Syntheses and in vitro evaluation of water-soluble "cationic metalloporphyrin-ellipticine" molecules having a high affinity for DNA

Synthesis, characterization, and photodynamic therapy activity of 5,10,15,20-Tetrakis(carboxyl)porphyrin

Water-soluble porphyrins are considered promising drug candidates for photodynamic therapy (PDT). This study investigated the PDT activity of a new water-soluble, anionic porphyrin (1-Zn), which possesses four negative charges. The photodynamic anticancer activity of 1-Zn was investigated by the MTT assay, with mTHPC as a positive control. The cellular distribution was determined by fluorescence microscopy. Holographic and phase contrast images were recorded after 1-Zn treatment with a HoloMonitor™ M3 instrument. The inhibition of A549 cell growth achieved by inducing apoptosis was investigated by flow cytometry and fluorescence microscopy. DNA damage was investigated by the comet assay. The expression of apoptosis-related proteins was also measured by western blot assays. 1-Zn had better phototoxicity against A549 cells than HeLa and HepG2 cancer cells. Interestingly, 1-Zn was clearly located almost entirely in the cell cytoplasmic region/organelles. The late apoptotic population was less than 1.0% at baseline in the untreated and only light-treated cells and increased to 40.5% after 1-Zn treatment and irradiation (P < 0.05). 1-Zn triggered significant ROS generation after irradiation, causing ΔΨm disruption (P < 0.01) and DNA damage. 1-Zn induced A549 cell apoptosis via the mitochondrial apoptosis pathway. In addition, 1-Zn bound in the groove of DNA via an outside binding mode by pi-pi stacking and hydrogen bonding. 1-Zn exhibits good photonuclease activity and might serve as a potential photosensitizer (PS) for lung cancer cells.

Synthesis andin vitroanticancer activity of water-soluble cationic pyridylporphyrins and their metallocomplexes

Tetrapyrrolic compounds such as porphyrins are known to be prospective chemotherapeutics and photosensitizers for cancer treatment and diagnosis. In this work, water-soluble, meso-substituted cationic pyridyl-porphyrins and their metallocomplexes bearing various central metal atoms ( Ag , Zn , Co , and Fe ) in the porphine ring and various functional groups (allyl, oxyethyl, butyl, and methallyl) at the nitrogen atom in the pyridine ring were synthesized and characterized by1H and13C NMR and UV-visible spectroscopy. Cytotoxic and photodynamic activities of new porphyrins and their metal derivatives were investigated in vitro (KCL-22 cancer cell line of human chronic myeloid leukemia). The cytotoxicity of porphyrins was shown to be dependent on the presence and type of the central metal atom in the porphine ring. Ag -derivatives were more cytotoxic than Co −, Zn −, and Fe − metallocomplexes. The porphyrins bearing allyl-functional groups were evidenced to be more cytotoxic than those which included butyl-, oxyethyl-, and methallyl-groups. The change of nitrogen position in the pyridine ring of Ag -metalloporphyrins from 3(3-N-pyridylporphyrins) to 4(4-N-pyridylporphyrins) induced an increase in the cytotoxic activity of metallocomplexes. All synthesized Ag-metalloporphyrins, except, the oxyethyl-containing one were more cytotoxic than cisplatin. Allyl containing free porphyrin and its Zn -metallocomplex had higher phototoxicity than Ag −, Co −, and Fe -metalloporphyrins. The results obtained can be useful for further investigation of new porphyrins as potential chemotherapeutics and photosensitizers.

Hybrid molecules with a dual mode of action: dream or reality?

