Plant lectins ConBr and CFL modulate expression toll-like receptors, pro-inflammatory cytokines and reduce the bacterial burden in macrophages infected with Salmonella enterica serovar Typhimurium.

BACKGROUND

Plant lectins have long been used in biomedical research as immunomodulators against tumor cells and microbial infections.

OBJECTIVE

To test the ability of plant lectins ConBr (Canavalia brasiliensis) and CFL (Cratylia argentea) to activate antimicrobial and immunomodulatory activities of murine peritoneal macrophages (pMØ) infected with a virulent strain of Salmonella enterica serovar Typhimurium (STm).

METHODS

We incubated pMØ with non-toxic amounts of ConBr and CFL either before (preventive schedule) or after (curative schedule) exposure to STm.

RESULTS

In uninfected pMØ, ConBr and CFL greatly increased levels of mRNA transcripts for IL-1β, TNF-α and IL-6 and the inducible nitric oxide synthase (iNOs), but not IL-10 and IL-12. Exposure to naïve splenocytes of culture supernatants of pMØ previously stimulated with CFL resulted in expression of IL-12 and IFN-γ. Both preventive and curative treatment schedules significantly reduced the intracellular load of Salmonella. Experiments in infected macrophages exposed to lectins in the preventive schedule showed that mRNA transcripts for IL-6 and TNF-α were increased by CFL, whereas ConBr enhanced IL-12 (subunit p40). In the curative schedule, CFL induced significant expression of IL-12 (p40) whereas ConBr enhanced expression IL-1β and TNF-α genes. The lectin treatments did not influence on iNOs expression in pMØ infected with STm C5 regardless of the treatment schedule. Curative treatments with CFL increased approximately 130-fold expression of TLR-4 whist expression of TLR-9 was increased by treatments with ConBr.

CONCLUSIONS

We conclude that lectins ConBr and CFL have immunomodulatory properties that are beneficial on control of cells infected by Salmonella.