DY-9760e Inhibits Endothelin-1-induced Cardiomyocyte Hypertrophy Through Inhibition of CaMKII and ERK Activities

Novel preventive effect of isorhamnetin on electrical and structural remodeling in atrial fibrillation

Isorhamnetin, a natural flavonoid, has strong antioxidant and antifibrotic effects, and a regulatory effect against Ca2+-handling. Atrial remodeling due to fibrosis and abnormal intracellular Ca2+ activities contributes to initiation and persistence of atrial fibrillation (AF). The present study investigated the effect of isorhamnetin on angiotensin II (AngII)-induced AF in mice. Wild-type male mice (C57BL/6J, 8 weeks old) were assigned to three groups: (1) control group, (2) AngII-treated group, and (3) AngII- and isorhamnetin-treated group. AngII (1000 ng/kg/min) and isorhamnetin (5 mg/kg) were administered continuously via an implantable osmotic pump for two weeks and intraperitoneally one week before initiating AngII administration, respectively. AF induction and electrophysiological studies, Ca2+ imaging with isolated atrial myocytes and HL-1 cells, and action potential duration (APD) measurements using atrial tissue and HL-1 cells were performed. AF-related molecule expression was assessed and histopathological examination was performed. Isorhamnetin decreased AF inducibility compared with the AngII group and restored AngII-induced atrial effective refractory period prolongation. Isorhamnetin eliminated abnormal diastolic intracellular Ca2+ activities induced by AngII. Isorhamnetin also abrogated AngII-induced APD prolongation and abnormal Ca2+ loading in HL-1 cells. Furthermore, isorhamnetin strongly attenuated AngII-induced left atrial enlargement and atrial fibrosis. AngII-induced elevated expression of AF-associated molecules, such as ox-CaMKII, p-RyR2, p-JNK, p-ERK, and TRPC3/6, was improved by isorhamnetin treatment. The findings of the present study suggest that isorhamnetin prevents AngII-induced AF vulnerability and arrhythmogenic atrial remodeling, highlighting its therapeutic potential as an anti-arrhythmogenic pharmaceutical or dietary supplement.

Trans-cinnamaldehyde protects against phenylephrine-induced cardiomyocyte hypertrophy through the CaMKII/ERK pathway

BACKGROUND

Trans-cinnamaldehyde (TCA) is one of the main pharmaceutical ingredients of Cinnamomum cassia Presl, which has been shown to have therapeutic effects on a variety of cardiovascular diseases. This study was carried out to characterize and reveal the underlying mechanisms of the protective effects of TCA against cardiac hypertrophy.

METHODS

We used phenylephrine (PE) to induce cardiac hypertrophy and treated with TCA in vivo and in vitro. In neonatal rat cardiomyocytes (NRCMs), RNA sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were carried out to identify potential pathways of TCA. Then, the phosphorylation and nuclear localization of calcium/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-related kinase (ERK) were detected. In adult mouse cardiomyocytes (AMCMs), calcium transients, calcium sparks, sarcomere shortening and the phosphorylation of several key proteins for calcium handling were evaluated. For mouse in vivo experiments, cardiac hypertrophy was evaluated by assessing morphological changes, echocardiographic parameters, and the expression of hypertrophic genes and proteins.

RESULTS

TCA suppressed PE-induced cardiac hypertrophy and the phosphorylation and nuclear localization of CaMKII and ERK in NRCMs. Our data also demonstrate that TCA blocked the hyperphosphorylation of ryanodine receptor type 2 (RyR2) and phospholamban (PLN) and restored Ca2+ handling and sarcomere shortening in AMCMs. Moreover, our data revealed that TCA alleviated PE-induced cardiac hypertrophy in adult mice and downregulated the phosphorylation of CaMKII and ERK.

CONCLUSION

TCA has a protective effect against PE-induced cardiac hypertrophy that may be associated with the inhibition of the CaMKII/ERK pathway.

