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

Unlocking the Power of Light on the Skin: A Comprehensive Review on Photobiomodulation

Photobiomodulation (PBM) is a procedure that uses light to modulate cellular functions and biological processes. Over the past decades, PBM has gained considerable attention for its potential in various medical applications due to its non-invasive nature and minimal side effects. We conducted a narrative review including articles about photobiomodulation, LED light therapy or low-level laser therapy and their applications on dermatology published over the last 6 years, encompassing research studies, clinical trials, and technological developments. This review highlights the mechanisms of action underlying PBM, including the interaction with cellular chromophores and the activation of intracellular signaling pathways. The evidence from clinical trials and experimental studies to evaluate the efficacy of PBM in clinical practice is summarized with a special emphasis on dermatology. Furthermore, advancements in PBM technology, such as novel light sources and treatment protocols, are discussed in the context of optimizing therapeutic outcomes and improving patient care. This narrative review underscores the promising role of PBM as a non-invasive therapeutic approach with broad clinical applicability. Despite the need for further research to develop standard protocols, PBM holds great potential for addressing a wide range of medical conditions and enhancing patient outcomes in modern healthcare practice.

Advances in 5-Aminolevulinic Acid Priming to Enhance Plant Tolerance to Abiotic Stress

Priming is an adaptive strategy that improves plant defenses against biotic and abiotic stresses. Stimuli from chemicals, abiotic cues, and pathogens can trigger the establishment of priming state. Priming with 5-aminolevulinic acid (ALA), a potential plant growth regulator, can enhance plant tolerance to the subsequent abiotic stresses, including salinity, drought, heat, cold, and UV-B. However, the molecular mechanisms underlying the remarkable effects of ALA priming on plant physiology remain to be elucidated. Here, we summarize recent progress made in the stress tolerance conferred by ALA priming in plants and provide the underlying molecular and physiology mechanisms of this phenomenon. Priming with ALA results in changes at the physiological, transcriptional, metabolic, and epigenetic levels, and enhances photosynthesis and antioxidant capacity, as well as nitrogen assimilation, which in turn increases the resistance of abiotic stresses. However, the signaling pathway of ALA, including receptors as well as key components, is currently unknown, which hinders the deeper understanding of the defense priming caused by ALA. In the future, there is an urgent need to reveal the molecular mechanisms by which ALA regulates plant development and enhances plant defense with the help of forward genetics, multi-omics technologies, as well as genome editing technology.

Follow-up of pressure ulcer treatment with photodynamic therapy, low level laser therapy and cellulose membrane

OBJECTIVE

A pressure ulcer (PU) is an area of tissue trauma caused by continuous and prolonged pressure, often associated with hospitalised patients immobilised due to neurological problems, negatively affecting their quality of life, and burdening the public budget. The aim of this study was to report the follow-up, for 45 weeks, of three patients with neurological lesions due to trauma who subsequently developed PUs, and who were treated with a combination of photodynamic therapy (PDT), low level laser therapy (LLLT) and cellulose membrane (CM).

METHOD

PDT was mediated by the photosensitiser curcumin on a 1.5% emulsion base. Blue LED light at 450 nm was delivered continuously for 12 minutes at an irradiance of 30mW/cm² and total energy delivered to the tissue was 22J/cm². LLLT was performed with 660 nm laser, punctuated and continuous, twice a week with parameters: spot size 0.04cm², power of 40mW, 10 seconds per point, fluence of 10J/cm² and irradiance of 1000mW/cm².

RESULTS

All PUs had a significant reduction (range: 95.2-100%) of their area after 45 weeks of follow-up and two PUs had complete healing at 20 weeks and 30 weeks. All of the PUs showed a reduction in contamination with the PDT treatments in different proportions.

CONCLUSION

From the results obtained, we conclude that the combination of PDT, LLLT and CM is a promising treatment for PU healing.

