Chlamydia pneumoniae and vascular disease

Atherosclerosis and Alzheimer--diseases with a common cause? Inflammation, oxysterols, vasculature

BACKGROUND

Aging is accompanied by increasing vulnerability to pathologies such as atherosclerosis (ATH) and Alzheimer disease (AD). Are these different pathologies, or different presentations with a similar underlying pathoetiology?

DISCUSSION

Both ATH and AD involve inflammation, macrophage infiltration, and occlusion of the vasculature. Allelic variants in common genes including APOE predispose to both diseases. In both there is strong evidence of disease association with viral and bacterial pathogens including herpes simplex and Chlamydophila. Furthermore, ablation of components of the immune system (or of bone marrow-derived macrophages alone) in animal models restricts disease development in both cases, arguing that both are accentuated by inflammatory/immune pathways. We discuss that amyloid β, a distinguishing feature of AD, also plays a key role in ATH. Several drugs, at least in mouse models, are effective in preventing the development of both ATH and AD. Given similar age-dependence, genetic underpinnings, involvement of the vasculature, association with infection, Aβ involvement, the central role of macrophages, and drug overlap, we conclude that the two conditions reflect different manifestations of a common pathoetiology.

MECHANISM

Infection and inflammation selectively induce the expression of cholesterol 25-hydroxylase (CH25H). Acutely, the production of 'immunosterol' 25-hydroxycholesterol (25OHC) defends against enveloped viruses. We present evidence that chronic macrophage CH25H upregulation leads to catalyzed esterification of sterols via 25OHC-driven allosteric activation of ACAT (acyl-CoA cholesterol acyltransferase/SOAT), intracellular accumulation of cholesteryl esters and lipid droplets, vascular occlusion, and overt disease.

SUMMARY

We postulate that AD and ATH are both caused by chronic immunologic challenge that induces CH25H expression and protection against particular infectious agents, but at the expense of longer-term pathology.

Outcome of Chlamydia pneumoniae associated acute ischemic stroke in elderly patients: a case-control study

BACKGROUND

Limited data exists about the role of Chlamydia pneumoniae elderly patients with acute ischemic stroke.

OBJECTIVE

To study the role of C. pneumoniae in elderly patients (age more than 65 years) with acute ischemic stroke and its impact on stroke out come.

METHODS

We recruited 100 elderly patients with acute ischemic stroke and 100 age and sex matched controls over a period of 2 years. IgG and IgA anti C. pneumoniae antibodies were measured by microimmunofluorescence technique in patients and controls. Good outcome was defined as a Modified Rankin score (mRS) of ≤2.

RESULTS

We found C. pneumoniae antibodies in 35% stroke patients and in 18% control subjects (p=0.01). Good out come at 90 days follow up was found in 20/35(57.1%) seropositive stroke patients compared to 37/65(56.9%) seronegative stroke patients (p=0.9).

CONCLUSIONS

C. pneumoniae antibody positivity was independently associated with ischemic stroke in elderly patients and its presence does not alter the stroke outcome.

Chlamydia pneumoniae seropositivity in adults with acute ischemic stroke: A case-control study

BACKGROUND

Causative role of Chlamydia pneumoniae infection in patients with acute ischemic stroke (AIS) remains unresolved till date.

AIM

To investigate the role of C. pneumoniae antibodies in AIS.

MATERIALS AND METHODS

Patients with AIS and sex- and environment-matched controls were enrolled. Antibodies to C. pneumoniae (IgA, IgG and IgM) were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

A total of 51 patients and 48 controls were enrolled. The IgA seropositivity was significantly associated with AIS (unadjusted odds ratio 3.1; 95% CI 1.38, 6.96; P = 0.005), whereas IgG (unadjusted OR 0.44; 95% CI 0.18, 1.09; P = 0.07) and IgM (unadjusted OR 1.1; 95% CI 0.36, 3.3; P = 0.88) were not. There was no difference in IgA or IgG positivity in different stroke subtypes. On multivariate analysis after adjusting for sex, hypertension, diabetes mellitus, smoking and alcohol, the IgA seropositivity yielded an adjusted OR for stroke (4.72; 95% CI 1.61, 13.83; P = 0.005), while IgG seropositivity did not (OR 0.25; 95% CI 0.08, 0.83; P = 0.23).

CONCLUSIONS

An increased risk of AIS was demonstrated in patients seropositive for C. pneumoniae for IgA antibodies.

