Toll-like receptors are potential therapeutic targets in rheumatoid arthritis

Toll-like Receptors as Pro-Thrombotic Drivers in Viral Infections: A Narrative Review

Toll-like receptors (TLRs) have a critical role in the pathogenesis and disease course of viral infections. The induced pro-inflammatory responses result in the disturbance of the endovascular surface layer and impair vascular homeostasis. The injury of the vessel wall further promotes pro-thrombotic and pro-coagulatory processes, eventually leading to micro-vessel plugging and tissue necrosis. Moreover, TLRs have a direct role in the sensing of viruses and platelet activation. TLR-mediated upregulation of von Willebrand factor release and neutrophil, as well as macrophage extra-cellular trap formation, further contribute to (micro-) thrombotic processes during inflammation. The following review focuses on TLR signaling pathways of TLRs expressed in humans provoking pro-thrombotic responses, which determine patient outcome during viral infections, especially in those with cardiovascular diseases.

The Relationship between Extracellular/intracellular microRNAs and TLRs May Be Used as a Diagnostic and Therapeutic Approach in Sepsis

One of the leading causes of death in the intensive care unit (ICU) is sepsis. Different studies have been performed on different markers to determine the cause of sepsis. microRNAs (miRNAs) are non-coding RNAs that can be released both inside and outside the cell and regulate the target gene expression by binding to the 3' untranslated region (3'UTR) of the target genes. TLRs play an important role in innate immunity that can be modulated by biological markers such as microRNAs. In this study, we summarized the recent progress on the role of extracellular and intracellular microRNAs in sepsis. It has also been focused on the association of TLRs with extracellular and intracellular micro RNAs in the regulation of sepsis. In conclusion, this study has provided new insight into the role of microRNAs as a regulator of the TLRs which may lead to the aberrant inflammatory response in sepsis. Therefore, it suggests that both intracellular and extracellular microRNAs may play a therapeutic role in the treatment of sepsis via regulating TLRs. However, yet sepsis and septic shock are medical emergencies and further studies are needed to specify the exact role of microRNAs and TLRs in sepsis.

Harmful effects of high amounts of glucose on the immune system: An updated review

Release and storage of energy can be regulated by the metabolic parameter dependent on the central nervous system. Macrophages are one of the most professional antigen-presenting cells that are formed by the accumulation of dead or damaged cells or in response to the infection, which has the main function of phagocytosis, secretion of cytokines, and presenting antigen to T cells. A proper immune response is needed for the production of effector cytokines along with comprehensive and rapid cell proliferation and growth. Activation of the immune system and immune cells is needed to increase glucose metabolism. When the immune system responds to pathogens, chemokines inform immune cells such as macrophages and T cells to travel to the infected area. Although glucose is vital for the proper function of immune cells and their proliferation, a high amount of glucose may lead to impaired function of the immune system and pathological conditions. However, a suitable amount of glucose is indispensable for the immune system, but its elevated amount leads to excessive proinflammatory cytokines production. In this study, we focused on the master regulatory role of glucose on the immune system.

Antimicrobial Peptide Epinecidin-1 Modulates MyD88 Protein Levels via the Proteasome Degradation Pathway

The cationic antimicrobial peptide epinecidin-1 was identified from Epinephelus coioides and possesses multiple biological functions, including antibacterial, antifungal, anti-tumor, and immunomodulatory effects. In addition, epinecidin-1 suppresses lipopolysaccharide (LPS)-induced inflammation by neutralizing LPS and ameliorating LPS/Toll-like receptor (TLR)-4 internalization. However, it is unclear whether the actions of epinecidin-1 depend on the regulation of TLR adaptor protein MyD88 or endogenous TLR signaling antagonists, which include A20, interleukin-1 receptor associated kinase (IRAK)-M, and suppressor of cytokine signaling (SOCS)-1. Our results demonstrate that epinecidin-1 alone does not affect A20, IRAK-M, or SOCS-1 protein levels. However, pre-incubation of epinecidin-1 significantly inhibits LPS-induced upregulation of A20, IRAK-M, and SOCS-1. In addition, epinecidin-1 significantly reduces the abundance of MyD88 protein. Both MG132 (a specific proteasome inhibitor) and Heclin (a specific Smurf E3 ligase inhibitor) are able to abolish epinecidin-1-mediated MyD88 degradation. Thus, our data suggest that epinecidin-1 directly inhibits MyD88 via induction of the Smurf E3 ligase proteasome pathway.

