Is delta-aminolevulinic acid dehydratase rate limiting in heme biosynthesis following exposure of cells to delta-aminolevulinic acid?

Metabolic comparison of aerial and submerged mycelia formed in the liquid surface culture of Cordyceps militaris

An entomopathogenic fungus, Cordyceps sp. has been known to produce cordycepin which is a purine nucleoside antimetabolite and antibiotic with potential anticancer, antioxidant and anti-inflammatory activities. Interestingly, Cordyceps militaris produces significantly higher amount in a liquid surface culture than in a submerged culture. The liquid surface culture consists of mycelia growing into the air (aerial mycelia) and mycelia growing toward the bottom into the medium (submerged mycelia). In this study, to clarify roles of aerial and submerged mycelia of C. militaris in the cordycepin production the difference in metabolism between these mycelia was investigated. From transcriptomic analyses of the aerial and submerged mycelia at the culture of 5, 12 and 19 days, the metabolism of the submerged mycelia switched from the oxidative phosphorylation to the fermentation pathway. This activated the pentose phosphate pathway to provide building block materials for the nucleotide biosynthetic pathway. Under hypoxic conditions, the 5-aminolevulinic acid synthase (CCM_01504), delta-aminolevulinic acid dehydratase (CCM_00935), coproporphyrinogen III oxidase (CCM_07483) and cytochrome c oxidase 15 (CCM_05057) genes of heme biosynthesis were significantly upregulated. In addition, the liquid surface culture revealed that metabolite coproporhyrinogen III and glycine, the product and precursor of heme, were increased at 12th day and decreased at 19th day, respectively. These results indicate that the submerged mycelia induce the activation of iron acquisition, the ergosterol biosynthetic pathway, and the iron cluster genes of cordycepin biosynthesis in a hypoxic condition. Even though, the expression of the cluster genes of cordycepin biosynthesis was not significantly different in both types of mycelia.

Semi-Automated Volumetric and Morphological Assessment of Glioblastoma Resection with Fluorescence-Guided Surgery

PURPOSE

Glioblastoma (GBM) neurosurgical resection relies on contrast-enhanced MRI-based neuronavigation. However, it is well-known that infiltrating tumor extends beyond contrast enhancement. Fluorescence-guided surgery (FGS) using 5-aminolevulinic acid (5-ALA) was evaluated to improve extent of resection (EOR) of GBMs. Preoperative morphological tumor metrics were also assessed.

PROCEDURES

Thirty patients from a phase II trial evaluating 5-ALA FGS in newly diagnosed GBM were assessed. Tumors were segmented preoperatively to assess morphological features as well as postoperatively to evaluate EOR and residual tumor volume (RTV).

RESULTS

Median EOR and RTV were 94.3 % and 0.821 cm(3), respectively. Preoperative surface area to volume ratio and RTV were significantly associated with overall survival, even when controlling for the known survival confounders.

CONCLUSIONS

This study supports claims that 5-ALA FGS is helpful at decreasing tumor burden and prolonging survival in GBM. Moreover, morphological indices are shown to impact both resection and patient survival.

Photosensitization in Porphyrias and Photodynamic Therapy Involves TRPA1 and TRPV1

Photosensitization, an exaggerated sensitivity to harmless light, occurs genetically in rare diseases, such as porphyrias, and in photodynamic therapy where short-term toxicity is intended. A common feature is the experience of pain from bright light. In human subjects, skin exposure to 405 nm light induced moderate pain, which was intensified by pretreatment with aminolevulinic acid. In heterologous expression systems and cultured sensory neurons, exposure to blue light activated TRPA1 and, to a lesser extent, TRPV1 channels in the absence of additional photosensitization. Pretreatment with aminolevulinic acid or with protoporphyrin IX dramatically increased the light sensitivity of both TRPA1 and TRPV1 via generation of reactive oxygen species. Artificial lipid bilayers equipped with purified human TRPA1 showed substantial single-channel activity only in the presence of protoporphyrin IX and blue light. Photosensitivity and photosensitization could be demonstrated in freshly isolated mouse tissues and led to TRP channel-dependent release of proinflammatory neuropeptides upon illumination. With antagonists in clinical development, these findings may help to alleviate pain during photodynamic therapy and also allow for disease modification in porphyria patients.

