Acute UV Research Articles

Cyclodextrin nano-organogels as a delivery vehicle for peppermint essential oil to enhance its physico-chemical properties and skin photoprotective performance

Acute sun exposure could lead to erythema and inflammation. This Investigation aims to determine the efficacy of the complexation of peppermint oil (PO) with cyclodextrin in enhancing its physicochemical properties. Nano-organogels were prepared by direct hot melting method. Cyclodextrin (CD) PO was prepared by co-lyophilized method and included in F6. The particle size values were all below 150 nm. F6 polymeric showed high antioxidant activity, in vitro SPF, and stability. CD nano-organogel showed the least release and the highest skin deposition values. This high skin deposition is assured by confocal microscopy. Histology revealed its anti-inflammatory effect against acute UV irradiation. PO CD nano-organogel demonstrates a promising modality for anti-inflammatory therapy against UV irradiation.

Efek Blueberry (Vaccinium sp.) Terhadap Kelembapan Kulit yang Terpapar Sinar Ultraviolet Akut

Introduction: Maintained skin moisture is an indication of healthy skin. Acute UV exposure can cause sunburn, which is characterized by a loss of moisture in the skin. Polyphenol compounds are one practical approach to protecting the skin from sunburn so that skin moisture is maintained. Blueberries are one of the natural ingredients consists of anthocyanin compounds, which are polyphenols from the flavonoid group.
 Aims: To determine the effect of blueberries on skin moisture exposed to acute ultraviolet rays.
 Methods: Literature study using references in the form of research articles and literature reviews from national and international journals and related books published in the last 10 years. In writing this literature review, 42 references were used which were accessed through Google Scholar, NCBI, Crossref, and Pubmed.
 Results: Blueberries anthocyanins can maintain skin moisture from increased transepidermal water loss (TEWL) due to acute UV ray exposure by reducing the formation of UV stimulated reactive oxygen species (ROS) and lipid peroxidation in keratinocyte cells to maintain the elastic modulus and mechanical properties of keratinocytes as well as can prevent sunburn by reducing the skin's modulation of UV exposure. However, the absorption of anthocyanin compounds in the intestine is so low that taking blueberries orally alone is not enough to achieve good biodistribution.
 Conclusion: Blueberries affect retaining moisture in skin exposed to acute UV rays, so they have the potential to be used as skincare ingredients. However, further research needs to be done, especially to determine the side effects that can be caused and the required extract concentration.

The hyaluronan metabolism in the UV-irradiated human epidermis and the relevance of in vitro epidermal models.

Exposure to the sun affects the skin and may eventually result in UV-induced skin damage. It is generally known that hyaluronan (HA) is one of the main structural and functional components of the skin. However, UV-related changes in the HA metabolism in the skin have not yet been elucidated. Using qRT-PCR, confocal microscopy and LC-MS/MS we compared the naturally sun-exposed (SE), sun-protected, experimentally repeatedly UVA + UVB-exposed and acutely (once) UVA + UVB irradiated skin of Caucasian women. The epidermis was harvested by means of suction blistering 24 h after the acute irradiation. In addition, the epidermis was compared with a UV-irradiated in vitro reconstituted 3D epidermis (EpiDerm) and an in vitro 2D culture of normal human keratinocytes (NHEK). The amount of HA was found to be statistically significantly enhanced in the acutely irradiated epidermis. The acute UV evinced the upregulation of HA synthases (HAS2 and HAS3), hyaluronidases (HYAL2 and HYAL3), Cluster of differentiation 44 (CD44), and Cell Migration Inducing Proteins (CEMIP and CEMIP2), while only certain changes were recapitulated in the 3D epidermis. For the first time, we demonstrated the enhanced gene and protein expression of CEMIP and CEMIP2 following UV irradiation in the human epidermis. The data suggest that the HA metabolism is affected by UV in the irradiated epidermis and that the response can be modulated by the underlying dermis.

