Hepatocellular carcinoma (HCC) is one of the most lethal cancers in Hong Kong and Southeast Asian countries. Cancer progression is often symptomless, making the early diagnosis difficult, thus leading to a high mortality rate. Treatments against HCC were often found to be less effective than other cancers. Systemic chemotherapy, which is widely used in cancer treatments, has a low response rate in HCC. New treatment regimes, such as targeted therapy, have shown partial responses in clinical trials and therefore continuous effort in searching new drug targets is warranted. Granulin-epithelin Precursor (GEP) is a pluripotent growth factor, and has been shown to be overexpressed in HCC and various cancers. Our group has demonstrated that GEP promotes tumor growth, and regulates chemoresistance in HCC. It shares a highly similar expression pattern with one of the members of ATP-binding cassette (ABC) transporter family, ABCF1. Blocking GEP, both in vitro and in vivo, showed inhibition on HCC growth. These suggest that GEP is a potential target for HCC treatment. However, there is still little information on how GEP and ABCF1 is overexpressed in HCC. This project aims to investigate the mechanisms involved. GEP and ABCF1 genes are located on chromosomes 17q and 6p, respectively, which both are frequently amplified in HCC. We used quantitative microsatellite analysis (QuMA) to detect GEP and ABCF1 amplification in HCC samples. Both GEP and ABCF1 showed about 20% of HCC cases having amplification, and their copy numbers correlated to the mRNA expression levels. The copy numbers of GEP were also found to correlate to those of ABCF1 significantly. Clinico-pathological analysis showed that GEP copy numbers correlated with gender, serum AFP levels and HBV status, while ABCF1 did not associate with any of the clinico-pathological features. Fluorescence in situ hybridization (FISH) was performed to validate the results on DNA copy number by QuMA. The cases with highest DNA copy number on GEP and ABCF1, were examined. The average difference between FISH and QuMA results ranged ± 0.3 copies, indicating QuMA and FISH results were corroborated on DNA copy number. Furthermore, the FISH results indicated that there are different degrees of aneuploidy involved in chromosome 6p and 17q in 5 out of 6 cases investigated. These suggest that the copy number variations in GEP and ABCF1 were partly caused by the abnormal number of chromosomes. In summary, we observed that GEP and ABCF1 gene copy numbers were increased in subsets of HCC cases, and the increase correlated to their respective transcript expression levels. Furthermore, these copy number variations partly could be explained by aneuploidy as demonstrated by FISH analysis. The current study may help to understand the complex genomic aberrations in HCC and allow better treatment designs in the future. / published_or_final_version / Surgery / Master / Master of Philosophy

The retinogeniculate synapse, the connection between retinal ganglion cells (RGCs) and thalamic relay neurons, undergoes extensive remodeling and refinement in the first few postnatal weeks. While many studies have focused on this process, little is known about the factors that influence excitatory transmission during this dynamic period. A major goal of my dissertation research was to identify mechanisms that regulate glutamate release and clearance at the developing synapse. First, we investigated the role of glutamate transporters and metabotropic glutamate receptors (mGluRs) in shaping excitatory transmission. Early in development, we found presynaptic group II/III mGluRs are present and are activated by glutamate released from RGCs following optic tract stimulation at natural frequencies. This response was found to diminish with age, but glutamate transporters continued to shape synaptic currents throughout development. The finding that glutamate is able to escape the synaptic cleft and bind extrasynaptic high-affinity mGluRs led us to speculate that glutamate might also diffuse to neighboring synapses and bind ionotropic glutamate receptors opposing quiescent release sites. Excitatory currents recorded from immature, but not mature, retinogeniculate synapses display a prolonged decay timecourse. We found evidence that both asynchronous release of glutamate as well as spillover of glutamate between neighboring synapses contributes to these slowly decaying synaptic currents. Furthermore, we uncovered and characterized a novel, purely spillover-mediated current from immature relay neurons, which strongly supports the presence of glutamate spillover between boutons of different RGCs. The results of my studies indicate that far more RGCs contribute to relay neuron firing than would be predicted by the anatomy alone. Finally, in an ongoing study, we investigated the functional role of the neuronal glutamate transporter GLT-1 at the immature retinogeniculate synapse. While GLT-1 has been found in both neurons and glia, excitatory currents at the retinogeniculate synapse were largely unaffected in mice lacking neuronal GLT-1, suggesting non-neuronal glutamate transporters are responsible for the majority of glutamate removal from the developing synapse. Taken together, these results provide insight into the synaptic environment of the developing retinogeniculate synapse and identify a number of mechanisms that shape excitatory transmission during this period of synaptic maturation and refinement.

