Weight-of-evidence versus strength-of-evidence in toxicologic hazard identification: Di(2-ethylhexyl)phthalate (DEHP)

Framework for the quantitative weight-of-evidence analysis of 'omics data for regulatory purposes

A framework for the quantitative weight-of-evidence (QWoE) analysis of 'omics data for regulatory purposes is presented. The QWoE framework encompasses seven steps to evaluate 'omics data (also together with non-'omics data): (1) Hypothesis formulation, identification and weighting of lines of evidence (LoEs). LoEs conjoin different (types of) studies that are used to critically test the hypothesis. As an essential component of the QWoE framework, step 1 includes the development of templates for scoring sheets that predefine scoring criteria with scores of 0-4 to enable a quantitative determination of study quality and data relevance; (2) literature searches and categorisation of studies into the pre-defined LoEs; (3) and (4) quantitative assessment of study quality and data relevance using the respective pre-defined scoring sheets for each study; (5) evaluation of LoE-specific strength of evidence based upon the study quality and study relevance scores of the studies conjoined in the respective LoE; (6) integration of the strength of evidence from the individual LoEs to determine the overall strength of evidence; (7) characterisation of uncertainties and conclusion on the QWoE. To put the QWoE framework in practice, case studies are recommended to confirm the relevance of its different steps, or to adapt them as necessary.

Improving the International Agency for Research on Cancer's consideration of mechanistic evidence

BACKGROUND

The International Agency for Research on Cancer (IARC) recently developed a framework for evaluating mechanistic evidence that includes a list of 10 key characteristics of carcinogens. This framework is useful for identifying and organizing large bodies of literature on carcinogenic mechanisms, but it lacks sufficient guidance for conducting evaluations that fully integrate mechanistic evidence into hazard assessments.

OBJECTIVES

We summarize the framework, and suggest approaches to strengthen the evaluation of mechanistic evidence using this framework.

DISCUSSION

While the framework is useful for organizing mechanistic evidence, its lack of guidance for implementation limits its utility for understanding human carcinogenic potential. Specifically, it does not include explicit guidance for evaluating the biological significance of mechanistic endpoints, inter- and intra-individual variability, or study quality and relevance. It also does not explicitly address how mechanistic evidence should be integrated with other realms of evidence. Because mechanistic evidence is critical to understanding human cancer hazards, we recommend that IARC develop transparent and systematic guidelines for the use of this framework so that mechanistic evidence will be evaluated and integrated in a robust manner, and concurrently with other realms of evidence, to reach a final human cancer hazard conclusion.

CONCLUSIONS

IARC does not currently provide a standardized approach to evaluating mechanistic evidence. Incorporating the recommendations discussed here will make IARC analyses of mechanistic evidence more transparent, and lead to assessments of cancer hazards that reflect the weight of the scientific evidence and allow for scientifically defensible decision-making.

Genotoxicity of phthalates

Many of the environmental, occupational and industrial chemicals are able to generate reactive oxygen species (ROS) and cause oxidative stress. ROS may lead to genotoxicity, which is suggested to contribute to the pathophysiology of many human diseases, including inflammatory diseases and cancer. Phthalates are ubiquitous environmental chemicals and are well-known peroxisome proliferators (PPs) and endocrine disruptors. Several in vivo and in vitro studies have been conducted concerning the carcinogenic and mutagenic effects of phthalates. Di(2-ethylhexyl)-phthalate (DEHP) and several other phthalates are shown to be hepatocarcinogenic in rodents. The underlying factor in the hepatocarcinogenesis is suggested to be their ability to generate ROS and cause genotoxicity. Several methods, including chromosomal aberration test, Ames test, micronucleus assay and hypoxanthine guanine phosphoribosyl transferase (HPRT) mutation test and Comet assay, have been used to determine genotoxic properties of phthalates. Comet assay has been an important tool in the measurement of the genotoxic potential of many chemicals, including phthalates. In this review, we will mainly focus on the studies, which were conducted on the DNA damage caused by different phthalate esters and protection studies against the genotoxicity of these chemicals.

