Arsenic effectively improves the degradation of fluorene by Rhodococcus sp. 2021 under the combined pollution of arsenic and fluorene.

The performance of bacterial strains in executing degradative functions under the coexistence of heavy metals/heavy metal-like elements and organic contaminants is understudied. In this study, we isolated a fluorene-degrading bacterium, highly arsenic-resistant, designated as strain 2021, from contaminated soil at the abandoned site of an old coking plant. It was identified as a member of the genus Rhodococcus sp. strain 2021 exhibited efficient fluorene-degrading ability under optimal conditions of 400 mg/L fluorene, 30 °C, pH 7.0, and 250 mg/L trivalent arsenic. It was noted that the addition of arsenic could promote the growth of strain 2021 and improve the degradation of fluorene - a phenomenon that has not been described yet. The results further indicated that strain 2021 can oxidize As3+ to As5+; here, approximately 13.1% of As3+ was converted to As5+ after aerobic cultivation for 8 days at 30 °C. The addition of arsenic could greatly up-regulate the expression of arsR/A/B/C/D and pcaG/H gene clusters involved in arsenic resistance and aromatic hydrocarbon degradation; it also aided in maintaining the continuously high expression of cstA that codes for carbon starvation protein and prmA/B that codes for monooxygenase. These results suggest that strain 2021 holds great potential for the bioremediation of environments contaminated by a combination of arsenic and polycyclic aromatic hydrocarbons. This study provides new insights into the interactions among microbes, as well as inorganic and organic pollutants.

Fluorene-induced stress in the benthic oligochaete Tubifex tubifex: A multi-biomarker assessment of toxicological pathways and mechanisms under acute and subchronic exposures.

This study examined the multifaceted impacts of fluorene exposure on Tubifex tubifex, encompassing acute (survival analysis and behavioral responses) and subchronic exposure regimens (antioxidant enzyme response and histopathology), molecular docking studies, and generalized read-across analysis. Survival analysis revealed concentration-dependent increases in toxicity over varying time intervals, with LC50 values decreasing from 30.072 mg/L at 24 h to 12.365 mg/L at 96 h, emphasizing the time-sensitive and concentration-responsive nature of the stressor. Behavioral responses were both concentration- and duration-dependent. While Erratic Movement and Clumping Tendency exhibited earlier responses (within 24 h) at lower concentrations, the wrinkling effect and mucus secretion) exhibited delayed onset, suggesting intricate regulatory mechanisms underlying adaptability to environmental challenges; moreover, the wrinkling effect was consistently induced at higher concentrations, indicating greater sensitivity to the toxic effects of fluorene. With sublethal environmentally relevant concentrations-1.24 mg/l and 2.47 mg/L i.e., 10% and 20% 96 h, respectively-the antioxidant enzyme response (i.e., upregulation of SOD, CAT, and GST) with increasing fluorene concentration, revealing a nonlinear, hormetic response, suggested adaptive protection at lower doses but inhibition at higher concentrations. Histopathological examination indicated that higher fluorene concentrations caused cellular proliferation, inflammation, and severe tissue damage in the digestive tract and body wall. Molecular docking studies demonstrated robust interactions between fluorene and major stress biomarker enzymes, disrupting their functions and inducing oxidative stress. Interactions with cytochrome c oxidase suggested interference with cellular energy production. Generalized Read-Across (GenRA) analysis unveiled shared toxicity mechanisms among fluorene and its analogs, involving the formation of reactive epoxides and the influence of cytochrome P450 enzymes. The diverse functional groups of these analogs, particularly chlorine-containing compounds, were implicated in toxicity through lipid peroxidation and membrane damage. Adverse outcome pathways and broader consequences for aquatic ecosystem health are discussed.

Benzo(k)fluoranthene and benzo(b)fluoranthene degradation by Selenastrum capricornutum and identification of metabolites using HPLC-FD and HPLC-ESI-QqQ-MS/MS.

