UVB-induced skin inflammation and cutaneous tissue injury is dependent on the MHC class I-like protein, CD1d

The effect of tomato and lycopene on clinical characteristics and molecular markers of UV-induced skin deterioration: A systematic review and meta-analysis of intervention trials

Lycopene as a natural antioxidant that have been studied for ultraviolet radiation (UVR) photo protection and is one of the most effective carotenoids to scavenge reactive oxygen species (ROS). This review aims to summarize the protective effect of tomato and lycopene on skin photo damage and skin photoaging in healthy subjects by reviewing the existing population intervention experiments. A total of five electronic databases including PubMed, Scopus, EBSCO, Web of Science and Cochrane Library were searched from inceptions to January 2021 without any restriction. Out of 19336 publications identified, 21 fulfilled the inclusion criteria and were meta-analysis. Overall, interventions supplementing tomato and lycopene were associated with significant reductions in Δa*, MMP-1, ICAM-1 and skin pigmentation; while tomato and lycopene supplementation were associated with significant increase in MED, skin thickness and skin density. Based on the results of this systematic review and meta-analysis, supplementation with tomato and lycopene could reduce skin erythema formation and improve the appearance and pigmentation of the skin, thereby preventing light-induced skin photodamage and skin photoaging. Lycopene-rich products could be used as endogenous sun protection and may be a potential nutraceutical for sun protection.

Childhood sunburn and risk of melanoma and non-melanoma skin cancer: a Mendelian randomization study

Previous evidence has suggested that childhood sunburn could be a risk factor for cutaneous malignant melanoma (MM) and non-melanoma skin cancer (NMSC). However, existing observational studies could not reveal the causal associations genetically. This study aimed to investigate whether there was a genetic causal relationship between childhood sunburn and skin cancers. Univariable Mendelian randomization (MR) and Causal Analysis Using Summary Effect analysis was carried out for causal estimates and evaluation for the horizontal pleiotropy. Multivariable MR and the mediation effects analysis were used to test whether the causal associations were mediated by potential confounders. A suggestively significant causal association between childhood sunburn and MM was indicated (OR = 4.74; 95% CI: 1.31-17.19; p = 1.79E-02). Genetically predicted childhood sunburn was significantly associated with increased risk of overall melanoma in situ (MIS) (OR = 4.02; 95% CI: 2.00-8.08; p = 9.40E-05), MIS of face (OR = 18.28; 95% CI: 5.28-63.35; p = 4.59E-06), and MIS of trunk (OR = 7.05; 95% CI: 2.06-24.13; p = 1.88E-03). Similar trends were found for childhood sunburn and NMSC (OR = 8.16; 95% CI: 6.07-10.99; p = 1.53E-20), including both basal cell carcinoma (BCC) (OR = 3.76; 95% CI:2.96-4.77; p = 2.19E-08) and squamous cell carcinoma (SCC) (OR = 7.44; 95% CI: 5.09-10.87; p = 2.19E-08). After adjustment for hair and skin color, facial ageing, vitamin D levels, body mass index, alcohol consumption, and smoking status, childhood sunburn showed an independent association with MIS, MIS of face, MIS of trunk, as well as NMSC, including both BCC and SCC. Mediation analysis showed no significant mediation effect. This study demonstrated a causal relationship between childhood sunburn and the risk of both MM and NMSC, which suggested that enhanced screening and prevention for childhood sunburn could contribute to the early detection and decreased risk of MM and NMSC.

Inhibition of cutaneous heat-sensitive Ca2+ -permeable transient receptor potential vanilloid 3 channels alleviates UVB-induced skin lesions in mice

Ultraviolet B (UVB) radiation causes skin injury by trigging excessive calcium influx and signaling cascades in the skin keratinocytes. The heat-sensitive Ca2+ -permeable transient receptor potential vanilloid 3 (TRPV3) channels robustly expressed in the keratinocytes play an important role in skin barrier formation and wound healing. Here, we report that inhibition of cutaneous TRPV3 alleviates UVB radiation-induced skin lesions. In mouse models of ear swelling and dorsal skin injury induced by a single exposure of weak UVB radiation, TRPV3 genes and proteins were upregulated in quantitative real-time PCR and Western blot assays. In accompany with TRPV3 upregulations, the expressions of proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were also increased. Knockout of the TRPV3 gene alleviates UVB-induced ear swelling and dorsal skin inflammation. Furthermore, topical applications of two selective TRPV3 inhibitors, osthole and verbascoside, resulted in a dose-dependent attenuation of skin inflammation and lesions. Taken together, our findings demonstrate the causative role of overactive TRPV3 channel function in the development of UVB-induced skin injury. Therefore, topical inhibition of TRPV3 may hold potential therapy or prevention of UVB radiation-induced skin injury.

Aloe Extracts Inhibit Skin Inflammatory Responses by Regulating NF-κB, ERK, and JNK Signaling Pathways in an LPS-Induced RAW264.7 Macrophages Model

Introduction

Inflammation generally refers to the body's defensive response to stimuli, and skin inflammation is still one of the major problems that affect human physical and mental health. While current pharmacological treatments are reported to have cytotoxicity and various side effects, herbal medicines with few side effects and low cytotoxicity are considered as alternative therapeutic approaches.

