Comprehensive multi-omics approaches reveal the hepatotoxic mechanism of perfluorohexanoic acid (PFHxA) in mice

Perfluorohexanoic acid (PFHxA), one of the short-chain perfluoroalkyl acids (PFAAs), is considered as a substitute of perfluorooctane sulfonate (PFOS). This emerging organic pollutant is persistent and highly bioavailable to humans, raising concerns about its potential health risks. There are currently few researches on the toxicity of PFHxA. Liver has been suggested to be the main target of PFHxA toxicity, and the mechanism remains unclear. Herein, we investigated the transcriptomic, proteomic, and metabolomic landscape in PFHxA-exposed mice. Using these approaches, we identified several valuable biological processes involved in the process of liver injury, comprising fatty acid biosynthesis and degradation pathways, which might be induced by peroxisome proliferator-activated receptor (PPAR) signaling pathway. These processes further promoted oxidative stress and induced liver injury. Meanwhile, abnormalities in purine metabolism and glutathione metabolism were observed during the liver injury induced by PFHxA, indicating the production of oxidative stress. Finally, our present multi-omics studies provided new insights into the mechanisms involved in PFHxA-induced liver injury.

Comparison of zebrafish in vitro and in vivo developmental toxicity assessments of perfluoroalkyl acids (PFAAs)

Perfluoroalkyl acids (PFAAs) are persistent environmental contaminants that are associated with various adverse health outcomes. Perfluorooctanoic acid (PFOA) is one of the most prominently detected PFAAs in the environment, which is now replaced with shorter chain carbon compounds including perfluorohexanoic acid (PFHxA) and perfluorobutyric acid (PFBA). The aim of this study was to compare the toxicity of four PFAAs as a function of chain length and head group (carboxylate versus sulfonate) with in vitro and in vivo zebrafish assessments, which were subsequently compared to other cell and aquatic models. Mortality rate increased with chain length (PFOA > PFHxA ≫ PFBA) in both whole embryo/larvae and embryonic cell models. The sulfonate group enhanced toxicity with perfluorobutane sulfonate (PFBS) showing higher toxicity than PFBA and PFHxA in both larvae and cells. Toxicity trends were similar among different aquatic models, but sensitivities varied. Discrepancies with other zebrafish studies were confirmed to be associated with a lack of neutralization of acidic pH of dosing solutions in these other investigations, demonstrating the need for rigor in reporting pH of exposure solutions in all experiments. The zebrafish embryonic cell line was also found to be similar to most other cell lines regardless of exposure length. Overall, results agree with findings in other cell lines and organisms where longer chain length and sulfonate group increase toxicity, except in investigations not neutralizing the exposure solutions for these acidic compounds.

Antimicrobial activity of organic acids against Campylobacter spp. and development of combinations-A synergistic effect?

Contaminated poultry meat is considered to be the main source of human infection with Campylobacter spp., a pathogen that asymptomatically colonizes broiler chickens during fattening and contaminates carcasses during slaughter. To prevent or reduce the colonization of broiler flocks with Campylobacter spp., applying different organic acids, especially in combinations, via feed or drinking water seems to be a promising approach. However, only very few combinations of organic acids have been tested for their antibacterial efficacy against Campylobacter spp. Therefore, the in vitro susceptibility of 30 Campylobacter spp. isolates (20 C. jejuni and ten C. coli) to ten organic acids and ten combinations was determined. The testing of minimum inhibitory concentration (MIC) values was performed at pH 6.0 and 7.3 by using the broth microdilution method and included the following organic acids: Caprylic acid, sorbic acid, caproic acid, benzoic acid, ascorbic acid, propionic acid, acetic acid, formic acid, fumaric acid and tartaric acid and combinations thereof. The lowest MIC values were seen for caprylic acid (MIC range at pH 7.3: 0.5-2 mmol/L) and sorbic acid (MIC range at pH 7.3: 1-4 mmol/L). One to two dilution steps lower MIC values were determined at the lower pH value of 6.0. Furthermore, ten combinations consisting of three to five organic acids were developed. In addition to the tested antibacterial activity, other criteria were included such as approval as feed additives, reported synergistic effects and chemical properties. For nine of ten combinations, the MIC90 values of the organic acids decreased 1.25- to 241.5-fold compared to the MIC90 values for the individual substances. Furthermore, nine of ten combinations exhibited synergistic activities against two or more of the tested C. jejuni and C. coli isolates. A combination of caprylic acid, sorbic acid and caproic acid exhibited synergistic activities against the largest number of Campylobacter spp. isolates (six C. jejuni and four C. coli) with fractional inhibitory concentration (FIC) indices (∑FIC) ranging from 0.33 to 1.42. This study shows in vitro synergistic activities of different organic acids in combinations against the major Campylobacter species and could therefore be a promising basis for reducing Campylobacter spp. in vivo.

Comparisons of tissue distributions and health risks of perfluoroalkyl acids (PFAAs) in two fish species with different trophic levels from Lake Chaohu, China

Perfluoroalkyl acids (PFAAs) are a type of persistent organic pollutants that are widely distributed in multiple environmental media and organisms and have a teratogenic effect on and toxicity to animals and humans. The residual levels of seventeen PFAAs in the tissues of two regular consumption fish species, Culter erythropterus and Aristichthys nobilis in Lake Chaohu were measured by a high-performance liquid chromatograph - mass spectrometer (HPLC-MS). The distributions of PFAAs and the effect of the lipid contents were analyzed, and the health risks of typical PFAAs were evaluated. The results showed that perfluorohexanoic acid (PFHxA) was the predominant contaminant (80.50 ± 58.31 ng/g and 19.17 ± 12.57 ng/g wet weight, ww), followed by perfluorooctanesulfonic acid (PFOS) (55.02 ± 34.82 and 14.79 ± 6.24 ng/g, ww) in both fish. The level of total PFAAs was the highest in the liver tissues of Culter erythropterus (359.87 ng/g, ww) and the lowest in the kidney tissues in A. nobilis (10.06 ng/g, ww). Due to the higher trophic level of C. erythropteru, the total PFAA concentrations were significantly higher in all tissues than those in A. nobilis. Liver muscle ratio of C. erythropteru was the highest, indicating the most accumulation in the liver. The concentrations of PFAAs in fish tissues were influenced by the lipid content, resulting in a difference between the lipid-normalized concentrations and the wet weight concentrations of the PFAAs. The non-carcinogenic risks of PFOS were higher than those of PFOA through the ingestion of C. erythropterus and A. nobilis. Both the carcinogenic and non-carcinogenic risks of C. erythropterus were greater than those of A. nobilis, and fish tissue intake could cause an increasing of risks up to 60%, indicating that long-term and large amount ingestion of carnivorous fish and related tissues with higher trophic level, such as C. erythropterus should be avoided.

In vitro and in silico modeling of perfluoroalkyl substances mixture toxicity in an amphibian fibroblast cell line

Poly and perfluoroalkyl substances (PFAS) are a large group of emerging organic pollutants that can persist in the environment and bioaccumulate in biota. They are found in complex mixtures, and although the exact number of PFAS is unknown, it has been estimated to be in the thousands. The objective of this study was two-fold. First, we examined the cytotoxicity of PFAS singly and in binary mixtures using an amphibian fibroblast cell line. Second, we used this experimental data to develop quantitative structure-activity relationship (QSAR) models for single and binary mixtures. We tested the cytotoxicity of four common PFAS: perfluorooctane sulfonate (PFOS); perfluorooctanoic acid (PFOA); perfluorohexane sulfonate (PFHxS); and perfluorohexanoic acid (PFHxA). PFOS was the most toxic and PFHxA the least cytotoxic. Binary mixtures allowed for the construction of isobolograms to test for additivity, synergism, or antagonism. Using this data, QSAR modeling was used for predicting the toxicity of 24 single and 1380 binary mixtures (theoretically generated). Overall, our experimental and modeling results showed that mixtures were approximately additive, with the exception of PFOS and PFOA, which were found to be weakly synergistic. This data shows that certain mixtures of PFAS may have increased toxicity potential above what the simple sum of PFAS concentrations would suggest. More studies are needed that test the toxicity of PFAS mixtures.

