Increased concentration of plasma TNFR1 and TNFR2 in paediatric lupus nephritis

Noninvasive biomarkers for lupus nephritis

Lupus nephritis (LN) is one of the most severe clinical manifestations of systemic lupus erythematosus (SLE). Notably, the clinical manifestations of LN are not always consistent with the histopathological findings. Therefore, the diagnosis and activity monitoring of this disease are challenging and largely depend on invasive renal biopsy. Renal biopsy has side effects and is associated with the risk of bleeding and infection. There is a growing interest in the development of novel noninvasive biomarkers for LN. In this review, we summarize most of the LN biomarkers discovered so far by correlating current knowledge with future perspectives. These biomarkers fundamentally reflect the biological processes of kidney damage and repair during disease. Furthermore, this review highlights the role of urinary cell phenotype detection in the diagnosis, monitoring, and treatment of LN and summarizes the limitations and countermeasures of this test.

Acute Kidney Injury-Induced Circulating TNFR1/2 Elevations Correlate with Persistent Kidney Injury and Progression to Fibrosis

Elevated levels of circulating tumor necrosis factor receptors 1 and 2 (cTNFR1/2) predict chronic kidney disease (CKD) progression; however, the mechanisms of their release remain unknown. Whether acute kidney injury (AKI) drives cTNFR1/2 elevations and whether they predict disease outcomes after AKI remain unknown. In this study, we used AKI patient serum and urine samples, mouse models of kidney injury (ischemic, obstructive, and toxic), and progression to fibrosis, nephrectomy, and related single-cell RNA-sequencing datasets to experimentally test the role of kidney injury on cTNFR1/2 levels. We show that TNFR1/2 serum and urine levels are highly elevated in all of the mouse models of kidney injury tested, beginning within one hour post injury, and correlate with its severity. Consistent with this, serum and urine TNFR1/2 levels are increased in AKI patients and correlate with the severity of kidney failure. Kidney tissue expression of TNFR1/2 after AKI is only slightly increased and bilateral nephrectomies lead to strong cTNFR1/2 elevations, suggesting the release of these receptors by extrarenal sources. The injection of the uremic toxin indoxyl sulfate in healthy mice induces moderate cTNFR1/2 elevations. Moreover, TNF neutralization does not affect early cTNFR1/2 elevations after AKI. These data suggest that cTNFR1/2 levels in AKI do not reflect injury-induced TNF activity, but rather a rapid response to loss of kidney function and uremia. In contrast to traditional disease biomarkers, such as serum creatinine or BUN, cTNFR1/2 levels remain elevated for weeks after severe kidney injury. At these later timepoints, cTNFR1/2 levels positively correlate with remaining kidney injury. During the AKI-to-CKD transition, elevations of TNFR1/2 kidney expression and of cTNFR2 levels correlate with kidney fibrosis levels. In conclusion, our data demonstrate that kidney injury drives acute increases in cTNFR1/2 serum levels, which negatively correlate with kidney function. Sustained TNFR1/2 elevations after kidney injury during AKI-to-CKD transition reflect persistent tissue injury and progression to kidney fibrosis.

MiR-125b-5p modulates the function of regulatory T cells in tumor microenvironment by targeting TNFR2

BACKGROUND

Tumor necrosis factor receptor type 2 (TNFR2) is primarily expressed by CD4⁺FoxP3⁺ regulatory T cells (Tregs), especially those present in tumor microenvironment. There is compelling evidence that TNFR2 plays a crucial role in the activation, expansion, and phenotypic stability of Tregs and promotes tumor immune evasion. Understanding of epigenetic regulation of TNFR2 expression in Tregs may help device a novel strategy in cancer immunotherapy.

METHODS

MiR-125b-5p-overexpressing or knockdown murine CD4 T cells and Tregs were constructed, and the effect of miR-125b-5p on Tregs proliferation, suppressive function and TNFR2 expression were examined. In vivo antitumor efficacy of Ago-125b-5p (miR-125b-5p agomir) was evaluated in MC38 tumor bearing mice, and tumor-infiltrating Tregs and CD8⁺ cytotoxic T lymphocytes (CTLs) were analyzed. RNA-seq analysis was applied to reveal the genes and signaling pathways regulated by miR-125b-5p in Tregs.

