The IRAK4 scaffold integrates TLR4-driven TRIF and MYD88 signaling pathways

Toll-like receptor agonists as cancer vaccine adjuvants

Cancer immunotherapy has emerged as a promising strategy to treat cancer patients. Among the wide range of immunological approaches, cancer vaccines have been investigated to activate and expand tumor-reactive T cells. However, most cancer vaccines have not shown significant clinical benefit as monotherapies. This is likely due to the antigen targets of vaccines, "self" proteins to which there is tolerance, as well as to the immunosuppressive tumor microenvironment. To help circumvent immune tolerance and generate effective immune responses, adjuvants for cancer vaccines are necessary. One representative adjuvant family is Toll-Like receptor (TLR) agonists, synthetic molecules that stimulate TLRs. TLRs are the largest family of pattern recognition receptors (PRRs) that serve as the sensors of pathogens or cellular damage. They recognize conserved foreign molecules from pathogens or internal molecules from cellular damage and propel innate immune responses. When used with vaccines, activation of TLRs signals an innate damage response that can facilitate the development of a strong adaptive immune response against the target antigen. The ability of TLR agonists to modulate innate immune responses has positioned them to serve as adjuvants for vaccines targeting infectious diseases and cancers. This review provides a summary of various TLRs, including their expression patterns, their functions in the immune system, as well as their ligands and synthetic molecules developed as TLR agonists. In addition, it presents a comprehensive overview of recent strategies employing different TLR agonists as adjuvants in cancer vaccine development, both in pre-clinical models and ongoing clinical trials.

Inhibiting the IRAK4/NF-κB/NLRP3 signaling pathway can reduce pyroptosis in hippocampal neurons and seizure episodes in epilepsy

BACKGROUND

Interleukin-1 receptor-associated kinase 4 (IRAK4) plays an important role in immune modulation in various central nervous system disorders. However, IRAK4 has not been reported in epilepsy models in animal and clinical studies, nor has its involvement in regulating pyroptosis in epilepsy.

METHOD

First, we performed transcriptome sequencing, quantitative real-time polymerase chain reaction, and western blot analysis on the hippocampal tissues of refractory epilepsy patients to measure the mRNA and protein levels of IRAK4 and pyroptosis-related proteins. Second, we successfully established a pentylenetetrazol (PTZ)-induced seizure mouse model. We conducted behavioral tests, electroencephalography, virus injection, and molecular biology experiments to investigate the role of IRAK4 in seizure activity regulation.

RESULTS

IRAK4 is upregulated in the hippocampus of epilepsy patients and PTZ-induced seizure model mice. IRAK4 expression is observed in the hilar neurons of PTZ-induced mice. Knocking down IRAK4 in PTZ-induced mice downregulated pyroptosis-related protein expression and alleviated seizure activity. Overexpressing IRAK4 in naive mice upregulated pyroptosis-related protein expression and increased PTZ-induced abnormal neuronal discharges. IRAK4 and NF-κB were found to bind to each other in patient hippocampal tissue samples. Pyrrolidine dithiocarbamate reversed the pyroptosis-related protein expression increase caused by PTZ. PF-06650833 alleviated seizure activity and inhibited pyroptosis in PTZ-induced seizure mice.

CONCLUSION

IRAK4 plays a key role in the pathological process of epilepsy, and its potential mechanism may be related to pyroptosis mediated by the NF-κB/NLRP3 signaling pathway. PF-06650833 has potential as a therapeutic agent for alleviating epilepsy.

