UV-induced Damage Research Articles

On binding specificity of (6–4) photolyase to a T(6–4)T DNA photoproduct

Different factors lead to DNA damage and if it is not repaired in due time, the damaged DNA could initiate mutagenesis and cancer. To avoid this deadly scenario, specific enzymes can scavenge and repair the DNA, but the enzymes have to bind first to the damaged sites. We have investigated this binding for a specific enzyme called (6–4) photolyase, which is capable of repairing certain UV-induced damage in DNA. Through molecular dynamics simulations we describe the binding between photolyase and the DNA and reveal that several charged amino acid residues in the enzyme, such as arginines and lysines turn out to be important. Especially R421 is crucial, as it keeps the DNA strands at the damaged site inside the repair pocket of the enzyme separated. DNA photolyase is structurally highly homologous to a protein called cryptochrome. Both proteins are biologically activated similarly, namely through flavin co-factor photoexcitation. It is, however, striking that cryptochrome cannot repair UV-damaged DNA. The present investigation allowed us to conclude on the small but, apparently, critical differences between photolyase and cryptochrome. The performed analysis gives insight into important factors that govern the binding of UV-damaged DNA and reveal why cryptochrome cannot have this functionality.

Tetraselmis as a challenge organism for validation of ballast water UV systems

Transport and release of waterborne organisms as a result of ballasting and de-ballasting operations is widely acknowledged to represent an important mechanism for invasions by non-indigenous species. Regulatory requirements have been implemented globally to require treatment of ballast water before its release to the environment as a means of minimizing risks of invasion. UV-based processes represent an option for ballast water treatment; however, their use will require development of appropriate methods for reactor validation. To address this need, Tetraselmis was examined as challenge organism using a most probable number (MPN) assay for quantification of the concentration of viable (reproductively active) cells in suspension. A low pressure collimated-beam reactor was used to investigate UV254 dose-response behavior of Tetraselmis. Based on the experimental conditions applied, Tetraselmis indicated 4.5–5 log10 units of inactivation for UV254 doses of approximately 120 mJ/cm2, with no apparent change of resistance resulting from repeated exposure. A medium pressure UV collimated-beam reactor equipped with a series of narrow bandpass optical filters was used to investigate the action spectrum of Tetraselmis for wavelengths ranging from 228 nm–297 nm. Radiation with wavelengths in the range 254–280 nm was observed to be most efficient for inactivation of Tetraselmis. Additionally, DNA was extracted from Tetraselmis to allow measurement of its absorption spectrum. These results indicated strong absorbance from 254 nm to 280 nm, thereby suggesting that damage to DNA plays an important role in the inactivation of Tetraselmis sp. However, deviations of the action spectrum shape from the shape of the DNA absorption spectrum suggest that UV-induced damage to biomolecules other than DNA may contribute to Tetraselmis inactivation at some wavelengths in the UVC range.

Dual-Prevention for UV-Induced Skin Damage: Incorporation of Melatonin-Loaded Elastic Niosomes into Octyl Methoxycinnamate Pickering Emulsions.

Incorporation of antioxidants into sunscreens is a logical approach, yet co-delivery of them with UV filters is a challenge. Here, we purposed a combination therapy, in which the chemical UV filter, octyl methoxycinnamate, was accumulated on upper skin while the antioxidant, melatonin, can penetrate deeper layers to show its effects. Melatonin-loaded elastic niosomes and octyl methoxycinnamate Pickering emulsion were prepared separately. Lyophilized elastic niosomes were dispersed into the Pickering emulsion to prepare the proposed combination formulation. The characterization studies of the formulations revealed that elastic niosomes can be prepared with tunable nanometer sizes, whereas Pickering emulsions can encapsulate the UV filter in micrometer-sized droplets. Melatonin-loaded elastic niosomes prepared with Tween80/Span80 mixture were 146nm with a PI of 0.438, and 58.42% entrapment efficiency was achieved. The mean diameter size of the combination formulation was 27.8μm. Ex vivo permeation studies revealed that 7.40% of octyl methoxycinnamate and 58% of melatonin were permeated through the rat skin while 27.6% octyl methoxycinnamate and 37% of melatonin accumulated in the skin after 24h. Cell culture studies with real-time cell analyzer showed that the proposed formulation consist of melatonin-loaded elastic niosomes and octyl methoxycinnamate Pickering emulsion had no negative effect on the cell proliferation and viability. According to α,α-diphenyl-β-picrylhydrazyl free radical scavenging method, the proposed formulation showed as high antioxidant activity as melatonin itself. It is concluded that the proposed formulation would be a promising dual therapy for UV-induced skin damage with co-delivery strategy.

