Factors influencing the distribution pattern of porphyrins in cell membranes

The mechanism of the sensitizer-membrane interactions has been studied by following the distribution properties of selected porphyrins, including haematoporphyrin (HP) and protoporphyrin (PP), into unilamellar liposomes of dipalmitoyl phosphatidylcholine (DPPC). The endomembrane distribution of HP and PP has been checked as a function of the membrane fluidity and composition by fluorescence polarization and quenching techniques. At porphyrin concentrations below 0.5 microM, HP and PP exclusively localize in the inner phospholipid monolayer; at higher concentrations, the outer monolayer also becomes populated. The porphyrin binding sites in liposomes, however, are different for HP and PP: HP preferentially distributes into water-accessible lipid regions, while PP localizes in the most hydrophobic loci of the lipid matrix. A porphyrin redistribution occurs when the fluidity properties of the liposomes are changed by addition of cholesterol or cardiolipin. In DPPC-cholesterol vesicles, all HP molecules dissolve in DPPC-rich regions while all PP molecules partition in cholesterol-rich environments. In DPPC-cardiolipin vesicles both porphyrins preferentially localize in regions accessible to the external medium. The effect of the nature of the carrier on porphyrin distribution in membranes has been studied by following the uptake and photosensitization properties of free and DPPC-incorporated PP and HP with rat liver mitochondria. The porphyrin photosensitizing efficiency has been checked by following the impairment of the respiratory function of mitochondria upon irradiation. Liposome-bound HP is less active than aqueous HP in determining membrane photodamage in mitochondria. On the contrary, aqueous PP is a very poor sensitizer as compared to a DPPC liposome-entrapped drug.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vitro EVALUATION OF PHOTOTOXIC PROPERTIES OF FOUR STRUCTURALLY RELATED BENZOPORPHYRIN DERIVATIVES

Four structural analogs of benzoporphyrin derivative (BPD) have been studied and compared for photosensitizing activity in vitro. All analogs have an identical reduced tetrapyrrol porphyrin ring, and differ by the position of a cyclohexadiene ring (fused at either ring A or ring B of the porphyrin) and the presence of either two acid groups or one acid and one ester group at rings C and D of the porphyrin. Photosensitizer activity was tested with the M1 tumor cell line using an assay (the MTT assay) which detects mitochondrial hydrogenases as a measure of cell viability. This assay was shown to be equivalent to the standard clonogenicity or [3H]thymidine uptake assay. Comparative studies with the BPD analogs showed that the monoacid derivatives had equivalent cytotoxicity and were about five-fold more active than the diacid forms. This was the case whether the assays were performed in the presence or absence of fetal calf serum.     

Influence of diamino acid derivatives of protoporphyrin IX on mouse immunological system: preliminary results

Immunological response related to photodynamic therapy (PDT) is one of the basic elements that influence on the efficiency of this cancer treatment method. Diamino acid derivatives of protoporphyrin IX are promising photosensitizing agents that are intended to be the components of new anti-tumor drug. The influence of three derivatives - PP(Ser)(2)Arg(2), PP(Ala)(2)Arg(2), PP(Phe)(2)Arg(2) and a mixture of these compounds called Sensyphyrine on mouse immunological system was investigated where animals were exposed and unexposed to the laser irradiation. Porphyrins solutions were injected intravenously, mice were irradiated with the red diode laser at lambda=632 nm. Cells and blood samples were taken at time intervals after irradiation. The levels of interleukin-6, interleukin-1beta and the production of reactive forms of nitrogen by macrophages were determined. The results show that all of the diamino acid derivatives of protoporphyrin IX indicate an immunological response when the light is applied. Each of the porphyrin revealed different impact on mice immunological system. The most potent stimulant properties disclosed PP(Phe)(2)Arg(2) derivative for which the highest values of IL-1beta, IL-6 and NO(2)(-) were noticed. The weakest immunological activation revealed PP(Ser)(2)Arg(2) derivative.     

