Effects of cadmium and pyrene on earthworm-associated bacterial communities: Unveiling new perspectives for soil pollution management

Earthworms are considered to be excellent bioindicators of soil pollution. In recent years, there has been increasing interest in examining the effects of soil pollution on earthworm-associated microbiomes, with a particular focus on the gut microbiomes. However, relatively little effort has been invested in comprehensively investigating other microbiomes associated with earthworms and their responses to soil pollution. To fill this gap, we systematically studied the effects of Cd, pyrene, and combined pollution on the bacterial community in different vermicompartments, i.e., burrow wall, gut, and cast, in both epigeic Eisenia fetida and anecic Metaphire guillelmi, using a 2D-terraria incubator and high-throughput sequencing techniques. The results showed that bacterial alpha diversity followed the order of burrow wall > cast > gut, and this did not vary with soil pollution or earthworm ecotypes. Moreover, the dominant phyla in the vermicompartments were similar across different pollution treatments. Principal coordinate analysis (PCoA) revealed that the bacterial communities in different vermicompartments and ecotypes of earthworm were separated from each other, whereas they were grouped together in polluted treatments and unpolluted conditions. These results imply that even in polluted soil, vermicompartment and earthworm ecotypes remain the most significant factors affecting earthworm-associated microbiomes. However, the impacts of soil pollution on the bacterial composition in each vermicompartment were still evident. A comprehensive analysis revealed that the gut bacterial communities are more sensitive to soil contamination than casts and burrow wall in different ecotypes. Additionally, linear discriminant analysis of effect size (LefSe) identified several bacteria in Gemmatimonadota, the Firmicutes phylum in the burrow walls, and Patescibacteria (phyla) in the gut as potential biomarkers for pyrene contamination in soil. This research provides a comprehensive understanding of the effects of soil pollution on earthworm-associated microbiomes, thereby enhancing our understanding of earthworm ecotoxicology and soil pollution management.

Toxic mechanism of pyrene to catalase and protective effects of vitamin C: Studies at the molecular and cell levels

Polycyclic aromatic hydrocarbons, distributing extensively in the soil, would potentially threaten the soil organisms (Eisenia fetida) by triggering oxidative stress. As a ubiquitous antioxidant enzyme, catalase can protect organisms from oxidative damage. To reveal the potential impact of polycyclic aromatic hydrocarbon pyrene (Pyr) on catalase (CAT) and the possible protective effect of Ascorbic acid (vitamin C), multi-spectral and molecular docking techniques were used to investigate the influence of structure and function of catalase by pyrene. Fluorescence and circular dichroism analysis showed that pyrene would induce the microenvironmental changes of CAT amino acid residues and increase the α-helix in the secondary structure. Molecular simulation results indicated that the main binding force of pyrene around the active center of CAT is hydrogen bonding force. Furthermore, pyrene inhibited catalase activity to 69.9% compared with the blank group, but the degree of inhibition was significantly weakened after vitamin C added into the research group. Cell level experiments showed that pyrene can increase the level of ROS in the body cavity cell of earthworms, and put the cells under the threat of potential oxidative damage. Antioxidants-vitamin C has a protective effect on catalase and maintains the stability of intracellular ROS levels to a certain extent.

Intriguing H-Aggregates of Heptamethine Cyanine for Imaging-Guided Photothermal Cancer Therapy

Organic small-molecule-based photothermal agents such as cyanine dyes have received increasing attention in developing novel cancer therapies with potential clinical utility but suffer from poor stability, low photothermal efficiency, and limited accumulation at tumor sites in molecular forms. Self-assembly of small-molecule dyes into supramolecular assemblies may address these concerns by controlling the molecular organization of dye monomers to form structures of a higher order. Among them, H-aggregates of dyes favor face-to-face contacts with strongly overlapping areas, which always have a negative connotation to exhibit low or no fluorescence in most cases but may emanate energy in nonradiative forms such as heat for photothermal cancer therapy applications. Here, the synergistic self-assembly of cyanine dyes into H-aggregates is developed as a new supramolecular strategy to fabricate small-molecule-based photothermal nanomaterials. Compared to the free cyanine dyes, the H-aggregates assembled from pyrene or tetraphenylethene (TPE) conjugating cyanine exhibit the expected absorption spectral blue shift and fluorescence self-quenching but unique photothermal properties. Remarkably, the obtained H-aggregates are saucer-shaped nanoparticles that exhibit passive tumor-targeting properties to induce imaging-guided photothermal tumor ablation under irradiation. This supramolecular strategy presented herein may open up new opportunities for constructing next-generation small-molecule-based self-assembly nanomaterials for PTT cancer therapy in clinics.

Intercalating pyrene with polypeptide as a novel self-assembly nano-carrier for colon cancer suppression in vitro and in vivo

Giving patients right dosage is an essential concept of precision medicine. Most of nanocarriers lack of flexible drug capacity and structural stability to be customized for specific treatment, resulting in low therapeutic efficacy and unexpected side effects. Thus, a growing need emerges for fast and rigorous approaches to develop nanoparticles with properties of adjustable dosage and controllable particle size. Poly-l-Lysine is known for its enhanced bioadhesivity and pH-triggered structural swelling effect, which is utilized as the main agent to activate the multistage drug releasing. Inspired by natural bio-assembly system, we report a simple method to self-assemble Poly-l-Lysine-based nanoparticles via supramolecular recognitions of cross-linked pyrenes, which provides noncovalent force to flexibly encapsulate Doxorubincin and to construct robust nanostructures. Pyrene-modified polypeptide self-assemblies are able to adjust drug payload from 1: 10 to 2:1 (drug: polypeptide) without changing its uniform nano-spherical morphology. This nanostructure remained the as-made morphology even after experiencing the long-term (~ 10 weeks) storage at room temperature. Also, the nanoparticles displayed multi-step drug release behaviours and exhibited great in vitro and in vivo cytotoxicity towards colon cancer cells. The as-mentioned nanoparticles provide a novel perspective to compensate the clinical needs of specific drug feedings and scalable synthesis with advantages of simple-synthesis, size-adaptivity, and morphology reversibility.

Effects of Pyrene on Human Liver HepG2 Cells: Cytotoxicity, Oxidative Stress, and Transcriptomic Changes in Xenobiotic Metabolizing Enzymes and Inflammatory Markers with Protection Trial Using Lycopene

Pyrene is one of the major polycyclic aromatic hydrocarbons formed during heat treatment of meat and in car exhausts; however, few studies have investigated pyrene-induced adverse effects on human cell lines. This study aimed at the investigation of pyrene-induced cytotoxicity and oxidative damage in human liver HepG2 cells at environmentally relevant concentrations. Pyrene-induced changes in mRNA expression of xenobiotic metabolizing enzymes (XMEs), xenobiotic transporters, antioxidant enzymes, and inflammatory markers were investigated using real-time PCR. As a protection trial, the ameliorative effects of lycopene, a carotenoid abundantly found in tomato, were investigated. The possible mechanisms behind such effects were examined via studying the co exposure effects of pyrene and lycopene on regulatory elements including the aryl hydrocarbon receptor (Air) and elytroid 2-related factor 2 (RF). The achieved results indicated that pyrene caused significant cytotoxicity at 50 n, with a clear production of reactive oxygen species (ROS) in a dose-dependent manner. Pyrene upregulated mRNA expression of phase I enzymes including CYP1A1, 1A2, and CYP1B1 and inflammatory markers including TNFα and Cox2. However, pyrene significantly downregulated phase II enzymes, xenobiotic transporters, and antioxidant enzymes. Interestingly, lycopene significantly reduced pyrene-induced cytotoxicity and ROS production. Moreover, lycopene upregulated detoxification and antioxidant enzymes, probably via its regulatory effects on Air- and RF-dependent pathways.

