Doctor of Philosophy (PhD), Wright State University, 2014, Environmental Sciences PhD

Transcriptional regulation of the murine immunoglobulin heavy chain gene involves several regulatory elements including the 3'Igh regulatory region (3'IghRR) composed of at least four enhancers (hs3A; hs1,2; hs3B; hs4). Enhancers hs1,2 and hs4 contain binding sites for several transcription factors including NF-κB/Rel proteins and the AhR. Interestingly, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) profoundly inhibits 3'IghRR and hs1,2 activation induced by the B-cell activator lipopolysaccharide (LPS), but enhances the activation of the hs4. Within the hs4, the AhR binding site overlaps an NF-κB/Rel binding site suggesting that both the AhR and the NF-κB together may modulate of the 3'IghRR. The objective of the current study was to evaluate the role of NF-κB/Rel and the AhR following LPS stimulation and TCDD treatment on 3'IghRR, hs1,2, and hs4. In our studies we utilized the CH12.LX B cell line; the CH12.IκBαAA cell line, which expresses an inducible IκBα super repressor (IκBαAA); the CH12.γ2b-3'IghRR cell line that stably expresses a γ2b-3'IghRR-regulated γ2b transgene reporter; and splenocytes derived from B6C3F1 mice. The stimulation of the CH12.γ2b-3'IghRR cell line with Toll-like receptor (TLR) agonists LPS, Resiquimod (R848), or Cytosine-phosphate-Guanine (CpG)-oligodeoxynucleotides combined with a co-treatment of TCDD significantly inhibited the TLR-induced activation of the 3'IghRR. Utilizing transiently expressed luciferase reporters, we found induction of IκBαAA expression partially attenuated LPS-induced activation of the 3'IghRR and hs4, partially reversed the effects of a TCDD and LPS co-treatment on the activity of the 3'IghRR and hs4, and the addition of an AhR antagonist, CH223191, markedly reversed the LPS and TCDD induced inhibition of the 3'IghRR and inhibited the synergistic activation of the hs4. Chromatin immunoprecipitation analysis of CH12.LX and murine splenocytes demonstrated a LPS and a LPS co-treatment with TCDD-dependent increase in Rel (open full item for complete abstract)

Committee: Courtney Sulentic Ph.D. (Advisor); Michael Leffak Ph.D. (Committee Member); Mill Miller Ph.D. (Committee Member); David Cool Ph.D. (Committee Member); Rodney DeKoter Ph.D. (Committee Member); Don Cipollini Ph.D. (Other) Subjects: Environmental Science; Immunology; Molecular Biology; Toxicology

PhD, University of Cincinnati, 2020, Medicine: Toxicology (Environmental Health)

The focus of this dissertation is the characterization of the epigenetic, structural, and functional consequences of exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin), a potent ligand of the aryl hydrocarbon receptor (AHR), in differentiated cardiomyocytes and the adult heart as a result of continuous exposure from fertilization through adulthood. Congenital heart disease (CHD) is the most common congenital abnormality and one of the leading causes of mortality worldwide. Ongoing scientific investigations show that a precise etiology remains elusive, but is likely to result from complex interactions between genetic and environmental factors during heart development, at a time when the heart adapts to diverse physiological and pathophysiological conditions. Crucial among these is the regulation of cardiomyocyte development and postnatal maturation, governed by dynamic changes in DNA methylation. Previous work from our laboratory showed that exposure to the environmental toxicant tetrachlorodibenzo-p-dioxin (TCDD) disrupts several molecular networks responsible for heart development and function. In addition, interference with endogenous developmental functions of the AHR, either by gene ablation or by in utero exposure to TCDD, was shown to cause structural, molecular and functional cardiac abnormalities and altered heart physiology in mouse embryos. These studies demonstrated the potential role of AHR in the pathogenesis of CHD by its disruption during development. The biological half-life of TCDD is 7-10 years in humans. Therefore, it is of clinical importance to understand the consequences of continuous activation of AHR by TCDD from development through adulthood on cardiac structure and function. Chapter One summarizes the current body of knowledge surrounding TCDD, the AHR, heart development, CHD, the risk and mechanisms of heart failure, and the role of DNA methylation in cardiomyocyte maturation. Chapter Two describes the effects of TCDD on DNA me (open full item for complete abstract)

