Changes in the rat heart proteome induced by exercise training: Increased abundance of heat shock protein hsp20

Exercise training and changes in skeletal muscle mitochondrial proteins: from blots to "omics"

Mitochondria are essential, membrane-enclosed organelles that consist of ∼1100 different proteins, which allow for many diverse functions critical to maintaining metabolism. Highly metabolic tissues, such as skeletal muscle, have a high mitochondrial content that increases with exercise training. The classic western blot technique has revealed training-induced increases in the relatively small number of individual mitochondrial proteins studied (∼5% of the >1100 proteins in MitoCarta), with some of these changes dependent on the training stimulus. Proteomic approaches have identified hundreds of additional mitochondrial proteins that respond to exercise training. There is, however, surprisingly little crossover in the mitochondrial proteins identified in the published human training studies. This suggests that to better understand the link between training-induced changes in mitochondrial proteins and metabolism, future studies need to move beyond maximizing protein detection to adopting methods that will increase the reliability of the changes in protein abundance observed.

Myocardial proteome changes in aortic stenosis rats subjected to long-term aerobic exercise

The effects of exercise training (ET) on the heart of aortic stenosis (AS) rats are controversial and the mechanisms involved in alterations induced by ET have been poorly clarified. In this study, we analyzed the myocardial proteome to identify proteins modulated by moderate-intensity aerobic ET in rats with chronic supravalvular AS. Wistar rats were divided into four groups: sedentary control (C-Sed), exercised control (C-Ex), sedentary aortic stenosis (AS-Sed), and exercised AS (AS-Ex). ET consisted of five treadmill running sessions per week for 16 weeks. Statistical analysis was performed by ANOVA or Kruskal-Wallis and Goodman tests. Results were discussed at a significance level of 5%. At the end of the experiment, AS-Ex rats had higher functional capacity, lower blood lactate concentration, and better cardiac structural and left ventricular (LV) functional parameters than the AS-Sed. Myocardial proteome analysis showed that AS-Sed had higher relative protein abundance related to the glycolytic pathway, oxidative stress, and inflammation, and lower relative protein abundance related to beta-oxidation than C-Sed. AS-Ex had higher abundance of one protein related to mitochondrial biogenesis and lower relative protein abundance associated with oxidative stress and inflammation than AS-Sed. Proteomic data were validated for proteins related to lipid and glycolytic metabolism. Chronic pressure overload changes the abundance of myocardial proteins that are mainly involved in lipid and glycolytic energy metabolism in rats. Moderate-intensity aerobic training attenuates changes in proteins related to oxidative stress and inflammation and increases the COX4I1 protein, related to mitochondrial biogenesis. Protein changes are combined with improved functional capacity, cardiac remodeling, and LV function in AS rats.

Prevalence of HSPB6 gene variants in peripartum cardiomyopathy: Data from the German PPCM registry

BACKGROUND

Heat shock protein family B (small) member 6 (HSPB6) mediates cardioprotective effects against stress-induced injury. In humans two gene variants of HSPB6 have been identified with a prevalence of 1% in patients with dilated cardiomyopathy (DCM). Peripartum cardiomyopathy (PPCM) is a potentially life-threatening heart disease of unknown etiology in previously healthy women of whom 16-20% of PPCM carry gene variants associated with cardiomyopathy. This study was designed to analyze the prevalence of pathogenic HSPB6 gene variants in PPCM.

METHODS AND RESULTS

Whole-exome sequencing was performed in whole blood samples of PPCM patients (n = 65 PPCM patients from the German PPCM registry) and screened subsequently for HSPB6 gene variants. In this PPCM cohort one PPCM patient carries a HSPB6 gene variant of uncertain significance (VUS), which was not associated with changes in the amino acid sequence and no likely pathogenic or pathogenic variants were detected.

CONCLUSION

HSPB6 gene variants did not occur more frequently in a cohort of PPCM patients from the German PPCM registry, compared to DCM patients. Genetic analyses in larger cohorts and in cohorts of different ethiologies of PPCM patients are needed to address the role of the genetic background in the pathogenesis of PPCM.

Skeletal Muscle CSE Deficiency Leads to Insulin Resistance in Mice

Cystathionine-γ-lyase (CSE) is expressed in various tissues and generates H₂S via an alternative desulfuration reaction. We sought to explore the functions of skeletal muscle CSE using skeletal muscle conditional knockout CSE (MCSEKO) mice. It was found that body weight, muscle morphology, and exercise capacity were not altered in MCSEKO mice compared with littermate wild-type mice. RNA-seq-based transcriptome analysis showed that 275 genes were differentially regulated in skeletal muscle and multiple signaling pathways including insulin signaling and mTOR, PI3K-AKT, and cGMP-PKG signaling pathways were enriched in MCSEKO mice. The intraperitoneal glucose tolerance test and insulin tolerance test showed that glucose tolerance and insulin sensitivity were reduced in MCSEKO mice. Glucose transporter 4 (GLU4) and PKG-1 expression levels and insulin receptor substrate-1(IRS1)/PI3K/Akt signaling pathway were downregulated whilst the mTOR/S6K/S6 pathway was enhanced in MCSEKO mice. These effects were reversed by the H₂S supplement. Aerobic treadmill training significantly promoted glucose tolerance and insulin sensitivity and improved GLU4 and PKG-1 levels, promoted IRS1/PI3K/Akt signaling and suppressed mTOR/S6K/S6 signaling pathway in MCSEKO mice. Our data suggest that skeletal muscle CSE/H₂S signaling is critical for the maintenance of insulin sensitivity, which is associated with maintaining the balance in PKG, PI3K/Akt, and mTOR/S6K/S6 signaling pathways in skeletal muscle.

When one says yes and the other says no; does calcineurin participate in physiologic cardiac hypertrophy?

Developing engaging activities that build skills for understanding and appreciating research is important for undergraduate and postgraduate science students. Comparing and contrasting opposing research studies does this, and more: it also appropriately for these cohorts challenges higher level cognitive processing. Here, we present and discuss one such scenario, that of calcineurin in the heart and its response to exercise training. This scenario is further accentuated by the existence of only two studies. The background is that regular aerobic endurance exercise training stimulates the heart to physiologically adapt to chronically increase its ability to produce a greater cardiac output to meet the increased demand for oxygenated blood in working muscles, and this happens by two main mechanisms: 1) increased cardiac contractile function and 2) physiologic hypertrophy. The major underlying mechanisms have been delineated over the last decades, but one aspect has not been resolved: the potential role of calcineurin in modulating physiologic hypertrophy. This is partly because the existing research has provided opposing and contrasting findings, one line showing that exercise training does activate cardiac calcineurin in conjunction with myocardial hypertrophy, but another line showing that exercise training does not activate cardiac calcineurin even if myocardial hypertrophy is blatantly occurring. Here, we review and present the current evidence in the field and discuss reasons for this controversy. We present real-life examples from physiology research and discuss how this may enhance student engagement and participation, widen the scope of learning, and thereby also further facilitate higher level cognitive processing.

