MyD88: a critical adaptor protein in innate immunity signal transduction

A highly selective inhibitor of interleukin-1 receptor-associated kinases 1/4 (IRAK-1/4) delineates the distinct signaling roles of IRAK-1/4 and the TAK1 kinase

Interleukin-1 receptor-associated kinase-1 (IRAK-1) and IRAK-4, as well as transforming growth factor β-activated kinase 1 (TAK1), are protein kinases essential for transducing inflammatory signals from interleukin receptors. IRAK family proteins and TAK1 have high sequence identity within the ATP-binding pocket, limiting the development of highly selective IRAK-1/4 or TAK1 inhibitors. Beyond kinase activity, IRAKs and TAK1 act as molecular scaffolds along with other signaling proteins, complicating the interpretation of experiments involving knockin or knockout approaches. In contrast, pharmacological manipulation offers the promise of targeting catalysis-mediated signaling without grossly disrupting the cellular architecture. Recently, we reported the discovery of takinib, a potent and highly selective TAK1 inhibitor that has only marginal activity against IRAK-4. On the basis of the TAK1-takinib complex structure and the structure of IRAK-1/4, here we defined critical contact sites of the takinib scaffold within the nucleotide-binding sites of each respective kinase. Kinase activity testing of takinib analogs against IRAK-4 identified a highly potent IRAK-4 inhibitor (HS-243). In a kinome-wide screen of 468 protein kinases, HS-243 had exquisite selectivity toward both IRAK-1 (IC50 = 24 nm) and IRAK-4 (IC50 = 20 nm), with only minimal TAK1-inhibiting activity (IC50 = 0.5 μm). Using HS-243 and takinib, we evaluated the consequences of cytokine/chemokine responses after selective inhibition of IRAK-1/4 or TAK1 in response to lipopolysaccharide challenge in human rheumatoid arthritis fibroblast-like synoviocytes. Our results indicate that HS-243 specifically inhibits intracellular IRAKs without TAK1 inhibition and that these kinases have distinct, nonredundant signaling roles.

Tissue Resident CCR2- and CCR2+ Cardiac Macrophages Differentially Orchestrate Monocyte Recruitment and Fate Specification Following Myocardial Injury

RATIONALE

Recent advancements have brought to light the origins, complexity, and functions of tissue-resident macrophages. However, in the context of tissue injury or disease, large numbers of monocytes infiltrate the heart and are thought to contribute to adverse remodeling and heart failure pathogenesis. Little is understood about the diversity of monocytes and monocyte-derived macrophages recruited to the heart after myocardial injury, including the mechanisms that regulate monocyte recruitment and fate specification.

OBJECTIVE

We sought to test the hypothesis that distinct subsets of tissue-resident CCR2- (C-C chemokine receptor 2) and CCR2+ macrophages orchestrate monocyte recruitment and fate specification after myocardial injury.

METHODS AND RESULTS

We reveal that in numerous mouse models of cardiomyocyte cell death (permanent myocardial infarction, reperfused myocardial infarction, and diphtheria toxin cardiomyocyte ablation), there is a shift in macrophage ontogeny whereby tissue-resident macrophages are predominately replaced by infiltrating monocytes and monocyte-derived macrophages. Using syngeneic cardiac transplantation to model ischemia-reperfusion injury and distinguish tissue-resident from recruited cell populations in combination with intravital 2-photon microscopy, we demonstrate that monocyte recruitment is differentially orchestrated by distinct subsets of tissue-resident cardiac macrophages. Tissue-resident CCR2+ macrophages promote monocyte recruitment through an MYD88 (myeloid differentiation primary response 88)-dependent mechanism that results in release of MCPs (monocyte chemoattractant proteins) and monocyte mobilization. In contrast, tissue-resident CCR2- macrophages inhibit monocyte recruitment. Using CD (cluster of differentiation) 169-DTR (diphtheria toxin receptor) and CCR2-DTR mice, we further show that selective depletion of either tissue-resident CCR2- or CCR2+ macrophages before myocardial infarction results in divergent effects on left ventricular function, myocardial remodeling, and monocyte recruitment. Finally, using single-cell RNA sequencing, we show that tissue-resident cardiac macrophages differentially instruct monocyte fate specification.

CONCLUSIONS

Collectively, these observations establish the mechanistic basis by which monocytes are initially recruited to the injured heart and provide new insights into the heterogeneity of monocyte-derived macrophages.

The role of microbiota in the development of colorectal cancer

Colorectal cancer is the third largest cancer in worldwide and has been proven to be closely related to the intestinal microbiota. Many reports and clinical studies have shown that intestinal microbial behavior may lead to pathological changes in the host intestines. The changes can be divided into epigenetic changes and carcinogenic changes at the gene level, which ultimately promote the production and development of colorectal cancer. This article reviews the pathways of microbial signaling in the intestinal epithelial barrier, the role of microbiota in inflammatory colorectal tumors, and typical microbial carcinogenesis. Finally, by gaining a deeper understanding of the intestinal microbiota, we hope to achieve the goal of treating colorectal cancer using current microbiota technologies, such as fecal microbiological transplantation.

Long-Term Pantethine Treatment Counteracts Pathologic Gene Dysregulation and Decreases Alzheimer's Disease Pathogenesis in a Transgenic Mouse Model

The low-molecular weight thiol pantethine, known as a hypolipidemic and hypocholesterolemic agent, is the major precursor of co-enzyme A. We have previously shown that pantethine treatment reduces amyloid-β (Aβ)-induced IL-1β release and alleviates pathological metabolic changes in primary astrocyte cultures. These properties of pantethine prompted us to investigate its potential benefits in vivo in the 5XFAD (Tg) mouse model of Alzheimer's disease (AD).1.5-month-old Tg and wild-type (WT) male mice were submitted to intraperitoneal administration of pantethine or saline control solution for 5.5 months. The effects of such treatments were investigated by performing behavioral tests and evaluating astrogliosis, microgliosis, Αβ deposition, and whole genome expression arrays, using RNAs extracted from the mice hippocampi. We observed that long-term pantethine treatment significantly reduced glial reactivity and Αβ deposition, and abrogated behavioral alteration in Tg mice. Moreover, the transcriptomic profiles revealed that after pantethine treatment, the expression of genes differentially expressed in Tg mice, and in particular those known to be related to AD, were significantly alleviated. Most of the genes overexpressed in Tg compared to WT were involved in inflammation, complement activation, and phagocytosis and were found repressed upon pantethine treatment. In contrast, pantethine restored the expression of a significant number of genes involved in the regulation of Αβ processing and synaptic activities, which were downregulated in Tg mice. Altogether, our data support a beneficial role for long-term pantethine treatment in preserving CNS crucial functions altered by Aβ pathogenesis in Tg mice and highlight the potential efficiency of pantethine to alleviate AD pathology.

The intestinal microbiota programs diurnal rhythms in host metabolism through histone deacetylase 3

Circadian rhythmicity is a defining feature of mammalian metabolism that synchronizes metabolic processes to day-night light cycles. Here, we show that the intestinal microbiota programs diurnal metabolic rhythms in the mouse small intestine through histone deacetylase 3 (HDAC3). The microbiota induced expression of intestinal epithelial HDAC3, which was recruited rhythmically to chromatin, and produced synchronized diurnal oscillations in histone acetylation, metabolic gene expression, and nutrient uptake. HDAC3 also functioned noncanonically to coactivate estrogen-related receptor α, inducing microbiota-dependent rhythmic transcription of the lipid transporter gene Cd36 and promoting lipid absorption and diet-induced obesity. Our findings reveal that HDAC3 integrates microbial and circadian cues for regulation of diurnal metabolic rhythms and pinpoint a key mechanism by which the microbiota controls host metabolism.

Functional Characterization of Duck STING in IFN-β Induction and Anti-H9N2 Avian Influenza Viruses Infections

The stimulator of interferon genes (STING) protein has been shown to play a pivotal role in response to both cytosolic RNA and dsDNA to elicit interferon (IFN) production in mammals. However, the role of duck STING (DuSTING) in antiviral innate immunity, especially in anti-RNA virus infection, has yet to be elucidated. In this study, the function of DuSTING in IFN induction and its role in anti-RNA virus infections were studied. DuSTING was amplified via reverse transcription-polymerase chain reaction (RT-PCR) from Pekin duck, showing that its cDNA sequence contains an open reading frame (ORF) of 1,149 bp and encodes 382 amino acids (aa). Sequence alignment showed that DuSTING protein shares 71.1, 43.4, and 33.3% identity with chickens, humans, and zebra fish, respectively. Overexpression of DuSTING in duck embryo fibroblasts (DEFs) strongly activated IFN-β promotor activity. Deletion mutant analysis revealed that the first 42 aa containing the first transmembrane (TM) domains and the last 32 aa containing a part of the C-terminal tail (CTT) are essential for its IFN-β activation. In vitro experiments showed that the mRNA levels of DuSTING and IFNs were all upregulated when the DEFs were infected with H9N2 avian influenza virus (AIV) SH010, while overexpression of DuSTING inhibited the replication of this virus. In vivo studies showed that DuSTING mRNA was widely expressed in different tissues, and was up-regulated in the spleen and lung of ducks challenged with SH010. In conclusion, our results indicate that DuSTING is an essential IFN mediator and plays a role in anti-RNA virus innate immunity.

