In vitro activity: Sirtinol potently inhibits recombinant yeast Sir2p activity in vitro with IC50 of 68 μM. Unlike TSA, Sirtinol has shown no effect on human HDAC1, indicating that it is a selective sirtuin inhibitor. Unlike TSA, treatment of human primary fibroblasts with Sirtinol does not cause global changes in acetylation of histones and tubulin, nor does it induce a morphological change in the HeLa tumor cell line. Sirtinol treatment at 100 μM for 24 hours causes a sustained growth arrest in MCF-7 and H1299 cells for up to 9 days after Sirtinol withdrawal. Sirtinol treatment induces increased SA-β-gal activity and expression of PAI-1 in both MCF-7 and H1299 cells, more potently than Splitomicin. Sirtinol inhibits colony formation at concentrations of 33 μM and higher in MCF-7 and H1299 cells, more effectively compared with Splitomicin. Sirtinol treatment (100 μM) significantly attenuates both basal and EGF- or IGF-I-stimulated phosphorylation of ERK, JNK/SAPK and p38 MAPK in MCF-7 and H1299 cells. Sirtinol blocks the basal and EGF-stimulated activation of Ras. Consistent, basal and EGF- or IGF-I-stimulated phosphorylation of Raf-1, MEK, SEK1/MKK4 and MKK7 is attenuated in Sirtinol-treated cells. Inhibition of Sirt1 by Sirtinol enhances UV- and H2O2-induced p53 acetylation to enhance cell death in cultured skin keratinocytes. Blocking of Sirt1 by Sirtinol treatment results in a significant inhibition in the growth and viability of human PCa cells while having no effect on normal prostate epithelial cells.

Kinase Assay: 1.5 μg of recombinant human GST-Sirt2 (amino acids 18-340) are incubated at 30°C for 2 hours in 50 μL of assay buffer (50 mM Tris-HCl, pH 8.8, 4 mM MgCl2, 0.2 mM dithiothreitol with different concentrations of Sirtinol, 50 μM NAD, and tritiated acetylated HeLa histones (1000 cpm), purified by acid extraction. HDAC activity is determined by scintillation counting of the ethyl acetate-soluble [3H]acetic acid.

Cell Assay: Cells are grown to 60% confluence and then treated with 30 μM or 120 μM sirtinol for 24 or 48 hours. Cells are trypsinized and collected. The cells are pelleted by centrifugation and resuspended in PBS (120 μL). Trypan blue (0.4% in PBS; 10 μL) is added to a smaller aliquot (10 μL) of cell suspension, and the number of cells (viable unstained and nonviable blue) are counted.

J Biol Chem. 2001 Oct 19;276(42):38837-43; Acta Anaesthesiol Scand. 2008 May;52(5):635-40.