Foxo4- and Stat3-dependent IL-10 production by progranulin in regulatory T cells restrains inflammatory arthritis

The role of progranulin in macrophages of a glioblastoma model

PURPOSE

Glioblastoma (GBM), characterized by astrocytic tumorigenesis, remains one of the most prognostically challenging tumor types. Targeting entire GBM microenvironment using novel therapeutic factors is currently desired investigation approach. In this study, we focused on progranulin (PGRN), a regulator of diverse cellular functions. Recent studies implicated PGRN in the poor prognostics of GBM patients. However, the specific role of PGRN in the GBM microenvironment remains elusive.

METHODS

We utilized public databases of GBM patient and previous single-cell RNA sequence to examine association between PGRN expression and patient survival/grade, and expression levels of PGRN in each cell constituting the tumor microenvironment. To clarify the role of PGRN in Tumor-associated macrophage (TAM), we examined cell proliferation and expression of some proteins in murine GBM cells when cell supernatants derived from TAM of PGRN knockout (Grn-/-) or wild type mice were treated with murine GBM cells.

RESULTS

Our results reveal significant PGRN expression in macrophages within the GBM environment, suggesting an association between increased PGRN expression in macrophages and tumor malignancy. TAM induction led to PGRN expression enhancement. Treatment with Grn-/- mouse -derived bone marrow-derived macrophage (BMDM) supernatant resulted in diminished GBM cell proliferation and cell cycle- and mesenchymal GBM subtype-associated reduced protein expression. Furthermore, the Grn-/- mouse-derived BMDM supernatant treatment reduced the phosphorylated STAT3 expression in GBM cells, while the expression of IL-6 and IL-10, known STAT3 pathway activators, diminished in Grn-/- mouse-derived BMDMs.

CONCLUSION

Our results suggest that macrophage-derived PGRN is pivotal for fostering malignant transformations within the tumor microenvironment.

Magnesium Ions Promote the Induction of Immunosuppressive Bone Microenvironment and Bone Repair through HIF-1α-TGF-β Axis in Dendritic Cells

The effect of immunoinflammation on bone repair during the recovery process of bone defects needs to be further explored. It is reported that Mg2+ can promote bone repair with immunoregulatory effect, but the underlying mechanism on adaptive immunity is still unclear. Here, by using chitosan and hyaluronic acid-coated Mg2+ (CSHA-Mg) in bone-deficient mice, it is shown that Mg2+ can inhibit the activation of CD4+ T cells and increase regulatory T cell formation by inducing immunosuppressive dendritic cells (imDCs). Mechanistically, Mg2+ initiates the activation of the MAPK signaling pathway through TRPM7 channels on DCs. This process subsequently induces the downstream HIF-1α expression, a transcription factor that amplifies TGF-β production and inhibits the effective T cell function. In vivo, knock-out of HIF-1α in DCs or using a HIF-1α inhibitor PX-478 reverses inhibition of bone inflammation and repair promotion upon Mg2+-treatment. Moreover, roxadustat, which stabilizes HIF-1α protein expression, can significantly promote immunosuppression and bone repair in synergism with CSHA-Mg. Thus, the findings identify a key mechanism for DCs and its HIF-1α-TGF-β axis in the induction of immunosuppressive bone microenvironment, providing potential targets for bone regeneration.

Progranulinopathy: A diverse realm of disorders linked to progranulin imbalances

Progranulin (PGRN), encoded by the GRN gene in humans, was originally isolated as a secreted growth factor that implicates in a multitude of processes ranging from regulation of tumorigenesis, inflammation to neural proliferation. Compelling evidence indicating that GRN mutation can lead to various common neuronal degenerative diseases and rare lysosomal storage diseases. These findings have unveiled a critical role for PGRN as a lysosomal protein in maintaining lysosomal function. The phenotypic spectrum of PGRN imbalance has expanded to encompass a broad spectrum of diseases, including autoimmune diseases, metabolic, musculoskeletal and cardiovascular diseases. These diseases collectively referred to as Progranulinopathy- a term encompasses the wide spectrum of disorders influenced by PGRN imbalance. Unlike its known extracellular function as a growth factor-like molecule associated with multiple membrane receptors, PGRN also serves as an intracellular co-chaperone engaged in the folding and traffic of its associated proteins, particularly the lysosomal hydrolases. This chaperone activity is required for PGRN to exert its diverse functions across a broad range of diseases, encompassing both the central nervous system and peripheral systems. In this comprehensive review, we present an update of the emerging role of PGRN in Progranulinopathy, with special focus on elucidating the intricate interplay between PGRN and a diverse array of proteins at various levels, ranging from extracellular fluids and intracellular components, as well as various pathophysiological processes involved. This review seeks to offer a comprehensive grasp of PGRN's diverse functions, aiming to unveil intricate mechanisms behind Progranulinopathy and open doors for future research endeavors.

Therapeutic potential of TNFR2 agonists: a mechanistic perspective

TNFR2 agonists have been investigated as potential therapies for inflammatory diseases due to their ability to activate and expand immunosuppressive CD4+Foxp3+ Treg cells and myeloid-derived suppressor cells (MDSCs). Despite TNFR2 being predominantly expressed in Treg cells at high levels, activated effector T cells also exhibit a certain degree of TNFR2 expression. Consequently, the role of TNFR2 signaling in coordinating immune or inflammatory responses under different pathological conditions is complex. In this review article, we analyze possible factors that may determine the therapeutic outcomes of TNFR2 agonism, including the levels of TNFR2 expression on different cell types, the biological properties of TNFR2 agonists, and disease status. Based on recent progress in the understanding of TNFR2 biology and the study of TNFR2 agonistic agents, we discuss the future direction of developing TNFR2 agonists as a therapeutic agents.

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.

Blimp1 suppressed CD4+ T cells-induced activation of fibroblast-like synoviocytes by upregulating IL-10 via the rho pathway

BACKGROUND

B lymphocyte-induced maturation protein 1 (Blimp1) is a risk allele for rheumatoid arthritis (RA), but its functional mechanism in RA remains to be further explored.

