Structure of the extracellular domains of the human interleukin-6 receptor alpha -chain

scBlood: A comprehensive single-cell accessible chromatin database of blood cells

The advent of single cell transposase-accessible chromatin sequencing (scATAC-seq) technology enables us to explore the genomic characteristics and chromatin accessibility of blood cells at the single-cell level. To fully make sense of the roles and regulatory complexities of blood cells, it is critical to collect and analyze these rapidly accumulating scATAC-seq datasets at a system level. Here, we present scBlood (https://bio.liclab.net/scBlood/), a comprehensive single-cell accessible chromatin database of blood cells. The current version of scBlood catalogs 770,907 blood cells and 452,247 non-blood cells from ∼400 high-quality scATAC-seq samples covering 30 tissues and 21 disease types. All data hosted on scBlood have undergone preprocessing from raw fastq files and multiple standards of quality control. Furthermore, we conducted comprehensive downstream analyses, including multi-sample integration analysis, cell clustering and annotation, differential chromatin accessibility analysis, functional enrichment analysis, co-accessibility analysis, gene activity score calculation, and transcription factor (TF) enrichment analysis. In summary, scBlood provides a user-friendly interface for searching, browsing, analyzing, visualizing, and downloading scATAC-seq data of interest. This platform facilitates insights into the functions and regulatory mechanisms of blood cells, as well as their involvement in blood-related diseases.

De novo design of miniprotein antagonists of cytokine storm inducers

Cytokine release syndrome (CRS), commonly known as cytokine storm, is an acute systemic inflammatory response that is a significant global health threat. Interleukin-6 (IL-6) and interleukin-1 (IL-1) are key pro-inflammatory cytokines involved in CRS and are hence critical therapeutic targets. Current antagonists, such as tocilizumab and anakinra, target IL-6R/IL-1R but have limitations due to their long half-life and systemic anti-inflammatory effects, making them less suitable for acute or localized treatments. Here we present the de novo design of small protein antagonists that prevent IL-1 and IL-6 from interacting with their receptors to activate signaling. The designed proteins bind to the IL-6R, GP130 (an IL-6 co-receptor), and IL-1R1 receptor subunits with binding affinities in the picomolar to low-nanomolar range. X-ray crystallography studies reveal that the structures of these antagonists closely match their computational design models. In a human cardiac organoid disease model, the IL-1R antagonists demonstrated protective effects against inflammation and cardiac damage induced by IL-1β. These minibinders show promise for administration via subcutaneous injection or intranasal/inhaled routes to mitigate acute cytokine storm effects.

Unveiling novel insights into human IL-6 - IL-6R interaction sites through 3D computer-guided docking and systematic site mutagenesis

The cytokine interleukin-6 (IL-6) plays a crucial role in autoimmune and inflammatory diseases. Understanding the precise mechanism of IL-6 interaction at the amino acid level is essential to develop IL-6-inhibiting compounds. In this study, we employed computer-guided drug design tools to predict the key residues that are involved in the interaction between IL-6 and its receptor IL-6R. Subsequently, we generated IL-6 mutants and evaluated their binding affinity to IL-6R and the IL-6R - gp130 complex, as well as monitoring their biological activities. Our findings revealed that the R167A mutant exhibited increased affinity for IL-6R, leading to enhanced binding to IL-6R - gp130 complex and subsequently elevated intracellular phosphorylation of STAT3 in effector cells. On the other hand, although E171A reduced its affinity for IL-6R, it displayed stronger binding to the IL-6R - gp130 complex, thereby enhancing its biological activity. Furthermore, we identified the importance of R178 and R181 for the precise recognition of IL-6 by IL-6R. Mutants R181A/V failed to bind to IL-6R, while maintaining an affinity for the IL-6 - gp130 complex. Additionally, deletion of the D helix resulted in complete loss of IL-6 binding affinity for IL-6R. Overall, this study provides valuable insights into the binding mechanism of IL-6 and establishes a solid foundation for future design of novel IL-6 inhibitors.

The impact of interleukin-6 (IL-6) and mesenchymal stem cell-derived IL-6 on neurological conditions

Interleukin-6 (IL-6) is a versatile cytokine crucial for immune response modulation, inflammation regulation, and various physiological processes in the body. Its wide-ranging functions underscore its importance in maintaining health. Dysregulated IL-6 is closely associated with many diseases, making it a key research and therapeutic target. Elevated IL-6 levels in the central nervous system worsen neuroinflammation in neurodegenerative diseases by activating microglia and astrocytes and releasing pro-inflammatory cytokines and neurotoxic molecules. Moreover, dysregulated IL-6 weakens the blood-brain barrier, exacerbating neuroinflammation and neuronal damage by allowing peripheral immune cells and inflammatory mediators to enter the brain. Mesenchymal stem cells (MSCs) show promise in modulating neuroinflammation by regulating IL-6 levels. They effectively suppress pro-inflammatory cytokines, including IL-6, while promoting anti-inflammatory factors. This therapeutic approach highlights the importance of targeting IL-6 and other inflammatory mediators to alleviate neuroinflammation and its adverse effects on neurological disorders. This review provides a comprehensive overview of IL-6's involvement in neurological disorders, examining endogenous IL-6 and IL-6 derived from MSCs. We explore IL-6's mechanisms affecting neuronal function, survival, and immune modulation in the central nervous system. Additionally, we discuss the potential of MSC-derived IL-6 in neuroregeneration and neuroprotection. By elucidating IL-6's interplay with neurological pathologies, this review offers insights into novel therapeutic strategies targeting IL-6 signaling pathways for neurological disorders.

Small protein blockers of human IL-6 receptor alpha inhibit proliferation and migration of cancer cells

BACKGROUND

Interleukin-6 (IL-6) is a multifunctional cytokine that controls the immune response, and its role has been described in the development of autoimmune diseases. Signaling via its cognate IL-6 receptor (IL-6R) complex is critical in tumor progression and, therefore, IL-6R represents an important therapeutic target.

METHODS

An albumin-binding domain-derived highly complex combinatorial library was used to select IL-6R alpha (IL-6Rα)-targeted small protein binders using ribosome display. Large-scale screening of bacterial lysates of individual clones was performed using ELISA, and their IL-6Rα blocking potential was verified by competition ELISA. The binding of proteins to cells was monitored by flow cytometry and confocal microscopy on HEK293T-transfected cells, and inhibition of signaling function was examined using HEK-Blue IL-6 reporter cells. Protein binding kinetics to living cells was measured by LigandTracer, cell proliferation and toxicity by iCELLigence and Incucyte, cell migration by the scratch wound healing assay, and prediction of binding poses using molecular modeling by docking.

