Small heat shock proteins and protection against ischemic injury in cardiac myocytes

Extracellular vesicles in nanomedicine and regenerative medicine: A review over the last decade

Small extracellular vesicles (sEVs) are known to be secreted by a vast majority of cells. These sEVs, specifically exosomes, induce specific cell-to-cell interactions and can activate signaling pathways in recipient cells through fusion or interaction. These nanovesicles possess several desirable properties, making them ideal for regenerative medicine and nanomedicine applications. These properties include exceptional stability, biocompatibility, wide biodistribution, and minimal immunogenicity. However, the practical utilization of sEVs, particularly in clinical settings and at a large scale, is hindered by the expensive procedures required for their isolation, limited circulation lifetime, and suboptimal targeting capacity. Despite these challenges, sEVs have demonstrated a remarkable ability to accommodate various cargoes and have found extensive applications in the biomedical sciences. To overcome the limitations of sEVs and broaden their potential applications, researchers should strive to deepen their understanding of current isolation, loading, and characterization techniques. Additionally, acquiring fundamental knowledge about sEVs origins and employing state-of-the-art methodologies in nanomedicine and regenerative medicine can expand the sEVs research scope. This review provides a comprehensive overview of state-of-the-art exosome-based strategies in diverse nanomedicine domains, encompassing cancer therapy, immunotherapy, and biomarker applications. Furthermore, we emphasize the immense potential of exosomes in regenerative medicine.

Desmin and its molecular chaperone, the αB-crystallin: How post-translational modifications modulate their functions in heart and skeletal muscles?

Maintenance of the highly organized striated muscle tissue requires a cell-wide dynamic network through protein-protein interactions providing an effective mechanochemical integrator of morphology and function. Through a continuous and complex trans-cytoplasmic network, desmin intermediate filaments ensure this essential role in heart and in skeletal muscle. Besides their role in the maintenance of cell shape and architecture (permitting contractile activity efficiency and conferring resistance towards mechanical stress), desmin intermediate filaments are also key actors of cell and tissue homeostasis. Desmin participates to several cellular processes such as differentiation, apoptosis, intracellular signalisation, mechanotransduction, vesicle trafficking, organelle biogenesis and/or positioning, calcium homeostasis, protein homeostasis, cell adhesion, metabolism and gene expression. Desmin intermediate filaments assembly requires αB-crystallin, a small heat shock protein. Over its chaperone activity, αB-crystallin is involved in several cellular functions such as cell integrity, cytoskeleton stabilization, apoptosis, autophagy, differentiation, mitochondria function or aggresome formation. Importantly, both proteins are known to be strongly associated to the aetiology of several cardiac and skeletal muscles pathologies related to desmin filaments disorganization and a strong disturbance of desmin interactome. Note that these key proteins of cytoskeleton architecture are extensively modified by post-translational modifications that could affect their functional properties. Therefore, we reviewed in the herein paper the impact of post-translational modifications on the modulation of cellular functions of desmin and its molecular chaperone, the αB-crystallin.

Single-cell RNA-seq reveals cellular heterogeneity from deep fascia in patients with acute compartment syndrome

Introduction

High stress in the compartment surrounded by the deep fascia can cause acute compartment syndrome (ACS) that may result in necrosis of the limbs. The study aims to investigate the cellular heterogeneity of the deep fascia in ACS patients by single-cell RNA sequencing (scRNA-seq).

Methods

We collected deep fascia samples from patients with ACS (high-stress group, HG, n=3) and patients receiving thigh amputation due to osteosarcoma (normal-stress group, NG, n=3). We utilized ultrasound and scanning electron microscopy to observe the morphologic change of the deep fascia, used multiplex staining and multispectral imaging to explore immune cell infiltration, and applied scRNA-seq to investigate the cellular heterogeneity of the deep fascia and to identify differentially expressed genes.

Results

Notably, we identified GZMK⁺interferon-act CD4 central memory T cells as a specific high-stress compartment subcluster expressing interferon-related genes. Additionally, the changes in the proportions of inflammation-related subclusters, such as the increased proportion of M2 macrophages and decreased proportion of M1 macrophages, may play crucial roles in the balance of pro-inflammatory and anti-inflammatory in the development of ACS. Furthermore, we found that heat shock protein genes were highly expressed but metal ion-related genes (S100 family and metallothionein family) were down-regulated in various subpopulations under high stress.

Conclusions

We identified a high stress-specific subcluster and variations in immune cells and fibroblast subclusters, as well as their differentially expressed genes, in ACS patients. Our findings reveal the functions of the deep fascia in the pathophysiology of ACS, providing new approaches for its treatment and prevention.

Emerging therapeutic roles of small heat shock protein-derived mini-chaperones and their delivery strategies

The small heat shock protein (sHsp) family is a group of proteins in which some are induced in response to external stimuli, such as environmental and pathological stresses, while others are constitutively expressed. They show chaperone-like activity, protect cells from apoptosis, and maintain cytoskeletal architecture. Short sequences or fragments ranging from approximately 19-20 residues in sHsps were shown to display chaperone activity in vitro. These sequences are termed sHsp-derived mini-peptides/mini-chaperones. These peptides offer an advantage in providing protective and therapeutic effects over full-length proteins owing to their small molecular weight and easy uptake into the cells. Research on sHsp mini-chaperone therapy has recently received attention and advanced tremendously. sHsp mini-chaperones have shown a wide range of therapeutic effects, such as anti-aggregation of proteins, anti-apoptotic, anti-inflammatory, anti-oxidant, senolytic, and anti-platelet activity. The administration of mini-chaperones into the several disease animal models, including experimental autoimmune encephalomyelitis, cataract, age-related macular degeneration, glaucoma, and thrombosis through various routes reduced symptoms or prevented the progression of the disease. However, it was found that the therapeutic potential of sHsp mini-chaperones is limited by their short turnover and enzymatic degradation in circulation. Nonetheless, carrier molecules approach such as nanoparticles, cell penetration peptides, and extracellular vesicles increased their efficacy by enhancing the uptake, retention time, protection from enzymatic degradation, and site-specific delivery without altering their biological activity. In this context, this review highlights the recent advances in the therapeutic potential of sHsp-derived mini-chaperones, their effect in experimental animal models, and approaches for increasing their efficacy.

Stress activated signalling impaired protein quality control pathways in human hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a complex myocardial disorder with no well-established disease-modifying therapy so far. Our study aimed to investigate how autophagy, oxidative stress, inflammation, stress signalling pathways, and apoptosis are hallmark of HCM and their contribution to the cardiac dysfunction. Demembranated cardiomyocytes from patients with HCM display increased titin-based stiffness (F_passive), which was corrected upon antioxidant treatment. Titin as a main determinant of F_passive was S-glutathionylated and highly ubiquitinated in HCM patients. This was associated with a shift in the balance of reduced and oxidized forms of glutathione (GSH and GSSG, respectively). Both heat shock proteins (HSP27 and α-ß crystalline) were upregulated and S-glutathionylated in HCM. Administration of HSPs in vitro significantly reduced HCM cardiomyocyte stiffness. High levels of the phosphorylated monomeric superoxide anion-generating endothelial nitric oxide synthase (eNOS), decreased nitric oxide (NO) bioavailability, decreased soluble guanylyl cyclase (sGC) activity, and high levels of 3-nitrotyrosine were observed in HCM. Many regulators of signal transduction pathways that are involved in autophagy, apoptosis, cardiac contractility, and growth including the mitogen-activated protein kinase (MAPK), protein kinase B (AKT), glycogen synthase kinase 3ß (GSK-3ß), mammalian target of rapamycin (mTOR), forkhead box O transcription factor (FOXO), c-Jun N-terminal protein kinase (JNK), and extracellular-signal-regulated kinase (ERK1/2) were modified in HCM. The apoptotic factors cathepsin, procaspase 3, procaspase 9 and caspase 12, but not caspase 9, were elevated in HCM hearts and associated with increased proinflammatory cytokines (Interleukin 6 (IL-6), interleukin 18 (IL-18), intercellular cell adhesion molecule-1 (ICAM1), vascular cell adhesion molecule-1 (VCAM1), the Toll-like receptors 2 (TLR2) and the Toll-like receptors 4 (TLR4)) and oxidative stress (3-nitrotyrosine and hydrogen peroxide (H₂O₂)). Here we reveal stress signalling and impaired PQS as potential mechanisms underlying the HCM phenotype. Our data suggest that reducing oxidative stress can be a viable therapeutic approach to attenuating the severity of cardiac dysfunction in heart failure and potentially in HCM and prevent its progression.

