Metallothionein (MT‐1) siRNA compromises the efficacy of Zn to ameliorate stress‐modulation of choline transport in choroid plexus

We have shown in primary cultures of neonatal rat choroid plexus that cadmium (Cd) induces oxidative stress and stimulates apical choline uptake. Glutathione (GSH) supplementation negates changes in redox state and choline uptake. Zinc (Zn), a trace mineral normally accumulated by choroid plexus ameliorates oxidative stress and stress‐modulation of choline uptake. We hypothesize that Zn abates oxidative stress and stress‐modulation of choline uptake via induction of MT‐1. Thus, in choroid plexus primary cultures we evaluated the effects of GSH depletion and silencing of MT‐1 gene expression on the efficacy of Zn to disrupt Cd‐induced modulation of apical 3 H‐choline uptake (10 μM, 30 min). Cells were supplemented with Zn (≤25 μM, 48 h) ± 100 μM buthionine sulfoximine (BSO) before 12‐h exposure to 500 nM Cd. Cd stimulated choline uptake by 78%; Zn attenuated stimulation irrespective of BSO treatment. Cells then were transfected with MT‐1 siRNA; this reduced MT‐1 RNA expression by 75%. In untreated cells, Cd stimulated choline uptake by 60%, and Zn abated stimulation; negative siRNA transfection did not alter modulation of uptake by either Cd or Zn. However, in cells transfected with MT‐1 siRNA Cd stimulated choline uptake by 100%, and Zn failed to abate stimulation. These preliminary data suggest the efficacy of Zn to disrupt stress‐modulation of choline uptake in choroid plexus is dependent on MT‐1 induction.