SIGNIFICANCE STATEMENT

Cutaneous porphyria patients suffer from burning pain upon exposure to sunlight and other patients undergoing photodynamic therapy experience similar pain, which can limit the therapeutic efforts. This study elucidates the underlying molecular transduction mechanism and identifies potential targets of therapy. Ultraviolet and blue light generates singlet oxygen, which oxidizes and activates the ion channels TRPA1 and TRPV1. The disease and the therapeutic options could be reproduced in models ranging from isolated ion channels to human subjects, applying protoporphyrin IX or its precursor aminolevulinic acid. There is an unmet medical need, and our results suggest a therapeutic use of the pertinent antagonists in clinical development.

Selective 5-aminolevulinic acid-induced protoporphyrin IX fluorescence in Gliomas

Malignant gliomas are locally invasive tumors that offer a poor prognosis. Evidence shows that complete resection of the tumor at the time of surgery confers a significant improvement in overall survival. In recent years, 5- aminolevulinic acid (ALA)-induced fluorescence has been used by neurosurgeons to good effect in increasing the rate of complete resection. Despite the considerable interest in the use of 5-ALA in fluorescence-guided neurosurgery, the mechanisms behind the accumulation of Protoporphyrin IX (PpIX) in neoplastic tissue are unclear. In this review, we summarize the evidence in the literature on the mechanisms underlying the selective production of PpIX with a specific focus on gliomas.

Hiding in the Shadows: CPOX Expression and 5-ALA Induced Fluorescence in Human Glioma Cells

Protoporphyrin IX (PpIX) is widely used in photodynamic diagnosis. To date, the details of molecular mechanisms underlying PpIX accumulation in malignant cells after 5-ALA administration remain unclear. The fluorescence of PpIX was studied in human glioma cells. Several cell cultures were established from glioma tumor tissue to study the differences between fluorescence-positive and fluorescence-negative human glioma tumors. The cell cultures demonstrated fluorescence profiles similar to those of source tumor tissues, which allows us to use these cultures in experimental research. Dynamics of the rates of synthesis and degradation of fluorescent protoporphyrin IX was studied in the cultures obtained. In addition, the expression of CPOX, an enzyme involved in PpIX synthesis, was evaluated. mRNA levels of heme biosynthesis enzymes were analyzed, and PpIX fluorescence proved to correlate with the CPOX protein level, whereas no such correlation was observed at the mRNA level. Fluorescence intensity decreased at low levels of the enzyme, which indicates its critical role in PpIX fluorescence. Finally, the fluorescence intensity proved to correlate with the proliferative activity.

Kinetic Evaluation of Determinant Factors for Cellular Accumulation of Protoporphyrin IX Induced by External 5-Aminolevulinic Acid for Photodynamic Cancer Therapy

Five-aminolevulinic acid (ALA) is a prodrug to generate phototoxic protoporphyrin IX (PPIX) for photodynamic cancer therapy. It remains unclear how PPIX accumulates in cancer cells; therefore, we aimed to clarify determinant factors by assessing ALA uptake, PPIX biosynthesis, conversion of PPIX to heme (ferrochelatase activity), and PPIX efflux, independently, in 10 human cancer cell lines. ALA-induced PPIX accumulation was not correlated with ALA uptake clearance. ALA uptake rates were far greater than maximum conversion rates of ALA to PPIX in the five cell lines, where ALA uptake activity was detected. A negative correlation of PPIX accumulation with ferrochelatase activity was found, but not statistically significant among all cell lines. As PPIX accumulation was restored in MCF-7 and DU145 cells by adding an inhibitor of PPIX efflux transporter BCRP, a compartment model incorporating PPIX synthesis, ferrochelatase activity, and PPIX efflux, was established, and hybrid parameters (π index) calculated using the model were significantly correlated with ALA-induced PPIX accumulation (r = 0.90, p = 0.005). Accordingly, kinetic analyses indicate that ALA-induced PPIX levels are determined by the three processes of PPIX biosynthesis, conversion of PPIX to heme, and PPIX efflux, suggesting that π index is a useful to predict ALA-induced PPIX accumulation.

Preclinical characterization of 5-amino-4-oxo-[6-11C]hexanoic acid as an imaging probe to estimate protoporphyrin IX accumulation induced by exogenous aminolevulinic acid

Preoperative noninvasive imaging to estimate the quantity and spatial distribution of protoporphyrin IX (PpIX) accumulation in tumors induced by 5-aminolevulinic acid (ALA) administration is expected to improve the efficacy of ALA-based fluorescence-guided resection and photo- and sonodynamic therapies. PpIX synthesis from exogenous ALA has been reported to be regulated by ALA influx or ALA dehydratase (ALAD) activity, which catalyzes the first step of the synthesis. In this study, we characterized the properties of a (11)C-labeled ALA analog, 5-amino-4-oxo-[6-(11)C]hexanoic acid ((11)C-MALA), as a PET tracer to estimate PpIX accumulation.

