Hemin modulates cytokine expressions in macrophage-derived foam cells via heme oxygenase-1 induction

Lipid-laden foam cells were considered to be targets for therapeutic intervention in atherosclerosis. Several studies proposed new approaches to alter both lipid accumulation and inflammatory responses in macrophages. Finding anti-inflammatory signals during foam cell formation would provide new valid targets for anti-atherosclerotic treatment. The aim of the present study was to see whether oxidized low-density lipoprotein (ox-LDL) can active heme oxygenase (HO)-1 expression level in a human monocyte line, U937 cells, associated with the increase of cytokine secretion. We used hemin (HO-1 activator) and zinc protoporphyrin IX (ZnPP IX, HO-1 inhibitor) to determine the effect of HO-1 on the regulation of cytokine expressions. The results showed that hemin can significantly decrease pro-inflammatory cytokines interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha levels, while enhancing IL-10 production in a dose-dependent manner in U937 foam cells. ZnPP IX did not significantly affect cytokine levels in foam cells. Our present results suggested that HO-1 is an important anti-inflammatory therapeutic target through inhibiting pro-inflammatory cytokines and enhancing anti-inflammatory cytokines for the management of atherogenesis.