Physiological responses in Nile tilapia (Oreochromis niloticus) induced by combined stress of environmental salinity and triphenyltin.

Triphenyltin (TPT) has attracted considerable attention owing to its vitality, bioaccumulation, and lurking damage. TPT widely exists in complex salinity areas such as estuaries and coastal regions. However, there are few studies on the toxicological behavior of TPT under different salinity. In the study, juvenile Nile tilapia (Oreochromis niloticus) were utilized as model animals to investigate the effects of environmental relevant TPT exposure on the osmoregulation and energy metabolism in gill under different salinity. The results showed that salinity and TPT single or combined exposure affected the morphology of the gill tissue. After TPT exposure, Na+-K+-ATPase (NKA) activity significantly decreased at 0 ppt, while NKA and Ca2+-Mg2+-ATPase (CMA) activities significantly increased at 15 ppt. In addition, significantly higher succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) activities were found in the control fish compared to the TPT-exposed ones at 15 ppt. Quantitative real-time PCR results showed that TPT exposure affected the expression of osmoregulation and energy metabolism-related genes under different salinity. Overall, TPT exposure interfered with osmoregulation and energy metabolism under different salinity. The study will provide reference data for assessing the toxicity of organotin compounds in complex-salinity areas.

A new perspective on endocrine disrupting effects of triphenyltin on marine medaka: From brain transcriptome, gut content metabolome and behavior.

Triphenyltin (TPT) is an endocrine contaminant that is often detected in the environment. However, the mechanism of the effects of TPT on biological systems is not fully understood. Here we exposed marine medaka (Oryzias melastigma) to TPT for 21 days. Brain transcriptome, intestinal content metabolism group, and behavior analysis were carried out. Through the comprehensive analysis of multiomics for the in-depth understanding of the ways related to health improvement, we determined that the glycine-serine-threonine metabolic axis was most perturbed by TPT. Through behavioral analysis, it was found that there was behavioral hyperactivity in the exposed group; behavioral hyperactivity may be caused by the interference of TPT with the neuroendocrine system. In order to gain a full understanding of the impacts of TPT on human health, transcriptomic screening of differential genes and an impartial attitude based on bioinformatics were used. Gene-disease interaction analysis using the Comparative Toxicogenomics Database (CTD) revealed the possible effects of TPT on human health. Finally, based on these findings, the relevant adverse outcome pathway (AOP), which is the "epigenetic modification of PPARG leading to adipogenesis," was identified from AOP Wiki. Further research is required to validate the potential AOP of TPT.

Dibutyltin dichloride exposure affects mouse oocyte quality by inducing spindle defects and mitochondria dysfunction.

Dibutyltin dichloride (DBTCl) is a widespread environmental pollutant that is frequently employed as a light and heat sustainer for polyvinyl chloride (PVC) plastics and is a teratogen in vivo. Nevertheless, its destructiveness in mammalian oocytes remains unclear. This study highlighted the consequences of DBTCl vulnerability on mouse oocyte. Our results revealed that exposure to 5.0 mg/kg/day of DBTCl for ten days reduced the number of mature follicles and oocytes in the ovaries and inhibited the meiotic maturation of oocytes. Single-cell transcriptomic analysis indicated that DBTCl exposure interfered with the expression of more than 400 genes in oocytes, including those involved in multiple biological pathways. Specifically, DBTCl exposure impaired spindle assembly and chromosome alignment. In addition, DBTCl exposure caused mitochondrial dysfunction, which led to the accumulation of reactive oxygen species (ROS) and induced apoptosis. In summary, our study illustrates that mitochondrial dysfunction and redox perturbation are the major causes of the reduced quality of oocytes exposed to DBTCl.

Reproductive toxicity of environmental levels of triphenyltin to the marine rotifer, Brachionus plicatilis.