Nandrolone combined with strenuous resistance training impairs myocardial proteome profile of rats

We aimed to investigate the effects of high doses of nandrolone decanoate and resistance training (RT) on the proteomic profile of the left ventricle (LV) of rats, using a label-free quantitative approach. Male rats were randomized into four groups: untrained vehicle (UTV), trained vehicle (TV), untrained nandrolone (UTN), and trained nandrolone (TN). Rats were familiarized with the exercise training protocol (jump exercise) for one week. Jump-exercise was performed five days a week for 6 weeks, with 30 s of inter-set rest intervals. Nandrolone was administrated for 6 weeks (5 mg/kg, twice a week, via intramuscular). Systolic and diastolic arterial pressure and heart rate were measured 48 h post-training. LV was isolated and collagen content was measured. The expression of cardiac proteins was analyzed by ultra-efficiency liquid chromatography with mass spectrometry high / low collision energy (UPLC/MSE). Nandrolone and RT led to cardiac hypertrophy, even though high doses of nandrolone counteracted the RT-induced arterial pressures lowering. Nandrolone also affected the proteome profile negatively in LV of rats, including critical proteins related to biological processes (metabolism, oxidative stress, inflammation), structural function and membrane transporters. Our findings show physiological relevance since high doses of nandrolone induced detrimental effects on the proteome profile of heart tissue and hemodynamic parameters of rats. Furthermore, as nandrolone abuse has become increasingly common among recreational athletes and casual fitness enthusiasts, we consider that our findings have clinical relevance as well.

The Cardioprotective PKA-Mediated Hsp20 Phosphorylation Modulates Protein Associations Regulating Cytoskeletal Dynamics

The cytoskeleton has a primary role in cardiomyocyte function, including the response to mechanical stimuli and injury. The small heat shock protein 20 (Hsp20) conveys protective effects in cardiac muscle that are linked to serine-16 (Ser16) Hsp20 phosphorylation by stress-induced PKA, but the link between Hsp20 and the cytoskeleton remains poorly understood. Herein, we demonstrate a physical and functional interaction of Hsp20 with the cytoskeletal protein 14-3-3. We show that, upon phosphorylation at Ser16, Hsp20 translocates from the cytosol to the cytoskeleton where it binds to 14-3-3. This leads to dissociation of 14-3-3 from the F-actin depolymerization regulator cofilin-2 (CFL2) and enhanced F-actin depolymerization. Importantly, we demonstrate that the P20L Hsp20 mutation associated with dilated cardiomyopathy exhibits reduced physical interaction with 14-3-3 due to diminished Ser16 phosphorylation, with subsequent failure to translocate to the cytoskeleton and inability to disassemble the 14-3-3/CFL2 complex. The topological sequestration of Hsp20 P20L ultimately results in impaired regulation of F-actin dynamics, an effect implicated in loss of cytoskeletal integrity and amelioration of the cardioprotective functions of Hsp20. These findings underscore the significance of Hsp20 phosphorylation in the regulation of actin cytoskeleton dynamics, with important implications in cardiac muscle physiology and pathophysiology.

Inducible expression of heat shock protein 20 protects airway epithelial cells against oxidative injury involving the Nrf2-NQO-1 pathway

BACKGROUND

Heat shock protein (HSP) 20 is a molecular chaperone that exerts multiple protective functions in various kinds of tissues. However, the expression of HSP20 and its specific functions in airway epithelial cells (AECs) remain elusive.

RESULTS

In current study, we first confirmed the inducible expression of HSP20 in mouse AECs and in a human bronchial epithelial cell line BEAS-2B cells, under different oxidant stressors. Then by establishing a HSP20-abundant mouse model with repeated low-level-ozone exposures and stimulating this model with a single high-level ozone exposure, we found that the HSP20 abundance along with its enhanced phosphorylation potentially contributed to the alleviation of oxidative injuries, evidenced by the decreases in the bodyweight reduction, the BAL neutrophil accumulation, the AECs shedding, and the BAL concentrations of albumin and E-cadherin. The biological function of HSP20 and its molecular mechanisms were further investigated in BEAS-2B cells that were transfected with HSP20-, unphosphorylatable HSP20(Ala) or empty vector plasmids prior to the stimulation of H2O2, of which its oxidant capacity has been proved to be similar with those of ozone in an air-liquid culture system. We found that the H2O2-induced intracellular ROS level and the early cell apoptosis were attenuated in the HSP20- but not HSP20(Ala)- transfected cells. The intracellular expression of NQO-1 (mRNA and protein) and the intranuclear content of Nrf2 were significantly increased in the HSP20- transfected cells but not in the HSP20(Ala)- and empty vector-transfected cells after the stimulation of H2O2.

CONCLUSIONS

The inducible expression of HSP20 in AECs by oxidative stress exerts protective roles against oxidative damages, which may involve the activation of the Nrf2-NQO-1 pathway.

Circadian modulation of the cardiac proteome underpins differential adaptation to morning and evening exercise training: an LC-MS/MS analysis

All living beings on earth are influenced by the circadian rhythm, the rising and the setting of the sun. The ubiquitous effect of exercise is widely believed to maximize health benefits but has not been formally investigated for cardiac responses in the exercise-induced circadian rhythms. We hypothesized that the exercise-related proteome is differentially influenced by circadian rhythm and analyzed the differences between the effects of morning and evening exercise. Twenty-four Sprague-Dawley rats were randomly divided into four groups (n = 6 per group): morning control, morning exercise, evening control, and evening exercise groups. The exercise groups were subjected to 12-week treadmill exercise (5 days/week) performed either during daytime or nighttime. After 12 weeks, the physiological characteristics (e.g., body weight, heart weight, visceral fat, and blood metabolites), cardiovascular capacity (ejection fraction (%) and fractional shortening (%)), circadian gene expression levels (clock, ball1, per1, per2, cry1, and cry2), and the proteomic data were obtained and subjected to univariate and multivariate analysis. The mRNA levels of per1 and cry2 increased in the evening group compared with those in the morning group. We also found that per2 decreased and cry2 increased in the evening exercise groups. The evening exercise groups showed more decreased triacylglycerides and increased blood insulin levels than the morning exercise group. The principal component analysis, partial least squares discriminant analysis, and orthogonal partial least squares discriminant analysis indicated that the circadian rhythm differently influenced the protein networks of the exercise groups. In the morning exercise group, the transcription-translation feedback loop (TTFL) (clock, per1, per2, cry1, and cry2) formed a protein-protein interaction network with Nme2, Hint1, Ddt, Ndufb8, Ldha, and Eef1a2. In contrast, the TTFL group appeared close to Maoa, Hist2h4, and Macrod1 in the evening exercise group. Interestingly, the evening exercise group decreased the mRNA level of per2 but not per1. Per1 and Per2 are known to transport Cry1 and Cry2 into the nucleus. Taken together, we summarized the characteristics of enriched proteins in the aspect of their molecular function, cellular component, and biological process. Our results might provide a better understanding of the circadian effect on exercise-related proteins.

Omics and the molecular exercise physiology

Exercise is a well-known non-pharmacologic agent used to prevent and treat a wide range of pathologic conditions such as metabolic and cardiovascular disease. In this sense, the classic field of exercise physiology has determined the main theoretical and practical bases of physiologic adaptations in response to exercise. However, the last decades were marked by significant advances in analytical laboratory techniques, where the field of biochemistry, genetics and molecular biology promoted exercise science to enter a new era. Regardless of its application, whether in the field of disease prevention or performance, the association of molecular biology with exercise physiology has been fundamental for unveiling knowledge of the molecular mechanisms related to the adaptation to exercise. This chapter will address the natural evolution of exercise physiology toward genetics and molecular biology, emphasizing the collection of integrated analytical approaches that composes the OMICS and their contribution to the field of molecular exercise physiology.

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.