Impact of temperature and pyrene exposure on the functional response of males and females of the copepod Calanus finmarchicus

We know very little about the effects of two global stressors, elevated temperature and contaminants, on the grazing of marine copepods. To address this issue, we tested the hypotheses that the individual and combined effects of these two stressors may reduce grazing rates and may depend on food availability and gender. We exposed male and female Calanus finmarchicus copepods to pyrene at two temperatures (10 and 14 °C) and six food concentrations (25-800 μg C Rhodomonas baltica L^-1) and measured fecal pellet size, and grazing rate (GR) from pellet production. Males had smaller fecal pellets and lower GR than did females. Temperature and pyrene exposure had no effect on pellet size. Temperature alone had no effect on GR of males, but females had lower GR at elevated temperature. Pyrene-exposed males and females had lower GR only at the food concentrations of 200-800 μg C R. baltica L^-1 and those patterns were independent of temperature. Pyrene-induced reduction in GR was stronger in females than in males. The negative effects of both elevated temperature and pyrene may reduce the abundance and trophic success of C. finmarchicus in a warmer, more polluted future.

In vitro and in silico approaches of antibiofilm activity of 1-hydroxy-1-norresistomycin against human clinical pathogens

In the present study, an attempt has been made to explore the antibiofilm activity of bioactive compound 1-hydroxy-1-norresistomycin (HNM) derived from coral mucus associated actinomycete Streptomyces variabilis. Initially, different concentration of HNM inhibited the biofilm formation of human clinical pathogens Escherichia coli, Vibrio cholerae and Staphylococcus aureus was determined using crystal-violet staining assay. The light microscopic analysis showed that HNM reduced the biofilm formation and adherence of bacterial cells on the surface of coverslip. HNM also damages the 3D architecture with reduced thickness as well as cell aggregation of biofilm forming bacteria analysed by confocal laser scanning microscopy (CLSM). In addition, HNM also demonstrated the efficiency in inhibiting theoretical adhesion by altering the surface hydrophobicity that can potentially hamper cellular adhesion and prevent biofilm formation. Furthermore, the molecular docking showed the significant interaction between HNM and key biofilm forming proteins proved an excellent antibiofilm activity of HNM. Together, these results suggest that the HNM can serve as potential antibiofilm agent in controlling the infections of E. coli, V. cholerae and S. aureus.

Chemoresistance to Cancer Treatment: Benzo-α-Pyrene as Friend or Foe?

Background: Environmental pollution such as exposure to pro-carcinogens including benzo-α-pyrene is becoming a major problem globally. Moreover, the effects of benzo-α-pyrene (BaP) on drug pharmacokinetics, pharmacodynamics, and drug resistance warrant further investigation, especially in cancer outpatient chemotherapy where exposure to environmental pollutants might occur. Method: We report here on the effects of benzo-α-pyrene on esophageal cancer cells in vitro, alone, or in combination with chemotherapeutic drugs cisplatin, 5-flurouracil, or paclitaxel. As the study endpoints, we employed expression of proteins involved in cell proliferation, drug metabolism, apoptosis, cell cycle analysis, colony formation, migration, and signaling cascades in the WHCO1 esophageal cancer cell line after 24 h of treatment. Results: Benzo-α-pyrene had no significant effect on WHCO1 cancer cell proliferation but reversed the effect of chemotherapeutic drugs by reducing drug-induced cell death and apoptosis by 30−40% compared to drug-treated cells. The three drugs significantly reduced WHCO1 cell migration by 40−50% compared to control and BaP-treated cells. Combined exposure to drugs was associated with significantly increased apoptosis and reduced colony formation. Evaluation of survival signaling cascades showed that although the MEK-ERK and Akt pathways were activated in the presence of drugs, BaP was a stronger activator of the MEK-ERK and Akt pathways than the drugs. Conclusion: The present study suggest that BaP can reverse the effects of drugs on cancer cells via the activation of survival signaling pathways and upregulation of anti-apoptotic proteins such as Bcl-2 and Bcl-xL. Our data show that BaP contribute to the development of chemoresistant cancer cells.

Impact of pyrene and cadmium co-contamination on prokaryotic community in coastal sediment microcosms

Acute ecological impacts of co-contamination of polycyclic aromatic hydrocarbons (PAHs) and heavy metals on diversity and composition of coastal benthic prokaryotes were unclear. We took pyrene (Pyr) and cadmium (Cd) as the representatives and mimicked an eight-week exposure of moderate and high levels of Pyr, Cd and their mixtures. 16S rRNA amplicon sequencing was used to investigate interaction of the contaminants in temporal succession of prokaryotes. Generally, concentrations of Pyr and HCl-extractable Cd in the sediments were stable over time. Effects and interaction of Pyr and Cd on prokaryotic α-diversity were temporally- and dose-dependent with a decreasing trend in richness and Shannon index under various contamination regimes, particularly in the single-Cd contaminated groups at the early stage. Temporal variability and Pyr-induced pattern in prokaryotic composition were observed. However, Pyr and Cd showed a persistent interaction in prokaryotic composition after 7 days, altering successional trajectories of communities. The communities under Pyr contamination regardless of Cd could be at a developing stage for an active PAH-degrading community with appearance of a pioneer Cycloclasticus phylotype, persistently showing a strong correlation with Pyr level. The associations of phylotypes and Cd level were short-lived and weak, corresponding to the overall resistance of prokaryotic composition to Cd. In the high-throughput sequencing era, using microcosm experiment, we renewed the knowledge about how prokaryotes vary in terms of α-diversity, composition and specific taxa in response to co-contamination of model contaminants at a temporal scale.

Phenanthrene and Pyrene Modify the Composition and Structure of the Cultivable Endophytic Bacterial Community in Ryegrass (Lolium multiflorum Lam)

This study provides new insights into the dynamics of bacterial community structure during phytoremediation. The communities of cultivable autochthonous endophytic bacteria in ryegrass exposed to polycyclic aromatic hydrocarbons (PAHs) were investigated with regard to their potential to biodegrade PAHs. Bacterial counts and 16S rRNA gene sequence were used in the microbiological evaluation. A total of 33 endophytic bacterial strains were isolated from ryegrass plants, which represented 15 different genera and eight different classes, respectively. Moreover, PAH contamination modified the composition and structure of the endophytic bacterial community in the plants. Bacillus sp., Pantoea sp., Pseudomonas sp., Arthrobacter sp., Pedobacter sp. and Delftia sp. were only isolated from the seedlings exposed to PAHs. Furthermore, the dominant genera in roots shifted from Enterobacter sp. to Serratia sp., Bacillus sp., Pantoea sp., and Stenotrophomonas sp., which could highly biodegrade phenanthrene (PHE). However, the diversity of endophytic bacterial community was decreased by exposure to the mixture of PAHs, and increased by respective exposure to PHE and pyrene (PYR), while the abundance was increased by PAH exposure. The results clearly indicated that the exposure of plants to PAHs would be beneficial for improving the effectiveness of phytoremediation of PAHs.