Methods

In order to investigate anti-inflammatory effects and mechanisms of ALOE, the potential cytotoxicity of A. vera extracts (ALOE) was determined in vitro at first. The production of the pro-inflammatory proteins (ie, IL-6, TNF-α) in lipopolysaccharides (LPS) and ultraviolet A (UVA)-stimulated HaCaT and RAW264.7 cells were then treated with ALOE to test its inhibitory effects using enzyme-linked immunosorbent assay (ELISA). To further explore the anti-inflammatory mechanisms of ALOE, quantitative Polymerase Chain Reaction (qPCR) was used to analyze the mRNA expression of inflammatory genes iNOS, COX-2 and NO production. For NF-κB and MAPK signaling pathways analysis, Western blotting and nuclear fluorescence staining were used to evaluate the expression of key factors.

Results

ALOE did not exhibit obvious cytotoxicity (0-3 mg/mL) in vitro. ALOE was able to inhibit the expression of pro-inflammatory cytokines IL-6, TNF-α and functioned more prominently in LPS-induced model. ALOE could also suppress the mRNA expression of LPS-induced iNOS and COX-2 and further down-regulate NO level. Furthermore, ALOE reduced the protein expression of P65 in NF-κB signaling pathway and suppressed LPS-induced activation of ERK and JNK, instead of p38 MAPK pathway.

Conclusion

Taken together, these results demonstrated that ALOE is a potential treatment in suppressing LPS-stimulated inflammation reactions targeting NF-κB, JNK and ERK signaling pathways. The anti-inflammatory effects of ALOE indicated that it has the potential to become an effective cosmetic ingredient.

Matching-adjusted indirect comparison of efficacy outcomes in trials of calcipotriol plus betamethasone dipropionate foam and cream formulations for the treatment of plaque psoriasis

BACKGROUND AND OBJECTIVES

Once-daily, fixed-combination calcipotriol 50 μg/g (Cal) plus betamethasone dipropionate 0.5 mg/g (BD) is available in aerosol foam and cream formulations. As no head-to-head data are available, we use a matching-adjusted indirect comparison (MAIC) approach to compare Cal/BD foam and cream.

METHODS

Anchored and unanchored MAIC analyses were conducted using individual patient data (IPD) from five Cal/BD foam trials and two trials of Cal/BD cream. Outcomes of interest were the proportion of patients with Physician's Global Assessment (PGA) success and the mean reduction in modified Psoriasis Area and Severity Index (mPASI).

RESULTS

In the anchored MAIC, patients were more likely to achieve PGA success after 4 weeks of Cal/BD foam than after 8 weeks of Cal/BD cream and had larger mean improvements in mPASI (p < .01 in EU mPASI analysis). In unanchored analyses, 4 weeks of Cal/BD foam treatment was statistically significantly more efficacious in inducing PGA success than 8 weeks of Cal/BD cream (p < .01 in five of six comparisons). Mean reductions in mPASI were consistently statistically significantly greater with Cal/BD foam than with Cal/BD cream.

CONCLUSIONS

Use of Cal/BD foam consistently shows significantly greater improvements in PGA and mPASI outcomes, compared with Cal/BD cream.

Protective Function of Malus baccata (L.) Borkh Methanol Extract against UVB/Hydrogen Peroxide-Induced Skin Aging via Inhibition of MAPK and NF-κB Signaling

Ultraviolet (UV) irradiation induces ROS production, which activates activator protein (AP)-1 and nuclear factor (NF)-κB signaling and downstream molecules, ultimately triggering the generation of matrix metalloproteinases (MMPs) and degradation of collagen. The aim of this study was to investigate the protective effect of methanol extract from Malus baccata (L.) Borkh (Mb-ME) against aging. DPPH and ABTS assays showed that Mb-ME had a significant antioxidant capacity. Flow cytometry results indicated that Mb-ME attenuated UVB and H₂O₂-stimulated apoptosis and reactive oxygen species (ROS) generation. RT-PCR analysis in HaCaT and HDF cells suggested that Mb-ME treatment blocked the expression of MMPs, COX-2, IL-1β, IL-6, HYALs, and p53 while promoting the levels of TGM1, FLG, HASs, Sirt1, and Col1A1. Mechanically, Mb-ME inhibited the phosphorylation of MAP kinases and NF-κB signaling. Overall, these results strongly suggest that Mb-ME can be developed as an antiaging therapy.

Roles and therapeutic potential of CD1d-Restricted NKT cells in inflammatory skin diseases

Natural killer T (NKT) cells are innate-like T lymphocytes that recognize glycolipid antigens rather than peptides. Due to their immunoregulatory properties, extensive work has been done to elucidate the immune functions of NKT cells in various immune contexts such as autoimmunity for more than two decades. In addition, as research on barrier immunity such as the mucosa-associated lymphoid tissue has flourished in recent years, the role of NKT cells to immunity in the skin has attracted substantial attention. Here, we review the contributions of NKT cells to regulating skin inflammation and discuss the factors that can modulate the functions of NKT cells in inflammatory skin diseases such as atopic dermatitis. This mini-review article will mainly focus on CD1d-dependent NKT cells and their therapeutic potential in skin-related immune diseases.

