title: Nitric oxide not apoptosis mediates differential killing of Mycobacterium bovis in bovine macrophages.
abstract: To identify the resistance phenotype against Mycobacterium bovis in cattle, we used a bactericidal assay that has been considered a marker of this trait. Three of 24 cows (12.5%) were phenotyped as resistant and 21 as susceptible. Resistance of bovine macrophages (MΦ) to BCG challenge was evaluated for its association with SLC11A1 GT microsatellite polymorphisms within 3'UTR region. Twenty-three cows (95.8%) had a GT13 genotype, reported as resistant, consequently the SLC11A1 polymorphism was not in agreement with our bactericidal assay results. MΦ of cows with resistant or susceptible phenotype were challenged in vitro with virulent M. bovis field strain or BCG, and nitric oxide production, bacterial killing and apoptosis induction were measured in resting and LPS-primed states. M. bovis field strain induced more apoptosis than BCG, although the difference was not significant. Resistant MΦ controlled better the replication of M. bovis (P<0.01), produced more nitric oxide (P<0.05) and were slightly more prone to undergo apoptosis than susceptible cells. LPS pretreatment of MΦ enhanced all the functional parameters analyzed. Inhibition of nitric oxide production with n (G)-monomethyl-L-arginine monoacetate enhanced replication of M. bovis but did not modify apoptosis rates in both resistant and susceptible MΦ. We conclude that nitric oxide production not apoptosis is a major determinant of macrophage resistance to M. bovis infection in cattle and that the influence of SLC11A1 gene 3'UTR polymorphism is not associated with this event.
authors.affiliation: Laboratorio de Investigación en Tuberculosis Bovina, Departamento de Microbiología e Inmunología, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Hugo
authors.initials: H
authors.lastname: Esquivel-Solís
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Vallecillo
authors.forename: Alejandro
authors.initials: A
authors.lastname: Benítez-Guzmán
authors.forename: L Garry
authors.initials: LG
authors.lastname: Adams
authors.forename: Yolanda
authors.initials: Y
authors.lastname: López-Vidal
authors.forename: José A
authors.initials: JA
authors.lastname: Gutiérrez-Pabello
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D002417:Cattle; D017931:DNA Primers; D005260:Female; D008264:Macrophages / Q000382:microbiology*; D009163:Mycobacterium bovis / Q000472:pathogenicity*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology*; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic
chemical_list: D020413:3' Untranslated Regions; D017931:DNA Primers; D009569:Nitric Oxide