Circulating heat shock protein 60 is associated with early cardiovascular disease

A non-receptor-mediated mechanism for internalization of molecular chaperones

The evolving realization that stress proteins, which have for many years been considered to be exclusively intracellular molecules under normal conditions, can be released from viable cells via a number of potential routes/pathways has prompted interest into their extracellular biology and intercellular signaling properties. That the stress proteins Hsp60, Hsp70 and gp96 can elicit both pro- and anti-inflammatory effects suggests that these molecules play a key role in the maintenance of immunological homeostasis, and a better understanding of the immunobiology of extracellular stress proteins might reveal new and more effective approaches for controlling and managing infectious disease, inflammatory disease and cancer. A number of cell surface receptors for stress proteins have been identified, and the intracellular consequences of these cell surface receptor-ligand interactions have been characterized. To date, studies into the intercellular signaling properties of stress proteins and their interactions with antigen presenting cells have focused on specific receptor-mediated uptake, and have not considered the fact that such cells can also take up proteins via non-specific endocytosis/pinocytosis. Herein we present a methodological approach for assessing receptor-mediated and non-receptor-mediated uptake of gp96 by rat bone marrow-derived dendritic cells.

Relationship between periodontal infections and systemic disease

Oral conditions such as gingivitis and chronic periodontitis are found worldwide and are among the most prevalent microbial diseases of mankind. The cause of these common inflammatory conditions is the complex microbiota found as dental plaque, a complex microbial biofilm. Despite 3000 years of history demonstrating the influence of oral status on general health, it is only in recent decades that the association between periodontal diseases and systemic conditions such as coronary heart disease and stroke, and a higher risk of preterm low birth-weight babies, has been realised. Similarly, recognition of the threats posed by periodontal diseases to individuals with chronic diseases such as diabetes, respiratory diseases and osteoporosis is relatively recent. Despite these epidemiological associations, the mechanisms for the various relationships remain unknown. Nevertheless, a number of hypotheses have been postulated, including common susceptibility, systemic inflammation with increased circulating cytokines and mediators, direct infection and cross-reactivity or molecular mimicry between bacterial antigens and self-antigens. With respect to the latter, cross-reactive antibodies and T-cells between self heat-shock proteins (HSPs) and Porphyromonas gingivalis GroEL have been demonstrated in the peripheral blood of patients with atherosclerosis as well as in the atherosclerotic plaques themselves. In addition, P. gingivalis infection has been shown to enhance the development and progression of atherosclerosis in apoE-deficient mice. From these data, it is clear that oral infection may represent a significant risk-factor for systemic diseases, and hence the control of oral disease is essential in the prevention and management of these systemic conditions.

Stimulation of cysteinyl leukotriene production in mast cells by heat shock and acetylsalicylic acid

Immunoglobulin (Ig) E-dependent activation of mast cells is central to the allergic response. The engagement of IgE-occupied receptors initiates a series of molecular events that causes the release of preformed, and de novo synthesis of, allergic mediators. Cysteinyl leukotrienes are able to contract airway smooth muscle and increase mucus secretion and vascular permeability and recruit eosinophils. Mast cells have also recently been recognized as active participants in innate immune responses. Heat stress can modulate innate immunity by inducing stress proteins such as heat-shock proteins (HSPs). We previously demonstrated that treatment of mast cells with heat shock or acetylsalicylic acid results in an increase of TNF-alpha and IL-6 release. This effect was paralleled by expression of HSP70. In the current study, we further investigated the effects of heat shock and acetylsalicylic acid on the activation of mast cells and the release of cysteinyl leukotrienes. In mouse mast cells, derived from a culture of bone marrow cells, responsiveness to heat shock, acetylsalicylic acid and exogenous or endogenous HSP70 was monitored by measuring leukotriene C4 release. We show that after heat shock treatment and exposure to acetylsalicylic acid leukotriene production was increased. Moreover, exogenous rHSP70 also induced leukotriene production. Because it has been reported that leukotriene production in mast cells may be mediated by Toll like receptor (TLR) activation, and HSP70 also activates TLRs signaling, we further explored these issues by using mast cells that are not able to produce HSP70, i.e. heat shock factor-1 (HSF-1) knockout cells. We found that in HSF-1 knockout bone marrow derived mast cells, heat shock and acetylsalicylic acid failed to induce release of leukotrienes. Moreover, in wild type cells the surface expression of TLR4 was attenuated, whereas the intracellular expression was up-regulated. We conclude that heat shock and acetylsalicylic acid induce the production and release of heat shock proteins from mast cells, which in turn stimulate leukotriene synthesis through activation of TLR4.

Inflammation — a lifelong companion

Inflammation is a key component of the immune system. It has important functions in both defense and pathophysiological events maintaining the dynamic homeostasis of a host organism including its tissues, organs and individual cells. On the cellular level it is controlled by more than 400 currently known genes. Their polymorphisms and environmental conditions give rise to different genotypes in human population. Pro-inflammatory genotype, which dominates in the present population, may be advantageous in childhood but not in elderly people because it is characterized by an increased vulnerability to, and intensity of, inflammatory reactions. These reactions may be the possible reasons of chronic inflammatory diseases, especially in old age. Better understanding of complex molecular and cellular inflammatory mechanisms is indispensable for detailed knowledge of pathogenesis of many diseases, their prevention and directed drug therapy. Here we summarize the basic current knowledge on these mechanisms.

HSP60 trafficking in adult cardiac myocytes: role of the exosomal pathway

The heat shock proteins (HSP) are a highly conserved family of proteins with critical functions in protein folding, protein trafficking, and cell signaling. These proteins also protect the cell against injury. HSP60 has been found in the extracellular space and has been identified in the plasma of some individuals. HSP60 is thought to be a "danger signal" to the immune system and is also highly immunogenic. Thus extracellular HSP60 is possibly toxic to the cell. The mechanism by which HSP60 is released into the extracellular space is unknown, as is whether it is released by cardiac myocytes. We investigated several different pathways controlling protein release including the classic, Golgi-mediated pathway. We found that HSP60 is released via exosomes, and that within the exosome, HSP60 is tightly attached to the exosome membrane.

Protective effect of human heat shock protein 60 suggested by its association with decreased seropositivity to pathogens

The presence of heat shock protein 60 (Hsp60) in human plasma has been linked with cardiovascular disease (CVD). In this study, the examination of the relationship between Hsp60 in plasma and seropositivity for three microbial agents, which are thought to be risk factors for CVD, surprisingly revealed a negative association between Hsp60 and seropositivity, suggesting a protective effect of this circulating stress protein.