Evaluation of the level of antibodies against Chlamydophila (Chlamydia) pneumoniae in post-surgery heart ischaemia patients and their clinical conditions - a six-year study

INTRODUCTION

Inflammatory conditions modulated by Chlamydophila (Chlamydia) pneumoniae are considered to play an important role in the onset of atherosclerosis. In this paper we present the results of progressive observation of C. pneumoniae antibody titres in patients who underwent coronary artery bypass graft (CABG).

MATERIAL AND METHODS

The objective of our research was a prospective observation of antibody titres in IgA and IgG class antibodies against C. pneumoniae using indirect immunofluorescence in a group of 155 post-surgery CABG patients suffering from heart ischaemia. The microbiological test results were compared with patients' present coronary complaints evaluated on the CCS scale during a six-year period.

RESULTS

Six years after CABG, 128 patients (82.6%) are still alive. During the study a positive serological conversion of antibody titres was observed in 36 patients in the IgA class antibodies, and in 26 patients in the IgG class. The group of patients with no antibodies against C. pneumoniae decreased from 23.2 to 3.4%, while the group of patients with antibodies in both IgG and IgA classes increased from 52.3 to 83.9%. The average CCS degree decreased from 3.18 before CABG to 1.65 in the present study.

CONCLUSIONS

These results show no connection between the serological symptoms of chronic C. pneumoniae infection and coronary complaints evaluated on the CCS scale during a six-year study on post-CABG patients suffering from heart ischaemia. The surgical treatment of heart ischaemia brought about long-term improvement in the coronary condition of the observed group of patients.

Chlamydia pneumoniae antibodies in various subtypes of ischemic stroke in Indian patients

BACKGROUND

As infections occur more frequently in developing countries, we carried out this prospective case-control study, to establish the association, if any, between C. pneumoniae antibodies and ischemic stroke particularly in relation to its subtypes.

DESIGN

Antibodies (IgG and IgA) to C. pneumoniae in serum were measured by microimmunofluorescence test in 200 consecutive ischemic stroke patients and 200 age and sex matched controls.

RESULTS

Seventy two out of 200 ischemic stroke patients (36%) had positive C. pneumoniae antibodies (IgG or IgA), compared to 35 out of 200 controls (17.5%) (p<0.0001). IgG antibody was positive in 64/200 (32%) ischemic stroke patients, compared to 34/200(17%) controls (p<0.0001) and IgA was positive in 20/200(10%) ischemic stroke patients compared to 1/200(0.5%) controls (p<0.0001). Logistic regression analysis showed statistically significant association between C. pneumoniae antibody positivity and ischemic stroke, thereby establishing it as an independent risk factor. Prevalence of C. pneumoniae antibodies was significantly higher in all stroke subtypes (except the stroke of undetermined etiology) compared to controls.

CONCLUSION

Significant and independent association was found between C. pneumoniae antibodies and ischemic stroke in this sample of south Indian population. The association was found in all ischemic stroke subtypes, except stroke of undetermined etiology.

The effect of Chlamydia pneumoniae on the expression of peroxisome proliferator-activated receptor-gamma in vascular smooth muscle cells

PURPOSE

This study was designed to investigate the change of peroxisome proliferator-activated receptor gamma (PPARgamma) after the infection of the human coronary artery smooth muscle cells (HCSMCs) with Chlamydia pneumoniae (C. pneumoniae) and the effect of PPARgamma agonist on the expression of PPARgamma of C. pneumoniae-infected HCSMCs.

MATERIALS AND METHODS

To determine the effect of PPARgamma agonist on the proliferation of C. pneumoniae-infected HCSMCs, rosiglitazone at various concentrations was applied 1 hour before inoculation of HCSMCs.

RESULTS

The expression of PPARgamma mRNA in HCSMCs increased from 3 hours after C. pneumoniae infection and reached that of noninfected HCSMCs at 24 hours (p<0.05). The expression of PPARgamma protein in HCSMCs also increased from 3 hours after C. pneumoniae and persisted until 24 hours as compared with that of noninfected HCSMCs (p<0.05). The pretreatment of HCSMCs with rosiglitazone followed by the infection with C. pneumoniae augmented the expression of PPARgamma mRNA and protein (p<0.05) and decreased cell proliferation.

CONCLUSION

Our results showed that the expression of PPARgamma increases in response to C. pneumoniae infection and rosiglitazone further augmented the expression of PPARgamma. It is suggested that rosiglitazone could ameliorate the chronic inflammation in the vessel wall induced by C. pneumoniae by augmenting PPARgamma expression.

