A longitudinal study of calprotectin in patients with polymyalgia rheumatica or temporal arteritis: relation to disease activity

New blood biomarkers and imaging for disease stratification and monitoring of giant cell arteritis

Relapses and late complications remain a concern in giant cell arteritis (GCA). Monitoring strategies are required to effectively tailor treatment and improve patients' outcomes. Current monitoring of GCA is based on clinical assessment and evaluation of traditional inflammatory markers such as C reactive protein and erythrocyte sedimentation rate; however, this approach has limited value in patients receiving interleukin (IL)-6 blocking agents. New blood biomarkers that are less dependent on the IL-6 axis such as IL-23, B cell activating factor, osteopontin and calprotectin have been explored, but none of them has yet accumulated sufficient evidence to qualify as a routine follow-up parameter. Imaging techniques, including ultrasound and 18F-fluorodeoxyglucose positron emission tomography/computed tomography, potentially offer additional insights; however, the choice of the imaging method as well as its interpretation must be investigated further. Future studies are required to investigate the outcome of patients with GCA whose treatment decisions are based on traditional plus novel (laboratory and imaging) biomarkers as compared with those undergoing conventional monitoring strategies.

Immune complex-mediated neutrophil activation in patients with polymyalgia rheumatica

OBJECTIVE

Neutrophils are important in host defence. However, neutrophils are also linked to inflammation and organ damage. The purpose of this study was to assess whether markers of neutrophil activation are increased in PMR.

METHODS

Levels of immune complexes (IC), calprotectin and neutrophil extracellular traps (NETs) were measured in plasma of healthy individuals (n = 30) and patients with PMR (n = 60), at flare and upon treatment with glucocorticoids using ELISA. Plasma-mediated neutrophil activation was assessed in presence of an FcγRIIA inhibitory antibody (IV.3).

RESULTS

Plasma levels of calprotectin and NETs were elevated in PMR (P < 0.001). Mechanistically, neutrophil activation was driven by ICs, present in plasma, able to up-regulate neutrophil activation markers CD66b and CD11b (P < 0.0001) in an FcγRIIA-dependent manner (P < 0.01). Of note, circulating levels of IC correlated with plasma induced CD66b and CD11b (r = 0.51, P = 0.004, and r = 0.46, P = 0.01, respectively) and decreased after glucocorticoid therapy. In contrast to NETs, calprotectin significantly decreased after glucocorticoid therapy (P < 0.001) and was higher in PMR without overlapping GCA compared with patients with overlapping disease (P = 0.014). Interestingly, musculoskeletal involvement was associated with elevated levels of calprotectin before initiation of glucocorticoid therapy (P = 0.036).

CONCLUSIONS

Neutrophil activation, including NET formation, is increased in PMR, through IC-mediated engagement of FcγRIIA. Clinically, neutrophil activation is associated with musculoskeletal involvement, with calprotectin, but not NETs, being a biomarker of treatment response in PMR patients. In all, IC-mediated neutrophil activation is a central process in PMR pathogenesis identifying potential novel therapeutic targets (FcγRIIA), as well as soluble markers for disease monitoring (calprotectin).

Assessment of Intestinal Permeability and Inflammation Bio-Markers in Patients with Rheumatoid Arthritis

Increased intestinal permeability and inflammation, both fueled by dysbiosis, appear to contribute to rheumatoid arthritis (RA) pathogenesis. This single-center pilot study aimed to investigate zonulin, a marker of intestinal permeability, and calprotectin, a marker of intestinal inflammation, measured in serum and fecal samples of RA patients using commercially available kits. We also analyzed plasma lipopolysaccharide (LPS) levels, a marker of intestinal permeability and inflammation. Furthermore, univariate, and multivariate regression analyses were carried out to determine whether or not there were associations of zonulin and calprotectin with LPS, BMI, gender, age, RA-specific parameters, fiber intake, and short-chain fatty acids in the gut. Serum zonulin levels were more likely to be abnormal with a longer disease duration and fecal zonulin levels were inversely associated with age. A strong association between fecal and serum calprotectin and between fecal calprotectin and LPS were found in males, but not in females, independent of other biomarkers, suggesting that fecal calprotectin may be a more specific biomarker than serum calprotectin is of intestinal inflammation in RA. Since this was a proof-of-principle study without a healthy control group, further research is needed to validate fecal and serum zonulin as valid biomarkers of RA in comparison with other promising biomarkers.