UBL4A Augments Innate Immunity by Promoting the K63-Linked Ubiquitination of TRAF6

Human UBL4A/GdX, encoding an ubiquitin-like protein, was shown in this study to be upregulated by viral infection and IFN stimulation. Then the functions of UBL4A in antiviral immune response were characterized. Overexpression of UBL4A promoted RNA virus-induced ISRE or IFN-β or NF-κB activation, leading to enhanced type I IFN transcription and reduced virus replication. Consistently, knockdown of UBL4A resulted in reduced type I IFN transcription and enhanced virus replication. Additionally, overexpression of UBL4A promoted virus-induced phosphorylation of TBK1, IRF3, and IKKα/β. Knockdown of UBL4A inhibited virus-induced phosphorylation of TBK1, IRF3, and IKKα/β. Coimmunoprecipitation showed that UBL4A interacted with TRAF6, and this interaction was enhanced upon viral infection. Ubiquitination assays showed that UBL4A promoted the K63-linked ubiquitination of TRAF6. Therefore, we reveal a novel positive feedback regulation of UBL4A in innate immune response combating virus invasion by enhancing the K63-linked ubiquitination of TRAF6.

The Plasmid-Encoded pGP3 Promotes Chlamydia Evasion of Acidic Barriers in Both Stomach and Vagina

Although Chlamydia trachomatis is a human genital tract pathogen, chlamydial organisms have frequently been detected in both vaginal and rectal swab samples of animals and humans. The plasmid-encoded pGP3, a genital tract virulence factor, is essential for Chlamydia muridarum to colonize the mouse gastrointestinal tract. However, intracolon inoculation to bypass the gastric barrier rescued the colonization ability of a pGP3-deficient C. muridarum mutant, suggesting that pGP3 is required for C. muridarum to reach but not to colonize the large intestine. The pGP3-deficient mutant was rapidly cleared in the stomach and was 100-fold more susceptible to gastric killing. In mice genetically deficient in gastrin, a key regulator for gastric acid production, or pharmacologically treated with a proton pump inhibitor, the ability of pGP3-deficient C. muridarum to colonize the gastrointestinal tract was rescued. The pGP3-dependent resistance was further recapitulated in vitro with treatments with HCl, pepsin, or sarkosyl. In the genital tract, deficiency in pGP3 significantly reduced C. muridarum survival in the mouse vagina and increased C. muridarum susceptibility to vaginal killing by ∼8 times. The pGP3-deficient C. muridarum was more susceptible to lactic acid killing, and the pGP3 deficiency also significantly increased C. trachomatis susceptibility to lactic acid. The above-described observations together suggest that Chlamydia may have acquired the plasmid-encoded pGP3 to overcome the gastric barrier during its adaptation to the gastrointestinal tract and the pGP3-dependent resistance may enable chlamydial evasion of the female lower genital tract barrier during sexual transmission.

Classical swine fever virus non-structural proteins modulate Toll-like receptor signaling pathways in porcine monocyte-derived macrophages

Toll-like receptors (TLRs) are crucial activators of the innate immune response that play various roles in viral infection. Studies have confirmed that classical swine fever virus (CSFV) infection has significant effects on the expression of immune effectors participating in TLR signaling pathways; however, the involvement of CSFV-encoded proteins in TLR signaling pathways remains unclear. In this study, lentiviral individually expressing CSFV non-structural proteins (NSPs) were constructed to identify the "key proteins" that affect TLR gene expression and to analyze the impacts of these proteins on factors downstream of the TLR signaling pathways. The results indicated that N^pro, NS2, NS3, NS3/4A, NS4B and NS5A all failed to induce the activation of NF-κB p65. Furthermore, NS4B was found to inhibit poly (I:C) stimulation-mediated activation of the TLR3 signaling pathway in porcine monocyte-derived macrophages (pMDMs), thereby suppressing the TRIF mRNA transcription, the IRF3 protein translation and the NF-κB p65 phosphorylation, and ultimately affecting the secretion of IL-6 and IFN-β; CSFV NS5A protein could significantly increase the activation of MyD88 and IRF7 as well as the consequent synthesis of IFN-α in pMDMs. The results suggest that CSFV NSPs affect TLR-mediated innate immune responses in pMDMs.

Targeting Type 1 Diabetes: Selective Approaches for New Therapies

The clinical onset of type 1 diabetes is characterized by the destruction of the insulin-producing β cells of the pancreas and is caused by autoantigen-induced inflammation (insulitis) of the islets of Langerhans. The current standard of care for type 1 diabetes mellitus patients allows for management of the disease with exogenous insulin, but patients eventually succumb to many chronic complications such as limb amputation, blindness, and kidney failure. New therapeutic approaches now on the horizon are looking beyond glycemic management and are evaluating new strategies from protecting and regenerating endogenous islets to treating the underlying autoimmunity through selective modulation of key immune cell populations. Currently, there are no effective treatments for the autoimmunity that causes the disease, and strategies that aim to delay or prevent the onset of the disease will play an important role in the future of diabetes research. In this review, we summarize many of the key efforts underway that utilize molecular approaches to selectively modulate this disease and look at new therapeutic paradigms that can transform clinical treatment.

FOXP1 negatively regulates tumor infiltrating lymphocyte migration in human breast cancer

Background

FOXP1, a transcriptional regulator of lymphocyte development, is abnormally expressed in some human tumors. This study investigated FOXP1-mediated regulation of tumor infiltrating lymphocytes (TIL) in untreated primary breast cancer (BC).

Methods

FOXP1 expression was analyzed in tissues from primary untreated breast tumors, BC cell lines and the METABRIC gene expression BC dataset. Cytokine and chemokine expression and lymphocyte migration in response to primary tumor supernatants (SN) was compared between FOXP1^hi and FOXP1^lo primary BC.

Finding

FOXP1 expression was higher in estrogen receptor positive compared to negative BC. FOXP1^hi tumors were significantly associated with lower TIL and fewer tertiary lymphoid structures (TLS) compared to FOXP1^lo BC. Silencing FOXP1 in BC cell lines positively impacted cytokine and chemokine expression with the inverse effect associated with overexpression. CXCL9, CXCL10, CXCL11, CXCL13, CX3CL, CCL20, IL2, IL21, GZMB and IFNG expression decreased while IL10 and TGFβ increased in FOXP1^hi compared to FOXP1^lo primary BC. Lymphocyte migration using primary BC supernatants detected decreased mobility toward FOXP1^hi supernatants. FOXP1^lo BC expresses higher levels of chemokines driving TIL migration. The METABRIC gene expression dataset analysis show FOXP1 expression is associated with unfavorable BC outcomes.

Interpretation

These data identify FOXP1 as an important negative regulator of immune responses in BC via its regulation of cytokine and chemokine expression.

Fund

Belgian Fund for Scientific Research (FNRS 3.4513.12F) and Opération Télévie (7.4636.13F and 7.4609.15F), Fonds J.C. Heuson and Fonds Lambeau-Marteaux.

