Medical Toxicology Commons^™

Identification Of Activities Involved In Cag/Ctg Repeat Instability, Nelson Lap Shun Chan

University of Kentucky Doctoral Dissertations

CAG/CTG repeat instability is associated with at least 14 neurological disorders, including Huntington’s disease and Myotonic dystrophy type 1. In vitro and in vivo studies have showed that CAG/CTG repeats form a stable hairpin that is believed to be the intermediate for repeat expansion and contraction.

Addition of extra DNA is essential for repeat expansion, so DNA synthesis is one of the keys for repeat expansion. In vivo studies reveal that 3’ CTG slippage with subsequent hairpin formation (henceforth called the 3’ CTG slippage hairpin) occurs during DNA synthesis. It is proposed that hairpin tolerance machinery is activated because prolonged …

Androgen Increases Angiotensin Receptor Type 1a On Smooth Muscle Cells To Promote Angiotensin Ii-Induced Abdominal Aortic Aneurysms, Xuan Zhang

University of Kentucky Doctoral Dissertations

The purpose of this study was to determine whether androgen promotes AT1aR expression on smooth muscle to confer high prevalence of AngII-induced AAAs in hyperlipidemic mice. In addition, we also investigate the role of androgen in the progression of established AngII-induced AAAs.

First, we sought to examine the role of endogenous androgen in the growth of established AngII-induced AAAs. By castrating male mice, we demonstrated that removal of endogenous androgen significantly decreased the progressive lumen dilation of established AngII-induced AAAs in male ApoE-/- mice, but had no effect on external AAA diameters. These results suggest that androgen contributes to the …

Biochemical Characterization Of Human Mismatch Recognition Proteins Mutsα And Mutsβ, Lei Tian

University of Kentucky Doctoral Dissertations

The integrity of an organism's genome depends on the fidelity of DNA replication and the efficiency of DNA repair. The DNA mismatch repair (MMR) system, which is highly conserved from prokaryotes to eukaryotes, plays an important role in maintaining genome stability by correcting base-base mismatches and insertion/deletion (ID) mispairs generated during DNA replication and other DNA transactions. Mismatch recognition is a critical step in MMR. Two mismatch recognition proteins, MutSα (MSH2-MSH6 heterodimer) and MutSβ (MSH2-MSH3 heterodimer), have been identified in eukaryotic cells. MutSα and MutSβ have partially overlapping functions, with MutSα recognizing primarily base-base mismatches and 1-2 nt ID mispairs …

The Radiosensitization Effect Of Parthenolide In Prostate Cancer: Implications For Selective Cancer Killing By Modulation Of Intracellular Redox State, Yulan Sun

University of Kentucky Doctoral Dissertations

Parthenolide (PN), a major active component of the traditional herbal medicine feverfew, has been shown to have anti-inflammatory and anti-tumor properties. More remarkably, the cytotoxicity of PN seems selective to tumor cells but not their normal cell counterparts. In the present study, we investigate whether and how PN selectively enhances tumor sensitivity to radiation therapy by using prostate cancer cells LNCaP, DU145 and PC3, as well as normal prostate epithelial cells PrEC.

Our study demonstrates that inhibition of NF-κB pathway and suppression of its downstream target MnSOD are common mechanisms for the radiosensitization effect of PN in prostate cancer cells. …

Structural Instability Of Human Ribosomal Rna Gene Clusters, Dawn Michelle Stults

University of Kentucky Doctoral Dissertations

The human ribosomal RNA genes are critically important for cell metabolism and viability. They code for the catalytic RNAs which, encased in a housing of more than 80 ribosomal proteins, link together amino acids by peptide bonds to generate all cellular proteins. Because the RNAs are not repeatedly translated, as is the case with messenger RNAs, multiple copies are required. The genes which code for the human ribosomal RNAs (rRNAs) are arranged as clusters of tandemly repeated sequences. Three of four catalytic RNAs are spliced from a single transcript. The genes are located on the short arms of the five …

Function Of Androgen Receptor In Prostate Cancer Epithelial Mesenchymal Transition And Microtubule Targeting, Menglei Zhu

University of Kentucky Doctoral Dissertations

Prostate cancer is the most frequently diagnosed non-skin cancer and the third leading cause of cancer mortality among men in the US. Androgens are functionally required for the normal growth of the prostate gland and play a critical role in prostate tumor development and progression. Epithelial-mesenchymal-transition (EMT) is an important process during normal development, and cancer cell metastasis.