Drosophila caspase activity is required independently of apoptosis to produce active TNF/Eiger during nociceptive sensitization

Tumor necrosis factor (TNF) signaling is required for inflammatory nociceptive (pain) sensitization in Drosophila and vertebrates. Nociceptive sensitization in Drosophila larvae following UV-induced tissue damage is accompanied by epidermal apoptosis and requires epidermal-derived TNF/Eiger and the initiator caspase, Dronc. Major gaps remain regarding TNF function in sensitization, including the relationship between apoptosis/tissue damage and TNF production, the downstream signaling in this context, and the target genes that modulate nociceptive behaviors. Here, apoptotic cell death and thermal nociceptive sensitization are genetically and procedurally separable in a Drosophila model of UV-induced nociceptive sensitization. Activation of epidermal Dronc induces TNF-dependent but effector caspase-independent nociceptive sensitization in the absence of UV. In addition, knockdown of Dronc attenuated nociceptive sensitization induced by full-length TNF/Eiger but not by a constitutively soluble form. UV irradiation induced TNF production in both in vitro and in vivo, but TNF secretion into hemolymph was not sufficient to induce thermal nociceptive sensitization. Downstream mediators of TNF-induced sensitization included two TNF receptor-associated factors, a p38 kinase, and the transcription factor nuclear factor kappa B. Finally, sensory neuron-specific microarray analysis revealed downstream TNF target genes induced during thermal nociceptive sensitization. One of these, enhancer of zeste (E(z)), functions downstream of TNF during thermal nociceptive sensitization. Our findings suggest that an initiator caspase is involved in TNF processing/secretion during nociceptive sensitization, and that TNF activation leads to a specific downstream signaling cascade and gene transcription required for sensitization. These findings have implications for both the evolution of inflammatory caspase function following tissue damage signals and the action of TNF during sensitization in vertebrates.

Ultraviolet-Induced DNA Damage Promotes RNA m6A Methylation

Abstract m6A RNA methylation rapidly recruits Pol κ to UV-induced damage sites to facilitate DNA repair.

Protective effects of fluoroquinolones on UV-induced damage of cultured ocular cell lines

Although the fluoroquinolones have strong antibacterial effects, some of them also have adverse ocular effects such as diplopia, uveitis, optic neuropathy, and retinal detachment. The purpose of this study was to determine whether low concentrations of fluoroquinolones can lessen the cytotoxic effects of ultraviolet (UV) light on different kinds of cultured ocular cells. We studied cultured human corneal endothelial cells (HCECs), a retinal ganglion cell line (RGC-5), a mouse-derived photoreceptor cell line (661W), a human adult retinal pigment epithelial cell line (ARPE-19), primary retinal cells, and primary human RPE cells. Levofloxacin, ciprofloxacin, and clinafloxacin were selected as the fluoroquinolones to test. The viabilities of the 661W, ARPE-19, and hRPE cells were assessed by Cell Counting Kit-8, and that of HCECs, 661W cells, and ARPE-19 cells by double fluorescent staining with Hoechst 33342 and propidium iodide (PI). Damage of retinal primary culture cells was assessed by immunostaining. Intracellular production of reactive oxygen species was measured in ARPE-19 cells by CM-H2DCFDA after UV light exposure. An activation of caspase by UV light in ARPE-19 cells was detected with a caspase-3/7 assay kit. UV exposure increased the number of dead cells, and the three fluoroquinolones tested suppressed this increase. Fluoroquinolones also protected the cells against the hydroxyperoxide (H2O2)-induced cell damage. Moreover, the fluoroquinolones decreased the production of reactive oxygen species and the activity of caspase-3/7, and low concentrations of fluoroquinolones reduced the oxidative stress in cultured ocular cell lines. We conclude that fluoroquinolones may have protective effects in these cells against UV exposure.

