Pharmacokinetics of Ampreloxetine, a Norepinephrine Reuptake Inhibitor, in Healthy Subjects and Adults with Attention-Deficit/Hyperactive Disorder or Fibromyalgia Pain.

BACKGROUND AND OBJECTIVE: Ampreloxetine is a novel norepinephrine reuptake inhibitor in development for the treatment of symptomatic neurogenic orthostatic hypotension. The objectives of this analysis were to define the pharmacokinetics of once-daily oral ampreloxetine and provide dose recommendations for clinical development. METHODS: We fitted a population pharmacokinetic model to ampreloxetine plasma concentrations from single- and multiple-ascending dose trials in healthy subjects and two phase II studies in adult subjects with attention-deficit/hyperactive disorder or fibromyalgia at doses of 2-50 mg. RESULTS: Ampreloxetine pharmacokinetics was best described by a two-compartment model with first-order absorption and elimination. The terminal half-life was 30-40 h, resulting in sustained drug concentrations for the entire 24-h dosing interval at steady state. Covariates of age, weight, or renal impairment did not impact ampreloxetine exposure. Cytochrome P450 2D6 phenotype had no influence on ampreloxetine exposure. Sex and smoking status were identified as statistically significant covariates, suggesting a role for cytochrome P450 1A2 in the elimination of ampreloxetine. Despite statistical significance, differences in ampreloxetine exposure in male vs female subjects and smokers vs non-smokers were not clinically meaningful at the recommended dose. At the 10-mg dose, > 75% norepinephrine transporter inhibition and < 50% serotonin transporter inhibition are anticipated for adult subjects. CONCLUSIONS: The population pharmacokinetic model effectively described the plasma concentration-time profile of ampreloxetine after single and multiple doses. Population pharmacokinetic/pharmacodynamic analysis justified using a fixed dosing regimen with no dose adjustments across a broad population and can be used to inform dosing strategies in future clinical studies. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifier numbers NCT01693692 (fibromyalgia); NCT01458340 (attention-deficit/hyperactive disorder).

In Vivo Visualization of ß-Cells by Targeting of GPR44.

GPR44 expression has recently been described as highly ß-cell selective in the human pancreas and constitutes a tentative surrogate imaging biomarker in diabetes. A radiolabeled small-molecule GPR44 antagonist, [11C]AZ12204657, was evaluated for visualization of ß-cells in pigs and nonhuman primates by positron emission tomography as well as in immunodeficient mice transplanted with human islets under the kidney capsule. In vitro autoradiography of human and animal pancreatic sections from subjects without and with diabetes, in combination with insulin staining, was performed to assess ß-cell selectivity of the radiotracer. Proof of principle of in vivo targeting of human islets by [11C]AZ12204657 was shown in the immunodeficient mouse transplantation model. Furthermore, [11C]AZ12204657 bound by a GPR44-mediated mechanism in pancreatic sections from humans and pigs without diabetes, but not those with diabetes. In vivo [11C]AZ12204657 bound specifically to GPR44 in pancreas and spleen and could be competed away dose-dependently in nondiabetic pigs and nonhuman primates. [11C]AZ12204657 is a first-in-class surrogate imaging biomarker for pancreatic ß-cells by targeting the protein GPR44.

Discovery of novel brain permeable and G protein-biased beta-1 adrenergic receptor partial agonists for the treatment of neurocognitive disorders.

The beta-1 adrenergic receptor (ADRB1) is a promising therapeutic target intrinsically involved in the cognitive deficits and pathological features associated with Alzheimer's disease (AD). Evidence indicates that ADRB1 plays an important role in regulating neuroinflammatory processes, and activation of ADRB1 may produce neuroprotective effects in neuroinflammatory diseases. Novel small molecule modulators of ADRB1, engineered to be highly brain permeable and functionally selective for the G protein with partial agonistic activity, could have tremendous value both as pharmacological tools and potential lead molecules for further preclinical development. The present study describes our ongoing efforts toward the discovery of functionally selective partial agonists of ADRB1 that have potential therapeutic value for AD and neuroinflammatory disorders, which has led to the identification of the molecule STD-101-D1. As a functionally selective agonist of ADRB1, STD-101-D1 produces partial agonistic activity on G protein signaling with an EC50 value in the low nanomolar range, but engages very little beta-arrestin recruitment compared to the unbiased agonist isoproterenol. STD-101-D1 also inhibits the tumor necrosis factor α (TNFα) response induced by lipopolysaccharide (LPS) both in vitro and in vivo, and shows high brain penetration. Other than the therapeutic role, this newly identified, functionally selective, partial agonist of ADRB1 is an invaluable research tool to study mechanisms of G protein-coupled receptor signal transduction.

