Gene transfer of heat-shock protein 70 reduces infarct size in vivo after ischemia/reperfusion in the rabbit heart

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.

Inhibition of heat shock protein 70 blocks the development of cardiac hypertrophy by modulating the phosphorylation of histone deacetylase 2

AIMS

Previously, we reported that phosphorylation of histone deacetylase 2 (HDAC2) and the resulting activation causes cardiac hypertrophy. Through further study of the specific binding partners of phosphorylated HDAC2 and their mechanism of regulation, we can better understand how cardiac hypertrophy develops. Thus, in the present study, we aimed to elucidate the function of one such binding partner, heat shock protein 70 (HSP70).

METHODS AND RESULTS

Primary cultures of rat neonatal ventricular cardiomyocytes and H9c2 cardiomyoblasts were used for in vitro cellular experiments. HSP70 knockout (KO) mice and transgenic (Tg) mice that overexpress HSP70 in the heart were used for in vivo analysis. Peptide-precipitation and immunoprecipitation assay revealed that HSP70 preferentially binds to phosphorylated HDAC2 S394. Forced expression of HSP70 increased phosphorylation of HDAC2 S394 and its activation, but not that of S422/424, whereas knocking down of HSP70 reduced it. However, HSP70 failed to phosphorylate HDAC2 in the cell-free condition. Phosphorylation of HDAC2 S394 by casein kinase 2α1 enhanced the binding of HSP70 to HDAC2, whereas dephosphorylation induced by the catalytic subunit of protein phosphatase 2A (PP2CA) had the opposite effect. HSP70 prevented HDAC2 dephosphorylation by reducing the binding of HDAC2 to PP2CA. HSP70 KO mouse hearts failed to phosphorylate S394 HDAC2 in response to isoproterenol infusion, whereas Tg overexpression of HSP70 increased the phosphorylation and activation of HDAC2. 2-Phenylethynesulfonamide (PES), an HSP70 inhibitor, attenuated cardiac hypertrophy induced either by phenylephrine in neonatal ventricular cardiomyocytes or by aortic banding in mice. PES reduced HDAC2 S394 phosphorylation and its activation by interfering with the binding of HSP70 to HDAC2.

CONCLUSION

These results demonstrate that HSP70 specifically binds to S394-phosphorylated HDAC2 and maintains its phosphorylation status, which results in HDAC2 activation and the development of cardiac hypertrophy. Inhibition of HSP70 has possible application as a therapeutic.

The Expression of and Preoperative Correlation between Heat-Shock Protein 70, EuroSCORE, and Lactate in Patients undergoing CABG with Cardiopulmonary Bypass

Objetive

Coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) improved symptoms and increased survival and quality of life in patients with coronary artery disease. However, it should be the main cause of a complex organic systemic inflammatory response that greatly contributes to several postoperative adverse effects.

Methods

We aimed to evaluate heat-shock protein 70 (HSP 70) expression as a morbimortality predictor in patients with preserved ventricular function undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) and to determine their association with the lactate as a marker of tissue hypoperfusion and the EuroSCORE risk score. This is a prospective, observational study including 46 patients and occurring between May and July 2016. Patients without ventricular dysfunction undergoing myocardial revascularization with extracorporeal circulation were included. They were divided into (1) complicated and (2) uncomplicated postoperative evolution groups. EuroSCORE, lactate levels, and HSP 70 expression and their correlations were determined.

Results

Statistical analysis showed that the group with complicated evolution had higher EuroSCORE values than the other group. HSP 70 protein levels were significantly increased in the group with uncomplicated evolution and showed similar results. According to our results, HSP family proteins may be independent predictors of uncomplicated evolution in patients without ventricular dysfunction undergoing CABG with CPB.

Conclusion

HSP 70 should be a good discriminator and protection marker for complications in cardiac surgery.

Heat Shock Proteins: Protection and Potential Biomarkers for Ischemic Injury of Cardiomyocytes After Surgery

The heat shock proteins are endogenous proteins with the ability to act as molecular chaperones. Methods that provide cell protection by way of some damage can positively influence the results of surgery. The present review summarizes current knowledge concerning the cardioprotective role of the heat shock proteins as occurs in heart damage, including relevant information about the stresses that regulate the expression of these proteins and their potential role as biomarkers of heart disease.

Remote Ischemic Preconditioning Ameliorates Acute Kidney Injury due to Contrast Exposure in Rats through Augmented O-GlcNAcylation

Remote ischemic preconditioning (RIPC) is an adaptive response, manifesting when local short-term ischemic preconditioning reduces damage to adjacent or distant tissues or organs. O-linked β-N-acetylglucosamine (O-GlcNAc) glycosylation of intracellular proteins denotes a type of posttranslational modification that influences multiple cytoplasmic and nuclear protein functions. Growing evidence indicates that stress can induce an acute increase in O-GlcNAc levels, which can be cytoprotective. The current study aimed to determine whether RIPC can provide renoprotection against contrast-induced acute kidney injury (CI-AKI) by augmenting O-GlcNAc signaling. We established a stable model of CI-AKI using 5/6 nephrectomized rats exposed to dehydration followed by iohexol injection via the tail vein. We found that RIPC increased UDP-GlcNAc levels through the hexosamine biosynthetic pathway as well as global renal O-GlcNAcylation. RIPC-induced elevation of O-GlcNAc signaling ameliorated CI-AKI based on the presence of less tubular damage and apoptosis and the amount of reactive oxygen species. In addition, the use of alloxan, an O-GlcNAc transferase inhibitor, and azaserine, a glutamine fructose-6-phosphate amidotransferase inhibitor, neutralized the protective effect of RIPC against oxidative stress and tubular apoptosis. In conclusion, RIPC attenuates local oxidative stress and tubular apoptosis induced by contrast exposure by enhancing O-GlcNAc glycosylation levels; this can be a potentially useful approach for lowering the risk of CI-AKI.

Damage to the myogenic differentiation of C2C12 cells by heat stress is associated with up-regulation of several selenoproteins

This study was conducted to profile the selenoprotein encoding genes or proteins in mouse C2C12 cells and integrate their roles in the skeletal cell damage induced by heat stress (HS). Cells were cultured at 37.0 °C or 41.5 °C for 4, 6 or 8 days. The mRNA expression of 24 selenoprotein encoding genes and abundance of 5 selenoproteins were investigated. HS suppressed myogenic differentiation and impaired the development of muscle myotubes. HS down-regulated (P < 0.01) mRNA abundance of MYOD and MYOGENIN, and decreased (P < 0.01) MYOGENIN protein expression, HS elevated (P < 0.01) HSP70 and (P < 0.01) the ratio of BCL-2 to BAX at both mRNA and protein level. Meanwhile, HS up-regulated (P < 0.01–0.05) expressions of 18, 11 and 8 selenoprotein encoding genes after 4, 6 and 8 days of hyperthermia, and only down-regulated (P < 0.01) DIO2 after 6 and 8 days of hyperthermia, respectively. Furthermore, HS influenced expression of selenoproteins and up-regulated (P < 0.01–0.05) GPX1, GPX4 and SEPN1 after 6 days of HS. The damage to development of mouse skeletal muscle myotubes by HS accompanied with the up-regulation of both selenoprotein encoding genes and proteins, which suggested a potential protective effect of selenoprotein on hyperthermia associated damage in C2C12 cells.

