The extracellular signal-regulated kinase/mitogen-activated protein kinase pathway induces the inflammatory factor interleukin-8 following Chlamydia trachomatis infection

Chlamydia in pigs: intriguing bacteria associated with sub-clinical carriage and clinical disease, and with zoonotic potential

Chlamydiae are bacteria that are intriguing and important at the same time. The genus Chlamydia encompasses many species of obligate intracellular organisms: they can multiply only inside the cells of their host organism. Many, perhaps most animals have their own specifically adapted chlamydial species. In humans, the clinically most relevant species is Chlamydia trachomatis, which has particular importance as an agent of sexually transmitted disease. Pigs are the natural host of Chlamydia suis but may also carry Chlamydia abortus and Chlamydia pecorum. C. abortus and possibly C. suis have anthropozoonotic potential, which makes them interesting to human medicine, but all three species bring a substantial burden of disease to pigs. The recent availability of genomic sequence comparisons suggests adaptation of chlamydial species to their respective hosts. In cell biological terms, many aspects of all the species seem similar but non-identical: the bacteria mostly replicate within epithelial cells; they are taken up by the host cell in an endosome that they customize to generate a cytosolic vacuole; they have to evade cellular defences and have to organize nutrient transport to the vacuole; finally, they have to organize their release to be able to infect the next cell or the next host. What appears to be very difficult and challenging to achieve, is in fact a greatly successful style of parasitism. I will here attempt to cover some of the aspects of the infection biology of Chlamydia, from cell biology to immune defence, epidemiology and possibilities of prevention. I will discuss the pig as a host species and the species known to infect pigs but will in particular draw on the more detailed knowledge that we have on species that infect especially humans.

Insights into Chlamydia Development and Host Cells Response

Chlamydia infections commonly afflict both humans and animals, resulting in significant morbidity and imposing a substantial socioeconomic burden worldwide. As an obligate intracellular pathogen, Chlamydia interacts with other cell organelles to obtain necessary nutrients and establishes an intracellular niche for the development of a biphasic intracellular cycle. Eventually, the host cells undergo lysis or extrusion, releasing infectious elementary bodies and facilitating the spread of infection. This review provides insights into Chlamydia development and host cell responses, summarizing the latest research on the biphasic developmental cycle, nutrient acquisition, intracellular metabolism, host cell fates following Chlamydia invasion, prevalent diseases associated with Chlamydia infection, treatment options, and vaccine prevention strategies. A comprehensive understanding of these mechanisms will contribute to a deeper comprehension of the intricate equilibrium between Chlamydia within host cells and the progression of human disease.

Chlamydia trachomatis T3SS Effector CT622 Induces Proinflammatory Cytokines Through TLR2/TLR4-Mediated MAPK/NF-κB Pathways in THP-1 Cells

BACKGROUND

The pathogenesis of Chlamydia trachomatis is associated with the induction of the host inflammatory response; however, the precise underlying molecular mechanisms remain poorly understood.

METHODS

CT622, a T3SS effector protein, has an important role in the pathogenesis of C trachomatis; however, whether CT622 can induce a host inflammatory response is not understood. Our findings demonstrate that CT622 induces the expression of interleukins 6 and 8 (IL-6 and IL-8). Mechanistically, these effects involve the activation of the MAPK/NF-κB signaling pathways (mitogen-activated protein kinase/nuclear factor κB).

RESULTS

Interestingly, we demonstrated that the suppression of toll-like receptor 4 using small interfering RNA markedly reduced the phosphorylation of ERK, p38, JNK, and IκBα, concomitant with a significant decrease in IL-6 and IL-8 secretion. Conversely, disruption of toll-like receptor 2 abrogated the CT622-induced upregulation of IL-8 and activation of ERK, whereas IL-6 expression and p38, JNK, and IκBα phosphorylation were unaffected.

CONCLUSIONS

Taken together, these results indicate that CT622 contributes to the inflammatory response through the toll-like receptor 2/4-mediated MAPK/NF-κB pathways, which provides insight into the molecular pathology of C trachomatis infection.

Effect of miR-412-5p-loaded exosomes in H9c2 cardiomyocytes via the MAPK pathway

Objectives

MicroRNAs (miRNAs) are small non-coding RNAs that function in all biological processes. Recent findings suggest that exosomes, which are small vesicles abundantly secreted by various cell types, can transport miRNAs to target cells. Here, we elucidated the effect of miRNA-loaded exosomes on lipopolysaccharide (LPS)-induced inflammation in H9c2 cardiomyocytes.

Materials and Methods

Exosomes were isolated from mesenchymal stem cells (MSC) and loaded with miR-412-5p. Additionally, the effect of the miR-412-5p-loaded exosomes on LPS-induced inflammation in H9c2 cardiomyocytes was evaluated by assessing the levels of nitric oxide (NO), reactive oxygen species (ROS), and prostaglandin E2 (PGE2). The expression of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), inflammatory cytokines, and mitogen-activated protein kinase (MAPK) signaling factors was evaluated using reverse transcription-quantitative PCR and western blotting.

Results

miR-412-5p-loaded exosomes inhibited LPS-induced secretion of inflammatory mediators (NO, PGE2, and ROS), pro-inflammatory cytokines (IL-1β and IL-6), and COX-2 and iNOS expression. Additionally, miR-412-5p-loaded exosomes significantly decreased the expression of MAPK signaling molecules, including p-extracellular signal-regulated kinase (ERK), p-p38, and p-Jun kinase (JNK), in H9c2 cardiomyocytes.

Conclusion

These findings showed that miR-412-5p-loaded exosomes ameliorated LPS-induced inflammation in H9c2 cardiomyocytes by inhibiting COX-2 and iNOS expression, inflammatory mediators, and pro-inflammatory cytokines via the MAPK pathway. The findings indicate that miR-412-5p-loaded exosomes may be effective for the prevention of myocardial injury.

Cytokine profiling of samples positive for Chlamydia trachomatis and Human papillomavirus

Persistent human papillomavirus (HPV) infection is closely associated with cervical carcinoma. Co-infection in the endocervical environment with other microorganisms, such as Chlamydia trachomatis, may increase the risk of HPV infection and neoplastic progression. While in some individuals, Chlamydia trachomatis infection is resolved with the activation of Th1/IFN-γ-mediated immune response, others develop a chronic infection marked by Th2-mediated immune response, resulting in intracellular persistence of the bacterium and increasing the risk of HPV infection. This work aimed to quantify cytokines of the Th1/Th2/Th17 profile in exfoliated cervix cells (ECC) and peripheral blood (PB) of patients positive for Chlamydia trachomatis DNA, patients positive for Papillomavirus DNA, and healthy patients. Cytokine levels were quantified by flow cytometry in ECC and PB samples from patients positive for C. trachomatis DNA (n = 18), patients positive for HPV DNA (n = 30), and healthy patients (n = 17) treated at the Hospital de Amor, Campo Grande-MS. After analysis, a higher concentration of IL-17, IL-6, and IL-4 (p <0.05) in ECC; INF-γ and IL-10 (p <0.05) in PB was found in samples from patients positive for C. trachomatis DNA compared to samples from healthy patients. When comparing samples from patients positive for HPV DNA, there was a higher concentration of cytokines IL-17, IL-10, IL-6, and IL-4 (p <0.05) in ECC and IL-4 and IL-2 (p <0.05) in PB of patients positive for C. trachomatis DNA. These results suggest that induction of Th2- and Th17 mediated immune response occurs in patients positive for C. trachomatis DNA, indicating chronic infection. Our results also demonstrate a high concentration of pro-inflammatory cytokines in ECC of patients positive for C. trachomatis DNA.

