Long-term exposure to small-sized silica nanoparticles (SiO2-NPs) induces oxidative stress and impairs reproductive performance in adult zebrafish (Danio rerio).

The widespread use of silica nanoparticles (SiO2-NPs) in various industries, including chemical polishing, cosmetics, varnishes, medical, and food products, has increased the risk of their release into aquatic ecosystems. The toxic effects of small-size SiO2-NPs on the reproductive performance of zebrafish (Danio rerio) have yet to be widely studied. This study aimed to investigate the impact of chronic exposure to small-sized (35 ± 6 nm) SiO2-NPs on adult zebrafish through waterborne exposure to concentrations of 5 (SNP5), 10 (SNP10), 15 (SNP15), and 20 (SNP20) µg/L of SiO2-NPs for 28 days. Our results showed that SiO2-NPs significantly impacted several biochemical parameters, including cholesterol, triglycerides, LDL, HDL, total protein, albumin, urea levels, and alkaline phosphatase and aspartate aminotransferase activity. Cortisol and glucose levels in the SNP20 group significantly differed from the control group. All the exposed groups, apart from SNP5, experienced a significant increase in their total immunoglobulin levels and lysozyme activity. While there was a considerable increase in the activity of catalase and superoxide dismutase in all exposed groups, the expression of antioxidant genes did not appear to be affected. Furthermore, the expression level of il8 was significantly higher in SNP5 and SNP10 than in other treatments. Exposure to SiO2-NPs caused a decrease in gonad weight, absolute fecundity, and larval survival rate, particularly in the SNP20 group. The present study indicates that SiO2-NPs can harm zebrafish and thus further research is necessary to assess their health and environmental risks.

Dietary immunostimulants reduced infectivity of Diplostomum spp. eye fluke in common carp, Cyprinus carpio L.

Juvenile common carp Cyprinus carpio L. (5.52 ± 1.66 cm, TL) were fed on four diets containing either beta-glucan (MacroGard, 1 g kg -1), nucleotides (Optimûn, 0.2 g kg - 1), chitosan (deacetylated chitin ≥75% shrimp shells, 10 g kg -1) or a basal control diet for 35 days to test whether these so-called "immunostimulants" could affect eye fluke Diplostomum spp. infection success. The immunostimulants diets reduced the number of eye fluke infecting the eyes of C. carpio, with significantly higher infections in the control diet (4.78 ± 1.27) compared with the chitosan (2.08 ± 0.87), nucleotide (2.98 ± 1.01), and beta-glucan (1.41 ± 0.79) diets. To our knowledge, this is the first study to provide evidence that beta-glucan, nucleotides, and chitosan diets can aid against a Diplostomum infection and provides valuable preliminary knowledge on the use of immunostimulants to ameliorate parasitic infections.

The stochastic association of nanoparticles with algae at the cellular level: Effects of NOM, particle size and particle shape.

Association of nanoparticles (NPs) with algae likely plays a critical role in their transfer in aquatic food chains. Although our understanding of the ecotoxicity and fate of NPs in the environment is increasing, it is still unclear how the physicochemical properties of NPs influence their interaction with algae at cellular levels and how this is reflected at a population level. This is due to the limitation in the existing analytical techniques to quantify the association of NPs with cells. To fill this data gap, we applied the novel technique of single-cell inductively coupled plasma mass spectrometry to quantify the cellular association of gold (Au)-NPs with algal cells (Pseudokirchneriella subcapitata) as a function of particle size, shape (spherical 10 nm, spherical 60 nm, spherical 100 nm, rod-shaped 10 × 40 nm, and rod-shaped 50 × 100 nm), and surface chemistry [citrate and natural organic matter (NOM) coating] on a cell-by-cell basis. The association of Au-NPs with algal cells was found to be a random probability following a so-called stochastic process; after 72 h of exposure, less than 45% of the cell population accumulated NPs on their surface. The number of Au-NPs per cell was found to be heterogeneously distributed as some cells were associated with a significantly higher number (e.g. up to 600 spherical 10 nm particles per cell) of Au-NPs than other cells present in the medium. The presence of NOM on the surface of the particles decreased the percentage of cells containing NPs except for the spherical 60 nm Au-NPs. We conclude that some algae within a population can accumulate NPs on their surface and this accumulation is influenced by the size, shape, and surface chemistry of NPs. It is important to understand how NPs may enter aquatic food chains to assess the possible risk.

Particle number-based trophic transfer of gold nanomaterials in an aquatic food chain.

