Mark Berneburg

SINGLET OXYGEN MEDIATES THE UVA-INDUCED GENERATION OF THE PHOTOAGING-ASSOCIATED MITOCHONDRIAL COMMON DELETION

Mutations of mitochondrial (mt) DNA accumulate during normal aging. The most frequent mutation is a 4,977-base pair deletion also called the common deletion, which is increased in photoaged skin. Oxidative stress may play a major role in the generation of large scale mtDNA deletions, but direct proof for this has been elusive. We therefore assessed whether the common deletion can be generated in vitro through UV irradiation and whether reactive oxygen species are involved in this process. Normal human fibroblasts were repetitively exposed to sublethal doses of UVA radiation and assayed for the common deletion employing a semiquantitative polymerase chain reaction technique. There was a time/dose-dependent generation of the common deletion, attributable to the generation of singlet oxygen, since the common deletion was diminished when irradiating in the presence of singlet oxygen quenchers, but increased when enhancing singlet oxygen half-life by deuterium oxide. The induction of the common deletion by UVA irradiation was mimicked by treatment of unirradiated cells with singlet oxygen produced by the thermodecomposition of an endoperoxide. These studies provide evidence for the involvement of reactive oxygen species in the generation of aging-associated mtDNA lesions in human cells and indicate a previously unrecognized role of singlet oxygen in photoaging of human skin.

Photoaging of human skin

Chronic sun exposure causes photoaging of human skin, a process that is characterized by clinical, histological and biochemical changes which differ from alterations in chronologically aged but sun‐protected skin. Within recent years, substantial progress has been made in unraveling the underlying mechanisms of photoaging. Induction of matrix metalloproteinases as a consequence of activator protein (AP)‐1 and nuclear factor (NF)‐κB activation as well as mutations of mitochondrial DNA have been identified recently. This has increased our understanding of photoaging significantly and has led to new prophylactic and therapeutic strategies aimed at the prevention and repair of the detrimental effects of chronic sun‐exposure on the skin.

Interleukin-12 suppresses ultraviolet radiation-induced apoptosis by inducing DNA repair

Induction of apoptosis of keratinocytes by ultraviolet (UV) radiation is a protective phenomenon relevant in limiting the survival of cells with irreparable DNA damage. Changes in UV-induced apoptosis may therefore have significant impact on photocarcinogenesis. We have found that the immunomodulatory cytokine IL-12 suppresses UV-mediated apoptosis of keratinocytes both in vitro and in vivo. IL-12 caused a remarkable reduction in UV-specific DNA lesions which was due to induction of DNA repair. In accordance with this, IL-12 induced the expression of particular components of the nucleotide-excision repair complex. Our results show that cytokines can protect cells from apoptosis induced by DNA-damaging UV radiation by inducing DNA repair, and that nucleotide-excision repair can be manipulated by cytokines.

High-dose UVA1 radiation therapy for localized scleroderma

BACKGROUND Fibrotic skin lesions in patients with localized scleroderma can cause muscle atrophy, disfigurement, and flexion contractures. There is no effective therapy for this disease. Skin fibrosis is thought to be caused by decreased collagenase activity. Collagenase activity can be induced in dermal fibroblasts by UVA1 irradiation. OBJECTIVE Our purpose was to assess whether UVA1 radiation therapy is effective for patients with localized scleroderma. METHODS Patients with localized scleroderma (n = 17) were exposed 30 times to 130 J/cm2 UVA1 (high-dose UVA1 therapy; n = 10) or 20 J/cm2 UVA1 (low-dose UVA1 therapy; n = 7). Therapeutic effectiveness was assessed by evaluation of (1) clinical features, (2) thickness of sclerotic plaques, and (3) cutaneous elastometry. Sequential biopsy specimens from treated lesions were analyzed for collagenase I messenger RNA (mRNA) expression by semiquantitative reverse transcriptase-polymerase chain reaction. RESULTS In all patients, high-dose UVA1 therapy softened sclerotic plaques, and complete clearance was observed in four of 10 patients. High-dose UVA1 therapy significantly reduced thickness and increased elasticity of plaques. These changes could not be detected in unirradiated control plaques and were still present in 9 of 10 patients 3 months after cessation of therapy. For all factors assessed, high-dose UVA1 was superior to low-dose UVA1 therapy (p = 0.001). High-dose UVA1 therapy increased collagenase I mRNA expression about 20-fold in treated plaques. CONCLUSION High-dose UVA1 therapy is effective in the treatment of localized scleroderma. Effectiveness is UVA1 dose dependent and is associated with induction of collagenase I expression.

