Abstract

Compared to several other metal ions with similar chemical properties, zinc is relatively harmless. Only exposure to high doses has toxic effects, making acute zinc intoxication a rare event. In addition to acute intoxication, long-term, high-dose zinc supplementation interferes with the uptake of copper. Hence, many of its toxic effects are in fact due to copper deficiency. While systemic homeostasis and efficient regulatory mechanisms on the cellular level generally prevent the uptake of cytotoxic doses of exogenous zinc, endogenous zinc plays a significant role in cytotoxic events in single cells. Here, zinc influences apoptosis by acting on several molecular regulators of programmed cell death, including caspases and proteins from the Bcl and Bax families. One organ where zinc is prominently involved in cell death is the brain, and cytotoxicity in consequence of ischemia or trauma involves the accumulation of free zinc. Rather than being a toxic metal ion, zinc is an essential trace element. Whereas intoxication by excessive exposure is rare, zinc deficiency is widespread and has a detrimental impact on growth, neuronal development, and immunity, and in severe cases its consequences are lethal. Zinc deficiency caused by malnutrition and foods with low bioavailability, aging, certain diseases, or deregulated homeostasis is a far more common risk to human health than intoxication.

Highlights

  • In the periodic table of the elements, zinc can be found in group IIb, together with the two toxic metals cadmium and mercury

  • We will briefly discuss the detrimental effects of zinc deficiency, because, unless they are exposed to zinc in the workplace or by accident, healthy individuals are at far greater risk of suffering from the adverse effects associated with zinc deficiency than from those associated with intoxication

  • Hyperzincuria and a high protein turnover due to increased hemolysis lead to moderate zinc deficiency in these patients, which causes clinical manifestations typical for zinc deficiency, such as growth retardation, hypogonadism in males, hyperammonemia, abnormal dark adaptation, and cell-mediated immune disorder [177] connected with thymic atrophy [178]

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Summary

Introduction

In the periodic table of the elements, zinc can be found in group IIb, together with the two toxic metals cadmium and mercury. Zinc is considered to be relatively non-toxic to humans [1]. In contrast to the other two metals, for which no role in human physiology is known, zinc is an essential trace element for humans, but for all organisms. It is a component of more than 300 enzymes and an even greater number of other proteins, which emphasizes its indispensable role for human health. We will briefly discuss the detrimental effects of zinc deficiency, because, unless they are exposed to zinc in the workplace or by accident, healthy individuals are at far greater risk of suffering from the adverse effects associated with zinc deficiency than from those associated with intoxication

Zinc Homeostasis
Exposure to Zinc
Exposure by Inhalation
Dermal Exposure
Oral Exposure
The Role of Zinc in Cell Death
Impact of Zinc on Apoptosis
Role of Zinc in Neuronal Death
Zinc Deficiency
Findings
Conclusions
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