Mitochondria-Targeted Hydrogen Sulfide Delivery Molecules Protect Against UVA-Induced Photoaging in Human Dermal Fibroblasts, and in Mouse Skin In Vivo

Aims: Oxidative stress and mitochondrial dysfunction play a role in the process of skin photoaging via activation of matrix metalloproteases (MMPs) and the subsequent degradation of collagen. The activation of nuclear factor E2-related factor 2 (Nrf2), a transcription factor controlling antioxidant and cytoprotective defense systems, might offer a pharmacological approach to prevent skin photoaging. We therefore investigated a pharmacological approach to prevent skin photoaging, and also investigated a protective effect of the novel mitochondria-targeted hydrogen sulfide (H₂S) delivery molecules AP39 and AP123, and nontargeted control molecules, on ultraviolet A light (UVA)-induced photoaging in normal human dermal fibroblasts (NHDFs) in vitro and the skin of BALB/c mice in vivo. Results: In NHDFs, AP39 and AP123 (50-200 nM) but not nontargeted controls suppressed UVA (8 J/cm²)-mediated cytotoxicity and induction of MMP-1 activity, preserved cellular bioenergetics, and increased the expression of collagen and nuclear levels of Nrf2. In in vivo experiments, topical application of AP39 or AP123 (0.3-1 μM/cm²; but not nontargeted control molecules) to mouse skin before UVA (60 J/cm²) irradiation prevented skin thickening, MMP induction, collagen loss of oxidative stress markers 8-hydroxy-2'-deoxyguanosine (8-OHdG), increased Nrf2-dependent signaling, as well as increased manganese superoxide dismutase levels and levels of the mitochondrial biogenesis marker peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α). Innovation and Conclusion: Targeting H₂S delivery to mitochondria may represent a novel approach for the prevention and treatment of skin photoaging, as well as being useful tools for determining the role of mitochondrial H₂S in skin disorders and aging. Antioxid. Redox Signal. 36, 1268-1288.

Jelly Fig (Ficus awkeotsang Makino) Exhibits Antioxidative and Anti-Inflammatory Activities by Regulating Reactive Oxygen Species Production via NFκB Signaling Pathway

Antioxidant and anti-inflammatory activities of Ficus awkeotsang Makino extract (FAE) on Hs68 fibroblasts and BALB/c nude-mouse models are evaluated in this study. FAE was found to be non-toxic and showed high levels of DPPH, H₂O₂, and hydroxyl radical scavenging abilities; a ferrous chelating capacity; as well as ferric-reducing antioxidant capability. The antioxidant activity of FAE was strongly associated with polyphenolic content (flavonoids at 10.3 mg QE g⁻¹ and total phenol at 107.6 mg GAE g⁻¹). The anti-inflammatory activity of FAE and the underlying molecular mechanisms were also investigated. The a* value of the mouse dorsal skin after treatment with FAE at 1.5 mg/mL in addition to chronic UVB exposure was found to decrease by 19.2% during a ten-week period. The anti-inflammatory effect of FAE was evidenced by the decreased accumulation of inflammatory cells and skin thickness. Expression levels of UVB-induced inflammatory proteins, including ROS, NF-κB, iNOS, COX-2, and IL-6, were significantly reduced upon FAE treatment in vitro and in vivo. Collectively, our results suggest that the inhibition of ROS and UVB-induced activation of the NF-κB downstream signaling pathway by FAE, indicating considerable potential as a versatile adjuvant against free radical damage in pharmaceutical applications.

The Yin and Yang dualistic features of autophagy in thermal burn wound healing

Burn healing should be regarded as a dynamic process consisting of two main, interrelated phases: (a) the inflammatory phase when neutrophils and monocytes infiltrate the injury site, through localized vasodilation and fluid extravasation, and (b) the proliferative-remodeling phase, which represents a key event in wound healing. In the skin, both canonical autophagy (induced by starvation, oxidative stress, and environmental aggressions) and non-canonical or selective autophagy have evolved to play a discrete, but, essential, “housekeeping” role, for homeostasis, immune tolerance, and survival. Experimental data supporting the pro-survival roles of autophagy, highlighting its Yang, luminous and positive feature of this complex but insufficient explored molecular pathway, have been reported. Autophagic cell death describes an “excessive” degradation of important cellular components that are necessary for normal cell function. This deadly molecular mechanism brings to light the darker, concealed, Yin feature of autophagy. Autophagy seems to perform dual, conflicting roles in the angiogenesis context, revealing once again, its Yin–Yang features. Autophagy with its Yin–Yang features remains the shadow player, able to decide quietly whether the cell survives or dies.

