Cleaved Form of Osteopontin in Urine as a Clinical Marker of Lupus Nephritis

Associations of serum keratin 1 with thyroid function and immunity in Graves' disease

BACKGROUND

Autoimmune thyroid disease (AITD) can cause enormous health burdens; however, trustworthy biomarkers in identifying the onset and progression of AITD are limited. In this study, we attempted to discover new potential serum biomarkers to discriminate AITD using mass spectrometry (MS).

METHODS

In the biomarker study cohort, 20 patients with Graves' disease (GD), 20 patients with Hashimoto's thyroiditis (HT), and 20 healthy controls were enrolled for a liquid chromatographic-tandem MS assessment. A novel biomarker, keratin 1 (KRT1), was selected for further evaluation in the validation cohort, including 125 patients with GD, 34 patients with HT, and 77 controls. Relationships of serum KRT1 with AITD-related immunomodulatory cytokines were also analyzed using enzyme-linked immunosorbent assays (ELISAs).

RESULTS

In the MS analysis, KRT1 was the single marker overexpressed in GD, while it was underexpressed in HT. In the ELISA analysis of the validation cohort, KRT1 was consistently upregulated in GD, while it was not downregulated in HT. There were significant associations of KRT1 levels with thyroid function in GD, AITD, and overall subjects. Additionally, a significant association of KRT1 levels with thyroid-stimulating hormone receptor antibody (TSHRAb) levels was observed. Moreover, there were significant associations of KRT1 with osteopontin (OPN) and B-cell activating factor (BAFF) levels in GD.

CONCLUSIONS

Serum KRT1 levels were upregulated in GD and were associated with thyroid function and TSHRAb levels. Moreover, KRT1 was correlated with the BAFF and OPN levels in GD patients. Further molecular-based research to elucidate the role of KRT1 in the pathogenesis of AITD is needed.

Angiogenesis in the Outer Membrane of Chronic Subdural Hematomas through Thrombin-Cleaved Osteopontin and the Integrin α9 and Integrin β1 Signaling Pathways

BACKGROUND

A chronic subdural hematoma (CSDH) is considered to be an inflammatory and angiogenic disease. The CSDH outer membrane, which contains inflammatory cells, plays an important role in CSDH development. Osteopontin (OPN) is an extracellular matrix protein that is cleaved by thrombin, generating the N-terminal half of OPN, which is prominently involved in integrin signal transduction. We explored the expression of the N-terminal half of OPN in CSDH fluid and the expression of integrins α9 and β1 and the downstream components of the angiogenic signaling pathways in the outer membrane of CSDHs.

METHODS

Twenty samples of CSDH fluid and eight samples of CSDH outer membrane were collected from patients suffering from CSDHs. The concentrations of the N-terminal half of OPN in CSDH fluid samples were measured using ELISA kits. The expression levels of integrins α9 and β1, vinculin, talin-1, focal adhesion kinase (FAK), paxillin, α-actin, Src and β-actin were examined by Western blot analysis. The expression levels of integrins α9 and β1, FAK and paxillin were also examined by immunohistochemistry. We investigated whether CSDH fluid could activate FAK in cultured endothelial cells in vitro.

RESULTS

The concentration of the N-terminal half of OPN in CSDH fluid was significantly higher than that in the serum. Western blot analysis confirmed the presence of these molecules. In addition, integrins α9 and β1, FAK and paxillin were localized in the endothelial cells of vessels within the CSDH outer membrane. FAK was significantly phosphorylated immediately after treatment with CSDH fluid.

CONCLUSION

Our data suggest that the N-terminal half of OPN in CSDH fluid promotes neovascularization in endothelial cells through integrins α9 and β1. The N-terminal half of OPN, which is part of the extracellular matrix, plays a critical role in the promotion of CSDHs.