No Evidence for Increased Skin Cancer Risk in Psoriasis Patients Treated with Broadband or Narrowband UVB Phototherapy: A First Retrospective Study

Phototherapy of skin diseases such as psoriasis is an effective and safe treatment modality. However, increasing the risk of skin cancer by phototherapy is a serious concern. An increased skin cancer risk occurs after prolonged photochemotherapy (PUVA). In contrast, the role of broadband UVB or narrowband UVB therapy in skin carcinogenesis of humans with psoriasis is less clear. Therefore, we investigated the incidence of skin tumours in a total of 195 psoriasis patients, receiving broadband (n=69) or narrowband (n=126) UVB from 1994 to 2000 with follow-up until 2003. Data were raised from the regional interdisciplinary cancer centre of the University of Tuebingen, Germany and compared with the tumour incidences given for the German population. In this study, with 80% statistical power to detect a 6-7-fold increase in skin cancer with broadband UVB and 83% power to detect a 5-6-fold increase with narrow band UVB at p=0.05, only one patient developed skin cancer - an in situ melanoma. The tumour occurred within the same year that phototherapy was initiated. Thus, the present study does not provide evidence for an increased skin cancer risk for patients treated with either broadband or narrowband UVB phototherapy

Chronically Ultraviolet-exposed Human Skin Shows a Higher Mutation Frequency of Mitochondrial DNA as Compared to Unexposed Skin and the Hematopoietic System

Normal ageing processes are associated with an accumulation of mutations within the mitochondrial (mt) DNA. The most frequent mutation is a 4977 base pair (bp) deletion known as common deletion. In order to test the hypothesis that chronically sun‐exposed skin is characterized by an increased mutation frequency of mtDNA, the mutation frequency of the common deletion between skin and another replicating tissue (the hematopoietic system) and chronically sun‐exposed versus sun‐protected skin was compared in the same individuals. This was done by comparing the amount of mutated mtDNA molecules with the whole mitochondrial genome in the same specimen with a semiquantitative polymerase chain reation method, thus allowing direct comparison of different tissues. In all skin specimens the common deletion could be observed. In contrast only 3 of 10 blood samples revealed detectable amounts of the common deletion. Comparison of sun‐exposed versus sun‐protected skin exhibited a higher content of the common deletion in sun‐exposed skin in 7 of 10 individuals. Additionally, a hitherto undescribed mtDNA mutation was detected exclusively in human skin. These studies indicate that exposure of human skin to solar radiation leads to an accumulation of mtDNA mutations, possibly via oxidative damage, which may play an important role in photoageing.

Granulomatous mycosis fungoides and granulomatous slack skin: a multicenter study of the Cutaneous Lymphoma Histopathology Task Force Group of the European Organization For Research and Treatment of Cancer (EORTC)

BACKGROUND Granulomatous cutaneous T-cell lymphomas (CTCLs) are rare and represent a diagnostic challenge. Only limited data on the clinicopathological and prognostic features of granulomatous CTCLs are available. We studied 19 patients with granulomatous CTCLs to further characterize the clinicopathological, therapeutic, and prognostic features. OBSERVATIONS The group included 15 patients with granulomatous mycosis fungoides (GMF) and 4 with granulomatous slack skin (GSS) defined according to the World Health Organization-European Organization for Research and Treatment of Cancer classification for cutaneous lymphomas. Patients with GMF and GSS displayed overlapping histologic features and differed only clinically by the development of bulky skin folds in GSS. Histologically, epidermotropism of lymphocytes was not a prominent feature and was absent in 9 of 19 cases (47%). Stable or progressive disease was observed in most patients despite various treatment modalities. Extracutaneous spread occurred in 5 of 19 patients (26%), second lymphoid neoplasms developed in 4 of 19 patients (21%), and 6 of 19 patients (32%) died of their disease. Disease-specific 5-year survival rate in GMF was 66%. CONCLUSIONS There are clinical differences between GMF and GSS, but they show overlapping histologic findings and therefore cannot be discriminated by histologic examination alone. Development of hanging skin folds is restricted to the intertriginous body regions. Granulomatous CTCLs show a therapy-resistant, slowly progressive course. The prognosis of GMF appears worse than that of classic nongranulomatous mycosis fungoides.

The role of ultraviolet radiation in melanomagenesis.

Please cite this paper as: The role of ultraviolet radiation in melanomagenesis. Experimental Dermatology 2010; 19: 81–88.

Photoimmunology, DNA repair and photocarcinogenesis

In recent years major progress has been made in identifying the molecular mechanisms by which UV radiation modulates the immune system of the skin. From these studies it appears that the generation of DNA damage and the subsequent activation of DNA repair enzymes play a critical role in the generation of UV-B-induced immunosuppression. These studies have made use of cells from both nucleotide excision repair (NER)-deficient individuals and mice. Results obtained from these studies have important clinical implications for DNA-repair-deficient patients in particular and for effective photoprotection of human skin in general.

Successful monotherapy of severe and intractable atopic dermatitis by photopheresis

BACKGROUND Patients with chronic atopic dermatitis can become unresponsive to standard immunosuppressive therapy and thus pose a serious therapeutic problem. OBJECTIVE Our purpose was to evaluate the therapeutic effectiveness of photopheresis in the management of patients with severe and intractable atopic dermatitis. METHODS Photopheresis was used as monotherapy in patients (n = 3) who previously did not respond to treatment with glucocorticosteroids, cyclosporine, phototherapy, or photochemotherapy. Patients were treated at 2-week intervals (total number of treatments = 10). RESULTS In all patients, photopheresis induced clinical improvement and reduction of elevated serum levels of eosinophil cationic protein and total IgE. Prolongation of the intervals between treatments from 2 to 4 weeks caused worsening in one patient, whereas shortening of treatment-free intervals improved both clinical and laboratory findings. CONCLUSION These studies indicate that photopheresis may be used as monotherapy for the treatment of patients with severe atopic dermatitis that has become intractable to standard therapeutic modalities.