The role of heat shock proteins and co-chaperones in heart failure

The ongoing contractile and metabolic demands of the heart require a tight control over protein quality control, including the maintenance of protein folding, turnover and synthesis. In heart disease, increases in mechanical and oxidative stresses, post-translational modifications (e.g., phosphorylation), for example, decrease protein stability to favour misfolding in myocardial infarction, heart failure or ageing. These misfolded proteins are toxic to cardiomyocytes, directly contributing to the common accumulation found in human heart failure. One of the critical class of proteins involved in protecting the heart against these threats are molecular chaperones, including the heat shock protein70 (HSP70), HSP90 and co-chaperones CHIP (carboxy terminus of Hsp70-interacting protein, encoded by the Stub1 gene) and BAG-3 (BCL2-associated athanogene 3). Here, we review their emerging roles in the maintenance of cardiomyocytes in human and experimental models of heart failure, including their roles in facilitating the removal of misfolded and degraded proteins, inhibiting apoptosis and maintaining the structural integrity of the sarcomere and regulation of nuclear receptors. Furthermore, we discuss emerging evidence of increased expression of extracellular HSP70, HSP90 and BAG-3 in heart failure, with complementary independent roles from intracellular functions with important therapeutic and diagnostic considerations. While our understanding of these major HSPs in heart failure is incomplete, there is a clear potential role for therapeutic modulation of HSPs in heart failure with important contextual considerations to counteract the imbalance of protein damage and endogenous protein quality control systems.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

Redox Aspects of Chaperones in Cardiac Function

Molecular chaperones are stress proteins that allow the correct folding or unfolding as well as the assembly or disassembly of macromolecular cellular components. Changes in expression and post-translational modifications of chaperones have been linked to a number of age- and stress-related diseases including cancer, neurodegeneration, and cardiovascular diseases. Redox sensible post-translational modifications, such as S-nitrosylation, glutathionylation and phosphorylation of chaperone proteins have been reported. Redox-dependent regulation of chaperones is likely to be a phenomenon involved in metabolic processes and may represent an adaptive response to several stress conditions, especially within mitochondria, where it impacts cellular bioenergetics. These post-translational modifications might underlie the mechanisms leading to cardioprotection by conditioning maneuvers as well as to ischemia/reperfusion injury. In this review, we discuss this topic and focus on two important aspects of redox-regulated chaperones, namely redox regulation of mitochondrial chaperone function and cardiac protection against ischemia/reperfusion injury.

Protein aggregation, cardiovascular diseases, and exercise training: Where do we stand?

Cells ensure their protein quality control through the proteostasis network. Aging and age-related diseases, such as neurodegenerative and cardiovascular diseases, have been associated to the reduction of proteostasis network efficiency and, consequently, to the accumulation of protein misfolded aggregates. The decline in protein homeostasis has been associated with the development and progression of atherosclerotic cardiovascular disease, cardiac hypertrophy, cardiomyopathies, and heart failure. Exercise training is a key component of the management of patients with cardiovascular disease, consistently improving quality of life and prognosis. In this review, we give an overview on age-related protein aggregation, the role of the increase of misfolded protein aggregates on cardiovascular pathophysiology, and describe the beneficial or deleterious effects of the proteostasis network on the development of cardiovascular disease. We subsequently discuss how exercise training, a key lifestyle intervention in those with cardiovascular disease, could restore proteostasis and improve disease status.

Exosomes: A Rising Star in Falling Hearts

Although exosomes were previously recognized as a mechanism for discharging useless cellular components, growing evidence has elucidated their roles in conveying information between cells. They contribute to cell-cell communication by carrying nucleic acids, proteins and lipids that can, in turn, regulate behavior of the target cells. Recent research suggested that exosomes extensively participate in progression of diverse cardiovascular diseases (CVDs), such as myocardial infarction, cardiomyopathy, pulmonary arterial hypertension and others. Here, we summarize effects of exosome-derived molecules (mainly microRNAs and proteins) on cardiac function, to examine their potential applications as biomarkers or therapeutics in CVDs.

Pharmacological postconditioning with atorvastatin calcium attenuates myocardial ischemia/reperfusion injury in diabetic rats by phosphorylating GSK3β

Diabetes is an independent risk factor for myocardial ischemia, and many epidemiological data and laboratory studies have revealed that diabetes significantly exacerbated myocardial ischemia/reperfusion injury and ameliorated protective effects. The present study aimed to determine whether pharmacological postconditioning with atorvastatin calcium lessened diabetic myocardial ischemia/reperfusion injury, and investigated the role of glycogen synthase kinase (GSK3β) in this. A total of 72 streptozotocin-induced diabetic rats were randomly divided into six groups, and 24 age-matched male non-diabetic Sprague-Dawley rats were randomly divided into two groups. Rats all received 40 min myocardial ischemia followed by 180 min reperfusion, except sham-operated groups. Compared with the non-diabetic ischemia/reperfusion model group, the diabetic ischemia/reperfusion group had a comparable myocardial infarct size, but a higher level of serum cardiac troponin I (cTnI) and morphological alterations to their myocardial cells. Compared with the diabetic ischemia/reperfusion group, the group that received pharmacological postconditioning with atorvastatin calcium had smaller myocardial infarct sizes, lower levels of cTnI, reduced morphological alterations to myocardial cells, higher levels of p-GSK3β, heat shock factor (HSF)-1 and heat shock protein (HSP)70. The cardioprotective effect conferred by atorvastatin calcium did not attenuate myocardial ischemia/reperfusion injury following application of TDZD-8, which phosphorylates and inactivates GSK3β. Pharmacological postconditioning with atorvastatin calcium may attenuate diabetic heart ischemia/reperfusion injury in the current context. The phosphorylation of GSK3β serves a critical role during the cardioprotection in diabetic rats, and p-GSK3β may accelerate HSP70 production partially by activating HSF-1 during myocardial ischemic/reperfusion injury.

Augmented O-GlcNAc signaling via glucosamine attenuates oxidative stress and apoptosis following contrast-induced acute kidney injury in rats

Contrast-induced acute kidney injury (CI-AKI) is an iatrogenic renal injury and associated with substantial morbidity and mortality in susceptible individuals. Despite extensive study of a variety of agents for renal protection, limited strategies have been shown to be effective in the reduction of CI-AKI. O-linked β-N-acetylglucosamine (O-GlcNAc) is a post-translational regulatory modification of intracellular proteins and governs the function of numerous proteins, both cytosolic and nuclear. Increasing evidence suggests that O-GlcNAc levels are increased in response to stress and that acute augmentation of this reaction is cytoprotective. However, the underlying mechanisms by which augmented OGlcNAc signaling provides renoprotection against contrast media insults is still unknown. Here, we investigated the effect of augmented O-GlcNAc signaling via glucosamine on CI-AKI and explored the underlying molecular mechanisms, particularly its relationship with PI3-kinase (PI3K)/Akt signaling. We used a novel and reliable CI-AKI model consisting of 5/6 nephrectomized (NE) rats, and a low-osmolar contrast media (iohexol, 10mL/kg, 3.5gI) injected via the tail vein after dehydration for 48h. The results showed that augmented O-GlcNAc signaling by glucosamine prevented the kidneys against iohexol-induced injury characterized by the attenuation of renal dysfunction, tubular damage, apoptosis and oxidative stress. Furthermore, this renoprotection was blocked by treatment with alloxan, an O-GlcNAc transferase inhibitor. Augmented O-GlcNAc signaling also increased the protein expression levels of phospho-Akt (Ser473, but not Thr308 and Thr450), phospho-GSK-3β, Nrf2, and Bcl-2, and decreased the levels of Bax and cleaved caspase-3. Both alloxan and specific inhibitors of PI3K (Wortmannin and LY294002) blocked the protection of glucosamine via inhibiting Akt signaling pathway. We further identified O-GlcNAcylated Akt through immunoprecipitation and western blot. We confirmed that Akt was modified by O-GlcNAcylation, and glucosamine pretreatment increased the O-GlcNAcylation of Akt. Collectively, the results demonstrate that glucosamine induces renoprotection against CI-AKI through augmented O-GlcNAc and activation of PI3K/Akt signaling, making it a promising strategy for preventing CI-AKI.