PP-1β and PP-2Aα modulate cAMP response element-binding protein (CREB) functions in aging control and stress response through de-regulation of αB-crystallin gene and p300-p53 signaling axis

The function of the transcription factor, cAMP response element‐binding protein (CREB), is activated through S133 phosphorylation by PKA and others. Regarding its inactivation, it is not well defined. cAMP response element‐binding protein plays an essential role in promoting cell proliferation, neuronal survival and the synaptic plasticity associated with long‐term memory. Our recent studies have shown that CREB is an important player in mediating stress response. Here, we have demonstrated that CREB regulates aging process through suppression of αB‐crystallin and activation of the p300‐p53‐Bak/Bax signaling axis. First, we determined that two specific protein phosphatases, PP‐1β and PP‐2Aα, can inactivate CREB through S133 dephosphorylation. Subsequently, we demonstrated that cells expressing the S133A‐CREB, a mutant mimicking constant dephosphorylation at S133, suppress CREB functions in aging control and stress response. Mechanistically, S133A‐CREB not only significantly suppresses CREB control of αB‐crystallin gene, but also represses CREB‐mediated activation of p53 acetylation and downstream Bak/Bax genes. cAMP response element‐binding protein suppression of αB‐crystallin and its activation of p53 acetylation are major molecular events observed in human cataractous lenses of different age groups. Together, our results demonstrate that PP‐1β and PP‐2Aα modulate CREB functions in aging control and stress response through de‐regulation of αB‐crystallin gene and p300‐p53‐Bax/Bak signaling axis, which regulates human cataractogenesis in the aging lens.

Exercise-Based Cardiac Rehabilitation Programs in Heart Failure Patients

Exercise training is recommended for patients with heart failure by major societies' guidelines. It improves exercise capacity and quality of life, reduces symptoms of depression, can improve survival, and reduce the risk for hospitalizations. Exercise-based cardiac rehabilitation can be offered with different modalities, such as continuous or interval aerobic training, resistance, and inspiratory muscle training. The intervention must follow an accurate evaluation of the patient's cardiovascular conditions and functional capacity. Despite the multiple benefits of exercise training, there is a lack of adherence to exercise-based programs, due to socioeconomic factors, patients' characteristics, and lack of referral.

Peptidomics Analysis Reveals Peptide PDCryab1 Inhibits Doxorubicin-Induced Cardiotoxicity

Doxorubicin (DOX) is limited due to dose-dependent cardiotoxicity. Peptidomics is an emerging field of proteomics that has attracted much attention because it can be used to study the composition and content of endogenous peptides in various organisms. Endogenous peptides participate in various biological processes and are important sources of candidates for drug development. To explore peptide changes related to DOX-induced cardiotoxicity and to find peptides with cardioprotective function, we compared the expression profiles of peptides in the hearts of DOX-treated and control mice by mass spectrometry. The results showed that 236 differential peptides were identified upon DOX treatment, of which 22 were upregulated and 214 were downregulated. Next, we predicted that 31 peptides may have cardioprotective function by conducting bioinformatics analysis on the domains of each precursor protein, the predicted score of peptide biological activity, and the correlation of each peptide with cardiac events. Finally, we verified that a peptide (SPFYLRPPSF) from Cryab can inhibit cardiomyocyte apoptosis, reduce the production of reactive oxygen species, improve cardiac function, and ameliorate myocardial fibrosis in vitro and vivo. In conclusion, our results showed that the expression profiles of peptides in cardiac tissue change significantly upon DOX treatment and that these differentially expressed peptides have potential cardioprotective functions. Our study suggests a new direction for the treatment of DOX-induced cardiotoxicity.

The transcription factor CREB acts as an important regulator mediating oxidative stress-induced apoptosis by suppressing αB-crystallin expression

The general transcription factor, CREB has been shown to play an essential role in promoting cell proliferation, neuronal survival and synaptic plasticity in the nervous system. However, its function in stress response remains to be elusive. In the present study, we demonstrated that CREB plays a major role in mediating stress response. In both rat lens organ culture and mouse lens epithelial cells (MLECs), CREB promotes oxidative stress-induced apoptosis. To confirm that CREB is a major player mediating the above stress response, we established stable lines of MLECs stably expressing CREB and found that they are also very sensitive to oxidative stress-induced apoptosis. To define the underlying mechanism, RNAseq analysis was conducted. It was found that CREB significantly suppressed expression of the αB-crystallin gene to sensitize CREB-expressing cells undergoing oxidative stress-induced apoptosis. CREB knockdown via CRISPR/CAS9 technology led to upregulation of αB-crystallin and enhanced resistance against oxidative stress-induced apoptosis. Moreover, overexpression of exogenous human αB-crystallin can restore the resistance against oxidative stress-induced apoptosis. Finally, we provided first evidence that CREB directly regulates αB-crystallin gene. Together, our results demonstrate that CREB is an important transcription factor mediating stress response, and it promotes oxidative stress-induced apoptosis by suppressing αB-crystallin expression.

A Mitochondrial Approach to Cardiovascular Risk and Disease

BACKGROUND

Cardiovascular diseases (CVDs) are a leading risk factor for mortality worldwide and the number of CVDs victims is predicted to rise through 2030. While several external parameters (genetic, behavioral, environmental and physiological) contribute to cardiovascular morbidity and mortality; intrinsic metabolic and functional determinants such as insulin resistance, hyperglycemia, inflammation, high blood pressure and dyslipidemia are considered to be dominant factors.

METHODS

Pubmed searches were performed using different keywords related with mitochondria and cardiovascular disease and risk. In vitro, animal and human results were extracted from the hits obtained.

RESULTS

High cardiac energy demand is sustained by mitochondrial ATP production, and abnormal mitochondrial function has been associated with several lifestyle- and aging-related pathologies in the developed world such as diabetes, non-alcoholic fatty liver disease (NAFLD) and kidney diseases, that in turn can lead to cardiac injury. In order to delay cardiac mitochondrial dysfunction in the context of cardiovascular risk, regular physical activity has been shown to improve mitochondrial parameters and myocardial tolerance to ischemia-reperfusion (IR). Furthermore, pharmacological interventions can prevent the risk of CVDs. Therapeutic agents that can target mitochondria, decreasing ROS production and improve its function have been intensively researched. One example is the mitochondria-targeted antioxidant MitoQ10, which already showed beneficial effects in hypertensive rat models. Carvedilol or antidiabetic drugs also showed protective effects by preventing cardiac mitochondrial oxidative damage.

CONCLUSION

This review highlights the role of mitochondrial dysfunction in CVDs, also show-casing several approaches that act by improving mitochondrial function in the heart, contributing to decrease some of the risk factors associated with CVDs.

Come Together: Protein Assemblies, Aggregates and the Sarcostat at the Heart of Cardiac Myocyte Homeostasis

Homeostasis in vertebrate systems is contingent on normal cardiac function. This, in turn, depends on intricate protein-based cellular machinery, both for contractile function, as well as, durability of cardiac myocytes. The cardiac small heat shock protein (csHsp) chaperone system, highlighted by αB-crystallin (CRYAB), a small heat shock protein (sHsp) that forms ∼3–5% of total cardiac mass, plays critical roles in maintaining proteostatic function via formation of self-assembled multimeric chaperones. In this work, we review these ancient proteins, from the evolutionarily preserved role of homologs in protists, fungi and invertebrate systems, as well as, the role of sHsps and chaperones in maintaining cardiac myocyte structure and function. We propose the concept of the “sarcostat” as a protein quality control mechanism in the sarcomere. The roles of the proteasomal and lysosomal proteostatic network, as well as, the roles of the aggresome, self-assembling protein complexes and protein aggregation are discussed in the context of cardiac myocyte homeostasis. Finally, we will review the potential for targeting the csHsp system as a novel therapeutic approach to prevent and treat cardiomyopathy and heart failure.

