Francesco Dall’Acqua

BIOCHEMICAL AND MEDICAL ASPECTS OF PSORALENS

A few studies have been devoted to the synthesis of new psoralen derivatives. A new route suitable for preparing psoralen and many of its derivatives has been described by Queval and Bisagni[56] and a semi-synthetic route to psoralen, starting from marmesin, by Loutfy and Abu-ShadyC381. Many new synthetic derivatives of psoralen have been prepared by Loutfy et al. [373 for testing their photosensitizing activity on skin and further investigating the relationship between chemical structure and photobiological activity. Some other tricyclic compounds (i.e. pyranocoumarins such as xanthyletin and dimethylallylxanthyletin) having structure analogous to furocoumarins, have been studied as to their possible photosensitizing activity and the ability to photoreact with DNA. These compounds appear to photosensitize biological substrates and able to form -both monoadducts and cross-linkings in double stranded DNA [22].

In vitro studies of the phototoxic potential of the antidepressant drugs amitriptyline and imipramine.

Amitriptyline and imipramine, two tricyclic antidepressant drugs, have been studied to evaluate their phototoxic potential using various models. Reactive oxygen species production was investigated. A negligible production of singlet oxygen was observed for both compounds whereas a significant production of superoxide anion was noted for amitriptyline in particular. Moderate red blood cell lysis under UVA light (365 nm) was induced in the presence of the two drugs at a concentration of 50 microM. Cellular phototoxicity was investigated on a murine fibroblast cell line (3T3). The two drugs were phototoxic causing cell death at a concentration of 100 microM and a UVA dose in the range of 3.3-6.6 J/cm2. Furthermore, the two drugs photosensitized the peroxidation of linoleic acid, as monitored by the formation of dienic hydroperoxides. The presence of BHA and GSH, two free radical scavengers, significantly reduced the lipid oxidation photoinduced by the drugs, suggesting a predominant involvement of radical species. Finally, the involvement of nucleic acids in the phototoxicity mechanism was also investigated using a pBR322 plasmid DNA as a model.

Pyrrolo[3,4-h]quinolinones a new class of photochemotherapeutic agents

Pyrrolo[3,4-h]quinolin-2-ones were synthesized as nitrogen isosters of the angular furocoumarin angelicin, with the aim of obtaining new photochemotherapeutic agents with increased antiproliferative activity and lower undesired toxic effects. A versatile synthetic pathway was approached to allow the isolation of derivatives of the new ring system with a good substitution pattern on the pyrrole moiety. Photobiological screenings of the new compounds revealed a potent phototoxic effect and a great UVA dose dependence, reaching IC(50) values at submicromolar level. The induced cellular photocytotoxicity was related to apoptosis with the involvement of mitochondria and lysosomes, alteration of cell cycle profile and membrane lipid peroxidation.

Synthesis of pyrrolo[3,2-h]quinolinones with good photochemotherapeutic activity and no DNA damage.

In the search for new photochemotherapeutic agents, a series of derivatives of the ring system pyrrolo[3,2-h]quinoline--bioisosters of the angular furocoumarin angelicin--were synthesized through a four-step synthetic approach, in reasonable overall yields. Eight of the synthesized derivatives showed a remarkable phototoxicity against a panel of four human tumor cell lines and a great dose UV-A dependence, reaching IC₅₀ values at submicromolar level. The mode of cellular death photoinduced by pyrrolo[3,2-h]quinolines was evaluated through a series of flow cytometric analysis and other tests were performed to clarify their mechanism of action.

Pyrano[2,3-e]isoindol-2-ones, new angelicin heteroanalogues.

A convenient synthesis of the pyrano[2,3-e]isoindol-2-one ring system, an heteroanalogue of angelicin, is reported. Our synthetic approach consists of the annelation of the pyran ring on the isoindole moiety using 5-dialkylamino- or 5-hydroxymethylene intermediates as building blocks. The photoantiproliferative activity of the new derivatives was studied. Some of them bearing the benzyl group at the 8 position were active with IC(50) in the micromolar range. Cell cytotoxicity involves apoptosis, alteration of cell cycle profile and membrane photodamage.

Development of a novel furocoumarin derivative inhibiting NF-κB dependent biological functions: design, synthesis and biological effects.

