Docosahexaenoic acid (DHA)-derived DHA generated 4-hydroxy hexenal (4-HHE) inhibits the expression of Mcp-1 Messenger RNA (mRNA), but induces heme oxygenase 1 (Hmox-1) mRNA in rat aorta. Rat arterial strips were treated with bovine serum albumin (BSA), DHA (50–100 μM), EPA (50–100 μM) or 4-HHE (25–50 μM) for 6 h under ex vivo conditions. (A,B) Relative mRNA expression of Mcp-1 (A) and Hmox-1 (B) in arterial strips was quantitated using the real-time quantitative polymerase chain reaction (RT-qPCR). Results were normalized against 18S rRNA and expressed as fold increase over control. (C) 4-HHE and 4-HNE content were measured by a liquid chromatography-tandem mass spectrometry (LC-MS/MS). (D,E) Relative mRNA expression of Mcp-1 (D) and Hmox-1 (E) in arterial strips was quantitated using RT-qPCR. Results were normalized as above. Results are expressed as mean ± SE of 4–8 animals (n = 3–22; A,B,D,E), or a single experiment (n = 3; C). * P < 0.05, *** P < 0.001, compared with BSA control. NS, no significant difference.