Characterization of methylation profiles in spontaneous preterm birth placental villous tissue

Preterm birth is a global public health crisis which results in significant neonatal and maternal mortality. Yet little is known regarding the molecular mechanisms of idiopathic spontaneous preterm birth, and we have few diagnostic markers for adequate assessment of placental development and function. Previous studies of placental pathology and our transcriptomics studies suggest a role for placental maturity in idiopathic spontaneous preterm birth. It is known that placental DNA methylation changes over gestation. We hypothesized that if placental hypermaturity is present in our samples, we would observe a unique idiopathic spontaneous preterm birth DNA methylation profile potentially driving the gene expression differences we previously identified in our placental samples. Our results indicate the idiopathic spontaneous preterm birth DNA methylation pattern mimics the term birth methylation pattern suggesting hypermaturity. Only seven significant differentially methylated regions fitting the idiopathic spontaneous preterm birth specific (relative to the controls) profile were identified, indicating unusually high similarity in DNA methylation between idiopathic spontaneous preterm birth and term birth samples. We identified an additional 1,718 significantly methylated regions in our gestational age matched controls where the idiopathic spontaneous preterm birth DNA methylation pattern mimics the term birth methylation pattern, again indicating a striking level of similarity between the idiopathic spontaneous preterm birth and term birth samples. Pathway analysis of these regions revealed differences in genes within the WNT and Cadherin signaling pathways, both of which are essential in placental development and maturation. Taken together, these data demonstrate that the idiopathic spontaneous preterm birth samples display a hypermature methylation signature than expected given their respective gestational age which likely impacts birth timing.

[Current view on the pathogenesis of immune-mediated inflammatory diseases associated with ocular manifestations]

This literature review discusses the new concept of pathogenesis of systemic immune-mediated inflammatory diseases (IMIDs), presents their classification and analyzes their association with ocular manifestations.

Roles of RNA Sensors in Host Innate Response to Influenza Virus and Coronavirus Infections

Influenza virus and coronavirus are two important respiratory viruses, which often cause serious respiratory diseases in humans and animals after infection. In recent years, highly pathogenic avian influenza virus (HPAIV) and SARS-CoV-2 have become major pathogens causing respiratory diseases in humans. Thus, an in-depth understanding of the relationship between viral infection and host innate immunity is particularly important to the stipulation of effective control strategies. As the first line of defense against pathogens infection, innate immunity not only acts as a natural physiological barrier, but also eliminates pathogens through the production of interferon (IFN), the formation of inflammasomes, and the production of pro-inflammatory cytokines. In this process, the recognition of viral pathogen-associated molecular patterns (PAMPs) by host pattern recognition receptors (PRRs) is the initiation and the most important part of the innate immune response. In this review, we summarize the roles of RNA sensors in the host innate immune response to influenza virus and coronavirus infections in different species, with a particular focus on innate immune recognition of viral nucleic acids in host cells, which will help to develop an effective strategy for the control of respiratory infectious diseases.

Insights into inflammasome regulation: cellular, molecular, and pathogenic control of inflammasome activation

Maintenance of immune homeostasis is an intricate process wherein inflammasomes play a pivotal role by contributing to innate and adaptive immune responses. Inflammasomes are ensembles of adaptor proteins that can trigger a signal following innate sensing of pathogens or non-pathogens eventuating in the inductions of IL-1β and IL-18. These inflammatory cytokines substantially influence the antigen-presenting cell's costimulatory functions and T helper cell differentiation, contributing to adaptive immunity. As acute and chronic disease conditions may accompany parallel tissue damage, we analyze the critical role of extracellular factors such as cytokines, amyloids, cholesterol crystals, etc., intracellular metabolites, and signaling molecules regulating inflammasome activation/inhibition. We develop an operative framework for inflammasome function and regulation by host cell factors and pathogens. While inflammasomes influence the innate and adaptive immune components' interplay modulating the anti-pathogen adaptive immune response, pathogens may target inflammasome inhibition as a survival strategy. As trapped between health and diseases, inflammasomes serve as promising therapeutic targets and their modus operandi serves as a scientific rationale for devising better therapeutic strategies.

Protective effects of the NLRP3 inflammasome against infectious bursal disease virus replication in DF-1 cells

Inflammatory responses are an important part of the innate immune response during viral infection. Various inflammasome complexes have been identified. The pyrin domain-containing 3 (NLRP3) inflammasome plays a critical role in detecting some RNA viruses, such as influenza virus. However, the effect of the NLRP3 inflammasome on infectious bursal disease virus (IBDV) replication is still unclear. Here, we report that IBDV-infection induces the transcription of NLRP3 inflammasome and IL-1β genes in the immortalized chicken embryo fibroblast cell line DF-1. Inhibition of caspase-1 by Belnacasan (VX-765) suppressed the transcription of IL-1β, reduced cell lysis, and significantly promoted IBDV replication in DF-1 cells. Furthermore, knockdown of NLRP3 by small interfering RNA promoted IBDV replication in the host cells. Thus, IBDV can induce NLRP3 inflammasome activation in DF-1 cells through a mechanism requiring viral replication, revealing a new antiviral mechanism employed by the host.

Blue Light Induces Impaired Autophagy through Nucleotide-Binding Oligomerization Domain 2 Activation on the Mouse Ocular Surface

In this study, we investigated the effects of blue light exposure on nucleotide-binding oligomerization domain 2 (NOD2) expression on the mouse ocular surface and evaluated the role of NOD2 activation in light-induced cell death. Mice were divided into wild-type (WT), NOD2-knock out (KO), WT + blue light (WT + BL), and NOD2-KO + blue light (NOD2-KO + BL) groups, and the mice in the WT+BL and NOD2-KO + BL groups were exposed to blue light for 10 days. After 10 days of blue light exposure, increased reactive oxygen species and malondialdehyde were observed in the WT + BL and NOD2-KO + BL groups, and the WT + BL group showed a higher expression of NOD2 and autophagy related 16 like 1. Although both WT+BL and NOD2-KO + BL groups showed an increase in the expression of light chain 3-II, NOD2-KO + BL mice had a significantly lower p62 expression than WT + BL mice. In addition, NOD2-KO+BL mice had significantly lower corneal epithelial damage and apoptosis than WT + BL mice. In conclusion, blue light exposure can induce impaired autophagy by activation of NOD2 on the ocular surface. In addition, the reactive oxygen species (ROS)-NOD2-autophagy related 16 like 1 (ATG16L) signaling pathway may be involved in the blue-light-induced autophagy responses, resulting in corneal epithelial apoptosis.

NOD1/RIP2 signalling enhances the microglia-driven inflammatory response and undergoes crosstalk with inflammatory cytokines to exacerbate brain damage following intracerebral haemorrhage in mice

BACKGROUND

Secondary brain damage caused by the innate immune response and subsequent proinflammatory factor production is a major factor contributing to the high mortality of intracerebral haemorrhage (ICH). Nucleotide-binding oligomerization domain 1 (NOD1)/receptor-interacting protein 2 (RIP2) signalling has been reported to participate in the innate immune response and inflammatory response. Therefore, we investigated the role of NOD1/RIP2 signalling in mice with collagenase-induced ICH and in cultured primary microglia challenged with hemin.