[Methods for assessment of disease activity of polymyalgia rheumatica]

Polymyalgia rheumatica (PMR) is the second most frequent inflammatory rheumatic disease in old age. Remission and recurrence are frequently used as endpoints in clinical trials; however, there is as yet no international consensus on the definition of these states, which limits the comparability of published studies. The PMR activity score (PMR-AS) is the only composite score specifically developed for PMR, which together with remission is used to define low, middle and high disease activity. In recent studies the PMR-AS was often used and low disease activity was established as endpoint. The most important limitation of the PMR-AS is the potential influence of the individual variables by comorbidities. The value of C‑reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) are of restricted value in studies using drugs that influence the interleukin 6 (IL-6) axis. In these cases, calprotectin and osteopontin are promising alternative biomarkers, as they have already been shown to reflect disease activity independently of CRP in rheumatoid arthritis. Furthermore, imaging modalities including sonography, magnetic resonance imaging and fluorodeoxyglucose (FDG) positron emission tomography could also be helpful in monitoring disease activity; however, these techniques must first be validated in further studies. The PMR impact scale (PMR-IS) is a composite score to assess the impact of PMR on the patients; however, it has not yet been used in clinical studies. The development of additional patient reported outcomes (PRO) for PMR and the definition of standardized criteria for documentation of remission and recurrence are important questions in the future research agenda for PMR.

Calprotectin (S100A8/S100A9) detects inflammatory activity in rheumatoid arthritis patients receiving tocilizumab therapy

Background

Assessing serological inflammation is difficult in tocilizumab (TCZ)-treated rheumatoid arthritis (RA) patients, as standard inflammation parameters, like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are influenced by interleukin-6-receptor inhibition. Calprotectin in the serum, also named S100A8/S100A9, might be a more useful inflammation parameter in TCZ-treated patients.

Methods

Sixty-nine RA patients taking TCZ were included. Serum-calprotectin levels were assessed, as well as ESR, CRP, need for a change in disease-modifying anti-rheumatic drugs due to RA activity (= active RA), and the RA clinical disease activity score (CDAI). Forty-five RA patients taking tumor-necrosis factor-inhibitors (TNFi) were investigated for the same parameters.

Results

TCZ-treated patients with active RA had higher calprotectin values than not active RA patients (4155.5 [inter quartile range 1865.3–6068.3] vs 1040.0 [676.0–1638.0] ng/ml, P < 0.001). A calprotectin cut-off value of 1916.5 ng/ml resulted in a sensitivity and specificity of 80.0 %, respectively, for the detection of RA disease activity. Calprotectin values correlated with CDAI-scores (r = 0.228; P = 0.011). ESR and CRP were less suitable to detect RA activity in TCZ-treated patients. Also TNFi-treated patients with active RA had higher calprotectin values compared to not active RA (5422.0 [3749.0–8150.8] vs 1845.0 [832.0–2569.0] ng/ml, P < 0.001). The calprotectin value with the best sensitivity and specificity for detecting RA activity was 3690.5 ng/ml among TNFi-treated patients.

Conclusion

Calprotectin in the serum can be a useful inflammation parameter despite TCZ-treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02887-7.

The Role of Plasma Calprotectin in Non-infectious Uveitis

PURPOSE

To investigate the role of plasma calprotectin in non-infectious uveitis.

METHODS

This is an observational both cross-sectional and prospective study. Patients with active non-infectious uveitis were recruited as well as nonuveitic controls. Plasma calprotectin was determined and an ophthalmological examination was performed for both patients and controls. Independent variables possibly influencing levels of plasma calprotectin were recorded and analyzed. Categorical variables were compared by chi-square test (applying correction by continuity if necessary). T-test (or Kruskal-Wallis when appropriate) was used to compare averages. Multiple linear regression analysis was used to assess relationship between plasma calprotectin levels and independent variables. Spearman coefficient was calculated in order to establish correlation between plasma calprotectin and anterior chamber cell grading. Changes in plasma calprotectin levels between the flare beginning and its resolution were determined with mixed model for repeated measures. R software (version 3.6.0) was used to perform the statistical analysis.

RESULTS

We included 74 patients and 40 controls in the cross-sectional study. Plasma calprotectin levels were higher in uveitis patients compared to those of controls (p = .003), being higher in younger patients and patients with posterior uveitis. No correlation between calprotectin and anterior chamber inflammation degree was found (p = .198). For the prospective study, we included 36 patients. We found no significant differences in calprotectin levels between active and inactive uveitis (p = .344).

CONCLUSIONS

Plasma calprotectin levels are elevated in uveitis patients and are influenced by age and anatomical location of uveitis. Further investigation is needed to assess the relationship between calprotectin and uveitis activity.