RESULTS

We demonstrated a collection of protein variants called NEF ligands, selected from an albumin-binding domain scaffold-derived combinatorial library, and showed their binding specificity to human IL-6Rα and antagonistic effect in HEK-Blue IL-6 reporter cells. The three most promising NEF108, NEF163, and NEF172 variants inhibited cell proliferation of malignant melanoma (G361 and A2058) and pancreatic (PaTu and MiaPaCa) cancer cells, and suppressed migration of malignant melanoma (A2058), pancreatic carcinoma (PaTu), and glioblastoma (GAMG) cells in vitro. The NEF binders also recognized maturation-induced IL-6Rα expression and interfered with IL-6-induced differentiation in primary human B cells.

CONCLUSION

We report on the generation of small protein blockers of human IL-6Rα using directed evolution. NEF proteins represent a promising class of non-toxic anti-tumor agents with migrastatic potential.

Combination of bazedoxifene with chemotherapy and SMAC-mimetics for the treatment of colorectal cancer

Excessive STAT3 signalling via gp130, the shared receptor subunit for IL-6 and IL-11, contributes to disease progression and poor survival outcomes in patients with colorectal cancer. Here, we provide evidence that bazedoxifene inhibits tumour growth via direct interaction with the gp130 receptor to suppress IL-6 and IL-11-mediated STAT3 signalling. Additionally, bazedoxifene combined with chemotherapy synergistically reduced cell proliferation and induced apoptosis in patient-derived colon cancer organoids. We elucidated that the primary mechanism of anti-tumour activity conferred by bazedoxifene treatment occurs via pro-apoptotic responses in tumour cells. Co-treatment with bazedoxifene and the SMAC-mimetics, LCL161 or Birinapant, that target the IAP family of proteins, demonstrated increased apoptosis and reduced proliferation in colorectal cancer cells. Our findings provide evidence that bazedoxifene treatment could be combined with SMAC-mimetics and chemotherapy to enhance tumour cell apoptosis in colorectal cancer, where gp130 receptor signalling promotes tumour growth and progression.

Navigating IL-6: From molecular mechanisms to therapeutic breakthroughs

This concise review navigates the intricate realm of Interleukin-6 (IL-6), an important member of the cytokine family. Beginning with an introduction to cytokines, this narrative review unfolds with the historical journey of IL-6, illuminating its evolving significance. A crucial section unravels the three distinct signaling modes employed by IL-6, providing a foundational understanding of its versatile interactions within cellular landscapes. Moving deeper, the review meticulously dissects IL-6's signaling mechanisms, unraveling the complexities of its pleiotropic effects in both physiological responses and pathological conditions. A significant focus is dedicated to the essential role IL-6 plays in inflammatory diseases, offering insights into its associations and implications for various health conditions. The review also takes a therapeutic turn by exploring the emergence of anti-IL-6 monoclonal inhibitors, marking a profound stride in treatment modalities. Diving into the molecular realm, the review explores small molecules as agents for IL-6 inhibition, providing a nuanced perspective on diverse intervention strategies. As the review embarks on the final chapters, it contemplates future aspects, offering glimpses into potential research trajectories and the evolving landscape of IL-6-related studies.

Structural insights into IL-6 signaling inhibition by therapeutic antibodies

Antibody inhibitors of the interleukin-6 (IL-6) signaling pathway, such as tocilizumab and sarilumab, have been used to treat rheumatoid arthritis, chimeric antigen receptor T cell-induced cytokine storm, and severe COVID-19 pneumonia. Here, we solve the cryogenic electron microscopy structures of sarilumab and tocilizumab in complex with IL-6R to resolutions of 3.2 and 3.3 Å, respectively. These structures reveal that both tocilizumab and sarilumab bind to the D3 domain of IL-6R. The binding surfaces of the two antibodies largely overlap, but the detailed interactions are different. Functional studies of various mutants show results consistent with our structural analysis of the antibodies and IL-6R interactions. Structural comparisons with the IL-6/IL-6R/gp130 complex indicate that sarilumab and tocilizumab probably inhibit IL-6/IL-6R signaling by competing for the IL-6 binding site. In summary, this work reveals the antibody-blocking mechanism of the IL-6 signaling pathway and paves the way for future antibody discovery.

Molecular Design of Novel Inhibitor by Targeting IL-6Rα using Combined Pharmacophore and Experimentally Verified Plant Products with Scaffold-Hopping Techniques: A Dual Therapeutic Strategy for COVID-19 and Cancer

The IL-6/IL-6R/gp130 complex serves as a significant indicator of cytokine release syndrome in COVID-19 and chronic inflammation, increasing the risk of cancer. Therefore, we identified IL-6Rα as a potential target to block gp130 interaction. Notably, there has been no reception of approval for an orally available drug to serve this purpose, to date. In this study, we targeted IL-6Rα to inhibit IL-6Rα/gp130 interaction. The selection of the lead candidate L821 involved the amalgamation of three drug discovery approaches. This library was screened employing tertiary structure-based pharmacophore models followed by molecular docking models, scaffold-hopping, MM/PBSA as well as MM/GBSA analysis, and assessments of pKi and ADMET properties. After evaluating the binding interactions with key amino acids, 15 potential ligands were chosen, with the top ligand undergoing further investigation by means of molecular dynamics simulations. Considering the stability of the complexes, the strong interactions observed between ligand and residues of IL-6Rα/gp130, and the favorable binding free energy calculations, L821 emerged as the prime candidate for inhibiting IL-6Rα. Notably, L821 exhibited a docking-based binding affinity of -9.5 kcal/mol. Our study presents L821 as a promising inhibitor for future in vitro analysis, potentially combatting SARS-CoV-2-related cytokine storms and serving as an oncogenic drug therapy.

Datura stramonium Flowers as a Potential Natural Resource of Bioactive Molecules: Identification of Anti-Inflammatory Agents and Molecular Docking Analysis

The present study investigated the antioxidant, antibacterial, antiviral and anti-inflammatory activities of different aerial parts (flowers, leaves and seeds) of Datura stramonium. The plant material was extracted with 80% methanol for about 24 h. The sensitivity to microorganisms analysis was performed by the microdilution technique. Antioxidant tests were performed by scavenging the DPPH and ABTS radicals, and by FRAP assay. Anti-inflammatory activity was evaluated through the inhibition of nitric oxide production in activated macrophage RAW 264.7 cells. Cell viability was assessed with an MTT assay. Results show that the flower extract revealed a powerful antimicrobial capacity against Gram-positive bacteria and strong antioxidant and anti-inflammatory activities. No significant cytotoxicity to activated macrophages was recorded. High resolution electrospray ionization mass spectrometry and nuclear magnetic resonance analysis identified two molecules with important anti-inflammatory effects: 12α-hydroxydaturametelin B and daturametelin B. Molecular docking analysis with both pro-inflammatory agents tumor necrosis factor alpha and interleukin-6 revealed that both compounds showed good binding features with the selected target proteins. Our results suggest that D. stramonium flower is a promising source of compounds with potential antioxidant, antibacterial, and anti-inflammatory activities. Isolated withanolide steroidal lactones from D. stramonium flower extract with promising anti-inflammatory activity have therapeutic potential against inflammatory disorders.