This study examined the ability of androgens to influence EMT of prostate cancer epithelial cells and evaluate the effect of taxol chemotherapy on androgen signaling in prostate cancer cells in prostate cancer. The EMT pattern was evaluated on the basis of expression …

Role Of Oxidative Stress And T Cell Homing In The Development Of Murine Syngeneic Graft-Versus-Host Disease, Jacqueline Perez-Rodriguez

University of Kentucky Doctoral Dissertations

Syngeneic graft-versus-host disease (SGVHD) is induced by reconstituting lethally irradiated mice with syngeneic BM cells followed by a 21 day treatment with the immunosuppressive agent cyclosporine A (CsA). Clinical symptoms of the disease appear 2-3 weeks following cessation of CsA therapy and disease-associated inflammation occurs primarily in the colon and liver.

The development of SGVHD is a complex process resulting from the cooperative interaction of multiple effector cell populations including NK cells, T cells and macrophages. T_H1 cytokines (IL-12, TNF-α, IFN- γ), produced by these effector cells, serve as inflammatory mediators contributing to the pathogenesis of SGVHD. The …

Angiotensin Ii Induction Of Regional Effects In Murine Vasculature, Albert Phillip Owens Iii

University of Kentucky Doctoral Dissertations

The renin angiotensin system (RAS) exerts many diverse physiological functions throughout the body, mediated by its effector peptide, angiotensin II (AngII). AngII has been linked with a variety of different functions ranging from the initiation of severe vascular pathologies, such as atherosclerosis and abdominal aortic aneurysm (AAA), to mundane physiological processes of fluid homeostasis, vascular contraction, and regulation of blood pressure. To provide a potential link between these functions, an in-depth analysis of regional effects of AngII on aortic vasculature was performed.

The studies presented in this dissertation tested the overall hypothesis of whether regional changes exist in the vasculature …

Role Of Mel-18 In Regulating Protein Sumoylation And Identification Of A New Polymorphism In Bmi-1, Jie Zhang

University of Kentucky Doctoral Dissertations

Small ubiquitin-like modifier (SUMO) regulates numerous biological functions. In a previous study we found that sumoylation of HSF2 is involved in regulating HSF2 bookmarking function, but the mechanism that mediates this regulation was unknown. The results in my work support the intriguing hypothesis that polycomb protein, Mel-18, actually functions as an anti-SUMO E3 protein, interacting both with HSF2 and the SUMO E2 Ubc9, but acting to inhibit Ubc9 activity and thereby decrease sumoylation of the HSF2.

This study also suggested that Mel-18 negatively regulates the sumoylation of other cellular proteins, and we extend its targets to RanGAP1 protein. The results …

Translational Regulatory Mechanisms Of The Rat And Human Multidrug Resistance Protein 2, Yuanyuan Zhang

University of Kentucky Doctoral Dissertations

Multidrug resistance protein 2 (MRP2) is the second member the C subfamily in the superfamily of adenosine triphosphate (ATP)-binding cassette (ABC) efflux transporters. MRP2 is a critical player for generation of bile acidindependent bile flow and biliary excretion of glutathione, glucuronate and sulfate conjugates of endo- and xenobiotics. Dysfunctional expression of MRP2 is associated with Dubin-Johnson Syndrome.

Pathological and physiological states or xenobiotics change the MRP2 expression level. Under some conditions, expression of the human MRP2 and rat Mrp2 proteins are regulated at the translation level. There are several transcription initiation sites in MRP2/Mrp2 gene. The 5’ untranslated regions (5’UTRs) …

Zinc Deficiency And Mechanisms Of Endothelial Cell Dysfunction, Huiyun Shen

University of Kentucky Doctoral Dissertations

Atherosclerosis is a chronic inflammatory disease thought to be initiated by endothelial cell dysfunction. Research described in this dissertation is focused on the role of zinc deficiency in endothelial cell activation with an emphasis on the function of the transcription factors nuclear factor-κB (NF-κB), peroxisome proliferator activated receptor (PPAR), and the aryl hydrocarbon receptor (AhR), which all play critical roles in the early pathology of atherosclerosis. Cultured porcine aortic vascular endothelial cells were deprived of zinc by the zinc chelator TPEN and/or treated with the NF-κB inhibitor CAPE or the PPARγ agonist rosiglitazone, followed by measurements of PPARα expression, cellular …