Biomarkers of acute kidney injury: the pathway from discovery to clinical adoption

Acute kidney injury (AKI) is a common complication of critical illnesses and has a significant impact on outcomes, including mortality and morbidities. Unfortunately, apart from prophylactic measures, no effective treatment for this syndrome is known. Therefore, early recognition of AKI not only can provide better opportunities for preventive interventions, but also opens many gates for research and development of effective therapeutic options. Over the last few years, several new AKI biomarkers have been discovered and validated to improve early detection, differential diagnosis, and differentiation of patients into risk groups for progressive renal failure, need for renal replacement therapy (RRT), or death. These novel AKI biomarkers complement serum creatinine (SCr) and urine output, which are the standard diagnostic tools for AKI detection. In this article, we review the available literature on characteristics of promising AKI biomarkers that are currently the focus of preclinical and clinical investigations. These biomarkers include neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), liver-type fatty acid-binding protein, interleukin 18 (lL-18), insulin-like growth factor-binding protein 7, tissue inhibitor of metalloproteinase 2 (TIMP-2), calprotectin, urine angiotensinogen (AGT), and urine microRNA. We then describe the clinical performance of these biomarkers for diagnosis and prognostication. We also appraise each AKI biomarker's advantages and limitations as a tool for early AKI recognition and prediction of clinical outcomes after AKI. Finally, we review the current and future states of implementation of biomarkers in the clinical practice.

Biomarkers in acute kidney injury - pathophysiological basis and clinical performance

Various biomarkers of acute kidney injury (AKI) have been discovered and characterized in the recent past. These molecules can be detected in urine or blood and signify structural damage to the kidney. Clinically, they are proposed as adjunct diagnostics to serum creatinine and urinary output to improve the early detection, differential diagnosis and prognostic assessment of AKI. The most obvious requirements for a biomarker include its reflection of the underlying pathophysiology of the disease. Hence, a biomarker of AKI should derive from the injured kidney and reflect a molecular process intimately connected with tissue injury. Here, we provide an overview of the basic pathophysiology, the cellular sources and the clinical performance of the most important currently proposed biomarkers of AKI: neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), liver-type fatty acid-binding protein (L-FABP), interleukin-18 (IL-18), insulin-like growth factor-binding protein 7 (IGFBP7), tissue inhibitor of metalloproteinase 2 (TIMP-2) and calprotectin (S100A8/9). We also acknowledge each biomarker's advantages and disadvantages as well as important knowledge gaps and perspectives for future studies.

Calprotectin in rheumatic diseases: a review

Calprotectin also known as MRP8/14 or S100A8/A9 is a heterodimeric complex of two S100 calcium-binding proteins: myeloid-related protein 8 (MRP-8 or S100A8) and MRP-14 (or S100A9). At present, according to many authors, it is considered that calprotectin MRP8/14 is a potentially more sensitive biomarker of disease activity in rheumatoid disease than conventional inflammatory indices such as the erythrocyte sedimentation rate, C-reactive protein and others. A review of the literature on concentration of calprotectin in patients with some rheumatic diseases (rheumatoid arthritis, juvenile idiopathic arthritis, adult-onset Still's disease, systemic vasculitis, polymyalgia rheumatica, ankylosis spondylitis, systemic lupus erythematosus, and primary Sjögren's syndrome) is presented.

Calprotectin in rheumatic diseases

Calprotectin is a heterodimer formed by two proteins, S100A8 and S100A9, which are mainly produced by activated monocytes and neutrophils in the circulation and in inflamed tissues. The implication of calprotectin in the inflammatory process has already been demonstrated, but its role in the pathogenesis, diagnosis, and monitoring of rheumatic diseases has gained great attention in recent years. Calprotectin, being stable at room temperature, is a candidate biomarker for the follow-up of disease activity in many autoimmune disorders, where it can predict response to treatment or disease relapse. There is evidence that a number of immunomodulators, including TNF-α inhibitors, may reduce calprotectin expression. S100A8 and S100A9 have a potential role as a target of treatment in murine models of autoimmune disorders, since the direct or indirect blockade of these proteins results in amelioration of the disease process. In this review, we will go over the biologic functions of calprotectin which might be involved in the etiology of rheumatic disorders. We will also report evidence of its potential use as a disease biomarker. Impact statement Calprotectin is an acute-phase protein produced by monocytes and neutrophils in the circulation and inflamed tissues. Calprotectin seems to be more sensitive than CRP, being able to detect minimal residual inflammation and is a candidate biomarker in inflammatory diseases. High serum levels are associated with some severe manifestations of rheumatic diseases, such as glomerulonephritis and lung fibrosis. Calprotectin levels in other fluids, such as saliva and synovial fluid, might be helpful in the diagnosis of rheumatic diseases. Of interest is also the potential role of calprotectin as a target of treatment.

