Simulated Solar UV Research Articles

Utilizing Zn(Cu/Cr)Al-Layered Double Hydroxide-Based Photocatalysts for Effective Photodegradation of Environmental Pollutants

Layered double hydroxides (LDHs) and their derived mixed oxides are emerging as a promising class of biocompatible inorganic lamellar nanomaterials. The detailed structure and textural characteristics of the synthesized LDH-based materials were examined using X-ray diffraction, Fourier transform infrared spectroscopy, and N2 adsorption/desorption isotherm. This study explored the removal efficiency of pharmaceutical tolperisone hydrochloride (TLP), as well as the herbicides quinmerac (QUI) and clomazone (CLO) from water, using dried and calcined LDH-based photocatalysts under simulated solar irradiation and UV irradiation. A higher removal efficiency was observed using UV irradiation, for all substrates. The most effective removal was achieved using ZnAl photocatalysts thermally treated at 100 °C (ZnAl 100) and 500 °C (ZnAl 500). The highest removal rates were observed in the TLP/ZnAl 100 and QUI/ZnAl 100 systems, achieving ~79% and ~86% removal after 75 min of treatment under UV. In contrast, the CLO/ZnAl 100 and CLO/ZnAl 500 systems achieved ~47% removal of CLO. Furthermore, this study investigated the role of reactive species to elucidate the mechanisms of photodegradation under UV. It was found that in the degradation of TLP and QUI in the presence of ZnAl 100 and ZnAl 500, the superoxide anion radical played the most important role.

Eradication of skin microbiota restores cytokine production and release in polymorphic light eruption.

Polymorphic light eruption (PLE) has been mechanistically linked to cytokine abnormalities. Emerging preclinical evidence posits the skin microbiome as a critical modulator of ultraviolet (UV)-induced cytokine expression, thereby influencing subsequent immune responses. This intricate relationship remains underexplored in the context of PLE. Hence, we investigated the differential responses between disinfected and non-disinfected skin following both single and repetitive exposures to solar-simulated UV radiation in patients with PLE. An experimental, half-body pilot study was conducted involving six PLE patients and 15 healthy controls. Participants' skin was exposed to single and multiple doses of solar-simulated UV radiation, both in disinfected and in non-disinfected skin areas. The co-primary outcomes were PLE score and cytokine expression in blister fluid analysed through OLINK proteomic profiling. Secondary outcomes were erythema, pigmentation, induction of apoptotic cells in vacuum-generated suction blisters, and density of infiltrate in skin biopsies of PLE patients. Among the 71 cytokines analysed, baseline expression levels of 20 specific cytokines-integral to processes such as apoptosis, inflammation, immune cell recruitment, cellular growth, and differentiation-were significantly impaired in PLE patients compared with healthy controls. Notably, skin disinfection reversed the observed cytokine imbalances following a single UV exposure at the minimal erythema dose (MED) level and exhibited even more pronounced effects after multiple UV exposures. However, no significant differences were evident in PLE score, erythema, pigmentation, or rates of apoptotic cell induction upon UV radiation. These findings provide evidence for UV-driven cytokine regulation by the skin microbiota and imply microbiome involvement in the PLE immune response.

Evaluation of MAA Analogues as Potential Candidates to Increase Photostability in Sunscreen Formulations

Avobenzone is one of the most widely used sunscreens in skin care formulations, but suffers from some drawbacks, including photo instability. To mitigate this critical issue, the use of octocrylene as a stabilizer is a common approach in these products. However, octocrylene has been recently demonstrated to show potential phototoxicity. The aim of this work is to analyze the performance of a series of mycosporine-like amino acid (MAA)-inspired compounds to act as avobenzone stabilizers as an alternative to octocrylene. Different avobenzone/MAA analogue combinations included in galenic formulations were followed under increasing doses of solar-simulated UV radiation. Some of the synthetic MAA analogues analyzed were able to increase by up to two times the UV dose required for 50% of avobenzone photobleaching. We propose some of these MAA analogues as new candidates to act as avobenzone-stabilizing compounds in addition to their UV absorbance and antioxidant properties, together with a facile synthesis.

