The garlic compound Z-ajoene, S-thiolates COX2 and STAT3 and dampens the inflammatory response in RAW264.7 macrophages.

Scope Garlic (Allium sativum) has been used for centuries as both a prophylactic and therapeutic medicinal agent to control inflammation-associated pathologies. To investigate the underlying mechanisms, we established an in vitro inflammatory model using RAW264.7 murine macrophages exposed to low-doses of lipopolysaccharide (LPS) in the presence of the garlic compounds allicin and Z-ajoene, mimicking regular garlic consumption. Methods and results Both allicin and Z-ajoene dampened both transcript and protein expression of the pro-inflammatory cytokines IL1β, IL6 and IL12β, and upregulated the expression of the anti-inflammatory cytokine IL10. Protein arrays of selected secreted inflammatory mediators confirmed that Z-ajoene has a pronounced down-regulatory effect on LPS-induced inflammatory cytokines and chemokines. Many of these proteins are known targets of the transcription factor STAT3; and indeed, Z-ajoene or its analogue dansyl-ajoene (DP) was found to decrease the phosphorylation and nuclear translocation of STAT3, and to covalently modify the protein by S-thiolation at Cys108, Cys367 and Cys687. It was further found that Z-ajoene dose-dependently and non-competitively inhibited the activity of COX2, possibly attributed to S-thiolation at Cys9 and Cys299. Conclusion The characterisation of Z-ajoene's activity of targeting and covalently modifying STAT3 and COX2, both important regulators of inflammation, may contribute to the health benefits of regular dietary garlic consumption. This article is protected by copyright. All rights reserved.