Biomedical subjects

J Moan

Publications and source records attributed to J Moan.

At least 37 records · Page 2Linked to original sources

PubMed2000

The bystander effect in photodynamic inactivation of cells.

Treatment of MDCK II cells with the lipophilic photosensitizer tetra(3-hydroxyphenyl)porphyrin and light was found to induce a rapid apoptotic response in a large fraction of the cells. Furthermore, the distribution of apoptotic cells in microcolonies of eight cells was found to be different from the binomial distribution, indicating that the cells are not inactivated independently, but that a bystander effect is involved in cell killing by photodynamic treatment. The observation of a bystander effect disagrees with the common view that cells are inactivated only by direct damage and indicates that communication between cells in a colony plays a role in photosensitized induction of apoptosis. The degree of bystander effect was higher for cells dying by necrosis than for cell dying by apoptosis.

Animals↗

PubMed2000

Increased binding of chlorin e6 to lipoproteins at low pH values.

It is well known that the extracellular pH in tumors is lower than that of normal tissue. This has been proposed to be one of the reasons for the tumor selective uptake of several photosensitizers. Photosensitizers like chlorin e(6) are bound to blood components and delivered to different sites in the organism. Thus, the effect of pH on their interaction with human plasma needs to be studied in order to understand a possible role of the acidic microenvironment in tumors for the drug distribution. Increasing amounts of human plasma in the sample resulted in a gradual red shift of the fluorescence emission maxima of chlorin e(6), indicating binding of the drug to some of the plasma components. Titration showed that the drug-plasma interaction was pH-dependent. The titration curve had an inflection point at 7.4+/-0.1. The relative distribution of the drug among plasma components, as found after ultracentrifugation of chlorin e(6)-doped plasma in a salt gradient, showed more binding of the drug to nonlipoproteins than to lipoprotein classes at both pH values studied (6.5 and 7.4). A decrease in the pH was connected with a significant increase in drug-lipoprotein binding. The pH of the environment affects chlorin e(6)-plasma interaction and the distribution of the drug among different plasma components. The results of this study indicate a possible role of the acidic microenvironment in tumors for the preferential uptake and retention of several photosensitiziers.

Chlorophyllides↗

PubMed2000

Induction of multinucleated cells caused by UVA exposure in different stages of the cell cycle.

Fibroblasts of the line 3T3 from swiss albino mice were exposed to ultraviolet A (UVA) irradiation. The cells were synchronized by treatment with nocodazole and mitotic shake-off, and then exposed to UVA irradiation in different stages of the cell cycle. Their photosensitivity varied through the cell cycle, being greatest in the G2 phase. UVA irradiation was found to induce the formation of multinucleated cells. Cells in the G1 phase were found to be most prone to multinucleation 15 min after UVA irradiation, while cells exposed to UVA irradiation in S and G2 phases contained the largest fractions of multinucleated cells 24 h after treatment. The present results indicate that multinucleated cells are formed by fusion of two or more cells shortly after UVA irradiation of early G1 cells, while impairment of cytokinesis is a possible explanation for the delayed formation of multinucleated cells after irradiation in S and G2.

3T3 Cells↗

PubMed2000

Photodynamic therapy of superficial basal cell carcinoma with 5-aminolevulinic acid with dimethylsulfoxide and ethylendiaminetetraacetic acid: a comparison of two light sources.

The aim of this prospective randomized study was to compare the clinical and cosmetic outcome of superficial basal cell carcinomas (BCC), using either laser or broadband halogen light, in photodynamic therapy with topical 5-aminolevulinic acid (ALA). A total of 83 patients with 245 superficial BCC were included in the study. Standard treatment involved 15 min of local pretreatment with 99% dimethylsulfoxide (DMSO) before topical application of 20% ALA with DMSO (2%) and ethylendiaminetetraacetic acid (2%) as cofactors for 3 h before light exposure with either laser or a broadband lamp (BL). A complete response was achieved in 95 lesions (86%) in the laser group and 110 lesions (82%) in the BL group 6 months after treatment. Of these, 80 lesions (84%) in the laser group and 101 lesions (92%) in the lamp group were independently evaluated to have an excellent or good cosmetic post-treatment score. No serious adverse events were reported. This study shows that there is no statistical significant difference in cure the rate (P = 0.49) and the cosmetic outcome (P = 0.075) with topical application of a modified ALA-cream between light exposure from a simple BL with continuous spectrum (570-740 nm) or from a red-light laser (monochromatic 630 nm). Cost and safety are further elements in favor of the BL in this setting.

Aminolevulinic Acid↗

PubMed2000

Phototransformations of 5-aminolevulinic acid-induced protoporphyrin IX in vitro: a spectroscopic study.

