattern early during progression. KIT is a receptor tyrosine kinase that binds to stem-cell factor (SCF), activating a series of downstream effector pathways (Fig 1). KIT is of critical importance in melanocyte development. It is expressed in early melanoblasts, which receive positional cues from SCF-expressing epithelia, while they migrate dorsoventrally through the superficial mesenchyme to reach their destination in the epidermis and hair follicles. Loss-of-function mutations reducing KIT signaling lead to distinctive pigment phenotypes, such as piebaldism, caused by an absence of melanocytes in the skin and/or hair follicles in frontomedial regions, such as the scalp or abdomen. Genetic alterations of KIT, including somatic gain-of-function mutations and copy number increases of wild-type KIT, occur in a minority of melanomas on skin with cumulative sun-induced damage (ie, CSD melanomas); on non–hair-bearing skin, such as palms, soles, or nail apparatus (ie, acral melanomas); and on the mucosal membrane (ie, mucosal melanomas). These melanomas are typically not associated with melanocytic nevi, and melanocytic nevi presenting on acral skin do not seem to harbor KIT mutations. The absence of a

The role of ultraviolet radiation and fish in regulating the vertical distribution of Daphnia

Previous studies have demonstrated independent effects of both solar ultraviolet radiation (UV; 280–400 nm) and planktivorous fish on the vertical distribution of Daphnia. We examined the behavioral response of adult and juvenile Daphnia to both UV and planktivorous fish simultaneously in a small temperate lake in eastern Pennsylvania by conducting a large‐scale (15 m deep) in situ mesocosm experiment with full factorial treatments (± UV and ± fish). UV induced an avoidance of the surface waters in both juvenile and adult Daphnia. In contrast, the response of Daphnia to fish depended on the presence of UV, with a clear interactive effect. In the presence of both UV and fish, Daphnia were deeper in the water column than they were in the absence of either UV or fish. Sampling of the lake also revealed a rapid upward shift in the depth distribution of both juveniles and adults following a rare and intense early‐summer storm that reduced the lake's transparency to both UV (for example, 380 nm UV‐A) and photosynthetically active radiation (400–700 nm) by 44% and 39%, respectively. Evidence of a novel benefit to UV avoidance behavior was also observed: surface avoidance of UV reduces the hazards of Daphnia getting caught in the surface air–water interface and perishing. These results highlight the interactive effects of fish and UV on Daphnia vertical distribution under near‐natural conditions in situ.

The Mechanisms and Consequences of Ultraviolet-Induced Immunosuppression in the Skin and Eye

Ultraviolet radiation (UVR) of the skin results in immune suppression to antigens encountered shortly after the exposure. The pathways leading to the downregulation in immunity are complex, initiated by chromophores located at the surface of the skin and ending with the generation of immunosuppressive mediators and regulatory cells. Ultraviolet-induced immunosuppression can be considered not only as beneficial, such as in preventing chronic inflammatory responses and allergic and automimmune reactions, but it can also be detrimental, such as in the lack of control of skin tumors and infectious diseases. The eye is an immune privileged site through a wide variety of mechanisms that allow selected immune responses without causing inflammation. The role of UVR in altering immune responses in the eye is not clear and is discussed in relation to photokeratitis, herpetic stromal keratitis, and pterygium.

A Review: Role of Ultraviolet Radiation in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness in the western world. The retina is highly susceptible to photochemical damage from continuous exposure of light and oxygen. The cornea and the lens block a major portion of the ultraviolet (UV) radiation from reaching the retina (<295 nm). The relationship between UV light exposure and AMD is unclear, although short wavelength radiation and the blue light induce significant oxidative stress to the retinal pigment epithelium. Epidemiologic evidence indicates a trend toward association between severity of light exposure and AMD. In this review, we discuss type 1 and type 2 photochemical damage that occurs in response to UV exposure. We examine the impact of different doses of exposure to UV radiation and the subsequent production of oxidative stress in AMD. Local and systemic protective mechanisms of the retina including antioxidant enzymes and macular pigments are reviewed. This article provides a review of possible cellular and molecular effects of UV radiation exposure in AMD and potential therapies that may prevent blindness resulting from this disease.

Role of ultra-violet radiation, mercury and copper on the stability of dissolved glutathione in natural and artificial freshwater and saltwater

The behavior and stability of dissolved reduced glutathione (GSH), an environmental antioxidant and metal transporter, is poorly known in natural waters. Glutathione oxidation rates were determined in both fresh- and brackish waters artificially submitted to different radiation wavebands. Photo-oxidation of GSH followed pseudo-first order kinetics, with half-lives ranging from 4 to 30 h in natural freshwater, and from 1.6 to 7 h in saltwater, with generally shorter persistence in UV-irradiated surface waters than in dark treatments. Chloride was shown to indirectly promote GSH photo-oxidation, probably through its role in the formation of radicals. The addition of Cu(II) to synthetic waters resulted in the rapid oxidation of GSH. The addition of Hg(II), a metal with strong affinity for thiols, protected GSH from oxidation by Cu(II) in the dark, but not under UV radiation. We conclude that UV-induced photo-oxidation is a key process altering the fate of GSH in natural waters. Also, the formation of stable GSH–Hg complexes could increase the bioavailability of Hg towards microorganisms in aquatic systems.

