Overexpression of heat shock protein 72 in transgenic mice decreases infarct size in vivo

Targeting mitochondrial shape: at the heart of cardioprotection

There remains an unmet need to identify novel therapeutic strategies capable of protecting the myocardium against the detrimental effects of acute ischemia-reperfusion injury (IRI), to reduce myocardial infarct (MI) size and prevent the onset of heart failure (HF) following acute myocardial infarction (AMI). In this regard, perturbations in mitochondrial morphology with an imbalance in mitochondrial fusion and fission can disrupt mitochondrial metabolism, calcium homeostasis, and reactive oxygen species production, factors which are all known to be critical determinants of cardiomyocyte death following acute myocardial IRI. As such, therapeutic approaches directed at preserving the morphology and functionality of mitochondria may provide an important strategy for cardioprotection. In this article, we provide an overview of the alterations in mitochondrial morphology which occur in response to acute myocardial IRI, and highlight the emerging therapeutic strategies for targeting mitochondrial shape to preserve mitochondrial function which have the future therapeutic potential to improve health outcomes in patients presenting with AMI.

Efficacy of Siwan Traditional Therapy on Erythrocyte Sedimentation Rate, Lipid Profile, and Atherogenic Index as Cardiac Risk Factors Related to Rheumatoid Arthritis

Background and Objectives: The most frequent cause of mortality in rheumatoid arthritis (RA) patients is cardiovascular disease (CVD). Inflammation, dyslipidemia, and decreased physical activity are some of the main risk factors for CVD. Siwan sand therapy is a type of traditional therapy used in Egypt to treat RA. The approach of this therapy depends on the experience of the healers. The aim of the current study was to compare the effects of three sessions of Siwan traditional therapy to five sessions on common CVD risk factors and physical function in rheumatoid arthritis patients. Materials and Methods: Thirty patients (9 male and 21 female) were assigned into two groups of equal size: group (A) received three sessions of Siwan traditional therapy in the form of a sand bath. Group (B) received the same form of therapy for five days. Erythrocyte sedimentation rate (ESR), lipid profile, atherogenic index of plasma (AIP), and a health assessment questionnaire (HAQ) were measured before and after treatment. Results: There was a significant increase above normal within group (A) for ESR (p = 0.001), triglycerides (TG; p = 0.015), total cholesterol (Tot-Chol; p = 0.0001), and low-density lipoprotein (LDL; p = 0.0001). However, there were no considerable differences in high-density lipoprotein (HDL; p = 0.106), very low-density lipoprotein (VLDL; p = 0.213), AIP (p = 0.648), and HAQ (p = 0.875). For the second group, there were significant changes within group B only in Tot-Chol (p = 0.0001), HDL (p = 0.0001), VLDL (p = 0.0001), AIP (p = 0.008), and HAQ (p = 0.014). There was a significant difference between both groups regarding HDL (p = 0.027), LDL (p = 0.005), AIP (p = 0.029), ESR (p = 0.016), and HAQ (p = 0.036). Conclusions: For RA patients, five days of Siwan traditional therapy caused significant changes regarding inflammation, Tot-Chol, LDL, HDL, AIP, and functional activity when compared to three days of Siwan hot sand therapy.

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.

Stochastic and Age-Dependent Proteostasis Decline Underlies Heterogeneity in Heat-Shock Response Dynamics

Significant non-genetic stochastic factors affect aging, causing lifespan differences among individuals, even those sharing the same genetic and environmental background. In Caenorhabditis elegans, differences in heat-shock response (HSR) are predictive of lifespan. However, factors contributing to the heterogeneity of HSR are still not fully elucidated. Here, the authors characterized HSR dynamics in isogenic C. elegans expressing GFP reporter for hsp-16.2 for identifying the key contributors of HSR heterogeneity. Specifically, microfluidic devices that enable cross-sectional and longitudinal measurements of HSR dynamics in C. elegans at different scales are developed: in populations, within individuals, and in embryos. The authors adapted a mathematical model of HSR to single C. elegans and identified model parameters associated with proteostasis-maintenance of protein homeostasis-more specifically, protein turnover, as the major drivers of heterogeneity in HSR dynamics. It is verified that individuals with enhanced proteostasis fidelity in early adulthood live longer. The model-based comparative analysis of protein turnover in day-1 and day-2 adult C. elegans revealed a stochastic-onset of age-related proteostasis decline that increases the heterogeneity of HSR capacity. Finally, the analysis of C. elegans embryos showed higher HSR and proteostasis capacity than young adults and established transgenerational contribution to HSR heterogeneity that depends on maternal age.

Exercise and cardiac health: physiological and molecular insights

The cardiac benefits of exercise have been recognized for centuries. Studies have undisputedly shown that regular exercise is beneficial for the cardiovascular system in young, old, healthy and diseased populations. For these reasons, physical activity has been recommended worldwide for cardiovascular disease prevention and treatment. Although the benefits of exercise are clear, understanding of the molecular triggers that orchestrate these effects remains incomplete and has been a topic of intense research in recent years. Here, we provide a comprehensive review of the cardiac effects of physical activity, beginning with a brief history of exercise in cardiovascular medicine and then discussing seminal work on the physiological effects of exercise in healthy, diseased and aged hearts. Later, we revisit pioneering work on the molecular mechanisms underlying the cardiac benefits of exercise, and we conclude with our view on the translational potential of this knowledge as a powerful platform for cardiovascular disease drug discovery.

Mechanisms Involved in Cardioprotection Induced by Physical Exercise

Significance: Regular exercise training can reduce myocardial damage caused by acute ischemia/reperfusion (I/R). Exercise can reproduce the phenomenon of ischemic preconditioning, due to the capacity of brief periods of ischemia to reduce myocardial damage caused by acute I/R. In addition, exercise may also activate the multiple kinase cascade responsible for cardioprotection even in the absence of ischemia. Recent Advances: Animal and human studies highlighted the fact that, besides to reduce risk factors related to cardiovascular disease, the beneficial effects of exercise are also due to its ability to induce conditioning of the heart. Exercise behaves as a physiological stress that triggers beneficial adaptive cellular responses, inducing a protective phenotype in the heart. The factors contributing to the exercise-induced heart preconditioning include stimulation of the anti-radical defense system and nitric oxide production, opioids, myokines, and adenosine-5'-triphosphate (ATP) dependent potassium channels. They appear to be also involved in the protective effect exerted by exercise against cardiotoxicity related to chemotherapy. Critical Issues and Future Directions: Although several experimental evidences on the protective effect of exercise have been obtained, the mechanisms underlying this phenomenon have not yet been fully clarified. Further studies are warranted to define precise exercise prescriptions in patients at risk of myocardial infarction or undergoing chemotherapy.

