Microorganisms in the aetiology of atherosclerosis

Thrombus Aspirates From Patients With Acute Ischemic Stroke Are Infiltrated by Viridans Streptococci

BACKGROUND

Acute ischemic stroke may be due to embolism from ruptured atherosclerotic carotid arteries. DNA of oral bacteria, mainly the viridans streptococci group, has been detected in thrombus aspirates of patients with ischemic stroke as well as in carotid endarterectomy samples. Because viridans streptococci are known to possess thrombogenic properties, we studied whether their presence in thrombus aspirates and in carotid artery specimens can be confirmed using bacterial immunohistochemistry.

METHODS AND RESULTS

Thrombus aspirates from 61 patients with ischemic stroke (70.5% men; mean age, 66.8 years) treated with mechanical thrombectomy, as well as carotid endarterectomy samples from 20 symptomatic patients (65.0% men; mean age, 66.2 years) and 48 carotid artery samples from nonstroke autopsy cases (62.5% men; mean age, 66.4 years), were immunostained with an antibody cocktail against 3 species (Streptococcus sanguinis, Streptococcus mitis, and Streptococcus gordonii) of viridans streptococci. Of the thrombus aspirates, 84.8% were immunopositive for viridans streptococci group bacteria, as were 80.0% of the carotid endarterectomy samples, whereas immunopositivity was observed in 31.3% of the carotid artery samples from nonstroke autopsies. Most streptococci were detected inside neutrophil granulocytes, but there were also remnants of bacterial biofilm as well as free bacterial infiltrates in some samples.

CONCLUSIONS

Oral streptococci were found in aspirated thrombi of patients with acute ischemic stroke as well as in carotid artery samples. Our results suggest that viridans streptococci group bacteria may play a role in the pathophysiology of ischemic stroke.

Oral Bacterial Signatures in Cerebral Thrombi of Patients With Acute Ischemic Stroke Treated With Thrombectomy

Background

Chronic infections have been reported to be risk factors for both coronary heart disease and ischemic stroke. DNA of oral bacteria, mainly from the viridans streptococci group, has been detected in coronary thrombus aspirates of myocardial infarction and cerebral aneurysms. Viridans streptococci are known to cause infective endocarditis and possess thrombogenic properties. We studied the presence of oral bacterial DNA in thrombus aspirates of patients with acute ischemic stroke treated with mechanical thrombectomy.

Methods and Results

Thrombus aspirates and arterial blood were taken from 75 patients (69% men; mean age, 67 years) with acute ischemic stroke. The presence of Streptococcus species, mainly the Streptococcus mitis group, belonging to viridans streptococci as well as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans in samples were determined using a quantitative polymerase chain reaction with specific primers and probes. The relative amount of bacterial DNA in a sample was determined with the comparative threshold cycle method. Bacterial DNA was detected in 84% (n=63) of aspired thrombi, and 16% (n=12) of samples were considered bacterial DNA negative. DNA of Streptococcus species, mainly the S mitis group, was found in 79% (n=59) of samples. The median relative amount of Streptococcus species DNA was 5.10‐fold higher compared with the control blood samples from the same patients. All thrombi were negative for both P gingivalis and A actinomycetemcomitans.

Conclusions

This is the first study showing the common presence of bacterial DNA from viridans streptococci in aspired thrombi of patients with acute ischemic stroke. Streptococcal bacteria, mostly of oral origin, may contribute to the progression and thrombotic events of cerebrovascular diseases.

Dyslipidemia and Associated Factors Among Patients Suspected to Have Helicobacter pylori Infection at Jimma University Medical Center, Jimma, Ethiopia

BACKGROUND

Dyslipidemia is a group of plasma lipid and lipoprotein abnormality that is metabolically associated, and it is categorized by low HDL-C and increased LDL-C, TGs, and total cholesterol (TC) levels. Colonization of the stomach by Helicobacter pylori (H. pylori) causes chronic inflammation of the stomach wall which can change some biochemical factors in the patient. On the association of H. pylori infection and its contributions to change in serum lipid profile, different studies reported varying outcomes.

OBJECTIVE

To assess the prevalence of dyslipidemia and associated factors among patients suspected for H. pylori infection in the outpatient department of Jimma University Medical Center, Jimma, Ethiopia.

MATERIALS AND METHODS

A hospital-based cross-sectional study was conducted from January 03 to April 05, 2019, at Jimma University Medical Center on 369 H. pylori suspected patients. The study subjects were selected by convenient sampling technique. About 5mL of blood was collected from an overnight fasting individual. Data were edited, coded, and entered into Epidata version 3.1 and exported to (SPSS) version 25 for analysis. Bivariate analysis was used to screen those variables which were candidates for multivariate analysis.

RESULTS

From the total study subjects 77.5% had at least one abnormality in lipid profile and 87.2% of H. pylori positive patients had at least one abnormality in lipid profile. Our study demonstrated that there was significant increase of mean ± SD of TC, TG, and LDL-C in H. pylori positive patients than H. pylori negative patients (P-value < 0.05). After adjusting for traditional dyslipidemia risk factors, H. pylori infection was an independent predictor of dyslipidemia (AOR 2.628, 95% CI 1.477-4.678, P=0.001).

CONCLUSION

An increase in prevalence of dyslipidemia among H. pylori positive patients indicates H. pylori infected patients have a possibility of altered lipid profile, therefore assessment of lipid profile in H. pylori infected patients is recommended.