5-Aminolaevulinic acid patch photodynamic therapy for the treatment of actinic keratoses: preliminary results from an Italian study in the real-life setting

BACKGROUND

Photodynamic therapy (PDT) is recommended for both lesion and field therapy of actinic keratoses (AKs). The 5-aminolaevulinic acid (5-ALA) patch PDT is indicated for the treatment of isolated mild AKs (≤1.8 cm) on the face and bald scalp. It was demonstrated to be effective and safe in clinical trials with a good tolerability profile.

METHODS

In this retrospective multicenter real-life study, 33 patients with a total of 99 AKs of the scalp, face, ears, and/or hands and 2 actinic cheilitis were treated with one treatment session of 5-ALA patch PDT with a red light source (total dose of 37 J/cm2).

RESULTS

Overall, 12 weeks after treatment, 68/99 (69%) lesions were completely cleared. Complete response was obtained in 82% of AKs on the ears, 78% on the face, 57% on the hands, and 56% on the scalp and in the two actinic cheilitis. The treatment was very effective on grade I AKs, cleared in 87% of the cases and less efficient on grade II-III lesions, cleared in 47% of the cases. 5-ALA patch PDT was well tolerated with a good to excellent cosmetic outcome in 97% of the patients and with 94% of the patients being satisfied or very satisfied with the treatment.

CONCLUSIONS

Our results confirm that 5-ALA patch PDT is a good option for AK treatment in clinical practice, it is easy to use, effective and well tolerated even in difficult-to-treat-areas. Moreover, it has an excellent cosmetic outcome.

Unilateral Basal Cell Carcinomas: An Unusual Entity Treated with Photodynamic Therapy

Background:

Unilateral localized basal cell carcinomas are an uncommon finding that presents both a diagnostic and therapeutic challenge. Exclusion of unilateral nevoid basal cell carcinoma syndrome is indicated. There are few reports in the literature regarding this entity and even less regarding therapeutic strategies.

Objective:

We present a patient with unilateral localized basal cell carcinomas who was successfully treated with photodynamic therapy.

Methods:

Photodynamic therapy was started using Levulan® Kerastick® as previously described. The topical solution was applied to the patient's back and illuminated the following day via the BLU-U Blue Light Illuminator.

Results:

The patient tolerated the procedure well and without complications. The patient had an excellent therapeutic response with no clinically apparent basal cell carcinomas for 18 months.

Conclusions:

We report a patient with unilateral basal cell carcinomas successfully treated with photodynamic therapy. This uncommon entity represents a diagnostic challenge in its inherent absence of the classic clinical and radiographic findings of nevoid basal cell carcinoma syndrome. Like nevoid basal cell carcinoma syndrome, unilateral basal cell carcinomas poses a therapeutic challenge with the sheer number of cutaneous tumors. The use of photodynamic therapy carries a proven therapeutic efficacy, a low rate of adverse events and excellent cosmesis.

Alternative mitochondrial electron transfer for the treatment of neurodegenerative diseases and cancers: Methylene blue connects the dots

Brain has exceptional high requirement for energy metabolism with glucose as the exclusive energy source. Decrease of brain energy metabolism and glucose uptake has been found in patients of Alzheimer's, Parkinson's and other neurodegenerative diseases, providing a clear link between neurodegenerative disorders and energy metabolism. On the other hand, cancers, including glioblastoma, have increased glucose uptake and rely on aerobic glycolysis for energy metabolism. The switch of high efficient oxidative phosphorylation to low efficient aerobic glycolysis pathway (Warburg effect) provides macromolecule for biosynthesis and proliferation. Current research indicates that methylene blue, a century old drug, can receive electron from NADH in the presence of complex I and donates it to cytochrome c, providing an alternative electron transfer pathway. Methylene blue increases oxygen consumption, decrease glycolysis, and increases glucose uptake in vitro. Methylene blue enhances glucose uptake and regional cerebral blood flow in rats upon acute treatment. In addition, methylene blue provides protective effect in neuron and astrocyte against various insults in vitro and in rodent models of Alzheimer's, Parkinson's, and Huntington's disease. In glioblastoma cells, methylene blue reverses Warburg effect by enhancing mitochondrial oxidative phosphorylation, arrests glioma cell cycle at s-phase, and inhibits glioma cell proliferation. Accordingly, methylene blue activates AMP-activated protein kinase, inhibits downstream acetyl-coA carboxylase and cyclin-dependent kinases. In summary, there is accumulating evidence providing a proof of concept that enhancement of mitochondrial oxidative phosphorylation via alternative mitochondrial electron transfer may offer protective action against neurodegenerative diseases and inhibit cancers proliferation.

