Toxicological Interactions Research Articles

Neurotoxic Effects Associated with Current Uses of Organophosphorus Compounds

Organophosphorus compounds (OPs) are a large and diverse class of chemicals that have been synthesized, since the XIX century for several purposes like chemical weapons, flame-retardants, ectoparasiticides and investigational new drugs, but mainly as agrochemicals in agriculture and indoor. Although the amount of OP pesticides being used is declining, especially in developed countries, OPs continue being one of the most important classes of insecticides and chemical warfare agents today due to its toxic effects on the enzyme acetylcholinesterase (AChE). Existing research on the toxicological effects of OPs is extensive, however, there is a lack of knowledge on the long-term effects of low levels of OPs and their exactly pathways of toxicity. Recent data prove that other molecular targets than AChE could be targeted by OPs, triggering these effects. Here these data are reviewed and it is highlighted that the current uses of OPs are producing several neurotoxic effects. It is also shown that, to protect people from possible uses and misuses of OPs, more regulations on OPs are needed. Moreover, more mechanistic studies are needed to completely understand their toxicological interactions and mechanisms of action and to identify the whole group of enzymes that interact with them.

Indoxacarb interaction alters immunotoxic and genotoxic potential of endotoxin.

Indoxacarb is commonly used to effectively control pests, cockroaches, termites, fleas, and houseflies. Although the toxicological profile of indoxacarb had already been well characterized, we examined the possible toxicological interaction with indoxacarb and endotoxin. Male Swiss albino mice aged 8-10 weeks were orally administered indoxacarb dissolved in groundnut oil at 4 mg/kg/day and 2 mg/kg/day for 90 days. On day 91, five animals from each group were challenged with lipopolysaccharides (LPS) at 80 µg/mouse, administered intranasally. Indoxacarb at 4 mg/kg significantly decreased Total leukocyte count, lymphocytopenia, and neutrophilia. Both doses of indoxacarb combined with LPS resulted in significant lymphocytopenia. Indoxacarb did not produce DNA damage in comet assay, but when combined with LPS, it resulted in a significant increase in tail length, tail moment, and olive moment. The data indicate that indoxacarb at 4 mg/kg administered orally for 90 days induced immune-response change. Further, both doses of indoxacarb, when combined with LPS, accelerate immunotoxicity and endotoxin-induced DNA damage.

The binary, ternary and quaternary mixture toxicity of benzo[a]pyrene, arsenic, cadmium and lead in HepG2 cells.

Polycyclic aromatic hydrocarbons (PAHs) and heavy metal/loid(s) are common environmental pollutants. Toxicological interaction data on benzo[a]pyrene (B[a]P) and heavy metal/loid(s) are lacking. In this study, we have determined the combined toxicity of B[a]P, arsenic (As), cadmium (Cd) and lead (Pb) in HepG2 cells. The binary, ternary and quaternary mixture toxicity of B[a]P and heavy metal/loid(s) was predicted by using the combination index (CI)-isobologram method. This method is useful to predict the quantitative nature of an interaction between chemicals at different effect (inhibitory concentration) levels from 0.1 to 99% using computerised quantitation. A total of 11 mixtures including six binary mixtures, four ternary and one quaternary mixtures of B[a]P and heavy metal/loid(s) were evaluated for their interactions. The cytotoxicity of individual and multi-component mixtures was evaluated by MTS assay. The selected concentrations for the individual dose response study were 0-100 μM - B[a]P; 0-40 μM - Cd; 0-400 μM - As and Pb. The individual dose response results showed that all four chemicals were toxic to liver cells with Cd being the most potent toxicant. Mixtures of B[a]P and heavy metal/loid(s) were prepared based on their individual Dm concentration using a 1 : 1 ratio and exposed to HepG2 cells. By using the CI-isobologram method, the predicted interactions between these chemicals were synergism, additivity or antagonism at different effect levels. All the mixtures except the ternary mixture of B[a]P + As + Pb displayed synergism at a lower effect level (IC10-IC30), and additivity, synergism or antagonism at 50-90% effect levels. Among these mixtures, mixtures of heavy metal/loid(s) (both binary and ternary combinations) and a quaternary mixture of B[a]P + As + Cd + Pb showed a strong synergistic response at lower effect levels compared to other mixtures. The predicted interaction response by the CI method was compared with classical models of concentration addition and independent action. The CI method displayed an improved prediction power compared to classical models. The predicted synergistic interaction between B[a]P and heavy metal/loid(s) may have important implications in the human health risk assessment of these mixed chemical mixtures at contaminated sites.