Solar urticaria involves rapid mast cell STAT3 activation and neutrophil recruitment, with FcεRI as an upstream regulator

Solar urticaria is a rare photodermatosis characterized by rapid-onset sunlight-induced urticaria, but its pathophysiology is not well understood. We sought to define cutaneous cellular and molecular events in the evolution of solar urticaria following its initiation by solar-simulated UV radiation (SSR) and compare with healthy controls (HC). Cutaneous biopsy specimens were taken from unexposed skin and skin exposed to a single low (physiologic) dose of SSR at 30 minutes, 3 hours, and 24 hours after exposure in 6 patients with solar urticaria and 6 HC. Biopsy specimens were assessed by immunohistochemistry and bulk RNA-sequencing analysis. In solar urticaria specimens, there was enrichment of several innate immune pathways, with striking early involvement of neutrophils, which was not observed in HC. Multiple proinflammatory cytokine and chemokine genes were upregulated (including IL20, IL6, and CXCL8) or identified as upstream regulators (including TNF, IL-1β, and IFN-γ). IgE and FcεRI were identified as upstream regulators, and phosphorylated signal transducer and activator of transcription 3 expression in mast cells was increased in solar urticaria at 30 minutes and 3 hours after SSR exposure, suggesting a mechanism of mast cell activation. Clinical resolution of solar urticaria by 24 hours mirrored resolution of inflammatory gene signature profiles. Comparison with available datasets of chronic spontaneous urticaria showed transcriptomic similarities relating to immune activation, but several transcripts were identified solely in solar urticaria, including CXCL8 and CSF2/3. Solar urticaria is characterized by rapid signal transducer and activator of transcription 3 activation in mast cells and involvement of multiple chemotactic and innate inflammatory pathways, with FcεRI engagement indicated as an early event.

Assessment of Recovery Time Effects on Human Primary Neonatal Dermal Fibroblasts After Exposure to Solar-Simulated Ultraviolet Radiation.

Introduction: Photoaging that is accompanied by gene expression alteration is known as early aging of the skin due to overexposure to natural and/or artificial ultraviolet radiation (UVR). The assessment of gene expression alteration in human primary neonatal dermal fibroblasts depending on recovery time after exposure to solar simulated ultraviolet radiation (ssUVR) is the main aim of this bioinformatic study. Methods: Data are extracted from Gene Expression Omnibus (GEO). The pre-evaluation is done via the GEO2R program. The Significant differentially expressed genes (DEGs) were assessed via protein-protein interaction (PPI) network analysis, and the central genes were identified. The central genes were enriched via gene ontology assessment. Results: Among 224 significant DEGs, 20 central genes including TOP2A, MKI67, BRCA1, HELLS, MAD2L1, ANLN, KIF11, MSH2, KRAS, NCAPG, RFC3, PLK4, WDHD1, BLM, CDKN3, KIF15, SMARCA5, and ATAD2 as hub genes and TOP2A, MKI67, BRCA1, ANLN, KRAS, PLK4, SMARCA5, MMP2, and TLR4 as bottleneck genes were determined. Eight central genes were associated with 16 biological terms. Conclusion: In conclusion, significant differences appeared between gene expression conditions of the cells after 1-day and 5-day recovery. Molecular events include the repair and continuation of photodamages. It is possible to introduce drug targets to prevent the progress of induced damages.

Exposure to solar ultraviolet radiation establishes a novel immune suppressive lipidome in skin-draining lymph nodes.