Discovery of Clinical Candidate 4-[2-(5-Amino-1H-pyrazol-4-yl)-4-chlorophenoxy]-5-chloro-2-fluoro-N-1,3-thiazol-4-ylbenzenesulfonamide (PF-05089771): Design and Optimization of Diaryl Ether Aryl Sulfonamides as Selective Inhibitors of NaV1.7.

A series of acidic diaryl ether heterocyclic sulfonamides that are potent and subtype selective NaV1.7 inhibitors is described. Optimization of early lead matter focused on removal of structural alerts, improving metabolic stability and reducing cytochrome P450 inhibition driven drug-drug interaction concerns to deliver the desired balance of preclinical in vitro properties. Concerns over nonmetabolic routes of clearance, variable clearance in preclinical species, and subsequent low confidence human pharmacokinetic predictions led to the decision to conduct a human microdose study to determine clinical pharmacokinetics. The design strategies and results from preclinical PK and clinical human microdose PK data are described leading to the discovery of the first subtype selective NaV1.7 inhibitor clinical candidate PF-05089771 (34) which binds to a site in the voltage sensing domain.

Clinical Micro-Dose Studies to Explore the Human Pharmacokinetics of Four Selective Inhibitors of Human Nav1.7 Voltage-Dependent Sodium Channels.

BACKGROUND: The emergence of genetic data linking Nav1.7 sodium channel over- and under- expression to human pain signalling has led to an interest in the treatment of chronic pain through inhibition of Nav1.7 channels. OBJECTIVE: We describe the pharmacokinetic (PK) results of a clinical microdose study performed with four potent and selective Nav1.7 inhibitors and the subsequent modelling resulting in the selection of a single compound to explore Nav1.7 pharmacology at higher doses. METHODS: A clinical microdose study to investigate the intravenous and oral PK of four compounds (PF-05089771, PF-05150122, PF-05186462 and PF-05241328) was performed in healthy volunteers. PK parameters were derived via noncompartmental analysis. A physiologically-based PK (PBPK) model was used to predict exposure and multiples of Nav1.7 50 % inhibitory concentration (IC50) for each compound at higher doses. RESULTS: Plasma clearance, volume of distribution and bioavailability ranged from 45 to 392 mL/min/kg, 13 to 36 L/kg and 38 to 110 %, respectively. The PBPK model for PF-05089771 predicted a 1 g oral dose would be required to achieve exposures of approximately 12× Nav1.7 IC50 at maximum concentration (C max), and approximately 3× IC50 after 12 h (minimum concentration [C min] for a twice-daily regimen). Lower multiples of Nav1.7 IC50 were predicted with the same oral doses of PF-05150122, PF-05186462, and PF-05241328. In a subsequent single ascending oral dose clinical study, the predictions for PF-05089771 compared well with observed data. CONCLUSION: Based on the human PK data obtained from the microdose study and subsequent modelling, PF-05089771 provided the best opportunity to explore Nav1.7 blockade for the treatment of acute or chronic pain conditions.

Phenyl Ether- and Aniline-Containing 2-Aminoquinolines as Potent and Selective Inhibitors of Neuronal Nitric Oxide Synthase.

Excess nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) is implicated in neurodegenerative disorders. As a result, inhibition of nNOS and reduction of NO levels is desirable therapeutically, but many nNOS inhibitors are poorly bioavailable. Promising members of our previously reported 2-aminoquinoline class of nNOS inhibitors, although orally bioavailable and brain-penetrant, suffer from unfavorable off-target binding to other CNS receptors, and they resemble known promiscuous binders. Rearranged phenyl ether- and aniline-linked 2-aminoquinoline derivatives were therefore designed to (a) disrupt the promiscuous binding pharmacophore and diminish off-target interactions and (b) preserve potency, isoform selectivity, and cell permeability. A series of these compounds was synthesized and tested against purified nNOS, endothelial NOS (eNOS), and inducible NOS (iNOS) enzymes. One compound, 20, displayed high potency, selectivity, and good human nNOS inhibition, and retained some permeability in a Caco-2 assay. Most promisingly, CNS receptor counterscreening revealed that this rearranged scaffold significantly reduces off-target binding.

