Low Levels of IgG Recognizing the α-1-Antitrypsin Peptide and Its Association with Taiwanese Women with Primary Sjögren’s Syndrome

Abstract

The aim of this study was to examine oxidative stress and low level of α-1-antitrypsin (A1AT) in primary Sjögren’s syndrome (pSS), and evaluate the associated autoreactivity against unmodified and their 4-hydroxy-2-nonenal (HNE)-modified peptides with pSS. Two differentially expressed proteins, α-1-acid glycoprotein 1 (A1AG1) and A1AT, exhibited 2-fold differences, and their HNE modifications were identified by depleted-albumin and immunoglobulin G (IgG) serum protein, in-solution digestion, in-gel digestion, and nano-liquid chromatography–tandem mass spectrometry (nano-LC-MS/MS) from pSS patients and age-matched healthy controls (HCs). Furthermore, levels of proteins, confirmation of HNE modifications, HNE-protein adducts and autoreactivity against unmodified and their HNE-modified peptides were further validated. Levels of the HNE-protein adduct and A1AG1 were significantly higher in pSS patients than HCs, but levels of A1AT were significantly lower in pSS patients compared to HCs. Only the HNE modification of A1AT was confirmed. Our study suggests that elevated HNE-protein adduct, oxidative stress, level (odds ratio (OR) 4.877, p = 0.003), lowered A1AT level (OR 3.910, p = 0.010) and a decreased level of anti-A1AT50–63 IgG (OR 3.360, p = 0.010) showed an increased risk in pSS patients compared to HCs, respectively.

Methodologies for the Determination of Blood Alpha1 Antitrypsin Levels: A Systematic Review

“…AAT has been detected by Western blotting in serum samples from primary Sjögren’s syndrome patients using primary mouse anti-AAT monoclonal antibody (sc-69752, Santa Cruz Biotechnology, Dallas, Texas, USA). In this syndrome, AAT is 2.5 times less expressed than in healthy individuals [ 33 ].…”

Low Levels of IgM and IgA Recognizing Acetylated C1-Inhibitor Peptides Are Associated with Systemic Lupus Erythematosus in Taiwanese Women

“…Serum protein concentrations were measured using a Bradford protein assay according to the protocol of Chang et al [52]. In the measurement, 50 µg of pooled serum protein samples from nine HCs and nine patients with SLE was analyzed using 8% SDS-PAGE, and the gel band was cut corresponded to the molecular weights of 96–105 kDa ( Figure 1A).…”

“…The 367–385 amino acid sequences of the human C1-INH peptide, namely LEDMEQALSPSVFKAIMEK (named C1-INH 367–385 ), and acetylated C1-INH peptide, namely LEDMEQALSPSVFK(Ac)AIMEK (named C1-INH 367–385 Ac), were synthesized (Yao-Hong Biotechnology, New Taipei City, Taiwan). Autoantibody isotypes (IgG, IgM, and IgA) against the C1-INH 367–385 and C1-INH 367–385 Ac peptides were detected using an ELISA according to the protocol of Chang et al [52]. In total, 144 serum samples were tested in duplicate.…”

“…Ac-protein adduct concentrations were determined using the ELISA with minor modification according to the protocol of Chang et al [52]. A total of 104 serum samples were determined in duplicate.…”