Subtle morphometric, behavioral and gene expression effects in larval zebrafish exposed to PFHxA, PFHxS and 6:2 FTOH

Recent studies of perfluoroalkylated substances (PFASs) have focused on the toxicity of long chain PFASs, such as PFOS or PFOA, which have been demonstrated to cause an array of developmental and behavioral effects. However, less is known about low molecular weight PFASs and alternatives. This study examined the morphometric and behavioral effects in zebrafish following developmental exposures of C6 PFASs: perfluorohexanoic acid, PFHxA, perfluorohexane sulfonate, PFHxS, and 6:2 fluorotelomer alcohol, 6:2 FTOH. Embryos were exposed to 0.02-20 μM concentrations of these compounds from the high stage (˜3 h post fertilization, hpf) until 120 hpf. Morphometric and gene expression endpoints were examined at 120 hpf. Genes selected for analysis were previously shown to be altered in zebrafish developmentally exposed to PFOS and PFOA. Additionally, exposed larvae were transferred to clean water and reared until 14 days post fertilization, dpf, when behavioral assays were completed and morphometric endpoints examined. While PFHxA was found to be the most acutely toxic at 120 hpf, few morphometric effects were observed. Gene expression was the most sensitive endpoint with significant increased tgfb1a, bdnf, and ap1s1 expression observed with PFHxA exposure. PFHxS exposure produced morphometric effects in the larvae, specifically increased length and yolk sac area at 2 and 20 μM. This phenotype persisted to the 14 dpf time point, where these larvae additionally displayed decreased distance traveled and crosses through the center of the arena of the behavioral assay. Exposure to 6:2 FTOH caused no morphometric effects at 120 hpf, and this compound was the least acutely toxic. However, expression of both tgfb1a and bdnf were increased by greater than 2 fold change at this time point. Effects also persisted to 14 dpf where a significant increase in distance traveled and velocity were observed in the behavioral assay. This study demonstrates effects on behavioral, morphometric and gene expression endpoints with developmental PFHxA, PFHxS, and 6:2 FTOH exposures in zebrafish.

Mixture-specific gene expression in zebrafish (Danio rerio) embryos exposed to perfluorooctane sulfonic acid (PFOS), perfluorohexanoic acid (PFHxA) and 3,3',4,4',5-pentachlorobiphenyl (PCB126)

Perfluorooctane sulfonic acid (PFOS) and 3,3',4,4',5-pentachlorobiphenyl (PCB126) are persistent organic pollutants of high concern because of their environmental persistence, bioaccumulation and toxic properties. Besides, the amphiphilic properties of fluorinated compounds such as PFOS and perfluorohexanoic acid (PFHxA) suggest a role in increasing cell membrane permeability and solubilizing chemicals. The present study aimed at investigating whether PFOS and PFHxA are capable of modifying the activation of PCB126 toxicity-related pathways. For this purpose, zebrafish embryos were exposed in semi-static conditions to 7.5μg/L of PCB126 alone, in the presence of 25mg/L of PFOS, 15.7mg/L of PFHxA or in the presence of both PFOS and PFHxA. Quantitative PCR was performed on embryos aged from 24h post fertilization (hpf) to 96 hpf to investigate expression changes of genes involved in metabolism of xenobiotics (ahr2, cyp1a), oxidative stress (gpx1a, tp53), lipids metabolism (acaa2, osbpl1a), and epigenetic mechanisms (dnmt1, dnmt3ba). Cyp1a and ahr2 expression were significantly induced by the presence of PCB126. However, after 72 and 78h of exposure, induction of cyp1a expression was significantly lower when embryos were co-exposed to PCB126+PFOS+PFHxA when compared to PCB126-exposed embryos. Significant upregulation of gpx1a occurred after exposure to PCB126+PFHxA and to PCB126+PFOS+PFHxA at 30 and 48 hpf. Besides, embryos appeared more sensitive to PCB126+PFOS+PFHxA at 78 hpf: acaa2 and osbpl1a were significantly downregulated; dnmt1 was significantly upregulated. While presented as environmentally safe, PFHxA demonstrated that it could affect gene expression patterns in zebrafish embryos when combined to PFOS and PCB126, suggesting that such mixture may increase PCB126 toxicity. This is of particular relevance since PFHxA is persistent and still being ejected into the environment. Moreover, it provides additional information as to the importance to integrate mixture effects of chemicals in risk assessment and biomonitoring frameworks.

Independent effect of polymeric nanoparticle zeta potential/surface charge, on their cytotoxicity and affinity to cells

OBJECTIVES

Up to now, little research has been focussed on discovering how zeta potential independently affects polymeric nanoparticle (NP) cytotoxicity.

METHODS

Polymeric nanoparticles of gradient zeta potential ranging from -30 mv to +40 mv were fabricated using the same poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBHHx) biopolymer. Interaction forces between nanoparticles and cells were measured by atomic force microscopy (AFM). Cytotoxicity of the nanoparticles to cells was investigated by using MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay.

RESULTS

Four kinds of nanoparticle with similar sizes and gradient zeta potentials, were fabricated. Those with positive surface charges were found to be more toxic than those with negative surface charges. Positively charged nanoparticles or nanoparticles with higher 'like' charges, offered higher interaction force with cells.

CONCLUSION

This work proposes a novel approach for investigating interaction between NPs and cells, and discloses the importance of controlling zeta potential in developing NPs-based formulations in the future.

Upgrading dilute ethanol from syngas fermentation to n-caproate with reactor microbiomes

Fermentation of syngas from renewable biomass, which is part of the syngas platform, is gaining momentum. Here, the objective was to evaluate a proof-of-concept bioprocessing system with diluted ethanol and acetic acid in actual syngas fermentation effluent as the substrate for chain elongation into the product n-caproic acid, which can be separated with less energy input than ethanol. Chain elongation is performed with open cultures of microbial populations (reactor microbiomes) as part of the carboxylate platform. The highest concentration of n-caproic acid of ~1 g L(-1) was produced at a pH of 5.44 and a production rate of 1.7 g L(-1) day(-1). A higher n-butyrate production rate of 20 g L(-1) day(-1) indicated that product toxicity was limiting the chain elongation step from n-butyric acid to n-caproic acid. This result shows that the syngas and carboxylate platforms can be integrated within a biorefinery, but that product separation is necessary.