Triphenyltin (TPT) is a representative organotin often used in marine antifouling coatings, herbicides, and pesticides. However, leaching of TPT into water may be toxic to aquatic life. In this study, environmental concentrations of TPT were used to explore reproductive toxicity of TPT to Brachionus plicatilis, a representative marine rotifer. Toxicity was examined at individual, biochemical, and molecular levels and via phenotypic traits. Rotifers exposed to 10 ng/L TPT group showed increased population size, improved reproductive rate, and a higher weekly growth rate. At 100 ng/L TPT group, the greatest degree of oxidative damage was seen. Exposure to 200 ng/L TPT group shorten generation time, delayed reproduction, and obscured the reproductive peak. Expression of the Vasa gene associated with reproduction was increased after exposure to 10 and 200 ng/L TPT group and decreased at 100 ng/L TPT group. High concentrations of TPT reduced rotifer body length and width and slowed swimming speed. Findings provide a better understanding of the adverse effects of changing TPT concentrations on marine rotifer, by the life cycle parameters, oxidative stress defense mechanisms, expression of a gene related to reproduction, and phenotypic traits. This paper firstly analyzed the reproductive toxicity of environmental levels of organotin compounds to zooplankton, which provided new data support for the comprehensive evaluation of its marine ecological toxicity.

Toxicity of organotin compounds and the ecological risk of organic tin with co-existing contaminants in aquatic organisms.

Although organotin (OT) use is restricted worldwide, with the development of industry and agriculture, a large amount of OT is still discharged into aquatic environments. These OTs may interact with other pollutants that cause adverse biological effects (through bioaccumulation and/or toxicity), resulting in combined toxicity. Most research on OTs have focused on the exposure of a single analyte. Information on the toxicity of OTs and coexisting pollutants is quite limited, but is developing rapidly. This is the first review paper evaluating the current state of knowledge on the combined effects of OTs with co-pollutants. This paper reviews 1) the degradation of organotin; and 2) the combined toxicity of OTs and emerging pollutants (EP), heavy metals, and organic pollutants. Future research needs are discussed to better understand the risks associated with co-exposure to OT pollutants.

A mass spectrometry-based approach gives new insight into organotin-protein interactions.

In this study, the combination of speciation analysis and native mass spectrometry is presented as a powerful tool to gain new insight into the diverse interactions of environmentally relevant organotin compounds (OTCs) with proteins. Analytical standards of model proteins, such as ß-lactoglobulin A (LGA), were thereby incubated with different phenyl- and butyltins. For adduct identification and characterization, the incubated samples were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and electrospray ionization-mass spectrometry (ESI-MS) in combination with size exclusion chromatography (SEC). It allowed for a mild separation, which was most crucial to preserve the acid-labile organotin-protein adducts during their analyses. The binding of triorganotin compounds, such as triphenyltin, was shown to be sulfhydryl-directed by using cysteine-specific protein labeling. However, the sole availability of reduced cysteine residues in proteins did not automatically enable adduct formation. This observation complements previous studies and indicates the necessity of a highly specific binding pocket, which was identified for the model protein LGA via enzymatic digestion experiments. In contrast to triorganotins, their natural di- and mono-substituted degradation products, such as dibutyltin, revealed to be less specific regarding their binding to several proteins. Further, it also did not depend on reduced cysteine residues within the protein. In this context, they can probably act as linker molecules, interconnecting proteins, and leading to dimers and probably to higher oligomers. Furthermore, dibutyltin was observed to induce hydrolysis of the protein's peptide backbone at a specific site. Concerning unknown long-term toxic effects, our studies emphasize the importance of future studies on di- and mono-substituted OTCs.

Functional characterization of retinoid X receptor with an emphasis on the mediation of organotin poisoning in the Pacific oyster (Crassostrea gigas).