Combined remediation of pyrene-contaminated soil with a coupled system of persulfate oxidation and phytoremediation with ryegrass

The in situ chemical oxidation technology (ISCO) and phytoremediation for PAHs have been studied respectively, but few focus on the feasibility of combining persulfate with ryegrass. This literature revealed the effect of persulfate oxidation on the growth of ryegrass and the removal ratios of pyrene in the couple system of persulfate oxidation and phytoremediation. The results demonstrated that half of pyrene in test soil was oxidized by persulfate in 7 days and then the residual pyrene concentration was decreased to a lower level by ryegrass in the following 2 months in oxidation treatment and drip washing and plants (OWP) and oxidation treatment and drip washing and plants and fertilization (OWFP) treatment. Ryegrass could grow well after persulfate oxidation with the oxidized soil washed by water. Ryegrass in OWP and OWFP treatments had higher ratios of overground and underground biomass. However, the seeds of ryegrass cannot germinate when drip washing was omitted. Pyrene together with residual persulfate changed soil enzyme activities. Drip washing and the growth of ryegrass made soil enzyme activities tend to returned to normal levels. Persulfate oxidation and phytoremediation were compatible to make contributions to the dissipation of pyrene. Persulfate oxidation activated by heat had higher removal efficiency of PAHs and phytoremediation could further decrease the pyrene concentration in spiked soil.

Synthesis and characterization of oligodeoxyribonucleotides modified with 2'-thio-2'-deoxy-2'-S-(pyren-1-yl)methyluridine

Pyrene-functionalized oligonucleotides are intensively explored for applications in materials science and diagnostics. Here, we describe a short synthetic route to 2'-S-(pyren-1-yl)methyl-2'-thiouridine monomer S, its incorporation into oligodeoxyribonucleotides (ONs), and biophysical characterization thereof. Pseudorotational analysis reveals that the furanose ring of this monomer has a slight preference for South-type conformations. ONs modified with monomer S display high cDNA affinity but decreased binding specificity. Hybridization is associated with bathochromic shifts of pyrene absorption bands and quenching of pyrene fluorescence consistent with an intercalative binding mode of the pyrene moiety. Monomer S was also evaluated as a building block for mixed-sequence recognition of double-stranded DNA via the Invader strategy. However, probes with +1 interstrand arrangements of monomer S were found to be less efficient than Invader probes based on 2'-O-(pyren-1-yl)methyluridine or 2'-N-(pyren-1-yl)methyl-2'-N-methyl-2'-aminouridine.

Synthesis and Characterization of 8-O-Carboxymethylpyranine (CM-Pyranine) as a Bright, Violet-Emitting, Fluid-Phase Fluorescent Marker in Cell Biology

To avoid spectral interference with common fluorophores in multicolor fluorescence microscopy, a fluid-phase tracer with excitation and emission in the violet end of the visible spectrum is desirable. CM-pyranine is easily synthesized and purified. Its excitation and emission maxima at 401.5 nm and 428.5 nm, respectively, are well suited for excitation by 405-nm diode lasers now commonly available on laser-scanning microscopes. High fluorescence quantum efficiency (Q = 0.96) and strong light absorption (ε405 > 25,000 M-1cm-1) together make CM-pyranine the brightest violet aqueous tracer. The fluorescence spectrum of CM-pyranine is invariant above pH 4, which makes it a good fluid-phase marker in all cellular compartments. CM-pyranine is very photostable, is retained for long periods by cells, does not self-quench, and has negligible excimer emission. The sum of its properties make CM-pyranine an ideal fluorescent tracer. The use of CM-pyranine as a fluid-phase marker is demonstrated by multicolor confocal microscopy of cells that are also labeled with lipid and nuclear markers that have green and red fluorescence emission, respectively.

Pyrene is a Novel Constitutive Androstane Receptor (CAR) Activator and Causes Hepatotoxicity by CAR

Polycyclic aromatic hydrocarbons (PAHs) are a class of ubiquitous persistent environmental pollutants which are primarily formed from the incomplete combustion of organic materials. Many potential sources of human exposure to PAHs exist, including daily exposures from the ambient environment or occupational settings. PAHs have been found to cause harmful effects on human health. Here, we evaluated the adverse effects of pyrene, a common PAH, on the liver. The present study demonstrates that pyrene is able to activate mouse constitutive androstane receptor (CAR). CAR protein, as measured by Western blot analysis, was observed to translocate into the nucleus from the cytoplasm in mouse liver after exposure to pyrene. Utilizing CAR null mice, we identified that CAR mediates pyrene-induced hepatotoxicity. Increased relative liver weight, hepatocellular hypertrophy, and elevated serum alanine aminotransferase levels were found in wild-type but not CAR null mice after orally administered pyrene. We further show that pyrene induced the expression of mouse liver metabolism enzymes including CYP2B10, CYP3A11, GSTm1, GSTm3, and SULT1A1, and caused hepatic glutathione depletion in wild-type but not CAR null mice. Moreover, by luciferase reporter assay and quantitative real-time PCR analysis, pyrene was found to be a potential inducer of CYP2B6 expression via activation of human CAR in HepG2 cells and human primary hepatocytes. Our observations suggest that pyrene is a novel CAR activator and that CAR is essential for mediating pyrene-induced liver injury.

⁹⁹mTc pyrene derivative complex causes double-strand breaks in dsDNA mainly through cluster-mediated indirect effect in aqueous solution

Radiation therapy for cancer patients works by ionizing damage to nuclear DNA, primarily by creating double-strand breaks (DSB). A major shortcoming of traditional radiation therapy is the set of side effect associated with its long-range interaction with nearby tissues. Low-energy Auger electrons have the advantage of an extremely short effective range, minimizing damage to healthy tissue. Consequently, the isotope ^99mTc, an Auger electron source, is currently being studied for its beneficial potential in cancer treatment. We examined the dose effect of a pyrene derivative ^99mTc complex on plasmid DNA by using gel electrophoresis in both aqueous and methanol solutions. In aqueous solutions, the average yield per decay for double-strand breaks is 0.011±0.005 at low dose range, decreasing to 0.0005±0.0003 in the presence of 1 M dimethyl sulfoxide (DMSO). The apparent yield per decay for single-strand breaks (SSB) is 0.04±0.02, decreasing to approximately a fifth with 1 M DMSO. In methanol, the average yield per decay of DSB is 0.54±0.06 and drops to undetectable levels in 2 M DMSO. The SSB yield per decay is 7.2±0.2, changing to 0.4±0.2 in the presence of 2 M DMSO. The 95% decrease in the yield of DSB in DMSO indicates that the main mechanism for DSB formation is through indirect effect, possibly by cooperative binding or clustering of intercalators. In the presence of non-radioactive ligands at a near saturation concentration, where radioactive Tc compounds do not form large clusters, the yield of SSB stays the same while the yield of DSB decreases to the value in DMSO. DSBs generated by ^99mTc conjugated to intercalators are primarily caused by indirect effects through clustering.

Energy metabolism in Mycobacterium gilvum PYR-GCK: insights from transcript expression analyses following two states of induction

Mycobacterium gilvum PYR-GCK, a pyrene degrading bacterium, has been the subject of functional studies aimed at elucidating mechanisms related to its outstanding pollutant bioremediation/biodegradation activities. Several studies have investigated energy production and conservation in Mycobacterium, however, they all focused on the pathogenic strains using their various hosts as induction sources. To gain greater insight into Mycobacterium energy metabolism, mRNA expression studies focused on respiratory functions were performed under two different conditions using the toxic pollutant pyrene as a test substrate and glucose as a control substrate. This was done using two transcriptomic techniques: global transcriptomic RNA-sequencing and quantitative Real-Time PCR. Growth in the presence of pyrene resulted in upregulated expression of genes associated with limited oxygen or anaerobiosis in M. gilvum PYR-GCK. Upregulated genes included succinate dehydrogenases, nitrite reductase and various electron donors including formate dehydrogenases, fumarate reductases and NADH dehydrogenases. Oxidative phosphorylation genes (with respiratory chain complexes I, III -V) were expressed at low levels compared to the genes coding for the second molecular complex in the bacterial respiratory chain (fumarate reductase); which is highly functional during microaerophilic or anaerobic bacterial growth. This study reveals a molecular adaptation to a hypoxic mode of respiration during aerobic pyrene degradation. This is likely the result of a cellular oxygen shortage resulting from exhaustion of the oxygenase enzymes required for these degradation activities in M. gilvum PYR-GCK.