Serum heat shock protein 70 level as a biomarker of exceptional longevity

Heat shock proteins are highly conserved proteins that, when produced intracellularly, protect stress exposed cells. In contrast, extracellular heat shock protein 70 (Hsp70) has been shown to have both protective and deleterious effects. In this study, we assessed heat shock protein 70 for its potential role in human longevity. Because of the importance of HSP to disease processes, cellular protection, and inflammation, we hypothesized that: (1) Hsp70 levels in centenarians and centenarian offspring are different from controls and (2) alleles in genes associated with Hsp70 explain these differences. In this cross-sectional study, we assessed serum Hsp70 levels from participants enrolled in either the New England Centenarian Study (NECS) or the Longevity Genes Project (LGP): 87 centenarians (from LGP), 93 centenarian offspring (from NECS), and 126 controls (43 from NECS, 83 from LGP). We also examined genotypic and allelic frequencies of polymorphisms in HSP70-A1A and HSP70-A1B in 347 centenarians (266 from the NECS, 81 from the LGP), 260 NECS centenarian offspring, and 238 controls (NECS: 53 spousal controls and 106 septuagenarian offspring controls; LGP: 79 spousal controls). The adjusted mean serum Hsp70 levels (ng/mL) for the NECS centenarian offspring, LGP centenarians, LGP spousal controls, and NECS controls were 1.05, 1.13, 3.07, 6.93, respectively, suggesting that a low serum Hsp70 level is associated with longevity; however, no genetic associations were found with two SNPs within two hsp70 genes.

Cardiovascular disease could be contained based on currently available data!

Largely due to better control of infectious diseases and significant advances in biomedical research, life expectancy worldwide has increased dramatically in the last three decades. However, as the average age of the population has risen, the incidence of chronic age-related diseases such as arthritis, Alzheimer's, Parkinson's, cardiovascular disease, cancer, osteoporosis, benign prostatic hyperplasia, and late-onset diabetes have increased and have become serious public health problem, as well. The etiology of these disorders is still incompletely understood, therefore, neither preventive strategies nor long-term effective treatment modalities are available for these disorders. In keeping with the aforementioned, the ultimate goal in cardiovascular research is to prevent the onset of cardiovascular episodes and thereby allow successful ageing without morbidity and cognitive decline. Herein, I argue that cardiovascular episodes could be contained with relatively simple approaches. Cardiovascular disorder is characterized by cellular and molecular changes that are commonplace in age-related diseases in other organ system, such alterations include increased level of oxidative stress, perturbed energy metabolism, and "horror autotoxicus" largely brought about by the perturbation of ubiquitin -proteasome system, and excessive oxidative stress damage to the cardiac muscle cells and tissues, and cross-reactions of specific antibodies against human heat shock protein 60 with that of mycobacterial heat shock protein 65. "Horror autotoxicus", a Latin expression, is a term coined by Paul Ehrlich at the turn of the last century to describe autoimmunity to self, or the attack of "self" by immune system, which ultimately results to autoimmune condition. Based on the currently available data, the risk of cardiovascular episodes and several other age-related disorders, including cancer, Alzheimer's disease and diabetes, is known to be influenced by the nature and level of food intake. Now, a wealth of scientific data from studies of rodents and monkeys has documented the significant beneficial effects of calorie restriction (CR) or dietary restriction (DR), and multiple antioxidant agents in extending life span and reducing the incidence of progeroid-related diseases. Reduced levels of cellular oxidative stress, protection of genome from deleterious damage, detoxification of toxic molecules, and enhancement of energy homeostasis, contribute to the beneficial effects of dietary restriction and multiple antioxidant agents. Recent findings suggest that employment of DR and multiple antioxidant agents (including, catalase, glutathione peroxidase, CuZn superoxide dismutase, and Mn superoxide dismutase = enzymes forming the primary defense against oxygen toxicity), and ozone therapy may mount an effective resistance to pathogenic factors relevant to the pathogenesis of cardiovascular episodes. Hence, while further studies will be needed to establish the extent to which CR and multiple antioxidant agents will reduce incidence of cardiovascular episodes in humans, it would seem prudent to recommend CR and multiple antioxidant agents as widely applicable preventive approach for cardiovascular disorders and other progeroid-related disorders.

Association between plasma levels of heat shock protein 60 and cardiovascular disease in patients with diabetes mellitus

AIMS

Evidence is accumulating to support the hypothesis that the release of heat shock protein (Hsp)60 into the circulation is associated with the development of coronary heart disease (CHD). As diabetes is a risk factor for CHD, it was of interest to determine Hsp60 blood levels in a cross-sectional cohort of diabetic patients, some of whom had cardiovascular disease, and relate levels to relevant biochemical markers.

METHODS AND RESULTS

A total of 855 patients with T1DM or T2DM, recruited as part of the UCL Diabetes and Cardiovascular disease Study (UDACS), were assayed for plasma levels of Hsp60. Immunoreactive Hsp60 was detected in 54% of the samples, with 26% having plasma levels > 1 microg/mL. Levels of Hsp60 were higher in Caucasians than in other ethnic groupings, with 56.5% of Caucasian subjects, 37.5% of African-Caribbean subjects, and 47.1% of Indian subjects having detectable levels (P = 0.007), and with a higher proportion of non-smokers having detectable Hsp60 levels than smokers (54.9 vs. 43.5%, P = 0.01). Of note was the finding of an association between higher mean plasma levels of Hsp60 in subjects with clinically manifest cardiovascular disease and those with a history of myocardial infarction having an adjusted odds ratio of having detectable Hsp60 of 2.17 (CI 1.26-3.73).

CONCLUSION

This is the first report of circulating Hsp60 levels in diabetic patients, which suggests that this secreted mitochondrial cell stress protein may be playing an unexpected role in the cardiovascular pathology associated with diabetes.

