Figure 3. SIRT1 knockdown in MIN6 cells attenuated Zn²⁺ toxicity.

Stably transfected MIN6 cell lines were established which overexpress a small inhibitory RNA to SIRT1 resulting in knockdown of its expression (28% of control). These cell lines were tested for their sensitivity to Zn²⁺ toxicity in the presence or absence of serum. A. Knockdown of SIRT1 (siRNA) and empty vector siRNA control (Control) MIN6 cell lines were assayed as in Figure 1. 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 alone at P < 0.05. $ signifies difference from similarly exposed Control cultures at P < 0.05. S means sirtinol, uM means micromol/L, Zn means zinc, naph means 2-hydroxynaphthaldehyde.