Endotoxin and TNF Lead to Reduced Plasma LCAT Activity and Decreased Hepatic LCAT MRNA Levels in Syrian Hamsters

Endotoxin (LPS) administration, which mimics infection, stimulates the production of many cytokines, including TNF, that are thought to mediate the alterations in lipid metabolism that occur during infection. The aims of this study were to determine the effect of LPS or TNF administration on plasma LCAT activity and hepatic LCAT mRNA levels in Syrian hamsters. Plasma LCAT activity was decreased 8 h after LPS administration, reached a maximum level of inhibition at 16 h which persisted for at least 24 h, at which time the activity was 53% of control values. The decrease in plasma LCAT activity was first seen at an LPS dose of 0.01 microgram/100 g body weight and reached a maximum at 50-100 micrograms/100 g body weight. The ratio of free to esterified cholesterol in the plasma increased in the LPS-treated animals. Moreover, LPS administration decreased LCAT mRNA levels in the liver. The decrease in hepatic LCAT mRNA levels preceded the decrease in plasma LCAT activity. Additionally, TNF treatment (16.7 micrograms/100 g body weight) decreased plasma LCAT activity by 35% and LCAT mRNA levels in the liver by 60% 16 h after administration. Lastly, in cultured rat H35 hepatocytes, TNF decreased LCAT mRNA levels in the liver by 60% 16 h after administration. Lastly, in cultured rat H35 hepatocytes, TNF decreased LCAT mRNA levels by 50% with a 1/2 maximal dose of approximately 1 ng/ml. Thus, plasma LCAT activity and hepatic mRNA levels are decreased by LPS or TNF treatment. LCAT is a member of a group of proteins that affect lipid and lipoprotein metabolism whose levels are altered during the host's acute phase response.