Topical κ-opioid receptor agonist asimadoline improves dermatitis in a canine model of atopic dermatitis.

This prospective, 4-week, placebo-controlled, cross-over study aimed to investigate the efficacy of 1% topical κ-opioid agonist, asimadoline, in a model of canine atopic dermatitis (AD). Fourteen beagles were challenged with house dust mites every 3-4 days for a total of 9 challenges. Severity of dermatitis was assessed, and pruritus was monitored using GoPro HERO cameras. Pruritus scoring was evaluated at 10 time periods; baseline, 4 h post allergen challenge and the last day of the study on Day 28. Scoring was done blindly by personnel using BORIS software. A global subjective score was also given using a visual analogue scale (VAS). A 4-week washout period occurred and dogs were crossed-over, the study was repeated, and the results were analysed using combined data. Gel was applied once daily on inguinal area (0.6 ml/dog). ANOVA showed significant effect of time (p < 0.0001) and group (p = 0.0001) on dermatitis scores. Overall, no statistically significant effect on pruritus was found due to a crossing of scores on Day 17. Overtime the placebo scores increased while the active ingredient showed decrease after first 3 weeks. It is concluded that this approach is promising in dogs with AD and longer studies with more frequent application may be beneficial.

Skin acidification with a water-in-oil emulsion (pH 4) restores disrupted epidermal barrier and improves structure of lipid lamellae in the elderly.

The pH of the skin surface increases with age and thus reduces epidermal barrier function. Aged skin needs appropriate skin care to counterbalance age-related pH increase and improve barrier function. This confirmatory randomized study investigated the efficacy of water-in-oil (w/o) emulsions with either pH 4 or pH 5.8 in 20 elderly subjects after 4 weeks of treatment. After the treatment, the skin was challenged with a sodium dodecyl sulphate (SDS) solution in order to analyze barrier protection properties of both formulations. The pH 4 w/o emulsion resulted in a significantly lower skin pH compared with the pH 5.8 w/o emulsion and an improved skin hydration after 4-week treatment. Further, the pH 4 emulsion led to more pronounced improvements in length of intercellular lipid lamellae, lamellar organization as well as lipid levels than the pH 5.8 emulsion. Following SDS-induced barrier damage to the skin, the pH of all test areas increased, but the area treated with the pH 4 emulsion showed the lowest increase compared with baseline. In addition, even after the SDS challenge the skin area treated with the pH 4 emulsion still maintained a significantly increased length of intercellular lipid lamellae compared with the beginning of the study. This study provides evidence that topical application of a w/o emulsion with pH 4 reacidifies the skin in elderly and has beneficial effects on skin moisturization, regeneration of lipid lamellae and lipid content. Application of a pH 4 emulsion can improve the epidermal barrier as well as the stratum corneum organization in aged skin.

Pharmacology, toxicology and clinical safety of glycopyrrolate.

The clinical use of the anticholinergic glycopyrrolate dates back to the early 1960s when it was first approved in the U.S. Since then, oral and inhalation formulations have been developed as therapeutic agents inhibiting the muscarinic acetylcholine receptor in various indications including chronic obstructive pulmonary disease (COPD), excessive salivation, and peptic ulcers. More recently, topical formulations of glycopyrrolate (GPB, also known as glycopyrronium bromide) have gained interest as a treatment option for excessive sweating (hyperhidrosis). The U.S. Food and Drug Administration (FDA) approved the first topical glycopyrronium product for the treatment of hyperhidrosis in 2018. Glycopyrrolate, as a quaternary amine, shows minimal penetration of the blood brain barrier which limits CNS side effects. In addition, lack of phototoxicity, genotoxicity and carcinogenicity makes it suitable for chronic indications. The information on the nonclinical and clinical safety profile of glycopyrronium supporting various therapeutically approved uses has been obtained from published literature, our own data as well as summary documents issued by regulatory bodies. Collectively, these data support the conclusion that the benefits of glycopyrronium generally outweigh the risks in chronic use indications that require muscarinic receptor antagonism to provide therapeutic effects.

