Acrolein-Derived DNA Adduct Formation in Human Colon Cancer Cells: Its Role in Apoptosis Induction by Docosahexaenoic Acid

Abstract

The apoptotic effects of docosahexaenoic acid (DHA) and other ω-3 polyunsaturated fatty acids (PUFAs) have been documented in cell and animal studies. The molecular mechanism by which DHA induces apoptosis is unclear. Although there is no direct evidence, some studies have suggested that DNA damage generated through lipid peroxidation may be involved. Our previous studies showed that DHA, because it is high degree of unsaturation, can give rise to the acrolein-derived 1,N2-propanodeoxyguanosine (Acr-dG) as a major class of DNA adducts via lipid oxidation. As a first step to investigate the possible role of oxidative DNA damage in apoptosis induced by DHA, we examined the relationships between oxidative DNA damage and apoptosis caused by DHA in human colon cancer HT-29 cells. The apoptosis and oxidative DNA damage, including Acr-dG and 8-oxo-deoxyguanosine (8-oxo-dG) formation, in cells treated with DHA and ω-6 PUFAs, including arachidonic acid (AA) and linoleic acid (LA), were measured. DHA induced apoptosis in a dose- and time-dependent manner with a concentration range from 0 to 300 µM as indicated by increased caspase-3 activity and PARP cleavage. In contrast, AA and LA had little or no effect at these concentrations. The Acr-dG levels were increased in HT-29 cells treated with DHA at 240 and 300µM, and the increases were correlated with the induction of apoptosis at these concentrations, while no significant changes were observed for 8-oxo-dG. Because proteins may compete with DNA to react with Acr, we then examined the effects of BSA on the DHA induced apoptosis and oxidative DNA damage. The addition of BSA to HT-29 cell culture media significantly decreases Acr-dG levels with a concomitant decrease in the apoptosis induced by DHA. The reduced Acr-dG formation is attributed to the reaction of BSA with acrolein as indicated by increased levels of total protein carbonyls. Similar correlations between Acr-dG formation and apoptosis were observed in HT-29 cells directly incubated with 0 to 200µM of acrolein. Additionally, DHA treatment increased level of DNA strand breaks and caused cell cycle arrested at G1 phase. Taken together, these results demonstrate the parallel relationships between the Acr-dG level and apoptosis in HT-29 cells, suggesting that the formation of Acr-dG in cellular DNA may contribute to apoptosis induced by DHA.

Acrolein, an Environmental Toxin, Induces Cardiomyocyte Apoptosis via Elevated Intracellular Calcium and Free Radicals

“…It was reported that acrolein caused apoptosis in the colon cancer cells by production of a cellular stress response [23,24]. In this study, we demonstrated that acrolein can cause cardiac myocytes injury and cell death in concentrationdependent manner.…”

Lipid Peroxidation by-Products and the Metabolic Syndrome

“…Acrolein-induced necrosis was described in few studies (Luo et al, 2005), but mitochondrial-driven cell death seems to be the canonical road and was widely studied. Acrolein-induced apoptosis was indeed confirmed in several cell types through DNA fragmentation, phosphatidylserine externalization, poly(ADP-ribose) polymerase cleavage and activation of caspases (Pan et al, 2009;Roy et al, 2010). Last but not least, hydroxyalkenals are potent activators of apoptosis.…”

Analysis of DNA adducts in human samples: Acrolein‐derived exocyclic DNA adducts as an example

“…In a recent study, correlations were established between AdG formation and DHA-induced apoptotic response, by measuring caspase-3 activity and poly(ADP-ribose) polymerase cleavage, as well as cell cycle arrest in human colon cancer cells. These results suggest an association between AdG adduct formation and the protective effect of DHA against colon tumorigenesis [65]. The potential role of AdG as the ''good'' adduct is intriguing.…”