Co-exposure to environmental microplastic and the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) induce distinctive alterations in the metabolome and microbial community structure in the gut of the earthworm Eisenia andrei

Microplastics (MPs) are recognized as emergent pollutants and have become a significant environmental concern, especially when combined with other contaminants. In this study, earthworms, specifically Eisenia andrei, were exposed to MPs (at a concentration of 10 μg kg-1 of soil), herbicide 2,4-D (7 mg kg-1 of soil), and a combination of the two for 7 and 14 days. The chemical uptake in the earthworms was measured, and the bacterial and archaeal diversities in both the soil and earthworm gut were analyzed, along with the metabolomic profiles. Additionally, data integration of the two omics approaches was performed to correlate changes in gut microbial diversity and the different metabolites. Our results demonstrated that earthworms ingested MPs and increased 2,4-D accumulation. More importantly, high-throughput sequencing revealed a shift in microbial diversity depending on single or mixture exposition. Metabolomic data demonstrated an important modulation of the metabolites related to oxidative stress, inflammatory system, amino acids synthesis, energy, and nucleic acids metabolism, being more affected in case of co-exposure. Our investigation revealed the potential risks of MPs and 2,4-D herbicide combined exposure to earthworms and soil fertility, thus broadening our understanding of MPs' toxicity and impacts on terrestrial environments.

Insights on biotic and abiotic 2,4-dichlorophenoxyacetic acid degradation by anaerobic iron-cycling bacteria

The use of the phenoxy herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been steadily increasing in recent years due to its selectivity against broad-leafed weeds and use on genetically modified crops resistant to 2,4-D. This increases the likelihood of 2,4-D persisting in agriculturally impacted soils, sediments, and aquatic systems. Aerobic microorganisms are capable of degrading 2,4-D enzymatically. Anaerobic degradation also occurs, though the enzymatic pathway is unclear. Iron-reducing bacteria (FeRB) have been hypothesized to augment anaerobic degradation through the production of a chemically reactive Fe(II) adsorbed to Fe(III) oxyhydroxides. To test whether this iron species can catalyze abiotic degradation of 2,4-D, an enrichment culture (BLA1) containing a photosynthetic Fe(II)-oxidizing bacterium (FeOB) "Candidatus Chlorobium masyuteum" and the FeRB "Candidatus Pseudopelobacter ferreus", both of which lacked known 2,4-D degradation genes was investigated. BLA1 produces Fe(II)-adsorbed to Fe(III) oxyhydroxides during alternating photoautotrophic iron oxidation and dark iron reduction (amended with acetate) cycles. No 2,4-D degradation occurred during iron oxidation by FeOB Ca. C. masyuteum or during iron reduction by FeRB Ca. P. ferreus under any incubation conditions tested (i.e., +/-Fe(II), +/-cells, and +/-light), or due to the presence of Fe(II) adsorbed to Fe(III) oxyhydroxides. Our results cast doubt on the hypothesis that the mineral-bound Fe(II) species augments the anaerobic degradation of 2,4-D in anoxic soils and waters by iron-cycling bacteria, and further justify the need to identify the genetic underpinnings of anaerobic 2,4-D degradation.

Combined toxicity of Cd and 2,4-dichlorophenoxyacetic acid on the earthworm Eisenia andrei under biochar amendment

Due to anthropogenic activities, various pollutants can be found in agricultural soil, such as cadmium (Cd) and 2,4-dichlorophenoxyacetic acid (2,4-D). They are highly toxic and can have a negative impact on soil fertility. For remediation strategies, biochar has acquired considerable attention due to its benefits for agriculture. However, we should recognize the ecological risk posed by biochar use. In addition, little is known about its non-desirable effects on soil organisms such as earthworms, especially in the case of soil remediation. In this study, earthworms (Eisenia andrei) were exposed to soil contaminated with Cd (0.7 mg/kg), (2,4-D) (7 mg/kg), and a mixture of the two in the presence and absence of biochar (2%). A 7- and 14-day incubation experiment was carried out for this purpose. Cd and 2,4-D uptakes in earthworms' tissues, oxidative stress, cytotoxic response, DNA damage, histopathological changes, and gene expression level were assessed. Results suggested that biochar increased the bioavailability of Cd and 2,4-D and the frequency of micronuclei (MNi) and decreased the lysosomal membrane stability (LMS) in earthworms. Also, histopathological examination detected numerous alterations in animals exposed to the contaminants without any amelioration when biochar was added. The biochemical response of earthworms in terms of oxidative stress demonstrates that in the presence of biochar, animals tend to alleviate the toxicity of Cd and 2,4-D. This was also supported by transcriptomic analyses where expression gene levels related to oxidative stress were upregulated in earthworms exposed to Cd and 2,4-D + biochar. The present investigation brought new insights concerning the use of biochar in agriculture.

2,4-Dichlorophenoxyacetic acid (2,4-D) affects DNA integrity and retina structure in zebrafish larvae

Monitoring the potential risk of herbicides in non-target organisms is a crucial issue for environmental safety. 2,4-D is an herbicide of high environmental relevance that has been shown to exert toxic effects to soil and aquatic biota. In the present study, we investigated the possible genotoxic and retinal development effects of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide in early life stages zebrafish (Danio rerio). Genotoxicity was evaluated by measuring DNA damage using the comet assay and also by the mRNA expression of genes implicated in apoptosis and/or DNA repair. Retinal development toxicity was evaluated with histological approach. The results obtained revealed that 2,4-D alters DNA integrity of zebrafish larvae. Moreover, transcriptomic data showed a significant induction of p-53 and casp-3 genes and a significant decrease of lig-4 in larvae exposed to the highest tested concentration of 2,4-D (0.8 mg/L). This suggested that p-53 gene regulates the process of DNA repair and apoptosis with increased levels of 2,4-D. The histopathological analysis revealed that early exposure to 2,4-D damaged the structure of larvae retina. Overall, this study is the first to report the DNA damage, casp-3, lig-4 and p-53 regulation, as well as the ocular developmental toxicity in zebrafish larvae at environmentally relevant concentrations of 2,4-D herbicide.