Molecular definition of the endogenous Toll-like receptor signalling pathways

Innate immune pattern recognition receptors, such as the Toll-like receptors (TLRs), are key mediators of the immune response to infection and central to our understanding of health and disease1. After microbial detection, these receptors activate inflammatory signal transduction pathways that involve IκB kinases, mitogen-activated protein kinases, ubiquitin ligases and other adaptor proteins. The mechanisms that connect the proteins in the TLR pathways are poorly defined. To delineate TLR pathway activities, we engineered macrophages to enable microscopy and proteomic analysis of the endogenous myddosome constituent MyD88. We found that myddosomes form transient contacts with activated TLRs and that TLR-free myddosomes are dynamic in size, number and composition over the course of 24 h. Analysis using super-resolution microscopy revealed that, within most myddosomes, MyD88 forms barrel-like structures that function as scaffolds for effector protein recruitment. Proteomic analysis demonstrated that myddosomes contain proteins that act at all stages and regulate all effector responses of the TLR pathways, and genetic analysis defined the epistatic relationship between these effector modules. Myddosome assembly was evident in cells infected with Listeria monocytogenes, but these bacteria evaded myddosome assembly and TLR signalling during cell-to-cell spread. On the basis of these findings, we propose that the entire TLR signalling pathway is executed from within the myddosome.

Tumor-associated characteristics and immune dysregulation in nasopharyngeal carcinoma under the regulation of m7G-related tumor microenvironment cells

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a type of malignant tumor with high morbidity. Aberrant levels of N7-methylguanosine (m7G) are closely associated with tumor progression. However, the characteristics of the tumor microenvironment (TME) in NPC associated with m7G modification remain unclear.

METHODS

A total of 68,795 single cells from single-cell RNA sequencing data derived from 11 NPC tumor samples and 3 nasopharyngeal lymphatic hyperplasia (NLH) samples were clustered using a nonnegative matrix factorization algorithm according to 61 m7G RNA modification regulators.

RESULTS

The m7G regulators were found differential expression in the TME cells of NPC, and most m7G-related immune cell clusters in NPC tissues had a higher abundance compared to non-NPC tissues. Specifically, m7G scores in the CD4+ and CD8+ T cell clusters were significantly lower in NPC than in NLH. T cell clusters differentially expressed immune co-stimulators and co-inhibitors. Macrophage clusters differentially expressed EIF4A1, and high EIF4A1 expression was associated with poor survival in patients with head and neck squamous carcinoma. EIF4A1 was upregulated in NPC tissues compared to the non-NPC tissues and mainly expressed in CD86+ macrophages. Moreover, B cell clusters exhibited tumor biological characteristics under the regulation of m7G-related genes in NPC. The fibroblast clusters interacted with the above immune cell clusters and enriched tumor biological pathways, such as FGER2 signaling pathway. Importantly, there were correlations and interactions through various ligand-receptor links among epithelial cells and m7G-related TME cell clusters.

CONCLUSION

Our study revealed tumor-associated characteristics and immune dysregulation in the NPC microenvironment under the regulation of m7G-related TME cells. These results demonstrated the underlying regulatory roles of m7G in NPC.

Biological role of mitochondrial TLR4-mediated NF-κB signaling pathway in central nervous system injury

Previous studies suggested that central nervous system injury is often accompanied by the activation of Toll-like receptor 4/NF-κB pathway, which leads to the upregulation of proapoptotic gene expression, causes mitochondrial oxidative stress, and further aggravates the inflammatory response to induce cell apoptosis. Subsequent studies have shown that NF-κB and IκBα can directly act on mitochondria. Therefore, elucidation of the specific mechanisms of NF-κB and IκBα in mitochondria may help to discover new therapeutic targets for central nervous system injury. Recent studies have suggested that NF-κB (especially RelA) in mitochondria can inhibit mitochondrial respiration or DNA expression, leading to mitochondrial dysfunction. IκBα silencing will cause reactive oxygen species storm and initiate the mitochondrial apoptosis pathway. Other research results suggest that RelA can regulate mitochondrial respiration and energy metabolism balance by interacting with p53 and STAT3, thus initiating the mitochondrial protection mechanism. IκBα can also inhibit apoptosis in mitochondria by interacting with VDAC1 and other molecules. Regulating the biological role of NF-κB signaling pathway in mitochondria by targeting key proteins such as p53, STAT3, and VDAC1 may help maintain the balance of mitochondrial respiration and energy metabolism, thereby protecting nerve cells and reducing inflammatory storms and death caused by ischemia and hypoxia.

