Hidradenitis Suppurativa After Radical Surgery-Long-Term Follow-up for Recurrences and Associated Factors.

BACKGROUND: Hidradenitis suppurativa (HS) is a chronic debilitating skin disease in inverse body areas. Wide excision is recommended in Hurley Stages II to III, but the rate and symptoms of recurrences in long-term follow-up remain unclear. OBJECTIVE: To analyze the allocation of recurrences regarding the operative field, the onset and quality of HS symptoms as well as factors associated with recurrences in long-term follow-up. MATERIAL AND METHODS: Forty-eight patients with Hurley Stage III disease who had undergone 91 wide excisions from 2010 to 2015 were clinically examined regarding postoperative complications and allocation and quality of recurrences. To determine the risk of recurrence, possible surgery, and lifestyle-related associated factors were investigated. RESULTS: Postoperative recurrences of HS were seen in 54.2%. Most recurrences (inflamed nodules) were detected in a <1-cm margin around the operative field (18.7%). Surgery under tumescence local anesthesia showed symptoms in 40.6% compared with 28.6% under general anesthesia. Increased alcohol consumption (p = .027) but not body mass index (p = .11) or smoking behavior (p = .45) had significant effect on relapse of HS. CONCLUSION: Caution must be given especially in surgery with local anesthesia only. Half of patients with HS showed long-term follow-up signs of recurrence after wide excision, most frequently nearby the operation field.

Transforming Growth Factor-ß1/Activin Receptor-like Kinase 5-Mediated Cell Migration is Dependent on the Protein Proteinase-Activated Receptor 2 but not on Proteinase-Activated Receptor 2-Stimulated Gq-Calcium Signaling.

Transforming growth factor-ß (TGF-ß), serine proteinases such as trypsin, and proteinase-activated receptor 2 (PAR2) promote tumor development by stimulating invasion and metastasis. Previously, we found that in cancer cells derived from pancreatic ductal adenocarcinoma (PDAC) PAR2 protein is necessary for TGF-ß1-dependent cell motility. Here, we show in the same cells that, conversely, the type I TGF-ß receptor activin receptor-like kinase 5 is dispensable for trypsin and PAR2 activating peptide (PAR2-AP)-induced migration. To reveal whether Gq-calcium signaling is a prerequisite for PAR2 to enhance TGF-ß signaling, we investigated the effects of PAR2-APs, PAR2 mutation and PAR2 inhibitors on TGF-ß1-induced migration, reporter gene activity, and Smad activation. Stimulation of cells with PAR2-AP alone failed to enhance basal or TGF-ß1-induced C-terminal phosphorylation of Smad3, Smad-dependent activity of a luciferase reporter gene, and cell migration. Consistently, in complementary loss of function studies, abrogation of the PAR2-Gq-calcium signaling arm failed to suppress TGF-ß1-induced cell migration, reporter gene activity, and Smad3 activation. Together, our findings suggest that the calcium-regulating motif is not required for PAR2 to synergize with TGF-ß1 to promote cell motility. Additional experiments in PDAC cells revealed that PAR2 and TGF-ß1 synergy may involve TGF-ß1 induction of enzymes that cause autocrine cleavage/activation of PAR2, possibly through a biased signaling function. Our results suggest that although reducing PAR2 protein expression may potentially block TGF-ß's prooncogenic function, inhibiting PAR2-Gq-calcium signaling alone would not be sufficient to achieve this effect.

Photodynamic Treatment of Oral Squamous Cell Carcinoma Cells with Low Curcumin Concentrations.

Objective: Curcumin is known for its anti-oxidative, anti-inflammatory and anti-tumorigenic qualities at concentrations ranging from 3.7µg/ml to 55µg/ml. Therefore it is pre-destined for tumour therapy. Due to high oral doses that have to be administered and the low bioavailability of curcumin new therapy concepts have to be developed. One of these therapy concepts is the combination of low curcumin concentrations and UVA or visible light. Aim of our study was to investigate the influence of this treatment regime on oral squamous cell carcinoma cells. Materials and Methods: A human oral squamous cell carcinoma cell line (HN) was pre-incubated with low curcumin concentrations (0.01µg/ml to 1µg/ml). Thereafter cell cultures were either left un-irradiated or were irradiated either with 1J/cm2 UVA or for 5min with visible light. Quantitative analysis of proliferation, membrane integrity, oxidative potential and DNA fragmentation were done. Results: It could be shown that low curcumin concentrations neither influenced proliferation, nor cell morphology, nor cell integrity nor apoptosis. When combining these curcumin concentrations with UVA or visible light irradiation cell proliferation as well as development of reactive oxygen species was reduced whereas DNA fragmentation was increased. Concentration as well as light entity specific effects could be observed. Conclusions: The present findings substantiate the potential of the combination of low curcumin concentrations and light as a new therapeutic concept to increase the efficacy of curcumin in the treatment of cancer of the oral mucosa.

