Biomarkers of manganese intoxication

Electrophysiological and biochemical response in rats on intratracheal instillation of manganese

Chronic exposure to excess manganese via inhalation of metal fumes causes central nervous system damage. For modelling Mn aerosol inhalation, male Wistar rats were intratracheally instilled with MnCl2 solution (0.5 mg/kg b.w. MnCl2; n=12) 5 days a week for 5 weeks. At the end of the treatment, somatosensory cortical evoked potentials, elicited by double-pulse stimulation, were recorded from the animals in urethane anaesthesia. Body weight gain, organ weights, and Mn level in brain, lung and blood samples were also measured. In brain samples, gene expression level of MnSOD (Mn superoxide dismutase) was determined. The effect of Mn was mainly seen on the evoked potential amplitudes, and on the second:first ratio of these. Tissue Mn concentration was elevated in brain and lungs, but changed hardly in the blood. Relative weight of heart, thymus, lungs and brain was significantly altered. The level of MnSOD transcript in brain tissue decreased. The observed effects showed that Mn had access to the brain and that somatosensory cortical responses evoked by double-pulse stimulation might be suitable biomarkers of Mn intoxication.

Regulation of brain iron and copper homeostasis by brain barrier systems: implication in neurodegenerative diseases

Iron (Fe) and copper (Cu) are essential to neuronal function; excess or deficiency of either is known to underlie the pathoetiology of several commonly known neurodegenerative disorders. This delicate balance of Fe and Cu in the central milieu is maintained by the brain barrier systems, i.e., the blood-brain barrier (BBB) between the blood and brain interstitial fluid and the blood-cerebrospinal fluid barrier (BCB) between the blood and cerebrospinal fluid (CSF). This review provides a concise description on the structural and functional characteristics of the brain barrier systems. Current understanding of Fe and Cu transport across the brain barriers is thoroughly examined, with major focuses on whether the BBB and BCB coordinate the direction of Fe and Cu fluxes between the blood and brain/CSF. In particular, the mechanism by which pertinent metal transporters in the barriers, such as the transferrin receptor (TfR), divalent metal transporter (DMT1), copper transporter (CTR1), ATP7A/B, and ferroportin (FPN), regulate metal movement across the barriers is explored. Finally, the detrimental consequences of dysfunctional metal transport by brain barriers, as a result of endogenous disorders or exogenous insults, are discussed. Understanding the regulation of Fe and Cu homeostasis in the central nervous system aids in the design of new drugs targeted on the regulatory proteins at the brain barriers for the treatment of metal's deficiency or overload-related neurological diseases.

Motor function in adults of an Ohio community with environmental manganese exposure

OBJECTIVES

The objective of the present study was to evaluate motor function in order to assess the effects of long-term, low-level environmental manganese (Mn) exposure in residents of an Ohio community where a large ferro- and silico-Mn smelter has been active for more than 50 years.

METHODS

One hundred residents from the Mn-exposed Ohio community were evaluated using the Unified Parkinson's Disease Rating Scale (UPDRS), a postural sway test, and a comprehensive questionnaire exploring demographics and general health. The results were compared to those of 90 residents from a demographically similar comparison town in Ohio. Mn exposure was assessed using modeled airborne Mn and blood Mn (Mn-B). The UPDRS was employed to evaluate parkinsonian motor features. Postural sway was measured using a CATSYS 2000 (Danish Product Development).

RESULTS

No significant difference between the exposed and comparison groups was evident as to Mn-B, demographics or major health outcomes. The risk of abnormal UPDRS performance using "Motor and Bradykinesia" criteria was increased in the Mn-exposed group after adjustment for potential confounders such as the presence of other neurotoxic metals, factors affecting susceptibility to Mn, potential factors influencing motor performance, and other possible demographic confounders. No participant was diagnosed with clinical manganism by neurological examination. After adjustment for various potential confounders, the Mn-exposed group showed significantly higher postural sway scores under eyes-open conditions than the comparison group.

CONCLUSIONS

Subclinical findings on the UPDRS and postural sway in the Mn-exposed group may possibly reflect early subtle effects of chronic low-level Mn exposure. However, the cross-sectional study design, the small to medium effect sizes, and the little biological plausibility are limiting the possibility of a causal relationship between the environmental Mn-air exposure and the early subclinical neurotoxic effects observed.

Relationship between blood manganese and blood pressure in the Korean general population according to KNHANES 2008

INTRODUCTION

We present data on the association of manganese (Mn) level with hypertension in a representative sample of the adult Korean population who participated in the Korean National Health and Nutrition Examination Survey (KNHANES) 2008.

METHODS

This study was based on the data obtained by KNHANES 2008, which was conducted for three years (2007-2009) using a rolling sampling design involving a complex, stratified, multistage, probability-cluster survey of a representative sample of the noninstitutionalized civilian population of South Korea.

RESULTS

Multiple regression analysis after controlling for covariates, including gender, age, regional area, education level, smoking, drinking status, hemoglobin, and serum creatinine, showed that the beta coefficients of log blood Mn were 3.514, 1.878, and 2.517 for diastolic blood pressure, and 3.593, 2.449, and 2.440 for systolic blood pressure in female, male, and all participants, respectively. Multiple regression analysis including three other blood metals, lead, mercury, and cadmium, revealed no significant effects of the three metals on blood pressure and showed no effect on the association between blood Mn and blood pressure. In addition, doubling the blood Mn increased the risk of hypertension 1.828, 1.573, and 1.567 fold in women, men, and all participants, respectively, after adjustment for covariates. The addition of blood lead, mercury, and cadmium as covariates did not affect the association between blood Mn and the prevalence of hypertension.

CONCLUSION

Blood Mn level was associated with an increased risk of hypertension in a representative sample of the Korean adult population.

Differential transition metal uptake and fluorescent probe localization in hippocampal slices

Metals are taken up by the combined action of metal transporters and ion channels. In this communication we have measured the uptake of the biologically important transition metals Mn, Fe, Co, Ni, Cu, Zn and Cd by rat and mouse hippocampal slices using the fluorescent probes FluoZin-3 (FZ3) and Newport Green (NPG), introduced by acetoxymethyl ester (AM) loading. The combination of metals and probes is also used to attempt to localize cellular sites into which metals translocate. We show that FZ3 and NPG partition into different cellular compartments; FZ3 into neuropil, whereas NPG localizes in neuropil and compartments within the cell bodies of neurons. Ni, Zn and Cd pass across the plasma membrane and then accumulate in intracellular vesicles and within intracellular membranes of cell bodies. The latter accumulate Cd, while synaptic vesicles take up Co. The passage of Mn, Cu and Fe into cells can be detected but there is some uncertainty about their disposition within the cell. All of our experiments are consistent with metals accumulating in intracellular compartments rather than the cytoplasm. Whether and to what extent there are transient elevations of free zinc levels in the cytoplasm remains unclear.