A Haylett

The sunburn response in human skin is characterized by sequential eicosanoid profiles that may mediate its early and late phases

Sunburn is a commonly occurring acute inflammatory process, with dermal vasodilatation and leukocyte infiltration as central features. Ultraviolet (UV) B‐induced hydrolysis of membrane phospholipids releases polyunsaturated fatty acids, and their subsequent metabolism by cyclooxygenases (COXs) and lipoxygenases (LOXs) may produce potent eicosanoid mediators modulating different stages of the inflammation. Our objective was to identify candidate eicosanoids formed during the sunburn reaction in relation to its clinical and histological course. We exposed skin of healthy humans (n=32) to UVB and, for 72 h, examined expression of proinflammatory and antiinflammatory eicosanoids using LC/ESI‐MS/MS, and examined immunohistochemical expression of COX‐2, 12‐LOX, 15‐LOX, and leukocyte markers, while quantifying clinical erythema. We show that vasodilatory prostaglandins (PGs) PGE2, PGF2a, and PGE3 accompany the erythema in the first 24–48 h, associated with increased COX‐2 expression at 24 h. Novel, potent leukocyte chemoattractants 11‐, 12‐, and 8‐monohydroxy‐eicosatetraenoic acid (HETE) are elevated from 4 to 72 h, in association with peak dermal neutrophil influx at 24 h, and increased dermal CD3+ lymphocytes and 12‐ and 15‐LOX expression from 24 to 72 h. Anti‐inflammatory metabolite 15‐HETE shows later expression, peaking at 72 h. Sunburn is characterized by overlapping sequential profiles of increases in COX products followed by LOX products that may regulate subsequent events and ultimately its resolution.—Rhodes, L. E., Gledhill, K., Masoodi, M., Haylett, A. K., Brownrigg, M., Thody, A. J., Tobin, D. J., Nicolaou, A. The sunburn response in human skin is characterized by sequential eicosanoid profiles that may mediate its early and late phases. FASEB J. 23, 3947–3956 (2009). www.fasebj.org

Systemic photoprotection in solar urticaria with α‐melanocyte‐stimulating hormone analogue [Nle4‐d‐Phe7]‐α‐MSH

Background  Solar urticaria is a rare photosensitivity disorder demonstrating a range of action spectra, which can inflict a very large impact on life quality despite available treatments. Melanin broadly reduces skin penetration by ultraviolet–visible wavelengths, thus increased melanization may protect in solar urticaria.

In vivo expression of the collagen-related heat shock protein HSP47, following hyperthermia or photodynamic therapy

Abstract. Heat shock protein 47 (HSP 47), a molecule expressed constitutively in cells that synthesise collagen, is involved in collagen type I biosynthesis, and after insult acts as a stress response molecule to sequester abnormal procollagen. Photodynamic therapy (PDT) is claimed not to result in extensive collagen damage, such as that which can occur after other laser treatments, e.g. hyperthermia (HT) or coagulation, thereby conferring on PDT a potential therapeutic advantage. In previous studies on mouse fibroblasts in vitro we demonstrated HSP47 elevation in the first hours after the application of conditions known to damage collagen, and an absence of HSP47 elevation following PDT with two well-established photosensitisers, haematoporphyrin ester (HpE) and meta-tetrahydroxyphenylchlorin (mTHPC).The present study examines HSP47 metabolism in murine skin following (1) HT, (2) PDT with HpE and (3) PDT with riboflavin (RB). Riboflavin was examined because of reports of collagen injury induced by its photoactivation. All three stresses were applied at grossly equitoxic, ‘tolerance’ doses. Three months after these doses, linear extensometry revealed the skin to have fibrotic characteristics after HT and RB PDT, but not after HpE PDT. HSP47 expression levels were analysed at transcriptional (Northern) and translational (Western) levels at early time intervals up to 24 h after the treatment application, starting immediately after the treatment for mRNA and 6 h post-treatment for protein. Highly significant upregulation of HSP47 was detected following HT, and PDT with RB. PDT mediated by HpE did not have any impact on HSP47 levels. These results were thus consistent with those from in vitro work and support the hypothesis of early elevation of HSP47 expression only by modalities affecting collagen or its precursors.

Prostaglandin-E2 is produced by adult human epidermal melanocytes in response to UVB in a melanogenesis-independent manner.

Excessive ultraviolet radiation (UVR) exposure induces erythema, mediated in part by prostaglandin‐E2 (PGE2). While keratinocytes are a major PGE2 source, epidermal melanocytes (EM) also express PGE2‐production machinery. It is unclear whether EM‐produced PGE2 contributes to UVR‐induced skin inflammation, and whether this is correlated with melanogenesis. Epidermal melanocytes were cultured from skin phototype‐1 and ‐4 donors, followed by assessment of PGE2 production and melanogenesis. Epidermal melanocytes expressed cytoplasmic phospholipase‐A2, cyclooxygenase‐1, cytoplasmic prostaglandin‐E synthase and microsomal prostaglandin‐E synthase‐1, ‐2. Epidermal melanocytes produced PGE2 under basal conditions, which increased further after arachidonic acid stimulation. Epidermal melanocytes expressed cyclooxygenase‐2 (COX‐2) mRNA and a selective COX‐2 inhibitor (NS‐398) reduced PGE2 production. Ultraviolet B‐induced PGE2 production was positively correlated with skin phototype‐1, despite variability between individual EM donors. By contrast, there was no correlation between PGE2 production by EM and their melanogenic status. Thus, EM may contribute to UVR‐induced erythema, with role of donor skin phototype more important than their melanogenic status.