Analytical limitations considerably hinder our understanding of the impacts of the physicochemical properties of nanomaterials (NMs) on their biological fate in organisms. Here, using a fit-for-purpose analytical workflow, including dosing and emerging analytical techniques, NMs present in organisms are characterized and quantified across an aquatic food chain. The size and shape of gold (Au)-NMs are shown to control the number of Au-NMs attached to algae that were exposed to an equal initial concentration of 2.9 × 1011 particles mL-1. The Au-NMs undergo size/shape-dependent dissolution and agglomeration in the gut of the daphnids, which determines the size distribution of the NMs accumulated in fish. The biodistribution of NMs in fish tissues (intestine, liver, gills, and brain) also depends on NM size and shape, although the highest particle numbers per unit of mass are almost always present in the fish brain. The findings emphasize the importance of physicochemical properties of metallic NMs in their biotransformations and tropic transfers.

An environmental ecocorona influences the formation and evolution of the biological corona on the surface of single-walled carbon nanotubes.

Nanomaterials (NMs) taken up from the environment carry a complex ecocorona consisting of dissolved organic matter. An ecocorona is assumed to influence the interactions between NMs and endogenous biomolecules and consequently affects the formation of a biological corona (biocorona) and the biological fate of the NMs. This study shows that biomolecules in fish plasma attach immediately (within <5 min) to the surface of SWCNTs and the evolution of the biocorona is a size dependent phenomenon. Quantitative proteomics data revealed that the nanotube size also influences the plasma protein composition on the surface of SWCNTs. The presence of a pre-attached ecocorona on the surface of SWCNTs eliminated the influence of nanotube size on the formation and evolution of the biocorona. Over time, endogenous biomolecules from the plasma partially replaced the pre-attached ecocorona as measured using a fluorescently labelled ecocorona. The presence of an ecocorona offers a unique surface composition to each nanotube. This suggests that understanding the biological fate of NMs taken up from the environment by organisms to support the environmental risk assessment of NMs is a challenging task because each NM may have a unique surface composition in the body of an organism.

Parental and trophic transfer of nanoscale plastic debris in an assembled aquatic food chain as a function of particle size.

The existing limitations in analytical techniques for characterization and quantification of nanoscale plastic debris (NPD) in organisms hinder understanding of the parental and trophic transfer of NPD in organisms. Herein, we used iron oxide-doped polystyrene (PS) NPD (Fe-PS-NPD) of 270 nm and Europium (Eu)-doped PS-NPD (Eu-PS-NPD) of 640 nm to circumvent these limitations and to evaluate the influence of particle size on the trophic transfer of NPD along an algae-daphnids food chain and on the reproduction of daphnids fed with NPD-exposed algae. We used Fe and Eu as proxies for the Fe-PS-NPD and Eu-Ps-NPD, respectively. The algae cells (Pseudokirchinella subcapitata) were exposed to 4.8 × 1010 particles/L of Fe-PS-NPD or Eu-PS-NPD for 72 h. A high percentage (>60%) of the NPD was associated with algal cells. Only a small fraction (<11%) of the NPD, however, was transferred to daphnids fed for 21 days on the NPD-exposed algae. The uptake and trophic transfer of the 270 nm Fe-PS-NPD were higher than those for the 640 nm Eu-PS-NPD, indicating that smaller NPD are more likely to transfer along food chains. After exposure to Fe-PS-NPD, the time to first brood was prolonged and the number of neonates per adult significantly decreased compared to the control without any exposure and compared to daphnids exposed to the Eu-Ps-NPD. The offspring of daphnids exposed to Eu-PS-NPD through algae, showed a traceable concentration of Eu, suggesting that NPD are transferred from parents to offspring. We conclude that NPD can be transferred in food chains and caused reproductive toxicity as a function of NPD size. Studies with prolonged exposure and weathered NPD are endeavored to increase environmental realism of the impacts determined.

Effects of dietary Origanum vulgare on gilthead seabream (Sparus aurata L.) immune and antioxidant status.

Origanum sp. is a very common genus of aromatic plants worldwide distributed around the Mediterranean area and O. vulgare (oregano) is the most important species of this genus throughout the world. Due the known medicinal properties of oregano, the effect of diets enriched with 0% (control), 0.5% and 1% oregano leaves powder was studied on the growth, immune and antioxidant status of gilthead seabream (Sparus aurata L.). Fish fed with oregano 0.5% and 1% enriched diets improved both humoral (IgM and bactericidal activity in skin mucus and protease activity in serum) and cellular (head kidney leucocytes phagocytic ability) immunity at 15 and 30 days. Furthermore, the addition of oregano did not provoke any significant effect neither in the growth promotion nor in the liver antioxidant enzymes activity studied in the serum and skin mucus. The possibility of using O. vulgare as a functional additive to fish diet is discussed.