A large-scale allosteric transition in cytochrome P450 3A4 revealed by luminescence resonance energy transfer (LRET)

Effector-induced allosteric transitions in cytochrome P450 3A4 (CYP3A4) were investigated by luminescence resonance energy transfer (LRET) between two SH-reactive probes attached to various pairs of distantly located cysteine residues, namely the double-cysteine mutants CYP3A4(C64/C468), CYP3A4(C377/C468) and CYP3A4(C64/C121). Successive equimolar labeling of these proteins with the phosphorescent probe erythrosine iodoacetamide (donor) and the near-infrared fluorophore DY-731 maleimide (acceptor) allowed us to establish donor/acceptor pairs sensitive to conformational motions. The interactions of all three double-labeled mutants with the allosteric activators α-naphthoflavone and testosterone resulted in an increase in the distance between the probes. A similar effect was elicited by cholesterol. These changes in distance vary from 1.3 to 8.5 Å, depending on the position of the donor/acceptor pair and the nature of the effector. In contrast, the changes in the interprobe distance caused by such substrates as bromocriptine or 1-pyrenebutanol were only marginal. Our results provide a decisive support to the paradigm of allosteric modulation of CYP3A4 and indicate that the conformational transition caused by allosteric effectors increases the spatial separation between the beta-domain of the enzyme (bearing residues Cys₆₄ and Cys₃₇₇) and the alpha-domain, where Cys₁₂₁ and Cys₄₆₈ are located.

Measurement and analysis of in vitro actin polymerization

The polymerization of actin underlies force generation in numerous cellular processes. While actin polymerization can occur spontaneously, cells maintain control over this important process by preventing actin filament nucleation and then allowing stimulated polymerization and elongation by several regulated factors. Actin polymerization, regulated nucleation, and controlled elongation activities can be reconstituted in vitro, and used to probe the signaling cascades cells use to control when and where actin polymerization occurs. Introducing a pyrene fluorophore allows detection of filament formation by an increase in pyrene fluorescence. This method has been used for many years and continues to be broadly used, owing to its simplicity and flexibility. Here we describe how to perform and analyze these in vitro actin polymerization assays, with an emphasis on extracting useful descriptive parameters from kinetic data.

Bioaccumulation and metabolisation of (14)C-pyrene by the Pacific oyster Crassostrea gigas exposed via seawater

The first objective of this study was to determine the bioaccumulation kinetics of pyrene in the soft tissues of Crassostrea gigas (mantle, muscle, gills, digestive gland, and the remaining soft tissues). As bivalves can biotransform hydrocarbons in more polar compounds (metabolites) that are more easily excreted, the second objective was to investigate the oyster capacity to metabolize pyrene into its metabolite, the 1-hydroxypyrene. To these ends, oysters were exposed 24 h to waterborne (14)C-pyrene then placed in depuration conditions for 15 d. Oysters efficiently bioaccumulated pyrene in their soft tissues and equilibrium was reached within the exposure time. The metabolite1-hydroxypyrene was also detected in oyster tissues but represented only 4-14% of the parent pyrene. At the end of the exposure period, the gills and the mantle showed the highest pyrene proportion of total soft tissue content, i.e. 47% and 26%, respectively. After 15 d of depuration, the mantle contained 32% and 30% of the remaining pyrene and 1-hydroxypyrene, respectively. As C. gigas did not display a high capacity for metabolizing pyrene, it can be considered as a good bioindicator species to survey and monitor pyrene contamination in the coastal marine environment.

Homocysteine upregulates soluble epoxide hydrolase in vascular endothelium in vitro and in vivo

RATIONALE

Hyperhomocysteinemia is a risk factor of atherogenesis. Soluble epoxide hydrolase (sEH) is a major enzyme that hydrolyzes epoxyeicosatrienoic acids and attenuates their cardiovascular protective effects. Whether homocysteine (Hcy) regulates sEH and the underlying mechanism remains elusive.

OBJECTIVE

To elucidate the mechanism by which Hcy regulates sEH expression and endothelial activation in vitro and in vivo.

METHODS AND RESULTS

Hcy treatment in cultured human endothelial cells dose-dependently and time-dependently upregulated sEH mRNA and protein. Hcy increased the expression of adhesion molecules, which was markedly reversed by inhibiting sEH activity. Hcy-induced sEH upregulation is associated with activation of activating transcription factor-6 (ATF6). Bioinformatics analysis revealed a putative ATF6-binding motif in the promoter region of the sEH gene, which was found at a methylation site. Site-directed mutagenesis and chromatin immunoprecipitation assays demonstrated that Hcy treatment or ATF6 overexpression promoted ATF6 binding to the promoter of sEH and increased its activity. Results of methylation-specific polymerase chain reaction revealed that the ATF6 binding site on the sEH promoter was partially methylated and was demethylated with Hcy. SiRNA knockdown of ATF6α or SP1 blocked and ATF6 overexpression and DNA methyltransferase inhibitor mimicked the effect of homocysteine on sEH upregulation. In vivo, immunofluorescence assay revealed elevated expression of sEH and adhesion molecules in the aortic intima of mice with mild hyperhomocysteinemia, which was attenuated by sEH deletion or inhibition.

CONCLUSION

ATF6 activation and DNA demethylation may coordinately contribute to Hcy-induced sEH expression and endothelial activation. Inhibition of sEH may be a therapeutic approach for treating Hcy-induced cardiovascular diseases.

Effect of pyrene on denitrification activity and abundance and composition of denitrifying community in an agricultural soil

Toxicity of pyrene on the denitrifiers was studied by spiking an agricultural soil with pyrene to a series of concentrations (0-500 mg kg(-1)) followed by dose-response and dynamic incubation experiments. Results showed a positive correlation between potential denitrification activity and copy numbers of denitrifying functional genes (nirK, nirS and nosZ), and were both negatively correlated with pyrene concentrations. Based on the comparison of EC(50) values, denitrifiers harboring nirK, nirS or nosZ gene were more sensitive than denitrification activity, and denitrifiers harboring nirS gene were more sensitive than that harboring nirK or nosZ genes. Seven days after spiking with EC(50) concentration of pyrene, denitrifiers diversity decreased and community composition changed in comparison with the control. Phylogenetic analyses of three genes showed that the addition of pyrene increased the proportion of Bradyrhizobiaceae, Rhodospirillales, Burkholderiales and Pseudomonadales. Some species belonging to these groups were reported to be able to degrade PAHs.

Elucidating cell-penetrating peptide mechanisms of action for membrane interaction, cellular uptake, and translocation utilizing the hydrophobic counter-anion pyrenebutyrate

Cell-penetrating peptides (CPPs) are membrane permeable vectors recognized for their intrinsic ability to gain access to the cell interior. The hydrophobic counter-anion, pyrenebutyrate, enhances cellular uptake of oligoarginine CPPs. To elucidate CPP uptake mechanisms, the effect of pyrenebutyrate on well-recognized CPPs with varying hydrophobicity and arginine content is investigated. The cellular CPP uptake and CPP-mediated oligonucleotide delivery is analyzed by fluorescence activated cell sorting, confocal microscopy, and a cell-based splice-switching assay. The splice-switching oligonucleotide is a mixmer of 2'-O-methyl RNA and locked nucleic acids delivered as a non-covalent complex with 10-fold molar CPP excess. CPP-induced membrane perturbation on large unilamellar vesicles is investigated in calcein release experiments. We observed that pyrenebutyrate facilitates cellular uptake and translocation of oligonucleotide mediated by oligoarginine nonamer while limited effect of pyrenebutyrate on more hydrophobic CPPs was observed. By combining the different experimental results we conclude that the pathway for cellular uptake of oligoarginine is dominated by direct membrane translocation, whereas the pathway for oligoarginine-mediated oligonucleotide translocation is dominated by endocytosis. Both mechanisms are promoted by pyrenebutyrate and we suggest that pyrenebutyrate has different sites of action for the two uptake and translocation mechanisms.

