Toll like receptors and autoimmunity: a critical appraisal

Resolution of chronic inflammation and cancer

Chronic inflammation poses challenges to effective cancer treatment. Although anti-inflammatory therapies have shown short-term benefits, their long-term implications may be unfavorable because they fail to initiate the necessary inflammatory responses. Recent research underscores the promise of specialized pro-resolving mediators, which play a role in modulating the cancer microenvironment by promoting the resolution of initiated inflammatory processes and restoring tissue hemostasis. This review addresses current insights into how inflammation contributes to cancer pathogenesis and explores recent strategies to resolve inflammation associated with cancer.

Herbal supplement Spirulina stimulates inflammatory cytokine production in patients with dermatomyositis in vitro

Spirulina, an herbal supplement and popular ingredient in health foods, is a potent stimulant of the immune system. Spirulina use is temporally associated with the onset or exacerbation of Dermatomyositis (DM), an autoimmune connective tissue disease that frequently affects the skin and muscle. In this study, we investigated the effect of Spirulina on peripheral blood mononuclear cells (PBMCs) in DM and Healthy Controls (HCs), showing that Spirulina stimulates Interferon β (IFNβ), Tumor necrosis factor α (TNFα), and Interferon γ (IFNγ) production of DM PBMCs primarily via Toll-Like Receptor 4 (TLR4) activation using ELISA (enzyme linked immunosorbent assay) and flow cytometry. We show that classical monocytes and monocyte-derived dendritic cells are stimulated by Spirulina and are activated via TLR4. Skin from patients with Spirulina-associated DM exhibits an inflammatory milieu similar to that of idiopathic DM but with a stronger correlation of TLR4 and IFNγ.

Immunological and Metabolic Causes of Infertility in Polycystic Ovary Syndrome

Infertility has been recognized as a civilizational disease. One of the most common causes of infertility is polycystic ovary syndrome (PCOS). Closely interrelated immunometabolic mechanisms underlie the development of this complex syndrome and lead to infertility. The direct cause of infertility in PCOS is ovulation and implantation disorders caused by low-grade inflammation of ovarian tissue and endometrium which, in turn, result from immune and metabolic system disorders. The systemic immune response, in particular the inflammatory response, in conjunction with metabolic disorders, insulin resistance (IR), hyperadrenalism, insufficient secretion of progesterone, and oxidative stress lead not only to cardiovascular diseases, cancer, autoimmunity, and lipid metabolism disorders but also to infertility. Depending on the genetic and environmental conditions as well as certain cultural factors, some diseases may occur immediately, while others may become apparent years after an infertility diagnosis. Each of them alone can be a significant factor contributing to the development of PCOS and infertility. Further research will allow clinical management protocols to be established for PCOS patients experiencing infertility so that a targeted therapy approach can be applied to the factor underlying and driving the "vicious circle" alongside symptomatic treatment and ovulation stimulation. Hence, therapy of fertility for PCOS should be conducted by interdisciplinary teams of specialists as an in-depth understanding of the molecular relationships and clinical implications between the immunological and metabolic factors that trigger reproductive system disorders is necessary to restore the physiology and homeostasis of the body and, thus, fertility, among PCOS patients.

Association of Single Nucleotide Polymorphisms from Angiogenesis-Related Genes, ANGPT2, TLR2 and TLR9, with Spontaneous Preterm Labor

In this study, we hypothesized that the changes localized at angiopoietin-2 (ANGPT2), granulocyte-macrophage colony-stimulating factor (CSF2), fms-related tyrosine kinase 1 (FLT1) and toll-like receptor (TLR) 2, TLR6 and TLR9 genes were associated with spontaneous preterm labor (PTL), as well as with possible genetic alterations on PTL-related coagulation. This case-control genetic association study aimed to identify single nucleotide polymorphisms (SNPs) for the aforementioned genes, which are correlated with genetic risk or protection against PTL in Polish women. The study was conducted in 320 patients treated between 2016 and 2020, including 160 women with PTL and 160 term controls in labor. We found that ANGPT2 rs3020221 AA homozygotes were significantly less common in PTL cases than in controls, especially after adjusting for activated partial thromboplastin time (APTT) and platelet (PLT) parameters. TC heterozygotes for TLR2 rs3804099 were associated with PTL after correcting for anemia, vaginal bleeding, and history of threatened miscarriage or PTL. TC and CC genotypes in TLR9 rs187084 were significantly less common in women with PTL, compared to the controls, after adjusting for bleeding and gestational diabetes. For the first time, it was shown that three polymorphisms-ANGPT2 rs3020221, TLR2 rs3804099 and TLR9 rs187084 -were significantly associated with PTL, adjusted by pregnancy development influencing factors.

Toll-like receptor 5 and Toll-like receptor 9 single nucleotide polymorphisms and risk of systemic lupus erythematosus and nephritis in Egyptian patients

Background

Toll-like (TLRs) play a crucial role in both adaptive and innate immunity. The aim of the present study was to assess the association of TLR5-rs5744168, TLR9-rs187084, and TLR9-rs352140 single nucleotide polymorphisms (SNPs) with susceptibility to systemic lupus erythematosus (SLE) and lupus nephritis (LN) in Egyptian patients.

Results

The C allele and homozygous CC genotype of the TLR9-rs352140 in co-dominant and recessive models were more prevalent in SLE patients than controls (P = 0.047, P = 0.017, and P = 0.005 respectively). In contrast, allelic and genotyping distribution of TLR5-rs5744168 and TLR9-rs187084 SNPs showed no association with the risk of SLE. The T allele of the TLR5-rs5744168 was more prevalent in LN patients than controls (P = 0.021). The homozygous TT genotype of TLR5-rs5744168 SNP was more prevalent in LN patients in the co-dominant and the recessive models than controls (P = 0.036 and P = 0.011 respectively). The C allele of the TLR9-rs352140 was more prevalent in LN patients than controls (P = 0.015). The homozygous CC genotype of the TLR9-rs352140 SNP was more prevalent in LN than controls in co-dominant and recessive models (P = 0.002 and P < 0.001). In the recessive model of the TLR5-rs5744168 SNP, the TT genotype was found in 3.2% of the SLE patients while none of the SLE patients without LN or controls had TT genotype (P = 0.036). Also, in the recessive model of the TLR9-rs352140 SNP, the CC genotype was significantly more frequent in SLE patients with LN than without LN (44.4% vs 29.9%, P = 0.045).

Conclusion

Our results support the potential role of TLR5-rs5744168 SNP and TLR9-rs3532140 SNP not only in increasing the risk for development of SLE, but also in increasing the risk of LN in SLE patients among the Egyptian population.

Impaired Innate Immunity in Pediatric Patients Type 1 Diabetes-Focus on Toll-like Receptors Expression

Type 1 diabetes (DM1) is classified as an autoimmune disease. An uncontrolled response of B and T lymphocytes to the body's own tissues develops in the absence of immune tolerance. The main aim of the study was to evaluate the effect of the duration of type 1 diabetes in children on the expression of TLR receptors and the relationship with the parameters of glycemic control in patients. As a result, we showed significant differences in the level of TLR2, TLR4 and TLR9 expression in patients with DM1 in the early stage of the disease and treated chronically compared to the healthy group. Additionally, in this study, we found that the numbers of CD19+ B cells, CD3+ CD4+, CD3+ CD8+ T cells and NK cells are different for newly diagnosed DM1 individuals, patients receiving chronic treatment and for healthy controls, indicating an important role of these cells in killing pancreatic beta cells. Moreover, higher levels of IL-10 in patients with newly diagnosed DM1 have also been found, confirming the reports found in the literature.