The role of cyclophilin D in interspecies differences in susceptibility to hepatotoxic drug-induced mitochondrial injury

Test compound A ((5Z)-6-[(2R,3S)-3-({[(4-Chloro-2-methylphenyl)sulfonyl]amino}methyl) bicyclo[2.2.2]oct-2-yl]hex-5-enoic acid) was withdrawn from premarketing clinical trials due to severe liver injury. Intracellular accumulation of lipids (steatosis) has been observed in human-derived cells and may account for the severe hepatotoxicity. Mitochondrial β-oxidation and ketogenesis play a fundamental role in energy homeostasis. Mitochondrial dysfunction can therefore cause severe deficiency in fatty acid oxidation and apoptosis which finally triggers the hepatocellular injury. Some of hepatotoxic drugs (e.g., salicylic acid, diclofenac and troglitazone) are known to induce mitochondrial dysfunction. This study therefore examined the effect of compound A on the mitochondrial permeability transition (MPT) and membrane potential in mitochondria isolated from mouse, rat and monkey livers. The incubation of rat and monkey mitochondria energized by succinate in the presence of Ca(2+) (20μM) and compound A (2.5-10μM) resulted in cyclosporin A (CsA)-sensitive MPT pore opening and a decline in mitochondrial membrane potential in a concentration-dependent manner. However, mouse mitochondria showed low susceptibility to compound A-induced dysfunction. Rat mitochondrial expression of cyclophilin D (CyPD) was about twice that of mouse mitochondria, but the expression levels of other MPT pore proteins (adenine nucleotide translocator and voltage-dependent anion channel) were comparable in both species. An assessment of the effect of compound A on CyPD knockdown cells demonstrated that mitochondrial susceptibility to compound A was attenuated in CyPD knockdown cells. These results suggest that an interspecies difference in the susceptibility to mitochondrial dysfunction induced by compound A exists as a result of species-specific discrepancies in CyPD expression.

Effects of di-(2-ethylhexyl) phthalate and four of its metabolites on steroidogenesis in MA-10 cells

Phthalate plasticizers are used in the plastics industry to aid in processing and impart flexibility to plastics. Due to the broad use of plastics, and the tendency of plasticizers to leach out of polymers, plasticizers have become ubiquitous in the environment. Concerns about the testicular toxicity of phthalate plasticizers, in particular di-(2-ethylhexyl) phthalate (DEHP), have arisen due to their ability to cause male reproductive tract abnormalities in animal models. It has been assumed that the DEHP metabolite, mono-(2-ethylhexyl) phthalate (MEHP), is the active compound, however, metabolites such as 2-ethylhexanol, 2-ethylhexanal and 2-ethylhexanoic acid, have not been thoroughly investigated. The aim of this study was to evaluate the anti-androgenic potential of these metabolites in vitro with a mouse Leydig tumor cell line, MA-10 cells. DEHP, MEHP and 2-ethylhexanal were found to decrease cell viability, as well as steroidogenic potential. The latter was assessed using an enzyme-linked immunosorbent assay (ELISA) to quantify steroid production and quantitative real-time polymerase chain reaction (qRT-PCR) to assess gene expression analysis of key steroidogenic enzymes. 2-Ethylhexanal proved to be the most potent steroidogenic disruptor, offering intriguing implications in the search for the mechanism of phthalate testicular toxicity. Overall, the study suggests the involvement of multiple active metabolites in the testicular toxicity of DEHP.

Induction of primary biliary cirrhosis in guinea pigs following chemical xenobiotic immunization

Although significant advances have been made in dissecting the effector mechanisms in autoimmunity, the major stumbling block remains defining the etiological events that precede disease. Primary biliary cirrhosis (PBC) illustrates this paradigm because of its high degree of heritability, its female predominance, and its extraordinarily specific and defined immune response and target destruction. In PBC, the major autoantigens belong to E2 components of the 2-oxo-acid dehydrogenase family of mitochondrially located enzymes that share a lipoylated peptide sequence that is the immunodominant target. Our previous work has demonstrated that synthetic mimics of the lipoate molecule such as 6-bromohexoanate demonstrate a high degree of reactivity with PBC sera prompted us to immunize groups of guinea pigs with 6-bromohexanoate conjugated to BSA. In this study, we provide serologic and immunohistochemical evidence that such immunized guinea pigs not only develop antimitochondrial autoantibody responses similar to human PBC, but also develop autoimmune cholangitis after 18 mo. Xenobiotic-immunized guinea pigs are the first induced model of PBC and suggest an etiology that has implications for the causation of other human autoimmune diseases. The data also reflect the likelihood that, in PBC, the multilineage antimitochondrial response is a pathogenic mechanism and that loss of tolerance and subsequent development of biliary lesions depends on either modification of the host mitochondrial Ag or a similar breakdown due to molecular mimicry.

Copolymers of ε-caprolactone and quaternized ε-caprolactone as gene carriers

New copolymers of epsilon-caprolactone (CL) and gamma-bromo-epsilon-caprolactone quaternized by pyridine (Py+CL) were investigated as non-viral vectors for gene delivery. Copolymers with two molar compositions (50 Py+CL/50 CL and 80 Py+CL/20 CL), each with a diblock or a random structure, were used to prepare nanoparticulate complexes with DNA. Average size and surface charge of the complexes and extent of the complexation were measured. The DNA condensation by the copolymers was analysed by a gel retardation assay. Cytotoxicity and transfection efficiency of the copolymers were also evaluated in HeLa cells and compared with polyethylenimine 50 kDa. The size of the polyplexes was approximately 200 nm. The zeta potential first increased with the copolymer/DNA charge ratio and became positive for charge ratios in the 2-4 range depending on the type of copolymer. DNA was completely condensed within the nanoparticles and the degree of interaction was very high. Cytotoxicity and transfection efficiency were found to be comparable to polyethylenimine 50 kDa. The experimental results suggest that the novel copolymers can be used as novel gene delivery vectors.

Biodegradability and biocompatibility of a pH- and thermo-sensitive hydrogel formed from a sulfonamide-modified poly(epsilon-caprolactone-co-lactide)-poly(ethylene glycol)-poly(epsilon-caprolactone-co-lactide) block copolymer

A pH- and thermo-sensitive block copolymer was synthesized by adding pH-sensitive sulfamethazine oligomers (SMOs) to either end of a thermo-sensitive poly(epsilon-caprolactone-co-lactide)-poly(ethylene glycol)-poly(epsilon-caprolactone-co-lactide) (PCLA-PEG-PCLA) block copolymer. The resulting pH- and thermo-sensitive SMO-PCLA-PEG-PCLA-SMO block copolymer solution did not form a gel at high pH (pH 8.0) or at increased temperatures (ca. 70 degrees C), but did form a stable gel under physiological conditions (pH 7.4 and 37 degrees C). The degradation rate of the pH- and thermo-sensitive block copolymer decreased substantially compared with the control block copolymer of PCLA-PEG-PCLA, due to the buffering effect of the SMO-PCLA-PEG-PCLA-SMO sulfonamide groups on the acidic monomer-induced rapid degradation of PCLA-PEG-PCLA. This suitable sol-gel transition and sustained biodegradability of the pH- and thermo-sensitive SMO-PCLA-PEG-PCLA-SMO block copolymer resolves two of the major drawbacks associated with thermo-sensitive block copolymers, namely premature gelation and rapid degradation. Interestingly, SMO-PCLA-PEG-PCLA-SMO showed no evidence of cytotoxicity in vitro. However, subcutaneous injection of the pH- and thermo-sensitive block copolymer solution (20wt% in PBS at pH 8.0) into Sprague-Dawley (SD) rats resulted in rapid, stable gel formation, with the injected hydrogel being completely degraded in vivo in just 6 weeks. The injected hydrogel in vivo presented a typical acute inflammation within 2 weeks, although chronic inflammation was not observed during the first 6-week period. As such, the pH- and thermo-sensitive hydrogel of the SMO-PCLA-PEG-PCLA-SMO block copolymer is a suitable candidate for use in drug delivery systems and cell therapy.

