Toxicogenomic approaches for understanding molecular mechanisms of heavy metal mutagenicity and carcinogenicity

Trace metal quantification in bladder biopsies from tumoral lesions of Tunisian cancer and controls subjects

The incidence of bladder tumors has been dramatically increasing since the 1970s, possibly as a consequence of ongoing environmental pollution. Previous studies have provided some evidence of an association between cancer and exposure to carcinogenic metals. In order to examine the association between levels of toxic metals in patients with bladder tumors and controls, the amounts of arsenic, cadmium, chromium, and nickel were measured in tumoral lesions and adjacent normal part of the bladder mucosa excised for carcinoma and compared with those in the bladder mucosa of volunteer subjects operated for non-neoplastic diseases. The quantification of metals in tissue was assessed by atomic absorption spectroscopy. In tumoral tissues of the excised bladder mucosa, content of Cr and Ni was significantly low compared to that of adjacent normal tissues and control tissues while that of As and Cd in normal tissues adjacent to the tumor were significantly elevated compared to controls. Though the sample size was small, the present study shows that concentrations of metals such as Cd, Cr, As, and Ni in bladder tissue may be used as a biomarker of exposure. On the basis of the results obtained in this study, high amounts of As and Cd in adjacent normal parts of the bladders with carcinomas compared to controls would strongly suggest possible, individual or synergistic, effects of these pollutants on enzymatic systems, priming an oncogenic pathway.

Assessment of mutagenic, genotoxic, and cytotoxic potential of water samples of Harike wetland: a Ramsar site in India using different ex vivo biological systems

Harike is a wetland of international importance under the Ramsar Convention. The present study entails the investigation of mutagenic, genotoxic and cytotoxic effect of surface water samples collected from five different areas of the Harike wetland by using the histidine reversion point mutation assay in Salmonella typhimurium (TA98 and TA100) strain with or without S9, bioluminescence mutagenicity assay using Vibrio harveyi (A16) strain, plasmid-nicking assay using pBR322 and 3(4,5-dimethyl-thiazol-2-yl)2,5-diphenyl-tetrazolium bromide assay as well as confocal imaging studies using Chinese hamster ovarian cell line, respectively. It was observed that although, the water sample of all the areas of wetland demonstrated mutagenic, genotoxic as well as cytotoxic activity, the effect was quite significant with the water samples from River Satluj and Khatan area (i.e. reservoir mainly contains Satluj water). The metal analysis of water samples was also conducted with atomic absorption spectrophotometer. The mutagenicity, genotoxicity and cytotoxicity of water samples emerged to be correlated with metal concentration. The source of toxic components seems to be associated with various industrial effluents and agricultural run-off. The results of the present study carry great importance in documenting the water quality monitoring data of the wetland.

New perspectives on oxidized genome damage and repair inhibition by pro-oxidant metals in neurological diseases

The primary cause(s) of neuronal death in most cases of neurodegenerative diseases, including Alzheimer's and Parkinson's disease, are still unknown. However, the association of certain etiological factors, e.g., oxidative stress, protein misfolding/aggregation, redox metal accumulation and various types of damage to the genome, to pathological changes in the affected brain region(s) have been consistently observed. While redox metal toxicity received major attention in the last decade, its potential as a therapeutic target is still at a cross-roads, mostly because of the lack of mechanistic understanding of metal dyshomeostasis in affected neurons. Furthermore, previous studies have established the role of metals in causing genome damage, both directly and via the generation of reactive oxygen species (ROS), but little was known about their impact on genome repair. Our recent studies demonstrated that excess levels of iron and copper observed in neurodegenerative disease-affected brain neurons could not only induce genome damage in neurons, but also affect their repair by oxidatively inhibiting NEIL DNA glycosylases, which initiate the repair of oxidized DNA bases. The inhibitory effect was reversed by a combination of metal chelators and reducing agents, which underscore the need for elucidating the molecular basis for the neuronal toxicity of metals in order to develop effective therapeutic approaches. In this review, we have focused on the oxidative genome damage repair pathway as a potential target for reducing pro-oxidant metal toxicity in neurological diseases.

Specific association of teratogen and toxicant metals in hair of newborns with congenital birth defects or developmentally premature birth in a cohort of couples with documented parental exposure to military attacks: observational study at Al Shifa Hospital, Gaza, Palestine

This study was undertaken in Gaza, Palestine, in a cohort of babies born in 2011. Hair samples of newborns were analyzed for metal load by DRC-ICP-MS. We report specific level of contamination by teratogen/toxicants metals of newborn babies, environmentally unexposed, according to their phenotypes at birth: normal full term babies, birth defects or developmentally premature. The occurrence of birth defects was previously shown to be correlated in this cohort to documented exposure of parents to weapons containing metal contaminants, during attacks in 2009. We detect, in significantly higher amounts than in normal babies, different specific teratogen or toxicant elements, known weapons' components, characteristic for each of birth defect or premature babies. This is the first attempt to our knowledge to directly link a phenotype at birth with the in utero presence of specific teratogen and/or toxicant metals in a cohort with known episodes of acute exposure of parents to environmental contamination by these same metals, in this case delivered by weaponry The babies were conceived 20-25 months after the major known parental exposure; the specific link of newborn phenotypes to war-remnant metal contaminants, suggests that mothers' contamination persists in time, and that the exposure may have a long term effect.