Stress-Induced Proliferation and Cell Cycle Plasticity of Intracellular Trypanosoma cruzi Amastigotes

Abstract

The mammalian stages of the parasite Trypanosoma cruzi, the causative agent of Chagas disease, exhibit a wide host species range and extensive within-host tissue distribution. These features, coupled with the ability of the parasites to persist for the lifetime of the host, suggest an inherent capacity to tolerate changing environments. To examine this potential, we studied proliferation and cell cycle dynamics of intracellular T. cruzi amastigotes experiencing transient metabolic perturbation or drug pressure in the context of an infected mammalian host cell. Parasite growth plasticity was evident and characterized by rapid and reversible suppression of amastigote proliferation in response to exogenous nutrient restriction or exposure to metabolic inhibitors that target glucose metabolism or mitochondrial respiration. In most instances, reduced parasite proliferation was accompanied by the accumulation of amastigote populations in the G1 phase of the cell cycle, in a manner that was rapidly and fully reversible upon release from the metabolic block. Acute amastigote cell cycle changes at the G1 stage were similarly observed following exposure to sublethal concentrations of the first-line therapy drug, benznidazole, and yet, unlike the results seen with inhibitors of metabolism, recovery from exposure occurred at rates inversely proportional to the concentration of benznidazole. Our results show that T. cruzi amastigote growth plasticity is an important aspect of parasite adaptation to stress, including drug pressure, and is an important consideration for growth-based drug screening.

Investigation of pyrimidine nucleoside analogues as chemical probes to assess compound effects on the proliferation of Trypanosoma cruzi intracellular parasites

“…Methods have been published to determine pre-and post S-phase in L. mexicana asynchronous promastigotes utilising total cellular DNA content and kinetoplast to nuclear counts [39], requiring flow cytometry. A recent study has also analysed the cell cycle of T. cruzi intracellular amastigotes with DAPI, utilising host cell lysis followed by flow cytometry, with Tulahuen strain parasites expressing β-galactosidase [40]. Tulahuen strain epimastigotes cannot be used as an axenic surrogate for cell cycle studies as they are not sensitive to POSA, even up to 120 hours exposure [9].…”

Low-Level Parasite Persistence Drives Vasculitis and Myositis in Skeletal Muscle of Mice Chronically Infected with Trypanosoma cruzi

“…During benznidazole treatment, the vast majority of amastigotes are depleted. But a small subpopulation may be drug resistant and remain dormant and nondividing (47). When drug treatment is discontinued, this dormant population is capable of reproducing, even after 90 days of benznidazole treatment.…”

“…Quantification of parasite tissue loads by real-time PCR. Real-time qPCR was performed as described previously (47). Briefly, samples of quadriceps muscle were removed from the mice, snapfrozen on dry ice, and stored at Ϫ20°C.…”

A novel mechanosensitive channel controls osmoregulation, differentiation and infectivity inTrypanosoma cruzi

“…cruzi regulates the size of the population. Recent studies show that intracellular amastigotes regulate their growth and metabolism in response to the host conditions (66,67). MSCs channels are regulators of homeocrowding, a mechanism that allows bacteria to maintain a constant level of macromolecular excluded volume at the expense of accumulating or releasing small osmolytes and metabolites (68,69).…”