Kinetic, spectroscopic and computational docking study of the inhibitory effect of the pesticides 2,4,5-T, 2,4-D and glyphosate on the diphenolase activity of mushroom tyrosinase

The inhibitory effect of 2,4,5-T, 2,4-D, glyphosate and paraquat on the diphenolase activity of mushroom tyrosinase for oxidation of L-DOPA has been investigated by kinetic measurements, fluorescence spectroscopy and computational docking analysis. 2,4,5-T and 2,4-D inhibit the diphenolase activity of the enzyme following a competitive mechanism, while glyphosate is a mixed inhibitor according to Lineweaver-Burk kinetic analysis. The inhibitory activity follows the order glyphosate >2,4,5-T > 2,4-D with IC50 values of 65, 90 and 106 μM, respectively. Intrinsic tyrosinase fluorescence quenching and computational docking analysis suggest that 2,4,5-T and 2,4-D interact with the active site of the enzyme through hydrophobic interactions, while glyphosate also interacts with external residues of the active site of the enzyme by hydrogen bonding and hydrophilic interactions inducing conformational changes in the protein structure.

2,4,5-Trichlorophenoxyacetic acid promotes somatic embryogenesis in the rose cultivar "Livin' Easy" (Rosa sp.)

Somatic embryogenesis (SE) offers vast potential for the clonal propagation of high-value roses. However, some recalcitrant cultivars unresponsive to commonly employed SE-inducing agents and low induction rates currently hinder the commercialization of SE technology in rose. Rose SE technology requires improvement before it can be implemented as a production system on a commercial scale. In the present work, we assessed 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), a synthetic auxin not previously tested in rose, for its effectiveness to induce SE in the rose cultivar "Livin' Easy" (Rosa sp.). We ran a parallel comparison to the commonly used 2,4-dichlorophenoxyacetic acid (2,4-D). We tested each auxin with two different basal media: Murashige and Skoog (MS) basal medium and woody plant medium (WPM). MS medium resulted in somatic embryo production, whereas WPM did not. 2,4,5-T induced SE over a greater concentration range than 2,4-D's and resulted in significantly greater embryo yields. 2,4,5-T at a concentration of 10 or 25 microM was better for embrygenic tissue initiation than 2,4,5-T at 5 microM. Further embryo development occurred when the tissue was transferred to plant growth regulator (PGR) free medium or media with 40% the original auxin concentration. However, the PGR-free medium resulted in a high percentage of abnormal embryos (32.31%) compared to the media containing auxins. Upon transfer to germination medium, somatic embryos successfully converted into plantlets at rates ranging from 33.3 to 95.2%, depending on treatment. Survival rates 3 months ex vitro averaged 14.0 and 55.6% for 2,4-D- and 2,4,5-T-derived plantlets, respectively. Recurrent SE was observed in 60.2% of the plantlets growing on germination medium. This study is the first report of SE in the commercially valuable rose cultivar 'Livin' Easy' (Rosa sp.) and a suitable methodology was developed for SE of this rose cultivar.

[Raoultella planticola, a new strain degrading 2,4,5-trichlorophenoxyacetic acid]

A new strain that degrades the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) was isolated from soil, which was exposed to factors related to the petrochemical industry. According to its physiological, biochemical, cultural, and morphological traits, together with the sequence of the 16S rRNA gene, the strain was identified as Raoultella planticola 33-4ch. The strain could consume 2,4,5-T as a sole source of carbon and energy. The amount of 2,4,5-T in the culture medium decreased by 51% after five days of incubation. Raoultella planticola 33-4ch consumes 2,4,5-T to produce 4-chlorophenoxyacetic, phenoxyacetic, and 3-methyl-2,6-dioxo-4-hexenoic acids.

[Inhibitory effects of phenolic ecotoxicants on photobacteria at various pH values]

Kinetic characteristics of light emission by intact cells of the photobacteria Photobacterium phosphoreum and Vibrio harveyi at pH 5.5, 7.0, and 8.0 were studied as well as specific features of inhibitory effects of 2,4-di- and 2,4,5-triphenoxyacetic acids (2,4-D and 2,4,5-T), pentachlorophenol (PCP), and 2,6-dimethylphenol (2,6-DMP) at the same pH values. Nonstationarity of emission kinetics was observed at all the pH values studied. Exponential luminescence decay in a 60-sec range was observed at pH 5.5; a 5-min luminescence activation, at pH 7.0 and 8.0. The cell respiratory activity drops by over one order of magnitude at pH 5.5 compared with the activities at pH 7.0 and 8.0. The inhibitory effects of 2,4-D, 2,4,5-T, and PCP differ by one-two orders of magnitude depending on pH. The maximal cell sensitivity to these compounds appears at pH 5.5; the minimal, at pH 8.0. The effect of 2,6-DMP is independent of pH. As is demonstrated, it is hydrophobicity of the molecule and pK values of the toxicants that determine the inhibitory effect. Characteristic of the substrate-starved photobacterial cells are higher sensitivity to chlorophenolic compounds compared with the cells provided with high energy supply at all the pH values.