Exercise Training Induced Cardioprotection with Moderate Hyperglycemia versus Sedentary Intensive Glycemic Control in Type 1 Diabetic Rats

Intensive insulin therapy (IIT; 4-7 mmol/L) is the preferred treatment for type 1 diabetes mellitus (T1DM) patients to reduce the risk of cardiovascular disease (CVD). However, this treatment strategy has been questioned as it is accompanied with a sedentary lifestyle leading to weight gain and insulin resistance. T1DM patients who partake in high-intensity aerobic training (AThigh) to reduce CVD often utilize conventional insulin therapy (CIT; 9-15 mmol/L) to offset the risk of hypoglycemia. Moreover, exercise modalities incorporating resistance training (RT) have been shown to further reduce this risk. The purpose of this investigation was twofold: (1) to determine if CIT paired with AThigh results in larger cardioprotection from an ischemia-reperfusion (I-R) injury than IIT and (2) to establish if the integration of RT with AThigh (ART) results in similar cardioprotection as AThigh. Diabetic (D) male Sprague-Dawley rats were divided into D-IIT (n = 12), D-CIT (n = 12), D-AThigh (n = 8), D-RT (n = 8), and D-ART (n = 8). T1DM was induced with streptozotocin, and blood glucose was adjusted with insulin. D-AThigh occurred on a treadmill (27 m/min; 1 hr), D-RT performed weighted ladder climbs, and D-ART alternated daily between AThigh and RT. Exercise occurred 5 days/wk for 12 wks. This investigation demonstrates that cardioprotection following an I-R injury was similar between D-AThigh and D-IIT. This cardioprotection is not exercise-specific, and each provides unique advantages. D-AThigh leads to improved glycemia while insulin sensitivity was enhanced following resistance exercises. Thus, exercise is an effective means to elicit cardioprotection in T1DM. However, in addition to glycemia, other factors should be considered when tailoring an exercise program for T1DM patients.

Cardioprotective Effects of HSP72 Administration on Ischemia-Reperfusion Injury

BACKGROUND

Although early reperfusion is the most desirable intervention after ischemic myocardial insult, it may add to damage through oxidative stress.

OBJECTIVES

This study investigated the cardioprotective effects of a single intravenous dose of heat shock protein-72 (HSP72) coupled to a single-chain variable fragment (Fv) of monoclonal antibody 3E10 (3E10Fv) in a rabbit ischemia-reperfusion model. The Fv facilitates rapid transport of HSP72 into cells, even with intact membranes.

METHODS

A left coronary artery occlusion (40 min) reperfusion (3 h) model was used in 31 rabbits. Of these, 12 rabbits received the fusion protein (Fv-HSP72) intravenously. The remaining 19 control rabbits received a molar equivalent of 3E10Fv alone (n = 6), HSP72 alone (n = 6), or phosphate-buffered saline (n = 7). Serial echocardiographic examinations were performed to assess left ventricular function before and after reperfusion. Micro-single-photon emission computed tomography imaging of ^99mTc-labeled annexin-V was performed with micro-computed tomography scanning to characterize apoptotic damage in vivo, followed by gamma counting of the excised myocardial specimens to quantify cell death. Histopathological characterization of the myocardial tissue and sequential cardiac troponin I measurements were also undertaken.

RESULTS

Myocardial annexin-V uptake was 43% lower in the area at risk (p = 0.0003) in Fv-HSP72-treated rabbits compared with control animals receiving HSP72 or 3E10Fv alone. During reperfusion, troponin I release was 42% lower and the echocardiographic left ventricular ejection fraction 27% higher in the Fv-HSP72-treated group compared with control animals. Histopathological analyses confirmed penetration of 3E10Fv-containing molecules into cardiomyocytes in vivo, and treatment with Fv-HSP72 showed fewer apoptotic nuclei compared with control rabbits.

CONCLUSIONS

Single-dose administration of Fv-HSP72 fusion protein at the time of reperfusion reduced myocardial apoptosis by almost one-half and improved left ventricular functional recovery after myocardial ischemia-reperfusion injury in rabbits. It might have potential to serve as an adjunct to early reperfusion in the management of myocardial infarction.

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.

Hsp70 inducer, 17-allylamino-demethoxygeldanamycin, provides neuroprotection via anti-inflammatory effects in a rat model of traumatic brain injury

Traumatic brain injury (TBI) is the predominant cause of mortality in young adults and children living in China. TBI induces inflammatory responses; in addition, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 are important pro-inflammatory cytokines. Considering the observation that Hsp-70 overexpression can exert neuroprotection, identifying a drug that is able to induce the upregulation of Hsp70 has the potential to be a promising therapy for the treatment of neurological diseases. Thus, the present study assessed the clinical effectiveness of an anticancer drug and Hsp70 activator, 17-allylamino-demethoxygeldanamycin (17-AAG), to evaluate its potential as a treatment for patients with TBI. The aim of present study was to determine the neuroprotective effects of 17-AAG following trauma and to investigate the underlying mechanisms of action. To establish rat models, rats were subjected to a controlled cortical impact injury and randomly divided into vehicle or 17-AAG groups. In the 17-AAG group, rats were administered with an intraperitoneal injection of 17-AAG (80 mg/kg) immediately following the establishment of TBI. The motor function was measured using Neurologic Severity Score, and neuronal death was evaluated using immunofluorescence. The expression levels of GLT-1, Bcl-2 and Hsp-70 were detected by western blot analysis and the expression levels of inflammatory cytokines were quantified using ELISA. The present study determined that 17-AAG significantly reduced brain edema and motor neurological deficits (P<0.05), in addition to increasing neuronal survival. The aforementioned findings are associated with a downregulation of the expression levels of pro-inflammatory cytokines TNF-α, IL-1β and IL-6. Conversely, no significant changes of glutamate transporter-1 expression were observed. The present results suggest that 17-AAG treatment may provide a neuroprotective effect by reducing inflammation following TBI.