N-(2-ozoazepan-3-yl)-pyrrolidine-2-carboxamide, a novel Octopus vulgaris ink-derived metabolite, exhibits a pro-apoptotic effect on A549 cancer cell line and inhibits pro-inflammatory markers

This research aimed to chemically synthesize and evaluate the antiproliferative and anti-inflammatory potential of ozopromide (OPC), a novel compound recently isolated from O. vulgaris ink. After chemical synthesis, OPC structural characterization was confirmed by COSY2D, FTIR, and C-/H-NMR. OPC inhibited the growth of human breast (MDA-MB-231), prostate (22Rv1), cervix (HeLa), and lung (A549) cancerous cells, being the highest effect on the latter (IC₅₀: 53.70 μM). As confirmed by flow cytometry, OPC induced typical apoptosis-derived morphological features on A549 cells, mostly at early and late apoptosis stages. OPC generated a dose-dependent effect inhibiting IL-6 and IL-8 on LPS-stimulated peripheral mononuclear cells (PBMCs). A major affinity of OPC to Akt-1 and Bcl-2 proteins in silico agreed with the observed pro-apoptotic mechanisms. Results suggested that OPC has the potential to alleviate inflammation and be further studied for anticancer activity. Marine-derived food products such as ink contains bioactive metabolites exhibiting potential health benefits.

Structural insights into the assembly of gp130 family cytokine signaling complexes

The interleukin-6 (IL-6) family cytokines signal through gp130 receptor homodimerization or heterodimerization with a second signaling receptor and play crucial roles in various cellular processes. We determined cryo-electron microscopy structures of five signaling complexes of this family, containing full receptor ectodomains bound to their respective ligands ciliary neurotrophic factor, cardiotrophin-like cytokine factor 1 (CLCF1), leukemia inhibitory factor, IL-27, and IL-6. Our structures collectively reveal similarities and differences in the assembly of these complexes. The acute bends at both signaling receptors in all complexes bring the membrane-proximal domains to a ~30 angstrom range but with distinct distances and orientations. We also reveal how CLCF1 engages its secretion chaperone cytokine receptor-like factor 1. Our data provide valuable insights for therapeutically targeting gp130-mediated signaling.

Neuronal growth regulator 1 may modulate interleukin-6 signaling in adipocytes

Interleukin-6 (IL-6) is a pleiotropic cytokine that plays both anti- and pro-inflammatory roles. Due to the restricted expression of membrane IL-6 receptor (IL-6R), most pro-inflammatory functions of IL-6 are attributed to its association with soluble IL-6R (sIL-6R). Neuronal growth regulator 1 (NEGR1) is a brain-enriched membrane protein that has recently been recognized as a risk factor for many human diseases including obesity, depression, and autism. In the present study, we report that the expression levels of IL-6 and IL-6R, as well as the phosphorylation of signal transducer and activator of transcription (STAT) 3, were significantly elevated in white adipose tissues of Negr1 knockout mice. Elevated levels of circulating IL-6 and sIL-6R have also been observed in Negr1 ^-/- mice. Furthermore, NEGR1 interacted with IL-6R, which was supported by subcellular fractionation and an in situ proximity ligation assay. Importantly, NEGR1 expression attenuated the phosphorylation of STAT3 by sIL-6R, suggesting that NEGR1 negatively regulates IL-6 trans-signaling. Taken together, we propose that NEGR1 may play a regulatory role in IL-6 signaling by interacting with IL-6R, which may contribute to a molecular link underlying obesity, inflammation, and the depression cycle.

Generation and characterization of a Müller-glial-cell-specific Il6ra knockout mouse to delineate the effects of IL-6 trans-signaling in the retina

Interleukin-6 (IL-6) is implicated in various retinal and vascular complications associated with diabetic retinopathy (DR). This cytokine functions through two main modalities: classical signaling, in cells expressing the membrane-bound receptor (IL-6Rα); and trans-signaling, possible in most cells through a soluble form of the receptor (sIL-6R). These pathways are considered to be anti-inflammatory and pro-inflammatory, respectively. Our recent studies in retinal endothelial cells and diabetic mice have shown that inhibiting only IL-6 trans-signaling is sufficient to prevent increased vascular leakage, oxidative stress, and inflammation characteristic of DR. Isolating the specific effects of each signaling pathway, however, remains difficult in cells expressing IL-6Rα that are thus capable of both classical and trans-signaling. Müller glial cells (MGCs), the most abundant retinal macroglial cells, span the entire retinal thickness with vital roles in maintaining retinal homeostasis and regulating the blood-retinal barrier through secreted factors. The specific effects of IL-6 trans-signaling in MGCs remain poorly understood given their responsiveness to both IL-6 signaling modalities. In this study, we addressed these concerns by generating an MGC-specific knockout mouse using Cre-loxP deletion of the Il6ra cytokine-binding region. We assessed transcriptional and translational Il6ra expression to confirm the knockout and characterized the effects of knockout on visual functioning in these mice.

IL-6: The Link Between Inflammation, Immunity and Breast Cancer

Breast cancer is one of the leading causes of mortality in females. Over the past decades, intensive efforts have been made to uncover the pathogenesis of breast cancer. Interleukin-6 (IL-6) is a pleiotropic factor which has a vital role in host defense immunity and acute stress. Moreover, a wide range of studies have identified the physiological and pathological roles of IL-6 in inflammation, immune and cancer. Recently, several IL-6 signaling pathway-targeted monoclonal antibodies have been developed for cancer and immune therapy. Combination of IL-6 inhibitory antibody with other pathways blockage drugs have demonstrated promising outcome in both preclinical and clinical trials. This review focuses on emerging studies on the strong linkages of IL-6/IL-6R mediated regulation of inflammation and immunity in cancer, especially in breast cancer.

Making sense of IL-6 signalling cues in pathophysiology

Unravelling the molecular mechanisms that account for functional pleiotropy is a major challenge for researchers in cytokine biology. Cytokine-receptor cross-reactivity and shared signalling pathways are considered primary drivers of cytokine pleiotropy. However, reports epitomized by studies of Jak-STAT cytokine signalling identify interesting biochemical and epigenetic determinants of transcription factor regulation that affect the delivery of signal-dependent cytokine responses. Here, a regulatory interplay between STAT transcription factors and their convergence to specific genomic enhancers support the fine-tuning of cytokine responses controlling host immunity, functional identity, and tissue homeostasis and repair. In this review, we provide an overview of the signalling networks that shape the way cells sense and interpret cytokine cues. With an emphasis on the biology of interleukin-6, we highlight the importance of these mechanisms to both physiological processes and pathophysiological outcomes.