Effects of Hypobaric Hypoxia on Rat Retina and Protective Response of Resveratrol to the Stress

High-altitude retinopathy represents retinal functional changes associated with environmental challenges imposed by hypobaric hypoxia, but the detailed cellular and molecular mechanism underlying this process remains unclear. Our current investigation was to explore the effect of hypobaric hypoxia on the rat retina and determine whether resveratrol has a protective efficacy on the hypoxic damage to the retina. Experiment rats were randomly grouped as the control group, hypoxia group and resveratrol intervention group. The hypoxia group and the resveratrol intervention group were maintained in a low-pressure oxygen cabin, and the resveratrol intervention group was given daily intraperitoneal injections with resveratrol. We found that hypobaric hypoxia increased thioredoxin 1 (Trx1) and thioredoxin 2 (Trx2) expression in retinas, and resveratrol treatment significantly reversed these changes (P < 0.05, P < 0.05 respectively). In comparison with controls, hypoxia upregulated the mRNA expression levels of caspase3 (P < 0.001), caspase9 (P < 0.01), heat shock protein 70 (Hsp70) (P < 0.05), heat shock protein 90 (Hsp90) (P < 0.001) and hypoxia-inducible factor-1 (HIF-1) (P < 0.05). Resveratrol administration caused a significant decrease in the gene expression of caspase3 (P< 0.001), HSP90 (P < 0.05) and HIF-1 mRNA (P < 0.01) as well as an increase in HSP70 mRNA when compared with the hypoxia group. These findings indicated that resveratrol exerted an anti-oxidative role by modulating hypoxia stress- associated genes and an anti-apoptosis role by regulating apoptosis-related cytokines. In conclusion, hypobaric hypoxia may have a pathological impact on rat retinas. The intervention of resveratrol reverses the effect induced by hypobaric hypoxia and elicits a protective response to the stress.

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.

HSP70: therapeutic potential in acute and chronic cardiac disease settings

Heat shock proteins are a family of proteins that are produced by cells in response to exposure to stressful conditions. The best studied heat shock protein is HSP70, which is known to act as a molecular chaperone to maintain cellular homeostasis and inhibit protein aggregation in response to stress. While early animal studies suggested that increasing HSP70 in the heart (using a transgenic, gene transfer or pharmacological approach) provided cardiac protection against acute cardiac stress, recent studies have found no benefit of increasing HSP70 in mouse models of chronic cardiac stress. As HSP70 has been considered a potential therapeutic target, it is important to comprehensively assess HSP70 therapies in preclinical models of acute and chronic cardiac disease.

Long-Term Overexpression of Hsp70 Does Not Protect against Cardiac Dysfunction and Adverse Remodeling in a MURC Transgenic Mouse Model with Chronic Heart Failure and Atrial Fibrillation

Previous animal studies had shown that increasing heat shock protein 70 (Hsp70) using a transgenic, gene therapy or pharmacological approach provided cardiac protection in models of acute cardiac stress. Furthermore, clinical studies had reported associations between Hsp70 levels and protection against atrial fibrillation (AF). AF is the most common cardiac arrhythmia presenting in cardiology clinics and is associated with increased rates of heart failure and stroke. Improved therapies for AF and heart failure are urgently required. Despite promising observations in animal studies which targeted Hsp70, we recently reported that increasing Hsp70 was unable to attenuate cardiac dysfunction and pathology in a mouse model which develops heart failure and intermittent AF. Given our somewhat unexpected finding and the extensive literature suggesting Hsp70 provides cardiac protection, it was considered important to assess whether Hsp70 could provide protection in another mouse model of heart failure and AF. The aim of the current study was to determine whether increasing Hsp70 could attenuate adverse cardiac remodeling, cardiac dysfunction and episodes of arrhythmia in a mouse model of heart failure and AF due to overexpression of Muscle-Restricted Coiled-Coil (MURC). Cardiac function and pathology were assessed in mice at approximately 12 months of age. We report here, that chronic overexpression of Hsp70 was unable to provide protection against cardiac dysfunction, conduction abnormalities, fibrosis or characteristic molecular markers of the failing heart. In summary, elevated Hsp70 may provide protection in acute cardiac stress settings, but appears insufficient to protect the heart under chronic cardiac disease conditions.

Plasma Heat Shock Proteins (HSPs) 70 and 47 levels in diabetic foot and its possible correlation with clinical variables in a North Indian Tertiary care hospital

OBJECTIVE

HSPs have been proposed to have a role in the wound healing process, supported by finding that its expression is rapidly induced after skin is wounded in animal models. Because of this phenomenon, we have made a hypothesis that circulating HSPs will have any relationship with DFU.

METHODS

The circulating levels of HSP 70 and HSP 47 were measured in diabetic patients with an ulcer (Group A: n=30), without ulcer (Group B: n=30) and healthy subjects (Group C: n=30).

RESULTS

Diabetic foot ulcer showed higher median plasma level of HSP 70 [3229.01 (1984.5-4137.1) vs 1625.7 (1435.1-2253.5) vs 1025.7 (835.1-1653.5)] ng/ml and HSP 47 [2.33 (2.118-2.58) vs 0.98 (0.83-1.07) vs 0.58 (0.42-0.68) pg/ml] of the diabetic foot, diabetic control and healthy subjects. Odds ratio and risk ratio for DFU after age adjusted were BMI (>25 kg/m(2)) [OR 1.78, RR 1.35], HbA1c>7% [OR 3.37), RR 1.76], neuropathy [OR 5.79, RR 3.13], retinopathy [OR 3.44, RR 1.82], hypertension [OR 1.54, RR 1.18], and smoking cessation [OR 4.53, RR 2.09].

CONCLUSION

In the near future, it would be interesting to find out whether this high plasma HSPs precedes in early would healing mechanism and will have a relationship with type of infections and/or nature of therapy for infection in such patients.

Cardiac and hepatic role of r-AtHSP70: basal effects and protection against ischemic and sepsis conditions

Heat shock proteins (HSPs), highly conserved in all organisms, act as molecular chaperones activated by several stresses. The HSP70 class of stress-induced proteins is the most studied subtype in cardiovascular and inflammatory disease. Because of the high similarity between plant and mammalian HSP70, the aim of this work was to evaluate whether recombinant HSP70 of plant origin (r-AtHSP70) was able to protect rat cardiac and hepatic function under ischemic and sepsis conditions. We demonstrated for the first time that, in ex vivo isolated and perfused rat heart, exogenous r-AtHSP70 exerted direct negative inotropic and lusitropic effects via Akt/endothelial nitric oxide synthase pathway, induced post-conditioning cardioprotection via Reperfusion Injury Salvage Kinase and Survivor Activating Factor Enhancement pathways, and did not cause hepatic damage. In vivo administration of r-AtHSP70 protected both heart and liver against lipopolysaccharide-dependent sepsis, as revealed by the reduced plasma levels of interleukin-1β, tumour necrosis factor alpha, aspartate aminotransferase and alanine aminotransferase. These results suggest exogenous r-AtHSP70 as a molecular modulator able to protect myocardial function and to prevent cardiac and liver dysfunctions during inflammatory conditions.

