Acute mastitis induces upregulation of expression of plasminogen activator-related genes by blood monocytes and neutrophils in dairy ewes

The main objective of the present study was to examine whether genes implicated in the plasminogen activating cascade: urokinase-type plasminogen activator (u-PA), u-PA receptor (u-PAR) and plasminogen activator inhibitors type 1 (PAI-1) and type 2 (PAI-2) are expressed in a differential manner in ovine blood monocytes and neutrophils obtained from healthy and mastitic dairy ewes. A total of 48 blood samples were collected from 8 healthy and 8 mastitic dairy ewes over a period of 3 weeks. Streptococcus agalactiae was detected in milk samples isolated from mastitic animals. Results indicated that expression of all four genes was very low in monocytes and neutrophils isolated from healthy animals. In contrast, there was a 2- to 5-fold increase (P<0.05) in expression of all four genes in monocytes and an 18- to 38-fold increase (P<0.01) in neutrophils isolated from mastitic animals. In conclusion, upregulation of expression of u-PA and u-PAR by monocytes and neutrophils is probably related to the rapidity of migration of these cells towards the mammary gland, while the upregulation of PAI-1 and PAI-2 is a rather enigmatic observation and it is probably related to the successful localization of the infection.