2,4,5-T and 2,4,5-TCP induce oxidative damage in human erythrocytes: the role of glutathione

The molecular basis of the toxic properties of phenoxy herbicides in humans and animals has been insufficiently studied. In this study, damage parameters [levels of reduced glutathione (GSH) and total glutathione; activity of glutathione reductase (GR); activities of catalase (CAT) and superoxide dismutase (SOD); levels of adenine nucleotides and adenine energy charge (AEC)] were measured in human erythrocytes exposed in vitro to 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and its metabolite 2,4,5-trichlorophenol (2,4,5-TCP). Both 2,4,5-T and 2,4,5-TCP decreased the level of reduced glutathione (GSH) in erythrocytes in comparison to the control, but did not significantly change the total glutathione (2GSH + GSSG). This suggests that GSH concentration decreases concomitantly with an increase in oxidized glutathione (GSSG). 2,4,5-TCP at 100 ppm significantly decreased catalase and SOD activities. 2,4,5-T and 2,4,5-TCP did not significantly change the activity of glutathione reductase. 2,4,5-TCP decreased the level of ATP and increased the content of ADP and AMP, indicating a fall in AEC. 2,4,5-T and 2,4,5-TCP significantly changed the erythrocyte morphology. All these data are evidence of oxidative stress in erythrocytes incubated with 2,4,5-T and 2,4,5-TCP; the stress appears to be more intense in the case of 2,4,5-TCP.

2,4,5-Trichlorophenoxyacetic acid inhibits apoptosis in PC12 cells

2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) is an endocrine disrupter that exerts cytotoxic effects on organisms. In this study, the influence of 2,4,5-T at low concentrations on apoptosis in PC 12 cells was investigated. Although no apoptotic features were observed in PC12 cells treated with 2,4,5-T, it inhibited the DNA fragmentation induced by serum deprivation. In addition, the cell viability of PC12 cells increased after treatment with 2,4,5-T. In conclusion, 2,4,5-T suppressed the apoptosis of the cultured cells. Since apoptosis is a morphological and biochemical description of a physiological mechanism of cell death that is commonly associated with programmed events necessary for development of individuals and organs, the inhibitory effect of 2,4,5-T on apoptosis might cause serious damage to cell homeostasis and differentiation.

Protection of tomato seed germination from the inhibitory effect of 2,4,5-trichlorophenoxyacetic acid by inoculation of soil with Burkholderia cepacia AC1100

The effect of 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) on the germination and seedling vigor of different crop seeds was tested. Seeds of rice, maize, sorghum, finger millet, and horse gram were comparatively more tolerant to the chemical with no marked effect up to a concentration of 200 mg 2,4,5-T L(-)(1) as tested by the filter paper method. Tomato and brinjal (egg plant) were highly susceptible. Even at 5 and 10 mg 2,4,5-T L(-)(1), marked reduction in the germination and seedling vigor of tomato and egg plant, respectively, was observed. At 20 and 30 mg L(-)(1), the germination of tomato and egg plant seeds, respectively, were completely inhibited on filter paper, whereas the inhibitory concentrations in soil was 40 mg 2,4,5-T kg(-)(1) soil. Several abnormalities were observed in the chemically affected seedlings. Protease activity of the seeds germinating in the presence of the chemical was drastically reduced. Bioremediation of the chemically contaminated soil with Burkholderia cepacia AC1100, by inoculation of the soil 7 days before sowing the seeds, completely protected the seeds, resulting in normal germination and an improved seedling vigor.

Effect of some herbicides on the production of lysine by Azotobacter chroococcum

Production of lysine by Azotobacter chroococcum strain H23 was studied in chemically-defined media amended with different concentrations of alachlor, metolachlor, 2,4-D, 2,4,5-T and 2,3,6-TBA. The presence of 5, 10, and 50 micrograms/ml of alachlor or 2,3,6-TBA significantly decreased quantitative production of lysine. However, the presence 2,4-D or 2,4,5-T at concentrations of 10 and 50 micrograms/ml enhanced the production of lysine. Quantitative production of lysine was not affected as consequence of the addition of metolachlor to the culture medium, showing that the release lysine to the culture media by A. chroococcum was not affected by that herbicide.

Induction of the multispecific organic anion transporter (cMoat/mrp2) gene and biliary glutathione secretion by the herbicide 2,4,5-trichlorophenoxyacetic acid in the mouse liver

The canalicular multispecific organic anion transporter, cMoat, is an ATP-binding-cassette protein expressed in the canalicular domain of hepatocytes. In addition to the transport of endo- and xenobiotics, cMoat has also been proposed to transport GSH into bile, the major driving force of bile-acid-independent bile flow. We have shown previously that the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), a peroxisome-proliferator agent, significantly increases bile-acid-independent bile flow in mice. On this basis, the effect of the herbicide on cMoat gene expression was studied. A 3.6-fold increase in cMoat mRNA levels and a 2.5-fold increase in cMoat protein content were observed in the liver of mice fed on a diet supplemented with 0.125% 2,4,5-T. These effects were due to an increased rate of gene transcription (3.9-fold) and were not associated with peroxisome proliferation. Significant increases in bile flow (2.23+/-0.39 versus 1.13+/-0.15 microl/min per g of liver; P<0.05) and biliary GSH output (7.40+/-3.30 versus 2.65+/-0.34 nmol/min per g of liver; P<0.05) were observed in treated animals. The hepatocellular concentration of total glutathione also increased in hepatocytes of treated mice (10.95+/-0.84 versus 5.12+/-0.47 mM; P<0.05), because of the induction (2.4-fold) of the heavy subunit of the gamma-glutamylcysteine synthetase (GCS-HS) gene. This is the first model of co-induction of cMoat and GCS-HS genes in vivo in the mouse liver, associated with increased glutathione synthesis and biliary glutathione output. Our observations are consistent with the hypothesis that the cMoat transporter plays a crucial role in the secretion of biliary GSH.

