Serum amyloid A protein enhances the activity of secretory non-pancreatic phospholipase A2.
The acute-phase proteins serum amyloid A protein (SAA) and secretory phospholipase A2 (sPLA2) are simultaneously expressed during inflammatory conditions. SAA associates with high-density lipoprotein (HDL) altering its physicochemical composition. We found that purified acute-phase SAA, but not the constitutive form, markedly enhances the lipolytic activity of sPLA2 in a dose-related manner with phosphatidylcholine/lysophosphatidylcholine or phosphatidylethanolamine/lysophosphatidylethanolamine liposomal substrates. Normal HDL was found to reduce activity of sPLA2 in a dose-dependent manner, but when acute-phase HDL containing 27% SAA was tested, it enhanced sPLA2 activity. Immunopurified monospecific antibodies against SAA completely abolished the enhancing activity of SAA and acute-phase HDL. Given the central role of HDL in lipoprotein metabolism, the interaction between HDL, SAA and sPLA2 may account for changes detected in lipoprotein metabolism during the acute phase.
Pruzanski
W
W
Inflammation Research Group, University of Toronto, Ont., Canada.
de Beer
F C
FC
de Beer
M C
MC
Stefanski
E
E
Vadas
P
P
D000209:Acute-Phase Proteins / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D008075:Lipoproteins, HDL / Q000378:metabolism; D010179:Pancreas / Q000201:enzymology; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D000685:Serum Amyloid A Protein / Q000037:antagonists & inhibitors / Q000502:physiology*
D000209:Acute-Phase Proteins; D008075:Lipoproteins, HDL; D000685:Serum Amyloid A Protein; D010741:Phospholipases A; D054467:Phospholipases A2