Tyrosol prevents ischemia/reperfusion-induced cardiac injury in H9c2 cells: involvement of ROS, Hsp70, JNK and ERK, and apoptosis

Ischemia-Reperfusion (I/R) injury causes ROS overproduction, creating oxidative stress, and can trigger myocyte death, resulting in heart failure. Tyrosol is an antioxidant abounded in diets and medicine. Our objective was to investigate the protective effect of tyrosol on I/R-caused mortality in H9c2 cardiomyocytes through its influence on ROS, Hsp70, ERK, JNK, Bcl-2, Bax and caspase-8. A simulated I/R model was used, myocytes loss was examined by MTT, and ROS levels were measured using DCFH-DA. Nuclear condensation and caspase-3 activity were assessed by DAPI staining and fluorometric assay. Phosphorylated ERK and JNK were determined by electrochemiluminescent ELISA, and Hsp70, Bcl-2, Bax and caspase-8 were examined by Western blotting. Results show that tyrosol salvaged myocyte loss, inhibited nuclear condensation and caspase-3 activity dose-dependently, indicating its protection against I/R-caused myocyte loss. Furthermore, tyrosol significantly inhibited ROS accumulation and activation of ERK and JNK, augmenting Hsp70 expression. Besides, tyrosol inhibited I/R-induced apoptosis, associated with retained anti-apoptotic Bcl-2 protein, and attenuated pro-apoptotic Bax protein, resulting in a preservation of Bcl-2/Bax ratio. Finally, tyrosol notably decreased cleaved caspase-8 levels. In conclusion, cytoprotection of tyrosol in I/R-caused myocyte mortality was involved with the mitigation of ROS, prohibition of the activation of ERK, JNK and caspase-8, and elevation of Hsp70 and Bcl-2/Bax ratio.

Hsp70 regulates the doxorubicin-mediated heart failure in Hsp70-transgenic mice

The aim of this study was to investigate the potential protective effect of the Hsp70 protein in the cardiac dysfunction induced by doxorubicin (DOX) and the mechanisms of its action. For this purpose, we used both wild-type mice (F1/F1) and Hsp70-transgenic mice (Tg/Tg) overexpressing human HSP70. Both types were subjected to chronic DOX administration (3 mg/kg intraperitoneally every week for 10 weeks, with an interval from weeks 4 to 6). Primary cell cultures isolated from embryos of these mice were also studied. During DOX administration, the mortality rate as well as weight reduction were lower in Tg/Tg compared to F1/F1 mice (P < 0.05). In vivo cardiac function assessment by transthoracic echocardiography showed that the reduction in left ventricular systolic function observed after DOX administration was lower in Tg/Tg mice (P < 0.05). The study in primary embryonic cell lines showed that the apoptosis after incubation with DOX was reduced in cells overexpressing Hsp70 (Tg/Tg), while the apoptotic pathway that was activated by DOX administration involved activated protein factors such as p53, Bax, caspase-9, caspase-3, and PARP-1. In myocardial protein extracts from identical mice with DOX-induced heart failure, the particular activated apoptotic pathway was confirmed, while the presence of Hsp70 appeared to inhibit the apoptotic pathway upstream of the p53 activation. Our results, in this DOX-induced heart failure model, indicate that Hsp70 overexpression in Tg/Tg transgenic mice provides protection from myocardial damage via an Hsp70-block in p53 activation, thus reducing the subsequent apoptotic mechanism.

Overexpression of the muscle-specific protein, melusin, protects from cardiac ischemia/reperfusion injury

Melusin is a muscle-specific protein which interacts with β1 integrin cytoplasmic domain and acts as chaperone protein. Its overexpression induces improved resistance to cardiac overload delaying left ventricle dilation and reducing the occurrence of heart failure. Here, we investigated possible protective effect of melusin overexpression against acute ischemia/reperfusion (I/R) injury with or without Postconditioning cardioprotective maneuvers. Melusin transgenic (Mel-TG) mice hearts were subjected to 30-min global ischemia followed by 60-min reperfusion. Interestingly, infarct size was reduced in Mel-TG mice hearts compared to wild-type (WT) hearts (40.3 ± 3.5 % Mel-TG vs. 59.5 ± 3.8 % WT hearts; n = 11 animals/group; P < 0.05). The melusin protective effect was also demonstrated by measuring LDH release, which was 50 % lower in Mel-TG compared to WT. Mel-TG hearts had a higher baseline level of AKT, ERK1/2 and GSK3β phosphorylation, and displayed increased phospho-kinases level after I/R compared to WT mice. Post-ischemic Mel-TG hearts displayed also increased levels of the anti-apoptotic factor phospho-BAD. Importantly, pharmacological inhibition of PI3K/AKT (Wortmannin) and ERK1/2 (U0126) pathways abrogated the melusin protective effect. Notably, HSP90, a chaperone known to protect heart from I/R injury, showed high levels of expression in the heart of Mel-TG mice suggesting a possible collaboration of this molecule with AKT/ERK/GSK3β pathways in the melusin-induced protection. Postconditioning, known to activate AKT/ERK/GSK3β pathways, significantly reduced IS and LDH release in WT hearts, but had no additive protective effects in Mel-TG hearts. These findings implicate melusin as an enhancer of AKT and ERK pathways and as a novel player in cardioprotection from I/R injury.

Keep your heart in shape: molecular chaperone networks for treating heart disease

Despite major advances in the treatment of cardiac diseases, there is still a great need for drugs capable of counteracting the deterioration of cardiac muscle function in congestive heart failure. The role of misfolded protein accumulation as a causal event in the physiopathology of common cardiac diseases is an important emerging concept. Indeed, diverse stress conditions, including mechanical stretching and oxidative stress, can induce misfolded protein accumulation, causing cardiomyocyte death. Cells react to these stress conditions by activating molecular chaperones, a class of proteins that represents an endogenous salvage machinery, essential for rescuing physiological cell functions and sustaining cell survival. Chaperones, also known as heat shock proteins (Hsps), prevent accumulation of damaged proteins by promoting either their refolding or degradation via the proteasome or the autophagosome systems. In addition, molecular chaperones play a key role in intracellular signalling by controlling conformational changes required for activation/deactivation of signalling proteins, and their assembly in specific signalosome complexes. The key role of molecular chaperones in heart function is highlighted by the fact that a number of genetic mutations in chaperone proteins result in different forms of cardiomyopathies. Moreover, a considerable amount of experimental evidence indicates that increasing expression of chaperone proteins leads to an important cardio-protective role in ischaemia/reperfusion injury, heart failure, and arrhythmia, implicating these molecules as potential innovative therapeutic agents.

