PubMed · 8310013
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T J Dougherty. 1993. Photodynamic therapy.. https://doi.org/10.1111/j.1751-1097.1993.tb04990.x
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This report suggests an important physiological role of a CYP in the accumulation of uroporphyrin I arising from catalytic oxidative conversion of uroporphyrinogen I to uroporphyrin I in the periplasm of Escherichia coli cultured in the presence of 5-aminolevulinic acid. A structurally competent Streptomyces griseus CYP105D1 was expressed as an engineered, exportable form in aerobically grown E. coli. Its progressive induction in the presence of 5-aminolevulinic acid-supplemented medium was accompanied by an accumulation of a greater than 100-fold higher amount of uroporphyrin I in the periplasm relative to cells lacking CYP105D1. Expression of a cytoplasm-resident engineered CYP105D1 at a comparative level to the secreted form was far less effective in promoting porphyrin accumulation in the periplasm. Expression at a 10-fold molar excess over the exported CYP105D1 of another periplasmically exported hemoprotein, the globular core of cytochrome b5, did not substitute the role of the periplasmically localized CYP105D1 in promoting porphyrin production. This, therefore, eliminated the possibility that uroporphyrin accumulation is merely a result of increased hemoprotein synthesis. Moreover, in the strain that secreted CYP105D1, uroporphyrin production was considerably reduced by azole-based P450 inhibitors. Production of both holo-CYP105D1 and uroporphyrin was dependent upon 5-aminolevulinic acid, except that at higher concentrations this resulted in a decrease in uroporphyrin. This study suggests that the exported CYP105D1 oxidatively catalyzes periplasmic conversion of uroporphyrinogen I to uroporphyrin I in E. coli. The findings have significant implications in the ontogenesis of human uroporphyria-related diseases.
The possibility of enhancing aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) by simultaneous application of localised hyperthermia (HT) was evaluated. Treatments of rat DS-sarcomas included: (i) control, (ii) ALA administration (375 mg kg(-1), i.p.), no illumination, (iii) 'nonthermal' illumination, (iv) ALA-PDT: that is, ALA administration, 'nonthermal' illumination, (v) localised HT, 43 degrees C, 60 min (vi) ALA-PDT+HT: ALA administration with full spectrum irradiation resulting in ALA-PDT and HT. Tumour volume was monitored for 90 days or until a target volume (3.5 ml) was reached. No differences were seen between the first three groups, with all tumours reaching the target volume by 8-11 days. A total of 13 and 15% of tumours did not reach the target volume by day 90 following HT or ALA-PDT treatment, respectively. ALA-PDT+HT showed the greatest antitumour effect (P=0.0001), with 61% of the tumours not reaching the target volume. Viability and in vitro growth were also assessed in cells from tumours excised after treatment. ALA-PDT+HT reduced the fraction of viable tumour cells by 85%, and in vitro culture showed pronounced growth delay compared to control cells. These results demonstrate an enhanced antitumour effect upon ALA+HT, which appears to involve direct cell toxicity rather than solely vascular damage.
Photodynamic therapy (PDT) is a minimally invasive procedure with increasing promise in treatment of malignant and nonmalignant diseases. Most PDT studies have focused on issues of how to enhance the photocytotoxic reaction leading to apoptosis and/or necrosis of targeted tumor cells. However, the reactions of surviving cancer cells, as well as normal host cells, are important elements that contribute to the outcome. Little is known about how these cells at sites of treatment react to inflammatory cytokines and growth factors that are elicited by PDT. To answer this question, we treated several epithelial cancer cell lines and normal epithelial and stromal cells with membrane- and mitochondria-damaging PDT. At different time points after PDT, cells were stimulated with interleukin 6 class cytokines or epidermal growth factor (EGF). Cellular responsiveness was determined by the activation of signaling proteins. We found that within the time period of PDT reaction, both normal and malignant cells lost their responsiveness to the cytokines and growth factor in a PDT dose-dependent manner. Photosensitizers targeted to the plasma membrane or mitochondria had similar effects. The recovery of responsiveness required 48-72 h and was accompanied by resumption of cell proliferation. Although the loss of EGF response could be explained by the immediate degradation of EGF receptor, the loss of cytokine response was only, in part, correlated with a reduction in cytokine receptor proteins. A PDT-mediated reduction of Janus protein tyrosine kinase-1 was also observed in HeLa cells. Our results demonstrate that PDT alters the regulatory capability of normal and tumor cells by lowering the responsiveness to factors that are known to assist in tissue repair and immune response. This effect of PDT has to be considered when predicting outcome of PDT.