Expression and location of HSP60 and HSP10 in the heart tissue of heat-stressed rats

The present study aimed to analyze the expression levels and localizations of heat shock protein (HSP) 60 and HSP10 in the heart tissue of rats subjected to heat stress (42°C) for 0, 20, 80 and 100 min. Histopathological injuries and increased serum activities of serum lactate dehydrogenase and creatine kinase isoenzyme MB were detected in the heated rat myocardial cells. These results suggested that heat stress-induced acute degeneration may be sufficient to cause sudden death in animals by disrupting the function and permeability of the myocardial cell membrane. In addition, the expression levels of HSP60 were significantly increased following 20 min heat stress, whereas the expression levels of its cofactor HSP10 were not. Furthermore, the location of HSP60, but not of HSP10, was significantly altered during periods of heat stress. These results suggested that HSP60 in myocardial tissue may be more susceptive to the effects of heat stress as compared with HSP10, and that HSP10 is constitutively expressed in the heart of rats. The expression levels and localizations of HSP60 and HSP10 at the different time points of heat stress were not similar, which suggested that HSP60 and HSP10 may not form a complex in the heart tissue of heat-stressed rats.

Rivaroxaban, a factor Xa inhibitor, induces the secondary prevention of cardiovascular events after myocardial ischemia reperfusion injury in mice

OBJECTIVES

Rivaroxaban has been shown to reduce overall death from cardiovascular causes in patients with recent acute coronary syndrome. Therefore, we evaluated the secondary prevention of cardiovascular events after myocardial ischemia reperfusion injury and its mechanisms in mice.

METHODS

After myocardial reperfusion injury, C57BL/6J mice were randomized to receive either no treatment or treatment for 14days with low and high doses of rivaroxaban. After 7days, mice were administered tissue factor as a secondary event.

RESULTS

Based on a Kaplan-Meier curve analysis, the high-dose rivaroxaban group showed a significantly higher % survival than the no-treatment group from day 7 (after the administration of tissue factor) to day 14 (at the end of the experimental period). Left ventricular (LV) ejection fraction in both the low- and high-dose rivaroxaban groups improved compared to that in the no-treatment group. Moreover, mRNA levels of interleukin-6 and collagens 1α2 and 3α1 in the LV in the high-dose group were significantly suppressed compared to those in the no-treatment group.

CONCLUSIONS

Rivaroxaban improved the survival rate, probably by improving cardiac function through the reduction of inflammatory and fibrotic factors in the LV. This effect may be due to the pleiotropic effects of rivaroxaban beyond its main effect as an anti-coagulant.

Heat shock protein 72 may improve hypotension by increasing cardiac mechanical efficiency and arterial elastance in heatstroke rats

OBJECTIVE

We attempted to test the hypothesis that preinduction of heat shock protein (HSP) 72 in the heart would improve left ventricular performance in rat heatstroke.

METHODS

Cardiac expression of HSP 72 was quantitatively evaluated by western blot analysis in rats 0h, 12h, or 72h after mild heat preconditioning (MHP; 43°C for 30min). They were subjected to severe heat stress (SHS; 43°C for 70min) to induce heatstroke. A 1.2F catheter-tip pressure transducer was inserted into the left ventricle of these group rats under general anesthesia to record hemodynamic in the closed chest with a pressure-volume loop module data recording and analysis system.

RESULTS

At the time point of heatstroke onset, compared with normothermic controls, group rats with 12h post-MHP had significantly increased cardiac HSP 72, decreased hyperthermia, decreased hypotension, decreased bradycardia, increased end-systolic pressure, increased end-diastolic pressure, increased stroke volume, decreased end-systolic volume, decreased end-diastolic pressure, increased cardiac output, increased ejection fraction, increased stroke work, increased arterial elastance, and decreased time constant of fall in ventricular pressure by Glantz-methods. With the loss of cardiac HSP 72 expression observed at 72h in post-MHP group rats, an insignificant protection against left ventricular performance was observed.

CONCLUSION

Preinduction of cardiac HSP 72 may improve hypotension in heatstroke rats by increasing both cardiac mechanical efficiency and arterial elastance.

The interactive association between heat shock factor 1 and heat shock proteins in primary myocardial cells subjected to heat stress

Heat shock factor 1 (HSF1) is a heat shock transcription factor that rapidly induces heat shock gene transcription following thermal stress. In this study, we subjected primary neonatal rat myocardial cells to heat stress in vitro to create a model system for investigating the trends in expression and association between various heat shock proteins (HSPs) and HSF1 under adverse environmental conditions. After the cells were subjected to heat stress at 42˚C for different periods of time, HSP and HSF1 mRNA and protein levels were detected by qPCR and western blot analysis in the heat-stressed cells. The HSF1 expression levels significantly increased in the cells following 120 min of exposure to heat stess compared to the levels observed at the beginning of heat stress exposure. HSP90 followed a similar trend in expression to HSF1, whereas HSP70 followed an opposite trend. However, no significant changes were observed in the crystallin, alpha B (CRYAB, also known as HSP beta-5) expression levels during the 480‑min period of exposure to heat stress. The interaction between the HSPs and HSF1 was analyzed by STRING 9.1, and it was found that HSF1 interacted with HSP90 and HSP70, and that it did not play a role in regulating CRYAB expression. Based on our findings, HSP70 may suppress HSF1 in rat myocardial cells under conditions of heat stress. Furthermore, our data demonstrate that HSF1 is not the key factor for all HSPs, and this was particularly the case for CRYAB.

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.

Genetic manipulation of cardiac Hsp72 levels does not alter substrate metabolism but reveals insights into high-fat feeding-induced cardiac insulin resistance

Heat shock protein 72 (Hsp72) protects cells against a variety of stressors, and multiple studies have suggested that Hsp72 plays a cardioprotective role. As skeletal muscle Hsp72 overexpression can protect against high-fat diet (HFD)-induced insulin resistance, alterations in substrate metabolism may be a mechanism by which Hsp72 is cardioprotective. We investigated the impact of transgenically overexpressing (Hsp72 Tg) or deleting Hsp72 (Hsp72 KO) on various aspects of cardiac metabolism. Mice were fed a normal chow (NC) or HFD for 12 weeks from 8 weeks of age to examine the impact of diet-induced obesity on metabolic parameters in the heart. The HFD resulted in an increase in cardiac fatty acid oxidation and a decrease in cardiac glucose oxidation and insulin-stimulated cardiac glucose clearance; however, there was no difference in Hsp72 Tg or Hsp72 KO mice in these rates compared with their respective wild-type control mice. Although HFD-induced cardiac insulin resistance was not rescued in the Hsp72 Tg mice, it was preserved in the skeletal muscle, suggesting tissue-specific effects of Hsp72 overexpression on substrate metabolism. Comparison of two different strains of mice (BALB/c vs. C57BL/6J) also identified strain-specific differences in regard to HFD-induced cardiac lipid accumulation and insulin resistance. These strain differences suggest that cardiac lipid accumulation can be dissociated from cardiac insulin resistance. Our study finds that genetic manipulation of Hsp72 does not lead to alterations in metabolic processes in cardiac tissue under resting conditions, but identifies mouse strain-specific differences in cardiac lipid accumulation and insulin-stimulated glucose clearance.

