Aziridine-2,3-Dicarboxylates, Peptidomimetic Cysteine Protease Inhibitors with Antileishmanial Activity

Abstract

Chemotherapy of leishmaniasis is mainly based on antimonials. However, they are extremely toxic and cause serious side effects, and there is a worldwide increasing frequency of chemoresistance to antimonials. These issues emphasize the urgent need for affordable alternative drugs against leishmaniasis. Leishmania cysteine proteases are essential for parasite growth, differentiation, pathogenicity, and virulence and are thus attractive targets for combating leishmaniasis. Herein we demonstrate that the cysteine protease inhibitors aziridine-2,3-dicarboxylates 13b and 13e impaired promastigote growth at mid-micromolar concentrations and decreased the infection rate of peritoneal macrophages at concentrations 8-to 13-fold lower than those needed to inhibit parasite replication. Simultaneous treatment of infected cells with compound 13b and gamma interferon resulted in an even further reduction of the concentration needed for a significant decrease in macrophage infection rate. Notably, treatment with the compounds alone modulated the cytokine secretion of infected macrophages, with increased levels of interleukin-12 and tumor necrosis factor alpha. Furthermore, the decreased infection rate in the presence of compound 13b correlated with increased nitric oxide production by macrophages. Importantly, at the concentrations used herein, compounds 13b and 13e were not toxic against fibroblasts, macrophages, or dendritic cells. Together, these results suggest that the aziridine-2,3-dicarboxylates 13b and 13e are potential antileishmanial lead compounds with low toxicity against host cells and selective antiparasitic effects.

Overexpression of the Natural Inhibitor of Cysteine Peptidases inLeishmania mexicanaLeads to Reduced Virulence and a Th1 Response

“…ICP in overexpressing mutants in this study could therefore function to promote MHC class II antigen presentation indirectly by inhibiting the degradative activity of parasite CPs. Inhibitors of cathepsin L-like CPs have also been associated with modulating host cell production of nitric oxide upon infection with L. donovani (7) or L. major (21), production of tumor necrosis factor alpha upon infection with L. major (21), and production of IL-12 upon infection with L. major (21) L. mexicana (6). All of these products are associated with, or would promote, a Th1 response and protection.…”

“…⌬cpa ⌬cpb mutants were less infective for BALB/c mice than ⌬cpb mutants (2,18), which also implicates CPA as a virulence factor. As ICP has been shown to preferentially inhibit clan CA, family C1, cathepsin L-like peptidases, such as CPB (22), and to bind specifically to CPA and CPB (3) (7), L. chagasi (11,15,26), L. tropica (15), and L. major (14,21), and a number of mechanisms have been implicated. However, ICPs may not necessarily operate by targeting parasite CPs directly but may act by inhibiting the crucial role of host CPs in the processing of antigen via major histocompatibility complex (MHC) class II.…”

Aziridine-2,3-Dicarboxylate-Based Cysteine Cathepsin Inhibitors Induce Cell Death inLeishmania majorAssociated with Accumulation of Debris in Autophagy-Related Lysosome-Like Vacuoles

“…Two derivatives of this series, Boc-(S)-Leu-(R)-Pro-(S,S)-Azi(OBn) 2 (compound 13b) and Boc-(R)-Leu-(S)-Pro-(S,S)-Azi(OBn) 2 (compound 13e) ( Fig. 1), reduced the growth and viability of Leishmania major promastigotes and the infection rate of macrophages with L. major amastigotes (23). The peptidomimetic inhibitors 13b and 13e were selectively active against L. major and did not display any cytotoxic effects against macrophages and fibroblasts (23).…”

“…On the basis of the activities of compounds 13b and 13e against various CAC1 cysteine proteases, it was hypothesized that these inhibitors also target the papain-like cysteine cathepsins CPA, CPB, and CPC of L. major (23). However, FIG.…”

Development of new antileishmanial drugs – current knowledge and future prospects

“…Moreover, these enzymes are involved in the survival of Leishmania within the macrophage cells [99]. The reduction of macrophage infection by cysteine protease inhibitors of aziridine-2,-dicarboxylate series could be mediated through the inhibition of parasite replication and the increase of nitric oxide production [100].…”