Aberrant gene expression of superoxide dismutases in Chlamydia trachomatis-infected recurrent spontaneous aborters

Study aimed to characterize the expression of antioxidant genes SOD1 and SOD2 in Chlamydia trachomatis-induced recurrent spontaneous aborters and further determine their role by in silico analysis. First void urine was collected from 130 non-pregnant women with history of recurrent spontaneous abortion (RSA) (Group I) and 130 non-pregnant women (Group II; control) attending Obstetrics and Gynecology Department, SJH, New Delhi, India. C. trachomatis detection was performed by conventional PCR in urine. Gene expression of SOD1 and SOD2 was performed by quantitative real-time PCR. Further, its interacting partners were studied by in silico analysis. 22 patients were positive for C. trachomatis in Group I. Significant upregulation was observed for SOD2 gene in C. trachomatis-infected RSA patients while SOD1 was found to be downregulated. Increased concentration of oxidative stress biomarkers 8-hydroxyguanosine and 8-isoprostane was found in C. trachomatis-infected RSA patients. Protein–protein interaction (PPI) of SOD proteins and its interacting partners viz.; CCS, GPX1, GPX2, GPX3, GPX4, GPX5, GPX7, GPX8, CAT, PRDX1, TXN, SIRT3, FOXO3, and AKT1 were found to be involved in MAPK, p53 and foxo signaling pathways. Molecular pathways involved in association with SODs indicate reactive oxygen species (ROS) detoxification, apoptotic pathways and cell cycle regulation. Overall data revealed alleviated levels of SOD2 gene and decreased expression of SOD1 gene in response to C. trachomatis-infection leading to production of oxidative stress and RSA.

Mixtures of natural antimicrobials can reduce Campylobacter jejuni, Salmonella enterica and Clostridium perfringens infections and cellular inflammatory response in MDCK cells

Background

The classification of natural antimicrobials as potential antibiotic replacements is still hampered by the absence of clear biological mechanisms behind their mode of action. This study investigated the mechanisms underlying the anti-bacterial effect of a mixture of natural antimicrobials (maltodextrin, citric acid, sodium citrate, malic acid, citrus extract and olive extract) against Campylobacter jejuni RC039, Salmonella enterica SE 10/72 and Clostridium perfringens ATCC® 13124 invasion of Madin–Darby Canine Kidney cells (MDCK).

Results

Minimum sub-inhibitory concentrations were determined for Campylobacter jejuni (0.25%), Salmonella enterica (0.50%) and Clostridium perfringens (0.50%) required for the in vitro infection assays with MDCK cells. The antimicrobial mixture significantly reduced the virulence of all three pathogens towards MDCK cells and restored the integrity of cellular tight junctions through increased transepithelial resistance (TEER) and higher expression levels of ZO-1 (zonula occludens 1) and occludin. This study also identified the ERK (external regulated kinase) signalling pathway as a key mechanism in blocking the pro-inflammatory cytokine production (IL-1β, IL-6, IL-8, TNF-α) in infected cells. The reduction in hydrogen peroxide (H₂O₂) production and release by infected MDCK cells, in the presence of the antimicrobial mixture, was also associated with less tetrathionate formed by oxidation of thiosulphate (p < 0.0001).

Conclusion

The present study describes for the first time that mixtures of natural antimicrobials can prevent the formation of substrates used by bacterial pathogens to grow and survive in anaerobic environments (e.g. tetrathionate). Moreover, we provide further insights into pathogen invasion mechanisms through restoration of cellular structures and describe their ability to block the ERK–MAPK kinase pathway responsible for inflammatory cytokine release

Chlamydia trachomatis glycogen synthase promotes MAPK-mediated proinflammatory cytokine production via TLR2/TLR4 in THP-1 cells

AIMS

To investigate the roles and mechanisms of C. trachomatis glycogen synthase (GlgA) in regulating the inflammatory response in THP-1 cells.

MAIN METHODS

In this work, after THP-1 cells were stimulated with GlgA, transcript and protein expression levels were measured by qRT-PCR and ELISA, respectively. Western blotting and immunofluorescence were used to determine the signaling pathway involved in the inflammatory mechanism.

KEY FINDINGS

GlgA elicited the expression of interleukin-8 (IL-8), interleukin-1beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in THP-1 cells, and the blockade of TLR2 and TLR4 signaling abrogated the induction of IL-8, TNF-α and IL-1β expression. Similarly, IL-8, IL-1β and TNF-α secretion was reduced by transfection with a dominant negative plasmid (pDeNyhMyD88). Moreover, Western blotting and immunofluorescence experiments further validated that MAPKs and NF-кB signaling are involved in the transcription and translation of these cytokines. Treatment of the cells with ERK and JNK inhibitors dramatically attenuated the induction of IL-8, IL-1β and TNF-α.

SIGNIFICANCE

These results suggest that GlgA contributes to inflammation during C. trachomatis infection via the TLR2, TLR4 and MAPK/NF-кB pathways, which may enhance our understanding of the pathogenesis of C. trachomatis.

Host cell response and distinct gene expression profiles at different stages of Chlamydia trachomatis infection reveals stage-specific biomarkers of infection

Background

Chlamydia trachomatis is the most common sexually transmitted infection and the bacterial agent of trachoma globally. C. trachomatis undergoes a biphasic developmental cycle involving an infectious elementary body and a replicative reticulate body. Little is currently known about the gene expression dynamics of host cell mRNAs, lncRNAs, and miRNAs at different stages of C. trachomatis development.

Results

Here, we performed RNA-seq and miR-seq on HeLa cells infected with C. trachomatis serovar E at 20 h post-infection (hpi) and 44 hpi with or without IFN-γ treatment. Our study identified and validated differentially expressed host cell mRNAs, lncRNAs, and miRNAs during infection. Host cells at 20 hpi showed the most differential upregulation of both coding and non-coding genes while at 44 hpi in the presence of IFN-γ resulted in a dramatic downregulation of a large proportion of host genes. Using RT-qPCR, we validated the top 5 upregulated mRNAs and miRNAs, which are specific for different stages of C. trachomatis development. One of the commonly expressed miRNAs at all three stages of C. trachomatis development, miR-193b-5p, showed significant expression in clinical serum samples of C. trachomatis-infected patients as compared to sera from healthy controls and HIV-1-infected patients. Furthermore, we observed significant upregulation of antigen processing and presentation, and T helper cell differentiation pathways at 20 hpi whereas T cell receptor, mTOR, and Rap1 pathways were modulated at 44 hpi. Treatment with IFN-γ at 44 hpi showed the upregulation of cytokine-cytokine receptor interaction, FoxO signaling, and Ras signaling pathways.

Conclusions

Our study documented transcriptional manipulation of the host cell genomes and the upregulation of stage-specific signaling pathways necessary for the survival of the pathogen and could serve as potential biomarkers in the diagnosis and management of the disease.

Hijacking and Use of Host Kinases by Chlamydiae

Chlamydia species are causative agents of sexually transmitted infections, blinding trachoma, and animal infections with zoonotic potential. Being an obligate intracellular pathogen, Chlamydia relies on the host cell for its survival and development, subverting various host cell processes throughout the infection cycle. A key subset of host proteins utilized by Chlamydia include an assortment of host kinase signaling networks which are vital for many chlamydial processes including entry, nutrient acquisition, and suppression of host cell apoptosis. In this review, we summarize the recent advancements in our understanding of host kinase subversion by Chlamydia.

Serine protease inhibitor MDSPI16 ameliorates LPS-induced acute lung injury through its anti-inflammatory activity

A previous study described a novel serine protease inhibitor 16 from Musca domestica (MDSPI16), which inhibited the elastase and chymotrypsin. It also exhibited a potential anti-inflammatory activity for acute lung injury (ALI), while its effects on ALI are yet to be elucidated. The present study aimed to investigate the effects and the underlying mechanisms of MDSPI16 on lipopolysaccharide (LPS)-challenged mice and bone marrow neutrophils. The ALI model based on the results of LPS-induced mice demonstrated that MDSPI16 markedly reduced the infiltration of inflammatory cells, protein exudation in lung tissues, and downregulated the level of interleukin-6 (IL-6), IL-1β and tumor necrosis factor-α (TNF-α). Furthermore, the LPS-stimulated mouse bone marrow neutrophils model was employed to determine the role of MDSPI16. The cytokine levels were quantified by both the enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR). Consequently, the expression of IL-6, IL-1β, and TNF-α was found to be inhibited by MDSPI16 in a dose-dependent manner. Moreover, MDSPI16 also inhibited the mouse neutrophils nuclear factor-κB (NF-κB) signaling pathway, c-Jun N-terminal kinase (JNK) signaling pathway, ERK1/2 and AP-1 signaling pathway in addition to the expression of iNOS and COX-2 proteins, which in turn, might alleviate the release of pro-inflammatory cytokines during ALI. Therefore, MDSPI16 could be proposed as a potential and novel drug therapy for ALI.

