The Garlic Compound Z-Ajoene, S-Thiolates COX2 and STAT3 and Dampens the Inflammatory Response in RAW264.7 Macrophages.

Affiliation

Hitchcock JK(1), Mkwanazi N(1), Barnett C(2), Graham LM(3), Katz AA(1)(4), Hunter R(2), Schäfer G(1)(4)(5), Kaschula CH(6).
Author information:
(1)Department of Integrative Biomedical Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa.
(2)Department of Chemistry, University of Cape Town, Rondebosch, Cape Town, 7700, South Africa.
(3)Department of Biomedical Sciences, Cape Peninsula University of Technology, Bellville, 7530, South Africa.
(4)Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town, 7925, South Africa.
(5)International Centre for Genetic Engineering and Biotechnology, Observatory, Cape Town, 7925, South Africa.
(6)Department of Chemistry and Polymer Science, Stellenbosch University, Stellenbosch, 7600, South Africa.

Abstract

SCOPE: Garlic (Allium sativum) has been used for centuries as a prophylactic and therapeutic medicinal agent to control inflammation-associated pathologies. To investigate the underlying mechanisms, an in vitro inflammatory model is established using RAW264.7 murine macrophages exposed to low-doses of lipopolysaccharide (LPS) in the presence of garlic compounds allicin and Z-ajoene (ZA), mimicking regular garlic consumption. METHODS AND RESULTS: Both allicin and Z-ajoene dampen both transcript and protein expression of the pro-inflammatory cytokines IL1β, IL6, and IL12β, and upregulate the expression of the anti-inflammatory cytokine IL10. Protein arrays of selected secreted inflammatory mediators confirm 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 signal transducer and activator of transcription 3 (STAT3); and indeed, Z-ajoene or its analogue dansyl-ajoene is found to decrease phosphorylation and nuclear translocation of STAT3, and to covalently modify the protein by S-thiolation at Cys108, Cys367, and Cys687. Z-Ajoene dose-dependently and non-competitively inhibit the activity of cyclooxygenase 2 (COX2), possibly attributed to S-thiolation at Cys9 and Cys299. CONCLUSION: The characterization 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.