Calmodulin-dependent Protein Kinase II Inhibitor Research Articles

Angiotensin II-mediated oxidative stress increased the vulnerability of ventricular arrhythmia in cardiac hypertrophy rabbit model, which is suppressed by CaMKII inhibitor

Abstract Objectives Angiotensin system is a major cause of heart failure and arrhythmia. Despite a lack of direct evidence that oxidative stress causes ventricular arrhythmia, reversal of oxidative stress is considered a plausible therapy. This study evaluated the Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor could suppress arrhythmia in cardiac hypertrophy rabbit model. Methods Angiotensin II (Ang II) or saline was administrated for 2 weeks via osmotic minipumps implanted subcutaneously in the midclavicular region. Hearts were perfused, mapped optically to analyze action potential durations (APD), and restitution kinetics, and tested for VF vulnerability. The intracellular calcium dynamics were measured in cardiomyocyte treated with Ang II (10 ng/ml) for 1 hours. Results In Ang II rabbit groups, 2(30%) rabbits died and had ventricular arrhythmia and hearts had enlarged left ventricle, longer APD90, slower conduction velocity (CV; P<0.01 versus control) and higher levels of transcripts for CaMKII, PLB, RyR2 (P<0.05 versus control). N-acetylcysteine treatment reversed the transcripts for APD90 and CV (P<0.01). Programmed stimulation triggered VF in Ang II (n=5/6) and Ang II + saline (n=4/6), but not in control (n=0/10, P<0.01). Cardiomyocyte induced with Ang II showed increased spontaneous Ca2+ release (Ca2+ Wave Frequency; 1.0±0.0 vs. 5.1±0.5, p=0.001, Ca2+ Amplitude; 1.0±0.0 vs. 1.3±0.1, p=0.001) with control. CaMKII inhibitor reversed the change of Ca2+. Conclusion The Ang II group had an increased incidence of arrhythmia caused by increased phosphorylation of Ca2+ handling proteins. These changes were partially reversed by CaMKII inhibition.

The adipose-neural axis is involved in epicardial adipose tissue-related cardiac arrhythmias

Dysfunction of the sympathetic nervous system and increased epicardial adipose tissue (EAT) have been independently associated with the occurrence of cardiac arrhythmia. However, their exact roles in triggering arrhythmia remain elusive. Here, using an invitro coculture system with sympathetic neurons, cardiomyocytes, and adipocytes, we show that adipocyte-derived leptin activates sympathetic neurons and increases the release of neuropeptide Y (NPY), which in turn triggers arrhythmia in cardiomyocytes by interacting with the Y1 receptor (Y1R) and subsequently enhancing the activity of the Na+/Ca2+ exchanger (NCX) and calcium/calmodulin-dependent protein kinase II (CaMKII). The arrhythmic phenotype can be partially blocked by a leptin neutralizing antibody or an inhibitor of Y1R, NCX, or CaMKII. Moreover, increased EAT thickness and leptin/NPY blood levels are detected in atrial fibrillation patients compared with the control group. Our study provides robust evidence that the adipose-neural axis contributes to arrhythmogenesis and represents a potential target for treating arrhythmia.

Differential sex-dependent susceptibility to diastolic dysfunction and arrhythmia in cardiomyocytes from obese diabetic HFpEF model.

Sex-differences in heart failure with preserved ejection fraction (HFpEF) are important, but key mechanisms involved are incompletely understood. While animal models can inform about sex-dependent cellular and molecular changes, many previous preclinical HFpEF models have failed to recapitulate sex-dependent characteristics of human HFpEF. We tested for sex-differences in HFpEF using a two-hit mouse model (leptin receptor-deficient db/db mice plus aldosterone infusion for 4 weeks; db/db+Aldo). We performed echocardiography, electrophysiology, intracellular Ca2+ imaging, and protein analysis. Female HFpEF mice exhibited more severe diastolic dysfunction in line with increased titin N2B isoform expression and PEVK element phosphorylation, and reduced troponin-I phosphorylation. Female HFpEF mice had lower BNP levels than males despite similar comorbidity burden (obesity, diabetes) and cardiac hypertrophy in both sexes. Male HFpEF mice were more susceptible to cardiac alternans. Male HFpEF cardiomyocytes (versus female) exhibited higher diastolic [Ca2+], slower Ca2+ transient decay, reduced L-type Ca2+ current, more pronounced enhancement of the late Na+ current, and increased short-term variability of action potential duration (APD). However, male and female HFpEF myocytes showed similar downregulation of inward rectifier and transient outward K+ currents, APD prolongation, and frequency of delayed afterdepolarizations. Inhibition of Ca2+/calmodulin-dependent protein kinase II (CaMKII) reversed all pathological APD changes in HFpEF in both sexes, and empagliflozin pretreatment mimicked these effects of CaMKII inhibition. Vericiguat had only slight benefits, and these effects were larger in HFpEF females. We conclude that the db/db+Aldo preclinical HFpEF murine model recapitulates key sex-specific mechanisms in HFpEF and provides mechanistic insights into impaired excitation-contraction coupling and sex-dependent differential arrhythmia susceptibility in HFpEF with potential therapeutic implications. In male HFpEF myocytes, altered Ca2+ handling and electrophysiology aligned with diastolic dysfunction and arrhythmias, while worse diastolic dysfunction in females may depend more on altered myofilaments properties.