RESULTS

In this study, we found that TNFR2 was a direct target of miR-125b-5p. Overexpression of miR-125b-5p decreased the proportion of Tregs and their expression of TNFR2 and consequently inhibited its proliferation and suppressive function by regulating the metabolism-related signaling pathways. Moreover, in colon cancer bearing mice, the administration of Ago-125b-5p markedly inhibited the tumor growth, which was associated with reduction of Tregs and increase of IFNγ⁺CD8⁺ T cells in tumor environment. Furthermore, in human colon adenocarcinoma patients, we verified that miR-125b-5p expression was downregulated, and low levels of miR-125b-5p were associated with poor prognosis. Interestingly, the expression of miR-125b-5p and TNFR2 were negatively correlated.

CONCLUSIONS

Our study for the first time found that the expression of TNFR2 by Tregs was regulated by miR-125b-5p. Our results showed that miR-125b-5p had the capacity to inhibit the expression of TNFR2 and immunosuppressive activity of Tregs and consequently enhanced the antitumor efficacy. This property of miR-125b-5p may be therapeutically harnessed in the treatment of human cancers.

Tumor necrosis factor‑α in systemic lupus erythematosus: Structure, function and therapeutic implications (Review)

Tumor necrosis factor‑α (TNF‑α) is a pleiotropic pro‑inflammatory cytokine that contributes to the pathophysiology of several autoimmune diseases, such as multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, psoriatic arthritis and systemic lupus erythematosus (SLE). The specific role of TNF‑α in autoimmunity is not yet fully understood however, partially, in a complex disease such as SLE. Through the engagement of the TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2), both the two variants, soluble and transmembrane TNF‑α, can exert multiple biological effects according to different settings. They can either function as immune regulators, impacting B‑, T‑ and dendritic cell activity, modulating the autoimmune response, or as pro‑inflammatory mediators, regulating the induction and maintenance of inflammatory processes in SLE. The present study reviews the dual role of TNF‑α, focusing on the different effects that TNF‑α may have on the pathogenesis of SLE. In addition, the efficacy and safety of anti‑TNF‑α therapies in preclinical and clinical trials SLE are discussed.

Silica Induction of Diverse Inflammatory Proteome in Lungs of Lupus-Prone Mice Quelled by Dietary Docosahexaenoic Acid Supplementation

Repeated short-term intranasal instillation of lupus-prone mice with crystalline silica (cSiO2) induces inflammatory gene expression and ectopic lymphoid neogenesis in the lung, leading to early onset of systemic autoimmunity and rapid progression to glomerulonephritis. These responses are suppressed by dietary supplementation with the ω-3 polyunsaturated fatty acid docosahexaenoic acid (DHA). Here, we tested the hypothesis that dietary DHA supplementation suppresses cSiO2-induced inflammatory proteins in bronchoalveolar alveolar lavage fluid (BALF) and plasma of lupus-prone mice. Archived tissue fluid samples were used from a prior investigation in which 6 wk-old lupus-prone female NZBWF1 mice were fed isocaloric diets containing 0 or 10 g/kg DHA for 2 wks and then intranasally instilled with 1 mg cSiO2 or vehicle once weekly for 4 wks. Cohorts were terminated at 1, 5, 9 or 13 wk post-instillation (PI). BALF and plasma from each cohort were analyzed by high density multiplex array profiling of 200 inflammatory proteins. cSiO2 time-dependently induced increases in the BALF protein signatures that were highly reflective of unresolved lung inflammation, although responses in the plasma were much less robust. Induced proteins in BALF included chemokines (e.g., MIP-2, MCP-5), enzymes (e.g., MMP-10, granzyme B), adhesion molecules (e.g., sE-selectin, sVCAM-1), co-stimulatory molecules (e.g., sCD40L, sCD48), TNF superfamily proteins (e.g., sTNFRI, sBAFF-R), growth factors (e.g., IGF-1, IGFBP-3), and signal transduction proteins (e.g., MFG-E8, FcgRIIB), many of which were blocked or delayed by DHA supplementation. The BALF inflammatory proteome correlated positively with prior measurements of gene expression, pulmonary ectopic lymphoid tissue neogenesis, and induction of autoantibodies in the lungs of the control and treatment groups. Ingenuity Pathway Analysis (IPA) revealed that IL-1β, TNF-α, and IL-6 were among the top upstream regulators of the cSiO2-induced protein response. Furthermore, DHA's effects were associated with downregulation of cSiO2-induced pathways involving i) inhibition of ARE-mediated mRNA decay, ii) bacterial and viral pattern recognition receptor activation, or iii) TREM1, STAT3, NF-κB, and VEGF signaling and with upregulation of PPAR, LXR/RXR and PPARα/RXRα signaling. Altogether, these preclinical findings further support the contention that dietary DHA supplementation could be applicable as an intervention against inflammation-driven autoimmune triggering by cSiO2 or potentially other environmental agents.