Effect of chlorophenoxyacetic acid herbicides on glycine conjugation of benzoic acid

1. 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) (0.1-0.5 mmol/kg i.p.) delayed the disappearance of injected benzoate from blood and diminished the urinary excretion of the formed benzoylglycine, but elevated the blood levels of benzoylglycine in rat, suggesting that these herbicides interfere with both the formation and the renal transport of benzoylglycine. 2. Inhibition of the renal excretion of benzoylglycine by 2,4-D or 2,4,5-T (0.5 mmol/kg i.p.) was directly demonstrated in rat injected with benzoylglycine. 3. Inhibition of benzoylglycine formation from benzoic acid by 2,4-D or 2,4,5-T (0.5 mmol/kg i.p.) was directly demonstrated in renal pedicles-ligated rats injected with benzoate. 4. Neither 2,4-D nor 2,4,5-T influenced the hepatic concentrations of ATP, coenzyme A (CoA) or glycine; therefore, it is unlikely that they inhibit glycine conjugation of benzoic acid by diminishing the availability of co-substrates. 5. Although the chlorophenoxyacetic acids did not appear to be a substrate for the mitochondrial acyl-CoA synthetases, both 2,4-D and 2,4,5-T diminished the activity of benzoyl-CoA synthetase (but not that of benzoyl-CoA:glycine N-acyltransferase) in solubilized hepatic mitochondria. These findings suggest that 2,4-D and 2,4,5-T impair benzoylglycine formation in rat by inhibiting benzoyl-CoA synthetase.

Purification and characterization of maleylacetate reductase from Nocardioides simplex 3E utilizing phenoxyalcanoic herbicides 2,4-D and 2,4,5-T

Maleylacetate reductase was isolated and purified from the Gram-positive strain Nocardioides simplex 3E which is able to utilize the phenoxyalcanoic herbicides 2,4-D and 2,4,5-T. Cells were grown on 2,4-D as the sole carbon source. The enzyme was purified by 380-fold with 3.0% yield. The purified maleylacetate reductase is a homodimer with subunit molecular mass of 37 kD. The enzyme required NADH as a cofactor; the Km for maleylacetate is 25 microM; Vmax (with NADH as cofactor) and kcat are 185 U/mg and 6845 min-1, respectively. The enzyme is very unstable; its pH and temperature optima are at 7.0-7.1 and 50 degrees C, respectively.

Overexpression of mdr2 gene by peroxisome proliferators in the mouse liver

BACKGROUND

In mice, fibrates induce mdr2 gene expression, and its encoded P-glycoprotein in the canalicular domain of hepatocytes, as well as increasing biliary phospholipid output. It is not known whether this effect is restricted to fibrates or is a common property of peroxisome proliferators.

AIMS

To test the effect of structurally unrelated peroxisome proliferators on mdr2 gene expression and biliary phospholipid output, and to explore the molecular mechanism(s) of mdr2 gene induction.

METHODS

Male CFI mice were fed on a diet supplemented with several peroxisome proliferators: phenoxyacetic acid herbicides, plasticizers, acetylsalicylic acid and partially hydrogenated fish oil.

RESULTS

Increased levels of mdr2 mRNAs, assessed by Northern blot analysis, were observed in the liver of mice treated with phenoxyacetic acid herbicides: 2,4,5-trichlorophenoxyacetic acid 570+/-133%, 2,4-dichlorophenoxyacetic acid 233+/-54% (p<0.005); plasticizers: di-(2-ethylhexyl)phthalate 282+/-78%, di-(isoheptyl)phthalate 163+/-40%, phthalic acid dinonyl ester 225+/-48% (p<0.01); and partially hydrogenated fish oil 372+/-138% (p<0.005). P-glycoprotein traffic ATPase content increased in the canalicular domain of hepatocyte of mice treated with the herbicide 2,4,5-trichlorophenoxyacetic acid and with partially hydrogenated fish oil (108% and 87%, respectively, p<0.05) as well as biliary phospholipid output (106% and 74%, respectively, p<0.05). In 2,4,5-trichlorophenoxyacetic acid-fed mice we found five-fold increase on mdr2 transcription rate, assessed by nuclear run-off assay.

CONCLUSIONS

Peroxisome proliferators induce mdr2 gene, its encoded P-gp in the canalicular domain of hepatocytes and increase biliary phospholipid output. The modulation of mdr2 gene might be part of the pleiotrophic response of peroxisome proliferation in mice liver and seems to be regulated mainly at a transcriptional level.

Interaction of 2,4-dichlorophenoxyacetic acid (2,4-D) with cell and model membranes

2,4-dichlorophenoxyacetic acid (2,4-D), a widely used herbicide, is a component of the "agent orange' whose toxicity has been extensively studied without definite conclusions. In order to evaluate its perturbing effect upon cell membranes, 2,4-D was made to interact with human erythrocytes and molecular models. These studies were performed by scanning electron microscopy on red cells, fluorescence spectroscopy on dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles and X-ray diffraction on multilayers of DMPC and dimyristoylphosphatidylethanolamine (DMPE). It was observed that 2,4-D induced a pronounced shape change to the erythrocytes. This effect is explained by the herbicide interaction with the outer monolayer of the red cell membrane.