Complex toxicological interaction between ionic liquids and pesticides to Vibrio qinghaiensis sp.-Q67

Ionic liquids (ILs) and pesticides may coexist in ecosystems, because more and more people try to extract pesticides from various samples using ILs.

In Response: The path forward for the adverse outcome pathway framework--A regulatory perspective.

In Response: The path forward for the adverse outcome pathway framework--A regulatory perspective.

Interaction of titanium dioxide nanoparticles with glucose on young rats after oral administration

Titanium dioxide nanoparticles (TiO2 NPs) have a broad application prospect in replace with TiO2 used as a food additive, especially used in sweets. Understanding the interaction of TiO2 NPs with sugar is meaningful for health promotion. We used a young animal model to study the toxicological effect of orally administrated TiO2 NPs at doses of 0, 2, 10 and 50mg/kg per day with or without daily consumption of 1.8g/kg glucose for 30days and 90days. The results showed that oral exposure to TiO2 NPs and TiO2 NPs+glucose both induced liver, kidney, and heart injuries as well as changes in the count of white and red blood cells in a dose, time and gender-dependent manner. The toxicological interactions between orally-administrated TiO2 NPs and glucose were evident, but differed among target organs. These results suggest that it is necessary to limit dietary co-exposure to TiO2 NPs and sugar. From the Clinical EditorNanotechnology has gained entrance in the food industry, with the presence of nanoparticles now in many food items. Despite this increasing trend, the potential toxic effects of these nanoparticles to human remain unknown. In this article, the authors studied titanium dioxide nanoparticles (TiO2 NPs), which are commonly used as food additive, together with glucose. The findings of possible adverse effects on liver, kidney, and heart might point to a rethink of using glucose and TiO2 NPs combination.

Does the presence of microplastics influence the acute toxicity of chromium(VI) to early juveniles of the common goby (Pomatoschistus microps)? A study with juveniles from two wild estuarine populations

Toxicological interactions between microplastics (MP) and other environmental contaminants are of grave concern. Here, the potential influence of MP in the short-term toxicity of chromium to early juveniles of Pomatoschistus microps was investigated. Three null hypotheses were tested: (1) exposure to Cr(VI) concentrations in the low ppm range does not induce toxic effects on juveniles; (2) the presence of microplastics in the water does not influence the acute toxicity of Cr(VI) to juveniles; (3) the environmental conditions of the natural habitat where fish developed do not influence their sensitivity to Cr(VI)-induced acute stress. Fish were collected in the estuaries of Minho (M-est) and Lima (L-est) Rivers (NW Iberian Peninsula) that have several abiotic differences, including in the water and sediment concentrations of various environmental contaminants. After acclimatization to laboratory conditions, two 96h acute bioassays were carried out with juveniles from both estuaries to: (i) investigate the effects of Cr(VI) alone; (ii) investigate the effects of Cr(VI) in the presence of MP (polyethylene spheres 1–5μm ∅). Cr(VI) alone induced mortality (96h-LC50s: 14.4–30.5mg/l) and significantly decreased fish predatory performance (≤74%). Thus, in the range of concentrations tested (5.6–28.4mg/l) Cr(VI) was found to be toxic to P. microps early juveniles, therefore, we rejected hypothesis 1. Under simultaneous exposure to Cr(VI) and MP, a significant decrease of the predatory performance (≤67%) and a significant inhibition of AChE activity (≤31%) were found. AChE inhibition was not observed in the test with Cr(VI) alone and MP alone caused an AChE inhibition ≤21%. Mixture treatments containing Cr(VI) concentration ≥3.9mg/l significantly increased LPO levels in L-est fish, an effect that was not observed under Cr(VI) or MP single exposures. Thus, toxicological interactions between Cr(VI) and MP occurred, therefore, we rejected hypothesis 2. In the presence of MP, the negative effect caused by high concentrations of Cr(VI) on the predatory performance was significantly reduced in L-est fish but not in M-est fish, and Cr(VI) concentrations higher than 3.9mg/l caused oxidative damage in L-est fish but not in M-est fish. The acclimatization and test conditions were similar for fish from the two estuaries and these ecosystems have environmental differences. Thus, long-term exposure to distinct environmental conditions in the natural habitat during previous developmental phases influenced the sensitivity and responses of juveniles to Cr(VI), therefore, we rejected hypothesis 3. Overall, the results of this study indicate toxicological interactions between MP and Cr(VI) highlighting the importance of further investigating the combined effects of MP and other common contaminants.

