Tissue expression of human Toll-like receptors and differential regulation of Toll-like receptor mRNAs in leukocytes in response to microbes, their products, and cytokines

Quantitative assessment of TLR4 gene polymorphisms and T2DM risk: A meta-analysis

BACKGROUND

Numerous studies have evaluated the association between TLR4 gene polymorphisms and T2DM risk. However, the findings were inconsistent and controversial.

METHODS

In order to drive a more precise estimation, we carried out a meta-analysis based on 41 studies involving 23,250 cases and 24,760 controls. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the strength of association.

RESULTS

Our meta-analysis provides evidence that rs4986790 polymorphism was associated with an increased risk of T2DM in Asian (AG vs. AA, OR = 1.23, 95% CI = 1.01-1.50, p = 0.042; G vs. A, OR = 1.21, 95% CI = 1.01-1.44, p = 0.041). Rs4986791 polymorphism was related to an increased risk of T2DM both in Asian (AG vs. AA, OR = 1.76, 95% CI = 1.11-2.80, p = 0.017; G vs. A, OR = 1.63, 95% CI = 1.04-2.55, p = 0.034) and Caucasian (GG vs. AA, OR = 2.42, 95% CI = 1.23-4.75, p = 0.010). Rs11536889 polymorphism may have a protective effect on T2DM in Chinese populations (CC vs. GG, OR = 0.62, 95% CI = 0.40-0.96, p = 0.031; GC vs. GG, OR = 0.77, 95% CI = 0.61-0.98, p = 0.034; CC vs. GC/GG, OR = 0.81, 95% CI = 0.69-0.96, p = 0.013; C vs. G, OR = 0.76, 95% CI = 0.59-0.97, p = 0.027), whereas rs1927911 may have no impact.

CONCLUSIONS

These findings supported that rs4986790, rs4986791, and rs11536889 may contribute to the risk of T2DM.

Innate Immune Responses to Acute Viral Infection During Pregnancy

Immunological adaptations in pregnancy allow maternal tolerance of the semi-allogeneic fetus but also increase maternal susceptibility to infection. At implantation, the endometrial stroma, glands, arteries and immune cells undergo anatomical and functional transformation to create the decidua, the specialized secretory endometrium of pregnancy. The maternal decidua and the invading fetal trophoblast constitute a dynamic junction that facilitates a complex immunological dialogue between the two. The decidual and peripheral immune systems together assume a pivotal role in regulating the critical balance between tolerance and defense against infection. Throughout pregnancy, this equilibrium is repeatedly subjected to microbial challenge. Acute viral infection in pregnancy is associated with a wide spectrum of adverse consequences for both mother and fetus. Vertical transmission from mother to fetus can cause developmental anomalies, growth restriction, preterm birth and stillbirth, while the mother is predisposed to heightened morbidity and maternal death. A rapid, effective response to invasive pathogens is therefore essential in order to avoid overwhelming maternal infection and consequent fetal compromise. This sentinel response is mediated by the innate immune system: a heritable, highly evolutionarily conserved system comprising physical barriers, antimicrobial peptides (AMP) and a variety of immune cells—principally neutrophils, macrophages, dendritic cells, and natural killer cells—which express pattern-receptors that detect invariant molecular signatures unique to pathogenic micro-organisms. Recognition of these signatures during acute infection triggers signaling cascades that enhance antimicrobial properties such as phagocytosis, secretion of pro-inflammatory cytokines and activation of the complement system. As well as coordinating the initial immune response, macrophages and dendritic cells present microbial antigens to lymphocytes, initiating and influencing the development of specific, long-lasting adaptive immunity. Despite extensive progress in unraveling the immunological adaptations of pregnancy, pregnant women remain particularly susceptible to certain acute viral infections and continue to experience mortality rates equivalent to those observed in pandemics several decades ago. Here, we focus specifically on the pregnancy-induced vulnerabilities in innate immunity that contribute to the disproportionately high maternal mortality observed in the following acute viral infections: Lassa fever, Ebola virus disease (EVD), dengue fever, hepatitis E, influenza, and novel coronavirus infections.

The Anti-Inflammatory Effect of Taurine on Cardiovascular Disease

Taurine is a non-protein amino acid that is expressed in the majority of animal tissues. With its unique sulfonic acid makeup, taurine influences cellular functions, including osmoregulation, antioxidation, ion movement modulation, and conjugation of bile acids. Taurine exerts anti-inflammatory effects that improve diabetes and has shown benefits to the cardiovascular system, possibly by inhibition of the renin angiotensin system. The beneficial effects of taurine are reviewed.

Increasing Evidence That Irritable Bowel Syndrome and Functional Gastrointestinal Disorders Have a Microbial Pathogenesis

The human gastrointestinal tract harbors most of the microbial cells inhabiting the body, collectively known as the microbiota. These microbes have several implications for the maintenance of structural integrity of the gastrointestinal mucosal barrier, immunomodulation, metabolism of nutrients, and protection against pathogens. Dysfunctions in these mechanisms are linked to a range of conditions in the gastrointestinal tract, including functional gastrointestinal disorders, ranging from irritable bowel syndrome, to functional constipation and functional diarrhea. Irritable bowel syndrome is characterized by chronic abdominal pain with changes in bowel habit in the absence of morphological changes. Despite the high prevalence of irritable bowel syndrome in the global population, the mechanisms responsible for this condition are poorly understood. Although alterations in the gastrointestinal microbiota, low-grade inflammation and immune activation have been implicated in the pathophysiology of functional gastrointestinal disorders, there is inconsistency between studies and a lack of consensus on what the exact role of the microbiota is, and how changes to it relate to these conditions. The complex interplay between host factors, such as microbial dysbiosis, immune activation, impaired epithelial barrier function and motility, and environmental factors, including diet, will be considered in this narrative review of the pathophysiology of functional gastrointestinal disorders.

Toll-like Receptor Expression Profile of Human Stem/Progenitor Cells Form the Apical Papilla

INTRODUCTION

Stem/progenitor cells from the apical papilla (SCAPs) demonstrate remarkable regenerative and immunomodulatory properties. During their regenerative events, SCAPs, similar to other stem/progenitor cells, could interact with their local inflammatory microenvironment via their expressed toll-like receptors (TLRs). The present study aimed to describe for the first time the unique TLR expression profile of SCAPs.

METHODS

Cells were isolated from the apical papilla of extracted wisdom teeth (n = 8), STRO-1 immunomagnetically sorted, and cultured to obtain single colony-forming units. The expression of CD14, 34, 45, 73, 90, and 105 were characterized on the SCAPs, and their multilineage differentiation potential was examined to prove their multipotent aptitude. After their incubation in basic or inflammatory medium (25 ng/mL interleukin 1 beta, 10³ U/mL interferon gamma, 50 ng/mL tumor necrosis factor alpha, and 3 × 10³ U/mL interferon alpha), a TLR expression profile for SCAPs under uninflamed as well as inflamed conditions was respectively generated.

RESULTS

SCAPs demonstrated all predefined stem/progenitor cell characteristics. In basic medium, SCAPs expressed TLRs 1-10. The inflammatory microenvironment up-regulated the expression of TLR1, TLR2, TLR4, TLR5, TLR6, and TLR9 and down-regulated the expression of TLR3, TLR7, TLR8, and TLR10 in SCAPs under the inflamed condition.

CONCLUSIONS

The present study defines for the first time a distinctive TLR expression profile for SCAPs under uninflamed and inflamed conditions. This profile could greatly impact SCAP responsiveness to their inflammatory microenvironmental agents under regenerative conditions in vivo.

Recurrent Glomerulonephritis after Renal Transplantation: The Clinical Problem

Glomerulonephritis (GN) continues to be one of the main causes of end-stage kidney disease (ESKD) with an incidence rating from 10.5% to 38.2%. Therefore, recurrent GN, previously considered to be a minor contributor to graft loss, is the third most common cause of graft failure 10 years after renal transplantation. However, the incidence, pathogenesis, and natural course of recurrences are still not completely understood. This review focuses on the most frequent diseases that recur after renal transplantation, analyzing rate of recurrence, epidemiology and risk factors, pathogenesis and bimolecular mechanisms, clinical presentation, diagnosis, and therapy, taking into consideration the limited data available in the literature. First of all, the risk for recurrence depends on the type of glomerulonephritis. For example, recipient patients with anti-glomerular basement membrane (GBM) disease present recurrence rarely, but often exhibit rapid graft loss. On the other hand, recipient patients with C3 glomerulonephritis present recurrence in more than 50% of cases, although the disease is generally slowly progressive. It should not be forgotten that every condition that can lead to chronic graft dysfunction should be considered in the differential diagnosis of recurrence. Therefore, a complete workup of renal biopsy, including light, immunofluorescence and electron microscopy study, is essential to provide the diagnosis, excluding alternative diagnosis that may require different treatment. We will examine in detail the biomolecular mechanisms of both native and transplanted kidney diseases, monitoring the risk of recurrence and optimizing the available treatment options.