Clofibric acid induces hepatic CYP 2B1/2 via constitutive androstane receptor not via peroxisome proliferator activated receptor alpha in rat

Peroxisome proliferator activated receptor α (PPARα) ligands, fibrates used to control hyperlipidemia. We demonstrated CYP2B induction by clofibric acid (CFA) however, the mechanism was not clear. In this study, HepG2 cells transfected with expression plasmid of mouse constitutive androstane receptor (CAR) or PPARα were treated with CFA, phenobarbital (PB) or TCPOBOP. Luciferase assays showed that CFA increased CYP2B1 transcription to the same level as PB, or TCPOBOP in HepG2 transfected with mouse CAR But failed to induce it in PPARα transfected cells. CYP2B expressions were increased with PB or CFA in Wistar female rats (having normal levels of CAR) but not in Wistar Kyoto female rats (having low levels of CAR). The induction of CYP2B by PB or CFA was comparable to nuclear CAR levels. CAR nuclear translocation was induced by CFA in both rat strains. This indicates that fibrates can activate CAR and that fibrates-insulin sensitization effect may occur through CAR, while hypolipidemic effect may operate through PPARα.

The effects of di(2-ethylhexyl)phthalate on rat liver in relation to selenium status

This study was performed to determine the hepatotoxicity of di(2-ethylhexyl)phthalate (DEHP) in relation to selenium status. In 3-week-old Sprague-Dawley rats, selenium deficiency was induced by a ≤0.05 selenium mg/kg. A selenium supplementation group was given 1 mg selenium/kg diet for 5 weeks. Di(2-ethylhexyl)phthalate-treated groups received 1000 mg/kg dose by gavage during the last 10 days of the experiment. Histopathology, peroxisome proliferation, catalase (CAT) immunoreactivity and activity and apoptosis were assessed. Activities of antioxidant selenoenzymes [glutathione peroxidase 1 (GPx1), glutathione peroxidase 4 (GPx4), thioredoxin reductase (TrxR1)], superoxide dismutase (SOD), and glutathione S-transferase (GST); aminotransferase, total glutathione (tGSH), and lipid peroxidation (LP) levels were measured. Di(2-ethylhexyl)phthalate caused cellular disorganization while necrosis and inflammatory cell infiltration were observed in Se-deficient DEHP group (DEHP/SeD). Catalase activity and immunoreactivity were increased in all DEHP-treated groups. Glutathione peroxidase 1 and GPx4 activities decreased significantly in DEHP and DEHP/SeD groups, while GST activities decreased in all DEHP-exposed groups. Thioredoxin reductase activity increased in DEHP and DEHP/SeS, while total SOD activities increased in all DEHP-treated groups. Lipid peroxidation levels increased significantly in SeD (26%), DEHP (38%) and DEHP/SeD (71%) groups. Selenium supplementation partially ameliorated DEHP-induced hepatotoxicity; while in DEHP/SeD group, drastic changes in hepatic histopathology and oxidative stress parameters were observed.

The therapeutic applications of celery oil seed extract on the plasticizer di(2-ethylhexyl) phthalate toxicity

The present study investigated the impact of two doses, 500 mg/kg and 1000 mg/kg, of di(2-ethylhexyl) phthalate (DEHP) and studied the possible therapeutic dose of celery oil seed extract for 6 weeks on some atheroscelerogenic, obesogenic, antioxidant and liver functions in rats. Both doses of DEHP caused over-expression of peroxisome proliferator-activated receptor alpha (PPARα) messenger RNA with significant increase in liver weights, relative liver weights, serum cholesterol (Chol), triglycerides, low-density lipoprotein Chol, liver total lipids, along with an increase in the activities of serum aspartate aminotransferase, alanine aminotransferase, serum endothelin 1 and liver tissue thiobarbituric acid reactive substances (TBARS). Additionally, DEHP administration to rats resulted in significant decrease in final body weights, serum total protein, albumin, liver total protein and serum total nitric oxide. Our study confirmed the role of oral combination of Apium graveolens (celery) oil seed extract at small cumulative doses (50 µl/kg for 6 weeks) with DEHP in ameliorating the toxicological effects of DEHP, which was revealed in reducing the expression of PPARα, lipid profile, with restoring liver functions, vascular oxidative stress and inhibition of TBARS activity.