Discovery of LC-MI-3: A Potent and Orally Bioavailable Degrader of Interleukin-1 Receptor-Associated Kinase 4 for the Treatment of Inflammatory Diseases

Interleukin-1 receptor-associated kinase 4 (IRAK4) is a promising therapeutic target in inflammation-related diseases. However, the inhibition of IRAK4 kinase activity may lead to moderate anti-inflammatory efficacy owing to the dual role of IRAK4 as an active kinase and a scaffolding protein. Herein, we report the design, synthesis, and biological evaluation of an efficient and selective IRAK4 proteolysis-targeting chimeric molecule that eliminates IRAK4 scaffolding functions. The most potent compound, LC-MI-3, effectively degraded cellular IRAK4, with a half-maximal degradation concentration of 47.3 nM. LC-MI-3 effectively inhibited the activation of downstream nuclear factor-κB signaling and exerted more potent pharmacological effects than traditional kinase inhibitors. Furthermore, LC-MI-3 exerted significant therapeutic effects in lipopolysaccharide- and Escherichia coli-induced acute and chronic inflammatory skin models compared with kinase inhibitors in vivo. Therefore, LC-MI-3 is a candidate IRAK4 degrader in alternative targeting strategies and advanced drug development.

The Tick Saliva Peptide HIDfsin2 TLR4-Dependently Inhibits the Tick-Borne Severe Fever with Thrombocytopenia Syndrome Virus in Mouse Macrophages

Ticks transmit a variety of pathogens to their hosts by feeding on blood. The interactions and struggle between tick pathogens and hosts have evolved bilaterally. The components of tick saliva can directly or indirectly trigger host biological responses in a manner that promotes pathogen transmission; however, host cells continuously develop strategies to combat pathogen infection and transmission. Moreover, it is still unknown how host cells develop their defense strategies against tick-borne viruses during tick sucking. Here, we found that the tick saliva peptide HIDfsin2 enhanced the antiviral innate immunity of mouse macrophages by activating the Toll-like receptor 4 (TLR4) signaling pathway, thereby restricting tick-borne severe fever with thrombocytopenia syndrome virus (SFTSV) replication. HIDfsin2 was identified to interact with lipopolysaccharide (LPS), a ligand of TLR4, and then depolymerize LPS micelles into smaller particles, effectively enhancing the activation of the nuclear factor kappa-B (NF-κB) and type I interferon (IFN-I) signaling pathways, which are downstream of TLR4. Expectedly, TLR4 knockout completely eliminated the promotion effect of HIDfsin2 on NF-κB and type I interferon activation. Moreover, HIDfsin2 enhanced SFTSV replication in TLR4-knockout mouse macrophages, which is consistent with our recent report that HIDfsin2 hijacked p38 mitogen-activated protein kinase (MAPK) to promote the replication of tick-borne SFTSV in A549 and Huh7 cells (human cell lines) with low expression of TLR4. Together, these results provide new insights into the innate immune mechanism of host cells following tick bites. Our study also shows a rare molecular event relating to the mutual antagonism between tick-borne SFTSV and host cells mediated by the tick saliva peptide HIDfsin2 at the tick-host-virus interface.

