H11 Kinase Prevents Myocardial Infarction by Preemptive Preconditioning of the Heart

Heat shock protein 22: A new direction for cardiovascular disease (Review)

Small heat shock proteins (sHSPs) are common molecular chaperone proteins that function in various biological processes, and serve indispensable roles in maintaining cellular protein homeostasis and regulating the hydrolysis of unfolded proteins. HSP22 is a member of the sHSP family that is primarily expressed in the heart and skeletal muscle, as well as in various types of cancer. There have been important findings concerning the role of HSP22 in cardiovascular diseases. The aim of the present study was to provide insights into the various molecular mechanisms by which HSP22 functions in the heart, including oxidative stress, autophagy, apoptosis, the subcellular distribution of proteins and the promoting effect of proteasomes. In addition, drugs and cytokines, including geranylgeranylacetone, can exert protective effects on the heart by regulating the expression of HSP22. Based on increasingly abundant research, HSP22 may be considered a potential therapeutic target in cardiovascular diseases.

Valosin-containing protein: A potential therapeutic target for cardiovascular diseases

Valosin-containing protein (VCP), also known as p97, plays a crucial role in various cellular processes, including protein degradation, endoplasmic reticulum-associated degradation, and cell cycle regulation. While extensive research has been focused on VCP's involvement in protein homeostasis and its implications in neurodegenerative diseases, emerging evidence suggests a potential link between VCP and cardiovascular health. VCP is a key regulator of mitochondrial function, and its overexpression or mutations lead to pathogenic diseases and cellular stress responses. The present review explores VCP's roles in numerous cardiovascular disorders including myocardial ischemia/reperfusion injury, cardiac hypertrophy, and heart failure. The review dwells on the roles of VCP in modifying mitochondrial activity, promoting S-nitrosylation, regulating mTOR signalling and demonstrating cardioprotective effects. Further research into VCP might lead to novel interventions for cardiovascular disease, particularly those involving ischemia/reperfusion injury and hypertrophy.

The role of heat shock protein B8 in neuronal protection against oxidative stress and mitochondrial dysfunction: A literature review

Excessive oxidative stress triggers cerebrovascular and neurodegenerative diseases resulting in acute and chronic brain injury. However, the underlying mechanisms remain unknown. Levels of small heat shock protein B8 (HSPB8), which is highly expressed in the brain, are known to be significantly elevated in cerebral injury models. Exogenous HSPB8 protects the brain against mitochondrial damage. One potential mechanism underlying this protection is that HSPB8 overexpression alleviates the mitochondria-dependent pathways of apoptosis; mitochondrial biogenesis, fission, and mitophagy. Overexpression of HSPB8 may therefore have potential as a clinical therapy for cerebrovascular and neurodegenerative diseases. This review provides an overview of advances in the protective effects of HSPB8 against excessive cerebral oxidative stress, including the modulation of mitochondrial dysfunction and potent signaling pathways.

Heat Shock Protein 22 Attenuates Nerve Injury-induced Neuropathic Pain Via Improving Mitochondrial Biogenesis and Reducing Oxidative Stress Mediated By Spinal AMPK/PGC-1α Pathway in Male Rats

Heat shock protein 22 (hsp22) plays a significant role in mitochondrial biogenesis and redox balance. Moreover, it's well accepted that the impairment of mitochondrial biogenesis and redox imbalance contributes to the progress of neuropathic pain. However, there is no available evidence indicating that hsp22 can ameliorate mechanical allodynia and thermal hyperalgesia, sustain mitochondrial biogenesis and redox balance in rats with neuropathic pain. In this study, pain behavioral test, western blotting, immunofluorescence staining, quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and Dihydroethidium staining are applied to confirm the role of hsp22 in a male rat model of spared nerve injury (SNI). Our results indicate that hsp22 was significantly decreased in spinal neurons post SNI. Moreover, it was found that intrathecal injection (i.t.) with recombinant heat shock protein 22 protein (rhsp22) ameliorated mechanical allodynia and thermal hyperalgesia, facilitated nuclear respiratory factor 1 (NRF1)/ mitochondrial transcription factor A (TFAM)-dependent mitochondrial biogenesis, decreased the level of reactive oxygen species (ROS), and suppressed oxidative stress via activation of spinal adenosine 5'monophosphate-activated protein kinase (AMPK)/ peroxisome proliferative activated receptor γ coactivator 1α (PGC-1α) pathway in male rats with SNI. Furthermore, it was also demonstrated that AMPK antagonist (compound C, CC) or PGC-1α siRNA reversed the improved mechanical allodynia and thermal hyperalgesia, mitochondrial biogenesis, oxidative stress, and the decreased ROS induced by rhsp22 in male rats with SNI. These results revealed that hsp22 alleviated mechanical allodynia and thermal hyperalgesia, improved the impairment of NRF1/TFAM-dependent mitochondrial biogenesis, down-regulated the level of ROS, and mitigated oxidative stress through stimulating the spinal AMPK/PGC-1α pathway in male rats with SNI.

Macrophage-specific autophagy-related gene HSPB8 is involved in the macrophage polarization in atherosclerosis

BACKGROUND

Atherosclerosis (AS) is a chronic inflammatory disease, as a main cause leading to vascular diseases worldwide. Although increasing studies have focused on macrophages in AS, the exact relating mechanism is still largely unclear. Our study aimed to explore the pathogenic role and diagnostic role of macrophage autophagy related genes (MARGs) in AS.

METHODS

All datasets were downloaded from Gene Expression Omnibus database and Human Autophagy Database. The differential expression analysis and cross analysis were performed to identify candidate MARGs. GO and KEGG enrichment analyses were conducted to obtain the functional information. Moreover, we analyzed the correlation between target gene and macrophage polarization in AS. The correlation between target gene and plaque instability, different stages of AS were also analyzed.

RESULTS

Compared with normal samples, a total of 575 differentially expressed genes (DEGs) were identified in AS samples. A total of 12 overlapped genes were obtained after cross-analysis of the above 575 DEGs and autophagy related genes (ARGs). Then, 10 MARGs were identified in AS samples, which were significantly enriched in 22 KEGG pathways and 61 GO terms. The expression of HSPB8 was significantly down-regulated in atherosclerotic samples compared with normal samples (with largest fold change). Meanwhile, the proportion of M-CSF in low HSPB8 expression AS group was higher than high expression AS group. Furthermore, the expression of HSPB8 was negatively correlated with most inflammatory factors.

CONCLUSION

The downregulation of MARG HSPB8 probably involves in the M2 macrophage polarization in AS samples. HSPB8 is a promising diagnostic marker for AS patients.

Heat shock proteins: Biological functions, pathological roles, and therapeutic opportunities

The heat shock proteins (HSPs) are ubiquitous and conserved protein families in both prokaryotic and eukaryotic organisms, and they maintain cellular proteostasis and protect cells from stresses. HSP protein families are classified based on their molecular weights, mainly including large HSPs, HSP90, HSP70, HSP60, HSP40, and small HSPs. They function as molecular chaperons in cells and work as an integrated network, participating in the folding of newly synthesized polypeptides, refolding metastable proteins, protein complex assembly, dissociating protein aggregate dissociation, and the degradation of misfolded proteins. In addition to their chaperone functions, they also play important roles in cell signaling transduction, cell cycle, and apoptosis regulation. Therefore, malfunction of HSPs is related with many diseases, including cancers, neurodegeneration, and other diseases. In this review, we describe the current understandings about the molecular mechanisms of the major HSP families including HSP90/HSP70/HSP60/HSP110 and small HSPs, how the HSPs keep the protein proteostasis and response to stresses, and we also discuss their roles in diseases and the recent exploration of HSP related therapy and diagnosis to modulate diseases. These research advances offer new prospects of HSPs as potential targets for therapeutic intervention.

