Vet. Res. 38 (2007) 655-668
DOI: 10.1051/vetres:2007024

Bovine blood neutrophil acyloxyacyl hydrolase (AOAH) activity during endotoxin and coliform mastitis

Jalil Mehrzad^{a, b}, Hilde Dosogne^{c, b}, Bart De Spiegeleer^d, Luc Duchateau^b and Christian Burvenich<sup>b

a</sup>  Ferdowsi University of Mashhad, Faculty of Veterinary Medicine, Department of Pathobiology, Section Immunology, PO Box 91775-1793, Mashhad, Iran
^b  Ghent University, Faculty of Veterinary Medicine, Department of Physiology and Biometrics, member of Phimadran, Salisburylaan 133, 9820 Merelbeke, Belgium
^c  DeLaval International AB, Product Portfolio Milk Quality and Animal Health, Industriepark 8-10, 9031 Drongen, Belgium
^d  Ghent University, Faculty of Pharmaceutical Sciences, Drug Quality and Registration (DruQuaR) group, member of Phimadran, Harelbekestraat 72, 9000 Gent, Belgium

(Received 7 December 2006; accepted 19 March 2007; published online 23 June 2007)

Abstract - The dynamics of blood neutrophil acyloxyacyl hydrolase (AOAH) activity, the appearance of endotoxin (lipopolysaccharide, LPS) in blood and the role of blood neutrophil AOAH in the severity of Escherichia coli and endotoxin mastitis were investigated in early postpartum dairy cows experimentally challenged with either endotoxin (n = 6) or E. coli (n = 6). The AOAH activity of blood neutrophils started to decrease significantly at post challenge hours (PCH) 6-24 and 12-24 in the endotoxin and E. coli-challenged groups, respectively; it returned to pre-challenged values at PCH 48 in both endotoxin- and E. coli-challenged groups. The cows were classified as moderate and severe responders according to milk production loss in the non-challenged quarters at PCH 48. There were no severe responders in the endotoxin-challenged group. In the E. coli-challenged group, only 1 severe responder was identified. The pre-challenge neutrophil AOAH activity of the severe responder was 30% lower than that of moderate responders. No LPS was detected in the plasma of endotoxin-challenged cows; neither was it found in the plasma of moderate responders in the E. coli-challenged group at any PCH. However, at PCH 6, a remarkable amount of LPS was detected in the plasma of the severe responder from the E. coli-challenged group. Furthermore, neutrophil AOAH activity was increased by 70% in the severe responder at PCH 6, but it increased by only 15% in moderate responders. This was followed by a decreased neutrophil AOAH activity at PCH 12-24 and 24-72 in moderate and severe responders, respectively; the decreased AOAH activity at those PCH was more pronounced in the severe responder. The pronounced decreased neutrophil AOAH activity during mastitis often coincided with extreme leukopenia, neutropenia and a maximal number of immature neutrophils in the blood. Our results demonstrate that a decrease in neutrophil AOAH activity results in the appearance of LPS in the blood, and low blood neutrophil deacylation activity could be considered as a risk factor for severe clinical coliform mastitis.

Key words: acyloxyacyl hydrolase (AOAH) / blood / endotoxin / mastitis / neutrophils

Corresponding author: christian.burvenich@ugent.be

© INRA, EDP Sciences 2007