High Porphyrin Concentration Research Articles

Expression and regulation of ABCG2/BCRP1 by sex steroids in the Harderian gland of the Syrian hamster (Mesocricetus auratus)

The ATP-Binding Cassette, subfamily G, member 2 (ABCG2) transporter is associated with the regulation of protoporphyrin IX transport and of other intermediates in heme biosynthesis. Because the hamster Harderian gland (HG) exhibits high concentrations of porphyrins and sexual dimorphism, we analyzed the hamster ABCG2. Cloned cDNA [2098-base pairs (bp)] contains an open-reading frame (ORF) of 1971-bp that encodes a 656 amino-acid protein with a molecular weight of 72844.56Da. The hamster ABCG2 sequence is conserved phylogenetically and shares a high percentage of identity with mouse (89%), rat (88%), and human (84%) transporters. Within its structure, a Walker A (G–X–X–G–X–G–K–S), a C signature motif characteristic of ABC transporters, and six putative transmembrane domains (TMDs) were identified. ABCG2 mRNA was detected in all hamster tissues, with higher amounts found in HG, brain, cerebellum, kidney, gut, ovary, and testis. Harderian ABCG2 expression exhibits a sexually dimorphic pattern where females display higher mRNA levels than males. Different patterns of transcriptional profiles of ABCG2 during the estrous cycle and after gonadectomy in both sexes were also observed. The differential expression between male and female HGs suggests that ABCG2 is under the regulation of gonadal steroids. The ABCG2 transporter is likely involved in the endogenous regulation of porphyrins in hamster HGs.

Spectroscopic investigations on chiral J-aggregates induced by tartaric acid in alcoholic solution

Chiral J-aggregates of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS[Formula: see text] have been obtained in ethanol solution triggered by addition of both enantiomeric forms of tartaric acid. A detailed spectroscopic investigation has been performed on aggregates obtained by a well-defined mixture protocol of reactants. Our findings show as both aggregation process and induced supramolecular chirality essentially depend on the concentration of the reactants. Contrary to what occurs in aqueous solution, TPPS4 in ethanol solution shows: (i) at low porphyrin concentration, an aggregation behavior characterized by a L-tartaric acid threshold whereas the D-tartaric does not work even at high concentrations, so revealing an enantiomeric discrimination; (ii) at high porphyrin concentration, a large kinetic discrimination of D- vs. L-enantiomer.

Organic and elemental elucidation of asphaltene fraction of Nigerian crude oils

This paper provides data on the chemical composition of the asphaltene component of Nigerian crude oils in order to ascertain its properties which can assist in the refining and processing paths of the natural resource. Crude oil samples were collected from three major oil fields in Nigeria and were deasphalted using n-pentane. The organic characteristics of the precipitated asphaltenes were determined using Fourier Transform Infrared (FT-IR) Spectrometry, while the elemental contents were measured by Inductively Coupled Plasma Atomic Emission spectroscopy (ICP-OES) and Carbon and Nitrogen Analyzer. Comparison of the average content of the Nigerian crude oils asphaltene with that of other nations shows that the Nigerian crude oil asphaltene content (3.65%, w/w) is less than that of other nations, except for Russian crude oil, but slightly higher than that of Brazilian crude oil, indicating that asphaltene deposition may pose less problems during Nigerian crude oil development than most of the crude oils from other nations. The IR spectra of the asphaltenes indicate the presence of alkanes, aromatic rings, phenyl rings, alcohols, ethers, carboxylic acids, esters, aldehydes, ketones, anhydrides, organic sulphoxides, sulphate salts and thiobenzophenones, confirming the fact that asphaltenes are composed of high molecular weight polycyclic constituents comprising of nitrogen, sulphur and oxygen heteroatoms. Ten elements (Cr, Cu, Fe, Mn, Ni, S, V, Zn, C and N) are examined and their concentrations determined. The results show that the values of all the elements are comparatively higher in the asphaltenes than the crude oils due to the presence of comparatively high concentrations of porphyrins in the asphaltenes than the crude oils. This is confirmed by their T-test values. Cross plot analysis result between the asphaltenes and crude oils using their elemental mean concentrations as variables indicates that moderate and positive correlation (R2=0.53) exists between them, indicating inter-element and geochemical relationships between them. Elemental clustering analysis results present two groups which are also fairly correlated. As expected, the elements show very close clustering because all the elements are known to associate with petroleum hydrocarbon formation. Also, apart from N, S and C; other elements are transition metals with similar chemical affinity.