Effect of high-dose vitamin D supplementation on antibody titers to heat shock protein 27 in adolescent girls

Background Although vitamin D deficiency is associated with several inflammatory conditions, there have been few studies on the effects of vitamin D supplementation on markers of oxidative stress (OS) and inflammation. The aim of the current study was to evaluate the effects of high-dose vitamin D supplementation on heat shock protein 27 antibody (anti-Hsp27) titers in adolescent girls. Methods Five hundred and fifty adolescent girls received vitamin D3 at a dose of 50,000 IU/week for 9 weeks. Demographic, clinical and biochemical markers including serum fasting blood glucose (FBG), lipid profile and anti-Hsp27 titers as well as hematological parameters including white blood cell (WBC) count and red blood cell (RBC) distribution width (RDW) were determined in all the subjects at baseline and at the end of the study. Results Serum vitamin D significantly increased from 6.4 (4.2-9.6) ng/mL to 35.6 (25.8-47.5) ng/mL (p < 0.001) following the intervention. Furthermore, serum anti-Hsp27 titers were significantly lower after the 9-week vitamin D administration period (0.22 [0.12-0.33] optical density [OD] vs. 0.19 [0.11-0.31] OD; p = 0.002). A significant correlation was found between serum anti-Hsp27 and RDW (r = 0.13, p = 0.037). The reduction in RDW values after intervention was particularly evident in subjects with the greatest increase in serum vitamin D levels. Conclusions High-dose vitamin D supplementation was found to reduce antibody titers to Hsp27. Further randomized placebo-controlled trials are warranted to determine the long-term effect of vitamin D administration on the inflammatory process especially that associated with chronic disease.

Modulation of Titin-Based Stiffness in Hypertrophic Cardiomyopathy via Protein Kinase D

The giant protein titin performs structure-preserving functions in the sarcomere and is important for the passive stiffness (F_passive) of cardiomyocytes. Protein kinase D (PKD) enzymes play crucial roles in regulating myocardial contraction, hypertrophy, and remodeling. PKD phosphorylates myofilament proteins, but it is not known whether the giant protein titin is also a PKD substrate. Here, we aimed to determine whether PKD phosphorylates titin and thereby modulates cardiomyocyte F_passive in normal and failing myocardium. The phosphorylation of titin was assessed in cardiomyocyte-specific PKD knock-out mice (cKO) and human hearts using immunoblotting with a phosphoserine/threonine and a phosphosite-specific titin antibody. PKD-dependent site-specific titin phosphorylation in vivo was quantified by mass spectrometry using stable isotope labeling by amino acids in cell culture (SILAC) of SILAC-labeled mouse heart protein lysates that were mixed with lysates isolated from hearts of either wild-type control (WT) or cKO mice. F_passive of single permeabilized cardiomyocytes was recorded before and after PKD and HSP27 administration. All-titin phosphorylation was reduced in cKO compared to WT hearts. Multiple conserved PKD-dependent phosphosites were identified within the Z-disk, A-band and M-band regions of titin by quantitative mass spectrometry, and many PKD-dependent phosphosites detected in the elastic titin I-band region were significantly decreased in cKO. Analysis of titin site-specific phosphorylation showed unaltered or upregulated phosphorylation in cKO compared to matched WT hearts. F_passive was elevated in cKO compared to WT cardiomyocytes and PKD administration lowered F_passive of WT and cKO cardiomyocytes. Cardiomyocytes from hypertrophic cardiomyopathy (HCM) patients showed higher F_passive compared to control hearts and significantly lower F_passive after PKD treatment. In addition, we found higher phosphorylation at CaMKII-dependent titin sites in HCM compared to control hearts. Expression and phosphorylation of HSP27, a substrate of PKD, were elevated in HCM hearts, which was associated with increased PKD expression and phosphorylation. The relocalization of HSP27 in HCM away from the sarcomeric Z-disk and I-band suggested that HSP27 failed to exert its protective action on titin extensibility. This protection could, however, be restored by administration of HSP27, which significantly reduced F_passive in HCM cardiomyocytes. These findings establish a previously unknown role for PKDin regulating diastolic passive properties of healthy and diseased hearts.

The effect of whole-body cryostimulation on body composition and leukocyte expression of HSPA1A, HSPB1, and CRP in obese men

In recent years, the prevalence of obesity has increased dramatically and has become a 21st century epidemic. Obesity is associated with the development of many diseases, and therefore treatments that can reduce body mass are actively sought. The aim of this study was to examine the effect of 20 cryostimulation sessions on body composition in obese/high body mass (HBM, n = 12) males and normal body mass (NBM, n = 9) controls. The HBM group had a mean age = 29.08 ± 4.19 years, body fat percentage = 32.08 ± 6.16%, body mass index = 36.23 ± 8.13 kg/m²) and NBM group had a mean age = 22.00 ± 2.45 years, body fat percentage = 12.14 ± 4.93%, body mass index = 23.58 ± 2.00 kg/m². Kilocalorie intake was similar for both groups. All participants received 20 sessions of systemic cryostimulation at -120°C for 2-3 min in a cryochamber. Blood samples were collected before the first session, 1 h after the 10th session, and 1 h after the 20th cryostimulation session. C-reactive protein (CRP) plasma concentrations, and expression of the heat shock protein genes (HSPA1A, HSPB1) and CRP mRNA in leukocytes were evaluated after 10 and 20 cryostimulation sessions. In both groups, 20 sessions were associated with a significant decrease in body mass, fat mass and the percentage of body fat. CRP concentrations were significantly higher in obese people before the first session and after 10 treatments, but not at the end of study. Expression of HSPA1A and HSPB1 mRNA gradually decreased with the number of cryostimulation sessions. A significant difference in HSPA1A expression was found after 20 sessions (NBM > HBM) and for HSPB1 at baseline and after 20 sessions (HBM > NBM). Our results show that cryostimulation influences body composition and that cryostimulation-induced HSP genes expression depends on the number of cryosessions and baseline body mass, and is differentially altered in HBM individuals. Further research on the interaction between body mass and cold adaptation is warranted.

Mechanisms of Small Heat Shock Proteins

Small heat shock proteins (sHSPs) are ATP-independent chaperones that delay formation of harmful protein aggregates. sHSPs' role in protein homeostasis has been appreciated for decades, but their mechanisms of action remain poorly understood. This gap in understanding is largely a consequence of sHSP properties that make them recalcitrant to detailed study. Multiple stress-associated conditions including pH acidosis, oxidation, and unusual availability of metal ions, as well as reversible stress-induced phosphorylation can modulate sHSP chaperone activity. Investigations of sHSPs reveal that sHSPs can engage in transient or long-lived interactions with client proteins depending on solution conditions and sHSP or client identity. Recent advances in the field highlight both the diversity of function within the sHSP family and the exquisite sensitivity of individual sHSPs to cellular and experimental conditions. Here, we will present and highlight current understanding, recent progress, and future challenges.

Exosomes from adipose-derived mesenchymal stem cells prevent cardiomyocyte apoptosis induced by oxidative stress

Exosomes from bone marrow stem cells or cardiac progenitor cells can reduce apoptosis in myocardial cells after ischemia and reperfusion injury. However, there is little known about the effects of exosomes from adipose-derived stem cells (ADSCs), which are more abundant and have a lower risk of side effects. The aim of this study was to characterize exosomes from ADSCs and evaluate their cardioprotective actions against ischemia reperfusion injury. The exosomes were isolated from ADSCs and analyzed by protein marker expression, transmission electron microscopy, and nanoparticle tracking analysis. The ADSC-exosomes were then used for ex vivo investigation of the cardioprotective effects on cardiomyocytes after exposure to oxidative stress. Exosomes from ADSCs exhibited a diameter of 150 nm and expressed the marker proteins, CD9 and CD29. ADSC-exosomes had no effect on proliferation of untreated cardiomyocytes. In contrast, ADSC-derived exosomes reduced apoptosis in myocardial cells subjected to oxidative stress. This study confirms that exosomes originating from ADSCs can protect cardiomyocytes from oxidative stress.