Chlamydia muridarum infection subverts dendritic cell function to promote Th2 immunity and airways hyperreactivity

There is strong epidemiological evidence that Chlamydia infection can lead to exacerbation of asthma. However, the mechanism(s) whereby chlamydial infection, which normally elicits a strong Th type 1 (Th1) immune response, can exacerbate asthma, a disease characterized by dominant Th type 2 (Th2) immune responses, remains unclear. In the present study, we show that Chlamydia muridarum infection of murine bone marrow-derived dendritic cells (BMDC) modulates the phenotype, cytokine secretion profile, and Ag-presenting capability of these BMDC. Chlamydia-infected BMDC express lower levels of CD80 and increased CD86 compared with noninfected BMDC. When infected with Chlamydia, BMDC secrete increased TNF-alpha, IL-6, IL-10, IL-12, and IL-13. OVA peptide-pulsed infected BMDC induced significant proliferation of transgenic CD4(+) DO11.10 (D10) T cells, strongly inhibited IFN-gamma secretion by D10 cells, and promoted a Th2 phenotype. Intratracheal transfer of infected, but not control noninfected, OVA peptide-pulsed BMDC to naive BALB/c mice, which had been i.v. infused with naive D10 T cells, resulted in increased levels of IL-10 and IL-13 in bronchoalveolar lavage fluid. Recipients of these infected BMDC showed significant increases in airways resistance and decreased airways compliance compared with mice that had received noninfected BMDC, indicative of the development of airways hyperreactivity. Collectively, these data suggest that Chlamydia infection of DCs allows the pathogen to deviate the induced immune response from a protective Th1 to a nonprotective Th2 response that could permit ongoing chronic infection. In the setting of allergic airways inflammation, this infection may then contribute to exacerbation of the asthmatic phenotype.

Role of Chlamydia pneumoniae in atherosclerosis

Cardiovascular disease, resulting from atherosclerosis, is a leading cause of global morbidity and mortality. Genetic predisposition and classical environmental risk factors explain much of the attributable risk for cardiovascular events in populations, but other risk factors for the development and progression of atherosclerosis, which can be identified and modified, may be important therapeutic targets. Infectious agents, such as Chlamydia pneumoniae, have been proposed as contributory factors in the pathogenesis of atherosclerosis. In the present review, we consider the experimental evidence that has accumulated over the last 20 years evaluating the role of C. pneumoniae in atherosclerosis and suggest areas for future research in this field.

Protective effect of doxycycline use on coronary artery disease?

OBJECTIVES

The potential role of Chlamydia pneumoniae infection in the pathogenesis of atherosclerosis has received increasing attention. The present study was conducted to test the hypothesis that use of doxycycline in doses prescribed in routine clinical practice for brucellosis, decreases the risk of coronary artery disease (CAD).

METHODS

A general practice (GP) database in Western Greece was used. One hundred and twenty-nine newly diagnosed patients with coronary artery disease from 2001 to 2003 were contrasted to 196 controls randomly selected from the same practice. General practice records were reviewed to confirm a diagnosis of incident CAD event and obtain information on other cardiovascular risk factors. CAD events were defined as: Stable/unstable angina, acute myocardial infarction or ischemic death.

RESULTS

The results indicate a significant association between doxycycline use and occurrence of CAD (OR: 0.37, 95% CI: 0.17-0.78).

CONCLUSIONS

These results persisted when adjustment for potential confounding factors was made. The findings should be interpreted cautiously because of lack of information about C. pneumoniae infection. However, the results suggest directions for future epidemiologic studies in this relatively uncharted field.

Detection of Chlamydia in the peripheral blood cells of normal donors using in vitro culture, immunofluorescence microscopy and flow cytometry techniques

BACKGROUND

Chlamydia trachomatis (Ct) and Chlamydia pneumoniae (Cp) are medically significant infectious agents associated with various chronic human pathologies. Nevertheless, specific roles in disease progression or initiation are incompletely defined. Both pathogens infect established cell lines in vitro and polymerase chain reaction (PCR) has detected Chlamydia DNA in various clinical specimens as well as in normal donor peripheral blood monocytes (PBMC). However, Chlamydia infection of other blood cell types, quantification of Chlamydia infected cells in peripheral blood and transmission of this infection in vitro have not been examined.

METHODS

Cp specific titers were assessed for sera from 459 normal human donor blood (NBD) samples. Isolated white blood cells (WBC) were assayed by in vitro culture to evaluate infection transmission of blood cell borne chlamydiae. Smears of fresh blood samples (FB) were dual immunostained for microscopic identification of Chlamydia-infected cell types and aliquots also assessed using Flow Cytometry (FC).