Hepatotoxicity of di-(2-ethylhexyl)phthalate is attributed to calcium aggravation, ROS-mediated mitochondrial depolarization, and ERK/NF-κB pathway activation

Di-(2-ethylhexyl)phthalate (DEHP) is a widely used plasticizer found in a variety of polyvinyl chloride medical products. Although DEHP-induced cytotoxicity and apoptosis are well studied in various cell types, the precise mechanisms are not well understood so far. This study, aimed at going beyond the toxicology approach, focuses on the molecular mechanisms through which DEHP causes hepatotoxicity. We show that DEHP induces apoptotic cell death in a dose-dependent manner, as proven by an increase in annexin V-positively stained cells, DAPI/PI staining, and immunofluorescence studies. The DEHP-induced decrease in cell viability was significantly inhibited by adding catalase (CAT), but CAT treatment did not suppress the DEHP-stimulated calcium flux in the hepatocytes, whereas BAPTA-AM significantly reduced the DEHP-stimulated DCF intensity. These results demonstrate that DEHP increases the intracellular calcium level, which mediates the generation of H(2)O(2) in hepatocytes. Investigating cell-signaling mechanisms, we found that DEHP induced apoptotic cell death by mitochondrial-dependent caspase-3 activation and PARP cleavage. These changes due to DEHP exposure were associated with increased IKK and NF-κB phosphorylation. Preexposure of hepatocytes to an IKK inhibitor (PS-1145) prevented DEHP-induced caspase-3 and PARP cleavage. DEHP also markedly increased the activity of ERK1/2 MAPK. Pretreatment with the ERK inhibitor PD98059 attenuated NF-κB and IKK phosphorylation, indicating that ERK MAPK is mainly involved in DEHP-induced NF-κB activation. These results, for the first time, reveal that DEHP induces apoptosis in hepatocytes via the activation of the ERK/NF-κB signaling pathway, in which calcium ions and hydrogen peroxide act as the pivotal mediators of the apoptotic signaling.

Health ranking of ingested semi-volatile organic compounds in house dust: an application to France

People spend most of their time indoors. Dust settled in the home may be contaminated by semi-volatile organic compounds (SVOCs). Exposure to these compounds is of great concern, in particular for infants. Their number is large so arose the question of which ones should be selected for dust ingestion exposure assessment. This work proposes a health ranking of SVOCs ingested through settled dust. This ranking is based on the toxicity and contamination of SVOCs in dust. Data on compounds and contamination was retrieved from a bibliographic review. Where possible, toxicity data was retrieved from databases, otherwise it was calculated from raw data. One hundred and fifty-six SVOCs were selected, 66 of which were prioritized. Forty-two could not be prioritized because contamination data was below the limit of detection, and 48 could not be prioritized because there was no contamination or toxicity data. The top-ranked compounds were phthalates, pesticides, short-chain chlorinated paraffins, PBDEs, PFCs, organotins, PCBs, and PAHs. As most of these have reprotoxic and neurotoxic properties, an integrated multi-pollutants approach to exposure is required and simultaneous measurement methods should be developed.

PRACTICAL IMPLICATIONS

The large number of compounds identified in settled dust in recent years should be considered for the assessment of exposure to dust ingestion. This work provides a health ranking of SVOCs ingested through settled dust. Most of the top-ranked compounds have reprotoxic and neurotoxic properties, and particular attention should, therefore, be paid to them in future studies.

Di-(2-ethylhexyl)-phthalate (DEHP) activates the constitutive androstane receptor (CAR): a novel signalling pathway sensitive to phthalates