METHODS

In vitro uptake of (11)C-MALA and (3)H-ALA was determined in 5 tumor cell lines after 10-min incubation with each tracer at 37°C. The expression levels of ALAD were determined by Western blot analysis. In vivo distribution and dynamic PET studies were conducted in tumor-bearing mice. In vitro and in vivo accumulation of ALA-induced PpIX was determined by measuring fluorescence in extracts of cells or tumors.

RESULTS

In vitro uptake of (11)C-MALA in 5 tumor cell lines was correlated with ALAD expression levels and PpIX accumulation. In vivo biodistribution and dynamic PET studies showed that (11)C-MALA was rapidly incorporated into tumors, and the tumor-to-muscle ratio of (11)C-MALA at 1 min after injection was significantly correlated with that of (3)H-ALA. (11)C-MALA in tumors was continuously decreased thereafter, and the elimination rate of (11)C-MALA from AsPC-1 tumors with the highest ALAD expression level was slower than from other tumors with lower expression levels. These results suggest that the influx and intracellular retention of (11)C-MALA reflect ALA influx and ALAD expression levels, respectively. Tumor accumulation of (11)C-MALA at 60 min after injection was strongly correlated with PpIX accumulation in tumor tissues.

CONCLUSION

(11)C-MALA PET has the potential to noninvasively estimate the quantitative and spatial accumulation of exogenous ALA-induced PpIX.

Vitamin D3 enhances the apoptotic response of epithelial tumors to aminolevulinate-based photodynamic therapy

Photodynamic therapy, mediated by exogenously administered aminolevulinic acid (ALA-PDT), followed by exposure to a laser or broadband light source, is a promising modality for treatment of many types of cancers; however, it remains inadequate to treat large, deep, solid tumors. In this article, we report that calcitriol, the active form of vitamin D3, can be administered before ALA as a nontoxic preconditioning regimen to markedly increase the efficacy of ALA-PDT. Using mouse models of squamous cell skin cancer for preclinical proof of concept, we showed that calcitriol, delivered topically or intraperitoneally, increased tumoral accumulation of the PDT-activated ALA product protoporphyrin-IX (PpIX) up to 10-fold, mainly by altering expression of the porphyrin-synthesis enzymes coproporphyrinogen oxidase (increased) and ferrochelatase (decreased). Calcitriol-pretreated tumors underwent enhanced apoptotic cell death after ALA-based PDT. Mechanistic studies have documented activation of the extrinsic apoptotic pathway, with specific cleavage of caspase-8 and increased production of TNF-α in tumors preconditioned by calcitriol treatment before receiving ALA-PDT. Very low doses of calcitriol (0.1-1 μg/kg body weight) were sufficient to elicit tumor-selective enhancement to ALA-PDT efficacy, rendering toxicity concerns negligible. Our findings define a simple, nontoxic, and highly effective preconditioning regimen to enhance the response of epithelial tumors to ALA-PDT, possibly broadening its clinical applications by selectively enhancing accumulation of photosensitizer PpIX together with TNF-α in tumors.

Serum-dependent export of protoporphyrin IX by ATP-binding cassette transporter G2 in T24 cells

Accumulation of protoporphyrin IX (PpIX) in cancer cells is a basis of 5-aminolevulinic acid (ALA)-induced photodymanic therapy. We studied factors that affect PpIX accumulation in human urothelial carcinoma cell line T24, with particular emphasis on ATP-binding cassette transporter G2 (ABCG2) and serum in the medium. When the medium had no fetal bovine serum (FBS), ALA induced PpIX accumulation in a time- and ALA concentration-dependent manner. Inhibition of heme-synthesizing enzyme, ferrochelatase, by nitric oxide donor (Noc18) or deferoxamine resulted in a substantial increase in the cellular PpIX accumulation, whereas ABCG2 inhibition by fumitremorgin C or verapamil induced a slight PpIX increase. When the medium was added with FBS, cellular accumulation of PpIX stopped at a lower level with an increase of PpIX in the medium, which suggested PpIX efflux. ABCG2 inhibitors restored the cellular PpIX level to that of FBS(-) samples, whereas ferrochelatase inhibitors had little effects. Bovine serum albumin showed similar effects to FBS. Fluorescence microscopic observation revealed that inhibitors of ABC transporter affected the intracellular distribution of PpIX. These results indicated that ABCG2-mediated PpIX efflux was a major factor that prevented PpIX accumulation in cancer cells in the presence of serum. Inhibition of ABCG2 transporter system could be a new target for the improvement of photodynamic therapy.