Regulation of heat shock proteins 27 and 70, p-Akt/p-eNOS and MAPKs by Naringin Dampens myocardial injury and dysfunction in vivo after ischemia/reperfusion

Naringin has antioxidant properties that could improve redox-sensitive myocardial ischemia reperfusion (IR) injury. This study was designed to investigate whether naringin restores the myocardial damage and dysfunction in vivo after IR and the mechanisms underlying its cardioprotective effects. Naringin (20–80 mg/kg/day, p.o.) or saline were administered to rats for 14 days and the myocardial IR injury was induced on 15^th day by occluding the left anterior descending coronary artery for 45 min and subsequent reperfusion for 60 min. Post-IR rats exhibited pronounced cardiac dysfunction as evidenced by significantly decreased mean arterial pressure, heart rate, +LVdP/dt_max (inotropic state), -LVdP/dt_max (lusitropic state) and increased left ventricular end diastolic pressure as compared to sham group, which was improved by naringin. Further, on histopathological and ultrastructural assessments myocardium and myocytes appeared more normal in structure and the infarct size was reduced significantly in naringin 40 and 80 mg/kg/day group. This amelioration of post-IR-associated cardiac injury by naringin was accompanied by increased nitric oxide (NO) bioavailability, decreased NO inactivation to nitrotyrosine, amplified protein expressions of Hsp27, Hsp70, β-catenin and increased p-eNOS/eNOS, p-Akt/Akt, and p-ERK/ERK ratio. In addition, IR-induced TNF-α/IKK-β/NF-κB upregulation and JNK phosphorylation were significantly attenuated by naringin. Moreover, western blotting and immunohistochemistry analysis of apoptotic signaling pathway further established naringin cardioprotective potential as it upregulated Bcl-2 expression and downregulated Bax and Caspase-3 expression with reduced TUNEL positivity. Naringin also normalized the cardiac injury markers (lactate dehydrogenase and creatine kinase-MB), endogenous antioxidant activities (superoxide dismutase, reduced glutathione and glutathione peroxidase) and lipid peroxidation levels. Thus, naringin restored IR injury by preserving myocardial structural integrity and regulating Hsp27, Hsp70, p-eNOS/p-Akt/p-ERK signaling and inflammatory response.

Cytoprotective regulation of the mitochondrial permeability transition pore is impaired in type 2 diabetic Goto-Kakizaki rat hearts

Our recent studies indicated that up-regulation of calcineurin activity and unfolded protein responses (UPRs) disrupt cytoprotective Akt- and ERK-signaling in OLETF, a model of obese type 2 diabetes (T2DM). To determine whether the mechanisms can be generalized, we used Goto-Kakizaki rats (GK), a model of non-obese T2DM, in this study. Infarct sizes after 20-min ischemia/2-h reperfusion were similar in GK and non-diabetic controls, Wistar rats (Wistar). However, erythropoietin (EPO) limited infarct size in Wistar (64.0±5.3% vs. 45.7±4.4%, p<0.05) but not in GK (56.2±2.2% vs. 52.6±2.3%). Levels of calcineurin activity and EPO-induced phosphorylation of Akt and ERK were similar in GK and Wistar, though cytosolic HSP70 level was 50% lower and mitochondrial HSP60 level was 60% higher in GK. EPO preserved mitochondrial calcium retention capacity (CRC), an index of the threshold for opening of the mitochondrial permeability transition pore (mPTP), after ischemia/reperfusion in Wistar but not in GK. Interaction of cyclophilin D (CypD) with mitochondrial inorganic phosphate carrier (PiC), which sensitizes the mPTP, was enhanced in GK. There was a negative exponential relationship between CypD-PiC interaction and CRC upon reperfusion, indicating that increase in CRC by reduction of CypD-PiC interaction is smaller when CypD-PiC interaction level is at a higher range. A chemical chaperone, 4-phenylbutyric acid, attenuated the changes in HSPs and CypD-PiC interaction and restored responses of CRC and infarct size to EPO in GK. These results suggest that cytoprotective regulation of the mPTP is impaired in GK by enhanced CypD-PiC interaction in which UPRs are involved.

Carboxyl terminus of heat shock protein 70-interacting protein inhibits angiotensin II-induced cardiac remodeling

BACKGROUND

The carboxyl terminus of heat shock protein 70-interacting protein (CHIP), an E3 ligase/chaperone, was found to protect cardiomyocytes against apoptosis induced by ischemic injury; however, the functional role of CHIP in remodeling induced by angiotensin II (Ang II) remains unclear.

METHODS

We generated CHIP-overexpressed transgenic (TG) mice infused with Ang II (1,500 ng/kg/min) or saline for days or small interfering RNA (siRNA) knockdown of neonatal rat cardiomyocytes. Heart sections were stained with hematoxylin and eosin, Masson trichrome, TdT-mediated dUTP nick-end labeling (TUNEL) staining, and immunohistochemistry, and the levels of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPK) were measured by western blot analysis.

RESULTS

Seven days after Ang II infusion, cardiac-specific overexpression of CHIP significantly enhanced cardiac contractile performance in mice and attenuated cardiac apoptosis, fibrosis, and inflammation: the number of TUNEL-positive cells, fibrotic areas, macrophage infiltration, and the expression of interleukin-1β (IL-1β), IL-6, monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule-1 (ICAM-1) in heart tissues were decreased as compared with wild-type (WT) mice (all P < 0.05). In contrast, CHIP siRNA knockdown markedly increased Ang II-induced apoptosis and the expression of proinflammatory cytokines, as compared with siRNA control. The mechanisms underlying these beneficial actions were associated with CHIP-mediated inhibition of NF-κB and MAPK (p38 and JNK) pathways.

CONCLUSIONS

CHIP plays an important role in regulating Ang II-triggered hypertensive cardiac apoptosis, inflammation, and fibrosis.

Dynamic microRNA expression during the transition from right ventricular hypertrophy to failure

MicroRNAs (miRs) are small, noncoding RNAs that are emerging as crucial regulators of cardiac remodeling in left ventricular hypertrophy (LVH) and failure (LVF). However, there are no data on their role in right ventricular hypertrophy (RVH) and failure (RVF). This is a critical question given that the RV is uniquely at risk in patients with congenital right-sided obstructive lesions and in those with systemic RVs. We have developed a murine model of RVH and RVF using pulmonary artery constriction (PAC). miR microarray analysis of RV from PAC vs. control demonstrates altered miR expression with gene targets associated with cardiomyocyte survival and growth during hypertrophy (miR 199a-3p) and reactivation of the fetal gene program during heart failure (miR-208b). The transition from hypertrophy to heart failure is characterized by apoptosis and fibrosis (miRs-34, 21, 1). Most are similar to LVH/LVF. However, there are several key differences between RV and LV: four miRs (34a, 28, 148a, and 93) were upregulated in RVH/RVF that are downregulated or unchanged in LVH/LVF. Furthermore, there is a corresponding downregulation of their putative target genes involving cell survival, proliferation, metabolism, extracellular matrix turnover, and impaired proteosomal function. The current study demonstrates, for the first time, alterations in miRs during the process of RV remodeling and the gene regulatory pathways leading to RVH and RVF. Many of these alterations are similar to those in the afterload-stressed LV. miRs differentially regulated between the RV and LV may contribute to the RVs increased susceptibility to heart failure.