Coagulation factor VIIa binds to herpes simplex virus 1-encoded glycoprotein C forming a factor X-enhanced tenase complex oriented on membranes

BACKGROUND

The cell membrane-derived initiators of coagulation, tissue factor (TF) and anionic phospholipid (aPL), are constitutive on the herpes simplex virus type 1 (HSV1) surface, bypassing physiological regulation. TF and aPL accelerate proteolytic activation of factor (F) X to FXa by FVIIa to induce clot formation and cell signaling. Thus, infection in vivo is enhanced by virus surface TF. HSV1-encoded glycoprotein C (gC) is implicated in this tenase activity by providing viral FX binding sites and increasing FVIIa function in solution.

OBJECTIVE

To examine the biochemical influences of gC on FVIIa-dependent FX activation.

METHODS

Immunogold electron microscopy (IEM), kinetic chromogenic assays and microscale thermophoresis were used to dissect tenase biochemistry. Recombinant TF and gC were solubilized (s) by substituting the transmembrane domain with poly-histidine, which could be orientated on synthetic unilamellar vesicles containing Ni-chelating lipid (Ni-aPL). These constructs were compared to purified HSV1 TF±/gC ± variants.

RESULTS

IEM confirmed that gC, TF, and aPL are simultaneously expressed on a single HSV1 particle where the contribution of gC to tenase activity required the availability of viral TF. Unlike viral tenase activity, the cofactor effects of sTF and sgC on FVIIa was additive when bound to Ni-aPL. FVIIa was found to bind to sgC and this was enhanced by FX. Orientation of sgC on a lipid membrane was critical for FVIIa-dependent FX activation.

CONCLUSIONS

The assembly of gC with FVIIa/FX parallels that of TF and may involve other constituents on the HSV1 envelope with implications in virus infection and pathology.

Updating the epidemiological transition model

The main feature of the epidemiological transition is a shift in the recorded causes of death from infectious diseases to other morbid conditions. This paper outlines modifications made to Omran's original model and stages of transition, and suggests that without a focus on aetiology and morbidity, these have been basically descriptive rather than explanatory, and potentially misleading because infections have been confirmed as causes of various chronic diseases. Common infections and related immune responses or inflammatory processes contribute to the multifactorial aetiology of morbid conditions that together make a substantial contribution to overall mortality, and infectious causation is suspected for many others because of strong evidence of association. Investigation into possible infectious causes of conditions frequently recorded as the underlying cause of death can be integrated into a framework for comparative research on patterns of disease and mortality in support of public health and prevention. A theory of epidemiological transition aimed at understanding changes in disease patterns can encompass the role in different conditions and chronic diseases of infections contracted over the life course, and their contribution to disability, morbidity and mortality relative to other causes and determinants.

Long-term trends in cardiovascular disease mortality and association with respiratory disease

The recent decline in cardiovascular disease mortality in Western countries has been linked with changes in life style and treatment. This study considers periods of decline before effective medical interventions or knowledge about risk factors. Trends in annual age-standardized death rates from cerebrovascular disease, heart disease and circulatory disease, and all cardiovascular disease are reviewed for three phases, 1881–1916, 1920–1939, and 1940–2000. There was a consistent decline in the cerebrovascular disease death rate between 1891 and 2000, apart from brief increases after the two world wars. The heart disease and circulatory disease death rate was declining between 1891 and 1910 before cigarette smoking became prevalent. The early peak in cardiovascular mortality in 1891 coincided with an influenza pandemic and a peak in the death rate from bronchitis, pneumonia and influenza. There is also correspondence between short-term fluctuations in the death rates from these respiratory diseases and cardiovascular disease. This evidence of ecological association is consistent with the findings of many studies that seasonal influenza can trigger acute myocardial infarction and episodes of respiratory infection are followed by increased risk of cardiovascular events. Vaccination studies could provide more definitive evidence of the role in cardiovascular disease and mortality of influenza, other viruses, and common bacterial agents of respiratory infection.

Chlamydia pneumoniae acute liver infection affects hepatic cholesterol and triglyceride metabolism in mice

OBJECTIVE

Chlamydia pneumoniae has been linked to atherosclerosis, strictly associated with hyperlipidemia. The liver plays a central role in the regulation of lipid metabolism. Since in animal models C. pneumoniae can be found at hepatic level, this study aims to elucidate whether C. pneumoniae infection accelerates atherosclerosis by affecting lipid metabolism.

METHODS

Thirty Balb/c mice were challenged intra-peritoneally with C. pneumoniae elementary bodies and thirty with Chlamydia trachomatis, serovar D. Thirty mice were injected with sucrose-phosphate-glutamate buffer, as negative controls. Seven days after infection, liver samples were examined both for presence of chlamydia and expression of genes involved in inflammation and lipid metabolism.

RESULTS

C. pneumoniae was isolated from 26 liver homogenates, whereas C. trachomatis was never re-cultivated (P < 0.001). C. pneumoniae infected mice showed significantly increased serum cholesterol and triglycerides levels compared both with negative controls (P < 0.001 and P = 0.0197, respectively) and C. trachomatis infected mice (P < 0.001). Liver bile acids were significantly reduced in C. pneumoniae compared to controls and C. trachomatis infected mice. In C. pneumoniae infected livers, cholesterol 7α-hydroxylase (Cyp7a1) and low-density lipoprotein receptor (Ldlr) mRNA levels were reduced, while inducible degrader of the low-density lipoprotein receptor (Idol) expression was increased. Hypertriglyceridemia was associated to reduced expression of hepatic carnitine palmitoyltransferase-1a (Cpt1a) and medium chain acyl-Coenzyme A dehydrogenase (Acadm). Pro-inflammatory cytokines gene expression was increased compared to negative controls. Conversely, in C. trachomatis infected animals, normal serum lipid levels were associated with elevated pro-inflammatory cytokines gene expression, linked to only a mild disturbance of lipid regulatory genes.

CONCLUSION

Our results indicate that C. pneumoniae mouse liver infection induces dyslipidemic effects with significant modifications of genes involved in lipid metabolism.

