The heat shock paradox and cardiac myocytes: role of heat shock factor

A signal peptide derived from Hsp60 induces protective cytotoxic T lymphocyte immunity against lymphoid malignancies independently of TAP and classical MHC-I

Hsp60sp, a signal peptide derived from the leader sequence of heat shock protein 60 kDa (Hsp60), is a Qa-1/HLA-E-binding peptide. We previously showed that Hsp60sp-specific CD8⁺ T cells are involved in the immunoregulation of autoimmune diseases by controlling the response of self-reactive lymphocytes. Here, we report that Hsp60sp-specific CD8⁺ T cells killed malignant lymphocytes in vitro independently of transporter associated with antigen processing (TAP) and classical MHC-I expression. Induction of this cytotoxic T lymphocyte (CTL) response in vivo, either by adoptive transfer of in vitro-amplified CTLs or peptide-loaded dendritic cell immunization, resulted in effective control of lymphoid tumors, including TAP- or classical MHC-I-deficient cells. Hsp60sp-specific immune activation combined with programmed cell death protein 1 (PD-1) blocking synergistically restrained mouse lymphoma development. Importantly, Hsp60sp-specific CD8⁺ T cells did not negatively affect normal tissues and cells. Our data suggest that Hsp60sp-based immunotherapy is an inviting strategy to control lymphoid malignancies.

Response of the maternal hypothalamus to cold stress during late pregnancy in rats

Maternal stress is a key risk factor in the development of offspring. We previously identified prenatal cold stress-induced anxiety-like behavior reduced in the offspring of rats along with negative feedback regulation from the maternal hippocampus on the hypothalamic-pituitary-adrenal (HPA) axis during prenatal cold stress. However, the precise function of the maternal hypothalamus response to cold stress during late pregnancy in rats has not yet been determined. Therefore, we examined proteins in the hypothalamus that respond to aldosterone, neurodevelopment, inflammation and apoptosis. Our results show that prenatal cold stress induced the expression of mineralocorticoid receptors (MR) and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), suggesting prenatal cold stress may promote the elevation of aldosterone levels in the hypothalamus. Remarkably, increased expression of brain derived neurotrophic factor (BDNF) helped to replenish intracellular peptidergic stores and ensure homeostatic balance during prenatal cold stress. Furthermore, prenatal cold stress reduced the expression of c-Fos via STAT3 and ERK1/2 pathways in the hypothalamus. Moreover, prenatal cold stress induced NF-κB phosphorylation at Ser536, then promoted the expression of inducible nitric oxide synthase (iNOS) and induced an apoptosis-related protein response. Together, this study confirms that changes in the maternal hypothalamus during cold stress in late pregnancy are directly reflective of the response of the HPA to cold stress and demonstrates how the hypothalamus coordinates cold stress. We suggest mechanisms which might explain how these states might be linked with an abnormal stress response.

Paying for the Tolls: The High Cost of the Innate Immune System for the Cardiac Myocyte

The cardiac myocyte differs strikingly from the specialized cells of the immune system, which has two different responses to invading organisms and tissue damage. Adaptive or acquired immunity generates highly specific antibodies in response to threats and is an essential component of immunity; however, adaptive immunity can take 4-7 days to mobilize, and a more primitive response, innate immunity, fills the gap. Innate immunity is expressed in complex and in primitive life forms. Specialized receptors, Toll-like receptors (TLRs), which are widely distributed throughout different tissues recognize danger signals and rapidly respond with the release of noxious substances, such as TNFα. The problem is that many endogenous molecules have been found to act as ligands for specific TLRs, and when these molecules are released into the extracellular environment, they can cause problems by activating innate immunity and an inflammatory response. In cardiac myocytes heat shock protein (HSP)60 can activate TLR4, as can HMGB1, and this type of response can amplify the response to ischemia/reperfusion leading to increased cell and tissue injury. Activation of TLRs can potentially amplify chronic, inflammatory diseases, such as ischemic heart failure. Thus, it is important to understand the regulation of the TLRs and their downstream effects. This chapter will focus on the TLRs and cardiac myocytes.

