Dissertations and Theses
Persistent link for this communityhttps://hdl.handle.net/11299/45272
Dissertations and theses in the University Digital Conservancy comprise the official, approved version of these works. The dissertations and theses in the Digital Conservancy are submitted through the Graduate School in accordance with University standards. Works contributed to the Conservancy serve as a permanent University of Minnesota record of graduate student scholarship. Electronic submission of dissertations to the Digital Conservancy date from 2007. Master's Plan A theses date from 2009.
Online availability of earlier dissertations and theses include a majority of works completed prior to 1923 as well as works made available by individual alumni. Earlier dissertations and theses may be accessed onsite in paper form, or through interlibrary loan, or through the online Digital Dissertations database. Check the University Libraries catalog for holdings information or contact the University of Minnesota Archives for these earlier works. For more information, please see the FAQ on Master's Theses and Dissertations.
Browse
Browsing Dissertations and Theses by Subject "1,3-butadiene"
- Results Per Page
- Sort Options
Item Ethnic differences in the metabolism of 1,3-butadiene and lung cancer risk(2019-01) Boldry, EmilyCigarette smoking remains one of the most preventable causes of death in the world, and is the leading cause of lung cancer. Epidemiological studies show inherent differences in lung cancer risk among smokers of different ethnic groups, with Native Hawaiian and African Americans have the highest risk, European Americans having an intermediate risk, and Latinos and Japanese Americans having the lowest risk. It has been proposed that these disparities in risk are due to ethnic differences in the metabolism, and ultimately bioactivation, of carcinogens in present in cigarette smoke. 1,3-butadiene (BD) is one of the most abundant and potent carcinogens present in cigarette smoke. BD is metabolically activated to the reactive species 3,4-epoxy-1-butene (EB), hydroxymethylvinylketone (HMVK), 3,4-epoxy-1,2-butanediol (EBD), and 1,2,3,4-diepoxybutane (DEB), which have the ability to form pro-mutagenic DNA adducts. These species can be detoxified through glutathione conjugation and excreted in urine; EB and HMVK are excreted as 2-(N-acetyl-L-cystein-S-yl)-1-hydroxybut-3-ene/ 1-(N-acetyl-L-cystein-S-yl)-2-hydroxybut-3-ene (MHBMA) and 4-(N-acetyl-L-cystein-S-yl)-1,2-dihydroxybutane (DHBMA). The research presented in this thesis focuses on ethnic differences in BD metabolism and the initial development of a DEB specific biomarker. A high throughput HPLC-ESI--MS/MS method for the simultaneous quantitation of MHBMA and DHBMA in humans previously developed in our laboratory was applied to quantify these mercapturic acids in smokers of different ethnic groups. In a large multi-ethnic study composed of African American, European American, and Japanese American smokers (N = 1,072). Urinary MHBMA and MHBMA/MHBMA+DHBMA were highest in African Americans, followed by European Americans, and Japanese Americans, and strongly influenced by GSTT1 genotype. A genome wide association study (GWAS) revealed strong associations between MHBMA and GSTT1: associations with 136 SNPs were detected, and all of them were located between 24.2—24.4 Mb near the GSTT1 gene on chromosome 22q11. Additional experiments with recombinant human GSTT1 and GSTT2 confirmed EB as a substrate for the first time. The same method was also applied to a separate smaller study of African American and European American smokers (N = 151). In contrast to the previous work, urinary MHBMA was higher in European Americans than African Americans in this study; this is likely due to decreased sample size. Statistical analyses revealed no correlation between urinary MHBMA or DHBMA and urinary N7-(1-hydroxy-3-buten-2-yl)guanine (EBGII), as well no significant associations between urinary EBGII, MHBMA, or DHBMA and various specific SNPs from BD-metabolizing genes (EPHX1 and CYP2E1) and DNA repair genes (FANCE). GSTT1 copy number was also included in this analysis, and showed a significant association with urinary MHBMA. Urinary MHBMA and DHBMA were also quantified in smokers (N=79) receiving treatment with the chemopreventative agent 2-phenethyl isothiocyanate (PEITC). Overall, PEITC treatment resulted in only slight increases in MHBMA and DHBMA as compared to treatment with a placebo, but was found to significantly increase MHBMA in individuals null for GSTT1 or both GSTT1 and GSTM1, indicating a potential protective effect of PEITC in these individuals. Lastly, an HPLC-ESI+-MS/MS method for the of detection of a novel DEB-specific biomarker, Nε, Nε-(2,3-dihydroxybutan-1,4-diyl)-L-lysine (DHB-Lys) was explored. Initial development focused on the use of an ion-pairing agent, perfluoroheptanoic acid (PFHA), which was chosen to increase HPLC retention of DHB-Lys. Though addition of PFHA to the aqueous mobile phase during HPLC-ESI+-MS/MS analysis did result in increased retention of the analyte, its use also presented additional challenges with analyte carryover, sample contamination, and ion suppression. Methodology utilizing derivatization of DHB-Lys through the addition of a 6-aminoquinolyl group (6-AQ) at the alpha nitrogen was tested on DEB-treated O6-alkylguanine DNA alkyltransferase (AGT), and showed a dose dependent increase in DHB-Lys formed.Item Mass spectrometry-based analysis of