Protein Quality Control at the Sarcomere: Titin Protection and Turnover and Implications for Disease Development

Sarcomeres are mainly composed of filament and signaling proteins and are the smallest molecular units of muscle contraction and relaxation. The sarcomere protein titin serves as a molecular spring whose stiffness mediates myofilament extensibility in skeletal and cardiac muscle. Due to the enormous size of titin and its tight integration into the sarcomere, the incorporation and degradation of the titin filament is a highly complex task. The details of the molecular processes involved in titin turnover are not fully understood, but the involvement of different intracellular degradation mechanisms has recently been described. This review summarizes the current state of research with particular emphasis on the relationship between titin and protein quality control. We highlight the involvement of the proteasome, autophagy, heat shock proteins, and proteases in the protection and degradation of titin in heart and skeletal muscle. Because the fine-tuned balance of degradation and protein expression can be disrupted under pathological conditions, the review also provides an overview of previously known perturbations in protein quality control and discusses how these affect sarcomeric proteins, and titin in particular, in various disease states.

Heat Shock Protein 22 in Physiological and Pathological Hearts: Small Molecule, Large Potentials

Small heat shock protein 22 (HSP22) belongs to the superfamily of heat shock proteins and is predominantly expressed in the heart, brain, skeletal muscle, and different types of cancers. It has been found that HSP22 is involved in variant cellular functions in cardiomyocytes and plays a vital role in cardiac protection against cardiomyocyte injury under diverse stress. This review summarizes the multiple functions of HSP22 in the heart and the underlying molecular mechanisms through modulating gene transcription, post-translational modification, subcellular translocation of its interacting proteins, and protein degradation, facilitating mitochondrial function, cardiac metabolism, autophagy, and ROS production and antiapoptotic effect. We also discuss the association of HSP22 in cardiac pathologies, including human dilated cardiomyopathy, pressure overload-induced heart failure, ischemic heart diseases, and aging-related cardiac metabolism disorder. The collected information would provide insights into the understanding of the HSP22 in heart diseases and lead to discovering the therapeutic targets.

Hsp22 ameliorates lipopolysaccharide-induced myocardial injury by inhibiting inflammation, oxidative stress, and apoptosis

Sepsis-induced myocardial dysfunction (SIMD) is ubiquitous in septic shock patients and is associated with high morbidity and mortality rates. Heat shock protein 22 (Hsp22), which belongs to the small HSP family of proteins, is involved in several biological functions. However, the function of Hsp22 in lipopolysaccharide (LPS)-induced myocardial injury is not yet established. This study was aimed at investigating the underlying mechanistic aspects of Hsp22 in myocardial injury induced by LPS. In this study, following the random assignment of male C57BL/6 mice into control, LPS-treated, and LPS + Hsp22 treated groups, relevant echocardiograms and staining were performed to scrutinize the cardiac pathology. Plausible mechanisms were proposed based on the findings of the enzyme-linked immunosorbent assay and Western blotting assay. A protective role of Hsp22 against LPS-induced myocardial injury emerged, as evidenced from decreased levels of creatinine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and enhanced cardiac function. The post-LPS administration-caused spike in inflammatory cytokines (IL-1β, IL-6, TNF-α and NLRP3) was attenuated by the Hsp22 pre-treatment. In addition, superoxide dismutase (SOD) activity and B-cell lymphoma-2 (Bcl2) levels were augmented by Hsp22 treatment resulting in lowering of LPS-induced oxidative stress and cardiomyocyte apoptosis. In summary, the suppression of LPS-induced myocardial injury by Hsp22 overexpression via targeting of inflammation, oxidative stress, and apoptosis in cardiomyocytes paves the way for this protein to be employed in the therapy of SIMD.

Hsp22 Deficiency Induces Age-Dependent Cardiac Dilation and Dysfunction by Impairing Autophagy, Metabolism, and Oxidative Response

Heat shock protein 22 (Hsp22) is a small heat shock protein predominantly expressed in skeletal and cardiac muscle. Previous studies indicate that Hsp22 plays a vital role in protecting the heart against cardiac stress. However, the essential role of Hsp22 in the heart under physiological conditions remains largely unknown. In this study, we used an Hsp22 knockout (KO) mouse model to determine whether loss of Hsp22 impairs cardiac growth and function with increasing age under physiological conditions. Cardiac structural and functional alterations at baseline were measured using echocardiography and invasive catheterization in Hsp22 KO mice during aging transition compared to their age-matched wild-type (WT) littermates. Our results showed that Hsp22 deletion induced progressive cardiac dilation along with declined function during the aging transition. Mechanistically, the loss of Hsp22 impaired BCL-2-associated athanogene 3 (BAG3) expression and its associated cardiac autophagy, undermined cardiac energy metabolism homeostasis and increased oxidative damage. This study showed that Hsp22 played an essential role in the non-stressed heart during the early stage of aging, which may bring new insight into understanding the pathogenesis of age-related dilated cardiomyopathy.

Secreted frizzled protein 3 is a novel cardioprotective mechanism unique to the clinically relevant fourth window of ischemic preconditioning

Most studies on ischemic preconditioning (IPC) use one or two ischemic stimuli before examining cardioprotection. To better simulate the clinical situation, we examined, in pigs, the effects of six episodes of 10 min coronary artery occlusion (CAO) 12 h apart, followed by 60 min CAO. We named this model the fourth window of IPC. To determine the novel mechanisms mediating cardioprotection in the fourth window, gene analysis was examined in fourth window IPC cardiac tissue 60 min after the last episode of 10 min CAO. Secreted frizzled-related protein 3 (sFRP3) was the most significantly upregulated gene that was unique to the fourth window, that is, not found in the first, second, or third window IPC. To study the effects of sFRP3 on cardioprotection, sFRP3 was injected in the hearts of wild-type (WT) mice. In the [CAO/coronary artery reperfusion (CAR)] model (30 min CAO followed by 24 h CAR), infarct size was less, P < 0.01, after sFRP3 injection (14% ± 1.7%) compared with vehicle injection (48% ± 1.6%). sFRP3 injection also protected the development of heart failure following permanent CAO for 2 wk. Left ventricular ejection fraction was significantly improved, P < 0.05, at 2 wk after CAO with sFRP3 (53% ± 5%) compared with vehicle (36% ± 2%) and was accompanied by significant, P < 0.01, reductions in myocardial fibrosis (53% ± 4%), myocyte size (17% ± 3%), apoptosis (100%), and mortality (56%). Thus, sFRP3, unique to the clinically relevant fourth window IPC model, is a novel mechanism mediating ischemic cardioprotection.NEW & NOTEWORTHY1) This investigation identifies the novel fourth window of ischemic preconditioning. 2) sFRP3 was identified as the most significantly upregulated gene in the fourth window and was shown to induce cardioprotection when administered to the hearts of wild-type mice.

Heat shock protein 22 modulates NRF1/TFAM-dependent mitochondrial biogenesis and DRP1-sparked mitochondrial apoptosis through AMPK-PGC1α signaling pathway to alleviate the early brain injury of subarachnoid hemorrhage in rats

Mitochondrial dysfunction has been widely accepted as a detrimental factor in subarachnoid hemorrhage (SAH)-induced early brain injury (EBI), which is eminently related to poor neurologic function outcome. Previous studies have revealed that enhancement of heat shock protein 22 (hsp22) under conditions of stress is a friendly mediator of mitochondrial homeostasis, oxidative stress and apoptosis, thus accelerating neurological recovery. However, no study has confirmed whether hsp22 attenuates mitochondrial stress and apoptosis in the setting of SAH-induced EBI. Our results indicated that endogenous hsp22, p-AMPK/AMPK, PGC1α, TFAM, Nrf1 and Drp1 were significantly upregulated in cortical neurons in response to SAH, accompanied by neurologic impairment, brain edema, neuronal degeneration, lower level of mtDNA and ATP, mitochondria-cytosol translocation of cytochrome c, oxidative injury and caspase 3-involved mitochondrial apoptosis. However, exogenous hsp22 maintained neurological function, reduced brain edema, improved oxidative stress and mitochondrial apoptosis, these effects were highly dependent on PGC1α-related mitochondrial biogenesis/fission, as evidenced by co-application of PGC1α siRNA. Furthermore, we demonstrated that blockade of AMPK with dorsomorphin also compromised the neuroprotective actions of hsp22, along with the alterations of PGC1α and its associated pathway molecules. These data revealed that hsp22 exerted neuroprotective effects by salvaging mitochondrial function in an AMPK-PGC1α dependent manner, which modulates TFAM/Nrf1-induced mitochondrial biogenesis with positive feedback and DRP1-triggered mitochondrial apoptosis with negative feedback, further reducing oxidative stress and brain injury. Boosting the biogenesis and repressing excessive fission of mitochondria by hsp22 may be an efficient treatment to relieve SAH-elicited EBI.

