Tumor necrosis factor alpha plays a role in the acceleration of atherosclerosis by Chlamydia pneumoniae in mice

The role of tumor necrosis factor alpha (TNF-alpha) in Chlamydia pneumoniae atherogenesis was evaluated in TNF-alpha p55 receptor-deficient C57BL/6J mice fed a high-fat/high-cholesterol diet. No acceleration of atherosclerotic lesion development was observed in infected mice compared to uninfected mice, indicating that TNF-alpha plays a role in the acceleration of atherosclerosis by C. pneumoniae.

Chlamydophila pneumoniae induces expression of toll-like receptor 4 and release of TNF-alpha and MIP-2 via an NF-kappaB pathway in rat type II pneumocytes

Background

The role of alveolar type II cells in the regulation of innate and adaptive immunity is unclear. Toll-like receptors (TLRs) have been implicated in host defense. The purpose of the present study was to investigate whether Chlamydophila pneumoniae (I) alters the expression of TLR2 and/orTLR4 in type II cells in a (II) Rho-GTPase- and (III) NF-κB-dependent pathway, subsequently (IV) leading to the production of (IV) pro-inflammatory TNF-α and MIP-2.

Methods

Isolated rat type II pneumocytes were incubated with C. pneumoniae after pre-treatment with calcium chelator BAPTA-AM, inhibitors of NF-κB (parthenolide, SN50) or with a specific inhibitor of the Rho-GTPase (mevastatin). TLR2 and TLR4 mRNA expressions were analyzed by PCR. Activation of TLR4, Rac1, RhoA protein and NF-κB was determined by Western blotting and confocal laser scan microscopy (CLSM) and TNF-α and MIP-2 release by ELISA.

Results

Type II cells constitutively expressed TLR4 and TLR2 mRNA. A prominent induction of TLR4 but not TLR2 mRNA was detected after 2 hours of incubation with C. pneumoniae. The TLR4 protein expression reached a peak at 30 min, began to decrease within 1–2 hours and peaked again at 3 hours. Incubation of cells with heat-inactivated bacteria (56°C for 30 min) significantly reduced the TLR4 expression. Treated bacteria with polymyxin B (2 μg/ml) did not alter TLR4 expression. C. pneumoniae-induced NF-κB activity was blocked by TLR4 blocking antibodies. TLR4 mRNA and protein expression were inhibited in the presence of BAPTA-AM, SN50 or parthenolide. TNF-α and MIP-2 release was increased in type II cells in response to C. pneumoniae, whereas BAPTA-AM, SN50 or parthenolide decreased the C. pneumoniae-induced TNF-α and MIP-2 release. Mevastatin inhibited C. pneumoniae-mediated Rac1, RhoA and TLR4 expression.

Conclusion

The TLR4 protein expression in rat type II cells is likely to be mediated by a heat-sensitive C. pneumoniae protein that induces a fast Ca²⁺-mediated NF-κB activity, necessary for maintenance of TLR4 expression and TNF-α and MIP-2 release through possibly Rac and Rho protein-dependent mechanism. These results indicate that type II pneumocytes play an important role in the innate pulmonary immune system and in inflammatory response mechanism of the alveolus.

Action and reaction: Chlamydophila pneumoniae proteome alteration in a persistent infection induced by iron deficiency

Chlamydophila pneumoniae is an obligate intracellular pathogen implicated in a variety of acute and chronic diseases. Long-term infections are associated with a persistent life stage, in which bacteria can stay for years. They are less accessible to antibiotic treatment but still prone to sustain an inflammatory response. Different in vitro models have been established to mimic and characterize chlamydial persistency. For C. pneumoniae and Chlamydia trachomatis, altered metabolic activities and changed antigenic profiles compared to acute infections have been reported. Most studies including transcriptome and proteome analyses describe persistency induced by IFNgamma treatment. Here, we use iron depletion of the infected cell culture that also leads into persistent infection. We describe differently regulated proteins found by subtractive proteome analysis comparing two early stages of infection with and without addition of the iron chelator deferoxamine-mesylate. While only one bacterial protein was up-regulated during iron deficiency up to 24 h post infection (p.i.), 11 were found to be up-regulated and eight to be down-regulated from 24-48 h p.i. Two down-regulated proteins could be identified by peptide mass fingerprinting as thioredoxin reductase and chromosome partitioning protein (ParB). The latter is involved in chromosome segregation. Thus, using a comparative approach we identified on a proteome level down-regulation of ParB in persistent chlamydial forms, which is in agreement with previous results describing changes in cell division and atypical altered morphology of persistent Chlamydiae.

