Increased levels of thymosin β4 in synovial fluid of patients with rheumatoid arthritis: association of thymosin β4 with other factors that are involved in inflammation and bone erosion in joints

Inflammatory arthritis and eye diseases: a Mendelian randomization study

Objectives

The aim of this study was to determine causal associations between inflammatory arthritis and eye diseases (disorders of sclera, cornea, iris, and ciliary body [DSCIC] and disorders of choroid and retina [DCR]).

Methods

Genome-wide association studies' summary data of rheumatoid arthritis (RA) from a large-scale meta-analysis were used to identify genetically predicted RA. UK Biobank source data predicted ankylosing spondylitis (AS), psoriatic arthritis (PsA), and juvenile idiopathic arthritis (JIA). Furthermore, data from the FinnGen Biobank were used to identify genetically predicted eye diseases. Two-sample Mendelian randomization analysis was used to assess the causal relationship between inflammatory arthritis and eye diseases in the European population. Inverse-variance weighting (IVW) was used as the primary method, while MR-Egger, weighted median, and MR-PRESSO outlier test were used to detect heterogeneity and pleiotropy.

Results

Genetically determined RA was indeed observed to have a causal effect on DSCIC (odds ratio [OR] = 1.084, p = 2.353 × 10-10) and DCR (OR = 1.151, p = 1.584 × 10-19). AS was causally associated with DSCIC (OR = 1.068, p < 2.024 × 10-8). In addition, PsA was also found to have a causal association with an increased risk of 17.9% for the development of DSCIC (OR = 1.179, p = 0.003). On the flip side, DSCIC increased the risk of JIA (OR = 2.276, p = 0.003).

Conclusion

Our study provided genetic evidence for the causal associations of RA, AS, and PsA with an increased risk of DSCIC, and a causal association between RA and DCR was also identified. In addition, DSCIC greatly increased the risk of JIA.

Soluble Urokinase Plasminogen Activator Receptor (suPAR) in Autoimmune Rheumatic and Non Rheumatic Diseases

The soluble urokinase plasminogen activator receptor (suPAR) is the bioactive form of uPAR, a membrane-bound glycoprotein, and it is primarily expressed on the surface of immunologically active cells. Mirroring local inflammation and immune activation, suPAR has gained interest as a potential prognostic biomarker in several inflammatory diseases. Indeed, in many diseases, including cancer, diabetes, cardiovascular diseases, kidney diseases, and inflammatory disorders, higher suPAR concentrations have been associated with disease severity, disease relapse, and mortality. Our review describes and discusses the supporting literature concerning the promising role of suPAR as a biomarker in different autoimmune rheumatic and non-rheumatic diseases.

The Association of uPA, uPAR, and suPAR System with Inflammation and Joint Damage in Rheumatoid Arthritis: suPAR as a Biomarker in the Light of a Personalized Medicine Perspective

BACKGROUND

In recent years, the involvement of the soluble urokinase Plasminogen Activator Receptor (suPAR) in the pathophysiological modulation of Rheumatoid Arthritis (RA) has been documented, resulting in the activation of several intracellular inflammatory pathways.

METHODS

We investigated the correlation of urokinase Plasminogen Activator (uPA)/urokinase Plasminogen Activator Receptor (uPAR) expression and suPAR with inflammation and joint damage in RA, evaluating their potential role in a precision medicine context.

RESULTS

Currently, suPAR has been shown to be a potential biomarker for the monitoring of Systemic Chronic Inflammation (SCI) and COVID-19. However, the effects due to suPAR interaction in immune cells are also involved in both RA onset and progression. To date, the literature data on suPAR in RA endorse its potential application as a biomarker of inflammation and subsequent joint damage.