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Hsp22 is notably upregulated in neurons at 24 h after SAH.

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Hsp22 boosts the NRF1/TFAM-dependent mitochondrial biogenesis.

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Hsp22 represses DRP1-sparked mitochondrial apoptosis.

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AMPK-PGC1α pathway is involved in hsp22-mediated neuroprotection after SAH.

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Modulation of mitochondrial biogenesis and fission may be efficient for treating SAH.

Phosphorylation Modifications Regulating Cardiac Protein Quality Control Mechanisms

Many forms of cardiac disease, including heart failure, present with inadequate protein quality control (PQC). Pathological conditions often involve impaired removal of terminally misfolded proteins. This results in the formation of large protein aggregates, which further reduce cellular viability and cardiac function. Cardiomyocytes have an intricately collaborative PQC system to minimize cellular proteotoxicity. Increased expression of chaperones or enhanced clearance of misfolded proteins either by the proteasome or lysosome has been demonstrated to attenuate disease pathogenesis, whereas reduced PQC exacerbates pathogenesis. Recent studies have revealed that phosphorylation of key proteins has a potent regulatory role, both promoting and hindering the PQC machinery. This review highlights the recent advances in phosphorylations regulating PQC, the impact in cardiac pathology, and the therapeutic opportunities presented by harnessing these modifications.

Repetitively hypoxic preconditioning attenuates ischemia/reperfusion-induced liver dysfunction through upregulation of hypoxia-induced factor-1 alpha-dependent mitochondrial Bcl-xl in rat

Repetitive hypoxic preconditioning (HP) enforces protective effects to subsequently severe hypoxic/ischemic stress. We hypothesized that HP may provide protection against ischemia/reperfusion (I/R) injury in rat livers via hypoxia-induced factor-1 alpha (HIF-1α)/reactive oxygen species (ROS)-dependent defensive mechanisms. Female Wistar rats were exposed to hypoxia (15 h/day) in a hypobaric hypoxic chamber (5500 m) for HP induction, whereas the others were kept in sea level. These rats were subjected to 45 min of hepatic ischemia by portal vein occlusion followed by 6 h of reperfusion. We evaluated HIF-1α in nuclear extracts, MnSOD, CuZnSOD, catalase, Bad/Bcl-xL/caspase 3/poly-(ADP-ribose)-polymerase (PARP), mitochondrial Bcl-xL, and cytosolic cytochrome C expression with Western blot and nitroblue tetrazolium/3-nitrotyrosine stain. Kupffer cell infiltration and terminal deoxynucleotidyl transferase-mediated nick-end labeling method apoptosis were determined by immunocytochemistry. The ROS value from liver surface and bile was detected by an ultrasensitive chemiluminescence-amplification method. Hepatic function was assessed with plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. HP increased nuclear translocation of HIF-1α and enhanced Bcl-xL, MnSOD, CuZnSOD, and catalase protein expression in a time-dependent manner. The response of HP enhanced hepatic HIF-1α, and Bcl-xL expression was abrogated by a HIF-1α inhibitor YC-1. Hepatic I/R increased ROS levels, myeloperoxidase activity, Kupffer cell infiltration, ALT and AST levels associated with the enhancement of cytosolic Bad translocation to mitochondria, release of cytochrome C to cytosol, and activation of caspase 3/PARP-mediated apoptosis. HP significantly ameliorated hepatic I/R-enhanced oxidative stress, apoptosis, and mitochondrial and hepatic dysfunction. In summary, HP enhances HIF-1α/ROS-dependent cascades to upregulate mitochondrial Bcl-xL protein expression and to confer protection against I/R injury in the livers.

Insights of heat shock protein 22 in the cardiac protection against ischemic oxidative stress

the acute and chronic myocardial ischemia results in oxidative stress that impairs myocardial contractility and eventually leads to heart failure. However, the underlying regulatory molecular mechanisms are not fully understood. The heat shock protein 22 (Hsp22), a small-molecular-weight protein preferentially expressed in the heart, was found to be dramatically increased in the cardiac oxidative stress conditions in both human and animal models after the acute and chronic ischemia. Overexpression of Hsp22 largely protects the heart against ischemic damage. Mechanistically, overexpression of Hsp22 attenuates hypoxia-induced oxidative phosphorylation in mitochondrial and the high rate of superoxide production. Short term gene delivery of Hsp22 reduces the infarct size caused by the ischemia/reperfusion, providing a clinical therapeutic potential. This review discusses the new progress of the studies on Hsp22 by focusing on its protective effect against the excessive cardiac oxidative stress, including its adaptive induction in myocardium upon the oxidative stress, its protective role in myocardial ischemia/reperfusion, its regulation in mitochondrial oxidative phosphorylation and the underlying molecular signaling pathways promoting cell survival. This information will increase our understanding of the molecular regulation of cardiac adaption under the oxidative stress and the potential therapeutic relevance.

Heat Shock Protein 22 Attenuates Doxorubicin-Induced Cardiotoxicity via Regulating Inflammation and Apoptosis

Background

The antitumor effect of doxorubicin (DOX) is limited by its acute and chronic toxicity to the heart, which causes heart injury. Heat shock protein 22 (Hsp22) is a protein proved to exert anti-apoptosis and anti-inflammatory effects in other diseases and physical conditions. In this study, we aim to explore whether Hsp22 could exert a protective role during cardiac injury in response to DOX.

Methods

The overexpression of Hsp22 was mediated via adenovirus vector to clarify the role of Hsp22 in the cardiac injury caused by DOX. DOX-induced acute heart injury mouse model was established by single intraperitoneal injection of DOX (15 mg/kg). Subsequently, cardiac staining and molecular biological analysis were performed to analyze the morphological and biochemical effects of Hsp22 on cardiac injury. H9c2 cells were used for validation in vitro.

Results

An increase in the expression level of Hsp22 was observed in DOX-treated heart tissue. Furthermore, cardiac-specific overexpression of Hsp22 showed reduced cardiac dysfunction, decrease in inflammatory response, and reduction in cell apoptosis in injury heart and cardiomyocytes induced by DOX in vivo and in vitro. Moreover, the suppression of Toll-like receptor (TLR)4/NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) was associated with the protective effect of Hsp22. Finally, the protective effect of Hsp22 cardiac function was almost abolished by overexpression of NLRP3 in DOX-treated mice.

Conclusion

In summary, Hsp22 overexpression in the heart could suppress cardiac injury in response to DOX treatment through blocking TLR4/NLRP3 activation. Hsp22 may become a new therapeutic method for treating cardiac injury induced by DOX in cancer patients.

Inhibition of Autophagy Signaling via 3-methyladenine Rescued Nicotine-Mediated Cardiac Pathological Effects and Heart Dysfunctions

Rationale: Cigarette smoking is a well-established risk factor for myocardial infarction and sudden cardiac death. The deleterious effects are mainly due to nicotine, but the mechanisms involved and theranostics remain unclear. Thus, we tested the hypothesis that nicotine exposure increases the heart sensitivity to ischemia/reperfusion injury and dysfunction, which can be rescued by autophagy inhibitor.