Inter-individual variability in drug response is a significant clinical concern and may lead to the development of adverse drug reactions, which are currently a top-ten cause of death in the United States. Recently, the manifestation of disease, which may alter normal physiological function, has gained increased attention for its role as a contributing factor in the development of inter-individual responses to drugs. One such disease, known as nonalcoholic fatty liver disease (NAFLD), is the most common chronic liver disease in Western society and represents a spectrum of clinical morbidities that range from the usually benign simple fatty liver to the more advanced nonalcoholic steatohepatitis (NASH). Prior investigations have identified liver-specific alterations in xenobiotic transporter and metabolizing enzymes in NASH, which lead to the functional disruption of drug disposition. To identify a useful model(s) that is representative of hepatic transporter expression profiles in humans with NASH, gene and protein expression profiles of liver membrane transporters were assayed across several commonly used experimental rodent models of the disease. NASH models that were representative of the human condition developed global, adaptive changes in transporter regulation in the liver, which was not present in models that failed to recapitulate human profiles. Specifically, decreased expression of hepatic uptake transporters was coupled with an induction of efflux transporters, which may serve as a hepatoprotective response by limiting hepatic exposure to potentially harmful substances during times of tissue stress. To link a possible molecular mechanism for these hepatic adaptations in NASH, the role of the oxidative stress-activated transcription factor, Nrf2, was investigated. A functional Nrf2 regulatory element was identified within the eighth intron of the human ABCC3 transporter gene, implicating Nrf2 activation in NASH as a contributor to the coordinated induction of hepatic efflux transporters in the disease. To further clarify the effects of NASH on renal membrane transporter regulation, a thorough analysis of gene and protein expression was conducted with the validated rodent models used previously. Following the manifestation of disease, a global induction of renal efflux was observed, suggesting a compensatory, coordinated response of membrane transporters in the kidney upon disease induction. The functional consequences of liver and kidney xenobiotic transporter dysregulation was shown to disrupt the disposition of the environmental toxicant, arsenic. Specifically, NASH results in increased excretion of arsenic into urine as well as altered hepatic and renal exposure. These findings are associated with hepatic and renal transporter dysregulation and demonstrate for the first time that NASH alters the disposition of environmental toxicants. In summary, these studies contribute novel findings that identify liver and kidney-specific adaptations in disease that may contribute to global alterations in xenobiotic disposition thereby increasing the likelihood of developing adverse drug reactions in patients with NASH.

