Publications by authors named "Joseph H Ashmore"

8 Publications

  • Page 1 of 1

Nicotine-'-Oxidation by Flavin Monooxygenase Enzymes.

Cancer Epidemiol Biomarkers Prev 2019 02 31;28(2):311-320. Epub 2018 Oct 31.

Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington.

Background: The major mode of metabolism of nicotine is by hydroxylation via cytochrome P450 (CYP) 2A6, but it can also undergo glucuronidation by UDP-glucuronosyltransferases and oxidation by flavin monooxygenases (FMO). The goal of this study was to examine the potential importance of FMOs in nicotine metabolism and assess the potential impact of missense polymorphisms in active FMOs on nicotine-'-oxide (NOX) formation.

Methods: Urine samples from 106 current Chinese smokers were analyzed for nicotine metabolites by mass spectrometry. Wild-type s 1-5 and their most prevalent nonsynonymous variants were cloned and overexpressed in HEK293 cells, and were tested in oxidation reactions against nicotine.

Results: A strong inverse correlation was observed between the ratio of urinary 3'-hydroxycotinine/cotinine, a measure of CYP2A6 activity, and the urinary levels of NOX alone ( = -0.383; < 0.001) or NOX measured as a ratio of total nicotine metabolites ( = -0.414; < 0.001) in smokers. In addition to FMO1 and FMO3, the functional FMO2 isoform was active against nicotine, whereas FMO4 and FMO5 exhibited low activity against nicotine ( > 5.0 mmol/L). Significant ( < 0.05) decreases in '-oxidation activity (/) were observed for the FMO1, FMO3, FMO3, FMO3, and FMO3 variants when compared with their respective wild-type isoforms; the truncated FMO2 isoform exhibited no enzyme activity.

Conclusions: These data indicate that increases in nicotine-'-oxidation occur in subjects with deficient CYP2A6 activity, and that several FMO enzymes are active in nicotine-'-oxidation.

Impact: Several common missense FMO variants are associated with altered enzyme activity against nicotine and may play an important role in nicotine metabolism in low-CYP2A6 activity subjects.
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February 2019

Carbonyl reduction of NNK by recombinant human lung enzymes: identification of HSD17β12 as the reductase important in (R)-NNAL formation in human lung.

Carcinogenesis 2018 07;39(8):1079-1088

Department of Pharmaceutical Sciences, Washington State University, Spokane, WA, USA.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is the most abundant and carcinogenic tobacco-specific nitrosamine in tobacco and tobacco smoke. The major metabolic pathway for NNK is carbonyl reduction to form the (R) and (S) enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) which, like NNK, is a potent lung carcinogen. The goal of this study was to characterize NNAL enantiomer formation in human lung and identify the enzymes responsible for this activity. While (S)-NNAL was the major enantiomer of NNAL formed in incubations with NNK in lung cytosolic fractions, (R)-NNAL comprised ~60 and ~95% of the total NNAL formed in lung whole cell lysates and microsomes, respectively. In studies examining the role of individual recombinant cytosolic reductase enzymes in lung NNAL enantiomer formation, AKR1C1, AKR1C2, AKR1C3, AKR1C4 and CBR1 all exhibited (S)-NNAL-formation activity. To identify the microsomal enzymes responsible for (R)-NNAL formation, 28 microsomal reductase enzymes were screened for expression by real-time PCR in normal human lung. HSD17β6, HSD17β12, KDSR, NSDHL, RDH10, RDH11 and SDR16C5 were all expressed at levels ≥HSD11β1, the only previously reported microsomal reductase enzyme with NNK-reducing activity, with HSD17β12 the most highly expressed. Of these lung-expressing enzymes, only HSD17β12 exhibited activity against NNK, forming primarily (>95%) (R)-NNAL, a pattern consistent with that observed in lung microsomes. siRNA knock-down of HSD17β12 resulted in significant decreases in (R)-NNAL-formation activity in HEK293 cells. These data suggest that both cytosolic and microsomal enzymes are active against NNK and that HSD17β12 is the major active microsomal reductase that contributes to (R)-NNAL formation in human lung.
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July 2018

Association Studies of HFE C282Y and H63D Variants with Oral Cancer Risk and Iron Homeostasis Among Whites and Blacks.

Cancers (Basel) 2015 Dec 9;7(4):2386-96. Epub 2015 Dec 9.

Department of Public Health Sciences, Penn State University College of Medicine, 500 University Drive, CH69, Hershey, PA 17033, USA.