Synthesis of fluorine analogues of protoporphyrin potentially useful for diagnosis and therapy of tumors

With the aim of obtaining a porphyrin derivative useful for diagnosis and therapy of cancer, fluorine analogues of protoporphyrin, in which the vinyl group(s) were replaced by difluorovinyl group(s), were synthesized by the reaction of the formylporphyrins with sodium chlorodifluoroacetate in the presence of triphenylphosphine. Some improvements in the reported procedures for the synthesis of formylporphyrins are also described. Preliminary results of biological tests of the products showed that 8(2),8(2)-difluoroprotoporphyrin accumulates to gastric cancer more selectively than other fluorine analogues and that 3(2),3(2),8(2),8(2)-tetrafluoroprotoporphyrin is taken up by rat hepatoma cells more readily than the others.     

PHOTOSENSITIZATION OF MITOCHONDRIA BY LIPOSOME-BOUND PORPHYRINS

We have compared the photodynamic activities of hematoporphyrin (HP) and protoporphyrin (PP) on isolated rat liver mitochondria by measuring the decline of the respiratory control ratio (RCR) after irradiation at 365 nm. Before addition to the respiratory mcdium, the dyes were dissolved in phosphate-buffered saline (PBS) or incorporated into unilamellar liposomes of dipalmitoyl-phosphatidylcholine (DPPC), sometimes enriched with cholesterol (Chol) or cardiolipin (Card), which are naturally present in mitochondrial membranes. Chol and especially Card strongly increase the porphyrin uptake by mitochondria. In all experimental conditions, PP is taken up by mitochondria to a higher extent than HP. Nevertheless, under conditions giving the same amount of mitochondriabound dye, HP is a morc efficient photosensitizer than PP. As the efficiency of singlet oxygen production has been shown to be equivalent for the two porphyrins in monomeric state, the resulting photobiological effects are explained in terms of different localization of HP and PP in the mitochondrial membrancs. In particular, HP preferentially localizes in the protein-rich polar domains of the inner mitochondrial membrane, whereas PP dissolvcs in the lipid regions of the mcmbrancs.     

Diamino Acid Derivatives of Porphyrins Penetrate into Yeast Cells, Induce Photodamage, but Have No Mutagenic Effect

The yeast Saccharomyces cerevisiae was used as a model eukaryotic organism to study the uptake of diamino acid derivatives of porphyrins and their phototoxicity with particular emphasis on possible mutagenic effects. The water-soluble hematoporphyrin derivatives diarginate (HpD[Arg]₂) and 1-arginin di(N-amino acid)-protoporphyrinate used in this study are effective photosensitizers in tumor photodynamic therapy. Depending on the amino acid substituent, the porphyrin derivatives differ in their affinity for yeast cells. It is shown that HpD(Arg)₂ and PP(Met)₂ (Arg)₂ penetrate into the yeast cell and are metabolized. Both compounds sensitize yeast cells to photodamage but have no mutagenic effect on nuclear or mitochondrial genomes.     

QUANTUM YIELDS AND KINETICS OF THE PHOTOBLEACHING OF HEMATOPORPHYRIN, PHOTOFRIN II, TETRA(4-SULFONATOPHENYL)-PORPHINE AND UROPORPHYRIN

Abstract Porphyrins used as sensitizers for the photodynamic therapy (PDT) of tumors are progressively destroyed (photobleached) during illumination. If the porphyrin bleaches too rapidly, tumor destruction will not be complete. However, with appropriate sensitizer dosages and bleaching rates, irreversible photodynamic injury to the normal tissues surrounding the tumor, which retain less sensitizer, may be significantly decreased. This paper surveys the quantum yields and kinetics of the photobleaching of four porphyrins: hematoporphyrin (HP), Photofrin II (PF II), tetra(4-sulfonatophenyOporphine (TSPP) and uroporphyrin I (URO). The initial quantum yields of photobleaching, as measured in pH 7.4 phosphate buffer in air, were: 4.7 × 10^-5, 5.4 × 10^-5, 9.8 × 10^-5, and 2.8 × 10^-5 for HP, PF II, TSPP and URO respectively; thus, the rates of photobleaching are rather slow. Low oxygen concentration (2 μM) significantly reduced the photobleaching yields. However, D₂O increased the yields only slightly, and the singlet oxygen quencher, azide, had no effect, even at 0.1 M. Photosensitizing porphyrins in body fluids, cells and tissues may be closely associated with various photooxidizable molecules and electron acceptors and donors. Therefore, selected model compounds in these categories were examined for their effects on porphyrin photobleaching. A number inhibited and/or accelerated photobleaching, depending on the compound, the porphyrin and the reaction conditions. For example, 1.0 mM furfuryl alcohol increased the photobleaching yields of HP and URO more than 5-fold, with little effect on PF II or TSPP. In contrast, the electron acceptor, methyl viologen, increased the photobleaching yield of TSPP more than 10-fold, with little accelerating effect on the other porphyrins. These results suggest that the mechanism(s) of the photobleaching of porphyrin photosensitizers in cells and tissues during PDT may be complex.     

