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. The differential susceptibility to PN in two radioresistant cancer cells, DU145 and PC3, is due, in part, to the fact that in addition to NF-κB inhibition, PN activates the PI3K/Akt pro-survival pathway in both cell lines. The presence of PTEN in DU145 cells enhances the radiosensitization effect of PN by suppression of the steady state level of activated p-Akt. We also demonstrate that PN selectively exhibits a radiosensitization effect on prostate cancer PC3 cells but not on normal prostate epithelial PrEC cells. PN causes oxidative stress in PC3 cells but not in PrEC cells, as determined by the oxidation of the ROS-sensitive probe H2DCFDA and intracellular reduced thiol and disulfide levels. In PC3 but not PrEC cells, PN activates NADPH oxidase leading to a decrease in the level of reduced thioredoxin, activation of PI3K/Akt and consequent FOXO3a phosphorylation, which results in the downregulation of FOXO3a targets, antioxidant enzyme MnSOD and catalase. Importantly, when combined with radiation, PN further increases ROS levels in PC3 cells, while it decreases radiation-induced oxidative stress in PrEC cells, possibly by increasing GSH level. Overall, our data support the concept that increasing oxidative stress in cancer cells, which are already under high constitutive oxidative stress, will lead to cell death, while the same stress may allow normal cells to maintain redox homeostasis through adaptive response. Thus, modulating cell redox status may be a novel approach to efficiently and selectively kill cancer cells.

<p>The Ras family of small GTPases, comprised of the KRAS, NRAS, and HRAS genes, are mutated to encode constitutively-active, GTP-bound, oncogenic proteins in upwards of one quarter or more of all human cancers, which is well established to promote tumorigenesis. Despite the prominent role these genes play in human cancer, the encoded proteins have proven difficult to pharmacologically inhibit. Therefore, it is important to understand how Ras proteins are activated. </p><p>RAS proteins cycle between a GDP-bound inactive state and a GTP-bound active state through guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). GEFs facilitate the GDP-to-GTP exchange of RAS and promote RAS activation. Similar to GEFs, reactive oxygen/nitrogen species can also promote RAS activation through reactions with the thiol residue of cysteine 118 (C118). This residue may therefore play a role in RAS activation in cancer. To test this possibility, I investigated the effect of mutating C118 to serine (C118S) in Kras on (1) carcinogen-induced lung tumorigenesis, and (2) xenograft tumor growth of HRAS12V-transformed cells.</p><p>To explore the impact of the C118S mutation in Kras on carcinogen-induced lung tumorigenesis, I introduced a C118S mutation into the endogenous murine Kras allele and exposed the resultant mice to the carcinogen urethane, which induces Kras mutation-positive lung tumors. Kras+/C118S and KrasC118S/C118S mice developed fewer and smaller lung tumors than Kras+/+ mice. Although the KrasC118S allele did not appear to affect tumorigenesis when the remaining Kras allele was conditionally oncogenic (KrasG12D), there was a moderate imbalance of oncogenic mutations favoring the native Kras allele in tumors from Kras+/C118S mice treated with urethane. Therefore, mutating C118 of Kras impedes urethane-induced lung tumorigenesis.</p><p>To explore the the impact of the C118S mutation in Kras on xenograft tumor growth of HRAS12V-transformed cells, I tested and found that redox-dependent reactions with cysteine 118 (C118) and activation of wild type KRAS are critical for oncogenic HRAS-driven tumorigenesis. Such redox-dependent activation of KRAS affected both PI3K-AKT and RAF-MEK-ERK pathways. These findings were confirmed in the endogenous mouse Kras gene. Speicfically, oncogenic HRAS-transformed KrasC118S/C118S MEFs grew in soft agar and as xenograft tumors more slowly than similarly transformed Kras+/+ MEFs, suggesting that redox-dependent reactions with C118 of Kras promotes transformation and tumorigenesis. </p><p>Taken together, I have demonstrated a critical role of redox-dependent reactions with Kras C118 in tumorigenesis.</p> / Dissertation

No description available.