Mechanisms of Key Innate Immune Cells in Early- and Late-Onset Preeclampsia

Preeclampsia is a complex cardiovascular disorder of pregnancy with underlying multifactorial pathogeneses; however, its etiology is not fully understood. It is characterized by the new onset of maternal hypertension after 20 weeks of gestation, accompanied by proteinuria, maternal organ damage, and/or uteroplacental dysfunction. Preeclampsia can be subdivided into early- and late-onset phenotypes (EOPE and LOPE), diagnosed before 34 weeks or from 34 weeks of gestation, respectively. Impaired placental development in early pregnancy and subsequent growth restriction is often associated with EOPE, while LOPE is associated with maternal endothelial dysfunction. The innate immune system plays an essential role in normal progression of physiological pregnancy and fetal development. However, inappropriate or excessive activation of this system can lead to placental dysfunction or poor maternal vascular adaptation and contribute to the development of preeclampsia. This review aims to comprehensively outline the mechanisms of key innate immune cells including macrophages, neutrophils, natural killer (NK) cells, and innate B1 cells, in normal physiological pregnancy, EOPE and LOPE. The roles of the complement system, syncytiotrophoblast extracellular vesicles and mesenchymal stem cells (MSCs) are also discussed in the context of innate immune system regulation and preeclampsia. The outlined molecular mechanisms, which represent potential therapeutic targets, and associated emerging treatments, are evaluated as treatments for preeclampsia. Therefore, by addressing the current understanding of innate immunity in the pathogenesis of EOPE and LOPE, this review will contribute to the body of research that could lead to the development of better diagnosis, prevention, and treatment strategies. Importantly, it will delineate the differences in the mechanisms of the innate immune system in two different types of preeclampsia, which is necessary for a more personalized approach to the monitoring and treatment of affected women.

Impaired lnc-IL7R modulatory mechanism of Toll-like receptors is associated with an exacerbator phenotype of chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) are susceptible to bacterial infections, which worsen lung inflammation and contribute to lung function decline and acute exacerbation. Long noncoding (lnc) RNAs are emerging regulators of inflammation with unknown clinical relevance. Herein, we report that levels of the Toll-like receptor (TLR)-related lnc interleukin (IL) 7 receptor (IL7R) were significantly reduced in peripheral blood mononuclear cells from patients with COPD compared with those from normal controls, and the levels were correlated with pulmonary function. Moreover lnc-IL7R levels were reduced in lavaged alveolar macrophages and primary human small airway epithelial cells (HSAEpCs) from patients with COPD. Lnc-IL7R knockdown in primary human macrophages, HSAEpCs, and human pulmonary microvascular endothelial cells (HPMECs) significantly augmented the induction of proinflammatory mediators after TLR2/4 activation. By contrast, lnc-IL7R overexpression attenuated inflammation after TLR2/4 activation. Similar results with lnc-IL7R-mediated inflammation were observed in COPD HSAEpCs. Mechanistically, lnc-IL7R mediated a repressive chromatin state of the proinflammatory gene promoter as a result of decreased acetylation (H3K9ac) and increased methylation (H3K9me3 and H3K27me3). Plasma lnc-IL7R levels were reduced in patients with COPD who experienced more acute exacerbation in the previous year. Notably, patients with lower lnc-IL7R levels in the subsequent year had increased exacerbation risk. Low lnc-IL7R expression in COPD may augment TLR2/4-mediated inflammation and be associated with acute exacerbation.

Differential toll like receptor expression in cystic fibrosis patients' airways during rhinovirus infection

OBJECTIVES

Since an inappropriate and sustained activation of TLRs may contribute to a chronic inflammatory response resulting in detrimental effects in cystic fibrosis (CF) patients, we sought to examine whether HRV infection might alter the respiratory expression of TLRs according to the microbiological status of CF patients.

METHODS

Respiratory samples were collected from the respiratory tract of CF patients (n = 294) over a period of 12 months. In addition to the usual microbiological investigation, HRV-RNA detection and typing were performed by RT-PCR and sequencing. HRV viral load and TLRs levels were measured by RT-Real Time PCR.

RESULTS

HRV-RNA was detected in 80 out of 515 respiratory samples (15.5%) with a similar rate in all age groups (0-10 years, 11-24 years, ≥ 25 years). Patients infected with different HRV A, B and C species exhibited higher levels of TLR2, TLR4 and TLR8 as compared to HRV negative patients. Moreover, the expression level of TLR2, TLR4 and TLR8 correlated with high level of HRV viral load. HRV positive patients co-colonized by Staphylococcus aureus or Pseudomonas aeruginosa showed also enhanced amounts of TLR2 and TLR2/4-mRNAs expression respectively. In the case of presence of both bacteria, TLR2, TLR4, TLR8 and TLR9 levels are elevated in positive HRV patients.

CONCLUSIONS

TLRs, especially TLR2 and TLR4, increased in HRV positive CF individuals and varies according to the presence of S. aureus, P. aeruginosa and both bacteria.

Host-Pathogen Interaction as a Novel Target for Host-Directed Therapies in Tuberculosis

Tuberculosis (TB) has been a transmittable human disease for many thousands of years, and M. tuberculosis is again the number one cause of death worldwide due to a single infectious agent. The intense 6- to 10-month process of multi-drug treatment, combined with the adverse side effects that can run the spectrum from gastrointestinal disturbances to liver toxicity or peripheral neuropathy are major obstacles to patient compliance and therapy completion. The consequent increase in multidrug resistant TB (MDR-TB) and extensively drug resistant TB (XDR-TB) cases requires that we increase our arsenal of effective drugs, particularly novel therapeutic approaches. Over the millennia, host and pathogen have evolved mechanisms and relationships that greatly influence the outcome of infection. Understanding these evolutionary interactions and their impact on bacterial clearance or host pathology will lead the way toward rational development of new therapeutics that favor enhancing a host protective response. These host-directed therapies have recently demonstrated promising results against M. tuberculosis, adding to the effectiveness of currently available anti-mycobacterial drugs that directly kill the organism or slow mycobacterial replication. Here we review the host-pathogen interactions during M. tuberculosis infection, describe how M. tuberculosis bacilli modulate and evade the host immune system, and discuss the currently available host-directed therapies that target these bacterial factors. Rather than provide an exhaustive description of M. tuberculosis virulence factors, which falls outside the scope of this review, we will instead focus on the host-pathogen interactions that lead to increased bacterial growth or host immune evasion, and that can be modulated by existing host-directed therapies.

Toll-like receptor signaling in hematopoietic stem and progenitor cells

PURPOSE OF REVIEW

The innate immune system is essential in the protection against microbial infection and facilitating tissue repair mechanisms. During these stresses, the maintenance of innate immune cell numbers through stress-induced or emergency hematopoiesis is key for our survival. One major mechanism to recognize danger signals is through the activation of Toll-like receptors (TLRs) on the surface of hematopoietic cells, including hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC), and nonhematopoietic cells, which recognize pathogen-derived or damaged-induced compounds and can influence the emergency hematopoietic response. This review explores how direct pathogen-sensing by HSC/HPC regulates hematopoiesis, and the positive and negative consequences of these signals.

RECENT FINDINGS

Recent studies have highlighted new roles for TLRs in regulating HSC and HPC differentiation to innate immune cells of both myeloid and lymphoid origin and augmenting HSC and HPC migration capabilities. Most interestingly, new insights as to how acute versus chronic stimulation of TLR signaling regulates HSC and HPC function has been explored.

SUMMARY

Recent evidence suggests that TLRs may play an important role in many inflammation-associated diseases. This suggests a possible use for TLR agonists or antagonists as potential therapeutics. Understanding the direct effects of TLR signaling by HSC and HPC may help regulate inflammatory/danger signal-driven emergency hematopoiesis.

The Association of rs1898830 in Toll-Like Receptor 2 with Lipids and Blood Pressure

BACKGROUND AND OBJECTIVE

Toll-like receptors (TLRs) are important components of the innate immune system, involved in establishing immunity to infections. Apart from being implicated in immunity, numerous studies have reported that many TLRs, including TLR2, are involved in the pathogenesis of cardiovascular diseases and their risk factors. Since rs1898830 is associated with TLR2-mediated cellular activation, we aimed to study its association with CVD risk factors, such as lipid levels and hypertension.

