A novel function of serum amyloid A: A potent stimulus for the release of tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-8 by humanblood neutrophil

High density lipoprotein (HDL) and its main apolipoproteins, AI and serum a myloid A (SAA), present in physiological and acute phase response condition s, respectively, affect the inflammatory process. This study focuses on the effect of AI, SAA, and HDL from healthy (N-HDL) and acute phase individual s (AP-HDL) on the release of TNF-alpha, IL-1 beta, and IL-8 by human blood neutrophils, It was observed that SAA (100 mu g/mL) causes a dramatic incre ase (75-400 times) in the basal liberation of the three cytokines assayed. This effect is not triggered by AP-HDL, Although Al (100 mu g/ml) increases the release of IL-1 beta and IL-8 modestly, N-HDL does not. Both HDLs (0.1 6-0.32 mg of protein/mL) had an anti-inflammatory action, decreasing the ba sal and LPS-stimulated cytokine release. Given that the biological role of SAA is still uncertain, the present study adds an important finding potenti ally pertinent to the biological role of this acute phase protein. (C) 2000 Academic Press.