A New Depigmenting-Antifungal Methylated Grindelane from Grindelia chiloensis.

The new methylated grindelane diterpenoid, 7β-hydroxy-8(17)-dehydrogrindelic acid (1b), together with the known 7α-hydroxy-8(17)-dehydrogrindelic acid (2a), 6-oxogrindelic acid (3a), 4β-hydroxy-6-oxo-19-norgrindelic (4a), 19-hydroxygrindelic acid (5a), 18-hydroxygrindelic acid (6a), 4α-carboxygrindelic acid (7a), 17-hydroxygrindelic acid (8a), 6α-hydroxygrindelic acid (9a), 8,17-bisnor-8-oxagrindelic acid (10a), 7α,8α-epoxygrindelic acid (11a), and strictanonic acid (12a) as methyl esters were obtained from an Argentine collection of Grindelia chiloensis (Cornel.) Cabrera. Their structures and relative configurations were established on the basis of spectroscopic analysis. CHCl3 extract from the aerial parts and their pure compounds were evaluated for their antifungal and depigmenting effects. Methyl ester derivative of 10a (10b) exhibited a remarkable mycelial growth inhibition against Botritis cinerea with an IC50 of 13.5μgml-1 . While the new grindelane 1b exerted a clear color reduction of the yellow-orange pigment developed by Fusarium oxysporum against UV-induced damage.

Parkin regulates translesion DNA synthesis in response to UV radiation.

Deficiency of Parkin is a major cause of early-onset Parkinson's disease (PD). Notably, PD patients also exhibit a significantly higher risk in melanoma and other skin tumors, while the mechanism remains largely unknown. In this study, we show that depletion of Parkin causes compromised cell viability and genome stability after ultraviolet (UV) radiation. We demonstrate that Parkin promotes efficient Rad18-dependent proliferating cell nuclear antigen (PCNA) monoubiquitination by facilitating the formation of Replication protein A (RPA)-coated ssDNA upon UV radiation. Furthermore, Parkin is found to physically interact with NBS1 (Nijmegen breakage syndrome 1), and to be required for optimal recruitment of NBS1 and DNA polymerase eta (Polη) to UV-induced damage sites. Consequently, depletion of Parkin leads to increased UV-induced mutagenesis. These findings unveil an important role of Parkin in protecting genome stability through positively regulating translesion DNA synthesis (TLS) upon UV damage, providing a novel mechanistic link between Parkin deficiency and predisposition to skin cancers in PD patients.

Phytochemicals for the Prevention of Photocarcinogenesis.

Ultraviolet (UV) exposure has an array of damaging effects and is the main cause of skin cancer in humans. Nonmelanoma skin cancer (NMSC), including basal cell carcinoma and squamous cell carcinoma, is the most common type of cancer. Incidence of NMSC has increased due to greater UV radiation, increased life expectancy and other changes in lifestyle; the annual cost of skin cancer treatment in the United States has increased concurrently to around eight billion dollars. Because of these trends, novel approaches to skin cancer prevention have become an important area of research to decrease skin cancer morbidity and defray the costs associated with treatment. Chemoprevention aims to prevent or delay the development of skin cancer through the use of phytochemicals. Use of phytochemicals as chemopreventive agents has gained attention due to their low toxicity and anticarcinogenic properties. Phytochemicals also exhibit antioxidant, anti-inflammatory and antiproliferative effects which support their use as chemopreventive agents, particularly for skin cancer. Preclinical and human studies have shown that phytochemicals decrease UV-induced skin damage and photocarcinogenesis. In this review article, we discuss the selected phytochemicals that may prevent or delay UV-induced carcinogenesis and highlight their potential use for skin protection.

From actinic keratosis to squamous cell carcinoma: pathophysiology revisited.