In vivo studies of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) based polymers: biodegradation and tissue reactions

The in vivo tissue reactions and biodegradations of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), poly(lactide) (PLA), poly(3-hydroxybutyrate) (PHB), blends of PHBHHx (X) and poly(ethylene glycol) (PEG) (E) with ratios of 1:1 (E1X1) and 1:5 (E1X5), respectively, were evaluated by subcutaneous implantation in rabbits. Results revealed that the degradation rate increased in the order of PHB < PHBHHx < PLA. During the implantation period, crystallinity of PHBHHx increased from 19% to 22% and then dropped to 14%. Gel permeation chromatography (GPC) displayed increasing polydispersity and typical bimodal distribution from 3 to 6 months. The above results suggested that rapid PHBHHx degradation occurred in amorphous region rather than in crystalline region. While the in vivo hydrolysis of PHB was found to start from a random chain scission both in amorphous and crystalline regions of the polymer matrix, as demonstrated by its hydrolysis process accompanied by a decrease in molecular weight with unimodal distribution and relatively narrow polydispersity. Compared to pure PHBHHx, PHBHHx-PEG blends showed accelerated weight loss of PHBHHx with weak molecular weight reduction. In general, PHBHHx elicited a very mild tissue response during implantation lasting 6 months compared with relative acute immunological reactions observed among PHB and PLA objects, respectively. Pronounced tissue responses were observed in the capsule surrounding E1X1 and E1X5 as characterized by the presence of lymphocytes, eosinophils and vascularization, which might be resulted from the continuous leaching of PEG.

Responses of the Liver to Perfluorinated Fatty Acids with Different Carbon Chain Length in Male and Female Mice:In Relation to Induction of Hepatomegaly, Peroxisomal .BETA.-Oxidation and Microsomal 1-Acylglycerophosphocholine Acyltransferase

The potency of the induction of hepatomegaly, peroxisomal beta-oxidation and microsomal 1-acylglycerophoshocholine (1-acyl-GPC) acyltransferase was compared among perfluorinated fatty acids (PFCAs) with 6-9 carbon chain length in the liver of male and female mice. All PFCAs examined induced hepatomegaly and peroxisomal beta-oxidation and the potency was in the order of perfluorononanonic acid (PFNA), perfluorooctanoic acid (PFOA), perfluoroheptanoic acid (PFHA) and perfluorohexanoic acid (PFHeA) when compared with the relative doses to induce the two parameters. Microsomal 1-acyl-GPC acyltransferase was induced by PFHA, PFOA and PFNA, as was peroxisomal beta-oxidation. No significant sex-related difference was observed in the induction of peroxisomal beta-oxidation by any PFCAs examined. PFNA and PFOA accumulated in the liver of both male and female mice in a dose-dependent manner. PFHA accumulated in the liver to a lesser extent; little PFHeA accumulated in the liver. Hepatic concentrations of PFNA, PFOA and PFHA were higher in male mice than those in female mice. One linear regression line was confirmed between the activities of peroxisomal beta-oxidation and hepatic concentrations of PFHeA, PFHA, PFOA and PFNA in male mice regardless of their carbon chain lengths, and the activities were saturable at the concentrations over approximately 500 nmol/g liver. Similar linear regression line was obtained between the two parameters in female mice. These results suggest (i) that the longer the perfluoroalkyl chain becomes, the more PFCA accumulates in the liver of both male and female mice, (ii) that the accumulated PFCAs induce hepatomegaly, peroxisomal beta-oxidation and microsomal 1-acyl-GPC acyltransferase, and (iii) that the difference observed in the accumulation of PFHA, PFOA and PFNA in the liver between male and female mice is not enough to produce obvious sex-related difference in the induction of peroxisomal beta-oxidation.

Effects of di-(2-ethylhexyl)-phthalate and its metabolites on the lipid profiling in rat HRP-1 trophoblast cells

The highly directional maternal-to-fetal transfer of essential fatty acids (EFAs) across the placenta plays a critical role in guiding proper fetal development. Exposure to xenobiotics that may alter the fetal supply of EFAs/lipids could lead to fetal toxicity. Since the placenta is the first fetal arising organ that regulates fetal fatty acid homeostasis, the fatty acid/lipid composition in the placenta may serve as an indicator of fetal composition. In this study, we investigated the effects of the peroxisome proliferator chemical di-(2-ethylhexyl)-phthalate (DEHP), a widely used plasticizer and ubiquitous environmental contaminant, and its selective metabolites, mono-(2-ethylhexyl)-phthalate (MEHP) and 2-ethylhexanoic acid (EHA) on the lipid metabolome in a rat HRP-1 trophoblast model. The concentrations of ten lipid classes (cholesterol esters, diacylglycerol, triacylglycerides, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, lysophosphatidylcholine, cardiolipin, and sphingomyelin) were determined, as well as the individual fatty acid compositions, especially the omega-3 and omega-6 family of EFAs. The level of each lipid class was significantly increased upon exposure to the agents, with MEHP and EHA generally showing higher increases than DEHP. The same trends were observed in comparing the fatty acid compositions. For example, the omega-3/omega-6 fatty acids ratio did not change, although the levels of omega-3 and omega-6 fatty acids were significantly elevated upon exposure. These results suggest that DEHP and its metabolites can alter lipid metabolome in a rat placental cell line, implying that these compounds may contribute to aberrant placental EFA/lipid homeostasis caused by peroxisome proliferation, and potentially result in abnormal fetal development.

Study on rat subcutaneous reaction to experimental polyurethane elastomers

The purpose of the study was to investigate the biocompatibility of experimental elastomers, E580 and E590. The experimental elastomers and the control--a clinically used elastomer--were implanted into the subcutaneous tissue of rats. The tissue reactions were examined histologically on the 3rd, 7th, 14th, 28th, and 56th day after implantation. It was found that there were some irritant responses in the tissues adjacent to the implanted elastomers during the first week. However, the inflammatory tissue reaction subsided substantially from the second week onwards. The stable fibrous capsule surrounding the elastomer was formed after eight weeks. The tissue responses of the control, E580, and E590 were similar. The results suggested that the long-term tissue irritation of the experimental elastomers was so low such that they have the potential to be applied clinically.

Effects of di-(2-ethylhexyl)-phthalate (DEHP) and its metabolites on fatty acid homeostasis regulating proteins in rat placental HRP-1 trophoblast cells

Di-(2-ethylhexyl)-phthalate (DEHP) is a widely used plasticizer and ubiquitous environmental contaminant. The potential health hazards, including teratogenicity, from exposure to DEHP may be related to the role of DEHP or its metabolites in the trans-activation of peroxisome proliferator-activated receptors (PPARs). Fetal essential fatty acid (EFA) homeostasis is controlled by directional transfer across the placenta through a highly regulated process, including PPAR activation. Using HRP-1 rat trophoblastic cells, the effects of DEHP and two of its metabolites, mono-(2-ethylhexyl)-phthalate (MEHP) and 2-ethylhexanoic acid (EHA), on the mRNA and protein expression of the three known PPAR isoforms (alpha, beta, and gamma), fatty acid transport protein 1 (FATP1), plasma membrane fatty acid binding protein (FABPpm), and the heart cytoplasmic fatty acid binding protein (HFABP) were investigated. This study also investigated the functional effects of exposure on the uptake and transport of six long chain fatty acids (LCFAs): arachidonic acid (AA), docosahexaenoic acid (DHA), linoleic acid (LA), alpha-linolenic acid (ALA), oleic acid (OA), and stearic acid (SA). In the presence of DEHP, MEHP, and EHA, the expression of PPARalpha, PPARgamma, FATP1, and HFABP were up-regulated in a dose- and time- dependent manner, while PPARbeta and FABPpm demonstrated variable expression. The uptake rates of EFAs (AA, DHA, LA, ALA) increased significantly upon exposure, and the transport of AA (omega-6) and DHA (omega-3) were directionally induced. These results suggest that DEHP, MEHP, and EHA can influence EFA transfer across HRP-1 cells, implying that these compounds may alter placental EFA homeostasis and potentially result in abnormal fetal development.

