Ultraviolet Radiation-Induced Production of Nitric Oxide:A multi-cell and multi-donor analysis

All-Cause and Cause-Specific Mortality among Patients with Vitiligo: A Nationwide Population-Based Study in Korea

Vitiligo is a common autoimmune skin disorder; however, there is limited information about risks of mortality among patients with vitiligo. Therefore, we aimed to investigate the mortality in patients with vitiligo. A population-based cohort study was conducted using the data linkage of the National Health Insurance Service database and the National Death Registry. Patients with incident vitiligo were matched with sociodemographic factors-matched controls without vitiligo in a 1:5 ratio. All-cause and cause-specific mortalities were compared between patients with vitiligo and controls. In total, 107,424 patients with incident vitiligo and 537,120 matched controls were included. The mortality rates were 34.8 and 45.3 per 10,000 person-years in patients and controls, respectively. Patients with vitiligo showed a significantly lower risk of mortality (adjusted hazard ratio = 0.75, 95% confidence interval = 0.72-0.78). The cause-specific mortality from infectious diseases, oncologic diseases, hematologic diseases, endocrine diseases, neurologic diseases, cardiovascular diseases, respiratory diseases, and renal/urogenital disease was significantly lower in patients with vitiligo. Patients with vitiligo were associated with a lower risk of mortality, suggesting that vitiligo-associated autoimmunity might contribute to reduced morbidity and mortality.

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

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

UV radiation and air pollution as drivers of major autoimmune conditions

Autoimmune diseases comprise a very heterogeneous group of disorders characterized by disruptive immune responses against self-antigens, chronic morbidity and increased mortality. The incidence and prevalence of major autoimmune conditions are particularly high in the western world, at northern latitudes, and in industrialized countries. This study will mainly focus on five major autoimmune conditions, namely type 1 diabetes, multiple sclerosis, inflammatory bowel diseases, rheumatoid arthritis, and autoimmune thyroid disorders. Epidemiological and experimental evidence suggests a protective role of sunlight exposure on the etiology of major autoimmune conditions mediated by the endogenous production of vitamin D and nitric oxide. A historical perspective shows how the rise of anthropogenic air pollutants is temporally associated with dramatic increases in incidence of these conditions. The scattering caused by ambient particulate matter and the presence of tropospheric ozone can reduce the endogenous production of vitamin D and nitric oxide, which are implicated in maintaining the immune homeostasis. Air pollutants have direct detrimental effects on the human body and are deemed responsible of an increasingly higher portion of the annual burden of human morbidity and mortality. Air pollution contributes in systemic inflammation, activates oxidative pathways, induces epigenetic alterations, and modulates the function and phenotype of dendritic cells, Tregs, and T-cells. In this review, we provide epidemiological and mechanistic insights regarding the role of UV-mediated effects in immunity and how anthropic-derived air pollution may affect major autoimmune conditions through direct and indirect mechanisms.

Determinant factors of bone health after long-term of Roux-en-Y gastric bypass surgery: A cross-sectional study

OBJECTIVES

The aim of this study was to evaluate bone health and the potential influencing factors of bone metabolism disorders in adults ≥5 y after Roux-en-Y gastric bypass (RYGB) surgery.

METHODS

In this cross-sectional study, patients who were ≥5 y post-RYGB were invited. Bone health considered as bone mineral content (BMC) and bone mineral density (BMD) in this study was assessed by dual x-ray absorptiometry. We also assessed 25-hydroxy-vitamin D concentrations, individual ultraviolet B radiation levels, serum ionized calcium, alkaline phosphatase, parathyroid, anthropometric, and body composition.

RESULTS

The study evaluated 104 adults (90% women; 49.6 ± 9.1 y old; postoperative period 8.7 ± 2.2 y). Lumbar and femoral BMC and BMD were positively correlated to body mass index (BMI), appendicular lean mass (ALM), and negatively to %excess of weight loss (EWL). Femoral BMD was negatively correlated to age, and both femoral BMD and BMC were positively correlated to weekly exposed body part score. Sex, age, BMI, ALM, and weekly exposed body part score explained 35% and 54% of the total variance of femoral BMD and BMC, respectively.

CONCLUSIONS

The present findings suggested that older age, lower BMI, higher %EWL, lower ALM, and lower weekly body part exposure score are important determinants in lowering BMD and BMC parameters in long-term post-bariatric surgery individuals, rather than serum 25-hydroxy-vitamin D and parathyroid.

THE ROLE OF NITRIC OXIDE AND PEROXYNITRITE IN THE ERYTHEMAL PERIOD OF ULTRAVIOLET-INDUCED SKIN DAMAGE

OBJECTIVE

The aim: To study the activity of inducible NO synthase in the blood, the content of NO metabolites and peroxynitrite in the skin and blood of guinea pigs during erythema periods after local ultraviolet skin irradiation.

PATIENTS AND METHODS

Materials and methods: The studies were carried out on 24 guinea pigs, subjected to local ultraviolet irradiation. The control group consisted of intact guinea pigs (n=6). After 2, 4 hours, on the 3rd, 8th day, the activity of inducible NO synthase (in blood), the content of total NO metabolites, nitrite anion, nitrates, peroxynitrite (in blood and skin) were determined.

RESULTS

Results: An increase in the level of peroxynitrite in the blood and of all NO metabolites in the skin was noted 2 hours after irradiation. After 4 hours activation of inducible NO synthase in the blood was observed, accompanied by an increase in the content of all NO metabolites and peroxynitrite both in the blood and in the skin. On the 3rd day high levels of excessive synthesis of NO and peroxynitrite in the blood and skin were also revealed due to the induced expression of this enzyme in the blood. On the 8th day the activity of inducible NO synthase remained high in the blood, which led to the accumulation of all NO metabolites and peroxynitrite in the blood and skin.

CONCLUSION

Conclusions: Thus, local ultraviolet irradiation of the skin of guinea pigs leads to the activation of inducible NO synthase in the blood and an increase in NO synthesis and peroxynitrite in the blood and skin.

