Biomedical subjects

Johan Moan

Publications and source records attributed to Johan Moan.

At least 37 records · Page 2Linked to original sources

PubMed2005

Lipid cubic phases for improved topical drug delivery in photodynamic therapy.

We have evaluated the efficacy of lipid cubic phases, highly ordered self-assembly systems on the nanometer level, as drug delivery vehicles for in vivo topical administration of delta-aminolevulinic acid (ALA) and its methyl ester (m-ALA) on nude mice skin. ALA, a precursor of heme, induces the production of the photosensitizer protoporphyrin IX (PpIX) in living tissue. Measuring the PpIX fluorescence at the skin surface, after topical administration, makes indirect quantification of the penetration of ALA into the tissue possible. Cubic phases were formed of lipid (monoolein or phytantriol), water and drug. In some cases, propylene glycol was included in the cubic phase as well. The drug concentration was 3% (w/w, based on the total sample weight) in all investigated vehicles. When the formulations were applied for 1 h, the monoolein cubic systems and the three-component phytantriol sample showed higher fluorescence compared to the standard ointment during the 10 h of measurement. Both ALA and m-ALA yielded similar results, although the differences between the investigated vehicles were more pronounced when using m-ALA. For the 24-h applications, the monoolein cubic systems with m-ALA showed faster PpIX formation than the standard ointment, implying higher PpIX levels at short application times (less than 4 h). The systemic PpIX fluorescence of ALA was elevated by using the lipid cubic formulations. Notably, a small systemic effect was also observed for the monoolein cubic sample with m-ALA. These results imply improved PpIX formation when using the lipid cubic systems, most probably due to enhanced drug penetration.

Administration, Topical↗

PubMed2005

Deferoxamine photosensitizes cancer cells in vitro.

Effect of the iron chelator deferoxamine (DF) on the production of endogenous porphyrins was studied in adenocarcinoma WiDr cells and erythroid K562 cells in vitro. Porphyrin fluorescence was observed in the cells in vitro incubated with DF. The fluorescence spectra recorded in the cells were similar to that of protoporphyrin IX (PpIX). The amount of PpIX generated by DF was around 5% of the ALA effect. Around 90% of the WiDr cells incubated in vitro with DF (0.5 mM, 24 h) and then exposed to light (400-460 nm, 20 min) were photodynamically inactivated. In conclusion, the present study describes a novel approach of using iron chelating agents without 5-aminolevulinic acid (ALA) to photosensitize cancer cells.

Adenocarcinoma↗

PubMed2005

Radiosensitization of tumours by porphyrins.

Our previous data indicate, that hematoporphyrin dimethyl ether (HPde) can totally inhibit the growth of aggressive Ehrlich ascite tumour, when combined with low doses (2Gy) of ionizing radiation. Taking into account these findings, it appears of particular interest to evaluate the dependence of radiosensitizing efficiency of porphyrins on tumour aggressiveness. For this purpose two experimental tumour models (aggressive murine Ehrlich ascite carcinoma, (EAT), and not-aggressive hepatoma MH-22A) were used. Moreover, radiosensitizing properties of three porphyrin-type compounds of different chemical heterogeneity were evaluated (hematoporphyrin dimethyl ether (HPde), photofrin II (PII) and hematoporphyrin derivative (HPD)). Data obtained indicate, that HPde is the most effective one in this context (HPde>PII>HPD). It is important to note, that only the aggressive EAT tumours were radiosensitized by these dyes. No signs of radiosensitization (inhibition of tumour growth, injury of tumour tissue, evaluated by histological analysis) were observed in not-aggressive MH-22A hepatoma. Moreover, it was shown, that ligands of peripheral benzodiazepine receptors (PBR) might diminish the cell growth in aggressive EAT, but not in not-aggressive MH-22A hepatoma. The mechanism of radiosensitization by porphyrins, proposed in our previous studies, was strongly confirmed by these data. Actually, dicarboxylic porphyrins, being ligands of PBR, which are highly expressed in just aggressive tumours, can inhibit tumour cell proliferation and act in concert with ionizing radiation. Thus, combination of porphyrin and ionising radiation reflects the action of two antiproliferative factors, what eventually increases the response of aggressive tumours to the low doses of ionising radiation.