Topical treatment of vaginal dryness with a non-hormonal cream in women undergoing breast cancer treatment - An open prospective multicenter study.

This open, prospective, multicenter, observational study was performed to investigate the efficacy and safety of a non-hormonal cream in women undergoing breast cancer treatment and experiencing vulvovaginal dryness symptoms. Overall, 128 patients from 22 study centers participated. The cream was applied to the vagina and vulva for 28 days. For the efficacy analysis, changes in subjective symptoms (feeling of dryness, itching, burning, pain independent of sexual intercourse, dyspareunia, urinary incontinence) were evaluated. Additionally, the following objective diagnostic findings were assessed by a physician: thinning of vaginal epithelium, redness, petechiae, and discharge. Safety and tolerability were assessed by evaluating type and frequency of adverse events, including adverse medical device-related effects. The frequency and intensity of all subjective symptoms significantly improved from baseline at 28 days (p<0.0001). Additionally, 21.4% of patients were completely free of symptoms (p<0.0001) and urinary incontinence was improved or eliminated in 30.8% of women. The overall sum score for all four objective findings was significantly improved from baseline at 28 days (p<0.0001). The frequency of petechial bleedings was significantly reduced (p<0.0001). Further, significant decreases in the severity of vaginal epithelium thinning, redness and petechiae were observed (p<0.0001). More than 88% of patients and investigators assessed the efficacy and tolerability as being good or very good. No serious adverse events were documented. This study demonstrates that the investigated cream is an effective and safe non-hormonal, topical option in the treatment of vulvovaginal dryness symptoms in patients undergoing breast cancer treatment for. However, the study duration and follow-up time of 4 weeks as well as the non-randomized trial design are limitations of the study.

Comparison of linoleic acid-containing water-in-oil emulsion with urea-containing water-in-oil emulsion in the treatment of atopic dermatitis: a randomized clinical trial.

BACKGROUND: Application of topical moisturizers is an essential part of the management of atopic dermatitis (AD). Linoleic acid (LA), the most abundant fatty acid in the epidermis, and its derivatives have an essential role in the structure and function of the epidermal barrier, and their defects are prominent in AD. The aim of this study was to compare the efficacy and safety of two cosmetic products containing either LA or urea in patients with AD. PATIENTS AND METHODS: A total of 20 patients with AD who met the eligibility criteria and provided written informed consents were enrolled in this randomized, intra-individual split-body, single-center trial. Symmetrical lesions of patients were randomized for treatment with LA- or urea-containing water-in-oil (w/o) emulsions applied two to three times daily for 4 weeks. The efficacy of the two products was evaluated by local Scoring Atopic Dermatitis (SCORAD) of both lesions and also patient (or guardian) satisfaction. In addition, trans-epidermal water loss (TEWL), stratum corneum (SC) hydration, pH, sebum, temperature, erythema, melanin content, and ultrasonographic thickness and echo density of epidermis and dermis were measured before, and 2 and 4 weeks after, treatment. RESULTS: Four weeks of treatment with the LA-containing product resulted in a significant decrease in local SCORAD, TEWL, erythema, and echo density of dermis, as well as an increase in SC hydration compared to baseline. The urea-containing product also reduced the local SCO-RAD and echo density of dermis and increased SC hydration. In contrast to the LA-containing product, changes in TEWL and erythema were not significant. Moreover, the reduction of erythema was significantly higher in the LA-containing product-treated side compared to the urea-containing product-treated side (p = 0.006). CONCLUSION: Both LA- or urea-containing w/o emulsions can significantly improve barrier dysfunction and clinical severity of AD. In agreement with literature, it was confirmed that an LA-containing w/o emulsion exhibited erythema-reducing effects. Since emollients should be used on a regular basis, patients should choose a product by individual preference following recommendation by their dermatologists.

Chemical probes to potently and selectively inhibit endocannabinoid cellular reuptake.