Methods: Nicotine or saline was administered to adult rats via subcutaneous osmotic minipumps in the absence or presence of an autophagy inhibitor, 3-methyladenine (3-MA). After 30 days of nicotine treatment, the rats underwent the cardiac ischemia/reperfusion (I/R) procedure and echocardiography analysis, and the heart tissues were isolated for molecular biological studies.

Results: Nicotine exposure increased I/R-induced cardiac injury and cardiac dysfunction as compared to the control. The levels of autophagy-related proteins including LC3 II, P62, Beclin1, and Atg5 were upregulated in the reperfused hearts isolated from nicotine-treated group. In addition, nicotine enhanced cardiac and plasma ROS production, and increased the phosphorylation of GSK3β (ser9) in the left ventricle tissues. Treatment with 3-MA abolished nicotine-mediated increase in the levels of autophagy-related proteins and phosphorylation of GSK3β, but had no effect on ROS production. Of importance, 3-MA ameliorated the augmented I/R-induced cardiac injury and dysfunction in the nicotine-treated group as compared to the control.

Conclusion: Our results demonstrate that nicotine exposure enhances autophagy signaling pathway, resulting in development of ischemic-sensitive phenotype of heart. It suggests a potentially novel therapeutic strategy of autophagy inhibition for the treatment of ischemic heart disease.

Neuromuscular Diseases Due to Chaperone Mutations: A Review and Some New Results

Skeletal muscle and the nervous system depend on efficient protein quality control, and they express chaperones and cochaperones at high levels to maintain protein homeostasis. Mutations in many of these proteins cause neuromuscular diseases, myopathies, and hereditary motor and sensorimotor neuropathies. In this review, we cover mutations in DNAJB6, DNAJB2, αB-crystallin (CRYAB, HSPB5), HSPB1, HSPB3, HSPB8, and BAG3, and discuss the molecular mechanisms by which they cause neuromuscular disease. In addition, previously unpublished results are presented, showing downstream effects of BAG3 p.P209L on DNAJB6 turnover and localization.

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.

HSP22 suppresses diabetes-induced endothelial injury by inhibiting mitochondrial reactive oxygen species formation

The induction of mitochondrial reactive oxygen species (mtROS) by hyperglycemia is a key event responsible for endothelial activation and injury. Heat shock protein 22 (HSP22) is a stress-inducible protein associated with cytoprotection and apoptosis inhibition. However, whether HSP22 prevents hyperglycemia-induced vascular endothelial injury remains unclear. Here, we investigated whether HSP22 protects the vascular endothelium from hyperglycemia-induced injury by reducing mtROS production. We used a high-fat diet and streptozotocin injection model to induce type 2 diabetes mellitus (T2DM, metabolic syndrome) and exposed human umbilical vein endothelial cells (HUVECs) to high glucose following overexpression or silencing of HSP22 to explore the role of HSP22. We found that HSP22 markedly inhibited endothelial cell activation and vascular lesions by inhibiting endothelial adhesion and decreasing cytokine secretion. We performed confocal microscopy and flow cytometry assays using HUVECs and showed that HSP22 attenuated mtROS and mitochondrial dysfunction in hyperglycemia-stimulated endothelial cells. Mechanistically, using the mtROS inhibitor MitoTEMPO, we demonstrated that HSP22 suppressed endothelial activation and injury by eliminating hyperglycemia-mediated increases in mtROS. Furthermore, we found that HSP22 maintained the balance of mitochondrial fusion and fission by mitigating mtROS in vitro. HSP22 attenuated the development of vascular lesions by suppressing mtROS-mediated endothelial activation in a T2DM mouse model. This study provides evidence that HSP22 may be a promising therapeutic target for vascular complications in T2DM.

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HSP22 reduces endothelial inflammation under diabetic conditions.

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HSP22 restrains hyperglycemia-induced oxidative stress in the vascular endothelium.

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HSP22 reduces hyperglycemia-induced mtROS and endothelial mitochondrial dysfunction.

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HSP22 maintains the balance of mitochondrial fusion and fission by mitigating mtROS.

The Different Expression Patterns of HSP22, a Late Embryogenesis Abundant-like Protein, in Hypertrophic H9C2 Cells Induced by NaCl and Angiotensin II

Background

High-NaCl diet is a contributing factor for cardiac hypertrophy. The role of HSP22 as a protective protein during cardiac hypertrophy due to hypernatremia is unclear. Accordingly, this study aimed to establish a cellular hypernatremic H9C2 model and to compare the expression of HSP22 in Ca²⁺ homeostasis between a high-NaCl and angiotensin II-induced hypertrophic cellular H9C2 model.

Methods

Real-time PCR was performed to compare the mRNA expression. Flow cytometry and confocal microscopy were used to analyze the cells.

Results

The addition of 30 mM NaCl for 48 h was the most effective condition for the induction of hypertrophic H9C2 cells (termed the in vitro hypernatremic model). Cardiac cellular hypertrophy was induced with 30 mM NaCl and 1 µM angiotensin II for 48 h, without causing abnormal morphological changes or cytotoxicity of the culture conditions. HSP22 contains a similar domain to that found in the consensus sequences of the late embryogenesis abundant protein group 3 from Artemia. The expression of HSP22 gradually decreased in the in vitro hypernatremic model. In contrast to the in vitro hypernatremic model, HSP22 increased after exposure to angiotensin II for 48 h. Intracellular Ca²⁺ decreased in the angiotensin II model and further decreased in the in vitro hypernatremic model. Impaired intracellular Ca²⁺ homeostasis was more evident in the in vitro hypernatremic model.

Conclusion

The results showed that NaCl significantly decreased HSP22. Decreased HSP22, due to the hypernatremic condition, affected the Ca²⁺ homeostasis in the H9C2 cells. Therefore, hypernatremia induces cellular hypertrophy via impaired Ca²⁺ homeostasis. The additional mechanisms of HSP22 need to be explored further.

Redox Aspects of Chaperones in Cardiac Function

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

Exploring the multifaceted roles of heat shock protein B8 (HSPB8) in diseases

HSPB8 is a member of ubiquitous small heat shock protein (sHSP) family, whose expression is induced in response to a wide variety of unfavorable physiological and environmental conditions. Investigation of HSPB8 structure indicated that HSPB8 belongs to the group of so-called intrinsically disordered proteins and possesses a highly flexible structure. Unlike most other sHSPs, HSPB8 tends to form small-molecular-mass oligomers and exhibits substrate-dependent chaperone activity. In cooperation with BAG3, the chaperone activity of HSPB8 was reported to be involved in the delivery of misfolded proteins to the autophagy machinery. Through this way, HSPB8 interferes with pathological processes leading to neurodegenerative diseases. Accordingly, published studies have identified genetic links between mutations of HSPB8 and some kind of neuromuscular diseases, further supporting its important role in neurodegenerative disorders. In addition to their anti-aggregation properties, HSPB8 is indicated to interact with a wide range of client proteins, modulating their maturations and activities, and therefore, regulates a large repertoire of cellular functions, including apoptosis, proliferation, inflammation and etc. As a result, HSPB8 has key roles in cancer biology, autoimmune diseases, cardiac diseases and cerebral vascular diseases.

The Long Noncoding RNA Landscape of the Ischemic Human Left Ventricle

BACKGROUND

The discovery of functional classes of long noncoding RNAs (lncRNAs) has expanded our understanding of the variety of RNA species that exist in cells. In the heart, lncRNAs have been implicated in the regulation of development, ischemic and dilated cardiomyopathy, and myocardial infarction. Nevertheless, there is a limited description of expression profiles for these transcripts in human subjects.