The drug market is still dominated by small molecules, and more than 80% of the clinical development of drug candidates in the top 20 pharmaceutical firms is still based on small molecules. The high cost of developing and manufacturing "biological drugs" will contribute to leaving an open space for drugs based on cheap small molecules. Four main routes can be explored to design affordable and efficient drugs: (i) a drastic reduction of the production costs of biological drugs, (ii) a real improvement of drug discovery via "computer-assisted combinatorial methods", (iii) going back to an extensive exploration of natural products as drug sources, and (iv) drug discovery by rational drug design and bio-inspired design that hopefully includes serendipity and human inspiration. At the border between bio-inspired design and rational design, one can imagine preparation of hybrid molecules with a dual mode of action to create efficient new drugs. In this Account, hybrid molecules are defined as chemical entities with two or more structural domains having different biological functions and dual activity, indicating that a hybrid molecule acts as two distinct pharmacophores. In order to obtain new antimalarial drugs that are affordable and able to avoid the emergence of resistant strains, we developed hybrid molecules with a dual mode of action (a "double-edged sword") able to kill multiresistant strains by oral administration. These hybrid molecules, named trioxaquines, with two pharmacophores able to interact with the heme target are made with a trioxane motif covalently linked to an aminoquinoline entity. More than 100 trioxaquines have been prepared by Palumed over a period of 4 years, and in collaboration with Sanofi-Aventis, the trioxaquine PA1103-SAR116242 has been selected in January 2007 as candidate for preclinical development.

In vitro antimalarial activity of metalloporphyrins against Plasmodium falciparum

The in vitro antimalarial activity against Plasmodium falciparum and heme polymerization were evaluated for ten metalloporphyrins: gallium protoporphyrin IX (GaPPIX), sodium salt of gallium protoporphyrin IX, silver protoporphyrin IX, palladium protoporphyrin IX, cobalt protoporphyrin IX, manganese protoporphyrin IX, tin protoporphyrin IX (SnPPIX), chromium protoporphyrin IX, gallium deuteroporphyrin IX (GaDPIX) and gallium hematoporphyrin IX. Metalloporphyrins inhibited parasite growth with 50% inhibitory concentrations (IC(50)) ranging from 15.5 microM to 190 microM. In trophozoite lysate-mediated heme polymerization assays, SnPPIX, GaPPIX and GaDPIX exerted potent inhibitory activity similar to that of artemisinin and chloroquine.

Synthesis and characterization of water-insoluble and water-soluble dibutyltin(IV) porphinate complexes based on the tris(pyridinyl)porphyrin moiety, their anti-tumor activity in vitro and interaction with DNA

The water-insoluble and water-soluble organotin(IV)porphinate complexes based on the tris-(4-pyridinyl)porphyrin and tris(N-methyl-4-pyridiniumyl)porphyrin moieties were synthesized and characterized by elemental analysis, (1)H NMR, IR and electrospray ionization mass spectra. The in vitro activity of the compounds against P388 leukemia and A-549 was determined. The results show that the anti-tumor activities of organotin(IV)porphinate is related to the water solubility of the compounds and the central ion in the porphyrin ring. The interaction between the water-soluble dibutyltin(IV) porphinate (7 and 10) complexes and DNA has been investigated. The result shows that compounds 7 and 10 cause DNA hypochromism measured by A(260), a slight increase in the viscosity of the DNA, and an increase in the melting point of DNA by 2.9 and 1.6 degrees C, respectively at DNA(base)/Drug(Por) ratios of 60. The binding constants to DNA were 1.35+/-0.16 x 10(7) M(-1) (7) and 1.45+/-0.12 x 10(6) M(-1) (10) determined using EB competition method based on the porphyrin concentration, which is 20 and five times greater than that of precursor porphyrins [5-p,o-(carboxy)methoxyphenyl-10,15,20-tris(N-methyl-4-pyridiniumyl)] porphyrin (p,o-tMPyPac) to DNA. Electrophoresis test shows that the compounds cannot cleave the DNA. According to the electrophoresis test result and all the above results, the cytotoxic activity against P388 and A-549 tumor cells appears not to come from the cleavage of DNA caused by the compounds but from the high affinity of compounds to DNA.

Synthesis and selective tumor targeting properties of water soluble porphyrin-Pt(II) conjugates

We have designed and synthesized a series of novel water soluble porphyrins and their platinum(II) conjugates, cis-[(Por)Pt(dmso)X], where Por=5-(4-pyridyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin) (PyTPPS) or 5-[4-(3-aminopropyl)pyridiniumyl]-10,15,20-tris(4-sulphonatophenyl)porphyrin (PyTPPS-NPn), X=2Cl, 1,1-cyclobutanedicarboxylic acid, oxalate, or malonate. Their biodistribution in tumor bearing mouse was examined along with their antitumor activity against murine leukemia L1210 cell line. The representative complex 1 exhibited a significant accumulation in tumor tissue with a tumor/muscle ratio of 7 after 24 h post injection. The antitumor activity of the title compounds was marginal (T/C: 95-117%), but it was found that platinum(II) coordination to the porphyrin periphery did not affect the tumor accumulating properties of the porphyrin permitting further derivatization for efficient delivery of the Pt(II) antitumor agent.

