Influence of topical photodynamic therapy with 5-aminolevulinic acid on porphyrin metabolism

Does 5-ALA Fluorescence Microscopy Improve Complete Resectability in Cerebral/Cerebellar Metastatic Surgery? A Retrospective Data Analysis from a Cranial Center

(1) Background: In this study, the intraoperative fluorescence behavior of brain metastases after the administration of 5-aminolevulinic acid (5-ALA) was analyzed. The aim was to investigate whether the resection of brain metastases using 5-ALA fluorescence also leads to a more complete resections and thus to a prolongation of survival; (2) Methods: The following variables have been considered: age, sex, number of metastases, localization, involvement of eloquent area, correlation between fluorescence and primary tumor/subtype, resection, and survival time. The influence on the degree of resection was determined with a control MRI within the first three postoperative days; (3) Results: Brain metastases fluoresced in 57.5% of cases. The highest fluorescence rates of 73.3% were found in breast carcinoma metastases and the histologic subtype adenocarcinoma (68.1%). No correlation between fluorescence behavior and localization, primary tumor, or histological subtype was found. Complete resection was detected in 82.5%, of which 56.1% were fluorescence positive. There was a trend towards improved resectability (increase of 12.1%) and a significantly longer survival time (p = 0.009) in the fluorescence-positive group; (4) Conclusions: 5-ALA-assisted extirpation leads to a more complete resection and longer survival and can therefore represent a low-risk addition to modern surgery for brain metastases.

Photodynamic application in diagnostic procedures and treatment of non-melanoma skin cancers

OPINION STATEMENT

Skin tumors commonly seen in dermatology are involved in all layers of the skin and appendages. While biopsy of affected skin remains an essential method to confirm diagnosis and to predicate tumor prognosis, it has its limitations. Recently, photodynamic diagnosis (PDD) has demonstrated high sensitivity in detecting affected skin and mucosal tissues, providing valuable guidance for precision surgery to resect skin and mucosal tumors. In this review, we summarized the literatures concerning the applications of PDD in diagnostic process and treatment of skin and mucosal conditions such as actinic keratoses (AK), basal cell carcinoma (BCC), squamous cell carcinoma (SCC), Bowen's disease (BD) and extramammary Paget's disease (EMPD). The findings suggest that PDD holds substantial promise for expanding clinical applications and deserves further research exploration.

In vitro bactericidal activity of 465-470 nm blue light phototherapy and aminolevulinic acid on Staphylococcus pseudintermedius

BACKGROUND

Staphylococcus pseudintermedius is the principal pathogen causing bacterial skin infections in dogs. Photodynamic therapy (PDT) involving the combination of light and a topical photosensitizer is used to treat human skin infections. Although the antimicrobial effects of PDT have been demonstrated using in vivo and in vitro studies in humans, its effects on dogs and their pathogens are unclear.

OBJECTIVES

The aim of this study was to demonstrate the in vitro efficacy of PDT over a 465-470 nm spectrum to kill S. pseudintermedius using δ-aminolevulinic acid (ALA) as the photosensitizer.

METHODS

Six S. pseudintermedius isolates from canine skin were exposed to blue light-emitting diodes (LEDs) at 465-470 nm, with or without ALA. The light doses were 18.4, 36.8 and 55.2 J/cm2 . The number of colony-forming units and optical densities of broth cultures were measured and then compared with Dunnett's test. Bacterial viability was monitored using fluorescence microscopy and the fluorescence intensity values were compared with a paired Student's t-test.

RESULTS

Blue light inhibited the growth of S. pseudintermedius; the effect significantly increased with the addition of ALA as a photosensitizer and with increasing light doses. Live/dead staining confirmed that PDT reduced bacterial viability and exerted an antibacterial effect.

CONCLUSION AND CLINICAL IMPORTANCE

Blue light has a strong antibacterial effect on S. pseudintermedius in a light dose-dependent manner. ALA alone did not exhibit bactericidal action, but its combination with blue light increased the effect of PDT compared to blue light alone.