CCN1 is predominantly elevated in human skin dermis by solar-simulated ultraviolet irradiation and accumulated in dermal extracellular matrix.

Skin primarily comprises a collagen-rich extracellular matrix (ECM) that provides structural and functional support to the skin. Aging causes progressive loss and fragmentation of dermal collagen fibrils, leading to thin and weakened skin (Dermal aging). We previously reported that CCN1 is elevated in naturally aged human skin, photoaged human skin, and acute UV-irradiated human skin dermal fibroblasts in vivo. Elevated CCN1 alters the expression of numerous secreted proteins that have deleterious effects on the dermal microenvironment, impairing the structural integrity and function of the skin. Here we show that CCN1 is predominantly elevated in the human skin dermis by UV irradiation and accumulated in the dermal extracellular matrix. Laser capture microdissection indicated that CCN1 is predominantly induced in the dermis, not in the epidermis, by acute UV irradiation in human skin in vivo. Interestingly, while UV-induced CCN1 in the dermal fibroblasts and in the medium is transient, secreted CCN1 accumulates in the ECM. We explored the functionality of the matrix-bound CCN1 by culturing dermal fibroblasts on an acellular matrix plate that was enriched with a high concentration of CCN1. We observed that matrix-bound CCN1 activates integrin outside-in signaling resulting in the activation of FAK and its downstream target paxillin and ERK, as well as elevated MMP-1 and inhibition of collagen, in human dermal fibroblasts. These data suggest that accumulation of CCN1 in the dermal ECM is expected to progressively promote the aging of the dermis and thereby negatively impact the function of the dermis.

33131 Modeling acute and cumulative erythemal sun exposure on vulnerable body sites during beach vacations using behavior encoded 3D body models

Vacationers in a high solar intensity beach setting often put themselves at risk of ultraviolet light (UV) overexposure that can lead to detrimental skin health consequences. However, existing dosimetry work does not fully capture the extent or anatomical distribution of UV exposure in the beach vacation setting. In this study, a radiative transfer model of the solar conditions of Tampa Bay, St. Petersburg, Florida, USA (27.8°N, 82.8°W) is combined with an in silico 3D-body model and typical beach vacation behaviors to calculate acute and cumulative body site-specific UV exposure risk during a beach vacation.

Abstract 3186: Keratinocyte desmosomal cadherin Desmoglein 1 as a mediator and target of paracrine signaling in the melanoma niche

Abstract Melanoma is an aggressive cancer arising from the transformation of melanocytes residing in the basal layer of the epidermis, where they are in direct contact with surrounding keratinocytes. The role of keratinocytes in shaping the melanoma tumor microenvironment, however, remains understudied. We previously showed that the keratinocyte-specific desmosomal cadherin, desmoglein 1 (Dsg1) is reduced in response to acute UV exposure. Here, we show that Dsg1 protein is reduced in keratinocytes surrounding melanoma lesions but is unchanged in keratinocytes adjacent to benign nevi. As Dsg1 reduction by UV exposure is transient, we hypothesized that the persistent loss of Dsg1 observed in the melanoma tumor niche is due to melanoma-keratinocyte paracrine crosstalk. To address this idea, keratinocytes were cultured in conditioned media from melanocytes or melanoma cells. Melanoma conditioned media reduced keratinocyte Dsg1 mRNA and protein levels, suggesting that Dsg1 downregulation in keratinocytes is maintained by melanoma cells post-transformation. Keratinocytes in melanoma conditioned media exhibited reduced Grhl1 (Grainyhead like 1), a transcriptional activator of Dsg1, and increased Snai2, a repressor of Grhl1 expression and epidermal differentiation. These data support the idea that increased Snai2 stimulated by factors secreted by melanoma cells reduces keratinocyte Dsg1 mRNA expression by repressing Grhl1. To determine the impact of keratinocyte Dsg1 loss on melanoma cell behavior, melanoma cells were grown in conditioned media from control or Dsg1-deficient keratinocytes. Melanoma cell migration increased in a trans-well assay when melanoma cells were grown in conditioned media from Dsg1-deficient keratinocytes compared to from control keratinocytes. Supporting the in vivo importance of this finding, we found a significant, negative correlation between keratinocyte Dsg1 expression and melanoma cell movement within the melanoma tumor niche in patient samples. Downregulation of keratinocyte Dsg1 by melanoma cell conditioned media increased Erk1/2 signaling upstream of pro-migratory CXCL1 production, while pharmacological inhibition of keratinocyte Erk1/2 abrogated this effect. Furthermore, inhibition of the CXCL1 receptor, CXCR2 on melanoma cells decreased migration in melanoma cells grown in Dsg1-depleted keratinocyte conditioned media. Together, these data support the idea that paracrine crosstalk between melanoma cells and keratinocytes resulting in chronic keratinocyte Dsg1 reduction is important for melanoma progression and melanoma cell movement in the early stages of metastasis. Citation Format: Hope E. Burks, Christopher Arnette, Jennifer Koetsier, Joshua Broussard, Quinn Roth-Carter, Pedram Gerami, Jodi Johnson, Kathleen Green. Keratinocyte desmosomal cadherin Desmoglein 1 as a mediator and target of paracrine signaling in the melanoma niche [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3186.