Heat shock factor-1 knockout enhances cholesterol 7α-hydroxylase (CYP7A1) and multidrug transporter (MDR1) gene expressions to attenuate atherosclerosis

AIMS

Stress response, in terms of activation of stress factors, is known to cause obesity and coronary heart disease such as atherosclerosis in human. However, the underlying mechanism(s) of these pathways are not known. Here, we investigated the effect of heat shock factor-1 (HSF-1) on atherosclerosis.

METHODS AND RESULTS

HSF-1 and low-density lipoprotein receptor (LDLr) double knockout (HSF-1(-/-)/LDLr(-/-)) and LDLr knockout (LDLr(-/-)) mice were fed with atherogenic western diet (WD) for 12 weeks. WD-induced weight gain and atherosclerotic lesion in aortic arch and carotid regions were reduced in HSF-1(-/-)/LDLr(-/-) mice, compared with LDLr(-/-) mice. Also, repression of PPAR-γ2 and AMPKα expression in adipose tissue, low hepatic steatosis, and lessened plasma adiponectins and lipoproteins were observed. In HSF-1(-/-)/LDLr(-/-) liver, higher cholesterol 7α-hydroxylase (CYP7A1) and multidrug transporter [MDR1/P-glycoprotein (P-gp)] gene expressions were observed, consistent with higher bile acid transport and larger hepatic bile ducts. Luciferase reporter gene assays with wild-type CYP7A1 and MDR1 promoters showed lesser luminescence than with mutant promoters (HSF-1 binding site deleted), indicating that HSF-1 binding is repressive of CYP7A1 and MDR1 gene expressions.

CONCLUSION

HSF-1 ablation not only eliminates heat shock response, but it also transcriptionally up-regulates CYP7A1 and MDR1/P-gp axis in WD-diet fed HSF-1(-/-)/LDLr(-/-) mice to reduce atherosclerosis.

TLR4 mutation and HSP60-induced cell death in adult mouse cardiac myocytes

Extracellular (ex) HSP60 is increasingly recognized as an agent of cell injury. Previously, we reported that low endotoxin exHSP60 causes cardiac myocyte apoptosis. Our findings supported a role for Toll-like receptor (TLR) 4 in HSP60 mediated apoptosis. To further investigate the involvement of TLR4 in cardiac injury, we studied adult cardiac myocytes from C3H/HeJ (HeJ) mice, which have a mutant, nonfunctional TLR4, and compared the results with parallel studies using wild-type (WT) mice. Nuclear factor κB (NFκB) activation is an early step downstream of TLR4. NFκB was activated 1 h after treatment with HSP60 in WT, but not HeJ mouse myocytes. ExHSP60 caused apoptosis in cardiac myocytes from WT mice, but not in myocytes from the HeJ mutants. To further elucidate the importance of exHSP60 in cardiac myocyte injury, both WT and HeJ mutant isolated mouse adult cardiac myocytes were exposed to hypoxia/reoxygenation. Anti-HSP60 antibody treatment reduced apoptosis in the WT group, but had no effect on the HeJ mutant myocytes. Unexpectedly, necrosis was also decreased in the HeJ mutants. Necrosis after hypoxia/reoxygenation in WT cardiac myocytes was mediated in part by TLR2 and TLR4 through rapid activation of PKCα, followed by increased expression of Nox2, and this was ameliorated by blocking antibodies to TLR2/4. These studies provide further evidence that TLR4 mediates exHSP60-associated apoptosis and that exHSP60 has an important role in cardiac myocyte injury, both apoptotic and necrotic.