METHODS AND RESULTS

We obtained left ventricular tissue from human patients undergoing cardiac surgery and used RNA sequencing to describe an lncRNA profile. We then identified a list of lncRNAs that were differentially expressed between pairs of samples before and after the ischemic insult of cardiopulmonary bypass. The expression of some of these lncRNAs correlates with ischemic time. Coding genes in close proximity to differentially expressed lncRNAs and coding genes that have coordinated expression with these lncRNAs are enriched in functional categories related to myocardial infarction, including heart function, metabolism, the stress response, and the immune system.

CONCLUSIONS

We describe a list of lncRNAs that are differentially expressed after ischemia in the human heart. These genes are predicted to function in pathways consistent with myocardial injury. As a result, lncRNAs may serve as novel diagnostic and therapeutic targets for ischemic heart disease.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00985049.

MicroRNA-126a-5p enhances myocardial ischemia-reperfusion injury through suppressing Hspb8 expression

Previously, we found several genes are involved in myocardial ischemia-reperfusion (M-I/R) injury. In this report, we first developed a mouse model of M-I/R injury and demonstrated microRNA-126a-5p was associated with the M-I/R injury by using high-throughput microRNA expression analysis. We further investigated the expression and function of microRNA-126a-5p during mouse M-I/R injury. We observed high expression of microRNA-126a-5p in the M-I/R mice and increased levels of LDH and CK-MB (damage markers) in the serum. H₂O₂ and hypoxia/reoxygenation (H/R) treatment significantly increased the expression of microRNA-126a-5p in H9C2 cells in concentration- and time-dependent manners. Moreover, microRNA-126a-5p overexpression in H9C2 cells inhibited cell viability but increased LDH release and caspase 3 activity. Cardiac function analysis based on the measurements of hemodynamic parameters showed that microRNA-126a-5p expression ablation in M-I/R injured mice led to the reversal of the symptoms caused by M-I/R injury. Transesophageal echocardiography also revealed that the values of LVIDd and LVIDs were decreased while the values of LVFS% and LVEF% were increased in M-I/R injured mice after treatment with microRNA-126a-5p inhibitor, compared with the M-I/R injured mice treated with the control. Bioinformatic analysis demonstrated that Hspb8, a protective protein in myocardium, was the target of microRNA-126a-5p. Thus, these findings indicated that microRNA-126a-5p was up-regulated in mouse M-I/R model and promoted M-I/R injury in vivo through suppressing the expression of Hspb8, which may shed light on the development of potential therapeutic target for M-I/R injury.

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.

The valosin-containing protein is a novel mediator of mitochondrial respiration and cell survival in the heart in vivo

The valosin-containing protein (VCP) participates in signaling pathways essential for cell homeostasis in multiple tissues, however, its function in the heart in vivo remains unknown. Here we offer the first description of the expression, function and mechanism of action of VCP in the mammalian heart in vivo in both normal and stress conditions. By using a transgenic (TG) mouse with cardiac-specific overexpression (3.5-fold) of VCP, we demonstrate that VCP is a new and powerful mediator of cardiac protection against cell death in vivo, as evidenced by a 50% reduction of infarct size after ischemia/reperfusion versus wild type. We also identify a novel role of VCP in preserving mitochondrial respiration and in preventing the opening of mitochondrial permeability transition pore in cardiac myocytes under stress. In particular, by genetic deletion of inducible isoform of nitric oxide synthase (iNOS) from VCP TG mouse and by pharmacological inhibition of iNOS in isolated cardiac myocytes, we reveal that an increase of expression and activity of iNOS in cardiomyocytes by VCP is an essential mechanistic link of VCP-mediated preservation of mitochondrial function. These data together demonstrate that VCP may represent a novel therapeutic avenue for the prevention of myocardial ischemia.

Tat-HSP22 inhibits oxidative stress-induced hippocampal neuronal cell death by regulation of the mitochondrial pathway

Oxidative stress plays an important role in the progression of various neuronal diseases including ischemia. Heat shock protein 22 (HSP22) is known to protect cells against oxidative stress. However, the protective effects and mechanisms of HSP22 in hippocampal neuronal cells under oxidative stress remain unknown. In this study, we determined whether HSP22 protects against hydrogen peroxide (H₂O₂)-induced oxidative stress in HT-22 using Tat-HSP22 fusion protein. We found that Tat-HSP22 transduced into HT-22 cells and that H₂O₂-induced cell death, oxidative stress, and DNA damage were significantly reduced by Tat-HSP22. In addition, Tat-HSP22 markedly inhibited H₂O₂-induced mitochondrial membrane potential, cytochrome c release, cleaved caspase-3, and Bax expression levels, while Bcl-2 expression levels were increased in HT-22 cells. Further, we showed that Tat-HSP22 transduced into animal brain and inhibited cleaved-caspase-3 expression levels as well as significantly inhibited hippocampal neuronal cell death in the CA1 region of animals in the ischemic animal model. In the present study, we demonstrated that transduced Tat-HSP22 attenuates oxidative stress-induced hippocampal neuronal cell death through the mitochondrial signaling pathway and plays a crucial role in inhibiting neuronal cell death, suggesting that Tat-HSP22 protein may be used to prevent oxidative stress-related brain diseases including ischemia.

Current knowledge on the role of P2Y receptors in cardioprotection against ischemia-reperfusion

During ischemia, numerous effective endogenous extracellular mediators have been identified, particularly, nucleosides such as adenosine as well as purinergic and pyrimidinergic nucleotides. They may play important regulatory roles within the cardiovascular system and notably as cardio-protectants. Indeed, the distribution of the P2Y receptors in mammalian heart includes several cellular constituents relevant for the pathophysiology of myocardial ischemia. Beside the well-known cardioprotective effect of adenosine, the additional protective role of P2Y receptors has emerged. However, interpretation of experimental results may be sometimes perplexing. This is due to the variability of: the experimental models, the endpoints criteria, the chemical structure of agonist and antagonist ligands and their concentrations, the sequences of drug administration with respect to the model used (before and/or during and/or after ischemia). The net effect may be in the opposite direction after a transient or a prolonged stimulation. Nevertheless, the overall reading of published data highlights the beneficial role of the P2Y_2/4 receptor stimulation, the useful and synergistic role of P2Y_6/11 receptor activation and even of the P2Y₁₁ receptor alone in cardioprotection. More, the P2Y₁₁ receptor could be involved in counter-regulation of profibrotic processes. Paradoxically, transient P2X₇ receptor stimulation could contribute to the net cardioprotective effect of ATP. Recently, experimental data have shown that blocking the P2Y₁₂ receptor after ischemia confers cardioprotection independently of platelet antiaggregatory effect. This suggests for P2Y receptors an important role in primary prevention and as a therapeutic target in myocardial protection during ischemia and reperfusion.

Overexpression of Cardiomyocyte α1A-Adrenergic Receptors Attenuates Postinfarct Remodeling by Inducing Angiogenesis Through Heterocellular Signaling

OBJECTIVE

Stimulation of cardiac α1A-adrenergic receptors (α1A-AR) has been proposed for treatment of heart failure, since it increases myocardial contractility. We investigated a different mechanism, induction of angiogenesis.

APPROACH AND RESULTS

Four to 6 weeks after permanent coronary artery occlusion, transgenic rats with cardiomyocyte-specific α1A-adrenergic receptor overexpression had less remodeling than their nontransgenic littermates, with less fibrosis, hypertrophy and lung weight, and preserved left ventricular ejection fraction and wall stress (all P<0.05). Coronary blood flow, measured with microspheres, increased in the infarct zone in transgenic rats compared with nontransgenic littermates (1.4±0.2 versus 0.5±0.08 mL min(-1) g(-1); P<0.05), which is consistent with angiogenesis, as reflected by a 20% increase in capillary density in the zone adjacent to the infarct. The question arose, how does transgenic overexpression of a gene in cardiomyocytes induce angiogenesis? We identified a paracrine mechanism, whereby vascular endothelial growth factor-A mRNA and protein were increased in isolated transgenic cardiomyocytes and also by nontransgenic littermate cardiomyocytes treated with an α1A-agonist, resulting in angiogenesis. Conditioned medium from cultured cardiomyocytes treated with an α1A agonist enhanced human umbilical vein endothelial cell tubule formation, which was blocked by an anti-vascular endothelial growth factor-A antibody. Moreover, improved cardiac function, blood flow, and increased capillary density after chronic coronary artery occlusion in transgenic rats were blocked by either a mitogen ERK kinase (MEK) or a vascular endothelial growth factor-A inhibitor.