Radiation dosimetry and biodistribution of the translocator protein radiotracer [(11)C]DAA1106 determined with PET/CT in healthy human volunteers.

INTRODUCTION: When microglia become activated (an integral part of neuroinflammation), cellular morphology changes and expression of translocator protein (TSPO) 18 kDa is increased. Over the past several years, [(11)C]DAA1106 has emerged as a reliable radiotracer for labeling TSPO with high affinity during positron emission tomography (PET) scanning. While [(11)C]DAA1106 PET scanning has been used in several research studies, a radiation dosimetry study of this radiotracer in humans has not yet been published. METHODS: Twelve healthy participants underwent full body dynamic [(11)C]DAA1106 PET scanning, with 8 sequential whole body scans (approximately 12 bed positions each), following a single injection. Regions of interest were drawn manually, and time activity curves (TACs) were obtained for 15 organs. OLINDA/EXM 1.1 was used to compute radiation absorbed doses to the target organs, as well as effective dose (ED) and effective dose equivalent (EDE). RESULTS: The ED and EDE were 4.06 ± 0.58 µSv/MBq and 5.89 ± 0.83 µSv/MBq, respectively. The highest absorbed doses were to the heart wall, kidney, liver, pancreas, and spleen. TACs revealed that peak dose rates are during the first scan (at 6 min) for all organs other than the urinary bladder wall, which had its peak dose rate during the fourth scan (at 30 min). CONCLUSIONS: The recently developed radiotracer [(11)C]DAA1106 has its EDE and target-organ absorbed dose such that, for a single administration, its radiation dosimetry is well within the U.S. FDA guidelines for basic research studies in adults. This dose level implies that the dosimetry for multiple [(11)C]DAA1106 scans within a given year also falls within FDA guidelines, and this favorable property makes this radiotracer suitable for examining microglial activation repeatedly over time, which may in the future be useful for longitudinal tracking of disease progression and monitoring of therapy response in conditions marked by neuroinflammation (e.g., head trauma and multiple sclerosis).

A new diphenyl ether from the endophytic fungus Verticillium sp. isolated from Rehmannia glutinosa.

AIM: To investigate the chemical constituents of the endophytic fungus Verticillium sp. isolated from Rehmannia glutinosa. METHODS: The compounds were isolated and purified by repeated column chromatography, and their structures were determined on the basis of physicochemical properties and spectral analysis. Their cytotoxic and antifungal activities were evaluated. RESULTS: Ten compounds were obtained and their structures were identified as 2, 4-dihydroxy-2', 6-diacetoxy-3'-methoxy-5'-methyl-diphenyl ether (1), paecilospirone (2), α-acetylorcinol (3), 2-methoxy-1,8-dimethyl-xanthen-9-one (4), 4-hydroxy-α-lapachone (5), enalin A (6), 2,3,4-trimethyl-5,7-dihydroxy-2,3-dihydrobenzofuran (7), 4-hydroxyethyl-phenol (8), 2,4-dihydroxy-3,5,6-trimethyl- methylbenzoate (9), and 3-isopropenyl-(Z)-monomethyl maleate (10). CONCLUSIONS: Compound 1 is a new diphenyl ether, and showed cytotoxic activity against HL-60 cells (IC50 2.24 µg · mL(-1)), and antifungal activities against Candida albicans (MIC 8 µg · mL(-1)) and Aspergillus fumigatus (MIC 16 µg · mL(-1)).

The absorption, distribution, metabolism and excretion of Riccardin D in rats.

The present study was designed to investigate the pharmacokinetics following oral and intravenous administration of Riccardin D, an anticancer drug candidate isolated from Chinese liverworts Dumortiera hirsute, in Wistar rats. An HPLC-MS/MS analytical method was developed and validated. The results demonstrated that Riccardin D's bioavailability was 13.4%, 11.4%, and 9.8% after oral administration at 20 mg/kg, 40 mg/kg, and 80 mg/kg, respectively. There was no significant difference in the elimination half-time of Riccardin D at these doses, suggesting that Riccardin D may have linear pharmacokinetic characteristics in rats. The metabolite of Riccardin D in rat was identified as the glucuronide of Riccardin D. Riccardin D showed a wide distribution in various tissues followed by a rapid elimination from most of the tissues tested. Riccardin D was found to distribute widely in the tissues 0.5 h after oral and intravenous administration. The tissue concentrations were markedly decreased 8 h and 6 h after oral and intravenous dosing, respectively. Both Riccardin D and its conjugated metabolite were detected in urine and bile samples while only Riccardin D was detected in feces. Taken together, the study provided valuable pharmacokinetic data for further drug development of Riccardin D.