Nuclear Factor kappaB (NF-êB) is a transcription factor whose activation is increased in settings of allergic asthma. At least two parallel NF-êB pathways exist: the classical pathway, which plays a role in inflammation and cell survival, and the alternative pathway, which regulates lymphoid cell development and organogenesis. The classical NF-êB pathway regulates inflammatory responses derived from lung epithelial cells; however, the role of the alternative pathway in lung epithelial cells remains unclear. We demonstrate that both classical and alternative NF-êB are activated in lung epithelial cells in response to multiple pro-inflammatory agonists, and siRNA-mediated knockdown of alternative NF-êB proteins largely attenuates pro-inflammatory cytokine production. Furthermore, simultaneous activation of both pathways leads to cooperative increases in pro-inflammatory responses, indicating a potential role for both classical and alternative NF-êB in the regulation of epithelial-derived pro-inflammatory responses. NF-êB activation in the epithelium modulates allergic inflammation in mouse models of allergic airway disease, however, its role in the context of an allergen relevant to human asthma remains unknown. In order to address the impact of inhibition of NF-êB in the epithelium in vivo, we utilized a House Dust Mite (HDM)-induced model of allergic airway disease. We demonstrate that HDM exposure activates classical and alternative NF-êB in both murine lung epithelium and human bronchial epithelial cells. Furthermore, following exposure to HDM, airway hyperresponsiveness, neutrophilic inflammation, and remodeling are attenuated in transgenic CC10-NF-êBSR (airway epithelial specific inhibitor of classical and alternative NF-êB) mice in comparison to wild type mice. Our data also demonstrate that specific knockdown of the alternative NF-êB protein, RelB, in the lung partially protects against HDM-induced pro-inflammatory responses, indicating that both classical and alternative NF-êB are important in HDM-induced responses. NF-êB proteins are modified by the redox-dependent post-translational modification, S-glutathionylation, under conditions of oxidative stress. S-glutathionylation of IKKâ, an upstream kinase in the NF-êB pathway, is known to decrease its catalytic activity; however, it is unknown how S-glutathionylation of IKKâ occurs. GSTP is an enzyme that catalyzes protein S-glutathionylation under conditions of oxidative stress and has been associated with the development of allergic asthma. We aimed to determine whether GSTP regulates NF-êB signaling, S-glutathionylation of IKKâ, and pro-inflammatory cytokine production. We demonstrate that siRNA-mediated knockdown of GSTP modulates NF-êB activation, NF-êB transcriptional activity, and pro-inflammatory cytokine production in response to LPS, a component of a bacterial cell wall. Furthermore, we demonstrate that GSTP associates with IKKâ in response to agonist stimulation and dampens IKKâ-induced pro-inflammatory cytokine production, surprisingly, independent of its catalytic activity. We also show that GSTP associates with other proteins of the NF-êB pathway, indicating a potential dual mechanism for repression of NF-êB-induced signaling. These studies collectively demonstrate that classical and alternative NF-êB contribute to epithelial-derived inflammatory responses, and GSTP may be a novel target by which NF-êB can be regulated.

Although it is known that the regenerative function of neural stem/progenitor cells (NSPCs) declines with age, causal mechanisms underlying this phenomenon are not understood. Here, we systematically analyze subventricular zone (SVZ) NSPCs, in various groups of rats across the aging spectrum, using in vitro and in vivo histological and behavioral techniques. These studies indicate that although NSPC function continuously declines with advancing age, there is a critical time period during middle age (13-15 months) when a striking reduction in NSPC survival and regeneration (proliferation and neuronal differentiation) occurs. The studies also indicate that this specific temporal pattern of NSPC deterioration is functionally relevant at a behavioral level and correlates with the decreasing expression of the redox-sensitive transcription factor, Nrf2, in the NSPCs. When Nrf2 expression was suppressed in 'young' NSPCs, using short interfering RNAs, the survival and regeneration of the NSPCs was significantly compromised and mirrored 'old' NSPCs. Conversely, Nrf2 overexpression in 'old' NSPCs rendered them similar to 'young' NSPCs, and they showed increased survival and regeneration. Furthermore, examination of newborn Nrf2 knockout (Nrf2-/-) mice revealed a lower number of SVZ NSPCs in these animals, when compared to wild-type controls. In addition, the proliferative and neurogenic potential of the NSPCs was also compromised in the Nrf2-/- mice. These results identify a novel regulatory role for Nrf2 in NSPC function during aging and have important implications for developing NSPC-based strategies to support healthy aging and to treat age-related neurodegenerative disorders.