METHODS

Adult male C57BL/6 mice were subjected to collagenase for induction of ICH model in vivo. Cultured primary microglia and BV2 microglial cells (microglial cell line) challenged with hemin aimed to simulate the ICH model in vitro. We first defined the expression of NOD1 and RIP2 in vivo and in vitro using an ICH model by western blotting. The effect of NOD1/RIP2 signalling on ICH-induced brain injury volume, neurological deficits, brain oedema, and microglial activation were assessed following intraventricular injection of either ML130 (a NOD1 inhibitor) or GSK583 (a RIP2 inhibitor). In addition, levels of JNK/P38 MAPK, IκBα, and inflammatory factors, including tumour necrosis factor-α (TNF-α), interleukin (IL)-1β, and inducible nitric oxide synthase (iNOS) expression, were analysed in ICH-challenged brain and hemin-exposed cultured primary microglia by western blotting. Finally, we investigated whether the inflammatory factors could undergo crosstalk with NOD1 and RIP2.

RESULTS

The levels of NOD1 and its adaptor RIP2 were significantly elevated in the brains of mice in response to ICH and in cultured primary microglia, BV2 cells challenged with hemin. Administration of either a NOD1 or RIP2 inhibitor in mice with ICH prevented microglial activation and neuroinflammation, followed by alleviation of ICH-induced brain damage. Interestingly, the inflammatory factors interleukin (IL)-1β and tumour necrosis factor-α (TNF-α), which were enhanced by NOD1/RIP2 signalling, were found to contribute to the NOD1 and RIP2 upregulation in our study.

CONCLUSION

NOD1/RIP2 signalling played an important role in the regulation of the inflammatory response during ICH. In addition, a vicious feedback cycle was observed between NOD1/RIP2 and IL-1β/TNF-α, which could to some extent result in sustained brain damage during ICH. Hence, our study highlights NOD1/RIP2 signalling as a potential therapeutic target to protect the brain against secondary brain damage during ICH.

Determination of the immunostimulatory drug-glucosoaminyl-muramyl-dipeptide-in human plasma using HPLC-MS/MS and its application to a pharmacokinetic study

GMDP (glucosoaminyl-muramyl-dipeptide), a synthetic analog of the peptidoglycan fragment of the bacterial cell wall, is an active component of the immunomodulatory drug Licopid. But the pharmacokinetic parameters of GMDP in humans after oral administration have not been investigated yet. The present study aimed at developing and validating a sensitive LC-MS/MS method for the analysis of GMDP in human plasma. The sample was prepared by solid-phase extraction using Strata-X 33 μm polymeric reversed-phase 60 mg/3 mL cartridges Phenomenex (Torrance, CA, USA). The analytes were separated using an Acquity UPLC BEN C18 column, 1.7 μm 2.1 × 50 mm Waters (Milford, USA). GMDP and internal standard growth hormone releasing peptide-2 (pralmorelin) were ionized in positive electrospray ionization mode and detected in multiple reaction monitoring mode. The developed method was validated within a linear range of 50-3000 pg/mL for GMDP. Accuracy for all analytes, given as the deviation between the nominal and measured concentration and assay variability , ranged from 1.61 to 3.02% and from 0.89 to 1.79%, respectively, for both within- and between-run variabilities. The developed and validated HPLC-MS/MS method was successfully used to obtain the plasma pharmacokinetic profiles of GMDP distribution in human plasma.

Expression and Role of Nucleotide-Binding Oligomerization Domain 2 (NOD2) in the Ocular Surface of Murine Dry Eye

Purpose

To investigate expression and role of nucleotide-binding oligomerization domain 2 (NOD2) in the ocular surface of experimental dry eye (EDE), which is a nod-like receptor member and is involved in innate immune response.

Methods

C57/BL6 female mice were divided into the groups: untreated (UT), EDE, and NOD2 knockout (KO) mice exposed to desiccating stress for 14 days. Clinical parameters and levels of inflammatory cytokine were measured at 3,5,7, and 14 days. Immunofluorescent staining for NOD2 and Western blot for RIP2 and NF-κB were performed at 14 days. Flow cytometry, PAS staining and TUNEL staining were performed.

Results

After EDE induction, NOD2 was expressed in the corneal epithelium of the EDE group. The EDE group showed a significantly increased RIP2 expression compared to the UT and NOD2-KO groups. A significantly lower expression of NF-κB and lower levels of IL-1β, IL-6, IFN-γ, and TNF-α were noted in the NOD2-KO group than in the EDE group. The NOD2-KO group had lower CD11b+ and CD4+CCR5+ T cells, TUNEL-positive cells and corneal staining score and higher density of conjunctival goblet cell density, tear volume, and tear film break-up time than the EDE group. The UT group showed significant differences in inflammatory and clinical parameters compared to the EDE and NOD2-KO groups.

Conclusions

The NOD2 receptor pathway induced inflammation and apoptosis by activation of RIP2 and NF-κB on the ocular surface of EDE, thereby reducing tear secretion. Therefore, NOD2 pathway may be involved in the pathogenesis of dry eye.

NOD1/NOD2-mediated recognition of non-typeable Haemophilus influenzae activates innate immunity during otitis media

Pathogen recognition following infection in mammals depends mainly on TLRs and NLRs. Herein, we evaluate the role of NOD1 and NOD2 signaling in the inflammatory responses of the middle ear (ME) mucosa and leukocytes recruitment to infection site during otitis media (OM). OM is a common pediatric disease with prevalent repercussions on hearing health. While many risk factors have been implicated to OM proneness, immunity and the triggering of inflammation are central to OM pathology. We observed that many genes encoding members of the NOD leucine-rich repeat and their downstream adaptor/effector molecules were strongly regulated during the course of OM. When compared to wild type C57BL/6 mice, NOD1- and NOD2-deficient mice were susceptible to prolonged OM infection by non-typeable Haemophilus influenza. NOD1-deficient mice appeared to have reduced macrophage enlistment with a delayed inflammatory response by neutrophils and prolonged mucosal hyperplasia, whereas NOD2 knockouts exhibited an overall reduction in the number of leukocytes recruited to the ME, leading to delayed bacterial clearance. Altogether, these data show that the NODs play a role in the pathogenesis and recovery of OM and reinforce the importance of innate immune signaling in the protective host response.

Peptidoglycan Muropeptides: Release, Perception, and Functions as Signaling Molecules

Peptidoglycan (PG) is an essential molecule for the survival of bacteria, and thus, its biosynthesis and remodeling have always been in the spotlight when it comes to the development of antibiotics. The peptidoglycan polymer provides a protective function in bacteria, but at the same time is continuously subjected to editing activities that in some cases lead to the release of peptidoglycan fragments (i.e., muropeptides) to the environment. Several soluble muropeptides have been reported to work as signaling molecules. In this review, we summarize the mechanisms involved in muropeptide release (PG breakdown and PG recycling) and describe the known PG-receptor proteins responsible for PG sensing. Furthermore, we overview the role of muropeptides as signaling molecules, focusing on the microbial responses and their functions in the host beyond their immunostimulatory activity.

