Anti-trypanosomatid activity of ceragenins

Abstract

Cationic steroid antibiotics (CSAs), or ceragenins, are amphiphilic compounds consisting of a cholic acid backbone that is attached to several cationic amines. In this study, we tested the hypothesis that CSAs possess antiparasitic activities with minimal to no effects on mammalian cells, and thus could be used as potential therapeutic agents against pathogenic trypanosomatids. To investigate this notion, we synthesized CSAs and determined their trypanocidal and leishmanicidal activities in vitro. The 3 ceragenins assayed, i.e., CSA-8, CSA-13, and CSA-54, showed several degrees of parasiticidal activity. CSA-13 was the most effective compound against Leishmania major promastigotes and Trypanosoma cruzi trypomastigotes, at LD(50) 4.9 and 9 microM, respectively. The trypanocidal activities of these ceragenins were also assessed by infectivity experiments. We found CSA-8 was more effective on T. cruzi intracellular amastigotes when the infected host cells were treated for 24 hr (LD(50), 6.7 microM). Macrophages and LLC-MK(2) (treated for 72 hr) showed relative low susceptibility to these compounds. Our results suggest that ceragenins are indeed promising chemotherapeutic agents against trypanosomatids, but they require further investigation.

FIGURE 1

Survival of mammalian cells treated with CSAs. Rhesus LLC-MK₂ epithelial cells and mouse Raw 264.7 macrophages were treated for 72 hr with several concentrations (1, 10, 25, 50, and 100 μM) of CSA-8, CSA-13, and CSA-54. The experiments were performed 3 times, in triplicate.

FIGURE 2

Viability assays of L. major promastigotes treated with 100, 33, 11, 3.3, and 1.25 μM CSA-8, CSA-13 or CSA-54. Surviving cells were detected by incubation with Alamar Blue and expressed as a percent of survived cells. Bars represent means ^± standard errors of 3 independent experiments. Controls represent parasites incubated only with culture media.

FIGURE 3

T. cruzi-Infected LLC-MK₂ cells treated with CSAs. (A) Percent of cells infected by T. cruzi after 24-hr treatment with CSA-8, CSA-13, or CSA-54. B) Number of intracellular T. cruzi amastigotes in 100 cells after 24-hr CSA treatment. Surviving cells were detected by incubation with Alamar Blue and expressed as a percent of survived cells. Bars represent means ^± standard errors of 3 independent experiments. Control represents LLC-MK₂ cells incubated only with culture media.

FIGURE 4