Association of serum antibodies to heat-shock protein 65 with borderline hypertension

HSP90 Family Members, Their Regulators and Ischemic Stroke Risk: A Comprehensive Molecular-Genetics and Bioinformatics Analysis

BACKGROUND

Disruptions in proteostasis are recognized as key drivers in cerebro- and cardiovascular disease progression. Heat shock proteins (HSPs), essential for maintaining protein stability and cellular homeostasis, are pivotal in neuroperotection. Consequently, deepening the understanding the role of HSPs in ischemic stroke (IS) risk is crucial for identifying novel therapeutic targets and advancing neuroprotective strategies.

AIM

Our objective was to examine the potential correlation between single nucleotide polymorphisms (SNPs) in genes that encode members of the Heat shock protein 90 (HSP90), small heat shock proteins (HSPB), and heat shock factors (HSF) families, and the risk and clinical characteristics of IS.

METHODS

953 IS patients and 1265 controls from Central Russia were genotyped for nine SNPs in genes encoding HSP90AA1, HSFs, and HSPBs using the MassArray-4 system and probe-based polymerase chain reaction (PCR).

RESULTS

In smokers, SNP rs1133026 HSPB8 increased the risk of IS (risk allele A, odds ratio (OR) = 1.43, 95% Confidence Interval (CI) 1.02-2.02, p = 0.035), and rs556439 HSF2 increased the brain infarct size (risk allele A, p = 0.02). In non-smokers, SNPs rs4279640 HSF1 (protective allele T, OR = 0.58, 95% CI 0.37-0.92, p = 0.02) and rs4264324 HSP90AA1 (protective allele C, OR = 0.11, 95% CI 0.01-0.78, p = 0.001) lowered the risk of recurrent stroke; SNP rs7303637 HSPB8 increased the age of onset of IS (protective allele T, p = 0.04). In patients with body mass index (BMI) ≥25, SNPs rs556439 HSF2 (risk allele A, OR = 1.33, 95% CI 1.04-1.69, p = 0.02) and rs549302 HSF2 (risk allele G, OR = 1.34, 95% CI 1.02-1.75, p = 0.03) were linked to a higher risk of IS.

CONCLUSIONS

The primary molecular mechanisms through which the studied SNPs contribute to IS pathogenesis were found to be the regulation of cell death, inflammatory and oxidative stress responses.

Malondialdehyde Conjugated With Albumin Induces Pro-Inflammatory Activation of T Cells Isolated From Human Atherosclerotic Plaques Both Directly and Via Dendritic Cell-Mediated Mechanism

Human dendritic cells were differentiated from blood monocytes and treated with malondialdehyde (MDA) conjugated with human serum albumin (HSA). Autologous T cells from human plaques or blood were co-cultured with the pre-treated dendritic cells or treated directly. MDA modifications were studied by mass spectrometry. MDA-HSA induced a pro-inflammatory DC-mediated T-cell activation and also a strong direct effect on T cells, inhibited by an inhibitor of oxidative stress and antibodies against MDA. Atherogenic heat shock protein-60 was strongly induced in T cells activated by MDA-HSA. Two peptide modifications in atherosclerotic patients' HSA were similar to those present in in vitro MDA-modified HSA.

Heat shock proteins and cardiovascular disease

The development of stress drives a host of biological responses that include the overproduction of a family of proteins named heat shock proteins (HSPs), because they were initially studied after heat exposure. HSPs are evolutionarily preserved proteins with a high degree of interspecies homology. HSPs are intracellular proteins that also have extracellular expression. The primary role of HSPs is to protect cell function by preventing irreversible protein damage and facilitating molecular traffic through intracellular pathways. However, in addition to their chaperone role, HSPs are immunodominant molecules that stimulate natural as well as disease-related immune reactivity. The latter may be a consequence of molecular mimicry, generating cross-reactivity between human HSPs and the HSPs of infectious agents. Autoimmune reactivity driven by HSPs could also be the result of enhancement of the immune response to peptides generated during cellular injury and of their role in the delivery of peptides to the major histocompatibility complex in antigen-presenting cells. In humans, HSPs have been found to participate in the pathogenesis of a large number of diseases. This review is focused on the role of HSPs in atherosclerosis and essential hypertension.

Induction of Dendritic Cell-Mediated Activation of T Cells From Atherosclerotic Plaques by Human Heat Shock Protein 60

BACKGROUND

Atherosclerosis is characterized by the presence of activated immune-competent cells including dendritic cells (DCs) and T cells, dead cells, and oxidized low-density lipoprotein. HSP60 (Heat shock protein 60) has been implicated in atherosclerosis. A plasma protein, Annexin A5, has atheroprotective properties.

METHODS AND RESULTS

Human DCs differentiated from peripheral blood monocytes were treated with human HSP60 or HSP90 and autologous T cells were cocultured with these pretreated DCs (mDCs). HSP60 induced mDCs and T-cell activation as determined by FACScan (Fluorescence associated cell scan), gene-activation, and cytokine production. HSP60-induced T-cell activation was partly major histocompatibility complex class II-dependent. T cells exposed to HSP60-treated mDCs produced interferon-γ, interleukin-17, but not transforming growth factor-β. HSP60 did not promote expression of Toll-like receptors 2 or 4. HSP90 promoted mDCs maturation but had no effect on T-cell activation. Annexin A5 inhibited HSP60-proinflammatory Th1/Th17 effects on mDCs and T cells, and partly bound HSP60. Further, Annexin A5 inhibited HSP-induced activation of mDCs and also oxidized low-density lipoprotein-induced HSP-production from mDCs. Experiments on mDCs and T cells derived from carotid atherosclerotic plaques from patients with symptomatic carotid disease gave similar results as from blood donors.

CONCLUSIONS

HSP60 induces mDCs activation and partly major histocompatibility complex class II-dependent activation of blood- and plaque-derived T cells, which is mostly of Th1/Th17 type. HSP60 could thus be an important T-cell antigen in plaques, and also mediate oxidized low-density lipoproteins immunogenic effects on DC-T-cell activation, promoting plaque rupture and clinical manifestations of cardiovascular disease. Annexin A5 inhibits both oxidized low-density lipoprotein-induced HSP60, and HSP60-mediated immune activation, which suggests a potential therapeutic role.