Osteopontin as a Biomarker in Chronic Kidney Disease

Osteopontin (OPN) is a ubiquitously expressed protein with a wide range of physiological functions, including roles in bone mineralization, immune regulation, and wound healing. OPN has been implicated in the pathogenesis of several forms of chronic kidney disease (CKD) where it promotes inflammation and fibrosis and regulates calcium and phosphate metabolism. OPN expression is increased in the kidneys, blood, and urine of patients with CKD, particularly in those with diabetic kidney disease and glomerulonephritis. The full-length OPN protein is cleaved by various proteases, including thrombin, matrix metalloproteinase (MMP)-3, MMP-7, cathepsin-D, and plasmin, producing N-terminal OPN (ntOPN), which may have more detrimental effects in CKD. Studies suggest that OPN may serve as a biomarker in CKD, and while more research is needed to fully evaluate and validate OPN and ntOPN as CKD biomarkers, the available evidence suggests that they are promising candidates for further investigation. Targeting OPN may be a potential treatment strategy. Several studies show that inhibition of OPN expression or activity can attenuate kidney injury and improve kidney function. In addition to its effects on kidney function, OPN has been linked to cardiovascular disease, which is a major cause of morbidity and mortality in patients with CKD.

Osteopontin—A Potential Biomarker for IgA Nephropathy: Machine Learning Application

Many potential biomarkers in nephrology have been studied, but few are currently used in clinical practice. One is osteopontin (OPN). We compared urinary OPN concentrations in 80 participants: 67 patients with various biopsy-proven glomerulopathies (GNs)—immunoglobulin A nephropathy (IgAN, 29), membranous nephropathy (MN, 20) and lupus nephritis (LN, 18) and 13 with no GN. Follow-up included 48 participants. Machine learning was used to correlate OPN with other factors to classify patients by GN type. The resulting algorithm had an accuracy of 87% in differentiating IgAN from other GNs using urinary OPN levels only. A lesser effect for discriminating MN and LN was observed. However, the lower number of patients and the phenotypic heterogeneity of MN and LN might have affected those results. OPN was significantly higher in IgAN at baseline than in other GNs and therefore might be useful for identifying patients with IgAN. That observation did not apply to either patients with IgAN at follow-up or to patients with other GNs. OPN seems to be a valuable biomarker and should be validated in future studies. Machine learning is a powerful tool that, compared with traditional statistical methods, can be also applied to smaller datasets.

Osteopontin in autoimmune disorders: current knowledge and future perspective

Osteopontin (OPN) is a multifunctional cytokine and adhesion molecule, as well as an unusual regulator for both innate and adaptive immune responses. Several immune cells can produce OPN, including dendritic cells (DCs), macrophages, and T lymphocytes. OPN expression is reported to be increased in a wide range of disorders, including autoimmunity, cancer, and allergy. The overexpression of OPN in several autoimmune disorders, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), Type 1 diabetes (T1D), inflammatory bowel disease (IBD), Sjögren's, and myasthenia gravis, have been shown to be correlated with disease severity. Regarding the important regulatory roles of OPN in the immune system, this study aimed to review the role of this molecule in autoimmune disorders and to provide a complete view of the current knowledge in this field.

T Cell Immunosenescence in Aging, Obesity, and Cardiovascular Disease

Although advances in preventive medicine have greatly improved prognosis, cardiovascular disease (CVD) remains the leading cause of death worldwide. This clearly indicates that there remain residual cardiovascular risks that have not been targeted by conventional therapies. The results of multiple animal studies and clinical trials clearly indicate that inflammation is the most important residual risk and a potential target for CVD prevention. The immune cell network is intricately regulated to maintain homeostasis. Ageing associated changes to the immune system occurs in both innate and adaptive immune cells, however T cells are most susceptible to this process. T-cell changes due to thymic degeneration and homeostatic proliferation, metabolic abnormalities, telomere length shortening, and epigenetic changes associated with aging and obesity may not only reduce normal immune function, but also induce inflammatory tendencies, a process referred to as immunosenescence. Since the disruption of biological homeostasis by T cell immunosenescence is closely related to the development and progression of CVD via inflammation, senescent T cells are attracting attention as a new therapeutic target. In this review, we discuss the relationship between CVD and T cell immunosenescence associated with aging and obesity.