Ischemia-reperfusion injury and hypoglycemia risk in insulin-treated T1DM rats following different modalities of regular exercise

While regular exercise is known to improve cardiovascular function, individuals with type 1 diabetes mellitus (T1DM) have an increased risk for exercise-induced hypoglycemia. Clinical data suggest that higher intensities of acute exercise may alleviate the onset of hypoglycemia; however, the cardiovascular benefit from these forms of exercise in patients with T1DM has yet to be established. The purpose of this study was to investigate the cardiovascular benefit of different regular exercise regimes, while monitoring blood glucose concentrations during the post-exercise period. Fifty rats (8-week-old Sprague-Dawley male) were equally divided into the following groups: nondiabetic sedentary (C), diabetic sedentary (DS), diabetic low-intensity aerobic exercise (DL), diabetic high-intensity aerobic exercise (DH) or diabetic resistance exercise (DR). Diabetes was induced using multiple streptozotocin injections (5×; 20 mg/kg) while subcutaneous insulin pellets maintained glycemia in a range typical for individuals that exercise with T1DM. Exercise consisted of six weeks of treadmill running (DL and DH) or weighted ladder climbs (DR). The cardiovascular benefit of each exercise program was determined by the myocardial recovery from ischemia-reperfusion injury. Exercise-related cardiovascular protection was dependent on the exercise modality, whereby DH demonstrated the greatest protection following an ischemic-reperfusion injury. Each exercise modality caused a significant decline in blood glucose in the post-exercise period; however, blood glucose levels did not reach hypoglycemic concentrations (<3.0 mmol/L) throughout the exercise intervention. These results suggest that elevating blood glucose concentrations prior to exercise allows patients with T1DM to perform exercise that is beneficial to the myocardium without the accompanying risk of hypoglycemia.

Mechanisms of exercise-induced cardioprotection

Myocardial ischemia-reperfusion (IR) injury can cause ventricular cell death and is a major pathological event leading to morbidity and mortality in those with coronary artery disease. Interestingly, as few as five bouts of exercise on consecutive days can rapidly produce a cardiac phenotype that resists IR-induced myocardial injury. This review summarizes the development of exercise-induced cardioprotection and the mechanisms responsible for this important adaptive response.

Pre-clinical functional Magnetic Resonance Imaging Part II: The heart

One third of all deaths worldwide in 2008 were caused by cardiovascular diseases (CVD), and the incidence of CVD related deaths rises ever more. Thus, improved imaging techniques and modalities are needed for the evaluation of cardiac morphology and function. Cardiac magnetic resonance imaging (CMRI) is a minimally invasive technique that is increasingly important due to its high spatial and temporal resolution, its high soft tissue contrast and its ability of functional and quantitative imaging. It is widely accepted as the gold standard of cardiac functional analysis. In the short period of small animal MRI, remarkable progress has been achieved concerning new, fast imaging schemes as well as purpose-built equipment. Dedicated small animal scanners allow for tapping the full potential of recently developed animal models of cardiac disease. In this paper, we review state-of-the-art cardiac magnetic resonance imaging techniques and applications in small animals at ultra-high fields (UHF).

Cardiac stem cells with electrical stimulation improve ischaemic heart function through regulation of connective tissue growth factor and miR-378

AIMS

In this study, we investigated whether pre-conditioning (PC) by electrical stimulation (EleS) induces cytoprotective effect on cardiac stem cells (CSCs) and determined its underlying molecular mechanisms.

METHODS AND RESULTS

Sca-1(+) CSCs were isolated from male C57BL6 mice (12 weeks) hearts. PC of CSCs with EleS ((EleS)CSCs) was carried out for 3 h at 1.5 V followed by exposure to 300 µM H2O2 for 5 h. Cytoprotective effects and cell adhesion ability were significantly increased by EleS as evaluated by transferase-mediated dUTP nick-end labelling (TUNEL), lactate dehydrogenase (LDH) release assay, and adhesion assay. EleS increased phosphorylation of AKT, focal adhesion kinase (FAK), and glycogen synthase kinase (GSK3β), as well as decreased caspase-3 cleavage. Interestingly, inhibition of AKT or FAK abolished the pro-survival effects of EleS. We found that connective tissue growth factor (Ctgf) was responsible for EleS-induced CSC survival and adhesion.The survival rate of (EleS)CSCs after transplantation in the infarcted myocardium was significantly increased together with improvement in cardiac function. Importantly, knockdown of Ctgf abolished EleS-induced cytoprotective effects and recovery of cardiac function. Furthermore, we identified miR-378 as a potential Ctgf regulator in (EleS)CSCs.

CONCLUSION

EleS enhanced CSC survival in vitro and in vivo as well as functional recovery of the ischaemic heart through an AKT/FAK/CTGF signalling pathway. It is suggested that Ctgf and miR-378 are novel therapeutic targets for stem cell-based therapy.

Tongguan Capsule Protects against Myocardial Ischemia and Reperfusion Injury in Mice

Myocardial ischemia/reperfusion (I/R) can induce lethal ventricular arrhythmia and myocardial infarction. One of the clinical strategies for managing patients with high risk of myocardial I/R is to prevent the occurrence of arrhythmias and limit the size of infarction following a coronary episode. Tongguan Capsule (TGC) is one of the popular herbal remedies in treating coronary artery disease in the clinics of Chinese medicine. However, the potential roles and mechanisms of TGC in reducing I/R injury are still unclear. The present study statistically assessed the effectiveness of TGC in reducing I/R injury by comparing the infarct size (IS), risk region (RR), and arrhythmia (in electrocardiogram) among four groups of surgically created mice models of myocardial I/R: SHAM, I/R, VER (I/R with verapamil 20 mg/kg pretreatment), and TGC (I/R with TGC 5 g/kg/d pretreatment). We found that IS was significantly smaller in the TGC and VER groups than I/R group, and the incidence of arrhythmias was reduced in the TGC group compared with I/R group, although there were no differences in RR among the four groups. We conclude that TGC is effective in reducing I/R injury in mice. These results provided an experimental basis for clinical application of TGC in reducing I/R injury.

