In VitroEvaluation of Leukemia Inhibitory Factor Receptor Antagonists as Candidate Therapeutics for Inflammatory Arthritis

The Pleiotropic role, functions and targeted therapies of LIF/LIFR axis in cancer: Old spectacles with new insights

The dysregulation of leukemia inhibitory factor (LIF) and its cognate receptor (LIFR) has been associated with multiple cancer initiation, progression, and metastasis. LIF plays a significant tumor-promoting role in cancer, while LIFR functions as a tumor promoter and suppressor. Epithelial and stromal cells secrete LIF via autocrine and paracrine signaling mechanism(s) that bind with LIFR and subsequently with co-receptor glycoprotein 130 (gp130) to activate JAK/STAT1/3, PI3K/AKT, mTORC1/p70s6K, Hippo/YAP, and MAPK signaling pathways. Clinically, activating the LIF/LIFR axis is associated with poor survival and anti-cancer therapy resistance. This review article provides an overview of the structure and ligands of LIFR, LIF/LIFR signaling in developmental biology, stem cells, cancer stem cells, genetics and epigenetics of LIFR, LIFR regulation by long non-coding RNAs and miRNAs, and LIF/LIFR signaling in cancers. Finally, neutralizing antibodies and small molecule inhibitors preferentially blocking LIF interaction with LIFR and antagonists against LIFR under pre-clinical and early-phase pre-clinical trials were discussed.

Applications and potential mechanisms of herbal medicines for rheumatoid arthritis treatment: a systematic review

In this review, we systematically discuss the role of traditional Chinese medicine (TCM) in rheumatoid arthritis (RA) disease treatment. TCM classifies the subtypes of RA through its own theoretical method, which is beneficial for more accurate diagnosis and treatment with Chinese herbal medicines (CHMs) that are more suitable for different syndromes. TCM mainly uses a flexible combination of CHMs to play an important role in RA treatment. The main components of these extracts can be subdivided into alkaloids, flavonoids, triterpenes, saponins and other compounds. Using a platform of transgenic and induced arthritis models, we explore the potential mechanisms of TCM against RA with the help of omics analysis techniques and methods. These mechanisms are mainly CHM and its extracts can inhibit RA patients and experimental animal models, including synovitis, vascular proliferation and bone injury; this involves many biological signal exchange targets and pathways. In conclusion, the role of TCM in RA treatment mainly involves reducing the expression and secretion of pro-inflammatory factors, thus decreasing the degree of abnormal immune response.

In this review, we systematically discuss the role of traditional Chinese medicine (TCM) in rheumatoid arthritis (RA) disease treatment.

Synovial tissue quantitative proteomics analysis reveals paeoniflorin decreases LIFR and ASPN proteins in experimental rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a common worldwide public health problem, which causes a chronic, systemic inflammatory disorder of synovial joints. Paeoniflorin (PA) has achieved positive results to some extent for the treatment of RA.

Purpose

This study aimed to reveal the potential druggable targets of PA in an experimental RA model using quantitative proteomics analysis.

Study design and methods

Thirty Sprague-Dawley rats were randomly divided into a normal group, model group and PA group. PA (1 mg/kg) was used to treat collagen-induced arthritis (CIA) rats for 42 days. We used isobaric tags for relative and absolute quantitation-based quantitative proteomics to analyze the synovial tissue of rats. Ingenuity pathway analysis (IPA) software was applied to process the data. The proteins that were targeted via IPA software were verified by Western blots.

Results

We found that PA caused 86 differentially expressed proteins (≥1.2-fold or ≤0.84-fold) compared with the CIA group. Of these varied proteins, 20 significantly changed (p<0.05) proteins referred to 41 CIA-relative top pathways after IPA pathway analysis. Thirteen of the PA-regulated pathways were anchored, which intervened in 24 biological functions. Next, network analysis revealed that leukemia inhibitory factor receptor (LIFR) and asporin (ASPN), which participate in two significant networks, contributed the most to the efficacy of PA treatment. Additionally, Western blots confirmed the aforementioned druggable targets of PA for the treatment of RA.

Conclusion

The results reveal that PA may treat RA by decreasing two key proteins, LIFR and ASPN. Our research helps to identify potential agents for RA treatment.