Metalloporphyrins inhibit beta-hematin (hemozoin) formation

Metal-substituted protoporphyrin IXs (Cr(III)PPIX (1), Co(III)PPIX (2), Mn(III)PPIX (3), Cu(II)PPIX (4), Mg(II)PPIX (5), Zn(II)PPIX (6), and Sn(IV)PPIX (7)) act as inhibitors to beta-hematin (hemozoin) formation, a critical detoxification biopolymer of malarial parasites. The central metal ion plays a significant role in the efficacy of the metalloprotoporphyrins to inhibit beta-hematin formation. The efficacy of these compounds correlates well with the water exchange rate for the octahedral aqua complexes of the porphyrin's central metal ion. Under these in vitro reaction conditions, metalloporphyrins 5, 6 and 7 are as much as six times more efficacious than the free ligand protoporphyrin IX in preventing beta-hematin formation and four times as efficacious as chloroquine, while metalloporphyrins 3 and 4 are three to four times more effective at preventing beta-hematin formation than the free protoporphyrin IX base. In contrast, the relatively exchange inert metalloporphyrins 1 and 2 are only as efficacious as the free ligand and only two-thirds as effective as chloroquine. Aggregation studies of the heme:MPPIX using UV-Vis and fluorescence spectroscopies are indicative of the formation of pi-pi hetero-metalloporphyrin assemblies. Thus, hemozoin inhibition is likely prevented by the formation of heme:MPPIX complexes through pi-stacking interactions. The ramifications of such hetero-metalloporphyrin assemblies, in the context of the emerging structural picture of hemozoin, are discussed.

Photocleavage of plasmid DNA by the prophyrin meso-tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin

meso-Tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin (H2T4CPP) cleaves pBR322 plasmid DNA to single strand breaks in the presence of molecular oxygen and visible light. The above photocleavage was much more efficient in D2O buffer of sodium phosphate (pD = 7.4) than H2O buffer of sodium phosphate (pH = 7.4). In addition this photocleavage of plasmid DNA was inhibited in the presence of sodium azide, lipoic acid, tert-butanol or mannitol suggesting the involvement of 1O2 and.OH in the photocleavage of plasmid DNA. The photocleavage was observed to be more efficient in the presence of H2T4CPP than in the presence of H2CPP [meso-tetrakis (4-carboxy-phenyl)porphyrin]. Our spectral studies using UV-visible, fluorescence and circular dichroism techniques suggest that H2T4CPP binds to DNA while H2CPP does not. Thus, the difference in photocleavage may be caused by the nonbinding of H2CPP and by the binding of H2T4CPP to calf thymus (CT) DNA.

Anti-human immunodeficiency virus effects of cationic metalloporphyrin-ellipticine complexes

A series of cationic metalloporphyrin-ellipticine complexes were found to inhibit the cytopathicity of human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus in MT-4 cells at concentrations ranging from 1.4 to 17 micrograms/mL, i.e. at a concentration that was 2.5-30-fold below the cytotoxicity threshold. These compounds were also found to inhibit syncytium formation between persistently HIV-1-infected HUT-78 and uninfected Molt/4 cells, to interfere with HIV-1 binding to the cells, and to suppress HIV-1-associated reverse transcriptase activity.