Photodynamic therapy in dermatology: current concepts in the treatment of skin cancer

Photodynamic therapy is a treatment modality that is developing rapidly and increasing in utilization within various medical specialties, including dermatology. This technique requires the presence of a photosensitizer, light energy and molecular oxygen to selectively destroy pathologic cells. A thorough understanding of photobiology and tissue optics is necessary to correctly and effectively utilize photodynamic therapy in dermatology. Photodynamic therapy has been approved by the US Food and Drug Administration to treat actinic keratoses. In Europe, photodynamic therapy is currently being used in the treatment of actinic keratoses and basal cell carcinoma. Other off-label uses of photodynamic therapy have included cutaneous lesions of Bowen's disease, psoriasis, cutaneous T-cell lymphoma and acne. Most recently, photodynamic therapy has been employed in photorejuvenation. The advantages of photodynamic therapy include the capacity for noninvasive targeted therapy via topical application of the drug and local irradiation of involved areas, as well as the ability to generate excellent cosmetic results with minimal discomfort. This review summarizes the fundamentals of photodynamic therapy and its role in the treatment of cutaneous disorders, particularly skin malignancies.

Squamous Cell Carcinoma of the Eyelid Treated with Photodynamic Therapy

The ocular tissues can be the site of a number of malignant tumors in adults. Approximately 5% to 10% of all skin tumors occur in the eyelid. Incidence studies indicate that basal cell carcinoma is the most frequent malignant eyelid tumor (90%) followed by squamous cell carcinoma (9%). A 55-year-old man presented a squamous cell carcinoma (SCC) of 8 mm diameter, localized in the middle third of the lower eyelid, 3 mm under the eyelid margin on the eyelids. The histopathologic examination of a biopsy specimen showed the typical features of squamous cell carcinoma. Photodynamic therapy (PDT) with topical 5-aminolevulic acid (ALA) after Frost suture was employed. Very good results were obtained with rapid healing, without invasiveness, and without anesthesia. There was no evidence of scar formation and no signs of recurrence at 6 months follow-up. Many therapeutic methods have been suggested for squamous cell carcinoma of the eyelid. We consider photodynamic treatment of eyelid skin malignancies to be of great interest and it may represent an interesting future perspective for their management especially when surgical intervention cannot be tolerated by the patient.

The effect of increasing fluence on the treatment of actinic keratosis and photodamage by photodynamic therapy with 5-aminolevulinic acid and intense pulsed light

BACKGROUND AND OBJECTIVE

Photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) and intense pulsed light (IPL) is a relatively new combination for the treatment of actinic keratosis (AK) and photodamage. The objective of this study was to determine the effect of increasing the fluence of IPL on the outcome of patients with these skin conditions.

METHODS

Patients (N = 24) were randomly assigned to five treatment treatment groups: control (IPL alone) and ALA with 20, 25, 40, and 50  J/cm(2) fluence of IPL. Each patient received a single treatment. ALA was applied twice and allowed to incubate 2  h before IPL irradiation. Results were evaluated 5-7 days and 8 weeks after treatment. Clearance of AK lesions was evaluated by counting lesions before and after treatment, and improvement in photodamage was assessed by comparing pre- and post-treatment photographs. Statistical evaluation was based at nonparametric tests with a cut-off level at p < 0.10 and a confidence interval at 95%.

