Protective effect of arctiin against Toxoplasma gondii HSP70-induced allergic acute liver injury by disrupting the TLR4-mediated activation of cytosolic phospholipase A2 and platelet-activating factor

Toxoplasma gondii ( T. gondii )-derived heat shock protein 70 ( T.g. HSP70) is a toxic protein that downregulates host defense responses against T. gondii infection. T.g. HSP70 was proven to induce fatal anaphylaxis in T. gondii infected mice through cytosolic phospholipase A 2 (cPLA 2 ) activated-platelet-activating factor (PAF) production via Toll-like receptor 4 (TLR4)-mediated signaling. In this study, we investigated the effect of arctiin (ARC; a major lignan compound of Fructus arctii ) on allergic liver injury using T.g. HSP70-stimulated murine liver cell line (NCTC 1469) and a mouse model of T. gondii infection. Localized surface plasmon resonance, ELISA, western blotting, co-immunoprecipitation, and immunofluorescence were used to investigate the underlying mechanisms of action of ARC on T. gondii -induced allergic acute liver injury. The results showed that ARC suppressed the T.g. HSP70-induced allergic liver injury in a dose-dependent manner. ARC could directly bind to T.g. HSP70 or TLR4, interfering with the interaction between these two factors, and inhibiting activation of the TLR4/mitogen-activated protein kinase/nuclear factor-kappa B signaling, thereby inhibiting the overproduction of cPLA 2 , PAF, and interferon-γ. This result suggested that ARC ameliorates T.g. HSP70-induced allergic acute liver injury by disrupting the TLR4-mediated activation of inflammatory mediators, providing a theoretical basis for ARC therapy to improve T.g. HSP70-induced allergic liver injury.