Topically Applied Taurine Chloramine Protects against UVB-Induced Oxidative Stress and Inflammation in Mouse Skin

Excessive exposure to solar light, especially its UV component, is a principal cause of photoaging, dermatitis, and photocarcinogenesis. In searching for candidate substances that can effectively protect the skin from photodamage, the present study was conducted with taurine chloramine (TauCl), formed from taurine in phagocytes recruited to inflamed tissue. Irradiation with ultraviolet B (UVB) of 180 mJ/cm² intensity caused oxidative damage and apoptotic cell death in the murine epidermis. These events were blunted by topically applied TauCl, as evidenced by the lower level of 4-hydroxynonenal-modified protein, reduced proportions of TUNEL-positive epidermal cells, and suppression of caspase-3 cleavage. In addition, the expression of two prototypic inflammatory enzymes, cyclooxygenase-2 and inducible nitric oxide synthase, and transcription of some pro-inflammatory cytokines (Tnf, Il6, Il1b, Il10) were significantly lower in TauCl-treated mice than vehicle-treated control mice. The anti-inflammatory effect of TauCl was associated with inhibition of STAT3 activation and induction of antioxidant enzymes, such as heme oxygenase-1 and NAD(P)H:quinone oxidoreductase 1, through activation of nuclear factor erythroid 2-related factor 2.

Influence of Caralluma adscendens Var. attenuata cold cream on UV-B damaged skin epidermal cells: a novel approach

Ultraviolet radiation-induced sunburns are characterized by pigmented, wrinkled, and dried skin, with rashes and red spots. Chemical sunscreen lotion shows beneficial effects, but it shows the adverse side effect while in continuous usage. Natural substances of plant origin are deemed a possible cause of UV radiation through sunscreen resources. On this basis, we formulated the cold cream from the Caralluma adscendens Var. attenuata (CAVA) plant extract. The phytocompounds were studied by using GC-MS. The antioxidant potential of the plant extract was determined, and the CAVA showed cytotoxicity on A375 skin melanoma cells determined by MTT assay. The FT-IR spectra analysis confirmed the chemical nature of crude and crosslinking between cold creams. The cream was applied topically to rats pre-exposed to UV-B radiation (32,800 J/m2) four times/week (on alternate days). UV-B exposed without any treatment rats showed increased red spots or wrinkles (5 cm2). In contrast, the cold cream treatment application on irradiated skin has significantly reduced the size of rashes and red spots and the wound was contracted in a dose-dependent manner. Furthermore, histopathology of the experimental rat skin confirmed that CAVA cream treatment significantly reduced the epidermal thickening, damage in dermis and epidermis layers, and restructured the hair follicles. This study suggests that the cream formulated using CAVA can alleviate the damages caused by the UV-B-irradiation at a high level and safeguard the skin tissues.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02694-y.

Radiofrequency Irradiation Attenuates High-Mobility Group Box 1 and Toll-like Receptor Activation in Ultraviolet B-Induced Skin Inflammation

Ultraviolet B (UVB) exposure activates various inflammatory molecules of keratinocytes in the epidermis layer. Such UVB-mediated skin inflammation leaves post-inflammatory hyperpigmentation (PIH). Reports show a close relationship between PIH and high-mobility group box 1 (HMGB1) and its receptors. General clinical treatments of PIH, such as oral medication and laser treatment, have reported side effects. Recent studies reported the effects of radiofrequency (RF) irradiation on restoring dermal collagen, modulating the dermal vasculature, and thickening the basement membrane. To validate how RF regulates the inflammatory molecules from UVB-irradiated keratinocytes, we used UVB-radiated keratinocytes and macrophages, as well as animal skin. In addition, we examined two cases of RF-irradiated skin inflammatory diseases. We validated the effects of RF irradiation on keratinocytes by measuring expression levels of HMGB1, Toll-like receptors (TLRs), and other inflammatory factors. The results show that the RF modulates UVB-radiated keratinocytes to secrete fewer inflammatory factors and also modulates the expression of macrophages from HMGB1, TLRs, and inflammatory factors. RF irradiation could alleviate inflammatory skin diseases in patients. RF irradiation can regulate the macrophage indirectly through modulating the keratinocyte and inflammatory molecules of macrophages reduced in vitro and in vivo. Although the study is limited by the low number of cases, it demonstrates that RF irradiation can regulate skin inflammation in patients.

Possible treatment for UVB-induced skin injury: Anti-inflammatory and cytoprotective role of metformin in UVB-irradiated keratinocytes

BACKGROUND

Excessive inflammation and cell death induced by ultraviolet (UV) cause skin photodamage. Metformin possesses anti-inflammatory and cytoprotective effects. However, whether metformin inhibits inflammation and cell death in UVB-induced acute skin damage is unclear.

OBJECTIVE

To evaluate the anti-inflammatory and cytoprotective effects of metformin in vitro and in vivo. Furthermore, its potential mechanism has been explored.

