Establishment of a Modified Collagen-Induced Arthritis Mouse Model to Investigate the Anti-inflammatory Activity of Progranulin in Inflammatory Arthritis

Tau deficiency inhibits classically activated macrophage polarization and protects against collagen-induced arthritis in mice

BACKGROUND

Tau protein serves a pro-inflammatory function in neuroinflammation. However, the role of tau in other inflammatory disorders such as rheumatoid arthritis (RA) is less explored. This study is to investigate the role of endogenous tau and the potential mechanisms in the pathogenesis of inflammatory arthritis.

METHODS

We established collagen-induced arthritis (CIA) model in wild-type and Tau-/- mice to compare the clinical score and arthritis incidence. Micro-CT analysis was used to evaluate bone erosion of ankle joints. Histological analysis was performed to assess inflammatory cell infiltration, cartilage damage, and osteoclast activity in the ankle joints. Serum levels of pro-inflammatory cytokines were measured by ELISA. The expression levels of macrophage markers were determined by immunohistochemistry staining and quantitative real-time PCR.

RESULTS

Tau expression was upregulated in joints under inflammatory condition. Tau deletion in mice exhibited milder inflammation and protected against the progression of CIA, evidenced by reduced serum levels of pro-inflammatory cytokines and attenuated bone loss, inflammatory cell infiltration, cartilage damage, and osteoclast activity in the ankle joints. Furthermore, tau deficiency led to the inhibition of classically activated type 1 (M1) macrophage polarization in the synovium.

CONCLUSION

Tau is a previously unrecognized critical regulator in the pathogenesis of RA and may provide a potential therapeutic target for autoimmune and inflammatory joint diseases.

Identification of potential ferroptosis-associated biomarkers in rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by inflammation and gradual joint degeneration, resulting in function disability. Recently, ferroptosis, a novel form of regulated cell death that involves iron-dependent lipid peroxidation, has been implicated in the pathogenesis of RA. However, the underlying molecular mechanisms and key genes involved in ferroptosis in RA remain largely unknown.

Methods

The GSE134420 and GSE77298 datasets were downloaded and DEGs were identified using R software. The DEGs were then mapped to the dataset of 619 ferroptosis-related genes obtained from the GeneCards database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to investigate the possible biological functions. Protein-protein interaction (PPI) networks were constructed to identify the hub genes. The relationship between hub genes and immune infiltration was estimated using the CIBERSORT algorithms. Gene Set Enrichment Analysis (GSEA) was used to explore the underlying signaling pathways of hub genes. Genome-wide association studies (GWAS) analysis was performed to confirm the pathogenic regions of the hub genes. RcisTarget and Gene-motif ranking databases were used to identify transcription factors (TFs) associated with the hub genes. The miRcode databases were utilized to construct the microRNA (miRNA)-messenger RNA (mRNA) network. Single-cell analysis was utilized to cluster cells and display the expression of hub genes in cell clusters. Finally, the expression and potential mechanism of hub genes were investigated in human and experimental samples.

Results

Three hub genes PTGS2, ENO1, and GRN highly associated with ferroptosis were identified. Four pathogenic genes HLA-B, MIF, PSTPIP, TLR1 were identified that were significantly and positively correlated with the expression levels of hub genes. The results of the GSEA showed that the hub genes were significantly enriched in pathways related to immunity, lysosome, phagocytosis and infection. ENO1 and PTGS2 were enriched in the TF-binding motif of cisbp_M5493. The hub genes were validated in experimental and patient samples and highly level of ENO1 expression was found to inhibit ACO1, which reduces ferroptosis in proliferating fibroblast-like synoviocytes (FLS).

Conclusion

PTGS2, ENO1 and GRN were identified and validated as potential ferroptosis-related biomarkers. Our work first revealed that ENO1 is highly expressed in RA synovium and that ferroptosis may be regulated by the ENO1-ACO1 axis, advancing the understanding of the underlying ferroptosis-related mechanisms of synovial proliferation and providing potential diagnostic and therapeutic targets for RA.

Progranulin in Musculoskeletal Inflammatory and Degenerative Disorders, Focus on Rheumatoid Arthritis, Lupus and Intervertebral Disc Disease: A Systematic Review

