|Long, E - MCGILL UNIVERSITY|
|Zhao, Z - MCGILL UNIVERSITY|
Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2000
Publication Date: July 24, 2000
Citation: Long, E., Capuco, A.V., Wood, D.L., Sonstegard, T.S., Tomita, G., Paape, M.J., Zhao, Z. 2000. Alteration of apoptosis-related gene expression and 92 kda-gelatinase activity in escherichia coli infected bovine mammary glands [abstract]. Joint Abstracts of the American Dairy Science and Society of Animal Science. Technical Abstract: Induction of programmed cell death during experimentally induced mastitis was assessed. Expression of the Bcl-2 family of proteins, that are important regulators of apoptosis, was compared between uninfected and mastitic glands. Five hundred CFU of Escherichia coli (P4: 032) were infused into the left quarters of six healthy lactating Holstein cows and left rear quarters were biopsied 24 or 72 h post-infusion. Uninfected right quarters, biopsied before E. coli infusion, served as controls. Somatic cell counts (SCC) increased in 4 of 6 infused rear quarters and peaked 24 h after bacterial infusion. Body temperature also increased, peaking 12 h after infusion (40.1 C). Bacteriological analysis of milk samples verified coliform infection in these 4 quarters. Western blot analyses were conducted using the mammary biopsies obtained at 0, 24 and 72 h post-infusion. Compared with uninfected controls, expression of the pro- -apoptotic protein, Bax, increased in mastitic tissues 130 and 100% at 24 and 72 h, respectively. Conversely, expression of the anti-apoptotic protein, Bcl-2, decreased 75% at 24 h but did not differ from controls 72 h post-infusion. Expression of Bcl-x was not affected by E. coli mastitis. Apart from altered expression of Bcl-2 family genes, activity of 92-dDa gelatinase increased 10- or 7-fold at 24 and 72 h after bacterial infusion. These results suggest that E. coli mastitis increases the incidence of programmed cell death in bovine mammary tissue. Degradation of the extracellular matrix by gelatinase may be a part of the apoptotic response to E. coli infection.