The modern paradigm of phototherapy

The recognition of medical benefits obtained with suberythemogenic doses of natural sunlight extends back centuries. Modern medical application of phototherapy has been in place for over 100 years. It is the nature of scientific discovery to depend upon the use of new investigational methods or new devices to gain a better understanding of the mechanisms involved with the observed effects. Advancements in the field of photobiology and in the development of delivery systems for light therapy, such as narrow band UVB and laser, has given us additional insight into why and how phototherapy works in regards to treatment of skin disease and conditions of the skin. This discussion will primarily focus on ultraviolet light, photochemotherapy and a brief mention of photodynamic therapy.

Photodynamic therapy of high-grade cervical intraepithelial neoplasia with 5-aminolevulinic acid

BACKGROUND AND OBJECTIVES

To determine the safety and efficacy of 5-aminolevulinic acid (ALA) as a topically applied photosensitizer for photodynamic therapy (PDT) of cervical intraepithelial neoplasia (CIN).

STUDY DESIGNS/MATERIALS AND METHODS

Forty women, who were at least 18 years old with persistent biopsy-proven CIN 2 and CIN 3 within the previous 3 months of enrollment, underwent PDT in a phase I and II design. Five escalating radiant energies (increments of 25 J/cm(2), beginning at 50-150 J/cm(2)) using a Coherent Dye Model 920 argon pumped dye laser providing light at 630 nm (maximum output 0.8 W) were used to perform PDT with a fixed dose of ALA (200 mg/ml). ALA was placed in a cervical cap fitted to the cervix. After 90 minutes, the cap was removed and the ectocervix was illuminated for 5-16 minutes, depending on the irradiance. Success was defined as the absence of CIN on Pap smear or colposcopic examination at 12-months. Patients were monitored for toxicity.

RESULTS

Thirty-two women (80%) completed the study with 1 year of follow-up. Sixty percent had CIN 3 and 40% CIN 2. Success rates at 4, 8, and 12 months were 51, 46, and 31%, respectively, and were not light-dose dependent. Three patients progressed from CIN 2 to CIN 3. Toxicity was tolerable and only consisted of spotting, vaginal discharge, mild cramping, and vaginal warmth. There was no apparent dose relationship to toxicity.

CONCLUSIONS

PDT at this light and ALA dose is well tolerated but has minimal activity in the treatment of CIN 2 and CIN 3. Other doses and schedules of light and ALA or novel photosensitizers may improve efficacy.

The 5-aminolevulinic acid-induced porphyrin biosynthesis in benign and malignant cells of the skin

In fluorescence diagnosis and photodynamic therapy of neoplastic tissues 5-aminolevulinic acid is used to synthesize endogenous porphyrins as photosensitizers. The efficacy of neoplastic tissues to fluorescence diagnosis and photodynamic therapy is thought to be dependent on the total level of intralesional formed porphyrins. The available profiles of porphyrin metabolites in normal and in neoplastic cell lines after administration of 5-aminolevulinic acid vary considerably. Thus, this is the first in-vitro study which compares the porphyrin biosynthesis in normal skin cells (HaCaT, fibroblasts) with melanoma cells (Bro, SKMel-23, SKMel-28). After incubation with 1 mM 5-aminolevulinic acid, kinetics of porphyrin levels and metabolites were determined in the cells and the corresponding supernatants. Exogenous 5-aminolevulinic acid induced porphyrin formation in all cells with maximum values after an incubation period of 16-36 h. Increase of porphyrin levels varied from 10- to 80-fold (SKMel-28>HaCaT>fibroblasts>SKMel-23>>Bro) with minimum 1.5 times higher levels of porphyrins in the supernatants than in the cells. In cells and supernatants protoporphyrin and coproporphyrin were the predominantly formed porphyrin metabolites. Metastatic melanoma cells (SKMel-23, SKMel-28) accumulated much higher porphyrin levels than primary melanoma cells (Bro). In conclusion, by optimizing the treatment modalities, especially the light source, topical photodynamic therapy (PDT) could become a treatment alternative of melanoma metastases in progressive disease.

