Aspirin Protects Melanocytes and Keratinocytes against UVB-Induced DNA Damage In Vivo

Aspirin Protects against UVB-Induced DNA Damage through Activation of AMP Kinase

The anti-inflammatory and chemopreventive activities of aspirin (ASA) may be mediated through its cyclooxygenase inhibitor function. We have previously shown that ASA can protect against UVR-induced skin inflammation and DNA damage; however, the role of inflammation in UV-induced DNA damage and the mechanism underlying ASA protection are poorly characterized. Using immunodeficient NOD scid gamma mice and immunocompetent C57BL/6 mice treated with immune cell‒depleting antibodies, we found that inflammation was not required for UVB-induced 8-oxoguanine and cyclobutane pyrimidine dimers in vivo. Unlike ASA, neither its immediate metabolite salicylate nor the cyclooxygenase inhibitor indomethacin reduced UVB-induced 8-oxoguanine or cyclobutane pyrimidine dimers in melanocyte Melan-a or keratinocyte HaCat cells in vitro. Moreover, addition of prostaglandin E₂ did not reverse the protective effect of ASA on UVB-treated cells. Phosphorylation of the 5' AMP protein kinase, observed in ASA-treated cells, could be blocked by the 5' AMP protein kinase inhibitor compound C. Compound C or 5' AMP protein kinase knockdown partially reduced ASA-mediated protection against UVB-induced DNA damage. Finally, injection of compound C partially reversed the protective effect of ASA on UVB-treated mouse skin in vivo. These studies suggest that ASA confers protection against UVB-induced DNA damage through the activation of 5' AMP protein kinase rather than through cyclooxygenase inhibition.

Cell-intrinsic melanin fails to protect melanocytes from ultraviolet-mutagenesis in the absence of epidermal melanin

Melanin is a free-radical scavenger, antioxidant, and broadband absorber of ultraviolet (UV) radiation which protects the skin from environmental carcinogenesis. However, melanin synthesis and UV-induced reactive melanin species are also implicated in melanocyte genotoxicity. Here, we attempted to reconcile these disparate functions of melanin using a UVB-sensitive, NRAS-mutant mouse model, TpN. We crossed TpN mice heterozygous for an inactivating mutation in Tyrosinase to produce albino and black littermates on a C57BL/6J background. These animals were then exposed to a single UVB dose on postnatal day three when keratinocytes in the skin have yet to be melanized. Approximately one-third (35%) of black mice were protected from UVB-accelerated tumor formation. However, melanoma growth rates, tumor mutational burdens, and gene expression profiles were similar in melanomas from black and albino mice. Skin from albino mice contained more cyclobutane pyrimidine dimer (CPD) positive cells than black mice 1-h post-irradiation. However, this trend gradually reversed over time with CPDs becoming more prominent in black than albino melanocytes at 48 h. These results show that in the absence of epidermal pigmentation, melanocytic melanin limits the tumorigenic effects of acute UV exposure but fails to protect melanocytes from UVB-induced mutagenesis.

Preparation of CPD Photolyase Nanoliposomes Derived from Antarctic Microalgae and Their Effect on UVB-Induced Skin Damage in Mice

UVB radiation is known to trigger the block of DNA replication and transcription by forming cyclobutane pyrimidine dimer (CPD), which results in severe skin damage. CPD photolyase, a kind of DNA repair enzyme, can efficiently repair CPDs that are absent in humans and mice. Although exogenous CPD photolyases have beneficial effects on skin diseases, the mechanisms of CPD photolyases on the skin remain unknown. Here, this study prepared CPD photolyase nanoliposomes (CPDNL) from Antarctic Chlamydomonas sp. ICE-L, which thrives in harsh, high-UVB conditions, and evaluated their protective mechanisms against UVB-induced damage in mice. CPDNL were optimized using response surface methodology, characterized by a mean particle size of 105.5 nm, with an encapsulation efficiency of 63.3%. Topical application of CPDNL prevented UVB-induced erythema, epidermal thickness, and wrinkles in mice. CPDNL mitigated UVB-induced DNA damage by significantly decreasing the CPD concentration. CPDNL exhibited antioxidant properties as they reduced the production of reactive oxygen species (ROS) and malondialdehyde. Through activation of the NF-κB pathway, CPDNL reduced the expression of pro-inflammatory cytokines including IL-6, TNF-α, and COX-2. Furthermore, CPDNL suppressed the MAPK signaling activation by downregulating the mRNA and protein expression of ERK, JNK, and p38 as well as AP-1. The MMP-1 and MMP-2 expressions were also remarkably decreased, which inhibited the collagen degradation. Therefore, we concluded that CPDNL exerted DNA repair, antioxidant, anti-inflammation, and anti-wrinkle properties as well as collagen protection via regulation of the NF-κB/MAPK/MMP signaling pathways in UVB-induced mice, demonstrating that Antarctic CPD photolyases have the potential for skincare products against UVB and photoaging.

