In vitro ANTIGIARDIAL ACTIVITY OF THE CYSTEINE PROTEASE INHIBITOR E-64

Abstract

The quest for new antiparasitic alternatives has led researchers to base their studies on insights into biology, host-parasite interactions and pathogenesis. In this context, proteases and their inhibitors are focused, respectively, as druggable targets and new therapy alternatives. Herein, we proposed to evaluate the in vitro effect of the cysteine protease inhibitor E-64 on Giardia trophozoites growth, adherence and viability. Trophozoites (105) were exposed to E-64 at different final concentrations, for 24, 48 and 72 h at 37 °C. In the growth and adherence assays, the number of trophozoites was estimated microscopically in a haemocytometer, whereas cell viability was evaluated by a dye-reduction assay using MTT. The E-64 inhibitor showed effect on growth, adherence and viability of trophozoites, however, its better performance was detected in the 100 µM-treated cultures. Although metronidazole was more effective, the E-64 was shown to be able to inhibit growth, adherence and viability rates by ≥ 50%. These results reveal that E-64 can interfere in some crucial processes to the parasite survival and they open perspectives for future investigations in order to confirm the real antigiardial potential of the protease inhibitors.

Diltiazem inhibits SARS-CoV-2 cell attachment and internalization and decreases the viral infection in mouse lung

“…To test whether diltiazem inhibits SARS-CoV-2 infection at a late stage in Vero-E6 cells, we added diltiazem/E64D at 6 h post-infection, and determined the viral titer at 24 h post-infection. E64D inhibits cathepsin L [ 35 ] and prevents the infection of progeny viruses. The results showed that the viral titer in diltiazem-treated Vero-E6 cells was comparable to that of control cells, indicating that diltiazem has no effect on SARS-CoV-2 infection at a late stage ( Fig 2F ).…”

Giardia duodenalis Surface Cysteine Proteases Induce Cleavage of the Intestinal Epithelial Cytoskeletal Protein Villin via Myosin Light Chain Kinase

“…Furthermore, our experiments used inhibitors, which have previously been shown to successfully attenuate catB and L cysteine proteases in mammalian and protozoan parasites [ 24 , 52 , 55 , 73 ], including G . duodenalis [ 34 , 67 ]. Results from this study corroborate previous observations that G .…”

“…Previous research has demonstrated that concentrations of 10μM E-64d or Ca-074Me do not affect G . duodenalis trophozoite viability, but significantly reduce cathepsin-like cysteine protease activity [ 34 , 67 ]. Therefore, experiments involving G .…”

Quinoline-triazole hybrids inhibit falcipain-2 and arrest the development ofPlasmodium falciparumat the trophozoite stage

“…1b ) an epoxide and an important irreversible inhibitor against general cysteine proteases and displayed a significant outcome on growth, adherence and viability of parasite trophozoites. 12 A representative of benzoxaboroles, AN3661 ( Fig. 1c ), has been found to markedly reduce the FP2 transcripts in malarial parasites.…”