Combined isotope and enantiomer analysis to assess the fate of phenoxy acids in a heterogeneous geologic setting at an old landfill

Phenoxy acid herbicides and their potential metabolites represent industrial or agricultural waste that impacts groundwater and surface waters through leaching from old landfills throughout the world. Fate assessment of dichlorprop and its putative metabolite 4-CPP (2-(4-chlorophenoxy)propionic acid) is frequently obstructed by inconclusive evidence from redox conditions, heterogeneous geologic settings (e.g. clay till) and ambiguous parent-daughter relationships (i.e. 4-CPP may be daughter product or impurity of dichlorprop). For the first time, a combination of four methods was tested to assess transformation of phenoxy acids at a contaminated landfill (Risby site): analysis of (i) parent and daughter compound concentrations, (ii) enantiomer ratios (iii) compound-specific isotope analysis and (iv) enantiomer-specific isotope analysis. Additionally, water isotopes and chloride were used as conservative tracers to delineate two distinct groundwater flow paths in the clay till. Metabolite concentrations and isotope ratios of chlorinated ethenes demonstrated dechlorination activity in the area with highest leachate concentrations (hotspot) indicating favorable conditions also for dechlorination of dichlorprop to 4-CPP and further to phenoxypropionic acid. Combined evidence from concentrations, enantiomer ratios and isotope ratios of dichlorprop and 4-CPP confirmed their dechlorination in the hotspot and gave evidence for further degradation of 4-CPP downgradient of the hotspot. A combination of 4-CPP enantiomer and isotope analysis indicated different enantioselectivity and isotope fractionation, i.e. different modes of 4-CPP degradation, at different locations. This combined information was beyond the reach of any of the methods applied alone demonstrating the power of the new combined approach.

Selection of a support matrix for the removal of some phenoxyacetic compounds in constructed wetlands systems

The efficiency of constructed wetlands systems in the removal of pollutants can be significantly enhanced by using a support matrix with a greater capacity to retain contaminants by sorption phenomena, ionic exchange or other physico-chemical processes. The aim of this work was to evaluate the efficiencies of 3 different materials, Light Expanded Clay Aggregates [LECA] (in two different particle sizes), Expanded Perlite and Sand, for the removal from water of one pharmaceutical compound (clofibric acid) and one pesticide (MCPA). Both belong to the class of phenoxyacetic compounds. In addition, relationships were established between the compounds' removal efficiencies and the physico-chemical properties of each material. LECA exhibited a high sorption capacity for MCPA, while the capacity for clofibric acid was more modest, but still significant. In contrast, perlite had a very limited sorption capacity while sand did not exhibit any sorption capacity for any of the compounds. LECA with smaller particle sizes showed higher efficiencies than larger grade LECA and can achieve efficiencies near 100% for the lower concentrations in the order of 1 mg l(-1). However, the use of these smaller particle media at larger scales may present problems with hydraulic conductivities. The results show that expanded clay presents important advantages in laboratory studies and could be used as a filter medium or a support matrix in constructed wetlands systems.

In vitro studies on the chemical reactivity of 2,4-dichlorophenoxyacetyl-S-acyl-CoA thioester

2,4-Dichlorophenoxyacetic acid (2,4-D) is a widely used broadleaf herbicide that has been associated with acute liver toxicity in exposed humans or animals. Chemically reactive metabolites of 2,4-D are proposed as mediators of 2,4-D-induced hepatotoxicity. The aim of the present study was to investigate a novel reactive metabolite of 2,4-D, namely 2,4-dichlorophenoxyacetyl-S-acyl-CoA (2,4-D-CoA), and to determine its involvement in 2,4-D covalent adduct formation. Thus, incubations of synthetic 2,4-D-CoA (106 microM) with GSH (1 mM) in phosphate buffer (pH 7.4) showed 2,4-D-CoA to be able to transacylate the cysteine sulfhydryl of GSH, resulting in the formation of 2,4-D-S-acyl-glutathione (2,4-D-SG) thioester and reaching a concentration of 65 microM after 1 h of incubation. Under similar conditions, 2,4-D-CoA was shown to covalently bind to nucleophilic groups on human serum albumin (HSA, 30 mg/ml), resulting in time-dependent 2,4-D-HSA covalent adduct formation that reached a maximum of 440 pmol/mg HSA after 1 h of incubation. In addition to these studies, incubations of [1-(14)C]2,4-D (1 mM) with rat hepatocytes showed a time-dependent covalent binding of 2,4-D to hepatocyte protein. Inhibition of acyl-CoA formation by trimethylacetic acid (2 mM) decreased the amount of covalent binding to protein in rat hepatocytes by 50%. These results indicate that 2,4-D-CoA thioester is a reactive metabolite of 2,4-D that may contribute to 2,4-D-protein adduct formation in vivo and therefore the associated hepatotoxicity.