CONCLUSION

Available evidence about suPAR utility in the RA field is promising, and future research should further investigate its use in clinical practice, resulting in a big step forward for precision medicine. As it is elevated in different types of inflammation, suPAR could potentially work as an adjunctive tool for the screening of RA patients. In addition, a suPAR system has been shown to be involved in RA pathogenesis, so new data about the therapeutic response to Jak inhibitors can represent a possible way to develop further studies.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

An Investigation on the Therapeutic Effect of Thymosin β4 and Its Expression Levels in Streptozotocin-Induced Diabetic Mice

Thymosin β4 (Tβ4) treatment was known to show the potential therapeutic effects on diabetic complications. This study was performed to determine if Tβ4 expression is changed in both serum and tissues under diabetic conditions and can be a serum biomarker. Type 1 diabetic mice were induced in C57/BL6J mice by intraperitoneal injection of streptozotocin (STZ) at a dose of 50 mg/kg body weight. The mice were sacrificed at 16 weeks after STZ injection. Tissues and plasmas were obtained to determine the expression levels of Tβ4 using ELISA, real time RT-PCR, and immunohistochemistry. The average serum glucose level was increased to approximately 400 mg/dL beginning 2 weeks after the five injections of STZ and lasting for at least 13 weeks until sacrifice. The plasma and tissue levels of Tβ4 in the age-matched control mice were not significantly different from those of the diabetic mice. In conclusion, the Tβ4 expression level in the plasmas and tissues of diabetic mice was not affected by diabetic conditions. It indirectly suggests that the therapeutic effect of Tβ4 on diabetic complications is due to its regenerative effects on damaged tissue but not to the changed expression level of Tβ4 in plasma and tissues of diabetes.

uPA/uPAR signaling in rheumatoid arthritis: Shedding light on its mechanism of action

Rheumatoid arthritis (RA) is a systemic and chronic autoimmune inflammatory disorder affecting multiple joints. Various cytokines, chemokines and growth factors synergistically modulate the joint physiology leading to bone erosion and cartilage degradation. Other than these conventional mediators that are well established in the past, the newly identified plasminogen activator (PA) family of proteins have been witnessed to possess a multifactorial approach in mediating RA pathogenesis. One such family of proteins comprises of the urokinase-type plasminogen activator (uPA) and its receptor (uPAR)/soluble-type plasminogen activator receptor (suPAR). PA family of proteins are classified into two types namely: uPA and tissue type plasminogen activator (tPA). Both these subtypes have been implicated to play a key role in RA disease progression. However during RA pathogenesis, uPA secreted by neutrophils, chondrocytes, and monocytes are designated to interact with uPAR expressed on macrophages, fibroblast-like synoviocytes (FLS), chondrocytes and endothelial cells. Interaction of uPA/uPAR promotes the disease progression of RA through secretion of several cytokines, chemokines, growth factors and matrix metalloproteinases (MMPs). Moreover, uPA/uPAR initiates inflammatory responses in macrophages and FLS through activation of PI3K/Akt signaling pathways. Furthermore, uPAR plays a dual role in osteoclastogenesis under the presence/absence of growth factors like monocyte-colony stimulating factor (M-CSF). Overall, this review emphasizes the role of uPA/uPAR on various immune cells, signaling pathways and osteoclastogenesis involved in RA pathogenesis.

Thymosin β4 in rheumatoid arthritis: Friend or foe

Rheumatoid arthritis (RA) has characteristic pannus tissues, which show tumor-like growth of the synovium through chronic joint inflammation. The synovium is highly penetrated by various immune cells, and the synovial lining becomes hyperplastic due to increased numbers of macrophage-like and fibroblast-like synoviocytes. Thus, a resultant hypoxic condition stimulates the expression of inflammation-related genes in various cells, in particular, vascular endothelial growth factor. Thymosin β4 (Tβ4), a 5-kDa protein, is known to play a significant role in various biological activities, such as actin sequestering, cell motility, migration, inflammation, and damage repair. Recent studies have provided evidence that Tβ4 may have a role in RA pathogenesis. The Tβ4 level has been shown to increase significantly in the joint fluid and serum of RA patients. However, whether Tβ4 stimulates or inhibits activation of RA immune responses remains to be determined. In the present study, we discuss the logical and clinical justifications for Tβ4 as a potential target for RA therapeutics.

