Bimodal induction of sister-chromatid exchanges by luminol, an inhibitor of poly(ADP-ribose) synthetase, during the S-phase of the cell cycle

Chemiluminescence in Combination with Organic Photosensitizers: Beyond the Light Penetration Depth Limit of Photodynamic Therapy

Photodynamic therapy (PDT) is a promising noninvasive medical technology that has been approved for the treatment of a variety of diseases, including bacterial and fungal infections, skin diseases, and several types of cancer. In recent decades, many photosensitizers have been developed and applied in PDT. However, PDT is still limited by light penetration depth, although many near-infrared photosensitizers have emerged. The chemiluminescence-mediated PDT (CL-PDT) system has recently received attention because it does not require an external light source to achieve targeted PDT. This review focuses on the rational design of organic CL-PDT systems. Specifically, PDT types, light wavelength, the chemiluminescence concept and principle, and the design of CL-PDT systems are introduced. Furthermore, chemiluminescent fraction examples, strategies for combining chemiluminescence with PDT, and current cellular and animal applications are highlighted. Finally, the current challenges and possible solutions to CL-PDT systems are discussed.

BODIPY and 2,3-Dihydrophthalazine-1,4-Dione Conjugates As Heavy Atom-Free Chemiluminogenic Photosensitizers

We disclose an interesting concept for developing heavy atom-free chemiluminogenic photosensitizers. To accomplish this, conjugates 2 and 3, which are composed of boron-dipyrromethene (BODIPY) and 2,3-dihydrophthalazine-1,4-dione units, are investigated. 2 and 3 are compared in terms of their photophysical properties, chemiluminescence responses, and singlet oxygen production. Strikingly, the results indicate that decoration of BODIPY with the 2,3-dihydrophthalazine-1,4-dione scaffold boosts the singlet oxygen generation. Furthermore, treatment of epidermoid laryngeal carcinoma Hep-2 (Hep-2) cells with conjugates 2 and 3 results in efficient cellular internalization which ensures live- cell imaging of Hep-2 cells. Finally, it is noteworthy that in vitro cytotoxicity assays reveal that both 2 and 3 induce cytotoxicity when illuminated with red light. Thus, 2 and 3 represent heavy atom-free chemiluminogenic photosensitizers.

Bioluminescence-activated deep-tissue photodynamic therapy of cancer

Optical energy can trigger a variety of photochemical processes useful for therapies. Owing to the shallow penetration of light in tissues, however, the clinical applications of light-activated therapies have been limited. Bioluminescence resonant energy transfer (BRET) may provide a new way of inducing photochemical activation. Here, we show that efficient bioluminescence energy-induced photodynamic therapy (PDT) of macroscopic tumors and metastases in deep tissue. For monolayer cell culture in vitro incubated with Chlorin e6, BRET energy of about 1 nJ per cell generated as strong cytotoxicity as red laser light irradiation at 2.2 mW/cm² for 180 s. Regional delivery of bioluminescence agents via draining lymphatic vessels killed tumor cells spread to the sentinel and secondary lymph nodes, reduced distant metastases in the lung and improved animal survival. Our results show the promising potential of novel bioluminescence-activated PDT.

Ablation of PARP-1 does not interfere with the repair of DNA double-strand breaks, but compromises the reactivation of stalled replication forks

Poly(ADP-ribose) polymerase-1 (PARP-1) is an abundant DNA end-sensing and binding molecule. Inactivation of PARP-1 by chemicals and genetic mutations slows cell proliferation, increases sister chromatid exchange (SCE), micronuclei formation and chromosome instability, and shortens telomeres. Given its affinity to DNA breaks and temporal occupation on DNA strand break sites, PARP-1 is proposed to prevent inappropriate DNA recombination. We investigated the potential role of PARP-1 in repair of DNA double-strand breaks (DSBs) and stalled replication forks. PARP-1-/- embryonic stem cells and embryonic fibroblast cells exhibited normal repair of DNA DSBs by either homologous recombination (HR) or nonhomologous end-joining (NHEJ) pathways. Inactivation of PARP-1 did not interfere with gene-targeting efficiency in ES cells. However, PARP-1-/- cells were hypersensitive to the replication damage agent hydroxyurea (HU)-induced cell death and exhibited enhanced SCE formation. Ablation of PARP-1 delayed reactivation of stalled replication forks imposed by HU and re-entry into the G2-M phase after HU release. These data indicate that PARP-1 is dispensable in HR induced by DSBs, but is involved in the repair and reactivation of stalled replication forks.

