Δ2,3 -Ivermectin ethyl secoester, a conjugated ivermectin derivative with leishmanicidal activity but without inhibitory effect on mammalian P-type ATPases

Abstract

Looking at a new putative target for the large spectrum antiparasitic drug ivermectin, we recently showed that avermectin-derived drugs are active against promastigote and amastigote forms of Leishmania amazonensis at low micromolar concentrations. However, we then reported that at this concentration range ivermectin is also able to inhibit three important mammalian P-type ATPases so that unacceptable adverse effects could occur if this drug were used at such high doses therapeutically. The present work aimed to test the activity of ten ivermectin analogs on these rat ATPases in search of a compound with similar leishmanicidal activity but with no effect on the mammalian (host) ATPases at effective concentrations. We synthesized three new ivermectin analogs for testing on rat SERCA (1a and 1b), Na+, K+-ATPase (α₁ and α₂/α₃ isoforms) and H+/K+-ATPase activity, along with seven analogs already characterized for their leishmanicidal activity. Our main finding is that one of the prepared derivatives, Δ²,³-ivermectin ethyl secoester 8, is equipotent to ivermectin 1 for the in vitro leishmanicidal effects but is nearly without effect on the rat ATPases, indicating that it could have a better therapeutic index in vivo and could serve as a candidate for hit-to-lead progression. This conclusion is further supported by the fact that compound 8 produced only 6% (vs 77% for ivermectin) inhibition of the human kidney enzyme at 5 μM, a concentration corresponding to the IC₅₀ for the activity against L. amazonensis amastigotes.

Marinobufagenin Inhibits Neutrophil Migration and Proinflammatory Cytokines

“…Protein concentration was determined by the Lowry protein assay method. According to Noël et al [29], with slight modifications, in a buffered medium containing 97.6 mM NaCl, 3 mM KCl, 3 mM MgCl 2 , 3 mM ATPNa 2 , 1 mM EGTA, and 20 mM maleic acid/Tris (pH 7.4), brain and kidney preparations were incubated at 37°C with increasing concentrations of marinobufagenin or ouabain. After 2 h, the reaction was stopped by the Fiske & Subbarow solution to measure the Pi released from ATP hydrolysis by a colorimetric method.…”

21-Benzylidene Digoxin: A Proapoptotic Cardenolide of Cancer Cells That Up-Regulates Na,K-ATPase and Epithelial Tight Junctions

“…The brain hemisphere preparations were incubated at 37°C for 2 h in medium containing 87.6 mM NaCl, 3 mM KCl, 3 mM MgCl 2 , 3 mM ATPNa 2 , 1 mM EGTA, 10 mM sodium azide and 20 mM maleic acid/Tris (pH 7.4), and the cell membrane preparations were incubated at 37°C for 1 h in 120 mM NaCl, 20 mM KCl, 2 mM MgCl 2 , 3 mM ATPNa 2 and 50 mM HEPES, (pH 7.5), both in the absence and presence of 1 mM ouabain or increasing concentrations of 21-BD and digoxin. Na,K-ATPase activity was determined by measuring the Pi released according to a colorimetric method described previously [69] , and specific activity was considered as the difference between the total and ouabain-resistant ATPase activities [70] .…”

Leishmaniasis treatment update of possibilities for drug repurposing

“…has already been demonstrated. Studies show that its analogues have specific activity against promastigote and amastigote forms of the parasite and specifically do not affect enzymes in the host (65)(66)(67).…”