Effects of solar radiation on barnacle settlement, early post-settlement mortality and community development in the intertidal zone

We examined the role of solar radiation, and particularly the role of ultraviolet radiation (UVR), in regulating small-scale settlement patterns and early post-settlement mortality in the barna- cle Balanus glandula, as well as community development of sessile organisms colonizing the upper mid-intertidal zone. Settlement of B. glandula cyprids was similar in treatments with and without UVR, suggesting that UVR does not directly influence site selection by cyprids. Once attached, mor- tality during the 1 to 2 d period from attachment to metamorphosis ranged from 60 to 100%, and half of the settlers that did metamorphose died during the following 5 d. Mortality during the period from attachment to metamorphosis was significantly lower in locations protected from UVR than in loca- tions exposed to the full spectrum of solar radiation, but only by ca. 10%. Furthermore, UVR expo- sure had no detectable effect on the mortality rate of metamorphosed early juveniles. Ambient UVR levels also appear to have had little effect on the colonization of mid-intertidal habitats by sessile organisms: our study locations were colonized by 2 sessile invertebrate species and 2 algal species over a period of 2.5 mo in mid-summer, and densities of these species were similar in treatments with and without UVR. Nevertheless, solar radiation dose explained 43 to 65% of the variation in mortal- ity among daily cohorts of B. glandula, and daily cohort mortality was often 100% during periods with the highest doses. This relationship between solar radiation and survival to metamorphosis was likely due to the effect of solar radiation on desiccation and heat stress. The high sensitivity of early post- settlement mortality rates to solar radiation suggests global climate change may significantly alter patterns of survivorship through this critical stage of life.

The two faces of metallothionein in carcinogenesis: photoprotection against UVR-induced cancer and promotion of tumour survival

Metallothionein is a multi-functional protein that protects the host against toxic heavy metals. Under stressful situations it can protect against oxidative damage, contribute to tissue repair, modulate immune responses and limit inflammatory processes. Recently, metallothionein's role in ultraviolet radiation (UVR)-induced injury has been investigated. These studies have shown that when metallothionein is upregulated following exposure to UVR, it can protect against UVR-induced damage and the subsequent development of skin cancer. We propose that this initial protection is achieved through its anti-oxidant role resulting in reduced oxidative stress, reduced apoptosis, reduced NFkappaB activation and enhanced repair of DNA damage. However, once UVR-induced neoplasia has occurred, the cancer cells can hijack metallothionein's protective functions, resulting in increased tumour progression and malignancy. These two discordant sets of attributes are context-dependent, and represent the two faces of metallothionein.

Clinical and laboratory study of rosacea in northern Greece

Numerous factors have been implicated in the pathogenesis of rosacea, which remains obscure. To examine the epidemiological characteristics of rosacea patients, the histopathological alterations, the prevalence of gastric Helicobacter pylori infection and the role of ultraviolet radiation, to detect the presence of Demodex folliculorum on affected skin and to elucidate the immunological nature of this disorder. The study included 100 patients with rosacea. Each patient was assessed with a clinical, haematological, biochemical and histological examination; serology test for the detection of antibodies against H. pylori; direct immunofluorescence on perilesional, sun exposed skin and indirect immunofluorescence with monkey oesophagus as a substrate; antinuclear antibody titre and a skin surface biopsy to search for Demodex folliculorum. Women were more frequently affected. Half of our patients were 51-70 years old. About two-thirds were photo-types I and II and 73% complained of worsening of conditions after sun exposure. An almost permanent histopathological feature was solar elastosis. Higher prevalence of H. pylori was not established. Prevalence and mean density of Demodex folliculorum were significantly increased in rosacea patients. Direct and indirect immunofluorescence tests were positive in 6.4% and 6.7% respectively. Antinuclear antibody titres were found in 21.1%. Our results suggest the pivotal role of chronic sun exposure in the pathogenesis of rosacea. Demodex folliculorum represents a significant cofactor that may contribute to the transition of the disease from a vascular to an inflammatory stage. The low positive results of direct and indirect immunofluorescence do not support a potential autoimmune role in the development of rosacea.

Ultraviolet radiation affects invasibility of lake ecosystems by warm‐water fish

Predicting where species invasions will occur remains a substantial challenge in ecology, but identifying factors that ultimately constrain the distribution of potential invaders could facilitate successful prediction. Whereas ultraviolet radiation (UVR) is recognized as an important factor controlling species distribution and community composition, the role of UVR in a habitat invasibility context has not been explored. Here we examine how underwater UVR can regulate warm-water fish invasion. In Lake Tahoe, California and Nevada, USA, established populations of exotic bluegill sunfish (Lepomis macrochirus) are currently limited to turbid, low-UVR embayments. An in situ incubation experiment that manipulated incident UVR exposure of larval bluegill, combined with an assessment of UVR exposure levels in nearshore habitats around Lake Tahoe, demonstrates that UVR can mediate habitat invasibility. Our findings suggest that the susceptibility to invasion by UVR sensitive species may increase in transparent aquatic systems threatened by declining water quality, and they highlight the importance of abiotic factors as regulators of invasion risk in ecosystems.