Background: Polymorphisms in the hemochromatosis (HFE) gene are associated with excessive iron absorption from the diet, and pro-oxidant effects of iron accumulation are thought to be a risk factor for several types of cancer.

Methods: The C282Y (rs1800562) and H63D (rs1799945) polymorphisms were genotyped in 301 oral cancer cases and 437 controls and analyzed in relation to oral cancer risk, and serum iron biomarker levels from a subset of 130 subjects.

Results: Individuals with the C282Y allele had lower total iron binding capacity (TIBC) (321.2 ± 37.2 µg/dL vs. 397.7 ± 89.0 µg/dL, p = 0.007) and higher percent transferrin saturation (22.0 ± 8.7 vs. 35.6 ± 22.9, p = 0.023) than wild type individuals. Iron and ferritin levels approached significantly higher levels for the C282Y allele (p = 0.0632 and p = 0.0588, respectively).

Conclusions: Iron biomarker levels were elevated by the C282Y allele, but neither (rs1800562) nor (rs1799945) was associated with oral cancer risk in blacks and whites.
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December 2015

No Association Between Vitamin D Intake, VDR Polymorphisms, and Colorectal Cancer in a Population-Based Case-Control Study.

Cancer Epidemiol Biomarkers Prev 2015 Oct 29;24(10):1635-7. Epub 2015 Jul 29.

Department of Pharmaceutical Sciences, Washington State University, Spokane, Washington.

Background: Epidemiologic evidence indicates that greater intakes of vitamin D may decrease the risk of colorectal cancer. Variants in the vitamin D receptor (VDR) gene have the potential to modify associations between vitamin D intake and colorectal cancer.

Methods: Associations between intakes of vitamin D and colorectal cancer were studied in a large case-control study conducted in central and northeastern Pennsylvania including 1,012 cases with histologically confirmed colorectal cancer and 1,080 population-based controls. Associations between 35 tagSNPs encompassing the VDR gene and risk for colorectal cancer as well as gene-diet associations were also assessed among a subset of the population (770 controls, 710 cases).

Results: No significant trends were observed between vitamin D intake and colorectal cancer risk. After adjustment for multiple comparisons, none of the SNPs or haplotypes within the VDR gene were associated with colorectal cancer. There were also no interactions between dietary factors and variants in the entire VDR gene.

Conclusions: Overall, results from this study suggest that vitamin D intake and variants in the VDR gene have little effect on risk for colorectal cancer.

Impact: Increasing vitamin D intake from the diet may not result in decreasing the incidence of colorectal cancer.
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October 2015

Dietary Iron and Colorectal Cancer Risk: A Review of Human Population Studies.

Crit Rev Food Sci Nutr 2016 ;56(6):1012-20

e Department of Epidemiology , Rollins School of Public Health and Winship Cancer Institute, Emory University , Atlanta , Georgia , USA.

Iron is an essential micronutrient that is involved in many redox processes and serves as an integral component in various physiological functions. However, excess iron can cause tissue damage through its pro-oxidative effects, potentiating the development of many diseases such as cancer through the generation of reactive oxidative species. The two major forms of iron in the diet are heme and nonheme iron, both of which are found in several different foods. In addition to natural food sources, intake of nonheme iron may also come from fortified foods or in supplement form. This review summarizes the results of human population studies that have examined the role of dietary iron (heme and nonheme), heme iron alone, and iron from supplements in colorectal carcinogenesis.
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January 2017

Association of dietary and supplemental folate intake and polymorphisms in three FOCM pathway genes with colorectal cancer in a population-based case-control study.

Genes Chromosomes Cancer 2013 Oct 26;52(10):945-53. Epub 2013 Jul 26.

Department of Nutritional Sciences, Pennsylvania State University, College of Health and Human Development, State College, PA, USA.

