Tim Smits

Pretreatment to Enhance Protoporphyrin IX Accumulation in Photodynamic Therapy

The response rates of photodynamic therapy (PDT) vary widely. Limited uptake of topically applied 5-aminolaevulinic acid (ALA), or its methyl ester (MAL), and suboptimal production of protoporphyrin IX (PpIX) may account for these differences. Recently, we demonstrated that hyperkeratosis is an important negative factor in ALA uptake. This review has its focus on pretreatment of the skin in order to improve the clinical outcome of ALA/MAL PDT. Pretreatment of hyperkeratosis can be achieved with keratolytics, curettage/debulking, tape stripping, microdermabrasion or laser ablation. Penetration enhancers may alter the composition or organization of the intercellular lipids of the stratum corneum. Several studies have been performed on the use of dimethyl sulfoxide, azone, glycolic acid, oleic acid and iontophoresis to increase the penetration of ALA. As PpIX production is also dominated by temperature-dependent processes, elevating skin temperature during ALA application may also improve treatment results. Another approach is the use of additives that interact with the heme biosynthetic pathway, e.g. by removing ferrous iron with iron-chelating substances such as: ethylenediaminetetraacetic acid; 3-hydroxypyridin-4-ones; 1,2-diethyl-3-hydroxypyridin-4-one-hydrochloride; and desferrioxamine. In conclusion, simple pretreatments or additions to the regular practice of PDT, aimed to optimize intralesional PpIX content, improve the clinical outcome.

Clinical and histological effects of blue light on normal skin.

Introduction: Phototherapy with visible light is gaining interest in dermatological practice. Theoretically, blue light could induce biological effects comparable to ultraviolet A (UVA) radiation.

A placebo-controlled randomized study on the clinical effectiveness, immunohistochemical changes and protoporphyrin IX accumulation in fractionated 5-aminolaevulinic acid-photodynamic therapy in patients with psoriasis

Background  Topical 5‐aminolaevulinic acid (ALA)‐photodynamic therapy (PDT) for the treatment of psoriasis has been evaluated in a few studies. In these studies different treatment parameters were used, there was a variable clinical response, and a nonhomogeneous fluorescence was seen after irradiation with Woods light.

Itch and scratching as predictors of time to clearance of psoriasis with narrow-band ultraviolet B therapy.

Background  Narrow‐band ultraviolet (UV) B phototherapy is an effective treatment for psoriasis. However, there is considerable variability in the number of treatment sessions needed to achieve psoriasis clearance. While several clinical and treatment‐related factors predict time to clearance, the effect of itching and scratching on the number of irradiation sessions is insufficiently understood.

Induction of protoporphyrin IX by aminolaevulinic acid in actinic keratosis, psoriasis and normal skin: preferential porphyrin enrichment in differentiated cells.

Background  In photodynamic therapy the endogenous photosensitizer protoporphyrin IX (PpIX) is synthesized following topical application of aminolaevulinic acid (ALA). However, different tissues have distinct PpIX‐accumulating properties, due to differences in penetration of ALA through the stratum corneum and/or alterations in the haem cycle. Preferential PpIX accumulation has been reported in terminally differentiated cell cultures but ex vivo data are lacking.

The effects of keratolytic pretreatment prior to fluorescence diagnosis and photodynamic therapy with aminolevulinic acid-induced porphyrins in psoriasis

Abstract Background: Psoriasis lesions accumulate protoporphyrin IX (PpIX) with a variable distribution within plaques due to variations in hyperkeratosis causing differences in penetration of cream or light. Objectives: To study the effects of different keratolytic pretreatments in PpIX-induced fluorescence diagnosis (FDAP) and during photodynamic therapy (PDT). Methods: Two psoriasis plaques of 10 patients were treated with either topical retinoic acid or with a hydrocolloid dressing. The hydrocolloid dressing gave the best results. Subsequently, two different contralateral plaques of eight patients were pretreated with a hydrocolloid dressing or the standard pretreatment, salicylic acid in petrolatum, during the 6 weeks of PDT. Biopsies were investigated with respect to stratum corneum thickness, proliferation, differentiation and inflammation. Results: Irritation and point bleedings were noticed after retinoic acid. A hydrocolloid dressing induced the best clinical improvement. Therefore, it was used as alternative pretreatment for psoriasis prior to PDT. We observed significant clinical and immunohistochemical improvement of psoriasis in the salicylic acid as well as the hydrocolloid dressing pretreated plaques. Conclusions: Salicylic acid in petrolatum and a hydrocolloid dressing prior to FDAP and PDT induce improvement of hyperkeratosis. Thus, a hydrocolloid dressing is a good alternative to the current keratolytic pretreatment regime.