A profile of multiple circulating tumor necrosis factor receptors associated with early progressive kidney decline in Type 1 Diabetes is similar to profiles in autoimmune disorders

This study comprehensively evaluated the association between known circulating tumor necrosis factor (TNF) superfamily ligands and receptors and the development of early progressive kidney decline (PKD) leading to end-stage kidney disease (ESKD) in Type 1 diabetes. Participants for the study were from the Macro-Albuminuria Study (198 individuals), and the Micro-Albuminuria Study (148 individuals) of the Joslin Kidney Study. All individuals initially had normal kidney function and were followed for seven-fifteen years to determine the slope of the estimate glomerular filtration rate and to ascertain onset of ESKD. Plasma concentrations of 25 TNF superfamily proteins were measured using proximity extension assay applied in the OLINK proteomics platform. In the both studies risk of early PKD, determined as estimated glomerular filtration rate loss greater than or equal to three ml/min/1.73m2/year, was associated with elevated circulating levels of 13 of 19 TNF receptors examined. In the Macro-Albuminuria Study, we obtained similar findings for risk of progression to ESKD. These receptors comprised: TNF-R1A, -R1B, -R3, -R4, -R6, -R6B, -R7, -R10A, -R10B, -R11A, -R14, -R21, and -R27. Serial measurements showed that circulating levels of these TNF receptors had increased before the onset of PKD. In contrast, none of the six measured TNF ligands showed association with risk of early PKD. Of significance, the disease process that underlies PKD leading to ESKD in Type 1 diabetes has a profile also seen in autoimmune disorders. The mechanisms of this enrichment may be causally related to the development of PKD in Type 1 diabetes and must be investigated further. Thus, some of these receptors may be used as new risk predictors of ESKD.

Soluble interleukin-6 receptor in young adults and its relationship with body composition and autonomic nervous system

BACKGROUND

The immune system generates inflammatory responses through cytokines like Interleukin 6 (IL-6) and the Tumor Necrosis Factor alpha (TNF α); these cytokines mediate cellular responses aided by the presence of soluble receptors such as: Soluble Interleukin 6 Receptor (sIL6R) and Soluble Tumor Necrosis Factor Receptors Type 1 and 2 (sTNFR1, sTNFR2); the literature is limited about the relationship between this cytokines and the role of its soluble receptors.

OBJECTIVES

This study is to determine a possible relationship between specific inflammatory markers and their soluble receptors with the autonomic nervous system's activity and body composition.

METHODS

27 subjects (13 men of 19.3 ± 1.6 years old and 14 women of 19.1 ± 1.7 years old) were evaluated. Body composition, autonomic nervous system activity and plasma concentration of inflammatory markers IL-6, TNF α, sIL6R, sTNFR1 and sTNFR2 were measured using bio-impedance, heart rate variability and ELISA respectively.

RESULTS

A positive association between body-fat percentage and the sIL6R (0.47, p = .013) as well as inverse relationship between muscular mass and the sIL6R (-0.45, p = .019) were found. The sIL6R was also positively correlated with sympathetic activity markers: Relation LF/HF (0.52, p = .006), cardiac sympathetic index (0.45, p = .008), and cardiac vagal index (-0.44, p = .022).

CONCLUSION

This study suggested that the IL-6 trans-signaling involving both the soluble receptor, sIL6R, and gp130 membrane co-receptor could produce inflammatory responses that generate an impact on the autonomic nervous system, possibly due to its direct action on the hypothalamus, the solitary tract nucleus, or the heart.