METHODS

Flow cytometry was performed to detect CD4⁺ T cell differentiation. ELISA was used to measure inflammatory factor secretion. Lentivirus mediated Blimp1 overexpression vector (LV-Blimp1) or short hairpin RNA (sh-Blimp1) were used to infect CD4⁺ T cells stimulated by anti-CD28 and anti-CD3 mAbs. RA fibroblast-like synoviocytes (FLSs) were co-cultured with CD4⁺ T cells or T cell conditioned medium (CD4CM), and cell proliferation, invasion, and expression of adhesion molecules and cytokines in FLSs were evaluated. Mice were injected intradermally with type II collagen to establish a collagen-induced arthritis (CIA) mouse model, and the severity of CIA was evaluated with H&E and Safranin-O staining.

RESULTS

Blimp1 knockdown increased pro-inflammatory factor secretion, but downregulated IL-10 concentration in activated CD4⁺ T cells. Blimp1 overexpression promoted regulatory T cells (Treg) CD4⁺ T cell differentiation and hindered T helper 1 (Th1) and T helper 17 (Th17) CD4⁺ T cell differentiation. Blimp1 overexpression suppressed the expression of pro-inflammatory factors and adhesion molecules in CD4⁺ T cells by upregulating IL-10. Moreover, Blimp1 overexpression impeded the enhanced effect of CD4⁺ T cells/CD4CM on cell adhesion, inflammation, proliferation, invasion and RhoA and Rac1 activities in FLSs by upregulating IL-10. Additionally, administration with LV-Blimp1 alleviated the severity of CIA.

CONCLUSION

Blimp1 restrained CD4⁺ T cells-induced activation of FLSs by promoting the secretion of IL-10 in CD4⁺ T cells via the Rho signaling pathway.

Progranulin from different gliocytes in the nucleus accumbens exerts distinct roles in FTD- and neuroinflammation-induced depression-like behaviors

BACKGROUND

Neuroinflammation in the nucleus accumbens (NAc) is well known to influence the progression of depression. However, the molecular mechanisms triggering NAc neuroinflammation in depression have not been fully elucidated. Progranulin (PGRN) is a multifunctional growth factor that is linked to the innate immune response and inflammation, and PGRN plays a key role in neurodegenerative diseases such as frontotemporal dementia (FTD). Here, the purpose of this study was to validate whether PGRN was involved in the NAc neuroinflammation-promoted depressive-like phenotype.

METHODS

A NAc neuroinflammation-relevant depression-like model was established using wild-type (WT) and PGRN-knockout (KO) mice after NAc injection with lipopolysaccharide (LPS), and various behavioral tests related to cognition, social recognition, depression and anxiety were performed with WT and PGRNKO mice with or without NAc immune challenge. RT‒PCR, ELISA, western blotting and immunofluorescence staining were used to determine the expression and function of PGRN in the neuroinflammatory reaction in the NAc after LPS challenge. The morphology of neurons in the NAc from WT and PGRNKO mice under conditions of NAc neuroinflammation was analyzed using Golgi-Cox staining, followed by Sholl analyses. The potential signaling pathways involved in NAc neuroinflammation in PGRNKO mice were investigated by western blotting.

RESULTS

Under normal conditions, PGRN deficiency induced FTD-like behaviors in mice and astrocyte activation in the NAc, promoted the release of the inflammatory cytokines interleukin (IL)-6 and IL-10 and increased dendritic complexity and synaptic protein BDNF levels in the NAc. However, NAc neuroinflammation enhanced PGRN expression, which was located in astrocytes and microglia within the NAc, and PGRN deficiency in mice alleviated NAc neuroinflammation-elicited depression-like behaviors, seemingly inhibiting astrocyte- and microglia-related inflammatory reactions and neuroplasticity complexity in the NAc via the p38 and nuclear factor of kappa (NF-κB) signaling pathways present in the NAc after neuroinflammation.

CONCLUSIONS

Our results suggest that PGRN exerts distinct function on different behaviors, showing protective roles in the FTD-like behavior and detrimental effects on the neuroinflammation-related depression-like behavior, resulting from mediating astrocyte and microglial functions from the NAc in different status.

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.

Adipokines as targets in musculoskeletal immune and inflammatory diseases

Adipokines are the principal mediators in adipose signaling. Nevertheless, besides their role in energy storage, these molecules can be produced by other cells, such as immune cells or chondrocytes. Given their pleiotropic effects, research over the past few years has also focused on musculoskeletal diseases, showing that these adipokines might have relevant roles in worsening the disease or improving the treatment response. In this review, we summarize recent advances in our understanding of adipokines and their role in the most prevalent musculoskeletal immune and inflammatory disorders.

Cell-based therapies for rheumatoid arthritis: opportunities and challenges

Rheumatoid arthritis (RA) is the most common immune-mediated inflammatory disease characterized by chronic synovitis that hardly resolves spontaneously. The current treatment of RA consists of nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, conventional disease-modifying antirheumatic drugs (cDMARDs), biologic and targeted synthetic DMARDs. Although the treat-to-target strategy has been intensively applied in the past decade, clinical unmet needs still exist since a substantial proportion of patients are refractory or even develop severe adverse effects to current therapies. In recent years, with the deeper understanding of immunopathogenesis of the disease, cell-based therapies have exhibited effective and promising interventions to RA. Several cell-based therapies, such as mesenchymal stem cells (MSC), adoptive transfer of regulatory T cells (Treg), and chimeric antigen receptor (CAR)-T cell therapy as well as their beneficial effects have been documented and verified so far. In this review, we summarize the current evidence and discuss the prospect as well as challenges for these three types of cellular therapies in RA.