Long-term residential sunlight exposure associated with cognitive function among adults residing in Finland

While sunlight may influence cognitive function through several pathways, associations of residential sunlight exposure with cognitive function are not well known. We evaluated associations of long-term residential sunlight exposure with cognitive function among a representative cohort of 1838 Finnish adults residing in Finland who underwent comprehensive cognitive assessment in midlife. We linked daily recordings of global solar radiation to study participants using residential information and calculated the average daily residential exposure to sunlight for four exposure time intervals: 2 months, 1 year, 2 years and 5 years prior to the date of the cognition assessment. Associations of the residential sunlight exposure with cognitive function were assessed using linear regression analyses adjusting for season, sex, age, and individual- and neighborhood-level socioeconomic characteristics. Greater average residential sunlight exposure over 2 and 5 years prior to the cognitive function assessment was associated with better global cognitive function (b = 0.13, 95% CI = 0.01, 0.25; b = 0.17, 95% CI = 0.05, 0.29, per 1 MJ/m² difference in sunlight exposure), while no associations with global cognitive function were observed at shorter exposure time intervals. In domain-specific analyses, greater residential exposure to sunlight over 1, 2 and 5 years prior to the cognitive function assessment was associated with better performance on new learning and visual memory (b = 0.10, 95% CI = 0.00, 0.20; b = 0.16, 95% CI = 0.04, 0.28; b = 0.19, 95% CI = 0.08, 0.31) and sustained attention (b = 0.15, 95% CI = 0.05, 0.25; b = 0.18, 95% CI = 0.06, 0.30; b = 0.17, 95% CI = 0.05, 0.29), but worse performance on reaction time (b =  - 0.12, 95% CI =  - 0.22, - 0.02; b = -0.15, 95% CI =  - 0.28, - 0.02; b =  - 0.18, 95% CI =  - 0.30, - 0.05). Residential sunlight exposure was not associated with executive function. These findings suggest long-term residential sunlight exposure may be an environmental factor influencing cognitive function among a cognitively healthy cohort residing in Northern Europe. Further studies in populations residing in different geographical locations are needed.

Association of sunshine duration with acute myocardial infarction hospital admissions in Beijing, China: A time-series analysis within-summer

BACKGROUND

Over the years, various epidemiological studies found that acute myocardial infarction (AMI) often shows seasonal rhythm patterning, which is usually influenced by the variations of environmental factors, such as air pollution, ambient temperature, solar activity, relative humidity. However, there are few studies on the impact of sunlight-induced AMI especially in developing countries, and they had inconsistent results. This study aimed to examine within-summer variations in the temporal association between sun exposure and AMI.

METHODS

We obtained hospitalization data for AMI of Beijing during 2013-2019. We used a distributed lag non-linear model (DLNM) combined with a quasi-Poisson regression model to estimate the non-linear lag effects of sunshine duration on AMI incidences. We evaluated the overall effect of AMI admissions with exposure to sunshine duration in the lag 0-21 days.

RESULTS

A total of 45,301 AMI cases were enrolled in our study during summer (June-September). The minimum of the morbidity was during days with a sunshine duration of 3.9 h. We found significant and U-shaped associations between sunshine duration and AMI, and the overall estimated relative risk was 1.29 (95% CI: 1.02,1.62) and 1.69 (95% CI: 1.28,2.24) for short (1st percentile) and long (99th percentile) sunshine duration, respectively. The males and younger people (<65 years) were most susceptible to these effects.

CONCLUSION

Our results suggest that both short and long sunshine duration could increase the risk of AMI admissions, especially for males and younger people. We suggest that public health policymakers should fully consider the balance of the pros and cons of solar exposure, and provide appropriate public health recommendations accordingly to gain the greatest benefits from sunlight.

Isolation of five different primary cell types from a single sample of human skin

We have developed a technique to isolate primary keratinocytes, melanocytes, fibroblasts, preadipocytes, and microvascular endothelial cells from an individual sample of human skin. The protocol describes step-by-step instructions for processing, cells isolation, and culture of neonatal foreskin, with adaptation for more demanding adult tissues. The availability of multiple isogenic cell types derived from individual skin samples offers the ability to investigate various areas of biology, in the context of cell-type specificity without potential confounding influence of inter-individual or genetic differences.

For complete details on the use and execution of this protocol, please refer to Holliman et al. (2017), Horvath et al. (2019), Horvath et al. (2018), Kabacik et al. (2018), Lowe et al. (2020), Lu et al. (2019), and Lu et al. (2018).

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Protocol to isolate five different primary cell types from human skin sample

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Modification for more demanding adult tissue

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Extensive characterization of each cell type

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Expansion and cryopreservation for biobanking

Post-exposure persistence of nitric oxide upregulation in skin cells irradiated by UV-A

Evidence suggests that exposure to UV-A radiation can liberate nitric oxide from skin cells eliciting vasodilation in-vivo. However, the duration of nitric oxide release in skin cells after UV exposure is not well studied, with emphasis on UV-B mediated iNOS upregulation. The current study demonstrated persistence of nitric oxide release in a dark reaction after moderate UV-A exposure, peaking around 48 h post exposure; this effect was shown in keratinocytes, fibroblasts and endothelial cells from neonatal donors and keratinocytes from aged donors and confirmed the hypothesis that UV-A exposure appeared to upregulate cNOS alongside iNOS. Release of nitric oxide in the skin cells induced by a moderate exposure to UV-A in sunlight may be especially beneficial for some demographic groups such as the elderly, hypertensive patients or those with impaired nitric oxide function, not only during exposure but many hours and days after that.

