Ethyl linoleate from garlic attenuates lipopolysaccharide-induced pro-inflammatory cytokine production by inducing heme oxygenase-1 in RAW264.7 cells

• Ethyl linoleate from garlic was isolated, and its structure was elucidated by 2D NMR.
• Ethyl linoleate down regulates iNOS and COX-2 expression.
• Ethyl linoleate attenuates pro-inflammatory cytokines.
• These activities were mediated by NF-κB and MAPKs.
• Ethyl linoleate induced HO-1 expression.

In the present study, an essential fatty acid, ethyl linoleate (ELA), was isolated from the cloves of Allium sativum, and its structure was elucidated by NMR and GC-MS analyses. In vitro systems were used to evaluate the anti-inflammatory activity of ELA. Our results indicate that ELA down-regulates inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression and thereby reduces nitric oxide (NO) and prostaglandin E2 production in lipopolysaccharide (LPS)-activated RAW 264.7 cells. Immunofluorescent microscopy and western blot analyses revealed that these effects were mediated by impaired translocation of nuclear factor (NF)-κB and inhibition of phosphorylation of mitogen activated protein kinases. Furthermore, ELA exerted its anti-inflammatory activity by inducing heme oxygenase-1 (HO-1) expression, as determined by HO-1 small interfering (Si) RNA system. Si RNA-mediated knock-down of HO-1 abrogated the inhibitory effects of ELA on the production of NO, TNF-α, IL-1β, and IL-6 in LPS-induced macrophages. These findings indicate the potential therapeutic use of ELA as an anti-inflammatory agent.