Acting at the interface between microcirculation and immunity, Trypanosoma cruzi induces modifications in peripheral tissues which translate into mutual benefits to host/parasite balance. In this chapter, we will review evidence linking
infection-associated vasculopathy to the proinflammatory activity of a small subset of T. cruzi molecules, namely GPI-linked
mucins,
cysteine proteases (
cruzipain),
surface glycoproteins of the
trans-sialidase family and/or parasite-derived
eicosanoids (
thromboxane A(2)). Initial insight into pathogenesis came from research in animal models showing that myocardial
fibrosis is worsened as result of
endothelin upregulation by infected cardiovascular cells. Paralleling these studies, the
kinin system emerged as a proteolytic mechanism that links oedematogenic
inflammation to immunity. Analyses of the dynamics of
inflammation revealed that tissue culture trypomastigotes elicit interstitial oedema in peripheral sites of
infection through synergistic activation of toll-like 2 receptors (TLR2) and
G-protein-coupled
bradykinin receptors, respectively, engaged by tGPI (TLR2
ligand) and
kinin peptides (
bradykinin B2 receptors (BK(2)R)
ligands) proteolytically generated by
cruzipain. Further downstream,
kinins stimulate lymph node dendritic cells via
G-protein-coupled BK(2)R, thus converting these specialized antigen-presenting cells into T(H)1 inducers. Tightly regulated by
angiotensin-converting enzyme, the intact
kinins (BK(2)R agonists) may be processed by
carboxypeptidase M/N, generating [des-Arg]-
kinins, which activates BK(1)R, a subtype of GPCR that is upregulated by cardiovascular cells during
inflammation. Ongoing studies may clarify if discrepancies between proinflammatory phenotypes of T. cruzi strains may be ascribed, at least in part, to variable expression of TLR2
ligands and
cruzipain isoforms.