The ability of ultraviolet radiation to suppress the immune system is thought to be central to both its beneficial (protection from autoimmunity) and detrimental (carcinogenic) effects. Previous work revealed a key role for lipids particularly platelet-activating factor and sphingosine-1-phosphate in mediating UV-induced immune suppression. We therefore hypothesized that there may be other UV-induced lipids that have immune regulatory roles. To assess this, mice were exposed to an immune suppressive dose of solar-simulated UV (8 J/cm2). Lipidomic analysis identified 6 lipids (2 acylcarnitines, 2 neutral lipids, and 2 phospholipids) with significantly increased levels in the skin-draining lymph nodes of UV-irradiated mice. Imaging mass spectrometry of the lipids in combination with imaging mass cytometry identification of lymph node cell subsets indicated a preferential location of UV-induced lipids to T cell areas. In vitro co-culture of skin-draining lymph node lipids with lymphocytes showed that lipids derived from UV-exposed mice have no effect on T cell activation but significantly inhibited T cell proliferation, indicating that the lipids play an immune regulatory role. These studies are important first steps in identifying novel lipids that contribute to UV-mediated immune suppression.

Evaluation of Photocatalytic Performance of Nano-Sized Sr0.9La0.1TiO3 and Sr0.25Ca0.25Na0.25Pr0.25TiO3 Ceramic Powders for Water Purification.

Water pollution is a significant issue nowadays. Among the many different technologies for water purification, photocatalysis is a very promising and environment-friendly approach. In this study, the photocatalytic activity of Sr0.9La0.1TiO3 (SLTO) and Sr0.25Ca0.25Na0.25Pr0.25TiO3 (SCNPTO) nano-sized powders were evaluated by degradation of pindolol in water. Pindolol is almost entirely insoluble in water due to its lipophilic properties. The synthesis of the SCNPTO was performed using the reverse co-precipitation method using nitrate precursors, whereas the SLTO was produced by spray pyrolysis (CerPoTech, Trondheim Norway). The phase purity of the synthesized powders was validated by XRD, while HR-SEM revealed particle sizes between 50 and 70 nm. The obtained SLTO and SCNPTO powders were agglomerated but had relatively similar specific surface areas of about 27.6 m2 g-1 and 34.0 m2 g-1, respectively. The energy band gaps of the SCNPTO and SLTO were calculated (DFT) to be about 2.69 eV and 3.05 eV, respectively. The photocatalytic performances of the materials were examined by removing the pindolol from the polluted water under simulated solar irradiation (SSI), UV-LED irradiation, and UV irradiation. Ultra-fast liquid chromatography was used to monitor the kinetics of the pindolol degradation with diode array detection (UFLC-DAD). The SLTO removed 68%, 94%, and 100% of the pindolol after 240 min under SSI, UV-LED, and UV irradiation, respectively. A similar but slightly lower photocatalytic activity was obtained with the SCNPTO under identical conditions, resulting in 65%, 84%, and 93% degradation of the pindolol, respectively. Chemical oxygen demand measurements showed high mineralization of the investigated mixtures under UV-LED and UV irradiation.

Removal of hydrochlorothiazide from drinking and environmental water: Hydrolysis, direct and indirect photolysis

Diuretic hydrochlorothiazide (HCTZ) has been detected in drinking and environmental water. Since HCTZ exhibited some toxic effects on the environment, it is essential to propose safe and economical ways of its removal. The influence of water quality on the removal efficiency of HCTZ from the environment was observed. The stability of HCTZ was investigated in ultrapure (UPW), tap, and two different environmental waters, by hydrolysis, photolysis, and indirect photolysis under simulated solar irradiation (SSI) and UV irradiation. Also, experiments were conducted at temperatures of (5 ± 1) °C and (25 ± 1) °C, in the dark. Comprehensive experimental and computational analysis was performed to examine the stability and reactivity. The results show that HCTZ is susceptible to hydrolysis. Photolysis and indirect photolysis were efficient under UV irradiation, wherein HCTZ was entirely degraded after 180 min of irradiation in UPW. Chloride ions, carbonates, calcium, and magnesium ions present in natural waters inhibited the degradation of HCTZ. This diuretic has significant interaction with •OH radicals. A 4-amino-6-chlorobenzene-1,3- disulfonamide (ABSA) was observed as a stable degradation product, and ABSA formation's degradation mechanism was proposed. Mineralization of HCTZ was above 50% in H2O2/UV system in UPW after 180 min of irradiation.