Understanding Key Mechanisms of Exercise-Induced Cardiac Protection to Mitigate Disease: Current Knowledge and Emerging Concepts

The benefits of exercise on the heart are well recognized, and clinical studies have demonstrated that exercise is an intervention that can improve cardiac function in heart failure patients. This has led to significant research into understanding the key mechanisms responsible for exercise-induced cardiac protection. Here, we summarize molecular mechanisms that regulate exercise-induced cardiac myocyte growth and proliferation. We discuss in detail the effects of exercise on other cardiac cells, organelles, and systems that have received less or little attention and require further investigation. This includes cardiac excitation and contraction, mitochondrial adaptations, cellular stress responses to promote survival (heat shock response, ubiquitin-proteasome system, autophagy-lysosomal system, endoplasmic reticulum unfolded protein response, DNA damage response), extracellular matrix, inflammatory response, and organ-to-organ crosstalk. We summarize therapeutic strategies targeting known regulators of exercise-induced protection and the challenges translating findings from bench to bedside. We conclude that technological advancements that allow for in-depth profiling of the genome, transcriptome, proteome and metabolome, combined with animal and human studies, provide new opportunities for comprehensively defining the signaling and regulatory aspects of cell/organelle functions that underpin the protective properties of exercise. This is likely to lead to the identification of novel biomarkers and therapeutic targets for heart disease.

Cardiac protein expression patterns are associated with distinct inborn exercise capacity in non-selectively bred rats

In the present study, we successfully demonstrated for the first time the existence of cardiac proteomic differences between non-selectively bred rats with distinct intrinsic exercise capacities. A proteomic approach based on two-dimensional gel electrophoresis coupled to mass spectrometry was used to study the left ventricle (LV) tissue proteome of rats with distinct intrinsic exercise capacity. Low running performance (LRP) and high running performance (HRP) rats were categorized by a treadmill exercise test, according to distance run to exhaustion. The running capacity of HRPs was 3.5-fold greater than LRPs. Protein profiling revealed 29 differences between HRP and LRP rats (15 proteins were identified). We detected alterations in components involved in metabolism, antioxidant and stress response, microfibrillar and cytoskeletal proteins. Contractile proteins were upregulated in the LVs of HRP rats (α-myosin heavy chain-6, myosin light chain-1 and creatine kinase), whereas the LVs of LRP rats exhibited upregulation in proteins associated with stress response (aldehyde dehydrogenase 2, α-crystallin B chain and HSPβ-2). In addition, the cytoskeletal proteins desmin and α-actin were upregulated in LRPs. Taken together, our results suggest that the increased contractile protein levels in HRP rats partly accounted for their improved exercise capacity, and that proteins considered risk factors to the development of cardiovascular disease were expressed in higher amounts in LRP animals.

Untargeted metabolomics analysis of ischemia-reperfusion-injured hearts ex vivo from sedentary and exercise-trained rats

INTRODUCTION

The effects of exercise on the heart and its resistance to disease are well-documented. Recent studies have identified that exercise-induced resistance to arrhythmia is due to the preservation of mitochondrial membrane potential.

OBJECTIVES

To identify novel metabolic changes that occur parallel to these mitochondrial alterations, we performed non-targeted metabolomics analysis on hearts from sedentary and exercise-trained rats challenged with isolated heart ischemia-reperfusion injury (I/R).

METHODS

Eight-week old Sprague-Dawley rats were treadmill trained 5 days/week for 6 weeks (exercise duration and intensity progressively increased to 1 h at 30 m/min up a 10.5% incline, 75-80% VO_2max). The recovery of pre-ischemic function for sedentary rat hearts was 28.8 ± 5.4% (N = 12) compared to exercise trained hearts, which recovered 51.9% ± 5.7 (N = 14) (p < 0.001).

RESULTS

Non-targeted GC-MS metabolomics analysis of (1) sedentary rat hearts; (2) exercise-trained rat hearts; (3) sedentary rat hearts challenged with global ischemia-reperfusion (I/R) injury; and (4) exercise-trained rat hearts challenged with global I/R (10/group) revealed 15 statistically significant metabolites between groups by ANOVA using Metaboanalyst (p < 0.001). Enrichment analysis of these metabolites for pathway-associated metabolic sets indicated a > 10-fold enrichment for ammonia recycling and protein biosynthesis. Subsequent comparison of the sedentary hearts post-I/R and exercise-trained hearts post-I/R further identified significant differences in three metabolites (oleic acid, pantothenic acid, and campesterol) related to pantothenate and CoA biosynthesis (p ≤ 1.24E-05, FDR ≤ 5.07E-4).

CONCLUSIONS

These studies shed light on novel mechanisms in which exercise-induced cardioprotection occurs in I/R that complement both the mitochondrial stabilization and antioxidant mechanisms recently described. These findings also link protein synthesis and protein degradation (protein quality control mechanisms) with exercise-linked cardioprotection and mitochondrial susceptibility for the first time in cardiac I/R.

The protective role of small heat shock proteins in cardiac diseases: key role in atrial fibrillation

Atrial fibrillation (AF) is the most common tachyarrhythmia which is associated with increased morbidity and mortality. AF usually progresses from a self-terminating paroxysmal to persistent disease. It has been recognized that AF progression is driven by structural remodeling of cardiomyocytes, which results in electrical and contractile dysfunction of the atria. We recently showed that structural remodeling is rooted in derailment of proteostasis, i.e., homeostasis of protein production, function, and degradation. Since heat shock proteins (HSPs) play an important role in maintaining a healthy proteostasis, the role of HSPs was investigated in AF. It was found that especially small heat shock protein (HSPB) levels get exhausted in atrial tissue of patients with persistent AF and that genetic or pharmacological induction of HSPB protects against cardiomyocyte remodeling in experimental models for AF. In this review, we provide an overview of HSPBs as a potential therapeutic target for normalizing proteostasis and suppressing the substrates for AF progression in experimental and clinical AF and discuss HSP activators as a promising therapy to prevent AF onset and progression.

Exosomes Mediate the Beneficial Effects of Exercise

It is known that moderate exercise can prevent the development of cardiovascular diseases, but the exact molecular mechanisms mediating cardioprotective effect of exercise remain unknown. Emerging evidence suggests that exercise has great impact on the biogenesis of exosomes, which have been found in both interstitial fluid and circulation, and play important roles in cellular communication. Exosomes carry functional molecules such as mRNAs, microRNA, and specific proteins, which can be used in the early diagnosis and targeted therapy of a variety of diseases. Our review focus on the current knowledge on exosome production, secretion, uptake and how exercise influence exosome content. We also highlight recent research development in exosome based approach for cardiac repair.

Expression and localization of the Xenopus laevis small heat shock protein, HSPB6 (HSP20), in A6 kidney epithelial cells

Small heat shock proteins (sHSPs) are molecular chaperones that bind to unfolded protein, inhibit the formation of toxic aggregates and facilitate their refolding and/or degradation. Previously, the only sHSPs that have been studied in detail in the model frog system, Xenopus laevis, were members of the HSP30 family and HSPB1 (HSP27). We now report the analysis of X. laevis HSPB6, an ortholog of mammalian HSPB6. X. laevis HSPB6 cDNA encodes a 168 aa protein that contains an α-crystallin domain, a polar C-terminal extension and some possible phosphorylation sites. X. laevis HSPB6 shares 94% identity with a X. tropicalis HSPB6, 65% with turtle, 59% with humans, 49% with zebrafish and only 50% and 43% with X. laevis HSPB1 and HSP30C, respectively. Phylogenetic analysis revealed that X. laevis HSPB6 grouped more closely with mammalian and reptilian HSPB6s than with fish HSPB6. X. laevis recombinant HSPB6 displayed molecular chaperone properties since it had the ability to inhibit heat-induced aggregation of citrate synthase. Immunoblot analysis determined that HSPB6 was present constitutively in kidney epithelial cells and that heat shock treatment did not upregulate HSPB6 levels. While treatment with the proteasomal inhibitor, MG132, resulted in a 2-fold increase in HSPB6 levels, exposure to cadmium chloride produced a slight increase in HSPB6. These findings were in contrast to HSP70, which was enhanced in response to all three stressors. Finally, immunocytochemical analysis revealed that HSPB6 was present in the cytoplasm in the perinuclear region with some in the nucleus.

