The efficacy of 2-nitrovinylfuran derivatives against Leishmania in vitro and in vivo

Abstract

Despite recent advances in the treatment of some forms of leishmaniasis, the available drugs are still far from ideal due to inefficacy, parasite resistance, toxicity and cost. The wide-spectrum antimicrobial activity of 2-nitrovinylfuran compounds has been described, as has their activity against Trichomonas vaginalis and other protozoa. Thus, the aim of this study was to test the antileishmanial activities of six 2-nitrovinylfurans in vitro and in a murine model of leishmaniasis. Minimum parasiticide concentration (MPC) and 50% inhibitory concentration (IC50) values for these compounds against the promastigotes of Leishmania amazonensis, Leishmania infantum and Leishmania braziliensis were determined, as were the efficacies of two selected compounds in an experimental model of cutaneous leishmaniasis (CL) caused by L. amazonensis in BALB/c mice. All of the compounds were active against the promastigotes of the three Leishmania species tested. IC50 and MPC values were in the ranges of 0.8-4.7 µM and 1.7-32 µM, respectively. The compounds 2-bromo-5-(2-bromo-2-nitrovinyl)-furan (furvina) and 2-bromo-5-(2-methyl-2-nitrovinyl)-furan (UC245) also reduced lesion growth in vivo at a magnitude comparable to or higher than that achieved by amphotericin B treatment. The results demonstrate the potential of this class of compounds as antileishmanial agents and support the clinical testing of Dermofural(r) (a furvina-containing antifungal ointment) for the treatment of CL.

Fig. 1:. structural difference between nitrofurans (nitrogen bonded to the furan ring) and nitrovinylfurans (nitrogen bonded to the side vinylic chain).

Fig. 2:. growth curves of Leishmania amazonensis, Leishmania infantum and Leishmania braziliensis in Schneider's medium. Exponentially growing promastigotes were seeded in 96-well plates at 5 x 105 promastigotes/mL. Every 24 h a group of wells was inactivated by addition of 5 μL, 2 μg/mL amphotericin B. After seven days of culture at 26ºC, cell density was estimated by measuring parasite phosphatases activity.

Fig. 3:. In vivo efficacy of 2-bromo-5-(2-bromo-2-nitrovinyl)-furan (furvina) and 2-bromo-5-(2-methyl-2-nitrovinyl)-furan (UC245) against experimental cutaneous leishmaniasis. Early stage lesions treated every 24 h. Mice were infected by intradermal injection with 5 x 106 stationary phase Leishmania amazonensis promastigotes. Six weeks later they were treated by intraperitoneal route every 24 h during 14 days with furvina (5 mg/Kg), UC245 (50 mg/Kg), amphotericin B (1 mg/Kg) or Miglyol 810 (0.1 mL). Control mice were infected, but received no treatment at all. Lesion size was measured every week using a Vernier caliper.

Fig. 4:. In vivo efficacy of 2-bromo-5-(2-bromo-2-nitrovinyl)-furan (furvina) and 2-bromo-5-(2-methyl-2-nitrovinyl)-furan (UC245) against experimental cutaneous leishmaniasis. Early stage lesions treated every 12 h. Mice were intradermally infected and treated by intraperitoneal route every 12 h during 14 days with furvina (2 mg/Kg), UC245 (100 mg/Kg) or amphotericin B (1 mg/Kg). Infected, nontreated control mice were also included. Once therapy started lesion size was measured every week for four weeks.

Fig. 5:. In vivo efficacy of 2-bromo-5-(2-bromo-2-nitrovinyl)-furan (furvina) and 2-bromo-5-(2-methyl-2-nitrovinyl)-furan (UC245) against chronic experimental cutaneous leishmaniasis. Eighteen weeks post-infection mice had developed lesions of 1.23 ± 0.24 x 1.24 ± 0.19 cm. Treatment was then initiated every 12 h for 14 days with furvina (2 mg/Kg), UC245 (100 mg/Kg) or amphotericin B (5 mg/Kg, every 48 h). The dorsoplantar and lateral diameters of lesions were measured and lesion size was estimated as their product.