Fluorescence diagnosis in actinic keratosis and squamous cell carcinoma

Background: As different tissue types have distinct capabilities to accumulate protoporphyrin IX, fluorescence diagnosis with aminolevulinic acid‐induced porphyrins (FDAP) could be used to discriminate between different types of tissue. Previous results demonstrated higher fluorescence ratios in squamous cell carcinoma (SCC) compared with actinic keratoses (AKs).

Treatment Nonadherence and Long-term Effects of Narrowband UV-B Therapy in Patients With Psoriasis

N onadherence to a treatment regimen is a common problem in patients with dermatologic conditions, including psoriasis. From 30% to 80% of patients report being nonadherent at some stage of their dermatologic treatment, and particularly high nonadherence has been reported for topical treatments. Patients’ adherence to the instructions and advice given by dermatologists, including self-management of topical treatments and medication intake for systematic treatments, can influence the effectiveness of therapies such as UV-B treatment. Particularly during follow-up treatment, patients may fail to comply with instructions to regularly apply topical medications. Nonadherence to treatment regimens might be a predictor of the longterm effectiveness and maintenance of results after successful UV-B therapy. In the present prospective study, we investigate the predictive value of nonadherence with dermatologic treatment on psoriasis outcome (Psoriasis and Area Severity Index [PASI]) at follow-up assessments 3 and 6 months after psoriasis clearance. In our analysis, we controlled for clinical and treatment variables (PASI at the start and end of treatment, skin type, irradiation regimen, minimal erythema dose [MED], cumulative dose, and protocol adjustments) and lifestyle variables (smoking habits and alcohol consumption).

Aneuploidy and proliferation in keratinocytic intraepidermal neoplasias

Abstract:  Cutaneous squamous (pre)malignancies can be classified according to the keratinocytic intraepidermal neoplasia (KIN) classification. Aneuploidy can be seen as the result of chromosomal aberrations leading to altered DNA content and has been strongly associated with malignancy. Hyperproliferation is also strongly associated with tumorigenesis. The aim of the study was to analyse the presence and the amount of aneuploidy and proliferation in the progression from intraepithelial neoplasm to microinvasive carcinoma (miSCC). For this purpose, nuclei were isolated from 116 formalin‐fixed KIN lesions from 68 patients in which DNA content was measured by flow cytometry. Proliferation was assessed by immunohistochemical staining for Ki67 as well as by flow cytometry. Aneuploidy was increasingly found in higher KIN lesions, but not in normal skin. However, in miSCC aneuploidy was relatively less frequently found. DNA indices (mean ± SE) of KIN III‐lesions (1.57 ± 0.05) were significantly lower compared with KIN I/II lesions (1.71 ± 0.05). Ki67 expression was strongly positively correlated with KIN grade, and proved to be a good adjunct in the classification of KINs. Thus, aneuploidy occurred more frequently in higher KIN lesions, indicating cumulative damage during KIN progression. The lower frequency of aneuploidy in miSCC compared with KIN III may point at alternative routes towards invasive carcinoma besides serial progression through all three KIN stages. Ki67 expression appears a valuable marker in the classification of KINs.

High-dose long wave visible light induces perinuclear vacuolization in vivo but does not result in early photoageing and apoptosis.

Abstract:  With the advancing widespread use of photodynamic therapy, questions have arisen about the necessity to protect the adjacent healthy skin from high‐dose long‐wave light. The aim of the present study was to investigate the effects of high dose visible light on the skin of healthy volunteers with focus on apoptosis, DNA damage, inflammation, melanogenesis and induction of matrix metalloproteinases (MMP). Fourteen healthy volunteers were included and irradiated daily on their buttocks with 1300 kJ/m2 long wave visible light (560–780 nm) on five consecutive days with a cumulative dose of 6500 kJ/m2. In each volunteer six biopsies were taken before and 24 h after irradiation on days 1, 2, 3 and 5 and on day 8 and 12. Frozen and paraffin sections were investigated by measuring parameters for photodamage (apoptosis, p53, phosphorylated c‐Jun), skin ageing (phosphorylated c‐Jun, MMP‐1, elastin content) melanogenesis (Melan A). Although no sunburn cells were seen, a significant increase in perinuclear vacuolization was noted (P < 0.0003) from day 5 till 7 days after the last irradiation. There was no expression of phosphorylated c‐Jun, whereas the expression of p53, Melan A, MMP‐1 and elastin content did not change. High‐dose visible light induces a significant increase in perinuclear vacuolization, but does not result in apoptosis, photodamage or early induction of skin ageing.