Infection of human fallopian tube epithelial cells with Neisseria gonorrhoeae protects cells from tumor necrosis factor alpha-induced apoptosis

IL-17C is a driver of damaging inflammation during Neisseria gonorrhoeae infection of human Fallopian tube

The human pathogen Neisseria gonorrhoeae ascends into the upper female reproductive tract to cause damaging inflammation within the Fallopian tubes and pelvic inflammatory disease (PID), increasing the risk of infertility and ectopic pregnancy. The loss of ciliated cells from the epithelium is thought to be both a consequence of inflammation and a cause of adverse sequelae. However, the links between infection, inflammation, and ciliated cell extrusion remain unresolved. With the use of ex vivo cultures of human Fallopian tube paired with RNA sequencing we defined the tissue response to gonococcal challenge, identifying cytokine, chemokine, cell adhesion, and apoptosis related transcripts not previously recognized as potentiators of gonococcal PID. Unexpectedly, IL-17C was one of the most highly induced genes. Yet, this cytokine has no previous association with gonococcal infection nor pelvic inflammatory disease and thus it was selected for further characterization. We show that human Fallopian tubes express the IL-17C receptor on the epithelial surface and that treatment with purified IL-17C induces pro-inflammatory cytokine secretion in addition to sloughing of the epithelium and generalized tissue damage. These results demonstrate a previously unrecognized but critical role of IL-17C in the damaging inflammation induced by gonococci in a human explant model of PID.

Mechanisms of host manipulation by Neisseria gonorrhoeae

Neisseria gonorrhoeae (also known as gonococcus) has been causing gonorrhoea in humans since ancient Egyptian times. Today, global gonorrhoea infections are rising at an alarming rate, in concert with an increasing number of antimicrobial-resistant strains. The gonococcus has concurrently evolved several intricate mechanisms that promote pathogenesis by evading both host immunity and defeating common therapeutic interventions. Central to these adaptations is the ability of the gonococcus to manipulate various host microenvironments upon infection. For example, the gonococcus can survive within neutrophils through direct regulation of both the oxidative burst response and maturation of the phagosome; a concerning trait given the important role neutrophils have in defending against invading pathogens. Hence, a detailed understanding of how N. gonorrhoeae exploits the human host to establish and maintain infection is crucial for combating this pathogen. This review summarizes the mechanisms behind host manipulation, with a central focus on the exploitation of host epithelial cell signaling to promote colonization and invasion of the epithelial lining, the modulation of the host immune response to evade both innate and adaptive defenses, and the manipulation of host cell death pathways to both assist colonization and combat antimicrobial activities of innate immune cells. Collectively, these pathways act in concert to enable N. gonorrhoeae to colonize and invade a wide array of host tissues, both establishing and disseminating gonococcal infection.

Application of thermosensitive-hydrogel combined with dental pulp stem cells on the injured fallopian tube mucosa in an animal model

Objectives: Fallopian tube (FT) injury is an important factor that can lead to tubal infertility. Stem-cell-based therapy shows great potential for the treatment of injured fallopian tube. However, little research has shown that mesenchymal stem cells (MSCs) can be used to treat fallopian tube damage by in situ injection. In this study, we in situ transplanted PF127 hydrogel encapsulating dental pulp stem cells (DPSCs) into the injured sites to promote the repair and regeneration of fallopian tube injury. Materials and methods: The properties of dental pulp stem cells were evaluated by flow cytometry, immunofluorescence analysis, and multi-differentiation detection. The immunomodulatory and angiogenic characteristics of dental pulp stem cells were analyzed on the basis of the detection of inflammatory factor expression and the formation of capillary-like structures, respectively. The biocompatibility of PF127 hydrogel was evaluated by using Live/Dead and CCK-8 assays. The effects of PF127 hydrogel containing dental pulp stem cells on the repair and regeneration of fallopian tube injury were evaluated by histological analysis [e.g., hematoxylin and eosin (H&E) and Masson's trichrome staining, TUNEL staining, immunofluorescence staining, and immunohistochemistry], Enzyme-linked immunosorbent assay (ELISA), and RT-PCR detections. Results: Dental pulp stem cells had MSC-like characteristics and great immunomodulatory and angiogenic properties. PF127 hydrogel had a thermosensitive feature and great cytocompatibility with dental pulp stem cells. In addition, our results indicated that PF127 hydrogel containing dental pulp stem cells could promote the repair and regeneration of fallopian tube damage by inhibiting cell apoptosis, stimulating the secretion of angiogenic factors, promoting cell proliferation, modulating the secretion of inflammatory factors, and restoring the secretion of epithelial cells. Conclusion: In this study, our results reported that in situ injection of PF127 hydrogel encapsulating dental pulp stem cells into the injured sites could provide an attractive strategy for the future treatment of fallopian tube injury in clinical settings.

Cellular heterogeneity of human fallopian tubes in normal and hydrosalpinx disease states identified using scRNA-seq

Fallopian tube (FT) homeostasis requires dynamic regulation of heterogeneous cell populations and is disrupted in infertility and ovarian cancer. Here, we applied single-cell RNA-seq to profile 59,738 FT cells from four healthy, pre-menopausal subjects. The resulting cell atlas contains 12 major cell types representing epithelial, stromal, and immune compartments. Re-clustering of epithelial cells identified four ciliated and six non-ciliated secretory epithelial subtypes, two of which represent potential progenitor pools: one leading to mature secretory cells and the other contributing to either ciliated cells or one of the stromal cell types. To understand how FT cell numbers and states change in a disease state, we analyzed 17,798 cells from two hydrosalpinx samples and observed shifts in epithelial and stromal populations and cell-type-specific changes in extracellular matrix and TGF-β signaling; this underscores fibrosis pathophysiology. This resource is expected to facilitate future studies aimed at expanding understanding of fallopian tube homeostasis in normal development and disease.

Systemic and Mucosal Concentrations of Nine Cytokines Among Individuals with Neisseria gonorrhoeae infection in Nairobi Kenya

Introduction: The human-restricted sexually transmitted Neisseria gonorrhoeae (NG) has been shown to modulate the immune response against it and consequently the cytokines produced. The levels of cytokines in NG infection in the African population have not been well described. We aimed to quantify the systemic and mucosal cytokines in NG infection. Methods: This was a comparative cross-sectional study. Levels of nine cytokines (IL-1β, IL-2, IL-4, 1L-6, 1L-10, 1L-12p70, IL-17A, TNF-α and INF-γ) were measured from plasma and genital samples (urethral swabs in men and cervicovaginal lavage in women) from 61 Neisseria gonorrhoeae infected individuals seeking treatment for sexually transmitted infections (STIs) at Casino Health Centre in Nairobi, Kenya. A comparative group of 61 NG-uninfected individuals, seeking treatment at the same facility but with laboratory-confirmed negative Neisseria gonorrhoeae, Chlamydia trachomatis (CT), Mycoplasma genitalium (MG) and Trichomonas vaginalis(TV) was also included. The Mann-Whitney U test was used to compare the cytokine levels between NG-infected and uninfected individuals. Data was analyzed using STATA ver. 15.1. Results: Overall, systemic IL-6, TNF-α and IL-10 were elevated while genital IL-10 and TNF-α were lower in NG positive participants. On subgroup analysis by sex, the levels of genital IL-1β and IL-6 and systemic IL-6 were elevated in NG-infected men. None of the genital cytokines were elevated in NG-infected women, while all systemic cytokines, except INF-γ, were elevated in NG-infected women. Conclusions: Neisseria gonorrhoeae induced the production of different cytokines in men and women, with men having a pro-inflammatory genital response. These differences should be taken into consideration during development of various interventions e.g. vaccine development.

