Characterization of Endogenous Protoporphyrin IX Induced by δ-Aminolevulinic Acid in Resting and Activated Peripheral Blood Lymphocytes by Four-Color Flow Cytometry

5-Aminolevulinic Acid as a Theranostic Agent for Tumor Fluorescence Imaging and Photodynamic Therapy

5-Aminolevulinic acid (ALA) is a naturally occurring amino acid synthesized in all nucleated mammalian cells. As a porphyrin precursor, ALA is metabolized in the heme biosynthetic pathway to produce protoporphyrin IX (PpIX), a fluorophore and photosensitizing agent. ALA administered exogenously bypasses the rate-limit step in the pathway, resulting in PpIX accumulation in tumor tissues. Such tumor-selective PpIX disposition following ALA administration has been exploited for tumor fluorescence diagnosis and photodynamic therapy (PDT) with much success. Five ALA-based drugs have now received worldwide approval and are being used for managing very common human (pre)cancerous diseases such as actinic keratosis and basal cell carcinoma or guiding the surgery of bladder cancer and high-grade gliomas, making it the most successful drug discovery and development endeavor in PDT and photodiagnosis. The potential of ALA-induced PpIX as a fluorescent theranostic agent is, however, yet to be fully fulfilled. In this review, we would like to describe the heme biosynthesis pathway in which PpIX is produced from ALA and its derivatives, summarize current clinical applications of ALA-based drugs, and discuss strategies for enhancing ALA-induced PpIX fluorescence and PDT response. Our goal is two-fold: to highlight the successes of ALA-based drugs in clinical practice, and to stimulate the multidisciplinary collaboration that has brought the current success and will continue to usher in more landmark advances.

5-aminolevulinic acid-mediated photodynamic therapy can target aggressive adult T cell leukemia/lymphoma resistant to conventional chemotherapy

Photodynamic therapy (PDT) is an emerging treatment for various solid cancers. We recently reported that tumor cell lines and patient specimens from adult T cell leukemia/lymphoma (ATL) are susceptible to specific cell death by visible light exposure after a short-term culture with 5-aminolevulinic acid, indicating that extracorporeal photopheresis could eradicate hematological tumor cells circulating in peripheral blood. As a bridge from basic research to clinical trial of PDT for hematological malignancies, we here examined the efficacy of ALA-PDT on various lymphoid malignancies with circulating tumor cells in peripheral blood. We also examined the effects of ALA-PDT on tumor cells before and after conventional chemotherapy. With 16 primary blood samples from 13 patients, we demonstrated that PDT efficiently killed tumor cells without influencing normal lymphocytes in aggressive diseases such as acute ATL. Importantly, PDT could eradicate acute ATL cells remaining after standard chemotherapy or anti-CCR4 antibody, suggesting that PDT could work together with other conventional therapies in a complementary manner. The responses of PDT on indolent tumor cells were various but were clearly depending on accumulation of protoporphyrin IX, which indicates the possibility of biomarker-guided application of PDT. These findings provide important information for developing novel therapeutic strategy for hematological malignancies.

Role of M1-polarized tumor-associated macrophages in the prognosis of advanced ovarian cancer patients

The identification of prognostic and predictive markers is crucial for choosing the most appropriate management method for ovarian cancer patients. We aimed to assess the prognostic role of tumor-associated macrophage (TAM) polarization in advanced ovarian cancer patients. We carried out a prospective observational study that included 140 consecutive patients with advanced-stage high-grade serous ovarian cancer as well as patients with other histotypes of ovarian cancer and patients with ovarian metastasis from other sites between June 2013 and December 2018. Patients were enrolled at the time of laparoscopic surgery before receiving any antineoplastic treatment. We found that patients with high-grade serous papillary ovarian cancers had a prevalence of M1 TAMs, a higher M1/M2 ratio, and a longer overall survival (OS) and progression-free survival (PFS) than other patients. Regression analysis confirmed that there was a significant positive association between the M1/M2 ratio and an improved OS, PFS and platinum-free interval (PFI), both in the entire population and in patients stratified according to tumor type and initial surgery. Kaplan-Meier analysis was performed after the patients were divided into 2 groups according to the median M1/M2 ratio and revealed that patients with a high M1/M2 ratio had a higher OS, PFS and PFI than those with a low M1/M2 ratio. In conclusion, the prognostic and predictive role of TAM polarization in the tumor microenvironment could be of great clinical relevance and may allow the early identification of patients who are likely to respond to therapy. Further studies in a larger prospective sample are warranted.

