Antiprotozoal activities of benzimidazoles and correlations with beta-tubulin sequence

Abstract

Benzimidazoles have been widely used since the 1960s as anthelmintic agents in veterinary and human medicine and as antifungal agents in agriculture. More recently, selected benzimidazole derivatives were shown to be active in vitro against two protozoan parasites, Trichomonas vaginalis and Giardia lamblia, and clinical studies with AIDS patients have suggested that microsporidia are susceptible as well. Here, we first present in vitro susceptibility data for T. vaginalis and G. lamblia using an expanded set of benzimidazole derivatives. Both parasites were highly susceptible to four derivatives, including mebendazole, flubendazole, and fenbendazole (50% inhibitory concentrations of 0.005 to 0.16 microgram/ml). These derivatives also had lethal activity that was time dependent: 90% of T. vaginalis cells failed to recover following a 20-h exposure to mebendazole at 0.17 microgram/ml. G. lamblia, but not T. vaginalis, was highly susceptible to five additional derivatives. Next, we examined in vitro activity of benzimidazoles against additional protozoan parasites: little or no activity was observed against Entamoeba histolytica, Leishmania major, and Acanthamoeba polyphaga. Since the microtubule protein beta-tubulin has been identified as the benzimidazole target in helminths and fungi, potential correlations between benzimidazole activity and beta-tubulin sequence were examined. This analysis included partial sequences (residues 108 to 259) from the organisms mentioned above, as well as the microsporidia Encephalitozoon hellem and Encephalitozoon cuniculi and the sporozoan Cryptosporidium parvum. beta-tubulin residues Glu-198 and, in particular, Phe-200 are strong predictors of benzimidazole susceptibility; both are present in Encephalitozoon spp. but absent in C. parvum.

Alveolar and cystic echinococcosis: towards novel chemotherapeutical treatment options

“…This indicates that cytotoxic effects of ABZ (or its metabolites) due to tubulin depolymerization may be hampered in Echinococcus by: (1) the presence of an ABZ-insensitive b-tubulin complementing the sensitive isoform; (2) rapid ABZ catabolism; (3) toxicity of ABZ catabolites rather than ABZSO itself; and/or (4) a good regenerative power due to insensitive stem cells. Sensitivity of mammalian cells (carrying the benzimidazole-resistant allele 200-Tyr) lies between an IC 50 around 0.25 mM in HL60 cells and 20 mM in Vero cells (nocodazole, another benzimidazole, is, however, 10-to 20-fold more toxic; Katiyar et al, 1994). This suggests that ABZ may also bind with low affinity to mammalian b-tubulin, and/or the existence of another, unknown, mode of action of ABZ that may be responsible for ABZ side-effects in patients, as mentioned above.…”

“…Molecular genetics revealed that sensitivity to benzimidazoles in evolutionary distant organisms such as fungi, nematodes, platyhelmithes and various protozoa was correlated with the presence of specific alleles of b-tubulin genes (Driscoll et al, 1989;Katiyar et al, 1994;Kwa et al, 1995;Henriquez et al, 2008), the substitution of Phe to Tyr in position 200 being sufficient for switching from benomyl sensitivity to resistance in nematodes (Kwa et al, 1995). Molecular modelling of the putative ABZ binding site in ABZ-resistant Acanthamoeba b-tubulin revealed 13 residues, four of which showed sequence variation as compared to tubulins of sensitive organisms.…”

Antifungal and anthelmintic activity of novel benzofuran derivatives containing thiazolo benzimidazole nucleus: an in vitro evaluation

“…Benzimidazoles have been widely used since the 1960s as anthelmintic agents in veterinary and human medicine and as antifungal agents in agriculture [8]. The target site of benzimidazole anthelmintic is β-tubulin which is indispensable to form microtubules, responsible for vital cell functions as motility, cellular shape, mitosis, coordination, transport and secretion in nematodes, cestodes and fluke [9,10].…”

A novel approach to synthesis of flibanserin

“…A variety of benzimidazoles are in used, like Thiabendazole, Flubendazole (antihelminthic), Omeprazole, Lansoprazole (anti-ulcerative) and Astemizole (anti-histaminic). The chemistry and pharmacology of benzimidazoles have been of great interest to medicinal chemistry [7,8] , because of its derivatives possessed various biological activities such as anti-oxidant [9,10], anti-microbial [11][12][13][14][15][16] , antihelmentic [17][18][19], anti-cancer [20], anti-hypertensive [21], anti-neoplastic [22], anti-inflammatory [23,24], analgesic [25], anti-protozoal [26,27], anti hepatitis activities [28] and also shows anti-depressant activity [29].…”