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

Role of inter-alpha-trypsin inhibitor heavy chain 4 and its citrullinated form in experimental arthritis murine models

Inter-α-trypsin inhibitor heavy chain 4 (ITIH4) is a major protein in serum and reported to be upregulated at the onset of rheumatoid arthritis (RA). Its citrullinated form, cit-ITIH4, is specifically found in the serum and synovial fluid of patients with RA. However, the detailed function of ITIH4 in arthritis remains unknown. The aim of this study was to clarify the role of ITIH4 and cit-ITIH4 using experimental arthritis models. ITIH4 and cit-ITIH4 expression was examined in steady-state mice and two different arthritis models, and their pathological effects were examined in Itih4-deficient mice. In naïve C57BL/6 (WT) mice, ITIH4 was expressed as mRNA in the liver and the lung and was expressed as protein in serum and hepatocytes. In K/BxN serum transferred arthritis (K/BxN-STA) and collagen-induced arthritis (CIA), ITIH4 and cit-ITIH4 in sera were increased before the onset of arthritis, and cit-ITIH4 was further increased at the peak of arthritis. In Itih4-deficient mice, citrullinated proteins in serum and joints, especially 120 kDa protein, were clearly diminished; however, there was no significant difference in arthritis severity between WT and itih-/- mice either in the K/BxN-STA or CIA model. CIA mice also exhibited pulmonary lesions and itih4-/- mice tended to show enhanced inflammatory cell aggregation compared to WT mice. Neutrophils in the lungs of itih4-/- mice were significantly increased compared to WT mice. In summary, ITIH4 itself did not alter the severity of arthritis but may inhibit autoimmune inflammation via suppression of neutrophil recruitment.

Serum interα-trypsin inhibitor heavy chain H4 may be an anti-inflammatory marker reflecting disease risk, activity and treatment outcome of ankylosing spondylitis

Interα-trypsin inhibitor heavy chain H4 (ITIH4) modulates inflammation and immunity, which take part in the pathogenesis of ankylosing spondylitis (AS). The current research intended to discover the clinical value of serum ITIH4 quantification for AS management. Serum ITIH4 among 80 AS patients before current treatment initiation (baseline) at weeks (W) 4, 8 and 12 after treatment was detected by ELISA. Serum ITIH4 from 20 disease controls (DCs) and 20 healthy controls (HCs) was detected. ITIH4 expression was lower in AS patients than in DCs (p = 0.002) and HCs (p < 0.001). Among AS patients, ITIH4 was negatively associated with C-reactive protein (CRP) (r = -0.311, p = 0.005), bath AS disease activity index (BASDAI) (r = -0.223, p = 0.047), total pack pain (r = -0.273, p = 0.014) and AS disease activity score (ASDAS) (CRP) (r = -0.265, p = 0.018). Meanwhile, ITIH4 was negatively related to tumor necrosis factor (TNF)-α (r = -0.364, p = 0.001), interleukin (IL)-1β (r = -0.251, p = 0.025), IL-6 (r = -0.292, p = 0.009) and IL-17A (r = -0.254, p = 0.023). After treatment, the assessment of the spondylitis arthritis international society 40 response rate was 28.7% at W4, 46.3% at W8 and 55.0% at W12; ITIH4 showed an increasing trend from baseline to W12 (p < 0.001). Furthermore, ITIH4 at W8 (p = 0.020) and W12 (p = 0.035), but not at baseline or W4 (both p > 0.05), was enhanced in response patients vs. nonresponse patients. Additionally, ITIH4 at W12 was increased in AS patients receiving TNF inhibitors vs. those receiving nonsteroidal anti-inflammatory drugs (NSAIDs) (p = 0.024). Serum ITIH4 increases after treatment, and its augmentation is correlated with lower disease activity, decreased inflammation and enhanced treatment response in AS patients.

