Mouse serum amyloid A (SAA) proteins isolated by two-dimensional electrophoresis: characterization of isotypes and the effect of separate and combined administrations of cytokines, dexamethasone and lipopolysaccharide (LPS) on serum levels and isotype distribution

ABSTRACT

Hydrophobic interaction chromatography and two-dimensional electrophoresis were used to isolate and characterize mouse SAA, and to study the in vivo effect of separate or combined administrations of cytokines, dexamethasone (DEX) and LPS on mouse SAA. Four SAA spots containing partial amino acid sequence in accordance with mouse apoSAA1 and apoSAA2/SAA_SJL/J pI 5.9 were demonstrated in serum. One of these proteins represents a previously undescribed, acidic acute-phase mouse SAA protein. Both DEX and interferon-gamma (IFN-γ) proved to be capable of increasing SAA serum levels. In contrast to what has been shown in previous in vivo studies, administration of IL-6 did increase the SAA levels to nearly the same magnitude as IL-1, and the effect of IL-6 and LPS on SAA production was not significantly altered by the addition of DEX. Irrespective of the inflammatory stimuli that was administered, a non-selective production of SAA1 and SAA2 was observed in most groups, including the group that received IL-6. The results illustrate that data obtained about mouse SAA are highly dependent on which models, isolation and identification methods are used.