Abstract

Fasciolosis is one of the parasitic diseases that exerts the greatest impact on sheep productive systems worldwide. Affected sheep generally show a decrease in their reproductive capacity, weight gain, meat and milk production, and wool quality. In the pathogenesis of Fasciola hepatica, the penetration and migration of parasitic stages through the liver provoke intense inflammatory immune responses and tissue damage. Following strong activation signals, polymorphonuclear neutrophils (PMNs) reportedly release chromatin and granular proteins into the extracellular space, forming DNA traps called neutrophil extracellular traps (NETs). It was recently demonstrated that F. hepatica induces NET formation in vivo in the liver parenchyma from naturally infected sheep. Thus, in this paper we investigated F. hepatica-mediated NET-derived cytotoxic effects in exposed hepatic cells in vitro as well as F. hepatica-triggered ovine NETs under hypoxic conditions (5% O2). Our results confirm the ability of ovine PMNs to form NETs in low-oxygen environments after F. hepatica antigen (FhAg) stimulation, as seen in many pathological and pro-inflammatory states, and their cytotoxic effects on exposed hepatic cells. In addition, we demonstrate that this defence mechanism is NADPH oxidase (NOX)-dependent and therefore a tightly regulated molecular process. Overall, we hypothesize that NET formation plays a role in the pathogenesis of fasciolosis, and NETs contribute to liver tissue damage if released in an uncontrolled manner. © 2024 by the authors.