The extracellular effects of the endocannabinoids anandamide and 2-arachidonoyl glycerol are terminated by enzymatic hydrolysis after crossing cellular membranes by facilitated diffusion. The lack of potent and selective inhibitors for endocannabinoid transport has prevented the molecular characterization of this process, thus hindering its biochemical investigation and pharmacological exploitation. Here, we report the design, chemical synthesis, and biological profiling of natural product-derived N-substituted 2,4-dodecadienamides as a selective endocannabinoid uptake inhibitor. The highly potent (IC50 = 10 nM) inhibitor N-(3,4-dimethoxyphenyl)ethyl amide (WOBE437) exerted pronounced cannabinoid receptor-dependent anxiolytic, antiinflammatory, and analgesic effects in mice by increasing endocannabinoid levels. A tailored WOBE437-derived diazirine-containing photoaffinity probe (RX-055) irreversibly blocked membrane transport of both endocannabinoids, providing mechanistic insights into this complex process. Moreover, RX-055 exerted site-specific anxiolytic effects on in situ photoactivation in the brain. This study describes suitable inhibitors to target endocannabinoid membrane trafficking and uncovers an alternative endocannabinoid pharmacology.

The tripeptide KdPT ameliorates ongoing psoriasis-like skin inflammation in murine and human skin.

Psoriasis is a chronic inflammatory disease appearing as scaly erythematous cutaneous lesions, which are characterized by parakeratosis and acanthosis as well as the infiltration of immune cells, such as T helper-1 and T helper-17 cells. Here, we demonstrated that KdPT, a tripeptide structurally related to the C-terminal amino acids of alpha-melanocyte-stimulating hormone, which was previously shown to exhibit anti-inflammatory effects in intestinal inflammation, ameliorated ongoing disease in the mouse model of imiquimod-induced psoriasis-like skin inflammation and in the small xenotransplant mouse model of psoriasis. We could show that systemic KdPT treatment significantly reduced hyperkeratosis and acanthosis in murine as well as human skin. Moreover, KdPT upregulated Foxp3 in CD4+ T cells from mice and from peripheral blood of individuals with psoriasis and decreased the expression of type 1 inflammatory cytokines, indicating that the beneficial effect of KdPT was, at least in part, mediated by the induction of functional regulatory T cells that suppressed the activation of pathogenic CD4+ IFN-γ+ and CD4+ IL-17+ T cells. Thus, these data might suggest KdPT as a potential novel therapeutic alternative for the treatment of psoriasis.

Clinical evaluation of a water-in-oil emulsion with protective and regenerative properties for the anogenital area.

Inadequate hygiene, aggressive cleansing, and chafing skin folds, as well as urine, feces, and sweat may trigger irritative contact dermatitis in the anogenital area. Serious recommendations for protection of the skin toward irritants include hygienic aspects and the use of appropriate skin care. Furthermore, preventing an accumulation of irritants on unprotected skin is mandatory. An intraindividual comparison study with 30 participants (17 female, 13 male; age: 44.2±8.3 years) was performed to evaluate the properties of a newly developed water-in-oil (W/O) balm on artificial sodium dodecyl sulfate-damaged epidermal barrier. The balm was applied 14 days twice daily, and transepidermal water loss and erythema were investigated. A significant improvement of both parameters after 12 days and even after 21 days could be confirmed. Two major clinical trials were performed to evaluate the safety and efficacy regarding protective and regenerative properties of the W/O balm on irritated skin in the anogenital area. Therefore, 29 children were enrolled (14 male, 15 female, age: 15.5±7.8 months) in an open-labeled 4-week clinical study. The balm was used in the area under disposable diapers at least after diaper change or if required. Furthermore, in a second open, multicenter study, 43 women (mean age: 46.2±16.9) with predisposition to skin irritation in the outer anogenital region were included. The product was applied for 4 weeks 1-2 times daily. In both studies, skin tolerability, applicability, scent, spreadability, and removability of the balm were evaluated by participants and practitioners predominantly as good or even very good, also skin hydration, protection, and regeneration were judged positively. The studies confirmed that the newly developed W/O balm exhibits excellent tolerability and is easy to remove. At the same time, excellent properties with respect to efficacy regarding regeneration and protection could be observed, without any undesired effects at any time.

