Regulation of cellular immunity prevents Helicobacter pylori-induced atherosclerosis

Bacterial Infections and Atherosclerosis – A Mini Review

Atherosclerosis is the most challenging subsets of coronary artery disease in humans, in which risk factors emerge from childhood, and its prevalence increases with age. Experimental research demonstrates that infections due to bacteria stimulate atherogenic events. Atherosclerosis has complex pathophysiology that is linked with several bacterial infections by damaging the inner arterial wall and heart muscles directly and indirectly by provoking a systemic pro-inflammation and acute-phase protein. Repeated bacterial infections trigger an inflammatory cascade that triggers immunological responses that negatively impact cardiovascular biomarkers includes triglycerides, high-density lipoprotein, C-reactive protein, heat shock proteins, cytokines, fibrinogen, and leukocyte count. Herein, we intended to share the role of bacterial infection in atherosclerosis and evaluate existing evidence of animal and human trials on the association between bacterial infections and atherosclerosis on update.

Infection and atherosclerosis: TLR-dependent pathways

Atherosclerotic vascular disease (ASVD) is a chronic process, with a progressive course over many years, but it can cause acute clinical events, including acute coronary syndromes (ACS), myocardial infarction (MI) and stroke. In addition to a series of typical risk factors for atherosclerosis, like hyperlipidemia, hypertension, smoking and obesity, emerging evidence suggests that atherosclerosis is a chronic inflammatory disease, suggesting that chronic infection plays an important role in the development of atherosclerosis. Toll-like receptors (TLRs) are the most characteristic members of pattern recognition receptors (PRRs), which play an important role in innate immune mechanism. TLRs play different roles in different stages of infection of atherosclerosis-related pathogens such as Chlamydia pneumoniae (C. pneumoniae), periodontal pathogens including Porphyromonas gingivalis (P. gingivalis), Helicobacter pylori (H. pylori) and human immunodeficiency virus (HIV). Overall, activation of TLR2 and 4 seems to have a profound impact on infection-related atherosclerosis. This article reviews the role of TLRs in the process of atherosclerosis after C. pneumoniae and other infections and the current status of treatment, with a view to providing a new direction and potential therapeutic targets for the study of ASVD.

Helicobacter pylori Infection Impairs Endothelial Function Through an Exosome-Mediated Mechanism

Background

Epidemiological studies have suggested an association between Helicobacter pylori (H pylori) infection and atherosclerosis through undefined mechanisms. Endothelial dysfunction is critical to the development of atherosclerosis and related cardiovascular diseases. The present study was designed to test the hypothesis that H pylori infection impaires endothelial function through exosome‐mediated mechanisms.

Methods and Results

Young male and female patients (18‐35 years old) with and without H pylori infection were recruited to minimize the chance of potential risk factors for endothelial dysfunction for the study. Endothelium‐dependent flow‐mediated vasodilatation of the brachial artery was evaluated in the patients and control subjects. Mouse infection models with CagA⁺H pylori from a gastric ulcer patient were created to determine if H pylori infection‐induced endothelial dysfunction could be reproduced in animal models. H pylori infection significantly decreased endothelium‐dependent flow‐mediated vasodilatation in young patients and significantly attenuated acetylcholine‐induced endothelium‐dependent aortic relaxation without change in nitroglycerin‐induced endothelium‐independent vascular relaxation in mice. H pylori eradication significantly improved endothelium‐dependent vasodilation in both patients and mice with H pylori infection. Exosomes from conditioned media of human gastric epithelial cells cultured with CagA⁺H pylori or serum exosomes from patients and mice with H pylori infection significantly decreased endothelial functions with decreased migration, tube formation, and proliferation in vitro. Inhibition of exosome secretion with GW4869 effectively preserved endothelial function in mice with H pylori infection.

Conclusions

H pylori infection impaired endothelial function in patients and mice through exosome‐medicated mechanisms. The findings indicated that H pylori infection might be a novel risk factor for cardiovascular diseases.