QUANTUM YIELDS AND KINETICS OF THE PHOTOBLEACHING OF HEMATOPORPHYRIN, PHOTOFRIN II, TETRA(4-SULFONATOPHENYL)-PORPHINE AND UROPORPHYRIN

Porphyrins used as sensitizers for the photodynamic therapy (PDT) of tumors are progressively destroyed (photobleached) during illumination. If the porphyrin bleaches too rapidly, tumor destruction will not be complete. However, with appropriate sensitizer dosages and bleaching rates, irreversible photodynamic injury to the normal tissues surrounding the tumor, which retain less sensitizer, may be significantly decreased. This paper surveys the quantum yields and kinetics of the photobleaching of four porphyrins: hematoporphyrin (HP), Photofrin II (PF II), tetra(4-sulfonatophenyl)porphine (TSPP) and uroporphyrin I (URO). The initial quantum yields of photobleaching, as measured in pH 7.4 phosphate buffer in air, were: 4.7 x 10(-5), 5.4 x 10(-5), 9.8 x 10(-6), and 2.8 x 10(-5) for HP, PF II, TSPP and URO respectively; thus, the rates of photobleaching are rather slow. Low oxygen concentration (2 microM) significantly reduced the photobleaching yields. However, D2O increased the yields only slightly, and the singlet oxygen quencher, azide, had no effect, even at 0.1 M. Photosensitizing porphyrins in body fluids, cells and tissues may be closely associated with various photooxidizable molecules and electron acceptors and donors. Therefore, selected model compounds in these categories were examined for their effects on porphyrin photobleaching. A number inhibited and/or accelerated photobleaching, depending on the compound, the porphyrin and the reaction conditions. For example, 1.0 mM furfuryl alcohol increased the photobleaching yields of HP and URO more than 5-fold, with little effect on PF II or TSPP. In contrast, the electron acceptor, methyl viologen, increased the photobleaching yield of TSPP more than 10-fold, with little accelerating effect on the other porphyrins. These results suggest that the mechanism(s) of the photobleaching of porphyrin photosensitizers in cells and tissues during PDT may be complex.     

Incorporation of glycoconjugated porphyrin derivatives into phospholipid monolayers: a screening method for the evaluation of their interaction with a cell membrane

The use of porphyrin derivatives in photodynamic therapy is of excellent prospect for the treatment of superficial or easily reachable tumors. The selection of porphyrin derivatives by tumor cells depends to a large extent of their ability to interact with the biological membrane. The evaluation of porphyrin interaction with phospholipids can thus be used as a screening method. In this work we report on the assessment of the interaction of three new porphyrin derivatives with various phospholipids forming Langmuir films by surface tension and surface pressure measurements, grazing incidence X-ray diffraction, and liquid chromatography on an IAM stationary phase. The results show that the hydroxylated phenylporphyrin (m-THPP) is able to interact with all studied phospholipids and to significantly disorganize the structure of their monolayers. Obviously, the interaction occurs at the level of the hydrophobic chains of a phospholipid. A triglucoconjugated phenylporphyrin (m-TPP(Glu)3) also interacts with the phospholipids though to a lesser extent. Conversely, the tetraglucoconjugated derivative (m-TPP(Glu)4) exhibits both a weak surface activity and a poor affinity for the studied phospholipids. Thus, whereas m-THPP and m-TPP(Glu)3 are expected to penetrate into a biological membrane, m-TPP(Glu)4 seems unlikely to do so.     