Selective Killing of Activated T Cells by 5-Aminolevulinic Acid Mediated Photodynamic Effect: Potential Improvement of Extracorporeal Photopheresis

Extracorporeal photopheresis (ECP), a modality that exposes isolated leukocytes to the photosensitizer 8-methoxypsoralen (8-MOP) and ultraviolet-A (UV-A) light, is used to treat conditions such as cutaneous T-cell lymphoma and graft-versus-host disease. However, the current procedure of ECP has limited selectivity and efficiency; and produces only partial response in the majority of treated patients. Additionally, the treatment is expensive and time-consuming, so the improvement for this modality is needed. In this study, we used the concept of photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA), a precursor of an endogenously synthesized photosensitizer protoporphyrin IX (PpIX) in combination with blue light to explore the possibility of targeting activated human blood T cells ex vivo. With various T-cell activation protocols, a high ALA-induced PpIX production took place in activated CD3⁺, CD4⁺CD25⁺, and CD8⁺ T cell populations with their subsequent killing after blue light exposure. By contrast, resting T cells were much less damaged by the treatment. The selective and effective killing effect on the activated cells was also seen after co-cultivating activated and resting T cells. Under our clinically relevant experimental conditions, ALA-PDT killed activated T cells more selectively and efficiently than 8-MOP/UV-A. Monocyte-derived dendritic cells (DCs) were not affected by the treatment. Incubation of ALA-PDT damaged T cells with autologous DCs induced a downregulation of the co-stimulatory molecules CD80/CD86 and also upregulation of interleukin 10 (IL-10) and indoleamine 2,3-dioxygenase expression, two immunosuppressive factors that may account for the generation of tolerogenic DCs. Overall, the data support the potential use of ALA-PDT strategy for improving ECP by selective and effective killing of activated T cells and induction of immune tolerance.

5-ALA-assistant automated detection of lymph node metastasis in gastric cancer patients

BACKGROUND

5-aminolevulinic acid (5-ALA) has been utilized for cancer diagnosis as a fluorescence probe. We have reported the feasibility of 5-ALA-induced protoporphyrin IX (PpIX) fluorescence for detecting lymph node (LN) metastasis in gastrointestinal malignancies. However, a major barrier to the fluorescence diagnosis has been that the evaluation has been highly dependent on the observers. In this study, we examined the validity of a developed device for automated detection without subjectivity.

METHODS

Gastric cancer patients who received oral administration of 5-ALA (20 mg/kg) prior to surgery were enrolled. For a total of 323 LNs obtained from 64 patients, the diagnostic results of the device were compared to those of conventional histopathological examination based on hematoxylin-and-eosin-stained slides. The accuracy with the device was compared to that of stereoscopic detection with conventional fluorescence microscopy for 211 LNs from 42 patients. We used two types of image processing that we previously developed to eliminate autofluorescence of background tissues: differential and ratio methods.

RESULTS

For detection of metastasis in 323 LNs, the areas under the receiver operating characteristic curves with the differential method and ratio method were 0.921 and 0.909, respectively. The sensitivity, specificity, and accuracy with the differential method were 78.0%, 96.8%, and 94.4%; while those with the ratio method were 78.0%, 96.1%, and 93.8%, respectively. In 211 LN analysis, the diagnostic accuracy with the device was comparable to that of stereoscopic examination.

CONCLUSION

Our device for automated detection of LN metastasis using 5-ALA can be a useful tool for intraoperative diagnosis.

Systemic MEK inhibition enhances the efficacy of 5-aminolevulinic acid-photodynamic therapy

BACKGROUND

Protoporphyrin IX (PpIX) gets accumulated preferentially in 5-aminolevulinic acid (5-ALA)-treated cancer cells. Photodynamic therapy (PDT) utilises the accumulated PpIX to trigger cell death by light-induced generation of reactive oxygen species (ROS). We previously demonstrated that oncogenic Ras/MEK decreases PpIX accumulation in cancer cells. Here, we investigated whether combined therapy with a MEK inhibitor would improve 5-ALA-PDT efficacy.

METHODS

Cancer cells and mice models of cancer were treated with 5-ALA-PDT, MEK inhibitor or both MEK inhibitor and 5-ALA-PDT, and treatment efficacies were evaluated.

