Collagen Autoantibodies and Their Relationship to CCP Antibodies and Rheumatoid Factor in the Progression of Early Rheumatoid Arthritis

Anti-citrullinated protein antibodies as biomarkers in rheumatoid arthritis

INTRODUCTION

The serological biomarker anti-citrullinated protein antibodies (ACPAs) may have several functions but is especially important for the diagnosis of rheumatoid arthritis (RA) along with clinical symptoms.

AREAS COVERED

This review provides an overview of ACPAs, which are useful in RA diagnostics and may improve our understanding of disease etiology. PubMed was searched with combinations of words related to antibodies recognizing epitopes containing the post-translationally modified amino acid citrulline in combination with rheumatoid arthritis; cyclic citrullinated peptide, CCP, anti-CCP, anti-citrullinated protein antibodies, ACPA, citrullination, peptide/protein arginine deiminase, PAD, filaggrin, vimentin, keratin, collagen, perinuclear factor, EBNA1, EBNA2, and others. From this search, we made a qualitative extract of publications relevant to the discovery, characterization, and clinical use of these antibodies in relation to RA. We highlight significant findings and identify areas for improvement.

EXPERT OPINION

ACPAs have high diagnostic sensitivity and specificity for RA and recognize citrullinated epitopes from several proteins. The best-performing single epitope originates from Epstein-Barr Virus nuclear antigen 2 and contains a central Cit-Gly motif, which is recognized by ACPAS when located in a flexible peptide structure. In addition, ACPAs may also have prognostic value, especially in relation to early treatment, although ACPAs' main function is to aid in the diagnosis of RA.

Significance of Type II Collagen Posttranslational Modifications: From Autoantigenesis to Improved Diagnosis and Treatment of Rheumatoid Arthritis

Collagen type II (COL2), the main structural protein of hyaline cartilage, is considerably affected by autoimmune responses associated with the pathogenesis of rheumatoid arthritis (RA). Posttranslational modifications (PTMs) play a significant role in the formation of the COL2 molecule and supramolecular fibril organization, and thus, support COL2 function, which is crucial for normal cartilage structure and physiology. Conversely, the specific PTMs of the protein (carbamylation, glycosylation, citrullination, oxidative modifications and others) have been implicated in RA autoimmunity. The discovery of the anti-citrullinated protein response in RA, which includes anti-citrullinated COL2 reactivity, has led to the development of improved diagnostic assays and classification criteria for the disease. The induction of immunological tolerance using modified COL2 peptides has been highlighted as a potentially effective strategy for RA therapy. Therefore, the aim of this review is to summarize the recent knowledge on COL2 posttranslational modifications with relevance to RA pathophysiology, diagnosis and treatment. The significance of COL2 PTMs as a source of neo-antigens that activate immunity leading to or sustaining RA autoimmunity is discussed.

Tripterygium wilfordii glycosides ameliorates collagen-induced arthritis and aberrant lipid metabolism in rats

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, and the dysregulation of lipid metabolism has been found to play an important role in the pathogenesis of RA and is related to the severity and prognosis of patients. Tripterygium wilfordii glycosides (TWG) is extracted from the roots of Tripterygium wilfordii Hook F. with anti-inflammatory and immunosuppressive effects, and numerous clinical trials have supported its efficacy in the treatment of RA. Some evidence suggested that TWG can modulate the formation of lipid mediators in various innate immune cells; however whether it can improve RA-related lipid disorders has not been systematically studied. In the study, type Ⅱ collagen-induced arthritis (CIA) model was used to investigate the efficacy of TWG in the treatment of RA and its effect on lipid metabolism. Paw volume, arthritis score, pathological changes of ankle joint, serum autoantibodies and inflammatory cytokines were detected to assess the therapeutic effect on arthritis in CIA rats. Then, shotgun lipidomics based on multi-dimensional mass spectrometry platform was performed to explore the alterations in serum lipidome caused by TWG. The study showed that TWG could effectively ameliorate arthritis in CIA rats, such as reducing paw volume and arthritis score, alleviating the pathological damages of joint, and preventing the production of anti-CII autoantibodies and IL-1β cytokine. Significant increase in ceramide and decrease in lysophosphatidylcholine were observed in CIA rats, and were highly correlated with arthritis score and IL-1β level. After TWG treatment, these lipid abnormalities can be corrected to a great extent. These data demonstrate that TWG exerts a beneficial therapeutic effect on aberrant lipid metabolism which may provide new insights for further exploring the role and mechanism of TWG in the treatment of RA.

