Excretory-Secretory products of Angiostrongylus cantonensis young-adult worm inhibit thrombin activity, an in vitro study

• Main Authors: Szu-Ting Fang, 方思婷
• Other Authors: Chuan-Min Yen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/22309083898376123678

碩士 === 高雄醫學大學 === 醫學研究所 === 101 === Angiostrongylus cantonensis is one of the most important zoonotic parasites in Taiwan. Humans are infected with A.cantonensis through eating undercooked snails which results in eosinophilic meningitis and/or meningoencephalitis. In our previous study, coagulated blood was obviously observed in the meninges of mice after infection with A.cantonensis. The activity of thrombin in the cerebrospinal fluid of mice was significantly increased after infection in this study. We believe that brain-stage worms of A.cantonensis can secrete substances to inhibit thrombin in the brain. Thus, worms of A.cantonensis can prevent themselves from being trapped in the coagulated blood. In this study, the excretory-secretory (ES) products from alive young-adult worms harvesting from the brain of a mouse 20 days after infection, and the extracts of somatic component of worms were examined for the inhibiting ability of thrombin activity. Only ES products of young-adult worms can inhibit the activity of thrombin. The ability of ES products in inhibiting the thrombin activity was not influenced by the treatment with high temperatures (56oC and 75 oC), low temperatures (-80 oC), acidic conditions (pH4.0), and carbohydrates (lactose, sucrose and galactose). However, ES products could not inhibit thrombin activity after alkaline treatment (pH10.0). The ES products could inhibit the enhancement of the coagulation reaction of platelet-poor plasma by thrombin. However, the clotting reaction of platelet-rich plasma by ADP could not be inhibited by ES products. In conclusion, young-adult worms of A.cantonensis release a substance which can inhibit the thrombin activity. This substance is not affected by temperature, acids or carbohydrates. It also inhibits thrombin catalyzed coagulation of platelet-poor plasma but, not ADP-induced platelet aggregation. So, the mechanism of ES products from A.cantonensis in inhibiting the catalysis of plasma by thrombin is different from that of thromboxane.