Contact of Chlamydophila pneumoniae with type II cell triggers activation of calcium-mediated NF-κB pathway

Nuclear factor-kappa B (NF-kappa B) plays an important role in inflammation, proliferation and regulation of apoptosis. The purpose of the present study on type II cells was to investigate whether Chlamydophila pneumoniae contact induces (I) a Ca2+ release, that (II) disrupts F-actin/beta-tubulin cytoskeletal association with NF-kappa B/I kappa B alpha, leading to (III) a subsequent NF-kappa B activation. Incubation of rat type II pneumocytes with C. pneumoniae caused an intracellular calcium release within seconds. Confocal laser scanning microscopy (CLSM) revealed that bacterial contact with cell surface leads to a disappearance of the microvilli and disturbs the co-localization between F-actin and NF-kappa B (p65). Using semi-quantitative CLSM, we show that at 10-30 min I kappa B alpha was decreased and p65 or p50 was simultaneously translocated from cytoplasm to the nucleus, resulting in a 19-fold and 17-fold increase versus control cells. During this time no bacteria were internalized into type II cells. The pre-treatment of cells with BAPTA-AM inhibited C. pneumoniae-mediated calcium release. BAPTA-AM or SN50 prevented the C. pneumoniae-induced changes in F-actin cytoskeleton and inhibited NF-kappa B activation. Paclitaxel reduced C. pneumoniae-mediated changes of beta-tubulin cytoskeleton and activation of NF-kappa B. These results suggest that calcium-mediated cytoskeleton reorganization is involved in C. pneumoniae-induced NF-kappa B activation in type II cells.

Interaction between components of the type III secretion system of Chlamydiaceae

Members of the family Chlamydiaceae possess at least 13 genes, distributed throughout the chromosome, that are homologous with genes of known type III secretion systems (TTS). The aim of this study was to use putative TTS proteins of Chlamydophila pneumoniae, whose equivalents in other bacterial TTS function as chaperones, to identify interactions between chlamydial proteins. Using the BacterioMatch Two-Hybrid Vector system (Stratagene, La Jolla, Calif.), lcrH-2 and sycE, positions 1021 and 0325, respectively, from C. pneumoniae CM-1 were used as "bait" to identify target genes (positions 0324, 0705, 0708, 0808 to 0810, 1016 to 1020, and 1022) in close proximity on the chromosome. Interaction between the products of the lcrH-2 (1021) and lcrE (copN) (0324) genes was detected and confirmed by pull-down experiments and enzyme immunoassays using recombinant LcrH-2 and LcrE. As further confirmation of this interaction, the homologous genes from Chlamydia trachomatis, serovar E, and Chlamydophila psittaci, Texas turkey, were also cloned in the two-hybrid system to determine if LcrH-2 and LcrE would interact with their orthologs in other species. Consistent with their genetic relatedness, LcrH-2 from C. pneumoniae interacted with LcrE produced from the three species of Chlamydiaceae; LcrH-2 from C. psittaci reacted with LcrE from C. pneumoniae but not from C. trachomatis; and C. trachomatis LcrH-2 did not react with LcrE from the other two species. Deletions from the N and C termini of LcrE from C. pneumoniae identified the 50 C-terminal amino acids as essential for the interaction with LcrH-2. Thus, it appears that in the Chlamydiaceae TTS, LcrH-2 interacts with LcrE, and therefore it may serve as a chaperone for this protein.

Presence of Chlamydia pneumoniae DNA in the artery wall--biomarker of coronary artery disease