A standardized Terminalia chebula fruit extract alters the expression of genes associated with skin architecture and barrier formation.

Terminalia chebula (TC) is a deciduous tree of which extracts have demonstrated efficacy for treatment of photodamage, skin aging, and wound healing. However, molecular and cellular mechanisms underlying these benefits remain unclear. To profile dermal expression responses to a standardized tannin-enriched TC fruit extract (Synastol® TC). Microarrays were used to evaluate gene expression in three-dimensional reconstituted human skin cultures. Genome-wide expression responses to TC were the opposite to those observed in cells exposed to oxidative stress, solar-simulated UV radiation, and wounding, with increased expression of genes associated with water homeostasis, skin barrier establishment, blood vessel development, and circadian rhythms. TC also increased expression of extracellular matrix components, such as collagens (COL1A1, COL1A2) and proteoglycans (PRELP, OGN), and in separate assays, we showed that TC inhibits MMP enzymes (MMP-1, MMP-2, MMP-3, MMP-9, MMP-12) and microbial activity (S. aureus, P. acnes). Unexpectedly, mRNA and protein levels of late keratinocyte (KC) differentiation markers (FLG, LOR) were increased by TC, and expression responses in skin cultures broadly resembled those that occur with KC differentiation. Consistent with these results, TC increased expression of transcription factors regulating KC differentiation (FOS, GHRL3, PPARG) and we noted enrichment of AP-1 binding sites in regions upstream of TC-increased genes. These results demonstrate that functionally important TC extract responses occur in the epidermis and are therefore not restricted to the dermal layer. Our findings thus suggest mechanisms by which TC may strengthen full-thickness skin architecture for treatment of skin aging and/or chronic wounds.

Effects of the Brookite Phase on the Properties of Different Nanostructured TiO2 Phases Photocatalytically Active Towards the Degradation of N-Phenylurea.

Different sol‐gel synthesis methods were used to obtain four nanostructured mesoporous TiO2 samples for an efficient photocatalytic degradation of the emerging contaminant N‐phenylurea under either simulated solar light (1 Sun) or UV light. Particularly, two TiO2 samples were obtained by means of as many template‐assisted syntheses, whereas other two TiO2 samples were obtained by a greener template‐free procedure, implying acidic conditions and, then, calcination at either 200 °C or 600 °C. In one case, anatase was obtained, whereas in the other three cases mixed crystalline phases were obtained. The four TiO2 samples were characterized by X‐ray powder diffraction (followed by Rietveld analysis); Transmission Electron Microscopy; N2 adsorption/desorption at −196 °C; Diffuse Reflectance UV/Vis spectroscopy and ζ‐potential measurements. A commercial TiO2 powder (i. e., Degussa P25) was used for comparison. Differences among the synthesized samples were observed not only in their quantitative phase composition, but also in their nanoparticles morphology (shape and size), specific surface area, pore size distribution and pHIEP (pH at isoelectric point), whereas the samples band‐gap did not vary sizably. The samples showed different photocatalytic behavior in terms of N‐phenylurea degradation, which are ascribed to their different physico‐chemical properties and, especially, to their phase composition, stemming from the different synthesis conditions.

Do topically aplied skin creams containing retinyl palmitate affect the photocarcinogenecity of simulated solar light?

Retinyl palmitate (all-trans-retinyl palmitate; RP) was nominated in 2001 by the U.S. Food and Drug Administration's Center for Food Safety and Applied Nutrition (CFSAN) to the National Toxicology Program (NTP) as a high priority compound for phototoxicity and photocarcinogenicity studies at the National Center for Toxicological Research (NCTR). Studies with SKH-1 hairless mice are required to test whether topical application of RP enhances the phototoxicity and photocarcinogenicity of simulated solar light and UV light. Mechanistic studies are needed to provide insight into the disposition of RP in vitro and on the skin of mice, and to test thoroughly whether genotoxic damage by UV-induced radicals may participate in any toxicity of topically applied RP in the presence of UV light.