Effect of poly-L-arginine on intestinal absorption of hydrophilic macromolecules in rats.

We have already reported that poly-L-arginine (PLA) remarkably enhanced the in vivo nasal absorption of hydrophilic macromolecules without producing any significant epithelial damage in rats. In the present study, we examined whether PLA could enhance the absorption of a model hydrophilic macromolecule, fluorescein isothiocyanate-dextran (FD-4), across the intestinal mucosa, as well as the nasal mucosa, by an in situ closed-loop method using the rat intestine. PLA was found to enhance the intestinal absorption of FD-4 in a concentration-dependent manner within the concentrations investigated in this study, but segment-specific differences were found to be associated with this effect (ileum>jejunum>duodenum≧colon). The factors responsible for the segment-specific differences were also investigated by intestinal absorption studies using aprotinin, a trypsin inhibitor, and an analysis of the expression of occludin, a tight junction protein. In the small intestine, the differences in the effect of PLA on the absorption of FD-4 may be related to the enzymatic degradation of PLA. In the colon, the reduced effect of PLA on the absorption of FD-4 may be related to the smaller surface area for absorption and the higher expression of occludin compared with other segments.

In vitro and in vivo evaluation of riccardin D nanosuspensions with different particle size.

Riccardin D (RD) is a novel compound extracted from Chinese liverwort Marchantia polymorpha L. It exhibits various anticancer activities and can be used during lung cancer treatment. However, the compound's low solubility hinders its development. Recently nanosuspension has been developed as one of the most promising formulations for poorly water-soluble drugs. In order to understand the dissolution behavior of riccardin D in vitro and in vivo, two nanosuspensions of riccardin D with markedly different sizes were prepared. The particle size of nanosuspension A prepared by bottom-up method was 184.1±3.15 nm, while that of nanosuspension B prepared by top-down method was 815.4±9.65 nm. The main purpose of this study was to investigate the effects of particle size on pharmacokinetics and tissue distribution after intravenous administration. Riccardin D dissolving in organic solution was studied as control group. In pharmacokinetics study in Wistar rats, nanosuspension A showed properties similar to the control group, while nanosuspension B exhibited rather different properties. In tissue distribution research on Kunming strain mice, nanosuspension A had a multi-peak phenomenon because of reticulate endothelial system (RES) while nanosuspension B showed a high uptake in RES organs that passively target to the lungs. In conclusion, particle size of riccardin D nanosuspensions had obvious effects on pharmacokinetics and tissue distribution.

The synthesis and evaluation of N1-(4-(2-[18F]-fluoroethyl)phenyl)-N8-hydroxyoctanediamide ([18F]-FESAHA), a PET radiotracer designed for the delineation of histone deacetylase expression in cancer.

INTRODUCTION: Given the significant utility of suberoylanilide hydroxamic acid (SAHA) in chemotherapeutic protocols, a PET tracer that mimics the histone deacetylase (HDAC) inhibition of SAHA could be a valuable tool in the diagnosis, treatment planning and treatment monitoring of cancer. Here, we describe the synthesis, characterization and evaluation of N(1)-(4-(2-[(18)F]-fluoroethyl)phenyl)-N(8)-hydroxyoctanediamide ([(18)F]-FESAHA), a PET tracer designed for the delineation of HDAC expression in cancer. METHODS: FESAHA was synthesized and biologically characterized in vivo and in vitro. [(18)F]-FESAHA was then synthesized in high radiochemical purity, and the logP and serum stability of the radiotracer were determined. In vitro cellular uptake experiments and acute biodistribution and small-animal PET studies were performed with [(18)F]-FESAHA in mice bearing LNCaP xenografts. RESULTS: [(18)F]-FESAHA was synthesized in high radiochemical purity via an innovative one-pot procedure. Enzymatic inhibition assays illustrated that FESAHA is a potent HDAC inhibitor, with IC(50) values from 3 nM to 1.7 µM against the 11 HDAC subtypes. Cell proliferation experiments revealed that the cytostatic properties of FESAHA very closely resemble those of SAHA in both LNCaP cells and PC-3 cells. Acute biodistribution and PET imaging experiments revealed tumor uptake of [(18)F]-FESAHA and substantially higher values in the small intestine, kidneys, liver and bone. CONCLUSION: The significant non-tumor background uptake of [(18)F]-FESAHA presents a substantial obstacle to the use of the radiotracer as an HDAC expression imaging agent. The study at hand, however, does present a number of lessons critical to both the synthesis of hydroxamic acid containing PET radiotracers and imaging agents aimed at delineating HDAC expression.

