Antiproliferative Effect of Dihydroxyacetone on Trypanosoma brucei Bloodstream Forms: Cell Cycle Progression, Subcellular Alterations, and Cell Death

Abstract

We evaluated the effects of dihydroxyacetone (DHA) on Trypanosoma brucei bloodstream forms. DHA is considered an energy source for many different cell types. T. brucei takes up DHA readily due to the presence of aquaglyceroporins. However, the parasite is unable to use it as a carbon source because of the absence of DHA kinase (DHAK). We could not find a homolog of the relevant gene in the genomic database of T. brucei and have been unable to detect DHAK activity in cell lysates of the parasite, and the parasite died quickly if DHA was the sole energy source in the medium. In addition, during trypanosome cultivation, DHA induced growth inhibition with a 50% inhibitory concentration of about 1 mM, a concentration that is completely innocuous to mammals. DHA caused cell cycle arrest in the G 2 /M phase of up to 70% at a concentration of 2 mM. Also, DHA-treated parasites showed profound ultrastructural alterations, including an increase of vesicular structures within the cytosol and the presence of multivesicular bodies, myelin-like structures, and autophagy-like vacuoles, as well as a marked disorder of the characteristic mitochondrion structure. Based on the toxicity of DHA for trypanosomes compared with mammals, we consider DHA a starting point for a rational design of new trypanocidal drugs.Trypanosoma brucei is the causative agent of sleeping sickness, a fatal illness that is endemic in many countries in subSaharan Africa. Nearly half a million people are currently infected with the parasite, and 50,000 to 60,000 new cases appear every year (40). Available drugs are not effective against all stages of the disease. Melarsoprol, a trivalent organic arsenical that was discovered in 1949, is still the first line of defense against sleeping sickness. This compound (together with eflornithine, a drug effective only against Trypanosoma gambiense) is the most effective medication for the late stage of the disease (5); however, it is not an ideal drug. Although melarsoprol has a high cure rate (80 to 90%), it remains ineffective in a number of cases. In addition, there has been an increase of treatment failure of up to 30% due to the emergence of melarsoprol resistance (17). Most importantly, however, the drug causes grave side affects. About 10% of patients develop a severe posttreatment reactive encephalopathy, which is fatal in approximately 50% of cases (17,18). This scenario clearly highlights the importance of a rational search for new trypanocidal compounds and/or biochemical targets to develop effective drugs that are safe, easy to use under field conditions, and inexpensive to produce.Recently, the three aquaglyceroporins (TbAQP1 to -3) of T. brucei have been cloned and characterized (38). They show high permeability for water and glycerol compared with other aquaglyceroporins. Surprisingly, however, this study also revealed for the first time that aquaglyceroporins from protozoa are highly permeable for dihydroxyacetone (DHA), a threecarbon sugar. This substance permeates these channels in the same range as, ...

Effect of glycerol and dihydroxyacetone concentrations in the culture medium on the growth of acetic acid bacteria Gluconobacter oxydans ATCC 621

“…The global demand for DHa is successively increasing, and its new application possibilities are still emerging [10,17,19,37]. It seems advisable, therefore, to search for novel solutions to attenuate or eliminate the problem of inhibition accompanying glycerol biotransformation to DHa.…”

Autophagy in protists

“…19,119 Many cells can use DHA as an energy substrate because, after its phosphorylation by DHA kinase, it may enter the glycolytic pathway. Trypanosomes, however, which take up DHA via aquaglyceroporins, lack this kinase.…”

Dihydroxyacetone Induced Autophagy in African Trypanosomes

“…In addition, fluorescence activated cell sorting analysis counting cells in G 1 , S and G 2 phase showed a 70% increase of cells in G 2 /M in the presence of DHA. 7 The morphology of treated cells has been analyzed by light and electron microscopy, which also supports the conclusion of a cell cycle arrest. Investigating the cell death mechanism revealed that an increase of necrosis or apoptosis markers was negligible, while induction of autophagy was clearly visible from transmission electron micrographs (Fig.…”