Among the micronutrients required by humans, zinc has particularly divergent modes of action. cDNA microarray and quantitative PCR technologies were used to investigate the zinc responsiveness of known genes that influence zinc homeostasis and to identify, through global screening, genes that may relate to phenotypic outcomes of altered dietary zinc intake. Human monocytic͞ macrophage THP-1 cells were either acutely zinc depleted, using a cell-permeable zinc-specific chelator, or were supplemented with zinc to alter intracellular zinc concentrations. Initially, genes associated with zinc homeostasis were evaluated by quantitative PCR to establish ranges for fold changes in transcript abundance that might be expected with global screening. Zinc transporter-1 and zinc transporter-7 expression increased when cellular zinc increased, whereas Zip-2 expression, the most zinc-responsive gene examined, was markedly increased by zinc depletion. Microarrays composed of Ϸ22,000 elements were used to identify those genes responsive to either zinc depletion, zinc supplementation, or both conditions. Hierarchal clustering and ANOVA revealed that Ϸ5% or 1,045 genes were zinc responsive. Further sorting based on this pattern of the zinc responsiveness of these genes into seven groups revealed that 104 genes were linearly zinc responsive in a positive mode (i.e., increased expression as cellular zinc increases) and 86 genes that were linearly zinc responsive in a negative mode (i.e., decreased expression as cellular zinc increases). Expression of some genes was responsive to only zinc depletion or supplementation. Categorization by function revealed numerous genes needed for host defense were among those identified as zinc responsive, including cytokine receptors and genes associated with amplification of the Th1 immune response.nutrition ͉ genomics ͉ functional genomics ͉ immunology ͉ microarray

Differential mRNA display and cDNA array analysis have identified zinc-regulated genes in small intestine, thymus and monocytes. The vast majority of the transcriptome is not influenced by dietary zinc intake, high or low. Of the genes that are zinc regulated, most are involved in signal transduction (particularly influencing the immune response), responses to stress and redox, growth and energy utilization. Among the genes identified are uroguanylin (UG), cholecystokinin, lymphocyte-specific protein tyrosine kinase (LCK), T-cell cytokine receptor, heat shock proteins and the DNA damage repair and recombination protein-23B. Zinc transporters (ZnT) help regulate the supply of this micronutrient to maintain cellular functions. Expression of ZnT-1 and -2 is regulated by dietary zinc in many organs including small intestine and kidney. ZnT-4 is ubiquitously expressed but is refractory to zinc intake. Expression of ZnT-1, -2 and -4 changes markedly during gestation and lactation from highly abundant to undetectable. Each ZnT has an endosomal-like appearance in the tissues examined. Upregulation of ZnT-1 and ZnT-2 by dietary zinc strongly implicates these transporters in zinc acquisition and/or storage for subsequent systemic needs. THP-1 cells were used as a model to examine the response of human cells to changes in zinc status. Based on mRNA quantities, Zip1 and ZnT-5 were the most highly expressed. Zinc depletion of these cells decreased expression of all transporters except Zip2, where expression increased markedly. Collectively, these findings provide a genomic footprint upon which to address the biological and clinical significance of zinc and new avenues for status assessment.

Cysteine-rich intestinal protein (CRIP), which contains a double zinc finger motif, is a member of the Group 2 LIM protein family. Our results showed that the developmental regulation of CRIP in neonates was not influenced by conventional vs. specific pathogen-free housing conditions. Thymic and splenic CRIP expression was not developmentally regulated. A line of transgenic (Tg) mice that overexpress the rat CRIP gene was created. When challenged with lipopolysaccharide, the Tg mice lost more weight, exhibited increased mortality, experienced greater diarrhea incidence, and had less serum interferon-gamma (IFN-gamma) and more interleukin (IL)-6 and IL-10. Similarly, splenocytes from the Tg mice produced less IFN-gamma and IL-2 and more IL-10 and IL-6 upon mitogen stimulation. Delayed-type hypersensitivity response was less in the Tg mice. Influenza virus infection produced greater weight loss in the Tg mice, which also showed delayed viral clearance. The observed responses to overexpression of the CRIP gene are consistent with a role for this LIM protein in a cellular pathway that produces an imbalance in cytokine pattern favoring Th2 cytokines.

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