Association of elevated serum heat-shock protein 70 concentration with transient hypertension of pregnancy, preeclampsia and superimposed preeclampsia: a case-control study

Our aim was to investigate the association between serum heat-shock protein (Hsp) 70 concentration and hypertensive disorders of pregnancy. One hundred and forty-two pregnant women with hypertensive disorders (93 with preeclampsia, 29 with transient hypertension of pregnancy and 20 with superimposed preeclampsia) and 127 normotensive, healthy pregnant women were included in the study. Serum Hsp70 concentration was measured using enzyme-linked immunosorbent assay. The serum Hsp70 concentration was significantly higher in patients with transient hypertension of pregnancy, in preeclamptic patients and in patients with superimposed preeclampsia than in the control group (median (25-75 percentile): 0.66 (0.52-0.84), 0.55 (0.42-0.80), 0.61 (0.42-0.91) ng/ml vs 0.31 (0.27-0.39) ng/ml, respectively; P<0.001). Multivariate logistic regression analysis showed independent association of elevated serum Hsp70 level with transient hypertension of pregnancy, preeclampsia and superimposed preeclampsia. The difference in serum Hsp70 concentration between preeclamptic patients and the control group was statistically significant in each gestational age category. In the groups of preeclamptic and superimposed preeclamptic patients, there was no significant difference in serum Hsp70 concentration between mild and severe preeclamptic patients, between patients with late and early onset of the disease, as well as between preeclamptic patients without and with foetal growth restriction. In conclusion, serum Hsp70 concentration is elevated in transient hypertension of pregnancy, in preeclampsia and in superimposed preeclampsia. Circulating Hsp70 may not only be a marker for these conditions, but might also play a role in their pathogenesis. However, further studies are needed to explore its role in the pathogenesis of hypertensive disorders of pregnancy.

Helper T cells and atherosclerosis: the cytokine web

There is growing evidence regarding the importance of inflammation in the pathogenesis of atherosclerosis and its ultimate progression to the clinical syndromes. Recently there has been an increasing interest in the role of helper T (Th) cells in atherosclerosis. The Th cells act with the macrophages and the dendritic cells via the various cytokines in bringing about a variety of changes thus leading to the progression of atherosclerosis. Atherosclerotic lesions have been seen to have increased expression of type 1 helper T (TH1) cells together with increased levels of the Th1 related cytokines. It is mainly the cytokines involved with Th1 functioning that seem to show a prominent effect, with the whole process centred around interferon gamma, making it seem like every pathway and the cytokines involved lead to a final common pathway of interferon gamma secretion; the increase or decrease of which dictates the progression of atherosclerosis and its final manifestation as the clinical syndromes.

Plasma antibodies to heat shock protein 60 and heat shock protein 70 are associated with increased risk of electrocardiograph abnormalities in automobile workers exposed to noise

In the living and working environment, stressful factors, such as noise, can cause health problems including cardiovascular diseases and noise-induced hearing loss. Some heat shock proteins (Hsps) play an important role in protecting cardiac cells against ischemic injury, and antibodies against these Hsps are associated with the development and prognosis of atherogenesis, coronary heart disease, and hypertension. Whether the presence of such antibodies is associated with abnormal electrocardiography (ECG) in stressed autoworkers exposed to chronic noise is presently unknown. Therefore, we investigated the association between the levels of plasma anti-Hsp60 and anti-Hsp70 with electrocardiograph abnormality in 396 autoworkers exposed to different noise levels by using Western blot, ECG, and multivariate logistic regression analysis. The results showed that the increase in levels of anti-Hsp70 was associated with a higher risk of ECG abnormalities characteristic of chronic myocardial ischemia (P < 0.05), conductive abnormality (P < 0.01), or heart displacement (P < 0.05); in contrast, elevated anti-Hsp60 was related to ECG abnormalities characteristic of sinus arrhythmia, chronic myocardial ischemia, and ectopic rhythm (P < 0.01 for all). Overall, high levels of both anti-Hsp70 and anti-Hsp60 were associated with significantly increased risk of ECG abnormalities (odds ratio [OR] = 1.73 and 95% confidence interval [Cl] = 1.04-2.86 for anti-Hsp70 and OR = 1.36 and 95% Cl = 1.07-1.72 for anti-Hsp60) with and without adjustment for cumulative noise exposure (OR = 1.96 and 95% Cl = 1.20-3.21 for anti-Hsp70 and OR = 3.93 and 95% Cl = 1.72-8.92 for anti-Hsp60). These findings suggest that the production of both anti-Hsp70 and anti-Hsp60 may be independent risk factors for the development and progression of abnormal ECG and therefore possibly cardiovascular diseases in autoworkers exposed to occupational noise.

Human heat shock protein 60 stimulates vascular smooth muscle cell proliferation through Toll-like receptors 2 and 4

Heat shock proteins (HSPs) of endogenous and exogenous origin are suspected contributors to the initiation and aggravation of vascular pathologies like atherosclerosis and restenosis. Toll-like receptors (TLRs) 2 and 4 are well-known receptors for exogenous pathogen-associated molecular patterns and have recently been thought to play a role in HSP60-induced cellular activation. We hypothesized that human HSP60 directly stimulates venous smooth muscle cell (VSMC) proliferation through a TLR-dependent mechanism. Localization of HSP60, TLR2 and TLR4 was studied in failed venous grafts and normal venous tissue by double immunostaining. In vitro VSMCs were incubated for 48 h with recombinant human HSP60. In other experiments, VSMCs were pre-incubated for 30 min with specific anti-TLR2 and anti-TLR4 antibodies. VSMC proliferation was determined by Ki67 immunoreactivity, and mean values were compared between experimental and control groups. In addition, human embryonic kidney (HEK) cells transfected with human TLR2 or TLR4/MD-2 were exposed to HSP60 for 48 h, and proliferation was determined by using a hemocytometer. Co-localization of HSP60 and TLRs was detected in all neointimal lesions but was virtually absent in normal veins. Human HSP60 stimulated VSMC proliferation in a concentration-dependent fashion. In addition, TLR2 and TLR4 antibodies attenuated VSMC proliferation. The role of TLR-mediated stimulation of cell proliferation by HSP60 was supported by the significant increase in proliferation of transfected HEK cells. These findings provide supporting evidence for the role of HSP60 and TLR2 and TLR4 in vascular disease. Moreover, our data surpass the infection- and autoimmunity-based hypotheses of cardiovascular disease and suggest an additional HSP60-related autocrine process.

Cytokines in Atherosclerosis: Pathogenic and Regulatory Pathways

Atherosclerosis is a chronic disease of the arterial wall where both innate and adaptive immunoinflammatory mechanisms are involved. Inflammation is central at all stages of atherosclerosis. It is implicated in the formation of early fatty streaks, when the endothelium is activated and expresses chemokines and adhesion molecules leading to monocyte/lymphocyte recruitment and infiltration into the subendothelium. It also acts at the onset of adverse clinical vascular events, when activated cells within the plaque secrete matrix proteases that degrade extracellular matrix proteins and weaken the fibrous cap, leading to rupture and thrombus formation. Cells involved in the atherosclerotic process secrete and are activated by soluble factors, known as cytokines. Important recent advances in the comprehension of the mechanisms of atherosclerosis provided evidence that the immunoinflammatory response in atherosclerosis is modulated by regulatory pathways, in which the two anti-inflammatory cytokines interleukin-10 and transforming growth factor-β play a critical role. The purpose of this review is to bring together the current information concerning the role of cytokines in the development, progression, and complications of atherosclerosis. Specific emphasis is placed on the contribution of pro- and anti-inflammatory cytokines to pathogenic (innate and adaptive) and regulatory immunity in the context of atherosclerosis. Based on our current knowledge of the role of cytokines in atherosclerosis, we propose some novel therapeutic strategies to combat this disease. In addition, we discuss the potential of circulating cytokine levels as biomarkers of coronary artery disease.