Animals↗

PubMed2005

pH dependent uptake of porphyrin-type photosensitizers by solid tumor cells in vitro is not induced by modification of transmembrane potential.

The uptake of HpIX, TPPS2a and mTHPC by WiDr, THX cells and skin fibroblasts at pH 7.4 and 6.8 was compared. In the absence of serum, the uptake of HpIX was higher at lower pH. The difference was significant in WiDr cells (P < 0.01) and skin fibroblasts (P < 0.05). TPPS2a nor mTHPC showed any pH dependent uptake. Lowering the extracellular pH resulted in a significant depolarization (3-8 mV) of the cells. Application of tetraethylammonium chloride did not affect the cellular uptake of any of the photosensitizers. We conclude that the pH dependent uptake of photosensitizers is not mainly related to altered transmembrane potential.

Cell Line, Tumor↗

PubMed2005

Ultraviolet photodegradation of folic acid.

The vitamin folate is vital for all living creatures. Scientists have suggested that ultraviolet degradation of folate in vivo played a role in the evolution of mankind. In order to better understand the photodegradation of folate, we have provided a spectroscopic study of the ultraviolet photodegradation of aqueous folic acid under aerobic conditions. We found strong indications that the folic acid molecule is cleaved into p-aminobenzoyl-L-glutamic acid and 6-formyl pterin when exposed to ultraviolet radiation. When the irradiation continues, 6-formyl pterin is degraded to pterin-6-carboxylic acid. The photodegradation of folic acid is divided into three phases. In the first phase, the formation of photoproducts follows a zero order rate law. In the second phase the presence of photoproducts sensitizes the degradation of folic acid and the degradation process is accelerated. In the third phase the degradation of 6-formyl pterin to pterin-6-carboxylic acid is the dominating process. This reaction follows a first order rate law. We show that both 6-formyl pterin and pterin-6-carboxylic acid sensitize the photodegradation of folic acid. However, experiments performed in heavy water indicate that generation of singlet oxygen is probably not the explanation for the photosensitizing of folic acid.

Folic Acid↗

PubMed2005

Solar radiation, vitamin D and survival rate of colon cancer in Norway.

Solar radiation contributes significantly to the status of serum calcidiol (25-hydroxyvitamin D3, 25-(OH)D3) in humans, even at the high latitudes of northern Norway. Thus, in late summer the serum concentration of calcidiol is roughly 50% larger than that in late winter, when the solar radiation in Norway contains too little ultraviolet radiation to induce any synthesis of vitamin D3 in human skin. This seems to influence the prognosis of colon cancer. We here report that the survival rate of colon cancer in men and women, assessed 18 months after diagnosis, is dependent on the season of diagnosis. A high serum concentration of calcidiol at the time of diagnosis, i.e. at the start of conventional therapy, seems to give an increased survival rate. This agrees with cell and animal experiments reported in the literature, as well as with epidemiological data from some countries relating colon cancer survival with latitude and vitamin D3 synthesis in skin. One possible interpretation of the present data is that, the level of calcidiol, or its derivative calcitriol (1alpha,25-dihydroxyvitamin D3, 1alpha,25-(OH)2D3), may act positively in concert with conventional therapies of colon cancer.

Cholecalciferol↗

PubMed2005

Influence of light exposure on the kinetics of protoporphyrin IX formation in normal skin of hairless mice after application of 5-aminolevulinic acid methyl ester.

The rates of protoporphyrin IX (PpIX) photodegradation and reappearance after light exposure at 420 and 632 nm were measured in mouse skin at different times after 1 h topical application of 5-aminolevulinic acid methyl ester (ALA-Me). After ALA-Me application (1 h) and removal, the fluorescence of PpIX increased for about 1 h, and then reached a maximum and started to decrease. Reappearance of PpIX fluorescence after exposures (degrading 60%-80% of the PpIX) was faster for exposures 0.5 h after ALA-Me application than for exposures 3 h. The bleaching rate was largest in the former case. This indicates that PpIX is located deeper in the skin after 3 h than after 0.5 h, whereas the pool of ALA-Me in the skin is largest at 0.5 h. In all cases, the reappearance was faster at a skin temperature of 35 degrees C than at 23 degrees C. Reappearance of PpIX fluorescence was faster after exposure to light at 420 nm than at 632 nm. The rate of elimination of PpIX from the volume of detection was faster after 420 nm light irradiation than that after 632 nm. These findings are discussed in view of penetration depths of light and ALA-Me, and diffusion of PpIX.