Impact of a Glycolic Acid-Containing pH 4 Water-in-Oil Emulsion on Skin pH.

The skin pH is crucial for physiological skin functions. A decline in stratum corneum acidity, as observed in aged or diseased skin, may negatively affect physiological skin functions. Therefore, glycolic acid-containing water-in-oil (W/O) emulsions adjusted to pH 4 were investigated regarding their effect on normal or increased skin pH. A pH 4 W/O emulsion was applied on three areas with pathologically increased skin surface pH in diabetics (n = 10). Further, a 28-day half-side trial (n = 30) was performed to test the long-term efficacy and safety of a pH 4 W/O emulsion (n = 30). In summary, the application of a pH 4 W/O emulsion reduced the skin pH in healthy, elderly and diabetic subjects, which may improve epidermal barrier functions.

Correlating FAAH and anandamide cellular uptake inhibition using N-alkylcarbamate inhibitors: from ultrapotent to hyperpotent.

Besides the suggested role of a putative endocannabinoid membrane transporter mediating the cellular uptake of the endocannabinoid anandamide (AEA), this process is intrinsically coupled to AEA degradation by the fatty acid amide hydrolase (FAAH). Differential blockage of each mechanism is possible using specific small-molecule inhibitors. Starting from the natural product-derived 2E,4E-dodecadiene scaffold previously shown to interact with the endocannabinoid system (ECS), a series of diverse N-alkylcarbamates were prepared with the aim of generating novel ECS modulators. While being inactive at cannabinoid receptors and monoacylglycerol lipase, these N-alkylcarbamates showed potent to ultrapotent picomolar FAAH inhibition in U937 cells. Overall, a highly significant correlation (Spearman's rho=0.91) was found between the inhibition of FAAH and AEA cellular uptake among 54 compounds. Accordingly, in HMC-1 cells lacking FAAH expression the effect on AEA cellular uptake was dramatically reduced. Unexpectedly, 3-(4,5-dihydrothiazol-2-yl)phenyl carbamates and the 3-(1,2,3-thiadiazol-4-yl)phenyl carbamates WOBE490, WOBE491 and WOBE492 showed a potentiation of cellular AEA uptake inhibition in U937 cells, resulting in unprecedented femtomolar (hyperpotent) IC50 values. Potential methodological issues and the role of cellular accumulation of selected probes were investigated. It is shown that albumin impacts the potency of specific N-alkylcarbamates and, more importantly, that accumulation of FAAH inhibitors can significantly increase their effect on cellular AEA uptake. Taken together, this series of N-alkylcarbamates shows a FAAH-dependent inhibition of cellular AEA uptake, which can be strongly potentiated using specific head group modifications. These findings provide a rational basis for the development of hyperpotent AEA uptake inhibitors mediated by ultrapotent FAAH inhibition.

A 10% glycolic acid containing oil-in-water emulsion improves mild acne: a randomized double-blind placebo-controlled trial.

BACKGROUND: Acne is characterized by hyperseborrhea, follicular hyperkeratosis, and growth of propionibacteria. Alpha hydroxy acids depending on the pH of the finished product exhibit comedolytic as well as antimicrobial properties. OBJECTIVES: The aim of this study was to investigate an oil-in-water emulsion-containing 10% glycolic acid (pH 4; Dr. August Wolff GmbH & Co. KG Arzneimittel, Bielefeld, Germany) as monotherapy in mild acne regarding clinical efficacy and tolerability for 90 days. PATIENTS AND METHODS: Patients (n = 120; 73 f, 47 m) suffering from mild acne (Leeds score 0.25-1) aged ≥12 (mean 21 ± 5.8) were included in this double-blind, placebo-controlled, randomized, monocentric trial. The cream was applied once daily in the evening. No additional products were used. Cleansing was standardized by supplying the same product to all patients. RESULTS: The number of patients (n = 115) in the per-protocol and intention-to-treat analysis was the same. Acne improved significantly in the verum group up to day 90. Already at day 45, there was a statistical significant (5% level) difference against placebo. The subjective evaluation of the verum by physicians and patients regarding clinical efficacy and tolerability was favorable. Regarding reported adverse effects, there was no statistically significant difference (5% level) between verum and placebo. CONCLUSIONS: The 10% glycolic acid containing oil-in-water emulsion improved mild acne applied as monotherapy in this study significantly, already after 45 days of treatment. Regarding tolerability, there was no objective or subjective difference between the 10% glycolic acid containing oil-in-water emulsion and the corresponding placebo.