An anti-inflammatory role for leukemia inhibitory factor receptor signaling in regenerating skeletal muscle

Skeletal muscle regeneration in pathology and following injury requires the coordinated actions of inflammatory cells and myogenic cells to remove damaged tissue and rebuild syncytial muscle cells, respectively. Following contusion injury to muscle, the cytokine leukemia inhibitor factor (LIF) is up-regulated and knockout of Lif negatively impacts on morphometric parameters of muscle regeneration. Although it was speculated that LIF regulates muscle regeneration through direct effects on myogenic cells, the inflammatory effects of LIF have not been examined in regenerating skeletal muscle. Therefore, the expression and function of LIF was examined using the antagonist MH35-BD during specific inflammatory and myogenic stages of notexin-induced muscle regeneration in mice. LIF protein and mRNA were up-regulated in two distinct phases following intramuscular injection of notexin into tibialis anterior muscles. The first phase of LIF up-regulation coincided with the increased expression of pro-inflammatory cytokines; the second phase coincided with myogenic differentiation and formation of new myotubes. Administration of the LIF receptor antagonist MH35-BD during the second phase of LIF up-regulation had no significant effects on transcript expression of genes required for myogenic differentiation or associated with inflammation; there were no significant differences in morphometric parameters of the regenerating muscle. Conversely, when MH35-BD was administered during the acute inflammatory phase, increased gene transcripts for the pro-inflammatory cytokines Tnf (Tumor necrosis factor), Il1b (Interleukin-1β) and Il6 (Interleukin-6) alongside an increase in the number of Ly6G positive neutrophils infiltrating the muscle were observed. This was followed by a reduction in Myog (Myogenin) mRNA, which is required for myogenic differentiation, and the subsequent number of myotubes formed was significantly decreased in MH35-BD-treated groups compared to sham. Thus, antagonism of the LIF receptor during the inflammatory phase of skeletal muscle regeneration appeared to induce an inflammatory response that inhibited subsequent myotube formation. We propose that the predominant role of LIF in skeletal muscle regeneration appears to be in regulating the inflammatory response rather than directly effecting myogenic cells.

Epigallocatechin-3-gallate suppresses the global interleukin-1beta-induced inflammatory response in human chondrocytes

Introduction

Epigallocatechin-3-gallate (EGCG) is a bioactive polyphenol of green tea and exerts potent anti-inflammatory effects by inhibiting signaling events and gene expression. Interleukin-1beta (IL-1β) is the principal cytokine linked to cartilage degradation in osteoarthritis (OA). The objective of this study was to evaluate the global effect of EGCG on IL-1β-induced expression of proteins associated with OA pathogenesis in human chondrocytes.

Methods

Primary OA chondrocytes were pretreated with EGCG (10 to 100 uM) and then stimulated with IL-1β (5 ng/ml) for 24 hours. Culture supernatants were incubated with cytokine antibody arrays and immunoreactive proteins (80 proteins) were visualized by enhanced chemiluminiscence. Effect of EGCG on IL-1β-induced expression of 18 selected genes was verified by Real time-PCR and effect on IL-6, IL-8 and tumor necrosis factor-alpha (TNF-α) production was determined using specific ELISAs. Western immunoblotting was used to analyze the effect of EGCG on the interleukin-1 receptor-associated kinase 1 (IRAK-1) and TNF receptor-associated factor 6 (TRAF-6) proteins in IL-1β-stimulated chondrocytes. The role of nuclear factor kappa-B (NF-κB) and mitogen activated protein kinases (MAPKs) in the regulation of selected genes and the mechanism involved in EGCG mediated modulation of these genes was determined by using specific inhibitors for NF- κB (MG132) and MAPKs (p38-MAPK, SB202190; JNK-MAPK, SP600125, ERK-MAPK, PD98059).

Results

Out of 80 proteins present on the array, constitutive expression of 14% proteins was altered by EGCG treatment. No significant stimulatory effect was observed on the proteins associated with cartilage anabolic response. Stimulation with IL-1β enhanced the expression of 29 proteins. Expression of all 29 proteins up-regulated by IL-1β was found to be suppressed by EGCG. EGCG also inhibited the expression of the signaling intermediate TRAF-6 at 50 and 100 uM concentrations (P < 0.05). Our results identified several new targets of EGCG, including epithelial neutrophil activating peptide-78 (ENA-78), granulocyte macrophage colony stimulation factor (GM-CSF), growth- related oncogene (GRO), GRO-α, IL-6, IL-8, monocyte chemotactic protein-1 (MCP-1), MCP-3, macrophage inflammatory protein-1beta (MIP-1β), granulocyte chemotactic protein-2 (GCP-2), MIP-3alpha, interferon-gamma-inducible protein-10 (IP-10), nucleosome assembly protein-2 (NAP-2) and leukemia inhibitory factor (LIF). The inhibitory effects of EGCG were mainly mediated by inhibiting the activation of NF-κB and c-Jun N-terminal Kinase (JNK)-MAPK in human chondrocytes.