Unraveling the role of high-intensity resistance training on left ventricle proteome: Is there a shift towards maladaptation?

High-intensity resistance training (RT) induces adaptations that improve physiological function. However, high intensity, volume and/or frequency may lead to injury and other health issues such as adverse cardiac effects. The aim of this study was to evaluate the effect of RT on left ventricle proteome, and to identify the pathways involved on the harmful adaptations induced by this protocol. Male Wistar rats were randomized into 2 groups: Trained (T) and Sedentary (S). Animals from T group were trained for 6weeks, and then all the animals were sacrificed and left ventricle was isolated for analysis. We identified 955 proteins, and 93 proteins were considered; 36 were expressed exclusively in T group, and 4 in S group. Based on quantitative analysis, 42 proteins were found overexpressed and 11 underexpressed in T group compared with S group. Using the Gene Ontology to relate the biological processes in which these proteins are involved, we conclude that RT protocol promotes changes similar to those found in the initial phase of heart failure, but we also observed a concomitant increased expression of protective proteins, suggesting the activation of pathways to avoid major damages on left ventricle and delay the onset of pathological hypertrophy.

STATEMENT OF SIGNIFICANCE OF THE STUDY

Our study shows that high-intensity RT protocol changes left ventricle proteome, modifying metabolic profile of heart tissue and inducing the expression of proteins that acts against cardiac injury. We hypothesize that these adaptations occur to prevent the onset of cardiac dysfunction. Despite highly significant, it remains to be determined whether these adaptations are sufficient to further keep left ventricle function and exert cardioprotection, and whether this panel will be shifted towards maladaptation, and heart failure.

Protecting against ischaemic stroke in rats by heat shock protein 20-mediated exercise

BACKGROUND

Exercise preconditioning (EP(+) ) has been widely accepted as a being of safe and effective preventive measure for stroke. The purpose of this study was to investigate whether EP(+) improves outcomes of ischaemic stroke by promoting neuronal and glial expression of heat shock protein (HSP) 20.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats (288 in number) were used to investigate the contribution of HSP20-containing neurons and HSP20-containing glial cells in the exercise-mediated neuroprotection in the stroke condition using middle cerebral artery occlusion.

RESULTS

Exercise preconditioning, in addition to increasing the numbers of both the HSP20-containg neurons (88 ± 8 vs. 43 ± 4; n = 8 each group; P < 0·05) and the HSP20-containg astrocytes (102 ± 10 vs. 56 ± 5; n = 8; P < 0·05) significantly attenuated stroke-induced brain infarct (140 ± 9 vs. 341 ± 20 mm(3) ; n = 8 per group; P < 0·01), neuronal apoptosis (20 ± 5 vs. 87 ± 7; n = 8 per group; n = 8; P < 0·01), glial apoptosis (29 ± 5 vs. 101 ± 4; n = 8; P < 0·01), and neurological deficits (6·6 ± 0·3 vs. 11·7 ± 0·8; n = 8 per group; P < 0·01). Reducing the numbers of both HSP20-containing neurons and HSP20-contaiing glia by intracerebral injection of pSUPER small interfering RNAί expressing HSP20 significantly reversed the beneficial effects of EP(+) in attenuating stroke-induced cerebral infarct, neuronal and glial apoptosis, and neurological deficits.

CONCLUSIONS

The numbers of both the HSP20-containing neurons and the HSP20-containing glia inversely correlated with the outcomes of ischaemic stroke. In addition, preischaemic treadmill exercise improves outcomes of ischaemic stroke by increasing the numbers of both the HSP20-containing neurons and the HSP20-containing glia.

Unraveling the exercise-related proteome signature in heart

Exercise training is a well-known non-pharmacological strategy for the prevention and treatment of cardiovascular diseases. Despite the established phenotypic knowledge, the molecular signature of exercise-induced cardiac remodeling remains poorly characterized. The great majority of studies dedicated to this topic use conventional reductionist methods, which only allow analyzing individual protein candidates. Nowadays, several methodologies based on mass spectrometry are available and have been successfully applied for the characterization of heart proteome, representing an attractive approach for the wide characterization of the complex molecular networks that underlie exercise-induced cardiac remodeling. Still, few studies have used these methodologies to understand the impact of exercise training on the remodeling of cardiac proteome. The present study analyzes the few available data obtained from mass spectrometry (MS)-based proteomic studies assessing the impact of distinct types of exercise training on the protein profile of heart (left ventricle and isolated mitochondria) and the potential cross-tolerance between exercise training and diseases as myocardial infarction and obesity. Network analysis was performed with bioinformatics to integrate data from distinct research papers, based on distinct exercise training protocols, animal models and methodological approaches applied in the characterization of heart proteome. The analysis revealed that exercise training confers a unique proteome signature characterized by the up-regulation of lipid and organic metabolic processes, vasculogenesis and tissue regeneration. Data retrieved from this analysis also suggested that cardiac mitochondrial proteome is highly dynamic in response to exercise training due, in part, to the action of specific kinases as PKA and PKG. Regarding to the type of exercise, treadmill training seems to have a greater effect on the modulation of cardiac proteome than swimming. Data from the present review will certainly open new perspectives on cardiac proteomics and will help to envisage future studies targeting the identification of the regulatory mechanisms underlying cardiac adaptive and maladaptive remodeling.

NanoUPLC/MS(E) proteomic analysis reveals modulation on left ventricle proteome from hypertensive rats after exercise training

NanoUPLC/MS(E) was used to verify the effects of 8weeks of low (SHR-LIT=4) and high (SHR-HIT=4) intensity training over the left ventricle proteome of hypertensive rats (SHR-C=4). Training enhanced the aerobic capacity and reduced the systolic blood pressure in all exercised rats. NanoUPLC/MS(E) identified 250 proteins, with 233 in common to all groups and 16 exclusive to SHR-C, 2 to SHR-LIT, and 2 to the SHR-HIT. Cardiac hypertrophy related proteins appeared only in SHR-C. The SHR-LIT enhanced the abundance of 30 proteins and diminished 6, while SHR-HIT enhanced the abundance of 39 proteins and reduced other 7. The levels of metabolic (β and γ-enolase, adenine phosphoribosultransferase, and cytochrome b-c1), myofibril (myosin light chain 4, tropomyosin α and β-chain), and transporter proteins (hemoglobin, serum albumin, and hemopexin) were increased by both intensities. Transcription regulator and histone variants were enhanced by SHR-LIT and SHR-HIT respectively. SHR-LIT reduced the concentration of myosin binding protein C, while desmin and membrane voltage dependent anion selective channel protein-3 were reduced only by SHR-HIT. In addition, polyubiquitin B and C, and transcription regulators decreased in both intensities. Exercise also increased the concentration of anti-oxidant proteins, peroxiredozin-6 and glutathione peroxidase-1.

BIOLOGICAL SIGNIFICANCE

Pathologic left ventricle hypertrophy if one of the major outcomes of hypertension being a strong predictor of heart failure. Among the various risk factors for cardiovascular disorders, arterial hypertension is responsible for the highest rates of mortality worldwide. In this way, this present study contribute to the understanding of the molecular mechanisms involved in the attenuation of hypertension and the regression of pathological cardiac hypertrophy induced by exercise training.

