Concanavalin A induced expression of Toll-like receptors in murine peritoneal macrophages in vitro.

The differential expression of Toll-like receptors (TLRs 1-9) and their associated proteins in murine peritoneal macrophages in vitro, on treatment with plant lectin concanavalin A (Con A) has been investigated. It is observed that there is enhanced expression of TLRs 2-9 and downstream molecules--MyD88, IRAK1, TRAF6 and IRF3 in murine peritoneal macrophages on in vitro treatment with Con A. Pretreatment of macrophages with inhibitors of JNK, p38, p42/44 and NF-kappaB, significantly decreased the Con A induced expression of TLRs. When cells are pre-treated with Con A and subsequently treated with TLR ligands--Zymosan A, PolyI:C, LPS, CpG DNA, there is enhanced production of proinflammatory cytokines (TNF-alpha, IL-1beta, IL-12 and IFN-gamma,), nitric oxide and iNOS expression in murine peritoneal macrophages. The results suggest that treatment of macrophages with Con A renders them more susceptible to subsequent activation and induction of proinflammatory cytokines and nitric oxide production by different TLR ligands.