83. Adenoviral Mediated Compartmentalized Liver Transduction Improves Safety and Yields Long-term Transgene Expression in a Porcine Model

To stringently control the viremia associated with conventional routes of vector administration and significantly reduce the astronomical quantities of virus commonly infused in gene therapy, our group described compartmentalized liver transduction. Compartmentalized liver transduction is based on known adenoviral spatio-temporal kinetics and is achieved by the intra-parenchymal injection of a vector dose into a blood flow isolated portion of the liver; perfusion is reestablished after viral endocytosis has been completed (30 min). Given the encouraging results documented in rodents (rats), our group assessed compartmentalized liver transduction in a porcine model. To this end, a surgical device was conceptualized, prototyped and utilized to safely and securely transiently isolate a portion of the liver in 25- 30 kg Vietnamese pigs. Implementing compartmentalized liver transduction in pigs, no viremia was detected during the procedure and transgene expression and presence were confined to the site of vector injection. Neither inflammation, apoptosis or significant biochemical liver damage were observed. Using porcine alpha fetoprotein as a reporter gene, serum levels were documented with low quantities of vector dose (10^5) and prolonged transgene expression was achieved (10 months). Our results further support that compartmetalized liver transduction has profound paradoxic effects on the classic toxicological interactions between the liver and adenovirus. The lack of acute liver inflammation observed suggests that conventional immunolgical thresholds and relays were not triggered. We further postulate that compartmentalized liver transduction induces the local synthesis of tolerance inducing cytokines central to thwarting the acute, intermediate and late adenoviral induced immune responses and are critical in generating an immune priviledge liver compartment capable of long term protein synthesis and secretion. Our results further demonstrate that compartmentalized liver transduction is a safe and effective route of vector delivery with a promising future in the field of gene therapy.

Nivalenol induces oxidative stress and increases deoxynivalenol pro-oxidant effect in intestinal epithelial cells

Mycotoxins are secondary fungal metabolites often found as contaminants in almost all agricultural commodities worldwide, and the consumption of food or feed contaminated by mycotoxins represents a major risk for human and animal health. Reactive oxygen species are normal products of cellular metabolism. However, disproportionate generation of reactive oxygen species poses a serious problem to bodily homeostasis and causes oxidative tissue damage. In this study we analyzed the effect of two trichothecenes mycotoxins: nivalenol and deoxynivalenol, alone and in combination, on oxidative stress in the non-tumorigenic intestinal epithelial cell line IEC-6. Our results indicate the pro-oxidant nivalenol effect in IEC-6, the stronger pro-oxidant effect of nivalenol when compared to deoxynivalenol and, interestingly, that nivalenol increases deoxynivalenol pro-oxidative effects. Mechanistic studies indicate that the observed effects were mediated by NADPH oxidase, calcium homeostasis alteration, NF-kB and Nrf2 pathways activation and by iNOS and nitrotyrosine formation. The toxicological interaction by nivalenol and deoxynivalenol reported in this study in IEC-6, points out the importance of the toxic effect of these mycotoxins, mostly in combination, further highlighting the risk assessment process of these toxins that are of growing concern.

Binary combinations of organophosphorus pesticides exhibit differential toxicity under oxidised and un-oxidised conditions

Acetylcholinesterase (AChE) inhibition has been demonstrated to be useful as a biomarker for exposure to organophosphorus (OP) insecticides in many environments. The objective of this study was to investigate the response of housefly (Musca domestica) head AChE (HF-AChE) exposed to five OPs as individual compounds and their binary mixtures under in vitro conditions. To examine the effects of oxidation on OP potency in the HF-AChE system, bromine water was used as an oxidisng agent. With oxidation, the sensitivity of HF-AChE to chlorpyrifos (CPF), malathion (MLT) and triazophos (TRZ) increased significantly. Monocrotophos (MCP) and profenofos (PRF) did not exhibit any significant differences in toxicity under oxidised and un-oxidised conditions. The toxicological interaction of five organophosphorus pesticides was evaluated using the concentration addition model, the combination index–isobologram equation and the toxic unit approach. All three models provided similar predictions for the 10 binary combinations of OPs under oxidised and un-oxidised conditions. In the present study, the antagonistic effects of the binary combination of OPs (CPF+PRF, CPF+MLT, MCP+MLT, PRF+MLT, MLT+TRZ and PRF+TRZ) were observed under oxidised conditions. This may be due to dispositional and/or receptor antagonism. Most of the binary combinations assayed under un-oxidised conditions exhibited synergistic responses. Triazophos showed very strong synergism in binary combinations with CPF, MCP and PRF un-oxidised conditions. In contrast, under oxidised conditions, only CPF+TRZ exhibited synergism. The results obtained indicate differential toxicity of binary combinations of OPs under oxidised and un-oxidised conditions. This information could be a valuable tool in understanding the mechanisms of OPs interactions and the interpretation of future in vivo studies with mixtures of OP insecticides.

