title: Ehrlichia ewingii infection delays spontaneous neutrophil apoptosis through stabilization of mitochondria.
abstract: The uncultivable obligate intracellular bacterium Ehrlichia ewingii, previously known only as a canine pathogen, is the most recently recognized agent of human ehrlichiosis. E. ewingii is the only Ehrlichia species known to infect neutrophils. In the blood or in ex vivo culture, neutrophils generally have a short life span. In the present study, we investigated the effect of E. ewingii infection on spontaneous apoptosis of neutrophils. E. ewingii infection significantly delayed dog neutrophil apoptosis during ex vivo culture. The inhibitory effect on neutrophil apoptosis by E. ewingii was reversible on clearance of the organism. By using the fluorescent mitochondrial dyes Mitotracker Red 580 and JC-1, we found that E. ewingii infection stabilized mitochondrial integrity by maintaining mitochondrial membrane potential in neutrophils. These results suggest that E. ewingii delays spontaneous apoptosis of neutrophils via stabilization of host cell mitochondria.
authors.affiliation: Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, USA.
authors.forename: Qingming
authors.initials: Q
authors.lastname: Xiong
authors.forename: Weichao
authors.initials: W
authors.lastname: Bao
authors.forename: Yan
authors.initials: Y
authors.lastname: Ge
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Rikihisa
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D004283:Dog Diseases / Q000097:blood / Q000382:microbiology*; D004285:Dogs; D004536:Ehrlichia / Q000502:physiology*; D016873:Ehrlichiosis / Q000097:blood / Q000382:microbiology / Q000662:veterinary*; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D006651:Histocytochemistry / Q000662:veterinary; D008297:Male; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000382:microbiology / Q000502:physiology*; D009504:Neutrophils / Q000382:microbiology* / Q000473:pathology / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D013047:Specific Pathogen-Free Organisms
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D053148:Caspase 3