Topical 5-aminolevulinic acid and photodynamic therapy in dermatology: a minireview

Photodynamic therapy (PDT) is a treatment modality using a photosensitizer, light and oxygen to cause photochemically induced selective cell death. When exposed to light with the proper wavelength, the topically applied photosensitizer or photosensitizer precursor can activate a biomolecule through electron transfer to yield free radicals or produce singlet oxygen from energy transferred from the excited sensitizer to molecular oxygen. The tissue damage is the result of the activation of reactive singlet oxygen or free radical production. Photodynamic therapy with topical application of 5-aminolevulinic acid (ALA) is a new technique and although it remains largely experimental, it has potential application for treatment of malignant skin tumors, various precancerous and selected benign skin diseases. This technique yields not only a high percentage of good therapeutic results but also excellent cosmetic outcome. This paper reviews the recently published data on clinical ALA-based PDT in dermatology.

Aminolevulinic acid: pharmacological profile and clinical indication

The role of aminolevulinic acid hydrochloride (ALA) in photodynamic therapy (PDT) of in situ neoplasias and tumours of epithelial tumours is steadily increasing and it has been shown to be the drug with most clinical use in PDT. In dermatology, topical PDT with ALA is already postulated to be the treatment of choice for actinic keratoses and superficial basal cell carcinomas. In gastroenterology, pulmonology, uro- and nephrology, neurology and gynaecology ALA has an important role as a photosensitiser not only in the diagnosis of neoplastic tissue but as therapy; first experiences have been made with PDT in these organs. Besides the therapeutic efficacy of this technique, the fluorescence of ALA-induced porphyrins can be effectively used to detect and delineate epithelial and endothelial neoplasms. In dermatology, other indications for ALA-treatment are non-tumoural applications, especially psoriasis, viral-induced diseases, or acne vulgaris. ALA is an effective compound in the diagnosis or therapy of various epithelial and endothelial neoplastic lesions.

Migraine and beyond: cardiovascular therapeutic potential for CGRP modulators

CGRP is a potent vasodilator that has been shown to have a physiological and/or pathological role in neurogenic inflammation, headaches including migraine, thermal injury, circulatory shock, pregnancy and menopause, hypertension and heart failure and is known to be cardioprotective. CGRP is also a positive inotrope and increases heart rate. Clinical trials have shown beneficial effects of the vasodilatory action of CGRP in hypertension, angina, heart failure, Raynaud's disease and venous stasis ulcers. However, the clinical potential of CGRP is limited as it has to be given by infusion and is quickly broken down. Oral long acting CGRP-mimetics may have potential in disorders in which CGRP has been shown to be beneficial. CGRP-mimetics include capsaicin/vanilloid receptor agonists and gene transfer of an adenoviral vector that encodes prepro-CGRP. CGRP inhibitors have therapeutic potential in conditions in which excessive CGRP-mediated vasodilatation is present; neurogenic inflammation, migraine and other headaches, thermal injury, circulatory shock and flushing in menopause. CGRP inhibitors include capsaicin, antagonists at capsaicin/vanilloid receptors, civamide, CGRP receptor antagonists and 5-HT1D-receptor agonists. Drugs that are 5-HT1D-receptor agonists, the 'triptans' are already commonly used in migraine and the first small molecule CGRP antagonist, BIBN4096BS, is under clinical investigation for the treatment of migraine.

Photodynamic therapy of skin cancers: sensitizers, clinical studies and future directives

Photodynamic therapy (PDT) is a new modality of skin cancer treatment. It involves the administration of photosensitizing drugs which, when localized in tumor tissue can produce its destruction by absorbing an adequate dose of light of an appropriate wavelength. A large number of photosensitizing agents have been tested in PDT experiments. Topical application of 5-aminolevulinic acid (5-ALA) followed by light irradiation is the most commonly used method. 5-ALA is a prodrug converted in situ via the heme cycle into protoporphyrin IX, an effective photosensitizer agent. Treatment of nonmelanoma skin cancers by PDT has met with varying degrees of success. In the case of 5-ALA, this therapy's main limitation is the poor penetration of 5-ALA into skin, due to hydrophilic and charge characteristics. However, the efficacy of 5-ALA-PDT may be improved by (a) development of adequate drug delivery systems; (b) use of enhancers of PpIX production and accumulation in target tissue, and (c) modifications of the 5-ALA molecule. Optimal timing, light sources, doses, and number of applications are also important factors for topical 5-ALA therapy and must be well defined. The aim of this review is to highlight recent progress in 5-ALA-PDT of skin cancer, and to present ways holding promise for its improvement.

