Synthesis, structures, redox and photophysical properties of benzodifuran-functionalised pyrene and anthracene fluorophores

Benzodifuran-functionalised pyrene and anthracene fluorophores 1 and 2 were obtained in reasonable yields. Their single crystal structures, electrochemical, optical absorption, and fluorescence characteristics have been described. They show strong luminescence with high quantum yields of 0.53 for 1 and 0.48 for 2.

Histopathological alterations, EROD activity, CYP1A protein and biliary metabolites in gilthead seabream Sparus aurata exposed to benzo(a)pyrene

This study compared for seabream, Sparus aurata exposed to benzo(a)pyrene-B(a)P-, the response of molecular cytochrome P450 1A (CYP1A) and cellular histopathology biomarkers. Male gilthead seabream, Sparus aurata specimens were exposed for 20 days via water to a series of high B(a)P concentrations. CYP1A was assessed by measuring enzymatic activity (EROD) and CYP1A protein content, and cellular responses were evaluated by routine histopathological methods. In addition, biliary metabolites were measured in order to verify that B(a)P was absorbed and metabolised. Histological lesions, both in liver and gills, increased in parallel to B(a)P concentrations, with the majority of changes representing rather non-specific alterations. Hepatic EROD and CYP1A proteins data showed a concentration-dependent induction, while in the gills, EROD activity but not CYP1A proteins showed a non-monotonous dose response, with a maximum induction level at 200 microg B(a)P.L-1 and decreasing levels thereafter. The findings provide evidence that short-term, high dose exposure of fish can result in significant uptake and metabolism of the lipophilic B(a)P, and in pronounced pathological damage of absorptive epithelia and internal organs.

Spectroscopic properties of pyrene-containing DNA mimics

DNA mimics containing non-nucleosidic pyrene building blocks are described. The modified oligomers form stable hybrids, although a slight reduction in hybrid stability is observed in comparison to the unmodified DNA duplex. The nature of the interaction between the pyrene residues in single and double stranded oligomers is analyzed spectroscopically. Intra- and inter-strand stacking interactions of pyrenes are monitored by UV-absorbance as well as fluorescence spectroscopy. Excimer formation is observed in both single and double strands. In general, intrastrand excimers show fluorescence emission at shorter wavelengths (approx. 5-10 nm) than excimers formed by interstrand interactions. The existence of two different forms of excimers (intra- vs. interstrand) is also revealed in temperature dependent UV-absorbance spectra. (C) 2007 Elsevier Ltd. All rights reserved.

Brain CYP1A in seabream, Sparus aurata exposed to benzo(a)pyrene

This study compares basal and induced expression of cytochrome P4501A-CYP1A in the brain of gilthead seabream, Sparus aurata. Larval or adult seabream were exposed to benzo(a)pyrene -B(a)P- and the CYP1A response was assessed by analyzing CYP1A mRNA (RT-PCR), CYP1A protein (expression levels: ELISA, western blotting; cellular localization: immunohistochemistry), and CYP1A catalytic activity (7-ethoxyresorufin-O-deethylase-EROD). In the brain of adult S. aurata, CYP1A immunostaining was generally detected in the vasculature. It was present in the neuronal fibers and glial cells of the olfactory bulbs and the ventral telencephalon. ELISA and RT-PCR analyses confirmed CYP1A expression in the brains of non-exposed seabream. B(a)P exposure led to increased CYP1A staining mainly in neuronal fibers and glial cells of the olfactory bulbs, but also in the vascular endothelia. EROD activity, however, could not be detected in the brain of adult seabream, neither in control nor in exposed fish. In the developing brain of S. aurata larvae, immunohistochemical staining detected CYP1A protein exclusively in endothelia of the olfactory placode and in retina. Staining intensity of CYP1A slightly increases with larval development, especially in vascular brain endothelia. Exposing the larvae to 0.3 or 0.5 microg B(a)P/L from hatching until 15 days post hatching (dph) did not result in enhanced CYP1A immunostaining in the brain. In samples of whole seabream larvae, both from controls and BaP treatments, neither CYP1A mRNA, protein nor catalytic activity were detectable. The results demonstrate that CYP1A is expressed already and inducible in the larval brain, but that the regional and cellular expression differs partly between larval and adult brain. This may have implications for the toxicity of CYP1A-inducing xenobiotics on early and mature life stages of seabream.

Tissue-specific metabolism of benzo[a]pyrene in rainbow trout (Oncorhynchus mykiss): a comparison between the liver and immune organs.