The synergistic toxicity of the multiple chemical mixtures: Implications for risk assessment in the terrestrial environment

The combined toxicity of five insecticides (chlorpyrifos, avermectin, imidacloprid, λ-cyhalothrin, and phoxim), two herbicides (atrazine and butachlor) and a heavy metal (cadmium) has been examined with the earthworm acute toxicity test. Toxicological interactions of these chemicals in four, five, six, seven, and eight-component mixtures were studied using the combination-index (CI) equation method. In four-component and five-component mixtures, the synergistic effects predominated at lower effect levels, while the patterns of interactions found in six, seven, and eight-component mixtures displayed synergism. The λ-CY+IMI+BUT+ATR+CPF+PHO combination displayed the most strongly synergistic interaction, with CI values ranging from 0.09 to 0.15. The nature of the interaction changes with the effect level and the relevance of synergistic effects increase with the complexity of the mixture. The CI method was compared with the classical models of concentration addition (CA) and independent action (IA) and we found that the CI method could accurately predict the combined toxicity. The predicted synergism resulted from co-existence of the pesticides and the heavy metal especially at low effect levels may have important implications in risk assessment for the real terrestrial environment.

Joint toxicity of chlorpyrifos, atrazine, and cadmium at lethal concentrations to the earthworm Eisenia fetida.

Contaminants in the environment often occur as complex mixtures, and their combined effect may exhibit toxicity to organisms. Risk assessments based on individual components tend to underestimate the effects associated with toxic action of mixtures. Toxicity studies on chemical mixtures are urgently required to assess their potential combined toxicities. The combination index (CI)-isobologram method was used to study chemical interactions to determine the nature of toxicological interactions of two pesticides chlorpyrifos and atrazine and a heavy metal cadmium toward earthworm Eisenia fetida by artificial soil and filter paper acute toxicity tests. The results showed that the binary mixture of chlorpyrifos and atrazine was antagonistic toward E. fetida at all f a levels in an artificial soil test. The combination of atrazine and Cd exhibited a slight degree of synergism throughout the exposure range, while chlorpyrifos plus Cd combination led to dual antagonistic/synergistic behavior. The nature of binary combinations in filter paper displayed opposite interaction to that in the artificial soil test, and the toxicity of ternary mixtures was not significantly synergistic than their binaries. The combination index (CI)-isobologram equation method could determine the interaction types for a series of effect levels of three chemicals in binary and ternary combinations in two types of acute earthworm tests. However, the nature of these interactions was not uniform along the f a level range in any of the two tests. Bioavailability, the nature of toxicological interaction, and the test organism need to be considered for understanding exposures and chemical measures. The synergistic effect for the particular binary combination suggests that a potential risk associated with the co-occurrence of these pollutants may still exist, which may have implications in risk assessment for the terrestrial environment. The combined effects between different contaminants might be influenced by the category of chemical, as well as the bioassay procedures. More studies of combined toxicities among these contaminants in the terrestrial environment should be conducted to identify the mixtures exhibiting synergistic pattern of interactions.

Application of the combination index integrated with confidence intervals to study the toxicological interactions of antibiotics and pesticides in Vibrio qinghaiensis sp.-Q67

It is necessary to explore the effect of confidence intervals on the combination index (CI) so that rationally evaluate the toxicological interaction (synergism or antagonism) which is dependent on the concentration ratio, the mixture concentration and the exposure time. To effectively detect the toxicological interaction taking place in mixtures, we combined the CI with the observation-based confidence intervals (OCI) which can characterize the uncertainty in toxicity test and in data fitting. In time scale, the short-term (15min) and long-term (12h) toxicities of three chemicals (imidacloprid (IMI), pirimicarb (PIR) and streptomycin sulfate (STR)) and their binary mixtures on Vibrio qinghaiensis sp.-Q67 were determined by the microplate toxicity analysis (MTA). The mixtures of IMI, PIR and STR have additive actions all but four IMI–PIR rays (R2–R5) at the effect levels above about 30–40% whose long-term toxicological interaction are synergism.