Synergistic Activation of Toll-Like and NOD Receptors by Complementary Antigens as Facilitators of Autoimmune Disease: Review, Model and Novel Predictions

Persistent activation of toll-like receptors (TLR) and nucleotide-binding oligomerization domain-containing proteins (NOD) in the innate immune system is one necessary driver of autoimmune disease (AD), but its mechanism remains obscure. This study compares and contrasts TLR and NOD activation profiles for four AD (autoimmune myocarditis, myasthenia gravis, multiple sclerosis and rheumatoid arthritis) and their animal models. The failure of current AD theories to explain the disparate TLR/NOD profiles in AD is reviewed and a novel model is presented that explains innate immune support of persistent chronic inflammation in terms of unique combinations of complementary AD-specific antigens stimulating synergistic TLRs and/or NODs. The potential explanatory power of the model is explored through testable, novel predictions concerning TLR- and NOD-related AD animal models and therapies.

Effect of Interferon alfa-2a Treatment on Adaptive and Innate Immune Systems in Patients With Behçet Disease Uveitis

Purpose

To investigate the effect of interferon alfa-2a on T regulatory (Treg) cells, T helper 17 (Th17) cells, and expression of Toll-like receptors (TLRs) in Behçet disease (BD) patients with uveitis.

Methods

Twenty-seven patients who received interferon alfa-2a for active BD uveitis despite conventional immunomodulatory therapies and healthy controls were enrolled. Peripheral blood Treg and Th17 cell frequencies were determined by flow cytometry as gated cells for CD3+CD4+Foxp3+ and CD3+CD4+IL17A+, respectively. Th17 RAR-related orphan receptor (ROR)γt mRNA expression was verified by real-time PCR (RT-PCR). Treg and Th17 cell cytokines were detected by ELISA in the supernatant of short-term cell cultures. RT-PCR was used to assess expression of TLR-2, TLR-3, TLR-4, TLR-8, and TLR-9 using cDNA prepared from CD4+ T cells and monocytes.

Results

Treg and Th17 cell frequencies and Th17 RORγt expression were significantly elevated, and IL-10 concentration in Treg cell supernatants was significantly lower in BD patients than in controls. Th17 IL-17, IL-6, IL-21, IL-22, IL-23, IFN-γ, and TNF-α concentrations were significantly higher and all TLR expressions were significantly elevated in patients. Interferon alfa-2a led to a significant reversal in Treg and Th17 cell frequencies, Th17 RORγt expression, Treg and Th17 cell cytokine production, and TLR expression by CD4+ T cells and monocytes.

Conclusions

Despite a relative increase in Treg cells, impaired IL-10 production suggests that Treg dysfunction may play a role in induction of BD uveitis. Favorable effects of interferon alfa-2a may be associated with recovery of Treg cell function, suppression of Th17 cells, and reduced expression of TLRs on CD4+ T cells and monocytes.

The Role of TLR4 Asp299Gly and TLR4 Thr399Ile Polymorphisms in the Pathogenesis of Urinary Tract Infections: First Evaluation in Infants and Children of Greek Origin

Urinary tract infections are one of the most common and serious bacterial infections in a pediatric population. So far, they have mainly been related to age, gender, ethnicity, socioeconomic level, and the presence of underlying anatomical or functional, congenital, or acquired abnormalities. Recently, both innate and adaptive immunities and their interaction in the pathogenesis and the development of UTIs have been studied. The aim of this study was to assess the role and the effect of the two most frequent polymorphisms of TLR4 Asp299Gly and Thr399Ile on the development of UTIs in infants and children of Greek origin. We studied 51 infants and children with at least one episode of acute urinary tract infection and 109 healthy infants and children. We found that 27.5% of patients and 8.26% of healthy children carried the heterozygote genotype for TLR4 Asp299Gly. TLR4 Thr399Ile polymorphism was found to be higher in healthy children and lower in the patient group. No homozygosity for both studied polymorphisms was detected in our patients. In the group of healthy children, a homozygote genotype for TLR4 Asp299Gly (G/G) as well as for TLR4 Thr399Ile (T/T) was showed (1.84% and 0.92 respectively). These results indicate the role of TLR4 polymorphism as a genetic risk for the development of UTIs in infants and children of Greek origin.

Carp Toll-like receptor 8 (Tlr8): An intracellular Tlr that recruits TIRAP as adaptor and activates AP-1 pathway in immune response

Toll-like receptor 8 (Tlr8) is a member of intracellular TLRs family and play a critical role in the innate immunity. In the present study, we aimed to identify tlr8 from common carp (Cyprinus carpio L.), and explored its expression profile, localization, adaptor, and signaling pathways. A novel tlr8 cDNA sequence (Cctlr8) was identified from the carp, containing a signal peptide, a LRR-N-terminal (LRR-NT), 14 leucine-rich repeats, a LRR-C-terminal (LRR-CT), a transmembrane region and a TIR domain. Phylogenetic analysis revealed that CcTlr8 exhibited closest relationship to that of Ctenopharyngodon idella and Danio. rerio. Subcellular localization analysis indicated that CcTlr8 was localized to the endoplasmic reticulum in both HeLa cells and EPC cells. Quantitative Real-Time PCR analysis demonstrated that Cctlr8 was constitutively expressed in all the examined tissues, with the highest expression observed in the spleen. After poly (I:C) injection, the expression of Cctlr8 was significantly up-regulated in all the tested tissues. In addition, the expression of Cctlr8 was up-regulated in both PBLs and HKLs following poly (I:C) stimulation. The results of immuofluorescence and coimmunoprecipitation analysis indicated that CcTlr8 might recruit TIRAP as the adaptor. Furthermore, Luciferase reporter assays revealed that CcTlr8 could activate AP-1 in 293 T cells. Taken altogether, these findings lay the foundations for future research to investigate the mechanisms underlying fish tlr8.

Mycobacterium tuberculosis: An Adaptable Pathogen Associated With Multiple Human Diseases

Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), is an extremely successful pathogen that adapts to survive within the host. During the latency phase of infection, M. tuberculosis employs a range of effector proteins to be cloud the host immune system and shapes its lifestyle to reside in granulomas, sophisticated, and organized structures of immune cells that are established by the host in response to persistent infection. While normally being restrained in immunocompetent hosts, M. tuberculosis within granulomas can cause the recrudescence of TB when host immunity is compromised. Aside from causing TB, accumulating evidence suggests that M. tuberculosis is also associated with multiple other human diseases, such as pulmonary complications, autoimmune diseases, and metabolic syndromes. Furthermore, it has been recently appreciated that M. tuberculosis infection can also reciprocally interact with the human microbiome, which has a strong link to immune balance and health. In this review, we highlight the adaptive survival of M. tuberculosis within the host and provide an overview for regulatory mechanisms underlying interactions between M. tuberculosis infection and multiple important human diseases. A better understanding of how M. tuberculosis regulates the host immune system to cause TB and reciprocally regulates other human diseases is critical for developing rational treatments to better control TB and help alleviate its associated comorbidities.