Tissue Models for Neisseria gonorrhoeae Research—From 2D to 3D

Neisseria gonorrhoeae is a human-specific pathogen that causes gonorrhea, the second most common sexually transmitted infection worldwide. Disease progression, drug discovery, and basic host-pathogen interactions are studied using different approaches, which rely on models ranging from 2D cell culture to complex 3D tissues and animals. In this review, we discuss the models used in N. gonorrhoeae research. We address both in vivo (animal) and in vitro cell culture models, discussing the pros and cons of each and outlining the recent advancements in the field of three-dimensional tissue models. From simple 2D monoculture to complex advanced 3D tissue models, we provide an overview of the relevant methodology and its application. Finally, we discuss future directions in the exciting field of 3D tissue models and how they can be applied for studying the interaction of N. gonorrhoeae with host cells under conditions closely resembling those found at the native sites of infection.

Potential of Mesenchymal Stem Cell-Derived Exosomes as a Novel Treatment for Female Infertility Caused by Bacterial Infections

Neisseria gonorrhoeae and Chlamydia trachomatis are the most common causes of bacterial sexually transmitted diseases (STDs) with complications in women, including pelvic inflammatory disease (PID), ectopic pregnancy, and infertility. The main concern with these infections is that 70% of infected women are asymptomatic and these infections ascend to the upper female reproductive tract (FRT). Primary infection in epithelial cells creates a cascade of events that leads to secretion of pro-inflammatory cytokines that stimulate innate immunity. Production of various cytokines is damaging to mucosal barriers, and tissue destruction leads to ciliated epithelial destruction that is associated with tubal scarring and ultimately provides the conditions for infertility. Mesenchymal stem cells (MSCs) are known as tissue specific stem cells with limited self-renewal capacity and the ability to repair damaged tissues in a variety of pathological conditions due to their multipotential differentiation capacity. Moreover, MSCs secrete exosomes that contain bioactive factors such as proteins, lipids, chemokines, enzymes, cytokines, and immunomodulatory factors which have therapeutic properties to enhance recovery activity and modulate immune responses. Experimental studies have shown that local and systemic treatment of MSC-derived exosomes (MSC-Exos) suppresses the destructive immune response due to the delivery of immunomodulatory proteins. Interestingly, some recent data have indicated that MSC-Exos display strong antimicrobial effects, by the secretion of antimicrobial peptides and proteins (AMPs), and increase bacterial clearance by enhancing the phagocytic activity of host immune cells. Considering MSC-Exos can secrete different bioactive factors that can modulate the immune system and prevent infection, exosome therapy is considered as a new therapeutic method in the treatment of inflammatory and microbial diseases. Here we intend to review the possible application of MSC-Exos in female reproductive system bacterial diseases.

S100A8 expression in oviduct mucosal epithelial cells is regulated by estrogen and affects mucosal immune homeostasis

Chronic inflammation can cause oviduct mucosal damage and immune dysfunction, leading to infertility, early pregnancy loss, ectopic pregnancy, tumors, and a decrease in reproductive capacities in female animals. Estrogen can suppress immune responses in different tissues and oviducts, and regulate the oviduct immune balance; however, the underlying mechanisms remain unclear. The objective of this study was to explore the mechanism of estrogen-regulated oviduct mucosal immunity and discover new estrogen targets for regulating oviduct mucosal immune homeostasis. Sheep oviduct epithelial cells (SOECs) were treated with 17-β estradiol (E2). Transcriptome sequencing and analysis showed differentially expressed S100 calcium-binding protein A (S100A) genes that may participate in the oviduct mucosa immunoregulation of estrogen. Quantitative polymerase chain reaction and immunocytochemistry analysis showed that S100A8 expression changed dynamically in E2-treated SOECs and peaked after 7 h of treatment. Estrogen nuclear receptors and G protein-coupled membrane receptors promoted E2-dependent S100A8 upregulation. The S100A8 gene was disrupted using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 method. Levels of inflammatory factors interleukin (IL)-1β and IL-4 were significantly upregulated in S100A8-knockdown SOECs, whereas those of the anti-inflammatory factor IL-10 was downregulated. Following S100A8 knockdown in SOECs treated with E2 for 7 h, IL-10 levels increased significantly. Estrogen affected oviduct mucosa immune function and dynamically regulated S100A8 in SOECs. S100A8 knockdown caused an excessive immune response, indicating that S100A8 is beneficial for maintaining immune homeostasis in the oviduct mucosa. Moreover, estrogen can compensate for the effect of S100A8 knockdown by upregulating IL-10.

Applying a novel approach to scoping review incorporating artificial intelligence: mapping the natural history of gonorrhoea

BACKGROUND

Systematic and scoping literature searches are increasingly resource intensive. We present the results of a scoping review which combines the use of a novel artificial-intelligence-(AI)-assisted Medline search tool with two other 'traditional' literature search methods. We illustrate this novel approach with a case study to identify and map the range of conditions (clinical presentations, complications, coinfections and health problems) associated with gonorrhoea infection.

METHODS

To fully characterize the range of health outcomes associated with gonorrhoea, we combined a high yield preliminary search with a traditional systematic search, then supplemented with the output of a novel AI-assisted Medline search tool based on natural language processing methods to identify eligible literature.

RESULTS

We identified 189 health conditions associated with gonorrhoea infection of which: 53 were identified through the initial 'high yield' search; 99 through the systematic search; and 124 through the AI-assisted search. These were extracted from 107 unique references and 21 International Statistical Classification of Diseases and Related Health Problems Ninth and Tenth Revision (ICD 9/10) or Read codes. Health conditions were mapped to the urogenital tract (n = 86), anorectal tract (n = 6) oropharyngeal tract (n = 5) and the eye (n = 14); and other conditions such as systemic (n = 61) and neonatal conditions (n = 7), psychosocial associations (n = 3), and co-infections (n = 7). The 107 unique references attained a Scottish Intercollegiate Guidelines Network (SIGN) score of ≥2++ (n = 2), 2+ (14 [13%]), 2- (30 [28%]) and 3 (45 [42%]), respectively. The remaining papers (n = 16) were reviews.

CONCLUSIONS

Through AI screening of Medline, we captured - titles, abstracts, case reports and case series related to rare but serious health conditions related to gonorrhoea infection. These outcomes might otherwise have been missed during a systematic search. The AI-assisted search provided a useful addition to traditional/manual literature searches especially when rapid results are required in an exploratory setting.

Intimate Relations: Molecular and Immunologic Interactions Between Neisseria gonorrhoeae and HIV-1

While the global incidence of human immunodeficiency virus (HIV-1) remains well above UNAIDS targets, sexual transmission HIV is surprisingly inefficient. A variety of host, viral and environmental factors can either increase HIV-1 shedding in the infected partner and/or increase mucosal susceptibility of the HIV-1 uninfected partner. Clinical and epidemiological studies have clearly established that Neisseria gonorrhoeae substantially enhances HIV-1 transmission, despite it not being an ulcerative infection. This review will consider findings from molecular, immunologic and clinical studies that have focused on each of these two human-restricted pathogens, in order to develop an integrative model that describes how gonococci can both increase mucosal shedding of HIV-1 from a co-infected person and facilitate virus establishment in a susceptible host.