RESULTS

ELISA demonstrated that 219 (47.7%) of the NBD samples exhibit elevated anti-Cp antibody titers. Imunofluorescence microscopy of smears demonstrated 113 (24.6%) of samples contained intracellular Chlamydia and monoclonals to specific CD markers showed that in vivo infection of neutrophil and eosinophil/basophil cells as well as monocytes occurs. In vitro culture established WBCs of 114 (24.8%) of the NBD samples harbored infectious chlamydiae, clinically a potentially source of transmission, FC demonstrated both Chlamydia infected and uninfected cells can be readily identified and quantified.

CONCLUSION

NBD can harbor infected neutrophils, eosinophil/basophils and monocytes. The chlamydiae are infectious in vitro, and both total, and cell type specific Chlamydia carriage is quantifiable by FC.

Chlamydia pneumoniae and atherosclerosis: from Koch postulates to clinical trials

Atherosclerosis is increasingly viewed as an inflammatory process. A number of infectious agents have been implicated in the pathogenesis of coronary artery disease. Chlamydia pneumoniae has been the most popular and well-studied of these pathogens. It is difficult to prove a causal relationship which requires the fulfillment of Koch's postulates, first developed in the late 1800s, to establish an infectious agent as the cause of a disease process. This paper reviews the evidence for and against Chlamydia pneumoniae infection as a contributing factor to atherosclerosis disease. It examines seroepidemiologic and histopathologic studies as well as animal models using Koch's postulates and then provides an analysis of current clinical trial data.

Association of raised titres of antibodies to Chlamydia pneumoniae with a history of pre-eclampsia

OBJECTIVE

To establish the prevalence of Chlamydia pneumoniae (C. pneumoniae) infection in a pregnant UK population and to investigate whether C. pneumoniae infection is more common in women with a previous history of pre-eclampsia.

DESIGN

Prospective study.

SETTING

Academic Hospital.

POPULATION

Ninety-one pregnant women (54 parous and 37 nulliparous) at 16-22 weeks of gestation were studied. Of the parous women, 32 had a previous history of pre-eclampsia.

METHODS

Peripheral blood was drawn for C. pneumoniae antibodies between 16-22 and 28-40 weeks of gestation. C. pneumoniae antibodies were measured using a solid-phase enzyme immunoassay. According to pregnancy outcome, women were categorised into normal, gestational hypertension and pre-eclampsia groups.

MAIN OUTCOME MEASURES

Serum levels of IgG, IgA and IgM C. pneumoniae antibodies.

RESULTS

Prevalence of seropositivity to C. pneumoniae was 77%. Parous women had significantly higher levels of IgA and IgM C. pneumoniae antibodies than nulliparous women (P < 0.04). Parous women with previous pre-eclampsia were found to have higher levels of antibodies than parous women with a normal obstetric history (P< or = 0.003). There was no difference in the antibody levels in women with different pregnancy outcomes.

CONCLUSIONS

The longitudinal data do not indicate an association between C. pneumoniae infection and pre-eclampsia. However, the subgroup analysis of parous women demonstrated raised C. pneumoniae antibodies in the women with previous pre-eclampsia, and therefore suggests that there may be an association between C. pneumoniae and the disease in this group.

New and emerging theories of cardiovascular disease: infection and elevated iron

Heart disease is the leading cause of death in both men and women in industrialized countries. Despite the tremendous gains made in decreasing the number of deaths due to cardiovascular disease, it still is health care's greatest challenge. Traditional risk factors account for only 50% of the incidence of cardiac disease. In fact, many individuals who develop heart disease have normal cholesterol and blood pressure levels. This suggests that other less well-studied risk factors may also play a role. The purpose of this report is to examine the role that recently suggested risk factors may play in the development of heart disease: coronary artery infection, specifically from Chlamydia pneumoniae, and elevated iron levels. Both initiate an inflammatory response, which might explain the elevated C-reactive protein levels frequently found in those who suffer from cardiac disease.