CONCLUSION

Cardiomyocyte-specific overexpression of the α1A-adrenergic receptors resulted in enhanced MEK-dependent cardiomyocyte vascular endothelial growth factor-A expression, which stimulates angiogenesis via a paracrine mechanism involving heterocellular cardiomyocyte/endothelial cell signaling, protecting against remodeling and heart failure after chronic coronary artery occlusion.

Molecular basis of cardioprotection: signal transduction in ischemic pre-, post-, and remote conditioning

Reperfusion is mandatory to salvage ischemic myocardium from infarction, but reperfusion per se contributes to injury and ultimate infarct size. Therefore, cardioprotection beyond that by timely reperfusion is needed to reduce infarct size and improve the prognosis of patients with acute myocardial infarction. The conditioning phenomena provide such cardioprotection, insofar as brief episodes of coronary occlusion/reperfusion preceding (ischemic preconditioning) or following (ischemic postconditioning) sustained myocardial ischemia with reperfusion reduce infarct size. Even ischemia/reperfusion in organs remote from the heart provides cardioprotection (remote ischemic conditioning). The present review characterizes the signal transduction underlying the conditioning phenomena, including their physical and chemical triggers, intracellular signal transduction, and effector mechanisms, notably in the mitochondria. Cardioprotective signal transduction appears as a highly concerted spatiotemporal program. Although the translation of ischemic postconditioning and remote ischemic conditioning protocols to patients with acute myocardial infarction has been fairly successful, the pharmacological recruitment of cardioprotective signaling has been largely disappointing to date.

Heat shock protein 22 (Hsp22) regulates oxidative phosphorylation upon its mitochondrial translocation with the inducible nitric oxide synthase in mammalian heart

Objectives

Stress-inducible heat shock protein 22 (Hsp22) confers protection against ischemia through induction of the inducible isoform of nitric oxide synthase (iNOS). Hsp22 overexpression in vivo stimulates cardiac mitochondrial respiration, whereas Hsp22 deletion in vivo significantly reduces respiration. We hypothesized that Hsp22-mediated regulation of mitochondrial function is dependent upon its mitochondrial translocation together with iNOS.

Methods and Results

Adenoviruses harboring either the full coding sequence of Hsp22 (Ad-WT-Hsp22) or a mutant lacking a N-terminal 20 amino acid putative mitochondrial localization sequence (Ad-N20-Hsp22) were generated, and infected in rat neonatal cardiomyocytes. Compared to β-Gal control, WT-Hsp22 accumulated in mitochondria by 2.5 fold (P<0.05) and increased oxygen consumption rates by 2-fold (P<0.01). This latter effect was abolished upon addition of the selective iNOS inhibitor, 1400W. Ad-WT-Hsp22 significantly increased global iNOS expression by about 2.5-fold (P<0.01), and also increased iNOS mitochondrial localization by 4.5 fold vs β-gal (P<0.05). Upon comparable overexpression, the N20-Hsp22 mutant did not show significant mitochondrial translocation or stimulation of mitochondrial respiration. Moreover, although N20-Hsp22 did increase global iNOS expression by 4.6-fold, it did not promote iNOS mitochondrial translocation.

Conclusion

Translocation of both Hsp22 and iNOS to the mitochondria is necessary for Hsp22-mediated stimulation of oxidative phosphorylation.

Salvianolate increases heat shock protein expression in a cerebral ischemia-reperfusion injury model

Stroke remains a worldwide health problem. Salvianolate exerts a protective effect in various mi-crocirculatory disturbance-related diseases, but studies of the mechanisms underlying its protective action have mainly focused on the myocardium, whereas little research has been carried out in brain tissue following ischemia-reperfusion. We assessed the neuroprotective effects of salvianolate in a rat model of cerebral ischemia-reperfusion injury induced using the suture method. At onset and 24 and 48 hours after reperfusion, rats were intraperitoneally injected with salvianolate (18 mg/kg) or saline. Neurological deficit scores at 72 hours showed that the neurological functions of rats that had received salvianolate were significantly better than those of the rats that had received saline. 2,3,5-Triphenyltetrazolium chloride was used to stain cerebral tissue to determine the extent of the infarct area. A significantly smaller infarct area and a significantly lower number of apoptotic cells were observed after treatment with salvianolate compared with the saline treatment. Expression of heat shock protein 22 and phosphorylated protein kinase B in ischemic brain tissue was significantly greater in rats treated with salvianolate compared with rats treated with saline. Our findings suggest that salvianolate provides neuroprotective effects against cerebral ischemia-reperfusion injury by upregulating heat shock protein 22 and phosphorylated protein kinase B expression.

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

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

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.

Sevoflurane induces cardioprotection through reactive oxygen species-mediated upregulation of autophagy in isolated guinea pig hearts

PURPOSE

Sevoflurane increases reactive oxygen species (ROS), which mediate cardioprotection against myocardial ischemia-reperfusion injury. Emerging evidence suggests that autophagy is involved in cardioprotection. We examined whether reactive oxygen species mediate sevoflurane preconditioning through autophagy.

METHODS

Isolated guinea pigs hearts were subjected to 30 min ischemia followed by 120 min reperfusion (control). Anesthetic preconditioning was elicited with 2 % sevoflurane for 10 min before ischemia (SEVO). The ROS-scavenger, N-(2-mercaptopropionyl) glycine (MPG, 1 mmol/l), was administered starting 30 min before ischemia to sevoflurane-treated (SEVO + MPG) or non-sevoflurane-treated (MPG) hearts. Infarct size was determined by triphenyltetrazolium chloride stain. Tissue samples were obtained after reperfusion to determine autophagy-related protein (microtubule-associated protein light chain I and II: LC3-I, -II) and 5' AMP-activated protein kinase (AMPK) expression using Western blot analysis. Electron microscopy was used to detect autophagosomes.

RESULTS

Infarct size was significantly reduced and there were more abundant autophagosomes in SEVO compared with control. Western blot analysis revealed that the ratio of LC3-II/I and phosphorylation of AMPK were significantly increased in SEVO. These effects were abolished by MPG.

CONCLUSIONS

Sevoflurane induces cardioprotection through ROS-mediated upregulation of autophagy.

Tongguan Capsule Protects against Myocardial Ischemia and Reperfusion Injury in Mice

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

The valosin-containing protein promotes cardiac survival through the inducible isoform of nitric oxide synthase

AIMS

Expression of the heat shock protein 22 (Hsp22) in the heart stimulates cardiac cell survival through activation of the Akt pathway and expression of the inducible nitric oxide (NO) synthase (iNOS), the mediator of ischaemic preconditioning and the most powerful prophylaxis against cardiac cell death. The goal of the present study was to elucidate the downstream effector by which Hsp22 and Akt increase iNOS expression. We tested both in vivo and in vitro the hypothesis that such an effector is the valosin-containing protein (VCP), an Akt substrate, which activates the transcription factor NF-κB, using a transgenic mouse with cardiac-specific over-expression of Hsp22, as well as isolated rat cardiac myocytes.