Sepsis Induces a Long-Lasting State of Trained Immunity in Bone Marrow Monocytes

Innate immune memory describes the functional reprogramming of innate immune cells after pathogen contact, leading to either a boosted (trained immunity) or a diminished (immune tolerance) response to a secondary stimulus. Immune tolerance or “sepsis-induced immunosuppression” is a typical hallmark of patients after sepsis survival, characterized by hypo-responsiveness of the host's immune system. This condition renders the host vulnerable for a persisting infection or the occurrence of secondary, often opportunistic infections, along with an increased mortality rate. The mechanisms involved in the maintenance of this long-lasting condition are not examined yet. Polymicrobial abdominal sepsis was induced in 12 week old male C57BL/6 mice by cecal ligation and puncture. Mice were euthanized 3 months after insult. Immune cell composition of the spleen and whole blood, as well as stem and progenitor cells of the bone marrow, were assessed by flow cytometry. Whole blood and bone marrow monocytes were stimulated with LPS and supernatant levels of TNF and IL-6 detected by ELISA. Furthermore, naïve bone marrow monocytes were analyzed for metabolic (Seahorse technology) and transcriptomic (RNA sequencing) changes. Flow cytometric analysis revealed an increase of inflammatory monocytes and regulatory T cells in the spleen, whereby immune composition of whole blood kept unchanged. Granulocyte-monocyte progenitor cells are increased in sepsis survivors. Systemic cytokine response was unchanged after LPS challenge. In contrast, cytokine response of post-septic naïve bone marrow monocytes was increased. Metabolic analysis revealed enhanced glycolytic activity, whereas mitochondrial indices were not affected. In addition, RNA sequencing analysis of global gene expression in monocytes revealed a sustained signature of 367 differentially expressed genes. We here demonstrate that sepsis via functional reprogramming of naïve bone marrow monocytes induces a cellular state of trained immunity, which might be counteracted depending on the compartmental localization of the cell. These findings shed new light on the complex aftermath of sepsis and open up a new pathophysiological framework in need for further research.

Potential role of Toll-like receptor 2 expression and polymorphisms in colon cancer susceptibility in the Saudi Arabian population

Background

Inflammation is a fundamental factor that contributes to the development and progression of several types of cancer including colon cancer. Toll-like receptors (TLRs) and their signaling pathways have been reported to be associated with chronic inflammation and thereby induced cancer. Our aim was to investigate the expression and polymorphisms of TLR2 and their association with colon cancer.

Methods

Real-time PCR and immunohistochemistry were used to investigate TLR2 gene expression and to evaluate the potential risk of predisposition to colon cancer caused by three tagging single-nucleotide polymorphisms (SNPs) on TLR2, including rs3804100, rs4696480, and rs3804099. TaqMan assay was conducted on samples from 115 patients with colon cancer and 102 age- and sex-matched normal individuals.

Results

We found that, TLR2 was highly expressed in epithelial colon cancer cells and both TLR2 mRNA and protein levels, and significantly decreased in tumor tissues compared to normal tissues. Two of three TLR2 SNPs increased the risk of colon cancer. However, TLR2 rs3804099 increased the risk of colon cancer development by more than 3.8- and 5-fold in female patients and patients aged less than 57 years, respectively. The T allele of TLR2 rs3804100 showed a significant association with patients less than 57 years. In silico analysis of the TLR2 nucleotide substitution in SNP rs3804100 and rs3804099 determined that 67% and 70% probability of these single nucleotide variants alter splicing phenotypes, rs3804100 more specifically result on activating an additional splice site. Genotype and allele frequencies of rs4696480 were similar between the overall study populations. Thus, TLR2 rs4696480 appear to be not involved in colon cancer in our study population.

Conclusions

There was a significant link between innate immunity deregulation through disruption of the TLRs and potential development of colon cancer. These SNPs can be used as screening markers for predicting colon cancer risk earlier in life to implement necessary prevention.

Piglet weight gain during the first two weeks of lactation influences the immune system development

The aim of this study was to investigate the effect of the piglet growth during the first week of life on ileal expression of genes and on development of the immune system. Eight litters adjusted to 12 piglets were used. Within each litter, the piglet that showed the lowest weight gain (LWG; n = 8) and the one that showed the highest weight gain (HWG; n = 8) in their first week of life were enrolled. Peripheral blood mononuclear cells (PBMC) were isolated on days 8 and 16 to characterize cellular population profiles and to assess ex-vivo secretion of interleukin-10 (IL-10), IL-6 and tumor necrosis factor-α (TNF-α). On day 16, piglets were euthanized and ileum samples were collected to extract RNA for microarray analysis and gene expression by qPCR. As expected, growth performance of LWG piglet was impaired compared to HWG piglets (P < 0.05). From day 8 to 16, the percentage of CD21⁺ B cells significantly increased in blood of heavier HWG piglets while the percentage remained constant in smaller LWG piglets (P weight x day = 0.01). For the CD4⁺CD8α^- Th cells, a marked increase was observed in LWG piglets from 8 to 16 days of age (P =  0.002) whereas no significant change occurred in HWG piglets. Percentages of CD14⁺ monocytes and other MHC-II⁺ cells were respectively higher and lower on day 8 compared to day 16 for both groups of piglets (P <  0.01). On day 8, LPS-activated PBMC from LWG piglets produced less IL-6 compared to HWG piglets (P <  0.05). Microarray analysis of gene expression in piglets' ileum tissue indicated that several genes involed in defense response and response to oxidative stress were modulated differently in LWG compared to HWG. Gene analysis by Q-PCR confirmed microarray results and revealed that IL-10, SOD1, NOS2, NOD2, TLR4, TLR9, CD40 and CD74 expressions were significantly decreased (P < 0.05) in LWG in comparison to HWG piglets, while MYD88 and NFkBiA showed a tendency to decrease (0.05 ≤ P < 0.07). These results suggest that birth weight and milk intake affect the growth performances and the development of immunity by modulating the expression of genes associated with immunity and oxidative stress in piglets' intestinal tissue, and by affecting the leukocyte populations involved in innate and cell-mediated immunity in nursing piglets. Therefore, impaired development of immune system in LWG piglets might have an impact on their resistance to infections later in life.

Identification and characterization of the myeloid differentiation factor 88 gene in yellow catfish

Myeloid differentiation factor 88 (MyD88) is an important adapter protein of the innate immune system, but it has never before been reported in yellow catfish (Pelteobagrus fulvidraco). In this study, we cloned and characterized the yellow catfish MyD88 gene. The gene was 1230 bp in length and contained an 876-bp open reading frame which encodes a polypeptide of 291 amino acid residues. The theoretical molecular mass and isoelectric point of this polypeptide were 33.4341 kDa and 5.17, respectively. Furthermore, bioinformatic and phylogenetic analyses grouped yellow catfish MyD88 with MyD88 of other fish. We found that the deduced amino acid sequence showed that the conserved N-terminal death domain and the C-terminal typical Toll/interleukin-1 receptor domain were very similar to those of other fish. Moreover, reverse transcription PCR showed that yellow catfish MyD88 is ubiquitously expressed in all tissues examined, with highest expression levels observed in the spleen and lowest levels in the intestine. Importantly, MyD88 was shown to be significantly up-regulated in the intestines after 30-day dietary supplement of Clostridium butyricum. Collectively, these results indicate that yellow catfish MyD88 has a conserved structure and is probably an important component of innate immunity in yellow catfish. This study is the first to identify and characterize MyD88 in yellow catfish, thereby providing a reference for further research into the yellow catfish innate immune system.

An analysis of the expression and function of myeloid differentiation factor 88 in human osteosarcoma

The aim of the present study was to investigate the expression and function of myeloid differentiation factor 88 (MyD88) in osteosarcoma. Immunohistochemical staining was used to detect MyD88 protein in osteosarcoma tissues and matched normal bone tissues. The association between MyD88 expression and the clinical characteristics of patients with osteosarcoma was analyzed. Furthermore, survival analysis of patients with osteosarcoma was performed to study the association between MyD88 expression and patient prognosis. Finally, the effect of the MyD88 inhibitor, ST2825, on the proliferation and apoptosis of the human osteosarcoma cell line U2OS was examined. Additionally, cell proliferation, invasion and apoptosis were examined using an MTT assay, Transwell assay and Annexin V-fluorescein isothiocyanate staining kit, respectively. The expression of proteins associated with the NF-κB signaling pathway was analyzed by western blotting. The positive expression rate of MyD88 in osteosarcoma and normal bone tissues was 71.4 and 6.1%, respectively. Statistical analysis demonstrated that MyD88 was not associated with gender, age, histological type or tumor location, but that it was associated with Enneking stage and tumor metastasis (P<0.05). According to the survival analysis, patients with osteosarcoma in the high MyD88 expression group displayed a reduced overall survival rate (P<0.05). Furthermore, inhibition of MyD88 by ST2825 in U2OS cells resulted in a marked decrease in cellular proliferation and migration, and an increase in the rate of apoptosis (P<0.05). Notably, ST2825 significantly decreased cyclin D1, matrix metallopeptidase-9 and nucleus p65 expression, but increased cleaved-caspase 3 expression in ST2825-treated U2OS cells (P<0.05). The results of the present study indicated that MyD88 expression is associated with the progression of osteosarcoma and may be a potential therapeutic target for the treatment of osteosarcoma.