Selenastrum capricornutum efficiently degrades high molecular weight polycyclic aromatic hydrocarbons (HMW PAHs). Until now, there are few studies on the benzo(k)fluoranthene (BkF) and benzo(b)fluoranthene (BbF) biodegradation by this microalga. For this reason, in the present work, extracts obtained from cultures of S. capricornutum were incubated with BkF and BbF individually, and analyzed by HPLC with fluorescence and different mass spectrometry detection modes: i) the HPLC-ESI(+)-MS/MS (MRM mode) analysis that confirmed the formation of monohydroxylated and dihydrodiol metabolites indicating that these PAHs could be simultaneously degraded through the monooxygenase and dioxygenase; ii) HPLC-ESI(+)-MS (full scan mode) that showed the formation of key metabolites containing four and two aromatic rings possibly resulting from aromatic ring-opening oxygenases, not known until now in microalgae; iii) HPLC-FD analysis that confirmed the individual BkF and BbF degradation occurring in extra- and intra-cellular extracts, indicating that an oxygenase enzyme complex is released by microalgae cells to the external environment to perform HMW PAHs biodegradation. So, this work presents new insights into the metabolic pathways of BkF and BbF biodegradation by S. capricornutum; likewise, the intra- and extra-cellular extracts of this microalgae have great potential to be applied in environmental procedures.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) by microbial consortium from paddy rice soil.

Polycyclic aromatic hydrocarbons (PAHs) are among the most widely spread pollutants in the environment including the agricultural soil. PAH degradation by indigenous bacteria is an effective and economical means to remove these pollutants from the environment. Here, we report a bacterial consortium (Pdy-1) isolated from paddy rice soil in northern Japan able to degrade polycyclic aromatic hydrocarbons (PAHs) at high rates. Pdy-1 was incubated with a mixture of PAH compounds (fluorene, phenanthrene, and pyrene) in Bushnell Haas Medium at a final concentration of 100 mg/L each. PDY-1 degraded 100% of fluorene, 95% of phenanthrene, and 52% of pyrene in 5 days. Phenanthrene and pyrene were completely degraded at 10 d and 15 d, respectively. Cloning of the 16S rRNA gene revealed that the consortium was composed of 40% Achromobacter and 7% each of Castelaniella, Rhodanobacter, and Hypomicrobium. Comamonas, Ferrovibrio, Terrimonas, Bordetella, Rhizobium, and Pseudonocardia were also detected. PCR-DGGE showed the dynamics of the consortium during the incubation period. Real-time PCR revealed that PAH degrading genes such as the gram-positive ring dihydroxylating genes (PAH-RDH) and pyrene dioxygenase (nidA) were most abundant at day 5 when the rapid biodegradation of the PAHs was observed. This study improves our understanding on dynamics and characteristics of an effective PAH-degrading bacterial consortium from paddy rice soil.

lA multiple PAHs-degrading Shinella sp. strain and its potential bioremediation in wastewater.

Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic derivatives are organic pollutants which threaten ecosystems and human beings. In this study, a new strain, Shinella sp. FLN 14, was isolated and characterized. It can utilize fluorene as its sole carbon source and effectively co-metabolize multiple PAHs and heterocyclic derivatives, including phenanthrene, acenaphthene, and fluoranthene. Two possible metabolic pathways are proposed (i.e., salicylic acid pathway and phthalic acid pathway). Whole-genome sequencing revealed that strain FLN14 possesses a chromosome and four plasmids. However, when combined with ensemble genetic information, novel fluorene-degrading functional gene clusters were not located within the genome of FLN 14, except for some new dioxygenases and electron transport chains, which typically initiate the oxidation of aromatic compounds. In wastewater bioremediation, strain FLN14 removed nearly 95 % of PAHs within 5 days and maintained high degrading activity during the 18-day reaction compared to the control. Overall, our study provides a promising candidate to achieve bioremediation of PAHs-contaminated environments.

Ecotoxicological evaluation of oxidative stress-mediated neurotoxic effects, genetic toxicity, behavioral disorders, and the corresponding mechanisms induced by fluorene-contaminated soil targeted to earthworm (Eisenia fetida) brain.