Progranulin (PGRN) is a glycoprotein formed by 593 amino acids encoded by the GRN gene. It has an important role in immunity and inflammatory response, as well as in tissue recovery. Its role in musculoskeletal inflammatory diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and intervertebral disc degeneration disease (IVDD), is, nowadays, an important target to investigate. The objective of this review is to systematically sum up all the recent findings concerning PGRN as a target in the development and resolution of the inflammatory diseases. PubMed was examined with the terms combinations (Progranulin) AND (Lupus Erythematosus, Systemic), (Progranulin) AND (Arthritis, Rheumatoid), and (Progranulin) AND (Intervertebral Disc Degeneration). PubMed was examined with the terms combinations (Atsttrin) AND (Lupus Erythematosus, Systemic), (Atsttrin) AND (Arthritis, Rheumatoid), and (Atsttrin) AND (Intervertebral Disc Degeneration). Moreover, research through Web of Science was performed searching the same items. The inclusion criteria were: studies whose main topic were progranulin, or atsttrin, with emphasis on the three selected diseases. On the other hand, the exclusion criteria were studies that only focused on diseases not related to RA, lupus or IVDD, in addition to the previous published literature reviews. Since few results were obtained, we did not filter by year. The records assessed for eligibility were 23, including all the studies with the information in state of art of progranulin and its capability to be a potential target or treatment for each one of the selected diseases. As these results are descriptive and not clinical trials, we did not perform risk of bias methods. Within these results, many studies have shown an anti-inflammatory activity of PGRN in RA. PGRN levels in serum and synovial fluids in RA patients were reported higher than controls. On the other hand, serum levels were directly correlated with SLE disease activity index, suggesting an important role of PGRN as a player in the progression of inflammatory diseases and a therapeutical approach for the recovery. This review has some limitations due to the small number of studies in this regard; therefore, we highlight the importance and the necessity of further investigation. No external funding was implicated in this systematical review.

Progranulin is essential for bone homeostasis and immunology

Intercellular communication or crosstalk between immune and skeletal cells is considered a crucial element in bone homeostasis modulation. Progranulin (PGRN) is an autocrine growth factor that is structured as beads-on-a-string and participates in multiple pathophysiological processes, including atherosclerosis, arthritis, neurodegenerative pathologies, cancer, and wound repair. PGRN functions as a competitor that binds to tumor necrosis factor receptor 1 (TNFR1), thereby blocking the TNF-α pathway. PGRN is regarded as an agonist of chondrogenesis and osteogenesis, delaying the progression of inflammation through the TNFR2 pathway. The exploitation of PGRN may bring benefits for inflammatory bone diseases and the stabilization of bone homeostasis. The PGRN-modified analog Atsttrin possesses three TNFR-binding fragments and thereby exerts superior therapeutic effects on multiple preclinical animal models compared to PGRN. In this review, we highlight the emerging roles of PGRN in bone formation, as well as in physiological and TNF-α-mediated inflammatory conditions revealed in recent discoveries. We address potential therapies for the treatment of inflammatory bone conditions, such as periodontitis, by the use of PGRN and its derivative Atsttrin.

Preclinical Rodent Models of Arthritis and Acute Inflammation Indicate Immunomodulatory and Anti-Inflammatory Properties of Juglans regia Extracts

Juglans regia has been used to treat inflammatory and arthritic disorders in traditional medicine. The present study aimed to investigate the antiarthritic and anti-inflammatory potential of ethanolic leaves extract of J. regia. Arthritis was induced in rodents with Freund’s complete adjuvant. J. regia treatment was started on 8th day of arthritis induction and sustained for 20 days. Acute inflammatory models were developed using carrageenan, histamine, serotonin, and dextran. Qualitative and GC-MS analyses were also performed. Arthritis was determined using an arthritis scoring index and histopathological examination of ankle joints. RT-PCR was performed to determine the expression of pro-inflammatory markers (TNF-α, NF-κB, IL-6, IL-1β, and COX-2) and anti-inflammatory IL-4. PGE2 levels were evaluated using an ELISA. Blood and biochemical parameters were also determined. Paw edema was measured using a digital plethysmometer. Treatment with extracts inhibited arthritic development and attenuated paw edema along with all histopathological parameters. The expression levels of pro-inflammatory cytokines and COX-2 were downregulated, while IL-4 was upregulated. PGE2 levels were also reduced in extract-treated groups. Blood and biochemical parameters were nearly normalized in the treatment groups. Both extracts significantly inhibited carrageenan, histamine, serotonin, and dextran-induced paw edema. Qualitative phytochemical screening and GC-MS analysis confirmed that extracts possessed potential medicinal compounds. In conclusion, ethanol and n-hexane extracts of J. regia leaves have immunomodulatory and anti-inflammatory effects that ameliorate experimentally induced arthritis and edema. The inhibition of autacoids may also be one of the mechanisms inducing the immunomodulatory effect.

Progranulin and Its Receptor Predict Kidney Function Decline in Patients With Type 2 Diabetes

Progranulin (PGRN), a growth factor, is abundantly expressed in a broad range of tissues and cell types with pleiotropic functions including inflammation, neurodegeneration, and facilitating lysosome acidification. PGRN binds to TNF receptors (TNFR) and inhibits downstream inflammatory signaling pathways. TNFR is a well-known predictor of glomerular filtration rate (GFR) decline in a variety of diseases. Therefore, we measured circulating PGRN in addition to TNFR using an enzyme-linked immunosorbent assay and explored whether it predicted renal prognosis in 201 Japanese patients with type 2 diabetes. During a median follow-up of 7.6 years, 21 participants reached primary renal endpoint, which involves a decline of at least 57% in eGFR from baseline, or the onset of end-stage renal disease. Univariate Cox regression analysis revealed that classical renal measures (GFR and albuminuria), two TNF-related biomarkers (PGRN and TNFR), and BMI were associated with this outcome. Multivariate analysis demonstrated that high levels of PGRN [HR 2.50 (95%CI 2.47-2.52)] or TNFR1 [HR 5.38 (95%CI 5.26-5.50)] were associated with this outcome after adjusting for relevant covariates. The high levels of PGRN as well as TNFR1 were associated with a risk of primary renal outcome in patients with type 2 diabetes after adjusting for established risk factors.