Previous research has shown that greater intakes of dietary folate are associated with reduced risk for colorectal cancer (CRC) and that single nucleotide polymorphisms (SNPs) in genes involved in folate-mediated one-carbon metabolism (FOCM) also may be involved in altering CRC risk. The objective of this study was to evaluate the role of folate intake (and intakes of related dietary components such as methionine), 35 SNPs in three FOCM pathway genes (MTHFD1, MTHFR, and TYMS), and their interactions on CRC risk in a population-based case-control study in Pennsylvania (686 cases, 740 controls). Diet and supplement use was assessed for the year before diagnosis or interview for cases and controls, respectively, with a modified Diet History Questionnaire from the National Cancer Institute. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using unconditional logistic regression. Using a dominant model for the variant allele, several SNPs were significantly associated with CRC including MTHFD1 rs8003379 (OR = 1.65; 95% CI = 1.00-2.73) and rs17824591 (OR = 1.98; 95% CI = 1.14-3.41) and the TYMS rs2853533 SNP (OR = 1.38; 95% CI = 1.05-1.80). Using a nondominant model, the AA genotype for MTHFR rs1476413 exhibited a marginally significant (OR = 1.56; 95% CI = 1.00-2.44) association with CRC. Two TYMS SNPs (rs16948305 and rs495139) exhibited significant (P = 0.024 and P = 0.040, respectively) gene-diet interactions with folate intake. One MTHFD1 (P = 0.019) and one MTHFR (P = 0.042) SNP exhibited gene-diet interactions with methionine intake. These findings suggest that allelic variants in genes involved in FOCM interact with dietary factors including folate and methionine to modify risk for CRC.
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October 2013

Association of dietary and supplemental iron and colorectal cancer in a population-based study.

Eur J Cancer Prev 2013 Nov;22(6):506-11

aDepartment of Nutritional Sciences, Pennsylvania State University, University Park bNortheast Regional Cancer Institute, Scranton Departments of cPublic Health Sciences dPharmacology, Pennsylvania State College of Medicine, Hershey eDepartment of Medicine, Lehigh Valley Hospital, Allentown, Pennsylvania fDepartment of Health Sciences, Exponent Inc., Chicago, Illinois gDepartment of Health and Human Services, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.

We evaluated the role of dietary iron, heme iron, and supplemental iron on colorectal cancer (CRC) risk in a population-based case-control study in Pennsylvania, including 1005 incident cases and 1062 controls. Diet was assessed through a modified food frequency questionnaire that included supplement use and a meat-specific module. Cases reported intakes for the year before diagnosis, whereas controls reported intakes for the year before interview. Heme iron intake was calculated using a new heme database developed by the US National Cancer Institute. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression. After multivariate adjustment, there were no significant associations between heme iron or total iron intake and CRC incidence. Dietary iron intake was inversely associated with CRC among women (OR Q5 vs. Q1=0.45; 95% CI=0.22-0.92), but not among men. Supplemental iron intake of more than 18 mg/day versus none was positively associated with CRC incidence (OR=2.31; 95% CI=1.48-3.59; P-trend<0.001), an effect that was observed in both men (OR=2.56; 95% CI=1.30-5.05) and women (OR=2.46; 95% CI=1.34-4.52). These findings suggest that consumption of more than 18 mg/day of supplemental iron may increase risk for CRC.
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November 2013

Effects of omega-3 acid ethyl esters and aspirin, alone and in combination, on platelet function in healthy subjects.

Thromb Haemost 2008 Oct;100(4):634-41

Sanford Research/USD, 1100 E. 21st Street, Sioux Falls, SD 57105, USA.

Omega-3 fatty acids (n-3 FA) from oily fish are clinically useful for lowering triglycerides and reducing risk of heart attacks. Accordingly, patients at risk are often advised to take both aspirin and n-3 FA. However, both of these agents can increase bleeding times, and the extent to which the combination inhibits platelet function is unknown. The purpose of this pilot study was to determine the effects of a prescription omega-3 FA product (P-OM3) and aspirin, alone and in combination, on platelet aggregation assessed by whole blood impedance aggregometry (WBA). Ten healthy volunteers provided blood samples on four separate occasions: Day 1, baseline; Day 2, one day after taking aspirin (2 x 325 mg tablets); Day 29, after 28 days of P-OM3 (4 capsules/day); and Day 30, after one day of combined P-OM3 and aspirin. WBA was tested with two concentrations of collagen, with ADP and with a thrombin receptor activating peptide (TRAP). Compared to baseline, aspirin alone inhibited aggregation only with low-dose collagen stimulation; P-OM3 alone did not inhibit aggregation with any agonist; and combined therapy inhibited aggregation with all agonists but TRAP. Significant interactions between interventions were not observed in response to any agonist. In conclusion, P-OM3 alone did not inhibit platelet aggregation, but did (with two agonists) when combined with aspirin. Since previous studies have not reported a clinically significant risk for bleeding in subjects on combined therapy, P-OM3 may safely enhance the anti-platelet effect of aspirin.
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October 2008