Cadmium exposure is an important problem in human toxicology. A major site of toxicity is the kidney where cadmium causes moderate renal failure including an inability to resorb nutrients such as glucose, phosphate, calcium, and amino acids. In mouse kidney cortical cells, which resemble proximal tubule cells, concentrations of cadmium, which do not affect cell viability, ATP levels, or the activity of the (Na+, K+)-ATPase, inhibit (Na+)-dependent glucose and phosphate co-transport. The cadmium ion apparently acts directly on transporter biochemistry not indirectly through disruption of energy conservation mechanisms. Indeed, cadmium ion down regulates (Na+)-glucose (SGLT1) and (Na+)-phosphate co-transporter mRNA. It has also been found that metallothionein (MT), the principal site of binding of cadmium ion, does not reverse inhibition of SGLT1 by cadmium ion even though it is an effective scavenger for protein-bound cadmium ion. To understand the mechanisms of down regulation of (Na+)-nutrient dependent co transporters involved in cadmium ion nephrotoxicity and their relationship to metallothionein induction and activity as a potent metal binding agent, the following specific aims will be pursued: 1) Define the effects of cadmium ion on SGLT1 hnRNA and mRNA. 2) Determine the rate constants for degradation of SGLT1 mRNA from control and cadmium treated cells. 3) Measure the impact of cadmium ion on SGLT1 protein degradation and synthesis. 4) Establish the relationship between cadmium ion-dependent inhibition of SGLT1 activity and reduction in SGLT1 mRNA. 5) Investigate the mechanism of down-regulation of SGLT1 mRNA concentration-inhibition of SGLT1 promoter-driven luciferase expression. 6) Develop an in vivo model that can be used to assess the significance of the in vitro mechanistic studies. 7) Carry out studies on the effects of cadmium ion on (Na+)-phosphate co transport that parallel aims 1-6. 8) Establish the mechanism of induction of MT mRNA synthesis by cadmium ion and zinc ion. 9) Examine the mechanism of down-regulation of SGLT1 mRNA concentration from a chemical perspective. 10) Probe the metal ion exchange competition between MT and other key molecules interacting with cadmium ion.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES004026-18
Application #
6607145
Study Section
Alcohol and Toxicology Subcommittee 4 (ALTX)
Program Officer
Thompson, Claudia L
Project Start
1987-07-01
Project End
2004-06-30
Budget Start
2003-07-01
Budget End
2004-06-30
Support Year
18
Fiscal Year
2003
Total Cost
$452,545
Indirect Cost
Name
University of Wisconsin Milwaukee
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
627906399
City
Milwaukee
State
WI
Country
United States
Zip Code
53201
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Meeusen, Jeffrey W; Tomasiewicz, Henry; Nowakowski, Andrew et al. (2011) TSQ (6-methoxy-8-p-toluenesulfonamido-quinoline), a common fluorescent sensor for cellular zinc, images zinc proteins. Inorg Chem 50:7563-73
Kothinti, Rajendra; Tabatabai, Niloofar M; Petering, David H (2011) Electrophoretic mobility shift assay of zinc finger proteins: competition for Zn(2+) bound to Sp1 in protocols including EDTA. J Inorg Biochem 105:569-76
Nowakowski, Andrew B; Petering, David H (2011) Reactions of the fluorescent sensor, Zinquin, with the zinc-proteome: adduct formation and ligand substitution. Inorg Chem 50:10124-33
Blodgett, Amy B; Kothinti, Rajendra K; Kamyshko, Ivan et al. (2011) A fluorescence method for measurement of glucose transport in kidney cells. Diabetes Technol Ther 13:743-51
Kothinti, Rajendra K; Blodgett, Amy B; Petering, David H et al. (2010) Cadmium down-regulation of kidney Sp1 binding to mouse SGLT1 and SGLT2 gene promoters: possible reaction of cadmium with the zinc finger domain of Sp1. Toxicol Appl Pharmacol 244:254-62
Ejnik, John; Shaw 3rd, C Frank; Petering, David H (2010) Mechanism of cadmium ion substitution in mammalian zinc metallothionein and metallothionein alpha domain: kinetic and structural studies. Inorg Chem 49:6525-34
Namdarghanbari, Mohammad Ali; Meeusen, Jeffrey; Bachowski, Gary et al. (2010) Reaction of the zinc sensor FluoZin-3 with Zn(7)-metallothionein: Inquiry into the existence of a proposed weak binding site. J Inorg Biochem 104:224-31
Kothinti, Rajendra; Blodgett, Amy; Tabatabai, Niloofar M et al. (2010) Zinc finger transcription factor Zn3-Sp1 reactions with Cd2+. Chem Res Toxicol 23:405-12

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