PFOS Elicits Cytotoxicity in Neuron Through Astrocyte-Derived CaMKII-DLG1 Signaling In Vitro Rat Hippocampal Model.

Both epidemiological investigation and animal experiments demonstrated that pre-/postnatal exposure to perfluorooctane sulfonic acid (PFOS) could induce neurodevelopmental disorders. Previous studies showed that astrocyte was involved in PFOS-induced neurotoxicity, while little information is available. In the present study, the role of astrocyte-derived calmodulin-dependent protein kinase II (CaMKII)-phosphorylated discs large homolog 1 (DLG1) signaling in PFOS eliciting cytotoxicity in neuron was explored with primary cultured hippocampal astrocyte and neuron. The application of PFOS showed a decreased cell viability, synapse length and glutamate transporter 1 (GLT-1) expression, but an increased CaMKII, DLG1 and cyclic AMP response element binding protein (CREB) expression in primary cultured astrocyte. With 2-(2-hydroxyethylamino)-6-aminohexylcarbamic acid tert-butyl ester-9-isopropylpurine (CK59), the CaMKII inhibitor, the disturbed cell viability and molecules induced by PFOS could be alleviated (CREB expression was excluded) in astrocytes. The cytotoxic effect of neuron exposed to astrocyte conditional medium collected from PFOS (PFOS-ACM) pretreated with CK59 was also decreased. These results indicated that PFOS mediated GLT-1 expression through astrocyte-derived CaMKII-DLG signaling, which might be associated with injuries on neurons. The present study gave an insight in further exploration of mechanism in PFOS-induced neurotoxicity.

Rem2 interacts with CaMKII at synapses and restricts long-term potentiation in hippocampus.

Synaptic plasticity, the process whereby neuronal connections are either strengthened or weakened in response to stereotyped forms of stimulation, is widely believed to represent the molecular mechanism that underlies learning and memory. The holoenzyme calcium/calmodulin-dependent protein kinase II (CaMKII) plays a well-established and critical role in the induction of a variety of forms of synaptic plasticity such as long-term potentiation (LTP), long-term depression (LTD) and depotentiation. Previously, we identified the GTPase Rem2 as a potent, endogenous inhibitor of CaMKII. Here, we report that knock out of Rem2 enhances LTP at the Schaffer collateral to CA1 synapse in hippocampus, consistent with an inhibitory action of Rem2 on CaMKII in vivo. Further, re-expression of WT Rem2 rescues the enhanced LTP observed in slices obtained from Rem2 conditional knock out (cKO) mice, while expression of a mutant Rem2 construct that is unable to inhibit CaMKII in vitro fails to rescue increased LTP. In addition, we demonstrate that CaMKII and Rem2 interact in dendritic spines using a 2pFLIM-FRET approach. Taken together, our data lead us to propose that Rem2 serves as a brake on synaptic potentiation via inhibition of CaMKII activity. Further, the enhanced LTP phenotype we observe in Rem2 cKO slices reveals a previously unknown role for Rem2 in the negative regulation of CaMKII function.