Di-(2-ethylhexyl)-phthalate (DEHP), a widely used plasticizer, is detected in consumer's body fluids. Contamination occurs through environmental and food chain sources. In mouse liver, DEHP activates the peroxisome proliferator-activated receptor alpha (PPARalpha) and regulates the expression of its target genes. Several in vitro investigations support the simultaneous recruitment of additional nuclear receptor pathways. We investigated, in vivo, the hepatic impact of low doses of DEHP on PPARalpha activation, and the putative activation of additional signalling pathways. Wild-type and PPARalpha-deficient mice were exposed to different doses of DEHP. Gene expression profiling delineated the role of PPARalpha and revealed a PPARalpha-independent regulation of several prototypic constitutive androstane receptor (CAR) target genes. Thus, we developed an original hepatic cell line expressing CAR to investigate its activation by DEHP. By means of a pharmacological inhibitor or CAR-targeting shRNAs, we established that CAR is required for the effect of DEHP on Cyp2b10, a recognized CAR target gene. Moreover, DEHP dose-dependently induced CYP2B6 in human primary hepatocyte cultures. This finding demonstrates that CAR also represents a transcriptional regulator sensitive to phthalates. CAR-mediated effects of DEHP provide a new rationale for most endpoints of phthalates toxicity described previously, including endocrine disruption, hepatocarcinogenesis and the metabolic syndrome.

Risk reduction of adverse effects due to di-(2-ethylhexyl) phthalate (DEHP) by utilizing microbial degradation

Di-(2-ethylhexyl) phthalate (DEHP), one of the major phthalates, was reported to be a suspected endocrine-disrupting chemical (EDC) that might produce developmental or reproductive toxicities. Therefore, much effort was undertaken to reduce the potential risk of adverse effects of DEHP on humans by diminishing environmental exposure to this chemical. A bacterium was isolated from soil contaminated with DEHP at a poly(vinyl chloride) (PVC) manufacturing site. Biodegradation kinetic experiments on DEHP-contaminated soil samples were performed in a slurry phase system. The DEHP concentration was decreased to a concentration of 0.5 g/kg by the addition of 1% culture medium to the soil. The microorganism degraded DEHP through the formation of a mono-2-ethylhexyl phthalate (MEHP), which was subsequently metabolized to phthalic acid (PA), as detected by GC-MS analysis. Micrococcus luteus was able to degrade almost 90% of the initial DEHP within 12 d. In addition, the microbial toxicity study of DEHP and its degradation products MEHP or PA, using recombinant bioluminescent bacteria, showed that PA or the mixture produced protein or DNA damage. Data thus suggest that a new strain of Micrococcus luteus with a strong ability to degrade DEHP into nontoxic metabolites may contribute to decontamination of environmental phthalates and consequently risk reduction of human exposure to DEHP.

A gene expression biomarker provides early prediction and mechanistic assessment of hepatic tumor induction by nongenotoxic chemicals

There are currently no accurate and well-validated short-term tests to identify nongenotoxic hepatic tumorigens, thus necessitating an expensive 2-year rodent bioassay before a risk assessment can begin. Using hepatic gene expression data from rats treated for 5 days with one of 100 structurally and mechanistically diverse nongenotoxic hepatocarcinogens and nonhepatocarcinogens, a novel multigenebiomarker (i.e., signature) was derived to predict the likelihood of nongenotoxic chemicals to induce liver tumors in longer term studies. Independent validation of the signature on 47 test chemicals indicates an assay sensitivity and specificity of 86% and 81%, respectively. Alternate short-term in vivo pathological and genomic biomarkers were evaluated in parallel for comparison, including liver weight, hepatocellular hypertrophy, hepatic necrosis, serum alanine aminotransferase activity, induction of cytochrome P450 genes, and repression of Tsc-22 or alpha2-macroglobulin messenger RNA. In contrast to these biomarkers, the gene expression-based signature was more accurate. Unlike existing tests, an understanding of potential modes of action for hepatic tumorigenicity can be derived by comparison of the signature profile of test chemicals to hepatic tumorigens of known mechanism, including regenerative proliferation, proliferation associated with xenobiotic receptor activation, peroxisome proliferation, and steroid hormone-mediated mechanisms. This signature is not only more accurate than current methods, but also facilitates the identification of mode of action to aid in the early assessment of human cancer risk.