The precursor of most cutaneous invasive squamous cell carcinomas (iSCCs) is intraepithelial UV-induced damage, known as field cancerization, which can eventually transform into actinic keratosis (AK). Although AK is the most common precursor of iSCC, many AKs will either persist in the same stage or regress, while only a few will progress into iSCC. Nevertheless, because the progression of individual AKs cannot be predicted, it has been proposed that all AKs, regardless of the grade, should be carefully monitored and appropriately treated in clinical practice. Modern imaging techniques such as dermatoscopy, reflectance confocal microscopy (RCM) and high-definition optical coherence tomography (HD-OCT) may have potential to monitor the evolution of actinic field damage. Dermatoscopy can be used to differentiate between AK, intraepidermal carcinoma (IEC) and SCC which may help clinicians to diagnose insitu or invasive lesions at an earlier stage. HD-OCT and RCM can be used to detect cellular and histological changes characteristic of subclinical lesions, allowing visualization of previously invisible lesions. As development of invasive AK directly from the cancer field cannot be ruled out, the ideal treatment should be able to eradicate AK lesions and reverse the underlying field cancerization.

What lies beneath actinic keratosis? Looking beyond visible lesions to optimize patient outcomes

This supplement presents a summary of the key topics discussed at two satellite symposia presented at the 23rd World Congress of Dermatology Meeting which took place in June 2015 in Vancouver, Canada, and at the 24th European Association of Dermatology and Venereology in Copenhagen, Denmark, held during October 2015. These meetings provided important opportunities to explore the need for treating the field in actinic keratosis (AK) and the role of AK treatment modalities and management styles in meeting patient needs. Intraepithelial UV-induced damage, known as field cancerization or field disease, which can eventually transform into AK, is the precursor of most cutaneous invasive squamous cell carcinomas (iSCCs).1 Traditionally, AK is classified using a three-tiered system depending on whether the focal atypia of basal keratinocytes involves the lower third of the epidermis (AK I), the lower two-thirds (AK II) or the full epidermal thickness (AK III). Until recently, it was widely accepted that progression form AK to iSCC could only occur after an almost complete transformation of the epidermis, following a ‘classical pathway’ of stepwise progression. Thus, AK I lesions were typically considered ‘low risk’.2 However, recent evidence suggests that AK I lesions are the most common precursors of iSCC (emerging through a ‘differentiated pathway’) suggesting that ‘low risk’ AK lesions cannot be easily identified.3 Dr Maria Fernandez Figueras discusses the implications of this finding in clinical practice. Mutations in the p53 tumor suppression gene caused by sunlight have been shown to occur not only in visible AK lesions but also in other skin that has been exposed to sunlight (known as the field).4, 5 Therefore, in the context of AK, field disease is an area of subclinical genetic changes in the periphery of visible AKs;6 indeed, new imaging techniques have confirmed that the disease often affects the entire field that has been exposed to sun.7, 8 Professor Eggert Stockfleth stresses the importance of treating the whole field with the goal of eliminating not just the visible lesions, but also the subclinical AKs, thereby minimizing the risk of recurrence, and potentially preventing progression to iSCC.9, 10 Dr Gary Goldenberg continues with this theme, focussing on the efficacy, safety and tolerability of current treatment options available for AK, paying particular attention to patient-applied field therapies and their suitability depending on specific disease characteristics and patient needs. Finally, Professor Rino Cerio discusses barriers to the effective treatment of AK, providing strategies to overcome these barriers, with a focus on patient education (including sun protection, using treatments correctly and self-checks) and timely follow-ups, delivered within the framework of patient-centered care. I hope that these discussions will assist you in making the best choices in close partnership with your patients, leading to improved treatment adherence, reduced subclinical damage, improved rates of sustained clearance of AKs and ultimately the potential for reduced risk of progression to iSCC. Dr Lear reports receiving funds from LEO Pharma during the development of the manuscript. This supplement was funded by LEO Pharma. It is a publication based on the content presented at the LEO Pharma supported satellite symposia to WCD (Canada) and JEADV (Denmark) in 2015. The publication presents views of the author(s) and not necessarily LEO Pharma. Lucid Group, funded by LEO Pharma, is gratefully acknowledged for editorial support in the preparation of this publication.