Role of the Immune System in Hypertension

High blood pressure is present in more than one billion adults worldwide and is the most important modifiable risk factor of death resulting from cardiovascular disease. While many factors contribute to the pathogenesis of hypertension, a role of the immune system has been firmly established by a large number of investigations from many laboratories around the world. Immunosuppressive drugs and inhibition of individual cytokines prevent or ameliorate experimental hypertension, and studies in genetically-modified mouse strains have demonstrated that lymphocytes are necessary participants in the development of hypertension and in hypertensive organ injury. Furthermore, immune reactivity may be the driving force of hypertension in autoimmune diseases. Infiltration of immune cells, oxidative stress, and stimulation of the intrarenal angiotensin system are induced by activation of the innate and adaptive immunity. High blood pressure results from the combined effects of inflammation-induced impairment in the pressure natriuresis relationship, dysfunctional vascular relaxation, and overactivity of the sympathetic nervous system. Imbalances between proinflammatory effector responses and anti-inflammatory responses of regulatory T cells to a large extent determine the severity of inflammation. Experimental and human studies have uncovered autoantigens (isoketal-modified proteins and heat shock protein 70) of potential clinical relevance. Further investigations on the immune reactivity in hypertension may result in the identification of new strategies for the treatment of the disease.

Primary hypertension is a disease of premature vascular aging associated with neuro-immuno-metabolic abnormalities

There is an increasing amount of data indicating that primary hypertension (PH) is not only a hemodynamic phenomenon but also a complex syndrome involving abnormal fat tissue distribution, over-activity of the sympathetic nervous system (SNS), metabolic abnormalities, and activation of the immune system. In children, PH usually presents with a typical phenotype of disturbed body composition, accelerated biological maturity, and subtle immunological and metabolic abnormalities. This stage of the disease is potentially reversible. However, long-lasting over-activity of the SNS and immuno-metabolic alterations usually lead to an irreversible stage of cardiovascular disease. We describe an intermediate phenotype of children with PH, showing that PH is associated with accelerated development, i.e., early premature aging of the immune, metabolic, and vascular systems. The associations and determinants of hypertensive organ damage, the principles of treatment, and the possibility of rejuvenation of the cardiovascular system are discussed.

Heat shock proteins and cardiovascular disease

Atherosclerosis is the leading global cause of mortality, morbidity, and disability. Heat shock proteins (HSPs) are a highly conserved family of proteins with diverse functions expressed by all cells exposed to environmental stress. Studies have reported that several HSPs may be potential risk markers of atherosclerosis and related cardiovascular diseases, or may be directly involved in the atherogenic process itself. HSPs are expressed by cells in atherosclerotic plaque and anti-HSP has been reported to be increased in patients with vascular disease. Autoimmune responses may be generated against antigens present within the atherosclerotic plaque, including HSP and may lead to a cycle of ongoing vascular injury. It has been suggested that by inducing a state of tolerance to these antigens, the atherogenic process may be limited and thus provide a potential therapeutic approach. It has been suggested that anti-HSPs are independent predictors of risk of vascular disease. In this review, we summarize the current understanding of HSP in cardiovascular disease and highlight their potential role as diagnostic agents and therapeutic targets.

Antibodies against Hsp60 and Hsp65 in the sera of women with ovarian cancer

Background

The aim of this study was to evaluate the concentrations of IgG antibodies against Hsp60 and Hsp65 in sera of patients with ovarian cancer at various stages of clinical progress and for different histopathological types of disease.

Methods

Serum samples from 149 patients with ovarian carcinoma and 80 healthy women were investigated. The concentrations of anti-Hsp60 and anti-Hsp65 antibodies were determined using the enzyme-linked immunosorbent assay technique.

Results

The mean concentrations of anti-Hsp60 and anti-Hsp65 antibodies in the patients with ovarian cancer did not differ significantly from the mean levels in healthy women. Analysis in relation to the clinical progression stage showed that the concentrations of these antibodies were higher when the neoplastic process was less advanced and at early stages significantly higher than in control group. Mean concentrations of both antibodies were not significantly different in relation to the histological type of the ovarian cancer. The use of chemotherapy as a primary anticancer treatment did not cause a significant change in the concentration of anti-Hsp60 antibodies, but the mean level of anti-Hsp65 after this treatment was significantly higher than in control group.

Conclusions

The immunological response to Hsp60/65 is increased in early clinical stages of ovarian cancer and the level of anti-hsp60/65 antibodies may be then a helpful diagnostic marker. Even antibodies against highly homologous Hsps may be cross-reactive only partially and differ by some functional properties.

Immune mechanisms in atherosclerosis, especially in diabetes type 2

Atherosclerosis and ensuing cardiovascular disease (CVD) are major complications of diabetes type 2. Atherosclerosis is a chronic inflammatory condition involving immunocompetent cells of different types present in the lesions. Even though inflammation and immune activation may be more pronounced in atherosclerosis in diabetes type 2, there does not appear to be any major differences between diabetics and non-diabetics. Similar factors are thus implicated in atherosclerosis-associated immune activation in both groups. The cause of immune activation is not known and different mutually non-exclusive possibilities exist. Oxidized and/or enzymatically modified forms of low-density lipoprotein (OxLDL) and dead cells are present in atherosclerotic plaques. OxLDL could play a role, being pro-inflammatory and immunostimulatory as it activates T-cells and is cytotoxic at higher concentrations. Inflammatory phospholipids in OxLDL are implicated, with phosphorylcholine (PC) as one of the exposed antigens. Antibodies against PC (anti-PC) are anti-atherogenic in mouse studies, and anti-PC is negatively associated with development of atherosclerosis and CVD in humans. Bacteria and virus have been discussed as potential causes of immune activation, but it has been difficult to find direct evidence supporting this hypothesis, and antibiotic trials in humans have been negative or inconclusive. Heat shock proteins (HSP) could be one major target for atherogenic immune reactions. More direct causes of plaque rupture include cytokines such as interleukin 1β (IL-1β), tumor necrosis factor (TNF), and also lipid mediators as leukotrienes. In addition, in diabetes, hyperglycemia and oxidative stress appear to accelerate the development of atherosclerosis, one mechanism could be via promotion of immune reactions. To prove that immune reactions are causative of atherosclerosis and CVD, further studies with immune-modulatory treatments are needed.

Immunity, atherosclerosis and cardiovascular disease

Atherosclerosis, the major cause of cardiovascular disease (CVD), is a chronic inflammatory condition with immune competent cells in lesions producing mainly pro-inflammatory cytokines. Dead cells and oxidized forms of low density lipoproteins (oxLDL) are abundant. The major direct cause of CVD appears to be rupture of atherosclerotic plaques. oxLDL has proinflammatory and immune-stimulatory properties, causes cell death at higher concentrations and contains inflammatory phospholipids with phosphorylcholine (PC) as an interesting epitope. Antibodies against PC (anti-PC) may be atheroprotective, one mechanism being anti-inflammatory. Bacteria and virus have been discussed, but it has been difficult to find direct evidence, and antibiotic trials have not been successful. Heat shock proteins could be one major target for atherogenic immune reactions. More direct causes of plaque rupture include pro-inflammatory cytokines, chemokines, and lipid mediators. To prove that inflammation is a cause of atherosclerosis and CVD, clinical studies with anti-inflammatory and/or immune-modulatory treatment are needed. The potential causes of immune reactions and inflammation in atherosclerosis and how inflammation can be targeted therapeutically to provide novel treatments for CVD are reviewed.