Function, Regulation, and Pathophysiological Relevance of the POT Superfamily, Specifically PepT1 in Inflammatory Bowel Disease

Mammalian members of the proton-coupled oligopeptide transporter family are integral membrane proteins that mediate the cellular uptake of di/tripeptides and peptide-like drugs and couple substrate translocation to the movement of H⁺ , with the transmembrane electrochemical proton gradient providing the driving force. Peptide transporters are responsible for the (re)absorption of dietary and/or bacterial di- and tripeptides in the intestine and kidney and maintaining homeostasis of neuropeptides in the brain. These proteins additionally contribute to absorption of a number of pharmacologically important compounds. In this overview article, we have provided updated information on the structure, function, expression, localization, and activities of PepT1 (SLC15A1), PepT2 (SLC15A2), PhT1 (SLC15A4), and PhT2 (SLC15A3). Peptide transporters, in particular, PepT1 are discussed as drug-delivery systems in addition to their implications in health and disease. Particular emphasis has been placed on the involvement of PepT1 in the physiopathology of the gastrointestinal tract, specifically, its role in inflammatory bowel diseases. © 2018 American Physiological Society. Compr Physiol 8:731-760, 2018.

Molecular characterization, expression and functional analysis of NOD1, NOD2 and NLRC3 in Nile tilapia (Oreochromis niloticus)

The nucleotide-binding oligomerization domain proteins NOD1, NOD2 and NLRC3 are cytoplasmic pattern recognition receptors (PRRs) of the Nod-like receptor (NLR) family. In the present study, the Nile tilapia (Oreochromis niloticus) NOD1 (ntNOD1), NOD2 (ntNOD2) and NLRC3 (ntNLRC3) genes were cloned and characterized. The full-length ntNOD1, ntNOD2 and ntNLRC3 genes were 3924, 3886 and 4574 bp, encoding 941, 986 and 1130 amino acids, respectively. The three Nod-like receptors have a NACHT domain and a C-terminal leucine-rich repeat (LRR) domain. In addition, ntNOD1 and ntNOD2 have a N-terminal CARD domain (ntNOD2 has two). Phylogenetic analysis showed that the three NLRs are highly conserved. Tissue expression analysis of the three receptors revealed that the highest mRNA and protein levels of ntNOD1, ntNOD2 and ntNLRC3 were in the spleen. The expression patterns of NLRs during embryonic development showed that the expression levels of ntNOD2 and ntNLRC3 significantly increased from 2 to 8 days post-fertilization (dpf). The expression levels of ntNOD1 significantly increased from 2 to 6 dpf, decreased at 7 dpf and then increased at 8 dpf. Upon stimulation with an intraperitoneal injection of Streptococcus agalactiae, expression levels of the ntNOD1, ntNOD2 and ntNLRC3 mRNA and protein were clearly altered in the blood, spleen, kidney, intestine and gill. Furthermore, after cotransfection with an NF-κB reporter plasmid, NF-κB activation in ntNOD1-overexpressing 293T cells significantly increased compared with that in control cells, before or after i-EDPA-stimulation. By contrast, compared with control, ntNOD2 and ntNLRC3 had no effect on NF-κB activation in 293T cells, when their potential ligands were not stimulated. However, after MDP-stimulation, ntNOD2 and ntNLRC3 overexpression increased NF-κB activation in 293T cells. NOD1 and NLRC3 were uniformly distributed throughout the cytoplasm in 293T cells, whereas NOD2 was distributed throughout the cytoplasm and nucleus. Our results indicate that the three Nod-like receptors are functionally conserved and may play pivotal roles in defense against pathogens such as Streptococcus agalactiae.

Expression and function of NOD-like receptors by human term gestation-associated tissues

INTRODUCTION

Nucleotide-binding oligomerization domain (NOD)-like receptors or NOD-like receptors (NLRs) have been implicated in several disease pathologies associated with inflammation. Since local and systemic inflammation is a hallmark of both term and preterm labour, a role for NLRs at the materno-fetal interface has been postulated.

METHODS

Gene expression and immunolocalisation of NLR family members in human placenta, choriodecidua, and amnion were examined. Tissue explants were used to examine the response to activators of NOD1 (Tri-DAP), NOD2 (MDP) and NLRP3 (nigericin). Cell/tissue-free supernatants were examined for the production of interleukin (IL)-1β, IL-6, IL-8 and IL-10 using specific ELISAs.

RESULTS

Expression of transcripts for NOD1, NOD2, NLRP3, NLRC4, NLRX1, NLRP1 and NAIP and protein expression of NOD1, NOD2 and NLRP3 were a broad feature of all term gestation-associated tissues. Production of cytokines was increased significantly in response to all ligands in placenta and choriodecidua, except for MDP-induced IL-10. Similarly, there was a significant in the amnion except for MDP induced IL-1β and IL-10 response to either agonist. IL-1β production was dependent on caspase-1 regardless of agonist used or tissue examined.

DISCUSSION

Term human gestation-associated tissues express functional NLRs which likely play a role in both sterile and pathogen-driven inflammatory responses at the materno-fetal interface.

Periodontal Initial Radiological Findings of Genetically Predisposed Finnish Adolescents

INTRODUCTION

Periodontitis is a multifactorial infectious disease of the supporting tissues of teeth in which bacterial, genetic and lifestyle factors such as smoking have an important role.

AIM

The aim was to examine if Bleeding On Probing (BOP ≥ 20%) and ≥ 4 mm deep pockets correlated with any suspicion of initial radiological findings of periodontitis and bone loss. We also investigated whether any pro-inflammatory-related candidate Single Nucleotide Polymorphisms (SNPs) were associated with any suspicion of radiological findings.

MATERIALS AND METHODS

Altogether 47 generally healthy adolescent patients of one birth cohort had given their approval for their saliva samples to be used for DNA analysis. One participant was excluded after discrepant gender check. An oral radiologist analysed right and left bitewing radiographs of 47 patients. Clinical parameters such as BOP ≥ 20%, ≥ 4 mm pockets, Visible Plaque Index of all teeth (VPI%), as well as smoking habits were recorded. DNA was extracted and 71 SNPs from candidate genes for initial periodontitis were genotyped. The association between ≥ 4 mm pockets and BOP ≥ 20% with radiological findings and selected SNPs was modelled using logistic regression.

RESULTS

Variants in Toll-Like Receptors 4 (TLR4) gene (rs498670) (OR=5.8, {CI95% 1.6-20.7}, p=0.02, FDR q-value=0.13) and TNFSF11 gene (rs2277438, OR=0.3 {CI95% 0.1-0.9}, p=0.002, FDR q-value=0.56) were associated with any suspicious radiological findings; however the significance vanished after False Discovery Rate analysis (FDR). The association between BOP ≥ 20% and any radiographic signs of periodontitis was found to be statistically significant, OR=1.6, CI 95% 1.0-2.4, p=0.04.

CONCLUSION

Only TLR4 (rs498670) and TNFSF11 (rs2277438) genes were found to have a positive correlation with radiological findings suggestive of initial periodontitis after adjustment for smoking and visible plaque.

