Effects-Directed Analysis of Dissolved Organic Compounds in Oil Sands Process-Affected Water

Acute toxicity of oil sands process-affected water (OSPW) is caused by its complex mixture of bitumen-derived organics, but the specific chemical classes that are most toxic have not been demonstrated. Here, effects-directed analysis was used to determine the most acutely toxic chemical classes in OSPW collected from the world's first oil sands end-pit lake. Three sequential rounds of fractionation, chemical analysis (ultrahigh resolution mass spectrometry), and acute toxicity testing (96 h fathead minnow embryo lethality and 15 min Microtox bioassay) were conducted. Following primary fractionation, toxicity was primarily attributable to the neutral extractable fraction (F1-NE), containing 27% of original organics mass. In secondary fractionation, F1-NE was subfractionated by alkaline water washing, and toxicity was primarily isolated to the ionizable fraction (F2-NE2), containing 18.5% of the original organic mass. In the final round, chromatographic subfractionation of F2-NE2 resulted in two toxic fractions, with the most potent (F3-NE2a, 11% of original organic mass) containing predominantly naphthenic acids (O2(-)). The less-toxic fraction (F3-NE2b, 8% of original organic mass) contained predominantly nonacid species (O(+), O2(+), SO(+), NO(+)). Evidence supports naphthenic acids as among the most acutely toxic chemical classes in OSPW, but nonacidic species also contribute to acute toxicity of OSPW.

Effects of novel brominated flame retardants on steroidogenesis in primary porcine testicular cells

Brominated flame retardants are chemicals with fire quenching properties which are extensively used in manufacturing. Historically, less regulated use of legacy brominated flame retardants (BFRs) for a number of years has resulted in ubiquitous contamination of the environment. As a result, some of the more persistent BFRs have been phased out and are being replaced by a next generation of brominated compounds for which there is little toxicological data. The study investigated effects of 2-ethylhexyl tetrabromobenzoate (TBB), 1,2,5,6-tetrabromocyclooctane (TBCO), and bis-(2-ethylhexyl) tetrabromophthalate (TBPH)on steroidogenesis in a porcine primary testicular cell model. TBB did not affect sex-steroid production in this cell model; rather the data suggest a flux towards synthesis of aldosterone and cortisol via up-regulation of CYP21A2. At the greatest concentrations of TBCO and TBPH tested greater production of sex hormones testosterone (T) and estradiol (E2) was observed. Effects were mediated by regulation of multiple molecular targets in the steroidogenesis pathway; CYP11A in the case of TBPH and CYP17A1 in the case of TBCO. This investigation is the first of its kind to use a testicular mixed population cell model to investigate mechanism(s) of action of three chemically diverse compounds currently used in commercial fire retardants.

Biological impact of phthalates

Esters of phthalic acid are chemical agents used to improve the plasticity of industrial polymers. Their ubiquitous use in multiple commercial products results in extensive exposure to humans and the environment. This study investigated cytotoxicity, endocrine disruption, effects mediated via AhR, lipid peroxidation and effects on expression of enzymes of xenobiotic metabolism caused by di-(2-ethy hexyl) phthalate (DEHP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and benzyl butyl phthalate (BBP) in developing fish embryos. Oxidative stress was identified as the critical mechanism of toxicity (CMTA) in the case of DEHP and DEP, while the efficient removal of DBP and BBP by phase 1 enzymes resulted in lesser toxicity. DEHP and DEP did not mimic estradiol (E(2)) in transactivation studies, but at concentrations of 10mg/L synthesis of sex steroid hormones was affected. Exposure to 10mg BBP/L resulted in weak transactivation of the estrogen receptor (ER). All phthalates exhibited weak potency as agonists of the aryl hydrocarbon receptor (AhR). The order of potency of the 4 phthalates studied was; DEHP>DEP>BBP>>DBP. The study highlights the need for simultaneous assessment of: (1) multiple cellular targets affected by phthalates and (2) phthalate mixtures to account for additive effects when multiple phthalates modulate the same pathway. Such cumulative assessment of multiple biological parameters is more realistic, and offers the possibility of more accurately identifying the CMTA.