Marine mollusks suffer harmful effects due to environmental organotin compounds such as tributyltin (TBT) and triphenyltin (TPT). It is known that gastropod imposex caused by organotins is mediated by a key nuclear receptor, retinoid X receptor (RXR). The organotin-mediated toxic effects on oysters grown in seawater include a thicker shell, incomplete growth, disrupted development and a high rate of mortality. However, few studies have been conducted to determine the role of RXR in the toxic effects of organotins on bivalves. Here, we cloned an RXR homolog (CgRXR) from the Pacific oyster (Crassostrea gigas) and characterized its molecular function. Expression of the CgRXR RNA transcripts was assessed in whole developmental stages and tissues, with the highest expression detected in the blastula and mantle, respectively. The subcellular localization experiment confirmed that CgRXR protein was expressed in the nucleus exclusively as a nuclear receptor. Electrophoretic mobility shift assay indicated that CgRXR could bind to the DNA motifs DR0-DR5. The dual-luciferase reporter assay demonstrated that the transcriptional activity of CgRXR was activated by conserved ligands (9-cis retinoic acid and cis-4,7,10,13,16,19-docosahexanoic acid) and endocrine-disrupting chemicals (TBT and TPT). These results revealed the conserved gene function involved in protein localization, ligand binding and heterodimer formation with thyroid hormone receptor. However, the DNA binding properties of CgRXR differed from those of other invertebrate and vertebrate RXRs. CgRXR had the highest expression level in the blastula and mantle, and the disrupted development or shell malformation induced by organotins suggested a possible correlation of CgRXR with shell formation in bivalves. The results indicated the potential involvement of CgRXR in the toxic effects of organotins (TBT and TPT) through signaling pathway disruption. Functional characterization of CgRXR will help us better understand the endocrinology of bivalves.

Of Retinoids and Organotins: The Evolution of the Retinoid X Receptor in Metazoa.

Nuclear receptors (NRs) are transcription factors accomplishing a multiplicity of functions, essential for organismal homeostasis. Among their numerous members, the retinoid X receptor (RXR) is a central player of the endocrine system, with a singular ability to operate as a homodimer or a heterodimer with other NRs. Additionally, RXR has been found to be a critical actor in various processes of endocrine disruption resulting from the exposure to a known class of xenobiotics termed organotins (e.g., tributyltin (TBT)), including imposex in gastropod molluscs and lipid perturbation across different metazoan lineages. Thus, given its prominent physiological and endocrine role, RXR is present in the genomes of most extant metazoan species examined to date. Here, we expand on the phylogenetic distribution of RXR across the metazoan tree of life by exploring multiple next-generation sequencing projects of protostome lineages. By addressing amino acid residue conservation in combination with cell-based functional assays, we show that RXR induction by 9-cis retinoic acid (9cisRA) and TBT is conserved in more phyla than previously described. Yet, our results highlight distinct activation efficacies and alternative modes of RXR exploitation by the organotin TBT, emphasizing the need for broader species sampling to clarify the mechanistic activation of RXR.

Uptake and elimination of butyl- and phenyltins by Ceratophyllum demersum L.

The widespread occurrence and distribution of organotin compounds (OTCs) in both marine and freshwater ecosystems has aroused considerable concerns in most countries worldwide. In this work, individual kinetics of the elimination of three butyltins and three phenyltins from C. demersum L. were systematically studied for over 240 h in clean water after a 48h period of accumulation. All OTCs were rapidly metabolized to nontoxic inorganic tin by C. demersum L. through stepwise debutylation or dephenylation. In addition to inorganic tin, monobutyltin (MBT) and monophenyltin (MPT) were the primary degradation products of tributyltin (TBT) and triphenyltin (TPT), with small amounts of dibutyltin (DBT) and diphenyltin (DPT), respectively, also being present. The estimated half-life of TPT (240 h) in C. demersum L. was longer than that of TBT (100 h), although the TPT was less hydrophobic. The corresponding degradation mechanisms may be attributed to a cascade of enzymatic reactions of CYP450 enzymes in C. demersum L. The pH played an important role in both plant growth and TBT degradation. Although pH 8.9 was more suitable for C. demersum L. growth, it uptook and metabolized more TBT at pH 5.0, which may be because the cationic species TBT+ (at pH 5.0) was metabolized more easily than the neutral hydroxide species TBTOH (at pH 8.9). C. demersum L. may thus be the plant with the most potential for the remediation of OTC-contaminated freshwater environments.

Organotins in obesity and associated metabolic disturbances.

