Ascaris suum-Derived Products Induce Human Neutrophil Activation via a G Protein-Coupled Receptor That Interacts with the Interleukin-8 Receptor Pathway

Abstract

Infection with tissue-migrating helminths is frequently associated with intense granulocyte infiltrations. Several host-derived factors are known to mediate granulocyte recruitment to the tissues, but less attention has been paid to how parasite-derived products trigger this process. Parasite-derived chemotactic factors which selectively recruit granulocytes have been described, but nothing is known about which cellular receptors respond to these agents. The effect of products from the nematodes Ascaris suum, Toxocara canis, and Anisakis simplex on human neutrophils were studied. We monitored four parameters of activation: chemotaxis, cell polarization, intracellular Ca 2؉ transients, and priming of superoxide anion production. Body fluids of A. suum (ABF) and T. canis (TcBF) induced strong directional migration, shape change, and intracellular Ca 2؉ transients. ABF also primed neutrophils for production of superoxide anions. Calcium mobilization in response to A. suum-derived products was completely abrogated by pretreatment with pertussis toxin, implicating a classical G protein-coupled receptor mechanism in the response to ABF. Moreover, pretreatment with interleukin-8 (IL-8) completely abrogated the response to ABF, demonstrating desensitization of a common pathway. However, ABF was unable to fully desensitize the response to IL-8, and binding to CXCR1 or CXCR2 was excluded in experiments using RBL-2H3 cells transfected with the two human IL-8 receptors. Our results provide the first evidence for a direct interaction between a parasite-derived chemotactic factor and the host's chemotactic network, via a novel G protein-coupled receptor which interacts with the IL-8 receptor pathway.Neutrophilic and eosinophilic granulocytes have evolved in the immune system as a first line of defense against invading pathogens. Remarkable numbers of eosinophils or neutrophils infiltrate lesions caused by tissue-invading parasites, as seen, e.g., in anisakiasis (57) and schistosomiasis. A series of chemokines and low-molecular-weight attractants are known to mediate recruitment of granulocytes to the site of infection (56), but less attention has been paid to the role of parasite-derived products in inflammatory infiltration. Indeed the question of whether host innate cells bear "danger" receptors for parasite products has barely been explored. In parasitic infections, there can be phenomenal intensity and selectivity of granulocyte recruitment, such as the eosinophilic phlegmons (large granulomatous infiltrations of eosinophils with marked submucosal oedema) caused by Anisakis simplex (anisakiasis or eosinophilic gastroenteritis) (17,28,30,31) and Ancylostoma caninum (eosinophilic enteritis) (52,70). Since most of the damage caused by tissue-invading parasites can be attributed to the recruited inflammatory cells, a clear picture of the mechanisms mediating granulocyte recruitment and activation is of pivotal importance to the understanding and management of pathology.The intensity and selectivity of inflammatory recruitment...

Necator americanus: The Na-ASP-2 protein secreted by the infective larvae induces neutrophil recruitment in vivo and in vitro

“…However, a closer examination of the published data unveiled that tissue-dwelling parasites (usually adults) often release inhibitory factors, possibly in an attempt to reduce the local immune response (Alkarmi and Behbehani, 1989;Culley et al, 2000;Keir et al, 2004;Leid et al, 1987;Lo et al, 1999). Conversely, tissue-migrating larvae usually secrete compounds that promote inflammation (Falcone et al, 2001;Horii et al, 1988;Niwa et al, 1998;Owhashi et al, 1985;Owhashi et al, 1997;Rubio de Kromer et al, 1998;Tanaka et al, 1979;Tanaka and Torisu, 1978). Local inflammation and, in particular, neutrophil-related edema could increase tissue permeability and favor a faster and more successful migration through the host's tissues.…”

“…The quantity and quality of inflammatory recruitment following parasitic helminth infection suggest that granulocytes are not simply responding to tissue injury caused by migrating larvae, but they are actively being targeted by molecules secreted by the parasite. Numerous parasite-derived chemotactic factors have been reported to recruit, often selectively, neutrophils or eosinophils (Falcone et al, 2001;Horii et al, 1988;Niwa et al, 1998;Owhashi et al, 1985;Owhashi et al, 1997;Rubio de Kromer et al, 1998;Tanaka et al, 1979;Tanaka and Torisu, 1978). In the few cases in which the mechanism has been studied, it has revealed some degree of interaction between parasite antigens and either β-integrin receptors or the IL-8 pathway (Falcone et al, 2001;Rubio de Kromer et al, 1998).…”

The intriguing normal acute inflammatory response in mice lacking vimentin

“…Mitochondrial ROS production was assessed using dihydrorhodamine 123 (DHR123), as described previously [14,27]. Briefly, neutrophils were incubated at a final concentration of 1 ¥ 10 6 cells/ml in HBSS-0·3% BSA containing 1 mM DHR123 for 5 min at 37°C before adding stimuli.…”

“…Mitochondrial ROS production was assessed by flow cytometry using DHR123 [14,27]. PMA was used as a positive control [14,27].…”

Signaling through Gαi2 protein is required for recruitment of neutrophils for antibody-mediated elimination of larvalStrongyloides stercoralisin mice

“…Killing of S. stercoralis requires neutrophils during the adaptive immune response, whose recruitment requires the G protein-dependent receptor CXCR2 [21]. Similarly, Ascaris suum-derived chemotactic products interact with PTXsensitive G proteins through the IL-8R pathway and induce activation and chemotaxis of human neutrophils [34]. In the present study, the total numbers of cells and specifically, neutrophils recruited into the micro-environment of the larvae were significantly lower in Gαi2 −/− mice as compared with wild-type mice.…”