Endothelial Cell Dysfunction By Environmental Contaminants, Elizabeth Grace Oesterling

University of Kentucky Doctoral Dissertations

Within the last few decades, epidemiological evidence has linked exposure to air pollution, both its particles and its organic components, with cardiovascular disease (CVD) progression. CVD is a life long disease with the disruption of the endothelium being the inaugural event in this inflammatory process. The vascular endothelium is extremely susceptible to environmental insults given its tremendous surface area and that it is in constant contact with blood and components circulating within the blood, including xenobiotics. The endothelium is important as a barrier from blood constituents however, dysfunction of this barrier leads to the influx of lymphocytes and granulocytes that …

Nitration And Inactivation Of Manganese Superoxide Dismutase Plays A Critical Role In Metabolic Switch, Muthuswamy Anantharaman

University of Kentucky Doctoral Dissertations

Alzheimer’s disease (AD) is a multifactorial, progressive, age-related neurodegenerative disease. Oxidative stress hypothesis is most prevalent and is gaining significant support. Inspite of the progress achieved on oxidative stress related damages in AD brain; the modification occurring on the various cellular antioxidant enzymes antioxidant has not been identified. Tyrosine nitration, a marker for peroxynitrite induced oxidative damage to protein is widespread in AD brain and Manganese superoxide dismutase (MnSOD), primary mitochondrial antioxidant enzyme is prone to peroxynitrite induced nitration and inactivation. Nitration of proteins involved in energy metabolism has been demonstrated in AD brain, which may explain the altered glucose …

Implications For The Hsf2/Prc1 Interaction And Regulation Of Condensin By Phosphorylation During Mitosis, Lynea Alene Murphy

University of Kentucky Doctoral Dissertations

At the beginning of mitosis, chromosomes are condensed and segregated to facilitate correct alignment later in cytokinesis. Condensin is the pentameric enzyme responsible for this DNA compaction and is composed of two structural maintenance of chromosomes (SMC) subunits and three non-SMC subunits. Condensin mutations generate chromosomal abnormalities due to improper segregation, leading to genome instability and eventual malignant transformation of the cell. Cdc2 phosphorylation of the non-SMC subunits, CAP-G, CAP-D2, and CAP-H, has been demonstrated to be important for condensin supercoiling activity and function. While these subunits are thought to be phosphorylated by Cdc2, the exact sites have not yet …

Reciprocal Regulation Of Par-4 And Caspase-8 In The Trail Signaling Pathway, Padhma Ranganathan

University of Kentucky Doctoral Dissertations

Par‐4 is a pro‐apoptotic tumor suppressor that is mutated, suppressed or inactivated in cancer. Par‐4 exploits components of the extrinsic pathway to cause apoptosis selectively of cancer cells. This study identified Par‐4 as an essential component of the apoptotic pathway induced by TRAIL, which selectively targets cancer cells. RNA interference‐mediated knockdown of Par‐4 rendered cancer cells unresponsive to TRAIL‐induced apoptosis. Cells with knocked‐down levels of Par‐4 were deficient in the activation of the apoptosis‐initiator caspase‐8 and the apoptosis‐effector caspase‐3 in response to TRAIL. Par‐4 was identified as a critical mediator of membrane translocation of caspase‐8 and the adapter protein FADD. …

Mechanism Of Cancer Selective Apoptosis By Par-4, Sushma Gurumurthy

University of Kentucky Doctoral Dissertations

Despite distinct dissimilarities, diverse cancers express several common pro-tumorigenic traits. We present here evidence that the pro-apoptotic protein Par-4 utilizes one such common tumorigenic trait to become selectively activated and induce apoptosis in cancer cells. Elevated PKA activity noted in cancer cells activated the apoptotic function of ectopic Par-4 or its SAC domain, which induces apoptosis selectively in cancer cells and not in normal or immortalized cells. PKA preferentially phosphorylated Par-4 at the T155 residue within the SAC domain in cancer cells. Moreover, pharmacological-, peptide- or siRNA-mediated inhibition of PKA activity in cancer cells resulted in abrogation of both T155 …