Aminolevulinic Acid↗

PubMed2004

The effect of sub-lethal ALA-PDT on the cytoskeleton and adhesion of cultured human cancer cells.

5-Aminolevulinic acid (ALA), a precursor of the endogenous photosensitizer protoporphyrin IX, is used in the photodynamic therapy (PDT) of cancer. Sub-lethal ALA-PDT (1-min irradiation with 370-450 nm blue light, 0.6 mW/cm(2) after 2-h incubation with 1 mM ALA) has been earlier shown to change cell morphology and to inhibit both trypsin-induced detachment of cultured cancer cells from the plastic substrata and cell attachment to the bottom of the plastic well plates. In the present study, we found that such treatment of human adenocarcinoma WiDr cells grown in dense colonies stimulated the formation of actin cortex between cells in the colonies and increased the number of actin stress fibres in some, but not in all, cells. However, ALA-PDT did not change the microtubular cytoskeleton in these cells. A similar treatment of glioblastoma D54Mg cells, which grow separately and communicate by protrusions, caused loss of fibrillar actin structures in growth cones, retraction of protrusions, and surface blebbing in some cells. The application of the cytoskeleton inhibitors cytochalasin D, colchicine or taxol showed that the inhibition of trypsin-induced detachment of photosensitized WiDr cells was related to ALA-PDT-induced changes in actin and microtubular cytoskeleton. Some signal transduction processes are suggested to be involved in ALA-PDT-induced changes in cytoskeleton, cell shape, and adhesion.

Actins↗

PubMed2004

Photodegradation and phototransformation of 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (m-THPBC) in solution.

The kinetics of photobleaching and formation of photoproducts upon irradiation (735 nm) of 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (m-THPBC) in phosphate buffer saline (PBS) supplemented with human serum albumin (HSA) were studied by means of absorption and steady-state fluorescence spectroscopy. Measurements were performed either immediately after the dye was dissolved in the HSA solution (0 h) or after six hours incubation in the HSA solution (6 h). Spectroscopic studies indicated that the dye was mainly present as aggregates in freshly prepared solutions, whereas incubation favored monomerisation. Irrespective to incubation time, the rates of photobleaching obtained by fluorescence measurements were higher than those obtained from absorbance measurements. Photobleaching of freshly prepared m-THPBC can be described by a single exponential decay, while the absorbance and fluorescence decays of the incubated dye solutions better fit a bi-exponential decay. Two photobleaching rates probably reflect differences in the photosensitivity of monomer (bound to proteins) and aggregated (non-bound) forms. Irradiation of the freshly prepared m-THPBC solution led to phototransformation of 50% of the bleached m-THPBC into 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (m-THPC), a clinically used second generation photosensitizer. For irradiation 6 h after dissolving m-THPBC, different kinetics of m-THPC formation were found. A rapid decrease in concentration of m-THPBC was accompanied by a slow formation of m-THPC. The quantum yield of this process was small since only 5% of m-THPBC was transformed to m-THPC. The kinetics characteristics of m-THPBC photobleaching reported in the present study, together with the different kinetics of photoproduct formation during m-THPBC photobleaching, may provide important indications in the m-THPBC-based PDT dosimetry.

Humans↗

PubMed2004

Erythrocytes-the 'house elves' of photodynamic therapy.