The objective of the present study was to review the mechanisms of organotin-induced adipogenesis, obesity, and associated metabolic disturbances. Peroxisome proliferator-activated receptor γ (PPARγ) and retinoid X receptor α (RXRα) activation is considered as the key mechanism of organotin-induced adipogenesis. Particularly, organotin exposure results in increased adipogenesis both in cell and animal models. Moreover, transgenerational inheritance of organotin-induced obese phenotype was demonstrated in vivo. At the same time, the existing data demonstrate that organotin compounds (OTCs) induces aberrant expression of PPARγ-targeted genes, resulting in altered of adipokine, glucose transporter, proinflammatory cytokines levels, and lipid and carbohydrate metabolism. The latter is generally characterized by hyperglycemia and insulin resistance. Other mechanisms involved in organotin-induced obesity may include estrogen receptor and corticosteroid signaling, altered DNA methylation, and gut dysfunction. In addition to cellular effects, organotin exposure may also affect neural circuits of appetite regulation, being characterized by neuropeptide Y (NPY) up-regulation in parallel with of pro-opiomelanocortin (POMC), Agouti-related protein (AgRP), and cocaine and amphetamine regulated transcript (CART) down-regulation in the arcuate nucleus. These changes result in increased orexigenic and reduced anorexigenic signaling, leading to increased food intake. The existing data demonstrate that organotins are potent adipogenic agents, however, no epidemiologic studies have been performed to reveal the association between organotin exposure and obesity and the existing indirect human data are contradictory.

Methylation and dealkykation of tin compounds by sulfate- and nitrate-reducing bacteria.

In this study, axenic cultures of sulfate-reducing (SRB) and nitrate-reducing (NRB) bacteria were examined for their ability to methylate inorganic tin and to methylate or dealkylate butyltin compounds. Environmentally relevant concentrations of natural abundance tributyltin (TBT) and 116Sn-enriched inorganic tin were added to bacterial cultures to identify bacterial-mediated methylation and dealkylation reactions. The results show that none of the Desulfovibrio strains tested was able to induce any transformation process. In contrast, Desulfobulbus propionicus strain DSM-6523 degraded TBT either under sulfidogenic or non-sulfidogenic conditions. In addition, it was able to alkykate 116Sn-enriched inorganic tin leading to the formation of more toxic dimethyltin and trimethyltin. A similar capacity was observed for incubations of Pseudomonas but with a much greater dealkykation of TBT. As such, Pseudomonas sp. ADR42 degraded 61% of the initial TBT under aerobic conditions and 35% under nitrate-reducing conditions. This is the first work reporting a simultaneous TBT degradation and a methylation of both inorganic tin species and TBT dealkykation products by SRB and NRB under anoxic conditions. These reactions are environmentally relevant as they can control the mobility of these compounds in aquatic ecosystems; as well as their toxicity toward resident organisms.

Poly Organotin Acetates against DNA with Possible Implementation on Human Breast Cancer.

Two known tin-based polymers of formula {[R3Sn(CH3COO)]n} where R = n-Bu⁻ (1) and R = Ph⁻ (2),were evaluated for their in vitro biological properties. The compounds were characterized via their physical properties and FT-IR, 119Sn Mössbauer, and ¹H NMR spectroscopic data. The molecular structures were confirmed by single-crystal X-Ray diffraction crystallography. The geometry around the tin(IV) ion is trigonal bi-pyramidal. Variations in O⁻Sn⁻O···Sn' torsion angles lead to zig-zag and helical supramolecular assemblies for 1 and 2, respectively. The in vitro cell viability against human breast adenocarcinoma cancer cell lines: MCF-7 positive to estrogens receptors (ERs) and MDA-MB-231 negative to ERs upon their incubation with 1 and 2 was investigated. Their toxicity has been studied against normal human fetal lung fibroblast cells (MRC-5). Compounds 1 and 2 exhibit 134 and 223-fold respectively stronger antiproliferative activity against MDA-MB-231 than cisplatin. The type of the cell death caused by 1 or 2 was also determined using flow cytometry assay. The binding affinity of 1 and 2 towards the CT-DNA was suspected from the differentiation of the viscosity which occurred in the solution containing increasing amounts of 1 and 2. Changes in fluorescent emission light of Ethidium bromide (EB) in the presence of DNA confirmed the intercalation mode of interactions into DNA of both complexes 1 and 2 which have been ascertained from viscosity measurements. The corresponding apparent binding constants (Kapp) of 1 and 2 towards CT-DNA calculated through fluorescence spectra are 4.9 × 104 (1) and 7.3 × 104 (2) M-1 respectively. Finally, the type of DNA binding interactions with 1 and 2 was confirmed by docking studies.