METHODS

Transcriptome sequencing and multiplex cytokines analysis were used to evaluate the validity of in vitro UVB-induced acute damage keratinocyte model and anti-inflammatory effects of metformin. We also determined the expression and nuclear translocation of CCAAT/enhancer-binding protein beta (C/EBPβ), an important transcriptional factor of Interleukin-1beta (IL-1β). Cell viability and cell death of keratinocytes were evaluated upon UVB irradiation in the presence or absence of metformin. 0.6% metformin cream was applied on UVB-irradiated mice to explore its pharmacological effects in vivo.

RESULTS

Transcriptional landscape of 50 mJ/cm² UVB-irradiated HaCaT cells is typical of UVB-induced acute damage keratinocyte model in vitro. Metformin alleviated transcription and secretion of IL-1β, Tumor Necrosis Factor-alpha, and Fibroblast Growth Factor 2, expression and nuclear translocation of C/EBPβ in this model. Metformin also protected keratinocytes from cell death caused by UVB-induced cellular secretions, which contributed to its cytoprotective effects. Topical administration of 0.6% metformin cream alleviated UVB-induced skin damage in mice.

CONCLUSION

We proved the protective roles of metformin in UVB-challenged keratinocytes and UVB-irradiated mice, which indicated the potential value of metformin in topical therapy against skin photodamage.

Application of adipose-derived stem cells in photoaging: basic science and literature review

Photoaging is mainly induced by continuous exposure to sun light, causing multiple unwanted skin characters and accelerating skin aging. Adipose-derived stem cells(ADSCs) are promising in supporting skin repair because of their significant antioxidant capacity and strong proliferation, differentiation, and migration ability, as well as their enriched secretome containing various growth factors and cytokines. The identification of the mechanisms by which ADSCs perform these functions for photoaging has great potential to explore therapeutic applications and combat skin aging. We also review the basic mechanisms of UV-induced skin aging and recent improvement in pre-clinical applications of ADSCs associated with photoaging. Results showed that ADSCs are potential to address photoaging problem and might treat skin cancer. Compared with ADSCs alone, the secretome-based approaches and different preconditionings of ADSCs are more promising to overcome the current limitations and enhance the anti-photoaging capacity.

Nanoencapsulation potentiates the cutaneous anti-inflammatory effect of p,p'-methoxyl-diphenyl diselenide: Design, permeation, and in vivo studies of a nanotechnological-based carrageenan gum hydrogel

This study aimed to investigate the feasibility of preparing a hydrogel based on (OMePhSe)₂-loaded poly(Ɛ-caprolactone) nanocapsules using carrageenan gum as a gel-forming agent. Furthermore, the anti-inflammatory action of hydrogel was assessed in an animal model of skin lesion induced by ultraviolet B (UVB) radiation in mice. Nanocapsules were prepared using the interfacial deposition of preformed polymer technique. The hydrogels were obtained by the direct addition of nanocapsules suspension in carrageenan gum (3%). Formulations with free compound, vehicle, and blank nanocapsules were also produced. The hydrogels were characterized by pH, compound content, diameter, spreadability, rheological behavior, and permeation profile. The pharmacological performance was assessed in an animal model of skin injury induced by UVB-radiation in male Swiss mice. All hydrogels had pH around 7.0, compound content close to the theoretical value (2.5 mg/g), an average diameter in nanometric range (around 350 nm), non-Newtonian flow with pseudoplastic behavior, and suitable spreadability factor. The nano-based hydrogel increased the compound content in the epidermis and dermis layers in comparison to the formulation prepared with non-encapsulated (OMePhSe)₂. Stability studies revealed that the hydrogels of nanoencapsulated compound had superior physicochemical stability in comparison to the formulation of free (OMePhSe)_2. Moreover, topical treatment with the hydrogel containing (OMePhSe)₂ loaded-nanocapsules was more effective in reducing ear thickness and the inflammatory process induced by UVB radiation in mice. Herein, a polysaccharide was applied as a gel-forming agent using a simple and low-cost method. Besides, a superior permeation profile and improved pharmacological action were achieved by the compound encapsulation.

Anti-Apoptotic and Anti-Inflammatory Activities of Edible Fresh Water Algae Prasiola japonica in UVB-Irradiated Skin Keratinocytes

Skin is the outer tissue layer and is a barrier protecting the body from various external stresses. The fresh water green edible algae Prasiola japonica has antiviral, antimicrobial, and anti-inflammatory properties; however, few studies of its effects on skin-protection have been reported. In this study, Prasiola japonica ethanol extract (Pj-EE) was prepared, and its skin-protective properties were investigated in skin keratinocytes. Pj-EE inhibited ROS production in UVB-irradiated HaCaT cells without cytotoxicity. Pj-EE also suppressed the apoptotic death of UVB-irradiated HaCaT cells by decreasing the generation of apoptotic bodies and the proteolytic activation of apoptosis caspase-3, -8, and -9. Moreover, Pj-EE downregulated the mRNA expression of the inflammatory gene cyclooxygenase-2 (COX-2), the pro-inflammatory cytokine genes interleukin (IL)-1β, IL-8, IL-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ, and the tissue remodeling genes matrix metalloproteinase (MMP)-1, -2, -3, and -9. The Pj-EE-induced anti-inflammatory effect was mediated by suppressing the activation of nuclear factor-kappa B (NF-κB) signaling pathway in the UVB-irradiated HaCaT cells. Taken together, these results suggest that Pj-EE exerts skin-protective effects through anti-oxidant, anti-apoptotic, and anti-inflammatory activities in skin keratinocytes.