Systemic inflammation in asocial BTBR T+ tf/J mice predisposes them to increased psoriatic inflammation

Autistic Spectrum disorder (ASD) is a neurobehavioral disorder characterized by defects in communication skills leading to restricted sociability. ASD has immense dysregulation in immune responses which is thought to affect neuronal system and thus behavior. ASD patients and BTBR T⁺ tf/J (BTBR) autistic mice have increased systemic inflammation due to dysfunction in innate and adaptive immune responses. Recent studies suggest that ASD patients are associated with several co-morbid autoimmune disorders including psoriasis. However underlying mechanisms for this phenomenon have not been explored. In this study, we used imiquimod (IMQ)-induced psoriatic inflammation in social C57BL/6 (C57) mice and asocial BTBR mice to investigate whether systemic inflammation in BTBR is associated with increased susceptibility to psoriatic inflammation. Our data shows that BTBR mice have increased expression of TLR7/IL-6/IL-23 in systemic DCs but not in skin as compared to C57 mice at baseline. This leads to much greater psoriatic inflammation in BTBR mice upon IMQ application than C57 mice. Consequently, BTBR mice also have higher Th17 related immune responses in the skin and systemic compartment. Overall our study suggests that systemic innate (TLR7/IL-23/IL-6 in DCs) and adaptive (Th17 related signaling) immune responses are heightened in BTBR mice at baseline which predisposes them for greater psoriatic inflammation than C57 mice upon IMQ application. This could be one of the reasons for increased psoriatic inflammation in patients with ASD. Therapies that aim to decrease immune activation may not only benefit ASD-associated neurobehavioral abnormalities but also comorbid disorders such as psoriasis.

Increased Abundance of Plasmacytoid Dendritic Cells and Interferon-Alpha Induces Plasma Cell Differentiation in Patients of IgA Nephropathy

The roles of pDC and IFN-α have not been well defined in IgA nephropathy (IgAN). In this study, we investigated the abundance of pDCs and IFN-α in IgAN patients and the response of peripheral blood mononuclear cells (PBMCs) after stimulation of the pDC-preferred TLR9 ligand CpG2216. The effects of IFN-α on plasma cell differentiation and leukocyte migration were also investigated. Here, we found that the percentages of pDCs were increased in PBMCs of IgAN patients, than in those of healthy controls. Plasma levels of IFN-α proteins and abundance of plasma cells were higher in IgAN patients than in healthy donors. Plasma IFN-α levels were positively associated with proteinuria, renal IgM deposition, and renal tubular atrophy/interstitial fibrosis grade in IgAN patients. Ex vivo activation of TLR9 on pDCs resulted in increased IFN-α production and enhanced plasma cell differentiation in IgAN patients as compared with healthy donors. IFN-α treatment led to increased plasma cell differentiation in vitro. IFN-α also significantly promoted expression of chemokines IP-10 and MCP-1 in human mesangial cells, which subsequently facilitated the transendothelial migration of human CD4⁺ and CD14⁺ cells. In conclusion, pDC and its secreted cytokine IFN-α may play important roles in pathological changes of IgA nephropathy.

Relevant genetic polymorphisms and kidney expression of Toll-like receptor (TLR)-5 and TLR-9 in lupus nephritis

Toll-like receptor (TLR) genetic polymorphisms may modify their expression causing inflammatory disorders and influencing both susceptibility and severity of lupus erythematosus. We aim to determine whether TLR-5 and TLR-9 gene polymorphisms are implicated in the susceptibility to systemic lupus erythematosus (SLE) and lupus nephritis (LN) and to evaluate their expressions and distributions in renal LN patients' biopsies. The frequencies of two SNP in the TLR-9 gene and one in the TLR-5 gene was examined in 106 SLE patients (among them 37 LN patients) and in 200 matched controls by polymerase chain reaction-restriction fragment-length polymorphisms (PCR-RFLP) analysis. TLR-9 and TLR-5 expressions were assessed by reverse transcription (RT)-PCR and immunohistochemistry carried on LN renal biopsies compared to healthy renal tissue. A significant genotypic and allelic association was revealed between TLR-9-rs352140 and both SLE and LN (P < 0·05). The TLR-9 transcript level was significantly higher in LN biopsies compared to control (P < 0·05). This increase was observed histochemically in the tubulointerstitial compartment. TLR-9 was detectable in LN glomeruli patients but not in normal control glomeruli. No allelic nor genotype association was found with TLR-5-rs5744168 in SLE. but the T allele and the TT genotype were raised significantly in the LN group (P < 0·05). A significant increase in TLR-5 gene expression in LN biopsies, which contrasted with normal kidneys (P < 0·05), was confirmed by an intense and diffuse staining for TLR-5 only in LN tubules (P < 0·05). Our data show that TLR-5 and TLR-9 are susceptible genes to LN and that their expression is dysregulated in LN patients' kidneys, supporting a role of these mediators in the pathogenesis of LN.

Small-molecule inhibition of TLR8 through stabilization of its resting state

Endosomal Toll-like receptors (TLR3/7/8/9) are highly analogous sensors for various viral or bacterial RNA/DNA molecular patterns. Nonetheless, few small-molecules can selectively modulate these TLRs. In this manuscript, we identified the first human TLR8-specific small-molecule antagonists via a novel inhibition mechanism. Crystal structures of two distinct TLR8-ligand complexes validated a unique binding site on the protein-protein interface of the TLR8 homodimer. Upon binding to this new site, the small-molecule ligands stabilize the preformed TLR8 dimer in its resting state, preventing activation. As a proof of concept of their therapeutic potential, we have demonstrated that these drug-like inhibitors are able to suppress TLR8-mediated proinflammatory signaling in various cell lines, human primary cells, and patient specimens. These results not only suggest a novel strategy for TLR inhibitor design, but also shed critical mechanistic insight into these clinically important immune receptors.

Toward a structural understanding of nucleic acid-sensing Toll-like receptors in the innate immune system

The history of mankind has been plagued by the tug of war with viral infections. Toll-like receptors (TLRs) and other receptors of the innate immune system constitute an early defense system against invading viruses by recognizing the viral genetic material, the nucleic acids (NAs). Agonistic ligands of NA-sensing TLRs play an emerging role in the treatment of viral diseases, demonstrating a crucial role of these receptors. Recently, crystal structures have afforded new insights into TLR recognition of NAs. An aberrant activation by self-NAs, which leads to the inflammation and autoimmunity, is avoided by strict regulation of NA-TLR interaction at multiple check-points. This Review summarizes the novel structural understanding of NA-sensing by TLRs and regulatory mechanisms of these receptors.

The Role of Toll-Like Receptors in Autoimmune Diseases through Failure of the Self-Recognition Mechanism

Toll-like receptors (TLRs), part of the innate immune system that recognises molecular signatures, are important in the recognition of pathogenic components. However, when specific cellular contexts develop in which TLRs are inappropriately activated by self-components, this may lead to sterile inflammation and result in the occurrence of autoimmunity. This review analyses the available data regarding TLR biochemistry, the specific mechanisms which are brought about by TLR activation, and the importance of these mechanisms in the light of any existing and potential therapies in the field of autoimmunity.