Critical analysis of the relationship between imposex and butyltin body burden in Nassarius reticulatus and Nucella lapillus.

Imposex is a disorder caused by organotins, mainly tributyltin, which results in the appearance of male sexual characteristics in females of gastropod mollusks. The main objective of this work was to make a critical analysis of the relationship between imposex and butyltin body burdens in Nucella lapillus and Nassarius reticulatus. Specifically, this study evaluates possible additive effects among butyltins, proposes scales of effects based on robust statistical criteria as alternatives to existing ones and defines the body burdens of TBT in N. lapillus and N. reticulatus corresponding to the assessment classes (ACs) of the Vas Deferens Sequence Index (VDSI) established by OSPAR. Data of organotin body burdens and biological effects was retrieved from the ICES Dataset and from scientific literature. All responses, except the percentage of females displaying Imposex (IMPF) in Nucella lapillus, showed a sigmoidal profile regarding to the body burden of mono- (MBT), di- (DBT) and tributyltin and sum of butyltins (SumBTs). TBT and the SumBTs were better indicators of the VDSI or Relative Penis Size Index/Relative Penis Length Index (RPSI/RPLI) responses than MBT or DBT in most cases. From a statistical point of view, RPSI/RPLI and VDSI were better indicators of contamination by TBT than IMPF, although both RPSI and RPLI showed lower sensitivity than VDSI. The model used for describing the joint effect of butyltins provided a statistically significant fitting to the data assuming a null effect for both MBT and DBT for N. lapillus, and a lower toxic contribution of MBT and DBT with respect to TBT for N. reticulatus. RPSI or RPLI values, equivalent to the ACs for VDSI, were proposed as alternative criteria when measuring moderate to high levels of imposex. TBT concentrations in N. reticulatus and N. lapillus tissues, corresponding to the ACs were calculated and provided valuable information for cross-species comparisons.

SugE belongs to the small multidrug resistance (SMR) protein family involved in tributyltin (TBT) biodegradation and bioremediation by alkaliphilic Stenotrophomonas chelatiphaga HS2.

Tributyltin (TBT) used in a variety of industrial processes, subsequent discharge into the environment, its fate, toxicity and human exposure are topics of current concern. TBT degradation by alkaliphilic bacteria may be a key factor in the remediation of TBT in high pH contaminated sites. In this study, Stenotrophomonas chelatiphaga HS2 were isolated and identified from TBT contaminated site in Mediterranean Sea. S. chelatiphaga HS2 has vigor capability to transform TBT into dibutyltin and monobutyltin (DBT and MBT) at pH 9 and 7% NaCl (w/v). A gene was amplified and characterized from strain HS2 as SugE protein belongs to SMR protein family, a reverse transcription polymerase chain reaction analysis confirmed that SugE protein involved in the TBT degradation by HS2 strain. TBT bioremediation was investigated in stimulated TBT contaminated sediment samples (pH 9) using S chelatiphaga HS2 in association with E. coli BL21 (DE3)-pET28a(+)-sugE instead of S chelatiphaga HS2 alone reduced significantly the TBT half-life from 12d to 5d, although no TBT degradation appeared using E. coli BL21 (DE3)-pET28a(+)-sugE alone. This finding indicated that SugE gene increased the rate and degraded amount of TBT and is necessary in enhancing TBT bioremediation.

Tributyltin induces premature hatching and reduces locomotor activity in zebrafish (Danio rerio) embryos/larvae at environmentally relevant levels.

