Ginsenoside Rb1 reduces oxidative/carbonyl stress damage and dysfunction of RyR2 in the heart of streptozotocin-induced diabetic rats.

BACKGROUND: Oxidative stress may contribute to cardiac ryanodine receptor (RyR2) dysfunction in diabetic cardiomyopathy. Ginsenoside Rb1 (Rb1) is a major pharmacologically active component of ginseng to treat cardiovascular diseases. Whether Rb1 treat diabetes injured heart remains unknown. This study was to investigate the effect of Rb1 on diabetes injured cardiac muscle tissue and to further investigate its possible molecular pharmacology mechanisms. METHODS: Male Sprague-Dawley rats were injected streptozotocin solution for 2 weeks, followed 6 weeks Rb1 or insulin treatment. The activity of SOD, CAT, Gpx, and the levels of MDA was measured; histological and ultrastructure analyses, RyR2 activity and phosphorylated RyR2(Ser2808) protein expression analyses; and Tunel assay were performed. RESULTS: There was decreased activity of SOD, CAT, Gpx and increased levels of MDA in the diabetic group from control. Rb1 treatment increased activity of SOD, CAT, Gpx and decreased the levels of MDA as compared with diabetic rats. Neutralizing the RyR2 activity significantly decreased in diabetes from control, and increased in Rb1 treatment group from diabetic group. The expression of phosphorylation of RyR2 Ser2808 was increased in diabetic rats from control, and were attenuated with insulin and Rb1 treatment. Diabetes increased the apoptosis rate, and Rb1 treatment decreased the apoptosis rate. Rb1 and insulin ameliorated myocardial injury in diabetic rats. CONCLUSIONS: These data indicate that Rb1 could be useful for mitigating oxidative damage, reduced phosphorylation of RyR2 Ser2808 and decreased the apoptosis rate of cardiomyocytes in diabetic cardiomyopathy.

PANoptosis: Novel insight into regulated cell death and its potential role in cardiovascular diseases (Review).

PANoptosis, a complex form of proinflammatory programmed cell death, including apoptosis, pyroptosis and necroptosis, has been an emerging concept in recent years that has been widely reported in cancer, infectious diseases and neurological disorders. Cardiovascular diseases (CVDs) are an important global health problem, posing a serious threat to individuals' lives. An increasing body of research shows that inflammation has a pivotal role in CVDs, which provides an important theoretical basis for PANoptosis to promote the progression of CVDs. To date, only sporadic studies on PANoptosis in CVDs have been reported and its role in the field of CVDs has not been fully explored. Elucidating the various modes of cardiomyocyte death, the specific molecular mechanisms and the links among the various modes of death under various stressful stimuli is of notable clinical significance for a deeper understanding of the pathophysiology of CVDs. The present review summarizes the molecular mechanisms of apoptosis, pyroptosis, necroptosis and PANoptosis and their prospects in the field of CVDs.

Activation of PPAR-α attenuates myocardial ischemia/reperfusion injury by inhibiting ferroptosis and mitochondrial injury via upregulating 14-3-3η.

This study aimed to explore the effects of peroxisome proliferator-activated receptor α (PPAR-α), a known inhibitor of ferroptosis, in Myocardial ischemia/reperfusion injury (MIRI) and its related mechanisms. In vivo and in vitro MIRI models were established. Our results showed that activation of PPAR-α decreased the size of the myocardial infarct, maintained cardiac function, and decreased the serum contents of creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and Fe2+ in ischemia/reperfusion (I/R)-treated mice. Additionally, the results of H&E staining, DHE staining, TUNEL staining, and transmission electron microscopy demonstrated that activation of PPAR-α inhibited MIRI-induced heart tissue and mitochondrial damage. It was also found that activation of PPAR-α attenuated MIRI-induced ferroptosis as shown by a reduction in malondialdehyde, total iron, and reactive oxygen species (ROS). In vitro experiments showed that intracellular contents of malondialdehyde, total iron, LDH, reactive oxygen species (ROS), lipid ROS, oxidized glutathione disulphide (GSSG), and Fe2+ were reduced by the activation of PPAR-α in H9c2 cells treated with anoxia/reoxygenation (A/R), while the cell viability and GSH were increased after PPAR-α activation. Additionally, changes in protein levels of the ferroptosis marker further confirmed the beneficial effects of PPAR-α activation on MIRI-induced ferroptosis. Moreover, the results of immunofluorescence and dual-luciferase reporter assay revealed that PPAR-α achieved its activity via binding to the 14-3-3η promoter, promoting its expression level. Moreover, the cardioprotective effects of PPAR-α could be canceled by pAd/14-3-3η-shRNA or Compound C11 (14-3-3η inhibitor). In conclusion, our results indicated that ferroptosis plays a key role in aggravating MIRI, and PPAR-α/14-3-3η pathway-mediated ferroptosis and mitochondrial injury might be an effective therapeutic target against MIRI.

