Effects of cumene hydroperoxide on adenosine diphosphate ribosyl transferase in mononuclear leukocytes of patients with adenomatous polyps in the colon

Genetic variation in base excision repair genes and the prevalence of advanced colorectal adenoma

Base excision repair (BER) corrects DNA damage caused by oxidative stress and low folate intake, which are putative risk factors for colorectal neoplasia. To examine the relationship between genetic variation in BER genes and colorectal adenoma risk, we conducted a case-control study of 767 cases of advanced colorectal adenoma and 773 controls from the baseline screening exam of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cases included participants diagnosed with advanced left-sided adenoma, and controls were subjects without evidence of a left-sided polyp by sigmoidoscopy, frequency-matched to cases on race and gender. Twenty single nucleotide polymorphisms were genotyped in four BER genes (APEX1, PARP1, POLB, and XRCC1), and conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI) for the association with colorectal adenoma. Two variants with possible functional significance were associated with risk. The APEX1 51H variant was associated with a borderline significant decreased risk of colorectal adenoma (OR, 0.66; 95% CI, 0.44-1.00), and the XRCC1 399Q variant was inversely associated with risk among Caucasians (OR, 0.80; 95% CI, 0.64-0.99). Homozygotes at two PARP1 loci (A284A and IVS13+118G>A) were also associated with a decreased risk of colorectal adenoma compared with wild-type carriers (OR, 0.70; 95% CI, 0.49-0.98 for both), which was restricted to advanced adenomas displaying histologically aggressive characteristics (OR, 0.51; 95% CI, 0.33-0.78, P = 0.002 for PARP1 A284A). This study suggests that polymorphisms in APEX1, XRCC1, and PARP1 may be associated with advanced colorectal adenoma.

Nutrition and ageing

The reviewed literature indicates that, even in industrialised countries, the nutrition of mature and aged subjects is often inadequate (because of deficiency or excess), which may lead to premature or pathological senescence. Recent nutritional research on ageing laboratory animals shows that dietary restriction may be the most effective procedure to achieve a long and disease-free life span, probably owing to a better protection against mitochondria-linked oxygen stress. Likewise, the experimental and clinical work from many laboratories, including our own, indicates that age-dependent changes in the cardiovascular and immune systems are linked to oxygen stress and that an adequate intake of dietary antioxidants may protect those systems against chronic degenerative syndromes in the physiopathology of which reactive oxygen species (ROS) play a key role. The extant data indicate that the antioxidant vitamins C and E are centrally involved in defending the above two systems against ROS attack. Moreover, recent research suggests that the glutathione-related thiolic antioxidants, thiazolidine carboxylic acid (thioproline) and N-acetylcysteine, as well as the phenolic liposoluble 'co-antioxidants' of Curcuma longa, may have a significant protective effect against age-related atherogenesis and immune dysfunction. Key messages from this paper are the following. (1) It is generally accepted that oxygen free radicals released in metabolic reactions play a key role in the physiopathology of 'normal ageing' and of many age-related degenerative diseases. (2) Consumption of adequate levels of antioxidants in the diet is essential in order to preserve health in old age. (3) A certain degree of protection against atherogenesis and immune dysfunction may be achieved by preventing vitamin E deficiency and an excessive oxidation of the glutathione-supported thiol pool.

Diet, genetic susceptibility and carcinogenesis

At least six types of gene-environment interactions (GEI) have been proposed (Kouhry and Wagener, 1993). In the first type, neither the environmental exposure (EE) nor the genetic risk factor (GRF) have any effect by themselves, but interaction between them causes disease. This is the case of phenylalanine exposure and the phenylketonuria genotype. Type 2 is a situation in which the GRF has no effect on disease in the absence of exposure, but exacerbates the effects of the latter. This is the most important type of GEI in relation to metabolic susceptibility genes and human carcinogenesis. The third type is the converse of the second (EE is ineffective per se, but enhances the effect of GRF). Type 4 occurs when both FE and GRF increase the risk for disease, but the combination is interactive or synergistic: an example is the interaction between Xeroderma Pigmentosum and LWV radiation. Types 5 and 6, according to the classification proposed by Kouhry, refer to cases in which the GRF is protective. The model of GEI that is emerging as the most important in chemical carcinogenesis refers to metabolic susceptibility genes. The general population can be divided into subgroups depending on their susceptibility to the action of carcinogens, based on their ability to metabolize such compounds to electrophilic, reactive metabolites (which form adducts with DNA), or, respectively, electrophobic metabolites that are excreted. The present contribution is a short review of the relevant literature, with particular emphasis on some polymorphisms involved in dietary exposures. In addition, the practical implications of genetic testing in this field are discussed.