The BAG3-dependent and -independent roles of cardiac small heat shock proteins

Small heat shock proteins (sHSPs) comprise an important protein family that is ubiquitously expressed, is highly conserved among species, and has emerged as a critical regulator of protein folding. While these proteins are functionally important for a variety of tissues, an emerging field of cardiovascular research reveals sHSPs are also extremely important for maintaining normal cardiac function and regulating the cardiac stress response. Notably, numerous mutations in genes encoding sHSPs have been associated with multiple cardiac diseases. sHSPs (HSPB5, HSPB6, and HSPB8) have been described as mediating chaperone functions within the heart by interacting with the cochaperone protein BCL-2-associated anthanogene 3 (BAG3); however, recent reports indicate that sHSPs (HSPB7) can perform other BAG3-independent functions. Here, we summarize the cardiac functions of sHSPs and present the notion that cardiac sHSPs function via BAG3-dependent or -independent pathways.

HSC70 is a chaperone for wild-type and mutant cardiac myosin binding protein C

Cardiac myosin binding protein C (MYBPC3) is the most commonly mutated gene associated with hypertrophic cardiomyopathy (HCM). Haploinsufficiency of full-length MYBPC3 and disruption of proteostasis have both been proposed as central to HCM disease pathogenesis. Discriminating the relative contributions of these 2 mechanisms requires fundamental knowledge of how turnover of WT and mutant MYBPC3 proteins is regulated. We expressed several disease-causing mutations in MYBPC3 in primary neonatal rat ventricular cardiomyocytes. In contrast to WT MYBPC3, mutant proteins showed reduced expression and failed to localize to the sarcomere. In an unbiased coimmunoprecipitation/mass spectrometry screen, we identified HSP70-family chaperones as interactors of both WT and mutant MYBPC3. Heat shock cognate 70 kDa (HSC70) was the most abundant chaperone interactor. Knockdown of HSC70 significantly slowed degradation of both WT and mutant MYBPC3, while pharmacologic activation of HSC70 and HSP70 accelerated degradation. HSC70 was expressed in discrete striations in the sarcomere. Expression of mutant MYBPC3 did not affect HSC70 localization, nor did it induce a protein folding stress response or ubiquitin proteasome dysfunction. Together these data suggest that WT and mutant MYBPC3 proteins are clients for HSC70, and that the HSC70 chaperone system plays a major role in regulating MYBPC3 protein turnover.

Cellular diversity of the somatosensory cortical map plasticity

Sensory maps are representations of the sensory epithelia in the brain. Despite the intuitive explanatory power behind sensory maps as being neuronal precursors to sensory perception, and sensory cortical plasticity as a neural correlate of perceptual learning, molecular mechanisms that regulate map plasticity are not well understood. Here we perform a meta-analysis of transcriptional and translational changes during altered whisker use to nominate the major molecular correlates of experience-dependent map plasticity in the barrel cortex. We argue that brain plasticity is a systems level response, involving all cell classes, from neuron and glia to non-neuronal cells including endothelia. Using molecular pathway analysis, we further propose a gene regulatory network that could couple activity dependent changes in neurons to adaptive changes in neurovasculature, and finally we show that transcriptional regulations observed in major brain disorders target genes that are modulated by altered sensory experience. Thus, understanding the molecular mechanisms of experience-dependent plasticity of sensory maps might help to unravel the cellular events that shape brain plasticity in health and disease.

Phosphorylation and degradation of αB-crystallin during enterovirus infection facilitates viral replication and induces viral pathogenesis

Protein quality control (PQC) plays a key role in maintaining cardiomyocyte function and homeostasis, and malfunction in PQC is implicated in various forms of heart diseases. Molecular chaperones serve as the primary checkpoint for PQC; however, their roles in the pathogenesis of viral myocarditis, an inflammation of the myocardium caused by viral infection, are largely unknown. AlphaB-crystallin (CryAB) is the most abundant chaperone protein in the heart. It interacts with desmin and cytoplasmic actin to prevent protein misfolding and aggregation and to help maintain cytoskeletal integrity and cardiac function. Here we showed that coxsackievirus infection induced desminopathy-like phenotype of the myocardium, as characterized by the accumulation of protein aggregates and the disruption of desmin organization. We further demonstrated that CryAB was phosphorylated during early and downregulated at later stages of infection. Moreover, we showed that phosphorylated CryAB had a shorter half-life and was targeted to the ubiquitin-proteasome system for degradation. Lastly, we found that overexpression of CryAB significantly attenuated viral protein production and progeny release, indicating an anti-viral function for CryAB. Together, our results suggest a mechanism by which coxsackieviral infection induces CryAB degradation and loss-of-function, resulting in desmin aggregation, ultimately contributing to compromised cytoskeletal integrity and viral cardiomyopathy.

Global gene expression profile of cerebral ischemia-reperfusion injury in rat MCAO model

It is well-established that reperfusion following cerebral ischemic injury gives rise to secondary injury accompanied by structural and functional damage. However, it remains unclear how global genes changes in cerebral ischemia-reperfusion injury (IRI). This study investigated global gene expression in the hippocampi of Wistar rats following transient cerebral IRI using an RNA-sequencing strategy. The results revealed ≥2-fold up-regulation of 156 genes and ≥2-fold down-regulation of 26 genes at 24 h post-reperfusion. Fifteen differentially expressed genes were selected to confirm the RNA-sequencing results. Gene expression levels were dynamic, with the peak expression level of each gene occurring at different time points post-reperfusion. Gene Ontology (GO) analysis classified the differentially expressed genes as mainly involved in inflammation, stress and immune response, glucose metabolism, proapoptosis, antiapoptosis, and biological processes. KEGG pathway analysis suggested that IRI activated different signaling pathways, including focal adhesion, regulation of actin cytoskeleton, cytokine-cytokine receptor interaction, MAPK signaling, and Jak-STAT signaling. This study describes global gene expression profiles in the hippocampi of Wistar rats using the middle cerebral artery occlusion (MCAO) model. These findings provide new insights into the molecular pathogenesis of IRI and potential drug targets for the prevention and treatment of IRI in the future.

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

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

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

Troponins, heat shock proteins and glycogen phosphorylase BB in umbilical cord blood of complicated pregnancies

PURPOSE OF THE STUDY

Heat shock proteins (Hsp) are evolutionary conserved molecules with a chaperone role in cell survival. We hypothesized that cord blood concentrations of molecules reflecting fetal cardiac muscle insult, including Hsp, troponins cTnI and cTnT, and glycol-phosphorylase BB (GP-BB) would be elevated in pregnancies complicated by gestational diabetes (GDM) or preeclampsia (PIH) compared to healthy controls.

MATERIALS AND METHODS

Pregnant women admitted for delivery at >28 weeks were divided into four groups: healthy patients delivered vaginally (VAG), healthy patients delivered by c-section (CS), patients with PIH, and patients with GDM. Demographics, clinical characteristics, and cord blood concentrations of Hsp, troponins cTnI and cTnT, and GP-BB were compared between groups. Statistical analyses included t-test, Chi square, and Wilcoxon rank sum as appropriate.

RESULTS

cTnI concentrations were significantly higher in the PIH group compared to the GDM and VAG groups and they were higher in the CS group compared to the VAG group. Concentrations of Hsp70 were higher in the GDM group compared to the VAG and CS groups. Concentration of GP-BB was higher in the PIH group compared to the VAG group.

CONCLUSIONS

GP-BB and cTNI are the most sensitive markers for PIH-related fetal myocyte injury as is Hsp70 in pregnancies complicated by GDM.