Individual and combined cytotoxic effects of aflatoxin B1, zearalenone, deoxynivalenol and fumonisin B1 on BRL 3A rat liver cells.

This study was performed to determine the individual and combined cytotoxic effects of Aflatoxin B1 (AFB1), zearalenone (ZEA), deoxynivalenol (DON) and fumonisin B1 (FB1) on BRL 3A rat liver cells. After the mycotoxins treated the BRL 3A cells for 12, 24 and 48h, cell viability was determined using the MTT assay. The cytotoxicity of individual mycotoxins on BRL 3A cell viability in decreasing order were DON>AFB1>ZEA>FB1. The central composite design (CCD) was used to assess the toxicity of binary and ternary mixtures of these mycotoxins. The mixtures of AFB1+ZEA and AFB1+DON showed the synergetic toxic effects on BRL 3A cells. These toxins decreased the viability of cells by inducing intracellular reactive oxygen species (ROS) production and promoting apoptosis in the BRL 3A cells. This effect was mediated by an upregulation of the stress and apoptotic genes Hsp70, p53, Bax, Caspase-3 and Caspase-8, along with a downregulation of the antiapoptotic gene Bcl-2. In conclusion, our results suggested that the coexistence of AFB1 and ZEA or DON in agricultural products could be more hepatotoxic than individually, suggests that the toxicological interactions of these toxins need to be better understood to assess health risks.

Occurrence, bioaccumulation and risk assessment of lipophilic pharmaceutically active compounds in the downstream rivers of sewage treatment plants

The occurrence, bioaccumulation and risk assessment of lipophilic pharmaceutically active compounds (LPhACs), such as antibiotics (roxithromycin, erythromycin and ketoconazole), anti-inflammatories (ibuprofen and diclofenac), β-blockers (propranolol), antiepileptics (carbamazepine) and steroid hormones (17α-ethinylestradiol), were investigated in the downstream rivers of sewage treatment plants in Nanjing, China. The results indicate that these LPhACs were widely detected in the surface water and fish samples, with the mean concentrations of the total LPhACs (ΣLPhACs) being in the range of 15.4 and 384.5ng/L and 3.0 and 128.4ng/g (wet weight), respectively. The bioaccumulation of the ΣLPhACs in wild fish tissues was generally in the order the liver>brain>gill>muscle. Among the target LPhACs, however, an interspecies difference in tissue distribution was evident for erythromycin. The bioaccumulation factors of LPhACs in the liver and brain, the two major targeted storage sites for toxicants, exhibited an obvious negative correlation with the aquatic concentrations (P<0.05). Finally, risk quotients posed by pharmaceuticals were assessed by comprehensive and comparative methods for different aquatic organisms (algae, daphnids and fish). The overall relative order of susceptibility was estimated to be algae>daphnids>fish. However, the results indicate that diclofenac, ibuprofen and 17α-ethinylestradiol each posed chronic risks for high trophic level organisms (fish). In all of the risk assessments, erythromycin was found to be the most harmful for the most sensitive algae group. In this work, however, the total BAF and toxicological interactions of pharmaceuticals were not performed due to the lack of metabolite information and combined toxicity data, which represents a major hindrance to the effective risk assessment of pharmaceuticals.

Effects of six antibiotics and their binary mixtures on growth of Pseudokirchneriella subcapitata

The effect of ampicillin (AMP), amoxicillin (AMX), cephalotin (CEP), ciprofloxacin (CPF), gentamycin (GEN), and vancomycin (VAN) have been examined individually and as binary mixtures, on a non-target aquatic organism, the green alga Pseudokichneriella subcapitata. The β-lactam antibiotics AMP and AMX were not toxic to the alga at concentrations up to 2000mgl−1 (less than 10% of algal growth inhibition), whereas the fluoroquinolone CPF, and the aminoglycoside GEN were the most toxic antibiotics, with an EC50=11.3±0.7mgl−1 and 19.2±0.5mgl−1, respectively. The cephalosporin CEP and the glycopeptide VAN were less toxic than the last two mentioned, showing an EC50>600mgl-1 and 724±20mgl−1, respectively. The toxicological interactions of binary mixtures were predicted by the two classical models of additivity: concentration addition (CA) and independent action (IA), and compared to the experimentally determined toxicities over a range of concentrations between 1 and 50mgl−1. In all cases a clear synergistic effect was observed, showing that single compound toxicity data are not adequate for the prediction of aquatic toxicities of antibiotic mixtures. Risk assessment was performed by calculating the ratio between predicted environmental concentrations (PEC) and the predicted no effect concentration (PNEC). All the antibiotics tested, excepting GEN, have a potential ecological risk, taking into account the PEC of hospital effluents from Buenos Aires, Argentina. These risks increase when antibiotics are present in binary mixtures.