Evidence of nanobacterial-like structures in calcified human arteries and cardiac valves

Mechanisms mediating vascular calcification remain incompletely understood. Nanometer scale objects hypothesized to be a type of bacteria (nanobacteria) are associated with calcified geological specimens, human kidney stones, and psammona bodies in ovarian cancer. Experiments were designed to evaluate human vascular tissue for the presence of similar nanometer-scale objects. Calcified human aneurysms (n = 8), carotid plaques (n = 2), femoral arterial plaques (n = 2), and cardiac valves (n = 2) and noncalcified aneurysms from patients with bicuspid aortic valve disease (n = 2) were collected as surgical waste from the Heart Hospital of Austin, Austin, Texas, and Mayo Clinic, Rochester, Minnesota. Whole mounts or adjacent sections from each specimen were examined by electron microscopy, stained for calcium phosphate, or stained with a commercially available antibody (8D10). Filtered (0.2 microm) homogenates of aneurysms were cultured and costained with 8D10 antibody followed by PicoGreen to detect DNA or incubated with [3H]uridine. Staining for calcium phosphate was heterogeneously distributed within all calcified tissues. Immunological staining with 8D10 was also heterogeneously distributed in areas with and without calcium phosphate. Analysis of areas with positive immunostaining identified spheres ranging in size from 30 to 100 nm with a spectral pattern of calcium and phosphorus (high-energy dispersive spectroscopy). Nanosized particles cultured from calcified but not from noncalcified aneurysms were recognized by a DNA-specific dye and incorporated radiolabeled uridine, and, after decalcification, they appeared via electron microscopy to contain cell walls. Therefore, nanometer-scale particles similar to those described as nanobacteria isolated from geological specimens and human kidney stones can be visualized in and cultured from calcified human cardiovascular tissue.

Induction of proinflammatory cytokines in human lung epithelial cells during Chlamydia pneumoniae infection

Chlamydia pneumoniae is an obligate intracellular human pathogen that causes acute respiratory diseases such as pneumonia and bronchitis. Previous studies have established that C. pneumoniae can induce cytokines in mouse and/or human cells, but little information is available on the cytokine response of respiratory epithelial cells, a first line of infection. In this study, heparin treatment of C. pneumoniae significantly reduced its ability to induce interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-alpha) mRNA in human lung carcinoma cells, indicating that cytadherence is an important early stimulus for induction of proinflammatory mediators. Although the IL-8, gamma interferon, and TNF-alpha message was consistently induced by infection of A549 cells not treated with heparin, only an elevation of IL-8 protein was detected in A549 supernatants. A549 IL-beta and IL-6 mRNA and supernatant protein profiles were not significantly changed by infection. Heat or UV inactivation of C. pneumoniae only partially reduced the cytokine response, and inhibition of C. pneumoniae protein or DNA synthesis did not affect its ability to induce cytokine gene expression. To prevent stress-induced cytokine release by the A549 cells, centrifugation was not utilized for infection experiments. These experiments establish the importance of cytadherence in cytokine release by cells of respiratory epithelial origin and suggest that further work in the area of cytokine mediators is warranted to gain valuable pathogenic and therapeutic insights.

Chlamydia pneumoniae in central retinal artery occlusion

PURPOSE

There is increasing evidence that the common respiratory human pathogen Chlamydia pneumoniae has a causative role in atherosclerosis. We investigated the association of this pathogen with acute central retinal artery occlusion (CRAO).

PATIENTS AND METHODS

Sera of 14 consecutive patients with CRAO and of 14 age- and sex-matched control subjects were examined. Antibodies against chlamydial lipopolysaccharide (LPS) and outer membrane proteins of C. pneumoniae were determined by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

In the CRAO group, seven patients (50%) were found to be IgA positive, 12 (86%) were IgG positive and one (7%) was IgM positive for chlamydial LPS antibodies. In the control group 36%, 79% and 14% were IgA, IgG and IgM positive, respectively. The results showed no significant difference between the groups. In the CRAO group, IgA, IgG and IgM antibodies to C. pneumoniae were found in 43%, 79% and 0% of subjects, respectively. These findings did not differ significantly from those pertaining to matched controls.

CONCLUSIONS

These data do not support an association between acute CRAO and current C. pneumoniae infection.

Chlamydia in anterior ischemic optic neuropathy

There is an increasing body of evidence linking the common respiratory human pathogen Chlamydia pneumoniae with atherosclerosis and other vascular disorders. Our research was designed to investigate the association of this organism with anterior ischemic optic neuropathy (AION), representing an acute ischemic disorder of the optic nerve head. Sera were examined of 14 consecutive patients with AION and of 14 age- and sex-matched control subjects with noncardiovascular, nonpulmonary disorders. Antibodies against chlamydial lipopolysaccharide (LPS) and outer membrane proteins of C. pneumoniae were determined by ELISA. Further, nucleic acid amplification tests were done in order to detect C. pneumoniae-specific nucleotide sequences. Four patients (29%) were IgA positive, 11 (79%) were IgG positive and 1 (7%) was IgM positive for chlamydial LPS antibodies. In the control group, 36, 79 and 7% were IgA, IgG and IgM positive and showed no significant difference. IgA, IgG and IgM antibodies to C. pneumoniae were found in 43, 79 and 0% and did not differ from matched controls. By the nucleic acid amplification test, specific C. pneumo niae sequences were neither detected in the AION patients nor in the control group. These data do not support the association of AION with previous C. pneumoniae infection. However, it remains unclear whether Chlamydia actually initiates atherosclerotic injury, facilitates its progression or plays another role in other vascular disorders.