Studies in this dissertation were conducted to explore the roles of organic cation transporters (OCTs) in the disposition of N-butylpyridinium Chloride (NBuPy-Cl) and structurally related ILs. Following a single i.v. dose to rats, the blood concentration of NBuPy-Cl and 1-butyl-1-methylpyrrolidinium chloride (BmPy-Cl) decreased in a biphasic manner with a clearance of 3.3 and 7 ml/min, respectively. More than 84% of dosed compounds were excreted in the urine. Depending on the vehicle, the dermal absorption of BmPy-Cl and NBuPy-Cl (5 mg/kg, 125 μg/cm²) was 10-35% at 96 h. Following a single oral (50 mg/kg) administration to rats, the maximum blood concentrations of both ILs were reached in less than 90 min in rats. Most of the orally dosed NBuPy-Cl (62-68 %) was excreted in the urine in 72 h. However, more of the dosed BmPy-Cl was eliminated in the feces Its oral bioavailability was only 47%. The elimination differences between BmPy-Cl and NBuPy-Cl were not altered by the size (0.5, 5, or 50 mg/kg) or frequency (1 or 5 administrations) of oral doses. In all urine and blood samples, only parent compounds were detected. Co-administration of NBuPy-Cl and inulin intravenously to rats revealed that the clearance of NBuPy-Cl exceeded the rat glomerular filtration rate, suggesting a renal secretion processing. The in vitro transport studies demonstrated that NBuPy-Cl, BmPy-Cl and 1-butyl-3-methylimidazolium chloride are substrates (Kt, 9~277 μM), as well as inhibitors (IC₅₀: 0.2~7.5 μM), of rOCT1/2 and hOCT2. Their inhibitory effects increased dramatically with increasing the alkyl chain length. The IC₅₀ values were 0.1, 3.8, 14 and 671 μM (hexyl-, butyl-, ethyl-pyridinium and pyridinium chloride) for rOCT2 mediated metformin transport. Similar structurally related inhibitory kinetics were observed for rOCT1 and hOCT2. In vivo co-administration of NBuPy-Cl prolonged the plasma half-life and reduced renal clearance of the diabetic drug, metformin. In summary, BmPy-Cl and NBuPy-Cl are partially absorbed from gastrointestinal tract. The present in blood is eliminated rapidly in the urine as parent, by renal filtration and OCT-mediated secretion. ILs also compete with other substrates of OCTs and have the potential to alter their pharmacokinetic profiles.

Lignin is a key component of plant secondary cell walls, providing strength to the plant and allowing water transport. Lignin is a polymer of monolignols that are synthesized in the cell and transported into the cellulose rich cell wall. The primary goal of this thesis is to understand the mechanism(s) of monolignol deposition during xylogenesis. The currently accepted theory is that monolignols are exported by Golgi-mediated vesicle delivery to the secondary cell wall. When this theory was re-examined using cryofixed developing pine, quantitative autoradiography showed that monolignols did not accumulate in Golgi but were rapidly translocated from cytosol to cell wall. This suggests alternative mechanisms, such as membrane transporters, work in monolignol export. ATP binding cassette (ABC) transporters were chosen because they transport other secondary metabolites and some ABC transporter encoding genes are highly expressed in lignifying cells. Four candidate ABC transporters were selected in Arabidopsis (ABCB11, ABCB14, ABCB15 from the ABCB/MDR subfamily and ABCG33 from the ABCG/PDR subfamily) and shown to have overlapping, high vasculature expression patterns. Mutants with T-DNA insertions in single ABC transporter genes had no change in lignification of inflorescence stems. However, a reduced polar auxin transport phenotype was detected in mutants of ABCB11, ABCB14 and ABCB15. An additional approach was the use of inhibitors of ABC transporters. A new assay, which was developed to quantify lignification in primary xylem of Arabidopsis roots, demonstrated that ABC inhibitors did not change lignin deposition. Monolignols are exported and polymerized in the polysaccharide matrix of the cell wall, which includes hemicelluloses that may organize monolignols during polymerization. Since diverse lignified cell types are enriched in either G- or S-lignin, I hypothesized that this pattern could reflect different hemicellulose distributions, which was examined using antibody labeling of xylans or mannans in hybrid poplar xylem. While xylans were generally distributed in all secondary cell walls, mannans were enriched in fibers but not in the ray and vessel walls. In summary, during secondary cell wall deposition, monolignols are exported by unknown transporter(s) rather than Golgi vesicles. In developing poplar wood, the monolignols are deposited into diverse hemicellulose domains in different cell types.

Protein synthesis is a highly conserved process across all domains of life, both structurally and functionally. This cyclic process is catalyzed by numerous soluble protein factors that interact with the ribosome to facilitate efficient protein synthesis. Many canonical translation factors bind and hydrolyze GTP to induce conformational changes that facilitate translation. For example, GTP hydrolysis by EF-Tu is required for the release of aminoacyl-tRNA into the ribosomal A site; GTP hydrolysis by EF-G facilitates the movement of tRNA and mRNA from the A site to the P site of the ribosome. However, protein synthesis seems to also have a requirement for ATP; the essential yeast protein eEF-3 facilitates release of deacyl-tRNA from the ribosomal E site. In Escherichia coli, the protein product of the open reading frame yhih has been suggested to have a similar function. However, the role of this unique prokaryotic protein is not understood. Preliminary characterization of this protein suggests a nucleotide-dependent conformational change occurs in a truncated form of the protein, ΔP541 Yhih. Interestingly, this phenomenon is not observed in ΔL432 Yhih. Both ΔP541 Yhih, and to a lesser extent ΔL432 Yhih, exhibit a ribosome-dependent ATPase activity, suggesting the primary region for binding with the ribosome lies between Leu432 and Pro541. / x, 101 leaves : ill. ; 29 cm.