Iminosugar idoBR1 Isolated from Cucumber Cucumis sativus Reduces Inflammatory Activity

Cucumbers have been anecdotally claimed to have anti-inflammatory activity for a long time, but the active principle was not identified. idoBR1, (2R,3R,4R,5S)-3,4,5-trihydroxypiperidine-2-carboxylic acid, is an iminosugar amino acid isolated from fruits of certain cucumbers, Cucumis sativus (Cucurbitaceae). It has no chromophore and analytically behaves like an amino acid making detection and identification difficult. It has anti-inflammatory activity reducing lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-α) in THP-1 cells and ex vivo human blood. It showed selective inhibition of human α-l-iduronidase and sialidases from both bacteria (Tannerella forsythia) and human THP-1 cells. idoBR1 and cucumber extract reduced the binding of hyaluronic acid (HA) to CD44 in LPS-stimulated THP-1 cells and may function as an anti-inflammatory agent by inhibiting induced sialidase involved in the production of functionally active HA adhesive CD44. Similar to the related iminosugars, idoBR1 is excreted unchanged in urine following consumption. Its importance in the diet should be further evaluated.

Water-filtered Infrared A and visible light (wIRA/VIS) treatment reduces Chlamydia caviae-induced ocular inflammation and infectious load in a Guinea pig model of inclusion conjunctivitis

Trachoma is a devastating neglected tropical disease caused by Chlamydia trachomatis and the leading global cause of infectious blindness. Although antibiotic treatment against trachoma is efficient (SAFE strategy), additional affordable therapeutic strategies are of high interest. Water-filtered infrared A and visible light (wIRA/VIS) irradiation has proven to reduce chlamydial infectivity in vitro and ex vivo. The aim of this study was to evaluate whether wIRA/VIS can reduce chlamydial infection load and/or ocular pathology in vivo, in a guinea pig model of inclusion conjunctivitis. Guinea pigs were infected with 1 × 10⁶ inclusion-forming units/eye of Chlamydia caviae via the ocular conjunctiva on day 0. In infected animals, wIRA/VIS irradiation (2100 W/m²) was applied on day 2 (single treatment) and on days 2 and 4 (double treatment) post-infection (pi). wIRA/VIS reduced the clinical pathology score on days 7 and 14 pi and the conjunctival chlamydial load on days 2, 4, 7, and 14 pi in comparison with C. caviae-infected, not irradiated, controls. Furthermore, numbers of chlamydial inclusions were decreased in wIRA/VIS treated C. caviae-infected guinea pigs on day 21 pi compared to C. caviae-infected, non-irradiated, controls. Double treatment with wIRA/VIS (days 2 and 4 pi) was more efficient than a single treatment on day 2 pi. wIRA/VIS treatment did neither induce macroscopic nor histologic changes in ocular tissues. Our results indicate that wIRA/VIS shows promising efficacy to reduce chlamydial infectivity in vivo without causing irradiation related pathologies in the follow-up period. wIRA/VIS irradiation is a promising approach to reduce trachoma transmission and pathology of ocular chlamydial infection.

Integrated Phosphoproteome and Transcriptome Analysis Reveals Chlamydia-Induced Epithelial-to-Mesenchymal Transition in Host Cells

Chlamydia trachomatis (Ctr) causes a range of infectious diseases and is epidemiologically associated with cervical and ovarian cancers. To obtain a panoramic view of Ctr-induced signaling, we performed global phosphoproteomic and transcriptomic analyses. We identified numerous Ctr phosphoproteins and Ctr-regulated host phosphoproteins. Bioinformatics analysis revealed that these proteins were predominantly related to transcription regulation, cellular growth, proliferation, and cytoskeleton organization. In silico kinase substrate motif analysis revealed that MAPK and CDK were the most overrepresented upstream kinases for upregulated phosphosites. Several of the regulated host phosphoproteins were transcription factors, including ETS1 and ERF, that are downstream targets of MAPK. Functional analysis of phosphoproteome and transcriptome data confirmed their involvement in epithelial-to-mesenchymal transition (EMT), a phenotype that was validated in infected cells, along with the essential role of ERK1/2, ETS1, and ERF for Ctr replication. Our data reveal the extent of Ctr-induced signaling and provide insights into its pro-carcinogenic potential.

Intracerebral Hemorrhage Induces Inflammatory Gene Expression in Peripheral Blood: Global Transcriptional Profiling in Intracerebral Hemorrhage Patients

To perform global transcriptome profiling using RNA-seq in the peripheral blood of intracerebral hemorrhage (ICH) patients. In 11 patients with ICH, peripheral blood was collected within 24 h of symptom onset or last known well, and a second blood draw occurred 72 h (±6) after the first. RNA-seq identified differentially expressed genes (DEGs) between the first and second samples. Biological pathway enrichment analysis was performed with Ingenuity® Pathway Analysis (IPA). A total of 16,640 genes were identified and 218 were significant DEGs after ICH (false discovery rate <0.1). IPA identified 97 disease and functional categories that were significantly upregulated (z-score >2) post-ICH; 46 categories were specifically related to immune cell activation, 22 to general cellular activation processes, and 4 to other inflammation-related responses. In the canonical pathway and network analysis, inflammatory mediators of particular importance included interleukin-8, NF-κB, ERK1/2, and members of the integrin class. ICH induced peripheral blood gene expression at 72 to 96 h compared with 0 to 24 h from symptom onset. DEGs that were highly expressed included those related to inflammation and activation of the immune response. Further research is needed to determine whether these changes affect outcomes and may represent new therapeutic targets.

Intracerebral hemorrhage induces monocyte-related gene expression within six hours: Global transcriptional profiling in swine ICH

Intracerebral hemorrhage (ICH) is a severe neurological disorder with no proven treatment. Our prior research identified a significant association with monocyte level and ICH mortality. To advance our understanding, we sought to identify gene expression after ICH using a swine model to test the hypothesis that ICH would induce peripheral blood mononuclear cell (PBMC) gene expression. In 10 pigs with ICH, two PBMC samples were drawn from each with the first immediately prior to ICH induction and the second six hours later. RNA-seq was performed with subsequent bioinformatics analysis using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Ingenuity® Pathway Analysis (IPA). There were 182 significantly upregulated and 153 significantly down-regulated differentially expressed genes (DEGs) after ICH. Consistent with findings in humans, significant GO and KEGG pathways were primarily related to inflammation and the immune response. Five genes, all upregulated post-ICH and known to be associated with monocyte activation, were repeatedly DEGs in the significant KEGG pathways: CD14, TLR4, CXCL8, IL-18, and CXCL2. In IPA, the majority of upregulated disease/function categories were related to inflammation and immune cell activation. TNF and LPS were the most significantly activated upstream regulators, and ERK was the most highly connected node in the top network. ICH induced changes in PBMC gene expression within 6 h of onset related to inflammation, the immune response, and, more specifically, monocyte activation. Further research is needed to determine if these changes affect outcomes and may represent new therapeutic targets.

Infection of HeLa cells with Chlamydia trachomatis inhibits protein synthesis and causes multiple changes to host cell pathways

The obligate intracellular bacterium Chlamydia trachomatis replicates in a cytosolic vacuole in human epithelial cells. Infection of human cells with C. trachomatis causes substantial changes to many host cell-signalling pathways, but the molecular basis of such influence is not well understood. Studies of gene transcription of the infected cell have shown altered transcription of many host cell genes, indicating a transcriptional response of the host cell to the infection. We here describe that infection of HeLa cells with C. trachomatis as well as infection of murine cells with Chlamydia muridarum substantially inhibits protein synthesis of the infected host cell. This inhibition was accompanied by changes to the ribosomal profile of the infected cell indicative of a block of translation initiation, most likely as part of a stress response. The Chlamydia protease-like activity factor (CPAF) also reduced protein synthesis in uninfected cells, although CPAF-deficient C. trachomatis showed no defect in this respect. Analysis of polysomal mRNA as a proxy of actively transcribed mRNA identified a number of biological processes differentially affected by chlamydial infection. Mapping of differentially regulated genes onto a protein interaction network identified nodes of up- and down-regulated networks during chlamydial infection. Proteomic analysis of protein synthesis further suggested translational regulation of host cell functions by chlamydial infection. These results demonstrate reprogramming of the host cell during chlamydial infection through the alteration of protein synthesis.

