Antioxidant enzymes in intramolluscan Schistosoma mansoni and ROS-induced changes in expression

• Published in: Parasitology 2004-05, Vol.128 (5), p.493-501
• Main Authors: ZELCK, U. E., VON JANOWSKY, B.
• Format: Article
• Language: English
• Subjects: Animals; Antioxidants; Biological and medical sciences; Biomphalaria - immunology; Biomphalaria - parasitology; Detoxification; Enzymes; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic; General aspects; General aspects and techniques. Study of several systematic groups. Models; glutathione peroxidase; Glutathione Peroxidase - biosynthesis; Glutathione Peroxidase - genetics; Glutathione Transferase - biosynthesis; Glutathione Transferase - genetics; glutathione-S-transferase; haemocyte; Hemocytes - immunology; Hemocytes - metabolism; Hemocytes - parasitology; Host-Parasite Interactions; Hydrogen peroxide; Hydrogen Peroxide - metabolism; immune evasion; Invertebrates; Metabolites; Oxygen; Parasites; Proteins; Reactive Oxygen Species - immunology; Reactive Oxygen Species - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; Schistosoma mansoni; Schistosoma mansoni - enzymology; Schistosoma mansoni - genetics; Schistosoma mansoni - immunology; Sequence Analysis, DNA; superoxide dismutase; Superoxide Dismutase - biosynthesis; Superoxide Dismutase - genetics; Xanthine Oxidase - metabolism
• ISSN: 0031-1820; 1469-8161
• DOI: 10.1017/S0031182004004895

Killing of intramolluscan schistosomes by host haemocytes is mediated by reactive oxygen metabolites. Hence, defence against oxidative damage is essential for the parasite to survive. In this study, expression of three key antioxidant enzymes, superoxide dismutase (EC 1.15.1.1), glutathione peroxidase (EC 1.11.1.9) and glutathione-S-transferase (EC 2.5.1.18) was determined in Schistosoma mansoni miracidia, sporocysts and cercariae. Stage-dependent expression of these enzymes was shown to be regulated at the transcriptional level. Second, the influence on enzyme expression of reactive oxygen species (ROS) and of haemocytes from schistosome-resistant and -susceptible host snails was determined. Generation of ROS by xanthine/xanthine oxidase resulted in increased transcript levels for all three enzymes. Addition of hydrogen peroxide induced a significantly increased expression of GPx and SOD but not GST. Snail haemocytes induced an up-regulation of SOD and GPx at 12 and 18 h post-exposure, respectively. Susceptible haemocytes elicited a stronger induction of transcript expression than resistant haemocytes. After 36–48 h, SOD remained up-regulated in sporocysts encapsulated by haemocytes from susceptible hosts, whereas a down-regulation of SOD and GPx occurred in schistosomes encapsulated by haemocytes from resistant snails. These observations indicate that schistosomes express elevated levels of antioxidant enzymes in interaction with haemocytes from susceptible snail hosts in which they survive. On the other hand, haemocytes of resistant snails may interfere with reactive oxygen detoxification via down-regulation of schistosome antioxidant enzymes, thus shifting the balance towards parasite killing.