Expression of heat shock protein 27 in human atherosclerotic plaques and increased plasma level of heat shock protein 27 in patients with acute coronary syndrome

Proteomic analysis of plasma proteins from patients with cardiac rupture after acute myocardial infarction using TMT-based quantitative proteomics approach

BACKGROUND

Cardiac rupture (CR) is a rare but catastrophic mechanical complication of acute myocardial infarction (AMI) that seriously threatens human health. However, the reliable biomarkers for clinical diagnosis and the underlying signaling pathways insights of CR has yet to be elucidated.

METHODS

In the present study, a quantitative approach with tandem mass tag (TMT) labeling and liquid chromatography-tandem mass spectrometry was used to characterize the differential protein expression profiles of patients with CR. Plasma samples were collected from patients with CR (n = 37), patients with AMI (n = 47), and healthy controls (n = 47). Candidate proteins were selected for validation by multiple reaction monitoring (MRM) and enzyme-linked immunosorbent assay (ELISA).

RESULTS

In total, 1208 proteins were quantified and 958 differentially expressed proteins (DEPs) were identified. The difference in the expression levels of the DEPs was more noticeable between the CR and Con groups than between the AMI and Con groups. Bioinformatics analysis showed most of the DEPs to be involved in numerous crucial biological processes and signaling pathways, such as RNA transport, ribosome, proteasome, and protein processing in the endoplasmic reticulum, as well as necroptosis and leukocyte transendothelial migration, which might play essential roles in the complex pathological processes associated with CR. MRM analysis confirmed the accuracy of the proteomic analysis results. Four proteins i.e., C-reactive protein (CRP), heat shock protein beta-1 (HSPB1), vinculin (VINC) and growth/differentiation factor 15 (GDF15), were further validated via ELISA. By receiver operating characteristic (ROC) analysis, combinations of these four proteins distinguished CR patients from AMI patients with a high area under the curve (AUC) value (0.895, 95% CI, 0.802-0.988, p < 0.001).

CONCLUSIONS

Our study highlights the value of comprehensive proteomic characterization for identifying plasma proteome changes in patients with CR. This pilot study could serve as a valid foundation and initiation point for elucidation of the mechanisms of CR, which might aid in identifying effective diagnostic biomarkers in the future.

Mechanistic insights into the anti-restenotic effects of HSP27 and HO1 modulated by reconstituted HDL on neointimal hyperplasia

High-density lipoprotein (HDL) therapy has demonstrated beneficial effects in acute stroke and acute myocardial infarction models by reducing infarct size. In this study, we investigated the inhibitory effects of reconstituted HDL (rHDL) on neointimal hyperplasia and elucidated its underlying mechanism using a balloon injury rat model. Our finding revealed a significant 37% reduction in the intima to media ratio in the arteries treated with 80 mg/kg rHDL compared to those subjected to injury alone (p < 0.05), indicating a specific inhibition of neointimal hyperplasia. In vivo analysis further supported the positive effects of rHDL by demonstrating a reduction in smooth muscle cell (SMC) proliferation and an increase in endothelial cell (EC) proliferation. Additionally, rHDL treatment led to decreased infiltration of leukocytes and downregulated the expression of matrix metallopeptidase 9 (MMP9) in the neointimal area. Notably, rHDL administration resulted in decreased expression of VCAM1 and HIF1α, alongside increased expression of heme oxygenase 1 (HO1) and heat shock protein 27 (HSP27). Overexpression of HSP27 and HO1 effectively inhibited SMC proliferation. Moreover, rHDL-mediated suppression of injury-induced HIF1α coincided with upregulation of HSP27. Interestingly, HSP27 and HO1 had varying effects on the expression of chemokine receptors and rHDL did not exert significant effect on chemokine receptor expression in THP1 cells. These findings underscore the distinct roles of HSP27 and HO1 as potential regulatory factors in the progression of restenosis. Collectively, our study demonstrates that rHDL exerts a potent anti-neointimal hyperplasia effect by reducing leukocytes infiltration and SMC proliferation while promoting EC proliferation.

Emerging role of heat shock proteins in cardiovascular diseases

Heat Shock Proteins (HSPs) are evolutionarily conserved proteins from prokaryotes to eukaryotes. They are ubiquitous proteins involved in key physiological and cellular pathways (viz. inflammation, immunity and apoptosis). Indeed, the survivability of the cells under various stressful conditions depends on appropriate levels of HSP expression. There is a growing line of evidence for the role of HSPs in regulating cardiovascular diseases (CVDs) (viz. hypertension, atherosclerosis, atrial fibrillation, cardiomyopathy and heart failure). Furthermore, studies indicate that a higher concentration of circulatory HSP antibodies correlate to CVDs; some are even potential markers for CVDs. The multifaceted roles of HSPs in regulating cellular signaling necessitate unraveling their links to pathophysiology of CVDs. This review aims to consolidate our understanding of transcriptional (via multiple transcription factors including HSF-1, NF-κB, CREB and STAT3) and post-transcriptional (via microRNAs including miR-1, miR-21 and miR-24) regulation of HSPs. The cytoprotective nature of HSPs catapults them to the limelight as modulators of cell survival. Yet another attractive prospect is the development of new therapeutic strategies against cardiovascular diseases (from hypertension to heart failure) by targeting the regulation of HSPs. Moreover, this review provides insights into how genetic variation of HSPs can contribute to the manifestation of CVDs. It would also offer a bird's eye view of the evolving role of different HSPs in the modulation and manifestation of cardiovascular disease.

Axonal transport deficits in the pathogenesis of diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is a chronic and prevalent metabolic disease that gravely endangers human health and seriously affects the quality of life of hyperglycemic patients. More seriously, it can lead to amputation and neuropathic pain, imposing a severe financial burden on patients and the healthcare system. Even with strict glycemic control or pancreas transplantation, peripheral nerve damage is difficult to reverse. Most current treatment options for DPN can only treat the symptoms but not the underlying mechanism. Patients with long-term diabetes mellitus (DM) develop axonal transport dysfunction, which could be an important factor in causing or exacerbating DPN. This review explores the underlying mechanisms that may be related to axonal transport impairment and cytoskeletal changes caused by DM, and the relevance of the latter with the occurrence and progression of DPN, including nerve fiber loss, diminished nerve conduction velocity, and impaired nerve regeneration, and also predicts possible therapeutic strategies. Understanding the mechanisms of diabetic neuronal injury is essential to prevent the deterioration of DPN and to develop new therapeutic strategies. Timely and effective improvement of axonal transport impairment is particularly critical for the treatment of peripheral neuropathies.

Heat shock proteins: Biological functions, pathological roles, and therapeutic opportunities

The heat shock proteins (HSPs) are ubiquitous and conserved protein families in both prokaryotic and eukaryotic organisms, and they maintain cellular proteostasis and protect cells from stresses. HSP protein families are classified based on their molecular weights, mainly including large HSPs, HSP90, HSP70, HSP60, HSP40, and small HSPs. They function as molecular chaperons in cells and work as an integrated network, participating in the folding of newly synthesized polypeptides, refolding metastable proteins, protein complex assembly, dissociating protein aggregate dissociation, and the degradation of misfolded proteins. In addition to their chaperone functions, they also play important roles in cell signaling transduction, cell cycle, and apoptosis regulation. Therefore, malfunction of HSPs is related with many diseases, including cancers, neurodegeneration, and other diseases. In this review, we describe the current understandings about the molecular mechanisms of the major HSP families including HSP90/HSP70/HSP60/HSP110 and small HSPs, how the HSPs keep the protein proteostasis and response to stresses, and we also discuss their roles in diseases and the recent exploration of HSP related therapy and diagnosis to modulate diseases. These research advances offer new prospects of HSPs as potential targets for therapeutic intervention.