Evidence on the pathogenic role of auto-antibodies in acute cardiovascular diseases

Atherothrombosis is the major determinant of acute ischaemic cardiovascular events, such as myocardial infarction and stroke. Inflammatory processes have been linked to all phases of atherogenesis In particular, the identification of autoimmunity mediators in the complex microenvironment of chronic inflammation has become the focus of attention in both early and advanced atherogenic processes. Auto-antibodies against self-molecules or new epitopes generated by oxidative processes infiltrate atherosclerotic plaques and were shown to modulate the activity of immune cells by binding various types of receptors. However, despite mounting evidence for a pathophysiological role of autoantibodies in atherothrombosis, the clinical relevance for circulating autoantibodies in cardiovascular outcomes is still debated. This review aims at illustrating the mechanisms by which different types of autoantibodies might either promote or repress atherothrombosis and to discuss the clinical studies assessing the role of auto-antibodies as prognostic biomarkers of plaque vulnerability.

Auto-antibodies as emergent prognostic markers and possible mediators of ischemic cardiovascular diseases

During the last 15 years, a growing body of evidence supported the fact that auto-antibodies represent not only emergent markers but also active mediators of cardiovascular disease (CVD), clinically represented mostly by acute coronary syndrome (ACS) and stroke. There is a contrasted relationship between auto-antibodies and CVD, some being protective, while others acting as potential risk factors. Therefore, we performed a review of the literature on the respective cardiovascular prognostic value of the most relevant auto-antibodies in ACS and stroke, and their putative pathophysiological properties in atherogenesis. This review highlights auto-antibodies as active modulators of the innate immune system in atherogenesis (either toward a pro- or anti-inflammatory response), or by affecting basal heart rate regulation (anti-apoA-1 IgG). Given their apparent prognostic independency towards traditional cardiovascular risk factors, the data available in the literature indicates that some of those auto-antibodies could be of valuable help for cardiovascular risk stratification in the future, especially because their deleterious effects have been shown to be potentially abrogated in vivo and in vitro by existing therapeutic modalities. Although evidence in humans is currently lacking, these studies may open innovative therapeutic perspectives for CVD in the future.

Pediatric Sepsis - Part V: Extracellular Heat Shock Proteins: Alarmins for the Host Immune System

Heat shock proteins (HSPs) are molecular chaperones that facilitate the proper folding and assembly of nascent polypeptides and assist in the refolding and stabilization of damaged polypeptides. Through these largely intracellular functions, the HSPs maintain homeostasis and assure cell survival. However, a growing body of literature suggests that HSPs have important effects in the extracellular environment as well. Extracellular HSPs are released from damaged or stressed cells and appear to act as local "danger signals" that activate stress response programs in surrounding cells. Importantly, extracellular HSPs have been shown to activate the host innate and adaptive immune response. With this in mind, extracellular HSPs are commonly included in a growing list of a family of proteins known as danger-associated molecular patterns (DAMPs) or alarmins, which trigger an immune response to tissue injury, such as may occur with trauma, ischemia-reperfusion injury, oxidative stress, etc. Extracellular HSPs, including Hsp72 (HSPA), Hsp27 (HSPB1), Hsp90 (HSPC), Hsp60 (HSPD), and Chaperonin/Hsp10 (HSPE) are especially attractrive candidates for DAMPs or alarmins which may be particularly relevant in the pathophysiology of the sepsis syndrome.

Natural antibodies against phosphorylcholine in cardiovascular disease

Atherosclerosis is a chronic inflammatory disease characterized by the presence of activated immune-competent cells in the lesions, producing mainly proinflammatory cytokines. Atherosclerosis is the underlying cause of cardiovascular disease (CVD), to a large extent occurring after damage and/or rupture of the atherosclerotic plaques. One major factor implicated as a cause of this immune activation is modified low-density lipoproteins (LDL), especially oxidized forms (oxLDL), which are abundant in plaques, both in foam cells and in the necrotic core. The LDL-oxidation process is very complex, and the nature of the antigens has been difficult to identify. We and others have focused on the phospholipids (PL) in oxLDL, especially oxidized forms of PL, including platelet-activating factor (PAF)-like lipids and lysophosphatidylcholine (LPC), and demonstrated that these could play a major role through proinflammatory effects. One common epitope is phosphorylcholine (PC), which is also exposed on some microorganisms (including Streptococcus pneumoneae) and on apoptotic cells. Natural IgM antibodies against PC (anti-PC) have been known for a long time, but little has been reported about their role in human disease, especially in CVD. We have demonstrated that anti-PC IgM are negatively associated with atherosclerosis development in hypertensive individuals and that low levels of anti-PC independently predict development of CVD. Anti-PC IgM could, therefore, be a novel risk marker in CVD. Animal experiments indicate that both active immunization with PC and passive immunization with anti-PC ameliorate atherosclerosis development. The possibility that anti-PC could be used therapeutically in humans deserves further study.

Low level natural antibodies against phosphorylcholine: a novel risk marker and potential mechanism in atherosclerosis and cardiovascular disease

Atherosclerosis is an inflammatory condition characterised by an abundance of activated immunocompetent cells in plaques which cause cardiovascular disease (CVD) when they rupture. Oxidized forms of low density lipoprotein (OxLDL) are a major constituent of atherosclerotic plaques and have proinflammatory effects, making oxLDL a candidate factor promoting atherosclerosis. In previous studies we and others demonstrated that platelet-activating factor (PAF)-like lipids in oxLDL may cause oxLDL-induced immune-stimulatory effects. A common denominator is phosphorylcholine (PC), a hapten-like epitope which is exposed on OxLDL and some microorganisms. We recently demonstrated that anti-PC has anti-inflammatory properties and that low levels of anti-PC predict the development of stroke and myocardial infarction. We hypothesize that low anti-PC represents a novel paradigm as a cause of chronic inflammatory diseases such as atherosclerosis where oxidized and/or inflammatory phospholipids play a role. It is possible that anti-PC can be used as a novel diagnostic tool and therapy in atherosclerotic disease.

