Figure 2. SIRT1 overexpression in MIN6 cells potentiated Zn²⁺ toxicity.

Stably transfected MIN6 cell lines were established which overexpress SIRT1 protein (760% of control). These cell lines were tested for their sensitivity to Zn²⁺ toxicity in the presence or absence of serum. A. SIRT1 overexpressing (SIRT1) and empty vector control (Control) MIN6 cell lines were assayed for their sensitivity to Zn²⁺ in the absence of serum (MS). Cells were grown to 50% confluence exposed as indicated, and cell death determined by propidium iodide staining (5 microg/mL) 20–22 hrs later compared to the complete death induced by 3 millimol/L Zn²⁺ (mean ± SEM, n=12–20 from three independent experiments). B. This cell line was also assayed in the presence of serum (requiring higher Zn²⁺ concentrations) as in A. * signifies difference from Zn²⁺ exposure in Control cultures; # signifies difference from similarly exposed Control cultures; and Δ signifies difference from Zn²⁺ exposure in SIRT1 cultures at P < 0.05. S means sirtinol, uM means micromol/L, Zn means zinc, naph means 2-hydroxynaphthaldehyde.