Given the early divergence of trypanosomatids in evolution and absence of genes central to “classical” cell death pathways, induction, and mechanisms of regulated cell death in these species will shed light on origin of these processes. The early divergence of eukaryotic cells can be observed with the Trypanosomatids taxa (Green, 2015)

Crithidia fasciculata is a trypanosomatid, mosquito parasite. We explored sensitivity of Crithidia to ethanol (≤20%) on cell death and externalization of phosphatidylserine (PS) using propidium iodide (PI) and annexin V-FITC (AV). While 20% ethanol killed cells necrotically (PI⁺ /AV⁺), 9% ethanol resulted elicited nonlethal, PS externalization in a subset (2%) of the population (PI^- /AV⁺). To elucidate the mechanism of this cell death-like phenotype, alcohol dehydrogenases (ADH) and aldehyde dehydrogenases (ALDH) were inhibited. I hypothesized inhibition of (ALDH) with disulfiram will increase proportion of stressed, alive cells (PI^-/AV⁺) because of (ALDH) is used to process acetaldehyde with the enzyme (ALDH) that produces acetate that is used in many metabolic processes. While disulfiram yielded an increase in this subset of cells, effects of inhibition were ethanol independent. In contrast, the (ADH) inhibitor 4- methyl pyrazole caused necrosis. The different patterns of cellular death can be observed by the different staining. These results suggest cell death pathways are sensitive to fermentation products produced by trypanosomatids and that early evolution of “classical,” cell death pathways could have been driven by responses to sublethal stress.