Many authors have shown an association between Chlamydia pneumoniae (CPn) infection and coronary artery disease (CAD). However, whether CPn infection demonstrated by CPn DNA presence in the artery wall plays an important role in pathogenesis of CAD and acute coronary events (i.e. unstable angina) remains to be elucidated. One hundred and fifteen consecutive patients with CAD (51 with unstable angina and 64 with stable angina) were compared with 52 control subjects with aortic valve disease without angiographic evidence of CAD. The presence of CPn DNA in the aortic wall was assessed with nested polymerase chain reaction (PCR), and the IgM, IgG and IgA anti-CPn titres were assessed with microimmunofluorescence test. CPn DNA presence in the artery (i.e. aortic) wall was associated with 3.7-fold increased risk of CAD (95% CI 1.2-11.3, P < 0.01); however, no statistically significant difference in CPn DNA presence was demonstrated between unstable and stable angina (17.6% vs. 25%). In the CPn DNA positive group more often than in the CPn DNA negative group, serological signs of chronic infection (55.2% vs. 27%, P = 0.004) were demonstrated, whereas no statistically significant differences were demonstrated in prevalence of either acute infection (9.3% vs. 0%) or reinfection (0% vs. 0%). In conclusion, CPn DNA presence in the artery (i.e. aortic) wall was associated with CAD, therefore may be used as a biomarker for CAD. Moreover, no statistically significant differences in CPn DNA presence in the artery wall and in serology were present between unstable and stable angina; therefore, CPn infection does not seem implicated in triggering an acute coronary event.

Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila in elderly patients with stroke (C-PEPS, M-PEPS, L-PEPS): a case-control study on the infectious burden of atypical respiratory pathogens in elderly patients with acute cerebrovascular disease

BACKGROUND AND PURPOSE

Multiple studies have suggested an association between Chlamydia pneumoniae and Mycoplasma pneumoniae infection and cardiovascular disease. We investigated whether the risk of cerebrovascular disease is associated with Legionella pneumophila infection and the aggregate number/infectious burden of these atypical respiratory pathogens.

METHODS

One hundred patients aged >65 years admitted with acute stroke or transient ischemic attack (TIA) and 87 control patients admitted concurrently with acute noncardiopulmonary, noninfective conditions were recruited prospectively. Using enzyme-linked immunosorbent assay (ELISA) kits, we previously reported the seroprevalences of C pneumoniae and M pneumoniae in these patients. We have now determined the seroprevalences of L pneumophila IgG and IgM in this cohort of patients using ELISA.

RESULTS

The seroprevalences of L pneumophila IgG and IgM were 29% (n=91) and 12% (n=81) in the stroke/TIA group and 22% (n=86) and 10% (n=72) in the controls, respectively. Using logistic regression to adjust for age, sex, hypertension, smoking, diabetes, ischemic heart disease, and ischemic ECG, the odds ratios for stroke/TIA in relation to L pneumophila IgG and IgM were 1.52 (95% CI, 0.70 to 3.28; P=0.29) and 1.49 (95% CI, 0.45 to 4.90; P=0.51), respectively. The odds ratios in relation to IgG seropositivity for 1, 2, or 3 atypical respiratory pathogens after adjustment were 3.89 (95% CI, 1.13 to 13.33), 2.00 (95% CI, 0.64 to 6.21), and 6.67 (95% CI, 1.22 to 37.04), respectively (P=0.06).

CONCLUSIONS

L pneumophila seropositivity is not significantly associated with stroke/TIA. However, the risk of stroke/TIA appears to be associated with the aggregate number of chronic infectious burden of atypical respiratory pathogens such as C pneumoniae, M pneumoniae, and L pneumophila.

High prevalence of Chlamydia pneumoniae seropositivity in Mexican patients with ischemic heart disease

BACKGROUND

Risk factors for development of atherosclerosis, such as hyperlipidemia, high blood pressure, smoking habit, and diabetes mellitus, have been identified. The possibility that infectious agents may unchain biological and biochemical reactions related to inflammation, atherogenesis, and vascular thromboses events have recently been described. Chlamydia pneumoniae has been associated with coronary artery disease in some seroepidemiology studies. Reports of this association are limited in the Latin American population; therefore, we conducted a case-control study to explore this issue in the Mexican population.

METHODS

Eighty nine patients with scintigraphic evidence of coronary artery disease compared with a control group of 105 individuals were analyzed. Serum levels of IgA, IgM, and IgG against Chlamydia pneumoniae were determined using enzyme immunoassay method in all subjects. Conventional risk factors were also analyzed.

RESULTS

High seroprevalence of IgA and IgG with no significant difference between the two groups was found. Prevalence of antibodies was as follows: IgA 56.2% (50/89 patients); IgG 66.3% (59/ 89 patients) in coronary artery disease group; IgA 56.2% (59/105 patients), and IgG 70.5% (74/105 patients) in control group. Among common risk factors for coronary artery disease, significant differences were found in males, in patients with diabetes, and in habitual smokers.