Inflammatory markers in systemic lupus erythematosus

While systemic lupus erythematosus (SLE) is an autoantibody and immune complex disease by nature, most of its organ manifestations are in fact inflammatory. SLE activity scores thus heavily rely on assessing inflammation in the various organs. This focus on clinical items demonstrates that routine laboratory markers of inflammation are still limited in their impact. The erythrocyte sedimentation rate (ESR) is used, but represents a rather crude overall measure. Anemia and diminished serum albumin play a role in estimating inflammatory activity, but both are reflecting more than one mechanism, and the association with inflammation is complex. C-reactive protein (CRP) is a better marker for infections than for SLE activity, where there is only a limited association, and procalcitonin (PCT) is also mainly used for detecting severe bacterial infection. Of the cytokines directly induced by immune complexes, type I interferons, interleukin-18 (IL-18) and tumor necrosis factor (TNF) are correlated with inflammatory disease activity. Still, precise and timely measurement is an issue, which is why they are not currently used for routine purposes. While somewhat more robust in the assays, IL-18 binding protein (IL-18BP) and soluble TNF-receptor 2 (TNF-R2), which are related to the respective cytokines, have not yet made it into clinical routine. The same is true for several chemokines that are increased with activity and relatively easy to measure, but still experimental parameters. In the urine, proteinuria leads and is essential for assessing kidney involvement, but may also result from damage. Similar to the situation in serum and plasma, several cytokines and chemokines perform reasonably well in scientific studies, but are not routine parameters. Cellular elements in the urine are more difficult to assess in the routine laboratory, where sufficient routine is not always available. Therefore, the analysis of urinary T cells may have potential for better monitoring renal inflammation.

Soluble TNF-R1, VEGF and other cytokines as markers of disease activity in systemic lupus erythematosus and lupus nephritis

Background

Current non-invasive methods of assessing disease activity in systemic lupus erythematosus (SLE) are of limited sensitivity and specificity. Testing includes acute phase markers, autoantibodies and complement levels. Although measurements of dsDNA antibodies and complement C3/C4 levels are routine, they remain of limited value. Improved blood and urine markers may help in early detection of flare, distinction between flare and chronic damage, and monitoring response to therapy.

Methods

A total of 87 patients with SLE were tested for the following cytokines in serum and urine: monocyte chemoattractant protein 1 (MCP-1), regulated upon activation, normal T cell expressed and secreted (RANTES), soluble tumour necrosis factor receptor 1 (sTNF-R1), interferon-inducible protein 10 (IP-10), monocyte inhibitory protein 1α (MIP-1α) and vascular endothelial growth factor (VEGF). Patients attending the Lupus Unit at St Thomas’ Hospital, London, UK were divided into active lupus nephritis (LN), inactive LN and non-renal SLE groups based on their renal pathology and SLE disease activity index (SLEDAI). Cytokine testing was performed using the FIDIS multiplex bead assay.

Results

The mean level of serum sTNF-R1 was higher in the active LN group compared with both inactive LN and non-renal SLE groups ( p < 0.001). For urine measurements there were significant differences between active LN and non-renal SLE for VEGF ( p = 0.016), after statistical correction for multiple testing. Both urinary and serum sTNF-R1 and IP-10 levels correlated with SLEDAI scores ( p < 0.001), while serum VEGF correlated weakly with SLEDAI ( p = 0.025). The optimum combination for differentiating active from inactive LN patients was serum VEGF, sTNF-R1, MCP-1 and glomerular filtration rate plus urinary sTNF-R1 and protein-creatinine ratio.

Conclusion

These results indicate that for active LN, sTNF-R1 could be a useful serum cytokine marker, with potential for VEGF in the urine. This study has confirmed the ability of the multiplex bead technique to detect cytokines in a good analytical range, including very low and high levels, in both serum and urine. Combining serum and urine markers provided additional sensitivity in distinguishing active from inactive LN.

Soluble tumor necrosis factor receptors are associated with severity of kidney dysfunction in pediatric chronic kidney disease

BACKGROUND

In adult chronic kidney disease (CKD) patients, there is a positive association between inflammation and progressive renal dysfunction. Higher levels of soluble receptors of tumor necrosis factor (sTNFR) have been related to worst prognosis of adult CKD patients. Therefore, the present study aimed to evaluate soluble TNF receptors in children and adolescents with CKD and to search for an association with clinical and laboratory features.

METHODS

Demographic, clinical, anthropometric, and laboratory data were evaluated in 34 pediatric patients with CKD and in 34 healthy sex- and age-matched controls. Blood samples were collected in both groups to measure sTNFR by enzyme-linked immunosorbent assay. The modified Schwartz formula was used to estimate glomerular filtration rate (GFR).

RESULTS

Pediatric patients with CKD had significantly higher plasma concentrations of soluble TNF receptors types 1 and 2 (sTNFR1 and sTNFR2) in comparison to sex- and age-matched healthy controls. Plasma levels of sTNFR1 and sTNFR2 increased progressively as renal function worsened, being inversely and significantly correlated with GFR (r = - 0.853 for sTNFR1 and GFR, r = - 0.729 for sTNFR2 and GFR).

CONCLUSIONS

Children and adolescents with CKD exhibited higher plasma levels of sTNFR1 and sTNFR2 than healthy controls, which increased in relation to renal function deterioration. Plasma levels of sTNFR1 and sTNFR2 emerge as markers of progressive CKD in pediatric patients.