Understanding the dynamics of Toll-like Receptor 5 response to flagellin and its regulation by estradiol

Toll-like receptors (TLRs) are major players of the innate immune system. Once activated, they trigger a signalling cascade that leads to NF-κB translocation from the cytoplasm to the nucleus. Single cell analysis shows that NF-κB signalling dynamics are a critical determinant of transcriptional regulation. Moreover, the outcome of innate immune response is also affected by the cross-talk between TLRs and estrogen signalling. Here, we characterized the dynamics of TLR5 signalling, responsible for the recognition of flagellated bacteria, and those changes induced by estradiol in its signalling at the single cell level. TLR5 activation in MCF7 cells induced a single and sustained NF-κB translocation into the nucleus that resulted in high NF-κB transcription activity. The overall magnitude of NF-κB transcription activity was not influenced by the duration of the stimulus. No significant changes are observed in the dynamics of NF-κB translocation to the nucleus when MCF7 cells are incubated with estradiol. However, estradiol significantly decreased NF-κB transcriptional activity while increasing TLR5-mediated AP-1 transcription. The effect of estradiol on transcriptional activity was dependent on the estrogen receptor activated. This fine tuning seems to occur mainly in the nucleus at the transcription level rather than affecting the translocation of the NF-κB transcription factor.

Identification of the long noncoding RNA NEAT1 as a novel inflammatory regulator acting through MAPK pathway in human lupus

Long noncoding RNAs (lncRNAs) have recently been identified to be tightly linked to diverse human diseases. However, our knowledge of Systemic Lupus Erythematosus (SLE)-related lncRNAs remains limited. In the present study we investigated the contribution of the lncRNA NEAT1 to the pathogenesis of SLE. Here, we found NEAT1 expression was abnormally increased in SLE patients and predominantly expressed in human monocytes. Additionally, NEAT1 expression was induced by LPS via p38 activation. Silencing NEAT1 significantly reduced the expression of a group of chemokines and cytokines, including IL-6, CXCL10, etc., which were induced by LPS continuously and in late stages. Furthermore, it was identified the involvement of NEAT1 in TLR4-mediated inflammatory process was through affecting the activation of the late MAPK signaling pathway. Importantly, there was a positive correlation between NEAT1 and clinical disease activity in SLE patients. In conclusion, the increased NEAT1 expression may be a potential contributor to the elevated production of a number of cytokines and chemokines in SLE patients. Our findings suggest lncRNA contributes to the pathogenesis of lupus and provides potentially novel target for therapeutic intervention.

Knockdown of Myeloid Differentiation Factor 88 Attenuates Lipopolysaccharide-Induced Inflammatory Response in Pancreatic Ductal Cells

OBJECTIVES

The aim of the study was to explore the potential role of myeloid differentiation factor 88 (MyD88), which acts as an adaptor in the TLR4 signalling pathway, in immune responses of the pancreatic duct during acute pancreatitis.

METHODS

Primary cultures of pancreatic duct epithelial cells from Wistar rats and cultures of the pancreatic ductal ARIP cell line were treated with lipopolysaccharide (LPS), and expression of toll-like receptor 4 mRNA was determined using real-time PCR, expression of MyD88 protein using Western blot, and levels of inflammatory cytokines using enzyme-linked immunosorbent assay. These experiments were repeated using ARIP cells in which MyD88 expression was stably knocked down.

RESULTS

Toll-like receptor 4 and MyD88 expression were similar between pancreatic duct epithelial cells and ARIP cells after LPS stimulation. Myeloid differentiation factor 88 knockdown led to significantly lower levels of inflammatory cytokines after LPS induction in ARIP cells.

CONCLUSIONS

Myeloid differentiation factor 88 knockdown attenuates LPS-induced inflammatory responses in pancreatic ductal cells, suggesting that the MyD88 pathway plays a critical role in their immune defense activity.

Toll-Like Receptors in the Pathogenesis of Autoimmune Diseases

Human Toll-like receptors (TLRs) are a family of transmembrane receptors, which play a key role in both innate and adaptive immune responses. Beside of recognizing specific molecular patterns that associated with different types of pathogens, TLRs may also detect a number of self-proteins and endogenous nucleic acids. Activating TLRs lead to the heightened expression of various inflammatory genes, which have a protective role against infection. Data rising predominantly from human patients and animal models of autoimmune disease indicate that, inappropriate triggering of TLR pathways by exogenous or endogenous ligands may cause the initiation and/or perpetuation of autoimmune reactions and tissue damage. Given their important role in infectious and non-infectious disease process, TLRs and its signaling pathways emerge as appealing targets for therapeutics. In this review, we demonstrate how TLRs pathways could be involved in autoimmune disorders and their therapeutic application.

TLR3/TRIF signalling pathway regulates IL-32 and IFN-β secretion through activation of RIP-1 and TRAF in the human cornea

Toll-like receptor-3 (TLR3) and RNA helicase retinoic-acid-inducible protein-1 (RIG-I) serve as cytoplasmic sensors for viral RNA components. In this study, we investigated how the TLR3 and RIG-I signalling pathway was stimulated by viral infection to produce interleukin (IL)-32-mediated pro-inflammatory cytokines and type I interferon in the corneal epithelium using Epstein-Barr virus (EBV)-infected human cornea epithelial cells (HCECs/EBV) as a model of viral keratitis. Increased TLR3 and RIG-I that are responded to EBV-encoded RNA 1 and 2 (EBER1 and EBER2) induced the secretion of IL-32-mediated pro-inflammatory cytokines and IFN-β through up-regulation of TRIF/TRAF family proteins or RIP-1. TRIF silencing or TLR3 inhibitors more efficiently inhibited sequential phosphorylation of TAK1, TBK1, NF-κB and IRFs to produce pro-inflammatory cytokines and IFN-β than RIG-I-siRNA transfection in HCECs/EBV. Blockade of RIP-1, which connects the TLR3 and RIG-I pathways, significantly blocked the TLR3/TRIF-mediated and RIG-I-mediated pro-inflammatory cytokines and IFN-β production in HCECs/EBV. These findings demonstrate that TLR3/TRIF-dependent signalling pathway against viral RNA might be a main target to control inflammation and anti-viral responses in the ocular surface.

TLR9 expressed on plasma membrane acts as a negative regulator of human B cell response

Toll-like receptors (TLRs) are positioned at the interface between innate and adaptive immunity. Unlike others, those such as TLR9, that recognize nucleic acids, are confined to the endosomal compartment and are scarce on the cell surface. Here, we present evidence for TLR9 expression on the plasma membrane of B cells. In contrast to endosomal TLR9, cell surface TLR9 does not bind CpG-B oligodeoxynucleotides. After B cell-receptor (BCR) stimulation, TLR9 was translocated into lipid rafts with the BCR, suggesting that it could serve as a co-receptor for BCR. Nevertheless, stimulation of B cells with anti-TLR9 antibodies did not modify the BCR-induced responses despite up-regulation of tyrosine phosphorylation of proteins. However, CpG-B activation of B cells, acting synergistically with BCR signals, was inhibited by anti-TLR9 stimulation. Induction of CD25 expression and proliferation of B cells were thus down-regulated by the engagement of cell surface TLR9. Overall, our results indicate that TLR9 expressed on the plasma membrane of B cells might be a negative regulator of endosomal TLR9, and could provide a novel control by which activation of autoreactive B cells is restrained.

