Abstract
Neutrophil defense mechanisms include phagocytosis, degranulation and the formation of extracellular traps (NET). These networks of DNA are triggered by several immune and microbial factors, representing a defense strategy to prevent microbial spread by trapping/killing pathogens. This may be important against Entamoeba histolytica, since its large size hinders its phagocytosis. The aim of this study was to determine whether E. histolytica and their lipopeptidophosphoglycan (EhLPPG) induce the formation of NETs and the outcome of their interaction with the parasite. Our data show that live amoebae and EhLPPG, but not fixed trophozoites, induced NET formation in a time and dose dependent manner, starting at 5 min of co-incubation. Although immunofluorescence studies showed that the NETs contain cathelicidin LL-37 in close proximity to amoebae, the trophozoite growth was only affected when ethylene glycol tetra-acetic acid (EGTA) was present during contact with NETs, suggesting that the activity of enzymes requiring calcium, such as DNases, may be important for amoeba survival. In conclusion, E. histolytica trophozoites and EhLPPG induce in vitro formation of human NETs, which did not affect the parasite growth unless a chelating agent was present. These results suggest that NETs may be an important factor of the innate immune response during infection with E. histolytica.
Highlights
Maternal and child undernutrition, highly prevalent in low- and middle-income countries, account for about 35% of deaths for children younger than 5 years[1]
Whole extracts from trophozoites at 1 mg/mL triggered scarce NET formation that increased slightly over time (Fig 1C). These results indicate that E. histolytica induced NET formation seems dependent on the trophozoite integrity
After 60 min, a network tangle containing cathelicidin LL-37 was found surrounding the trophozoites (Fig 2B, white arrows; Upper and lower panels). These results suggest that E. histolytica trophozoites could be resistant to the cathelicidin LL-37 and other antimicrobial peptides found within human NETs induced in vitro by the parasite
Summary
Highly prevalent in low- and middle-income countries, account for about 35% of deaths for children younger than 5 years[1]. The limitation of nutrients negatively impacts the immune response, predisposing to infectious diseases, among them amoebiasis and other diarrheal infections[2]. Amoebiasis caused by the protozoan parasite Entamoeba histolytica is ranked as the third leading parasite-associated cause of human mortality worldwide, behind malaria and schistosomiasis[3], and the second leading cause of intestinal. NETs Induced by E. histolytica Trophozoites and LPPG
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