Validation of a suite of biomarkers of fish health in the tropical bioindicator species,tambaqui (Colossoma macropomum)

Here we explore the dose-dependent response of the tropical fish tambaqui (Colossoma macropomum) to intraperitoneal injection of benzo[a]pyrene (BaP) at doses of 0 (carrier control), 1, 10, 100 and 1000 μmolar BaP Kg⁻¹ Hepatic ethoxyresorufin-O-deethylase (EROD) activity showed a bell-shaped dose-dependent response curve, where the highest injected BaP dose caused enzyme inactivation. Activities of hepatic catalase (CAT) and superoxide dismutase (SOD) increased at the highest dose relative to the carrier control group. Lipid peroxidation (LPO), serum-sorbitol dehydrogenase (s-SDH) and DNA damage in blood cells were higher for all BaP doses when compared to the carrier control group. At high dosage, the production of BaP metabolites was paralleled by induced activity of the antioxidant enzyme SOD, and high levels of DNA damage in blood cells. In a similar way, high LPO was concomitant to elevated s-SDH in the bloodstream, suggesting that lipid peroxidation caused the loss of membrane integrity and leakage of s-SDH from hepatocytes into the bloodstream. These biomarkers were also positively co-correlated. The results demonstrate the potential use of a suite of biomarkers for tambaqui living in contaminated tropical aquatic environments. In particular, we recommend the analysis of DNA damage in blood cells, as this was highly correlated with all other biomarkers.     

Estimation of Toxicity Equivalency and Probabilistic Health Risk on Lifetime Daily Intake of Polycyclic Aromatic Hydrocarbons from Urban Residential Soils

In this study, toxicity equivalents and health risks, based on concentration of 16 priority polycyclic aromatic hydrocarbons (PAHs) in urban residential soils were estimated for the human population in Gwalior, India. Benzo(a)pyrene total potency equivalents (BaP TPE) were estimated for assessment of human health risk from direct contact with PAH-contaminated soil. Potential risk to contaminated groundwater from leaching of carcinogenic PAHs was assessed by estimating the index of additive cancer risk (IACR). On the basis of lifetime average daily intake of 16 PAHs through ingestion of PAH-contaminated soils, lifetime cancer risk to human adults and children was estimated. The concentration of probable human carcinogenic PAHs in soils accounted for 38% of ∑16PAHs. BaP TPE and index of additive cancer risk (IACR) were lower than guideline values of 0.6 mg kg^?1 and <1, respectively. Estimated lifetime average daily intakes of PAHs via soil ingestion were lower than recommended dose. However, the ILCR for human adults was within acceptable limits recommended by regulatory agencies, but may need action for children in Gwalior, India.     

Short androgen receptor poly‐glutamine‐promoted endometrial cancer is associated with benzo[a]pyrene‐mediated aryl hydrocarbon receptor activation

The androgen receptor (AR) poly‐glutamine polymorphism (AR‐Q) was reported to play role in endometrial cancer (EMCA) development, yet controversial. Environmental factors interact with genetic variation have been reported in EMCA. Aerosol toxins, polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP), are EMCA facilitators. This report examined the interplay between AR‐Qs and BaP in EMCA. During analysing patient AR‐Q polymorphism and Aryl hydrocarbon Receptor (AhR) expressions, we found overall survival (OS) benefit is ascending with AR‐Q lengths (5‐year OS of 61.3% in Q length <20 and 88% in Q length >23). And AhR is higher expressed in short AR‐Q tumour compared to that in long AR‐Q patient. In vitro study found androgen‐response element (ARE) activity descends with AR‐Qs length (Q13 > Q25 > Q35), whereas BaP suppresses ARE activities in EMCA cells. Furthermore, AR‐Q13 (but not AR‐Q25, or ‐35) enhances BaP‐induced dioxin‐responsive element (DRE) activity. Lastly, AR‐Q13 exerts higher colony‐forming capacity than other AR‐Qs, and knock‐down AhR abolished AR‐Q13‐mediated colony numbers. This study demonstrated a possible interaction of gene (AR‐Q polymorphism) and environmental toxins (e.g. BaP) to affect cancer progression. A large‐scale epidemiology and public health survey on the interaction of environmental toxin and AR poly‐Q in EMCA is suggested.     

Biochemical basis for the acquisition of resistance to benzo[a]pyrene in clones of mouse liver cells in culture