DNA Damage and Repair in Gorlin Syndrome and Normal Fibroblasts After Aminolevulinic Acid Photodynamic Therapy: A Comet Assay Study ¶

Using normal, untransformed, human fibroblasts, the effectiveness of aminolevulinic (ALA)‐mediated photodynamic therapy (PDT) was investigated in terms of both clonogenic survival and DNA damage. The response of normal fibroblasts was then compared with Gorlin syndrome–derived fibroblasts (basal cell nevus syndrome [BCNS]). In terms of clonogenic survival, no significant differences were observed between the two groups of cells. Using the alkaline comet assay, initial DNA damage after PDT was measured. Some DNA damage was detected at higher doses, but this was fully repaired within 24 h of treatment. The BCNS‐derived cells showed levels of initial damage that did not differ significantly from normal lines.

Voriconazole-induced photosensitivity: photobiological assessment of a case series of 12 patients

Background  Voriconazole, a broad‐spectrum triazole antifungal agent increasingly used to treat aspergillosis, has been linked with acute photosensitivity and skin carcinogenesis. The action spectrum of the photosensitivity is unknown, while an indirect retinol effect secondary to the antifungal’s impact on CYP450 enzymes has been proposed to contribute to the underlying mechanism.

Singlet oxygen and superoxide characteristics of a series of novel asymmetric photosensitizers

The singlet oxygen quantum yields and superoxide quantum yields for a series of novel compounds based on an asymmetrical protoporphyrin molecule have been examined. Electron spin resonance was used to measure superoxide yield and time resolved luminescence for singlet oxygen. A comparison between these results and previously published cell survival data was carried out. A broad association was found between singlet oxygen quantum yield and clonogenic cell kill.

The effect of ultraviolet B-induced vitamin D levels on host resistance to Mycobacterium tuberculosis: A pilot study in immigrant Asian adults living in the United Kingdom

Asian immigrants to the United Kingdom demonstrate much higher tuberculosis rates than the indigenous population. This is postulated to be because of their low vitamin D levels, consequent upon a combination of diet and their reduced ultraviolet (UV) exposure in the United Kingdom, because vitamin D enhances antimycobacterial activity in in vitro systems. The aim of this study was to examine the relationship between UVB exposure, vitamin D levels and tuberculo‐immunity in Asian immigrants in the United Kingdom. Suberythemal UVB treatments were given to eight subjects on 3 consecutive days, using broadband UVB fluorescent lamps. Blood was sampled for 25‐hydroxyvitamin D (25‐OH D) and whole blood functional assays were performed for antimycobacterial immunity. The mean 25‐OH D level increased from a baseline of 11.23 ng/ml (95% CI 6.7–20.39) to 20.39 ng/ml (95% CI 16.6–20) following UVB treatment, P<0.01. However, no significant change in antimycobacterial immunity occurred following UVB exposure. This pilot study in Asian subjects with good baseline tuberculo‐immunity has not supported a role for UVB‐induced 25‐OH D in the immune response to Mycobacterium tuberculosis.

The eicosanoid response to high dose UVR exposure of individuals prone and resistant to sunburn

High personal UVR doses can be gained during leisure activities, causing intense self-resolving inflammation (sunburn) of unprotected skin. UVR activates release of membrane fatty acids and upregulates their metabolism by cyclooxygenases (COX) and lipoxygenases (LOX) to different eicosanoids. While COX-derived prostaglandin (PG)E(2) is a potent mediator of sunburn vasodilatation, LOX-derived 15-hydroxyeicosatetraenoic acid (HETE) and its lipoxin metabolites may contribute to sunburn limitation. We explored the relationships between expression of these lipid mediators and the clinical and histological outcomes, comparing responses of individuals prone and more resistant to sunburn. An acute UVR exposure of 12 SED (standard erythema dose) was applied to buttock skin of 32 white Caucasians (n = 16 phototype I/II, n = 16 phototype III/IV), and over the subsequent 72 h assessments were made of skin erythema, immunohistochemical expression of leukocyte markers, COX-2, 12-LOX, 15-LOX and nitric oxide synthase (NOS), and eicosanoid levels by LC/ESI-MS/MS. Evidence of a significant inflammatory response was seen earlier in phototype I/II with regard to expression of erythema (4 h, p < 0.001), neutrophil infiltration (24 h, p = 0.01), epidermal COX-2 (24 h, p < 0.05) and 12-LOX (24 h, p < 0.01), and dermal eNOS (24 h, p < 0.05) proteins, although CD3+ lymphocyte infiltration showed an earlier increase in phototype III/IV (24 h, p < 0.05). Although erythema was equivalent at 72 h in both groups, phototype I/II showed higher PGE(2) accompanied by elevated 15-HETE, and a strong positive correlation was seen between these mediators (n = 18, r = 0.805, p = 0.0001). Hence anti-inflammatory eicosanoid 15-HETE may temper the pro-inflammatory milieu in sunburn, having greater influence in those prone to sunburn than those more resistant, given the same high UVR exposure conditions.

Photodynamic therapy of ovarian tumours and normal cells using 5,10,15,20-tetra-(3-carboxymethoxyphenyl)-chlorin.

The photosensitizing ability of the second generation photosensitizer 5,10,15,20-tetra-(3-carboxymethoxyphenyl)-chlorin (m-TCMPC), a derivative of m-THPC, was tested on both three-dimensional multicellular spheroids of varying sizes and on monolayer cultures. These experiments were carried out on two spheroid-forming cell lines, A2780 (a human ovarian adenocarcinoma) and CHO (Chinese hamster ovarian cells). For both cell lines, photodynamic therapy (sensitizer plus visible light) treatments were carried out. The chlorin m-TCMPC was shown to have considerable promise as a photosensitizing agent. Cell kill was achieved for all situations tested, i.e. monolayer, 100, 500 and 750 microm spheroids. In addition no significant dark toxicity was observed.