RESULTS

Ras/MEK negatively regulates the cellular sensitivity to 5-ALA-PDT as cancer cells pre-treated with a MEK inhibitor were killed more efficiently by 5-ALA-PDT. MEK inhibition promoted 5-ALA-PDT-induced ROS generation and programmed cell death. Furthermore, the combination of 5-ALA-PDT and a systemic MEK inhibitor significantly suppressed tumour growth compared with either monotherapy in mouse models of cancer. Remarkably, 44% of mice bearing human colon tumours showed a complete response with the combined treatment.

CONCLUSION

We demonstrate a novel strategy to promote 5-ALA-PDT efficacy by targeting a cell signalling pathway regulating its sensitivity. This preclinical study provides a strong basis for utilising MEK inhibitors, which are approved for treating cancers, to enhance 5-ALA-PDT efficacy in the clinic.

Paracrine Wnt5a-β-Catenin Signaling Triggers a Metabolic Program that Drives Dendritic Cell Tolerization

Despite recent advances, many cancers remain refractory to available immunotherapeutic strategies. Emerging evidence indicates that the tolerization of local dendritic cells (DCs) within the tumor microenvironment promotes immune evasion. Here, we have described a mechanism by which melanomas establish a site of immune privilege via a paracrine Wnt5a-β-catenin-peroxisome proliferator-activated receptor-γ (PPAR-γ) signaling pathway that drives fatty acid oxidation (FAO) in DCs by upregulating the expression of the carnitine palmitoyltransferase-1A (CPT1A) fatty acid transporter. This FAO shift increased the protoporphyrin IX prosthetic group of indoleamine 2,3-dioxgenase-1 (IDO) while suppressing interleukin(IL)-6 and IL-12 cytokine expression, culminating in enhanced IDO activity and the generation of regulatory T cells. We demonstrated that blockade of this pathway augmented anti-melanoma immunity, enhanced the activity of anti-PD-1 antibody immunotherapy, and suppressed disease progression in a transgenic melanoma model. This work implicates a role for tumor-mediated metabolic reprogramming of local DCs in immune evasion and immunotherapy resistance.

Revisiting photodynamic therapy dosimetry: reductionist & surrogate approaches to facilitate clinical success

Photodynamic therapy (PDT) can be a highly complex treatment, with many parameters influencing treatment efficacy. The extent to which dosimetry is used to monitor and standardize treatment delivery varies widely, ranging from measurement of a single surrogate marker to comprehensive approaches that aim to measure or estimate as many relevant parameters as possible. Today, most clinical PDT treatments are still administered with little more than application of a prescribed drug dose and timed light delivery, and thus the role of patient-specific dosimetry has not reached widespread clinical adoption. This disconnect is at least partly due to the inherent conflict between the need to measure and understand multiple parameters in vivo in order to optimize treatment, and the need for expedience in the clinic and in the regulatory and commercialization process. Thus, a methodical approach to selecting primary dosimetry metrics is required at each stage of translation of a treatment procedure, moving from complex measurements to understand PDT mechanisms in pre-clinical and early phase I trials, towards the identification and application of essential dose-limiting and/or surrogate measurements in phase II/III trials. If successful, identifying the essential and/or reliable surrogate dosimetry measurements should help facilitate increased adoption of clinical PDT. In this paper, examples of essential dosimetry points and surrogate dosimetry tools that may be implemented in phase II/III trials are discussed. For example, the treatment efficacy as limited by light penetration in interstitial PDT may be predicted by the amount of contrast uptake in CT, and so this could be utilized as a surrogate dosimetry measurement to prescribe light doses based upon pre-treatment contrast. Success of clinical ALA-based skin lesion treatment is predicted almost uniquely by the explicit or implicit measurements of photosensitizer and photobleaching, yet the individualization of treatment based upon each patients measured bleaching needs to be attempted. In the case of ALA, lack of PpIX is more likely an indicator that alternative PpIX production methods must be implemented. Parsimonious dosimetry, using surrogate measurements that are clinically acceptable, might strategically help to advance PDT in a medical world that is increasingly cost and time sensitive. Careful attention to methodologies that can identify and advance the most critical dosimetric measurements, either direct or surrogate, are needed to ensure successful incorporation of PDT into niche clinical procedures.

Alopecia areata: an evidence-based treatment update

BACKGROUND

There is no cure for alopecia areata, nor is there any universally proven therapy that induces and sustains remission. Treatment choices are frequently based on disease duration, extent, and activity as well as the age of the patient.