28713 Dermoscopic changes observed in acute UV radiation

A 55-year-old male with a history of melanoma of unknown primary which was metastatic to the right parietal scalp as well as metastatic squamous cell carcinoma status post radiation therapy, presented for surveillance exam. His wife was concerned about a changing spot on his back which was also his only concern at this visit. On exam he was severely sunburned. He stated that he had been at the lake all day a few days previously and had not reapplied any sunscreen. Examination of his back revealed a dark brown, irregularly pigmented papule with a reticular network and symmetric focus of irregular dark brown-purple blotches on dermoscopy. A shave removal was performed. Pathology demonstrated a compound melanocytic nevus with background changes compatible with recent sunburn. It was found that the brown-purple blotches observed on dermoscopy correlated with keratinocyte dyskeratosis and necrosis observed on histopathology. The patient was informed of these results and will continue to follow with routine surveillance. This case is important because it highlights an underreported but previously demonstrated fact that melanocytic nevi can have acute changes secondary to ultraviolet radiation which may be concerning for melanoma. Greater awareness in this area could allow more clinicians to reasonably follow patients with similar changes in nevi in the setting of an acute sunburn thus preventing unnecessary biopsies and decreasing patient anxiety by waiting for these biopsy reports.

Increased PD-L1 Expression in Human Skin Acutely and Chronically Exposed to UV Irradiation.

Overexpression of PD-L1 (CD274) on tumor cells may represent a hallmark of immune evasion, and overexpression has been documented in several tumors including cutaneous squamous cell carcinoma (cSCC). While PD-L1/PD-1 activity in the skin has been primarily described in inflammatory models, our goal was to examine PD-L1 expression in human keratinocytes exposed to UV irradiation. We assessed PD-L1 expression in human sun-protected (SP) and sun-damaged (SD) skin, actinic keratosis (AK), and cSCC using IHC and protein microarray. Both methods found low baseline levels of PD-L1 in SP and SD skin and significantly increased expression in cSCC. Next, we examined PD-L1 expression in acute models of UV exposure. In human SP skin exposed to 2-3 MED of UV (n=20), epidermal PD-L1 was induced in 70% of subjects after 24h (P=0.0001). SKH-1 mice exposed to acute UV also showed significant epidermal PD-L1 induction at 16, 24 and 48h. A time- and dose-dependent induction of PD-L1 was confirmed in cultured human keratinocytes after UV, which was markedly reduced in the presence of MEK/ERK, JNK or STAT3 inhibitors. These findings suggest that UV induces upregulation of PD-L1 through established, pharmacologically targetable stress-signaling pathways in keratinocytes.