METHODS

A cross-sectional study was conducted on 460 individuals free from chronic diseases. Clinical and biological data were collected and DNA was extracted and genotyped using Kompetitive allele specific PCR (KASP™). Multiple logistic regression models, adjusted for six covariates, were used. A power calculation analysis was also performed.

RESULTS

We found that rs1898830 in TLR2 was positively associated with hypertension (OR = 2.18, p = 0.03) and negatively associated with high-density lipoprotein cholesterol (OR = 0.66, p = 0.05). In contrast, no relation was found with total cholesterol and low-density lipoprotein cholesterol.

CONCLUSION

The present results provide additional evidence supporting the implication of TLR2 in CVD risk factors.

Formation of Lung Inducible Bronchus Associated Lymphoid Tissue Is Regulated by Mycobacterium tuberculosis Expressed Determinants

Mycobacterium tuberculosis (Mtb) is the causative agent of the infectious disease tuberculosis (TB), which is a leading cause of death worldwide. Approximately one fourth of the world's population is infected with Mtb. A major unresolved question is delineating the inducers of protective long-lasting immune response without inducing overt, lung inflammation. Previous studies have shown that the presence of inducible Bronchus-Associated Lymphoid Tissue (iBALT) correlate with protection from Mtb infection. In this study, we hypothesized that specific Mtb factors could influence the formation of iBALT, thus skewing the outcome of TB disease. We infected non-human primates (NHPs) with a transposon mutant library of Mtb, and identified specific Mtb mutants that were over-represented within iBALT-containing granulomas. A major pathway reflected in these mutants was Mtb cell wall lipid transport and metabolism. We mechanistically addressed the function of one such Mtb mutant lacking mycobacteria membrane protein large 7 (MmpL7), which transports phthiocerol dimycocerosate (PDIM) to the mycobacterial outer membrane (MOM). Accordingly, murine aerosol infection with the Mtb mutant Δmmpl7 correlated with increased iBALT-containing granulomas. Our studies showed that the Δmmpl7 mutant lacking PDIMs on the surface overexpressed diacyl trehaloses (DATs) in the cell wall, which altered the cytokine/chemokine production of epithelial and myeloid cells, thus leading to a dampened inflammatory response. Thus, this study describes an Mtb specific factor that participates in the induction of iBALT formation during TB by directly modulating cytokine and chemokine production in host cells.

Cordyceps cicadae polysaccharides ameliorated renal interstitial fibrosis in diabetic nephropathy rats by repressing inflammation and modulating gut microbiota dysbiosis

Diabetic nephropathy (DN), a complication of diabetes mellitus, has been the leading cause of death in people with chronic kidney disease. This study was conducted to examine the potential health benefits of Cordyceps cicadae polysaccharides (CCP) on kidney injury and renal interstitial fibrosis that occur in DN rats. First, a DN model was established using SD rats fed with a high-fat diet for 8 weeks, then injected with STZ (35 mg/kg) intraperitoneally. The rats were then supplemented with CCP (75, 150 and 300 mg/kg) for 4 weeks. The results indicated that CCP improve insulin resistance and glucose tolerance in DN rats. Furthermore, CCP intervention significantly suppressed the inflammation, renal pathological changes and renal dysfunction, slowing down the progression of renal interstitial fibrosis. Moreover, high-throughput pyrosequencing of 16S rRNA suggested that CCP modulated the dysbiosis of gut microbiota by enhancing the relative abundance and proliferation capacity of probiotics. In vitro, CCP can markedly decrease LPS-induced inflammatory cytokine levels and TGF-β1-induced fibroblast activation. In summary, the results provided evidence that CCP exerted a beneficial effect on tubulointerstitial fibrosis in DN rats by possibly suppressing the inflammatory response and modulating gut microbiota dysbiosis, via blocking the TLR4/NF-κB and TGF-β1/Smad signaling pathway.

Contribution of Aberrant Toll Like Receptor Signaling to the Pathogenesis of Myelodysplastic Syndromes

Toll like receptors (TLRs) are a family of pattern recognition receptors that play a central role in the innate immune response. These receptors are expressed on a wide variety of immune and non-immune cells, and they help shape the immune response to infection and injury through the recognition of pathogen-associated molecular patterns (PAMPs) as well as endogenous damage-associated molecular patterns (DAMPs). Accumulating evidence suggests that, in addition to regulating mature effector immune cells, TLRs can influence the immune response from the level of the hematopoietic stem cell (HSC). HSCs express TLRs, and exposure to TLR ligands influences the cycling, differentiation, and function of HSCs, with chronic TLR stimulation leading to impairment of normal HSC repopulating activity. Moreover, enhanced TLR expression and signaling is associated with myelodysplastic syndromes (MDS), a heterogenous group of HSC disorders characterized by ineffective hematopoiesis and a high risk of transformation to acute leukemias. In this review, we will discuss the role of TLR signaling in the pathogenesis of MDS, focusing on the known direct and indirect effects of this type of signaling on HSCs, the mechanisms of TLR signaling upregulation in MDS, the changes in TLR expression with disease progression, and the therapeutic implications for modulating TLR signaling in the treatment of MDS.

Insight Into TLR4-Mediated Immunomodulation in Normal Pregnancy and Related Disorders

Unlike organ transplants where an immunosuppressive environment is required, a successful pregnancy involves an extremely robust, dynamic, and responsive maternal immune system to maintain the development of the fetus. A specific set of hormones and cytokines are associated with a particular stage of pregnancy. Any disturbance that alters this fine balance could compromise the development and function of the placenta. Although there are numerous underlying causes of pregnancy-related complications, untimely activation of Toll-like receptors (TLR), primarily TLR4, by intrauterine microbes poses the greatest risk. TLR4 is an important Pattern Recognition Receptor (PRR), which activates both innate and adaptive immune cells. TLR4 activation by LPS or DAMPs leads to the production of pro-inflammatory cytokines via the MyD88 dependent or independent pathway. Immune cells modulate the materno–fetal interface by TLR4-mediated cytokine production, which changes at different stages of pregnancy. In most pregnancy disorders, such as PTB, PE, or placental malaria, the TLR4 expression is upregulated in immune cells or in maternal derived cells, leading to the aberrant production of pro-inflammatory cytokines at the materno–fetal interface. Lack of functional TLR4 in mice has reduced the pro-inflammatory responses, leading to an improved pregnancy, which further strengthens the fact that abnormal TLR4 activation creates a hostile environment for the developing fetus. A recent study proposed that endothelial and perivascular stromal cells should interact with each other in order to maintain a homeostatic balance during TLR4-mediated inflammation. It has been reported that depleting immune cells or supplying anti-inflammatory cytokines can prevent PTB, PE, or fetal death. Blocking TLR4 signaling or its downstream molecule by inhibitors or antagonists has proven to improve pregnancy-related complications to some extent in clinical and animal models. To date, there has been a lack of knowledge regarding whether TLR4 accessories such as CD14 and MD-2 are important in pregnancy and whether these accessory molecules could be promising drug targets for combinatorial treatment of various pregnancy disorders. This review mainly focuses on the activation of TLR4 during pregnancy, its immunomodulatory functions, and the upcoming advancement in this field regarding the improvement of pregnancy-related issues by various therapeutic approaches.

Maternal Immune Activation by Poly I:C as a preclinical Model for Neurodevelopmental Disorders: A focus on Autism and Schizophrenia

Maternal immune activation (MIA) in response to a viral infection during early and mid-gestation has been linked through various epidemiological studies to a higher risk for the child to develop autism or schizophrenia-related symptoms.. This has led to the establishment of the pathogen-free poly I:C-induced MIA animal model for neurodevelopmental disorders, which shows relatively high construct and face validity. Depending on the experimental variables, particularly the timing of poly I:C administration, different behavioural and molecular phenotypes have been described that relate to specific symptoms of neurodevelopmental disorders such as autism spectrum disorder and/or schizophrenia. We here review and summarize epidemiological evidence for the effects of maternal infection and immune activation, as well as major findings in different poly I:C MIA models with a focus on poly I:C exposure timing, behavioural and molecular changes in the offspring, and characteristics of the model that relate it to autism spectrum disorder and schizophrenia.