OBJECTIVE

Our objective was to review all randomized controlled studies on the treatment of alopecia areata.

METHODS

We performed a search in the biomedical literature database PubMed, and used the terms 'alopecia areata treatment' and article type 'randomized controlled trials'.

RESULTS

Following this algorithm, we reviewed, analyzed, and reported on 29 trials that examined the efficacy of anthralin, antidepressants, biologics, calcineurin inhibitors, corticosteroids (topical and systemic), minoxidil, prostaglandin analogs, sensitizers, and a miscellaneous group of topical and oral drugs with less scientific evidence (aromatherapy, photodynamic therapy, azelaic acid, garlic gel, bexarotene, triiodothyronine, inosiplex, and total glucosides of paeony).

CONCLUSION

Using the American College of Physicians Guideline grading system, our assessment is that the majority of published randomized controlled studies of alopecia areata are only of moderate quality. A number of treatments were found to be effective, for example, topical and oral corticosteroids and the sensitizing agents diphenylcyclopropenone and dinitrochlorobenzene; however, most studies had major limitations that hinder the interpretation of these results.

Modification of extracorporeal photopheresis technology with porphyrin precursors. Comparison between 8-methoxypsoralen and hexaminolevulinate in killing human T-cell lymphoma cell lines in vitro

BACKGROUND

Extracorporeal photopheresis that exposes isolated white blood cells to 8-methoxypsoralen (8-MOP) and ultraviolet-A (UV-A) light is used for the management of cutaneous T-cell lymphoma and graft-versus-host disease. 8-MOP binds to DNA of both tumor and normal cells, thus increasing the risk of carcinogenesis of normal cells; and also kills both tumor and normal cells with no selectivity after UV-A irradiation. Hexaminolevulinate (HAL)-induced protoporphyrin-IX is a potent photosensitizer that localizes at membranous structures outside of the nucleus of a cell. HAL-mediated photodynamic therapy selectively destroys activated/transformed lymphocytes and induces systemic anti-tumor immunity. The aim of the present study was to explore the possibility of using HAL instead of 8-MOP to kill cells after UV-A exposure.

METHODS

Human T-cell lymphoma Jurkat and Karpas 299 cell lines were used to evaluate cell photoinactivation after 8-MOP and/or HAL plus UV-A light with cell proliferation and long term survival assays. The mode of cell death was also analyzed by fluorescence microscopy.

RESULTS

Cell proliferation was decreased by HAL/UV-A, 8-MOP/UV-A or HAL/8-MOP/UV-A. At sufficient doses, the cells were killed by all the regimens; however, the mode of cell death was dependent on the treatment conditions. 8-MOP/UV-A produced apoptotic death exclusively; whereas both apoptosis and necrosis were induced by HAL/UV-A.

CONCLUSION

8-MOP can be replaced by HAL to inactivate the Jurkat and Karpas 299 T-cell lymphoma cells after UV-A irradiation via apoptosis and necrosis. This finding may have an impact on improved efficacy of photopheresis.

Detection of lymph node metastases in human colorectal cancer by using 5-aminolevulinic acid-induced protoporphyrin IX fluorescence with spectral unmixing

Accurate evaluation of metastatic lymph nodes (LNs) is indispensable for adequate treatment of colorectal cancer (CRC) patients. Here, we demonstrate detection of metastases of human CRC in removed fresh LNs using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence. A spectral unmixing method was employed to reduce the overlap of collagen autofluorescence on PpIX fluorescence. A total of 17 surgery patients with advanced CRC were included in this study. After 5-ALA at a dose of 15 mg/kg of body weight was applied orally 2 h prior to surgery, 87 LNs were subjected to spectral fluorescence imaging and histopathological diagnosis, and statistical analysis was performed. No apparent side effect was observed to be associated with 5-ALA administration. The spectral unmixing fluorescence intensity of PpIX in metastatic LNs was 10.2-fold greater than that in nonmetastaic LNs. The receiver-operating-characteristic (ROC) analysis showed that the area under the curve (AUC) was calculated as 0.95. Our results show the potential of 5-ALA-induced PpIX fluorescence processed by spectral unmixing for detecting metastases in excised fresh LNs from patients with CRC, suggesting that this rapid and feasible method is applicable to gross evaluation of resected LN samples in pathology laboratories.