Induction of a hypertrophic growth status of coronary smooth muscle cells is associated with an overexpression of TGF-beta

Hypertrophy of vascular smooth muscle cells occurs during hypertension-induced remodelling of arteries and during development of arteriosclerosis and restenosis following angioplasty but the pathogenesis of the hypertrophic status is not yet fully understood. In a previous study we demonstrated that the synthetic non-sulfated, non-toxic heparin-mimicking compound RG-13577 is capable of inducing a cell cycle-arrested hypertrophic phenotype of coronary smooth muscle cells. In this study we clarify the mode of action of RG-13577 and demonstrate that the RG-13577-induced hypertrophy is associated with an increased expression of TGF-beta1 as indicated by an increase in TGF-beta1-specific protein and mRNA level. Furthermore we show that RG-13577-treated hypertrophic smooth muscle cells maintain full metabolic activity as indicated by a continuous de novo synthesis of protein and proteoglycans and that the RG-13577-induced growth arrest is caused not only by a higher expression of TGF-beta, but also by a reduced response of RG-treated cells to the mitogenic activity of bFGF, PDGF and EGF. The growth inhibitory activity of RG-13577 is reduced in the presence of neutralizing antibodies against TGF-beta. TGF-beta itself has anti-proliferative activity in serum-depleted medium. The RG-13577 effect is reversible since incubation of hypertrophic cells in RG-13577-free medium restores cell volume and [3H]thymidine incorporation to the values of untreated control cells within 4 days. We conclude, that the active metabolic status of RG-13577-treated cells in association with the overexpression of TGF-beta could promote repair processes of injured arteries after angioplasty without stimulating cell proliferation.

Physiological and genetic characteristics of two bacterial strains utilizing phenoxypropionate and phenoxyacetate herbicides

Two strains, Rhodoferax sp. P230 and Delftia (Comamonas) acidovorans MCI, have previously been shown to carry activities for the degradation of the two enantiomers of (RS)-2-(2,4-dichlorophenoxy-)propionate (dichlorprop) and (RS)-2-(4-chloro-2-methylphenoxy-)propionate (mecoprop) and, in addition, are capable of degrading phenoxyacetate derivatives 2.4-dichlorophenoxyacetate (2,4-D) and 4-chloro-2-methylphenoxyacetate (MCPA). Metabolism of the herbicides is initiated by alpha-ketoglutarate-dependent dioxygenases for both enantiomers of the phenoxypropionate herbicides and for 2,4-D. These activities were constitutively expressed for both enantiomers of dichlorprop in strain MC1 and for the Renantiomer in strain P230. Enzyme activities for the complete degradation of phenoxyacetate and phenoxypropionate herbicides were induced during incubation on either of these herbicides. Strain MC1 has about threefold higher activities for the degradation of dichlorprop and for growth on this substrate (mumax = 0.15 h(-1)) than strain P230; the maximum growth rate on 2,4-D amounts to 0.045 h(-1) with strain MC1. Dichlorprop is utilized faster than mecoprop and the R-enantiomers are cleaved with higher rates than the S-enantiomers. The degradation of the chlorophenolic intermediates seems to proceed via the modified ortho cleavage pathway as indicated by activities of the respective enzymes. The enzymatic results were supported by genetic investigations by which the presence of the genes tfdB (encoding a dichlorophenol hydroxylase), tfdC (encoding a chlorocatechol 1,2-dioxygenase) and tfdD (encoding a chloromuconate cycloisomerase) could be demonstrated in both strains by PCR after application of respective primers. The presence of the tfdA gene (encoding a 2,4-D/alpha-ketoglutarate dioxygenase) was only shown for strain P230 but was lacking in strain MC1. Sequence analysis of the tfd gene fragments revealed high homology to the degradative genes of other proteobacterial strains degrading chloroaromatic compounds. Strain MC1 carries a plasmid of about 120 kb which apparently harbors herbicide degradative genes as concluded from deletion mutants which have lost 2,4-D[phenoxalkanoate]/alpha-ketoglutarate dioxygenase activities for cleavage of the R- and S-enantiomer, and of 2,4-D. For strain P230, no plasmid could be demonstrated; the activity was stably conserved in this strain during growth under nonselective conditions.

A synthetic heparin-mimicking polyanionic compound binds to the LDL receptor-related protein and inhibits vascular smooth muscle cell proliferation

A synthetic heparin-mimicking polyaromatic anionic compound RG-13577 (polymer of 4-hydroxyphenoxy acetic acid and formaldehyde ammonium salt, Mr approximately 5800) exhibits specific binding to vascular smooth muscle cells (SMCs) and inhibits their proliferative response to growth promoting factors. Receptor binding of (14)C-RG-13577 was efficiently competed by apolipoprotein E3 (apoE), lactoferrin, and the LRP (LDL receptor-related protein) receptor associated 39 kDa protein (RAP). Unlike cell surface binding of apoE, binding of RG-13577 to SMCs was not affected by heparin, heparan sulfate degrading enzymes, or low density lipoprotein (LDL). Moreover, wild-type and heparan sulfate-deficient Chinese hamster ovary (CHO) cells, as well as normal- and LDL receptor negative- human skin fibroblasts bind RG-13577, but not apoE, to a similar extent. On the other hand, homozygous mouse embryonic fibroblasts deficient in the LDL receptor-related protein (LRP) expressed a markedly reduced binding of RG-13577 as compared to normal mouse embryonic fibroblasts. These results indicate that RG-13577 and related compounds bind to the LRP receptor on the surface of vascular SMCs. Addition of lactoferrin to cultured SMCs protected the cells against the antiproliferative effect of compound RG-13577, suggesting that this inhibition is mediated by RG-13577 binding to LRP receptors on the SMC surface. Altogether, we have identified a series of synthetic polyaromatic anionic molecules that exhibit specific binding to LRP and thereby exert an antiproliferative effect on vascular SMCs. These compounds are applied to suppress SMC proliferation associated with restenosis and accelerated atherosclerosis.

