Key result
SAA2 and S100A8/S100A9 proteins were significantly overexpressed in rheumatoid arthritis patients compared to controls, with SAA1 isoforms differentially present based on disease activity.
Why the study?
Although serum amyloid A and S100 proteins are biomarkers of interest for rheumatoid arthritis, the clinical relevance of specific SAA allelic variants was not established.
Do plasma levels of SAA variants and S100A8/S100A9 proteins measured by targeted proteomics differ between rheumatoid arthritis patients, other inflammatory diseases, and healthy controls?
Observational (n=224)
Do plasma levels of SAA variants and S100A8/S100A9 proteins measured by targeted proteomics differ between rheumatoid arthritis patients, other inflammatory diseases, and healthy controls?
Targeted proteomics reveals that specific SAA variants and S100A8/S100A9 proteins are differentially expressed in rheumatoid arthritis, suggesting their potential as biomarkers for disease activity and early onset.
Answers are grounded in this paper and cite their sources.
SAA/S100 variant assay may aid RA biomarker research; hypothesis-generating and requires validation before clinical consideration.
Serum amyloid A (SAA) and S100 (S100A8, S100A9 and S100A12) proteins were previously identified as biomarkers of interest for rheumatoid arthritis (RA). Among SAA family, two closely related isoforms (SAA-1 and SAA-2) are linked to the acute-phase of inflammation. They respectively exist under the form of three (α, β, and γ) and two (α and β) allelic variants. We developed a single run quantitative method for these protein variants and investigated their clinical relevance in the context of RA. The method was developed and validated according to regulations before being applied on plasma coming from RA patients (n = 46), other related inflammatory pathologies (n = 116) and controls (n = 62). Depending on the activity score of RA, SAA1 isoforms (mainly of SAA1α and SAA1β subtypes) were found to be differentially present in plasma revealing their dual role during the development of RA. In addition, the weight of SAA1α in the total SAA response varied from 32 to 80% depending on the pathology studied. A negative correlation between SAA1α and SAA1β was also highlighted for RA early-onset (r = −0.41). SAA2 and S100A8/S100A9 proteins were significantly overexpressed compared to control samples regardless of RA stage. The pathophysiological relevance of these quantitative and qualitative characteristics of the SAA response remains unknown. However, the significant negative correlation observed between SAA1α and SAA1β levels in RA early-onset suggests the existence of still unknown regulatory mechanisms in these diseases. • Targeted bottom-up proteomics is used to discriminate closely-related biomarkers of rheumatoid arthritis. • A novel analytical approach was employed to access the absolute concentration of proteins. • Serum amyloid A and S100A8/S100A9 proteins are studied in healthy controls and patients suffering from inflammatory diseases. • Differences among serum amyloid A variants were highlighted in rheumatoid arthritis patients.
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Nys et al. (2019) conducted an observational in Rheumatoid arthritis (n=224). Rheumatoid arthritis and other inflammatory pathologies vs. Healthy controls was evaluated on Plasma levels of SAA variants and S100A8/S100A9 proteins. SAA2 and S100A8/S100A9 proteins were significantly overexpressed in rheumatoid arthritis patients compared to controls, with SAA1 isoforms differentially present based on disease activity.
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