Human microsporidiosis in the acquired immunodeficiency syndrome

BACKGROUND AND OBJECTIVE: Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) for sensitization is a promising treatment for carcinoma in situ and diffuse premalignant changes of the bladder. We studied the biodistribution of PpIX in a range of tissues with oral and intravesical routes of administration of ALA and compared the photodynamic effects on bladder and skin. STUDY DESIGN/MATERIALS AND METHODS: Normal Wistar rats were given oral or intravesical ALA and PpIX levels in the liver, kidney, skin, and bladder measured by fluorescence microscopy on tissue sections. At the time of maximum PpIX levels, the bladder and skin on the back were illuminated with light at 630 nm and the PDT effects compared. RESULTS: PpIX fluorescence in the urothelium after 200 mg/kg given intravesically was comparable to that found after 100 mg/kg orally. The ratio of PpIX levels between the urothelium and the underlying muscle was the same for both routes of administration, although there appeared to be more selectivity of urothelial PDT necrosis after intravesical administration. Skin photosensitization was greater after oral ALA, the epidermal PpIX level being three times higher than after intravesical administration for comparable urothelial levels and the PDT effect being more marked. CONCLUSIONS: Intravesical instillation is preferable to oral administration of ALA for PDT ablation of the urothelium of the rat bladder without damage to the underlying tissue layers and for minimizing skin photosensitivity. The technique is now ready for clinical trials.     

In vivo fluorescence kinetics of porphyrins following intravesical instillation of 5-aminolaevulinic acid in normal and tumour-bearing rat bladders

The fluorescence kinetics of protoporphyrin IX (PPIX) following intravesical instillation of 5-aminolaevulinic acid (5-ALA) have been studied in vivo in a rat bladder tumour model. 5-ALA dissolved in NaHCO3 was intravesically instilled for 60 min in tumour-bearing and normal bladders of Wistar rats. The fluorescence was excited with the violet lines of a Kr(+)-laser and recorded in vivo by means of a fibre coupled optical multichannel analyser. The fluorescence emission bands of PPIX at lambda = 636 nm and lambda = 708 nm were detected in normal and tumorous urothelium after only 30 min. The maximum fluorescence intensity was obtained in tumorous and normal urothelium 3-4 h after instillation. The ratio of the fluorescence intensity in tumorous to normal urothelium decreased continuously from four to about two during the time range of 6 h. PPIX fluorescence following 5-ALA instillation could also be observed in kidney and liver. Fluorescence from further porphyrin species with emission bands at lambda = 617 nm and lambda = 682 nm was detected in the bladder, indicating an efflux of hydrophilic porphyrins from the hepatic pathway.     

Accumulation of 5-aminolevulinic acid-induced protoporphyrin IX in normal and neoplastic human endometrial epithelial cells

The aim of this study was to evaluate 5-Aminolevulinic acid (ALA)-induced fluorescence of normal and neoplastic endometrial epithelial cells for diagnosis and photodynamic treatment. Fluorescence of ALA-induced PpIX in vitro was measured by flow cytometry in two different human endometrial adenocarcinoma cell lines and in normal cells cultivated from fresh endometrial tissue of three premenopausal patients. The cells were analysed after incubation with different concentrations of ALA during 3, 6, or 24 hours. Both tumor cell lines showed a statistically significant higher fluorescence of PpIX than normal epithelial cells after incubation with 1 mg ALA per ml medium during 24 hours. The well-differentiated cancer cells produced significantly more PpIX than the poorly differentiated cancer cells. Relative PpIX intensity of the two cancer cell lines correlated with cell proliferation rate as measured by the doubling times of the cells. Higher accumulation of Pp IX in neoplastic endometrium compared to normal endometrial epithelial cells may provide targeted biopsies and selective photodynamic destruction of neoplastic micro-lesions.     

The influence of hypoxia and pH on aminolaevulinic acid-induced photodynamic therapy in bladder cancer cells in vitro

