Fasciola hepatica Glutathione S-tranferase suppresses the expression of inflammatory cytokines from murine macrophages in vitro and boosts the survival rate of C57Bl/6 mice against lethal doses of lipopolysaccharide

Abstract

Abstract Fasciola hepatica, a world-wide parasitic helminth, is a well-known master of immunomodulation. The survival of this parasite in the mammalian host is highly dependent on its ability to avoid immune responses of the host for which the parasite employs excretory-secretory products (ESPs). Glutathione S-transferase (GST), one of the proteins in the repertoire of parasite ESPs, is an enzyme recognized for its anti-oxidant properties. GST has been studied as a vaccine candidate against animal fascioliasis, but its role in the immunomodulation has been poorly studied. In a previous study, we demonstrated that GST alone incites no activation of the nuclear factor NF-κB, yet it can suppress NF-κB when THP1-CD14 cells are exposed to GST 30 minutes before stimulation with TLR ligands. In this study, we investigate whether GST could exert a similar suppressive effect on NF-κB activation in THP1-CD14 cells when added several hours after TLR-ligand stimulation and if GST is able to suppress the expression of inflammatory cytokines in bone marrow derived macrophages (bmMØs) from naïve mice induced by LPS. Finally, we performed in vivo experiments to investigate whether one 200ug intraperitoneal (IP) injection with GST could increase the survival rate of C57BL/6 mice exposed to a lethal dose of LPS. Our results demonstrate that 10ug of GST on THP1-CD14 cells up to 3 hours after TLR-ligand stimulation significantly suppressed (p≤0.01) NF-kB activation. GST also suppressed the expression of TNF-α and IL-1β cytokines (p<0.05) in bmMØs in a dose dependent manner. Importantly, a single IP injection of GST boosted the survival rate of mice by 80% against lethal doses of LPS, suggesting GST is an anti-inflammatory molecule.