Interferon-beta induction by Chlamydia pneumoniae in human smooth muscle cells

Clinical studies have suggested a causal or contributory role of Chlamydia pneumoniae infection in asthma and atherosclerosis. The activation of synthetic functions of smooth muscle cells (SMC) including the production of cytokines and growth factors plays a major role in the formation of fibrous atherosclerotic plaques as well as in structural remodelling of the airway wall in chronic asthma. In this study we demonstrated that C. pneumoniae induced the production of low levels of interferon (IFN)-beta in bronchial and vascular SMC when infected cells were treated with tumour necrosis factor-alpha (TNF-alpha). IFN-beta production was analysed by reverse transcription-PCR and enzyme-linked immunosorbent assay. The upregulation of IFN-beta was paralleled by an increase in mRNA levels of interferon regulatory factor-1 and interferon-stimulated gene factor 3gamma, two transcription factors activating the expression of the IFN-beta gene. In addition, C. pneumoniae infection enhanced the mRNA level of indoleamine 2,3-dioxygenase, an IFN-inducible factor mediating the restriction of intracellular chlamydial growth, in TNF-alpha-stimulated SMC. C. pneumoniae-induced IFN-beta production by SMC may modulate inflammation and tissue remodelling during respiratory and vascular infection.

cDNA array analysis of altered gene expression in human endothelial cells in response to Chlamydia pneumoniae infection

Strong epidemiological and pathological evidence supports a role for Chlamydia pneumoniae infection in atherosclerosis and human coronary heart disease. Animal models have shown that C. pneumoniae disseminates hematogenously in infected monocytes and macrophages, while in vitro data suggest that infected macrophages can transmit C. pneumoniae infection directly to endothelial cells. Endothelial cells may be key in vivo targets for C. pneumoniae infection; given that these cells are important in regulating the dynamics of the vessel wall, we used cDNA microarrays to study the transcriptional response of endothelial cells to infection with C. pneumoniae. cDNA arrays were used to characterize the mRNA expression profiles for 268 human genes following infection with C. pneumoniae, which were compared to mRNA profiles of uninfected cells. Selected genes of interest were further investigated by reverse transcription-PCR throughout a 24-h period of infection. C. pneumoniae infection upregulated mRNA expression for approximately 20 (8%) of the genes studied. Genes coding for cytokines (interleukin-1), chemokines (monocyte chemotactic protein 1 and interleukin-8), and cellular growth factors (heparin-binding epidermal-like growth factor, basic fibroblast growth factor, and platelet-derived growth factor B chain) were the most prominently upregulated. In addition to these families of genes, increases in mRNA levels for intracellular kinases and cell surface receptors with signal transduction activities were observed. Time course experiments showed that mRNA levels were upregulated within 2 h following infection. These results expand our knowledge of the response of endothelial cells to C. pneumoniae by further defining the repertoire of C. pneumoniae-inducible genes and provide new insight into potential mechanisms of atherogenesis. In addition, the use of cDNA microarrays may prove useful for the study of host cell responses to C. pneumoniae infection during latent and replicative stages of infection and related pathology.

Correlation between detection methods of Chlamydia pneumoniae in atherosclerotic and non-atherosclerotic tissues

Polymerase chain reaction (PCR) and immunohistochemistry (IHC) have been used to detect Chlamydia (C.) pneumoniae in vascular tissues. Discrepancies between the results of these two methods have frequently been reported. However, the correlation between PCR and IHC has not been analyzed yet. This study assesses the correlation between the detection of C. pneumoniae by PCR and IHC in 45 atherosclerotic and 50 non-atherosclerotic tissue specimens. Also, the presence of Mycoplasma (M.) pneumoniae in these 95 specimens was investigated. Correlation was found between the detection of C. pneumoniae by PCR and IHC in the atherosclerotic tissues. Both tests were positive in 10 specimens and negative in 17 specimens (p = 0.003). There was no significant correlation between PCR and IHC in non-atherosclerotic specimens (p = ns). M. pneumoniae was detected, by PCR, in one atherosclerotic specimen.The results show correlation between PCR and IHC in the detection of C. pneumoniae in atherosclerotic tissues, emphasize the association between C. pneumoniae and atherosclerosis, and support the specificity of the association between C. pneumoniae and atherosclerosis.