AF-353, a novel, potent and orally bioavailable P2X3/P2X2/3 receptor antagonist.

BACKGROUND AND PURPOSE: Purinoceptors containing the P2X3 subunit (P2X3 homotrimeric and P2X2/3 heterotrimeric) are members of the P2X family of ion channels gated by ATP and may participate in primary afferent sensitization in a variety of pain-related diseases. The current work describes the in vitro pharmacological characteristics of AF-353, a novel, orally bioavailable, highly potent and selective P2X3/P2X2/3 receptor antagonist. EXPERIMENTAL APPROACH: The antagonistic potencies (pIC(50)) of AF-353 for rat and human P2X3 and human P2X2/3 receptors were determined using methods of radioligand binding, intracellular calcium flux and whole cell voltage-clamp electrophysiology. KEY RESULTS: The pIC(50) estimates for these receptors ranged from 7.3 to 8.5, while concentrations 300-fold higher had little or no effect on other P2X channels or on an assortment of receptors, enzymes and transporter proteins. In contrast to A-317491 and TNP-ATP, competition binding and intracellular calcium flux experiments suggested that AF-353 inhibits activation by ATP in a non-competitive fashion. Favourable pharmacokinetic parameters were observed in rat, with good oral bioavailability (%F = 32.9), reasonable half-life (t(1/2) = 1.63 h) and plasma-free fraction (98.2% protein bound). CONCLUSIONS AND IMPLICATIONS: The combination of a favourable pharmacokinetic profile with the antagonist potency and selectivity for P2X3 and P2X2/3 receptors suggests that AF-353 is an excellent in vivo tool compound for study of these channels in animal models and demonstrates the feasibility of identifying and optimizing molecules into potential clinical candidates, and, ultimately, into a novel class of therapeutics for the treatment of pain-related disorders.

Metabolism of 2,6-dichloro-4-(3,3-dichloroallyloxy)phenyl 3-[5-(trifluoromethyl)-2-pyridyloxy]propyl ether (pyridalyl) in rats after repeated oral administration and a simple physiologically based pharmacokinetic modeling in brown and white adipose tissues.

Male and female Sprague-Dawley rats received repeated oral administration of 14C-2,6-dichloro-4-(3,3-dichloroallyloxy)phenyl 3- [5-(trifluoromethyl)-2-pyridyloxy]propyl ether (14C-pyridalyl) at 5 mg/kg/day for 14 consecutive days, and 14C excretion, 14C concentration in tissues, and the metabolic fate were determined. Most 14C was excreted into feces. The 14C concentrations in the blood and tissues attained steady-state levels at days 6 to 10, whereas those in white adipose tissues increased until day 14. Tissue 14C concentrations were highest in brown and white adipose tissue (38.37-57.50 ppm) but were 5.60 ppm or less in all the other tissues. Total 14C residues in blood and tissues on the 27th day after the first administration accounted for 2.6 to 3.2% of the total dose. A major fecal metabolite resulted from O-dealkylation. Analysis of metabolites in tissues revealed that the majority of 14C in perirenal adipose tissue and lungs was pyridalyl, accounting for greater than 90 and 60%, respectively, of the total, whereas a major metabolite in whole blood, kidneys, and liver was a dehalogenated metabolite. The experimental data were simulated with simple physiologically based pharmacokinetics using four-compartment models with assumption of lymphatic absorption and membrane permeability in adipose tissues. The different kinetics in brown and white adipose tissues was reasonably predicted in this model, with large distribution volume in adipose tissues and high hepatic clearance in liver. Sex-related difference of pyridalyl concentration in liver was considered to be a result of different unbound fraction times the hepatic intrinsic clearance (f x CL(int)) of 1.8 and 12 l/h for male and female, respectively.