활성 RAW 264.7 세포에서 항염증 및 자외선 유도 마우스 피부손상의 개선에 대한 새송이 추출물의 효과

본 연구는 먼저 새송이버섯 추출물인 PEE가 활성화된 면역세포에서 항염증 효과가 있는지 알아보았다. 그 결과 LPS로 자극된 RAW 264.7 세포에 PEE를 처리했을 때 5과 15 mg/mL 등 높은 농도에서 NO를 효과적으로 억제하였다. 그리고 LPS가 유도하는 <TEX>$IL-1{\beta}$</TEX>와 IL-6는 5 mg/mL 농도에서는 억제 없었으나, 15 mg/mL 농도에서 현저히 억제하는 효과가 있었다. 다음은 UVB가 유도하는 C57BL/6 마우스 피부손상에 대한 PEE의 개선 효과에 대해서 알아보았다. PEE를 7일간 경구투여한 후 7일, 10, 13일 등 3일 간격으로 하루에 1회씩 UVB (<TEX>$250mJ/cm^2$</TEX>)로 마우스 등 피부에 조사하여 피부손상을 유발하였다. UVB 조사 후부터는 PEE를 경구투여와 함께 피부에 도포하여 PEE가 피부 손상에 대한 개선 효과를 조사하였다. 그 결과 PEE 투여군은 UVB로 유도되는 표피두께, 홍반지수 및 멜라닌 지수가 참고약물로 사용한 비타민 C(AA) 투여군과 유사한 개선되는 효과가 있었다. 또한 PEE 투여군은 UVB가 유도하는 비만세포를 비롯한 염중세포 침윤이 현저히 억제되는 효과가 있었다. 이상의 결과를 종합해볼 때 PEE는 항염증 효과와 더불어 UVB가 유도하는 피부손상을 개선하는 우수한 효과가 있어 기능성 식품소재 및 화장품 소재로 활용할 수 있을 것으로 판단된다. The aim of this study was to investigate the anti-inflammatory and ultraviolet (UV)-protective effect of Pleurotus eryngii extract (PEE) in activated RAW 264.7 cells and UV-induced mouse skin damage. The results showed that PEE strongly inhibited the production of inflammatory mediators such as nitric oxide, interleukin <TEX>$(IL)-1{\beta}$</TEX>, and IL-6 at high concentrations in LPS-stimulated RAW 264.7 macrophages. In addition, PEE treatment suppressed erythema, melanin index, and epidermal thickness to a greater degree than ascorbic acid (AA) treatment in UV-irradiated mice. Finally, PEE treatment inhibited the infiltration of mast cell to a similar degree of AA treatment. Therefore, these results indicate that PEE could improve inflammation and skin damage in immune cells and UV-irradiated mice. This study may provide positive insights into PEE as a functional food and cosmetic ingredient for treatment of inflammation and skin damage.

Protective effects of Polypodium leucotomos extract against UVB-induced damage in a model of reconstructed human epidermis.

Polypodium leucotomos (PL) exerts potent antioxidant, photo-protective, and immune-modulatory activities. A reconstructed human epidermis (RHE) (Episkin) is a suitable model for the evaluation of acute UV-induced cell damage. No data regarding the photo-protective action of PL in this model are available. We evaluated the effects of PL on the prevention of UVB-induced cell damage assessing sunburn cells, CPD formation, p53, Ki-67, p21 expression, and epidermal growth factor (EGF) production. RHE was incubated in standard conditions. PL was topically applied at the concentration of 2 mg/cm2 , immediately before UVB exposition. UVB exposition (300 mJ/cm2 ) was performed using a dedicated UVB lamp. Irradiated samples without PL and non-irradiated samples were used as positive and negative controls. Expression of p53, p21, and Ki-67 was evaluated with immune-histochemical methods. CPD were measured using a monoclonal antibody. PL significantly reduced sunburned cells (-80%) in comparison with positive control. PL significantly prevented the increase in EGF production at tested times. PL significantly reduced the p53 (-80%), p21 (-84%), and Ki-67 (-48%) positive cells. Finally, PL prevented the formation of CPD (0% vs. 20% positive cells). In this model, PL has shown to prevent UVB cell damage, the upregulation of proliferating proteins, and fully blocking the formation of CPD.