[Genetics of cryopyrin-associated periodic syndrome]

Familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS) and chronic infantile neurological, cutaneous and articular syndrome/neonatal onset multisystem inflammatory disease (CINCA/NOMID) were originally described as three distinct diseases. After the identification of their common genetic origin in 2001 and 2002, they are now perceived as a continuum of one disease entity and labelled cryopyrin-associated periodic syndromes (CAPS). Mutations in the NLRP3 gene on chromosome 1q44 can be detected in many affected patients. These lead to the synthesis of an altered gene product named cryopyrin. This is part of the NLRP3 inflammasome and causes the activation of caspase 1 and an excess production of IL-1β, which is the driving force behind the inflammatory reactions observed in CAPS patients. In symptomatic patients, confirmation of a mutation using traditional methods of genetic analysis may not always be successful (up to 40% in the case of CINCA/NOMID phenotypes); however, in many cases somatic mutations can be found using modern methods, such as next generation sequencing (NGS) technologies. In contrast, low-penetrance NLRP3 variants may also be identified in healthy family members and are present in low frequencies in the general population. Some of the mutation carriers nevertheless present with typical signs of autoinflammation; however, their phenotype is different compared to the classical CAPS presentation. These patients display unspecific systemic inflammatory signs more frequently but show an organ involvement less often. While the detection of NLRP3 gene mutations may be viewed as confirmatory, CAPS is still predominantly a clinical diagnosis; therefore, recently published diagnostic criteria do not require the demonstration of a mutation.

Crohn's disease and sarcoidosis in siblings: follow-up of a published report with a new case and brief review of the literature

Reported in 1971 were the cases of three brothers, two of whom had developed sarcoidosis and the third Crohn's disease. That now presented concerns one brother who, 50 years after the diagnosis and successful treatment of his sarcoidosis, was found incidentally, at colonoscopy performed to exclude malignancy, to have Crohn's colitis in the absence of any symptoms attributable to this. The report concludes with a brief review of the literature.

Ischemia as a factor affecting innate immune responses in kidney transplantation

PURPOSE OF REVIEW

Ischemic injury inevitably occurs during the procurement of organs for transplantation, and the injury is worsened by inflammation following reperfusion. The purpose of this review is to describe the role of the innate immune system in ischemia-induced renal injury in kidneys procured for transplantation. The key role of pattern recognition receptors in immune responses to ischemia is described. Innate immune receptors are emerging novel targets for the amelioration of ischemic injury of donor kidneys.

RECENT FINDINGS

Several families of pattern recognition receptors are direct mediators of early injurious events during kidney procurement, and also innate and adaptive immune responses after transplantation. The deleterious events associated with the activation of the innate immune system in donor kidneys significantly contribute to short and long-term allograft outcomes.

SUMMARY

Although a number of therapies have been proposed to decrease ischemic donor kidney injury, targeting the innate immune system is an exciting new area that is gaining significant interest in transplantation. As we learn more about how these important receptors are regulated by ischemia, strategies will likely evolve to allow their modulation in ischemic renal injury.

On the translocation of bacteria and their lipopolysaccharides between blood and peripheral locations in chronic, inflammatory diseases: the central roles of LPS and LPS-induced cell death

We have recently highlighted (and added to) the considerable evidence that blood can contain dormant bacteria. By definition, such bacteria may be resuscitated (and thus proliferate). This may occur under conditions that lead to or exacerbate chronic, inflammatory diseases that are normally considered to lack a microbial component. Bacterial cell wall components, such as the endotoxin lipopolysaccharide (LPS) of Gram-negative strains, are well known as potent inflammatory agents, but should normally be cleared. Thus, their continuing production and replenishment from dormant bacterial reservoirs provides an easy explanation for the continuing, low-grade inflammation (and inflammatory cytokine production) that is characteristic of many such diseases. Although experimental conditions and determinants have varied considerably between investigators, we summarise the evidence that in a great many circumstances LPS can play a central role in all of these processes, including in particular cell death processes that permit translocation between the gut, blood and other tissues. Such localised cell death processes might also contribute strongly to the specific diseases of interest. The bacterial requirement for free iron explains the strong co-existence in these diseases of iron dysregulation, LPS production, and inflammation. Overall this analysis provides an integrative picture, with significant predictive power, that is able to link these processes via the centrality of a dormant blood microbiome that can resuscitate and shed cell wall components.

Intestinal barrier dysfunction: implications for chronic inflammatory conditions of the bowel

The intestinal epithelium of adult humans acts as a differentially permeable barrier that separates the potentially harmful contents of the lumen from the underlying tissues. Any dysfunction of this boundary layer that disturbs the homeostatic equilibrium between the internal and external environments may initiate and sustain a biochemical cascade that results in inflammation of the intestine. Key to such dysfunction are genetic, microbial and other environmental factors that, singularly or in combination, result in chronic inflammation that is symptomatic of inflammatory bowel disease (IBD). The aim of the present review is to assess the scientific evidence to support the hypothesis that defective transepithelial transport mechanisms and the heightened absorption of intact antigenic proinflammatory oligopeptides are important contributing factors in the pathogenesis of IBD.

Structural models of zebrafish (Danio rerio) NOD1 and NOD2 NACHT domains suggest differential ATP binding orientations: insights from computational modeling, docking and molecular dynamics simulations

Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) and NOD2 are cytosolic pattern recognition receptors playing pivotal roles in innate immune signaling. NOD1 and NOD2 recognize bacterial peptidoglycan derivatives iE-DAP and MDP, respectively and undergoes conformational alternation and ATP-dependent self-oligomerization of NACHT domain followed by downstream signaling. Lack of structural adequacy of NACHT domain confines our understanding about the NOD-mediated signaling mechanism. Here, we predicted the structure of NACHT domain of both NOD1 and NOD2 from model organism zebrafish (Danio rerio) using computational methods. Our study highlighted the differential ATP binding modes in NOD1 and NOD2. In NOD1, γ-phosphate of ATP faced toward the central nucleotide binding cavity like NLRC4, whereas in NOD2 the cavity was occupied by adenine moiety. The conserved ‘Lysine’ at Walker A formed hydrogen bonds (H-bonds) and Aspartic acid (Walker B) formed electrostatic interaction with ATP. At Sensor 1, Arg328 of NOD1 exhibited an H-bond with ATP, whereas corresponding Arg404 of NOD2 did not. ‘Proline’ of GxP motif (Pro386 of NOD1 and Pro464 of NOD2) interacted with adenine moiety and His511 at Sensor 2 of NOD1 interacted with γ-phosphate group of ATP. In contrast, His579 of NOD2 interacted with the adenine moiety having a relatively inverted orientation. Our findings are well supplemented with the molecular interaction of ATP with NLRC4, and consistent with mutagenesis data reported for human, which indicates evolutionary shared NOD signaling mechanism. Together, this study provides novel insights into ATP binding mechanism, and highlights the differential ATP binding modes in zebrafish NOD1 and NOD2.

Collaborative action of Toll-like and NOD-like receptors as modulators of the inflammatory response to pathogenic bacteria

Early sensing of pathogenic bacteria by the host immune system is important to develop effective mechanisms to kill the invader. Microbial recognition, activation of signaling pathways, and effector mechanisms are sequential events that must be highly controlled to successfully eliminate the pathogen. Host recognizes pathogens through pattern-recognition receptors (PRRs) that sense pathogen-associated molecular patterns (PAMPs). Some of these PRRs include Toll-like receptors (TLRs), nucleotide-binding oligomerization domain-like receptors (NLRs), retinoic acid-inducible gene-I- (RIG-I-) like receptors (RLRs), and C-type lectin receptors (CLRs). TLRs and NLRs are PRRs that play a key role in recognition of extracellular and intracellular bacteria and control the inflammatory response. The activation of TLRs and NLRs by their respective ligands activates downstream signaling pathways that converge on activation of transcription factors, such as nuclear factor-kappaB (NF-κB), activator protein-1 (AP-1) or interferon regulatory factors (IRFs), leading to expression of inflammatory cytokines and antimicrobial molecules. The goal of this review is to discuss how the TLRs and NRLs signaling pathways collaborate in a cooperative or synergistic manner to counteract the infectious agents. A deep knowledge of the biochemical events initiated by each of these receptors will undoubtedly have a high impact in the design of more effective strategies to control inflammation.