Committee: Alvaro Puga Ph.D. (Committee Chair); Katherine Burns Ph.D. (Committee Member); Jack Rubinstein M.D. (Committee Member); Ying Xia Ph.D. (Committee Member); Xiang Zhang Ph.D. (Committee Member) Subjects: Toxicology

Master of Science (MS), Wright State University, 2020, Microbiology and Immunology

Aryl hydrocarbon receptor (AhR) mediates the immunosuppressive effects of 2,3,7,8 -tetrachlorodibenzodioxin (TCDD) in murine B cells. The effects of AhR activation on the regulation of expression of human immunoglobulin isotypes (μ, γ1-4, α1-2 and ε) and Ig secretion is unclear. Our previous results using CL-01 cell-line originating from a Burkitt's lymphoma patient, demonstrated an inhibitory effect of TCDD on IgG expression but a surprising and marked loss of IgG secretion when the AhR was knocked out by siRNA or CRISPR/Cas9 gene editing. To determine if the AhR is a critical mediator of IgG expression, current study is focused on characterizing IgG expression in another human B-cell line (SKW 6.4 or SKW WT) originating from a different, non-related Burkitt's lymphoma. We confirmed that SKW WT cells do not have endogenous expression of AhR using PCR analysis and Western blotting. We also demonstrated that SKW 6.4 cells can be stimulated in-vitro using CD40L and IL-4 to produce more IgM antibodies as detected by ELISA assays. Further, we demonstrate that total IgG secretion induced by CD40L and IL-4 stimulation is severely impaired in SKW WT cells. Conversely, the Qt-PCR studies show that the expression of ε, γ2-4 transcripts that code for IgE and IgG2-4 respectively is significantly increased with stimulation as compared to un-stimulated SKW cell lines. The expression of γ1 was low in naive as well as stimulated SKW WT cells. The α1-2 transcripts coding for IgA1-2 respectively are not expressed at all in SKW cells regardless of stimulation. To further investigate, we used CL-01 AhRTA cells that express AhR with functional TAD, to compare the expression of different isotypes. It was found that the expression of γ1-4 and ε transcripts was significantly higher in AhR expressing CL-01 AhRTA cells as compared to SKW WT cells. Our observations imply that AhR plays a critical role in expression of the IgH gene.

Committee: Courtney Sulentic Ph.D. (Advisor); Thomas Brown Ph.D. (Committee Member); Nancy Bigley Ph.D. (Committee Member) Subjects: Immunology; Toxicology

Master of Science (MS), Wright State University, 2017, Microbiology and Immunology

The immunoglobulin heavy chain gene (Igh) in various animal models is regulated by numerous regulatory elements including the 3'Igh regulatory region (3'IghRR). Several transcription factors are involved in modulating the 3'IghRR including the aryl hydrocarbon receptor (AhR). The AhR is a ligand-activated transcription factor that mediates the transcription of genes involved in the metabolism of environmental toxicants such as TCDD. TCDD binds AhR and regulates immunoglobulin (Ig) expression in B cells. This modulation appears to be directly mediated by binding of the AhR to dioxin response elements (DRE) within the 3'IghRR. In human B cells, IgG secretion inhibited by TCDD and increased by chemical antagonist of the AhR (AhRA). AhR can interact with different transcription factors like NFκB and AP-1, and modulate signaling pathways such as Src and Akt pathways. the human CL-01 cells express a nonfunctional transactivation domain (AhR TA) in one of its alleles. Therefore, we hypothesized that in human cells the AhR regulates IGH expression by altering 3'IGHRR activation through both genomic and non-genomic mediated mechanisms. The current study focuses on determining the potential non-genomic effects of the AhR on the activation of cytosolic signaling proteins such as Src and Akt, and transcription factors like NFκB and AP-1. In addition, it evaluates the genomic effects of the nonfunctional AhR TA on the 3'IGHRR reporter activity and evaluates the role of AhR in the effect of the TCDD and AhRA on Ig expressing and 3'IGHRR activity. Our results showed that the AhR has non-genomic effects by activating cytosolic signaling protein like Akt and increasing the Iγ3-3'IGHRR reporter activity in response to AhRA that could lead to an increase in IgG secretion. The nonfunctional AhR TA decreased the AhR binding to DRE sites as demonstrated in a DRE reporter but it did not affect 3'IGHRR activity in response to TCDD or AhRA. AhR knockdown by gene editing demonstrated inhibit (open full item for complete abstract)

