CaMKIIδ subtypes differentially regulate infarct formation following ex vivo myocardial ischemia/reperfusion through NF-κB and TNF-α

CaMK II in Cardiovascular Diseases, Especially CaMK II-δ: Friends or Enemies

Cardiovascular diseases (CVDs) tend to affect the young population and are associated with a significant economic burden and psychological distress to the society and families. The physiological and pathological processes underlying CVDs are complex. Ca2+/calmodulin-dependent kinase II (CaMK II), a protein kinase, has multiple biological functions. It participates in multiple pathological processes and plays a central role in the development of CVDs. Based on this, this paper analyzes the structural characteristics and distribution of CaMK II, the mechanism of action of CaMK II, and the relationship between CaMK II and CVDs, including ion channels, ischemia-reperfusion injury, arrhythmias, myocardial hypertrophy, cardiotoxicity, hypertension, and dilated cardiomyopathy. Given the different regulatory mechanisms of different isoforms of CaMK II, the clinical use of specific targeted inhibitors or novel compounds should be evaluated in future research to provide new directions.

Sweroside alleviates pressure overload-induced heart failure through targeting CaMKⅡδ to inhibit ROS-mediated NF-κB/NLRP3 in cardiomyocytes

Ongoing inflammation in the heart is positively correlated with adverse remodeling, characterized by elevated levels of cytokines that stimulate activation of cardiac fibroblasts. It was found that CaMKIIδ response to Ang II or TAC triggers the accumulation of ROS in cardiomyocytes, which subsequently stimulates NF-κB/NLRP3 and leads to an increase in IL-6, IL-1β, and IL-18. This is an important causative factor in the occurrence of adverse remodeling in heart failure. Sweroside is a biologically active natural iridoids extracted from Lonicerae Japonicae Flos. It shows potent anti-inflammatory and antioxidant activity in various cardiovascular diseases. In this study, we found that sweroside inhibited ROS-mediated NF-κB/NLRP3 in Ang II-treated cardiomyocytes by directly binding to CaMKIIδ. Knockdown of CaMKⅡδ abrogated the effect of sweroside regulation on NF-κB/NLRP3 in cardiomyocytes. AAV-CaMKⅡδ induced high expression of CaMKⅡδ in the myocardium of TAC/Ang II-mice, and the inhibitory effect of sweroside on TAC/Ang Ⅱ-induced elevation of NF-κB/NLRP3 was impeded. Sweroside showed significant inhibitory effects on CaMKIIδ/NF-κB/NLRP3 in cardiomyocytes from TAC/Ang Ⅱ-induced mice. This would be able to mitigate the adverse events of myocardial remodeling and contractile dysfunction at 8 weeks after the onset of the inflammatory response. Taken together, our findings have revealed the direct protein targets and molecular mechanisms by which sweroside improves heart failure, thereby supporting the further development of sweroside as a therapeutic agent for heart failure.

Construction of a molecular inflammatory predictive model with histone modification-related genes and identification of CAMK2D as a potential response signature to infliximab in ulcerative colitis

Background

Ulcerative colitis (UC) is a lifelong inflammatory disease affecting the rectum and colon with numerous treatment options that require an individualized treatment plan. Histone modifications regulate chromosome structure and gene expression, resulting in effects on inflammatory and immune responses. However, the relationship between histone modification-related genes and UC remains unclear.

Methods

Transcriptomic data from GSE59071 and GSE66407 were obtained from the Gene Expression Omnibus (GEO), encompassing colonic biopsy expression profiles of UC patients in inflamed and non-inflamed status. Differentially expressed gene (DEG) analyses, functional enrichment analyses, weighted gene co-expression network analysis (WGCNA), and random forest were performed to identify histone modification-related core genes associated with UC inflammation. Features were screened through the least absolute shrinkage and selection operator (LASSO) and support vector machine-recursive feature elimination (SVM-RFE), establishing a molecular inflammatory predictive model using logistic regression. The model was validated in the GSE107499 dataset, and the performance of the features was assessed using receiver operating characteristic (ROC) and calibration curves. Immunohistochemistry (IHC) staining of colonic biopsy tissues from UC patients treated with infliximab was used to further confirm the clinical application value. Univariate logistic regression on GSE14580 highlighted features linked to infliximab response.

Results

A total of 253 histone modification-related DEGs were identified between inflammatory and non-inflammatory patients with UC. Seven key genes (IL-1β, MSL3, HDAC7, IRF4, CAMK2D, AUTS2, and PADI2) were selected using WGCNA and random forest. Through univariate logistic regression, three core genes (CAMK2D, AUTS2, and IL-1β) were further incorporated to construct the molecular inflammatory predictive model. The area under the curve (AUC) of the model was 0.943 in the independent validation dataset. A significant association between CAMK2D protein expression and infliximab response was observed, which was validated in another independent verification set of GSE14580 from the GEO database.

Conclusion

The molecular inflammatory predictive model based on CAMK2D, AUTS2, and IL-1β could reliably distinguish the mucosal inflammatory status of UC patients. We further revealed that CAMK2D was a predictive marker of infliximab response. These findings are expected to provide a new evidence base for personalized treatment and management strategies for UC patients.

Sotagliflozin attenuates cardiac dysfunction and remodeling in myocardial infarction rats

Objective

Sotagliflozin is a dual sodium-glucose co-transporter-1 and 2 (SGLT1/2) inhibitor with selectivity towards SGLT2. Previous studies showed that SGLT2 inhibitors can improve cardiac function and reduce myocardial infarction size in animal models of myocardial infarction (MI). However, it remains unknown whether the dual inhibition of SGLT1/2 by sotagliflozin has beneficial effects in this context. In this study, we investigated the potential cardioprotective effects of sotagliflozin in an animal model of MI.

Methods

Sprague Dawley (SD) rats underwent left anterior descending coronary artery ligation or sham ligation then were randomly assigned to receive either sotagliflozin (10 mg/kg) or vehicle via intraperitoneal injection. Fourteen days post-MI, we assessed cardiac function using echocardiography and evaluated histological and molecular markers of cardiac remodeling and inflammation in the left ventricle.

Results

Our findings indicate that sotagliflozin treatment resulted in improved cardiac function and reduced infarct size compared with the vehicle-treated group. Additionally, sotagliflozin improved cardiac remodeling as shown by the decreased cardiac hypertrophy and cardiac apoptosis in the post-MI heart. Mechanistically, an apparent reduction in the cardiac inflammatory response in sotagliflozin-treated hearts was observed in the post-MI rats.

Conclusion

Overall, our results suggest that sotagliflozin may have cardioprotective effects against myocardial infarction.

CaMKII, 'jack of all trades' in inflammation during cardiac ischemia/reperfusion injury

Myocardial infarction and revascularization cause cardiac ischemia/reperfusion (I/R) injury featuring cardiomyocyte death and inflammation. The Ca2+/calmodulin dependent protein kinase II (CaMKII) family are serine/ threonine protein kinases that are involved in I/R injury. CaMKII exists in four different isoforms, α, β, γ, and δ. In the heart, CaMKII-δ is the predominant isoform，with multiple splicing variants, such as δB, δC and δ9. During I/R, elevated intracellular Ca2+ concentrations and reactive oxygen species activate CaMKII. In this review, we summarized the regulation and function of CaMKII in multiple cell types including cardiomyocytes, endothelial cells, and macrophages during I/R. We conclude that CaMKII mediates inflammation in the microenvironment of the myocardium, resulting in cell dysfunction, elevated inflammation, and cell death. However, different CaMKII-δ variants exhibit distinct or even opposite functions. Therefore, reagents/approaches that selectively target specific CaMKII isoforms and variants are needed for evaluating and counteracting the exact role of CaMKII in I/R injury and developing effective treatments against I/R injury.

DNAzyme loaded nano-niosomes attenuate myocardial ischemia/reperfusion injury by targeting apoptosis, inflammation in a NF-κB dependent mechanism

Although DNAzymes have been found to reduce injury after myocardial ischemia/reperfusion (MI/R), their efficiency have been limited due to rapid degradation in vivo. Thus, this study was conducted to extend their half-life by encapsulation into nano‑niosomes and examine their cardioprotective effects in a rat model of myocardial infarction (MI). In order to synthesize nano‑niosomes, surface active agent film hydration method was used. Characterization of nano‑niosomes was performed using the atomic force microscopy (AFM). In order to establish MI/R model in rats, left anterior descending coronary artery (LAD) was ligated for 30 min. A single dose (150µL) of drug formulations was injected into the infarcted region. The cardiac function was evaluated using echocardiography. The expression of pro-inflammatory cytokines, apoptotic factors, and nuclear factor-κB (NF-κB) were evaluated using Western blot and immunohistochemistry, respectively. Particle size of only nano-niosomes was in the range of 60-90 nm, while a shift to 70-110 nm was seen after DNAzyme encapsulation. MI rats treated with DNAzyme‑loaded nano‑niosomes could markedly reduce Bax, caspase3, TNF-α, IL-1β, and NF-κB as well as increase Bcl-2 compared to only MI/R group. Collectively, our finding show that nano‑niosomes can be considered excellent drug delivery platforms to extend half-life and stability of DNAzyme, when it is used to reduce myocardial I/R injury.

