Hermann H. Dieter

Copper in disorders with neurological symptoms: Alzheimer’s, Menkes, and Wilson diseases

Copper is an essential element for the activity of a number of physiologically important enzymes. Enzyme-related malfunctions may contribute to severe neurological symptoms and neurological diseases: copper is a component of cytochrome c oxidase, which catalyzes the reduction of oxygen to water, the essential step in cellular respiration. Copper is a cofactor of Cu/Zn-superoxide-dismutase which plays a key role in the cellular response to oxidative stress by scavenging reactive oxygen species. Furthermore, copper is a constituent of dopamine-beta-hydroxylase, a critical enzyme in the catecholamine biosynthetic pathway. A detailed exploration of the biological importance and functional properties of proteins associated with neurological symptoms will have an important impact on understanding disease mechanisms and may accelerate development and testing of new therapeutic approaches. Copper binding proteins play important roles in the establishment and maintenance of metal-ion homeostasis, in deficiency disorders with neurological symptoms (Menkes disease, Wilson disease) and in neurodegenerative diseases (Alzheimers disease). The Menkes and Wilson proteins have been characterized as copper transporters and the amyloid precursor protein (APP) of Alzheimers disease has been proposed to work as a Cu(II) and/or Zn(II) transporter. Experimental, clinical and epidemiological observations in neurodegenerative disorders like Alzheimers disease and in the genetically inherited copper-dependent disorders Menkes and Wilson disease are summarized. This could provide a rationale for a link between severely dysregulated metal-ion homeostasis and the selective neuronal pathology.

Epidemiological investigation on chronic copper toxicity to children exposed via the public drinking water supply.

Copper in drinking water has been associated with Non-Indian Childhood Cirrhosis (NICC), a form of early childhood liver cirrhosis. This epidemiological study examines the exposition of infants to increased copper concentrations through drinking water from public water supplies in Berlin, Germany, and if this dietary copper intake can cause liver damage in early childhood. In total, water samples from 2944 households with infants were tested for copper. Mean copper concentrations in the two different types of collected composite samples were 0.44 and 0.56 mg/l, respectively. Families having a copper concentration at or above 0.8 mg/l in one or both of the composite samples (29.9% of all sampled households) and a defined minimum ingestion of tap water of their infant were recommended to undergo a paediatric examination. Nearly every of the 541 recommended infants were examined by a local paediatrician and of these 183 received a blood serum analysis, too. None of the infants had clear signs of a liver disease although a few serum parameters lay outside the accompanying reference range and abdominal ultrasound imaging gave slightly unusual results in five cases. Additionally, no signs of a negative health effect could be found in the statistical analysis of the serum parameters GOT, GPT, GGT, total bilirubin, serum copper, or ceruloplasmin in relation to estimated daily and total copper intakes of the infants from tap water. No dose relation of serum parameters and estimated copper intakes could be established. From the results of the study, no confirmed indication of a liver malfunction in infants whose food had been prepared using tap water with an elevated copper concentration could be found and, therefore, no indication of a hazard due to copper pipes connected to public water supplies could be detected.

Perfluorinated compounds (PFC) hit the headlines : meeting report on a satellite symposium of the annual meeting of the German Society of Toxicology.

