Roles of porphyrin and iron metabolisms in the δ-aminolevulinic acid (ALA)-induced accumulation of protoporphyrin and photodamage of tumor cells.

δ-Aminolevulinic acid (ALA)-induced porphyrin accumulation is widely used in the treatment of cancer, as photodynamic therapy. To clarify the mechanisms of the tumor-preferential accumulation of protoporphyrin, we examined the effect of the expression of heme-biosynthetic and -degradative enzymes on the ALA-induced accumulation of protoporphyrin as well as photodamage. The transient expression of heme-biosynthetic enzymes in HeLa cells caused variations of the ALA-induced accumulation of protoporphyrin.

Quinolone compounds enhance delta-aminolevulinic acid-induced accumulation of protoporphyrin IX and photosensitivity of tumour cells.

Exogenous δ-aminolevulinic acid (ALA)-induced photodynamic therapy (PDT) has been used in the treatment of cancer. To obtain a high efficacy of ALA-PDT, we have screened various chemicals affecting ALA-induced accumulation of protoporphyrin in cancerous cells. When HeLa cells were treated with quinolone chemicals including enoxacin, ciprofloxacin or norfloxacin, the ALA-induced photodamage accompanied by the accumulation of protoporphyrin was stronger than that with ALA alone.

Dual mitochondrial localization and different roles of the reversible reaction of mammalian ferrochelatase.

Ferrochelatase catalyzes the insertion of ferrous ions into protoporphyrin IX to produce heme. Previously, it was found that this enzyme also participates in the reverse reaction of iron removal from heme. To clarify the role of the reverse reaction of ferrochelatase in cells, mouse liver mitochondria were fractionated to examine the localization of ferrochelatase, and it was found that the enzyme localizes not only to the inner membrane, but also to the outer membrane.

Heme-binding to the nuclear receptor retinoid X receptor alpha (RXRalpha) leads to the inhibition of the transcriptional activity.

Heme acts as a ligand for transcription factors and regulates the expression of several genes. The nuclear receptor retinoid X receptor alpha (RXRalpha) plays important roles in various nuclear receptor-dependent signaling pathways. We here show that heme binds to RXRalpha and impairs its DNA-binding activity.

Heme synthase (ferrochelatase) catalyzes the removal of iron from heme and demetalation of metalloporphyrins.

The red pigments in meat products, including cooked cured ham, arise from the reaction of myoglobin with nitric oxide generated from exogenous nitrite. Since carcinogenic nitrosoamines may be generated by the treatment of meats with nitrite, the production of nitrite-free meat products is an attractive alternative. Raw dry-cured (Parma) hams are produced by the treatment of meats with salts other than nitrite.

The role of nitric oxide in delta-aminolevulinic acid (ALA)-induced photosensitivity of cancerous cells.

Application of delta-aminolevulinic acid (ALA) results in the endogenous accumulation of protoporphyrin IX and is a useful approach in the photodynamic therapy (PDT) of cancers. To investigate the role of nitric oxide (NO) in the specific accumulation of protoporphyrin and ALA-induced PDT of cancerous cells, we transfected inducible-nitric oxide synthase (NOS2) cDNA into human embryonic kidney (HEK) 293T cells and examined the ALA-induced photo-damage as well as the accumulation of porphyrin in the cells. When the NOS2-expressing HEK293T cells were treated with ALA and then exposed to visible light, they became more sensitive to the light with accumulating porphyrins, as compared with the ALA-treated control cells.

Mechanisms involved in delta-aminolevulinic acid (ALA)-induced photosensitivity of tumor cells: relation of ferrochelatase and uptake of ALA to the accumulation of protoporphyrin.

Photodynamic therapy (PDT) using delta-aminolevulinic acid (ALA)-induced accumulation of protoporphyrin IX is a useful approach to the early detection and treatment of cancers. To investigate the role of ferrochelatase in the accumulation of protoporphyrin, we first made mouse fibroblast Balb/3T3 cells highly expressing ferrochelatase and examined the ALA-induced photo-damage as well as the accumulation of porphyrin in the cells. When the ferrochelatase-transfected cells were treated with ALA and then exposed to visible light, they became resistant to the light without accumulating porphyrins, with a concomitant increase in the formation of heme.

Ferrochelatase consisting of wild-type and mutated subunits from patients with a dominant-inherited disease, erythropoietic protoporphyria, is an active but unstable dimer.

Erythropoietic protoporphyria (EPP) is an autosomal inherited disease of heme biosynthesis caused by a partial deficiency of the enzyme ferrochelatase. Patients with EPP show only 20-30% normal activity because of mutations in one of the alleles of the ferrochelatase gene. To clarify the molecular mechanisms of this low level of activity, we co-expressed human ferrochelatase carrying His- and HA-tags in a tandem fashion in Escherichia coli.