Inhibition of the MyD88/NF-κB pathway alters the Th1/Th2 balance to exacerbate liver injury and hepatic fibrosis in alveolar echinococcosis

Abstract

Alveolar echinococcosis (AE) is a severe human-veterinary parasitic disease. However, the Myeloid differentiation factor 88 (MyD88) signaling pathway has seldom been explored in the context of AE. Protoscoleces (PSC) of alveolar echinococcosis were obtained from the liver tissues of gerbils for breeding purposes, and then used to establish a mouse model of alveolar echinococcosis. This mouse model was utilized to block the MyD88 signaling pathway, with the aim of analyzing the associated fibrotic and inflammatory responses. To evaluate the expression of fibrotic molecules, Masson staining and Quantitative reverse transcription polymerase chain reaction (qRT-PCR) were performed. Moreover, qRT-PCR and Western blotting (WB) were adopted to investigate the alterations in the protein expression levels of MyD88 and Nuclear factor-κB p65 (NF-κB p65). In parallel, the human monocyte cell line RAW 264.7was cultured in vitro. After stimulation of RAW 264.7 with Echinococcus multilocularis protein (Emp), the MyD88 signaling pathway was blocked using TJ-M2010-5. Subsequently, the protein and mRNA expression levels of MyD88 and NF-κB p65 were determined by WB and qRT-PCR, respectively, while the dynamic changes in the proportion of macrophages were monitored by flow cytometry. The results demonstrated that the compound TJ-M2010-5 could effectively suppress the MyD88 signaling pathway, leading to a significant down-regulation of the expression levels of both MyD88 and Nuclear factor-κB p65 (NF-κB p65). Moreover, the blockade of the MyD88 signaling pathway perturbed the balance of the Th1/Th2 immune response. Consequently, this imbalance further aggravated liver fibrosis and liver injury. The blockade of the MyD88 signaling pathway led to a disruption of the balance among T-lymphocyte subpopulations, an enhancement of Th2 type immune responses, and a reduction in pro-inflammatory responses. These alterations ultimately culminated in aggravated liver injury and fibrosis in the context of alveolar echinococcosis.