Water-filtered near-infrared influences collagen synthesis of keloid-fibroblasts in contrast to normal foreskin fibroblasts.

Hypertrophic scar development is associated to impaired wound healing, imbalanced fibroblast proliferation and extracellular matrix synthesis. Stigmatization, physical restrictions and high recurrence rates are only some aspects that illustrate the severe influence impaired wound healing can have on patients' life. The treatment of hypertrophic scars especially keloids is still a challenge. In recent years water-filtered near-infrared irradiation (wIRA) composed of near-infrared (NIR) and a thermal component is applied for an increasing penal of clinical purposes. It is described to beneficially influence e.g. wound healing. But discrimination between the thermal and the NIR dependent components of these effects has not been conclusively elucidated. Aim of our study was therefore to investigate the influence of the light fraction on the thermal impact of wIRA irradiation in dermal cells. We concentrated our analysis on morphological properties and collagen synthesis. Foreskin fibroblasts and the keloid fibroblast cell line KF111 were exposed to temperatures between 37°C and 46°C with or without additional irradiation with 360J/cm(2) NIR. Our results show that viability was not influenced by irradiation. Independent of the analysed fibroblast species temperature dependent occurrence of spheric cells could be observed. These morphological changes were clearly counteracted by additional light exposure. Convective heat reduced collagen type I synthesis in both cell species depending on the applied temperature. Co-treatment with NIR significantly reversed this effect in keloid fibroblast cultures treated at 46°C whereas no difference could be observed in the foreskin fibroblasts. The observed influence on collagen type I synthesis was associated to a temperature dependent TGF-ß1 secretion reduction. Co-stimulation of keloid cultures with NIR at 46°C completely abolished the temperature dependent TGF-ß1 secretion reduction. In foreskin fibroblast cultures co-treatment with NIR had no additional influence on TGF-ß1 secretion. The observed influence of convective heat treatment with and without NIR on keloid and foreskin fibroblasts indicates a possible clinical application that has to be evaluated in further basic research and clinical studies in context of hypertrophic scar treatment.

Impact of Different Spa Waters on Inflammation Parameters in Human Keratinocyte HaCaT Cells.

BACKGROUND: The treatment of different skin conditions with spa waters is a long tradition dating back to at least late Hellenism. Interestingly, independent scientific examinations studying the effect of spa waters are scarce. OBJECTIVE: In the present in vitro study, we compared the effect of culture media supplemented with (a) thermal spa waters (La Roche-Posay, Avène) and (b) two natural mineral drinking waters (Heppinger, Adelholzener) on physiological parameters in HaCaT keratinocytes. METHODS: The different medium preparations were investigated with regard to cell proliferation and cell damage. Moreover, the impact on inflammation parameters with and without ultraviolet B (UVB) irradiation was examined. RESULTS: Two popular thermal spring waters were found to suppress cell proliferation and cell damage. Moreover, these waters reversed the induction of interleukin-6, as measured using enzyme-linked immunosorbent assay and promoter transactivation, and the formation of reactive oxygen species after UVB stimulation. Of note, the two natural mineral waters, which are distributed as drinking waters, had some effect on the above-mentioned parameters but to a lesser extent. CONCLUSION: In summary, our results show that spa waters, and particularly those derived from thermal springs, reduce parameters associated with inflammation. It seems likely that trace elements such as selenium and zinc are critical for the observed effects.

Green tea polyphenol epigallocatechin-3-gallate inhibits thrombin-induced hepatocellular carcinoma cell invasion and p42/p44-MAPKinase activation.