Analysis of the Seasonal Fluctuation of γδ T Cells and Its Potential Relation with Vitamin D3

In addition to its role in bone metabolism, vitamin D3 exerts immunomodulatory effects and has been proposed to contribute to seasonal variation of immune cells. This might be linked to higher vitamin D3 levels in summer than in winter due to differential sun exposure. γδ T cells comprise a numerically small subset of T cells in the blood, which contribute to anti-infective and antitumor immunity. We studied the seasonal fluctuation of γδ T cells, the possible influence of vitamin D3, and the effect of the active metabolite 1α,25(OH)2D3 on the in vitro activation of human γδ T cells. In a retrospective analysis with 2625 samples of random blood donors, we observed higher proportions of γδ T cells in winter when compared with summer. In a prospective study over one year with a small cohort of healthy adults who did or did not take oral vitamin D3 supplementation, higher proportions of γδ T cells were present in donors without oral vitamin D3 uptake, particularly in spring. However, γδ T cell frequency in blood did not directly correlate with serum levels of 25(OH)D3. The active metabolite 1α,25(OH)2D3 inhibited the in vitro activation of γδ T cells at the level of proliferation, cytotoxicity, and interferon-γ production. Our study reveals novel insights into the seasonal fluctuation of γδ T cells and the immunomodulatory effects of vitamin D3.

Role of nitric oxide in regulating epidermal permeability barrier function

Nitric oxide (NO), a free radical molecule synthesized by nitric oxide synthases (NOS), regulates multiple cellular functions in a variety of cell types. These NOS, including endothelial NOS (eNOS), inducible NOS (iNOS) and neural NOS (nNOS), are expressed in keratinocytes. Expression levels of both iNOS and nNOS decrease with ageing, and insufficient NO has been linked to the development of a number of disorders such as diabetes and hypertension, and to the severity of atherosclerosis. Conversely, excessive NO levels can induce cellular oxidative stress, but physiological levels of NO are required to maintain the normal functioning of cells, including keratinocytes. NO also regulates cutaneous functions, including epidermal permeability barrier homeostasis and wound healing, through its stimulation of keratinocyte proliferation, differentiation and lipid metabolism. Topical applications of a diverse group of agents which generate nitric oxide (called NO donors) such as S-nitroso-N-acetyl-D,L-penicillamine (SNAP) can delay permeability barrier recovery in barrier-disrupted skin, but iNOS is still required for epidermal permeability barrier homeostasis. This review summarizes the regulatory role that NO plays in epidermal permeability barrier functions and the underlying mechanisms involved.

On the anti-correlation between COVID-19 infection rate and natural UV light in the UK

While it is well established that the rate of COVID-19 infections can be suppressed by social distancing, environmental effects may also affect it. We consider the hypothesis that natural Ultra-Violet (UV) light is reducing COVID-19 infections by enhancing human immunity through increasing levels of Vitamin-D and Nitric Oxide or by suppressing the virus itself. We focus on the United Kingdom (UK), by examining daily COVID-19 infections (F) and UV Index (UVI) data from 23 March 2020 to 10 March 2021. We find an intriguing empirical anti-correlation between log10(F) and log10(UVI) with a correlation coefficient of -0.934 from 11 May 2020 (when the first UK lockdown ended) to 10 March 2021. The anti-correlation may reflect causation with other factors which are correlated with the UVI. We advocate that UVI should be added as a parameter in modelling the pattern of COVID-19 infections and deaths. We started quantifying such correlations in other countries and regions.

Light-induced nitric oxide release in the skin beyond UVA and blue light: Red & near-infrared wavelengths

Nitric oxide (NO) is omnipresent in the body and synthesized by 3 isoenzymes (nNOS, eNOS and iNOS), all detected in human skin. NO can be stored in a pool of compounds readily converted to NO following skin irradiation by UVR and blue light. This non-enzymatic (without NOS involvement) photolytic reaction mobilizes cutaneous stores of NO derivatives to the bloodstream, lowering blood pressure. However, with the likelihood of skin deleterious effects caused by UVR/blue light, safer wavelengths in the red/near-infrared (NIR) spectrum are becoming potential contenders to release cutaneous NO, possibly via NOS temperature-dependent effects. The use of red/NIR light to mobilize NO stores from the body's largest organ (the skin) is auspicious. This review focuses on UVR, blue, red, and NIR spectra and their capacity to release NO in human skin. PubMed and Google Scholar were used as article databases to find relevant publications related to this particular field.

The photoprotective properties of α-tocopherol phosphate against long-wave UVA1 (385 nm) radiation in keratinocytes in vitro

UVA1 radiation (340–400 nm), especially longwave UVA1 (> 370 nm), is often ignored when assessing sun protection due to its low sunburning potential, but it generates reactive oxygen species (ROS) and is poorly attenuated by sunscreens. This study aimed to investigate if α-tocopherol phosphate, (α-TP) a promising new antioxidant, could protect against long-wave UVA1 induced cell death and scavenge UVA1 induced ROS in a skin cell model. HaCaT keratinocyte cell viability (24 h) was assessed with Alamar Blue and Neutral Red assays. The metabolism of α-TP into α-T, assessed using mass spectrometry, and the compound's radical scavenging efficacy, assessed by the dichlorodihydrofluorescein (H2DCFDA) ROS detection assay, was monitored in HaCaTs. The mechanism of α-TP ROS scavenging was determined using non-cell based DPPH and ORAC assays. In HaCaT keratinocytes, irradiated with 226 J/cm² UVA1 in low-serum (2%, starved) cell culture medium, pretreatment with 80 µM α-TP significantly enhanced cell survival (88%, Alamar Blue) compared to control, whereas α-T pre-treatment had no effect survival (70%, Alamar Blue). Pre-treatment of cells with 100 μM α-TP or 100 μM α-T before 57 J/cm² UVA1 also significantly reduced ROS generation over 2 h (24.1% and 23.9% respectively) compared to the control and resulted in α-TP bioconversion into α-T. As α-TP displayed weak antioxidant activity in the cell-free assays thus its photoprotection was assigned to its bioconversion to α-T by cellular phosphatases. Through this mechanism α-TP prevented long-wave UVA1 induced cell death and scavenged UVA1 induced ROS in skin cells when added to the starved cell culture medium before UVA1 exposure by bioconversion into α-T.

