[Cadmium content of vegetable foods in the effective range of a lead smelting plant]

Cadmium alters heat shock protein pathways in SN56 cholinergic neurons, leading to Aβ and phosphorylated Tau protein generation and cell death

Cadmium, a neurotoxic environmental compound, produces cognitive disorders, although the mechanism remains unknown. Cadmium induces a more pronounced cell death on cholinergic neurons from basal forebrain (BF), mediated, in part, by increase in Aβ and total and phosphorylated Tau protein levels, which may explain cadmium effects on learning and memory processes. Cadmium downregulates the expression of heat shock proteins (HSPs) HSP 90, HSP70 and HSP27, and of HSF1, the master regulator of the HSP pathway. HSPs proteins reduce the production of Aβ and phosphorylated Tau proteins and avoid cell death pathways induction. Thus, we hypothesized that cadmium induced the production of Aβ and Tau proteins by HSP pathway disruption through HSF1 expression alteration, leading to BF cholinergic neurons cell death. Our results show that cadmium downregulates HSF1, leading to HSP90, HSP70 and HSP27 gene expression downregulation in BF SN56 cholinergic neurons. In addition, cadmium induced Aβ and total and phosphorylated Tau proteins generation, mediated partially by HSP90, HSP70 and HSP27 disruption, leading to cell death. These results provide new understanding of the mechanisms contributing to cadmium harmful effects on cholinergic neurons.

Muscarinic M1 receptor partially modulates higher sensitivity to cadmium-induced cell death in primary basal forebrain cholinergic neurons: A cholinesterase variants dependent mechanism

Cadmium is a toxic compound reported to produce cognitive dysfunctions, though the mechanisms involved are unknown. In a previous work we described how cadmium blocks cholinergic transmission and induces greater cell death in primary cholinergic neurons from the basal forebrain. It also induces cell death in SN56 cholinergic neurons from the basal forebrain through M1R blockage, alterations in the expression of AChE variants and GSK-3β, and an increase in Aβ and total and phosphorylated Tau protein levels. It was observed that the silencing or blockage of M1R altered ChAT activity, GSK-3β, AChE splice variants gene expression, and Aβ and Tau protein formation. Furthermore, AChE-S variants were associated with the same actions modulated by M1R. Accordingly, we hypothesized that cholinergic transmission blockage and higher sensitivity to cadmium-induced cell death of primary basal forebrain cholinergic neurons is mediated by M1R blockage, which triggers this effect through alteration of the expression of AChE variants. To prove this hypothesis, we evaluated, in primary culture from the basal forebrain region, whether M1R silencing induces greater cell death in cholinergic neurons than cadmium does, and whether in SN56 cells M1R mediates the mechanisms described so as to play a part in the cadmium induction of cholinergic transmission blockage and cell death in this cell line through alteration of the expression of AChE variants. Our results prove that M1R silencing by cadmium partially mediates the greater cell death observed on basal forebrain cholinergic neurons. Moreover, all previously described mechanisms for blocking cholinergic transmission and inducing cell death on SN56 cells after cadmium exposure are partially mediated by M1R through the alteration of AChE expression. Thus, our results may explain cognitive dysfunctions observed in cadmium toxicity.

Higher sensitivity to cadmium induced cell death of basal forebrain cholinergic neurons: a cholinesterase dependent mechanism

Cadmium is an environmental pollutant, which is a cause of concern because it can be greatly concentrated in the organism causing severe damage to a variety of organs including the nervous system which is one of the most affected. Cadmium has been reported to produce learning and memory dysfunctions and Alzheimer like symptoms, though the mechanism is unknown. On the other hand, cholinergic system in central nervous system (CNS) is implicated on learning and memory regulation, and it has been reported that cadmium can affect cholinergic transmission and it can also induce selective toxicity on cholinergic system at peripheral level, producing cholinergic neurons loss, which may explain cadmium effects on learning and memory processes if produced on central level. The present study is aimed at researching the selective neurotoxicity induced by cadmium on cholinergic system in CNS. For this purpose we evaluated, in basal forebrain region, the cadmium toxic effects on neuronal viability and the cholinergic mechanisms related to it on NS56 cholinergic mourine septal cell line. This study proves that cadmium induces a more pronounced, but not selective, cell death on acetylcholinesterase (AChE) on cholinergic neurons. Moreover, MTT and LDH assays showed a dose dependent decrease of cell viability in NS56 cells. The ACh treatment of SN56 cells did not revert cell viability reduction induced by cadmium, but siRNA transfection against AChE partially reduced it. Our present results provide new understanding of the mechanisms contributing to the harmful effects of cadmium on the function and viability of neurons, and the possible relevance of cadmium in the pathogenesis of neurodegenerative diseases.

Etiology of pancreatic cancer, with a hypothesis concerning the role of N-nitroso compounds and excess gastric acidity

In the United States, pancreatic cancer is the fourth most frequent cause of cancer death in males as well as females, after lung, prostate or breast, and colorectal cancer. Each year, approximately 30 000 Americans are diagnosed with pancreatic cancer and about the same number die of it. Germline mutations in a few genes including p16 and BRCA2 have been implicated in a small fraction of cases, as has chronic pancreatitis. The one established risk factor for pancreatic cancer is cigarette smoking: current smokers have two to three times the risk of nonsmokers. Studies of dietary factors have not been entirely consistent but do suggest associations of higher risk with consumption of smoked or processed meats or with animal foods in general and lower risk with consumption of fruits and vegetables. Colonization by Helicobacter pylori appears to increase risk, and a history of diabetes mellitus may also increase risk. The purpose of this epidemiologic review is to consider the possibility that risk of pancreatic cancer is increased by factors associated with pancreatic N-nitrosamine or N-nitrosamide exposures and with chronic excess gastric or duodenal acidity. Host genetic variation in inflammatory cytokine mechanisms may also be involved in this process. Many features of the evidence bearing on the pathophysiology of pancreatic cancer appear to support connections with N-nitroso compounds and with gastric acidity.