ENHANCEMENT OF PORPHYRIN-PHOTOSENSITIZATION OF YEAST CELLS BY ETHANOL

Abstract In porphyrin photosensitization, the localization of porphyrin in the cell and the sensitizing activity have been of recent concern. Hydrophobic porphyrins are usually in a highly aggregated state in aqueous systems. This study was designed to see whether the change in the polarity of the environment by adding ethanol could modify the sensitizing effects of porphyrins using a fermentable (alcohol tolerant) yeast ( Saccharomyces cerevisiae ) cells. The results showed that (1) the addition of ethanol (˜15%) to the aqueous suspension remarkably increased inactivation and cell membrane damage both in the hematoporphyrin (HP) and protoporphyrin (PP) photosensitizations, and (2) a sharp induction of genetic changes occurred concomitantly both in HP and PP sensitized cells in the presence of ethanol. In view of the fact that the addition of ethanol modified the absorption spectra and fluorescence intensity of porphyrins in favor of deaggregation, these results may be interpreted to mean that deaggregation of porphyrins promoted by ethanol enhanced their solubility in the lipophilic environment of the cell membrane and even further inside, thereby increasing the sensitizing activities.     

Chemoenzymatic Platform for Synthesis of Chiral Organofluorines Based on Type II Aldolases

Aldolases are C?C bond forming enzymes that have become prominent tools for sustainable synthesis of complex synthons. However, enzymatic methods of fluorine incorporation into such compounds are lacking due to the rarity of fluorine in nature. Recently, the use of fluoropyruvate as a non‐native aldolase substrate has arisen as a solution. Here, we report that the type II HpcH aldolases efficiently catalyze fluoropyruvate addition to diverse aldehydes, with exclusive (3S)‐selectivity at fluorine that is rationalized by DFT calculations on a mechanistic model. We also measure the kinetic parameters of aldol addition and demonstrate engineering of the hydroxyl group stereoselectivity. Our aldolase collection is then employed in the chemoenzymatic synthesis of novel fluoroacids and ester derivatives in high stereopurity (d.r. 80–98 %). The compounds made available by this method serve as precursors to fluorinated analogs of sugars, amino acids, and other valuable chiral building blocks.     

Thermodynamics of porphyrin binding to human serum albumin using affinity capillary electrophoresis

Summary The interaction thermodynamics of heptacarboxylporphyrin (HCP) and protoporhyrin (PP) with human serum albumin (HSA) was studied by affinity capillary electrophoresis (ACE) over the temperature range of 25–50°C, where HCP and PP bound to HSAvia 1:1 molecular association. The binding equilibrium constants (pH 7.4, phosphate buffer) for the binding of HCP with HSA were found to decrease with an increase in temperature, whereas the binding constants of the PP/HSA system appeared to be independent of temperature changes over the range studied. The van’t Hoff relationship (25–50°C) was found to be linear for the interaction of either HCP or PP with HSA. However, the interaction thermodynamics for both of these porphyrins with HSA were found to be quite different. In particular, the interaction of HCP (a hydrophilic porphyrin) with HSA appeared to be based on an enthalpy-driven process, whereas the binding between PP (a hydrophobic porphyrin) and HSA driven by a favorable change in entropy. The ability of using ACE to evaluate the interaction thermodynamics of serum proteins (e.g., HSA) with ligands (e.g., porphyrins and related compounds) should aid in the development of new and more effective photosensitizers in the photodynamic therapy of cancer.     