Variable Responsiveness to Agonists for TLR2 and TLR7 in Myometrial Cells from Different Sources: Correlation with Receptor Expression

The myometrium plays a vital role in maintenance of pregnancy. Disruption of myometrial sensitivity to pro-contractile stimuli might lead to preterm labor. Inflammation and/or infection are common precursors to preterm birth, in part by initiating pro-contractile stimuli through toll-like receptor (TLRs) activation. In this study, we investigated the responses specific to inflammatory stimuli for both human primary myometrial cells (HPMCs) and PHM1-41 cells, a human immortalized myometrial cell line. Both these types of cells are commonly used to study labor and pregnancy. Both cell lines were treated with lipopolysaccharide (LPS), peptidoglycan (PGN), or imiquimod (IQ) (ligands for TLRs 2, 4, and 7, respectively). We demonstrate that inflammatory cytokines increase significantly with LPS treatment; however, no change occurs with PGN and IQ, suggesting lack of TLR2- and TLR7-specific signaling in both HPMCs and in the PHM1-41 cell line. Absence of TLR2- and TLR7-specific protein bands on western blots confirmed the lack of these receptors in both HPMCs maintained in long-term culture and PHM1-41 cells. However, TLR2 expression was present in freshly collected matched human myometrial tissue (i.e., the tissues used to create the HPMC cultures), showing loss of TLR2 receptors by HPMCs during the cell culturing process. TLR7 protein expression was lacking both in myometrial tissue and in cultured cells. These results demonstrate the limited applicability and reliability of cellular models to investigate the role of the myometrium during pregnancy and labor.

Characterization and expression analysis of rockfish (Sebastes schlegelii) myeloid differentiation factor-88 (SsMyD88) and evaluation of its ability to induce inflammatory cytokines through NF-ĸB

Innate immunity is characterized by nonspecific, prompt reactions toward armada of antigens. Animals funnel down a repertoire of immune stimulants to activate non-selective defense mechanisms rapidly. This study was conducted to characterize the rockfish (Sebastes schlegelii) adaptor protein MyD88 (SsMyD88), which interacts with both toll-like receptors and interleukin receptors. The tissue expression of unchallenged SsMyD88 was evaluated by quantitative real time PCR (qPCR). Fish were intraperitoneally injected with immune stimulants including poly I:C, lipopolysaccharides, and Streptococcus iniae. Then, the temporal expression of SsMyD88 was analyzed. Finally, the inflammatory gene expression and downstream promoter activation were analyzed. Strongest expressions were reported in the liver, gills and spleen in unchallenged conditions. All diverse immune stimulants were found to be capable of significantly altering SsMyD88 transcription during the challenge experiment. Evaluation of downstream promoter biases by SsMyD88 found a predominant activation of NF-ĸB transcription factors when compared with the AP-1, revealing significant and substantial upregulation of major inflammatory mediators such as IL-1-β, IL-6, iNOS, COX-2 and TNF-α. Fluorescent detection confirmed an intense production of NO and the predominant differentiation of macrophages into M1 lineage with the overexpression of SsMyD88 in vitro. These results further corroborate the role of SsMyD88 as a mediatory molecule that bridges distinct immune stimulants to induce drastic immune responses in fish.

MyD88-dependent and -independent signalling via TLR3 and TLR4 are differentially modulated by Δ9-tetrahydrocannabinol and cannabidiol in human macrophages

Toll-like receptors (TLRs) are sensors of pathogen-associated molecules that trigger inflammatory signalling in innate immune cells including macrophages. All TLRs, with the exception of TLR3, promote intracellular signalling via recruitment of the myeloid differentiation factor 88 (MyD88) adaptor, while TLR3 signals via Toll-Interleukin-1 Receptor (TIR)-domain-containing adaptor-inducing interferon (IFN)-β (TRIF) adaptor to induce MyD88-independent signalling. Furthermore, TLR4 can activate both MyD88-dependent and -independent signalling (via TRIF). The study aim was to decipher the impact of the highly purified plant-derived (phyto) cannabinoids Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD), when delivered in isolation and in combination (1:1), on MyD88-dependent and -independent signalling in macrophages. We employed the use of the viral dsRNA mimetic poly(I:C) and endotoxin lipopolysaccharide (LPS), to induce viral TLR3 and bacterial TLR4 signalling in human Tamm-Horsfall protein-1 (THP-1)-derived macrophages, respectively. TLR3/TLR4 stimulation promoted the activation of interferon (IFN) regulatory factor 3 (IRF3) and TLR4 promoted the activation of nuclear factor (NF)-κB signalling, with downstream production of the type I IFN-β, the chemokines CXCL10 and CXCL8, and cytokine TNF-α. THC and CBD (both at 10 μM) attenuated TLR3/4-induced IRF3 activation and induction of CXCL10/IFN-β, while both phytocannabinoids failed to impact TLR4-induced IκB-α degradation and TNF-α/CXCL8 expression. The role of CB₁, CB₂ and PPARγ receptors in mediating the effect of THC and CBD on MyD88-independent signalling was investigated. TLRs are attractive therapeutic targets given their role in inflammation and initiation of adaptive immunity, and data herein indicate that both CBD and THC preferentially modulate TLR3 and TLR4 signalling via MyD88-independent mechanisms in macrophages. This offers mechanistic insight into the role of phytocannabinoids in modulating cellular inflammation.

Pattern of expression of Toll like receptor (TLR)-3 and -4 genes in drug-naïve and antipsychotic treated patients diagnosed with schizophrenia

Toll like receptors (TLRs), a class of conserved immune molecules are crucially involved in initiating innate immune response to infection. TLR activation and subsequent inflammation are linked to pathogenesis of many brain disorders. Preliminary studies indicate a possible role of TLR-driven immuno-inflammatory responses in schizophrenia. However, gene expression data of TLRs in drug-naïve as well as antipsychotic treated patients diagnosed with schizophrenia are albeit limited. In this study, expression profile of TLR3 and TLR4 genes in peripheral blood mononuclear cells (PBMCs) was compared between drug-naïve patients diagnosed with schizophrenia (N = 31) and healthy controls (N = 30). In addition, the pattern of expression of TLR3 and TLR4 genes were also examined after three months of antipsychotic medication in patients. Compared to healthy controls, gene expression levels of only TLR4 (F = 3.87, p = 0.05, η_p² = 0.06), not TLR3 (F = 0.17, p = 0.71, η_p² = 0.003) was significantly up-regulated in drug-naïve patients. The changes in the levels of gene expression of TLR3 (t = 0.09, p = 0.93, d = 0.02) and TLR4 (t = 0.29, p = 0.77, d = 0.06) before and after antipsychotic medication were not found to be statistically significant. This finding suggests possible contribution of TLR4 in immunopathogenetic pathway of schizophrenia.

Milk fermented with Lactobacillus rhamnosus R0011 induces a regulatory cytokine profile in LPS-challenged U937 and THP-1 macrophages

Fermented dairy products have become attractive functional foods for the delivery of probiotics and their biologically active metabolites. The aim of this study was to examine the immunomodulatory activity of milk fermented with the probiotic lactic acid bacterium Lactobacillus rhamnosus R0011 (LrF) on macrophages challenged with lipopolysaccharide (LPS), a potent pro-inflammatory stimulus. To this end, human THP-1 or U937 monocytes were differentiated into resting macrophages then stimulated with LPS and co-incubated with the LrF or with milk controls. Levels of pro-inflammatory and immunoregulatory cytokines were determined by enzyme-linked immunosorbent assays. Culturing of LPS-stimulated U937 macrophages with either the whole or filtered LrF resulted in an increase in Interleukin (IL)-1Ra production relative to the negative control. THP-1 macrophages cultured with the LrF demonstrated an increase in LPS-induced IL-10 and IL-1β production, while production of LPS-induced IL-6, sCD54, IL-8, IL-1β, TNF-α, IL-12p70 and Transforming Growth Factor-β (TGF-β) was unaffected. Further, the LrF induced the expression of DC-SIGN and CD206, markers of immunoregulatory M2 macrophage polarization, in LPS-challenged THP-1 macrophages. Taken together, milk fermented with L. rhamnosus R0011 increased regulatory cytokine production from LPS-challenged U937 and THP-1 macrophages, while simultaneously up-regulating the production of IL-1β and expression of DC-SIGN and CD206, a profile characteristic of polarization into the immunoregulatory M2 macrophage phenotype.

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Milk fermented with Lactobacillus rhamnosus R0011 (Lrf) induces a regulatory macrophage phenotype.

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Modulation of cytokine profiles induced by lipopolysaccharide challenge consistent with an alternatively activated (M2) macrophage phenotype.

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Fermented milk conditioning induced macrophage expression of genes characteristic of M2 macrophage polarization (DC-SIGN and CD206).