Functions and Clinical Significance of Myocardial Cell-Derived Immunoglobulins.

Immunoglobulins (Igs) have been widely accepted to be exclusively expressed by B cells. Nonetheless, this theory is challenged by mounting evidence which suggests that Igs can also be generated by non B cells (non B-Ig), including cardiomyocytes (CM). Non B-Ig exhibits unique physical and chemical characteristics, unique variable region sequences and functions, which diverge from those of B-Ig. For instance, non B-Ig demonstrates hydrophobicity, limited diversity in the variable region, and extracellular matrix protein activity. Likewise, cardiomyocytes can express different classes of Igs, including IgM, IgG, and free Igκ light chains (cardiomyocyte derived-Igs, CM-Igs). In particular, CM-Igs can be secreted into the extracellular space in various cardiovascular diseases, such as myocardial ischaemia and myocardial fibrosis where they might be involved in complement activation and direct damage to cardiomyocytes. Nevertheless, the precise pathological activity of CM-Igs remains unclear. Recently, Zhu et al. focused on studying the sequence characteristics and functions of CM-Igκ; they discovered that the CM-Igκ exhibits a unique VJ recombination pattern, high hydrophobicity, and is principally located on the intercalated discs and cross striations of the cardiomyocytes. Interestingly, loss of Igκ in cardiomyocytes results in structural disorders in intercalated discs and dysfunction in myocardial contraction and conduction. Mechanically, Igκ promotes the stabilisation of plectin, a cytoskeleton cross-linker protein that connects desmin to desomsome, to maintain the normal structure of the intercalated disc. This finding indicates that CM-Igκ plays an integral role in maintaining cytoskeleton structure. Consequently, it is imperative to reveal the physiological functions and mechanisms of pathological injury associated with CM-Igs.

Keeping it fresh: ribosomal protein SA sustains sarcomeric function via localized translation.

Mechanical stress from cardiomyocyte contraction causes misfolded sarcomeric protein replacement. Sarcomeric maintenance utilizes localized pools of mRNAs and translation machinery, yet the importance of localized translation remains unclear. In this issue of the JCI, Haddad et al. identify the Z-line as a critical site for localized translation of sarcomeric proteins, mediated by ribosomal protein SA (RPSA). RPSA localized ribosomes at Z-lines and was trafficked via microtubules. Cardiomyocyte-specific loss of RPSA in mice resulted in mislocalized protein translation and caused structural dilation from myocyte atrophy. These findings demonstrate the necessity of RPSA-dependent spatially localized translation for sarcomere maintenance and cardiac structure and function.

Frameshift variants in C10orf71 cause dilated cardiomyopathy in human, mouse, and organoid models.

Research advances over the past 30 years have confirmed a critical role for genetics in the etiology of dilated cardiomyopathies (DCMs). However, full knowledge of the genetic architecture of DCM remains incomplete. We identified candidate DCM causal gene, C10orf71, in a large family with 8 patients with DCM by whole-exome sequencing. Four loss-of-function variants of C10orf71 were subsequently identified in an additional group of492 patients with sporadic DCM from 2 independent cohorts. C10orf71 was found to be an intrinsically disordered protein specifically expressed in cardiomyocytes. C10orf71-KO mice had abnormal heart morphogenesis during embryonic development and cardiac dysfunction as adults with altered expression and splicing of contractile cardiac genes. C10orf71-null cardiomyocytes exhibited impaired contractile function with unaffected sarcomere structure. Cardiomyocytes and heart organoids derived from human induced pluripotent stem cells with C10orf71 frameshift variants also had contractile defects with normal electrophysiological activity. A rescue study using a cardiac myosin activator, omecamtiv mecarbil, restored contractile function in C10orf71-KO mice. These data support C10orf71 as a causal gene for DCM by contributing to the contractile function of cardiomyocytes. Mutation-specific pathophysiology may suggest therapeutic targets and more individualized therapy.