Metabolic and hormonal responses to isoenergetic high-intensity interval exercise and continuous moderate-intensity exercise

This study investigated the effects of high-intensity interval training (HIIT) vs. work-matched moderate-intensity continuous exercise (MOD) on metabolism and counterregulatory stress hormones. In a randomized and counterbalanced order, 10 well-trained male cyclists and triathletes completed a HIIT session [81.6 ± 3.7% maximum oxygen consumption (V̇o2 max); 72.0 ± 3.2% peak power output; 792 ± 95 kJ] and a MOD session (66.7 ± 3.5% V̇o2 max; 48.5 ± 3.1% peak power output; 797 ± 95 kJ). Blood samples were collected before, immediately after, and 1 and 2 h postexercise. Carbohydrate oxidation was higher (P = 0.037; 20%), whereas fat oxidation was lower (P = 0.037; -47%) during HIIT vs. MOD. Immediately after exercise, plasma glucose (P = 0.024; 20%) and lactate (P < 0.01; 5.4×) were higher in HIIT vs. MOD, whereas total serum free fatty acid concentration was not significantly different (P = 0.33). Targeted gas chromatography-mass spectromtery metabolomics analysis identified and quantified 49 metabolites in plasma, among which 11 changed after both HIIT and MOD, 13 changed only after HIIT, and 5 changed only after MOD. Notable changes included substantial increases in tricarboxylic acid intermediates and monounsaturated fatty acids after HIIT and marked decreases in amino acids during recovery from both trials. Plasma adrenocorticotrophic hormone (P = 0.019), cortisol (P < 0.01), and growth hormone (P < 0.01) were all higher immediately after HIIT. Plasma norepinephrine (P = 0.11) and interleukin-6 (P = 0.20) immediately after exercise were not significantly different between trials. Plasma insulin decreased during recovery from both HIIT and MOD (P < 0.01). These data indicate distinct differences in specific metabolites and counterregulatory hormones following HIIT vs. MOD and highlight the value of targeted metabolomic analysis to provide more detailed insights into the metabolic demands of exercise.

Effects of hypertension and exercise on cardiac proteome remodelling

Left ventricle hypertrophy is a common outcome of pressure overload stimulus closely associated with hypertension. This process is triggered by adverse molecular signalling, gene expression, and proteome alteration. Proteomic research has revealed that several molecular targets are associated with pathologic cardiac hypertrophy, including angiotensin II, endothelin-1 and isoproterenol. Several metabolic, contractile, and stress-related proteins are shown to be altered in cardiac hypertrophy derived by hypertension. On the other hand, exercise is a nonpharmacologic agent used for hypertension treatment, where cardiac hypertrophy induced by exercise training is characterized by improvement in cardiac function and resistance against ischemic insult. Despite the scarcity of proteomic research performed with exercise, healthy and pathologic heart proteomes are shown to be modulated in a completely different way. Hence, the altered proteome induced by exercise is mostly associated with cardioprotective aspects such as contractile and metabolic improvement and physiologic cardiac hypertrophy. The present review, therefore, describes relevant studies involving the molecular characteristics and alterations from hypertensive-induced and exercise-induced hypertrophy, as well as the main proteomic research performed in this field. Furthermore, proteomic research into the effect of hypertension on other target-demerged organs is examined.

Effects of acute exercise over heart proteome from monogenic obese (ob/ob) mice

Exercise is recognized to prevent and attenuate several metabolic and cardiovascular disorders. Obesity is commonly related to cardiovascular diseases, frequently resulting in heart failure and death. To elucidate the effects of acute exercise in heart tissue from obese animals, 12-week-old C57BL6/J obese (ob/ob) and non-obese (ob/OB) mice were submitted to a single bout of swimming and had their hearts analyzed by proteomic techniques. Mice were divided into three groups: control (ob/ob, n = 3; ob/OB, n = 3); a moderate intensity consisting of 20 min of swimming around 90% of Maximal Lactate Steady State (ob/ob, n = 3; ob/OB, n = 3), and a high intensity exercise performed as an incremental overload test (ob/ob, n = 3; ob/OB, n = 3). Obesity modulations were analyzed by comparing ob/ob and ob/OB control groups. Differential 2-DE analysis revealed that single session of exercise was able to up-regulate: myoglobin (ob/ob), aspartate aminotransferase (ob/OB) and zinc finger protein (ob/OB) and down-regulate: nucleoside diphosphate kinase B (ob/OB), mitochondrial aconitase (ob/ob and ob/OB) and fatty acid binding protein (ob/ob). Zinc finger protein and α-actin were up-regulated by the effect of obesity on heart proteome. These data demonstrate the immediate response of metabolic and stress-related proteins after exercise so as contractile protein by obesity modulation on heart proteome.

Proteomic analysis of skeletal muscle in insulin-resistant mice: response to 6-week aerobic exercise

Aerobic exercise has beneficial effects on both weight control and skeletal muscle insulin sensitivity through a number of specific signaling proteins. To investigate the targets by which exercise exerts its effects on insulin resistance, an approach of proteomic screen was applied to detect the potential different protein expressions from skeletal muscle of insulin-resistant mice after prolonged aerobic exercise training and their sedentary controls. Eighteen C57BL/6 mice were divided into two groups: 6 mice were fed normal chow (NC) and 12 mice were fed high-fat diet (HFD) for 10 weeks to produce an IR model. The model group was then subdivided into HFD sedentary control (HC, n = 6) and HFD exercise groups (HE, n = 6). Mice in HE group underwent 6 weeks of treadmill running. After 6 weeks, mice were sacrificed and skeletal muscle was dissected. Total protein (n = 6, each group) was extracted and followed by citrate synthase, 2D proteome profile analysis and immunoblot. Fifteen protein spots were altered between the NC and HC groups and 23 protein spots were changed between the HC and HE groups significantly. The results provided an array of changes in protein abundance in exercise-trained skeletal muscle and also provided the basis for a new hypothesis regarding the mechanism of exercise ameliorating insulin resistance.

Large potentials of small heat shock proteins

Modern classification of the family of human small heat shock proteins (the so-called HSPB) is presented, and the structure and properties of three members of this family are analyzed in detail. Ubiquitously expressed HSPB1 (HSP27) is involved in the control of protein folding and, when mutated, plays a significant role in the development of certain neurodegenerative disorders. HSPB1 directly or indirectly participates in the regulation of apoptosis, protects the cell against oxidative stress, and is involved in the regulation of the cytoskeleton. HSPB6 (HSP20) also possesses chaperone-like activity, is involved in regulation of smooth muscle contraction, has pronounced cardioprotective activity, and seems to participate in insulin-dependent regulation of muscle metabolism. HSPB8 (HSP22) prevents accumulation of aggregated proteins in the cell and participates in the regulation of proteolysis of unfolded proteins. HSPB8 also seems to be directly or indirectly involved in regulation of apoptosis and carcinogenesis, contributes to cardiac cell hypertrophy and survival and, when mutated, might be involved in development of neurodegenerative diseases. All small heat shock proteins play important "housekeeping" roles and regulate many vital processes; therefore, they are considered as attractive therapeutic targets.

Proteomic analysis and protein carbonylation profile in trained and untrained rat muscles

Understanding the relationship between physical exercise, reactive oxygen species and skeletal muscle modification is important in order to better identify the benefits or the damages that appropriate or inappropriate exercise can induce. Unbalanced ROS levels can lead to oxidation of cellular macromolecules and a major class of protein oxidative modification is carbonylation. The aim of this investigation was to study muscle protein expression and carbonylation patterns in trained and untrained animal models. We analyzed two muscles characterized by different metabolisms: tibialis anterior and soleus. Whilst tibialis anterior is mostly composed of fast-twitch fibers, the soleus muscle is mostly composed of slow-twitch fibers. By a proteomic approach we identified 15 protein spots whose expression is influenced by training. Among them in tibialis anterior we observed a down-regulation of several glycolitic enzymes. Concerning carbonylation, we observed the existence of a high basal level of protein carbonylation. Although this level shows some variation among individual animals, several proteins (mostly involved in energy metabolism, muscle contraction, and stress response) appear carbonylated in all animals and in both types of skeletal muscle. Moreover we identified 13 spots whose carbonylation increases after training.