Resveratrol inhibits the IL-1β-induced expression of MMP-13 and IL-6 in human articular chondrocytes via TLR4/MyD88-dependent and -independent signaling cascades

The natural polyphenolic compound, resveratrol, has been shown to exhibit anti-osteoarthritic activity. Therefore it is hypothesized that resveratrol may serve as a nutritional supplement to counteract osteoarthritis (OA). However, the mechanisms responsible for these anti-osteoarthritic effects have not yet been fully elucidated. The aim of this study was to determine whether the biological effects of resveratrol against interleukin (IL)-1β‑induced inflammation in human articular chondrocytes involved both Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)-dependent and -independent signaling pathways. Human articular chondrocytes derived from patients with OA were stimulated with IL-1β, and then co-treated with resveratrol. Cell viability was subsequently evaluated by MTS assays, and the concentrations of matrix metalloproteinase (MMP)-13 and the pro-inflammatory factor, IL-6, were detected in culture supernatants using ELISA. The mRNA and protein levels of downstream mediators of TLR4/MyD88-dependent and -independent signaling pathways were also assayed by RT-qPCR and western blot analysis, respectively. Our results revealed that resveratrol prevented the IL-1β-induced reduction in cell viability. Furthermore, stimulation of the chondrocytes with IL-1β resulted in a significant upregulation of TLR4 and downstream targets of both TLR4/MyD88-dependent and -independent signaling pathways that are associated with the synthesis of MMP-13 and IL-6. Correspondingly, IL-1β-induced catabolic and inflammatory responses were effectively reversed by resveratrol. Taken together, these data suggest that resveratrol exerted protective effects against matrix degradation and inflammation in OA-affected chondrocytes by inhibiting both TLR4/MyD88-dependent and -independent signaling pathways. Thus, resveratrol represents a potential treatment for OA and warrants further investigation.

Pharmacological effects of β-d-mannuronic acid (M2000) on miR-146a, IRAK1, TRAF6 and NF-κB gene expression, as target molecules in inflammatory reactions

BACKGROUND

Impaired expression and function of microRNAs (miRNAs) are involved in the pathogenesis of many autoimmune and inflammatory diseases. Moreover, there is a close relationship between TLRs and miRNAs and impairment in regulating their expression which can play a vital role in the immunopathogenesis of many inflammatory reactions. This research aimed to study the pharmaceutical effects of M2000 (β-d-mannuronic acid) on the expression of miR-146a and its two target molecules (IRAK1 and TRAF6), and the transcription factor NF-κB in the HEK-Blue hTLR2 cell line.

METHODS

The cytotoxicity of M2000 was assessed by the MTT assay, and the qRT-PCR technique was employed in the presence and absence of M2000 treatment to measure gene-expression levels of miR-146a, IRAK1, TRAF6, and NF-κB.

RESULTS

MTT assay indicated that M2000 (before the concentration of 500μg/ml) had no cytotoxic effect on HEK-Blue hTLR2 cells. Our results showed that M2000 at low and high doses (5 and 25μg/well) could significantly reduce gene expression levels of miR-146a (p<0.01). Furthermore, it was found that this medication at two different doses could considerably decrease IRAK1 and TRAF6 gene expression (p<0.001). Moreover, this study revealed that expression level of NF-κB also significantly declined at these two doses (p<0.01).

CONCLUSIONS

This study for the first time shows that M2000 as a novel NSAID with immunosuppressive properties is able to modify TLR signaling through suppressing the adaptor molecules IRAK1 and TRAF6, the transcription factor NF-κB and miR-146a as a new therapeutic approach.

Evidence of NI-0101 pharmacological activity, an anti-TLR4 antibody, in a randomized phase I dose escalation study in healthy volunteers receiving LPS

Toll-like receptor-4 (TLR4) pathways are major contributors to pathological inflammatory responses induced by tissue damage. NI-0101 is the first monoclonal antibody (mAb) blocking TLR4 signaling. This activity is independent of the ligand type and concentration, therefore, potentially blocking any TLR4 ligands. A phase I single ascending dose study was conducted in 73 healthy volunteers to evaluate NI-0101 tolerability, preliminary safety, pharmacokinetics (PKs), and pharmacodynamics (PDs), in absence and in presence of a systemic challenge with lipopolysaccharide (LPS), a TLR4 ligand. NI-0101 was well tolerated without safety concern. The PK profile was characterized by a half-life of ∼10 days at high concentrations and by a rapid elimination at low concentrations due to expected target-mediated drug disposition. NI-0101 prevented cytokine release following ex vivo and in vivo LPS administration and prevented the C-reactive protein (CRP) increase and the occurrence of flu-like symptoms expected following the in vivo administration of LPS.