Function and distribution of beta3-adrenoceptors in rat, rabbit and human urinary bladder and external urethral sphincter

1. Activation of beta-adrenoceptors causes relaxation of the urinary bladder and contraction of the external urethral sphincter, which consists of fast-contracting skeletal muscles. A beta2-adrenoceptor agonist, clenbuterol, recently has been developed as a therapeutic drug for the treatment of urinary incontinence, however beta2-adrenoceptor agonists have undesirable effects on cardiac and striated muscle function. 2. In this study, we compared the effects of the beta2-adrenoceptor agonist, clenbuterol and of a novel beta3-adrenoceptor agonist, GS332, on urinary bladder and external urethral sphincter function in rat, rabbit and human. We also determined the distribution of beta3-adrenoceptors in human urinary bladder and external urethral sphincter, using radioligand-binding techniques. 3. Clenbuterol induced marked relaxations in rat, rabbit and human urinary bladder smooth muscles and also induced marked contractions in rat periurethral striated muscles (external urethral sphincter), while GS332 induced marked relaxations in rat and human, but not in rabbit, urinary bladder smooth muscles and induced small contractions in rat periurethral striated muscles. 4. The radioligand binding studies showed presence of beta2- and beta3-adrenoceptors in human urinary bladder, external urethral sphincter and abdominal rectus muscles. The affinities of GS332 were the highest in urinary bladder and the lowest in the skeletal (abdominal rectus) muscles, while the affinities of clenbuterol were similar in urinary bladder, external urethral sphincter and the skeletal (abdominal rectus) muscles. 5. These results suggest that GS332 could, similarly clenbuterol, have a role in the treatment of urinary frequency and urinary incontinence.

Characterization and regulation of catabolic genes

Although a wide range of microorganisms have been discovered that are able to degrade highly stable, toxic xenobiotics, still many pollutants persist in the environment. Recent advances in the field of r-DNA technology has provided solutions to these problems. One important factor limiting the bioremediation of sites contaminated with certain hazardous wastes is the slow rate of degradation. This slow rate limits the practicality of using bacteria in remediating contaminated sites. It is possible to extend the range of substrates that an organism can utilize. It is even possible to endow an organism with the ability to degrade a predetermined range of xenobiotics. Because biotechnological processes are based on natural activities of microorganisms and constitute variations in classic domestic waste treatment processes, they are publicly more accepted. This is an area where genetic engineering can make a marked improvement by manipulating catabolic genes of microorganisms. Advances in r-DNA technology have opened up new avenues to move toward the goal of genetically engineered microorganisms to function as "designer biocatalysts" in which certain desirable biodegradation pathways or enzymes from different organisms are brought together in a single host with the aim of performing specific detoxification. In the last 2 decades much progress has been made in this direction, and as a result catabolic genes have been cloned and characterized for organochlorines, polychlorinated biphenyls, chlorobenzoates, naphthalene etc. The aim of this review is to provide an insight in the recent advances made on characterization and expression of catabolic genes that encode the degradation/detoxification of these persistent and toxic xenobiotic compounds.

Utilization of phenoxyacetic acid, by strains using either the ortho or meta cleavage of catechol during phenol degradation, after conjugal transfer of tfdA, the gene encoding a 2,4-dichlorophenoxyacetic acid/2-oxoglutarate dioxygenase

The degradation of recalcitrant pollutants in contaminated soils and waters could be facilitated by broadening the degradative capabilities of indigenous microbes by the conjugal transfer of catabolic genes. The feasibility of establishing bacterial populations that degrade phenoxyacetic acid by conjugal transfer of tfdA, the gene encoding 2,4-dichlorophenoxyacetic acid/2-oxoglutarate dioxygenase, to phenol-degrading strains of Pseudomonas and Ralstonia was examined. The mobilizable plasmid pKJS32 served as a vector for delivery of tfdA and the regulatory gene, tfdS. Transconjugant strains that degraded phenol by an ortho cleavage of catechol grew well on phenoxyacetic acid while those employing a meta cleavage could only grow on phenoxyacetic acid in the presence of benzoic acid or after a prolonged lag period and the appearance of mutants that had gained catechol 1,2-dioxygenase activities. Thus, an ortho cleavage of catechol was essential for degradation of phenoxyacetic acid, suggesting that a product of the ortho-cleavage pathway, probably cis, cis-muconic acid, is an inducer of tfdA gene expression. Establishment of phenoxyacetic-acid-degrading soil populations by conjugal transfer of tfdA would depend on the presence of phenol-degrading recipients employing an ortho cleavage of catechol.

