Differential infection outcome of Chlamydia trachomatis in human blood monocytes and monocyte-derived dendritic cells.

BACKGROUND: Chlamydia trachomatis is an intracellular bacteria which consist of three biovariants; trachoma (serovars A-C), urogenital (serovars D-K) and lymphogranuloma venereum (L1-L3), causing a wide spectrum of disease in humans. Monocytes are considered to disseminate this pathogen throughout the body while dendritic cells (DCs) play an important role in mediating immune response against bacterial infection. To determine the fate of C. trachomatis within human peripheral blood monocytes and monocyte-derived DCs, these two sets of immune cells were infected with serovars Ba, D and L2, representative of the three biovariants of C. trachomatis. RESULTS: Our study revealed that the different serovars primarily infect monocytes and DCs in a comparable fashion, however undergo differential infection outcome, serovar L2 being the only candidate to inflict active infection. Moreover, the C. trachomatis serovars Ba and D become persistent in monocytes while the serovars predominantly suffer degradation within DCs. Effects of persistence gene Indoleamine 2, 3-dioxygenase (IDO) was not clearly evident in the differential infection outcome. The heightened levels of inflammatory cytokines secreted by the chlamydial infection in DCs compared to monocytes seemed to be instrumental for this consequence. The immune genes induced in monocytes and DCs against chlamydial infection involves a different set of Toll-like receptors, indicating that distinct intracellular signalling pathways are adopted for immune response. CONCLUSION: Our results demonstrate that the host pathogen interaction in chlamydia infection is not only serovar specific but manifests cell specific features, inducing separate immune response cascade in monocytes and DCs.

Calcium Dobesilate Modulates PKCδ-NADPH Oxidase- MAPK-NF-κB Signaling Pathway to Reduce CD14, TLR4, and MMP9 Expression during Monocyte-to-Macrophage Differentiation: Potential Therapeutic Implications for Atherosclerosis.

Monocyte-to-macrophage differentiation results in the secretion of various inflammatory mediators and oxidative stress molecules necessary for atherosclerosis pathogenesis. Consequently, this differentiation represents a potential clinical target in atherosclerosis. Calcium dobesilate (CaD), an established vasoactive and angioprotective drug in experimental models of diabetic microvascular complications reduces oxidative stress and inhibits inflammation via diverse molecular targets; however, its effect on monocytes/macrophages is poorly understood. In this study, we investigated the anti-inflammatory mechanism of CaD during phorbol 12-myristate 13-acetate (PMA)-induced monocyte-to-macrophage differentiation in in vitro models of sepsis (LPS) and hyperglycemia, using THP-1 monocytic cell line. CaD significantly suppressed CD14, TLR4, and MMP9 expression and activity, lowering pro-inflammatory mediators, such as IL1ß, TNFα, and MCP-1. The effects of CaD translated through to studies on primary human macrophages. CaD inhibited reactive oxygen species (ROS) generation, PKCδ, MAPK (ERK1/2 and p38) phosphorylation, NOX2/p47phox expression, and membrane translocation. We used hydrogen peroxide (H2O2) to mimic oxidative stress, demonstrating that CaD suppressed PKCδ activation via its ROS-scavenging properties. Taken together, we demonstrate for the first time that CaD suppresses CD14, TLR4, MMP9, and signature pro-inflammatory cytokines, in human macrophages, via the downregulation of PKCδ/NADPH oxidase/ROS/MAPK/NF-κB-dependent signaling pathways. Our data present novel mechanisms of how CaD alleviates metabolic and infectious inflammation.

Correction: Calcium dobesilate reduces VEGF signaling by interfering with heparan sulfate binding site and protects from vascular complications in diabetic mice.

[This corrects the article DOI: 10.1371/journal.pone.0218494.].

Calcium dobesilate reduces VEGF signaling by interfering with heparan sulfate binding site and protects from vascular complications in diabetic mice.

Inhibiting vascular endothelial growth factor (VEGF) is a therapeutic option in diabetic microangiopathy. However, VEGF is needed at physiological concentrations to maintain glomerular integrity; complete VEGF blockade has deleterious effects on glomerular structure and function. Anti-VEGF therapy in diabetes raises the challenge of reducing VEGF-induced pathology without accelerating endothelial cell injury. Heparan sulfate (HS) act as a co-receptor for VEGF. Calcium dobesilate (CaD) is a small molecule with vasoprotective properties that has been used for the treatment of diabetic microangiopathy. Preliminary evidence suggests that CaD interferes with HS binding sites of fibroblast growth factor. We therefore tested the hypotheses that (1) CaD inhibits VEGF signaling in endothelial cells, (2) that this effect is mediated via interference between CaD and HS, and (3) that CaD ameliorates diabetic nephropathy in a streptozotocin-induced diabetic mouse model by VEGF inhibition. We found that CaD significantly inhibited VEGF165-induced endothelial cell migration, proliferation, and permeability. CaD significantly inhibited VEGF165-induced phosphorylation of VEGFR-2 and suppressed the activity of VEGFR-2 mediated signaling cascades. The effects of CaD in vitro were abrogated by heparin, suggesting the involvement of heparin-like domain in the interaction with CaD. In addition, VEGF121, an isoform which does not bind to heparin, was not inhibited by CaD. Using the proximity ligation approach, we detected inhibition of interaction in situ between HS and VEGF and between VEGF and VEGFR-2. Moreover, CaD reduced VEGF signaling in mice diabetic kidneys and ameliorated diabetic nephropathy and neuropathy, suggesting CaD as a VEGF inhibitor without the negative effects of complete VEGF blockade and therefore could be useful as a strategy in treating diabetic nephropathy.