A model of poorly controlled type 1 Diabetes Mellitus and its treatment with aerobic exercise training

BACKGROUND

Modern exogenous insulin therapy can improve the quality of life of Type 1 Diabetic Mellitus (T1DM) patients, although maintenance of normal glycaemic levels is often a challenge given the variety of factors that alter it. A number of studies have examined the effect of exercise in T1DM; however, the majority of experimental studies have utilized diabetic rodents with severe hyperglycaemia. Given that T1DM patients are likely to refrain from hyperglycaemia, studies examining the effects of regular exercise in which blood glucose is poorly controlled would better represent the T1DM population.

METHODS

The current study examined the ability of a ten-week aerobic exercise training program to modify markers of cardiovascular function and bone health in STZ-induced diabetic rodents maintained in the 9-15 mM glycaemic range through insulin therapy.

RESULTS

Moderate hyperglycaemia, when prolonged, leads to significant changes in cardiac structure, bone health, and glucose handling capacity. Ten weeks of exercise was able to alleviate many of these deleterious events as no significant cardiovascular functional alterations were evident except a reduction in resting heart rate and an increase in stroke volume index. Further, despite changes in cardiac dimensions, exercise was able to elevate cardiac output index and increase the E/A ratio of exercising diabetic animals which would be indicative of improvements of cardiac function.

CONCLUSIONS

Together, this study demonstrates that despite moderate hyperglycaemia, the combined role of a ten-week exercise training program coupled with insulin therapy is able to alleviate many of the well-known complications associated with diabetes progression.

Anandamide enhances expression of heat shock protein 72 to protect against ischemia-reperfusion injury in rat heart

Anandamide (AEA), one of endocannabinoids, has been reported to exhibit a cardioprotective ability to limit the damage produced by ischemia-reperfusion injury. AEA reportedly enhanced heat shock protein 72 (HSP72) and HSP25 expression in lungs to protect against lung inflammation. This study tested the hypothesis that intravenously injected AEA would induce HSP72 in the heart and thus render cardioprotection against ischemia-reperfusion injury in rats. Cardiac expression of HSPs was quantitatively evaluated in rats by Western blot analysis. That intravenously injected AEA 1 mg/kg in vivo induced expression of HSP72, which peaked at 24 h after administration. The enhancement of HSP72 by AEA was blocked by cannabinoid 2 (CB(2)) receptor antagonist AM630, but not cannabinoid 1 (CB(1)) receptor antagonist AM251. Therefore, the rats were induced with a 30-min coronary occlusion followed by a 120-min reperfusion in vivo at 24 h after administration of drugs or vehicle, and then the infarct size was measured. AEA reduced myocardial infarct size compared to control group. Pretreatment with AM630 but not AM251 abolished the infarct size-limiting effect of AEA. Further study demonstrated pretreatment with phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, Akt inhibitor MK-2206 and AM630 attenuated phosphorylation of Akt and AEA-induced HSP72 expression. The results suggest that AEA is cardioprotective against ischemia-reperfusion insult through its induction of HSP72, which might be mediated by the PI3K/Akt signaling pathway. These effects were mediated by CB(2) but not CB(1) receptors.

There are many potential medical therapies for atraumatic osteonecrosis

Atraumatic osteonecrosis is a common complication of SLE and is seen in other connective tissue diseases, in patients treated with high doses of CSs, in HIV-infected patients and in alcoholic patients. Standard care is confined to analgesia, core decompression if the condition is early and affects the femoral head and joint replacement. However, consideration of the underlying biological mechanisms leads to the recognition of many potential therapies that might either prevent progression or, even, reverse the process if it is not yet too far advanced. These potential therapies merit detailed consideration. Critical points are that (i) histopathological evidence shows that the initial cellular event is apoptosis of osteocytes; and (ii) another requisite, as homeostasis requires that death and rebirth of osteocytes be balanced, is an accompanying inadequate proliferative capacity of osteoblasts. Thus, a logical approach to treatment includes measures that (i) reduce apoptosis of osteocytes and (ii) enhance proliferation of osteoblasts/pre-osteoblasts. Measures to reduce the ongoing apoptosis of osteocytes require reinforcing the effects of members of the Bcl-2 family (Bcl-2 itself and Mcl-1), the Wnt/catenin pathways (using an available sclerostin antibody) and HSPs (by application of local heat using US, deep wave diathermy or infrared), as well as administration of bisphosphonates and nitrates. Measures to enhance proliferation of osteoblasts/pre-osteoblasts include the use of stem cells, extracorporeal shock wave therapy, aspirin, the proteosome inhibitor bortezomib, melatonin and application of local heat. Use of VEGF would encourage proliferation of blood vessels and osteogenesis. Certain drugs that inhibit osteoblast proliferation should be avoided, including NSAIDs, serotonin reuptake inhibitors and thiazolidinediones.

Genetic background, gender, age, body temperature, and arterial blood pH have a major impact on myocardial infarct size in the mouse and need to be carefully measured and/or taken into account: results of a comprehensive analysis of determinants of infarct size in 1,074 mice

In order to determine whether the myocardial response to ischemia/reperfusion (I/R) injury varies depending on genetic background, gender, age, body temperature, and arterial blood pH, we studied 1,074 mice from 19 strains (including 129S6/SvEvTac (129S6), B6/129P2-Ptgs2(tm1Unc), B6/129SvF(2)/J, B6/129/D2, B6/CBAF1, B6/DBA/1JNcr, BALB/c, BPH2/J, C57BL/6/J (B6/J), C3H/DBA, C3H/FB/FF, C3H/HeJ-Pde6b(rd1), FVB/N/J [FVB/N], FVB/B6, FVB/ICR and Crl:ICR/H [ICR]) and distributed them into 69 groups depending on strain and: (1) two phases of ischemic preconditioning (PC); (2) coronary artery occlusion (O) time; (3) gender; (4) age; (5) blood transfusion; (6) core body temperature; and (7) arterial blood pH. Mice underwent O either without (non-preconditioned [naive]) or with prior cyclic O/reperfusion (R) (PC stimulus) consisting of six 4-min O/4-min R cycles 10 min (early PC, EPC) or 24 h (late PC, LPC) prior to 30 or 45-min O and 24 h R. In B6/J and B6/129/D2 mice, almost the entire risk region was infarcted after a 60-min O. Of the naive mouse hearts, B6/ecSOD(WT) and FVB/N mice had infarct sizes significantly smaller than those of the other mice. All strains except FVB/N benefited from the cardioprotection afforded by the early phase of PC; in contrast, development of LPC was inconsistent amongst groups and was strain-dependent. Female gender (1) was associated with reduced infarct size in ICR mice, (2) determined whether LPC developed in ICR mice, and (3) limited the protection afforded by EPC in 129S6 mice. Importantly, mild hypothermia (1 °C decrease in core temperature) and mild acidosis (0.18 decrease in blood pH) resulted in a striking cardioprotective effect in ICR mice: 67.5 and 43.0 % decrease in infarct size, respectively. Replacing blood losses with crystalloid fluids (instead of blood) during surgery also reduced infarct size. To our knowledge, this is the largest analysis of the determinants of infarct size in mice ever published. The results demonstrate that genetic background, gender, age (but not in ICR), body temperature and arterial blood pH have a major impact on infarct size, and thus need to be carefully measured and/or taken into account when designing a study of myocardial infarction in mice; failure to do so makes results uninterpretable. For example, core temperature and blood pH need to be measured, respiratory acidosis (or alkalosis) and hypothermia (or hyperthermia) must be avoided, and comparisons cannot be made between mouse strains or genders that exhibit different susceptibility to I/R injury (e.g., FVB/N male mice and ICR female mice are inherently protected against I/R injury).

