Phototherapy : photobiological aspects and therapeutical developments

Abstract

Contains fulltext : 19240_phot.pdf (publisher's version ) (Open Access)Several therapeutical modalities are nowadays used in photodermatology. In this thesis several new developments, like narrow band UVB, highdose visible light, are compared with regard to aspects of phototageing and photodamage. When broad band UVB and UVA are compared maximal photoinduced infiltrate accumulations were comparable. However UVB showed earlier induction of markers for inflammation and a more pronounced induction of markers for photodamage was seen following UVB as compared to UVA. In contrast, markers for oxidative damage were expressed substantially more following UVA exposure as compared to UVB exposure. It was hypothesised that the early induction of oxidative damage following UVA postpones photodamage and inflammation as compared to the dynamics of UVB. When 3 minimal erythema doses (MED) narrow band UVB and broad band are compared UVB safety parameters for carcinogenesis and inflammation were induced to the same extent. Narrow band UVB is more effective than broad band UVB in the treatment of chronic inflammatory diseases and it is suggested that narrow band UVB is the treatmentmodality with the better benefit risk ratio. High dose visible light is used in photodynamic therapy in combination of 5-aminolevulinic acid derivates. To study the effects on the surrounding skin unintentially treated skin we studied the effects of high dose visible light without application of a photosensitizer. This induced a significant increase in perinuclear vacuolization, but did not result in apoptosis, photodamage or early induction of skin ageing in healthy skin. Anti-TNF-alpha is curently used in chronic and auto-immune inflammatory diseases. The effect of anti-TNF-alpha on the photoresponse was studied and it was shown that anti-TNF-alpha at therapeutic doses did not influence on the UV response in patients with rheumatoid arthritis. Narrow band UVB is especially used as a therpay for psoriasis and eczema and more recently it has been introduced as a possible treatment for vitiligo. Our study reconfirmed that narrow band UVB phototherapy is an effective treatment for vitiligo and shows that co-treatment with vitamin B12 and folic acid does not improve the outcome of treatment of vitiligo with narrow band UVB phototherapy. Quality of life was also measured after long term treatment with narrow band UVB. Remarkably, after long-term narrow band UVB phototherapy, skin appearance did not play a major role in the life of vitiligo patients, while well being only improved in a minority of patients120 p