Progranulin as a Potential Therapeutic Target in Immune-Mediated Diseases

Progranulin (PGRN), a secretory glycoprotein consisting of 593 amino acid residues, is a key actor and regulator of multiple system functions such as innate immune response and inflammation, as well as tissue regeneration. Recently, there is emerging evidence that PGRN is protective in the development of a variety of immune-mediated diseases, including rheumatoid arthritis (RA), inflammatory bowel disease (IBD), type 1 diabetes mellitus (T1DM) and multiple sclerosis (MS) by regulating signaling pathways known to be critical for immunology, particularly the tumor necrosis factor alpha/TNF receptor (TNF-α/TNFR) signaling pathway. Whereas, the role of PGRN in psoriasis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) is controversial. This review summarizes the immunological functions of PGRN and its role in the pathogenesis of several immune-mediated diseases, in order to provide new ideas for developing therapeutic strategies for these diseases.

Imbalanced inflammatory response in subchronic arsenic-induced liver injury and the protective effects of Ginkgo biloba extract in rats: Potential role of cytokines mediated cell-cell interactions

Arsenic is a well-known environmental toxicant and carcinogen, which has been epidemiologically proved related to the increased hepatic disorders. Researches have shown that aseptic inflammation and abnormal immune response are associated with arsenic-induced liver injury. However, the immunotoxic effects of liver have not been extensively characterized. Ginkgo biloba extract (GBE), a natural products of G. biloba leaves with proven anti-inflammatory and potential immunoregulatory activities, was used as intervention agent to explore its protective effects on arsenic-induced hepatotoxicity. Thus, the underlying mechanism of the immunotoxic effects on arsenic-induced liver injury were investigated in 2.5, 5.0, and 10.0 mg/kg NaAsO₂ of Wistar rats for 16 weeks. Subsequently, GBE was used as intervention agent in 50 mg/kg for 6 weeks after cessation of arsenic exposure. The ratio of Th17 to Treg cells in peripheral blood as well as the secretion of inflammatory cytokines IL-17A, IL-6, TGF-β1, and IL-10 in serum and liver were detected. Meanwhile, the notable activation of aseptic inflammation-related molecule TLR4 and its downstream targets MyD88 and NF-κB in the liver were observed. In this work, we confirmed that subchronic exposed to arsenic triggered the infiltration of inflammatory cells in rat liver, coupled with obvious histopathological changes and aberrant hepatic serum biochemical parameters. Meanwhile, imbalanced immune response was verified by the notable abnormal ratio of Th17 to Treg cells in peripheral blood as well as the secretion of inflammatory cytokines IL-17A, IL-6, TGF-β1, and IL-10 in serum and liver of arsenic exposed rats. Further, the level of TLR4, MyD88, and NF-κB in liver both transcription and translation activity were raised. Subsequently, GBE markedly mitigated arsenic-induced liver injury, most impressively, post treatment with GBE prominently suppressed the overactivated inflammatory-related TLR4-MyD88-NF-κB pathway and evidently decreased the secretion of inflammation cytokines. Meanwhile, the disturbance of pro- and anti-inflammatory response was reversed. We concluded that the disruption of pro- and anti-inflammatory T-cells balance caused by cytokines mediated cell-cell interactions may be one of the mechanisms underlying arsenic-induced liver injury and that GBE intervention exerts an evidence protective effects, which might be closely associated with the suppression of inflammatory-related TLR4 pathway.

TNFR2/14-3-3ε signaling complex instructs macrophage plasticity in inflammation and autoimmunity

TNFR1 and TNFR2 have received prominent attention because of their dominance in the pathogenesis of inflammation and autoimmunity. TNFR1 has been extensively studied and primarily mediates inflammation. TNFR2 remains far less studied, although emerging evidence demonstrates that TNFR2 plays an antiinflammatory and immunoregulatory role in various conditions and diseases. Herein, we report that TNFR2 regulates macrophage polarization, a highly dynamic process controlled by largely unidentified intracellular regulators. Using biochemical copurification and mass spectrometry approaches, we isolated the signaling molecule 14-3-3ε as a component of TNFR2 complexes in response to progranulin stimulation in macrophages. In addition, 14-3-3ε was essential for TNFR2 signaling-mediated regulation of macrophage polarization and switch. Both global and myeloid-specific deletion of 14-3-3ε resulted in exacerbated inflammatory arthritis and counteracted the protective effects of progranulin-mediated TNFR2 activation against inflammation and autoimmunity. TNFR2/14-3-3ε signaled through PI3K/Akt/mTOR to restrict NF-κB activation while simultaneously stimulating C/EBPβ activation, thereby instructing macrophage plasticity. Collectively, this study identifies 14-3-3ε as a previously unrecognized vital component of the TNFR2 receptor complex and provides new insights into the TNFR2 signaling, particularly its role in macrophage polarization with therapeutic implications for various inflammatory and autoimmune diseases with activation of the TNFR2/14-3-3ε antiinflammatory pathway.

14-3-3 epsilon is an intracellular component of TNFR2 receptor complex and its activation protects against osteoarthritis

OBJECTIVES

Osteoarthritis (OA) is the most common joint disease; however, the indeterminate nature of mechanisms by which OA develops has restrained advancement of therapeutic targets. TNF signalling has been implicated in the pathogenesis of OA. TNFR1 primarily mediates inflammation, whereas emerging evidences demonstrate that TNFR2 plays an anti-inflammatory and protective role in several diseases and conditions. This study aims to decipher TNFR2 signalling in chondrocytes and OA.

METHODS

Biochemical copurification and proteomics screen were performed to isolate the intracellular cofactors of TNFR2 complex. Bulk and single cell RNA-seq were employed to determine 14-3-3 epsilon (14-3-3ε) expression in human normal and OA cartilage. Transcription factor activity screen was used to isolate the transcription factors downstream of TNFR2/14-3-3ε. Various cell-based assays and genetically modified mice with naturally occurring and surgically induced OA were performed to examine the importance of this pathway in chondrocytes and OA.