Localization and characterization of a putative cysteine desulfurase in Chlamydia psittaci

Chlamydia psittaci is an obligate intracellular pathogen with a biphasic developmental life cycle. It is auxotrophic for a variety of essential metabolites and obtains amino acids from eukaryotic host cells. Chlamydia can develop inside host cells within chlamydial inclusions. A pathway secreting proteins from inclusions into the host cellular cytoplasm is the type III secretion system (T3SS). The T3SS is universal among several Gram-negative bacteria. Here, we show that CPSIT_0959 of C. psittaci is expressed midcycle and secreted into the infected cellular cytoplasm via the T3SS. Recombinant CPSIT_0959 possesses cysteine desulfurase and PLP-binding activity, which removes sulfur from cysteine to produce alanine, and helps chlamydial replication. Our study shows that CPSIT_0959 improve the infectivity of offspring elementary bodies and seems to promote the replication by its product. This phenomenon has inhibited by the PLP-dependent enzymes inhibitor. Moreover, CPSIT_0959 increased expression of Bim and tBid, and decreased the mitochondrial membrane potential of host mitochondria to induce apoptosis in the latecycle for release of offspring. These results demonstrate that CPSIT_0959 has cysteine desulfurase and PLP-binding activity and is likely to contribute to apoptosis of the infected cells via a mitochondria-mediated pathway to improve the infectivity of progeny.

Orchestration of the mammalian host cell glucose transporter proteins-1 and 3 by Chlamydia contributes to intracellular growth and infectivity

Chlamydia are gram-negative obligate intracellular bacteria that replicate within a discrete cellular vacuole, called an inclusion. Although it is known that Chlamydia require essential nutrients from host cells to support their intracellular growth, the molecular mechanisms for acquiring these macromolecules remain uncharacterized. In the present study, it was found that the expression of mammalian cell glucose transporter proteins 1 (GLUT1) and glucose transporter proteins 3 (GLUT3) were up-regulated during chlamydial infection. Up-regulation was dependent on bacterial protein synthesis and Chlamydia-induced MAPK kinase activation. GLUT1, but not GLUT3, was observed in close proximity to the inclusion membrane throughout the chlamydial developmental cycle. The proximity of GLUT1 to the inclusion was dependent on a brefeldin A-sensitive pathway. Knockdown of GLUT1 and GLUT3 with specific siRNA significantly impaired chlamydial development and infectivity. It was discovered that the GLUT1 protein was stabilized during infection by inhibition of host-dependent ubiquitination of GLUT1, and this effect was associated with the chlamydial deubiquitinase effector protein CT868. This report demonstrates that Chlamydia exploits host-derived transporter proteins altering their expression, turnover and localization. Consequently, host cell transporter proteins are manipulated during infection as a transport system to fulfill the carbon source requirements for Chlamydia.

Chlamydia trachomatis paralyses neutrophils to evade the host innate immune response

Chlamydia trachomatis, an obligate intracellular human pathogen, is a major cause of sexually transmitted diseases. Infections often occur without symptoms, a feature that has been attributed to the ability of the pathogen to evade the host immune response. We show here that C. trachomatis paralyses the host immune system by preventing the activation of polymorphic nuclear leukocytes (PMNs). PMNs infected with Chlamydia fail to produce neutrophil extracellular traps and the bacteria are able to survive in PMNs for extended periods of time. We have identified the secreted chlamydial protease-like activating factor (CPAF) as an effector mediating the evasion of the innate immune response since CPAF-deficient Chlamydia activate PMNs and are subsequently efficiently killed. CPAF suppresses the oxidative burst and interferes with chemical-mediated activation of neutrophils. We identified formyl peptide receptor 2 (FPR2) as a target of CPAF. FPR2 is cleaved by CPAF and released from the surface of PMNs. In contrast to previously described subversion mechanisms that mainly act on already activated PMNs, we describe here details of how Chlamydia actively paralyses PMNs, including the formation of neutrophil extracellular traps, to evade the host's innate immune response.

Lactobacilli-lactoferrin interplay in Chlamydia trachomatis infection

In the cervicovaginal microenvironment, lactobacilli are known to protect against genital infections and, amongst the host defence compounds, lactoferrin has recently acquired importance for its anti-microbial and anti-inflammatory properties. An abnormal genital microenvironment facilitates the acquisition of pathogens like Chlamydia trachomatis, the leading cause of bacterial sexually transmitted infections worldwide. The aim of our study is to investigate the effects of Lactobacillus crispatus, Lactobacillus brevis and bovine lactoferrin on chlamydial infection, in order to shed light on the complex interplay between host defence mechanisms and C. trachomatis. We have also evaluated the effect of these defence factors to modulate the chlamydia-mediated inflammatory state. To this purpose, we have determined the infectivity and progeny production of C. trachomatis as well as interleukin-8 and interleukin-6 synthesis. The main result of our study is that the combination of L. brevis and bovine lactoferrin is the most effective in inhibiting the early phases (adhesion and invasion) of C. trachomatis infection of cervical epithelial cells and in decreasing the levels of both cytokines. In conclusion, the interaction between L. brevis and lactoferrin seems to play a role in the protection against C. trachomatis, reducing the infection and regulating the immunomodulatory activity, thus decreasing the risk of severe complications.

Chlamydia trachomatis inhibits the production of pro-inflammatory cytokines in human PBMCs through induction of IL-10

PURPOSE

Previous research demonstrated that IL-10 was up-regulated in Chlamydia trachomatis-infected cells and that exogenous IL-10 was able to inhibit the secretion of pro-inflammatory cytokines by infected cells. However, the mechanisms are not well understood. The aim of this study was to investigate the mechanisms for up-regulation of IL-10 and inhibition of pro-inflammatory cytokine secretion in C. trachomatis-stimulated peripheral blood mononuclear cells (PBMCs).

METHODOLOGY

Human PBMCs were isolated from the blood of healthy human donors by standard Ficoll-Hypaque density gradient centrifugation. Cells were exposed to C. trachomatis in the presence or absence of MEK inhibitor U0126, the p38 inhibitor SB203580, the STAT3 inhibitor Ruxolitinib or anti-human IL-10 antibody. Cytokines were measured from culture supernatants using ELISA kits. Cells were harvested for real-time quantitative PCR to determine IL-10 mRNA levels and for Western blot assay to detect the expression of ERK1/2, p-ERK1/2, p38, p-p38, STAT3 and p-STAT3.

RESULTS

Both mRNA and protein levels of IL-10 were up-regulated in stimulated cells, and the production of IL-10 was reduced when cells were treated with U0126 or SB203580. The expression of cytokines IL-6, IL-8 and TNF-α was enhanced in stimulated cells treated with anti-human IL-10 antibody. Moreover, neutralization of IL-10 resulted in a significant decrease of phosphorylated STAT3 in stimulated cells. Ruxolitinib caused a significant increase in the production of IL-6, IL-8 and TNF-α in stimulated cells.

CONCLUSION

IL-10 is up-regulated in an ERK- and p38-dependent fashion in stimulated human PBMCs. IL-10 inhibits the production of pro-inflammatory cytokines by activating the JAK/STAT signalling pathway.

P2Y6 receptors are involved in mediating the effect of inactivated avian influenza virus H5N1 on IL-6 & CXCL8 mRNA expression in respiratory epithelium

One of the key pathophysiologies of H5N1 infection is excessive proinflammatory cytokine response (cytokine storm) characterized by increases in IFN-β, TNF-α, IL-6, CXCL10, CCL4, CCL2 and CCL5 in the respiratory tract. H5N1-induced cytokine release can occur via an infection-independent mechanism, however, detail of the cellular signaling involved is poorly understood. To elucidate this mechanism, the effect of inactivated (β-propiolactone-treated) H5N1 on the cytokine and chemokine mRNA expression in 16HBE14o- human respiratory epithelial cells was investigated. We found that the inactivated-H5N1 increased mRNA for IL-6 and CXCL8 but not TNF-α, CCL5 or CXCL10. This effect of the inactivated-H5N1 was inhibited by sialic acid receptor inhibitor (α-2,3 sialidase), adenosine diphosphatase (apyrase), P2Y receptor (P2YR) inhibitor (suramin), P2Y6R antagonist (MRS2578), phospholipase C inhibitor (U73122), protein kinase C inhibitors (BIM and Gö6976) and cell-permeant Ca2+ chelator (BAPTA-AM). Inhibitors of MAPK signaling, including of ERK1/2 (PD98059), p38 MAPK (SB203580) and JNK (SP600125) significantly suppressed the inactivated-H5N1-induced mRNA expression of CXCL8. On the other hand, the inactivated-H5N1-induced mRNA expression of IL-6 was inhibited by SB203580, but not PD98059 or SP600125, whereas SN-50, an inhibitor of NF-κB, inhibited the effect of virus on mRNA expression of both of IL-6 and CXCL8. Taken together, our data suggest that, without infection, inactivated-H5N1 induces mRNA expression of IL-6 and CXCL8 by a mechanism, or mechanisms, requiring interaction between viral hemagglutinin and α-2,3 sialic acid receptors at the cell membrane of host cells, and involves activation of P2Y6 purinergic receptors.