RESULTS

Responses to treatment were greatest in patients who received ALA and IPL fluences of 40 and 50  J/cm(2). Responses were "marked" in 19% of the patients receiving 50  J and "moderate" in 19% of the patients receiving 40  J. Compared to the mean pre-treatment AK grades, the mean post-treatment grades were 56% lower in the 50  J treatment group, 32% lower in the 25  J group, 50% lower in the 40  J group, 20% lower in the 20  J group, and 7% lower in the control group. Erythema, edema, crusts and erosion, and pain did not cause any patient to discontinue the study.

CONCLUSION

AK clearance, but not photorejuvenation, appears to improve with increasing fluence at the ALA PDT-IPL levels used in this study without serious adverse effects.

Recent advances in the prevention and treatment of skin cancer using photodynamic therapy

Photodynamic therapy (PDT) is a noninvasive procedure that involves a photosensitizing drug and its subsequent activation by light to produce reactive oxygen species that specifically destroy target cells. Recently, PDT has been widely used in treating non-melanoma skin malignancies, the most common cancer in the USA, with superior cosmetic outcomes compared with conventional therapies. The topical 'photosensitizers' commonly used are 5-aminolevulinic acid (ALA) and its esterified derivative methyl 5-aminolevulinate, which are precursors of the endogenous photosensitizer protoporphyrin IX. After treatment with ALA or methyl 5-aminolevulinate, protoporphyrin IX preferentially accumulates in the lesion area of various skin diseases, which allows not only PDT treatment but also fluorescence diagnosis with ALA-induced porphyrins. Susceptible lesions include various forms of non-melanoma skin cancer such as actinic keratosis, basal cell carcinoma and squamous cell carcinoma. The most recent and promising developments in PDT include the discovery of new photosensitizers, the exploitation of new drug delivery systems and the combination of other modalities, which will all contribute to increasing PDT therapeutic efficacy and improving outcome. This article summarizes the main principles of PDT and its current clinical use in the management of non-melanoma skin cancers, as well as recent developments and possible future research directions.

Photodynamic therapy of superficial nasal planum squamous cell carcinomas in cats: 55 cases

BACKGROUND

Squamous cell carcinomas (SCCs) are common skin tumors in cats. We investigated photodynamic therapy (PDT) using the photosensitizing agent 5-aminolaevulinic acid (5-ALA) topically and a high-intensity red light source.

HYPOTHESIS

PDT is a safe and effective treatment for feline SCCs.

ANIMALS

Fifty-five client-owned cats with superficial nasal planum SCCs.

METHODS

Prospective, uncontrolled clinical trial. PDT was performed using topical 5-ALA and light of peak wavelength 635 nm. Adverse effects, response, and tumor control were evaluated.

RESULTS

53/55 (96%) cats responded to therapy, and there was a complete response in 47/55 (85%). Six cats (11%) had a partial response. Of the 47 cats with complete response to a single treatment, 24 recurred (51%), with a median time to recurrence of 157 days (95% confidence interval, 109-205 days). Repeat PDT was performed in 22 cats, and at a median follow-up of 1,146 days, 23 (45%) cats were alive and disease free, 17 (33%) had to be euthanized due to tumor recurrence, and 11 (22%) were euthanized for other reasons. Only transient mild local adverse effects were observed after treatment.

CONCLUSIONS AND CLINICAL IMPORTANCE

PDT using 5-ALA and a red light source was safe, well tolerated, and effective in the treatment of superficial nasal planum SCCs of cats and offers an alternative to conventional therapy. Although initial response rates were high, this treatment did not lead to a durable remission or cure in all cases.

Targeted photodynamic therapy with multiply-loaded recombinant antibody fragments

Current photodynamic therapy (PDT) of cancer is limited by inefficiencies involved in specifically targeting photosensitizers to tumors. Although antibodies are being explored as targeting vehicles, they present significant challenges, particularly in terms of pharmacokinetics and drug-coupling. We describe here a novel and effective system to covalently attach multiple photosensitizer molecules (both preclinical, pyropheophorbide-a and clinically approved, verteporfin photosensitizers) to single-chain Fvs. Further, we demonstrate that not only do the resulting photoimmunoconjugates retain photophysical functionality, they are more potent than either free photosensitizer, effectively killing tumor cells in vitro and in vivo. For example, treatment of human breast cancer xenografts with a photoimmunoconjugate comprising an anti-HER-2 scFv linked to 8-10 molecules of pyropheophorbide-a leads to significant tumor regression. These results give an insight into the important features that make scFvs good carriers for PDT drugs and provide proof of concept of our unique approach to targeted photodynamic therapy (tPDT). This promises to significantly improve on current photodynamic therapies for the treatment of cancer.