Plasma Heat Shock Protein 70 Is Associated With the Onset of Acute Myocardial Infarction and Total Occlusion in Target Vessels

Background: Whether the role of plasma heat shock protein 70 (HSP70) in acute myocardial infarction (AMI) is protective or detrimental remains debated, and the relationship between HSP70 and total occlusion remains elusive.

Methods: A total of 112 patients with primary diagnosis of AMI and 52 patients with chronic coronary syndrome (CCS) were enrolled into the study. Plasma HSP70 level was determined by ELISA on day 1 and day 7 after the onset of AMI and was examined before angiography in patients with CCS. Peak NT-proBNP, high-sensitivity C-reactive protein (CRP), troponin T (cTnT), and left ventricular ejection fraction were measured.

Results: Plasma HSP70 was significantly higher in CCS than AMI (P < 0.0001), and it showed a significant decrease from day 1 to day 7 after AMI (P < 0.01). Elevated HSP70 was associated with decreased levels of LDL-C (P < 0.05), peak cTnT (R = −0.3578, P < 0.0001), peak NT-proBNP (R = −0.3583, P < 0.0001), and peak CRP (R = −0.3539, P < 0.0001) and a lower diagnosis of AMI (R = −0.4016, P < 0.0001) and STEMI (R = −0.3675, P < 0.0001), but a higher diagnosis of total occlusion in target vessels (R = 0.1702, P < 0.05). HSP70 may provide certain predictive value for the diagnosis of AMI, STEMI, and total occlusion in target vessels, and the area under the receiver operating characteristic curves were 0.7660, 0.7152, and 0.5984, respectively. HSP70 was also negatively associated with in-hospital stay (P < 0.001) and positively correlated with left ventricular ejection fraction (LVEF) at 1-year follow-up (P < 0.05), despite no association with in-hospital major adverse cardiovascular events (MACE).

Conclusion: Plasma HSP70 level was found to decrease from day 1 to day 7 post-AMI, but the overall level of patients with AMI was lower than that of patients with CCS. However, the ability of HSP70 to identify clinically significant AMI and STEMI was moderate, and the predictive value to total occlusion was slight.

Heat Shock Proteins: Connectors between Heart and Kidney

Over the development of eukaryotic cells, intrinsic mechanisms have been developed in order to provide the ability to defend against aggressive agents. In this sense, a group of proteins plays a crucial role in controlling the production of several proteins, guaranteeing cell survival. The heat shock proteins (HSPs), are a family of proteins that have been linked to different cellular functions, being activated under conditions of cellular stress, not only imposed by thermal variation but also toxins, radiation, infectious agents, hypoxia, etc. Regarding pathological situations as seen in cardiorenal syndrome (CRS), HSPs have been shown to be important mediators involved in the control of gene transcription and intracellular signaling, in addition to be an important connector with the immune system. CRS is classified as acute or chronic and according to the first organ to suffer the injury, which can be the heart (CRS type 1 and type 2), kidneys (CRS type 3 and 4) or both (CRS type 5). In all types of CRS, the immune system, redox balance, mitochondrial dysfunction, and tissue remodeling have been the subject of numerous studies in the literature in order to elucidate mechanisms and propose new therapeutic strategies. In this sense, HSPs have been targeted by researchers as important connectors between kidney and heart. Thus, the present review has a focus to present the state of the art regarding the role of HSPs in the pathophysiology of cardiac and renal alterations, as well their role in the kidney–heart axis.

HSP25 Vaccination Attenuates Atherogenesis via Upregulation of LDLR Expression, Lowering of PCSK9 Levels and Curbing of Inflammation

[Figure: see text].

Heat shock protein 27 immune complex altered signaling and transport (ICAST): Novel mechanisms of attenuating inflammation

Blood levels of heat shock protein (HSP27) and natural IgG auto-antibodies to HSP27 (AAbs) are higher in healthy controls compared to cardiovascular disease patients. Vaccination of mice with recombinant HSP25 (rHSP25, murine ortholog of human rHSP27) increased AAb levels, attenuated atherogenesis and reduced plaque inflammation and cholesterol content. We sought to determine if the HSP27 immune complex (IC) altered MΦ inflammation signaling (Toll Like Receptor 4; TLR4), and scavenger receptors involved in cholesterol uptake (SR-AI, CD-36). Combining a validated polyclonal IgG anti-HSP27 antibody (PAb) with rHSP27 enhanced binding to THP-1 MΦ cell membranes and activation of NF-κB signaling via TLR4, competing away LPS and effecting an anti-inflammatory cytokine profile. Similarly, adding the PAb with rHSP27 enhanced binding to SR-AI and CD-36, as well as lowered oxLDL binding in HEK293 cells separately transfected with SR-AI and CD-36, or THP-1 MΦ. Finally, the PAb enhanced the uptake and internalization of rHSP27 in THP-1 MΦ. Thus, the HSP27 IC potentiates HSP27 cell membrane signaling with receptors involved in modulating inflammation and cholesterol uptake, as well as HSP27 internalization. Going forward, we are focusing on the development of HSP27 Immune Complex Altered Signaling and Transport (ICAST) as a means of modulating inflammation.

Intermittent Hypoxic Exposure Reduces Endothelial Dysfunction

Intermittent exposure to hypoxia (IHE) increases the production of reactive oxygen and nitrogen species as well as erythropoietin (EPO), which stimulates the adaptation to intense physical activity. However, several studies suggest a protective effect of moderate hypoxia in cardiovascular disease (CVD) events. The effects of intense physical activity with IHE on oxi-inflammatory mediators and their interaction with conventional CVD risk factors were investigated. Blood samples were collected from elite athletes (control n = 6, IHE n = 6) during a 6-day IHE cycle using hypoxicator GO2 altitude. IHE was held once a day, at least 2 hours after training. In serum, hydrogen peroxide (H₂O₂), nitric oxide (NO), 3-nitrotyrosine (3-Nitro), proinflammatory cytokines (IL-1β and TNFα), high sensitivity C-reactive protein (hsCRP), and heat shock protein 27 (HSP27) were determined by the commercial immunoenzyme (ELISA kits) or colorimetric methods. Serum erythropoietin (EPO) level was measured by ELISA kit every day of hypoxia. IHE was found to significantly increase H₂O₂, NO, and HSP27 but to decrease 3NT concentrations. The changes in 3NT and HSP27 following hypoxia proved to enhance NO bioavailability and endothelial function. In the present study, the oxi-inflammatory mediators IL-1β and hsCRP increased in IHE group but they did not exceed the reference values. The serum EPO level increased on the 3^rd day of IHE, then decreased on 5^th day of IHE, and correlated with NO/H₂O₂ ratio (r _s = 0.640, P < 0.05). There were no changes in haematological markers contrary to lipoproteins such as low-density lipoprotein (LDL) and non-high-density lipoprotein (non-HDL) which showed a decreasing trend in response to hypoxic exposure. The study demonstrated that IHE combined with sports activity reduced a risk of endothelial dysfunction and atherogenesis in athletes even though the oxi-inflammatory processes were enhanced. Therefore, 6-day IHE seems to be a potential therapeutic and nonpharmacological method to reduce CVD risk, especially in elite athletes participating in strenuous training.