Identification of CNS Injury-Related microRNAs as Novel Toll-Like Receptor 7/8 Signaling Activators by Small RNA Sequencing

Toll-like receptors (TLRs) belong to pattern recognition receptors, which respond to danger signals such as pathogen-associated molecular patterns or damage-associated molecular patterns. Upon TLR activation in microglia, the major immune cells in the brain, distinct signaling cascades trigger the production of inflammatory molecules, being a critical feature in neuroinflammation and neurodegenerative processes. Recently, individual microRNAs (miRNAs) were shown to act as endogenous TLR ligands. Here, we conducted systematic screening for miRNAs as potential TLR7/8 ligands by small RNA sequencing of apoptotic neurons and their corresponding supernatants. Several miRNA species were identified in both supernatants and injured neurons, and 83.3% of the media-enriched miRNAs activated murine and/or human TLR7/8 expressed in HEK293-derived TLR reporter cells. Among the detected extracellular miRNAs, distinct miRNAs such as miR-340-3p and miR-132-5p induced cytokine and chemokine release from microglia and triggered neurotoxicity in vitro. Taken together, our systematic study establishes miRNAs released from injured neurons as new TLR7/8 activators, which contribute to inflammatory and neurodegenerative responses in the central nervous system (CNS).

Sensing of HIV-1 by TLR8 activates human T cells and reverses latency

During HIV infection, cell-to-cell transmission results in endosomal uptake of the virus by target CD4+ T cells and potential exposure of the viral ssRNA genome to endosomal Toll-like receptors (TLRs). TLRs are instrumental in activating inflammatory responses in innate immune cells, but their function in adaptive immune cells is less well understood. Here we show that synthetic ligands of TLR8 boosted T cell receptor signaling, resulting in increased cytokine production and upregulation of surface activation markers. Adjuvant TLR8 stimulation, but not TLR7 or TLR9, further promoted T helper cell differentiation towards Th1 and Th17. In addition, we found that endosomal HIV induced cytokine secretion from CD4+ T cells in a TLR8-specific manner. TLR8 engagement also enhanced HIV-1 replication and potentiated the reversal of latency in patient-derived T cells. The adjuvant TLR8 activity in T cells can contribute to viral dissemination in the lymph node and low-grade inflammation in HIV patients. In addition, it can potentially be exploited for therapeutic targeting and vaccine development.

Signalling, sorting and scaffolding adaptors for Toll-like receptors

Toll-like receptors (TLRs) are danger-sensing receptors that typically propagate self-limiting inflammatory responses, but can unleash uncontrolled inflammation in non-homeostatic or disease settings. Activation of TLRs by pathogen- and/or host-derived stimuli triggers a range of signalling and transcriptional pathways to programme inflammatory and anti-microbial responses, including the production of a suite of inflammatory cytokines and other mediators. Multiple sorting and signalling adaptors are recruited to receptor complexes on the plasma membrane or endosomes where they act as scaffolds for downstream signalling kinases and effectors at these sites. So far, seven proximal TLR adaptors have been identified: MyD88, MAL, TRIF (also known as TICAM1), TRAM (TICAM2), SARM (SARM1), BCAP (PIK3AP1) and SCIMP. Most adaptors tether directly to TLRs through homotypic Toll/interleukin-1 receptor domain (TIR)-TIR interactions, whereas SCIMP binds to TLRs through an atypical TIR-non-TIR interaction. In this Review, we highlight the key roles for these adaptors in TLR signalling, scaffolding and receptor sorting and discuss how the adaptors thereby direct the differential outcomes of TLR-mediated responses. We further summarise TLR adaptor regulation and function, and make note of human diseases that might be associated with mutations in these adaptors.

TLR4 (Toll-Like Receptor 4) Mediates the Development of Intracranial Aneurysm Rupture

Inflammation is emerging as a critical factor in the pathophysiology of intracranial aneurysm. TLR4 (toll-like receptor 4) contributes not only to the innate immune responses but also to the inflammatory processes associated with vascular disease. Therefore, we examined the contribution of the TLR4 pathway to the development of the rupture of intracranial aneurysm. We used a mouse model of intracranial aneurysm. TLR4 inhibition significantly reduced the development of aneurysmal rupture. In addition, the rupture rate and levels of proinflammatory cytokines were lower in TLR4 knockout mice than the control littermates. Macrophage/monocyte-specific TLR4 knockout mice had a lower rupture rate than the control littermate mice. Moreover, the deficiency of MyD88 (myeloid differentiation primary-response protein 88), a key mediator of TLR4, reduced the rupture rate. These findings suggest that the TLR4 pathway promotes the development of intracranial aneurysmal rupture by accelerating inflammation in aneurysmal walls. Inhibition of the TLR4 pathway in inflammatory cells may be a promising approach for the prevention of aneurysmal rupture and subsequent subarachnoid hemorrhage.

The Unique Microbiome and Innate Immunity During Pregnancy

A successful pregnancy depends on not only the tolerance of the fetal immune system by the mother but also resistance against the threat of hazardous microorganisms. Infection with pathogenic microorganisms during pregnancy may lead to premature delivery, miscarriage, growth restriction, neonatal morbidity, and other adverse outcomes. Moreover, the host also has an intact immune system to avoid these adverse outcomes. It is important to note the presence of normal bacteria in the maternal reproductive tract and the principal role of the maternal-placental-fetal interaction in antimicrobial immunity. Previous studies mainly focused on maternal infection during pregnancy. However, this review summarizes the new views on the study of the maternal microbiome and expounds the innate immune defense mechanism of the maternal vagina and decidua as well as how cytotrophoblasts and syncytiotrophoblasts recognize and kill bacteria in the placenta. Fetal immune systems, thought to be weak, also exhibit an immune defense function that is indispensable for maintaining the safety of the fetus. The skin, lungs, and intestines of the fetus during pregnancy constitute the main immune barriers. These findings will provide a new understanding of the effects of normal microbial flora and how the host resists harmful microbes during pregnancy. We believe that it may also contribute to the reference on the clinical prevention and treatment of gestational infection to avoid adverse pregnancy outcomes.

Selection of an inadequate housekeeping gene leads to misinterpretation of target gene expression in zinc deficiency and zinc supplementation models

BACKGROUND

Numerous studies try to find the most stable housekeeping gene for a specific experimental setup. However, there is no universal housekeeping gene described so far and, therefore, new testing of housekeeping genes at the beginning of a new experiment is of high importance.

METHODS

In the present study, target gene expression of mitochondrial serine/threonine-protein phosphatase (PGAM)5, nuclear factor erythroid 2-related factor (Nrf)2, dynamin related protein (Drp)1 and kelch like ECH associated protein (Keap)1 was tested in zinc-deficient and zinc-supplemented THP-1 cells and compared to control cells. Normalization of results obtained by quantitative real-time polymerase chain reaction (qRT-PCR) was performed by using the housekeeping genes porphobilinogen deaminase (PBGD), β-actin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Additionally, this 3 housekeeping genes were tested in Jurkat cells under these conditions.

RESULTS

Surprisingly, analyses of one and the same target gene revealed opposite results depending on the used housekeeping gene. This was caused by significant altered housekeeping gene expressions due to zinc availability.

CONCLUSION

Therefore, this study highlights the importance of choosing adequate housekeeping genes, which might comprise the use of more than one housekeeping gene when different conditions are tested, such as zinc deficiency and zinc supplementation. Related to the herein used experimental setup, the use ofGAPDH to study gene expression upon zinc deficiency and PBGD to study gene expression after zinc supplementation is recommended.

Minor C allele of the SNP rs7873784 associated with rheumatoid arthritis and type-2 diabetes mellitus binds PU.1 and enhances TLR4 expression

Toll-like receptor 4 (TLR4) is an innate immunity receptor predominantly expressed on myeloid cells and involved in the development of various diseases, many of them with complex genetics. Here we present data on functionality of single nucleotide polymorphism rs7873784 located in the 3'-untranslated region (3'-UTR) of TLR4 gene and associated with various pathologies involving chronic inflammation. We demonstrate that TLR4 3'-UTR strongly enhanced the activity of TLR4 promoter in U937 human monocytic cell line while minor rs7873784(C) allele created a binding site for transcription factor PU.1 (encoded by SPI1 gene), a known regulator of TLR4 expression. Increased binding of PU.1 further augmented the TLR4 transcription while PU.1 knockdown or complete disruption of the PU.1 binding site abrogated the effect. We hypothesize that additional functional PU.1 site may increase TLR4 expression in individuals carrying minor C variant of rs7873784 and modulate the development of certain pathologies, such as rheumatoid arthritis and type-2 diabetes mellitus.