Nuclear Factor kappaB (NF-κB) plays a very important role in the control of gene expression and is deeply involved in several human pathologies. Accordingly, molecules targeting NF-κB dependent biological functions are considered of great interest. Virtual screening of furocoumarin libraries against NF-κB p50 allowed to rank compounds in respect to their expected ability to bind NF-κB and the identified compound might be considered for the development of analogs to be tested for biological activity on inhibition of NF-κB/DNA complex formation. The data reported in the present paper suggest that, following this approach, the best ranked compounds identified by virtual screening (a) strongly bind in silico to NF-κB and (b) efficiently inhibit the molecular interactions between (32)P-labeled NF-κB double stranded DNA and p50 or p50/p65 complex. These data allowed to develop a novel lead of great interest for inhibiting NF-κB dependent biological functions. This novel molecule (compound 2), bearing a methyl group in the 9 position of the psoralen nucleus, exhibits high efficiency in inhibiting NF-κB/DNA interactions. In addition, we found that compound 2 is a potent inhibitor of IL-8 gene expression in TNF-α treated IB3-1 cystic fibrosis cells. Taken together, our data indicate that compound 2 might find an important place in the set of molecules of interest for the development of pharmaceutical strategies against the inflammatory phenotype of cystic fibrosis.

Photostability of pitavastatin—A novel HMG-CoA reductase inhibitor

The photostability of pitavastatin, an HMG-CoA reductase inhibitor used in the treatment of hypercholesterolemia, was investigated. The sample solution was exposed to UV-A radiation and the photodegradation process was monitored by means of spectrophotometric method and HPLC-DAD. Pitavastatin was shown to be photolabile and its photodegradation reaction followed the first-order kinetics with the rate constant k=3.54 x 10(-4)+/-9.43 x 10(-6)s(-1). The chromatograms revealed the presence of four major photoproducts (PP-1-PP-4). The separated and isolated photolytic products were identified using a mass spectrometer coupled with a time of flight (TOF) analyzer. The main reaction observed during exposure to radiation of pitavastatin was photocyclisation leading to formation of four-ring photoproducts.

Increase in γ-globin mRNA content in human erythroid cells treated with angelicin analogs

The aim of the present study was to identify molecular analogs of angelicin (ANG) able to increase erythroid differentiation of K562 cells and expression of γ-globin genes in human erythroid precursor cells, with low effects on apoptosis. ANG-like molecules are well-known photosensitizers largely used for their antiproliferative activity in the treatment of different skin diseases (i.e., psoriasis, vitiligo, eczema, and mycosis fungoides). To verify the activity of these derivatives, we employed three experimental cell systems: (1) the human leukemic K562 cell line, (2) K562 cell clones stably transfected with a pCCL construct carrying green-EGFP under the γ-globin gene promoter, and (3) the two-phase liquid culture of human erythroid progenitors isolated from normal donors and β-thalassemia patients. The results of our study suggest that trimethyl ANG is a powerful inducer of erythroid differentiation, compared with known inducers, such as ANG, cytosine arabinoside, mithramycin, and cisplatin. These data could have practical relevance, because pharmacologically mediated regulation of human γ-globin gene expression, with the consequent induction of fetal hemoglobin, is considered a potential therapeutic approach in hematological disorders including β-thalassemia and sickle cell anemia.

Indolo[2,3-b]-Quinolizinium Bromide: An Efficient Intercalator with DNA-Photodamaging Properties

The associative interactions of indolo[2,3‐b]‐quinolizinium bromide with DNA and its DNA photocleavage properties were studied in detail. Absorption and emission spectroscopy, linear dichroism, and energy‐transfer measurements indicate that the indoloquinolizinium binds to DNA primarily by intercalation, with a preference for GC base pairs. In agreement with this data, the results of primer extension analysis indicate that photocleavage occurrs prevalently at the GC nucleotides. Molecular modeling studies confirm that intercalative stacking between adjacent base pairs is energetically favorable. However, it is also observed that the location of the dye in the minor groove of the DNA is energetically even more favorable. Upon UVA irradiation, the indoloquinolizinium causes single‐strand cleavage with an efficiency that varies with the dye–DNA ratio. This observation is rationalized in terms of more efficient photocleavage by the externally bound dye compared with the intercalated one. The kinetics of strand degradation under aerobic and anaerobic conditions suggest that a Type I reaction occurs, that is, radical‐mediated DNA damage.

Photophysical Properties and Photobiological Behavior of Amodiaquine, Primaquine and Chloroquine

This article describes the results of a coupled photophysical and photobiological study aimed at understanding the phototoxicity mechanism of the antimalarial drugs amodiaquine (AQ), primaquine (PQ) and chloroquine (CQ). Photophysical experiments were carried out in aqueous solutions by steady‐state and time‐resolved spectrometric techniques to obtain information on the different decay pathways of the excited states of the drugs and on the transient species formed upon laser irradiation. The results showed that all three drugs possess very low fluorescence quantum yields (10−2–10−4). Laser flash photolysis experiments proved the occurrence of photoionization processes leading to the formation of a radical cation in all three systems. In the case of AQ the lowest triplet state was also detected.