Photodynamic therapy (PDT) is a cancer treatment based on the interaction of light and a photosensitizing chemical. The photosensitizer protoporphyrin IX (PpIX) is generated via the haem biosynthetic pathway after administration of aminolaevulinic acid (ALA). The cellular microenvironment of tumours is hypoxic and acidotic relative to normal tissue, which may influence PpIX generation and compromise PDT efficacy. This study used bladder cancer cells, incubated with ALA at various oxygen tensions and H+ ion concentrations, and assessed the effects on PpIX generation and PDT sensitivity. PpIX production was reduced at 0%, 2.5% (19 mmHg) and 5% (38 mmHg) oxygen compared with that at 21% (160 mmHg) oxygen (0.15, 0.28 and 0.398 ng microg(-1) protein compared with 0.68 ng microg(-1) respectively; P < 0.05). The response to PDT was abolished by hypoxia, as a result of both reduced PpIX synthesis and reduced PDT toxicity. PpIX production was greater at pH 7.0 and 6.5 (0.75 and 0.66 ng microg(-1)) compared with that at pH 7.4 and 5.5 (0.41 and 0.55 ng microg(-1) respectively). PDT cytotoxicity was enhanced at lower pH values. These results suggest that ALA-induced PDT may be inhibited by hypoxia due to reduced intrinsic PpIX synthesis. Acidosis may slightly enhance the efficacy of ALA-induced PDT.     

Delta-aminolevulinic acid-induced fluorescence in normal human lymphocytes

Endogenously generated protoporphyrin IX (PpIX) from exogenous delta-aminolevulinic acid (ALA) has the photodynamic capacity to inactive cancer cells of different origins. The aim of this study was to characterize the ability of normal lymphocytes to transform ALA into PpIX in order to appreciate through further studies changes in pathologic lymphocytes. We investigated in this study PpIX synthesis by normal human lymphocytes using a confocal laser microspectrofluorometer. Live lymphocytes were identified by monoclonal antibody fluorescent labeling. B and T lymphocytes synthesized PpIX (80-100 counts), with a maximum being reached after 4 h ALA incubation. When T subpopulations of lymphocytes were labeled, T4 and T8 changes in fluorescence kinetics were similar, reaching a maximum after 5 h ALA incubation. The influence of monoclonal antibody labeling on this delayed increase for maximum fluorescence is considered. Phytohemagglutinin (PHA, incubation for 72 h) lymphocyte stimulation induced a 100% increase in PpIX fluorescence for T lymphocytes, whereas pokeweed mitogen activation produced an increase of about 50% in the B- or T-lymphocyte signal. Finally, the scanning fluorescence image clearly indicated the inhomogeneity of cytoplasmic ALA-induced PpIX fluorescence, which was probably due to the distribution of mitochondria. The influence of this heterogeneity on PpIX photosensitivity effects is discussed.     

Where does venous reflux start?

To examine the potential of using photodynamic therapy (PDT) in condylomata, we studied the distribution and kinetics of protoporphyrin IX (PpIX) formation in condylomata acuminata and adjacent normal skin after topical application of 5-aminolaevulinic acid (ALA). PpIX fluorescence spectra were measured hourly in vivo after ALA application. After gross fluorescence imaging, the lesions were biopsied, and fluorescence microscopy was performed. All three PpIX fluorescence detection modalities suggested selectivity of PpIX formation in condylomata after topical ALA application. In 17 of 25 condylomata, there was significantly greater fluorescence compared with adjacent normal skin. The greatest lesional to normal skin fluorescence ratios occurred after 2 h. The most likely mechanism for increased lesional PpIX formation in condylomata is enhanced stratum corneum permeability. Based on our results, ALA/PDT is a potential field therapy for condylomata. PpIX fluorescence imaging after ALA application may also be useful for localizing condylomata prior to treatment.     

The effect of a subnormal dose of vitamin B6 on plasma lipid in the rat

In order to understand the mechanisms by which capsaicin at high concentrations affects the micturition reflex and detrusor contractility, in vivo and in vitro whole bladder studies were conducted using ganglionic blockers and a neurokinin receptor antagonist. Thirty-eight adult rats were divided into control (normal saline cystometry) and experimental (1,000 microM capsaicin cystometry) groups. Both groups were subdivided to receive pretreatment with intravesical hexamethonium, perivesical hexamethonium, or intravesical spantide ([D-Arg1, D-Trp7,9, Leu11]-substance P). After in vivo cystometry, the bladders were removed and in vitro whole bladder contractility studies using electrical field stimulation as well as bethanechol and KCl stimulations were performed. In the bladders pretreated with perivesical hexamethonium, the amplitudes of contractions and in vitro detrusor contractility under electrical stimulation were decreased. Other bladder preparations showed no significant differences from the controls. However, when 1,000 microM capsaicin was infused into the bladders, both control and experimental bladders showed an initial excitation and a final inhibition with an elevated basal intravesical pressure and retention. Capsaicin at 100 microM did not have this effect. The results of this study conclude that blockage of perivesical ganglia or neurokinin receptors in the submucosa did not influence the depressant effects of 1,000 microM capsaicin on the micturition reflex and detrusor contractility in rats. Nonspecific toxic effects on detrusor muscle or nerves is likely when intravesical high-concentration capsaicin is administered.     