RESULTS

Signalling molecule 14-3-3ε was identified as an intracellular component of TNFR2 complexes in chondrocytes in response to progranulin (PGRN), a growth factor known to protect against OA primarily through activating TNFR2. 14-3-3ε was downregulated in OA and its deficiency deteriorated OA. 14-3-3ε was required for PGRN regulation of chondrocyte metabolism. In addition, both global and chondrocyte-specific deletion of 14-3-3ε largely abolished PGRN's therapeutic effects against OA. Furthermore, PGRN/TNFR2/14-3-3ε signalled through activating extracellular signal-regulated kinase (ERK)-dependent Elk-1 while suppressing nuclear factor kappa B (NF-κB) in chondrocytes.

CONCLUSIONS

This study identifies 14-3-3ε as an inducible component of TNFR2 receptor complex in response to PGRN in chondrocytes and presents a previously unrecognised TNFR2 pathway in the pathogenesis of OA.

Serum- and Glucocorticoid-Inducible Kinase 1 Promotes Alternative Macrophage Polarization and Restrains Inflammation through FoxO1 and STAT3 Signaling

Expression and activity of serum- and glucocorticoid-inducible kinase 1 (SGK1) are associated with many metabolic and inflammatory diseases. In this study, we report that SGK1 promotes alternative macrophage polarization and restrains inflammation in the infectious milieu of the gingiva. Inhibition of SGK1 expression or activity enhances characteristics of classically activated (M1) macrophages by directly activating the transcription of genes encoding iNOS, IL-12P40, TNF-α, and IL-6 and repressing IL-10 at message and protein levels. Moreover, SGK1 inhibition robustly reduces the expression of alternatively activated (M2) macrophage molecular markers, including arginase-1, Ym-1, Fizz1, and Mgl-1. These results were confirmed by multiple gain- and loss-of-function approaches, including small interfering RNA, a plasmid encoding SGK1, and LysM-Cre-mediated sgk1 gene knockout. Further mechanistic analysis showed that SGK1 deficiency decreases STAT3 but increases FoxO1 expression in macrophages under M2 or M1 macrophage-priming conditions, respectively. Combined with decreased FoxO1 phosphorylation and the subsequent suppressed cytoplasmic translocation observed, SGK1 deficiency robustly enhances FoxO1 activity and drives macrophage to preferential M1 phenotypes. Furthermore, FoxO1 inhibition abrogates M1 phenotypes, and STAT3 overexpression results in a significant increase of M2 phenotypes, indicating that both FoxO1 and STAT3 are involved in SGK1-mediated macrophage polarization. Additionally, SGK1 differentially regulates the expression of M1 and M2 molecular markers, including CD68 and F4/F80 and CD163 and CD206, respectively, and protects against Porphyromonas gingivalis-induced alveolar bone loss in a mouse model. Taken together, these results have demonstrated that SGK1 is critical for macrophage polarization and periodontal bone loss, and for the first time, to our knowledge, we elucidated a bifurcated signaling circuit by which SGK1 promotes alternative, while suppressing inflammatory, macrophage polarization.

In Vitro Physical and Functional Interaction Assays to Examine the Binding of Progranulin Derivative Atsttrin to TNFR2 and Its Anti-TNFα Activity

TNFα/TNFR signaling plays a critical role in the pathogenesis of various inflammatory and autoimmune diseases, and anti-TNFα therapies have been accepted as the effective approaches for treating several autoimmune diseases. Progranulin (PGRN), a multi-faced growth factor-like molecule, directly binds to TNFR1 and TNFR2, particularly to the latter with higher affinity than TNFα. PGRN derivative Atsttrin is composed of three TNFR-binding domain of PGRN and exhibits even better therapeutic effects than PGRN in several inflammatory disease models, including collagen-induced arthritis. Herein we describe the detailed methodology of using (1) ELISA-based solid phase protein-protein interaction assay to demonstrate the direct binding of Atsttrin to TNFR2 and its inhibition of TNFα/TNFR2 interaction; and (2) tartrate-resistant acid phosphatase (TRAP) staining of in vitro osteoclastogenesis to reveal the cell-based anti-TNFα activity of Atsttrin. Using the protocol described here, the investigators should be able to reproducibly detect the physical inhibition of TNFα binding to TNFR and the functional inhibition of TNFα activity by Atsttrin and various kinds of TNF inhibitors.

Monitoring Atsttrin-Mediated Inhibition of TNFα/NF-κβ Activation Through In Vivo Bioluminescence Imaging

The NF-κβ transcription factor is a molecular mediator crucial to many biological functions and a central regulator of inflammatory and immune responses. NF-κβ is activated by multiple immunologically relevant stimuli, including members of the tumor necrosis factor (TNF) superfamily, and targeting TNF/NFκβ activity is a therapeutic objective in many inflammatory and autoimmune conditions. Here, we describe the generation of a transgenic reporter mouse model, expressing the human tumor necrosis factor α (TNF-α) transgene (TNF-tg) and carrying the luciferase gene under control of the NFκB-responsive element (NF-κB-Luc). Bioluminescence imaging shows that overexpression of TNF-α effectively activates NF-κB luciferase in vivo. To evaluate this system as a screen for potential therapeutics targeting the TNF/NFκβ signaling pathway, we treated double mutant mice with PGRN-derived Atsttrin, an engineered molecule comprising the minimal progranulin (PGRN):TNFR binding fragments previously demonstrated as therapeutic in multiple models of TNF/NFκβ-driven disease. Administration of Atsttrin could effectively inhibit luciferase activity in TNF-tg:NF-κB-Luc double mutant mice and demonstrates that this transgenic model can be used to non-invasively monitor the in vivo efficacy of modulators of TNF-activated NF-κB signaling pathway.

