CaMKIIδ inhibition protects against myocardial ischemia/reperfusion injury: Role of Beclin-1-dependent autophagy

The link between ferroptosis and autophagy in myocardial ischemia/reperfusion injury: new directions for therapy

Myocardial ischemia/reperfusion (I/R)-induced cell death, such as autophagy and ferroptosis, is a major contributor to cardiac injury. Regulating cell death may be key to mitigating myocardial ischemia/reperfusion injury (MI/RI). Autophagy is a crucial physiological process involving cellular self-digestion and compensation, responsible for degrading excess or malfunctioning long-lived proteins and organelles. During MI/RI, autophagy plays both "survival" and "death" roles. A growing body of research indicates that ferroptosis is a type of autophagy-dependent cell death. This article provides a comprehensive review of the functions of autophagy and ferroptosis in MI/RI, as well as the molecules mediating their interaction. Understanding the link between autophagy and ferroptosis may offer new therapeutic directions for MI/RI, bearing significant clinical implications.

Autosis: a new form of cell death in myocardial ischemia-reperfusion injury

Cardiomyocytes undergo a variety of cell death events during myocardial ischemia‒reperfusion injury (MIRI). Understanding the causes of cardiomyocyte mortality is critical for the prevention and treatment of MIRI. Among the various types of cell death, autosis is a recently identified type of autophagic cell death with distinct morphological and chemical characteristics. Autosis can be attenuated by autophagy inhibitors but not reversed by apoptosis or necrosis inhibitors. In recent years, it has been shown that during the late phase of reperfusion, autosis is activated, which exacerbates myocardial injury. This article describes the characteristics of autosis, autophagic cell death, and the relationship between autophagic cell death and autosis; reviews the mechanism of autosis in MIRI; and discusses its clinical significance.

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.

KN-93 promotes HDAC4 nucleus translocation to promote fatty acid oxidation in myocardial infarction

Myocardial infarction (MI) is a potentially fatal disease that causes a significant number of deaths worldwide. The strategy of increasing fatty acid oxidation in myocytes is considered a therapeutic avenue to accelerate metabolism to meet energy demands. We conducted the study aiming to investigate the effect of KN-93, which induces histone deacetylase (HDAC)4 shuttling to the nucleus, on fatty acid oxidation and the expression of related genes. A mouse model of myocardial infarction was induced by isoprenaline administration. Heart damage was assessed by the detection of cardiac injury markers. The level of fatty acid oxidation level was evaluated by testing the expression of related genes. Both immunofluorescence and immunoblotting in the cytosol or nucleus were utilized to observe the distribution of HDAC4. The interaction between HDAC4 and specificity protein (SP)1 was confirmed by co-immunoprecipitation. The acetylation level of SP1 was tested after KN-93 treatment and HDAC4 inhibitor. Oxygen consumption rate and immunoblotting experiments were used to determine whether the effect of KN-93 on increasing fatty acid oxidation is through HDAC4 and SP1. Administration of KN-93 significantly reduced cardiac injury in myocardial infarction and promoted fatty acid oxidation both in vitro and in vivo. KN-93 was shown to mediate nuclear translocation of HDAC4. HDAC4 was found to interact with SP1 and reduce SP1 acetylation. HDAC4 or SP1 inhibitors attenuated the effect of KN-93 on fatty acid oxidation. In conclusion, KN-93 promotes HDAC4 translocation to the nucleus, thereby potentially enhancing fatty acid oxidation by SP1.