Heme biosynthesis and its regulation: towards understanding and improvement of heme biosynthesis in filamentous fungi

Heme biosynthesis in fungal host strains has acquired considerable interest in relation to the production of secreted heme-containing peroxidases. Class II peroxidase enzymes have been suggested as eco-friendly replacements of polluting chemical processes in industry. These peroxidases are naturally produced in small amounts by basidiomycetes. Filamentous fungi like Aspergillus sp. are considered as suitable hosts for protein production due to their high capacity of protein secretion. For the purpose of peroxidase production, heme is considered a putative limiting factor. However, heme addition is not appropriate in large-scale production processes due to its high hydrophobicity and cost price. The preferred situation in order to overcome the limiting effect of heme would be to increase intracellular heme levels. This requires a thorough insight into the biosynthetic pathway and its regulation. In this review, the heme biosynthetic pathway is discussed with regards to synthesis, regulation, and transport. Although the heme biosynthetic pathway is a highly conserved and tightly regulated pathway, the mode of regulation does not appear to be conserved among eukaryotes. However, common factors like feedback inhibition and regulation by heme, iron, and oxygen appear to be involved in regulation of the heme biosynthesis pathway in most organisms. Therefore, they are the initial targets to be investigated in Aspergillus niger.

Delta-aminolevulinic dehydratase is a proteasome interacting protein

The proteasome interacts with a large number of proteins which regulate specific cellular functions. The focus of this study is to examine the proteasome interaction with Delta-aminolevulinate dehydratase (ALAD). ALAD is involved in the heme biosynthesis pathway and was co-isolated, with the 20S proteasome using several chromatographic purification steps. The MALDI-TOF mass spectrometry analysis identified this proteasome co-isolated protein as ALAD. When the proteasome was isolated using density-gradient centrifugation, ALAD was also found in the 26S proteasome fractions. It co-isolated with the 20S more than with the 26S proteasome. Furthermore, immunoprecipitated ALAD stained positive with antibodies to proteasome subunits. These results indicate that ALAD might interact with the proteasome. It is possible that ALAD is involved in modulating proteasome activity. When purified proteasomes were incubated with ALAD it was found that ALAD changes proteasome activity in a dose dependent manner. This indicates that ALAD may play a significant role in regulating proteasome activity. The data supports the hypothesis that ALAD, an important enzyme for heme synthesis, is also important as a proteasome interacting protein.

Zonation of heme synthesis enzymes in mouse liver and their regulation by β-catenin and Ha-ras

Cytochrome P450 (CYP) hemoproteins play an important role in hepatic biotransformation. Recently, β-catenin and Ha-ras signaling have been identified as players controlling transcription of various CYP genes in mouse liver. The aim of the present study was to analyze the role of β-catenin and Ha-ras in the regulation of heme synthesis. Heme synthesis-related gene expression was analyzed in normal liver, in transgenic mice expressing activated β-catenin or Ha-ras, and in hepatomas. Regulation of the aminolevulinate dehydratase promoter was studied in vitro. Elevated expression of mRNAs and proteins involved in heme biosynthesis was linked to β-catenin activation in perivenous hepatocytes, in transgenic hepatocytes, and in hepatocellular tumors. Stimulation of the aminolevulinate dehydratase promoter by β-catenin was independent of the β-catenin/T-cell-specific transcription factor dimer. By contrast, activation of Ha-ras repressed heme synthesis-related gene expression. The present data suggest that β-catenin enhances the expression of both CYPs and heme synthesis-related genes, thus coordinating the availability of CYP apoprotein and its prosthetic group heme. The reciprocal regulation of heme synthesis by β-catenin and Ha-ras-dependent signaling supports our previous hypothesis that antagonistic action of these pathways plays a major role in the control of zonal gene expression in healthy mouse liver and aberrant expression patterns in hepatocellular tumors.