Augmentation of Autoantibodies by Helicobacter pylori in Parkinson's Disease Patients May Be Linked to Greater Severity

Parkinson's disease (PD) is the second most common chronic and progressive neurodegenerative disorder. Its etiology remains elusive and at present only symptomatic treatments exists. Helicobacter pylori chronically colonizes the gastric mucosa of more than half of the global human population. Interestingly, H. pylori positivity has been found to be associated with greater of PD motor severity. In order to investigate the underlying cause of this association, the Sengenics Immunome protein array, which enables simultaneous screening for autoantibodies against 1636 human proteins, was used to screen the serum of 30 H. pylori-seropositive PD patients (case) and 30 age- and gender-matched H. pylori-seronegative PD patients (control) in this study. In total, 13 significant autoantibodies were identified and ranked, with 8 up-regulated and 5 down-regulated in the case group. Among autoantibodies found to be elevated in H. pylori-seropositive PD were included antibodies that recognize Nuclear factor I subtype A (NFIA), Platelet-derived growth factor B (PDGFB) and Eukaryotic translation initiation factor 4A3 (eIFA3). The presence of elevated autoantibodies against proteins essential for normal neurological functions suggest that immunomodulatory properties of H. pylori may explain the association between H. pylori positivity and greater PD motor severity.

Infection and Atherosclerosis Development

Atherosclerosis is a chronic disease hallmarked by chronic inflammation, endothelial dysfunction and lipid accumulation in the vasculature. Although lipid modification and deposition are thought to be a major source of the continuous inflammatory stimulus, a large body of evidence suggests that infectious agents may contribute to atherosclerotic processes. This could occur by either direct effects through infection of vascular cells and/or through indirect effects by induction of cytokine and acute phase reactant proteins by infection at other sites. Multiple bacterial and viral pathogens have been associated with atherosclerosis by seroepidemiological studies, identification of the infectious agent in human atherosclerotic tissue, and experimental studies demonstrating an acceleration of atherosclerosis following infection in animal models of atherosclerosis. This review will focus on those infectious agents for which biological plausibility has been demonstrated in animal models and on the challenges of proving a role of infection in human atherosclerotic disease.

Helicobacter pylori-an infectious risk factor for atherosclerosis?

Accumulating evidence implicates Helicobacter pylori (H. pylori) infection in the pathogenesis of certain diseases localized outside the stomach, particularly those characterized by persistent and low-grade systematic inflammation. Recently, the role of H. pylori infection in the development of atherosclerosis and its clinical complications has received attention. Atherosclerosis is a high-cost disease, and acute events resulting from this condition rank first among morbidity and mortality statistics in most industrialized countries. Atherosclerosis is a multifactorial disorder, and traditional risk factors explain only 50% of its etiology. Therefore, identifying new risk factors for atherosclerosis is necessary. Serological studies indicate that chronic H. pylori infection, especially that with more virulent strains, may predispose patients to the onset of atherosclerosis and related adverse clinical events, and PCR studies have detected H. pylori DNA in atherosclerotic plaques, although this finding remains controversial. If this association were to be confirmed, its importance to public health would be substantial, as the eradication of H. pylori is more straightforward and less costly than the long-term treatment of other risk factors. This review investigates the potential relationship between H. pylori infection and atherosclerosis from both epidemiological and pathogenic perspectives and characterizes the potential mechanisms underlying this correlation.

Infectious burden and atherosclerosis: A clinical issue

Atherosclerotic cardiovascular diseases, chronic inflammatory diseases of multifactorial etiology, are the leading cause of death worldwide. In the last decade, more infectious agents, labeled as “infectious burden”, rather than any single pathogen, have been showed to contribute to the development of atherosclerosis through different mechanisms. Some microorganisms, such as Chlamydia pneumoniae (C. pneumoniae), human cytomegalovirus, etc. may act directly on the arterial wall contributing to endothelial dysfunction, foam cell formation, smooth muscle cell proliferation, platelet aggregation as well as cytokine, reactive oxygen specie, growth factor, and cellular adhesion molecule production. Others, such as Helicobacter pylori (H. pylori), influenza virus, etc. may induce a systemic inflammation which in turn may damage the vascular wall (e.g., by cytokines and proteases). Moreover, another indirect mechanism by which some infectious agents (such as H. pylori, C. pneumoniae, periodontal pathogens, etc.) may play a role in the pathogenesis of atherosclerosis is molecular mimicry. Given the complexity of the mechanisms by which each microorganism may contribute to atherosclerosis, defining the interplay of more infectious agents is far more difficult because the pro-atherogenic effect of each pathogen might be amplified. Clearly, continued research and a greater awareness will be helpful to improve our knowledge on the complex interaction between the infectious burden and atherosclerosis.

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.

Impact of viral and bacterial infections in coronary artery disease patients

Atherosclerosis is becoming an alarming disease for the existence of healthy human beings in the 21^st century. There are a growing number of agents, either modernized life style generated, competitive work culture related or infection with some bacterial or viral agents, documented every year. These infectious agents do not have proper diagnostics or detection availability in many poor and developing countries. Hence, as active medical researchers, we summarize some aspects of infectious agents and their related mechanisms in this review which may be beneficial for new beginners in this field and update awareness in the field of cardiovascular biology.