The Role of the Immune System in Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer. In immunosuppressed populations it is a source of considerable morbidity and mortality due to its enhanced recurrence and metastatic potential. In common with many malignancies, leucocyte populations are both protective against cancer development and also play a role in 'sculpting' the nascent tumor, leading to loss of immunogenicity and tumor progression. UV radiation and chronic viral carriage may represent unique risk factors for cSCC development, and the immune system plays a key role in modulating the response to both. In this review, we discuss the lessons learned from animal and ex vivo human studies of the role of individual leucocyte subpopulations in the development of cutaneous SCC. We then discuss the insights into cSCC immunity gleaned from studies in humans, particularly in populations receiving pharmacological immunosuppression such as transplant recipients. Similar insights in other malignancies have led to exciting and novel immune therapies, which are beginning to emerge into the cSCC clinical arena.

Vitamin D improves sunburns by increasing autophagy in M2 macrophages

Cutaneous inflammation from UV radiation exposure causes epidermal damage, cellular infiltration, and secretion of pro-inflammatory mediators that exacerbate tissue destruction. Recovery is mediated chiefly by anti-inflammatory M2 macrophages that suppress inflammation and augment epidermal regeneration. Vitamin D enables anti-inflammation to promote tissue repair in response to injury. Since vitamin D enhances cellular macroautophagy/autophagy, we investigated the role of autophagy in vitamin D protection of UV-mediated sunburn and inflammation. Using a UV-mediated acute skin injury mouse model, we demonstrate that a single dose of vitamin D resolves injury with sustained inhibition of inflammatory cytokines associated with enhanced autophagy in myeloid anti-inflammatory M2 macs. Increased MAP1LC3B/LC3 expression corroborated with complete autolysosome formation detected by electron microscopy and correlated with degradation of SQSTM1/p62 in the skin following vitamin D treatment. Specifically, pharmacological inhibition of autophagy increased UV-induced apoptosis, suppressed M2 macs recruitment, and prevented vitamin D downregulation of Tnf and Mmp9 in the skin. Furthermore, selective deletion of autophagy in myeloid cells of atg7 cKO mice abrogated vitamin D-mediated protection and recapitulated UV-induced inflammation. Mechanistically, vitamin D signaling activated M2-autophagy regulators Klf4, Pparg, and Arg1. Lastly, analysis of UV-exposed human skin biopsies detected a similar increase in macrophage autophagy following vitamin D intervention, identifying an essential role for autophagy in vitamin D-mediated protection of skin from UV damage.

Abbreviations: ARG1: arginase 1; ATG7 cKO: autophagy related 7 conditional knockout; HPF: high powered field; KLF4: Kruppel like factor 4; MAP1LC3B/LC3: microtubule-associated protein 1 light chain 3 beta; macs: macrophage; 3-MA: 3-methyladenine; MMP9: matrix metallopeptidase 9; NOS2: nitric oxide synthase 2, inducible; PPARG: peroxisome proliferator activated receptor gamma; SQSTM1/p62: sequestosome 1; TNF: tumor necrosis factor; UV: ultraviolet; VD: vitamin D, 25-hydroxy vitamin D₃; 1,25-VD: 1, 25-dihydroxy vitamin D₃

Long non-coding RNA HOTAIR promotes UVB-induced apoptosis and inflammatory injury by up-regulation of PKR in keratinocytes

Excessive exposure to ultraviolet (UV) rays can cause damage of the skin and may induce cancer, immunosuppression, photoaging, and inflammation. The long non-coding RNA (lncRNA) HOX antisense intergenic RNA (HOTAIR) is involved in multiple human biological processes. However, its role in UVB-induced keratinocyte injury is unclear. This study was performed to investigate the effects of HOTAIR in UVB-induced apoptosis and inflammatory injury in human keratinocytes (HaCaT cells). Quantitative real-time polymerase chain reaction was performed to analyze the expression levels of HOTAIR, PKR, TNF-α, and IL-6. Cell viability was measured using trypan blue exclusion method and cell apoptosis using flow cytometry and western blot. ELISA was used to measure the concentrations of TNF-α and IL-6. Western blot was used to measure the expression of PKR, apoptosis-related proteins, and PI3K/AKT and NF-κB pathway proteins. UVB induced HaCaT cell injury by inhibiting cell viability and promoting cell apoptosis and expressions of IL-6 and TNF-α. UVB also promoted the expression of HOTAIR. HOTAIR suppression increased cell viability and decreased apoptosis and expression of inflammatory factors in UVB-treated cells. HOTAIR also promoted the expression of PKR. Overexpression of HOTAIR decreased cell viability and increased cell apoptosis and expression of inflammatory factors in UVB-treated cells by upregulating PKR. Overexpression of PKR decreased cell viability and promoted cell apoptosis in UVB-treated cells. Overexpression of PKR activated PI3K/AKT and NF-κB pathways. Our findings identified an essential role of HOTAIR in promoting UVB-induced apoptosis and inflammatory injury by up-regulating PKR in keratinocytes.