Review of Neurosurgical Fluorescence Imaging Methodologies

Fluorescence imaging in neurosurgery has a long historical development, with several different biomarkers and biochemical agents being used, and several technological approaches. This review focuses on the different contrast agents, summarizing endogenous fluorescence, exogenously stimulated fluorescence and exogenous contrast agents, and then on tools used for imaging. It ends with a summary of key clinical trials that lead to consensus studies. The practical utility of protoporphyrin IX (PpIX) as stimulated by administration of δ-aminolevulinic acid (ALA) has had substantial pilot clinical studies and basic science research completed. Recently multi-center clinical trials using PpIx fluorescence to guide resection have shown efficacy for improved short term survival. Exogenous agents are being developed and tested pre-clinically, and hopefully hold the potential for long term survival benefit if they provide additional capabilities for resection of micro-invasive disease or certain tumor sub-types that do not produce PpIX or help delineate low grade tumors. The range of technologies used for measurement and imaging ranges widely, with most clinical trials being carried out with either point probes or modified surgical microscopes. At this point in time, optimized probe approaches are showing efficacy in clinical trials, and fully commercialized imaging systems are emerging, which will clearly help lead to adoption into neurosurgical practice.

Co-expression of ferrochelatase allows for complete heme incorporation into recombinant proteins produced in E. coli

Over-expression of heme binding proteins in Escherichia coli often results in sub-optimal heme incorporation and the amount of heme-bound protein produced usually varies with the protein of interest. Complete heme incorporation is important for biochemical characterization, spectroscopy, structural studies, and for the production of homogeneous commercial proteins with high activity. We have determined that recombinant proteins expressed in E. coli often contain less than a full complement of heme because they rather are partially incorporated with free-base porphyrin. Porphyrin-incorporated proteins have similar spectral characteristics as the desired heme-loaded targets, and thus are difficult to detect, even in purified samples. We present a straightforward and inexpensive solution to this problem that involves the co-expression of native ferrochelatase with the protein of interest. The method is shown to be effective for proteins that contain either Cys- or His-ligated hemes.

Silencing of ALA dehydratase affects ALA-photodynamic therapy efficacy in K562 erythroleukemic cells

Synthesis of protoporphyrin IX (PpIX) by malignant cells is essential for the success of ALA-based photodynamic therapy (PDT). Two key enzymes that were described as affecting PpIX accumulation during ALA treatment are porphobilinogen deaminase (PBGD) and ferrochelatase. Here, we show that down regulation of ALA dehydratase (ALAD) expression and activity by specific shRNA induced a marked decrease in PpIX synthesis in K562 erythroleukemic cells. Photo-inactivation efficacy following ALA-PDT was directly correlated with ALAD-silencing and cellular levels of PpIX. MTT metabolism following ALA-PDT was shown to be 60% higher in ALAD-silenced cells in comparison to control cells, indicating that mitochondria were protected in the silenced cells. Morphological analysis by scanning electron microscopy (SEM) of cells treated by ALA-PDT showed no morphological changes in ALAD-silenced cells, in contrast to controls exhibiting cell deformations and lysis. Membrane integrity following ALA-PDT was kept intact and undamaged in ALAD-silenced cells as examined by Annexin V-FITC/PI staining and LDH-L leakage. We conclude that ALAD, although it is present in the cell at abundant levels, has a major and limiting role in regulating PpIX synthesis and ALA-PDT outcome.

Designing photosensitizers for photodynamic therapy: strategies, challenges and promising developments

Photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) are techniques that combine the effects of visible light irradiation with subsequent biochemical events that arise from the presence of a photosensitizing drug (possessing no dark toxicity) to cause destruction of selected cells. Despite its still widespread clinical use, Photofrin® has several drawbacks that limit its general clinical use. Consequently, there has been extensive research into the design of improved alternative photosensitizers aimed at overcoming these drawbacks. While there are many review articles on the subject of PDT and PACT, these have focused on the photosensitizers that have been used clinically, with little emphasis placed on how the chemical aspects of the molecule can affect their efficacy as PDT agents. Indeed, many of the PDT/PACT agents used clinically may not even be the most appropriate within a given class. As such, this review aims to provide a better understanding of the factors that have been investigated, while aiming at improving the efficacy of a molecule intended to be used as a photosensitizer. Recent publications, spanning the last 5 years, concerning the design, synthesis and clinical usage of photosensitizers for application in PDT and PACT are reviewed, including 5-aminolevulinic acid, porphyrins, chlorins, bacteriochlorins, texaphyrins, phthalocyanines and porphycenes. It has been shown that there are many important considerations when designing a potential PDT/PACT agent, including the influence of added groups on the lipophilicity of the molecule, the positioning and nature of these added groups within the molecule, the presence of a central metal ion and the number of charges that the molecule possesses. The extensive ongoing research within the field has led to the identification of a number of potential lead molecules for application in PDT/PACT. The development of the second-generation photosensitizers, possessing shorter periods of photosensitization, longer activation wavelengths and greater selectivity for diseased tissue provides hope for attaining the ideal photosensitizer that may help PDT and PACT move from laboratory investigation to clinical practice.

