Comparative toxic potency ranking of chlorophenols

Tourmaline guiding the electric field and dechlorination pathway of 2,3-dichlorophenol by Desulfitobacterium hafniense

The dehalogenation of organohalides has been a research hotspot in bioremediation field; however, the influence of tourmaline, a natural ore that can generate spontaneous electric field, on organohalide-respiring bacteria (OHRB) and their dechlorination process is not well known. In this study, the effect and mechanism of tourmaline on the reductive dechlorination of 2,3-dichlorophenol (2,3-DCP) by Desulfitobacterium hafniense DCB-2T were explored. The characterization results confirmed that tourmaline had good stability and the optimal dosage of tourmaline was 2.5 g/L, which shortened the total time required for dechlorination reaction to 72 hr. Besides, tourmaline amendment also increased the proportion of 2-chlorophenol (2-CP) from 18% to 30% of end products, while that of 3-CP decreased correspondingly. The theoretical calculations showed that the bond charge of the ortho-substituted chlorine declined from -0.179 to -0.067, and that of meta-substituted chlorine increased from -0.111 to -0.129, which indicated that the spontaneous electric field of tourmaline affected the charge distribution of 2,3-DCP and was more conducive to the generation of 2-CP. Overall, tourmaline with the spontaneous electric field affected the reductive dechlorination pathway of Desulfitobacterium,and the tourmaline-OHRB combining system might serve as a novel strategy for the bioremediation of environments polluted with chlorinated phenols.

Unprecedented enantio-selective live-cell mitochondrial DNA super-resolution imaging and photo-sensitizing by the chiral ruthenium polypyridyl DNA "light-switch"

Mitochondrial DNA (mtDNA) is known to play a critical role in cellular functions. However, the fluorescent probe enantio-selectively targeting live-cell mtDNA is rare. We recently found that the well-known DNA 'light-switch' [Ru(phen)2dppz]Cl2 can image nuclear DNA in live-cells with chlorophenolic counter-anions via forming lipophilic ion-pairing complex. Interestingly, after washing with fresh-medium, [Ru(phen)2dppz]Cl2 was found to re-localize from nucleus to mitochondria via ABC transporter proteins. Intriguingly, the two enantiomers of [Ru(phen)2dppz]Cl2 were found to bind enantio-selectively with mtDNA in live-cells not only by super-resolution optical microscopy techniques (SIM, STED), but also by biochemical methods (mitochondrial membrane staining with Tomo20-dronpa). Using [Ru(phen)2dppz]Cl2 as the new mtDNA probe, we further found that each mitochondrion containing 1-8 mtDNA molecules are distributed throughout the entire mitochondrial matrix, and there are more nucleoids near nucleus. More interestingly, we found enantio-selective apoptotic cell death was induced by the two enantiomers by prolonged visible light irradiation, and in-situ self-monitoring apoptosis process can be achieved by using the unique 'photo-triggered nuclear translocation' property of the Ru complex. This is the first report on enantio-selective targeting and super-resolution imaging of live-cell mtDNA by a chiral Ru complex via formation and dissociation of ion-pairing complex with suitable counter-anions.

Miniaturized ternary deep eutectic solvent-based matrix solid-phase dispersion: A green sample preparation method for the determination of chlorophenols in river sediment

New ternary deep eutectic solvents were prepared and applied as efficient green dispersing solvents in miniaturized matrix solid-phase dispersion to extract chlorophenols from river sediments for the first time. High-performance liquid chromatography coupled with a photodiode array detector was used to analyze the target analytes. The significant factors affecting the extraction were optimized as follows: dispersant (100 mg), sample (100 mg), ternary eutectic solvents (150 μl), grinding for 1 min, 450 μl of acetonitrile as the elution solvent, and vortex mixing for 20 s. Under the optimal conditions, the method exhibited excellent linearity (correlation coefficient > 0.9980), low limits of detection between 1.039-2.478 μg/g, and extraction recoveries between 93.9% and 99.2%. Furthermore, the method demonstrated excellent precision in the intra- and inter-day analysis with a relative standard deviation below 6%. When compared to conventional extraction techniques, the miniaturized matrix solid-phase dispersion considerably reduced samples and solvent usag, offering important environmental benefits. The green profile of the method was assessed using the complementary green analytical procedure index tool confirming its eco-friendship. The technique was finally employed to evaluate sediment samples from three distinct locations along the Zuibaiji River, indicating its applicability for monitoring environmental samples.

