Journal
GLYCOCONJUGATE JOURNAL
Volume 27, Issue 6, Pages 583-600Publisher
SPRINGER
DOI: 10.1007/s10719-010-9302-5
Keywords
Thymoquinone; Cell signaling; Receptor activation; TOLL-like receptor 4; Neu4 sialidase; Cellular sialidase; NF kappa B; Cytokines
Categories
Funding
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Queen's University Research Award
- Queen's Graduate Awards
- Interuniversitaire Attractiepolen [IAP6/18]
- Fonds voor Weten-schappelijk Onderzoek-Vlaanderen (FWO) [3G010505]
- Ghent University [01G06B6]
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Thymoquinone (TQ) derived from the nutraceutical black cumin oil has been reported to be a novel agonist of Neu4 sialidase activity in live cells (Glycoconj J DOI 10.1007/s10719-010-9281-6). The activation of Neu4 sialidase on the cell surface by TQ was found to involve GPCR-signaling via membrane targeting of G alpha i subunit proteins and matrix metalloproteinase-9 activation. Contrary to other reports, TQ had no anti-inflammatory effects in vitro. Here, we show that MyD88/TLR4 complex formation and subsequent NF kappa B activation are induced by the Neu4 activity associated with TQ-stimulated live primary bone marrow (BM) macrophage cells from WT and Neu1-deficient mice, HEK-TLR4/MD2 cells and BMC-2 macrophage cell line but not with primary macrophage cells from Neu4-knockout mice. Tamiflu (oseltamivir phosphate), pertussis toxin (PTX), a specific inhibitor of G alpha i proteins of G-protein coupled receptor (GPCR) and the broad range inhibitor of matrix metalloproteinase (MMP) galardin applied to live primary BM macrophage cells completely block TQ-induced MyD88/TLR4 complex formation. Using immunocytochemistry and western blot analyses, Tamiflu, galardin and PTX inhibit NF kappa B activation induced by Neu4 activity associated with TQ-stimulated BMC-2 cells, HEK-TLR4/MD2 cells and primary BM macrophages from WT mice. EMSA analyses on HEK-TLR4/MD2 nuclear cell extracts confirm the nuclear localization and DNA binding of TQ-induced NF kappa B activation in a biphasic manner within 30 min. Co-immunoprecipitation experiments reveal for the first time that MMP-9 may be an important intermediate link in the TQ-induced Neu4 activity circuitously targeting TLR4 receptors. Central to this process is that Neu4 forms a complex with MMP-9, which is already bound to TLR4 receptors. Fluorescence spectrophotometer analyses of live CD14-THP1 cells treated with TQ show Neu4 sialidase activity over 5 min. Using flow cytometry analyses, CD14-THP1 cells treated with TQ express stable protein levels of Neu4, TLR4 and MMP9 on the cell surface over 30 min except for a marked diminution of MMP9 at 15 min. Using cytokine array profiling analyses of serum, Neu4-knockout mice respond poorly to TQ in producing pro-inflammatory cytokines and chemokines after 5-h treatment compared to the wild-type or hypomorphic cathepsin A mice with a secondary 90% Neu1 deficient mice. Our findings establish an unprecedented signaling paradigm for TQ-induced Neu4 sialidase activity. It signifies that MMP-9 forms an important molecular signaling platform in complex with TLR4 receptors at the ectodomain and acts as the intermediate link for TQ-induced Neu4 sialidase in generating a functional receptor with subsequent NF kappa B activation and pro-inflammatory cytokine production in vivo.
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