Effect of the acyl group and the dodecylsulfonate chain on the inclusion of pyrene inside the cavity of beta-cyclodextrin

The solubilization of pyrene in aqueous solution of beta-cyclodextrin (beta-CD) or its derivatives such as beta-CD-hexanoyl, beta-CD-benzoyl and beta-CD-dodecylsulfonate was investigated by spectrophotometry. Linear and non-linear regression methods were used to estimate the association constants (K(1)). A 1:1 stoichiometric ratio and different effects of the hexanoyl, benzoyl and dodecylsulfonate groups on the association constant were observed for the binary inclusion complex between pyrene and beta-CD. The formation constant was shown to decrease when beta-CD was modified by a dodecylsulfonate chain. The value of K(1) was 190+/-10 L mol(-1) for the [pyrene/beta-CD] complex and 145 L mol(-1) for the [pyrene/beta-CD-dodecylsulfonate] complex. Partitioning of the pyrene molecules between the dodecylsulfonate chains and cyclodextrin cavities can explain the decrease in the association constant value. In the cases of beta-CD-hexanoyl and beta-CD-benzoyl derivatives, no association constants were detected. Results suggest that the high hydrophobicity of the hexanoyl and benzoyl groups prevents the inclusion of pyrene molecules inside the cyclodextrin cavity.

Slt2 (Mpk1) MAP kinase is involved in the response of Saccharomyces cerevisiae to 8-methoxypsoralen plus UVA

The bifunctional furocoumarin 8-methoxypsoralen (8-MOP) is a well established drug in the photochemotherapy of psoriasis and other skin diseases. In eukaryotic cells, this compound intercalates into DNA and undergoes photocycloaddition with pyrimidines to form monoadducts and interstrand crosslinks initiating a cascade of events leading to cytotoxic, mutagenic and carcinogenic responses. In yeast cells, exposure to 8-MOP plus UVA induces transcription of a large set of genes, and cellular reaction is different from an overall DNA damage response and specific to 8-MOP/UVA [M. Dardalhon, W. Lin, A. Nicolas, D. Averbeck, Specific transcriptional responses induced by 8-methoxypsoralen and UVA in yeast, FEMS Yeast Res. 7 (2007) 866-878]. To further define the relationship between induced genes and genotoxic consequences after 8-MOP/UVA treatment, the survival responses of mutants deleted for genes that are specifically induced by 8-MOP plus UVA were analysed in terms of survival. Six mutants deleted for RAD51, RAD54, DUN1, DIN7, already known to be implicated in DNA damage responses, and for SLT2/MPK1 and PDE2 involved in cell wall stress responses, were found sensitive to 8-MOP plus UVA treatment. Further characterization of slt2 mutant provides evidence for the existence of an 8-MOP/UVA response in yeast in which the yeast Slt2 MAPK pathway is implicated. Activation by 8-MOP plus UVA of this MAP kinase previously observed at the transcriptional level is now confirmed at the protein level. In addition to sensitivity to 8-MOP/UVA, yeast cells lacking SLT2 show reduced survival after 3-carbethoxypsoralen plus UVA and 1,6-dioxapyrene plus UVA. Osmotic support could suppress the sensitivities to these genotoxic agents, suggesting that these sensitivities are related to cell integrity defects and/or cell wall defects.

Interactions between selected PAHs and the microbial community in rhizosphere of a paddy soil

This study investigated the interaction of three polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene (NAP), phenanthrene (PHN), and pyrene (PYR), with the microbial community in the rhizosphere of a paddy soil and the influence of the rice (Oryza sativa) rhizosphere on the microbial community structure. A range of initial NAP, PHN and PYR levels in soil (50-200, 18-72, and 6.6-26.6 mg kg(-1), respectively) were prepared and the soil samples were then aged for 4 months (to yield PAH concentrations at 1.02-1.42, 1.32-4.77, and 2.98-18.5 mg kg(-)(1), respectively) before the soil samples were planted with rice seedlings. The microbial phospholipid-fatty-acid (PLFA) patterns in PAH-contaminated soils were analyzed to elucidate the changes of the microbial biomass and community composition. Results indicated that at the applied concentrations the PAHs were not toxic to rice seedlings, as evidenced by no growth inhibition during the 8-week planting period. However, the microbial biomass, as revealed by PLFAs, decreased significantly with increasing PAH concentration in both rhizospheric and non-rhizospheric soils. The PAHs in soils were obviously toxic to microorganisms, and the toxicity of PHN was greater than PYR due likely to the higher PHN bioavailability. Total PLFAs in rhizospheric soils were profoundly higher than those in non-rhizospheric soils, suggesting that the inhibitive effect of PAHs on microbial activities was alleviated by the rice roots. The principal component analysis (PCA) of the PLFA signatures revealed pronounced changes in PLFA pattern in rhizospheric and non-rhizospheric soils with or without spiked PAHs. Using the PLFA patterns as a biomarker, it was found that Gram-positive bacteria were more sensitive to PAHs than Gram-negative bacteria, and the rhizosphere of rice roots stimulated the growth of aerobic bacteria.

Calcium channel blocker, azelnidipine, reduces lipid hydroperoxides in patients with type 2 diabetes independent of blood pressure

Anti-hypertensive agents with antioxidative effects are potentially useful for diabetic patients with hypertension to prevent the onset and progression of their complication. While dihydropyridine-type calcium antagonists are among the frequently used anti-hypertensive drugs, azelnidipine, a novel calcium antagonist, has been reported to have a unique anti-oxidative effect in vitro and in animals. In this study, we measured lipid hydroperoxides in human sample using diphenyl-1-pyrenylphosphine for the first time, and used the value of lipid hydroperoxides as an index of oxidative stress. Then, we compared the antioxidative properties of azelnidipine and amlodipine, a frequently used calcium antagonist in hypertensive diabetic patients. Administration of vitamin C and E for 8 weeks significantly reduced lipid hydroperoxides in erythrocyte membrane in normal subjects. In hypertensive diabetic patients, azelnidipine treatment for 12 weeks induced a more significant fall in erythrocyte lipid hydroperoxide level than amlodipine, though blood pressure during each treatment was comparable. Our data confirm the usefulness of lipid hydroperoxides in erythrocyte membrane as a marker of oxidative stress in vivo, and indicate that azelnidipine has a unique antioxidative property in human.

