Quantitative analysis of UV photolesions suggests that cyclobutane pyrimidine dimers produced in mouse skin by UVB are more mutagenic than those produced by UVC

UV-induced skin's green autofluorescence is a biomarker for both non-invasive evaluations of the dosages of UV exposures of the skin and non-invasive prediction of UV-induced skin damage

It is crucial to discover biomarkers for non-invasive evaluations of the dosages of UV exposures to a person during post-UV exposure period, and for non-invasive prediction of UV-induced skin damage. Our current study has obtained findings: UVB exposures produced dose-dependent increases in skin's green autofluorescence (AF) intensity of mice, which were significantly associated with the UVB dosages. The UVC-induced green AF increases were dose dependent, which were highly associated with the UVC dosages. Moreover, both previous reports and our current study have collectively shown significant association between UVB/UVC dosages and UVB/UVC-induced skin damage. Collectively, our study has indicated that the UVB/UVC-induced skin's AF are first biomarkers for both non-invasive evaluations of the dosages of UV exposures to a person during post-UV exposure period and non-invasive and label-free prediction of UVB/UVC-induced skin damage.

Worenine Prevents Solar Ultraviolet–Induced Sunburn by Inhibiting JNK2

Excessive solar ultraviolet (SUV) radiation often causes dermatitis, photoaging, and even skin cancer. In the pathological processes of SUV-induced sunburn, JNK is activated by phosphorylation, and it in turn phosphorylates its downstream transcription factors, such as ATF2 and c-jun. The transcription factors further regulate the expression of pro-inflammatory genes, such as IL-6 and TNF-α, which ultimately leads to dermatitis. Therefore, inhibiting JNK may be a strategy to prevent dermatitis. In this study, we screened for worenine as a potential drug candidate for inhibiting sunburn. We determined that worenine inhibited the JNK-ATF2/c-jun signaling pathway and the secretion of IL-6 and TNF-α in cell culture and in vivo, confirming the role of worenine in inhibiting sunburn. Furthermore, we determined that worenine bound and inhibited JNK2 activity in vitro through the MST, kinase, and in vitro kinase assays. Therefore, worenine might be a promising drug candidate for the prevention and treatment of SUV-induced sunburn.

Effect of ultraviolet C emitted from KrCl excimer lamp with or without bandpass filter to mouse epidermis

It has been reported that 222-nm ultraviolet C (UVC) exerts a germicidal effect on bacteria and viruses as well as UV radiation emitted from a conventional germicidal lamp but is less toxic to the mammalian cells than that from a germicidal lamp. An excimer lamp filled with krypton chloride (KrCl) gas principally emits 222-nm UVC. However, the lamp also emits a wide band of wavelengths other than 222 nm, especially UVC at a longer wavelength than 222 nm and ultraviolet B, which cause DNA damage. There are some reports on the critical role of bandpass filters in reducing the harmful effect of UVC emitted from a KrCl excimer lamp in a human skin model and human subjects. However, the effectiveness of a bandpass filter has not been demonstrated in animal experiments. In the present study, mice were irradiated with UVC emitted from a KrCl excimer lamp with or without a bandpass filter. UVC emitted from an unfiltered KrCl lamp at doses of 50, 150 and 300 mJ/cm² induced cyclobutyl pyrimidine dimer (CPD)-positive cells, whereas UVC emitted from a filtered lamp did not significantly increase CPD-positive cells in the epidermis. The present study suggested that the bandpass filter serves a critical role in reducing the harmful effect of emission outside of 222 nm to mouse keratinocytes.