Promotion of atherosclerosis by Helicobacter cinaedi infection that involves macrophage-driven proinflammatory responses

Helicobacter cinaedi is the most common enterohepatic Helicobacter species that causes bacteremia in humans, but its pathogenicity is unclear. Here, we investigated the possible association of H. cinaedi with atherosclerosis in vivo and in vitro. We found that H. cinaedi infection significantly enhanced atherosclerosis in hyperlipidaemic mice. Aortic root lesions in infected mice showed increased accumulation of neutrophils and F4/80⁺ foam cells, which was due, at least partly, to bacteria-mediated increased expression of proinflammatory genes. Although infection was asymptomatic, detection of cytolethal distending toxin RNA of H. cinaedi indicated aorta infection. H. cinaedi infection altered expression of cholesterol receptors and transporters in cultured macrophages and caused foam cell formation. Also, infection induced differentiation of THP-1 monocytes. These data provide the first evidence of a pathogenic role of H. cinaedi in atherosclerosis in experimental models, thereby justifying additional investigations of the possible role of enterohepatic Helicobacter spp. in atherosclerosis and cardiovascular disease.

Evidence for the role of Epstein Barr Virus infections in the pathogenesis of acute coronary events

BACKGROUND

The role of viral infections in the pathogenesis of atherosclerosis remains controversial largely due to inconsistent detection of the virus in atherosclerotic lesions. However, viral infections elicit a pro-inflammatory cascade known to be atherogenic and to precipitate acute ischemic events. We have published in vitro data that provide the foundation for a mechanism that reconciles these conflicting observations. To determine the relation between an early viral protein, deoxyuridine triphosphate nucleotidohydrolase (dUTPase), produced following reactivation of Epstein Barr Virus (EBV) to circulating pro-inflammatory cytokines, intercellular adhesion molecule-1 (ICAM-1) and acute coronary events.

METHODOLOGY/PRINCIPAL FINDINGS

Blood samples were obtained from 299 patients undergoing percutaneous coronary intervention for stable angina (SA), unstable angina (UA), or acute myocardial infarction (AMI). Plasma concentrations of pro-inflammatory cytokines and neutralizing antibody against EBV-encoded dUTPase were compared in the three patient groups. AMI was associated with the highest measures of interleukin-6 (ANOVA p<0.05; 4.6 ± 2.6 pg/mL in patients with AMI vs. 3.2 ± 2.3 pg/mL in SA). ICAM-1 was significantly higher in patients with AMI (ANOVA p<0.05; 304 ± 116 pg/mL in AMI vs. 265 ± 86 pg/mL SA). The highest values of ICAM-1 were found in patients having an AMI and who were antibody positive for dUTPase (ANOVA p=0.008; 369 ± 183 pg/mL in AMI and positive for dUTPase vs. 249 ± 70 pg/mL in SA negative for dUTPase antibody).

CONCLUSIONS/SIGNIFICANCE

These clinical data support a model, based on in vitro studies, by which EBV may precipitate AMI even under conditions of low viral load through the pro-inflammatory action of the early protein dUTPase that is produced even during incomplete viral replication. They further support the putative role of viral infections in the pathogenesis of atherosclerosis and coronary artery events.

[Manganese in atherogenesis: detection, origin, and role]

The role of transition metal ions in atherogenesis is controversial; they can participate in the hydroxyl radical generation and catalyze the reactive oxygen species neutralization reaction as cofactors of antioxidant enzymes. Using EPR spectroscopy, we revealed that 70% of the samples of aorta with atherosclerotic lesions possessed superoxide dismutase activity, 100% of the samples initiated Fenton reaction and demonstrated the presence of manganese paramagnetic centers. The sodA gene encoding manganese-dependent bacterial superoxide dismutase was not found in the samples of atherosclerotic plaques by PCR using degenerate primers. The data obtained indicates the perspectives of manganese analysis as a marker element in the express diagnostics of atherosclerosis.

An atherogenic lipid profile with low serum paraoxonase-1 activity during nematode infection in rats

BACKGROUND

Inflammation and oxidative stress are associated with cardiovascular diseases and underlying atherosclerosis. The high density lipoprotein (HDL)-associated paraoxonase-1 (PON1) enzyme is known to be involved in the protection of serum lipids from such oxidation. Nonetheless, the disturbances of lipid profile during nematode-infected model have not yet been studied. Therefore, we aimed to explore the effects of Nippostrongylus brasiliensis infection in male Wistar rats, a model of human gastrointestinal nematode infections, on hepatic PON1 synthesis and the levels of lipid parameters.

MATERIALS AND METHODS

Nippostrongylus brasiliensis-infected rats fed standard and high-fat diets. Serum paraoxonase and arylesterase activities were measured on day 0, 2, 4, 7, and 14 post-infection (PI). Hepatic PONs and pro-inflammatory cytokines mRNA expression levels were evaluated in a standard diet-fed groups, and the disturbances in lipid profile as well as the levels of thiobarbituric acid reactive species (TBARS) and oxidized-LDL (Ox-LDL) were measured in high-fat diet-fed groups.

RESULTS

We found that N. brasiliensis-infected rats fed the standard diet show a significant reduction in serum PON1 activity and down-regulation of hepatic PON1 mRNA expression as well as up-regulation of hepatic IL-1β, IL-β receptor (R), TNF-α, and TNFR1 mRNA expressions in association with hepatic recruitments of Kupffer cells and neutrohils. In the presence of the high-fat diet, N. brasiliensis infection increases serum triglycerides, total cholesterol, LDL/VLDL, TBARS and Ox-LDL as well as decreases serum HDL coinciding with a maximum serum PON1 reduction.