Fluorene is a commonly identified PAH pollutant in soil and exhibits various worrisome hazardous effects to soil organisms. Currently, the toxicity profiles of fluorene on earthworm brain are rare, and the mechanisms and their corresponding pathways involved in fluorene-triggered neurotoxicity, genotoxicity, and behavior changes have not been reported hitherto. Herein, earthworm (Eisenia fetida) brain was chosen as targeted receptor to explore the neurotoxic effects, genetic toxicity, behavioral disorders, and related mechanisms caused by fluorene-induced oxidative stress pathways. The results showed excess fluorene initiated the release of excessive quantities of ROS in earthworm brain, which have caused oxidative stress and accompanied by serious oxidative effects, including LPO (lipid peroxidation) and DNA injury. To minimize the damage effects, the antioxidant defense mechanisms (antioxidant enzymes and non-enzymatic antioxidants) were activated, and entailed a decrease of the antioxidant capacity in E. fetida brain, which, in turn, causes further ROS-induced ROS release. Exposure of fluorene induced the abnormal mRNA expression of genes relevant to oxidative stress (e.g., GST, SOD, CAT, GPx, MT, and Hsp70) and neurotoxicity (e.g., H02, C04, D06, and E08) in E. fetida brain. Specifically, fluorene can bind directly to AChE, destroying the conformation of this protein, and even affecting its physiological functions. This occurrence caused the inhibition of AChE activity and excess ACh accumulation at the nicotinic post-synaptic membrane, finally triggering neurotoxicity by activation of pathways related to oxidative stress. Moreover, the avoidance responses and burrowing behavior were obviously disturbed by oxidative stress-induced neurotoxicity after exposure to fluorene. The results form IBR suggested more severe poisoning effects to E. fetida brain initiated by high-dose and long-term exposure of fluorene. Among, oxidative stress injury and genotoxic potential are more sensitive endpoint than others. Collectively, fluorene stress can provoke potential neurotoxicity, genotoxicity, and behavioral disturbances targeted to E. fetida brain through the ROS-mediated pathways involving oxidative stress. These findings are of great significance to estimate the detrimental effects of fluorene and the corresponding mechanisms on soil eco-safety.

Effects of polycyclic aromatic hydrocarbons on marine and freshwater microalgae - A review.

The first synthetic review of the PAHs effects on microalgae in experimental studies and aquatic ecosystems is provided. Phytoplankton and phytobenthos from marine and freshwaters show a wide range of sensitivities to PAHs, and can accumulate, transfer and degrade PAHs. Different toxicological endpoints including growth, chlorophyll a, in vivo fluorescence yield, membrane integrity, lipid content, anti-oxidant responses and gene expression are reported for both freshwater and marine microalgal species exposed to PAHs in culture and in natural assemblages. Photosynthesis, the key process carried out by microalgae appears to be the most impacted by PAH exposure. The effect of PAHs is both dose- and species-dependent and influenced by environmental factors such as UV radiation, temperature, and salinity. Under natural conditions, PAHs are typically present in mixtures and the toxic effects induced by single PAHs are not necessarily extrapolated to mixtures. Natural microalgal communities appear more sensitive to PAH contamination than microalgae in monospecific culture. To further refine the ecological risks linked to PAH exposure, species-sensitivity distributions (SSD) were analyzed based on published EC50s (half-maximal effective concentrations during exposure). HC5 (harmful concentration for 5% of the species assessed) was derived from SSD to provide a toxicity ranking for each of nine PAHs. The most water-soluble PAHs naphthalene (HC5 = 650 µg/L), acenaphthene (HC5 = 274 µg/L), and fluorene (HC5 = 76.8 µg/L) are the least toxic to microalgae, whereas benzo[a]pyrene (HC5 = 0.834 µg/L) appeared as the more toxic. No relationship between EC50 and cell biovolume was established, which does not support assumptions that larger microalgal cells are less sensitive to PAHs, and calls for further experimental evidence. The global PAHs HC5 for marine species was on average higher than for freshwater species (26.3 and 1.09 µg/L, respectively), suggesting a greater tolerance of marine phytoplankton towards PAHs. Nevertheless, an important number of experimental exposure concentrations and reported toxicity thresholds are above known PAHs solubility in water. The precise and accurate assessment of PAHs toxicity to microalgae will continue to benefit from more rigorously designed experimental studies, including control of exposure duration and biometric data on test microalgae.

Biodegradation kinetics and metabolism of Benzo(a)fluorene by Pseudomonas strains isolated from refinery effluent.

