title: Intracellular proteolysis of kininogen by malaria parasites promotes release of active kinins.
abstract: BACKGROUND
  The malaria burden remains a major public health concern, especially in sub-Saharan Africa. The complex biology of Plasmodium, the apicomplexan parasite responsible for this disease, challenges efforts to develop new strategies to control the disease. Proteolysis is a fundamental process in the metabolism of malaria parasites, but roles for proteases in generating vasoactive peptides have not previously been explored.
  
  
  RESULTS
  In the present work, it was demonstrated by mass spectrometry analysis that Plasmodium parasites (Plasmodium chabaudi and Plasmodium falciparum) internalize and process plasma kininogen, thereby releasing vasoactive kinins (Lys-BK, BK and des-Arg9-BK) that may mediate haemodynamic alterations during acute malaria. In addition, it was demonstrated that the P. falciparum cysteine proteases falcipain-2 and falcipain-3 generated kinins after incubation with human kininogen, suggesting that these enzymes have an important role in this process. The biologic activity of peptides released by Plasmodium parasites was observed by measuring ileum contraction and activation of kinin receptors (B1 and B2) in HUVEC cells; the peptides elicited an increase in intracellular calcium, measured by Fluo-3 AM fluorescence. This effect was suppressed by the specific receptor antagonists Des-Arg9[Leu8]-BK and HOE-140.
  
  
  CONCLUSIONS
  In previously undescribed means of modulating host physiology, it was demonstrated that malaria parasites can generate active kinins by proteolysis of plasma kininogen.
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, Rua Pedro de Toledo, 669 - 7 andar, 04039-032, São Paulo, Brazil.
authors.forename: Piero
authors.initials: P
authors.lastname: Bagnaresi
authors.forename: Nilana Mt
authors.initials: NM
authors.lastname: Barros
authors.forename: Diego M
authors.initials: DM
authors.lastname: Assis
authors.forename: Pollyana Ms
authors.initials: PM
authors.lastname: Melo
authors.forename: Raphael G
authors.initials: RG
authors.lastname: Fonseca
authors.forename: Maria A
authors.initials: MA
authors.lastname: Juliano
authors.forename: João B
authors.initials: JB
authors.lastname: Pesquero
authors.forename: Luiz
authors.initials: L
authors.lastname: Juliano
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Rosenthal
authors.forename: Adriana K
authors.initials: AK
authors.lastname: Carmona
authors.forename: Marcos L
authors.initials: ML
authors.lastname: Gazarini
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D007082:Ileum / Q000187:drug effects; D007704:Kininogens / Q000378:metabolism*; D007705:Kinins / Q000378:metabolism*; D013058:Mass Spectrometry; D009119:Muscle Contraction / Q000187:drug effects; D016788:Plasmodium chabaudi / Q000201:enzymology* / Q000378:metabolism; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000378:metabolism; D059748:Proteolysis
chemical_list: D007704:Kininogens; D007705:Kinins; D003546:Cysteine Endopeptidases; C416224:falcipain 2; C443101:falcipain 3; D002118:Calcium