Entamoeba Histolytica Induces Pro-Inflammatory Mediator Hmgb1 Release In Early Contact With Macrophage

Entamoeba histolytica ( Eh ) is an invasive extracellular parasite that causes amebiasis in ~10% of infected individuals resulting in 10 5 deaths/year. The host and/or parasite factors that influence disease susceptibility remain unknown. Interaction between Eh and host macrophages has been shown to trigger a strong pro‐inflammatory response characterized by IL‐1β and TNF‐α release. High Mobility Group Box1 (HMGB1) is a non‐histone nuclear protein secreted by macrophages upon stimulation with various bacterial, viral and cellular components. HMGB1 binds TLRs (TLR‐2 and 4) and induce pro‐inflammatory responses in neighboring cells. In this study, we investigated whether Eh could trigger the release of the pro‐inflammatory molecule HMGB1 as an early “alarmin” signal and the putative parasitic virulent factors involved. Only stimulation with live Eh but not Eh components triggered prompt (1‐5min) and robust secretion of HMGB1 in human macrophages. This event was contact‐dependent as inhibiting Eh adhesin, Gal‐lectin with exogenous galactose abrogated HMGB1 release. HMGB1 secretion was independent of the major surface virulent factor cysteine proteinase 5 ( Eh CP5) as CP5‐deficient Eh , or cysteine protease inhibitor pretreatment of Wt Eh had no effect. HMGB1 secretion was independent of caspase‐1 activation, as revealed by using pan caspase inhibitor, Z‐VAD‐fmk. Eh ‐induced HMGB1 release upon contact with macrophage acts as a sensor for the host to detect invasive Eh that can attract bystander cells to amplify innate host defenses and/or promote an acute pro‐inflammatory response critical in disease pathogenesis. Grant Support: NSERC