CONCLUSIONS

These results suggest a high prevalence of C. pneumoniae infection in the studied population. However, in this series seroprevalence was not evidently associated with coronary artery disease (CAD). To clarify the possible relation between C. pneumoniae and coronary atherosclerosis, additional studies must be performed.

Short Communication– Presentation of differentially regulated proteins within a web-accessible proteome database system of microorganisms

Web-accessible proteome databases represent indispensable tools for quantitative and comparative proteomics research. The majority of two-dimensional gel electrophoresis (2-DE) databases contains clickable 2-DE gel images and descriptive textual information such as protein name, Mr/pI values, methods of identification, cellular localization and other information on proteins. Although a great part of the work in comparative proteomics consists of the analysis of 2-DE gels using image analysis approaches, most proteome databases lack the ability to present protein abundance data and their alterations within experiments via the web. Now, differentially regulated proteins detected in microbial experiments by quantitative gel image analysis are presented in a web-accessible relational database DIFF (Differentially Regulated Proteins). The DIFF database is a part of the proteome database system for microbial research available at http://www.mpiib-berlin.mpg.de/2D-PAGE.

Amphiphysin IIm is required for survival of Chlamydia pneumoniae in macrophages

Macrophages play a critical role in both innate and acquired immunity because of their unique ability to internalize, kill, and degrade bacterial pathogens through the process of phagocytosis. The adaptor protein, amphiphysin IIm, participates in phagocytosis and is transiently associated with early phagosomes. Certain pathogens, including Chlamydia pneumoniae, have evolved mechanisms to subvert macrophage phagosome maturation and, thus, are able to survive within these cells. We report here that, although amphiphysin IIm is usually only transiently associated with the phagosome, it is indefinitely retained on vacuoles containing C. pneumoniae. Under these wild-type conditions, C. pneumoniae do not elicit significant nitric oxide (NO) production and are not killed. Abrogation of amphiphysin IIm function results in C. pneumoniae–induced NO production and in the sterilization of the vacuole. The data suggest that C. pneumoniae retains amphiphysin IIm on the vacuole to survive within the macrophage.

Chlamydia pneumoniae stimulates IFN-gamma synthesis through MyD88-dependent, TLR2- and TLR4-independent induction of IL-18 release

Recent studies suggest that inflammation plays a central role in the pathogenesis of atherosclerosis, and IFN-gamma is a prominent proinflammatory mediator in this context. However, it is unclear what stimuli are responsible for initial stimulation of IFN-gamma synthesis in the vessel wall. In the present study, we demonstrate that Chlamydia pneumoniae is an important stimulus for IFN-gamma synthesis, and this production depends on release of endogenous IL-18, IL-12, and IL-1, but not of TNF. The production of the proinflammatory cytokines TNF and IL-1beta from PBMC by sonicated C. pneumoniae was mediated through TLR2-dependent pathways. In contrast, C. pneumoniae stimulated the production of IL-18 through MyD88-dependent, TLR2-, TLR4-, and CD14-independent pathways, mediated by posttranscriptional mechanisms not involving de novo protein synthesis. In conclusion, C. pneumoniae is a potent stimulus of IFN-gamma production, in addition to the proinflammatory cytokines TNF and IL-1beta, which may contribute to its proatherogenic effects. Most interestingly, C. pneumoniae is also a potent inducer of IL-18 production through pathways independent of TLR2 and TLR4.

Effects of glucocorticoids on the respiratory burst of Chlamydia-primed THP-1 cells

We previously observed that the respiratory burst of human monocytes (THP-1 cell line) triggered by phorbol myristate acetate was strongly enhanced by a priming of the cells by Chlamydia pneumoniae [Biochem. Biophys. Res. Commun. 287 (2001) 781]. We describe here the modifications of the responses of Chlamydia-primed THP-1 cells to hydrocortisone (HCT) and methylprednisolone (MPL). HCT and MPL inhibited the production of the cytokines TNFalpha and IL-8. But HCT, which inhibited the respiratory burst in LPS-primed monocytes, paradoxically stimulated the phenomenon in Chlamydia-primed cells; MPL exerted no significant effect. Both glucocorticoids did not significantly modify the triggering effect of Chlamydia on NF-kappaB binding activity. On the expression of p22(phox), a protein subunit of the NADPH oxidase, HCT had an increasing and MPL a decreasing effect. Glucocorticoids thus had unexpected effects on the inflammatory response of Chlamydia-primed monocytes.