Urine Proteomics Differentiate Primary Thrombotic Antiphospholipid Syndrome From Obstetric Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a multisystem disorder characterized by thrombosis and/or recurrent fetal loss. This clinical phenotype heterogeneity may result in differences in response to treatment and prognosis. In this study, we aimed to identify primary thrombotic APS (TAPS) from primary obstetric APS (OAPS) using urine proteomics as a non-invasive method. Only patients with primary APS were enrolled in this study from 2016 to 2018 at a single clinical center in Shanghai. Urine samples from 15 patients with TAPS, 9 patients with OAPS, and 15 healthy controls (HCs) were collected and analyzed using isobaric tags for relative and absolute quantification (iTRAQ) labeling combined with liquid chromatography-tandem mass spectrometry analysis to identify differentially expressed proteins. Cluster analysis of urine proteomics identified differentiated proteins among the TAPS, OAPS, and HC groups. Urinary proteins were enriched in cytokine and cytokine receptor pathways. Representative secreted cytokines screened out (fold change >1.20, or <0.83, p<0.05) in these differentiated proteins were measured by enzyme-linked immunosorbent assay in a validation cohort. The results showed that the levels of C-X-C motif chemokine ligand 12 (CXCL12) were higher in the urine of patients with TAPS than in those with OAPS (p=0.035), while the levels of platelet-derived growth factor subunit B (PDGFB) were lower in patients with TAPS than in those with OAPS (p=0.041). In addition, correlation analysis showed that CXCL12 levels were positively correlated with immunoglobulin G anti-β2-glycoprotein I antibody (r=0.617, p=0.016). Our results demonstrated that urinary CXCL12 and PDGFB might serve as potential non-invasive markers to differentiate primary TAPS from primary OAPS.

Both Full-Length and Protease-Cleaved Products of Osteopontin Are Elevated in Infectious Diseases

Circulating full-length osteopontin (FL-OPN) is elevated in plasma from patients with various infectious diseases, such as adult T-cell leukemia, Mycobacterium tuberculosis (TB), hepatitis virus infection, leptospirosis, acquired immune deficiency syndrome (AIDS), AIDS/TB, and coronavirus disease 2019 (COVID-19). Proteolysis of OPN by thrombin, matrix metalloproteases, caspase 8/3, cathepsin D, plasmin, and enterokinase generates various cleaved OPNs with a variety of bioactivities by binding to different target cells. Moreover, OPN is susceptible to gradual proteolysis. During inflammation, one of the cleaved fragments, N-terminal thrombin-cleaved OPN (trOPN or OPN-Arg¹⁶⁸ [OPN-R]), induces dendritic cell (DC) adhesion. Further cleavage by carboxypeptidase B2 or carboxypeptidase N removes Arg¹⁶⁸ from OPN-R to OPN-Leu¹⁶⁷ (OPN-L). Consequently, OPN-L decreases DC adhesion. In particular, the differences in plasma level over time are observed between FL-OPN and its cleaved OPNs during inflammation. We found that the undefined OPN levels (mixture of FL-OPN and cleaved OPN) were elevated in plasma and reflected the pathology of TB and COVID-19 rather than FL-OPN. These infections are associated with elevated levels of various proteases. Inhibition of the cleavage or the activities of cleaved products may improve the outcome of the therapy. Research on the metabolism of OPN is expected to create new therapies against infectious diseases.

Plasma Osteopontin Levels is Associated with Biochemical Markers of Kidney Injury in Patients with Leptospirosis

Leptospirosis becomes severe, with a fatality rate of >10%, and manifests as severe lung injury accompanied by acute kidney injury. Using urine and blood samples of 112 patients with leptospirosis, osteopontin (OPN), galectin-9 (Gal-9) and other kidney-related biomarkers were measured to understand the pathological and diagnostic roles of OPN and Gal-9 in leptospirosis. Plasma levels of full-length (FL)-OPN (pFL-OPN) (p < 0.0001), pFL-Gal-9(p < 0.0001) and thrombin-cleaved OPN (p < 0.01) were significantly higher in patients with leptospirosis than in healthy controls (n = 30), as were levels of several indicators of renal toxicity: serum cystatin C (p < 0.0001), urine N-acetyl-β-glucosaminidase (NAG)/creatinine (p < 0.05), and urine clusterin/creatinine (p < 0.05). pFL-Gal-9 levels were negatively correlated with pFL-OPN levels (r = −0.24, p < 0.05). pFL-OPN levels were positively correlated with serum cystatin C (r = 0.41, p < 0.0001), urine NAG/creatinine (r = 0.35, p < 0.001), urine clusterin/creatinine (r = 0.33, p < 0.01), and urine cystatin C/creatinine (r = 0.33, p < 0.05) levels. In a group of patients with abnormally high creatinine levels, significantly higher levels of serum cystatin C (p < 0.0001) and pFL-OPN (p < 0.001) were observed. Our results demonstrate that pFL-OPN reflect kidney injury among patients with leptospirosis.

