Excretory/secretory products from plerocercoids of Spirometra erinacei reduce iNOS and chemokine mRNA levels in peritoneal macrophages stimulated with cytokines and/or LPS SOJI FUKUMOTO 1,2 , KAZUMITSU HIRAI 2 , TAKEO TANIHATA 2 , YOSHIHIRO OHMORI 1 , DENNIS J.STUEHR 1 & THOMAS A.HAMILTON 1 1 Department of Immunology, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA 2 Department of Medical Zoology, Faculty of Medicine, Tottori University, Yonago 683, Japan SUMMARY During infection with plerocercoids of Spirometra erinacei, organisms in the peritoneal cavity of infected animals have many bound inflammatory leukocytes yet survive apparently unharmed. Coculture of IFNg and LPS stimulated mouse peritoneal macrophages with live plerocercoids suppressed the mRNA expression of the inducible isoform of nitric oxide synthase (iNOS) and JE, the murine homologue of monocyte chemotactic protein-1 (MCP-1). Excretory/secretory (ES) products from plerocercoids also suppressed the induced iNOS and JE mRNA and reduced nitrite production of macrophages in a dose dependent manner. The suppression of inducible mRNA levels in macrophages cultured for 24 h with ES products varied with the nature of the stimuli; IFNg/ LPS-induced iNOS mRNA levels were effected less than were iNOS mRNA levels induced by IFNg/IL-2 or IFNg/ TNFa. Similar findings were obtained when nitrite produc- tion was measured. Thus modulation of LPS and cytokine inducible mRNA levels appear to be the primary target of ES products. We speculate that a major physiological role for this inhibitory activity in ES products might be the down regulation of pro-inflammatory gene expression. Keywords Spirometra erinacei, peritoneal macrophage, iNOS mRNA, chemokine, NO, plerocercoid, excretory/ secretory products INTRODUCTION Successful infection of potential hosts by parasites require avoidance of an array of sophisticated and normally effec- tive host defence systems. For example, plerocercoids of Spirometra erinacei found in the peritoneal cavity of infected animals have many bound inflammatory leukocytes yet survive apparently unharmed. Thus it is possible that plerocercoids may produce a factor which can suppress the development of inflammatory anti-parasite response. Abundant evidence indicates that nitric oxide (NO) con- tributes to the host defence functions of mononuclear phagocytes (James & Glaven 1989, Adams et al. 1990, Green et al. 1990, Liew, Li & Millott 1990, Liew et al. 1990, Denis & Ghadirian 1992, Lin & Chadee 1992, Stenger et al. 1994, Silva et al. 1995, Stenger et al. 1996, Taylor et al. 1996). The expression of iNOS mRNA in murine peritoneal macrophages is induced by stimuli such as lipopolysacch- aride (LPS) generally in combination with T cell-derived cytokines. These two stimuli, either alone or in combination are well known to promote the expression of other pro- inflammatory agents such as the chemoattractant cytokines or chemokines (Koerner et al. 1987, Tannenbaum et al. 1988, Ohmori & Hamilton 1990). Pro-inflammatory responses by macrophages are known to be inhibited by such agents as glucocorticoids (Di Rosa et al. 1990), transforming growth factor b (Ding et al. 1990, Chesrown et al. 1994, Vodovotz et al. 1994), IL-4 (Al- Ramadi et al. 1992, Cox et al. 1992, Bogdan et al. 1994, Deng, Ohmori & Hamilton 1994, Kolb et al. 1994), IL-10 (Gazzinelli et al. 1992, Oswald et al. 1992), prostaglandin E2 (Marotta, Sautebin & Di Rosa 1992) and human macro- phage-stimulating protein (MSP) (Wang et al. 1994). In the present report we wished to determine if the excretory/ secretory (ES) products of Spirometra erinacei plerocer- coids might also produce negative control of inducible inflammatory gene expression as a means of evading host Parasite Immunology, 1997: 19: 325–332  1997 Blackwell Science Ltd 325 Correspondence: Soji Fukumoto, Department of Medical Zoology, Faculty of Medicine, Tottori University, Yonago 683, Japan Received: 14 May 1996 Accepted for publication: 1 May 1997