The final sinkers of polyaromatic hydrocarbons are water sources, where they undergo bioaccumulation and biomagnification, leading to adverse mutagenic, carcinogenic, and teratogenic effects on exposure in flora, fauna, and humans. Two indigenous strains, Pseudomonas sp. WDE11 and Pseudomonas sp. WD23, isolated from refinery effluent, degraded over 97.5% of benzo(a)fluorene (10 mg/L) in 7 days. On growth at concentration dependent amounts (50 mg/L and 100 mg/L), the degradation reduced to approximately 90% and 80% respectively in 56 days. Degradation kinetics was concentration dependent, as degradation followed first-order and second-order kinetics for 50 mg/L and 100 mg/L respectively. The half-life for degradation of benzo(a)fluorene ranged between 11.64 - 12.26 days and 13.11-14.5 days for strains WDE11 and WD23 respectively. The values of Andrew-Haldane kinetic parameters i.e. µmax, Ks, and Ki were 0.306 day-1, 11.11 mg/L, and 120.41 mg/L for strain WDE11 respectively, while for strain WD23, the respective values were 0.312 day-1, 9.97 mg/L, and 152 mg/L. Degradation metabolites were identified by their MS patterns as 3,4-dihydroxy fluorene, 2-(1-oxo-2,3-dihydro-1H-inden-2-yl) acetic acid, 3,4-dihydrocoumarin, salicylic acid, catechol, and oxalic acid. Metabolic pathway of degradation constructed, revealed that benzo(a)fluorene was metabolized via the formation of fluorene, further metabolized by salicylate pathway forming catechol. The catechol formed was degraded into simpler metabolites by meta-cleavage pathway, which was validated by catechol 2,3 dioxygenase enzyme activity.

Evaluation of fluorene-caused ecotoxicological responses and the mechanism underlying its toxicity in Eisenia fetida: Multi-level analysis of biological organization.

Fluorene is an important toxic chemical that exists ubiquitously in the environment, and it has also been suggested to exert potential deleterious effects on soil invertebrates. However, knowledge about the toxic effects of fluorene and its underlying mechanisms of the effects on key soil organism earthworms remains limited. From this view point, this study was undertaken to explore the potential effects of fluorene and its underlying mechanisms in Eisenia fetida at the level of experimental animals, tissue, cell, and molecule. It was concluded that fluorene exerted lethal activity to adult E. fetida on day 14 with the LC50 determined to be 88.61 mg/kg. Fluorene-induced ROS caused oxidative stress in E. fetida, resulting in DNA damage, protein carbonylation, and lipid peroxidation. Moreover, changed antioxidative enzymatic activities, non-enzymatic antioxidative activities, and total antioxidative capacity in E. fetida by fluorene stress are associated with antioxidative and protective effects. High-dose fluorene (> 2.5 mg/kg) exposure significantly caused histopathological lesions including the microstructure of body wall, intestine, and seminal vesicle of earthworms. Also, the reproductive system of E. fetida was clearly disrupted by fluorene stress, leading to poor reproduction ability (decreased cocoon and juvenile production) in earthworms. It is found that E. fetida growth was significantly inhibited when treated with high-dose fluorene, thereby causing normal growth disorders. Additionally, fluorene stress triggered the abnormal mRNA expression related to oxidative stress (e.g., metallothionein and heat shock protein 70), growth (translationally controlled tumour protein), reproduction (annetocin precursor) in E. fetida. Together, both high-dose and long-term exposure elicited more severe poisoning effects on earthworms using the Integrated Biological Response (IBR) index, and E. fetida coelomocyte DNA was the most negatively affected by fluorene stress. This study comprehensively evaluated fluorene-induced toxicity in E. fetida, and its underlying molecular mechanisms mediating the toxic responses have been elucidated. These findings provide valuable data for assessing potential ecological risks posed by fluorene-contaminated soil.

Binding interaction of a ring-hydroxylating dioxygenase with fluoranthene in Pseudomonas aeruginosa DN1.

