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.
AuthorsJosé A Gutiérrez-Pabello, David N McMurray, L Garry Adams
JournalInfection and immunity (Infect Immun) Vol. 70 Issue 4 Pg. 2121-7 (Apr 2002) ISSN: 0019-9567 [Print] United States
PMID11895978 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • RNA, Messenger
  • Thymosin
  • thymosin beta(10)
  • Amino Acid Sequence
  • Animals
  • Apoptosis
  • Cattle
  • Cell Line
  • DNA Fragmentation
  • Macrophages (microbiology, physiology)
  • Mice
  • Molecular Sequence Data
  • Mycobacterium bovis (physiology)
  • RNA, Messenger (analysis)
  • Thymosin (biosynthesis, genetics)
  • Transformation, Bacterial
  • Up-Regulation

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