Cyclobutane Pyrimidine Dimers Produced with Narrowband UVB Are on Average More Mutagenic than Those with Broadband UVB in Mouse Skin

Although narrowband UVB (NB-UVB) has replaced broadband UVB (BB-UVB) because of its greater effectiveness in dermatological phototherapy, it is twice as carcinogenic as BB-UVB at an equivalent inflammatory dose. To clarify the basis of the different genotoxicities, we comparatively evaluated the mutagenicities in mouse skin of the two UVB types along with their efficiencies in the formation of cyclobutane pyrimidine dimer (CPD), which is a major mutagenic DNA photolesion specifically produced by UVR. We found that the mutagenicity averaged per single molecule of CPD was 2.5- and 1.8-fold higher in NB-UVB-exposed epidermis and dermis, respectively, which indicates that NB-UVB is more mutagenic for the skin than BB-UVB at doses producing an equimolar amount of CPD. Analysis of effective wavelengths for UV photolesion formation with each UVB source revealed a remarkable difference in the peak effective wavelengths for CPD formation: 15 nm longer for NB-UVB in the epidermis. Although the analysis of mutation profiles showed largely similar UV-specific signatures between the two UVB types, a relatively stronger preference for UVA-specific mutations was observed for NB-UVB. These results suggest that the difference in the effective wavelengths for CPD formation leads to the different mutagenicities and carcinogenicities between the UVB sources.

Computer Modeling Indicates Dramatically Less DNA Damage from Far-UVC Krypton Chloride Lamps (222 nm) than from Sunlight Exposure

This study aims to investigate, with computer modeling, the DNA damage (assessed by cyclobutane pyrimidine dimer (CPD) formation) from far-ultraviolet C (far-UVC) in comparison with sunlight exposure in both a temperate (Harwell, England) and Mediterranean (Thessaloniki, Greece) climate. The research utilizes the published results from Barnard et al. [Barnard, I.R.M (2020) Photodermatol. Photoimmunol. Photomed. 36, 476-477] to determine the relative CPD yield of unfiltered and filtered far-UVC and sunlight exposure. Under current American Conference of Governmental Industrial Hygienists (ACGIH) exposure limits, 10 min of sunlight at an ultraviolet (UV) Index of 4-typical throughout the day in a temperate climate from Spring to Autumn-produces equivalent numbers of CPD as 700 h of unfiltered far-UVC or more than 30 000 h of filtered far-UVC at the basal layer. At the top of the epidermis, these values are reduced to 30 and 300 h, respectively. In terms of DNA damage induction, as assessed by CPD formation, the risk from sunlight exposure greatly exceeds the risk from far-UVC. However, the photochemistry that will occur in the stratum corneum from absorption of the vast majority of the high-energy far-UVC photons is unknown, as are the consequences.

Photosensitization Reactions of Biomolecules: Definition, Targets and Mechanisms

Photosensitization reactions have been demonstrated to be largely responsible for the deleterious biological effects of UV and visible radiation, as well as for the curative actions of photomedicine. A large number of endogenous and exogenous photosensitizers, biological targets and mechanisms have been reported in the past few decades. Evolving from the original definitions of the type I and type II photosensitized oxidations, we now provide physicochemical frameworks, classifications and key examples of these mechanisms in order to organize, interpret and understand the vast information available in the literature and the new reports, which are in vigorous growth. This review surveys in an extended manner all identified photosensitization mechanisms of the major biomolecule groups such as nucleic acids, proteins, lipids bridging the gap with the subsequent biological processes. Also described are the effects of photosensitization in cells in which UVA and UVB irradiation triggers enzyme activation with the subsequent delayed generation of superoxide anion radical and nitric oxide. Definitions of photosensitized reactions are identified in biomolecules with key insights into cells and tissues.

Inhibitors of Nucleotide Excision Repair Decrease UVB-Induced Mutagenesis-An In Vitro Study