Human adenocarcinoma cells of the line WiDr were incubated with 5-aminolevulinic acid to induce protoporphyrin IX (PpIX) and then exposed to laser light of wavelength 635 nm. The PpIX fluorescence decreased with increasing exposure. The decay rate was slightly dependent on the initial PpIX concentration. The PpIX fluorescence was halved by a fluence of about 40 J/cm2. Several fluorescing photoproducts were formed. The main one, supposedly the chlorine-type photoprotoporphyrin (Ppp), had a fluorescence excitation spectrum stretching out to about 680 nm with a maximum at around 668 nm. The formation kinetics of this product was dependent on the initial PpIX concentration. Moreover, it was selectively bleached by exposure to light at 670 nm. A photoproduct with an emission maximum at 652 nm, different from Ppp, remained after this exposure. Traces of a photoproduct(s) with fluorescence emission slightly blue-shifted compared with that of PpIX, supposedly water-soluble porphyrins, were also detected after light exposure.

Aminolevulinic Acid↗

PubMed2000

Topical application of 5-aminolevulinic acid hexyl ester and 5-aminolevulinic acid to normal nude mouse skin: differences in protoporphyrin IX fluorescence kinetics and the role of the stratum corneum.

An important limitation of topical 5-aminolevulinic acid (ALA)-based photodetection and photodynamic therapy is that the amount of the fluorescing and photosensitizing product protoporphyrin IX (PpIX) formed is limited. The reason for this is probably the limited diffusion of ALA through the stratum corneum. A solution to this problem might be found in the use of ALA derivatives, as these compounds are more lipophilic and therefore might have better penetration properties than ALA itself. Previous studies have shown that ALA hexyl ester (ALAHE) is more successful than ALA for photodetection of early (pre)malignant lesions in the bladder. However, ALA pentyl ester slightly increased the in vivo PpIX fluorescence in early (pre)malignant lesions in hairless mouse skin compared to ALA. The increased PpIX fluorescence is located in the stratum corneum and not in the dysplastic epidermal layer. In the present study, ALA- and ALAHE-induced PpIX fluorescence kinetics are compared in the normal nude mouse skin, of which the permeability properties differ from the bladder. Application times and ALA(HE) concentrations were varied, the effect of a penetration enhancer and the effect of tape stripping the skin before or after application were investigated. Only during application for 24 h, did ALAHE induce slightly more PpIX fluorescence than ALA. After application times ranging from 1 to 60 min, ALA-induced PpIX fluorescence was higher than ALAHE-induced PpIX fluorescence. ALA also induced higher PpIX production than ALAHE after 10 min of application with concentrations ranging from 0.5 to 40%. The results of experiments with the penetration enhancer and tape stripping indicated that the stratum corneum acts a barrier against ALA and ALAHE. Use of penetration enhancer or tape stripping enhanced the PpIX production more in the case of ALAHE application than in the case of ALA application. This, together with the results from the different application times and concentrations indicates that ALAHE diffuses more slowly across the stratum corneum than ALA.

Aminolevulinic Acid↗

PubMed1999

[Use of short wave ultraviolet radiation for disinfection in operating rooms].

Over a number of years, short wave ultraviolet radiation (UVC; 200-280 nm) has been used to disinfect air and surfaces in operating rooms, patient rooms, laboratories and so on, as well as air in ventilation ducts. Despite the well-documented effect of ultraviolet radiation on air quality, thus reducing the occurrence of infections, this technology has been relatively little used. One advantage of this method is that the UVC sources ensure a continuous reduction in the number of airborne microorganisms that are generated all the time. There are, however, some disadvantages with this method. Human exposure to ultraviolet C may cause keratoconjunctivitis and erythema and requires protection of the skin and the eyes of people exposed to levels above recommended exposure limits. However, by enclosing the UVC sources or by irradiating in the absence of human activity, human exposure is eliminated. These and other aspects concerning the use of short wave ultraviolet radiation as a disinfection agent in operating rooms are discussed in this article.

Air Microbiology↗

PubMed1999

Photochemotherapy of tumours with mesotetrahydroxyphenyl chlorin is pH dependent.

Human colon carcinoma cells of the WiDr line were incubated with the tumour-localizing and photosensitizing drug mesotetrahydroxyphenyl chlorin (mTHPC) at either pH 6.8, 7.2 or 7.8. The cellular uptake of the drug was found to be independent of the pH value. However, under conditions where the cells contained the same amount of the drug (i.e. after incubation at different pH values) and were exposed to light, their photosensitivity increased with decreasing pH value. Furthermore, the cells were more photosensitive at 4 degrees C than at 37 degrees C. The shoulder on the survive curves, observed for irradiation at 37 degrees C and at pH 7.2-7.8 was practically absent for irradiation at 4 degrees C and even at 37 degrees C when the light exposure took place at pH 6.8. The observations may be related to a reduced repair of photochemotherapy (PCT)-induced damage at 4 degrees C and at pH 6.8. The high PCT efficiency at pH 6.8 may contribute to the tumour selectivity of PCT with mTHPC.