Effect of introduced phthalate-degrading bacteria on the diversity of indigenous bacterial communities during di-(2-ethylhexyl) phthalate (DEHP) degradation in a soil microcosm

Four previously isolated di-butyl-phthalate (DBP) degraders were tested for their abilities to degrade di-(2-ethylhexyl) phthalate (DEHP). In aqueous medium supplemented with 100mg/l of DEHP, both isolate G1 and Rhodococcus rhodochrous G2 showed excellent degradative activity; in three days they were able to degrade more than 97% of the added DEHP. Rhodococcus rhodochrous G7 degraded 32.5% of the added DEHP and Corynebacterium nitrilophilus G11 showed the least amount of DEHP degradation. The addition of surfactant Brij 30 at 0.1x critical micelle concentration (2mg/l) significantly improved DEHP degradation by Rhodococcus rhodochrous G2 (more than 90% of the added DEHP was degraded within 24 hours), but slightly inhibited the degradation of DEHP by the isolate G1 and Rhodococcus rhodochrous G7. Based on the 16S rDNA sequence data, isolate G1 was identified as Gordonia polyisoprenivorans. Soil inhibited DEHP degradation by G. polyisoprenivorans G1; fourteen days after a second addition of DEHP, 11.5% of the total added DEHP (i.e., 243.4 microg/g soil) remained detectable. Changes in the bacterial community were monitored using denaturing gradient gel electrophoresis (DGGE) and respective dendrogram analysis. It is clear that DEHP and DEHP plus G. polyisoprenivorans G1 substantially affected the bacterial community structure in the soils. However, as the population of indigenous DEHP degraders increased in the DEPH-treated soil, its bacterial communities resembled those in the DEHP plus G. polyisoprenivorans G1-inoculated soil by Day 17.

A mono-2-ethylhexyl phthalate hydrolase from a Gordonia sp. that is able to dissimilate di-2-ethylhexyl phthalate

Gordonia sp. strain P8219, a strain able to decompose di-2-ethylhexyl phthalate, was isolated from machine oil-contaminated soil. Mono-2-ethylhexyl phthalate hydrolase was purified from cell extracts of this strain. This enzyme was a 32,164-Da homodimeric protein, and it effectively hydrolyzed monophthalate esters, such as monoethyl, monobutyl, monohexyl, and mono-2-ethylhexyl phthalate. The K(m) and V(max) values for mono-2-ethylhexyl phthalate were 26.9 +/- 4.3 microM and 18.1 +/- 0.9 micromol/min . mg protein, respectively. The deduced amino acid sequence of the enzyme exhibited less than 30% homology with those of meta-cleavage hydrolases which are serine hydrolases but exhibited no significant homology with the sequences of serine esterases. The pentapeptide motif GXSXG, which is conserved in serine hydrolases, was present in the sequence. The enzymatic properties and features of the primary structure suggested that this enzyme is a novel enzyme belonging to an independent group of serine hydrolases.

Weight of evidence: a review of concept and methods

"Weight of evidence" (WOE) is a common term in the published scientific and policy-making literature, most often seen in the context of risk assessment (RA). Its definition, however, is unclear. A systematic review of the scientific literature was undertaken to characterize the concept. For the years 1994 through 2004, PubMed was searched for publications in which "weight of evidence" appeared in the abstract and/or title. Of the 276 papers that met these criteria, 92 were selected for review: 71 papers published in 2003 and 2004 (WOE appeared in abstract/title) and 21 from 1994 through 2002 (WOE appeared in title). WOE has three characteristic uses in this literature: (1) metaphorical, where WOE refers to a collection of studies or to an unspecified methodological approach; (2) methodological, where WOE points to established interpretative methodologies (e.g., systematic narrative review, meta-analysis, causal criteria, and/or quality criteria for toxicological studies) or where WOE means that "all" rather than some subset of the evidence is examined, or rarely, where WOE points to methods using quantitative weights for evidence; and (3) theoretical, where WOE serves as a label for a conceptual framework. Several problems are identified: the frequent lack of definition of the term "weight of evidence," multiple uses of the term and a lack of consensus about its meaning, and the many different kinds of weights, both qualitative and quantitative, which can be used in RA. A practical recommendation emerges: the WOE concept and its associated methods should be fully described when used. A research agenda should examine the advantages of quantitative versus qualitative weighting schemes, how best to improve existing methods, and how best to combine those methods (e.g., epidemiology's causal criteria with toxicology's quality criteria).