Committee: Courtney Sulentic Ph.D. (Advisor); Nancy Bigley Ph.D. (Committee Member); Mauricio Di Fulvio Ph.D. (Committee Member) Subjects: Immunology; Toxicology

Master of Science (MS), Wright State University, 2015, Microbiology and Immunology

The aryl hydrocarbon receptor (AhR) is a ligand-activated cytosolic transcription factor that regulates xenobiotic-metabolizing enzymes. It mediates the toxicity of various environmental chemicals such as 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD). TCDD inhibits the differentiation of B cells into antibody-secreting cells and inhibits immunoglobulin (Ig) expression in various animal models. We have previously determined that TCDD-induced inhibition of the mouse Ig heavy chain gene (mo-Igh) is AhR-dependent. This inhibition may be mediated by binding of the AhR to dioxin response elements (DREs) within the 3'Igh regulatory region (3'IghRR) and inhibition of 3'IghRR activity, a significant transcriptional regulator of Ig expression. However, there are structural differences between the mouse and human 3'IghRR. The mouse contains four enhancers (hs3A; hs1,2; hs3B; and hs4), whereas the human contains three (hs3; hs1,2; and hs4). In addition, the human hs1,2 is known to be highly polymorphic and has been associated with several autoimmune diseases. The current study focuses on elucidating the role of the AhR in human Ig expression and class switch recombination (CSR). We disrupted the AhR signaling pathway in a human B-cell line (CL-01) using two different shRNA constructs or with the chemical AhR antagonist (CH-223191). Although the CL-01 AhR has three heterozygous single nucleotide polymorphisms (SNPs) that results in loss of CYP1A1 gene induction, TCDD significantly inhibits IgG expression, whereas IgM expression has very low sensitivity to TCDD. Interestingly, decreased AhR protein levels results in low IgG expression, while there was no change in IgM expression. In contrast, the AhR antagonist induced greater IgG secretion in stimulated B cells, which was not replicated by the AhR knockdown suggesting a mechanistic difference between the chemical antagonist and AhR knockdown. Reduced AhR levels caused an isotype-specific inhibition of the CSR to IgG1, but not to I (open full item for complete abstract)

Committee: Courtney Sulentic Ph.D. (Advisor); Barbara Hull Ph.D. (Committee Member); Nancy Bigley Ph.D. (Committee Member); Katherine Excoffon Ph.D. (Committee Member) Subjects: Immunology; Microbiology; Toxicology

Master of Science (MS), Wright State University, 2015, Pharmacology and Toxicology

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent and persistent environmental toxin known to inhibit immunoglobulin (Ig) gene expression in various animal models. TCDD is thought to modulate gene expression through the aryl hydrocarbon receptor (AhR) and thereby a subsequent alteration in gene expression. The AhR is a ligand-activated transcription factor that regulates xenobiotic-metabolizing enzymes. The mouse 3'Ig heavy chain regulatory region (3'IghRR) is a sensitive transcriptional target of TCDD that may mediate, in an AhR-dependent manner, the inhibitory effect of TCDD on Ig expression. Human B cells could also be a sensitive target of TCDD. The current study focuses on determining the effects of TCDD and the AhR on human Ig expression utilizing a human Burkitt lymphoma cell line (CL-01) model that can be activated to secrete Ig and undergo class switch recombination (CSR) from IgM to IgA, IgG or IgE antibody isotypes. Our results suggest that TCDD has variable effects on IgM secretion, but significantly inhibits IgG secretion, an effect reversed by addition of the AhR antagonist. Surprisingly, the AhR antagonist alone markedly increased IgG secretion above stimulation. At transcript level, TCDD has variable effects on µ IGH functional transcripts, inhibits γ1-4 germline/functional transcripts and Cε germline transcripts. Additionally, CD40L and IL-4 stimulation induced de novo synthesis of Cε germline transcripts, a precursor to CSR. However, α1-2 germline/functional transcripts increased in response to TCDD. Notably, TCDD and stimulation had no effect on CYP1A1 transcript expression. Additionally, in CL-01 cells, we recently discovered SNPs in the Exon-10 of the AhR, the transactivation domain of the AhR that regulates expression of other genes but does not affect ligand binding and the AhR is heterozygous with one non-functional transactivation domain. Results also indicate that a small proportion of the cells have undergone spontaneous class switch (open full item for complete abstract)