Conclusions

Our results suggest that the potential of EGCG in OA treatment/prevention may be related to its ability to globally suppress the inflammatory response in human chondrocytes. These results identify additional new targets of EGCG and advocate that EGCG may be a potent chondroprotective agent in OA.

Caspase-3, myogenic transcription factors and cell cycle inhibitors are regulated by leukemia inhibitory factor to mediate inhibition of myogenic differentiation

BACKGROUND

Leukemia inhibitory factor (LIF) is known to inhibit myogenic differentiation as well as to inhibit apoptosis and caspase-3 activation in non-differentiating myoblasts. In addition caspase-3 activity is required for myogenic differentiation. Therefore the aim of this study was to further investigate mechanisms of the differentiation suppressing effect of LIF in particular the possibility of a caspase-3 mediated inhibition of differentiation.

RESULTS

LIF dependent inhibition of differentiation appeared to involve several mechanisms. Differentiating myoblasts that were exposed to LIF displayed increased transcripts for c-fos. Transcripts for the cell cycle inhibitor p21 as well as muscle regulatory factors myoD and myogenin were decreased with LIF exposure. However, LIF did not directly induce a proliferative effect under differentiation conditions, but did prevent the proportion of myoblasts that were proliferating from decreasing as differentiation proceeded. LIF stimulation decreased the percentage of cells positive for active caspase-3 occurring during differentiation. Both the effect of LIF inhibiting caspase-3 activation and differentiation appeared dependent on mitogen activated protein kinase and extracellular signal regulated kinase kinase (MEK) signalling. The role of LIF in myogenic differentiation was further refined to demonstrate that myoblasts are unlikely to secrete LIF endogenously.

CONCLUSIONS

Altogether this study provides a more comprehensive view of the role of LIF in myogenic differentiation including LIF and receptor regulation in myoblasts and myotubes, mechanisms of inhibition of differentiation and the link between caspase-3 activation, apoptosis and myogenic differentiation.

Recent advances in neutralizing the IL-6 pathway in arthritis

Recent advances in understanding the mechanism(s) of how IL-6 trans-signaling regulates immune cell function and promotes inflammation in autoimmune arthritis are critically reviewed. Serum and/or synovial fluid (SF) IL-6 is markedly elevated in adult and juvenile rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS) and osteoarthritis (OA). IL-6, in concert with IL-17, determines the fate of CD4⁺ lymphocytes and therefore TH₁₇ cell differentiation. IL-6 also plays a critical role in modulating B-lymphocyte activity. The recognition that IL-6 trans-signaling regulates inflammation resulted in the development of tocilizumab, a fully humanized monoclonal antibody that neutralizes the biological activity of the IL-6-receptor (IL-6R). Significant clinical benefit was demonstrated as well as reduced serum IL-6 levels with suppression of X-ray progression of disease in several clinical trials in which juvenile or adult RA patients were treated with tocilizumab monotherapy or tocilizumab plus methotrexate. However, levels of serum and/or SF IL-6 cytokine protein superfamily members, adiponectin, oncostatin M, pre-B-cell colony enhancing factor/visfatin and leukemia inhibitory factor are also elevated in RA. Additional studies will be required to determine if anti-IL-6 trans-signaling inhibition strategies with tocilizumab or recombinant soluble IL-6R reduce the level of these cytokines.

Interleukin-6 subfamily cytokines and rheumatoid arthritis: role of antagonists

Many cytokines have been implicated in the inflammatory pathways that characterize rheumatoid arthritis (RA) and related inflammatory diseases of the joints. These include members of the interleukin-6 (IL-6) family of cytokines, several of which have been detected in excess in the synovial fluid from RA patients. What makes the IL-6 group of cytokines a family is their common use of the glycoprotein 130 (gp130) receptor subunit, to which they bind with different affinities. Several strategies have been developed to block the pro-inflammatory activities of IL-6 subfamily cytokines. These include the application of monoclonal antibodies, the creation of mutant form(s) of the cytokine with enhanced binding affinity to gp130 receptor and the generation of antagonists by selective mutagenesis of the specific cytokine/gp130 receptor-binding site(s). The rationale for the use of anti-cytokine therapy in inflammatory joint diseases is based on evidence from studies in vitro and in vivo, which implicate major cytokines such as interleukin-1 (IL-1), tumour necrosis factor (TNF)-alpha and IL-6 in RA pathogenesis. In particular, IL-6 subfamily antagonists have a wide range of potential therapeutic and research applications. This review focuses on the role of some of the IL-6 subfamily cytokines in the pathogenesis of the inflammatory diseases of the joints (IJDs), such as RA. In addition, an overview of the recently developed antagonists will be discussed.