Modelling of the protonophoric uncoupling by phenoxyacetic acid of the plasma membrane potential of Penicillium chrysogenum

Physiological effects of phenoxyacetic acid, the penicillin V side-chain precursor, on steady-state continuous cultures of Penicillium chrysogenum have been studied both theoretically and experimentally. Theoretical calculations show that at an extracellular pH of 6.50, phenoxyacetic acid has negligible influence on the growth energetics due to protonophoric uncoupling of membrane potentials by passive diffusive uptake. On the other hand, when the extracellular pH is lowered to 5.00, a severe maintenance-related uncoupling effect of phenoxyacetic acid is calculated. These findings were confirmed experimentally by steady-state continuous cultivations with a high-yielding penicillin strain of P. chrysogenum performed on a chemically defined and glucose-limited medium at pH 6.50 and pH 5.00, both with and without phenoxyacetic acid present. The yield and maintenance coefficients were determined from steady-state measurements of the specific uptake rates of glucose and oxygen and the specific production rate of carbon dioxide as functions of the specific growth rate. Combining these data with a simple stoichiometric model for the primary metabolism of P. chrysogenum allows quantitative information to be extracted on the growth energetics in terms of ATP spent in maintenance- and growth-related processes, i.e. mATP and YxATP. The increased maintenance-related ATP consumption when adding phenoxyacetic acid at pH 5.00 agrees with the theoretical calculations on the uncoupling effect of phenoxyacetic acid. When YxATP is compared with earlier reported values for the theoretical ATP requirement for biosynthesis of P. chrysogenum, i.e. YxATP, growth, it is found that YxATP,growth is only 40-50% of YxATP, which stresses that a large amount of ATP is wasted in turnover of macromolecules, leaks, and futile cycles.

Percutaneous penetration of 2-phenoxyethanol through rat and human skin

2-Phenoxyethanol applied in methanol was absorbed (64 +/- 4.4% at 24 hr) through unoccluded rat skin in vitro in the static diffusion cell with ethanol/water as receptor fluid. By comparison (43 +/- 3.7% in 24 hr) was absorbed in the flow-through diffusion system with tissue culture medium as receptor fluid. 2-Phenoxyethanol applied in methanol was absorbed (59.3 +/- 7.0% at 6 hr) through unoccluded human skin in vitro in the flow-through diffusion cell with tissue culture medium. With both unoccluded cells, 2-phenoxyethanol was lost by evaporation but occlusion of the static cell reduced evaporation and increased total absorption to 98.8 +/- 7.0%. Skin, post mitochondrial fraction, metabolized phenoxyethanol to phenoxyacetic acid at 5% of the rate for liver. Metabolism was inhibited by 1 mM pyrazole, suggesting involvement of alcohol dehydrogenase. However, first-pass metabolism of phenoxyethanol to phenoxyacetic acid was not detected during percutaneous penetration through viable rat skin in the flow-through system. First-pass metabolism in the skin does not therefore have an influence on systemic availability of dermally absorbed phenoxyethanol. These measures of phenoxyethanol absorption through rat and human skin in vitro agree well with those obtained previously in vivo.

The acid metabolite of ZD7114 is a partial agonist of lipolysis mediated by the rat beta 3-adrenoceptor

Experiments were performed to characterise the lipolytic effects of the acid metabolite, ZM215001, ((S)-4-[2-hydroxy-3-phenoxy-propylamino-ethoxy] phenoxyacetic acid) of the putative beta 3-adrenoceptor agonist, ZD7114 ((S)-4-[2-hydroxy-3-phenoxy-propylamino-ethoxy]-N-(2-methoxyethyl) phenoxyacetamide) on isolated rat white adipocytes. ZM215001 was used for these studies since it is the predominant moiety after in vivo administration of ZD7114. The agonist properties of ZM215001 were assessed in comparison to the standard nonselective beta-adrenoceptor agonist (+/-)-isoprenaline and the beta 3-adrenoceptor-selective agonist BRL 37344. Isoprenaline, BRL 37344 and ZM215001 all stimulated the rate of free fatty acid release from isolated adipocytes with the order of potency being BRL > isoprenaline > ZM215001. The maximum effect of BRL 37344 was equivalent to that of isoprenaline, but ZM215001 achieved only 30% of the maximum isoprenaline response. ZM215001 competitively antagonised the lipolytic response to BRL 37344 (pA2 = 7.26), whereas the agonist effects of BRL 37344 were not antagonised competitively by the selective antagonists ICI 118551 and CGP 20712A, at concentrations which would be expected to block beta 1- and beta 2-adrenoceptors respectively. These results indicate that ZM215001 has low intrinsic activity at the rat adipocyte beta 3-adrenoceptor, and is a partial agonist of lipolysis in rat white adipocytes.

Uptake of phenoxyacetic acid by Penicillium chrysogenum

The uptake of phenoxyacetic acid by two different strains of Penicillium chrysogenum was studied. Phenoxyacetic acid (POA) was taken up by P. chrysogenum in a defined medium. Plots of initial velocity of POA uptake versus external substrate concentration, in the range 2-5000 microM, gave linear plots. Uptake of POA by induced and uninduced cells was identical. The initial velocity of POA uptake decreased as the pH of the suspension was increased from 5.4 to 7.2; the decrease closely paralleled the decline in the non-ionic form of the acid over this pH range. The initial velocity of POA uptake was not affected by the presence of phenylacetic acid. POA uptake proceeded until the cellular concentration was equal to the external concentration. It is concluded that POA is passively transported into P. chrysogenum by unmediated diffusion.

Antiproliferative activity to vascular smooth muscle cells and receptor binding of heparin-mimicking polyaromatic anionic compounds

Proliferation of bovine aortic smooth muscle cells (SMCs) induced by thrombin, basic fibroblast growth factor, or serum is inhibited by anionic, nonsulfated aromatic compounds that mimic many of the effects of heparin. Among these compounds are aurintricarboxylic acid (ATA) and a newly synthesized polymer of 4-hydroxyphenoxy acetic acid (compound RG-13577). Iodinated- or 14C-labeled compound RG-13577 binds to cultured SMCs in a highly specific and saturable manner. Scatchard analysis of the binding data revealed the presence of an estimated 1 x 10(7) binding sites per cell with an apparent dissociation constant of 3 x 10(-6) mol/L. Binding of radiolabeled RG-13577 was efficiently competed for by related aromatic anionic compounds and by apolipoprotein E, but not by heparin, heparan sulfate, suramin, or various purified growth factors and extracellular matrix proteins. Receptor cross-linking of SMC-bound 125I-RG-13577 revealed a single species of high M(r) (approximately 280 kD) cell surface receptors detected in the absence but not the presence of excess unlabeled compound RG-13577. Binding was susceptible to downregulation and restoration of receptor levels in a manner similar to that of hormone and growth factor receptors. We suggest that the antiproliferative activity of compound RG-13577 and related compounds is initiated by binding to specific growth-inhibiting cell surface receptors. Heparin-mimicking compounds may be applied to inhibit SMC proliferation associated with atherosclerosis and restenosis.