The high incidence of skin cancers in the Caucasian population is primarily due to the accumulation of DNA damage in epidermal cells induced by chronic ultraviolet B (UVB) exposure. UVB-induced DNA photolesions, including cyclobutane–pyrimidine dimers (CPDs), promote mutations in skin cancer driver genes. In humans, CPDs are repaired by nucleotide excision repair (NER). Several commonly used and investigational medications negatively influence NER in experimental systems. Despite these molecules’ ability to decrease NER activity in vitro, the role of these drugs in enhancing skin cancer risk is unclear. In this study, we investigated four molecules (veliparib, resveratrol, spironolactone, and arsenic trioxide) with well-known NER-inhibitory potential in vitro, using UVB-irradiated CHO epithelial and HaCaT immortalized keratinocyte cell lines. Relative CPD levels, hypoxanthine phosphoribosyltransferase gene mutation frequency, cell viability, cell cycle progression, and protein expression were assessed. All four molecules significantly elevated CPD levels in the genome 24 h after UVB irradiation. However, veliparib, spironolactone, and arsenic trioxide reduced the mutagenic potential of UVB, while resveratrol did not alter UVB-induced mutation formation. UVB-induced apoptosis was enhanced by spironolactone and arsenic-trioxide treatment, while veliparib caused significantly prolonged cell cycle arrest and increased autophagy. Spironolactone also enhanced the phosphorylation level of mammalian target of rapamycin (mTOR), while arsenic trioxide modified UVB-driven mitochondrial fission. Resveratrol induced only mild changes in the cellular UVB response. Our results show that chemically inhibited NER does not result in increased mutagenic effects. Furthermore, the UVB-induced mutagenic potential can be paradoxically mitigated by NER-inhibitor molecules. We identified molecular changes in the cellular UVB response after NER-inhibitor treatment, which may compensate for the mitigated DNA repair. Our findings show that metabolic cellular response pathways are essential to consider in evaluating the skin cancer risk–modifying effects of pharmacological compounds.

Seasonal Differences in the UVA/UVB Ratio of Natural Sunlight Influence the Efficiency of the Photoisomerization of (6-4) Photoproducts into their Dewar Valence Isomers

The UVA and UVB components of sunlight can produce three classes of bipyrimidine DNA photolesions [cyclobutane pyrimidine dimers (CPDs), pyrimidine (6‐4) pyrimidone photoproducts (6‐4PPs) and related Dewar valence isomers (DewarPPs)]. The UVA/UVB ratio of sunlight is high in winter and low in summer in the Northern Hemisphere. Since UVB radiation produces 6‐4PPs and UVA radiation converts them into DewarPPs through photoisomerization, it is expected that there may be differences in the photoisomerization of 6‐4PPs between summer and winter, although that has never been documented. To determine that, isolated DNA was exposed to natural sunlight for 8 h in late summer and in winter, and absolute levels of the three classes of photolesions were quantified using calibrated ELISAs. It was found that sunlight produces CPDs and 6‐4PPs in DNA at a ratio of about 9:1 and converts approximately 80% of 6‐4PPs into DewarPPs within 3 h. Moreover, photoisomerization is more efficient in winter than in late summer after sunlight irradiation for the same duration, at similar solar UV doses and with the same induction level of CPDs. These results demonstrate that seasonal differences in the UVA/UVB ratio influence the efficiency of the photoisomerization of 6‐4PPs into DewarPPs.

Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma represents 20% of all skin cancers, resulting in 1 million cases in the United States each year. The lifetime risk of developing squamous cell carcinoma continues to increase annually and will likely continue to increase because of the aging population. Most cutaneous squamous cell carcinoma are treated locally, with a subset leading to recurrence, metastasis, and death. This review of cutaneous squamous cell carcinoma covers incidence, recurrence rates, mortality rates, risk factors, staging systems, treatment, prevention, and monitoring.

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

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

Formic Acid of ppm Enhances LC-MS/MS Detection of UV Irradiation-Induced DNA Dimeric Photoproducts

Cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) are genotoxic DNA lesions and mainly generated on thymine-thymine (T-T) dinucleotides upon UV irradiation. Regarding the sensitivity, specificity, and accuracy of analytical methods, it is of first choice to develop a reliable assay for simultaneous detection of these DNA lesions using liquid chromatography-tandem mass spectrometry (LC-MS/MS). However, the dilemma is the low detection sensitivity of the phosphate-containing dimeric photoproducts even using most favorable negative-ion mode for LC-MS/MS analysis. Unexpectedly, we observed that the detection sensitivity of T-T CPD and 6-4PP could be significantly improved using formic acid/acetic acid (∼ppm) as an additive of the mobile phase for reversed-phase LC-MS/MS analysis. This is the first demonstration of the enhancement of LC-MS/MS signals by formic acid/acetic acid in negative-ion mode. Of note, these acidic agents are often used for positive-ion mode in LC-MS assays. Benefited from the developed method, we could quantify both T-T CPD and 6-4PP in mouse embryonic stem cells upon UVC irradiation at low dosage. This sensitive method is applicable to the screening and identification of genes involved in formation, signaling, and repair of UV lesion.