urinary metabolites of 1,3-Butadiene (BD) in humans and influence of BD-DNA adducts on DNA replication(2013-10) Kotapati, SrikanthCigarette smoking is a known risk factor for the development of lung cancer: approximately 1 out of 5 heavy smokers will develop the disease. However, there are significant differences in risk of lung cancer among smokers from different ethnic/racial groups. African American and Native Hawaiian smokers are at a higher risk of lung cancer than European American, Japanese American or Latin American smokers. Cigarette smoke has more than 70 known carcinogens. Following metabolic activation to electrophilic species, these carcinogens can form covalent DNA adducts, which are capable of inducing heritable mutations ultimately resulting in lung cancer. It has been hypothesized that the observed ethnic/racial differences in lung cancer risk in smokers are due to different frequencies of specific polymorphisms in drug metabolizing genes, leading to a different degree of carcinogen bioactivation to DNA-reactive intermediates. 1,3-Butadiene (BD) is among the most abundant and potent carcinogens present in cigarette smoke. BD is metabolically activated primarily by CYP2E1 to form 3,4-epoxy-1-butene (EB), hydroxymethyl vinylketone (HMVK), 3,4-epoxy-1,2-butanediol (EBD), and 1,2,3,4-diepoxybutane (DEB). EB, HMVK, EBD, and DEB have been shown to modify DNA bases to form promutagenic adducts. Alternatively, EB, EBD, and DEB can undergo detoxification via epoxide hydrolysis (the main pathway in humans) or glutathione conjugation and further metabolic conversion into urinary mercapturic acids, 1-hydroxy 2-(N-acetylcysteinyl)-3-butene (MHBMA), 1,2-dihydroxy-4-(N-acetyl cysteinyl)-butane (DHBMA), 1,2,3-trihydroxy-4-(N-acetylcysteinyl)-butane (THBMA), and 1,4-bis-(N-acetylcysteinyl)butane-2,3-diol (bis-BDMA), respectively. The research presented in this thesis focuses on revealing any ethnic/racial differences in metabolism of BD in smokers and examining the ability of BD-DNA adducts to cause mutations. In the first part of the thesis, we have identified two novel metabolites of BD which have not been previously detected in vivo: 1,2,3-trihydroxy-4-(N-acetylcysteinyl)-butane (THBMA), and 1,4-bis-(N-acetylcysteinyl)butane-2,3-diol (bis-BDMA). To enable their detection in smokers, sensitive and specific HPLC-ESI--MS/MS methods were developed for both metabolites in human urine. We observed significant amounts of THBMA in samples from smokers, non-smokers and occupationally exposed workers. In contrast, bis-BDMA amounts in urine of smokers and occupationally exposed workers were below the method's limit of detection, although it was found in urine of F344 rats exposed to 62.5 or 200 ppm BD. Additionally we found significant interspecies differences in BD metabolism between laboratory rats and humans. DHBMA accounted for only 47% of BD urinary mercapturic acids in rats while the corresponding percentage in humans is 93%. We further developed a high throughput HPLC-ESI--MS/MS method for the quantification of MHBMA and DHBMA in humans and applied this method to quantify urinary BD-mercapturic acids metabolites in workers from a BD and styrene butadiene rubber (SBR) manufacturing facility and smokers belonging to different ethnic groups in two separate multi-ethnic cohort studies. Workers occupationally exposed to BD excreted significantly more BD-mercapturic acids than administrative workers at the same plant. In a small multi-ethnic study of smokers belonging to European American, Native Hawaiian and Japanese American (N = 200 per group), mean urinary MHBMA and MHBMA/DHBMA+MHBMA metabolic ratio were highest in European American and lowest in Japanese American smokers. Similar results were obtained in the larger study (N = 450 per group) composed of European American and African American smokers. Urine of European American smokers contained higher concentrations of MHBMA than that of African Americans. Genome-wide association study (GWAS) analysis conducted for the larger multi-ethnic group has revealed significant associations between single-nucleotide polymorphisms (SNPs) in chromosome 22 (22564172bp - 22735492 bp, nearby genes GSTT1, GSTT2, DDT and MIF) and urinary BD-mercapturic acid levels in smokers, providing the first evidence for genetic and ethnic/racial differences in metabolism of BD.The second part of my thesis work has focused on evaluating the mutagenic ability of three recently discovered BD-dA lesions: N6-(2-hydroxy-3-buten-1-yl)-adenine (N6-HB-dA), N6,N6-(2,3-dihydroxybutan-1,4-diyl)-2'-deoxyadenosine (N6,N6-DHB-dA), and 1,N6-(2-hydroxy-3-hydroxymethylpropan-1,3-diyl)-2'-deoxyadenosine (1,N6-&gamma-HMHP-dA). In vitro translesion synthesis experiments were performed on synthetic oligonucleotides containing each of the three lesions at a site-specific position by gel electrophoresis and HPLC-MS/MS. We found that human translesion synthesis (TLS) polymerases hPols &eta, &kappa, &iota and human polymerase &beta were able to bypass (S)-N6-HB-dA in an error-free manner because of the conserved Watson-Crick base pairing with dT. However, replication past both (R,R)-N6,N6-DHB-dA and (R,S)-1,N6-&gamma-HMHP-dA lesions by TLS polymerases hPols &eta and &kappa was highly error-prone, resulting in A&rarrT, A&rarrC mutations and frameshift deletions. This is the first study that identifies (R,R)-N6,N6-DHB-dA and (R,S)-1,N6-&gamma-HMHP-dA as BD-DNA adducts potentially responsible for the induction of A*rarrT mutations by BD.