Effects of food-borne ZnO nanoparticles on intestinal microbiota of common carp (Cyprinus carpio L.).

Ingestion of nanoparticles (NPs) with antimicrobial properties may disrupt the balance of intestinal microbiota. To investigate the effects of zinc oxide (ZnO) NPs on intestinal flora, common carp Cyprinus carpio were fed a commercial feed containing 500 mg kg-1 ZnO NPs for 6 weeks and compared to a control group receiving a similar feed-only regime. Sequencing data were analyzed both in individual fish and in pooled samples. Sequencing of 16S rRNA encoding gene of individual specimens revealed high variation in intestinal microbial composition. Assessment of pooled results can obscure high individual variation in data. ZnO NPs consumption was not associated with a significant difference in the intestinal microbial community compared to untreated controls. Our results indicated a high individual variation in the intestinal microbiome, which may further point out the importance of functional study over microbial composition to address nanomaterials-microbiome relationship.

Analytical approaches for characterizing and quantifying engineered nanoparticles in biological matrices from an (eco)toxicological perspective: old challenges, new methods and techniques.

To promote the safer by design strategy and assess environmental risks of engineered nanoparticles (ENPs), it is essential to understand the fate of ENPs within organisms. This understanding in living organisms is limited by challenges in characterizing and quantifying ENPs in biological media. Relevant literature in this area is scattered across research from the past decade or so, and it consists mostly of medically oriented studies. This review first introduces those modern techniques and methods that can be used to extract, characterize, and quantify ENPs in biological matrices for (eco)toxicological purposes. It then summarizes recent research developments within those areas most relevant to the context and field that are the subject of this review paper. These comprise numerous in-situ techniques and some ex-situ techniques. The former group includes techniques allowing to observe specimens in their natural hydrated state (e.g., scanning electron microscopy working in cryo mode and high-pressure freezing) and microscopy equipped with elemental microanalysis (e.g., energy-dispersive X-ray spectroscopy); two-photon laser and coherent anti-Stokes Raman scattering microscopy; absorption-edge synchrotron X-ray computed microtomography; and laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). The latter group includes asymmetric flow field flow fractionation coupled with ICP-MS and single particle-ICP-MS. Our review found that most of the evidence gathered for ENPs actually focused on a few metal-based ENPs and carbon nanotube and points to total mass concentration but no other particles properties, such as size and number. Based on the obtained knowledge, we developed and presented a decision scheme and analytical toolbox to help orient scientists toward selecting appropriate ways for investigating the (eco)toxicity of ENPs that are consistent with their properties.

Method for Extraction and Quantification of Metal-Based Nanoparticles in Biological Media: Number-Based Biodistribution and Bioconcentration.

A multistep sample preparation method was developed to separate metal-based engineered nanoparticles (ENPs) from biological samples. The method was developed using spiked zebrafish tissues and standard titanium dioxide (TiO2) and cerium dioxide (CeO2) ENPs. Single-particle inductively coupled plasma mass spectrometry was used to quantify the separated particles in terms of number concentration. This method demonstrated mass recoveries of more than 90% and did not strikingly alter the median particles size. High number recoveries were calculated for CeO2 ENPs (>84%). Particle number recoveries were poor for TiO2 ENPs (<25%), which could be due to the interference of 48Ca with the measured isotope 48Ti. The method was verified using zebrafish exposed to CeO2 ENPs to test its applicability for nanotoxicokinetic investigations. Total mass of Ce and particle number concentration of CeO2 ENPs were measured in different tissues. Notably, the mass-based biodistribution of Ce in the tissues did not follow the number-based biodistribution of CeO2. Moreover, the calculated mass-based bioconcentration factors showed a different pattern in comparison to the number-based bioconcentration factors. Our findings suggest that considering mass as the sole dose-metric may not provide sufficient information to investigate toxicity and toxicokinetics of ENPs.

Insight into the modulation of intestinal proteome of juvenile common carp (Cyprinus carpio L.) after dietary exposure to ZnO nanoparticles.