Photodynamic therapy: basic principles and potential uses for the veterinary ophthalmologist

Photodynamic therapy (PDT) involves the use of photochemical reactions mediated through the interaction of photosensitizing agents, light and oxygen. PDT, while now commonly used in physician ophthalmology and oncology, is uncommonly used for the veterinary ophthalmic patient. It is an emerging new therapy in veterinary ophthalmology for the treatment of periocular tumors. This article reviews the basic principles of PDT to provide the veterinary ophthalmologic community with a succinct reference for this emerging treatment modality in our field.

Unilateral Basal Cell Carcinomas: An Unusual Entity Treated with Photodynamic Therapy

BACKGROUND

Unilateral localized basal cell carcinomas are an uncommon finding that presents both a diagnostic and therapeutic challenge. Exclusion of unilateral nevoid basal cell carcinoma syndrome is indicated. There are few reports in the literature regarding this entity and even less regarding therapeutic strategies.

OBJECTIVE

We present a patient with unilateral localized basal cell carcinomas who was successfully treated with photodynamic therapy.

METHODS

Photodynamic therapy was started using Levulan) Kerastick) as previously described. The topical solution was applied to the patient's back and illuminated the following day via the BLU-U Blue Light Illuminator.

RESULTS

The patient tolerated the procedure well and without complications. The patient had an excellent therapeutic response with no clinically apparent basal cell carcinomas for 18 months.

CONCLUSIONS

We report a patient with unilateral basal cell carcinomas successfully treated with photodynamic therapy. This uncommon entity represents a diagnostic challenge in its inherent absence of the classic clinical and radiographic findings of nevoid basal cell carcinoma syndrome. Like nevoid basal cell carcinoma syndrome, unilateral basal cell carcinomas poses a therapeutic challenge with the sheer number of cutaneous tumors. The use of photodynamic therapy carries a proven therapeutic efficacy, a low rate of adverse events and excellent cosmesis.

Oleic acid as optimizer of the skin delivery of 5-aminolevulinic acid in photodynamic therapy

PURPOSE

In photodynamic therapy (PDT), topically applied aminolevulinic acid (5-ALA) is converted to protoporphyrin IX (PpIX), which upon light excitation induces tumor destruction. To optimize 5-ALA-PDT via improving the highly hydrophilic 5-ALA limited penetration into the skin, we propose the use of the known skin penetration enhancer, oleic acid (OA).

METHODS

In vitro skin penetration and retention of 5-ALA (1% w/w) were measured in the presence or absence of OA (2.5, 5.0, and 10.0% w/w) in propylene glycol (PG) using porcine ear skin as the membrane. In vivo accumulation of PpIX, 4 h after application, was determined fluorometrically in healthy mice skin by chemical extraction of skin samples. In vivo PpIX fluorescence kinetics was also investigated by noninvasive techniques using an optical fiber probe, for 30 min up to 24 h after topical application of 1.0% 5-ALA + 10.0% OA in PG on hairless mice skins.

RESULTS

The flux and in vitro retention of 5-ALA in viable epidermis increased in the presence of 10.0% (w/w) OA. The amounts of PpIX, evaluated both by chemical tissue extractions and in vivo measurements by an optical fiber probe, increased after applying 5-ALA formulations containing 5.0 or 10.0% OA. Moreover, in vivo kinetic studies showed an increase in skin PpIX accumulation when formulations containing 10% OA were used; PpIX accumulation was also maintained longer compared to controls.

CONCLUSIONS

Both in vitro and in vivo results show the OA potential as an optimizer of 5-ALA skin delivery.