Indazole and its Derivatives in Cardiovascular Diseases: Overview, Current Scenario, and Future Perspectives

Indazoles are a class of heterocyclic compounds with a bicyclic ring structure composed of a pyrazole ring and a benzene ring. Indazole-containing compounds with various functional groups have important pharmacological activities and can be used as structural motifs in designing novel drug molecules. Some of the indazole-containing molecules are approved by FDA and are already in the market. However, very few drugs with indazole rings have been developed against cardiovascular diseases. This review aims to summarize the structural and pharmacological functions of indazole derivatives which have shown efficacy against cardiovascular pathologies in experimental settings.

Context-specific network modeling identifies new crosstalk in β-adrenergic cardiac hypertrophy

Cardiac hypertrophy is a context-dependent phenomenon wherein a myriad of biochemical and biomechanical factors regulate myocardial growth through a complex large-scale signaling network. Although numerous studies have investigated hypertrophic signaling pathways, less is known about hypertrophy signaling as a whole network and how this network acts in a context-dependent manner. Here, we developed a systematic approach, CLASSED (Context-specific Logic-bASed Signaling nEtwork Development), to revise a large-scale signaling model based on context-specific data and identify main reactions and new crosstalks regulating context-specific response. CLASSED involves four sequential stages with an automated validation module as a core which builds a logic-based ODE model from the interaction graph and outputs the model validation percent. The context-specific model is developed by estimation of default parameters, classified qualitative validation, hybrid Morris-Sobol global sensitivity analysis, and discovery of missing context-dependent crosstalks. Applying this pipeline to our prior-knowledge hypertrophy network with context-specific data revealed key signaling reactions which distinctly regulate cell response to isoproterenol, phenylephrine, angiotensin II and stretch. Furthermore, with CLASSED we developed a context-specific model of β-adrenergic cardiac hypertrophy. The model predicted new crosstalks between calcium/calmodulin-dependent pathways and upstream signaling of Ras in the ISO-specific context. Experiments in cardiomyocytes validated the model’s predictions on the role of CaMKII-Gβγ and CaN-Gβγ interactions in mediating hypertrophic signals in ISO-specific context and revealed a difference in the phosphorylation magnitude and translocation of ERK1/2 between cardiac myocytes and fibroblasts. CLASSED is a systematic approach for developing context-specific large-scale signaling networks, yielding insights into new-found crosstalks in β-adrenergic cardiac hypertrophy.

Pathological cardiac hypertrophy is a disease in which the heart grows abnormally in response to different motivators such as high blood pressure or variations in hormones and growth factors. The shape of the heart after its growth depends on the context in which it grows. Since cell signaling in the cardiac cells plays a key role in the determination of heart shape, a thorough understanding of cardiac cells signaling in each context enlightens the mechanisms which control response of cardiac cells. However, cell signaling in cardiac hypertrophy comprises a complex web of pathways with numerous interactions, and predicting how these interactions control the hypertrophic signal in each context is not achievable by only experiments or general computational models. To address this need, we developed an approach to bring together the experimental data of each context with a signaling network curated from literature to identify the main players of cardiac cells response in each context and attain the context-specific models of cardiac hypertrophy. By utilizing our approach, we identified the main regulators of cardiac hypertrophy in four important contexts. We developed a network model of β-adrenergic cardiac hypertrophy, and predicted and validated new interactions that regulate cardiac cells response in this context.

Differential ERK1/2 Signaling and Hypertrophic Response to Endothelin-1 in Cardiomyocytes from SHR and Wistar-Kyoto Rats: A Potential Target for Combination Therapy of Hypertension

