The GARD™skin assay: Investigation of the applicability domain for metals.

New approach methodologies (NAMs) for hazard identification of skin sensitizing chemicals were adopted as test guidelines by the OECD during the last decade. These alternatives to animal models align to individual key events (KE) in the adverse outcome pathway (AOP) for skin sensitization for which the molecular initiating event (MIE) is covalent binding to proteins. As it currently stands, the AOP does not include mechanistic events of sensitization by metals, and limited information is available on whether NAMs accurately predict the sensitization potential of such molecules, which have been proposed to act via alternative mechanisms to organic chemicals. Methods for assessing the sensitization potential of metals would be valuable tools to support risk management within, e.g., occupational settings during production of new metal salts or within the medical device industry to evaluate leachables from metal alloys. This paper describes a systematic evaluation of the applicability domain of the GARD™skin assay for the assessment of metals. Hazard classifications were supplemented with an extended analysis of gene expression profiles induced by metal sensitizers to compare the induction of toxicity pathways between metals and organic sensitizers. Based on the results of this study, the accuracy, sensitivity, and specificity of GAR­D™skin for the prediction of skin sensitizing hazard were 92% (12/13), 100% (7/7), and 83% (5/6), respectively. Thus, the performance of GARD™skin for the assessment of metals was found to be similar to that observed for conventional organic substances, providing support for inclusion of metals within the applicability domain of the test method.

Detection of malondialdehyde DNA adducts in human colorectal mucosa: relationship with diet and the presence of adenomas.

Colorectal biopsies from normal mucosa of participants in the United Kingdom Flexible Sigmoidoscopy Trial and European Prospective Investigation on Cancer (EPIC; n = 162) were analyzed for the presence of malondialdehyde-deoxyguanosine (M(1)-dG), a DNA adduct derived from lipid peroxidation. The aim was to investigate whether dietary factors can modulate M(1)-dG levels and whether M(1)-dG in normal mucosa is a risk factor for colorectal adenomas. Samples were analyzed using a sensitive immunoblot blot assay. This study has shown for the first time that M(1)-dG is present in human colorectal tissue. M(1)-dG levels ranged from undetectable (n = 13) to 12.23 per 10(7) total bases. Mean levels were 4.3 +/- 3 and 4.6 +/- 2.9 per 10(7) total bases in men and women, respectively. In men, there were positive associations of adduct levels with height and age, and inverse associations with body mass index. Legumes, fruit, salad, and whole meal bread were inversely associated with M(1)-dG adducts, whereas consumption of offal, white meat, beer, and alcohol were positively associated with elevated levels. In women, there was an inverse association of the adduct with the ratio of polyunsaturated:saturated fatty acids (P = 0.019) and a weak positive correlation with saturated fat (P < 0.061). When levels of adducts were compared in individuals with and without adenomas, there was a trend for higher levels in individuals presenting with adenomas especially in the highest category of M(1)-dG adducts (P < 0.005).