A dose ranging study of photodynamic therapy with porfimer sodium (Photofrin®) for treatment of basal cell carcinoma

BACKGROUND AND OBJECTIVES

While basal cell carcinoma (BCC) is effectively treated by several methods, many patients with numerous or frequently occurring lesions seek alternatives that can treat multiple cancers, with improved cosmetic outcome. PDT for esophageal and lung carcinomas is approved at a porfimer sodium (Photofrin) dose of 2 mg/kg, but lower doses increase selectivity and decrease both cutaneous phototoxicity and cost. We evaluated low doses of porfimer sodium PDT for treatment of multiple BCC.

MATERIALS AND METHODS

Seventy-seven patients with 2,041 BCC were injected with 0.75, 0.875, or 1.0 mg/kg porfimer sodium and treated 2 days later with 630-nm light. Clinical responses were determined at 6 months, then periodically to 5 years.

RESULTS

Increasing porfimer sodium dose increased complete responses (CR), with initial CR rates of 72.7% (66-78%, 95% CI), 79.9% (73-86%, 95% CI), and 92.2% (91-93%, 95% CI), albeit with some lower selectivity at the highest dose. At 1 mg/kg, 5-year recurrence rates were 28% (21-35%, 95% CI) and 15% (11-18%, 95% CI) for sporadic and nevoid basal cell carcinoma syndrome (NBCCS) lesions, respectively.

CONCLUSIONS

This is the largest dose-ranging study of porfimer sodium, and the largest number of lesions treated in a single study. We found that with 1 mg/kg porfimer sodium, PDT can be a selective and durable treatment for sporadic and NBCCS-associated BCC.

New proposal for the treatment of nodular basal cell carcinoma with intralesional 5-aminolevulinic acid

Photodynamic therapy (PDT) is a treatment modality using a photosensitizer, light and oxygen to cause photochemically-induced selective cell death. Topical PDT is most suitable for thin lesions such as superficial basal cell carcinoma and actinic keratoses in dermatology. Results with PDT as treatment of thicker lesions such as nodular basal cell carcinoma appear to have a limited role because the photosensitizer or the light cannot penetrate deeply enough into the thicker tumor volume. In this preliminary study we use intralesional administration of 5-aminolevulinic acid to enhance the efficacy of the photosensitivity of nodular basal cell carcinomas, thus improving clinical cure.

Bowen's disease of the nipple—a new method of treatment

Squamous cell carcinoma in situ (Bowen's disease) is a common skin condition but has only rarely been described on the nipple. All reported cases have been treated with wide local excision and observation. A new treatment for Bowen's disease is photodynamic therapy. This has been reported as being able to treat Bowen's disease in other sites effectively with an acceptable local recurrence rate. We describe two patients presenting with itching and scaling of the nipple which were histologically proven Bowen's disease, one of these patients was treated successfully with a combination of photodynamic therapy and cryotherapy: this is the first time such a lesion has been treated in this way.

5-aminolevulinic acid photodynamic therapy: where we have been and where we are going

BACKGROUND

Photodynamic therapy, utilizing the topical administration of 20% 5-aminolevulinic acid, has generated a great deal of interest in the dermatology community over the past several years.

OBJECTIVE

The purpose of this article is to review the history of photodynamic therapy in dermatology and to review recent new advances with this technology that will increase its appeal to all dermatologists.

METHODS

A literature review and results of new clinical trials with regards to photorejuvenation and acne vulgaris treatments with 5-aminolevulinic acid photodynamic therapy are presented.

RESULTS

Short-contact, full-face 5-aminolevulinic acid photodynamic therapy treatments with a variety of lasers and light sources have shown to be successful in treating all facets of photorejuvenation and the associated actinic keratoses as well as disorders of sebaceous glands, including acne vulgaris. The treatments are relatively pain-free, efficacious, and safe. They are also making already available laser/light source therapies work better for acne vulgaris and photorejuvenation.

CONCLUSIONS

The use of 5-aminolevulinic acid photodynamic therapy with short-contact, full-face broad-application therapy is now able to bridge the world of medical and cosmetic dermatologic surgery. This therapy is available for all dermatologists to utilize in the care of their patients.