DNA cleavage photoinduced by new water-soluble zinc porphyrins linked to 9-methoxyellipticine

Two hybrid molecules based on a water-soluble zinc porphyrin covalently linked to 9-methoxyellipticine, 1 and 2, were studied as photoactivable DNA cleavers. The behaviour and efficiency of these photosensitizers were compared with the constitutive units of the hybrid molecules: meso-tetrakis(4-N-methylpyridiniumyl)porphyrinato-zinc(II) tetraacetate (ZnTMPyP, 3) and 9-methoxy-N2methylellipticinium acetate (9-OMe-NME, 4). On irradiation at 436 nm, the efficiency of these hybrids is similar to that of ZnTMPyP and 50-fold greater than that of haematoporphyrin derivative (HPD). This photoinduced DNA cleavage is markedly reduced in the absence of oxygen and also depends on the DNA base pair to porphyrin ratio. It is inhibited by N-acetylhistidine and sodium azide, unaffected by mannitol and superoxide dismutase (SOD) and enhanced when changing H2O for D2O. The same scavenger effects are observed on irradiation at 514 nm. At 313 nm, the efficiency of hybrids 1 and 2 is intermediate between those of ZnTMPyP and 9-OMe-NME. In these conditions, a slight inhibitory effect of mannitol is observed, suggesting the participation of radicals probably derived from partial decomposition of the porphyrins. At these three wavelengths, singlet oxygen seems to be the main species responsible for DNA cleavage. In contrast with expectation, the great affinity of these molecules for DNA does not enhance their efficiency as DNA cleavers. This effect is discussed taking into account the long lifetime of singlet oxygen which may be generated far from the target. These molecules which are only photoactivable in the presence of DNA appear to be an efficient "molecular light switch".

Preferential hydroxylation by the chemical nuclease meso-tetrakis-(4-N-methylpyridiniumyl)porphyrinatomanganeseIII pentaacetate/KHSO5 at the 5' carbon of deoxyriboses on both 3' sides of three contiguous A.T base pairs in short double-stranded oligonucleotides

Selected double-stranded oligodeoxyribonucleotides have been used to probe, at the molecular level, DNA chain breakages induced by the chemical nuclease mesotetrakis(4-N- methylpyridiniumyl)porphyrinatomanganeseIII pentaacetate/KHSO5. The results show that cleavage selectively occurs on the two 3' sides of three contiguous A.T base pairs (an A.T triplet). Hydroxylation at 5' carbon of the deoxyribose targets represents the initial damage on the sugar-phosphodiester backbone and leaves a 3' phosphate and a 5' aldehyde at the ends. The fragments were separated by HPLC and unambiguously identified through chemical and biochemical reactions and/or sequencing after enzymatic conversion to mononucleosides. Also studied was the degradation of a 22-nucleotide DNA molecule containing two A.T triplets. Gel electrophoresis analyses on the corresponding 5'-32P-end-labeled substrate supported the above cleavage specificity and mechanism.

Mechanism of DNA cleavage by cationic manganese porphyrins: hydroxylations at the 1'-carbon and 5'-carbon atoms of deoxyriboses as initial damages

Cationic manganese-porphyrin complexes, free or targetted with an intercalating agent, are able to cleave DNA using oxygen atom donors like potassium monopersulfate or magnesium monoperphthalate as coreactants. Detailed studies of the cleavage of calf thymus DNA, before and after a heating step, show that free bases and 5-methylene-2-furanone are the main reaction products, indicating that hydroxylation at the 1'-carbon atom is the main target of these chemical agents. These data confirm that metalloporphyrin derivatives interact with the minor groove of double-stranded DNA. Hydroxylation of one of the two C-H bonds at position-5' is another initial DNA damage, characterized by the formation of furfural as sugar degradation product. Besides these two main initial damage sites, a low contribution of a hydroxylation reaction at C4' can not be definitively discounted, while an hydroperoxidation route at C4' can be excluded.

31P NMR characterization of terminal phosphates induced on DNA by the artificial nuclease 'Mn-TMPyP/KHSO5' in comparison with DNases I and II

Phosphorus-31 NMR has been applied to the characterization of terminal phosphates on fragments of calf thymus DNA induced by three different nuclease systems: DNase I, DNase II and the artificial nuclease 'Mn-TMPyP/KHSO5'. In this last case, the oxidative damage to deoxyribose leads to two monophosphates esters (at the 3' and 5' ends) on both sides of the cleavage site. This method constitutes a promising approach to visualise the phosphate termini generated in DNA or RNA cleavage by cytotoxic drugs or chemical nucleases and provides a novel insight into the molecular aspects of their mechanism of action.