Treatment of acute radiodermatitis with an oil-in-water emulsion following radiation therapy for breast cancer: a controlled, randomized trial.

BACKGROUND: A side effect of radiotherapy for breast cancer is acute radiodermatitis. It is a common practice to keep irradiated skin dry on account of data from the 1950s that suggested this regimen limits dermatitis. However, severe dryness of the skin induced by irradiation results in itching and discomfort. Dry skin is characterized by scaliness, epidermal barrier dysfunction, and reduced stratum corneum hydration, and these signs and symptoms are reduced by treatment with an emulsion. PATIENTS AND METHODS: We performed a randomized, controlled, open-label study with 66 patients (ITT population), treating the irradiated skin in one group (n = 34) with an oil-in-water emulsion (WO1932), while leaving the other group untreated (n = 32). Clinical scoring (ONS radiation skin reaction scoring, pruritus) and biophysical measurements (stratum corneum hydration and transepidermal water loss (TEWL), as a marker of skin barrier function) were determined at day 1 (directly after termination of the radiation therapy), day 8, and day 47 (± 7). RESULTS: Irradiation increased the ONS score and pruritus, whereas skin hydration and TEWL were reduced. The primary hypothesis that the increase in skin hydration was significantly greater in the emulsion-treated compared to the untreated group as early as after 8 days of treatment could not be confirmed. At the end of the study (day 47 ± 7), however, normalization of stratum corneum hydration was more advanced in the treatment group compared to the untreated group and nearly reached the values of the contralateral healthy breast skin. ONS score and pruritus also revealed an advantage for the emulsion-treated group. TEWL did not show significant changes during emulsion treatment. No adverse events were caused by the treatment regimens CONCLUSION: Treatment of radiodermatitis with an oil-in-water emulsion was well tolerated, enhanced stratum corneum hydration, improved clinical indicators, and provided relief from itching.

Alpha-melanocyte-stimulating hormone and related tripeptides: biochemistry, antiinflammatory and protective effects in vitro and in vivo, and future perspectives for the treatment of immune-mediated inflammatory diseases.

Alpha-MSH is a tridecapeptide derived from proopiomelanocortin. Many studies over the last few years have provided evidence that alpha-MSH has potent protective and antiinflammatory effects. These effects can be elicited via centrally expressed melanocortin receptors that orchestrate descending neurogenic antiinflammatory pathways. alpha-MSH can also exert antiinflammatory and protective effects on cells of the immune system and on peripheral nonimmune cell types expressing melanocortin receptors. At the molecular level, alpha-MSH affects various pathways implicated in regulation of inflammation and protection, i.e., nuclear factor-kappaB activation, expression of adhesion molecules and chemokine receptors, production of proinflammatory cytokines and mediators, IL-10 synthesis, T cell proliferation and activity, inflammatory cell migration, expression of antioxidative enzymes, and apoptosis. The antiinflammatory effects of alpha-MSH have been validated in animal models of experimentally induced fever; irritant and allergic contact dermatitis, vasculitis, and fibrosis; ocular, gastrointestinal, brain, and allergic airway inflammation; and arthritis, but also in models of organ injury. One obstacle limiting the use of alpha-MSH in inflammatory disorders is its pigmentary effect. Due to its preserved antiinflammatory effect but lack of pigmentary action, the C-terminal tripeptide of alpha-MSH, KPV, has been delineated as an alternative for antiinflammatory therapy. KdPT, a derivative of KPV corresponding to amino acids 193-195 of IL-1beta, is also emerging as a tripeptide with antiinflammatory effects. The physiochemical properties and expected low costs of production render both agents suitable for the future treatment of immune-mediated inflammatory skin and bowel disease, fibrosis, allergic and inflammatory lung disease, ocular inflammation, and arthritis.