Diphenyl ether non-nucleoside reverse transcriptase inhibitors with excellent potency against resistant mutant viruses and promising pharmacokinetic properties.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are part of the preferred treatment regimens for individuals infected with HIV. These NNRTI-based regimens are efficacious, but the most popular NNRTIs have a low genetic barrier to resistance and have been associated with adverse events. There is therefore still a need for efficacious antiviral medicines that facilitate patient adherence and allow durable suppression of viral replication. As part of an extensive program targeted toward the discovery of NNRTIs that have favorable pharmacokinetic properties, good potency against NNRTI-resistant viruses, and a high genetic barrier to drug resistance, we focused on the optimization of a series of diaryl ether NNRTIs. In the course of this effort, we employed molecular modeling to design a new set of NNRTIs that that are active against wild-type HIV and key NNRTI-resistant mutant viruses. The structure-activity relationships observed in this series of compounds provide insight into the structural features required for NNRTIs that inhibit the replication of a wide range of mutant viruses. Selected compounds have promising pharmacokinetic profiles.

Hydroxylated metabolites of the polybrominated diphenyl ether mixture DE-71 are weak estrogen receptor-alpha ligands.

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) are widely found in the environment and are suspected endocrine disruptors. We previously identified six hydroxylated metabolites of PBDE (OH-PBDEs) in treated mice. OBJECTIVE: We tested the hypothesis that OH-PBDEs would interact with and alter activity of estrogen receptor-alpha (ER-alpha). METHODS: We tested estrogenicity using two assays: 3H-estradiol (3H-E2) displacement from recombinant ER-alpha and induction of reporter gene (ERE-luciferase) in cultured cells. We incubated the PBDE mixture DE-71 with rat liver microsomes and tested the resultant metabolite mixture for estrogenic activity. We also determined relative estrogenic potential of individual hydroxylated PBDE congeners. RESULTS: Reporter gene activity was increased by DE-71 that had been subjected to microsomal metabolism. DE-71 did not displace E2 from ER-alpha, but all six of the OH-PBDE metabolites did. para-Hydroxylated metabolites displayed a 10- to 30-fold higher affinity for ER-alpha compared with ortho-hydroxylated PBDEs, and one produced a maximal effect 30% higher than that produced by E2. Coadministration of E2 and DE-71, or certain of its metabolites, yielded reporter activity greater than either chemical alone. Two ortho-OH-PBDEs were antiestrogenic in the reporter assay. CONCLUSIONS: The observations--that the DE-71 mixture did not displace 3H-E2 from ER-alpha while the hydroxylated metabolites did-suggest that the weak estrogenic effects of DE-71 are due to metabolic activation of individual congeners. However, the behavior of DE-71 and its metabolites, when co-administered with E2, suggest a secondary, undetermined mechanism from classical ER-alpha activation.

A 28-day oral dose toxicity study in Wistar rats enhanced to detect endocrine effects of decabromodiphenyl ether (decaBDE).

Decabromodiphenyl ether (decaBDE) is a widely used brominated flame retardant, considered to be of low toxicity. However, previous toxicity studies applied exposure methods with low bioavailability of this compound, and the actual hazard of decaBDE for humans, which are environmentally exposed to decaBDE, may thus be underestimated in current risk assessments. The present 28 days oral toxicity study in Wistar rats was designed to facilitate detection of endocrine and immune modulating effects of decaBDE using an exposure protocol with improved bioavailability. A technical preparation of high purity decaBDE was thus tested by daily exposure through gavage with an emulsion of soy phospholipon/lutrol as a carrier. Most sensitive effect in males were increased weight of seminal vesicle/coagulation gland with BMDL of 0.2mg/kg bw/day and increased expression of hepatic CYP1A and CYP2B (BMDLs 0.5-0.7 mg/kg bw/day). In females the most sensitive effect was decreased activity of P450c17 (CYP17), which is a key enzyme in the androgen synthesis pathway, in adrenals (BMDL 0.18 mg/kg bw/day). These results suggest that decaBDE may represent an as yet unreported hazard for reproductive health.

Dietary accumulation, disposition, and metabolism of technical pentabrominated diphenyl ether (de-71) in pregnant mink (Mustela vison) and their offspring.