Identification of a meta-cleavage pathway for metabolism of phenoxyacetic acid and phenol in Pseudomonas cepacia AC1100

Pseudomonas cepacia strain AC1100 grows luxuriantly on 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) but does not utilize phenoxyacetic acid. After long-term selective pressure on phenoxyacetic acid, mutants designated as strain PAA, capable of utilizing phenoxyacetic acid as well as phenol, emerged spontaneously at a frequency of 1 x 10(-8). A deletion mutant strain PT88, which is devoid of a part of 2,4,5-T metabolic pathway, generated neither phenoxyacetic acid utilizing nor phenol-utilizing mutants. The wild type (Wt) strain AC1100 and all its mutants utilized benzoate via ortho-cleavage pathway. However, only mutant strain PAA harbored the whole set of enzymes required for utilization of phenol via meta-cleavage pathway. The results suggest that Wt strain AC1100 carries silent genes for meta-cleavage pathway which are expressed in strain PAA enabling it to utilize phenoxyacetic acid and phenol. Gene activation is presumed to be due to the translocation of insertion elements.

Biodegradation of phenoxyacetic acid in soil by Pseudomonas putida PP0301(pR0103), a constitutive degrader of 2,4-dichlorophenoxyacetate

The efficacy of using genetically engineered microbes (GEMs) to degrade recalcitrant environmental toxicants was demonstrated by the application of Pseudomonas putida PP0301(pR0103) to an Oregon agricultural soil amended with 500 micrograms/g of a model xenobiotic, phenoxyacetic acid (PAA). P. putida PP0301(pR0103) is a constitutive degrader of 2,4-dichlorophenoxyacetate (2,4-D) and is also active on the non-inducing substrate, PAA. PAA is the parental compound of 2,4-dichlorophenoxyacetic acid (2,4-D) and whilst the indigenous soil microbiota degraded 500 micrograms/g 2,4-D to less than 10 micrograms/g, PAA degradation was insignificant during a 40-day period. No significant degradation of PAA occurred in soil inoculated with the parental strain P. putida PP0301 or the inducible 2,4-D degrader P. putida PP0301(pR0101). Moreover, co-amendment of soil with 2,4-D and PAA induced the microbiota to degrade 2,4-D; PAA was not degraded. P. putida PP0301-(pR0103) mineralized 500-micrograms/g PAA to trace levels within 13 days and relieved phytotoxicity of PAA to Raphanus sativus (radish) seeds with 100% germination in the presence of the GEM and 7% germination in its absence. In unamended soil, survival of the plasmid-free parental strain P. putida PP0301 was similar to the survival of the GEM strain P. putida PP0301(pR0103). However, in PAA amended soil, survival of the parent strain was over 10,000-fold lower (< 3 colony forming units per gram of soil) than survival of the GEM strain after 39 days.

Utilization of side-chain precursors for penicillin biosynthesis in a high-producing strain of Penicillium chrysogenum

Utilization of the side-chain precursors phenoxyacetic acid (POA) and phenylacetic acid (PA) for penicillin biosynthesis by Penicillium chrysogenum was studied in shake flasks. Precursor uptake and penicillin production were followed by HPLC analysis of precursors and products in the medium and in the cells. P. chrysogenum used both POA and PA as precursors, producing phenoxymethylpenicillin (penicillin V) and benzylpenicillin (penicillin G), respectively. If both precursors were present simultaneously, the formation of penicillin V was blocked and only penicillin G was produced. When PA was added at different times to cells that were induced initially for POA utilization and were producing penicillin V, the POA utilization and penicillin V formation were blocked, whereas the cells started utilizing PA and produced penicillin G. The blocking of the POA turnover lasted for as long as PA was present in the medium. If POA was added to cultures induced initially for PA utilization and producing penicillin G, this continued irrespective of the presence of POA. Utilization of POA increased concomitant with depletion of PA from the medium. Analysis of cellular pools from a growing cell system with POA as precursor to which PA was added after 48 h showed that the cellular concentration of POA was kept high without production of penicillin V and at a concentration comparable to the concentration in the medium. The cellular concentration of POA was higher than the concentration of PA that was utilized for penicillin G production.

A colorimetric assay for penicillin-V amidase

The hydrolysis of penicillin-V to phenoxyacetic acid and 6-aminopenicillanic acid by the fungal enzyme penicillin-V amidase is of industrial importance since the 6-aminopenicillanic acid produced is an intermediate for semisynthetic penicillins. A rapid colorimetric assay of penicillin-V amidase was developed which uses 2-nitro-5-(phenoxyacetamido)-benzoic acid as a substrate. The released chromophore, 2-amino-5-nitrobenzoic acid, was detected at 405 nm. Using penicillin-V amidase from the fungus Fusarium oxysporum, the KM and Vmax for this substrate were 0.89 mM and 2.6 mumol/min/mg enzyme, respectively. Hydrolysis could be competitively inhibited by penicillin-V with a Ki of 4 mM. The change in the initial velocity of hydrolysis of 2-nitro-5-(phenoxyacetamido)-benzoic acid at 500 microM was linear over the range of 0.5 to 10 micrograms/ml enzyme. These results show that this new compound is useful in determining the presence and levels of penicillin-V amidase.