Plasticizer metabolites in the environment

Earlier work with pure cultures had shown that the interaction of microbes with plasticizers leads to the formation of metabolites including 2-ethylhexanoic acid and 2-ethylhexanol that resist further degradation. The presence of these metabolites is now reported in a variety of environmental samples. Thus, even in a complex ecosystem, when plasticizers are degraded, the breakdown is not complete and significant amounts of 2-ethylhexanoic acid and 2-ethylhexanol are observed. These compounds have been shown to exhibit acute toxicity using Microtox, Daphnia, rainbow trout and fathead minnow toxicity assays. Since it is already well established that plasticizers are ubiquitous in the environment, it is expected that their recalcitrant metabolites will also be ubiquitous. This is of concern because, while the plasticizers do not exhibit acute toxicity, their metabolites do.

Fragrance material review on linalyl hexanoate

A toxicologic and dermatologic review of linalyl hexanoate when used as a fragrance ingredient is presented.

Developmental toxicity of 2-ethylhexyl stearate

2-Ethylhexyl stearate was investigated in an embryo-/foetotoxicity and teratogenicity study on rats according to OECD guidelines for the testing of chemicals (No. 414). Dose levels of 0 (arachidis oil), 100, 300 and 1000mg/kg body weight/day were administered by gavage. Dams tolerated the applied dose levels without any toxic effects. Pre- and post-implantation loss and mean numbers of resorptions were unaffected by treatment. All parameters were comparable with the animals of the control group. Skeletal and visceral investigations revealed no treatment-related malformations. For embryo-/foetotoxicity, teratogenicity and maternal toxicity a NOAEL of 1000mg/kg was deduced.

Tissue biocompatibility of a new caprolactone-coated self-reinforced self-expandable poly-L-lactic acid bioabsorbable urethral stent

BACKGROUND AND PURPOSE

The bioabsorption time as well as other properties of bioabsorbable polymers can be affected by the choice of the basic molecule, by the degree of its polymerization, and by the coating material used in the device. The aim of our present study was to evaluate the biocompatibility of a new caprolactone copolymer-coated, self-reinforced poly-L-lactic acid (SR-PLLA) urethral stent by means of a rabbit muscle implantation test. This new material has previously been tested for cytotoxicity using the thymidine incorporation method (DNA synthesis inhibition test), no toxicity being evidenced.

MATERIALS AND METHODS

Fifteen male rabbits were used as experimental animals. Rods made from pure lactic acid, pure caprolactone copolymer, and caprolactone-coated lactic acid were placed on both sides of the dorsal muscles, eight implants per rabbit. Rods made from latex and silicone were used as positive and negative controls, respectively. The animals were sacrificed after 1 week, 1 month, or 6 months. Tissue reactions around the implants were analyzed and scored semiquantitatively.

RESULTS

Acute tissue reactions attributable to operative trauma were seen in all specimens at 1 week. After 6 months, chronic inflammatory changes and foreign-body reactions were seen only in the positive controls.

CONCLUSION

The new caprolactone copolymer material is highly biocompatible.

Larval tolerance in the Drosophila melanogaster species complex toward the two toxic acids of the D. sechellia host plant

The toxicity of hexanoic (C6) and octanoic (C8) acids, the two major components of the host plant of Drosophila sechellia, was investigated upon larvae of the four species included in the D. melanogaster complex and on interspecific hybrids between D. sechellia and D. simulans. Specific methods had to be devised for obtaining reproducible toxicity results. The three generalist species (D. melanogaster, D. mauritiana and D. simulans) were found to be very sensitive, as indicated by low lethal concentrations and an increase in development duration. By contrast D. sechellia was much more tolerant, especially toward C8 which is the most abundant product in the natural resource. Interspecific hybrids (F1 and backcrosses) exhibited intermediate characteristic, but a dominance of D. simulans sensitivity was observed for both acids and especially for C8. Data on larvae are quite different from those previously obtained on adults, and are more likely to reflect the natural selective pressures existing in the wild.

2-Ethylhexanoic acid: subchronic oral toxicity studies in the rat and mouse

Groups of 10 male and 10 female Fischer 344 rats and B6C3F1 mice were fed diets containing either 0.0, 0.1, 0.5 or 1.5% 2-ethylhexanoic acid (EHA) for 13 wk. Additional groups of 10 male and 10 female rats or mice. were fed either 0.0 or 1.5% EHA for 13 wk followed by a 4-wk recovery (non-treatment) period. Based on food consumption and body weight, the EHA diets provided doses of 61, 303 or 917 mg/kg/day for male rats and 71, 360 or 1068 mg/kg/day for female rats. The EHA diets provided doses of 180, 885 or 2728 mg/kg/day for male mice and 205, 1038 or 3139 mg/kg/day for female mice. No mortality or significant clinical signs of toxicity were observed during the study. Body weights and food consumption of both rats and mice fed 1.5% EHA were lower beginning after the first week of treatment, consistent with a reduction in food consumption. Other groups were unaffected by treatment. After 13 wk, lower triglyceride levels occurred in male mice fed 1.5% EHA and female mice fed 0.5 or 1.5% EHA, but not in other groups. Cholesterol levels were higher in all male rat test groups and in female rats and male and female mice fed either 0.5 or 1.5% EHA, although this effect was reversible following a 28-day recovery period. The principal effects of EHA involved the liver or metabolic processes associated with the liver. The 0.5 and 1.5% diets in both rats and mice were associated with increased relative liver weight and histological changes in hepatocytes, specifically hepatocyte hypertrophy and reduced cytoplasmic vacuolization. Observed histopathological and clinical pathological changes were reversible following recovery. These results indicate that EHA does not produce persistent. overt toxicity in rats or mice following subchronic dietary exposure at concentrations up to 1.5% in feed. The no-observed-adverse-effect level (NOAEL) for male rats was 61 mg/kg/day and the no-observed-effect level (NOEL) for female rats was 71 mg/kg/day, while 180 and 205 mg/kg/day represent NOELs for male and female mice, respectively.

Altered zinc metabolism contributes to the developmental toxicity of 2-ethylhexanoic acid, 2-ethylhexanol and valproic acid

It has been hypothesized that the developmental toxicity of certain compounds is, in part, due to maternal toxicity resulting in alterations in zinc (Zn) metabolism that affects the developing conceptus. In the present work the effects of developmentally toxic doses of 2-ethylhexanoic acid (EHXA), 2-ethylhexanol (EHXO), and valproic acid (VPA) on Zn metabolism were investigated in the pregnant rat. In experiment 1, dams were intubated with EHXA (3.13, 6.25, 9.38 or 12.5 mmol/kg), EHXO (6.25, 9.38 or 12.5 mmol/kg), VPA (1.56, 3.13, 6.25 or 9.38 mmol/kg), or corn oil (control; 1.0 ml/kg) at 14:00 h on gestation day (GD) 11.5, intubated with 32 microCi 65Zn at 22:00 h, and then killed at 08:00 h on GD 12.5. At the higher dose levels of EHXA and EHXO, and at all dosages of VPA, the percentage of 65Zn retained in maternal liver was higher, while that in the embryos was lower, than in controls. Chemical-associated changes in 65Zn distribution were associated with increased maternal liver metallothionein (MT) concentrations. In experiment 2, dams were fed diets containing 1, 25 or 97 microg Zn/g from GD 0-16 and intubated with 3.5 mmol EHXA or 1.0 ml corn oil/kg/d from GD 8-15. Dams were killed on GD 16 or 19. High incidences of encephalocele and tail defects were noted in the GD 16 fetuses of EHXA-treated dams fed either the low or adequate Zn diet, the highest incidences being in the low Zn group. On GD 19 the incidence of tail defects tended to be higher in the EHXA groups than in oil-treated controls, the highest incidence occurring in the low Zn EHXA group. Encephalocele was only observed in the low Zn EHXA-treated group. Fetal weight and crown-rump lengths were decreased by EHXA treatment and low dietary Zn. The incidence of rib anomalies was higher in the EHXA-exposed groups than in their respective oil controls. In experiment 3, GD 10.5 embryos collected from control dams were cultured for 48 h in serum from control or EHXA-treated male rats fed 4.5 or 25.0 microg Zn/g diets. Embryos cultured in either EHXA or low Zn sera exhibited delayed development; the addition of Zn to these sera eliminated their developmental toxicity. These results support the hypothesis that certain chemicals which induce maternal toxicity act, in part, to influence embryonic Zn metabolism and trigger abnormal development. Importantly, the teratogenic effects of these chemicals can be modulated by dietary Zn intake.

