ABSTRACT
Leishmania parasites expose phosphatidylserine (PS) on their surface, a process that has been associated with regulation of host's immune responses. In this study we demonstrate that PS exposure by metacyclic promastigotes of Leishmania amazonensis favours blood coagulation. L. amazonensis accelerates in vitro coagulation of human plasma. In addition, L. amazonensis supports the assembly of the prothrombinase complex, thus promoting thrombin formation. This process was reversed by annexin V which blocks PS binding sites. During blood meal, Lutzomyia longipalpis sandfly inject saliva in the bite site, which has a series of pharmacologically active compounds that inhibit blood coagulation. Since saliva and parasites are co-injected in the host during natural transmission, we evaluated the anticoagulant properties of sandfly saliva in counteracting the procoagulant activity of L. amazonensis . Lu. longipalpis saliva reverses plasma clotting promoted by promastigotes. It also inhibits thrombin formation by the prothrombinase complex assembled either in phosphatidylcholine (PC)/PS vesicles or in L. amazonensis . Sandfly saliva inhibits factor X activation by the intrinsic tenase complex assembled on PC/PS vesicles and blocks factor Xa catalytic activity. Altogether our results show that metacyclic promastigotes of L. amazonensis are procoagulant due to PS exposure. Notably, this effect is efficiently counteracted by sandfly saliva.
Subject(s)
Animals , Humans , Blood Coagulation/physiology , Leishmania/metabolism , Phosphatidylserines/metabolism , Psychodidae/parasitology , Saliva/metabolism , Anticoagulants/metabolism , Cysteine Endopeptidases , Factor V/antagonists & inhibitors , Factor X/antagonists & inhibitors , Factor Xa/antagonists & inhibitors , Insect Vectors/parasitology , Neoplasm Proteins/antagonists & inhibitors , Partial Thromboplastin Time , Phosphatidylcholines/metabolism , Psychodidae/metabolism , Thrombin/antagonists & inhibitors , Tissue Extracts/metabolismABSTRACT
Há poucos estudos sobre a microbiota do trato digestivo de flebotomíneos, considerando-se que o sangue näo é o único alimento ingerido. Os flebotomíneos, tanto os machos como as fêmeas, alimentam-se de açúcares, provenientes de várias fontes, possibilitando a ingestäo de microrganismos. As chances de contaminaçäo aumentam nos insetos criados em laboratório e pode interferir no desenvolvimento da Leishmania spp. Foi separado um total de 300 fêmeas, divididas em dois lotes, das quais extraímos o trato digestivo. No lote 1 (fêmeas alimentadas com sangue e sacarose) das 10 espécies bacterianas isoladas, a família Enterobacteriaceae esteve representada pelos gêneros Serratia, Enterobacter e Yokenella, e o grupo dos näo fermentadores pelos gêneros Pseudomonas, Acinetobacter e Stenotrophomonas. No lote 2 (fêmeas alimentadas apenas com sanue) das 8 espécies isoladas o grupo dos näo fermentadores esteve representado pelos gêneros Acinetobacter, Stenotrophomonas, Burkolderia e Pseudomonas, e a família Enterobacteriaceae, pelos gêneros Enterobacter e Serratia.
Subject(s)
Animals , Female , Microbiology , PsychodidaeABSTRACT
No presente trabalho foram dissecados o trato digestivo de 245 fêmeas de Lutzomyia longipalpis originários da Gruta da Lapinha, Município de Lagoa Santa, MG, formando 7 grupos de 35 flebotomíneos. Das 8 espécies de bactérias isoladas houve uma predominância de bactérias Gram negativas (BGN) pertencentes ao grupo de näo fermentadoras de açúcar das seguintes espécies: Acinetobacter lowffii, Stenotrophomonas maltophhilia, Pseudomonas putida e Flavimonas orizihabitans. No grupo das fermentadoras tivemos: Enterobacter cloacae e Klebsiella ozaenae. No grupo dos Gram positivos foram identificados Bacillus thuringiensis e Staphylococcus spp