Photodynamic therapy (PDT) and fluorescence diagnosis (FD) are being developed for a number of clinical applications. Since fluorophores and photosensitising drugs are usually given systemically their effect on blood elements are of significant importance. Photodynamic effects on erythrocytes occur naturally in patients with erythropoietic protoporphyria (EPP). Exposure to small fluences, as obtained by the erythrocytes when they pass capillaries in the skin, leads to transfer of the photosensitiser protoporphyrin IX (PP IX), from EPP erythrocytes to endothelial cells. Thus, the erythrocytes are partly protected while the endothelial cells suffer photodamage. During photodynamic therapy in vivo erythrocytes are regularly photosensitised. This side effect is partly intended but mostly unwanted, and a summary of this topic is given. Furthermore, the effect of UV-A on erythrocytes that is accompanied with the formation of bilirubin is reviewed. Erythrocytes serve as convenient model cells for experimental research. Such use of erythrocytes to screen new photosensitisers may be of limited value. A combination of photohaemolysis and haemoglobin oxygenation may become the basis for an assay for in vitro phototoxicity. Erythrocytes from birds are good model cells for exploration of physiological and molecular mechanisms involved in PDT. A potential mechanism of PDT induced behaviour resembling apoptosis in erythrocytes is provided.PDT for sterilisation of erythrocyte concentrates has a potential for medical use. Photodynamic effects on the erythrocytes themselves should be avoided. This is realised by choosing a virus-selective photosensitiser, low fluences and treatment of the concentrates with agents like dipyridamole and antioxidants. Future aspects of applications of photosensitisation of red blood cells are discussed.

Erythrocytes↗

PubMed2004

Effectiveness of different light sources for 5-aminolevulinic acid photodynamic therapy.

Many medical applications, including photodynamic therapy for cancer (PDT), involve the use of lasers. However, the coherence of laser light is not necessary for PDT, and attempts have been made to construct non-coherent light sources for PDT, which are relatively inexpensive, stable and easy to operate, require simple maintenance but differ fundamentally from the lasers in their output characteristics. In the present work we compared two clinically used lamps, CureLight1, which is a broadband source (560-740 nm) based on a filtered halogen lamp, and CureLight2, which is a narrowband source based on light-emitting diodes (LEDs), with respect to several parameters of crucial significance for PDT efficiency in vivo: (a) depth of action in tissues, (b) heating effects, (c) pain generation, (d) photodegradation of PpIX in solution, in cells and in mouse skin and (e) photo-inactivation of cells in vitro. We conclude that CureLight2 (LED), relative to CureLight1 (halogen) has deeper PDT action in tissue, similar efficiency for bleaching PpIX in mouse skin, better efficiency for bleaching PpIX in cells and solutions and good efficiency for inactivating cells in vitro. CureLight2 gives less heating of the tissue and less pain in unsensitised human skin. All these differences are related to difference in the spectra of the lamps. Thus, PDT light sources with emissions that are visually similar have significantly different photobiological properties.

Adenocarcinoma↗

PubMed2004

Spectroscopic evidence of monomeric aluminium phthalocyanine tetrasulphonate in aqueous solutions.

Aqueous solutions of aluminium phthalocyanine tetrasulphonate (AlPcS(4)) were investigated by means of absorption and fluorescence spectroscopy. The absorption spectrum of AlPcS(4) is independent of concentration in a wide range (from 10(-8) to 10(-4) M). The fluorescence spectrum measured with a standard setup is strongly dependent on AlPcS(4) concentration, and the fluorescence maximum is gradually red-shifted with increasing concentration. Calculations that take into account reabsorption of fluorescence (inner-filter effect) fit the experimental observations at low concentrations (up to 10(-6) M). Disagreement between the calculations and spectra recorded at higher concentrations (above 10(-5) M) shows that the reabsorbed light may be reemitted as fluorescence. The influence of inner-filter effects on the spectral shape was demonstrated by the experiments where a fibre-optic front-face fluorescence setup was applied: Under such conditions the shape of the fluorescence spectra for a high concentration (10(-3) M) coincided with that of a low concentration (10(-8) M). In conclusion, the present spectroscopic results show that AlPcS(4) does not form aggregates and is a very stable compound in aqueous solutions.

Fluorescent Dyes↗

PubMed2004

Photodynamic inhibition of enzymatic detachment of human cancer cells from a substratum.