The Heat Shock Protein 27 Immune Complex Enhances Exosomal Cholesterol Efflux

Previously, we demonstrated that Heat Shock Protein 27 (HSP27) reduces the inflammatory stages of experimental atherogenesis, is released by macrophage (MΦ) exosomes and lowers cholesterol levels in atherosclerotic plaques. Recently, we discovered that natural autoantibodies directed against HSP27 enhance its signaling effects, as HSP27 immune complexes (IC) interact at the cell membrane to modulate signaling. We now seek to evaluate the potential role of the HSP27 IC on MΦ exosomal release and cholesterol export. First, in human blood samples, we show that healthy control subjects have 86% more exosomes compared to patients with coronary artery disease (p < 0.0001). Treating human THP-1 MΦ with rHSP27 plus a validated anti-HPS27 IgG antibody increased the abundance of exosomes in the culture media (+98%; p < 0.0001) as well as expression of Flotillin-2, a marker reflective of exosomal release. Exosome cholesterol efflux was independent of Apo-A1. THP-1 MΦ loaded with NBD-labeled cholesterol and treated with the HSP27 IC showed a 22% increase in extracellular vesicles labeled with NBD and a 95% increase in mean fluorescent intensity. In conclusion, exosomal abundance and secretion of cholesterol content increases in response to HSP27 IC treatment, which may represent an important therapeutic option for diseases characterized by cholesterol accumulation.

Role of Heat Shock Protein 27 in Modulating Atherosclerotic Inflammation

Atherosclerosis is the primary cause of heart attacks, and while efforts to prevent its development or progression have historically focused largely on reducing cholesterol levels, there is now important proof-of-principle data that supports the role that inflammation plays in atherogenesis. Heat shock protein 27 (HSP27) is a novel biomarker of atherosclerosis that is also atheroprotective. Through a series of murine and in vitro experiments, an iterative narrative is emerging that demonstrates how HSP27 can act as an extracellular mediator that reduces plaque inflammation-either directly via transcriptional pathways, or indirectly via important effects on macrophage biology. While there is much more to learn about the biology of HSP27, we now review the strong foundation of knowledge that highlights the potential anti-inflammatory role of HSP27 as a novel therapeutic for not only atherosclerosis but potentially other inflammatory disorders.

Circulating heat shock protein 27 as a novel marker of subclinical atherosclerosis in type 2 diabetes: a cross-sectional community-based study

Background

Heat shock protein 27 (HSP27) has been proposed as a vital protective factor in atherosclerosis. The objective of the present study was to evaluate the association between circulating HSP27 and carotid intima–media thickness (IMT) in individuals with type 2 diabetes and to determine whether HSP27 represents an independent marker of subclinical atherosclerosis in this patient population.

Methods

We performed a cross-sectional community-based study in 186 Chinese subjects with a median duration of type 2 diabetes of 8.2 years who underwent ultrasound carotid IMT measurement. Serum HSP27 levels were assessed by ELISA.

Results

Serum HSP27 levels were significantly higher in the IMT (+, > 1.0 mm) group than in the IMT (−, ≤1.0 mm) group, with the median values of 8.80 ng/mL (5.62–12.25) and 6.93 ng/mL (4.23–9.60), respectively (P = 0.006). The discriminative value of HSP27 to evaluate IMT was 7.16 ng/mL and the area under the curve was 0.72 (95%CI = 0.64–0.80, P = 0.0065). Spearman’s rank correlation analysis demonstrated that the concentrations of circulating HSP27 were positively associated with carotid IMT (r = 0.198, P = 0.007) and blood urea nitrogen (r = 0.170, P < 0.05). Furthermore, in the logistic model, serum HSP27 levels were found to be independent predictors for carotid IMT in type 2 diabetic patients after adjustment for onset age of diabetes, blood pressure, total cholesterol and C-reactive protein (OR = 1.085, P = 0.022).

Conclusions

Circulating HSP27, positively correlates with carotid IMT, is an independent predictor for early atherosclerotic changes in diabetes, and may represent a novel marker of subclinical atherosclerosis in type 2 diabetes.

Molecular signatures of atherosclerotic plaques: An up-dated panel of protein related markers

Atherosclerosis remains the leading cause of ischemic syndromes such as myocardial infarction or brain stroke, mainly promoted by plaque rupture and subsequent arterial blockade. Identification of vulnerable or high-risk plaques constitutes a major challenge, being necessary to identify patients at risk of occlusive events in order to provide them with appropriate therapies. Clinical imaging tools have allowed the identification of certain structural indicators of prone-rupture plaques, including a necrotic lipidic core, intimal and adventitial inflammation, extracellular matrix dysregulation, and smooth muscle cell depletion and micro-calcification. Additionally, alternative approaches focused on identifying molecular biomarkers of atherosclerosis have also been applied. Among them, proteomics has provided numerous protein markers currently investigated in clinical practice. In this regard, it is quite uncertain that a single molecule can describe plaque rupture, due to the complexity of the process itself. Therefore, it should be more accurate to consider a set of markers to define plaques at risk. Herein, we propose a selection of 76 proteins, from classical inflammatory to recently related markers, all of them identified in at least two proteomic studies analyzing unstable atherosclerotic plaques. Such panel could be used as a prognostic signature of plaque instability.

Heat shock protein 27 as a predictor of prognosis in patients admitted to hospital with acute COPD exacerbation

Episodes of acute exacerbations are major drivers of hospitalisation and death from COPD. To date, there are no objective biomarkers of disease activity or biomarkers to predict patient outcome. In this study, 211 patients hospitalised for an acute exacerbation of COPD have been included. At the time of admission, routine blood tests have been performed including complete blood count, C-reactive protein, cardiac troponin T and NT-proBNP. Heat shock protein 27 (HSP27) serum concentrations were determined at time of admission, discharge and 180 days after discharge by ELISA. We were able to demonstrate significantly increased HSP27 serum concentrations in COPD patients at time of admission to hospital as compared to HSP27 concentrations obtained 180 days after discharge. In univariable Cox regression analyses, a HSP27 serum concentration ≥ 3098 pg/mL determined at admission was a predictor of all-cause mortality at 90 days, 180 days, 1 year and 3 years. In multivariable analyses, an increased HSP27 serum concentration at admission retained its prognostic ability with respect to all-cause mortality for up to 1-year follow-up. However, an increased HSP27 serum concentration at admission was not an independent predictor of long-term all-cause mortality at 3 years. Elevated serum HSP27 concentrations significantly predicted short-term mortality in patients admitted to hospital with acute exacerbation of COPD and could help to improve outcomes by identifying high-risk patients.