Acetylsalicylic acid-induced release of HSP70 from mast cells results in cell activation through TLR pathway

OBJECTIVE

Mast cells are considered major players in IgE-mediated allergic responses, but have also recently been recognized as active participants in innate as well as specific immune responses. Heat stress can modulate innate immunity by inducing stress proteins such as heat shock proteins (HSPs). It has been reported that HSPs are capable of inducing the production of pro-inflammatory cytokines by the monocyte-macrophage system. In the current study, we explored whether the stress response induces HSPs and affects the signaling pathways of mast cells.

METHODS

In mouse mast cells, derived from a culture of bone marrow cells of male BALB/cBy and null HSF-1(-/-) mice, responsiveness to exogenous and endogenous HSP70 was monitored by measuring cytokine release.

RESULTS

Using BMMC, we show that treatment with heat shock or acetylsalicylic acid results in a selective induction of HSPs, and leads to release of HSP70 into the extracellular environment. The release of HSP70 from mast cells may be of functional importance. We found that after induction of HSP70, the production of TNF-alpha and IL-6 was increased. In a number of experiments, we demonstrated that exogenous/secreted HSP70 is most likely responsible for the activation of mast cells to produce cytokines. Extracellular HSP70 induced production of TNF-alpha and IL-6 through the activation of the TLR4 receptor pathway, which was evidenced by an abrogation of the response in mast cells cultured from TLR4(null) or HSF-1(-/-) mice.

CONCLUSION

Our experiments suggest that stress conditions can induce pro-inflammatory cytokine production by mast cells through an autocrine or paracrine stimulation of TLR receptors after a heat shock response. The recognition that heat shock proteins induce mast cell activation suggests an involvement of these cells in the immunological processes induced by heat shock response.

Precocious intima-media thickening in patients with primary Sjögren's syndrome

OBJECTIVE

Systemic lupus erythematosus and rheumatoid arthritis represent independent risk factors for atherosclerosis (ATS), although this may be confounded by continuous pharmacologic treatment. Primary Sjögren's syndrome (SS) shares several features of these diseases and may therefore represent an interesting model for verifying the presence of accelerated ATS in the absence of pharmacologic interference. The present study therefore used this model to describe the presence of accelerated ATS in a group of young women.

METHODS

Thirty-seven untreated white women with primary SS were evaluated clinically and serologically. Carotid and femoral artery intima-media thickness (IMT) was evaluated in the patients and in 35 age-matched healthy women who served as controls.

RESULTS

The patients had a higher IMT than did the controls at both the carotid (mean +/- SD 0.82 +/- 0.24 mm versus 0.63 +/- 0.20 mm; P < or = 0.001) and the femoral (0.81 +/- 0.26 mm versus 0.67 +/- 0.23 mm; P < or = 0.019) levels, and had a higher prevalence of carotid intima-media thickening (49% versus 11% of controls; P < or = 0.001). The patient subset with high carotid IMT showed an increased prevalence of leukopenia and circulating anti-SSA antibodies; interestingly, the number of leukocytes was inversely correlated with the level of arterial IMT in patients with SS. Multivariate analysis demonstrated that anti-SSA antibodies were independent predictors of carotid artery thickening, while leukopenia was a predictor of both carotid and femoral artery thickening.

CONCLUSION

Subclinical ATS was evident in about one-half of the patients with SS. Its association with some features typical of connective tissue diseases, such as the presence of anti-SSA and leukopenia, suggests that the immune dysregulation characterizing this autoimmune disorder may play a key role in inducing early ATS.

Induction of endothelial cell apoptosis by the binding of anti-endothelial cell antibodies to Hsp60 in vasculitis-associated systemic autoimmune diseases

OBJECTIVE

Anti-endothelial cell antibodies (AECAs), which recognize a number of endothelial antigens, are seen in patients with systemic autoimmune diseases, more often in the presence of vasculitis than in its absence. Some AECAs induce apoptosis of endothelial cells (ECs), but their target antigens remain unknown. The aim of this study was to determine whether Hsp60 is a target antigen and whether AECAs induce apoptosis in ECs.

METHODS

Two-dimensional electrophoresis and conventional Western blotting techniques were used to characterize AECA targets. Hsp60 reactivity was determined by enzyme-linked immunosorbent assay.

RESULTS

Hsp60 was shown to be targeted by a proportion of AECAs. The level of reactivity was higher in patients with systemic autoimmune disease and vasculitis than in those without vasculitis and in patients with systemic lupus erythematosus than in patients with other systemic autoimmune diseases. Hsp60 was expressed on the plasma membrane of heat-stressed ECs, and this followed Hsp60 messenger RNA transcription, confinement of the protein to the cytoplasm, and translocation of the protein to the surface. Shedding of Hsp60 from ECs was induced by stress and resulted in the binding of soluble Hsp60 to the surface of ECs, particularly stressed ECs. Apoptosis of ECs was triggered by anti-Hsp60-containing AECA-positive sera and was inhibited by preincubation of the ECs with recombinant Hsp60.

CONCLUSION

Our data support the notion that Hsp60 is an important target for AECAs and that such an interaction contributes to pathogenic effects, especially in vasculitis-associated systemic autoimmune disease.

Defects in regulation of local immune responses resulting in atherosclerosis

Atherosclerosis is nowadays generally accepted as an inflammatory disease but the mechanism of its origin and development have not yet been fully clarified. The present review focuses on the role of the local immune system as one of the key players in the pathogenesis of the complex process. Its part represented by vascular-associated lymphoid tissue (VALT) within the arterial wall participates directly in the vascular wall's homeostatis. Its inordinate activation during ontogenic development of an individual, this formerly defensive and physiologic mechanism transform into a pathological process resulting in an impairing inflammation. Hsp60, CRP and oxidized or otherwise modified LDL are serious candidates for triggering these pathological changes. The principal role is played by anti-Hsp60 antibodies and by shear stress originating on the surface of endothelium due to blood flow. The experimental and clinical data supporting this immunological hypothesis of atherosclerosis are discussed.