Concomitant DNA methylation and transcriptome signatures define epidermal responses to acute solar UV radiation

The simultaneous analysis of different regulatory levels of biological phenomena by means of multi-omics data integration has proven an invaluable tool in modern precision medicine, yet many processes ultimately paving the way towards disease manifestation remain elusive and have not been studied in this regard. Here we investigated the early molecular events following repetitive UV irradiation of in vivo healthy human skin in depth on transcriptomic and epigenetic level. Our results provide first hints towards an immediate acquisition of epigenetic memories related to aging and cancer and demonstrate significantly correlated epigenetic and transcriptomic responses to irradiation stress. The data allowed the precise prediction of inter-individual UV sensitivity, and molecular subtyping on the integrated post-irradiation multi-omics data established the existence of three latent molecular phototypes. Importantly, further analysis suggested a form of melanin-independent DNA damage protection in subjects with higher innate UV resilience. This work establishes a high-resolution molecular landscape of the acute epidermal UV response and demonstrates the potential of integrative analyses to untangle complex and heterogeneous biological responses.

Physiological performance by growth rate, pigment and protein content of the brown seaweed <em>Sargassum filipendula</em> (Ochrophyta: Fucales) induced by moderate UV radiation exposure in the laboratory

UV radiation is a factor affecting the distribution and physiology of photosynthetic organisms in an aquatic ecosystem. Studies with macroalgae indicate diverse biological disturbances in response to UV radiation. This work aimed to study sensitivity of the brown macroalga Sargassum filipendula exposed to UV radiation: PAR (control), PAR+UVA+UVB(++) and PAR+UVA(++)+UVB. Changes in the physiological parameters growth rate, total soluble proteins, photosynthetic pigments and the UV-vis absorbing compounds were analysed after T0, T4, T7 and T10 (days) of UV exposure. Physiological parameters showed little variation between treatments and over time, suggesting that moderate UV radiation doses could regulate resistance responses to re-establish the cellular homoeostasis condition through activation of an antioxidant defence system, such as an overproduction of phenolic compounds. Responses recorded in S. filipendula would be related to acclimation mechanisms against acute UV radiation stress, triggering resistance responses to avoid serious damage to the metabolic machinery, activating control systems to maintain hormesis, and homoeostasis of deleterious actions of reactive species, similar to the phenomenon known as preparation for oxidative stress. Finally, UV-visible absorption spectra showed absorption bands evidencing the presence of mainly UV-absorbing compounds with photoprotective function, such as phlorotannins, flavonoids and carotenoids, which could provide adaptive advantages for organisms exposed to UV radiation.

The alkaloid brachycerine contributes to protection against acute UV-B damage in Psychotria

Plants developed several strategies to cope with ultraviolet radiation (UV) exposure, including accumulation of specialized metabolites, with a recognized major role played by flavonoids. The unique alkaloid brachycerine of Psychotria brachyceras (Rubiaceae) is induced by leaf exposure to high UV intensity and is a potent antioxidant, so it is likely to participate as a protecting factor against this radiation. The capacity of brachycerine as a putative agent in acute UV protection was tested by comparison of P. brachyceras with P. carthagenensis, a closely related and co-ocurring species devoid of alkaloids, in UV-B exposure experiments. Leaves of P. brachyceras were very tolerant to high UV doses when compared with P. carthagenensis, lacking chlorophyll loss and membrane lipid peroxidation. Overall, well known leaf defenses against UV-B, such as flavonoids and cuticular waxes, were not markedly different between Psychotria species. The alkaloid was found both in the epidermis and mesophyll in leaves of P. brachyceras. Brachycerine is an effective in vitro superoxide scavenger and, when applied to the surface of P. carthagenensis leaves, significantly increased UV-B tolerance, improving chlorophyll concentration and several photosynthetic parameters under this treatment. Profiles of brachycerine extracted from alkaloid-treated P. carthagenensis leaves showed partial degradation after UV exposure, suggesting alkaloid involvement in chemical quenching of reactive oxygen species. In addition to flavonoids, the alkaloid brachycerine may improve tolerance to acute UV-B, representing a chemical tool to protect plants against this harmful condition.