Adenine Nucleotide Translocase 1 Expression is Coupled to the HSP27-Mediated TLR4 Signaling in Cardiomyocytes

The cardiac-specific overexpression of the adenine nucleotide translocase 1 (ANT1) has cardioprotective effects in various experimental heart disease models. Here, we analyzed the link between ANT1 expression and heat shock protein 27 (HSP27)-mediated toll-like receptor 4 (TLR4) signaling, which represents a novel communication pathway between mitochondria and the extracellular environment. The interaction between ANT1 and HSP27 was identified by co-immunoprecipitation from neonatal rat cardiomyocytes. ANT1 transgenic (ANT1-TG) cardiomyocytes demonstrated elevated HSP27 expression levels. Increased levels of HSP27 were released from the ANT1-TG cardiomyocytes under both normoxic and hypoxic conditions. Extracellular HSP27 stimulated TLR4 signaling via protein kinase B (AKT). The HSP27-mediated activation of the TLR4 pathway was more pronounced in ANT1-TG cardiomyocytes than in wild-type (WT) cardiomyocytes. HSP27-specific antibodies inhibited TLR4 activation and the expression of HSP27. Inhibition of the HSP27-mediated TLR4 signaling pathway with the TLR4 inhibitor oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) reduced the mitochondrial membrane potential (∆ψ_m) and increased caspase 3/7 activity, which are both markers for cell stress. Conversely, treating cardiomyocytes with recombinant HSP27 protein stimulated TLR4 signaling, induced HSP27 and ANT1 expression, and stabilized the mitochondrial membrane potential. The activation of HSP27 signaling was verified in ischemic ANT1-TG heart tissue, where it correlated with ANT1 expression and the tightness of the inner mitochondrial membrane. Our study shows a new mechanism by which ANT1 is part of the cardioprotective HSP27-mediated TLR4 signaling.

Heat-Shock Protein 27 (HSPB1) Is Upregulated and Phosphorylated in Human Platelets during ST-Elevation Myocardial Infarction

Heat-shock proteins are a family of proteins which are upregulated in response to stress stimuli including inflammation, oxidative stress, or ischemia. Protective functions of heat-shock proteins have been studied in vascular disease models, and malfunction of heat-shock proteins is associated with vascular disease development. Heat-shock proteins however have not been investigated in human platelets during acute myocardial infarction ex vivo. Using two-dimensional electrophoresis and immunoblotting, we observed that heat-shock protein 27 (HSPB1) levels and phosphorylation are significantly increased in platelets of twelve patients with myocardial infarction compared to patients with nonischemic chest pain (6.4 ± 1.0-fold versus 1.0 ± 0.9-fold and 5.9 ± 1.8-fold versus 1.0 ± 0.8-fold; p < 0.05). HSP27 (HSPB1) showed a distinct and characteristic intracellular translocation from the cytoskeletal fraction into the membrane fraction of platelets during acute myocardial infarction that did not occur in the control group. In this study, we could demonstrate for the first time that HSP27 (HSPB1) is upregulated and phosphorylated in human platelets during myocardial infarction on a cellular level ex vivo with a characteristic intracellular translocation pattern. This HSP27 (HSPB1) phenotype in platelets could thus represent a measurable stress response in myocardial infarction and potentially other acute ischemic events.

Roles of Extracellular HSPs as Biomarkers in Immune Surveillance and Immune Evasion

Extracellular heat shock proteins (ex-HSPs) have been found in exosomes, oncosomes, membrane surfaces, as well as free HSP in cancer and various pathological conditions, also known as alarmins. Such ex-HSPs include HSP90 (α, β, Gp96, Trap1), HSP70, and large and small HSPs. Production of HSPs is coordinately induced by heat shock factor 1 (HSF1) and hypoxia-inducible factor 1 (HIF-1), while matrix metalloproteinase 3 (MMP-3) and heterochromatin protein 1 are novel inducers of HSPs. Oncosomes released by tumor cells are a major aspect of the resistance-associated secretory phenotype (RASP) by which immune evasion can be established. The concepts of RASP are: (i) releases of ex-HSP and HSP-rich oncosomes are essential in RASP, by which molecular co-transfer of HSPs with oncogenic factors to recipient cells can promote cancer progression and resistance against stresses such as hypoxia, radiation, drugs, and immune systems; (ii) RASP of tumor cells can eject anticancer drugs, targeted therapeutics, and immune checkpoint inhibitors with oncosomes; (iii) cytotoxic lipids can be also released from tumor cells as RASP. ex-HSP and membrane-surface HSP (mHSP) play immunostimulatory roles recognized by CD91+ scavenger receptor expressed by endothelial cells-1 (SREC-1)+ Toll-like receptors (TLRs)+ antigen-presenting cells, leading to antigen cross-presentation and T cell cross-priming, as well as by CD94+ natural killer cells, leading to tumor cytolysis. On the other hand, ex-HSP/CD91 signaling in cancer cells promotes cancer progression. HSPs in body fluids are potential biomarkers detectable by liquid biopsies in cancers and tissue-damaged diseases. HSP-based vaccines, inhibitors, and RNAi therapeutics are also reviewed.

Biophysical analyses and functional implications of the interaction between Heat Shock Protein 27 and antibodies to HSP27

Heat Shock Protein 27 (HSP27) is a small molecular chaperone that reduces the development of atherosclerosis by lowering plasma cholesterol levels as well as inflammation. Human studies show an inverse correlation between atherosclerotic burden and HSP27 expression, and are supported by murine models in which augmenting HSP27 levels curbs experimental atherogenesis. Natural HSP27 auto-antibodies (AAb) are found in human plasma, however their role in modulating the athero-protective effects of HSP27 is unknown. The purpose of this study is to characterize the biophysical interaction between human recombinant HSP27 and AAb. A validated polyclonal anti-HSP27 IgG antibody (PAb) was used to mimic natural AAb. Homology modeling and secondary structure prediction tools facilitated the design of HSP27 truncation and phosphorylation mutants. Secondary structural changes were identified using Circular Dichroism (CD) and Dynamic Light Scattering (DLS). Similar to prior structural investigations of HSP27, there was a predominance of α-helical content in the N-terminal truncation and dephosphorylation ("AA") mutants. The α-crystallin domain (ACD) predominantly consists of β-strands, with the addition of the N-terminal increasing helical content and the C-terminal maintaining β structure. With increasing ratios of PAb to HSP27 β structure abundance and particle size increased, with a similar trend observed with the N-terminus, C-terminus and ACD peptides but an opposite trend with the phosphorylation peptides. Taken together, these studies provide insights into the interaction of HSP27 and its AAb that ultimately may aid in optimizing the design of HSP27 peptidomimetics with anti-atherogenic potential.

Heat Shock Protein 27 Expression in EUS-FNA Samples Can Predict Gemcitabine Sensitivity in Pancreatic Cancer

BACKGROUND/AIM

Gemcitabine (GEM) sensitivity can help select the appropriate treatment for pancreatic cancer. We examined the association between HSP27 expression and GEM sensitivity.