CONCLUSIONS

Nippostrongylus brasiliensis infection can induce atherogenic lipid profile and reduce serum PON1 activity.

Number of teeth as a predictor of cardiovascular mortality in a cohort of 7,674 subjects followed for 12 years

BACKGROUND

That oral health is related to the development of different cardiovascular disorders is reported in a number of studies. This study investigates if different parameters of oral health are associated with future mortality in different cardiovascular disorders in a dose-dependent manner.

METHODS

A total of 7,674 subjects (3,300 males and 4,374 females; age range 20 to 89 years) received a dental examination by specialists in periodontology between the years 1976 and 2002. Number of remaining teeth, severity of periodontal disease, number of deepened periodontal pockets, and bleeding on probing were evaluated in relation to cause of death.

RESULTS

During a median follow-up period of 12 years, 629 of the subjects died. For 299 subjects the cause of mortality was cardiovascular disease (CVD); 167 of these subjects died from coronary heart disease (CHD); 83 died from stroke; and 49 died from aortic aneurysm or congestive heart failure. The causes of death for the remaining 330 subjects were other than CVD. After adjustment for age, gender, and smoking, number of remaining teeth predicted in a dose-dependent manner all-cause mortality and mortality in CVD and in CHD (P <0.0001 for all), but not mortality from stroke (P = 0.15). Cox regression analysis revealed a seven-fold increased risk for mortality from CHD in subjects with <10 teeth compared to those with >25 teeth. Severity of periodontal disease, number of deepened periodontal pockets, and bleeding on probing were not related to mortality in a dose-dependent manner after adjustment for confounders.

CONCLUSION

This fairly large, prospective study with a long follow-up period presents for the first time a dose-dependent relationship between number of teeth and both all-cause and CVD mortality, indicating a link between oral health and CVD, and that the number of teeth is a proper indicator for oral health in this respect.

Cryptococcus neoformans causes lipid peroxidation; therefore it is a potential inducer of atherogenesis

Certain viral and bacterial species play a role in the development of atherosclerosis. Our hypothesis was that yeasts, such as Cryptococcus neoformans, also may be a cause of lipid peroxidation (LPO), which can lead to atherosclerosis. Rabbits were inoculated with heat-killed C neoformans several times during the first 6 wk in 10 wk observation. These tests were done at regular intervals: (i) blood cell count, (ii) the nitroblue tetrazolium (NBT) test on isolated neutrophils to determine their super oxide anion production and (iii) LPO of plasma. The histopathology of the lungs also was evaluated. In the inoculated rabbits we found an increase in the number of neutrophils in blood with an elevated NBT reduction, an increase in lipid peroxidation of plasma and bronchopneumonia with various types of inflammatory cells. Our findings suggest that the ability of C. neoformans to induce LPO in human asymptomatic carriers should be studied. Moreover the cryptococcal rabbit model we use rapidly induces LPO and may be of value in the assessment of therapy for atherosclerosis.

Intracellular infections enhance interleukin-6 and plasminogen activator inhibitor 1 production by cocultivated human adipocytes and THP-1 monocytes

Obesity is associated with a chronic inflammatory state, and adipocyte dysfunction is thought to play a crucial role in this. Infection of adipose tissue may trigger the production of inflammatory cytokines, leading to increased recruitment of macrophages into adipose tissue, which in turn may exacerbate the inflammatory state in obesity. Low-grade inflammation was mimicked in an in vitro coculture model with human adipocytes and THP-1 monocytes. Adipocytes and monocytes were infected with adenovirus, cytomegalovirus (CMV), or influenza A virus. After 48 h, transinfection was evaluated and interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), adiponectin, and plasminogen activator inhibitor 1 (PAI-1) were measured. IL-6 production was upregulated in cocultures of uninfected adipocytes and THP-1 macrophages in a THP-1 cell number-dependent fashion. IL-6 production by CMV-infected adipocytes was increased relative to that of uninfected adipocytes (P < 0.01). IL-6 production by CMV-infected cocultures was 16- to 37-fold higher than that of uninfected adipocytes (P < 0.001). IL-6 production in influenza A virus-infected cocultures was increased 12- to 20-fold (P < 0.05). Only CMV infection increased levels of PAI-1 in cocultures (fourfold; P < 0.05). Soluble factors produced by THP-1 macrophages rather than by adipocytes were responsible for the increased production of IL-6 in cocultures. Infection of cocultivated human adipocytes and THP-1 monocytes with CMV or influenza A virus led to increased production of IL-6 and PAI-1. Thus, infection of adipose tissue evokes an inflammatory response, leading to adipose tissue dysfunction and subsequent overproduction of IL-6 and PAI-1. This may further compound the atherogenic effects of obesity.

Emerging role of Toll-like receptors in atherosclerosis

Atherosclerosis is inflammation of the vessel wall of the arterial tree. This inflammation arises at specific areas that experience disturbed blood flow such as bifurcations and the lesser curvature of the aortic arch. Although all endothelial cells are exposed to comparable levels of circulating plasma cholesterol, only endothelial cells overlaying lesions display an inflamed phenotype. This occurs even in the absence of any additional exacerbating disease factors because blood flow controls the expression of Toll-like receptors (TLR), which are initiators of cellular activation and inflammation. TLR2- and 4-expression exert an overall proatherogenic effect in hyperlipidemic mice. TLR activation of the endothelium promotes lipid accumulation and leukocyte accumulation within lesions.

Increased infiltration of Chlamydophila pneumoniae in the vessel wall of human veins after perfusion

BACKGROUND

Several studies have suggested an association between Chlamydophila pneumoniae (Cp) infection and atherosclerosis. A recent study detected Cp DNA in the saphenous vein of 12% of all patients before bypass grafting and in 38% of failed grafts. We used a system in which human veins were perfused with autologous blood under arterial pressure.