MyD88 signaling causes autoimmune sialadenitis through formation of high endothelial venules and upregulation of LTβ receptor-mediated signaling

Autoimmune sialadenitis (AS), chronic inflammation of the salivary glands (SGs) with focal lymphocyte infiltration, appears in autoimmune diseases such as Sjӧgren’s syndrome. The pathological role of MyD88-dependent innate immune signaling in autoimmune diseases including AS has been studied using mouse models, such as NOD mice. Although AS development in NOD mice was reported to be suppressed by Myd88 deficiency, its specific role remains unclear. Here, we determined the potent suppressive effects of Myd88 deficiency on AS development in lupus-prone B6/lpr mice, which have lymphoproliferation abnormalities, and also in NOD mice, which have no lymphoproliferation abnormalities. This indicates that MyD88 signaling triggers AS through both lymphoproliferation-dependent and -independent mechanisms. To address the MyD88-dependent lymphoproliferation-independent AS manifestation, SGs from C57BL/6 mice were analyzed. Remarkable upregulation of Glycam1 and high endothelial venule (HEV)-associated changes were unexpectedly found in Myd88^+/+ mice, compared with Myd88^−/− mice. MyD88-dependent HEV-associated changes were also observed in NOD mice. Additionally, Lta, Ltb, and Ltbr in SGs of NOD mice were lowered by Myd88 deficiency. Interestingly, LTβR-induced HEV-associated gene expression in cultured cells was impaired by Myd88 deficiency. Our findings highlight novel roles for MyD88 in AS development, which imply the existence of MyD88-dependent HEV formation in ectopic lymphoid neogenesis.

Anti-inflammatory action of cysteine derivative S-1-propenylcysteine by inducing MyD88 degradation

The degradation of target proteins by small molecules utilizing the cellular proteolytic system is featured as a treatment strategy of several diseases. We found that S-1-propenylcysteine (S1PC) among several cysteine derivatives in aged garlic extract inhibited TLR-mediated IL-6 production by inducing the degradation of adaptor protein MyD88. We showed that S1PC directly denatured MyD88 and induced the formation of protein aggregates. Consequently, MyD88 was degraded by aggresome-autophagy pathway. On the other hand, S-allylcysteine, a structural analog of S1PC, failed to induce the degradation of MyD88 because of its inability to denature MyD88 although it also activated autophagy. Our findings suggest that S1PC induces MyD88 degradation through the denaturation of MyD88 and the activation of autophagy. Thus, S1PC may serve as the base to develop a therapeutic means for immune diseases associated with aberrant TLR signaling pathways.

Functional Evidence of Pulmonary Extracellular Vesicles in Infectious and Noninfectious Lung Inflammation

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a highly complex process that can be triggered by both noninfectious (sterile) and infectious stimuli. Inflammatory lung responses are one of the key features in the pathogenesis of this devastating syndrome. How ALI/ARDS-associated inflammation develops remains incompletely understood, particularly after exposure to sterile stimuli. Emerging evidence suggests that extracellular vesicles (EVs) regulate intercellular communication and inflammatory responses in various diseases. In this study, we characterized the generation and function of pulmonary EVs in the setting of ALI/ARDS, induced by sterile stimuli (oxidative stress or acid aspiration) and infection (LPS/Gram-negative bacteria) in mice. EVs detected in bronchoalveolar lavage fluid (BALF) were markedly increased after exposure of animals to both types of stimuli. After sterile stimuli, alveolar type-І epithelial cells were the main source of the BALF EVs. In contrast, infectious stimuli-induced BALF EVs were mainly derived from alveolar macrophages (AMs). Functionally, BALF EVs generated in both the noninfectious and infectious ALI models promoted the recruitment of macrophages in in vivo mouse models. Furthermore, BALF EVs differentially regulated AM production of cytokines and inflammatory mediators, as well as TLR expression in AMs in vivo. Regardless of their origin, BALF EVs contributed significantly to the development of lung inflammation in both the sterile and infectious ALI. Collectively, our results provide novel insights into the mechanisms by which EVs regulate the development of lung inflammation in response to diverse stimuli, potentially providing novel therapeutic and diagnostic targets for ALI/ARDS.

A Synthetic Disaccharide Derivative of Diphyllin, TAARD, Activates Human Natural Killer Cells to Secrete Interferon-Gamma via Toll-Like Receptor-Mediated NF-κB and STAT3 Signaling Pathways

Natural products and their derivatives have long been used as pharmacological agents in the fight against cancer. Human natural killer (NK) cells are critical in our immune system in that they are capable of destroying tumor cells directly. However, there are few reports that elucidate the role of natural products in activating NK cells. In this study, we discovered that a synthetic disaccharide derivative of diphyllin, 4-O-{[2′′,3′′,4′′-tri-O-acetyl-α-D-arabinopyranosyl-(1′′→4′)]-2′,3′-di-O-acetyl-α-L-rhamnopyranosyl}diphyllin (TAARD), can alone stimulate interferon (IFN)-γ secretion in primary human NK cells and the NKL cell line. Additionally, it had an additive effect with IL-12 or IL-15 on IFN-γ production, but little adverse effects on NK cells. Mechanistically, TAARD induced the phosphorylation of NF-κB and STAT3, resulting in their binding on the IFNG promoter, which was dependent on TLR1 and TLR3 signaling, respectively. STAT3 and NF-κB knockdown with lentivirus shRNA as well as the NF-κB-specific inhibitor, N-tosyl-l-phenylalaninechloromethyl ketone, significantly suppressed TAARD-induced IFN-γ generation in primary NK cells. Blockade of TLR1 and TLR3 with neutralizing antibodies considerably decreased TAARD-induced activation of NF-κB and STAT3, respectively, as well as IFN-γ generation in NK cells. Collectively, our data suggest that TAARD can induce NK cell IFN-γ production through TLR1-NF-κB and TLR3-STAT3 signaling pathways, rendering its potential use as an agent for cancer prevention or treatment.

Streptococcus pneumoniae's Virulence and Host Immunity: Aging, Diagnostics, and Prevention

Streptococcus pneumoniae is an infectious pathogen responsible for millions of deaths worldwide. Diseases caused by this bacterium are classified as pneumococcal diseases. This pathogen colonizes the nasopharynx of its host asymptomatically, but overtime can migrate to sterile tissues and organs and cause infections. Pneumonia is currently the most common pneumococcal disease. Pneumococcal pneumonia is a global health concern and vastly affects children under the age of five as well as the elderly and individuals with pre-existing health conditions. S. pneumoniae has a large selection of virulence factors that promote adherence, invasion of host tissues, and allows it to escape host immune defenses. A clear understanding of S. pneumoniae's virulence factors, host immune responses, and examining the current techniques available for diagnosis, treatment, and disease prevention will allow for better regulation of the pathogen and its diseases. In terms of disease prevention, other considerations must include the effects of age on responses to vaccines and vaccine efficacy. Ongoing work aims to improve on current vaccination paradigms by including the use of serotype-independent vaccines, such as protein and whole cell vaccines. Extending our knowledge of the biology of, and associated host immune response to S. pneumoniae is paramount for our improvement of pneumococcal disease diagnosis, treatment, and improvement of patient outlook.

Probing the molecular regulation of lipopolysaccharide stress in piglet liver by comparative proteomics analysis

Lipopolysaccharide (LPS) can induce inflammatory responses in piglets, causing immunological stress and tissue damage. However, chronic LPS infection may lead to LPS-induced immunological stress resistance. The molecular mechanisms underlying LPS stress have not been fully elucidated. Here, we conducted a global comparative proteomics analysis to investigate the molecular regulation of LPS stress using an immunological stress model of weaned piglets. A shotgun-based SWATH-MS workflow was used for global proteomes of the piglet livers after 15-day LPS treatment. Out of 3700 quantified proteins, 93 proteins showed differential changes under LPS stress. Bioinformatics analysis indicated that the differentially expressed proteins were mainly involved in inflammatory response, oxidation-redox processes and defense reactions, and were enriched in a phagosome pathway. Several key proteins associated with oxidative stress (SOD2), inflammation response (STEAP4 and S100 family) and the phagosome pathway were verified by activity and targeted-MS analyses. The observed responses appear to mitigate hepatic damage due to excessive oxidative stress, inflammation, and repression of the phagosome pathway. Our results reveal that an increased STEAP4 expression in piglets appears involved in cellular regulation by LPS stress and subsequent immunological stress resistance. This study sheds new light on the mechanism of prevention and relieving injury by LPS-induced immune responses.

