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.

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

Progranulin (PGRN) restrains inflammation and is therapeutic against inflammatory arthritis; however, the underlying immunological mechanism remains unknown. In this study, we demonstrated that anti-inflammatory cytokine IL-10 was a critical mediator for PGRN-mediated anti-inflammation in collagen-induced arthritis by using PGRN and IL-10 genetically modified mouse models. IL-10 green fluorescent protein reporter mice revealed that regulatory T (Treg) cells were the predominant source of IL-10 in response to PGRN. In addition, PGRN-mediated expansion and activation of Treg cells, as well as IL-10 production, depends on JNK signaling, but not on known PGRN-activated ERK and PI3K pathways. Furthermore, microarray and chromatin immunoprecipitation sequencing screens led to the discovery of forkhead box protein O4 and signal transducer and activator of transcription 3 as the transcription factors required for PGRN induction of IL-10 in Treg cells. These findings define a previously unrecognized signaling pathway that underlies IL-10 production by PGRN in Treg cells and present new insights into the mechanisms by which PGRN resolves inflammation in inflammatory conditions and autoimmune diseases, particularly inflammatory arthritis.-Fu, W., Hu, W., Shi, L., Mundra, J. J. Xiao, G., Dustin, M. L., Liu, C. Foxo4- and Stat3-dependent IL-10 production by progranulin in regulatory T cells restrains inflammatory arthritis.

Progranulin inhibits expression and release of chemokines CXCL9 and CXCL10 in a TNFR1 dependent manner.

Progranulin (PGRN), a pleiotrophic growth factor, is known to play an important role in the maintenance and regulation of the homeostatic dynamics of normal tissue development, proliferation, regeneration, and host-defense. PGRN also has potent anti-inflammatory functionality, and deregulated PGRN is associated with rheumatoid arthritis and inflammatory bowel disease. We have previously reported that PGRN directly binds to TNFR and significantly enhances Treg population and stimulates IL-10 production. To further investigate PGRN's function in the immune system we performed a gene array analysis on CD4+ T cells from wild type B6 mice and PGRN -/- mice. We identified many chemokines and their receptors, among which CXCL9 and CXCL10 were most prominent, that were significantly induced in PGRN null mice. Administration of recombinant PGRN protein strongly inhibited TNF and IFN-γ-induced CXCL9 and CXCL10 expression. In addition, CXCL9 expression is strongly upregulated in PGRN KO mice and its level is correlated with severity of inflammation in a dermatitis model. Further, we have demonstrated that PGRN-mediated inhibition of chemokine expression largely depends on TNFR1. Taken together, this study provides new insights into the mechanisms underlying PGRN mediated regulation of various inflammatory and autoimmune diseases.

Stn1 is critical for telomere maintenance and long-term viability of somatic human cells.

Disruption of telomere maintenance pathways leads to accelerated entry into cellular senescence, a stable proliferative arrest that promotes aging-associated disorders in some mammals. The budding yeast CST complex, comprising Cdc13, Stn1, and Ctc1, is critical for telomere replication, length regulation, and end protection. Although mammalian homologues of CST have been identified recently, their role and function for telomere maintenance in normal somatic human cells are still incompletely understood. Here, we characterize the function of human Stn1 in cultured human fibroblasts and demonstrate its critical role in telomere replication, length regulation, and function. In the absence of high telomerase activity, shRNA-mediated knockdown of hStn1 resulted in aberrant and fragile telomeric structures, stochastic telomere attrition, increased telomere erosion rates, telomere dysfunction, and consequently accelerated entry into cellular senescence. Oxidative stress augmented the defects caused by Stn1 knockdown leading to almost immediate cessation of cell proliferation. In contrast, overexpression of hTERT suppressed some of the defects caused by hStn1 knockdown suggesting that telomerase can partially compensate for hStn1 loss. Our findings reveal a critical role for human Stn1 in telomere length maintenance and function, supporting the model that efficient replication of telomeric repeats is critical for long-term viability of normal somatic mammalian cells.

Multi-level cervical disc arthroplasty (CDA) versus single-level CDA for the treatment of cervical disc diseases: a meta-analysis.

PURPOSE: Cervical disc arthroplasty (CDA) was developed to treat cervical degenerated disc diseases with the advantages of preserving the kinematics of the functional spinal unit. However, the safety and reliability of multi-level CDA are still controverted when comparing to the single-level CDA. It has shown unclear benefits in terms of clinical results, functional recovery, heterotopic ossification, and the need for secondary surgical procedures. The purpose of this study is to estimate the effectiveness of multi-level cervical arthroplasty over single-level CDA for the treatment of cervical spondylosis and disc diseases. METHODS: To compare the studies of multi-level CDA versus single-level CDA in patients with cervical spondylosis that reported at least one of the following outcomes: functionality, neck pain, arm pain, quality of life, reoperation and incidence of heterotopic ossification, electronic databases (Medline, Embase, Pubmed, Cochrane library, and Cochrane Central Register of Controlled Trials) were searched. No language restrictions were used. Two authors independently assessed the methodological quality of included studies and extracted the relevant data. RESULTS: Out of Eight cohorts that were included in the study, four were prospective cohorts and the other four were retrospective. The results of the meta-analysis indicated that there was no significant difference in neck disability index scores, neck visual analog scale (VAS), arm VAS, morbidity of reoperation, heterotopic ossification, and parameters of living quality when comparing multi-level CDA with single-level CDA at 1 and 2 years follow-up postoperatively (p > 0.05). CONCLUSIONS: The meta-analysis revealed that the outcomes and functional recovery of patients performed with multi-level CDA are equivalent to those with single-level CDA, which suggests the multi-level CDA is as effective and safe as single-level invention for the treatment of cervical spondylosis. Nonetheless, more well-designed studies with large groups of patients are needed to provide further evidence for the benefit and reliability of multi-level CDA in the treatment of cervical disc diseases.