MATERIALS AND METHODS

A total of 19 patients with unresectable pancreatic cancer who underwent endoscopic ultrasonography-guided fine needle aspiration (EUS-FNA) were enrolled and treated with GEM alone. We measured the expression of heat shock protein 27 (HSP27) and phosphorylated HSP27(p-HSP27) in EUS-FNA samples and evaluated the effects of GEM treatment.

RESULTS

The rate of GEM resistance was significantly higher in patients who showed overexpression of p-HSP27 (p<0.05). When we set the cut-off p-HSP27 (Ser82) detection rate at 51.6%, the group with a detection rate of >51.6% showed a significantly lower survival rate, and GEM was administered for a shorter period of time (p<0.05).

CONCLUSION

It was suggested that the HSP27 expression in EUS-FNA samples was useful for predicting GEM sensitivity.

Characterization of heat shock protein 27 in extracellular vesicles: a potential anti-inflammatory therapy

Previously, we reported that elevated serum levels of heat shock protein 27 (HSP27) are predictive of a lower risk of having a heart attack, stroke, or death from cardiovascular disease. Moreover, augmenting HSP27 (or the murine ortholog, HSP25) attenuated experimental atherogenesis, reduced inflammation, and lowered cholesterol levels. Recently, we noted that HSP27 activates NF-κB via TLR-4, resulting in attenuation of plaque inflammation; however, the precise anti-atherosclerosis mechanisms mediated by extracellular HSP27 are incompletely understood. Our purpose in this study was to investigate the existence of HSP27 in extracellular vesicles (EVs) and whether HSP27 elicited atheroprotective effects on target cells. Here, we provide evidence that HSP27 localizes to EVs derived from THP-1 cells using transmission electron microscopy (TEM) and immunogold labeling, Western blotting, ELISA, and fluorescence-activated cell sorting. TEM imaging indicated that HSP27 is found at the exosomal membrane. Multiple reactor monitor-mass spectrometric analysis of large vesicles, which included microparticles and exosomes, isolated from human plasma, also led to detection of HSP27 using the unique signature peptide, R.LFDQAFGLPR.L. Studies using THP-1 and human embryonic kidney cells show that HSP27-laden exosomes significantly stimulated NF-κB activation ( P < 0.001) and release of IL-10 ( P < 0.0001), suggesting that HSP27 may be important exosomal cargo with beneficial anti-inflammatory effects.-Shi, C., Ulke-Lemée, A., Deng, J., Batulan, Z., O'Brien, E. R. Characterization of heat shock protein 27 in extracellular vesicles: a potential anti-inflammatory therapy.

Coronary artery disease in post-menopausal women: are there appropriate means of assessment?

The recognition of sex differences in cardiovascular disease, particularly the manifestations of coronary artery disease (CAD) in post-menopausal women, has introduced new challenges in not only understanding disease mechanisms but also identifying appropriate clinical means of assessing the efficacy of management strategies. For example, the majority of treatment algorithms for CAD are derived from the study of males, focus on epicardial stenoses, and inadequately account for the small intramyocardial vessel disease in women. However, newer investigational modalities, including stress perfusion cardiac magnetic resonance imaging and positron emission tomography are providing enhanced diagnostic accuracy and prognostication for women with microvascular disease. Moreover, these investigations may soon be complemented by simpler screening tools such as retinal vasculature imaging, as well as novel biomarkers (e.g. heat shock protein 27). Hence, it is vital that robust, sex-specific cardiovascular imaging modalities and biomarkers continue to be developed and are incorporated into practice guidelines that are used to manage women with CAD, as well as gauge the efficacy of any new treatment modalities. This review provides an overview of some of the sex differences in CAD and highlights emerging advances in the investigation of CAD in post-menopausal women.

Extracellular small heat shock proteins: exosomal biogenesis and function

Small heat shock proteins (sHsps) belong to the family of heat shock proteins (Hsps): some are induced in response to multiple stressful events to protect the cells while others are constitutively expressed. Until now, it was believed that Hsps, including sHsps, are present inside the cells and perform intracellular functions. Interestingly, several groups recently reported the extracellular presence of Hsps, and sHsps have also been detected in sera/cerebrospinal fluids in various pathological conditions. Secretion into the extracellular milieu during many pathological conditions suggests additional or novel functions of sHsps in addition to their intracellular properties. Extracellular sHsps are implicated in cell-cell communication, activation of immune cells, and promoting anti-inflammatory and anti-platelet responses. Interestingly, exogenous administration of sHsps showed therapeutic effects in multiple disease models implying that extracellular sHsps are beneficial in pathological conditions. sHsps do not possess signal sequence and, hence, are not exported through the classical Endoplasmic reticulum-Golgi complex (ER-Golgi) secretory pathway. Further, export of sHsps is not inhibited by ER-Golgi secretory pathway inhibitors implying the involvement of a nonclassical secretory pathway in sHsp export. In lieu, lysoendosomal and exosomal pathways have been proposed for the export of sHsps. Heat shock protein 27 (Hsp27), αB-crystallin (αBC), and Hsp20 are shown to be exported by exosomes. Exosomes packaged with sHsps have beneficial effects in in vivo disease models. However, secretion mechanisms and therapeutic use of sHsps have not been elucidated in detail. Therefore, this review aimed at highlighting the current understanding of sHsps (Hsp27, αBC, and Hsp20) in the extracellular medium.

Prophylactic salpingo-oophorectomy & surgical menopause for inherited risks of cancer: the need to identify biomarkers to assess the theoretical risk of premature coronary artery disease

Background

Some women with genetic risk of breast and/or ovarian cancer (e.g., BRCA1/2) opt to undergo prophylactic salpingo-oophorectomy (PSO, or surgical removal of the ovaries & fallopian tubes) in order to reduce their risk of cancer. As a consequence, these women experience “surgical menopause” – accompanied by more severe climacteric symptoms that occur in a much shorter time frame. While the risk of coronary artery disease (CAD) rises with menopause, little is known about how the sudden loss of ovarian function from PSO alters the whole-body physiology, and whether it predisposes women to premature CAD.

Methods/Design

To manage CAD risk there is a prerequisite for reliable biomarkers that can help guide risk assessment and therapeutic interventions. To address these needs, this prospective, observational cohort study will evaluate surrogate markers reflective of CAD health in women experiencing surgical menopause after PSO. Twenty women representing each of the following groups will be enrolled over 3 years (total participants = 240): (i) pre-menopausal PSO, (ii) post-menopausal PSO, (iii) pre-menopausal women undergoing other pelvic surgery, and (iv) pre-menopausal controls (no surgery). All participants will provide blood plasma samples pre- and 1, 3, 6, & 12 months post-operatively, with serial samples collectively assessed for measurements of the study’s primary endpoints of interest. These include a hormone profile (estradiol, follicle stimulating hormone (FSH), luteinizing hormone (LH), and progesterone) and both conventional (lipid profile) and novel biomarkers (Heat Shock Protein 27 (HSP27), HSP27-antibodies (HSP27 Ab), proprotein convertase subtilisin/kexin 9 (PCSK9), inflammatory cytokines) of CAD. Another aspect of this study is the measurement and analysis of retinal vessel diameters – an emerging physiological parameter reflective of CAD risk. Finally, a patient engagement exercise will result in the drafting of patient-generated questionnaires that address the well-being and health concerns of these women as they transition through premature menopause and work with our research team to identify and discuss their health priorities.