Boronated protohaemins: synthesis and in vivo antitumour efficacy

The conjugates of porphyrin macrocycles with boron-containing polyhedra are under investigation as agents for binary treatment strategies of cancer. Aiming at the design of photoactive compounds with low-to-zero dark toxicity, we synthesized a series of carboranyl and monocarbon-carboranyl derivatives of protohaemin IX using the activation of porphyrin carboxylic groups with di-tert-butyl pyrocarbonate or pivaloyl chloride. The water-soluble 1,3,5,8-tetramethyl-2,4-divinyl-6(7)-[2'-(closo-monocarbon-carborane-1'-yl)methoxycarbonylethyl]-7(6)-(2'-carboxyethyl)porphyrin Fe(III) (compound 9) exerted no discernible cytotoxicity for cultured mammalian cells, nor did it cause general toxicity in rats. Importantly, 9 demonstrated dose-dependent activity as a phototoxin in photodynamic therapy of M-1 sarcoma-bearing rats. In animals injected with 20 mg kg(-1) of 9, the tumours shrank by day 3 after one single irradiation of the tumour with red laser light. Between 7 and 14 days post-irradiation, 88.9% of rats were tumour-free; no recurrence of the disease was detectable within at least 90 days. Protohaemin IX alone was without effect, indicating that boronation is important for the phototoxic activity of 9. This is the first study that presents the synthesis and preclinical in vivo efficacy of boronated derivatives of protohaemin as phototoxins. The applicability in photodynamic treatment broadens the therapeutic potential of boronated porphyrins beyond their conventional role as radiosensitizers in boron neutron capture therapy.     

Polymeric porphyrins as new photocatalysts in photodynamic therapy of cancer

Photodynamic therapy and diagnosis (PDT) is described as an efficient clinical method for the treatment of cancer patients using hematoporphyrin derivative (Hpd) as sensitizer. Newly developed metal-containing porphyrin type compounds are potential agents for PDT. A concept for covalently bound polymeric metal-containing or metal-free sensitizers is discussed. First results of these polymeric sensitizers are reported from in vivo experiments. High tumor accumulation up to 30% was observed. Results of fluorescence diagnosis are shown.     

1,3-偶极环加成反应修饰卟啉化合物

利用1,3-偶极环加成反应对卟啉大环进行修饰是近年来卟啉研究的一个新热点。环加成产物因在可见光谱长波段范围的特征吸收,在构筑人工光反应体系和用作光动力疗法中的光敏剂等领域有重要应用价值。本文综述了1,3-偶极环加成反应在修饰卟啉化合物方面的研究进展,包括：卟啉作为亲偶极体能与甲亚胺叶立德、硝酮、重氮烷、羰基叶立德、腈氧化物等1,3-偶极子反应生成各种新型杂环稠合卟吩类化合物;卟啉化合物作为1,3-偶极子能与C₆₀等亲偶极体反应,生成β位取代的各种新型卟啉化合物;以及扩展卟啉也可以作为亲偶极体与甲亚胺偶极子发生1,3-偶极环加成反应等。     

Synthesis and properties of monofluorinated dimyristoylphosphatidylcholine derivatives: potential fluorinated probes for the study of membrane topology

The synthesis of three monofluorinated dimyristoylphosphatidylcholine derivatives (F-DMPC), with the fluorine atom located on the acyl chain in position 2 of the glycerol (sn-2) is described. The synthetic strategy relies on the coupling of 1-myristoyl-2-hydroxy-sn-glycero-3-phosphocholine (lyso-PC) and three different fluorinated fatty acids. The latter were obtained from two different and complementary synthetic routes. Preliminary FTIR studies suggest that the presence of the fluorine atom does not significantly perturb the lipid conformational order and phase transition temperature and that these monofluorinated PC derivatives could be used as probes for the study of membrane topology, i.e. the location of drugs, peptides or proteins in membranes.     

Synthesis of peptidyl phosphonates containing 5‐(4′‐carboxyphenyl)‐10,15,20‐tritolylporphyrin

The synthesis and characterization of three new porphyrin‐peptidyl‐phosphonate derivatives, containing a diphenyl 3‐pyridylmethyl‐phosphonate moiety, is described. These compounds could serve as potential photosensitizers for the PDT method of tumor therapy and displayed activity as inhibitors of aminopeptidase N. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:107–111, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20407     

Spectroscopic properties and photodynamic effects of new lipophilic porphyrin derivatives: efficacy, localisation and cell death pathways