Circulating anti-heat-shock-protein antibodies in normal pregnancy and preeclampsia

It has been previously reported that circulating anti-heat-shock-protein (Hsp) antibody levels are elevated in cardiovascular disorders. The aim of the present study was to determine circulating antihuman Hsp60, antimycobacterial Hsp65, and antihuman Hsp70 antibody levels in healthy pregnant women and preeclamptic patients and to investigate their relationship to the clinical characteristics of the study subjects, as well as to the markers of inflammation (C-reactive protein (CRP)), endothelial activation (von Willebrand factor antigen), or endothelial injury (fibronectin), oxidative stress (malondialdehyde) and to serum Hsp70 levels. Ninety-three preeclamptic patients and 127 normotensive healthy pregnant women were involved in this case control study. Serum anti-Hsp60, anti-Hsp65, anti-Hsp70, and Hsp70 levels were measured with enzyme-linked immunosorbent assay (ELISA). Serum CRP levels were determined by an autoanalyzer using the manufacturer's kit. Plasma von Willebrand factor antigen levels were quantified by ELISA, while plasma fibronectin concentration by nephelometry. Plasma malondialdehyde levels were measured by the thiobarbituric-acid-based colorimetric assay. For statistical analyses, nonparametric methods were applied. Anti-Hsp60, anti-Hsp65, and anti-Hsp70 antibodies were detected in all of our serum samples. There were no significant differences in serum anti-Hsp60, anti-Hsp65, and anti-Hsp70 antibody levels between the control and preeclamptic groups. Serum levels of Hsp70 and CRP, as well as plasma levels of VWF antigen, fibronectin, and malondialdehyde, were significantly higher in preeclamptic patients than in normotensive healthy pregnant women. Serum anti-Hsp60 antibody levels showed significant correlations with serum anti-Hsp65 antibody levels both in the control and the preeclamptic groups (Spearman R = 0.55 and 0.59; p < 0.001, respectively). However, no other relationship was found between clinical features (maternal age, smoking status, parity, body mass index, gestational age at blood draw, systolic and diastolic blood pressure, gestational age at delivery, and fetal birth weight) and measured laboratory parameters of the study subjects and serum anti-Hsp antibody levels in either study group. In conclusion, anti-Hsp60 and anti-Hsp70 antibodies as naturally occurring autoantibodies are present in the peripheral circulation of healthy pregnant women. Nevertheless, humoral immunity against heat shock proteins was not associated with preeclampsia. Further studies are warranted to explore the role of heat shock proteins and immune reactivity to them in the immunobiology of normal pregnancy and preeclampsia.

Joint Effects of Antibody to Heat Shock Protein 60, Hypertension, and Diabetes on Risk of Coronary Heart Disease in Chinese

Background: Several studies have suggested an association between antibody to human heat shock protein 60 (anti-Hsp60) and coronary atherosclerosis, but the results have been inconsistent. The aim of this study was to investigate the association between anti-Hsp60 and coronary heart disease (CHD) and to determine whether anti-Hsp60, hypertension, and diabetes have joint effects on CHD risk.

Methods: We measured the concentrations of anti-Hsp60 in 1003 CHD patients and 1003 age- and sex-matched control subjects without CHD events.

Results: Concentrations of anti-Hsp60 were significantly higher in CHD patients than in controls. Increasing concentrations of anti-Hsp60 were significantly associated with higher risk of CHD (P for trend &lt;0.0001) and with increasing severity of CHD as assessed by number of diseased vessels detected with angiography [odds ratio (OR) 3.67, 95% CI 1.56–8.64, P = 0.003] after multivariate adjustment for traditional CHD risk factors. There were strong joint effects of high concentrations of anti-Hsp60 and hypertension (OR 5.17, 95% CI 3.95–6.75, P &lt; 0.0001) and diabetes (OR 6.49, 95% CI 4.52–9.33, P &lt; 0.0001) on CHD risk; simultaneous occurrence of high anti-Hsp60 concentrations, hypertension, and diabetes conferred a dramatically higher risk of CHD (OR 20.99, 95% CI 12.50–35.24, P &lt; 0.0001) in multivariate analyses.

Conclusions: Anti-Hsp60 is independently associated with CHD risk, and a combination of high anti-Hsp60, hypertension, and diabetes is particularly detrimental for CHD risk.

Chronic infections and atherosclerosis

Immunoinflammatory processes due to chronic infection are thought to be one of the definitive atherogenetic processes. Especially, anti-heat shock protein antibodies have been related to the prevalence of disease such as coronary artery disease or cerebral infarction, etc., resulted from atherosclerosis. Furthermore, the presence of HSP60-specific T lymphocytes in circulation may increase the risk of atherosclerosis. We have recently demonstrated the evidences that Helicobacter pylori infection induced atherosclerosis in apoe+/- ldlr+/- mice and that Hp-anti-heat-shock protein specific Th1-dominant immune responses had a major involvement in the progression of atherosclerosis. These cellular immune responses caused autoimmunity against endogenous HSP60 (expressed on the stressed cells of vascular endothelium), due to the molecular mimicry. Therefore, an appropriate treatment with antibiotics or with anti-HSP60 antibodies, which regulates the Th1 induction, could sufficiently reduce the progression of atherosclerosis.

Identification of atherosclerosis-associated conformational heat shock protein 60 epitopes by phage display and structural alignment

Autoimmune reactions to HSP60 are believed to play a key role during development of early atherosclerosis. Due to the high degree of phylogenetic conservation between microbial and human HSP60, bacterial infections might be responsible for inducing cross-reactivity to self HSP60, which is expressed on the surface of arterial endothelial cells stressed by classical atherosclerosis risk factors. Conformational epitopes recognized by polyclonal anti-mycobacterial HSP60 antibodies from subjects with atherosclerosis were identified using a phage displayed random library of cyclic constrained 7mer peptides. After five rounds of selection, DNA sequencing of strongly binding clones revealed that one peptide motif (CIGSPSTNC) was present in 64% of all clones, and a second motif (CSFHYQNRC) in 14%. Using a newly developed method for structural alignment of small constrained peptides onto a protein surface, we located the motif present in 14% of all clones on the surface of mycobacterial HSP60. The motif present in 64% of all clones was found on the surface of mycobacterial HSP60 as well as in the homologous region of human HSP60, which makes this epitope a promising candidate for further investigations on cross-reactive epitopes involved in early atherogenesis.

Antibodies against heat shock proteins in environmental stresses and diseases: friend or foe?

Heat shock proteins (Hsps) can be found in two forms, intracellular and extracellular. The intracellular Hsps are induced as a result of stress and have been found to be cytoprotective in many instances due to their chaperone functions in protein folding and in protein degradation. The origin and role of extracellular Hsps is less clear. Although they were suspected originally to be released from damaged cells (necrosis), their presence in most normal individuals rather suggests that they have regulatory functions in circulation. As immunodominant molecules, Hsps can stimulate the immune system, leading to the production of autoantibodies recognizing epitopes shared by microbial and human Hsps. Thus, extracellular Hsps can influence the inflammatory response as evidenced by the production of inflammatory cytokines. Antibodies to Hsps have been found under normal conditions but seem to be increased in certain stresses and diseases. Such antibodies could regulate the inflammatory response positively or negatively. Here, we review the literature on the findings of antibodies to Hsps in situations of environmental or occupational stress and in a number of diseases and discuss their possible significance for the diagnosis, prognosis, or pathogenesis of these diseases.