Ursolic acid inhibits the synaptic release of glutamate and prevents glutamate excitotoxicity in rats

The present study evaluated the effect of ursolic acid, a natural pentacyclic triterpenoid, on glutamate release in rat cortical nerve terminals (synaptosomes) and its neuroprotection in a kainic acid-induced excitotoxicity rat model. In cortical synaptosomes, ursolic acid produced a concentration-dependent inhibition of evoked glutamate release with a half-maximum inhibition of release value of 9.5 μM, and calcium-free medium and the P/Q -type Ca2+ channel blocker, ω-agatoxin IVA, but not ω-conotoxin GVIA, an N-type Ca2+ channel blocker, prevented the ursoloic acid effect. The molecular docking study indicated that ursolic acid interacted with P/Q-type Ca2+ channels. Ursolic acid also significantly decreased the depolarization-induced activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and the subsequent phosphorylation of synapsin I, and the ursolic acid effect on evoked glutamate release was inhibited by the CaMKII inhibitor KN 62 in synaptosomes. In addition, in rats that were intraperitoneally injected with ursolic acid 30 min before kainic acid intraperitoneal injection, cortical neuronal degeneration was attenuated. This effect of ursolic acid in the improvement of kainic acid-induced neuronal damage was associated with the reduction of kainic acid-induced glutamate increase in the cortex of rats; this was characterized by the reduction of glutamate and glutaminase levels and elevation of glutamate dehydrogenase, glutamate transporter 1, glutamate-aspartate transporter, and glutamine synthetase protein levels. These results suggest that ursolic acid inhibits glutamate release from cortical synaptosomes by decreasing P/Q-type Ca2+ channel activity and subsequently suppressing CaMKII and exerts a preventive effect against glutamate neurotoxicity by controlling glutamate levels.

Hippocampal CaMKII inhibition induces reactivation-dependent amnesia for extinction memory and causes fear relapse

Hippocampal GluN2B subunit-containing NMDAR (GluN2B-NMDAR) activation during recall destabilizes fear extinction memory, which must undergo brain-derived neurotrophic factor (BDNF)-dependent reconsolidation to persist. Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a Ser/Thr protein kinase essential for hippocampus-dependent memory processing that acts downstream GluN2B-NMDAR and controls BDNF expression, but its participation in fear extinction memory reconsolidation has not yet been studied. Using a combination of pharmacological and behavioral tools, we found that in adult male Wistar rats, intra dorsal-CA1 administration of the CaMKII inhibitors autocamtide-2-related inhibitory peptide (AIP) and KN-93, but not of their inactive analogs scrambled AIP and KN-92, after fear extinction memory recall impaired extinction and caused GluN2B-NMDAR-dependent recovery of fear. Our results indicate that hippocampal CaMKII is necessary for fear extinction reconsolidation, and suggest that modulation of its activity around the time of recall controls the inhibition that extinction exerts on learned fear.

Abstract 13500: An Improved Reporter Identifies Ruxolitinib as a Potent and Cardioprotective CaMKII Inhibitor

Background: Ca 2+ /Calmodulin-dependent protein kinase II (CaMKII) hyperactivity is an established driver of cardiac arrhythmias. Despite proven benefits of CaMKII inhibition in numerous preclinical arrhythmia models, translation of CaMKII antagonists into humans has remained unsuccessful, and today, there are no clinically approved CaMKII inhibitors. Our ability to identify potent CaMKII inhibitors has been hamstrung by a lack of a CaMKII biosensor with sufficient sensitivity for high throughput drug discovery. Research question: We hypothesized that development of a CaMKII biosensor with high throughput capabilities would enable identification of CaMKII inhibitors capable of preventing arrhythmias. Methods: To address this problem, we engineered and validated a new genetically encoded CaMKII biosensor: CaMKAR (CaMKII Activity Reporter). CaMKAR enjoys a dynamic range of 227 ± 11.1 %, seconds-scale kinetics, robust specificity, and dual in cellulo and in vitro functionality. This makes CaMKAR the fastest and most sensitive CaMKII biosensor to date and the first that is amenable for in cellulo drug screening. Results: Using CaMKAR, we carried out a drug repurposing screen (4,475 compounds in clinical use) in human cells. This yielded five previously unrecognized CaMKII inhibitors: ruxolitinib, baricitinib, silmitasertib, crenolanib, and abemaciclib (false discovery-adjusted p<3 x 10 -5 ). Stand out among these, ruxolitinib, an FDA-approved Janus kinase inhibitor, blocked CaMKII kinase activity with an inhibitory constant of 23.5 ± 2.2 nM. In patient-derived cardiomyocytes, ruxolitinib ameliorated arrhythmogenic Ca 2+ release events (p<0.0001), and in mice, ruxolitinib prevented catecholaminergic polymorphic ventricular tachycardia (p<0.01) and rescued pre-existing atrial fibrillation (p<0.0001). Conclusion: Our work presents three impactful Conclusions: 1) Our biosensor, CaMKAR, provides the highest CaMKII activity reporting performance to date. 2) Long sought-after CaMKII inhibitors already exist within the human pharmacopeia. 3) Our results demonstrate that ruxolitinib—a drug already in human use—is a cardioprotective CaMKII inhibitor and a suitable candidate for cardiovascular repurposing.