NOD1 expression elicited by iE-DAP in first trimester human trophoblast cells and its potential role in infection-associated inflammation

OBJECTIVES

The underlying mechanisms of protective immunity of placental trophoblast cells against bacterial infection remain largely unknown. NOD1 are intracellular pattern recognition receptors that are activated by bacterial peptides and mediate innate immunity. This study aimed to investigate the expression and function of NOD1 in first trimester trophoblast cells, and evaluate the potential role of trophoblast cells in infection-associated inflammation.

STUDY DESIGN

Human extravillous trophoblast cell line HTR8 cells were stimulated with various concentrations of iE-DAP for various periods of time. NOD1 expression was detected by immunofluorescence, and the changes in NOD1 and RICK mRNA and protein in H8 cells were determined by real-time polymerase chain reaction and Western blot analysis. The concentrations of interleukin (IL)-8 and IL-6 secreted by H8 cells were examined by enzyme-linked immunosorbent assay. NF-κB transcription activity and P65 expression were detected by electrophoretic mobility shift assay and Western blot analysis.

RESULTS

H8 cells expressed NOD1, and the effects of iE-DAP on NOD1 were dose- and time-dependent. The concentration of IL-8 increased gradually with increasing concentration of iE-DAP, and the levels of IL-8 and IL-6 were associated with the duration of exposure to iE-DAP. The dose of iE-DAP was significantly associated with expression of RICK and P65, and stimulation of H8 cells by iE-DAP altered NF-κB transcription activity.

CONCLUSIONS

NOD1 may have a role in mediating infection-associated inflammation. Once iE-DAP is recognized by NOD1, the inflammatory response may be induced via NOD1-RICK-NF-κB-mediated pathways.

Identification of MDP (muramyl dipeptide)-binding key domains in NOD2 (nucleotide-binding and oligomerization domain-2) receptor of Labeo rohita

In lower eukaryotes-like fish, innate immunity contributed by various pattern recognition receptor (PRR) plays an essential role in protection against diseases. Nucleotide-binding and oligomerization domain (NOD)-2 is a cytoplasmic PRR that recognizes MDP (muramyl dipeptide) of the Gram positive and Gram negative bacteria as ligand and activates signalling to induce innate immunity. Hypothesizing a similar NOD2 signalling pathway of higher eukaryotes, the peripheral blood leucocytes (PBLs) of rohu (Labeo rohita) was stimulated with MDP. The data of quantitative real-time PCR (qRT-PCR) revealed MDP-mediated inductive expression of NOD2 and its down-stream molecule RICK/RIP2 (receptor-interacting serine-threonine protein kinase-2). This observation suggested the existence of MDP-binding sites in rohu NOD2 (rNOD2). To investigate it, 3D model of ligand-binding leucine-rich repeat (LRR) region of rNOD2 (rNOD2-LRR) was constructed following ab initio and threading approaches in I-TASSER web server. Structural refinement of the model was performed by energy minimization, and MD (molecular dynamics) simulation was performed in GROMACS (Groningen Machine for Chemical Simulations). The refined model of rNOD2-LRR was validated through SAVES, ProSA, ProQ, WHAT IF and MolProbity servers, and molecular docking with MDP was carried out in GOLD 4.1. The result of docking identified LRR3-7 comprising Lys820, Phe821, Asn822, Arg847, Gly849, Trp877, Trp901 and Trp931 as MDP-binding critical amino acids in rNOD2. This is the first study in fish to provide an insight into the 3D structure of NOD2-LRR region and its important motifs that are expected to be engaged in MDP binding and innate immunity.

Innate immunity in donor procurement

PURPOSE OF REVIEW

Ischaemic kidney injury occurs during organ procurement and can lead to delayed graft function or nonviable grafts. The innate immune system is a key trigger of inflammation in renal ischaemia. This review discusses the components of innate immunity known to be involved in renal ischaemic reperfusion injury (IRI). Understanding how inflammatory damage is initiated in renal IRI is important for the development of targeted therapies aimed at preserving the donor organ.

RECENT FINDINGS

Much remains to be determined about the role of innate immune signalling in renal ischaemia/reperfusion injury. Recently, discoveries about complement receptors, Toll-like receptors (TLRs), NOD-like receptors (NLRs) and inflammasomes have opened new avenues of exploration. We are also now learning that macrophages, complement and TLR activation may have additional roles in renal repair following IRI.

SUMMARY

A greater understanding of the mechanisms that contribute to innate immune-mediated renal ischaemic damage will allow for the development of therapeutics targeted to the donor organ. New data suggest that treatment limited to specific receptors on specific cells, or localized to specific regions within the kidney, may provide novel approaches to maximize our use of donor organs, particularly those that may have been discarded due to prolonged preimplantation ischaemia.

Innate immunity and the regulation and mobilization of keratinocyte stem cells: are the old players playing a new game?

The skin provides an anatomical barrier to physical, chemical and biological agents. Hence, it is not surprising that it has well-developed innate immunity. What we find surprising is that the CD49f(+) /CD34(+) hair follicle stem cells should have an enriched expression profile of so many genes involved in innate immunity. Do these stem cells require extra protection from environmental insults? Or, could there be a new role for these genes? To probe these questions, we first summarize the roles of some key players in epidermal innate immunity. We next focus on their expression in CD49f(+) /CD34(+) hair follicle stem cells. Then, we consider recent data suggesting a new role for these 'old players' in the regulation and mobilization of haematopoietic and mesenchymal stem cells. Finally, we hypothesize that the 'old players' in these hair follicle stem cells may be playing a 'new game'.

Nod-like receptors in intestinal host defense: controlling pathogens, the microbiota, or both?

PURPOSE OF REVIEW

Nod-like receptors (NLRs) are intracellular innate immune sensors of microbes and danger signals that control multiple aspects of inflammatory responses. We review the evidence that highlights the critical importance of NLRs in the host response to intestinal pathogens. Moreover, we discuss the potential roles played by NLRs in the dynamic control of the intestinal microbiota and how commensal microorganisms may affect host susceptibility to enteric bacterial pathogens through interactions with NLRs as well as with invading pathogens.

RECENT FINDINGS

Recent studies targeting the intestinal microbiota in the context of NLR deficiencies suggest inherent alterations in bacterial density or abundance may underlie the development of inflammatory diseases. As commensal microorganisms may also affect host susceptibility to enteric bacterial pathogens, NLRs might promote intestinal innate immune defense through mechanisms more complex than previously anticipated.

SUMMARY

The inclusion of the intestinal microbiota as a critical parameter in innate immunity represents an exciting new dimension for understanding NLR functioning and the clinical implications for human health.

