Fe- and Zn-induced inhibition of Cd uptake in human lung cell lines: Speciation studies with H441 and A549 cells

The Influence of Heavy Metals and Trace Elements on Comatose Patients with Severe Traumatic Brain Injury in the First Week of Admission

Purpose

The aim of this study is to investigate the possible role of heavy metals (lead and cadmium) and imbalance of trace elements (chromium, iron, zinc, copper, and manganese) in death among patients with severe traumatic brain injury.

Material and Methods

A case-control study was conducted with 64 comatose patients with severe TBI, in the Department of Anesthesiology and Reanimation, Ibn Sina University Hospital and Hospital of Specialties in Rabat, Morocco; 22 healthy volunteers were recruited in Blood Transfusion Center of Rabat. Blood samples were collected from TBI patients, in the first week (3h after admission and each 48h during one week) and from healthy volunteers one time. Concentration of heavy metals and trace elements in serum was determined by electrochemical atomic absorption spectrometry. Statistical analysis was performed using Statistical software (SPSS) and the cases and controls were compared using the Mann–Whitney U test and Student's t-test for cadmium according to gender and final evolution. A P-value <0.05 was considered to be statistically significant.

Results

Our data showed that the difference of heavy metals concentration (lead and cadmium) between patients and healthy subjects was not statistically significant. However, the difference of some trace elements concentration (iron, copper, chromium, and selenium) between patients and healthy subjects was statistically significant. According to the final evolution, the concentration of manganese was higher in dead patients and statistically significant (p = 0.04) for heavy metals; the concentration of lead was not statistically significant while the concentration in cadmium was statistically significant (p = 0.004). By sex, lead and cadmium were statistically significant, respectively p = 0.02, p = 0.001, and cadmium was higher in women, while lead was higher in men.

Conclusion

Among all studied heavy metals (lead and cadmium) and trace elements (iron, zinc, copper, selenium, chromium, and manganese), manganese and cadmium may play a role in the death of patients from severe traumatic brain injury.

Cadmium

Cadmium is not an essential element for life. It is geologically marginal but anthropogenic activities have contributed significantly to its dispersion in the environment and to cadmium exposure of living species. The natural speciation of the divalent cation Cd2+ is dominated by its high propensity to bind to sulfur ligands, but Cd2+ may also occupy sites providing imidazole and carboxylate ligands. It binds to cell walls by passive adsorption (bio-sorption) and it may interact with surface receptors. Cellular uptake can occur by ion mimicry through a variety of transporters of essential divalent cations, but not always. Once inside cells, Cd2+ preferentially binds to thiol-rich molecules. It can accumulate in intracellular vesicles. It may also be transported over long distances within multicellular organisms and be trapped in locations devoid of efficient excretion systems. These locations include the renal cortex of animals and the leaves of hyper-accumulating plants. No specific regulatory mechanism monitors Cd2+ cellular concentrations. Thiol recruitment by cadmium is a major interference mechanism with many signalling pathways that rely on thiolate-disulfide equilibria and other redox-related processes. Cadmium thus compromises the antioxidant intracellular response that relies heavily on molecules with reactive thiolates. These biochemical features dominate cadmium toxicity, which is complex because of the diversity of the biological targets and the consequent pleiotropic effects. This chapter compares the cadmium-handling systems known throughout phylogeny and highlights the basic principles underlying the impact of cadmium in biology.