MATERIALS AND METHODS

Veins were surplus segments of saphenous veins of coronary artery bypass grafting (CABG) patients. Vein grafts were perfused with the blood of the same patient after CABG procedures. Veins were analysed for Cp-specific membrane protein using immunohistochemical and PCR analysis. Veins were analysed before and after perfusion (up to 4 h). The number of Cp positive cells was then quantified in the vein layers.

RESULTS

Cp protein was detected within macrophages only. In non-perfused veins, Cp was present in the adventitia in 91% of all patients, in the circular (64%) and longitudinal (23%) layer of the media. No positivity was found in the intima. Perfusion subsequently resulted in a significant increase of Cp positive cells within the circular layer of the media that, however, differed strongly between different patients. Cp DNA was not detected by PCR in those specimens.

CONCLUSION

Cp protein was present in 91% of veins, but the number of positive cells differed remarkably between patients. Perfusion of veins resulted in increased infiltration of Cp into the circular layer. These results may point to a putative discriminating role of Cp with respect to graft failure between different patients.

Human immunodeficiency virus infection and macrophage cholesterol metabolism

Macrophages play a central role in the pathogenesis of atherosclerosis and are also a host for a number of viruses, most importantly, HIV. Many viruses, including HIV, require cholesterol for their replication and as a structural element. Cholesterol also plays a pivotal role in innate antiviral immune responses. Although impairing innate immune response by increasing cell cholesterol content may be a deliberate strategy used by a pathogen to improve its infectivity, enhancing the risk of atherosclerosis is likely a byproduct. Consistent association between HIV infection and elevated risk of atherosclerosis suggested a connection between virus-induced changes in cholesterol metabolism and atherogenesis, but the mechanisms of such connection have not been identified. We describe in this review various mechanisms enabling viruses to exploit macrophage pathways of cholesterol metabolism, thus diverting cholesterol for a purpose of increasing viral replication and/or for altering innate immune responses. To alter the cellular cholesterol content, viruses "hijack" the pathways responsible for maintaining intracellular cholesterol metabolism. The damage to these pathways by viral infection may result in the inability of macrophages to control cholesterol accumulation and may lead to formation of foam cells, a characteristic feature of atherosclerosis. Further elucidation of the mechanisms connecting viral infection and macrophage cholesterol metabolism may be fruitful for developing approaches to treatment of atherosclerosis and viral diseases.

Enterovirus in arteriosclerosis: A pilot study

BACKGROUND

Various pathogens have been suspected to play a role in the initiation or amplification of the atherosclerotic lesions. Both experimental and epidemiological arguments plead for a possible role of enterovirus in this process.

OBJECTIVE

To determine the prevalence of enterovirus genome in atherosclerotic plaques, in comparison with Chlamydia pneumoniae, human cytomegalovirus (hCMV) and herpes simplex virus.

STUDY DESIGN

Pilot study on 18 patients who underwent artery resection. Five artery samples were tested for each patient and each pathogen by using PCR techniques whose sensitivity was evaluated for this kind of specimen. The quality of the extraction step was assessed by amplification of a fragment of the human aldolase A gene.

RESULTS

The genome of at least one infectious agent was detected in artery samples from 7 of the 18 patients (38.9%). In all cases, only one of the five aliquots was found positive; a confirmation was done by sequencing the PCR product. With regards to enterovirus, four patients (22.2%) were detected positive (one of them being also positive for hCMV).

CONCLUSIONS

These results suggest that small amounts of enterovirus genome are commonly found in lesions of patients with advanced arteriosclerosis. Further studies are needed to evaluate the clinical significance of this association.

Human immunodeficiency virus impairs reverse cholesterol transport from macrophages

Several steps of HIV-1 replication critically depend on cholesterol. HIV infection is associated with profound changes in lipid and lipoprotein metabolism and an increased risk of coronary artery disease. Whereas numerous studies have investigated the role of anti-HIV drugs in lipodystrophy and dyslipidemia, the effects of HIV infection on cellular cholesterol metabolism remain uncharacterized. Here, we demonstrate that HIV-1 impairs ATP-binding cassette transporter A1 (ABCA1)-dependent cholesterol efflux from human macrophages, a condition previously shown to be highly atherogenic. In HIV-1–infected cells, this effect was mediated by Nef. Transfection of murine macrophages with Nef impaired cholesterol efflux from these cells. At least two mechanisms were found to be responsible for this phenomenon: first, HIV infection and transfection with Nef induced post-transcriptional down-regulation of ABCA1; and second, Nef caused redistribution of ABCA1 to the plasma membrane and inhibited internalization of apolipoprotein A-I. Binding of Nef to ABCA1 was required for down-regulation and redistribution of ABCA1. HIV-infected and Nef-transfected macrophages accumulated substantial amounts of lipids, thus resembling foam cells. The contribution of HIV-infected macrophages to the pathogenesis of atherosclerosis was supported by the presence of HIV-positive foam cells in atherosclerotic plaques of HIV-infected patients. Stimulation of cholesterol efflux from macrophages significantly reduced infectivity of the virions produced by these cells, and this effect correlated with a decreased amount of virion-associated cholesterol, suggesting that impairment of cholesterol efflux is essential to ensure proper cholesterol content in nascent HIV particles. These results reveal a previously unrecognized dysregulation of intracellular lipid metabolism in HIV-infected macrophages and identify Nef and ABCA1 as the key players responsible for this effect. Our findings have implications for pathogenesis of both HIV disease and atherosclerosis, because they reveal the role of cholesterol efflux impairment in HIV infectivity and suggest a possible mechanism by which HIV infection of macrophages may contribute to increased risk of atherosclerosis in HIV-infected patients.