The weight of scientific evidence in policy and law

The term "weight of evidence" (WOE) appears in regulatory rules and decisions. However, there has been little discussion about the meaning, variations of use, and epistemic significance of WOE for setting health and safety standards. This article gives an overview of the role of WOE in regulatory science, discusses alternative views about the methodology underlying the concept, and places WOE in the context of the Supreme Court's decision in Daubert v Merrell Dow Pharmaceuticals, Inc (1993). I argue that whereas the WOE approach to evaluating scientific evidence is gaining favor among regulators, its applications in judicial processes may be in conflict with some interpretations of how the Daubert criteria for judging reliable evidence should be applied.

A TWO-GENERATION REPRODUCTIVE TOXICITY STUDY OF BUTYL BENZYL PHTHALATE IN RATS

A two-generation reproductive toxicity study with extra parameters was performed for Butyl benzyl phthalate (BBP). The compound was administered orally by gavage with the doses of 0, 100, 200, or 400 mg/kg/day to groups of 24 Crj:CD (SD)IGS rats of both sexes to confirm the utility of the protocol for identification of non-steroid chemicals with endocrine activity by ssessing effects on parental animals and offspring. Softening of the testes, diffuse atrophy of testicular seminiferous tubules, decreased spermatozoa and/or residual germ cells in the epididymal lumina were observed in the F1generation after doses more than 100 mg/kg, lowering of the F1 epididymal weights at doses more than 200 mg/kg, along with low F0 epididymal weights, Leydig cell hyperplasia, residual germ cells in the epidimymal lumina, and low seminal vesicle weights, small testes and epididymes, partial aplasia or aplasia of the epididymes, and Leydig cell hyperplasia in the F1 generation with 400 mg/kg. With regard to effects on the reproductive capacity, F1 parents at the dose of 400mg/kg showed a reduced fertility index and delayed preputial separation of the penis. In the offspring, lowered body weights in the F1 case, and change in anogenital distance in the F1 females and F2 males were observed at doses more than 100 mg/kg, with low splenic weights at 400 mg/kg in both generations. Thus, the utility of this protocol was confirmed. In the parental animals, the no observed effect level (NOEL) and the no observed adverse effect level (NOAEL) were less than 100 mg/kg/day, and no serious effects on the reproductive capacity were induced at doses less than 200 mg/kg/day. The NOEL and NOAEL for the growth and development of offspring were concluded to be less than 100 mg/kg/day.

Suppression by phthalates of the calcium signaling of human nicotinic acetylcholine receptors in human neuroblastoma SH-SY5Y cells

Phthalates are widely used in industry and cause public concern since they have genomic estrogenic-like effects via estrogen receptors. We previously found that some phthalates have nongenomic effects, exerting inhibitory effects on the functional activities of nicotinic acetylcholine receptors (nAChRs) in bovine chromaffin cells. In this study, we investigated the effects of eight phthalates on the calcium signaling of human nAChR by using human neuroblastoma SH-SY5Y cells. All eight phthalates, with different potency, have inhibitory roles on the calcium signaling coupled with human nAChR, but not muscarinic acetylcholine receptors (mAChRs). For inhibition of human nAChR, the strongest to weakest potencies were observed as di-n-pentyl phthalate (DPP) --> butyl benzyl phthalate (BBP) --> di-n-butyl phthalate (DBP) --> dicyclohexyl phthalate (DCHP) --> di-n-hexyl phthalate (DHP) --> di-(2-ethyl hexyl) phthalate (DEHP) --> di-n-propyl phthalate (DPrP) --> diethyl phthalate (DEP). The potencies of phthalates were associated with their structures such that the most effective ones had dialkyl group carbon numbers of C4 or C5, with shorter or longer numbers resulting in decreased potency. At as low as 0.1 microM, DPP, DBP, BBP, DCHP and DHP significantly inhibited the calcium signaling of human nAChR. The IC50 of phthalates on human nAChR, ranging from 0.32 to 7.96 microM, were 10-50 lower than those for bovine nAChR. We suggest that some phthalates effectively inhibit the calcium signaling of human nAChR, and these nongenomic effects are cause for concern.