Microorganisms in the aetiology of atherosclerosis

Recent publications have suggested that infective pathogens might play an important role in the pathogenesis of atherosclerosis. This review focuses on these microorganisms in the process of atherosclerosis. The results of in vitro studies, animal studies, tissue studies, and serological studies will be summarised, followed by an overall conclusion concerning the strength of the association of the microorganism with the pathogenesis of atherosclerosis. The role of the bacteria Chlamydia pneumoniae and Helicobacter pylori, and the viruses human immunodeficiency virus, coxsackie B virus, cytomegalovirus, Epstein-Barr virus, herpes simplex virus, and measles virus will be discussed.

Chlamydia pneumoniae seropositivity is associated with carotid artery intima-media thickness

BACKGROUND AND PURPOSE

Infection may both augment the atherosclerotic process and contribute to later manifestations of overt clinical disease. Chlamydia pneumoniae elementary bodies have been detected in atherosclerotic lesions. The aim of the present study was to investigate whether elevated titers of antibodies and circulating immune complexes to C pneumoniae were associated with ultrasound findings indicating presence of atherosclerosis in the carotid artery.

METHODS

Serum titers of antibodies to C pneumoniae (IgM, IgA, IgG, and circulating immune complex) were related to intima-media thickness (IMT) and plaque status measured by B-mode ultrasound in the carotid artery in 113 men with treated hypertension and at least 1 of the following risk factors: hypercholesterolemia, smoking, or diabetes.

RESULTS

Any of the titers was elevated in 56 (50%) men, and common carotid artery IMT was thicker in this group compared with the 57 men without any elevated titers (1.00 versus 0.92 mm, P<0.05). There were no accompanying differences in blood pressure, lipid levels, blood glucose, or smoking. Elevation of separate antibody types and circulation immune complex were also associated with increased IMT. In the latter group, systolic blood pressure was higher among seropositive patients compared with those who had no circulating immune complex. Seropositivity was not related to plaque status.

CONCLUSIONS

Seropositivity for C pneumoniae was associated with an increased intima-media thickness in the common carotid artery but not plaque status in hypertensive men at high risk for cardiovascular disease.

Production of basic fibroblast growth factor and interleukin 6 by human smooth muscle cells following infection with Chlamydia pneumoniae

Chlamydia pneumoniae infection has been associated with asthma and atherosclerosis. Smooth muscle cells represent host cells for chlamydiae during chronic infection. In this study we demonstrated that C. pneumoniae infection of human smooth muscle cells in vitro increased production of interleukin 6 (IL-6) and basic fibroblast growth factor (bFGF) as shown by reverse transcription-PCR, immunoblotting, and enzyme-linked immunosorbent assay. In contrast, levels of platelet-derived growth factor A-chain mRNA were not affected after infection. The stimulation of bFGF and IL-6 production was most effective when viable chlamydiae were used as inoculum. Furthermore, inhibition of bacterial protein synthesis with chloramphenicol prevented up-regulation of IL-6 and bFGF in infected cells. Addition of IL-6 antibody to infected cultures diminished bFGF expression, indicating involvement of produced IL-6. These findings suggest that chlamydial infection of smooth muscle cells elicits a cytokine response that may contribute to structural remodeling of the airway wall in chronic asthma and to fibrous plaque formation in atherosclerosis.

Chlamydia pneumoniae and anti-infective therapy: their role in the pathogenesis and treatment of coronary artery disease

Cardiovascular disease remains the most common cause of death in the United States; however, conventional cardiovascular risk factors fail to explain completely the pathogenesis of atherosclerosis and coronary artery disease. There has been recent interest in the association between Chlamydia pneumoniae and the risk of development or progression of atherosclerotic disease. This association has become evident through serologic, pathologic, and animal-based models and, more recently, through limited trials of antichlamydial antibiotics in humans. Whether C. pneumoniae is a causative agent or "innocent bystander" or whether antibiotic therapy has any role in the treatment of cardiovascular disease remains to be determined.

Uptake of tetracycline by aortic aneurysm wall and its effect on inflammation and proteolysis

BACKGROUND

Proteolytic degradation of the aortic wall by matrix metalloproteinases (MMPs) is considered important in the pathogenesis of abdominal aortic aneurysms (AAAs). Many of these MMPs are inhibited by tetracycline derivatives, which may have the potential to retard aneurysm growth.