Heat shock proteins in cardiovascular disease and the prognostic value of heat shock protein related measurements

Are heat shock protein antibodies directly involved in the pathogenesis of cardiovascular disease?

SLE, atherosclerosis and cardiovascular disease

Atherosclerosis is an inflammatory disease and the major cause of cardiovascular disease (CVD) in general. Atherosclerotic plaques are characterized by the presence of activated immune competent cells, but antigens and underlying mechanisms causing this immune activation are not well defined. During recent years and with improved treatment of acute disease manifestations, it has become clear that the risk of CVD is very high in a prototypic autoimmune disease, systemic lupus erythematosus (SLE). SLE-related CVD and atherosclerosis are important clinical problems but may in addition also shed light on how immune reactions are related to premature atherosclerosis and atherothrombosis. A combination of traditional and nontraditional risk factors, including dyslipidaemia (and to a varying degree hypertension, diabetes and smoking), inflammation, antiphospholipid antibodies (aPL) and lipid oxidation are related to CVD in SLE. Premature atherosclerosis in some form leading to atherothrombosis is likely to be a major underlying mechanism, though distinctive features if any, of SLE-related atherosclerosis when compared with 'normal' atherosclerosis are not clear. One interesting possibility is that factors such as inflammation or aPL make atherosclerotic lesions in autoimmune disease more prone to rupture than in 'normal' atherosclerosis. Whether premature atherosclerosis is a general feature of SLE or only affects a subgroup of patients remains to be demonstrated. Treatment of SLE patients should also include a close monitoring of traditional risk factors for CVD. In addition, attention should also be paid to nontraditional risk factors such as inflammation and SLE-related factors such as aPL. Hopefully novel therapeutic principles will be developed that target the causes of the inflammation and immune reactions present in atherosclerotic lesions.

Frequency-specific association of antibodies against heat shock proteins 60 and 70 with noise-induced hearing loss in Chinese workers

Noise exposure may result in production of auto-antibodies against heat shock proteins (Hsps), which might be of significance in the pathogenesis or prognosis (or both) of auto-immune ear diseases. However, it is not known whether these antibodies are associated with noise-induced hearing loss (NIHL) in workers exposed to noise in occupational settings. Using immunoblotting with human recombinant Hsps, audiological assessment, and multivariate logistic regression models, we investigated the presence of antibodies against Hsp60 and Hsp70 and hearing levels, and analyzed their associations with NIHL in 399 workers exposed to noise between 75 and 115 dB. Our findings showed that the prevalence of positive anti-Hsp70 was significantly higher in the workers with slight and moderate high-frequency hearing loss than in normal workers (P < 0.05). Furthermore, the prevalence of positive anti-Hsp60 in workers with moderate low-frequency NIHL was significantly higher than in the normal (P < 0.01). The levels of anti-Hsp70 and anti-Hsp60 seemed correlated, and the level of anti-Hsp70 better predicted the level of anti-Hsp60. An elevated plasma level of anti-Hsp70 was associated with a nonsignificantly increased risk of high-frequency NIHL (adjusted OR = 1.45; 95% CI = 0.89-2.36) and an elevated plasma level of anti-Hsp60 was associated with a nonsignificantly increased risk of the low-frequency NIHL (adjusted OR = 2.25; 95% CI = 0.85-5.96). These results suggest that the production of anti-Hsp60 and anti-Hsp70 may play a role in the pathogenesis of NIHL, and that anti-Hsps may be a risk factor. The precise mechanisms for the elevation of antibodies against Hsps caused by noise exposure and their possible role in the development of NIHL warrant further investigations.

Autoimmune mechanisms of atherosclerosis

Accumulating evidence supports an autoimmune mechanism as one of the prime pathogenic processes involved in the development of atherosclerosis. So far, three proteins, including heat shock proteins (HSPs), oxidized low-density lipoprotein (oxLDL), and beta2 glycoprotein1 (beta2GP1) have been recognized as autoantigens. It has been demonstrated that risk factors for atherosclerosis, such as hypercholesterolemia, hypertension, infections, and oxidative stress, evoke increased expression of HSPs in cells of atherosclerotic lesions. Autoantibody levels against HSPs are significantly increased in patients with atherosclerosis and T lymphocytes specifically responding to these autoantigens have been demonstrated within atherosclerotic plaques. Subcutaneous immunization of animals with HSP65 induced atheroma formation in the arterial wall. Furthermore, circulating immunoglobulin (Ig) G and IgM oxidized low-density lipoprotein (oxLDL) antibodies are present in the plasma of animals and humans and form immune complexes with oxLDL in atherosclerotic lesions. These antibodies closely correlate with the progression and regression of atherosclerosis in murine models. Interestingly, recent reports demonstrated that pneumococcal vaccination to LDL receptor-deficient mice results in elevation of anti-oxLDL IgM Ab EO6, which is inversely correlated with the development of atherosclerosis. Finally, it has been observed that autoantigen beta2GP1 localizes in the atheroma and that autoantibodies to beta2GP1 are correlated with the incidence of atherosclerosis in patients. Hence, these autoimmune reactions to HSPs, oxLDL and beta2GP1 can contribute to the initiation and progression of atherosclerosis.

Platelet-activating factor-acetylhydrolase and other novel risk and protective factors for cardiovascular disease in systemic lupus erythematosus

OBJECTIVE

There is an important inflammatory component to atherosclerosis and cardiovascular disease (CVD). It is therefore interesting that the risk of CVD is high in inflammatory diseases such as systemic lupus erythematosus (SLE). In this study, we investigated nontraditional risk factors for the development of CVD in patients with SLE.

METHODS

Twenty-six women (mean age 52 years) with SLE and a history of CVD were compared with 26 age-matched women with SLE and no clinical manifestations of CVD (SLE controls) and 26 age-matched healthy women (population controls). Serum levels of several novel nontraditional risk and protective factors were determined: heat-shock protein (HSP)-related factors (Hsp60, Hsp70, anti-human Hsp60, anti-human Hsp70, and anti-mycobacterial Hsp65), platelet-activating factor-acetylhydrolase (PAF-AH) activity, secretory phospholipase A(2) GIIA (sPLA(2)), and anti-endothelial cell antibody (AECA). The intima-media thickness and the presence of plaques in the common carotid arteries were determined by B-mode ultrasound as a surrogate measure of atherosclerosis.