Committee: Courtney Sulentic Ph.D. (Advisor); Nancy Bigley Ph.D. (Committee Member); David Cool Ph.D. (Committee Member); Mauricio Di Fulvio Ph.D. (Committee Member) Subjects: Immunology; Toxicology

PhD, University of Cincinnati, 2015, Medicine: Toxicology (Environmental Health)

The focus of this dissertation is on the identification of novel cardiac specific genes regulated by the aryl hydrocarbon receptor (AHR) and the mechanisms through which TCDD exposure induces cardiotoxicity, primarily regarding the dual roles of the receptor in both regulating cardiomyocyte differentiation and in mediating TCDD-caused cardiotoxicity. The AHR is a ligand-activated transcription factor that belongs to the basic-region-helix-loop-helix PER/ARNT/SIM (bHLH-PAS) super¬family of transcription factors. AHR has a wide range of ligands with the prototypical ligand being the persistent environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Exposure to TCDD causes toxicity in multiple organs and organisms including the heart that is primarily mediated through AHR. The binding of TCDD to AHR leads to the translocation of the receptor from the cytosol to the nucleus where the receptor heterodimerizes with Aryl Hydrocarbon Receptor Translocator (ARNT) and consequently binds as a heterodimer to DNA, resulting the regulation of expression for hundreds of downstream genes. A battery of genes that have been extensively studied function in the metabolism of xenobiotics, i.e. cytochrome P450, family1 (Cyp1). Beyond the role in xenobiotic metabolism, the Ah receptor has an important role in basic physiologic processes such as cardiovascular development. The goal of this dissertation is to characterize the developmental role of the receptor as well as the consequences of developmental exposure to TCDD during cardiomyocyte differentiation. Chapter I gives a brief background on the chemical properties and toxicology of TCDD with a focus on the cardiotoxicity. The structure and molecular action of AHR as well as its role in cardiovascular development and homeostasis are described. In chapter II, we used next generation sequencing to analyze temporal trajectories of TCDD-dependent global gene expression in differentiating cells expressing the Ah recep (open full item for complete abstract)

Committee: Alvaro Puga Ph.D. (Committee Chair); Michael Borchers Ph.D. (Committee Member); Susan Kasper Ph.D. (Committee Member); Peter Stambrook Ph.D. (Committee Member); Ying Xia Ph.D. (Committee Member) Subjects: Toxicology

Master of Science (MS), Wright State University, 2013, Pharmacology and Toxicology

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a ubiquitous environmental contaminant that inhibits immunoglobulin (Ig) expression and Ig heavy (IgH) chain gene transcription. Transcription of the IgH gene involves several regulatory elements including the 3'lgh regulatory region (3'lghRR) which is composed of four enhancers (hs3A, hs1,2, hs4, and hs3B). Dioxin responsive elements (DRE) in the hs4 and hs1,2 enhancers of the 3lghRR that bind the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that regulates dioxin sensitive genes suggest that the 3'lghRR may be a transcriptional target of TCDD. The current study utilized an IgA secreting mouse B-cell line that stably expresses a γ 2b transgene regulated by the 3'lghRR (CH12.γ 2b-3'lghRR cells). Both shRNA knock down of AhR and an AhR antagonist (CH-223191) reduced TCDD-induced inhibition of endogenous IgA and the γ 2b transgene expression. With the growing number of immune-related disorders correlated with polymorphisms of the human hs1,2 enhancer, ubiquitously found AhR ligands, and sensitivity of human Ig expression to TCDD, our findings may provide indispensible information for human health risk assessment and insight into the development of therapeutic interventions for immune-related disease.

