Submitted to: Cell Death and Differentiation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2001
Publication Date: 8/1/2001
Citation: Long, E., Capuco, A.V., Wood, D.L., Sonstegard, T.S., Tomita, G., Paape, M.J., Zhao, X. 2001. Apoptosis and cell proliferation are induced in escherichia coli infected bovine lactating mammary glands. Cell Death And Differentiation. 8(8):808-816. Interpretive Summary: Bovine mastitis costs the US dairy industry more than two billion dollars annually due in part to the deleterious effect of intramammary infection on milk production. The objective of this experiment was to determine the influence of mastitis on the death and proliferation of mammary secretory cells. Intramammary infection with Escherichia coli increased the incidence eof programmed cell death (apoptosis) in the mammary gland while also increasing cell proliferation. Expression of genes that promote apoptosis was increased and genes that inhibit apoptosis decreased in mastitic tissue. This study helps to identify the apoptotic pathway involved in eliciting a death response to mastitis and suggest that proliferative repair mechanisms may also come into play. This lays a foundation for future research to develop strategies that will reduce secretory cell death and lessen the impact of mastitis on milk production. This in turn will provide considerable benefits to the dairy industry.
Technical Abstract: Apoptosis and cell proliferation during bovine coliform mastitis were assessed. Escherichia coli was injected into the left quarters of six healthy lactating cows. Bacteriological analysis of foremilk samples revealed coliform infection in 4 injected rear quarters. Milk somatic cell counts increased in these quarters and peaked at 24 h after bacterial injection. Body temperature also increased, peaking at 12 h postinjection. Number of apoptotic cells was significantly higher in the mastitic tissue than in the uninfected control. Expression of Bax and interleukin-1-Beta converting enzyme increased in the mastitic tissue at 24 h and 72 h postinfection, whereas Bcl-2 expression decreased at 24 h but did not differ significantly from the control at 72 h postinfection. Induction of matrix metalloproteinase-9, stromelysin-1 and urokinase-type plasminogen activator was also observed in the mastitic tissue. Moreover, cell proliferation increased in the infected tissue. These results demonstrate that coliform mastitis promotes apoptosis and cell proliferation.