Pseudomonas aeruginosa DN1 can efficiently utilize fluoranthene as its sole carbon source, and the initial reaction in the biodegradation process is catalyzed by a ring-hydroxylating dioxygenase (RHD). To clarify the binding interaction of RHD with fluoranthene in the strain DN1, the genes encoding alpha subunit (RS30940) and beta subunit (RS05115) of RHD were functionally characterized through multi-technique combination such as gene knockout and homology modeling as well as molecular docking analysis. The results showed that the mutants lacking the characteristic alpha subunit and/or beta subunit failed to degrade fluoranthene effectively. Based on the translated protein sequence and Ramachandran plot, 96.5% of the primary amino-acid sequences of the alpha subunit in the modeled structure of the RHD were in the permitted region, 2.3% in the allowed region, but 1.2% in the disallowed area. The catalytic mechanism mediated by key residues was proposed by the simulations of molecular docking, wherein the active site of alpha subunit constituted a triangle structure of the mononuclear iron atom and the two oxygen atoms coupled with the predicted catalytic ternary of His217-His222-Asp372 for the dihydroxylation reaction with fluoranthene. Those amino acid residues adjacent to fluoranthene were nonpolar groups, and the C7-C8 positions on the fluoranthene ring were estimated to be the best oxidation sites. The distance of C7-O and C8-O was 3.77 Å and 3.04 Å respectively, and both of them were parallel. The results of synchronous fluorescence and site-directed mutagenesis confirmed the roles of the predicted residues during catalysis. This binding interaction could enhance our understanding of the catalytic mechanism of RHDs and provide a solid foundation for further enzymatic modification.

Prospective Drug Candidates as Human Multidrug Transporter ABCG2 Inhibitors: an In Silico Drug Discovery Study.

Breast cancer resistance protein (ABCG2) is a human ATP-binding cassette (ABC) that plays a paramount role in multidrug resistance (MDR) in cancer therapy. The discovery of ABCG2 inhibitors could assist in designing unprecedented therapeutic strategies for cancer treatment. There is as yet no approved drug targeting ABCG2, although a large number of drug candidates have been clinically investigated. In this work, binding affinities of 181 drug candidates in clinical-trial or investigational stages as ABCG2 inhibitors were inspected using in silico techniques. Based on available experimental data, the performance of AutoDock4.2.6 software was first validated to predict the inhibitor-ABCG2 binding mode and affinity. Combined molecular docking calculations and molecular dynamics (MD) simulations, followed by molecular mechanics-generalized Born surface area (MM-GBSA) binding energy calculations, were then performed to filter out the studied drug candidates. From the estimated docking scores and MM-GBSA binding energies, six auspicious drug candidates-namely, pibrentasvir, venetoclax, ledipasvir, avatrombopag, cobicistat, and revefenacin-exhibited auspicious binding energies with value < -70.0 kcal/mol. Interestingly, pibrentasvir, venetoclax, and ledipasvir were observed to show even higher binding affinities with the ABCG2 transporter with binding energies of < -80.0 kcal/mol over long MD simulations of 100 ns. The stabilities of these three promising candidates in complex with ABCG2 transporter were demonstrated by their energetics and structural analyses throughout the 100 ns MD simulations. The current study throws new light on pibrentasvir, venetoclax, and ledipasvir as curative options for multidrug resistant cancers by inhibiting ABCG2 transporter.

Further lead optimization on Bax activators: Design, synthesis and pharmacological evaluation of 2-fluoro-fluorene derivatives for the treatment of breast cancer.

To further pursue potent Bax activators with better safety profiles for the treatment of breast cancer, structural optimization was conducted based on lead compound CYD-4-61 through several strategies, including scaffold hopping on the 2-nitro-fluorene ring, replacement of the nitro group with bioisosteres to avoid potential toxicity, and further optimization on the upper pyridine by exploring diverse alkylamine linkers as a tail or replacing the pyridine with bioisosteric heterocycles. F-containing compound 22d (GL0388) exhibited a good balance between the activity and toxicity, displaying submicromolar activities against a variety of cancer cell lines with 5.8-10.7-fold selectivity of decreased activity to MCF-10A human mammary epithelial cell line. Compound 22d dose-dependently blocked colony formation of breast cancer cells and prevented the migration and invasion of MDA-MB-231 cells. Mechanism of action studies indicate that 22d activated Bax, rendering its insertion into mitochondrial membrane, thereby leading to cytochrome c release from the mitochondria into the cytoplasm, subsequently inducing release of apoptotic biomarkers. Further in vivo efficacy studies of 22d in human breast cancer xenografts arisen from MDA-MB-231 cells demonstrated that this drug candidate significantly suppressed tumor growth, indicating the therapeutic promise of this class of compounds for the treatment of breast cancer as well as the potential for developing F-radiolabeled imaging ligands as anticancer chemical probes.

Biodegradation of fluorene by the newly isolated marine-derived fungus, Mucor irregularis strain bpo1 using response surface methodology.