From Fractal to Nanorod Porphyrin J-Aggregates. Concentration-Induced Tuning of the Aggregate Size

A structural change from fractal to nanorod J-aggregates of tetrakis(4-sulfonatophenyl)porphyrin has been obtained by acting on the intermolecular interaction potential. The size and shape of these self-assembled porphyrin clusters have been monitored under different experimental conditions, by means of polarized and depolarized dynamic light scattering and small and wide angle elastic light scattering. At sufficiently low porphyrin concentration and high ionic strength, the shielded repulsive potential seems to be responsible for the fractal structure of the aggregates. On the contrary, at low ionic strength (nonshielded potential) and high porphyrin concentration, these species self-assemble in a rodlike arrangement. The length of the so-formed rod-shaped aggregates decreases on increasing porphyrin concentration. Moreover, both fractals and rods display a structure-dependent optical activity induced by a chiral template.

Photodynamic activity of monocationic and non-charged methoxyphenylporphyrin derivatives in homogeneous and biological media

A novel 5-[4-(trimethylammonium)phenyl]-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin iodide (2) has been synthesized. A positive charge was incorporated at a peripheral position to increase the amphiphilic character of the structure. The photodynamic effect of the cationic porphyrin 2 was compared with that of non-charged 5-(4-aminophenyl)-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin (1), both in a homogeneous medium bearing photooxidizable substrates and in vitro on the Hep-2 human larynx carcinoma cell line. Absorption and fluorescence spectroscopic studies in different media show that 2 is essentially unaggregated in solution, and also in human cells. The singlet molecular oxygen, O2(1delta(g)), production was evaluated using 9,10-dimethylanthracene in N,N-dimethylformamide, yielding phi(delta) values of approximately 0.66 for both porphyrins. The addition of beta-carotene suppresses the O2(1delta(g))-mediated photooxidation. L-Tryptophan and guanosine 5'-monophosphate were used as biological substrate models. Porphyrin 2 sensitizes the decomposition of both compounds faster than does 1. In the biological medium, no dark cytotoxicity was observed, even though a high porphyrin concentration (10 microM) and a long incubation time (24 h) were employed. Cell treatments were performed with 5 microM of porphyrin for 24 h. Under these conditions, the uptake of porphyrin 2 into Hep-2 was about 3 times higher than that of 1. Cell survival after irradiation with visible light was dependent upon both the light exposure level and intracellular sensitizer concentration. Thus, a higher photocytotoxic effect was found for porphyrin 2 in comparison to 1. These results show that the amphiphilic monocationic porphyrin 2 could be a promising model for phototherapeutic agents with potential applications in tumor cell inactivation by photodynamic therapy.

Effects of continuous light exposure on antioxidant enzymes, porphyric enzymes and cellular damage in the Harderian gland of the Syrian hamster.

The Syrian hamster Harderian gland (HG), an organ present in the male two secretory cell types (type-I and type-II cells), is physiologically exposed to high oxidative stress because of high concentrations of porphyrins and their precursor, 5-aminolevulinic acid. Because of its juxtaorbital location, the HG is accessible to light, and subject to phototoxic effects of these substances. After having previously demonstrated circadian rhythms in antioxidant enzymes, porphyric enzymes and oxidative damage of proteins and lipids, as well as influences of melatonin on these parameters, we have now studied the effects of continuous light (LL), which suppresses melatonin secretion by the pineal gland. Measurements were performed in two different circadian phases, in order to detect the presence or absence of day/night differences. In LL, no differences between circadian phases of subjective day and subjective night were demonstrable for 5-aminolevulinate synthase, 5-aminolevulinate dehydratase, porphobilinogen deaminase, or superoxide dismutase; temporal differences in glutathione reductase and catalase were markedly diminished, whereas all these parameters showed marked day/night differences in the rats exposed to a light/dark cycle of 14:10. In LL, oxidative damage to lipids was minimally effected, while protein damage was enhanced. LL also caused a reduction in the percentage of type-II cells. Therefore, cell differentiation in the HG does not seem to be controlled only by the androgen, but, unexpectedly, also by melatonin.

Structural and Photophysical Properties of a Water-Soluble Porphyrin Associated with Polycations in Solution and Electrostatically-Assembled Ultrathin Films

A water-soluble porphyrin, meso-tetra(4-sulfonatophenyl)porphyrin (TSPP), has been associated with two different polycations, poly(diallyldimethylammonium chloride) (PDDA) and poly(ethyleneimine) (PEI), to investigate the effects of polymer binding upon the TSPP structure and excited-state dynamics both in solution and in ultrathin (∼10−30 A) films deposited on glass slides by electrostatic assembly. Association of the porphyrin with PEI intrinsically quenches the singlet state dynamics of TSPP, both in solution and in films, while quenching is observed upon association with PDDA only for high concentrations of porphyrins or in films where TSPP aggregates are observed. For PDDA:TSPP films without significant aggregate content, the fluorescence decay time (τ1/e ∼ 5−6 ns) approaches that observed for monomeric or polymer-bound porphyrins in dilute solution (τ1/e = 10.2 and 11.3 ns, respectively). However, rapid (<1 ns) deactivation of the singlet states can be observed whenever appreciable aggregates are pr...