Serum peptides as putative modulators of inflammation in psoriasis

BACKGROUND

Psoriasis is a refractory inflammatory disease, however, its pathophysiology is still not fully understood.

OBJECTIVE

We tried to identify novel serum peptides associated with the pathophysiology of psoriasis.

METHODS

Serum peptides from 24 patients with psoriasis vulgaris (PV), 10 patients with psoriatic arthritis (PsA), 14 patients with atopic dermatitis (AD), and 23 healthy control (HC) subjects were analyzed by mass spectrometry. The effects of some peptides on the secretion of humoral factors from dermal cells were investigated by cytokine arrays and ELISAs.

RESULTS

A total of 93 peptides were detected. 24, 20, 23, and 2 peptides showed at least 1.2-fold difference in ion intensity between the psoriasis (PV+PsA) and HC groups, between the PV+PsA and AD groups, between the PV and PsA groups, and between patients with severe-to-moderate PV (n=6) and those with mild PV (n=18), respectively (p<0.05). 13 out of 27 peptides that showed at least 1.5-fold ion intensity difference in the abovementioned 4 comparisons were identified. The parent proteins of the identified peptides included a coagulation factor, proteins involved in the maintenance of skin, and a protein relating to cytoskeleton. We focused on 2 peptides that were increased in the PV+PsA group: a fibrinogen α chain-derived peptide (1462m/z), the unmodified form of which was fibrinopeptide A-des-alanine (FPAdA), and a filaggrin (FLG)-derived peptide (1977m/z), a modified form of FLG_2099-2118 (Q₂₀₉₉pE, Q₂₁₁₅E; FLG-pEE). FPAdA stimulation increased the secretion of GROα from dermal microvascular endothelial cells (dMVECs) and decreased the secretion of lipocalin-2 from keratinocytes in comparison to FPAdA-resequenced peptide stimulation (GROα, 280.9±7.3pg/mL vs. 229.6±5.0pg/mL, p<0.001; lipocalin-2, 273±13pg/mL vs. 350±10pg/mL, p<0.01). Interestingly, FLG-pEE stimulation decreased the secretion of GROα, IL-8, and MCP-1 from dMVECs in comparison to FLG-derived control peptide stimulation (GROα, 844.3±47.5pg/mL vs. 1038.5±96.9pg/mL, p<0.05; IL-8, 2240.1±172.6pg/mL vs. 3221.8±523.7pg/mL, p<0.05; MCP-1, 4057.8±157.2pg/mL vs. 4619.1±213.4pg/mL, p<0.05).

CONCLUSIONS

The results suggested that some serum peptides are involved in the pathophysiology of psoriasis, regulating the secretion of inflammatory chemokines and an antimicrobial protein. The modulation of serum peptides may be a potential therapeutic strategy for psoriasis.

Escape from X inactivation varies in mouse tissues

X chromosome inactivation (XCI) silences most genes on one X chromosome in female mammals, but some genes escape XCI. To identify escape genes in vivo and to explore molecular mechanisms that regulate this process we analyzed the allele-specific expression and chromatin structure of X-linked genes in mouse tissues and cells with skewed XCI and distinguishable alleles based on single nucleotide polymorphisms. Using a binomial model to assess allelic expression, we demonstrate a continuum between complete silencing and expression from the inactive X (Xi). The validity of the RNA-seq approach was verified using RT-PCR with species-specific primers or Sanger sequencing. Both common escape genes and genes with significant differences in XCI status between tissues were identified. Such genes may be candidates for tissue-specific sex differences. Overall, few genes (3-7%) escape XCI in any of the mouse tissues examined, suggesting stringent silencing and escape controls. In contrast, an in vitro system represented by the embryonic-kidney-derived Patski cell line showed a higher density of escape genes (21%), representing both kidney-specific escape genes and cell-line specific escape genes. Allele-specific RNA polymerase II occupancy and DNase I hypersensitivity at the promoter of genes on the Xi correlated well with levels of escape, consistent with an open chromatin structure at escape genes. Allele-specific CTCF binding on the Xi clustered at escape genes and was denser in brain compared to the Patski cell line, possibly contributing to a more compartmentalized structure of the Xi and fewer escape genes in brain compared to the cell line where larger domains of escape were observed.