Inflammatory processes in cardiovascular disease: a route to targeted therapies

Inflammatory processes are firmly established as central to the development and complications of cardiovascular diseases. Elevated levels of inflammatory markers have been shown to be predictive of future cardiovascular events. The specific targeting of these processes in experimental models has been shown to attenuate myocardial and arterial injury, reduce disease progression, and promote healing. However, the translation of these observations and the demonstration of clear efficacy in clinical practice have been disappointing. A major limitation might be that tools currently used to measure 'inflammation' are insufficiently precise and do not provide information about disease site and activity, or discriminate between functionally important activation pathways. The challenge, therefore, is to make measures of inflammation that are more meaningful, and which can guide specific targeted therapies. In this Review, we consider the roles of inflammatory processes in the related pathologies of atherosclerosis and acute myocardial infarction, by providing an evaluation of the known and emerging inflammatory pathways. We highlight contemporary techniques to characterize and quantify inflammation, and consider how they might be used to guide specific treatments. Finally, we discuss emerging opportunities in the field, including their current limitations and challenges that are the focus of ongoing study.

Myocardial Preconditioning: Characteristics, Mechanisms, and Clinical Applications

Perioperative myocardial ischemia and dysfunction re main prevalent after cardiac surgery despite the use of conventional measures to provide myocardial protec tion. Myocardial preconditioning is a powerful, endog enously regulated means of myocardial protection that may also have some clinical usage for patients undergo ing cardiac surgical procedures. The paradoxical con cept of using ischemia as a stimulus for myocardial protection has been studied extensively in animals and humans. The specific characteristics and constituents of preconditioning have been well identified. The mecha nism remains to be completely elucidated due to differ ences among species and experimental models. Some pharmacologic agents are capable of mimicking the classic mechanism of ischemic preconditioning. Pharma cologic and ischemic preconditioning may have signifi cant clinical use and therapeutic efficacy as a means of providing myocardial protection during cardiac surgery, especially in procedures that do not use cardioplegia and cardiopulmonary bypass, such as minimally inva sive coronary artery bypass grafting. This article re views the characteristics, mechanisms, potential clini cal applications, and therapeutic efficacy of myocardial preconditioning.

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

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

Prolonged Survival of Transplanted Osteoblastic Cells Does Not Directly Accelerate the Healing of Calvarial Bone Defects

Considering the increased interest in cell-based bone regeneration, it is necessary to reveal the fate of transplanted cells and their substantive roles in bone regeneration. The aim of this study was to analyze the fate of transplanted cells and the effect of osteogenic cell transplantation on calvarial bone defect healing. An anti-apoptotic protein, heat shock protein (HSP) 27, was overexpressed in osteoblasts. Then, the treated osteoblasts were transplanted to calvarial bone defect and their fate was analyzed to evaluate the significance of transplanted cell survival. Transient overexpression of Hsp27 rescued MC3T3-E1 osteoblastic cells from H2 O2 -induced apoptosis without affecting osteoblastic differentiation in culture. Transplantation of Hsp27-overexpressing cells, encapsulated in collagen gel, showed higher proliferative activity, and fewer apoptotic cells in comparison with control cells. After 4-week of transplantation, both control cell- and Hsp27 overexpressed cell-transplanted groups showed significantly higher new bone formation in comparison with cell-free gel-transplantation group. Interestingly, the prolonged survival of transplanted osteoblastic cells by Hsp27 did not provide additional effect on bone healing. The transplanted cells in collagen gel survived for up to 4-week but did not differentiate into bone-forming osteoblasts. In conclusion, cell-containing collagen gel accelerated calvarial bone defect healing in comparison with cell-free collagen gel. However, prolonged survival of transplanted cells by Hsp27 overexpression did not provide additional effect. These results strongly indicate that cell transplantation-based bone regeneration cannot be explained only by the increment of osteogenic cells. Further studies are needed to elucidate the practical roles of transplanted cells that will potentiate successful bone regeneration. J. Cell. Physiol. 231: 1974-1982, 2016. © 2016 Wiley Periodicals, Inc.

Analysis of Mitochondrial Proteins in the Surviving Myocardium after Ischemia Identifies Mitochondrial Pyruvate Carrier Expression as Possible Mediator of Tissue Viability

The endogenous mechanisms contributing to tissue survival following myocardial infarction are not fully understood. We investigated the alterations in the mitochondrial proteome after ischemia-reperfusion (I/R) and its possible implications on cell survival. Mitochondrial proteomic analysis of cardiac tissue from an in vivo porcine I/R model found that surviving tissue in the peri-infarct border zone showed increased expression of several proteins. Notably, these included subunits of the mitochondrial pyruvate carrier (MPC), namely MPC1 and MPC2. Western blot, immunohistochemistry, and mRNA analysis corroborated the elevated expression of MPC in the surviving tissue. Furthermore, MPC1 and MPC2 protein levels were found to be markedly elevated in the myocardium of ischemic cardiomyopathy patients. These findings led to the hypothesis that increased MPC expression is cardioprotective due to enhancement of mitochondrial pyruvate uptake in the energy-starved heart following I/R. To test this, isolated mouse hearts perfused with a modified Krebs buffer (containing glucose, pyruvate, and octanoate as metabolic substrates) were subjected to I/R with or without the MPC transport inhibitor UK5099. UK5099 increased myocardial infarction and attenuated post-ischemic recovery of left ventricular end-diastolic pressure. However, aerobically perfused control hearts that were exposed to UK5099 did not modulate contractile function, although pyruvate uptake was blocked as evidenced by increased cytosolic lactate and pyruvate levels. Our findings indicate that increased expression of MPC leads to enhanced uptake and utilization of pyruvate during I/R. We propose this as a putative endogenous mechanism that promotes myocardial survival to limit infarct size.

Low T3 State Is Correlated with Cardiac Mitochondrial Impairments after Ischemia Reperfusion Injury: Evidence from a Proteomic Approach

Mitochondria are major determinants of cell fate in ischemia/reperfusion injury (IR) and common effectors of cardio-protective strategies in cardiac ischemic disease. Thyroid hormone homeostasis critically affects mitochondrial function and energy production. Since a low T3 state (LT3S) is frequently observed in the post infarction setting, the study was aimed to investigate the relationship between 72 h post IR T3 levels and both the cardiac function and the mitochondrial proteome in a rat model of IR. The low T3 group exhibits the most compromised cardiac performance along with the worst mitochondrial activity. Accordingly, our results show a different remodeling of the mitochondrial proteome in the presence or absence of a LT3S, with alterations in groups of proteins that play a key role in energy metabolism, quality control and regulation of cell death pathways. Overall, our findings highlight a relationship between LT3S in the early post IR and poor cardiac and mitochondrial outcomes, and suggest a potential implication of thyroid hormone in the cardio-protection and tissue remodeling in ischemic disease.

Phosphorylation of αB-crystallin: Role in stress, aging and patho-physiological conditions

BACKGROUND

αB-crystallin, once thought to be a lenticular protein, is ubiquitous and has critical roles in several cellular processes that are modulated by phosphorylation. Serine residues 19, 45 and 59 of αB-crystallin undergo phosphorylation. Phosphorylation of S45 is mediated by p44/42 MAP kinase, whereas S59 phosphorylation is mediated by MAPKAP kinase-2. Pathway involved in S19 phosphorylation is not known.

SCOPE OF REVIEW

The review highlights the role of phosphorylation in (i) oligomeric structure, stability and chaperone activity, (ii) cellular processes such as apoptosis, myogenic differentiation, cell cycle regulation and angiogenesis, and (iii) aging, stress, cardiomyopathy-causing αB-crystallin mutants, and in other diseases.

MAJOR CONCLUSIONS

Depending on the context and extent of phosphorylation, αB-crystallin seems to confer beneficial or deleterious effects. Phosphorylation alters structure, stability, size distribution and dynamics of the oligomeric assembly, thus modulating chaperone activity and various cellular processes. Phosphorylated αB-crystallin has a tendency to partition to the cytoskeleton and hence to the insoluble fraction. Low levels of phosphorylation appear to be protective, while hyperphosphorylation has negative implications. Mutations in αB-crystallin, such as R120G, Q151X and 464delCT, associated with inherited myofibrillar myopathy lead to hyperphosphorylation and intracellular inclusions. An ongoing study in our laboratory with phosphorylation-mimicking mutants indicates that phosphorylation of R120GαB-crystallin increases its propensity to aggregate.