The sunless tanning agent dihydroxyacetone induces stress response gene expression and signaling in cultured human keratinocytes and reconstructed epidermis

Sunless (chemical) tanning is widely regarded as a safe alternative to solar UV-induced skin tanning known to be associated with epidermal genotoxic stress, but the cutaneous biology impacted by chemical tanning remains largely unexplored. Chemical tanning is based on the formation of melanin-mimetic cutaneous pigments (‘melanoidins’) from spontaneous amino-carbonyl (‘glycation’) reactions between epidermal amino acid/protein components and reactive sugars including the glycolytic ketose dihydroxyacetone (DHA). Here, we have examined the cutaneous effects of acute DHA-exposure on cultured human HaCaT keratinocytes and epidermal reconstructs, profiled by gene expression array analysis and immunodetection. In keratinocytes, DHA-exposure performed at low millimolar concentrations did not impair viability while causing a pronounced cellular stress response as obvious from rapid activation of phospho-protein signal transduction [p-p38, p-Hsp27(S15/S78), p-eIF2α] and gene expression changes (HSPA6, HMOX1, CRYAB, CCL3), not observable upon exposure to the non-ketose, tanning-inactive DHA-control glycerol. Formation of advanced glycation end products (AGEs) from posttranslational protein-adduction was confirmed by quantitative mass spectrometric detection of N-ε-(carboxyethyl)-l-lysine (CEL) and N7-carboxyethyl-l-arginine, and skin cells with CRISPR-Cas9-based elimination of the carbonyl stress response gene GLO1 (encoding glyoxalase 1) displayed hypersensitivity to DHA-cytotoxicity. In human epidermal reconstructs a topical use-relevant DHA-dose regimen elicited a comparable stress response as revealed by gene expression array (HSPA1A, HSPA6, HSPD1, IL6, DDIT3, EGR1) and immunohistochemical analysis (CEL, HO-1, p-Hsp27-S78). In DHA-treated SKH-1 hairless mouse skin IHC-detection revealed epidermal occurrence of CEL- and p-Hsp27-epitopes. For comparison, stress response gene expression array analysis was performed in epidermis exposed to a supra-erythemal dose of solar simulated UV (2 MEDs), identifying genes equally or differentially sensitive to either one of these cutaneous stimuli [DHA (‘sunless tanning’) versus solar UV (‘sun-induced tanning’)]. Given the worldwide use of chemical tanners in consumer products, these prototype data documenting a DHA-induced specific cutaneous stress response deserve further molecular exploration in living human skin.

Photodegradation of algae and macrophyte-derived dissolved organic matter: A multi-method assessment of DOM transformation

Due to the frequent occurrence of algal bloom and eutrophication, algae and macrophyte-derived dissolved organic matter (DOM) play a more important role in the lake environment. In the study, algae and macrophyte-derived DOM were exposed for 30 days either in the dark or light in order to develop a broader understanding of their photochemical and microbial transformation. Changes of quantification and quality of DOM were characterized by Uv–vis spectroscopy, fluorescence spectroscopy, Fourier infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Simulated solar UV exposure (30 d) without sterilization removed 49.7% and 42.4% of the dissolved organic carbon (DOC) from chlorella and water chestnut DOM, respectively. In contrast, 31.6% and 22.2% of DOC were removed under dark conditions accordingly. Compared with humic OM, autochthonous DOM was more biolabile and less photolabile, with less photochemical removal of DOC in this study. Molecular structures of studied DOM exhibited selective alterations during incubation. Fluorescence spectroscopy revealed that fulvic acid-like substances were susceptible to photodegradation, while protein-like substances were susceptible to both photodegradation and biodegradation. Furthermore, analytic results of carbon functional groups suggested that polysaccharides were more biolabile; aromatics were more photolabile; and phenols/aromatic proteins were both biolabile and photolabile. The higher proportion of aliphatics and lower proportion of aromatics in autochthonous DOM might be the primary cause of their greater biodegradation and weaker photodegradation.