Neutrophil attachment via Mac-1 (αMβ2; CD11b/CD18; CR3) integrins induces PAD4 deimination of profilin and histone H3

Neutrophil adhesion to endothelia, entry into tissues and chemotaxis constitute essential steps in the immune response to infections that drive inflammation. Neutrophils bind to other cells and migrate via adhesion receptors, notably the αMβ2 integrin dimer (also called Mac-1, CR3 or CD11b/CD18). Here, the response of neutrophils to integrin engagement was examined by monitoring the activity of peptidylarginine deiminase 4 (PAD4). Histone H3 deimination was strongly stimulated by manganese, an integrin-activating divalent cation, even in the absence of additional inflammatory stimuli. Manganese-induced cell attachment resulted in neutrophil swarm formation that paralleled histone deimination, whereas antibodies that impair integrin binding prevented both cell adhesion and histone deimination. Manganese treatment led to putative deimination of profilin, a protein that functions as an actin-organizing hub, as detected by two-dimensional gel electrophoresis and citrulline immunoblotting. Cl-amidine, a covalent inhibitor of PAD4, and GSK484, a specific PAD4 inhibitor, blocked profilin deimination. Neutrophil migration toward leukotriene B4 and toward synovial fluid from a rheumatoid arthritis patient were inhibited by chloramidine, thus supporting the contribution of deimination to chemotaxis. The data, based on a simplified system for integrin activation, imply a mechanism whereby integrin attachment coordinates neutrophil responses to inflammation and orchestrates deimination of nuclear and cytoskeletal proteins. This article is part of the Theo Murphy meeting issue 'The virtues and vices of protein citrullination'.

Network proteomic analysis identifies inter-alpha-trypsin inhibitor heavy chain 4 during early human Achilles tendon healing as a prognostic biomarker of good long-term outcomes

The suboptimal or protracted regeneration of injured connective tissues often results in significant dysfunction, pain, and functional disability. Despite the prevalence of the condition, few studies have been conducted which focused on biomarkers or key molecules involved in processes governing healing outcomes. To gain insight into injured connective tissue repair, and using the Achilles tendon as a model system, we utilized quantitative proteomic and weighted co-expression network analysis of tissues acquired from Achilles tendon rupture (ATR) patients with different outcomes at 1-year postoperatively. Two modules were detected to be associated with prognosis. The initial analysis identified inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4) as a biomarker or hub protein positively associated with better healing outcomes. Additional analysis identified the beneficial role of ITIH4 in inflammation, cell viability, apoptosis, proliferation, wound healing, and for the synthesis of type I collagen in cultured fibroblasts. Functionally, the effects of ITIH4 were found to be mediated by peroxisome proliferator-activated receptor gamma (PPARγ) signaling pathways. Taken together, these findings suggest that ITIH4 plays an important role in processes of connective tissue repair and advocate for the potential of ITIH4 as a therapeutic target for injured connective tissue repair.

Trial registration

http://clinicaltrials.gov, identifiers NCT02318472, NCT01317160.

Serum ITIH4 in coronary heart disease: a potential anti-inflammatory biomarker related to stenosis degree and risk of major adverse cardiovascular events

Aim: This study aimed to investigate the correlation of ITIH4 with inflammatory cytokines, stenosis degrees and prognosis in coronary heart disease (CHD) patients. Methods: Serum ITIH4 levels of 300 CHD patients and 30 controls, together with levels of TNF-α, IL-6, IL-8 and IL-17A of CHD patients, were determined using ELISA. Results: Serum ITIH4 was reduced in CHD patients versus controls (p < 0.001). ITIH4 was negatively linked with TNF-α, IL-6, IL-8, IL-17A, C-reactive protein, serum creatinine and Gensini score in CHD patients (all p < 0.050). ITIH4 quartile level negatively correlated with the cumulative major adverse cardiovascular event rate (p = 0.041). Conclusion: Serum ITIH4 may serve as an anti-inflammatory biomarker that negatively associates with stenosis degree and major adverse cardiovascular event risk in CHD patients.

Inter‐alpha‐trypsin inhibitor heavy chain 4: A serologic marker relating to disease risk, activity, and treatment outcomes of rheumatoid arthritis

Objective

Inter‐alpha‐trypsin inhibitor heavy chain 4 (ITIH4) regulates immunity and inflammation, but its clinical role in rheumatoid arthritis (RA) patients remains unclear. Hence, this study was conducted to explore the association of circulating ITIH4 with disease risk, clinical features, inflammatory cytokines, and treatment outcomes of RA.

Methods

After the enrollment of 93 active RA patients and 50 health controls (HCs), their serum ITIH4 level was analyzed by enzyme‐linked immunosorbent assay (ELISA). For RA patients only, serum ITIH4 level at week (W) 6 and W12 after treatment was also analyzed. Besides, serum tumor necrosis factor‐alpha (TNF‐α), interleukin (IL)‐1β, IL‐6, and IL‐17A at baseline of RA patients were also detected by ELISA.