Prospects on the nano-plastic particles internalization and induction of cellular response in human keratinocytes

BACKGROUND

Today, cosmetic products are very popular with both men and women to improve their appearance and increase their social acceptability.

RESULTS

In this study, nano-sized (30-300 nm) plastic particles were isolated from the commercial face-scrubs and treated on the human keratinocytes. The observed adherence of polyethylene nano-plastics (PENPs), polystyrene NPs (PSNPs), and face-scrubs isolated nano-plastics (NPs) on the keratin layer reveals a significant attachment of NPs from the cosmetics that are applied on the skin for a short duration. This attachment property could facilitate further adherence of protein molecules on NPs and the protein-corona formation. The protein-corona mimics protein aggregates, thereby triggers macropinocytosis, followed by the macropinolysosomal process in the cell. These internalized NPs induced the concentration-dependent cytotoxic, cytostatic and cytoprotective activity in keratinocytes. Both single dose and chronic long-term exposure of lethal and sub-lethal concentrations of NPs resulted in oxidative stress-mediated down-regulation of cell growth and proliferation inhibition. Autophagic structures and premature aging were also observed using an electron microscopy and a senescence marker, respectively in the NPs internalized HaCaT cells incubated in a fresh, NPs-free medium.

CONCLUSION

Though 2D culture models have many limitations, it produces significant conceptual advancements. This work provides an insight into the NPs concentration-dependent regulatory, cytoprotective, and cytotoxic effects in HaCaT cells. However, 3D model studies are required to identify the detailed mechanisms of NPs toxicity and cytoprotective events in cells at the molecular level.

Neuropeptides and neurohormones in immune, inflammatory and cellular responses to ultraviolet radiation

Humans are exposed to varying amounts of ultraviolet radiation (UVR) through sunlight. UVR penetrates into human skin leading to release of neuropeptides, neurotransmitters and neuroendocrine hormones. These messengers released from local sensory nerves, keratinocytes, Langerhans cells (LCs), mast cells, melanocytes and endothelial cells (ECs) modulate local and systemic immune responses, mediate inflammation and promote differing cell biologic effects. In this review, we will focus on both animal and human studies that elucidate the roles of calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF), nitric oxide and proopiomelanocortin (POMC) derivatives in mediating immune and inflammatory effects of exposure to UVR as well as other cell biologic effects of UVR exposure.

Temporal patterns of suicide and circulatory system disease-related mortality are inversely correlated in several countries

BACKGROUND

Nearly 800,000 suicides occur worldwide annually and suicide rates are increasing faster than population growth. Unfortunately, the pathophysiology of suicide remains poorly understood, which has hindered suicide prevention efforts. However, mechanistic clues may be found by studying effects of seasonality on suicide and other mortality causes. Suicides tend to peak in spring-summer periods and nadir in fall-winter periods while circulatory system disease-related mortality tends to exhibit the opposite temporal trends. This study aimed to determine for the first time whether monthly temporal cross-correlations exist between suicide and circulatory system disease-related mortality at the population level. If so and if common biological factors moderate risks for both mortality types, such factors may be discoverable and utilized to improve suicide prevention.

METHODS

We conducted time series analyses of monthly mortality data from northern (England and Wales, South Korea, United States) and southern (Australia, Brazil) hemisphere countries during the period 2009-2018 (N = 41.8 million all-cause mortality cases). We used a Poisson regression variant of the standard cosinor model to determine peak months of mortality. We also estimated cross-correlations between monthly mortality counts from suicide and from circulatory system diseases.

RESULTS

Suicide and circulatory disease-related mortality temporal patterns were negatively correlated in Australia (- 0.32), Brazil (- 0.57), South Korea (- 0.32), and in the United States (- 0.66), but no temporal correlation was discernable in England and Wales.

CONCLUSIONS

The negative temporal cross-correlations between these mortality types we found in 4 of 5 countries studied suggest that seasonal factors broadly and inversely moderate risks for circulatory disease-related mortality and suicide, but not in all regions, indicating that the effect is not uniform. Since the seasonal factors of temperature and light exert opposite effects on suicide and circulatory disease-related mortality in several countries, we propose that physiologically-adaptive circulatory system responses to heat and light may increase risk for suicide and should be studied to determine whether they affect suicide risk. For example, heat and light increase production and release of the bioactive gas nitric oxide and reduce circulatory system disease by relaxing blood vessel tone, while elevated nitric oxide levels are associated with suicidal behavior, inverse effects that parallel the inverse temporal mortality patterns we detected.

Synthetic, Natural, and Semisynthetic Polymer Carriers for Controlled Nitric Oxide Release in Dermal Applications: A Review

Nitric oxide (NO•) is a free radical gas, produced in the human body to regulate physiological processes, such as inflammatory and immune responses. It is required for skin health; therefore, a lack of NO• is known to cause or worsen skin conditions related to three biomedical applications- infection treatment, injury healing, and blood circulation. Therefore, research on its topical release has been increasing for the last two decades. The storage and delivery of nitric oxide in physiological conditions to compensate for its deficiency is achieved through pharmacological compounds called NO-donors. These are further incorporated into scaffolds to enhance therapeutic treatment. A wide range of polymeric scaffolds has been developed and tested for this purpose. Hence, this review aims to give a detailed overview of the natural, synthetic, and semisynthetic polymeric matrices that have been evaluated for antimicrobial, wound healing, and circulatory dermal applications. These matrices have already set a solid foundation in nitric oxide release and their future perspective is headed toward an enhanced controlled release by novel functionalized semisynthetic polymer carriers and co-delivery synergetic platforms. Finally, further clinical tests on patients with the targeted condition will hopefully enable the eventual commercialization of these systems.