Role of electron-donating cosubstrates in the anaerobic biotransformation of chlorophenoxyacetates to chlorophenols by a bacterial consortium enriched on phenoxyacetate

A bacterial consortium that anaerobically mineralized phenoxyacetate, with transient production of phenol as an intermediate, was obtained from a methanogenic aquifer site near the Norman, OK municipal landfill. This consortium was able to convert the eight halogenated chlorophenoxyacetates tested to the corresponding chlorophenols. The chlorophenols were not subsequently metabolized. The addition of reduced substrates increased the rate of degradation of all chlorophenoxyacetates, with 78% of mono- and di-chlorinated substrates being transformed to chlorophenols in butyrate-amended cultures, compared to less than 37% transformed in unsupplemented cultures. Butyrate increased the transformation of 2,4,5-trichlorophenoxyacetate from 10% to 20%. An experiment evaluating the effects of several compounds on the side-chain cleavage reaction of 3-chlorophenoxyacetate showed that addition of compounds which readily act as hydrogen donors (butyrate, crotonate, ethanol, propionate, and hydrogen) resulted in 2 to 5 times the amount of 3-chlorophenoxyacetate transformed compared to controls with no amendment, formate had a slight stimulatory effect, and acetate and methanol had no effect. Butyrate addition also increased the rate of phenoxyacetate degradation, resulting in transient phenol accumulation not observed in butyrate-unamended controls. These results support the hypothesis that the side-chain cleavage of phenoxyacetate is a reductive process that is stimulated by the oxidation of reduced cosubstrates.

Decreased production ofpara-hydroxypenicillin V in penicillin V fermentations

Penicillin V (phenoxymethyl penicillin) is produced by industrial strains of Penicillium chrysogenum in the presence of phenoxyacetic acid (POAc), a side-chain precursor for the penicillin V molecule. The wild-type strain of P. chrysogenum produces an undesirable penicillin byproduct, para-hydroxypenicillin V (p-OH penicillin V), in addition to penicillin V, via para-hydroxylation of POAc and subsequent incorporation of the p-OH phenoxyacetic acid into the penicillin molecule. Most of the p-OH penicillin V is produced late in cycle when the POAc concentration in the medium is nearly depleted. The level of p-OH penicillin V produced by the control strain ranges up to 10-15% of the total penicillins produced. 3-Phenoxypropionic acid and p-bromophenylacetic acid partially inhibit the formation of p-OH penicillin V with a minimal effect on penicillin V productivity. Mutants deficient in their ability to hydroxylate POAc were found to produce lower levels of p-OH penicillin V. Multi-step mutation and screening, starting with the wild-type strain, have culminated in isolation of mutants which produce p-OH penicillin V as 1% of the total penicillins with no adverse effect on penicillin V productivity.

Characterization of the requirements and substrates for reductive dehalogenation by strain DCB-1

An obligately anaerobic bacterium known as strain DCB-1 was grown under a variety of conditions to determine the requirements for dehalogenation as well as factors which stimulated or inhibited the process. Dechlorination was obligately anaerobic since introduction of O2 immediately inhibited the reaction. Sulfuroxy anions, which also serve as electron acceptors for DCB-1, inhibited dechlorination but NO3- and fumarate did not. The optimum growth medium for dechlorination was 0.2% Na pyruvate and 20% rumen fluid in basal salts. Media with either pyruvate or rumen fluid alone did not support dechlorination. DCB-1 also consumed H2 but typical substrate concentrations of H2 (80 kPa) delayed dechlorination. Once the H2 concentration was reduced to less than 20 microM (2.67 kPa), dechlorination resumed. Dehalogenation by DCB-1 was restricted to the meta substituted benzoates as halogens in other positions and chloroaromatic compounds with other functional groups were not dechlorinated.

Phenoxyacetic acid degradation by the 2,4-dichlorophenoxyacetic acid (TFD) pathway of plasmid pJP4: mapping and characterization of the TFD regulatory gene, tfdR

Plasmid pJP4 enables Alcaligenes eutrophus JMP134 to degrade 3-chlorobenzoate and 2,4-dichlorophenoxyacetic acid (TFD). Plasmid pRO101 is a derivative of pJP4 obtained by insertion of Tn1721 into a nonessential region of pJP4. Plasmid pRO101 was transferred by conjugation to several Pseudomonas strains and to A. eutrophus AEO106, a cured isolate of JMP134. AEO106(pRO101) and some Pseudomonas transconjugants grew on TFD. Transconjugants with a chromosomally encoded phenol hydroxylase also degraded phenoxyacetic acid (PAA) in the presence of an inducer of the TFD pathway, namely, TFD or 3-chlorobenzoate. A mutant of one such phenol-degrading strain, Pseudomonas putida PPO300(pRO101), grew on PAA as the sole carbon source in the absence of inducer. This isolate carried a mutant plasmid, designated pRO103, derived from pRO101 through the deletion of a 3.9-kilobase DNA fragment. Plasmid pRO103 constitutively expressed the TFD pathway, and this allowed the metabolism of PAA in the absence of the inducer, TFD. Complementation of pRO103 in trans by a DNA fragment corresponding to the fragment deleted in pRO101 indicates that a negative control-regulatory gene (tfdR) is located on the BamHI E fragment of pRO101. Other subcloning experiments resulted in the cloning of the tfdA monooxygenase gene on a 3.5-kilobase fragment derived from pRO101. This subclone, in the absence of other pRO101 DNA, constitutively expressed the tfdA gene and allowed PPO300 to grow on PAA. Preliminary evidence suggests that the monooxygenase activity encoded by this DNA fragment is feedback-inhibited by phenols.