Detection of metastatic lymph nodes using 5-aminolevulinic acid in patients with gastric cancer

BACKGROUND

Precise diagnosis of lymph node metastases is essential to select therapeutic strategy for patients with gastric cancer, and rapid intraoperative diagnosis is useful for performing less invasive surgery. In this study, we focused on a known photosensitizer, 5-aminolevulinic acid (5-ALA), and examined the feasibility of 5-ALA-induced protoporphyrin IX (PpIX) fluorescence to detect metastatic foci in excised lymph nodes of patients with gastric cancer.

METHODS

A total of 144 lymph nodes obtained from 14 gastric cancer patients were examined. The patients were administered 5-ALA orally before surgery. Excised lymph nodes were cut in half and observed by fluorescence microscopy. The diagnostic results were compared to those of the routine histopathological examination.

RESULTS

Observed red fluorescence of PpIX was identical to the metastatic focus, with 84 % accuracy. Twelve non-metastatic lymph nodes showed unexpected PpIX accumulation to lymphoid follicles, but these could be discriminated based on their characteristic fluorescence patterns. With incorporation of this morphological consideration, this method demonstrated good diagnostic power with 92.4 % accuracy. On the quantitative analysis using the signal intensity ratio of red to the sum of red, green, and blue (R/(R + G + B) ratio) as an index corresponding to red fluorescence of PpIX, metastatic lymph nodes showed significantly higher value than non-metastatic lymph nodes (p < 0.0001). The area under the curve was calculated as 0.832 throughout Receiver operating characteristic analysis.

CONCLUSIONS

Our results demonstrated that 5-ALA-induced fluorescence diagnosis is a simple and safe method and is a potential candidate for a novel rapid intraoperative diagnostic method applicable to clinical practice.

[Accumulation of porphyrins in cells of system of blood induced by 5-aminolaevulinic acid]

The levels and rates of accumulation of porphyrins in lymphoid cells and bone marrow cells treated with exogenous 5-aminolaevulinic acid (ALA) were studied. The dependence of the quantity of porphyrins accumulated in cell on ALA concentrations in the medium had maximum at 0.7-1.0 mM ALA for all the cell types studied (splenocytes, thymocytes, peripheral blood lymphocytes and bone marrow cells). The rate of accumulation of uro-, copro- and protoporphyrins depended on cell types. The lowest and the highest levels were found in splenocytes and highest in bone marrow cells respectively. It is suggested that photodynamic therapy employing ALA is potentially dangerous for blood cells.

PDT-induced inflammatory and host responses

Photodynamic therapy (PDT) is used in the management of neoplastic and nonmalignant diseases. Its unique mechanisms of action include direct cytotoxic effects exerted towards tumor cells, destruction of tumor and peritumoral vasculature and induction of local acute inflammatory reaction. The latter develops in response to (1) damage to tumor and stromal cells that leads to the release of cell death-associated molecular patterns (CDAMs) or damage associated molecular patterns (DAMPs), (2) early vascular changes that include increased vascular permeability, vascular occlusion, and release of vasoactive and proinflammatory mediators, (3) activation of alternative pathway of complement leading to generation of potent chemotactic factors, and (4) induction of signaling cascades and transcription factors that trigger secretion of cytokines, matrix metalloproteinases, or adhesion molecules. The majority of studies indicate that induction of local inflammatory response contributes to the antitumor effects of PDT and facilitates development of systemic immunity. However, the degree of PDT-induced inflammation and its subsequent contribution to its antitumor efficacy depend on multiple parameters, such as chemical nature, concentration and subcellular localization of the photosensitizers, the spectral characteristics of the light source, light fluence and fluence rate, oxygenation level, and tumor type. Identification of detailed molecular mechanisms and development of therapeutic approaches modulating PDT-induced inflammation will be necessary to tailor this treatment to particular clinical conditions.

Cellular and Antitumor Activity of a New Diethylene Glycol Benzoporphyrin Derivative (Lemuteporfin)†

A newly synthesized diethylene glycol functionalized chlorin-type photosensitizer, lemuteporfin, was characterized for use in photodynamic therapy (PDT) in a panel of in vitro and in vivo test systems. The photosensitizer was highly potent, killing cells at low nanomolar concentrations upon exposure to activating light. The cellular uptake of lemuteporfin was rapid, with maximum levels reached within 20 min. Mitogen-activated lymphoid cells accumulated more of the lemuteporfin than their quiescent equivalents, supporting selectivity. Photosensitizer fluorescence in the skin increased rapidly within the first few minutes following intravenous administration to mice, then decreased over the next 24 h. Skin photosensitivity reactions indicated rapid clearance of the photosensitizer. Intravenous doses as low as 1.4 micromol/kg combined with exposure to 50 J/cm2 red light suppressed tumor growth in a mouse model. In conclusion, this new benzoporphyrin was found to be an effective photosensitizer, showing rapid uptake and clearance both in vitro and in vivo. This rapid photosensitization of tumors could be useful in therapies requiring a potent, rapidly accumulating photosensitizer, while minimizing the potential for skin photosensitivity reactions to sunlight following treatment.