Pathogenesis of Neisseria gonorrhoeae and the Host Defense in Ascending Infections of Human Fallopian Tube

Neisseria gonorrhoeae is an obligate human pathogen that causes mucosal surface infections of male and female reproductive tracts, pharynx, rectum, and conjunctiva. Asymptomatic or unnoticed infections in the lower reproductive tract of women can lead to serious, long-term consequences if these infections ascend into the fallopian tube. The damage caused by gonococcal infection and the subsequent inflammatory response produce the condition known as pelvic inflammatory disease (PID). Infection can lead to tubal scarring, occlusion of the oviduct, and loss of critical ciliated cells. Consequences of the damage sustained on the fallopian tube epithelium include increased risk of ectopic pregnancy and tubal-factor infertility. Additionally, the resolution of infection can produce new adhesions between internal tissues, which can tear and reform, producing chronic pelvic pain. As a bacterium adapted to life in a human host, the gonococcus presents a challenge to the development of model systems for probing host-microbe interactions. Advances in small-animal models have yielded previously unattainable data on systemic immune responses, but the specificity of N. gonorrhoeae for many known (and unknown) host targets remains a constant hurdle. Infections of human volunteers are possible, though they present ethical and logistical challenges, and are necessarily limited to males due to the risk of severe complications in women. It is routine, however, that normal, healthy fallopian tubes are removed in the course of different gynecological surgeries (namely hysterectomy), making the very tissue most consequentially damaged during ascending gonococcal infection available for laboratory research. The study of fallopian tube organ cultures has allowed the opportunity to observe gonococcal biology and immune responses in a complex, multi-layered tissue from a natural host. Forty-five years since the first published example of human fallopian tube being infected ex vivo with N. gonorrhoeae, we review what modeling infections in human tissue explants has taught us about the gonococcus, what we have learned about the defenses mounted by the human host in the upper female reproductive tract, what other fields have taught us about ciliated and non-ciliated cell development, and ultimately offer suggestions regarding the next generation of model systems to help expand our ability to study gonococcal pathogenesis.

The role of mating in oviduct biology

The oviduct connects the ovary to the uterus, and is subject to changes that influence gamete transport, fertilization, and early embryo development. The ovarian steroids estradiol and progesterone are largely responsible for regulating oviduct function, although mating signals also affect the female reproductive tract, both indirectly, through sensory stimulation, and directly, through contact with seminal plasma or spermatozoa. The resulting alterations in gene and protein expression help establish a microenvironment that is appropriate for sperm storage and selection, embryo development, and gamete transport. Mating may also induce the switch from a non-genomic to a genomic pathway of estradiol-accelerated oviduct egg transport, reflecting a novel example of the functional plasticity in well-differentiated cells. This review highlights the physiological relevance of various aspects of mating to oviduct biology and reproductive success. Expanding our knowledge of the mating-associated molecular and cellular events in oviduct cells would undoubtedly facilitate new therapeutic strategies to treat infertility attributable to oviduct pathologies. Mol. Reprod. Dev. 83: 875-883, 2016 © 2016 Wiley Periodicals, Inc.

Neisseria gonorrhoeae-Induced Inflammatory Pyroptosis in Human Macrophages is Dependent on Intracellular Gonococci and Lipooligosaccharide

Neisseria gonorrhoeae, the human obligate pathogen responsible for the sexually transmitted disease gonorrhea, has evolved several mechanisms to evade the host immune response. One such mechanism is the modulation of host cell death pathways. In this study, we defined cell death pathways induced by N gonorrhoeae in human monocyte-derived macrophages (MDMs). In a dose-dependent manner, N gonorrhoeae stimulation of MDMs resulted in caspase 1 and 4-dependent cell deaths, indicative of canonical and noncanonical pyroptosis, respectively. Internalization of bacteria or stimulation with lipooligosaccharide (LOS) specifically induced pyroptosis in MDMs and increased secretion of IL-1β. Collectively, our results demonstrate that N gonorrhoeae induces inflammatory pyroptosis in human macrophages due in part to intracellular LOS. We propose that this in turn may exacerbate inflammatory outcomes observed during mucosal infection.

Treatment evaluation of Wharton's jelly-derived mesenchymal stem cells using a chronic salpingitis model: an animal experiment

Background

The present study was conducted to evaluate new methods to repair the reproductive function of the oviduct, thereby allowing gametes to combine and grow in vivo under natural circumstances.

Methods

Sixty pathogen-free female New Zealand rabbits were divided into three groups: a wild-type group, an untreated control group, and a treatment group. Disposable sterile newborn sputum suction tubes were inserted into the urogenital tract to instill an Escherichia coli suspension into the uterine cavity to establish the chronic salpingitis model. Wharton’s jelly-derived mesenchymal stem cells (WJMSCs) or normal saline were used to treat this infection via different methods. The therapeutic effect was assessed by evaluating morphology, inflammatory factors, proteinology, and pregnancy outcomes.

Results

Oviducts of New Zealand rabbits in the untreated control group showed structural failure and abnormal supermicrostructure of epithelial cells. WJMSCs could partially repair the structure and supermicrostructure of the tubal epithelium. The concentration of tumor necrosis factor (TNF)-α in the untreated control group was significantly higher than that in the wild-type group (P = 0.015). The concentration of TNF-α in the local treatment group was significantly lower than that in the untreated control group (P = 0.011). The expression of oviductal glycoprotein (OVGP) and OVGP mRNA in the wild-type group was significantly higher than those in the untreated control group (P = 0.024 and P = 0.013, respectively). The litter size of the treatment group was 2 ± 2.39 kits, which was higher than that of the untreated control group (P = 0.035).

Conclusion

Chronic inflammation can destroy the structure of the oviduct and the supermicrostructure of epithelial cells as well as leading to infertility. WJMSC transplantation therapy in rabbits with chronic salpingitis partially restored fertility. WJMSCs also repaired the structure of the tubal epithelium subjected to chronic inflammation, decreased the level of inflammatory factors, and partially restored the secretion level of OVGP.

Modified Profile of Matrix Metalloproteinase 2 and 9 Production by Human Fallopian Tube Epithelial Cells After Infection In Vitro With Neisseria gonorrhoeae

Epithelial shedding and scarring of fallopian tube mucosa are the main consequences of sexually transmitted Neisseria gonorrhoeae infection and probably involve an imbalance of host extracellular matrix components and their regulators such as matrix metalloproteinases (MMPs). In the current study, primary human fallopian tube epithelial cells were infected with N. gonorrhoeae, and MMP patterns were examined. Gonococcal infection induced a significant increase in secreted MMP-9 and an accumulation of cytoplasmic MMP-2 over time, but no significant MMP-3 or MMP-8 production was observed. Thus, MMP-9 in particular could play a role in tubal scarring in response to gonococcal infection.

Neisseria gonorrhoeae Challenge Increases Matrix Metalloproteinase-8 Expression in Fallopian Tube Explants

Background:Neisseria gonorrhoeae (Ngo) is the etiological agent of gonorrhea, a sexually transmitted infection that initially infects the female lower genital tract. In untreated women, the bacteria can ascend to the upper genital reproductive tract and infect the fallopian tube (FTs), which is associated with salpingitis and can lead to impaired FT function and infertility. The extracellular matrix (ECM) plays an important role in cell migration and differentiation in the female genital tract, and some pathogens modify the ECM to establish successful infections. The ECM is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), their endogenous inhibitors; MMP deregulation causes pathological conditions in a variety of tissues.