Expression of toll-like receptors 3, 7, and 9 in peripheral blood mononuclear cells from patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown aetiology. The results of experimental studies point to the involvement of innate immunity receptors-toll-like receptors (TLR)-in the pathogenesis of the disease. The aim of the study was to assess the expression of TLR3, 7, and 9 in the population of peripheral blood mononuclear cells (PBMC) and in B lymphocytes (CD19(+)), T lymphocytes (CD4(+) and CD8(+)) using flow cytometry. The study group included 35 patients with SLE and 15 healthy controls. The patient group presented a significantly higher percentage of TLR3- and TLR9-positive cells among all PBMCs and their subpopulations (CD3(+), CD4(+), CD8(+), and CD19(+) lymphocytes) as well as TLR7 in CD19(+) B-lymphocytes, compared to the control group. There was no correlation between the expression of all studied TLRs and the disease activity according to the SLAM scale, and the degree of organ damage according to the SLICC/ACR Damage Index. However, a correlation was observed between the percentage of various TLR-positive cells and some clinical (joint lesions) and laboratory (lymphopenia, hypogammaglobulinemia, anaemia, and higher ESR) features and menopause in women. The results of the study suggest that TLR3, 7, and 9 play a role in the pathogenesis of SLE and have an impact on organ involvement in SLE.

Toxoplasma gondii: bystander or cofactor in rheumatoid arthritis

Parasitic infections may induce variable immunomodulatory effects and control of autoimmune disease. Toxoplasma gondii (T. gondii) is a ubiquitous intracellular protozoan that was recently associated with autoimmunity. This study was undertaken to investigate the seroprevalence and clinical correlation of anti-T. gondii antibodies in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). We evaluated sera from European patients with RA (n = 125) and SLE (n = 164) for the prevalence of anti-T. gondii IgG antibodies (ATXAb), as well as other common infections such as Cytomegalovirus, Epstein-Barr, and Rubella virus. The rates of seropositivity were determined utilizing the LIAISON chemiluminescent immunoassays (DiaSorin, Italy). Our results showed a higher seroprevalence of ATXAb in RA patients, as compared with SLE patients [63 vs. 36 %, respectively (p = 0.01)]. The rates of seropositivity of IgG against other infectious agents were comparable between RA and SLE patients. ATXAb-seropositivity was associated with older age of RA patients, although it did not correlate with RA disease activity and other manifestations of the disease. In conclusion, our data suggest a possible link between exposure to T. gondii infection and RA.

Identifying functional modules for coronary artery disease by a prior knowledge-based approach

Until recently, the underlying genetic mechanisms for coronary artery disease (CAD) have been largely unknown, with just a list of genes identified accounting for very little of the disease in the population. Hence, a systematic dissection of the sophisticated interplays between these individual disease genes and their functional involvements becomes essential. Here, we presented a novel knowledge-based approach to identify the functional modules for CAD. First, we selected 266 disease genes in CADgene database as the initial seed genes, and used PPI knowledge as a guide to expand these genes into a CAD-specific gene network. Then, we used Newman's algorithm to decompose the primary network into 14 compact modules with high modularity. By analysis of these modules, we further identified 114 hub genes, all either directly or indirectly associated with CAD. Finally, by functional analysis of these modules, we revealed several novel pathogenic mechanisms for CAD (for examples, some yet rarely concerned like peptide YY receptor activity, Fc gamma R-mediated phagocytosis and actin cytoskeleton regulation etc.).

Nucleic Acid sensors and type I interferon production in systemic lupus erythematosus

The characteristic serologic feature of systemic lupus erythematosus (SLE) is autoantibodies against one’s own nucleic acid or nucleic acid-binding proteins – DNA and RNA-binding nuclear proteins. Circulating autoantibodies can deposit in the tissue, causing inflammation and production of cytokines such as type 1 interferon (IFN). Investigations in human patients and animal models have implicated environmental as well as genetic factors in the biology of the SLE autoimmune response. Viral/Bacterial nucleic acid is a potent stimulant of innate immunity by both toll-like receptor (TLR) and non-TLR signaling cascades. Additionally, foreign DNA may act as an immunogen to drive an antigen-specific antibody response. Self nucleic acid is normally restricted to the nucleus or the mitochondria, away from the DNA/RNA sensors, and mechanisms exist to differentiate between foreign and self nucleic acid. In normal immunity, a diverse range of DNA and RNA sensors in different cell types form a dynamic and integrated molecular network to prevent viral infection. In SLE, pathologic activation of these sensors occurs via immune complexes consisting of autoantibodies bound to DNA or to nucleic acid-protein complexes. In this review, we will discuss recent studies outlining how mismanaged nucleic acid sensing networks promote autoimmunity and result in the over-production of type I IFN. This information is critical for improving therapeutic strategies for SLE disease.

TLR9 deficiency promotes CD73 expression in T cells and diabetes protection in nonobese diabetic mice

TLR9-deficient (TLR9⁻/⁻) NOD mice develop a significantly reduced incidence of diabetes. This study was to investigate the molecular mechanisms of the protective role of TLR9 deficiency. Through gene screening and confirmation by both mRNA and protein expression, we found a significant increase in CD73-expressing immune cells from peripheral lymphoid tissues in TLR9⁻/⁻ NOD mice. The elevated frequency of CD73-expressing immune cells seemed to be specific for TLR9 deficiency and was MyD88 independent. Moreover, the increased frequency of CD73 expression was limited to the NOD background. Increased frequency of CD73 expression was also associated with lower levels of proinflammatory cytokines and more anti-inflammatory cytokine production in CD4⁺ T cells in TLR9⁻/⁻ NOD mice. Purified CD73⁺CD4⁺ T cells showed stronger immunosuppressive function in vitro and delayed diabetes development in vivo. The immunosuppression appeared to be mediated by TGF-β. In addition, elevated frequency of CD73-expressing cells was associated with improved β cell function. Our observations were further confirmed by protection from diabetes with similar alterations in CD73 in the NY8.3 TCR NOD mouse model crossed with TLR9⁻/⁻ mice and by the use of a TLR9 inhibitor in NOD mice. Our novel findings suggest an important immune-regulatory role of CD73 in regulation of diabetes development and may offer a new therapeutic strategy for specific intervention to prevent type 1 diabetes.

Interleukin-10 inhibits lipopolysaccharide induced miR-155 precursor stability and maturation

The anti-inflammatory cytokine interleukin-10 (IL-10) is essential for attenuating the inflammatory response, which includes reducing the expression of pro-inflammatory microRNA-155 (miR-155) in lipopolysaccharide (LPS) activated macrophages. miR-155 enhances the expression of pro-inflammatory cytokines such as TNFα and suppresses expression of anti-inflammatory molecules such as SOCS1. Therefore, we examined the mechanism by which IL-10 inhibits miR-155. We found that IL-10 treatment did not affect the transcription of the miR-155 host gene nor the nuclear export of pre-miR-155, but rather destabilized both pri-miR-155 and pre-miR-155 transcripts, as well as interfered with the final maturation of miR-155. This inhibitory effect of IL-10 on miR-155 expression involved the contribution of both the STAT3 transcription factor and the phosphoinositol phosphatase SHIP1. This is the first report showing evidence that IL-10 regulates miRNA expression post-transcriptionally.