No correlation between giant cell arteritis and Chlamydia pneumoniae infection: investigation of 189 patients by standard and improved PCR methods.

A total of 189 temporal artery biopsy samples from giant cell arteritis (GCA) patients were investigated using sensitive PCR targeting Chlamydia pneumoniae. Chlamydial DNA was detected in 17 samples, 11 of which were positive for chlamydial antigens. Our data did not reveal strong evidence that C. pneumoniae plays an important role in the pathogenesis of GCA.

Transmission of Chlamydophila pneumoniae from dendritic cells to macrophages does not require cell-to-cell contact in vitro.

Chlamydophila pneumoniae (C. pneumoniae) has been detected in macrophages (Mø) and dendritic cells (DC) in vascular diseases. To understand the importance of these cell types in C. pneumoniae infection and transmission, we infected DC and cultivated them with Mø in a coculture model system which precludes cell-to-cell contact during chlamydial infection. C. pneumoniae inside living DC were labeled and tracked with a red fluorescent ceramide dye. Subsequently, red-coloured chlamydial inclusions were detected 3 and 5 days later in cocultured Mø. Moreover, standard assays revealed infectious elementary bodies in infected DC and cocultured Mø. Assays for chlamydial gene expression indicated vital and dividing chlamydiae in both cell types. In summary, the results suggest that the transwell system employed here is a suitable model to investigate the transmission of C. pneumoniae from DC to Mø. Importantly, the observations presented demonstrate that transmission is independent of cell-to-cell contact.

Staining of Chlamydia trachomatis elementary bodies: a suitable method for identifying infected human monocytes by flow cytometry.

Persistence of Chlamydia trachomatis (C. trachomatis) in the joint is the most frequent cause of reactive arthritis following urogenital tract infection. The resulting changes of host cell antigen- and cytokine-expression are not precisely understood. We developed and evaluated a direct cytometric approach to visualize in vitro C. trachomatis-infected monocytes. Infectious elementary bodies (EBs) of C. trachomatis serovar K were labelled by incubation with 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester (CFSE). Afterwards, human peripheral blood monocytes were cultured with the CFSE-labelled EBs and analysed by flow cytometry. Real-time polymerase chain reaction (PCR) was used to demonstrate intracellular uptake and viability of CFSE-labelled C. trachomatis by the determination of gene expression. Labelling EBs with CFSE may become a valuable tool for studying the interaction between C. trachomatis and the host cell.

Pharmacological Tie2 activation in kidney transplantation.

AIM: To investigate the therapeutic potential of vasculotide (VT) - a Tie2 activating therapeutic - in kidney transplantation. METHODS: We performed a murine MHC-mismatched renal transplant model (C57Bl/6 male into Balb/c female) with 60 min cold and 30 min warm ischemia time. 500 ng VT was administered i.p. to donor mice 1 h before organ removal. In addition, recipients received 500 ng VT i.p. directly and 3 d after surgery. Survival was monitored and remaining animals were sacrificed 28 d after transplantation. In this model, we analyzed: (1) organ function; (2) Kaplan-Meier survival; (3) organ damage (periodic acid Schiff staining) via semi-quantitative scoring [0-4 (0 = no injury/inflammation to 4 = very severe injury/inflammation)]; (4) expression of renal endothelial adhesion molecules (ICAM-1) via immunofluorescence (IF) staining, immunoblotting and qPCR; (5) infiltration of inflammatory cells (IF Gr-1, F4/80); and (6) fibrosis via staining of α-smooth muscle actin (αSMA), Sirius red staining and immunoblotting of SMAD3 activation. RESULTS: Exogenous activation of Tie2 with VT resulted in diminished expression of peritubular and glomerular endothelial adhesion molecules. Consequently, infiltration of inflammatory cells (analyzed as ICAM-1, Gr-1 and F4/80 positive cells) was reduced in VT-treated mice compared to controls. Additionally, VT was protective against fibrogenesis after kidney transplantation. Trends towards lower serum creatinine (vehicle: 142 ± 17 µmol/L vs VT: 94 ± 23 µmol/L), urea (vehicle: 76 ± 5 mmol/L vs VT: 60 ± 8 mmol/L) and lactate dehydrogenase (vehicle: 1288 ± 383 iU vs VT: 870 ± 275 iU) were observed on day 6 after transplantation. Kaplan-Meier survival analysis showed improved survival rates in the VT-treated mice that did not reach statistical significance (27% vs 54%, P = 0.24, n = 11 per group). Exogenous activation of Tie2 via VT might reduce infiltration of inflammatory cells into renal tissue thereby protecting the transplant from early graft dysfunction potentially affecting long-term function. CONCLUSION: Protection of the endothelial microvasculature via the Tie2 axis in the early transplant setting might hold promise as a therapeutic target.