Results: The aim of this work was to analyze the expression and localization of MMP-3, MMP-8, MMP-9, and TIMP-1 in FT explants during Ngo infection using real-time PCR, immunohistochemistry, zymography and ELISA. No significant variations in MMP-3, MMP-9, and TIMP-1 transcript levels were observed. In contrast, a significant increase (p < 0.05) was observed for MMP-8 expression and was accompanied by stromal immunoreactivity in infected explants. ELISA results supported these findings and showed that MMP-8 release increased upon gonococcal infection.

Conclusions: Our results indicate that gonococcal infection induces increased MMP-8 expression, which might contribute to FT damage during infection.

Is gonococcal disease preventable? The importance of understanding immunity and pathogenesis in vaccine development

Gonorrhea is a major, global public health problem for which there is no vaccine. The continuing emergence of antibiotic-resistant strains raises concerns that untreatable Neisseria gonorrhoeae may become widespread in the near future. Consequently, there is an urgent need for increased efforts towards the development of new anti-gonococcal therapeutics and vaccines, as well as suitable models for potential pre-clinical vaccine trials. Several current issues regarding gonorrhea are discussed herein, including the global burden of disease, the emergence of antibiotic-resistance, the status of vaccine development and, in particular, a focus on the model systems available to evaluate drug and vaccine candidates. Finally, alternative approaches to evaluate vaccine candidates are presented. Such approaches may provide valuable insights into the protective mechanisms, and correlates of protection, required to prevent gonococcal transmission, local infection and disease sequelae.

Edwardsiella tarda-Induced Inhibition of Apoptosis: A Strategy for Intracellular Survival

Edwardsiella tarda is a Gram-negative bacterial pathogen that can infect a wide range of freshwater and marine fish. One salient feature of E. tarda is the ability to survive and replicate in various host cells. In this study, we observed that E. tarda replicated robustly in the zebrafish cell line ZF4, and that E. tarda-infected cells exhibited no detectable signs of apoptosis. Global transcriptome analysis and quantitative real-time RT-PCR revealed that E. tarda infection generally significantly downregulated pro-apoptotic genes and upregulated anti-apoptotic genes. To investigate the role of apoptosis in E. tarda infection, two upregulated anti-apoptotic genes (Fech and Prx3) and two downregulated pro-apoptotic genes (Brms1a and Ivns1a) were overexpressed in zebrafish. Subsequent infection study showed that Fech and Prx3 overexpression significantly promoted E. tarda dissemination in and colonization of fish tissues, while Brms1a and Ivns1a overexpression significantly reduced E. tarda dissemination and colonization. Consistently, when Fech and Prx3 were knocked down in zebrafish, E. tarda infection was significantly inhibited, whereas Brms1a and Ivns1a knockdown significantly enhanced E. tarda infection. These results indicate for the first time that E. tarda prevents apoptosis in teleost as a strategy for intracellular survival, and that some putative apoptotic genes of teleost function in the apoptosis pathway probably in a manner similar to that in mammalian systems.

Burkholderia pseudomallei Differentially Regulates Host Innate Immune Response Genes for Intracellular Survival in Lung Epithelial Cells

Background

Burkholderia pseudomallei, the causative agent of melioidosis poses a serious threat to humankind. B. pseudomallei secretes numerous virulence proteins that alter host cell functions to escape from intracellular immune sensors. However, the events underlying disease pathogenesis are poorly understood.

Methods

We determined the ability of B. pseudomallei to invade and survive intracellularly in A549 human lung epithelial cells, and also investigated the early transcriptional responses using an Illumina HumanHT-12 v4 microarray platform, after three hours of exposure to live B. pseudomallei (BCMS) and its secreted proteins (CCMS).

Results

We found that the ability of B. pseudomallei to invade and survive intracellularly correlated with increase of multiplicity of infection and duration of contact. Activation of host carbohydrate metabolism and apoptosis as well as suppression of amino acid metabolism and innate immune responses both by live bacteria and its secreted proteins were evident. These early events might be linked to initial activation of host genes directed towards bacterial dissemination from lungs to target organs (via proposed in vivo mechanisms) or to escape potential sensing by macrophages.

Conclusion

Understanding the early responses of A549 cells toward B. pseudomallei infection provide preliminary insights into the likely pathogenesis mechanisms underlying melioidosis, and could contribute to development of novel intervention strategies to combat B. pseudomallei infections.

Burkholderia pseudomallei, the causative agent of the fatal infectious disease melioidosis, is endemic across parts of South East Asia and Northern Australia. Melioidosis poses a serious worldwide emerging infectious disease problem and bioterrorism threat. Of the key features of B. pseudomallei, is its ability to remain latent in the host causing recrudescent disease years after initial infection. Relapses are also commonly reported despite appropriate and prolonged antibiotic therapy, suggesting the bacteria’s ability to escape the host’s front-line immune defenses and to manipulate the host’s responses to sustain survival in the host. However, the likely underlying mechanisms of bacterial persistence still remain unclear. Thus, here we proposed to study the host responses towards early interaction of the cell with live B. pseudomallei and its secretory proteins, in order to understand the potential roles of innate responses against the bacteria.

Neisseria gonorrhoeae Modulates Cell Death in Human Endocervical Epithelial Cells through Export of Exosome-Associated cIAP2

Several bacterial pathogens persist and survive in the host by modulating host cell death pathways. We previously demonstrated that Neisseria gonorrhoeae, a Gram-negative pathogen responsible for the sexually transmitted infection gonorrhea, protects against exogenous induction of apoptosis in human cervical epithelial cells. However, induction of cell death by N. gonorrhoeae has also been reported in other cell types. The mechanisms by which N. gonorrhoeae modulates cell death are not clear, although a role for the inhibitor of apoptosis-2 (cIAP2) has been proposed. In this study, we confirmed that N. gonorrhoeae induces production of cIAP2 in human cervical epithelial cells. High levels of intracellular cIAP2 were detected early after N. gonorrhoeae stimulation, which was followed by a marked decrease at 24 h. At this time point, we observed increased levels of extracellular cIAP2 associated with exosomes and an overall increase in production of exosomes. Inhibition of cIAP2 in N. gonorrhoeae-stimulated epithelial cells resulted in increased cell death and interleukin-1β (IL-1β) production. Collectively these results indicate that N. gonorrhoeae stimulation of human endocervical epithelial cells induces the release of cIAP2, an essential regulator of cell death and immune signaling.