MAPK Activation Is Essential for Waddlia chondrophila Induced CXCL8 Expression in Human Epithelial Cells

Background

Waddlia chondrophila (W. chondrophila) is an emerging agent of respiratory and reproductive disease in humans and cattle. The organism is a member of the order Chlamydiales, and shares many similarities at the genome level and in growth studies with other well-characterised zoonotic chlamydial agents, such as Chlamydia abortus (C. abortus). The current study investigated the growth characteristics and innate immune responses of human and ruminant epithelial cells in response to infection with W. chondrophila.

Methods

Human epithelial cells (HEp2) were infected with W. chondrophila for 24h. CXCL8 release was significantly elevated in each of the cell lines by active-infection with live W. chondrophila, but not by exposure to UV-killed organisms. Inhibition of either p38 or p42/44 MAPK significantly inhibited the stimulation of CXCL8 release in each of the cell lines. To determine the pattern recognition receptor through which CXCL8 release was stimulated, wild-type HEK293 cells which express no TLR2, TLR4, NOD2 and only negligible NOD1 were infected with live organisms. A significant increase in CXCL8 was observed.

Conclusions/Significance

W. chondrophila actively infects and replicates within both human and ruminant epithelial cells stimulating CXCL8 release. Release of CXCL8 is significantly inhibited by inhibition of either p38 or p42/44 MAPK indicating a role for this pathway in the innate immune response to W. chondrophila infection. W. chondrophila stimulation of CXCL8 secretion in HEK293 cells indicates that TLR2, TLR4, NOD2 and NOD1 receptors are not essential to the innate immune response to infection.

Subversion of Cell-Autonomous Host Defense by Chlamydia Infection

Obligate intracellular bacteria entirely depend on the metabolites of their host cell for survival and generation of progeny. Due to their lifestyle inside a eukaryotic cell and the lack of any extracellular niche, they have to perfectly adapt to compartmentalized intracellular environment of the host cell and counteract the numerous defense strategies intrinsically present in all eukaryotic cells. This so-called cell-autonomous defense is present in all cell types encountering Chlamydia infection and is in addition closely linked to the cellular innate immune defense of the mammalian host. Cell type and chlamydial species-restricted mechanisms point a long-term evolutionary adaptation that builds the basis of the currently observed host and cell-type tropism among different Chlamydia species. This review will summarize the current knowledge on the strategies pathogenic Chlamydia species have developed to subvert and overcome the multiple mechanisms by which eukaryotic cells defend themselves against intracellular pathogens.

Chlamydia muridarum infection of macrophages elicits bactericidal nitric oxide production via reactive oxygen species and cathepsin B

The ability of certain species of Chlamydia to inhibit the biogenesis of phagolysosomes permits their survival and replication within macrophages. The survival of macrophage-adapted chlamydiae correlates with the multiplicity of infection (MOI), and optimal chlamydial growth occurs in macrophages infected at an MOI of ≤1. In this study, we examined the replicative capacity of Chlamydia muridarum in the RAW 264.7 murine macrophage cell line at different MOIs. C. muridarum productively infected these macrophages at low MOIs but yielded few viable elementary bodies (EBs) when macrophages were infected at a moderate (10) or high (100) MOI. While high MOIs caused cytotoxicity and irreversible host cell death, macrophages infected at a moderate MOI did not show signs of cytotoxicity until late in the infectious cycle. Inhibition of host protein synthesis rescued C. muridarum in macrophages infected at a moderate MOI, implying that chlamydial growth was blocked by activated defense mechanisms. Conditioned medium from these macrophages was antichlamydial and contained elevated levels of interleukin 1β (IL-1β), IL-6, IL-10, and beta interferon (IFN-β). Macrophage activation depended on Toll-like receptor 2 (TLR2) signaling, and cytokine production required live, transcriptionally active chlamydiae. A hydroxyl radical scavenger and inhibitors of inducible nitric oxide synthase (iNOS) and cathepsin B also reversed chlamydial killing. High levels of reactive oxygen species (ROS) led to an increase in cathepsin B activity, and pharmacological inhibition of ROS and cathepsin B reduced iNOS expression. Our data demonstrate that MOI-dependent TLR2 activation of macrophages results in iNOS induction via a novel ROS- and cathepsin-dependent mechanism to facilitate C. muridarum clearance.

Diversity of Cervicovaginal Cytokine Response to Incident Chlamydia trachomatis Infection Among a Prospective Cohort of Young Women

PROBLEM

Animal, in vitro, and ex vivo studies have identified several cytokines involved in host immunity to genital Chlamydia trachomatis (CT) infection. However, in vivo cytokine responses are not well described. Our objectives were to document cervicovaginal cytokine levels and intrawoman cytokine changes during incident CT in a prospective cohort.

METHODS

From our prospective cohort, 62 women had incident CT, comprising a CT-negative visit followed by a CT-positive visit. At these visits, cytokine protein levels (IL-6, IL-8, IL-1α, IL-1β, MIP-1α, RANTES, IFN-γ) were measured using cervicovaginal lavages and the MILLIPLEX(™) /Luminex(®) multiplex assay. Quartiles were defined for each cytokine from all 124 visits.

RESULTS

At the group level, RANTES was higher (P < 0.01) at the CT-positive visit than at baseline, but the other cytokines did not significantly differ. For intrawoman cytokine changes, women with a cytokine level that increased at least one quartile higher (going from baseline to the CT-positive visit) ranged between 26 and 53%. Women with a cytokine level staying in the same quartile ranged between 32 and 48%. Women with a cytokine level that decreased at least one quartile lower ranged between 15 and 37%.

CONCLUSION

Intrawoman cervicovaginal cytokine changes during incident CT appear heterogeneous and may reflect differences in natural host immunity.

Progesterone antagonizes the positive influence of estrogen on Chlamydia trachomatis serovar E in an Ishikawa/SHT-290 co-culture model

Studies indicate that estrogen enhances Chlamydia trachomatis serovar E infection in genital epithelial cells. Hormones have direct and indirect effects on endometrial epithelial cells. Estrogen and progesterone exposure induces endometrial stromal cells to release effectors that subsequently regulate growth and maturation of uterine epithelial cells. Estrogen enhances C. trachomatis infection by aiding entry and intracellular development in endometrial epithelial cell (Ishikawa, IK)/SHT-290 stromal cell co-culture. Enhanced chlamydial infection was mediated by direct estrogen-stimulated signaling events in epithelial cells and indirectly via estrogen-induced stromal cell effectors. The current study investigates the effects of hormones on chlamydial development using culture conditions representative of the menstrual cycle. Chlamydia trachomatis-infected IK or IK/SHT-290 cultures were exposed to 10(-8) M estrogen (E2), 10(-7) M progesterone (P4) or a combination of both hormones (10(-8) M E2 followed by 10(-9) M E2/10(-7) M P4). Chlamydial infectivity and progeny production were significantly decreased (30-66%) in cultures exposed to progesterone or estrogen/progesterone combination compared to estrogen alone. Thus, progesterone antagonized the positive effects of estrogen on chlamydial infection. These data indicate the susceptibility of endometrial epithelial cells to C. trachomatis infection during the menstrual cycle is altered by phase specific actions of sex hormones in the genital tract.

The type III secretion system (T3SS) of Chlamydophila psittaci is involved in the host inflammatory response by activating the JNK/ERK signaling pathway

Chlamydophila psittaci (C. psittaci) is a human zoonotic pathogen, which could result in severe respiratory disease. In the present study, we investigated the role and mechanism of the type III secretion system (T3SS) of C. psittaci in regulating the inflammatory response in host cells. C. psittaci-infected THP-1 cells were incubated with the specific T3SS inhibitor INP0007, inhibitors of ERK, p38, or JNK, and the levels of inflammatory cytokines were analyzed using Q-PCR and ELISA. The levels of ERK, p38, and JNK phosphorylation were analyzed by Western blot. Our results verified that INP0007 inhibited chlamydial growth in vitro, but the coaddition of exogenous iron completely reversed the growth deficit. INP0007 inhibited the growth of C. psittaci and decreased the levels of IL-8, IL-6, TNF-α, and IL-1β. Exogenous iron restored the chlamydial growth but not the production of inflammatory cytokines. These results demonstrated that the expression of inflammatory cytokines during infection was associated with the T3SS which reduced by incubation with ERK and JNK inhibitors, but not with p38 inhibitor. We concluded that the T3SS elicited inflammatory responses by activating the JNK or ERK signaling pathways in the infection of C. psittaci.