RESULTS

Levels of PAF-AH, but not HSP-related factors, AECA, or sPLA(2), were significantly increased in SLE cases. Only PAF-AH discriminated between SLE cases and SLE controls (P = 0.005). PAF-AH was significantly associated with low-density lipoprotein (LDL) cholesterol and total cholesterol in the SLE cases (r = 0.50, P = 0.0093 and r = 0.54, P = 0.0045), but not in either control group.

CONCLUSION

The increased levels of PAF-AH in SLE cases and the association between PAF-AH and LDL cholesterol adds support to the notion that PAF-AH may promote atherothrombosis in SLE. The role of HSPs in CVD is complex, since anti-Hsp65 appears to be associated with the presence of CVD, whereas Hsp70 might protect against it. In this cross-sectional study, levels of HSP-related factors, AECA, and sPLA(2) were not associated with CVD in SLE.

Expression of the 60 kDa and 71 kDa heat shock proteins and presence of antibodies against the 71 kDa heat shock protein in pediatric patients with immune thrombocytopenic purpura

Background

Immune thrombocytopenic purpura (ITP) is an autoimmune disease characterized by platelet destruction resulting from autoantibodies against platelet proteins, particularly platelet glycoprotein IIb/IIIa. Heat shock proteins (Hsp) have been shown to be major antigenic determinants in some autoimmune diseases. Antibodies to Hsps have also been reported to be associated with a number of pathological states.

Methods

Using western blot, we measured the levels of the 60 kDa heat shock protein (Hsp60) and of the inducible 71 kDa member of the Hsp70 family (Hsp71) in lymphocytes and the presence of antibodies against these hsps in plasma of 29 pediatric patients with ITP before the treatment and in 6 other patients before and after treatment.

Results

Interestingly only one out of 29 patients showed detectable Hsp60 in lymphocytes while this heat shock protein was detected in the 30 control children. Hsp71 levels were slightly lower in lymphocytes of patients with ITP than in controls (1567.8 ± 753.2 via 1763.2 ± 641.8 integrated optical density (IOD) units). There was a small increase of Hsp71 after recovery from ITP. The titers of plasma antibodies against Hsp60 and Hsp71 were also examined. Antibodies against Hsp71 were more common in ITP patients (15/29) than in control children (5/30). The titer of anti-Hsp71 was also higher in children patients with ITP. The prevalence of ITP children with antibodies against Hsp71 (51.7%) was as high as those with antibodies against platelet membrane glycoproteins (58.3%).

Conclusions

In summary, pediatric patients with ITP showed no detectable expression of Hsp60 in lymphocytes and a high prevalence of antibody against Hsp71 in plasma. These changes add to our understanding of the pathogenesis of ITP and may be important for the diagnosis, prognosis and treatment of ITP.

Heat Shock Proteins in Cardiovascular Disease

Cells have the capability of defending themselves from various stressors by activating a genetic program with the production of substances known as heat shock proteins and their regulatory partners, the heat shock transcription factors. In this article, heat shock proteins are discussed, including their roles in pathophysiology and as possible pharmacologic targets to treat disease. Multiple investigations have demonstrated an elevation in heat shock proteins in patients with systemic hypertension, coronary artery disease, carotid atherosclerosis, and myocardial infarction and ischemia. As we further understand how to manipulate their expression, we can explore pharmacologic interventions and gene transfection techniques that can safely be used in humans.

Antibodies to human heat shock protein 60, hypertension and dyslipidemia. A study of joint effects on coronary risk

OBJECTIVE

High IgA-class (but not IgG-class) Anti-Heat-shock-protein 60 antibody level is a predictor of coronary risk in dyslipidemic middle-aged men. In this paper we studied the joint effects of high Anti-Hsp60-antibody level and the classical coronary risk factors.

METHODS

We used nested case-control design and logistic regression analyses. The cases consisted of 233 middle-aged men with myocardial infarction or coronary death during 8.5-year follow-up in Helsinki Heart Study, a coronary primary prevention study with gemfibrozil. The controls were subjects without coronary events, matched for drug treatment and the geographical area.

RESULTS

The relative coronary risks (Odds Ratios (ORs); 95% confidence interval) were 1.41 (0.96-2.05) for high IgA-class Anti-Hsp60 antibody level and 1.98 (1.35-2.90) for hypertension, defined as mean arterial pressure >114 mmHg. With simultaneous occurrence of high Anti-Hsp60 antibody level and hypertension, the ORs were 2.32 (1.26-4.27) for systolic and 2.99 (1.63-5.48) for diastolic hypertension. Similar patterns of joint effects were found between high Anti-Hsp60 antibody and lipoprotein cholesterol levels as well as antibodies against oxidized low-density lipoprotein.

CONCLUSIONS

Our results suggest that, while high IgA-class Anti-Hsp60 antibody level predicts coronary risk, the effect is modest without simultaneous occurrence of other classical risk factors.

Infections, heat shock proteins, and atherosclerosis

Recent evidence indicates that infections or a pathogen burden contribute to the development and progression of atherosclerosis. While the mechanism of infection contributing to the pathogenesis is not fully elucidated, I hypothesize that heat shock proteins may be a link between infections and atherosclerosis. Heat shock proteins are a highly conserved family of proteins expressed in most cell types and have been shown to play a general role in protecting cells in response to stress. It has been demonstrated that Chlamydia and human HSP60 coexist in atherosclerotic lesions. Bacterial and human heat shock proteins have been found in soluble form in the general circulation of patients with atherosclerosis. Both heat shock proteins can stimulate cells to express adhesion molecules and proinflammatory cytokines. Certain organisms synthesize heat shock proteins that have close structural homology with human heat shock proteins. Because of the immunologic molecular mimicry between bacterial and human HSP60, it could be an autoantigen involved in eliciting cell-mediated and humoral immune responses that cause vessel injury leading to atherosclerosis. The aim of this review is to provide an update overview on the involvement of heat shock proteins in the pathogenesis of atherosclerosis in response to infections.