Fluorene, a low molecular weight polycyclic aromatic hydrocarbon (PAH), is of immense environmental interest because of its carcinogenicity, teratogenicity, mutagenicity, toxicity and persistence to microbial degradation. Existentially, there is paucity of information on PAH degradation by fungi isolated from marine environment. Therefore, this study investigated fluorene degradation efficiency of marine derived filamentous fungus, Mucor irregularis strain bpo1 (GenBank Accession Number: MK373020). Response Surface Methodology (RSM) using Box-Behnken Design (BBD) was successfully deployed in the optimization of process parameters (pH-7, temperature-32.5 °C, substrate concentration-100 mg L-1 and dry weight-2 g) resulting in 81.50% fluorene degradation on 5th day. The design and regression model were found to be statistically significant, adequate and appropriate with p < 0.0001, F value= 202.39, and predicted coefficient of determination (R2 =0.9991). Optimization of the vital constituents of the mineral salt medium (MSM) used for the study using RSM-Central Composite Design (CCD) resulted in 79.80% fluorene degradation rate. Enhanced fluorene degradation efficiency (82.50%) was recorded when the optimized process variables were subjected to growth-linked validation experiments. The enzyme activities revealed 87%, 59% and 31% induction of laccase, manganese peroxidase and lignin peroxidase respectively. Four metabolites; 9H-fluoren-9-one, benzene-1,2-dicarboxylic acid, 2-hydroxybenzoic acid and phenol obtained after the experiment were characterized and confirmed with GC-MS analysis. The findings revealed the promising potentials of M. irregularis in PAH degradation and by extension green remediation technology.

Investigation of biosurfactants produced by three indigenous bacterial strains, their growth kinetics and their anthracene and fluorene tolerance.

The study explored the polycyclic aromatic hydrocarbon tolerance of indigenous biosurfactant producing microorganisms. Three bacterial species were isolated from crude oil contaminated sites of Haldia, West Bengal. The three species were screened for biosurfactant production and identified by 16S rRNA sequencing as Brevundimonas sp. IITISM 11, Pseudomonas sp. IITISM 19 and Pseudomonas sp. IITISM 24. The strains showed emulsification activities of 51%, 57% and 63%, respectively. The purified biosurfactants were characterised using FT-IR, GC-MS and NMR spectroscopy and found to have structural similarities to glycolipopeptides, cyclic lipopeptides and glycolipids. The biosurfactants produced were found to be stable under a wide range of temperature (0-100 °C), pH (4-12) and salinity (up to 20% NaCl). Moreover, the strains displayed tolerance to high concentrations (275 mg/L) of anthracene and fluorene and showed a good amount of cell surface hydrophobicity with different hydrocarbons. The study reports the production and characterisation of biosurfactant by Brevundimonas sp. for the first time. Additionally, the kinetic parameters of the bacterial strains grown on up to 300 mg/L concentration of anthracene and fluorene, ranged between 0.0131 and 0.0156 µmax (h-1), while the Ks(mg/L) ranged between 59.28 and 102.66 for Monod's Model. For Haldane-Andrew's model, µmax (h-1) varied between 0.0168 and 0.0198. The inhibition constant was highest for Pseudomonas sp. IITISM 19 on anthracene and Brevundimonas sp. IITISM 11 on fluorene. The findings of the study suggest that indigenous biosurfactant producing strains have tolerance to high PAH concentrations and can be exploited for bioremediation purposes.

Discovery of Pamiparib (BGB-290), a Potent and Selective Poly (ADP-ribose) Polymerase (PARP) Inhibitor in Clinical Development.

Poly (ADP-ribose) polymerase (PARP) plays a significant role in DNA repair responses; therefore, this enzyme is targeted by PARP inhibitors in cancer therapy. Here we have developed a number of fused tetra- or pentacyclic dihydrodiazepinoindolone derivatives with excellent PARP enzymatic and cellular PARylation inhibition activities. These efforts led to the identification of pamiparib (BGB-290, 139), which displays excellent PARP-1 and PARP-2 inhibition with IC50 of 1.3 and 0.9 nM, respectively. In a cellular PARylation assay, this compound inhibits PARP activity with IC50 = 0.2 nM. Cocrystal of pamiparib shows similar binding sites with PARP with other PARP inhibitors, but pamiparib is not a P-gp substrate and shows excellent drug metabolism and pharmacokinetics (DMPK) properties with significant brain penetration (17-19%, mice). The compound is currently being investigated in phase III clinical trials as a maintenance therapy in platinum-sensitive ovarian cancer and gastric cancer.