Committee: Courtney Sulentic Ph.D. (Committee Chair); Michael Leffak Ph.D. (Committee Member); Katherine Excoffon Ph.D. (Committee Member) Subjects: Immunology; Pharmacology; Toxicology

Master of Science (MS), Wright State University, 2010, Microbiology and Immunology

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a disrupter, of B-cell differentiation, induces binding of the aryl hydrocarbon receptor (AhR) nuclear complex to dioxin responsive elements (DRE) within the mouse immunoglobulin heavy chain regulatory region (3'IgHRR), and produces a marked inhibition of 3'IgHRR activation, IgH expression, and antibody secretion in a well-characterized mouse B-cell line (CH12.LX). The mouse 3'IgHRR consists of at least four enhancers (hs3a; hs1,2; hs3b; hs4), and is highly homologous with the three enhancers (hs3; hs1,2; hs4) of the human 3'IgHRR. A polymorphism of the human hs1,2 enhancer (resulting in varying numbers of tandem repeats containing a DRE and κB site) has been correlated with several autoimmune diseases. Although the human and mouse hs1,2 enhancers are share a ~90% identity, luciferase reporter studies in mouse CH12.LX B-cells showed that TCDD inhibited LPS stimulation of the mouse hs1,2 enhancer but co-treatment with TCDD and LPS synergistically activated human hs1,2 enhancer activity. To evaluate transcriptional differences between the human and mouse hs1,2 enhancers, our objectives were to characterize the IM-9 cells as a potential human B-cell model, and to evaluate TCDD-induced transcriptional regulation of the polymorphic human hs1,2 enhancer in a human cell line. We confirmed AhR expression and TCDD-induced CYP1A1 induction in IM-9 cells. Then we transiently transfected IM-9 cells with the human hs1,2 reporters and determined that TCDD activates the human hs1,2 enhancer in IM-9 B-cells, as seen in CH12.LX B-cells. However, the TCDD-induced fold-activation in human IM-9 cells appeared less compared to results in mouse CH12.LX B-cells perhaps due to differences between the mouse and human AhR. Our data suggests that the TCDD-induced inhibition of the mouse hs1,2 enhancer versus the activation of the human hs1,2 enhancer may be related to an inhibitory BSAP site located on the mouse hs1,2 enhancer that is absent from th (open full item for complete abstract)

Committee: Courtney E Sulentic PhD (Advisor); Michael Leffak PhD (Committee Member); Nancy Bigley Phd (Committee Member) Subjects: Biochemistry; Biology; Biomedical Research; Cellular Biology; Environmental Science; Immunology; Microbiology; Molecular Biology; Pharmacology; Toxicology

Master of Science (MS), Wright State University, 2009, Pharmacology and Toxicology

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent environmental toxin that inhibits immunoglobulin (Ig) gene expression in mice. Transcriptional regulation of the Ig heavy chain (IgH) involves the 3'IgH regulatory region (3'IgH RR). The murine 3'IgH RR consists of four enhancers (hs3A, hs1,2, hs3B, and hs4), which are homologous to the human 3'IgH RR enhancers (hs3, hs1,2, and hs4). In humans, a polymorphism of the hs1,2 enhancer, resulting in a varying number of tandem repeats of a 53 bp sequence, has been correlated with autoimmune diseases like IgA nephropathy and Celiac disease. The repeated sequence contains a kB and DRE binding site. Previous studies have shown that TCDD inhibits the murine 3'IgH RR but activates the hs4 enhancer in a well-characterized mouse B-cell line, CH12.LX. Therefore, the objective of the current study was to determine if TCDD inhibits the murine 3'IgH RR by repressing hs1,2 enhancer activity and if this effect will be mirrored by the human polymorphic hs1,2 enhancer in the CH12.LX model. Using transient luciferase studies and CH12.LX cells that stably express a transgene under the regulation of the hs1,2/hs3A enhancer pair, we have found that indeed the mouse hs1,2 enhancer is inhibited by TCDD in LPS-induced B cells. However the human hs1,2 undergoes a striking activation after TCDD treatment, much like the murine hs4 enhancer. These results suggest a difference in transcriptional regulation between the mouse and human hs1,2 sequence. Mutational analyses determined that DRE, kB, AP-1, and Oct binding motifs found within the human hs1,2 enhancer act in concert to mediate TCDD-induced activation of the human polymorphic hs1,2 enhancer. Since TCDD represents a large class of chemicals found in the environment, diet, and pharmaceuticals, understanding chemical-induced modulation of the 3'IgH RR enhancers may provide a clue to the etiology of certain autoimmune diseases.