Effect of peroxisome proliferators on glutathione-dependent sulphobromophthalein excretion

1. The effect of pretreatment of rats with the peroxisome proliferator 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) on sulphobromophthalein excretion from the isolated perfused rat liver has been investigated and compared with the effect of clofibrate which is also a peroxisome proliferator. 2. Rats fed 2,4,5-T at a dose of 0.25% in the diet showed a decrease in food intake, compared with controls and clofibrate-fed rats. 3. Treatment with either 2,4,5-T or clofibrate was associated with significant inhibition of the biliary excretion of unchanged, conjugated, and total sulphobromophthalein from perfused rat liver, compared with diet-matched controls. 4. There was a decrease in bile flow in the clofibrate-treated group, but not in the 2,4,5-T-treated group. 5. The results of the present study confirm previous studies that have shown an association between peroxisome proliferation treatment and inhibition of glutathione S-transferase-mediated sulphobromophthalein excretion.

2,4,5-trichlorophenoxyacetic acid influence on 2,6-dinitrotoluene-induced urine genotoxicity in Fischer 344 rats: effect on gastrointestinal microflora and enzyme activity

2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) and 2,6-dinitrotoluene (2,6-DNT) are hazardous chemicals that have potential harmful effects. 2,6-DNT is recognized as a hepatotoxicant while 2,4,5-T, a component of Agent Orange, is also suspect. 2,6-DNT requires both oxidative and reductive metabolism to elicit genotoxic effects. To determine what effect 2,4,5-T had on 2,6-DNT metabolism, intestinal enzymes, microbial populations, and urine mutagenicity were examined during 2,4,5-T treatment. Weanling Fischer 344 male rats were treated daily with 54.4 mg/kg 2,4,5-T by gavage for 4 weeks. One, two, and four weeks after the initial 2,4,5-T dose, rats were administered (po) 2,6-DNT (75 mg/kg) and urine was collected for 24 hr in metabolism cages. Azo reductase, nitroreductase, beta-glucuronidase, dechlorinase, and dehydrochlorinase activities were examined concurrently. Treatment of rats for 1 week reduced the transformation of 2,6-DNT to mutagenic urinary metabolites. This was accompanied by a decrease in the fecal anaerobic microorganisms. The elimination of Lactobacillus fermentum from the small intestine and cecum of treated animals accompanied a significant increase in oxygen-tolerant lactobacilli and other unidentified aerobic microorganisms. However, there were no significant alterations in the intestinal enzyme activities examined. By 2 weeks of 2,4,5-T treatment, microbiota and urine genotoxicity returned to the levels observed in control animals. This trend continued for the duration of the experiment. After 2 weeks, while cecal nitroreductase and azo reductase activities increased, small intestinal beta-glucuronidase activity decreased. By 4 weeks, treated and untreated animal intestinal enzyme activities were indistinguishable.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning and characterization of a chromosomal DNA region required for growth on 2,4,5-T by Pseudomonas cepacia AC1100

A series of spontaneous 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) nonmetabolizing mutants of Pseudomonas cepacia AC1100 were characterized to be defective in either 2,4,5-T uptake or conversion of this compound to 2,4,5-trichlorophenol (2,4,5-TCP). Two of these mutants, RHC22 and RHC23, were complemented for growth on 2,4,5-T using an AC1100 genomic library constructed in the cosmid vector pCP13. Recombinant cosmids isolated from the complemented mutants contained a 27.5-kb insert which frequently underwent various-sized deletions in Escherichia coli. Hybridization studies showed this DNA to be of chromosomal origin and totally deleted in RHC22, RHC23 and other similar mutants. Complementation analyses of RHC22 with a series of subcloned fragments and spontaneously deleted derivatives of the recombinant cosmid pRHC21 showed the 2,4,5-T (tft) genes to occur within an 8.9-kb region. Pseudomonas aeruginosa cells transformed with this DNA acquired the ability to convert 2,4,5-T to 2,4,5-TCP. The genetic determinant for this function was further localized within a 3.7-kb region. This DNA, in the absence of other sequences from the 8.9-kb tft gene region allowed RHC22 cells to metabolize 2,4,5-T, but at low rates which were insufficient to support growth. Copies of the insertions sequence element IS931 were identified either adjacent to or within this tft gene region in the genomes of two independent wild-type AC1100 isolates. Preliminary evidence suggests that these sequences either facilitate or are required for growth on 2,4,5-T and hence may be implicated in the genetic evolution of the 2,4,5-T metabolic pathway.

Comparison of uncoupling activities of chlorophenoxy herbicides in rat liver mitochondria

The effects of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2-(2,4,5-trichlorophenoxy)propionic acid (2,4,5-TP) on respiration and oxidative phosphorylation in rat liver mitochondria were examined in vitro. Respiration rates of glutamate, malate and succinate were investigated in the presence of each herbicide (0.1-4.0 mM). At lower concentrations, all herbicides stimulated state 4 respiration, decreased the respiratory control ratio and the ADP/O ratio. The respiration rate in state 3 and uncoupled state was unaffected. At higher concentrations all bioenergetic parameters, respiration in state 4, 3 and uncoupled state, as well as respiratory control ratio and ADP/O, were inhibited in a concentration-dependent manner. These data indicate that these herbicides alter energy metabolism in rat liver mitochondria by uncoupling of oxidative phosphorylation. 2,4,5-TP possesses the strongest uncoupling properties followed by 2,4,5-T, MCPA and 2,4-D in that order.

