Topical photodynamic therapy is immunosuppressive in humans

Background Visible light irradiation after application of a photosensitizer (topical photodynamic therapy; PDT) is increasingly used to treat nonmelanoma skin cancers and premalignant actinic keratoses. PDT can provide a cosmetically superior alternative to surgery, but carries failure rates of 10–40%. While some murine studies have suggested immune enhancement by PDT, others reported immunosuppressive effects, which may indicate impaired antitumour immunity and thus compromised tumour clearance. Objectives This study aimed to determine the in vivo immune effects of PDT in humans. Methods Using healthy, Mantoux‐positive volunteers, we irradiated discrete areas of the back with narrowband red light (630 nm; 37 J cm^?2), with and without prior application of 5‐aminolaevulinic acid (ALA) or methyl aminolaevulinate (MAL). Adjacent, untreated areas served as immunologically intact control sites. Delayed‐type hypersensitivity responses to tuberculin purified protein derivative (Mantoux reactions) were then elicited in each of the irradiated, unirradiated and control sites, and the intensity of the reactions was quantitated with an erythema meter and by measurement of Mantoux diameter. By comparing Mantoux intensity at treated and control sites, immunosuppression was determined in each volunteer for each intervention. Results We found that both MAL‐PDT and ALA‐PDT significantly suppressed Mantoux erythema (by 30% and 50%, respectively) and diameter (41% and 38%). Red light alone significantly suppressed diameter (22%) but not erythema (13%). Conclusions Topical PDT induced significant immune suppression, which could impair local antitumour immune responses and may thus contribute to treatment failure.     

Effects of low-dose ultraviolet radiation on in vivo human cutaneous recall responses

Relatively few studies have examined the effects of low-dose ultraviolet (UV) radiation on in vivo human cutaneous immunity, or the ability of sunscreens to prevent UV-induced immunosuppression. We have studied the effects of solar-simulated UV radiation on nickel contact hypersensitivity (CHS) in nickel-allergic volunteers, and on delayed type hypersensitivity responses in Mantoux-positive volunteers. Nickel CHS and Mantoux responses were significantly suppressed by acute, suberythemal UV exposures equivalent to less than 8 min summer sunlight. Both UVA and UVB wavebands were immunosuppressive, but UVA-induced immunosuppression was transient, whereas UVB had a more sustained effect. Dose-responses for UV immunosuppression were determined using the nickel method, enabling calculation of in vivo sunscreen immune protection factors in a manner analogous with sun protection factor measurement. Sunscreens were found to confer significantly less protection against UV-induced immunosuppression than against UV-induced erythema.     

Topical cholesterol treatment ameliorates hapten‐evoked cutaneous hypersensitivity by sustaining expression of 11β‐HSD1 in epidermis

Changes in the stratum corneum extracellular matrix impair epidermal barrier function and may cause dermatoses. The aim of this study was to examine the effect of exogenous cholesterol application on skin barrier function and cutaneous inflammation. Skin barrier‐disrupted or hapten‐stimulated mice were treated with topical cholesterol. The effect of topical cholesterol application on an oxazolone (OXA)‐induced hypersensitivity reaction was evaluated. Topical application of cholesterol efficiently decreased transepidermal water loss in areas of barrier‐disrupted skin and ameliorated OXA‐induced cutaneous hypersensitivity. These favourable effects may have resulted from sustained expression of 11β‐hydroxysteroid dehydrogenase type 1 (11β‐HSD1) in the cholesterol‐treated skin. As 11β‐HSD1 is known to produce active cortisol, topical cholesterol may attenuate contact hypersensitivity by normalizing secretion of hormonally active cortisol from the skin.     

Topical riboflavin attenuates ultraviolet B‐ and ultraviolet A‐induced immunosuppression in humans

Background: Riboflavin (vitamin B₂) plays a key role in cellular energy metabolism. We have observed previously that nicotinamide (vitamin B₃), which is also centrally involved in cellular energy restoration after UV irradiation, is highly immune protective in humans. We thus hypothesized that riboflavin might also confer immune protection. Methods: We irradiated healthy, nickel‐allergic volunteers with narrowband UVA (385 nm) and UVB (300 nm) at separate sites on the lower back. These areas were treated with riboflavin solution or vehicle at 24 h and again at 30 min before UV exposure. Forty‐eight hours after irradiation, volunteers were patch tested with nickel‐containing Finn chambers, at both irradiated and nonirradiated sites, with and without prior riboflavin treatment. The resulting contact hypersensitivity reactions at each site were then measured 72 h later with a reflectance erythema meter in order to determine and compare the immune suppressive effects of each intervention. Results: We observed that low doses of both UVB and longwave UVA1 were immune suppressive in humans. Topical riboflavin conferred immune protection against both wavebands. Conclusions: Riboflavin is immune protective in humans, and this may reflect the role of the B group vitamins in cellular energy restoration after UV exposure.     