Estradiol increases cAMP in the oviductal secretory cells through a nongenomic mechanism

In the rat oviduct, estradiol (E2) accelerates egg transport by a nongenomic action that requires previous conversion of E2 to methoxyestrogens via catechol-O-methyltranferase (COMT) and activation of estrogen receptor (ER) with subsequent production of cAMP and inositol triphosphate (IP3). However, the role of the different oviductal cellular phenotypes on this E2 nongenomic pathway remains undetermined. The aim of this study was to investigate the effect of E2 on the levels of cAMP and IP3 in primary cultures of secretory and smooth muscle cells from rat oviducts and determine the mechanism by which E2 increases cAMP in the secretory cells. In the secretory cells, E2 increased cAMP but not IP3, while in the smooth muscle cells E2 decreased cAMP and increased IP3. Suppression of protein synthesis by actinomycin D did not prevent the E2-induced cAMP increase, but this was blocked by the ER antagonist ICI 182 780 and the inhibitors of COMT OR 486, G protein-α inhibitory (Gαi) protein pertussis toxin and adenylyl cyclase (AC) SQ 22536. Expression of the mRNA for the enzymes that metabolizes estrogens, Comt, Cyp1a1, and Cyp1b1 was found in the secretory cells, but this was not affected by E2. Finally, confocal immunofluorescence analysis showed that E2 induced colocalization between ESR1 (ERα) and Gαi in extranuclear regions of the secretory cells. We conclude that E2 differentially regulates cAMP and IP3 in the secretory and smooth muscle cells of the rat oviduct. In the secretory cells, E2 increases cAMP via a nongenomic action that requires activation of COMT and ER, coupling between ESR1 and Gαi, and stimulation of AC.

Suppression of ERK activation in urethral epithelial cells infected with Neisseria gonorrhoeae and its isogenic minD mutant contributes to anti-apoptosis

In gonococci-infected transduced human urethral epithelial cells (THUEC), the role of ERK, a mitogen-activated protein kinase (MAPK), in apoptosis is unknown. We observed lowering of ERK activation in THUEC following infection with anti-apoptosis-inducing Neisseria gonorrhoeae strain CH811. An isogenic cell division mutant of this strain, Ng CJSD1 (minD deficient), which is large and abnormally shaped, reduced ERK phosphorylation levels even more than its parental strain in THUEC. This led to higher anti-apoptosis in mutant-infected cells as compared to the parental strain-infected cells. Our results suggest that N. gonorrhoeae infection reduces ERK activation in THUEC contributing to anti-apoptosis.

The biology of Neisseria adhesins

Members of the genus Neisseria include pathogens causing important human diseases such as meningitis, septicaemia, gonorrhoea and pelvic inflammatory disease syndrome. Neisseriae are found on the exposed epithelia of the upper respiratory tract and the urogenital tract. Colonisation of these exposed epithelia is dependent on a repertoire of diverse bacterial molecules, extending not only from the surface of the bacteria but also found within the outer membrane. During invasive disease, pathogenic Neisseriae also interact with immune effector cells, vascular endothelia and the meninges. Neisseria adhesion involves the interplay of these multiple surface factors and in this review we discuss the structure and function of these important molecules and the nature of the host cell receptors and mechanisms involved in their recognition. We also describe the current status for recently identified Neisseria adhesins. Understanding the biology of Neisseria adhesins has an impact not only on the development of new vaccines but also in revealing fundamental knowledge about human biology.

Tumour necrosis factor-α is the signal induced by mating to shutdown a 2-methoxyestradiol nongenomic action necessary to accelerate oviductal egg transport in the rat

Mating shut down a 2-methoxyestradiol (2ME) nongenomic action necessary to accelerate egg transport in the rat oviduct. Herein, we investigated whether tumour necrosis factor-α (TNF-α) participates in this mating effect. In unmated and mated rats, we determined the concentration of TNF-α in the oviductal fluid and the level of the mRNA for Tnf-a (Tnf) and their receptors Tnfrsf1a and Tnfrsf1b in the oviduct tissues. The distribution of the TNFRSF1A and TNFRSF1B proteins in the oviduct of unmated and mated was also assessed. Finally, we examined whether 2ME accelerates oviductal egg transport in unmated rats that were previously treated with a rat recombinant TNF-α alone or concomitant with a selective inhibitor of the NF-κB activity. Mating increased TNF-α in the oviductal fluid, but Tnf transcript was not detected in the oviduct. The mRNA for TNF-α receptors as well as their distribution was not affected by mating, although they were mainly localized in the endosalpinx. Administration of TNF-α into the oviduct of unmated rats prevented the effect of 2ME on egg transport. However, the NF-κB activity inhibitor did not revert this effect of TNF-α. These results indicate that mating increased TNF-α in the oviductal fluid, although this not associated with changes in the expression and localization of TNF-α receptors in the oviductal cells. Furthermore, TNF-α mimicked the effect of mating on the 2ME-induced egg transport acceleration, independently of the activation of NF-κB in the oviduct. We concluded that TNF-α is the signal induced by mating to shut down a 2ME nongenomic action in the rat oviduct.

Differential expression of extracellular matrix components in the Fallopian tubes throughout the menstrual cycle

BACKGROUND

One of the unique characteristics of the female genital tract is the extensive tissue remodeling observed throughout the menstrual cycle. Multiple components of the extracellular matrix take part in this tissue rebuilding; however, the individual components involved have not been identified.

METHODS

In the present study, the expression of extracellular matrix proteins and selected matrix metalloproteinase (MMP) activities in Fallopian tubes (FT) throughout the menstrual cycle were examined by PCR array, immunocytochemistry, zymography and bioinformatics.

RESULTS

Of the eighty-four genes analyzed, eighty-three were expressed in the FT during at least one stage of the menstrual cycle. We observed a significant increase (>/=2-fold) in ADAMTS1, ADAMTS13, COL7A1, MMP3, MMP9, PECAM1, and THBS3 in the periovulatory phase compared to the follicular phase. Meanwhile, we observed a significant decrease (>/= 2-fold) in COL7A1, ICAM1, ITGA8, MMP16, MMP9, CLEC3B, SELE and TIMP2 in the lutheal phase compared to the periovulatory phase. Immunocytochemistry showed that MMP-3 and MMP-9 were localized in the endosalpinx during all phases of the menstrual cycle. Gelatin zymograms detected non-cycle-dependent protease activity.

CONCLUSIONS

Several extracellular matrix components were regulated throughout the menstrual cycle in a cyclic pattern, suggesting a possible steroid regulation and a role in tissue remodeling and FT functions.

Increased expression of the von Hippel-Lindau gene in the implantation site of human tubal pregnancy

The objective of this study was to investigate the expression of the von Hippel-Lindau (VHL) gene in tissues of human fallopian tube and tubal pregnancy. Twenty patients undergoing salpingectomy for tubal pregnancy were recruited into the study group. Tissues of tubal pregnancy were separated into both the implantation and non-implantation sites as the implantation group and the non-implantation group, respectively. Samples of ampullary fallopian tube during mid-secretory phase were collected from twenty patients with benign uterine disease as the control group. Immunohistochemistry, real-time reverse transcription polymerase chain reaction, and Western blotting analysis were performed to detect expressions of VHL mRNA and protein. The results showed that VHL immunostaining appeared in the cytoplasm of tubal epithelial cells. Expression of VHL mRNA in the implantation group was higher than that in the non-implantation group or the control group (P < 0.01). Intensity of VHL protein in the implantation group was increased compared with that in the non-implantation group (P < 0.05) or in the control group (P < 0.01). There was no difference on expressions of VHL mRNA and protein between the non-implantation group and the control group (P > 0.05). In conclusion, VHL mRNA and protein are present in human tubal tissues. The VHL gene expression is increased in the implantation site of tubal pregnancy, and locally elevated expression of the VHL gene might be associated with human tubal pregnancy.