Photodynamic parameters in the chick chorioallantoic membrane (CAM) bioassay for topically applied photosensitizers

The relative efficacy of Photofrin-based photodynamic therapy (PDT) has been compared with that of the second-generation photosensitizers 5-aminolevulinic acid (ALA), sulfonated chloro-aluminum phthalocyanine (AlPcSn), benzoporphyrin derivative monoacid ring A (BPD-MA), and lutetium texaphyrin (Lutex). PDT-induced vascular damage in the chick chorioallantoic membrane (CAM) is measured following topical application of the photosensitizers. In order to make meaningful comparisons, care is taken to keep treatment variables the same. These include light dose (5 and 10 J/cm2), power density (33 and 100 mW/cm2), and drug uptake time (30 and 90 min). The drug dose ranges from 0.1 microgram/cm2 for BPD to 5000 micrograms/cm2 for ALA. Results are also analyzed statistically according to CAM vessel type (arterioles versus venules), vessel diameter, and vessel development (embryonic age). For each photosensitizer, the order of importance for the various PDT parameters is found to be unique. The differences between the sensitizers are most likely due to variation in biophysical and biochemical characteristics, biodistribution, and uptake kinetics.

Tissue distribution and kinetics of endogenous porphyrins synthesized after topical application of ALA in different vehicles

The use of 5-aminolaevulinic acid (ALA) is gaining increasing attention for photosensitization in photodynamic therapy of superficially localized tumours. The aim of this work was to determine the kinetics of porphyrin generation in tissues after topical application of ALA delivered in different vehicles on the skin overlying the tumour and normal skin of mice. Maximal accumulation was found in tumour 3 h after ALA application in both cream and lotion preparations. Normal and overlying tumour skin tissues showed different kinetic patterns, reflecting histological changes when the latter is invaded by tumour cells. Liver, kidney, spleen and blood porphyrins also raised from basal levels, showing that ALA and/or ALA-induced porphyrins reach all tissues after topical application. During the first 24 h of ALA topical application, precursors and porphyrins are excreted by both urine and faeces. ALA lotion applied on the skin overlying the tumour induced higher accumulation of tumoural porphyrins than cream, and lotion applied on normal skin appeared to be the most efficient upon inducing total body porphyrins. This work has demonstrated the great influence of the formulation of ALA vehicle on penetration through the skin. Knowledge of the kinetics of porphyrin generation after different conditions of ALA application is needed for the optimization of diagnosis and phototherapy in human tumours.

Optimum porphyrin accumulation in epithelial skin tumours and psoriatic lesions after topical application of delta-aminolaevulinic acid

Photodynamic therapy with topically applied delta-aminolaevulinic acid is used to treat skin tumours by employing endogenously formed porphyrins as photosensitizers. This study examines the time course of porphyrin metabolite formation after topical application of delta-aminolaevulinic acid. Porphyrin biosynthesis in human skin tumours (basal cell carcinoma, squamous cell carcinoma), in psoriatic lesions, and in normal skin was investigated. Skin areas were treated with delta-aminolaevulinic acid, and levels of total porphyrins, porphyrin metabolites and proteins were measured in samples excised after 1, 2, 4, 6, 9, 12 and 24 h. There was an increase in porphyrin biosynthesis in all tissues with maximum porphyrin levels in tumours between 2 and 6 h and in psoriatic lesions 6 h after treatment. The pattern of porphyrins showed no significant difference between normal and neoplastic skin, protoporphyrin being the predominant metabolite. The results suggest that optimum irradiation time for superficial epithelial skin tumours may be as soon as 2 h after application of delta-aminolaevulinic acid, whereas for treatment of psoriatic lesions an application time of 6 h is more suitable.

Intraoperative detection of malignant gliomas by 5-aminolevulinic acid-induced porphyrin fluorescence

OBJECTIVE

Survival after surgery and radiotherapy for the treatment of malignant gliomas is linked to the completeness of tumor removal. Therefore, methods that permit intraoperative identification of residual tumor tissue may be of benefit. In a preliminary investigation, we have studied the value of fluorescent porphyrins that accumulate in malignant tissue after administration of a precursor (5-aminolevulinic acid) for labeling of malignant gliomas in nine patients.