Polarization-sensitive resonance CARS spectroscopy of magnesium octaethylporphine

Polarization-sensitive resonance coherent anti-Stokes Raman scattering spectroscopy of magnesium octaethylporphine (MgOEP) in dichloromethane is reported. The measurements were performed in resonance with the Q-band electronic absorption where linear resonance Raman spectroscopic measurements were foiled by excessive fluorescence. A high porphyrin concentration allowed direct identification of the different vibrational mode symmetries. Complementary vibrational information was obtained from B-band resonance Raman spectra. MgOEP was found to be structurally similar to nickel octaethylporphine, but with an expanded porphyrin core. Copyright ” 1999 John Wiley & Sons, Ltd.

Antioxidative effect of protoporphyrin on lipid peroxidation in tissue homogenates of intravenously administered rats.

Effect of intravenous administration of protoporphyrin IX (PP) on lipid peroxidation was studied in rats. PP and/or PP-derived porphyrins were found to be mainly distributed in livers, spleen and lungs. Dose-dependent decreases in the Fe2+ and L-ascorbic acid-stimulated lipid peroxidation in homogenates of livers and dose-dependent increases in porphyrin concentration in livers were observed after the PP injection. In the experiments with a 20 mg/kg dose of PP, the peroxidation level in the liver homogenates reached its minimum level during the period of 3 to 24 h accompanying the high porphyrin concentration in livers after the administration. After 96 h, a relatively high porphyrin concentration was still retained, but decreases in the peroxidation levels had ceased. PP administration caused a dose-dependent decrease in the endogenous lipid peroxides in livers within 0.5 h and the low levels were maintained throughout the course of the 168-h study. These results clearly show that the administered PP is distributed in the liver and inhibits the lipid peroxidation in vivo.

UPTAKE and PHOTODYNAMIC EFFICIENCY OF HEM ATOPORPH YRIN, HYDROXYETHYLVINYLDEUTEROPORPHYRIN and HEMATOPORPHYRIN DERIVATIVE (PHOTOFRIN II®): A STUDY WITH ISOLATED MITOCHONDRIA

The uptake of Photofrin II (PFII), hematoporphyrin (Hp) and hydroxyethylvinyldeuteroporphyrin (HVD) by isolated mitochondria was studied using the high performance liquid chromatography (HPLC) technique. The various PFII components show a high affinity for mitochondria. At 5.75 micrograms/ml PFII, their ratio of incorporation was found to be very similar, except for Hp which is about two times less incorporated. These results were reproduced with pure Hp and pure HVD. The uptake of Hp and HVD increases with concentration but, while that of Hp reaches a plateau, the uptake of HVD continues to increase. At a high porphyrin concentration (approximately 10(-5) M), the loss of respiratory control is obtained with the same light dose for Hp and PFII. Taking into account the uptake and the known photophysical parameters of the various porphyrins, the photodynamic efficiency of HVD seems equivalent to that of Hp. The present results and known data on cell photoinactivation suggest that the activity of these porphyrins is mainly dependent on their incorporation.

The inhibitory effect of coproporphyrins on amino acid uptake into proteins by porphyric liver cells

Steroids, drugs and certain chemicals stimulate the synthesis of porphyrins in avian liver cells by inducing the de novo formation of 6-aminolevulinate synthetase (ALAS), the rate-limiting enzyme in the porphyrinheme biosynthetic pathway [l-3]. This chemicallyinduced hepatic porphyria has proved to be a useful experimental model for examining pathogenetic mechanisms in the natural disorders of porphyrin metabolism in man. The excess porphyrins synthesized by avian liver cells treated with porphyrinogenic chemicals accumulate in these cells in very high concentrations [ 1,4] ; similarly high concentrations of porphyrins accumulate in the liver in certain of the human porphyrias. The pharmacological effects which these porphyrins may have on the various metabolic processes of hepatic cells are not known. In the course of other studies, we observed that in liver cells treated with the potent porphyrinogenic agent allylisopropylacetamide (AIA), the incorporation of “C-leucine into proteins in vitro was significantly less than in untreated cultures. This effect was unexpected in light of the known increase in liver enzyme synthesis which takes place in experimental porphyria [5,6] ; moreover the inhibition of 14C-leucine incorporation into protein was observed only during the latter part of the induction period when porphyrins are present in great excess in the treated hepatic cells. Such inhibition was also noted when exogenous b-aminolevulinic acid (ALA) was added to the cultures and transformed by the cell into porphyrins. These findings led us to examine the direct effects of porphyrins on amino acid incorporation into protein by cultured liver cells. The results of these experi-