CYP enzymes catalyze the formation of a terminal olefin from 2-ethylhexanoic acid in rat and human liver

1. The metabolism of 2-ethylhexanoic acid (2-EHA) was studied in rat, mouse and human liver microsomes in vitro. The metabolites of 2-EHA were identified as methylated derivatives by gas chromatography-mass spectrometry. 2. 2-Ethyl-1,6-hexanedioic acid was the main metabolite produced in rat, mouse and human liver microsomes. Unsaturated 2-ethyl-5-hexenoic acid, a terminal olefin, was produced only in human liver microsomes and phenobarbital-induced rat liver microsomes. The cytochrome P450 (CYP) inhibitors metyrapone, SKF 525A, triacetyloleandomycin (TAO), quinidine and the cytochrome P450 reductase antibody abolished its formation both in rat and human microsomes. 3. The metabolites were analyzed also in vivo in urine of 2-EHA-exposed rats and in urine of sawmill workers exposed occupationally to 2-EHA. Both rat and human urine contained 2-ethyl-1,6-hexanedioic acid as the main metabolite and also 2-ethyl-5-hexenoic acid. Metyrapone, SKF 525A and TAO all decreased drastically the formation of 2-ethyl-5-hexenoic acid in the rat. 4. The data indicate that (1) several CYP families (CYP2A, CYP2B, CYP2D and CYP3A) could be responsible for the hepatic metabolism of 2-EHA, (2) the same metabolites were formed in rats and man and (3) an unsaturated terminal olefin, 2-ethyl-5-hexenoic acid is formed in the liver.

Pharmacokinetic determinants of embryotoxicity in rats associated with organic acids

We have studied four organic acids of similar structure to further understand the basis of their developmental toxicity. Valproic acid (2-propyl pentanoic acid), ethylhexanoic acid, and octanoic acid are isomeric C8 organic acids but their teratologic potency varied widely. Valproic acid induced a moderate to severe teratologic outcome after a single oral administration of 6.25 mmoles/kg on day 12 of rat pregnancy. Twice as much ethylhexanoic acid (12.5 mmoles/kg) induced a less severe response. Octanoic acid was nonteratogenic even at the very high dose of 18.75 mmoles/kg. This latter result is undoubtedly due to poor intestinal absorption of octanoic acid, as the maternal plasma levels never reached half of those measured for valproic acid and ethylhexanoic acid. Moreover, only a tiny fraction of that in maternal plasma was actually transferred into the embryo. On the other hand, the peak concentration and duration of exposure to valproic acid and ethylhexanoic acid were very similar despite a more severe teratologic outcome following valproic acid, which indicated higher intrinsic activity of this latter agent. A fourth agent, methylhexanoic acid, was also studied and had no teratogenic effects when given at 14.1 mmoles/kg. Pharmacokinetic studies of this agent revealed higher peak concentrations in maternal plasma and embryo than valproic acid or ethylhexanoic acid, but the duration of exposure was shorter. We conclude that pharmacokinetic parameters can be important determinants of teratologic outcome and thereby help explain differing potencies of structurally similar chemicals.

Effects of 2-ethylhexanoic acid on reproduction and postnatal development in Wistar rats

Reproductive toxicity of 2-ethylhexanoic acid (2-EHA) was studied in Wistar rats. The animals (24 animals per sex per group) were given 2-EHA as a sodium salt in drinking water at daily doses of 100, 300, or 600 mg/kg. Control animals received plain water. Male rats were exposed to 2-EHA for 10 weeks and females for 2 weeks prior to mating, both sexes during the mating period and females during the entire gestation and lactation period. 2-EHA caused a slight but dose-dependent decrease in fertility; time to mating increased at 300 and 600 mg/kg and even total infertility ensued. 2-EHA slightly decreased sperm quality in males. The spermatozoa were significantly less motile at 100 and 600 mg/kg and abnormal sperm occurred more frequently at the two highest dose levels. The average litter size was reduced by 16% in the dose group receiving 600 mg/kg. The birth weights of the pups were unaffected but the body weight gain was transiently slower during lactation at 600 mg/kg. Several pups appeared abnormal (kinky tail, lethargic, slightly paralyzed legs) and the physical development assessed by several landmarks (opening of eyes, eruption of teeth, hair growth) and reflexes (grip reflex, cliff avoidance) was delayed at 300 and 600 mg/kg. In another experiment, a single dose of 600 mg/kg 2-EHA was given to pregnant females by gavage on Gestational Day 4, 5, 6, or 7 and the number of implantations were counted on Gestational Day 10. Administration on Day 6 decreased the number of implantations and caused resorptions.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of the developmental toxicity of 2-ethylhexanoic acid in rats and rabbits

This study was carried out to assess the developmental toxicity of orally administered 2-ethylhexanoic acid (2-EHA) throughout organogenesis in the rat and the rabbit. Treatment of Fischer 344 inbred rats with doses of 100 to 1000 mg 2-EHA/kg/day on (Gestation Days) (GD) 6-15 in a range-finding and a definitive study resulted in a high level of maternal death at 1000 mg/kg/day. Clinical signs of maternal toxicity, including increased liver weight, as well as increased resorptions, dead fetuses, and growth retardation, but no malformations, were observed at 500 mg/kg/day. Slight developmental toxicity, manifested as a reduction in skeletal ossification, occurred in fetuses exposed to 250 mg/kg/day. No adverse effects of treatment were associated with the lower 2-EHA doses (100 and 125 mg/kg/day). Maternal toxicity was also observed in range-finding and definitive studies in New Zealand white rabbits exposed to 25 to 1000 mg 2-EHA/kg/day on GD 6-18 with excessive mortality observed at the highest doses (500 and 1000 mg/kg/day). A low incidence of maternal death as well as abortion occurred following treatment with 125 and 250 mg 2-EHA/kg/day. Less severe clinical signs (reduced weight and food consumption and hypoactivity) were also observed in the 250 mg/kg/day group. There were no adverse effects on fetal viability, growth, or morphology at any dose level. Thus, exposure to 2-EHA during the entire period of organogenesis caused developmental toxicity only at maternally toxic doses in the rat or adverse maternal effects in the absence of developmental toxicity in the rabbit. No evidence of teratogenicity was associated with 2-EHA in this classical safety assessment regimen in either species. The no observed adverse effect levels (NOAELs) for maternal and developmental toxicities in rats are 250 and 100 mg/kg/day, respectively; the corresponding NOAELs for rabbits are 25 mg/kg/day (maternal) and > or = 250 mg/kg/day (developmental).