Antagonism of major histocompatibility complex class II invariant chain peptide during chronic lipopolysaccharide treatment rescues autoregulatory behavior

Toll-like receptor 4 (TLR4) activation contributes to vascular dysfunction in pathological conditions such as hypertension and diabetes, but the role of chronic TLR4 activation on renal autoregulatory behavior is unknown. We hypothesized that subclinical TLR4 stimulation with low-dose lipopolysaccharide (LPS) infusion increases TLR4 activation and blunts renal autoregulatory behavior. We assessed afferent arteriolar autoregulatory behavior in male Sprague-Dawley rats after prolonged LPS (0.1 mg·kg^-1·day^-1 sq) infusion via osmotic minipump for 8 or 14 days. Some rats also received daily cotreatment with either anti-TLR4 antibody (1 μg ip), competitive antagonist peptide (CAP; 3 mg/kg ip) or tempol (2 mmol/l, drinking water) throughout the 8-day LPS treatment period. Autoregulatory behavior was assessed using the in vitro blood-perfused juxtamedullary nephron preparation. Selected physiological measures, systolic blood pressure and baseline diameters were normal and similar across groups. Pressure-dependent vasoconstriction averaged 72 ± 2% of baseline in sham rats, indicating intact autoregulatory behavior. Eight-day LPS-treated rats exhibited significantly impaired pressure-mediated vasoconstriction (96 ± 1% of baseline), whereas it was preserved in rats that received anti-TLR4 antibody (75 ± 3%), CAP (84 ± 2%), or tempol (82 ± 2%). Using a 14-day LPS (0.1 mg·kg^-1·day^-1 sq) intervention protocol, CAP treatment started on day 7, where autoregulatory behavior is already impaired. Systolic blood pressures were normal across all treatment groups. Fourteen-day LPS treatment retained the autoregulatory impairment (95 ± 2% of baseline). CAP intervention starting on day 7 rescued pressure-mediated vasoconstriction with diameters decreasing to 85 ± 1% of baseline. These data demonstrate that chronic subclinical TLR4 activation impairs afferent arteriolar autoregulatory behavior through mechanisms involving reactive oxygen species and major histocompatibility complex class II activation.

Toll-like receptors and their therapeutic potential in Parkinson's disease and α-synucleinopathies

Toll-like receptors (TLRs) are pattern recognition receptors which mediate an inflammatory response upon the detection of specific molecular patterns found on foreign organisms and on endogenous damage-related molecules. These receptors play a major role in the activation of microglia, the innate immune cells of the CNS, and are also expressed in peripheral tissues, including blood mononuclear cells and the gut. It is well established that immune activation, in both the brain and periphery, is a feature of Parkinson's disease as well as other α-synucleinopathies. Aggregated forms of α-synuclein can act as ligands for TLRs (particularly TLR2 and TLR4), and hence these receptors may play a critical role in mediating a detrimental immune response to this protein, as well as other inflammatory signals in Parkinson's and related α-synucleinopathies. In this review, the potential role of TLRs in contributing to the progression of these disorders is discussed. Existing evidence comes predominantly from studies in in vitro and in vivo models, as well as analyses of postmortem human brain tissue and pre-clinical studies of TLR inhibitors. This evidence is evaluated in detail, and the potential for therapeutic intervention in α-synucleinopathies through TLR inhibition is discussed.

DAMP-sensing receptors in sterile inflammation and inflammatory diseases

The innate immune system has the capacity to detect 'non-self' molecules derived from pathogens, known as pathogen-associated molecular patterns, via pattern recognition receptors. In addition, an increasing number of endogenous host-derived molecules, termed damage-associated molecular patterns (DAMPs), have been found to be sensed by various innate immune receptors. The recognition of DAMPs, which are produced or released by damaged and dying cells, promotes sterile inflammation, which is important for tissue repair and regeneration, but can also lead to the development of numerous inflammatory diseases, such as metabolic disorders, neurodegenerative diseases, autoimmune diseases and cancer. Here we examine recent discoveries concerning the roles of DAMP-sensing receptors in sterile inflammation and in diseases resulting from dysregulated sterile inflammation, and then discuss insights into the cross-regulation of these receptors and their ligands.

TLR7 activation in epilepsy of tuberous sclerosis complex

BACKGROUND

Neuroinflammation and toll-like receptors (TLR) of the innate immune system have been implicated in epilepsy. We previously reported high levels of microRNAs miR-142-3p and miR-223-3p in epileptogenic brain tissue resected for the treatment of intractable epilepsy in children with tuberous sclerosis complex (TSC). As miR-142-3p has recently been reported to be a ligand and activator of TLR7, a detector of exogenous and endogenous single-stranded RNA, we evaluated TLR7 expression and downstream IL23A activation in surgically resected TSC brain tissue.

METHODS

Gene expression analysis was performed on cortical tissue obtained from surgery of TSC children with pharmacoresistent epilepsy. Expression of TLRs 2, 4 and 7 was measured using NanoString nCounter assays. Real-time quantitative PCR was used to confirm TLR7 expression and compare TLR7 activation, indicated by IL-23A levels, to levels of miR-142-3p. Protein markers characteristic for TLR7 activation were assessed using data from our existing quantitative proteomics dataset of TSC tissue. Capillary electrophoresis Western blots were used to confirm TLR7 protein expression in a subset of samples.

RESULTS

TLR7 transcript expression was present in all TSC specimens. The signaling competent form of TLR7 protein was detected in the membrane fraction of each sample tested. Downstream activation of TLR7 was found in epileptogenic lesions having elevated neuroinflammation indicated by clinical neuroimaging. TLR7 activity was significantly associated with tissue levels of miR-142-3p.

CONCLUSION

TLR7 activation by microRNAs may contribute to the neuroinflammatory cascade in epilepsy in TSC. Further characterization of this mechanism may enable the combined of use of neuroimaging and TLR7 inhibitors in a personalized approach towards the treatment of intractable epilepsy.

Extracellular vesicles in host-pathogen interactions and immune regulation - exosomes as emerging actors in the immunological theater of pregnancy

This review correlates and summarizes the role of the maternal-fetal interface in the immune tolerance of the fetus and the processes that lead to infection avoidance, emphasizing the participation of exosomes and other extracellular vesicles in both situations. Exosomes are released into the extracellular medium by several cell types and are excellent carriers of biomolecules. Host-derived exosomes and the transport of pathogen-derived molecules by exosomes impact infections in different ways. The interactions of exosomes with the maternal immune system are pivotal to a favorable gestational outcome. In this review, we highlight the potential role of exosomes in the establishment of an adequate milieu that enables embryo implantation and discuss the participation of exosomes released at the maternal-fetal interface during the establishment of an immune-privileged compartment for fetal development. The placenta is a component where important strategies are used to minimize the risk of infection. To present a contrast, we also discuss possible mechanisms used by pathogens to cross the maternal-fetal interface. We review the processes, mechanisms, and potential consequences of dysregulation in all of the abovementioned phenomena. Basic information about exosomes and their roles in viral immune evasion is also presented. The interactions between extracellular vesicles and bacteria, fungi, parasites and proteinaceous infectious agents are addressed. The discovery of the placental microbiota and the implications of this new microbiota are also discussed, and current proposals that explain fetal/placental colonization by both pathogenic and commensal microbes are addressed. The comprehension of such interactions will help us to understand the immune dynamics of human pregnancy and the mechanisms of immune evasion used by different pathogens.

IFN-I response timing relative to virus replication determines MERS coronavirus infection outcomes

Type 1 IFNs (IFN-I) generally protect mammalian hosts from virus infections, but in some cases, IFN-I is pathogenic. Because IFN-I is protective, it is commonly used to treat virus infections for which no specific approved drug or vaccine is available. The Middle East respiratory syndrome-coronavirus (MERS-CoV) is such an infection, yet little is known about the role of IFN-I in this setting. Here, we show that IFN-I signaling is protective during MERS-CoV infection. Blocking IFN-I signaling resulted in delayed virus clearance, enhanced neutrophil infiltration, and impaired MERS-CoV-specific T cell responses. Notably, IFN-I administration within 1 day after infection (before virus titers peak) protected mice from lethal infection, despite a decrease in IFN-stimulated gene (ISG) and inflammatory cytokine gene expression. In contrast, delayed IFN-β treatment failed to effectively inhibit virus replication, increased infiltration and activation of monocytes, macrophages, and neutrophils in the lungs, and enhanced proinflammatory cytokine expression, resulting in fatal pneumonia in an otherwise sublethal infection. Together, these results suggest that the relative timing of the IFN-I response and maximal virus replication is key in determining outcomes, at least in infected mice. By extension, IFN-αβ or combination therapy may need to be used cautiously to treat viral infections in clinical settings.

Toll-Like Receptor 9 Deficiency Breaks Tolerance to RNA-Associated Antigens and Up-Regulates Toll-Like Receptor 7 Protein in Sle1 Mice

Objective

Toll‐like receptors (TLRs) 7 and 9 are important innate signaling molecules with opposing roles in the development and progression of systemic lupus erythematosus (SLE). While multiple studies support the notion of a dependency on TLR‐7 for disease development, genetic ablation of TLR‐9 results in severe disease with glomerulonephritis (GN) by a largely unknown mechanism. This study was undertaken to examine the suppressive role of TLR‐9 in the development of severe lupus in a mouse model.

