title: Invasion by Toxoplasma gondii protects human-derived HL-60 cells from actinomycin D-induced apoptosis.
abstract: Intracellular microorganisms have to rely on the integrity of their host cells to persist. We, therefore, investigated the effect of infections with different Toxoplasma gondii strains on apoptosis of human-derived HL-60 cells at the single cell level. Infection with either mouse-avirulent (NTE strain) or virulent parasites (RH strain) did not induce apoptosis of HL-60 cells as compared to uninfected controls. In contrast, treatment with actinomycin D (act D) led to apoptosis in 15-25% of the cells. However, concomitant infection with T. gondii clearly abrogated act D-induced apoptosis. This was especially apparent in those host cells that were actually infected; in these parasite-positive cells the rate of apoptosis decreased by 82.8+/-4.3% (mean+/-SEM, P=0.017, Student's t-test) and 91.7+/-3.4% (P= 0.024) after infection with either the NTE or the RH strain, respectively. Inhibition of host cell apoptosis was similarly observed in cells which had been invaded by UV-irradiated, non-replicating parasites (P=0.001, Student's t-test). However, incubation with heat-killed parasites or T. gondii lysates did not abrogate act D-induced apoptosis. In conclusion, inhibition of apoptosis by living, but not necessarily replicating T. gondii may facilitate parasite survival and persistence within its host cell.
authors.affiliation: Institute of Hygiene and Microbiology, Würzburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Goebel
authors.forename: C G
authors.initials: CG
authors.lastname: Lüder
authors.forename: U
authors.initials: U
authors.lastname: Gross
mesh_terms: D000818:Animals; D017209:Apoptosis; D003609:Dactinomycin / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D018922:HL-60 Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D014122:Toxoplasma / Q000472:pathogenicity / Q000502:physiology*; D014774:Virulence
chemical_list: D003609:Dactinomycin