PGRN protects against colitis progression in mice in an IL-10 and TNFR2 dependent manner.

This study was aimed to determine the role and regulation of progranulin (PGRN) in the pathogenesis of inflammatory bowel diseases (IBD). Dextran sulfate sodium (DSS)-, picrylsulfonic acid (TNBS)-induced, bone marrow chimera and CD4+CD45Rb(hi) T cell transfer colitis model were established and analyzed in wild-type and several genetically-modified mice, including PGRN, IL-10 and TNFR2 deficient mice. Elevated levels of PGRN were found in colitis samples from human IBD patients and mouse colitis models in comparison to the corresponding controls. PGRN-deficient mice became highly susceptible to DSS- and TNBS-induced colitis, whereas recombinant PGRN ameliorated the pathology and reduced the histological score in both DSS and TNBS colitis models. In addition, hematopoietic-derived PGRN was critical for protection against DSS-induced colitis, and lack of PGRN signaling in CD4+ T cells also exacerbated experimental colitis. PGRN-mediated protective effect in colitis was compromised in the absence of IL-10 signaling. In addition, PGRN's effect was also largely lost in the TNFR2-deficient colitis model. Collectively, these findings not only provide the new insight into PGRN's anti-inflammatory action in vivo, but may also present PGRN and its derivatives as novel biological agent for treating IBD.

Three TNFR-binding domains of PGRN act independently in inhibition of TNF-alpha binding and activity.

PGRN was previously reported to bind to TNF receptors (TNFR) and is therapeutic against inflammatory arthritis. Here we present further evidences demonstrating the PGRN inhibition of TNF-alpha binding and activity, and clarifying the distinct mechanisms underlying TNF-alpha inhibition between PGRN and classic TNF-alpha-binding inhibitors. In addition, we present evidences indicating that three TNFR binding domains of PGRN act independently in binding to TNFR. Furthermore, changing the order of three TNFR-binding domains in Atsttrin, a PGRN-derived molecule composed of these TNFR-binding domains, does not affect its anti-inflammatory and anti-TNF activities in both collagen-induced inflammatory arthritis and human TNF-alpha transgenic mouse model. Taken together, these findings provide the additional molecular basis underlying PGRN/TNFR interaction and PGRN-mediated anti-inflammatory activity in various inflammatory diseases and conditions.

Progranulin directly binds to the CRD2 and CRD3 of TNFR extracellular domains.

We previously reported that PGRN directly bound to TNF receptors (TNFR) in vitro and in chondrocytes (Tang, et al., Science, 2011). Here we report that PGRN also associated with TNFR in splenocytes, and inhibited the binding of TNFα to immune cells. Proper folding of PGRN is essential for its binding to TNFR, as DTT treatment abolished its binding to TNFR. In contrast, the binding of PGRN to Sortilin was enhanced by DTT. Protein interaction assays with mutants of the TNFR extracellular domain demonstrated that CRD2 and CRD3 of TNFR are important for the interaction with PGRN, similar to the binding to TNFα. Taken together, these findings provide the molecular basis underlying PGRN/TNFR interaction and PGRN-mediated anti-inflammatory activity in various autoimmune diseases and conditions.

Naltrindole inhibits human multiple myeloma cell proliferation in vitro and in a murine xenograft model in vivo.

It has been demonstrated previously that immune cell activation and proliferation were sensitive to the effects of naltrindole, a nonpeptidic δ-opioid receptor-selective antagonist; therefore, we hypothesized that human multiple myeloma (MM) would be a valuable model for studying potential antineoplastic properties of naltrindole. [(3)H]naltrindole exhibited saturable, low-affinity binding to intact human MM cells; however, the pharmacological profile of the binding site differed considerably from the properties of δ-, κ-, and µ-opioid receptors, and opioid receptor mRNA was not detected in MM cells by reverse transcriptase-polymerase chain reaction. Naltrindole inhibited the proliferation of cultured human U266 MM cells in a time- and dose-dependent manner with an EC(50) of 16 µM. The naltrindole-induced inhibition of U266 cell proliferation was not blocked by a 10-fold molar excess of naltrexone, a nonselective opioid antagonist. Additive inhibition of MM cell proliferation was observed when using a combination of naltrindole with the histone deacetylase inhibitor sodium valproate, the proteasome inhibitor bortezomib, the glucocorticoid receptor agonist dexamethasone, and the HMG CoA reductase inhibitor simvastatin. Treatment of U266 cells with naltrindole significantly decreased the level of the active, phosphorylated form of the kinases, extracellular signal-regulated kinase and Akt, which may be related to its antiproliferative activity. The antiproliferative activity of naltrindole toward MM cells was maintained in cocultures of MM and bone marrow-derived stromal cells, mimicking the bone marrow microenvironment. In vivo, naltrindole significantly decreased tumor cell volumes in human MM cell xenografts in severe combined immunodeficient mice. We hypothesize that naltrindole inhibits the proliferation of MM cells through a nonopioid receptor-dependent mechanism.