Influence of 5-aminolevulinic acid and red light on collagen metabolism of human dermal fibroblasts

Patients with localized scleroderma receiving topical photodynamic therapy with 5-aminolevulinic acid show a reduction in skin tightness, suggesting that this therapy reduces skin sclerosis. To investigate potential mechanisms, the effects of 5-aminolevulinic acid and light on collagen metabolism were studied in vitro. Normal and scleroderma fibroblasts were treated with sublethal doses of 5-aminolevulinic acid and red light and transferred to three-dimensional collagen lattices. Cell supernatants were taken 6-72 h after photodynamic therapy to determine protein levels of the matrix metalloproteinases 1, 2, and 3, and of their inhibitors, tissue inhibitor of metalloproteinase 1 and 2 by enzyme-linked immunosorbent assay. Cellular mRNA expression of these proteins and of collagen type I and III was measured by quantitative real-time polymerase chain reaction. A significant, time-dependent induction of matrix metalloproteinase 1 (up to 2.4-fold after 48 h) and matrix metalloproteinase 3 (up to 4.3-fold after 48 h) protein levels was seen after 5-aminolevulinic acid-photodynamic therapy. Irradiation with ultraviolet A light, used as a positive control, showed a similar induction of matrix metalloproteinase 1 (2.3-fold after 48 h). The mRNA levels of matrix metalloproteinase 1 and matrix metalloproteinase 3 were significantly increased 12 h after irradiation, whereas collagen type I mRNA was strongly decreased already 6 h following irradiation. Collagen type III, tissue inhibitor of metalloproteinase 1, and matrix metalloproteinase 2 did not change after photodynamic therapy. Addition of nontoxic concentrations of sodium azide, a singlet-oxygen quencher, significantly inhibited induction of matrix metalloproteinase 1 by 5-aminolevulinic acid and light. These data show that 5-aminolevulinic acid and light induce matrix metalloproteinase 1 and matrix metalloproteinase 3 expression in normal and scleroderma fibroblasts in a singlet oxygen-dependent way while reducing collagen type I mRNA expression. Induction of collagen-degrading enzymes together with reduction of collagen production might be responsible for the anti-sclerotic effects of 5-aminolevulinic acid-photodynamic therapy observed in vivo.

Oral aminolevulinic acid induces protoporphyrin IX fluorescence in psoriatic plaques and peripheral blood cells

Photodynamic therapy (PDT) with topical aminolevulinic acid (ALA) has been shown in previous studies to improve psoriasis. However, topical ALA-PDT may not be practical for the treatment of extensive disease. In order to overcome this limitation we have explored the potential use of oral ALA administration in psoriatic patients. Twelve patients with plaque psoriasis received a single oral ALA dose of 10, 20 or 30 mg/kg followed by measurement of protoporphyrin IX (PpIX) fluorescence in the skin and circulating blood cells. Skin PpIX levels were determined over time after ALA administration by the quantification of the 635 nm PpIX emission peak with in vivo fluorescence spectroscopy under 442 nm laser excitation. Administration of ALA at 20 and 30 mg/kg induced preferential accumulation of PpIX in psoriatic as opposed to adjacent normal skin. Peak fluorescence intensity in psoriatic and normal skin occurred between 3 and 5 h after the administration of 20 and 30 mg/kg, respectively. Ratios of up to 10 for PpIX fluorescence between psoriatic versus normal skin were obtained at the 30 mg/kg dose of ALA. Visible PpIX fluorescence was also observed on normal facial skin, and nonspecific skin photosensitivity occurred only in patients who received the 20 or 30 mg/kg doses. PpIX fluorescence intensity was measured in circulating blood cells by flow cytometry. PpIX fluorescence was higher in monocytes and neutrophils as compared to CD4+ and CD8+ T lymphocytes. PpIX levels in these cells were higher in patients who received higher ALA doses and peaked between 4 and 8 h after administration of ALA. There was only a modest increase in PpIX levels in circulating CD4+ and CD8+ T lymphocytes. In conclusion oral administration of ALA induced preferential accumulation of PpIX in psoriatic plaques as compared to adjacent normal skin suggesting that PDT with oral ALA should be further explored for the treatment of psoriasis.