HIV1-Nef impairs ABCA1-dependent cholesterol efflux from infected macrophages, promoting the transformation of virally infected macrophages into foam cells (a condition that may put HIV patients at risk for atherosclerosis).

Severity of periodontal disease and number of remaining teeth are related to the prevalence of myocardial infarction and hypertension in a study based on 4,254 subjects

BACKGROUND

During the past 15 years, mounting evidence for the association between periodontal and cardiovascular disease has been presented in epidemiological studies. The aim of this study was to investigate how the severity of periodontal disease and number of remaining teeth relates to myocardial infarction (MI) and hypertension (HT).

METHODS

Self-reported history of HT and MI was collected in 3,352 patients referred to the Department of Periodontology, Gävle County Hospital, and in 902 subjects randomly selected from the general population. Severity of periodontitis was estimated by a combination of the amount of bone loss around each tooth investigated from a full-mouth x-ray, the presence or absence of bleeding on probing (BOP), and involvement of furcations.

RESULTS

The severity of periodontitis was significantly associated with HT (prevalence 16%; P<0.0005), even after adjustment for age, gender, number of teeth, and smoking in the total sample, and with MI (prevalence 1.7%, P<0.03) after above-mentioned adjustments, but in middle-aged (40 to 60 years) subjects only. The number of diseased periodontal pockets was related to HT only (P<0.0001), and this relationship remained after the above-mentioned adjustments. The number of teeth was associated with MI (P<0.03) even after correction for age, gender, and smoking but was not related to hypertension.

CONCLUSIONS

The severity of periodontal disease was related to HT independent of age but to the prevalence of MI in middle-aged subjects only. The number of diseased pockets was significantly related to HT only. On the other hand, the number of teeth was associated with the prevalence of MI independent of age but not to HT. These data support the view that oral health is related to cardiovascular disease in a dose-dependent manner.

No evidence of association between NOD2/CARD15 gene polymorphism and atherosclerotic events after renal transplantation

Stable renal transplant recipients (RTR) display high rates of atherosclerotic events (AE). Innate immunity and especially vascular inflammation play a role in the pathogenesis of atherosclerosis. It is illustrated both by an increased occurrence of postrenal transplant cardiovascular events in patients with elevated levels of C-reactive protein and by a correlation between posttransplant AE and Toll-like receptor-4 Asp299Gly polymorphism. Here, we analyze the influence NOD2/CARD15 gene polymorphism since NOD2 can modulate macrophage pro-inflammatory activity and macrophage is present in early atherosclerotic lesions. The incidence of single nucleotide polymorphism (SNP) in the three major polymorphic region of NOD2 gene (SNP8, SNP12 and SNP13) was assessed in 182 RTR and the correlation between such polymorphism and the development of AE was analyzed. No correlation was observed between NOD2 gene polymorphism and the occurrence of AE after renal transplantation. NOD2 gene polymorphism thus does not appear to influence cardiovascular complications in RTR.

Chlamydia Pneumoniae Infection: An Additional Factor for Chronic Allograft Rejection

INTRODUCTION

Chronic rejection (CHR) of organ allografts, one of the most significant problems in modern transplantation, is not fully understood. This study sought to evaluate the influence of selected parameters on late kidney transplant function.

PATIENTS AND METHOD

The studied group consisted of eighty-six patients who received allogeneic transplants between 1988 and 1999 for leukocyte Chlamydia pneumoniae-DNA, immunoglobulin (Ig)A/IgG anti-C pneumoniae, blood lipids, ischemic damage in the donor and during organ preservation, HLA mismatch, and acute rejection episodes.

RESULTS

Eighty-six patients were segregated as 26 patients (30%) with histologically proven chronic graft rejection (CHR[+]) and 59 patients (70%) without (CHR[-]). The presence of C pneumoniae-DNA in peripheral blood leukocytes was significantly more frequent in CHR(+) than CHR(-) group (46% vs 20%). Patients with leukocytes positive for C pneumoniae-DNA more frequently (50%) had CHR than patients negative for C pneumoniae-DNA (22%). CHR(+) patients showed significantly lower HDL levels (47 mg/dL vs 58 mg/dL) and higher triglyceride levels (193 mg/dL vs 148 mg/dL). To study the cumulative effect of differences between the CHR(+) and CHR(-) groups, we applied a multiple binary logistic regression analysis. An econometric model enabled us to calculate the probability of CHR for a given patient taking into account covariates chosen by means of stepwise selection: the presence of C pneumoniae-DNA in blood leukocytes, the use of continuous pulsatile perfusion in hypothermia, myocardial infarction occurrence, and triglyceride concentrations.

CONCLUSION

The presence of C pneumoniae-DNA in peripheral blood leukocytes increased the risk of CHR, which may be predicted by a multifactor analysis of chosen parameters.

Chlamydia pneumoniae (C. pneumoniae) infection upregulates atherosclerosis-related gene expression in human umbilical vein endothelial cells (HUVECs)

There is accumulating evidence that supports a role of infection in atherosclerosis, with possible mechanism by injuring to the endothelium and inducing an autoimmune response to heat shock proteins (HSPs). In this study, a cDNA array, containing 588 human cardiovascular genes, was utilized to analyze the gene expression profile of Chlamydia pneumoniae (C. pneumoniae) infected human umbilical vein endothelial cells (HUVECs). After 48h of C. pneumoniae infection, the HUVECs were harvested and subjected to immunofluorescent staining, electron microscopy, cDNA array hybridization, RT-PCR, and immunoblotting. This study found a panel of human host genes that were upregulated by C. pneumoniae. The majority of these genes were related to complex lipid metabolism, adhesion receptors, hormones, hormone receptors, and a metalloproteinase that may contribute to atherosclerosis in vivo. Representatives of upregulated gene products, i.e., heat shock protein 60 (HSP60), macrophage scavenger receptor, cytochrome P450, and VEGF165R were immunofluorescently detected in HUVECs, with their greater expression induced by C. pneumoniae infection. These findings supported the opinion that C. pneumoniae might contribute to atherosclerotic development in vivo.