Chlamydophila (Chlamydia) pneumoniae induces histidine decarboxylase production in the mouse lung

Chlamydophila (Chlamydia) pneumoniae (C. pneumoniae) is the third most common cause of community-acquired pneumonia and is probably involved in the development of certain chronic inflammatory diseases, including atherosclerosis and adult-onset asthma. Histamine, synthesized by histidine decarboxylase (HDC) from L-histidine, plays an essential role in allergic and inflammatory processes and in cell differentiation. The effect of C. pneumoniae infection on the expression of HDC has not been examined. In the present study, normal Balb/c mice and HDC knockouts, and control mice with a CD1 background were infected intranasally with C. pneumoniae. On days 1, 3, 7, 16 and 31 after infection, the normal Balb/c mice were sacrificed and divided into three groups. In the homogenized lungs of the first group, C. pneumoniae titres were determined and demonstrated peak levels on day 7. HDC production was revealed by a Western blot assay throughout the observation period of 1-16 days, and cytokine concentrations were determined by ELISA. The interleukin-3 (IL-3) and interleukin-6 (IL-6) levels were highest on day 1 and on days 1-3, respectively; the interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) levels reached the maximum on day 7, but the quantity of IL-4 was still three times higher than that in the control group 16 days after infection. The lungs of the mice in the second group were processed for the in situ demonstration of HDC activity, while the lungs in the third group were stained for C. pneumoniae antigen. The HDC activity was increased predominantly in the bronchial epithelial cells, while C. pneumoniae antigens were expressed especially in the interstitial macrophages. The HDC knockout mice exhibited a higher survival rate after C. pneumoniae infection than did the control mice. These results point to a strong association between local histamine production and other inflammatory mediators and are novel in demonstrating the role of histamine in the pathomechanism of C. pneumoniae infections.

Chlamydia pneumoniae accelerates coronary artery disease progression in transgenic hyperlipidemia-genetic hypertension rat model

Chlamydia pneumoniae (Cpn) has been associated with human coronary artery disease but causal relevance as a risk factor has not been shown. Several rabbit and mouse model studies demonstrate exacerbation of aortic atherosclerosis by Cpn, however impact of Cpn on coronary artery disease (CAD) and survival outcomes has not been shown. To study this, we used specific pathogen-free, inbred, transgenic-CAD Dahl salt-sensitive (S) hypertensive (Tg53) rats and control inbred, non-transgenic Dahl S (nonTg) rats to analyze the effects of Cpn infection on macrophage foam cell formation, coronary artery disease progression, and effect on survival. Cpn infection induced acceleration of foam cell formation in hyperlipidemic Tg53 recruited peritoneal macrophages. This effect is hyperlipidemia-dependent. The transcription profile of Tg53-Cpn macrophage foam cells is different from control mock-inoculated (Tg53-spg) and heat-inactivated (Tg53-iCpn) macrophages (ANOVA P < 0.0001). Decreased survival was detected in Tg53-Cpn compared with control nonTg-Cpn and mock-infected Tg53-mouse pneumonitic rats (P = 0.009) and was associated with "culprit" coronary plaques and left atrial thrombi. These data demonstrate that in the presence of significant hyperlipidemia and hypertension, one-time Cpn infection at 5 mo of age (associated with early CAD stage) accelerates progression to overt-CAD in the Tg53 rat model. The data support the hypothesis that untreated Cpn infection is a causal risk factor for CAD progression most likely mediated by Cpn-induced accelerated macrophage foam cell formation.

Analysis of Altered Protein Expression Patterns of Chlamydia pneumoniae by an Integrated Proteome-Works System

We have identified, analyzed, and quantified differential protein expression profile of five C. pneumoniae proteins, Adk (adenylate kinase), AhpC (thiol-specific antioxidant), CrpA (15 KD cysteine rich protein), Map (methionine aminopeptidae), and Cpn0710 (hypothetical protein) under normal versus persistent growth conditions induced by interferon-gamma, at different time intervals of their replicative cycle by successfully employing the latest proteomic analysis tool, PDQuest 2-D analysis software. We have also determined that this software represents a reliable analytical tool for mapping protein expression patterns in C. pneumoniae.