Nuclear PTEN enhances the maturation of a microRNA regulon to limit MyD88-dependent susceptibility to sepsis

Sepsis-induced organ damage is caused by systemic inflammatory response syndrome (SIRS), which results in substantial comorbidities. Therefore, it is of medical importance to identify molecular brakes that can be exploited to dampen inflammation and prevent the development of SIRS. We investigated the role of phosphatase and tensin homolog (PTEN) in suppressing SIRS, increasing microbial clearance, and preventing lung damage. Septic patients and mice with sepsis exhibited increased PTEN expression in leukocytes. Myeloid-specific Pten deletion in an animal model of sepsis increased bacterial loads and cytokine production, which depended on enhanced myeloid differentiation primary response gene 88 (MyD88) abundance and resulted in mortality. PTEN-mediated induction of the microRNAs (miRNAs) miR125b and miR203b reduced the abundance of MyD88. Loss- and gain-of-function assays demonstrated that PTEN induced miRNA production by associating with and facilitating the nuclear localization of Drosha-Dgcr8, part of the miRNA-processing complex. Reconstitution of PTEN-deficient mouse embryonic fibroblasts with a mutant form of PTEN that does not localize to the nucleus resulted in retention of Drosha-Dgcr8 in the cytoplasm and impaired production of mature miRNAs. Thus, we identified a regulatory pathway involving nuclear PTEN-mediated miRNA generation that limits the production of MyD88 and thereby limits sepsis-associated mortality.

Synergy between the Host Immune System and Bacteriophage Is Essential for Successful Phage Therapy against an Acute Respiratory Pathogen

The rise of multi-drug-resistant (MDR) bacteria has spurred renewed interest in the use of bacteriophages in therapy. However, mechanisms contributing to phage-mediated bacterial clearance in an animal host remain unclear. We investigated the effects of host immunity on the efficacy of phage therapy for acute pneumonia caused by MDR Pseudomonas aeruginosa in a mouse model. Comparing efficacies of phage-curative and prophylactic treatments in healthy immunocompetent, MyD88-deficient, lymphocyte-deficient, and neutrophil-depleted murine hosts revealed that neutrophil-phage synergy is essential for the resolution of pneumonia. Population modeling of in vivo results further showed that neutrophils are required to control both phage-sensitive and emergent phage-resistant variants to clear infection. This "immunophage synergy" contrasts with the paradigm that phage therapy success is largely due to bacterial permissiveness to phage killing. Lastly, therapeutic phages were not cleared by pulmonary immune effector cells and were immunologically well tolerated by lung tissues.

The enhanced antitumor-specific immune response with mannose- and CpG-ODN-coated liposomes delivering TRP2 peptide

PURPOSE

Dendritic cell (DC)-based cancer vaccines is a newly emerging and potent form of immune therapy. As for any new technology, there are still considerable challenges that need to be addressed. Here, we investigate the antitumor potential of a novel liposomal vaccine, M/CpG-ODN-TRP2-Lipo.

METHODS

We developed a vaccination strategy by assembling the DC-targeting mannose and immune adjuvant CpG-ODN on the surface of liposomes, which were loaded with melanoma-specific TRP2_180-188 peptide as liposomal vaccine. M/CpG-ODN-TRP2-Lipo treatment was used to intendedly induce activation of DCs and antitumor- specific immune response in vivo.

RESULTS

Our results demonstrated in vitro that the prepared liposomal particles were efficiently taken up by DCs. This uptake led to an enhanced activation of DCs, as measured by the upregulation of MHC II, CD80, and CD86. Furthermore, M/CpG-ODN-TRP2-Lipo effectively inhibited the growth of implanted B16 melanoma and prolonged the survival of mice. This therapy significantly reduced the number of myeloid-derived suppressor cells (MDSCs) and regulatory T cells, while simultaneously increasing the number of activated T cells, tumor antigen-specific CD8⁺ cytotoxic T cells, and interferon-γ-producing cells. At the same time, it was found to suppress tumor angiogenesis and tumor cell proliferation, as well as up-regulate their apoptosis. Interestingly, MyD88-knockout mice had significantly shorter median survival times compared to wild-type mice following the administration of M/CpG-ODN-TRP2-Lipo.

CONCLUSIONS

The results suggested that the antitumor activities of the vaccine partially rely on the Myd88 signaling pathway. Interestingly, compared to whole tumor cell lysate-based vaccine, M/CpG-ODN-TRP2-Lipo, tumor specific antigen peptide-based vaccine, improved survival of tumor-bearing mice as well as enhanced their antitumor responses. All in all, we describe a novel vaccine formulation, M/CpG-ODN-TRP2-Lipo, with the aim of improving antitumor responses by alleviating the immunosuppressive environment in tumors.

Redox-Dependent Inflammation in Islet Transplantation Rejection

Type 1 diabetes is an autoimmune disease that results in the progressive destruction of insulin-producing pancreatic β-cells inside the islets of Langerhans. The loss of this vital population leaves patients with a lifelong dependency on exogenous insulin and puts them at risk for life-threatening complications. One method being investigated to help restore insulin independence in these patients is islet cell transplantation. However, challenges associated with transplant rejection and islet viability have prevented long-term β-cell function. Redox signaling and the production of reactive oxygen species (ROS) by recipient immune cells and transplanted islets themselves are key players in graft rejection. Therefore, dissipation of ROS generation is a viable intervention that can protect transplanted islets from immune-mediated destruction. Here, we will discuss the newly appreciated role of redox signaling and ROS synthesis during graft rejection as well as new strategies being tested for their efficacy in redox modulation during islet cell transplantation.

MyD88 in antigen-presenting cells is not required for CD4+ T-cell responses during peptide nanofiber vaccination

Self-assembled peptide nanofibers raise significant antibody and T cell responses without adjuvants, but the mechanism by which they achieve this has not been fully elucidated. Myeloid differentiation primary response gene 88 (MyD88) previously has been shown to be critical for the antibody response to antigens presented by peptide nanofibers. The present study sought to determine the cell subset in which MyD88 is essential for T cell responses. Mice deficient in MyD88 or CD11c⁺ cells had severely attenuated T cell responses. However, mice lacking MyD88 in only CD11c⁺ cells remained capable of internalizing, processing, and presenting nanofiber-derived epitopes to stimulate T cell responses. The necessity of inflammasome pathway was ruled out. Using adoptive transfer models where MyD88 was eliminated in CD4⁺ T cells or in the host, we observed that deficiency only in T cells or only in the host had no impact on the T cell response to nanofiber vaccines. Therefore, knocking out MyD88 in either antigen presenting cells (APCs) or CD4 T cells could not compromise the CD4 T cell responses, suggesting that self-assembled peptide nanofibers trigger redundant MyD88-dependent and MyD88-independent signaling pathways in APCs and T cells. Similar redundancy has been observed for other adjuvants, and this is discussed.

Inhalation Exposure to PM2.5 Counteracts Hepatic Steatosis in Mice Fed High-fat Diet by Stimulating Hepatic Autophagy

Air pollution is associated with the increased risk of metabolic syndrome. In this study, we performed inhalation exposure of mice fed normal chow or a high-fat diet to airborne fine particulate matters (PM_2.5), and then investigated the complex effects and mechanisms of inhalation exposure to PM_2.5 on hepatic steatosis, a precursor or manifestation of metabolic syndrome. Our studies demonstrated that inhalation exposure of mice fed normal chow to concentrated ambient PM_2.5 repressed hepatic transcriptional regulators involved in fatty acid oxidation and lipolysis, and thus promoted hepatic steatosis. However, PM_2.5 exposure relieved hepatic steatosis in high-fat diet-induced obese mice. Further investigation revealed that inhalation exposure to PM_2.5 induced hepatic autophagy in mouse livers in a manner depending on the MyD88-mediated inflammatory pathway. The counteractive effect of PM_2.5 exposure on high-fat diet-induced hepatic steatosis was mediated through PM_2.5-induced hepatic autophagy. The findings from this study not only defined the effects and mechanisms of PM_2.5 exposure in metabolic disorders, but also revealed the pleotrophic acts of an environmental stressor in a complex stress system relevant to public health.

