2,4-Decadienal downregulates TNF-α gene expression in THP-1 human macrophages

Oxidized lipoproteins inhibit TNF-α secretion by human THP-1 macrophages due, at least in part, to aldehydes derived from the oxidation of polyunsaturated fatty acids. This study extends these findings by investigating the effect of three aldehydes (2,4-decadienal (2,4-DDE), hexanal and 4-hydroxynonenal (4-HNE)) on TNF-α and IL-1β mRNA expression. The 2,4-DDE and 4-HNE showed considerable biological activity which induced cytotoxicity on THP-1 macrophages at concentration of 50 μM. Hexanal, on the other hand, had a lower cytotoxic capacity and concentration of 1000 μM was needed for the effect to be observed. Exposure of THP-1 macrophages to aldehydes for 24 h inhibited TNF-α mRNA expression but increased or did not affect IL-1β mRNA levels. The inhibitory action of 2,4-DDE was dose dependent and began at 5 μM (46%, P<0.001). The effect of 4-HNE was less inhibitory than 4-DDE but only when cytotoxic concentrations were used (50 μM). Very high concentrations of hexanal (200 μM) were needed to inhibit TNF-α expression (23%, P<0.001). This downregulation of TNF-α gene expression by 2,4-DDE was parallel to a lower protein production. These data indicate that low levels of 2,4-DDE may modulate inflammatory action by inhibiting TNF-α mRNA gene expression and that the biological activity of 2,4-DDE may be involved in the development of atherosclerosis.