Proteomic responses of skeletal and cardiac muscle to exercise

Regular exercise is effective in the prevention of chronic diseases and confers a lower risk of death in individuals displaying risk factors such as hypertension and dyslipidemia. Thus, knowledge of the molecular responses to exercise provides a valuable contrast for interpreting investigations of disease and can highlight novel therapeutic targets. While exercise is an everyday experience and can be conceptualized in simple terms, it is also a complex physiological phenomenon and investigation of exercise responses requires sophisticated analytical techniques and careful standardization of the exercise stimulus. Proteomic investigation of exercise is in its infancy but the ability to link changes in function with comprehensive changes in protein expression and post-translational modification holds great promise for advancing physiology. This article highlights recent pioneering work investigating the effects of exercise in skeletal and cardiac muscle that has uncovered novel mechanisms underlying the benefits of physical activity.

Cardiac proteomic responses to ischemia-reperfusion injury and ischemic preconditioning

Cardiac ischemia and ischemia-reperfusion (I/R) injury are major contributors to morbidity and mortality worldwide. Pathological mechanisms of I/R and the physiological mechanisms of ischemic preconditioning (IPC), which is an effective cardiac protective response, have been widely investigated in the last decade to search for means to prevent or treat this disease. Proteomics is a powerful analytical tool that has provided important information to identify target proteins and understand the underlying mechanisms of I/R and IPC. Here, we review the application of proteomics to I/R injury and IPC to discover target proteins. We analyze the functional meaning of the accumulated data on hundreds of proteins using various bioinformatics applications. In addition, we review exercise-induced proteomic alterations in the heart to understand the potential cardioprotective role of exercise against I/R injury. Further developments in the proteomic field that target specialized proteins will yield new insights for optimizing therapeutic targets and developing a wide range of therapeutic agents against ischemic heart disease.

Small heat shock protein 20 interacts with protein phosphatase-1 and enhances sarcoplasmic reticulum calcium cycling

BACKGROUND

Heat shock proteins (Hsp) are known to enhance cell survival under various stress conditions. In the heart, the small Hsp20 has emerged as a key mediator of protection against apoptosis, remodeling, and ischemia/reperfusion injury. Moreover, Hsp20 has been implicated in modulation of cardiac contractility ex vivo. The objective of this study was to determine the in vivo role of Hsp20 in the heart and the mechanisms underlying its regulatory effects in calcium (Ca) cycling.

METHODS AND RESULTS

Hsp20 overexpression in intact animals resulted in significant enhancement of cardiac function, coupled with augmented Ca cycling and sarcoplasmic reticulum Ca load in isolated cardiomyocytes. This was associated with specific increases in phosphorylation of phospholamban (PLN) at both Ser16 and Thr17, relieving its inhibition of the apparent Ca affinity of SERCA2a. Accordingly, the inotropic effects of Hsp20 were abrogated in cardiomyocytes expressing nonphosphorylatable PLN (S16A/T17A). Interestingly, the activity of type 1 protein phosphatase (PP1), a known regulator of PLN signaling, was significantly reduced by Hsp20 overexpression, suggesting that the Hsp20 stimulatory effects are partially mediated through the PP1-PLN axis. This hypothesis was supported by cell fractionation, coimmunoprecipitation, and coimmunolocalization studies, which revealed an association between Hsp20, PP1, and PLN. Furthermore, recombinant protein studies confirmed a physical interaction between AA 73 to 160 in Hsp20 and AA 163 to 330 in PP1.

CONCLUSIONS

Hsp20 is a novel regulator of sarcoplasmic reticulum Ca cycling by targeting the PP1-PLN axis. These findings, coupled with the well-recognized cardioprotective role of Hsp20, suggest a dual benefit of targeting Hsp20 in heart disease.

Myocardial tolerance to ischemia-reperfusion injury, training intensity and cessation

Training has been shown to induce cardioprotection. The mechanisms involved remain still poorly understood. Aims of the study were to examine the relevance of training intensity on myocardial protection against ischemia/reperfusion (I/R) injury, and to which extent the beneficial effects persist after training cessation in rats. Sprague-Dawley rats trained at either low (60% [Formula: see text]) or high (80% [Formula: see text]) intensity for 10 weeks. An additional group of highly trained rats was detrained for 4 weeks. Untrained rats served as controls. At the end of treatment, rats of all groups were split into two subgroups. In the former, rats underwent left anterior descending artery (LAD) ligature for 30 min, followed by 90-min reperfusion, with subsequent measurement of the infarct size. In the latter, biopsies were taken to measure heat-shock proteins (HSP) 70/72, vascular endothelial growth factor (VEGF) protein levels, and superoxide dismutase (SOD) activity. Training reduced infarct size proportionally to training intensity. With detraining, infarct size increased compared to highly trained rats, maintaining some cardioprotection with respect to controls. Cardioprotection was proportional to training intensity and related to HSP70/72 upregulation and Mn-SOD activity. The relationship with Mn-SOD was lost with detraining. VEGF protein expression was not affected by either training or detraining. Stress proteins and antioxidant defenses might be involved in the beneficial effects of long-term training as a function of training intensity, while HSP70 may be one of the factors accounting for the partial persistence of myocardial protection against I/R injury in detrained rats.

Small heat shock protein 20 (HspB6) in cardiac hypertrophy and failure

Hsp20, referred to as HspB6, is constitutively expressed in various tissues. Specifically, HspB6 is most highly expressed in different types of muscle including vascular, airway, colonic, bladder, and uterine smooth muscle; cardiac muscle; and skeletal muscle. It can be phosphorylated at Ser-16 by both cAMP- and cGMP-dependent protein kinases (PKA/PKG). Recently, Hsp20 and its phosphorylation have been implicated in multiple physiological and pathophysiological processes including smooth muscle relaxation, platelet aggregation, exercise training, myocardial infarction, atherosclerosis, insulin resistance and Alzheimer's disease. In the heart, key advances have been made in elucidating the significance of Hsp20 in contractile function and cardioprotection over the last decade. This mini-review highlights exciting findings in animal models and human patients, with special emphasis on the potential salutary effects of Hsp20 in heart disease. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure."

What can we learn about cardioprotection from the cardiac mitochondrial proteome?

This review will summarize proteomic methods that are useful in studying the role of mitochondria in cardioprotection. The strengths and weaknesses of some of the different approaches are discussed. We focus on the cardiac mitochondrial proteome with emphasis on changes associated with cell death and protection, and we summarize how proteomic data have contributed to addressing the role of mitochondria in cardioprotection.

Mechanisms of exercise-induced improvements in the contractile apparatus of the mammalian myocardium

One of the main outcomes of aerobic endurance exercise training is the improved maximal oxygen uptake, and this is pivotal to the improved work capacity that follows the exercise training. Improved maximal oxygen uptake in turn is at least partly achieved because exercise training increases the ability of the myocardium to produce a greater cardiac output. In healthy subjects, this has been demonstrated repeatedly over many decades. It has recently emerged that this scenario may also be true under conditions of an initial myocardial dysfunction. For instance, myocardial improvements may still be observed after exercise training in post-myocardial infarction heart failure. In both health and disease, it is the changes that occur in the individual cardiomyocytes with respect to their ability to contract that by and large drive the exercise training-induced adaptation to the heart. Here, we review the evidence and the mechanisms by which exercise training induces beneficial changes in the mammalian myocardium, as obtained by means of experimental and clinical studies, and argue that these changes ultimately alter the function of the whole heart and contribute to the changes in whole-body function.