Analysis of parameters associated with prevention of cellular apoptosis by pathogenic Neisseriae and purified porins

The process of cellular apoptosis is mediated by a number of microbial pathogens to modulate host defense mechanisms. Inhibition of apoptosis is thought to favor microbial survival, replication or immune evasion, while induction of apoptosis is likely to promote escape of the organisms from host cells. Several studies have reported that infection with Neisseria spp. can inhibit or reduce apoptotic cell death, thus allowing adaptation, intracellular replication, and immune evasion, events that are likely to spread infection. In this chapter, various techniques are described for direct measurement of host cell responses to infection with Neisseria meningitidis and to treatment with pure Neisseria porins, the major proteins found in the outer membrane of the pathogen.

Neisseria gonorrhoeae induced disruption of cell junction complexes in epithelial cells of the human genital tract

Pathogenic microorganisms, such as Neisseria gonorrhoeae, have developed mechanisms to alter epithelial barriers in order to reach subepithelial tissues for host colonization. The aim of this study was to examine the effects of gonococci on cell junction complexes of genital epithelial cells of women. Polarized Ishikawa cells, a cell line derived from endometrial epithelium, were used for experimental infection. Infected cells displayed a spindle-like shape with an irregular distribution, indicating potential alteration of cell-cell contacts. Accordingly, analysis by confocal microscopy and cellular fractionation revealed that gonococci induced redistribution of the adherens junction proteins E-cadherin and its adapter protein β-catenin from the membrane to a cytoplasmic pool, with no significant differences in protein levels. In contrast, gonococcal infection did not induce modification of either expression or distribution of the tight junction proteins Occludin and ZO-1. Similar results were observed for Fallopian tube epithelia. Interestingly, infected Ishikawa cells also showed an altered pattern of actin cytoskeleton, observed in the form of stress fibers across the cytoplasm, which in turn matched a strong alteration on the expression of fibronectin, an adhesive glycoprotein component of extracellular matrix. Interestingly, using western blotting, activation of the ERK pathway was detected after gonococcal infection while p38 pathway was not activated. All effects were pili and Opa independent. Altogether, results indicated that gonococcus, as a mechanism of pathogenesis, induced disruption of junction complexes with early detaching of E-cadherin and β-catenin from the adherens junction complex, followed by a redistribution and reorganization of actin cytoskeleton and fibronectin within the extracellular matrix.

Neisseria gonorrhoeae-mediated inhibition of apoptotic signalling in polymorphonuclear leukocytes

The human pathogen Neisseria gonorrhoeae recruits and interacts extensively with polymorphonuclear leukocytes (PMNs) during infection. N. gonorrhoeae is able to survive the bactericidal activity of these innate immune cells and can actively modulate PMN functions in vitro. PMNs are short-lived cells which readily undergo apoptosis, and thus the effect of N. gonorrhoeae infection on PMN survival has implications for whether PMNs might serve as an important site of bacterial replication during infection. We developed and validated an HL-60 myeloid leukemia cell culture model for PMN infection and used both these cells and primary PMNs to show that N. gonorrhoeae infection alone does not induce apoptosis and furthermore that N. gonorrhoeae can inhibit both spontaneous apoptosis and apoptosis induced by the intrinsic and extrinsic apoptosis inducers staurosporine (STS) and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), respectively. N. gonorrhoeae infection also results in the activation of NF-κB signaling in neutrophils and induces secretion of an identical profile of proinflammatory cytokines and chemokines in both HL-60 cells and primary PMNs. Our data show that the HL-60 cell line can be used to effectively model N. gonorrhoeae-PMN interactions and that N. gonorrhoeae actively inhibits apoptosis induced by multiple stimuli to prolong PMN survival and potentially facilitate bacterial survival, replication, and transmission.

Genome-wide identification of Chlamydia trachomatis antigens associated with tubal factor infertility

OBJECTIVE

To identify Chlamydia trachomatis antigens that can be used to differentially diagnose tubal factor infertility in comparison with previously reported heat shock protein 60.

DESIGN

In vitro study.

SETTING

Academic medical center.

PATIENT(S)

Infertile women with and without tubal pathology diagnosed laparoscopically.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Antibody responses to C. trachomatis in infertile women with or without tubal pathologies using a C. trachomatis genome-wide proteome array.

RESULT(S)

Comparison of the antibody profiles revealed 30 C. trachomatis antigens that were preferentially recognized in women with tubal factor infertility, with a detection sensitivity and specificity of 80.6% and 56.5%, respectively, 10 of which showed 100% specificity. A combination of CT443 and CT381 antigens yielded the highest detection sensitivity (67.7%) while maintaining 100% specificity.

CONCLUSION(S)

These findings have demonstrated that antibodies to CT443 and CT381, when used in combination, have higher sensitivity and specificity in predicting tubal factor infertility than other indicators for tubal factor infertility, such as heat shock protein 60 antibodies (35.5%, 100%) or hysterosalpingogram (65%, 83%). Using a panel of C. trachomatis antigens to serologically diagnose tubal factor infertility can save the patients from undertaking expensive and invasive procedures for determining tubal pathology and choosing treatment plans.

Protective role of Akt2 in Salmonella enterica serovar typhimurium-induced gastroenterocolitis

The Salmonella effector protein SopB has previously been shown to induce activation of Akt and protect epithelial cells from apoptosis in vitro. To characterize the role of Akt2 in host defense against Salmonella enterica serovar Typhimurium infection, wild-type (WT) mice and mice lacking Akt2 (Akt2 knockout [KO] mice) were infected using a Salmonella acute gastroenteritis model. Infected Akt2 KO mice showed a more pronounced morbidity and mortality associated with higher bacterial loads in the intestines and elevated levels of proinflammatory cytokines, including tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), and MCP-1, in the colons at 1 day postinfection compared to those shown in WT mice. Histopathological assessment and immunohistochemical analysis of cecal sections at 1 day postinfection revealed more severe inflammation and higher levels of neutrophil infiltration in the ceca of Akt2 KO mice. Flow cytometry analysis further confirmed an increase in the recruitment of Gr-1(+) CD11b(+) neutrophils and F4/80(+) CD11b(+) macrophages in the intestines of infected Akt2 KO mice. Additionally, enhanced levels of annexin V(+) and terminal transferase dUTP nick end labeling-positive (TUNEL(+)) apoptotic cells in the intestines of infected Akt2 KO mice were also observed, indicating that Akt2 plays an essential role in protection against apoptosis. Finally, the differences in bacterial loads and cecal inflammation in WT and Akt2 KO mice infected with WT Salmonella were abolished when these mice were infected with the sopB deletion mutant, indicating that SopB may play a role in protecting the mice from Salmonella infection through the activation of Akt2. These data demonstrate a definitive phenotypic abnormality in the innate response in mice lacking Akt2, underscoring the important protective role of Akt2 in Salmonella infection.