Protective effects of silkworm hemolymph extract and its fractions on UV-induced photoaging

Ultraviolet (UV) irradiation induces skin photoaging by generating reactive oxygen species (ROS). ROS caused by UV-irradiation results in loss of skin cells and degradation of extracellular matrix. A number of antioxidants have been chemically synthesized or naturally extracted to prevent ROS-mediated skin photoaging. In our previous work, silkworm hemolymph extract (SHEX) was prepared, and its antioxidant activity was tested by free radical-scavenging assay. This study assessed the protective effects of SHEX on UV-induced photoaging of human immortalized keratinocytes (HaCaT). UVA (365 nm)-induced ROS generation was inhibited by supplementation of silkworm hemolymph (SH). Treatment with SHEX prepared by boiling SH inhibited death of HaCaT cells caused by UVB (315 nm) and UVA irradiation in a dose-dependent manner. Seven fractions were obtained by separating SHEX by gel permeation chromatography and the antioxidant activity of the fractions was examined. The fraction showing the highest protective efficacy on UV-induced cell damage corresponded to the lutein-containing fraction isolated in our previous study. Moreover, the SHEX fraction suppressed the expression of MMP-1 (matrix metalloproteinase-1), a matrix-degrading enzyme, suggesting that the active constituent of SHEX has the potential to inhibit skin photoaging. These results suggest that SHEX can be developed as a dietary and cosmetic supplement for prevention of skin photoaging.

Autophagy in UV Damage Response.

UV radiation exposure from sunlight and artificial tanning beds is the major risk factor for the development of skin cancer and skin photoaging. UV-induced skin damage can trigger a cascade of DNA damage response signaling pathways, including cell cycle arrest, DNA repair and, if damage is irreparable, apoptosis. Compensatory proliferation replaces the apoptotic cells to maintain skin barrier integrity. Disruption of these processes can be exploited to promote carcinogenesis by allowing the survival and proliferation of damaged cells. UV radiation also induces autophagy, a catabolic process that clears unwanted or damaged proteins, lipids and organelles. The mechanisms by which autophagy is activated following UV exposure, and the functions of autophagy in UV response, are only now being clarified. Here, we summarize the current understanding of the mechanisms governing autophagy regulation by UV, the roles of autophagy in regulating cellular response to UV-induced photodamage and the implications of autophagy modulation in the treatment and prevention of photoaging and skin cancer.

Amplification of unscheduled DNA synthesis signal enables fluorescence-based single cell quantification of transcription-coupled nucleotide excision repair.

Nucleotide excision repair (NER) comprises two damage recognition pathways: global genome NER (GG-NER) and transcription-coupled NER (TC-NER), which remove a wide variety of helix-distorting lesions including UV-induced damage. During NER, a short stretch of single-stranded DNA containing damage is excised and the resulting gap is filled by DNA synthesis in a process called unscheduled DNA synthesis (UDS). UDS is measured by quantifying the incorporation of nucleotide analogues into repair patches to provide a measure of NER activity. However, this assay is unable to quantitatively determine TC-NER activity due to the low contribution of TC-NER to the overall NER activity. Therefore, we developed a user-friendly, fluorescence-based single-cell assay to measure TC-NER activity. We combined the UDS assay with tyramide-based signal amplification to greatly increase the UDS signal, thereby allowing UDS to be quantified at low UV doses, as well as DNA-repair synthesis of other excision-based repair mechanisms such as base excision repair and mismatch repair. Importantly, we demonstrated that the amplified UDS is sufficiently sensitive to quantify TC-NER-derived repair synthesis in GG-NER-deficient cells. This assay is important as a diagnostic tool for NER-related disorders and as a research tool for obtaining new insights into the mechanism and regulation of excision repair.

Pheomelanin content of cultured human melanocytes from lightly and darkly pigmented skin: A pyrolysis-gas chromatography/tandem mass spectrometry study

The diverse susceptibility of human skin with various degree of constitutive pigmentation to UV-induced damage, including carcinogenesis, may result from the differences in both total melanin content and the pigment composition, in particular the proportion of potentially harmful pheomelanin. The aim of this study was to compare a pheomelanin content of human epidermal melanocytes derived from lightly and darkly pigmented neonatal skin, using the previously developed method based on the thermal degradation of the pigment. Melanin was isolated from the cultured cells and pyrolysed at 500°C with a microfurnace-type device. The obtained pyrolysates were analyzed for the presence of the marker degradation products using a gas chromatography/tandem mass spectrometry system operating in a multiple reaction monitoring mode. The pheomelanin content was calculated from a calibration curve, generated with the use of a series of synthetic melanin pigments with known percentages of incorporated pheomelanin. We have found that the pheomelanin content of human epidermal melanocytes from neonatal skin does not exceed 10pg per cell, and depends on the degree of constitutive pigmentation. Heavily pigmented melanocytes derived from dark skin produce approximately four times as much pheomelanin as the cells from light skinned donors.