Glial-derived lipoparticles facilitate the transport of cholesterol and lipids between cells within the CNS and have been shown to support neuronal growth and synaptogenesis. Partial deafferentation of the hippocampus by unilateral entorhinal cortex lesioning (uECL) induces well-described cytoarchitectural reorganisation and reactive sprouting in the dentate gyrus (DG). Previous studies have demonstrated a dynamic regulation of cholesterol homeostasis in the hippocampus following deafferentation, and suggest that mechanisms facilitating cholesterol transport are important during reinnervation. Furthermore, there is growing evidence that statins, a family of cholesterol-lowering drugs which inhibit the rate-limiting enzyme of cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCoA-R), may confer neuroprotection following trauma. / The ATP binding cassette transporters (ABC) A1 and G1 assist the generation of lipoparticles by mediating cholesterol and phospholipid efflux to extracellular apolipoprotein E (APOE), the brain's primary lipoprotein. To examine a role for these transporters in the regulation of cholesterol efflux during synaptic remodelling, and the effects of low-dose pravastatin (a potent HMGCoA-R inhibitor) on such intercellular transport mechanisms, we measured the expression of ABCA1, ABCG1, APOE, apoE(LDL)R and HMGCoA-R in the hippocampus of saline and pravastatin treated mice over time following uECL. It is shown here that ABCA1 and not ABCG1 is up-regulated at the level of mRNA and protein expression, along with APOE, in the hippocampus during active regeneration (14DPL) as determined by histochemical analysis of acetylcholinesterase staining density in the DG. While pravastatin treatment was observed to differentially influence the expression of ABCA1 mRNA and protein over time, no effects on APOE or ABCG1 mRNA expression were observed following uECL. Additionally, HMGCoA-R mRNA expression was significantly down-regulated at 21 DPL in the deafferented hippocampus in pravastatin-treated animals. While the low-dose pravastatin treatment applied here was sufficient to inhibit HMGCoA-R activity in the liver, enzymatic activity was unaffected in the cortex. / These findings suggest that ABCA1 and not ABCG1 may be important in the APOE-mediated cholesterol recycling observed during the active phase of neural reinnervation in response to uECL. In addition, the results presented here suggest that the administration of clinically-relevant statin therapy may be sufficient to influence the regulation of cerebral cholesterol homeostasis following trauma in the adult mouse brain.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Atherosclerosis is a chronic inflammatory disease leading to plaque buildup in the major arteries. The plaques consist of cholesterol, calcium, inflammatory cells, extracellular matrix and fibrous material. Under inflammatory conditions IFN-• stimulation of human monocytes and macrophages generates reduced pteridine, 7,8-dihydroneopterin (78NP) which has been shown to be an effective cytoprotective agent to some cell types against oxidative damage by reactive oxygen species (ROS). 7,8-dihydroneopterin is oxidized to fluorescent neopterin in the presence of hypochlorite (HOCl). Although a considerable amount of work has been published on the composition of neopterin in atherosclerotic plaques, very little is known about the variation of 78NP and other oxidative biomarkers across the length of the carotid and femoral and their contribution to plaque progression, which was researched in this work. Atherosclerotic plaques excised from patients with carotid and femoral plaques were sliced into 3-5 mm sections, and each section was analyzed for concentrations of neopterin, 7,8- dihydroneopterin, •-tocopherol, TBARS, DOPA, cholesterol, dityrosine, protein carbonyls •- aminoadipic semialdehyde (AAS) and •-glutamic semialdehyde (GGS), free and esterified 7- ketocholesterol (7-KC). Cultured live plaque as a source of 7,8-dihydroneopterin and neopterin was also investigated in this study. It was shown that carotid plaques significantly vary from femoral plaques, in the levels and range of most oxidative biomarkers. Carotid plaques showed a high variation in the biomarker concentrations between plaques but also between sections of an individual plaque. Femoral