Regulatory effects of trimetazidine in cardiac ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is a tissue damage during reperfusion after an ischemic condition. I/R injury is induced by pathological cases including stroke, myocardial infarction, circulatory arrest, sickle cell disease, acute kidney injury, trauma, and sleep apnea. It can lead to increased morbidity and mortality in the context of these processes. Mitochondrial dysfunction is one of the hallmarks of I/R insult, which is induced via reactive oxygen species (ROS) production, apoptosis, and autophagy. MicroRNAs (miRNAs, miRs) are non-coding RNAs that play a main regulatory role in gene expression. Recently, there are evidence, which miRNAs are the major modulators of cardiovascular diseases, especially myocardial I/R injury. Cardiovascular miRNAs, specifically miR-21, and probably miR-24 and miR-126 have protective effects on myocardial I/R injury. Trimetazidine (TMZ) is a new class of metabolic agents with an anti-ischemic activity. It has beneficial effects on chronic stable angina by suppressing mitochondrial permeability transition pore (mPTP) opening. The present review study addressed the different mechanistic effects of TMZ on cardiac I/R injury. Online databases including Scopus, PubMed, Web of Science, and Cochrane library were assessed for published studies between 1986 and 2021. TMZ, an antioxidant and metabolic agent, prevents the cardiac reperfusion injury by regulating AMP-activated protein kinase (AMPK), cystathionine-γ-lyase enzyme (CSE)/hydrogen sulfide (H2S), and miR-21. Therefore, TMZ protects the heart against I/R injury by inducing key regulators such as AMPK, CSE/H2S, and miR-21.

Cellular mechanisms and molecular pathways linking bitter taste receptor signalling to cardiac inflammation, oxidative stress, arrhythmia and contractile dysfunction in heart diseases

Heart diseases and related complications constitute a leading cause of death and socioeconomic threat worldwide. Despite intense efforts and research on the pathogenetic mechanisms of these diseases, the underlying cellular and molecular mechanisms are yet to be completely understood. Several lines of evidence indicate a critical role of inflammatory and oxidative stress responses in the development and progression of heart diseases. Nevertheless, the molecular machinery that drives cardiac inflammation and oxidative stress is not completely known. Recent data suggest an important role of cardiac bitter taste receptors (TAS2Rs) in the pathogenetic mechanism of heart diseases. Independent groups of researchers have demonstrated a central role of TAS2Rs in mediating inflammatory, oxidative stress responses, autophagy, impulse generation/propagation and contractile activities in the heart, suggesting that dysfunctional TAS2R signalling may predispose to cardiac inflammatory and oxidative stress disorders, characterised by contractile dysfunction and arrhythmia. Moreover, cardiac TAS2Rs act as gateway surveillance units that monitor and detect toxigenic or pathogenic molecules, including microbial components, and initiate responses that ultimately culminate in protection of the host against the aggression. Unfortunately, however, the molecular mechanisms that link TAS2R sensing of the cardiac milieu to inflammatory and oxidative stress responses are not clearly known. Therefore, we sought to review the possible role of TAS2R signalling in the pathophysiology of cardiac inflammation, oxidative stress, arrhythmia and contractile dysfunction in heart diseases. Potential therapeutic significance of targeting TAS2R or its downstream signalling molecules in cardiac inflammation, oxidative stress, arrhythmia and contractile dysfunction is also discussed.

CaMKII as a Therapeutic Target in Cardiovascular Disease

CaMKII (the multifunctional Ca2+ and calmodulin-dependent protein kinase II) is a highly validated signal for promoting a variety of common diseases, particularly in the cardiovascular system. Despite substantial amounts of convincing preclinical data, CaMKII inhibitors have yet to emerge in clinical practice. Therapeutic inhibition is challenged by the diversity of CaMKII isoforms and splice variants and by physiological CaMKII activity that contributes to learning and memory. Thus, uncoupling the harmful and beneficial aspects of CaMKII will be paramount to developing effective therapies. In the last decade, several targeting strategies have emerged, including small molecules, peptides, and nucleotides, which hold promise in discriminating pathological from physiological CaMKII activity. Here we review the cellular and molecular biology of CaMKII, discuss its role in physiological and pathological signaling, and consider new findings and approaches for developing CaMKII therapeutics.

Red light-green light: T-cell trafficking in cardiac and vascular inflammation

Extravasation of T cells from the bloodstream into inflamed tissues requires interactions between T cells and vascular endothelial cells, a necessary step that allows T cells to exert their effector function during the immune response to pathogens and to sterile insults. This cellular cross talk involves adhesion molecules on both the vascular endothelium and the T cells themselves that function as receptor-ligand pairs to slow down circulating T cells. These will eventually extravasate into sites of inflammation when they receive the correct chemokine signals. Accumulation of T cells within the vascular wall can lead to vessel thickening and vascular disease, whereas T-cell extravasation into the myocardium often leads to cardiac chronic inflammation and adverse cardiac remodeling, hallmarks of heart failure. On the flip side, T-cell trafficking is required for pathogen clearance and to promote tissue repair after injury resulting from cardiac ischemia. Thus, a better understanding of the central players mediating these interactions may help develop novel therapeutics to modulate vascular and cardiac inflammation. Here, we review the most recent literature on pathways that regulate T-cell transendothelial migration, the last step leading to T-cell infiltration into tissues and organs in the context of vascular and cardiac inflammation. We discuss new potential avenues to therapeutically modulate these pathways to enhance or prevent immune cell infiltration in cardiovascular disease.

Guanxinning Injection Combined With Ischemic Postconditioning Attenuate Myocardial Ischemic Reperfusion Injury in Chronic Renal Failure Rats by Modulating Mitochondrial Dynamics

Purpose

Salvia miltiorrhiza Bge. (Danshen, DS) and Ligusticum chuanxiong Hort. (Chuanxiong, CX) have been widely used in traditional Chinese medicine to prevent and treat myocardial ischemia and renal insufficiency, and their extracts (Guanxinning injection, GXN) have been reported to exhibit antioxidant, anti-inflammatory, and anti-ischemia-reperfusion injury properties. It is well-established that ischemic postconditioning (IPOC) can protect against myocardial ischemia-reperfusion (I/R) injury in rats with chronic renal failure (CRF). However, little is known on whether GXN combined with IPOC may affect myocardial I/R injury in CRF rats. We sought to observe the effect of GXN combined with IPOC on myocardial I/R injury in CRF rats by quantifying changes in the expression of proteins related to mitochondrial dynamics.

Materials and Methods

In a survey, 90 Wistar rats were randomly divided into 6 groups (15 rats per group): CRF group, I/R group, comorbid group (CRF + I/R), IPOC group, IPOC + GXN group and the sham group. Changes in blood myocardial injury markers, urea, and creatinine were analyzed. Heart tissues were harvested for histomorphometry and western blotting when rats were sacrificed. Myocardial infarction area was measured by Evans blue and Triphenyltetrazolium chloride solution staining. The expressions of mitochondrial fission relative proteins (DRP1 and FIS1) and mitochondrial fusion relative proteins (OPA1 and MFN1) were detected by western blotting.

Results

IPOC could significantly decrease myocardial injury markers and myocardial area of necrosis (AN)/area at risk (AAR) of the comorbid model rats. Further results showed that GXN combined with IPOC could significantly reduce CK-MB levels and myocardial AN/AAR in comorbid model rats compared with the IPOC group. Meanwhile, both IPOC and IPOC + GXN significantly reduced DRP1 levels and increased the MFN1 and OPA1 protein levels in the comorbid model rats. However, compared with the IPOC group, MFN1 and OPA1 protein levels increased significantly in the IPOC + GXN group.

Conclusion

Extracts of DS and CX combined with IPOC exert a protective effect against myocardial I/R injury in rats with CRF, mediated by increased expression of mitochondrial fusion proteins (MFN1 and OPA1).

Novel CaMKII-δ Inhibitor Hesperadin Exerts Dual Functions to Ameliorate Cardiac Ischemia/Reperfusion Injury and Inhibit Tumor Growth

BACKGROUND

Cardiac ischemia/reperfusion (I/R) injury has emerged as an important therapeutic target for ischemic heart disease, the leading cause of morbidity and mortality worldwide. At present, there is no effective therapy for reducing cardiac I/R injury. CaMKII (Ca²⁺/calmodulin-dependent kinase II) plays a pivotal role in the pathogenesis of severe heart conditions, including I/R injury. Pharmacological inhibition of CaMKII is an important strategy in the protection against myocardial damage and cardiac diseases. To date, there is no drug targeting CaMKII for the clinical therapy of heart disease. Furthermore, at present, there is no selective inhibitor of CaMKII-δ, the major CaMKII isoform in the heart.