Oral cadmium exposure of adults in Germany. 1: Cadmium content of foodstuffs and beverages

The cadmium contents of 94 and 105 foodstuffs bought in six-fold repetition in 1988 and in nine-fold repetition in 1991, respectively were analysed within the framework of a market-basket study. These foodstuffs were typical of German eating habits. Additionally, 170 samples of drinking water were investigated. The cadmium concentrations of the foodstuffs were comparable with results of recent studies carried out in Europe and North America. Fruit, milk and dairy products, sugar and sugar-rich foodstuffs as well as beverages showed mean cadmium contents < or = 5 ng/g fresh matter or ng/ml, respectively. The cadmium content of meat, sausage, fish and tinned fish was also low. Pork and beef, the most important kinds of meat, contained 5.4 and 2.5 ng/g on average. The majority of the vegetables investigated, including potatoes, had cadmium concentrations < 25 ng/g. However, individuals samples of lettuce showed very high cadmium levels. The cadmium content of bread, cakes and pastries as well as farinaceous products were within the range of 20-40 ng/g. The most important bread, cakes and pastries (wheat and rye bread, toasted bread, rolls) contained 25-35 ng/g. A median cadmium concentration of 0.2 micrograms/l was found in the drinking water. As expected, liver and kidneys showed the highest cadmium levels of 73 and 204 ng/g, respectively on average.

Cadmium in foods and the diet

Information on the sources of cadmium in food are presented and the effects of raised environmental levels of cadmium on the concentration of cadmium in plant based foods, fish and shellfish, meat and offals, and dairy produce are discussed. Information is also presented on normal dietary intakes of cadmium and how these intakes may be elevated by environmental pollution or atypical dietary habits. The estimation of dietary intakes of cadmium using data about extreme intakes of specific foods is described.

Cadmium in foods and the diet

Information on the sources of cadmium in food are presented and the effects of raised environmental levels of cadmium on the concentration of cadmium in plant based foods, fish and shellfish, meat and offals, and dairy produce are discussed. Information is also presented on normal dietary intakes of cadmium and how these intakes may be elevated by environmental pollution or atypical dietary habits. The estimation of dietary intakes of cadmium using data about extreme intakes of specific foods is described.

[Lead and cadmium contamination of foods and feeds from selected areas of the Erfurt district. 4. Lead in vegetables grown in culture centers of the Erfurt region]

For the purpose of determining the effect of heavy metal emissions of a great town on the lead and cadmium levels of vegetables that are of relevance to food supply, we analyzed 193 samples of vegetables from the important vegetable-growing centre of Erfurt during a 3-year period. With regard to the main wind direction and the infrastructure of the town, the samples were collected at four different areas under vegetable. Apart from a single exception, the lead and cadmium contents were inferior to the maximum tolerances provided by the regulation concerning the contents of foreign substances in foods, the metal contents of leaf vegetables being higher than those of brassicaceous plants. Vegetable samples from areas with heavier emission burdens showed somewhat higher metal contents. In contrast to this, the cadmium contents did not exhibit such differences. The highest lead and cadmium contents were found in spinach. To elucidate the effect of the washing and blanching techniques used in industrial processing, 23 spinach preserves were analyzed in addition; as expected, the heavy metal contents were reduced by these techniques. In summary, our investigations evidence that the main vegetables cauliflower, white cabbage, red cabbage, savoy cabbage, as well as lettuce and spinach (grown in the district of Erfurt) contribute but little to total food contamination if we consider the amounts consumed on an average.

[Heavy metal content of cereals and potatoes]

By means of atomic absorption spectrometry, the authors determined the cadmium, zinc, copper and manganese contents in potatoes and cereals from three territories differently burdened by heavy-metal immissions (rural region, overcrowded urban region, region with non-ferrous metal industry). Of these elements, cadmium was most enriched, followed (by a wide margin) by zinc and copper, whereas the manganese level was slightly higher in the burdened region II (compared to the burdened region I) and somewhat lower in the burdened region III. Compared to normal values (0.035--0.080 p.p.m.), i. e., values found in non-burdened regions, the cadmium contents were some 2- to 6-fold higher in air-dry samples of wheat, barley and rye from the burdened regions, some 30-fold higher in oats, and some 3- to 4-fold higher in potatoes (normal values, on a dry-weight basis, (0.140 p.p.m.). As to cereals, the zinc levels were, at the most, some 2-fold higher than the normal values (29--34 p.p.m.), the copper contents were, at the most, some 1.5-fold higher than the normal values (4.1 bis 4.8 p.p.m.), whereas the manganese levels (normal values, 14--30 p.p.m.) were less by half. In potatoes, the zinc contents were but slightly higher than the normal values (18.5 p.p.m., on a dry-weight basis), the copper levels (4.6 p.p.m., on a dry-weight basis) were some 2-fold higher, and the manganese contents (7.2 p.p.m., on a dry-weight basis) were somewhat reduced. On an average 26% (region with non-ferrous metal industry) or 13% (normal region) of the heavy metals are removable from potatoes by washing. On the basis of the results obtained and of data from the literature, an estimate is calculated for the expected values in territories differently burdened by heavy-metal immissions. Finally, targeted suggestions are given for preventing or impeding the entrance of heavy metals into the biocycle.