Extrapolation of biodegradation results to groundwater aquifers: reductive dehalogenation of aromatic compounds

The reductive biodegradation of a variety of haloaromatic substrates was monitored in samples from two sites within a shallow anoxic aquifer and was compared with freshwater sediment and sewage sludge. The metabolic capacity existing in methane-producing aquifer material was very similar to that in sediment in that three of four chlorobenzoates, five of seven chlorophenols, and one of two chlorophenoxyacetate herbicides were reductively dehalogenated in both types of incubations. The 2,4-dichlorophenoxyacetate was first converted to a dichlorophenol before dehalogenation occurred. Sewage sludge microorganisms dehalogenated four of seven chlorophenols tested and degraded both phenoxyacetate herbicides by first converting them to the corresponding chlorophenols, but the microorganisms did not transform the chlorobenzoates. In general, the same suite of initial metabolites were produced from a test substrate in all types of samples, as confirmed by cochromatography of the intermediates with authentic material. Aquifer microbiota from a sulfate-reducing site was unable to significantly degrade any of the haloaromatic substrates tested. Biological removal of the sulfate in samples from this site permitted dehalogenation of a model substrate, while stimulation of methanogenesis without removal of sulfate did not. These results demonstrate that dehalogenating microorganisms were present at this site but that their activity was at least partially inhibited by the high sulfate levels.

Anaerobic degradation of veratrylglycerol-beta-guaiacyl ether and guaiacoxyacetic acid by mixed rumen bacteria

Veratrylglycerol-beta-guaiacyl ether (0.2 g/liter), a lignin model compound, was found to be degraded by mixed rumen bacteria in a yeast extract medium under strictly anaerobic conditions to the extent of 19% within 24 h. Guaiacoxyacetic acid, 2-(o-methoxyphenoxy)ethanol, vanillic acid, and vanillin were detected as degradation products of veratrylglycerol-beta-guaiacyl ether by thin-layer chromatography, gas chromatography, and gas chromatography-mass spectrometry. Guaiacoxyacetic acid (0.25 g/liter), when added into the medium as a substrate, was entirely degraded within 36 h, resulting in the formation of phenoxyacetic acid, guaiacol, and phenol. These results suggest that the beta-arylether bond, an important intermonomer linkage in lignin, can be cleaved completely by these rumen anaerobes.

N-dealkylation of oxprenolol: formation of 3-aryloxypropane-1,2-diol, 3-aryloxylactic acid, and 2-aryloxyacetic acid metabolites in the rat

Oxprenolol (1), like related beta-adrenergic antagonists, undergoes oxidative N-dealkylation to form the corresponding 3-aryloxypropane-1,2-diol (2), 3-aryloxylactic acid (3), and 2-aryloxyacetic acid (4) metabolites. Compounds 3 and 4 were synthesized by conversion of 2-allyloxyphenol (5) to the aryloxyacetaldehyde 6 and subsequent elaboration to the desired acids. Both acids (3 and 4) and glycol 2 were confirmed as metabolites formed from 1 in vivo in the rat and in vitro in the rat liver 9000 X g supernatant fraction. Incubation of a pseudoracemate of 1, made up of equal molar amounts of (2S)-1-d0 and (2R)-1-d2, showed that 2 and 3 arise principally from (2S)-1 by S/R ratios of approximately 5:1 and 2:1, respectively. On the other hand, acetic acid derivative 4 arises about equally from both enantiomers of 1.

Binding of toxic metabolites of isoniazid by aconiazide

Isoniazid, the hydrazide of isonicotinic acid, is widely used in the treatment and prophylaxis of tuberculosis. The toxicity and carcinogenicity of isoniazid have been attributed to the action of its metabolites, hydrazine and acetylhydrazine. Aconiazide, the isonicotinylhydrazone of 2-formylphenoxyacetic acid, has been used in the treatment and prophylaxis of tuberculosis. Aconiazide is hydrolyzed in the body to isoniazid and 2-formylphenoxyacetic acid. 2-Formylphenoxyacetic acid has been shown to bind hydrazine and acetylhydrazine. This binding could explain the lower toxicity of aconiazide and also could provide a reason for postulating its lack of carcinogenicity.

Mechanism of the lethal and mutagenic effects of phenoxyacetic acids in Saccharomyces cerevisiae

MCPA and salicylic acid, two compounds with similar structures and almost the same dissociation pattern, were tested for lethal and mutagenic effects on, and uptake by, cells of Saccharomyces cerevisiae strain rad18. The results obtained with the two compounds were similar, suggesting a common mechanism of action. It is proposed that they act by increasing the concentration of hydrogen ions within the cell, so that killing and mutation occur. Mutations were induced only when killing reached 95--99%. The compounds are considered weak mutagens for yeast cells. The methyl ester of MCPA also induced killing and reverse mutation, but only at concentrations about 100 times higher than for the undissociated acid. MCPA methyl ester did not increase the number of revertants in the Salmonella/liver microsome test. It is suggested that the effects of the methyl ester of MCPA depends on the ester being hydrolysed to the acid by yeast cells and the liver microsome preparation.