METHODS

A small-molecule kinase inhibitor library and a high-throughput screening system for the kinase activity assay of CaMKII-δ9 (the most abundant CaMKII-δ splice variant in human heart) were used to screen for CaMKII-δ inhibitors. Using cultured neonatal rat ventricular myocytes, human embryonic stem cell-derived cardiomyocytes, and in vivo mouse models, in conjunction with myocardial injury induced by I/R (or hypoxia/reoxygenation) and CaMKII-δ9 overexpression, we sought to investigate the protection of hesperadin against cardiomyocyte death and cardiac diseases. BALB/c nude mice with xenografted tumors of human cancer cells were used to evaluate the in vivo antitumor effect of hesperadin.

RESULTS

Based on the small-molecule kinase inhibitor library and screening system, we found that hesperadin, an Aurora B kinase inhibitor with antitumor activity in vitro, directly bound to CaMKII-δ and specifically blocked its activation in an ATP-competitive manner. Hesperadin functionally ameliorated both I/R- and overexpressed CaMKII-δ9-induced cardiomyocyte death, myocardial damage, and heart failure in both rodents and human embryonic stem cell-derived cardiomyocytes. In addition, in an in vivo BALB/c nude mouse model with xenografted tumors of human cancer cells, hesperadin delayed tumor growth without inducing cardiomyocyte death or cardiac injury.

CONCLUSIONS

Here, we identified hesperadin as a specific small-molecule inhibitor of CaMKII-δ with dual functions of cardioprotective and antitumor effects. These findings not only suggest that hesperadin is a promising leading compound for clinical therapy of cardiac I/R injury and heart failure, but also provide a strategy for the joint therapy of cancer and cardiovascular disease caused by anticancer treatment.

Elevated MCU Expression by CaMKIIδB Limits Pathological Cardiac Remodeling

Background: Calcium (Ca²⁺) is a key regulator of energy metabolism. Impaired Ca²⁺ homeostasis damages mitochondria, causing cardiomyocyte death, pathological hypertrophy, and heart failure. This study investigates the regulation and the role of the mitochondrial Ca²⁺ uniporter (MCU) in chronic stress-induced pathological cardiac remodeling. Methods: MCU knockout or transgenic mice were infused with isoproterenol (ISO, 10 mg/kg/day, 4 weeks). Cardiac hypertrophy and remodeling were evaluated by echocardiography and histology. Primary cultured rodent adult cardiomyocytes were treated with ISO (1 nM, 48 hr). Intracellular Ca²⁺ handling and cell death pathways were monitored. Adenovirus-mediated gene manipulations were used in vitro. Results: Chronic administration of the β-adrenergic receptor (β-AR) agonist ISO increased the levels of the MCU and the MCU complex in cardiac mitochondria, raising mitochondrial Ca²⁺ concentrations, in vivo and in vitro. ISO also upregulated MCU without affecting its regulatory proteins in adult cardiomyocytes. Interestingly, ISO-induced cardiac hypertrophy, fibrosis, contractile dysfunction, and cardiomyocyte death were exacerbated in global MCU knockout (KO) mice. Cardiomyocytes from KO mice or mice overexpressing a dominant negative MCU exhibited defective intracellular Ca²⁺ handling and activation of multiple cell death pathways. Conversely, cardiac-specific overexpression of MCU maintained intracellular Ca²⁺ homeostasis and contractility, suppressed cell death, and prevented ISO-induced heart hypertrophy. ISO upregulated MCU expression through activation of Ca²⁺/calmodulin kinase II δB (CaMKIIδB) and promotion of its nuclear translocation via calcineurin-mediated dephosphorylation at serine 332. Nuclear CaMKIIδB phosphorylated cAMP-response element binding protein (CREB), which bound the MCU promotor to enhance MCU gene transcription. Conclusions: The β-AR/CaMKIIδB/CREB pathway upregulates MCU gene expression in the heart. MCU upregulation is a compensatory mechanism that counteracts stress-induced pathological cardiac remodeling by preserving Ca²⁺ homeostasis and cardiomyocyte viability.

Targeting CaMKII-δ9 Ameliorates Cardiac Ischemia/Reperfusion Injury by Inhibiting Myocardial Inflammation

BACKGROUND

CaMKII (Ca²⁺/calmodulin-dependent kinase II) plays a central role in cardiac ischemia/reperfusion (I/R) injury-an important therapeutic target for ischemic heart disease. In the heart, CaMKII-δ is the predominant isoform and further alternatively spliced into 11 variants. In humans, CaMKII-δ9 and CaMKII-δ3, the major cardiac splice variants, inversely regulate cardiomyocyte viability with the former pro-death and the latter pro-survival. However, it is unknown whether specific inhibition of the detrimental CaMKII-δ9 prevents cardiac I/R injury and, if so, what is the underlying mechanism. Here, we aim to investigate the cardioprotective effect of specific CaMKII-δ9 inhibition against myocardial I/R damage and determine the underlying mechanisms.

METHODS

The role and mechanism of CaMKII-δ9 in cardiac I/R injury were investigated in mice in vivo, neonatal rat ventricular myocytes, and human embryonic stem cell-derived cardiomyocytes.

RESULTS

We demonstrate that CaMKII-δ9 inhibition with knockdown or knockout of its feature exon, exon 16, protects the heart against I/R-elicited injury and subsequent heart failure. I/R-induced cardiac inflammation was also ameliorated by CaMKII-δ9 inhibition, and compared with the previously well-studied CaMKII-δ2, CaMKII-δ9 overexpression caused more profound cardiac inflammation. Mechanistically, in addition to IKKβ (inhibitor of NF-κB [nuclear factor-κB] kinase subunit β), CaMKII-δ9, but not δ2, directly interacted with IκBα (NF-κB inhibitor α) with its feature exon 13-16-17 combination and increased IκBα phosphorylation and consequently elicited more pronounced activation of NF-κB signaling and inflammatory response. Furthermore, the essential role of CaMKII-δ9 in myocardial inflammation and damage was confirmed in human cardiomyocytes.

CONCLUSIONS

We not only identified CaMKII-δ9-IKK/IκB-NF-κB signaling as a new regulator of human cardiomyocyte inflammation but also demonstrated that specifically targeting CaMKII-δ9, the most abundant CaMKII-δ splice variant in human heart, markedly suppresses I/R-induced cardiac NF-κB activation, inflammation, and injury and subsequently ameliorates myocardial remodeling and heart failure, providing a novel therapeutic strategy for various ischemic heart diseases.

CaMKII-δ9 Induces Cardiomyocyte Death to Promote Cardiomyopathy and Heart Failure

Heart failure is a syndrome in which the heart cannot pump enough blood to meet the body's needs, resulting from impaired ventricular filling or ejection of blood. Heart failure is still a global public health problem and remains a substantial unmet medical need. Therefore, it is crucial to identify new therapeutic targets for heart failure. Ca²⁺/calmodulin-dependent kinase II (CaMKII) is a serine/threonine protein kinase that modulates various cardiac diseases. CaMKII-δ9 is the most abundant CaMKII-δ splice variant in the human heart and acts as a central mediator of DNA damage and cell death in cardiomyocytes. Here, we proved that CaMKII-δ9 mediated cardiomyocyte death promotes cardiomyopathy and heart failure. However, CaMKII-δ9 did not directly regulate cardiac hypertrophy. Furthermore, we also showed that CaMKII-δ9 induced cell death in adult cardiomyocytes through impairing the UBE2T/DNA repair signaling. Finally, we demonstrated no gender difference in the expression of CaMKII-δ9 in the hearts, together with its related cardiac pathology. These findings deepen our understanding of the role of CaMKII-δ9 in cardiac pathology and provide new insights into the mechanisms and therapy of heart failure.

DMIL-IsoFun: predicting isoform function using deep multi-instance learning

MOTIVATION

Alternative splicing creates the considerable proteomic diversity and complexity on relatively limited genome. Proteoforms translated from alternatively spliced isoforms of a gene actually execute the biological functions of this gene, which reflect the functional knowledge of genes at a finer granular level. Recently, some computational approaches have been proposed to differentiate isoform functions using sequence and expression data. However, their performance is far from being desirable, mainly due to the imbalance and lack of annotations at isoform-level, and the difficulty of modeling gene-isoform relations.

RESULT

We propose a deep multi-instance learning based framework (DMIL-IsoFun) to differentiate the functions of isoforms. DMIL-IsoFun firstly introduces a multi-instance learning convolution neural network trained with isoform sequences and gene-level annotations to extract the feature vectors and initialize the annotations of isoforms, and then uses a class-imbalance Graph Convolution Network to refine the annotations of individual isoforms based on the isoform co-expression network and extracted features. Extensive experimental results show that DMIL-IsoFun improves the Smin and Fmax of state-of-the-art solutions by at least 29.6% and 40.8%. The effectiveness of DMIL-IsoFun is further confirmed on a testbed of human multiple-isoform genes, and Maize isoforms related with photosynthesis.