[Infectious features of atherosclerosis]

As an inflammatory focus, the atherosclerotic plaque is viewed as a response to aggressions. Suppressing these causal injuries appears as the best means for preventing the disease. Infection is among the clues for answering the etiological challenge of atherosclerosis. Through direct or indirect, and specific or non specific pathways, some candidate viruses or bacteria are suspected to induce or stimulate plaque formation or complications. Yet, none of these working hypotheses has reached the level of proof required for establishing a valid concept. Although submitted to intensive investigations, anti-infectious drugs and antimicrobial vaccinations are still far-sighted expectations in the treatment and prevention of coronary artery disease.

Procoagulant and inflammatory response of virus-infected monocytes

BACKGROUND

Monocytes play a prominent role in inflammation, coagulation and atherosclerosis by their ability to produce tissue factor (TF) and cytokines. The aim of the present study was to establish whether virus-infected monocytes initiate coagulation. In addition, the production of cytokines by monocytes may accelerate the chronic process of atherosclerosis and may contribute to coronary syndromes by eliciting plaque instability.

MATERIALS AND METHODS

Monocytes were isolated by Vacutainer(R), BD Biosciences, Alphen aan den Rijn, Netherlands and subsequent magnetic cell sorting (MACS(R), Milteny Biotec, Bergish Gladbach, Germany). Coagulation times in normal pooled plasma and Factor VII-deficient plasma were measured after infection with cytomegalovirus (CMV), Chlamydia pneumoniae (Cp) and influenza A\H1N1. Anti-TF antibodies were added to neutralize TF expressed on monocytes. Interleukins (IL) 6, 8 and 10 were measured in the supernatants.

RESULTS

Chlamydia pneumoniae- and CMV-infected monocytes decreased the clotting time by 60%, and influenza-infected monocytes by 19%, as compared to uninfected monocytes. Procoagulant activity was absent when Factor VII-deficient plasma or anti-TF antibodies were used. Monocytes produced both IL-6 and IL-8 after infection with CMV (317 pg mL-1 and 250 pg mL-1) or Cp (733 pg mL-1 and 268 pg mL-1). Similar results were obtained for influenza virus-infected monocytes, but the levels of both cytokines were 3-5-fold higher (1797 pg mL-1 and 725 pg mL-1). Interleukin-10 was not produced by infected monocytes.

CONCLUSION

The procoagulant activity of virus-infected monocytes is TF-dependent. Although influenza infection did not generate a significant reduction in clotting time, the pronounced expression of IL-6 and IL-8 may induce local and/or systemic inflammatory reactions, which may be associated with plaque rupture and atherosclerosis. The lack of production of the anti-inflammatory cytokine IL-10 may even accelerate these processes.

The other side of the coin: impact of toxin generation and nutrition on the uremic syndrome

Both the morbidity of the uremic syndrome and the generation of uremic toxins are attributed to malnutrition. If protein intake and catabolism result in the generation of solutes, then nutritional intake should be related directly to toxicity. On the other hand, inadequate nutrition has been linked to inflammation and mortality. It remains difficult to reconcile these two lines of thought. Several possibilities exist that might account for this apparent paradox: 1) not all nutritional and protein degradation products are toxic; 2) toxins generated from increased protein intake are removed if protein intake is linked to dialysis dose; 3) albumin acts as a buffer for toxicity-hypoalbuminemia favors liberation of protein-bound toxins from their binding sites, enhancing their toxicity; 4) solutes generated from tissue breakdown are more toxic than those generated by nutritional protein; 5) both high and low concentrations of solutes have a negative impact; 6) toxic compounds unrelated to protein breakdown are specific causes of malnutrition and inflammation; 7) and/or residual renal function plays a key role in the elimination of compounds discussed under possibility 6. Thus the uremic syndrome should be considered as a potentially fatal interaction among inflammation, malnutrition, low levels of albumin in the plasma, accumulated protein-bound solutes and generation of nonnutritionally related toxins. Not only optimal dialysis, but also optimal nutritional intake and optimal utilization of these nutrients should help neutralize this chain of events.

Advanced coronary and carotid arteriopathy in young adults with childhood-onset chronic renal failure

BACKGROUND

Cardiovascular mortality is excessive in young adults with end-stage renal disease (ESRD). The factors contributing to ESRD-related vascular disease are incompletely understood. Young adults with childhood-onset chronic renal failure (CRF) are uniquely suited for risk factor assessment because of their long-term exposure at an age when vascular pathology in the general population is still minimal.

METHODS AND RESULTS

We used novel noninvasive technologies to screen for coronary and carotid artery disease in 39 patients with ESRD aged 19 to 39 years with childhood-onset CRF presently treated by dialysis or renal transplantation. Coronary artery calcification burden was assessed by CT scan with ECG gating and the intima-media thickness (IMT) of the carotid arteries by high-resolution ultrasound. Coronary artery calcifications were present in 92% of patients; calcium scores exceeded the 95th age- and sex-specific percentiles >10-fold on average. Carotid IMT was significantly increased compared with matched control subjects. Both coronary calcium scores and IMT were associated with cumulative dialysis and ESRD time and the cumulative serum calcium-phosphate product. Coronary calcium scores were strongly correlated with C-reactive protein and Chlamydia pneumoniae seropositivity, time-averaged mean serum parathyroid hormone, and plasma homocysteine. C-reactive protein and parathyroid hormone independently predicted coronary calcium accumulation. Smoking, obesity, and HbA1c were correlated with IMT in the control subjects but not in the patients.

