Toxoplasma gondii infection inhibits the mitochondrial apoptosis through induction of Bcl-2 and HSP70

• Published in: Parasitology research (1987) Vol. 107; no. 6; pp. 1313 - 1321
• Main Authors: Hwang, Il-Young, Quan, Juan Hua, Ahn, Myoung-Hee, Hassan Ahmed, Hassan Ahmed, Cha, Guang-Ho, Shin, Dae-Whan, Lee, Young-Ha
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.11.2010; Springer-Verlag; Springer
• Subjects: Apaf-1 protein; Apoptosis; Apoptosis-inducing factor; Arsenic; Arsenic trioxide; Arsenicals; Bcl-2 protein; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Blotting, Western; Caspase 3 - metabolism; Caspase 7 - metabolism; Caspase-3; Cell Line; Chaperones; Colorimetry; Cytochrome c; Cytochromes; Data processing; DNA Fragmentation; Fundamental and applied biological sciences. Psychology; General aspects; General aspects and techniques. Study of several systematic groups. Models; Health aspects; Heat shock proteins; HSP70 Heat-Shock Proteins - biosynthesis; Hsp70 protein; Humans; Immunology; Immunoprecipitation; Infection; Invertebrates; Macrophages; Macrophages - parasitology; Medical Microbiology; Microbiology; Mitochondria; Mitochondrial DNA; Original Paper; Oxides - toxicity; Parasites; Proto-Oncogene Proteins c-bcl-2 - biosynthesis; Toxoplasma - pathogenicity; Toxoplasma gondii; Translocation; Western blotting; HSP70 Expression; Arsenic Trioxide; Mitochondrial Apoptosis; As2O3; Parasite Load; Infection; Protozoa; Apicomplexa; Mitochondria; Toxoplasma gondii; Induction; Parasite; Apoptosis
• ISSN: 0932-0113; 1432-1955
• DOI: 10.1007/s00436-010-1999-3

Heat-shock protein 70 (HSP70) is highly expressed in Toxoplasma gondii-infected cells. However, the role of this protein is not well understood, especially during apoptosis. This study addresses the mechanism behind the antiapoptotic chaperone activity of HSP70 in Toxoplasma-infected host cells using a human macrophage cell line, THP-1 by Western blot, DNA fragmentation assay, immunoprecipitation, and a caspase-3/7 activity assay based on cleavage of the colorimetric substrate DEVD-pNA. Apoptosis induced by arsenic trioxide (As₂O₃) was inhibited in T. gondii-infected THP-1 cells, but not in uninfected cells. Without As₂O₃ induction of apoptosis, T. gondii infection caused increased expression of Bcl-2 and HSP70, but not caspase-3. However, active form caspase-3 levels were lower in As₂O₃-treated infected cells as compared with As₂O₃-treated uninfected cells. Bcl-2 expression in As₂O₃-treated infected cells was similar to that in cells infected with T. gondii. Translocation of apoptosis-inducing factor (AIF) and release of cytochrome c from mitochondria were inhibited in As₂O₃-treated infected cells as compared with As₂O₃-treated uninfected cells. Increased parasite loads in Toxoplasma-infected macrophages caused higher HSP70 and Bcl-2 expression in whole-cell extracts and fractionated components, respectively. However, expression of AIF and cytochrome c was unaffected. Toxoplasma dose-dependently inhibited caspase-3 activation, thus revealing an anti-apoptotic parasite activity on cytochrome c-mediated caspase activation in subcellular components. In addition, immunoprecipitation analysis suggested that HSP70 is capable of binding to the pro-apoptotic factors AIF and Apaf-1, but not to cytochrome c or procaspase-9. Taken together, these data demonstrate that T. gondii infection inhibits mitochondrial apoptosis through overproduction of anti-apoptotic Bcl-2 as well as HSP70, which are increased parasite loads dependently.