The potential of short-chain fatty acid epigenetic regulation in chronic low-grade inflammation and obesity

Obesity and chronic low-grade inflammation, often occurring together, significantly contribute to severe metabolic and inflammatory conditions like type 2 diabetes (T2D), cardiovascular disease (CVD), and cancer. A key player is elevated levels of gut dysbiosis-associated lipopolysaccharide (LPS), which disrupts metabolic and immune signaling leading to metabolic endotoxemia, while short-chain fatty acids (SCFAs) beneficially regulate these processes during homeostasis. SCFAs not only safeguard the gut barrier but also exert metabolic and immunomodulatory effects via G protein-coupled receptor binding and epigenetic regulation. SCFAs are emerging as potential agents to counteract dysbiosis-induced epigenetic changes, specifically targeting metabolic and inflammatory genes through DNA methylation, histone acetylation, microRNAs (miRNAs), and long non-coding RNAs (lncRNAs). To assess whether SCFAs can effectively interrupt the detrimental cascade of obesity and inflammation, this review aims to provide a comprehensive overview of the current evidence for their clinical application. The review emphasizes factors influencing SCFA production, the intricate connections between metabolism, the immune system, and the gut microbiome, and the epigenetic mechanisms regulated by SCFAs that impact metabolism and the immune system.

The IRAK1/IRF5 axis initiates IL-12 response by dendritic cells and control of Toxoplasma gondii infection

Activation of endosomal Toll-like receptor (TLR) 7, TLR9, and TLR11/12 is a key event in the resistance against the parasite Toxoplasma gondii. Endosomal TLR engagement leads to expression of interleukin (IL)-12 via the myddosome, a protein complex containing MyD88 and IL-1 receptor-associated kinase (IRAK) 4 in addition to IRAK1 or IRAK2. In murine macrophages, IRAK2 is essential for IL-12 production via endosomal TLRs but, surprisingly, Irak2-/- mice are only slightly susceptible to T. gondii infection, similar to Irak1-/- mice. Here, we report that upon T. gondii infection IL-12 production by different cell populations requires either IRAK1 or IRAK2, with conventional dendritic cells (DCs) requiring IRAK1 and monocyte-derived DCs (MO-DCs) requiring IRAK2. In both populations, we identify interferon regulatory factor 5 as the main transcription factor driving the myddosome-dependent IL-12 production during T. gondii infection. Consistent with a redundant role of DCs and MO-DCs, mutations that affect IL-12 production in both cell populations show high susceptibility to infection in vivo.

Exploring TLR signaling pathways as promising targets in cervical cancer: The road less traveled

Cervical cancer is the leading cause of cancer-related deaths for women globally. Despite notable advancements in prevention and treatment, the identification of novel therapeutic targets remains crucial for cervical cancer. Toll-like receptors (TLRs) play an essential role in innate immunity as pattern-recognition receptors. There are several types of pathogen-associated molecular patterns (PAMPs), including those present in cervical cancer cells, which have the ability to activate toll-like receptors (TLRs). Recent studies have revealed dysregulated toll-like receptor (TLR) signaling pathways in cervical cancer, leading to the production of inflammatory cytokines and chemokines that can facilitate tumor growth and metastasis. Consequently, TLRs hold significant promise as potential targets for innovative therapeutic agents against cervical cancer. This book chapter explores the role of TLR signaling pathways in cervical cancer, highlighting their potential for targeted therapy while addressing challenges such as tumor heterogeneity and off-target effects. Despite these obstacles, targeting TLR signaling pathways presents a promising approach for the development of novel and effective treatments for cervical cancer.

Targeting fusion proteins of the interleukin family: A promising new strategy for the treatment of autoinflammatory diseases

As a means of communication between immune cells and non-immune cells, Interleukins (ILs) has the main functions of stimulating the proliferation and activation of inflammatory immune cells such as dendritic cells and lymphocytes, promote the development of blood cells and so on. However, dysregulation of ILs expression is a major feature of autoinflammatory diseases. The drugs targeting ILs or IL-like biologics have played an important role in the clinical treatment of autoinflammatory diseases. Nevertheless, the widespread use of IL products may result in significant off-target adverse reactions. Thus, there is a clear need to develop next-generation ILs products in the biomedical field. Fusion proteins are proteins created through the joining of two or more genes that originally coded for separate proteins. Over the last 30 years, there has been increasing interest in the use of fusion protein technology for developing anti-inflammatory drugs. In comparison to single-target drugs, fusion proteins, as multiple targets drugs, have the ability to enhance the cytokine therapeutic index, resulting in improved efficacy over classical drugs. The strategy of preparing ILs or their receptors as fusion proteins is increasingly used in the treatment of autoimmune and chronic inflammation. This review focuses on the efficacy of several fusion protein drugs developed with ILs or their receptors in the treatment of autoinflammatory diseases, in order to illustrate the prospects of this new technology as an anti-inflammatory drug development protocol in the future.