Meningococcal porin PorB prevents cellular apoptosis in a toll-like receptor 2- and NF-kappaB-independent manner

Meningococcal porin PorB is an inhibitor of apoptosis induced via the intrinsic pathway in various cell types. This effect is attributed to prevention of mitochondrial depolarization and of subsequent release of proapoptotic mitochondrial factors. To determine whether apoptosis is globally inhibited by PorB, we compared the intrinsic and extrinsic pathways in HeLa cells. Interestingly, PorB does not prevent extrinsic apoptosis induced by tumor necrosis factor alpha plus cycloheximide, suggesting a unique mitochondrial pathway specificity. Several intracellular factors regulated by NF-kappaB, including members of the Bcl-2 family and of the inhibitor of apoptosis (IAP) family, play major roles in controlling apoptosis, and some of them are thought to contribute to the antiapoptotic effect of the gonococcal porin, PIB. However, most of the members of the Bcl-2 family and the IAP family are not induced by meningococcal PorB in HeLa cells, with the exception of Bfl-1/A1. Interestingly, PorB does not induce NF-kappaB activation in HeLa cells, likely due to a lack of Toll-like receptor 2 (TLR2) expression in these cells. Bfl-1/A1 expression is also regulated by CBF1, a nuclear component of the Notch signaling pathway, independent of NF-kappaB activation. Since HeLa cells are protected by PorB from intrinsic apoptosis events, regardless of TLR2 and NF-kappaB expression, the possibility of a contribution of alternative signaling pathways to this effect cannot be excluded. In this paper, we describe an initial dissection of the cascade of cellular events involved in the antiapoptotic effect of PorB in the absence of TLR2.

Mouse strain-dependent differences in susceptibility to Neisseria gonorrhoeae infection and induction of innate immune responses

Acute gonorrhea in women is characterized by a mucopurulent exudate that contains polymorphonuclear leukocytes (PMNs) with intracellular gonococci. Asymptomatic infections are also common. Information on the innate response to Neisseria gonorrhoeae in women is limited to studies with cultured cells, isolated immune cells, and analyses of cervicovaginal fluids. 17beta-Estradiol-treated BALB/c mice can be experimentally infected with N. gonorrhoeae, and a vaginal PMN influx occurs in 50 to 80% of mice. Here, we compared the colonization loads and proinflammatory responses of BALB/c, C57BL/6 and C3H/HeN mice to N. gonorrhoeae. BALB/c and C57BL/6 mice were colonized at similar levels following inoculation with 10(6) CFU of N. gonorrhoeae. BALB/c, but not C57BL/6, mice exhibited a marked vaginal PMN influx. Tumor necrosis factor alpha, interleukin-6, macrophage inflammatory protein 2 (MIP-2), and keratinocyte-derived chemokine were elevated in vaginal secretions from infected BALB/c mice, but not in those from C57BL/6 mice. MIP-2 levels positively correlated with a vaginal PMN influx. In contrast to BALB/c and C57BL/6 mice, C3H/HeN mice were resistant to infection, and there was no evidence of an inflammatory response. We conclude that N. gonorrhoeae causes a productive infection in BALB/c mice that is characterized by the induction of proinflammatory cytokines and chemokines and the recruitment of PMNs. Infection of C57BL/6 mice, in contrast, is more similar to asymptomatic infection. C3H/HeN mice are inherently resistant to N. gonorrhoeae infection, and this resistance is not due to an overwhelming inflammatory response to infection. Host genetic factors can therefore impact susceptibility and the immune response to N. gonorrhoeae.

Neisseria gonorrhoeae infection protects human endocervical epithelial cells from apoptosis via expression of host antiapoptotic proteins

Several microbial pathogens can modulate the host apoptotic response to infection, which may contribute to immune evasion. Various studies have reported that infection with the sexually transmitted disease pathogen Neisseria gonorrhoeae can either inhibit or induce apoptosis. N. gonorrhoeae infection initiates at the mucosal epithelium, and in women, cells from the ectocervix and endocervix are among the first host cells encountered by this pathogen. In this study, we defined the antiapoptotic effect of N. gonorrhoeae infection in human endocervical epithelial cells (End/E6E7 cells). We first established that N. gonorrhoeae strain FA1090B failed to induce cell death in End/E6E7 cells. Subsequently, we demonstrated that stimulation with N. gonorrhoeae protected these cells from staurosporine (STS)-induced apoptosis. Importantly, only End/E6E7 cells incubated with live bacteria and in direct association with N. gonorrhoeae were protected from STS-induced apoptosis, while heat-killed and antibiotic-killed bacteria failed to induce protection. Stimulation of End/E6E7 cells with live N. gonorrhoeae induced NF-kappaB activation and resulted in increased gene expression of the NF-kappaB-regulated antiapoptotic genes bfl-1, cIAP-2, and c-FLIP. Furthermore, cIAP-2 protein levels also increased in End/E6E7 cells incubated with gonococci. Collectively, our results indicate that the antiapoptotic effect of N. gonorrhoeae in human endocervical epithelial cells results from live infection via expression of host antiapoptotic proteins. Securing an intracellular niche through the inhibition of apoptosis may be an important mechanism utilized by N. gonorrhoeae for microbial survival and immune evasion in cervical epithelial cells.

Neisseria gonorrhoeae activates the proteinase cathepsin B to mediate the signaling activities of the NLRP3 and ASC-containing inflammasome

Neisseria gonorrhoeae is a common sexually transmitted pathogen that significantly impacts female fertility, neonatal health, and transmission of HIV worldwide. N. gonorrhoeae usually causes localized inflammation of the urethra and cervix by inducing production of IL-1beta and other inflammatory cytokines. Several NLR (nucleotide-binding domain, leucine-rich repeat) proteins are implicated in the formation of pro-IL-1beta-processing complexes called inflammasomes in response to pathogens. We demonstrate that NLRP3 (cryopyrin, NALP3) is the primary NLR required for IL-1beta/IL-18 secretion in response to N. gonorrhoeae in monocytes. We also show that N. gonorrhoeae infection promotes NLRP3-dependent monocytic cell death via pyronecrosis, a recently described pathway with morphological features of necrosis, including release of the strong inflammatory mediator HMBG1. Additionally, N. gonorrhoeae activates the cysteine protease cathepsin B as measured by the breakdown of a cathepsin B substrate. Inhibition of cathepsin B shows that this protease is an apical controlling step in the downstream activities of NLRP3 including IL-1beta production, pyronecrosis, and HMGB1 release. Nonpathogenic Neisseria strains (Neisseria cinerea and Neisseria flavescens) do not activate NLRP3 as robustly as N. gonorrhoeae. Conditioned medium from N. gonorrhoeae contains factors capable of initiating the NLRP3-mediated signaling events. Isolated N. gonorrhoeae lipooligosaccharide, a known virulence factor from this bacterium that is elaborated from the bacterium in the form of outer membrane blebs, activates both NLRP3-induced IL-1beta secretion and pyronecrosis. Our findings indicate that activation of NLRP3-mediated inflammatory response pathways is an important venue associated with host response and pathogenesis of N. gonorrhoeae.

Differential modulation of TNF-alpha-induced apoptosis by Neisseria meningitidis

Infections by Neisseria meningitidis show duality between frequent asymptomatic carriage and occasional life-threatening disease. Bacterial and host factors involved in this balance are not fully understood. Cytopathic effects and cell damage may prelude to pathogenesis of isolates belonging to hyper-invasive lineages. We aimed to analyze cell–bacteria interactions using both pathogenic and carriage meningococcal isolates. Several pathogenic isolates of the ST-11 clonal complex and carriage isolates were used to infect human epithelial cells. Cytopathic effect was determined and apoptosis was scored using several methods (FITC-Annexin V staining followed by FACS analysis, caspase assays and DNA fragmentation). Only pathogenic isolates were able to induce apoptosis in human epithelial cells, mainly by lipooligosaccharide (endotoxin). Bioactive TNF-α is only detected when cells were infected by pathogenic isolates. At the opposite, carriage isolates seem to provoke shedding of the TNF-α receptor I (TNF-RI) from the surface that protect cells from apoptosis by chelating TNF-α. Ability to induce apoptosis and inflammation may represent major traits in the pathogenesis of N. meningitidis. However, our data strongly suggest that carriage isolates of meningococci reduce inflammatory response and apoptosis induction, resulting in the protection of their ecological niche at the human nasopharynx.