Elevation of ADP-ribosylation as an indicator of mononuclear leucocyte responsiveness in breast cancer patients treated with tamoxifen

82 women who had had surgery for removal of breast cancer were randomised during the primary care period before initiation of any chemotherapy or radiotherapy into two groups: no drug treatment (n = 40) and 20 mg tamoxifen per day for 2 years (n = 42). Mononuclear leucocyte (MNL) fractions from blood samples were collected during the first 368 days of the study and ADP-ribosylation was quantified. Tamoxifen treatment resulted in a dose-duration increase in ADP-ribosylation. This was true even after adjustment for covariates such as age, smoking habits, oestrogen use, menstruation and tumour size. These data suggest that part of the antitumour effects of tamoxifen treatment in vivo relates to an enhanced immune cell responsiveness, as indicated by the increased MNL ADP-ribosylation.

Modulation of the cancer susceptibility measure, adenosine diphosphate ribosyl transferase (ADPRT), by differences in low-dose n-3 and n-6 fatty acids

Adenosine diphosphate ribosyl transferase (ADPRT) is related to oxidants, and lower values for ADPRT in white cells suggest increased cancer susceptibility. Ordinarily, oxidants are generated intracellularly via metabolism of n-6 fatty acids common in western diets. However, n-3 fatty acids in fish oils might limit oxidants via competitive inhibition of key enzymes, elevate ADPRT, and lower cancer risk. In this controlled trial, 47 women were assigned either lecithin (an n-6 fatty acid, 7.2 g daily) or eicosapentaenoic acid-docosahexaenoic acid (n-3 fatty acids, 1.5 g daily) for six weeks, and 45 women completed all four visits. After six weeks, ADPRT increased by 9.3 +/- 10.8% (SD) for the n-3 fatty acid group relative to the n-6 fatty acid group. For the subset of 39 women with good compliance, ADPRT increased by 20.9 +/- 11.1% (nonparametric p = 0.039). This increase persisted after adjustment for regression to the mean. The trial suggests a "normalizing" effect of low-dose n-3 fatty acids on the ADPRT measure.

Mitogenic induction of ornithine decarboxylase in human mononuclear leukocytes: relationships with adenosine diphosphate ribosyltransferase

1. Relationships between ornithine decarboxylase (ODC) and adenosine diphosphate ribosyl transferase (ADPRT) in human mononuclear leukocytes (HML) were tested by statistical comparisons of their values in a group of 46 people, and by use of inhibitors of ADPRT. 2. ODC was assayed following exposure of HML, for 20 hr, to mitogens [phytohemagglutinin (PHA) and pokeweed mitogen]; ADPRT was measured following exposure of HML to H2O2 (100 microM) for 1 hr (activated ADPRT), and in parallel cultures without H2O2 (constitutive ADPRT). 3. Significant correlations were found between ODC and ADPRT values; the effects of smoking disturbed the correlations. PHA induction of ODC was negatively influenced by age (standardized beta coefficient = -2.95, P = 0.005), while age also influenced ADPRT values negatively in non-smokers (for H2O2 activated ADPRT, standardized beta coefficient = -2.74, P less than 0.008). 4. Inhibitors of ADPRT, nicotinamide, caffeine and benzamide inhibited the induction of ODC by PHA in a concentration-dependent manner, in the range (0.6-10 mM) known to inhibit ADPRT.

Ornithine decarboxylase in resting human mononuclear leucocytes: evidence for an endogenous inhibitor

1. Ornithine decarboxylase (ODC) was measured in human mononuclear leucocytes (HML) by retention of putrescine on cation exchange paper. 2. The method was validated with unstimulated HML, phytohemagglutinin-stimulated HML, and a commercial preparation of ODC. The average enzyme activity of unstimulated HML (50 samples) was 22.6 +/- 7.3 pmol/hr 10(7) cells, with 29 values less than 5 pmol/hr 107 cells. 3. The results show that an endogenous inhibitor or inactivator of ODC exists in unstimulated HML: enzyme activity in extracts of mitogen-stimulated cells were inhibited by extracts of unstimulated cells (37-55%) inhibition under the conditions used.

Hydrogen peroxide induced adenosine diphosphate ribosyl transferase (ADPRT) response in patients with inflammatory bowel disease

The sample population in this initial case control study of the adenosine diphosphate ribosyl transferase (ADPRT) response of inflammatory bowel disease patients included: 23 patients with ulcerative colitis (UC)-active and inactive, 13 patients with Crohn's disease (CD)-active and inactive, 14 first degree relatives of UC and CD patients, and 19 age-matched controls. Adenosine diphosphate ribosyl transferase activity was determined after one hour incubation with 1% plasma (the constitutive value) or with 1% plasma and 100 microM H2O2 (the activated value) with the resulting difference designated as the induced value. Statistically significant decrease in ADPRT activity was found for the constitutive, activated and induced values in human mononuclear leucocytes of UC and CD patients, compared with controls. The values in the first degree relatives of UC and CD patients were not significantly different from either the control or disease populations, indicating an intermediate ADPRT response. These results may be related to the nature of the immunological response of IBD patients and comparable with similar findings in other diseases with known DNA repair deficiencies--for example, colon cancer.