Methods

We crossed Sle1 lupus‐prone mice with TLR‐9–deficient mice to generate Sle1TLR‐9^−/− mice. Mice ages 4.5–6.5 months were evaluated for severe autoimmunity by assessing splenomegaly, GN, immune cell populations, autoantibody and total Ig profiles, kidney dendritic cell (DC) function, and TLR‐7 protein expression. Mice ages 8–10 weeks were used for functional B cell studies, Ig profiling, and determination of TLR‐7 expression.

Results

Sle1TLR‐9^−/− mice developed severe disease similar to TLR‐9–deficient MRL and Nba2 models. Sle1TLR‐9^−/− mouse B cells produced more class‐switched antibodies, and the autoantibody repertoire was skewed toward RNA‐containing antigens. GN in these mice was associated with DC infiltration, and purified Sle1TLR‐9^−/− mouse renal DCs were more efficient at TLR‐7–dependent antigen presentation and expressed higher levels of TLR‐7 protein. Importantly, this increase in TLR‐7 expression occurred prior to disease development, indicating a role in the initiation stages of tissue destruction.

Conclusion

The increase in TLR‐7–reactive immune complexes, and the concomitant enhanced expression of their receptor, promotes inflammation and disease in Sle1TLR9^−/− mice.

Alterations in membrane fluidity are involved in inhibition of GM-CSF-induced signaling in myeloid cells by zinc

Zinc has a strong influence on the function of the immune system and is a driving factor for immune cell development. In this regard, studies revealed cell type specific effects of zinc. During zinc deficiency for example, development and activity of myeloid cells seems to be prioritized at the cost of cells from the lymphoid lineage. In T-cells, the altered proliferation was found to be due to zinc's effect on IL-2-induced signaling processes, but in contrast to lymphoid cells, effects of zinc homeostasis on growth-factor-induced signaling in myeloid cells have not been investigated yet. The granulocyte-macrophage colony-stimulating factor (GM-CSF) is one of the major factors inducing monopoiesis. Considering the structural similarities between the GM-CSF receptor and those of the IL-receptor family as well as a similar set of signaling molecules involved, an impact of zinc on the GM-CSF signaling seems to be likely. Therefore, the effect of zinc on GM-CSF-induced signaling molecules was investigated here, using U937 cells as a model myeloid cell line. GM-CSF stimulation significantly increased STAT5 phosphorylation which was prevented completely by pre-incubation with zinc and pyrithione. U937 cells showed a strong pre-activation regarding c-Raf, which was significantly decreased by zinc and pyrithione incubation, independently from GM-CSF stimulation. As current literature was not sufficient to explain the observed effects, we hypothesized an altered receptor-complex assembly. As membrane composition and plasticity, subsumed under the term of membrane fluidity, was found to affect receptor multimerization, the impact of zinc on membrane fluidity was considered as a completely novel approach. Indeed, addition of zinc also decreased GM-CSFR expression on the cell surface and most interestingly altered membrane fluidity. In conclusion, we hypothesize that the incubation with zinc causes an alteration of membrane fluidity that hinders efficient receptor assembly as well as phosphorylation of signal molecules and therefore signal transduction.

Activation of multiple Toll-like receptors serves different roles in sepsis-induced acute lung injury

The activation of Toll-like receptors (TLRs) is involved in the innate immune response and the acute inflammatory response following sepsis-induced acute lung injury (ALI). Increasing evidence has demonstrated that sepsis-induced ALI may be closely associated with several abnormal TLRs, activated by components of microorganisms. However, the number of TLRs involved in this process and the extent of their involvement has not been fully elucidated. The current study examined the simultaneous activation of four TLRs closely associated with sepsis-induced ALI. The results demonstrated that in contrast to the sham-operated group, the mRNA and protein expression levels of TLR2/4/9 were significantly increased in the cecal ligation and puncture (CLP)-operated group. In addition, TLR2^-/-, TLR3^-/-, TLR4^-/- and TLR9^-/- C57BL/6 mice were used to establish a CLP-induced ALI animal model and measure the expression levels of TNF-α and IL-6 in plasma and lung tissue samples. The expression of both TNF-α and IL-6 were significantly decreased in TLR2^-/-, TLR4^-/- and TLR9^-/- mice compared with WT mice. In addition, the results revealed that knockdown of TLR2, 4 or 9 decreased immune cell infiltration and therefore may attenuate lung injury. Furthermore, the overall survival was significantly increased in TLR2^-/-, 4^-/- and 9^-/- CLP-induced ALI mice compared with the WT CLP-induced ALI mice. However, there was no statistical significance between TLR3^-/- CLP-induced ALI and WT CLP-induced ALI in the current study. Taken together, these results suggest that in the sepsis-induced ALI model, several TLRs are upregulated and participate in the inflammatory response. Therefore, inhibition of multiple TLRs including TLR2, 9, and especially TLR4 simultaneously, but not TLR3, may be a potential therapeutic target for the treatment of sepsis-induced ALI.

Adaptive immune cells in calcific aortic valve disease

Calcific aortic valve disease (CAVD) is highly prevalent and has no pharmaceutical treatment. Surgical replacement of the aortic valve has proved effective in advanced disease but is costly, time limited, and in many cases not optimal for elderly patients. This has driven an increasing interest in noninvasive therapies for patients with CAVD. Adaptive immune cell signaling in the aortic valve has shown potential as a target for such a therapy. Up to 15% of cells in the healthy aortic valve are hematopoietic in origin, and these cells, which include macrophages, T lymphocytes, and B lymphocytes, are increased further in calcified specimens. Additionally, cytokine signaling has been shown to play a causative role in aortic valve calcification both in vitro and in vivo. This review summarizes the physiological presence of hematopoietic cells in the valve, innate and adaptive immune cell infiltration in disease states, and the cytokine signaling pathways that play a significant role in CAVD pathophysiology and may prove to be pharmaceutical targets for this disease in the near future.

Toll-like receptor-induced cytokines as immunotherapeutic targets in cancers and autoimmune diseases

Immune cells of the myeloid and lymphoid lineages express Toll-like receptors (TLRs) to recognize pathogenic components or cellular debris and activate the immune system through the secretion of cytokines. Cytokines are signaling molecules that are structurally and functionally distinct from one another, although their secretion profiles and signaling cascades often overlap. This situation gives rise to pleiotropic cell-to-cell communication pathways essential for protection from infections as well as cancers. Nonetheless, deregulated signaling can have detrimental effects on the host, in the form of inflammatory or autoimmune diseases. Because cytokines are associated with numerous autoimmune and cancerous conditions, therapeutic strategies to modulate these molecules or their biological responses have been immensely beneficial over the years. There are still challenges in the regulation of cytokine function in patients, even in those who take approved biological therapeutics. In this review, our purpose is to discuss the differential expression patterns of TLR-regulated cytokines and their cell type specificity that is associated with cancers and immune-system-related diseases. In addition, we highlight key structural features and molecular recognition of cytokines by receptors; these data have facilitated the development and approval of several biologics for the treatment of autoimmune diseases and cancers.

Mitochondrial DNA plays an important role in lung injury induced by sepsis

The effects and mechanisms of mitochondrial DNA (mtDNA) in the development of sepsis-induced lung injury is not well understood. In our present study, we studied the mtDNA effects in sepsis-induced lung injury model, in vitro and in vivo. Compared with the Normal group, the lung histopathological score, the number of positive apoptosis cell, wet/dry (W/D) ratio and TNF-α, IL-1β, and IL-6 concentrations of lipopolysaccharides (LPSs) and mtDNA groups were significantly increased (P < 0.001, respectively). Meanwhile, the lung histopathological score, positive W/D ratio, number of apoptosis cell and tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 concentrations of LPS + mtDNA and small interfering RNA (siRNA)-NC + LPS + mtDNA groups were significantly upregulated compared with those of LPS group (P < 0.05, respectively). However, the lung histopathological score, the number of positive apoptosis cell, W/D ratio and TNF-α, IL-1β, and IL-6 concentrations were significantly improved within the toll-like receptor (TLR9)siRNA + LPS + mtDNA group compared with the LPS group (P < 0.01, respectively). The TLR9, MyD88, and NF-κB proteins or gene expressions of the LPS group and mtDNA group were significantly upregulated compared with those of Normal group by Western blot analysis or immunohistochemistry assay (P < 0.01, respectively), and the TLR9, MyD88, and NF-κB proteins or gene expressions of LPS + mtDNA and siRNA-NC + LPS + mtDNA groups were significantly enhanced compared with those of LPS group (P < 0.05, respectively). However, the TLR9, MyD88, and NF-κB proteins or gene expressions of TLR9siRNA + LPS + mtDNA group were significantly suppressed compared with those of the LPS group (P < 0.01, respectively). In conclusion, mtDNA could provoke lung injury induced by sepsis via regulation of TLR9/MyD88/NF-κB pathway in vitro and in vivo.