GENERAL SIGNIFICANCE

Phosphorylation of αB-crystallin has dual role that manifests either beneficial or deleterious consequences depending on the extent of phosphorylation and interaction with cytoskeleton. Considering that disease-causing mutants of αB-crystallin are hyperphosphorylated, moderation of phosphorylation may be a useful strategy in disease management. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

A change of heart: oxidative stress in governing muscle function?

Redox/cysteine modification of proteins that regulate calcium cycling can affect contraction in striated muscles. Understanding the nature of these modifications would present the possibility of enhancing cardiac function through reversible cysteine modification of proteins, with potential therapeutic value in heart failure with diastolic dysfunction. Both heart failure and muscular dystrophy are characterized by abnormal redox balance and nitrosative stress. Recent evidence supports the synergistic role of oxidative stress and inflammation in the progression of heart failure with preserved ejection fraction, in concert with endothelial dysfunction and impaired nitric oxide-cyclic guanosine monophosphate-protein kinase G signalling via modification of the giant protein titin. Although antioxidant therapeutics in heart failure with diastolic dysfunction have no marked beneficial effects on the outcome of patients, it, however, remains critical to the understanding of the complex interactions of oxidative/nitrosative stress with pro-inflammatory mechanisms, metabolic dysfunction, and the redox modification of proteins characteristic of heart failure. These may highlight novel approaches to therapeutic strategies for heart failure with diastolic dysfunction. In this review, we provide an overview of oxidative stress and its effects on pathophysiological pathways. We describe the molecular mechanisms driving oxidative modification of proteins and subsequent effects on contractile function, and, finally, we discuss potential therapeutic opportunities for heart failure with diastolic dysfunction.

Plasma exosomes protect the myocardium from ischemia-reperfusion injury

BACKGROUND

Exosomes are nanometer-sized vesicles released from cells into the blood, where they can transmit signals throughout the body. Shown to act on the heart, exosomes' composition and the signaling pathways they activate have not been explored. We hypothesized that endogenous plasma exosomes can communicate signals to the heart and provide protection against ischemia and reperfusion injury.

OBJECTIVES

This study sought to isolate and characterize exosomes from rats and healthy volunteers, evaluate their cardioprotective actions, and identify the molecular mechanisms involved.

METHODS

The exosome-rich fraction was isolated from the blood of adult rats and human volunteers and was analyzed by protein marker expression, transmission electron microscopy, and nanoparticle tracking analysis. This was then used in ex vivo, in vivo, and in vitro settings of ischemia-reperfusion, with the protective signaling pathways activated on cardiomyocytes identified using Western blot analyses and chemical inhibitors.

RESULTS

Exosomes exhibited the expected size and expressed marker proteins CD63, CD81, and heat shock protein (HSP) 70. The exosome-rich fraction was powerfully cardioprotective in all tested models of cardiac ischemia-reperfusion injury. We identified a pro-survival signaling pathway activated in cardiomyocytes involving toll-like receptor (TLR) 4 and various kinases, leading to activation of the cardioprotective HSP27. Cardioprotection was prevented by a neutralizing antibody against a conserved HSP70 epitope expressed on the exosome surface and by blocking TLR4 in cardiomyocytes, identifying the HSP70/TLR4 communication axis as a critical component in exosome-mediated cardioprotection.

CONCLUSIONS

Exosomes deliver endogenous protective signals to the myocardium by a pathway involving TLR4 and classic cardioprotective HSPs.

Differential hypoxic tolerance is mediated by activation of heat shock response and nitric oxide pathway

The fall in ambient oxygen pressure in high-altitude milieu elicits a wide range of physiological responses in the myocardium, which may differ from individual to individual. This condition, known as hypobaric hypoxia, invokes the cardioprotective heat shock response. The present study focuses on the role played by this ubiquitous response in mediating a differential tolerance to acute hypoxic stress. Sprague Dawley rats were exposed to simulated hypoxia equivalent to 223 mmHg pressure, screened on the basis of time taken for onset of a characteristic hyperventilatory response, and categorized as susceptible (<10 min), normal (10-25 min), or tolerant (>25 min). The tolerant animals displayed a significant upregulation of heat shock protein (Hsp)70/HSPA, evident through immunohistochemical staining of the cardiac tissue. The increased expression of transcription factor heat shock factor-1 led to the downstream activation of other chaperones, including Hsp90/HSPC, Hsp60/HSPD1, and Hsp27/HSPB1. The higher induction of HSPs in tolerant animals contributed to higher nitric oxide synthesis mediated by both endothelial nitric oxide synthase and inducible nitric oxide synthase activation. Conversely, susceptible animals showed significantly higher expression of the proinflammatory markers tumor necrosis factor alpha and nuclear factor kappa-light-chain enhancer of activated B cells in the myocardium. Evaluation of circulatory stress markers identified increased levels of reactive oxygen species, corticosterone and endothelin-1 in the susceptible animals highlighting their vulnerability to hypoxic stress. The heat shock response, through the action of chaperones and enhanced NO generation thus contributes substantially to the ability to sustain survival under acute sub lethal hypoxia.

Different effects of prolonged β-adrenergic stimulation on heart and cerebral artery

The aim of this review was to understand the effects of β-adrenergic stimulation on oxidative stress, structural remodeling, and functional alterations in the heart and cerebral artery. Diverse stimuli activate the sympathetic nervous system, leading to increased levels of catecholamines. Long-term overstimulation of the β-adrenergic receptor (βAR) in response to catecholamines causes cardiovascular diseases, including cardiac hypertrophy, stroke, coronary artery disease, and heart failure. Although catecholamines have identical sites of action in the heart and cerebral artery, the structural and functional modifications differentially activate intracellular signaling cascades. βAR-stimulation can increase oxidative stress in the heart and cerebral artery, but has also been shown to induce different cytoskeletal and functional modifications by modulating various components of the βAR signal transduction pathways. Stimulation of βAR leads to cardiac dysfunction due to an overload of intracellular Ca²⁺ in cardiomyocytes. However, this stimulation induces vascular dysfunction through disruption of actin cytoskeleton in vascular smooth muscle cells. Many studies have shown that excessive concentrations of catecholamines during stressful conditions can produce coronary spasms or arrhythmias by inducing Ca²⁺-handling abnormalities and impairing energy production in mitochondria, In this article, we highlight the different fates caused by excessive oxidative stress and disruptions in the cytoskeletal proteome network in the heart and the cerebral artery in responsed to prolonged βAR-stimulation.

Heat shock proteins and cardiovascular disease

Atherosclerosis is the leading global cause of mortality, morbidity, and disability. Heat shock proteins (HSPs) are a highly conserved family of proteins with diverse functions expressed by all cells exposed to environmental stress. Studies have reported that several HSPs may be potential risk markers of atherosclerosis and related cardiovascular diseases, or may be directly involved in the atherogenic process itself. HSPs are expressed by cells in atherosclerotic plaque and anti-HSP has been reported to be increased in patients with vascular disease. Autoimmune responses may be generated against antigens present within the atherosclerotic plaque, including HSP and may lead to a cycle of ongoing vascular injury. It has been suggested that by inducing a state of tolerance to these antigens, the atherogenic process may be limited and thus provide a potential therapeutic approach. It has been suggested that anti-HSPs are independent predictors of risk of vascular disease. In this review, we summarize the current understanding of HSP in cardiovascular disease and highlight their potential role as diagnostic agents and therapeutic targets.

Immunohistochemical profiling of the heat shock response in obese non-diabetic subjects revealed impaired expression of heat shock proteins in the adipose tissue

BACKGROUND

Obesity is characterized by a chronic low-grade inflammation and altered stress responses in key metabolic tissues. Impairment of heat shock response (HSR) has been already linked to diabetes and insulin resistance as reflected by decrease in heat shock proteins (HSPs) expression. However, the status of HSR in non-diabetic human obese has not yet been elucidated. The aim of the current study was to investigate whether obesity triggers a change in the HSR pattern and the impact of physical exercise on this pattern at protein and mRNA levels.

