Oxidized lipoproteins inhibit TNF-alpha secretion by human THP-1 macrophage
s due, at least in part, to aldehydes derived from the oxidation of polyuns
aturated fatty acids. This study extends these findings by investigating th
e effect of three aldehydes (2,4-decadienal (2,4-DDE), hexanal and 4-hydrox
ynonenal (4-HNE)) on TNF-alpha and IL-1 beta mRNA expression. The 2,4-DDE a
nd 4-HNE showed considerable biological activity which induced cytotoxicity
on THP-1 macrophages at concentration of 50 muM. Hexanal, on the other han
d, had a lower cytotoxic capacity and concentration of 1000 muM was needed
for the effect to be observed. Exposure of THP-1 macrophages to aldehydes f
or 24 h inhibited TNF-alpha mRNA expression but increased or did not affect
IL-1 beta mRNA levels. The inhibitory action of 2,4-DDE was dose dependent
and began at 5 muM (46%, P < 0.001). The effect of 4-HNE was less inhibito
ry than 4-DDE but only when cytotoxic concentrations were used (50 muM). Ve
ry high concentrations of hexanal (200 muM) were needed to inhibit TNF-alph
a expression (23%, P < 0.001). This downregulation of TNF-alpha gene expres
sion by 2,4-DDE was parallel to a lower protein production. These data indi
cate that low levels of 2,4-DDE may modulate inflammatory action by inhibit
ing TNF-alpha mRNA gene expression and that the biological activity of 2,4-
DDE may be involved in the development of atherosclerosis. (C) 2001 Elsevie
r Science Ireland Ltd. All rights reserved.