Protoporphyrin IX

About: Protoporphyrin IX is a research topic. Over the lifetime, 2250 publications have been published within this topic receiving 65544 citations. The topic is also known as: PpIX.

Is δ-Aminolevulinic Acid Dehydratase Rate Limiting in Heme Biosynthesis Following Exposure of Cells to δ-Aminolevulinic Acid?¶

Abstract: Understanding the regulation and control of heme/porphyrin biosynthesis is critical for the optimization of the delta-aminolevulinic-acid (ALA)-mediated photodynamic therapy of cancer, in which endogenously produced protoporphyrin IX (PPIX) is the photosensitizer. The human breast cancer cell line MCF-7, the rat mammary adenocarcinoma cell line R3230AC, the mouse mammary tumor cell line EMT-6 and the human mesothelioma cell line H-MESO-1 were used to study ALA-induced PPIX levels and their relationship to delta-aminolevulinic acid dehydratase (ALA-D) activity in vitro. Incubation of these cell lines with 0.5 mM ALA for 3 h resulted in a significant increase in PPIX accumulation, compared with control cells, but there was no significant change in ALA-D activity. Exposure of cells incubated with ALA to 30 mJ/cm2 of fluorescent light, a dose that would cause a 50% reduction in cell proliferation, did not significantly alter the activity of ALA-D. Increasing the activity of porphobilinogen deaminase (PBGD), the enzyme immediately subsequent to ALA-D, by four- to seven-fold via transfection of cells with PBGD complementary DNA did not alter the activity of ALA-D. However, incubation of cells with various concentrations of succinyl acetone, a potent inhibitor of ALA-D, caused a concomitant decline in both PPIX accumulation and ALA-D activity. These data imply that when cells are exposed to exogenous ALA, ALA-D is an important early-control step in heme/porphyrin biosynthesis and that regulation of PPIX synthesis by this dehydratase may impact the effectiveness of ALA-mediated photosensitization.

In vivo pharmacokinetics of protoporphyrin IX accumulation following intracutaneous injection of 5-aminolevulinic acid

Abstract: Photodynamic therapy with 5-aminolevulinic acid (ALA) derived protoporphyrin IX (PpIX) as photosensitizer is a promising treatment for basal cell carcinomas. Until now ALA has been administered topically as an oil-in-water cream in most investigations. The disadvantage of this administration route is insufficient penetration in deeper, nodular tumours. Therefore we investigated intracutaneous injection of ALA as an alternative administration route. ALA was administered in 6-fold in the normal skin of three 6-week-old female Dutch pigs by intracutaneous injection of an aqueous solution of ALA (pH 5.0) in volumes of 0.1–0.5 ml and concentrations of 0.5–2% and by topical administration of a 20% ALA cream. During 8 h fluorescence of ALA derived PpIX was measured under 405 nm excitation. For the injection the measured fluorescence was shown to be dose dependent. All injected doses of 3 mg ALA or more lead to a faster initial increase rate of PpIX synthesis and significantly greater fluorescence than that measured after topical administration of ALA. Irradiation (60 Jcm−2 for 10 min) of the spots was performed at 3.5 h after ALA administration. After 48 and 96 h visual damage scores were evaluated and biopsies were taken for histopathological examination. After injection of 2 mg ALA or more the PDT damage after illumination was shown to be significantly greater than after topical application of 20% ALA. An injected dose of 10 mg ALA (0.5 ml of a 2% solution) resulted in significantly more tissue damage after illumination than all other injected doses.

Differential effects of photofrin, 5-aminolevulinic acid and calphostin C on glioma cells

Abstract: The invasive nature of malignant gliomas makes treatment by surgery alone extremely difficult. However, the preferential accumulation of photosensitisers in neoplastic tissues suggests photodynamic therapy (PDT) may be useful as an adjuvant therapy following tumour resection. In this study, the potential use of three different photosensitisers, namely Photofrin, 5-aminolevulinic acid (5-ALA) and calphostin C in the treatment of glioma was investigated. The uptake, cytotoxicity on U87 and GBM6840 glioma cell lines were determined by flow cytometry and MTT assay respectively. Their effect on glioma cell invasiveness was evaluated by (1) measuring the levels of matrix degradation enzymes matrix metalloproteinase (MMP)-2 and -9 using gelatin zymography, and (2) Matrigel invasion assay. The results showed that uptake of calphostin C reached saturation within 2 h, while Photofrin and 5-ALA induced protoporphyrin IX (PpIX) levels elevated steadily up to 24 h. Photocytotoxic effect on the two glioma cell lines was similar with LD50 at optimal uptake: 1 μg/mL Photofrin at 1.5 J/cm2; 1 mM 5-ALA at 2 J/cm2 and 100 nM calphostin C at 2 J/cm2. The inhibition in cell proliferation after Photofrin treatment was similar for both cell lines, which correlated to more cells being arrested in the G0/G1 phase of the cell cycle (P