ZnO nanoparticles (NPs) are widely used in industrial and consumer products. Therefore understanding their interaction with biological systems is key to their safe application. Proteomics was applied to assess the sub-lethal effects of dietary ZnO NPs on two parts of carp intestine, the intestinal folds and the muscular parts. A commercial carp feed containing 500mgkg-1 of ZnO NPs was fed to fish for six weeks. The abundances of 32 proteins in the treated intestinal folds were significantly changed and in addition, 28 proteins were significantly changed in the muscular parts. Pathways analysis revealed downregulation of pathways attributed to protein synthesis in both parts of the treated intestine. Remodelling of actin cytoskeleton pathways were regulated positively and negatively in intestinal folds and muscular parts, respectively, albeit via different mechanisms. Apoptosis response was indicated in exposed intestinal folds, whereas elevated levels of protein associated with cancerous cell survival were observed in the muscular parts. Results showed that ZnO NPs affected the protein abundances associated with cell motility, immune system response, oxidative stress response, as well as cell metabolism. Data are available via ProteomeXchange with identifier PXD006867.

Chronic dietary toxicity of zinc oxide nanoparticles in common carp (Cyprinus carpio L.): Tissue accumulation and physiological responses.

Concerns regarding the potential toxic effects of zinc oxide nanoparticles (ZnO NPs) on aquatic organisms are growing due to the fact that NPs may be released into aquatic ecosystems. This study aimed to investigate the effects of dietary exposure to ZnO NPs on juvenile common carp (Cyprinus carpio). Fish were fed a spiked diets at doses 50 and 500mg of ZnO NPs per kg of feed for 6 weeks followed by a 2-week recovery period. Fish were sampled every 2 weeks for haematology trends, blood biochemistry measures, histology analyses, and determination of the accumulation of zinc in tissues. At the end of the exposure and post-exposure periods, fish were sampled for an assessment of lipid peroxidation levels. Dietborne ZnO NPs had no effects on haematology, blood biochemistry, and lipid peroxidation levels during the exposure period. After the recovery period, aspartate aminotransferase activity significantly (p < 0.05) increased and alanine transferase activity significantly (p < 0.05) decreased in the higher exposure group. The level of lipid peroxidation significantly (p < 0.05) decreased in liver of treated fish after 2 weeks post-exposure period. A histological examination revealed mild histopathological changes in kidneys during exposure. Our results did not show a significant increase of zinc content at the end of experiment in any of tested organs. However, chronic dietary exposure to ZnO NPs might affect kidney and liver function.

Responses of immune organs after single-dose exposure to phenanthrene in yellowfin seabream (Acanthopagrus latus): CYP1A induction and oxidative stress.

The effect of phenanthrene (Phe) on induction of ethoxyresorufinO-deethylase (EROD) activity and oxidative stress was examined in immune organs of yellowfin seabream Acanthopagrus latus. Fish were treated with a single intraperitoneal injection at 2, 20, or 40 mg kg-1. The Phe concentration in spleen, EROD activity, superoxide dismutase (SOD) and catalase (CAT) activity, ascorbic acid (AsA), total glutathione (GSH), lipid peroxidation (LPO), and protein carbonylation (PC) levels in spleen and head kidney were assessed at one, four, seven, and 14 days post-injection. Dose response relationship was explored for data on day four. Phe concentration reached the highest observed level on day four, showed decline on day seven, and was undetectable at the end of trial. EROD activity in both organs followed the pattern of Phe level in all treated groups. Catalase and SOD activity at low Phe concentrations was significantly higher than controls, while LPO and PC level showed no differences from controls. In contrast, at 20 and 40 mg kg-1, CAT and SOD activity, an indicator of oxidative stress, was significantly lower than in untreated controls, while AsA, GSH, LPO, and PC levels were higher on days 4 and 7. No parameter of any treatment group in either organ tissue showed difference from control values at the end of the experiment. The SOD and CAT activity in both organs exhibited a biphasic (initial stimulatory effect) effect, whereas other parameters showed a monophasic effect in terms of dose-response. Results suggest that Phe induced CYP1A and antioxidant responses in immune organs.

Quantification of egg proteome changes during fertilization in sterlet Acipenser ruthenus.