Photodynamic therapy on rat urinary bladder with intravesical instillation of 5-aminolevulinic acid: light diffusion and histological changes

PURPOSE: Photodynamic therapy (PDT) has the potential to treat extensive premalignant lesions and microinvasive tumors in the bladder, but its use has been hampered by the risk of detrusor muscle damage and prolonged skin photosensitivity. We have shown that the rat urothelium can be sensitized by selectively using a 10% solution of 5-aminolevulinic acid (ALA) at pH 5.5 administered intravesically. This paper evaluates the photodynamic effects on sensitized bladders. MATERIALS AND METHODS: The bladders ofs Wistar rats were instilled with ALA solutions of different concentrations at pH 5.5 and subsequently treated with laser light at 630 nm. Bladders were harvested 1 to 7 days after PDT for histological assessment. RESULTS: Under optimum conditions (10% intralipid diffusion medium, light dose 50J) uniform urothelial necrosis was seen after 1 to 2 days; it healed in 7 days without damage to the underlying muscle layer although some increase in collagen was seen in the lamina propria. Overtreatment or poor light distribution resulted in muscle necrosis and scarring. CONCLUSIONS: Selective urothelial necrosis is possible with PDT using intravesical ALA. There is now sufficient data for pilot clinical trials to start photodynamic therapy for management of superficial bladder cancer or carcinoma in situ.     

In vitro studies on the potential use of 5-aminolaevulinic acid-mediated photodynamic therapy for gynaecological tumours

Results are reported on the sensitivity of various gynaecological tumour cell lines to 5-aminolaevulinic acid-induced protoporphyrin IX-sensitised photodynamic therapy (ALA-PDT) in vitro. All cell lines tested accumulated ALA-induced protoporphyrin IX (PpIX) and demonstrated good sensitivity to ALA-PDT. Localisation of PpIX in the mitochondria was demonstrated by fluorescence microscopy. Subcellular damage following ALA-PDT was observed using transmission electron microscopy. This damage was localised initially to the mitochondria, with damage to membranes and the nucleus and complete loss of intracytoplasmic organisation being observed subsequently. There was no apparent difference in ALA-PDT response between a multidrug-resistant ovarian carcinoma cell line and its parent line. These results indicate that ALA-PDT has potential for application to therapy of gynaecological malignancies.     

Investigation of the role of 5-HT3 receptors in the secretion of prolactin, ACTH and renin

Photodynamic therapy using i.v. injected porphyrin photosensitizers have been used to treat selected cases of superficial bladder cancer. Since cutaneous photosensitivity, lasting 6-8 weeks, is a well known undesirable side effect of this therapy, we instilled the photosensitizers intravesically in rats and compared the uptake of photosensitizers in different tissues by this route of administration with the uptake after intravenous injection. The intravesical mode of delivery enhanced photosensitizer uptake in the bladder wall, while giving low concentrations in extravesical organs. Intravesical instillation of the photosensitizers may therefore increase their efficacy and reduce phototoxicity as compared with intravenous injection. Comparing the results obtained by two assays, one based on porphyrin fluorescence and the other based on the application of radioactively labelled photosensitizers, it was concluded that the i.v. administration route may result in tissue uptake of significant amounts of aggregated non-fluorescent, supposedly inactive drug, while the intravesical administration led to less uptake of aggregates relative to active drug monomers.     

5-Aminolevulinic acid induced endogenous porphyrin fluorescence in 9L and C6 brain tumours and in the normal rat brain