Abstract 12726: Novel, Potent, and Highly Selective Calcium/Calmodulin-Dependent Protein Kinase II (CaMKII) Inhibitors Reduce Substrate Phosphorylation in Rat Hearts and Prolong Survival in a Mouse Model of Severe Heart Failure

Introduction: CaMKII is a target of longstanding interest in drug development and has been validated in multiple preclinical models of heart failure, as well as in arrhythmia diseases, including catecholaminergic polymorphic ventricular tachycardia and atrial fibrillation. We describe here the pharmacological profiles of a novel oral CaMKII inhibitor, CRD-2015. We demonstrate the ability of CRD-2015 to reduce substrate phosphorylation in rat hearts, and to strongly prolong survival in the calsequestrin transgenic (CSQ-Tg) mouse model of severe heart failure. Results: CRD-2015 is a potent (IC 50 0.62nM), highly selective CaMKII inhibitor. Oral administration of CRD-2015 dose-dependently decreased phospholamban (P-PLN) and ryanodine receptor 2 (P-RyR2) phosphorylation at their CaMKII-specific sites (Thr17 and Ser2814, respectively) in normal rat hearts, with strong correlation between the plasma concentrations (PK) and the reduction in phosphorylation (PD) (Figure, A). In CSQ-Tg mice, CRD-2015 also decreased cardiac P-PLN and P-RyR2 in a dose-dependent manner. Chronic administration of CRD-2015 prolonged survival in a dose-dependent manner (Figure, B). At the maximum dose level, all CSQ-Tg mice survived for 27 days (n=15/15) with the treatment of CRD-2015, while no mice survived past 24 days in the vehicle-treated group (n=0/15). Similar dose and concentration-dependent reductions in P-PLN and P-RyR2 and prolongation of survival in CSQ-Tg mice were also detected with a second potent (IC 50 0.40nM) and selective CaMKII inhibitor, CRD-2959. Conclusions: Our novel CaMKII inhibitor, CRD-2015 shows a clear PK/PD relationship in normal rats and prolongs survival in a mouse model of severe heart failure. These results demonstrate the successful creation of specific CaMKII inhibitors with efficacy in preclinical models and support their clinical development for the treatment of heart failure and other cardiovascular diseases.

Merazin hydrate produces rapid antidepressant effects by activating CaMKII to promote neuronal activities and proliferation in hippocampus

In our previous studies, we demonstrated that merazin hydrate (MH) had rapid antidepressant effects, but the deep mechanism needed to be further investigated. In this study, we used depressive-like model, behavioral tests, molecular biology and pharmacological interventions to reveal the underlying mechanisms of MH’s rapid antidepressants. We found that a single administration of MH was able to produce rapid antidepressant effects in chronic unpredictable mild stress (CUMS) exposed mice at 1 day later, similar to ketamine. Moreover, MH could not only significantly up-regulated the expressions of cFOS, but also obviously increased the number of Ki67 positive cells in hippocampal dentate gyrus (DG). Furthermore, we also found that the phosphorylated expression of calcium/calmodulin-dependent protein kinase II (CaMKII) was significantly reduced by CUMS in hippocampus, which was also reversed by MH. In addition, pharmacological inhibition of CaMKII by using KN-93 (a CaMKII antagonist) blocked the MH’s up-regulation of cFOS and Ki67 in hippocampal DG. To sum up, this study demonstrated that MH produced rapid antidepressant effects by activating CaMKII to promote neuronal activities and proliferation in hippocampus.

Regulation of mitochondrial calcium uniporter expression and calcium-dependent cell signalling by lncRNA Tug1 in cardiomyocytes.

