Korean J Parasitol.  2012 Mar;50(1):1-6. 10.3347/kjp.2012.50.1.1.

Anti-Apoptotic Effects of SERPIN B3 and B4 via STAT6 Activation in Macrophages after Infection with Toxoplasma gondii

Affiliations
  • 1The Catholic Institute of Parasitic Diseases, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea. howoo@catholic.ac.kr
  • 2Department of Parasitology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.

Abstract

Toxoplasma gondii penetrates all kinds of nucleated eukaryotic cells but modulates host cells differently for its intracellular survival. In a previous study, we found out that serine protease inhibitors B3 and B4 (SERPIN B3/B4 because of their very high homology) were significantly induced in THP-1-derived macrophages infected with T. gondii through activation of STAT6. In this study, to evaluate the effects of the induced SERPIN B3/B4 on the apoptosis of T. gondii-infected THP-1 cells, we designed and tested various small interfering (si-) RNAs of SERPIN B3 or B4 in staurosporine-induced apoptosis of THP-1 cells. Anti-apoptotic characteristics of THP-1 cells after infection with T. gondii disappeared when SERPIN B3/B4 were knock-downed with gene specific si-RNAs transfected into THP-1 cells as detected by the cleaved caspase 3, poly-ADP ribose polymerase and DNA fragmentation. This anti-apoptotic effect was confirmed in SERPIN B3/B4 overexpressed HeLa cells. We also investigated whether inhibition of STAT6 affects the function of SERPIN B3/B4, and vice versa. Inhibition of SERPIN B3/B4 did not influence STAT6 expression but SERPIN B3/B4 expression was inhibited by STAT6 si-RNA transfection, which confirmed that SERPIN B3/B4 was induced under the control of STAT6 activation. These results suggest that T. gondii induces SERPIN B3/B4 expression via STAT6 activation to inhibit the apoptosis of infected THP-1 cells for longer survival of the intracellular parasites themselves.

Keyword

Toxoplasma gondii; macrophage; SERPIN B3, B4; STAT6; anti-apoptosis
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