Using antiserum against the recombinant isoform 3 of mouse brain metallothionein (MT3), the amount of MT3 protein was determined in whole brain homogenates from the Tg2576 transgenic mouse model of Alzheimer's Disease. Twenty-two month old transgenic positive mice showed a 27% decrease of MT3 normalized to the total protein in the extracts compared to same age, control transgenic negative mice. Metallothioneins bind seven molar equivalents of divalent metal ions per mole of protein so metal levels also were measured in these whole brain extracts using inductively coupled plasma atomic absorption (ICP-AA) spectrometry. No significant difference was observed for any metal assayed. Because neuronal nitric oxide synthase (nNOS) is involved in neurodegenerative disease and nitric oxide specifically interacts with MT3, the concentration and total nNOS activity also were evaluated. The transgenic positive mice showed a decrease of 28% in nNOS protein compared to the same age transgenic negative mice. Normalized to the amount of nNOS protein, total NOS activity was higher in the transgenic positive mice. These data showed that protein levels of both MT3 and nNOS were reduced in transgenic positive mice that show many characteristics of Alzheimer's Disease. In vitro studies suggested that MT3 was not a likely candidate for directly affecting nNOS activity in the brain.
Bibliographical noteFunding Information:
This research was supported by funds from the Minnesota Medical Foundation (B.L.M.) and from the Minnesota Medical Foundation and University of Minnesota Graduate School (I.M.A.). Marc A. Denn is thanked for technical assistance with the analysis of metal levels in brain samples. The authors are grateful to Dr. Karen Hsiao-Ashe (University of Minnesota) for providing the Tg2576 mice used in these experiments. Patrick T. McCarthy, Brendan S. Doms, and Andrew A. Davis were participants of the Breck School Advanced Science Research Program (Golden Valley, Minnesota) co-ordinated by Lois Fruen of the Breck School. The authors are grateful to Mrs. Fruen for her efforts.
- Alzheimer's disease
- Nitric oxide synthase
- Transgenic mouse