Chlamydia trachomatis-induced alterations in the host cell proteome are required for intracellular growth

Intracellular pathogens directly alter host cells in order to replicate and survive. While infection-induced changes in host transcription can be readily assessed, posttranscriptional alterations are more difficult to catalog. We applied the global protein stability (GPS) platform, which assesses protein stability based on relative changes in an adjoining fluorescent tag, to identify changes in the host proteome following infection with the obligate intracellular bacteria Chlamydia trachomatis. Our results indicate that C. trachomatis profoundly remodels the host proteome independently of changes in transcription. Additionally, C. trachomatis replication depends on a subset of altered proteins, such as Pin1 and Men1, that regulate the host transcription factor AP-1 controlling host inflammation, stress, and cell survival. Furthermore, AP-1-dependent transcription is activated during infection and required for efficient Chlamydia growth. In summary, this experimental approach revealed that C. trachomatis broadly alters host proteins and can be applied to examine host-pathogen interactions and develop host-based therapeutics.

Host immune responses after hypoxic reactivation of IFN-γ induced persistent Chlamydia trachomatis infection

Genital tract infections with Chlamydia trachomatis (C. trachomatis) are the most frequent sexually transmitted disease worldwide. Severe clinical sequelae such as pelvic inflammatory disease (PID), tubal occlusion, and tubal infertility are linked to inflammatory processes of chronically infected tissues. The oxygen concentrations in the female urogenital tract are physiologically low and further diminished (0.5–5% O₂, hypoxia) during an ongoing inflammation. However, little is known about the effect of a low oxygen environment on genital C. trachomatis infections. In this study, we investigated the host immune responses during reactivation of IFN-γ induced persistent C. trachomatis infection under hypoxia. For this purpose, the activation of the MAP-kinases p44/42 and p38 as well as the induction of the pro-inflammatory cytokines IL-1β, IL-6, IL-8, and MCP-1 were analyzed. Upon hypoxic reactivation of IFN-γ induced persistent C. trachomatis infection, the phosphorylation of the p44/42 but not of the p38 MAP-kinase was significantly diminished compared to IFN-γ induced chlamydial persistence under normoxic condition. In addition, significantly reduced IL-6 and IL-8 mRNA expression levels were observed for reactivated Chlamydiae under hypoxia compared to a persistent chlamydial infection under normoxia. Our findings indicate that hypoxia not only reactivates IFN-γ induced persistent C. trachomatis infections resulting in increased bacterial growth and progeny but also dampens inflammatory host immune signaling responses that are normally observed in a normoxic environment.

Chlamydia trachomatis inhibits telomeric DNA damage signaling via transient hTERT upregulation

Epidemiological data exist to support a positive association between Chlamydia trachomatis (Ctr) infection and gynecological cancers; however, putative cellular mechanisms for this association are lacking. Here, we identified Ctr-induced perturbations to host cell phenotypes in vitro that persisted after clearance of infection and could directly contribute to host cell transformation. In particular, human telomerase catalytic subunit (hTERT) mRNA expression and catalytic subunit activity were increased in acute infected late passage IMR90E1A cells. hTERT upregulation was accompanied by recruitment of ceramide, a known regulator of hTERT, to the chlamydial inclusion and was abrogated following doxycycline-mediated infection clearance. In cells cleared of Ctr infection, average telomere length was slightly increased and immunofluorescence staining of the DNA damage marker γH2A.X was reduced after clearance of infection compared with cells that had not been infected. Reduced p53 binding to the promoter of the cell cycle checkpoint regulator p21 was also detected in cells cleared of infection and p21 levels were reduced; moreover, this cell population exhibited increased resistance to etoposide-induced DNA damage. Thus, Ctr infection altered cell aging and survival pathways, which persisted after infection clearance. Cells that survive infection are likely to exhibit altered physiology, as evidenced by an increased resistance to DNA damage-induced apoptosis, which may support cellular transformation.

Thymosin beta-4 promotes mesenchymal stem cell proliferation via an interleukin-8-dependent mechanism

Mesenchymal stem cells (MSCs) hold great promise for the field of tissue regeneration. Because only a limited number of MSCs can be obtained from each donor site, it is important to establish standard methods for MSC expansion using growth and trophic factors. Thymosin β4 (Tβ4) is a novel trophic factor that has antimicrobial effects and the potential to promote tissue repair. Tβ4 is a ubiquitous, naturally-occurring peptide in the wound bed. Therefore, the relationship between Tβ4 and MSCs, especially adjacent adipose tissue-derived stem cells (ASCs), merits consideration. Exogenous Tβ4 treatment enhanced the proliferation of human ASCs, resulting in prominent nuclear localization of PCNA immunoreactivity. In addition, exogenous Tβ4 also increased IL-8 secretion and blocking of IL-8 with neutralizing antibodies decreased Tβ4-induced ASC proliferation, suggesting that IL-8 is a critical mediator of Tβ4-enhanced proliferation. Moreover, Tβ4 activated phosphorylation of ERK1/2 and increased the nuclear translocation of NF-κB. These observation provide that Tβ4 promotes the expansion of human ASCs via an IL-8-dependent mechanism that involves the ERK and NF-κB pathways. Therefore, Tβ4 could be used as a tool for MSC expansion in cell therapeutics.

Flavonoid naringenin: a potential immunomodulator for Chlamydia trachomatis inflammation

Chlamydia trachomatis, the agent of bacterial sexually transmitted infections, can manifest itself as either acute cervicitis, pelvic inflammatory disease, or a chronic asymptomatic infection. Inflammation induced by C. trachomatis contributes greatly to the pathogenesis of disease. Here we evaluated the anti-inflammatory capacity of naringenin, a polyphenolic compound, to modulate inflammatory mediators produced by mouse J774 macrophages infected with live C. trachomatis. Infected macrophages produced a broad spectrum of inflammatory cytokines (GM-CSF, TNF, IL-1β, IL-1α, IL-6, IL-12p70, and IL-10) and chemokines (CCL4, CCL5, CXCL1, CXCL5, and CXCL10) which were downregulated by naringenin in a dose-dependent manner. Enhanced protein and mRNA gene transcript expressions of TLR2 and TLR4 in addition to the CD86 costimulatory molecule on infected macrophages were modulated by naringenin. Pathway-specific inhibition studies disclosed that p38 mitogen-activated-protein kinase (MAPK) is involved in the production of inflammatory mediators by infected macrophages. Notably, naringenin inhibited the ability of C. trachomatis to phosphorylate p38 in macrophages, suggesting a potential mechanism of its attenuation of concomitantly produced inflammatory mediators. Our data demonstrates that naringenin is an immunomodulator of inflammation triggered by C. trachomatis, which possibly may be mediated upstream by modulation of TLR2, TLR4, and CD86 receptors on infected macrophages and downstream via the p38 MAPK pathway.

Chlamydia trachomatis infection results in a modest pro-inflammatory cytokine response and a decrease in T cell chemokine secretion in human polarized endocervical epithelial cells

The endocervical epithelium is a major reservoir for Chlamydia trachomatis in women, and genital infections are extended in their duration. Epithelial cells act as mucosal sentinels by secreting cytokines and chemokines in response to pathogen challenge and infection. We therefore determined the signature cytokine and chemokine response of primary-like endocervix-derived epithelial cells in response to a common genital serovar (D) of C. trachomatis. For these studies, we used a recently-established polarized, immortalized, endocervical epithelial cell model (polA2EN) that maintains, in vitro, the architectural and functional characteristics of endocervical epithelial cells in vivo including the production of pro-inflammatory cytokines. PolA2EN cells were susceptible to C. trachomatis infection, and chlamydiae in these cells underwent a normal developmental cycle as determined by a one-step growth curve. IL1α protein levels were increased in both apical and basolateral secretions of C. trachomatis infected polA2EN cells, but this response did not occur until 72h after infection. Furthermore, protein levels of the pro-inflammatory cytokines and chemokines IL6, TNFα and CXCL8 were not significantly different between C. trachomatis infected polA2EN cells and mock infected cells at any time during the chlamydial developmental cycle up to 120h post-infection. Intriguingly, C. trachomatis infection resulted in a significant decrease in the constitutive secretion of T cell chemokines IP10 and RANTES, and this required a productive C. trachomatis infection. Examination of anti-inflammatory cytokines revealed a high constitutive apical secretion of IL1ra from polA2EN cells that was not significantly modulated by C. trachomatis infection. IL-11 was induced by C. trachomatis, although only from the basolateral membrane. These results suggest that C. trachomatis can use evasion strategies to circumvent a robust pro-inflammatory cytokine and chemokine response. These evasion strategies, together with the inherent immune repertoire of endocervical epithelial cells, may aid chlamydiae in establishing, and possibly sustaining, an intracellular niche in microenvironments of the endocervix in vivo.