Cardiomyocyte calcium homeostasis is a tightly regulated process. The mitochondrial calcium uniporter (MCU) complex can buffer elevated cytosolic Ca2+ levels and consists of pore-forming proteins including MCU, and various regulatory proteins such as mitochondrial calcium uptake proteins 1 and 2 (MICU1/2). The stoichiometry of these proteins influences the sensitivity to Ca2+ and activity of the complex. However, the factors that regulate their gene expression remain incompletely understood. Long non-coding RNAs (lncRNAs) regulate gene expression through various mechanisms, and we recently found that the lncRNA Tug1 increased the expression of Mcu and associated genes. To further explore this, we performed antisense LNA knockdown of Tug1 (Tug1 KD) in H9c2 rat cardiomyocytes. Tug1 KD increased MCU protein expression, yet pyruvate dehydrogenase dephosphorylation, which is indicative of mitochondrial Ca2+ uptake, was not enhanced. However, RNA-seq revealed that Tug1 KD increased Mcu along with differential expression of >1000 genes including many related to Ca2+ regulation pathways in the heart. To understand the effect of this on Ca2+ signalling, we measured phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and its downstream target cAMP Response Element-Binding protein (CREB), a transcription factor known to drive Mcu gene expression. In response a Ca2+ stimulus, the increase in CAMKII and CREB phosphorylation was attenuated by Tug1 KD. Inhibition of CaMKII, but not CREB, partially prevented the Tug1 KD-mediated increase in Mcu. Together, these data suggest that Tug1 modulates MCU expression via a mechanism involving CAMKII and regulates cardiomyocyte Ca2+ signalling which could have important implications for cardiac function.

Abstract P3195: Mitochondrial CaMKII Drives Cardiometabolic Dysfunction In Heart Failure

Background: Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) is an established negative regulator of cardiac injury. Both the expression and activity levels of CaMKII delta, the primary cardiac isoform of this kinase, are elevated in models of heart failure (HF) such as ischemia-reperfusion (I/R) injury and following myocardial infarction (MI). This upregulation is due in part to CaMKII’s role in the regulation of excitation-contraction coupling, apoptosis, activation of hypertrophic programming, arrhythmias and pro-inflammatory signaling. Recently, a pool of mitochondrial CaMKII (mtCaMKII) has been identified; we have demonstrated that there is an observed increase in mitochondrial CaMKII activation with left ventricular dilation acutely following injury in a mouse model of MI. This deleterious post-MI phenotype is rescued with genetic mitochondrial CaMKII inhibition; conversely, mice with myocardial mitochondrial CaMKII overexpression present with a severe dilated cardiomyopathy phenotype, alterations in electron transport chain (ETC) activity, and decreased ATP production. Objective: To date, the molecular mechanisms by which CaMKII regulates mitochondrial energetics are unknown and present a novel therapeutic target for HF which we are currently studying. Methods: As we have identified changes in the activity of enzymes, particularly complexes I and II, in the mitochondrial ETC as well as TCA cycle in response to increased CaMKII levels or activity, we are in the process of assessing changes in the mitochondrial CaMKII interactome between uninjured and failing hearts. Utilizing liquid chromatography-mass spectrometry (LCMS) and proteomics analysis of both scaffolding interactions alongside a novel ATP analogue labeling technique, we have mapped novel mitochondrial proteins which interact with mtCaMKII. Significance: The identification of previously unknown mitochondrial pathways involving CaMKII may uncover promising pharmacological targets for cardiovascular therapeutics, as this kinase is a critical player in the progression of HF.

NMDA receptor inhibitor MK801 alleviated pro-inflammatory polarization of BV-2 microglia cells

Microglia have both protective and pathogenic properties, while polarization plays a decisive role in their functional diversity. Apart from being an energetic organelle, mitochondria possess biological capabilities of signaling and immunity involving mitochondrial dynamics. The N-methyl-D-aspartate (NMDA)-type glutamate receptor displays excitatory neurotransmission, excitatory neurotoxicity and pro-inflammatory properties in a membrane location- and cell context-dependent manner. In this study, we have provided experimental evidence showing that by acting on mitochondrial dynamics, NMDA receptors displayed pro-inflammatory properties, while its non-competitive inhibitor MK801 exhibited anti-inflammatory potential in Lipopolysaccharide (LPS)-challenged BV-2 microglia cells. LPS stimulation increased the protein phosphorylation of cells regarding their NMDA receptor component subunits and Calcium/Calmodulin-dependent Protein Kinase II (CaMKII), along with mobilizing intracellular calcium. Additionally, parallel changes occurred in the activation of Transforming Growth Factor-β (TGF-β)-Activated Kinase 1 (TAK1), NF-κB p65 and NF-κB DNA binding activity, acquisition of pro-inflammatory M1 polarization and expression of pro-inflammatory cytokines. LPS-treated cells further displayed signs of mitochondrial dysfunction with higher expressions of the active form of Dynamin-Related Protein 1 (Drp1), NADPH Oxidase-2 (NOX2) expression and the generation of DCFDA-/MitoSOX-sensitive Reactive Oxygen Species (ROS). NMDA receptor blockade by MK801, along with CaMKII inhibitor KN93, Drp1 inhibitor Mdivi-1 and antioxidant apocynin alleviated LPS-induced pro-inflammatory changes. Other than the reported CaMKII/TAK1/NF-κB axis, our in vitro study revealed the CaMKII/Drp1/ROS/NF-κB axis being an alternative cascade for shaping pro-inflammatory phenotypes of microglia upon LPS stimulation, and MK801 having the potential for inhibiting microglia activation and any associated inflammatory damages.