Cyclooxygenase-2 is a possible target of treatment approach in conjunction with photodynamic therapy for various disorders in skin and oral cavity

BACKGROUND

Anti-cancer effects of cyclooxygenase (COX)-2 inhibitors have been reported, but not fully investigated in skin and oral diseases. 5-aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) for treating those patients with skin and oral lesions is a highly sophisticated procedure, but the incidence of disease recurrence after treatment is rather significant.

OBJECTIVE

To confirm that COX-2 could be a molecular target in adjunctive therapy to ALA-based PDT, we investigated (i) COX-2 expression in various skin and oral diseases, and (ii) the inhibitory effects on cellular growth of COX-2 selective inhibitor (nimesulide), ALA-based PDT and their combination on human oral squamous cell carcinoma (SCC) cell lines.

METHODS

A total of 129 biopsy samples from the skin and oral mucosal lesions were tested immunohistochemically for COX-2 expression. Then the in vitro effects of nimesulide, ALA-based PDT, and their combination were determined on two SCC cell lines, HSC-2 and HSC-4. Three different methods (MTT assay, double-staining for annexin V and propidium iodide, caspase-3/CPP32 fluorometric protease assay) were applied for evaluation of their inhibitory effects on these two cell lines.

RESULTS

Among the skin diseases, a considerable number of COX-2 high expressers were found in actinic keratosis (15 of 25, 60%), Bowen's disease (13 of 17, 76%) and extramammary Paget's disease (15 of 15, 100%). In contrast, only one of 33 (3%) basal cell carcinoma tumours was a COX-2 high expresser. Among the oral mucosal biopsies, the proportion of COX-2 high expressers increased gradually from hyperplasia (one of six, 17%) through mild dysplasia (five of eight, 63%) and moderate dysplasia (20 of 23, 87%) to severe dysplasia (two of two, 100%). Nimesulide had an inhibitory effect in vitro on HSC-2 (proven to be a COX-2 high expresser), but not on HSC-4 (a COX-2 non-expresser). While ALA-based PDT showed an inhibitory effect on both HSC-2 and HSC-4, most importantly the combination of nimesulide and ALA-based PDT demonstrated a significant synergistic effect on the cellular growth inhibition of only HSC-2, but not of HSC-4.

CONCLUSIONS

Our study strongly suggests that COX-2 can be one of the molecular targets in treating various skin and oral diseases. The results from our in vitro experiments also prompt us to develop a new protocol with a combination of COX-2 selective inhibitor and ALA-based PDT for more effective treatment of those diseases.

Cellular damage to human hepatocytes through repeated application of 5-aminolevulinic acid

BACKGROUND/AIMS

5-Aminolevulinic acid (ALA), a precursor of porphyrins is used for photodynamic diagnosis and therapy within topical or systemic applications. A potential toxic effect on the human liver is of major interest and therefore we investigated the impact of a repeated application of ALA without illumination on cultures of human hepatocytes.

METHODS

After ALA treatment of hepatocytes in vitro the porphyrin synthesis, albumin secretion, liver-specific enzyme release, and malondialdehyde levels were determined. In order to reduce levels of reactive oxygen substances, mannitol and the antioxidant enzymes superoxide dismutase and catalase were supplemented.

RESULTS

Porphyrin biosynthesis by human hepatocytes in vitro was repeatedly stimulated by ALA (0.001-1.0 mM), which was indicated by an accumulation of protoporphyrin IX. A repetitive treatment (up to four times) of hepatocytes with ALA resulted in an impairment of the hepatic function and viability, depending on the ALA concentration (0.1-1.0 mM) and frequency of application (2-3 times). This was also accompanied by increased malondialdehyde levels indicating enhanced lipid peroxidation. Only superoxide dismutase was able to reduce cellular damage and prevent specific function.

CONCLUSIONS

Repeated, not single, ALA treatment without illumination may cause deleterious effects to the liver, which are mediated by oxygen radicals and inhibited by an antioxidant.