Progranulin promotes bone fracture healing via TNFR pathways in mice with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) significantly increases bone fragility and fracture risk. Progranulin (PGRN) promotes bone fracture healing in both physiological and type 1 diabetic conditions. The present study aimed to investigate the role of PGRN in T2DM bone fracture healing. MKR mice (with an FVB/N genetic background) were used as the T2DM model. Drill-hole and Bonnarens and Einhorn models were used to investigate the role of PGRN in T2DM fracture healing in vivo. Primary bone marrow cells were isolated for molecular and signaling studies, and reverse transcription-polymerase chain reaction, immunohistochemical staining, and western blotting were performed to assess PGRN effects in vitro. PGRN mRNA and protein expression were upregulated in the T2DM model. Local administration of recombinant PGRN effectively promoted T2DM bone fracture healing in vivo. Additionally, PGRN could induce anabolic metabolism during endochondral ossification through the TNFR2-Akt and Erk1/2 pathways. Furthermore, PGRN showed anti-inflammatory activity in the T2DM bone regeneration process. These findings suggest that local administration of exogenous PGRN may be an alternative strategy to support bone regeneration in patients with T2DM. Additionally, PGRN might hold therapeutic potential for other TNFR-related metabolic disorders.

Innate Lymphocytes in Inflammatory Arthritis

Inflammatory arthritis (IA) refers to a group of chronic diseases, including rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS), and other spondyloarthritis (SpA). IA is characterized by autoimmune-mediated joint inflammation and is associated with inflammatory cytokine networks. Innate lymphocytes, including innate-like lymphocytes (ILLs) expressing T or B cell receptors and innate lymphoid cells (ILCs), play important roles in the initiation of host immune responses against self-antigens and rapidly produce large amounts of cytokines upon stimulation. TNF (Tumor Necrosis Factor)-α, IFN (Interferon)-γ, Th2-related cytokines (IL-4, IL-9, IL-10, and IL-13), IL-17A, IL-22, and GM-CSF are involved in IA and are secreted by ILLs and ILCs. In this review, we focus on the current knowledge of ILL and ILC phenotypes, cytokine production and functions in IA. A better understanding of the roles of ILLs and ILCs in IA initiation and development will ultimately provide insights into developing effective strategies for the clinical treatment of IA patients.

Progranulin Improves Acute Lung Injury through Regulating the Differentiation of Regulatory T Cells and Interleukin-10 Immunomodulation to Promote Macrophage Polarization

Progranulin (PGRN), which plays an anti-inflammatory role in acute lung injury (ALI), is promising as a potential drug. Studies have shown that regulatory T cells (Tregs) and interleukin- (IL-) 10 can repress inflammation and alleviate tissue damage during ALI. In this study, we built a lipopolysaccharide- (LPS-) induced ALI mouse model to illustrate the effect of PGRN on regulation of Treg differentiation and modulation of IL-10 promoting macrophage polarization. We found that the proportion of Tregs in splenic mononuclear cells and peripheral blood mononuclear cells was higher after treatment with PGRN. The increased proportion of Tregs after PGRN intratracheal instillation was consistent with the decreased severity of lung injury, the reduction of proinflammatory cytokines, and the increase of anti-inflammatory cytokines. In vitro, the percentages of CD4⁺CD25⁺FOXP3⁺ Tregs from splenic naïve CD4⁺ T cells increased after PGRN treatment. In further research, it was found that PGRN can regulate the anti-inflammatory factor IL-10 and affect the polarization of M1/M2 macrophages by upregulating IL-10. These findings show that PGRN likely plays a protective role in ALI by promoting Treg differentiation and activating IL-10 immunomodulation.

Ginkgo biloba extract attenuates the disruption of pro-and anti-inflammatory T-cell balance in peripheral blood of arsenicosis patients

Endemic arsenicosis is a public health problem that affects thousands of people worldwide. However, the biological mechanism involved is not well characterized, and there is no specific treatment. Exposure to arsenic may be associated with immune-related problems. In the present work, we performed an investigation to determine whether the Th17/Treg balance was abnormal in peripheral blood mononuclear cells (PBMCs) of patients with arsenicosis caused by burning coal. Furthermore, we investigated the effect of Ginkgo biloba extract (GBE) on the Th17/Treg imbalance in patients with arsenicosis. In this trial, 81 arsenicosis patients and 37 controls were enrolled. The numbers of Th17 and Treg cells, as well as related transcription factors and serum cytokines, were determined at the beginning and end of the study. Patients with arsenicosis exhibited higher levels of Th17 cells, Th17-related cytokines (IL-17A and IL-6), and the transcription factor RORγt. There were lower levels of Treg cells, a Treg-related cytokine (IL-10), and the transcription factor Foxp3 as compared with controls. There was a positive correlation between the levels of Th17 cells and IL-17A and the levels of arsenic in hair. Arsenicosis patients were randomly assigned to a GBE treatment group or a placebo group. After 3 months of follow-up, 74 patients completed the study (39 cases in the GBE group and 35 in the placebo group). Administration of GBE to patient upregulated the numbers of Treg cells and the level of IL-10 and downregulated the numbers of Th17 cells and the levels of cytokines associated with Th17 cells. The mRNA levels of Foxp3 and RORγt were increased and decreased, respectively. These results indicated that exposure to arsenic is associated with immune-related problems. The present investigation describes a previously unknown mechanism showing that an imbalance of pro- and anti-inflammatory T cells is involved in the pathogenesis of arsenicosis and that a GBE exerts effects on arsenicosis through regulation of the pro- and anti-inflammatory T cell balance.

Recent advances in the study of progranulin and its role in sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The mortality rate of in-hospital patients whose conditions are complicated by sepsis remains high in spite of intensive-care treatment, therefore placing a significant financial burden on the health care system. In recent years, progranulin (PGRN), a cysteine-rich secretory protein (CRISP), has been found to play a crucial role in sepsis. PGRN participates in the pathogenesis of sepsis via diverse pathways, including bacterial clearance, cell growth and survival, tissue repair, and the regulation of inflammation. PGRN knockout mice suffer from serious infectious processes, whereas therapeutic administration of recombinant PGRN to such mice enhances bacterial clearance and reduces organ injury and mortality rate. Even though PGRN plays an important role in regulating sepsis, its potential mechanisms have not been completely clarified. In this review, we summarize the most recent research advances in the study of PGRN and its role in sepsis.

