Differential Effects of the Toll-like Receptor 2 Agonists, PGN and PAM3CSK4, on Substance P-Induced Human Mast Cell Activation

• Published in: European journal of inflammation Vol. 11; no. 3; pp. 709 - 718
• Main Authors: Yu, Y.Y., Yip, K.H., Tam, I.Y.S., Sam, S.W., Ng, C.W., Lau, H.Y.A.
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.09.2013; SAGE PUBLICATIONS, INC; SAGE Publishing
• Subjects: mast cells; substance P; G protein; toll-like receptor 2
• ISSN: 2058-7392; 1721-727X; 2058-7392
• DOI: 10.1177/1721727X1301100314

Mast cells play important roles in innate immunity through their activation via toll-like receptors (TLRs) but also contribute to neuroimmunological responses and inflammation through their activation by the neuropeptide substance P (SP) via Gαi/o proteins. This study aims to compare the effects of the TLR2 agonists peptidoglycan (PGN) and tripalmitoyl-S-glycero-Cys-(Lys)4 (Pam3CSK4) on SP-induced human mast cell activation. The human mast cell line LAD2 was employed and mast cell activation was determined by assays of β-hexosaminidase, IL-8 and intracellular calcium. TLR2 agonists did not cause degranulation, but induced the release of IL-8. Pretreatment of PGN and Pam3CSK4 inhibited SP induced degranulation but only Pam3CSK4 blocked SP induced calcium mobilization. SP-induced IL-8 release was synergistically enhanced by PGN but abolished by Pam3CSK4. Studies with inhibitors of key enzymes implicated in mast cell signaling revealed that synergistic release of IL-8 induced by PGN and SP involved calcineurin, ERK, NF-κB and PI3K signaling cascades whereas Pam3CSK4 inhibited SP induced mast cell activation by interfering with the interaction between SP and Gαi/o proteins. These findings suggest that activation of human mast cells can be differentially modified by TLR2 agonists via distinct signaling pathways through facilitating formation of different TLR2 heterodimers with other TLRs.