Light-Mediated Inhibition of Colonic Smooth Muscle Constriction and Colonic Motility via Opsin 3

Opsin photoreceptors outside of the central nervous system have been shown to mediate smooth muscle photorelaxation in several organs. We hypothesized that opsin receptor activation in the colon would have a similar effect and influence colonic motility. We detected Opsin 3 (OPN3) protein expression in the colonic wall and demonstrated that OPN3 was present in enteric neurons in the muscularis propria of the murine colon. Precontracted murine colon segments demonstrated blue light (BL) -mediated relaxation ex vivo. This photorelaxation was wavelength specific and was increased with the administration of the chromophore 9-cis retinal and a G protein receptor kinase 2 (GRK2) inhibitor. Light-mediated relaxation of the colon was not inhibited by L-NAME or tetrodotoxin (TTX). Furthermore, BL exposure in the presence of 9-cis retinal decreased the frequency of colonic migrating motor complexes (CMMC) in spontaneously contracting mouse colons ex vivo. These results demonstrate for the first time a receptor-mediated photorelaxation of colonic smooth muscle and implicate opsins as possible new targets in the treatment of spasmodic gastrointestinal dysmotility.

State-of-the-art and current challenges for TiO2/UV-LED photocatalytic degradation of emerging organic micropollutants

The development of ultraviolet light-emitting diodes (UV-LED) opens new possibilities for water treatment and photoreactor design. TiO₂ photocatalysis, a technology that has been continuously drawing attention, can potentially benefit from LEDs to become a sustainable alternative for the abatement of organic micropollutants (OMPs). Recently reported data on photocatalytic degradation of OMPs and their parameters of influence are here critically evaluated. The literature on OMP degradation in real water matrices, and at environmentally relevant concentrations, is largely missing, as well as the investigations of the impact of photoreactor design in pollutant degradation kinetics. The key factors for reducing UV-LED treatment technology costs are pointed out, like the increase in external quantum and wall-plug efficiencies of UV-LEDs compared to other technologies, as well as the need for an appropriate design optimizing light homogeneity in the reactor. Controlled periodic illumination, wavelength coupling and H₂O₂ addition are presented as efficiency enhancement options. Although electrical energy per order (E_EO) values for UV-LED photocatalysis have decreased to the range of traditional mercury lamps, values are still not low enough for practical employment. Moreover, due to the adoption of high initial OMP concentration in most experiments, it is likely that most literature E_EO values are overestimated. Given the process characteristics, which are favoured by translucent matrices and small diameters for more homogenous light distribution and better transportation of radicals, innovative reactor designs should explore the potential of point-of-use applications to increase photocatalysis applicability at large scale.

Effect of Short-Term Sunlight Exposure on Blood Pressure and Pulse Rate in Vitamin D3-Insufficient, Prehypertensive Patients: A Pilot Study

INTRODUCTION

This study was conducted to evaluate the effect of short-term sunlight exposure on blood pressure (BP) and pulse rate (PR) in vitamin D3-insufficient, prehypertensive patients.

METHODS

Twenty prehypertensive male participants were prospectively enrolled in this pilot study. BP and PR were measured using 24-hour ambulatory BP monitoring and endocrine biomarkers were assessed.

RESULTS

Sunlight exposure decreased 24-hour systolic BP (SBP), diastolic BP (DBP), and PR (SBP: 132.6 mm Hg to 129.3 mm Hg, DBP: 77.6 mm Hg to 75.7 mm Hg, and PR: 76.1 bpm to 71.3 bpm, p values: 0.0011, 0.0012, and <0.0001, respectively). The decrement patterns of SBP, DBP, and PR during nighttime (SBP: 123.5 mm Hg to 117.9 mm Hg, DBP: 72.2 mm Hg to 68.0 mm Hg, and PR: 68.2 bpm to 59.1 bpm, p values: 0.0015, 0.0003, and <0.0001, respectively) were more profound compared between daytime and nighttime. Blood levels of 25-hydroxyvitamin D3 were significantly increased (p = 0.0001) but aldosterone levels were significantly decreased (p = 0.0014) after sunlight exposure. In addition, an inverse relationship between 25-hydroxyvitamin D3 and aldosterone levels was observed (R = -0.4709, p = 0.0419).

DISCUSSION/CONCLUSION

The pilot study gives promising results that it is worthwhile to evaluate short-term sunlight exposure as a potentially effective approach in decreasing BP and PR in 25-hydroxyvitamin D3-insufficient prehypertensive patients in a larger trial with a control group.

Melanopsin mediates UVA-dependent modulation of proliferation, pigmentation, apoptosis, and molecular clock in normal and malignant melanocytes

Cutaneous melanocytes and melanoma cells express several opsins, of which melanopsin (OPN4) detects temperature and UVA radiation. To evaluate the interaction between OPN4 and UVA radiation, normal and malignant Opn4WT and Opn4KO melanocytes were exposed to three daily low doses (total 13.2 kJ/m2) of UVA radiation. UVA radiation led to a reduction of proliferation in both Opn4WT cell lines; however, only in melanoma cells this effect was associated with increased cell death by apoptosis. Daily UVA stimuli induced persistent pigment darkening (PPD) in both Opn4WT cell lines. Upon Opn4 knockout, all UVA-induced effects were lost in three independent clones of Opn4KO melanocytes and melanoma cells. Per1 bioluminescence was reduced after 1st and 2nd UVA radiations in Opn4WT cells. In Opn4KO melanocytes and melanoma cells, an acute increase of Per1 expression was seen immediately after each stimulus. We also found that OPN4 expression is downregulated in human melanoma compared to normal skin, and it decreases with disease progression. Interestingly, metastatic melanomas with low expression of OPN4 present increased expression of BMAL1 and longer overall survival. Collectively, our findings reinforce the functionality of the photosensitive system of melanocytes that may subsidize advancements in the understanding of skin related diseases, including cancer.