Discussion

The protocol of our planned study investigating the effects of PSO on CAD is described herein. Characterization of novel CAD markers in women experiencing surgical menopause will yield new insights into the role of the functional ovary in modulating lipid parameters and other CAD risk factors such as HSP27 and HSP27 Ab.

Heat shock protein-27 and sex-selective regulation of muscarinic and proteinase-activated receptor 2-mediated vasodilatation: differential sensitivity to endothelial NOS inhibition

BACKGROUND AND PURPOSE

Previously, we demonstrated that exogenous heat shock protein 27 (HSP27/gene, HSPB1) treatment of human endothelial progenitor cells (EPCs) increases the synthesis and secretion of VEGF, improves EPC-migration/re-endothelialization and decreases neo-intima formation, suggesting a role for HSPB1 in regulating EPC function. We hypothesized that HSPB1 also affects mature endothelial cells (ECs) to alter EC-mediated vasoreactivity in vivo. Our work focused on endothelial NOS (eNOS)/NO-dependent relaxation induced by ACh and the coagulation pathway-activated receptor, proteinase-activated receptor 2 (PAR2).

EXPERIMENTAL APPROACH

Aorta rings from male and female wild-type, HSPB1-null and HSPB1 overexpressing (HSPB1o/e) mice were contracted with phenylephrine, and NOS-dependent relaxation responses to ACh and PAR2 agonist, 2-furoyl-LIGRLO-NH₂ , were measured without and with L-NAME and ODQ, either alone or in combination to block NO synthesis/action. Tissues from female HSPB1-null mice were treated in vitro with recombinant HSP27 and then used for bioassay as above. Furthermore, oestrogen-specific effects were evaluated using a bioassay of aorta isolated from ovariectomized mice.

KEY RESULTS

Relative to males, HSPB1-null female mice exhibited an increased L-NAME-resistant relaxation induced by activation of either PAR2 or muscarinic ACh receptors that was blocked in the concurrent presence of both L-NAME and ODQ. mRNAs (qPCR) for eNOS and ODQ-sensitive guanylyl-cyclase were increased in females versus males. Treatment of isolated aorta tissue with HSPB1 improved tissue responsiveness in the presence of L-NAME. Ovariectomy did not affect NO sensitivity, supporting an oestrogen-independent role for HSPB1.

CONCLUSIONS AND IMPLICATIONS

HSPB1 can regulate intact vascular endothelial function to affect NO-mediated vascular relaxation, especially in females.

Percutaneous Sampling of Local Biomolecule Gradients Across Coronary Artery Atherosclerotic Plaques

A percutaneous catheter device, the Liquid Biopsy System, was developed to sample the unstirred boundary layer of blood upstream and downstream of intact and disrupted human coronary atherosclerotic plaques. Using multiplexed proximity extension assays, release of 20 biomolecules was simultaneously detected in samples taken across plaques before balloon angioplasty, including the soluble form of the endothelial lectin-like oxidized LDL receptor. Additional biomolecules, including matrix metalloproteinase-12, were released after plaque disruption with angioplasty. These experiments demonstrate the power of the Liquid Biopsy System to yield new scientific insights and its ultimate potential to generate new biomarkers and surrogate endpoints for clinical trials.

Heat Shock Proteins in Vascular Diabetic Complications: Review and Future Perspective

Heat shock proteins (HSPs) are a large family of proteins highly conserved throughout evolution because of their unique cytoprotective properties. Besides assisting protein refolding and regulating proteostasis under stressful conditions, HSPs also play an important role in protecting cells from oxidative stress, inflammation, and apoptosis. Therefore, HSPs are crucial in counteracting the deleterious effects of hyperglycemia in target organs of diabetes vascular complications. Changes in HSP expression have been demonstrated in diabetic complications and functionally related to hyperglycemia-induced cell injury. Moreover, associations between diabetic complications and altered circulating levels of both HSPs and anti-HSPs have been shown in clinical studies. HSPs thus represent an exciting therapeutic opportunity and might also be valuable as clinical biomarkers. However, this field of research is still in its infancy and further studies in both experimental diabetes and humans are required to gain a full understanding of HSP relevance. In this review, we summarize current knowledge and discuss future perspective.

Hsp-27 levels and thrombus burden relate to clinical outcomes in patients with ST-segment elevation myocardial infarction

High thrombus burden, subsequent distal embolization, and myocardial no-reflow remain a large obstacle that may negate the benefits of urgent coronary revascularization in patients with ST-segment elevation myocardial infarction (STEMI). However, the biological function and clinical association of Hsp-27 with thrombus burden and clinical outcomes in patients with STEMI is not clear. Consecutive patients (n = 146) having STEMI undergoing primary percutaneous coronary intervention (pPCI) within 12 hours from the onset of symptoms were enrolled in this prospective study in the Affiliated Yantai Yuhuangding Hospital of Qingdao University, Yantai, Shangdong, P.R. China. Patients were divided into low thrombus burden and high thrombus burden groups. The present study demonstrated that patients with high-thrombus burden had higher plasma Hsp-27 levels ([32.0 ± 8.6 vs. 58.0 ± 12.3] ng/mL, P < 0.001). The median value of Hsp-27 levels in all patients with STEMI was 45 ng/mL. Using the receiver operating characteristic (ROC) curve analysis, plasma Hsp-27 levels were of significant diagnostic value for high thrombus burden (AUC, 0.847; 95% CI, 0.775–0.918; P < 0.01). The multivariate cox regression analysis demonstrated that Hsp-27 > 45 ng/mL (HR 2.801, 95% CI 1.296–4.789, P = 0.001), were positively correlated with the incidence of major adverse cardiovascular events (MACE). Kaplan-Meier survival analysis demonstrated that MACE-free survival at 180-day follow-up was significantly lower in patients with Hsp-27 > 45 ng/mL (log rank = 10.28, P < 0.001).

Our data demonstrate that plasma Hsp-27 was positively correlated with high thrombus burden and the incidence of MACE in patients with STEMI who underwent pPCI.

In vitro Stability of Heat Shock Protein 27 in Serum and Plasma Under Different Pre-analytical Conditions: Implications for Large-Scale Clinical Studies

The effects of storage temperatures, repeated freeze-thaw cycles, or delays in separating plasma or serum from blood samples are largely unknown for heat shock protein 27 (HSP27). We evaluated (1) the imprecision of the HSP27 assay used in this study; (2) the in vitro stability of HSP27 in blood samples stored at 4℃ for up to 6 hr with immediate and delayed serum/plasma separation from cells; and (3) the in vitro stability of HSP27 in blood samples stored at -80℃ after repeated freeze-thaw cycles. The ELISA to detect HSP27 in this study showed a within-run CV of <9% and a total CV of <15%. After 4-6 hr of storage at 4℃, HSP27 concentrations remained stable when using serum tubes irrespective of sample handling, but HSP27 concentrations decreased by 25-45% when using EDTA plasma tubes. Compared with baseline HSP27, one freeze-thaw cycle had no effect on serum concentrations. However, plasma concentrations increased by 3.1-fold after one freeze-thaw cycle and by 7.3-fold after five freeze-thaw cycles. In conclusion, serum is an appropriate biological sample type for use in epidemiological and large-scale clinical studies.