METHODS

Patients undergoing elective repair of an AAA (n = 5) received an intravenous bolus of tetracycline (500 mg) on induction of anaesthesia and levels of tetracycline in serum, aneurysm wall and mural thrombus were assessed by microbiological assay. In a separate series of patients (n = 7) aneurysm biopsies were placed into explant culture (with and without tetracyline) and the accumulation of protein, hydroxyproline, MMP-9, interleukin (IL) 6 and monocyte chemoattractant protein (MCP) 1 in the medium was assessed by colorimetric assay or immunoassay.

RESULTS

At aortic cross-clamping the median concentration of tetracycline was 8.3 microg/ml in serum, 2.9 microg per g tissue in aortic wall and zero in mural thrombus. Tetracycline inhibited, in a concentration-dependent manner, both MMP-9 and MCP-1 secretion (P = 0.022 and P = 0.018 respectively), but did not alter hydroxyproline or IL-6 secretion. At the highest concentration of tetracycline (100 microg/ml) median MMP-9 secretion was reduced from 27 to 5 ng/ml (P = 0.007) and median MCP-1 secretion was reduced from 50 to 10 ng/ml (P = 0.008).

CONCLUSION

Tetracycline rapidly penetrates the aortic wall, but the concentration achieved may be insufficient to alter collagen turnover through limitation of MMP production or activity.

Chlamydia pneumoniae infection of human endothelial cells induces proliferation of smooth muscle cells via an endothelial cell-derived soluble factor(s)

An association of Chlamydia pneumoniae with atherosclerosis and coronary heart disease has been determined epidemiologically and by the detection of C. pneumoniae organisms in atherosclerotic lesions in both humans and animal models of atherosclerosis. Previously, it has been shown that C. pneumoniae is capable of replicating in cell types found within atheromatous lesions, viz., endothelial cells, smooth muscle cells (SMC), and macrophages, yet the role of C. pneumoniae in the pathogenesis of atherosclerosis has not been determined. Since intimal thickening is a hallmark of atherosclerosis, we investigated whether C. pneumoniae infection of human umbilical vein endothelial cells (HUVEC) could induce the expression of a soluble factor(s) with mitogenic potential for SMC by using [3H]thymidine incorporation and direct cell counting. Conditioned medium harvested from HUVEC infected with C. pneumoniae stimulated SMC replication in a time- and dose-dependent fashion. Infection studies using various multiplicities of infection (MOIs) ranging from 0.001 to 1 demonstrated a dose-dependent production of the soluble factor(s). At an MOI of 1, SMC stimulation indices were 8.4 (P < 0.01) and 12.2 (P < 0.01) for conditioned media harvested at 24 and 48 h, respectively. To determine whether viable C. pneumoniae was required for production of the soluble factor(s), HUVEC were infected with heat-inactivated C. pneumoniae or with viable organisms in the presence of chloramphenicol. Both treatments produced stimulation indices similar to those for live C. pneumoniae in the absence of chloramphenicol (P > 0.05), indicating that the factor(s) was produced by HUVEC and not by C. pneumoniae and that signal transduction events following chlamydia endocytosis may be important in the production of a soluble factor(s). The ability of C. pneumoniae to elicit an endothelial cell-derived soluble factor(s) that stimulates SMC proliferation may be important in the pathogenesis of atherosclerosis.

Is cardiovascular disease preventable by vaccination?

The possibility of using vaccination as a tool in the prevention of atherosclerotic disease was opened by the findings that infection with Chlamydia pneumoniae was an independent risk factor for cardiovascular disease, including acute myocardial infarction. Since this finding, data have accumulated confirming the initial epidemiological association and demonstrating the presence of C. pneumoniae and/or its components in vascular lesions. Recent intervention trials with antimicrobial drugs have furthermore suggested a pathogenetic relationship. The role of C. pneumoniae needs, however, to be further confirmed before deciding on the use of a possible vaccine. At present, a vaccine for C. pneumoniae is not available but development is ongoing. The task is far from easy: the intracellular bacteria cannot be reached by antibodies, and the stimulation of CD8+ T cells required for protection is difficult with a nonliving vaccine. On the other hand, recent advances in biotechnology, including the sequence of the full genome of C. pneumoniae, provide unique tools for the work. With enough interest in the development of a C. pneumoniae vaccine the first clinical trials could be expected in several years' time. They will, however, have to be extensive in order to ascertain the safety of such a new type of vaccine intended for use in populations in which many have already been infected with the bacteria and many are chronic carriers. Who should be vaccinated is a question to be considered at that point.