Gastric protective effect of Alpinia officinarum flavonoids: mediating TLR4/NF-κB and TRPV1 signalling pathways and gastric mucosal healing

CONTEXT

Our previous studies have found that total flavonoid of Alpinia officinarum Hance (Zingiberaceae) (F.AOH) had protective effects on gastric ulcer (GU).

OBJECTIVE

To investigate the protective mechanism of F.AOH on acetic acid-induced chronic GUs in rats and ethanol-induced GES-1 cells damage.

MATERIALS AND METHODS

In vivo: Gastric damage was induced in SD rats by administering acetic acid after oral treatment with F-AOH at 54, 27 and 13.5 mg/kg (2 weeks of continuous gavage). After a comprehensive evaluation of rats' serum and gastric tissue-related indicators, gene transcriptome sequencing, qPCR and Western blotting were used to investigate the mechanism further. In vivo: GES-1 cells were incubated with F-AOH (8, 4 and 2 μg/mL) for 16 h and treated with 7% ethanol for 4 h. Transwell and flow cytometry were employed to detect migration and apoptosis of cells.

RESULTS

F.AOH effectively reduced the area of GUs in rats (from 11.2 ± 1.89 to 2.19 ± 0.95), reversing ethanol-induced cells apoptosis (from 23 ± 1.3 to 8.11 ± 0.93%). It also inhibited the expression of endothelin-1 (ET-1) and iNOS proteins, decreasing the levels of TNF-α IL-6 in serum, improving oxidative stress levels and increasing the expression of Bcl-2/Bax dimer genes. In addition, 4005 differentially expressed genes between the acetic acid model and the drug groups. Through experimental verification, F.AOH can inhibit the activation of TLR4/NF-κB signalling pathway and TRPV1 receptor.

CONCLUSIONS

F.AOH, as an effective gastric protective plant component, had potential therapeutic value in anti-inflammatory pain and antioxidative stress gastrointestinal diseases.

Innate Immunity and CKD: Is There a Significant Association?

Chronic kidney disease (CKD) constitutes a worldwide epidemic, affecting approximately 10% of the global population, and imposes significant medical, psychological, and financial burdens on society. Individuals with CKD often face elevated morbidity and mortality rates, mainly due to premature cardiovascular events. Chronic inflammation has been shown to play a significant role in the progression of CKD, as well as in the acceleration of CKD-related complications, including atherosclerosis, cardiovascular disease (CVD), protein-energy wasting, and the aging process. Over the past two decades, a substantial body of evidence has emerged, identifying chronic inflammation as a central element of the uremic phenotype. Chronic inflammation has been shown to play a significant role in the progression of CKD, as well as in the acceleration of CKD-related complications in dialysis patients, including atherosclerosis, CVD, protein-energy wasting, and the aging process. Remarkably, chronic inflammation also impacts patients with CKD who have not yet required renal replacement therapy. While extensive research has been conducted on the involvement of both the adaptive and innate immune systems in the pathogenesis of CKD-related complications, this wealth of data has not yet yielded well-established, effective treatments to counteract this ongoing pathological process. In the following review, we will examine the established components of the innate immune system known to be activated in CKD and provide an overview of the current therapeutic approaches designed to mitigate CKD-related chronic inflammation.