Use of Nonsteroidal Anti-Inflammatory Drugs and Incidence of Melanoma in the United States Radiologic Technologists Study

Although NSAIDs have been associated with both reduced and increased cutaneous melanoma risk, few studies have examined these associations by ultraviolet radiation (UVR) or personal sun-sensitivity. We examined the associations between NSAID use and first primary invasive cutaneous melanoma among 58,227 non-Hispanic white participants in the United States Radiologic Technologists cohort study. Poisson regression was used to calculate rate ratios (RR) and 95% likelihood-based confidence intervals (CI), adjusting for attained age, birth cohort, and ambient UVR. No significant association of melanoma was observed for any use of NSAIDs (RR, 0.87; 95% CI, 0.71-1.09). The relative risks of melanoma for the highest categories of aspirin and other NSAID use (≥5 times per month vs. none) were 0.93 (95% CI, 0.74-1.16) and 1.02 (95% CI, 0.83-1.25), respectively. Further analyses did not reveal dose-response for trends in frequency of NSAID use or interactions with sex, UVR, eye and hair color, and skin complexion. In this large nationwide study, NSAID use was not associated with melanoma risk.

PREVENTION RELEVANCE

NSAIDs have been associated with both reduced and increased melanoma risk. However, few studies have examined the role of UVR or personal sun-sensitivity on these associations. Our findings strengthen the evidence that NSAID use is not associated with melanoma risk, even in sun-sensitive subgroups.

Photoprotective effect of solid lipid nanoparticles of rutin against UVB radiation damage on skin biopsies and tissue-engineered skin

Solid lipid nanoparticles (SLNs) containing rutin were prepared to enhance their photochemopreventive effect on the skin. SLNs were produced by the hot melt microemulsion technique. Two 3D skin models: ex vivo skin explants and 3D tissue engineering skin were used to evaluate the photochemopreventive effect of topical formulations containing rutin SLNs, against ultraviolet B (UVB) radiation, inducing sunburn cells, caspase-3, cyclobutane pyrimidine dimers, lipid peroxidation, and metalloproteinase formation. The rutin SLNs presented average size of 74.22 ± 2.77 nm, polydispersion index of 0.16 ± 0.04, encapsulation efficiency of 98.90 ± 0.25%, and zeta potential of -53.0 ± 1.61 mV. The rutin SLNs were able to efficiently protect against UVB induced in the analysed parameters in both skin models. Furthermore, the rutin SLNs inhibited lipid peroxidation and metalloproteinase formation. These results support the use of rutin SLNs as skin photochemopreventive agents for topical application to the skin.

Hair Follicle Melanocytes Initiate Autoimmunity in Alopecia Areata: a Trigger Point

Alopecia areata (AA) is characterized by common non-scarring alopecia due to autoimmune disorders. To date, the specific pathogenesis underlying AA remains unknown. Thus, AA treatment in the dermatological clinic is still a challenge. Numerous clinical observations and experimental studies have established that melanocytes may be the trigger point that causes hair follicles to be attacked by the immune system. A possible mechanism is that the impaired melanocytes, under oxidative stress, cannot be repaired in time and causes apoptosis. Melanocyte-associated autoantigens are released and presented, inducing CD8⁺ T cell attacks. Thereafter, amplification of the immune responses further spreads to the entire hair follicle (HF). The immune privilege of HF subsequently collapses, leading to AA. Herein, we present a narrative review on the roles of melanocytes in AA pathogenesis, aiming to provide a better understanding of this disease from the melanocyte's perspective.