Thrombin has been recently demonstrated to promote hepatocellular carcinoma (HCC) cell migration by activation of the proteinase-activated receptor (PAR) subtypes PAR1 and PAR4 suggesting a role of these proteinase-receptor systems in HCC progression. In this study, we investigated the effect of (-)-epigallocatechin-3-gallate (EGCG), the major polyphenolic compound of green tea on thrombin-PAR1/PAR4-mediated hepatocellular carcinoma cell invasion and p42/p44 MAPKinase activation. In this study we used the permanent liver carcinoma cell line HEP-3B and two primary cultures established from surgically resected HCCs. We found that stimulation of HCC cells with thrombin, the PAR1-selective activating peptide, TFLLRN-NH2, and the PAR4-selective activating peptide, AYPGKF-NH2, increased cell invasion across a Matrigel-coated membrane barrier and stimulated activation of p42/p44 MAPKinase phosphorylation. Both the effects on p42/p44 MAPKinases, and on cell invasiveness induced by thrombin and the PAR1/4 subtype-selective agonist peptides were effectively blocked by EGCG. The results clearly identify EGCG as a potent inhibitor of the thrombin-PAR1/PAR4-p42/p44 MAPKinase invasive signaling axis in hepatocellular carcinoma cells as a previously unrecognized mode of action for EGCG in cancer cells. Moreover, the results suggest that (-)-epigal-locatechin-3-gallate might have therapeutic potential for hepatocellular carcinoma.

Lipophilic prodrugs of amino acids and vitamin E as osmolytes for the compensation of hyperosmotic stress in human keratinocytes.

Skin keratinocytes are subjected to changing osmotic conditions and evolved counteracting mechanisms. Particularly, the expression of osmolyte transporters serves for the maintenance of cell volume in a hypertonic environment. In this study, we show that hyperosmotic stress significantly decreases the proliferation in HaCaT keratinocytes. Supplementation of the culture medium with the amino acids glycine, sarcosine, betaine, taurine and proline restored the proliferation indicating osmoprotective properties of these substances. Amino acids are highly polar molecules and therefore unable to penetrate into deeper epidermal layers after topical application. Thus, we utilized a prodrug concept in which the tested amino acids are coupled to a lipophilic moiety. Ethyl glycinate as a first model compound also showed an osmoprotective effect. In addition, improved penetration of the glycine derivative into deeper epidermal layers could be demonstrated. The prodrug concept was further developed by using the lipid soluble antioxidant alpha-tocopherol as a lipophilic moiety. The derivatives d,l-alpha-tocopheryl-(mono-) glycinate (TMG) and d,l-alpha-tocopheryl-(mono-) prolinate caused an increase in proliferation of HaCaT keratinocytes under salt stress and a decrease in apoptosis induced by hypertonic conditions. Furthermore, the osmoprotective effect of d,l-TMG could be corroborated in normal human keratinocytes. Therefore, it seems feasible that amino acids and their lipophilic derivatives may help to improve the osmotic balance and the hydration of skin. Clinical and cosmetic indications such as atopic eczema, UV exposed skin or aged skin may benefit from this new concept.

Curcumin in combination with visible light inhibits tumor growth in a xenograft tumor model.

It is known that curcumin, a dietary pigment from the plant Curcuma longa, inhibits cell proliferation and induces apoptosis in different cell lines; however, the therapeutic benefit is hampered by very low absorption after transdermal or oral application. Recent studies from our laboratory have demonstrated that curcumin at low concentrations (0.2-1 microg/ml) offered the described effects only when applied with UVA or visible light. Nevertheless, the in vivo efficacy of this combination is lacking. In the present study, we used a xenograft tumor model with human epithelial carcinoma A431 cells to test the effect of curcumin and visible light on tumor growth. It was found that tumor growth was significantly inhibited in mice that were i.p. injected with curcumin and consecutively irradiated with visible light. Furthermore, immunohistochemistry showed a reduction of Ki 67 expression, indicating a decrease of cycling cells and induction of apoptotic bodies. The effect on apoptosis was further confirmed by Western blot analysis showing enhanced activation of caspases-9. Vice versa inhibition of extracellular regulated kinases (ERK) 1/2 and epidermal growth factor receptor (EGF-R) was observed which may aid inhibition of proliferation and induction of apoptosis. In summary, the present findings suggest a combination of curcumin and light as a new therapeutic concept to increase the efficacy of curcumin in the treatment of cancer.

Low concentrations of curcumin induce growth arrest and apoptosis in skin keratinocytes only in combination with UVA or visible light.