Amelioration of murine passive immune thrombocytopenia by IVIg and a therapeutic monoclonal CD44 antibody does not require the Myd88 signaling pathway

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by a low platelet count and the production of anti-platelet antibodies. The majority of ITP patients have antibodies to platelet integrin α_IIbβ₃ (GPIIbIIIa) which can direct platelet phagocytosis by macrophages. One effective treatment for patients with ITP is intravenous immunoglobulin (IVIg) which rapidly reverses thrombocytopenia. The exact mechanism of IVIg action in human patients is unclear, although in mouse models of passive ITP, IVIg can rapidly increase platelet counts in the absence of adaptive immunity. Another antibody therapeutic that can similarly increase platelet counts independent of adaptive immunity are CD44 antibodies. Toll-like receptors (TLRs) are pattern recognition receptors which play a central role in helping direct the innate immune system. Dendritic cells, which are notable for their expression of TLRs, have been directly implicated in IVIg function as an initiator cell, while CD44 can associate with TLR2 and TLR4. We therefore questioned whether IVIg, or the therapeutic CD44 antibody KM114, mediate their ameliorative effects in a manner dependent upon normal TLR function. Here, we demonstrate that the TLR4 agonist LPS does not inhibit IVIg or KM114 amelioration of antibody-induced thrombocytopenia, and that these therapeutics do not ameliorate LPS-induced thrombocytopenia. IVIg was able to significantly ameliorate murine ITP in C3H/HeJ mice which have defective TLR4. All known murine TLRs except TLR3 utilize the Myd88 adapter protein to drive TLR signaling. Employing Myd88 deficient mice, we found that both IVIg and KM114 ameliorate murine ITP in Myd88 deficient mice to the same extent as normal mice. Thus both IVIg and anti-CD44 antibody can mediate their ameliorative effects in murine passive ITP independent of the Myd88 signaling pathway. These data help shed light on the mechanism of action of IVIg and KM114 in the amelioration of murine ITP.

Allelic variants in TLR10 gene may influence bilateral affectation and clinical course of Meniere's disease

Toll-like receptors trigger the innate immune response by activating various cell types such us macrophages and lymphocytes. We genotyped SNV of TLR3, TRL7, TLR8 and TLR10 in 863 Spanish and 150 Italian patients with Meniere's disease (MD) and 1,013 controls by using Taqman assays. Real-Time qPCR was used to measure the expression level of TLR10 in peripheral blood leukocytes. The overall dataset showed that the C allele and the CC genotype of rs11096955 in TLR10 gene were more commonly observed in controls than patients (corrected p = 1 × 10(-3), OR = 0.68 [95 % confidence interval, 0.54-0.84] for CC genotype; corrected p = 1.5 × 10(-5), OR = 0.75 [0.66-0.85] for allele C). Moreover, the CC genotype was more frequent in patients with uni- (19 %) than bilateral sensorineural hearing loss (SNHL) (13 %). Logistic regression demonstrated that the time since the onset of MD, Tumarkin crises, hearing stage and rs11096955 were independent factors influencing the risk of bilateral SNHL. In addition, rs11096955 influenced hearing loss progression in patients with bilateral MD. No change in expression of TLR10 was observed according to CC, CA or AA genotypes. Our data suggest that allelic variants of TLR10 gene may influence the susceptibility and time-course of hearing loss of MD in the European population.

Attenuation of acute pancreatitis by peroxisome proliferator-activated receptor-α in rats: the effect on Toll-like receptor signaling pathways

OBJECTIVES

The peroxisome proliferator-activated receptor-α (PPAR-α) has attracted considerable attention for its anti-inflammatory properties; however, Toll-like receptor (TLR) pathways have an essential proinflammatory role in acute pancreatitis (AP). This study aimed to evaluate the attenuation of inflammation by PPAR-α and to investigate the interaction between PPAR-α and TLR pathways in AP.

METHODS

Acute pancreatitis was induced in rats by administration of cerulein. The PPAR-α agonist WY14643 and/or antagonist MK886 was administered. The severity of AP was determined by measuring serum amylase, lipase, Ca(2+), pathological changes, myeloperoxidase activity, serum levels of interleukin (IL)-6, and intercellular adhesion molecule-1 (ICAM-1). The TLR2 and TLR4 messenger RNA (mRNA) and proteins were determined by real-time reverse transcriptase polymerase chain reaction and Western blotting, respectively. The mRNA expressions of target molecules of TLR pathways, including IL-6, IL-10, ICAM-1, and tumor necrosis factor α were also measured.

RESULTS

Treatment with WY14643 significantly decreased amylase, lipase, myeloperoxidase activity, pathological scores, IL-6, and ICAM-1 levels. The TLR2 and TLR4 mRNA and proteins were markedly decreased after treatment with WY14643, along with IL-6, ICAM-1, and tumor necrosis factor α mRNA levels. However, these effects were completely reversed by the coadministration of MK886.

CONCLUSIONS

Activation of PPAR-α played a protective role in AP, partially mediated by modulation of TLR pathways.

Thyroid peroxidase gene expression is induced by lipopolysaccharide involving nuclear factor (NF)-κB p65 subunit phosphorylation

Thyroid peroxidase (TPO), a tissue-specific enzyme expressed in differentiated thyroid follicular cells, is a major antigen that has been linked to autoimmune thyroid disease. We have previously reported the functional expression of the lipopolysaccharide (LPS) receptor Toll-like receptor 4 on thyroid follicular cells. Here we investigated the effect of LPS in TPO expression and analyzed the mechanisms involved. We found a dose-dependent enhancement of TSH-induced TPO expression in response to LPS stimulation. EMSAs demonstrated that LPS treatment increased thyroid transcription factor-1 and -2 binding to the B and Z regions of TPO promoter, respectively. Moreover, LPS increased TSH-stimulated TPO promoter activity. Using bioinformatic analysis, we identified a conserved binding site for transcription nuclear factor-κB (NF-κB) in the TPO promoter. Chemical inhibition of NF-κB signaling and site-directed mutagenesis of the identified κB-cis-acting element abolished LPS stimulation. Furthermore, chromatin immunoprecipitation assays confirmed that TPO constitutes a novel NF-κB p65 subunit target gene in response to LPS. Additionally, our results indicate that p65 phosphorylation of serine 536 constitutes an essential step in the p65-dependent, LPS-induced transcriptional expression of TPO. In conclusion, here we demonstrated that LPS increases TPO expression, suggesting a novel mechanism involved in the regulation of a major thyroid autoantigen. Our results provide new insights into the potential effects of infectious processes on thyroid homeostasis.

Toll-like receptors in autoimmunity with special reference to systemic lupus erythematosus

The Toll-like receptor (TLR) family plays a fundamental role in host innate immunity by mounting a rapid and potent inflammatory response to pathogen infection. TLRs recognize distinct microbial components and activate intracellular signaling pathways that induce expression of host inflammatory genes. Several studies have indicated that TLRs are implicated in many inflammatory and immune disorders. Extensive research in the past decade to understand TLR-mediated mechanisms of innate immunity has enabled pharmaceutical companies to begin to develop novel therapeutics for the purpose of controlling an inflammatory disease. The roles of TLRs in the development of autoimmune diseases have been studied. TLR7 and TLR9 have key roles in production of autoantibodies and/or in development of systemic autoimmune disease. It remains to be determined their role in apoptosis, in the pathogenesis of RNA containing immune complexes, differential expression of TLRs by T regulatory cells.