Modeling Susceptibility to Periodontitis

Chronic inflammatory diseases like periodontitis have a complex pathogenesis and a multifactorial etiology, involving complex interactions between multiple genetic loci and infectious agents. We aimed to investigate the influence of genetic polymorphisms and bacteria on chronic periodontitis risk. We determined the prevalence of 12 single-nucleotide polymorphisms (SNPs) in immune response candidate genes and 7 bacterial species of potential relevance to periodontitis etiology, in chronic periodontitis patients and non-periodontitis control individuals (N = 385). Using decision tree analysis, we identified the presence of bacterial species Tannerella forsythia, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and SNPs TNF -857 and IL-1A -889 as discriminators between periodontitis and non-periodontitis. The model reached an accuracy of 80%, sensitivity of 85%, specificity of 73%, and AUC of 73%. This pilot study shows that, on the basis of 3 periodontal pathogens and SNPs, patterns may be recognized to identify patients at risk for periodontitis. Modern bioinformatics tools are valuable in modeling the multifactorial and complex nature of periodontitis.

Phenotyping of Nod1/2 double deficient mice and characterization of Nod1/2 in systemic inflammation and associated renal disease

It is indispensable to thoroughly characterize each animal model in order to distinguish between primary and secondary effects of genetic changes. The present study analyzed Nod1 and Nod2 double deficient (Nod1/2 DKO) mice under physiological and inflammatory conditions. Nod1 and Nod2 are members of the Nucleotide-binding domain and Leucine-rich repeat containing Receptor (NLR) family. Several inflammatory disorders, such as Crohn's disease and asthma, are linked to genetic changes in either Nod1 or Nod2. These associations suggest that Nod1 and Nod2 play important roles in regulating the immune system.

Three-month-old wildtype (Wt) and Nod1/2 DKO mice were sacrificed, body and organ weight were determined, and blood was drawn. Except for lower liver weight in Nod1/2 DKO mice, no differences were found in body/organ weight between both strains. Leukocyte count and composition was comparable. No significant changes in analyzed plasma biochemical markers were found. Additionally, intestinal and vascular permeability was determined. Nod1/2 DKO mice show increased susceptibility for intestinal permeability while vascular permeability was not affected. Next we induced septic shock and organ damage by administering LPS+PGN intraperitoneally to Wt and Nod1/2 DKO mice and sacrificed animals after 2 and 24 hours. The systemic inflammatory and metabolic response was comparable between both strains. However, renal response was different as indicated by partly preserved kidney function and tubular epithelial cell damage in Nod1/2 DKO at 24 hours. Remarkably, renal inflammatory mediators Tnfα, KC and Il-10 were significantly increased in Nod1/2 DKO compared with Wt mice at 2 hours.

Systematic analysis of Nod1/2 DKO mice revealed a possible role of Nod1/2 in the development of renal disease during systemic inflammation.

Expression profiles of NODs in channel catfish (Ictalurus punctatus) after infection with Edwardsiella tarda, Aeromonas hydrophila, Streptococcus iniae and channel catfish hemorrhage reovirus

NLRs are a large family of intracellular pathogen recognition receptors (PRRs) that recognize pathogen associated molecular patterns (PAMPs). In the previous study, the identification of NLRs subfamily A (NODs) and gene expression was carried out in channel catfish (Ictalurus punctatus). However, the gene expression profiles of channel catfish NODs (NOD1, NOD2, NLRC3, NLRC5 and NLRX1) after infection with various bacteria and virus are still unclear. In this study, expression of five NODs genes was analyzed by quantitative real-time PCR method. In healthy catfish tissues, all tested NODs genes were found to be ubiquitously expressed. After infection with Edwardsiella tarda, Aeromonas hydrophila, Streptococcus iniae, or channel catfish hemorrhage reovirus (CCRV), expression of NOD1, NOD2, NLRC3, NLRC5 showed a significant up-regulation in the intestine, liver and head kidney, whereas down-regulation was observed in the spleen after infection with A. hydrophila and CCRV. Expression of NLRX1 gene was up-regulated in the intestine, liver and head kidney, while obviously decreased in the spleen after infection with four pathogens. Among four different pathogens, S. iniae largely up-regulated NODs mRNAs, while CCRV only slightly enhanced NODs gene expression. Among four immune-related tissues, the order for NODs up-regulation was liver, head kidney, intestine, and spleen after infection with various pathogens. All data suggest NODs are involved in the immune responses of channel catfish against the intracellular bacterial and virus pathogens in tissue-specific and pathogen-specific manners, and provide the evidence for exploring the precise immune-related molecular mechanism of NODs in channel catfish.

Down-regulation of NOD1 in neutrophils of periparturient dairy cows

Increased susceptibility of periparturient dairy cows to infectious diseases has been linked to neutrophil dysfunction. Cytoplasmic nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) mediate numerous aspects of innate immunity in humans and experimental animals. The authors hypothesized that neutrophils in periparturient cows have reduced NLR expression, resulting in declined immune responses to NLR activation. In this study, blood neutrophils from periparturient and mid-lactating cows were isolated and assessed for mRNA and protein expression of NOD1 and NOD2. Neutrophil phagocytosis and oxidative burst activity following NLR agonist-induced activation were also investigated. Periparturient cows demonstrated weak-to-absent NOD1 mRNA expression along with a significant reduction in NOD1 protein in their neutrophils. However, no difference in NOD2 protein expression was observed between groups although NOD2 mRNA abundance in periparturient cows was significantly reduced. Phagocytosis and oxidative burst activity measured by production of reactive oxygen species (ROS) were diminished in periparturient cows. NOD1 activation enhanced phagocytosis and ROS production in both isolated cell populations, regardless of the lactation stage. Nevertheless, NOD1-activated neutrophils showed reduced phagocytosis and ROS generation in periparturient cows with respect to mid-lactating subjects. Collectively, our findings suggest that NOD1 down-regulation in neutrophils may be a mechanism involved in periparturient neutrophil dysregulation.

TLR9-dependent and independent pathways drive activation of the immune system by Propionibacterium acnes

Propionibacterium acnes is usually a relatively harmless commensal. However, under certain, poorly understood conditions it is implicated in the etiology of specific inflammatory diseases. In mice, P. acnes exhibits strong immunomodulatory activity leading to splenomegaly, intrahepatic granuloma formation, hypersensitivity to TLR ligands and endogenous cytokines, and enhanced resistance to infection. All these activities reach a maximum one week after P. acnes priming and require IFN-γ and TLR9. We report here the existence of a markedly delayed (1-2 weeks), but phenotypically similar TLR9-independent immunomodulatory response to P. acnes. This alternative immunomodulation is also IFN-γ dependent and requires functional MyD88. From our experiments, a role for MyD88 in the IFN-γ-mediated P. acnes effects seems unlikely and the participation of the known MyD88-dependent receptors, including TLR5, Unc93B-dependent TLRs, IL-1R and IL-18R in the development of the alternative response has been excluded. However, the crucial role of MyD88 can partly be attributed to TLR2 and TLR4 involvement. Either of these two TLRs, activated by bacteria and/or endogenously generated ligands, can fulfill the required function. Our findings hint at an innate immune sensitizing mechanism, which is potentially operative in both infectious and sterile inflammatory disorders.