METHODS AND RESULTS

Using two-dimensional gel electrophoresis and mass spectrometry combined with immunoprecipitation, we found that Hsp22 and Akt co-localize and interact together with VCP. Adeno-mediated over-expression of VCP in isolated cardiac myocytes activated NF-κB and dose-dependently increased the expression of iNOS, which was abolished upon NF-κB inhibition. Over-expression of a dominant-negative (DN) mutant of VCP did not increase iNOS expression. VCP, but not its DN mutant, protected against chelerythrine-induced apoptosis, which was suppressed by inhibition of either NF-κB or iNOS. VCP-mediated activation of the NF-κB/iNOS pathway was also prevented upon inhibition of Akt.

CONCLUSION

We conclude that the Akt substrate, VCP, mediates the increased expression of iNOS downstream from Hsp22 through an NF-κB-dependent mechanism.

The α crystallin domain of small heat shock protein b8 (Hspb8) acts as survival and differentiation factor in adult hippocampal neurogenesis

Adult hippocampal neurogenesis is to a large degree controlled at the level of cell survival, and a number of potential mediators of this effect have been postulated. Here, we investigated the small heat shock protein Hspb8, which, because of its pleiotropic prosurvival effects in other systems, was considered a particularly promising candidate factor. Hspb8 is, for example, found in plaques of Alzheimer disease but exerts neuroprotective effects. We found that expression of Hspb8 increased during differentiation in vitro and was particularly associated with later stages (48-96 h) of differentiation. Gain-of-function and loss-of-function experiments supported the hypothesis that Hspb8 regulates cell survival of new neurons in vitro. In the dentate gyrus of adult mice in vivo, lentiviral overexpression of Hspb8 doubled the surviving cells and concomitantly promoted differentiation and net neurogenesis without affecting precursor cell proliferation. We also discovered that the truncated form of the crystallin domain of Hspb8 was sufficient to affect cell survival and neuronal differentiation in vitro and in vivo. Precursor cell experiments in vitro revealed that Hspb8 increases the phosphorylation of Akt and suggested that the prosurvival effect can be produced by a cell-autonomous mechanism. Analysis of hippocampal Hspb8 expression in mice of 69 strains of the recombinant inbred set BXD revealed that Hspb8 is a cis-acting gene whose expression was associated with clusters of transcript enriched in genes linked to growth factor signaling and apoptosis. Our results strongly suggest that Hspb8 and its α-crystallin domain might act as pleiotropic prosurvival factor in the adult hippocampus.

H11/HspB8 and Its Herpes Simplex Virus Type 2 Homologue ICP10PK Share Functions That Regulate Cell Life/Death Decisions and Human Disease

Small heat shock proteins (sHsp) also known as HspB are a large family of widely expressed proteins that contain a 90 residues domain known as α-crystallin. Here, we focus on the family member H11/HspB8 and its herpes simplex virus type 2 (HSV-2) homologue ICP10PK, and discuss the possible impact of this relationship on human disease. H11/HspB8 and ICP10PK are atypical protein kinases. They share multi-functional activity that encompasses signaling, unfolded protein response (UPR) and the regulation of life cycle potential. In melanocytes H11/HspB8 causes growth arrest. It is silenced in a high proportion of melanoma prostate cancer, Ewing's sarcoma and hematologic malignancies through aberrant DNA methylation. Its restored expression induces cell death and inhibits tumor growth in xenograft models, identifying H11/HspB8 as a tumor suppressor. This function involves the activation of multiple and distinct death pathways, all of which initiate with H11/HspB8-mediated phosphorylation of transforming growth factor β-activated kinase 1 (TAK1). Both ICP10PK and H11/HspB8 were implicated in inflammatory processes that involve dendritic cells activation through Toll-like receptor-dependent pathways and may contribute to the onset of autoimmunity. The potential evolutionary relationship of H11/HspB8 to ICP10PK, its impact on human disorders and the development of therapeutic strategies are discussed.

Transcriptional regulation of small HSP-HSF1 and beyond

The members of the small heat shock protein (sHSP) family are molecular chaperones that play major roles in development, stress responses, and diseases, and have been envisioned as targets for therapy, particularly in cancer. The molecular mechanisms that regulate their transcription, in normal, stress, or pathological conditions, are characterized by extreme complexity and subtlety. Although historically linked to the heat shock transcription factors (HSFs), the stress-induced or developmental expression of the diverse members, including HSPB1/Hsp27/Hsp25, αA-crystallin/HSPB4, and αB-crystallin/HSPB5, relies on the combinatory effects of many transcription factors. Coupled with remarkably different cis-element architectures in the sHsp regulatory regions, they confer to each member its developmental expression or stress-inducibility. For example, multiple regulatory pathways coordinate the spatio-temporal expression of mouse αA-, αB-crystallin, and Hsp25 genes during lens development, through the action of master genes, like the large Maf family proteins and Pax6, but also HSF4. The inducibility of Hsp27 and αB-crystallin transcription by various stresses is exerted by HSF-dependent mechanisms, by which concomitant induction of Hsp27 and αB-crystallin expression is observed. In contrast, HSF-independent pathways can lead to αB-crystallin expression, but not to Hsp27 induction. Not surprisingly, deregulation of the expression of sHSP is associated with various pathologies, including cancer, neurodegenerative, or cardiac diseases. However, many questions remain to be addressed, and further elucidation of the developmental mechanisms of sHsp gene transcription might help to unravel the tissue- and stage-specific functions of this fascinating class of proteins, which might prove to be crucial for future therapeutic strategies. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.

Small heat shock proteins in redox metabolism: implications for cardiovascular diseases

A timely review series on small heat shock proteins has to appropriately examine their fundamental properties and implications in the cardiovascular system since several members of this chaperone family exhibit robust expression in the myocardium and blood vessels. Due to energetic and metabolic demands, the cardiovascular system maintains a high mitochondrial activity but irreversible oxidative damage might ensue from increased production of reactive oxygen species. How equilibrium between their production and scavenging is achieved becomes paramount for physiological maintenance. For example, heat shock protein B1 (HSPB1) is implicated in maintaining this equilibrium or redox homeostasis by upholding the level of glutathione, a major redox mediator. Studies of gain or loss of function achieved by genetic manipulations have been highly informative for understanding the roles of those proteins. For example, genetic deficiency of several small heat shock proteins such as HSPB5 and HSPB2 is well-tolerated in heart cells whereas a single missense mutation causes human pathology. Such evidence highlights both the profound genetic redundancy observed among the multigene family of small heat shock proteins while underscoring the role proteotoxicity plays in driving disease pathogenesis. We will discuss the available data on small heat shock proteins in the cardiovascular system, redox metabolism and human diseases. From the medical perspective, we envision that such emerging knowledge of the multiple roles small heat shock proteins exert in the cardiovascular system will undoubtedly open new avenues for their identification and possible therapeutic targeting in humans. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.

Cardiac H11 kinase/Hsp22 stimulates oxidative phosphorylation and modulates mitochondrial reactive oxygen species production: Involvement of a nitric oxide-dependent mechanism

H11 kinase/Hsp22 (Hsp22), a small heat shock protein upregulated by ischemia/reperfusion, provides cardioprotection equal to ischemic preconditioning (IPC) through a nitric oxide (NO)-dependent mechanism. A main target of NO-mediated preconditioning is the mitochondria, where NO reduces O₂ consumption and reactive oxygen species (ROS) production during ischemia. Therefore, we tested the hypothesis that Hsp22 overexpression modulates mitochondrial function through an NO-sensitive mechanism. In cardiac mitochondria isolated from transgenic (TG) mice with cardiac-specific overexpression of Hsp22, mitochondrial basal, ADP-dependent, and uncoupled O₂ consumption was increased in the presence of either glucidic or lipidic substrates. This was associated with a decrease in the maximal capabilities of complexes I and III to generate superoxide anion in combination with an inhibition of superoxide anion production by the reverse electron flow. NO synthase expression and NO production were increased in mitochondria from TG mice. Hsp22-induced increase in O₂ consumption was abolished either by pretreatment of TG mice with the NO synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) or in isolated mitochondria by the NO scavenger phenyltetramethylimidazoline-1-oxyl-3-oxide. L-NAME pretreatment also restored the reverse electron flow. After anoxia, mitochondria from TG mice showed a reduction in both oxidative phosphorylation and H₂O₂ production, an effect partially reversed by L-NAME. Taken together, these results demonstrate that Hsp22 overexpression increases the capacity of mitochondria to produce NO, which stimulates oxidative phosphorylation in normoxia and decreases oxidative phosphorylation and reactive oxygen species production after anoxia. Such characteristics replicate those conferred by IPC, thereby placing Hsp22 as a potential tool for prophylactic protection of mitochondrial function during ischemia.