Activation of heat shock transcription factor 1 in atherosclerosis

Previous work established that increased expression of heat shock proteins (HSPs) in the vessel wall might evoke proinflammatory and autoimmune reactions in the pathogenesis of atherosclerosis. The present study was designed to further scrutinize the molecular mechanisms of HSP expression involving activation of heat shock transcription factors (HSFs) in atherosclerotic lesions in animal models. Severe atherosclerotic lesions developed in the aortas of rabbits 16 weeks after feeding a 0.2% cholesterol diet. When protein extracts from the aortas were subjected to Western blot analysis, the level of HSF1 in proteins from atherosclerotic lesions of hypercholesterolemic rabbits were significantly higher than those of normal vessels. Gel mobility shift assays revealed the formation of protein-heat shock element complexes containing HSF1 in protein extracts from atherosclerotic lesion. Furthermore, triglyceride-rich lipoprotein, oxidized-triglyceride-rich lipoprotein, low-density lipoprotein, and oxidized low-density lipoprotein did not activate HSF1 in cultured smooth muscle cells, whereas HSF1 was highly activated in cells treated with tumor necrosis factor-alpha. Interestingly, mechanical stretching of smooth muscle cells resulted in HSF1 translocation from the cytoplasm to the nucleus and hyperphosphorylation followed by increased HSP70 expression. Thus, our findings provide the first evidence that HSF1 is activated and highly expressed in atherosclerotic lesions and that cytokine stimulation and disturbed mechanical stress to the vessel wall may be responsible for such activation.

Circulating heat shock protein and heat shock protein antibody levels in established hypertension

OBJECTIVE

Serum Hsp60 and anti-Hsp65 antibody levels are raised in subjects with borderline hypertension, and there is an association between circulating Hsp60 levels and early atherosclerosis. Given the recognized relationship between hypertension and atherosclerosis, this study determined heat shock protein and heat shock protein antibody levels in subjects with established hypertension.

METHODS

Samples from 111 men with hypertension were obtained from the European Lacidipine study on Atherosclerosis and samples from 75 normotensive controls were taken from a population-screening programme (diastolic pressure, 95 and 80 mmHg, respectively). Hsp60, Hsp70 and anti-human Hsp60, anti-human Hsp70 and anti-mycobacterial Hsp65 antibody levels were measured by enzyme immunoassay. Intima-media thickness (I-M) and the presence of carotid atherosclerosis were determined by ultrasonography.

RESULTS

Hsp60, Hsp70 and anti-Hsp60 antibody levels in hypertension were similar to those in normotensive controls, whereas anti-Hsp70 and anti-Hsp65 antibody levels were elevated ( 0.001). Hsp60 levels and atherosclerosis were not associated. Anti-Hsp70 and anti-Hsp65 antibody levels were both associated with hypertension, independently of age, smoking habits and blood lipids.

CONCLUSIONS

This study demonstrates elevated levels of selected heat shock protein antibodies in subjects with hypertension. Although the association between heat shock protein antibody levels and human cardiovascular stress/disease appears to be robust, the relationship of the latter with heat shock protein levels is more complex. Further studies are required before the factors inducing, and the clinical significance of, circulating heat shock proteins can be evaluated.

Autoimmunity, oxidized LDL and cardiovascular disease

Atherosclerosis is the major cause of cardiovascular disease (CVD) and in addition to established risk factors as smoking, hypertension, diabetes and dyslipidemia, inflammation and autoimmune reactions have been much discussed recently. Several lines of evidence indicate that also inflammation and autoimmune reactions are highly relevant in atherosclerosis and CVD. Inflammatory cells and cytokines are present in lesions, already at an early stage; animal experiments suggest that immune reactions, though not necessary for development of atherosclerosis, can modulate disease development and systemic inflammation is associated with an enhanced risk of CVD. The enhanced risk of CVD in a major autoimmune disease, systemic lupus erythematosus (SLE), is therefore highly relevant, and in addition to being an important clinical problem, SLE-related CVD could give insights into the nature of autoimmunity in atherosclerosis and CVD in general. We recently defined traditional and non-traditional risk factors for CVD in SLE. These include increased atherosclerosis (as determined by intima-media thickness of carotid artery); raised oxidized low density lipoprotein (OxLDL) and autoantibodies to OxLDL; dyslipidemia with raised triglycerides and Lp(a) and decreased HDL-cholesterol concentrations; raised systemic inflammation; presence of anti-phospholipid antibodies including lupus anticoagulant, homocysteine-levels and more frequent osteoporosis. Disease duration, smoking, blood pressure or diabetes mellitus did not differ significantly between the groups. Taken together, immune reactions are highly relevant in atherosclerosis, and patients with autoimmune disease like SLE are at high-risk of CVD. If confirmed prospectively, non-traditional risk factors like OxLDL in the circulation, autoantibodies against OxLDL and phospholipids and inflammation could lead to new therapeutic strategies and insight into disease mechanisms.

Presence of antibody against the inducible Hsp71 in patients with acute heat-induced illness

Antibodies against heat shock or stress proteins (Hsps) have been reported in a number of diseases in which they may be involved in the pathogenesis of the disease or may be of use for prognosis. Heat-induced diseases, such as heat cramps, heat exhaustion, or heat stroke, are frequent in hot working or living environments. There are still few investigations on the presence and possible significance of autoantibodies against Hsps in heat-induced illnesses. Using an immunoblotting technique with recombinant human Hsps, we analyzed the presence and titers of antibodies against Hsp60, Hsp71, and Hsp90alpha, and Hsp90beta in a group of 42 young male patients who presented with acute heat-induced illness during training. We also examined the presence of antibody against Hsp71 in a second group of 57 patients with acute heat-induced illness and measured the changes in titers of anti-Hsp71 antibodies in 9 patients hospitalized by emergency physicians. In the first group of young persons exercising in a hot environment, the occurrence of antibodies against Hsp71 and Hsp90alpha was significantly higher among individuals with symptoms of heat-induced illness (P < 0.05) than in the matched group of nonaffected exercising individuals. Moreover titers of antibody against Hsp71 were higher in individuals of the severe and mild heat-induced illness groups, the highest titer being found in the most severe cases. The results from the second group of 57 heat-affected patients exposed to extreme heat were similar. Again, patients with the more severe heat-induced symptoms showed a significantly higher incidence of antibodies to Hsp71 than controls and the titer of anti-Hsp71 was higher in the severely affected group. Finally, in a study of 9 patients, it was observed that the titer of anti-Hsp71 decreased during recovery from severe heat symptoms. These results suggest that measurement of antibodies to Hsps may be useful in assessing how individuals are responding to abnormal stress within their living and working environment and may be used as one biomarker to evaluate their susceptibility to heat-induced diseases.