The Impact of Glycosylation of Osteopontin on Urinary Stone Formation

Osteopontin (OPN) is a matrix glycoprotein of urinary calculi. This study aims to identify the role of aberrant glycosylation of OPN in urolithiasis. We retrospectively measured urinary glycosylated OPN normalized by urinary full-length-OPN levels in 110 urolithiasis patients and 157 healthy volunteers and 21 patients were prospectively longitudinal follow-up during stone treatment. The urinary full-length-OPN levels were measured using enzyme-linked immunosorbent assay and glycosylated OPN was measured using a lectin array and lectin blotting. The assays were evaluated using the area under the receiver operating characteristics curve to discriminate stone forming urolithiasis patients. In the retrospective cohort, urinary Gal3C-S lectin reactive- (Gal3C-S-) OPN/full-length-OPN, was significantly higher in the stone forming urolithiasis patients than in the healthy volunteers (p < 0.0001), with good discrimination (AUC, 0.953), 90% sensitivity, and 92% specificity. The Lycopersicon esculentum lectin analysis of urinary full-length-OPN showed that urinary full-length-OPN in stone forming urolithiasis patients had a polyLacNAc structure that was not observed in healthy volunteers. In the prospective longitudinal follow-up study, 92.8% of the stone-free urolithiasis group had Gal3C-S-OPN/full-length-OPN levels below the cutoff value after ureteroscopic lithotripsy (URS), whereas 71.4% of the residual-stone urolithiasis group did not show decreased levels after URS. Therefore, Gal3C-S-OPN/full-length-OPN levels could be used as a urolithiasis biomarker.

Synchronized expressions of serum osteopontin and B cell-activating factor in autoimmune thyroid disease

BACKGROUND

Osteopontin (OPN) is recognized as a potent immunoregulator of autoimmune disease. In the study, we tried to explore the association of serum OPN levels with autoimmune thyroid disease, including Graves' disease (GD) and Hashimoto's thyroiditis (HT), in an ethnic Chinese population.

MATERIALS AND METHODS

We enrolled 131 patients with GD, 33 patients with HT and 123 healthy controls. Serum OPN, B cell-activating factor (BAFF) and interferon (IFN)-α levels were quantified. Graves' disease patients with high thyroid function at the time of sample collection were defined as having active GD, while the other patients were defined as having inactive GD.

RESULTS

Serum OPN levels were higher in active GD than in inactive GD and the control groups (P = 0.001 and P = 0.018, respectively). In GD, significant associations of OPN levels with thyroid-stimulating hormone receptor antibody (TSHRAb) levels were observed in women (r = -0.344, P = 0.002, and r = 0.440, P = 0.004, respectively) but not in men. Osteopontin levels were associated with BAFF levels only in women with GD or HT (r = 0.506, P < 0.001 and r = 0.430, P = 0.025, respectively), but not in men with GD or HT.

CONCLUSIONS

Serum OPN levels were upregulated in active GD, and serum OPN levels were associated with thyroid function and TSHRAb levels in GD. Additionally, OPN levels were correlated with BAFF levels in GD and HT. The associations of OPN levels with clinical phenotypes of GD and BAFF levels showed a dimorphic pattern.

Osteopontin Gene Polymorphism and Urinary OPN Excretion in Patients with Immunoglobulin A Nephropathy