Stimulation of actin polymerization by vacuoles via Cdc42p-dependent signaling

We have previously shown that actin ligands inhibit the fusion of yeast vacuoles in vitro, which suggests that actin remodeling is a subreaction of membrane fusion. Here, we demonstrate the presence of vacuole-associated actin polymerization activity, and its dependence on Cdc42p and Vrp1p. Using a sensitive in vitro pyrene-actin polymerization assay, we found that vacuole membranes stimulated polymerization, and this activity increased when vacuoles were preincubated under conditions that support membrane fusion. Vacuoles purified from a VRP1-gene deletion strain showed reduced polymerization activity, which could be recovered when reconstituted with excess Vrp1p. Cdc42p regulates this activity because overexpression of dominant-negative Cdc42p significantly reduced vacuole-associated polymerization activity, while dominant-active Cdc42p increased activity. We also used size-exclusion chromatography to directly examine changes in yeast actin induced by vacuole fusion. This assay confirmed that actin undergoes polymerization in a process requiring ATP. To further confirm the need for actin polymerization during vacuole fusion, an actin polymerization-deficient mutant strain was examined. This strain showed in vivo defects in vacuole fusion, and actin purified from this strain inhibited in vitro vacuole fusion. Affinity isolation of vacuole-associated actin and in vitro binding assays revealed a polymerization-dependent interaction between actin and the SNARE Ykt6p. Our results suggest that actin polymerization is a subreaction of vacuole membrane fusion governed by Cdc42p signal transduction.

Allosteric mechanisms in cytochrome P450 3A4 studied by high-pressure spectroscopy: pivotal role of substrate-induced changes in the accessibility and degree of hydration of the heme pocket

Allosteric mechanisms in human cytochrome P450 3A4 (CYP3A4) in oligomers in solution or monomeric enzyme incorporated into Nanodiscs (CYP3A4ND) were studied by high-pressure spectroscopy. The allosteric substrates 1-pyrenebutanol (1-PB) and testosterone were compared with bromocriptine (BCT), which shows no cooperativity. In both CYP3A4 in solution and CYP3A4ND, we observed a complete pressure-induced high-to-low spin shift at pressures of <3 kbar either in the substrate-free enzyme or in the presence of BCT. In addition, both substrate-free and BCT-bound enzyme revealed a pressure-dependent equilibrium between two states with different barotropic parameters designated R for relaxed and P for pressure-promoted conformations. This pressure-induced conformational transition was also observed in the studies with 1-PB and testosterone. In CYP3A4 oligomers, the transition was accompanied by an important increase in homotropic cooperativity with both substrates. Surprisingly, at high concentrations of allosteric substrates, the amplitude of the spin shift in both CYP3A4 in solution and Nanodiscs was very low, demonstrating that hydrostatic pressure induces neither substrate dissociation nor an increase in the heme pocket hydration in the complexes of the pressure-promoted conformation of CYP3A4 with 1-PB or testosterone. These findings suggest that the mechanisms of interactions of CYP3A4 with 1-PB and testosterone involve an effector-induced transition that displaces a system of conformational equilibria in the enzyme toward the state(s) with decreased solvent accessibility of the active site so that the flux of water into the heme pocket is impeded and the high-spin state of the heme iron is stabilized.

Identification of tau stem loop RNA stabilizers

Alternative splicing of tau exon 10 produces tau isoforms with either 3 (3R) or 4 (4R) repeated microtubule-binding domains. Increased ratios of 4R to 3R tau expression, above the physiological 1:1, leads to neurofibrillary tangles and causes neurodegenerative disease. An RNA stem loop structure plays a significant role in determining the ratio, with decreasing stability correlating with an increase in 4R tau mRNA expression. Recent studies have shown that aminoglycosides are able to bind and stabilize the tau stem loop in vitro, suggesting that other druglike small molecules could be identified and that such molecules might lead to decreased exon 10 splicing in vivo. The authors have developed a fluorescent high-throughput fluorescent binding assay and screened a library of approximately 110,000 compounds to identify candidate drugs that will bind the tau stem loop in vitro. In addition, they have developed a fluorescent-based RNA probe to assay the stabilizing effects of candidate drugs on the tau stem loop RNA. These assays should be applicable to the general problem of identifying small molecules that interact with mRNA secondary structures.

Capillary Isoelectric Focusing and Fluorometric Detection of Proteins and Microorganisms Dynamically Modified by Poly(ethylene glycol) Pyrenebutanoate

The nonionogenic pyrene-based tenside, poly(ethylene glycol) pyrenebutanoate, was prepared and applied in capillary isoelectric focusing with fluorometric detection. This dye was used here as a buffer additive in capillary isoelectric focusing for a dynamic modification of the sample of proteins and microorganisms. The values of the isoelectric points of the labeled bioanalytes were calculated with use of the fluorescent pI markers and were found comparable with pI of the native compounds. The mixed cultures of proteins and microorganisms, Escherichia coli CCM 3954, Staphylococcus epidermidis CCM 4418, Proteus vulgaris, Enterococcus faecalis CCM 4224, and Stenotrophomonas maltophilia, the strains of the yeast cells, Candida albicans CCM 8180, Candida krusei, Candida parapsilosis, Candida glabrata, Candida tropicalis, and Saccharomyces cerevisiae were reproducibly focused and separated by the suggested technique. Using UV excitation for the on-column fluorometric detection, the minimum detectable amount was down to 10 cells injected on the separation capillary.

Polycyclic aromatic hydrocarbon (PAH) metabolizing enzyme activities in human lung, and their inducibility by exposure to naphthalene, phenanthrene, pyrene, chrysene, and benzo(a)pyrene as shown in the rat lung and liver

In order to survey changes and activities in the polycyclic aromatic hydrocarbon (PAH)-metabolizing enzymes implicated in lung cancer susceptibility studies, we investigated enzyme induction by 2-5-ring-sized 'biomarker' PAHs in rat liver and lung, and the activities in five human lung specimens. Naphthalene, phenanthrene, pyrene, chrysene, and benzo[a]pyrene (BaP) were administered to rats for 3 days (25-128 mg/kg/day) and the responses compared with those of model inducers. PAH treatment increased the CYP1A-catalyzed activity of pyrene 1-hydroxylation and 7-ethoxyresorufin O-deethylation in rat liver by up to 28- and 279-fold, and in rat lung by up to 22- and 51-fold, respectively. 1-Naphthol (hUGT1A6), 1-hydroxypyrene (hUGT1A6/1A9), and entacapone (hUGT1A9) are markers of PAH-glucuronidating human uridine diphosphate-glucuronosyltransferases (UGT). These activities increased up to 6.4-fold in rat liver and up to 1.9-fold in rat lung. NADPH:quinone oxidoreductase 1 (NQO1) and glutathione S-transferase activities increased up to 5.3- and 1.6-fold (liver), and up to 4.4- and 1.4-fold (lung), respectively. CYP1A showed the best liver-to-lung relationship (R (2 )=( )0.90). The inducing efficiency by PAHs differed extensively: control <or= naphthalene < phenanthrene, pyrene << chrysene < BaP. In human lung (non-smokers), the marker activities of CYP1A1, UGT1A6/1A9, and NQO1 were lower than those in rat lung. Epoxide hydrolase activity was 1,000-fold higher than the pulmonary CYP1A1 activities. Human UGT and NQO1 displayed large variations (>60-fold), many times greater than the experimental (inducible/constitutive) variation in the rat. Kinetics of 1-hydroxypyrene glucuronidation showed two low-K (m) forms both in rat and human lung. Since the 2-4-ring PAHs (major constituents) were poor enzyme inducers, it appears that the PAH-metabolizing pathways are mainly induced by BaP-type minor constituents. Gene-environmental interactions which magnify polymorphic variability in pulmonary bioactivation/detoxification capacity probably play a key role in individual susceptibility to (or protection against) chemically induced lung cancer. Hence, human exposure to PAH mixtures with high content of BaP-type hydrocarbons confers a potentially higher health risk than PAH mixtures with low content of procarcinogens.