Morphological transformation and catalase activity of Syrian hamster embryo cells treated with hepatic peroxisome proliferators, TPA and nickel sulphate

The abilities of the hepatic peroxisome proliferators (HPPs) clofibrate, di(2-ethylhexyl)phthalate (DEHP), mono(2-ethylhexyl)-phthalate (MEHP), 2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and tiadenol to induce morphological transformation and to increase the catalase activity of Syrian hamster embryo (SHE) cells were studied. DEHP, MEHP, clofibrate and tiadenol induced morphological transformation of SHE cells and increased the catalase activity. DEHP was more potent than clofibrate and tiadenol in both inducing catalase and morphological transformation, while MEHP seemed more potent than DEHP in inducing catalase, but not morphological transformation, 2,4,5-T and 2,4-D did not induce morphological transformation, but 2,4,5-T was more potent than clofibrate in increasing the catalase activity. These results show that several HPPs induce morphological transformation of SHE cells and an increase in the catalase activity. There is, however, no direct connection between these two parameters, as seen from the results of 2,4,5-T. The tumor promoter TPA, and the metal salt nickel sulphate, induced morphological transformation of SHE cells without any appreciable increase in the catalase activity. These results further corroborate the dissociation between induction of morphological transformation and the increase in catalase activity.

Studies on antifungal properties of phenol complexes with secondary amines. 2. Antifungal properties in vitro of the complex of 2,4,5-trichlorophenol with dicyclohexylamine

In studies in vitro it has been found that 2,4,5-trichlorophenol in the form of a complex with dicyclohexylamine is two times more active an antifungal agent than free chlorophenol.

Effect of exposure of Pieris brassicae larvae to 2,4,5-trichlorophenoxyacetic acid on the natural antibacterial activity of serum

Larvae of the cabbage white butterfly, Pieris brassicae, were reared on a semisynthetic diet with or without 20 ppm of the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and using three assays the sera were subsequently tested for natural antibacterial activity against Bacillus cereus, Escherichia coli K12, and Micrococcus luteus. These assays showed that exposure of larvae to 2,4,5-T lowered the antibacterial activity of the serum against E. coli and M. luteus compared with control animals. Spectrophotometric tests for the presence of a lysozyme-like principle in the serum also revealed similar trends with a significant loss of enzyme activity in 2,4,5-T-treated insects. Overall total serum protein levels of control and 2,4,5-T-treated insects were similar, suggesting a specific effect of the herbicide on certain serum components such as lysozyme. The possible mode of action of the herbicide on production of antibacterial factors is discussed.

Characterization of the activation of rat liver glutathione S-transferases by nonsubstrate ligands

In previous work (D.A. Vessey and T.D. Boyer, 1986, Biochem. Pharmacol., 35, 289-295) the activity of glutathione S-transferase form YcYc from rat liver was found to be stimulated by the herbicide 2,4,5-T. We have extended that work and examined the effect of over 40 structural analogs on the activity of YcYc. Over half of these compounds stimulated by 10 to 232% when added to assays at a concentration of 1 mM. The best activators all contained the "2,4,5-trichlorophenyl-" structure. While 2,4,5-T gave the greatest activation at 1 mM (2.3-fold), 2,4,5-trichlorobenzene sulfonate gave the greatest maximum activation (6.0-fold). Compounds that had no effect on activity did not affect activation by 2,4,5-T suggesting that they have a poor affinity for the enzyme. Two of the analogs tested (chloramine-T and 6-hydroxydopamine) proved to be good inhibitors and ethacrynic acid was an extremely potent inhibitor. Indomethacin activated at low concentrations but inhibited above 2 mM. Activations were greater at low temperature (5 degrees C) and decreased with increasing temperature. The extent of activation was largely unaffected by the concentration of either substrate. Examination of the organic peroxidase activity of the enzyme revealed inhibition by 2,4,5-T and 2,4-D rather than activation.

Ontogeny of swimming behavior and brain catecholamine turnover in rats prenatally exposed to a mixture of 2,4-dichlorophenoxyacetic and 2,4,5-trichlorophenoxyacetic acids

Rats exposed in utero on gestational days 6-15, to nonfetotoxic and grossly nonteratogenic mixtures (50 or 100 mg/kg) of 2,4-D/2,4,5-T as found in Agent Orange (but without significant contamination with 2,3,7,8 tetrachloro-p-dioxin) manifested subtle developmental neurotoxicity. Maturation of swimming behavior was significantly delayed on postnatal day 7 in both treatment groups. The concentration of norepinephrine (NE) in whole brain was significantly increased on postnatal day 15 in both treatment groups, whereas the concentration of dopamine (DA) was increased on postnatal day 15 at 100 mg/kg. The turnover and efflux rate constant of DA in whole brain were significantly reduced whereas the turnover time increased on postnatal day 3. The efflux rate constant for NE decreased and the turnover time increased significantly on postnatal day 15 at 100 mg/kg. These data indicate the value of ontogenic assessment following exposure to small doses, which result in functional alterations in the absence of overt toxic signs.

Induction of cytosolic and microsomal epoxide hydrolases and proliferation of peroxisomes and mitochondria in mouse liver after dietary exposure to p-chlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid

The effects of dietary exposure to 0.125% (w/w) p-chlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid or 2,4,5-trichlorophenoxyacetic acid on the content of peroxisomes and levels of certain xenobiotic-metabolizing enzymes in mouse liver have been investigated. In agreement with the literature on rat liver 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid were found to cause extensive proliferation of peroxisomes (as judged by the total levels of "mitochondrial" protein, carnitine acetyltransferase, cyanide-insensitive palmitoyl-CoA oxidation and catalase) in mouse liver. On the other hand, exposure to p-chlorophenoxyacetic acid did not significantly affect any of these parameters. As with certain other peroxisome proliferators, 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid increased total cytochrome oxidase activity as well. In addition, dietary exposure to 2,4-dichlorophenoxyacetic acid and to 2,4,5-trichlorophenoxyacetic acid resulted in increases in the activities of cytosolic and microsomal epoxide hydrolases in mouse liver and generally less pronounced increases in the total cytosolic glutathione transferase activity and microsomal content of cytochrome P-450. In the case of cytochrome P-450, this process can be said to be a true induction (i.e. the amount of enzyme protein is increased), because the assay procedure for cytochrome P-450 measures holoenzyme amount. Immunoquantitation demonstrated that this was also the case for the changes in cytosolic epoxide hydrolase. The dramatic differences in proliferation of peroxisomes and induction of xenobiotic-metabolizing enzymes seen here with compounds differing relatively little in structure may indicate that a receptor mechanism of some kind is involved.