Mitochondrial therapeutics for cardioprotection

Mitochondria represent approximately one-third of the mass of the heart and play a critical role in maintaining cellular function-however, they are also a potent source of free radicals and pro-apoptotic factors. As such, maintaining mitochondrial homeostasis is essential to cell survival. As the dominant source of ATP, continuous quality control is mandatory to ensure their ongoing optimal function. Mitochondrial quality control is accomplished by the dynamic interplay of fusion, fission, autophagy, and mitochondrial biogenesis. This review examines these processes in the heart and considers their role in the context of ischemia-reperfusion injury. Interventions that modulate mitochondrial turnover, including pharmacologic agents, exercise, and caloric restriction are discussed as a means to improve mitochondrial quality control, ameliorate cardiovascular dysfunction, and enhance longevity.

Effect of an 8-weeks aerobic training program in elderly on oxidative stress and HSP72 expression in leukocytes during antioxidant supplementation

OBJECTIVE

To investigate the effect of aerobic training in the context of antioxidant supplementation on systemic oxidative stress and leukocytes heat shock protein (Hsp)72 expression in the elderly.

DESIGN

Sixteen septuagenarians (8 males and 8 females, mean age 74.6) were supplemented with Vitamin C and E (respectively 500 and 100mg per day) and randomly assigned either to sedentary (AS) or individualized aerobically trained (AT) group for 8 weeks.

METHODS

Plasma Vitamin C and E concentrations and aerobic fitness, as well as resting and post graded exercise (GXT) Hsp72 expression in leukocytes, plasma levels of thiobarbituric acid reactive substances (TBARS) and advanced oxidation protein product (AOPP) were measured pre and post training / supplementation.

RESULTS

At the end of the intervention, the two groups showed a significant increase in resting plasma vitamin C and E (approximately 50 and 20% increase respectively) and a significant decrease in both resting and post GXT plasma TBARS and AOPP (approximately 25 and 20% decrease respectively). These changes were of similar magnitude in the two groups. The reduced oxidative stress was concomitant with a 15% decreased expression of Hsp72 in monocytes and granulocytes in both groups.

CONCLUSION

This study provides evidence that in elderly, increased concentration of antioxidant vitamins C and E is associated with a reduction in oxidative stress and leukocytes Hsp72. In this context, 8 weeks of aerobic training has no impact on oxidative stress or leukocytes Hsp72 expression in elderly people.

Mucosal tolerance induction in autoimmune myocarditis and myocardial infarction

BACKGROUND

Antigen-specific therapy is a compelling approach for the treatment of autoimmune conditions. Primary goal is to induce the specific tolerization of self-reactive immune cells without altering host immunity against pathogens. We studied the effects of mucosal tolerance induction on cTnI-induced experimental autoimmune myocarditis (EAM) and post-infarct remodeling.

METHODS

Mucosal tolerance was induced by intranasal application of cTnI, alternatively anti-CD3 p.o. Protocols varied in frequency, dosage and time point of application before EAM. We then applied the most effective regimen to mice undergoing myocardial infarction in order to verify its effectiveness in post-infarct cardiac remodeling. The myocardium was evaluated on histological slides and for the cytokine secretion pattern, while echocardiography determined cardiac function.

RESULTS

A single dose of 100 μg of cTnI 7 days prior to myocarditis appeared to be most effective in suppressing inflammation and fibrosis (p = 0.03), while improving fractional shortening (p = 0.02). Treatment with intranasal cTnI upregulated IL-10 expression. On the other hand, frequent intranasal application of high doses of cTnI increased myocardial inflammation. Anti-CD3 p.o. showed the propensity to reduce myocardial inflammation and improve cardiac function. The single dose regimen of i.n. cTnI applied 7 days before a myocardial infarction reduced inflammation by trend (p=0.07) and improved heart function (p=0.002). Moreover, expression of matrix metalloproteinases 9 and 14 significantly decreased when treated with intranasal cTnI (p<0.01).

CONCLUSIONS

Depending on the optimal amount, the time period and the choice of antigen, effective mucosal tolerance can be achieved and represents an appealing therapeutic approach in the inflammatory process of cardiac remodeling.

Causes and mechanisms of intrauterine hypoxia and its impact on the fetal cardiovascular system: a review

Until today the role of oxygen in the development of the fetus remains controversially discussed. It is still believed that lack of oxygen in utero might be responsible for some of the known congenital cardiovascular malformations. Over the last two decades detailed research has given us new insights and a better understanding of embryogenesis and fetal growth. But most importantly it has repeatedly demonstrated that oxygen only plays a minor role in the early intrauterine development. After organogenesis has taken place hypoxia becomes more important during the second and third trimester of pregnancy when fetal growth occurs. This review will briefly adress causes and mechanisms leading to intrauterine hypoxia and their impact on the fetal cardiovascular system.

Heat-shock protein 60 and cardiovascular disease: a paradoxical role

Heat-shock proteins (HSPs) are members of a highly conserved group of proteins that are induced in response to stress and injury. These proteins have protective properties, and can protect the heart from injury. HSP60 is found in the mitochondria and cytosol, and has essential intracellular functions including folding key proteins after their import into the mitochondria. In the cytosol, HSP60 binds to proapoptotic proteins, sequestering them. HSPs are highly conserved and, thus, are similar to bacterial proteins. Many individuals have antibodies to HSP60, possibly from prior infections. HSP60 can be found in the plasma membrane and in the serum in disease states. Serum HSP60 may be a marker for coronary artery disease. Once extracellular, HSP60 can cause cell injury. Thus, this protein has dichotomous functions for which the role in disease remains to be fully elucidated.

