Metal elements and gene expression.

The transcriptional regulation of genes by metals is a biological function separate from structural and catalytic roles for metals in gene expression. Each of these functions relies on metals that enter cells from metabolic compartments derived from and influenced by the dietary metal supply. The intracellular metal pools provide an available source for binding to metalloregulatory proteins for transcriptional regulation.

Amino acid substitutions in HIV-1 reverse transcriptase with corresponding residues from HIV-2. Effect on kinetic constants and inhibition by non-nucleoside analogs.

Nevirapine is a highly potent and specific inhibitor of human immunodeficiency virus type 1 (HIV-1) polymerase, but is inactive against HIV-2 and other polymerase. Previous studies demonstrated that residues 176-190 of HIV-1 reverse transcriptase (RT) can confer nevirapine sensitivity to HIV-2 RT. To better characterize the role of this sequence in HIV-1 RT, we have progressively substituted residues 176-190 of HIV-2 RT for those of HIV-1 RT and monitored the impact on the kinetic properties; inhibitory activity of nevirapine (11-cyclopropyl-5,11-dihydro-4-methyl-6H-dipyrido[2,3-b:2',3'-e] [1,4]diazepin-6-one), E-BPU (5-ethyl-1-benzyloxymethyl-6-(phenylthio)-uracil), and TIBO-R82150 ((+)-S-4,5,6,7-tetrahydro-5-methyl-6-(3-methyl-2-butenyl)imidazo[4,5,1-j k] [1,4]benzodiazepin-2(1H)-thione); and inhibitor-induced fluorescence changes of the mutant enzymes.

Malabsorption of zinc in rats with acetic acid-induced enteritis and colitis.

Acute intestinal inflammation was established in rats by intraluminal administration of acetic acid into loops of distal ileum, proximal jejunum or ascending colon. The study included two control groups of intact (untreated) rats and sham-operated (saline-treated) rats for each intestinal segment. A third group of rats received acetic acid.

Zinc metabolism and metallothionein expression in bone marrow during erythropoiesis.

Zinc metabolism and metallothionein induction in rat bone marrow were investigated during induced erythropoiesis. Redistribution of body zinc was measured with 65Zn after acute blood loss in rats fed zinc-restricted or zinc-adequate diets. Uptake of 65Zn by bone marrow was related to time after blood loss, metallothionein induction, and dietary zinc status.

Metallothionein expression in rat bone marrow is dependent on dietary zinc but not dependent on interleukin-1 or interleukin-6.

The comparative influence of dietary zinc status and recombinant human interleukin-1 alpha (rhIL-1 alpha) and recombinant human interleukin-6 (rhIL-6) on metallothionein (MT) gene expression was examined in rat bone marrow and liver. Growing male rats were fed a diet with 5 (restricted), 30 (control), or 180 (supplemented) mg Zn/kg for 14 d. On d 15, rats were injected with 5 micrograms of rhIL-1 alpha or rhIL-6.

Regulation of cysteine-rich intestinal protein by dexamethasone in the neonatal rat.

The cysteine-rich intestinal protein (CRIP) is an intestinal zinc-binding protein containing a single copy of a cysteine-rich domain known as the LIM motif. CRIP mRNA and protein levels increased in the rat small intestine throughout the suckling period, reaching highest levels by the late weanling stage. A similar developmental pattern of CRIP protein levels was also detected by an increase in zinc binding to CRIP-containing HPLC fractions of intestinal cytosol.

Cloning of rat intestinal mRNAs affected by zinc deficiency.

Male rats were fed a purified diet containing 1 mg Zn/kg to induce zinc deficiency (-Zn). A second set of rats were fed a 30 mg Zn/kg diet, which supplied adequate levels of zinc (+Zn). The zinc-adequate rats were pair-fed to the rats fed the 1 mg Zn/kg diet to eliminate differences in diet intake.

Erythrocyte metallothionein response to dietary zinc in humans.

The response of erythrocyte metallothionein to dietary zinc in human subjects was evaluated in a controlled metabolic protocol including standard indices of zinc status. Fifteen male subjects, age 27 +/- 3.6 y, participated in a 90-d, four-phase study consisting of acclimation (7 d; 15 mg Zn/d), treatment (6 wk; either 3.

Altered zinc metabolism occurs in murine lethal milk syndrome.