Tributyltin (TBT) is an organotin compound that is the active ingredient of many biocides and antifouling agents. In addition to its well established role as an endocrine disruptor, TBT is also associated with adverse effects on the nervous system and behavior. In this study, zebrafish (Danio rerio) embryos were exposed to environmentally relevant concentrations of TBT (0.01, 0.1, 1 nM) to determine how low levels affected development and behavior. Fish exposed to 1 nM TBT hatched earlier when compared to controls. Following a 96-h exposure, total swimming distance, velocity, and activity of zebrafish larvae were reduced compared to controls. To identify putative mechanisms for these altered endpoints, we assessed embryo bioenergetics and gene expression. We reasoned that the accelerated hatch time could be related to ATP production and energy, thus embryos were exposed to TBT for 24 and 48-h exposure prior to hatch. There were no differences among groups for endpoints related to bioenergetics (i.e. basal, ATP-dependent, and maximal respiration). To address mechanisms related to changes in behavioral activity, we measured transcripts associated with muscle function (myf6, myoD, and myoG) and dopamine signaling (th, dat, dopamine receptors) as dopamine regulates behavior. No transcript was altered in expression by TBT in larvae, suggesting that other mechanisms exist that may explain changes in higher level endpoints. These results suggest that endpoints related to the whole animal (i.e. timing of hatch and locomotor behavior) are more sensitive to environmentally-relevant concentrations of TBT compared to the molecular and metabolic endpoints examined here.

Microwave-assisted synthesis of mixed ligands organotin(IV) complexes of 1,10-phenanthroline and l-proline: Physicochemical characterization, DFT calculations, chemotherapeutic potential validation by in vitro DNA binding and nuclease activity.

Diorganotin(IV) and triphenyltin(IV) derivatives of L-proline (HPro) having general formula R2Sn(Pro)2 (R=n-Bu (1), Ph (2)) and Ph3Sn(Pro) (3), respectively, and the mixed ligands di-/triorganotin(IV) derivatives of L-proline and 1,10-phenanthroline (phen) with general formula [R2Sn(Pro)(Phen)Cl] and [R3Sn(Pro)(Phen)] (where R=Me (4 and 7), n-Bu (5 and 8), Ph (6 and 9)), respectively, have been synthesized by microwave-assisted method and characterized by elemental analysis, IR, NMR (1H, 13C and 119Sn) and DART-mass spectral studies. The results suggest bicapped tetrahedron or a skew trapezoidal-bipyramid geometry for R2Sn(Pro)2, a distorted tetrahedral geometry for Ph3Sn(Pro) and a distorted octahedral geometry for [R2Sn(Pro)(Phen)Cl] and [Ph3Sn(Pro)(Phen)] around the Sn atom, and the same has been validated by density functional theory calculations (DFT). In vitro DNA binding studies of 1-9 have been investigated by UV-Vis, fluorescence and circular dichroism titrations, viscosity and DNA melting experiments. The observed hypochromic shift in UV-Vis and fluorescence studies evidenced a partial intercalative mode of binding of complexes to CT-DNA. The binding affinity and quenching ability have been quantified in terms of intrinsic binding constant (Kb) and Stern-Volmer quenching constant (Ksv). The determined values suggest that di- and triorganotin(IV) derivatives of L-proline possess lesser affinity to bind with CT-DNA in comparison to the mixed ligands di-/triorganotin(IV) derivatives of L-proline and 1,10-phenanthroline. The partial intercalative mode of binding of these complexes with CT DNA has also been supported by a change in the viscosity and melting point of DNA as well as a change in the intensity of positive and negative bands in circular dichroism spectra. The cleavage studies by agarose gel electrophoresis indicate effective cleavage of supercoiled plasmid DNA into its nicked form by all the complexes and even to its linear form in presence of 9.

Organotin compounds in Brachidontes rodriguezii mussels from the Bahía Blanca Estuary, Argentina.

Levels of tributyltin and its breakdown compounds, including the first record of monobutyltin (MBT) in history for Latin America, were determined in native mussels (Brachidontes rodriguezii) by means of CG-MS, after extraction/derivatization assisted by ultrasound. The samples were collected in 2013 in Bahía Blanca Estuary (Argentina) at 6 sites, which reflect different levels of maritime activities. Total butyltins (TBts = TBT+ DBT+ MBT) levels ranged from 19.64 to 180.57ng Sn g-1 dry weight. According to the Oslo-Paris commission, the results indicated that 73.9% of mussels could be under biological effects risks associated with TBT pollution. In accordance with the calculated bioaccumulation factors, approximately 56% of samples appeared to have accumulated TBT through the sediments. All sampling sites were shown to be impacted by organotin compounds (OTCs) showing variable levels through seasons, which could be related with the variation of the water temperature. Degradation index analyses suggested aged inputs of TBT possibly under a general degradation process at the area of study. In addition, the occurrence of DBT and MBT could not be uniquely attributed to the degradation pathway of the TBT; in fact, results outlined the possible contribution of some punctual and diffuse sources at the area such as proximity to plastic industries, industrial effluents, sewage outlets and domestic wastewaters.