Discovery and characterization of a monoclonal antibody targeting a conformational epitope of IL-6/IL-6Rα to inhibit IL-6/ IL-6Rα/gp130 hexameric signaling complex formation

The functional interleukin 6 (IL-6) signaling complex is a hexameric structure composed of IL-6, IL-6Rα, and the signaling receptor gp130. There are three different modes of IL-6 signaling, classic signaling, trans-signaling, and trans-presentation, which are not functionally redundant and mediate pleiotropic effects on both physiological and pathophysiological states. Monoclonal antibodies against IL-6 or IL-6Rα have been successfully developed for clinical application. However, designing therapeutic interventions that block specific modes of IL-6 signaling in a pathologically relevant manner remains a great challenge. Here, we constructed a fusion protein Hyper-IL-6 (HyIL-6) composed of human IL-6 and IL-6Rα to develop specific blocking antibodies against the IL-6/IL-6Rα complex. We successfully screened the monoclonal antibody C14mab, which can bind to HyIL-6 with the binding constant 2.86 × 10^-10 and significantly inhibit IL-6/IL-6Rα/gp130 complex formation. In vitro, C14mab effectively inhibited HyIL-6-stimulated signal transducer and activator of transcription 3 (STAT3) activation and related vascular endothelial growth factor (VEGF) induction. Moreover, C14mab efficaciously suppressed HyIL-6-induced acute phase response in vivo. Our data from hydrogen-deuterium exchange mass spectrometry demonstrate that C14mab mainly binds to site IIIa of IL-6 and blocks the final step in the interaction between gp130 and IL-6/IL-6Rα complex. Additionally, data from enzyme-linked immunosorbent assays and kinetics assays indicate that C14mab interacts simultaneously with IL-6 and IL-6Rα, while it does not interact with IL-6Rα alone. The unique features of C14mab may offer a novel alternative for IL-6 blockade and illuminate a better therapeutic intervention targeting IL-6.

Soluble Interleukin-6 Receptor Regulates Interleukin-6-Dependent Vascular Remodeling in Long-Distance Runners

Little is known about the effects of training load on exercise-induced plasma increase of interleukin-6 (IL-6) and soluble IL-6 receptor (sIL-6R) and their relationship with vascular remodeling. We sought to evaluate the role of sIL 6R as a regulator of IL-6-induced vascular remodeling. Forty-four male marathon runners were recruited and allocated into two groups: low-training (LT, <100 km/week) and high-training (HT, ≥100 km/week), 22 athletes per group. Twenty-one sedentary participants were used as reference. IL-6, sIL-6R and sgp130 levels were measured in plasma samples obtained before and immediately after finishing a marathon (42.2-km). Aortic diameter was measured by echocardiography. The inhibitory effect of sIL-6R on IL-6-induced VSMC migration was assessed using cultured A7r5 VSMCs. Basal plasma IL-6 and sIL-6R levels were similar among sedentary and athlete groups. Plasma IL-6 and sIL-6R levels were elevated after the marathon, and HT athletes had higher post-race plasma sIL-6R, but not IL-6, level than LT athletes. No changes in sgp130 plasma levels were found in LT and HT groups before and after running the marathon. Athletes had a more dilated ascending aorta and aortic root than sedentary participants with no differences between HT and LT athletes. However, a positive correlation between ascending aorta diameter and plasma IL-6 levels corrected by training load and years of training was observed. IL-6 could be responsible for aorta dilation because IL-6 stimulated VSMC migration in vitro, an effect that is inhibited by sIL-6R. However, IL-6 did not modify cell proliferation, collagen type I and contractile protein of VSMC. Our results suggest that exercise induces vascular remodeling. A possible association with IL-6 is proposed. Because sIL-6R inhibits IL-6-induced VSMC migration, a possible mechanism to regulate IL-6-dependent VSMC migration is also proposed.

Punicalagin and ellagic acid containing Punica granatum L. fruit rind extract prevents vincristine-induced neuropathic pain in rats: an in silico and in vivo evidence of GABAergic action and cytokine inhibition

Objectives: We aimed to investigate the protective potential of Punica granatum L. fruit rind extract (PFE) containing punicalagin (10.3% W/W), ellagic acid (EA) (2.7%W/W) in vincristine (75 µg/kg i.p.)- induced neuropathic pain in Wistar rats.Methods: Docking simulation studies were done on the three-dimensional (3D) structure of the GABA_A and PPAR γ receptor for the binding of EA as well as punicalagin docking studies on TNF-α, and IL-6. The Present Study conceptualized a test battery to evaluate the behavioral, biochemical and histological changes.Results: Vincristine -induced significant cold allodynia, mechanical hyperalgesia, and functional deficit on 12th and 21st days. It also increased in the levels of TNF-α (Tumor necrosis factor-α), IL-6 (Interleukin-6), and MPO (Myeloperoxidase). Administration of PFE (100 and 300 mg/kg, p.o.), EA (50 mg/kg), and gabapentin (100 mg/kg) attenuated Vincristine-induced behavioral and biochemical changes significantly (P < .05). PFE showed better antinociceptive activity to EA. The histopathological evaluation also revealed the protective effects of PFE. Pretreatment of bicuculline (selective antagonist of GABAA receptors) reversed antinociceptive action of PFE, but administration of γ aminobutyric acid potentiated the action of PFE. PPAR-γ antagonist BADGE did not modify the effect of PFE. Docking results revealed that EA properly positioned into GABA and PPARγ binding site and acts as a partial agonist. Docking score of Punicalagin found to be - 9.02 kcal/mol and - 8.32 kcal/mol on IL-6 and TNFα respectively.Discussion: Conclusively, the attenuating effect of PFE may be attributed to the GABAergic system, cytokine inhibition, and anti-inflammatory activities.

Computational assessment of saikosaponins as adjuvant treatment for COVID-19: molecular docking, dynamics, and network pharmacology analysis

Saikosaponins are major biologically active triterpenoids, usually as glucosides, isolated from Traditional Chinese Medicines (TCM) such as Bupleurum spp., Heteromorpha spp., and Scrophularia scorodonia with their antiviral and immunomodulatory potential. This investigation presents molecular docking, molecular dynamics simulation, and free energy calculation studies of saikosaponins as adjuvant therapy in the treatment for COVID19. Molecular docking studies for 23 saikosaponins on the crystal structures of the extracellular domains of human lnterleukin-6 receptor (IL6), human Janus Kinase-3 (JAK3), and dehydrogenase domain of Cylindrospermum stagnale NADPH-oxidase 5 (NOX5) were performed, and selected protein-ligand complexes were subjected to 100 ns molecular dynamics simulations. The molecular dynamics trajectories were subjected to free energy calculation by the MM-GBSA method. Molecular docking and molecular dynamics simulation studies revealed that IL6 in complex with Saikosaponin_U and Saikosaponin_V, JAK3 in complex with Saikosaponin_B4 and Saikosaponin_I, and NOX5 in complex with Saikosaponin_BK1 and Saikosaponin_C have good docking and molecular dynamics profiles. However, the Janus Kinase-3 is the best interacting partner for the saikosaponin compounds. The network pharmacology analysis suggests saikosaponins interact with the proteins CAT Gene CAT (Catalase) and Checkpoint kinase 1 (CHEK1); both of these enzymes play a major role in cell homeostasis and DNA damage during infection, suggesting a possible improvement in immune response toward COVID-19.