Mitochondrial Structure and Function in Human Heart Failure.

Despite clinical and scientific advancements, heart failure is the major cause of morbidity and mortality worldwide. Both mitochondrial dysfunction and inflammation contribute to the development and progression of heart failure. Although inflammation is crucial to reparative healing following acute cardiomyocyte injury, chronic inflammation damages the heart, impairs function, and decreases cardiac output. Mitochondria, which comprise one third of cardiomyocyte volume, may prove a potential therapeutic target for heart failure. Known primarily for energy production, mitochondria are also involved in other processes including calcium homeostasis and the regulation of cellular apoptosis. Mitochondrial function is closely related to morphology, which alters through mitochondrial dynamics, thus ensuring that the energy needs of the cell are met. However, in heart failure, changes in substrate use lead to mitochondrial dysfunction and impaired myocyte function. This review discusses mitochondrial and cristae dynamics, including the role of the mitochondria contact site and cristae organizing system complex in mitochondrial ultrastructure changes. Additionally, this review covers the role of mitochondria-endoplasmic reticulum contact sites, mitochondrial communication via nanotunnels, and altered metabolite production during heart failure. We highlight these often-neglected factors and promising clinical mitochondrial targets for heart failure.

Novel roles of κ-opioid receptor in myocardial ischemia-reperfusion injury.

Acute heart attack is the primary cause of cardiovascular-related death worldwide. A common treatment is reperfusion of ischemic tissue, which can cause irreversible damage to the myocardium. The number of mitochondria in cardiomyocytes is large, which generate adenosine triphosphate (ATP) to sustain proper cardiac contractile function, and mitochondrial dysfunction plays a crucial role in cell death during myocardial ischemia-reperfusion, leading to an increasing number of studies investigating the impact of mitochondria on ischemia-reperfusion injury. The disarray of mitochondrial dynamics, excessive Ca2+ accumulation, activation of mitochondrial permeable transition pores, swelling of mitochondria, ultimately the death of cardiomyocyte are the consequences of ischemia-reperfusion injury. κ-opioid receptors can alleviate mitochondrial dysfunction, regulate mitochondrial dynamics, mitigate myocardial ischemia-reperfusion injury, exert protective effects on myocardium. The mechanism of κ-OR activation during myocardial ischemia-reperfusion to regulate mitochondrial dynamics and reduce myocardial ischemia-reperfusion injury will be discussed, so as to provide theoretical basis for the protection of ischemic myocardium.

Metabolic remodeling and calcium handling abnormality in induced pluripotent stem cell-derived cardiomyocytes in dilated phase of hypertrophic cardiomyopathy with MYBPC3 frameshift mutation.

Hypertrophic cardiomyopathy (HCM) is an inherited disorder characterized by left ventricular hypertrophy and diastolic dysfunction, and increases the risk of arrhythmias and heart failure. Some patients with HCM develop a dilated phase of hypertrophic cardiomyopathy (D-HCM) and have poor prognosis; however, its pathogenesis is unclear and few pathological models exist. This study established disease-specific human induced pluripotent stem cells (iPSCs) from a patient with D-HCM harboring a mutation in MYBPC3 (c.1377delC), a common causative gene of HCM, and investigated the associated pathophysiological mechanisms using disease-specific iPSC-derived cardiomyocytes (iPSC-CMs). We confirmed the expression of pluripotent markers and the ability to differentiate into three germ layers in D-HCM patient-derived iPSCs (D-HCM iPSCs). D-HCM iPSC-CMs exhibited disrupted myocardial sarcomere structures and an increased number of damaged mitochondria. Ca2+ imaging showed increased abnormal Ca2+ signaling and prolonged decay time in D-HCM iPSC-CMs. Cell metabolic analysis revealed increased basal respiration, maximal respiration, and spare-respiratory capacity in D-HCM iPSC-CMs. RNA sequencing also showed an increased expression of mitochondrial electron transport system-related genes. D-HCM iPSC-CMs showed abnormal Ca2+ handling and hypermetabolic state, similar to that previously reported for HCM patient-derived iPSC-CMs. Although further studies are required, this is expected to be a useful pathological model for D-HCM.

