In vitro uptake of HDL-SAA by tissue macrophages during the development of AA amyloidosis in mice

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Abstract
Purified spleen macrophages (SM) and liver Kupffer cells (KC) were incubated with HDL3−SAA for up to 72 h. The uptake of serum amyloid A (SAA) by cells was determined by comparing the amount of SAA, as measured by ELISA, remaining in the supernatant at different time points of incubation. The uptake of SAA by SM significantly increased during the 72 h incubation period. SM obtained from animals undergoing an amyloidosis induction protocol had a similar uptake of SAA when compared to SM obtained from normal animals, thus suggesting that the uptake (and/ or catabolism) of HDL−−SAA by SM during induction of amyloidosis remains stable. No significant increase in the uptake of HDL3−SAA, however, was seen in KC over the 72 h incubation period. The addition of serum amyloid P protein (SAP) to the culture abrogated the uptake of SAA by SM but did not modify the uptake seen with KC. Amyloid P protein (AP) may contribute to the pathogenesis of the disease by inhibiting the cellular uptake of the precursor in the affected organs.