Synthesis of Formononetin Derivatives and Cardioprotective Effects

This study aims to design and synthesize a series of novel formononetin (FMN) derivatives and explore their protective effects on oxygen glucose deprivation/relapse (OGD/R) damage to H9C2 cells, along with their molecular regulatory mechanisms. The OGD/R model was established to simulate myocardial ischemia-reperfusion injury. The protective effects of these novel compounds on H9C2 cells were evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method, while the apoptosis rate, myocardial enzyme activity, and autophagy reaction post-compound treatment were assessed using kit-based methods. The formation of autophagosomes in H9C2 cells was observed via transmission electron microscopy, and the expression levels of autophagy-related proteins phosphatidylinositol 3-kinase (PI3K), Akt, Beclin-1, and P62 were determined using Western blotting. The experimental findings demonstrated that compounds 1-6 (C1-6) exhibited varying degrees of protective effects on damaged H9C2 cells, generally outperforming the parent compound FMN. Among these compounds, C4 demonstrated the most significant activity, even surpassing the positive control drug diltiazem. Further mechanistic investigations revealed that C4 could mitigate apoptosis rates, reduce the activity of myocardial enzyme (such as aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and CK), diminish the number of autophagic vesicles, and restore excessive autophagy. Additionally, C4 exerted its protective effects by downregulating the expression of autophagic proteins PI3K, Akt, Beclin-1, P62, LC3 and ATG12. These results indicated that C4 regulates autophagy through the PI3K/Akt/Beclin-1 signaling pathway, thereby exerting a protective effect on cardiomyocytes. Therefore, C4 emerges as a potential myocardial protective drug, offering a new research direction and strategy for the treatment of myocardial ischemia-reperfusion injury.

GRK2 participation in cardiac hypertrophy induced by isoproterenol through the regulation of Nrf2 signaling and the promotion of NLRP3 inflammasome and oxidative stress

OBJECTIVE

In cases of heart failure, cardiac hypertrophy may be caused by the upregulation of G-protein-coupled receptor kinase 2 (GRK2). Both NLRP3 inflammasome and oxidative stress contribute to cardiovascular disease. In this study, we clarified the effect of GRK2 on cardiac hypertrophy in H9c2 cells induced by isoproterenol (ISO) and examined the underlying mechanisms.

METHODS

We randomly categorized H9c2 cells into five groups: an ISO group, a paroxetine plus ISO group, a GRK2 small-interfering RNA (siRNA) plus ISO group, a GRK2 siRNA combined with ML385 plus ISO group, and a control group. To determine the effect of GRK2 on cardiac hypertrophy induced by ISO, we carried out CCK8 assays, RT-PCR, TUNEL staining, ELISA assay, DCFH-DA staining, immunofluorescence staining, and western blotting.

RESULTS

By using paroxetine or siRNA to inhibit GRK2, we significantly decreased cell viability; reduced the mRNA levels of ANP, BNP, and β-MHC; and limited the apoptosis rate and protein levels of cleaved caspase-3 and cytochrome c in H9c2 cells treated with ISO. We also found that oxidative stress induced by ISO could be mitigated with paroxetine or GRK2 siRNA. This result was validated by decreased activities of the antioxidant enzymes CAT, GPX, and SOD and increased MDA levels and ROS production. We observed that the protein expression of NLRP3, ASC, and caspase-1 and the intensity of NLRP3 could be inhibited by paroxetine or GRK2 siRNA. Both paroxetine and GRK2 siRNA were able to abolish the increase in GRK2 expression induced by ISO. They also could increase protein levels of HO-1, nuclear Nrf2, and Nrf2 immunofluorescence intensity; however, they could not change the protein level of cytoplasmic Nrf2. By combining treatment with ML385, we were able to reverse GRK2 inhibition on H9c2 cells treated with ISO.

CONCLUSION

According to the results of this study, GRK2 participated in cardiac hypertrophy induced by ISO by mitigating NLRP3 inflammasome and oxidative stress through the signaling of Nrf2 in H9c2 cells.

Cadmium exposure induces autophagy via PLC-IP3 -IP3 R signaling pathway in duck renal tubular epithelial cells