It is well known that curcumin, a dietary pigment from the plant Curcuma longa, inhibits cell proliferation and induces apoptosis in different cell lines at concentrations ranging from 10 to 150 microM (3.7-55 microg/ml). In this study, we show that curcumin at low concentrations (0.2-1 microg/ml) also has an antiproliferative effect when applied in combination with UVA or visible light. We demonstrate that such a treatment induces apoptosis in human skin keratinocytes represented by the increase of fragmented cell nuclei, release of cytochrome c from mitochondria, activation of caspases-9 and -8, and inhibition of NF-kappaB activity. Furthermore, inhibition of extracellular regulated kinases 1/2 and protein kinase B was found to ensure the proapoptotic effect. Additionally, the EGFR, an upstream regulator of both kinases, was inhibited indicating that apoptosis is induced by blocking survival- and proliferation-associated signal cascades at the receptor level. In summary, these findings suggest a new therapeutic concept for the treatment of hyperproliferative diseases by combining topical curcumin with UVA or visible light. In particular, the latter avoids the use of carcinogenic irradiation that is part of regular phototherapy.

Calciphylaxis: no therapeutic concepts for a poorly understood syndrome?

Calciphylaxis is a very uncommon and severe disease which mainly appears in patients with chronic renal insufficiency. It presents with ischemia and necrosis of the skin, subcutaneous adipose tissue, muscles and rarely viscera. The pathogenetic mechanisms inducing calciphylaxis are for the most part unknown. The mortality rate of 80% in the first year is very high. Patients experience marked pain, recurrent infections and the constant risk of secondary sepsis. Even multidisciplinary therapeutic strategies are limited, although there are recent case reports providing promising new therapeutic options including sodium thiosulfate and cinacalcet. This review summarizes the important aspects of diagnosis, pathogenesis, prevention and the possible therapeutic strategies of this intriguing, rare and often fatal disease.

Transcriptional regulation of ADAMTS13.

The metalloproteinase ADAMTS13 cleaves VWF multimers instantaneously when they are released from endothelial cells. Absent or manifestly diminished proteolytic activity of ADAMTS13 results in the appearance and accumulation of ultralarge VWF multimers (ULVWFM) in plasma, characterised by the manifestation of Thrombotic Thrombocytopenic Purpura (TTP). Despite congenital defects, infections and the actions of drugs such as cyclosporine A, doxycycline and corticosteroids apparently are involved in its development. To examine the possibility of transcriptional regulation of ADAMTS13 activity, we analyzed RNA levels in various cell culture systems and the response to known and assumed modulators of gene expression. We demonstrate the expression of ADAMTS13 in liver homogenates and a parenchyma liver cell culture system Hep3B, supporting the hypothesis that liver is an important source of plasma ADAMTS13, whereas there was no alteration in gene expression after stimulation of liver cells with proinflammatory stimuli such as endotoxin, TNF-alpha, IL-6, IL-1beta as well as immuno-suppressive agents, such as cyclosporine A, a variety of steroids as well as doxycycline. Therefore, we analysed the ADAMTS13 gene for binding sites of transcription factors in silico and compared the data with those found in two sets of 24 genes considered either as differentially regulated by prototypic inflammatory regulation or as unvaried under various conditions. On the basis of these data, the promotor of ADAMTS13 features the characteristics of a gene, which remains unvaried under a variety of conditions. To our knowledge, the current data demonstrate for the first time, that an alteration in transcriptional activity is negligible in accounting for diminished proteolytic activity as observed under various experimental and, in particular, clinical conditions.

Narrowband UVB and cream psoralen-UVA combination therapy for plaque-type psoriasis.

