Visualization of labile zinc and its role in apoptosis of primary airway epithelial cells and cell lines

Abstract

The respiratory epithelium is vulnerable to noxious substances, resulting in the shedding of cells and decreased protection. Zinc (Zn), an antioxidant and cytoprotectant, can suppress apoptosis in a variety of cells. Here we used the novel Zn-specific fluorophore Zinquin to visualize and quantify labile intracellular Zn in respiratory epithelial cells. Zinquin fluorescence in isolated ciliated tracheobronchial epithelial cells and intact epithelium from sheep and pigs revealed an intense fluorescence in the apical and mitochondria-rich cytoplasm below the cilia. Zinquin fluorescence was quenched by the Zn chelator N,N,N', N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) and increased by the Zn ionophore pyrithione. We also assessed whether changes in intracellular labile Zn would influence susceptibility of these cells to apoptosis by hydrogen peroxide. Our results confirm that Zn deficiency enhanced hydrogen peroxide-induced caspase activation from 1.24 +/- 0.12 to 2.58 +/- 0.53 units. microg protein(-1). h(-1) (P </= 0.05); Zn supplementation suppressed these effects. These findings are consistent with the hypothesis that Zn protects upper respiratory epithelial cells and may have implications for human asthma where there is hypozincemia and epithelial damage.

Zinc Deficiency Mediates Alcohol-Induced Alveolar Epithelial and Macrophage Dysfunction in Rats

“…This pool is much more susceptible to depletion during periods of dietary zinc deficiency. As free zinc can be toxic to some proteins and enzymes, the labile pool is largely bound to zinc-carrying proteins; prominent among these are the metallothioneins, a family of cysteine-rich proteins that bind zinc and other metals (13,24). The movement of zinc across plasma and organellar membranes is tightly regulated by zinc transporters.…”

Measuring steady-state and dynamic endoplasmic reticulum and Golgi Zn 2+ with genetically encoded sensors

“…It is now well established that mammalian cells contain a small but measurable pool of free or labile Zn 2þ in the cytosol that is buffered in the picomolar range (4)(5)(6). Fluctuations in cytosolic Zn 2þ have been shown to influence signaling cascades such as the mitogen activated protein kinase pathway (7), as well as cellular processes such as mitochondrial function (8,9), apoptosis (10,11), and dendritic cell maturation (12). Although many studies have focused on cytosolic Zn 2þ , the overall distribution of zinc at the subcellular level is not well defined.…”

Zinc is Involved in the Expression of a Nuclear-encoded Alternative Oxidase Gene in the YeastHansenula anomala

“…21) Accordingly, to focus on the role of zinc in AO gene expression, we explored the eŠects of pyrithione, which has been used to demonstrate the essential role of zinc in various stages within the cell. 22,23) The present study using pyrithione is theˆrst report on possible involvement of zinc ions in AO gene expression. In the yeast H. anomala, antimycin A3 (AA3)-dependent AO gene expression detected by reverse transcriptase (RT) PCR was suppressed, when certain intracellular metal ions were removed by either membrane-permeable or impermeable chelators added with pyrithione, and was restored by the addition of zinc ions.…”