Comparison of the ventricle muscle proteome between patients with rheumatic heart disease and controls with mitral valve prolapse: HSP 60 may be a specific protein in RHD

Objective. Rheumatic heart disease (RHD) is a serious autoimmune heart disease. The present study was aimed at identifying the differentially expressed proteins between patients with RHD and controls with mitral valve prolapse. Methods. Nine patients with RHD and nine controls with mitral valve prolapsed were enrolled for this study. Two-dimensional difference in-gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were performed. Results. A total of 39 protein spots with differential expressions were identified between the two groups (P < 0.05, Average Ratio > 1.2 or Average Ratio < −1.2) and four upregulated proteins (including heat shock protein 60 (HSP 60), desmin, PDZ and LIM domain protein 1, and proteasome subunit alpha type-1) and three downregulated proteins (including tropomyosin alpha-1 chain, malate dehydrogenase, and chaperone activity of bc1 complex homolog) were determined. Conclusion. These seven proteins, especially HSP 60, may serve as potential biomarkers for the diagnosis of RHD and provide evidence to explain the mechanisms of this complex disease in the future.

[Remote ischemic conditioning: short-term effects on rat liver ischemic-reperfusion injury]

INTRODUCTION

Several techniques have been developed to reduce ischemic-reperfusion injury. A novel method is the remote ischemic perconditioning, applied parallel with target organ ischemia.

AIM

The aim of the study was to determine the extent of liver ischemic-reperfusion injury via the application of this novel method.

METHODS

Male Wistar rats (n = 30, 10/group) were subjected to 60-minute partial liver ischemia and 60-minute reperfusion. Rats in the perconditioned group received conditioning treatment during the last 40 minutes of liver ischemia by infrarenal aortic clamping. Hepatic and lower limb microcirculation was monitored by laser Doppler flowmeter during reperfusion. After reperfusion, liver samples were taken for routine histological examination and redox-state assessment. Serum transaminase activities and liver tissue heat-shock protein-72 expression were measured.

RESULTS

Parameters of microcirculation showed significant (p<0.05) improvement in the perconditioned group in comparison with the control. Besides the significant improvement observed in the serum alanine amino-transferase activities, significantly milder tissue injury was detected histologically in the liver sections of the perconditioned group. Moreover, significant improvement was found in the redox-state parameters.

CONCLUSION

Perconditioning may be a reasonable possibility to reduce liver ischemic-reperfusion injury.

Remote ischemic perconditioning--a simple, low-risk method to decrease ischemic reperfusion injury: models, protocols and mechanistic background. A review

Interruption of blood flow can cause ischemic reperfusion injury, which sometimes has a fatal outcome. Recognition of the phenomenon known as reperfusion injury has led to initial interventional approaches to lessen the degree of damage. A number of efficient pharmacologic agents and surgical techniques (e.g., local ischemic preconditioning and postconditioning) are available. A novel, alternative approach to target organ protection is remote ischemic conditioning triggered by brief repetitive ischemia and reperfusion periods in distant organs. Among the different surgical techniques is so-called remote ischemic perconditioning, a method that applies short periods of ischemic reperfusion to a distant organ delivered during target organ ischemia. Although ischemic reperfusion injury is reduced by this technique, the explanation for this phenomenon is still unclear, and approximately only a dozen reports on the topic have appeared in the literature. In our study, therefore, we investigated the connective mechanisms, signal transduction, and effector mechanisms behind remote perconditioning, with a review on molecular background and favorable effects. In addition, we summarize the various treatment protocols and models to promote future experimental and clinical research.

Heat shock protein 25-enriched plasma transfusion preconditions the heart against doxorubicin-induced dilated cardiomyopathy in mice