Piperidylmethyloxychalcone improves immune-mediated acute liver failure via inhibiting TAK1 activity

Mice deficient in the toll-like receptor (TLR) or the myeloid differentiation factor 88 (MyD88) are resistant to acute liver failure (ALF) with sudden death of hepatocytes. Chalcone derivatives from medicinal plants protect from hepatic damages including ALF, but their mechanisms remain to be clarified. Here, we focused on molecular basis of piperidylmethyloxychalcone (PMOC) in the treatment of TLR/MyD88-associated ALF. C57BL/6J mice were sensitized with D-galactosamine (GalN) and challenged with Escherichia coli lipopolysaccharide (LPS, TLR4 agonist) or oligodeoxynucleotide containing unmethylated CpG motif (CpG ODN, TLR9 agonist) for induction of ALF. Post treatment with PMOC sequentially ameliorated hepatic inflammation, apoptosis of hepatocytes, severe liver injury and shock-mediated death in ALF-induced mice. As a mechanism, PMOC inhibited the catalytic activity of TGF-β-activated kinase 1 (TAK1) in a competitive manner with respect to ATP, displaced fluorescent ATP probe from the complex with TAK1, and docked at the ATP-binding active site on the crystal structure of TAK1. Moreover, PMOC inhibited TAK1 auto-phosphorylation, which is an axis in the activating pathways of nuclear factor-κB (NF-κB) or activating protein 1 (AP1), in the liver with ALF in vivo or in primary liver cells stimulated with TLR agonists in vitro. PMOC consequently suppressed TAK1-inducible NF-κB or AP1 activity in the inflammatory injury, an early pathogenesis leading to ALF. The results suggested that PMOC could contribute to the treatment of TLR/MyD88-associated ALF with the ATP-binding site of TAK1 as a potential therapeutic target.

Hyaluronic acid 35 normalizes TLR4 signaling in Kupffer cells from ethanol-fed rats via regulation of microRNA291b and its target Tollip

TLR4 signaling in hepatic macrophages is increased after chronic ethanol feeding. Treatment of hepatic macrophages after chronic ethanol feeding with small-specific sized hyaluronic acid 35 (HA35) normalizes TLR4 signaling; however, the mechanisms for HA35 action are not completely understood. Here we used Next Generation Sequencing of microRNAs to identify negative regulators of TLR4 signaling reciprocally modulated by ethanol and HA35 in hepatic macrophages. Eleven microRNAs were up-regulated by ethanol; only 4 microRNAs, including miR291b, were decreased by HA35. Bioinformatics analysis identified Tollip, a negative regulator of TLR4, as a target of miR291b. Tollip expression was decreased in hepatic macrophages from ethanol-fed rats, but treatment with HA35 or transfection with a miR291b hairpin inhibitor restored Tollip expression and normalized TLR4-stimulated TNFα expression. In peripheral blood monocytes isolated from patients with alcoholic hepatitis, expression of TNFα mRNA was robustly increased in response to challenge with lipopolysaccharide. Importantly, pre-treatment with HA35 reduced TNFα expression by more than 50%. Taken together, we have identified miR291b as a critical miRNA up-regulated by ethanol. Normalization of the miR291b → Tollip pathway by HA35 ameliorated ethanol-induced sensitization of TLR4 signaling in macrophages/monocytes, suggesting that HA35 may be a novel therapeutic agent in the treatment of ALD.

Innate Immune Recognition: Implications for the Interaction of Francisella tularensis with the Host Immune System

The intracellular bacterial pathogen Francisella tularensis causes serious infectious disease in humans and animals. Moreover, F. tularensis, a highly infectious pathogen, poses a major concern for the public as a bacterium classified under Category A of bioterrorism agents. Unfortunately, research has so far failed to develop effective vaccines, due in part to the fact that the pathogenesis of intracellular bacteria is not fully understood and in part to gaps in our understanding of innate immune recognition processes leading to the induction of adaptive immune response. Recent evidence supports the concept that immune response to external stimuli in the form of bacteria is guided by the primary interaction of the bacterium with the host cell. Based on data from different Francisella models, we present here the basic paradigms of the emerging innate immune recognition concept. According to this concept, the type of cell and its receptor(s) that initially interact with the target constitute the first signaling window; the signals produced in the course of primary interaction of the target with a reacting cell act in a paracrine manner; and the innate immune recognition process as a whole consists in a series of signaling windows modulating adaptive immune response. Finally, the host, in the strict sense, is the interacting cell.

Mesenchymal Cell-Specific MyD88 Signaling Promotes Systemic Dissemination of Salmonella Typhimurium via Inflammatory Monocytes

Enteric pathogens including Salmonella enteric serovar Typhimurium can breach the epithelial barrier of the host and spread to systemic tissues. In response to infection, the host activates innate immune receptors via the signaling molecule MyD88, which induces protective inflammatory and antimicrobial responses. Most of these innate immune responses have been studied in hematopoietic cells, but the role of MyD88 signaling in other cell types remains poorly understood. Surprisingly, we found that Dermo1-Cre;Myd88^fl/fl mice with mesenchymal cell-specific deficiency of MyD88 were less susceptible to orogastric and i.p. STyphimurium infection than their Myd88^fl/fl littermates. The reduced susceptibility of Dermo1-Cre;Myd88^fl/fl mice to infection was associated with lower loads of S. Typhimurium in the liver and spleen. Mutant analyses revealed that S. Typhimurium employs its virulence type III secretion system 2 to promote its growth through MyD88 signaling pathways in mesenchymal cells. Inflammatory monocytes function as a major cell population for systemic dissemination of S. Typhimurium Mechanistically, mesenchymal cell-specific MyD88 signaling promoted CCL2 production in the liver and spleen and recruitment of inflammatory monocytes to systemic organs in response to STyphimurium infection. Consistently, MyD88 signaling in mesenchymal cells enhanced the number of phagocytes including Ly6C^hiLy6G^- inflammatory monocytes harboring STyphimurium in the liver. These results suggest that S. Typhimurium promotes its systemic growth and dissemination through MyD88 signaling pathways in mesenchymal cells.

Amplification and propagation of interleukin-1β signaling by murine brain endothelial and glial cells

BACKGROUND

During acute infections and chronic illnesses, the pro-inflammatory cytokine interleukin-1β (IL-1β) acts within the brain to elicit metabolic derangements and sickness behaviors. It is unknown which cells in the brain are the proximal targets for IL-1β with respect to the generation of these illness responses. We performed a series of in vitro experiments to (1) investigate which brain cell populations exhibit inflammatory responses to IL-1β and (2) examine the interactions between different IL-1β-responsive cell types in various co-culture combinations.

METHODS

We treated primary cultures of murine brain microvessel endothelial cells (BMEC), astrocytes, and microglia with PBS or IL-1β, and then performed qPCR to measure inflammatory gene expression or immunocytochemistry to evaluate nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation. To evaluate whether astrocytes and/or BMEC propagate inflammatory signals to microglia, we exposed microglia to astrocyte-conditioned media and co-cultured endothelial cells and glia in transwells. Treatment groups were compared by Student's t tests or by ANOVA followed by Bonferroni-corrected t tests.

RESULTS

IL-1β increased inflammatory gene expression and NF-κB activation in primary murine-mixed glia, enriched astrocyte, and BMEC cultures. Although IL-1β elicited minimal changes in inflammatory gene expression and did not induce the nuclear translocation of NF-κB in isolated microglia, these cells were more robustly activated by IL-1β when co-cultured with astrocytes and/or BMEC. We observed a polarized endothelial response to IL-1β, because the application of IL-1β to the abluminal endothelial surface produced a more complex microglial inflammatory response than that which occurred following luminal IL-1β exposure.

CONCLUSIONS

Inflammatory signals are detected, amplified, and propagated through the CNS via a sequential and reverberating signaling cascade involving communication between brain endothelial cells and glia. We propose that the brain's innate immune response differs depending upon which side of the blood-brain barrier the inflammatory stimulus arises, thus allowing the brain to respond differently to central vs. peripheral inflammatory insults.

Downregulation of adaptor protein MyD88 compromises the angiogenic potential of B16 murine melanoma

The mechanisms that link inflammatory responses to cancer development remain a subject of intense investigation, emphasizing the need to better understand the cellular and molecular pathways that create a tumor promoting microenvironment. The myeloid differentiation primary response protein MyD88 acts as a main adaptor molecule for the signaling cascades initiated from Toll-like receptors (TLRs) and the interleukin 1 receptor (IL-1R). MyD88 has been shown to contribute to tumorigenesis in many inflammation-associated cancer models. In this study, we sought to better define the role of MyD88 in neoplastic cells using a murine melanoma model. Herein, we have demonstrated that MyD88 expression is required to maintain the angiogenic switch that supports B16 melanoma growth. By knocking down MyD88 we reduced TLR-mediated NF-κB activation with no evident effects over cell proliferation and survival. In addition, MyD88 downregulation was associated with a decrease of HIF1α levels and its target gene VEGF, in correlation with an impaired capability to induce capillary sprouting and tube formation of endothelial cells. Melanomas developed from cells lacking MyD88 showed an enhanced secretion of chemoattractant ligands such as CCL2, CXCL10 and CXCL1 and have an improved infiltration of macrophages to the tumor site. Our results imply that cell-autonomous signaling through MyD88 is required to sustain tumor growth and underscore its function as an important positive modulator of tumor angiogenesis.

