Contact-independent cell death of human microglial cells due to pathogenic Naegleria fowleri trophozoites.
Free-living Naegleria fowleri leads to a fatal infection known as primary amebic meningoencephalitis in humans. Previously, the target cell death could be induced by phagocytic activity of N. fowleri as a contact-dependent mechanism. However, in this study we investigated the target cell death under a non-contact system using a tissue-culture insert. The human microglial cells, U87MG cells, co-cultured with N. fowleri trophozoites for 30 min in a non-contact system showed morphological changes such as the cell membrane destruction and a reduction in the number. By fluorescence-activated cell sorter (FACS) analysis, U87MG cells co-cultured with N. fowleri trophozoites in a non-contact system showed a significant increase of apoptotic cells (16%) in comparison with that of the control or N. fowleri lysate. When U87MG cells were co-cultured with N. fowleri trophozoites in a non-contact system for 30 min, 2 hr, and 4 hr, the cytotoxicity of amebae against target cells was 40.5, 44.2, and 45.6%, respectively. By contrast, the cytotoxicity of non-pathogenic N. gruberi trophozoites was 10.2, 12.4, and 13.2%, respectively. These results suggest that the molecules released from N. fowleri in a contact-independent manner as well as phagocytosis in a contact-dependent manner may induce the host cell death.
Kim
Jong-Hyun
JH
Department of Microbiology, Ajou University School of Medicine, Suwon 443-721, Korea.
Kim
Daesik
D
Shin
Ho-Joon
HJ
D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D006801:Humans; D017628:Microglia / Q000166:cytology* / Q000469:parasitology*; D016848:Naegleria fowleri / Q000502:physiology*; D010587:Phagocytosis / Q000502:physiology