Polycyclic aromatic hydrocarbons (PAHs) are immunotoxicants in fish. In mammals, phase I metabolites are believed to be critically involved in the immunotoxicity of PAHs. This mechanism has been suggested for fish as well. The present study investigates the capacity of immune organs (head kidney, spleen) of rainbow trout, Oncorhynchus mykiss, to metabolize the prototypic PAH, benzo[a]pyrene (BaP). To this end, we analyzed 1) the induction of enzymatic capacity measured as 7-ethoxyresorufin-O-deethylase (EROD) activity in immune organs compared with liver, 2) the organ profiles of BaP metabolites generated in vivo, and 3) rates of microsomal BaP metabolite production in vitro. All measurements were done for control fish and for fish treated with an intraperitoneal injection of 15 mg BaP/kg body weight. In exposed trout, the liver, head kidney, and spleen contained similar levels of BaP, whereas EROD induction differed significantly between the organs, with liver showing the highest induction factor (132.8×), followed by head kidney (38.4×) and spleen (1.4×). Likewise, rates of microsomal metabolite formation experienced the highest induction in the liver of BaP-exposed trout, followed by the head kidney and spleen. Microsomes from control fish displayed tissue-specific differences in metabolite production. In contrast, in BaP-exposed trout, microsomes of all organs produced the potentially immunotoxic BaP-7,8-dihydrodiol as the main metabolite. The findings from this study show that PAHs, like BaP, are distributed into immune organs of fish and provide the first evidence that immune organs possess inducible PAH metabolism leading to in situ production of potentially immunotoxic PAH metabolites.

The teleostean liver as an immunological organ: Intrahepatic immune cells (IHICs) in healthy and benzo[a]pyrene challenged rainbow trout (Oncorhynchus mykiss).

The existence of a resident population of intrahepatic immune cells (IHICs) is well documented for mammalian vertebrates, however, it is uncertain whether IHICs are present in the liver of teleostean fish. In the present study we investigated whether trout liver contains an IHIC population, and if so, what the relative cellular composition of this population is. The results provide clear evidence for the existence of an IHIC population in trout liver, which constitutes 15-29% of the non-hepatocytes in the liver, and with a cellular composition different to that of the blood leukocyte population. We also analyzed the response of IHICs to a non-infectious liver challenge with the hepatotoxic and immunotoxic chemical, benzo[a]pyrene (BaP). Juvenile trout were treated with BaP (25 or 100mg/kgbw) at levels sufficient to induce the molecular pathway of BaP metabolism while not causing pathological and inflammatory liver changes. The IHIC population responded to the BaP treatments in a way that differed from the responses of the leukocyte populations in trout blood and spleen, suggesting that IHICs are an independently regulated immune cell population.

DNA-Grafted Supramolecular Polymers: Helical Ribbon Structures Formed by Self-Assembly of Pyrene-DNA Chimeric Oligomers

The controlled arraying of DNA strands on adaptive polymeric platforms remains a challenge. Here, the noncovalent synthesis of DNA-grafted supramolecular polymers from short chimeric oligomers is presented. The oligomers are composed of an oligopyrenotide strand attached to the 5′-end of an oligodeoxynucleotide. The supramolecular polymerization of these oligomers in an aqueous medium leads to the formation of one-dimensional (1D) helical ribbon structures. Atomic force and transmission electron microscopy show rod-like polymers of several hundred nanometers in length. DNA-grafted polymers of the type described herein will serve as models for the development of structurally and functionally diverse supramolecular platforms with applications in materials science and diagnostics.

Hydrodynamic and Thermophoretic Effects on the Supramolecular Chirality of Pyrene-Derived Nanosheets

Chiroptical properties of two-dimensional (2D) supramolecular assemblies (nanosheets) of achiral, charged pyrene trimers (Py3) are rendered chiral by asymmetric physical perturbations. Chiral stimuli in a cuvette can originate either from controlled temperature gradients or by very gentle stirring. The chiroptical activity strongly depends on the degree of supramolecular order of the nanosheets, which is easily controlled by the method of preparation. The high degree of structural order ensures strong cooperative effects within the aggregates, rendering them more susceptible to external stimuli. The samples prepared by using slow thermal annealing protocols are both CD and LD active (in stagnant and stirred solutions), whereas for isothermally aged samples chiroptical activity was in all cases undetectable. In the case of temperature gradients, the optical activity of 2D assemblies could be recorded for a stagnant solution due to migration of the aggregates from the hottest to the coldest regions of the system. However, a considerably stronger exciton coupling, coinciding with the J-band of the interacting pyrenes, is developed upon subtle vortexing (0.5 Hz, 30 rpm) of the aqueous solution of the nanosheets. The sign of the exciton coupling is inverted upon switching between clockwise and counter-clockwise rotation. The supramolecular chirality is evidenced by the appearance of CD activity. To exclude artefacts from proper CD spectra, the contribution from LD to the observed CD was determined. The data suggest that the aggregates experience asymmetrical deformation and alignment effects because of the presence of chiral flows.