Mechanism of Acrolein Toxicity:The Effect on Epigenetic Changes

Acrolein, an alpha‐beta unsaturated aldehyde and a very reactive toxic compound, is released into the environment from different sources such as combustion of fossil fuel, cigarette smoke, overheating of frying oil, as well as endogenously being produced in body via lipid peroxidation. As a pervasive environmental pollutant, acrolein poses a serious environmental health threat acknowledged by investigators, health, and environmental government agencies. Epigenetics is the modifications in gene expression that do not alter the DNA sequence of a gene. This alteration could occur naturally or by factors such as age, environmental exposure, individual lifestyle, and disease condition. Phosphorylation, Methylations and acetylation are the most common epigenetic changes. N‐ Acetyl cysteine (NAC) is an antioxidant involved in the production of cellular glutathione. The aim of the study was to determine the effect of acrolein on histone phosphorylation, acetylation and methylation in vascular smooth muscle cells (VSMCs) and to establish the beneficial effect of NAC in prevention of acrolein toxicity through blockage of histones modification. VSMCs were treated with 3μg/ml acrolein for 6 hours in the presence and absence of 0.2 mM NAC. At the end of the treatment, cytotoxicity of acrolein was measured using tetrazolium‐calorimetric assay. Additionally, free radical generation was measured by fluorometric methods, histone H3 modification by ELISA kit, and protein expression by western blotting. Results indicated that six‐hour exposure of VSMC to 3μg/ml of acrolein resulted in 99% decrease in cell viability and addition of 0.2Mm of NAC provided complete protection of VSMCs from toxicity caused by acrolein. In the absence of NAC, acrolein increased level of reactive oxygen species (ROS) generation by 85%. Addition of NAC abolished high level of ROS by 75%. ELISA analysis showed acrolein‐induced modification of histones 3 (H3) at different lysine and serine residues including SER‐10P and SER‐28P, K4ME, K9ME, K27ME, K79ME, K9AC, K14AC, K18AC. Western blot analysis of two of these residues indicated 45% increase in Ser10P1, 59% increase in Ser28p1, and addition of NAC decreased these modifications by 86% and 76% respectively. Additionally, we observed a 66% increase in the expression of methylated H3K9 and 66% in acetylated H3k9 protein, which was attenuated by addition of NAC by 71% and 65% respectively. In conclusion, this study revealed that exposure of VSMCs to acrolein causes modification of H3 histones at different residues and NAC is effective in inhibiting the effects of acrolein. Support or Funding Information NIH SC3GM103746‐04