Recently, agricultural land in the rural area Sauerland in North Rhine-Westphalia, Germany, has been contaminated with perXuorinated compounds (PFC) (Kraft et al. 2007). Industrial waste containing mainly perXuorooctanoic acid (PFOA) has been illegally manufactured into a so-called “soil improver” by a recycling company and disseminated by farmers, leading to increased levels of PFOA after leaching into surface raw water for drinking water production (Fig. 1). Irrespective of this headline-catching incident PFC represent a group of emerging chemicals of concern (Table 1). An increasing number of studies show that humans are exposed to a large number of PFCs (Kärrman et al. 2007; So et al. 2007). PFOA and PFOS, the two most important PFCs in the environment, are auxiliary substances for the industrial production of perXuorinated polymers. These are widely used for non-stick coatings for instance on cooking pans and stain repellent coatings on items such as fast-food packaging, furniture and carpets. The major source of PFOA and PFOS in the environment seems to be their dissemination with waste water and their release in traces from consumer products. In order to achieve a realistic risk assessment an expert panel met during the Annual Meeting of the German Society of Toxicology. Detlef WölXe (Federal Institute for Risk Assessment, BfR, Berlin) reported on the persistence and toxicology of PFCs. Some compounds, e.g. PFOA and PFOS, are resistant to biotransformation and were ubiquitously found in human blood with half-lives of several years. Oral toxicity studies in rats and monkeys showed that liver is the primary target organ. While PFCs were not considered to be genotoxic, PFOA and PFOS are tumor promoters in rats (COT 2006a, b). Following in utero exposure in rodents PFOA (Hernderson and Smith 2007; Wolf et al. 2007) and PFOS produced reduced viability, body weights deWcits and other postnatal eVect on pups (Fig. 2). Jürgen Angerer (University of Erlangen) presented epidemiological data. Several studies have reported an increase in PFC concentrations in humans up to the late 1990s. Recent eVorts have not yet resulted in declining environmental concentrations. In two independent studies, median values of blood plasma concentrations of PFOS and PFOA were determined. They amount to 12–22 g/l and 5– 7 g/l, respectively. Blood levels did not correlate with age. Interestingly, the levels were higher in male compared to female individuals. Importantly, lactation is a considerable source of exposure for infants (Kärrman et al. 2007). Furthermore, PFCs undergo trans-placental transfer (Midasch et al. 2007). The total amount of PFCs transferred to a breast fed infant is approximately 200 ng/day. Michael Wilhelm (University of Bochum) presented brand-new data P. H. Roos (&) · J. G. Hengstler Institut für Arbeitsphysiologie an der Universität Dortmund, Ardeystr. 67, 44139 Dortmund, Germany e-mail: roos@ifado.de

Experimental induction of liver fibrosis in young guinea pigs by combined application of copper sulphate and aflatoxin B1

Aflatoxin B1 alone (0.05 mg resp. 0.037 mg/kg/d), copper alone (6.6 mg/kg/d or 200 mg/l drinking water) or a combination of both was administered orally for 6 months to young guinea pigs from the first/second day of life. In the copper group there were no pathomorphological changes. For the aflatoxin B1 group, liver damage was established. In the combined group, liver injury was more frequent and more severe compared to the aflatoxin B1 group and biliary copper excretion was diminished compared with the copper group. Histologically, only the livers of this group exhibited degeneration, atrophy and steatosis of liver cells, inflammatory processes and a more or less prominent fibrosis. For childhood cirrhosis (ICC and ICT) a combined etiology--a liver damaging agent plus elevated alimentary copper--is a plausible hypothesis.

Recent experimental results of effects of perfluoroalkyl substances in laboratory animals – Relation to current regulations and guidance values

The detection of perfluoroalkyl substances (PFAS) in surface and drinking water from various countries raised the attention to the presence of these chemicals in environmental probes and led to several regulatory actions to limit exposure in human beings. There was particular concern about perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), due to their former wide-spread use. Recently, several institutions published revisions of former regulatory or recommended maximum concentrations in drinking water and food, which are markedly lower than the former values. The present short overview describes the current regulations for PFAS and compares them with the outcome of several experimental studies in laboratory animals at low-level exposure to PFOA and PFOS. In addition, regulations for short-chain PFAS are presented which, due to lack of toxicological information, are evaluated according to the concepts of Threshold of Toxicological Concern (TTC) or the Health-related Indication Values (HRIV).