Induction of heat shock proteins for protection against oxidative stress

Heat shock proteins (Hsps) have been studied for many years and there is now a large body of evidence that demonstrates the role of Hsp upregulation in tissue and cell protection in a wide variety of stress conditions. Oxidative stress is known to be involved in a number of pathological conditions, including neurodegeneration, cardiovascular disease and stroke, and even plays a role in natural aging. In this review we summarize the current understanding of the role of Hsps and the heat shock response (HSR) in these pathological conditions and discuss the therapeutic potential of an Hsp therapy for these disorders. However, although an Hsp based therapy appears to be a promising approach for the treatment of diseases that involve oxidative damage, there are some significant hurdles that must be overcome before this approach can be successful. For example, to be effective an Hsp based therapy will need to ensure that the upregulation of Hsps occurs in the right place (i.e. be cell specific), at the right time and to a level and specificity that ensures that all the important binding partners, namely the co-chaperones, are also present at the appropriate levels. It is therefore unlikely that strategies that involve genetic modifications that result in overexpression of specific Hsps will achieve such sophisticated and coordinated effects. Similarly, it is likely that some pharmaceutical inducers of Hsps may be too generic to achieve the desired specific effects on Hsp expression, or may simply fail to reach their target cells due to delivery problems. However, if these difficulties can be overcome, it is clear that an effective Hsp based therapy would be of great benefit to the wide range of depilating conditions in which oxidative stress plays a critical role.

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.

Interaction between Hsp70 and the SR Ca2+pump: a potential mechanism for cytoprotection in heart and skeletal muscle

The overexpression of heat shock protein 70 (Hsp70) provides cytoprotection to cells, making them resistant to otherwise lethal levels of stress. In this review, the role Hsp70 plays in protecting both cardiac and skeletal muscle against the pathophysiological effects of oxidative stress are examined, with a focus on the molecular basis for the cytoprotective effects of Hsp70. The ability of Hsp70 to maintain cell survival undoubtedly involves the regulation of multiple steps within apoptotic pathways, but could also involve the regulation of key upstream mediators of apoptosis (i.e., oxidative stress, Ca2+overload). Hsp70 can stabilize the structure and function of both the skeletal muscle and cardiac Ca2+pump under heat stress conditions. Given that Ca2+overload has long been implicated in cell death, Hsp70 might protect muscle cells by maintaining cellular Ca2+homeostasis, thereby preventing the initiation of apoptosis. The functional interaction between Hsp70 and Ca2+pumps might also promote improvements in muscle contractility after exposure to oxidative stress.

Expression and localization of Hsps in the heart and blood vessel of heat-stressed broilers

The objective of this study was to investigate the kinetics of Hsp60, Hsp70, Hsp90 protein, and messenger RNA (mRNA) expression levels and to correlate these heat shock protein (Hsp) levels with tissue damage resulting from exposure to high temperatures for varying amounts of time. One hundred broilers were heat-stressed for 0, 2, 3, 5, and 10 h, respectively, by rapidly increasing the ambient temperature from 22 +/- 1 degrees C to 37 +/- 1 degrees C. Obvious elevations of plasma creatine kinase indicate damage to myocardial cells after heat stress. Hsp70 and Hsp90, and their corresponding mRNAs in the heart tissue of heat-stressed broilers, elevated significantly after 2 h of heat exposure and decreased quickly with continued heat stress. However, the levels of hsp60 mRNA in the heart of heat-stressed broilers increased sharply (P < 0.01) at 2 h of heat stress but then decreased quickly after 3 h, while the level of Hsp60 protein in the heart increased (P < 0.01) at 2 h of heat stress and maintained a high level throughout heat exposure. The results indicate that the elevation of the three Hsps, especially Hsp60 in heart, may be important markers at the beginning of heat stress and act as protective proteins in adverse environments. The reduction of Hsp signals in the cytoplasm of myocardial cells implies that myocardial cell lesions may have an adverse impact on the function of Hsps during heat stress. Meanwhile, the localization of Hsp70 in blood vessels of broiler hearts suggests another possible mechanism for protection of the heart after heat exposure.

Exogenous heat shock protein-70 inhibits cigarette smoke-induced intimal thickening

Cigarette smoke is associated with increased carotid intimal thickening or stroke. Preliminary work showed that exposure to smoke resulted in a 4.5-fold reduction of heat shock protein-70 (HSP70) expression in spleens of mice using gene microarray analysis. In the current study, we investigated the role of extracellular HSP70 in carotid intimal thickening of mice exposed to cigarette smoke. Intimal thickening was induced by placement of a cuff around the right carotid artery of mice. Cuff injury resulted in increased HSP70 mRNA expression in carotid arteries that persisted for 21 days. Cigarette smoke exposure decreased arterial HSP70 expression and significantly increased intimal thickening compared with mice exposed to air. Treatment of mice exposed to cigarette smoke with intravenous recombinant HSP70 attenuated intimal thickening through reduced phosphorylated extracellular signal-regulated kinase (pERK) expression in the arterial wall. In vitro experiments with rat aortic smooth muscle cells confirmed that recombinant HSP70 decreases pERK and proliferating cell nuclear antigen (PCNA) expression in cells exposed to cigarette smoke extract and H(2)O(2). Our study suggests that decreased expression of arterial HSP70 is an important mechanism by which exposure to cigarette smoke augments intimal thickening. The effects of recombinant HSP70 suggest a role for extracellular HSP70.

Strategies to promote donor cell survival: combining preconditioning approach with stem cell transplantation

Stem cell transplantation has emerged as a potential modality in cardiovascular therapeutics due to their inherent characteristics of self-renewal, unlimited capacity for proliferation and ability to cross lineage restrictions and adopt different phenotypes. Constrained by extensive death in the unfriendly milieu of ischemic myocardium, the results of heart cell therapy in experimental animal models as well as clinical studies have been less than optimal. Several factors which play a role in early cell death after engraftment in the ischemic myocardium include: absence of survival factors in the transplanted heart, disruption of cell-cell interaction coupled with loss of survival signals from matrix attachments, insufficient vascular supply and elaboration of inflammatory cytokines resulting from ischemia and/or cell death. This article reviews various signaling pathways involved in triggering highly complex forms of cell death and provides critical appreciation of different novel anti-death strategies developed from the knowledge gained from using an ischemic preconditioning approach. The use of pharmacological preconditioning for up-regulation of pro-survival proteins and cardiogenic markers in the transplanted stem cells will be discussed.