Cell-type specific protoporphyrin IX metabolism in human bladder cancer in vitro

5-Aminolevulinic acid (ALA)-supported fluorescence endoscopy of the urinary bladder results in a detection rate of bladder cancer superior to that of white light endoscopy. The different accumulation of the metabolite protoporphyrin IX (PPIX) in tumor cells after ALA instillation is poorly understood; however, it is crucial to optimize diagnosis and potential phototherapy. For systematic analysis of cell-type specific PPIX accumulation and metabolism two human bladder carcinoma cell lines (RT4 and J82), a normal urothelial cell line (UROtsa), and a fibroblast cell line (N1) were chosen, and grown in two different growth states to model important tissue components of the urinary bladder, i.e. tumor, normal epithelium and stroma. To quantitate PPIX content, fluorescence intensities measured by flow cytometry were matched with cellular PPIX extraction values, and related to relative ferrochelatase activity, cellular iron content, number of transferrin receptors per cell and porphobilinogen deaminase (PBGD) activity. For in vitro experiments, the initial correlation of relative flow cytometric and spectrometric measurements of PPIX provides a calibration curve for consequent flow cytometric PPIX quantification. Lower fluorescence of normal cells could be explained by significant differences of ferrochelatase activity and iron content in comparison to tumor cells. However, the content of iron was not related to transferrin receptor content. PBGD activity seemed to play a minor role for the differential accumulation of PPIX in urothelial cells. In conclusion, the in vitro culture of urothelial cells and fibroblasts indicates that the most important metabolic step for PPIX accumulation in the urinary bladder is the transition from PPIX to heme. Further investigation of PPIX metabolism does support the validation of photodynamic diagnosis, and might also lead the way to a highly specific tumor related molecule.

Influence of photodynamic therapy on immunological aspects of disease - an update

Photodynamic therapy (PDT) utilises light-absorbing compounds combined with directed photo-irradiation to produce clinical effects. This review updates advances in the understanding of the biochemical pathways triggered by PDT within cells, its influence upon different immune parameters and progress in the use of PDT against human immune-mediated disease. Several works have further defined the notable capacity of PDT to foster anticancer immunity.

The iron regulatory protein can determine the effectiveness of 5-aminolevulinic acid in inducing protoporphyrin IX in human primary skin fibroblasts

The level of endogenous photosensitiser, protoporphyrin IX (PPIX), can be enhanced in the cells by 5-aminolevulinic acid (ALA). We investigated the effect of critical parameters such as growth state of the cells and availability of intracellular iron in modulating the level of PPIX, in human primary cultured skin fibroblasts (FEK4) maintained either in exponentially growing or growth-arrested phase, following treatment with ALA. The addition of ALA to exponentially growing cells increased the level of PPIX 6-fold relative to control cells; however, in growth-arrested cells the same treatment increased the level of PPIX up to 34-fold. The simultaneous addition of the hydrophilic iron-chelator Desferal with ALA, boosted the level of PPIX up to 47-fold in growing cells and up to 42-fold in growth-arrested cells, suggesting that iron is limiting under the latter conditions. The strict dependence of PPIX enhancement on free available iron levels was examined by the level of activation of iron regulatory protein in band shift assays. This analysis revealed that the basal level of iron regulatory protein in growth-arrested cells was 6-fold higher than in growing cells, reflecting the influence of the free available iron pool in exponentially growing cells. Interestingly, the same ratio was found between the basal level concentration of PPIX in growing and growth-arrested cells. We propose that iron regulatory protein activation could serve as a marker for developing photodynamic therapy protocols because it identifies cells and tissues with a propensity to accumulate PPIX and it is therefore likely to predict the effectiveness of such therapies.

