Mechanisms of zinc deficiency-induced cell death

Zinc is an essential trace element that is a required co-factor in well over 300 proteins. Thus, zinc-deficient diets are particularly detrimental to health. While the effects of zinc deficiency are well known, the mechanisms responsible for the pathology remain less well characterized. The overall purpose of this dissertation was to investigate some of the mechanisms by which zinc deficiency leads to cell death by examining the mitochondrial involvement in induction of apoptosis. Disruption of mitochondria interrupts pro-survival and cell proliferation pathways, while also leading to release of reactive oxygen species, all of which leads to apoptosis.;We found an increase in the active fragment of PKC-delta, which is known to depolarize the mitochondrial membrane and initiate apoptosis. Addition of rottlerin, a chemical inhibitor of PKC-delta, decreased PKC-delta fragmentation and partially rescued zinc deficient cells from apoptosis. In addition, we observed an attenuation of AKT phosphorylation in zinc deficient cells, a protein responsible for promoting cell proliferation through phosphorylation of p27Kip1, and for cell survival through phosphorylation of the pro-apoptosic protein BAD. Transfection of -Zn cells with a plasmid vector encoding a constitutively active AKT resulted in decreased caspase-3 activity and a 75% increase in cell number relative to mock transfected -Zn cells, but had no impact on cell cycle.;Cells deficient in zinc are characterized by an increase in markers of oxidation. Interestingly, zinc deficient cells have also been shown to accumulate iron, which participates in oxidation reactions through the Fenton Reaction. We showed that the increase in cellular iron is associated with an increase in the Ferritin Light (FtL) chain and a decrease in the Divalent Metal Transporter (DMT)-1, and an increase in the transferrin receptor 1 (TfR1). Regulation of these proteins involved in iron metabolism is conferred by the Iron Regulatory Protein (IRP) 1 and 2, which we observed were differentially regulated during Zn deficiency. The accumulation of IRP2 was attenuated by the addition of the antioxidants N-acetyl cysteine or ascorbate to the zinc deficient medium, which decreased the level of TfR1.