Antimutagenicity of cinnamaldehyde and vanillin in human cells: Global gene expression and possible role of DNA damage and repair

Vanillin (VAN) and cinnamaldehyde (CIN) are dietary flavorings that exhibit antimmagenic activity against mutagen-induced and spontaneous mutations in bacteria. Although these compounds were antimutagenic against chromosomal mutations in mammalian cells, they have not been studied for antimutagenesis against spontaneous gene mutations in mammalian cells. Thus, we initiated studies with VAN and CIN in human mismatch repair-deficient (hMLH1(-)) HCT 116 colon cancer cells, which exhibit high spontaneous mutation rates (mutations/cell/generation) at the HPRT locus, permitting analysis of antimutagenic effects of agents against spontaneous mutation. Long-term (1-3 weeks) treatment of HCT1 16 cells with VAN at minimally toxic concentralions (0.5-2.5 mM) reduced the spontaneous HPRT mutant fraction (MR, mutants/10(6) survivors) in a concentration-related manner by 19-73%. A similar treatment with CIN at 2.5-7.5 mu M yielded a 13-56% reduction of the spontaneous MR Short-term (4-h) treatments also reduced the spontaneous MF by 64% (VAN) and 31% (CIN). To investigate the mechanisms of antimmagenesis, we evaluated the ability of VAN and CIN to induce DNA damage (comet assay) and to alter global gene expression (Affymetrix GeneChip((R))) after 4-h treatments. Both VAN and CIN induced DNA damage in both mismatch repair-proficient (HCT116 + chr3) and deficient (HCT 116) cells at concentrations that were antimutagenic in HCT 116 cells. There were 64 genes whose expression was changed similarly by both VAN and CIN; these included genes related to DNA damage, stress responses, oxidative damage, apoptosis, and cell growth. RT-PCR results paralleled the Affymetrix results for four selected genes (HMOX1, DDIT4, GCLM, and CLK4). Our results show for the first time that VAN and CIN are antimutagenic against spontaneous mutations in mammalian (human) cells. These and other data lead us to propose that VAN and CIN may induce DNA damage that elicits recombinational DNA repair, which reduces spontaneous mutations. (c) 2006 Elsevier B.V. All rights reserved.