Potent Anti- Trypanosoma cruzi Activities of Oxidosqualene Cyclase Inhibitors

Abstract

Trypanosoma cruzi is the protozoan agent that causes Chagas' disease, a major health problem in Latin America. Better drugs are needed to treat infected individuals. The sterol biosynthesis pathway is a potentially excellent target for drug therapy against T. cruzi. In this study, we investigated the antitrypanosomal activities of a series of compounds designed to inhibit a key enzyme in sterol biosynthesis, oxidosqualene cyclase. This enzyme converts 2,3-oxidosqualene to the tetracyclic product, lanosterol. The lead compound, N-(4E,8E)-5,9, 13-trimethyl-4,8, 12-tetradecatrien-1-ylpyridinium, is an electron-poor aromatic mimic of a monocyclized transition state or high-energy intermediate formed from oxidosqualene. This compound and 27 related compounds were tested against mammalian-stage T. cruzi, and 12 inhibited growth by 50% at concentrations below 25 nM. The lead compound was shown to cause an accumulation of oxidosqualene and decreased production of lanosterol and ergosterol, consistent with specific inhibition of the oxidosqualene cyclase. The data demonstrate potent anti-T. cruzi activity associated with inhibition of oxidosqualene cyclase.

CYP51 from Trypanosoma cruzi

“…In both cases formation of the preferred CYP51 substrate presumes a preceding modification of L, which is the first cyclized compound in the pathway (20,46). Although in TC L has to be 24-methylated to form M, in TB one additional step, 4␤-demethylation, is absolutely required.…”

A preliminary crystallographic analysis of the putative mevalonate diphosphate decarboxylase fromTrypanosoma brucei

“…The enzymes of the mevalonate (MVA) pathway of isoprenoid precursor biosynthesis represent potential drug targets in trypanosomes since active sterol biosynthesis has been shown to be essential for growth and survival in T. cruzi (Urbina, 1997(Urbina, , 2002. For example, sterol-synthesis inhibitors such as terbinafine (an inhibitor of squalene epoxidase, downstream of the MVA pathway) have been shown to retard growth and lead to parasite death (Buckner et al, 2001) and inhibitors of T. cruzi HMGCoA reductase (a central enzyme of the MVA pathway) have been shown to potentiate the anti-proliferative effects of terbinafine (Urbina et al, 1993). This would suggest that inhibition of the MVA pathway offers hope for future drug development against trypanosomatid parasites.…”

Analogs of squalene and oxidosqualene inhibit oxidosqualene cyclase of Trypanosoma cruzi expressed in Saccharomyces cerevisiae

“…In addition to the antifungal activity, some of these compounds were shown to inhibit the growth of Trypanosoma and other kinetoplastid parasites (8). Kinetoplastid parasites have also been shown recently to be susceptible to inhibitors of squalene synthase (9,10) and oxidosqualene cyclase (11,12). The enzyme oxidosqualene cyclase (OSC; EC 5.4.99.7), which catalyzes the formation of the first cyclic precursor of sterols, is considered a good target for the inhibition of sterol biosynthesis in both humans and fungi.…”

“…OSC of different origins can have significantly different susceptibilities to the inhibitors, showing the possibility of selective inhibition (19,20). Therefore, it would be worth testing the activity of these inhibitors on the OSC of the pathogen protozoon Trypanosoma cruzi, which recently has been shown to be susceptible to pyridinium ionbased inhibitors and to some umbelliferone aminoalkyl derivatives (11,12). Trypanosoma cruzi, like other pathogenic protozoa, is difficult to culture for an extensive, preliminary screening of the many available, effective inhibitors of OSC.…”