Geroscience-guided repurposing of FDA-approved drugs to target aging: A proposed process and prioritization

Common chronic diseases represent the greatest driver of rising healthcare costs, as well as declining function, independence, and quality of life. Geroscience-guided approaches seek to delay the onset and progression of multiple chronic conditions by targeting fundamental biological pathways of aging. This approach is more likely to improve overall health and function in old age than treating individual diseases, by addressing aging the largest and mostly ignored risk factor for the leading causes of morbidity in older adults. Nevertheless, challenges in repurposing existing and moving newly discovered interventions from the bench to clinical care have impeded the progress of this potentially transformational paradigm shift. In this article, we propose the creation of a standardized process for evaluating FDA-approved medications for their geroscience potential. Criteria for systematically evaluating the existing literature that spans from animal models to human studies will permit the prioritization of efforts and financial investments for translating geroscience and allow immediate progress on the design of the next Targeting Aging with MEtformin (TAME)-like study involving such candidate gerotherapeutics.

A Randomized Double-blind Placebo-controlled Trial of Oral Aspirin for Protection of Melanocytic Nevi Against UV-induced DNA Damage

DNA damage plays a role in ultraviolet (UV)-induced melanoma. We previously showed that aspirin (ASA) can suppress prostaglandin-E2 (PGE2) and protect melanocytes from UV-induced DNA damage in mice, and suggested that taking ASA before acute sun exposure may reduce melanoma risk. We conducted a prospective randomized placebo-controlled trial to determine if orally administered ASA could suppress PGE2 in plasma and nevi and protect nevi from UV-induced DNA damage. After obtaining plasma and determining the minimal erythemal dose (MED) in 95 subjects at increased risk for melanoma, they were randomized to receive a daily dose of placebo, 81 mg ASA, or 325 mg ASA, in double-blind fashion for one month. After this intervention, one nevus was irradiated (dose = 1 or 2 MED) using a solar simulator. One day later, MED was re-determined, a second plasma sample was obtained, and the UV-irradiated nevus and an unirradiated nevus were removed. ASA metabolites were detected in the second plasma sample in subjects in the ASA arms. There were no significant differences in the pre- and post-intervention MED between those patients receiving ASA and placebo. Significantly reduced PGE2 levels were detected in plasma (second vs. first samples) and in nevi (both unirradiated and UV-treated) in subjects receiving ASA compared to placebo. Comparing UV-treated nevi from the ASA and placebo cohorts, however, did not reveal significant reductions in CD3-cell infiltration or 8-oxoguanine and cyclobutane pyrimidine dimers. Thus ASA did not effectively protect nevi from solar-simulated UV-induced inflammation and DNA damage under the conditions examined. PREVENTION RELEVANCE: Despite promising rationale, ASA at conventional dosing was not able to protect nevi against UV-induced DNA damage under the conditions examined.See related Spotlight, p. 71.

The Challenge of Melanoma Chemoprevention

Melanoma is a treatment-resistant cancer of melanocytes. There is a serious unmet need for chemopreventive agents that can inhibit their evolution from preexisting dysplastic nevi. Low-dose aspirin and NSAIDs are potential chemopreventive candidates because they inhibit the enzyme COX-2 which has a number of procarcinogenic effects. Unfortunately, the clinical trial reported by Okwundu and colleagues in this issue of Cancer Prevention Research did not show an effect of aspirin on biomarkers associated with progression of premalignant dysplastic nevi to melanomas. Further clinical trials with other aspirin or NSAID biomarkers or clinical trials with other potential chemopreventive agents offer hope to those who are at increased risk for melanomas.See related article, p. 129.

Elucidating the Size-dependent FRET Efficiency in Interfacially Engineered Quantum Dots attached PBSA Sunscreen

Applying sunscreen on human skin provides photoprotection against the harmful ultraviolet (UV) radiation of the sun. Sunscreen absorbs UV radiations and dissipates the absorbed energy through various radiative and non-radiative pathways. The attachment of functionalized quantum dots (QDs) to the sunscreen component is a novel idea to enhance the absorption cross-section of UV radiations. Therefore, the attachment of the sunscreen component to the ligand functionalized biocompatible QDs and the absorbed energy transfer from sunscreen to the QDs could work as a model system to overall improve the efficiency of the sunscreen. This study elucidates the mechanism of size-dependent Förster resonance energy transfer (FRET) efficiency and its rate between 2-phenylbenzimidazole-5-sulfonic acid (PBSA) and mercaptoacetic acid (MAA) functionalized CdS QDs. In the PBSA-QDs dyad, the PBSA (donor) dissipates UV-absorbed energy to the CdS QDs (acceptor). Following excitation at 306 nm, the steady-state photoluminescence (SSPL) and time-resolved photoluminescence (TRPL) techniques measurements demonstrate that both the non-radiative energy transfer efficiency and rate are QDs size-dependent in addition to donor-acceptor distance, and suggest that bigger sized-QDs result in an increase of the FRET efficiency.