Photodynamic therapy (PDT) is currently used for cancer treatment. It is shown that sublethal PDT of human WiDr adenocarcinoma cells and D54Mg glioblastoma cells with 5-aminolevulinic acid (ALA), disulfonated tetraphenylporphyrine (TPPS(2a)), or MitoTracker Red (MTR) inhibits their trypsin-induced detachment from a plastic substratum. TPPS(2a) was bound selectively to the plasma membrane, whereas MTR was found in mitochondria. Both granular and diffuse fluorescence of ALA-derived protoporphyrin IX (PpIX) was observed in the perinuclear cytoplasm but not in the plasma membrane of WiDr cells stained for 2 h with 1 mM ALA. In D54Mg cells, PpIX fluorescence was observed not only in the cytoplasm but also in the plasma membrane. Fluorescence measurements showed a progressive accumulation of PpIX in the WiDr cells during incubation with ALA and a PpIX efflux into the medium after 1 h or longer incubation. PpIX retained in the plasma membrane during efflux may be responsible for PDT-induced impairment of cell adhesion. On the other hand, MTR-PDT or ALA-PDT after 15-min incubation, when the newly synthesized PpIX should remain in mitochondria, also inhibited enzymatic cell detachment. Therefore, photodynamic targeting of mitochondria, remote from the cell surface where adhesion occurs, may disturb cell adhesion. Photodynamic inhibition of enzymatic cell detachment may be related to PDT-induced inhibition of tumour metastasis.

Adenocarcinoma↗

PubMed2004

Vitamin D3 from sunlight may improve the prognosis of breast-, colon- and prostate cancer (Norway).

OBJECTIVE: To investigate whether prognosis of breast-, colon- and prostate cancer may be related to vitamin D(3), induced from solar ultra-violet (UV) radiation, through studies on geographical and seasonal variations in UV radiation. METHODS: This study includes 115,096 cases of breast-, colon- or prostate cancer, diagnosed between 1964 and 1992. Among these, 45,667 deaths due to the cancer were registered. On the basis of a north-south gradient in solar UV radiation and geographical climatic differences, Norway was divided into eight residential regions. According to seasonal variations in UV radiation, four periods of diagnosis during the year were used. Case fatality according to residential region and to season of diagnosis was estimated using Cox regression. The effects of occupational sun exposure, childbearing pattern and educational level were also evaluated. RESULTS: No geographic variation in case fatality was observed for the three cancer types studied. A significant variation in prognosis by season of diagnosis was observed. Diagnoses during summer and fall, the seasons with the highest level of vitamin D(3), revealed the lowest risk of cancer death. CONCLUSION: The results suggest that a high level of vitamin D(3) at the time of diagnosis, and thus, during cancer treatment, may improve prognosis of the three cancer types studied.

Breast Neoplasms↗

PubMed2004

Electrostatic properties of cells estimated by absorption and fluorescence spectroscopy.

A colloid titration method was used to determine the surface charge of cells of a human colon adenocarcinoma cell line WiDr; 6.2 +/- 0.8 degrees - 108 charges per cell were found. The apparent surface charge density was calculated using the cell surface area estimated by a Coulter counter. Alternatively, the lower limit of the cell surface area was estimated by visible microscopy. The same procedure was applied for human skin fibroblasts, resulting in the value 9.4 +/- 1.1 x 108 charges per cell. This is significantly higher (p < 0.05) than that of WiDr cells, presumably because of the different size of the cells. According to the estimations using the Coulter counter, the median diameter was higher in the case of skin fibroblasts. Fluorimetric titration of the fluorescent probe U-6 was used to estimate the interfacial potential of the WiDr cells. A shift of the titration curve of the U-6 probe toward higher pH values compared to that in pure buffer solutions was found in the presence of the WiDr cells. From the displacement of the midpoints of the titration curves, the interfacial potential of the WiDr cells was found to be about -35.8 mV. Incubation of the cells at two different pH values (7.4 and 6.8) did not result in any significant modification of the electrostatic properties of the cells under the experimental conditions of the present study. Electron microscopy revealed a distinct difference in the surface morphology of the WiDr cells compared to human skin fibroblasts. Numerous microvilli present on the surface of WiDr cells indicated marked uncertainties in cell surface area estimations. This gives large uncertainties in the real surface charge densities of cells.