BACKGROUND: Psoralen-UVA (PUVA) and narrowband UVB (311-nm) therapy are considered to be first-line phototherapies for patients with moderate to severe psoriasis. To reduce side effects as a result of systemic resorption of psoralens, topical PUVA therapies have been developed and proven to be effective in the treatment of psoriasis. OBJECTIVE: We sought to evaluate the combination therapy of narrowband UVB plus cream PUVA on selected psoriatic plaques compared with narrowband UVB or cream PUVA alone. METHODS: A total of 30 patients (Psoriasis Area and Severity Index score of 8-15) were included in the randomized study. The combination therapy consisting of narrowband UVB whole-body irradiation followed by cream PUVA therapy for selected psoriatic plaques was evaluated in 10 patients with chronic plaque-stage psoriasis. For comparison, the therapeutic efficacy, number of treatments, and cumulative UV doses until remission (Psoriasis Area and Severity Index score < 4) of cream PUVA therapy or narrowband UVB alone was determined in 10 patients, respectively. RESULTS: Both monotherapies induced clearance of psoriatic lesions in all patients within 5 to 7 weeks. Mean number of treatments for cream PUVA was 24 +/- 5; for narrowband UVB was 21 +/- 3. The mean cumulative UVA dose was 45.0 +/- 16.3 J/cm(2) and the mean cumulative UVB dose was 17.1 +/- 4.1 J/cm(2). Combination therapy resulted in complete clearance of lesions in all patients after 3 to 4 weeks. Mean number of treatment was 14 +/- 2, mean cumulative UVA dose was 18.7 +/- 4.7 J/cm(2), and mean cumulative UVB dose was 8.2 +/- 3.3 J/cm(2). The number of treatments (P <.001, analysis of variance), UVA dose (P <.001, t test), and UVB dose (P <.001, t test) were significantly reduced compared with both monotherapies. CONCLUSIONS: Our results indicate that a combination therapy of narrowband UVB plus cream PUVA appears to have a significantly higher efficacy compared with either monotherapy. The cumulative UV doses were significantly lower in the combination therapy. We conclude that cream PUVA can be used in addition to narrowband UVB for areas that tend to clear less quickly than the rest of the body.

[Pseudomelanoma following laser treatment or laser-treated melanoma?]. / Pseudomelanom nach Lasertherapie oder lasertherapiertes Melanom?

BACKGROUND: The increasing use of lasers for the removal of pigmented skin lesions has led to a growing risk of erroneously treated malignant melanocytic tumours. PATIENTS AND METHODS: In two patients, both of whom developed a melanoma, the lesions were initially misdiagnosed clinically as a benign naevus and treated with laser vaporisation. RESULTS: On recurrence of the tumours, the diagnosis of melanoma was finally established by histological examination of the excised tumours in which differentiation from pseudomelanoma remained difficult. CONCLUSIONS: In such cases of initially misdiagnosed melanomas, laser removal not only complicates and delays the correct diagnosis but might also worsen the prognosis after recurrence of an incompletely removed tumour.

Narrowband UV-B phototherapy in the treatment of cutaneous graft versus host disease.

Graft versus host disease (GVHD) is an important problem following allogenic bone marrow transplantation (BMT). The beneficial effects of photochemotherapy with psoralens plus UVA irradiation (PUVA) have been described repeatedly; however, PUVA is limited by a wide range of unwanted effects. A novel improved form of UV-B phototherapy, narrowband UV-B, has been proven to be very effective in T-cell mediated dermatoses. Therefore, we investigated the effect of narrowband UV-B phototherapy (5 times per week) in 10 patients with cutaneous GVHD (grade 2-3) resistant to standard immunosuppressive drugs. It was tolerated well by all patients, and no side effects were observed. Skin lesions showed complete clearance in 7 out of 10 patients within 3 to 5 weeks. 3 patients showed significant improvement of GVHD. We suggest that narrowband UV-B phototherapy is a nonaggressive treatment that may benefit patients with cutaneous GVHD who already take high doses of immunosuppressive drugs.

Spatial distribution of 8-methoxypsoralen penetration into human skin after systemic or topical administration.

AIMS: Photochemotherapy employing psoralens combined with UVA irradiation (PUVA) is a standard therapy for a variety of dermatoses. Psoralens can be administered orally or topically in the form of bath or cream preparations. Recommendations for the time of UVA irradiation are mainly based on the time course of minimal phototoxic doses. However, the time course and depth of skin penetration of psoralens is not well characterized. METHODS: We assessed the time course of 8-MOP concentrations in horizontal epidermal and dermal skin sections in 10 patients undergoing oral (n = 3), cream (n = 4) and bath (n = 3) PUVA therapy. Punch biopsies (4 mm) were taken from "healthy" skin sites. A highly sensitive LC-MS-MS method was employed for 8-MOP analysis. RESULTS: Epidermal concentrations following cream or bath were highest at the end of the application period (time zero) when irradiation is performed. At this time, 8-MOP cream provided significantly higher epidermal concentrations (mean +/- s.e. mean 128.0 +/- 22.6 pg mm-3; 95% CI: 77.6, 178.4) than oral 8-MOP (27.0 +/- 25.3 pg mm-3; 95% CI: 29.3, 83.3 at 1 h; P = 0.025). Conversely, concentrations in the papillary dermis were significantly higher with oral 8-MOP (20.2 +/- 3.1 and 16.2 +/- 2.2 pg mm-3 at 1 and 2 h, respectively) than with 8-MOP cream (7.1 +/- 2.8 and 8.4 +/- 2.0 pg mm-3 time zero and 0.5 h, respectively; P = 0.020 and 0.045, respectively) or bath (8.8 +/- 3.1 and 7.7 +/- 2.2 pg mm-3; P = 0.050 and 0.039, respectively). The observed time courses of 8-MOP concentrations correspond to time courses of photosensitivity found previously with the different treatment modalities. CONCLUSIONS: The higher epidermal 8-MOP concentrations found after topical 8-MOP may explain the lower UVA doses needed with the topical route. These results suggest that topical 8-MOP may be superior in patients where the pathology is localized in the epidermis. In sclerosing diseases, which mainly affect the dermis oral PUVA might be advantageous because dermal concentrations are highest with this route of administration.

