Sesamol protects against LPS-induced inflammation in rat peritoneal macrophages by promoting SIRT1-induced repression of NF-κB.

Objectives: Sesamol, a polyphenolic compound isolated from roasted sesame seeds exhibits significant anti-inflammatory effect, but the molecular mechanism is poorly understood. Peritoneal macrophages play a pivotal role in the control of infections and inflammatory pathologies and are also found in injured tissues along with resident macrophages. The present study aimed to examine the anti-inflammatory effect of sesamol and the molecular mechanisms involved, particularly the role of sesamol in modulating SIRT1- and SIRT1-mediated deacetylation of NF-κB p65 using in vivo activated peritoneal macrophages.

Materials: Sprague Dawley rats were injected with LPS to induce inflammation and sesamol was intraperitoneally administered to study its anti-inflammatory effect. ELISA and real time PCR were used to study the expression of proinflammatory cytokines. Effects of sesamol on iNOS and COX-2 were studied with activity assays and ELISA. ICAM-1, MMP-9 and TIMP-1 expressions were analysed by ELISA, RT PCR and zymography. Western blot analysis was performed to determine p65 acetylation. Nuclear translocation of p65 was evaluated by ELISA. The gene and protein expression of SIRT1 was analysed with ELISA and real time PCR.

Results: Sesamol downregulated the expression of proinflammatory markers TNF-α, IL-6, iNOS, COX-2, TLR-4, ICAM-1 and MMP-9 in rat peritoneal macrophages. Additionally, sesamol upregulated SIRT1expression and attenuated the nuclear translocation of NF-κB p65 by promoting its deacetylation. Inhibition of SIRT1 by its specific inhibitor EX527 diminished the inhibitory effect of sesamol on TNF-α and IL-6. Moreover, EX527 reduced the suppressive impact of sesamol on p65 acetylation and subsequent nuclear translocation.

Conclusion: Our findings suggest that the anti-inflammatory effect of sesamol involves upregulation of SIRT-1, leading to the downregulation of the nuclear translocation of NF-κB p65 through its deacetylation. Therefore, the dietary bioactive compound sesamol shows potential as a promising strategy for preventing inflammatory diseases by modulating SIRT1 expression.