Progranulin promotes osteogenic differentiation of human periodontal ligament stem cells via tumor necrosis factor receptors to inhibit TNF-α sensitized NF-kB and activate ERK/JNK signaling

OBJECTIVE

To investigate the molecular mechanism of Progranulin (PGRN) in promoting osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) in inflammatory environment.

BACKGROUND

Progranulin is an antagonist of tumor necrosis factor (TNF) receptors (TNFRs) and is known to promote inflammatory periodontal bone defect regeneration.

METHODS

TNFR1- and TNFR2-silenced hPDLSCs designed as hPDLSCs-sh-TNFR1 and hPDLSCs-sh-TNFR2 were cultured with osteoinductive medium containing TNF-α and (or) PGRN. Immunofluorescence, quantitative real-time PCR, and western blot were used to, respectively, detect expressions of TNFR1\TNFR2 and osteogenic differentiation markers as well as phosphorylation level in NF-κB\MAPK-related pathways.

RESULTS

Immunofluorescence and real-time PCR showed that TNFR1 and TNFR2 positively expressed in hPDLSCs. TNF-α stimulation could significantly decrease the expressions of ALP and RUNX2 in hPDLSCs, whereas PGRN treatment could significantly enhance their expressions, and reverse TNF-α-mediated expression suppression of ALP and RUNX2 in hPDLSCs. In hPDLSCs-sh-TNFR1, TNF-α mediated osteogenic inhibition decreased, but both TNF-α + PGRN and alone PGRN significantly promoted expression of ALP and RUNX2. PGRN significantly enhanced expression of P-ERK1/2 and P-JNK, while corresponding inhibitors eliminated PGRN-stimulated osteogenic differentiation. In hPDLSCs-sh-TNFR2, no significant difference existed in osteogenic markers and P-JNK expression between the PGRN group and the control group. However, PGRN still activated P-ERK1/2 expression. Besides, PGRN antagonized TNF-α-enhanced NF-κB P65 expression.

CONCLUSION

Progranulin promotes osteogenic differentiation of hPDLSCs via TNFR1 to inhibit TNF-α-sensitized NF-κB and via TNFR2 to activate JNK signaling. The mechanism by which PGRN activates ERK signaling remains to be explored.

Progranulin deficiency confers resistance to autoimmune encephalomyelitis in mice

Progranulin is a secreted neurotrophin that assists in the autophagolysosomal pathways that contribute to MHC-mediated antigen processing, pathogen removal, and autoimmunity. We showed that patients with multiple sclerosis (MS) have high levels of circulating progranulin and that its depletion in a mouse model by a monoclonal antibody aggravates MS-like experimental autoimmune encephalomyelitis (EAE). However, unexpectedly, progranulin-deficient mice (Grn^−/−) were resistant to EAE, and this resistance was fully restored by wild-type bone marrow transplantation. FACS analyses revealed a loss of MHC-II-positive antigen-presenting cells in Grn^−/− mice and a reduction in the number of CD8+ and CD4+ T-cells along with a strong increase in the number of scavenger receptor class B (CD36+) phagocytes, suggesting defects in antigen presentation along with a compensatory increase in phagocytosis. Indeed, bone marrow-derived dendritic cells from Grn^−/− mice showed stronger uptake of antigens but failed to elicit antigen-specific T-cell proliferation. An increase in the number of CD36+ phagocytes was associated with increased local inflammation at the site of immunization, stronger stimulation-evoked morphological transformation of bone marrow-derived macrophages to phagocytes, an increase in the phagocytosis of E. coli particles and latex beads and defects in the clearance of the material. Hence, the outcomes in the EAE model reflect the dichotomy of progranulin-mediated immune silencing and autoimmune mechanisms of antigen recognition and presentation, and our results reveal a novel progranulin-dependent pathway in autoimmune encephalomyelitis.

Preconditioned adipose-derived stem cells ameliorate cardiac fibrosis by regulating macrophage polarization in infarcted rat hearts through the PI3K/STAT3 pathway

Stem cells can modify macrophage phenotypes; however, the mechanisms remain unclear. We investigated whether n-butylidenephthalide (BP) primed adipose-derived stem cells (ADSCs) attenuated cardiac fibrosis via regulating macrophage phenotype by a PI3K/STAT3-dependent pathway in postinfarcted rats. Male Wistar rats after coronary ligation were allocated to receive either intramyocardial injection of vehicle, ADSCs (1 × 10⁶ cells), BP-preconditioned ADSCs, (BP + lithium)-preconditioned ADSCs, (BP + LY294002)-preconditioned ADSCs, and (BP + S3I-201)-preconditioned ADSCs. ADSCs were primed for 16 h before implantation. BP-pretreated ADSCs increased the cell viability compared with naive ADSCs in the in vitro experiments. Infarct sizes were similar among the infarcted groups at the acute and chronic stages of infarction. At day 3 after infarction, post-infarction was associated with increased M1 macrophage infiltration, which was inhibited by administering naive ADSCs. Compared with naive ADSCs, BP-preconditioned ADSCs provided a significant increase of Akt and STAT3 phosphorylation, STAT3 activity, STAT3 nuclear translocation, myocardial IL-10 levels, and the percentage of M2 macrophage infiltration. The effects of BP on M2 polarization were reversed by LY294002 or S3I-201. Furthermore, the phosphorylation of both Akt and STAT3 was abolished by LY294002, whereas Akt phosphorylation was not affected following the inhibition of STAT3. The addition of lithium did not have additional effects compared with BP alone. After 4 weeks of implantation, ADSCs remained in the myocardium, and reduced fibrosis and improved cardiac function. BP-preconditioned ADSCs provided superior cardioprotection, greater ADSC engraftment, and antifibrotic effects compared with naive ADSCs. These results suggest that BP-pretreated ADSCs polarize macrophages into M2 cells more efficiently than naive ADSCs via the PI3K/STAT3 pathway.