Concentrations of polybrominated diphenyl ethers (PBDEs) in humans and wildlife suggest significant bioaccumulation potential in mammals, but no quantitative biomagnification data from controlled experiments are currently available. As part of a larger study examining the effects of PBDEs on mink (Mustela vison) reproduction and development, we examined congener-specific tissue distribution, maternal transfer, biotransformation, and biomagnification of the technical penta-BDE mixture, DE-71, in farmed mink. Adult female mink were fed one of four concentrations of DE-71 (0-2.5 microg/g) in the diet from breeding through gestation and until weaning at 6 weeks postparturition. Parent PBDEs were measured in tissues and excreta of adult mink, kits, and juveniles, whereas hydroxylated PBDEs (OH-PBDEs) were measured in juveniles only. Similar lipid-normalized concentrations of PBDEs were detected in most tissues of adult mink with the exception of brain, in which concentrations were significantly lower. Kits, however, had a higher proportion of PBDEs in brain compared with adults, presumably because of incomplete development of the blood-brain barrier. Maternal transfer favored lower-brominated PBDE congeners, and the bulk of the body burden in kits at weaning resulted from lactational rather than transplacental transfer. Lipid-normalized, whole-body biomagnification factors ranged from 0.5 to 5.2 for the major congeners and were highest for BDEs 47 and 153. Metabolism clearly limited the biomagnification of some PBDEs, and OH-PBDEs were detectable in plasma, liver, and feces. On a mass basis, OH-PBDEs accounted for 28 to 32% of the excreted fraction, indicating metabolism was an important elimination pathway. Further studies are required to understand the mechanisms of PBDE biotransformation.

A 28-day oral dose toxicity study enhanced to detect endocrine effects of a purified technical pentabromodiphenyl ether (pentaBDE) mixture in Wistar rats.

A 28-day subacute oral toxicity study was performed in Wistar rats with a purified preparation of the commercial pentabromodiphenyl ether (pentaBDE), DE-71. The applied OECD407 protocol was enhanced for endocrine and immune parameters, and to enable benchmark dose analysis. A vehicle control group and 7 dose groups were included, which received 0.27, 0.82, 2.47, 7.4, 22.2, 66.7 or 200 mg pentaBDE/kg bw/d (mkd). The liver appeared to be a key target organ, showing a marked increase of weight and centrilobular hepatocellular hypertrophy, probably due to the observed induction of P450 enzymes, notably CYP1A and CYP2B. A marked decrease of circulating total thyroxine (TT4) and an increase of plasma cholesterol were probably secondary to the liver effects. Furthermore, dose-dependently decreased weight of epididymis, seminal vesicles, and prostate, as well as sperm head deformities in males, and induction of CYP17 activity in adrenals in females were observed, all possibly related to anti-androgenic activity. Finally, we observed a substantial increase of large unstained cells in the blood and a decrease of apolar retinoids in the liver. All these effects had benchmark doses at the lower confidence bound (BMDL) in the low- or mid-dose range, but particular sensitive, potentially adverse effects were TT4 decrease (BMDLs 1.1 in males and 1.8 mkd in females), and decrease of hepatic apolar retinoids (BMDLs 0.5 mkd in males and 2.3 mkd in females). These results contribute to refinement of the hazard identification of pentaBDE and improved risk assessment of human exposure to this industrial chemical and environmental pollutant.

Effects of settling organic matter on the bioaccumulation of cadmium and BDE-99 by Baltic Sea benthic invertebrates.

Settling organic matter (OM) is the major food source for heterotrophic benthic fauna. The high sorption affinity of many contaminants for OM implies that OM can influence both the distribution and bioavailability of contaminants. Here, we experimentally examine the role of settling OM of various nutritional qualities on the bioaccumulation of cadmium and the flame retardant BDE-99 by three benthic invertebrates; Macoma balthica, Monoporeia affinis and Marenzelleria sp. Contaminants were associated with three types of OM; a microalgae (Tetraselmis spp.), lignin and sediment. Bioaccumulation of Cd was proportional to OM nutritional quality for all three species, and was species-specific in the order Marenzelleria>M. balthica>M. affinis. BDE-99 bioaccumulation was highest in the treatment with the most nutritious OM (Tetraselmis). Consequently, both benthic species composition and the nutritive value of organic matter settling to the seafloor can have a substantial effect on the bioaccumulation of both metals and organic contaminants.