Photothermolysis of blood vessels using indocyanine green and pulsed diode laser irradiation in the dorsal skinfold chamber model.

BACKGROUND AND OBJECTIVE: For the treatment of vascular lesions, the use of laser light absorbed by the endogenous chromophore hemoglobin may still be improved. MATERIALS AND METHODS: Laser treatment (lambda(em) = 805 nm; fluence rate: 106 kW/cm2; fluence: 3.2 J/cm2 (3 milliseconds)), of blood vessels directly after i.v. application of indocyanine green (ICG) (ICG-concentration: 0, 2, or 4 mg/kg body weight (b.w.)) (n = 14,117) was investigated in the skinfold chamber model. Vessel diameters (1-351 microm) were measured using intravital fluorescence microscopy up to 24 hours following irradiation. Histology was taken 1 or 24 hours after irradiation. Results were compared to a mathematical model based on the finite element method. RESULTS: The reduction of blood vessel perfusion was proportional to ICG-concentration and pulse duration; only a 30 milliseconds pulse duration (2 or 4 mg/kg b.w. ICG-concentration) induced a loss of perfusion even of blood vessels with a diameter <30 microm. Histology revealed photocoagulation of blood vessels up to 24 hours. Results were in agreement with mathematical calculations. CONCLUSION: ICG-mediated laser irradiation induces irreversible photocoagulation of blood vessels of all diameters in this model.

Photodynamic therapy with 5-aminolevulinic acid induces distinct microcirculatory effects following systemic or topical application.

In photodynamic therapy (PDT) the photosensitiser 5-aminolaevulinic acid (ALA) can be used by systemic or topical application. Previous experiments showed that the photodynamic effects might not be mediated solely by porphyrins localized in the parenchyma, but also by porphyrins in the microvasculature. Therefore, the microcirculatory effects of PDT following systemic versus topical application of ALA have been investigated. Amelanotic melanomas were implanted in the dorsal skin fold chamber of Syrian Golden hamsters. ALA was injected i.v. for systemic PDT before irradiation, whereas ALA was applied to the chambers for topical PDT before irradiation with an incoherent lamp. FITC-labelled erythrocytes were injected to determine red blood cell velocity (RBCV) and functional vessel density (FVD). Twenty-four hours after PDT tissue was taken for histology and immunohistochemistry to reveal the degree of apoptosis and to show the accumulation of leukocytes. FVD or RBCV was not altered significantly by systemic or topical low-dose PDT (10 J cm(-2)), whereas a significant reduction of RBCV and FVD was detected after high-dose PDT (100 J cm(-2)) following systemic or topical application of ALA. Systemic PDT with 100 J cm(-2) stopped the flow only in the tumor center, whereas topical PDT with 100 J cm(-2) lead to a breakdown of RBCV in all chamber areas. Two hours and 24 h after systemic high-dose PDT, perfused microvessels and capillaries could be detected in normal tissue and tumor periphery, in contrast to topical high-dose PDT leading to a shut down of FVD 24 h after irradiation in all areas of the chamber tissue. Histological staining revealed a more pronounced intracellular oedema and swelling of cells after topical high-dose PDT than systemic high-dose PDT. These results indicate that topical high-dose PDT with ALA has a more pronounced effect on microcirculation as compared to systemic high-dose PDT in this model.

In vivo phosphorescence imaging of pO2 using planar oxygen sensors.