AVAILABILITY

The code and data are available at http://www.sdu-idea.cn/codes.php?name=DMIL-Isofun.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

CaMKII in Regulation of Cell Death During Myocardial Reperfusion Injury

Cardiovascular disease is the leading cause of death worldwide. In spite of the mature managements of myocardial infarction (MI), post-MI reperfusion (I/R) injury results in high morbidity and mortality. Cardiomyocyte Ca²⁺ overload is a major factor of I/R injury, initiating a cascade of events contributing to cardiomyocyte death and myocardial dysfunction. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) plays a critical role in cardiomyocyte death response to I/R injury, whose activation is a key feature of myocardial I/R in causing intracellular mitochondrial swelling, endoplasmic reticulum (ER) Ca²⁺ leakage, abnormal myofilament contraction, and other adverse reactions. CaMKII is a multifunctional serine/threonine protein kinase, and CaMKIIδ, the dominant subtype in heart, has been widely studied in the activation, location, and related pathways of cardiomyocytes death, which has been considered as a potential targets for pharmacological inhibition. In this review, we summarize a brief overview of CaMKII with various posttranslational modifications and its properties in myocardial I/R injury. We focus on the molecular mechanism of CaMKII involved in regulation of cell death induced by myocardial I/R including necroptosis and pyroptosis of cardiomyocyte. Finally, we highlight that targeting CaMKII modifications and cell death involved pathways may provide new insights to understand the conversion of cardiomyocyte fate in the setting of myocardial I/R injury.

Store-Operated Calcium Entry: Shaping the Transcriptional and Epigenetic Landscape in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) displays a particularly poor prognosis and low survival rate, mainly due to late diagnosis and high incidence of chemotherapy resistance. Genomic aberrations, together with changes in the epigenomic profile, elicit a shift in cellular signaling response and a transcriptional reprograming in pancreatic tumors. This endows them with malignant attributes that enable them to not only overcome chemotherapeutic challenges, but to also attain diverse oncogenic properties. In fact, certain genetic amplifications elicit a rewiring of calcium signaling, which can confer ER stress resistance to tumors while also aberrantly activating known drivers of oncogenic programs such as NFAT. While calcium is a well-known second messenger, the transcriptional programs driven by aberrant calcium signaling remain largely undescribed in pancreatic cancer. In this review, we focus on calcium-dependent signaling and its role in epigenetic programs and transcriptional regulation. We also briefly discuss genetic aberration events, exemplifying how genetic alterations can rewire cellular signaling cascades, including calcium-dependent ones.

Attenuating ischemia/reperfusion injury in rat cardiac transplantation by intracoronary infusion with siRNA cocktail solution

Tumor necrosis factor-α (TNF-α), caspase-8, and complement component 5a receptor (C5aR) are known to play a crucial role in the myocardial ischemia/reperfusion (I/R) injury in cardiac transplantation. We hypothesized that the intracoronary infusion of TNF-α, caspase-8, and C5aR small interfering RNAs (siRNA) would protect cardiac allograft function and improve graft survival from I/R injury-induced organ failure. I/R injury of cardiac allograft was induced by syngeneic rat cardiac transplantation, in which the transplanted hearts were infused with saline or different amounts of siRNA cocktail solution targeting TNF-α, caspase-8, and C5aR via coronary arteries, and subsequently subjected to 18 h of preservation at 4°C in histidine–tryptophan–ketoglutarate (HTK) solution. The effects of siRNA cocktail solution on prolonged cold I/R injury were determined by assessing graft survival, histopathological changes, myeloperoxidase (MPO) activity, and malondialdehyde (MDA) concentration. The perfused siRNA cocktail solution successfully knocked down the expression of TNF-α, caspase-8, and C5aR in vitro and in vivo. Approximately 91.7% of control hearts that underwent 18 h of cold ischemia ceased their function after transplantation; however, 87.5% of cardiac allografts from the highest dose siRNA cocktail solution-pretreated hearts survived >14 days and exhibited minimal histological changes, with minimal cellular infiltration, interstitial edema, and inflammation and maximal reduced MPO activity and MDA concentration in the cardiac allograft. We demonstrated the feasibility and efficiency of infusion of TNF-α, caspase-8, and C5aR siRNA via the intracoronary route as a promising strategy for gene silencing against I/R injury in cardiac transplantation.

CaMKIIδ Splice Variants in the Healthy and Diseased Heart

RNA splicing has been recognized in recent years as a pivotal player in heart development and disease. The Ca²⁺/calmodulin dependent protein kinase II delta (CaMKIIδ) is a multifunctional Ser/Thr kinase family and generates at least 11 different splice variants through alternative splicing. This enzyme, which belongs to the CaMKII family, is the predominant family member in the heart and functions as a messenger toward adaptive or detrimental signaling in cardiomyocytes. Classically, the nuclear CaMKIIδB and cytoplasmic CaMKIIδC splice variants are described as mediators of arrhythmias, contractile function, Ca²⁺ handling, and gene transcription. Recent findings also put CaMKIIδA and CaMKIIδ9 as cardinal players in the global CaMKII response in the heart. In this review, we discuss and summarize the new insights into CaMKIIδ splice variants and their (proposed) functions, as well as CaMKII-engineered mouse phenotypes and cardiac dysfunction related to CaMKIIδ missplicing. We also discuss RNA splicing factors affecting CaMKII splicing. Finally, we discuss the translational perspective derived from these insights and future directions on CaMKIIδ splicing research in the healthy and diseased heart.

Conditioned medium from adipose-derived stem cells attenuates ischemia/reperfusion-induced cardiac injury through the microRNA-221/222/PUMA/ETS-1 pathway

Rationale: Cardiovascular diseases, such as myocardial infarction (MI), are the leading causes of death worldwide. Reperfusion therapy is the common standard treatment for MI. However, myocardial ischemia/reperfusion (I/R) causes cardiomyocyte injury, including apoptosis and fibrosis. We aimed to investigate the effects of conditioned medium from adipose-derived stem cells (ADSC-CM) on apoptosis and fibrosis in I/R-treated hearts and hypoxia/reoxygenation (H/R)-treated cardiomyocytes and the underlying mechanisms.

Methods: ADSC-CM was collected from ADSCs. The effects of intramuscular injection of ADSC-CM on cardiac function, cardiac apoptosis, and fibrosis examined by echocardiography, Evans blue/TTC staining, TUNEL assay, and Masson's trichrome staining in I/R-treated mice. We also examined the effects of ADSC-CM on apoptosis and fibrosis in H/R-treated H9c2 cells by annexin V/PI flow cytometry, TUNEL assay, and immunocytochemistry.

Results: ADSC-CM treatment significantly reduced heart damage and fibrosis of I/R-treated mice and H/R-treated cardiomyocytes. In addition, the expression of apoptosis-related proteins, such as p53 upregulated modulator of apoptosis (PUMA), p-p53 and B-cell lymphoma 2 (BCL2), as well as the fibrosis-related proteins ETS-1, fibronectin and collagen 3, were significantly reduced by ADSC-CM treatment. Moreover, we demonstrated that ADSC-CM contains a large amount of miR-221/222, which can target and regulate PUMA or ETS-1 protein levels. Furthermore, the knockdown of PUMA and ETS-1 decreased the induction of apoptosis and fibrosis, respectively. MiR-221/222 overexpression achieved similar results. We also observed that cardiac I/R markedly increased apoptosis and fibrosis in miR-221/222 knockout (KO) mice, while ADSC-CM decreased these effects. The increased phosphorylation of p38 and NF‐κB not only mediated myocardial apoptosis through the PUMA/p53/BCL2 pathway but also regulated fibrosis through the ETS-1/fibronectin/collagen 3 pathway.

Conclusions: Overall, our results show that ADSC-CM attenuates cardiac apoptosis and fibrosis by reducing PUMA and ETS-1 expression, respectively. The protective effect is mediated via the miR-221/222/p38/NF-κB pathway.

CaMKIIδC Drives Early Adaptive Ca2+ Change and Late Eccentric Cardiac Hypertrophy

Supplemental Digital Content is available in the text.

CaMKII (Ca²⁺-Calmodulin dependent protein kinase) δC activation is implicated in pathological progression of heart failure (HF) and CaMKIIδC transgenic mice rapidly develop HF and arrhythmias. However, little is known about early spatio-temporal Ca²⁺ handling and CaMKII activation in hypertrophy and HF.

Overexpression of IκBα in cardiomyocytes alleviates hydrogen peroxide-induced apoptosis and autophagy by inhibiting NF-κB activation

Background

Inflammation and oxidative stress play predominant roles in the initiation and progression of ischaemia/reperfusion (I/R) injury, with nuclear factor kappa B (NF-κB) serving as a crucial mediator. Overexpression of the inhibitor of κB alpha (IκBα) gene is hypothesized to have protective effects against apoptosis and autophagy in cardiomyocytes subjected to hydrogen peroxide (H₂O₂) by inhibiting the NF-κB pathway.

Methods

The IκBα^{S32A, S36A} gene was transfected via adeno-associated virus serotype 9 (AAV9) delivery into neonatal rat ventricular cardiomyocytes (NRVMs) prior to H₂O₂ treatment. NRVMs were divided into control, H₂O₂, GFP + H₂O₂, IκBα+H₂O₂, and pyrrolidine dithiocarbamate (PDTC) + H₂O₂ groups. Nuclear translocation of the NF-κB p65 subunit was evaluated by immunofluorescence and Western blotting. Cell viability was assessed by Cell Counting Kit-8 assay. Supernatant lactate dehydrogenase (LDH) and intracellular malondialdehyde (MDA) were measured to identify H₂O₂-stimulated cytotoxicity. Apoptosis was determined by Annexin V-PE/7-AAD staining, and the mitochondrial membrane potential (ΔΨm) was detected by JC-1 staining. Western blotting was used to detect apoptosis- and autophagy-related proteins.