Safe, mild ultraviolet-B exposure: An essential human requirement for vitamin D and other vital bodily parameter adequacy: A review

The enigma of skin sunburning, skin ageing and skin cancer and essential vitamin D production both resulting from solar ultraviolet‐B (280‐315 nm) (UVB) exposure has long puzzled photobiologists. Advice to patients by non‐photobiological clinicians is now often to sunbathe to acquire vitamin D adequacy. However, modern work shows only mild UVB exposure is needed to maintain satisfactory levels, which have been demonstrated as very similar in summer and winter from about 25° to 70° north. Even very careful high protection factor 15 sunscreen use does not prevent adequate production, although it is slightly reduced, such that obsessive use of very protective screens of 50 + might. Dark skin pigmentation too usually at most minimally impairs production. However, confinement indoors and widespread clothing cover can, but oral supplementation overcomes any such deficiency. Thus, vitamin D adequacy needs just mild regular UVB skin exposure well under sunburning levels, unlikely to cause significant skin damage. This suggests mild UVB exposure may also be needed for other bodily requirements, which is indeed so. Thus, it also prevents the development of contact dermatitis and polymorphic light eruption through suppressing adaptive immunity. It also prevents the occurrence of multiple skin infections resulting from this suppression through stimulating innate immunity and cutaneous bacterial defensin production. Finally, blood pressure is reduced through low‐dose UVB‐induced production of the vasodilator nitric oxide (though UVA, 315‐400 nm, is more efficient). Thus, mild UVB exposure is important for several aspects of internal health, whereas high‐dose exposure is extremely detrimental to cutaneous health.

Radiation-Induced Senescence Bystander Effect: The Role of Exosomes

Ionizing Radiation (IR), especially at high doses, induces cellular senescence in exposed cultures. IR also induces “bystander effects” through signals released from irradiated cells, and these effects include many of the same outcomes observed following direct exposure. Here, we investigate if radiation can cause senescence through a bystander mechanism. Control cultures were exposed directly to 0, 0.1, 2, and 10 Gy. Unirradiated cells were treated with medium from irradiated cultures or with exosomes extracted from irradiated medium. The level of senescence was determined post-treatment (24 h, 15 days, 30 days, and 45 days) by β-galactosidase staining. Media from cultures exposed to all four doses, and exosomes from these cultures, induced significant senescence in recipient cultures. Senescence levels were initially low at the earliest timepoint, and peaked at 15 days, and then decreased with further passaging. These results demonstrate that senescence is inducible through a bystander mechanism. As with other bystander effects, bystander senescence was induced by a low radiation dose. However, unlike other bystander effects, cultures recovered from bystander senescence after repeated passaging. Bystander senescence may be a potentially significant effect of exposure to IR, and may have both beneficial and harmful effects in the context of radiotherapy.

Both cardiovascular and cerebrovascular events are decreased following long-term narrowband ultraviolet B phototherapy in patients with vitiligo: a propensity score matching analysis

BACKGROUND

Systemic effects of long-term narrowband ultraviolet B (NB-UVB) phototherapy have not been well studied in vitiligo patients. An 11-year nationwide population-based retrospective cohort study was conducted using the Korean National Health Insurance claims database (2007-2017).

OBJECTIVES

To investigate the effects of long-term NB-UVB phototherapy on the risk of cardiovascular and cerebrovascular events in vitiligo patients.

METHODS

This study included vitiligo patients with ≥100 phototherapy sessions (phototherapy group, n = 3229) and <3 phototherapy sessions (no phototherapy group, n = 9687), in which covariables with age, sex, insurance type and comorbidities such as diabetes, hypertension and hyperlipidemia were matched by 1 : 3 propensity score matching. The outcomes of interest were cardiovascular (ischaemic heart disease and myocardial infarction) and cerebrovascular events (cerebrovascular infraction and haemorrhage). Cox proportional hazards models were used to assess the associations between NB-UVB phototherapy and each event.

RESULTS

The risk of cardiovascular or cerebrovascular events was significantly decreased in the phototherapy group compared with the no phototherapy group [hazard ratio (HR) 0.637, 95% confidence interval (CI) 0.523-0.776]. Subgroup analysis revealed that the risk of cardiovascular (HR: 0.682, 95% CI: 0.495-0.940) and cerebrovascular events (HR: 0.601, 95% CI: 0.470-0.769) were significantly lower in the phototherapy group than the no phototherapy group, respectively.

CONCLUSIONS

Our findings suggest that long-term NB-UVB phototherapy could decrease the risk of cardiovascular and cerebrovascular events in patients with vitiligo.

Public Health Implications of Solar UV Exposure during Extreme Cold and Hot Weather Episodes in 2018 in Chilton, South East England

Consideration of the implications of solar UV exposure on public health during extreme temperature events is important due to their increasing frequency as a result of climate change. In this paper public health impacts of solar UV exposure, both positive and negative, during extreme hot and cold weather in England in 2018 were assessed by analysing environmental variations in UV and temperature. Consideration was given to people’s likely behaviour, the current alert system and public health advice. During a period of severe cold weather in February-March 2018 UV daily doses were around 25–50% lower than the long-term average (1991–2017); however, this would not impact on sunburn risk or the benefit of vitamin D production. In spring 2018 unseasonably high temperatures coincided with high UV daily doses (40–75% above long-term average) on significant days: the London Marathon (22 April) and UK May Day Bank Holiday weekend, which includes a public holiday on the Monday (5–7 May). People were likely to have intermittent excess solar UV exposure on unacclimatised skin, causing sunburn and potentially increasing the risk of skin cancers. No alerts were raised for these events since they occurred outside the alerting period. During a heat-wave in summer 2018 the environmental availability of UV was high—on average of 25% above the long-term average. The public health implications are complex and highly dependent on behaviour and sociodemographic variables such as skin colour. For all three periods Pearson’s correlation analysis showed a statistically significant (p<0.05) positive correlation between maximum daily temperature and erythema-effective UV daily dose. Public health advice may be improved by taking account of both temperature and UV and their implications for behaviour. A health impact-based alert system would be of benefit throughout the year, particularly in spring and summer.