Are there differences in immune responses following delivery of vaccines through acutely or chronically sun-exposed compared with sun-unexposed skin?

The majority of human vaccines are administered above the deltoid muscle of the arm, a site that is chronically sun-exposed in many people. It is known that exposure of the skin to the UV wavelengths in sunlight stimulates systemic immunosuppression, an outcome that is associated with reduced immunity to microbial infections in animal models. Here we consider whether immunization of humans through a UV-irradiated skin site will lead to a less effective immune response compared with immunization through an unexposed site. Studies showing that the efficacy of vaccination can be reduced when surrogates of increased levels of sun exposure, such as latitude of residence and season of the year, are considered. Results from a limited number of intervention experiments in humans demonstrate a similar pattern. To provide an explanation for these findings, changes in the number and functional potential of immune cells in chronically sun-exposed compared with unexposed skin are outlined. UV radiation-induced changes to skin cells are also relevant when considering skin sites for administration of immune-tolerizing peptides. The review provides the basis for further research into the effects of acute and chronic UV radiation exposure on skin cells in the context of vaccination.

554 Skin ageing continues long after ultraviolet radiation damage

Wrinkling has been attributed to the cumulative effects of acute Ultraviolet Radiation (UVR) exposure on the dermis. Previous studies have shown that the collagenase MMP-1 is secreted by dermal fibroblasts and degrades collagen immediately after UV exposure. However, skin ages gradually, and not intermittently after sun exposure. In this study we sought to examine the mechanism underpinning the gradual appearance of wrinkles, and to determine whether this is a result of intrinsic changes in the biology of the dermis. In vitro studies were performed using patient-derived human dermal fibroblasts from healthy skin, HFF and HDF cell lines. Cell lines were UV-protected or repeatedly exposed to UVB. Dermal fibroblasts from fairer skin types had higher levels of UV-induced mutations which, in multivariate analysis, was linked to higher expression of extracellular matrix degradation genes. This suggests that the background UVR exposure history influences the composition of the dermis as it ages. We investigated the mechanism driving collagen degradation in dermal fibroblasts with and without a history of UV damage. Fibroblasts with high background UV exposure have elevated levels of MMP-1 at rest. In addition, they show increased collagen degradation activity, which persists in the absence of acute UV exposure. Our study shows that dermal fibroblasts with a history of chronic UV exposure have higher levels of collagenase expression and activity, even in the absence of acute UV exposure. Importantly, these findings explain the mechanism driving gradual collagen degradation and wrinkling in the absence of UV light.

771 Increased PD-L1 expression in human skin acutely and chronically exposed to UV irradiation

Overexpression of the ligand PD-L1 on tumor cells may represent a hallmark of tumor immune evasion, and such overexpression has been documented in several tumors including cutaneous squamous cell carcinoma (cSCC). While PD-L1/PD-1 activity in the skin has been primarily described in inflammatory models, we focus on PD-L1 expression in human keratinocytes exposed to UV irradiation. We first assessed PD-L1 expression in archived samples from acute human studies implementing different UV exposures in sun protected (SP) skin ranging from 2-3 minimal erythema doses (MED). PD-L1 expression was measured by immunohistochemistry (IHC). From the 20 samples evaluated 14 (70%) demonstrated > 5% epidermal PD-L1 expression at 24 hours. PD-L1 in dermal endothelial cells was also noted to be increased at 24 hrs. Thereafter, we determined that HaCaT cells also respond to acute UV by increasing PD-L1 protein expression in a time- and dose-dependent manner (2-4 fold over control at 24-48 hours), an effect which is markedly reduced in the presence of MEK/ERK or JNK inhibitors. Subsequently, we investigated PD-L1 expression in chronically UV exposed human skin using matched samples representing SP skin, sun damaged skin (SD), actinic keratosis (AK) and cSCC using IHC and reverse phase protein microarray technology (RPPA). The RPPA methodology revealed negligible PD-L1 expression in SP, SD and AK, with significantly measurable expression in cSCC. IHC analysis of PD-L1 in another cohort of matched samples revealed a similar profile, with negligible expression of PD-L1 in SP and SD skin, slight staining in AK (mean 4.2%, +/- 9.5), and significant staining in cSCC (mean 19.5%, +/- 26.6). These findings suggest that upregulation of PD-L1 may be induced by UV through established, pharmacologically targetable stress-signaling pathways in keratinocytes.

