Upregulation of thymosin beta-10 by Mycobacterium bovis infection of bovine macrophages is associated with apoptosis.
Bovine macrophages underwent apoptosis as a result of infection with a Mycobacterium bovis field strain. Macrophages infected with a multiplicity of infection (MOI) of 25:1 developed chromatin condensation and DNA fragmentation at 4 h and 8 h, respectively, whereas changes in chromatin condensation induced by MOIs of 10:1 and 1:1 required more time and had a reduced number of apoptotic cells. Not only infected macrophages underwent apoptosis, but also uninfected bystander macrophages became apoptotic. Increased differential expression of thymosin beta-10 was identified in M. bovis-infected bovine macrophages by differential display reverse transcriptase PCR. Phagocytosis of latex beads had no effect on the expression of thymosin beta-10, whereas bacterial suspensions upregulated thymosin beta-10 expression, suggesting that M. bovis or mycobacterial products are essential in the process. Heat-inactivated M. bovis induced a slight increase in thymosin beta-10 mRNA, whereas live virulent and attenuated M. bovis organisms increased the gene expression almost twofold. A mouse macrophage cell line (RAW 264.7) overexpressing the bovine thymosin beta-10 transgene had spontaneous apoptosis at a higher rate (66.5%) than parental cells (4.7%) or RAW cells harboring the empty vector (22.8%). The apoptotic rates of the overexpressing cells were significantly higher when compared with both the empty vector transfected (P < 0.01) and parental cells (P < 0.001). Our evidence suggests that upregulation of thymosin beta-10 in M. bovis-infected macrophages is linked with increased cell death due to apoptosis.
Gutiérrez-Pabello
José A
JA
Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, Texas 77843, USA.
McMurray
David N
DN
Adams
L Garry
LG
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002417:Cattle; D002460:Cell Line; D053938:DNA Fragmentation; D008264:Macrophages / Q000382:microbiology / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009163:Mycobacterium bovis / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D013947:Thymosin / Q000096:biosynthesis* / Q000235:genetics; D014169:Transformation, Bacterial; D015854:Up-Regulation
D012333:RNA, Messenger; D013947:Thymosin; C039302:thymosin beta(10)