Biochemical and immunological characterization of Toxoplasma gondii macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a proinflammatory molecule in mammals that, unusually for a cytokine, exhibits tautomerase and oxidoreductase enzymatic activities. Homologues of this well conserved protein are found within diverse phyla including a number of parasitic organisms. Herein, we produced recombinant histidine-tagged Toxoplasma gondii MIF (TgMIF), a 12-kDa protein that lacks oxidoreductase activity but exhibits tautomerase activity with a specific activity of 19.3 μmol/min/mg that cannot be inhibited by the human MIF inhibitor ISO-1. The crystal structure of the TgMIF homotrimer has been determined to 1.82 Å, and although it has close structural homology with mammalian MIFs, it has critical differences in the tautomerase active site that account for the different inhibitor sensitivity. We also demonstrate that TgMIF can elicit IL-8 production from human peripheral blood mononuclear cells while also activating ERK MAPK pathways in murine bone marrow-derived macrophages. TgMIF may therefore play an immunomodulatory role during T. gondii infection in mammals.

Chlamydial intracellular survival strategies

Chlamydia trachomatis is the most common sexually transmitted bacterial pathogen and the causative agent of blinding trachoma. Although Chlamydia is protected from humoral immune responses by residing within remodeled intracellular vacuoles, it still must contend with multilayered intracellular innate immune defenses deployed by its host while scavenging for nutrients. Here we provide an overview of Chlamydia biology and highlight recent findings detailing how this vacuole-bound pathogen manipulates host-cellular functions to invade host cells and maintain a replicative niche.

Lactobacillus plantarum lipoteichoic acid alleviates TNF-α-induced inflammation in the HT-29 intestinal epithelial cell line

We recently observed that lipoteichoic acid (LTA) isolated from Lactobacillus plantarum inhibited endotoxin-mediated inflammation of the immune cells and septic shock in a mouse model. Here, we examined the inhibitory role of L. plantarum LTA (pLTA) on the inflammatory responses of intestinal epithelial cells (IEC). The human colon cell line, HT-29, increased interleukin (IL)-8 expression in response to recombinant human tumor necrosis factor (TNF)-alpha, but not in response to bacterial ligands and interferon (IFN)-gamma. TNF-α also increased the production of inducible nitric oxide synthase (iNOS), nitric oxide (NO), and intercellular adhesion molecule 1 (ICAM-1) through activation of p38 mitogen-activated protein kinase (MAPK) from HT-29 cells. However, the inflammatory response of HT-29 on TNF-α stimulation was significantly inhibited by pLTA treatment. This pLTA-mediated inhibition accompanied the inhibition of nuclear factor (NF)-kappa B and MAPKs. Our data suggest that pLTA regulates cytokine-mediated immune responses and may be a good candidate for maintaining intestinal homeostasis against excessive inflammation.

Serum interleukin-1β, interleukin-8 and anti-heat shock 60 Chlamydia trachomatis antibodies as markers of ectopic pregnancy

Anti-Chlamydial trachomatis (anti-CT) responses, particularly anti-heat shock 60 (Hsp60), antibodies confer a higher risk of ectopic pregnancy. With emerging evidence supporting the pivotal role of interleukin-1β (IL-1β) and IL-8 in the immunopathogenesis of CT-specific tubal obstruction, we determined anti-CT Hsp60 antibody reactivity and serum concentrations of IL-1β and IL-8 in failed pregnancies consisting of 30 consecutive ectopic pregnancies and 30 missed abortions, with 32 viable intrauterine pregnancies tested as normal controls. ELISAs were utilised to measure IgA or IgG anti-CT major outer membrane outer protein (MOMP) antibodies, IgG anti-CT Hsp60 antibodies and IL-1β and IL-8. IgG anti-CT Hsp60 antibodies were more prevalent in ectopic pregnancy cases (43.3%, 13/30) than in intrauterine pregnancies (16%, 5/32, p=0.016). All 13 ectopic pregnancy anti-CT Hsp60-positive cases had anti-CT MOMP antibodies. CT-specific antibodies were more frequent in merged ectopic pregnancy and missed abortions cases (35%, 21/60) than in intrauterine pregnancies (16%, p=0.049). The median (range) levels of IL-1β in ectopic pregnancy, missed abortions and normal intrauterine pregnancies were 1.74 (0.2-8.7), 1.14 (0.2-16) and 1.22 (0.2-16.2) pg/ml, respectively (p>0.05, for all). Serum IL-8 levels were comparable amongst groups: ectopic pregnancy (median [range]: 25.1 [18.3-1000]); missed abortions (32.9 [15.39-1000]); and intrauterine pregnancies (25.11 [18.3-1000] pg/ml). Anti-CT antibody-positive ectopic pregnancy had significantly lower IL-1β levels (1.29 [0.2-2.93]) pg/ml than sero-negative ectopic pregnancy cases (2.09 [1.10-8.70]) pg/ml, (p=0.022), but IL-8 did not differ. Our data demonstrate that anti-CT Hsp60 immunity is a predominant feature of ectopic pregnancy. We conclude that neither IL-1β nor IL-8 can be considered markers of failed pregnancy, although lower levels of the former cytokine are associated with CT-related ectopic pregnancy.

The anti-inflammatory cytokine, interleukin-10, inhibits inflammatory mediators in human epithelial cells and mouse macrophages exposed to live and UV-inactivated Chlamydia trachomatis

Chlamydia trachomatis infects macrophages and epithelial cells evoking acute and chronic inflammatory conditions, which, if not controlled, may put patients at risk for major health issues such as pelvic inflammatory disease, chronic abdominal pain, and infertility. Here we hypothesized that IL-10, with anti-inflammatory properties, will inhibit inflammatory mediators that are produced by innate immune cells exposed to C. trachomatis. We used human epithelial (HeLa) cells and mouse J774 macrophages as target cells along with live and UV-inactivated C. trachomatis mouse pneumonitis (MoPn) as stimulants. Confocal microscopy employing an anti-Chlamydia antibody confirmed cells infectivity by day 1, which persisted up to day 3. Kinetics studies revealed that live C. trachomatis induced TNF, IL-6, and IL-8, as a function of time, with day-2 infection inducing the highest cytokine levels. Exogenous IL-10 inhibited TNF, IL-6, and IL-8 as secreted by day-2 infected cells. Similarly, IL-10 diminished cytokine levels as produced by macrophages exposed to UV-inactivated Chlamydia, suggesting the IL-10-mediated inhibition of cytokines is not restricted to live organisms. Our data imply that IL-10 is an important regulator of the initial inflammatory response to C. trachomatis infection and that further investigations be made into IL-10 use to combat inflammation induced by this bacterium.

Chlamydia trachomatis co-opts the FGF2 signaling pathway to enhance infection

The molecular details of Chlamydia trachomatis binding, entry, and spread are incompletely understood, but heparan sulfate proteoglycans (HSPGs) play a role in the initial binding steps. As cell surface HSPGs facilitate the interactions of many growth factors with their receptors, we investigated the role of HSPG-dependent growth factors in C. trachomatis infection. Here, we report a novel finding that Fibroblast Growth Factor 2 (FGF2) is necessary and sufficient to enhance C. trachomatis binding to host cells in an HSPG-dependent manner. FGF2 binds directly to elementary bodies (EBs) where it may function as a bridging molecule to facilitate interactions of EBs with the FGF receptor (FGFR) on the cell surface. Upon EB binding, FGFR is activated locally and contributes to bacterial uptake into non-phagocytic cells. We further show that C. trachomatis infection stimulates fgf2 transcription and enhances production and release of FGF2 through a pathway that requires bacterial protein synthesis and activation of the Erk1/2 signaling pathway but that is independent of FGFR activation. Intracellular replication of the bacteria results in host proteosome-mediated degradation of the high molecular weight (HMW) isoforms of FGF2 and increased amounts of the low molecular weight (LMW) isoforms, which are released upon host cell death. Finally, we demonstrate the in vivo relevance of these findings by showing that conditioned medium from C. trachomatis infected cells is enriched for LMW FGF2, accounting for its ability to enhance C. trachomatis infectivity in additional rounds of infection. Together, these results demonstrate that C. trachomatis utilizes multiple mechanisms to co-opt the host cell FGF2 pathway to enhance bacterial infection and spread.