plaques on the other hand showed lower amounts of biomarkers with very little variation in biomarker concentrations. High variation with pterin concentrations and other biomarkers suggests dynamic and active changes in inflammation within the plaque. Collectively, it was observed that every plaque was unique with respect to its composition and correlations between the biomarkers. Though shown to be a well-known antioxidant and a radical scavenger, there is no published literature on 7,8-dihydroneopterin’s mode of entry into and out of the cell. To understand how it enters the cells could explain the difference in its protective ability of different cell types Abstract xxviii against oxidative stress-mediated cell death. Knowledge of transport of 7,8-dihydroneopterin will provide insights about its protection of monocyte/macrophage cell death which could potentially reduce atherosclerotic plaque growth and progression. As 7,8-dihydroneopterin is produced from guanosine, a nucleoside that is transported using specialized nucleoside transporters (equilibrative nucleoside transporters (ENT's) and concentrative nucleoside transporters (CNT's), their role was examined and characterized for 7,8-dihydroneopterin transport. It was found that 7,8-dihydroneopterin and neopterin are transported via nucleoside transporters in U937 cells, THP-1 cells and human monocytes. ENT 2 was the major transporter in U937 cells while ENT 1 transported bulk of 7,8-dihydroneopterin in THP-1 cells. Both ENT's and CNT's are involved in 7,8-dihydroneopterin uptake in human monocytes. In all the cell lines tested, 7,8-dihydroneopterin protection against AAPH mediated oxidative cell death was inhibited by nucleoside transport inhibitors, suggesting that nucleoside transporters are indispensible for 7,8-dihydroneopterin mediated intracellular protection against oxidative stress. Accurate measurement of neopterin, as a biomarker of inflammation in plaques and cells is critical aspect to assess disease progression. The current C18 HPLC method used in our laboratory for neopterin measurement lacks sensitivity due to interference of acetonitrile (ACN) over time. Acidic tri-iodide conversion of 7,8-dihydroneopterin to neopterin was also variable at times giving inconsistent measurement of neopterin so the manganese oxide (MnO2) method was looked at as an alternative. Electrochemical detector (ECD) was another option studied as it did not require any precolumn oxidation of 7,8-dihydroneopterin to neopterin. A new method using strong cation exchange (SCX) column was developed for a precise, sensitive neopterin assay which got rid of the ACN interference completely. The MnO2 method of 7,8-dihydroneopterin oxidation did not work with biological samples such as serum or plaque homogenates. Electrochemical detection was also found to be very unreliable and inconsistent.

ATP-binding cassette transporters ABCA1 and ABCG1 initiate reverse cholesterol transport generating HDL particles, whereas ABCG5/G8 promote biliary cholesterol secretion thereby facilitating the last step of reverse cholesterol transport. Mutations in the leptin axis result in obesity and dyslipidemia in ob/ob and db/db mice. These mice have defective HDL clearance, increased plasma cholesterol and decreased biliary cholesterol elimination. My studies demonstrate that ABCG5/G8 protein is low in these animals and can be restored with caloric restriction or leptin replacement. To directly test whether ABCG5/G8 alone is able to correct reverse cholesterol transport defect, liver specific ABCG5/G8 expression was achieved in db/db mice by administration of adenoviral ABCG5 and ABCG8. Restoration of biliary cholesterol is able partially to correct dyslipidemia in obese mice, but only in the presence of ezetimibe, an inhibitor of cholesterol absorption. ABCG5/G8 is the body’s primary defense against toxic effects of plant sterols. Plant sterols are used as cholesterol lowering food supplements. However, increased plasma plant sterol concentrations are associated with vascular lesions in dyslipidemic patients and animals. My in vitro studies demonstrate that individual plant sterol alter ABCA1 and ABCG1 abundance, cholesterol efflux and inflammatory cytokine secretion in macrophage foam cells at levels found in humans that consume plant sterol supplements.