Thesis advisor: Jeffery A. Byers / Chapter 1. Poly(lactic acid) (PLA) is a biodegradable polymer derived from renewable resources that has garnered much interest in recent years as an environmentally friendly substitute to conventional petroleum-derived engineering polymers. PLA has many applications in textiles, packaging, compostable consumables, and biomedical devices, as PLA displays excellent biocompatibility. This polymer is primarily produced from the ring-opening polymerization of lactide, a cyclic dimer of lactic acid. This introductory chapter highlights mechanistic features of this ring-opening polymerization reaction as well as metal-based catalysts that have been reported for lactide polymerization. In addition, switchable catalysis is an emerging field that has gained interest with polymer chemists for the potential of creating original polymer compositions and architectures. The utilization of redox-switchable catalysis to control lactide polymerization is discussed in this chapter. Chapter 2. Bis(imino)pyridine iron bis(alkoxide) complexes have been synthesized and utilized in the polymerization of (rac)-lactide. The activities of the catalysts were particularly sensitive to the identity of the initiating alkoxide with more electron-donating alkoxides resulting in faster polymerization rates. The reaction displayed characteristics of a living polymerization with production of polymers that exhibited low molecular weight distributions, linear relationships between molecular weight and conversion, and polymer growth observed for up to fifteen sequential additions of lactide monomer to the polymerization reaction. Mechanistic experiments revealed that iron bis(aryloxide) catalysts initiate polymerization with one alkoxide ligand, while iron bis(alkylalkoxide) catalysts initiate polymerization with both alkoxide ligands. Oxidation of an iron(II) catalyst precursor lead to a cationic iron(III) bis(alkoxide) complex that was completely inactive towards lactide polymerization. When redox reactions were carried out during lactide polymerization, catalysis could be switched off and turned back on upon oxidation and reduction of the iron catalyst, respectively. In addition, preliminary investigations of copolymerization reactions of lactide with ethylene are reported. Chapter 3. A cationic iron(III) complex is active for the polymerization of various epoxides, whereas the analogous neutral iron(II) complex is inactive. Cyclohexene oxide polymerization could be "switched off" upon in situ reduction of the Fe(III) complex and “switched on” upon in situ oxidation, which is orthogonal to what was observed previously for lactide polymerization. Conducting copolymerization reactions in the presence of both monomers resulted in block copolymers whose identity can be controlled by the oxidation state of the complex: selective lactide polymerization was observed in the iron(II) oxidation state and selective epoxide polymerization was observed in the iron(III) oxidation state. Evidence for the formation of block copolymers was obtained from solubility differences, GPC, and DOSY-NMR studies.  Chapter 4. Formally iron(I) bis(imino)pyridine monoalkoxide complexes were synthesized through protonolysis of a bis(imino)pyridine iron alkyl species with p-methoxyphenol or neopentyl alcohol. The resulting complexes were characterized by X-ray crystallography, 1H NMR, EPR, and Mössbauer spectroscopy, and preliminary characterization of the electronic structure of these complexes is discussed. These iron complexes were found to be highly active catalysts for the polymerization of various cyclic esters and carbonates, with the iron mono(neopentoxide) complex being much more active and giving more narrow molecular weight distributions than the mono(aryloxide) complex. The bis(imino)pyridine iron neopentoxide complex was highly active in particular for the polymerization of ε-caprolactone (CL), giving full conversion within 10 minutes at room temperature in toluene, making it one of the most active iron complexes reported for this transformation ([Fe]:[CL] = 1:2000). Comparison of the polymerization activity of these iron mono(alkoxide) complexes with the analogous iron(II) bis(alkoxide) complexes is reported. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Ethan F. Baxter / Subduction zones are the primary areas of chemical and mass transfer between the Earth’s surface and the mantle. Dehydration during subduction has been linked to subduction seismicity, arc volcanism, and redox (fO2) changes in the subducting slab and overlying mantle wedge. Despite this, no petrologic record tracing the source of oxidizing fluids from the down going slab has yet been observed. To address this, this study shows a direct record of progressive redox change recorded in zoned garnet crystals from Sifnos and Syros, Greece that grew through the breakdown of the hydrous mineral lawsonite during subduction. Oxygen fugacities (fO2) calculated using garnet-epidote oxybarometry for multiple growth zones within single garnet grains have been compared with stable iron isotope compositions in the same growth zone. These combined measurements reveal that garnet cores grew under oxidized conditions, recording higher fO2 and lower 56Fe values, whereas garnet rims grew under more reduced conditions with lower fO2 and higher 56Fe values. This is consistent with the release of oxidizing fluids into the sub-arc mantle accompanying lawsonite breakdown and dehydration, leaving behind a progressively reduced residual slab mineral assemblage. These coupled fO2 and Fe isotope data show that slab dehydration accompanying lawsonite breakdown plays an important and measureable role in the global redox budget, and provides a mechanism for sub-arc mantle oxidation. / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

The current option for the management of Intermediate-Level Waste (ILW) and High-Level Waste (HLW) in the UK is to store it in stainless steel containers and then placed in a deep underground Geological Disposal Facility (GDF). This may subsequently be backfilled with a cementitious material generating very high pH conditions. The eventual corrosion of the stainless steel canisters containing the waste used for disposal will lead to reducing conditions thereby promoting a low Eh environment. Electrochemical experiments are needed to determine which uranium species is/are present at a particular pH and to model the redox behaviour of aqueous uranium in a potential GDF. The main aim of this project is to use cyclic voltammetry to deduce peak potentials for the various uranium redox couples in aqueous solution across the pH range and in particular the hyperalkaline range, as the surroundings of a GDF will be in high pH conditions. Data in the literature have been obtained only under acidic conditions where they were subsequently extrapolated to obtain data for alkaline conditions in some reports. Is this valid however? Experiments are therefore needed to obtain fundamental data under alkaline conditions to fill in gaps in the literature. In addition to radionuclides, complexing organic ligands present in a cementitious repository could have an important effect on the immobilisation of radionuclides in concrete. This is due to the ability of the ligands to form complexes with cations, thereby enhancing their solubility and mobility in the cement pore water. Four different ligands were investigated in this project that are relevant to nuclear waste disposal which comprised of carbonate, ethylenediaminetetraacetic acid (EDTA), gluconic acid and α-isosaccharinic acid (α-ISA). The peak potentials of each uranium redox reaction in aqueous solution were measured and the potentials were compared in ligand and non-ligand systems. The voltammograms were compared to obtain their similarities and differences in terms of the shape of the cyclic voltammograms, peak potentials, reversibility, current responses and etc. Analysis of the similarities and differences was needed to be able to increase the understanding of the complexation effects of these ligands with uranium under different pH conditions in aqueous solution.

