title: Molecular and biochemical mechanisms of Pasteurella haemolytica leukotoxin-induced cell death.
abstract: Pasteurella haemolytica leukotoxin (LKT) is a member of the RTX family of pore-forming toxins that kill bovine immune cells. Several studies have suggested that RTX toxins kill target cells by the induction of apoptosis. In the present study, BL3 bovine leukaemia cells were exposed to LKT and assessed by molecular and flow cytometric techniques that measure different aspects of apoptotic cell death. The intoxicated cells demonstrated morphological, light scatter and Hoechst 33258 staining characteristics consistent with cells undergoing apoptosis. The cells also exhibited internucleosomal DNA fragmentation and poly (ADP-ribose) polymerase (PARP) cleavage, both indicators of apoptosis. LKT-treated cells bound annexin-V-FITC indicating that phosphatidylserine groups were translocated from the inner to the outer leaflet of the cell membrane. The effect of LKT on cells was dose dependent and inhibitable by incubation with anti-LKT monoclonal antibody. Finally, an early step for induction of apoptosis appears to be the binding of LKT to a beta2 integrin since pre-incubating cells with anti-beta2 integrin antibodies inhibited LKT-induced apoptosis. This study provides new insights into understanding the pathogenesis of bovine pasteurellosis and could lead to the development of both preventative and therapeutic strategies for disease management.
authors.affiliation: Leon Levy Research Center for Oral Biology, School of Dental Medicine, University of Pennsylvania, 4010 Locust Street, Philadelphia, Pennsylvania, 19104-6002, USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Wang
authors.forename: I R
authors.initials: IR
authors.lastname: Kieba
authors.forename: J
authors.initials: J
authors.lastname: Korostoff
authors.forename: T L
authors.initials: TL
authors.lastname: Guo
authors.forename: N
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: H
authors.initials: H
authors.lastname: Rozmiarek
authors.forename: P C
authors.initials: PC
authors.lastname: Billings
authors.forename: B J
authors.initials: BJ
authors.lastname: Shenker
authors.forename: E T
authors.initials: ET
authors.lastname: Lally
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000918:Antibody Specificity; D017209:Apoptosis / Q000187:drug effects; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000633:toxicity*; D015153:Blotting, Western; D018821:CD18 Antigens / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects; D004247:DNA / Q000187:drug effects / Q000235:genetics; D053938:DNA Fragmentation; D005098:Exotoxins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000633:toxicity*; D005434:Flow Cytometry; D016978:Mannheimia haemolytica / Q000737:chemistry*; D008854:Microscopy, Electron; D011065:Poly(ADP-ribose) Polymerases / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins; D018821:CD18 Antigens; D005098:Exotoxins; C018579:leukotoxin; D004247:DNA; D011065:Poly(ADP-ribose) Polymerases