Cadmium (Cd) is detrimental to animals, but nephrotoxic effects of Cd on duck have not been fully elucidated. To evaluate the impacts of Cd on Ca homeostasis and autophagy via PLC-IP₃ -IP₃ R pathway, primary duck renal tubular epithelial cells were exposed to 2.5 μM and 5.0 μM Cd, and combination of 5.0 μM Cd and 10.0 μM 2-APB or 0.125 μM U-73122 for 12 h (U-73122 pretreated for 1 h). These results evidenced that Cd induced [Ca²⁺ ]_c overload mainly came from intracellular Ca store. Cd caused [Ca²⁺ ]_mit and [Ca²⁺ ]_c overload with [Ca²⁺ ]_ER decrease, elevated Ca homeostasis related factors (GRP78, GRP94, CRT, CaN, CaMKII, and CaMKKβ) expression, PLC and IP₃ activities and IP₃ R expression, but subcellular Ca²⁺ redistribution was reversed by 2-APB. PLC inhibitor U-73122 dramatically relieved the changes of the above indicators induced by Cd. Additionally, U-73122 obviously reduced the number of autophagosomes and LC3 accumulation spots, Atg5, LC3A, LC3B mRNA levels and LC3II/LC3I, Beclin-1 protein levels induced by Cd, and markedly elevated p62 mRNA and protein levels. Overall, the results verified that Cd induced [Ca²⁺ ]_c overload mainly originated from ER Ca²⁺ release mediated by PLC-IP₃ -IP₃ R pathway, then triggered autophagy in duck renal tubular epithelial cells.

TRPM2 mediates CaMKⅡ-Beclin-1 signaling in early cortical injury after induced subarachnoid hemorrhage in mice

BACKGROUND

Though early brain injury (EBI) is the primary cause of poor outcomes among patients with subarachnoid hemorrhage (SAH), its exact molecular mechanisms remain unclear. Improved the understanding of how transient receptor potential melastatin-related 2 (TRPM2) is involved in SAH-induced EBI will help develop novel interventions.

METHODS

Wild type (WT) male C57BL/6J mice were subjected to SAH for 12 h, 24 h or 48 h, after which neurological scores and pathological changes in the hippocampus (CA3, DG, and CA1) and temporal base cortex were observed. Expressions of TRPM2, Ca²⁺/calmodulin (CaM)-dependent protein kinase Ⅱ (CaMKⅡ), and Beclin-1 in hippocampus (CA3, DG, and CA1) and temporal base cortex were compared across post-SAH timepoints. TRPM2-deficient (TRPM2^-/-) male C57BL/6 J mice and a CaMKⅡ inhibitor (KN-93) were used to analyze the effects oTRPM2 on the CaMKⅡ-Beclin-1 signaling post SAH.

RESULTS

Neurological and temporal base cortex deterioration were more severe with increased time post-SAH induction, whereas hippocampal damage was not observed. Post-SAH, TRPM2-CaMKⅡ-Beclin-1 cascade was activated in the temporal base cortex, but not the hippocampus. Using TRPM2^-/- mice and KN-93 administration, SAH-induced EBI was improved, and CaMKⅡ and Beclin-1 expressions in the temporal base cortex were significantly decreased compared with WT mice. TRPM2^-/- mice also showed better neurological improvement compared with KN-93 treated mice.

CONCLUSION

TRPM2 mediates CaMKⅡ-Beclin-1 signaling that aggravates SAH-induced EBI in the temporal base cortex. TRPM2 may be an alternative therapy target in EBI after SAH.

DATA AVAILABILITY

The datasets generated and/or analysed during the current study are available from the corresponding author.

The Regulatory Mechanism and Effect of RIPK3 on PE-induced Cardiomyocyte Hypertrophy

