Differential Effects of Two Widely Used Solvents, DMSO and Ethanol, on the Growth and Recovery of Trypanosoma cruzi Epimastigotes in Culture

Abstract

Trypanosoma cruzi is the etiological agent of Chagas disease. Epimastigote forms of T. cruzi can be readily cultured in axenic conditions. Ethanol and dimethyl sulfoxide (DMSO) are commonly used solvents employed as vehicles for hydrophobic compounds. In order to produce a reference plot of solvent dependent growth inhibition for T. cruzi research, the growth of epimastigotes was analyzed in the presence of different concentrations of ethanol (0.1-4.0%) and DMSO (0.5-7.5%). The ability of the parasites to resume growth after removal of these solvents was also examined. As expected, both ethanol and DMSO produced a dose-dependent inhibition of cellular growth. Parasites could recover normal growth after 9 days in up to 2% ethanol or 5% DMSO. Since DMSO was better tolerated than ethanol, it is thus recommended to prefer DMSO over ethanol in the case of a similar solubility of a given compound.

Keywords: DMSO; Trypanosoma cruzi; drug screening; ethanol; kinetoplastidia; solvent.

Fig. 1

Effects of ethanol and DMSO on T. cruzi growth. The growth of T. cruzi epimastigotes was periodically monitored for 9 days, as indicated. All cultures were started at an initial cellular concentration of 1×10⁶ parasites/ml. LIT medium without solvent was used as a control. (A) Growth curves of epimastigotes cultured in different ethanol concentrations, as indicated. (B) Growth curves of epimastigotes cultured in different DMSO concentrations, as indicated. Plotted values represent the arithmetic means from 3 independent experiments. (C, D) Final cellular density of 9 day-old epimastigotes cultured in the presence of different amounts of the indicated solvents, relative to the solvent-free LIT growth controls.

Fig. 2

Growth recovery of T. cruzi epimastigotes after treatment with either ethanol (A) or DMSO (B). Nine day-old epimastigote cultures, pre-grown in the presence of the indicated solvents, were washed with PBS and placed in solvent-free LIT medium at an adjusted cellular density of 1 million parasites per ml. Control cultures of cells previously grown in LIT medium were also included. Cellular growth was monitored at the indicated times. Plotted values represent the means of at least 2 independent experiments.