Exposure to solar ultraviolet radiation limits diet-induced weight gain, increases liver triglycerides and prevents the early signs of cardiovascular disease in mice

Background and aimsSunlight exposure is associated with a number of health benefits including protecting us from autoimmunity, cardiovascular disease, obesity and diabetes. Animal studies have confirmed that ultraviolet (UV)-B radiation, independently of vitamin D, can limit diet-induced obesity, metabolic syndrome and atherosclerosis. The aim of this study is to investigate whether exposure to the UV radiation contained in sunlight impacts on these disease parameters. Methods and resultsWe have trialled an intervention with solar UV in obese and atherosclerosis-prone mice. We have discovered that solar-simulated UV can significantly limit diet-induced obesity and reduce atheroma development in mice fed a diet high in sugar and fat. The optimal regime for this benefit was exposure once a week to solar UV equivalent to approximately 30 min of summer sun. Exposure to this optimal dose of solar UV also led to a significant increase in liver triglycerides which may protect the liver from damage. ConclusionOur results show that the UV contained in sunlight has the potential to prevent and treat chronic disease at sites distant from irradiated skin. A major health challenge going forward will be to harness the power of the sun safely, without risking an increase in skin cancers.

Phenotypic and lipidomic characterization of primary human epidermal keratinocytes exposed to simulated solar UV radiation

BackgroundUltraviolet (UV) radiation is known to be one of the most important environmental hazards acting on the skin. The most part of UV radiation is absorbed in the epidermis, where keratinocytes are the most abundant and exposed cell type. Lipids have an important role in skin biology, not only for their important contribution to the maintenance of the permeability barrier but also for the production and storage of energy, membrane organization and cell signalling functions. However, the effects on the lipid composition of keratinocytes under UV radiation are little explored. ObjectiveThe present work aims to explore the effects on the phenotype and lipid content of primary human keratinocytes exposed to simulated solar UV radiation. MethodsKeratinocytes were exposed to a single (acute exposure) and repeated simulated solar UV irradiations for 4 weeks (chronic exposure). Cell viability and morphology were explored, as well as the production of reactive oxygen species. Then, lipid extracts were analysed through liquid chromatography coupled to mass spectrometry (LC–MS) and the data generated was processed using the ROIMCR chemometric methodology together with partial least squares discriminant analysis (PLS-DA), to finally reveal the most relevant lipid changes that occurred in keratinocytes upon UV irradiation. Also, the potential induction of keratinocyte differentiation was explored by measuring the increase of involucrin. ResultsUnder acute irradiation, cell viability and morphology were not altered. However, a general increase of phosphatidylcholines (PC) phosphatidylethanolamines (PE) and phosphatidylglycerol (PG) together with a slight sphingomyelin (SM) decrease were found in UV irradiated cells, among other changes. In addition, keratinocyte cultures did not present any differentiation hallmark. Contrary to acute-irradiated cells, in chronic exposures, cell viability was reduced and keratinocytes presented an altered morphology. Also, hallmarks of differentiation, such as the increase of involucrin protein and the autophagy induction were detected. Among the main lipid changes that accompanied this phenotype, the increase of long-chain ceramides, lysoPC and glycerolipid species were found. ConclusionImportant lipid changes were detected under acute and chronic UV irradiation. The lipid profile under chronic exposure may represent a lipid fingerprint of the keratinocyte differentiation phenotype.

