title: Leptospira interrogans induces apoptosis in macrophages via caspase-8- and caspase-3-dependent pathways.
abstract: Apoptosis of host cells plays an important role in modulating the pathogenesis of many infectious diseases. It has been reported that Leptospira interrogans, the causal agent of leptospirosis, induces apoptosis in macrophages and hepatocytes. However, the molecular mechanisms responsible for host cell death remained largely unknown. Here we demonstrate that L. interrogans induced apoptosis in a macrophage-like cell line, J774A.1, and primary murine macrophages in a time- and dose-dependent manner. Apoptosis was associated with the activation of cysteine aspartic acid-specific proteases (caspase-3, caspase-6, and caspase-8), the increased expression of Fas-associated death domain (FADD), and the cleavage of the caspase substrates poly(ADP-ribose) polymerase (PARP) and nuclear lamina protein (lamin A and lamin C). Caspase-9 was activated to a lesser extent, whereas no release of cytochrome c from mitochondria was detectable. Inhibition of caspase-8 impaired L. interrogans-induced caspase-3 and -6 activation, as well as PARP and lamin A/C cleavage and apoptosis, suggesting that apoptosis is initiated via caspase-8 activation. Furthermore, caspase-3 was required for the activation of caspase-6 and seemed to be involved in caspase-9 activation through a feedback amplification loop. These data indicate that L. interrogans-induced apoptosis in macrophages is mediated by caspase-3 and -6 activation through a FADD-caspase-8-dependent pathway, independently of mitochondrial cytochrome c-caspase-9-dependent signaling.
authors.affiliation: School of Life Sciences, Department of Medical Microbiology and Parasitology, School of Medicine, Zhejiang University, 388 Yu-Hang-Tang Road, Hangzhou 310058, China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Jin
authors.forename: David M
authors.initials: DM
authors.lastname: Ojcius
authors.forename: Dexter
authors.initials: D
authors.lastname: Sun
authors.forename: Haiyan
authors.initials: H
authors.lastname: Dong
authors.forename: Yihui
authors.initials: Y
authors.lastname: Luo
authors.forename: Yafei
authors.initials: Y
authors.lastname: Mao
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D045304:Cytochromes c / Q000378:metabolism; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D007921:Leptospira interrogans / Q000502:physiology*; D008264:Macrophages / Q000166:cytology / Q000201:enzymology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C
chemical_list: D053200:Fas-Associated Death Domain Protein; D045304:Cytochromes c; D053148:Caspase 3; D053181:Caspase 8