Extracellular signal regulated kinase½ (ERK1/2) signaling is critical to endothelin-1 (ET-1)-induced cardiomyocyte hypertrophy. This study was to investigate ERK1/2 signaling and hypertrophic response to ET-1 stimulation in cardiomyocytes (CMs) from spontaneous hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Primary neonatal SHR and WKY CMs were exposed to ET-1 for up to 24 hrs. Minimal basal ERK1/2 phosphorylation was present in WKY CMs, while a significant baseline ERK1/2 phosphorylation was observed in SHR CMs. ET-1 induced a time- and dose-dependent increase in ERK1/2 phosphorylation in both SHR and WKY CMs. However, ET-1-induced ERK1/2 activation occurred much earlier with significantly higher peak phosphorylation level, and stayed elevated for longer duration in SHR CMs than that in WKY CMs. ET-1-induced hypertrophic response was more prominent in SHR CMs than that in WKY CMs as reflected by increased cell surface area, intracellular actin density, and protein synthesis. Pre-treatment with ERK1/2 phosphorylation inhibitor PD98059 completely prevented ET-1-induced ERK1/2 phosphorylation and increases in cell surface area and protein synthesis in SHR and WKY CMs. The specific PI3 kinase inhibitor LY294002 blocked ET-1-induced Akt and ERK1/2 phosphorylation, and protein synthesis in CMs. These data indicated that ERK1/2 signaling was differentially enhanced in CMs, and was associated with increased cardiac hypertrophic response to ET-1 in SHR. ET-1-induced ERK1/2 activation and cardiac hypertrophy appeared to be mediated via PI3 kinase/Akt signaling in SHR and WKY. The differential ERK1/2 activation in SHR CMs by ET-1 might represent a potential target for combination therapy of hypertension.

Targeting the CaMKII/ERK Interaction in the Heart Prevents Cardiac Hypertrophy

Aims

Activation of Ca²⁺/Calmodulin protein kinase II (CaMKII) is an important step in signaling of cardiac hypertrophy. The molecular mechanisms by which CaMKII integrates with other pathways in the heart are incompletely understood. We hypothesize that CaMKII association with extracellular regulated kinase (ERK), promotes cardiac hypertrophy through ERK nuclear localization.

Methods and Results

In H9C2 cardiomyoblasts, the selective CaMKII peptide inhibitor AntCaNtide, its penetratin conjugated minimal inhibitory sequence analog tat-CN17β, and the MEK/ERK inhibitor UO126 all reduce phenylephrine (PE)-mediated ERK and CaMKII activation and their interaction. Moreover, AntCaNtide or tat-CN17β pretreatment prevented PE induced CaMKII and ERK nuclear accumulation in H9C2s and reduced the hypertrophy responses. To determine the role of CaMKII in cardiac hypertrophy in vivo, spontaneously hypertensive rats were subjected to intramyocardial injections of AntCaNtide or tat-CN17β. Left ventricular hypertrophy was evaluated weekly for 3 weeks by cardiac ultrasounds. We observed that the treatment with CaMKII inhibitors induced similar but significant reduction of cardiac size, left ventricular mass, and thickness of cardiac wall. The treatment with CaMKII inhibitors caused a significant reduction of CaMKII and ERK phosphorylation levels and their nuclear localization in the heart.

Conclusion

These results indicate that CaMKII and ERK interact to promote activation in hypertrophy; the inhibition of CaMKII-ERK interaction offers a novel therapeutic approach to limit cardiac hypertrophy.

Phenotypic screening with human iPS cell-derived cardiomyocytes: HTS-compatible assays for interrogating cardiac hypertrophy

A major hurdle for cardiovascular disease researchers has been the lack of robust and physiologically relevant cell-based assays for drug discovery. Derivation of cardiomyocytes from human-induced pluripotent stem (iPS) cells at high purity, quality, and quantity enables the development of relevant models of human cardiac disease with source material that meets the demands of high-throughput screening (HTS). Here we demonstrate the utility of iPS cell-derived cardiomyocytes as an in vitro model of cardiac hypertrophy. Exposure of cardiomyocytes to endothelin 1 (ET-1) leads to reactivation of fetal genes, increased cell size, and robust expression of B-type natriuretic peptide (BNP). Using this system, we developed a suite of assays focused on BNP detection, most notably a high-content imaging-based assay designed for phenotypic screening. Miniaturization of this assay to a 384-well format enabled the profiling of a small set of tool compounds known to modulate the hypertrophic response. The assays described here provide consistent and reliable results and have the potential to increase our understanding of the many mechanisms underlying this complex cardiac condition. Moreover, the HTS-compatible workflow allows for the incorporation of human biology into early phases of drug discovery and development.