CONCLUSIONS

Young adults with childhood-onset CRF have a high prevalence of arteriopathy associated with indicators of microinflammation, hyperparathyroidism, calcium-phosphate overload, and hyperhomocysteinemia but not traditional atherogenic risk factors. These risk factors persist even after successful renal transplantation.

Enhanced atherogenesis is not an obligatory response to systemic herpesvirus infection in the apoE-deficient mouse: comparison of murine gamma-herpesvirus-68 and herpes simplex virus-1

Viral and bacterial infectious agents have been implicated in the etiology of atherosclerosis. We have previously shown that a gamma-herpesvirus can accelerate atherosclerosis in the apolipoprotein E-deficient (apoE-/-) mouse. To address whether a virally induced systemic immune response is sufficient to trigger enhanced atheroma formation, we infected apoE-/- mice with murine gamma-herpesvirus-68 (MHV-68) or herpes simplex virus-1 (HSV-1). In this study, we show that both viruses were able to induce a cell-mediated and humoral immune response in the apoE-/- mouse, which was sustained over a period of 24 weeks. Although intranasal or intraperitoneal infection with MHV-68 induced similar levels of virus-specific IgG1 and IgG2a antibodies in the serum of apoE-/- mice, those infected with HSV-1 showed higher anti-HSV-1 IgG2a compared with IgG1 antibody levels. In addition, viral message was not detected in the aortas of HSV-1-infected animals, whereas we have shown previously that MHV-68 mRNA can be detected in the aortas of infected mice as early as 5 days after infection. Compared with control mice, apoE-/- mice infected with MHV-68 showed accelerated atherosclerosis, whereas mice infected with HSV-1 did not. These data indicate that a systemic immune response to any particular infectious agent is insufficient to induce enhanced atherosclerosis in the apoE-/- mouse and point to specific infections or immune mechanisms that might be essential for virally enhanced atherogenesis.

Chlamydia pneumoniae in infrequently examined blood vessels

AIM

To determine the prevalence of Chlamydia pneumoniae DNA in infrequently examined blood vessels.

METHODS

Vessels obtained from 15 men and six women at coronary artery bypass surgery were tested by a nested polymerase chain reaction (PCR) assay for C pneumoniae DNA.

RESULTS

Chlamydia pneumoniae DNA was detected in four of six atheromatous ascending aorta specimens but in none of eight non-atheromatous aorta specimens, in six of 11 atheromatous internal mammary artery specimens but in none of seven non-atheromatous internal mammary artery specimens, in five of seven long saphenous vein specimens showing evidence of disease but in none of 12 specimens without evidence of disease, and in two of three previously grafted veins. Overall, C pneumoniae occurred significantly more often in diseased than in normal vessels (p = < 0.00001).

CONCLUSIONS

Chlamydia pneumoniae is often present in diseased areas of arteries, including the internal mammary arteries, and even in diseased areas of veins. It is not present in apparently healthy areas of either type of vessel.

Herpesvirus (HSV-1, EBV and CMV) infections in atherosclerotic compared with non-atherosclerotic aortic tissue

The viral nucleic acid of herpes simplex virus type 1 (HSV-1), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) was studied by polymerase chain reaction (PCR), Southern blotting and in situ hybridization (ISH) in aortic tissues from 33 autopsies. In 23 cases involving persons who ranged from 23 weeks to 75 years of age at the time of death, the tissue was histologically non-atherosclerotic. Of these 23, aortic tissues tested positive for HSV-1 in 13%, for EBV in 13% and for CMV in 4%. In the other 10 cases involving persons who were 53-75 years old at death, atherosclerotic aortic tissue tested positive for HSV-1 in 80%, for EBV in 80% and for CMV in 40%. Neither double nor triple infections occurred in the non-atherosclerotic group, whereas six of 10 were positive for two viruses, and two of 10 were positive for three viruses in the atherosclerotic group. By in situ hybridization, the viruses were localized in cells morphologically consistent with endothelial cells and smooth muscle cells. We detected HSV-1, EBV and CMV DNA in cells in the upper portion of the non-atherosclerotic aortic wall, whereas viral DNA was detected more extensively in atherosclerotic lesions than in non-atherosclerotic tissue. We also are the first to show the existence of EBV DNA in the human aortic wall. In conclusion, we suggest that the high incidence and kinds of herpesviruses are related to the high incidence of atherosclerosis.

Asymptomatic Internal Carotid Artery Origin Stenosis

Proper therapy for patients with internal carotid artery stenosis requires a precise pathophysiologic diagnosis that includes characterization and localization of ischemic disease of the brain and knowledge of the arterial disease and the collateral cerebral circulation. Noninvasive techniques such as duplex ultrasound and transcranial Doppler, magnetic resonance angiography, and CT angiography allow precise determination of the stroke subtype and parent arterial pathology. Antiplatelet agents prevent the formation of thrombus on carotid artery atherosclerotic plaque. 3-Hydroxy-3-methyglutaryl coenzyme A reductase inhibitors may help stabilize carotid plaques by altering the plaque morphology and reducing inflammation. Carotid endarterectomy, which is the only procedure proven to be beneficial for patients with asymptomatic disease, should be considered primary intervention. Until ongoing trials for interventional procedures are completed, carotid artery angioplasty and stenting should be considered only in patients with contraindications to carotid endarterectomy. It can be argued that an ideal clinical trial in a high-risk population has not yet been completed. This factor has become even more important with the development of stenting procedures. We have long advocated a trial of only treating patients with hemodynamically significant stenotic lesions (70% to 99%).