760 Melanin may mediate visible light induced phototoxicity in darker skin types

Visible light (VL), a major component of solar radiation, differentially induces pigmentation in skin of color, an effect likely related to inherent melanization. A chromophore, melanin absorbs light within the VL wavelength. We hypothesize that clinical and histologic responses to VL are determined by epidermal melanin content and distribution. Nuclear matrix metalloproteinase (MMP-1), a proapoptotic mediator of photodamage may play a central role in skin type specific responses to VL. Enrolled participants were grouped by skin type (light=6,dark=6). Photoprotected sites were exposed daily x4days to 480J/cm2 of VL at 200mW(FiberLite High Intensity Illuminator Series 180,Dolan Jenner Industries) for a total dose of 1920J/cm2as tolerated. Treated and control sites were biopsied 24h after the last exposure and stained with Masson’s Trichrome and Fontana-Masson (FM) to assess collagen and melanin deposition, respectively. MMP-1 deposition was detected by indirect immunofluorescence (IF). Dark skin types did not tolerate the full VL regimen with blistering occurring in all subjects at doses of 220-880J/cm2. We found epidermal MMP-1 expression and nuclear localization in keratinocytes in dark but not in light skin. Nuclear localization correlated with areas of highest melanin density per FM stain. While there was no significant difference in MMP expression of treated light skin from control, collagen stains showed decreased stain intensity and thickened, wavy collagen bundles in both light (mean fold change[FC]=1.46,SEM+0.11), and dark skin (FC=1.19,+0.05). Herein, we demonstrate the acute effects of high power VL exposure in light and dark skin. VL can cause degenerative changes in collagen similar to acute UV irradiation or thermal injury, occurring independent of skin melanization. While the role of melanin in photoprotection is well defined, given the pro-apoptotic function of nuclear MMPs, our findings suggest a potential mechanism by which melanin may mediate VL induced phototoxicity. These observations show a “light” and “dark” side to melanin that warrants further investigation.

Effect of acute UV irradiation of barley in different stages of organogenesis on yield

The negative effect of acute barley irradiation depends both on the spectrum of UV radiation and on the stage of plant development. UV-B radiation, having a higher photon energy, has the greater negative effect compared to UV-A radiation at the same dose of irradiation. During the vegetation, barley is the most sensitive to the influence of ultraviolet at the II-V stages of organogenesis (in the transition from the vegetative to the generative stage of development). The adverse effect of UV-B radiation on the grain yield shows in the substantial reduction of flowers in the ear during their laying and probably in the pollen sterility.