Post-treatment effects of DNA topoisomerase inhibitors on UVB- and X-ray-induced chromosomal aberration formations

Post-treatments with nogalamycin, an inhibitor of DNA topoisomerase I, for last 3h of the culture (during the G2 phase) drastically enhanced the yield of ultraviolet light B (UVB)-induced exchange-type chromatid aberrations, while showing little effect on the formation of breakage-type aberrations in Chinese hamster V79 cells. These results are very similar to those obtained with ICRF-193, an inhibitor of topoisomerase II, with respect to the effect on UVB-induced chromatid aberrations. Thus, both types of topoisomerases may suppress the formation of exchange-type chromatid aberrations in the G2 phase which is suggested to be the principal stage of the cell cycle for chromatid aberration formation.In human lymphocytes irradiated with X-rays before phytohaemagglutinin (PHA) stimulation, post-treatments with nogalamycin through the whole cell cycle enhanced only the yield of dicentrics, while showing little effect on the yields of any other chromosome-type aberrations. Nogalamycin added 6h after PHA stimulation to irradiated cells also showed almost the same effects, whereas, addition of nogalamycin 24h after PHA stimulation showed no effect on X-ray-induced chromosome-type aberrations. These results suggest that X-ray-induced DNA damage lead to chromosome-type aberrations before the start of S phase and topoisomerase I may suppress the formation of dicentrics, exchange-type chromosome aberrations. Post-treatments with ICRF-193 showed no effect on the formation of X-ray-induced chromosome-type aberrations, suggesting nonparticipation of topoisomerase II in this process.

Novel point mutations in mitochondrial 16S rRNA gene of Chinese hamster cells

To know the nature and mechanisms of spontaneous mutations in mitochondrial DNA (mtDNA), we determined, by direct cycle sequencing, the nucleotide sequence of the 3' terminal region of the mitochondrial 16S rRNA gene from chloramphenicol-resistant (CAP-R) mutants isolated in Chinese hamster V79 cells. Four different base substitutions were identified in common for the six CAP-R mutants. All mutations were heteroplasmic. One A to G transition was mapped at a site within the putative peptidyl transferase domain, the target region for chloramphenicol, and one G to A transition and two T to G transversions were located within the two different segments which form the stems of the hairpin loop structures attached to this key domain in the predicted secondary structure of 16S rRNA. The mutations detected in this study do not map to the same sites where CAP-R mutations were found previously in mammalian cells. Allele specific-PCR analyses revealed that all four mutations occurred on a single mutant-DNA molecule, but not on several ones independently. Together with the other previous reports, our data suggest that spontaneous mtDNA mutations may not be caused exclusively by oxidative DNA damage at least in 16S rRNA gene.

Metabolism and disposition of luminol in the rat

1. The metabolism and disposition of Luminol (LMN, 3-aminophthalhydrazide), a widely used forensic and laboratory reagent that chemiluminesses upon oxidation, was determined as part of its overall toxicological characterization. 2. Radiolabelled LMN was well absorbed, metabolized and excreted following p.o. administration of a range of doses. About 90% of the total dose was recovered within 24 h of administration in urine in the form of two metabolites identified as LMN N8-glucuronide and LMN N8-sulphamic acid. 3-Aminophthalic acid, the oxidative product of LMN in the light-emitting reaction, was apparently not formed in vivo. 3. Metabolism and disposition of an i.v. administered dose was similar to that following gavage. Little or no LMN-derived radioactivity was present in tissue within 12 h post-dosing. Excretion of radioactivity in bile following i.v. injection was minimal (approximately 8% of the total dose in 6 h) and consisted of the same urinary-excreted glucuronide and sulphate conjugates. 4. LMN was not absorbed dermally in rat, potentially a major route of exposure to human. If the fate of LMN is similar between species, this compound should have little potential for either dermal absorption, bioaccumulation in tissues following other routes of exposure or chronic toxicity in humans.

Nucleotide changes in mitochondrial 16S rRNA gene from different mammalian cell lines

The partial nucleotide sequences of mitochondrial 16S rRNA gene were analyzed in five rodent cell lines, prior to the analysis of mutation spectrum in the gene. Total DNA was isolated from V79 and CHO-K1 cell lines from Chinese hamster and murine cell lines, Balb Y SV and PCC4 AG Cap, and the 3' terminal regions including the peptidyl transferase domain which is the target for chloramphenicol, a selective inhibitor of mitochondrial protein synthesis, were amplified by polymerase chain reaction (PCR) using two sets of primers and directly sequenced. In Chinese hamster cells, C to T transition at one site was observed in CHO-K1, and either A was deleted at the sequence of AA in all three cell lines, relative to the V79-cell sequence registered in GenBank. One G to A transition mutation in heteroplasmic state was observed in mouse PCC4 AG Cap cells which have chloramphenicol resistant phenotype, whereas there was no change in the Balb Y SV cell line, relative to the L-cell sequence. These mutation sites were located outside the peptidyl transferase domain.