Increased CaMKII activation and contrast changes of cardiac β1-and β3-Adrenergic signaling pathways in a humanized angiotensinogen model of hypertension

AimsUpregulation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) contributes to the pathogenesis of cardiovascular disease, including hypertension. Transgenic rats expressing the human angiotensinogen gene [TGR (hAGT)L1623] are a new novel humanized model of hypertension that associates with declines in cardiac contractile function and β-adrenergic receptor (AR) reserve. The molecular mechanisms are unclear. We tested the hypothesis that in TGR (hAGT)L1623 rats, left ventricular (LV) myocyte CaMKIIδ and β3-AR are upregulated, but β1-AR is down-regulated, which are important causes of cardiac dysfunction and β-AR desensitization. Main methodsWe compared LV myocyte CaMKIIδ, CaMKIIδ phosphorylation (at Thr287) (pCaMKIIδ), and β1-and β3-AR expressions and determined myocyte functional and [Ca2+]I transient ([Ca2+]iT) responses to β-AR stimulation with and without pretreatment of myocytes using an inhibitor of CaMKII, KN-93 (10−6 M, 30 min) in male Sprague Dawley (SD; N = 10) control and TGR (hAGT)L1623 (N = 10) adult rats. Key findingsHypertension in TGR (hAGT)L1623 rats was accompanied by significantly increased LV myocyte β3-AR protein levels and reduced β1-AR protein levels. CaMKIIδ phosphorylation (at Thr287), pCaMKIIδ was significantly increased by 35%. These changes were followed by significantly reduced basal cell contraction (dL/dtmax), relaxation (dR/dtmax), and [Ca2+]iT. Isoproterenol (10−8 M) produced significantly smaller increases in dL/dtmax, dR/dtmax, and [Ca2+]iT. Moreover, only in TGR (hAGT)L1623 rats, pretreatment of LV myocytes with KN-93 (10−6 M, 30 min) fully restored normal basal and isoproterenol-stimulated myocyte contraction, relaxation, and [Ca2+]iT. SignificanceLV myocyte CaMKIIδ overactivation with associated contrast changes in β3-AR and β1-AR may be the key molecular mechanism for the abnormal contractile phenotype and β-AR desensitization in this humanized model of hypertension.

An improved reporter identifies ruxolitinib as a potent and cardioprotective CaMKII inhibitor.

Ca2+/calmodulin-dependent protein kinase II (CaMKII) hyperactivity causes cardiac arrhythmias, a major source of morbidity and mortality worldwide. Despite proven benefits of CaMKII inhibition in numerous preclinical models of heart disease, translation of CaMKII antagonists into humans has been stymied by low potency, toxicity, and an enduring concern for adverse effects on cognition due to an established role of CaMKII in learning and memory. To address these challenges, we asked whether any clinically approved drugs, developed for other purposes, were potent CaMKII inhibitors. For this, we engineered an improved fluorescent reporter, CaMKAR (CaMKII activity reporter), which features superior sensitivity, kinetics, and tractability for high-throughput screening. Using this tool, we carried out a drug repurposing screen (4475 compounds in clinical use) in human cells expressing constitutively active CaMKII. This yielded five previously unrecognized CaMKII inhibitors with clinically relevant potency: ruxolitinib, baricitinib, silmitasertib, crenolanib, and abemaciclib. We found that ruxolitinib, an orally bioavailable and U.S. Food and Drug Administration-approved medication, inhibited CaMKII in cultured cardiomyocytes and in mice. Ruxolitinib abolished arrhythmogenesis in mouse and patient-derived models of CaMKII-driven arrhythmias. A 10-min pretreatment in vivo was sufficient to prevent catecholaminergic polymorphic ventricular tachycardia, a congenital source of pediatric cardiac arrest, and rescue atrial fibrillation, the most common clinical arrhythmia. At cardioprotective doses, ruxolitinib-treated mice did not show any adverse effects in established cognitive assays. Our results support further clinical investigation of ruxolitinib as a potential treatment for cardiac indications.