Serum Heat Shock Protein Levels and the Relationship of Heat Shock Proteins with Various Parameters in Chronic Obstructive Pulmonary Disease Patients

OBJECTIVES

Chronic Obstructive Pulmonary Disease (COPD) is accompanied by increased cellular stress and inflammation. Most of the Heat Shock Proteins (HSPs) have strong cytoprotective effects. The role of HSPs in COPD pathogenesis has not determined completely. We investigated the serum level of HSPs in COPD patients, smokers without COPD and healthy non-smoking controls. Also, we evaluated the relationship of HSPs with various parameters (inflammatory, oxidative, functional status, quality of life) in COPD patients.

MATERIAL AND METHODS

The levels of stress protein (HSP27, HSP70, HSP60, HSP90, CyPA), interleukin-6, C-reactive protein and malondialdehyde were measured in 16 healthy non-smoker, 14 smokers without COPD and 50 patients with stable COPD. Pulmonary function tests (PFT) and arterial blood gases parameters were measured. Health Related Quality of Life was evaluated and exercise capacity was measured with 6 minute walking test.

RESULTS

Only HSP27 levels was significantly higher in COPD patients when compared with both healthy non-smoker and smokers without COPD (for both, p< 0.001). There was a weak-moderate negative correlation between serum levels of HSP27 and PFT parameters and between HSP27 levels and PaO2. Serum levels of HSP27 showed a weak-moderate positive correlation with symptom, activity and total scores. Subjects evaluated only smokers without COPD and patients with COPD; HSP27 had an area under the curve (AUC) in the receiver operating characteristic (ROC) curve of 0.819 (0.702-0.935; 95% CI; p= 0.000).

CONCLUSION

Increased serum levels of HSP27 was found in COPD patients and our results showed sensitivity and specificity of serum HSP27 as diagnostic markers for COPD.

Extracellular Release and Signaling by Heat Shock Protein 27: Role in Modifying Vascular Inflammation

Heat shock protein 27 (HSP27) is traditionally viewed as an intracellular chaperone protein with anti-apoptotic properties. However, recent data indicate that a number of heat shock proteins, including HSP27, are also found in the extracellular space where they may signal via membrane receptors to alter gene transcription and cellular function. Therefore, there is increasing interest in better understanding how HSP27 is released from cells, its levels and composition in the extracellular space, and the cognate cell membrane receptors involved in effecting cell signaling. In this paper, the knowledge to date, as well as some emerging paradigms about the extracellular function of HSP27 is presented. Of particular interest is the role of HSP27 in attenuating atherogenesis by modifying lipid uptake and inflammation in the plaque. Moreover, the abundance of HSP27 in serum is an emerging new biomarker for ischemic events. Finally, HSP27 replacement therapy may represent a novel therapeutic opportunity for chronic inflammatory disorders, such as atherosclerosis.

Increased expression of phosphorylated forms of heat-shock protein-27 and p38MAPK in macrophage-rich regions of fibro-fatty atherosclerotic lesions in the rabbit

We aimed to assess the expression and distribution of Hsp27, pHsp27 (Ser82), p38MAPK and p-p38MAPK in fibro-fatty atherosclerotic lesions and the myocardium of hypercholesterolaemic rabbits. Male New Zealand white rabbits were fed a high-cholesterol diet for 18 weeks, maintaining serum cholesterol at approximately 20 mmol/l over this period. Aortic arch and myocardial tissues were analysed by Western blot, immunohistochemistry and double immunofluorescence. Plasma Hsp27 levels were measured by ELISA. There was a significant increase in the expression of monomeric and dimeric forms of Hsp27, together with pHsp27 (Ser82), p38MAPK and p-p38MAPK in the fibro-fatty atherosclerotic lesions (P < 0.01; P < 0.05; P < 0.001; and P < 0.001, respectively) and the myocardial tissues (P < 0.001) from the cholesterol-fed rabbits compared with equivalent tissues from controls when the plasma concentration was low. Immunohistochemical analysis of the fibro-fatty lesions showed marked increases in Hsp27 and pHsp27 (Ser82) immunoreactivity. Double immunostaining showed intense expression of pHsp27 and p-p38MAPK in regions that were rich in macrophages, suggesting a close association with these inflammatory cells, whereas, in regions rich in smooth muscle cells, only p-p38MAPK was found to be strongly expressed. An increased expression of pHsp27 (Ser82) was spatially associated with increased p-p38MAPK within fibro-fatty atherosclerotic lesions and was colocalized to regions rich in macrophages. The initial increase in plasma Hsp27 levels may reflect the increase in systemic inflammation and oxidative stress in the early phases of disease. The falling concentrations subsequently may be coincident with the development of the advanced atherosclerotic lesions.

Aortic wall proteomic analysis in spontaneously hypertensive rats with a blood pressure decrease induced by 6-week load-free swimming

Decreased arterial compliance is one of the earliest detectable manifestations of adverse structural and functional changes within the vessel wall in hypertension. The proteomic approach is a powerful technique to analyze a complex mixture of proteins in various settings. Physical activity level was negatively associated with blood pressure. Sixteen 4-week-old male spontaneously hypertensive rats (SHR) and 16 Wistar-Kyoto (WKY) rats were randomly divided into four groups: i) SHR exercise group, ii) SHR rest group, iii) WKY exercise group and iv) WKY rest group. In the SHR and WKY exercise groups, rats were treated with a 6-week load-free swimming protocol (1 h/day, 5 days/week). The blood pressure of the rats was tested by the CODA^TM2 single non-invasive blood pressure measurement appliance. After the 6-week swimming protocol, the total aorta excluding abdominal aorta was extracted. The proteins were separated by two-dimensional gel electrophoresis and identified via LC-mass spectrometry (MS)/MS. After 6-week load-free swimming, blood pressure decreased in the SHRs. Compared with sedentary SHRs, 11 spots on the 2D-gel showed a significant difference in exercised SHRs. Nine of these were chosen for further identification. There were 5 upregulated proteins (long-chain specific acyl-CoA dehydrogenase, heat shock protein β-1, isocitrate dehydrogenase subunit α, actin, α cardiac muscle 1 preprotein and calmodulin isoform 2) and 4 downregulated proteins (adipocyte-type fatty acid-binding protein, tubulin β-2C chain, 78 kDa glucose-regulated protein precursor and mimecan). Proteomics is an effective method to identify the target proteins of exercise intervention for hypertension.

Heat Shock Proteins, L-Arginine, and Asymmetric Dimethylarginine Levels in Patients With Obstructive Sleep Apnea Syndrome

OBJECTIVE

Vascular endothelial inflammation and enhanced oxidative stress are important factors in the pathogenesis of obstructive sleep apnea syndrome (OSAS). The aim of this study was to determine the levels of heat shock protein (HSP) 27, HSP70, HSP90, L-arginine, and asymmetric dimethylarginine (ADMA) in patients with OSAS and determine their relationship with cardiovascular (CV) risk factors.