Role of Interleukin-6 in Vascular Health and Disease

IL-6 is usually described as a pleiotropic cytokine produced in response to tissue injury or infection. As a pro-inflammatory cytokine, IL-6 activates innate and adaptative immune responses. IL-6 is released in the innate immune response by leukocytes as well as stromal cells upon pattern recognition receptor activation. IL-6 then recruits immune cells and triggers B and T cell response. Dysregulated IL-6 activity is associated with pathologies involving chronic inflammation and autoimmunity, including atherosclerosis. However, IL-6 is also produced and released under beneficial conditions, such as exercise, where IL-6 is associated with the anti-inflammatory and metabolic effects coupled with physical adaptation to intense training. Exercise-associated IL-6 acts on adipose tissue to induce lipogenesis and on arteries to induce adaptative vascular remodeling. These divergent actions could be explained by complex signaling networks. Classical IL-6 signaling involves a membrane-bound IL-6 receptor and glycoprotein 130 (gp130), while trans-signaling relies on a soluble version of IL-6R (sIL-6R) and membrane-bound gp130. Trans-signaling, but not the classical pathway, is regulated by soluble gp130. In this review, we discuss the similarities and differences in IL-6 cytokine and myokine signaling to explain the differential and opposite effects of this protein during inflammation and exercise, with a special focus on the vascular system.

3D-Bioprinted Inflammation Modulating Polymer Scaffolds for Soft Tissue Repair

Development of inflammation modulating polymer scaffolds for soft tissue repair with minimal postsurgical complications is a compelling clinical need. However, the current standard of care soft tissue repair meshes for hernia repair is highly inflammatory and initiates a dysregulated inflammatory process causing visceral adhesions and postsurgical complications. Herein, the development of an inflammation modulating biomaterial scaffold (bioscaffold) for soft tissue repair is presented. The bioscaffold design is based on the idea that, if the excess proinflammatory cytokines are sequestered from the site of injury by the surgical implantation of a bioscaffold, the inflammatory response can be modulated, and the visceral adhesion formations and postsurgical complications can be minimized. The bioscaffold is fabricated by 3D-bioprinting of an in situ phosphate crosslinked poly(vinyl alcohol) polymer. In vivo efficacy of the bioscaffold is evaluated in a rat ventral hernia model. In vivo proinflammatory cytokine expression analysis and histopathological analysis of the tissues have confirmed that the bioscaffold acts as an inflammation trap and captures the proinflammatory cytokines secreted at the implant site and effectively modulates the local inflammation without the need for exogenous anti-inflammatory agents. The bioscaffold is very effective in inhibiting visceral adhesions formation and minimizing postsurgical complications.

Mitigate the cytokine storm due to the severe COVID-19: A computational investigation of possible allosteric inhibitory actions on IL-6R and IL-1R using selected phytochemicals

The novel corona virus 2019 (COVID 19) is growing at an increasing rate with high mortality. Meanwhile, the cytokine storm is the most dangerous and potentially life-threatening event related to COVID 19. Phyto-compounds found in existing Ayurveda drugs have the ability to inhibit the Interleukin 6 (IL-6R) and Interleukin 1 (IL-1R) receptors. IL-6R and IL-1R receptors involve in cytokine storm and recognition of phytochemicals with proven safety profiles could open a pathway to the development of the most effective drugs against cytokine storm. In this study, we intend to perform an in silico investigation of effective phyto compounds, which can be isolated from selected medicinal herbs to avoid cytokine storm, inhibiting the IL-6 and IL-1 receptor binding process. An extensive literature survey followed by virtual screening was carried out to identify phytochemicals with potential anti-hyper-inflammatory action. Flexible docking was conducted for validated models of IL-1R and IL-6R-α with the most promising phytochemicals at possible allosteric sites using AutoDock Vina. Molecular dynamics (MD) studies were conducted for selected protein-ligand complexes using LARMD server and conformational changes were evaluated. According to the results, taepeenin J had Gibbs energy (ΔG) of -10.85 kcal/mol towards IL-1R but had limited oral bioavailability. MD analysis revealed that taepeenin J can cause significant conformational movements in IL-1R. Nortaepeenin B showed a ΔG of -8.5 kcal/mol towards IL-6R-α with an excellent oral bioavailability. MD analysis predicted that it can cause significant conformational movements in IL-6R-α. Hence, the evaluated phytochemicals are potential candidates for further in vitro studies for the development of medicine against cytokine storm on behalf of SARS-COV-2 infected patients.

Exploitation of Elevated Extracellular ATP to Specifically Direct Antibody to Tumor Microenvironment

The extracellular adenosine triphosphate (ATP) concentration is highly elevated in the tumor microenvironment (TME) and remains tightly regulated in normal tissues. Using phage display technology, we establish a method to identify an antibody that can bind to an antigen only in the presence of ATP. Crystallography analysis reveals that ATP bound in between the antibody-antigen interface serves as a switch for antigen binding. In a transgenic mouse model overexpressing the antigen systemically, the ATP switch antibody binds to the antigen in tumors with minimal binding in normal tissues and plasma and inhibits tumor growth. Thus, we demonstrate that elevated extracellular ATP concentration can be exploited to specifically target the TME, giving therapeutic antibodies the ability to overcome on-target off-tumor toxicity.

The bio-mission of interleukin-6 in the pathogenesis of COVID-19: A brief look at potential therapeutic tactics

Interleukin-6 (IL-6), known as an inflammatory cytokine, can be involved in many innate and adaptive immune responses. The role of IL-6 in the pathogenesis of the novel coronavirus disease 2019 (COVID-19) has recently received much more attention due to the spread of the virus and its pandemic potential. Cytokine storm is among the most critical pathological events in patients affected with coronaviruses (CoVs), i.e., severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and COVID-19, causing inflammation-induced lung injury and also occurring as a result of dysregulation of immune responses to the mentioned viruses. IL-6, along with some other inflammatory cytokines, including IL-1 beta (β), IL-8, and tumor necrosis factor-alpha (TNF-α), as well as inflammatory chemokines, can significantly contribute to, fever, lymphopenia, coagulation, lung injury, and multi-organ failure (MOF). Therefore, researchers are to explore novel approaches to treat the disease through targeting of IL-6 and its receptors based on prior experience of other disorders. In this review article, the latest findings on the role of IL-6 in the pathogenesis of COVID-19, as well as therapeutic perspectives, were summarized and discussed.

