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| Underlying mechanism revealed for horsefly as an antithrombotic drug |
Horseflies are a blood-feeding arthropod, notorious as a common pest of animals and sometimes of humans. While being a target of the biological control in the green farming and animal husbandry, processed dried bodies of female horseflies, known as mengchong, are used by traditional Chinese medicine (TCM) to treat cardiovascular diseases. Although the unique drug is believed as a source various bioactive substances, little has been known about its biochemical functions in the secretion of its salivary glands and, in particular, on its immune suppressants.
The recent research work of Prof. LAI Ren and his colleagues with the CAS Kunming Institute of Zoology (KIZ) shed new light on the horsefly's blood-feeding mechanism at the molecular level. Their work was reported in the Dec. 17, 2007 issue of the journal Molecular Cellular Proteomics.
Using the approaches of proteomics or peptidomics and transcriptome analysis coupling with pharmacological testing, the researchers identified and characterized several families of proteins or peptides, which act mainly on haemostatic system or immune system of the host, from 30, 000 pairs of salivary glands of the horsefly of Tabanus Yao (Diptera, Tabanidae).
Their findings include: (1) A novel family of inhibitors against platelet aggregation which involves two members very likely capable of inhibiting platelet aggregation by a novel mechanism and acting on the platelet membrane; (2) A new 12-membered family of immuno-suppressant peptides to stem the production of interferon but increase the secretion of interleukin-10; (3) A serine protease with 56 amino acid residues working as an anticoagulant inhibitor; (4) A serine protease noted for its anti-coagulant activity; v). A protease with fibrinogenolytic activity; (5) Three families of anti-microbial peptides including six members; vii). A hyaluronidase; (6) A vasodilator peptide, an isoform vasotab identified from Hybomitra bimaculata; (7) More interestingly, two metallo-thioneins were characterized as the first report about such substances of this kind extracted from an invertebrate's saliva. Scientists believe the substances are capable of regulating the host's immunity system and being resistant to microbes, thrombosis and blood coagulation.
More importantly, the work reveals the molecular mechanism of mengchong as an antithrombotic drug. It also made discoveries on a couple of novel vaccine targets and novel leading pharmacological compounds with potential medical values for blood and immune systems. Experts say the work laid a solid foundation for the modernization of Mengchong as a TCM drug. It is hailed as an outstanding "tour de force" work.
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