Toll-like receptors: promising therapeutic targets for inflammatory diseases

The health of living organisms is constantly challenged by bacterial and viral threats. The recognition of pathogenic microorganisms by diverse receptors triggers a variety of host defense mechanisms, leading to their eradication. Toll-like receptors (TLRs), which are type I transmembrane proteins, recognize specific signatures of the invading microbes and activate a cascade of downstream signals inducing the secretion of inflammatory cytokines, chemokines, and type I interferons. The TLR response not only counteracts the pathogens but also initiates and shapes the adaptive immune response. Under normal conditions, inflammation is downregulated after the removal of the pathogen and cellular debris. However, a dysfunctional TLR-mediated response maintains a chronic inflammatory state and leads to local and systemic deleterious effects in host cells and tissues. Such inappropriate TLR response has been attributed to the development and progression of multiple diseases such as cancer, autoimmune, and inflammatory diseases. In this review, we discuss the emerging role of TLRs in the pathogenesis of inflammatory diseases and how targeting of TLRs offers a promising therapeutic strategy for the prevention and treatment of various inflammatory diseases. Additionally, we highlight a number of TLR-targeting agents that are in the developmental stage or in clinical trials.

Inhibitory effect of G2013 molecule as a novel immunomodulatory agent, on miR-155 gene expression in HEK-Blue hTLR4 cell line

Lack of regulation of microRNAs (miRNAs) expression has been observed in some autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus. G2013, as a novel non-steroidal anti-inflammatory drug (NSAID) with the immunomodulatory property, has been shown the positive effects in multiple sclerosis and anti-ageing experimental models. This research aimed to study the inhibitory effect of G2013 on miR-155 gene expression using HEK-Blue hTLR4 and Null2 cell lines. Total RNA was extracted from the treated and control cells. cDNA was made for miRNA and expression levels of miR-155 were detected by quantitative Real-time PCR using a specific primer together with U6 as the internal reference gene. A non-significant reduction was observed in the gene expression level of miR-155 in the HEK-Blue hTLR4 and Null2 cell lines under the influence of a low dose of G2013. In contrast, adding lipopolysaccharide (LPS) to the mentioned cells led to a significant increase in miR-155 expression, whereas addition of LPS four hours after exposing the cells with G2013 could not increase the expression level of this miRNA ( P < 0.05). Collectively, this research showed that G2013, as a novel NSAID with immunomodulatory property is able to significantly decrease the gene expression of miR-155 following stimulation by LPS.

Activation of Toll-Like Receptors 2 by High-Mobility Group Box 1 in Monocytes from Patients with Ischemic Stroke

Background:

Stroke is a leading cause of death all around the world, and ischemic stroke is considered to be the most common stroke type. Toll-like receptors (TLRs) are important molecules for detection of both pathogen invasion and tissue damage. In this regard, the purpose of this study was to assess the expression level of TLR2 on monocytes in patients with ischemic stroke and to evaluate the expression change profile following high-mobility group box 1 (HMGB1) stimulation.

Methods:

A total of 30 patients with ischemic stroke were enrolled from November 2013 to September 2014. The real-time PCR and ELISA assays were applied to detect the concentrations of TLR2 mRNAs.

Results:

TLR2 expression was found to be increased in patients with ischemic stroke, as compared to the healthy control group (P<0.001). Also, anti-TLR2 antibodies were able to decrease the expression levels of IL-17, IL-6 and IL-33. This result implies that the enhanced TLR2 pathway and Th17 cell polarization may be due to HMGB1 stimulation in ischemic stroke.

Conclusion:

Further clinical studies are needed for development of a new treatment strategy to inhibit the HMGB1 pathway, thus preventing the inflammation in ischemic stroke patients.

Role of toll-like receptors in multiple myeloma and recent advances

Multiple myeloma (MM) is a hematologic malignancy characterized as an abnormal proliferation and invasion of plasma cells into the bone marrow. Toll-like receptors (ТLRs) connect the innate and adaptive immune responses and represent a significant and potentially linking element between inflammation and cancer. When TLRs bind to their ligands, they trigger two major signaling pathways such that both share overlapping downstream signals: one is a myeloid differentiation primary response 88 (MyD88)-dependent production and activation of nuclear factor-κB, whereas the other is a MyD88-independent production of type-I interferon. Whereas the MyD88 pathway results in proinflammatory cytokine production, the other pathway stimulates cell proliferation. Dysregulations of these pathways may eventually lead to abnormal cell proliferation and MM. Despite recent biomedical advances, MM continues to be an incurable disease. There are an increasing number of TLR-based therapeutic approaches currently being tested in a number of preclinical and clinical studies. We here attempt to outline in detail the currently available information on TLRs in various types of cancer.