A Novel Mutation in the IL6R Gene Identified in a Family with Asthma Patients

Background: Allergic diseases, including asthma, atopic dermatitis, allergic rhinitis, and food allergies, are caused by both environmental and genetic factors. The allergic condition, where genetic factors make up the largest proportion (up to 95%), is asthma. Aim: To identify polymorphisms and mutations in potentially disease-causing genes in a family affected with allergic asthma. Methods: Whole exome sequencing of the index patient was performed via next-generation sequencing. Variants in known allergy-associated susceptibility genes were identified by comparison with the reference genome GRChr37. Results: Seven common polymorphisms and three rare mutations were identified in the allergy-susceptibility genes of the index patient. Only four of these variants co-segregated with a second patient in the same family. These variants occurred in the TENS1, NPSR1, RAD50, and IL6R genes. Discussion: The variants observed in TENS1 and NPSR1 are relatively common (minor allele frequency, MAF ∼0.4), whereas the mutation in RAD50 is rare (MAF 0.0035). The mutation identified in IL6R (S409P) has never been found before. IL6R encodes an important receptor of the inflammatory system. The mutation occurs in the intracellular domain within a tyrosine-based motif, which is required for sorting of the IL6R protein to the basolateral side of polarized cells. It is likely that this rare mutation contributes-together with the other variants-to the predisposition to asthma and other allergic diseases.

Biosensing Cytokine IL-6: A Comparative Analysis of Natural and Synthetic Receptors

Cytokines are a family of proteins which play a major role in the regulation of the immune system and the development of several diseases, from rheumatoid arthritis to cancer and, more recently, COVID-19. Therefore, many efforts are currently being developed to improve therapy and diagnosis, as well as to produce inhibitory drugs and biosensors for a rapid, minimally invasive, and effective detection. In this regard, even more efficient cytokine receptors are under investigation. In this paper we analyze a set of IL-6 cytokine receptors, investigating their topological features by means of a theoretical approach. Our results suggest a topological indicator that may help in the identification of those receptors having the highest complementarity with the protein, a feature expected to ensure a stable binding. Furthermore, we propose and discuss the use of these receptors in an idealized experimental setup.

Structural Understanding of Interleukin 6 Family Cytokine Signaling and Targeted Therapies: Focus on Interleukin 11

Cytokines are small signaling proteins that have central roles in inflammation and cell survival. In the half-century since the discovery of the first cytokines, the interferons, over fifty cytokines have been identified. Amongst these is interleukin (IL)-6, the first and prototypical member of the IL-6 family of cytokines, nearly all of which utilize the common signaling receptor, gp130. In the last decade, there have been numerous advances in our understanding of the structural mechanisms of IL-6 family signaling, particularly for IL-6 itself. However, our understanding of the detailed structural mechanisms underlying signaling by most IL-6 family members remains limited. With the emergence of new roles for IL-6 family cytokines in disease and, in particular, roles of IL-11 in cardiovascular disease, lung disease, and cancer, there is an emerging need to develop therapeutics that can progress to clinical use. Here we outline our current knowledge of the structural mechanism of signaling by the IL-6 family of cytokines. We discuss how this knowledge allows us to understand the mechanism of action of currently available inhibitors targeting IL-6 family cytokine signaling, and most importantly how it allows for improved opportunities to pharmacologically disrupt cytokine signaling. We focus specifically on the need to develop and understand inhibitors that disrupt IL-11 signaling.

The structure of the extracellular domains of human interleukin 11α receptor reveals mechanisms of cytokine engagement

Interleukin (IL) 11 activates multiple intracellular signaling pathways by forming a complex with its cell surface α-receptor, IL-11Rα, and the β-subunit receptor, gp130. Dysregulated IL-11 signaling has been implicated in several diseases, including some cancers and fibrosis. Mutations in IL-11Rα that reduce signaling are also associated with hereditary cranial malformations. Here we present the first crystal structure of the extracellular domains of human IL-11Rα and a structure of human IL-11 that reveals previously unresolved detail. Disease-associated mutations in IL-11Rα are generally distal to putative ligand-binding sites. Molecular dynamics simulations showed that specific mutations destabilize IL-11Rα and may have indirect effects on the cytokine-binding region. We show that IL-11 and IL-11Rα form a 1:1 complex with nanomolar affinity and present a model of the complex. Our results suggest that the thermodynamic and structural mechanisms of complex formation between IL-11 and IL-11Rα differ substantially from those previously reported for similar cytokines. This work reveals key determinants of the engagement of IL-11 by IL-11Rα that may be exploited in the development of strategies to modulate formation of the IL-11-IL-11Rα complex.

A panoramic review of IL-6: Structure, pathophysiological roles and inhibitors

Interleukin-6 (IL-6) is a pleiotropic pro-inflammatory cytokine. Its deregulation is associated with chronic inflammation, and multifactorial auto-immune disorders. It mediates its biological roles through a hexameric complex composed of IL-6 itself, its receptor IL-6R, and glycoprotein 130 (IL-6/IL-6R/gp130). This complex, in turn, activates different signaling mechanisms (classical and trans-signaling) to execute various biochemical functions. The trans-signaling mechanism activates various pathological routes, like JAK/STAT3, Ras/MAPK, PI3K-PKB/Akt, and regulation of CD4+ T cells and VEGF levels, which cause cancer, multiple sclerosis, rheumatoid arthritis, anemia, inflammatory bowel disease, Crohn's disease, and Alzheimer's disease. Involvement of IL-6 in pathophysiology of these complex diseases makes it an important target for the treatment of these diseases. Though some anti-IL-6 monoclonal antibodies are being used clinically, but their high cost, only parenteral administration, and possibility of immunogenicity have limited their use, and warranted the development of novel small non-peptide molecules as IL-6 inhibitors. In the present report, all molecules reported in literature as IL-6 inhibitors have been classified as IL-6 production, IL-6R, and IL-6 signaling inhibitors. Reports available till date are critically studied to identify important and salient structural features common in these molecules. These analyses would assist medicinal chemists to design novel and potent IL-6 production and signaling inhibitors, through knowledge- and/or computer-based approaches, for the treatment of complex multifactorial diseases.

Inhibition of Tyrosine-Phosphorylated STAT3 in Human Breast and Lung Cancer Cells by Manuka Honey is Mediated by Selective Antagonism of the IL-6 Receptor

Aberrantly high levels of tyrosine-phosphorylated signal transducer and activator of transcription 3 (p-STAT3) are found constitutively in ~50% of human lung and breast cancers, acting as an oncogenic transcription factor. We previously demonstrated that Manuka honey (MH) inhibits p-STAT3 in breast cancer cells, but the exact mechanism remained unknown. Herein, we show that MH-mediated inhibition of p-STAT3 in breast (MDA-MB-231) and lung (A549) cancer cell lines is accompanied by decreased levels of gp130 and p-JAK2, two upstream components of the IL-6 receptor (IL-6R) signaling pathway. Using an ELISA-based assay, we demonstrate that MH binds directly to IL-6Rα, significantly inhibiting (~60%) its binding to the IL-6 ligand. Importantly, no evidence of MH binding to two other cytokine receptors, IL-11Rα and IL-8R, was found. Moreover, MH did not alter the levels of tyrosine-phosphorylated or total Src family kinases, which are also constitutively activated in cancer cells, suggesting that signaling via other growth factor receptors is unaffected by MH. Binding of five major MH flavonoids (luteolin, quercetin, galangin, pinocembrin, and chrysin) was also tested, and all but pinocembrin could demonstrably bind IL-6Rα, partially (30-35%) blocking IL-6 binding at the highest concentration (50 μM) used. In agreement, each flavonoid inhibited p-STAT3 in a dose-dependent manner, with estimated IC50 values in the 3.5-70 μM range. Finally, docking analysis confirmed the capacity of each flavonoid to bind in an energetically favorable configuration to IL-6Rα at a site predicted to interfere with ligand binding. Taken together, our findings identify IL-6Rα as a direct target of MH and its flavonoids, highlighting IL-6R blockade as a mechanism for the anti-tumor activity of MH, as well as a viable therapeutic target in IL-6-dependent cancers.