Results

IκBα transfection significantly increased cell viability and ΔΨm but decreased the supernatant LDH and cellular MDA levels in cardiomyocytes exposed to H₂O₂. Meanwhile, IκBα overexpression decreased H₂O₂-induced apoptosis by upregulating the Bcl-2/Bax ratio and reduced autophagy by downregulating the expression of Beclin-1 and the LC3-II/LC3-I ratio. These effects partly accounted for the ability of IκBα to inhibit the NF-κB signalling pathway, as evidenced by decreases in p65 phosphorylation and nuclear translocation. Indeed, the effects of inactivation of NF-κB signalling with the specific inhibitor PDTC resembled the cardioprotective effects of IκBα during H₂O₂ stimulation.

Conclusion

IκBα overexpression can ameliorate H₂O₂-induced apoptosis, autophagy, oxidative injury, and ΔΨm loss through inhibition of the NF-κB signalling pathway. These findings suggest that IκBα transfection can result in successful resistance to oxidative stress-induced damage by inhibiting NF-κB activation, which may provide a potential therapeutic target for the prevention of myocardial I/R injury.

CaMKII/calpain interaction mediates ischemia/reperfusion injury in isolated rat hearts

Previous studies indicated that Ca²⁺/calmodulin-dependent kinase II (CaMKII), a kinase involved in the modulation of ryanodine receptor activity, activates Ca²⁺-regulated protease μ-calpain to promote myocardial ischemia/reperfusion injury. This study was performed to explore the underlying mechanisms in CaMKII-induced calpain activation to better understand heart injury. To examine the Ca²⁺ paradox and ischemia/reperfusion injury, isolated rat hearts were subjected to a Ca²⁺-free solution for 3 min, or left coronary artery occlusion for 40 min, prior to restoration of normal perfusion. Blockade of trans-sarcoplasmic reticulum Ca²⁺ flux using ryanodine and thapsigargin failed to prevent Ca²⁺ paradox-induced heart injury. In contrast, the Ca²⁺ paradox increased CaMKII auto-phosphorylation at Thr²⁸⁷, while the CaMKII inhibitor KN-62 and the Na⁺/Ca²⁺ exchanger inhibitor KB-R7943 alleviated heart injury and calpain activity. Intriguingly, the binding of μ-calpain large subunit calpain-1 (CAPN1) to phospho-CaMKII was blunted by both inhibitors. Thus, a Ca²⁺ leak via the ryanodine receptor is not an essential element in CaMKII-elicited calpain activation. In hearts receiving vector injection, ischemia/reperfusion caused elevated calpain activity and α-fodrin degradation, along with membrane integrity damage, similar to the effects noted in control hearts. Importantly, all these alterations were diminished with delivery of adeno-associated virus expressing mutant CaMKIIδC T287A. Ischemia/reperfusion increased CaMKII auto-phosphorylation and binding of CAPN1 to phospho-CaMKII, and facilitated the translocation of phospho-CaMKII and CAPN1 to the plasma membrane, all of which were reversed by injecting CaMKII mutant. Furthermore, the relocation capacity and the interaction of CaMKII with CAPN1 appeared to be dependent upon CaMKII autophosphorylation, as its mutant delivery increased the level of CaMKII, but did not increase membrane content of CaMKII and CAPN1, or their interactions. Together, CaMKII/calpain interaction represents a new avenue for mediating myocardial ischemia/reperfusion injury, and CaMKII likely serves as both a kinase and a carrier, thereby promoting calpain membrane translocation and activation.

The protective effect of polyphyllin I on myocardial ischemia/reperfusion injury in rats

Background

Myocardial ischemia/reperfusion (I/R) injury has become a global public health concern. An increasing amount of evidence has shown that polyphyllin I (PPI) has anti-apoptotic and antioxidant functions. This study was performed to evaluate the cardioprotective effects of PPI in a rat model of myocardial I/R injury and the underlying mechanism.

Methods

We exposed induced a rat model of I/R injury by exposing rat hearts to left anterior descending coronary artery ligation for 30 min, followed by 24 h of reperfusion. Cardiac function was analyzed by echocardiography and HE staining. Myocardial apoptosis, inflammation, and oxidative stress were detected to analyze the PPI's role in I/R injury.

Results

The results showed that pretreatment with PPI improved impaired histological morphology, as shown by histopathological examination. Echocardiography analysis showed that PPI increased the levels of HR, left ventricular ejection fraction (LVEF), and left ventricular wall thickness (LVWT), accompanied by decreased left ventricular end-systolic volume (LVESV). Also, PPI decreased the expression of CK-MB, Mb, cTnI, and LDH. Specifically, PPI also changed the expression of apoptotic makers (Caspase-3, Bax, and Bcl-2), inflammatory cytokines (TNF-α, IL-6, iNOS, and IL-10) and oxidative stress markers (SOD, GSH, ROS, and MDA). Notably, western blot (WB) showed that PPI treatment inhibited the phosphorylation activity of NF-κB p65.

Conclusions

The findings showed that PPI exerted a favorable protective effect on I/R injury by inhibiting the inflammatory response and oxidative stress. It offered new drug candidates for the treatment of myocardial I/R injury.

Melatonin elicits protective effects on OGD/R‑insulted H9c2 cells by activating PGC‑1α/Nrf2 signaling

Melatonin (Mel) elicits beneficial effects on myocardial ischemia/reperfusion injury. However, the underlying mechanism of Mel against oxygen-glucose deprivation/ reperfusion (OGD/R)-induced H9c2 cardiomyocyte damage remains largely unknown. The aim of the present study was to investigate the biological roles and the potential mechanisms of Mel in OGD/R-exposed H9c2 cardiomyocytes. The results of the present study demonstrated that Mel significantly elevated the viability and reduced the activity of lactate dehydrogenase and creatine kinase myocardial band in a doseand time-dependent manner in OGD/R-insulted H9c2 cells. In addition, Mel suppressed OGD/R-induced oxidative stress in H9c2 cells, as demonstrated by the decreased reactive oxygen species and malondialdehyde levels, as well as the increased activities of superoxide dismutase, catalase and glutathione peroxidase. Mel exerted an antioxidant effect by activating the peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. Mel reduced the expression of OGD/R-enhanced pro-inflammatory tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-1β, IL-8 and monocyte chemotactic protein-1. Mel also abolished the OGD/R-induced increase in H9c2 apoptosis, as evidenced by mitochondrial membrane potential restoration and caspase-3 and caspase-9 inactivation, as well as the upregulation of Bcl-2 and down-regulation of cleaved caspase-3 and Bax. The Mel-induced antiapoptotic effects were dependent on PGC-1α/TNF-α signaling. Overall, the results of the present study demonstrated that Mel alleviated OGD/R-induced H9c2 cell injury via the inhibition of oxidative stress and inflammation by regulating the PGC-1α/Nrf2 and PGC-1α/TNF-α signaling pathways, suggesting a promising role for Mel in the treatment of ischemic heart disease.

Ghrelin as an anti-inflammatory and protective agent in ischemia/reperfusion injury

Ischemia/reperfusion (I/R) continue to be the most frequent cause of damaged tissues. Injured tissues resulted from the first ischemic insult, which is determined by the interruption in the blood supply, followed by subsequent impairment induced by reperfusion. In addition, ischemia-reperfusion injury is mediated by tumor necrosis factor (TNF) and other cytokines that activate complements and proteases responsible for free radical production. However, earlier studies have reported the protective roles of bioactive peptides during ischemia reperfusion injury. In fact, ghrelin is a peptide hormone discovered since 1999 as GH secretagogue and its production was identified in gastric X/A-like endocrine cells in rats and P/D1 type cells in humans. To date, this peptide receives growing attention due to its pleiotropic action in the organism and its role in maintaining energy homeostasis. Ghrelin is also involved in stress responses, assuming a modulatory action on immune pathways. Previous studies have identified many other functions related to an anti-inflammatory role in ischemia reperfusion injury. Under these challenging conditions, studies described acylated and unacylated ghrelin in activation and/or inhibition processes related to ischemia-reperfusion injury. The aim of this article is to provide a minireview about ghrelin mechanisms involved in the proinflammatory response of I/R injury. However, the regulatory processes of ghrelin in this pathologic event are still very limited and warrant further investigation.