Synthesis of cuboid BiOCl nanosheets coupled with CdS quantum dots by region-selective deposition process with enhanced photocatalytic activity

A facile region-selective deposition process was adopted to prepare high-dispersed CdS QDs on BiOCl nanosheets with the surface modification of thioglycollic acid (TGA). The samples were systematically characterized by XRD, SEM, TEM, HRTEM, EDS, XPS, UV–vis DRS, EIS and PL. The results indicate that CdS QDs with size of 5–10 nm dispersed uniformly on the surface of cuboid BiOCl nanosheets. The photocatalytic performance tests reveal that the CdS QDs-3%/BiOCl composite exhibits an excellent photocatalytic activity, which is over 4.0 and 4.8 times as high as pure BiOCl for methyl orange (MO) and phenol photodegradation rate under simulated solar light and UV light illumination, respectively. The enhanced photocatalytic performance of the CdS QDs/BiOCl composites should be attributed to the improved visible light absorption and the high migration efficiency of the photogenerated electron-holes due to the matched band gap and the widespread heterostructure between CdS QDs and BiOCl.

Transcription factors and stress response gene alterations in human keratinocytes following Solar Simulated Ultra Violet Radiation

Ultraviolet radiation (UVR) from sunlight is the major effector for skin aging and carcinogenesis. However, genes and pathways altered by solar-simulated UVR (ssUVR), a mixture of UVA and UVB, are not well characterized. Here we report global changes in gene expression as well as associated pathways and upstream transcription factors in human keratinocytes exposed to ssUVR. Human HaCaT keratinocytes were exposed to either a single dose or 5 repetitive doses of ssUVR. Comprehensive analyses of gene expression profiles as well as functional annotation were performed at 24 hours post irradiation. Our results revealed that ssUVR modulated genes with diverse cellular functions changed in a dose-dependent manner. Gene expression in cells exposed to a single dose of ssUVR differed significantly from those that underwent repetitive exposures. While single ssUVR caused a significant inhibition in genes involved in cell cycle progression, especially G2/M checkpoint and mitotic regulation, repetitive ssUVR led to extensive changes in genes related to cell signaling and metabolism. We have also identified a panel of ssUVR target genes that exhibited persistent changes in gene expression even at 1 week after irradiation. These results revealed a complex network of transcriptional regulators and pathways that orchestrate the cellular response to ssUVR.

Abstract 2244: Pharmacological TLR4 antagonism using topical resatorvid blocks solar UV-induced skin tumorigenesis in SKH-1 mice

Abstract An urgent need exists for the development of more efficacious molecular strategies targeting non-melanoma skin cancer (NMSC), the most common malignancy worldwide. Inflammatory signaling downstream of Toll-like receptor 4 (TLR4) is a causative factor in several forms of tumorigenesis, yet its role in solar UV-induced skin carcinogenesis remains undefined. In our recently published work based upon immunohistochemical (IHC) analysis of NMSC tissue microarrays and proteomic analysis of reverse-phase protein microarrays (RPPA) from banked human tissue, we observed increased TLR4 expression in association with tumorigenic progression from normal skin to actinic keratosis and cutaneous squamous cell carcinoma. In immortalized keratinocytes expressing luciferase reporter constructs, resatorvid potently inhibits UV-induced AP-1 and NF-κB signaling, associated with downregulation of inflammatory mediators (IL-6, IL-8, IL-10) and MAP Kinase phosphorylation. In a subsequent acute exposure model in SKH-1 mice, topical resatorvid efficiently antagonized UV-induced stress signaling while potentiating UV-induced epidermal apoptosis. In the current report, we show for the first time that pharmacological inhibition of TLR4 using the specific antagonist resatorvid (TAK-242) blocks UV-induced tumorigenesis in SKH-1 mice. After assessing photostability, efficient cutaneous delivery, and skin residence time of topical resatorvid, we then tested the feasibility of TLR4-directed inhibition of UV-induced tumorigenesis. To this end, SKH-1 mice were split into three groups (n = 20). Each group was exposed to solar-simulated UV (three times a week; 15 weeks duration), followed by another 10 weeks in the absence of UV exposure (sacrifice at week 25). The control group received topical vehicle (acetone) on their backs 1 hour prior to UV exposure (three times a week until sacrifice). The “Prevention” group received topical resatorvid following an analogous dosing regimen. The “Intervention” group received vehicle 1hr prior to each UV treatment but switched to topical resatorvid three times a week only after UV was terminated. In the Prevention model, topical treatment with resatorvid significantly inhibited both tumor area (66% reduction, p = 0.0052) and tumor multiplicity (32% reduction, p = 0.0329; cross sectional Kruskal-Wallis test). In the Intervention model, a marked inhibition of both measures of tumor yield was observed, yet they did not reach statistical significance. Likewise, suppression of UV-induced TLR4-driven signaling was also confirmed in murine skin harvested at week 14 (prior to tumor onset), as assessed by IHC and RPPA analysis. Taken together, these data generated using resatorvid in a murine photocarcinogenesis model suggest that pharmacological TLR4 antagonism may represent a novel molecular strategy for topical prevention of solar UV-induced NMSC. Citation Format: Sally E. Dickinson, Karen Blohm-Mangone, Nichole B. Burkett, Shekha Tahsin, Paul B. Myrdal, Kelly L. Karlage, Jaroslav Janda, Kathylynn Saboda, Denise J. Roe, Zigang Dong, Ann M. Bode, Emanuel F. Petricoin, Valerie S. Calvert, Clara Curiel-Lewandrowski, David S. Alberts, Georg T. Wondrak. Pharmacological TLR4 antagonism using topical resatorvid blocks solar UV-induced skin tumorigenesis in SKH-1 mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2244. doi:10.1158/1538-7445.AM2017-2244