Myocardial heat shock protein changes in the failing heart following coronary artery ligation

BACKGROUND

Production of several heat shock proteins (Hsp) is enhanced after exposure to stress. There is little information concerning changes in myocardial Hsp under pathophysiological conditions. The aim of this study was to determine alterations in Hsp content in the viable left ventricular myocardium during the development of heart failure following coronary artery ligation (CAL).

METHODS

Myocardial infarction was produced by CAL of Wistar rats. One and eight weeks after the operation, haemodynamic parameters of rats with CAL were determined and then expression of Hsp27, Hsp60 and Hsp72 was measured by western blotting.

RESULTS

Animals showed a decrease in cardiac output and an increase in left ventricular end-diastolic pressure, symptoms of chronic heart failure (CHF), 8 weeks after CAL. Myocardial Hsp27 and Hsp72 at 1 week after CAL significantly increased, whereas expression of both proteins at 8 weeks was similar to that in rats which underwent a sham operation (without coronary artery ligation). In contrast, Hsp60 at 8 weeks, but not at 1 week, significantly increased in the sham rats.

CONCLUSIONS

Diverse changes in myocardial Hsp occurred during the development of CHF.

Heat stroke and cytokines

Heat stroke is a life-threatening illness that affects all segments of society, including the young, aged, sick, and healthy. The recent high death toll in France (Dorozynski, 2003) and the death of high-profile athletes has increased public awareness of the adverse effects of heat injury. However, the etiology of the long-term consequences of this syndrome remains poorly understood such that preventive/treatment strategies are needed to mitigate its debilitating effects. Cytokines are important modulators of the acute phase response (APR) to stress, infection, and inflammation. Current data implicating cytokines in heat stroke responses are mainly from correlation studies showing elevated plasma levels in heat stroke patients and experimental animal models. Correlation data fall far short of revealing the mechanisms of cytokine actions such that additional research to determine the role of these endogenous substances in the heat stroke syndrome is required. Furthermore, cytokine determinations have occurred mainly at end-stage heat stroke, such that the role of these substances in progression and long-term recovery is poorly understood. Despite several studies implicating cytokines in heat stroke pathophysiology, few studies have examined the protective effect(s) of cytokine antagonism on the morbidity and mortality of heat stroke. This is particularly surprising since heat stroke responses resemble those observed in the endotoxemic syndrome, for which a role for endogenous cytokines has been strongly implicated. The implication of cytokines as mediators of endotoxemia and the presence of circulating endotoxin in heat stroke patients suggests that much knowledge can be gained from applying our current understanding of endotoxemic pathophysiology to the study of heat stroke. Heat shock proteins (HSPs) are highly conserved proteins that function as molecular chaperones for denatured proteins and reciprocally modulate cytokine production in response to stressful stimuli. HSPs have been shown repeatedly to confer protection in heat stroke and injury models. Interactions between HSPs and cytokines have received considerable attention in the literature within the last decade such that a complex pathway of interactions between cytokines, HSPs, and endotoxin is thought to be occurring in vivo in the orchestration of the APR to heat injury. These data suggest that much of the pathophysiologic changes observed with heat stroke are not a consequence of heat exposure, per se, but are representative of interactions among these three (and presumably additional) components of the innate immune response. This chapter will provide an overview of current knowledge regarding cytokine, HSP, and endotoxin interactions in heat stroke pathophysiology. Insight is provided into the potential therapeutic benefit of cytokine neutralization for mitigation of heat stroke morbidity and mortality based on our current understanding of their role in this syndrome.

Comparison of effects of total enteral versus total parenteral nutrition on ischemia/reperfusion-induced heart injury in rats

BACKGROUND

The long-term effect of nutrition on cardiac function remains to be elucidated. One possible link is the newly discovered gastric hormone ghrelin, which has been reported to be cardioprotective.

AIM

The present study examined whether total enteral nutrition (TEN) and total parenteral nutrition (TPN) differ in their modulation of ghrelin production and their effects on cardiac function after ischemia/reperfusion injury.

METHODS

Rats received isocaloric parenteral or enteral nutrition through implanted vascular catheters or gastrostomy tubes. TEN was administered in a conventional (TEN-C) or immunonutrition (TEN-I) form. After 7 days, serum ghrelin levels were determined by enzyme-linked immunosorbent assays and myocardial function was assessed using the Langendorff isolated heart technique.

RESULTS

TEN-I animals had significantly higher plasma ghrelin levels than the other groups. After ischemia/reperfusion injury, left ventricular developed pressure decreased in animals receiving TPN when compared to animals receiving TEN-I. Animals receiving TPN also had significant reductions in their maximal rates of increase and decrease in left ventricular pressure when compared to animals receiving TEN-I (unpaired t test, p < 0.05).

CONCLUSION

TEN-I increases serum levels of ghrelin, which protects cardiac function after ischemic/reperfusion injury. Because TEN-I more effectively protects cardiac function, we recommend it for long-term nutritional support.

Exercise-induced cardioprotection against myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion (IR) injury is a major contributor to the morbidity and mortality associated with coronary artery disease. Muscular exercise is a countermeasure to protect against IR-induced cardiac injury in both young and old animals. Specifically, regular bouts of endurance exercise protect the heart against all levels of IR-induced injury. Proposed mechanisms to explain the cardioprotective effects of exercise include alterations in coronary circulation, expression of endoplasmic reticulum stress proteins, increased cyclooxygenase-2 activity, induction of myocardial heat shock proteins, improved cardiac antioxidant capacity, and/or elevation of ATP-sensitive potassium channels on both the sarcolemmal and the mitochondrial inner membranes. Moreover, it seems possible that other, yet to be defined, mechanisms of exercise-induced cardioprotection may also exist. Of the known putative cardioprotective mechanisms, current evidence suggests that elevated myocardial levels of antioxidants and increased expression of sarcolemmal ATP-sensitive potassium channels are both contributors to exercise-induced cardioprotection against IR injury. At present, it is unclear if these two protective mediators act independently or interact to contribute to exercise-induced cardioprotection. Understanding the molecular basis for exercise-induced cardioprotection will provide the required knowledge base to develop therapeutic approaches to protect the heart during an IR insult.