Ternary toxicological interactions of insecticides, herbicides, and a heavy metal on the earthworm Eisenia fetida

The combined toxicities of five insecticides (chlorpyrifos, avermectin, imidacloprid, λ-cyhalothrin, and phoxim), two herbicides (atrazine and butachlor), and a heavy metal (cadmium) have been examined using the acute toxicity test on the earthworm. With a concentration of 2.75mg/kg being lethal for 50% of the organisms, imidacloprid exhibited the highest acute toxicity toward the earthworm Eisenia fetida. Toxicological interactions of these chemicals in ternary mixtures were studied using the combination-index (CI) equation method. Twenty-one ternary mixtures exhibited various interactive effects, in which 11 combinations showed synergistic effects, four led to dual synergistic/additive behaviors, one exhibited an additive effect, and five showed increasing antagonism within the entire range of effects. The CI method was compared with the classical models of concentration addition and independent action, and it was found that the CI method could accurately predict combined toxicity of the chemicals studied. The predicted synergism in the majority of the mixtures, especially at low-effect levels, might have implications in the real terrestrial environment.

Toxicity of mixtures of λ-cyhalothrin, imidacloprid and cadmium on the earthworm Eisenia fetida by combination index (CI)-isobologram method

Contaminants in the environment do not appear singly and usually occur as mixtures. We applied the combination index (CI)-isobologram method which allows computerized quantitation of synergism, additive effect and antagonism to determine the nature of toxicological interactions of two pesticides λ-cyhalothrin, imidacloprid, and heavy metal cadmium towards earthworm Eisenia fetida. In an artificial soil test, λ-cyhalothrin and Cd combination was slightly synergistic at low effect levels which turned into a slight antagonism above fa values of 0.6, while the binary mixtures containing imidacloprid exhibited antagonism. The presence of imidacloprid in the ternary mixture also resulted in an antagonistic effect to the earthworms. This behavior became more antagonistic in the ternary mixture in filter paper tests.

Restraint stress exacerbates alcohol-induced reproductive toxicity in male rats

Cumulative exposure to multiple stresses may lead to aggravating the toxicity of each stress, qualitatively or quantitatively altering biological responses because of toxicological interaction. In this study, we intended to determine the possible effects of restraint stress on reproductive toxicity due to ethanol usage in male rats. Early pubertal male Wistar rats were subjected to either restraint stress (5 h/day) or alcohol intoxication (2 mg/kg body weight) or both for 60 days. Body weights of control and experimental rats were similar during the 60 days of this study. Testes were harvested, weighed, and prepared for enzyme assays, and cauda epididymides were isolated for the determination of density, motility, and viability of stored spermatozoa. Restraint stress or alcohol treatment significantly reduced testis weight and caused significant reductions in steroidogenesis and spermatogenesis. Mean density, motility, and viability of stored spermatozoa were reduced in experimental rats. Plasma testosterone concentrations in rats subjected to restraint stress or alcohol were decreased compared with those of controls, concomitant with increased concentrations of LH and FSH in experimental rats. These data suggest that sub-chronic exposure to restraint stress or alcohol contribute to reduce testicular and epididymal function in exposed rats. The study also suggests that restraint stress exacerbates alcohol-induced reproductive toxicity in rats.

Mercury metallation of the copper protein azurin and structural insight into possible heavy metal reactivity

Mercury(II) metallation of Pseudomonas aeruginosa azurin has been characterized structurally and biochemically. The X-ray crystal structure at 1.5Å of mercury(II) metallated azurin confirms the coordination of mercury at the copper binding active site and a second surface site. These findings are further validated by NMR, Matrix-assisted laser desorption/ionization spectrometry (MALDI), and UV–visible spectroscopic methods indicating copper displacement from the wild-type protein. Bioinformatic analysis has identified homologous human protein domains computationally, and compared them to the structure of azurin, providing a model for human mercury interactions. Study of the mercury–azurin adduct, in combination with other known examples of protein–heavy metal interactions, could provide further insight into the chemical mechanisms of toxicological interactions, leading toward a global understanding of the biological speciation of toxic heavy metals.