Cocaine and amphetamine-regulated transcript improves myocardial ischemia-reperfusion injury through PI3K/AKT signalling pathway.

Myocardial ischemia-reperfusion injury (MIRI) is a common clinic scenario that occurs in the context of reperfusion therapy for acute myocardial infarction. It has been shown that cocaine and amphetamine-regulated transcript (CART) can ameliorate cerebral ischemia-reperfusion (I/R) injury, but the effect of CART on MIRI has not been studied yet. Here, we revealed that CART protected the heart during I/R process by inhibiting apoptosis and excessive autophagy, indicating that CART would be a potential drug candidate for the treatment of MIRI. Further analysis showed that CART upregulated the activation of phospho-AKT, leading to downregulation of lactate dehydrogenase (LDH) release, apoptosis, oxidative stress and excessive autophagy after I/R, which was inhibited by PI3K inhibitor, LY294002. Collectively, CART attenuated MIRI through inhibition of cardiomyocytes apoptosis and excessive autophagy, and the protective effect was dependent on PI3K/AKT signalling pathway.

The Role of TPM3 in Protecting Cardiomyocyte from Hypoxia-Induced Injury via Cytoskeleton Stabilization.

Ischemic heart disease (IHD) remains a major global health concern, with ischemia-reperfusion injury exacerbating myocardial damage despite therapeutic interventions. In this study, we investigated the role of tropomyosin 3 (TPM3) in protecting cardiomyocytes against hypoxia-induced injury and oxidative stress. Using the AC16 and H9c2 cell lines, we established a chemical hypoxia model by treating cells with cobalt chloride (CoCl2) to simulate low-oxygen conditions. We found that CoCl2 treatment significantly upregulated the expression of hypoxia-inducible factor 1 alpha (HIF-1α) in cardiomyocytes, indicating the successful induction of hypoxia. Subsequent morphological and biochemical analyses revealed that hypoxia altered cardiomyocyte morphology disrupted the cytoskeleton, and caused cellular damage, accompanied by increased lactate dehydrogenase (LDH) release and malondialdehyde (MDA) levels, and decreased superoxide dismutase (SOD) activity, indicative of oxidative stress. Lentivirus-mediated TPM3 overexpression attenuated hypoxia-induced morphological changes, cellular damage, and oxidative stress imbalance, while TPM3 knockdown exacerbated these effects. Furthermore, treatment with the HDAC1 inhibitor MGCD0103 partially reversed the exacerbation of hypoxia-induced injury caused by TPM3 knockdown. Protein-protein interaction (PPI) network and functional enrichment analysis suggested that TPM3 may modulate cardiac muscle development, contraction, and adrenergic signaling pathways. In conclusion, our findings highlight the therapeutic potential of TPM3 modulation in mitigating hypoxia-associated cardiac injury, suggesting a promising avenue for the treatment of ischemic heart disease and other hypoxia-related cardiac pathologies.

Loss of connectin novex-3 leads to heart dysfunction associated with impaired cardiomyocyte proliferation and abnormal nuclear mechanics.

