Identification of novel biomarker as citrullinated inter-alpha-trypsin inhibitor heavy chain 4, specifically increased in sera with experimental and rheumatoid arthritis

Abstract

BackgroundAnticitrullinated protein antibodies (ACPA) and citrullinated proteins play key roles in the pathogenesis of rheumatoid arthritis (RA). Many candidate citrullinated antigens have been identified in joints, but citrullinated proteins in sera are mostly uncertain in patients with RA. We explored the expression of citrullinated proteins in joints and sera of experimental arthritis, and we further investigated their specific expression correlated with the disease activity in patients with RA.MethodsCitrullinated protein expression in tissues was examined by IHC in peptide glucose-6-phosphate isomerase-induced arthritis (pGIA). Serum citrullinated proteins from pGIA were examined by Western blotting, and the sequence was identified by MS. With the same methods, serum citrullinated proteins were analyzed in patients with RA, primary Sjögren’s syndrome, systemic lupus erythematosus, and osteoarthritis as well as in healthy subjects, by Western blotting and MS. In patients with RA, the relationship between the expression of the identified protein (inter-alpha-trypsin inhibitor heavy chain 4 [ITIH4]) and clinical features was evaluated, and the levels of citrullinated ITIH4 were compared before and after biological treatment. The antibody response against citrullinated ITIH4 peptide was measured by enzyme-linked immunosorbent assay.ResultsCitrullinated proteins were detected specifically in arthritic joints and sera from pGIA relative to controls. In sera, a common band of citrullinated protein at 120 kDa was revealed, and it fluctuated in parallel with arthritis score of pGIA by Western blotting. Interestingly, in 82% of RA patient sera, similar bands of citrullinated protein were specifically detected. These proteins were identified as citrullinated ITIH4, and especially the R438 site was commonly citrullinated between mice and humans. Citrullinated ITIH4 levels were associated with clinical parameters such as C-reactive protein (CRP), rheumatoid factor, and Disease Activity Score in 28 joints as measured by CRP in patients with RA. Its levels were decreased in correlation with the reduction of disease activity score after effective treatment in patients with RA. Moreover, antibody response to citrullinated epitope in ITIH4 was specifically observed in patients with RA.ConclusionsOur results suggest that serum citrullinated ITIH4 was specifically increased in patients with RA and could be a novel biomarker for assessing disease activity in patients with RA.Electronic supplementary materialThe online version of this article (10.1186/s13075-018-1562-7) contains supplementary material, which is available to authorized users.

Remission of Diabetes Following Bariatric Surgery: Plasma Proteomic Profiles

“…An imbalance between SERPINA1 and neutrophil elastase might contribute to the development of obesity and related inflammation, insulin resistance, and liver steatosis [43]. ITIH4 is a liver serine protease inhibitor that is highly expressed during liver development, and is an anti-inflammatory protein proposed to serve as a potential biomarker for acute ischemic stroke and rheumatoid arthritis [44,45]. Our results showed that four isoforms of ITIH4 and one isoform of SERPINA1 (spots 669 and 683) had lower abundance in the diabetes remission group than in the non-diabetic group and an intermediate value in the persistent diabetes group.…”

Δ9‐Tetrahydrocannabinolic acid alleviates collagen‐induced arthritis: Role of PPARγ and CB1 receptors

“…We identified 27 plasma proteins in CIA mice whose levels were totally reversed with Δ 9 ‐THCA‐A treatment through PPARγ and CB 1 receptor activation. Interestingly, our study revealed a preventive effect over inter‐α‐trypsin inhibitor heavy chain H3/4 (Itih3/Itih4) and proteasome subunit β type‐2 (Pmbs2) whose increased concentration in sera of patients with RA was associated with disease activity and has been used as specific biomarkers (Kawaguchi et al, 2018; Liao et al, 2016). In addition, Δ 9 ‐THCA‐A treatment also prevented the secretion of acute‐phase proteins, including haemopexin (Hpx) and haptoglobin (Hp), synthesized in response to a proinflammatory milieu (Baig et al, 2018; Park, Oh, Kim, Cho, & Kim, 2013).…”

Citrullinated inter-alpha-trypsin inhibitor heavy chain 4 in arthritic joints and its potential effect in the neutrophil migration

“…In our study, we speculated that the over‐expression of PAD4 enzyme in infiltrating neutrophils from pGIA mice would induce the citrullination of ITIH4 in joints. Considering the dominant distribution of cit‐ITIH4 in arthritic joints both from pGIA mice and RA patients, it was reasonable to assume that cit‐ITIH4 chiefly originates in inflamed joints and acts as a serum‐specific serum biomarker of arthritis, as we have previously reported [25]. Additionally, as with other citrullinated proteins [30], abundant intraarticular cit‐ITIH4 could be a major source of autoantigens and stimulate antibody production against ITIH4, as we have previously reported [25].…”

“…We previously reported a specific increase of the citrullinated form of ITIH4 (cit‐ITIH4) in the blood from peptide glucose‐6‐phosphate isomerase‐induced arthritis (pGIA) mice and RA patients by mass spectrometry analysis. The blood levels of cit‐ITIH4 fluctuated according to arthritis scores in pGIA mice and disease activity in RA patients, while antibodies to the cit‐ITIH4 epitope were specifically observed in RA patients [25]. However, the mechanism of ITIH4 citrullination and its role in arthritis has not been clarified.…”