RAGE-mediated intestinal pro-inflammatory responses triggered by Giardia duodenalis.

Abstract

Giardia duodenalis is a waterborne zoonotic protozoan that causes gastrointestinal inflammation. Giardiasis and metabolic illnesses share features such as chronic inflammation and intestinal symptoms. Receptor for advanced glycation end products (RAGE) signaling plays a role in metabolic illnesses and intestinal inflammatory responses. The presence of protozoan viruses can influence host immunological responses triggered by protozoa. However, these effects of G. duodenalis remain unknown. In this study, mice treated with the RAGE inhibitor FPS-ZM1 showed more severe intestinal damage, including increased intestinal permeability and lesions, compared to that of the untreated group. Next, we found that G. duodenalis infection activated RAGE, leading to increased secretion of pro-inflammatory cytokines, including IL-1 β, IL-6, IL-12, TNF-α and IFN-γ in mouse intestinal epithelial cells. Notably, these pro-inflammatory responses were significantly higher in Giardiavirus (GLV)-free Giardia than those of GLV-containing Giardia, except for IFN-γ. Additionally, lactate dehydrogenase (LDH) release, GSDMD-N cleavage, and the morphological observation of pyroptosis were significantly higher in cells induced by GLV-free Giardia than those infected with GLV-carrying Giardia. Differences were also observed in the MAPK (p-JNK, p-38, p-ERK) and NF-κB pathway activation, as well as reactive oxygen species (ROS) levels, with higher activation in cells infected by GLV-free Giardia, and the ROS was involved in the regulation of p38 MAPK and JNK activation. These findings reveal the potential of RAGE as a target for developing vaccines or drugs, suggesting the differences in the regulation of host immune responses induced by GLV-free Giardia or GLV-containing Giardia, providing new insights for the prevention and treatment of Giardia.