Progranulin Regulates Inflammation and Tumor

Progranulin (PGRN) mediates cell cycle progression and cell motility as a pleiotropic growth factor and acts as a universal regulator of cell growth, migration and transformation, cell cycle, wound healing, tumorigenesis, and cytotoxic drug resistance as a secreted glycoprotein. PGRN overexpression can induce the secretion of many inflammatory cytokines, such as IL-8, -6,-10, TNF-α. At the same time, this protein can promote tumor proliferation and the occurrence and development of many related diseases such as gastric cancer, breast cancer, cervical cancer, colorectal cancer, renal injury, neurodegeneration, neuroinflammatory, human atherosclerotic plaque, hepatocarcinoma, acute kidney injury, amyotrophic lateral sclerosis, Alzheimer’s disease and Parkinson’s disease. In short, PGRN plays a very critical role in injury repair and tumorigenesis, it provides a new direction for succeeding research and serves as a target for clinical diagnosis and treatment, thus warranting further investigation. Here, we discuss the potential therapeutic utility and the effect of PGRN on the relationship between inflammation and cancer.

Atsttrin Promotes Cartilage Repair Primarily Through TNFR2-Akt Pathway

Background

Cartilage defects account for substantial economic and humanistic burdens and pose a significant clinical problem. The efficacy of clinical approaches to cartilage repair is often inadequate, in part, owing to the restricted proliferative capacity of chondrocytes. Molecules have the capacity to promote the differentiation of multipotent mesenchymal stem cells into chondrocytes and may also gain the ability to repair the damaged cartilage.

Objective

This study aimed to investigate the role of Atsttrin (progranulin-derived engineered protein) in cartilage repair as well as the signaling pathway involved.

Methods

Primary and mesenchymal stem cell lines were used for the micromass culture. A murine cartilage defect model was used to determine the role of Atsttrin in cartilage repair in vivo. Real-time polymerase chain reaction and Western blot analysis were used to monitor the effect of Atsttrin on the transcriptional and protein levels, respectively, of key anabolic and catabolic signaling molecules.

Results

Atsttrin stimulated chondrogenesis in vitro and accelerated cartilage repair in vivo. In addition, Atsttrin-mediated cartilage repair occurred primarily through tumor necrosis factor receptor 2-initiated Akt signaling and downstream JunB transcription factor.

Conclusion

Atsttrin might serve as a promising therapeutic modality for cartilage regeneration.

Deficiency of Pdk1 contributes to primordial follicle activation via the upregulation of YAP expression and the pro‑inflammatory response

The molecular mechanisms underlying the activation of primordial follicles are poorly understood. The serine/threonine protein kinase phosphoinositide‑dependent kinase 1 (PDK1), a pivotal downstream effector of phosphatidyl inositol‑3 kinase (PI3K) signaling, plays a vital role in cellular signaling. In order to identify the function of PDK1 in ovarian follicle development, this study used conditional Pdk1 deletion in mouse oocytes by crossing Pdk1loxP/loxP mice with transgenic mice carrying Gdf‑9 promoter‑mediated Cre recombinase and found that Pdk1flx/flxGdf9Cre mice were subfertile with increased serum follicle‑stimulating hormone (FSH) and luteinizing hormone (LH) levels compared with Pdk1flx/flx mice. The deletion of Pdk1 in oocytes induced massive primordial follicle activation, leading to premature ovarian failure (POF). Further investigation revealed that enhanced Yes‑associated protein (YAP) expression and an increased pro‑inflammatory response also contributed to massive primordial follicle activation. PDK1 formed the complex with the core kinases of Hippo signaling and regulated the expression levels of YAP. On the whole, the findings of the present study demonstrate that PDK1 serves as an indispensable gatekeeper for maintaining the primordial follicle pool and provide a deeper understanding of POF treatment.

Progranulin: A conductor of receptors orchestra, a chaperone of lysosomal enzymes and a therapeutic target for multiple diseases

Progranulin (PGRN), a widely expressed glycoprotein with pleiotropic function, has been linked to a host of physiological processes and diverse pathological states. A series of contemporary preclinical disease models and clinical trials have evaluated various therapeutic strategies targeting PGRN, highlighting PGRN as a promising therapeutic target. Herein we summarize available knowledge of PGRN targeting in various kinds of diseases, including common neurological diseases, inflammatory autoimmune diseases, cancer, tissue repair, and rare lysosomal storage diseases, with a focus on the functional domain-oriented drug development strategies. In particular, we emphasize the role of extracellular PGRN as a non-conventional, extracellular matrix bound, growth factor-like conductor orchestrating multiple membrane receptors and intracellular PGRN as a chaperone/co-chaperone that mediates the folding and traffic of its various binding partners.