Is there any relationship between Chlamydophila pneumoniae and coronary atherosclerosis among Iranians?

Background:

Atherosclerosis is a coronary heart disease, andis the most common cause of death in the industrialized world. Some studies suggested that atherosclerosis may be triggered by infectious agents, mostly Chlamydophila pneumoniae. However, the role of C. pneumoniae in the pathogenesis of coronary atherosclerosis is still controversial.

Objectives:

This study was performed to evaluate whether there is a significant association between coronary artery atherosclerosis and C. pneumoniae by the polymerase chain reaction (PCR) method.

Materials and Methods:

This case-control study was carried out on formalin-fixed paraffin-embedded tissue biopsies of the coronary arteries obtained from 30 patients with coronary atherosclerosis and 30 subjects without atherosclerosis living in Northeast of Iran. All subjects' weight and height were determined, and the body mass index was calculated. We also reviewed the medical history and previous laboratory reports of patients. Deoxyribonucleic acid (DNA) was extracted, and C. pneumonia DNA was amplified and detected using PCR assay.

Results:

The age of the patients in the study group was from 18 to 50 years, and the male to female ratio was 5:1. Only oneout of the 30 coronary tissue samples had positive PCR for C. pneumoniae (3.3%), while it was negative for patients in the control group.

Conclusions:

This study showed that C. pneumoniae infection is not strongly associated with coronary artery atherosclerosis in Northeast of Iran.

Alzheimer's Disease: APP, Gamma Secretase, APOE, CLU, CR1, PICALM, ABCA7, BIN1, CD2AP, CD33, EPHA1, and MS4A2, and Their Relationships with Herpes Simplex, C. Pneumoniae, Other Suspect Pathogens, and the Immune System

Alzheimer's disease susceptibility genes, APP and gamma-secretase, are involved in the herpes simplex life cycle, and that of other suspect pathogens (C. pneumoniae, H. pylori, C. neoformans, B. burgdorferri, P. gingivalis) or immune defence. Such pathogens promote beta-amyloid deposition and tau phosphorylation and may thus be causative agents, whose effects are conditioned by genes. The antimicrobial effects of beta-amyloid, the localisation of APP/gamma-secretase in immunocompetent dendritic cells, and gamma secretase cleavage of numerous pathogen receptors suggest that this network is concerned with pathogen disposal, effects which may be abrogated by the presence of beta-amyloid autoantibodies in the elderly. These autoantibodies, as well as those to nerve growth factor and tau, also observed in Alzheimer's disease, may well be antibodies to pathogens, due to homology between human autoantigens and pathogen proteins. NGF or tau antibodies promote beta-amyloid deposition, neurofibrillary tangles, or cholinergic neuronal loss, and, with other autoantibodies, such as anti-ATPase, are potential agents of destruction, whose formation is dictated by sequence homology between pathogen and human proteins, and thus by pathogen strain and human genes. Pathogen elimination in the ageing population and removal of culpable autoantibodies might reduce the incidence and offer hope for a cure in this affliction.

Seroprevalence of 13 common pathogens in a rapidly growing U.S. minority population: Mexican Americans from San Antonio, TX

Background

Infection risks vary among individuals and between populations. Here we present information on the seroprevalence of 13 common infectious agents in a San Antonio-based sample of Mexican Americans. Mexican Americans represent the largest and most rapidly growing minority population in the U.S., and they are also considered a health disparities population.

Methods

We analyzed 1227 individuals for antibody titer to Chlamydophila pneumoniae, Helicobacter pylori, Toxoplasma gondii, cytomegalovirus, Epstein-Barr virus, herpes simplex virus-1, herpes simplex virus-2 (HSV-2), human herpesvirus-6 (HHV-6), varicella zoster virus (VZV), adenovirus-36, hepatitis A virus, and influenza A and B. Seroprevalence was examined as a function of sex, age, household income, and education.

Results

Seroprevalence estimates ranged from 9% for T. gondii to 92% for VZV, and were similar in both sexes except for HSV-2, which was more prevalent in women. Many pathogens exhibited a significant seroprevalence change over the examined age range (15-94 years), with 7 pathogens increasing and HHV-6 decreasing with age. Socioeconomic status significantly correlated with serostatus for some pathogens.

Conclusions

Our findings demonstrate substantial seroprevalence rates of these common infections in this sample of Mexican Americans from San Antonio, Texas that suffers from high rates of chronic diseases including obesity and type-2 diabetes.