Molecular cloning and characterization of nucleotide binding and oligomerization domain-1 (NOD1) receptor in the Indian Major Carp, rohu (Labeo rohita), and analysis of its inductive expression and down-stream signalling molecules following ligands exposure and Gram-negative bacterial infections

Nucleotide binding and oligomerization domain-1 (NOD1) is a cytoplasmic pattern recognition receptor (PRR), and is a member of the NOD-like receptor (NLR) family. It senses a wide range of bacteria and viruses or their products, and plays a key role in inducing innate immunity. In this report, NOD1 gene was cloned and characterized in rohu (Labeo rohita), a fish species of highest commercial importance in the Indian subcontinent. The full-length rohu NOD1 (rNOD1) cDNA comprised of 3168 bp with a single open reading frame (ORF) of 2814 bp, encoding a polypeptide of 937 amino acids (aa) with an estimated molecular mass of 106.13 kDa. Structurally, it comprised of one caspase recruitment domain (CARD) at N-terminal, seven leucine rich repeat (LRR) regions at C-terminal and one NACHT domain in between N and C-terminals. Phylogenetically, rNOD1 was closely related to grass carp NOD1 (gcNOD1), and exhibited significant similarity (95.8%) and identity (91.0%) in their amino acids. Ontogenic expression analysis of rNOD1 and its associated down-stream signaling molecule RICK (receptor interacting serine–threonine kinase) by quantitative real-time PCR (qRT-PCR) revealed their constitutive expression in all embryonic developmental stages. Basal expression analysis of rNOD1 showed its wide range of expression in all examined tissues, highest was in spleen and the lowest was in blood. Inductive expression of rNOD1 was observed following LPS and poly I:C exposure, and Aeromonas hydrophila, Edwardsiella tarda and Shigella flexneri infections. Expression of RICK in various organs was significantly enhanced by ligands exposure and bacterial infections, and was correlated with the inductive expression of rNOD1. Together, these findings highlighted the important role of NOD1 in fish in response to pathogenic invasion.

Genetic and immunological evidence implicates interleukin 6 as a susceptibility gene for leprosy type 2 reaction

In leprosy, type 1 reaction (T1R) and type 2 reaction (T2R) are major causes of nerve injury and permanent disabilities. A previous study on plasma levels of 27 cytokines in patients with T1R or T2R and controls with nonreactional leprosy identified the gene for interleukin 6 (IL-6) as a candidate for genetic analysis. Two nested case-control studies were built from a cohort of 409 patients with leprosy from central Brazil, monitored for T1R and T2R. There was evidence for association between T2R and IL-6 tag single-nucleotide polymorphisms rs2069832 (P = .002), rs2069840 (P = .03), and rs2069845 (P = .04), with information on the entire IL-6 locus, as well as functional IL-6 variant rs1800795 (P = .005). Moreover, IL-6 plasma levels in patients with T2R correlated with IL-6 genotypes (P = .04). No association was found between IL-6 variants and T1R. Identifying genetic predictive factors for leprosy reactions may have a major impact on preventive strategies.

Genome-wide association study of skin complex diseases

Complex diseases are caused by both genetic and environmental factors. Over decades, scientists endeavored to uncover the genetic myth of complex diseases by linkage and association studies. Since 2005, the genome-wide association study (GWAS) has been proved to be the most powerful and efficient study design thus far in identifying genetic variants that are associated with complex diseases. More than 230 complex diseases and traits have been investigated by this approach. In dermatology, 10 skin complex diseases have been investigated, a wealth of common susceptibility variants conferring risk for skin complex diseases have been discovered. These findings point to genes and/or loci involved in biological systems worth further investigating by using other methodologies. Certainly, as our understanding of the genetic etiology of skin complex diseases continues to mature, important opportunities will emerge for developing more effective diagnostic and clinical management tools for these diseases.

Molecular characterization of nucleotide binding and oligomerization domain (NOD)-2, analysis of its inductive expression and down-stream signaling following ligands exposure and bacterial infection in rohu (Labeo rohita)

Nucleotide-binding and oligomerization domain (NOD)-2 is a cytoplasmic pattern recognition receptor (PRR) and is a member of NOD like receptor (NLR) family. It senses a wide range of bacteria and viruses or their products and is involved in innate immune responses. In this report, NOD-2 gene was cloned and characterized from rohu (Labeo rohita) which is highly commercially important fish species in the Indian subcontinent. The full length rohu NOD-2 (rNOD-2) cDNA comprised of 3176 bp with a single open reading frame (ORF) of 2949 bp encoding a polypeptide of 982 amino acids (aa) with an estimated molecular mass of 109.65 kDa. The rNOD-2 comprised two N-terminal CARD domains (at 4-91 aa and 111-200 aa), one NACHT domain (at 271-441 aa) and seven C-terminal leucine rich repeat (LRR) regions. Phylogenetically, rNOD-2 was closely related to grass carp NOD-2 (gcNOD2) and exhibited significant similarity (94.2%) and identity (88.6%) in their amino acids. Ontogeny analysis of rNOD-2 showed its constitutive expression across the developmental stages, and highlighted the embryonic innate defense system in fish. Tissue specific analysis of rNOD-2 by quantitative real-time PCR (qRT-PCR) revealed its wide distribution; highest expression was in liver followed by blood. In response to PGN and LTA stimulation, Aeromonas hydrophila and Edwardsiella tarda infection, and poly I:C treatment, expression of rNOD-2 and its associated downstream molecules RICK and IFN-γ were significantly enhanced in the treated fish compared to control. These findings suggested the key role of NOD-2 in augmenting innate immunity in fish in response to bacterial and viral infection. This study may be helpful for the development of preventive measures against infectious diseases in fish.

Detection of single-nucleotide polymorphisms in the intron 9 region of the nucleotide oligomerization domain-1 gene in ulcerative colitis patients of North India

BACKGROUND AND AIM

The nucleotide-binding oligomerization domain-1 (NOD1) gene encodes a pattern recognition receptor that senses pathogens. NOD1/caspase recruitment domain (CARD4) signaling leads to the activation of nuclear factor-kB, and plays an important role in innate immunity. Certain polymorphisms and mutations in NOD1/CARD4 might result in a dysfunctional innate immune response during bacterial recognition, which might have direct implications in inflammatory bowel disease (IBD) pathogenesis.

METHODS

We carried out a systemic analysis for the presence of polymorphic variants in the intron 9 region of the leucine-rich repeat (LRR) domain encompassing the exon-intron boundaries of the NOD1 gene. To detect unknown single-nucleotide polymorphisms, we used the denaturing high-performance liquid chromatography (DHPLC) screening technique and validated our data by restriction fragment length polymorphism and direct sequencing.

RESULT

Genotype and allele frequencies showed significant differences in their distribution. The mutations discriminating alleles in the intron 9 region of the LRR domain of the NOD1 gene were correctly predicted by DHPLC technique and statistically verified in IBD and non-IBD individuals. Of the seven mutations detected, only four showed a significant association with disease activity. Mutations detected earlier in the exon 6 region of NOD1 were also used for the haplotype analysis. The GTTG haplotype was found to be significantly overrepresented in ulcerative colitis (UC) patients, as compared to the controls (P = 3.3726E(-6) ).

CONCLUSION

Our study has revealed a polymorphism association in the LRR domain of the NOD1 gene with the severity of UC disease. This might be due to disruption of the LRR region critical for NOD1-mediated bacterial sensing. A gene-wide, haplotype-based approach shows that GTTG haplotype carriers are overrepresented in UC patients, and that could increase the risk of the disease.