Tolerogenic dendritic cells and TLR4/IRAK4/NF-κB signaling pathway in allergic rhinitis

Dendritic cells (DCs), central participants in the allergic immune response, can capture and present allergens leading to allergic inflammation in the immunopathogenesis of allergic rhinitis (AR). In addition to initiating antigen-specific immune responses, DCs induce tolerance and modulate immune homeostasis. As a special type of DCs, tolerogenic DCs (tolDCs) achieve immune tolerance mainly by suppressing effector T cell responses and inducing regulatory T cells (Tregs). TolDCs suppress allergic inflammation by modulating immune tolerance, thereby reducing symptoms of AR. Activation of the TLR4/IRAK4/NF-κB signaling pathway contributes to the release of inflammatory cytokines, and inhibitors of this signaling pathway induce the production of tolDCs to alleviate allergic inflammatory responses. This review focuses on the relationship between tolDCs and TLR4/IRAK4/NF-κB signaling pathway with AR.

The recent advance of Interleukin-1 receptor associated kinase 4 inhibitors for the treatment of inflammation and related diseases

The interleukin-1 receptor associated kinase 4 (IRAK-4) is a member of serine-threonine kinase family, which plays an important role in the regulation of interleukin-1 receptors (IL-1R) and Toll-like receptors (TLRs) related signaling pathways. At present, the IRAK-4 mediated inflammation and related signaling pathways contribute to inflammation, which are also responsible for other autoimmune diseases and drug resistance in cancers. Therefore, targeting IRAK-4 to develop single-target, multi-target inhibitors and proteolysis-targeting chimera (PROTAC) degraders is an important direction for the treatment of inflammation and related diseases. Moreover, insight into the mechanism of action and structural optimization of the reported IRAK-4 inhibitors will provide the new direction to enrich the clinical therapies for inflammation and related diseases. In this comprehensive review, we introduced the recent advance of IRAK-4 inhibitors and degraders with regards to structural optimization, mechanism of action and clinical application that would be helpful for the development of more potent chemical entities against IRAK-4.

IRAK4 inhibition: an effective strategy for immunomodulating peri-implant osseointegration via reciprocally-shifted polarization in the monocyte-macrophage lineage cells

BACKGROUND

The biomaterial integration depends on its interaction with the host immune system. Monocyte-macrophage lineage cells are immediately recruited to the implant site, polarized into different phenotypes, and fused into multinucleated cells, thus playing roles in tissue regeneration. IL-1R-associated kinase 4 (IRAK4) inhibition was reported to antagonize inflammatory osteolysis and regulate osteoclasts and foreign body giant cells (FBGCs), which may be a potential target in implant osseointegration.

METHODS

In in-vitro experiments, we established simulated physiological and inflammatory circumstances in which bone-marrow-derived macrophages were cultured on sand-blasted and acid-etched (SLA) titanium surfaces to evaluate the induced macrophage polarization, multinucleated cells formation, and biological behaviors in the presence or absence of IRAK4i. Then, bone marrow stromal stem cells (BMSCs) were cultured in the conditioned media collected from the aforementioned induced osteoclasts or FBGCs cultures to clarify the indirect coupling effect of multinucleated cells on BMSCs. We further established a rat implantation model, which integrates IRAK4i treatment with implant placement, to verify the positive effect of IRAK4 inhibition on the macrophage polarization, osteoclast differentiation, and ultimately the early peri-implant osseointegration in vivo.

RESULTS

Under inflammatory conditions, by transforming the monocyte-macrophage lineage cells from M1 to M2, IRAK4i treatment could down-regulate the formation and activity of osteoclast and relieve the inhibition of FBGC generation, thus promoting osteogenic differentiation in BMSCs and improve the osseointegration.

CONCLUSION

This study may improve our understanding of the function of multinucleated cells and offer IRAK4i as a therapeutic strategy to improve early implant osseointegration and help to eliminate the initial implant failure.