Hypoxia and reoxygenation modulate the arrhythmogenic activity of the pulmonary vein and atrium

Ischaemia and reperfusion contribute to the genesis of AF (atrial fibrillation). PVs (pulmonary veins) and the atria are important foci for AF initiation and maintenance. However, the effect of ischaemia and reperfusion on PVs and the atria has not yet been fully elucidated. In the present study, conventional microelectrodes were used to record the APs (action potentials) in isolated rabbit PV, LA (left atrium) and RA (right atrium) specimens during hypoxia and reoxygenation, and pharmacological interventions. Hypoxia reduced the PV beating rates from 1.8±0.1 to 1.3±0.2 and 0.8±0.1 Hz at 30 and 60 min respectively (n=8, P<0.005), and induced EAD (early after depolarization) in three (37.5%) of the PVs and DAD (delayed after depolarization) in one (12.5%) of the PVs. Reoxygenation increased the PV spontaneous rate to 1.4±0.2 Hz (P<0.05) and induced PV burst firings (3.5±0.1 Hz, P<0.001) in six (75%) of the PVs. Hypoxia shortened the AP duration in the LA and PVs, but not in the RA. Pretreatment with glibenclamide attenuated hypoxia-induced decreases in the PV spontaneous activity and the shortening of the LA and PV AP duration. Similar to those in hypoxia, the K(ATP) (ATP-sensitive potassium) channel opener pinacidil (30 μM) decreased PV spontaneous activity and shortened the AP duration. Pretreatment with 5 mM N-MPG [N-(mercaptopropionyl)glycine; a hydroxyl (•OH) free-radical scavenger] or 300 μM chloramphenicol [a cytochrome P450 inhibitor that reduces ROS (reactive oxygen species)] attenuated the rate changes induced by hypoxia and reoxygenation, and also decreased the burst firing incidence. In conclusion, hypoxia and reoxygenation significantly increased PV arrhythmogenesis and induced different electrophysiological responses in the RA and LA, which may play a role in the pathophysiology of AF.

Extracellular heat shock protein 70 induces cardiomyocyte inflammation and contractile dysfunction via TLR2

BACKGROUND

Toll-like receptors (TLRs) are expressed on cardiomyocytes and recognize pathogen-associated molecular patterns. Whether endogenous molecules produced by tissue injury (damage associated molecular patterns, DAMPs) can induce cardiomyocyte inflammation via TLR signalling pathways and/or reduce cardiomyocyte contractility is unknown.

METHODS AND RESULTS

Primary cardiomyocytes isolated from nuclear factor κ B (NFκB)-luciferase knock-in mice were used to assess NFκB signalling. DAMPs, HSP60, HSP70 and HMGB1, increased NFκB transcriptional activity compared to controls. HSP70 stood out compared to other DAMPs and even lipopolysaccharide (LPS). Subsequent experiments focused on HSP70. Cardiomyocytes exposed to HSP70 had a 58% decrease in contractility without a decrease in calcium flux. Exposure of cultured HL-1 cardiomyocytes to HSP70 resulted in increased expression of intercellular adhesion molecule 1 (ICAM-1), interleukin 6 (IL-6) and keratinocyte-derived chemokine (KC) compared to controls. Knock-out mice for TLR2, TLR4 and MyD88, plus background strain controls (C57BL/6) were used to assess induction of cardiomyocyte inflammation by HSP70. The cardiomyocyte expression of ICAM-1 induced by HSP70 was significantly reduced in TLR2 and MyD88 knock-out mice but not TLR4 knock-out mice; implicating the TLR2 signalling pathway. Furthermore, blocking antibodies to TLR2 were able to abrogate HSP70-induced contractile dysfunction and cell death.

CONCLUSIONS

Extracellular HSP70 acting via TLR2 and its obligate downstream adaptor molecule, MyD88, activate NFκB. This causes cardiomyocyte inflammation and decreased contractility.

Gene transfer as a strategy to achieve permanent cardioprotection I: rAAV-mediated gene therapy with inducible nitric oxide synthase limits infarct size 1 year later without adverse functional consequences

The ultimate goal of prophylactic gene therapy is to confer permanent protection against ischemia. Although gene therapy with inducible nitric oxide synthase (iNOS) is known to protect against myocardial infarction at 3 days and up to 2 months, the long-term effects on myocardial ischemic injury and function are unknown. To address this issue, we created a recombinant adeno-associated viral vector carrying the iNOS gene (rAAV/iNOS), which enables long-lasting transgene expression. The ability of rAAV/iNOS to direct the expression of functional iNOS protein was confirmed in COS-7 cells before in vivo gene transfer. Mice received injections in the anterior LV wall of rAAV/LacZ or rAAV/iNOS; 1 year later, they underwent a 30-min coronary occlusion (O) and 4 h of reperfusion (R). iNOS gene transfer resulted in elevated iNOS protein expression (+3-fold vs. the LacZ group, n = 6; P < 0.05) and iNOS activity (+4.4-fold vs. the LacZ group, n = 6; P < 0.05) 1 year later. Infarct size (% of risk region) was dramatically reduced at 1 year after iNOS gene transfer (13.5 ± 2.2%, n = 12, vs. 41.7 ± 2.9%, n = 10, in the LacZ group; P < 0.05). The infarct-sparing effect of iNOS gene therapy at 1 year was as powerful as that observed 24 h after ischemic preconditioning (six 4-min O/4-min R cycles) (19.3 ± 2.3%, n = 11; P < 0.05). Importantly, compared with the LacZ group (n = 11), iNOS gene transfer (n = 10) had no effect on LV dimensions or function for up to 1 year (at 1 year: FS 34.5 ± 2.0 vs. 34.6 ± 2.6%, EF 57.0 ± 2.0 vs. 59.7 ± 2.9%, LVEDD 4.3 ± 0.1 vs. 4.2 ± 0.2 mm, LVESD 2.8 ± 0.1 vs. 2.9 ± 0.2 mm) (echocardiography). These data demonstrate, for the first time, that rAAV-mediated iNOS gene transfer affords long-term, probably permanent (1 year), cardioprotection without adverse functional consequences, providing a strong rationale for further preclinical testing of prophylactic gene therapy.

Role of microRNAs in cardiac preconditioning

Preconditioning (PC) of the heart by sublethal ischemia, mild heat shock, or hypoxia has evolved as a powerful experimental tool to discover novel signaling mechanisms in cardioprotection. The ultimate goal is to determine novel therapeutic targets for potential application in humans to protect the heart against ischemia-related injuries. In recent years, there has been a tremendous interest in understanding the role of small noncoding RNAs, microRNAs (miRs), in cardiovascular diseases. miRs have been recognized as regulators of gene expression by destabilization and translational inhibition of target messenger RNAs. Studies have shown that several miRs, including miR-1, miR-133, miR-21, miR-126, miR-320, miR-92a, and miR-199a, are regulated after preconditioning and play an active role in protecting the heart against ischemia/reperfusion injury. These miRs also drive the synthesis of important cardioprotective proteins including heat shock protein (HSP)-70, endothelial nitric oxide synthase, inducible nitric oxide synthase, HSP-20, Sirt1, and hypoxia-inducible factor 1a. We believe that identification and targeted delivery of miR(s) in the heart could have an immense therapeutic potential in reducing myocardial infarction in patients suffering from heart disease.

Responses of muscle mass, strength and gene transcripts to long-term heat stress in healthy human subjects

The present study was performed to investigate the effects of long-term heat stress on mass, strength and gene expression profile of human skeletal muscles without exercise training. Eight healthy men were subjected to 10-week application of heat stress, which was performed for the quadriceps muscles for 8 h/day and 4 days/week by using a heat- and steam-generating sheet. Maximum isometric force during knee extension of the heated leg significantly increased after heat stress (~5.8%, P < 0.05). Mean cross-sectional areas (CSAs) of vastus lateralis (VL, ~2.7%) and rectus femoris (~6.1%) muscles, as well as fiber CSA (8.3%) in VL, in the heated leg were also significantly increased (P < 0.05). Statistical analysis of microarrays (SAM) revealed that 10 weeks of heat stress increased the transcript level of 925 genes and decreased that of 1,300 genes, and gene function clustering analysis (Database for Annotation, Visualization and Integrated Discovery: DAVID) showed that these regulated transcripts stemmed from diverse functional categories. Transcript level of ubiquinol-cytochrome c reductase binding protein (UQCRB) was significantly increased by 10 weeks of heat stress (~3.0 folds). UQCRB is classified as one of the oxidative phosphorylation-associated genes, suggesting that heat stress can stimulate ATP synthesis. These results suggested that long-term application of heat stress could be effective in increasing the muscle strength associated with hypertrophy without exercise training.