An in vivo model for testing genotoxicity of environmental fibre-associated nitroarenes

The environmental carcinogens nitroarenes are frequently adsorbed by asbestos fibres. An effective dose of 1-nitropyrene was studied in vivo. The mutagenic pattern of excreted urine of orally and intraperitoneally exposed rats was tested by the Ames mutagenicity assay. The characteristics of detected mutagenicity proved to be different in the two routes of exposure. TA 100 mutagenicity was only detected following i.p. exposure, while TA 98 revertant frequencies were increased significantly only after deconjugation, in both groups. Since environmental asbestos exposure involves carcinogenic effects of adsorbed polycyclic aromatic hydrocarbons, this animal model provides a useful tool for testing fibre-associated nitroarenes, in both mechanistic and risk assessment studies.

A Formal Total Synthesis of the Marine Diterpenoid Diisocyanoadociane

[Structure: see text] A formal total synthesis of diisocyanoadociane, a marine diterpenoid with potent antimalarial properties, has been completed. The synthesis begins with a phenanthrenoid precursor that is transformed into a pyrene-derived intermediate by means of an intramolecular Michael reaction. Nitrogen functionality is introduced via a double Curtius reaction.

Role of sediment organic matter quality and feeding history in dietary absorption and accumulation of pyrene in the mud snail (Hydrobia ulvae)

Organic matter (OM) input to marine sediments varies seasonally both in quantity and quality. Because sedimentary OM (SOM) constitutes food for many benthic organisms, its properties should affect the dietary uptake of sediment-associated contaminants. We explored the effect of SOM quality/food value on short- and long-term pyrene accumulation in the mud snail (Hydrobia ulvae) and performed dual-tracer pulse-chase experiments to investigate the feeding mechanisms driving dietary pyrene uptake. The quality of the SOM was manipulated by enriching sediments either with high-quality microalgae or low-quality lignin, adding equal amounts of total organic carbon. Long- and short-term bioaccumulation increased with increasing SOM quality, as did pyrene ingestion rate (IR(pyr)), which also was affected by feeding history. By feeding selectively, snails concentrated pyrene 10-fold in ingested compared to ambient sediment, independent of SOM quality. Average pyrene absorption efficiency (AE(pyr): -65%) varied inversely with SOM quality and IR(pyr). Both AE(pyr) and gut passage time (alpha 1/IR(pyr)) agreed with theoretical models incorporating the time-dependence of absorption efficiency. Thus, SOM quality moderates dietary contaminant uptake in deposit feeders, and in H. ulvae, this occurs via OM-induced alterations of ingestion rate. Consequently, enhanced sediment-associated contaminant uptake is predicted for deposit feeders following phytoplankton blooms, principally because of OM quality-driven increases in the ingestion rate.

CYP1A1 in polycyclic aromatic hydrocarbon-induced B lymphocyte growth suppression

The AhR is a ligand-activated transcription factor that mediates immunosuppression by environmental PAH. Previous studies demonstrated that activation of mature human B cells up-regulates AhR expression, suggesting that human B cells are direct PAH targets. To test this hypothesis and to determine the metabolic requirements for PAH toxicity in a human model, the effects of a prototypic PAH, B[a]P, on B cell growth were evaluated. B[a]P and its proximal (B[a]P-7,8-dihydrodiol) and terminal (B[a]P-7,8-dihydrodiol-9,10-epoxide) metabolites inhibited growth in a dose-dependent manner. A poorly metabolized AhR ligand had no effect, suggesting that biotransformation is required for growth inhibition. Inhibition of the CYP1A1 monooxygenase completely blocked growth inhibition induced by B[a]P or B[a]P-7,8-dihydrodiol, but not by B[a]P-dihydrodiol-9,10-epoxide, indicating that CYP1A1-dependent metabolism of B[a]P into the terminal B[a]P-7,8-dihydrodiol-9,10-epoxide metabolite is required for growth inhibition. These studies show for the first time the metabolic requirements for PAH-mediated suppression of human B cell growth.

Supramolecular fluorophores for biological studies: phenylene vinylene-amino acid amphiphiles

We report here on a family of self-assembling fluorescent organic amphiphiles with a biomolecular L-lysine hydrophile and a photonically active phenylene vinylene hydrophobe. Unlike conventional amphiphiles, these segmented dendrimers feature a rigid, branched hydrophobe, and have packing characteristics controlled by the ratio of cross-sectional areas of the hydrophobe and hydrophile. In dilute solution, the amphiphiles form supramolecular aggregates, which are easily taken in by cells through an endocytic pathway, and have no discernible effect on cell proliferation or morphology. An analogous pyrene-based amphiphile was cytotoxic, suggesting that cell survival may be linked either to the self-assembling nature of the amphiphiles, or to the specific properties of the phenylene vinylene segment. The combination of photonic and biological components in these amphiphiles provides great potential for applications in sensing or delivery of molecules to intracellular targets.

Synthesis and biological properties of the fluorescent ether lipid precursor 1-O-[9'-(1''-pyrenyl)]nonyl-sn-glycerol

The synthesis of an omega-pyrene-labeled 1-O-alkyl-sn-glycerol was performed using a chirospecific method starting from R-(-)-2,3-O-isopropylidene-sn-glycerol. The product, 1-O-[9'-(1''-pyrenyl)]nonyl-sn-glycerol (pAG), is a fluorescent ether lipid that has a pyrene moiety covalently attached at the alkyl chain terminus. pAG was taken into CHO-K1 cells and a plasmalogen-deficient variant of CHO-K1, NRel-4. This variant is defective in dihydroxyacetonephosphate acyltransferase, which catalyzes the first step in plasmenylethanolamine (PlsEtn) biosynthesis. pAG was incorporated primarily into ethanolamine and choline phospholipids as well as a neutral lipid fraction tentatively identified as alkyldiacylglycerol. NRel-4 accumulated more fluorescence in the phospholipid fraction than CHO-K1, specifically in the ethanolamine phospholipids. Analysis of the fluorescent lipids showed that 93% of the pAG was incorporated into glycerolipids with the ether bond intact. Although the addition of 20 microM 1-O-hexadecyl-sn-glycerol to the medium fully restored PlsEtn biosynthesis in NRel-4 cells, pAG only partially restored PlsEtn synthesis. Incubation of cells with pAG followed by irradiation with long-wavelength (>300 nm) ultraviolet light resulted in cytotoxicity. NRel-4 cells displayed an increased sensitivity to this treatment compared with CHO-K1 cells. This photodynamic cytotoxicity approach could be used to select for mutants that are defective in downstream steps in ether lipid biosynthesis.

Synthesis and Biological Activity of Isoxazolidinyl Polycyclic Aromatic Hydrocarbons: Potential DNA Intercalators

Isoxazolidinyl polycyclic aromatic hydrocarbons (isoxazolidinyl-PAHs) have been synthesized in good yields by 1,3-dipolar cycloaddition methodology promoted by microwave irradiation. The structures of the obtained cycloadducts have been determined by NOE experiments and supported by computational studies at the AM1 level. The cytotoxicity and antiviral activity of the synthesized compounds have been investigated. In particular, compounds 7c and 7e show high levels of cytotoxicity on MOLT-3 leukemia cells; 7e exerts a remarkable enhancing activity on apoptosis caused by anti-fas antibody addition. Furthermore, compounds 7b and 8b exhibit specific antiviral effects against the Punta Toro virus.