METHODS

Three hours before the induction of anesthesia, 10 mg 5-aminolevulinic acid/kg body weight was administered orally. Intraoperatively, red porphyrin fluorescence was observed with a 455-nm long-pass filter after excitation with violet-blue (375-440 nm) xenon light and was verified by analysis of fluorescence spectra. Fluorescing and nonfluorescing samples taken from the tumor perimeters were examined histologically or used to study the photobleaching of porphyrins by excitation light and white light from the operating microscope. Plasma and erythrocyte porphyrin levels were determined by fluorescence photometry.

RESULTS

Normal brain tissue revealed no porphyrin fluorescence, whereas tumor tissue was distinguished by bright red fluorescence. For a total of 89 tissue biopsies, sensitivity was 85% and specificity was 100% for the detection of malignant tissue. For seven of nine patients, visible porphyrin fluorescence led to further resection of the tumor. Under operating light conditions, fluorescence decayed to 36% in 25 minutes for violet-blue light and in 87 minutes for white light. Plasma and erythrocyte porphyrin contents increased slightly, without exceeding normal levels.

CONCLUSION

Our observations suggest that 5-aminolevulinic acid-induced porphyrin fluorescence may label malignant gliomas safely and accurately enough to enhance the completeness of tumor removal.

Ex vivo application of delta-aminolevulinic acid induces high and specific porphyrin levels in human skin tumors: possible basis for selective photodynamic therapy

In photodynamic therapy with topically applied delta-aminolevulinic acid porphyrins are acting as photosensitizers. The profile of porphyrin metabolites in normal or in neoplastic skin after administration of delta-aminolevulinic acid has not been determined in detail yet. Thus, to study porphyrin biosynthesis in human skin an organ culture model was developed. Explant pieces of normal skin, keratoacanthoma, and basal cell carcinoma were incubated with 1 mM delta-aminolevulinic acid for 36 h. Levels of delta-aminolevulinic acid, porphyrins and porphyrin metabolites were measured in tissues and supernatants. After incubation with delta-aminolevulinic acid, higher porphyrin levels were demonstrated in tumors as compared to normal skin. In supernatants, most of formed porphyrins, preferentially highly carboxylated porphyrin metabolites, were measured. The pattern of synthesized porphyrins differed between normal and neoplastic skin explants. In tissues of basal cell carcinomas protoporphyrin was preferentially shown and tissues of keratoacanthomas were characterized by a predominance of coproporphyrin as compared to normal skin. The results show that explant cultures offer an easy approach to examine the porphyrin biosynthesis of various tissues. The tumor-specific delta-aminolevulinic acid metabolism indicates additional porphyrin metabolites such as coproporphyrin apart from protoporphyrin as effective photosensitizers and may offer a novel approach to tumor-selective photodynamic damage.

Porphyrins preferentially accumulate in a melanoma following intravenous injection of 5-aminolevulinic acid

Systemically, as opposed to topically, administered 5-aminolevulinic acid (ALA) is of increasing interest for photodynamic therapy (PDT) because of more selective and more homogeneous accumulation of porphyrins in neoplastic tissues. This study investigates the profile and the time course of porphyrin metabolites in various tissues following intravenous injection of ALA (0.5 g/kg body weight) into hamsters bearing an amelanotic melanoma (A-Mel-3). ALA injection led to maximum levels of ALA and porphyrins in erythrocytes after 45 min. In tissues, maximum porphyrin levels were detected after 45 min (tumor), 4 h (skin, kidney), and 24 h (liver). Sixfold higher porphyrin levels were observed in tumors as compared to surrounding normal skin at 45 min. Predominant porphyrin metabolites were protoporphyrin (tumor, skin, liver, kidney), coproporphyrin (tumor) and highly carboxylated porphyrins (tumor, skin, kidney). These data suggest optimum efficacy of light irradiation in systemic PDT with ALA within the first two hours after injection. Tumor-specific ALA metabolism yields protoporphyrin and coproporphyrin as the prevailing porphyrin metabolites.