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.

Progranulin Is Positively Associated with Intervertebral Disc Degeneration by Interaction with IL-10 and IL-17 Through TNF Pathways

Progranulin (PGRN) is a widely expressed growth factor that effectively inhibits tumor necrosis factor α (TNFα)-mediated inflammatory response. TNFα is involved in intervertebral disc degeneration (IDD) and plays a key role. This study aims to determine the role of PGRN in the intervertebral disc degeneration process. We collected intervertebral discs (IVDs) from humans and mice with different genetic backgrounds. We examined the expression of PGRN in IVD tissues by immunohistochemistry staining and Western blotting assay. We examined the peripheral serum level of PGRN by ELISA assay. Murine IVD tissue samples were taken to undergo safranin O, HE, and immunohistochemistry staining. Primary human nucleus pulposus cells were used for ELISA and RT-PCR assays. PGRN as well as interlukin-10 (IL-10) and interlukin-17 (IL-17) expressions were elevated in degenerative discs and peripheral blood sera. Loss of PGRN led to accelerated disc degeneration in the animal model, along with decreased expression of IL-10 and increased expression of IL-17. Additionally, the PGRN level was positively related to levels of IL-10 and IL-17. In vitro study suggested that PGRN protected against disc degeneration by inducing IL-10 and reducing IL-17. PGRN is associated with intervertebral disc degeneration through interfering with IL-10 and IL-17; thus, PGRN could be an interesting biomarker for diagnosis and a potential treatment target.

Progranulin associates with hexosaminidase A and ameliorates GM2 ganglioside accumulation and lysosomal storage in Tay-Sachs disease

Tay-Sachs disease (TSD) is a lethal lysosomal storage disease (LSD) caused by mutations in the HexA gene, which can lead to deficiency of β-hexosaminidase A (HexA) activity and consequent accumulation of its substrate, GM2 ganglioside. Recent reports that progranulin (PGRN) functions as a chaperone of lysosomal enzymes and its deficiency is associated with LSDs, including Gaucher disease and neuronal ceroid lipofuscinosis, prompted us to screen the effects of recombinant PGRN on lysosomal storage in fibroblasts from 11 patients affected by various LSDs, which led to the isolation of TSD in which PGRN demonstrated the best effects in reducing lysosomal storage. Subsequent in vivo studies revealed significant GM2 accumulation and the existence of typical TSD cells containing zebra bodies in both aged and ovalbumin-challenged adult PGRN-deficient mice. In addition, HexA, but not HexB, was aggregated in PGRN-deficient cells. Furthermore, recombinant PGRN significantly reduced GM2 accumulation and lysosomal storage in these animal models. Mechanistic studies indicated that PGRN bound to HexA through granulins G and E domain and increased the enzymatic activity and lysosomal delivery of HexA. More importantly, Pcgin, an engineered PGRN derivative bearing the granulin E domain, also effectively bound to HexA and reduced the GM2 accumulation. Collectively, these studies not only provide new insights into the pathogenesis of TSD but may also have implications for developing PGRN-based therapy for this life-threatening disorder. KEY MESSAGES: GM2 accumulation and the existence of typical TSD cells containing zebra bodies are detected in both aged and ovalbumin-challenged adult PGRN deficient mice. Recombinant PGRN significantly reduces GM2 accumulation and lysosomal storage both in vivo and in vitro, which works through increasing the expression and lysosomal delivery of HexA. Pcgin, an engineered PGRN derivative bearing the granulin E domain, also effectively binds to to HexA and reduces GM2 accumulation.

miR-34b-5p inhibition attenuates lung inflammation and apoptosis in an LPS-induced acute lung injury mouse model by targeting progranulin

Inflammation and apoptosis play important roles in the initiation and progression of acute lung injury (ALI). Our previous study has shown that progranulin (PGRN) exerts lung protective effects during LPS-induced ALI. Here, we have investigated the potential roles of PGRN-targeting microRNAs (miRNAs) in regulating inflammation and apoptosis in ALI and have highlighted the important role of PGRN. LPS-induced lung injury and the protective roles of PGRN in ALI were first confirmed. The function of miR-34b-5p in ALI was determined by transfection of a miR-34b-5p mimic or inhibitor in intro and in vivo. The PGRN level gradually increased and subsequently significantly decreased, reaching its lowest value by 24 hr; PGRN was still elevated compared to the control. The change was accompanied by a release of inflammatory mediators and accumulation of inflammatory cells in the lungs. Using bioinformatics analysis and RT-PCR, we demonstrated that, among 12 putative miRNAs, the kinetics of the miR-34b-5p levels were closely associated with PGRN expression in the lung homogenates. The gain- and loss-of-function analysis, dual-luciferase reporter assays, and rescue experiments confirmed that PGRN was the functional target of miR-34b-5p. Intravenous injection of miR-34b-5p antagomir in vivo significantly inhibited miR-34b-5p up-regulation, reduced inflammatory cytokine release, decreased alveolar epithelial cell apoptosis, attenuated lung inflammation, and improved survival by targeting PGRN during ALI. miR-34b-5p knockdown attenuates lung inflammation and apoptosis in an LPS-induced ALI mouse model by targeting PGRN. This study shows that miR-34b-5p and PGRN may be potential targets for ALI treatments.

Targeting tumor necrosis factor receptors in ankylosing spondylitis

Over the past two decades, considerable advances in our understanding of inflammatory and immune pathways have allowed for the growing use of targeted biologic therapy. Most notably, the introduction of tumor necrosis factor (TNF) inhibitors has dramatically changed the management of autoimmune inflammatory disorders, including ankylosing spondylitis (AS). Despite the efficacy of TNF inhibitors documented in multiple clinical trials, anti-TNF therapy in AS is far from foolproof; it is associated with serious adverse effects and limited response to therapy in some patients. Moreover, specific questions regarding the role of TNF as a mediator of AS remain unanswered. Therefore, additional efforts are needed in order to better understand the role of TNF in the pathogenesis of AS and to develop safer and more effective treatment strategies. The purpose of this review is to better the understanding of the physiologic and pathogenic roles of TNF signaling in the course of AS. Relevant TNF biology and novel approaches to TNF blockade in AS are discussed.