Connectin (also known as titin) is a giant striated muscle protein that functions as a molecular spring by providing elasticity to the sarcomere. Novex-3 is a short splice variant of connectin whose physiological function remains unknown. We have recently demonstrated using in vitro analyses that in addition to sarcomere expression, novex-3 was also expressed in cardiomyocyte nuclei exclusively during fetal life, where it provides elasticity/compliance to cardiomyocyte nuclei and promotes cardiomyocyte proliferation in the fetus, suggesting a non-sarcomeric function. Here, we analyzed novex-3 knockout mice to assess the involvement of this function in cardiac pathophysiology in vivo. Deficiency of novex-3 compromised fetal cardiomyocyte proliferation and induced the enlargement of individual cardiomyocytes in neonates. In adults, novex-3 deficiency resulted in chamber dilation and systolic dysfunction, associated with Ca2+ dysregulation, resulting in a reduced life span. Mechanistic analyses revealed a possible association between impaired proliferation and abnormal nuclear mechanics, including stiffer nuclei positioned peripherally with stabilized circumnuclear microtubules in knockout cardiomyocytes. Although the underlying causal relationships were not fully elucidated, these data show that novex-3 has a vital non-sarcomeric function in cardiac pathophysiology and serves as an early contributor to cardiomyocyte proliferation.

Dexmedetomidine ameliorates x-ray-induced myocardial injury via alleviating cardiomyocyte apoptosis and autophagy.

BACKGROUND: Radiotherapy is a primary local treatment for tumors, yet it may lead to complications such as radiation-induced heart disease (RIHD). Currently, there is no standardized approach for preventing RIHD. Dexmedetomidine (Dex) is reported to have cardio-protection effects, while its role in radiation-induced myocardial injury is unknown. In the current study, we aimed to evaluate the radioprotective effect of dexmedetomidine in X-ray radiation-treated mice. METHODS: 18 male mice were randomized into 3 groups: control, 16 Gy, and 16 Gy + Dex. The 16 Gy group received a single dose of 16 Gy X-ray radiation. The 16 Gy + Dex group was pretreated with dexmedetomidine (30 µg/kg, intraperitoneal injection) 30 min before X-ray radiation. The control group was treated with saline and did not receive X-ray radiation. Myocardial tissues were collected 16 weeks after X-ray radiation. Hematoxylin-eosin staining was performed for histopathological examination. Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining was performed to assess the state of apoptotic cells. Immunohistochemistry staining was performed to examine the expression of CD34 molecule and von Willebrand factor. Besides, western blot assay was employed for the detection of apoptosis-related proteins (BCL2 apoptosis regulator and BCL2-associated X) as well as autophagy-related proteins (microtubule-associated protein 1 light chain 3, beclin 1, and sequestosome 1). RESULTS: The findings demonstrated that 16 Gy X-ray radiation resulted in significant changes in myocardial tissues, increased myocardial apoptosis, and activated autophagy. Pretreatment with dexmedetomidine significantly protects mice against 16 Gy X-ray radiation-induced myocardial injury by inhibiting apoptosis and autophagy. CONCLUSION: In summary, our study confirmed the radioprotective effect of dexmedetomidine in mitigating cardiomyocyte apoptosis and autophagy induced by 16 Gy X-ray radiation.

Inhibiting AGTR1 reduces AML burden and protects the heart from cardiotoxicity in mouse models.

Clinical treatment of acute myeloid leukemia (AML) largely relies on intensive chemotherapy. However, the application of chemotherapy is often hindered by cardiotoxicity. Patient sequence data revealed that angiotensin II receptor type 1 (AGTR1) is a shared target between AML and cardiovascular disease (CVD). We found that inhibiting AGTR1 sensitized AML to chemotherapy and protected the heart against chemotherapy-induced cardiotoxicity in a human AML cell-transplanted mouse model. These effects were regulated by the AGTR1-Notch1 axis in AML cells and cardiomyocytes from mice. In mouse cardiomyocytes, AGTR1 was hyperactivated by AML and chemotherapy. AML leukemogenesis increased the expression of the angiotensin-converting enzyme and led to increased production of angiotensin II, the ligand of AGTR1, in an MLL-AF9-driven AML mouse model. In this model, the AGTR1-Notch1 axis regulated a variety of genes involved with cell stemness and chemotherapy resistance. AML cell stemness was reduced after Agtr1a deletion in the mouse AML cell transplant model. Mechanistically, Agtr1a deletion decreased γ-secretase formation, which is required for transmembrane Notch1 cleavage and release of the Notch1 intracellular domain into the nucleus. Using multiomics, we identified AGTR1-Notch1 signaling downstream genes and found decreased binding between these gene sequences with Notch1 and chromatin enhancers, as well as increased binding with silencers. These findings describe an AML/CVD association that may be used to improve AML treatment.