Cardiac-specific BACH1 ablation attenuates pathological cardiac hypertrophy by inhibiting the Ang II type 1 receptor expression and the Ca2+/CaMKII pathway.

BACH1 is upregulated in hypertrophic hearts, but its function in cardiac hypertrophy remains largely unknown. This research investigates the function and mechanisms of BACH1 in the regulation of cardiac hypertrophy. Male cardiac-specific BACH1 knockout mice or cardiac-specific BACH1 transgenic (BACH1-Tg) mice and their respective wild-type littermates developed cardiac hypertrophy induced by angiotensin II (Ang II) or transverse aortic constriction (TAC). Cardiac-specific BACH1 knockout in mice protected the hearts against Ang II- and TAC-induced cardiac hypertrophy and fibrosis, and preserved cardiac function. Conversely, cardiac-specific BACH1 overexpression markedly exaggerated cardiac hypertrophy and fibrosis and reduced cardiac function in mice with Ang II- and TAC-induced hypertrophy. Mechanistically, BACH1 silencing attenuated Ang II- and norepinephrine-stimulated calcium/calmodulin-dependent protein kinase II (CaMKII) signaling, the expression of hypertrophic genes, and hypertrophic growth of cardiomyocytes. Ang II stimulation promoted the nuclear localization of BACH1, facilitated the recruitment of BACH1 to the Ang II type 1 receptor (AT1R) gene promoter, and then increased the expression of AT1R. Inhibition of BACH1 attenuated Ang II-stimulated AT1R expression, cytosolic Ca2+ levels, and CaMKII activation in cardiomyocytes, whereas overexpression of BACH1 led to the opposite effects. The increased expression of hypertrophic genes induced by BACH1 overexpression upon Ang II stimulation was suppressed by CaMKII inhibitor KN93. The AT1R antagonist, losartan, significantly attenuated BACH1-mediated CaMKII activation and cardiomyocyte hypertrophy under Ang II stimulation in vitro. Similarly, Ang II-induced myocardial pathological hypertrophy, cardiac fibrosis, and dysfunction in BACH1-Tg mice were blunted by treatment with losartan. This study elucidates a novel important role of BACH1 in pathological cardiac hypertrophy by regulating the AT1R expression and the Ca2+/CaMKII pathway, and highlights potential therapeutic target in pathological cardiac hypertrophy. Transcription factor BACH1 is increased in failing human myocardium and hypertrophic human hearts. We revealed that cardiomyocyte-specific BACH1 ablation in mice protected the hearts against Ang II- and pressure overload-induced cardiac hypertrophy and fibrosis, and preserved cardiac function. BACH1 activated AT1R promoter activity under Ang II stimulation, and BACH1-mediated facilitation of cardiac hypertrophy under Ang II stimulation was regulated at least in part by AT1R expression. Moreover, BACH1 silencing attenuated the norepinephrine-stimulated CaMKII signaling pathway and hypertrophic growth of cardiomyocytes. Our findings suggest that BACH1 may pose a promising therapeutic target in pathological cardiac hypertrophy and heart failure.

Short-term CaMKII inhibition with tatCN19o does not erase pre-formed memory in mice and is neuroprotective in pigs

The Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a central regulator of learning and memory, which poses a problem for targeting it therapeutically. Indeed, our study supports prior conclusions that long-term interference with CaMKII signaling can erase pre-formed memories. By contrast, short-term pharmacological CaMKII inhibition with the neuroprotective peptide tatCN19o interfered with learning in mice only mildly and transiently (for less than 1h) and did not at all reverse pre-formed memories. These results were obtained with ≥500-fold of the dose that protected hippocampal neurons from cell death after a highly clinically relevant pig model of transient global cerebral ischemia: ventricular fibrillation followed by advanced life support and electrical defibrillation to induce the return of spontaneous circulation. Of additional importance for therapy development, our preliminary cardiovascular safety studies in mice and pig did not indicate any concerns with acute tatCN19o injection. Taken together, although prolonged interference with CaMKII signaling can erase memory, acute short-term CaMKII inhibition with tatCN19o did not cause such retrograde amnesia that would pose a contraindication for therapy.