MiR-338-5p ameliorates pathological cardiac hypertrophy by targeting CAMKIIδ

Pathological cardiac hypertrophy (PCH) is characterized by an increase in cardiomyocyte size and thickening of the ventricular walls during the adaptive response to maintain cardiac function, which often progresses to a maladaptive response and, ultimately, to heart failure. Previous studies have demonstrated that miRNAs play roles in the pathogenesis of PCH. In this study, we first found that the regulation of miR-338-5p was aberrant in cardiac tissues of heart failure patients and transverse aortic constriction (TAC)-induced PCH mice. Overexpression of miR-338-5p in the heart using recombinant adeno-associated virus serotype 9 (rAAV9) ameliorated TAC-induced PCH, as indicated by a decreased heart weight/body weight (HW/BW) ratio. Furthermore, miR-338-5p mitigated the TAC-induced damage in heart contraction and relaxation function, as measured by echocardiography and a cardio hemodynamic measurement, respectively. We also identified CAMKIIδ as a direct target of miR-338-5p using bioinformatics tools and the luciferase reporter assay. Finally, we observed that the miR-338-5p-mediated downregulation of CAMKIIδ reversed the cell surface area enlargement induced by the Ang-II treatment in H9c2 cells. Therefore, we highlight a novel molecular mechanism of the miR-338-5p/CAMKIIδ axis that contributes to the pathogenesis of PCH.

Inhibitor 1 of Protein Phosphatase 1 Regulates Ca2+/Calmodulin-Dependent Protein Kinase II to Alleviate Oxidative Stress in Hypoxia-Reoxygenation Injury of Cardiomyocytes

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), regulated by inhibitor 1 of protein phosphatase 1 (I1PP1), is vital for maintaining cardiovascular homeostasis. However, the role and mechanism of I1PP1 against hypoxia-reoxygenation (H/R) injury in cardiomyocytes remain a question. In our study, after I1PP1 overexpression by adenovirus infection in the neonatal cardiomyocytes followed by hypoxia for 4 h and reoxygenation for 12 h, the CaMKIIδ alternative splicing subtype, ATP content, and lactate dehydrogenase (LDH) release were determined. CaMKII activity was evaluated by phosphoprotein phosphorylation at Thr17 (p-PLB Thr17), CaMKII phosphorylation (p-CaMKII), and CaMKII oxidation (ox-CaMKII). Reactive oxygen species (ROS), mitochondrial membrane potential, dynamin-related protein 1 (DRP1), and optic atrophy 1 (OPA1) expressions were assessed. Our study verified that I1PP1 overexpression attenuated the CaMKIIδ alternative splicing disorder; suppressed PLB phosphorylation at Thr17, p-CaMKII, and ox-CaMKII; decreased cell LDH release; increased ATP content; attenuated ROS production; increased mitochondrial membrane potential; and decreased DRP1 expression but increased OPA1 expression in the cardiomyocytes after H/R. Contrarily, CaMKIIδ alternative splicing disorder, LDH release, ATP reduction, and ROS accumulation were aggravated after H/R injury with the I1PP1 knockdown. Collectively, I1PP1 overexpression corrected disorders of CaMKIIδ alternative splicing, inhibited CaMKII phosphorylation, repressed CaMKII oxidation, suppressed ROS production, and attenuated cardiomyocyte H/R injury.

Investigation of the underlying hub genes and mechanisms of reperfusion injury in patients undergoing coronary artery bypass graft surgery by integrated bioinformatic analyses

Background

Although coronary artery bypass graft (CABG) surgery is the main method to revascularize the occluded coronary vessels in coronary artery diseases, the full benefits of the operation are mitigated by ischemia-reperfusion (IR) injury. Although many studies have been devoted to reducing IR injury in animal models, the translation of this research into the clinical field has been disappointing. Our study aimed to explore the underlying hub genes and mechanisms of IR injury.

Methods

A weighted gene co-expression network analysis (WGCNA) was executed based on the expression profiles in patients undergoing CABG surgery (GSE29396). Functional annotation and protein-protein interaction (PPI) network construction were executed within the modules of interest. Potential hub genes were predicted, combining both intramodular connectivity (IC) and degrees. Meanwhile, potential transcription factors (TFs) and microRNAs (miRNAs) were predicted by corresponding bioinformatics tools.

Results

A total of 336 differentially expressed genes (DEGs) were identified. DEGs were mainly enriched in neutrophil activity and immune response. Within the modules of interest, 5 upregulated hub genes (IL-6, CXCL8, IL-1β, MYC, PTGS-2) and 6 downregulated hub genes (C3, TIMP1, VSIG4, SERPING1, CD163, and HP) were predicted. Predicted miRNAs (hsa-miR-333-5p, hsa-miR-26b-5p, hsa-miR-124-3p, hsa-miR-16-5p, hsa-miR-98-5p, hsa-miR-17-5p, hsa-miR-93-5p) and TF (STAT1) might have regulated gene expression in the most positively related module, while hsa-miR-333-5p and HSF-1 were predicted to regulate the genes within the most negatively related module.

Conclusions

Our study illustrates an overview of gene expression changes in human atrial samples from patients undergoing CABG surgery and might help translate future research into clinical work.

Inflammation in nonischemic heart disease: initiation by cardiomyocyte CaMKII and NLRP3 inflammasome signaling

There is substantial evidence that chronic heart failure in humans and in animal models is associated with inflammation. Ischemic interventions such as myocardial infarction lead to necrotic cell death and release of damage associated molecular patterns, factors that signal cell damage and induce expression of proinflammatory chemokines and cytokines. It has recently become evident that nonischemic interventions are also associated with increases in inflammatory genes and immune cell accumulation in the heart and that these contribute to fibrosis and ventricular dysfunction. How proinflammatory responses are elicited in nonischemic heart disease which is not, at least initially, associated with cell death is a critical unanswered question. In this review we provide evidence supporting the hypothesis that cardiomyocytes are an initiating site of inflammatory gene expression in response to nonischemic stress. Furthermore we discuss the role of the multifunctional Ca2+/calmodulin-regulated kinase, CaMKIIδ, as a transducer of stress signals to nuclear factor-κB activation, expression of proinflammatory cytokines and chemokines, and priming and activation of the NOD-like pyrin domain-containing protein 3 (NLRP3) inflammasome in cardiomyocytes. We summarize recent evidence that subsequent macrophage recruitment, fibrosis and contractile dysfunction induced by angiotensin II infusion or transverse aortic constriction are ameliorated by blockade of CaMKII, of monocyte chemoattractant protein-1/C-C chemokine receptor type 2 signaling, or of NLRP3 inflammasome activation.

Voluntary exercise may activate components of pro-survival risk pathway in the rat heart and potentially modify cell proliferation in the myocardium

Although physical exercise is known to reduce size of infarction, incidence of ventricular arrhythmias, and to improve heart function, molecular mechanisms of this protection are not fully elucidated. We explored the hypothesis that voluntary running, similar to adaptive interventions, such as ischemic or remote preconditioning, may activate components of pro-survival (RISK) pathway and potentially modify cell proliferation. Sprague-Dawley adult male rats freely exercised for 23 days in cages equipped with running wheels, while sedentary controls were housed in standard cages. After 23 days, left ventricular (LV) myocardial tissue samples were collected for the detection of expression and activation of RISK proteins (WB). The day before, a marker of cell proliferation 5-bromo-2'-deoxyuridine (BrdU) was given to all animals to detect its incorporation into DNA of the LV cells (ELISA). Running increased phosphorylation (activation) of Akt, as well as the levels of PKC? and phospho-ERK1/2, whereas BrdU incorporation into DNA was unchanged. In contrast, exercise promoted pro-apoptotic signaling - enhanced Bax/Bcl-2 ratio and activation of GSK-3ß kinase. Results suggest that in the rat myocardium adapted to physical load, natural cardioprotective processes associated with physiological hypertrophy are stimulated, while cell proliferation is not modified. Up-regulation of pro-apoptotic markers indicates potential induction of cell death mechanisms that might lead to maladaptation in the long-term.

Targeting MIAT reduces apoptosis of cardiomyocytes after ischemia/reperfusion injury

This study aims to investigate the role of targeting lncRNA myocardial infarction-associated transcript (MIAT) in protection against hypoxia/reoxygenation (H/R) injury in H9c2 cells in vitro and myocardial ischemia/reperfusion (I/R) injury in vivo by regulating expression of NF-kB and p53 upregulated modulator of apoptosis (PUMA). H9C2 cells were infected with lentivirus expressing the short-hairpin RNA direct against human MIAT gene (Lv-MIAT shRNA) or lentivirus expressing scrambled control (Lv-NC shRNA) or PUMA siRNA or p65 siRNA or their control siRNA respectively. Then the H9c2 cells were infected with Lv-shRNA to 2 hours of hypoxia (H) and 24 hour of reoxygenation (R). 100 ul of Lv-MIAT shRNA (1 × 10⁸ PFU) or Lv-NC shRNA was transfected into mouse hearts, then the hearts were subjected to I/R (1h/72 h). We discovered targeting MIAT remarkably enhanced H9c2 cell viability, decreased H/R-induced cell apoptosis and LDH leakage and significantly decreased I/R-induced myocardial infarct size, reduced myocardial apoptosis and enhanced the heart function. Targeting MIAT downregulated p65 nuclear translocation, NF-κB activity and anti-apoptotic protein cleaved-caspase-3, Bax, and upregulated anti-apoptotic protein Bcl-2 induced by H/R or I/R. Our study suggests that targeting MIAT may protect against H9c2 cardiomyoblasts H/R injury or myocardial I/R injury via inhibition of cell apoptosis, mediated by NF-κB and PUMA signal pathway.