Review: immunoassays in DNA damage and instability detection

The review includes information on the current state of knowledge of immunometric methods with emphasis on the possibility of deoxyribonucleic acid (DNA) damage detection. Beginning with basic immunoassay enzyme-linked immunosorbent assay (ELISA), this review describes methods such as tyramide signal amplification (TSA), enhanced polymer one-step staining (EPOS), and time resolved amplified cryptate emission (TRACE) as improvements of ELISA's developed over time to obtain more accurate results. In the second part of the review, surface plasmon resonance (SPR) and quantum dots (QDs) are presented as the newest outlooks in the context of immunoanalysis of biological material and molecular studies. The aim of this review is to briefly present immunoassays with emphasis on DNA damage detection; therefore, the types of methods are listed and described, types of signal indicators, basic definitions such as antigen and antibody are given. Every method is considered with an exemplary application focusing on DNA studies, DNA damage and instability detection.

Wavelength- and Tissue-dependent Variations in the Mutagenicity of Cyclobutane Pyrimidine Dimers in Mouse Skin

The cyclobutane pyrimidine dimer (CPD) is a main mutagenic photolesion in DNA produced by UVR. We previously studied the wavelength-dependent kinetics of mutation induction efficiency using monochromatic UVR sources and transgenic mice developed for mutation assay and established the action spectra of UVR mutagenicity in the mouse epidermis and dermis. Here, we further established the action spectra of CPD and pyrimidine(6-4)pyrimidone photoproduct formation in the same tissues and in naked DNA using the same sources and mouse strain. Quantitative ELISA helped us estimate the photolesion formation efficiencies on a molecule-per-nucleotide basis. Using these action spectra, we confirmed that the UVR mutation mostly depends on CPD formation. Moreover, the mutagenicity of a CPD molecule (CPD mutagenicity) was found to vary by wavelength, peaking at approximately 313 nm in both the epidermis and dermis with similar wavelength-dependent patterns. Thus, the CPD formation efficiency is a main determinant of UVR mutagenicity in mouse skin, whereas a wavelength-dependent variation in the qualitative characteristics of CPD molecules also affects the mutagenic consequences of UVR insults. In addition, the CPD mutagenicity was always higher in the epidermis than in the dermis, suggesting different cellular responses to UVR between the two tissues irrespective of the wavelength.

Radicals generated in alternating guanine-cytosine duplexes by direct absorption of low-energy UV radiation

Recent studies have evidenced that oxidatively damaged DNA, which potentially leads to carcinogenic mutations and aging, may result from the direct absorption of low-energy photons (>250 nm). Herein, the primary species, i.e., ejected electrons and base radicals associated with such damage in duplexes with an alternating guanine-cytosine sequence are quantified by nanosecond transient absorption spectroscopy. The one-photon ionization quantum yield at 266 nm is 1.2 × 10-3, which is similar to those reported previously for adenine-thymine duplexes. This means that the simple presence of guanine, the nucleobase with the lowest ionization potential, does not affect photo-ionization. The transient species detected after 3 μs are identified as deprotonated guanine radicals, which decay with a half-time of 2.5 ms. Spectral assignment is made with the help of quantum chemistry calculations (TD-DFT), which for the first time, provide reference absorption spectra for guanine radicals in duplexes. In addition, our computed spectra predict the changes in transient absorption expected for hole localization as well as deprotonation (to cytosine and bulk water) and hydration of the radical cation.