Role of distinct fibroblast lineages and immune cells in dermal repair following UV radiation induced tissue damage

Solar ultraviolet radiation (UVR) is a major source of skin damage, resulting in inflammation, premature ageing, and cancer. While several UVR-induced changes, including extracellular matrix reorganisation and epidermal DNA damage, have been documented, the role of different fibroblast lineages and their communication with immune cells has not been explored. We show that acute and chronic UVR exposure led to selective loss of fibroblasts from the upper dermis in human and mouse skin. Lineage tracing and in vivo live imaging revealed that repair following acute UVR is predominantly mediated by papillary fibroblast proliferation and fibroblast reorganisation occurs with minimal migration. In contrast, chronic UVR exposure led to a permanent loss of papillary fibroblasts, with expansion of fibroblast membrane protrusions partially compensating for the reduction in cell number. Although UVR strongly activated Wnt signalling in skin, stimulation of fibroblast proliferation by epidermal β-catenin stabilisation did not enhance papillary dermis repair. Acute UVR triggered an infiltrate of neutrophils and T cell subpopulations and increased pro-inflammatory prostaglandin signalling in skin. Depletion of CD4- and CD8-positive cells resulted in increased papillary fibroblast depletion, which correlated with an increase in DNA damage, pro-inflammatory prostaglandins, and reduction in fibroblast proliferation. Conversely, topical COX-2 inhibition prevented fibroblast depletion and neutrophil infiltration after UVR. We conclude that loss of papillary fibroblasts is primarily induced by a deregulated inflammatory response, with infiltrating T cells supporting fibroblast survival upon UVR-induced environmental stress.

Salicinoyl Quinic Acids and Their Prostaglandin E2 Production Inhibitory Activities from the Fruits of Casearia grewiifolia

Phytochemical investigation on the dried fruits of Casearia grewiifolia led to the identification of 10 new salicinoyl quinic acid derivatives (1-10), a new benzoyl quinic acid (11), and two known compounds (12 and 13). The structures of the new compounds were elucidated by interpreting 1D and 2D NMR spectroscopic data including HMBC and EXSIDE along with a chemical method for sugar unit analysis. All isolates were evaluated for their inhibitory activities against prostaglandin E₂ (PGE₂) production in ultraviolet B (UVB)-irradiated HaCat keratinocytes. Of the isolates tested, compounds 6 and 12 were found to inhibit PGE₂ production with IC₅₀ values of 20.5 and 28.8 μM, respectively.

Keratinocyte Carcinoma and Photoprevention: The Protective Actions of Repurposed Pharmaceuticals, Phytochemicals and Vitamins

Simple Summary

Keratinocyte carcinoma is the most common type of cancer. Sun exposure and ultraviolet radiation are significant contributors to the development of carcinogenesis, mediated by DNA damage, increased oxidative stress, inflammation, immunosuppression and dysregulated signal transduction. Photoprevention involves using different compounds to delay or prevent ultraviolet radiation-induced skin cancer. In this review, we look at new avenues for systemic photoprevention that are based on pharmaceuticals, plant-derived phytochemicals and vitamins. We also investigate the mechanisms underlying these strategies for preventing the onset of carcinogenesis.

Abstract

Ultraviolet radiation (UVR) arising from sun exposure represents a major risk factor in the development of keratinocyte carcinomas (KCs). UVR exposure induces dysregulated signal transduction, oxidative stress, inflammation, immunosuppression and DNA damage, all of which promote the induction and development of photocarcinogenesis. Because the incidence of KCs is increasing, better prevention strategies are necessary. In the concept of photoprevention, protective compounds are administered either topically or systemically to prevent the effects of UVR and the development of skin cancer. In this review, we provide descriptions of the pathways underlying photocarcinogenesis and an overview of selected photoprotective compounds, such as repurposed pharmaceuticals, plant-derived phytochemicals and vitamins. We discuss the protective potential of these compounds and their effects in pre-clinical and human trials, summarising the mechanisms of action involved in preventing photocarcinogenesis.