Effects of an inhibitor of topoisomerase II, ICRF-193 on the formation of ultraviolet-induced chromosomal aberrations

Treatments of Chinese hamster V79 cells during one cell cycle with a new type of topoisomerase II inhibitor, ICRF-193, which does not accumulate cleavable topoisomerase-DNA complexes induced both chromosome- and chromatid-type aberrations with high frequencies. Furthermore, ICRF-193 synergistically enhanced the yield of UVB-induced chromatid-type aberrations, chromatid exchanges in particular. Treated with ICRF-193 for the last 3 h before harvest, cells showed frequent incidence of chromatid-type aberrations and synergistic enhancement of UVB-induced chromatid-type aberrations, chromatid exchanges in particular. These results suggest that spontaneous and UVB-induced lesions might be ultimately transformed into chromatid-type aberrations by topoisomerase II-dependent checkpoint process(es) in the G2 phase of the cell cycle.

Inhibitors and activators of ADP-ribosylation reactions

ADP-ribosylation reaction, that is the transfer of the ADP-ribose moiety of NAD+ to acceptor protein, is catalyzed by two classes of ADP-ribosyltransferases, i.e., poly(ADP-ribose) synthetase and mono(ADP-ribosyl)transferases. These two types differ not only in the number of transferring ADP-ribose units but also in the acceptor amino acid(s) and protein. Their inhibitors, particularly those of poly(ADP-ribose) synthetase, have been successfully employed in studies on biological functions of the enzymes and other related fields of research. Recently, we found many potent and specific inhibitors of poly(ADP-ribose) synthetase, and broadened their chemical as well as biochemical variety. More recently, we found several potent inhibitors of arginine-specific mono(ADP-ribosyl)transferases and activators of poly(ADP-ribose) synthetase.

Inhibition of HIV-1 IIIb replication in AA-2 and MT-2 cells in culture by two ligands of poly (ADP-ribose) polymerase: 6-amino-1,2-benzopyrone and 5-iodo-6-amino-1,2-benzopyrone

The effects of two adenosine diphosphoribose transferase (ADPRT) enzyme inhibitory ligands, 6-amino-1,2-benzopyrone and its 5-iodo-derivative, were determined in AA-2 and MT-2 cell cultures on the replication of HIV-1 IIIb, assayed by an immunochemical test for the HIV protein p24, and syncytium formation, characteristic of HIV-infected cells. Intracellular concentrations of both drugs were sufficient to inhibit poly(ADP-ribose) polymerase activity within the intact cell. Both drugs inhibited HIV replication parallel to their inhibitory potency on ADPRT, but distinct differences were ascertained between the two cell lines. In AA-2 cells both p24 and syncytium formation were depressed simultaneously, whereas in MT-2 cells only syncytium formation was inhibited by the drugs, and the p24 production, which remained unchanged during viral growth, was unaffected. Both drugs only moderately depressed the growth rate of the AA-2 and MT-2 cells and there was no detectable cellular toxicity. Results suggest the feasibility of the development of a new line of ADPRT ligand anti-HIV drugs that fundamentally differ in their mode of action from currently used chemotherapeutics.

Destabilization of Zn2+ coordination in ADP-ribose transferase (polymerizing) by 6-nitroso-1,2-benzopyrone coincidental with inactivation of the polymerase but not the DNA binding function

6-Nitroso-1,2-benzopyrone, an oxidation product of 6-amino-1,2-benzopyrone, binds to the DNA-recognizing domain of the ADP-ribose transferase protein and preferentially destabilizes Zn2+ from one of the two zinc finger polypeptide complexes present in the intact enzyme, as determined by the loss of 50% of 65Zn2+ from the 65Zn(2+)-isolated protein molecule, coincidental with the loss of 99% of enzymatic activity. The 50% zinc-deficient enzyme still binds to a DNA template, consisting of a 17-mer DNA primer annealed to M13 positive strand, resulting in the blocking of DNA synthesis by the Klenow fragment of Pol I. Auto-poly-ADP-ribosylated ADP-ribose transferase, which is the probable physiological state of this protein in intact cells, does not bind to primer-template DNA and does not block DNA synthesis by the Klenow fragment. On the basis of this in vitro model it is proposed that molecules which inhibit or inactivate ADP-ribose transferase in intact cells can induce significant alteration in DNA structure and replication.