Suppressive effect of 1-nitropyrene on benzo[a]pyrene-induced CYP1A1 protein expression in HepG2 cells

The genotoxicity of polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs may be influenced by the interaction of the compounds. In this study, our data showed that benzo[a]pyrene (BaP)-DNA adduct levels were decreased in a dose-dependent manner when the human hepatoma cell line HepG2 simultaneously treated with BaP and 1-nitropyrene (1-NP). To further investigate the molecular mechanism by which 1-NP interferes with the covalent binding of BaP to DNA, we conducted experiments to analyze the mRNA level and protein stability of cytochrome P450 1A1 (CYP1A1), which is engaged in the activation of BaP, leading to the generation of BaP-DNA adducts. Northern blot analysis presented that 1-NP attenuated BaP-induced CYP1A1 mRNA expression by 30.4-39.6% (p < 0.05). Western blot analysis revealed that the co-treatment with BaP and 1-NP resulted in a significant inhibition of BaP-induced CYP1A1 protein expression (70.7-88.2%, p < 0.05). However, the decrease in CYP1A1 protein levels was significantly larger than that in CYP1A1 mRNA levels. To confirm the effect of 1-NP on the CYP1A1 protein expression, in vitro proteolysis of CYP1A1 protein was evaluated. The results demonstrated that the addition of 1-NP enhanced CYP1A1 protein degradation and the proteolysis of CYP1A1 protein was inhibited by the addition of an antioxidant, dithiothreitol. In addition, the relative levels of reactive oxygen species (ROS) were elevated in HepG2 cells co-treated with BaP and 1-NP, indicating that the decrease of CYP1A1 protein level was probably attributed to the production of ROS generated by binary mixture. Taken together, these findings suggested that the transcriptional suppression and posttranslational mechanism may be involved in loss of CYP1A1 protein, causing the decrease of BaP-DNA adduct levels in the presence of binary mixtures of 1-NP and BaP.

1-Hydroxy-1-norresistomycin, a New Cytotoxic Compound from a Marine Actinomycete, Streptomyces chibaensis AUBN1/7 †

In our systematic screening programme for marine actinomycetes, a bioactive streptomycete was isolated from marine sediment samples of the Bay of Bengal, India. The isolate yielded a new cytotoxic compound. This was obtained by solvent extraction followed by chromatographic purification. The pure compound was identified from spectroscopic data as a quinone-related antibiotic, 1-hydroxy-1-norresistomycin (1). It showed a potent cytotoxic activity against cell lines viz. HMO2 (gastric adenocarcinoma) and HePG2 (hepatic carcinoma) in vitro. It also exhibited antibacterial activities against Gram-positive and Gram-negative bacteria.

DNA sequence analysis of 1-nitropyrene-4,5-oxide and 1-nitropyrene-9,10-oxide induced mutations in the hprt gene of Chinese hamster ovary cells

Nitropyrene, the predominant nitropolycyclic hydrocarbon found in diesel exhaust, is a mutagenic and tumorigenic environmental pollutant that requires metabolic activation via nitroreduction and ring oxidation. In order to determine the role of ring oxidation in the mutagenicity of 1-nitropyrene, its oxidative metabolites, 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide, were synthesized and their mutation spectra were determined in the coding region of hprt gene of CHO cells by a PCR amplification of reverse-transcribed hprt mRNA, followed by a DNA sequence analysis. A comparison of the two metabolites for mutation frequencies showed that 1-nitropyrene 9,10-oxide was 2-times higher than 1-nitropyrene 4,5-oxide. The mutation spectrum for 1-nitropyrene 4,5-oxide was base substitutions (33/49), one base deletions (11/49) and exon deletions (5/49). In the case of 1-nitropyrene 9,10-oxide, base substitutions (27/50), one base deletions (15/50), and exon deletions (8/50) were observed. Base substitutions were distributed randomly throughout the hprt gene. The majority of the base substitutions in mutant from 1-nitropyrene 4,5-oxide treated cells were A-->G transition (15/33) and G-->A transition (8/33). The predominant base substitution, A-->G transition (11/27) and G-->A transition (8/27), were also observed in mutant from 1-nitropyrene 9,10-oxide treated cells. The mutation at the site of adenine and guanine was consistent with the previous results, where the sites of DNA adduct formed by these compounds were predominant at the sites of purines. A comparison of the mutational patterns between 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide showed that there were no significant differences in the overall mutational spectrum. These results indicate that each oxidative metabolite exhibits an equal contribution to the mutagenicity of 1-nitropyrene, and ring oxidation of 1-nitropyrene is an important metabolic pathway to the formation of significant lethal DNA lesions.

Dynamic modification of microorganisms by pyrenebutanoate for fluorometric detection in capillary zone electrophoresis

Pyrenebutanoate, a fluorescent amphiphilic probe, is suggested here as a capillary zone electrophoresis (CZE) buffer additive for dynamic modification and analysis of microbial cells. Mixed cultures of microorganisms Escherichia coli, Candida albicans, Enterococcus faecalis and Staphylococcus epidermidis were concentrated, resolved by CZE and detected. Using UV excitation for on-column fluorometric detection, a detection sensitivity for the microorganisms on the order of from one to tens of injected cells was achieved.

Differential regulation and xenobiotic induction of tandem P450 monooxygenase genes pc-1 (CYP63A1) and pc-2 (CYP63A2) in the white-rot fungus Phanerochaete chrysosporium

The two tandem P450 monooxygenase genes (pc-1 and pc-2) reported by us earlier in Phanerochaete chrysosporium were investigated for their regulation under nutrient-limited and nutrient-rich culture conditions. Transcript analysis based on real-time quantitative RT-PCR showed higher expression of pc-1 in defined low-nitrogen and pc-2 in defined high-nitrogen media, with maximum expression on day 4, indicating that the two genes, though tandemly linked, are regulated in a non-coordinate manner. Transcript levels of pc-1 and pc-2 were differentially influenced by the type of carbon source, incubation temperature, and oxygenation. Both genes were inducible by organic xenobiotic chemicals. Of the 42 xenobiotics tested in nutrient-rich cultures, pc-1 transcription was induced 2.12(+/-0.40)-fold to 6.27(+/-0.48)-fold in the presence of 19 compounds and pc-2 transcription was induced 2.00(+/-0.73)-fold to 29.39(+/-9.40)-fold in the presence of 22 compounds. Particularly, it is significant that both pc-1 and pc-2 are induced by polycyclic aromatic hydrocarbons (PAHs) of varying ring size, including naphthalene (4.35+/-0.09, 6.02+/-1.39), phenanthrene (2.82+/-0.12, 2.14+/-0.61), pyrene (3.93+/-0.01, 1.0+/-0.12), benzanthracene (1.67+/-0.03, 6.08+/-1.50), and benzo(a)pyrene (1.55+/-0.01, 5.54+/-2.75) respectively. This study constitutes the first report on the identification of P450 genes in a fungus that are responsive to environmentally significant pollutant chemicals (PAHs, DDT, long-chain alkyl phenols) and lignin derivatives.

Synthesis of a novel fluorescent poly(D,L-lactide) end-capped with 1-pyrenebutanol used for the preparation of nanoparticles

A new fluorescent polymer based on D,L-lactic acid units end-capped with 1-pyrenebutanol (PLAP) was synthesized by ring-opening polymerization. PLAP having different molecular weight could be obtained by varying the ratio of D,L-lactide and 1-pyrenebutanol. Fluorescent nanoparticles (NP) were prepared using blends of poly(D,L-lactic acid) (PLA) and the new PLAP of 6 kDa by the salting-out process. Incubation of these nanoparticles with human blood monocytes was performed in serum and the cell-associated fluorescence was analysed by flow cytometry. Monocytes in contact with NP containing increasing amounts of PLAP showed a regular increase of the fluorescence. Cells incubated with NP containing 5% (w/w) of PLAP showed high signals of fluorescence with no possible overlap with those given by blank monocytes. This demonstrated that flow cytometry performed in the UV domain was very specific. In addition, the results of cytotoxicity tests using a MTT assay method indicated that PLAP did not increase the cytotoxicity when incorporated into PLA nanoparticles.