Derivatives of 5-Aminolevulinic Acid for Photodynamic Therapy

Photodynamic therapy (PDT) is a clinical treatment that combines the effects of visible light irradiation with subsequent biochemical events that arise from the presence of a photosensitising drug (possessing no dark toxicity) to cause destruction of selected cells. Today, the most common agent used in dermatological PDT is 5-aminolevulinic acid (ALA). As a result of its hydrophilic character, ALA penetrates skin lesions poorly when applied topically. Its systemic bioavailability is limited and it is known to cause significant side effects when given orally or intravenously. Numerous chemical derivatives of ALA have been synthesised with the aims of either improving topical penetration or enhancing systemic bioavailability, while reducing side effects. In vitro cell culture experiments with ALA derivatives have yielded promising results. However, if ALA derivatives are to demonstrate meaningful clinical benefits, a rational approach to topical formulation design is required, along with a systematic study aimed at uncovering the true potential of ALA derivatives in photodynamic therapy. With respect to systemic ALA delivery, more study is required in the developing area of ALA-containing dendrons and dendrimers.

Protoporphyrin IX level correlates with number of mitochondria, but increase in production correlates with tumor cell size

Protoporphyrin IX (PpIX) is produced in cells via the heme synthesis pathway, from the substrate aminolevulinic acid (ALA), and can be used for tumor detection, monitoring or photodynamic therapy. PpIX production varies considerably between tumor cell types, and determining the cell types and methods to optimize production is a central issue in properly utilizing this drug. A panel of eight cancer cell types was examined for PpIX production capacity, including breast, prostate, and brain cancer tumors, and the production varied up to 10-fold among cell types. A positive correlation was seen between mitochondrial content and naturally occurring PpIX prior to ALA administration, but mitochondrial content did not correlate to the yield of PpIX resulting from the addition of ALA. Interestingly, total cell size was positively correlated to the yield of PpIX from ALA administration. Addition of an iron chelator, 1,2-dimethyl-3-hydroxy-4-pyridone (L1) in combination with ALA allows the final step in the heme synthesis pathway, conversion of PpIX to heme, to be delayed, thereby further increasing the yield of PpIX. Those cell types that had the lowest ALA to PpIX production without L1 showed the largest percentage increase in production with L1. The study indicates that use of L1 in tumors with a lower innate production of PpIX with ALA alone may be the most productive approach to this combined delivery.

Integral spectrophotometric analysis of 5-aminolaevulinic acid-induced fluorescence cytology of the urinary bladder

OBJECTIVE

To evaluate whether tumour cells can be detected in bladder lavage fluid samples by an objective spectrofluorometric method, as 5-aminolaevulinic acid (ALA)-induced fluorescence endoscopy (AFE) and cytology are promising valuable tools for detecting transitional cell carcinoma of the urinary bladder (TCCB).

MATERIALS AND METHODS

After instilling ALA into the urinary bladder, lavage samples were collected and their sediments analysed spectroscopically under blue excitation at approximately 400 nm wavelength. During AFE, biopsies were taken. From 62 cases, 24 patients had a histologically confirmed TCCB (group A), 28 had a history of TCCB but no evidence of disease (group B) and 10 were negative for TCCB (group C).

RESULTS

Lavage sediments of all patients fluoresced in the green spectral range, typical of cellular autofluorescence. Sediments of all patients of group A caused red fluorescence peaking at 635 nm, indicating protoporphyrin IX (PPIX). The PPIX signals derived from bleaching spectra were significantly different between benign and malignant findings (P = 0.001). There was another red fluorescence peak at approximately 620 nm; in 19 cases its intensity exceeded the intensity of the PPIX signal.

