Relevance of paraoxonase-1, platelet- activating factor acetylhydrolase and serum amyloid A in bovine mastitis

Abstract

Bovine mastitis is the most economically important production disease in dairy cows. The pathogenesis of mastitis involves an inflammatory reaction resulting from production of cytokines at the site of infection. Proinflammatory cytokines stimulate the synthesis of acute phase proteins (APPs) predominantly in liver but also in other tissues including mammary gland (Eckersall et al., 2006). Serum amyloid A (SAA) is one of the major APP in ruminants whose concentration rises dramatically during acute phase response (APR). During APR, SAA associates rapidly with high density lipoproteins (HDL), displacing apo A-1 (the major apolipoprotein of native HDL) and becoming the predominant apolipoprotein (apo SAA) in HDL. Native HDL contains paraoxonase-1 (PON1) and platelet-activating factor acetylhydrolase (PAF-AH), both antioxidative/anti-inflammatory enzymes being responsible for anti-inflammatory/anti-oxidative properties of HDL. Concomitantly with SAA enrichment of HDL during APR, PON1 and PAF-AH levels decrease within HDL, what impairs anti-oxidative properties of HDL which from an anti-inflammatory particle becomes a proinflammatory particle, i.e. acute phase HDL (AP-HDL) (Van Lenten at al., 1995).