ABSTRACT

As a critical regulatory molecule, receptor-interacting protein kinase 3 (RIPK3) can mediate the signaling pathway of programmed necrosis. Calcium/calmodulin-dependent protein kinase II (CaMKII) has been proved as a new substrate for RIPK3-induced necroptosis. In the present study, we aimed to investigate the regulatory mechanism of RIPK3 on phenylephrine (PE)-induced cardiomyocyte hypertrophy. Cardiomyocyte hypertrophy was induced by exposure to PE (100 μM) for 48 h. Primary cardiomyocytes were pretreated with RIPK3 inhibitor GSK'872 (10 μM), and RIPK3 siRNA was used to deplete the intracellular expression of RIPK3. The indexes related to myocardial hypertrophy, cell injury, necroptosis, CaMKII activation, gene expression, oxidative stress, and mitochondrial membrane potential were measured. We found that after cardiomyocytes were stimulated by PE, the expressions of hypertrophy markers, atrial and brain natriuretic peptides (ANP and BNP), were increased, the release of lactate dehydrogenase (LDH) was increased, the level of adenosine triphosphate (ATP)was decreased, the oxidation and phosphorylation levels of CaMKII were increased, and CaMKIIδ alternative splicing was disturbed. However, both GSK'872 and depletion of RIPK3 could reduce myocardial dysfunction, inhibit CaMKII activation and necroptosis, and finally alleviate myocardial hypertrophy. In addition, the pretreatment of RIPK3 could also lessen the accumulation of reactive oxygen species (ROS) induced by PE and stabilize the membrane potential of mitochondria. These results indicated that targeted inhibition of RIPK3 could suppress the activation of CaMKII and reduce necroptosis and oxidative stress, leading to alleviated myocardial hypertrophy. Collectively, our findings provided valuable insights into the clinical treatment of hypertrophic cardiomyopathy.

Calenduloside E protects against myocardial ischemia-reperfusion injury induced calcium overload by enhancing autophagy and inhibiting L-type Ca2+ channels through BAG3

Calenduloside E (CE) is a saponin isolated from Aralia elata (Miq) Seem, which has anti-cardiovascular disease effects. This study aims to evaluate the anti-myocardial ischemia-reperfusion injury (MIRI) mechanisms of CE and regulation of BAG3 on calcium overload. We adopted siRNA to interfere with BAG3 expression in H9c2 cardiomyocytes and used adenovirus to interfere with BAG3 expression (Ad-BAG3) in primary neonatal rat cardiomyocytes (PNRCMs) to clarify the role of BAG3 in mitigating MIRI by CE. The results showed that CE reduced calcium overload, and Ad-BAG3 had a significant regulatory effect on L-type Ca²⁺ channels (LTCC) but no effects on other calcium-related proteins. And BAG3 and LTCC were colocalized in myocardial tissue and BAG3 inhibited LTCC expression. Surprisingly, CE had no regulatory effect on LTCC mRNA, but CE promoted LTCC degradation through the autophagy-lysosomal pathway rather than the ubiquitination-protease pathway. Autophagy inhibitor played a negative regulation of cardiomyocyte contraction rhythm and field potential signals. Ad-BAG3 inhibited autophagy by regulating the expression of autophagy-related proteins and autophagy agonist treatment suppressed calcium overload. Therefore, CE promoted autophagy through BAG3, thereby regulating LTCC expression, inhibiting calcium overload, and ultimately reducing MIRI.

Calcium/Calmodulin-Dependent Protein Kinase II in Cerebrovascular Diseases

Cerebrovascular disease is the most common life-threatening and debilitating condition that often leads to stroke. The multifunctional calcium/calmodulin-dependent protein kinase II (CaMKII) is a key Ca2+ sensor and an important signaling protein in a variety of biological systems within the brain, heart, and vasculature. In the brain, past stroke-related studies have been mainly focused on the role of CaMKII in ischemic stroke in neurons and established CaMKII as a major mediator of neuronal cell death induced by glutamate excitotoxicity and oxidative stress following ischemic stroke. However, with growing understanding of the importance of neurovascular interactions in cerebrovascular diseases, there are clearly gaps in our understanding of how CaMKII functions in the complex neurovascular biological processes and its contributions to cerebrovascular diseases. Additionally, emerging evidence demonstrates novel regulatory mechanisms of CaMKII and potential roles of the less-studied CaMKII isoforms in the ischemic brain, which has sparked renewed interests in this dynamic kinase family. This review discusses past findings and emerging evidence on CaMKII in several major cerebrovascular dysfunctions including ischemic stroke, hemorrhagic stroke, and vascular dementia, focusing on the unique roles played by CaMKII in the underlying biological processes of neuronal cell death, neuroinflammation, and endothelial barrier dysfunction triggered by stroke. We also highlight exciting new findings, promising therapeutic agents, and future perspectives for CaMKII in cerebrovascular systems.

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.