Activation of trout gill AMP deaminase by an endogenous proteinase--II. Modification of the properties of the enzyme during starvation, pollution and salinity changes

The relative amount of modified AMP deaminase has been determined by taking advantage of the different effects of monovalent cations on the two enzymatic forms. When trout were subjected to different environmental perturbations (starvation, pollution of the water by a pesticide, transfer to sea water or reverse transfer to fresh water), modified AMP deaminase could be detected in the gill extracts. Depending on the nature of the stress and the period of experimentation, 8 to 100% of the enzyme had been modified by limited proteolysis. As a consequence of the much higher activity of the proteolyzed AMP deaminase form, a 2 to 12 times increase of the intracellular AMP deaminase activity could be expected. At the same time, limited proteolysis will modify the regulatory properties of the enzyme, since it can be estimated that 50 to 100% of the enzyme activity expressed in the cell will be an AMP deaminase form less sensitive to inhibition by inorganic phosphate and ionic strength, and to variations of the intracellular pH. Limited proteolysis will result in increased AMP deaminase activity under conditions of increased energy demand, where the concentration of inorganic phosphate is dramatically increased. The consequence should be stabilization of the adenylate energy charge.

Inhibition of human glutathione S-transferases by 2,4-dichlorophenoxyacetate (2,4-D) and 2,4,5-trichlorophenoxyacetate (2,4,5-T)

The phenoxyacid herbicides, 2,4-dichlorophenoxyacetate (2,4-D) and 2,4,5-trichlorophenoxyacetate (2,4,5-T), inhibit all known isoenzymes of human liver and erythrocyte glutathione (GSH) S-transferase. However, the maximal inhibition and the I50 values vary significantly for different isoenzymes. GSH peroxidase II activity of GSH S-transferases is also inhibited by both these compounds. These studies suggest that the effect of these compounds on human GSH S-transferases is significantly different from that reported for rat liver enzymes.

Rapid induction of selective transcription by auxins

Nuclei isolated from excised soybean plumules that were treated with 2,4-dichlorophenoxyacetic acid (2,4-D) were active in transcription of four auxin-regulated genes or DNA sequences, which have been described previously (G. Hagen, A. Kleinschmidt, and T. Guilfoyle, Planta 162:147-153, 1984). The rates of transcription of the auxin-responsive sequences were 10- to 100-fold greater with nuclei isolated from auxin-treated plumules than with those from untreated plumules. The transcriptional response was also observed with hypocotyls of intact soybean seedlings and hypocotyl sections, as well as with green bean and mung bean plumules that were treated with 2,4-D. Other auxins, including 2,4,5-trichlorophenoxyacetic acid, alpha-naphthaleneacetic acid, and indole-3-acetic acid, also induced the transcriptional response. Increased transcription rates were observed within 5 min after application of auxins to excised plumules, and half-maximal to maximal transcription rates were achieved by 15 min after application of auxins. As little as 10(-7) to 10(-8) M 2,4-D induced a transcriptional response, but maximal transcription rates were achieved at 10(-3) M 2,4-D. Brief treatment with the protein synthesis inhibitor cycloheximide did not inhibit the induction of transcription by auxins. These results clearly demonstrated that auxin-regulated gene expression is under rapid transcriptional control.

Induction of microsomal stearoyl-CoA desaturase by the administration of various phenoxyacetic acid derivatives

The potency of seven phenoxyacetic acid derivatives to induce microsomal stearoyl-CoA desaturation activity in rat liver was compared with that of 2-(4-chlorophenoxy)-2-methyl-propionic acid (clofibric acid). These compounds were given to rats with diet. Of seven phenoxyacetic acid derivatives tested, both 2-(4-chlorophenoxy)-propionic acid and 2-(2-chlorophenoxy)-2-methyl-propionic acid increased considerably the desaturation activity as was observed with clofibric acid. Moreover, 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) also increased the desaturation activity, although the inducing effect on desaturation activity was very weak compared to that of clofibric acid. These three compounds increased activity of terminal desaturase without accompanying marked changes in reduced nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase activity and cytochrome b5 content as was the case with clofibric acid. The other four phenoxyacetic acid derivatives, 2-(phenoxy)-propionic acid, 4-chlorophenoxyacetic acid, 2-chlorophenoxyacetic acid and 2, 4-dichlorophenoxyacetic acid (2,4-D) changed scarcely the desaturation activity. These compounds had no influence on NADH-cytochrome b5 reductase activity, cytochrome b5 content and terminal desaturase activity. Correlating with the changes in the desaturation activity, concentration of octadecenoic acid was increased in hepatic microsomes, whole liver and serum. Treatment with clofibric acid did not change the concentration of octadecenoic acid in brain, lung, heart, spleen, testis and adipose tissue.