Characterization of a selective CaMKII peptide inhibitor

Analogs of potent CaMKinase II inhibitor, CaM-KNtide, were prepared to explore new structural requirements for the inhibitory activity. The full potency of CaMKII inhibition by CaM-KIINα is contained within a minimal region of 19 amino acids. Here, analysis of the homologous CaM-KIINβ showed that a 17 mer peptide (CN17β) was the shortest sequence that still retained useful inhibitory potency. Ala substitution of almost any residue of CN17β dramatically reduced potency, except for substitution of P3, R14, and V16. Fusion with the tat sequence generated the cell-penetrating inhibitor version tat-5. This tat-5 fusion peptide maintained selectivity for CaMKII over CaMKI and CaMKIV, and appeared to slightly further enhance potency (IC50 ∼30 nM). Within a breast cancer cell line and in primary human fibroblasts, tat-5 inhibited the Erk signaling pathway and proliferation without any measurable cytotoxicity. Structural analysis of CN17β by CD and NMR indicated an α-helix conformation in the Leu6-Arg11 segment well overlapping with the crystal structure of 21-residue segment of CaM-KNtide bound to the kinase domain of CaMKII.

Mitogen-activated protein kinase signaling in the heart: angels versus demons in a heart-breaking tale

Among the myriad of intracellular signaling networks that govern the cardiac development and pathogenesis, mitogen-activated protein kinases (MAPKs) are prominent players that have been the focus of extensive investigations in the past decades. The four best characterized MAPK subfamilies, ERK1/2, JNK, p38, and ERK5, are the targets of pharmacological and genetic manipulations to uncover their roles in cardiac development, function, and diseases. However, information reported in the literature from these efforts has not yet resulted in a clear view about the roles of specific MAPK pathways in heart. Rather, controversies from contradictive results have led to a perception that MAPKs are ambiguous characters in heart with both protective and detrimental effects. The primary object of this review is to provide a comprehensive overview of the current progress, in an effort to highlight the areas where consensus is established verses the ones where controversy remains. MAPKs in cardiac development, cardiac hypertrophy, ischemia/reperfusion injury, and pathological remodeling are the main focuses of this review as these represent the most critical issues for evaluating MAPKs as viable targets of therapeutic development. The studies presented in this review will help to reveal the major challenges in the field and the limitations of current approaches and point to a critical need in future studies to gain better understanding of the fundamental mechanisms of MAPK function and regulation in the heart.

Transcriptional upregulation of calcineurin Abeta by endothelin-1 is partially mediated by calcium/calmodulin-dependent protein kinase IIdelta3 in rat cardiomyocytes

Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and calcineurin (CaN) are positive regulators of cardiac hypertrophy, but the nature of cross-talk between CaMKII and CaN signaling pathways in hypertrophic cardiomyocytes remains unclear. Here we documented that CaMKIIdelta3 activation enhances transcription of the CaN gene through activation of the CaN-Abeta subunit (CnAbeta) promoter in rat cultured cardiomyocytes. Co-immunoprecipitation assays showed that MEF2 forms a complex with GATA4 following transfection of an active CaMKIIdelta3 (T278D) mutant in neonatal cardiomyocytes. Inversely, transfection of a dominant negative CaMKIIdelta3 mutant failed to promote a MEF2-GATA4 complex. Consistent with these observations, immunocytochemistry indicated nuclear co-localization of MEF2 with GATA4 after hypertrophic agonist stimulation or CaMKIIdelta3 (T278D) transfection. These data demonstrate that CaMKII can enhance CnAbeta promoter activity by enhancing MEF2-GATA4 synergy, suggesting a novel mechanism for CaMKII-mediated hypertrophic signaling, which contributes to induction and development of the hypertrophic response through CaN activation.