Reduced Serum Lecithin:Cholesterol Acyltransferase Activity and Cholesteryl Ester Concentration in Calves Experimentally Inoculated with Pasteurella haemolytica and Bovine Herpes Virus-1

Abstract

ABSTRACT. Lecithin:cholesterol acyltransferase (LCAT), the enzyme responsible for esterification of cholesterol in plasma, is reported to be implicated in the regulation of inflammation in laboratory animals. The purpose of the present study was to elucidate the possible relevance of LCAT in the pathogenesis of calf pneumonia induced by inoculations of Pasteurella haemolytica and bovine herpes virus-1 into the calf lung. Serum LCAT activity was significantly (P<0.01) reduced in calves inoculated with Pasteurella haemolytica. The concentration of cholesteryl esters (CE), the product of the LCAT reaction, was also decreased in the inoculated group. Decreases in LCAT activity and the CE concentration were similarly observed in calves in which bovine herpes virus-1 was inoculated. In both bacteria-and virus-inoculated calves, CE concentrations in the high-density lipoprotein fractions were distinctly decreased, whereas those in the low-density lipoprotein fractions were practically unaltered. The acute-phase proteins haptoglobin and serum amyloid A were detected in sera from the bacteria-and virus-inoculated calves; however, the two acute-phase proteins were also found in sera from the control calves. These results suggest that decreases in LCAT activity and the CE concentration are involved in the pathogenesis of pneumonia induced by inoculation of calves with Pasteurella haemolytica and bovine herpes virus-1, and also that the change in the LCAT system is more intimately related to the occurrence of calf pneumonia than the induction of acute-phase proteins such as haptoglobin.-KEY WORDS: bovine, cholesteryl ester, high-density lipoprotein, lecithin:cholesterol acyltransferase, pneumonia.J. Vet. Med. Sci. 61(10): [1101][1102][1103][1104][1105][1106] 1999 enzyme is also reported to be responsible for hydrolyzing platelet-activating factor, the phospholipid (PL) having a broad range of biologic effects, including neutrophil activation and smooth muscle contraction [10]. An association of hypocholesterolemia with calf penumonia is observed in field cases (Nakagawa, unpublished results).The decreased cholesterol concentration in calves with pneumonia implies that LCAT activity is also reduced in those calves, because CE (in cattle serum, more than 80% of cholesterol is CE) is the product of the LCAT reaction. The purpose of the present study was to examine whether LCAT activity and the LCAT-related lipid concentrations are affected in experimental calf pneumonia. Pneumonia was induced by inoculation of calf lungs with Pasteurella haemolytica and bovine herpes virus-1 (BHV-1), the two major pathogens for calf pneumonia [5,7,19]. We report here that LCAT activity and the CE concentration are reduced in calves with pneumonia induced by both pathogens. MATERIALS AND METHODS Bacterial and viral inoculations:Twenty 2-to 3-monthold male Holstein calves weighing 72 to 108 kg were used to induce experimental pneumonic pasteurellosis [9,20]. Calves were housed individually in pens, and were acclimated for 2 weeks. Room temper...

Decreased Apolipoprotein C-III Concentration in the High-Density Lipoprotein Fraction from Calves Inoculated with Pasteurella haemolytica and Bovine Herpes Virus-1

“…The rationale for the decrease is thought to be suppression of the reverse-transport of cholesterol to the liver from injured tissues, in which cholesterol is required for repair and regeneration of damaged membranes. The concentration of cholesteryl esters, the product of the LCAT reaction, is decreased in HDL fractions prepared from sera of bacteria-and virusinoculated calves [10]. ApoC-III acts as an activator of LCAT [6].…”

“…Pneumonia was experimentally induced by inoculations of Pasteurella haemolytica and BHV-1 into calf lung lobes, as described previously [7,8,10,17]. Briefly, a suspension of Pasteurella haemolytica (serotype 1, I29 strain; 1 × 10 9 colony forming units) was administered to right lung lobes of 10 Holstein male calves (2 to 3 months old) using a fiberoptic bronchoscope.…”

“…Blood was obtained at 0, 0.25, 1, 2, 3 and 4 days after treatment. Clinical symptoms observed after the bacterial and viral inoculations were as described previously [7,8,10,17].…”

“…These results, coupled with the previous findings on LCAT activity and the cholesteryl ester concentration, indicate that a decreased HDL concentration is one of the early events occurring during the acute-phase response evoked by infections with Pasteurella haemolytica and bovine herpes virus-1. inoculated with Pasteurella haemolytica and bovine herpes virus-1 (BHV-1), the two major pathogens for calf pneumonia [3,12,14,16,20], we have shown that LCAT activity and the cholesteryl ester concentration are decreased [10]. Because apoC-III also is distributed in the HDL fraction, it is conceivable that the apoC-III concentration is decreased in experimental pneumonia.…”

“…inoculated with Pasteurella haemolytica and bovine herpes virus-1 (BHV-1), the two major pathogens for calf pneumonia [3,12,14,16,20], we have shown that LCAT activity and the cholesteryl ester concentration are decreased [10]. Because apoC-III also is distributed in the HDL fraction, it is conceivable that the apoC-III concentration is decreased in experimental pneumonia.…”