Heterogeneity in the sensitivity of microtubules of Giardia lamblia to the herbicide oryzalin

Abstract

Giardia lamblia is a protozoan that inhabits the small intestine of vertebrates, attaching to the epithelial cells by means of cytoskeletal elements. G. lamblia trophozoites possess several microtubular structures, namely the adhesive disc, the median body, the funis and the four pairs of flagella. Several drugs that target cytoskeletal proteins have been used in the study of cytoskeletal function and dynamics. In this work, we used oryzalin, which binds to alpha-tubulin, as a tool to study the Giardia cytoskeleton. The trophozoites were treated with oryzalin, and its effects were analysed by immunofluorescency, transmission and scanning electron microscopies. Oryzalin inhibited Giardia proliferation. Treated cells were not able to complete cell division and had flagella showing extensive shortening. Strikingly, the drug did not interfere with the adhesive disc, in contrast to what happens when other drugs are used.

Unveiling the Possible Oryzalin-Binding Site in the α-Tubulin of Toxoplasma gondii

“…Something similar occurs with the nematode model Caenorhabditis elegans and in mammalian cell lines, where cytotoxic activities have been observed at IC 50 values greater than 25 and 50 μM, respectively. 4 , 5 , 9 , 34 , 35 In agreement with the conclusions made by Terra et al 11 and Hirst et al, 33 G. intestinalis , C. elegans , and mammals could be considered ORY-non-susceptible organisms.…”

“… 32 Similarly, treatment with dinitroaniline derivatives has shown microtubule disruption activity in protozoa with low half-maximal inhibitory concentrations (IC 50 ). T. gondii (IC 50 = 0.1 μM), 4 P. falciparum (IC 50 = 3.9 μM), 33 and L. mexicana (IC 50 < 20 μM) 7 , 11 are some of the most relevant ORY-susceptible protozoan parasites. A previous study suggested that the protozoan Giardia intestinalis was also susceptible to ORY treatment.…”

“…A previous study suggested that the protozoan Giardia intestinalis was also susceptible to ORY treatment. 11 However, higher concentrations of this dinitroaniline are required to kill this parasite (IC 50 > 50 μM). Something similar occurs with the nematode model Caenorhabditis elegans and in mammalian cell lines, where cytotoxic activities have been observed at IC 50 values greater than 25 and 50 μM, respectively.…”

“… 4 − 8 The low effect on mammalian tubulin polymerization and low inhibitory concentrations required to kill the parasites have pinpointed ORY as a lead compound for the development of new antiprotozoal compounds. 5 , 7 , 9 − 11 …”

Herbicides as Potential Chemotherapeutic Agents Against Parasitic Protozoa

“…At 50 and 100 µM, most of the protozoa were killed. Morphological studies showed curling of the flagella in about 60% of the cells, elongation of the median body (i.e., a structure made of microtubules), changes in the shape of the cell, and blockage of cell division (Figures 1-3) [27]. …”