Ca2+/Calmodulin-dependent kinase II delta B is essential for cardiomyocyte hypertrophy and complement gene expression after LPS and HSP60 stimulation in vitro

Inflammation plays an important role in the development of cardiovascular diseases (CVDs), suggesting that the immune system is a target of therapeutic interventions used for treating CVDs. This study evaluated mechanisms underlying inflammatory response and cardiomyocyte hypertrophy associated with bacterial lipopolysaccharide (LPS)- or heat shock protein 60 (HSP60)-induced Toll-like receptor (TLR) stimulation and the effect of a small interfering RNA (siRNA) against Ca²⁺/calmodulin-dependent kinase II delta B (CaMKIIδB) on these outcomes. Our results showed that treatment with HSP60 or LPS (TLR agonists) induced cardiomyocyte hypertrophy and complement system C3 and factor B gene expression. In vitro silencing of CaMKIIδB prevented complement gene transcription and cardiomyocyte hypertrophy associated with TLR 2/4 activation but did not prevent the increase in interleukin-6 and tumor necrosis factor-alfa gene expression in primary cultured cardiomyocytes. Moreover, CaMKIIδB silencing attenuated nuclear factor-kappa B expression. These findings supported the hypothesis that CaMKIIδB acts as a link between inflammation and cardiac hypertrophy. Furthermore, the present study is the first to show that extracellular HSP60 activated complement gene expression through CaMKIIδB. Our results indicated that a stress stimulus induced by LPS or HSP60 treatment promoted cardiomyocyte hypertrophy and initiated an inflammatory response through the complement system. However, CaMKIIδB silencing prevented the cardiomyocyte hypertrophy independent of inflammatory response induced by LPS or HSP60 treatment.

Myocardial death and dysfunction after ischemia-reperfusion injury require CaMKIIδ oxidation

Reactive oxygen species (ROS) contribute to myocardial death during ischemia-reperfusion (I/R) injury, but detailed knowledge of molecular pathways connecting ROS to cardiac injury is lacking. Activation of the Ca²⁺/calmodulin-dependent protein kinase II (CaMKIIδ) is implicated in myocardial death, and CaMKII can be activated by ROS (ox-CaMKII) through oxidation of regulatory domain methionines (Met281/282). We examined I/R injury in mice where CaMKIIδ was made resistant to ROS activation by knock-in replacement of regulatory domain methionines with valines (MMVV). We found reduced myocardial death, and improved left ventricular function 24 hours after I/R injury in MMVV in vivo and in vitro compared to WT controls. Loss of ATP sensitive K⁺ channel (KATP) current contributes to I/R injury, and CaMKII promotes sequestration of KATP from myocardial cell membranes. KATP current density was significantly reduced by H₂O₂ in WT ventricular myocytes, but not in MMVV, showing ox-CaMKII decreases KATP availability. Taken together, these findings support a view that ox-CaMKII and KATP are components of a signaling axis promoting I/R injury by ROS.

miR-221 alleviates the inflammatory response and cell apoptosis of neuronal cell through targeting TNFAIP2 in spinal cord ischemia-reperfusion

This study aimed to examine the role of miR-221 in inflammatory response and apoptosis of neuronal cells after spinal cord ischemia/reperfusion (I/R) injury. Blood samples were obtained from 20 I/R patients and that of 20 healthy individuals were used as a control. AGE1.HN and SY-SH-5Y neuronal cell lines subjected to oxygen-glucose deprivation (OGD) stress were used in cell experiments. Real-time PCR and western blot were used to evaluate the expression of miR-221, tumor necrosis factor-α, and TNFAIP2. TUNEL assay analyzed cell apoptosis. I/R patients had lower serum levels of miR-221 than healthy controls. In OGD-AGE1.HN and SY-SH-5Y cells, miR-221 was significantly downregulated and TNFAIP2 mRNA and protein were upregulated; meanwhile, both proinflammatory cytokine tumor necrosis factor-α and anti-inflammation cytokine interleukin-6 were elevated and the percentage of apoptotic cells was increased. This inflammatory response and cell apoptosis induced by OGD stress were attenuated by miR-221 overexpression and enhanced by miR-221 knockdown. TNFAIP2 is a target gene for miR-221 and could be regulated negatively by the miR-221 mimic or the miR-221 inhibitor with or without OGD stress. Accordingly, TNFAIP2 overexpression reversed the inflammatory response and cell apoptosis induced by miR-221 under OGD stress. Downregulation of miR-221 occurs in spinal cord I/R injury and in cell lines subjected to oxygen-glucose deprivation. miR-221 regulates the inflammatory response and apoptosis of neuronal cells through its impact on TNFAIP2.

CaMKII signaling in heart diseases: Emerging role in diabetic cardiomyopathy

Calcium/calmodulin-dependent protein kinase II (CaMKII) is upregulated in diabetes and significantly contributes to cardiac remodeling with increased risk of cardiac arrhythmias. Diabetes is frequently associated with atrial fibrillation, coronary artery disease, and heart failure, which may further enhance CaMKII. Activation of CaMKII occurs downstream of neurohormonal stimulation (e.g. via G-protein coupled receptors) and involve various posttranslational modifications including autophosphorylation, oxidation, S-nitrosylation and O-GlcNAcylation. CaMKII signaling regulates diverse cellular processes in a spatiotemporal manner including excitation-contraction and excitation-transcription coupling, mechanics and energetics in cardiac myocytes. Chronic activation of CaMKII results in cellular remodeling and ultimately arrhythmogenic alterations in Ca²⁺ handling, ion channels, cell-to-cell coupling and metabolism. This review addresses the detrimental effects of the upregulated CaMKII signaling to enhance the arrhythmogenic substrate and trigger mechanisms in the heart. We also briefly summarize preclinical studies using kinase inhibitors and genetically modified mice targeting CaMKII in diabetes. The mechanistic understanding of CaMKII signaling, cardiac remodeling and arrhythmia mechanisms may reveal new therapeutic targets and ultimately better treatment in diabetes and heart disease in general.

Cardioprotection of Ginkgolide B on Myocardial Ischemia/Reperfusion-Induced Inflammatory Injury via Regulation of A20-NF-κB Pathway

Inflammation urges most of the characteristics of plaques involved in the pathogenesis of myocardial ischemia/reperfusion injury (MI/RI). In addition, inflammatory signaling pathways not only mediate the properties of plaques that precipitate ischemia/reperfusion (I/R) but also influence the clinical consequences of the post-infarction remodeling and heart failure. Here, we studied whether Ginkgolide B (GB), an effective anti-inflammatory monomer, improved MI/RI via suppression of inflammation. Left anterior descending (LAD) coronary artery induced ischemia/reperfusion (I/R) of rats or A20 silencing mice, as well as hypoxia/reoxygenation (H/R) induced damages of primary cultured rat neonatal ventricular myocytes or A20 silencing ventricular myocytes, respectively, served as MI/RI model in vivo and in vitro to discuss the anti-I/R injury properties of GB. We found that GB significantly alleviated the symptoms of MI/RI evidently by reducing infarct size, preventing ultrastructural changes of myocardium, depressing Polymorphonuclears (PMNs) infiltration, lessening histopathological damage and suppressing the excessive inflammation. Further study demonstrated that GB remarkably inhibited NF-κB p65 subunit translocation, IκB-α phosphorylation, IKK-β activity, as well as the downstream inflammatory cytokines and proteins expressions via zinc finger protein A20. In conclusion, GB could alleviate MI/RI-induced inflammatory response through A20-NF-κB signal pathway, which may give us new insights into the preventive strategies for MI/RI disease.

CaMKII Isoforms in Learning and Memory: Localization and Function

Calcium/calmodulin-dependent protein kinase II (CaMKII) is a key protein kinase in neural plasticity and memory, as have been shown in several studies since the first evidence in long-term potentiation (LTP) 30 years ago. However, most of the studies were focused mainly in one of the four isoforms of this protein kinase, the CaMKIIα. Here we review the characteristics and the role of each of the four isoforms in learning, memory and neural plasticity, considering the well known local role of α and β isoforms in dendritic terminals as well as recent findings about the γ isoform as calcium signals transducers from synapse to nucleus and δ isoform as a kinase required for a more persistent memory trace.