Effects of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid on peroxisomal enzymes in rat liver

The effects of feeding 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) on the level of peroxisomal enzymes in rat liver were studied. The concentration of triglyceride in serum was decreased and the activity of cyanide-insensitive palmitoyl-CoA oxidation, catalase and carnitine acetyltransferase increased. However, the extent of the increase in the activity of these enzymes by treatment with 2,4-D was less pronounced than that by 2,4,5-T treatment. The administration of 2,4-D or 2,4,5-T increased the concentration of polypeptide with a mol. wt of 80,000 in the light mitochondrial fractions of the liver from the rats.

Properties of the lysosomes from liver and gill of rainbow trout, Salmo gairdnerii R.: effect of starvation, salinity and 2,4,5-T

Three isolation procedures were used to test the labilization of the lysosomes after adaptation of the animals to seawater, starvation or acute and chronic treatments with 2,4,5-T, an organochlorine pesticide. The lysosomes from gill and liver had different properties with respect to their resistance to osmotic and mechanical shocks, or treatments with digitonin. Starvation induced a significant labilization of the lysosomes in liver, but not in gill. Salinity changes were without effect on the stability of the gill lysosomes, but induced an increase of the specific activity of the lysosomal enzyme beta-acetylglucosaminidase. Acute treatments with 2,4,5-T increased lysosomal fragility in the gill but not in the liver, while chronic treatments with this herbicide increased lysosomal lability in the two tissues. Liver lysosomes were much more susceptible to in vitro treatments with 2,4,5-T than gill lysosomes. The results are discussed with respect to the different functions of gill and liver, their exposure to the environment, and the possible discrimination between different lysosomal populations.

In vivo effects of 3-methylcholanthrene, phenobarbital, pyrethrum and 2,4,5-T isooctylester on liver, lung and kidney microsomal mixed-function oxidase system of guinea-pig: a comparative study

The optimum conditions (pH, microsomal protein amount and substrate concentration) of guinea-pig liver, lung and kidney microsomal aniline 4-hydroxylase, ethylmorphine N-demethylase and benzo[a]pyrene hydroxylase activities were determined. Male guinea-pigs weighing 500-700 g were administered 3-methylcholanthrene (25 mg/kg, i.p. 3 days), phenobarbital (75 mg/kg, i.p. 3 days), pyrethrum (120 mg/kg, i.p. 2 days) and 2,4,5-T isooctylester (200 mg/kg, i.p. 3 days). 3-Methylcholanthrene treatment caused significant increases in liver microsomal benzo[a]pyrene hydroxylase and kidney microsomal aniline 4-hydroxylase activities. However, with phenobarbital treatment the only significant increase was observed in liver microsomal ethylmorphine N-demethylase activity. Pyrethrum treatment decreased kidney microsomal ethylmorphine N-demethylase activity significantly. 2,4,5-T isooctylester treatment increased liver microsomal aniline 4-hydroxylase and lung microsomal ethylmorphine N-demethylase activities significantly. Liver microsomal NADPH-cytochrome c reductase activity was increased significantly by phenobarbital and pyrethrum treatment. The other treatments did not cause any significant changes in microsomal NADPH-cytochrome c reductase activities of liver, lung and kidney. Cytochrome P-450 content of guinea-pig liver microsomes were increased significantly about 2.5-fold and 2-fold by treatment with 3-methylcholanthrene and phenobarbital, respectively. 3-Methylcholanthrene also caused 1 nm spectral shift in the absorption maxima of CO difference spectrum of the dithionite-reduced liver microsomal cytochrome P-450, forming P-449.

Biodegradation of 2,4,5-trichlorophenoxyacetic acid in soil by a pure culture of Pseudomonas cepacia

A pure culture of Pseudomonas cepacia AC1100 was able to degrade and grow in presence of 2,4,5-trichlorophenoxyacetic acid in soil. At optimum temperature (30 degrees C) and moisture content (15 to 50% [wt/vol]) strain AC1100 could degrade as much as 95% of 2,4,5-trichlorophenoxyacetic acid at high concentration (1 mg/g of soil) within 1 week.

Effects of anionic xenobiotics on rat kidney. I--Tissue and mitochondrial respiration

The polar 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) metabolite, 2,2-bis(p-chlorophenyl)acetic acid (DDA), and the phenoxyacetic acid herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), were previously shown to be accumulated to high levels in liver and kidney via the organic acid transport system, raising the possibility of organ-specific toxicity secondary to transport. In these studies, accumulation of DDA was shown to depress oxygen consumption by renal cortical slices at high doses (0.1 and 1mM). Isolated renal and hepatic mitochondria were uncoupled by low doses of DDA (5-10 nmoles/mg mitochondrial protein. Maximal uncoupling was seen at 50-70 nmoles/mg. 2,4-D and 2,4,5-T also produced uncoupling, but at doses of 70 nmoles/mg or higher. All agents were more effective with alpha-ketoglutarate or pyruvate-malate), all three agents also depressed State 3 (ADP-stimulated) respiration. Again, DDA was more effective than 2,4-D or 2,4,5-T. These results suggest that accumulation of these or other anionic xenobiotics may lead to toxicity in those tissues possessing the organic anion transport system.