Wie problemgerecht ist die humantoxikologische Bewertung von pestiziden (PBSM) im Trinkwasser

ZusammenfassungÜber wissenschaftlich gestüzte oder begründete Grenzkonzentrationen und ihren Anwendungsbereich wird im gesellschaftlichen Kontext auf drei Ebenen entschieden:-wissenschaftlich durchBeurteilung von Vollständigkeit und Qualität der Datenbasis (Ebene 1)-human- oderökotoxikologisch durchBewertung wissenschaftlich beschriebener Wirkungen als, ‘schädlich’ und durch Angabe dementsprechend ‘unschädlicher’ Belastungshöhen (Ebene 2)-gesellschaftlich durchZuordnung von vorgeschlagenen Grenzkonzentrationen als maximale Sollwerte (Grenzwerte) zu bestimmten, unterschiedlich bewerteten Umweltbereichen (Ebene 3). Die auf den Ebenen 2 und 3 gültigen Bewertungsskalen bilden die Interessen verschiedener Gesellschaftsgruppen — einschließlich der Wissenschaftler der verschiedenen Fachrichtungen — an den jewei-ligen Umweltbereichen ab.Trinkwasser ist unser wichtigstes Lebensmittel. Auf Ebene 3 gilt für Trinkwasser in der EU seit 1986 der Grenzwert (maximale Sollwert) für Pestizide (PBSM i.S. der TrinkwV) in Höhe von 0,10μg/L pro Struktureinheit und 0,50 μg/L als Summenwert. Er steht mit Ebene 2 nicht in einem streng toxikologischen Bewertungszusammenhang, dient aber i.S.des Bundesseuchengesetzes der Abwehr unwägbarer gesundheitlicher Risiken und gewährleistet hier den für Trinkwasser notwendigen Handlungsspielraum.Trinkwasser ist in seinen Vorstufen als Rohwasser auch Teil des Wasserkreislaufs und Lebensbedingung aquatischer Ökosysteme. Es werden deshalb über den humantoxikologischen Bezug hinaus ökologische Basisdaten bei der Definition des Pestizidgrenzwertes im Roh- und Trinkwasser benötigt. Ergebnisse einzelner Freiland-experimente in Flüssen und Seen lassen den Schluß zu, daß dies schon heute zu teilweise niedrigeren Pestizidgrenzwerten als den in der Trinkwasser-Direktive angegebenen führen würde. Berücksichtigt man weiterhin die natürlichen Zeitmaße, innerhalb derer sich Veränderungen in Ökosystemen bemerkbar machen und die gegebenenfalls — wenn überhaupt möglich — zur Reparatur anthropogen verursachter Schäden nötig sind, sowie die Komplexität und Offenheit von Ökosystemen, so sind Grenzwerte mit dem Anspruch der vollständigen Erfassung der Einflüsse von Pestiziden in einem Ökosystem wissenschaftlich nicht zu ermitteln. Stattdessen müssen, analog zum gesundheitlichen Vorsorgewert der Trinkwasser-Direktive, in den EG-Direktiven mit direktem aquatischem Bezugökologisch orientierte Vorsorgewerte verankert werden. Solange die ökologische Ausrichtung dieser Direktiven nicht gewährleistet und das Ergebnis in Form entsprechender maximaler Soll werte nicht rechtlich verankert ist, muß ersatzweise dergesundheitliche Vorsorgewert der EG-Trinkwasser-Driektive, obgleich ökotoxikologisch kaum abgesichert, beibehalten werden.

Effect of methoxyethanol, cyclophosphamide and cadmium on metallothionein levels during prenatal development in the mouse.

Three known teratogenic agents--methoxyethanol (ME), cyclophosphamide (CP) and cadmium (Cd)--are possible inducers of metallothionein (MT) in the embryo and/or in the fetus. Their effect on the MT levels of forelimbs, brain and liver during prenatal development and in dams liver was studied in the mouse to elucidate whether MT could be used as an early biochemical indicator of teratogenicity. Pregnant mice were injected with 2 doses of each teratogen at different days of the middle gestational phase and their embryos and fetuses were obtained thereafter. Quantitative estimation of MT in the S9 from homogenates of the embryo/fetal tissues and organs and maternal liver showed major alterations in the dams hepatic MT content but only small changes in prenatal MT levels. These results do not support MT as an early indicator of teratogenicity. However, a causal relationship between the maternal MT changes induced by the tested agents and their teratogenic effect could be possible.

