Heme oxygenase-1 mediates the anti-inflammatory effect of propyl gallate in LPS-stimulated macrophages

Abstract

This work aimed to elucidate the anti-inflammatory mechanism of the phenolic antioxidant propyl gallate (PG). PG-induced heme oxygenase-1 (HO-1) mRNA and protein of the RAW264.7 macrophages in time- and concentration-dependent manner. It suppressed induction of inducible nitric oxide synthase (iNOS) and subsequent production of nitric oxide (NO) through the downregulation of iNOS promoter activity in lipopolysaccharide (LPS)-activated macrophages. Western-blot data showed that induction of HO-1 expression was coincident with the anti-inflammatory action of PG. Inhibition of HO-1 activity by Zn(II) protoporphyrin IX (ZnPP), a specific inhibitor of HO-1, or knockdown of the HO-1 by small interfering RNA (siRNA) oligonucleotides significantly blocked suppression by PL on iNOS expression, NO production and NF-κB activation which were elevated in LPS-stimulated macrophages. Collectively, PG shows its anti-inflammatory activity via mediation of HO-1 in an in vitro inflammation model.