Pathogens and atherosclerosis: update on the potential contribution of multiple infectious organisms to the pathogenesis of atherosclerosis

It is currently unclear what causes the chronic inflammation within atherosclerotic plaques. One emerging paradigm suggests that infection with bacteria and/or viruses can contribute to the pathogenesis of atherosclerosis either via direct infection of vascular cells or via the indirect effects of cytokines or acute phase proteins induced by infection at non-vascular sites. This paradigm has been supported by multiple epidemiological studies that have established positive associations between the risk of cardiovascular disease morbidity and mortality and markers of infection. It has also been supported by experimental studies showing an acceleration of the development of atherosclerosis following infection of hyperlipidaemic animal models. There are now a large number of different infectious agents that have been linked with an increased risk of cardiovascular disease. These include: Chlamydia pneumoniae, Porphyromonas gingivalis, Helicobacter pylori , influenza A virus, hepatitis C virus, cytomegalovirus, and human immunodeficiency virus. However, there are significant differences in the strength of the data supporting their association with cardiovascular disease pathogenesis. In some cases, the infectious agents are found within the plaques and viable organisms can be isolated suggesting a direct effect. In other cases, the association is entirely based on biomarkers. In the following review, we evaluate the strength of the data for individual or groups of pathogens with regard to atherosclerosis pathogenesis and their potential contribution by direct or indirect mechanisms and discuss whether the established associations are supportive of the infectious disease paradigm. We also discuss the failure of antibiotic trials and the question of persistent infection.

Extragastric manifestations of Helicobacter pylori infection

The possible role of Helicobacter pylori as a trigger for some extragastric diseases has been largely investigated in the last year. There are, in fact, several studies concerning cardiovascular diseases, neurological disorders, diabetes mellitus, ear and eyes diseases, immunological and hematological disorders, liver and bile tract diseases, gynecological and respiratory tract pathologies. Among them, idiopathic sideropenic anemia and idiopathic thrombocytopenic purpura still remain the extragastric diseases showing the most convincing results. Concerning ischemic heart disease, there are new interesting data playing in favor of the association, even though there are still some open issues to be clarified. For the other diseases, more studies are needed to clarify the reality of the proposed association.

"Gum bug, leave my heart alone!"--epidemiologic and mechanistic evidence linking periodontal infections and atherosclerosis

Evidence from epidemiologic studies suggests that periodontal infections are independently associated with subclinical and clinical atherosclerotic vascular disease. Although the strength of the reported associations is modest, the consistency of the data across diverse populations and a variety of exposure and outcome variables suggests that the findings are not spurious or attributable only to the effects of confounders. Analysis of limited data from interventional studies suggests that periodontal treatment generally results in favorable effects on subclinical markers of atherosclerosis, although such analysis also indicates considerable heterogeneity in responses. Experimental mechanistic in vitro and in vivo studies have established the plausibility of a link between periodontal infections and atherogenesis, and have identified biological pathways by which these effects may be mediated. However, the utilized models are mostly mono-infections of host cells by a limited number of 'model' periodontal pathogens, and therefore may not adequately portray human periodontitis as a polymicrobial, biofilm-mediated disease. Future research must identify in vivo pathways in humans that may (i) lead to periodontitis-induced atherogenesis, or (ii) result in treatment-induced reduction of atherosclerosis risk. Data from these studies will be essential for determining whether periodontal interventions have a role in the primary or secondary prevention of atherosclerosis.

Autoimmunity, infectious immunity, and atherosclerosis

INTRODUCTION

Vascular inflammation is common in certain systemic autoimmune diseases and contributes to the oxidation of low-density lipoprotein (oxLDL) and oxLDL/beta2-glycoprotein I (beta2GPI) complex formation. These complexes have been implicated as proatherogenic autoantigens that participate in the development of atherosclerotic disease.

DISCUSSION

We have demonstrated that the in vitro macrophage uptake of oxLDL/beta2GPI complexes increases in the presence of IgG anti-beta2GPI antibodies and that IgG immune complexes containing oxLDL/beta2GPI upregulate the expression of both scavenger and Fcgamma receptors to activate beta2GPI specific T cells. Some persistent infections may cause immune responses that promote atherogenesis. Cellular immunity (Th1) against Helicobacter pylori (H. pylori) derived heat shock protein 60 (Hp-HSP60) cross-reacts with endogenous HSP60 to cause cardiovascular disease likely by molecular mimicry.

CONCLUSION

Infectious cellular response may be proatherogenic,while the humoral response (antibody production) maybe protective. We review the recent progress in our understanding of autoimmunity and infectious immunity that promote atherosclerosis.