Virtual Screening of IL-6 Inhibitors for Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) is a heterogeneous disease characterized by the arthritis of unknown origin and IL6 is a known target for JIA. 20 known inhibitors towards IL-6 were screened and Methotrexate (MTX) having PubChem ID: 126941 showed high binding capacity with the receptor IL-6. The similarity searching with this compound gave 269 virtual screened compounds. The said screening presented 269 possible drugs having structural similarity to Methotrexate. The docking studies of the screened drugs separated the compound having PubChem CID: 122677576 (re-rank value of -140.262). Toxicity and interaction profile validated this compound for having a better affinity with the target protein. Conclusively, this study shows that according to ADMET profile and BOILED-Egg plot, the compound (PubChem CID: 122677576) obtained from Virtual Screen could be the best drug in future during the prevention of juvenile idiopathic arthritis. In the current study, the drug CID: 122677576 is a potent candidate for treating JIA. The pharmacophore study revealed that the drug CID: 122677576 is a non-inhibitor of CYP450 microsomal enzymes and was found to be non-toxic, similar to the established drug Methotrexate (CID: 126941). It has a lower LD50 value of 2.6698mol/kg as compared to the established compound having LD50 value as 23.4955mol/kg. Moreover, the compound was found to be non-carcinogenic.

Interleukin 6: The biology behind the therapy

The cytokine interleukin (IL)−6 performs a diverse portfolio of functions in normal physiology and disease. These functions extend beyond the typical role for an inflammatory cytokine, and IL-6 often displays hormone-like properties that affect metabolic processes associated with lipid metabolism, insulin resistance, and the neuroendocrine system. Consequently, the biology of IL-6 is complex. Recent advances in the field have led to novel interpretations of how IL-6 delivers immune homeostasis in health and yet drives disease pathology during infection, autoimmunity, and cancer. Various biological drugs that target IL-6 are in clinical practice or emerging in clinical trials and pre-clinical development programmes. The challenge is knowing how and when to apply these therapies. In this review, we will explore the biology behind IL-6 directed therapies and identify some key hurdles for future investigation.

Comparative Study of Protein Expression Levels of Five Plaque Biomarkers and Relation with Carotid Plaque Type Classification in Patients after Carotid Endarterectomy

Atherosclerosis is an inflammatory process resulting in local plaque deposition in the vessel wall of arteries with symptoms to various areas of vascular tree. Identification of patients with progressive advanced atherosclerotic disease is mainly based on the known characteristics of the vulnerable or recently ruptured plaque. Molecular and cellular features associated with the vulnerable plaque are considered potential diagnostic markers for plaque rupture and thrombosis. Here, protein expression levels of the metalloproteases MMP-1, MMP-9, osteopontin (OPN), and cytokines TNFα and IL-6 in tissue extracts of carotid plaques in patients after endarterectomy were estimated by Western immunoblotting, after SDS-PAGE analysis and evaluated based on the ultrasonographic plaque morphology. The gender and age effect was also examined. MMP-1, MMP-9, and IL-6 were expressed in higher levels compared to OPN and TNFa as well as in symptomatic (with type II and III carotid plaque classification) than asymptomatic (type IV) patients with differences considered statistically significant (P values <0.05). A significant positive correlation between MMP-1 and IL-6 (with Pearson correlation coefficient 0.748) is also notable. The data give further insight into the possible role of specific biomarker and enhance the need for further studies in order to clarify the proper one(s) for detection of the vulnerable plaque and help identify patients at risk for cardiovascular events.

Discovery of a junctional epitope antibody that stabilizes IL-6 and gp80 protein:protein interaction and modulates its downstream signaling

Protein:protein interactions are fundamental in living organism homeostasis. Here we introduce VHH6, a junctional epitope antibody capable of specifically recognizing a neo-epitope when two proteins interact, albeit transiently, to form a complex. Orthogonal biophysical techniques have been used to prove the "junctional epitope" nature of VHH6, a camelid single domain antibody recognizing the IL-6-gp80 complex but not the individual components alone. X-ray crystallography, HDX-MS and SPR analysis confirmed that the CDR regions of VHH6 interact simultaneously with IL-6 and gp80, locking the two proteins together. At the cellular level, VHH6 was able to alter the response of endothelial cells to exogenous IL-6, promoting a sustained STAT3 phosphorylation signal, an accumulation of IL-6 in vesicles and an overall pro-inflammatory phenotype supported further by transcriptomic analysis. Junctional epitope antibodies, like VHH6, not only offer new opportunities in screening and structure-aided drug discovery, but could also be exploited as therapeutics to modulate complex protein:protein interactions.

Structure-based virtual screening and characterization of a novel IL-6 antagonistic compound from synthetic compound database

According to the three-dimensional (3D) complex structure of (hIL-6⋅hIL-6R⋅gp 130)₂ and the binding orientation of hIL-6, three compounds with high affinity to hIL-6R and bioactivity to block hIL-6 in vitro were screened theoretically from the chemical databases, including 3D-Available Chemicals Directory (ACD) and MDL Drug Data Report (MDDR), by means of the computer-guided virtual screening method. Using distance geometry, molecular modeling and molecular dynamics trajectory analysis methods, the binding mode and binding energy of the three compounds were evaluated theoretically. Enzyme-linked immunosorbent assay analysis demonstrated that all the three compounds could block IL-6 binding to IL-6R specifically. However, only compound 1 could effectively antagonize the function of hIL-6 and inhibit the proliferation of XG-7 cells in a dose-dependent manner, whereas it showed no cytotoxicity to SP2/0 or L929 cells. These data demonstrated that the compound 1 could be a promising candidate of hIL-6 antagonist.