Eggs of sterlet are discharged outside into ambient aquatic environment where egg activation and fertilization occur. Effects of different activation media including freshwater and clay suspension on protein abundances of egg were quantified in sterlet Acipenser ruthenus. In-gel digestion and high resolution mass spectrometry were used for label-free protein quantification in the eggs of five females. No significant (p > 0.05) difference was found between protein abundances in eggs activated with different media. However, results showed significant (p < 0.05, fold change ≥2) reduction in the abundances of nine proteins including six glycoproteins, enolase and heat shock protein in activated groups compared to freshly ovulated eggs as control. The fact that abundance of proteasome subunit alpha significantly reduced only in eggs which were activated by clay suspension suggests that activation medium can somehow intervene with protein regulation during fertilization. In conclusion, external fertilization in sturgeon egg is accompanied by huge release of proteins into the external environment that may participate in the construction of a transient microenvironment around egg for attraction and protection of spermatozoa to ensure ensuing fertilization. Data are available via ProteomeXchange with identifier PXD006232.

Effects of chronic dietary exposure of zinc oxide nanoparticles on the serum protein profile of juvenile common carp (Cyprinus carpio L.).

Zinc oxide (ZnO) nanoparticles (NPs) have been dramatically used in industry, biology, and medicine. Despite their interesting physico-chemical properties for application in various industrial, medical, and consumer products, safe use of ZnO NPs are under challenges due to the inadequate information related to their toxicological endpoints. Proteomics was applied to evaluate the sub-lethal effects of dietary exposure to ZnO NPs on serum proteome profile of juvenile common carp, (Cyprinus carpio). Therefore, ZnO NPs solution (500mgkg-1 of feed) was added to a commercial carp feed for six weeks. We compared the serum proteome profile from 7 controls and 7 treated fish. In addition, zinc accumulation were measured in intestine, liver, gill and brain. In total, we were able to identify 326 proteins from 6845 distinct peptides. As a result of the data analysis, the abundance levels of four proteins were significantly altered (fold change (fc) ≥2 and p<0.05) after dietary exposure to ZnO NPs. The protein levels of the complement component C4-2 (fc 2.5) and the uncharacterised protein encoded by kng1 (fc 5.8) were increased and major histocompatibility class I (fc 4.9) and the uncharacterised protein encoded by lum (fc 3.5) were decreased (fc 2.5). Molecular pathway analysis revealed four canonical pathways including acute-phase response signalling, liver and retinoid X receptors activation, and intrinsic and extrinsic prothrombin activation pathways as significantly regulated in the treated fish. No significant difference was observed for zinc accumulation in exposed fish compared to controls. In summary, despite no apparent accumulation, ZnO NPs exposure to common carp probably disturbs the fish homeostasis by affecting proteins of the haematological and the immune systems.

Histological changes and antioxidant enzyme activity in signal crayfish (Pacifastacus leniusculus) associated with sub-acute peracetic acid exposure.

Peracetic acid (PAA) is a powerful disinfectant recently adopted as a therapeutic agent in aquaculture. A concentration of 10 mg L(-1) PAA effectively suppresses zoospores of Aphanomyces astaci, the agent of crayfish plague. To aid in establishing safe therapeutic guideline, the effects of PAA on treated crayfish were investigated through assessment of histological changes and oxidative damage. Adult female signal crayfish Pacifastacus leniusculus (n = 135) were exposed to 2 mg L(-1) and 10 mg L(-1) of PAA for 7 days followed by a 7 day recovery period in clean water. Superoxide dismutase activity was significantly lower in gill and hepatopancreas after three days exposure to 10 mg L(1) PAA than in the group treated with 2 mg L(-1) PAA and a control in only clean water. Catalase activity in gill and hepatopancreas remained unaffected by both exposures. Glutathione reductase was significantly decreased in gill of 10 mg L(-1) PAA treated crayfish and increased in group exposed to 2 mg L(-1) compared to control after 7 days exposure. Antioxidant enzyme activity in exposed groups returned to control values after recovery period. Gill, hepatopancreas, and antennal gland showed slight damage in crayfish treated with 2 mg L(-1) of PAA compared to the control group. The extent and frequency of histological alterations were more pronounced in animals exposed to 10 mg L(-1). The gill was the most affected organ, infiltrated by granular hemocytes and displaying malformations of lamella tips and disorganization of epithelial cells. After a 7 day recovery period, the infiltrating cells in affected tissues of the exposed crayfish began to return to normal levels. Results suggested that the given concentrations could be applied to signal crayfish against crayfish plague agent in aquaculture; however, further studies are required for safe use.

Enzymatic and histopathologic biomarkers in the flatfish Euryglossa orientalis from the northwestern Persian Gulf.