Association of plasma antibodies against the inducible Hsp70 with hypertension and harsh working conditions

Autoantibodies against certain stress or heat shock proteins (Hsps) may play a role in the pathogenesis and/ or prognosis of some diseases. Using immunoblotting with human recombinant Hsps and univariate and multivariate logistic regression models, we have investigated the presence of antibodies against Hsp70, the inducible member of the 70-kDa family of heat shock proteins, and analyzed its possible association with hypertension and working conditions. Plasma and serum were collected from 764 steel mill workers from 6 work sites exposed to (1) severe noise; (2) severe noise and dust; (3) noise, dust, and heat; (4) noise and heat; (5) severe noise and heat; and (6) office conditions (control). Workers with prolonged exposure to stresses such as noise, dust, and high temperature and a combination of these in the workplace had a high incidence (26.6% to 40.2%) of antibodies to Hsp70 compared to the lowest incidence (18.6%) of antibodies to Hsp70 in the control group of office workers. Moreover, there was a statistical association of antibodies against Hsp70 with hypertension. The statistical correlation between the presence of antibodies to Hsp70 and hypertension is higher in the group of workers with blood pressure of 160/95 mmHg than in the 140/90-mmHg group after excluding possible effects of the workplace stresses. These results suggest that harsh workplace conditions can increase the production of antibodies against Hsp70 and that the presence of antibodies to this stress protein may be associated with hypertension. The precise mechanism for the elevation of antibodies against Hsps by environmental and workplace stresses and their relation to hypertension remains to be established.

Heat shock proteins, anti-heat shock protein reactivity and allograft rejection

Heat shock proteins are families of highly conserved immunodominant molecules, reactivity to which has been implicated in the pathogenesis of a number of autoimmune and vascular disease states. However, heat shock proteins are cytoprotective, and in clinical and experimental arthritis, anti-heat shock protein reactivity can down modulate immune responses via a self-Hsp reactive, Th2-type mechanism. Despite a number of studies associating heat shock protein expression and anti-heat shock protein reactivity with allograft rejection, the balance between protective and damaging effects and the precise influence of these responses on graft outcome is unclear. This article reviews current knowledge surrounding heat shock proteins, autoimmunity, and allograft rejection and presents a perspective on the potential influence of these proteins and the stress response on allograft outcome.

Presence of antibody against the inducible Hsp71 in patients with acute heat-induced illness

Antibodies against heat shock or stress proteins (Hsps) have been reported in a number of diseases in which they may be involved in the pathogenesis of the disease or may be of use for prognosis. Heat-induced diseases, such as heat cramps, heat exhaustion, or heat stroke, are frequent in hot working or living environments. There are still few investigations on the presence and possible significance of autoantibodies against Hsps in heat-induced illnesses. Using an immunoblotting technique with recombinant human Hsps, we analyzed the presence and titers of antibodies against Hsp60, Hsp71, and Hsp90alpha, and Hsp90beta in a group of 42 young male patients who presented with acute heat-induced illness during training. We also examined the presence of antibody against Hsp71 in a second group of 57 patients with acute heat-induced illness and measured the changes in titers of anti-Hsp71 antibodies in 9 patients hospitalized by emergency physicians. In the first group of young persons exercising in a hot environment, the occurrence of antibodies against Hsp71 and Hsp90alpha was significantly higher among individuals with symptoms of heat-induced illness (P < 0.05) than in the matched group of nonaffected exercising individuals. Moreover titers of antibody against Hsp71 were higher in individuals of the severe and mild heat-induced illness groups, the highest titer being found in the most severe cases. The results from the second group of 57 heat-affected patients exposed to extreme heat were similar. Again, patients with the more severe heat-induced symptoms showed a significantly higher incidence of antibodies to Hsp71 than controls and the titer of anti-Hsp71 was higher in the severely affected group. Finally, in a study of 9 patients, it was observed that the titer of anti-Hsp71 decreased during recovery from severe heat symptoms. These results suggest that measurement of antibodies to Hsps may be useful in assessing how individuals are responding to abnormal stress within their living and working environment and may be used as one biomarker to evaluate their susceptibility to heat-induced diseases.

Antibodies to platelet-activating factor are associated with borderline hypertension, early atherosclerosis and the metabolic syndrome

OBJECTIVE

Platelet-activating factor (PAF) is a phospholipid inflammatory mediator which is synthesized by a variety of cells, including monocytes and endothelial cells, and PAF can be retained in activated endothelial cell membranes. Furthermore, PAF-like lipids are produced in other phospholipid membranes as in oxidized LDL. Atherosclerosis is a chronic inflammation in the artery wall, but little is known about the role of immune reactions in the early stages of development of cardiovascular disease. In the present study we investigated if there are antibodies to PAF (aPAF) that may play a role in borderline hypertension and early atherosclerosis.

DESIGN

Seventy-three men with borderline hypertension (BHT) and 73 age-matched normotensive (NT) men (diastolic blood pressure 85-94 and <80 mmHg, respectively) were recruited from a population screening programme. Antibody levels were determined by use of ELISA. Carotid intima-media (IM)-thickness and atherosclerosis was determined by B-mode ultrasonography.

RESULTS

BHT men had 49.3% higher aPAF levels of IgG class than NT controls (P = 0.0007). Antibodies to the biologically inactive lysoPAF did not differ between BHT and NT group. aPAF levels were associated with IM-thickness in the left (P = 0.02) and right (P = 0.009) carotid artery. Furthermore, aPAF levels were enhanced in individuals with the metabolic syndrome (n = 44) as compared to those without (n = 102; P = 0.009), and also significantly associated with insulin levels (P = 0.02) and insulin resistance (P = 0.02).

CONCLUSIONS

aPAF antibodies may reflect early vascular changes and thus serve as novel markers for disease, and they may also be pathogenic, by eliciting an inflammatory reaction in the vascular wall.

Lysophosphatidylcholine (LPC) induces proinflammatory cytokines by a platelet-activating factor (PAF) receptor-dependent mechanism

Oxidized low-density lipoprotein (oxLDL) consists of both lipid components and apoprotein B100. OxLDL has both proinflammatory and cytotoxic properties. The present study was undertaken to investigate the effects of components in the lipid moiety of oxLDL on immune activation as determined by cytokine and immunoglobulin secretion. LPC induced interferon-gamma (IFN-gamma) secretion in peripheral blood mononuclear leucocytes from healthy blood donors. The effect varied between individuals, and there were both responders and non-responders. Furthermore, LPC induced enhanced antibody production, indicating B cell activation. None of eight oxysterols, arachidonic acid (AA), or 15-lipoxygenase products of AA tested had immune stimulatory properties. We recently demonstrated that PAF and oxLDL induce IFN-gamma secretion by a common mechanism. LPC-induced IFN-gamma secretion was inhibited by a specific PAF receptor antagonist, WEB 2170, indicating that the PAF receptor is involved in LPC-induced immune activation. Both oxLDL- and LPC-induced antibody formation was inhibited by WEB 2170. Furthermore LPC also induced tumour necrosis factor-alpha secretion, and this effect was inhibited by WEB 2170. LPC is produced during lipid oxidation (as in oxLDL), but also by enzymes such as phospholipase A2. The findings indicate that LPC may play an important role in inflammatory reactions, including atherosclerosis.