Extracellular heat shock proteins (eHsps) in the circulation have recently been found to activate both apoptotic and protective signaling in the heart. However, the role of eHsps in doxorubicin (Dox)-induced heart failure has not yet been studied. The objective of the present study was to determine how Dox affects circulating eHsp25 in blood plasma and how eHsp25 affects Dox-induced dilated cardiomyopathy. Wild-type mice [HSF-1(+/+)] were pretreated with 100 μl of heterozygous heat shock factor-1 [HSF-1(+/-)] mouse plasma (which contained 4-fold higher eHsp25 compared with wild-type mice), HSF-1(+/+) plasma, or saline, before treatment with Dox (6 mg/kg). After 4 weeks of this treatment protocol, HSF-1(+/-) plasma-pretreated mice showed increased eHsp25 in plasma and improved cardiac function (percentage of fractional shortening 37.3 ± 2.1 versus 26.4 ± 4.0) and better life span (31 ± 2 versus 22 ± 3 days) compared with the HSF-1(+/+) plasma or saline-pretreated mice. Preincubation of isolated adult cardiomyocytes with HSF-1(+/-) plasma or recombinant human Hsp27 (rhHsp27) significantly reduced Dox-induced activation of nuclear factor-κB and cytokine release and delayed cardiomyocyte death. Moreover, when cardiomyocytes were incubated with fluorescence-tagged rhHsp27, a saturation in binding was observed, suggesting that eHsp25 can bind to surface receptors. Competitive assays with a Toll-like receptor 2 (TLR2) antibody reduced the rhHSP27 binding, indicating that Hsp25 interacts with TLR2. In conclusion, transfusion of Hsp25-enriched blood plasma protected the heart from Dox-induced cardiotoxicity. Hsp25 antagonized Dox binding to the TLR2 receptor on cardiomyocytes.

Identification of the HSPB4/TLR2/NF-κB axis in macrophage as a therapeutic target for sterile inflammation of the cornea

Sterile inflammation underlies many diseases of the cornea including serious chemical burns and the common dry eye syndrome. In search for therapeutic targets for corneal inflammation, we defined the kinetics of neutrophil infiltration in a model of sterile injury to the cornea and identified molecular and cellular mechanisms triggering inflammatory responses. Neutrophil infiltration occurred in two phases: a small initial phase (Phase I) that began within 15 min after injury, and a larger second phase (Phase II) that peaked at 24–48 h. Temporal analysis suggested that the neuropeptide secretoneurin initiated Phase I without involvement of resident macrophages. Phase II was initiated by the small heat shock protein HSPB4 that was released from injured keratocytes and that activated resident macrophages via the TLR2/NF-κB pathway. The Phase II inflammation was responsible for vision-threatening opacity and was markedly suppressed by different means of inhibition of the HSPB4/TLR2/NF-κB axis: in mice lacking HSPB4 or TLR2, by antibodies to HSPB4 or by TNF-α stimulated gene/protein 6 that CD44-dependently inhibits the TLR2/NF-κB pathway. Therefore, our data identified the HSPB4/TLR2/NF-κB axis in macrophages as an effective target for therapy of corneal inflammation.

Celastrol inhibits aminoglycoside-induced ototoxicity via heat shock protein 32

Hearing loss is often caused by death of the mechanosensory hair cells of the inner ear. Hair cells are susceptible to death caused by aging, noise trauma, and ototoxic drugs, including the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Ototoxic drugs result in permanent hearing loss for over 500 000 Americans annually. We showed previously that induction of heat shock proteins (HSPs) inhibits both aminoglycoside- and cisplatin-induced hair cell death in whole-organ cultures of utricles from adult mice. In order to begin to translate these findings into a clinical therapy aimed at inhibiting ototoxic drug-induced hearing loss, we have now examined a pharmacological HSP inducer, celastrol. Celastrol induced upregulation of HSPs in utricles, and it provided significant protection against aminoglycoside-induced hair cell death in vitro and in vivo. Moreover, celastrol inhibited hearing loss in mice receiving systemic aminoglycoside treatment. Our data indicate that the major heat shock transcription factor HSF-1 is not required for celastrol-mediated protection. HSP32 (also called heme oxygenase-1, HO-1) is the primary mediator of the protective effect of celastrol. HSP32/HO-1 inhibits pro-apoptotic c-Jun N-terminal kinase (JNK) activation and hair cell death. Taken together, our data indicate that celastrol inhibits aminoglycoside ototoxicity via HSP32/HO-1 induction.