UVA1 radiation triggers two different final apoptotic pathways

Because ultraviolet-A1 (UVA1; 340-400 nm) radiation is used therapeutically, this in vitro study addressed the question "how does it work?" To begin addressing this question, UVA1 radiation was first established to reduce the survival of transformed T and B lymphocytes in a linear dose-dependent manner using clonogenic reproductive assays, and that cell death occurs by apoptosis using transmission electron microscopy, Annexin V, and flow cytometry. The primary mechanism was determined to be immediate pre-programmed cell death, an apoptotic mechanism that does not require protein synthesis post-insult, by quantifying the apoptotic cells over time in the absence or presence of a translation inhibitor. To explore how UVA1 radiation induces immediate pre-programmed cell death apoptosis, reactive oxygen species and mitochondrial activity were altered during exposure using a variety of agents, while a specific fluorescent probe, 5,5',6,6'tetrachloro- 1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide, was used to examine mitochondrial transmembrane depolarization. To show that UVA1 mediates singlet-oxygen damage to the mitochondrial membranes, X-rays, UVB (290-320 nm), 8-methoxypsoralen and UVA, vitamin K3, anti-Fas antibody, and blocking antibody were the negative controls, while rose bengal or protoporphyrin IX with visible light were the positive controls. Cyclosporine A, which inhibits the mitochondrial megapore from opening, was used with singlet-oxygen and superoxide-anion generators to distinguish between the two final apoptotic pathways. The collective results show that UVA1 radiation primarily mediates singlet-oxygen damage triggering immediate pre-programmed cell death apoptosis (T < 20 min) by immediately opening the cyclosporine A-sensitive ("S" site) mitochondrial megapore, while superoxide anions initiate another cyclosporine A-insensitive ("P" site) final apoptotic pathway.

Consequences of the photodynamic treatment of resting and activated peripheral T lymphocytes

The impact of the immunomodulatory photosensitizer benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) and visible light on the survival and surface receptor pattern of resting and activated murine T cells was evaluated. T cells treated for 48 h with immobilized anti-CD3 monoclonal antibody upregulated expression of the interleukin-2 receptor alpha-chain (CD25), transferrin receptor (CD71), the apoptosis-regulating Fas receptor (CD95), contained a greater level of the anti-apoptotic protein Bcl-2 and accumulated significantly more BPD-MA than their unactivated counterparts. Activated T cells displayed a modestly greater susceptibility to the photodynamic induction of DNA fragmentation than resting T cells. Resting T cells treated with sub-lethal levels of BPD-MA and light did not exhibit changes in surface levels of CD3, CD4, CD8, CD28, CD45 or T cell receptor (TCR) beta-chain structures. However, levels of major histocompatibility complex (MHC) class I antigens were decreased while the density of Thy-1.2 (CD90) increased on these cells. Photodynamically treated T cells failed to express optimal CD25 levels when exposed to the mitogenic anti-CD3 antibody. Activated T cells treated with sub-lethal levels of BPD-MA and light exhibited lower CD25 levels, a temporary block in cell cycle transition, but unaltered expression of MHC Class I, CD3, CD4, CD8, CD45, CD54, CD71, CD122 (IL-2R beta-chain) or TCR beta-chain antigens 24 h afterward. Resting and activated T lymphocytes differ in susceptibility to PDT-mediated apoptosis but both types are sensitive to anti-proliferative effects the treatment exerts at sub-lethal photosensitizer levels. The marked sensitivity of activated T cells to photodynamic inactivation likely contributes to the immunomodulatory action of BPD-MA.

Antigen specific and nonspecific modulation of the immune response by aminolevulinic acid based photodynamic therapy

Photosensitizers used normally in treating cancers have considerable potential for treatment of other diseases. One such photosensitizer is the endogenously synthesized photosensitizer protoporphyrin IX (PpIX). To better understand how protoporphyrin might be used in transplantation or in treating autoimmune diseases, information must be obtained on how the photosensitizer affects all immune cells. We used a combination of flow cytometry and in vitro activation assays (recall assays and mixed-lymphocyte reactions) to examine the effects of PpIX on the antigen specific component, lymphocytes and the non-antigen specific component, the macrophages/monocytes and dendritic cells of the immune system. Whereas, lymphocytes accumulate PpIX only when activated, both macrophages and dendritic cells accumulated PpIX immediately, without in vitro activation, as measured by flow cytometry. ALA-PDT (aminolevulenic acid-photodynamic therapy) treated adherent cells in the recall assay had a decreased capability to activate lymphocytes. By increasing the light dose in the recall assay, antigen primed lymphocytes were selectively eliminated from a population of cells. Stimulator cells in an MLR had a decreased stimulatory capacity following ALA-PDT treatment. Functional alterations are seen in both the antigen specific