Biocompatibility of adenoviral vectors in poly(vinyl chloride) tubing catheters with presence or absence of plasticizer di-2-ethylhexyl phthalate

Adenoviral (Ad) vectors feature attractive characteristics for gene therapy of a wide variety of diseases. In many cases, the Ad vector must be administered using catheters and other plastic medical devices. Although poly(vinyl chloride) is one of the most frequently used catheter materials, it is relatively rigid and requires the addition of a plasticizer such as di-2-ethylhexyl phthalate (DEHP) to increase its flexibility. In this study, we demonstrated that exposure to a DEHP-containing catheter decreased the infectivity of Ad vectors but not the total particle number of the vector. Loss of Ad vector infectivity was directly related to the time of exposure to the DEHP-containing catheter, but it was not due to simple leaching of the chemical from the plastic. The loss of Ad vector infectivity could be prevented by preflushing the tube with albumin. Careful consideration of the compatibility between gene therapy vectors and medical delivery devices will be critical to the success of human gene therapy applications.

Donor exposure to the plasticizer di(2-ethylhexyl)phthalate during plateletpheresis

BACKGROUND

Di(2-ethylhexyl)phthalate (DEHP) is a plasticizer that is contained in most PVC devices, including apheresis disposables. Because DEHP can be extracted from apheresis disposables as the blood passes through the apheresis device, DEHP exposure was determined in healthy donors undergoing plateletpheresis performed with commercially available apheresis systems.

STUDY DESIGN AND METHODS

The study population consisted of 36 healthy PLT donors undergoing plateletpheresis with either continuous or discontinuous apheresis devices. Serum concentrations of DEHP were determined from peripheral blood obtained before and after plateletpheresis, with gas chromatography-mass spectroscopy.

RESULTS

Plateletpheresis performed with standard collection disposables resulted in a median increase of 232 percent of serum DEHP compared to levels before apheresis, corresponding to a total amount of DEHP exposed during a single apheresis of a median of 6.46 (range, 1.8-20.3) microg per kg of body weight. Endogenous levels of triglycerides showed a positive correlation with the amount of DEHP released. Increase in serum DEHP was short-term as serum DEHP rapidly returned to levels obtained before apheresis within 3 hours after completion of the apheresis course. Donor exposure to DEHP led to no variation in liver cell function within 48 hours after plateletpheresis.

CONCLUSION

Commercial plateletpheresis disposables release considerable amounts of DEHP during the apheresis procedure, but the total dose of DEHP retained by the donor is within the normal range of DEHP exposure of the general population.

Evidence that peroxisome proliferator-activated receptor alpha is complexed with the 90-kDa heat shock protein and the hepatitis virus B X-associated protein 2

The peroxisome proliferator-activated receptor alpha (PPARalpha) is a ligand-inducible transcription factor, which belongs to the nuclear receptor superfamily. PPARalpha mediates the carcinogenic effects of peroxisome proliferators in rodents. In humans, PPARalpha plays a fundamental role in regulating energy homeostasis via control of lipid metabolism. To study the possible role of chaperone proteins in the regulation of PPARalpha activity, a monoclonal antibody (mAb) was made against PPARalpha and designated as 3B6/PPAR. The specificity of mAb 3B6/PPAR in recognizing PPARalpha was tested in immunoprecipitations using in vitro translated PPAR subtypes. The mAb 3B6/PPAR recognized PPARalpha, failed to bind to PPARbeta or PPARgamma, and is efficient in both immunoprecipitating and visualizing the receptor on protein blots. The immunoprecipitation of PPARalpha in mouse liver cytosol using mAb 3B6/PPAR has resulted in the detection of two co-immunoprecipitated proteins, which are heat shock protein 90 (hsp90) and the hepatitis B virus X-associated protein 2 (XAP2). The concomitant depletion of PPARalpha in hsp90-depleted mouse liver cytosol was also detected. Complex formation between XAP2 and PPARalpha/FLAG was also demonstrated in an in vitro translation binding assay. hsp90 interacts with PPARalpha in a mammalian two-hybrid assay and binds to the E/F domain. Transient expression of XAP2 co-expressed with PPARalpha resulted in down-regulation of a peroxisome proliferator response element-driven reporter gene activity. Taken together, these results indicate that PPARalpha is in a complex with hsp90 and XAP2, and XAP2 appears to function as a repressor. This is the first demonstration that PPARalpha is stably associated with other proteins in tissue extracts and the first nuclear receptor shown to functionally interact with XAP2.