Serum amyloid A: A typical acute-phase reactant in rainbow trout?

Monokine-induced hepatic secretion of serum amyloid A protein (apo-SAA), an acute-phase reactant, is followed by rapid association with high-density lipoprotein (HDL) in plasma. Plasma clearance of apo-SAA is more rapid than any of the other HDL apolipoproteins. It has been shown that, of the acute-phase HDL3 apolipoproteins, apo-SAA preferentially associates with neutrophil membranes. HDL apolipoproteins have been shown to activate protein kinase C in endothelial cells. We therefore investigated potential phosphorylation of HDL3 apolipoproteins by protein kinase C. Apo-SAA was the only apolipoprotein phosphorylated (Km = 12 mM). Phosphorylation of the apo-SAA-containing HDL3 particle was selective for the more basic isoforms of apo-SAA (pI 7.0, 7.4, 7.5 and 8.0), with more acidic isoforms being phosphorylated when delipidated acute-phase apolipoproteins were used as substrate. However, phosphorylation was not in itself responsible for the establishment of the apo-SAA isoforms.

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Abstract 388: Impact of Individual Acute Phase Serum Amyloid A Isoforms on HDL Metabolism in Mice

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.388 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Maria C De Beer ◽

Myung-Hee Kim ◽

Joanne M Wroblewski ◽

Richard C Charnigo ◽

Ailing Ji ◽

...

Keyword(s):

Acute Phase ◽

Plasma Clearance ◽

Serum Amyloid A ◽

Biological Activities ◽

Acute Phase Reactant ◽

Serum Amyloid ◽

Minor Role ◽

Clearance Rates ◽

Amyloid A ◽

Significant Difference

The acute phase reactant serum amyloid A (SAA) is an HDL apolipoprotein that exhibits biological activities as a pro-inflammatory mediator, but its physiological function(s) are poorly understood. Possible functional differences between SAA1.1 and SAA2.1, the two major SAA isoforms, are also unclear. Mice deficient in either SAA1.1 or SAA2.1 were used to investigate SAA isoform plasma clearance rates and effects on HDL structure, composition and apolipoprotein catabolism. The absence of either isoform did not affect the size of the normally enlarged HDL found in acute phase wild type mice, and did not result in significant changes in HDL lipid composition. Plasma clearance rates of normal and acute phase HDL apolipoproteins were determined using native HDL particles. The fractional clearance rates (FCR’s) of apoA-I, apoA-II and SAA were distinct, indicating that neither normal nor acute phase particles are cleared as intact particles. No significant difference was found between the FCR’s of SAA1.1 and SAA2.1 in acute phase mice, suggesting that the selective deposition of SAA1.1 observed in amyloid plaques is not associated with a difference in the rates of plasma clearance of the isoforms. In the absence of the HDL receptor SR-BI, the clearance rate of SAA was reduced by about 30% and remained significantly greater compared to that of apoA-I and apoA-II, indicating a relatively minor role of SR-BI in SAA clearance. These studies contribute to our understanding of the metabolism of SAA and its effects on acute phase HDL composition and catabolism.

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Serum Amyloid A Level in Egyptian Children with Familial Mediterranean Fever

International Journal of Rheumatology ◽

10.1155/2016/7354018 ◽

2016 ◽

Vol 2016 ◽

pp. 1-6 ◽

Cited By ~ 3

Author(s):

Hala M. Lofty ◽

Huda Marzouk ◽

Yomna Farag ◽

Mohammad Nabih ◽

Iman A. S. Khalifa ◽

...

Keyword(s):

Familial Mediterranean Fever ◽

Serum Amyloid A ◽

Acute Phase Reactant ◽

Serum Amyloid ◽

Amyloid A ◽

Inflammatory Conditions ◽

Phase Reactant ◽

Egyptian Children ◽

Mediterranean Fever ◽

Colchicine Therapy

Background and Objectives. SAA is an acute-phase reactant detected during an FMF attack or other inflammatory conditions. High SAA levels may increase the risk of amyloidosis. The aim of the study is to measure the serum amyloid A (SAA) level in a group of Egyptian children with familial Mediterranean fever (FMF) and study its various correlates, if any.Methods. The study enrolled seventy-one children with FMF.Results. SAA level was high in 78.9% of the studied patients with a mean of81.62±31.6 mg/L, and CRP was positive in 31% of patients. There was no significant releation between SAA level and any demographic or clinical manifestation. High SAA was more frequent in V726A allele (16.9%) followed by M694V allele (12.3%). Elevated SAA levels were more frequent in patients on low colchicine doses. Forty-five percent (45%) of patients have low adherence to colchicine therapy.Interpretation and Conclusion. High SAA levels were detected two weeks after last FMF attack in a large percentage of Egyptian FMF children. This indicates that subclinical inflammation continues during attack-free periods, and SAA could be used as a marker of it.

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