Cells lacking the fumarase tumor suppressor are protected from apoptosis through a hypoxia-inducible factor-independent, AMPK-dependent mechanism

Loss-of-function mutations of the tumor suppressor gene encoding fumarase (FH) occur in individuals with hereditary leiomyomatosis and renal cell cancer syndrome (HLRCC). We found that loss of FH activity conferred protection from apoptosis in normal human renal cells and fibroblasts. In FH-defective cells, both hypoxia-inducible factor 1α (HIF-1α) and HIF-2α accumulated, but they were not required for apoptosis protection. Conversely, AMP-activated protein kinase (AMPK) was activated and required, as evidenced by the finding that FH inactivation failed to protect AMPK-null mouse embryo fibroblasts (MEFs) and AMPK-depleted human renal cells. Activated AMPK was detected in renal cysts, which occur in mice with kidney-targeted deletion of Fh1 and in kidney cancers of HLRCC patients. In Fh1-null MEFs, AMPK activation was sustained by fumarate accumulation and not by defective energy metabolism. Addition of fumarate and succinate to kidney cells led to extracellular signal-regulated kinase 1/2 (ERK1/2) and AMPK activation, probably through a receptor-mediated mechanism. These findings reveal a new mechanism of tumorigenesis due to FH loss and an unexpected pro-oncogenic role for AMPK that is important in considering AMPK reactivation as a therapeutic strategy against cancer.

Prevention of heart failure in mice by an antiviral agent that inhibits type 5 cardiac adenylyl cyclase

Despite numerous discoveries from genetically engineered mice, relatively few have been translated to the bedside, mainly because it is difficult to translate from genes to drugs. This investigation examines an antiviral drug, which also has an action to selectively inhibit type 5 adenylyl cyclase (AC5), a pharmaceutical correlate of the AC5 knockout (KO) model, which exhibits longevity and stress resistance. Our objective was to examine the extent to which pretreatment with this drug, adenine 9-β-d-arabinofuranoside (Ara-A), favorably ameliorates the development of heart failure (HF). Ara-A exhibited selective inhibition for AC5 compared with the other major cardiac AC isoform, AC6, i.e., it reduced AC activity significantly in AC5 transgenic (Tg) mice, but not in AC5KO mice and had little effect in either wild-type or AC6Tg mice. Permanent coronary artery occlusion for 3 wk in C57Bl/6 mice increased mortality and induced HF in survivors, as reflected by reduced cardiac function, while increasing cardiac fibrosis. The AC5 inhibitor Ara-A significantly improved all of these end points and also ameliorated chronic isoproterenol-induced cardiomyopathy. As with the AC5KO mice, Ara-A increased mitogen/extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK) phosphorylation. A MEK inhibitor abolished the beneficial effects of the AC5 inhibitor in the HF model, indicating the involvement of the downstream MEK-ERK pathway of AC5. Our data suggest that pharmacological AC5 inhibition may serve as a new therapeutic approach for HF.

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.

The Gln32Lys polymorphism in HSP22 of Zhikong scallop Chlamys farreri is associated with heat tolerance

Background

Heat shock protein 22 is a member of small heat shock proteins with molecular chaperone activity. Though their multiple functions have been well characterized, there is no report about the association between the polymorphisms of HSP22 and heat tolerance.

Methodology

Three single nucleotide polymorphisms were identified in HSP22 from scallop Chlamys farreri (CfHSP22), and the +94 C-A locus was found to be nonsynonymous. Three genotypes at locus +94, A/A, A/C and C/C, were revealed by using Bi-PASA PCR analysis, and their frequencies were 19.5%, 27.6% and 52.9% in the heat resistant stock, while 9.3%, 17.4% and 73.3% in the heat susceptible stock, respectively. The frequency differences of the three genotypes were significant (P<0.05) between the two stocks. After incubating at 30°C for 84 h, the cumulative mortality of scallops with +94 C/C genotype and +94 A/C genotypes was 95% and 90%, respectively, which was significantly higher (P<0.01) than that of scallops with +94 A/A genotype (70%). The molecular chaperone activity of two His-tagged fusion proteins, rCfHSP22Q with +94 C/C genotype and rCfHSP22K with +94 A/A genotype were analyzed by testing the ability of protecting citrate synthase (CS) against thermal inactivation in vitro. After incubated with rCfHSP22Q or rCfHSP22K at 38°C for 1 h, the activity of CS lost 50% and 45%, and then recovered to 89% and 95% of the original activity following 1 h restoration at 22°C, respectively, indicating that the mutation from Gln to Lys at this site might have an impact on molecular chaperone activities of CfHSP22.

Conclusions

These results implied that the polymorphism at locus +94 of CfHSP22 was associated with heat tolerance of scallop, and the +94 A/A genotype could be a potential marker available in future selection of Zhikong scallop with heat tolerance.

H11 kinase/heat shock protein 22 deletion impairs both nuclear and mitochondrial functions of STAT3 and accelerates the transition into heart failure on cardiac overload

BACKGROUND

Cardiac overload, a major cause of heart failure, induces the expression of the heat shock protein H11 kinase/Hsp22 (Hsp22).

METHODS AND RESULTS

To determine the specific function of Hsp22 in that context, a knockout mouse model of Hsp22 deletion was generated. Although comparable to wild-type mice in basal conditions, knockout mice exposed to pressure overload developed less hypertrophy and showed ventricular dilation, impaired contractile function, increased myocyte length and accumulation of interstitial collagen, faster transition into heart failure, and increased mortality. Microarrays revealed that hearts from knockout mice failed to transactivate genes regulated by the transcription factor STAT3. Accordingly, nuclear STAT3 tyrosine phosphorylation was decreased in knockout mice. Silencing and overexpression experiments in isolated neonatal rat cardiomyocytes showed that Hsp22 activates STAT3 via production of interleukin-6 by the transcription factor nuclear factor-κB. In addition to its transcriptional function, STAT3 translocates to the mitochondria where it increases oxidative phosphorylation. Both mitochondrial STAT3 translocation and respiration were also significantly decreased in knockout mice.

CONCLUSIONS

This study found that Hsp22 represents a previously undescribed activator of both nuclear and mitochondrial functions of STAT3, and its deletion in the context of pressure overload in vivo accelerates the transition into heart failure and increases mortality.

The Levels of H11/HspB8 DNA methylation in human melanoma tissues and xenografts are a critical molecular marker for 5-Aza-2'-deoxycytidine therapy

H11/HspB8 is a functionally distinct small heat shock protein. It causes growth arrest in melanocytes, associated with the inhibition of Cyclin E/Cdk2 and β-catenin phosphorylation at the transcriptional activity site Ser(552) and is silenced through DNA methylation in 27/35 (77%) melanoma tissues/early cultures. 5-Aza-2'-deoxycytidine (Aza-C) induces melanoma cell death correlated with the levels of H11/HspB8 DNA methylation (p < .001). In line with low/moderate H11/HspB8 methylation, PI3-K inhibition increases Aza-C-induced cell death. Aza-C inhibits the growth of melanoma xenografts related to the levels of H11/HspB8 methylation, and a nonmethylated/non-TAK1 binding H11/HspB8 mutant confers Aza-C resistance. H11/HspB8 is a potential molecular marker for demethylation therapies.