METHODS

Two groups of adult non-diabetic human subjects consisting of lean and obese (n = 47 for each group) were enrolled in this study. The expression pattern of HSP-27, DNAJB3/HSP-40, HSP-60, HSC-70, HSP72, HSP-90 and GRP-94 in the adipose tissue was primarily investigated by immunohistochemistry and then complemented by western blot and qRT-PCR in Peripheral blood mononuclear cells (PBMCs). HSPs expression levels were correlated with various physical, clinical and biochemical parameters. We have also explored the effect of a 3-month moderate physical exercise on the HSPs expression pattern in obese subjects.

RESULTS

Obese subjects displayed increased expression of HSP-60, HSC-70, HSP-72, HSP-90 and GRP-94 and lower expression of DNAJB3/HSP-40 (P < 0.05). No differential expression was observed for HSP-27 between the two groups. Higher levels of HSP-72 and GRP-94 proteins correlated positively with the indices of obesity (body mass index and percent body fat) and circulating levels of IFN-gamma-inducible protein 10 (IP-10) and RANTES chemokines. This expression pattern was concomitant with increased inflammatory response in the adipose tissue as monitored by increased levels of Interleukin-6 (IL-6), Tumor necrosis factor-α (TNF-α), and RANTES (P < 0.05). Physical exercise reduced the expression of various HSPs in obese to normal levels observed in lean subjects with a parallel decrease in the endogenous levels of IL-6, TNF-α, and RANTES.

CONCLUSION

Taken together, these data indicate that obesity triggers differential regulation of various components of the HSR in non-diabetic subjects and a 3-month physical moderate exercise was sufficient to restore the normal expression of HSPs in the adipose tissue with concomitant attenuation in the inflammatory response.

Protective effect of geranylgeranylacetone via enhanced induction of HSPB1 and HSPB8 in mitochondria of the failing heart following myocardial infarction in rats

The mechanisms underlying mitochondrial impairment in the failing heart are not yet clear. In a previous study, we found that the levels of small heat shock proteins (HSP) such as mitochondrial HSPB1 and HSPB8 in the failing heart following myocardial infarction were decreased. In the present study, to verify the hypothesis that mitochondrial dysfunction in the failing heart is associated with alterations in mitochondrial small heat shock proteins, we examined the effects of geranylgeranylacetone, a heat shock protein inducer, on the cardiac mitochondrial function after myocardial infarction. When hemodynamic parameters of rats with myocardial infarction were measured at the 8th (8W) week after coronary artery ligation (CAL), the 8W-CAL showed signs of chronic heart failure concomitant with a reduced mitochondrial oxygen consumption rate. HSPB1 and HSPB8 contents in the mitochondrial fraction prepared from the failing heart were decreased, suggesting that an attenuation of mitochondrial translocation of HSPB1 and HSPB8 had led to an impairment of mitochondrial energy-producing ability. Geranylgeranylacetone treatment from the 2nd to 8th week after myocardial infarction attenuated the reduction in mitochondrial HSPB1 and HSPB8 contents. Furthermore, the mitochondrial energy-producing ability and cardiac pump function were preserved by orally administered geranylgeranylacetone during the development of heart failure. These results suggest that the induction of small heat shock proteins in the infarcted heart by geranylgeranylacetone treatment contributed to the preservation of mitochondrial function, leading to an improvement of cardiac contractile function.

Contribution of small heat shock proteins to muscle development and function

Investigations undertaken over the past years have led scientists to introduce the concept of protein quality control (PQC) systems, which are responsible for polypeptide processing. The PQC system monitors proteostasis and involves activity of different chaperones such as small heat shock proteins (sHSPs). These proteins act during normal conditions as housekeeping proteins regulating cellular processes, and during stress conditions. They also mediate the removal of toxic misfolded polypeptides and thereby prevent development of pathogenic states. It is postulated that sHSPs are involved in muscle development. They could act via modulation of myogenesis or by maintenance of the structural integrity of signaling complexes. Moreover, mutations in genes coding for sHSPs lead to pathological states affecting muscular tissue functioning. This review focuses on the question how sHSPs, still relatively poorly understood proteins, contribute to the development and function of three types of muscle tissue: skeletal, cardiac and smooth.

A phase 1, dose-escalation, pharmacokinetic and pharmacodynamic study of BIIB021 administered orally in patients with advanced solid tumors

PURPOSE

BIIB021 is the first oral, synthetic, non-geldanamycin-based HSP90 inhibitor that showed activity in preclinical models at low nanomolar concentrations. We performed a phase 1 trial of BIIB021 administered to subjects with advanced solid tumors.

EXPERIMENTAL DESIGN

Sixty patients received BIIB021 capsules orally on days 1, 4, 8, 11, 15, and 18 of each course in schedule 1, and on days 1, 4, 8, 11, 15, 18, 22, and 25 of each course in schedule 2. The treatment schedules were repeated every 28 days. In addition to determining the MTD, we evaluated pharmacokinetics of BIIB021 and pharmacodynamic effects of BIIB021 [Hsp70, HER2 extracellular domain (HER2-ECD)].

RESULTS

The MTD was 700 mg twice weekly when BIIB021 was dosed for 3 weeks out of each 4-week course. The MTD for continuous dosing regimen was established at 600 mg twice weekly. Gastrointestinal (nausea, vomiting), hot flashes, and neurologic (dizziness) events characterize the safety profile of BIIB021 dosed twice weekly, with events mostly mild or moderate. Plasma exposure to BIIB021 was dose-dependent. Cmax occurred at approximately 90 minutes and t1/2 was approximately 1 hour across dosing cohorts of 25 to 800 mg BIIB021 twice weekly. The biologic activity of BIIB021 was demonstrated in serum, PBMCs, and tumor tissue. Hsp70 levels were increased (>150% from baseline) and serum HER2-ECD was significantly decreased (>15% inhibition from baseline).

CONCLUSIONS

BIIB021 twice weekly, given with or without the 1 of 4-week rest period was tolerated in subjects with advanced solid tumors at doses that are pharmacodynamically active.

Human myocytes are protected from titin aggregation-induced stiffening by small heat shock proteins

Small heat shock proteins translocate to unfolded titin Ig domains under stress conditions to prevent titin aggregation and myocyte stiffening.

In myocytes, small heat shock proteins (sHSPs) are preferentially translocated under stress to the sarcomeres. The functional implications of this translocation are poorly understood. We show here that HSP27 and αB-crystallin associated with immunoglobulin-like (Ig) domain-containing regions, but not the disordered PEVK domain (titin region rich in proline, glutamate, valine, and lysine), of the titin springs. In sarcomeres, sHSP binding to titin was actin filament independent and promoted by factors that increased titin Ig unfolding, including sarcomere stretch and the expression of stiff titin isoforms. Titin spring elements behaved predominantly as monomers in vitro. However, unfolded Ig segments aggregated, preferentially under acidic conditions, and αB-crystallin prevented this aggregation. Disordered regions did not aggregate. Promoting titin Ig unfolding in cardiomyocytes caused elevated stiffness under acidic stress, but HSP27 or αB-crystallin suppressed this stiffening. In diseased human muscle and heart, both sHSPs associated with the titin springs, in contrast to the cytosolic/Z-disk localization seen in healthy muscle/heart. We conclude that aggregation of unfolded titin Ig domains stiffens myocytes and that sHSPs translocate to these domains to prevent this aggregation.

Adrenergic signaling and oxidative stress: a role for sirtuins?