New Fluorene Derivatives from Dendrobium gibsonii and Their α-Glucosidase Inhibitory Activity.

Two new compounds, dihydrodengibsinin (1) and dendrogibsol (2), were isolated from the whole plant of Dendrobium gibsonii, together with seven known compounds (3-9). The structures of the new compounds were elucidated by their spectroscopic data. All these isolates were evaluated for their α-glucosidase inhibitory activities. Dendrogibsol (2) and lusianthridin (7) showed strong α-glucosidase inhibitory activity when compared with acarbose. An enzyme kinetic study revealed that dendrogibsol (2) is a noncompetitive inhibitor of α-glucosidase.

Acute toxicities of fluorene, fluorene-1-carboxylic acid, and fluorene-9-carboxylic acid on zebrafish embryos (Danio rerio): Molecular mechanisms of developmental toxicities of fluorene-1-carboxylic acid.

In this study, fluorene (FL), FL-1-carboxylic acid (FC-1), and FL-9-carboxylic acid (FC-9) were investigated to understand their acute toxicity by measuring inhibitory effects on hatching rates and developmental processes of zebrafish embryos (Danio rerio). For exposure concentrations up to 3000 µg/L, FC-1 alone showed acute toxicity at 1458 µg/L for LC50 value. FC-1 caused yolk sac and spinal deformities, and pericardial edema. Molecular studies were undertaken to understand FC-1 toxicity examining 61 genes after exposure to 5 µM (equivalent to LC20 value of FC-1) in embryos. In the FC-1-treated embryos, the expression of the cyp7a1 gene, involved in bile acid biosynthesis, was dramatically decreased, while the expression of the Il-1ß gene involved in inflammation was remarkably increased. In addition to these findings, in FC-1-treated embryos, the expression of nppa gene related to the differentiation of the myocardium was 3-fold increased. On the other hand, cyp1a, cyp3a, ugt1a1, abcc4, mdr1, and sult1st1 responsible for detoxification of xenobiotics were upregulated in FC-9-treated embryos. Taken together, carboxylation on carbon 1 of FL increased acute toxicity in zebrafish embryos, and its toxicity might be related to morphological changes with modification of normal biological functions and lowered defense ability.

Differential responses in the biotransformation systems of the oyster Crassostrea gigas (Thunberg, 1789) elicited by pyrene and fluorene: Molecular, biochemical and histological approach - Part II.

Pyrene (PYR) and fluorene (FLU) are among the sixteen priority Polycyclic Aromatic Hydrocarbons (PAH) of the United States Environmental Protection Agency and are both frequently detected in contaminated sites. Due to the importance of bivalve mollusks in biomonitoring programs and the scarce information on the biotransformation system in these organisms, the aim of this study was to investigate the effect of PYR and FLU at the transcriptional level and the enzymatic activities of some biotransformation systems in the Pacific oyster Crassostrea gigas, and to evaluate the histological effects in their soft tissues. Oysters C. gigas were exposed for 24 h and 96 h to PYR (0.25 and 0.5 µM) and FLU (0.6 and 1.2 µM). After exposure, transcript levels of cytochrome P450 coding genes (CYP1-like, CYP2-like, CYP2AU2, CYP356A1, CYP17α-like), glutathione S tranferase genes (omega GSTO-like and microsomal, MGST-like) and sulfotransferase gene (SULT-like), and the activity of ethoxyresorufin O-deethylase (EROD), Glutathione S-transferase (GST) and microssomal GST (MGST) were evaluated in gills. Histologic changes were also evaluated after the exposure period. PYR and FLU bioconcentrated in oyster soft tissues. The half-life time of PYR in water was lower than fluorene, which is in accordance to the higher lipophilicity and bioconcentration of the former. EROD activity was below the limit of detection in all oysters exposed for 96 h to PYR and FLU. The reproductive stage of the oysters exposed to PYR was post-spawn. Exposure to PYR caused tubular atrophy in digestive diverticula, but had no effect on transcript levels of biotransformation genes. However, the organisms exposed for 96 h to PYR 0.5 µM showed higher MGST activity, suggesting a protective role against oxidative stress in gills of oysters under higher levels of PYR in the tissues. Increased number of mucous cells in mantle were observed in oysters exposed to the higher FLU concentration, suggesting a defense mechanisms. Oysters exposed for 24 h to FLU 1.2 µM were in the ripe stage of gonadal development and showed higher transcript levels of CYP2AU2, GSTO-like and SULT-like genes, suggesting a role in the FLU biotransformation. In addition, after 96 h of exposure to FLU there was a significant increase of mucous cells in the mantle of oysters but no effect was observed on the EROD, total GST and MGST activities. These results suggest that PAH have different effects on transcript levels of biotransformation genes and enzyme activities, however these differences could also be related to the reproductive stage.