Heat-stress responses modulate beta-adrenergic agonist and angiotensin II effects on the arrhythmogenesis of pulmonary vein cardiomyocytes

INTRODUCTION

Heat stress-induced responses reduce the occurrence of atrial fibrillation (AF). Pulmonary vein (PV) cardiomyocytes with pacemaker activity play a critical role in the pathophysiology of AF. In this study, we examined whether heat-stress responses alter the electrophysiological characteristics of PV cardiomyocytes and protect the PV against angiotensin II- or isoproterenol-induced arrhythmogenesis.

METHODS AND RESULTS

We used whole-cell patch clamp techniques to investigate the spontaneous activity and ionic currents in single isolated rabbit PV pacemaker cardiomyocytes with or without (control) exposure to heat stress (43°C, 15 minutes) 5 ± 1 hours before the experiments. Compared to control cardiomyocytes, heat-stressed PV cardiomyocytes had slower beating rates. Heat-stressed PV cardiomyocytes had larger L-type calcium currents, transient outward currents, smaller inward rectifier potassium currents, but similar sodium-calcium exchanger currents. Additionally, heat-stressed PV cardiomyocytes had a lower incidence of pacemaker currents than control PV cardiomyocytes. Moreover, isoproterenol increased the beating rate of control cardiomyocytes but not heat-stressed PV cardiomyocytes. Similarly, angiotensin II also increased the beating rate of control cardiomyocytes, but not heat-stressed PV cardiomyocytes, in association with decreased expression of the angiotensin II type 1 receptor.

CONCLUSION

Heat-stress responses altered the electrophysiological characteristics of PV cardiomyocytes and attenuated the effects of isoproterenol and angiotensin II on PV arrhythmogenesis, which may play a role in the protective potential of heat-stress responses.

Gene therapy for ischemic heart disease

Current pharmacologic therapy for ischemic heart disease suffers multiple limitations such as compliance issues and side effects of medications. Revascularization procedures often end with need for repeat procedures. Patients remain symptomatic despite maximal medical therapy. Gene therapy offers an attractive alternative to current pharmacologic therapies and may be beneficial in refractory disease. Gene therapy with isoforms of growth factors such as VEGF, FGF and HGF induces angiogenesis, decreases apoptosis and leads to protection in the ischemic heart. Stem cell therapy augmented with gene therapy used for myogenesis has proven to be beneficial in numerous animal models of myocardial ischemia. Gene therapy coding for antioxidants, eNOS, HSP, mitogen-activated protein kinase and numerous other anti apoptotic proteins have demonstrated significant cardioprotection in animal models. Clinical trials have demonstrated safety in humans apart from symptomatic and objective improvements in cardiac function. Current research efforts are aimed at refining various gene transfection techniques and regulation of gene expression in vivo in the heart and circulation to improve clinical outcomes in patients that suffer from ischemic heart disease. In this review article we will attempt to summarize the current state of both preclinical and clinical studies of gene therapy to combat myocardial ischemic disease. This article is part of a Special Section entitled "Special Section: Cardiovascular Gene Therapy".

Hsp20-engineered mesenchymal stem cells are resistant to oxidative stress via enhanced activation of Akt and increased secretion of growth factors

Although heat-shock preconditioning has been shown to promote cell survival under oxidative stress, the nature of heat-shock response from different cells is variable and complex. Therefore, it remains unclear whether mesenchymal stem cells (MSCs) modified with a single heat-shock protein (Hsp) gene are effective in the repair of a damaged heart. In this study, we genetically engineered rat MSCs with Hsp20 gene (Hsp20-MSCs) and examined cell survival, revascularization, and functional improvement in rat left anterior descending ligation (LAD) model via intracardial injection. We observed that overexpression of Hsp20 protected MSCs against cell death triggered by oxidative stress in vitro. The survival of Hsp20-MSCs was increased by approximately twofold by day 4 after transplantation into the infarcted heart, compared with that of vector-MSCs. Furthermore, Hsp20-MSCs improved cardiac function of infarcted myocardium as compared with vector-MSCs, accompanied by reduction of fibrosis and increase in the vascular density. The mechanisms contributing to the beneficial effects of Hsp20 were associated with enhanced Akt activation and increased secretion of growth factors (VEGF, FGF-2, and IGF-1). The paracrine action of Hsp20-MSCs was further validated in vitro by cocultured adult rat cardiomyocytes with a stress-conditioned medium from Hsp20-MSCs. Taken together, these data support the premise that genetic modification of MSCs before transplantation could be salutary for treating myocardial infarction.

Mesenchymal stem cells pretreated with delivered Hph-1-Hsp70 protein are protected from hypoxia-mediated cell death and rescue heart functions from myocardial injury

Mesenchymal stem cell (MSC) therapy for myocardial injury has inherent limitations due to the poor viability of MSCs after cell transplantation. In this study, we directly delivered Hsp70, a protein with protective functions against stress, into MSCs, using the Hph-1 protein transduction domain ex vivo for high transfection efficiency and low cytotoxicity. Compared to control MSCs in in vitro hypoxic conditions, MSCs delivered with Hph-1-Hsp70 (Hph-1-Hsp70-MSCs) displayed higher viability and anti-apoptotic properties, including Bcl2 increase, reduction of Bax, JNK phosphorylation and caspase-3 activity. Hsp70 delivery also attenuated cellular ATP-depleting stress. Eight animals per group were used for in vivo experiments after occlusion of the left coronary artery. Transplantation of Hph-1-Hsp70-MSCs led to a decrease in the fibrotic heart area, and significantly reduced the apoptotic positive index by 19.5 +/- 2%, compared to no-treatment controls. Hph-1-Hsp70-MSCs were well-integrated into the infarcted host myocardium. The mean microvessel count per field in the infarcted myocardium of the Hph-1-Hsp70-MSC-treated group (122.1 +/- 13.5) increased relative to the MSC-treated group (75.9 +/- 10.4). By echocardiography, transplantation of Hph-1-Hsp70-MSCs resulted in additional increases in heart function, compared to the MSCs-transplanted group. Our results may help formulate better clinical strategies for in vivo MSC cell therapy for myocardial damage.

Cardioprotection by CaMKII-deltaB is mediated by phosphorylation of heat shock factor 1 and subsequent expression of inducible heat shock protein 70

RATIONALE

Ca2+/calmodulin-dependent protein kinase (CaMK)II is a multifunctional kinase involved in vital cellular processes such as Ca(2+) handling and cell fate regulation. In mammalian heart, 2 primary CaMKII isoforms, deltaB and deltaC, localize in nuclear and cytosolic compartments, respectively. Although previous studies have established an essential role of CaMKII-deltaC in cardiomyocyte apoptosis, the functional role of the more abundant isoform, CaMKII-deltaB, remains elusive.

OBJECTIVE

Here, we determined the potential role of CaMKII-deltaB in regulating cardiomyocyte viability and explored the underlying mechanism.