Paeoniflorin suppresses vascular damage and the expression of E‐selectin and ICAM‐1 in a mouse model of cutaneous Arthus reaction

Paeoniflorin (PF) extracted from the root of Paeonia lactiflora pall, displays anti‐inflammation properties in several animal models. Adhesion molecules are important for the recruitment of leucocyte to the vessel wall and involved in the pathogenesis of various autoimmune and inflammatory diseases. Herein, we investigate the effects of PF on adhesion molecule expression in a mouse model of cutaneous Arthus reaction and cultured human dermal microvascular endothelial cells (HDMECs). We showed that PF significantly ameliorated the immune complex (IC) induced vascular damage, leucocyte infiltrates and adhesion molecules expression. Furthermore, PF markedly blocked tumor necrosis factor‐α (TNF‐α)‐induced E‐selectin and intercellular adhesion molecule‐1 (ICAM‐1) expression in HDMECs at both mRNA and protein levels. PF also suppressed TNF‐α‐induced adhesion of polymorphonuclear leucocytes (PMNs) to HDMECs. Finally, western blot data revealed that PF can inhibit the phosphorylation of p38, JNK in TNF‐α‐treated HDMECs. These data suggest that PF, as an anti‐inflammatory agent, can downregulate adhesion molecules expression. PF may be a candidate medicine for the treatment of IC‐induced inflammatory response.     

Protective effects of a topical antioxidant mixture containing vitamin C,ferulic acid,and phloretin against ultraviolet‐induced photodamage in human skin

Background Ultraviolet (UV) irradiation of the skin leads to acute inflammatory reactions, such as erythema, sunburn, and chronic reactions, including premature skin aging and skin cancer. Aim In this study, the effects of a topical antioxidant mixture consisting of vitamin C, ferulic acid, and phloretin on attenuating the harmful effects of UV irradiation on normal healthy volunteers were studied using biomarkers of skin damage. Subjects/methods Ten subjects (age, 18–60 years; Fitzpatrick skin types II and III) were randomized and treated with antioxidant product or vehicle control on the lower back for four consecutive days. On day 3, the minimal erythema dose (MED) was determined for each subject at a different site on the back. On day 4, the two test sites received solar‐simulated UV irradiation 1–5× MED at 1× MED intervals. On day 5, digital images were taken, and 4‐mm punch biopsies were collected from the two 5× MED test sites and a control site from each subject for morphology and immunohistochemical studies. Results UV irradiation significantly increased the erythema of human skin in a linear manner from 1× to 5× MED. As early as 24 h after exposure to 5× MEDs of UV irradiation, there were significant increases in sunburn cell formation, thymine dimer formation, matrix metalloproteinase‐9 expression, and p53 protein expression. All these changes were attenuated by the antioxidant composition. UV irradiation also suppressed the amount of CD1a‐expressing Langerhans cells, indicating immunosuppressive effects of a single 5× MED dose of UV irradiation. Pretreatment of skin with the antioxidant composition blocked this effect. Conclusion This study confirms the protective role of a unique mixture of antioxidants containing vitamin C, ferulic acid, and phloretin on human skin from the harmful effects of UV irradiation. Phloretin, in addition to being a potent antioxidant, may stabilize and increase the skin availability of topically applied vitamin C and ferulic acid. We propose that antioxidant mixture will complement and synergize with sunscreens in providing photoprotection for human skin.     

Unique microRNAs appear at different times during the course of a delayed‐type hypersensitivity reaction in human skin