Piper retrofractum Vahl. Extract, as a PPARδ and AMPK Activator, Suppresses UVB-Induced Photoaging through Mitochondrial Biogenesis and MMPs Inhibition in Human Dermal Fibroblasts and Hairless Mice

Photoaging occurs by UVB-irradiation and involves production of reactive oxygen species (ROS) and overexpression of matrix metalloproteinases (MMPs), leading to extracellular matrix damage. Piper retrofractum Vahl. is used as a traditional medicine for antiflatulence, expectorant, sedative, and anti-irritant; however, its antiphotoaging effect has not yet been studied. The current study investigated the antiphotoaging effect of standardized Piper retrofractum extract (PRE) on UVB-damaged human dermal fibroblasts and hairless mouse skin. PRE treatment activated the peroxisome proliferator-activated receptor delta (PPARδ) and the adenosine monophosphate-activated protein kinase (AMPK), consequently upregulating mitochondrial synthesis and reducing ROS production. Additionally, PRE inhibited MMPs expression via suppressing mitogen-activated protein kinase (MAPK) and activator protein-1 (AP-1). PRE downregulated UVB-induced inflammatory reactions by inhibiting the nuclear factor-kappa B (NF-κB) activity. PRE also enhanced transforming growth factor-beta (TGF-β) and the Smad signaling pathway, thereby promoting procollagen gene transcription. Furthermore, oral administration of PRE (300 mg/kg/day) similarly regulated the signaling pathways and increased antioxidant enzyme expression, thus attenuating physiological deformations, such as wrinkle formation and erythema response. Collectively, these results suggest that PRE acts as a potent antiphotoaging agent via PPARδ and AMPK activation.

Anti-Inflammatory Role of Langerhans Cells and Apoptotic Keratinocytes in Ultraviolet-B-Induced Cutaneous Inflammation

UV radiation, particularly UVB, is the major risk factor for the induction of skin cancer, and it induces skin inflammation and immunosuppression. Although reports documented that Langerhans cells (LCs) play various roles in photobiology, little is known about whether they contribute to UVB-induced cutaneous inflammation. Recently, the anti-inflammatory effect of apoptotic cells was noted. This study focuses on the roles of LCs and apoptotic cells in UVB-induced cutaneous inflammation. We show that LCs are essential for resolution of UVB-induced cutaneous inflammation. Administration of quinolyl-valyl-O-methylaspartyl-[2,6-difluophenoxy]-methyl ketone, a broad-spectrum caspase inhibitor with potent antiapoptotic properties, inhibited the formation of UVB-induced apoptotic cells and aggravated UVB-induced cutaneous inflammation in wild-type mice. In contrast, exacerbation of UVB-induced cutaneous inflammation following quinolyl-valyl-O-methylaspartyl-[2,6-difluophenoxy]-methyl ketone administration was not observed in LC-depleted mice. These results suggest that the interaction between LCs and apoptotic cells is critical for resolution of UVB-induced cutaneous inflammation. Interestingly, UVB-induced apoptotic keratinocytes were increased in LC-depleted mice. In addition, we revealed that UVB-induced apoptotic keratinocytes were phagocytosed by LCs ex vivo and that prolongation of UVB-induced cutaneous inflammation following treatment with Cytochalasin D, an inhibitor of phagocytosis, was partially attenuated in LC-depleted mice. Collectively, our findings demonstrate that the interaction between LCs and apoptotic cells, possibly via LC-mediated phagocytosis of apoptotic keratinocytes, has an essential anti-inflammatory role in the resolution of UVB-induced cutaneous inflammation.

Inflammation Shapes Stem Cells and Stemness during Infection and Beyond

The outcome of an inflammatory incident can hang in the balance between restoring health and tissue integrity on the one hand, and promoting aberrant tissue homeostasis and adverse outcomes on the other. Both microbial-related and sterile inflammation is a complex response characterized by a range of innate immune cell types, which produce and respond to cytokine mediators and other inflammatory signals. In turn, cells native to the tissue in question can sense these mediators and respond by migrating, proliferating and regenerating the tissue. In this review we will discuss how the specific outcomes of inflammatory incidents are affected by the direct regulation of stem cells and cellular plasticity. While less well appreciated than the effects of inflammatory signals on immune cells and other differentiated cells, the effects are crucial in understanding inflammation and appropriately managing therapeutic interventions.