Macrophage L-type Ca2+ channel antagonists alter Chlamydia pneumoniae MOMP and HSP-60 mRNA gene expression, and improve antibiotic susceptibility

Recent data have shown a unique relationship between Ca2+ signaling in macrophages through L-type channels and the outcome of C. pneumoniae infection of such cells. The present investigation seeks to provide insights into the manner in which macrophage L-type Ca2+ channel operation affects major outer membrane protein (MOMP) and heat shock protein-60 (HSP-60) mRNA gene expression (factors associated with Chlamydia chronicity), and the possible effect of this on antibiotic susceptibility. Intracellular calcium ([Ca2+]i) chelation using varying doses of 1,2-bis (o-aminophenoxy) ethane-N,N,N'N'--tetra acetic acid (acetoxymethyl) ester (BAPTA-AM) induced an increase in MOMP and a decrease in HSP-60 mRNA gene expression. L-type Ca2+ channel antagonists produced an identical but enhanced effect. Since these findings associate specialized Ca2+ channels to Chlamydia chronicity, it was important to determine Ca2+ channel effect on the usual antibiotic refractory form of C. pneumoniae in macrophages. Inhibition of macrophage L-type Ca2+ channel operation improved C. pneumoniae antibiotic susceptibility assessed by decreased inclusion counts or down-regulated MOMP and HSP-60 mRNA gene expression. These findings provide molecular insights into how specialized Ca2+ channels influence Chlamydia chronic course in macrophages and demonstrates a role for L-type Ca2+ channel inhibitors in enhanced C. pneumoniae susceptibility to antibiotic therapy.

More than just innate immunity: comparative analysis of Chlamydophila pneumoniae and Chlamydia trachomatis effects on host-cell gene regulation

Chlamydophila pneumoniae and Chlamydia trachomatis cause infections of the respiratory or urogenital tract. In addition, both species have been associated with atherosclerosis or reactive arthritis respectively. For these intracellular pathogens the interaction with their host-cells is of particular importance. To get insight into this relationship, we conducted a comparative analysis of the host-cell gene regulation of human epithelial cells during infection with Chlamydia. In a screening of HeLa cells by Affymetrix-microchips, numerous regulated host-genes were identified. A detailed expression profile was obtained for 14 genes by real-time RT-PCR - comparing C. pneumoniae, C. trachomatis and intracellular S. typhimurium. The transcriptional responses induced by C. pneumoniae were similar (but usually smaller) compared to C. trachomatis, some were absent. UV-inactivated bacteria induced no differential gene expression suggesting that pathomechanisms other than those associated with innate immunity play here an important role. The expression pattern induced by Salmonella differed substantially. These genus- or group-specific transcriptional response patterns elicited by viable intracellular pathogens may considerably contribute to the different pathologies encountered in the clinic.

IFN-gamma induced persistent Chlamydia pneumoniae infection in HL and Mono Mac 6 cells: characterization by real-time quantitative PCR and culture

Growth of Chlamydia pneumoniae during gamma interferon (IFN-gamma) induced persistent infection in epithelial (HL) and monocyte-macrophage (Mono Mac 6) cell lines was studied by a quantitative real-time PCR and passage. When HL cultures were treated with IFN-gamma (25 U/ml), the replication of C. pneumoniae DNA was unaffected while differentiation into infectious elementary bodies (EB) was strongly inhibited, and in contrast to the untreated cultures, no second cycle of infection was observed. The estimated doubling time of C. pneumoniae genomes was 6-7 h in both IFN-gamma treated and untreated HL cultures. At 72 h post inoculation, most infectious EBs were released from untreated cultures, whereas in IFN-gamma treated HL cells >90% of C. pneumoniae genomes were in non-infectious form. A higher dose (1000 U/ml) of IFN-gamma was needed to restrict growth of C. pneumoniae in Mono Mac 6 cells. In untreated Mono Mac 6 cultures, the growth curve of C. pneumoniae resembled that observed in HL cells, except that no second cycle of infection could be detected. In IFN-gamma treated Mono Mac 6 cultures, the number of infectious C. pneumoniae EBs recovered decreased gradually after 3 days post inoculation, while C. pneumoniae genome load remained unaltered suggesting persistence of C. pneumoniae also in these cells.

