In vitro effects of lonidamine and 6-aminonicotinamide against Echinococcus granulosussensu stricto and Echinococcus multilocularis

Abstract

Echinococcosis is a zoonotic disease caused by cestode species of the genus Echinococcus, which demonstrates considerable medical and veterinary concerns. The development of novel drugs for echinococcosis treatment is urgently needed. In this study, we demonstrated that lonidamine (LND) and 6-aminonicotinamide (6-AN) exhibited considerable in vitro effects against both larval- and adult-stage of E. granulosussensu stricto (s. s.) and E. multilocularis. The combination of LND and 6-AN exhibited a significantly higher activity than the single drug treatment. These results highlight the therapeutic potential of LND, 6-AN and the combination of LND and 6-AN for the treatment of echinococcosis.

Figure 1

In vitro efficacy of the drugs againstE. granulosus s. s.protoscoleces. A Survival of protoscoleces after treatment with LND, 6-AN, and their combination. B Morphologies of protoscoleces after 3 days of treatment with LND, 6-AN, and their combination. a Untreated protoscoleces. White arrow points towards calcareus corpuscles (cc); b Protoscoleces in culture medium containing 0.2% DMSO; c, d, and e Protoscoleces incubated with 40 μM NTZ, 40 μM 6-AN and 40 μM LND, respectively; f Protoscoleces incubated with 20 μM LND + 20 μM 6-AN. Note the distortion and vesiculation of protoscoleces (black arrow), the collapse of suckers (white arrowhead) and the decrease of calcareus corpuscles; g Protoscoleces incubated with 40 μM LND + 40 μM 6-AN.

Figure 2

In vitro efficacy of the drugs againstE. multilocularismetacestodes. A The release of alkaline phosphatase activity from E. multilocularis metacestodes (EmAP) after treatment with LND, 6-AN, and their combination. *p < 0.05 vs. DMSO control. B Morphologies of metacestodes after 5 days of treatment with LND, 6-AN, and their combination. a Metacestodes in culture medium containing 0.2% DMSO. Note the typical morphology of the germinal cells. GL, germinal layer; b–e Metacestodes treated with 40 μM 6-AN, 40 μM LND, 20 μM LND + 20 μM 6-AN and 40 μM LND + 40 μM 6-AN, respectively.

Figure 3

In vitro efficacy of the drugs against adultE. granulosus s. s.A The release of alkaline phosphatase from adult E. granulosus s. s. (EgAP) after treatment with LND, 6-AN, and their combination. *p < 0.05 vs. DMSO control. B Morphologies of adult E. granulosus s. s. after treatment with LND, 6-AN, and their combination. a, b Tapeworms incubated in culture medium containing 0.2% DMSO. Note the concave suckers (Su) on the scolex (S), the intact first proglottid (P1), second proglottid (P2) and terminal proglottid (P3) with genital pore (Gp) as well as the complete hooks (H); c–l Tapeworms treated with 200 μM PZQ (c, d), 200 μM 6-AN (e, f), 200 μM LND (g, h), 100 μM LND + 100 μM 6-AN (i, j) and 200 μM LND + 200 μM 6-AN (k, l), respectively; C Ultrastructures of adult E. granulosus s. s. after 4 h of treatment with LND, 6-AN, and their combination. a Tapeworms incubated in culture medium containing 0.2% DMSO. Note the normal and distinct morphology (m, microtriches; mi, mitochondria; mic, microfilament; cm, circular muscle bundle; lm, longitudinal muscle bundle; bm, basement membrane; p, perikarya) and the large number and the length of microtriches; b–h Tapeworms treated with 200 μM PZQ (b), 200 μM 6-AN (c), 200 μM LND (d), 100 μM LND + 100 μM 6-AN (e, f) and 200 μM LND + 200 μM 6-AN (g, g), respectively. ld: lipid droplet.