Showing papers by "Graeme Nixon published in 2013"

Marginal dietary zinc deficiency in vivo induces vascular smooth muscle cell apoptosis in large arteries

Abstract: Aims Dietary zinc deficiency has been associated with the development of atherosclerosis although the effects on vascular smooth muscle cells (VSMCs), important in maintaining atherosclerotic plaque integrity, are unknown. The main aim of this study was to elucidate the effect of a zinc-deficient environment on VSMCs using an in vivo model. Methods and results Rats were maintained for 2 weeks on a marginally zinc-deficient diet which resulted in a significant reduction in plasma zinc levels. Large arteries from zinc-deficient rats had significantly increased apoptosis within the VSMC layers compared with arteries from rats on a zinc-adequate diet. This apoptosis occurred in parallel with a known apoptotic pathway, namely dephosphorylation of the pro-apoptotic protein Bcl-2-associated death promoter protein (BAD). Activation of extracellular signal-regulated kinase (ERK)1/2, which maintains BAD phosphorylation as a pro-survival mechanism, was decreased in arteries from zinc-deficient rats. The mechanisms of this in vivo effect were investigated in vitro . Cultured rat VSMCs incubated with plasma from zinc-deficient rats similarly resulted in increased apoptosis in parallel with BAD dephosphorylation and decreased ERK1/2 activation. Further related apoptotic mechanisms induced by plasma from zinc-deficient rats involved a prolonged rise in [Ca2+]i leading to subsequent activation of the phosphatase calcineurin. Calcineurin activation was required to dephosphorylate BAD. In addition, an increase in oxidative stress contributed to the apoptotic effect induced by plasma from zinc-deficient rats. Conclusion In conclusion, a marginally zinc-deficient diet is pro-apoptotic for VSMCs and this may contribute to cardiovascular disease.

Plasma zinc's alter ego is a low-molecular-weight humoral factor

Abstract: Mild dietary zinc deprivation in humans and rodents has little effect on blood plasma zinc levels, and yet cellular consequences of zinc depletion can be detected in vascular and other tissues. We proposed that a zinc-regulated humoral factor might mediate the effects of zinc deprivation. Using a novel approach, primary rat vascular smooth muscle cells (VSMCs) were treated with plasma from zinc-deficient ( 2500 genes, compared to incubation of cells with zinc-adequate rat plasma. We demonstrated that this effect was caused by a low-molecular-weight (∼2-kDa) zinc-regulated humoral factor but that changes in gene expression were mostly reversed by adding zinc back to zinc-deficient plas...