Comparison of two ELISAs for the determination of Hsp70 in serum

We have compared a previously developed in-house Sandwich-ELISA with a commercial kit for the determination of heat shock protein (Hsp) 70 in serum. Samples from 64 participants were tested and there was a significant correlation between results obtained using the two assays (r = 0.807, p < 0.0001). Additionally, when ranking samples on a categorical scale, the agreement was good (72%). In the commercial test system Hsp70 was detectable in 42 (66%) of the sera, compared with 61 (95%) in the in-house ELISA method. The three samples with undetectable levels of Hsp70 in the in-house ELISA were among the 22 samples with undetectable levels of Hsp70 in the commercial ELISA kit. The apparent serum concentrations detected were different in the two systems. This dissimilarity can be ascribed to differences in the matrix used. We conclude that the in-house ELISA is more economical and performs well when measuring physiologically high, as well as low, concentrations of Hsp70.

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?

Alternative mechanism by which IFN-gamma enhances tumor recognition: active release of heat shock protein 72

IFN-gamma exhibits differential effects depending on the target and can induce cellular activation and enhance survival or mediate cell death via activation of apoptotic pathways. In this study, we demonstrate an alternative mechanism by which IFN-gamma enhances tumor recognition, mediated by the active release of Hsp72. We demonstrate that stimulation of 4T1 breast adenocarcinoma cells and K562 erythroleukemic cells with IFN-gamma triggers the cellular stress response, which results in the enhanced expression of total Hsp72 expression without a significant increase in cell death. Intracellular expression of Hsp72 was abrogated in cells stably transfected with a mutant hsf-1 gene. IFN-gamma-induced Hsp72 expression correlated with enhanced surface expression and consequent release of Hsp72 into the culture medium. Pretreatment of tumors with compounds known to the block the classical protein transport pathway, including monensin, brefeldin A, tunicamycin, and thapsigargin, did not significantly block Hsp72 release. However, pretreatment with intracellular calcium chelator BAPTA-AM or disruption of lipid rafts using methyl beta-cyclodextrin completely abrogated IFN-gamma-induced Hsp72 release. Biochemical characterization revealed that Hsp72 is released within exosomes and has the ability to up-regulate CD83 expression and stimulate IL-12 release by naive dendritic cells. Pretreatment with neutralizing mAb or depletion of Hsp72 completely abrogated its chaperokine function. Taken together, these findings are indicative of an additional previously unknown mechanism by which IFN-gamma promotes tumor surveillance and furthers our understanding of the central role of extracellular Hsp72 as an endogenous adjuvant and danger signal.

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.

Gene expression profile and aortic vessel distensibility in voluntarily exercised spontaneously hypertensive rats: potential role of heat shock proteins

Physical exercise is considered to be beneficial for cardiovascular health. Nevertheless, the underlying specific molecular mechanisms still remain unexplored. In this study, we aimed to investigate the effects of voluntary exercise on vascular mechanical properties and gene regulation patterns in spontaneously hypertensive rats. By using ultrasound biomicroscopy in an ex vivo perfusion chamber, we studied the distensibility of the thoracic aorta. Furthermore, exercise-induced gene regulation was studied in aortae, using microarray analysis and validated with real-time PCR. We found that distensibility was significantly improved in aortas from exercising compared with control rats (P < 0.0001). Exercising rats demonstrated a striking pattern of coordinated downregulation of genes belonging to the heat shock protein family. In conclusion, voluntary exercise leads to improved vessel wall distensibility and reduced gene expression of heat shock protein 60 and 70, which may indicate decreased oxidative stress in the aortic vascular wall.

Glucose ingestion attenuates the exercise-induced increase in circulating heat shock protein 72 and heat shock protein 60 in humans

Heat shock protein (Hsp) 72 is a cytosolic stress protein that is highly inducible by several factors including exercise. Hsp60 is primarily mitochondrial in cellular location, plays a key role in the intracellular protein translocation and cytoprotection, is increased in skeletal muscle by exercise, and is found in the peripheral circulation of healthy humans. Glucose deprivation increases Hsp72 in cultured cells, whereas reduced glycogen availability elevates Hsp72 in contracting human skeletal muscle. To determine whether maintained blood glucose during exercise attenuates the exercise-induced increase in intramuscular and circulating Hsp72 and Hsp60, 6 males performed 120 minutes of semirecumbent cycling at approximately 65% maximal oxygen uptake on 2 occasions while ingesting either a 6.4% glucose (GLU) or sweet placebo (CON) beverage throughout exercise. Muscle biopsies, obtained before and immediately after exercise, were analyzed for Hsp72 and Hsp60 protein expression. Blood samples were simultaneously obtained from a brachial artery, a femoral vein, and the hepatic vein before and during exercise for the analysis of serum Hsp72 and Hsp60. Leg and hepatosplanchnic blood flow were measured to determine Hsp72-Hsp60 flux across these tissue beds. Neither exercise nor glucose ingestion affected the Hsp72 or Hsp60 protein expression in, or their release from, contracting skeletal muscle. Arterial serum Hsp72 increased (P < 0.05) throughout exercise in both trials but was attenuated (P < 0.05) in GLU. This may have been in part because of the increased (P < 0.05) hepatosplanchnic Hsp72 release in CON, being totally abolished (P < 0.05) in GLU. Serum Hsp60 increased (P < 0.05) after 60 minutes of exercise in CON before returning to resting levels at 120 minutes. In contrast, no exercise-induced increase in serum Hsp60 was observed in GLU. We detected neither hepatosplanchnic nor contracting limb Hsp60 release in either trial. In conclusion, maintaining glucose availability during exercise attenuates the circulating Hsp response in healthy humans.

Heat shock protein 60: specific binding of lipopolysaccharide

Human heat shock protein 60 (HSP60) has been shown to bind to the surface of innate immune cells and to elicit a proinflammatory response. In this study we demonstrate that the macrophage stimulatory property of recombinant human HSP60 is tightly linked to the HSP60 molecule and is lost after protease treatment. However, inhibition of macrophage stimulation was reached by the LPS-binding peptide magainin II amide. Indeed, HSP60 specifically bound [(3)H]LPS. [(3)H]LPS binding to HSP60 was saturable and competable by the unlabeled ligand. To identify the epitope region of the HSP60 molecule responsible for specific LPS binding, we analyzed the effect of several anti-HSP60 mAbs on HSP60-induced production of inflammatory mediators from macrophages. We identified only one mAb, clone 4B9/89, which blocked the macrophage stimulatory activity of the chaperone. The epitope specificity of this mAb points to the region aa 335-366 of HSP60. Clone 4B9/89 also strongly inhibited [(3)H]LPS binding to HSP60. A more detailed analysis was performed by screening with selected overlapping 20-mer peptides of the HSP60 sequence, covering the region aa 331-380. Only one peptide blocked LPS binding to HSP60, thereby restricting the potential LPS-binding region to aa 351-370 of HSP60. Finally, analysis of selected 15-mer peptides and a 13-mer peptide of the HSP60 sequence revealed that most of the LPS-binding region was accounted for by aa 354-365 of HSP60, with the motif LKGK being critical for binding. Our studies identified a defined region of HSP60 involved in LPS binding, thereby implicating a physiological role of human HSP60 as LPS-binding protein.

