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- Title
TNFα-mediated plasminogen activation on neutrophils is involved in the high plasmin activity in mammary secretion of drying-off cows.
- Authors
Chou, Wen K.; Yu, Ting C.; Chen, Shuen E.; Peh, Ho C.; Liu, Wen B.; Chen, Ming T.; Nagahata, Hajime; Chang, Chai J.
- Abstract
Interactions between inflammatory cytokines and plasminogen (Pg) activation system on immune cells are yet to be established. In previous studies we reported a somatic cell-associated elevation of proteolytic activity in mammary secretion of drying-off goats and cows. The purposes of the present study were to examine the role of TNFα in polymorphonuclear neutrophil (PMN)-associated Pg activation, and the significance of this activation pathway for overall plasmin (Pm) activity in mammary secretion of drying-off cows. Results of experiments in vitro showed that the spontaneous Pg activation observed on fresh preparations of bovine blood PMN was completely blocked by anti bovine TNFα antibody, and was further up-regulated by exogenous bovine TNFα. Monitoring the parameters of mammary secretion of drying-off cows revealed that both somatic cell counts and differential PMN ratio was significantly elevated at weeks 1, 2 and 3 of milk stasis. Nevertheless, specific activity of soluble Pm in mammary secretion increased and the level of 17-kDa TNFα decreased immediately following milk stasis. Iimmunoblotting revealed that although both 26-kDa pro-TNFα and 17-kDa TNFα were consistently present in somatic cells of mammary secretion collected at weeks 0, 1, 2 and 3 of milk stasis, only 26-kDa pro-TNFα was present in somatic cells of milk during lactation. In-vitro assay indicated that cell-free mammary secretion of drying-off cows exerted no Pg activation bioactivity towards bovine blood PMN. Altogether, the current study suggests the existence of an active TNFα-Pg-Pm autocrine/paracrine loop on the massively infiltrated PMN inside udders of drying-off cows, which involves extensive binding and internalization of 17-kDa TNFα on PMN and consequently activation of Pg, resulting in high Pm activity and low 17-kDa TNFα level in mammary secretion. These coordinated mechanisms may play a role in the defence of drying-off mammary gland.
- Subjects
GOAT milk yield; MILK yield; SOMATIC cells; PLASMINOGEN; FIBRINOLYTIC agents
- Publication
Journal of Dairy Research, 2009, Vol 76, Issue 4, p459
- ISSN
0022-0299
- Publication type
Article
- DOI
10.1017/S0022029909990069