Detection of cellular metabolites by redox enzymatic cascades

Detection of cellular metabolites that are disease biomarkers is important for human healthcare monitoring and assessing prognosis and therapeutic response. Accurate and rapid detection of microbial metabolites and pathway intermediates is also crucial for the process optimization required for development of bioconversion methods using metabolically engineered cells. Various redox enzymes can generate electrons that can be employed in enzyme-based biosensors and in the detection of cellular metabolites. These reactions can directly transform target compounds into various readout signals. By incorporating engineered enzymes into enzymatic cascades, the readout signals can be improved in terms of accuracy and sensitivity. This review critically discusses selected redox enzymatic and chemoenzymatic cascades currently employed for detection of human- and microbe-related cellular metabolites including, amino acids, d-glucose, inorganic ions (pyrophosphate, phosphate, and sulfate), nitro- and halogenated phenols, NAD(P)H, fatty acids, fatty aldehyde, alkane, short chain acids, and cellular metabolites.

Determination of environmental properties and toxicity of octyl-dimethyl-para-aminobenzoic acid and its degradation products

Octyl-dimethyl-para-aminobenzoic acid (ODPABA) is one of compounds of emerging concern. It undergoes transformations under the influence of oxidizing or chlorinating agents and UV radiation forming products with different properties. There is very little experimental data concerning the environmental fate of ODPABA and its transformation products. Therefore, the purpose of the studies was to determine environmental parameters: water solubility, soil - water partition coefficient, octanol - air partition coefficient, bioconcentration factor as well as half-life in air, water and soil. Based on the results obtained, the persistence and migration possibilities of ODPABA and its transformation products in the aquatic environment were estimated. Moreover, the ecological toxicity of oxidation and chlorination products was investigated. Microtox®, Daphtoxkit F® and Artoxkit M® tests were used to determine toxicity. LC₅₀ for Fish and Daphnia magna was calculated by Ecosar module. Studies have shown that as a result of ODPABA transformations, chloroorganic products are formed, which are lipophilic, are bioconcentrated in organic matter, are characterized by significant environmental persistence, can spread over considerable distances and are toxic. Oxidation products have significantly smaller impact on the environment. They are characterized by higher water solubility, lower bioconcentration factor and are less toxic.

Bioaccumulation and biochemical effects of ethylhexyl methoxy cinnamate and its main transformation products in zebrafish

The purpose of this study was to investigate the bioaccumulation and biochemical responses exposed to one of the main organic ultraviolet (UV) pollutants in the environment, ethylhexyl methoxy cinnamate (EHMC), and its main transformation product, either alone or in combination in zebrafish (Danio rerio). Four-month-old zebrafish were exposed to EHMC (34.4, 344 nmol/L) solution for 14 days, the species and contents of EHMC transformation products in zebrafish were determined and 3,5-dichloro-2-hydroxyacetophenone (3,5DCl₂HAcP) was the one with the highest concentration in transformation products. Then, zebrafish were exposed to EHMC, 3,5DCl₂HAcP alone and mixed solution for 21 days. At 7, 14 and 21 d, the related indexes of antioxidant defense system were determined. Results showed that both EHMC and 3,5DCl₂HAcP can lead to the increase of malondialdehyde (MDA) and glutathione (GSH) contents, superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) activities in visceral mass compared with the corresponding control group, thus produced oxidative stress effect in organism and 3,5DCl₂HAcP even showed stronger oxidative stress than EHMC. The effects of the two lower concentration co-exposure groups were similar and more significant to that of single exposure groups, while excessive oxidative stress occurred at the highest co-exposure group indicated by the decrease of GSH content, SOD, CAT, GR activities and the continued increase of MDA content. At 21 d, estradiol (E₂), vitellogenin (Vtg) and testosterone (T) contents, estrogen receptor (Esr), progesterone receptor (Pgr), androgen receptor (Ar), Vtg1, P450 aromatase (Cyp19a1) and 17β-hydroxysteroid dehydrogenase (Hsd17b3) expression were all significantly increased when exposed to 3,5DCl₂HAcP alone, showing complex estrogen and androgen effects. When exposed to EHMC alone, E₂ and Vtg contents, Esr, Pgr, Vtg1, Cyp19a1 and Hsd17b1 gene expression levels decreased significantly, and T content and Ar and Hsd17b3 expression increased significantly, indicated that EHMC can produce anti-estrogen and androgen effect. Last, the decrease of estrogen effect and increase of androgen effect in co-exposure group suggested that 3,5DCl₂HAcP might weaken the estrogen effect and promote the androgen effect of EHMC.