Hsp72 is present in plasma from Holstein-Friesian dairy cattle, and the concentration level is repeatable across days and age classes

Although heat shock proteins (Hsps) are primarily considered as being intracellular, this study identified the presence of Hsp72 in plasma from female Holstein-Friesian dairy cattle. Plasma samples were collected from the same animals at different ages and on different days after calving and accordingly divided into 5 age classes. The age classes were calves less than 235 days of age, young heifers between 235 and 305 days of age, older heifers between 305 and 560 days of age, cows early in lactation, and cows later in lactation. For a subsample of animals within each age class, replicate plasma samples were collected from 1 to 7 days apart to test whether the Hsp72 concentration levels are repeatable on this shorter timescale. Hsp72 was observed in plasma samples from animals of all 5 age classes. For animals with blood samples taken a few days apart, the repeatability (within age class) of the Hsp72 concentration was 0.52 +/- 0.06. Age and days from calving significantly affected the Hsp72 concentration level. The highest Hsp72 level was observed in older heifers (305-560 days of age). The repeatability of Hsp72 concentrations across age classes within animal was 0.22 +/- 0.06. High environmental sensitivity and negative genetic associations between production and health traits in this high-producing breed have been documented earlier. Hsp72 is believed to be strictly stress inducible, and the finding of Hsp72 in plasma indicates that even apparently healthy individuals may experience extrinsic or intrinsic stress (or both).

Heat-shock response is associated with decreased production of interleukin-6 in murine aortic vascular smooth muscle cells

Heat shock has been known to change cellular responses to noxious stimuli by inducing heat-shock proteins (Hsps). We hypothesized that a heat-shock response modulates cytokine production in murine aortic vascular smooth muscle cells (VSMCs). VSMCs were exposed to 44 degrees C for 15-60 min, and subjected to interleukin-1beta (IL-1beta) or tumor necrosis factor alpha (TNFalpha), which induced interleukin-6 (IL-6) production. Expression of Hsps was examined with immunoblots, immunocytochemistry, or enzyme-linked immunosorbent assay (ELISA), and that of IL-6 with reverse transcription-polymerase chain reaction (RT-PCR) or ELISA. Heat shock (44 degrees C for 45 min) induced Hsp72 in VSMCs at 4 h and elicited its maximal expression at 8 h after the end of heat shock. Treatment with IL-1beta increased IL-6 transcription in VSMCs up to 24 h in an incubation time-dependent manner. Treatment with IL-1beta or TNFalpha caused a concentration-dependent increase in IL-6 production in culture medium, which was attenuated by heat shock. Although treatment with Hsp72 or Hsp60 alone did not significantly affect basal IL-6 release into culture medium statistically, cotreatment with IL-1beta and Hsp72, but not Hsp60 or boiled Hsp72, decreased IL-1beta-induced IL-6 production in culture medium. Introduction of Hsp72, but not Hsp60, into VSMCs decreased IL-1beta-induced IL-6 production in culture medium. These results indicate that the heat-shock response transcriptionally attenuated production of IL-6 in murine aortic VSMCs.

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.

Hsp70 release from peripheral blood mononuclear cells

There are an increasing number of studies reporting the presence of Hsps in human serum. We have investigated the release of Hsp70 into blood and culture medium from peripheral blood mononuclear cells (PBMCs), and whether this release is due to cell damage or active secretion from the cells. Intact Hsp70 was released from cells within whole blood and from purified PBMCs under normal culture conditions. Hsp70 release was rapid (0.1 ng/10(6) cells/h) over the first 2 h of culture and continued at a reduced rate up to 24 h (<0.025 ng/10(6) cells/h). Using viable cell counts and lactate dehydrogenase release we were able to confirm that the release of Hsp70 was not due to cellular damage. Hsp70 release was inhibited by monensin, methyl-beta-cyclodextrin, and methylamine, but not by brefeldin A. These data suggest that Hsp70 is released from cells via a non-classical pathway, possibly involving lysosomal lipid rafts.

Vascular proteomics: Linking proteomic and metabolomic changes

Cardiovascular diseases constitute the largest of death in the Western world. Various stressors, including elevated blood pressure, smoking, diabetes, and hypercholesterolemia directly or indirectly damage the vessel wall, eventually inducing arterial stiffness (arteriosclerosis) and lipid accumulation (atherosclerosis). However, the molecular mechanisms of atheroma formation are not yet fully clarified. While many investigators have used proteomic techniques to study cardiac diseases, vascular proteomics is still in its infancy. The present review highlights studies, in which proteomics has been successfully applied to study protein alterations in the vasculature. Furthermore, we will summarize our recent progress in combining proteomic and metabolomic techniques to reveal protein and metabolite alterations in the cardiovascular system: two-dimensional (2-D) gel electrophoresis proved to be highly complementary to nuclear magnetic resonance (NMR) spectroscopy, in that post-translational modifications of the most abundant enzymes were displayed on 2-D gels while NMR spectroscopy revealed changes in the corresponding metabolites. Importantly, the simultaneous assessment of protein and metabolite changes translated purely descriptive proteomic and metabolomic profiles into a functional context and provided important insights into pathophysiological mechanisms that would not have been obtained by other techniques.

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.

Autoimmune and inflammatory mechanisms in atherosclerosis

The present review focuses on the concept that cellular and humoral immunity to the phylogenetically highly conserved antigen heat shock protein 60 (HSP60) is the initiating mechanism in the earliest stages of atherosclerosis. Subjecting arterial endothelial cells to classical atherosclerosis risk factors leads to the expression of HSP60 that then may serve as a target for pre-existent cross-reactive antimicrobial HSP60 immunity or bona fide autoimmune reactions induced by biochemically altered autologous HSP60. Endothelial cells can also bind microbial or autologous HSP60 via Toll-like receptors, providing another possibility for targetting adaptive or innate immunological effector mechanisms.