"In situ polymerizing hydrogel systems play an important role in many tissue engineering applications. They have proven to be useful in biomedical applications that require conversion of liquid macromer solution to tissue compliant hydrogel under physiological conditions. A series of poly(ethylene glycol)-co-poly(lactate) diacrylate macromers were synthesized with variable PEG molecular weight and lactate content. The macromer compositions were confirmed by NMR spectroscopy and ion chromatography. These macromers were polymerized to form hydrogels by free radical polymerization using either redox or photochemical initiators. The current study focused on the optimization of polymerization conditions. Compressive modulus and residual acrylate analysis were used to evaluate polymerization efficiency. To characterize the network structure, the swelling ratio values were converted to the average molecular weight between crosslinks ( ) and mesh sizes (ξ) using Flory-Rehner theory. Current study suggested hydrophobic modification is desired to achieve high polymerization efficiency. Electrospinning is a developing technique to produce ultra fine fibrous structures from polymer solutions. Current research efforts have focused on understanding the effects of principal parameters such as molecular weight distribution (MWD) and polymer surfactant interactions on the morphology of the electrospun patterns. Fundamental understanding of the dilute solution rheology of the polydisperse polymer/solvent and polymer/solvent/surfactant systems was first established. Using viscometry, the on-set of entanglement concentrations could be obtained for various systems. Electrospinning was then carried out to evaluate the effects of polymer molecular weight, molecular weight distribution (MWD) and the polymer-surfactant interaction on the fiber formation and morphological features. The importance of increased chain entanglements due to high molecular weight component within the polydisperse system and the expansion of the coil dimension by binding the surfactant micelles have been recognized. The critical concentrations for incipient as well as stable fiber formation were determined. "

OBJECTIVES: Recent studies have elucidated that diabetes mellitus (DM) patients exhibit an accelerated tumor progression, but the mechanism of its regulation is not yet fully understood. The following study seeks to examine the role of angiogenic factors in the growth of subcutaneously injected melanoma cancer using a diet-induced type II diabetic mouse model. METHODS: C57BL/6 mice were fed either a regular or high-fat, high-sucrose (HFHS) diet for 2 months (T2DM model; confirmed through a GTT) and subcutaneously injected with B16F0 melanoma cells. After a 1-week or 2-week incubation period, the tumor was extracted to examine its size, weight, vascularity, and gene/protein expression. In vitro studies were performed using endothelial cells to assess the effects of high-glucose on endothelial cell proliferation, migration, and tube formation. GLRX expression was examined in both tumor samples and endothelial cells. RESULTS: The results of the study showed that T2DM induced by a HFHS diet is able to promote tumor growth in both weight (2-week, p = 0.0070) and volume (1-week, p = 0.0351; 2-week, p = 0.0002). Tumors extracted from the HFHS diet group showed reduced expressions of angiogenic markers (ACTA2 (1-week, p = 0.0239; 2-week, p = 0.0123), KDR (1-week, p = 0.0091)) by western blot and a slightly reduced trend of angiogenesis (PECAM1) in histological analyses. GLRX expression was reduced in HFHS tumor samples (1-week, p = 0.0090) and, interestingly, lower amounts of GSH adducts (2-week, p = 0.0317) could be seen in 2-week tumors as well. In vitro studies of endothelial cells showed reduced trends of endothelial cell function (proliferation, migration, and tube formation) in high glucose medium. Also, it has been observed that high glucose may be able to stimulate GLRX expression in endothelial cells. CONCLUSION: The results of the following study have confirmed that B16F0 melanoma growth is, in fact, augmented in diet-induced diabetic mice; however, the vascularity and levels of angiogenic markers from the tumor tissues did not parallel the growth in its size. In vitro studies suggested that high glucose can impair EC function (i.e. proliferation, migration, and tube formation capabilities) as well as promote GLRX expression, which may be related to this discrepancy. Glutaredoxin-1 (GLRX), an enzyme which controls redox signaling, is upregulated in DM. Endothelial cell-specific GLRX overexpression in transgenic mice was found to stimulate subcutaneously injected melanoma (B16F0) growth, despite hindering limb revascularization after hind limb ischemia. The augmented tumor progression in DM may be associated with GLRX upregulation, alongside impaired ischemic limb revascularization and tumor angiogenesis; however, the mechanism of tumor growth in diabetes still lies inconclusive and further studies need to be examined to elucidate this phenomenon.