Diphencyprone (DPCP) is a hapten that induces delayed‐type hypersensitivity (DTH) reactions. MicroRNAs (miRNAs) are short non‐coding RNAs that negatively regulate gene expression and have been implicated in various inflammatory skin diseases, but their role in DTH reactions is not well understood. We generated global miRNA expression profiles (using next‐generation sequencing) of DPCP reactions in skin of seven healthy volunteers at 3, 14 and 120 days after challenge. Compared to placebo‐treated sites, DPCP‐challenged skin at 3 days (peak inflammation) had 127 miRNAs significantly deregulated. At 14 days (during resolution of inflammation), 43 miRNAs were deregulated and, at 120 days (when inflammation had completely resolved), six miRNAs were upregulated. While some miRNAs have been observed in psoriasis or atopic dermatitis, most of the deregulated miRNAs have not yet been studied in the context of skin biology or immunology. Across the three time points studied, many but not all miRNAs were uniquely expressed. As various miRNAs may influence T cell activation, this may indicate that the miRNAs exclusively expressed at different time points function to promote or resolve skin inflammation, and therefore, may inform on the paradoxical ability of DPCP to treat both autoimmune conditions (alopecia areata) and conditions of ineffective immunity (melanoma).     

Polidocanol inhibits cowhage ‐ but not histamine‐induced itch in humans

Polidocanol is a local anaesthetic and antipruritic compound that is used in the treatment of itching skin conditions such as eczema. Its mechanisms of action are largely ill defined. This study has compared the antipruritic efficacy of topical polidocanol in histamine‐induced itch and a histamine‐independent, cowhage‐induced model of pruritus. Polidocanol (3%) or vehicle was applied topically under occlusion for 1 h to the forearms of 45 healthy volunteers before itch was provoked by rubbing in 40–45 spicules of cowhage or skin prick testing with 10 mg/ml histamine. Itch was recorded at 1‐min intervals for 30 min on a 100‐mm visual analogue scale. Polidocanol significantly reduced the area under the curve for cowhage‐induced itch by 58% (P < 0.05), but had no significant effect on histamine‐induced itch. This result underlines the importance of histamine‐independent itch models in the development of topical antipruritic agents.     

Suppression of UV‐induced damage by a liposomal sunscreen: a prospective,open‐label study in patients with cutaneous lupus erythematosus and healthy controls

This study aimed to determine whether a broad‐spectrum liposomal sunscreen with a very high sun protection factor (Daylong actinica) can prevent damage induced by ultraviolet (UV) irradiation in patients with cutaneous lupus erythematosus (CLE) and healthy controls (HCs) under standardised conditions. In 20 patients with CLE and 10 HCs, defined areas of sunscreen‐untreated and sunscreen‐treated skin on the upper back were irradiated with combined UVA/UVB light. Disease‐specific skin lesions were induced by UVA/UVB light in the untreated areas of nine patients with CLE; no specific eruptions or any sun damage was observed in the sunscreen‐treated areas in any of the CLE patients, nor in the HCs. Histological analysis of skin biopsy specimens confirmed the clinical results. In conclusion, the use of a high‐protection, broad‐spectrum sunscreen can prevent UV‐induced damage in patients with CLE and HCs.     

UVB‐ and NGF‐induced cutaneous sensitization in humans selectively augments cowhage‐ and histamine‐induced pain and evokes mechanical hyperknesis

Exaggerated itch responses to pruritic chemical provocations and mechanical stimuli are evident in patients with chronic itch, for example, in atopic dermatitis. Currently used human models of itch do not account for such itch sensitization features, and the mechanisms underlying clinical itch sensitization are unknown. This study utilized two established human models of cutaneous nociceptive sensitization to explore how pre‐established inflammatory hyperalgesia (ultraviolet‐B‐irradiation; “UVB”) and non‐inflammatory neurotrophic pain sensitization (nerve growth factor; “NGF”) alter sensitivity to chemical and mechanically evoked itch. Twenty healthy volunteers participated in the UVB experiment. Six volar forearm areas (2 cm diameter) were UVB irradiated with ≤2 × minimal erythemal dose, and two non‐irradiated areas were used as controls. Sixteen healthy volunteers participated in the NGF experiment and had 2 μg intradermally injected (4 × 50 μL in 2 cm diameter areas) into both volar forearms. Isotonic saline was applied as control. Pain sensitivity measurements (mechanical and heat pain thresholds) were conducted to validate the models. Subsequently, itch was evoked using histamine and cowhage spicules in the sensitized skin areas, and itch/pain was rated using visual analogue scales. Mechanical hyperknesis (increased itch to punctuate stimuli) was probed with von Frey filaments before/after each itch provocation. Both UVB‐ and NGF models induced robust primary mechanical hyperalgesia (P < .01) and hyperknesis (P < .05). Neither of the models augmented itch in response to chemical itch provocations but significant increases specifically for pain ratings were observed for both histamine and cowhage (P < .05). This suggests that these models are of limited value as proxies for itch sensitization to pruritogens observed, e.g., in inflammatory dermatoses.     