Role of p53 in silibinin-mediated inhibition of ultraviolet B radiation-induced DNA damage, inflammation and skin carcinogenesis

Non-melanoma skin cancers (NMSC) are a growing problem given that solar ultraviolet B (UVB) radiation exposure is increasing most likely due to depletion of the atmospheric ozone layer and lack of adequate sun protection. Better preventive methods are urgently required to reduce UV-caused photodamage and NMSC incidence. Earlier, we have reported that silibinin treatment activates p53 and reduces photodamage and NMSC, both in vitro and in vivo; but whether silibinin exerts its protective effects primarily through p53 remains unknown. To address this question, we generated p53 heterozygous (p53^+/-) and p53 knockout (p53^-/-) mice on SKH-1 hairless mouse background, and assessed silibinin efficacy in both short- and long-term UVB exposure experiments. In the chronic UVB-exposed skin tumorigenesis study, compared to p53^+/+ mice, p53^+/- mice developed skin tumors earlier and had higher tumor number, multiplicity and volume. Silibinin topical treatment significantly reduced the tumor number, multiplicity and volume in p53^+/+ mice but silibinin' protective efficacy was significantly compromised in p53^+/- mice. Additionally, silibinin treatment failed to inhibit precursor skin cancer lesions in p53^-/- mice but improved the survival of the mice. In short-term studies, silibinin application accelerated the removal of UVB-induced DNA damage in p53^+/+ mice while its efficacy was partially compromised in p53^-/- mice. Interestingly, silibinin treatment also inhibited the UVB-induced inflammatory markers in skin tissue. These results further confirmed that absence of the p53 allele predisposes mice to photodamage and photocarcinogenesis, and established that silibinin mediates its protection against UVB-induced photodamage, inflammation and photocarcinogenesis partly through p53 activation.

The photoprotective effects of 2-benzoyl-3-phenylquinoxaline 1,4-dioxide against UVB-induced damage in HaCaT cells

With the increasing levels of atmospheric ozone depletion, there has been much concern about the causal effects of high levels of ultraviolet radiation reaching the Earth's surface on skin cancer. This has led to growing interest in identifying new active ingredients for use in commercial sunscreens. In our study, the chemical compound 2-benzoyl-3-phenylquinoxaline 1,4-dioxide (BPQ) prepared by the Beirut reaction was tested for its ability to protect a human keratinocyte cell line (HaCaT) against ultraviolet B radiation (280-315 nm). We show that BPQ exhibited strong absorbance in the UVB range, with an overall absorption spectrum very similar to that of Padimate-O, a well-known active ingredient used in commercial sunscreens. HaCaT cells, which were irradiated with UVB in the presence of multiple doses of BPQ, exhibited, in a dose-dependent fashion, a significantly higher viability and lower oxidative stress levels than cells irradiated in the absence of drug. Our results show that BPQ is a potential photoprotective drug that holds great promise for use as an active ingredient in commercial sunscreens.

Dietary fermented soybean suppresses UVB-induced skin inflammation in hairless mice via regulation of the MAPK signaling pathway

Soybean may be a promising ingredient for regulating UVB-induced inflammatory damage to the skin. We investigated the anti-inflammatory effects of diets supplemented with fermented soybean on UVB-induced skin photodamage and the effectiveness of soybean (S) and fermented soybean (FS) dietary supplementation. To investigate the effects of two major isoflavones-daidzein and genistein-from FS, we used cocultures with keratinocytes and fibroblasts. Genistein treatment strongly inhibited the production of IL-6 and MAPK signaling. Forty hairless male mice divided into four groups were fed with a control diet (group N: normal, group C; +UVB) or diets with 2.5% S+UVB or 2.5% FS+UVB (group S, group FS) for 8 weeks. Macrophage infiltration to the dermis was reduced more in groups S and FS than in group C. The expression levels of iNOS and COX-2 were significantly decreased in group FS (by 7.7% ± 0.4% and 21.2% ± 0.3%, respectively [p < 0.05]).

Topically applied ZnO nanoparticles suppress allergen induced skin inflammation but induce vigorous IgE production in the atopic dermatitis mouse model

BACKGROUND

Metal oxide nanoparticles such as ZnO are used in sunscreens as they improve their optical properties against the UV-light that causes dermal damage and skin cancer. However, the hazardous properties of the particles used as UV-filters in the sunscreens and applied to the skin have remained uncharacterized.

METHODS

Here we investigated whether different sized ZnO particles would be able to penetrate injured skin and injured allergic skin in the mouse atopic dermatitis model after repeated topical application of ZnO particles. Nano-sized ZnO (nZnO) and bulk-sized ZnO (bZnO) were applied to mechanically damaged mouse skin with or without allergen/superantigen sensitization. Allergen/superantigen sensitization evokes local inflammation and allergy in the skin and is used as a disease model of atopic dermatitis (AD).

RESULTS

Our results demonstrate that only nZnO is able to reach into the deep layers of the allergic skin whereas bZnO stays in the upper layers of both damaged and allergic skin. In addition, both types of particles diminish the local skin inflammation induced in the mouse model of AD; however, nZnO has a higher potential to suppress the local effects. In addition, especially nZnO induces systemic production of IgE antibodies, evidence of allergy promoting adjuvant properties for topically applied nZnO.

CONCLUSIONS

These results provide new hazard characterization data about the metal oxide nanoparticles commonly used in cosmetic products and provide new insights into the dermal exposure and hazard assessment of these materials in injured skin.