Proteomic analysis reveals late exercise effects on cardiac remodeling following myocardial infarction

Exercise has been shown to improve function of the left ventricle (LV) following myocardial infarction (MI). The mechanisms to explain this benefit have not been fully delineated, but may involve improved mechanics resulting in unloading effects and increased endothelial nitric oxide synthase levels [1,2]. Accordingly, the goal of this study was to determine how the LV infarct proteome is altered by a post-MI exercise regimen. Sprague-Dawley rats underwent ligation of the left descending coronary artery to induce MI. Exercise training was initiated four weeks post-MI and continued for 8 weeks in n=12 rats. Compared with the sedentary MI group (n=10), the infarct region of rats receiving exercise showed 20 protein spots with altered intensities in two-dimensional gels (15 increased and 5 decreased; p<0.05). Of 52 proteins identified in 20 spots, decreased levels of voltage-dependent anion-selective channel 2 and increased levels of glutathione perioxidase and manganese superoxide were confirmed by immunoblotting. Cardiac function was preserved in rats receiving exercise training, and the beneficial effect was linked with changes in these 3 proteins. In conclusion, our results suggest that post-MI exercise training increases anti-oxidant levels and decreases ion channel levels, which may explain, in part, the improved cardiac function seen with exercise.

Proteomic Profiling of the Dystrophin-Deficient MDX Heart Reveals Drastically Altered Levels of Key Metabolic and Contractile Proteins

Although Duchenne muscular dystrophy is primarily classified as a neuromuscular disease, cardiac complications play an important role in the course of this X-linked inherited disorder. The pathobiochemical steps causing a progressive decline in the dystrophic heart are not well understood. We therefore carried out a fluorescence difference in-gel electrophoretic analysis of 9-month-old dystrophin-deficient versus age-matched normal heart, using the established MDX mouse model of muscular dystrophy-related cardiomyopathy. Out of 2,509 detectable protein spots, 79 2D-spots showed a drastic differential expression pattern, with the concentration of 3 proteins being increased, including nucleoside diphosphate kinase and lamin-A/C, and of 26 protein species being decreased, including ATP synthase, fatty acid binding-protein, isocitrate dehydrogenase, NADH dehydrogenase, porin, peroxiredoxin, adenylate kinase, tropomyosin, actin, and myosin light chains. Hence, the lack of cardiac dystrophin appears to trigger a generally perturbed protein expression pattern in the MDX heart, affecting especially energy metabolism and contractile proteins.

Molecular distinction between physiological and pathological cardiac hypertrophy: experimental findings and therapeutic strategies

Cardiac hypertrophy can be defined as an increase in heart mass. Pathological cardiac hypertrophy (heart growth that occurs in settings of disease, e.g. hypertension) is a key risk factor for heart failure. Pathological hypertrophy is associated with increased interstitial fibrosis, cell death and cardiac dysfunction. In contrast, physiological cardiac hypertrophy (heart growth that occurs in response to chronic exercise training, i.e. the 'athlete's heart') is reversible and is characterized by normal cardiac morphology (i.e. no fibrosis or apoptosis) and normal or enhanced cardiac function. Given that there are clear functional, structural, metabolic and molecular differences between pathological and physiological hypertrophy, a key question in cardiovascular medicine is whether mechanisms responsible for enhancing function of the athlete's heart can be exploited to benefit patients with pathological hypertrophy and heart failure. This review summarizes key experimental findings that have contributed to our understanding of pathological and physiological heart growth. In particular, we focus on signaling pathways that play a causal role in the development of pathological and physiological hypertrophy. We discuss molecular mechanisms associated with features of cardiac hypertrophy, including protein synthesis, sarcomeric organization, fibrosis, cell death and energy metabolism and provide a summary of profiling studies that have examined genes, microRNAs and proteins that are differentially expressed in models of pathological and physiological hypertrophy. How gender and sex hormones affect cardiac hypertrophy is also discussed. Finally, we explore how knowledge of molecular mechanisms underlying pathological and physiological hypertrophy may influence therapeutic strategies for the treatment of cardiovascular disease and heart failure.

The small heat shock protein, HSPB6, in muscle function and disease

The small heat shock protein, HSPB6, is a 17-kDa protein that belongs to the small heat shock protein family. HSPB6 was identified in the mid-1990s when it was recognized as a by-product of the purification of HSPB1 and HSPB5. HSPB6 is highly and constitutively expressed in smooth, cardiac, and skeletal muscle and plays a role in muscle function. This review will focus on the physiologic and biochemical properties of HSPB6 in smooth, cardiac, and skeletal muscle; the putative mechanisms of action; and therapeutic implications.

Metabolic control exerted by the 2-oxoglutarate dehydrogenase reaction: a cross-kingdom comparison of the crossroad between energy production and nitrogen assimilation

Mechanism-based inhibitors and both forward and reverse genetics have proved to be essential tools in revealing roles for specific enzymatic processes in cellular function. Here, we review experimental studies aimed at assessing the impact of OG (2-oxoglutarate) oxidative decarboxylation on basic cellular activities in a number of biological systems. After summarizing the catalytic and regulatory properties of the OGDHC (OG dehydrogenase complex), we describe the evidence that has been accrued on its cellular role. We demonstrate an essential role of this enzyme in metabolic control in a wide range of organisms. Targeting this enzyme in different cells and tissues, mainly by its specific inhibitors, effects changes in a number of basic functions, such as mitochondrial potential, tissue respiration, ROS (reactive oxygen species) production, nitrogen metabolism, glutamate signalling and survival, supporting the notion that the evolutionary conserved reaction of OG degradation is required for metabolic adaptation. In particular, regulation of OGDHC under stress conditions may be essential to overcome glutamate excitotoxicity in neurons or affect the wound response in plants. Thus, apart from its role in producing energy, the flux through OGDHC significantly affects nitrogen assimilation and amino acid metabolism, whereas the side reactions of OGDHC, such as ROS production and the carboligase reaction, have biological functions in signalling and glyoxylate utilization. Our current view on the role of OGDHC reaction in various processes within complex biological systems allows us a far greater fundamental understanding of metabolic regulation and also opens up new opportunities for us to address both biotechnological and medical challenges.

Gene expression profile of rat left ventricles reveals persisting changes following chronic mild exercise protocol: implications for cardioprotection

Background

Epidemiological studies showed that physical exercise, specifically moderate lifelong training, is protective against cardiovascular morbidity and mortality. Most experimental work has focused into the effects and molecular mechanisms underlying intense, rather than mild exercise, by exploring the acute effect of training. Our study aims at investigating the cardioprotective effect of mild chronic exercise training and the gene expression profile changes at 48 hrs after the exercise cessation. Rats were trained at mild intensity on a treadmill: 25 m/min, 10%incline, 1 h/day, 3 days/week, 10 weeks; about 60% of the maximum aerobic power. By Affymetrix technology, we investigated the gene expression profile induced by exercise training in the left ventricle (LV) of trained (n = 10) and control (n = 10) rats. Cardioprotection was investigated by ischemia/reperfusion experiments (n = 10 trained vs. n = 10 control rats).