Adenocarcinoma↗

PubMed2004

pH-dependent modification of lipophilicity of porphyrin-type photosensitizers.

Structural modifications of photosensitizers (changes in protonation, ionic state and aggregation state) under different environmental conditions should be precisely determined to understand the interaction of the photosensitizers with biological systems. In the present study partition coefficients of hematoporphyrin IX (HpIX), disulfonated meso-tetraphenylporphine, meso-tetra(3-hydroxyphenyl)porphine (mTHPP) and meso-tetra(3-hydroxyphenyl)chlorin in the 1-octanol-phosphate buffer system were determined in the pH region 4.0-8.0. Only the partition coefficients of HpIX and mTHPP were found to be pH dependent. Computer processing of fluorimetric titration data was applied to estimate pKa values of the imino nitrogens of mTHPP. Monoprotonated species of mTHPP seem to be unstable or nonexistent. The possibility that both imino nitrogens of this dye are protonated according to a common pKa is proposed. The pKa value of the imino nitrogens of mTHPP was found to be 2.99 +/- 0.04 after the application of a model taking aggregation of the drug into account. The contributions of various aqueous ionic species of mTHPP as functions of pH were calculated and compared with partition coefficients.

1-Octanol↗

PubMed2004

On the selectivity of 5-aminolevulinic acid-induced protoporphyrin IX formation.

Due to its capability to induce accumulation of protoporphyrin IX (PpIX) selectively in a multitude of different pathologies, 5-aminolevulinic acid (ALA) and its derivatives have attracted enormous attention in the field of photodynamic therapy (PDT) in the past two decades. The photochemical and photophysical properties of PpIX have been used for the fluorescence photodetection and photodynamic treatment of neoplasms in several medical indications in which conversion of ALA into PpIX seems to take place preferentially. Recently, this has led to the approval of this therapy for the treatment of actinic keratosis and basal cell carcinoma. When applied topically or systemically, ALA bypasses the negative feedback control that haem exerts on the enzyme ALA synthase (ALAS), which catalyses the natural production of this delta-amino acid, thereby temporarily boosting the generation of PpIX, the direct precursor of haem. Despite considerable interest in this treatment methodology, only little is known concerning the reasons for the selective accumulation of PpIX in neoplastic tissue upon ALA administration. Following an introduction into the biochemical as well as the chemical principles of haem synthesis, the present review tries to summarise experimental evidences of the mechanisms underlying preferential production of PpIX in neoplastic tissues. Thereby, morphological, environmental, enzymatic, as well as cell-specific factors will be discussed.

Aminolevulinic Acid↗

PubMed2003

Photodynamic effect of hypericin and a water-soluble derivative on isolated crayfish neuron and surrounding glial cells.

Hypericin (Hyp) has been proposed as a fluorochrome for fluorescence diagnostics and as a photosensitizer for photodynamic therapy of cancer. However, its insolubility in water is a serious drawback. A novel water-soluble hypericin derivative (Hyp-S) has been constructed, using polyvinylpyrrolidone as a carrier. We used the crayfish stretch receptor, consisting of receptor neuron and satellite glial cells, for comparison of the photodynamic effects of Hyp and Hyp-S. Hyp-S was more toxic in the dark than Hyp and inactivated the neurons at concentrations exceeding 4 microM while Hyp was toxic to the neurons only at the concentrations larger than 20 microM. Electrophysiological investigations revealed polyphasic neuron responses to photosensitization with Hyp as well as with Hyp-S (1 microM concentration, 30 min incubation; irradiation with filtered light from a lamp with an emission maximum near 600 nm and an intensity of 0.2 W/cm2). In the concentration range 1-4 microM Hyp-S was more phototoxic than Hyp. Fluorescence microscopy showed that both sensitizers were predominately localized in the glial envelope surrounding the neuron. A minor fraction of hypericin was found in the neuron perinuclear area rich in cytoplasm organelles. This suggests the potential application of Hyp and Hyp-S for visualization and selective photodynamic treatment of malignant gliomas.

Animals↗