Structure and target interaction of a G-quadruplex RNA-aptamer

G-quadruplexes have recently moved into focus of research in nucleic acids, thereby evolving in scientific significance from exceptional secondary structure motifs to complex modulators of gene regulation. Aptamers (nucleic acid based ligands with recognition properties for a specific target) that form Gquadruplexes may have particular potential for therapeutic applications as they combine the characteristics of specific targeting and Gquadruplex mediated stability and regulation. We have investigated the structure and target interaction properties of one such aptamer: AIR-3 and its truncated form AIR-3A. These RNA aptamers are specific for human interleukin-6 receptor (hIL-6R), a key player in inflammatory diseases and cancer, and have recently been exploited for in vitro drug delivery studies. With the aim to resolve the RNA structure, global shape, RNA:protein interaction site and binding stoichiometry, we now investigated AIR-3 and AIR-3A by different methods including RNA structure probing, Small Angle X-ray scattering and microscale thermophoresis. Our findings suggest a broader spectrum of folding species than assumed so far and remarkable tolerance toward different modifications. Mass spectrometry based binding site analysis, supported by molecular modeling and docking studies propose a general Gquadruplex affinity for the target molecule hIL-6R.

JAK-STAT signaling in cancer: From cytokines to non-coding genome

In the past decades, studies of the Janus kinases (JAKs) and signal transducers and activators of transcription (STATs) signaling have uncovered highly conserved programs linking cytokine signaling to the regulation of essential cellular mechanisms such as proliferation, invasion, survival, inflammation and immunity. Inhibitors of the JAK/STAT pathway are used for treatment of autoimmune diseases, such as rheumatoid arthritis or psoriasis. Aberrant JAK/STAT signaling has been identified to contribute to cancer progression and metastatic development. Targeting of JAK/STAT pathway is currently one of the most promising therapeutic strategies in prostate cancer (PCa), hematopoietic malignancies and sarcomas. Notably, newly identified regulators of JAK/STAT signaling, the non-coding RNAs transcripts and their role as important targets and potential clinical biomarkers are highlighted in this review. In addition to the established role of the JAK/STAT signaling pathway in traditional cytokine signaling the non-coding RNAs add yet another layer of hidden regulation and function. Understanding the crosstalk of non-coding RNA with JAK/STAT signaling in cancer is of critical importance and may result in better patient stratification not only in terms of prognosis but also in the context of therapy.

A Miniature Protein Stabilized by a Cation-π Interaction Network

The design of folded miniature proteins is predicated on establishing noncovalent interactions that direct the self-assembly of discrete thermostable tertiary structures. In this work, we describe how a network of cation-π interactions present in proteins containing "WSXWS motifs" can be emulated to stabilize the core of a miniature protein. This 19-residue protein sequence recapitulates a set of interdigitated arginine and tryptophan residues that stabilize a distinctive β-strand:loop:PPII-helix topology. Validation of the compact fold determined by NMR was carried out by mutagenesis of the cation-π network and by comparison to the corresponding disulfide-bridged structure. These results support the involvement of a coordinated set of cation-π interactions that stabilize the tertiary structure.

Diacerein-mediated inhibition of IL-6/IL-6R signaling induces apoptotic effects on breast cancer

Interleukin-6 (IL-6) signaling network has been implicated in oncogenic transformations making it attractive target for the discovery of novel cancer therapeutics. In this study, potent antiproliferative and apoptotic effect of diacerein were observed against breast cancer. In vitro apoptosis was induced by this drug in breast cancer cells as verified by increased sub-G1 population, LIVE/DEAD assay, cell cytotoxicity and presence of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells, as well as downregulation of antiapoptotic proteins Bcl-2 and Bcl-xL and upregulation of apoptotic protein Bax. In addition, apoptosis induction was found to be caspase dependent. Further molecular investigations indicated that diacerein instigated apoptosis was associated with inhibition of IL-6/IL-6R autocrine signaling axis. Suppression of STAT3, MAPK and Akt pathways were also observed as a consequence of diacerein-mediated upstream inhibition of IL-6/IL-6R. Fluorescence study and western blot analysis revealed cytosolic accumulation of STAT3 in diacerein-treated cells. The docking study showed diacerein/IL-6R interaction that was further validated by competitive binding assay and isothermal titration calorimetry. Most interestingly, it was found that diacerein considerably suppressed tumor growth in MDA-MB-231 xenograft model. The in vivo antitumor effect was correlated with decreased proliferation (Ki-67), increased apoptosis (TUNEL) and inhibition of IL-6/IL-6R-mediated STAT3, MAPK and Akt pathway in tumor remnants. Taken together, diacerein offered a novel blueprint for cancer therapy by hampering IL-6/IL-6R/STAT3/MAPK/Akt network.

Active immunization with Tocilizumab mimotopes induces specific immune responses

BACKGROUND

Tocilizumab is a humanized monoclonal antibody showing high-affinity binding to both soluble interleukin-6 receptor (sIL-6R) and membrane bound IL-6R (mIL-6R), thereby preventing pro-inflammatory effects of IL-6. However, therapeutic antibodies still have practical limitations. To overcome these limitations, we generated Tocilizumab specific epitope mimics by using the phage display technology and tested whether the peptide mimics could induce similar humoral responses in mice immunized with the peptides.

RESULTS

Seven phage mimics were obtained by using phage display peptide library. Four phage mimics (YHTTDKLFYMMR, YSAYEFEYILSS, KTMSAEEFDNWL and LTSHTYRSQADT) were shown to mimic Tocilizumab epitope using immunoassays. The mimotopes were conjugated to immunogenic carrier proteins and used to intraperitoneally immunize BALB/c mice. Sera from the mimotopes immunized mice not only showed specific binding to recombinant IL-6R, but can also IL-6R expressed in Hela, U-937, Jurkat cell lines and in fibroblast-like synoviocytes from patients with RA (FLS-RA). Furthermore, sera from mice immunized with mimotopes-KLH conjugate could reduce the level of phosphorylated- signal transducers and activator of transcription (STAT3), STAT3, phosphorylated- extracellular signal-regulated kinase (Erk) 1/2 and Erk1/2 in HeLa and Jurkat cells. Antibody-dependent cellular cytotoxicity (ADCC) assay showed that antibodies induced by mimotopes-KLH conjugate could elicit specific lysis in Hela and U-937 cells.

CONCLUSIONS

From phage display library, we successfully isolated four Tocilizumab mimotopes which induced specific humoral and cellular reponses in vitro and in vivo.

IL-6 as a keystone cytokine in health and disease

Interleukin 6 (IL-6) has a broad effect on cells of the immune system and those not of the immune system and often displays hormone-like characteristics that affect homeostatic processes. IL-6 has context-dependent pro- and anti-inflammatory properties and is now regarded as a prominent target for clinical intervention. However, the signaling cassette that controls the activity of IL-6 is complicated, and distinct intervention strategies can inhibit this pathway. Clinical experience with antagonists of IL-6 has raised new questions about how and when to block this cytokine to improve disease outcome and patient wellbeing. Here we discuss the effect of IL-6 on innate and adaptive immunity and the possible advantages of various antagonists of IL-6 and consider how the immunobiology of IL-6 may inform clinical decisions.