Results

Mild exercise did not induce cardiac hypertrophy and was cardioprotective as demonstrated by the decreased infarct size (p = 0.02) after ischemia/reperfusion experiments in trained with respect to control rats. Ten genes and 2 gene sets (two pathways) resulted altered in LV of exercised animals with respect to controls. We validated by real-time PCR the increased expression of four genes: similar to C11orf17 protein (RGD1306959), caveolin 3, enolase 3, and hypoxia inducible factor 1 alpha. Moreover, caveolin 3 protein levels were higher in exercised than control rats by immunohistochemistry and Western Blot analysis. Interestingly, the predicted gene similar to C11orf17 protein (RGD1306959) was significantly increased by exercise. This gene has a high homology with the human C11orf17 (alias: protein kinase-A interacting protein 1 or breast cancer associated gene 3). This is the first evidence that this gene is involved in the response to the exercise training.

Conclusion

Our data indicated that few, but significant, genes characterize the gene expression profile of the rat LV, when examined 48 hrs since the last training section and that mild exercise training determines cardioprotection without the induction of hypertrophy.

Overexpression of Hsp20 prevents endotoxin-induced myocardial dysfunction and apoptosis via inhibition of NF-kappaB activation

The occurrence of cardiovascular dysfunction in sepsis is associated with a significantly increased mortality rate of 70% to 90% compared with 20% in septic patients without cardiovascular impairment. Thus, rectification or blockade of myocardial depressant factors should partly ameliorate sepsis progression. Heat shock protein 20 (Hsp20) has been shown to enhance myocardial contractile function and protect against doxorubicin-induced cardiotoxicity. To investigate the possible role of Hsp20 in sepsis-mediated cardiac injury, we first examined the expression profiles of five major Hsps in response to lipopolysaccharide (LPS) challenge, and observed that only the expression of Hsp20 was downregulated in LPS-treated myocardium, suggesting that this decrease might be one of the mechanisms contributing to LPS-induced cardiovascular defects. Further studies using loss-of-function and gain-of-function approaches in adult rat cardiomyocytes verified that reduced Hsp20 levels were indeed correlated with the impaired contractile function. In fact, overexpression of Hsp20 significantly enhanced cardiomyocyte contractility upon LPS treatment. Moreover, after administration of LPS (25 microg/g) in vivo, Hsp20 transgenic mice (10-fold overexpression) displayed: 1) an improvement in myocardial function; 2) reduced the degree of cardiac apoptosis; and 3) decreased NF-kappaB activity, accompanied with reduced myocardial cytokines IL-1beta and TNF-alpha production, compared to the LPS-treated non-transgenic littermate controls. Thus, the increases in Hsp20 levels can protect against LPS-induced cardiac apoptosis and dysfunction, associated with inhibition of NF-kappaB activity, suggesting that Hsp20 may be a new therapeutic agent for the treatment of sepsis.

MicroRNA-320 is involved in the regulation of cardiac ischemia/reperfusion injury by targeting heat-shock protein 20

BACKGROUND

Recent studies have identified critical roles for microRNAs (miRNAs) in a variety of cellular processes, including regulation of cardiomyocyte death. However, the signature of miRNA expression and possible roles of miRNA in the ischemic heart have been less well studied.

METHODS AND RESULTS

We performed miRNA arrays to detect the expression pattern of miRNAs in murine hearts subjected to ischemia/reperfusion (I/R) in vivo and ex vivo. Surprisingly, we found that only miR-320 expression was significantly decreased in the hearts on I/R in vivo and ex vivo. This was further confirmed by TaqMan real-time polymerase chain reaction. Gain-of-function and loss-of-function approaches were employed in cultured adult rat cardiomyocytes to investigate the functional roles of miR-320. Overexpression of miR-320 enhanced cardiomyocyte death and apoptosis, whereas knockdown was cytoprotective, on simulated I/R. Furthermore, transgenic mice with cardiac-specific overexpression of miR-320 revealed an increased extent of apoptosis and infarction size in the hearts on I/R in vivo and ex vivo relative to the wild-type controls. Conversely, in vivo treatment with antagomir-320 reduced infarction size relative to the administration of mutant antagomir-320 and saline controls. Using TargetScan software and proteomic analysis, we identified heat-shock protein 20 (Hsp20), a known cardioprotective protein, as an important candidate target for miR-320. This was validated experimentally by utilizing a luciferase/GFP reporter activity assay and examining the expression of Hsp20 on miR-320 overexpression and knockdown in cardiomyocytes.

CONCLUSIONS

Our data demonstrate that miR-320 is involved in the regulation of I/R-induced cardiac injury and dysfunction via antithetical regulation of Hsp20. Thus, miR-320 may constitute a new therapeutic target for ischemic heart diseases.

Adaptation of the rat cardiac proteome in response to intensity-controlled endurance exercise

Endurance training improves cardiac function and protects against heart disease. The rodent intensity-controlled running model replicates endurance exercise in humans and can be used to investigate molecular adaptations in the heart. Rats (n = 6, 280 +/- 3 g) performed exercise tests to measure their peak oxygen uptake (VO2peak) and training was prescribed at 70-75% VO2 peak for 30 min, 4 days/wk. Hearts were isolated 4 h after a final VO2peak test and left ventricle proteomes compared to weight-matched control animals (n = 6, 330 +/- 2 g) using differential analysis of 2-D gels. Proteins were identified by searching MS and MS/MS spectra against Swiss-Prot using MASCOT (www.matrixscience.com). Average VO2peak increased 23% (p = 0.008) over the 6-week regimen and 23 gel spots differed (p<0.05) between exercised and control hearts. Expression of myofibrillar proteins (e.g. alpha-myosin heavy chain and cardiac alpha-actin) and proteins associated with fatty acid metabolism (e.g. heart fatty acid binding protein, acetyl coenzyme A dehydrogenase and mitochondrial thioesterase-1) increased. In addition, this work discovered a novel increase in phosphorylation of heat shock protein 20 at serine 16. Previously this modification has been associated with improved cardiomyocyte contractility and protection against apoptosis.

Human mutation in the anti-apoptotic heat shock protein 20 abrogates its cardioprotective effects

The small heat shock protein Hsp20 protects cardiomyocytes against apoptosis, and phosphorylation at its Ser16 site enhances its cardioprotection. To determine whether genetic variants exist in human Hsp20, which may modify these beneficial effects, we sequenced the coding region of the Hsp20 gene in 1347 patients suffering from dilated cardiomyopathy and 744 subjects with no heart disease. We identified a C59T substitution in the human Hsp20 gene in one patient and three individuals without heart disease. All subjects were heterozygous for this mutation, which changes a fully conserved proline residue into leucine at position 20 (P20L), resulting in secondary structural alterations. To examine the potential functional significance of the P20L-Hsp20 human variant, adult rat cardiomyocytes were infected with Ad.GFP (where Ad is adenovirus and GFP is green fluorescent protein), Ad.WT-Hsp20 (where WT is wild-type), and Ad.P20L-Hsp20 and subjected to simulated ischemia/reperfusion injury. Expression of WT-Hsp20 resulted in significant attenuation of apoptosis compared with the GFP control. However, the P20L-Hsp20 mutant showed no protection against apoptosis, assessed by Hoechst staining and DNA fragmentation. The loss of cardioprotection by the mutant Hsp20 was associated with its diminished phosphorylation at Ser16 compared with WT-Hsp20. Furthermore, maximal stimulation of cardiomyocytes with isoproterenol or protein kinase A-mediated phosphorylation in vitro confirmed the impaired ability of the mutant Hsp20 to become phosphorylated at Ser16. In conclusion, we have identified a P20L substitution in human Hsp20, which is associated with diminished phosphorylation at Ser16 and complete abrogation of the Hsp20 cardioprotective effects which may adversely affect the ability of human carriers to cope with cellular stress.