Prognostic Significance of Serum Interleukins and Soluble ST2 in Traditional Chinese Medicine (TCM) Syndrome-Differentiated Rheumatoid Arthritis

Backgrounds

The aim of this study was to explore the possible correlations of serum interleukins and soluble ST2 (sST2) protein with clinical features and inflammatory cytokines in rheumatoid arthritis (RA) patients, as well as to assess ability of TCM (Traditional Chinese Medicine) syndromes to differentiate RA patients and evaluate prognosis.

Material/Methods

Thirty RA patients and 25 healthy individuals were enrolled. Syndrome activity was evaluated, and lab tests were performed. Serum levels of IL-10, IL-17, IL-33, and sST2 were assessed by ELISA.

Results

Serum levels of sST2, IL-33, and pro-inflammation cytokine IL-17 were all up-regulated, while the immunosuppressive cytokine IL-10 was decreased in RA patients. Serum IL-33 level was positively associated with ESR, CRP, and RF, as well as with HAQ score, VAS score, and DAS28 scores (P<0.05). Serum sST2 level was correlated with the morning stiffness time and ESR, as well as scores of HAQ and DAS28 (P<0.05). In addition, IL-33 level was positively corelated with IL-17 (r=0.83, P<0.01) and the relative ratio of IL-10/IL-17 (r=0.904, P<0.01), and was negatively related with IL-10 (r=−0.632, P<0.01). TCM syndrome differentiation was conducted for RA patients, including the hot syndromes and cold syndromes groups. Hot syndromes RA patients had significantly more severe inflammation compared with cold syndromes patients.

Conclusions

IL-33 is a possible index for monitoring disease activity and inflammation condition in RA. IL-33 contributes to RA pathogenesis through unbalancing IL-10 and IL-17. In terms of TCM, hot syndromes RA presented more serious inflammation and more active disease activity, indicating a poorer prognosis.

Molecular regulations and therapeutic targets of Gaucher disease

Gaucher disease (GD) is the most common lysosomal storage disease caused by deficiency of beta-glucocerebrosidase (GCase) resulting in lysosomal accumulation of its glycolipid substrate glucosylceramide. The activity of GCase depends on many factors such as proper folding and lysosomal localization, which are influenced by mutations in GCase encoding gene, and regulated by various GCase-binding partners including Saposin C, progranulin and heat shock proteins. In addition, proinflammatory molecules also contribute to pathogenicity of GD. In this review, we summarize the molecules that are known to be important for the pathogenesis of GD, particularly those modulating GCase lysosomal appearance and activity. In addition, small molecules that inhibit inflammatory mediators, calcium ion channels and other factors associated with GD are also described. Discovery and characterization of novel molecules that impact GD are not only important for deciphering the pathogenic mechanisms of the disease, but they also provide new targets for drug development to treat the disease.

Concentration-dependent, dual roles of IL-10 in the osteogenesis of human BMSCs via P38/MAPK and NF-κB signaling pathways

Microenvironmental conditions can influence the differentiation and functional roles of mesenchymal stem cells (MSCs). Recent studies have suggested that an inflammatory microenvironment can significantly affect the osteogenic differentiation of MSCs. Here, we show, for the first time, that IL-10 has concentration-dependent, dual roles in the osteogenesis of human bone marrow mesenchymal stem cells (hBMSCs). Low physiologic concentrations of IL-10 (0.01-1.0 ng/ml) activate the p38/MAPK signaling pathway to promote the osteogenesis of hBMSCs, but higher pathologic doses of IL-10 (10-100 ng/ml) inhibit p38/MAPK signaling by activating NF-κB, inhibiting osteogenesis. These results demonstrate that p38/MAPK and NF-κB signaling mediates the double-edged sword effect of IL-10 on hBMSCs. The osteogenic impairment was reversed at higher doses of IL-10 when cells were supplemented with the NF-κB inhibitor BAY11-7082. These data provide important insights into the regulatory effects of IL-10 on the biologic behavior of hBMSCs.-Chen, E., Liu, G., Zhou, X., Zhang, W., Wang, C., Hu, D., Xue, D., Pan, Z. Concentration-dependent, dual roles of IL-10 in the osteogenesis of human BMSCs via P38/MAPK and NF-κB signaling pathways.

Chitinase-3-like Protein 1: A Progranulin Downstream Molecule and Potential Biomarker for Gaucher Disease

We recently reported that progranulin (PGRN) is a novel regulator of glucocerebrosidase and its deficiency associates with Gaucher Diseases (GD) (Jian et al., 2016a; Jian et al., 2018). To isolate the relevant downstream molecules, we performed a whole genome microarray and mass spectrometry analysis, which led to the isolation of Chitinase-3-like-1 (CHI3L1) as one of the up-regulated genes in PGRN null mice. Elevated levels of CHI3L1 were confirmed by immunoblotting and immunohistochemistry. In contrast, treatment with recombinant Pcgin, a derivative of PGRN, as well as imigluerase, significantly reduced the expressions of CHI3L1 in both PGRN null GD model and the fibroblasts from GD patients. Serum levels of CHIT1, a clinical biomarker for GD, were significantly higher in GD patients than healthy controls (51.16±2.824ng/ml vs 35.07±2.099ng/ml, p<0.001). Similar to CHIT1, serum CHI3L1 was also significantly increased in GD patients compared with healthy controls (1736±152.1pg/ml vs 684.7±68.20pg/ml, p<0.001). Whereas the PGRN level is significantly reduced in GD patients as compared to the healthy control (91.56±3.986ng/ml vs 150.6±4.501, p<0.001). Collectively, these results indicate that CHI3L1 may be a previously unrecognized biomarker for diagnosing GD and for evaluating the therapeutic effects of new GD drug(s).