Cell Survival↗

PubMed1999

Photochemical internalization: a novel technology for delivery of macromolecules into cytosol.

The therapeutic usefulness of macromolecules, such as in gene therapy, is often limited by an inefficient transfer of the macromolecule to the cytosol and a lack of tissue-specific targeting. The possibility of photochemically releasing macromolecules from endosomes and lysosomes into the cytosol was examined. Endocytosed macromolecules and photosensitizer were exposed to light and intracellular localization and the expression of macomolecules in the cytosol was analyzed. This novel technology, named photochemical internalization (PCI), was found to efficiently deliver type I ribosome-inactivating proteins, horseradish peroxidase, a p21ras-derived peptide, and a plasmid encoding green fluorescent protein into cytosol in a light-dependent manner. The results presented here show that PCI can induce efficient light-directed delivery of macromolecules into the cytosol, indicating that PCI may have a variety of useful applications for site-specific drug delivery, e.g., in gene therapy, vaccination, and cancer treatment.

Cytosol↗

PubMed1999

The effect of glucose and temperature on the in vivo efficiency of photochemotherapy with meso-tetra-hydroxyphenyl-chlorin.

Balb/c athymic nude mice bearing WiDr human colon adenocarcinoma have been employed to investigate the effect of glucose administration, cooling or slight heating on the anti-tumor activity of photochemotherapy (PCT) with meso-tetra-hydroxyphenyl-chlorin (mTHPC). An apparent delay in the tumor growth is found by combining PCT with either single or multiple injections of glucose. The anti-tumor effect of PCT is slightly enhanced by cooling the tumor to 5 degrees C. Cooling also enhances the efficiency of PCT and glucose injection combined. Heating the tumor to 37 degrees C has no significant effect on either PCT alone or on the combination of PCT and glucose injection. Furthermore, the kinetics of the accumulation of mTHPC in tissue have been studied. Single or multiple injections of glucose have an enhancing effect on the accumulation of mTHPC in the tumor.

Adenocarcinoma↗

PubMed1999

Uptake of topically applied 5-aminolevulinic acid and production of protoporphyrin IX in normal mouse skin: dependence on skin temperature.

The temperature dependence of the uptake phase of 5-aminolevulinic acid (ALA) and the following production phase of protoporphyrin IX (PpIX) in normal mouse skin was investigated. A cream containing 20% ALA was topically applied on the skin for 10 min. The amount of ALA-induced PpIX was evaluated by measuring the fluorescence of PpIX from the treated skin. No measurable amount of PpIX was found in the skin immediately after 10 min application of ALA. The penetration of ALA into the skin was almost temperature independent while the following production of PpIX was found to be a strongly temperature-dependent process. Practically no PpIX was formed in the skin as long as skin temperature was kept low (12 degrees C).

Aminolevulinic Acid↗

PubMed1999

Cooperative inactivation of cells in microcolonies treated with UVA radiation.

Microcolonies of Madison-Darby canine kidney cells (MDCK II) were exposed to UVA radiation, and the number of cells with membrane damage was determined by staining with propidium iodide and fluorescence microscopy. The cells were clearly damaged in a nonrandom manner: The distribution of damaged cells per microcolony was incompatible with the assumption that the cells were damaged independently. The data were accurately described by a so-called propagated damage model in which a damaged cell can influence its neighbors in a propagating manner. These findings do not agree with the common view that optical radiation interacts with cells in a way in which damage manifested in a cell is the result of absorption of light in the same cell.

Animals↗

PubMed1999

Early induction of binucleated cells by ultraviolet A (UVA) radiation: a possible role of microfilaments.

The effects of UVA (365 nm) radiation on the cellular distribution of F-actin and formation of binucleated cells have been studied using 3T3 Swiss albino mouse fibroblasts and V79 Chinese hamster fibroblasts. Ultraviolet A at biologically relevant fluences was found to disintegrate the actin filaments in the cells shortly (5 min) after irradiation, concomitant with the formation of cells with two nuclei. In 76-100% of the bi- and multinucleated cells the distribution of F-actin was clearly altered. Cells in GI phase of the cell cycle were most probably involved in the formation of binucleated cells. The disintegration of F-actin was presumably not due to depolymerization of F-actin to G-actin, as the amount of F-actin in the cells was unaltered after UVA exposure but rather due to direct breakage of the actin filaments. Ultraviolet B (297/302 nm) had no effect on the cellular distribution of microfilaments, not even at highly lethal fluences.

3T3 Cells↗

PubMed1999

Epidemiological support for an hypothesis for melanoma induction indicating a role for UVA radiation.