Restriction of Chlamydia pneumoniae replication in human dendritic cell by activation of indoleamine 2,3-dioxygenase.

Infection with Chlamydia pneumoniae, a human respiratory pathogen, has been associated with various chronic diseases such as asthma and atherosclerosis, possibly because the pathogen can exist in a persistent form. C. pneumoniae persistently infect DCs in a TNF-alpha dependent manner. The present study investigated whether C. pneumoniae infection can induce indoleamine 2,3-dioxygenase (IDO) activity in dendritic cells, and whether the restriction of chlamydial growth in the DCs by TNF-alpha is IDO dependent. Our data indicate that infection of DCs with C. pneumoniae resulted in the induction of IDO expression. Reporting on our use of anti-TNF-alpha antibody adalimumab and varying concentrations of TNF-alpha, we further demonstrate that IDO induction following infection of DCs with C. pneumoniae is TNF-alpha dependent. The anti-chlamydial activity induced by TNF-alpha and the expression of chlamydial 16S rRNA gene, euo, groEL1, ftsk and tal genes were correlated with induction of IDO. Addition of excess amounts of tryptophan to the DC cultures resulted in abrogation of the TNF-alpha-mediated chlamydial growth restriction. These findings suggest that infection of DCs by C. pneumoniae induces production of functional IDO, which subsequently causes depletion of tryptophan. This may represent a potential mechanism for DCs to restrict bacterial growth in chlamydial infections.

Identification of high- and low-virulent strains of Chlamydia pneumoniae by their characterization in a mouse pneumonia model.

Contradicting reports exist about the pathogenicity of Chlamydia pneumoniae and the severity of the respiratory disease they cause. This study aimed to clarify, in mice, our hypothesis that marked differences in virulence of well-defined C. pneumoniae strains might exist for lung infections. C57BL/6J mice were intranasally infected with equal amounts of five different, identically prepared laboratory strains of C. pneumoniae. Based on the clinical score, weight, histopathological score, the granulocyte marker-enzyme myeloperoxidase, and the amount of Chlamydiae in the lung tissue, the C. pneumoniae isolates exhibited clear differences in overall growth characteristics or clearance, and pathological potential. Thus, we could identify chlamydial strains (Kajaani-K6 and CWL-029), where mice became seriously ill, as well as a relatively low-virulent isolate (TWAR-183). Cytokine profiles also varied drastically between the five strains in extent and kinetic. Our results indicate that C. pneumoniae isolates differ markedly with regard to their interaction with the host and their pathological potential. This might also be true for the infection in humans. Because the genomic diversity of C. pneumoniae is rather small, more subtle genomic deviations account most likely for the apparent functional differences. Our results will be useful to identify additional virulence factors in the future.

In vitro neutralization of tumor necrosis factor-alpha during Chlamydia pneumoniae infection impairs dendritic cells maturation/function and increases chlamydial progeny.

Dendritic cells (DCs) produce tumor necrosis factor (TNF)-alpha upon infection and contribute in various ways to defense against pathogenic agents. Several biological agents have been designed to inhibit TNF-alpha activity. However, the use of these inhibitors has been associated with an increased rate of certain opportunistic infections. To study the effect of TNF-alpha inhibition, human monocyte-derived DCs were infected with Chlamydia pneumoniae. TNF-alpha was neutralized by adalimumab, a human anti-TNF-alpha monoclonal antibody. Chlamydiae induced the maturation of DC as determined by flow cytometry and quantitative real-time PCR. However, DC maturation was impaired in the presence of adalimumab. Moreover, neutralization of TNF-alpha resulted in a significant increase of infectious progeny, 16S rRNA gene copy number and development of larger inclusions consisting of different stages of chlamydial development. Additionally, chlamydial infection induced secretion of cytokines/chemokines, which were downregulated by adalimumab treatment. Our data reveal an indirect effect on maturation of DC by C. pneumoniae and that maturation is crucial for the restriction of chlamydial development. The results also demonstrate an increase in infectious progeny after TNF-alpha inhibition, suggesting a contribution of TNF-alpha produced by DCs to chlamydial growth arrest. These data suggest a possible mechanism by which TNF-alpha inhibition enhances the risk of intracellular infections.