A new approach in photodynamic therapy is the use of endogenous porphyrins for sensitisation of tumours to light. The induction of endogenous porphyrins after intravenous injection of 5-aminolevulinic acid (ALA, 200 mg kg-1) was studied in 23 rats, bearing intracranial 9L or C6 tumours. After 0, 2, 4, 6, 8, and 22 hours the rats were sacrificed and the fluorescence distribution of endogenous porphyrins was studied in brain tissue sections with a standard fluorescence microscope and a confocal laser scanning microscope. The role of blood-brain barrier disruption on porphyrin production was studied in 2 rats with a cryo-lesion of the cortex. Additionally, 9L and C6 tumour cell cultures were incubated with ALA for 8 hours in vitro. Fluorescence was measured with a fluorescence spectrophotometer in cell cultures and in the brain sections. Porphyrins were detected in vitro in the tumour cells from 2 hours onwards and ex vivo in the tumour sections mainly from 2 to 8 hours, by 22 hours porphyrin fluorescence had almost disappeared. The contralateral brain showed low fluorescence levels between 2 and 6 hours after ALA administration. At the site of the cryo-lesions low fluorescence was measured 6 hours after ALA administration. The 9L tumours fluoresced homogeneously, with a sharp demarcation towards normal brain tissue. Fluorescence in the C6 tumours was patchy, with a poorly fluorescing edge. In both tumour models fluorescence was also detected in brain surrounding the tumour and sometimes in contralateral white matter and ventricle ependyma and pia mater. The slight increase of porphyrin fluorescence in the normal brain of tumour bearing rats, compared to the absence of this in rats without a tumour, was attributed to transport by bulk flow of porphyrins made in the tumours, and possibly also of circulating porphyrins or ALA leaking from the tumour vessels.     

Penetration of intravesical doxorubicin in human bladders

The bladder wall penetration kinetics of intravesical doxorubicin were examined in radical cystectomy patients, to provide insight into drug concentrations at target tumor sites. The dosing solution (40 mg/20 ml) was instilled just prior to the start of surgery and maintained for 60-115 min until just prior to bladder excision. The data showed considerable inter-patient variability in the peak plasma concentration (24-fold), urine concentration (7- fold), and tissue concentration (28-fold). The urine concentration at the time of tissue harvest was about 17% of the concentration in the dosing solution. This was due to the dilution by post-catheterization residual urine and urine produced during treatment. The doxorubicin concentration dropped by 32-fold across the urothelium, and declined semi-logarithmically with respect to depth in the capillary-perfused tissues beneath the urothelium with a 50% decrease over about 500 micromole. In three of six patients from whom tumor tissue was obtained, the doxorubicin concentration was higher than the adjacent non-tumor-bearing tissues of comparable tissue depth, whereas the reverse was seen in the remaining three tumors. The plasma concentrations were 0.02, 0.03, 0.05, 0.27, and 0.69% of the concentrations in the tumors, urothelium, lamina propria, superficial and deep muscle layers, respectively. These data indicate: (a) a considerable intra- and inter-patient variability in bladder tissue concentrations, in part due to the variability in the urine concentration; (b) the urothelium is an effective barrier to doxorubicin penetration; and (c) a targeting advantage of intravesical therapy for the treatment of superficial bladder cancer yielding superficial bladder tissue concentrations at least 2000-fold higher than in the systemic circulation. A comparison of the data of doxorubicin with our previously published data on mitomycin C shows similar bladder tissue pharmacokinetics for the two drugs, suggesting that there is no pharmacokinetic preference for either drug.     

Production of protoporphyrin IX induced by 5-aminolevulinic acid in transplanted human colon adenocarcinoma of nude mice can be increased by ultrasound

BALB/c nude mice bearing WiDr human colon adenocarcinoma were used to determine the effect of ultrasound on the production of 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) both in the tumors and in skin overlying the tumors. Ultrasound (1 MHz) with pulsed irradiation at an average intensity of 3 W/cm2 was given 10 min to the tumor area 10 min after administration of ALA (20% in an oil-in-water emulsion applied topically on the surface of the tumor for 30 min to 3 hr). An approximately 45% increase in the amount of PpIX produced by ALA in the tumors was obtained within 1 to 2 hr following ultrasound treatment. In particular, 1 hr after ultrasound treatment, the amount of PpIX in the tumors was at the same level as that 3 hr after ALA application alone. However, pulsed ultrasound irradiation for 5 min or continuous irradiation for 5 or 10 min had no significant effect on the production of PpIX by the tumor 1 hr after topical ALA application. Furthermore, in most cases, the amount of PpIX in the tumors was significantly decreased when ultrasound was given immediately before ALA application. There was no significant change in the ratio of the amount of PpIX in tumor to that in skin after ultrasound treatment. Most likely, the distribution of PpIX fluorescence in the tumors treated with ultrasound was more homogeneous than that in the tumors given ALA only. Our results provide a theoretical basis for possible clinical use of ultrasound-combined ALA or ALA based photodynamic therapy.     