Osteopontin (OPN) is a glycoprotein involved in the pathogenesis of multiple autoimmune and inflammatory conditions. However, the association of variants of secreted phosphoprotein 1 gene (SPP1), which encodes OPN, with immunoglobulin A nephropathy (IgAN) has not been examined up to date. Moreover, the role of OPN in disease pathogenesis and clinical manifestations is not fully known. Therefore, the aim of the study was to determine the frequency of four single nucleotide polymorphisms (SNiPs) of SPP1 gene, as well as the urinary OPN excretion in IgAN patients and healthy controls. In total, 58 Caucasian patients with biopsy-proven IgAN and 184 gender-, age-, and ethnically-matched healthy controls were genotyped for rs1126616, rs1126772, rs9138, and rs7687316/rs3841116 polymorphisms by real time polymerase chain reaction (RT-PCR). Urinary OPN concentration was determined by enzyme-linked immunosorbent assay (ELISA) in 58 IgAN patients and 19 controls. SPP1 SNiPs, as well as urinary OPN excretion, were analyzed in relation to their possible associations with the clinicopathological parameters. The frequency of the minor TT/CT genotypes of rs1126616 was significantly higher in IgAN patients compared to controls (P = 0.0217). Similarly, the minor (CC/AC) genotypes and the C allele of rs9138 were more frequent in IgAN patients (P = 0.0425 and P = 0.0112, respectively). Moreover, these two SNiPs were associated with the higher urinary OPN excretion (P < 0.05). These findings suggest that rs1126616, as well as rs9138, may be associated with IgAN development, however future studies in this field are required.

Associations of secreted phosphoprotein 1 and B lymphocyte kinase gene polymorphisms with autoimmune thyroid disease

BACKGROUND

Dysregulation of the type 1 interferon (IFN)-related signalling pathway predisposes one to autoimmune diseases. Possible associations of single-nucleotide polymorphisms (SNPs) of secreted phosphoprotein 1 (SPP1) and B lymphocyte kinase (BLK) of the type 1 IFN-related signalling pathway with autoimmune thyroid disease (AITD) in an ethnic Chinese (ie Taiwanese) population were tested.

METHODS

Totally, 83 Hashimoto's thyroiditis (HT) patients, 319 Graves' disease (GD) patients and 369 controls were enrolled. Genotypes of the two SNPs (rs1126772 and rs1126616) of SPP1 and two SNPs (rs13277113 and rs2736340) of BLK were determined.

RESULTS

Our results showed reduced percentages of the G allele of rs13277113 of BLK in GD (P = 0.037, odds ratio [OR] = 0.78, 95% confidence interval [CI] = 0.62-0.99) and HT (P = 0.002, OR = 0.54, 95% CI = 0.36-0.81), compared to the controls. At the same time, lower frequencies of the C allele of rs2736340 of BLK in GD (P = 0.025, OR = 0.76, 95% CI = 0.60-0.97) and HT (P = 0.003, OR = 0.53, 95% CI = 0.35-0.81) than the controls were also observed. There were significantly higher AT haplotype frequencies of rs1327713 and rs2736340 in GD and HT patients than in the controls (P = 0.025, OR = 1.31, 95% CI = 1.03-1.67, and P = 0.003, OR = 1.89, 95% CI = 1.24-2.87, respectively). Moreover, the anti-microsomal antibody titre was associated with rs2736340.

CONCLUSIONS

Genetic variants of rs13277113 and rs2736340 of BLK were associated with susceptibility to GD, HT and AITD in an ethnic Chinese population. Our results suggest the BLK may participate in the pathogenesis of GD, HT and AITD.

Utility of osteopontin in cerebrospinal fluid as a diagnostic marker for neuropsychiatric systemic lupus erythematosus

The whole protein of osteopontin (OPN full) and its cleaved form (OPN N-half) are involved in the immune response and the migration of immune cells to an inflammatory lesion. We have reported that serum OPN full and urine OPN N-half are elevated in lupus nephritis (LN). Neuropsychiatric systemic lupus erythematosus (NPSLE) is a refractory complication of SLE. To investigate whether OPN full and OPN N-half could serve as diagnostic markers for NPSLE, and to elucidate their role in NPSLE pathogenesis, the concentrations of OPN full and OPN N-half in cerebrospinal fluid (CSF) were measured in NPSLE and non-NPSLE patients. We found that the concentration of OPN full in the CSF was significantly higher in NPSLE than in non-NPSLE, and it decreased after treatment. When the cutoff value of OPN full in CSF was set to 963.4 ng/ml, the sensitivity and specificity for the diagnosis of NPSLE were 70% and 100%, respectively. The correlation analysis of OPN full, OPN N-half and various cytokines/chemokines suggested that the cytokines/chemokines could be divided into two clusters: cluster A, which contains OPN full and cluster B, which contains interleukin-6. OPN full in CSF could be a novel diagnostic marker for NPSLE.