Photodynamic therapy (PDT) and photodynamic diagnostics (PDD) of cancer are based on the use of non-toxic dyes (photosensitisers) in combination with harmless visible light. This paper reports physicochemical properties, cell uptake, localisation as well as photodynamic efficiency of two novel lipophilic porphyrin derivatives, suitable for use as PDT sensitisers. Both compounds are characterised by high quantum yield of singlet oxygen generation which was measured by time-resolved phosphorescence. Photodynamic in vitro studies were conducted on three cancer cell lines. Results of cell survival tests showed negligible dark cytotoxicity but high phototoxicity. The results also indicate that cell death is dependent on energy dose and time following light exposure. Using confocal laser scanning microscopy both compounds were found to localise in the cytoplasm around the nucleus of the tumour cells. The mode of cell death was evaluated based on the morphological changes after differential staining. In summary, good photostability, high quantum yield of singlet oxygen and biological effectiveness indicate that the examined lipophilic porphyrin derivatives offer quite interesting prospects of photodynamic therapy application.     

Synchronously synthesizing and immobilizing porphyrins on crosslinked polystyrene microspheres and preliminary study on catalytic activity of supported metalloporphyrins

A novel method for immobilizing porphyrins as well as metalloporphyrins (MPs) on polymeric supports was found, and it is the way to synchronously synthesize and immobilize porphyrins on polymeric microspheres. By using 4‐hydroxybenzaldehyde (HBA)‐bound crosslinked polystyrene (CPS) microspheres, pyrrole, and benzaldehyde in a solution as co‐reactants and through the Adler's reaction between solid–liquid phases, it was successfully realized to simultaneously synthesize and immobilize phenyl porphyrin (PP) on CPS microspheres, resulting in PP‐supported microspheres PP–CPS. With the same method, substituted PPs, 4‐chlorophenyl porphyrin (CPP) and 4‐nitrophenyl porphyrin (NPP), were also successfully immobilized on CPS microspheres by using substituted benzaldehydes, 4‐chlorobenzaldehyde and 4‐nitrobenzaldehyde, as one reactant in the solution, respectively, and other two porphyrin‐supported microspheres, CPP–CPS and NPP–CPS, were obtained. The effects of various factors on the process of synchronously synthesizing and immobilizing porphyrins on CPS microspheres were mainly studied. Further, the coordination reaction of cobalt salt with PP–CPS as well as CPP–CPS and NPP–CPS was conducted, forming three solid catalysts, CoPP–CPS, CoCPP–CPS, and CoNPP–CPS. The catalytic properties of these catalysts in the catalytic oxidation of ethylbenzene to acetophenone by dioxygen were preliminarily examined. The experimental results indicate that the Adler's reaction between solid–liquid phases, namely the reaction between HBA‐bound CPS microspheres and pyrrole as well as free benzaldehyde or analogs in the solution can favorably be carried out. For this process, the fitting protonic acid catalyst is p‐nitrobenzoic acid and appropriate solvent is dimethyl sulfoxide (DMSO). By comparison, the process of preparing CPP–CPS microspheres is easier to be carried out. The obtained three solid catalysts can effectively catalyze the oxidation of ethylbenzene to acetophenone by dioxygen. In comparison, the catalytic activity of CoNPP–CPS is the highest. Copyright © 2009 John Wiley & Sons, Ltd.     

Relative axial ligand orientation in bis(imidazole)iron(II) porphyrinates: are "picket fence" derivatives different?

The synthesis of three new bis(imidazole)-ligated iron(II) picket fence porphyrin derivatives, [Fe(TpivPP)(1-RIm) 2] 1-RIm = 1-methyl-, 1-ethyl-, or 1-vinylimidazole) are reported. X-ray structure determinations reveal that the steric requirements of the four alpha,alpha,alpha,alpha-o-pivalamidophenyl groups lead to very restricted rotation of the imidazole ligand on the picket side of the porphyrin plane; the crowding leads to an imidazole plane orientation eclipsing an iron-porphyrin nitrogen bond. An unusual feature for these diamagnetic iron(II) species is that all three derivatives have the two axial ligands with a relative perpendicular orientation; the dihedral angles between the two imidazole planes are 77.2 degrees , 62.4 degrees , and 78.5 degrees . All three derivatives have nearly planar porphyrin cores. M?ssbauer spectroscopic characterization shows that all three derivatives have quadrupole splitting constants around 1.00 mm/s at 100K.