Urodynamically controlled management of spinal cord injury in children

Spinal cord injuries in children are relatively uncommon. However, infants with cervical spine injury have an especially high risk of renal damage. Six patients, 4 of them tetraplegic, aged 15 months to 8 years, were primarily treated by oral anticholinergic medication and intermittent catheterization. With this concept, satisfactory results were achieved in 4 of 6 children for a mean follow-up of 17.7 months. Mean bladder capacity increased by 128% and intravesical pressure was reduced by 35%. While all patients initially presented with a detrusor leak point pressure above 40 cm H2O, in 4 patients detrusor leak point pressure could be sufficiently reduced by initial treatment. One patient required intravesical instillation of oxybutynin; in another patient sphincterotomy was performed. No patient had signs of renal damage. In summary, even in tetraplegic infants, oral anticholinergic medication and intermittent catheterization is a safe and well-tolerated treatment.     

Effect of intravesical capsaicin and vehicle on bladder integrity control and spinal cord injured rats

PURPOSE: To determine the acute effect of intravesical capsaicin on bladder mucosal integrity in normal and spinal cord injured (SCI) rats. MATERIALS AND METHODS: Intravesical reagents were instilled in 5 groups of age and weight matched female rats: 1) control + normal saline solution (NSS), 2) control + ethanol (EtOH), 3) control + capsaicin/EtOH, 4) SCI + NSS, 5) SCI + capsaicin/EtOH. Intravesical instillations were performed 4 weeks after a standard T10 SCI. Intravesical capsaicin (1 mM.) was dissolved in 30% EtOH/NSS. The animals (n = 3 each group) were sacrificed at 30 minutes, 24 hours, 72 hours, and 7 days after intravesical instillation. Whole bladders were harvested, fixed in 10% buffered formalin, and paraffin embedded. Tissue blocks were blind coded and sectioned (5 microns thickness) for histopathological analysis. All sections were initially stained with hematoxylin and eosin (H & E). Specific staining for mucin carbohydrate moieties included periodic acid-Schiff (PAS) and alcian blue. Also, immunohistochemical staining for GP51 (a urinary glycoprotein) was performed. RESULTS: Control and SCI rats exhibited similar bladder mucosal histology by H & E and mucin specific stains. Instillation of saline demonstrated no effect on bladder histology, whereas instillation of intravesical capsaicin induced a profound acute effect of thinning of the epithelium, submucosal edema, and diminished presence of GP51. EtOH produced similar pathological findings, but to a lesser degree than capsaicin. Intravesical capsaicin demonstrated a similar effect in both control and SCI animals. The peak effect was seen after 30 minutes and continued for 24 hours. Partial recovery was noted after 72 hours and complete recovery was evident by 1 week. CONCLUSIONS: The control and SCI rats demonstrated a histologically similar mucosa and glycosaminoglycan layer. The effect of saline instillation on the mucosa was negligible. Intravesical capsaicin dissolved in 30% ethanol/NSS had a profound effect on the bladder urothelium submucosa that was more pronounced than that seen with the ethanol vehicle alone in normal animals.     

Detrusor myopathy: an accurate predictor of bladder hypocompliance and contracture in interstitial cystitis

OBJECTIVE: To determine whether any histological characteristics within the detrusor in cases of early interstitial cystitis (IC) predict the subsequent development of severe symptoms due to bladder contracture. PATIENTS AND METHODS: The detrusor muscle component of bladder biopsies from 21 patients with IC was examined in sections stained with haematoxylin and eosin. Videocystometrography was performed at least 2 months after the biopsy and the patients were then followed up clinically for at least 3 years. RESULTS: The detrusor appeared normal in 13 patients; in eight there was evidence of detrusor myopathy. Patients with biopsies confirming detrusor myopathy were significantly more likely to have hypocompliant bladders than those with normal detrusor muscle histology (P < 0.02). Over the following 3 years, six of the eight patients with detrusor myopathy developed progressively severe symptoms and required subtotal cystectomy and enterocystoplasty. None of the 13 patients without detrusor myopathy required bladder substitution. CONCLUSION: In IC, detrusor myopathy is associated with bladder hypocompliance. Patients with detrusor myopathy appear to have more severe disease and are more likely to progress to bladder contracture requiring substitution enterocystoplasty.     