Therapeutic effect of Schistosoma japonicum cystatin on bacterial sepsis in mice

BACKGROUND

Sepsis is a life-threatening complication of an infection and remains one of the leading causes of mortality in surgical patients. Bacteremia induces excessive inflammatory responses that result in multiple organ damage. Chronic helminth infection and helminth-derived materials have been found to immunomodulate host immune system to reduce inflammation against some allergic or inflammatory diseases. Schistosoma japonicum cystatin (Sj-Cys) is a cysteine protease inhibitor that induces regulatory T-cells and a potential immunomodulatory. The effect of Sj-Cys on reducing sepsis inflammation and mortality was investigated.

METHODS

Sepsis was induced in BALB/c mice using cecal ligation and puncture (CLP), followed by intraperitoneal injection of different doses (10, 25 or 50 μg) of recombinant Sj-Cys (rSj-Cys). The therapeutic effect of rSj-Cys on sepsis was evaluated by observing the survival rates of mice for 96 h after CLP and the pathological injury of liver, kidney and lung by measuring the levels of alanine transaminase (ALT), aspartate transaminase (AST), blood urea nitrogen (BUN) and creatinine (Cr) in sera and the tissue sections pathology, and the expression of MyD88 in liver, kidney and lung tissues. The immunological mechanism was investigated by examining pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) and IL-10 and TGF-β1 in mice sera and in culture of macrophages stimulated by lipopolysaccharides (LPS).

RESULTS

rSj-Cys treatment provided significant therapeutic effects on CLP-induced sepsis in mice demonstrated with increased survival rates, alleviated overall disease severity and tissue injury of liver, kidney and lung. The rSj-Cys conferred therapeutic efficacy was associated with upregualted IL-10 and TGF-β1 cytokines and reduced pro-inflammatory cytokines TNF-α, IL-6, IL-1β. MyD88 expression in liver, kidney and lung tissues of rSj-Cys-treated mice was reduced. In vitro assay with macrophages also showed that rSj-Cys inhibited the release of pro-inflammatory cytokines and mediator nitric oxide (NO) after being stimulated by lipopolysaccharide (LPS).

CONCLUSIONS

The results suggest the anti-inflammatory potential of rSj-Cys as a promising therapeutic agent on sepsis. The immunological mechanism underlying its therapeutic effect may involve the downregulation of pro-inflammatory cytokines and upregulation of IL-10 and TGF-β1 cytokines possibly via downregulation of the TLR adaptor-transducer MyD88 pathway. The findings suggest rSj-Cys is a potential therapeutic agent for sepsis and other inflammatory diseases.

The natural product bergenin ameliorates lipopolysaccharide-induced acute lung injury by inhibiting NF-kappaB activition

ETHNOPHARMACOLOGICAL RELEVANCE

Bergenin, an active constituent of the plants of the genus Bergenia, was reported to have anti-inflammatory effects in the treatment of chronic bronchitis and chronic gastritis clinically. However, its therapeutic effect on lipopolysaccharide (LPS)-induced acute lung injury (ALI) and its potential mechanisms of actions were still unknown.

AIM OF THIS STUDY

To evaluate the effect of bergenin on murine model of acute lung injury induced by LPS and also to explore its potential mechanisms.

MATERIALS AND METHODS

Half an hour and 12h after an intranasal inhalation of LPS, male BALB/c mice were treated with bergenin (50,100 and 200mg/kg) or dexamethasone (DEX, 5mg/kg) by gavage. Twenty-four hours after LPS exposure, the lung wet/dry ratio, histological changes, myeloperoxidase (MPO) in lung tissues, inflammatory cells (in BALF) and cytokines (in BALF and serum) were detected. Meanwhile, the protein expression of MyD88 and the phosphorylation of NF-κB p65 in lung tissue were analyzed using immunoblot analysis. Moreover, the nuclear translocation and the phosphorylation of NF-κB p65 in Raw264.7 cells were also analyzed. The viability of Raw264.7 cells was determined by MTT assay.

RESULTS

Results showed that bergenin significantly decreased pulmonary edema, improved histological changes and reduced MPO activity in lung tissues. Moreover, bergenin obviously decreased inflammatory cells, IL-1β and IL-6 production in BALF, as well as IL-1β, TNF-α and IL-6 production in serum of LPS-induced ALI mice. Furthermore, bergenin markedly inhibited LPS-induced NF-κB p65 phosphorylation, as well as the expression of MyD88 but not the expression of NF-κB p65 in lung tissues. Additionally, bergenin also significantly inhibited the nuclear translocation and the phosphorylation of NF-κB p65 stimulated by LPS in Raw264.7 cells.

CONCLUSIONS

These findings suggested that bergenin had a therapeutic effect on LPS-induced ALI by inhibiting NF-κB activition.

Toll-Like Receptor Ligand-Based Vaccine Adjuvants Require Intact MyD88 Signaling in Antigen-Presenting Cells for Germinal Center Formation and Antibody Production

Vaccines are critical in the fight against infectious diseases, and immune-stimulating adjuvants are essential for enhancing vaccine efficacy. However, the precise mechanisms of action of most adjuvants are unknown. There is an urgent need for customized and adjuvant formulated vaccines against immune evading pathogens that remain a risk today. Understanding the specific role of various cell types in adjuvant-induced protective immune responses is vital for an effective vaccine design. We have investigated the role of cell-specific MyD88 signaling in vaccine adjuvant activity in vivo, using Neisserial porin B (PorB), a TLR2 ligand-based adjuvant, compared with an endosomal TLR9 ligand (CpG) and toll-like receptor (TLR)-independent (alum, MF59) adjuvants. We found that intact MyD88 signaling is essential, separately, in all three antigen-presenting cell types [B cells, macrophages, and dendritic cells (DCs)] for optimal TLR ligand-based adjuvant activity. The role of MyD88 signaling in B cell and DC in vaccine adjuvant has been previously investigated. In this study, we now demonstrate that the immune response was also reduced in mice with macrophage-specific MyD88 deletion (Mac-MyD88-/-). We demonstrate that TLR-dependent adjuvants are potent inducers of germinal center (GC) responses, but GCs are nearly absent in Mac-MyD88-/- mice following immunization with TLR-dependent adjuvants PorB or CpG, but not with TLR-independent adjuvants MF59 or alum. Our findings reveal a unique and here-to-for unrecognized importance of intact MyD88 signaling in macrophages, to allow for a robust vaccine-induced immune responses when TLR ligand-based adjuvants are used.

The Role of Intestinal Alkaline Phosphatase in Inflammatory Disorders of Gastrointestinal Tract

Over the past few years, the role of intestinal alkaline phosphatase (IAP) as a crucial mucosal defence factor essential for maintaining gut homeostasis has been established. IAP is an important apical brush border enzyme expressed throughout the gastrointestinal tract and secreted both into the intestinal lumen and into the bloodstream. IAP exerts its effects through dephosphorylation of proinflammatory molecules including lipopolysaccharide (LPS), flagellin, and adenosine triphosphate (ATP) released from cells during stressful events. Diminished activity of IAP could increase the risk of disease through changes in the microbiome, intestinal inflammation, and intestinal permeability. Exogenous IAP exerts a protective effect against intestinal and systemic inflammation in a variety of diseases and represents a potential therapeutic agent in diseases driven by gut barrier dysfunction such as IBD. The intestinal protective mechanisms are impaired in IBD patients due to lower synthesis and activity of endogenous IAP, but the pathomechanism of this enzyme deficiency remains unclear. IAP has been safely administered to humans and the human recombinant form of IAP has been developed. This review was designed to provide an update in recent research on the involvement of IAP in intestinal inflammatory processes with focus on IBD in experimental animal models and human patients.

MyD88 in Mycobacterium tuberculosis infection

MyD88 adaptor protein mediates numerous biologically important signal transduction pathways in innate immunity. MyD88 signaling fosters bacterial containment and is necessary to raise an adequate innate and acquired immune response to Mycobacterium tuberculosis (Mtb). The phagosome is a crucial cellular location not only for Mtb replication, but it is also where components of the Myddosome and inflammasome are recruited. Besides its function as a TLR-adaptor protein, MyD88 may help stabilizing cytosolic receptors that are recruited to the phagosome. MyD88 plays a critical role not only in the generation of an inflammatory response, but also in inducing regulatory signals to prevent excessive inflammation and cellular damage in the lung.