Interaction of Staphylococcus aureus with osteoblasts (Review)

Orthopedic infection is refractory to cure. Staphylococcus aureus (S. aureus) is the main causative pathogen responsible for orthopedic infection. S. aureus is capable of not only colonizing bone matrix, but also invading osteoblasts, which may play a significant role in the persistence and recurrence of osteomyelitis. Internalization requires the involvement of cytoskeletal elements, including actin microfilaments, microtubules and clathrin-coated pits. Microfilaments are most significant in the invasion process. S. aureus is capable of remaining alive in osteoblasts for a long period of time. Decreased sensitivity to antibiotics capable of penetrating host cells increases the difficulties of eradicating S. aureus. Osteoblasts, invaded by S. aureus, play a significant role in the initiation and maintenance of inflammatory immune responses. These osteoblasts recruit leukocytes and phagocytes to the site of inflammation via the expression of cytokines. Apoptosis is observed in osteoblasts invaded by S. aureus. Recruitment of osteoclasts and other immunocytes plays a crucial role in the resorption and destruction of bone.

Interactions between microbes and the gut epithelium

Gut microbes interact with the epithelium through cell surface components, fermentation products, and extracellular secreted proteins. Host-microbial interactions primarily involve TLRs (toll-like receptors) and NLR (nucleotide-binding oligomerization domain and leucine-rich repeat containing proteins). In a strain and dose-dependent manner, several probiotic strains directly alter tight junction protein expression and/or localization in gut epithelial cells through the release of secreted compounds. Interactions between gut microbes and intestinal epithelial and immune cells are necessary for the development and maintenance of intestinal homeostasis.

NOD-like receptors and RIG-I-like receptors in human eosinophils: activation by NOD1 and NOD2 agonists

NOD-like receptors (NLRs) and RIG-I-like receptors (RLRs) are newly discovered pattern-recognition receptors. They detect substructures of bacterial peptidoglycan and viral RNA, respectively, thereby initiating an immune response. However, their role in eosinophil activation remains to be explored. The aim of this study was to characterize the expression of a range of NLRs and RLRs in purified human eosinophils and assess their functional importance. Expression of NOD1, NOD2, NLRP3, RIG-I and MDA-5 was investigated using real-time reverse transcription PCR, flow cytometry and immunohistochemistry. The effects of the corresponding agonists iE-DAP (NOD1), MDP (NOD2), alum (NLRP3) and poly(I:C)/LyoVec (RIG-I/MDA-5) were studied in terms of cytokine secretion, degranulation, survival, expression of adhesion molecules and activation markers, and chemotactic migration. Eosinophils expressed NOD1 and NOD2 mRNA and protein. Low levels of RIG-I and MDA-5 were found, whereas expression of NLRP3 was completely absent. In accordance, stimulation with iE-DAP and MDP was found to induce secretion of interleukin-8, up-regulate expression of CD11b, conversely down-regulate CD62 ligand, increase expression of CD69 and induce migration. The MDP also promoted release of eosinophil-derived neurotoxin, whereas iE-DAP failed to do so. No effects were seen upon stimulation with alum or poly(I:C)/LyoVec. Moreover, the NOD1-induced and NOD2-induced activation was mediated via the nuclear factor-κB signalling pathway and augmented by interleukin-5 and granulocyte-macrophage colony-stimulating factor, but not interferon-γ. Taken together, the NLR system represents a novel pathway for eosinophil activation. The responses are enhanced in the presence of cytokines that regulate T helper type 2 immunity, suggesting that the NLRs constitute a link between respiratory infections and exacerbations of allergic disease.

The PepT1-NOD2 signaling pathway aggravates induced colitis in mice

BACKGROUND & AIMS

The human di/tripeptide transporter human intestinal H-coupled oligonucleotide transporter (hPepT1) is abnormally expressed in colons of patients with inflammatory bowel disease, although its exact role in pathogenesis is unclear. We investigated the contribution of PepT1 to intestinal inflammation in mouse models of colitis and the involvement of the nucleotide-binding oligomerization domain 2 (NOD2) signaling pathway in the pathogenic activity of colonic epithelial hPepT1.

METHODS

Transgenic mice were generated in which hPepT1 expression was regulated by the β-actin or villin promoters; colitis was induced using 2,4,6-trinitrobenzene sulfonic acid (TNBS) or dextran sodium sulfate (DSS) and the inflammatory responses were assessed. The effects of NOD2 deletion in the hPepT1 transgenic mice also was studied to determine the involvement of the PepT1-NOD2 signaling pathway.

RESULTS

TNBS and DSS induced more severe levels of inflammation in β-actin-hPepT1 transgenic mice than wild-type littermates. Intestinal epithelial cell-specific hPepT1 overexpression in villin-hPepT1 transgenic mice increased the severity of inflammation induced by DSS, but not TNBS. Bone marrow transplantation studies showed that hPepT1 expression in intestinal epithelial cells and immune cells has an important role in the proinflammatory response. Antibiotics abolished the effect of hPepT1 overexpression on the inflammatory response in DSS-induced colitis in β-actin-hPepT1 and villin-hPepT1 transgenic mice, indicating that commensal bacteria are required to aggravate intestinal inflammation. Nod2-/-, β-actin-hPepT1 transgenic/Nod2-/-, and villin-hPepT1 transgenic/Nod2-/- littermates had similar levels of susceptibility to DSS-induced colitis, indicating that hPepT1 overexpression increased intestinal inflammation in a NOD2-dependent manner.

CONCLUSIONS

The PepT1-NOD2 signaling pathway is involved in aggravation of DSS-induced colitis in mice.

Leprosy susceptibility: genetic variations regulate innate and adaptive immunity, and disease outcome

The past few years have been very productive concerning the identification of genes associated with leprosy. Candidate gene strategies using both case-control and family-based designs, as well as large-scale approaches such as linkage and gene-expression genomic scans and, more recently, genome-wide association studies, have refined and enriched the list of genes highlighting the most important innate and adaptive immune pathways associated with leprosy susceptibility or resistance. During the early events of host-pathogen interaction identified genes are involved in pattern recognition receptors, and mycobacterial uptake (TLRs, NOD2 and MRC1), which modulate autophagy. Another gene, LTA4H, which regulates the levels of lipoxin A4 and possibly interacts with lipid droplet-related events, also plays a role in the early immune responses to Mycobacterium leprae. Together, the activation of these pathways regulates cellular metabolism upon infection, activating cytokine production through NF-κB and vitamin D-vitamin D receptor pathways, while PARK2 and LRRK2 participate in the regulation of host-cell apoptosis. Concomitantly, genes triggered to form and maintain granulomas (TNF, LTA and IFNG) and genes involved in activating and differentiating T-helper cells (HLA, IL10, as well as the TNF/LTA axis and the IFNG/IL12 axis) bridge immunological regulation towards adaptive immunity. Subtle variations in these genes, mostly single nucleotide polymorphisms, alter the risk of developing the disease or the severity of leprosy. Knowing these genes and their role will ultimately lead to better strategies for leprosy prevention, treatment and early diagnosis. Finally, the same genes associated with leprosy were also associated with autoimmune (Crohn's disease, rheumathoid arthritis, psoriasis) or neurodegenerative diseases (Parkinson's and Alzheimer's). Thus, information retrieved using leprosy as a model could be valuable to understanding the pathogenesis of other complex diseases.