Pattern recognition receptors--molecular orchestrators of inflammation in inflammatory bowel disease

Pattern recognition receptors (PRRs) are a family of germline encoded receptors responsible for the detection of "pathogen associated molecular patterns" (PAMPs) or host derived "damage associated molecular patterns" (DAMPs) which induce innate immune signalling to generate a pro-inflammatory profile within the host. Four main classes of PRRs are recognised, Toll-like receptors (TLRs), NOD-like receptors (NLRs), RIG-like receptors (RLRs) and C-type lectin receptors (CLRs). Abnormal activation of PRRs has been implicated in various autoimmune and inflammatory conditions including rheumatoid arthritis and asthma. Recent growing evidence has implicated these PRRs as contributory elements to the pathogenesis of inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). Here, the current literature which implicates PRRs in IBD and CAC is comprehensively reviewed.

Profile of toll-like receptors on peripheral blood cells in relation to acute graft-versus-host disease after allogeneic stem cell transplantation

Toll-like receptors (TLRs) play a key role in the cross-talk between the innate and adaptive immune systems. Previous studies investigating associations between certain TLRs and acute graft-versus-host disease (aGVHD) have reported contrasting results, and no studies relating aGVHD to the expression and function of all human TLRs together have been published to date. We prospectively evaluated the expression of 9 TLRs on T lymphocytes and monocytes by flow cytometry in relation to aGVHD in 34 patients. Induction of TNF-α, IL-4, IFN-γ, and monocyte chemotactic protein 1 on TLR activation was assessed by ELISA on cell supernatants. Nineteen patients developed aGVHD, at a median time of 28 days (range, 20-50 days) after transplantation. A 2-step multivariate analysis was performed using principal component analysis and multifactor analysis of variance. The levels of TLR-5 expression on monocytes and T lymphocytes were positively correlated to aGVHD (P = .01), whereas levels of TLR-1 and -9 were negative predictors (P = .03 and .01, respectively). This profile of TLR-1, -5, and -9 can promote an overall immunostimulatory/proinflammatory response. If our findings are confirmed by further studies, this TLR profile could be a useful biomarker of aGVHD.

The use of monoclonal antibodies in immune-mediated hematologic disorders

In this article, the evidence on the clinical use of monoclonal antibodies in the treatment of immune-mediated hematologic disorders is described. Insights into pathogenic mechanisms have revealed a major role of both B and T cells. Controlled trials have shown conflicting results, necessitating further research regarding pathogenesis, mechanism of action, and resistance. Although the use of more potent and specific monoclonal antibody therapy, mainly targeting costimulation signals, may improve response rates and long-term outcome, its use should be carefully balanced against potential side effects.

Immuno-inhibitory PD-L1 can be induced by a peptidoglycan/NOD2 mediated pathway in primary monocytic cells and is deficient in Crohn's patients with homozygous NOD2 mutations

Peptidoglycan (PGN) is a ubiquitous bacterial membrane product that, despite its well known pro-inflammatory properties, has also been invoked in immuno-tolerance of the gastrointestinal tract. PGN-induced mucosal IL-10 secretion and downregulation of Toll like receptors are potential mechanisms of action in the gut but there are few data on tolerogenic adaptive immune responses and PGN. Here, using blood-derived mononuclear cells, we showed that PGN induced marked cell surface expression of PD-L1 but not PD-L2 or CD80/CD86, and specifically in the CD14(+) monocytic fraction. This was reproduced at the gene level with rapid induction (<4 h) and, unlike for LPS stimulation, was still sustained at 24 h. Using transfected and native muramyl dipeptide (MDP), which is a cleavage product of PGN and a specific NOD2 agonist, in assays with wild type cells or those from patients with Crohn's disease carrying the Leu1007 frameshift mutation of NOD2, we showed that (i) both NOD2 dependent and independent signalling (appearing TLR2 mediated) occurred for PGN upregulation of PD-L1 (ii) upregulation is lost in response to MDP in patients with the homozygous mutation and (iii) PD-L1 upregulation was unaffected in patients with heterozygous mutations as previously reported for cytokine responses to MDP. The uptake of PGN and its cleavage products by the intestinal mucosa is well recognised and further work should consider PD-L1 upregulation as one potential mechanism of the commensal flora-driven intestinal immuno-tolerance. Indeed, recent work has shown that loss of PD-L1 signalling in the gut breaks CD8(+) T cell tolerance to self antigen and leads to severe autoimmune enteritis.

Immunolocalization of Toll-like receptors 2 and 4 as well as their endogenous ligand, heat shock protein 70, in rat traumatic brain injury

OBJECTIVE

Toll-like receptors (TLRs) are essential to the innate immune system for recognizing not only microbial pathogens but also endogenous ligands from injured cells, suggesting that TLRs are a sensitive detection system to tissue injury and play roles in initiating tissue degeneration/regeneration. In this study, the effects of traumatic brain injury (TBI) on lesional expression of TLR2, TLR4, their most common adaptor molecule myeloid differentiation factor 88 (MyD88) and their endogenous ligand, heat shock protein 70 (HSP70), were investigated.

METHODS

Rat TBI was induced using an open-skull weight-drop model. TLR2, TLR4, MyD88 and HSP70 expression was studied by immunohistochemistry.

RESULTS

TLR2, TLR4, HSP70 and MyD88 were mainly found in lesioned regions and subcortical white matter. While infiltration of TLR2+ cells became significant on day 2, significant accumulation of TLR4+, MyD88+ and HSP70+ cells was already seen on day 1, and the numbers of immunopositive cells increased continuously until day 4. Furthermore, double staining together with morphological classification showed that major cellular sources for TLR2, TLR4 and MyD88 were macrophages/microglia in lesioned areas and astrocytes in subcortical white matter. But for HSP70, the major cellular sources were neurons in perilesion and macrophages/microglia in lesion areas and astrocytes in subcortical white matter.

DISCUSSION

In summary, our data reveal distinct patterns of localization of TLR+ resident and infiltrating cells in TBI rat brain. Infiltrating activated monocytic cells are the major source of TLR+ cells. These findings warrant further investigation of the roles of TLRs in controlling immune and degenerative/regenerative processes after TBI.

Heat shock factor 1 protects against lung mycoplasma pneumoniae infection in mice

Heat shock factor 1 (HSF1) is a transcriptional factor that controls the induction of heat shock proteins (e.g. HSP70) in response to stress. Bacterial infections contribute to the pathobiology of chronic lung diseases such as chronic obstructive pulmonary disease and asthma. Whether HSF1 is critical to lung bacterial infection remains unknown. This study is aimed at investigating the impact of HSF1 deficiency on lung Mycoplasma pneumoniae (Mp) infection and elucidating the underlying molecular mechanisms, such as Toll-like receptor 2 (TLR2) signaling. HSF1(-/-) and HSF1(+/+) mice were intranasally infected with Mp or saline and sacrificed 4, 24 and 72 h after treatment. HSF1(-/-) mice had a higher lung Mp load than HSF1(+/+) mice. Mp-induced lung TLR2, nuclear factor-κB and associated inflammation [e.g. keratinocyte-derived chemokine (KC), neutrophils and histopathology] were delayed in HSF1(-/-) mice as compared to HSF1(+/+) mice. HSP70 protein levels in bronchoalveolar lavage fluid of HSF1(-/-) mice were decreased. Furthermore, in response to Mp infection, HSF1(-/-) alveolar macrophages had less TLR2 mRNA expression and KC production than HSF1(+/+) counterparts. Nuclear factor-κB activity and KC production in HSF1(-/-) macrophages could be rescued by addition of exogenous HSP70 protein. These data suggest that HSF1 is necessary to initiate host defense against bacterial infection partly through promoting early TLR2 signaling activation.