The lethal milk (lm) mutation in mice causes Zn deficiency in pups nursed by lm dams. To examine tissue Zn distribution and Zn transport to milk and pups, 65Zn was administered to lactating normal and lm dams. Transport of 65Zn to milk of lm dams was approximately 50% of that transported to milk of normal dams.

Treatment of Wilson's disease with zinc: X. Intestinal metallothionein induction.

Oral zinc therapy is effective in controlling copper balance in patients with Wilson's disease and blocks the intestinal absorption of copper, as demonstrated by uptake of copper 64 and copper balance measurements. In this study, 64Cu uptake measurements were concomitantly carried out with intestinal biopsies to investigate the relationship of reduced copper absorption to the levels of intestinal metallothionein in patients with Wilson's disease at different stages of zinc therapy. A pronounced increase in intestinal metallothionein levels and a sharp drop in 64Cu absorption were found 4 to 5 days after the initiation of zinc treatment.

Mechanisms of caeruloplasmin biosynthesis in normal and copper-deficient rats.

To examine the mechanisms of holo-caeruloplasmin biosynthesis, we measured the serum caeruloplasmin concentration and oxidase activity, hepatic caeruloplasmin mRNA content and hepatocyte caeruloplasmin biosynthesis and secretion in normal and copper-deficient rats. Copper deficiency resulted in a near-complete loss of serum caeruloplasmin oxidase activity, yet only a 60% reduction in serum caeruloplasmin concentration and no change in the abundance of hepatic caeruloplasmin mRNA or the rate of caeruloplasmin biosynthesis. Both interleukin-1 alpha and lipopolysaccharide increased hepatic caeruloplasmin mRNA content and caeruloplasmin biosynthesis in normal and copper-deficient animals, but neither mediator increased caeruloplasmin oxidase activity in the copper-deficient group.

Cysteine-rich intestinal protein and intestinal metallothionein: an inverse relationship as a conceptual model for zinc absorption in rats.

Dietary zinc may regulate zinc absorption in part via the inhibitory effect of intestinal metallothionein, but the mechanism is unknown. We recently showed that cysteine-rich intestinal protein (CRIP) binds zinc during transmucosal zinc transport, and that CRIP may function as an intracellular zinc carrier. The present experiments examine the interaction of CRIP and metallothionein with zinc to evaluate their potential roles in the mechanism of zinc absorption.

Nuclear zinc uptake and interactions and metallothionein gene expression are influenced by dietary zinc in rats.

Regulation of metallothionein gene expression by dietary zinc and the relationship of dietary zinc to nuclear zinc uptake was examined in growing rats. Zinc was fed at 5, 30 or 180 mg/kg, either in pelleted form for a 2-wk period (ad libitum) or for 2 h as a liquefied preparation (1 g in 4 mL). Two hours after the oral dose, the intestine and liver took up more zinc than other tissues.

Cysteine-rich intestinal protein binds zinc during transmucosal zinc transport.

The mechanism of zinc absorption has not been delineated, but kinetic studies show that both passive and carrier-mediated processes are involved. We have identified a low molecular mass zinc-binding protein in the soluble fraction of rat intestinal mucosa that could function as an intracellular zinc carrier. The protein was not detected in liver or pancreas, suggesting a role specific to the intestine.

Intestinal metallothionein gene expression and zinc absorption in rats are zinc-responsive but refractory to dexamethasone and interleukin 1 alpha.

The effects of dexamethasone and interleukin 1 alpha on intestinal metallothionein gene expression and zinc absorption were studied. Rats given parenteral zinc served as positive controls. A single intraperitoneal or intravenous dose of dexamethasone, interleukin 1 alpha or zinc markedly increased liver metallothionein synthesis 3-9 h after injection.

Maintenance of zinc-dependent hepatic functions in rat hepatocytes cultured in medium without added zinc.

Hepatocytes were cultured with Waymouth's media containing zinc at concentrations of 1 (the endogenous zinc concentration of basal medium), 16 and 48 mumols Zn/L to examine the effects of extracellular zinc on a variety of zinc-related functions. The zinc concentrations were chosen with the intention of simulating zinc-deficient, adequate and excess extracellular conditions. Basal medium had no effect on cell zinc, metallothionein (MT) or MTmRNA for up to 48 h but reduced delta-aminolevulinic acid dehydratase (delta-ALA-D) activity to 75% of the initial level by 3 h.