An hypothesis for melanoma induction is presented: UV radiation absorbed by melanin in melanocytes generates products that may activate the carcinogenic process. Products formed by UV absorption in the upper layers of the epidermis cannot diffuse down as far as to the melanocytes. Thus, melanin in the upper layer of the skin may be protective, while that in melanocytes may be photocarcinogenic. Observations that support this hypothesis include: (1) Africans with dark skin have a reduced risk of getting all types of skin cancer as compared with Caucasians, but the ratio of their incidence rates of cutaneous malignant melanoma to that of squamous cell carcinoma is larger than the corresponding ratio for Caucasians. (2) Albino Africans, as compared with normally pigmented Africans, seem to have a relatively small risk of getting cutaneous malignant melanomas compared to nonmelanomas. This is probably also true for albino and normally pigmented Caucasians. (3) Among sun-sensitive, poorly tanning persons, frequent UV exposures are associated with increased risk of melanoma, whereas among sun-resistant, well-tanning persons, increased frequency of exposure is associated with decreased melanoma risk. (4) It is likely that UVA, being absorbed by melanin, might have a melanoma-inducing effect. This is in agreement with some epidemiological investigations which indicate that sun-screen lotions may not protect sufficiently against melanoma induction. The relative latitude gradient for UVA is much smaller than that for UVB. The same is true for the relative latitude gradient of cutaneous malignant melanoma as compared with squamous cell carcinoma and basal cell carcinoma. Under the assumption that the average slopes of the curves relating incidence rates with fluences of carcinogenic UV radiation are similar for melanomas and nonmelanomas, these facts are in agreement with the assumption that UVA plays a significant role in the induction of melanomas in humans. This is in agreement with the experimental results with Xiphophorus.

Animals↗

PubMed1999

The mode of cell death induced by photodynamic treatment depends on cell density.

Madison Darby canine kidney II (MDCK II) cells were seeded out at two different densities and incubated with 125 micrograms/mL of the photosensitizer meso-tetra(4-sulfonatophenyl)porphine (TPPS4) for 18 h, washed and irradiated with blue light. Four hours later the cells were studied by fluorescence microscopy. Apoptotic cells were detected by virtue of the distinct condensation and fragmentation of chromatin, and necrotic cells were detected by uptake of propidium iodide. In addition apoptosis was measured by the TdT assay. The fraction of apoptotic cells and the fraction of necrotic cells were determined for both cell densities at various levels of survival. With < 55% total cell death the apoptotic fraction was significantly higher for cells in confluent monolayers than for cells growing in microcolonies at equitoxic doses. Confluent cells were 2.9 times more sensitive than cells in microcolonies partly due to a 1.5 times higher uptake of TPPS4 in monolayer cells. The difference in mode of cell death for the different cell densities was not related to any observable difference in subcellular localization pattern of TPPS4 at equitoxic doses of photodynamic treatment.

Animals↗

PubMed1999

The temperature dependence of protoporphyrin IX production in cells and tissues.

The formation of protoporphyrin IX (PpIX) in human skin during topical application of 5-aminolevulinic acid (ALA) was found to be strongly temperature dependent, with an activation energy of about 17 kcal/mol. This temperature dependence is mainly related to porphyrin production and not to ALA penetration into the skin. The penetration of ALA into mouse and human skin was almost temperature independent. The activation energy of PpIX production in mouse skin was practically identical with that in human skin. The activation energy of ALA uptake by cells in vitro was about 10 kcal/mol and that for PpIX production was about 13 kcal/mol. The latter activation energy was within the error limits similar to that for the activity of the enzyme porphobilinogen deaminase, suggesting that this enzyme might represent a rate-limiting step for PpIX production in living tissue.

Administration, Topical↗

PubMed1998

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.

Adenocarcinoma↗

PubMed1998

Photodynamic therapy.

Photodynamic therapy involves administration of a tumor-localizing photosensitizing agent, which may require metabolic synthesis (i.e., a prodrug), followed by activation of the agent by light of a specific wavelength. This therapy results in a sequence of photochemical and photobiologic processes that cause irreversible photodamage to tumor tissues. Results from preclinical and clinical studies conducted worldwide over a 25-year period have established photodynamic therapy as a useful treatment approach for some cancers. Since 1993, regulatory approval for photodynamic therapy involving use of a partially purified, commercially available hematoporphyrin derivative compound (Photofrin) in patients with early and advanced stage cancer of the lung, digestive tract, and genitourinary tract has been obtained in Canada, The Netherlands, France, Germany, Japan, and the United States. We have attempted to conduct and present a comprehensive review of this rapidly expanding field. Mechanisms of subcellular and tumor localization of photosensitizing agents, as well as of molecular, cellular, and tumor responses associated with photodynamic therapy, are discussed. Technical issues regarding light dosimetry are also considered.

Antineoplastic Agents↗