Committee: Courtney Sulentic PhD (Advisor); Thomas Brown PhD (Committee Member); David Cool PhD (Committee Member) Subjects: Immunology; Molecular Biology; Toxicology

PhD, University of Cincinnati, 2010, Medicine: Cell and Molecular Biology

Dioxin and dioxin like compounds (DLCs) are environmental contaminants released during many industrial processes. Halogenated and polycyclic aromatic hydrocarbons, such as 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), DLCs, and benzo[a]pyrene (BaP) are known or suspected human carcinogens and developmental teratogens and induce expression of the cytochrome P450 encoded by the substrate responsive CYP1A1 gene. CYP1A1 gene induction requires trans-activation by the heterodimeric transcriptional complex formed by ligand bound Aromatic Hydrocarbon Receptor (AHR) and the AHR Nuclear Translocator proteins (ARNT). We have shown that with BaP induced activation of Cyp1a1 gene expression in mouse hepatoma Hepa-1 cells, there is a concomitant change in the pattern of histone modifications associated with the Cyp1a1 promoter and distal enhancer. At the promoter of the Cyp1a1 gene this pattern of histone modification that accompanies BaP induced Cyp1a1 transcription includes trimethylation of Lys4 of histone H3 (3MeK4H3) and hyperacetylation of Lysine 14 of histone H3 (AcK14H3). At the distal enhancer of the Cyp1a1 gene BaP leads to an increase in phosphorylation of Ser10 on histone H3(pS10H3) and a hyperacetylation of Lysine 16 of histone H4 (AcK16H4). Here we find that in mouse embryonic fibroblast, treatment with BaP shows a similar increase in Cyp1a1 transcription as in Hepa-1 cells accompanied by at the same pattern of histone modifications at both the distal enhancer and proximal promoter as in Hepa-1 cells. In MEFs these changes are dependent on the AHR binding to BaP and MEFs with an AHR allele which encodes an AHR protein with low binding affinity for ligand do not elicit the same modifications of histone marks in the Cyp1a1 gene promoter or distal enhancer as those with an allele encoding an AHR protein with higher affinity for ligand. We determine that treatment with various different AHR ligands all lead to similar patterns of histone modifications upstream of the Cyp (open full item for complete abstract)

Committee: Alvaro Puga PhD (Committee Chair); Sohaib Khan PhD (Committee Member); Ying Xia PhD (Committee Member); Daniel Nebert MD (Committee Member); Susan Waltz PhD (Committee Member) Subjects: Cellular Biology

PhD, University of Cincinnati, 2007, Medicine : Toxicology (Environmental Health)

Polychlorinated biphenyls (PCBs) are persistent organic pollutants linked to numerous human health problems, including learning and memory deficits in children of exposed mothers. PCBs exist in the environment as complex mixtures. Both coplanar and non-coplanar PCBs are reported to have neurotoxic effects in animal studies, but individual congeners do not always produce the same effects as PCB mixtures. We used a mixture of eight PCBs to model human exposures based on their reported concentrations in human tissue, breast milk, and the human food supply. Individual risk to PCBs varies by genetic makeup. We developed a mouse model to explore the role of two genes that may be responsible for some of the reported inter-individual differences: the aryl hydrocarbon receptor (AHR) and CYP1A2. There are >12-fold differences between humans with regard to AHR affinity and >60-fold differences in hepatic basal CYP1A2 levels. Our mouse model used Cyp1a2(+/+)wild-type and Cyp1a2(-/-)knockout mice with either a high-affinity or poor-affinity Ahrgene. We hypothesized that high-affinity Ahr bCyp1a2(-/-)would be most susceptible and poor-affinity dCyp1a2(+/+)most resistant to PCB-induced developmental neurotoxicity. Using GC-ECD, we determined that offspring of Cyp1a2(-/-)mothers were exposed to higher levels of coplanar PCBs during development and that Ahr bmice metabolized all PCB congeners more quickly. Differences in PCB exposure were closely correlated with changes in CYP1A1 and CYP1A2 mRNA and protein levels and with well-known endpoints of AHR-mediated toxicity: immunosuppression and hepatotoxicity. In addition, we conducted behavioral phenotyping of exposed offspring. We found significant deficits in learning and memory in Ahr bCyp1a2(-/-)mice, including impairments in novel object recognition and an increased failure rate in the Morris water maze. However, all PCB-treated groups and all genotypes showed significant differences in at least one measure of learning (open full item for complete abstract)

Committee: Dr. Daniel Nebert (Advisor) Subjects: