Identification of Somatostatin Receptors on Schistosoma Mansoni Stages

摘要

Our recent studies have elucidated a direct association between severe hepatic fibrosis and low levels of circulating somatostatin levels in S. mansoni infected patients in Senegal. Using somatostatin for therapy in S. mansoni infected mice resulted in a reduction in the number of parasite eggs and/ or the secretion of fibrosis inducing-mediators in the infected host. Since the inhibitory activity of somatostatin occurs via binding to specific receptors, this study explored the presence of such receptors (SSTRs) on S. mansoni parasite stages. Immunohistochemistry localized SSTR2 & SSTR3 on the worm stages of S. mansoni, specifically on the tegument (with knob like protrusions) and in the internal parts of the worm pair. Receptors were found at the level of the excretory organs (flame cells) ending in a narrow canal in the cuticle. Eggs deposited in the liver and ileum also expressed these somatostatin receptors. Dot blot and Western blot identified protein bands of 70-100 and 200-250 kD molecular weight on the parasite stages. Our study indicated that circulating somatostatin levels in 5. mansoni infected mammalian host might interact with the parasite stages via these receptors thereby influencing the hepatic fibrosis caused by this infection.