The developmental toxicity of 2-ethylhexanoic acid in Wistar rats

The developmental toxicity of 2-ethylhexanoic acid (2-EHA), a wood preservative and a mammalian metabolite of di-(2-ethylhexyl) phthalate was examined in Wistar rats (20-21 pregnant females/dose). Mated animals were exposed to 2-EHA in their drinking water at doses of 100, 300, or 600 mg/kg/day on Days 6-19 of gestation. Control animals received vehicle water. The fetuses were examined (on Gestational Day 20) for external, visceral, and skeletal malformations and variations. 2-EHA was marginally toxic to the dams at 600 mg/kg, but not at lower doses, since the mean near term body weight was reduced by 11%. This dose level was also slightly fetotoxic as indicated by a 5 to 8% decrease in the mean fetal body weight both in males and females. No treatment-related effects were observed in the number of implantations or live fetuses. At doses of 100 mg/kg and above, 2-EHA caused skeletal malformations (clubfoot, absence of fibula, polydactyly), while the development of visceral tissues was less affected. The number of affected fetuses increased in a dose-dependent way (4.9, 8.9, and 15.3% of treated offspring at 100, 300, and 600 mg/kg/day, respectively, vs 2.4% control). These results indicate that 2-EHA is teratogenic in rats already at doses which are not yet maternally toxic. The skeleton appears to be the main target of 2-EHA in developing rats.

Peroxisome proliferation due to di (2-ethylhexyl) adipate, 2-ethylhexanol and 2-ethylhexanoic acid

The dose-response relationships for peroxisome proliferation due to Di (2-ethylhexyl) adipate (DEHA), 2-ethylhexanol (EH), 2-ethylhexanoic acid (EHA) have been investigated in rats and mice. Linear dose-response relationships were observed for induction of cyanide-insensitive palmitoyl CoA oxidation (PCO), used as a enzyme marker of peroxisome proliferation, by DEHA, EH and EHA in both species. Relative liver weights were also increased in a dose related manner. On a molar basis, DEHA was twice as potent as EH or EHA which were equipotent and PCO was stimulated to a greater extent in male mice than in rats or female mice. At doses above 8 mmol/kg/day, EH was toxic to rats (both sexes) and similarly EHA at 13.5 mmol/kg/day lead to the death of female rats. In a attempt to explain the species difference in carcinogenicity of DEHA previously reported, we also used Fischer 344 rats and B6C3F1 mice. DEHA administration (2.5 g/kg/day) to Fischer 344 rats and B6C3F1 mice lead to toxicity in female rats. Relative liver weights were increased in a dose related fashion by DEHA administration to both rats and mice, PCO but not catalase was markedly increased (up to 15 fold in male rats). Light microscopy examination indicated some glycogen loss, a dose related hypertrophy and increased eosinophilia in both rats and mice. Electron microscopy confirmed peroxisome proliferation accompanied by a marked reduction of lipid in the centrilobular hepatocytes. These data suggest EHA to be the proximate peroxisome proliferator derived from DEHA.(ABSTRACT TRUNCATED AT 250 WORDS)

Murine teratology and pharmacokinetics of the enantiomers of sodium 2-ethylhexanoate

A mouse model for the induction of exencephaly with sodium (+/-)-2-ethylhexanoate has been developed using multiple administration regimes. With three consecutive administrations at one-half-day intervals, the most sensitive time to induce exencephaly was Gestational Days 8-9. Using the racemic substance it was determined that the SWV strain was more sensitive to the induction of exencephaly than the C57BL/6NCrlBR strain. The enantiomers of 2-ethylhexanoic acid were separated via preparative HPLC to greater than 99.8% optical purity, and greater than 99% purity according to a gas chromatographic analysis. It was demonstrated that the (R)-enantiomer is a more potent teratogen than the (S)-enantiomer for the induction of exencephaly as well as malformations of other organ systems. Pharmacokinetic analyses for each of the enantiomers were performed in maternal plasma, maternal muscle, and embryo. The pharmacokinetics showed that the peak concentration (Cmax) for both enantiomers in the three compartments was approximately equivalent and was attained within 15 min following the third administration. The area under the concentration versus time curve values for the two enantiomers were approximately 10% higher for the (R)-antipode because of a slightly slower elimination of this compound. There was negligible (or no) racemization of the two enantiomers in the biological samples. The results suggest that teratologic differences in the enantiomers of sodium 2-ethylhexanoate are not due to differences in the concentrations of these antipodes in the embryo, but more likely result from the specific interaction of the enantiomers with chiral molecules in the embryo.

Enantioselectivity in the induction of peroxisome proliferation by 2-ethylhexanoic acid

The stereoselectivity of the peroxisome proliferation potency of 2-ethylhexanoic acid (2-EHA), a metabolite of the plasticizer di-(2-ethylhexyl) adipate, was investigated in vitro. The enantiomers of 2-EHA were prepared via the semipreparative HPLC resolution of their diastereoisomeric (+)-(R)-1-phenylethylamine derivatives and the subsequent hydrolytic cleavage. Monolayers of hepatocytes were incubated 3 days with solution of (-)-(R), (+)-(S), and (+/-)-2-EHA. The peroxisome proliferation potency was measured by means of determination of the peroxisomal palmitoyl coenzyme A oxidation. The theoretical induction component due to each enantiomer were calculated from the experimental data considering the enantiomeric purities of the acids. The (+)-(S)-enantiomer was found to be the most potent inducer e.g., the eutomer, while the (-)-(R) was the distomer. The eudismic ratio was about 1.6 and the racemic mixture exhibited an intermediary potency. These results, obtained in vitro in conditions avoiding confounding factors such as pharmacokinetics, suggest that the peroxisome proliferation induced by 2-ethylhexanoic acid is a stereoselective phenomenon.

Additive incidence of developmental malformation for Xenopus embryos exposed to a mixture of ten aliphatic carboxylic acids

A modified FETAX (Frog Embryo Teratogenesis Assay: Xenopus) protocol was used to assess the joint action of ten aliphatic carboxylic acids on Xenopus embryo development. Stock solutions of each acid alone, made up at twice the EC50 of the individual acids, were prepared for testing alone and in a mixture with an equal volume of each acid stock solution. For each treatment, five concentrations and a control dish, each with 25 embryos, were tested for 96 h, with solution renewal every 24 h. The embryos were then fixed and evaluated for gross malformations. For each dish, the number and types of malformations were recorded. An EC50 was calculated for each acid alone and this value was defined as 1.0 toxic unit (TU) for malformation induced by the acid. An EC50 was also calculated for the mixture. The concentration of each acid at the mixture EC50 and the TU values corresponding to these concentrations were then determined. A TU value of 0.990 (0.923-1.060) was obtained for the mixture by adding the TU values for each acid in the mixture. This represents a concentration additive rate of malformation. Microcephaly, TU = 1.09 (1.01-1.18), was the primary malformation, but did not completely account for the response. The concentration additive rate of malformation indicates that all ten acids are likely to induce malformation in Xenopus embryos in a similar manner. Quantitative structure-activity relationship (QSAR) analysis revealed developmental malformation induced by the acids was highly correlated (r2 = 0.979) with hydrophobicity and molar refractivity (r2 = 0.949). The approach has potential application in determining compounds that induce developmental malformations in a similar manner, when metabolism and pharmacokinetic factors are considered.