Mimosine accumulation in Leucaena leucocephala in response to stress signaling molecules and acute UV exposure

Mimosine is a non-protein amino acid of Fabaceae, such as Leucaena spp. and Mimosa spp. Several relevant biological activities have been described for this molecule, including cell cycle blocker, anticancer, antifungal, antimicrobial, herbivore deterrent and allelopathic activities, raising increased economic interest in its production. In addition, information on mimosine dynamics in planta remains limited. In order to address this topic and propose strategies to increase mimosine production aiming at economic uses, the effects of several stress-related elicitors of secondary metabolism and UV acute exposure were examined on mimosine accumulation in growth room-cultivated seedlings of Leucaena leucocephala spp. glabrata. Mimosine concentration was not significantly affected by 10 ppm salicylic acid (SA) treatment, but increased in roots and shoots of seedlings treated with 84 ppm jasmonic acid (JA) and 10 ppm Ethephon (an ethylene-releasing compound), and in shoots treated with UV-C radiation. Quantification of mimosine amidohydrolase (mimosinase) gene expression showed that ethephon yielded variable effect over time, whereas JA and UV-C did not show significant impact. Considering the strong induction of mimosine accumulation by acute UV-C exposure, additional in situ ROS localization, as well as in vitro antioxidant assays were performed, suggesting that, akin to several secondary metabolites, mimosine may be involved in general oxidative stress modulation, acting as a hydrogen peroxide and superoxide anion quencher.

Agro-Industrial By-Products and Their Bioactive Compounds—An Ally against Oxidative Stress and Skin Aging

The increased consumer awareness towards hazards related with sun exposure has given a boost in the cosmetics industry and particularly the sun care market. Human skin is continually being threatened by the UV irradiation present in sunlight and acute UV exposure leads to skin photoaging. Cosmetic and/or dermatological applications include several bioactive compounds that contribute to the regulation of epidermal homeostasis by providing protection against solar radiation and improving the antioxidant activity of epidermis. Plant extracts are sources of active ingredients with intense therapeutic properties, and the topical application or oral intake of these compounds could ameliorate skin condition. Nowadays, there is a growing demand for the application of the bioactive agents contained in agro-industrial byproducts in sun care products, since many of them have shown promising properties as skin photoprotectants. However, well-conducted clinical studies are required to prove their safety and efficacy before they could be regularly used. Environmentally friendly extraction and sustainable techniques are therefore under examination for recovering such compounds from agro-industrial byproducts and converting them into innovative high-value natural ingredients used in cosmetic formulations.

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.

Abstract 406: A proteome-transcriptome-miRnome integrated analysis identifies similarity between UV-exposed skin and wounding skin

Abstract Cutaneous squamous cell carcinoma (cuSCC) is the second most common skin cancer, for which long term UV exposure and chronic wounding are the dominant risk factors. Despite these clinically established connections, little is understood about the early molecular response of human skin to UV exposure and its connection to acute wounding and cuSCC. Thus, our goal is to find common and specific signatures driven by UV-exposure and wounding as a means of developing new approaches for treating and preventing cuSCC. Here, we perform integrated analyses of proteomic, RNA-seq and miR-seq on 3 datasets: (1) UV-unexposed and acute UV-exposed human skin, (2) public dataset on acute wound healing and (3) our previously published dataset on normal skin and cuSCC from humans. We find that biological signatures and processes regulated by acute UV exposure and wounding has profound similarity. miR-seq data shows that miR-223, miR-132 and miR-142 are significantly upregulated in both acute events. Combined gene set enrichment analysis shows that G-protein-coupled-receptors (GPCRs) pathways are upregulated, possibly through Gαi activation. While ECM remodeling is significantly enriched in all three datasets, gene expression regulated by PPARα is suppressed. Interestingly, upregulation of matrisome components is observed among all three datasets. This suggests that these changes are important early events that regulated by both UV-exposure and wounding which eventually can promote cuSCC initiation. Thus, our findings suggest that these common signatures can be potentially validated as chemopreventive targets for cuSCC. Citation Format: Tran N. Nguyen, Kimal Rajapakshe, Stanislav Avdieiev, Courtney Nicholas, Vida Chitsazzadeh, Eric Welsh, Bin Fang, John Koomen, Cristian Coarfa, Janine Einspahr, Kenneth Y. Tsai. A proteome-transcriptome-miRnome integrated analysis identifies similarity between UV-exposed skin and wounding skin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 406.