11 research outputs found
Grouping of UVCB substances with dose-response transcriptomics data from human cell-based assays
The application of in vitro biological assays as new approach methodologies (NAMs) to support grouping of UVCB (unknown or variable composition, complex reaction products, and biological materials) substances has recently been demonstrated. In addition to cell-based phenotyping as NAMs, in vitro transcriptomic profiling is used to gain deeper mechanistic understanding of biological responses to chemicals and to support grouping and read-across. However, the value of gene expression profiling for characterizing complex substances like UVCBs has not been explored. Using 141 petroleum substance extracts, we performed dose-response transcriptomic profiling in human induced pluripotent stem cell (iPSC)-derived hepatocytes, cardiomyocytes, neurons, and endothelial cells, as well as cell lines MCF7 and A375. The goal was to determine whether transcriptomic data can be used to group these UVCBs and to further characterize the molecular basis for in vitro biological responses. We found distinct transcriptional responses for petroleum substances by manufacturing class. Pathway enrichment informed interpretation of effects of substances and UVCB petroleum-class. Transcriptional activity was strongly correlated with concentration of polycyclic aromatic compounds (PAC), especially in iPSC-derived hepatocytes. Supervised analysis using transcriptomics, alone or in combination with bioactivity data collected on these same substances/cells, suggest that transcriptomics data provide useful mechanistic information, but only modest additional value for grouping. Overall, these results further demonstrate the value of NAMs for grouping of UVCBs, identify informative cell lines, and provide data that could be used for justifying selection of substances for further testing that may be required for registration
Integrative Chemical–Biological Grouping of Complex High Production Volume Substances from Lower Olefin Manufacturing Streams
Human cell-based test methods can be used to evaluate potential hazards of mixtures and products of petroleum refining (“unknown or variable composition, complex reaction products, or biological materials” substances, UVCBs). Analyses of bioactivity and detailed chemical characterization of petroleum UVCBs were used separately for grouping these substances; a combination of the approaches has not been undertaken. Therefore, we used a case example of representative high production volume categories of petroleum UVCBs, 25 lower olefin substances from low benzene naphtha and resin oils categories, to determine whether existing manufacturing-based category grouping can be supported. We collected two types of data: nontarget ion mobility spectrometry-mass spectrometry of both neat substances and their organic extracts and in vitro bioactivity of the organic extracts in five human cell types: umbilical vein endothelial cells and induced pluripotent stem cell-derived hepatocytes, endothelial cells, neurons, and cardiomyocytes. We found that while similarity in composition and bioactivity can be observed for some substances, existing categories are largely heterogeneous. Strong relationships between composition and bioactivity were observed, and individual constituents that determine these associations were identified. Overall, this study showed a promising approach that combines chemical composition and bioactivity data to better characterize the variability within manufacturing categories of petroleum UVCBs
Assessment of the Mitigative Capacity of Dietary Zinc on PCB126 Hepatotoxicity and the Contribution of Zinc to Toxicity
Hepatic
levels of the essential micronutrient, zinc, are diminished
by several hepatotoxicants, and the dietary supplementation of zinc
has proven protective in those cases. 3,3′,4,4′,5-Pentachlorobiphenyl
(PCB126), a liver toxicant, alters hepatic nutrient homeostasis and
lowers hepatic zinc levels. The current study was designed to determine
the mitigative potential of dietary zinc in the toxicity associated
with PCB126 and the role of zinc in that toxicity. Male Sprague–Dawley
rats were divided into three dietary groups and fed diets deficient
in zinc (7 ppm Zn), adequate in zinc (30 ppm Zn), and supplemented
in zinc (300 ppm). The animals were maintained for 3 weeks on these
diets, then given a single IP injection of vehicle or 1 or 5 ÎĽmol/kg
PCB126. After 2 weeks, the animals were euthanized. Dietary zinc increased
the level of ROS, the activity of CuZnSOD, and the expression of metallothionein
but decreased the levels of hepatic manganese. PCB126 exposed rats
exhibited classic signs of exposure, including hepatomegaly, increased
hepatic lipids, increased ROS and CYP induction. Liver histology suggests
some mild ameliorative properties of both zinc deficiency and zinc
supplementation. Other metrics of toxicity (relative liver and thymus
weights, hepatic lipids, and hepatic ROS) did not support this trend.
Interestingly, the zinc supplemented high dose PCB126 group had mildly
improved histology and less efficacious induction of investigated
genes than did the low dose PCB126 group. Overall, decreases in zinc
caused by PCB126 likely contribute little to the ongoing toxicity,
and the mitigative/preventive capacity of zinc against PCB126 exposure
seems limited
Machine Learning Models for Estrogen Receptor Bioactivity and Endocrine Disruption Prediction
Does Dietary Copper Supplementation Enhance or Diminish PCB126 Toxicity in the Rodent Liver?
Copper
is essential for the function of the mitochondrial electron
transport chain and several antioxidant proteins. However, in its
free form copper can participate in Fenton-like reactions that produce
reactive hydroxyl radicals. Aryl-hydrocarbon receptor (AhR) agonists,
including the most potent polychlorinated biphenyl (PCB) congener,
3,3′,4,4′,5-pentachlorobiphenyl (PCB126), increase copper
levels in rodent livers. This is accompanied by biochemical and toxic
changes. To assess the involvement of copper in PCB toxicity, male
Sprague–Dawley rats were fed an AIN-93G diet with differing
dietary copper levels: low (2 ppm), adequate (6 ppm), and high (10
ppm). After three weeks, rats from each group were given a single
ip injection of corn oil (control), 1, or 5 ÎĽmol/kg body weight
PCB126. Two weeks following injections, biochemical and morphological
markers of hepatic toxicity, trace metal status, and hepatic gene
expression of metalloproteins were evaluated. Increasing dietary copper
was associated with elevated tissue levels of copper and ceruloplasmin.
In the livers of PCB126-treated rats, the hallmark signs of AhR activation
were present, including increased cytochrome P450 and lipid levels
and decreased glutathione. In addition, a doubling of hepatic copper
levels was seen, and overall metal homeostasis was disturbed, resulting
in decreased hepatic selenium, manganese, zinc, and iron. Expression
of key metalloproteins was either decreased (cytochrome <i>c</i> oxidase), unchanged (ceruloplasmin and CuZnSOD), or increased (tyrosinase
and metallothioneins 1 and 2) with exposure to PCB126. Increases in
metallothionein may contribute/reflect the increased copper seen.
Alterations in dietary copper did not amplify or abrogate the hepatic
toxicity of PCB126. PCB126 toxicity, i.e., oxidative stress and steatosis,
is clearly associated with disturbed metal homeostasis. Understanding
the mechanisms of this disturbance may provide tools to prevent liver
toxicity by other AhR agonists