TNIP3 protects against pathological cardiac hypertrophy by stabilizing STAT1.

Pathological cardiac hypertrophy is one of the major risk factors of heart failure and other cardiovascular diseases. However, the mechanisms underlying pathological cardiac hypertrophy remain largely unknown. Here, we identified the first evidence that TNFAIP3 interacting protein 3 (TNIP3) was a negative regulator of pathological cardiac hypertrophy. We observed a significant upregulation of TNIP3 in mouse hearts subjected to transverse aortic constriction (TAC) surgery and in primary neonatal rat cardiomyocytes stimulated by phenylephrine (PE). In Tnip3-deficient mice, cardiac hypertrophy was aggravated after TAC surgery. Conversely, cardiac-specific Tnip3 transgenic (TG) mice showed a notable reversal of the same phenotype. Accordingly, TNIP3 alleviated PE-induced cardiomyocyte enlargement in vitro. Mechanistically, RNA-sequencing and interactome analysis were combined to identify the signal transducer and activator of transcription 1 (STAT1) as a potential target to clarify the molecular mechanism of TNIP3 in pathological cardiac hypertrophy. Via immunoprecipitation and Glutathione S-transferase assay, we found that TNIP3 could interact with STAT1 directly and suppress its degradation by suppressing K48-type ubiquitination in response to hypertrophic stimulation. Remarkably, preservation effect of TNIP3 on cardiac hypertrophy was blocked by STAT1 inhibitor Fludaradbine or STAT1 knockdown. Our study found that TNIP3 serves as a novel suppressor of pathological cardiac hypertrophy by promoting STAT1 stability, which suggests that TNIP3 could be a promising therapeutic target of pathological cardiac hypertrophy and heart failure.

Dynamic Changes in Ion Channels during Myocardial Infarction and Therapeutic Challenges.

In different areas of the heart, action potential waveforms differ due to differences in the expressions of sodium, calcium, and potassium channels. One of the characteristics of myocardial infarction (MI) is an imbalance in oxygen supply and demand, leading to ion imbalance. After MI, the regulation and expression levels of K+, Ca2+, and Na+ ion channels in cardiomyocytes are altered, which affects the regularity of cardiac rhythm and leads to myocardial injury. Myocardial fibroblasts are the main effector cells in the process of MI repair. The ion channels of myocardial fibroblasts play an important role in the process of MI. At the same time, a large number of ion channels are expressed in immune cells, which play an important role by regulating the in- and outflow of ions to complete intracellular signal transduction. Ion channels are widely distributed in a variety of cells and are attractive targets for drug development. This article reviews the changes in different ion channels after MI and the therapeutic drugs for these channels. We analyze the complex molecular mechanisms behind myocardial ion channel regulation and the challenges in ion channel drug therapy.

A novel function of claudin-5 in maintaining the structural integrity of the heart and its implications in cardiac pathology.

This study aims to investigate the role of claudin-5 (Cldn5) in cardiac structural integrity. Proteomic analysis was performed to screen the protein profiles in enlarged left atrium from atrial fibrillation (AF) patients. Cldn5 shRNA adeno-associated virus (AAV) or siRNA was injected into the mouse left ventricle or added into HL1 cells respectively to knockdown Cldn5 in cardiomyocytes to observe whether the change of Cldn5 influences cardiac morphology and function, and affects those protein expressions stem from the proteomic analysis. Mitochondrial density and membrane potential were also measured by Mitotracker staining and JC-1 staining under the confocal microscope in HL1 cells. Cldn5 was reduced in cardiomyocytes from the left atrial appendage of AF patients compared to non-AF donors. Proteomic analysis showed 83 proteins were less abundant and 102 proteins were more abundant in AF patients. KEGG pathway analysis showed less abundant CACNA2D2, CACNB2, MYL2 and MAP6 were highly associated with dilated cardiomyopathy. Cldn5 shRNA AAV injection caused severe cardiac atrophy, dilation and myocardial dysfunction in mice. The decreases in mitochondrial numbers and mitochondrial membrane potentials in HL1 cells were observed after Cldn5 knockdown. We demonstrated for the first time the mechanism of Cldn5 downregulation-induced myocyte atrophy and myocardial dysfunction might be associated with the downregulation of CACNA2D2, CACNB2, MYL2 and MAP6, and mitochondrial dysfunction in cardiomyocytes.