Results

ITIH4 was downregulated in RA patients (151.1 (interquartile range (IQR): 106.2–213.5) ng/mL) than in HCs (306.8 (IQR: 238.9–435.1) ng/mL) (p < 0.001). Furthermore, ITIH4 was negatively related to C‐reactive protein (CRP) (r_s = −0.358, p < 0.001) and 28‐joint disease activity score using erythrocyte sedimentation rate (DAS28‐ESR) (r_s = −0.253, p = 0.014) in RA patients, but not correlated with other clinical features (all p > 0.05). Besides, ITIH4 was negatively linked with TNF‐α (r_s = −0.337, p = 0.001), IL‐6 (r_s = −0.221, p = 0.033), and IL‐17A (r_s = −0.368, p < 0.001) in RA patients, but not correlated with IL‐1β (r_s = −0.195, p = 0.061). Moreover, ITIH4 was gradually elevated in RA patients from baseline to W12 after treatment (p < 0.001). Additionally, the increment of ITIH4 at W6 and W12 was linked with treatment response and remission in RA patients (all p < 0.05).

Conclusion

Circulating ITIH4 possesses clinical utility in monitoring disease risk, inflammation, disease activity, and treatment outcomes of RA.

Serum inter-alpha-trypsin inhibitor heavy chain 4 in patients with inflammatory bowel disease: correlation with disease risk, inflammation, activity, and its variation after treatment

BACKGROUND

Inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4) plays vital roles in inflammatory and auto-immune diseases, but its correlations with disease risk and clinical features in inflammatory bowel disease (IBD) need further investigation. The present study intended to explore the correlation of ITIH4 with disease activity and inflammation, as well as its change after treatment in IBD patients.

METHODS

Totally, 40 active Crohn's disease (A-CD) patients, 40 clinical-remission CD (R-CD) patients, 40 active ulcerative colitis (A-UC) patients, 40 clinical-remission UC (R-UC) patients, and 40 health controls (HCs) were enrolled. ITIH4 in serum was assessed by ELISA.

RESULTS

ITIH4 was lower in A-CD, R-CD, A-UC, and R-UC patients than in HCs (P < 0.001). Notably, ITIH4 reduced in A-CD patients than in R-CD patients (P = 0.017), and in A-UC patients compared with R-UC patients (P = 0.010). Besides, in A-CD patients, ITIH4 negatively correlated with tumor necrosis factor-alpha (TNF-α), interleukin (IL)-17A, IL-1β, C-reactive protein (CRP), and clinical disease activity index score (all P < 0.05). In A-UC patients, ITIH4 negatively correlated with TNF-α, IL-17A, IL-1β, IL-6, CRP, and Mayo score (all P < 0.05). However, in R-CD and R-UC patients, these correlations were less obvious than in A-CD and A-UC patients. ITIH4 was increased after treatment (all P < 0.05), and its expression at W12 after treatment was higher in response patients compared with no response patients in A-CD (P = 0.022) and A-UC groups (P = 0.038).

CONCLUSION

ITIH4 correlates with IBD susceptibility, active risk, inflammation level, and its elevation after treatment relates to clinical response in IBD patients.

Specific Increase in Joint Neutrophil Extracellular Traps and Its Relation to Interleukin 6 in Autoimmune Arthritis

Neutrophils and their extracellular traps have been shown to play an important role in the pathogenesis of rheumatoid arthritis (RA), but the detailed mechanisms in joints are still unclear, and their regulation remains to be solved. Here, we explored neutrophil extracellular trap (NET)osis in experimental models of arthritis and further investigated the effects of interleukin-6 (IL-6) inhibition in neutrophils and NETosis. In skins of peptide GPI-induced arthritis (pGIA), citrullinated protein was detected as well as citrullinated histone expression in immunized skin but this was not specific to pGIA. Citrullinated histone expression in pGIA joints was specific to pGIA and was merged with neutrophil elastase, suggesting NETosis. Neutrophils in joints tend to upregulate IL-6 receptors when compared with bone marrow neutrophils. Administration of mouse anti-IL-6 receptor antibodies in pGIA suppressed arthritis in association with a decrease in neutrophil infiltration and NETosis in joints. In the plasma of RA patients, citrullinated protein was significantly reduced after tocilizumab treatment. Our results suggest that IL-6 enhances neutrophil chemotaxis and NETosis in inflammatory joints and could be the source of citrullinated proteins.