Membrane plasmalogen composition and cellular cholesterol regulation: a structure activity study

Background

Disrupted cholesterol regulation leading to increased circulating and membrane cholesterol levels is implicated in many age-related chronic diseases such as cardiovascular disease (CVD), Alzheimer's disease (AD), and cancer. In vitro and ex vivo cellular plasmalogen deficiency models have been shown to exhibit impaired intra- and extra-cellular processing of cholesterol. Furthermore, depleted brain plasmalogens have been implicated in AD and serum plasmalogen deficiencies have been linked to AD, CVD, and cancer.

Results

Using plasmalogen deficient (NRel-4) and plasmalogen sufficient (HEK293) cells we investigated the effect of species-dependent plasmalogen restoration/augmentation on membrane cholesterol processing. The results of these studies indicate that the esterification of cholesterol is dependent upon the amount of polyunsaturated fatty acid (PUFA)-containing ethanolamine plasmalogen (PlsEtn) present in the membrane. We further elucidate that the concentration-dependent increase in esterified cholesterol observed with PUFA-PlsEtn was due to a concentration-dependent increase in sterol-O-acyltransferase-1 (SOAT1) levels, an observation not reproduced by 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibition.

Conclusion

The present study describes a novel mechanism of cholesterol regulation that is consistent with clinical and epidemiological studies of cholesterol, aging and disease. Specifically, the present study describes how selective membrane PUFA-PlsEtn enhancement can be achieved using 1-alkyl-2-PUFA glycerols and through this action reduce levels of total and free cholesterol in cells.

Circulating plasmalogen levels and Alzheimer Disease Assessment Scale-Cognitive scores in Alzheimer patients

BACKGROUND

Plasmalogens, which are key structural phospholipids in brain membranes, are decreased in the brain and serum of patients with Alzheimer disease (AD). We performed this pilot study to evaluate the relation between the levels of circulating plasmalogens and Alzheimer Disease Assessment Scale-Cognitive (ADAS-Cog) scores in patients with AD.

METHODS

We evaluated participants' ADAS-Cog scores and serum plasmalogen levels. For the 40 included AD patients with an ADAS-Cog score between 20 and 46, were tested their ADAS-Cog score 1 year later. The levels of docosahexaenoic acid plasmalogen were measured by use of liquid chromatography-tandem mass spectrometry.

RESULTS

We found that the ADAS-Cog score increased significantly in AD patients with circulating plasmalogen levels that were <or= 75% of that of age-matched controls at entry into the study. There was no change in score among participants with normal serum plasmalogen levels at baseline (> 75%).

LIMITATIONS

This was a pilot study with 40 patients, and the results require validation in a larger population.

CONCLUSION

Our study demonstrates that decreased levels of plasmalogen precursors in the central nervous system correlate with functional decline (as measured by ADAS-Cog scores) in AD patients. The use of both ADAS-Cog and serum plasmalogen data may be a more accurate way of predicting cognitive decline in AD patients, and may be used to decrease the risk of including patients with no cognitive decline in the placebo arm of a drug trial.

Erythroid Kruppel-like factor (EKLF) is recruited to the gamma-globin gene promoter as a co-activator and is required for gamma-globin gene induction by short-chain fatty acid derivatives

OBJECTIVES

The erythroid Kruppel-like factor (EKLF) is an essential transcription factor for beta-type globin gene switching, and specifically activates transcription of the adult beta-globin gene promoter. We sought to determine if EKLF is also required for activation of the gamma-globin gene by short-chain fatty acid (SCFA) derivatives, which are now entering clinical trials.

METHODS

The functional and physical interaction of EKLF and co-regulatory molecules with the endogenous human globin gene promoters was studied in primary human erythroid progenitors and cell lines, using chromatin immunoprecipitation (ChIP) assays and genetic manipulation of the levels of EKLF and co-regulators.