Expression and localization of type III secretion-related proteins of Chlamydia pneumoniae

The entire developmental cycle of the obligate intracellular bacteria Chlamydia pneumoniae takes place within the inclusion body. As many gram negative bacteria, Chlamydia possess a type III-secretion system (TTSS), which allows them to target effector molecules into the host cell. The expression and localization of several proteins constituting the TTSS apparatus and of proteins supposed to be secreted by the TTSS have been investigated. For the TTSS-constituting proteins, we selected representatives such as YscN (ATPase), LcrE (putative "lid" of the TTSS) and LcrH1 (postulated to be a chaperone). Furthermore, we focused on the putative effector proteins IncA, IncB, IncC, Cpn0809 and Cpn1020. Expression of these proteins was detected by reverse transcriptase-PCR followed by immunoblot analysis using antisera that were generated against the corresponding recombinant proteins. Thereby, expression could be detected on the RNA and/or protein level. Intracellular localization of proteins under investigation was determined by immunofluorescence assays using the respective antisera. YscN was shown to be distributed equally throughout the inclusion body, whereas LcrE gave a more prominent staining of the inclusion membrane. IncA was detected mainly on the membrane of the inclusion body, whereas IncB and IncC were shown to be located within the inclusion. Immunofluorescence assays with antisera raised against Cpn0809 and Cpn1020 showed completely different labeling. Signals corresponding to Cpn0809 and Cpn1020 were distributed within the host cell rather than inside the inclusions. Taken together, the different localization patterns of the effector proteins indicate differences in function and interplay with the host cell.

Chlamydia pneumoniae affect surfactant trafficking and secretion due to changes of type II cell cytoskeleton

Understanding the surfactant dysfunction by gram-negative bacteria pulmonary infection, the intracellular fate of Chlamydia pneumoniae (Cpn), its interaction with uptake, recycling, and secretion of surfactant and with the cytoskeleton of type II pneumocytes was investigated. Bacteria colocalized with surfactant protein (SP)-A-mediated endocytosed lipid and early endosomes (EEA1- and Rab5-positive) after 3 and 6 h of infection. No specific contact with late endosomes (Rab7- and M6PR-positive), lysosomal, or lamellar body markers (CD63, 3C9) was found after 12 h of infection. In Cpn-infected cells, SP-A-mediated lipid uptake was significantly increased. After SP-A-mediated lipid uptake followed by "re-secretion," 90% of the internalized lipid remained intracellularly. SP-A and lipid did strongly colocalize with early endosomes. Internalized SP-A cannot be resecreted rapidly to plasma membrane, and lipid is not transported toward late endosomes (Rab7- and M6PR-positive) or lamellar bodies (CD63- and 3C9-positive). These results indicate that increased surfactant internalization is caused by an inhibition in intracellular surfactant transport. Accumulation of SP-A-mediated lipid was associated with changes in beta-tubulin. Increases in surfactant secretion were associated with changes in F-actin. We postulate that Cpn infection of type II cells causes changes of the cytoskeleton, and that these effects are associated with alterations in intracellular transport and secretion of surfactant.

Chlamydophila pneumoniae induces ICAM-1 expression in human aortic endothelial cells via protein kinase C-dependent activation of nuclear factor-kappaB

Chlamydophila pneumoniae has an epidemiological link with atherosclerosis and acute cardiovascular events. One mechanism that may explain such a link is the increased expression of intracellular adhesion molecule-1 (ICAM-1) in C pneumoniae-infected endothelial cells. Upregulation of ICAM-1 by C pneumoniae is well recognized and has been extensively studied, but the signaling pathways involved are not yet defined. Because upregulation of ICAM-1 by cytokines and other stimuli has been shown to be mediated by either mitogen-activated protein kinase, protein kinase C (PKC), or nuclear factor-kappaB (NF-kappaB) pathways, we examined whether these pathways were involved in the ICAM-1 upregulation induced by C pneumoniae. Our data show a time-dependent phosphorylation of p44/p42 and SAPK/JNK pathways in C pneumoniae-infected cells. However, inhibition of the classic mitogen-activated protein kinase pathway using the PD98059 and U0126 inhibitors and inhibition of SAPK/JNK pathway did not suppress C pneumoniae-induced ICAM-1 expression. C pneumoniae also activates the NF-kappaB pathway at 30 minutes after infection. Treatment of human aortic endothelial cells (HAECs) with the NF-kappaB inhibitors BAY117085 and caffeic acid phenethyl ester led to a concentration-dependent inhibition of C pneumoniae-induced ICAM-1 upregulation. Finally, C pneumoniae-infected HAECs show membrane translocation of total PKC 30 minutes after cell infection. Calphostin C, a general PKC inhibitor, blocked both C pneumoniae-induced ICAM-1 expression and C pneumoniae-induced NF-kappaB translocation. In conclusion, we demonstrated that C pneumoniae-induced ICAM-1 expression in HAECs requires NF-kappaB and PKC activation and that NF-kappaB activation is PKC dependent.