Potential role of soluble TNF-α receptors in diagnosis of idiopathic membranous nephropathy

Soluble tumor necrosis factor alpha (TNF-α) receptors contain two receptors: soluble tumor necrosis factor receptor (sTNFR) 1 and 2, and the aim of our study was to discover their concentration and diagnostic value for idiopathic membranous nephropathy (IMN). In total, 58 patients with IMN, 51 patients with chronic kidney disease (CKD), and 30 healthy volunteers were enrolled in this study. Levels of serum sTNFR1 and sTNFR2 were determined by enzyme-linked immunosorbent assay (ELISA). Serum cystatin C (CysC), urea, creatinine (CREA), uric acid (UA), total protein (TP), albumin (ALB), and 24-h urinary protein (proteinuria, PRO) were examined by automatic biochemical analyzer. Levels of sTNFR1 and sTNFR2 were significantly higher in IMN group than CKD and control group ( P < 0.05). In IMN group, there were significant correlation between sTNFR1 and sTNFR2 ( P < 0.01). Both sTNFR1 and sTNFR2 were positively related to serum urea, CREA, CysC, UA, 24-h PRO ( P < 0.05) and negatively related to ALB ( P < 0.01). Receiver operating characteristic (ROC) analysis showed that the area under the curve (AUC) of sTNFR1 and sTNFR2 were 0.997 and 0.993, respectively, when control was healthy volunteers. When sTNFR1 cut-off was 959.15 pg/mL, the sensitivity and specificity were 96.6% and 100%, respectively. When sTNFR2 cut-off was 2449.43 pg/mL, the sensitivity and specificity were 93.1% and 100%, respectively. While the control was CKD group, AUC of sTNFR1 and sTNFR2 were 0.647 and 0.626, respectively. When sTNFR1 cut-off was 3356.57 pg/mL, the sensitivity and specificity were 72.4% and 60.8%, respectively. When sTNFR2 cut-off was 6497.34 pg/mL, the sensitivity and specificity were 72.4% and 58.8%, respectively. This is the first study to show that both levels of sTNFR1 and sTNFR2 increased and correlated with serum urea, CREA, CysC, UA, ALB, 24-h PRO and could be usable for IMN diagnosis and differential diagnosis between IMN and CKD.

Beneficial effect of magnolol on lupus nephritis in MRL/lpr mice by attenuating the NLRP3 inflammasome and NF‑κB signaling pathway: A mechanistic analysis

Lupus nephritis (LN) is a common complication of systemic lupus erythematosus. The present study aimed to elucidate the protective effect of magnolol (MG) on the progression of LN, via inhibition of key signaling pathways. The results of the present study demonstrated that administration of MG caused inhibition of the activation of NACHT, LRR and PYD domains‑containing protein 3 and interleukin‑1β production. Histopathological analysis confirmed that the vehicle‑treated group exhibited characteristic glomerular disease, which was observed to be suppressed following the administration of MG; a marked decrease in glomerular and vascular lesions was observed compared with the vehicle control. This decrease was further demonstrated through analysis of kidney sections. The expression level of cell surface glycoprotein F4/80 was demonstrated to be markedly decreased in the MG‑treated mice compared with the vehicle control group. The MG‑treated mice exhibited a marked decrease in serum and renal tumor necrosis factor‑α expression levels.

Regulation of MiR-146a and TRAF6 in the Diagnose of Lupus Nephritis

BACKGROUND Lupus nephritis (LN) is a major complication of systemic lupus erythematosus (SLE). This study tested miR-146a and its target gene TRAF6 expression in LN patients and discussed their relationship with LN. MATERIAL AND METHODS One hundred twenty-eight LN patients and 30 healthy controls were enrolled in this study. MiR-146a and TRAF6 expression in peripheral blood mononuclear cells (PBMCs) were detected. Serum cytokines content was determined by ELISA. The diagnostic role of miR-146a and TRAF6 in LN activity was evaluated by ROC curve. The impact of miR-146a and TRAF6 on end-stage renal disease (ESRD) was compared by survival curve. The effect of miR-146a and TRAF6 on LN recurrence was analyzed. RESULTS Compared with healthy controls, miR-146a expression was significantly reduced and TRAF6 was upregulated in LN patients. The expression was related to LN activity. MiR-146a expression was negatively correlated, whereas TRAF6 was positively correlated with serum IL-1β, IL-6, IL-8, and TNF-α activity. The area under the ROC curve (AUC) of miR-146a and TRAF6 on the diagnosis of LN was 0.821 and 0.897, respectively. The AUC of miR-146a and TRAF6 on LN activity differentiation was 0.921 and 0.872, respectively. Downregulation of miR-146a and upregulation of TRAF6 increased the incidence of ESRD progression. Downregulation of miR-146a and upregulation of TRAF6 elevated the possibility of recurrence within one year. CONCLUSIONS MiR-146a declined, while TRAF6 increased in LN patients compared with healthy controls. Their expression can be used to effectively differentiate LN and evaluate activity. MiR-146a reduction and TRAF6 upregulation increased the possibility of ESRD progress and recurrence within one year.