Immunological aspects of heat-shock proteins-the optimum stress of life

This review summarizes the complex role of heat-shock proteins (Hsp) in immune reactions, especially the cellular effects of heat-shock proteins during the recognition processes by innate immunity. The role of heat-shock proteins in the pathogenesis of two multifactorial diseases, i.e. inflammatory bowel disease (IBD) and atherosclerosis is highlighted. A new hypothesis on "immunodeficiency burden" is presented. According to this hypothesis, susceptibility to any multifactorial disease in any given subject and in the presence of specific environmental factors is the aggregate effect of polymorphisms resulting in the failure of protective immunity with consequent disease.

Expression and Localization of GRP75 in Human Epithelial Tumors and Normal Tissues

Using differential display mRNA techniques, the authors found cDNA of the heat shock 70 protein known as GRP75 overexpressed in ovarian cancer cell lines. In the current study, the authors used immunohistochemistry to characterize the expression pattern of GRP75 in ovarian carcinomas and compared it with epithelial tumors originating from the female reproductive tract, epithelial neoplasms from non-gynecologic sites (colon, pancreas, breast, and lung), and various normal tissues. The authors also developed an antigen capture ELISA assay to determine if GRP75 can be detected in tumors, ascites, or sera of patients with advanced mullerian adenocarcinomas. All epithelial tumors from the ovary and the female reproductive tract were positive for GRP75 expression with moderate to strong staining intensity; stromal expression of GRP75 was generally weak or absent. Adenocarcinomas from the colon, lung, pancreas, and breast also stained strongly positive for GRP75. The epithelial cells of all normal tissues examined were positive for GRP75, and strong staining was also seen in the corpora lutea, hepatocytes, enteric neural plexus of the esophagus and colon, and placental cytotrophoblast and syncytiotrophoblast, and in subpopulations of pancreatic acinar cells. The ELISA assay detected GRP75 in tumor lysates and ascitic fluid, but not sera, of patients with mullerian adenocarcinomas. The authors conclude that GRP75 is highly expressed in both benign and malignant epithelium, as well as cells of specialized function from a variety of tissues.

Induction of cytokines by heat shock proteins and endotoxin in murine macrophages

Extensive studies in the past 10 years have suggested that heat shock protein 60 (Hsp60) and Hsp70 may be potent activators of the innate immune system capable of inducing pro-inflammatory cytokine production by macrophages. However, we have recently demonstrated that the reported pro-inflammatory cytokine-inducing effect of Hsp60 and Hsp70 was due to contaminating lipopolysaccharide (LPS) and LPS-associated molecules. In the current study, we determined whether highly purified, essentially LPS-free recombinant human Hsp60 (rhHsp60) and rhHsp70 had any cytokine-inducing effect. Using gene expression array, we demonstrated that at 2 and 4h after treatment, while LPS (1 ng/ml) markedly enhanced the expression of a number of cytokine genes, rhHsp60 and rhHsp70 (5 microg/ml) had no effect on any of the 96 common cytokine genes. Reverse transcriptase-polymerase chain reaction analysis and enzyme-linked immunosorbent assay of tumor necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta) supported the above observation. These data suggest that rhHsp60 and rhHsp70 do not activate cytokine genes in murine macrophages.

Cytokine function of heat shock proteins

Extensive work in the last 10 years has suggested that heat shock proteins (HSPs) may be potent activators of the innate immune system. It has been reported that Hsp60, Hsp70, Hsp90, and gp96 are capable of inducing the production of proinflammatory cytokines by the monocyte-macrophage system and the activation and maturation of dendritic cells (antigen-presenting cells) in a manner similar to the effects of lipopolysaccharide (LPS) and bacterial lipoprotein, e.g., via CD14/Toll-like receptor2 (TLR2) and CD14/TLR4 receptor complex-mediated signal transduction pathways. However, recent evidence suggests that the reported cytokine effects of HSPs may be due to the contaminating LPS and LPS-associated molecules. The reasons for previous failure to recognize the contaminant(s) as being responsible for the reported HSP cytokine effects include failure to use highly purified, low-LPS preparations of HSPs; failure to recognize the heat sensitivity of LPS; and failure to consider contaminant(s) other than LPS. Thus it is essential that efforts should be directed to conclusively determine whether the reported HSP cytokine effects are due to HSPs or to contaminant(s) present in the HSP preparations before further exploring the implication and therapeutic potential of the putative cytokine function of HSPs.

Expression levels of heat shock protein 60 in human endothelial cells in vitro are unaffected by exposure to 50 Hz magnetic fields

Magnetic fields (MFs) from domestic power sources have been implicated as being a potential risk to human health. A number of epidemiological studies have found a significant link between exposure to MFs and increased rates of cancers. There have also been a number of in vivo and in vitro studies reporting effects of MFs in animal disease models and on the expression or activity of a range of proteins. In the past decade, our group proposed that atherosclerosis may have an autoimmune component, with heat shock protein 60 (Hsp60) expressed in endothelial cells as the dominant autoantigen. A number of stressors have been shown to induce the expression of Hsp60, including the classical risk factors for atherosclerosis. We were interested to see if the exposure of endothelial cells to an MF elicited increased expression of Hsp60, as has been reported previously for Hsp70. The present work describes the exposure of endothelial cells to domestic power supply (50 Hz) MFs at an intensity of 700 microT. The results from our system indicate that cultured endothelial cells exposed to a high intensity of MF either alone or in combination with classical heat stress show no effects on the expression of Hsp60 at either the messenger ribonucleic acid or the protein level. As such, there is no evidence that exposure to extremely low-frequency MF would be expected to increase the expression of Hsp60 and therefore the initiation or progression of atherosclerosis.

Identification of T-cell epitopes of Porphyromonas gingivalis heat-shock-protein 60 in periodontitis

The heat shock proteins (hsp) of bacterial species are considered to be involved in regulating the autoimmune mechanism in human diseases due to the considerable homology of their sequences with human hsp. To elucidate how stress proteins contribute to the immunopathogenesis of periodontitis, mononuclear cells from gingival connective tissue of 10 periodontitis patients were simulated with Porphyromonas gingivalis hsp60. T-cell lines reactive to P. gingivalis hsp60 were established from each patient to define T-cell epitope specificities. Anti-P. gingivalis IgG antibody titres were elevated in all patients. We could establish P. gingivalis hsp-reactive T-cell lines from gingival mononuclear cells that were mixtures of CD4+ and CD8+ cells. Of 108 overlapping synthetic peptides spanning the whole P. gingivalis hsp60 molecule, 10 peptides with epitope specificities for T-cells were identified, and were identical to those reported be B-cell epitopes in periodontitis.