2,4,5-T effects on cardiac and serum lactic dehydrogenase (LDH) and creatine kinase (CK) isozymes. I. Maternal enzyme activities and isozyme profiles

Pregnant mice were exposed to 100 mg/kg 2,4,5-T, IG, on gestation days 6 through 17, and sacrificed on postpartum day 1 or 21. Toxicologic evaluation showed no changes in body weight, heart weight, heart to body weight ratio, or cardiac supernate protein between corn oil control and 2,4,5-T treated mice on days 1 or 21 postpartum (pp). There were no effects of 2,4,5-T treatment on the total LDH enzyme activity of cardiac supernate on day 1 or 21pp. Serum LDH total activity was depressed on day 1pp and comparable to control values on day 21pp. Cardiac CK total activity was elevated on day 1pp, but not on day 21pp. Serum CK total activity on day 1 was comparable to control values; however, on day 21, a significant decrease in activity was observed. Cardiac LDH and CK isozyme profiles were normal on days 1 and 21pp. The serum LDH isozyme profile was normal at both times. The serum CK isozyme profile on Day 1 was markedly altered by athe appearance of two aberrant isozyme bands while on day 21, there was a profile shift with an increase in the BB band and a compensatory decrease in the MM band. These changes in creatine kinase suggest metabolic or pathologic changes in the cardiac muscle.

2,4,5-T effects on cardiac and serum lactic dehydrogenase (LDH) and creatine kinase (CK) isozymes. II. Neonatal enzyme activities and isozyme profiles

Neonates from CD-1 mice, which were treated during gestation with 100 mg/kg of 2,4,5-T, were studied from day 1 to 30 postpartum (pp) for effects on cardiac development by determining total cardiac activities and isozyme profiles of LDH and CK. On day 1pp, the total activities and isozyme profiles of LDH of the neonatal hearts were normal. During the developmental period of day 7 through 15, changes were noted in the developmental pattern of LDH isozymes some of which continued to day 30. The CK isozyme profile on day 1pp showed a significant change and changes continued throughout the lactational period. During this period, the normal developmental isozyme patterns of LDH and CK were altered by prenatal exposure to 2,4,5-T suggesting metabolic derangement or pathological changes in the neonatal heart.

Chlorinated phenoxyacetic acids and chlorophenols in the modified Allium test

The chlorinated phenoxyacetic acids 2-methyl-4-chlorophenoxyacetic acid (MCPA), 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,4,5-T butoxyethyl ester and the chlorophenols 2,4-dichlorophenol and 2,4,5-trichlorophenol were tested for genotoxicity in the modified Allium test, which is based on exposure to the test chemicals of growing onions. The mean length of growing roots were measured and chromosome damage was recorded. Of the substances tested, MCPA was the most toxic and the chlorophenoxyacetic acids were more toxic than the chlorophenols. The lower threshold values for growth retardation were below 0.1 ppm for the acids, approx. at 0.1 ppm for the ester and less than 5 ppm for the phenols. Though a monocotyledon, Allium cepa was sensitive enough to respond to even low concentrations of these dicotyledon-selecting pesticides.

2,4,5-trichlorophenoxyacetic acid causes behavioral effects in chickens at environmentally relevant doses

Administration of the herbicide 2,4,5-trichlorophenoxyacetic acid to incubating chicken eggs alters behavior after hatching. Single doses, with no morphological effects, retard learning (lowest dose, 7 milligrams per kilogram of body weight) and increase general activity (27 milligrams per kilogram) and jumping (13 milligrams per kilogram). Day 15 of incubation is the most susceptible stage of development.

Assessment of adult skeletons to detect prenatal exposure to 2,4,5-T or Trifluralin in mice

A group of 88 spontaneously occurring variations of the skeleton were studies in adult CD-1 mice which had been exposed in utero to the herbicides 2,4,5-T or Trifluralin, administered to their dams by gavage, in an attempt to detect subtle biological effects of these compounds even in the absence of gross malformations. Sixty-seven characters showed variation in this population. Of these, 19 were significantly different in frequency from untreated controls in mice having receiving a teratogenic dose of 2,4,5-T, with an average difference of 23.7%. Seventeen of them were increased in frequency. By contrast, only three traits differed from untreated among mice receiving a no-effect dose of 2,4,5-T. Twelve traits differed significantly from untreated in the Trifluralin-treated group; the average difference was 18.8%, with 10 of the traits being increased in frequency. Two clusters of affected variants specific to the 2,4,5-T high dose group included frontal bone variants in the skull (presence of an interfrontal bone and fusion of the frontals) and variants in the cervical vertebrae (imperfect foramina in the first and second cervicals, dyssymphysis of the second cervical, and a shift of the arch foramen from the fourth to the fifth cervical). Two other effects peculiar to the 2,4,5-T-treated specimens were a loss of the prominent dorsal spine of the second thoracic vertebra and a reduction in the number of caudal vertebrae. The most obvious effects specific to the Trifluralin treatment were an increase in occurrence of 14 ribs, an undoubled foramen ovale, and the occurrence of accessory foramina in the cervical vertebrae. A striking increase in frequency of parted frontals was seen in both 2,4,5-T high dose and Trifluralin-treated groups. The skeletal variant assay system may be used as a postnatal screen for detecting prenatal exposure to potentially noxious substances.

Statistical analysis of teratologic data: problems and advancements

A large scale replicated dose-response teratology study of 2,4,5-T was done in mice. Variability and variance of fecundity parameters and fetotoxicity endpoints are discussed. Another study on rats indicated less variation among teratologic endpoints than in mice. Calculations for the number of animals in strains of mice and rats needed to detect a 5 percent and 10 percent reduction in mean fetal weight or increase in resorptions are given. We concluded that at least 3 replicates with appropriate numbers of pregnant animals are needed to estimate variance for comparison among laboratories or among species. The utility of these calculations for standardizing teratologic studies is discussed.