In a Namru mouse liver epithelial cell strain designated NMuLi, aryl hydrocarbon hydroxylase (AHH) activity peaked at 12 h post-induction with 1 μg/ml of benzo(a)pyrene (BaP) in both confluent and growing cells. Maximal levels of AHH activity were reached on day two post-plating. This induced activity was inhibited in vitro 78% by gassing the incubation mixture with carbon monoxide for 15 s, and inhibited 93% by addition of 40 μg/ml of 7,8 benzoflavone(BF).Induced AHH levels were higher in epithelial clones that were sensitive to the toxicity of BaP than in resistant clones. The survival fraction of clones from NMuLi and of subclones derived from a sensitive clone of NMuLi after BaP treatment was a negative exponential function of the maximal induced AHH activity in the clones.One of the clones, NMuLi cl 8, was extremely susceptible to the toxic effects of BaP, the ±(trans)-7α, 8β-dihydroxy-7,8-dihydro-BaP(7,8-diol), and the (±)-7α,8β-dihydroxy-9β,10β-epoxy-7,8,9,10-tetrahydro-BaP (diolepoxide), known metabolites of BaP. The toxicity of BaP and the 7,8 diol to this clone was inhibited by BF, suggesting that these cells possessed an enzyme activity inhibitable by BF that could epoxidize BaP to the 7,8 oxide and then epoxidize the resultant 7,8 diol to the diol-epoxide. Another clone derived from NMuLi, clone 7, was relatively resistant to the toxic effects of BaP and the 7,8-diol, but still extremely susceptible to the toxic effects of the diol-epoxide. The slight toxicity to BaP in this clone was inhibited by BF, but the toxicity of the 7,8-diol to this clone was not inhibited by BF. A typical cytochrome P450 inhibitor, metyrapone, had no effect on the toxicity of BaP, the 7,8-diol, or the diol-epoxide to either clone 7 or clone 8.The results suggest that these liver cells possess two enzymes that play some role in polycyclic hydrocarbon-induced toxicity. Enzyme A, a BaP-inducible enzyme that is inhibitable by BF, efficiently metabolizes BaP to the 7,8-diol and the 7,8-diol to the diol-epoxide. It is responsible for most of the hydrocarbon toxicity. Enzyme B is not inhibitable by BF and metabolizes the 7,8-diol less efficiently to the diol-epoxide or efficiently to other, less toxic products.     

Recent developments and applications of immobilized laccase

Laccase is a promising biocatalyst with many possible applications, including bioremediation, chemical synthesis, biobleaching of paper pulp, biosensing, textile finishing and wine stabilization. The immobilization of enzymes offers several improvements for enzyme applications because the storage and operational stabilities are frequently enhanced. Moreover, the reusability of immobilized enzymes represents a great advantage compared with free enzymes. In this work, we discuss the different methodologies of enzyme immobilization that have been reported for laccases, such as adsorption, entrapment, encapsulation, covalent binding and self-immobilization. The applications of laccase immobilized by the aforementioned methodologies are presented, paying special attention to recent approaches regarding environmental applications and electrobiochemistry.     

Benzo[a]pyrene-collagen interactions

In vitro interactions of benzo[a]pyrene (BaP) with acid-soluble type I collagen from rat tail tendon have been investigated. The fluorescence of BaP increases in the presence of collagen. Bound BaP inhibits the formation of collagen fibrils in solution. When BaP-collagen complexes are irradiated in air with UV (365 nm) light, BaP rapidly undergoes photooxidation with the further inhibition of fibril formation. Viscosity and circular dichroism (CD) studies show that neither BaP nor further UV-irradiation alters the size or helical conformation of the protein. During thermal denaturation of collagen, BaP fluorescence changes. Collagen from young rat tail tendon shows a pronounced drop at about 38 degrees C, whereas that from old rat tail tendon exhibits an increase with a plateau in the same temperature range. These anomalous changes are observed when tyrosine residues, present only in the non-helical terminal telopeptides of collagen, are excited at 275 nm, but not by direct BaP excitation at 387 nm. These findings suggest that the specific hydrophobic telopeptide region, which plays an important role in fibril formation, are affected by bound BaP.     

Sanguinarine causes DNA damage and p53-independent cell death in human colon cancer cell lines

The benzophenanthridine alkaloid sanguinarine has antimicrobial and possibly anticancer properties but it is not clear to what extent these activities involve DNA damage. Thus, we studied its ability to cause DNA single and double strand breaks, as well as increased levels of 8-oxodeoxyguanosine, in human colon cancer cells and found DNA damage consistent with oxidation. Since the tumor suppressor p53 is frequently involved in inducing apoptosis following DNA damage we investigated the effect of sanguinarine in wild type, p53-mutant and p53-null colon cancer cell lines. We found them to be equally sensitive to this plant compound, indicating that cell death is not mediated by p53 in this case. In addition, our observation that apoptosis induced by sanguinarine is initiated very rapidly raised the question whether there is enough time for cellular signaling in response to DNA damage. Moreover, the abundance of double strand breaks is not consistent with only oxidative damage to DNA. We conclude that the majority of DNA double strand breaks in sanguinarine-treated cells are likely the result, rather than the cause, of apoptotic cell death and that apoptosis induced by sanguinarine is independent of p53 and most likely independent of DNA damage.     

Regulation of cytochrome P450 gene expression in the olfactory mucosa

The mammalian olfactory mucosa (OM) is unique among extrahepatic tissues in having high levels, and tissue-selective forms, of cytochrome P450 (CYP) enzymes. These enzymes may have important toxicological implications, as well as biological functions, in this chemosensory organ. In addition to a tissue-selective, abundant expression of CYP1A2, CYP2A, and CYP2G1, some of the OM CYPs are also known to have an early developmental expression, a resistance to xenobiotic inducers, and a lack of responsiveness to circadian rhythm. Efforts to fully characterize the regulation of CYP expression in the OM, and to identify the underlying mechanisms, are important for our understanding of the physiological functions and toxicological significance of these biotransformation enzymes, and may also shed unique light on the general mechanisms of CYP regulation. The aim of this mini-review is to provide a summary of current knowledge of the various modes of regulation of CYPs expressed in the OM, an update on our mechanistic studies on tissue-selective CYP expression, and a review of the literature on xenobiotic inducibility of OM CYPs. Our goal is to stimulate further studies in this exciting research area, which is of considerable importance, in view of the constant exposure of the human nasal tissues to inhaled, as well as systemically derived, chemicals, the prevalence of olfactory system damage in individuals with neurodegenerative diseases, and the current uncertainty in risk assessments for potential olfactory toxicants.