The ex-vivo intestinal absorption rate of uranium is a two-phase function of supply

The concentration-dependent absorption behaviour of uranium was investigated with surviving intestinal segments of rat jejunums, using an ex-vivo model. The results showed a monotonic slightly nonlinear increase in absorption as uranium concentrations increased. This trend was observed over the entire concentration range tested. In the lower concentration range a slower linear ascent was observed while a steeper linear ascent was found for the higher concentration range. Statistical fit was only slightly poorer for an exponential function in the range of lower values and a logarithmic function in the range of higher values. The proportion of uranium absorbed expressed as percent of uranium concentrations in the perfusion solutions followed a monotonically increasing trend from 20 to around 200 μg/l uranium in the perfusion solutions, which thereafter appears to reach a plateau, as further increase towards concentrations around 400 μg/l is not substantial. The uranium concentration administered had no effect on the vitality and consequently the functionality of the intestinal segments, measured in terms of active glucose transport. The results imply that uranium concentrations of more than 20 μg/l in drinking water, for example, could lead to elevated absorption rates and thus to higher internal exposures to consider when setting of Guideline values in this concentration range.

Role of Copper and Other Transition Metal Ions in the Pathogenesis of Parkinson’s Disease, Prion Diseases, Familial Amyotrophic Lateral Sclerosis, and Alzheimer’s Disease

During the last few years, there has been growing evidence based on experimental data that Cu and other transition metal ions may have important roles in the pathogenesis of a series of hereditary and sporadic disorders of the central nervous system (CNS). It is suggested that metal ions such as Cu exert toxicity during electron-transfer reactions and also play a structural role by changing the conformation of proteins upon specific binding. In contrast, Zn is assumed to play a purely structural role because it exists exclusively in one oxidation state. According to presently accumulating knowledge, Cu complexes are especially sensitive to redox reactions (in the form of “free”) -Cu ions in the Fenton-type reaction). On the other hand, copper is an essential element—being a cofactor of detoxifying enzymes such as of Cu/Zn-superoxide dismutase (SOD). According to the high-affinity binding of Cu to the native amyloid precursor protein (APP) and the prion protein (PrP), Cu is suggested to exert conformation stabilizing functions, to act as a redox active detoxifying cofactor, and is involved in metabolic transport (APP) or absorption-secretory (PrP and APP) functions. Currently, there are no data to confirm the hypothesis that an enhanced exogeneous exposure to Cu (or other transition metal ions) may accelerate the progression of neurodegenerative diseases or even to show a significant association with increased metal-ion levels in general, or what may occur with a higher frequency in response to exogenous exposure. In contrast, a causal relationship has been shown for neurodegenerative symptoms and chronic inhalatory exposure of Mn because of its unique ability to cross the blood-brain barrier via the olfactory epithelium.

Environmental hygiene and management of chemicals.

Limit values (LVs) are legal concentration limits for constituents, residues and contaminants in consumer products or for emissions from production processes into environmental compartments. They are a traditional regulatory aid to manage chemicals in human environments. To make them proactive, LVs should become enforced by means of a transparent and informed decision process whose starting point is the Basic Rule of Environmental Hygiene, BREH:Avoid useless exposure as far as possible, minimize useful exposure in a reasonable manner, and prevent that exposure which is dangerous. The BREH calls upon minimizing exposure not only according toon site risk potentials and acceptance, but also tooff site avoidability and acceptability.Limit values (LVs) are legal concentration limits for constituents, residues and contaminants in consumer products or for emissions from production processes into environmental compartments. They are a traditional regulatory aid to manage chemicals in human environments. To make them proactive, LVs should become enforced by means of a transparent and informed decision process whose starting point is the Basic Rule of Environmental Hygiene, BREH:Avoid useless exposure as far as possible, minimize useful exposure in a reasonable manner, and prevent that exposure which is dangerous. The BREH calls upon minimizing exposure not only according to on site risk potentials and acceptance, but also to off site avoidability and acceptability.