Triphenyltin recognition by primary structures of effector proteins and the protein network of Bacillus thuringiensis during the triphenyltin degradation process.

Herein, triphenyltin (TPT) biodegradation efficiency and its transformation pathway have been elucidated. To better understand the molecular mechanism of TPT degradation, the interactions between amino acids, primary structures, and quaternary conformations of effector proteins and TPT were studied. The results verified that TPT recognition and binding depended on amino acid sequences but not on secondary, tertiary or quaternary protein structure. During this process, TPT could change the molecular weight and isoelectric point of effector proteins, induce their methylation or demethylation, and alter their conformation. The effector proteins, alkyl hydroperoxide reductase and acetyl-CoA acetyltransferase, recognizing TPT were crucial to TPT degradation. Electron transfer flavoprotein subunit alpha, phosphoenolpyruvate carboxykinase, aconitate hydratase, branched-chain alpha-keto acid dehydrogenase E1 component, biotin carboxylase and superoxide dismutase were related to energy and carbon metabolism, which was consistent with the results in vivo. The current findings develop a new approach for investigating the interactions between proteins and target compounds.

In vitro evaluation of the cytotoxic and bactericidal mechanism of the commonly used pesticide triphenyltin hydroxide.

Triphenyltin hydroxide (TPTH) is a widely used pesticide that is highly toxic to a variety of organisms including humans and a potential contender for the environmental pollutant. In the present study, the cytotoxic mechanism of TPTH on mammalian cells was analyzed using HeLa cells and the antibacterial activity was analyzed using B. subtilis and E. coli cells. TPTH inhibited the growth of HeLa cells with a half-maximal inhibitory concentration of 0.25 µM and induced mitotic arrest. Immunofluorescence microscopy analysis showed that TPTH caused strong depolymerization of interphase microtubules and spindle abnormality with the appearance of colchicine type mitosis and condensed chromosome. TPTH exhibited high affinity for tubulin with a dissociation constant of 2.3 µM and inhibited the in vitro microtubule assembly in the presence of glutamate as well as microtubule-associated proteins. Results from the molecular docking and in vitro experiments implied that TPTH may have an overlapping binding site with colchicine on tubulin with a distance of about 11 Å between them. TPTH also binds to DNA at the A-T rich region of the minor groove. The data presented in the study revealed that the toxicity of TPTH in mammalian cells is mediated through its interactions with DNA and its strong depolymerizing activity on tubulin. However, its antibacterial activity was not through FtsZ, the prokaryotic homolog of tubulin but perhaps through its interactions with DNA.

Levels of Organotin Compounds in Selected Fish Species from the Arabian Gulf.

In the present work, data on the levels of hazardous Organotin compounds in eight commercially important fish species, caught from Arabian Gulf, has been reported. Highest levels of tributyltin (TBT) (98.5 ng/g dry weight) were detected in Epinephelus Tauvina whereas minimum (43.7 ng/g) were found in Acanthoparagus Bifasciatus. Highest levels of triphenyltin (TPT) were detected in Lethrinus Miniatus (107.5 ng/g) whereas lowest were encountered in Acanthoparagus Bifasciatus (64.9 ng/g). Highest value of total butyltin compounds (∑BT) were found in emperors (Lethrinus Miniatus) (228.4 ng/g) whereas minimum was found in Acanthoparagus Bifasciatus (126.4 ng/g). Similarly highest value of total phenyltin compounds (∑PT) was encountered in Epinephelus Tauvina (281.9 ng/g) followed closely by Acanthoparagus Bifasciatus (281.7 ng/g). In addition, the estimated daily intake (EDI) of the local population from consumption of these fish was also evaluated. Highest EDI was found to be 10.8 ng/kg bw/day for epinephelus microdan. The data are also compared internationally.