In Vitro Effects of Nonesterified Fatty Acids on Bovine Neutrophils Oxidative Burst and Viability

Abstract

An in vitro study was conducted to examine the influence of nonesterified fatty acids (NEFA) on bovine polymorphonuclear leukocytes (PMN). Eight healthy, midlactating Holstein cows were used as blood donors. Blood PMN were isolated and incubated with a mixture of NEFA, reflecting composition of bovine plasma NEFA at concentrations that were intended to mimic those found in blood of cows undergoing high, moderate, or low lipomobilization intensity (2, 1, 0.5, 0.25, 0.125, and 0.0625 mM). Control samples were incubated in absence of NEFA. Phagocytosis and oxidative burst activities were assessed by a 2-color flow cytometric method, which was based on oxidation of intracellular dihydrorhodamine 123 to green fluorescent rhodamine 123. Oxidative burst products were generated by incubating PMN with Staphylococcus aureus labeled with propidium iodide. A flow cytometric technique was used to detect PMN viability, necrosis, and apoptosis using fluorescein isothiocyanate-labeled annexin-V and propidium iodide. Phagocytic activity was not affected by NEFA. The highest concentration of NEFA (2 mM) was associated with a dramatic increase of phagocytosisassociated oxidative burst activities with a reduction in cell viability (48.0 vs. 97.5% in control samples) and with a marked increase of necrosis (49.4 vs. 0.5% in control samples). Conversely, the mixture of NEFA did not affect the occurrence of apoptosis. Enhancement of the oxidative burst associated with the highest concentration of NEFA might explain the reduced viability and higher percentage of necrosis observed under the same conditions. This study demonstrated a substantial resistance of bovine PMN to an overload of fatty acids. However, observation that the highest concentration of NEFA regulated some PMN functions encourages the possibility of in vivo studies to assess the rela-

Nutrition, immune function and health of dairy cattle

“…Several studies have also reported that NEFA alter the oxidative burst, apoptosis and necrosis of PMN and macrophages in vitro that may be responsible for host cell damage and death via necrosis during early lactation. In bovine PMN, high NEFA concentrations (2.0 mM) increased phagocytosis-associated oxidative burst activities and reduced cell viability by 50% when compared with controls (Scalia et al, 2006). In addition, necrosis was increased by 48% in PMN incubated with NEFA, whereas the occurrence of apoptosis was similar between NEFA and control cell cultures.…”

Reproductive tract inflammatory disease in postpartum dairy cows

“…It is clear that there are interactions between energy status and immune function. For example, there is evidence that concentrations of NEFA as seen in circulation of cows around calving are associated with impaired PMN function (Scalia et al, 2006;Ster et al, 2012). However, the direct or indirect effects of concentrations of BHBA in cows with ketosis on PMN functions are less consistent (Suriyasathaporn et al, 2000;Ster et al, 2012).…”

“…Cows with severe metritis ate less (2 to 6 kg of dry matter per day) than healthy cows in the 2 to 3 weeks preceding the clinical signs of metritis (Huzzey et al, 2007). Lower feed intake is associated with increased circulating concentrations of NEFA, which may directly (Scalia et al, 2006;Ster et al, 2012) or indirectly (Hammon et al, 2006) inhibit neutrophil function. As discussed above, the high metabolic demands and pathogen challenges in early lactation result in substantial oxidative stress (Sordillo et al, 2009), which also contributes to a pro-inflammatory state that may not be effective for immune defence.…”

Monitoring Metabolic Health of Dairy Cattle in the Transition Period

“…Lower feed intake is associated with increased NEFA which contributes to the risk of fatty liver [21], which in turn is associated with impaired neutrophil function [22]. Additionally, NEFA have been shown to inhibit neutrophil function in vitro [7]. Healthy cows clear the uterus of bacteria by approximately 3 weeks postpartum but important gaps remain in understanding of the immunobiology of the reproductive tract of cattle.…”

“…Dairy cattle also go through a period of substantial lipolysis and a high flux of fatty acids to the liver. High circulating non-esterified fatty acid (NEFA) concentrations are a major risk factor for fatty liver and may also have direct effects on neutrophil function [7]. Because of both high metabolic demands and pathogen challenges, cattle also routinely experience substantial oxidative stress at the same time [8].…”