Mycosis-fungoides-type cutaneous T cell lymphoma of the hands and soles: a variant causing delay in diagnosis and adequate treatment of patients with palmoplantar eczema.

BACKGROUND: The etiopathology of chronic eczematous lesions of the palms and/or soles remains elusive in a considerable proportion of patients. Accumulating evidence suggests that a rare variant of mycosis fungoides (MF)-type cutaneous T cell lymphoma (CTCL) restricted to the palms and/or soles may mimic common palmoplantar dermatoses. OBJECTIVE: In the present study, we analyzed the clinical and histological characteristics of 3 adult patients with preexisting nonclassified chronic palmoplantar eczema poorly responding to standard therapies. Palmar and/or plantar MF was eventually diagnosed. METHODS: The course of the disease, response to previous therapies and dermatological features are described, results of histochemical and immunohistochemical analyses are reported, including T cell receptor gamma gene rearrangement where obtainable. RESULTS: Onset of cutaneous lesions with broad clinical variation was experienced 2-10 years prior to diagnosis; conventional therapies led to short-time or partial remission only; except for 1 patient, the epidermotropic infiltrate was predominantly composed of CD4-positive cells; topical photochemotherapy seems to result in more durable responses. CONCLUSION: As therapeutic strategies for this disease variant differ from symptomatic standard treatment regimens, awareness of MF-type CTCL as a relevant differential diagnosis of palmoplantar eczema should be expanded to prevent delay in diagnosis and adequate therapy.

Time course of 8-methoxypsoralen concentrations in skin and plasma after topical (bath and cream) and oral administration of 8-methoxypsoralen.

BACKGROUND: The combination of 8-methoxypsoralen with ultraviolet A exposure (PUVA therapy) is a standard treatment for a variety of dermatoses. The following three variants have been described: oral, bath, or cream PUVA. To achieve optimal therapeutic effects, ultraviolet A irradiation should be performed at the time of maximum photosensitivity, that is, at the time of maximum 8-methoxypsoralen tissue concentrations. METHODS: To further specify this point of time, we assessed the concentration-time courses of 8-methoxypsoralen in the skin after oral, bath, and cream administration of 8-methoxypsoralen in a 3-way crossover microdialysis study of 8 healthy subjects. RESULTS: Tissue concentrations after oral administration of 0.6 or 1 mg/kg 8-methoxypsoralen were low (peak plasma concentration range, 1.7-6.6 ng/ml) compared with topical administration for which maximum concentrations of 200 to 520 ng/ml and 720 to 970 ng/ml were achieved with 0.1% 8-methoxypsoralen cream and 3 mg/L 8-methoxypsoralen bath, respectively. Plasma concentrations after oral 8-methoxypsoralen, however, were up to 1000-fold higher than those found after topical application. With both topical applications, the tissue peak concentration uniformly occurred in the first 20 minutes after the end of the application time. In contrast, the time to reach the tissue peak concentration after oral administration ranged from 1 to 4 hours. CONCLUSIONS: The time course of tissue concentrations corresponds closely with the time course of minimal phototoxic doses found in previous studies. Because tissue concentrations after topical administration of 8-methoxypsoralen (bath and cream) were high compared with plasma concentrations and because they were less variable and occurred at better predictable time points than those after oral administration, we suggest that topical PUVA is superior to systemic PUVA, at least from a pharmacokinetic point of view.