Most of the chemicals in the petrochemical sewages cause oxidative stress in marine organisms. Antioxidant enzymes (catalase (CAT) and superoxide dismutase (SOD)) as biomarkers of oxidative stress and liver histopathological alterations were investigated in the current study to evaluate the toxic effects of petrochemical pollutions in flatfish, Euryglossa orientalis The enzymatic and histopathological changes were assessed in the liver of E. orientalis from Khowr-e Jafari (one of the creeks from Khowr-e Musa estuary) and Sajafi harbor as polluted and clean areas, respectively. A significant increase in the antioxidant enzyme activities was observed in response to aquatic pollutions of Khowr-e Jafari. Liver lesions were diagnosed and categorized using standard methods. The results of histopathological examinations showed more lesion scores in the fish from Khowr-e Jafari. Various histopathological changes including hepatocyte degeneration, inflammatory lesions, peliosis hepatis and pancreatic acinar cell adenoma, and increase in the number of pigmented macrophage aggregates were observed in the fish from polluted site. It is suggested that activities of CAT and SOD along with semi-quantitative histopathologic analysis of E. orientalis can be used for biomonitoring programs in Persian Gulf.

Evaluation of the toxic effect of peracetic acid on grass carp (Ctenopharyngodon idella) juveniles.

OBJECTIVES: The aim of present study was to evaluate the effect of peracetic acid (PAA) on haematotological and biochemical indices, antioxidant status, micronucleus induction and histopathological alterations of liver and gill in grass carp. METHODS: Grass carp (Ctenopharyngodon idella) juveniles were exposed to therapeutic concentrations (1, and 3 mg x l(-1)) of PAA for a period of 10 days. Selected haematotological indices--the erythrocyte count (RBC), haematocrit (PCV), haemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC) and leukocyte count (WBC), and biochemical indices--glucose (Glu), total protein (TP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), and lactate dehydrogenase (LDH) were evaluated in plasma. Activity of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR), as well as levels of thiobarbituric acid reactive substances (TBARS) were assessed in gill and liver. Micronucleus frequency in peripheral erythrocytes was counted in control and experimental fish. Histological examinations of gill and liver were performed. RESULTS: No significant differences were found in haematological parameters measured. Statistically significant (p < 0.05) alterations in the activities of AST, CK and LDH were found in treated fish compared to control groups. Fish exposed to 1 mg x l(-1) of PAA showed significantly lower (p < 0.05) SOD activity in liver and gill while catalase activity indicated a significant decrease (p < 0.05) only in gill tissue. Other significant changes were observed in GR activity in gill in both PAA exposed groups, while GR activity in liver remained unchanged. There was no significant difference in the count of micronuclei between control and exposed fish. Haemorrhage, fusion of primary lamellae, degeneration of secondary lamellae, some clubbing on primary and secondary lamellae tips, and lifting of epithelial cells were found in gill tissues in both control and treated fish. CONCLUSION: The results show that PAA could induce alterations in biochemical parameters in blood plasma, antioxidant enzymes response and histopathological changes in gill; however, it seems that these changes are reversible. Subsequently, lower concentration (1 mg x l(-1)) is useable as a treatment concentration for grass carp.

Novel inhibitor discovery against aromatase through virtual screening and molecular dynamic simulation: a computational approach in drug design.

Inhibition of aromatase (CYTP450) as a key enzyme in the estrogen biosynthesis could result in regression of estrogen-dependent tumors and even preventing the promotion of breast cancer. Although today potent steroid and non-steroid inhibitors of aromatase are available, isoflavanone derivatives as natural compounds with least side effects have been described as the candidate for a new generation of aromatase inhibitors. 2a as an isoflavanone derivative is the most potent inhibitor of aromatase, synthesized by Bonfield et al. (2012[7]). In our computational study, the mentioned compound was used as the template for virtual screening. Between 286 selected compounds with 70 % of structural similarity to 2a, 150 of them showed lower docking energy in comparison with 2a. Compound 2a_1 with 11.2 kcal/mol had the lowest docking energy. Interaction of 2a_1 with aromatase was further investigated and compared with 2a and androstenedione (ASD) as a natural substrate of aromatase, through 20 ns of molecular dynamic simulation. Analysis of trajectories showed, while ASD interacts with aromatase through hydrogen bonds and 2a just interacts via hydrophobic forces, 2a_1 not only accommodates in the hydrophobic active site of aromatase in a suitable manner but it also makes a stable coordination with iron atom of aromatase heme group via OB.