Inflammatory bowel diseases: interrelationships between dietary vitamin D, exposure to UV radiation and the fecal microbiome

Introduction: Environmental factors and an altered fecal microbiome are believed to be central to the pathogenesis of inflammatory bowel diseases (IBD). Vitamin D and ultraviolet radiation (UVR) are environmental factors that are associated by several pathways, including changes to the gastrointestinal microbiome, with the development and course of IBD.Area covered: This review explores the interaction of vitamin D, and UVR, with the intestinal innate and adaptive immune systems, and how they may influence the gut microbiome and the subsequent development, and progression, of IBD.Expert opinion: Vitamin D and UVR both regulate innate and adaptive immunity through a combination of common and independent mechanisms, with the overall effect being the promotion of immune tolerance. Vitamin D, and to a lesser extent UVR, can modify the gastrointestinal microbiome either directly, or through immune-mediated mechanisms and this may explain the effect on intestinal inflammation in animal models of IBD and some clinical studies. Thus, both vitamin D and UVR exposure can be considered potential 'master regulators' of gastrointestinal immunity, fine-tuning the complex interaction between genetics, host immunity and the gut microbiome. Further research and increased understanding of environment-host interactions is essential to achieving the ultimate goal of preventing and curing IBD.

Ultraviolet B irradiation induced Nrf2 degradation occurs via activation of TRPV1 channels in human dermal fibroblasts

Ultraviolet (UV) irradiation causes cellular oxidative stress. Under redox imbalance, Keap1-dependent Nrf2 degradation is minimal. In this study, we examined the role of Ca²⁺ in Nrf2 homeostasis after UVB irradiation using human dermal fibroblasts. UVB irradiation stimulates 12-lipoxygenase and the product 12-hydroxyeicosatetraenoic acid then activates TRPV1 increasing the cell's cytosolic Ca²⁺ concentration. UVB irradiation induced reactive oxygen species generation and apoptosis are inhibited in the absence of Ca²⁺ or in the presence of either a 12-lipoxygenase inhibitor or a TRPV1 inhibitor during and after UVB irradiation. Thus, the Ca²⁺ increase via TRPV1 is a critical factor in UVB irradiation induced oxidative stress. UVB irradiation induces a Ca²⁺ dependent Nrf2 degradation and thus activation of TRPV1 with 12-hydroxyeicosatetraenoic acid also decreasing Nrf2 levels. UVB irradiation induced Nrf2 degradation is inhibited by co-treatment of cells with W-7, cyclosporin A, SB-216763 or MG-132, which are inhibitors of calmodulin, calcineurin, GSK3β and the proteasome, respectively. Furthermore, UVB irradiation in parallel induces GSK3β dephosphorylation in a Ca²⁺ dependent manner. Co-immunoprecipitation showed that UVB irradiation induces an increase in Nrf2 phosphorylation, an increase in the binding of β-TrCP and Nrf2, and an increase in Nrf2 ubiquitination; these effects are all Ca²⁺ dependent. These findings suggest that UVB irradiation induced GSK3β activation in a Ca²⁺ dependent manner, which then stimulates the phosphorylation and ubiquitination of Nrf2 via β-TrCP. Indeed, silencing of β-TrCP was found to inhibit UVB irradiation-induced oxidative stress, Nrf2 degradation and apoptosis, while it had no effect on the Ca²⁺ increase. Taken together, our results suggest that a Ca²⁺ influx via TRPV1 is responsible for UVB irradiation-induced Nrf2 degradation and that modulation of the Ca²⁺-calmodulin-calcineurin-GSK3β-Nrf2-β-TrCP-Cullin-1 pathway may explain Ca²⁺ dependent Nrf2 degradation.

The UV/Visible Radiation Boundary Region (385-405 nm) Damages Skin Cells and Induces "dark" Cyclobutane Pyrimidine Dimers in Human Skin in vivo

The adverse effects of terrestrial solar ultraviolet radiation (UVR) (~295–400 nm) on the skin are well documented, especially in the UVB region (~295–320 nm). The effects of very long-wave UVA (>380 nm) and visible radiation (≥400 nm) are much less known. Sunscreens have been beneficial in inhibiting a wide range of photodamage, however most formulations provide very little protection in the long wave UVA region (380–400 nm) and almost none from shortwave visible wavelengths (400–420 nm). We demonstrate photodamage in this region for a number of different endpoints including cell viability, DNA damage (delayed cyclobutane pyrimidine dimers), differential gene expression (for genes associated with inflammation, oxidative stress and photoageing) and induction of oxidizing species in vitro in HaCaT keratinocytes and in vivo in human volunteers. This work has implications for phototherapy and photoprotection.

Exposure to Ultraviolet Radiation in the Modulation of Human Diseases

This review focuses primarily on the beneficial effects for human health of exposure to ultraviolet radiation (UVR). UVR stimulates anti-inflammatory and immunosuppressive pathways in skin that modulate psoriasis, atopic dermatitis, and vitiligo; suppresses cutaneous lesions of graft-versus-host disease; and regulates some infection and vaccination outcomes. While polymorphic light eruption and the cutaneous photosensitivity of systemic lupus erythematosus are triggered by UVR, polymorphic light eruption also frequently benefits from UVR-induced immunomodulation. For systemic diseases such as multiple sclerosis, type 1 diabetes, asthma, schizophrenia, autism, and cardiovascular disease, any positive consequences of UVR exposure are more speculative, but could occur through the actions of UVR-induced regulatory cells and mediators, including 1,25-dihydroxy vitamin D₃, interleukin-10, and nitric oxide. Reduced UVR exposure is a risk factor for the development of several inflammatory, allergic, and autoimmune conditions, including diseases initiated in early life. This suggests that UVR-induced molecules can regulate cell maturation in developing organs.