MHY1485 ameliorates UV-induced skin cell damages via activating mTOR-Nrf2 signaling.

Ultra Violet (UV)-caused skin cell damage is a main cause of skin cancer. Here, we studied the activity of MHY1485, a mTOR activator, in UV-treated skin cells. In primary human skin keratinocytes, HaCaT keratinocytes and human skin fibroblasts, MHY1485 ameliorated UV-induced cell death and apoptosis. mTOR activation is required for MHY1485-induced above cytoprotective actions. mTOR kinase inhibitors (OSI-027, AZD-8055 and AZD-2014) or mTOR shRNA knockdown almost abolished MHY1485-induced cytoprotection. Further, MHY1485 treatment in skin cells activated mTOR downstream NF-E2-related factor 2 (Nrf2) signaling, causing Nrf2 Ser-40 phosphorylation, stabilization/upregulation and nuclear translocation, as well as mRNA expression of Nrf2-dictated genes. Contrarily, Nrf2 knockdown or S40T mutation almost nullified MHY1485-induced cytoprotection. MHY1485 suppressed UV-induced reactive oxygen species production and DNA single strand breaks in skin keratinocytes and fibroblasts. Together, we conclude that MHY1485 inhibits UV-induced skin cell damages via activating mTOR-Nrf2 signaling.

Ultraviolet Radiations: Skin Defense-Damage Mechanism.

UV-radiations are the invisible part of light spectra having a wavelength between visible rays and X-rays. Based on wavelength, UV rays are subdivided into UV-A (320-400nm), UV-B (280-320nm) and UV-C (200-280nm). Ultraviolet rays can have both harmful and beneficial effects. UV-C has the property of ionization thus acting as a strong mutagen, which can cause immune-mediated disease and cancer in adverse cases. Numbers of genetic factors have been identified in human involved in inducing skin cancer from UV-radiations. Certain heredity diseases have been found susceptible to UV-induced skin cancer. UV radiations activate the cutaneous immune system, which led to an inflammatory response by different mechanisms. The first line of defense mechanism against UV radiation is melanin (an epidermal pigment), and UV absorbing pigment of skin, which dissipate UV radiation as heat. Cell surface death receptor (e.g. Fas) of keratinocytes responds to UV-induced injury and elicits apoptosis to avoid malignant transformation. In addition to the formation of photo-dimers in the genome, UV also can induce mutation by generating ROS and nucleotides are highly susceptible to these free radical injuries. Melanocortin 1 receptor (MC1R) has been known to be implicated in different UV-induced damages such as pigmentation, adaptive tanning, and skin cancer. UV-B induces the formation of pre-vitamin D3 in the epidermal layer of skin. UV-induced tans act as a photoprotection by providing a sun protection factor (SPF) of 3-4 and epidermal hyperplasia. There is a need to prevent the harmful effects and harness the useful effects of UV radiations.

Plasmon-induced photoelectrochemical biosensor for in situ real-time measurement of biotin-streptavidin binding kinetics under visible light irradiation

We developed a localized surface plasmon-induced visible light-responsive photoelectrochemical (PEC) biosensor using a titanium dioxide (TiO2) photoelectrode loaded with gold nanoislands (AuNIs) for in situ real-time measurement of biotin-streptavidin association. As a proof of concept, self-assembled thiol-terminated biotin molecules bound on a AuNIs/TiO2 photoelectrode were successfully utilized to explore the photocurrent response to streptavidin-modified gold nanoparticle (STA-AuNP) solutions. This plasmon-induced PEC biosensor is simple and easy to miniaturize. Additionally, the PEC biosensor achieves highly sensitive measurements under only visible light irradiation and prevents the UV-induced damage of samples. Furthermore, a novel approach has been proposed to realize the real-time monitoring of biotin-STA binding affinities and kinetics by analyzing the PEC sensing characteristics. This PEC biosensor and novel analysis method could provide a new approach for the specific electrical detection and real-time kinetic measurements for clinical diagnostics and drug development.