MyD88 and not TRIF knockout is sufficient to abolish LPS-induced inflammatory responses in bone-derived macrophages

Macrophages play an important role in the response to infection and/or repair of injury in tissues. To examine the NF-κB pathway in response to an inflammatory stimulus, we used wild-type bone-marrow-derived macrophages (BMDMs) or BMDMs with knockout (KO) of myeloid differentiation primary response 88 (MyD88) and/or Toll/interleukin-1 receptor domain-containing adapter-inducing interferon-β (TRIF) via CRISPR/Cas9. Following treatment of BMDMs with lipopolysaccharide (LPS) to induce an inflammatory response, translational signalling of NF-κB was quantified via immunoblot and cytokines were measured. Our findings reveal that MyD88 KO, but not TRIF KO, decreased LPS-induced NF-κB signalling, and 10% expression of basal MyD88 expression was sufficient to partially rescue the abolished inflammatory cytokine secretion observed upon MyD88 KO.

A small molecule potent IRAK4 inhibitor abrogates lipopolysaccharide-induced macrophage inflammation in-vitro and in-vivo

Increasing evidence supports vanillin and its analogs as potent toll-like receptor signaling inhibitors that strongly attenuate inflammation, though, the underlying molecular mechanism remains elusive. Here, we report that vanillin inhibits lipopolysaccharide (LPS)-induced toll-like receptor 4 activation in macrophages by targeting the myeloid differentiation primary-response gene 88 (MyD88)-dependent pathway through direct interaction and suppression of interleukin-1 receptor-associated kinase 4 (IRAK4) activity. Moreover, incubation of vanillin in cells expressing constitutively active forms of different toll-like receptor 4 signaling molecules revealed that vanillin could only able to block the ligand-independent constitutively activated IRAK4/1 or its upstream molecules-associated NF-κB activation and NF-κB transactivation along with the expression of various proinflammatory cytokines. A significant inhibition of LPS-induced IRAK4/MyD88, IRAK4/IRAK1, and IRAK1/TRAF6 association was evinced in response to vanillin treatment. Furthermore, mutations at Tyr262 and Asp329 residues in IRAK4 or modifications of 3-OMe and 4-OH side groups in vanillin, significantly reduced IRAK4 activity and vanillin function, respectively. Mice pretreated with vanillin followed by LPS challenge markedly impaired LPS-induced IRAK4 activation and inflammation in peritoneal macrophages. Thus, the present study posits vanillin as a novel and potent IRAK4 inhibitor and thus providing an opportunity for its therapeutic application in managing various inflammatory diseases.

Manganese potentiates lipopolysaccharide-induced innate immune responses and septic shock

Divalent metal ions such as magnesium (Mg²⁺), manganese (Mn²⁺), and zinc (Zn²⁺) play important roles in regulating innate immune responses. Lipopolysaccharide stimulation led to increased intracellular Mn and Zn in macrophages. However, the effect of those metal ions in regulating lipopolysaccharide-induced innate immune responses remains unclear. Here, we uncovered that both Mn²⁺ and Zn²⁺ have immunostimulatory effects, which could potentiate the lipopolysaccharide-induced expression of interferon-stimulated genes (ISGs), cytokines and pro-inflammatory genes in a dose-dependent manner. Enhancement of lipopolysaccharide-induced innate immune gene expression by Mn²⁺ varies between 10 % and 900 %. Conversely, the chelating of Mn²⁺ almost totally diminished Mn²⁺-enhanced lipopolysaccharide-induced gene expression. In addition, Mn²⁺ exerted its ability to potentiate LPS-induced innate immune gene expression regardless of slight pH changes. Importantly, we found that Mn²⁺ potentiates lipopolysaccharide-induced immune responses independent of TLR4 but partially relies on cGAS-STING pathway. Further in vivo study showed that colloidal Mn²⁺ salt (Mn jelly [MnJ]) pretreatment exacerbated lipopolysaccharide-induced septic shock and mice death. In conclusion, we demonstrated that Mn²⁺ plays an essential role in boosting lipopolysaccharide-induced innate immune responses. These findings greatly expand the current understanding of the immunomodulatory potential of divalent metal Mn²⁺ and may provide a potential therapeutic target to prevent excessive immune responses.