RESULTS AND CONCLUSIONS

Knockdown of EKLF prevents SCFA-induced expression of the gamma-globin promoter in a stably expressed microLCRbeta(pr)R(luc) (A)gamma(pr)F(luc) cassette, and prevents induction of the endogenous gamma-globin gene in primary human erythroid progenitors. EKLF is actively recruited to endogenous gamma-globin gene promoters after exposure of primary human erythroid progenitors, and murine hematopoietic cell lines, to SCFA derivatives. The core ATPase BRG1 subunit of the human SWI/WNF complex, a ubiquitous multimeric complex that regulates gene expression by remodeling nucleosomal structure, is also required for gamma-globin gene induction by SCFA derivatives. BRG1 is actively recruited to the endogenous gamma-globin promoter of primary human erythroid progenitors by exposure to SCFA derivatives, and this recruitment is dependent upon the presence of EKLF. These findings demonstrate that EKLF, and the co-activator BRG1, previously demonstrated to be required for definitive or adult erythropoietic patterns of globin gene expression, are co-opted by SCFA derivatives to activate the fetal globin genes.

Short-chain fatty acids induce gamma-globin gene expression by displacement of a HDAC3-NCoR repressor complex

High-level induction of fetal (gamma) globin gene expression for therapy of beta-hemoglobinopathies likely requires local chromatin modification and dissociation of repressor complexes for gamma-globin promoter activation. A novel gamma-globin-inducing short-chain fatty acid derivative (SCFAD), RB7, which was identified through computational modeling, produced a 6-fold induction in a reporter assay that detects only strong inducers of the gamma-globin gene promoter and in cultured human erythroid progenitors. To elucidate the molecular mechanisms used by high-potency SCFADs, chromatin immunoprecipitation (ChIP) assays performed at the human gamma- and beta-globin gene promoters in GM979 cells and in erythroid progenitors demonstrate that RB7 and butyrate induce dissociation of HDAC3 (but not HDAC1 or HDAC2) and its adaptor protein NCoR, specifically from the gamma-globin gene promoter. A coincident and proportional recruitment of RNA polymerase II to the gamma-globin gene promoter was observed with exposure to these gamma-globin inducers. Knockdown of HDAC3 by siRNA induced transcription of the gamma-globin gene promoter, demonstrating that displacement of HDAC3 from the gamma-globin gene promoter by the SCFAD is sufficient to induce gamma-globin gene expression. These studies demonstrate new dynamic alterations in transcriptional regulatory complexes associated with SCFAD-induced activation of the gamma-globin gene and provide a specific molecular target for potential therapeutic intervention.

Distinct phospholipase C-gamma-dependent signaling pathways in the Drosophila eye and wing are revealed by a new small wing allele

The Drosophila genome contains a single phospholipase C-gamma (PLC-gamma) homolog, encoded by small wing (sl), that acts as an inhibitor of receptor tyrosine kinase (RTK) signaling during photoreceptor R7 development. Although the existing sl alleles behave genetically as nulls, they may still produce truncated Sl products that could in theory still provide limited PLC-gamma function. Both to identify a true null allele and to probe structure-function relationships in Sl, we carried out an F(1) screen for new sl mutations and identified seven new alleles. Flies homozygous for any of these alleles are viable, with the same short-wing phenotype described previously; however, two of the alleles differ from any of those previously isolated in the severity of the eye phenotype: sl(9) homozygotes have a slightly more extreme extra-R7 phenotype, whereas sl(7) homozygotes have an almost wild-type eye. We determined the mutant defect in all seven alleles, revealing that sl(9) is a molecular null due to a very early stop codon, while sl(7) has a missense mutation in the highly conserved Y catalytic domain. Together with in vitro mutagenesis of the residue affected by the sl(7) mutation, these results confirm the role of Sl in RTK signaling and provide evidence for two genetically separable PLC-gamma-dependent pathways affecting the development of the eye and the wing.