AUTHOR=Shahi Preeti , Moreau France , Chadee Kris 

TITLE=Entamoeba histolytica Cyclooxygenase-Like Protein Regulates Cysteine Protease Expression and Virulence

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=8

YEAR=2019

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2018.00447

DOI=10.3389/fcimb.2018.00447

ISSN=2235-2988

ABSTRACT=<p>The intestinal protozoan parasite <italic>Entamoeba histolytica</italic> (<italic>Eh</italic>) causes amebiasis associated with severe diarrhea and/or liver abscess. <italic>Eh</italic> pathogenesis is multifactorial requiring both parasite virulent molecules and host-induced innate immune responses. <italic>Eh</italic>-induced host pro-inflammatory responses plays a critical role in disease pathogenesis by causing damage to tissues allowing parasites access to systemic sites. <italic>Eh</italic> cyclooxygenase (<italic>Eh</italic>Cox) derived prostaglandin E<sub>2</sub> stimulates the chemokine IL-8 from mucosal epithelial cells that recruits neutrophils to the site of infection to exacerbate disease. At present, it is not known how <italic>Eh</italic>Cox is regulated or whether it affects the expression of other proteins in <italic>Eh</italic>. In this study, we found that gene silencing of <italic>Eh</italic>Cox (<italic>EhCoxgs</italic>) markedly increased endogenous cysteine protease (CP) protein expression and virulence without altering CP gene transcripts. Live virulent <italic>Eh</italic> pretreated with arachidonic acid substrate to enhance PGE<sub>2</sub> production or aspirin to inhibit <italic>Eh</italic>Cox enzyme activity or addition of exogenous PGE<sub>2</sub> to <italic>Eh</italic> had no effect on <italic>Eh</italic>CP activity. Increased CP enzyme activity in <italic>EhCoxgs</italic> was stable and significantly enhanced erythrophagocytosis, cytopathic effects on colonic epithelial cells and elicited pro-inflammatory cytokines in mice colonic loops. Acute infection with <italic>EhCoxgs</italic> in colonic loops increased inflammation associated with high levels of myeloperoxidase activity. This study has identified <italic>Eh</italic>Cox protein as one of the important endogenous regulators of cysteine protease activity. Alterations of CP activity in response to Cox gene silencing may be a negative feedback mechanism in <italic>Eh</italic> to limit proteolytic activity during colonization that can inadvertently trigger inflammation in the gut.</p>