Serum soluble tumour necrosis factor receptor-2 (sTNFR2) as a biomarker of kidney tissue damage and long-term renal outcome in lupus nephritis

OBJECTIVES

We investigated the performance of soluble tumour necrosis factor receptor-2 (sTNFR2) as a biomarker of renal activity, damage, treatment response, and long-term outcome in lupus nephritis (LN).

METHOD

Serum sTNFR2 levels were assessed in 64 LN patients (52 proliferative, 12 membranous) before and after induction treatment, and in 314 non-lupus controls. In LN patients, renal biopsies were performed at baseline and post-treatment. Patients with ≥ 50% reduced proteinuria, normal or improved estimated glomerular filtration rate (eGFR) by ≥ 25%, and inactive urinary sediment were considered clinical responders (CRs). Patients with ≥ 50% improved renal activity index were considered histopathological responders (HRs). Long-term renal outcome was determined using the chronic kidney disease (CKD) stage after a median follow-up of 11.3 years.

RESULTS

sTNFR2 levels were elevated in LN patients versus controls both at baseline (p < 0.001) and post-treatment (p < 0.001), and decreased following treatment (p < 0.001). Baseline sTNFR2 correlated with Chronicity Index scores in both baseline (r = 0.34, p = 0.006) and post-treatment (r = 0.43, p < 0.001) biopsies. In membranous LN, baseline sTNFR2 levels were higher in CRs (p = 0.048) and HRs (p = 0.03) than in non-responders, and decreased only in CRs (p = 0.03). Both baseline (p = 0.02) and post-treatment (p = 0.03) sTNFR2 levels were associated with decreasing eGFR throughout long-term follow-up, and post-treatment levels were higher in patients with long-term follow-up CKD stage ≥ 3 versus 1-2 (p = 0.008).

CONCLUSIONS

Our data suggest serum sTNFR2 as a marker of kidney tissue damage and a predictor of long-term prognosis in LN, and merit further evaluation of sTNFR2 as a predictor of clinical and histopathological treatment outcomes in membranous LN.

Identification of definitive serum biomarkers associated with disease activity in primary Sjögren's syndrome

Background

In this study, we sought to identify definitive biomarkers associated with disease activity in primary Sjögren’s syndrome (pSS).

Methods

Serum protein concentrations in pSS patients and healthy controls (HCs) were comprehensively screened using high-throughput proteomic analysis, and differentially expressed proteins were extracted. Correlation between differentially expressed proteins and European League Against Rheumatism Sjögren’s Syndrome Disease Activity Index (ESSDAI) scores was analyzed and disease activity-associated biomarkers were identified. These biomarkers were validated by enzyme-linked immunosorbent assay (ELISA) in a separate pSS cohort.

Results

The serum concentrations of 1100 proteins were compared between 30 pSS patients and 30 HCs, with 82 differentially expressed proteins identified as pSS-associated proteins. Of these 82 proteins, 9 were identified as disease activity-associated biomarkers. These nine biomarkers underwent validation by ELISA in a separate pSS validation cohort (n = 58), with five proteins (CXCL13, TNF-R2, CD48, B-cell activating factor (BAFF), and PD-L2) subsequently being confirmed as candidate biomarkers. Of these five candidate biomarkers, CXCL13 exhibited the most significant correlation with the lymphadenopathy, glandular, and pulmonary domains of the ESSDAI. CXCL13, TNF-R2 and CD48 exhibited a positive correlation with the biological domain of the ESSDAI. TNF-R2 exhibited the most negative correlation with uptake in the submandibular gland on technetium 99m-pertechnetate salivary gland scintigraphy.

Conclusions

Our approach successfully identified serum biomarkers associated with disease activity in pSS patients. These markers might be potential therapeutic targets in pSS patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1006-1) contains supplementary material, which is available to authorized users.