Acquisition of Neisseria meningitidis often leads to asymptomatic colonization (carriage) and rarely results in invasive disease associated with tissue injury. The reasons that make disease-associated isolates (pathogenic isolates) but not asymptomatic carriage isolates able to invade the host to establish disease are not understood. Isolates belonging to the ST-11 clonal complex are most frequently associated with the disease and rarely found in carriers. These hyper-invasive isolates may be able to induce cytopathic effects in target cells. We aimed to investigate the cytopathic effect of meningococcal isolates on epithelial cells using both ST-11 pathogenic isolates and carriage isolates. We showed that cytopathic effects were strongly associated with pathogenic isolates and infected cells exhibited features of apoptosis. This effect is mainly mediated by bacterial endotoxin (lipooligosaccharide) and involved an autocrine signaling mechanism of secreted TNF-α through its receptor TNF-RI. In contrast, carriage isolates down-regulate TNF-RI on the surface of infected cells by increasing TNF-RI shedding into the medium. We suggest that chelating secreted TNF-α protects cells from apoptosis. Our results unravel a differential modulation of TNF-α signaling by meningococcal isolates leading to cell survival or death and would therefore contribute to better understanding of the duality between carriage and invasiveness.

Functional group/guild modelling of inter-specific pathogen interactions: a potential tool for predicting the consequences of co-infection

Although co-infection is the norm in most human and animal populations, clinicians currently have no practical tool to assist them in choosing the best treatment strategy for such patients. Given the vast range of potential pathogens which may co-infect the host, obtaining such a practical tool may seem an intractable problem. In ecology the joint concepts of functional groups and guilds have been used to conceptually simplify complex ecosystems, in order to understand how their component parts interact and may be manipulated. Here we propose a mechanism by which to apply these concepts to pathogen co-infection systems. Further, we describe how these groups could be incorporated into a mathematical modelling framework which, after validation, could be used as a clinical tool to predict the outcome of any particular combination of pathogens co-infecting a host.

Extracellular signal-regulated kinase activation by Neisseria gonorrhoeae downregulates epithelial cell proapoptotic proteins Bad and Bim

Neisseria gonorrhoeae expressing type IV pili (Tfp) activates extracellular signal-regulated kinase (ERK) and induces a cytoprotective state in the epithelial cell in a manner that is enhanced by pilT. As the ERK signaling pathway is well-known for its role in cytoprotection and cell survival, we tested the hypothesis that ERK is involved in producing this cytoprotective effect. Inhibiting ERK activation prior to infection attenuated the ability of these bacteria to induce cytoprotection. Activated ERK specifically targeted two proapoptotic Bcl-2 homology domain 3 (BH3)-only proteins, Bim and Bad, for downregulation at the protein level. Bim downregulation occurred through the proteasome. ERK, in addition, inactivated Bad by triggering its phosphorylation at Ser112. Finally, reducing the level of either Bad or Bim alone by small interfering RNA was sufficient to protect uninfected cells from staurosporine-induced apoptosis. We conclude that Tfp-induced cytoprotection is due in part to ERK-dependent modification and/or downregulation of proapoptotic proteins Bad and Bim.

Staying alive: bacterial inhibition of apoptosis during infection

The ability of bacterial pathogens to inhibit apoptosis in eukaryotic cells during infection is an emerging theme in the study of bacterial pathogenesis. Prevention of apoptosis provides a survival advantage because it enables the bacteria to replicate inside host cells. Bacterial pathogens have evolved several ways to prevent apoptosis by protecting the mitochondria and preventing cytochrome c release, by activating cell survival pathways, or by preventing caspase activation. This review summarizes the most recent work on bacterial anti-apoptotic strategies and suggests new research that is necessary to advance the field.

Dynamics of Neisseria gonorrhoeae attachment: microcolony development, cortical plaque formation, and cytoprotection

Neisseria gonorrhoeae is the bacterium that causes gonorrhea, a major sexually transmitted disease and a significant cofactor for human immunodeficiency virus transmission. The retactile N. gonorrhoeae type IV pilus (Tfp) mediates twitching motility and attachment. Using live-cell microscopy, we reveal for the first time the dynamics of twitching motility by N. gonorrhoeae in its natural environment, human epithelial cells. Bacteria aggregate into microcolonies on the cell surface and induce a massive remodeling of the microvillus architecture. Surprisingly, the microcolonies are motile, and they fuse to form progressively larger structures that undergo rapid reorganization, suggesting that bacteria communicate with each other during infection. As reported, actin plaques form beneath microcolonies. Here, we show that cortical plaques comigrate with motile microcolonies. These activities are dependent on pilT, the Tfp retraction locus. Cultures infected with a pilT mutant have significantly higher numbers of apoptotic cells than cultures infected with the wild-type strain. Inducing pilT expression with isopropyl-beta-D-thiogalactopyranoside partially rescues cells from infection-induced apoptosis, demonstrating that Tfp retraction is intrinsically cytoprotective for the host. Tfp-mediated attachment is therefore a continuum of microcolony motility and force stimulation of host cell signaling, leading to a cytoprotective effect.

Effect of gonococcal lipooligosaccharide variation on human monocytic cytokine profile

Background

Neisseria gonorrhoeae is an obligate human pathogen that causes significant worldwide morbidity. N. gonorrhoeae expresses lipooligosaccharide (LOS), a phase variable molecule that plays an important role during pathogenesis of the organism. Alteration in the structure of gonococcal LOS correlates with altered disease presentation. In addition, LOS sialylation occurs readily in vivo, though the role of this sialylation during disease is unknown.

Results

Challenge of human monocytes with purified LOS preparations isolated from strains expressing distinct structurally defined LOSs resulted in identical production of the proinflammatory cytokines tumor necrosis factor alpha (TNFα) and interleukin-12 (IL-12). Similar results were seen when monocytes were challenged with either live or gentamicin-killed whole cell gonococcal variants expressing these LOS structures, although greater cytokine production was observed in comparison with challenge by purified LOS. Challenge of a human primary monocyte model with distinct LOS variants resulted in similar production of TNFα, IL-12, interleukin-10 (IL-10), and interleukin-8 (IL-8). A cytokine array was employed to allow measurement of a broad range of cytokines in samples challenge with gonococcal LOS variants as well as variants expressing sialylated LOS. Challenge of primary monocytes with sialylated gonococci was shown to elicit the production of more MCP-2 (monocyte chemoattractant protein-2) in comparison with challenge by unsialylated gonococci.

Conclusion

We demonstrated that while alterations in the carbohydrate moiety of LOS do not impact the production of most cytokines by human monocytes, whole-cell bacterial challenge is more stimulatory than challenge with purified LOS, implying that other gonococcal cell surface antigens are important for the elicitation of cytokines. Challenge with gonococci expressing sialylated LOS resulted in elicitation of more of the chemokine MCP-2 from challenged cells in comparison with gonococci expressing unsialylated LOS. As MCP-2 is an important chemoattractant, this indicates that in vivo sialylation may play an important role during the pathogenesis of N. gonorrhoeae.