Porcine reproductive and respiratory syndrome virus infection triggers autophagy via ER stress-induced calcium signaling to facilitate virus replication.

Calcium (Ca2+), a ubiquitous second messenger, plays a crucial role in many cellular functions. Viruses often hijack Ca2+ signaling to facilitate viral processes such as entry, replication, assembly, and egress. Here, we report that infection by the swine arterivirus, porcine reproductive and respiratory syndrome virus (PRRSV), induces dysregulated Ca2+ homeostasis, subsequently activating calmodulin-dependent protein kinase-II (CaMKII) mediated autophagy, and thus fueling viral replication. Mechanically, PRRSV infection induces endoplasmic reticulum (ER) stress and forms a closed ER-plasma membrane (PM) contacts, resulting the opening of store operated calcium entry (SOCE) channel and causing the ER to take up extracellular Ca2+, which is then released into the cytoplasm by inositol trisphosphate receptor (IP3R) channel. Importantly, pharmacological inhibition of ER stress or CaMKII mediated autophagy blocks PRRSV replication. Notably, we show that PRRSV protein Nsp2 plays a dominant role in the PRRSV induced ER stress and autophagy, interacting with stromal interaction molecule 1 (STIM1) and the 78 kDa glucose-regulated protein 78 (GRP78). The interplay between PRRSV and cellular calcium signaling provides a novel potential approach to develop antivirals and therapeutics for the disease outbreaks.

Asenapine as a Potential Lead Inhibitor against Central Ca2+/Calmodulin-Dependent Protein Kinase II: Investigation by Docking Simulation and Experimental Validation

Aim: The aim of this potential repurposing study is to investigate the potential inhibitory activity of asenapine against central nervous system CaMKII isozymes using docking experiments and enzymatic assay. Background: The Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a multifunctional protein kinase ubiquitously expressed throughout the brain. Emerging biological data have indicated that inhibiting central nervous system CaMKII isoforms, namely, CaMKIIα and CaMKIIβ, may be a promising therapeutic strategy for the potential treatment of many neurological diseases including schizophrenia, depression, epilepsy, and learning deficit. Objective: 1- Study the possible attractive interactions of asenapine within the binding sites of the central CaMKII isozymes. 2- Evaluate the inhibitory activities of asenapine against central CaMKII isozymes. Methods: Docking experiments of asenapine and other known CaMKII inhibitors were performed. Docking settings were validated using ROC analysis. After that, the inhibitory activities of asenapine against central CaMKII alpha and beta were evaluated by enzymatic assay. Result: Docking and scoring experiments of asenapine showed several binding interactions anchoring asenapine within CaMKIIα and CaMKIIβ catalytic sites while enzymatic assay results revealed that asenapine can inhibit CaMKIIα and CaMKIIβ in the micromolar range. Conclusion: Our study provides evidence that asenapine can serve as a promising lead for the development of new CaMKIIα and CaMKIIβ inhibitors. Moreover, this study reinforces how the investment in drug repurposing could boost the drug discovery process.

Heparan Sulfates Regulate Axonal Excitability and Context Generalization through Ca2+/Calmodulin-Dependent Protein Kinase II.

Our previous studies demonstrated that enzymatic removal of highly sulfated heparan sulfates with heparinase 1 impaired axonal excitability and reduced expression of ankyrin G at the axon initial segments in the CA1 region of the hippocampus ex vivo, impaired context discrimination in vivo, and increased Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity in vitro. Here, we show that in vivo delivery of heparinase 1 in the CA1 region of the hippocampus elevated autophosphorylation of CaMKII 24 h after injection in mice. Patch clamp recording in CA1 neurons revealed no significant heparinase effects on the amplitude or frequency of miniature excitatory and inhibitory postsynaptic currents, while the threshold for action potential generation was increased and fewer spikes were generated in response to current injection. Delivery of heparinase on the next day after contextual fear conditioning induced context overgeneralization 24 h after injection. Co-administration of heparinase with the CaMKII inhibitor (autocamtide-2-related inhibitory peptide) rescued neuronal excitability and expression of ankyrin G at the axon initial segment. It also restored context discrimination, suggesting the key role of CaMKII in neuronal signaling downstream of heparan sulfate proteoglycans and highlighting a link between impaired CA1 pyramidal cell excitability and context generalization during recall of contextual memories.