Activation of CaMKIIδA promotes Ca2+ leak from the sarcoplasmic reticulum in cardiomyocytes of chronic heart failure rats

Activation of the Ca²⁺/calmodulin-dependent protein kinase II isoform δA (CaMKIIδA) disturbs intracellular Ca²⁺ homeostasis in cardiomyocytes during chronic heart failure (CHF). We hypothesized that upregulation of CaMKIIδA in cardiomyocytes might enhance Ca²⁺ leak from the sarcoplasmic reticulum (SR) via activation of phosphorylated ryanodine receptor type 2 (P-RyR2) and decrease Ca²⁺ uptake by inhibition of SR calcium ATPase 2a (SERCA2a). In this study, CHF was induced in rats by ligation of the left anterior descending coronary artery. We found that CHF caused an increase in the expression of CaMKIIδA and P-RyR2 in the left ventricle (LV). The role of CaMKIIδA in regulation of P-RyR2 was elucidated in cardiomyocytes isolated from neonatal rats in vitro. Hypoxia induced upregulation of CaMKIIδA and activation of P-RyR2 in the cardiomyocytes, which both were attenuated by knockdown of CaMKIIδA. Furthermore, we showed that knockdown of CaMKIIδA significantly decreased the Ca²⁺ leak from the SR elicited by hypoxia in the cardiomyocytes. In addition, CHF also induced a downregulation of SERCA2a in the LV of CHF rats. Knockdown of CaMKIIδA normalized hypoxia-induced downregulation of SERCA2a in cardiomyocytes in vitro. The results demonstrate that the inhibition of CaMKIIδA may improve cardiac function by preventing SR Ca²⁺ leak through downregulation of P-RyR2 and upregulation of SERCA2a expression in cardiomyocytes in CHF.

Natural lavender oil (Lavandula angustifolia) exerts cardioprotective effects against myocardial infarction by targeting inflammation and oxidative stress

BACKGROUND

The study was conducted to examine therapeutic effects of lavender oil (LO) against myocardial infarction (MI) and its potential mechanisms.

METHODS

A rat model of MI was established and LO (100, 200 and 300 mg/kg) was intraperitoneally administrated immediately after ischemia. Anti-inflammatory and antioxidant activity of LO were evaluated by immunohistochemical assay and measurement of SOD, GSH, and MDA. The myocardial injury markers, apoptotic activity and infarct volume were examined by ELISA, TUNEL and TTC staining, respectively.

RESULTS

Compared with the control I/R-Vehicle, the expression of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) significantly reduced 8 h after reperfusion and expression of interleukin-10 (IL-10) elevated 48 h after reperfusion in LO-treated rats (P < 0.05). Likewise, significant decreases in apoptotic activity, infarct volume and significant restoration of antioxidant endogenous defenses were observed in LO-treated rats (P < 0.05).

CONCLUSION

Collectively, these findings confirm that LO can be a good candidate to reduce injury after MI.

CaMKIIδ interacts directly with IKKβ and modulates NF-κB signalling in adult cardiac fibroblasts

Calcium/calmodulin dependent protein kinase IIδ (CaMKIIδ) acts as a molecular switch regulating cardiovascular Ca²⁺ handling and contractility in health and disease. Activation of CaMKIIδ is also known to regulate cardiovascular inflammation and is reported to be required for pro-inflammatory NF-κB signalling. In this study the aim was to characterise how CaMKIIδ interacts with and modulates NF-κB signalling and whether this interaction exists in non-contractile cells of the heart. Recombinant or purified CaMKIIδ and the individual inhibitory -κB kinase (IKK) proteins of the NF-κB signalling pathway were used in autoradiography and Surface Plasmon Resonance (SPR) to explore potential interactions between both components. Primary adult rat cardiac fibroblasts were then used to study the effects of selective CaMKII inhibition on pharmacologically-induced NF-κB activation as well as interaction between CaMKII and specific IKK isoforms in a cardiac cellular setting. Autoradiography analysis suggested that CaMKIIδ phosphorylated IKKβ but not IKKα. SPR analysis further supported a direct interaction between CaMKIIδ and IKKβ but not between CaMKIIδ and IKKα or IKKγ. CaMKIIδ regulation of IκΒα degradation was explored in adult cardiac fibroblasts exposed to pharmacological stimulation. Cells were stimulated with agonist in the presence or absence of a CaMKII inhibitor, autocamtide inhibitory peptide (AIP). Selective inhibition of CaMKII resulted in reduced NF-κB activation, as measured by agonist-stimulated IκBα degradation. Importantly, and in agreement with the recombinant protein work, an interaction between CaMKII and IKKβ was evident following Proximity Ligation Assays in adult cardiac fibroblasts. This study provides new evidence supporting direct interaction between CaMKIIδ and IKKβ in pro-inflammatory signalling in cardiac fibroblasts and could represent a feature that may be exploited for therapeutic benefit.

CaMKIIδ-mediated inflammatory gene expression and inflammasome activation in cardiomyocytes initiate inflammation and induce fibrosis

Inflammation accompanies heart failure and is a mediator of cardiac fibrosis. CaMKIIδ plays an essential role in adverse remodeling and decompensation to heart failure. We postulated that inflammation is the mechanism by which CaMKIIδ contributes to adverse remodeling in response to nonischemic interventions. We demonstrate that deletion of CaMKIIδ in the cardiomyocyte (CKO) significantly attenuates activation of NF-κB, expression of inflammatory chemokines and cytokines, and macrophage accumulation induced by angiotensin II (Ang II) infusion. The inflammasome was activated by Ang II, and this response was also diminished in CKO mice. These events occurred prior to any evidence of Ang II-induced cell death. In addition, CaMKII-dependent inflammatory gene expression and inflammasome priming were observed as early as the third hour of infusion, a time point at which macrophage recruitment was not evident. Inhibition of either the inflammasome or monocyte chemoattractant protein 1 (MCP1) signaling attenuated macrophage accumulation, and these interventions, like cardiomyocyte CaMKIIδ deletion, diminished the fibrotic response to Ang II. Thus, activation of CaMKIIδ in the cardiomyocyte represents what we believe to be a novel mechanism for initiating inflammasome activation and an inflammatory gene program that leads to macrophage recruitment and ultimately to development of fibrosis.

Physiological and unappreciated roles of CaMKII in the heart

In the cardiomyocyte, CaMKII has been identified as a nodal influencer of excitation-contraction and also excitation-transcription coupling. Its activity can be regulated in response to changes in intracellular calcium content as well as after several post-translational modifications. Some of the effects mediated by CaMKII may be considered adaptive, while effects of sustained CaMKII activity may turn into the opposite and are detrimental to cardiac integrity and function. As such, CaMKII has long been noted as a promising target for pharmacological inhibition, but the ubiquitous nature of CaMKII has made it difficult to target CaMKII specifically where it is detrimental. In this review, we provide a brief overview of the physiological and pathophysiological properties of CaMKII signaling, but we focus on the physiological and adaptive functions of CaMKII. Furthermore, special consideration is given to the emerging role of CaMKII as a mediator of inflammatory processes in the heart.

[Inhibition of CaMKII alleviates myocardial ischemia?reperfusion injury by reducing mitochondrial oxidative stress in isolated perfused rat heart]

OBJECTIVE

To investigate the role of calcium/calmodulin-dependent protein kinase II (CaMKII) in myocardial ischemia-reperfusion (IR) injury in isolated perfused rat heart and explore the underlying mechanisms.

METHODS

An ischemia-reperfusion (IR) model was prepared using isolated rat hearts perfused with Krebs-Henseleit solution were randomly divided into control group, 2.5 µmol/L KN-93 group, IR (induced by ischemia for 45 min followed by reperfusion for 120 min) group and KN-93+IR group. The myocardial performance was evaluated by assessing the left ventricular pressure. Lactate dehydrogenase (LDH) activity and cTnI content in the coronary flow and the infarct size were determined to evaluate the myocardial injury. The phosphorylation of CaMKII (p-CaMKII) and PLN (p-PLN) and oxidation of CaMKII (ox--CaMKII) were measured with Western blotting. The activity of mitochondrial superoxide dismutase (SOD) and the content of malondialdehyde (MDA) were determined using ELISA.

RESULTS

Compared with the control group, KN-93 treatment at 2.5 µmol/L produced no significant effects on cardiac function or performance in rat hearts without IR injury. Myocardial IR injury significantly decreased myocardial performance and mitochondrial SOD activity in the perfused hearts (P<0.01) and caused significantly increased infarct size, LDH activity, cTnI content, expressions of p-CaMKII, ox-CaMKII and p-PLN, and also increased mitochondrial MDA content (P<0.01). KN-93 treatment at 2.5 µmol/L administered before ischemia and before reperfusion markedly attenuated such changes induced by ischemia and reperfusion (P<0.01).

CONCLUSION

CaMKII participates in myocardial IR injury in isolated rat heart, and inhibiting CaMKII can alleviate myocardial injury by relieving mitochondrial oxidation stress.

CaMKII in Vascular Signalling: "Friend or Foe"?

Signalling mechanisms within and between cells of the vasculature enable function and maintain homeostasis. However, a number of these mechanisms also contribute to the pathophysiology of vascular disease states. The multifunctional signalling molecule calcium/calmodulin-dependent kinase II (CaMKII) has been shown to have critical functional effects in many tissue types. For example, CaMKII is known to have a dual role in cardiac physiology and pathology. The function of CaMKII within the vasculature is incompletely understood, but emerging evidence points to potential physiological and pathological roles. This review discusses the evidence for CaMKII signalling within the vasculature, with the aim to better understand both positive and potentially deleterious effects of CaMKII activation in vascular tissue.