The eye: a window of opportunity in rheumatoid arthritis?

Rheumatoid arthritis (RA), the most common autoimmune disorder associated with dry eye syndrome, is also associated with sight-threatening ocular diseases such as peripheral ulcerative keratitis, scleritis and corneal melts. Tissue damage on the ocular surface of patients with RA is autoimmune-mediated. Findings from patients with dry eye have implicated defects in innate immunity (Toll-like receptors, S100A and resident antigen-presenting cells), cytokines, chemokines and T helper (TH)-cell subsets (including TH1 and TH17) in disease pathogenesis. Some of these features are probably important in dry eye related to RA, which can occur at a different time from articular disease and is more clinically severe than idiopathic dry eye. Ocular surface immune factors can be influenced by the systemic immune landscape. Depending on the severity of ocular inflammation in RA, treatment can include ciclosporin, topical corticosteroids, tacrolimus, autologous serum and systemic immunosuppression. Tissue damage is treated by inhibiting matrix metalloproteinases. Potential therapeutic strategies benefit from an improved understanding of ocular surface immunology, and include targeting of T-cell subsets, B-cell signalling or cytokines.

Increased thymosin β4 levels in the serum and SF of knee osteoarthritis patients correlate with disease severity

OBJECTIVE

Thymosin β4, a member of a large family of thymic proteins, plays an important role in the process of articular cartilage degeneration which is a common cause of osteoarthritis (OA). This study aims to determine thymosin β4 levels in the serum and synovial fluid (SF) of patients with knee OA and analyze the correlation of thymosin β4 levels with the radiographic severity of OA.

METHODS

This study consisted of 216 patients with knee OA and 152 healthy controls. OA progression was classified based on Kellgren-Lawrence by evaluating x-ray changes observed in anteroposterior knee radiography. Thymosin β4 levels in the serum and SF were measured by enzyme-linked immunosorbent assay method.

RESULTS

The knee OA patients had higher levels of serum thymosin β4 than the healthy controls. Knee OA patients with KL grade 4 showed significantly elevated thymosin β4 levels in the serum and SF compared with those with KL grades 2 and 3. Knee OA patients with KL grade 3 had significantly higher SF levels of thymosin β4 than those with KL grade 2. Thymosin β4 levels in the serum and SF of knee OA patients were significantly correlated with disease severity according to KL grading criteria.

CONCLUSION

The thymosin β4 levels in the serum and SF may serve as effective biomarkers for the severity of OA.

Association between serum thymosin β4 levels of rheumatoid arthritis patients and disease activity and response to therapy

The aim of this study was to evaluate whether thymosin β4 (Tβ4) levels are increased in the serum of rheumatoid arthritis (RA) patients, and if this increase is associated with RA disease activity and resistance to treatment. Blood samples from 40 patients with RA were collected at baseline and 6 months after starting treatment with disease-modifying antirheumatic drugs (DMARD) and/or tumor necrosis factor (TNF)-α blocker. Serum levels of Tβ4 were measured by ELISA. Tβ4 levels (mean ± standard deviation) in RA patients were significantly (approximately tenfold) higher than in healthy controls (577.4 ± 67.92 vs. 56.61 ± 5.72 ng/mL). Serum Tβ4 levels in patients with severe disease activity before therapy were slightly higher than in patients with moderate disease activity (662.4 ± 491.5 vs. 462.5 ± 305.3 ng/ml, P > 0.05). Tβ4 levels were significantly associated with disease activity according to the 28-joint Disease Activity Score. The mean Tβ4 level at baseline in the DMARD treatment group was significantly lower than in the DMARD + TNF-α blocker treatment group. Tβ4 levels were increased in the serum of patients with RA and were positively associated with disease activity. Levels of Tβ4 may also be relevant in determining or predicting resistance to RA treatment. Further studies are necessary to determine if Tβ4 is an appropriate therapeutic target for controlling inflammation associated with RA.