CONCLUSIONS

Spectrofluorometric analysis of lavage sample sediments can be used to detect tumour-associated red fluorescence of PPIX in TCCB. Immediate significant and objective measurements are possible, which could be further automated for the rapid diagnosis of TCCB.

Developmental profiles of 5-aminolevulinate, porphobilinogen and porphobilinogen synthase activity in Pieris brassicae related to the synthesis of the bilin-binding protein

The bilin-binding protein (BBP) occurs as a major soluble protein in haemolymph, fat body, epidermis and wings of Pieris brassicae. It is a member of the lipocalin protein superfamily with yet unknown function. Here, we studied the developmental regulation of tetrapyrrole biosynthesis that provides the bilin ligand as the predominating end product. The levels of the precursors 5-aminolevulinate (ALA) and porphobilinogen (PBG) varied during larval-pupal transition in accordance with the activity of the related enzyme porphobilinogen synthase (PBGS). During adult development, both precursors were low while PBGS activity increased parallel to the formation of BBP, as shown in previous work. A competitive inhibitor of PBGS was partially purified from the meconium and characterised as a heat-stabile acidic compound. Label from [14C]ALA, injected into developing pupae of different age, was found to 80% in the hind wings and to 20% in the forewings after adult eclosion, reflecting the unequal distribution of BBP between the pairs of wings. This contrasted to the activity of PBGS that was equally active in forewings and hind wings. Together with the variation of enzyme activity during wing development our results led us propose that the (hind) wings may play a role in the synthesis of the tetrapyrrole ligand of BBP.

Mechanistic studies on delta-aminolevulinic acid uptake and efflux in a mammary adenocarcinoma cell line

Delta-aminolevulinic acid (ALA) is the precursor in the biosynthesis of porphyrins. The knowledge of both the regulation of ALA entrance and efflux from the cells and the control of porphyrin biosynthesis is essential to improve ALA-mediated photodynamic therapy. In this work, we studied the regulation of ALA uptake and efflux by endogenously accumulated ALA and/or porphyrins in murine mammary adenocarcinoma cells. Under our set of conditions, the haem synthesis inhibitor succinyl acetone completely prevented porphobilinogen and porphyrin synthesis from ALA, and led to an increase in the intracellular ALA pool. However, neither intracellular ALA nor porphyrin pools regulate ALA uptake or efflux during the first 15 min of the process. Based on temperature dependence data, ALA but not gamma-aminobutyric acid (GABA) efflux is mediated by a diffusion mechanism. Moreover, the addition of extracellular GABA not only did not influence the rate of ALA efflux but on the contrary it affected ALA uptake, showing the contribution of a saturable mechanism for the uptake, but not for the efflux of ALA from the cells.

Fluorescence cytology of the urinary bladder

OBJECTIVES

To assess, on the basis of the tumor-associated fluorescence characteristics of 5-aminolevulinic acid-induced fluorescence endoscopy, the value of fluorescence microscopy and compare it with standard cytologic techniques. 5-Aminolevulinic acid-induced fluorescence endoscopy has proved to be a valuable detection method with a high sensitivity for the endoscopic diagnosis of bladder cancer.

METHODS

We instilled 1.5 g of 5-aminolevulinic acid, dissolved in 50 mL of 5.7% sodium monohydrogen phosphate, into the urinary bladder of 162 patients with suspected transitional cell carcinoma 2 to 3 hours before endoscopy. A lavage solution was obtained for urinary cytology and for fluorescence cytology. The sediments were evaluated for tumor cells.

RESULTS

Transitional cells suspicious for tumor demonstrated the red 5-aminolevulinic acid-induced protoporphyrin IX fluorescence under the microscope. Fluorescence cytology identified 50 of 58 histologically confirmed neoplastic lesions (G1, 14 of 17; G2, 12 of 14; G3, 15 of 16; and carcinoma in situ, 9 of 11). With urinary cytology, we identified 46 of 58 histologically confirmed tumor lesions (G1, 9 of 17; G2, 12 of 14; G3, 15 of 16; and carcinoma in situ, 10 of 11). The sensitivity of fluorescence cytology was 86% and that of urinary cytology 79%. The specificity of fluorescence cytology was 75% and that of urinary cytology 88%.

CONCLUSIONS

Fluorescence cytology promises to be an effective procedure for the diagnosis of bladder cancer, especially in highly differentiated and flat premalignant tumor lesions. Automated analysis for an objective and a reproducible result appears possible.