OBJECTIVE: Oxygen-dependent quenching of luminescence of metal porphyrin complexes has been used to image the pO(2) distribution over tumor and normal tissue. METHODS: An experimental setup is described using a platinum(II)-octaethyl-porphyrin immobilized in a polystyrene matrix as transparent planar sensor. RESULTS: Sensitivity over a broad range is high at low pO(2) values (+/- 0.2 mm Hg at 0 mm Hg; +/- 1.5 mm Hg at 160 mm Hg pO(2)). Due to intrinsically referencing via lifetime encoding there was no modification of the sensor response in vivo in the dorsal skinfold chamber model with amelanotic melanoma (A-MEL-3) in awake hamsters when compared to the in vitro calibration. pO(2) measurements over normal tissue (25.8 +/- 5.1 mm Hg) and tumor tissue (9.2 +/- 5.1 mm Hg) were in excellent agreement with previous results obtained in this model using a surface multiwire electrode. CONCLUSIONS: Using the presented method the surface pO(2) distribution can be mapped with a high temporal resolution of approximately 100 ms and a spatial resolution of at least 25 mu m. Moreover, the transparent sensor allows the simultaneous visualization of the underlying microvasculature.

Selective photothermolysis of blood vessels following flashlamp-pumped pulsed dye laser irradiation: in vivo results and mathematical modelling are in agreement.

Laser therapy using the pulsed dye laser is the standard treatment for port-wine stains (PWS). But the mechanism of action has not been elucidated completely, yet. The dorsal skin-fold chamber model in hamsters was used to investigate the effects of laser treatment (lambda(em)=585 nm; pulse duration: 0.45 ms; fluence: 6 J per cm2) on blood vessels. Vessels (n=3394) were marked with FITC dextran (MW 150 kDa) and diameters (2-186 microm) were measured using intravital fluorescence microscopy up to 24 h following irradiation. Histology (H&E, TUNEL, CD31) was taken 1 or 24 h after irradiation. The experimental results were compared with the predictions of a mathematical model based on the finite-element method. Following irradiation treatment the number of unperfused vessels decreases with decreasing vessel diameter in vivo. Histology indicated a restriction of tissue injury to the irradiated area after 1 h. Blood vessels contained aggregated red blood cells. After 24 h tissue damage occurred also outside the irradiated area and thrombus formation was visible. These results were in agreement with the mathematical calculations. In addition to initial physical effects after pulsed dye laser treatment delayed biological processes contribute significantly to the reduction of perfused blood vessels. Because of incomplete photocoagulation of smaller blood vessels (diameter 2-16 microm) a complete bleaching of PWS seems to be unlikely.

Targeting of the vascular system of solid tumours by photodynamic therapy (PDT).

Owing to morphological and rheological differences of the tumour vascular system as compared to the vascular system of the surrounding tissue, the efficacy of several experimental and clinical therapeutic approaches is limited. This fact has put the vascular system of solid tumours into focus and two new therapeutic strategies, anti-angiogenesis and vascular targeting, have emerged. Under the term vascular targeting various therapeutic approaches are summarized, e.g. chemoembolization, chemotherapy, hyperthermia, vascular targeting agents (VTA) and photodynamic therapy (PDT). As shown using the clinically approved photosensitiser Photofrin the irreversible destruction of the tumour vascular system is primarily responsible for an effective PDT of solid tumours. However, the clinical disadvantages of Photofrin are well known. Thus, several new photosensitisers, e.g. aminolaevulinic acid (ALA), porphycenes and indocyanine green (ICG), have been evaluated in vitro and in vivo regarding their suitability for vascular targeting of solid tumours. The promising experimental findings with the photosensitiser ICG led to first clinical results in treating Kaposi's sarcomas. In summary, systemic PDT is only effective when leading to complete ischaemia of solid tumours with subsequent necrosis. An essential prerequisite is the use of a chemically and photophysically defined photosensitiser localizing in the intravascular space due to e.g. a high molecular weight. The specific properties of such a photosensitiser are outlined.