METHODS AND RESULTS

In cultured neonatal rat cardiomyocytes, the expression of CaMKII-deltaB and CaMKII-deltaC was inversely regulated in response to H2O2-induced oxidative stress with a profound reduction of the former and an increase of the later. Similarly, in vivo ischemia/reperfusion (IR) led to an opposite regulation of these CaMKII isoforms in a rat myocardial IR model. Notably, overexpression of CaMKII-deltaB protected cardiomyocytes against oxidative stress-, hypoxia-, and angiotensin II-induced apoptosis, whereas overexpression of its cytosolic counterpart promoted apoptosis. Using cDNA microarray, real-time PCR and Western blotting, we demonstrated that overexpression of CaMKII-deltaB but not CaMKII-deltaC elevated expression of heat shock protein (HSP)70 family members, including inducible (i)HSP70 and its homolog (Hst70). Moreover, overexpression of CaMKII-deltaB led to phosphorylation and activation of heat shock factor (HSF)1, the primary transcription factor responsible for HSP70 gene regulation. Importantly, gene silencing of iHSP70, but not Hst70, abolished CaMKII-deltaB-mediated protective effect, indicating that only iHSP70 was required for CaMKII-deltaB elicited antiapoptotic signaling.

CONCLUSIONS

We conclude that cardiac CaMKII-deltaB and CaMKII-deltaC were inversely regulated in response to oxidative stress and IR injury, and that in contrast to CaMKII-deltaC, CaMKII-deltaB serves as a potent suppressor of cardiomyocyte apoptosis triggered by multiple death-inducing stimuli via phosphorylation of HSF1 and subsequent induction of iHSP70, marking both CaMKII-delta isoforms as promising therapeutic targets for the treatment of ischemic heart disease.

Controlled delivery of heat shock protein using an injectable microsphere/hydrogel combination system for the treatment of myocardial infarction

Myocardial infarction causes a high rate of morbidity and mortality worldwide, and heat shock proteins as molecular chaperones have been attractive targets for protecting cardiomyoblasts under environmental stimuli. In this study, in order to enhance the penetration of heat shock protein 27 (HSP27) across cell membranes, we fused HSP27 with transcriptional activator (TAT) derived from human immunodeficiency virus (HIV) as a protein transduction domain (PTD). We loaded the fusion protein (TAT-HSP27) into microsphere/hydrogel combination delivery systems to control the release behavior for prolonged time periods. We found that the release behavior of TAT-HSP27 was able to be controlled by varying the ratio of PLGA microspheres and alginate hydrogels. Indeed, the released fusion protein maintained its bioactivity and could recover the proliferation of cardiomyoblasts cultured under hypoxic conditions. This approach to controlling the release behavior of TAT-HSP27 using microsphere/hydrogel combination delivery systems may be useful for treating myocardial infarction in a minimally invasive manner.

Hsp70 and cardiac surgery: molecular chaperone and inflammatory regulator with compartmentalized effects

Open heart surgery is a unique model to study the interplay between cellular injury, regulation of inflammatory responses and tissue repair. Stress-inducible heat shock protein 70-kDa (Hsp70) provides a molecular link between these events. In addition to molecular chaperoning, Hsp70 exerts modulatory effects on endothelial cells and leukocytes involved in inflammatory networks. Hsp70 residing in the intracellular compartment is part of an inhibitory feedback loop that acts on nuclear factor kappaB (NF-kappaB). In contrast, extracellular Hsp70 is recognized by multiple germline-encoded immune receptors, e.g., Toll-like receptor (TLR) 2, TLR4, LOX-1, CD91, CD94, CCR5 and CD40. Hsp70 is thereby able to enhance chemotaxis, phagocytosis and cytolytic activity of innate immune cells and stimulate antigen-specific responses. These apparent contradictory pro- and anti-inflammatory effects of endogenous Hsp70 in the context of cardiac surgery are still not fully understood. An all-embracing model of the compartmentalized effects of endogenous Hsp70 in the orchestration of inflammatory responses in cardiac surgery is proposed.

Activation of caspase-3 may not contribute to postresuscitation myocardial dysfunction

We have previously reported that postresuscitation myocardial dysfunction is accompanied by the release of cytochrome c and caspase-3 activation. We now investigated the role of caspase-3 activation by examining whether such process prompts apoptotic DNA fragmentation, whether caspase-3 inhibition attenuates myocardial dysfunction, and whether myocardial protective effects of sodium-hydrogen exchanger isoform-1 (NHE-1) inhibition involve caspase-3 inhibition using a rat model of ventricular fibrillation (VF) of closed-chest resuscitation. Resuscitation after 4 or 8 min of untreated VF caused significant reductions in left ventricular stroke work index averaging 23% of sham control rats at 4 h postresuscitation. Left ventricular dysfunction was accompanied by increases in cytosolic cytochrome c, decreases in pro- and cleaved caspase-9 fragments, increases in 17-kDa caspase-3 fragments, and increases in caspase-3 activity indicating the activation of the mitochondrial apoptotic pathway but without evidence of apoptotic DNA fragmentation. In addition, levels of heat shock protein 70 were increased and levels of X-linked inhibitor of apoptosis protein and alphabeta-crystallin were preserved, all of which can exert antiapoptotic effects. In a separate series, the caspase-3 inhibitor z-Asp-Glu-Val-Asp chloromethyl ketone given before the induction of VF failed to prevent postresuscitation myocardial dysfunction despite reductions in caspase-3 activity (2.3 +/- 0.5 vs. 1.3 +/- 0.5 pmol fluorophore AFC released.mg protein(-1).min-1; P < 0.03). Treatment with the NHE-1 inhibitor cariporide had no effect on caspase-3 activity. Accordingly, in this rat model of VF and severe postresuscitation myocardial dysfunction, activation of caspase-3 did not lead to DNA fragmentation or contribute to myocardial dysfunction. Concomitant activation of intrinsic antiapoptotic mechanisms could play a protective role downstream to caspase-3 activation.

Toll-like receptor signaling: a critical modulator of cell survival and ischemic injury in the heart

Toll-like receptors (TLRs) represent the first line of host defense against microbial infection and play a pivotal role in both innate and adaptive immunity. TLRs recognize invading pathogens through molecular pattern recognition, transduce signals via distinct intracellular pathways involving a unique set of adaptor proteins and kinases, and ultimately lead to the activation of transcription factors and inflammatory responses. Among 10 TLRs identified in humans, at least two exist in the heart, i.e., TLR2 and TLR4. In addition to the critical role of these in mediating cardiac dysfunction in septic conditions, emerging evidence suggests that the TLRs can also recognize endogenous ligands and may play an important role in modulating cardiomyocyte survival and in ischemic myocardial injury. In animal models of ischemia-reperfusion injury or in hypoxic cardiomyocytes in vitro, the administration of a sublethal dose of lipopolysaccharide, which signals through TLR4, reduces subsequent myocardial infarction, improves cardiac functions, and attenuates cardiomyocyte apoptosis. By contrast, a systemic deficiency of TLR2, TLR4, or myeloid differentiation primary-response gene 88, an adaptor critical for all TLR signaling, except TLR3, leads to an attenuated myocardial inflammation, a smaller infarction size, a better preserved ventricular function, and a reduced ventricular remodeling after ischemic injury. These loss-of-function studies suggest that both TLRs contribute to myocardial inflammation and ischemic injury in the heart although the exact contribution of cardiac (vs. circulatory cell) TLRs remains to be defined. These recent studies demonstrate an emerging role for TLRs as a critical modulator in both cell survival and tissue injury in the heart.