Contrasting patterns of diversity and population differentiation at the innate immunity gene toll-like receptor 2 (TLR2) in two sympatric rodent species

Comparing patterns of diversity and divergence between populations at immune genes and neutral markers can give insights into the nature and geographic scale of parasite-mediated selection. To date, studies investigating such patterns of selection in vertebrates have primarily focused on the acquired branch of the immune system, whereas it remains largely unknown how parasite-mediated selection shapes innate immune genes both within and across vertebrate populations. Here, we present a study on the diversity and population differentiation at the innate immune gene Toll-like receptor 2 (TLR2) across nine populations of yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) in southern Sweden. In yellow-necked mice, TLR2 diversity was very low, as was TLR2 population differentiation compared to neutral loci. In contrast, several TLR2 haplotypes co-occurred at intermediate frequencies within and across bank vole populations, and pronounced isolation by distance between populations was observed. The diversity and differentiation at neutral loci was similar in the two species. These results indicate that parasite-mediated selection has been acting in dramatically different ways on a given immune gene in ecologically similar and sympatric species. Furthermore, the finding of TLR2 population differentiation at a small geographical scale in bank voles highlights that vertebrate innate immune defense may be evolutionarily more dynamic than has previously been appreciated.

Extra domain A-positive fibronectin-positive feedback loops and their association with cutaneous inflammatory disease

Cutaneous inflammation can show Th1 or Th2 predominance, but the precise mechanisms by which such selectivity is determined are unknown. A recent study has demonstrated that Th1 cells, but not Th2 cells, produce an endogenous ligand for Toll-like receptor (TLR) 4, namely extradomain A+ fibronectin containing extra type III domain A (FnEDA+). As TLR4 stimulation leads to production of proinflammatory cytokines that recruit (via altered endothelial adhesion molecule expression and chemokine production) more Th1/Th17 cells, a positive feedback mechanism for Th1/Th17 inflammation exists. We propose that FnEDA+ positive feedback loops are a potential driver of Th1/Th17 inflammation. Conversely, the inflammatory EDA+ fibronectin loop is negatively regulated in atopic dermatitis, Th2 cytokines actively suppress TLR4 expression of Th1 cytokines, and recruited Th2 cells do not produce FnEDA+. In psoriasis, there are multiple FnEDA+ loops, comprising inflammatory, keratinocyte, and autoimmune loops. In allergic contact dermatitis, a single inflammatory loop operates. In atopic dermatitis, the FnEDA+ loop is actively suppressed by Th2 cytokines, and recruited Th2 cells do not "feedback" FnEDA+. We review endogenous ligands for TLR in relation to inflammatory disease, FnEDA+ function, and the potential role for FnEDA+ in psoriasis, allergic contact dermatitis, and atopic dermatitis.

Preprotachykinin-A gene deletion regulates hydrogen sulfide-induced toll-like receptor 4 signaling pathway in cerulein-treated pancreatic acinar cells

OBJECTIVE

This study aimed to determine the effect of hydrogen sulfide (H2S) on Toll-like receptor 4 (TLR4)-mediated innate immune signaling in acute pancreatitis (AP) via substance P.

METHODS

Male Swiss mice were treated with hourly intraperitoneal injections of cerulein (50 μg/kg) for 10 hours. dl-propargylglycine ([PAG] 100 mg/kg, intraperitoneally), an inhibitor of H2S formation, was administered 1 hour after the induction of AP. Pancreatic acinar cells from male preprotachykinin-A gene-knockout mice (PPTA) and their wild-type counterparts were incubated with or without cerulein (10 M for 60 minutes). To better understand the effect of H2S in inflammation, acinar cells were stimulated with cerulein after addition of H2S donor, sodium hydrosulfide. In addition, cerulein-treated pancreatic acinar cells were pretreated with PAG (30 μM) for 1 hour.

RESULTS

The H2S inhibitor PAG eliminated TLR4, interleukin 1 receptor-associated kinase 4, tumor necrosis factor receptor-associated factor 6, and nuclear factor-κB (NF-κB) levels in in vitro and in vivo models of cerulein-induced AP. PPTA gene deletion reduced TLR4, myeloid differentiation factor 88, interleukin 1 receptor-associated kinase 4, tumor necrosis factor receptor-associated factor 6, and NF-κB in cerulein-treated pancreatic acinar cells, whereas administration of sodium hydrosulfide resulted in a further rise in TLR4 and NF-κB levels in cerulein-treated pancreatic acinar cells.

CONCLUSION

The present findings show for the first time that in AP, H2S may up-regulate the TLR4 pathway and NF-κB via substance P.

The vascular repair process after injury of the carotid artery is regulated by IL-1RI and MyD88 signalling

AIM

The aim of this study was to determine whether innate immune signalling influences the vascular repair process in response to mechanical injury of arteries in mice.

METHODS AND RESULTS

A non-obstructive collar was introduced around the carotid artery of MyD88-deficient mice, and neointima formation was compared with that observed in MyD88-competent mice. MyD88-deficient mice are characterized by impaired signal transduction from interleukin (IL)-1/IL-18 receptors and most Toll-like receptors (TLRs). The vascular response to injury was severely impaired in MyD88-deficient mice as neointima formation was not different from sham-operated mice, whereas MyD88-competent mice displayed robust neointima formation. Furthermore, infiltration of CD68-positive leucocytes was dependent on MyD88. During the early response to injury, 3 days after collar placement, a transient increase in the expression of TLR4 on vascular smooth muscle cells was observed. To determine the relative importance of IL-1 receptor and TLR4 activation in the vascular response to injury, mice were injected with blocking antibodies to these receptors prior to the collar placement. Neointima formation was reduced by 80% in mice administered IL-1RI blocking antibodies compared with mice given a control antibody, whereas administration of TLR4 blocking antibodies was without effect.

CONCLUSION

These results show that inhibition of MyD88- or IL-1 receptor signalling reduces neointima formation in response to vascular injury and could offer therapeutic options for reducing clinical complications of excessive smooth muscle cell proliferation, such as that observed in in-stent restenosis.

Toll-like receptor 4 signaling in liver injury and hepatic fibrogenesis

Toll-like receptors (TLRs) are a family of transmembrane pattern recognition receptors (PRR) that play a key role in innate and adaptive immunity by recognizing structural components unique to bacteria, fungi and viruses. TLR4 is the most studied of the TLRs, and its primary exogenous ligand is lipopolysaccharide, a component of Gram-negative bacterial walls. In the absence of exogenous microbes, endogenous ligands including damage-associated molecular pattern molecules from damaged matrix and injured cells can also activate TLR4 signaling. In humans, single nucleotide polymorphisms of the TLR4 gene have an effect on its signal transduction and on associated risks of specific diseases, including cirrhosis. In liver, TLR4 is expressed by all parenchymal and non-parenchymal cell types, and contributes to tissue damage caused by a variety of etiologies. Intact TLR4 signaling was identified in hepatic stellate cells (HSCs), the major fibrogenic cell type in injured liver, and mediates key responses including an inflammatory phenotype, fibrogenesis and anti-apoptotic properties. Further clarification of the function and endogenous ligands of TLR4 signaling in HSCs and other liver cells could uncover novel mechanisms of fibrogenesis and facilitate the development of therapeutic strategies.