Aspirin inhibits Chlamydia pneumoniae-induced NF-kappa B activation, cyclo-oxygenase-2 expression and prostaglandin E2 synthesis and attenuates chlamydial growth

Infection with Chlamydia pneumoniae has been implicated as a potential risk factor for atherosclerosis. This study was designed to investigate the mechanisms of the anti-chlamydial activity of aspirin. A reporter gene assay for NF-kappa B activity, immunoblot analysis for cyclo-oxygenase (COX)-2 and radioimmunoassay for prostaglandin E(2) (PGE(2)) were performed. Following infection of HEp-2 cells with C. pneumoniae, NF-kappa B was activated, COX-2 was induced and PGE(2) was elevated. Aspirin inhibited NF-kappa B activation at a concentration of 0.1 mM, partially inhibited COX-2 induction and blocked PGE(2) synthesis completely. In addition, high doses of aspirin (1 and 2 mM) inhibited chlamydial growth in HEp-2 cells, decreasing the number and size of inclusion bodies; this effect could be overcome by adding tryptophan to the culture. Indomethacin also blocked the synthesis of PGE(2), but had no effect on COX-2 expression or chlamydial growth. These results indicate that aspirin not only has an anti-inflammatory activity through prevention of NF-kappa B activation but also has anti-chlamydial activity at high doses, possibly through depletion of tryptophan in HEp-2 cells.

Role of Chlamydia pneumoniae-infected macrophages in atherosclerosis developments of the carotid artery

Chlamydia pneumoniae (C. pneumoniae) infection has been recently accepted as an important cause of atherosclerosis. However, the precise mechanisms remain unclear. The present study was aimed to clarify the distribution link among C. pneumoniae, chlamydial HSP 60, and activated macrophages. Atheromatous carotid plaques were obtained from 40 consecutive carotid endarterectomies (CEA). The specimens were prepared for HE and elastica-van Gieson staining. Parallel sections were stained immunocytochemically with monoclonal antibodies for a C. pneumoniae-specific antigen, chlamydial HSP 60, activated macrophages, and smooth muscle cells. Immunoreactivity for the C. pneumoniae-specific antigen was observed within the endothelial cells, activated macrophages, and smooth muscle cells in 36 of 40 specimens (90%). Chlamydial HSP 60 was found in all specimens positive for the C. pneumoniae-specific antigen, and mainly co-localized with the C. pneumoniae-specific antigen within the activated macrophages. The present results suggest that C. pneumoniae is a key microbial organ that causes atheroma developments in the carotid artery. Chlamydia pneumoniae-infected macrophages may come into the arterial intima and mediate inflammatory and autoimmune processes through the production of chlamydial HSP 60, leading to atherosclerosis.

Chlamydia pneumoniae survival in macrophages is regulated by free Ca2+ dependent reactive nitrogen and oxygen species

OBJECTIVES

Despite an efficient macrophage immune capability, Chlamydia pneumoniae infects host cells and causes chronic diseases. To gain better insights into C. pneumoniae survival mechanisms in macrophages, its growth in regular RAW-264.7 cells (nitric oxide sufficient NO (+)) and RAW-264.7 cells (nitric oxide insufficient NO (-)) were studied.

METHODS

Role of Ca(2+), NO and reactive oxygen species (ROS) during C. pneumoniae infection in macrophages were determined.

RESULTS

RAW-264.7 NO (-) cells supported significantly Chlamydia growth, showing an upregulation of ROS, superoxide dismutase (SOD) and catalase activities as compared with RAW-264.7 NO (+) cell. Ascorbic acid, inducible nitric oxide synthase inhibitor and glutathione significantly prompted Chlamydia inclusion formation. Cytosolic Ca(2+) had regulatory effect on organism growth, NO generation, SOD and catalase activities in both cell types.

CONCLUSIONS

These findings suggest that minimal Ca(2+) signaling in macrophages at early stages of infection, NO and ROS release have modulatory effects onC. pneumoniae survival, onset of persistence and chronicity, processes which are needed for the initiation of diseases in which C. pneumoniae has been implicated as a possible etiologic agent.