Abstract
The mechanisms associated with metallothionein (MT) gene regulation are complex and poorly understood. Only a modest increase in brain MT expression levels is attained by exposure to metals, MT gene transfection, and MT gene knock-in techniques. Accordingly, in the present study, MT null astrocytes isolated from transgenic mice deficient in MT-I and MT-II genes were introduced as a zero background model of MT expression. MT protein levels were determined by western blot analysis. MT proteins in MT-I and MT-II null astrocytes were undetectable. Transient MT-I gene transfection increased the levels of foreign MT expression in MT-I and MT-II null astrocytes by 2.3-fold above basal levels in wild-type astrocytes. Intracellular Na251CrO4 efflux and D-[2,3-3H]aspartate uptake were studied as indices of acute methylmercury (MeHg) (5 μM) cytotoxicity. In MT-I and MT-II knockout astrocytes MeHg led to significant (p < 0.01) increase in Na251CrO4 efflux and a significant (p < 0.05) decrease in the initial rate (1 min) of D-[2,3-3H]aspartate uptake compared to MT-I and MT-II knockout controls. Transfection of the MT-I gene in MT-I and MT-II null mice significantly (p < 0.01) decreased the effect of MeHg on Na251CrO4 efflux in MT null, as well as wild-type astrocytes. MT-I gene transfection in MT-I and MT-II null astrocytes reversed the inhibitory effect of MeHg on D-[2,3-3H]aspartate uptake, such that initial rates of uptake in MT-I transfected cells in the presence and absence of MeHg (5 μM) were indistinguishable. These results demonstrate that: (1) astrocytes lacking MTs are more sensitive to MeHg than those with basal MT protein levels, (2) the MT-I gene can be overexpressed in MT-I and MT-II null astrocytes by transient MT-I gene transfection, and (3) that foreign MT expression endows astrocytes with increased resistance to MeHg. (C) 2000 Elsevier Science B.V.
Original language | English (US) |
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Pages (from-to) | 32-38 |
Number of pages | 7 |
Journal | Brain research |
Volume | 855 |
Issue number | 1 |
DOIs | |
State | Published - Feb 7 2000 |
Externally published | Yes |
Keywords
- Knock-in
- Knockout
- MT-I and MT-II null astrocytes
- Metallothionein
- Methylmercury
- Transgenic mouse
ASJC Scopus subject areas
- General Neuroscience
- Molecular Biology
- Clinical Neurology
- Developmental Biology