Proteomic Analysis of Serum Amyloid A as a Potential Marker in Intestinal Behçet's Disease

Data regarding biomarkers to understand disease pathogenesis and to assess disease activity of intestinal Behçet's disease (BD) are limited. Therefore, we aimed to investigate the differentially expressed proteins in sera from patients with intestinal BD and to search for biomarkers using mass spectrometry-based proteomic analysis.

Serum samples were pooled for the screening study, and two-dimensional electrophoresis (2-DE) was performed to characterize the proteins present in intestinal BD patients. Candidate protein spots were identified using matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF/TOF MS) and bioinformatic analysis. To validate the proteomic results, serum samples from an independent cohort were assessed by enzyme-linked immunosorbent assay.

Pooled serum samples were used for 2-DE, and approximately 400 protein spots were detected in the sera of intestinal BD patients. Of the 22 differentially expressed proteins, 3 were successfully identified using MALDI-TOF/TOF MS. The three up-regulated proteins identified in the intestinal BD group included fibrin, apolipoprotein A-IV, and serum amyloid A (SAA). Serum SAA in intestinal BD patients (2.76 ± 2.50 ng/ml) was significantly higher than that in controls (1.68 ± 0.90 ng/ml, p = 0.007), which is consistent with the proteomic results. In addition, the level of IL-1β in patients with intestinal BD (8.96 ± 1.23 pg/ml) was higher than that in controls (5.40 ± 0.15 pg/ml, p = 0.009). SAA released by HT-29 cells was markedly increased by tumor necrosis factor-α (TNF-α) and lipopolysaccharides stimulation.

Our proteomic analysis revealed that SAA was up-regulated in intestinal BD patients.