The adrenergic system plays a central role in stress signaling and stress is often associated with increased production of ROS. However, ROS overproduction generates oxidative stress, that occurs in response to several stressors. β-adrenergic signaling is markedly attenuated in conditions such as heart failure, with downregulation and desensitization of the receptors and their uncoupling from adenylyl cyclase. Transgenic activation of β2-adrenoceptor leads to elevation of NADPH oxidase activity, with greater ROS production and p38MAPK phosphorylation. Inhibition of NADPH oxidase or ROS significantly reduced the p38MAPK signaling cascade. Chronic β2-adrenoceptor activation is associated with greater cardiac dilatation and dysfunction, augmented pro-inflammatory and profibrotic signaling, while antioxidant treatment protected hearts against these abnormalities, indicating ROS production to be central to the detrimental signaling of β2-adrenoceptors. It has been demonstrated that sirtuins are involved in modulating the cellular stress response directly by deacetylation of some factors. Sirt1 increases cellular stress resistance, by an increased insulin sensitivity, a decreased circulating free fatty acids and insulin-like growth factor (IGF-1), an increased activity of AMPK, increased activity of PGC-1a, and increased mitochondrial number. Sirt1 acts by involving signaling molecules such P-I-3-kinase-Akt, MAPK and p38-MAPK-β. βAR stimulation antagonizes the protective effect of the AKT pathway through inhibiting induction of Hif-1α and Sirt1 genes, key elements in cell survival. More studies are needed to better clarify the involvement of sirtuins in the β-adrenergic response and, overall, to better define the mechanisms by which tools such as exercise training are able to counteract the oxidative stress, by both activation of sirtuins and inhibition of GRK2 in many cardiovascular conditions and can be used to prevent or treat diseases such as heart failure.

Adrenergic signaling and oxidative stress: a role for sirtuins?

The adrenergic system plays a central role in stress signaling and stress is often associated with increased production of ROS. However, ROS overproduction generates oxidative stress, that occurs in response to several stressors. β-adrenergic signaling is markedly attenuated in conditions such as heart failure, with downregulation and desensitization of the receptors and their uncoupling from adenylyl cyclase. Transgenic activation of β2-adrenoceptor leads to elevation of NADPH oxidase activity, with greater ROS production and p38MAPK phosphorylation. Inhibition of NADPH oxidase or ROS significantly reduced the p38MAPK signaling cascade. Chronic β2-adrenoceptor activation is associated with greater cardiac dilatation and dysfunction, augmented pro-inflammatory and profibrotic signaling, while antioxidant treatment protected hearts against these abnormalities, indicating ROS production to be central to the detrimental signaling of β2-adrenoceptors. It has been demonstrated that sirtuins are involved in modulating the cellular stress response directly by deacetylation of some factors. Sirt1 increases cellular stress resistance, by an increased insulin sensitivity, a decreased circulating free fatty acids and insulin-like growth factor (IGF-1), an increased activity of AMPK, increased activity of PGC-1a, and increased mitochondrial number. Sirt1 acts by involving signaling molecules such P-I-3-kinase-Akt, MAPK and p38-MAPK-β. βAR stimulation antagonizes the protective effect of the AKT pathway through inhibiting induction of Hif-1α and Sirt1 genes, key elements in cell survival. More studies are needed to better clarify the involvement of sirtuins in the β-adrenergic response and, overall, to better define the mechanisms by which tools such as exercise training are able to counteract the oxidative stress, by both activation of sirtuins and inhibition of GRK2 in many cardiovascular conditions and can be used to prevent or treat diseases such as heart failure.

Effects of hyperbaric oxygen preconditioning on cardiac stress markers after simulated diving

Hyperbaric oxygen preconditioning (HBO-PC) can protect the heart from injury during subsequent ischemia. The presence of high loads of venous gas emboli (VGE) induced by a rapid ambient pressure reduction on ascent from diving may cause ischemia and acute heart failure. The aim of this study was to investigate the effect of diving-induced VGE formation on cardiac stress marker levels and the cardioprotective effect of HBO-PC. To induce high loads of VGE, 63 female Sprague-Dawley rats were subjected to a rapid ambient pressure reduction from a simulated saturation dive (50 min at 709 kPa) in a pressure chamber. VGE loads were measured for 60 min in anesthetized animals by the use of ultrasonography. The animals were divided into five groups. Three groups were exposed to either diving or to HBO-PC (100% oxygen, 38 min at 303 kPa) with a 45 or 180 min interval between HBO-PC and diving. Two additional groups were used as baseline controls for the measurements; one group was exposed to equal handling except for HBO-PC and diving, and the other group was completely unexposed. Diving caused high loads of VGE, as well as elevated levels of the cardiac stress markers, cardiac troponin T (cTnT), natriuretic peptide precursor B (Nppb), and αB-crystallin, in blood and cardiac tissue. There were strong positive correlations between VGE loads and stress marker levels after diving, and HBO-PC appeared to have a cardioprotective effect, as indicated by the lower levels of stress marker expression after diving-induced VGE formation.

Postnatal shifts in ischemic tolerance and cell survival signaling in murine myocardium

The immature heart is known to be resistant to ischemia-reperfusion (I/R) injury; however, key proteins engaged in phospho-dependent signaling pathways crucial to cell survival are not yet defined. Our goal was to determine the postnatal changes in myocardial tolerance to I/R, including baseline expression of key proteins governing I/R tolerance and their phosphorylation during I/R. Hearts from male C57Bl/6 mice (neonates, 2, 4, 8, and 12 wk of age, n = 6/group) were assayed for survival signaling/effectors [Akt, p38MAPK, glycogen synthase kinase-3β (GSK-3β), heat shock protein 27 (HSP27), connexin-43, hypoxia-inducible factor-1α (HIF-1α), and caveolin-3] and regulators of apoptosis (Bax and Bcl-2) and autophagy (LC3B, Parkin, and Beclin1). The effect of I/R on ventricular function was measured in isolated perfused hearts from immature (4 wk) and adult (12 wk) mice. The neonatal myocardium exhibits a large pool of inactive Akt; high phospho-activation of p38MAPK, HSP27 and connexin-43; phospho-inhibition of GSK-3β; and high expression of caveolin-3, HIF-1α, LC3B, Beclin1, Bax, and Bcl-2. Immature hearts sustained less dysfunction and infarction following I/R than adults. Emergence of I/R intolerance in adult vs. immature hearts was associated with complex proteomic changes: decreased expression of Akt, Bax, and Bcl-2; increased GSK-3β, connexin-43, HIF-1α, LC3B, and Bax:Bcl-2; enhanced postischemic HIF-1α, caveolin-3, Bax, and Bcl-2; and greater postischemic GSK-3β and HSP27 phosphorylation. Neonatal myocardial stress resistance reflects high expression of prosurvival and autophagy proteins and apoptotic regulators. Notably, there is high phosphorylation of GSK-3β, p38MAPK, and HSP27 and low phosphorylation of Akt (high Akt "reserve"). Subsequent maturation-related reductions in I/R tolerance are associated with reductions in Akt, Bcl-2, LC3B, and Beclin1, despite increased expression and reduced phospho-inhibition of GSK-3β.

The mechanisms of the widespread production of phosphorylated HSP25 after fatiguing muscle stimulation

We previously showed that a widespread heat shock protein (HSP) response to fatigue of a single hindlimb muscle was responsible for a global adaptive response to an acute localized stress. We also demonstrated that the HSP response resulted from the activation of nerve afferents from the stimulated muscle. However, we did not examine the role played by the different muscle afferents or the efferent arm of HSP response. In the present study we measured the changes in phosphorylated HSP25 (pHSP25) levels in resting hindlimb muscles and the diaphragm, kidney and brain in response to a fatiguing stimulation of one tibialis anterior muscle that was repeated in five series of experiments: (1) intact muscle innervation, (2) during the selective procaine block of conduction in group IV muscle afferents, (3) after muscle nerve transection to suppress all the sensory messages, and under pharmacological blockade of the (4) alpha-adrenergic or (5) glutamatergic neurotransmission. The data showed that: (1) the pHSP25 response in hindlimb muscles resulted from the stimulation of both group III and IV muscle afferents while the pHSP25 response in the diaphragm, kidney and brain resulted from the sole activation of the group IV fibres, and (2) the blockade of alpha-adrenergic, but not glutamatergic, neurotransmission suppressed the pHSP25 response in all explored tissues except the brain. The present study highlights the role played by the group III and IV muscle afferents in the fatigue-induced pHSP25 response and shows that the sympathetic nerve supply to the muscles and kidney represents the efferent arm of the pHSP25 activation. However, the pHSP25 changes in the brain cannot be explained by the pathways investigated here.