Serum calprotectin--a promising diagnostic marker for adult-onset Still's disease

Calprotectin is a calcium-binding cytosolic protein, mainly expressed in immune cells, such as neutrophils, monocytes, and macrophages. Our study aimed to evaluate the diagnostic value of calprotectin for adult-onset Still’s disease (AOSD), by comparing serum calprotectin concentrations in patients with AOSD (n = 46), rheumatoid arthritis (RA, n = 34), primary Sjögren syndrome (pSS, n = 40), systemic lupus erythematosus (SLE, n = 39), osteoarthritis (OA, n = 20), and healthy controls (HCs, n = 49). Calprotectin concentrations were significantly higher in patients with AOSD (55.26 ± 18.00 ng/ml), compared to patients with RA (39.17 ± 18.90 ng/ml), pSS (35.31 ± 19.47 ng/ml), SLE (32.21 ± 25.01 ng/ml), OA (19.24 ± 10.67 ng/ml), and HCs (8.46 ± 5.17 ng/ml). All the differences were highly significant (p < 0.001). Using receiver-operating characteristic curve, the cut-off value of calprotectin was defined as 45.488 ng/ml, and its sensitivity and specificity for AOSD diagnosis were 63.0 and 80.1 %, respectively. The positive rate of calprotectin was significantly higher in AOSD cases compared to patients with other diseases and healthy controls (p < 0.001). Serum calprotectin was positively correlated with ferritin (r = 0.294, p < 0.05), and concentration of hemoglobin was significantly lower in calprotectin-positive patients compared to negative patients in AOSD (103.49 ± 20.21 g/l vs 115.71 ± 15.59 g/l, t = −2.142, p = 0.038). These findings suggest that serum calprotectin may serve as a promising marker for the diagnosis of AOSD and monitor disease activity to a certain extent.

Increased levels of calprotectin in obesity are related to macrophage content: impact on inflammation and effect of weight loss

Calprotectin has been recently described as a novel marker of obesity. The aim of this study was to determine the circulating concentrations and expression levels of calprotectin subunits (S100A8 and S100A9) in visceral adipose tissue (VAT), exploring its impact on insulin resistance and inflammation and the effect of weight loss. We included 53 subjects in the study. Gene expression levels of the S100A8/A9 complex were analyzed in VAT as well as in both adipocytes and stromovascular fraction cells (SVFCs). In addition, circulating calprotectin and soluble receptor for the advanced glycation end product (sRAGE) concentrations were measured before and after weight loss achieved by Roux-en-Y gastric bypass (RYGB) (n = 26). Circulating concentrations and VAT expression of S100A8/A9 complex were increased in normoglycemic and type 2 diabetic obese patients (P < 0.01) and associated with markers of inflammation (P < 0.01). Oppositely, concentrations of sRAGE were significantly lower (P < 0.001) in both obese groups compared to lean volunteers. Elevated calprotectin levels in obese patients decreased (P < 0.00001) after RYGB, whereas sRAGE concentrations tended to increase. Calprotectin was mainly expressed by SVFCs, and its expression was significantly correlated (P < 0.01) with mRNA levels of the monocyte-macrophage-related molecules macrophage-specific antigen CD68 (CD68), monocyte chemotactic protein 1 (MCP1), integrin α-M (CD11B), and NADPH oxidase 2 (NOX2). Tumor necrosis factor-α treatment significantly enhanced (P < 0.05) the mRNA levels of S100 calcium-binding protein A8 (S100A8) of human visceral adipocytes. The increased levels of calprotectin in obesity and obesity-associated type 2 diabetes, its positive association with inflammation as well as the higher expression levels in the SVFCs in VAT suggests a potential role of this protein as a chemotactic factor in the recruitment of macrophages to VAT, increasing inflammation and the development of obesity-associated comorbidities.

Clinical Manifestations but not Cytokine Profiles Differentiate Adult-onset Still’s Disease and Sepsis

Objective.

To analyze clinical manifestations, serum ferritin, and serum cytokine levels in patients with adult-onset Still’s disease (AOSD) or bacterial sepsis and to evaluate their potential use for differential diagnosis.

Methods.

