Interplay between parasite cysteine proteases and the host kinin system modulates microvascular leakage and macrophage infection by promastigotes of the Leishmania donovani complex

Abstract

Kinins, the vasoactive peptides proteolytically liberated from kininogens, were recently recognized as signals alerting the innate immune system. Here we demonstrate that Leishmania donovani and Leishmania chagasi, two etiological agents of visceral leishmaniasis (VL), activate the kinin system. Intravital microscopy in the hamster cheek pouch showed that topically applied promastigotes induced macromolecular leakage (FITC-dextran) through postcapillary venules. Peaking at 15 min, the parasite-induced leakage was drastically enhanced by captopril (Cap), an inhibitor of angiotensin-converting enzyme (ACE), a kinin-degrading metallopeptidase. The enhanced microvascular responses were cancelled by HOE-140, an antagonist of the B2 bradykinin receptor (B2R), or by pre-treatment of promastigotes with the irreversible cysteine proteinase inhibitor N-methylpiperazine-urea-Phe-homoPhe-vinylsulfone-benzene (N-Pip-hF-VSPh). In agreement with the above-mentioned data, the promastigotes vigorously induced edema in the paw of Cap-treated J129 mice, but not Cap-B2R-/- mice. Analysis of parasite-induced breakdown of high molecular weight kininogens (HK), combined with active site-affinity-labeling with biotin-N-Pip-hF-VSPh, identified 35-40 kDa proteins as kinin-releasing cysteine peptidases. We then checked if macrophage infectivity was influenced by interplay between these kinin-releasing parasite proteases, kininogens, and kinin-degrading peptidases (i.e. ACE). Our studies revealed that full-fledged B2R engagement resulted in vigorous increase of L. chagasi uptake by resident macrophages. Evidence that inflammatory macrophages treated with HOE-140 became highly susceptible to amastigote outgrowth, assessed 72 h after initial macrophage interaction, further suggests that the kinin/B2R activation pathway may critically modulate inflammation and innate immunity in visceral leishmaniasis.

NF-κB-mediated repression of iNOS expression in Leishmania amazonensis macrophage infection

“…Our data demonstrated that L. amazonensis infection led to reduction of total p65 levels. Although we have not investigated the mechanisms involved in p65 cleavage, it is conceivable that L. amazonensis proteases [38][39][40][41][42][43] are mediators of this process.…”

Salivary Gland Homogenates of <i>Lutzomyia longipalpis</i> and Its Vasodilatory Peptide Maxadilan Cause Plasma Leakage via PAC1 Receptor Activation

“…Treatment of the HCP with HOE-140 or L -NA prior to maxadilan resulted in no visible changes, suggesting that kinin formation does not play an important role in the microvascular effects induced by maxadilan (data not shown). Given indications that L. chagasi promastigotes can induce edema and infect macrophages through the activation of the kinin pathway [34], it will be interesting to determine if the convergence of these responses may have short- or long-lasting effects on the host-parasite relationship. This hypothesis merits analysis in light of recent studies showing that bradykinin, recently characterized as a potent maturation signal for dendritic cells, links innate to type-1 adaptive immunity in mice infected with Trypanosoma cruzi [51] (for a review, see Scharfstein et al [52]).…”

“…A tracheal cannula (PE 190) was inserted to facilitate spontaneous breathing, and the body temperature was maintained at 37°C using a heating pad connected to a rectal thermistor probe. HCP was prepared and used for intravital microscopy as previously reported [32,33,34]. Briefly, the cheek pouch was everted and mounted on a microscope stage, and an area of about 1 cm 2 was prepared for intravital microscopy observations of the microcirculation.…”

Biological Roles of Peptidases in Trypanosomatids~!2009-11-26~!2010-02-15~!2010-03-18~!

“…Furthermore, it was proposed that L. donovani and L. chagasi cysteine peptidases activate the kinin system, a group of potent vasoactive peptides proteolytically liberated from kininogens, which have been recognized as signals alerting the innate immune system [141].…”