Regulation of innate immune signaling by IRAK proteins

The Toll-like receptors (TLRs) and interleukin-1 receptors (IL-1R) families are of paramount importance in coordinating the early immune response to pathogens. Signaling via most TLRs and IL-1Rs is mediated by the protein myeloid differentiation primary-response protein 88 (MyD88). This signaling adaptor forms the scaffold of the myddosome, a molecular platform that employs IL-1R-associated kinase (IRAK) proteins as main players for transducing signals. These kinases are essential in controlling gene transcription by regulating myddosome assembly, stability, activity and disassembly. Additionally, IRAKs play key roles in other biologically relevant responses such as inflammasome formation and immunometabolism. Here, we summarize some of the key aspects of IRAK biology in innate immunity.

Endotoxemia and Gastrointestinal Cancers: Insight into the Mechanisms Underlying a Dangerous Relationship

Lipopolysaccharide (LPS), also known as endotoxin, is a component of the membrane of gram-negative bacteria and a well-recognized marker of sepsis. In case of disruption of the intestinal barrier, as occurs with unhealthy diets, alcohol consumption, or during chronic diseases, the microbiota residing in the gastrointestinal tract becomes a crucial factor in amplifying the systemic inflammatory response. Indeed, the translocation of LPS into the bloodstream and its interaction with toll-like receptors (TLRs) triggers molecular pathways involved in cytokine release and immune dysregulation. This is a critical step in the exacerbation of many diseases, including metabolic disorders and cancer. Indeed, the role of LPS in cancer development is widely recognized, and examples include gastric tumor related to Helicobacter pylori infection and hepatocellular carcinoma, both of which are preceded by a prolonged inflammatory injury; in addition, the risk of recurrence and development of metastasis appears to be associated with endotoxemia. Here, we review the mechanisms that link the promotion and progression of tumorigenesis with endotoxemia, and the possible therapeutic interventions that can be deployed to counteract these events.

Inhibition of Mogroside IIIE on isoproterenol-induced myocardial fibrosis through the TLR4/MyD88/NF-κB signaling pathway

Objectives

To investigate the effect of mogroside IIIE (MGIIIE) on isoproterenol (ISO)-induced myocardial fibrosis and explore its possible mechanisms.

Materials and Methods

Forty C57BL/6 male mice (6-8 weeks) were randomly divided into a control group (n=10), model group (n=10), low MGIIIE dose group (n=10), and high MGIIIE dose group (n=10). Myocardial fibrosis was established by subcutaneous ISO injection. After 2 weeks of continuous gastric administration of MGIIIE, the cardiac structure was evaluated by echocardiography. Myocardial inflammation and fibrosis were evaluated by histology examination. Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), p-IκBα, p-NF-κB, transforming growth factor β1 (TGF-β1), and α-smooth muscle actin (α-SMA) expression were detected by western blot. Inflammatory cytokines (IL-1β, IL-6, and TNF-α) in the serum were examined by ELISA. In the in vitro study, Ang II (1 μmol/l) was used to stimulate the fibroblasts, then inflammation and fibrosis index were detected.

Results

MGIIIE inhibited inflammation and fibrosis and down-regulated TLR4, MyD88, TGF-β1, and α-SMA expression in the myocardium. In the in vitro study, MGIIIE ameliorates the deposition of Col Ш and Col I and decreases the release of inflammatory cytokines. MGIIIE increased p-IκBα and reduced p-NF-κB expression both in vivo and in vitro.

Conclusion

MGIIIE plays a role in anti-myocardial fibrosis, by inhibiting TLR4/MyD88/NF-κB signaling expression, and decreasing inflammatory cytokine release. MGIIIE may represent a novel therapeutic strategy for treating cardiac fibrosis.