The acute phase response in Syrian hamsters elevates apolipoprotein serum amyloid A (apoSAA) and disrupts lipoprotein metabolism

Abstract

Lipoprotein metabolism was assessed in hamsters following subcutaneous injection of AgNO₃. Apolipoprotein serum amyloid A (apoSAA) peaked at 36 h, followed by elevations in plasma cholesterol at 56 h and triglycerides at 96 h. There was a striking increase in LDL and a de-crease in HDL. Migration of all acute phase (AP) lipoproteins was retarded compared to controls and SDS-PAGE electrophoretic analysis was consistent with agarose gel profiles that revealed increased apoB-rich VLDL, IDL and LDL and decreased apoAl-rich HDL₂ fractions. Cholesterol transported by LDL of AgNO₃ treated hamsters was double that of controls while the pool of HDL-cholesterol was only two-thirds that of controls. Fasting triglyceride and cholesterol secretion rates were depressed sharply at 24 h. After E. coli lipopolysaccharide (LPS) injection, apoSAA-HDL particles bound avidly to cultured peritoneal macrophages (møs) but in vitro exposure of tissue møs to LPS did not alter the binding characteristics of either control-or apoSAA-HDL, Finally, ¹²⁵I radiolabelled apoSAAHDL and apoAl-HDL decreased during 2–4 h exposure to møs but only apoAl remained associated with cells. Collectively, these data support the hypothesis that apoSAA may commandeer HDL during the AP response in order to deliver phospholipids and cholesterol to cells involved in tissue repair at sites of inflammation.

Key Words:

• CHOLESTEROL
• TRIGLYCERIDE
• INFLAMMATION
• LIPOPROTEIN
• SERUM AMYLOID A
• HAMSTER