Mutation of the IFNAR-1 receptor binding site of human IFN-alpha2 generates type I IFN competitive antagonists

Type I interferons (IFNs) are multifunctional cytokines that activate cellular responses by binding a common receptor consisting of two subunits, IFNAR-1 and IFNAR-2. Although the binding of IFNs to IFNAR-2 is well characterized, the binding to the lower affinity IFNAR-1 remains less well understood. Previous reports identified a region of human IFN-alpha2 on the B and C helices ("site 1A": N65, L80, Y85, Y89) that plays a key role in binding IFNAR-1 and contributes strongly to differential activation by various type I IFNs. The current studies demonstrate that residues on the D helix are also involved in IFNAR-1 binding. In particular, residue 120 (Arg in IFN-alpha2; Lys in IFN-alpha2/alpha1) appears to be a "hot-spot" residue: substitution by alanine significantly decreased biological activity, and the charge-reversal mutation of residue 120 to Glu caused drastic loss of antiviral and antiproliferative activity for both IFN-alpha2 and IFN-alpha2/alpha1. Mutations in residues of helix D maintained their affinity for IFNAR-2 but had decreased affinity for IFNAR-1. Single-site or multiple-site mutants in the IFNAR-1 binding site that had little or no detectable in vitro biological activity were capable of blocking in vitro antiviral and antiproliferative activity of native IFN-alpha2; i.e., they are type I IFN antagonists. These prototype IFN antagonists can be developed further for possible therapeutic use in systemic lupus erythematosus, and analogous molecules can be designed for use in animal models.

Novel inhibitors for murine and human leukemia inhibitory factor based on fused soluble receptors

Fusion proteins of the extracellular parts of cytokine receptors, also known as cytokine traps, turned out to be promising cytokine inhibitors useful in anti-cytokine therapies. Here we present newly designed cytokine traps for murine and human leukemia inhibitory factor (LIF) as prototypes for inhibitors targeting cytokines that signal through a heterodimer of two signaling receptors of the glycoprotein 130 (gp130) family. LIF signals through a receptor heterodimer of LIF receptor (LIFR) and gp130 and induces the tyrosine phosphorylation of STAT3 leading to target gene expression. The analysis of various receptor fusion and deletion constructs revealed that a truncated form of the murine LIF receptor consisting of the first five extracellular domains was a potent inhibitor for human LIF. For the efficient inhibition of murine LIF, the cytokine-binding module of murine gp130 had to be fused to the first five domains of murine LIFR generating mLIF-RFP (murine LIFR fusion protein). The tyrosine phosphorylation of STAT3 and subsequent gene induction induced by human or murine LIF are completely blocked by the respective inhibitor. Furthermore, both inhibitors are specific and do not alter the bioactivities of the closely related cytokines interleukin (IL)-6 and oncostatin M. The gained knowledge on the construction of LIF inhibitors can be transferred to the design of inhibitors for related cytokines such as IL-31, IL-27, and oncostatin M for the treatment of inflammatory and malignant diseases.

Generation of mutant leukaemia inhibitory factor (LIF)–IgG heavy chain fusion proteins as bivalent antagonists of LIF

Two leukaemia inhibitory factor (LIF) mutants, designated MH35-BD and LIF05, have been shown to have a capacity to inhibit the biological activities of not only human LIF (hLIF) but also other interleukin-6 (IL-6) subfamily cytokines such as human oncostatin M (hOSM). These cytokines share the same receptor complex in which the glycoprotein 130 (gp130) subunit is a common constituent. However, at low concentrations and in their monomeric forms, such molecules have a relatively short plasma half-life due to rapid clearance from the kidneys. Here, to prolong their serum half-lives, we have used a multi-step polymerase chain reaction (PCR) to fuse each of the LIF05 and MH35-BD cDNA fragments to a sequence encoding the Fc portion, and the hinge region, of the human immunoglobulin G (hIgG) heavy chain. The linking was achieved through an oligomer encoding a thrombin-sensitive peptide linker thus generating MH35-BD:Fc and LIF05:Fc, respectively. Both Fc fusion constructs were expressed in insect cell Sf21 and the proteins were purified by two successive affinity chromatography steps using nickel-nitrilotriacetic acid (Ni-NTA) agarose and protein A beads. The Ba/F3 cell-based proliferation assay was used to confirm that the proteins were biologically active. In addition, preliminary pharmacokinetics indicates that the Fc fusion constructs have a longer serum half-life compared to their non-fusion counterparts.