Circular RNA circNUP214 Modulates the T Helper 17 Cell Response in Patients With Rheumatoid Arthritis

Circular RNAs (circRNAs) are important transcriptional regulators of genome expression that participate in the pathogenesis of human diseases. Mechanistically, circRNAs, as competitive endogenous RNAs (ceRNAs), can sponge microRNAs (miRNAs) with miRNA response elements. A previous study identified that hsa_circ_0089172 (circNUP214) is abnormally expressed in Hashimoto's thyroiditis. However, the role of circNUP214 in rheumatoid arthritis (RA) remains unclear. In total, 28 RA patients and 28 healthy controls were enrolled in this study. We found that circNUP214 is an abundant and stable circRNA in RA patients that can potentially differentiate RA patients from healthy subjects. Additionally, the elevated levels of IL-23R positively correlated with circNUP214 expression. The knockdown of circNUP214 resulted in the reduction of IL-23R at both transcriptional and translational levels in human CD4+ T cells. The proportion of circulating Th17 cells and the transcript levels of IL-17A were increased in RA patients and were both positively correlated with IL-23R expression. Moreover, positive correlations between the transcript levels of circNUP214 and the percentage of Th17 cells and the transcript levels of IL-17A were observed in RA patients. The downregulation of circNUP214 decreased the proportion of Th17 cells and the transcript levels of IL-17A in vitro. Furthermore, circNUP214 functioned as a ceRNA for miR-125a-3p in RA patients. Taken together, our results indicate that elevated levels of circNUP214 contribute to the Th17 cell response in RA patients.

Hyperbaric oxygen in animal model of rheumatoid arthritis: Analysis Of HIF-1α, ACPA and IL-17a

Antigen and collagen-induced arthritis (ACIA) is animal model of rheumatoid arthritis. The aim of this study was to identify the effect of different doses of hyperbaric oxygen (HBO) exposure in reducing inflammation on ACIA through analysis hypoxia inducible factor-1α (HIF-1α), anticyclic citrullinated peptide antibody (ACPA) and interleukine 17a (IL-17a). 24 male Balb/C mice were divided into 3 groups, 8 mice did not receive HBO exposure as a control group (G1) and 16 mice received HBO exposure as treatment group (G2 and G3). G2 was ACIA which was exposed to HBO 2.4 ATA O2 100% 90 minutes divided by 3 each 30 minutes intervals 2 times 5 minutes breathing with normal air for 10 consecutive days. G3 was ACIA which was exposed to HBO 2.4 ATA O2 100% 90 minutes divided by 3 each 30 minutes intervals 2 times 5 minutes breathing with normal air for 5 consecutive days, break 5 days, 5 consecutive days.ACPA and IL-17a were measured by enzyme-linked immunosorbent assay (ELISA) technique. The expression of HIF-1α was measured by immunohistochemistry technique. There was significant decrease of ACPA levels, IL-17a levels and HIF-1α expression (P< 0.05) in G2 and G3 compared to G1. There was not significant decrease of ACPA levels (P> 0.05), there was significant decrease of IL-17a levels and HIF-1α expression (P<0.05) in G2 compared to G3. G2 was a group with a higher oxygen partial pressure than G3. HBO 2.4 ATAO2 100% 90 minutes divided by 3 each 30 minutes intervals 2 times 5 minutes breathing with normal air for 10 consecutive days more effective in reducing inflammation than exposure 5 consecutive days, break 5 days, 5 consecutive days in ACIA. HBO has therapeutic potential for the treatment of RA.