Two-Dimensional Deep Learning Frameworks for Drug-Induced Cardiotoxicity Detection.

The identification of drug-induced cardiotoxicity remains a pressing challenge with far-reaching clinical and economic ramifications, often leading to patient harm and resource-intensive drug recalls. Current methodologies, including in vivo and in vitro models, have severe limitations in accurate identification of cardiotoxic substances. Pioneering a paradigm shift from these conventional techniques, our study presents two deep learning-based frameworks, STFT-CNN and SST-CNN, to assess cardiotoxicity with markedly improved accuracy and reliability. Leveraging the power of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) as a more human-relevant cell model, we record mechanical beating signals through impedance measurements. These temporal signals were converted into enriched two-dimensional representations through advanced transformation techniques, specifically short-time Fourier transform (STFT) and synchro-squeezing transform (SST). These transformed data are fed into the proposed frameworks for comprehensive analysis, including drug type classification, concentration classification, cardiotoxicity classification, and new drug identification. Compared to traditional models like recurrent neural network (RNN) and 1-dimensional convolutional neural network (1D-CNN), SST-CNN delivered an impressive test accuracy of 98.55% in drug type classification and 99% in distinguishing cardiotoxic and noncardiotoxic drugs. Its feasibility is further highlighted with a stellar 98.5% average accuracy for classification of various concentrations, and the superiority of our proposed frameworks underscores their promise in revolutionizing drug safety assessments. With a potential for scalability, they represent a major leap in drug safety assessments, offering a pathway to more robust, efficient, and human-relevant cardiotoxicity evaluations.

Impaired Cardiac AMPK (5'-Adenosine Monophosphate-Activated Protein Kinase) and Ca2+-Handling, and Action Potential Duration Heterogeneity in Ibrutinib-Induced Ventricular Arrhythmia Vulnerability.

BACKGROUND: We recently demonstrated that acute administration of ibrutinib, a Bruton's tyrosine kinase inhibitor used in chemotherapy for blood malignancies, increases ventricular arrhythmia (VA) vulnerability. A pathway of ibrutinib-induced vulnerability to VA that can be modulated for cardioprotection remains unclear. METHODS AND RESULTS: The effects of ibrutinib on cardiac electrical activity and Ca2+ dynamics were investigated in Langendorff-perfused hearts using optical mapping. We also conducted Western blotting analysis to evaluate the impact of ibrutinib on various regulatory and Ca2+-handling proteins in rat cardiac tissues. Treatment with ibrutinib (10 mg/kg per day) for 4 weeks was associated with an increased VA inducibility (72.2%±6.3% versus 38.9±7.0% in controls, P<0.002) and shorter action potential durations during pacing at various frequencies (P<0.05). Ibrutinib also decreased heart rate thresholds for beat-to-beat duration alternans of the cardiac action potential (P<0.05). Significant changes in myocardial Ca2+ transients included lower amplitude alternans ratios (P<0.05), longer times-to-peak (P<0.05), and greater spontaneous intracellular Ca2+ elevations (P<0.01). We also found lower abundance and phosphorylation of myocardial AMPK (5'-adenosine monophosphate-activated protein kinase), indicating reduced AMPK activity in hearts after ibrutinib treatment. An acute treatment with the AMPK activator 5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside ameliorated abnormalities in action potential and Ca2+ dynamics, and significantly reduced VA inducibility (37.1%±13.4% versus 72.2%±6.3% in the absence of 5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside, P<0.05) in hearts from ibrutinib-treated rats. CONCLUSIONS: VA vulnerability inflicted by ibrutinib may be mediated in part by an impairment of myocardial AMPK activity. Pharmacological activation of AMPK may be a protective strategy against ibrutinib-induced cardiotoxicity.