Twenty-two consecutive patients with the first flare of AOSD and 6 patients with an established diagnosis of AOSD under immunosuppressive therapy were compared with 14 patients with bacterial sepsis. Clinical manifestations were scored in a Pouchot AOSD activity score including elevated serum ferritin levels to obtain a modified Pouchot score. Serum cytokine profiles were analyzed from each patient.

Results.

The scores of clinical manifestations using a modified Pouchot activity score were significantly higher in patients with active untreated AOSD (mean 5.60 ± 1.93) compared with patients with chronic AOSD (mean 1.16 ± 0.98; p < 0.001) and patients with sepsis (mean 2.38 ± 1.19; p < 0.001). A modified Pouchot score ≥ 4 shows a sensitivity of 92% and a specificity of 93% for active AOSD. Serum cytokine levels of interleukin 1ß (IL-1ß), IL-6, IL-8, IL-10, IL-12, IL-18, interferon-γ, tumor necrosis factor-α, and calprotectin were elevated in acute AOSD and sepsis. Significant differences were detected only in patients with sepsis who had higher levels of IL-6 and IL-8. The overlap of the 2 groups limits the use of cytokines for differential diagnosis in individual patients.

Conclusion.

A modified Pouchot AOSD activity score including elevated serum ferritin levels was more useful to confirm the diagnosis of AOSD compared to patients with sepsis. Elevated serum cytokines correlate with inflammation but are of limited use to differentiate between active AOSD and bacterial sepsis.

Proposal to decrease the number of negative temporal artery biopsies

OBJECTIVE

The percentage of negative temporal artery biopsies (TABs) remains very high in patients with suspected giant cell arteritis (GCA). The aim of our study was to identify the clinical predictors of TAB results to improve the effectiveness of this diagnostic procedure.

METHODS

We performed a cross-sectional study of 125 consecutive patients who underwent TAB in the Department of Internal Medicine of a public tertiary hospital, from January 1997 to March 2002. We compared patients with a positive and a negative biopsy result.

RESULTS

Forty-six of the 125 biopsies (36.8%) were positive for GCA and 79 (63.2%) negative. Temporal artery (TA) thickening (8.01), decreased pulse (5.58), jaw claudication (4.87), and scalp tenderness (4.29) presented the highest positive likelihood ratios (LR+). Erythrocyte sedimentation rate (ESR) (0.11), headache (0.39), TA thickening (0.42), and decreased pulse (0.48) had the lowest negative likelihood ratios (LR-). Only TA abnormalities [odds ratio (OR) 12.3] and scalp tenderness (OR 6) were independent predictors of biopsy results. By excluding patients with no evidence of TA abnormalities, scalp tenderness, or jaw claudication, only 48% of the 125 biopsies would have been performed; 59 negative biopsies would have been prevented, but six positive biopsies would have been missed.

CONCLUSION

Careful assessment of patients with clinically suspected GCA to rule out artery abnormalities, scalp tenderness, and jaw claudication can lead to a dramatic decrease in the percentage of negative biopsies. This observation may contribute to improving the physician's decision-making process when contemplating TAB.

The endogenous Toll-like receptor 4 agonist S100A8/S100A9 (calprotectin) as innate amplifier of infection, autoimmunity, and cancer

The innate immune system is crucial for initiation and amplification of inflammatory responses. During this process, phagocytes are activated by PAMPs that are recognized by PRRs. Phagocytes are also activated by endogenous danger signals called alarmins or DAMPs via partly specific, partly common PRRs. Two members of the S100 protein family, S100A8 and S100A9, have been identified recently as important endogenous DAMPs. The complex of S100A8 and S100A9 (also called calprotectin) is actively secreted during the stress response of phagocytes. The association of inflammation and S100A8/S100A9 was discovered more than 20 years ago, but only now are the molecular mechanisms involved in danger signaling by extracellular S100A8/S100A9 beginning to emerge. Taking advantage of mice lacking the functional S100A8/S100A9 complex, these molecules have been identified as endogenous activators of TLR4 and have been shown to promote lethal, endotoxin-induced shock. Importantly, S100A8/S100A9 is not only involved in promoting the inflammatory response in infections but was also identified as a potent amplifier of inflammation in autoimmunity as well as in cancer development and tumor spread. This proinflammatory action of S100A8/S100A9 involves autocrine and paracrine mechanisms in phagocytes, endothelium, and other cells. As a net result, extravasation of leukocytes into inflamed tissues and their subsequent activation are increased. Thus, S100A8/S100A9 plays a pivotal role during amplification of inflammation and represents a promising new therapeutic target.