Moderate UV Exposure Enhances Learning and Memory by Promoting a Novel Glutamate Biosynthetic Pathway in the Brain

Sunlight exposure is known to affect mood, learning, and cognition. However, the molecular and cellular mechanisms remain elusive. Here, we show that moderate UV exposure elevated blood urocanic acid (UCA), which then crossed the blood-brain barrier. Single-cell mass spectrometry and isotopic labeling revealed a novel intra-neuronal metabolic pathway converting UCA to glutamate (GLU) after UV exposure. This UV-triggered GLU synthesis promoted its packaging into synaptic vesicles and its release at glutamatergic terminals in the motor cortex and hippocampus. Related behaviors, like rotarod learning and object recognition memory, were enhanced after UV exposure. All UV-induced metabolic, electrophysiological, and behavioral effects could be reproduced by the intravenous injection of UCA and diminished by the application of inhibitor or short hairpin RNA (shRNA) against urocanase, an enzyme critical for the conversion of UCA to GLU. These findings reveal a new GLU biosynthetic pathway, which could contribute to some of the sunlight-induced neurobehavioral changes.

The effects of two different doses of ultraviolet-A light exposure on nitric oxide metabolites and cardiorespiratory outcomes

Purpose

The present study investigated different doses of ultraviolet-A (UV-A) light on plasma nitric oxide metabolites and cardiorespiratory variables.

Methods

Ten healthy male participants completed three experimental conditions, 7 days apart. Participants were exposed to no light (CON); 10 J cm² (15 min) of UV-A light (UVA10) and 20 J cm² (30 min) of UV-A light (UVA20) in a randomized order. Plasma nitrite [NO₂⁻] and nitrate [NO₃⁻] concentrations, blood pressure (BP), and heart rate (HR) were recorded before, immediately after exposure and 30 min post-exposure. Whole body oxygen utilization (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\dot{V}}}{\rm O}_{2}$$\end{document}V˙O2), resting metabolic rate (RMR) and skin temperature were recorded continuously.

Results

None of the measured parameters changed significantly during CON (all P > 0.05). \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\dot{V}}}{\rm O}_{2}$$\end{document}V˙O2 and RMR were significantly reduced immediately after UVA10 (P < 0.05) despite no change in plasma [NO₂⁻] (P > 0.05). Immediately after exposure to UVA20, plasma [NO₂⁻] was higher (P = 0.014) and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\dot{V}}}{\rm O}_{2}$$\end{document}V˙O2 and RMR tended to be lower compared to baseline (P = 0.06). There were no differences in [NO₂⁻] or \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\dot{V}}}{\rm O}_{2}$$\end{document}V˙O2 at the 30 min time point in any condition. UV-A exposure did not alter systolic BP, diastolic BP or MAP (all P > 0.05). UV-A light did not alter plasma [NO₃⁻] at any time point (all P > 0.05).

Conclusions

This study demonstrates that a UV-A dose of 20 J cm² is necessary to increase plasma [NO₂⁻] although a smaller dose is capable of reducing \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\dot{V}}}{\rm O}_{2}$$\end{document}V˙O2 and RMR at rest. Exposure to UV-A did not significantly reduce BP in this cohort of healthy adults. These data suggest that exposure to sunlight has a meaningful acute impact on metabolic function.

Environmental effects of ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2017

The Environmental Effects Assessment Panel (EEAP) is one of three Panels of experts that inform the Parties to the Montreal Protocol. The EEAP focuses on the effects of UV radiation on human health, terrestrial and aquatic ecosystems, air quality, and materials, as well as on the interactive effects of UV radiation and global climate change. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than previously held. Because of the Montreal Protocol, there are now indications of the beginnings of a recovery of stratospheric ozone, although the time required to reach levels like those before the 1960s is still uncertain, particularly as the effects of stratospheric ozone on climate change and vice versa, are not yet fully understood. Some regions will likely receive enhanced levels of UV radiation, while other areas will likely experience a reduction in UV radiation as ozone- and climate-driven changes affect the amounts of UV radiation reaching the Earth's surface. Like the other Panels, the EEAP produces detailed Quadrennial Reports every four years; the most recent was published as a series of seven papers in 2015 (Photochem. Photobiol. Sci., 2015, 14, 1-184). In the years in between, the EEAP produces less detailed and shorter Update Reports of recent and relevant scientific findings. The most recent of these was for 2016 (Photochem. Photobiol. Sci., 2017, 16, 107-145). The present 2017 Update Report assesses some of the highlights and new insights about the interactive nature of the direct and indirect effects of UV radiation, atmospheric processes, and climate change. A full 2018 Quadrennial Assessment, will be made available in 2018/2019.

Melanopsin and rhodopsin mediate UVA-induced immediate pigment darkening: Unravelling the photosensitive system of the skin

The mammalian skin has a photosensitive system comprised by several opsins, including rhodopsin (OPN2) and melanopsin (OPN4). Recently, our group showed that UVA (4.4 kJ/m²) leads to immediate pigment darkening (IPD) in murine normal and malignant melanocytes. We show the role of OPN2 and OPN4 as UVA sensors: UVA-induced IPD was fully abolished when OPN4 was pharmacologically inhibited by AA9253 or when OPN2 and OPN4 were knocked down by siRNA in both cell lines. Our data, however, demonstrate that phospholipase C/protein kinase C pathway, a classical OPN4 pathway, is not involved in UVA-induced IPD in either cell line. Nonetheless, in both cell types we have shown that: a) intracellular calcium signal is necessary for UVA-induced IPD; b) the involvement of CaMK II, whose inhibition, abolished the UVA-induced IPD; c) the role of CAMK II/NOS/sGC/cGMP pathway in the process since inhibition of either NOS or sGC abolished the UVA-induced IPD. Taken altogether, we show that OPN2 and OPN4 participate in IPD induced by UVA in murine normal and malignant melanocytes through a conserved common pathway. Interestingly, upon knockdown of OPN2 or OPN4, the UVA-driven IPD is completely lost, which suggests that both opsins are required and cooperatively signal in murine both cell lines. The participation of OPN2 and OPN4 system in UVA radiation-induced response, if proven to take place in human skin, may represent an interesting pharmacological target for the treatment of depigmentary disorders and skin-related cancer.