Skin Erythema, Pigmentation and Hydration Kinetics after Ultraviolet Radiation-induced Photodamage in Southern Chinese Women.

Although there have been some studies about changes of skin erythema and pigmentation following ultraviolet radiation in other races, the relevant data in Chinese have never been achieved. Thus, we evaluated the long-time course of skin erythema, pigmentation and hydration changes after different doses of solar-simulated ultraviolet (SSUV) irradiation in 26 Chinese women for 168 days. The erythema index increased abruptly and peaked during 3 days of SSUV exposure, then slowly returned to the baseline level starting at day 7 and completely recovered during 168-day course of this study only in one minimal erythema doses (MED) SSUV irradiation. The melanin index started to slowly increase at day 3 of SSUV exposure, peaking at day 14 and gradually returned to the baseline level thereafter, but did not return to the baseline level during 168-day course in all doses. Skin hydration slowly declined at day 3 of exposure, hitting the lowest point at day 7, then slowly recovered starting at day 14 and completely returned to the baseline level at day 28 only in 1.5MED. These results will serve as baseline data on Chinese skin and provide useful references for the treatment of serious skin photodamage in Chinese.

Phototoxic target lipid model of single polycyclic aromatic hydrocarbons.

A phototoxic target lipid model (PTLM) is developed to predict phototoxicity of individual polycyclic aromatic hydrocarbons (PAHs) measured either as median lethal concentration (LC50) or median lethal time (LT50) for a 50% toxic response. The model is able to account for the differences in the physical/chemical properties of PAHs, test species sensitivities, and variations in light source characteristics, intensity, and length of exposure. The PTLM is based on the narcotic target lipid model (NTLM) of PAHs. Both models rely on the assumption that mortality occurs when the toxicant concentration in the target lipid of the organism reaches a threshold concentration. The PTLM is applied to observed LC50s and LT50s for 20 individual PAHs, 15 test species-including arthropods, fishes, amphibians, annelids, mollusks, and algae-exposed to simulated solar and various UV light sources, for exposure times varying from less than 1 h to 100 h, a total of 333 observations. The LC50 concentrations range from less than 0.1 µg/L to greater that 104 µg/L. The model has 2 fitting parameters that are constant and apply to all PAHs and organisms. The root mean square errors of prediction for log(LC50) and log(LT50) are 0.473 and 0.382, respectively. The results indicate that the PTLM can predict the phototoxicity of single PAHs over a wide range of exposure conditions and to organisms with a wide range of sensitivities. Environ Toxicol Chem 2017;36:926-937. © 2016 SETAC.