Immunopathogenesis of Behçet Disease

BACKGROUND

Behçet's Disease (BD, OMIM 109650) is a chronic relapsing inflammatory disease of unknown etiology with unpredictable exacerbations and remissions. First described in 1937 by the Turkish dermatologist HulusiBehçet, as a trisympton complex (oral and genital ulcers and uveitis), it is now recognized as a multisystemic disease. The syndrome can manifest in diverse ways and can involve nearly every organ system. Several studies have implicated T cells and monocytes in the pathogenesis of BD especially when these cells are stimulated by heat shock proteins and streptococcal antigen. This article presents a review of the relevant published literature about the immunopathogenesis of BD.

RESULT

The authors used MeSH terms "Behçet's disease" with "pathophysiology," "pathogenesis," "genetic", "epigenetic", "immunogenetic" or "immune response" to search the PubMed database. All the relevant studies identified were included.

TLR3 is involved in paraquat-induced acute renal injury

AIMS

To investigate the role of Toll-like receptor 3 (TLR3) in mouse paraquat-induced acute renal injury.

MATERIALS AND METHODS

Acute renal injury was established in C57BL/6J mice by intraperitoneal injection of paraquat (28 mg/kg). The mice were also injected intraperitoneally with TLR3 agonist poly I:C (20 mg/kg) or TLR3/dsRNA complex inhibitor (1 mg) 1 h before paraquat exposure. At 72 hour post paraquat exposure, the mice were sacrificed and the blood and renal tissues were collected to examine TLR3 expression in renal tissues, pathological injury in renal tissues, renal function, inflammation, and cell apoptosis.

KEY FINDINGS

After paraquat exposure, TLR3 expression in mouse renal tissues was significantly increased, and pathological changes to the renal tissues and remarkable renal impairment were present. Compared to the paraquat group, the poly I:C group showed no significant difference in renal pathology, renal function, inflammation, or cell apoptosis. However, TLR3 inhibitor treatment significantly alleviated injury to the renal tissues, improved renal function, inhibited NF-κB activation, suppressed the infiltration of neutrophils, and lessened the expression of IL-1β, TNF-α, and keratinocyte chemoattractant (KC) in renal tissues. TLR3 inhibitor treatment also suppressed the activation of caspase-8 and caspase-3 and reduced apoptosis in the renal tissues.

SIGNIFICANCE

Paraquat exposure significantly upregulates TLR3 expression in renal tissues, and activation of the TLR3 signaling pathway is an important contributor to paraquat nephrotoxicity. TLR3 activation exacerbates inflammation and cell apoptosis in renal tissues by activating NF-κB and caspase-8, thus promoting paraquat-induced acute renal injury.

Goose toll-like receptor 3 (TLR3) mediated IFN-γ and IL-6 in anti-H5N1 avian influenza virus response

Induction of the innate immune pathways is critical for early anti-viral defense. How geese recognize viral molecules and activate these pathways is not well understood. In mammals, Toll-like receptor 3 (TLR3) recognizes double-stranded RNA. Activation of TLR3 induces the activation of NF-кB and the production of type-I interferon. In this study, the goose TLR3 gene was cloned using rapid amplification of cDNA ends. Goose TLR3 encoded an 896-amino-acid protein, containing a signal secretion peptide, 14 extracellular leucine-rich repeat domains, a transmembrane domain, a Toll/interleukin-1 receptor signaling domain, and shared 46.7-84.4% homology with other species. Tissue expression of goose TLR3 varied markedly and was highest in the pancreas and lowest in the skin. Human embryonic kidney 293 cells transfected with goose TLR3 and NF-κB-luciferase-containing plasmids responded significantly to poly i:c. The expression of TLR3, IL-6 and IFN-γ mRNA, but not IL-1 mRNA, was significantly upregulated after poly i:c or high pathogenic avian influenza virus (H5N1) stimulation in goose peripheral blood mononuclear cells cultured in vitro. Furthermore, geese infected with H5N1 showed significant upregulation of TLR3, especially in the lung and brain. We conclude that goose TLR3 is a functional TLR3 homologue of the protein in other species and plays an important role in virus recognition.

TLR4 Polymorphisms and Expression in Solid Cancers

Toll-like receptors (TLRs) are a type of pattern-recognition receptor (PRR) that are part of the innate immune system known to recognize pathogen-associated molecular patterns and thereby play a crucial role in host immune response. Among the various known TLRs, TLR4 is one of the most extensively studied PRRs expressed by immune, certain nonimmune, and tumor cells. When TLR4 binds with the bacterial lipopolysaccharide, it induces production of proinflammatory cytokines, chemokines, and effector molecules as part of the immune response. Continuous exposure to pathogens and TLR4 signaling results in chronic inflammation that may further lead to malignant transformation. TLR4 is a highly polymorphic gene, and genetic variations are known to influence host immune response, leading to dysregulation of signaling pathway, which may affect an individual's susceptibility to various diseases, including cancer. Furthermore, TLR4 expression in different tumor types may also serve as a marker for tumor proliferation, differentiation, metastasis, prognosis, and patient survival. This review aims to summarize various reports related to TLR4 polymorphisms and expression patterns and their influences on different cancer types with a special focus on solid tumors.

The expression and localization of Toll-like receptors 2, 4, 5 and 9 in the epididymis and vas deferens of a adult tom cats

Toll-like receptors (TLRs) are important molecules, which provide protection against infections of the reproductive tract. This study demonstrates for the first time the expression and localization patterns of TLRs in the caput, corpus and cauda segments of the epididymal duct (ED) and the vas deferens (VD) of adult domestic cats using immunohistochemistry and western blotting. While immunoblot analyses revealed relatively similar protein levels for TLRs 2, 4, 5, and 9 in three segments of the ED, the protein levels of TLR2 and TLR4 in the VD were found to be significantly higher than those measured in the ED segments (P < 0.05). On the other hand, immunostaining showed that TLRs exhibited regional- and cell-specific localization patterns. TLR2 and TLR5 were immunolocalized to the nucleus and cytoplasm of the principal cells in all ducts. TLR4 was restricted to the stereocilia, and TLR9 was located in the cytoplasm of the principal cells. Narrow cells displayed positive immunoreactions for TLR4 and TLR5. The basal cells of the different ED segments were positive for all four TLRs. TLR2, TLR5 and TLR9 were detected in the cytoplasmic droplets of the spermatozoa. TLR4 and TLR9 were detected along the entire length of the sperm tail, whilst TLR2 and TLR5 were absent in the midpiece. TLR2 and TLR5 were also detected in the equatorial segment of the sperm head. These results suggest that TLR2, TLR4, TLR5 and TLR9 are important not only for the protection of the ED, VD and spermatozoa but also for the maturation and storage of spermatozoa in the ED and VD, respectively.

Evidence that inflammation promotes estradiol synthesis in human cerebellum during early childhood

Discovering and characterizing critical and sensitive periods in brain development is essential for unraveling the myriad variables that impact disease risk. In previous work, we identified a critical period in cerebellar development in the rat that depends upon an intrinsic gene expression program and links increased prostaglandin production to local estradiol synthesis by stimulating Cyp19a, the estradiol synthetic enzyme, aromatase. This intrinsic critical period is sensitive to disruption by either inflammation or administration of cyclooxygenase (COX) inhibitors, ultimately impacting Purkinje cell dendritic growth. In a first step towards determining if a similar sensitive period exists in humans, the same gene expression profile was characterized in post-mortem cerebellar tissue of 58 children aged 0 to 9 years. Subjects were categorized as experiencing inflammation or not at the time of death. In individuals experiencing inflammation and over 1 year of age, there was a significant increase in the messenger RNA (mRNA) of the COX-1 and COX-2 enzymes and this strongly correlated with mRNA levels of aromatase. A step-wise linear model accounted for 94% of the variance in aromatase mRNA levels by co-variance with the COX enzymes, prostaglandin E2 synthase and other inflammatory mediators (Toll-like receptor 4), and Purkinje cell markers (calbindin, estrogen receptor 2). The influence of inflammation on these measures was not seen in subjects younger than 1 year. These data suggest a sensitive period to inflammation in the human cerebellum begins at about 1 year of age and may provide insight into sources of vulnerability of very young children to either inflammation or drugs designed to treat it.