Elevated serum heat-shock protein 70 levels in patients with acute infection: use of an optimized enzyme-linked immunosorbent assay

Heat-shock proteins (Hsps) are highly conserved throughout evolution and evoke great interest both in basic biology and in medicine. They are expressed in small quantities under normal conditions, and their expression can be strongly induced by several stressors. Although their action is basically intracellular, it is now obvious that these proteins can be released into the extracellular environment from viable cells. In this study, the human Hsp 70 serum concentrations were determined using an optimized, cost-effective enzyme-linked immunosorbent assay (ELISA). The average intra-assay variation was 6%, whereas the average interassay variation was 9%. The sensitivity of the assay was 10 ng/ml, and spiking experiments showed recoveries between 101 and 109%. As an application of the technique, we have investigated the serum levels of human Hsp 70 in patients with infection and in healthy subjects. Our data show significantly higher levels of Hsp 70 (P = 0.003) in patients compared to control subjects. Positive correlations were noticed between the serum levels of Hsp 70 and various markers of inflammation (IL-6; r = 0.579, P = 0.009, TNF-alpha; r = 0.552, P = 0.012, IL-10; r = 0.361, P = 0.002). We conclude that Hsp 70 is involved in inflammation of infectious origin. The interindividual variation in the serum concentration of Hsp 70 precludes the use of serum Hsp 70 levels to distinguish patients from healthy subjects.

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.

Facets of heat shock protein 70 show immunotherapeutic potential

Amongst the families of intracellular molecules that chaperone and assist with the trafficking of other proteins, notably during conditions of cellular stress, heat shock protein (hsp) 70 is one of the most studied. Although its name suggests that expression is exclusively induced during cellular hyperthermia, members of the hsp70 family of proteins can be constitutively expressed and/or induced by a range of other cellular insults. The ubiquitous presence of hsp70 in eukaryotic and prokaryotic cells, combined with its high degree of sequence homology and intrinsic immunogenicity, have prompted the suggestion that inappropriate immune reactivity to hsp70 might lead to pro-inflammatory responses and the development of autoimmune disease. Indeed, hsp70 has been shown to be a potent activator of innate immunity and aberrant expression of hsp70 in certain organs promotes immunopathology. However, studies also suggest that hsp70 might have immunotherapeutic potential, as hsp70 purified from malignant and virally infected cells can transfer and deliver antigenic peptides to antigen-presenting cells to elicit peptide-specific immunity and, in contrast to its reported pro-inflammatory effects, the administration of recombinant hsp70 can attenuate experimental autoimmune disease. This review focuses on the immunoregulatory capacity of hsp70 and its potential therapeutic value.

Heat shock proteins as regulators of the immune response

Until recently, heat shock proteins (also known as heat stress proteins) have mostly been regarded as intracellular molecules that mediate a range of essential housekeeping and cytoprotective functions. However, interest in their role as intercellular signalling molecules has been fuelled by the observations that these molecules can be released and are present in the extracellular environment under physiological conditions. They can elicit cytokine production by, and adhesion molecule expression of, a range of cell types, and they can deliver maturation signals and peptides to antigen presenting cells through receptor-mediated interactions. These functions suggest that heat shock proteins could be immunoregulatory agents with potent and widely-applicable therapeutic uses. Furthermore, the induction of self heat shock protein immune reactivity can attenuate autoimmunity and delay transplant rejection, and heat shock proteins derived from tumours and pathogens can elicit specific, protective immunity. This review will focus on this rapidly evolving area of heat shock protein biology.

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.

Recombinant human heat shock protein 60 does not induce the release of tumor necrosis factor alpha from murine macrophages

Recent studies have shown that commercially available recombinant human heat shock protein 60 (rhHSP60) could induce tumor necrosis factor alpha (TNF-alpha) release from macrophages and monocytes in a manner similar to that of lipopolysaccharide (LPS), e.g. via CD14 and Toll-like receptor 4 complex-mediated signal transduction pathway. In this study, we demonstrated that a highly purified rhHSP60 preparation with low endotoxin activity (designated rhHSP60-1) was unable to induce TNF-alpha release from murine macrophages at concentrations of up to 10 microg/ml. In contrast, a less purified rhHSP60 preparation (designated rhHSP60-2) was able to induce a marked TNF-alpha release at concentrations as low as 1 microg/ml. Failure of rhHSP60-1 to induce TNF-alpha release was not due to defective physical properties because rhHSP60-1 and rhHSP60-2 contained a similar amount of HSP60 as determined by SDS gels stained with Coomassie Blue and Western blots probed with an anti-rhHSP60 antibody. Both rhHSP60 preparations also had similar enzymatic activities as judged by their ability to hydrolyze ATP. Polymyxin B added in the incubation media abolished the endotoxin activity but inhibited only about 50% of the TNF-alpha-inducing activity of rhHSP60-2. However, both the endotoxin activity and the TNF-alpha-inducing activity of rhHSP60-2 were essentially eliminated after passing through a polymyxin B-agarose column that removes LPS and LPS-associated molecules from the rhHSP60 preparation. The TNF-alpha-inducing activities of both rhHSP60-2 and LPS with equivalent endotoxin activity present in rhHSP60-2 were equally sensitive to heat inactivation. These results suggest that rhHSP60 does not induce TNF-alpha release from macrophages. Approximately 50% of the observed TNF-alpha-inducing activity in the rhHSP60-2 preparation is due to LPS contamination, whereas the rest of the activity was due to the contamination of LPS-associated molecule(s).

Hormone replacement therapy increases levels of antibodies against heat shock protein 65 and certain species of oxidized low density lipoprotein

Hormone replacement therapy (HRT) reduces cardiovascular risks, although the initiation of therapy may be associated with transient adverse ischemic and thrombotic events. Antibodies against heat shock protein (Hsp) and oxidized low density lipoprotein (LDL) have been found in atherosclerotic lesions and plasma of patients with coronary artery disease and may play an important role in the pathogenesis of atherosclerosis. The aim of the present study was to assess the effects of HRT on the immune response by measuring plasma levels of antibodies against Hsp 65 and LDL with a low and high degree of copper-mediated oxidative modification of 20 postmenopausal women before and 90 days after receiving orally 0.625 mg equine conjugate estrogen plus 2.5 mg medroxyprogesterone acetate per day. HRT significantly increased antibodies against Hsp 65 (0.316 +/- 0.03 vs 0.558 +/- 0.11) and against LDL with a low degree of oxidative modification (0.100 +/- 0.01 vs 0.217 +/- 0.02) (P<0.05 and P<0.001, respectively, ANOVA). The hormone-mediated immune response may trigger an inflammatory response within the vessel wall and potentially increase plaque burden. Whether or not this immune response is temporary or sustained and deleterious requires further investigation.