Dendritic cell vaccines based on immunogenic cell death elicit danger signals and T cell-driven rejection of high-grade glioma

The promise of dendritic cell (DC)-based immunotherapy has been established by two decades of translational research. Of the four malignancies most targeted with clinical DC immunotherapy, high-grade glioma (HGG) has shown the highest susceptibility. HGG-induced immunosuppression is a roadblock to immunotherapy, but may be overcome by the application of T helper 1 (T(H)1) immunity-biased, next-generation, DC immunotherapy. To this end, we combined DC immunotherapy with immunogenic cell death (ICD; a modality shown to induce T(H)1 immunity) induced by hypericin-based photodynamic therapy. In an orthotopic HGG mouse model involving prophylactic/curative setups, both biologically and clinically relevant versions of ICD-based DC vaccines provided strong anti-HGG survival benefit. We found that the ability of DC vaccines to elicit HGG rejection was significantly blunted if cancer cell-associated reactive oxygen species and emanating danger signals were blocked either singly or concomitantly, showing hierarchical effect on immunogenicity, or if DCs, DC-associated MyD88 signal, or the adaptive immune system (especially CD8(+) T cells) were depleted. In a curative setting, ICD-based DC vaccines synergized with standard-of-care chemotherapy (temozolomide) to increase survival of HGG-bearing mice by ~300%, resulting in ~50% long-term survivors. Additionally, DC vaccines also induced an immunostimulatory shift in the brain immune contexture from regulatory T cells to T(H)1/cytotoxic T lymphocyte/T(H)17 cells. Analysis of the The Cancer Genome Atlas glioblastoma cohort confirmed that increased intratumor prevalence of T(H)1/cytotoxic T lymphocyte/T(H)17 cells linked genetic signatures was associated with good patient prognosis. Therefore, pending final preclinical checks, ICD-based vaccines can be clinically translated for glioma treatment.

A Zebrafish Model for Chlamydia Infection with the Obligate Intracellular Pathogen Waddlia chondrophila

Obligate intracellular chlamydial bacteria of the Planctomycetes-Verrucomicrobia-Chlamydiae (PVC) superphylum are important pathogens of terrestrial and marine vertebrates, yet many features of their pathogenesis and host specificity are still unknown. This is particularly true for families such as the Waddliacea which, in addition to epithelia, cellular targets for nearly all Chlamydia, can infect and replicate in macrophages, an important arm of the innate immune system or in their free-living amoebal counterparts. An ideal pathogen model system should include both host and pathogen, which led us to develop the first larval zebrafish model for chlamydial infections with Waddlia chondrophila. By varying the means and sites of application, epithelial cells of the swim bladder, endothelial cells of the vasculature and phagocytosing cells of the innate immune system became preferred targets for infection in zebrafish larvae. Through the use of transgenic zebrafish, we could observe recruitment of neutrophils to the infection site and demonstrate for the first time that W. chondrophila is taken up and replicates in these phagocytic cells and not only in macrophages. Furthermore, we present evidence that myeloid differentiation factor 88 (MyD88) mediated signaling plays a role in the innate immune reaction to W. chondrophila, eventually by Toll-like receptor (TLRs) recognition. Infected larvae with depleted levels of MyD88 showed a higher infection load and a lower survival rate compared to control fish. This work presents a new and potentially powerful non-mammalian experimental model to study the pathology of chlamydial virulence in vivo and opens up new possibilities for investigation of other members of the PVC superphylum.

MyD88 NEDDylation negatively regulates MyD88-dependent NF-κB signaling through antagonizing its ubiquitination

Myeloid differentiation factor 88 (MyD88) plays a central role in innate immunity response, however, how its activity is tightly regulated remains largely unknown. In this study, we identify MyD88 as a novel substrate of NEDD8, and demonstrate that MyD88 NEDDylation antagonizes its ubiquitination. Interestingly, in response to the stimulation of IL-1β, MyD88 NEDDylation is downregulated while its ubiquitination is upregulated. We also show that deNEDDylase NEDP1 serves as a regulator of this process. Furthermore, we demonstrate that NEDD8 negatively regulates the dimerization of MyD88 and suppresses MyD88-dependent NF-κB signaling. Taken together, this study reveals that NEDDylation of MyD88 regulates NF-κB activity through antagonizing its ubiquitination, suggesting a novel mechanism of modulating NF-κB signaling pathway.

Guanine nucleotide exchange factor RABGEF1 regulates keratinocyte-intrinsic signaling to maintain skin homeostasis

Epidermal keratinocytes form a structural and immune barrier that is essential for skin homeostasis. However, the mechanisms that regulate epidermal barrier function are incompletely understood. Here we have found that keratinocyte-specific deletion of the gene encoding RAB guanine nucleotide exchange factor 1 (RABGEF1, also known as RABEX-5) severely impairs epidermal barrier function in mice and induces an allergic cutaneous and systemic phenotype. RABGEF1-deficient keratinocytes exhibited aberrant activation of the intrinsic IL-1R/MYD88/NF-κB signaling pathway and MYD88-dependent abnormalities in expression of structural proteins that contribute to skin barrier function. Moreover, ablation of MYD88 signaling in RABGEF1-deficient keratinocytes or deletion of Il1r1 restored skin homeostasis and prevented development of skin inflammation. We further demonstrated that epidermal RABGEF1 expression is reduced in skin lesions of humans diagnosed with either atopic dermatitis or allergic contact dermatitis as well as in an inducible mouse model of allergic dermatitis. Our findings reveal a key role for RABGEF1 in dampening keratinocyte-intrinsic MYD88 signaling and sustaining epidermal barrier function in mice, and suggest that dysregulation of RABGEF1 expression may contribute to epidermal barrier dysfunction in allergic skin disorders in mice and humans. Thus, RABGEF1-mediated regulation of IL-1R/MYD88 signaling might represent a potential therapeutic target.

Lipopolysaccharide and IL-1β coordinate a synergy on cytokine production by upregulating MyD88 expression in human gingival fibroblasts

Both lipopolysaccharide (LPS) and interleukin (IL)-1β activate the MyD88-dependent signaling pathways to stimulate proinflammatory cytokine expression. However, it remains unknown how LPS and IL-1β interact with each other to coordinate the stimulation. In this study, we sought to investigate the interaction between LPS and IL-1β on MyD88-dependent signaling pathways in human gingival fibroblasts (HGFs). Results showed that LPS derived from Porphyromonas gingivalis (Pg LPS) and IL-1β cooperatively stimulated mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NFκB) signaling pathways, and subsequent expression of proinflammatory cytokine expression. Furthermore, our results showed that Pg LPS and IL-1β exerted a synergy on MyD88 expression and knockdown of MyD88 expression by small interfering RNA diminished the synergistic effect of Pg LPS and IL-1β on IL-6 expression, suggesting that upregulation of MyD88 is involved in the coordinated stimulation by Pg LPS and IL-1β of proinflammatory cytokine expression. Finally, our results showed that pharmacological inhibitors for MAPK and NFκB significantly reduced IL-6 secretion stimulated by Pg LPS and IL-1β, indicating that the MyD88-dependent MAPK and NFκB signaling pathways are essential for the upregulation of proinflammatory cytokine expression by Pg LPS and IL-1β. Taken together, this study showed that LPS and IL-1β coordinate a synergy on cytokine production by upregulating MyD88 expression in HGFs.

TLR9 re-expression in cancer cells extends the S-phase and stabilizes p16(INK4a) protein expression

Toll-like receptor 9 (TLR9) recognizes bacterial, viral or cell damage-associated DNA, which initiates innate immune responses. We have previously shown that TLR9 expression is downregulated in several viral induced cancers including HPV16-induced cervical neoplasia. Findings supported that downregulation of TLR9 expression is involved in loss of anti-viral innate immunity allowing an efficient viral replication. Here we investigated the role of TLR9 in altering the growth of transformed epithelial cells. Re-introducing TLR9 under the control of an exogenous promoter in cervical or head and neck cancer patient-derived cells reduced cell proliferation, colony formation and prevented independent growth of cells under soft agar. Neither TLR3, 7, nor the TLR adapter protein MyD88 expression had any effect on cell proliferation, indicating that TLR9 has a unique role in controlling cell growth. The reduction of cell growth was not due to apoptosis or necrosis, yet we observed that cells expressing TLR9 were slower in entering the S-phase of the cell cycle. Microarray-based gene expression profiling analysis highlighted a strong interferon (IFN) signature in TLR9-expressing head and neck cancer cells, with an increase in IFN-type I and IL-29 expression (IFN-type III), yet neither IFN-type I nor IL-29 production was responsible for the block in cell growth. We observed that the protein half-life of p16(INK4a) was increased in TLR9-expressing cells. Taken together, these data show for the first time that TLR9 affects the cell cycle by regulating p16(INK4a) post-translational modifications and highlights the role of TLR9 in the events that lead to carcinogenesis.