MATERIAL AND METHODS

Forty patients with OSAS, comprising 26 with and 14 without traditional CV risk factors (obesity, hypercholesterolemia, diabetes, hypertension, and smoking), and 20 control subjects without OSAS were included. All patients underwent a full polysomnographic evaluation, and blood samples were obtained in the morning after the night the diagnostic study was performed.

RESULTS

No significant differences were found in serum HSP27 and HSP70 levels between the groups. HSP90 and ADMA levels increased significantly, whereas L-arginine levels decreased significantly in patients with OSAS, both with and without CV risk factors, compared with controls, but were not different among the subgroups. In all patients with OSAS, serum HSP70 levels were positively correlated with a percent time with saturation<90% (r=.349, P=.027). Serum L-arginine levels were negatively correlated with desaturation number (r=-.360, P=.022) and apnea-hypopnea index (r=-.354, P=.025) and positively correlated with mean oxygen saturation (r=.328, P=.039).

CONCLUSION

Serum levels of HSP90 and ADMA increased, whereas those of L-arginine decreased in patients with OSAS regardless of CV risk factors. These findings indicate the presence of oxidative stress and endothelial dysfunction in patients with OSAS.

Small heat shock proteins: Role in cellular functions and pathology

Small heat shock proteins (sHsps) are conserved across species and are important in stress tolerance. Many sHsps exhibit chaperone-like activity in preventing aggregation of target proteins, keeping them in a folding-competent state and refolding them by themselves or in concert with other ATP-dependent chaperones. Mutations in human sHsps result in myopathies, neuropathies and cataract. Their expression is modulated in diseases such as Alzheimer's, Parkinson's and cancer. Their ability to bind Cu2+, and suppress generation of reactive oxygen species (ROS) may have implications in Cu2+-homeostasis and neurodegenerative diseases. Circulating αB-crystallin and Hsp27 in the plasma may exhibit immunomodulatory and anti-inflammatory functions. αB-crystallin and Hsp20 exhitbit anti-platelet aggregation: these beneficial effects indicate their use as potential therapeutic agents. sHsps have roles in differentiation, proteasomal degradation, autophagy and development. sHsps exhibit a robust anti-apoptotic property, involving several stages of mitochondrial-mediated, extrinsic apoptotic as well as pro-survival pathways. Dynamic N- and C-termini and oligomeric assemblies of αB-crystallin and Hsp27 are important factors for their functions. We propose a "dynamic partitioning hypothesis" for the promiscuous interactions and pleotropic functions exhibited by sHsps. Stress tolerance and anti-apoptotic properties of sHsps have both beneficial and deleterious consequences in human health and diseases. Conditional and targeted modulation of their expression and/or activity could be used as strategies in treating several human disorders. The review attempts to provide a critical overview of sHsps and their divergent roles in cellular processes particularly in the context of human health and disease.

Plasma heat shock protein 27 is associated with coronary artery disease, abdominal aortic aneurysm and peripheral artery disease

Low protein levels of Hsp27 have been reported in atherosclerotic plaques. In addition, human studies have indicated that circulating Hsp27 levels are lower in coronary artery disease patients compared with controls. It remains, however, unclear whether this applies to other forms of atherosclerotic disease.

Plasma Hsp27 from 280 subjects was examined by ELISA. The cohort included 80 coronary artery disease (CAD), 40 peripheral artery disease (PAD) and 80 abdominal aortic aneurysm (AAA) patients. Eighty elderly subjects, without any clinical history of vascular diseases, were used as a control group. Receiver operating curve (ROC) and logistic regression model analysis were performed to evaluate the potential value of Hsp27 as a circulating biomarker.

Patients with atherosclerotic vascular diseases had significantly lower levels of Hsp27 than control subjects (p < 0.001). Moreover, Hsp27 was significantly lower in CAD patients than other atherosclerotic vascular disease groups (p < 0.001). There was no difference in Hsp27 levels between the AAA and PAD groups. Using the ROC-generated optimal cut-off values for Hsp27, logistic regression modeling indicated that low plasma Hsp27 was independently associated with the presence of multiple forms of atherosclerotic disease.

In conclusion, circulating Hsp27 is significantly lower in patients with multiple forms of atherosclerotic arterial disease.

Heat shock protein-27 delays acute rejection after cardiac transplantation: an experimental model

Supplemental digital content is available in the text.

Background

Rejection is the major obstacle to survival after cardiac transplantation. We investigated whether overexpression of heat shock protein (Hsp)-27 in mouse hearts protects against acute rejection and the mechanisms of such protection.

Methods

Hearts from B10.A mice overexpressing human Hsp-27 (Hsp-27tg), or Hsp-27–negative hearts from littermate controls (LCs) were transplanted into allogeneic C57BL/6 mice. The immune response to B10.A hearts was investigated using quantitative polymerase chain reaction for CD3+, CD4+, CD8+ T cells, and CD14+ monocytes and cytokines (interferon-γ, interleukin [IL]-2, tumor necrosis factor-α, IL-1β, IL-4, IL-5, IL-10, transforming growth factor-β) in allografts at days 2, 5, and 12 after transplantation. The effect of Hsp-27 on ischemia-induced caspase activation and immune activation was investigated.

Results

Survival of Hsp-27tg hearts (35±10.37 days, n=10) was significantly prolonged compared with LCs (13.6±3.06 days, n=10, P=0.0004). Hsp-27tg hearts expressed significantly more messenger RNA (mRNA) markers of CD14+ monocytes at day 2 and less mRNA markers of CD3+ and CD8+T cells at day 5 compared with LCs. There was more IL-4 mRNA in Hsp-27tg hearts at day 2 and less interferon-γ mRNA at day 5 compared with LCs. Heat shock protein-27tg hearts subjected to ischemia or to 24 hr ischemia-reperfusion injury demonstrated significantly less apoptosis and activation of caspases 3, 9, and 1 than LCs. T cells removed from C57BL/6 recipients of Hsp-27tg hearts produced a vigorous memory response to B10.A antigens, suggesting immune activation was not inhibited by Hsp-27.

Conclusion

Heat shock protein-27 delays allograft rejection, by inhibiting tissue damage, through probably an antiapoptotic pathway. It may also promote an anti-inflammatory subset of monocytes.

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.

The role of heat shock proteins in atherosclerosis

Atherosclerosis is a chronic, multifactorial disease that starts in youth, manifests clinically later in life, and can lead to myocardial infarction, stroke, claudication, and death. Although inflammatory processes have long been known to be involved in atherogenesis, interest in this subject has grown in the past 30-40 years. Animal experiments and human analyses of early atherosclerotic lesions have shown that the first pathogenic event in atherogenesis is the intimal infiltration of T cells at arterial branching points. These T cells recognize heat shock protein (HSP)60, which is expressed together with adhesion molecules by endothelial cells in response to classic risk factors for atherosclerosis. Although these HSP60-reactive T cells initiate atherosclerosis, antibodies to HSP60 accelerate and perpetuate the disease. All healthy humans develop cellular and humoral immunity against microbial HSP60 by infection or vaccination. Given that prokaryotic (bacterial) and eukaryotic (for instance, human) HSP60 display substantial sequence homology, atherosclerosis might be the price we pay for this protective immunity, if risk factors stress the vascular endothelial cells beyond physiological conditions.