The role of ultraviolet radiation in melanomagenesis

The role of ultraviolet radiation (UV) in the pathogenesis has been discussed controversially for many decades. Studies in mice (SCID, HGF/SF, SV40T) which develop malignant melanoma, show a role of UVB in melanomagenesis. In contrast to this, the role of UVA is less clear. We will review the recent in vitro and in vivo data in support of the hypothesis that UVA is also involved in the development of malignant melanoma. The role of UVA in p53 activation, apoptosis, cell cycle arrest and photoproduct formation is discussed.

Malignant melanoma: how error amplification by screening creates spurious disease

The increased incidence of melanoma with little or no change in mortality has been attributed to the histopathological reclassification of benign disease as malignant, the consequence of diagnostic drift. An entirely new, additional explanation has now been found, and is defined as error amplification by screening. This previously unrecognized artefact is shown to be an inevitable consequence of the uneven operation of routine histopathological error in the diagnosis of borderline malignancy; thus, as the equality of diagnostic plus/minus is lost, it is no longer self-correcting, and the overdiagnosis of malignancy therefore outweighs its underdiagnosis: the error is then amplified by patient screening. The magnitude of this new artefact is a function of the reproducibility of routine histopathological diagnosis and the number of patients screened, and the evidence on this, and from studies done for other purposes, shows the error to be considerable. The artefact of error amplification by screening detracts from a possible role for ultraviolet radiation in the increase in melanoma incidence and provides an explanation of their erroneous association; in addition to melanoma, it could be a major source of misdiagnosis of other cancers associated with patient screening programmes.

A Quantitative Assessment of the Burden and Distribution of Lisch Nodules in Adults with Neurofibromatosis Type 1

The presence of two or more Lisch nodules (melanocytic hamartomas of the iris) is one of seven diagnostic criteria for neurofibromatosis type 1 (NF1), a common monogenic disorder of dysregulated neurocutaneous growth. The hypothesis that Lisch nodules arise secondary to exposure to ultraviolet (UV) radiation from sunlight was investigated. Lisch nodule burden was mapped and quantified in the irides of 77 adults with NF1. Lifetime sunlight (UV radiation) exposure was inventoried, NF1 neurocutaneous severity determined, and two NF1 mutations predictive of severity selectively genotyped. There was high interindividual variability in Lisch nodule burden. Lisch nodules were primarily located in the inferior hemifield (half) of the iris, regardless of its color (P = 3.0 x 10(-20)). Light irides harbored significantly more Lisch nodules than dark irides (P = 4.8 x 10(-5)). There was no statistically significant correlation of Lisch nodule burden to lifetime sunlight exposure "dose" or NF1 neurocutaneous severity. The difference in Lisch nodule burden between the superior and inferior iris hemifields is most likely due to the sunlight-shielding effects on the superior half by periocular structures. The difference in Lisch nodule burden between light and dark irides is probably due to the photoprotective effects of pigmentation. The genes underlying the control of iris color may thus be viewed as modifiers of severity of Lisch nodule burden in NF1. Given the role of UV radiation and, presumably, DNA damage in Lisch nodule pathogenesis, "benign tumor of the iris," not "hamartoma," may be a better descriptor.

Elevated risk for squamous cell carcinoma of the conjunctiva among adults with AIDS in the United States

Squamous cell carcinoma of the conjunctiva (SCCC) has been associated with HIV infection in equatorial Africa, but the evidence for association with HIV in developed countries, where SCCC is rarer, is controversial. We investigated the risk for SCCC and other eye cancers in the updated U.S. HIV/AIDS Cancer Match Registry Study. We calculated standardized incidence ratios (SIRs) to estimate excess risk for SCCC, primary ocular lymphoma, ocular Kaposi sarcoma (KS), and other eye tumors among 491, 048 adults (age > 15 years or older) with HIV/AIDS diagnosed from 1980 to 2004. We calculated relative proportions (per 105) to gain insight into risk factors. We identified 73 eye cancers (15 SCCC, 35 primary ocular lymphoma, 17 ocular KS, and 6 other). Overall SIRs were elevated for SCCC (SIR, 12.2, 95% CI 6.8 – 20.2), primary ocular lymphoma (21.7, 95% CI 15.1–30.2), and ocular KS (109, 95% CI 63.5–175). Risk for SCCC was elevated regardless of HIV acquisition category, CD4 lymphocyte count, and time-relative to AIDS-onset. Relative proportions of SCCC risk were highest with age ≥50 (8/105), Hispanic ethnicity (7/105), and residence in regions with high solar ultraviolet radiation (10/105). We show significantly increased incidence of SCCC among persons with HIV/AIDS in the United States. The associations with age and geography are in accord with etiological role for ultraviolet radiation in SCCC.