Inhibitory effects of dietary soyasaponin on 2,4‐dinitrofluorobenzene‐induced contact hypersensitivity in mice

Soyasaponins (SSs) abundant in soybean have anti‐inflammatory activities; however, their therapeutic effects on allergic contact dermatitis (ACD) remain unknown. To assess the effects of SS‐enriched diets on ACD, we used a mouse model of contact hypersensitivity (CHS). Mice were fed low‐dose or high‐dose SS‐containing diets for 3 weeks prior to CHS induction with 2,4‐dinitrofluorobenzene (DNFB). The low‐dose SS diet attenuated DNFB‐induced ear swelling and tissue oedema, and reduced the number of infiltrating Gr‐1‐positive myeloid cells. Low‐dose, but not high‐dose, SSs decreased chemokine (C‐X‐C motif) ligand 2 (CXCL2) and triggering receptor expressed on myeloid cells (TREM)‐1 production in ear tissues, compared to a control. Taxonomic 16S rRNA analysis revealed significant alterations in faecal microbiota caused by CHS, which were reversed by low‐dose SSs. The low‐dose SS and non‐CHS groups clustered together, while the high‐dose SS group split between CHS and non‐CHS clusters. Our results demonstrated that low‐dose SSs alleviated CHS symptoms by attenuating inflammation and improving the intestinal microbiota composition, suggesting that dietary SSs may have beneficial effects on ACD.     

miRNA miR‐17‐92 cluster is differentially regulated in the imiqumod‐treated skin but is not required for imiqumod‐induced psoriasis‐like dermatitis in mice

MicroRNAs (miRNAs) play very important roles in the control of immune cell and keratinocyte development and function and are implicated in skin inflammatory diseases, including psoriasis. miRNA miR‐17‐92 was reported to promote the differentiation of Th1 and Th1 cells and to regulate cell proliferation and apoptosis. Here we showed that imiquimod (IMQ) differentially regulates the expression of miR‐17‐92 cluster in the mouse skin, upregulating miR‐17 and miR‐19 families and downregulating miR‐92. To investigate whether miR‐17‐92 cluster is functionally involved in the psoriasis, we have generated three mutant mice with specific deletion or overexpression of miR‐17‐92 cluster in keratinocytes, or with deletion of miR‐17‐92 cluster in T cells. Interestingly, deletion or overexpression of miR‐17‐92 cluster in keratinocytes, or deletion of miR‐17‐92 in T cells did not significantly affect IMQ‐induced psoriasis‐like dermatitis development in the mutant mice compared with wild‐type littermates. Thus, miRNA miR‐17‐92 cluster may not be a key factor regulating imiqumod‐induced psoriasis‐like dermatitis.     

Topical retinol attenuates stress‐induced ageing signs in human skin ex vivo,throughEGFR activation viaEGF,but notERK andAP‐1 activation

Stress‐induced oxidative damage and the inflammatory response lead to degradation of collagen and elastic fibres and wrinkle formation. Topical retinol (or vitamin A) can be a strategy to attenuate the effects of stress in skin as it promotes collagen and elastic fibre production and reduces protease synthesis. This study investigated the effect of topical retinol in stressed human skin using in vitro and ex vivo models. Human skin explants were treated with high levels of epinephrine (as observed in stressed patients) and topically with retinol for 13 days. Human dermal fibroblasts were treated with conditioned medium of ex vivo retinol‐treated and non‐stressed (without epinephrine) human skin for 24 hours. In ex vivo human skin, retinol reversed the epinephrine‐induced reduction in epidermal proliferation and differentiation, normalizing epidermal thickness. Retinol also inhibited the epinephrine‐induced reduction in elastic fibre deposition and organization, restoring dermal thickness. In addition, retinol reversed the epinephrine‐induced increase in c‐JUN protein expression, but it did not alter extracellular signal‐regulated kinase 1/2 (ERK) phosphorylation in ex vivo human skin. Conditioned medium of ex vivo retinol‐treated and non‐stressed human skin presented an increased protein expression of epidermal growth factor (EGF). In human dermal fibroblasts, conditioned medium of ex vivo retinol‐treated and non‐stressed human skin increased protein and gene expression of fibrillin‐1 and protein expression of EGF receptor (EGFR). In conclusion, topical retinol attenuates stress‐induced skin ageing signs in human skin ex vivo, probably through EGFR activation via EGF, but not by the stress‐activated ERK 1/2 and c‐JUN pathways.