Estimation of physicochemical properties of 2-ethylhexyl-4-methoxycinnamate (EHMC) degradation products and their toxicological evaluation

The organic UV filters, commonly used in personal protection products, are of concern because of their potential risk to aquatic ecosystems and living organisms. One of UV filters is ethylhexyl-4-methoxycinnamate (EHMC) acid. Studies have shown that, in the presence of oxidizing and chlorinating factors, EHMC forms a series of products with different properties than the substrate. In this study, the toxicities of EHMC and its transformation/degradation products formed under the influence of NaOCl/UV and H₂O₂/UV systems in the water medium were tested using Microtox® bioassay and by observation of mortality of juvenile crustaceans Daphnia magna and Artemia Salina. We have observed that oxidation and chlorination products of EHMC show significantly higher toxicity than EHMC alone. The toxicity of chemicals is related to their physicochemical characteristic such as lipophilicity and substituent groups. With the increase in lipophilicity of products, expressed as log K_OW, the toxicity (EC₅₀) increases. On the basis of physicochemical properties such as vapour pressure (VP), solubility (S), octanol-water partition coefficient (K_OW), bioconcentration factor (BCF) and half-lives, the overall persistence (P_OV) and long-range transport potential (LRTP) of all the products and EHMC were calculated. It was shown that the most persistent and traveling on the long distances in environment are methoxyphenol chloroderivatives, then methoxybenzene chloroderivatives, EHMC chloroderivatives, methoxybenzaldehyde chloroderivatives and methoxycinnamate acid chloroderivatives. These compounds are also characterised by high toxicity.

The toxic effects of chlorophenols and associated mechanisms in fish

Chlorophenols (CPs) are ubiquitous contaminants in the environment primarily released from agricultural and industrial wastewater. These compounds are not readily degraded naturally, and easily accumulate in organs, tissues and cells via food chains, further leading to acute and chronic toxic effects on aquatic organisms. Herein, we review the available literature regarding CP toxicity in fish, with special emphasis on the potential toxic mechanisms. CPs cause oxidative stress via generation of reactive oxygen species, induction of lipid peroxidation and/or oxidative DNA damage along with inhibition of antioxidant systems. CPs affect immune system by altering the number of mature B cells and macrophages, while suppressing phagocytosis and down-regulating the expression of immune factors. CPs also disrupt endocrine function by affecting hormone levels, or inducing abnormal gene expression and interference with hormone receptors. CPs at relatively higher concentrations induce apoptosis via mitochondria-mediated pathway, cell death receptor-mediated pathway, and/or DNA damage-mediated pathway. CPs at relatively lower concentrations promote cell proliferation, and foster cancers-prone environment by increasing the rate of point mutations and oxidative DNA lesions. These toxic effects in fish are induced directly by CPs per se or indirectly by their metabolic products. In addition, recent studies on the alteration of DNA methylation by CPs through high-throughput DNA sequencing analysis provide new insights into our understanding of the epigenetic mechanisms underlying CPs toxicity.

Nucleotide prodrugs for HCV therapy

HCV infection is a significant worldwide health problem and is a major cause of hepatocellular carcinoma. The current standard of care, interferon and ribavirin, is only effective against a proportion of the patient population infected with HCV. To address the shortcomings of existing therapy, the development of direct acting antiviral agents is under investigation. The HCV RNA dependent RNA polymerase is an essential enzyme for viral replication and is therefore a logical target against which to develop novel anti-HCV agents. Nucleosides have been shown to be effective as antiviral agents for other viral diseases and therefore, have been investigated as inhibitors of HCV replication. The development of prodrugs of nucleoside 5'-monophosphates has been pursued to address limitations associated with poor nucleoside phosphorylation. This is required to produce the nucleoside 5'-triphosphate which is the anabolite that is the actual inhibitor of the polymerase enzyme. Prodrugs of nucleoside 5'-monophosphates have been developed that enable their delivery into cells and in vivo into the liver. The implementation of these prodrug strategies has ultimately led to the identification of several prodrugs of nucleoside 5'-monophosphates that are potent inhibitors of HCV replication in vitro. They have progressed into the clinic and the early data demonstrate greatly reduced viral load levels in HCV-infected patients. This review will survey the state of nucleotide prodrugs for the treatment of HCV.

Cancer and occupational exposure to pentachlorophenol and tetrachlorophenol (Canada)

OBJECTIVE

The objective of this study is to assess the carcinogenicity of pentachlorophenol and tetrachlorophenol using data from the BC sawmill workers cohort study.

METHODS

The cohort consisted of 27,464 men employed by 14 sawmills for 1 year or more between 1950 and 1995. Fatal (1950-1995) and incident (1969-1995) cancers were identified using national registries. Plant records and systematic interviews with senior employees were used to estimate dermal exposure. Comparisons were made with the general BC population and dose-response relationships were assessed using Poisson regression.

RESULTS

There were 1,495 fatal cancer and 2,571 incident cancers. There were no large or statistically significant excesses of any of the specific cancers were observed compared to the general population. Internal analyses showed strong dose-response relationships for non-Hodgkin's lymphoma, multiple myeloma, and kidney cancer. These relationships were strongest when exposure was restricted to pentachlorophenol. The strength of the dose-response increased when exposure was lagged by 20 years.

CONCLUSIONS

Dermal exposure to pentachlorophenol was associated with non-Hodgkin's lymphoma, multiple myeloma, and kidney cancer, but not with other cancers of a priori interest.