Fluorene exposure among PAH-exposed workers is associated with epigenetic markers related to lung cancer.

OBJECTIVES: Exposure to high-molecular-weight polycyclic aromatic hydrocarbons (PAHs) may cause cancer in chimney sweeps and creosote-exposed workers, however, knowledge about exposure to low-molecular-weight PAHs in relation to cancer risk is limited. In this study, we aimed to investigate occupational exposure to the low-molecular-weight PAHs phenanthrene and fluorene in relation to different cancer biomarkers. METHODS: We recruited 151 chimney sweeps, 19 creosote-exposed workers and 152 unexposed workers (controls), all men. We measured monohydroxylated metabolites of phenanthrene and fluorene in urine using liquid chromatography coupled to tandem mass spectrometry. We measured, in peripheral blood, the cancer biomarkers telomere length and mitochondrial DNA copy number using quantitative PCR; and DNA methylation of F2RL3 and AHRR using pyrosequencing. RESULTS: Median PAH metabolite concentrations were higher among chimney sweeps (up to 3 times) and creosote-exposed workers (up to 353 times), compared with controls (p<0.001; adjusted for age and smoking). ∑OH-fluorene (sum of 2-hydroxyfluorene and 3-hydroxyfluorene) showed inverse associations with percentage DNA methylation of F2RL3 and AHRR in chimney sweeps (B (95% CI)=-2.7 (-3.9 to -1.5) for F2RL3_cg03636183, and -7.1 (-9.6 to -4.7) for AHRR_cg05575921: adjusted for age and smoking), but not in creosote-exposed workers. In addition, ∑OH-fluorene showed a 42% mediation effect on the inverse association between being a chimney sweep and DNA methylation of AHRR CpG2. CONCLUSIONS: Chimney sweeps and creosote-exposed workers were occupationally exposed to low-molecular-weight PAHs. Increasing fluorene exposure, among chimney sweeps, was associated with lower DNA methylation of F2RL3 and AHRR, markers for increased lung cancer risk. These findings warrant further investigation of fluorene exposure and toxicity.

Understand the Specific Regio- and Enantioselectivity of Fluostatin Conjugation in the Post-Biosynthesis.

Fluostatins, benzofluorene-containing aromatic polyketides in the atypical angucycline family, conjugate into dimeric and even trimeric compounds in the post-biosynthesis. The formation of the C-C bond involves a non-enzymatic stereospecific coupling reaction. In this work, the unusual regio- and enantioselectivities were rationalized by density functional theory calculations with the M06-2X (SMD, water)/6-311 + G(d,p)//6-31G(d) method. These DFT calculations reproduce the lowest energy C1-(R)-C10'-(S) coupling pathway observed in a nonenzymatic reaction. Bonding of the reactive carbon atoms (C1 and C10') of the two reactant molecules maximizes the HOMO-LUMO interactions and Fukui function involving the highest occupied molecular orbital (HOMO) of nucleophile p-QM and lowest unoccupied molecular orbital (LUMO) of electrophile FST2- anion. In particular, the significant π-π stacking interactions of the low-energy pre-reaction state are retained in the lowest energy pathway for C-C coupling. The distortion/interaction-activation strain analysis indicates that the transition state (TScp-I) of the lowest energy pathway involves the highest stabilizing interactions and small distortion among all possible C-C coupling reactions. One of the two chiral centers generated in this step is lost upon aromatization of the phenol ring in the final difluostatin products. Thus, the π-π stacking interactions between the fluostatin 6-5-6 aromatic ring system play a critical role in the stereoselectivity of the nonenzymatic fluostatin conjugation.