Chlamydia trachomatis is an obligate intracellular bacterium that is an important cause of human disease, including sexually transmitted diseases and acquired blindness in developing countries. The inability to carry out conventional genetic manipulations limits our understanding of the mechanisms of C. trachomatis binding, entry, and spread. Previous studies have shown that heparan sulfate proteoglycans (HSPGs) play a role in early binding events. As cell surface HSPGs facilitate the interactions of many growth factors with their receptors, we investigated whether HSPG-associated growth factors affect C. trachomatis binding or entry. Here, we report the novel finding that Fibroblast Growth Factor 2 (FGF2), a ubiquitously expressed growth factor, enhances C. trachomatis binding to host cells in an HSPG-dependent manner. Furthermore, C. trachomatis infection stimulates production and release of FGF2 through distinct signaling pathways. Released FGF2 is sufficient to enhance the subsequent rounds of infection. Together, these results demonstrate that C. trachomatis utilizes multiple mechanisms to co-opt the host cell FGF2 pathway that sets up a positive feedback loop to enhance bacterial infection and spread.

Ehrlichia chaffeensis induces monocyte inflammatory responses through MyD88, ERK, and NF-κB but not through TRIF, interleukin-1 receptor 1 (IL-1R1)/IL-18R1, or toll-like receptors

Human monocytic ehrlichiosis, an influenza-like illness accompanied by signs of hepatitis, is caused by infection of monocytes/macrophages with a lipopolysaccharide-deficient bacterium, Ehrlichia chaffeensis. The E. chaffeensis strain Wakulla induces diffuse hepatitis with neutrophil infiltration in mice with severe combined immunodeficiency, which is accompanied by strong CXCL2 (mouse functional homolog of interleukin-8 [IL-8]) and tumor necrosis factor alpha (TNF-α) expression in the liver. In this study, we found that expression of IL-1β, CXCL2, and TNF-α was induced by strain Wakulla in mouse bone marrow-derived macrophages; this expression was dependent on MyD88, but not on TRIF, TLR2/4, IL-1R1/IL-18R1, or endosome acidification. When the human leukemia cell line THP-1 was exposed to E. chaffeensis, significant upregulation of IL-8, IL-1β, and TNF-α mRNA and extracellular regulated kinase 2 (ERK2) activation were detected. U0126 (inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2 [MEK1/2] upstream of ERK), manumycin A (Ras inhibitor), BAY43-9006 (Raf-1 inhibitor), and NS-50 (inhibitor of NF-κB nuclear translocation) inhibited the cytokine gene expression. A luciferase reporter assay using HEK293 cells, which lack Toll-like receptors (TLRs), showed activation of both the IL-8 promoter and NF-κB by E. chaffeensis. Activation of the IL-8 promoter in transfected HEK293 cells was inhibited by manumycin A, BAY43-9006, U0126, and transfection with a dominant-negative Ras mutant. These results indicate that the E. chaffeensis Wakulla strain can induce inflammatory responses through MyD88-dependent NF-κB and ERK pathways, without the involvement of TRIF and TLRs.

The functional role of reactive stroma in benign prostatic hyperplasia

The human prostate gland is one of the only internal organs that continue to enlarge throughout adulthood. The specific mechanisms that regulate this growth, as well as the pathological changes leading to the phenotype observed in the disease benign prostatic hyperplasia (BPH), are essentially unknown. Recent studies and their associated findings have made clear that many complex alterations occur, involving persistent and chronic inflammation, circulating hormonal level deregulation, and aberrant wound repair processes. BPH has been etiologically characterized as a progressive, albeit discontinuous, hyperplasia of both the glandular epithelial and the stromal cell compartments coordinately yielding an expansion of the prostate gland and clinical symptoms. Interestingly, the inflammatory and repair responses observed in BPH are also key components of general wound repair in post-natal tissues. These responses include altered expression of chemokines, cytokines, matrix remodeling factors, chronic inflammatory processes, altered immune surveillance and recognition, as well as the formation of a prototypical 'reactive' stroma, which is similar to that observed across various fibroplasias and malignancies of a variety of tissue sites. Stromal tissue, both embryonic mesenchyme and adult reactive stroma myofibroblasts, has been shown to exert potent and functional regulatory control over epithelial proliferation and differentiation as well as immunoresponsive modulation. Thus, the functional biology of a reactive stroma, within the context of an adult disease typified by epithelial and stromal aberrant hyperplasia, is critical to understand within the context of prostate disease and beyond. The mechanisms that regulate reactive stroma biology in BPH represent targets of opportunity for new therapeutic approaches that may extend to other tissue contexts. Accordingly, this review seeks to address the dissection of important factors, signaling pathways, genes, and other regulatory components that mediate the interplay between epithelium and stromal responses in BPH.

The multifaceted role of oestrogen in enhancing Chlamydia trachomatis infection in polarized human endometrial epithelial cells

The oestrogen receptor (ER) α-β+ HEC-1B and the ERα+β+ Ishikawa (IK) cell lines were investigated to dissect the effects of oestrogen exposure on several parameters of Chlamydia trachomatis infection. Antibody blockage of ERα or ERβ alone or simultaneously significantly decreased C. trachomatis infectivity (45-68%). Addition of the ERβ antagonist, tamoxifen, to IK or HEC-1B prior to or after chlamydial infection caused a 30-90% decrease in infectivity, the latter due to disrupted eukaryotic organelles. In vivo, endometrial glandular epithelial cells are stimulated by hormonally influenced stromal signals. Accordingly, chlamydial infectivity was significantly increased by 27% and 21% in IK and HEC-1B cells co-cultured with SHT-290 stromal cells exposed to oestrogen. Endometrial stromal cell/epithelial cell co-culture revealed indirect effects of oestrogen on phosphorylation of extracellular signal-regulated kinase and calcium-dependant phospholipase A2 and significantly increased production of interleukin (IL)-8 and IL-6 in both uninfected and chlamydiae-infected epithelial cells. These results indicate that oestrogen and its receptors play multiple roles in chlamydial infection: (i) membrane oestrogen receptors (mERs) aid in chlamydial entry into host cells, and (ii) mER signalling may contribute to inclusion development during infection. Additionally, enhancement of chlamydial infection is affected by hormonally influenced stromal signals in conjunction with direct oestrogen stimulation of the human epithelia.

Host Kinase Activity is Required for Coxiella burnetii Parasitophorous Vacuole Formation

Coxiella burnetii is the etiologic agent of human Q fever and targets alveolar phagocytic cells in vivo wherein the pathogen generates a phagolysosome-like parasitophorous vacuole (PV) for replication. C. burnetii displays a prolonged growth cycle, making PV maintenance critical for bacterial survival. Previous studies showed that C. burnetii mediates activation of eukaryotic kinases to inhibit cell death, indicating the importance of host signaling during infection. In the current study, we examined the role of eukaryotic kinase signaling in PV establishment. A panel of 113 inhibitors was analyzed for their impact on C. burnetii infection of human THP-1 macrophage-like cells and HeLa cells. Inhibition of 11 kinases or two phosphatases altered PV formation and prevented pathogen growth, with most inhibitor-treated cells harboring organisms in tight-fitting phagosomes, indicating kinase/phosphatase activation is required for PV maturation. Five inhibitors targeted protein kinase C (PKC), suggesting a critical role for this protein during intracellular growth. The PKC-specific substrate MARCKS was phosphorylated at 24 h post-infection and remained phosphorylated through 5 days post-infection, indicating prolonged regulation of the PKC pathway by C. burnetii. Infection also altered the activation status of p38, myosin light chain kinase, and cAMP-dependent protein kinase, suggesting C. burnetii subverts numerous phosphorylation cascades. These results underscore the importance of intracellular host signaling for C. burnetii PV biogenesis.