The role of osteopontin in kidney diseases

BACKGROUND

Osteopontin (OPN) is a pleiotropic glycoprotein expressed in various cell types in animals and in humans, including bone, immune, smooth muscle, epithelial and endothelial cells. Moreover, OPN is found in kidneys (in the thick ascending limbs of the loop of Henle and in distal nephrons) and urine. The protein plays an important role in mineralization and bone resorption. In addition, OPN is involved in the regulation of immunity and inflammation, angiogenesis and apoptosis. It was demonstrated that OPN and some OPN gene polymorphic variants are associated with the pathogenesis and progression of multiple disorders, such as cancer, autoimmune, neurodegenerative and cardiovascular diseases. Moreover, recent studies suggested that OPN is associated with the pathogenesis of renal failure.

METHODS

In this review, I briefly discussed the role of OPN and its gene polymorphisms in kidney physiology, as well as in various kidney diseases.

FINDINGS AND CONCLUSION

Most studies reported that OPN expression is elevated in urolithiasis, and also in acute and chronic kidney diseases, and in renal allograft dysfunction. Moreover, it was demonstrated that polymorphic variants of the OPN gene may be associated with renal failure. However, some reports suggested that OPN is essential for tubulogenesis, and that it inhibits calcium oxalate crystal formation and retention, nitric oxide synthesis, cell apoptosis and promotes cell regeneration. Thus, further studies are required to fully understand the role of OPN in kidney physiology and pathology. Eventually, these studies may result in the identification of OPN as a valuable marker for renal dysfunction prognosis and treatment.

Precision medicine in lupus nephritis: can biomarkers get us there?

Patients with systemic lupus erythematosus frequently develop lupus nephritis (LN), a condition that can lead to end-stage kidney disease. Multiple serum and urine biomarkers for LN have been proposed in recent years, yet none have become incorporated into clinical use. The majority of studies have been single center with significant variability in cohorts, assays, and sample storage, leading to inconclusive results. It has become clear that no single biomarker is likely to be sufficient to diagnose LN, identify flares, and define the response to therapy and prognosis. A more likely scenario is a panel of urine, serum, tissue, and genetic biomarkers. In this review, we summarize traditional and novel biomarkers and discuss how they may be utilized in order to bring precision medicine to clinical practice in LN.

Clinical application of protein biomarkers in lupus erythematosus and lupus nephritis

Systemic lupus erythematosus (SLE) is a type of autoimmune disease that damages multiple organs, including the heart, joints, liver and kidneys. The main characteristics of SLE are the deposition of circulating autoantibodies; autoantigen complexes in the renal system; and abnormal expression of complements, cytokines and chemokines. Lupus nephritis (LN) is the most serious manifestation of SLE and is characterized by inflammation of the kidney. This review summarizes recent clinical applications of protein biomarkers including autoantibodies, complements, cytokines and chemokines and some new protein biomarkers in SLE and LN. The clinical differential diagnosis of protein biomarkers related to prognosis and diagnosis is discussed and highlighted. Protein biomarkers play crucial roles in the study of SLE and LN. Useful biomarkers will provide insights into effective treatments for these diseases.

Is Osteopontin a Friend or Foe of Cell Apoptosis in Inflammatory Gastrointestinal and Liver Diseases?

Osteopontin (OPN) is involved in a variety of biological processes, including bone remodeling, innate immunity, acute and chronic inflammation, and cancer. The expression of OPN occurs in various tissues and cells, including intestinal epithelial cells and immune cells such as macrophages, dendritic cells, and T lymphocytes. OPN plays an important role in the efficient development of T helper 1 immune responses and cell survival by inhibiting apoptosis. The association of OPN with apoptosis has been investigated. In this review, we described the role of OPN in inflammatory gastrointestinal and liver diseases, focusing on the association of OPN with apoptosis. OPN changes its association with apoptosis depending on the type of disease and the phase of disease activity, acting as a promoter or a suppressor of inflammation and inflammatory carcinogenesis. It is essential that the roles of OPN in those diseases are elucidated, and treatments based on its mechanism are developed.