Characterization of a monoclonal antibody recognizing a DAG-containing epitope conserved in aphid transmissible potyviruses: evidence that the DAG motif is in a defined conformation

Fetal and postnatal bovine bladders were examined for expression of elastic fiber components by immunohistochemistry as well as by measurement of steady state mRNA levels. Expression of fibrillin-1, microfibril-associated glycoprotein (MAGP) and elastin during the fetal period were compared with that of postnatal two year old animals (heifers) and adults. Each bladder was separated into two distinct tissue samples: 1) the outer smooth muscle layer (detrusor) and 2) the inner epithelium (urothelium) lined lamina propria (urotherial-lamina propria). Each of these samples was analyzed separately. Distribution of the elastic fiber components, determined by immunohistochemistry with matrix-specific antibodies, was different depending upon the region of the bladder wall examined and its developmental stage. In particular, MAGP and fibrillin-1 were conspicuously present in the urothelium during the later fetal stages. RNA products of elastic fiber genes were detectable both in the detrusor smooth muscle and urothelial-lamina propria fractions. The highest level of expression occurred in the urothelial-lamina propria fraction during the late second-early third trimester. Elastin expression was different from that of MAGP and fibrillin-1. The highest levels of steady-state elastin mRNA occurred at the earliest developmental stages examined and then progressively decreased through term. A high level of elastin expression occurred within the inner or lamina propria layer of the bladder. Since this layer is the functional capacitance layer within the bladder, its flexibility is likely related to the structural integration of elastin and associated microfibrillar components.     

Absolute or relative measurement of carbohydrate-deficient transferrin in serum? Experiences with three immunological assays

The mechanism of anti-tumour activity by BCG is not known clearly. However, many studies suggest that immunological response is related to effectiveness of intravesical instillation of BCG in the therapy for superficial bladder carcinoma. Peripheral blood mononuclear cells (PBMC), urine and serum were obtained from patients with superficial carcinoma at various times during the course of BCG instillation. Urine of patients showed increased levels of IL-1beta, IL-2, IL-6, tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) and macrophage colony-stimulating factor (M-CSF) after BCG instillation. Levels of IL-2 and IFN-gamma in the serum also increased after BCG instillation, but IL-1beta, IL-6, TNF-alpha and M-CSF were not detectable. Maximal levels of IL-2 and IFN-gamma in the urine or serum were shown after the fourth instillation. BCG-induced killer cell activity in PBMC increased significantly after the third BCG instillation. These results suggest that BCG instillation involved not only local immunological efforts but also systemic immune responses. Tumour-free patients produced higher BCG-induced killer cell activity than tumour recurrence patients. BCG-induced killer cell activity may be useful for monitoring the effectiveness of intravesical BCG instillation.     

Treatment of experimental mouse bladder tumour by LPS-induced epithelial cell shedding

The purpose of the present study was to explore the therapeutic potential of serial administration of shedding-inducing endotoxin in a mouse tumour bladder model. The studies were conducted with two variants derived from the MBT-2 tumour namely, T5 and T50, the latter being far more aggressive than the former. It was found that T5 tumours responded to intravesical lipopolysaccharides (LPS) instillation by a considerable reduction in their pace of growth (P < 0.0001) when treatment was initiated 3 days after tumour implantation, but not when started after 7 days. The T50 variant did not respond to LPS when treated 3 days after implantation, but a considerable reduction in rate of growth occurred when treatment was started after 1-2 days. Shedding induced by intravesically instilled LPS was found to retard considerably the progression rate of experimental bladder tumour.     

Enhancement of 5-aminolaevulinic acid-induced photodynamic therapy in normal rat colon using hydroxypyridinone iron-chelating agents

Currently, the clinical use of 5-aminolaevulinic acid (ALA)-induced protoporphyrin IX (PPIX) for photodynamic therapy (PDT) is limited by the maximum tolerated oral ALA dose (60 mg kg(-1)). This study investigates whether hydroxypyridinone iron-chelating agents can be used to enhance the tissue levels of PPIX, without increasing the administered dose of ALA. Quantitative charge-coupled device (CCD) fluorescence microscopy was employed to study PPIX fluorescence pharmacokinetics in the colon of normal Wistar rats. The iron chelator, CP94, when administered with ALA was found to produce double the PPIX fluorescence in the colonic mucosa, compared with the same dose of ALA given alone and to be more effective than the other iron chelator studied, CP20. Microspectrofluorimetric studies demonstrated that PPIX was the predominant porphyrin species present. PDT studies conducted on the colonic mucosa showed that the simultaneous administration of 100 mg kg(-1) CP94 i.v. and 50 mg kg(-1) ALA i.v. produced an area of necrosis three times larger than similar parameters without the iron-chelating agent with the same light dose. It is possible, therefore, to increase the amount of necrosis produced by ALA-induced PDT substantially, without increasing the administered dose of ALA, through the simultaneous administration of the iron-chelating agent, CP94.