Hyaline droplet nephropathy resulting from exposure to 3,5,5-trimethylhexanoyloxybenzene sulfonate

Acute oral dosing of 3,5,5-trimethylhexanoyloxybenzene sulfonate (THBS) to adult male and female rats causes a male rat-specific nephrotoxicity manifested as exacerbation of hyaline droplet formation. This chemical is structurally distinct from the volatile hydrocarbons known to cause male rat-specific kidney lesions. Therefore, to classify THBS as a hyaline droplet-inducing agent, experiments were conducted to determine whether [14C]THBS equivalents bound to alpha 2 mu-globulin and caused the protein to accumulate in male rat kidney cortex. Two-dimensional gel electrophoretic separation of male rat kidney proteins indicated that alpha 2u-globulin levels in kidney increased 24 hr after a single oral dose of THBS (500 mg/kg). Furthermore, a sex-dependent retention THBS was noted as there was approximately 10 times more THBS equivalents in male rat kidney than in female rat kidney. Equilibrium dialysis experiments indicated that 40% of THBS equivalents bound reversibly to male rat kidney proteins, whereas no interaction between THBS and female rat kidney proteins was detected. Specific binding of THBS to alpha 2mu-globulin was determined by anion-exchange HPLC after which metabolites in the alpha 2u-globulin fraction were identified by gas chromatography with parallel radioactivity-mass spectrometry and mass spectrometry-matrix isolation Fourier-transform infrared analysis. Four metabolites of THBS were found in this protein fraction, and the major component (approximately 70%) was identified as the cis gamma-lactone of 3,5,5-trimethylhexanoic acid. Experiments were also conducted in mice to determine whether THBS bound to any mouse kidney proteins, particularly mouse urinary protein. The results indicated that there was no interaction between THBS and mouse urinary protein, a protein which shares significant homology with alpha 2u-globulin. These results indicate that THBS treatment exacerbates hyaline droplet formation in male rat kidneys by binding to alpha 2mu-globulin, thereby causing the protein to accumulate in the renal cortex. The interaction between THBS and alpha 2mu-globulin appears to be unique to this male rat-specific protein as THBS does not interact with a very similar protein found in mice.

Effects of valproic acid, some of its metabolites and analogues on prenatal development of rats in vitro and comparison with effects in vivo

Using a whole-embryo culture system valproic acid (VPA) and some of its metabolites (2-en-VPA, 4-en-VPA, 4,4'-dien-VPA) and analogues (ethyl-propyl-acetic acid, propyl-butyl-acetic acid, di-butyl-acetic acid, 2-methyl-2-ethyl-hexanoic acid, 1-methyl-1-cyclohexanoic acid) were tested for their potential to induce abnormal development. With regard to embryonic growth, development and abnormality rate, the tested compounds showed a wide range of "teratogenic potency" in vitro. In order to verify some of the in vitro results, in vivo experiments were performed. Pregnant rats were treated subcutaneously on day 10 of gestation with 2 x 330 mg VPA/kg, or 2 x 400 mg 2-en-VPA/kg, respectively. Evaluation of the embryos was performed on day 11.5 of gestation, corresponding to the in vitro experiments. VPA showed a high potential to induce abnormal development in vivo as well as in vitro, whereas 2-en-VPA was inactive under our experimental conditions. Problems connected with the evaluation of the predictive value of an in vitro test system for the detection of embryotoxic effects, such as "validation" and significance of pharmacokinetic data, are discussed.

Penicillic acid as Na+,K+ and Ca2+ channel blocker in isolated frog's heart at toxic levels

The effect of penicillic acid on isolated frog's heart has been studied along with ions of Na+,K+ and Ca2+. Penicillic acid has been found to inhibit the entry of these ions into cardiac tissue thereby arresting the action of the heart. The blockage can be washed away by perfusion with Ringer's solution.

Asymmetric synthesis and teratogenic activity of (R)- and (S)-2-ethylhexanoic acid, a metabolite of the plasticizer di-(2-ethylhexyl)phthalate

The stereoselectivity of the teratogenic activity of 2-ethylhexanoic acid (EHXA), a metabolite of the widely-used plasticizer di-(2-ethylhexyl)phthalate, was investigated. The enantiomers of EHXA were prepared via asymmetric synthesis with the aid of the chiral auxiliaries (R)- and (S)-1-amino-2-(methoxymethyl)pyrrolidine (RAMP, SAMP). The aqueous solutions of the sodium salts of (R)- and (S)-EHXA and the racemic EHXA [+/- )-EHXA) were injected each morning and evening of day 7 and 8 of gestation in the NMRI mouse (500 mg/kg, i.p.), a period highly sensitive in regard to the production of neural tube defects (exencephaly) by branched-chain carboxylic acids. (S)-EHXA did not yield any teratogenic or embryotoxic response in this model, while (R)-EHXA was highly teratogenic (59% of living fetuses exhibited exencephaly) and embryotoxic (as indicated by embryolethality and fetal weight retardation); the exencephaly rate induced by (+/- )-EHXA was between those of the two enantiomeres (32%). It is therefore likely that stereoselective interactions of the enantiomers of EHXA with chiral molecules in the embryo are decisive in regard to the teratogenic response. This first example of the stereoselectivity of the teratological activity of an environmental pollutant suggests that the safety of man-made chemicals can be improved by the use of pure enantiomers instead of racemates.

Teratogenicity of di(2-ethylhexyl) phthalate, 2-ethylhexanol, 2-ethylhexanoic acid, and valproic acid, and potentiation by caffeine

It is hypothesized that the teratogen di(2-ethylhexyl) phthalate (DEHP) acts by in vivo hydrolysis to 2-ethylhexanol (2-EHXO), which in turn is metabolized to 2-ethylhexanoic acid (2-EHXA), the proximate teratogen. Teratological studies were conducted with Wistar rats, with administration of these agents on day 12 of gestation. On an equimolar basis DEHP was least potent, 2-EHXO was intermediate, and 2-EXHA was the most potent of the three agents, which is consistent with the hypothesis. Similarity in the types of defects found with these agents also suggests a common mechanism, with 2-EHXA as the proximate teratogen. All three agents were potentiated by caffeine. Valproic acid, which is an isomer of 2-EXHA, also produced similar defects, and was approximately twice as potent as 2-EHXA.

Bacterial tests as indicators for the detoxification of the mycotoxin penicillic acid by ammonia treatment

The detoxification of penicillic acid by reaction with ammonia was examined by means of a polymerase assay using two strains of Escherichia coli (pol A+ and pol A-1) and a recombination assay using two strains of Bacillus subtilis (rec+ and rec-). A 100-fold surplus of ammonia added to penicillic acid abolished the cytotoxic and genotoxic effects of penicillic acid towards the bacteria under the test conditions. The study presents the possibility of detoxifying mycotoxins in feeds by ammonia treatment and demonstrates the suitability of bacterial assays as indicators for mycotoxins.

Toxic effects of fatty acids on yeast cells: possible mechanisms of action

As shown in a previous paper, threshold concentrations of lower and intermediate fatty acids inhibit the uptake of inorganic phosphate, growth, and cell division in yeast cells. This demonstrates that, apart from these effects, the acids cause an increase in the respiration quotient (RQ), inhibition of CO2 fixation, production of ethanol at the expense of anabolic processes, and inhibition of active amino acid transport in the yeast Candida utilis. On the other hand, the threshold concentrations have no effect on intracellular pH. The inhibition of the inorganic phosphate uptake cannot be the sole primary mode of action of fatty acids since the omission of inorganic phosphate in the incubation medium brings about an inhibition of anabolic processes that is lower than that brought about by fatty acids since the omission of inorganic phosphate in the incubation medium brings about an inhibition of anabolic processes that is lower than that brought by fatty acids at concentrations still premitting some phosphate uptake. Although 2,4-dinitrophenol and caproic acid at low concentrations cause an analogous decrease in biomass yield, their combination does not bring about any marked increase in the effect. Considering the physicochemical properties of fatty acids and their preferential action on energy-requiring processes, one of the key sites of action can be assumed to be the mitochondrial membrane. Fatty acids might inhibit the transport of anions, especially phosphate, across the membrane, and disturb the membrane potential by affecting the transport protons. The physiocochemical properties of fatty acids may also give rise to their binding to other intracellular membranes and to a subsequent interference with the function of the corresponding organelles.